US3615566A - Photosensitive article and method of using same incorporating leuco dye precursors and fluorescein activators - Google Patents

Abstract

A direct printout photographic system suitable for photocopy work, particularly for microfilm blowups. A leuco base of a dior triarylmethane, xanthene, thioxanthene, selenaxanthene, anthracene or acridine dye and a halogen-substituted fluorescein derivative activator, supported in a binder or distributed within a portion of a substrate, form the photosensitive system which is activated when exposed to a range of electromagnetic radiation extending from ultraviolet through the visible spectrum. The system is adaptable to making monochrome and black-and-white prints and transparencies.

Description

United States Patent [7 2] Inventors Ian D. Robinson Auburndale; Joanne C. Gerlach, Watertown; Richard P. Muse, Cambridge, all of Mass. [21] Appl. No. 832,540 [22] Filed May 8, 1969 [45] Patented Oct. 26, 1971 [73] Assignee Arthur D. Little, lnc.

Cambridge, Mass.

[54] PHOTOSENSITIVE ARTICLE AND METHOD OF USING SAME INCORPORATING LEUCO DYE PRECURSORS AND FLUORESCEIN ACTIVATORS 30 Claims, 4 Drawing Figs.

52 US. Cl 96/90, 96/27, 96/48 [51] Int. Cl G03c 1/52 [50] Field of Search 96/90, 88, 27, 48

[56] References Cited UNITED STATES PATENTS 3,112,200 ll/l963 Wainer 96/90 Primary Examiner-Norman G. Torchin Assistant Examiner-Won H. Louie, Jr. Attorney-Bessie A. Lepper PATENIEDBBI 26 I971 Fig.4

Ian D. Robinson Joonne C. Gerloch Richard P. Muse INVENTORS AHorney methane,

EIIOTOSENSITIVE ARTICLE AND METIIOD OF USING SAME INCORPORATING LEUCO DYE PRECURSORS AND FLUORESCEIN ACTIVATORS CROSS-REFERENCES TO RELATED APPLICATIONS In two copending applications we have disclosed two other printout systems. These applications are Ser. No. 822,990 filed May 8, 1969 directed to combinations of dior triarylxanthene, thioxanthene, selenaxanthene, anthracene and acridine dye precursors with quinone activators; and Ser. No. 823,065 filed May 8, 1969 directed to combinations of leuco esters of indigoid dyes and activators.

This invention relates to a photographic method and article and more particularly to a direct printout photographic system suitable for making black-and-white and monochrome copies from negatives and to processes and articles which involve as at least one step or product the making of a photographic copy from-a negative. The system of this invention is particularly suitable for making microfilm blowup copies.

There is, of course, a large body of prior art concerned with the general fields of producing positive prints or transparencies from negatives or transparencies. This body of prior art includes the use of silver halide emulsions with their attendant darkroom processing techniques as well as several negative diazo processes, some of which require development with ammonia. However, since these prior art techniques are completely distinguishable from that of the present invention, they need only be considered with regard to their use in microfilm blowup processes. The prior art which is more closely associated with this invention is set forth in a series of US. Pat. Nos. among which may be listed U.S. Pat. Nos. 3,113,024, 3,121,632, 3,121,633, 3,140,948, 3,140,949, 3,272,635, 3,284,205, 3,285,744, 3,342,595, 3,342,602, 3,351,467 and 3,377,167. These patents describe a number of photosensitive printout systems employing a light-sensitive combination of leuco bases of dyes and a number of different activators. Exposure of these light-sensitive materials activates the leuco bases to form the dyes in those areas exposed to light of a predetermined wavelength range. The unexposed areas remain the color of the original photosensitive system, thus forming a contrast which gives rise to a copy or photograph. It is necessary, subsequent to exposure, to destroy remove or inactivate the leuco bases in the unexposed areas,

