US3856521A

US3856521A - Diffusion transfer color film and process

Info

Publication number: US3856521A
Application number: US00247022A
Authority: US
Inventors: R Bilofsky; H Rogers
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1972-04-24
Filing date: 1972-04-24
Publication date: 1974-12-24
Anticipated expiration: 1991-12-24
Also published as: CA1012817A; BE798619A; NL7305705A; AU5444973A; IT980343B; GB1425835A; NL179236C; JPS4948326A; DE2319469A1; FR2181915B1; JPS539738B2; AU464590B2; DE2319469C2; FR2181915A1

Abstract

Diffusion transfer color processes are described for providing integral negative-positive reflection prints. Discoloration of the ''''whites'''' or highlights of such integral negative-positive reflection prints is minimized by performing the process in the presence of a metal chelating or complexing agent effective to form a less colored and more stable metal chelate than any other reagent present.

Description

United States Patent Bilofsky et al.

[ Dec. 24, 1974 DIFFUSION TRANSFER COLOR FILM AND PROCESS Inventors: Ruth C. Bilofsky, Arlington;

Howard G. Rogers, Weston, both of Mass.

Polaroid Corporation, Cambridge, Mass.

Filed: Apr. 24, 1972 Appl. No.: 247,022

[73] Assigne e:

US. Cl 96/3, 96/29 D, 96/76 R, 96/77, 96/84 R Int. Cl. G03c 7/00, G03c 5/54, G030 1/40, G03c 1/48, G030 1/84 Field of Search. 96/76 R, 3, 29 D, 84 R, 96/77 [56] References Cited UNITED STATES PATENTS 3,477,849 ll/l969 Becker ..96/3

12/1969 3/l972 5/1973 l/l974 Karlson 96/[09 Land 96/3 Milligan 96/3 Land et al 96/3 Primary ExaminerDavid Klein Assistant Examiner-Richard L. Schilling Attorney, Agent, or Firm-Stanley H. Mervis ABSTRACT 32 Claims, 2 Drawing Figures l8 OPA QUE SUPPORT l6+ DEVELOPED SILVER HALIDE l LlGHT-REFLECTING LAYER IZ DY E IMAGE 20+ TRANSPARENT SUPPORT PATENTED 3.856.521

|8+ OPAQUE SUPPORT |6+ DEVELOPED SILVER HALIDE NAN LIGHT-REFLECTING LAYER IZ I DYE IMAGE 20% TRANSPARENT SUPPORT 247 TRANSPARENT SUPPORT j 22+ OPAQUE LAYER l6+ DEVELOPED SILVER HALIDE 20+ TRANSPARENT SUPPORT DIFFUSION TRANSFER COLOR FILM AND PROCESS This invention is concerned with photography and, more particularly, with the formation of images in color by diffusion transfer processing.

A number of diffusion transfer photographic processes have been proposed wherein the resulting photograph comprises the developed silver halide emulsions retained with the dye-image carrying layer as part of a permanent laminate. The image-carrying layer is separated from the developed silver halide emulsions in said laminate by a light-reflecting layer, preferably a layer containing titanium dioxide. Illustrative of patents de scribing such products and processes are U.S. Pat. No. 2,983,606 issued Mar. 9, 1961 to Howard G. Rogers, U.S. Pat. No. 3,415,644, 3,415,645 and 3,415,646 issued Dec. 10, 1968 to Edwin H. Land, U.S. Pat. Nos. 3,594,164 and 3,594,165 issued July 20, 1971 to Howard G. Rogers, and U.S. Pat. No. 3,646,347 issued Mar. 7, 1972 to Edwin H. Land.

Referring more specifically to the aforementioned U.S. Pat. No. 3,415,644, said patent discloses photographic products and processes employing dye developers wherein a photosensitive element and an imagereceiving layer are maintained in fixed relationship prior to photoexposure and this fixed relationship is maintained after processing and image formation to provide a laminate including the processed silver halide emulsions and the image-receiving layer. Photoexposure is made through a transparent (support) element and application of a processing composition provides a layer of light-reflecting material to. provide a white background for viewing the image and to mask the developed silver halide emulsions. The desired color transfer image is viewed through said transparent support against said white background.

It has been found that such processes provide very useful and good quality images but that such images have a tendency to discolor in time.

It is therefore a primary object of this invention to provide novel diffusion transfer products and processes which provide high quality dye images as part of a permanent laminate, said'dye images exhibiting good resistance to discoloration with time.

Yet another object of this invention is to provide color diffusion transferprocesses wherein a metal chelating agent is provided to increase the resistance to discoloration of diffusion transfer dye images containing a light-reflecting pigment.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the followiong detailed description of the invention taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a diagrammatic enlarged schematic illustration of a diffusion transfer dye image formed in accordance with one embodiment of this invention, and

FIG. 2 is a similar schematic illustration of a diffusion transfer dye image formed in accordance with another embodiment of this invention.

As noted above, this invention is concerned with diffusion transfer processes wherein the layer containing the diffusion transfer dye image, i.e., the imagereceiving layer, is not separated from the developed photosensitive layers after processing but both components are retained together as part ofa permanent laminate. Film units particularly adapted to provide such diffusion transfer images have frequently been referred to as integral negative-positive film units. The resulting image may be referred to as an integral negativepositive reflection print" and as so used is intended to refer to a reflection print wherein the developed photosensitive layers have not been separated from the image. A light-reflecting layer between the developed photosensitive layer(s) and the image layer provides a white background for the dye image and masks the developed photosensitive layer(s). These layers are part of a permanent laminate which usually includes dimensionally stable outer or support layers, the transfer dye image being viewable through one of said supports. This invention is concerned with preventing or at least minimizing discoloration of the whites or highlights of such integral negative-positive reflection prints.

