US2458104A - Fluorescent materials - Google Patents

Description

Patented Jan. 4, 1949 FLUORESCENT MATERIALS Ernest Schweizer, East Orange, N. J., assignor to Celanese Corporation of America, a corporation of Delaware N Drawing. Application March 1, 1945, Serial No. 580,488

' Claim. (Cl. 154-40) This invention relates to colored objects which are fluorescent under the excitation of ultra-violet light and relates more particularly to fluorescent, colored objects whose color under light in the visible portion of the spectrum is substantially identical to the fluorescent color exhibited under the action of ultra-violet light.

An object of thisinvention is the provision of improved colored objects capable of fluorescence under the excitation of ultra-violet light in a color substantially identical with that of the object under visible light.

Another object of this invention is the production of colored objects which are readily identifiable by their color whether illuminated by visible light or invisible ultra-violet light.

Other objects of this invention will appear from the following detailed description.

Objects such as control knobs, indicators, signs, safety markers, valves, fire-fighting equipment and other accessories in tanks, aircraft, motorized equipment and industrial plants are frequently colored in accordance with a predetermined scheme so that they may be readily identified or recognized at all times by color alone.

Where complete darkness is required in certain particular circumstances or operations, thus making the reading of normal printed material or recognition of a particular color impossible, an identifying color visible in total darkness becomes essential. To provide a color visible in total darkness, it has been customary to incorporate fluorescent materials in the objects to be rendered visible and to cause said materials to fluoresce by illuminating the latter with ultra-violet light. The fluorescent coloreifect obtained is satisface tory where the objects or signs are always under the influence of ultra-violet light since the color observed does not change. Where, however, the control knobs, indicators, signs or safety markers must also be provided with a recognition color which must be visible under normal daylight as well as under ultra-violet light, substantial difficulties are encountered. The fluorescent color of a particular material and its normal color under visible light are never alike. Such a situation where two distinct colors must serve to identify a particular object practically defeats the main purpose of employing recognition colors. The combination of a fluorescent dye or pigment with the usual type of dye or pigment in asingle formulation to obtain a color which is practically the same under daylight and ultra-violet light is unsatisfactory. A bright and easily recognized daylight color requires a high concentration of pigment. The addition of a dye or pigment normally fluorescent in the same color to such a composition is practically ineifective since the heavy concentration of ordinary pigment screens the fluorescent material and only the outermost layer of fluorescent dye or pigment will be effective when the material is subjected to the influence of ultra-violet light. The illumination by ultra-violet light of such a relatively small amount of fluorescent material does not give the desired bright and easily recognized color.

I have now found that colored materials exhibiting the'identical color under both daylight and the excitation of ultra-violet light may be obtained by incorporating a suitable dye or pigment in any desired vehicle whereby an opaque surface of the desired daylight color is obtained and then superimposing thereon a layer of a colored transparent material containing a fluorescent dye or pigment fluorescent in the background or base color. The fluorescent dye or pigment incorporated in and coloring the transparent layer is employed in suflicient amount to yield the desired fluorescent effect, the additive eflect of the colored transparent layer and the colored opaque surface below being such as to yield the identical color underboth daylight and ultra-violet light. With a suitable choice of dye or pigment to give the desired opaque colored surface in combination with a suitable fluorescent dye or pigment in the transparent layer many satisfactory colors may be obtained, which colors will be identical whether viewed under daylight or illuminated by invisible, ultra-violet light.

The colored opaque surface may be obtained in any convenient manner and may be formed of any suitable material. It may be wood, cement, ceramic, metal, and the like, covered with a'suitable opaque pigmented coating which may be obtained, for example, by applying a colored paint or enamel to the surface. The opaque colored surface may also comprise an opaque colored glass or other opaque colored refractory or ceramic material. Suitably pigmented thermosetting or thermoplastic materials also may be employed for forming the colored opaque surface.

As examples of colored opaque base materials there may be mentioned pigmented cellulose esters, such as, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose acetate-butyrate and cellulose nitrate as well as colored cellulose ethers such as ethyl cellulose or benzyl cellulose. Pigmented phenol-formaldehyde or urea-formaldehyde condensation condensation products, pigmented alkyd resins, such as glycerol-phthalic anhydride condensation products, polymerized vinyl resins having a basis of a polymerized vinyl ester such as polyvinyl acetate, copolymers of vinyl chloride and vinyl acetate, vinylidene chloride polymers, polyvinyl alcohol, polystyrene, polymerized methacrylic acid esters, suchas polymerized methyl methacrylate and other polymeric resin forming compounds which may be pigmented in the desired opaque color and shaped to any desired form are also suitable.

The coloring matters employed may be organic or inorganic pigments ordyestuffs having the desired color characteristics. inorganic materials such as ochre, sienna, chrome yellow, tin bronze, etc., may be employed. For a red color, Venetian red, red lead, vermillion, etc., may be employed. For a blue color. ultramarine, Prussian blue, milori blue, etc., may be For a yellow color.

products, melamineformaldehyde I on suitable wheels or bands.

4 lulose acetate or other thermoplastic derivative of cellulose since the desirable properties of the cellulose derivative material enable it to be applied to the base material in practically any manner, as heretofore described, depending upon the form and purpose or the object which is to be provided with a recognition color visible under normal daylight and fluorescent in the same color under ultra-violet light.