Printout systems of this type have certain marked advantages, among which may be listed the absence of graininess, the elimination of one or more development steps and rapidity of access. However, the prior art systems, although realizing these advantages at least in part, possess certain inherent disadvantages. As activators for the dye precursors, the prior art uses colorless components such as sulfur-containing compounds as organic sulfonyl halides, mercapto compounds, disulfides, thiourea or acyclic thioacetanilides; organic O= containing compounds such as alkyl, aryl, alkyl aryl, acyclic and heterocyclic ketones; carboxylic aliphatic and aromatic acids; carboxylic acid anhydrides; and nitrogen-containing compounds such as benzotriazoles and heterocyclic ketimides. Many of these activators used in-the prior art are toxic, noxious or both toxic and noxious to use. Some of them are sensitive only to ultraviolet activation while others are sensitive only to a limited range of the visible spectrum.

Since the photosensitive systems of this invention are particularly suited for making enlarged prints of microfilms, a very brief description of the prior art systems used for this purpose is in order. These include a wet diazo process which requires the use of ammonia, a dry diazo process which is relatively slow, a process based upon the use of a silver halide using a stabilization paper and involving wet processing which is expensive, a process requiring a silver nitrate bath, and several other processes based upon the formation of electrostatic or electromagnetic images which must be toned. None of these prior art processes combines all of the desired features (rapidity of access, ease of handling, elimination of noxious and/or toxic fumes, dry processing and low cost) which are sought in a system for producing microfilm blowups.

It would, therefore, be desirable to have a printout photographic system which retained all the advantages inherent in such a system and which at the same time is capable of overcoming at least some of the more restrictive disadvantages associated with the prior art systems.

It is, therefore, a primary object of this invention to provide a light-sensitive, printout photographic system which is capable of providing a sharp, grainless copy of rapid access. It is another object of this invention to provide a light-sensitive system of the character described which can be chosen to be nontoxic and to eliminate any noxious or unpleasant aspects in its formulation, application to a substrate, use and developing. It is yet another object to provide such a system which is particularly suitable for microfilm blowup prints.

Itis another primary object of this invention to provide a method of photography or photocopying which is capable, through the choice of dyes and structure of the light-sensitive system, of producing prints or transparencies in black-andwhite and monochrome.

It is another primary object of this invention to provide photosensitive articles of the character described and methods of using them which are simple to formulate and use and which may be relatively inexpensive. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

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

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

FIG. 1 is an enlarged cross section of the light-sensitive system of this invention applied to a substrate to form a photosensitive sheet;

FIG. 2 illustrates the step of exposing the photosensitive sheet of FIG. I to a negative for copying by direct contact;

FIG. 3 illustrates the formation of the image made by the exposure illustrated in FIG. 2; and

FIG. 4 is a diagram illustrating the formation of a copy by projection.

The photosensitive printout system of this invention may be defined as one which comprises a leuco base of a class of dyes which includes diand triarylmethanes, xanthenes, thioxanthenes, selenaxanthenes, anthracenes and acridines, and a colored photoreducible dye containing halogen substituents as the activator. More specifically, these activators are compounds which are reduced when exposed to a predetermined wavelength range of the electromagnetic spectrum. This wavelength range extends from ultraviolet through the visible spectrum, not all combinations of dye precursor and activator being sensitive over the entire range.

The dye precursors usable in the photosensitive system of this invention may be defined as leuco bases of certain dyes, namely those generally referred to as the dior triarylmethanes, the xanthenes, thioxanthenes and selenaxanthenes, the dihydroanthracenes and the acridines.

The leuco bases of the diand triarylmethane dyes may be represented by the general formula I wherein R, is H, alkyl, aralkyl or aryl and may be the same or different R is H, aryl, alkyl, or Ra wherein 3 R is H or N\ R being the same as defined X and Y are H or water-solubilizing functional groups such as SO Na, OH, OCH;,, NHSO R and the like.

The leuco bases of this group of dyes give rise, upon oxidation, to a wide range of colors. Typical leuco bases of this group include, but are not limited to leuco crystal violet, leuco opal blue, leuco malachite green, leuco rosaniline, leuco pararosaniline, p,p',p"-trimethyl leuco opal blue, p,p,ptrichloro leuco opal blue and p,p'-bis(dimethylamino)diphenyl methane.

