US3480433A - Thermally activatable diazotype compositions - Google Patents

Description

United States Patent Int. Cl. G03c 1/58 US. Cl. 96-49 17 Claims ABSTRACT OF THE DISCLOSURE Substituted s-triazinyl-thioketones and triazinyl ketones are couplers in thermally developable photographic elements incorporating diazonium compounds as the lightsensitive component, which development does not require additional alkali or alkaline release materials.

The scope of this invention is described by the following specification and claims.

This invention relates to photography and in particular to light-sensitive, thermally activatable diazotype compositions, to heat-developable photographic elements wherein such diazotype compositions constitute the light-sensitive material, and to a thermal process for producing images upon such photographic elements.

It is known that diazotype compositions are useful for image reproduction purposes, such utility being derived from the fact that diazo compounds (aromatic diazonium salts in particular) are lightsensitive. When exposed to light, diazo compounds are destroyed to the extent that they can no longer form a dye by reacting with a coupling component. It is currently believed that where light energy impinges upon a surface coated with a diazotype composition, the diazo compound reacts to form a compound having the corresponding hydroxylated moiety at the sight of the diazo moiety. In those areas where light energy is prevented from striking the surface, this diazo destruction reaction does not take place. During the development of an imagewise exposed photographic element in which a diazotype composition constitutes the lightsensitive component, the unexposed diazo compound reacts with the coupling component under alkaline conditions to form a dye image which is a positive reproduction of the original.

Commercially useful photographic elements incorporating diazotype compositions as the light-sensitive material typically require development according to one of two well-known types of processes, the miost (or semi-dry) process and the dry process.

The moist process involves a one-component system. The light-sensitive photographic element is prepared by coating a support material with a diazo compound and other materials such as an acidic stabilizing agent. There is no coupling component present in the coating. A photographic element so prepared is exposed to a light source through the original which is to be copied. Development is accomplished by treating the exposed element with an alkaline solution comprising a coupling component and a pH adjusting agent, which development produces a dye image in the unexposed areas. Such developing solutions are generally corrosive and difficult to handle.

The above mentioned dry process avoids the corrosive nature of the alkaline medium developing solution of the semi-dry process and also provides a significant advantage by forming dry reproductions. To prepare a photographic element suitable for use in the dry process, a support material is coated with a diazo compound or compounds in combination with one or more coupling comice ponents and preferably with other known additives, such as acidic stabilizing agents. After exposure to a light source, as above described, the photographic element is developed by exposing it to an alkaline atmosphere. A typically utilized atmosphere is moist ammonia fumes. The dry process sutfers from the limitation that noxious ammonia fumes must be adequately stored, transported and vented out of the developing machine.

In order to overcome the limitations imposed by such corrosive developing solutions and noxious ammonia fumes, emphasis has been placed on processes involving thermal activation of alkali-releasing agents. Accordingly, heat activated alkali-releasing agents have been included in the diazotype composition. Such a. composition, incorporating a heat activated alkali-releasing agent, can be coated onto a support material. Alternately, such an alkali-releasing agent can be used independently in the developing machine. In either case, the application of heat causes the agent to decompose with the attendant formation of an alkaline material, thus triggering the coupling reaction. For example, ammonium carbonate, bicarbonate, acetate and formate generate ammonia when heated. Also, ureas, thioureas, and organic amines have been suggested with varying degrees of success. These known alkali-releasing agents, however, tend to cause crystallization and to reduce the effective storage life of the photographic element incorporating a diazonium compound as the lightsensitive component. Moreover, continued safeguards have been required to properly control the alkali released in the developing machine.

Accordingly, it is an object of this invention to provide, for photographic purposes, a novel, thermally activatable diazotype composition which does not require either a separate alkaline atmosphere or separate alkali-releasing agent for coupling.

Another object of this invention is to provide, for photographic purposes, a new diazotype composition which couples upon the application of heat.

Still another object of the present invention is to provide, for photographic purposes, a new diazotype composition which when coated on a support is' susceptible of extended storage and is transparent, free from haze, nontacky and non-crystalline.

An additional object of this invention is to provide a novel photographic element which incorporates a diazotype composition in a light-sensitive layer and which photographic element is developable without either a separate alkaline atmosphere or a separate alkali-releasing agent.

Yet another object of the instant invention is to provide a new photographic element which incorporates a diazotype composition in the light-sensitive layer and which photographic element is developable solely upon the application of heat.

