US3454458A - Dry transfer sheet for transferring images having varied surface characteristics - Google Patents

Description

vDRY TRANSFER SHEETFOR TRANSFERRING IMAGES I July 8,1969 E. BOIRREGARIDIY 1 3,454,458

HAVING VARIED SURFACE CHARACTERISTICS F118;} May 20. 1966 III/JIIIII/I/{ Z/i!!!((IlIIIII/IIIIIA I l INVENTOR.

'ERNST BQR REGARD United States Patent 3,454,458 DRY TRANSFER SHEET FOR TRANSFER- RING IMAGES HAVING VARIED SURFACE CHARACTERISTICS Ernst Borregard, 27 Sylvan Point, West Islip, N.Y. 11795 Filed May 20, 1966, Ser. No. 551,617 Int. Cl. B32b 7/06; C09j 3/04 US. Cl. 161167 18 Claims ABSTRACT OF THE DISCLOSURE This invention relates to dry transfer sheets and to methods for their use.

Techniques for transferring images from one surface to another have long been known and have assumed a variety of forms. One such technique involves the use of decalcomania transfers. Such transfers usually comprise a backing of an opaque Water-absorbent paper having a coating of a water-soluble adhesive. The adhesive coating ordinarily contains a superposed coating of clear lacquer upon which an image, ordinarily of opaque lacquer, is printed. The image in such decalcomania transfers is normally transferred to a receiving surface by dampening the transfer, permitting water to soak through to the water-absorbent paper backing to soften the adhesive layer, following which the clear lacquer film and superposed films are bodily slid from the backing sheet onto the receiving surface.

The use of such decalcomania transfers and the like is obviously quite limited in that it is ordinarily difiicult to properly position the decalcomania on the receiving surface and the entire practice is generally unduly cumbersome.

In applicants copending application Ser. No. 300,743, filed Aug. 8, 1963, a novel dry transfer sheet is disclosed which is capable of producing an extremely high quality image and which eliminates many of the problems associated not only with decalcomania transfers as described above but with other dry transfer sheets which had previously been developed in the field. This dry transfer sheet is essentially comprised of a light transmissive supporting sheet, a release film on one side of the sheet in the form of a plurality of discrete portions spaced from one another and a film of pressure-sensitive adhesive material superposed on the release film (with the option of interposing a pigmented film between such two films), with the spaces between the discrete film portions free of adhesive material. The nature of the materials used to form this dry transfer sheet of said copending application is such that .the pressure-sensitive adhesive material is adherable to a receiving surface under ambient temperature conditions only upon rubbing of the side of the sheet opposite the adhesive and not merely by placing the dry transfer sheet in contact with the receiving surface without such rubbing. By virtue of this arrangement, the dry transfer sheet may be placed in contact with and moved across the receiving surface without adhesion of the ad- Patented July 8, 1969 "ice hesive material to said surface so as to permit the accurate location of selected images to be transferred to such surface.

The conventional and preferred manner of preparing the dry transfer sheets of said copending application involves the use of three superposed films of material printed in registry on the light transmissive supporting surface, such films including a release film, a pigmented film and a pressure-sensitive adhesive film. The images normally transferred from such dry transfer sheets by the rubbing operation described above are ordinarily glossy in their appearance.

In accordance with the present invention, a novel dry transfer sheet has been developed which, while retaining many of the significant advantages of the dry transfer sheet of applicants copending application, provides significant additional advantages in that it makes possible the transfer of letters whose surface can be adjusted from one which is extremely glossy to one which is extremely dull or matte in texture. In addition, the preferred embodiment of the dry transfer sheet of the present application involves only two superposed films atop a supporting sheet, thus facilitating the production of such sheets and significantly reducing their cost.

It is accordingly an important object of the present invention to provide a novel dry transfer sheet which makes possible the transfer of images having varied surface characteristics.

It is another important object of the present invention to provide a dry transfer sheet employing a pressuresensitive adhesive material containing a solvent which is capable of penetrating through a release film interposed between it and a supporting sheet without dissolving the release film and which solvent is capable of chemically attacking the surface of the supporting sheet, as a result of which the texture of the surface of the image to be transferred is modified.

It is another significant object of the present invention to provide a novel dry transfer sheet comprised of a release film in the form of discrete film portions on one side of a supporting sheet, with said discrete film portions and the spaces between them covered with a pressure-sensitive adhesive material, said release film containing a plasticized material capable of migrating up into the adhesive film in contact with the solvent of the latter, whereby selected portions of said adhesive film located immediately above said discrete release film portions are rendered more tacky than the remaining portions of said adhesive film.