A second group of dyes, the leuco bases of which are suitable as dye precursors for the photosensitive system of this invention, may be considered to be generally similar in structure to the diary] methanes and are characterized by the presence of one or more bridging atoms to join the two phenyl groupings. Such leuco dye bases may be represented by one of three general formulas II, III or IV:

4 X 4 R4 X Y R \N Z N/ \N /Z\ N R4 \R4 114 R4 0 Rs \H H II III X Y HO- Z\ OH \C/ H/ \R5 where R; is H, lower alkyl, or aryl and may be the same or different R is H, alkyl, aryl or N wherein R is H, alkyl, aralkyl or aryl X and Y are the same as in Formula I 1 Z 1s O, S, Se, orNH C\ where R is H or alkyl When in formula [I Z is O, the leuco dye base is a xanthene; when Z is S, the leuco dye base is a thioxanthene; and when 5 5 I Z is the leuco base is a dihydroanthracene.

The following dyes may be cited as exemplary of this group. This list is illustrative and not meant to be limiting:

3,6-bis(dimethylamino)-9 (p-dimethylaminophenyl) xanthene 3,6-bis(diethylamino)-9-(p-dimethylaminophenyl) xanthene The leuco bases of a final group of dyes, the acridines, may be used as the dye precursors. They may be represented by the general formula V:

dyes well known in the art as photoreducible dyes (see for example Light-Sensitive System" by J aromir Kosar, John Wiley & Sons, Inc., New York, 1965, pp. l84l87). The photoreducible dyes suitable for the practice of this invention are halogen-substituted fluorescein derivatives having the following general formula where X is H,Cl, Br or] Y and Z are H, Cl, Br, I or SO X' X is H or an alkali metal ion Y' is H, Cl, Br, I, CO X' or SO X' Z is H, Cl, Br, I, OH or SO X As examples of suitable activators we may cite the following X Y Z X Y Z eosin YB Dr H Na H H erylhrosin B l l H Na H H phloxine B Br Br Cl Na Cl Cl rose bengal I 1 Cl Na Cl Cl solvent red 72 Br H H Na H H chromoxane brilliant Br Br H H CO,H OH

red RD Although we do not completely understand the mechanism by which these halogenated photoreducible dyes behave so effectively as activators in the photosensitive system, it is possible that the presence of the relatively heavy halogen substituent atoms enhances triplet formation in the exposure of the system to radiation. Energy transfer from the long-lived triplet of the activator to the dye precursor may lead to dye formation.

In forming the photosensitive system of this invention, the mole ratio of activator to dye precursor may range from about 0.01 to l to about to l, with about 0.1 to 1 being typical and generally preferred. The activator-dye precursor ratio employed will, of course, depend upon the activator-dye precursor system as well as upon the performance characteristics desired from the photosensitive system. Generally it will be desirable to use the minimum amount of activator compatible with the access speed required since this minimizes the amount of obscuring color contributed by the activator which may have to be removed or decolorized in one of the ways to be described.

In compounding the photosensitive composition, it may also be desirable to incorporate one or more additives. For exam-- ple, such additives may include, but are not limited to, plasticizers for the binder, agents to control the coating properties, and compounds capable of color filtering. In addition, encapsulated fixing precursors may be included for thermal or mechanical release (e.g., application of heat or pressure to break the capsules) after exposure. Inasmuch as activation of the system is by oxidation, it may also be desirable to include inhibitors and stabilizers such as free radical traps and antioxidants. Many free radical traps and antioxidants are known, among which may be listed phenols, aromatic amines, sulfur compounds and polyfunctional acids. Specific compounds which are illustrative of such a class of additives include, but are not limited to, 2-t-butyl-4-hydroxy-anisole, 3-t-butyl-4- hydroxyanisole, propyl gallate, 2,6-di-t-butyl-p-cresol, zinc dimethyldithiocarbamate and zinc dibutylphosphorodithioate.