Yet an additional object of the present invention is to provide a novel photographic element which incorporates a diazotype composition as the light-sensitive component, and which diazotype composition is transparent, free from haze, and resistant to deterioration upon storage.

Still an additional object of the present invention is to provide a new thermal process for producing photographic images.

These and other objects of the present invention will become apparent from a consideration of the following specification and appended claims.

The objects of this invention are accomplished with diazotype compositions containing a light-sensitive diazo compound and a S-Substituted s-triazine as the coupler component.

The S-Substituted s-triazines which can be employed in the practice of the present invention include compounds having the formula:

wherein R is a monovalent radical such as a lower alkyl radical, a lower alkoxy radical or a lower cycloalkyl radical; and Z is a divalent atom such as sulfur or oxygen. Typically such lower alkyl radicals have 1 to 8 carbon atoms and include substituted alkyl radicals such as hydroxyalkyl radicals, for example, methyl, ethyl, npropyl, t-butyl, n pentyl, n-hexyl, n-heptyl, n-octyl, hydroxyethyl, l-hydroxyoctyl, etc. Typically such lower alkoxy radicals have 1 to 8 carbon atoms such as methoxy, ethoxy, n-propoxy, n-butoxy, n-octoxy, etc. Typically such lower cycloalkyl radicals have 4 to 8 carbon atoms and include cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl, with cyclohexyl being particularly useful.

Typical S-Substituted s-triazines used as couplers in the invention include:

S-methyl-tetrahydro-s-triazino-2 1H) thione,

-n-propyl-tetrahydro-s-triazino-2( 1H thione, 5-n-butyl-tetrahydro-s-triazino-Z( 1H thione, fi-n octyl-tetrahydro-s-triazino-Z-( 1H one, S-cyclohexyl-tetrahydro-s-triazino-2 1H thione, S-cyclohexyl-tetrahydro-s-triazino-2( 1H one, S-hydroxyethyl-tetrahydro-s-triazino-2( 1H)-thione, 5-n-hydroxyoctyl-tetrahydro-s-triazino-2( 1H thione, 5-n-hydroxyoctyl-tetrahydro-s-triazino-2 1H one, 5 -methoxytetrahydro-s-triazino-Z( 1H thione, S-n-butoxy-tetrahydro-s-triazino-Z( 1H one, S-octoxy-tetrahydro-s-triazino-Z-( 1H one, S-n-pentoxy-tetrahydro-s-triazino-2 1H thione,

and other like derivatives within the class described.

This 5-substituted-s-triazine coupling component precludes the need for either separate alkaline material or alkaline-release material in the developing process. Although the actual mechanism is not completely understood, it is believed that under the heating conditions of the developing process, the saturated triazine coupling component is rearranged or reacted into a molecular structure which is alkaline in character. Given such a shift, however, the coupling compound is not destroyed with respect to its coupling potential with the diazonium salt. Without rendering an exacting description of the kinetics of the reaction, it has been found that thermal activation of this coupling component in a diazotype composition results in a clear positive image developed on the support material without added alkaline materials.

The diazotype compositions of this invention comprise any of the usual diazo compounds (diazonium salts) suitable for producing images, which diazonium salts are well known in the art. They are light-sensitive and are stable at ambient temperatures and under conditions of mechanical agitation. Suitably, they are soluble in water or other common solvents. Additionally, the diazo compound should devolop into a dye having a sufliciently dark color to contrast with the background surface of the support.

The diazonium salts are preferably aromatic compounds having a diazo moiety attached directly to a carbon atom of the aromatic nucleus. The remaining valence bond of the diazo moiety is filled by a suitable cation such as halogen, phosphate, nitrate, borate, oxalate, citrate, and the like. The diazonium salts can be employed to advantage as the stabilized double salts such as metal halides and non-metallic fluorides. For example, zinc chloride, cadium chloride, stannic chloride, boron trifluoride and fiuoboric acid double salts are used. Exemplary of diazonium compounds useful in diazotype compositions of the invention are the diazonium salts resulting from diazotization of the following amines:

p-amin0-N,N-dimethylaniline, p-amino-N,N-diethylaniline, p-amino-N-ethylaniline, pamino-N-ethyl-N-fl-hydroxyethylaniline, p-amino-Nmethyl-N-p-hydroxyethylaniline, p-amino-N,Ndi-,8-hydroxyethylaniline, p-amino-m-ethoxy-N-N-diethylaniline, p-arnino-N-ethyl-o-toluidine, p-amino-N-ethyl-m-toludine, p-amino-N,N-diethyl-m-toluidine, p-a-mino-N-ethyl-N-benzylaniline, p-amino-N-ethyl-N-,8-hydroxyethyl-m-toluidine, N-p-amino-phenylmorpholine, p-amino-diphenylamine,

