CA1186502A

CA1186502A - Encapsulated liquid crystal and method

Info

Publication number: CA1186502A
Application number: CA000411447A
Authority: CA
Inventors: James L. Fergason
Original assignee: James L. Fergason; Manchester R & D Partnership; Manchester R & D Limited Partnership
Current assignee: Manchester R&D Partnership
Priority date: 1981-09-16
Filing date: 1982-09-15
Publication date: 1985-05-07
Also published as: WO1983001016A1; KR970000345B1; EP0268877A2; DE3280302D1; GB2128626B; JPH04305620A; EP0088126B2; EP0088126A1; US4435047A; EP0268877A3; SG11089G; JPH0352843B2; GB8311442D0; JPH079512B2; EP0088126B1; US4616903A; JPS58501631A; AU567868B2; SU1620056A3; BR8207867A

Abstract

ABSTRACT
Briefly, according to one aspect of the invention, liquid crystal material, and especially nematic material, is encapsulated; according to another aspect the encapsulated liquid crystal material is used in liquid crystal devices, such as relatively large size visual display devices; and according to further aspects there are provided methods for encapsulating liquid crystal material and for making a liquid crystal device using such encapsulated liquid crystal material.

Description

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TITLE: ENCAPSULATED LIQUID CRYSTAL AND METHOD

TECHNICAL FIELD
The present invention relates generally to liquid crystal and, more particularly! to encapsulated liquid crystal. Morleover, the invention relates to devices using such encapsulated liquid crystals and to method of making such encapsldated liquid crystals and devices.

BACKGROUND OF PRIOR ART
Liquid crystals currently are used in a wide variety of devices, including optical devices such as visual displays. Such devices usually require relatively low power and have satisfactory response time7 provide reasonable contrast, and are relatively economical. The property of liquid crystals enabling use, for example, in visual displays, is the ability of liquidcrystals to transmit light on one hand, and to scatter light and/or to absorb light, on the other, in dependence on whether the liquid crystals are in a relatively free, i.e. deener~ized or field o~f state or in a strictly aligned, i.e. an energized or field on state, e.g. with an electric îield applied a~ross the liquid crystal material. An example of electrically responsive liquid crystal material and use thereof is provid~d in IJ.S. Patent 3,3~2,~8S.
Certain liquid crystal materi~l is responsive to tempe~ture, challging optical characteristics in response to temperature of the liquid crystal material.
The invention of the present application is disclosed hereinafter particularly with reference to use of liquid crystal material that is particularly responsive to electric field.
Currently there are three categories of liquid crystal mnterials, namely cholesteric, nem&tic and smectic types. The invention of the present application relates in the preferred embodiment described below to use of nematic liquid cryst~l material or to a combination of nematic and some cholesteric type. However, various principles of the invention rnay be employed with various one or ones of the known types of liquid crystal material or combinations thereof. The various characteristics of the cholesteric, nematic and smectic types of liquid crystal material are 6~

described in the prior art. One known characteristic of liquid crystal material is that of reversibility; in partic~dar it is noted here that nematic liquid crystal material is known to be reversible, but cholosteric material is not reversible.
To enhance contrast and possibly other properties of liquid crystal materi~l, pleochroic dyes have been mixed with the liquid crystal material to form a solution therewith. The molecules of pleochroic materi~l generally align with the molecules of the liquid crystal material. Therefore, such pleochroic dyes will tend to function optically in a manner similar to that of the liquid crystal material in response to a changing parameter, such as application or non-application of an electric field. Examples of pleochroic dyes with liquid crystal material are described in U.S. Patents 3,499,702 and 3,551,026.
An important characteristic of liquid crystal material is anisotropy.
Anisotropic material has dif~erent physical propf3rties in different direc-tions. For example, liquid crystnls m~,y be optically nnisotropic such th~t when the molecules are randomly orient~d they permit light trllrlsmission and, when they are aligned due lo application of an electric field thereacross, light may be transmitted through the liquid crystal material.
Liquid crystal material also has electrical anisotropy. For example, the dielectric constant ~or nematic liquid crystal material may be one value when the liquid crystal molecules are parallel to the electric field and may have a different value when the liquid crystal molecules are aligned perpendicular to an electric field. Since such dielectric value is a f~mction of alignment, for example, reference to the same as R "dielectric coefficient" may be more apt than the usual "dielectric constant" label.
Similar properties are true for other types of liquid crystals.
Some brief discussion of encapsulation of cholesteric liquid crystal material is presented in U.S. Patents 3,720,623, 3,341,466, anà 2,8U0,457, the latter two patents being referred to in the former patent.
In the past devices using liquid crystals, such as visual display devices or other devices, have been of relatively small size. Large size devices using liquid crystals, such as, for example, a billboard display or a sign have not been able to be made satisfactorily for a number of reasons. One reason is the fluidity of the liquid crystals, ~the liquid crystal material may tend to f~ow creating areas of the display that have differen$ thicknesses). As a result, the optical characteristics of the display may lack uniformity, have varying contrast characteristics at different portions of the display, etc; the thickness variations cause variations or gradations in optical properties of 5 the liquid crystal device. Moreover, the varying thickness of the liquid crystal material will cause corresponding variations in the electrical properties of the liquid crystal material, such as capacitance and impedance, fur$her reducing uniformity of a large size liqui~d crystal deYice. The varying electrical properties of the liquid crystal material, then, also may 10 cause a corresponding variation in the effective electric field applied across the liquid crystal material and/or in response to a constant electric field wo~d respond differently at areas of the liquid crystal that are of different thicknesses.
A pleochroic display, i.e. one in which pleocroic dye and liquid crystal 15 material are in solution, has the adyflnt~ge of not requiring a polarizer.
IIowever, such a pleochroic device has a disadvnntnge of relatively low contrast when used dir~ctly in the nematic form. It wus discovered in the past, though, that a cholesteric liquid crystal material could be added to the nematic one together with the dye to improve the contrast ratio. See White 20 et al article, '~Journal of Applied Physics", Volume 45~ No. 11, November 1974, at pages 4718-4723, for example. The cholesteric material would tend not to return to its original zero field form when the electric field is removed.
Another problem encountered with pleochroic dye included in solution 2S with liquid crystnl material, regardless of the particular type of liquid crystal material, ;s that the absorbtion of the dye is not 2ero in the field-on cond;tion; rather such absorbtion in the fiel~on condition fo~lows a so-called ordering parameter, which relates to or is a function of the relative alignment of the dyes. The optical transmission characteristic of liquid 30 crystal material is an exponential function of thickness of the liquid crystal material; specifically, the on state or fiel~on or energized stAte of the liquid crystal material is an exponential function of thickness of the liquid crystal material, and the absorbing state or off state also is a different exponential function of thickness.
3S To overcome those proMems described in the two immediately pre-ceding paragraphs, the liquid crystal material should have an optimum ~r uniform thickness. (As used herein liquid crystal material means the liquid crystals themselves and, depending on context, the pleochroic dye in solution therewith.) There also should be ~n optimum spacing of the electrodes by which the electric field is applied to the liquid cryst~l materi~. To 5 maintain such optimum thickness and spacing, ratlher close tolerances must be maintained. To maintain close tolerances, there is a limit as to the size of the device using such liquid crystals, for it is quite difficult to maintain close tolerances over large surface areas, for example.