The present invention is applicable to a wide variety of color diffusion transfer processes and the arrange ment and order of the individual layersof the film used in such color processes may vary in many ways as is known in the art, provided the final image is an integral negative-positive reflection print as described above. For convenience, however, the more specific description of the invention may be by use of dye developed diffusion transfer color processes and of integral negative-positive film units of this type contemplated in the previously mentioned U.S. Pat. No. 3,415,644

In such integral negative-positive reflection prints, the various layers comprising the laminate tend to remain wet for a period of time much longer than the processing time, i.e., the time required simply to develop the exposed silver halide and to form the transfer image. This extended wet condition thus may permit reactions to occur which will adversely affect the color transfer image; These further reactions are most readily evidenced by changes in the highlights or whites of the color image. The incorporation within the film unit of a mechanism to reduce the pH, such as the acidic polymer layer set forth in the above-mentioned U.S. Pat.

No. 3,415,644, has been found to greatly reduce these problems to the point where such darkening may not be evidenced until a number of days have elapsed.

It has been observed that under certain conditions, the highlights or whites of integral negative-positive reflection prints develop a stain which, by a process of elimination. could not be attributed to undesired image dye, oxidized auxiliary developing agent or transferred silver ion. This stain is not particularly evident in fresh integral negative-positive prints, but'appears with the passage of time; accelerated ageing tests using heat or a Xenon arc may be used to bring out this stain.

It has now been found that such stains may be minimized or eliminated by performing the process in the presence of a metal chelating or complexing agent effective to form a less colored and. more stable metal chelate than any other reagent present.

While the precise mechanism by which the addition of a metal chelating agent is effective to prevent stain is not completely understood, certain reagents used in the process include functional groups which are capable of forming colored metal complexes.

Thus, for example, the optical filter agent OH on ooon nooo CHHUO-K contains two acid -type groups.

-CO OH which product absorbsblue light at acidic pH levels well below the pKa of this optical filter agent, i.e., well below the pH at which this optical filter agent no longer absorbs visible light. A yellow stain is in fact observed when a dye developer integral negative-positive reflection print processed in the presence of this optical filter agent is allowed to age in room light or is artificially aged under a Xenon are, even if the pH has been reduced to 5 or 6. The inclusion of ethylene diamine tetraacetic acid in the processing of such prints has been found to reduce if not prevent the formation of such yellow stain. It has further been found that the effective'ness of ethylene diamine tetraacetic acid in supressing such stain when the above optical filter agent is used may be increased by providing ions of another metal, particularly aluminum ions. From these experiments, it is reasonable to conclude that stain arising from a chelation of ions of the light-reflecting pigment with a component of the process may be controlled or prevented by adding a chelating agent which forms a less colored or colorless species with said metal ion. Ethylene diamine tetraacetic acid, and similar chelating agents containing the on, e 0 o H cm 0 o o H group, which are unable to form a conjugated system,

such asthat possible with salicylic acid-like chelating functions, are preferred as they provide metal chelates which are less colored or colorless.

Ethylene diamine tetraacetic acid and related compounds are known to have a buffering action at certain pH levels. Careful study has shown that the beneficial uracil, with a o-alkylaminopurine of the formula:

wherein R is an alkyl group, it being understood that alkyl is intended to include aralkyl, such as I OCHJ effect of ethylene diamine tetraacetic acid is not due to a buffer action, as other compounds known to buffer at the same or similar pH levels do not prevent the formation of this stain. The beneficial effect of the addition of other metal ions, such as aluminum ions, is considered to be strong-additional evidence that a buffer action is not to be credited. In addition, since an acid reacting reagent is generally present to reduce the pH by neutralizing the alkaline system, the final pH within the integral negative-positive print is likely to be below the pH at which ethylene diamine tetraacetic acid is a buffer.

The beneficial effects of the metal chelating agent are particularly useful in dye developer diffusion transfer processes wherein development is effected in the presence of a sulfur-free silver halide solvent and a second sulfurfree silver halide complexing agent which forms a relatively less soluble silver complex. Particu larly useful are combinations of a cyclic imide, preferably a uracil such as uracil, S-methyl uracil or 6-methyl Where the alkyl group is a simple alkyl group, better results are generally obtained when the alkyl group contains more than one or two carbons. As will be apparent from the above, the alkyl group may be substi-v tuted, e.g., by halogen, alkoxy, etc. (The use of such 6- alkylamino-purines in dye developer processes is the subject of the copending application of Edwin H. Land, Stanley M. Bloom and Howard G. Rogers application, Ser. No. 211,718, filed Dec. 23, 1971, now U.S. Pat. No. 3,785,814 issued Jan. 15, 1974 and of a continuation-in-part thereof, Ser. No. 246,669 filed concurrently herewith (now U.S. Pat. No. 3,801,318 issued Apr. 2, 1974.)

FIGS. 1 and 2 illustrate in a simplified or schematic form the arrangement of layers in photographic films of the type with which this invention is concerned, the film or film unit being depicted as an integral laminate after processing and image formation. Since the two film units shown have many elements in common, the two Figures will be described together. As will be evident from the Figures, a diffusion transfer image in an image-receiving or image-carrying layer 12 is viewed through a transparent support 20 against a lightreflecting layer 12 which in turn masks the developed silver halide emulsion(s) 16. In FIG. I, an' opaque support 18 completes the film unit 10. The light-reflecting layer 14 preferably-comprises a white pigment, particularly titanium dioxide. While only one layer 16 of silver halide emulsion is shown, it will be understood that in multicolor embodiments the silver halide emulsion layer" 16 may comprise a plurality of silver halide emulsions (blue-, greenand red-sensitive) arranged in overlying coplanar relationship or in a side-by-side or screen-like arrangement as is well known in the art. An image dye-providing material associated with each of the silver halide emulsions, in the same layer or in a contiguous layer, provides an image dye or an intermediate for an image dye having a color complementary to the light by which the associated silver halide emulsion is exposable, as is well known in subtractive color processes.