It is still a further important object of the present invention to provide a novel dry transfer sheet in which discrete release film portions and pressure-sensitive adhesive film portions superposed thereon are coated on one side of a light transmissive sheet, said release film containing mica for the purpose of modifying the surface characteristics of images transferred from said dry transfer sheet.

Further objects and advantages of the present invention will become more apparent upon reference to the ensuing description and claims, and drawings, wherein:

FIGURE 1 represents a fragmentary front elevation of the novel dry transfer sheet of the present invention looking at such sheet from the side opposite that containing the images to be transferred.

FIGURE 2 illustrates a vertical section through lines 22 of FIGURE I greatly enlarged to show the discrete film portions forming the images on the dry transfer sheet; and

FIGURE 3 is an enlarged vertical section similar to that of FIGURE 2 but representing a modified form of the dry transfer sheet of the present invention.

The present invention may best be described by reference to the single sheet of drawings appended hereto. FIG- URE 1 illustrates a typical form of a dry transfer sheet made in accordance with the present invention viewed from the side of thesheet opposite that on which the image to be transferred is positioned. As illustrated therein, a plurality of discrete images 12 are positioned in spaced relation to one another on a backing or supporting sheet 10. As illustrated in FIGURE 1, these discrete images take the form of upper and lower case letters of the alphabet, Arabic numerals and various symbols of punctuation and the like, though it will be obvious that the present invention would apply to any symbols taking the form of Separate discrete images. When viewing the discrete images from the side of the transfer sheet on which they are positioned (as in FIGURE 1), one sees such images as they are intended to appear on the final receiving surfaces after the transfer process. As will be readily apparent, such images appear in reverse form when looking at the sheet from the reverse side on which said images are positioned, as is the case with the type used in a conventional printing process.

Supporting sheet may be fabricated of any light transmissive material which is substantially dimensionally stable and which is capable of supporting the discrete images 12. Included 'in such materials will, of course, be those which are clear and transparent as well as those which are translucent. The preferred material for use as backing or supporting sheet is a biaxially oriented polystyrene material such as that sold by the Monsanto Chemical Company under the trademark Polyflex. While polystyrene sheets are highly preferred over all other materials of which applicant is aware, for reasons to be pointed out below, other light transmissive materials may be employed for use as supporting sheet 10, including but not restricted to polyethylene and various rigid and semirigid vinyl sheets (such, for example, as those made out of polyvinyl chloride materials).

As shown in the preferred embodiment of FIGURE 2, discrete images 12 each comprise two films, 14 and 16, which as shown are superposed and in registry with one another. Film 14 is comprised of a plurality of discrete film portions of a release agent which is preferably ap plied to one side of supporting sheet 10 by means of a silk screen or other printing process. Release film 14 is pigmented in the preferred embodiment of the present invention and, as will be pointed out further below, preferably contains mica. Superposed on discrete release film portions 14 and in registry therewith is a film of pressuresensitive adhesive material 16. As was the case in connection with the dry transfer sheet of applicants copending application, several conditions should exist so that the discrete images 12 may be transferred to a receiving surface by rubbing the side of supporting sheet 10 opposite that on which images 12 are positioned. In the first place, the pressure-sensitive adhesive material should be of such a nature that it is adherable to the receiving surface under ambient temperature conditions upon the rubbing of the side of the sheet opposite that on which the image is positioned. On the other hand, since it is necessary with respect to a sheet containing a plurality of images 12 to be able to place the sheet against the receiving surface and move it across and in contact with such surface to permit the accurate location of selected ones of the discrete images in the desired position on the receiving surface without adhesion of the adhesive material to said surface, the adhesive material should be adherable to such receiving surface only by such rubbing (and not merely by being placed in contact with said other surface without such rubbing) to avoid the transfer of other images not desired to be transferred. In fact, so as to avoid undesired transfer of such images, the pressure necessary to transfer the images to the receiving surfaces should be an extremely highly localized pressure such as that obtained by rubbing the supporting sheet with a stylus or other hard object, as distinguished from the type of pressure equivalent to light finger pressure.

Still further, the materials of films 14 and 16 should be so selected that the adhesive affinity of the film 14 for the adhesive material 16 is greater than the adhesive affinity of the film 14 for the supporting sheet 10 and, furthermore, that the adhesive affinity of the adhesive material 16 for the receiving surface when rubbed as indicated above is greater than the adhesive affinity of the film 14 for the supporting sheet 10.