BRIEF SUMMARY OF INVENTION
Briefly, according to one aspect of the invention, liquid crystal material, and especially nematic material, is encapsulated; according to another aspect the encapsulated liquid crystal material is used in liquid crystal devices, such as relatively large size visual displny devices; and 15 according to further aspects there are provided m~thods for encnpsulating liquid crystal muterial and for making n liquid crystnl device using such encapsulated liquid crystal material.
Some terms used herein generally are defined as follows: liquid crystal material broadly refers to any type of liquid crystal material that will work 20 in the context of the present invention, but preferably refers to nematic type. Such liquid crystal material also may include pleochroic dye or other ingredient. A caps~e refers to a containment device or medium that confines a quantity of liquid cystal material, and encapsulating medium or material is that medium or material of which such capsules are formed. An 25 encapsulated liquid crystal or encapsulated liquid crystal material means a quantity of liquid crystal material confined or contained in the encapsulating medium, such as the noted capsules. A liquid crystal device is a device formed of liquid crystal material, in the present invention such devices are formed of encapsulated liquid crystals capable of providing a function of the 30 type typically inuring to-liquid crystal material; for example, such a liquidcrystal device may be a visual display that in response to application and removal of ar~ electric field effects a selected attenuation of visible light.
One method of making encapsulated liquid crystals includes mixing together liquid crystal material and an encapsulating medium in which the 35 liquid crystal material will not dissolve and permitting formation of discrete capsules containing the liquid crystal material.
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~ 3, A method of making a liquid crystal device including such encapsulated liquid crystal includes, for example applying such encapsulated liquid crystal material to a substrate. Moreover, such method may include providing means for applying an electric field to the liquid crystal material to affect a 5 property thereof.
According to another feature of the invention a nematic material with positive dielectric anisotropy in which is dissolved a pleochroic dye is placed in a generally sphericPl capsule. The caps~e wall distorts the liquid crystal molecules so they and the dye when no field is applied will tend to absorb all 10 directions of polarized light. When a suitable electric field is applied across such a capsule, for example across an a~is thereof, the liquid crystal material will tend to align parallel to such field causing the absorbtion characteristic of such material to be reduced to one assumed when the liquid crystal material is in planar configuration. To help assure that ad~quat~
lS electric field is applied across th~ liquid crystal materi~l in the capsule, nncl not just across or through the encapsulating medium, and, in fact, with a minimum voltage drop across the wall thickness of the respective capsules, the encapsulating material sho~d have a dielectric eonstant near to that of the liquid cryst~l material, on the one hand, and a relatively large 20 impedance, on the other hand, and the liquid crystal material itself should have a positive dielectric anisotropy.
Contrast of a liquid crystal device employing encaps~ated liquid crystals may be improved by selecting an encaps~ating medium that has an index of refraction that is matched to the ordinary index of refraction of the 25 liquid crystal material. The encapsulating medium may be used not only to encapsulate liquid crystal material but also to adhere the capsules to a substrate for support thereon. Alternatively, a further binding medium may be used to hold the liquid crystal capsules relative to a substrate. In the latter case, though, preferrably the additional binding medium has an index 30 of refraction which is matched to that of the encapsulating medium for maintaining the improved contrast characteristic described above.
A feature of the spherical or otherwise curved capsule which confines the liquid crystal material therein in accordance with the present invent;on - is that the liquid crystal material tends to follow the curvature or otherwise 35 to align generally parallel with the curved surfaces o such capsule.

Accordingly, the individual liquid crystal molecules tend to be forced or distorted to a specific form, being folded back on themselves in a sense as they follow the capsule wall, so that the resulting c,ptical characteristic of agiven caps~e containing liquid crystal material is such that substantially all 5 light delivered thereto will be absorbed when no electric field is applied, regardless of the polarization direction of $he incident light. Even without dye this effect causes scattering and thus opacity.
Another feature is the ability to control the e~fective thickness of the liquid crystal material contained in a caps~e by controlling the internal 10 diameter of such capsule. Such diameter control may be effected by a separation process dur;ng the method of making the encapsulated liquid crystals using any one of a variety of conventional or novel sorting techniques as well as by controlling the rnixing process, the quRntities of ingredients, and/or the nature of the ingredients provided during mixing. By controlling such thickness pnrameter to relatively close tolerances, then, the subseguent tolerance requirements when the final liquid crystal device is made using the encapsulated liquid crystals will not be as critical as was required in the past.
Moreover, a further and very significant feature of the present 20 invention is that there appears to be no limitation on the size of a high quality liquid crystal device that can be made using the encapsulated liquid crystals in accordance with the present invention. More specifically, by providing confinement for discrete quantities of liquid crystal material, for example, in the described capsules, the various problems encountered in the 25 past that prevented use of liquid crystal material in largre size devices nreovercome, for each individual capsule in effect can still operate a~ an independent liquid crystal device. Moreover, each capsule, then, preferably has physical properties enabling it to be mounted in virtually any environment including one containing a plurality of further such liquid 30 crystal capsules mounted to a substrate or otherwise supported for use in response to application and removal of some type of excitation source, such as, for example, an electric field or the like.
Important considerations in accordance with the invention, and the discovery of the inventor, are that an encapsulating medium having 35 electrical properties matched in a prescribed way to the electrical , properties of liquid crystal material encapsulated thereby and additionally preferably optically matched to optical properties of such liquid crystal material permits efficient and high quality functioning of the liquid crystal material in response to excitation or non-excitation by an e~ternal source;
and that the interaction of the encapsulating meclium with the liquid crystal material distorts the latter in a prescribed manner changing an operational mode of liquid crystal material. Regarding the latter, by forcing the liquid crystal molecules to distort into generally parallel or conforming alignment with the capsule wall, the liquid crystals will absorb or block, rather than transmit, light when not subject to an electric field and will be unetional with respect to all manners of incident light regardless of the direction of polarization of such incident light.
With the foregoing in mind, a primary object of the invention is to enable the use of liquid crystal matsrial over relatively lElr~ surf~cc~, and e~pecially to effeot the snme while maintaining relntively high quality of operation, controlled unlformity of output and satisfuctory contrast.
Another primary object is to confine liquid crystal material while maintaining optical characteristics of such material, and especially to effect the same also maintaining electrical responsiveness of the liguid crystal

2~ material.
An additional primary object is to encapsulate nematic liguid crystal material in a non-interacting medium.
A further primary object is to achieve a useful encaps~ation of nemaffc liquid crystal material.
Still another primary object is to utilize both physical e.g. alignment, and opffcal, eOg. index of refraction, characteristics of material of the liquidcrystal type.
Still an additional primary object is to utilize resin material for encapsulating liquid crystal material, and especially to effect the same to form curved and most preferably spherical caps~des containing discrete quantities of liquid crystal material.
Still a further primary object is to eliminate restrictions on size of displays or other devices of the liquid crystal type, especially while achieving high quality operation, satisfactory contrast, wide viewing angle and adequate response time.

Even another primary object is to force a liquid crystal material to its zero field form, particularly when such material includes a combination of liquid crystal material and pleochroic dye material and even when the liquid crystal material includes more than one type of liquid crystal materiRl.
Another object is to enable use o~ nematic liquid crystal rnaterial with pleochroic dye in solution therewith while obtaining an effect of having cholesteric material added thereto even without the latter. More specifically, an object is to enable liquid crystal material that contains pleochroic dye to absorb light in all directions and to minimize partial light transmission when in field off conditions, i.e. when no electric field is applied to the ljguid crystal material.
An additional object is to distort the internal structure of liquid crystal material to achieve enhanced optical properties.
A further ob~ect is to achieve controlled light distortion nnd especially such controlled distortion o~ light entering liquid arystnl mRterial that i~
contoured in an encapsulating medium.
Still another object is to provide a uniform area over which a constant ~nd uniform electric field may be delivered to discrete quantities of liquid crystal material and especially when such material is contained in discrete 20 capsules.
Still an additional object is to control the size of the electric field required to operate the liguid crystal device.
Still a further object is tc improve the uniformity of turn on or operation of a liquid crystal device, and especially to facilitate the control 25 of such turn on ~r operation.
Yet another object is to control the uniforrnity of the size and/or other dimensional characteristics of liquid crystal capsules.
Yet an additional object is to encapsulate liquid crystal material in a resin or other material and most preferably to effec$ such encapsulation 30 while forming discrete capsules containing liguid crystal material.
Yet a further object is to use a single medium for encapsulating liquid crystal material in discrete capsules or the like and for binding the capsules together and/or to a support substrate or the like.
Yet still another object is t~ use an optically anisotropic liquid crystal 35 irl a limited optically isotropic manner, e.g. by causing a polarization direction sensiffve liquid crystal material to eliminate such sensitivity.

Yet still an additional object is to impose elastie energy on liquid crystal material, and especi~lly to effect the same to cause unusual properties in such liquid crystal material.
Yet even ~nother object is physically to control the ease nf alignment 5 of liquid crystals.
Yet even an addition object is to facilitate applying liquid crgstal material to ~ substrate.
Yet even a further object is to facilitate interfacing or applying of electrodes with respect to liquid crystal type material.
Another object is to apply electrodes directly to liquid crystal material.
An additionaI object is to improve a method for making liquid crystal devices, especi~lly by encapsulating the liquid crystal materials.
A further object is to control the requirements ol~ voltage or electric 15 field required to operate a liquid crystal device.
Moreover another object is to stop scattering or absorbtion by liquid crystal material when an electric field is applied thereto.
Moreover an additional object is to control the amount of voltage dlop that occurs across liquid crystal material.
These and other objects and advantages of thé present invention will become more apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described in the specification and particularly polnted out in the claims, the following 25 description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF DRAWING
In the annexed drawing:
Fig. 1 is a schematic representation of a prior art liquid crystal device;
Fig. 2 is ~ schematic representation of a liquid crystal device in accordance with the present invention;

