US3360371A - Heat-developable two-component diazotype reproduction material - Google Patents

Description

United States Patent Ofilice 3,360,371 Patented Dec. 26, 1967 3,360,371 HEAT-DEVELOPABLE TWO-COMPONENT DIAZO- TYPE REPRODUCTION MATERIAL Johannes Munder, Wiesbaden-Biebrich, and Hellmut Ziegler, Wiesbaden-Schierstein, Germany, assignors, by mesne assignments, to Keulfel & Esser Company, Hoboken, NJ.

No Drawing. Filed Dec. 27, 1963, Ser. No. 334,029 Claims priority, application Germany, Dec. 29, 1962, K 48,608 9 Claims. (Cl. 96-91) The present invention relates to diazotype reproduction materials and refers more particularly to heat-developable two-component diazotype reproduction materials and methods for their preparation.

In the preparation of copies by means of the diazotype procedure, three methods of development are used: the dry process using ammonia, the semi-wet process, and the thermal process. Copies are obtained by exposing the light-sensitive material behind a master to destroy the diazo compound in the image-free area but not in the image areas. The undestroyed diazo compound together with the coupling component already present or added by developer bat-h then forms an azo dyestuff under the proper pH conditions. This is accomplished by shifting the pH value from an acid to an alkaline value in the case of the dry process, by heating in the case of the thermal process, or by applying the coupling component in a pH- controlled developer solution in the case of the semi-wet process.

The coupling process proceeds without difficulties only if it is effected in the alkaline to neutral pH range. Thus, in most of the heat-developing processes hitherto known, the original acid pH value of the light-sensitive layer was shifted from acid to neutral to alkaline values as the temperature was increased by the presence of suitable additives. This effect was obtained by using a solid acid easily volatilized by heat or a non-alkaline substance which is transformed by heat to an alkaline substance. Urea is generally used for this purpose since it has a neutral reaction at room temperature whereas it is decomposed to biuret and ammonia at 150 to 160 C.

Urea-containing papers, however, have the disadvantage that they are hygroscopic and thus are subject to undesirable pre-coupling due to the presence of absorbed moisture. Furthermore, the decomposition temperature of urea is high. Thus, susceptible diazo compounds start to decompose appreciably and the water necessary for the coupling reaction escapes from the paper, thus markedly lessening the contrast. In addition, the reproduction material used for diazotype purposes develops unpleasant vapors when heated strongly and the guide rollers of the reproduction apparatus become contaminated with decomposition products from the copying material when used for long periods of time.

The present invention relates to a heat-developable twocomponent diazotype reproduction material which contains in the light sensitive layer: a diazo compound, an azo compound, and a component which under the influence of heat increases the pH-value in the layer and thus permits coupling to occur. It is characterized by the fact that the component or developing agent consists of a substance which is alkaline in aqueous medium, and is present in the form of small particles which are individually enveloped by an organic substance insoluble in water and melting between 50 and 200 C.

Therefore, one object of the present invention is to provide a heat-developable two-component diazotype reproduction material utilizing an alkaline developing agent in the form of small enveloped particles.

Another object is to provide a heat-developable twocomponent diazotype reproduction material which has good keeping and good contrast.

Another object is to provide methods for making a heat-developable two-component diazotype reproduction material.

Other objects will become apparent during the course of the specification.

For the preparation of the enveloped alkaline substances, the finely divided substance is introduced into a melt of a suitable wax or resin, substantially homogenized, solidified, pulverized and washed with a solvent, preferably a diluted acid, to remove any alkaline nonenveloped material adhering to the particles.

Another process for the production of the finely divided enveloped alkaline material comprises distributing a finely divided base in a solution of an organic water-insoluble substance melting between and 200 C. so that a uniform dispersion is obtained, spraying the latter and drying the spray and, if necessary, washing the fine powder thus obtained with dilute acid in order to remove any nonenveloped basic material adhering to the particles.

Spraying and drying of the dispersion can be effected in a large upright chute into which the dispersion is injected through a nozzle from the top and a stream of heated air or gas is passed upward to meet the falling sprayed droplets. The hot gas stream rapidly evaporates the solvent from the droplets so that the dispersed material falls to the bottom as a fine dust. According to another process for spray drying, the dispersion is caused to drip in a closed container onto a spray disc which is rotated at high speed, e.g., 5,000 to 20,000 revolutions per minute, whereby the liquid is atomized. The sprayed particles are dried by means of a heated gas stream passed through the container to produce a fine powder. These processes can be varied in numerous ways. Thus, the spray drying can be effected in an ambient atmosphere of very high pressure. The heated gas can be passed down together with the dispersion to be dried instead of being passed countercurrently.