The foregoing properties may be attained by preparing a dry transfer sheet in the manner described in said copending application- The images or symbols resulting from such sheets, however, will normally be glossy in their appearance. In accordance with the present invention, the texture of the surface of such images may be significantly modified by incorporating in the pressure-sensitive adhesive material 16 a solvent which is capable of penetrating through the release film 14 without dissolving it and which is also capable of chemically attacking the surface of supporting sheet 10. By means of such a solvent, the solvent will actually eat away a portion of the surface of the supporting sheet 10 which is in contact with the release film 14 with the result being that such chemically attacked surface portion will be roughened. Because of this roughening, when the proper pressure is applied to the back of the supporting sheet 10 as previously described, the surface of the release film 14 which had been in contact with the supporting sheet 10 will be correspondingly roughened and the result will be that the transferred image 12 will have a matte appearance.

In addition to the foregoing, the material used to form the release film 14 should be substantially inert with respect to the material of supporting sheet 10 and should release therefrom in the manner described previously.

A material which has been found to :be extremely effec tive for use as the release film 14 is a nitrocellulose ink in a butyl Cellosolve solvent, with ethylcellulose added to impart the desired viscosity to the material.

Nitrocellulose inks are particularly advantageous for use in the release fil-m 14 because of their high solubility in butyl Cellosolve, the latter being a particularly desirable solvent since it is inert to the polystyrene which is the preferred supporting sheet 10. This combination of materials also releases readily from polystyrene supports. Other inks, such as an ethyl cellulose lacquer dissolved in butyl Cellosolve, can be employed but is not as effective as the nitrocellulose-butyl Cellosolve combination since it tends to adhere to supports (such as those made of polystyrene) more than is desirable. Nitrocellulose is also particularly preferred due to its inertness to styrene and its excellent film-forming properties. In addition, while other solvents (such as others of the Cellosolves) may be employed in release film 14, the butyl Cellosolve is highly preferred.

A preferred pigment for incorporation in the release film 14 is an alkyd dispersion which is appropriately mixed with the nitrocellulose in the butyl Cellosolve solvent. A nitrocellulose dispersion may also be used for the pigment though it is not as convenient in use as the alkyd dispersion previously mentioned.

Because ethylcellulose is soluble in the pressure-sensitive adhesive materials utilized in connection with the present invention, whereas nitrocellulose is not, the use of ethylcellulose as a portion of the release film 14 serves another important purpose in that it serves to enhance the penetration of the solvent used to formulate the pressuresensitive adhesive material 16 into the release film 14, which penetration is necessary for the proper functioning of the dry transfer sheet of the present invention.

To obtain particularly desirable results from the dry transfer sheets of the present invention, mica (preferably -20 microns in diameter) is incorporated in the release film 14. The mica gives body to the material used to form the release film so that it will print sharply and cleanly. A more important function served by the mica is that it definitely has an effect on the texture of the images transferred. More specifically, images transferred from a dry transfer sheet without mica incorporated in the release film 14 have a texture which is less matte than those with mica included in such film.

It is also desirable to include in the release film 14 a plasticizer for the purpose of strengthening the film so that the images will not break during transfer. An extremely effective plasticizer is a polymerized castor oil sold under the designation No. 40 Oil by the Baker Castor Oil Company.

As previously indicated, the pressure-sensitive adhesive material 16 should contain a solvent which is capable of penetrating through the release film 14 without dissolving it and which is also capable of chemically attacking the surface of the supporting sheet 10. Solvents satisfying this requirement are aromatic hydrocarbons, preferably of the slow-drying variety.

The specific type of aromatic hydrocarbon solvent which will be selected will vary within reasonable limits to suit the specific purposes desired. If silk screening techniques are used to print images 12 on the supporting sheet 1 0, the drying characteristics of the solvent will be extremely important. If the material dies too quickly, this will make it extremely diflicult to print with the material; on the other hand, it is important that the pressure-sensitive adhesive material 16 dries within a reasonable length of time so that the dry transfersheet may be properly handled. While the invention is not so limited, extremely satisfactory results are obtained with these considerations in mind utilizing aromatic hydrocarbon solvents having a kauri-butanol value in the range of at least about 80 and preferably about 80-90. An aromatic hydrocarbon solvent having a kauri-butanol value of approximately 87 which is extremely advantageous in connection with the present invention is a petroleum solvent sold by American Mineral Spirits Company under the designation Amsco G.