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Fig. 3 is an isometric view of a liquid crystal display device in accordance with the present invention;
Fig. 4 is an enlarged fragmentary view, partly broken away, of a portion of the liquid crystal display device of Fig. 3;
Fig. 5 is an enlarged schematic illustration of a liquid crystal capsule in accordance with the present invention under a no field condition;
Fig. 6 is a view similar to Fig. 5 under an applied electric field condition; and Fig. 7 is a schematic electric circuit diagram representation of the capsule with an applied field.
SUMMARY OF PRIOR ART LIQI~ID CRYSTAL DEVICE
Referring now in detail to the drawings, wherein like reference numerals designate like parts in the several figures, and initially to Fig. 1, aprior art liquid crystal device is generally indicated at 1. Such device 1 includes liquid crystal material 2 sandwiched between electrodes 3 of, for example, indium tin oxide that are deposited for support on respective mounting or confining substrates 4, such as glass, plastic sheets or the like~
The sheets 4 may be clear as may be the electrodes 3 so that the device 1 is an optical transmission control device, whereby incident light rnay be scattered when no electric field is applied by the electrodes 3 across a liquid crystal material 2 and the incident light may be transmitted through the liquid crystal material 2 when an electric field is applied thereacross.
Electric leads 5 and switch 6 selectively couple voltage source 7 across the electrodes 3 to provide such electric field. The voltage source 7 may be either an AC or a DC voltage source.
The liquid crystal material 2, and specifically the individual mole-cules thereof, in the device 1 are somewhat confined by the substrates ~ for retention in a desired location, say for example, to be used overall as part of a digital display device. On the other hnnd, the liquid crystal material 2, and specifically the individual molecules thereof, must have ndequate freedom of movement so that they may assume either a random orientation or distribution when no electric field is applied or a prescribed distributionalor orientational alignment when an electric field is applied across the electrodes 3. If desired, one of the substrates 4 may be reflective to reflect incident light received through the liquid crystal material 2 back through 6s~D2 the latter for delivery through the other substrate 4 for subsequent use. The various principles of operation and features and disadvantages OI the liquid crystal device 1 are summarized above and are described in the prior art literature.
The liquid crystal material 2 may be of virtually any type that is responsive to an electric field applied thereacross so as to have a desired operating characteristic intended for the device 1~ the liquid crystal material 2 also may include, if desired, pleochroic dye material in solution therewith.
DE~CRIPTION OF THE PREFERRED EMBODIMENT
-Turning now to ~ig. 2, an improved liquid crystal device in accor-dance with the present invention is indicated at 10. ~he device 10 includes an encapsulated liquid crystal 11 which is supported from a mounting substrate 12 across which an electric field may be applied via electrodes 13, 1~.
The electrode 13 may be, for example, a quantity vacuum deposited indium tin oxide applied to the substrnte 12, und the electrodc 14 may be, for example, electrically conductive ink~ A protective layer or coating 15 may be applied over the electrode 14 for protective purposes but such layer 15 ordinarily would not be necessary for supporting or confining the encapsulated liquid crystal 11 or the electrode 14. Voltage may be applied to the electrodes 13, 14 from an AC or DC voltage source 16, selectively closable switch 17, and electrical leads 18, 1~ in turn to apply an electric field across the encapsulated liquid crystal 11 when the switch 17 is closed.
The encapsulated liquid crystal 11 includes liquid crystal material 20 contained within the confines or interior volume 21 of a capsule ~2.
According to the preferred embodiment and the best mode ot` the present invention, the capsule 22 is generally spherical. However, the principles of the invention would npply when the capsule 22 is of a shape other than spherical; such shape should porovide the desired optical and electricaI
characteristics that will satisfactorily coexist with the optical character-istics of the liquid crystal 20, e.g. index of refraction, and will permit an adequate portion of the electric field to occur across the liquid crystal material 20 itself for effecting desired alignment of the liquid s~æ

crystal molecules when it is desired to have a field on condition. A
particular advantage to the preferred spherical configuration of the capsule 22 will be described below with respect to the distortion it effects on the liquid crystal molecules.
The mounting substrate 12 and the electrodes 13, 14 as well as the protective coating 15 may be optically transmissive so that the liquid crystal device 10 is capable OI controlling transmission of light therethrough in response to whether or not an electric field is applied across the electrodes 13,14 and, thus, across the encaps~ated liquid crystal 11. Alternatively, the 10 mounting substrate 12 may be optically reflective or may have thereon an optically reflective coating so that reflection by such reflective coating of incident light received through the protective coating 15 will be a function of whether or not there is an electric field applied across the encnpsulRted liquid crystal 11.
lS According to the preferred cmbodiment and best rnode of the invention a plurality of encapsulated liquid crystals 11 would be applied to the mounting substrate 12 in a manner such that the encapsulated liquid crystals adhere to the mounting substrate 12 or to an interface material, such as the electrode 13, for support by the mounting substrate l2 and retention in 20 position fixed relative to the other encapsulated liquid crystals 11. Most preferably the encapsulating medium of which the capsule 22 is formed is also suitable Ior binding or otherwise adhering the capsule 22 to the substrate 12. Alternatively, a further binding medium (not shown) may be used to adhere the encapsulated liquid crystals 11 to the substrate 12. Since 25 the capsules aa are adhered to the substrate 12, and since each capsule 22 provides the needed confinement for the liquid crystal materiRl 20, ~l second mounting substrate, such as the additional one shown in the prior art liquid crystal device l o$ Fig. 1, ordinarily should be unnecessary. However, for the purpose of providing protection from scarring, electrochemical 30 deterioration, e.g. oxidation, or the like, of the electrode 14, the protective coating 15 may be provided on the side or surface of the liquid crystal device 10 opposite the mounting substrate 12, the latter providing he desired physical protection on its own side of the device 10.
Since the encapsulated liquid crystals 11 are relatively securely adhered 35 to the substrate 12 and since there ordinarily would be no need for ~n 6S~2 addition~l substrate, as was mentioned above, the electrode 14 may be applied directly to the encapsulated liquid crystals 11.
Turning no-w to Pig. 3, an example of a liquid crystal device 10' in accordance with the invention is shown in the form of a liquid crystal display device, which appears as a square cornered figure eight 30 on the substrate 12, which in this case preferably is a plastic material, such as Mylar, or may alternatively be anolher material, such as glass, for example.
The shaded area appearing in ~ig. 3 to form the square cornered figure eight is formed of plural encapsulated liquid crystals 11 arranged in one or more layers on and adhered to the substrate 12.
An enla~ged fragmentary section view of a portion 32 of the figure eight 30 and substrate 12 is illustrated in Fig. 4. As is seen in Fig. 4, Oll the surface 31 of the substrate 12, which may be approximately 10 rnils thick, is deposited a 200 flngstrom thick electrode layer 33 of indium tin oxide. One or more layers 34 of plural encapsulated liquid crystals 11 are applied and adhered directly to the electrode layer 33. Such adherence according to the preferred embodiment and best mode is effected by the encapsulnting medium that forms respective capsules 22, although, if desir~3dJ ~s W~IS
mentioned above, an additional adhering or binding material may be used for such adherence purposes. The thickness of the layer 34 may be, for example, approximately 1 mil. A further electrode layer 35 is deposited on the layer 34 either directly to the material of which the capsules 22 are formed or, alternatively, to the additional binding material used to bind the individual encapsulated liquid crystals 11 to each other and to the mounting substrate 12. The electrode layer 35 may be, for example, approximately 1/2 mil thick and may be formed, for example, of electrically conductive ink. A
protective coating layer 36 for the purposes described above with respect to the coating 15 in Fig. 3 ulso may be provided as is shown in Fig. 4.
In a conventional visual display device either of the liquid crystal or light emitting diode type, the figure eight element 30 ordinarily would be divided into seven electrically isolated segments, each of which may be selectively energized or not so as to create various numeral characters ~or example, energization of the segments 30a and 3Qb would display the numeral "1" and energization of the segments 30a, 30b, 30c would display the numeral "7".