For practical purposes the finely divided enveloped basic particles according to the present invention are preferably used up to a grain size of 30 microns. When a coarser powder is used it is difficult to obtain a uniformly coated diazotype reproduction material. The separation of the fraction having the desired particle size is effected by screening or wind sifting. Under suitable conditions, enveloped particles of 30 microns and less can be obtained directly by spray drying.

As suitable bases of the present invention, all substances which are insoluble in the wax or resin used as enveloping material and in the solvent used for the spraying process can be used. Bases which are only slightly soluble in water are preferred, since very thin films of wax or resin with slight permeability to water can burst open due to osmotic pressure when suspended in water if the enclosed substances are too readily soluble in water. The following are mentioned as examples for suitable bases which are only slightly soluble in water: oxides and hydroxides of the elements of the second and third group of the Periodic System, preferably those of the alkaline earth metals, of cadmium, aluminum, zinc and the rare earths; and the salts of these bases with weak acids such as carbonic acid, boric acid,,acetic acid, citric acid, and salicylic acid. When relatively water impermeable substances such as vinylidene chloride-vinyl chloride copolymers are used for the envelopes, derivatives of the alkaline metals such as sodium tetraborate may also be used. Furthermore, organic bases such as triethylammonium-carbonate as well as tri-tertiary-butylamine, triisopropylamine, triethylamine and the salts thereof with weak organic acids are suitable.

Suitable films for enveloping the basic substance are those which are water insoluble, melt between 50 and 200 C., are colorless or only weakly colored in a thin layer, are relatively fluid in molten form and sufficiently hard and brittle at room temperature and can be finely divided, and which do not react with other substances also used for the coating. For instance, wax-like or resinous substances having these properties can be used. They include natural resins such a colophony, root resin and shellac; conversion products of natural resins such as hydrogenated resins, hardened rosins and zinc resins, resin esters and synthetic resins modified with natural resins; maleinate resins; oil-free alkyd resins; light-colored phenolic resins of the novolac type; alkyl phenolic resins and terpene phenolic resins; coumarone resins; vinyl polymers such as polyvinyl acetals, polyvinyl acetates, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyacrylic ester, polystyrene and copolymers of the vinyl compounds with each other and with other polymerizable compounds; polymers of aliphatic unsaturated hydrocarbons; ketone resins; chlorodiphenyl resins; epoxy resins and silicone resins. Substances with a low melting point within the above range should preferably have a narrow melting range of not more than 10 C.

All compounds conventionally used in diazotype processes can be employed as the azo coupling component provided they can couple under the influence of heat in the alkaline or neutral pI-I-range with suitable diazo compounds to produce a dyestutf and provided that they do not react with the resin or wax used for enveloping the base. Compounds of poor solubility in water are similarly preferred and they can also be present in the form of finely divided material enveloped by a film of organic material. Furthermore, it is advantageous that the melting point of the coupling component be within or below the melting range of the resin or wax. Some examples are: 2,3-dihydroxynaphth-alene; aceto acetic anilide; 2,3-dihydroxynaphthalene-6-sulfonic acid sodium salt; 2-naphthol- 3-carboxylic acid methyl ester; 3,5-dihydroxybenzic acid; 2,4-dihydroxy-benzamide; l-methyl-3-hydroxy-benzene-4- glutaric iacid; phenol-B-urea; 2-naphth0l 3,6 disulfonic acid sodium salt.

Diazo compounds which are sufficiently stable in the temperature range of the heat-development, couple with the azo coupling component in alkaline or neutral pH range under the influence of heat to form a dyestuff, and do not react with the resin or wax used for enveloping the basic substance or the azo coupling component can be used. Examples of such compounds are: 2,5-diethoxy-4- benzoylamino-benzene diazonium chloride; 4-phenylamino-benzene diazonium hydrogen sulfate; 4-diazo-2,5-dimethoxy 4' methyl-diphenylsulfide (HCl salt); 4 morpholincrbenzene diazonium fluoborate; 4-morpholino-2,5- diethoxybenzene diazonium chloride; 4-dimethyl-aminobenzene diazonium chloride; 4-(4'-ethoxy-phenyl)-2,5-diethoxybenzene diazonium chloride; 4-ethylbenzylaminobenzene diazonium chloride; 2-ethoxy-4-diethylaminobenzene diazonium chloride; and 4-benylamino-2,S-diethoxybenzene diazonium chloride.