It will be understood that the elements of the film may be superposed and comprise an integral film unit during photographic exposure, i.e., photoexposure being effected through the transparent support 20 as shown, for example, in the aforementioned U.S. Pat. No. 3,426,644. Alternatively, the image-receiving layer 12 and its transparent support 2.0 may be separated from the photosensitive layers during exposure, the resulting laminate 110 being formed by the superposing of the respective elements with a processing composition containing a light-reflecting pigment distributed therebetween, as described, for example, in the aforementioned US. Pat. No. 2,983,606.

If the film unit is to be processed outside of a dark chamber, i.e., if it is to be removed from the camera priorto image completion and while the film is still photosensitive, appropriate opacifying reagents and/or layers should be provided. A particularly useful opacifying system for film units providing integral prints of the type shown in FIG. 1 and in the aforementioned US. Pat. No. 3,426,644 utilizes a color dischargeable reagent, preferably a pH-sensitive optical filter agent or dye, as is described in detail in US. Pat. No. 3,647,437 issued Mar. 7, 1972 to Edwin H. Land. In film units adapted to provide a laminate of the type shown in FIG. 2, photoexposure is effected from the side opposite the side from which the image is viewed, and an appropriate opaque layer 22 is provided over the silver halide emulsion(s) layer 116. This may be done by distributing a processing composition providing an opaque layer 22, e.g., containing carbon black, between the photo sensitive layer 16 and the transparent support 24. Alternatively, opaque layer 22; may be omitted and lightprotection provided by an opaque layer (not shown) superposed over the transparent support 24 or directly over the photosensitive layer 16 after exposure.

In the preferred film structures for obtaining integral negative-positive reflection prints of the type shown FIG. I, photoexposure is effected through the same transparent support 20 through which the final dye transfer image is viewed.

In the preferrred film units for obtaining integral negative-positive reflection prints of the type shown in FIG. 2, photoexposure is effected through the transparent support 24 and an opaque layer 22 to protect the exposed silver halide from further exposure may be provided by including a light-absorbing opacifying agent, e.g., carbon black, in the processing composition which is distributed between the photosensitive layer 16 and a transparent support 24. In such film units, it may be desirable to include a preformed opaque layer (not shown), e.g., a dispersion of carbon black in a polymer permeable to the processing composition, between a preformed light-reflecting layer 14 and the silver halide emulsion(s) 16. These embodiments are shown and described in the aforementioned US. Pat.

Nos. 3,594,164 and 3,594,165. The image dyeproviding materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible or provide a diffusible product in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color cou plers. The requisite differential in mobility or solubility may, for example, be obtained by achemical action such as a redox reaction or a coupling reaction.

0 As examples ofinitially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S.. Pat. Nos. 2,774,668; 2,968,554; 2,983,606; 2,087,817; 3,185,567; 3,230,082; 3,345,163; and 3,443,943. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in US. Pat. Nos. 3,185,567; 3,443,939; 3,443,940; 3,227,550; and 3,227,552. Both types of image dye providing substances and film units useful therewith also are discussed in the aforementioned US. Pat. No. 3,647,437 to which reference rr ay be made. 0

In any of these systems, multicolor images are ob tained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith an image dye-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing blue-, a greenand a red-sensitive silver halide layers having associated therewith, respectively, a. yellow, a magenta and a cyan image dyeproviding material, as disclosed in U.S. Pat. No. 3,345,163 issued Oct. 3, 1967 to Edwin H. Land and Howard G. Rogers.

A particularly useful system for forming color images by diffusion transfer is that described in US. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the image dyeproviding materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated therewith (in the same or in an adjacent layer) is developed by applying an aqueous alkaline processing composition. Exposed and developable silver halide is developed by the dye developer which in turn becomes oxidized to provide an oxi dation product which is appreciably less diffusible than the unreacted dye developer, thereby providing an imagewise distribution of diffusible dye developer in terms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, by diffusion, to a dyeab'le stratum to inpart thereto a positive dye transfer image. Multicolor images may be obtained with a photosensitive element having two or more selectively sensitized silver halide layers and associated dye developers, a tripaclt structure of the type described above in various patents including the aforementioned US. Pat. Nos. 2,983,606 and 3,345,163 being especially suitable for accurate color recordation oforiginal subject matter.

In such color diffusion transfer system, color transfer images are obtained by exposing a photosensitive element, sometimes referred to as a negative compoto a superposed image-receiving layer, sometimes referred to as a positive component, comprising at least a dyeable stratum to provide a color transfer image. The negative and positive components initially may be carried on separate supports which are brought together during processing and thereafter retained together as the final integral negative-positive reflection print, or they may initially comprise a unitary structure,

e.g., integral negative-positive film units wherein the negative and positive components are part of a photosensitive laminate or they may otherwise by physically retained together in superposed relationship prior to, during and after image formation. (Procedures for forming such film units wherein the positive and negative components are temporarily laminated together prior to exposure are described, for example in U.S. Pat. No. 3,652,281 to Albert J. Bachelder and Frederick J. Binda and in U.S. Pat. No. 3,652,282 to Edwin H. Land, both issued Mar. 28, 1972.) In either instance, the positive component is not removed from the negative component for viewing purposes. The preferred film units comprise a plurality of essential layers including a negative component comprising at least one light-sensitive silver halide and associated dye imageproviding material and a positive component comprising a dyeable stratum. These components may be laminated together or otherwise secured together in physical juxtaposition as an essentially integral structure.

