US3369902A

US3369902A - Lithographic plates sensitized with oxacarbocyanine and benzimidazole carbocyanine dyes

Info

Publication number: US3369902A
Application number: US459784A
Authority: US
Inventors: Abbott Thomas Irving
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1965-05-28
Filing date: 1965-05-28
Publication date: 1968-02-20
Anticipated expiration: 1985-02-20
Also published as: DE1572306A1; GB1141597A

Description

Feb. 20, 1968 T. I. ABBOTT 3,369,902

LITHOGRAPHIC PLATES SENSITIZED WITH OXACARBOCYANINE AND BENZIMIDAZOLE CARBOCYANINE DYES Filed May 28, 1965 EXPOSURE l2 EMULSION DEVELOP/N6 AGE/VT II////////////////) lO-SUPPORT F/G/ ALKALINE ACTIVATION, lNK/NG EXPOSURE 23 EMULSION (FOGGED) 22 EMULSION 2/ DEVELOP/N6 AGENT 20 SUPPORT THOMAS ABBOTT INVENTOR.

BY M

A T TORNE Y5 United States Patent 3,369,902 LITHOGRAPHIC PLATES SENSITIZED WITH OXA- CARBOCYANINE AND BENZIMIDAZOLE CAR- BOCYANINE DYES Thomas Irving Abbott, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed May 28, 1965, Ser. No. 459,784 19 Claims. (Cl. 96-76) ABSTRACT OF THE DISCLOSURE Spectrally sensitized photographic elements, useful in processes adapted to the production of lithographic printing plates, having materially increased speed relative to the use of cyanine, styryl or merocyanine dyes therein are obtained by the use of oxacarbocyanine dyes or benzimidazole carbocyanine dyes.

This invention relates to spectrally sensitized novel high speed photographic elements useful in processes adapted to the production of lithographic printing plates.

Lithographic printing plates and the printing therefrom on a lithographic printing press involves the use of a plate, the printing surface of which is differentially inkreceptive when moistened with water. Usually the plate includes oleophilic characters or designs which are receptive of greasy printing ink and hydrophilic areas which repel ink when moistened with water. Thus, the printing of the plate does not depend upon the printing characters being either substantially above or below the hydrophilic nonprinting surface as opposed to other plates such as relief or intaglio printing plates.

A great many processes have been suggested for preparing lithographic printing plates. A well-known process involves forming an oleophilic design on a hydrophilic surface by photographic means, e.g., by differentially hardening a light-sensitive organic colloid layer or a lithographic surface with actinic rays and removing the unhardened areas to bare the hydrophilic non-printing areas. In other processes a preformed design may be transerred from one. support to another to provide the requisite differentially ink-receptive element. Also, an oleophilic design may be formed photographically or by other means on a hydrophobic surface and the design used as a resist,

to convert the uncovered hydrophobic areas to hydrophilic areas, for example, by hydrolysis as in the case of cellulose ester printing plates.

A simple photographic method for preparing lithographic printing plates is described in E. C. Yackel and T. I. Abbott US. Patent 3,146,104, issued Aug. 25, 1964, which inolves formation of a developable silver halide image, as by means of exposure to a line or halftone subject, of a hydrophilic organic colloid-silver halide film such as a gelatino-silver halide sensitized plate, followed by silver halide development. No additional steps, such as etching or washing off the unhardened areas, are required for producing the plates. Moreover, the process in its various forms can be adapted to the production of positive plates from either positive or negative subjects.

US. Patent 3,146,104 thus includes the formation of a developable silver halide image by exposure to a subject of a silver halide emulsion layer and contiguous silver ice halide developing agent (developing agent present in the emulsion or a layer effectively adjacent thereto) which when oxidized in the development reaction in the presence of the hydrophilic organic colloid vehicle present in the silver halide emulsion layer, forms an oleophilic image (ink-receptive image), followed by treatment of the exposed emulsion with alkaline solution which may contain a developing agent if it is not present in the sensitive element, to initiate development of the exposed silver halide and the formation thereby of the oleophilic image areas receptive of printing ink. Upon inking the moistened plate and printing on a lithographic printing press, the desired lithographic reproduction, which will be negative to the original subpect will be obtained. If, however, a positiveworking plate is desired, the photographic element described above may contain, in addition, a fogged silver halide emulsion as the uppermost layer. This photographic element when exposed to a subject, and its contiguous silver halide developing agent is activated, the developing agent will react with the sensitive lower silver halide emulsion layer to form the negative image and the unused silver halide developing agent present in the unexposed areas of said sensitive lower silver halide emulsion layer will then migrate upward to the fogged surface silver halide emulsion layer and, when oxidized in the presence of the hydrophilic organic colloid present in this layer, will form an oleophilic image in the surface which is positive in respect to the original subject. A positive working plate also can be obtained by using a direct-positive emulsion such as those described in Kendall and Hill US. Patent 2,541,472 or Fallesen U.S. Patent 2,497,875. If desired, a positive working plate also can be obtained by processing the exposed plate first in a nontanning developer such as one containing hydroquinone and sulfite, exposing the undeveloped silver halide by flashing to white light and then processing in an alkaline solution containing, the developing agent which when oxidized in the development reaction in the presence of the hydrophilic organic colloid vehicle present in the silver halide emulsion layer forms an ink-receptive image.