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z A feature of the present invention utilizing the encapsulated liquid crystals 11 is that a versatile substrate 12 can be created to be capable of displaying virtually any desired display as a function of only the selective segments of conductive ink electrodes printed on the l;quid crystal material.
5 In this case, the entire surface 31 of the substrate 12 may be coated with electrode material 33, and even the entire surface of that electrode material may be coated substantially contiguously with layer 34 of encapsulated liquid crystals 11. Thereafter, a prescribed pattern of electrode segments of conductive ink 35 may be printed where desired on the layer 34.
10 A single electrical lead may attach the surface 31 to a voltage source, and respective electrical leads may couple the respective conductive ink segments vîa respective controlled switches to such voltage source.
Alternatively, the encapsulated liquid crystals 11 and/or the lelectrode material 33 may be applied to the surface 31 only at those areas where 15 display segments are desired.
Although a detailed description of operation of the individual encapsulated liquid crystals 11 will be presented below, it will suffice here tonote that the encapsulated liquid crystals in the layer 34 function to attenuate or not to attenuate light incident thereon in dependence on 20 whether or not an electric field is applied thereacross. Such an electric field may be, for example, one produced as a result of coupling of the electrode layer portions 33, 35 at an individual segment, such &S segment 30a, of the liquid crystal device 10' to an electrical voltage source. The magnitude of the electric field required to switch the encapsulated liquid 25 crystals 11 from a no field (deenergized) condition to a field on (energi~ed)condition may be Q function of several parameters, including, for example, the thickness of the layer 34, wllich in turn may depend on the diameter of individual capsules 22 and the number of such capsules in the thickness direction of layer 34. Importantly, it will be appreciated that since the 30 liquid crystal material 20 is confined in respective capsules 22 and since the individual encaps~ated liquid crystals 11 are secured to the substrate 12, the size of the liquid crystal device 10' or any other liquid crystal device employing encapsulated liquid crystals in accordance with the present invention is nearly unlimited. Of course, at those areas where it is intended 35 to effect a change in the optical properties of the encaps~dated liquid s~æ

crystals of such a device in response to a no field or field on condition9 it would be necessary to have there electrodes or other means for applying to such liquid crystals a suitable electric field.
The electrode layer 33 may be applied to the substrate 12 by evaporation, by vacuum deposition, by sputtering, by prislting or by any other technique that may be desired. Moreover7 the layer 34 of encaps~ated liquid crystals 11 may be applied, for example, by a web or gravu~e roller or by reverse roller printing techniques. The electrode layer 35 also may be applied by various printing, stenciling or other techniques. If desired, the electrode layer 33 may be prepared as a full coating of the substrate 12, such as Mylar, as was described above, as part of the process in which the DIylar sheet material is manufactured, and the layer 34 also may be applied as part of such manufacturing process.
The ability to make and to use successfully liquid crystal clevices of the type just described using encapsulated liquid crystals i3 due to the ~billtyto make encapsulated liquid crystals and to the properties of such encapsulated liquid crystals, both of which are features of the present invention. These features now will be described with reference to Figs. 5, 6 and 7 in particular.
Referring specifically to Fig. S, the caps-de 22 has a generally smooth curved interior wall surface 50 defining the boundary of the volume 21. The actual dimensional parameters of the wall surface 50 and of the overall capsule 22 are related to the quantity of liquid crystal material 20 contained therein and to the size of the i~dividual liquid crystal molecules.
25 Additionally, the capsule 22 applies a force to the liquid crystals 20 tending to pressuri~e or at least to maintain substantially constant the pressure within the volume 21. As a resu~t of the foregoing, and due to the surface wetting nature of the liquid crystal molecules, such molecules, which ordinarily in free form would tend to be straight, although perhaps randomly 30 distributed, are distorted to curve in a direction that generally is parallel to a relatively proximate portion of the interior wall surfnce 50. Due to such distortion the liquid crystals store elastic energy. ~or simplicity of illustration, and for facility of comprehending the foregoing concept, a layer 51 of liquid crystal molecules represented by respective dashed lines 52 is 35 shown in closest proximity to the interior wall surface 50. The molecules 5~

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are distorted to curve in the direction that is parallel to a pro~amate area of the wall surface 50. Other layers, such as layer 53, etc.7 OI liquid crystal molecules 52 are shown in the caps~e 22. The liquid crystal molecules are shown in such layers, although it will be appreciated that the liquid crystal 5 molecules may be oriented somewhat more randomly than in the ordered layers illustrated in ~ig. 5i however, such molecules nevertheless will ten to align with some degree of parallel relationship to the respective proximate areas of the interior wall surface 50.
In the preferred embodiment and best mode of the present invention 10 the liquid crystal molecules 52 are of the nematic type. Such molee~es usually assume a straight line thread-like configuration, and a liquid crystal material comprised of such ncmatic molecules usually is optical polarization direction sensitive. However, since the molecules 52 in the enc~psulated liquid crystal ll are distorted or forccd to curved form in th~ full thre~
15 dimensions of the capsule 22, ~ uch nem~tic liquid crystal muterinl in ~uoh capsule takes on an improved characteristic of being insensitive to the direction of optical polarization of light incident thereon. The inventor has discovered, moreover, that when the liquid crystal material 20 in the capsule 22 has pleochroic dye ~issolved therein, such dye, which ordinarily also 20 would be expected to have optical polarization sensitivity, no longer is polarization sensitive because the dye tends to follow the same kind oi curvature orientation or distortion as that of the individual liquid crystal molecules 52.
It is noted here that the liquid crystal material ao in the capsule 22 has 25 a discontinuity 55 in the generally spherical orientation thereof. Such discontinuity is caused by the incapability of the liquid crystal to align uniformly in a manner compatible with parallel alignment with the wall 54 and a requirement for minimum elastic energy. The liquid crystal molecules 52, though, will tend to follow around the discontinuity in the manner shown 30 in planar form in Fig. 5, but in reality in three dimensions, following a pattern along the three dimensional generally cylindrical internal boundary wall surface 50a of the protruding discontinuity 55. Such discontinuity further distorts the liquid crystal molecules which further decreases the possibility that the liquid crystal material 20 would be sensitive to optical 35 polarization direction of incident light.

With the individua~ liquid crystal molecules 52 being distorted to fold in on themselves generally in the manner ilIustrated in Fig. 5, the encapsulated liquid crystal 11 ordinarily will absorb or block light from being transmitted therethrough when no electric field iis applied across the 5 encapsulated liquid crystal 11 and particularly across the liquid crystal material 20 thereof.
However, when an electric field is applied across the encaps~dated liquid crystal 11 in the manner illustrated in Fig~ 6, the liquid crystal molecules 52 and any pleochroic dye in solution therewith will align in 10 response to the electric field in the mamler shown in such figure. Such alignment permits light to be transmitted through the encapsulated liquid crystal 11, for example as described above with reference to Figs. 2~ 3 and 4.
In the field off condition since the liquid crystal molecules 52 are distorted to curved form, they have a certain elastic energy. Such elastic energy causes the crystals to ~unction doing things that otherwise were not possible when the liquid crystal molecules assume their ordinary linear form.
For example, the discontinuity protrusion 55 would tend to cause scattering and absorbtion within the capsule, and the tangential or parallel alignment of the liquid crystal molec~es to r espective portions of interior wall surface 20 50 both cause scattering and absorption within the capsule 22. On the other hand, when the electric field is applied in the manner illustrated in Fig. 6, not only do the liquid crystal molec~es 52 align as shown, but also the discontinuity 55 tends to align in parallel with the electric field.
Accordingly, such discontinuity will have a minimum effect on optical 25 transmission when the encapsulated liquid crystal 11 is in a field on condition.
To optimize contrast characteristics of a liquid crystal device, such as that shown at 10' in Fig. 3, comprised of encapsulated liquid crystals ll, and, more particularly, to avoid optical distortion due to refraction of incident light passing from the encapsulating medium into the liquid crystal material 30 and vice versa of the encaps~ated liquid crystal 11 of ~ig. 6, the index of refraction of the encapsulating medium and that the ordinary index of refraction of the liquid crystal material should be matched to be as much as possible the same.
However, when no field is applied there will be a difference in indices 35 of refraction at the boundary of the liquid crystal and capsule wall due to ._ ...~

the extraordinary index of refraction of the liquid crystal being greater than the encaps~ating medium. This causes refraction at that interface or boundary and thus further scattering and is a reason why the invention of encapsulated nematic liquid crystal material, in particular, will function to 5 prevent transmission of light even withollt the use of pleochroic dye Ordinarily the encapsulated liquid crystals 11 would be applied to the substrate 12 (Fig. 3) such that the individual encapsulated liquid crystals 11 are relatively randomly oriented and preferably several capsules thick to assure an adequate quantity of liquid crystal material on the surface 31 of 10 the substrate to provide the desired level of light blockage and/or transmission characteristics for, for example, a liguid crystal device 10' or the like.
In a liquid crystal device, such as that shown in 10' in Fig. 3, which is comprised of liquid crystal material 20 including pleochroic dye to form 15 encapsulated liquid crystals 11 according to the invention, it has been discovered that the degree of optical absorbency is at least about the ~ame as that of relatively free (Lmencapsulated) liquid crystal material, including pleochroic dye such as that shown in Fig. 1. It also has been discovered lmexpectedly that when the electric field is applied in the manner illustrated 20 in Fig. 6, for example, the clarity or lack of opaqueness of the encapsulatedliquid crystal material 20 including pleochroic dye is at least about the same as that of the ordinary case in the prior art device 1 having dye in solution with the relatively free liquid crystal material.
It is important that electrical field E shown in Fig. 6 is applied to the 25 liquid crystal material 20 in the capsule 22 for the most part rather than being dissipated or dropped substanti~lly in the encapsulating material of which the capsule itself is formed. In other words, it is important that there not be a substantial voltage drop across or through the material o~ which the wall 54 of the capsule 22 is formed; rather, the voltage drop should occur 30 across the liquid crystal material 2D within the volume 21 of the capsule 22. The electrical impedance OI the encapsulating medium preferably should be larger than that of the liquid crystal material in the encapsulated liquid crystal 11 ~Fig. 6) and also should be large enough that a short circuit will not occur exclusively through the wall 54 bypassing the l;quid crystal 35 rnaterial. Therefore, for example, the impedance to current flow through ~&~