A particularly desirable material to provide the adhesive qualities of pressure-sensitive material 16 is polyvinylisobutylether, an example of this being the material sold under the designation 0-125 by B.A.S.F. Color & Chemical Co. of Charlotte, NC. As previously indicated, while various support sheets may be employed to prepare the dry transfer sheets of the present invention, polystyrene is preferred for a variety of reasons. In the first place, it is avail-able in clear, transparent and rigid sheets, facilitating the positioning of the sheet on the receiving surface. Secondly, it is highly glossy, facilitating the removal of the images 12 from its surface. Furthermore, it is extremely sensitive to petroleum solvents, making possible the variation in the degree of glossiness of the images to be transferred by means of the aromatic hydrocarbon solvent.

The particular texture of the images transferred from the dry transfer sheets of the present invention may be varied within wide limits through manipulation of the ingredients used to form the films 14 and 16. Merely by way of example, the greater the quantity of mica present in the film 14, the more dull or matte the resulting image surface will be; reduction in the quantity of mica present in such film will tend to detract from the matteness of such surface. A practical limitation on the upper quantity of mica which is used in the film 14 is created by the fact that too great a quantity of mica will cause sufficient enhancement of the release properties of such film that the images 12 may tend to fall off the supporting sheet 10 prematurely.

Similarly, the matte texture of the images 12 can be significantly influenced by the nature of the solvent employed in the adhesive film 16. A high kauri-butanol value of such solvent will tend to increase the penetration capacity of the solvent and, as a result, to increase the attack by such solvent on the surface of supporting sheet 10. The result will be the enhancement of the matte nature of the transferred images. Correspondingly, a decrease in the kauri-butanol value of the aromatic hydrocarbon solvent will tend to increase the glossiness of such images.

The proper quantities of the ingredients to be utilized in the formulations employed to prepare the dry transfer sheets of the present invention can be readily determined in light of the foregoing considerations by those skilled in the art to achieve the desired purpose. Generally speaking, the release film 14 will be prepared by adding to a preliminarily formed plasticized nitrocellulose formulation about 10 25 by weight (of such formulation) of a pigment dispersion and from 0-15% by weight (and preferably 0-12% by weight) of mica. [The lower limit of 0% mica is mentioned since no mica would be used for transparent letters; the presence of mica in such case would negatively afiect the transparency of the image.]

A typical formulation for use in preparing a black pigmented release film 14 involves the preparation of a base formulation as follows:

Ingredient: Parts by weight Nitrocellulose lacquer /2-second nitrocellulose cotton 16 Butyl Cellosolve 76 Raw castor oil 4 Dibutylphthalate plasticizer 4 Ethylcellulose powder (sold by the Hercules Powder Company under the designation N-7) 10 Castor oil (sold by the Baker Castor Oil Company under the designation No. 40) 10 To 20 parts by weight of the basic formulation prepared as described above, the following should be added:

diameter) 4 Castor oil (No. 40) 1 Butyl Cellosolve 4 This material is applied to a supporting sheet such as one made of polystyrene as previously indicated by means of a silk screen technique to form discrete image portions of the black pigmented release film. After such film has dried, pressure-sensitive adhesive material is printed in registry with such discrete film portions also by means of a silk screen technique.

An appropriate pressure-sensitive adhesive formulation may be prepared in the following manner. The first step involves the preparation of a basic formulation as follows:

Ingredient: Parts by weight Aromatic hydrocarbon solvent (a petroleum solvent sold by American Mineral Spirits Company under the designation Amsco G having a kauri-butanol value of 87) Polyvinylisobutylether (sold by the B.A.S.F.

Color & Chemical Co. of Charlotte, N.C., under the designation (J-) Tackifier (a polyvinylisobutylether in a toluol solvent containing approximately 50% solids and sold by the B.A.S.F. Color & Chemical Co. of Charlotte, N.C., under the designation J-60) 2 Tackifier (a solid polyvinylisobutylether sold by B.A.S.F. Color & Chemical Co. of Charlotte, N.C., under the designation J-30) To 17 /2 parts by weight of the basic formulation prepared as described above are added the following:

Ingredient: Parts by weight Zinc soap 8% Amsco G 21% Methyl alcohol 1 Zinc soap powder 2 /2 Chlorinated phenyl plasticizer (sold by Monsanto Chemical Company under the designation Arochlor-No. 1254) 1% In the embodiment described above (that of FIGURE 2) the pressure-sensitive adhesive film 16 was printed in registry wtih release film 14 so that the spaces between the resulting images 12 were left free of pressure-sensitive adhesive material. This embodiment is preferred since it makes possible the transfer of images to a receiving surface without the presence of the bothersome penumbra which accompanied prior art transfer techniques and sheets and which are generally undesirable. Notwithstanding this fact, the significant advantages of the present invention are also obtainable with dry transfer sheets prepared as described in connection with FIGURE 3 hereof in which the adhesive film 16 is coated throughout the extent of supporting sheet so that the spaces between discrete film portions 14 are filled with adhesive material. This embodiment may be prepared by using the formulation and materials previously described.