A number of other ways are described in US. Patent 3,146,104 for providing the silver halide image which is developed to form the oleophilic image. For example, a silver halide complex image resulting from the transfer of silver halide in a silver halide diffusion transfer process can be developed to form the oleophilic image. Likewise silver halide images arising from the rehalogenation of silver images can be developed with the developing agents described below to yield the oleophilic images. It was also found possible to prepare a suitable planographic printing plate of the type described above by transferring the unused developing agent, after initial development of a silver halide image, to a receiving sheet comprising a hydrophilic organic colloid, e.g., gelatin, and which may also contain, as oxidizing agents, manganese dioxide or fogged silver halide on a suitable support. When the unused developer agent is transferred to receiving sheets of the type described above, it is oxidized in the presence of the hydrophilic organic colloid present to form the imagewise oleophilic areas used in forming a planographic printing plate. A further modification of the above procedure is to transfer the unused developing agent to a receiving sheet composed of a hydrophilic organic colloid layer on. a suitable support. This layer is then swabbed with a solution of a suitable oxidizing agent, e.g., ferric 3 chloride or ferric sulfate ethylene-diaminetetraacetic acid complex to oxidize the unused developer agent present in the receiver sheet apparently causing it to react-with the hydrophilic organic colloid layer and form the imagewise oleophilic areas.

It has been desired to increase the sensitivity of photographic elements utilized in the preparation of lithographic printing plates. Such increases in sensitivity should be obtained without any concomitant changes which would disadvantageously affect other sensitometric characteristics, e.g., contrast, or the use of said materials.

I have found that when the oxac'arbocyanine or benzimidazole carbocyanine dyes described hereinafter are in cluded in photographic elements of the type described in US. Patent 3,146,104, for example, an unexpectedly large increase in speed, i.e., at least 25 percent greater, is obtained relative to the use of cyanine, styryl or merocyanine dyes therein. Furthermore, the increase in speed is obtained without deleteriously affecting other photographic characteristics therein.

An object of my invention is to provide a new and improved spectrally-sensitive photographic element useful in the preparation of the lithographic printing plates.

Another object of my invention is to provide a new spectrally-sensitive photographic element of improved sensitivity useful in the preparation of lithographic printing plates.

Another object of my invention is to obtain highlysensitive materials of the type described hereinbefore without producing a concomitant decrease in photographic or lithographic quality.

A further object is to provide a new spectrallysensitive photographic element useful in the preparation of lithographic printing plates, said photographic element containing a dye selected from the oxacarbocyanine and benzimidazole carbocyanine dyes described herein and having greater sensitivity than said element sensitized with a cyanine, styryl or merocyanine dye.

Other objects will become apparent from a consideration of the following description and examples.

I have found that these and other objects of my invention can be obtained by including in photographic silver halide materials utilized in the preparation of lithographic printing plates, an oxacarbocyanine dye of the following general Formula I and/ or a benzimidazole dye of Formula II.

The oxacarbocyanine compounds employed in the practice of the invention have the formula:

wherein Q and Q each represents the non-metallic atoms necessary to complete a phenyl nucleus, R and R each represents an alkyl substituent, R represents hydrogen, a lower alkyl group or an aryl group, X is an anion such as Cl-, Br or SO and toluene sulfonate, including inner salts, for example, and Y represents sulfur, oxygen, nitrogen or selenium.

The benzimidazole carbocyanine compounds employed in the practice of the invention have the formula:

Cir

wherein A represents an alkyl substituent, Z represents or NR wherein R R and R each represents 'a lower alkyl group and wherein Q, Q, R R R and X have the meaning previously assigned to them.

The term alkyl as used herein, unless otherwise indicated, refers to an alkyl hydrocarbon group.

The phenyl nuclei represented by Q and Q can be unsubstituted or substituted. Substituents that can be attached to the phenyl nuclei represented by Q and Q include, for example, a halogen atom, such as a chlorine atom or a bromine atom, an alkoxy group such as methoxy, ethoxy, propoxy, isopropoxy or butoxy, an alkyl group such as methyl, ethyl, propyl, isopropyl or butyl, a hydroxy group, an amino group such as -NH an alkylamino group such as methylamino, ethylamino, propylamino or butylamino, a dialkylamino group such as dimethylamino, diethylamino, dipropylamino, dibutylamino, methylethylamino, methylbutylamino, or ethylbutylamino, an aryl group such as phenyl, chlorophenyl, bromophenyl, methylphenyl, ethylphenyl, methoxyphenyl, ethoxyphenyl, unaphthyl, B-naphthyl, 2-hydroxynaphthyl, Z-methoxynaphthyl, or 2- ethoxynaphthyl, a carbomethoxy group and a carbethoxy group. The substituents mentioned are intended to be illustrative and not limitative of the substituents that can be present on the phenyl nuclei Q and Q. The phenyl nuclei Q and Q when substituted can be substituted with the same or different substituents. Also, as shown hereinafter the phenyl nuclei Q and Q can have more than 1 substituent.