The diazotype reproduction material according to the present invention can also contain a solid acid such as tartaric or citric acid. Furthermore, additives conventionally used in the diazotype processes can be used. Zinc chloride and thiourea are examples. It is also convenient to add a wetting agent, such as saponine, to effect better suspension of the particles. It is also preferable to use a binding agent such as carboxymethyl cellulose, soluble starch, casein, gelatine, or synthetic resin dispersions to ensure the adhesion of the particles on the carrier material. As sheet-like supports conventional raw papers can be used. Transparent foils of converted cellulose products such as cellulose hydrate or cellulose esters or of plastics such as polyamides, polyesters, polycarbonates, and polyvinyl compounds can also be employed. Paper and similar cellulose products are preferably used.

The individual components of the coating are preferably applied to the carrier material in a one-step process.

When using the reproduction material, it is exposed behind a master and then developed by heating by contact with a warm body such as a warm roller or plate. The development occurs when the envelope base is liberated as the envelope is melted and changes the pH of the layer, thus permitting the coupling reaction to proceed.

By means of the reproduction material according to the present invention a heat-image can be obtained by the contact process by placing a suitable master between an infrared source and the reproduction material in such a way that the image side of the master is in contact with the uncoated side of the reproduction material. During exposure to the infrared radiation, the image areas of the master are more intensely heated than the image-free areas. With suitable dosage, this heating is suflicient to melt the water insoluble film enveloping the particles in the image areas, thus producing a dye image in the reproduction material. The images are fixed by subsequent exposure to destroy diazo compound retained in the image-free areas.

Example By wet grinding with 1500 grams of trichloroethylene, 150 grams of 2,7-dih-ydroxy-naphthalene were converted into a finely divided material. Then a solution of 300 grams of a maleinate resin having a melting range from 69 to 77 C., such as Hobimal P 59, in 4,500 grams of trichloroethylene were added and the total mixture was homogenized by means of a high speed mixer (Ultra- Turrax). This mixture was sprayed into a heated conic vessel, so that solvent was evaporated and resin enveloped the particles of the azo coupling component as a protective film. By wind sifting, the portion with a maximum particle size of 30 microns was separated. The powder obtained was designated as powder I.

A 2% aqueous solution of zinc sulfate was adjusted to a pH value of 8 by the addition of ammonia with vigorous stirring, and the zinc hydroxide thus obtained was separated as a finely divided material by spray drying. The ammonium sulfate contained in the finely divided dry product was removed by washing with water and the residue was dried at 60 C. Then 120 grams of the zinc hydroxide were dispersed in a solution of 240 grams of a maleinate resin (Hobimal P 59), dissolved in 4,000 grams of trichloroethylene and atomized as described above. No wind sifting was necessary. The powder obtained was designated as powder II.

An aqueous suspension was made up of:

15 grams of powder I 20 grams of powder II 4 grams of 4-dimethylamino-benzene diazonium chloride-zinc chloride 0.5 gram of tartaric acid 2 grams of trichloroacetic acid 3 grams of naphthalene-1,3,6-trisulfonic acid 8 grams of thiourea 2 grams of polyvinyl acetate (Mowilith DV) 0.4 gram of saponine 150 grams of water and homogenized by means of a high-speed mixer.

The above mentioned resin sold under the trade name Hobimal P 59 is a polyester resin prepared by condensing maleic acid, rosin, and a polyhydric alcohol.

The aqueous suspension was applied to a raw paper and the carrier material coated in this way was dried in an air stream at 30 to 40 C.

After exposure to a UV are lamp behind a master, the material obtained was developed by short contact with plates heated to a temperature of to C. A blue copy corresponding to the master was thus obtained.

It is apparent that the described example is capable of many variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

What is claimed is:

1. A heat-developable two-component diazotype reproduction material comprising a sheet-like support and a light-sensitive layer coated on said support, said layer comprising diazo compound, coupler and a finely divided heat-activatable alkaline developing agent, said agent consisting essentially of dry solid particles of low water solubility inorganic alkali enveloped by .a water-insoluble organic substance melting between about 50 and 200 C.

2. A material in accordance with claim 1 in which said diazo compound is selected from the group consisting of: 2,5-diethoxy-4-benzoylamino-benzene diazonium chloride; 4-phenylamino-benzene diazonium hydrogen sulfate; 4-diazo-2,5-dimethoxy-4'-methyl-dipheny1 sulfide (HCl-salt); 4-m0rph01in0 benene diazonium fluoborate; 4-morpholino-2,S-diethoxy-benzene diazonium chloride; 4 dimethylamino-benzene diazonium chloride; 4-(4'-ethoxy-phenyl)-2,5-diethoxy-benzene diazonium chloride; 4-:ethylbenzylamino-benzene diazonium chloride; 2-ethoxy-4-diethylamino-benzene diazonium chloride; and 4-benzylamino- 2,5-diethoxy-benzene diazonium chloride.