'Filmunits intended to provide multicolor images comprise two or more selectively sensitized silver halide layers each having associated therewith an appropriate image dye-providing material providing an image dye spectral absorption characteristics substantially complementary to the light by which'the associated silver halide is exposed. The most commonly employed negative components for forming multicolor images are of the tripack structure and contain blue-, greenand redsensitive silver halide layers each having associated therewith in the same or in a contiguous layer a yellow, a magenta and a cyan image dye-providing material respectively. lnterlayers or spacer layers may, if desired, be provided between the respective silver halide layers and associated image dye-providing materials or between other layers. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer between the dyeable stratum and the negative component in order to mask effectively the silver image or images formed as a function of development of the silver halide layer or layers and also to mask image dye-providing material which is not transferred, thereby providing a background, preferably white, for viewing the color image formed in the dyeable stratum, without separation, by reflected light. This reflecting layer may comprise a preformed layer of a reflecting agent included in the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition-The dye transfer image is then viewable through a dimensionally stable protective layer or support. Mostpreferably another dimensionally stable layer or support, which may be transparent or opaque, is positioned on the opposed surface of the essential layers so that the aforementioned essential layers are between a pair of dimensionally stable layers or support members, one of which is transparent to permit viewing therethrough of the color transfer image. A rupturable container of known description contains the requisite processing composition and is adapted upon application of pressure to release its contents for development of the exposed film unit, e.g., by distributing the processing composition in a substantially uniform layer between a pair of predetermined layers. 1n film units providing an integral negative-positive reflection print of the type illustrated in FIG. 1, a processing composition containing a white pigment may be distributed between the dyeable stratum and the negative component to providethe light-reflecting layer 14.

A preferred opacification system to be contained in the processing composition .to effect processing outside of a camera is that described in the above-mentioned U.S. Pat. No. 3,647,437, and comprises a dispersion of an inorganic light-reflecting pigment which also contains at least one light-absorbing agent, i.e,, optical filter agent, at a pH above the pKa of the optical filter agent in 'a concentration effective when the processing composition is applied, to provide a layer exhibiting optical transmission density about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide and optical reflection density about 1.0 density units with respect to incident visible radiation.

In lieu of having the light-reflecting pigment in the processing composition, the light-reflecting pigment used to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be present initially in whole or in part as a performed layer in the film.

unit. As an example of such a preformed layer, mention may be made of that disclosed in U.S. Pat. No. 3,615,421 issued Oct. 26, 1971 and in U.S. Pat. No. 3,620,724 issued Nov. 16, 1971, both in the name of Edwin H. Land. The reflecting agent may be generated in situ as is disclosed in U.S. Pat. No. 3,647,434 and 3,647,435, both issued Mar. 7, 1972 to Edwin H. Land.

The dye developers (or other image dye-providing substances) are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. They may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective silver halide emulsion. Thus a dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution containing the respective dye developer distributed, in a concentration calculated to give the desired coverage of dye developer per unit area, in a filmforming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the processing composition.

Dye developers, as noted above, are compounds which contain the chromophoric system of a dye and also a silver halide developing function. By silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and ortho-and para-amino substituted hydroxyphenyl groups. in general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

The image-receiving layer may comprise one of the materials known in the art, such as polyvinyl alcohol, gelatin, etc. It may contain agents adapted to mordant or otherwise fix the transferred image dye(s). Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061, issued Sept. 8, 1964 to Howard C. Haas. 1f the color of the transferred image dye(s) is affected by changes in pH, the pH of the image layer may be adjusted to provide a pH affording the desired color.

In the various color diffusion transfer systems which have previously been described and which employ an aqueous alkaline processing fluid, it is well known to employ an acid-reacting reagent in a layer of the film unit to lower the environmental pl-l following substantial dye transfer in order to increase the image stability and/or to adjust the pH from the first pH at which the image dyes are diffusible to a second (lower) pH at which they are not. For example, the previously mentioned U.S. Pat. No. 3,415,644 discloses systems wherein the desired pH reduction may be effected by providing a polymeric acid layer adjacent the dyeable stratum. These polymeric acids may be polymers which contain acid groups, e.g., carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals or with organic bases; or potentially acidyielding groups such as anhydrides or lactones. Preferably the acid polymer contains free carboxyl groups. A1- ternatively, the acid-reflecting reagent may be in a layer adjacent the silver halide most distant from the image-receiving layer, as disclosed in U.S. Pat. No. 3,573,043 issued Mar. 30, 1971 to Edwin H. Land. Another system for providing an acid-reacting reagent is disclosed in U.S. Pat. No. 3,576,625 issued Apr. 27, 1971 to Edwin H. Land.

An inert interlayer or spacer layer may be and is preferably disposed between the polymeric acid layer and the dyeable stratum in order to control or time the pH reduction so that it is not premature and interfere with the development process. Suitable spacer or timing layers for this purpose are described with particularity in U.S. Pat. Nos. 3,362,819; 3,419,389; 3,421,893; 3,455,686; and 3,575,701.

While the acid layer and associated spacer layer are preferably contained in the positive component employed in systems wherein the dyeable stratum and photosensitive strata are contained on separate supports, e.g., between the support for the receiving element and the dyeable stratum; or associated with the dyeable stratum in those integral film units, e.g., on the side of the dyeable stratum opposed from the negative components, they may, if desired, be associated with the photosensitive strata, as is disclosed, for example, in U.S. Pat. Nos. 3,362,821 and 3,573,043.1n film units such as those described in the aforementioned US. Pat. Nos. 3,594,164 and 3,594,165, they also may be contained on the spreader sheet employed to facilitate application of the processing fluid.