R and R can each be the same alkyl substituent or different alkyl substituents. Alkyl, carboxyalkyl, sulfoalkyl and sulfoalkoxyalkyl, for example, are illustrative of the alkyl substituents R and R can be. When R and R represent an alkyl group, preferably each represents an alkyl group having 1 to 4 cabon atoms such as methyl, ethyl, propyl, isopropyl and butyl, although each can be a higher alkyl group such as pentyl and hexyl. Illustrative of the carboxyalkyl groups represented by each of the members R and R are carboxymethyl, fl-carboxyethyl, 'y-carboxypropyl and B-carboxybutyl, for example. fi-sulfopropyl, 'y-sulfopropyl and 6-sulfobutyl are illustrative of the sulfoalkyl groups each of the members R and R can be.

,G-Sulfomethoxyethyl, B-(B-sulfoethoxy)ethyl, 'y- (fi-sulfoethoxy)propyl, ,B-(y-sulfopropoxykthyl and fi-(fi-sulfoethoxy)butyl, for example, are illustrative of the sulfoalkoxyalkyl groups each of the members R and R can be.

When R is a lower alkyl group it can be methyl, ethyl, propyl, isopropyl, butyl and isobutyl, for example. When R is an aryl group it can be phenyl, chlorophenyl, bromophenyl, methylphenyl, ethylphenyl, methoxyphenyl, ethoxyphenyl, .a-naphthyl, p-naphthyl, Z-hydroxynaphthyl, Z-methoxynaphthyl or 2-ethoxynaphthyl, for example.

Methyl, ethyl, propyl, isopropyl, butyl and isobutyl are illustrative of the lower alkyl groups each of the members R R and R can be.

Illustrative of the alkyl substituents A can be are lower alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl, for example, carboxyalkyl groups such as carboxymethyl, p-carboxyethyl, 'y-carboxypropyl and 6-carboxybutyl and dialkylaminoalkyl groups such as diethylaminoethyl and dimethylaminoethyl, for example.

Typical oxacarbocyanine dyes having the Formula I useful in my invention are set forth in the following tabulation. In these compounds R is hydrogen and Y is 0. Under the heading Q and Q are illustrations'of various substituents that can be attached to these nuclei. More than one substitutent can be attached to each of the nuclei Q and Q. Thus dichloro means that two chlorine atoms are attached thereto.

6 Q R1 R2 In the foregoing processes, the ink-receptive areas of the printing plates on a background of hydrophilic ma- I 322355 g f f i gfgi g f fi ggi terial are obtained by alkaline activation of asilver halide e hyl ethyl developmg agent in the presence of a hydrophilic orgamc zggggggi 5 colloid silver halide emulsion layer. The result is to form dichlorodichlorosulfopropyl sulfopropyl a silver image and oxidized developing agent 1n the region i ggggf g ffigf of development. The organic colloid of the emulsion phenylchlorosulfobutyl sulfobutyl layer may undergo some additional hardening at the same z g f g'g gf time. However, the hardening of the hydrophilic organic chlorobromosulfobntyl sulfobutyl COliOld layer in the region of development is incidental to gig? g ggg' gf gggf successful operation of the invention since some silver b r r obtrgmontigtiiyl n r u l halide developing agents, such as catechol, hydroquinone 3, 1% 3,, 2,1',, f i g and toluhydroqumone, which are known to be strong 17 arg n htlrllietli Sun b t 1 H b t 1 gelatin-tanning silver halide developing agents, are not ch10, 3 g; g gg 3 3 Y useful in the sensitive elements presumably because the q i fly y gy oxidation products formed in the presence of the hydroc p any Opmpy e y philic organic colloid silver halide emulsion layer do not Typical benzimidazole carbocyanine dyes having the form oleophilic images, whereas other closely related Formula II useful in my invention are tabulated hereinsilver halide deveolping agents such as chlorohydroquL after. 20 none, are quite useful in the process of the invention. Also,