or via the wall 54, say ~rom point A to point B, would be rather substantial as opposed to the impedance that would be encountered in a current path directly from point A to point A' inside the interior wall surface 50, directly through the liquid crystal material 20 to point B' still within the volume 21, ~dtimately to point B again.
The dielectric constants (coeIficients) of the rnaterial of which the encapsulating medium is formed und of which the liquid crystal material is comprised and the effective capacitance values of the capsule w-all 54 particularly in a radial direction and of the liquid clystal m~terial across which the electric field E is imposed all should be so related that the wall 54 of the caps~de 22 does not substantially drop the magnitude of the applied electric field E.
~ schematic electric circuit diagram representing the circuit across which the electric field E of Fig. fi is imposed is illustrated in Fig. 7. The electric field is derived ~rom the voltage source lB when the switch 17 is closed. A capacitor 70 represents the capacitance of the liquid crystal material 20 in the encapsulated liquid crystal 11 when such electric field is applied in the manner illustrated in Fig. 6. The capacitor 71 represents the capacitance of the capslde 22 wall 54 at an upper area (the direction ~onveniently referring to the drawing but having no other particldar intentional meaning) and is, accordingly, curved in a manner similar to that of the upper portion of the capsule 22 of Eigs. 5 and 6. The capacitor 72 similarly represents the capacitance of the lower portion of the capsule exposed to the electric field E. The magnitudes of capacitance for each capacitor 70-72 will be a function of the dielectric constant (coe~f;cient) of the material of which the respective capacitors are formed and of the spacing o~ the effective plates thereof. It is desirable that the eapacitors 71, 72 be larger in magnitude than the capacitor 70 so that the voltage drop occurring across the respective capacitors 71, 72 will be less than the voltage drop across the capacitor 70; the result? then, is application of a maximum portion of the electric field E across the liquid crystal material 20 in the encapsulated liquid crystal 11 for achieving optimized operation, i.e.
alignment, of the liquid crystal molecules thereof with a minimum total energy requirement of the voltage source 16.
In connection with capacitor 71, for example, the dielectric material is that of which the wall 54 is formed relatively near the upper portion of the capsule 22. The effective plates of such capacitor 71 are the exterior and interior wall surfaces 73, 51, and the same is true for the capacitor 72 at the lower portion of the capsule 22 relative to the illustration of Fig. 6, for example. By making the wall 54 as thin as possible, while still providing 5 adequate strength for containment of the liquid crystal material 20 in the volume 21, the magnitudes of capacitors 71, 72 can be maximized, this especially in comparison to the Father thick or lengthy distance between the upper portion 74 ~f the liquid crystal material 20 of the lower portion 75 thereof which approximately or equivalently form the plates of the same 10 number of the capacitor 70.
The liquid crystal material 20 will have a dielectric constant value that is anisotropic. It is preferable that the dielectric constant (coefficient)of the wall 54 be no lower than the lower dielectric constant (coeff;cient) of the anisotropic liquid crystal material 2U to help meet the above conditions.
The encapsulated liquid crystlll ll hn~ fe~tur~s that ~inc~ th~ liqliicl crystal molecules 52 are distorted nnd since the pleochroic dye similarly is distorted, absorbency or blockage of light transmission through the encapsulated liquid crystals will be highly effective when no electric field E
is applied thereacross. On the other hand, due both to the efficient 20 application of electric field across the liquid crystal material 20 in the encapsulated liquid crystals 11 to align the liquid crystal molecules and the dye along therewith as well as the above described preferred index of refraction matching, i.e. of the encapsulating medium and of the liquid crystal material, so that incident light will not be refracted or bent at the 25 interface between the capsule wDll 54 and the liquid crystfll material 20, when an electric field is applied the encapsulated liquid crystal ll will have agood optically transmissive characteristic.
Since a plurality of encapsulated liquid ¢rystals 11 ordinarily is required to construct a final liquid crystal device, such as the device 10' of Fig. 3, and 30 since those encapsulated liquid crystals are in several layers, it is desirable to have a relatively high dielectric anisotropy in order to reduce the Yoltage requirements for the electric field E. More specifically, the differential between the dielectric constant (coefficient) for the liquid crystal material 20 when no electric field is applied which constant (coefficient) should be 3S rather small, and the dielectric constant (coefficient) for the liquid crystal material when it is aligned upon application of an electric field, which constant (coefficient) sho~d be relatively large, should be as large as possible.
The capsules 22 may be of various sizes. The srnaller the capsule size, though, the higher the requirements will be for the electric field to effect alignment of the liquid crystal molecules in the capsule. Also, when the capsule size is relatively sm~ll, more capsldes are required per unit area of the layer 34, and, there~ore, more electric voltage drop losses will occur in the encapsulating mediurn than for lPrger size capsules, the density per unit area of which would be smaller. According to the preferred embodiment and best mode of the present invention, though, a device made with the encapsulated liquid crystals 11, such as the liquid crystal device 10', should use caps~es of uniform size parameters so that the device 10' can be energized or deenergized in a relatively uniform and wcll controlled mnnner.
In contrast, when the capsules ar~ of a non-uniform siæe, tllcn non uniform energization of the respective capsules, i.e. alignment of the liq~lid clystal molec~es of each, would occur upon application of the electric field.
Ordinarily the capsules 22 should have a size on the order of from about 2 to about 25 microns in diameter.
2D As was noted above, the larger the capsule size, the smaller the electric field required to effect alignment of the liquid cryst~l molecules therein. However, the larger the sphere, the longer the response time.
Regardless of the caps~e size and the particular field off arrangement of liquid crystal molecules within the capsule 22, it is important to know what the field off alignrnent would be and what would be the distorted alignment when there is a field on condition so that the encapsulated liquid crystals 11 may be used effectively.
Ln the preferred embodiment and best mode of the present invention the liquid crystal material used in the encaps~ated liquid cryst~l 11 is of the 30 nematic type.
Currently a most preferred liquid cryst&l material is that as nematic material NM8250 sold by American Liquid Xtal Chemical Corp., Kent, Ohio, U.S.A. Others may be ester combinations, biphenyl combinntions, and the like.
The encapsulating medium forming respective capsules 22 should be of a type that is substantially completely unaffected by and does not affect the liquid crystal material. The other characteristics described above collcerning dielectric constants (coefficients) and ind;ces of refraction with respect to the liquid crystal rnaterial and to the encapsulating medium also constrain material selection. Moreover, when pleochroic dye is employed, 5 the encapsulating medium also should be totally unaffected by and should not affect the dye material. On the other hand, the dye should be oil soluble and not subject to absorption by the water phase (see below) or polymer phase of the encaps~ating medium. Additionslly, to achieve the desired relatively high impedance for the encapsulating medium, such medium 10 should have a relatiYely high level of purity.
An example of a pleochroic dye that may be used in the encapsulated liquid crystals 11 in accordance with the present invention are indophenol blue, Sudan black B, Sudan 3, and Sudan 2.
Various resins nnd/or polymers may be used ns the encapslllating 15 medium. However, ~n encapsulating medium according to th~ pref~3rr{~d embodiment and best mode of the present invention is polyvinyl alcohol (PVA), which has been found to have the desired properties mentioned above, especially in relation to the above described preferred liquid crystal and pleochroic dye material. Specifically, PVA has a good, relatively high, 20 dielectric constant and has an index of refraction that is relatively closely matched to th~t of the preferred liquid crystal material.
To purify PVA, the same may be dissolved in water and washed out with alcohol using a precipitate technique. Other techniques also may be used for purifying PVA so that it will have minimum s~lt or other content 25 that would reduce appreciably the electrical impedance thereof. The prefelred purified PVA is S~72 sold by American Liquid Xtal Chemical Corp. If PVA i5 properly cleaned or purified, as aforesaid, it will serve well as its own emulsifier and as a wetting agent for facilitating the method of making encapsulated liquid crystals which will be described below. Other 30 types of encapsulating medium may be, for example, gelatin9 Carbopole, GantrezTl~he latter two being polyeIectrolytes; and these media may be used alone or in combination with other polymers, such as PVA. The wetting ability of the PVA also assists in allowing freedom of movement of the liquid crystal molecules in the respective capsules 22 facilitating the preferred 5~Z
--~3--parallel ali~nment especially at the interior wall su~face 50 in the field off condition and easy changing to the aligned posi~ion of Fig. 6 when an electric field is applied.
A method for making encapsulated liquid crystals 11 may include S rnixing together the encapsulating medium, the liquid crystal material ~including, if used, the pleochroic dye material), and perhaps a carrier medium~ such as water. Mixing may occur in a variety of mixer devices, such as a blender, a colloid mill, which is most preferred, or the like. What occurs during such mixing is the formation of an emulsion of the ingredients, 10 which subseguently can be dried elimina~ing the carrier medium, such as water, and satisfactorily curing the encapsulating medium, such as the P~tA.
Although the caps~e 22 of each thusly made encapsulated liquic~ crystal 11 may not be a perfect sphere, each caps~e will be substantially spherical in configuration because a sphere is tile lowest free energy state of the 15 individual droplets, globules or capsules of the emulsion, both whcn originally formed and after drying and/or curing has occurred.
It is noted here briefly that the characteristic of the pleochroie dye that it must be oil soluble provides for solution thereof with the liquid crystal material and that it not be subject to absorpffon by the water phase 20 or polymer phase assures that such pleochroic dye will not be absorbed by the PVA or other encapsulating medium or by the carrier medium, such as the water, used during the manufacturing process for the encapsulated liquid crystals 11.