As is now well known and illustrated, for example, in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example sodium hydroxide, potassium hydroxide, and the like, and preferably possessing a pH in excess of 12, and most preferably include a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, water-soluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally, filmforming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for a long period of time are so disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of cps. at a temperature of approximately 24C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

This invention will be further illustrated by the following example intended to be illustrative only. 7

EXAMPLE A multicolor photosensitive element using, as the cyan, magenta and yellow dye developers cyan:

CH: ni-mn-ms-Q H N=C/ C- CH: OH \N% H ?07 NH +H C N-Cu-N in, I HO- N H NHO2S 5,, I

2 =C C-N OH: OH SOzNH-H HO H:

magenta; Ho om-om /N- SO1 -N:N CH:t HO--CH;CH N or-eno (I) 0 OH ginseng AH yellow: N 02 O (I) (I) (L-CHr--CH 1 0 was prepared by coating a gelatin-subcoated 4 mi] opaque polyethylene teraphthalate film base with the following layers:

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about 100 mgs/ft. of

dye and about 80 mgs/ft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 140 mgs/ft. of silver and about 70 mgs./ft. of gelatin;

3. a layer of a 60-30-4.-6 copolymer of butylacrylate diacetone acrylarnide, styrene and methacrylic acid 5 tin and coated at a coverage of about ll2 mgs./ft. of

dye and about 100 mgs/ft. of gelatin;

5. a green sensitive gelatino silver iodobromide emulsion coated at a coverage of about lOO mgs./ft'. of silver and about 50 mgs./ft. of gelatin;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 rngsjft. of copolymer and about l2 mgs./ft. of polyacrylamide;

7. a layer of yellow dye developer dispersed in gellatin and coated at a coverage of about 70 mgs/ft. of dye and about 56 mgs./ft. of gelatin;

8. a blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4'- methylphenyl hydroquinone coated at a coverage of about 120 mgs./ft. of silver, about 60 mgs./ft. of gelatin and about 30 mgs./ft. of auxiliary developer; and

' 9. a layer of gelatin coated at a coverage of about mgs./ft. of gelatin. 50

A transparent 4 mil. polyethylene teraphthalate film base was coated, in succession, with the following layers to form an image-receiving component:

-30-4-6 copolymer of butylacrylate, diacetone acrylamicle, styrene and methacrylic acid and polyacrylamide at a coverage of about 500mgs./ft. and

3. a polymeric image-receiving layer containing a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine, at a coverage of about 300 mgs./ft. The two components thus prepared were then taped together, in laminate form, at their respective edges to provide an integral film unit, with a rupturable container retaining an aqueous alkaline processing solution fixedly mounted on the leading edge of each of the components, by pressure-sensitive tapes, so that, upon application of compressive pressure to the container to rupture the containers marginal seal, its contents were distributed in a layer approximately 0.0026 inches thick between the image-receiving layer and the gelatin overcoat layer of the photosensitive component. The aqueous alkalineprocessing composition comprised:

Potassium hydroxide 5 .3 g

N-benzyl-a-picolinium bromide (50% solution in water) 1 1.3 g.

N-phenethyl-cr-picolinium bromide 0 .775g.

dodium carboxyrnethyl cellulose (Hercules Type 7H4F providing a viscosity of 3000 cps at 1% in water at 25C.) 0 .59 9'.

Titanium dioxide 44.9 g.

6-methyl uracil 0 .63 g.

bis-(fi-aminoethyl)-sulfide 0.045

Lithium nitrate 0 .l g.

Benzotriazole 0 .6 g.

G-methyl-S-bromo- I d-azabenzimidazole 0 .03 g.

Colloidal silica aqueous dispersion (30% SiO 1.96 g.

Lithium hydroxide O .2 g.

6-benzylamino-purine 0 .42 g.

Polyethylene glycol (molecular weight 6000) O .58 g.

Ethylene-diamine tetraacetic acid dipotassium salt 0 .87 9.

Water to make g.

The photosensitive element was exposed through the transparent support and the layers thereon, the processing composition distributed by passing the film unit between a pair of pressure-applying rolls and into a lighted area. The laminate obtained by distribution of the processing composition was maintained intact to provide an integral negative-positive reflection print which exhibited good color quality and separation. Accelerated ageing of the print showed essentially no yellow stain which was observed in the absence of the ethylene diamine tetraacetic acid.

The use of colloidal silica in the processing composition is the subject of the copending application of Edwin H. Land, Ser, No. 247,025, filed concurrently herewith (now U.S. Pat. No. 3,776,726 issued Dec. 3, 1973). The use of polyethylene glycol in the processing composition is the subject of the copending application of Edwin H. Land, Ser. No. 247,023, filed concurrently herewith (now U.S. Pat. No. 3,793,023 issued Feb. 19, I974) as a continuation-in-part of application Ser. No. 209,754, filed Dec. 20, 1971, now abandoned.

In the above example, the ethylene diamine tetraacetic acid was added as the dipotassium salt; if it is added as the free acid, additional alkali may be added to cmpensate for the alkali consumed by the acid.