Q Q, R1 R: Z A

dichloro diehloro sulfobutyl sulfobutyl NC2H5 ethyl dibromo dibromo sulfobutyl ethyl NC2H5 ethyl unsubstiunsubstisuliobutyl sulfobutyl NC;H5 ethyl tuted tuted CH3 4..." nnsubstidichloro methyl ethyl C/ earboxytuted methyl CH CH3 5 unsubstidichloro methyl ethyl 0 diethylaminotuted ethyl While the oxacyanine compounds employed in the practhe invention is operative with various hydrophilic ortice of the invention have been illustrated primarily with ganic colloid silver halide emulsions which have been respect to those compounds having the Formula I wheresensitized with an oxacarbocyanine orbenzimidazole dye. in Y is oxygen it will be understood that compounds The silver halide developing agents used in my invenwherein Y is sulfur, nitrogen or selenium can be prepared 40 tion should be capable of oxidation in the presence of the and are useful in carrying out the invention. Similarly, hydrophilic organic colloid present in the silver halide while the invention is illustrated primarily with respect to emulsion layer to produce an image receptive to greasy compounds wherein R is hydrogen it will be understood printing ink. The polyhydroxybenzene developing agents that compounds wherein R is lower alkyl or aryl can be substituted with halogen, a mono-cyclic aryl nucleus of the prepared and are useful in carrying out the invention. R benzene series or an alkyl group of at least 2 and preferin the benzimidazole carbocyanine compounds of the foreably from 2 to 6 carbon atoms have this property. The going tabulation is hydrogen. 1,2-hydroxybenzene developing agents substituted by halo- In one embodiment of the invention a photographic gen, a rnonocyclic aryl nucleus of the benzene series or emulsion containing an oxacarbocyanine dye is merely an alkyl group of at least 2 carbon atoms and preferably exposed to the subject in the presence of the developing 0 2 to 6 carbon atoms are particularly useful in the process. agent, followed by treatment with an alkaline solution Silver halide developing agents possessing the necessary inking the resultant plate and printing. Thedeveloping properties thus include certain polyhydroxybenzene deagent can be incorporated in the photosensitive material or veloping agents and esters thereof, such as pyrogallol and in the alkaline processing solution. If the photographic substituted polyhydroxybenzene developing agents, paremulsion used is an ordinary developing-out emulsion, the ticularly dihydroxybenzenes substituted with, for explate obtained is a negative with regard to the subject. By ample, halogen (e.g chlorine and bromine), an alkyl group use of direct positive emulsions, the plate obtained is a of at least 2 and preferably from 2 to 6 carbon atoms and positive. 7 a rnonocyclic aryl nucleus of the benzene series, e.g., In another embodiment of the invention wherein a posio-chlorohydroquinone, o-bromohydroquinone, 4-phenyl tive working plate is used, the same comprises a layer of 0 catechol, 4-t-butyl catechol, pyrogallol, 4-n-butylpyr0- a silver halide emulsion sensitized with an oxacarbocyagallol, nordihydroguaniaretic acid, 4,5-dibromocatechol, nine or benzimidazole dye and contiguous developing agent 3,5,6 tribromo 4 phenylcatechol and l-phenyl3-(N-n of the type mentioned. Superimposed on this emulsion is hexylcarboxamide)-4,[p({3 hydroquinolylethyl) phenyla fogged silver halide emulsion layer. After exposure, aZ0]-5-pyrazolone. Esters of such developing agents, e.g., activation oft he exposed plate with alkaline solution reformates and acetates of pyrogallol hydrolyze in alkaline sults in the formation of a negative image in the exposed solutions can be used in the processes of the invention. In regions of the negative emulsion layer, the residual silver certain cases it has been found to be advantageous to inhalide developing agent migrates to and then develops the clude with the polyhydroxybenzene developing agent such fogged emulsion in the positive regions thereby producing as pyrogallol, an auxiliary developing agent such as monoa positive oleophilic design at the surface of the sensitive 7 methyl-p-aminophenol or a 3-pyrazolidone, which latter element which takes printing ink and can be printed on a developing agents by themselves do not yield oleophilic lithographic printing press. Direct positive emulsions can images in the processes described, but which do appear I also be used in this embodiment of the invention if a negato act synergistically in combination with the polyhytive working plate is desired. Other specific embodiments droxybenzenes to yield oleophilic images. of my invention are described hereinafter. 7 In the accompanying drawings representative sensitive elements of the invention are shown in greatly enlarged cross-sectional view at various stages of the preparation of lithographic printing plates.

In FIG. 1 a negative-positive process is illustrated and in FIG. 2 is shown a positive-positive process contemplated by my invention.

In FIG. 1, layer of the element of Stage 1 represents a support such as paper, film base, etc., layer 11 is a hydrophilic organic colloid layer .such as gelatin containing the developing agent and a quantity of black colloidal silver or carbon black, etc. for antihalation protection, layer 12 contains a gelatino-silver halide emulsion sensitized with an oxacarbocyanine or benzimidazole dye, for recording the line or halftone image.

In the process of FIG. 1, after exposure to a subject as shown in area 13, followed by alkaline activation and inking, the element appears substantially as shown in Stage 2, area 14 being composed of silver and the reaction product of the oxidized developing agent and the hydrophilic organic colloid present in the sensitized silver halide emulsion layer produced in the development reaction, carrying the ink image 15, the undeveloped area 16 of layer 12 remaining hydrophilic and repellent of printing ink when moistened with water.

In FIG. 2 is shown a positive-positive system in Stage 1 of which the element includes a support 20 such as a paper or film support, layer 21 an antihalation hydrophilic colloid layer containing developing agent and black colloidal silver, carbon black, etc., layer 22 a hydrophilic organic colloid orthosensitized silver halide emulsion layer, and layer 23 a fogged silver halide emulsion layer. Upon image exposure in region 24 followed by alkaline activation and inking, the element appears substantially as shown in Stage 2, the silver halide developing agent of layer 21 which has not been utilized in developing the negative silver image in areas 24 of layer 22 having developed a positive silver halide image to silver in areas 25 of layer 23. The ink images 26 are accepted in areas 25 which are composed of silver and the reaction product of the hydrophilic organic colloid present in the silver halide emulsion layer and the oxidized developing agent. The remaining areas 27 are hydrophilic and repel printing ink when the plate is moistened in the lithographic printing press.

In the sensitive elements described the emulsion layers should be substantially hardened, particularly the outermost emulsion layer, e.g., layer 12 of FIG. 1 and layer 23 of FIG. 2, in order to prevent the alkaline activated and inked emulsions from adhering to printing blankets, printing paper, etc. For this purpose the emulsion should be as hard as a gelatin layer containing at least about 2 grams and preferably from about 2 to grams of dry formaldehyde per lb. of gelatin.

In a preferred arrangement of my invention, the developing agent is incorporated in a separate layer under the orthochromatically-sensitized, silver halide emulsion layer since this arrangement gives improved sharpness, latitude and better quality ink images than when developing agent is incorporated directly in the emulsion layer.