EXAMPL~3 I
A .45% Sudan blaclc B pleochroic dye wns dissolved in a liquid crystal which was composed of aromatic esters. Such combined mnterial is commercially sold under the designation 8250 by American Liquid Xtal Chemical Corp. of Kent, Ohio. Such material was mixed with a solution of 30 7% PVA, which was treated to remove all salts. The solution also was made with ASTM-100 water. The resulting mixture was put into a colloid mill whose conegap setting was 4 mils9 and the material was milled for four minutes to give a rather uniform particle suspension size. The result was a staMe emulsion whose suspended~article si~e was approximately 3 microns.
35 The emulsion was cast on a Mylar film which was precoated with a ~00 ohm ~ per square inch layer of tin oxide electrode purchased from Sierracin. A
. ,, ~,, 6~
-2~

doctor blade was used to cast the emulsion material on the Mylar film on the electrode coated side.
A 7 mil lay-down of the em~dsion material was placed on such electrode and was allowed to dry to a total thickness of 0.8 mil. A second layer of such emulsion subsequently was layed on the first with a res~ting aggregate layer of liquid crystal droplets in a polyvinyl alcohol matrix having a thickness of 1.6 mil. Preferably, though9 the encapsulated liquid crystals may be laid down in a single layer one or plural capsules thiek.
The thusly formed liquid crystal device, including the layer of l\![ylar, electrode, and encapsulated liquid crystals then was tested by applying an electric field, whereupon the material changed from blacl~ to nearly clea~
transparent. The material exhibited a very wide viewing angle, i.e. the angle at which light was transmitted, and the contrast ratio wns 7:1 at 50 volts of applied electric field. The switching speed was nhout two milliseconds on and about 4 millIseconds off.
In accordance with the present invention the guantities of ingredients îor making the encapsulated liquid crystals 11, for example in the manner described above, may be, as follows:
The liquid crystal material - This material may be from about 5% to about 20% and preferably about 10%9 including the pleochroic dye, by volume of the total solution delivered to the mixing apparatus, such as the colloid mill. The actual arnount of liquid crystal material used, though, ordinarily should exceed the volume quantity of encaps~ating medium, e.g. PVA to opt;mize the capsule size.
The PVA - The qURrltity of PV~ in the solution should be on the order of from about 5% to about 20% and preferably9 as was described above, about 7%, this depending, though, on the molecular weight of the PVA. Yor example, if the PVA has too large a molecular weight, the resulting material will be like glass, especially if too much PVA is used in the solution. On the 30 other hand, if the molecular weight is too low, use of too little PVA will result in too low a viscosity of the material, and the resulting emuls;on will not hold up well~ nor will the droplets of the emulsion solidi~y adequately to the desired spherical encapsulated liquid crystals.
Carrier medium - The remainder of the solution would be water or 35 other carrier medium, as described above, with which the emulsion can be ~ ~3~

made and $he material Iaid down appropriately on a substrate, electrode or the like.
It will be appreciated that since the uncured capsules or droplets of encapsulating medium and liquid crystal material are carried in a liquid, 5 various conventional or other techniques may be employed to grade the capsules according to size so that the capsules can be reformed if of an undesirable size by feeding again through the mixing apparatus, for example, and so that the finally used capsules will be of a desired uniformity for the reasons expressed above.
Although the presently preferred invention operates in response to application and removal of an electric field, operation also may be effected by application and removal of a magnetic field.

~ ,.
,~J ~,j

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A liquid crystal apparatus, comprising liquid crystal material having positive dielectric anisotropy, and surface means for affecting the natural structure of said liquid crystal material to induce a distorted alignment thereof in the absence of an electric field to reduce optical transmission independent of polarization, said liquid crystal material being responsive to the presence of an electric field to increase such optical transmission.

2. A liquid crystal apparatus, comprising liquid crystal material having positive dielectric anisotropy, surface means for affecting the natural structure of said liquid crystal material to induce a distorted alignment thereof in the absence of an electric field to reduce optical transmission independent of polarization, said liquid crystal material being responsive to the presence of an electric field to increase such optical transmission, and pleochroic dye contained in said liquid crystal material.

3. An electro-optic display apparatus comprising the apparatus of claim 1 or 2, and further comprising electrical means for applying such electric field.

4. Liquid crystal material and a medium for containing dis-crete quantities of said liquid crystal material, said material having positive dielectric anisotropy, said medium having a dielectric constant that is no less than the lower dielectric constant value of said material, and wherein when exposed to an electric field the electrical impedance of said medium and liquid crystal material exposed to such field along an electrical path through both said medium and liquid crystal material are related such that the electrical impedance of said medium is less than the electrical im-pedance of said liquid crystal material exposed to such field.

5. An electro-optic display apparatus comprising the material of claim 4, and further comprising electrical means for applying such electric field.

6. Liquid crystal material and a medium for containing dis-crete quantities of said liquid crystal material, said material having positive dielectric anisotropy, said medium having a dielectric constant that is no less than the lower dielectric constant value of said material, wherein said medium is an encapsulating medium for said liquid crystal material, and wherein said liquid crystal material and said encapsulating medium have electrical properties such that upon application of an electric field across a capsule along an electrical path through said encapsulating medium and liquid crystal material there is a greater voltage drop across said liquid crystal material than across said encapsulating medium.

7. An electro-optic display apparatus comprising the material and medium of claim 4 or 6, and further comprising electrical means for applying such electric field.

8. A material comprising a containment medium having an index of refraction, and optically anisotropic liquid crystal means contained in said containment medium and having an ordinary index of refraction in the presence of an electric field substantially equal to the index of refraction of said containment medium for maximizing optical transmission in the presence of an electric field.

9. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium, a nematic liquid crystal material, and a pleochroic dye.

10. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has a positive dielectric anisotropy and the dielectric constant of such encapsulating medium is at least as great as the lower dielectric constant of such liquid crystal material.

11. The method of claim 10, said selecting further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has an ordinary index of refraction substan-tially the same as the index of refraction of the encapsulating medium.

12. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has an ordinary index of refraction substantially the same as the index of refraction of the encapsulating medium.

13. The method of claim 12, further comprising selecting such liquid crystal material and encapsulating medium such that the liquid crystal material has an extraordinary index of refraction that is different from the index of refraction of the encapsulating medium.

14. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising causing such liquid crystal material to perform substantially independently of the optical polarization direction of incident light, including confining such liquid crystal material in n capsuleformed by such encapsulating medium that causes distortion of the direction of the liquid crystal molecules when no electric field is applied thereto.

15. The method of claim 9, wherein such encapsulating medium comprises polyvinyl alcohol.

16. The method of claim 10, wherein such encapsulating medium comprises polyvinyl alcohol.

17. The method of claim 12, wherein such encapsulating medium comprises polyvinyl alcohol.

18. The method of claim 14, wherein such encapsulating medium comprises polyvinyl alcohol.

19. The method of claim 9, further comprising mixing a carrier material with such encapsulating medium and liquid crystal material to form an emulsion therewith, such liquid crystal material and encapsulating medium being insoluble in such carrier material.

20. The method of claim 10, further comprising mixing a carrier material with such encapsulating medium and liquid crystal material to form an emulsion therewith, such liquid crystal material and encap-sulating medium being insoluble in such carrier material.

21. The method of claim 12, further comprising mixing a carrier material with such encapsulating medium and liquid crystal material to form an emulsion therewith, such liquid crystal material and encap-sulating medium being insoluble in such carrier material.

22. The method of claim 14, further comprising mixing a carrier material with such encapsulating medium and liquid crystal material to form an emulsion therewith, such liquid crystal material and encap-sulating medium being insoluble in such carrier material.