The photosensitive system (dye precursor plus activator) will generally be affixed to a substrate through a film-forming binder. This is most conveniently done by forming a solution of the binder along with any additives such as plasticizers, etc., in a suitable solvent and then adding the dye and activator to the solution under conditions of temperature and exposure to light which will not effect any premature activation of the dye precursor. The film-forming binder must not, of course, have any adverse effects on the ability of the desired electromagnetic radiation to generate the dye.

A number of film-forming resins may be used as the binder; and the preferred one is nitrocellulose applied as a solution in acetone. Other suitable binders include, but are not limited to, polystyrene, ethyl cellulose, Carbowax 6000 (a polyethylene glycol sold by Union Carbide and Carbon Corporation), cellulose acetate butyrate and polyvinyl acetate. The solvent system chosen must also be a solvent for the activator and must, of course, be compatible with the binder. Typical solvents include, but are not limited to, acetone, toluene, methylene chloride, and mixed solvents such as toluene/tetrahydrofuran and benzene/acetone.

It is also within the scope of this invention to apply a solution of the dye precursor and activator (with any desired additives) to a substrate such as an absorptive paper without a binder, relying on at least the surface of the paper to contain and hold the photosensitive system.

The concentration of the dye and activator in the solution of the film-forming material will be governed by the final coating weight desired and the technique used to apply the coating solution to the substrate surface. The coating weight in turn will generally influence the image quality and it may have some control the speed of the photosensitive system. In general, the heavier the coating weight the greater will be the intensity of the copy. The optimum coating weight will also depend upon the solubility of the dye precursor and the extinction coefficient of the photosensitive system. It may be desirable in the case of difficulty soluble dye precursors'to apply more than one coat to the substrate. A preferred final coating weight range is between about lXlO" to lXlO" grams of dye precursor/square centimeter.

The concentration of the dye precursor in the coating solution will depend upon the coating technique used and the final coating weight desired; while the amount of activator present will, of course, be governed by the selected mole ratio of activator to dye as defined above.

The thickness of the liquid coating at the time of application to the substrate may vary over a wide range and will also be governed by the final coating weight desired, the solids concentration of the coating solution and the method by which the coating is accomplished. These parameters may readily be balanced and determined for any given system.

The coating composition may be applied to the substrate by any suitable, well-known coating technique including roller coating, spraying, brushing, knife coating, and the like. Coating and drying must, of course, be accomplished under conditions which will not cause any premature activation of the dye precursor.

The substrate material will, of course, be chosen to give the characteristics desired in the final photograph or photocopy, and such materials are well known in the art. Thus, for example, if prints or photocopies are desired, the substrate will be an opaque paper material, typically a photographic print paper with satisfactory dimensional stability and reflection characteristics. If on the other hand the final product is to be a transparency, then the substrate will be a transparent film, typically of a synthetic resin. The substrate may be flexible or nonfiexible as desired, and if a protective or barrier film is interposed between the substrate and the photosensitive film, little attention need be given to the chemical characteristics of the substrate.

The interposition of an intermediate layer between the substrate and the photosensitive film may be desirable for one or more of a number of reasons. This intermediate layer may be a coating of the same film-forming material used for forming the photosensitive layer or it may be formed of any other suitable type of material. It may serve as a barrier to prevent unwanted chemical components of the substrate from making contact with the photosensitive layer or to prevent undesirable absorption of the coating solution by the substrate. The intermediate layer may also be used to enhance the physical properties of the substrate such as to render it smooth or to make it more adhesive to the coating solution. The intermediate layer may also be used to enhance the optical properties of the photosensitive layer. As examples we may cite antihalation layers which are well known in the art and/or a layer of a material capable of absorbing light within a given wavelength range.