The following examples illustrate representative photographic elements and processes of my invention.

EXAMPLE 1 Two spectrally-sensitized, fine-grain silver chloride emulsions were treated in the following general manner:

Fine grain silver chloride emulsion containing 1 mole of Ag per 4350 cc Paraflin dispersion prepared as follows: g. molten parafiin dispersed in 400 cc. 10% photographic gelatin solution containing 5 cc. of 10% Alkanol B solution g III 4-phenyl catechol dispersion prepared as follows:

50 g. 4-pheny1 catechol dissolved in cc. di-

butylphthalate at 60-70 cc. dispersed in 500 cc.

10% photographic gelatin and 50 cc. 7 /2% saponin solution and passed through the colloid mill five times g 10.0 15% saponin solution g 1.0 10% formaldehyde solution g 1.0 Water cc 20.0

The above emulsions were coated at the rate of 6.5 grams per square foot on a film base and dried.

The films were exposed to a line negative, then activated for 20 seconds in a 4 percent solution of sodium carbonate monohydrate. Thereafter, the plates were placed in a lithographic printing press, inked in the conventional manner and about 50 copies were printed. The ink-receptive regions of the plates corresponded to the exposed regions 14 of FIGURE 1 and the prints obtained therefrom were positives of the subject used for making the original line negative. During the process of making the above printing plates, the following sensitometric characteristic comparisons were noted for Emulsions A and B.

In the above example, if desired, the developing solution may contain the silver halide developing agent rather than having the developing agent contiguous to the emulsion layer. In addition, in order to obtain an excellent degree of differentiation between the oleophilic and hydrophilic areas the printing surface may also contain a material such as ZnO, A1 0 carboxy lower alkyl hydroxy ethyl cellulose or polyacrylamide. Acidifying the plate surface after its alkaline image development and stop bath steps may be done with a conventional lithographic desensitizing etch formula such as a 0.05% H PO solution or the like.

EXAMPLE 2 Three radiation-sensitive elements having a structure substantially as shown in FIGURE 2, Stage 1, where prepared in the following general manner:

LAYER 21 room temperature 2025 C. Disperse the solution in:

10% gelatin solution grams 290 7.5% saponin solution ml 25 Water ml at 40 C., pass through well-cooled colloid mill three times and then coat it on a suitable paper support as follows:

Developer dispersion grams 400 3% gelatin solution containing 12.5 grams of neutral collodial silver per 454 grams of solution grams 400 15% saponin solution ml 20 2% formaldehyde solution ml 2.5 Water ml 27.5

.9 Coat at 40 C., at 11.7 grams per square foot.

LAYER 22 Silver chloroiodide emulsion containing 100 grams of gelatin per silver mole (mole weight 2.48 kg.) grams 2480 Sensitizing dye in ethyl alcohol 1 ml 300 10% gelatin solution ml 840 7% Triton X200 solution ml 90 10% formaldehyde solution ml 68 Water ml 222 This was coated at 5.35 ml. per square foot over layer 21.

LAYER 23 Layer 23 was coated from the following composition at 7.0 ml. per square foot of coating surface.

Silver chloride gelatin emulsion (3600 grams/ mole) 3 60 Water ml 200 Sodium hydroxide (0.25 N aqueous solution) ml 24 2% aqueous formaldehyde solution ml 4.6

The above mixture of ingredients was chemically fogged by holding 40 minutes at 40 C. with stirring. If desired, light or other known methods may be used for fogging the emulsion.

The following ingredients were then added to the Samples of the three elements were exposed to a line positive, processed for 60 seconds in a 4 percent aqueous sodium carbonate monohydrate solution, treated in a 2 percent aqueous acetic acid stop bath for 1 minute, squeegeed to remove excess liquid and run on a lithographic printing press using 0.1 percent phosphoric acid fountain solution. About 50 copies were obtained. The inked plate from which the copies were obtained appeared substantially as shown in FIGURE 2, Stage 2, of the drawings. In this procedure, the residual developing agent from the negative development step develops an image- Wise distribution of non-imagewise exposed silver halide in the originally fogged' layer 23.

During the process of making the above printing plates, the following sensitometric characteristic comparisons were noted for Emulsions C, D and E.

Relative Contrast; Development Speed Rate Emulsion O 100 Control Control. Emulsion D 398 Easter Higher. Emulsion E 447 do D0.

1 The three sensitive elements diifered in that one emulsion, Emulsion C, contained 150 mg. of 'the merocyanine dye of-ethyl- 5 [(3 ethyl 2(3H) benzoxazolylidene)isopropyl1dene1- rhodanine per silver mole; the second emulsion, Emulsion D, contained 600 mg. of the oxacarbocyanine dye, anhydro-5,5- dichloro 9 ethyl-3,3-di(3-sulfopr0pyl)oxacarbocyanine hydroxide, sodium salt per silver mole; and the third emulsion, Emulsion E, contained 100 mg. of anhydr0-5 ,5,6.6-tetrachl0- ro-1,1 diethyl 3,3-di (3-sulfobutyl)benzlmidazolocarbocyanine hydroxide per silver mole in addition to the oxacarbocyanine dye contained in Emulsion D.

velopment rate and in some cases even improve these characteristics.