In addition to ethylene diamine tetracetic acid HO O C-CHz other metal complexing agentswhich have demon-' strated an ability to reduce stain otherwise evidenced when an alkaline solution containing titanium dioxide and the above salicylic acid-group containing optical filter agent neutralized, e.g., to a pH of6 to 6, include N-( carboxymethyl )-N -2-hydroxyethyl-N,N

ethylene glycine diamino-cyclohexane tetraacetic acid may vary, ofcourse, with the particular metal complexing agent and may be readily determined by routine testing. Other metal complexing agents which are use ful maybe readily determined by a simple screening test wherein the pigment (or other source of metal ions) and the reagent which itself is colorless in acid but which with such metal ions can form a reaction product which would be colored at the final pH of the transfer image are allowed to contact under strong alkaline conditions before being neutralized to a pH of about 7, and preferably a pH of about 5. A thin layer of the resulting mixture, preferably confined between two transparent polyester supports, may be heated at 120F. for 18 hours in the dark. Useful metal complex-.

ing agents will prevent or at least substantially reduce the stain observed in their absence. It will be recognized that a particular metal complexing agent may be more effective with a given metal ion than with another metal ion. Where the pigment is titanium dioxide, reflection density curves ofa layer formed from an aqueous potassium hydroxide solution of the above optical filter agent containing a salicylic acid-like group, sodium carboxymethyl cellulose and titanium dioxide fol lowing neutralization with acetic acid to a pH of about 5 to 6 show a sizeable increase in blue absoprtion, i.e., the appearance of a yellow stain, after -l6 hours at 120F. Inclusion of the above-noted metal complexing agents gave substantial if not complete elimination of this yellow stain.

As noted above, the inclusion of aluminum ions has been found to cooperate with the metal complexing agent to more effectively reduce the buildup of such titania stain. In one test, the addition of 2% by weight of Al(NO -9H O, gave a 50% reduction in the yellow stain remaining after ethylene diamine tetraacetic acid (sodium salt) was added. The mechanism by which this beneficial effect is obtained is not known, but may involve a competitive chelation in which the added metal ion forms a stronger but less colored metalcomplex.

The added metal complexing agent may even be a member of a ternary complex of one metal with two different complexing groups. Aluminum ions may be introduced by adding a soluble salt. of aluminum to the processing composition. If the pigment, e.g., titanium dioxide, includes an aluminum oxide, contact with a strongly'alkaline processing composition may dissolve sufficient aluminum ions for this purpose.

It is recognized that the use of metal complexing or sequestering agents, including ethylene diamine tetraacetic acid, has previously been proposed in U.S. Pat. No. 3,477,849. The disclosure thereof may be readily distinguished as the function of the sequestering agent was to decomplex metal moiety from a polymeric interlayer to increase the permeability of the interlayer.

It will be understood that dye transfer images which are neutral or black-and-white instead of multicolor may be obtained by use of a mixture of dyes of the appropriate colors, the transfer of which may be controlled by a single layer of silver halide, in accordance with known techniques. It is also to be understood that direct positive silver halide emulsions may also be used, depending upon the particular dye imagematter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimedis:

l. A photographic product for forming a diffusion transfer image in dye within a permanent laminate including at least one developed silver halide layer, said photographic product comprising, in combination, an image-receiving layer; at least one silver halide emulsion, each said silver halide emulsion having associated therewith an image dye-providing substance selected from the group consisting of image dyes and image dye intermediates; means providing a light-reflecting layer containing a metal pigment between said imagereceiving layer and said silver halide emulsion(s) to mask said silver halide emulsion(s) after development thereof and to provide a white background for viewing a dye image in said image-receiving layer; a transparent support through which image-receiving layer may be viewed; means providing a processing composition for developing said silver halide emulsion(s) after photoexposure and for forming a transfer image in at least one dye in said image-receiving layer; said product including a silver halide solvent and a second silver halide complexing agent, said second silver halide complexing agent being capable of forming a relatively insoluble complex with silver halide; said product further including a compound which will form a colored product with ions of said metal at an acidic pH and said processing composition containing a metal complexing agent in a concentration effective to at leastsubstantially prevent the formation of said colored product, said metal complexing agent being N-(carboxymethyl)-N-2- hydroxyethyl-N,N-ethylene glycine.

2. A photographic product as defined in claim 1 wherein-said metal pigment is titanium dioxide.

3. A photographic product as defined in claim 2 wherein said'titanium dioxide is dispersed in said processing composition 4. A photographic film as defined in claim 1 wherein each said image dye-providing substance is a dye.

5. A photographic film as defined in claim 4 wherein each said dye is a dye developer.

6. A photographic film as defined in claim 1 wherein each said image dye-providing substance is an intermediate for an image dye.

7. A photographic product as defined in claim ll wherein said silver halide emulsion(s) are adapted to be exposed through said transparent support.

8. A photographic product as defined in claim 1 wherein said means providing a light-reflecting layer 50 comprise a white pigment dispersed in said processing composition, and said processing composition is contained in a rupturable container positioned to distribute said processing composition containing said pigment between said image-receiving layer and said silver halide emulsion(s).

9. A photographic product as defined in claim 1 -wherein said second silver halide complexing agent confined between two dimensionally stable supports, at least one of said supports being transparent. the bond between a predetermined pair of layers being weaker than the bond between other pairs of layers, and including a rupturable container releasably holding said processing composition, said rupturable container being so positioned as to distribute said processing composition between said predetermined layers, said processing composition being adapted to provide said permanent laminate following distribution and drying.

13. A photographic product comprising a first support; a redsensitive silver halide emulsion; a green sensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, an imagereceiving layer for receiving image dyes transferred thereto by diffusion as a function of exposure and development of said silver halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed, a rupturable container releasably holding a processing composition adapted, upon distribution between predetermined layers of said film to develop said:

silver halide emulsions and to effect the formation of a transfer image in'dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developed silver halide emulsions and said imagereceiving layer; and means providing a light reflecting layer containing a metal pigment between said image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed silver halide emulsions; said processing composition including a compound which will give a colored product with ions of said metal at an acidic pH and a metal complexing agent in a concentration effective to at least substantially prevent the formation of said colored product; said processing composition containing ions of a second metal which ions are effective to further reduce the formation of said colored product.

14. A photographic product as defined in claim 13 wherein said means for providing a light-reflecting layer comprises a preformed layer of a white pigment.