FIG. 1 illustrates, in somewhat diagrammatic cross section, a photosensitive article constructed in accordance with this invention. Such an article normally takes the form of sheet 10 formed of a substrate 11, an intermediate layer 12, and a photosensitive layer 13. The article of FIG. 1 would be particularly suitable for making black-and-white or monochrome copies or transparencies, depending on the characteristics of the substrate 11. Thus, if the substrate I1 is an opaque sheet, the final result will be a photocopy or a print, while if the substrate ll is, for example, a transparent film, the final copy will be a transparency. As explained above, the intermediate layer 12 is optional and may be used to perform one or more of several functions. Similarly, the photosensitive layer 13 may be covered, such as with an antiabrasion coating 18.

FIG. 2 illustrates the manner in which a photosensitive sheet such as that shown in FIG. I may be used to form a copy of a negative 14 having a dark or opaque background [5 (indicated by cross-hatching) and light or transparent indicia [6, an arrangement such as would be found in a microfilm. The photosensitive sheet 10 with the photosensitive layer 13 in contact with the negative '14 is exposed to a suitable light source, in this example a source 17 of visible light. The visible light frornsource 17 will, of course, be transmitted through the light or transparent indicia areas 16 to strike the photosensitive layer l3 and to activate the dye precursor in those areas which are thus exposed. However, since the visible light is not transmitted through the dark or opaque areas of background 15, the dye precursor in these areas remains unactivated. The result is the copy illustrated in FIG. 3 wherein the numeral 20 designates the activated or colored indicia areas corresponding to the light or transparent areas of the negative. The light, unactivated areas 21 correspond directly to the opaque background of the negative. As will be described in the examples, it is necessary to fix the dye precursor in the unactivated areas 21 to render it insensitive to light. Since the activator is also colored, it may also be desirable to remove or decolorize it.

Because the photosensitive system of this invention is free of any graininess, it is particularly suited for making enlarged copies from microfilms without loss of definition. The projection optics for achieving such enlargements are well known and not part of this invention. A suitable arrangement is, however, represented diagrammatically in FIG. 4. Radiation from light source 17 is directed by means of a lens 22 (or other optical device) through the microfilm 14 (in negative form) containing an image and then through a projection lens or lenses 23 onto the photosensitive sheet 10. The extent to which the original image is enlarged is well within the skill of the optical apparatus designer.

Since the exposed photosensitive sheet or surface contains areas having inactivated dye precursors and activators, and since these dye precursors are gradually or even relatively rapidly activated by ambient light, it is necessary to fix the photocopy or transparency by removing or inactivating the dye precursors in those areas. It may also be desirable to remove or decolorize the activators in the same areas to minimize or eliminate any color contributions which they make to the background (unexposed) areas of the copy.

In fixing the copy, that part of the dye precursor which has not been activated may be removed, destroyed or inactivated. Removal is most conveniently achieved by a solvent rinse, the solvent serving to wash out the dye precursor. The solvent must, of course, be a nonsolvent for the dye so that the dye image is not removed. A typical solvent rinse for a leuco base dye precursor is a suitably balanced mixture of acetone, toluene and petroleum ether.

Destruction of the dye precursor may be accomplished through a chemical reaction which converts the dye precursor to a colorless, light-insensitive compound or which converts it to a compound removable or inactivatable by heat. Inactivation may also be achieved through inhibition, such as by the use of an antioxidant or an oxygen-barrier overcoat. The chemical reactant or reactants or inhibiting agents may be incorporated directly into the photosensitive layer at the time of its application to a substrate or applied subsequent to exposure. it may be a material which requires some heat to effect the necessary chemical reaction or inhibition, or it may be encapsulated, in which case the capsules may be broken either by pressure or by heat.

A number of antioxidants are known in the art, examples having been given in connection with the discussion on additives. As oxygen barriers we may apply a binder coating containing an inhibitor to the exposed photosensitive sheet. Typical inhibitors include ascorbic acid, l-phenyl-3-pyrazolidone, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butylphenol, N,N'-diphenyl-pphenylenediamine, ferric chloride, cobalt chloride, cobalt naphthenate and cobaltous thiocyanate.