EXAMPLE 3 The dyes 2,3-diethyl-4-methyloxathiazolocarbocyanine iodide and 3,3',9-triethyl-5,5'-diphenyloxacarbocyanine iodide were tested in the manner described in Example 2. They were found to yield increased speeds of, respectively, 26 percent and 400 percent relative to a control element. Thus, while oxathiacarbocyanine dyes yield slight increases in speed, the use of the oxacarbocyanine dyes is to be preferred.

EXAMPLE 4 In order to further establish the superiority .of the oxacarbocyanine and benzimidazole dyes of my invention over known sensitizing dyes of other types, the following experiments were performed:

A number of elements similar to that described in Example 1 were prepared. The sensitized emulsions, containing 500 mg. of the dyes listed below per mole of silver halide, were coated over the layer containing a 4-phenyl catechol dispersion, at mg. of silver per square foot.

Samples of these coatings were exposed on an Eastman Type, IB Sensitometer and processed for 1 minute in Kodak D-72 Developer (1:1), fixed, washed and dried.

The results obtained are tabulated hereinafter.

The following dyes are typical known merocyanine, styryl and cyanine dyes which do not fulfill the objects of my invention.

DYE I-STYRYL TYPE DYE IITHIACYANINE TYPE DYE III-THIACARBOCYANINE TYPE Merocyanine type CzHs DYE IV (a) H, (b) CH COOH DYE V (a) H, (b) CH-CH2COOH C )O OH II DYE VI Merocyanine type O=ON(b) C=CHCH=0 c=s l C 2H5 DYE VII z a 2 4 2 )2 H DYE VIII (b) C2115, (0) H DYE IX Merocyanine type H YO C 2S g C=CHC=C l T (b) s DYE X (a) CH (b) CH (g) CH COOH DYE XI (a) CH (b) H, (g) --CH COOI-I DYE XII 3, s s, (g) CH COOH DYE XIII (a) C H COOH, (b) CH (g) C H COOH Merocyanine type DYE XVII DYE XVIII 4 a s a 5 s 5 The following dyes are typical examplas of oxacarbocyanine and benzimidazole dyes which fulfill the objects of my invention.

1 2 DYE XIX Oxathiacarbocyanine type Oxacarbocyanine type l 6115, ($1) CuHa", (R) CH2CH2CHSO DYE XXVII C6H5 1) e s" CH -CH COO Oxabenzimidazolocarbocyanine type 2) (Re) 0 N C=CHCH=CHC (g1) \I\II 6:9/ (R) (R1) DYE XXVIII H, 1) 2 z z z a F (mcmcmcfisofi, (R2)C2H5, (11902115 DYE XXIX H, (:21) C12, (R) z z z z a (R1) CHaCHzCHsO (R2) 02115, (R3) 02m DYE XXX 1) 2, z s 1) z s,

( R CH CI-I COOH, R H

DYE XXXI 1 3 DYE XXXII Benzimidazolocarbocyam'ne type CzHs cz s CH2 ER E-CH2 Benzimidazo loindocarbocyanine type DYE XXXIII (a) CH COOH DYE XXXIV Dye Speed Increase Relative Remarks (Relative to Un- Number to Unsensitized Control sensitized Control) (log E Units) 0. 8O 0. 50 0. 15 Increased fog on incubation. 0. 63 Low contrast, increased fog on incubation. 0. 22 D0. 0 85 Do. 0. 75 Increased fog on incubation. O. 68 0. 15 Do. 0. 58 0.30 0. 60 0. 45 0. 65 0. 30 Do. 0. 50 0. 65 0. 43 1. 03 Less fog on incubation. 1. 32 1. 48 1. 30 1. 55 1. 46 1. 48 1. 40 1. 42 1. 22 1. 04 Do. 1. 26 D0. 1. 1. 1. 1.

The high-speed spectrally sensitized photographic emulsions of my invention may be utilized to advantage in various processes designed for the production of lithographic printing plates such as in the various transfer processes described in Examples 7-9 of US. Patent 3,146,104;

They may also be utilized in a positive-positive process in which an imagewise distribution of developable silver halide emulsion is processed to produce any oleophilic image at the surface of the emulsion layer as is described in the following example.

EXAMPLE The large speed differential obtained by the use of an oxacarbocyanine sensitized emulsion of my invention relative to the same emulsion sensitized with a merocyanine dye may be utilized to form a positive-positive process plate. Thus, when the merocyanine Dye III of Example 4 is added to a fine-grain silver chloride emulsion and the emulsion is exposed and processed and a relative speed of is assigned thereto, I have found that the same emulsion when sensitized with the oxacarbocyanine Dye XXIII of Example 4 yields a relative speed of 2510. Thus, the emulsion sensitized with Dye XXIII is 25 times faster than the same emulsion sensitized with Dye III. This large speed differential is then utilized in the following manner:

A paper support was coated with a gelatin-silver chloride photographic emulsion sensitized with Dye III of Example 4 to yield about 50 grams of gelatin, 20 grams of silver (as silver halide) and 4 grams of 4-phenyl catechol per 100 square foot. Over this slow-speed emulsion layer was coated a similar silver chloride emulsion but in which themajor amount of the colloid vehicle was alkali-soluble acid-insoluble cellulose ether phthalate and the sensitizing dye was Dye XXIII of Example 4. This latter, considerably higher-speed emulsion, was coated to yield 28 grams of colloid vehicle and 30 grams of silver per 100 square foot.