3-aminocar-bazole,

p-amino-N-methylaniline,

p-amino-N- 8-hydroxyethyl aniline, p-amino-N- 2,6-dibromobenzyl) aniline, p-amino-N-benzyl-N-ethylaniline, p-amino-N,N-dirnethyl-3-methy1aniline, p-amino-N-cyclohexyl-2-methoxyaniline, p-aminoN,N-di fi-hydroxyethyl) 3 -ethoxyaniline, p-amino-N-benzyl-Z,S-diethoxyaniline, p-amino-3-carboxy-N,N-diethylaniline, p-amino-Z-hydroxynaphthalene-4-sulfonic acid, p-arninO-N-mOrpholine-Z,S-dibutoxyaniline, and the like.

In a preferred embodiment of this invention, an acidic stabilizing agent is included in the diazotype composition to prevent premature coupling.

Acidic stabilizing agents are used to control the pH of the diazonium salt-coupling component admixture. Although elevated temperatures are required to fully activate the coupling reaction, it has been found that some coupling does take place after extended storage at ambient temperatures. The acidic agent restrains such premature coupling. Examples of useful organic and inorganic acidic stabilizing agents commonly employed for this purpose include citric acid, acetic acid, tartaric acid, oxalic acid, boric acid, succinic acid, crotonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, 3-nitrophthalic acid, phosphoric acid, sulfamic acid, and other sulfamic acid derivatives such as cyclohexylsulfamic acid.

Other substances can be incorporated in the diazotype compositions of the invention, for example, background stabilizers or materials for inhibiting discoloration of the image reproductions after they are made. These include thiourea, thiocinnamine, napthalene trisulfonic acid and the like. Other additives which can also be added are substances that are intended to reduce the tendency of the paper to curl, such as ethylene glycol, glycerol, or a polyethylene glycol; dyestutf image intensifiers such as metal salts, including, for example, zinc chloride, ammonium sulfate, nickel sulfate, and the like; coating aids such as colloidal silica and the like; a small amount of a wetting agent such as saponin, lauryl sulfonate, cetyl benzene sulfonate, the oleic acid amide of N-methyl taurine, and the like; and other known additives useful for known purposes in the present art.

The components of the present diazotype compositions can be admixed with a carrier or binder material prior to coatlng on a support material. Preferably, the carrier is capable of forming a film on the support after drying. EX- amples of such carriers include cellulose acetate, ethyl cellulose trimellitate, cellulose acetate phthalate, ethyl cellulose hexahydrophthalate, cellulose ether phthalate, cellulose acetate butyrate, cellulose butyrate, cellulose bu tyrate hexahydrophthalate, ethyl cellulose, cellulose propionate and the like. The carrier is generally dissolved in .5 a volatile solvent for ease of handling, such as methanol, acetone, dichloromethane and other well-known organic solvents.

The choice of a base or support material can be widely. varied; it is usually made on the basis of the requirements to be served. Generally, paper and plastics or resins in the form of films have found wide acceptance especially where the reproduction itself is to be used as a master. Particularly useful for work where the reproduction is to be used as a master are transparent polymeric films, such as polyethylene terephthalate, cellulose, cellulose triacetate, cellulose acetate butyrate, cellulose propionate, polycarbonates, polystyrenes, polysulfones, polyphenylene oxides, etc. Wood, metals, such as steel, copper, zinc, and aluminum, and ceramics, glass, and textiles are also useful as supports for the diazotype compositions of the invention. g

The components of the diazotype compositions, namely, the diazonium salt, the coupling component described, and other additives, are combined with the carrier as by mixing the components. The admixture may be coated onto the base in conventional manner as, for example, doctor blade, air knife, roller, or hand painting, followed by drying. It is noted that the dried coating typically forms a transparent, continuous film free of crystallization.

Coating proportions of the diazotype composition can be varied in accordance with usual practice. Useful results have been obtained in the range of between about .013.0 grams of dry diazotype composition per square foot of coated base surface.