It may, for aesthetic reasons, be desirable to remove or decolorize the colored activators. This may be accomplished by solvent removal using either the same or a different solvent used to remove the dye precursor. Any solvent used must, of

course, be a nonsolvent for the dye image formed. Destruction of the activators may be through reaction with a reducing agent encapsulated in the photosensitive coating composition or applied subsequent to exposure or through bleaching after the dye precursor has been fixed by one of the methods described. The steps of fixing the dye precursor and of removing or decolorizing the activator may be combined. It will generally be preferable, especially where the photosensitive product is to be used in more-or-less automatic equipment, to

choose a fixing technique which is rapid and dry" (i.e., which does not require the use of any externally applied liquid).

The following examples, which are meant to be illustrative and not limiting, are given further to describe the invention. All of the steps in the following examples were carried out under subdued light.

EXAMPLE 1 Sufficient acetone was added to a mixture of IO g. of nitrocellulose (Hercules RS5-6 seconds wet with 30 percent by weight isopropyl alcohol) and 5 g. of dibutylphthalate (plasticizer) to make g. of a standard binder solution. To 0.1 g. leuco crystal violet (dye precursor) dissolved in 8 ml. of the standard binder solution and 4 ml. of acetone was added each of the activators given below. Each solution was coated at 6-mil wet thickness on a smooth paper, dried and exposed to the light source indicated for l minute through a Kodak No. 2 silver step tablet (density range 0.05 to 3.05). In the use of this standard device for measuring photosensitivity the number of steps which have a discernible higher density than the unexposed portion of the photosensitive layer is a measure of its photosensitivity. This means, of course, that the greater the number of steps, the greater is the sensitivity of the system. The number of steps which could be distinguished from the background is given for each photosensitive system including a control which contained no activator.

T50-wntt tungsten lamp ll int-hes from surface 1 Example o. wt-(ie) A etivator None... 7 EosinYll... 0.023 l4 Eosin YB. 0.234 13 Erythrosin B, 0.031 11 lhloxine 8.... 0. 12

1 Light passed through a series of lenses in projector before striking the photosensitive surf-nee.

Fixing was done by three l-minute solvent rinses with 1:1:4 (by volume) mixture of acetoneztoluenezpetroleum ether. The pink color of the background of the fixed sheet of example l was removed by overcoating at l0-mil thickness with a solution of 0. 1 5 g. of citric acid and 0.23 g. of allyl thiourea in a mixture of 5 ml. of methanol and 5 ml. of the standard 'binder solution.

EXAMPLE 5 EXAMPLE 6 The composition of example 2 was coated at 6-mil wet thickness over a 2-mil binder precoat applied to a smooth paper substrate. The photosensitive coating was dried and exposed through a silver negative (transparency) to a SOO-watt photoflood lamp at a distance of 6 inches for 5 seconds to give a purple image on a red background. Fixing was accomplished as in examples l-4.

It will thus be seen that the photosensitive systems of this invention provide direct printout copies relatively rapidly and through the use of activators which are not noxious or toxic to formulate or use. Moreover, the systems are not subject to graininess and are adaptable to making relatively inexpensive blowups of microfilms.

We claim:

1. A photosensitive composition which prints out to form an image upon exposure to electromagnetic radiation, comprising in combination a dye precursor which is a leuco base of a dior triarylmethane, xanthene, thioxanthene, selenaxanthene, anthracene or acridine dye and an activator which is a halogen substituted fluorescein photoreducible dye of the general formula wherein X is H, Cl, Br or I; Y and Z are H, Cl, Br, I or SO X'; X is H or an alkali metal ion; Y is H, Cl, Br, I, CO X' or SO X; and Z is H, Cl, Br, I, OH or SO X.

2. A photosensitive composition in accordance with claim 1 wherein said dye precursor is leuco crystal violet.

3. A photosensitive composition in accordance with claim 1 wherein said dye precursor is 3,6-bis(dimethylamino)-9-(pdimethylaminophenyl) xanthene.

