US3649332A

US3649332A - Color printing

Info

Publication number: US3649332A
Application number: US869008A
Authority: US
Inventors: Douglas H Dybvig
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1969-10-24
Filing date: 1969-10-24
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

Porous intermediates printed with color transfer images serve as barriers during heat transfer of dye simultaneously from imaged intermediate and overlying dye transfer source sheet to provide brilliantly colored image and background areas on receptor sheet or film.

Description

United States Patent D bvi Mar. 14 1972 [54] COLOR PRINTING 2,770,534 11/1956 Marx, .lr. ..41/41 3,121,650 2/1964 Meissner .1..156/240 [72] Invent Paul 3,280,735 10/1966 Clark et al. .101/149.2 [73] Assignee: Minnesota Mining and Manufacturing 3,330,711 7/1967 Marx, Jr. et al... ..1 17/38 Company, St. Paul, Minn. 3,360,367 12/1967 Stricklin ....1l7/1.7 X 3,379,526 4/1968 Limberger et al. ..96/1 [221 1969 3,453,310 7/1969 Arneth et a1 ..96/1.2 [21] Appl. No.: 869,008 3,490,371 1/1970 Games ..117/1.7 X

Primary ExaminerRobert F. Burnett [52] US. "117/38, l Assistant Examiner-Raymond Linker, Jr.

1 36.7, 1 17/ 37 R Attorneyl(inney, Alexander, Sell, Steldt & Delahunt [51] Int. Cl ..B4lm 5/00 [58] Field of Search ..1 17/1 .7, 36.2, 36.7, 38,138.8, [57] ABSTRACT 30 u 8/2 5 Porous intermediates printed with color transfer images serve as barriers during heat transfer of dye simultaneously from [56] References Cited imaged intermediate and overlying dye transfer source sheet to provide brilliantly colored image and background areas on UNITED STATES PATENTS receptor Sheet or Sanders ..117/1.7

6 Claims, 2 Drawing Figures PATENTEDMAR 14 m2 3,649 33 2 I N VENTOR 0006M: #076 we COLOR PRINTING This invention relates to the preparation of colored prints, and has for a major object the preparation on transparent film of colored prints wherein the image areas may be in one or several colors and the background areas in another color, the prints being useful as color projection transparencies.

A method of making prints of multicolored originals in full color has recently been described in Wiese application Ser. No. 728,167, and apparatus useful in accomplishing such method has been described in Dybvig et al. application Ser. No. 728,169 now abandoned, both filed on May 10, 1968. The method involves exposing a series of photosensitive dye transfer sheet segments to a light pattern from the multicolor original through appropriate monocolor filters, developing a transposed differentially radiation-absorptive pattern at each segment, and briefly subjecting each patterned segment to intense radiation while in registry and in contact with a receptor sheet to transfer the appropriate complementary dyes from the segment to the receptor.

The apparatus includes a vacuum platen means for supporting the dye transfer sheet against and in close pressure contact with the receptor sheet. The receptor must therefore be porous; and porous paper, or film which has been perforated to provide porosity, is therefore commonly used as the receptor sheet. But papers of sufficient porosity to permit close contact with the transfer sheet are found to permit passage of volatile dyes. As an example, such paper is found to be inadequate as a liner when wound up in a roll of the segmented source sheet. Under moderately prolonged storage the volatilizable dyes are found to penetrate through the liner in amount sufficient to cause discoloration of the photosensitive surface coating on the reverse side of the sheet.

In view of the slow migration of dye through the porous paper under normal storage conditions, it might be expected that the application of much higher temperatures would greatly increase the migration of the dye. Surprisingly, it has been discovered that, under the conditions here employed, the porous receptor serves as a completely effective barrier to the passage of the volatilized dye. Accordingly it has been found possible first to form a full-color dye image on a porous receptor by the techniques and with the apparatus to which reference has hereinbefore been made, and then to retransfer the image to a permanent receptor while simultaneously transferring thereto a different color exclusively at background or nonimage areas from a color source sheet overlying the entire area.

In the drawing,

FIG. 1 is an exploded view in perspective showing the relationship of the various components in preparing a color projection transparency, and

FIG. 2 is a plan view of the resulting transparency.

Referring to FIG. 1, a permanent receptor 10, which may for example be a full lOXlO inch sheet of clear transparent dye-receptive polyester film, is supported on a suitable platen 11.

Segments

12, 13, 14 of temporary receptor sheet material which have previously been imprinted with transfer dye images are placed face down at desired positions on the receptor 10, as indicated by dotted lines. A further full size portion 15 ofa dye source sheet is placed face down over the segments and the receptor. A heated platen 16 is then pressed temporarily against the composite, causing volatilization and transfer of dyes and a corresponding coloration of the receptor 10. The platens are then separated and the sheet 10 removed.

The finished product is shown in FIG. 2 as the transparent film 10 now uniformly colored over the entire background area 17, printed with multicolored images or designs 18-20, and uncolored at closely surrounding areas 21-23 corresponding in external dimension to segments 12-14 respectively.

EXAMPLE As described in said application Ser. No. 728,167, the photosensitive dye transfer sheets may comprise a photoconductive zinc oxide coating on one surface and separate coatings of magenta, yellow and cyan dyes in sequence on the reverse surface. With these three dyes a close approximation of the colored original may be formed.

The dye source sheet 15 may contain a single dye or a mixture of dyes, and in any desired concentration, depending on the specific color and intensity desired for the background areas. Ethyl cellulose is a preferred binder and toluene a preferred solvent, although other materials may be used. The addition of an inert powder such as silica powder is helpful both in obtaining a smooth homogeneous coating Composition and in obtaining rapid and uniform transfer of dye.