In use, the coated support is imagewise exposed through an original pattern to a light source which pattern is disposed between the light and the sensitized base. Typically, the light energy is in the wavelength range of about 3,500- 4,500 A. After exposure, the base is heated within the temperature range sufiicient to cause a dye image to appear in the unexposed areas, giving a positive reproduction of the original pattern. Processing temperatures can be widely varied and are largely dependent on the materials used. However, usual operation is within the range of about ZOO-400 F. The upper temperature limit is essentially fixed by the deformation and decomposition temperature of the support material and the coating composition present thereon. Special care should be exercised when the support material is a plastic film such as cellulose acetate. The lower temperature is fixed by practical development time available, since lower temperatures reduce the activity of the coupling component.

Storage of the unexposed coated support of this invention does not substantially impair the quality of the image formed thereafter. In one stability evaluation, a coated cellulose acetate film was incubated for 3 days at 120 F. and 35% relative humidity. After exposure to a light source, the incubated coating was heat developed as described above, and the image produced was of substantially the same acceptable quality that of the non-incubated material.

In the examples of preferred embodiments of the invention that follow and elsewhere herein, proportions are expressed as parts by weight unless otherwise specifically stated.

EXAMPLE 1 A solution of 10 parts of cellulose acetate, 12 parts of methyl alcohol, and 56 parts of acetone is prepared. Into 25 ml. of this solution are admixed 0.5 gram of p-diazodiethylaniline zinc chloride, 0.5 gram of cyclohexylsulfamic acid, and 0.5 gram of -n-propyl-tetrahydro-s-triazino-2 (1H) thione. The admixture is coated onto a poly (ethyleneterephthalate) film base-to a wet thickness of about .003 inch, or about 1.5 grams dry weight per square foot and dried at about 20 C. The dry coating is transparent, clear (free from haze), hard (free from tack), and no crystallization is observed thereon. The dried coated film is image-wise exposed through a master to a light source rich in ultraviolet energy, and passed through a belt processor over a heated drum with a 10-second cycle. The drum temperature is kept at 330 F. A brown dye image of good quality is formed in the unexposed areas, giving a positive reproduction of the master.

EXAMPLE 2 The procedure of Example 1 is repeated except that the S n propyl tetrahydro s triazino 2 (1H) thione is replaced separately and in turn by 0.5 gram portions of other triazinyl compounds, namely,

5-methyl-tetrahydro-s-triazino-2 (1H) thione, S-n-propyl-tetrahydro-s-triazino-2 (1H) thione, 5-nbutyl-tetrahydro-s-triazino-2 (1H) thione, S-n-octyl-tetrahydro-s-triazino-2 (1H) one, 5-cyclohexyl-tetrahydro-s-triazino-2 (1H) thione, S-cyclohexyl-tetrahydro-s-triazino-2-(1H) one, S-hydroxyethyl-tetrahydro-s-triazino-2 (1H) thione, 5-n-hydroxyoctyl-tetrahydro-s-triazino-Z (1H) thione, S-n-hydroxyoctyl-tetrahydro-3-triazino-2 (1H) one, 5-methoxy-tetrahydro-s-triazino-2 (1H) thione, S-n-butoxy-tetrahydro-s-triazino-2 (1H) one, 5-n-octoxytetrahydro-s-triazino-2 (1H) one, and S-n-pentoxy-tetrahydro-s-triazino-2-(1H) thione.

Brown dye images of the same good quality of the image of Example 1 are obtained in the unexposed areas in each instance. 1

EXAMPLE 3 In a modification of Example 1, a paper sheet is used in place of the polyester film. A dye image of good quality is obtained in the paper, which dye image corresponds to the unexposed image area-s.

EXAMPLE 4 An image is made as in Example 1 except that the triazinyl compound used is 5-n-butyl-tetrahydro-s-triazino-Z- (1H) thione. This image-bearing film is in turn used as a master on a new second sample prepared as in Example 1. The resulting second generation dye image has characteristics essentially the same as the dye image of Example 1.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A thermally activatable light-sensitive diazo-type composition comprising:

(1) a light-sensitive diazonium salt;

(2) a coupling component having the general formula:

wherein R is a monovalent radical selected from the group consisting of a lower alkyl radical, a lower alkoxy radical, and a lower cycloalkyl radical, and Z is selected from the group consisting of a sulfur atom and an oxygen atom; and,

(3) an acidic compound employed to prevent the composition from precoupling.

2. A thermally activatable diazotype light-sensitive composition comprising:

( 1) an aromatic light-sensitive diazonium salt;

(2) a coupling component having the general formula:

wherein R is an alkyl radical having 1 to 8 carbon atoms; and, (3) an acidic compound employed to prevent the composition from precoupling. 3. A composition as described in claim 2 wherein the R substituent is an n-propyl radical.