23. The method of claim 14, the nematic liquid crystal material comprising from about 5 to about 20% by volume, the encapsulating medium comprising from about 5 to about 20% by volume, and the remainder of the material mixed comprising water.

24. The method of claim 19, 20, or 21, further comprising removing such carrier material from such emulsion and curing such encap-sulating medium.

25. The method of claim 22, further comprising removing such carrier material from such emulsion and curing such encapsulating medium.

26. The method of claim 19, 20, or 21, such carrier material comprising water, and further comprising removing such carrier material from such emulsion by drying, and curing such encapsulating medium.

27. The method of claim 22, such carrier material comprising water, and further comprising removing such carrier material from such emulsion by drying, and curing such encapsulating medium.

28. The method of claim 19, said mixing further comprising mixing in a colloid mill to obtain particles suspended in such emulsion of substantially uniform size.

29. The method of claim 20, said mixing further comprising mixing in a colloid mill to obtain particles suspended in such emulsion of substantially uniform size.

30. The method of claim 21, said mixing further comprising mixing in a colloid mill to obtain particles suspended in such emulsion of substantially uniform size.

31. The method of claim 22, said mixing further comprising mixing in a colloid mill to obtain particles suspended in such emulsion of substantially uniform size.

32. The method of claim 19, further comprising forming cap-sules from such emulsion of a size on the order of from about 2 microns to about 25 microns.

33. The method of claim 20, further comprising forming cap-sules from such emulsion of a size on the order of from about 2 microns to about 25 microns.

34. The method of claim 21, further comprising forming cap-sules from such emulsion of a size on the order of from about 2 microns to about 25 microns.

35. The method of claim 22, further comprising forming cap-sules from such emulsion of a size on the order of from about 2 microns to about 25 microns.

36. The method of claim 9, said encapsulating medium forming plural capsules of such nematic liquid crystal material, and further com-prising applying the plural capsules of such encapsulated liquid crystal material to a substrate or to an electrode thereof.

37. The method of claim 10, said encapsulating medium form-ing plural capsules of such nematic liquid crystal material, and further comprising applying the plural capsules of such encapsulated liquid crystal material to a substrate or to an electrode thereof.

38. The method of claim 12, said encapsulating medium form-ing plural capsules of such nematic liquid crystal material, and further comprising applying the plural capsules of such encapsulated liquid crystal material to a substrate or to an electrode thereof.

39. The method of claim 14, said encapsulating medium form-ing plural capsules of such nematic liquid crystal material, an further comprising applying the plural capsules of such encapsulated liquid crystal material to a substrate or to an electrode thereof.

40. The method of claim 36, 37 or 38, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate.

41. The method of claim 39, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate.

42. The method of claim 36, 37 or 38, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate and applying a protective coating over such second mentioned electrode.

43. The method of claim 39, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate and applying a protective coating over such second mentioned electrode.

44. The method of claim 36, 37 or 38, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate, forming at least one of such electrodes in a preestablished pattern and forming both of such electrodes to be substantially optically transparent to electromagnetic radiation in at least a portion of the visible range.

45. The method of claim 39, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate, forming at least one of such electrodes in a preestablished pattern and forming both of such electrodes to be substantially optically transparent to electromagnetic radiation in at least a portion of the visible range.

46. A method of causing nematic liquid crystal material to perform substantially independently of the optical polarization direction of incident light, comprising confining such nematic liquid crystal material in a capsule which causes distortion of the direction of the liquid crystal material.

47. A method of causing liquid crystal material to perform substantially independently of the optical polarization direction of incident light, comprising combining pleochroic dye with the liquid crystal material and confining such dyed liquid crystal material as a suspension in a confining medium.

48. Liquid crystal apparatus, comprising liquid crystal material, and containment means for inducing a distorted alignment of said liquid crystal material which in response to such alignment at least one of scatters and absorbs light and which in response to a prescribed input reduces the amount of such scattering or absorption.

49. The apparatus of claim 48, said liquid crystal material consisting essentially of nematic liquid crystal material.

50. The apparatus of claim 49, said liquid crystal material comprising nematic NM8250 liquid crystal material.

51. The apparatus of claim 48, said liquid crystal material being reversible.

52. The apparatus of claim 48, wherein such containment means forms a capsule containing such liquid crystal material, and wherein the size of such capsules is from about 2 microns to about 25 microns.

53. The apparatus of claim 48, said containment means com-prising resin or polymer.

54. The apparatus of claim 53, said containment means being selected from the group comprising gelatin, Carbopole, Gantrez; and poly-vinyl alcohol.

55. The apparatus of claim 54, said containment means com-prising polyvinyl alcohol.

56. The apparatus of claim 48, wherein said containment means forms a generally spherical capsule for containing such liquid crystal material.

57. The apparatus of claim 56, wherein the dielectric constant of the wall of such capsule results in a capacitance in a radial direction that does not drop the voltage appreciably relative to the voltage drop across the liquid crystal material upon application of an electric field across the capsule.

58. The apparatus of claim 48, said containment means com-prising a containment medium that tends to align at least some of the liquid crystal material generally parallel to a wall of such medium when in the absence of an electric field.

59. The apparatus of claim 48, said containment means com-prising an encapsulating medium that distorts the internal structure of the liquid crystal material in the absence of an electric field.

60. The apparatus of claim 48, further comprising substrate means for supporting the combination of said liquid crystal material and containment means.

61. The apparatus of claim 60, further comprising means for adhering the combination of said liquid crystal material and containment means to said substrate means.

62. The apparatus of claim 60, further comprising electrode means of said substrate means for applying an electric field to said liquid crystal material.

63. The apparatus of claim 62, further comprising means for adhering the combination of said liquid crystal material and containment means to said electrode means.

64. The apparatus of claim 48, said containment means form-ing discrete curved volumes containing discrete quantities of liquid crystal material, and said distorted alignment comprising alignment at least partly paralleling the curvature of such volumes.

65. The apparatus of claim 48, said liquid crystal material having positive dielectric anisotropy.

66. The apparatus of claim 48, said liquid crystal material having optical anisotropy.

67. The apparatus of claim 48, the combination of said liquid crystal material and containment means forming a plurality of encapsulated liquid crystals, and further comprising substrate means for supporting said plurality of encapsulated liquid crystals.

68. The apparatus of claim 48, further comprising electrode means for applying an electrical field to said liquid crystal material as such prescribed input.

69. The apparatus of claim 68, further comprising circuit means for applying electrical energy to said electrode means to enable the same to apply such electric field.

70. The apparatus of claim 48, wherein such prescribed input is an electric field, and further comprising means for applying such electric field to such liquid crystal material.

71. The apparatus of claim 48, further comprising pleochroic dye in combination with said liquid crystal material.

72. The apparatus of claim 48, said liquid crystal material and containment means being cooperative at least one of to absorb and to scatter light independently of the polarization of the incident light.

73. The apparatus of claim 48, said liquid crystal material and said containment means having substantially matched indices of refraction in the presence of such prescribed input.

74. The apparatus of claim 73, said liquid crystal material and said containment means having different indices of refraction in the absence of such prescribed input.

75. The apparatus of claim 48, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that the electrical impedance of the containment means exposed to such field is less than the electrical impedance of the liquid crystal material exposed to such field.

76. The apparatus of claim 75, wherein said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

77. The apparatus of claim 48, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

78. The apparatus of claim 48, said containment means com-prising means for containing discrete quantities of such liquid crystal material causing the structure of such material to fold in on itself creating storage of elastic energy in such structure.

79. An article made in accordance with claim 78

80. Liquid crystal material and a medium for containing dis-crete quantities of said liquid crystal material, said liquid crystal material having positive dielectric anisotropy, and wherein when exposed to an electric field the electrical impedance of said medium and liquid crystal material exposed to such field along an electrical path through both said medium and liquid crystal material are related such that the electrical impedance of said medium is less than the electrical impedance of said liquid crystal material exposed to such field.

81. Liquid crystal material and a medium for containing dis-crete quantities of said liquid crystal material, said liquid crystal material having positive dielectric anisotropy, wherein said medium is an encap-sulating medium for said liquid crystal material, and wherein said liquid crystal material and said encapsulating medium have electrical properties such that upon application of an electric field across a capsule along an electrical path through said encapsulating medium and liquid crystal material there is a greater voltage drop across said liquid crystal material than across said encapsulating medium.

82. Liquid crystal material and a medium for containing dis-crete quantities of such liquid crystal material, said material having positive dielectric anisotropy, and mixed with the liquid crystal material a pleo-chroic dye that is soluble in the liquid crystal material.

83. The combination of claim 82, said pleochroic dye being selected from the group consisting of indophenol blue, Sudan black, Sudan 3 and Sudan 2.