15. A photographic product as defined in claim 13 wherein said means for providing a light-reflecting layer comprises a titanium dioxide dispersed in said processing composition.

16. A photographic product as defined in claim l3 wherein said first support is opaque.

17. A photographic product as defined in claim 13 wherein said transparent support is a polyester.

18. A photographic product as defined in claim 17 wherein said polyester is polyethylene teraphthalate.

19. A photographic product as defined in claim 18 wherein said opaque support is polyethylene teraphthalate.

20. A photographic product as defined in claim 13 wherein said transparent support is cellulose acetate.

2i. A photographic product as defined in claim 13 wherein said metal complexing agent is ethylene diamine tetraacetic acid.

22. A photographic product as defined in claim 13 including means to reduce the pH of a layer of said pro cessing composition from a first pH to a second pH.

23. A photographic product as defined in claim 22 wherein said means to reduce the pH comprises a layer of an acid-reacting reagent positioned between said transparent support and said image-receiving layer.

24.-A photographic product as defined in claim 23 wherein said acid-reacting reagent is a polymer.

25. A photographic product as defined in claim 13 wherein said processing composition includes an optical filter agent which is colored at the pH of said processing composition, said optical filter agent being adapted to be rendered colorless by reducing said pH.

26. A photographic product as defined in claim 25 wherein said optical filter agent contains a salicylic acid group.

27. A photographic product as defined in claim 13 wherein said processing composition contains titanium dioxide and said second metal ions are aluminum ions.

28. A photographic product as defined in claim 13 wherein said metal complexing agent is N- (carboxymethyl)-N-2-hydroxyethyl-N,N"ethylene glycine.

29. In a method of forming a diffusion transfer dye image by developing an exposed silver halide emulsion, forming an imagewise distribution of a diffusible dye image-providing substance as a function of said development, and transferring at least a portion of said imagewise distribution of diffusible dye image-providing substance to an image-receiving layer in superposed relationship with said silver halide emulsion to provide said dye image, said image-receiving layer and said silwherein said process is performed in the presence of N-(carboxymethyl )-N -2-hydroxyethyl-N,N '-ethylene vglycine in a concentration effective to prevent the formation ofa product, absorbing visible light at an acidic pH, by ions of said metal pigment with a compound used in said process.

30. The method as defined in claim 29 wherein said diffusible dye image-providing substance is a dye developer.

31. The method as defined in claim 29 wherein a redsensitive silver halide emulsion, a green-sensitive silver halide emulsion and a blue-sensitive silver halide emulsion are present, said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, and said dye image is a multicolor image.

32. The method as defined in claim 29, wherein said light-reflecting layer is provided by titanium dioxide present in the processing composition used to perform said process, and said processing composition further includes a compound containing a salicylic acid group, said N-(carboxymethyl)-N-2-hydroxyethyl-N,N- ethylene glycine being effective to provide a less colored metal complex with titanium ions than if said metal complex were formed with said salicylic acid group.

Page 1 of 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,856,521 Dated December 24, 1974 Invengo -(s) Ruth C. Bilofsky and Howard G. Rogers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 20, "3,646,347" should be --3,647,437--.

Column 1, lines 62 and 63, "followiong" should be --following--.

Column 2, lines 16 and 17, after "image" insert -layer, i.'e., the layer containing the transfer dye imag e.

Column 2, line 35, "developed" should be -developer--. I

Column 2, line 37, "this" should be --the-.

Column 4, transpose lines 1-18 to appear after line 38.

Column 6, line 57, "inpart" should be -impart--. I

Column 6, line 66, "system" should be --systems-.

Column 8, line 38, "performed" should be --preformed--.

Paga 2 of 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,856,521 Dated December 24, 1974 Inventor) Ruth C. Bilofsky and Howard G. Rogers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as' shown below:

magenta: Column 10, line 55, no-cm-cm N-SO N=N ----CH1 l Ho-cm-cm 11K};

r-HaO 0H K -D)CHr-CHI L should be HO-CH -cH I N HO-CH cn N Q 0 v magenta: -\H2O Page 5 of 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,856,521 D t d December 24, 1974 I Ruth C. Bilofsky and Howard G. Rogers 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column ll, lines 39 and 40, "gellatin" should be -gelatin-.

Column 13, line 15, "Dec. 3" should be -Dec. 4-.

I Column 13, line 26, "tetracetic" should be tet'raacetic--.

' Column 13, line 36, "6 to 6" should be --5 to 6-.

Column 14, line 25, "absoprtion" should be --absorption--.

1 Column 15, line 18, after "which" insert -said-.

Column 16, line 17, "imagereceiving" should be -imagereceiving--.

Signed and Bealedthis I Twenty-second Day f November 1977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks

Claims

1. A PHOTOGRAPHIC PRODUCT FOR FORMING A DIFFUSION TRANSFER IMAGE IN DYE WITHIN A PERMANENT LAMINATE INCLUDING AT LEAST ONE DEVELOPED SILVER HALIDE LAYER, SAID PHOTOGRAPHIC PRODUCT COMPRISING, IN COMBINATION, AN IMAGE-RECEIVING LAYER, AT LAST ONE SILVER HALIDE EMULSION, EACH SAID SILVER HALIDE EMULSION HAVING ASSOCIATED THEREWITH AN IMAGE DYE-PROVIDING SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF IMAGE DYES AND IMAGE DYE INTERMEDIATES; MEANS PROVIDING A LIGHT-REFLECTING LAYER CONTAINING A METAL PIGMENT BETWEEN SAID IMAGE-RECEIVING LAYER AND SAID SILVER HALIDE EMULSION (S) TO MASK SAID SILVER HALIDE EMULSION (S) AFTER DEVELOPMENT THEREOF AND TO PROVIDE A WHITE BACKGROUND FOR VIEWING A DYE IMAGE IN SAID IMAGERECEIVING LAYER, A TRANSPARENT SUPPORT THROUGH WHICH IMAGERECEIVING LAYER MAY BE VIEWED; MEANS PROVIDING A PROCESSING COMPOSITION FOR DEVELOPING SAIS SILVER HALIDE EMULSION (S) AFTER PHOTO-EXPOSURE AND FOR FORMING A TRANSFER IMAGE IN AT LEAST ONE DYE IN SAID IMAGE-RECEIVING LAYER; SAID PRODUCT INCLUDING A SILVER HALIDE SOLVENT AND A SECOND SILVER HALIDE COMPLEXING AGENT, SAID SECOND SILVER HALIDE COMPLEXING AGENT BEING COAPBLE OF FORMING A RELATIVELY INSOLUBLE COMPLEX WITH SILVER HALIDE; SAID PRODUCT FURTHER INCLUDING A COMPOUND WHICH WILL FROM A COLORED PRODUCT WITH IONS OF SAID METAL AT AN ACIDIC PH AND SAID PROCESSING COMPOSITION CONTAINING A METAL COMPLEXING AGENT IN A CONCENTRATION EFFECTIVE TO AT LEAST SUBSTANTIALLY PREVENT THE FORMATION OF SAID COLORED PRODUCT, SAID METAL COMPLEXING AGENT BEING N-(CARBOXYMETHYL)-N''-2HYDROXYETHYL-N,N''-ETHYLENE GLYCINE.

2. A photographic product as defined in claim 1 wherein said metal pigment is titanium dioxide.

3. A photographic product as defined in claim 2 wherein said titanium dioxide is dispersed in said processing composition

4. A photographic film as defined in claim 1 wherein each said image dye-providing substance is a dye.

7. A photographic product as defined in claim 1 wherein said silver halide emulsion(s) are adapted to be exposed through said transparent support.

8. A photographic product as defined in claim 1 wherein said means providing a light-reflecting layer comprise a white pigment dispersed in said processing composition, and said processing composition is contained in a rupturable container positioned to distribute said processing composition containing said pigment between said image-receiving layer and said silver halide emulsion(s).

9. A photographic product as defined in claim 1 wherein said second silver halide complexing agent contains a mercapto group or a group which provides a mercapto group during processing.

10. A photographic product as defined in claim 1 wherein said silver halide solvent contains no sulfur atoms.

11. A photographic product as defined in claim 1 wherein said second silver halide complexing agent contains no sulfur atoms.

12. A photographic product as defined in claim 1 comprising a temporary laminate including said layers confined between two dimensionally stable supports, at least one of said supports being transparent, the bond between a predetermined pair of layers being weaker than the bond between other pairs of layers, and including a rupturable container releasably holding said processing composition, said rupturable container being so positioned as to distribute said processing composition between said predetermined layers, said processing composition being adapted to provide said permanent laminate following distribution and drying.

13. A photographic product comprising a first support; a red-sensitive silver halide emulsion; a green-sensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, an imagereceiving layer for receiving image dyes transferred thereto by diffusion as a function of exposure and development of said silver halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed, a rupturable container releasably holding a processing composition adapted, upon distribution between predetermined layers of said film to develop said silver halide emulsions and to effect the formation of a transfer image in dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developed silver halide emulsions and said image-receiving layer; and means providing a light reflecting layer containing a metal pigment between said image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed silver halide emulsions; said processing composition including a compound which will give a colored product with ions of said metal at an acidic pH and a metal complexing agent in a concentration effective to at least substantially prevent the formation of said colored product; said processing composition containing ions of a second metal which ions are effective to further reduce the formation of said colored product.

16. A photographic product as defined in claim 13 wherein said first support is opaque.

21. A photographic product as defined in claim 13 wherein said metal complexing agent is ethylene diamine tetraacetic acid.

22. A photographic product as defined in claim 13 including means to reduce the pH of a layer of said processing composition from a first pH to a second pH.

24. A photographic product as defined in claim 23 wherein said acid-reacting reagent is a polymer.

28. A photographic product as defined in claim 13 wherein said metal complexing agent is N-(carboxymethyl)-N''-2-hydroxyethyl-N, N''-ethylene glycine.

29. In a method of forming a diffusion transfer dye image by developing an exposed silver halide emulsion, forming an imagewise distribution of a diffusible dye image-providing substance as a function of said development, and transferring at least a portion of said imagewise distribution of diffusible dye image-providing substance to an image-receiving layer in superposed relationship with said silver halide emulsion to provide said dye image, said image-receiving layer and said silver halide emulsion forming a permanent laminate including a light-reflecting layer containing a metal pigment positioned between said image-receiving layer and said silver halide emulsion, the improvement wherein said process is performed in the presence of N-(carboxymethyl)-N''-2-hydroxyethyl-N,N''-ethylene glycine in a concentration effective to prevent the formation of a product, absorbing visible light at an acidic pH, by ions of said metal pigment with a compound used in said process.

31. The method as defined in claim 29 wherein a red-sensitive silver halide emulsion, a green-sensitive silver halide emulsion and a blue-sensitive silver halide emulsion are present, said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, and said dye image is a multicolor image.

32. The method as defined in claim 29, wherein said light-reflecting layer is provided by titanium dioxide present in the processing composition used to perform said process, and said processing composition further includes a compound containing a salicylic acid group, said N-(carboxymethyl)-N''-2-hydroxyethyl-N, N''-ethylene glycine being effective to provide a less colored metal complex with titanium ions than if said metal complex were formed with said salicylic acid group.