This photographic element was exposed to record a latent-image in only the high-speed outer emulsion layer after which development was carried out with a conventional Elon-hydroquinone developer until a visible negative silver image was obtained. Thereafter the lower emulsion was flashed to light through the negative image and development initiated with a 4 percent sodium carbonate monohydrate solution with the result that the 4- phenyl catechol caused tanning development of the silver halide emulsion in the positive region of the lower emulsion. Upon Washing the element with water the overlying negative emulsion layer was washed off leaving the positive oleophilic image at the surface of the emulsion on the paper support, which image was inked and printed litho graphically.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be elfected within the spirit and scope of the invention as described hereinbefore, and as defined in the appended claims.

I claim:

1. In a light-sensitive photographic element capable of use as a lithographic printing plate, comprising a support having thereon a gelatin layer containing a sufficient amount of a polyhydroxybenzene silver halide developing agent to develop the exposed silver halide in the lightsensitive layer above it, the oxidation product of which renders gelatin oleophilic, and over said gelatin layer an unfogged gelatino-silver halide emulsion layer hardened with a hardener such that the gelatin has a hardness equivalent to that of a gelatin layer hardened with about 2 grams to about 15 grams of dry formaldehyde per pound of gelatin, the improvement which comprises the spectral-sensitization of said emulsion layer by incorporating therein at least one dye selected from the class consisting of benzimidazole and oxacarbocyanine dye compounds and wherein the amount of spectral sensitizing dye present in said emulsion layer ranges from about 500 milligrams and upwards per mole of silver halide.

2. A photographic element according to claim 1 in which the oxacarbocyanine dye compounds have the formula:

wherein Q and Q each represents the non-metallic atoms necessary to complete a phenyl nucleus, R and R each represents an alkyl substituent, R represents a member selected from the group consisting of hydrogen, lower alkyl and aryl, Y represents a member selected from the group consisting of S, O, N and Se and X- is an anion, and the benzimidazole carbocyanine dye compounds have the formula:

wherein Q, Q, R R R and X- have the meaning given hereinbefore, Z represents a member selected from the group consisting of R and NR wherein R R and R each represents lower alkyl and A represents an alkyl substituent.

3. A photographic element according to claim 2 in which the silver halide developing agent is a member selected from the group consisting of a halogen substituted polyhydroxybenzene, a phenyl substituted polyhydroxybenzene and an alkyl substituted polyhydroxybenzene, said alkyl substituent COntaining 2 to 6 carbon atoms.

4. A photographic element according to claim 2 in which the dye is anhydro-l-carboxymethyl-S,6-dichloro- 3-ethyl-l',3,3 trimethylbenzimidazoloindocarbocyanine hydroxide.

5. A photographic element according to claim 2 in which the dye is anhydro-S,5,6,6-tetrach1oro-l,l-diethyl- 3,3-di(3-sulfobutyl)-benzimidazolocarbocyanine hydroxide.

6. A photographic element according to claim 2 in which the dye is anhydro 5,5'-dichloro-9-ethyl-3,3'-di(3- sulfopropyl) oxacarbocyanine hydroxide.

7. A photographic element according to claim 2 in which the dye is anhydro-S-chloro-9-ethyl-5-phenyl-3'- (3 sulfobutyl) 3 (3 sulfopropyl) oxacarbocyanine hydroxide.

8. A photographic element according to claim 2 in which the dye is anhydro-9-ethyl-5,5-dimethoxy-3,3'-di- (3-sulfopropyl) oxacarbocyanine hydroxide.

9. In a light-sensitive photographic element capable of use as a lithographic printing plate, comprising a support having thereon a gelatin layer containing a sufiicient amount of a polyhydroxybenzene silver halide developing agent to develop the exposed silver halide in the light- :sensitive layer above it, the oxidation product of which renders gelatin oleophilic, over said gelatin layer an unfogged gelatino silver halide emulsion layer and over said emulsion layer a fogged gelatino-silver halide emulsion layer hardened with a hardener such that the gelatin has a hardness equivalent to that of a gelatin layer hardened with about 2 grams to about 15 grams of dry formaldehyde per pound of gelatin, the improvement which comprises the spectral-sensitization of the unfogged silver halide emulsion layer by incorporating therein at least one dye selected from the group consisting of beuzimidazole and oxacarbocyanine dye compounds and wherein the amount of spectral sensitizing dye present in said emulsion layer ranges from about 500 milligrams and upwards per mole of silver halide.

10. A photographic element according to claim 9 in which the oxacarbocyanine and the benzimidazole carbocyanine dye compounds are as defined in claim 2.

11. A photographic element according to claim 10 in which the silver halide developing agent is a member selected from the group consisting of a halogen substituted polyhydroxybenzene, a phenyl substituted polyhydroxybenzene and an alkyl substituted polyhydroxyben zene, said alkyl substituent containing 2 to 6 carbon atoms.

12. A photographic element according to claim 9 in which the dye is anhydro-l-carboxymethyl-5,6-dichloro- 3 ethyl 1',3,3' trimethylbenzimidazoloindocarbocyanine hydroxide.