In connection with the dry transfer sheets of the present invention (and particularly with respect to the embodiment of FIGURE 3), it should be particularly noted that the plasticizer which is used in release film 14 tends to migrate up into the pressure-sensitive adhesive film 16 immediately above discrete film portions 14 rendering the corresponding overlying portions of the pressure-sensitive adhesive material more tacky than the remaining adhesive portions between discrete film portions 14. The result is that this facilitates the removal of the desired images from the dry transfer sheet as a whole and significantly improves the effectiveness of the sheet.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. A dry transfer sheet comprising:

(a) a light transmissive supporting sheet;

(b) a release film on one side of said sheet, said film being in the form of a plurality of discrete portions spaced apart from one another;

(c) and a film of pressure-sensitive adhesive material superposed on said release film;

(d) said pressure-sensitive adhesive material containing a solvent which is capable of penetrating through said release film without dissolving it and which is also capable of chemically attacking the surface of said supporting sheet.

2. A dry transfer sheet as defined in claim 1 wherein said release film is pigmented.

3. A dry transfer sheet as defined in claim 2 wherein said adhesive material is adherable to another surface under ambient conditions only upon rubbing the side of said supporting sheet other than said one side at the location opposite said adhesive material and not merely by being placed in contact with said other surface without such rubbing, whereby said dry transfer sheet can be placed against said other surface and moved across and into contact with said surface and adjusted to accurately locate a selected one of said discrete portions of release film in any selected position on said surface without adhesion of the adhesive material to said surface.

4. A dry transfer sheet as defined in claim 3 wherein the adhesive affinity of said discrete release film portions for said adhesive material is greater than the adhesive afiinity of said discrete release film portions for said supporting sheet; the adhesive afifinity of said adhesive material for said other surface when rubbed as set forth in claim 3 being greater than the adhesive afiinity of said discrete release film portions for said supporting sheet.

5. A dry transfer sheet as defined in claim 2 wherein said solvent is an aromatic hydrocarbon solvent.

6. A dry transfer sheet as defined in claim 2 wherein said release film contains mica.

7. A dry transfer sheet as denfied in claim 2 wherein said supporting sheet is comprised of polystyrene.

8. A dry transfer sheet as defined in claim 2 wherein said release film contains a plasticizer which will migrate up into said film of adhesive material to increase the tackiness of said adhesive material.

9. A dry transfer sheets as defined in claim 8 wherein said adhesive material is superposed on said release film and also overlaps onto said supporting sheet in the spaces between said discrete portions of release film.

10. A dry transfer sheet as defined in claim 2 wherein the spaces between said discrete portions of release film are substantially free of said adhesive material.

11. A dry transfer sheet as defined in claim 2 wherein said release film is comprised of a nitrocellulose ink in a butyl Cellosolve solvent.

12. A dry transfer sheet as defined in claim 11 wherein said release film includes ethylcellulose.

13. A dry transfer sheet as defined in claim 3 wherein said supporting sheet is comprised of polystyrene; said release film is comprised of nitrocellulose in a butyl Cellosolve solvent and contains mica; and said adhesive film contains an aromatic hydrocarbon solvent.

14. A dry transfer sheet as defined in claim 13 wherein said release film contains a plasticizer which will migrate up into said adhesive film to increase the tackiness of said adhesive material.

15. A dry transfer sheet as defined in claim 14 wherein said release film includes ethylcellulose.

16. A dry transfer sheet as defined in claim 15 wherein said adhesive material is superposed on said release film and also overlaps onto said supporting sheet in the spaces between said discrete portions of release film.

17. A dry transfer sheet as defined in claim 1 wherein said release film is formed of a material which is substantially inert to the material of said supporting sheet.

18. A dry transfer sheet as defined in claim 1 wherein at least one of said release and adhesive films is pigmented.

References Cited UNITED STATES PATENTS 3,298,850 l/1967 Reed et a1 117-3.l

EARL M. BERGERT, Primary Examiner. M. L. KATZ, Assistant Examiner.

U.S. c1. X.R. 161-406; 156-230

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