84. Liquid crystal material and a medium for containing dis-crete quantities of such liquid crystal material, said material having positive dielectric anisotropy, said liquid crystal material having an ordinary index of refraction substantially the same as the index of refraction of said medium.

85. The combination of claim 84, said liquid crystal material having an extraordinary index of refraction that is different from the index of refraction of said medium.

86. Liquid crystal material and a medium for containing dis-crete quantities of such liquid crystal material, said material having positive dielectric anisotropy, said liquid crystal material comprising nematic liquid crystal material, and said medium comprising means for aligning the liquid crystal material to achieve a substantially maximum absorption of light energy under a no field condition.

87. The combination of claim 86, further comprising pleochroic dye in said liquid crystal material.

88. Liquid crystal material and a medium for containing dis-crete quantities of said liquid crystal material, said material comprising nematic liquid crystal material having positive dielectric anisotropy, said medium having a dielectric constant that is no less than the lower dielectric constant value of said material.

89. The combination of nematic liquid crystal material con-tained in a generally spherical capsule of encapsulating medium, said encapsulating medium having a wall, and wherein the ordinary index of refraction of said liquid crystal material is approximately the same as the index of refraction of the encapsulating medium.

90. The combination of claim 89, wherein the extraordinary index of refraction of such liquid crystal material is different from the index of refraction of the encapsulating medium.

91. The combination of claim 90, wherein said encapsulating medium aligns the liquid crystal material substantially parallel to at least a portion of the direction of a proximate wall portion of such encapsulating medium, thereby distorting the internal structure of the liquid crystal material.

92. Liquid crystal material and a medium for containing dis-crete quantities of such liquid crystal material, said material comprising an operationally nematic material having positive dielectric anisotropy, and said medium comprising means for tending physically to align said liquid crystal material with respect to said medium, said medium comprising encapsulating means for substantially encapsulating said material in sub-stantially spherical capsules, and said means for tending physically to align comprising wall means of said capsules for tending to align said liquid crystal material generally in parallel with said wall means in the absence of an electric field.

93. An operationally nematic liquid crystal material and a containment means for containing discrete quantities of such liquid crystal material causing said material to fold in on itself creating storage of elastic energy in said material.

94. A display device comprising a substrate and supported thereby encapsulated liquid crystal which is operationally nematic and has a positive dielectric anisotropy.

95. The device of claim 94, said encapsulated liquid crystal comprising plural encapsulated liquid crystals, each capsule including liquid crystal material and an encapsulating medium, electrode means for applying an electric field across at least some of said encapsulated liquid crystals, and means for adhering said encapsulated liquid crystal to at least one of said electrode means and said substrate.

96. A liquid crystal apparatus comprising an operationally nematic liquid crystal material contained in discrete quantities by a matrix formed of an emulsion of such liquid crystal material and a further medium.

97. A display device apparatus formed of the liquid crystal apparatus of claim 96.

98. The article of claim 79, said liquid crystal material having positive dielectric anisotropy.

99. The combination of claim 89, said liquid crystal material having positive dielectric anisotropy.

100. The combination of claim 93, said liquid crystal material having positive dielectric anisotropy.

101. The apparatus of claim 96, said liquid crystal material having positive dielectric anisotropy.

102. The apparatus of claim 97, said liquid crystal material having positive dielectric anisotropy.

103. The article of claim 79, said liquid crystal material con-sisting essentially of nematic liquid crystal material.

104. The combination of claim 80, said liquid crystal material consisting essentially of nematic liquid crystal material.

105. The combination of claim 81, said liquid crystal material consisting essentially of nematic liquid crystal material.

106. The combination of claim 82, said liquid crystal material consisting essentially of nematic liquid crystal material.

107. The combination of claim 84, said liquid crystal material consisting essentially of nematic liquid crystal material.

108. The combination of claim 88, said liquid crystal material consisting essentially of nematic liquid crystal material.

109. The article of claim 79, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

110. The combination of claim 80, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

111. The combination of claim 81, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

112. The combination of claim 82, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

113. The combination of claim 84, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

114. The combination of claim 88, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

115. The combination of claim 89, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

116. The apparatus of claim 48, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

117. The article of claim 79, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

118. The combination of claim 80, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

119. The combination of claim 81, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

120. The combination of claim 82, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

121. The combination of claim 84, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

122. The combination of claim 88, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

123. The combination of claim 89, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

124. The article of claim 79, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

125. The combination of claim 80, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

126. The combination of claim 81, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

127. The combination of claim 82, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

128. The combination of claim 84, further comprising means for applying an electric field to said liquid crystal material to afffect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

129. The combination of claim 88, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

130. The combination of claim 89, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby, and said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

131. The article of claim 124, said means for applying further comprising circuit means for providing electrical energy to said electrode means to create such electric field.

132. Liquid crystal apparatus, comprising liquid crystal material, and containment means for inducing a distorted alignment of said liquid crystal material which in response to such alignment absorbs light and which in response to a prescribed input reduces the amount of such absorption.

133. The apparatus of claim 132, said liquid crystal material having positive dielectric anisotropy.

134. The apparatus of claim 132, further comprising substrate means for supporting the combination of said liquid crystal material and containment means.

135. The apparatus of claim 134, further comprising means for adhering the combination of said liquid crystal material and containment means to said substrate means

136. The apparatus of claim 134, further comprising electrode means on said substrate means for applying an electric field to said liquid crystal material.

137. The apparatus of claim 136, further comprising means for adhering the combination of said liquid crystal material and containment means to said electrode means.

138. The apparatus of claim 132, said containment means form-ing discrete curved volumes containing discrete quantities of liquid crystal material, and said distorted alignment comprising alignment at least partly paralleling the curvature of such volumes.

139. The apparatus of claim 132, said liquid crystal material having positive dielectric anisotropy.

140. The apparatus of claim 132, said liquid crystal material having optical anisotropy.

141. The apparatus of claim 132, the combination of said liquid crystal material and containment means forming a plurality of encapsulated liquid crystals, and further comprising substrate means for supporting said plurality of encapsulated liquid crystals.

142. The apparatus of claim 132, further comprising electrode means for applying an electrical field to said liquid crystal material is such prescribed input.

143. The apparatus of claim 142, further comprising circuit means for applying electrical energy to said electrode means to enable the same to apply such electric field.

144. The apparatus of claim 132, wherein such prescribed input is an electric field, and further comprising means for applying such electric field to such liquid crystal material.

145. The apparatus of claim 132, further comprising pleochroic dye in combination with said liquid crystal material.

146. The apparatus of claim 132, said liquid crystal material and containment means being cooperative to absorb light independently of the polarization of the light incident thereon.

147. The apparatus of claim 132, said liquid crystal material and said containment means having substantially matched indices of refraction in the presence of such prescribed input.

148. The apparatus of claim 147, said liquid crystal material and said containment means having different indices of refraction in the absence of such prescribed input.

149. The apparatus of claim 132, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that the electrical impedance of the containment means exposed to such field is less than the electrical impedance of the liquid crystal material exposed to such field.

150. The apparatus of claim 132, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

151. The apparatus of claim 132, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

152. A liquid crystal device comprising liquid crystal material and containment means) said containment means forming a plurality of capsules each having a curved interior wall surface, said capsules containing said liquid crystal material; which liquid crystal material in the absence of an applied electric field at least one of scatters or absorbs incident light independently of the polarization of said light, and which device in the presence of an applied electric field displays decreased scattering or absorption at least in the direction of the applied electric field.

153. The device of claim 152, wherein the liquid crystal material consists essentially of nematic liquid crystal material having a positive dielectric anisotropy.

154. The device of claim 152, wherein the liquid crystal material contains a pleochroic dye.

155. The device of claim 152, wherein the liquid crystal material is optically anisotropic and the ordinary refractive index of the liquid crystal is substantially the same as the refractive index of the containment means.

156. The device of claim 152, which further comprises elec-trodes for applying such electric field.

157. The device of claim 156, which further comprises a sub-strate means for supporting said electrodes, liquid crystal material and containment means.

158. The device of claim 156, which further comprises circuit means for energizing said electrodes to apply such electric field.

159. Liquid crystal apparatus, comprising nematic liquid crystal material having positive dielectric anisotropy, and a plurality of contain-ment means with curved surfaces for inducing a distorted alignment of said liquid crystal material which in response to such distortion at least one of scatters and absorbs light when pleochroic dye is present in the liquid crystal material and which in response to a prescribed input reduces the amount of such scattering or absorption.

160. The combination of claim 125, 126 or 127, said means for applying further comprising circuit means for providing electrical energy to said electrode means to create such electric field.

161. The combination of claim 128, 129 or 130, said means for applying further comprising circuit means for providing electrical energy to said electrode means to create such electric field.