Where the colored opaque basematerial and the colored transparentfluorescent outer layer are employed in sheet form, any suitable method of preparing the sheet material may be utilized. The sheets may be formed by mixing the base material and the pigments or fluorescent materials at ordinary or elevated temperature in the desired proportions with or without the addition of volatile solvents, and then flowing or casting the plastic mixture obtained into films Thicker sheets may be cut from blocks or extruded in the desired width or thickness through a suitable slit.

used. For' green, Guignets green, verdigris,

chrome green may be employed. For brown, raw umber, burnt umber or Vandyke brown may be used. To obtain any othercolors, the pigments may be mixed as is will understood in the art. Increased opacity, if desired, may be obtained by incorporating a suitable white pigment in the colored opaque base material. Examples of white inorganic pigments are tin oxide, tin phosphate, antimony oxide, titanium dioxide, barium sulfate, lead sulfate, calcium sulfate, zinc oxide, zinc carbonate, aluminum oxide, silicon dioxide, barium borate, calcium borate, and silicates such as china clay or other clays, talc or mica.

The layer of transparent material containing the desired fluorescent dye and superimposed on the opaque colored base material may have a basis of any suitable transparent material such as glass. a transparent cellulose derivative, clear, cast phenol-formaldehyde resins, or of a thermoplastic polymeric substance as mentioned-heretofore, namely polystyrene, polymerized methyl methacrylate, polyvinyl chloride, polyvinyl acetate, or co-polymerized vinyl chloride and vinyl acetate.

Wliere laminating operations under heat and pressure are employed for joining the transparent fluorescent outer layer to the colored opaque base, the outer layer is preferably of a thermoplastic material. The transparent outer layer may also be joined to the opaque under layer by a suitable colorless-adhesive or the transparent outer layer may be applied by dissolving the desired transparent film-forming base in a volatile solvent, adding the fluorescent pigment or dyestufi thereto and applying the dope or lacquer obtained to the base in the form of a coating of the desired thickness as by brushing, spraying or the like. The transparent outer layer may also be applied by injection or compression molding operations using the opaque colored base as a core or insert.

Especially valuable results are obtained employing a transparent outer layer formed of cel- As stated, the desired compositions may also be employed in the form of a molding powder of suitable composition which may be prepared in v accordance with methods well known in the art.

. base material is employed, plasticizers such as,

for example, dimethyl phthalate, tricresyl phosphate, diethyl phthalate, triacetin, tripropionin, triphenyl phosphate, dibutyl phthalate, dimethoxy ethyl phthalate, dibutyl tartrate, ethyl tolu e'ne sulfonamide, camphor and methyl fphthallyl ethyl glycollate are, suitable. The plasticizer may be present in amounts up to 60% or more on the weight of cellulose derivative in the composition.

In order further to illustrate my invention but without being limited thereto the following examples are given:

. Example I To obtain a composite sheet material exhibiting a. brilliant green color in daylight as well as a brilliant green fluorescence under ultra-violet light, an opaque sheet material 0.125 inch in thickness is prepared from the following composition: I

Parts by weight Cellulose acetate (53% acetyl, calculated as acetic acid Dimethyl phthalate ,30

C. P. Glen Green XXLT (color index r v No. 1298) V i 1.23

This sheet is combined with a transparent fluorescent cellulose acetate sheet 0.02 inch thick of the following composition:

Parts by weight Cellulose acetate (53% acetyl) 100f Dimethyl phthalate 30 Brilliant sulfo flavine FFA' (General Dyestuif N. Y.) 0.152

Rhodamine B Extra (0. I. No. 749) daylight color and a bright, glowing fluorescent color under ultra-violet light which colors are substantially identical whether viewed under daylight or ultra-violet light.

Example II A brilliantly colored orange sheet material may be obtained by combining an opaque base sheet of the following composition:

Methyl phthallyl ethyl glycollate 30 The orange color of the composite material exhibited under ultra-violet light is substantially I identical to that under daylight. r

Example III A brilliantly colored yellow sheet material having a bright yellow color under daylight and a bright yellow glow under ultra-violet light is obtained employing an opaque base sheet of the following composition:

Cellulose nitrate 10o Camphor g Chrome yellow (C. I. 1270) 1.85

and combining itwith a transparent sheet .020 inch in thickness comprising Parts by weight Parts by weight Parts by weight Cellulose acetate (53% acety1) 100 AlizarineLake 63 (C. I. No. 1027) 0.021 Titanium dioxide (0. I. No. 1264) 0.301 Ultramarine blue 3P (0.1. No. 1290) 0.857 Triacetin 20 v witha transparent fluorescent sheet 0.020 inches 1 in thickness of the following composition:

' Parts by weight Cellulose acetate (56% acetyl) 10o Calco Condensation Fluorescent Blue I..- Tripropionin.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

In a process for the production of orange colored materials capable of fiuorescing brightly under the influence of ultra-violet light in sub-' stantially the same orange color, the step which comprises laminating a sheet of a colored, transparent cellulose acetate material having diethyl- M-amino-phenolphthalein incorporated therein to. a non-fluorescent, opaque, colored cellulose acetate base material pigmented with lead chromate, the resulting laminated material exhibiting an orange color substantially identical under both visible light and ultra-violet-light.

ERNEST SCHWEIZER.

REFERENCES CITED The following references are of record in the file of this patent:

Ethyl cellulose Diethyl phthalate 30 Calcozlne Red 6 G Extra (C. I. No. 752) 0.044

' Example Ill A bright blue material having a clear bright blue color under both visible light and ultra- I violet light is produced by combining a colored opaque base sheet o! the tollowing composition:

UNITED STATES PATENTS Number Name Date R 12,812 Hammer .June 16, 1908 1,244,058 Langer Oct. 23, 1917 1,813,491 Gillard July 7, 1931 1,967,261 Ripper July 24, 1934 2,246,095 Graves June 17, 1941 2,319,222

Ferris May 18, 1943