13. A photographic element according to claim 9 in Which the dye is anhydro-5,5',6,6'-tetrachloro-l,1-diethyl- 3,3 di(3 sulfobutyl) benzimidazolocarbocyanine hydroxide.

14. A photographic element according to claim 9 in which the dye is anhydro-5,5-dichloro-9-etl1yl-3,3-di(3- sulfopropyl) oxacarbocyanine hydroxide.

15. A photographic element according to claim 9 in which the dye is anhydro-S-chloro-9-ethyl-5'-phenyl-3'- (3 sulfobutyl) 3 (3 sulfopropyl) oxacarbocyanine hydroxide.

16. A photographic element according to claim 9 in which the dye is anhydro-9-ethyl-5,5'-dimethoxy-3,3-di- (3 sulfopropyl)oxacarbocyanine hydroxide.

17. A lithographic printing process which comprises (a) exposing to a subject a photographic element comprising a support having thereon an unfogged gelatinosilver halide emulsion layer containing at least one spectral sensitizer selected from the oxacarbocyanine dyes having the formula set forth in claim 2 and the benzimidazole carbocyanine dyes having the formula set forth in claim 2 and wherein the amount of spectral sensitizing dye present in said emulsion layer ranges from about 500 milligrams and upwards per mole of silver halide and hardened with a hardener such that the gelatin has a hardness equivalent to that of a gelatin layer hardened with about 2 grams to about 15 grams of dry formaldehyde per pound of gelatin; (b) developing said exposed emulsion layer with an alkaline solution of a silver halide developing agent selected from the group consisting of a halogen substituted polyhydroxybenzene, a phenyl substituted polyhydroxybenzene and an alkyl substituted polyhydroxybenzene, said alkyl substituent containing 2 to 6carbon atoms, the oxidation product of which renders gelatin oleophilic, to produce on said emulsion layer a printing surface in which the oxidation product of said developing agent is bound to the gelatin in the developed areas of the layer and has an oleophilic residue receptive of greasy printing ink, and (c) inking the developed areas with greasy printing ink and printing therefrom in a lithographic printing press.

18. A lithographic printing process which comprises (a) exposing to a subject a photographic element compris ing a support having thereon a layer containing a sufficient amount of a polyhydroxybenzene silver halide developing agent to develop the exposed silver halide in the lightsensitive layer above it, said silver halide developing agent being a member selected from the group consisting of a halogen substituted polyhydroxybenzene, a phenyl substituted polyhydroxybenzene, and an alkyl substituted polyhydroxybenzene, said alkyl substituent containing 2 to 6 carbon atoms, the oxidation product of which renders gelatin oleophilic and over said layer an unfogged gelatinosilver halide emulsion layer containing at least one spectral sensitizer selected from the oxacarbocyanine dyes having the formula set forth in claim 2 and the benzimidazole carbocyanine dyes having the formula set forth in claim 2 and wherein the amount of spectral sensitizing dye present in said emulsion layer ranges from about 500 milligrams and upwards per mole of silver halide and hardened with a hardener, such that the gelatin has a hardness equivalent to that of a gelatin layer hardened with about 2 grams to about 15 grams of dry formaldehyde per pound of gelatin, and (b) developing said exposed emulsion layer with an alkaline solution to produce on said emulsion layer a 17 printing surface in which the oxidation product of said developing agent is bound to the gelatin in the developed areas of the layer and has an oleophilic residue receptive of greasy printing ink,

19. A lithographic printing process which comprises (a) exposing to a subject a photographic element comprising a support having thereon a layer containing a sufficient amount of a polyhydroxybenzene silver halide developing agent to develop the exposed silver halide in the lightsensitive layer above it, said silver halide developing agent being a member selected from the group consisting of a halogen substituted polyhydroxybenzene, a phenyl substituted polyhydroxybenzene and an alkyl substituted polyhydroxybenzene, said alkyl substituent containing 2 to 6 carbon atoms, the oxidation product of which renders gelatin oleophilic and over said layer an unfogged gelatinosilver halide emulsion layer containing at least one spectral sensitizer selected from the oxacar-bocyanine dyes having the formula set forth in claim 2 and the benzimidazole carbocyanine dyes having the formula set forth in claim 2 and wherein the amount of spectral sensitizing dye present in said emulsion layer ranges from about 500 milligrams and upwards per mole of silver halide, and over said emulsion layer a fogged gelatino-silver halide emulsion layer hardened with a hardener, such that the gelatin has a hardness equivalent to that of a gelatin layer hardened with about 2 grams to about 15 grams of dry formaldehyde per pound of gelatin, and (b) developing said exposed emulsion layer containing said developing agent with an alkaline solution to produce on said fogged emu1- sion layer a printing surface which is positive with respect to the original subject and in which the oxidation product of said developing agent is bound to the gelatin of the fogged emulsion layer in the areas corresponding to unexposed areas of the layer and has an oleophilic residue receptive of greasy printing ink.

References Cited UNITED STATES PATENTS 2,921,067 1/1960 Larive et al 96-106 3,146,104 8/ 1964 Yackel et al 96-33 3,264,110 8/1966 Depoorta et al. 96-106 J. TRAVIS BROWN, Acting Primary Examiner.

NORMAN G. TORCHIN, Examiner.

R. E. MARTIN, Assistant Examiner.