4. A composition as described in claim 2 wherein the R substituent is an n-butyl radical.

5. A thermally activatable diazotype light-sensitive composition comprising:

(I) an aromatic light-sensitive diazonium salt; (2) a coupling component having the general formula:

wherein R is a hydroxyalkyl radical having 1 to 8 carbon atoms; and,

(3) an acidic compound employed to prevent the composition from precoupling.

6. A thermally activatable diazotype light-sensitive composition comprising:

(1) an aromatic light-sensitive diazonium salt; (2) a coupling component having the general formula:

S H C wherein R is an alkoxy radical having 1 to 8 carbon atoms; and,

(3) an acidic compound employed to prevent the composition from precoupling.

7. A thermally activatable diazotype light-sensitive composition comprising:

(1) an aromatic light-sensitive diazoniu-m salt; (2) a coupling component having the general formula:

wherein R is a cycloalkyl radical having 4 to 8 carbon atoms; and,

(3) an acidic compound employed to prevent the composition from precoupling.

8. A thermally activatable diazotype light-sensitive composition comprising:

(1) an aromatic light-sensitive diazonium salt;

(2) a coupling component having the general formula:

wherein R is an alkyl radical having 1 to 8 carbon atoms; and,

(3) an acidic compound employed to prevent the composition from precoupling.

9. A thermally activatable diazotype light-sensitive composition comprising:

( 1) an aromatic light-sensitive diazonium salt; (2) a coupling component having the general formula:

g HN NH H35 CH2 wherein R is a hydroxyalkyl radical having 1 to 8 carbon atoms; and,

(3) an acidic compound employed to prevent the composition from precoupling.

10. A thermally activatable diazotype light-sensitive composition comprising:

(1) an aromatic light-sensitive diazonium salt; (2) a coupling component having the general formula:

wherein R is an alkoxy radical having 1 to 8 carbon atoms; and,

( 3) an acidic compound employed to prevent the composition from precoupling.

11. A thermally activatable diazotype light-sensitive composition comprising:

( 1) an aromatic light-sensitive diazoniurn salt; (2) a coupling component having the general formula:

9 -cyclohexyl-tetrahydro-s-triazino-2 (1H) one, 5hydroxyethyl-tetrahydro-s-triazino-2 (1H) thione, S-n-hydroxyoctyl-tetrahydro-s-triazino-2 (1H) thione, 5-n-hydroxyoctyl-tetrahydro-s-triazino-Z (1H) one, S-methoxy-tetrahydro-s-triazino-Z (1H) thione, S-n-butoxy-tetrahydro-s-triazino-2 (1H) one, 5-n-octoxy-tetrahydro-s-triazino-2 (1H) one, and 5-npentoxy-tetrahydro-s-triazino-2 (1H) thione.

14. A thermally activata ble light-sensitive diazotype composition as described in claim 1 wherein the lightsensitive diazonium salt is an aromatic compound having a diazo moiety attached directly to a carbon atom of an aromatic nucleus.

15. A photographic element comprising a support having a layer coated thereon said layer comprising a thermally activatable light-sensitive diazotype composition as described in claim 1.

16. A photographic process for treating an imagewise exposed photographic element comprising a support having a layer coated thereon said layer being a thermally activatable light-sensitive diazotype composition compris- (1) a light-sensitive diazonium salt;

(2) a coupling component having the general formula:

Z II 0 wherein R is a monovalent radical selected from the group consisting of a lower alkyl radical, a lower alkoxy radical, and a lower cycloalkyl radical, and

Z is selected from the group consisting af a sulfur atom and an oxygen atom; and,

(3) an acidic compound employed to prevent the composition from precoupling, said process comprising heating such photographic element Within the temperature range necessary to thermally activate said diazotype composition and thereby producing a positive visible image.

17. The process of claim 16 wherein said heating is carried out in the range of about 200 to 400 F.

References Cited UNITED STATES PATENTS 2,016,521 10/ 1935 Steindorif. 2,536,398 10/1947 Slifkin 96-91 2,688,543 9/1954 Von Glahn et al. 96-91 XR 2,826,500 3/1958 Keim. 3,039,872 6/1962 De Boer et al. 96-91 3,140,180 7/1964 Fritz 96-75 3,199,982 8/1965 Kashiwabava 96-91 XR FOREIGN PATENTS 983,665 2/ 1965 Great Britain. 1,115,496 5/ 1968 Great Britain.

864,951 7/1949 Germany.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner U.S. Cl. X.R.