The dyes employed in the dye source sheet should have sub stantially the same volatility as those of the photosensitive dye transfer sheets, and indeed the identical dyes may be used in both instances. Specific examples include N,N-dielh vl-ptricyanovinyl aniline as the magenta dye. Sudan Yellow G.R. Conc. as the yellow dye, and 2-chloro-2'-methyl-n,n-diethylindoaniline as the cyan dye. A typical coating formula includes 7.9 parts by weight of ethyl cellulose, 1 part ofpowdered silica (Syloid 244), 91.1 parts of toluene, and 1 part of magenta or cyan dye or 1.5 parts of yellow dye. Smooth coating properties are obtained by thorough homogenization of the mixture and by selection of an ethyl cellulose of appropriate viscosity or by variation in the proportion of volatile solvent. The several mixtures are coated on 37 lb. paper at a coating weight, after drying, ofapproximately 9.4 g./sq. ft. (4.3 g./sq. m.). Mixtures of these same dyes may be used to provide other desired colors. As an example, a coating containing 0.9 part of the cyan dye and 0.1 part of the magenta dye produces a deep blue color on the receptor sheet. Again, a coating containing 0.24 part of the magenta dye and 0.013 part of the yellow dye produces a pastel pink color on the receptor sheet.

An illustrative procedure will now be described. A first photosensitive dye transfer sheet is placed against a porous paper temporary receptor sheet on a vacuum platen and a vacuum is established, holding the two in close contact and in fixed position. The transfer sheet carries a dye coating on the surface contacting the receptor sheet, and a photoconductive zinc oxide coating on the outer surface. The outer surface is exposed to a color separation light image from a positive color print original, to impart a latent image. A conductive roller carrying a coating of conductive radiation-absorptive toner particles and at a high potential is passed over the exposed surface to deposit toner at the nonlight-struck areas. The surface is then briefly exposed to intense infra-red radiation, causing transfer of dye to the temporary receptor at the infrared absorptive toned areas. The vacuum is released, the photosensitive sheet is removed and replaced with a second photosensitive sheet carrying a second dye, and the process is repeated using an appropriate color separation filter. The process is again repeated using a third filter and sensitive sheet, to produce a full three-color intermediate but of dull, lifeless appearance.

One or more portions of the intermediate, for example three detail sections as indicated by segments 12-14 of FIG. 1, are cut from the sheet. These segments are placed against a transparent dye-receptive film in desired arrangement, and over them is placed a paper dye source sheet having a blue dye coating as previously described herein but minus the photoconductive coating of the transfer sheet. The three layers are pressed together and briefly heated, i.e., for 2 minutes at 275 R, either between platens as in FIG. 1 or by holding under tension over a single convexly curved platen. The film is removed and is found to retain a brilliantly clear full color copy of the detail sections on an equally clear blue background.

The dye-receptive film consists of a transparent Mylar polyester film coated with a transparent coating of a mixture of 1.5 parts of nickel acetate tetrahydrate and 10 parts of polyvinyl alcohol, applied from solution in Water which may if necessary contain just sufficient wetting agent and antifoaming agent to provide smooth uniform coating characteristics.

The dry weight of the coating is about one-half g./sq. ft. (5.4 g./sq. m.). The coating serves as a solvent and fixative for the dyes so that the colored areas do not cause diffusion of light transmitted therethrough and the colored film serves as a color projection transparency. Similar coatings may be applied to nontransparent substrates, e.g., to paper or metal, where transparency is not required.

What is claimed is as follows:

1. Method of simultaneously imprinting a colored design and a colored background on a permanent color receptor sheet comprising applying a said design in volatilizable dye to a temporary intermediate receptor sheet segment, placing said segment against said permanent receptor sheet, placing a color source sheet carrying a volatilizable dye over said segment and against said permanent receptor sheet, and heating said source sheet to an extent sufficient to cause transfer of said dyes to said permanent receptor sheet, the said segment serving as a mask for preventing the dye from reaching said permanent receptor sheet from said source sheet at the masked area.

24 Method of claim 1 wherein said intermediate sheet is a porous paper and said design is applied to said paper by selective transfer of dye from separate monocolor source sheets by selective heating of color separation image areas while said source sheets are in close pressurecontact with said intermediate sheet.

3. Method of claim 1 wherein said permanent receptor sheet is a clear transparent film having at least a surface stratum in which said dye is soluble.

4. Method of claim 2 wherein the porosity of said intermediate sheet is sufficient to permit attaining close contact between said sheet and a photoconductive zinc oxide coated dye transfer sheet on a vacuum platen.

5. Method of claim 3 wherein said surface stratum comprises a nickel salt and polyvinyl alcohol.

6. Method of claim 1 wherein said color source sheet is uniformly coated over one entire surface with said volatilizable dye.

Claims

2. Method of claim 1 wherein said intermediate sheet is a porous paper and said design is applied to said paper by selective transfer of dye from separate monocolor source sheets by selective heating of color separation image areas while said source sheets are in close pressure-contact with said intermediate sheet.
3. Method of claim 1 wherein said permanent receptor sheet is a clear transparent film having at least a surface stratum in which said dye is soluble.
4. Method of claim 2 wherein the porosity of said intermediate sheet is sufficient to permit attaining close contact between said sheet and a photoconductive zinc oxide coated dye transfer sheet on a vacuum platen.
5. Method of claim 3 wherein said surface stratum comprises a nickel salt and polyvinyl alcohol.
6. Method of claim 1 wherein said color source sheet is uniformly coated over one entire surface with said volatilizable dye.