3. A material in accordance with claim 1 in which said coupler is a member selected from the group consisting of: 2,3-dihydroxy-naphthalene; acetoacetic anilide; 2,3-dihydroxy-naphthalene-6-sulfonic acid, sodium salt; 2-naphthol-3-carboxylic acid methyl ester; 3,5-dihydroxy-benzoic acid; 2,4adihydroxy-benzamide; 1-methy1-3-hydroxy-benzene-4-glutaric acid; phenol-3-urea; 2-naphthol-3,6-disulfonic acid, sodium salt; and 2,7-dihydroxy-naphthalene.

4. A material in accordance with claim 1 in which said diazo compound is 4-dimethylamino-benzene diazonium chloride zinc chloride salt, said coupler is 2,7-dihydroxynaphthalene, said alkali is zinc hydroxide and said substance is a polyester resin condensate of maleic acid, rosin, and a polyhydric alcohol melting between 69 C. and 77 C.

5. A heat-developable two-component diazotype reproduction material according to claim 1 wherein said coupler is in the form of particles enveloped separately from said alkali by a water-insoulble organic substance melting between about 50 C. and 200 C.

6. A material in accordance with claim 5 in which said diazo compound is a member selected from the group consisting of: 2,5-diethoxy-4-benzoylamino-benzene diazonium chloride; 4-phenylamino-benzene-diazonium hydrogen sulfate; 4-diazo-2,S-dimethoxy-4-methyl-diphenyl sulfide (HCl-salt); 4-morpholino-benzene diazonium fluoborate; 4-morpholino 2,5 diethoxy-benzene diazonium chloride; 4-dimethylamino benzene diazonium chloride; 4-(4'-ethoxyphenyl) 2,5 diethoxy benzene diazonium chloride; 4 ethylbenzylamino benzene diazonium chloride; 2-ethox'y-4-diethylamino-benzene diazonium chloride; and 4-benzylamino-2,S-diethoxy-benzene diazonium chloride.

7. A material in accordance with claim 5 in which said coupler is a member selected from the group consisting of: 2,3-dihydroxy-naphthalene; acetoacetic anilide; 2,3-dihydroxy-naphthalene-6-sulfonic acid, sodium salt; 2-naphthol-3-carboxylic acid methyl ester; 3,5-dihydroxy-benzoic acid; 2,4-dihydroxy-benzamide; 1-methyl-3-hydroxy-benzen'e-4 glutaric acid; phenol-B-urea, 2-naphthol-3,6-disu lfonic acid, sodium salt; and 2,7-dihydroxynaphthalene.

8. A material in accordance with claim 5 in which said diazo compound is 4-dimethylamino-benzene diazonium chloride zinc chloride salt, said coupler is 2,7-dihydroxynaphthalene, said alkali is zinc hydroxide, and said substance is a polyester resin condensate of maleic acid, rosin and a polyhydric alcohol melting between 69 C. and 77 C.

9. Material according to claim 1 wherein said inorganic alkali is selected from the group consisting of low water solubility oxides and hydroxides of alkaline earth metals, and weak acid salts of said oxides and hydroxides.

References Cited UNITED STATES PATENTS 3,016,308 1/1962 Macaulay 96 3,041,289 6/1962 Katchen et al. 117-36.8 XR 3,111,407 11/1963 Lindquist et a1 -9675 XR 3,113,865 12/1963 Sagura et al 9675 XR 3,173,878 3/1965 Reyes 11736. 8 XR 3,202,510 8/1965 Hollmann 9649 XR 3,281,244 10/1966 Endermann et al. 9649 XR FOREIGN PATENTS 898,668 6/ 1962 Great Britain. 905,621 9/1962 Great Britain.

NORMAN G. TORCHIN, Primary Examiner. C. L. BOWERS, Jm, Assistant Examiner.

Claims (1)

1. A HEAT-DEVELOPABLE TWO-COMPONENT DIAZOTYPE REPRODUCTION MATERIAL COMPRISING A SHEET-LIKE SUPPORT AND A LIGHT-SENSITIVE LAYER COATED ON SAID SUPPORT, SAID LAYER COMPRISING DIAZO COMPOUND, COUPLER AND A FINELY DIVIDED HEAT-ACTIVATABLE ALKALINE DEVELOPING AGENT, SAID AGENT CONSISTING ESSENTAILLY FO DRY SOLID PARTICLES OF LOW WATER SOLUBILITY INORGANIC ALKALI ENVELOPED BY A WATER-INSOLUBLE ORGANIC SUBSTANCE MELTING BETWEEN ABOUT 50 AND 200*C.