4. A photosensitive composition in accordance with claim I wherein said dye precursor is leuco pararosaniline.

5. A photosensitive composition in accordance with claim 1 wherein said activator is eosin YB.

6. A photosensitive composition in accordance with claim 1 wherein said activator is erythrosin B.

7. A photosensitive composition in accordance with claim 1 wherein said activator is phloxine B.

8. A photosensitive composition in accordance with claim 1 wherein said activator is rose bengal.

9. A photosensitive composition in accordance with claim 1 which is activated by ultraviolet radiation.

10. A photosensitive composition in accordance with claim 1 which is activated by visible light.

11. A photosensitive composition in accordance with claim 1 wherein the mole ratio of activator to dye precursor ranges between about 0.01 to l to about 10 to l.

12. A photosensitive composition in accordance with claim 1 wherein said composition is incorporated in a binder.

13. A photosensitive composition in accordance with claim 12 including a plasticizer for said binder.

14. A photosensitive composition in accordance with claim 12 wherein said binder is nitrocellulose.

15. A photosensitive composition in accordance with claim 12 wherein said binder is polystyrene.

16. A photosensitive composition in accordance with claim 1 including one or more additives serving as color filters, oxidation inhibitors and stabilizers, and fixing agents for said dye precursor.

17. A photosensitive composition in accordance with claim 16 wherein said additive is contained within capsules which may be broken by heating or through pressure.

18. A photosensitive composition in accordance with claim 16 wherein said additive is an encapsulated fixing agent for said dye precursor.

a. a substrate; and b, at least one layer of a photosensitive composition affixed to said substrate in a binder, said photosensitive composition comprising in combination 1. a dye precursor which is a leuco base of a dior triarylmethane, xanthene, thioxanthene, selenaxanthene, anthracene or acridine dye; and 2. an activator for said dye precursor which is a halogensubstituted fluorescein photoreducible dye of the general formula wherein X is H, Cl, Br or I; Y and Z are H, Cl, Br, I or So X X is H or an alkali metal ion; Y is H, Cl, Br, I, CO X or SO X'; and Z is H, Cl, Br, I, OH or SO X'.

20. A photosensitive article in accordance with claim 19 wherein said substrate is an opaque paper.

21. A photosensitive article in accordance with claim l9 wherein said substrate is an essentially transparent film.

22. A photosensitive article in accordance with claim 20 further characterized by having an intermediate coating layer interposed between said substrate and said layer of said photosensitive composition, said coating layer serving as a chemical barrier, as a modifier of the physical properties of said substrate, or as a modifier of the optical properties of said photosensitive composition.

23. A method of forming an image of a transparency by direct printout, characterized by exposing a photosensitive article through said transparency to electromagnetic radiation of a predetennined wavelength range, said photosensitive article comprising in combination a dye precursor which is a leuco base of a dior triarylmethane, xanthene, thioxanthene, selenaxanthene, anthracene or acridine dye and an activator which is a halogen-substituted fluorescein photoreducible dye, and fixing the image in the resulting print, said fluorescein dye being one having the general formula wherein X is H,Cl, Bror I; Y and Zare H,C1,Br,lorSO;,X';

X is H or an alkali metal ion; Y' is H, Cl, Br, I, CO X or SO X; and Z is H, Cl, Br, I, OH or SO X.

24. A method in accordance with claim 23 wherein said transparency is placed in contact with said photosensitive article.

25. A method in accordance with claim 23, wherein optical elements adapted to project and enlarge an image are placed ing comprises destroying the dye precursor which was not activated to form said image with a reactant capable of converting said dye precursor to a colorless, light-insensitive compound.

29. A method in accordance with claim 23 wherein said fixing comprises applying an oxygen-barrier overcoat to said print.

30. A method in accordance with claim 23 wherein said fixing comprises applying an overcoat comprising a mixture of citric acid and allyl thiourea dissolved in a binder solution.

Claims (30)

1. 2. A photosensitive composition in accordance with claim 1 wherein said dye precursor is leuco crystal violet.
2. 2. an activator for said dye precursor which is a halogen-substituted fluorescein photoreducible dye of the general formula
3. 3. A photosensitive composition in accordance with claim 1 wherein said dye precursor is 3,6-bis(dimethylamino)-9-(p-dimethylaminophenyl) xanthene.
4. 4. A photosensitive composition in accordance with claim 1 wherein said dye precursor is leuco pararosaniline.
5. 5. A photosensitive composition in accordance with claim 1 wherein said activator is eosin YB.
6. 6. A photosensitive composition in accordance with claim 1 wherein said activator is erythrosin B.
7. 7. A photosensitive composition in accordance with claim 1 wherein said activator is phloxine B.
8. 8. A photosensitive composition in accordance with claim 1 wherein said activator is rose bengal.
9. 9. A photosensitive composition in accordance with claim 1 which is activated by ultraviolet radiation.
10. 10. A photosensitive composition in accordance with claim 1 which is activated by visible light.
11. 11. A photosensitive composition in accordance with claim 1 wherein the mole ratio of activator to dye precursor ranges between about 0.01-to-1 to about 10-to-1.
12. 12. A photosensitive composition in accordance with claim 1 wherein said composition is incorporated in a binder.
13. 13. A photosensitive composition in accordance with claim 12 including a plasticizer for said binder.
14. 14. A photosensitive composition in accordance with claim 12 wherein said binder is nitrocellulose.
15. 15. A photosensitive composition in accordance with claim 12 wherein said binder is polystyrene.
16. 16. A photosensitive composition in accordance with claim 1 including one or more additives serving as color filters, oxidation inhibitors and stabilizers, and fixing agents for said dye precursor.
17. 17. A photosensitive composition in accordance with claim 16 wherein said additive is contained within capsules which may be broken by heating or through pressure.
18. 18. A photosensitive composition in accordance with claim 16 wherein said additive is an encapsulated fixing agent for said dye precursor.
19. 19. A photosensitive article suitable for exposure to radiant energy for forming an image by direct printout, comprising in combination a. a substrate; and b. at least one layer of a photosensitive composition affixed to said substrate in a binder, said photosensitive composition comprising in combination
20. 20. A photosensitive article in accordance with claim 19 wherein said substrate is an opaque paper.
21. 21. A photosensitive article in accordance with claim 19 wherein said substrate is an essentially transparent film.
22. 22. A photosensitive article in accordance with claim 20 further characterized by having an intermediate coating layer interposed between said substrate and said layer of said photosensitive composition, said coating layer serving as a chemical barrier, as a modifier of the physical properties of said substrate, or as a modifier of the optical properties of said photosensitive composition.
23. 23. A method of forming an image of a transparency by direct printout, characterized by exposing a photosensitive article through said transparency to electromagnetic radiation of a predetermined wavelength range, said photosensitive article comprising in combination a dye precursor which is a leuco base of a di- or triarylmethane, xanthene, thioxanthene, selenaxanthene, anthracene or acridine dye and an activator which is a halogen-substituted fluorescein photoreducible dye, and fixing the image in the resulting print, said fluorescein dye being one having the general formula
24. 24. A method in accordance with claim 23 wherein said transparency is placed in contact with said photosensitive article.
25. 25. A method in accordance with claim 23, wherein optical elements adapted to project and enlarge an image are placed between said transparency and said photosensitive article whereby the image of said transparency is optically projected as an enlargement onto said photosensitive article.
26. 26. A method in accordance with claim 23 wherein said fixing comprises removing at least the dye precursor which was not activated to form said image.
27. 27. A method in accordance with claim 26 wherein said removing comprises washing said print with a liquid which is a solvent for said dye precursor and a nonsolvent for the dye image formed.
28. 28. A method in accordance with claim 23 wherein said fixing comprises destroying the dye precursor which was not activated to form said image with a reactant capable of converting said dye precursor to a colorless, light-insensitive compound.
29. 29. A method in accordance with claim 23 wherein saId fixing comprises applying an oxygen-barrier overcoat to said print.
30. 30. A method in accordance with claim 23 wherein said fixing comprises applying an overcoat comprising a mixture of citric acid and allyl thiourea dissolved in a binder solution.

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