US3288627A

US3288627A - Heat-sensitive diazotype material coated sheet

Info

Publication number: US3288627A
Application number: US477594A
Authority: US
Inventors: Edward C Bialczak
Original assignee: Multigraphics Inc
Current assignee: AB Dick Co
Priority date: 1965-08-05
Filing date: 1965-08-05
Publication date: 1966-11-29
Anticipated expiration: 1983-11-29

Description

United States Patent 3,288,627 HEAT-SENSITTVE DIAZOTYPE MATERIAL COATED SHEET Edward C. Bialczak, Mount Prospect, IlL, assignor to Adtiressograph-Multigraph Corporation, Cleveland, Ohio, a corporation of Delaware No Drawing. Filed Aug. 5, 1965, Ser. No. 477,594 Claims. (Cl. 11736.8)

This invention relates to heat-sensitive diazotype materials and to alkaline donor developers incorporated in such materials. More particularly, it relates to metallic dialkyldithiocarbamate-amine complexes and heat-sensitive diazotype materials coated with such complexes.

Heat-sensitive diazotype materials comprise a base member coated with a formulation containing a diazo compound and a coupling component with which the diazo compound reacts under proper conditions to form an azo dye which produces a visible image. In making a print, the diazotype material is exposed to light under a translucent master. In those areas of the diazotype material which are exposed to light, the light-sensitive diazo compound is at least partially destroyed, but is unaffected in the shaded areas. The print is then developed by heating the diazotype material and causing the alkaline donor developing agent to emit ammonia or an organic amine which produces the proper pH conditions for interaction of the diazo compound and the coupling component. These react to produce a dye image in the shaded area which corresponds to the graphic material on the master.

In conventional heat-sensitive diazotype materials the alkaline donor developer is commonly a urea or thiourea compound which on decomposition at elevated temperatures yields ammonia which induces the coupling reaction to form the azo dye. Urea and thiourea compounds produce diazotype materials having a relatively poor shelf life due to precoupling of the diazo compound and the coupling component at ambient temperatures. Other heat-sensitive diazotype materials which have longer shelf lives usually require higher temperatures to induce coupling. Generally, these temperatures are too high for office equipment and often they are so high that the diazo compound decomposes more rapidly than it reacts with the coupling component to form the azo dye. To cope with the problem of precoupling, increased amounts of acid have been used to stabilize the formulations, thus requiring increased amounts of alkaline donor to be incorporated into the formula to provide a suflicient source of ammonia to give a suitably dense image. For example, British Patent No. 909,491 proposes the use of certain types of acids which lose their acidity on heating and thereby reduce the required quantity of alkaline donor since at developing temperatures the acid is dissipated.

It is an object of this invention to provide heat-sensitive diazotype materials wherein the alkaline donor is stable at ambient temperature, decomposes to produce alkaline substances at relatively low temperature and does not contribute to precoupling. It is another object of this invention to provide heat-sensitive diazotype materials which form good prints and which have extended shelf life. It is a further object to provide alkaline donor materials for heat-sensitive diazotype materials which decompose at relatively low temperatures to provide alkaline materials which induce dye formation. These and other objects are apparent from and are achieved in accordance with the following disclosure.

In accordance with this invention it has been discovered that metallic dialkyldithiocarbamates form complexes with relatively strong organic amines. In these com- Patented Nov. 29, 1966 ICC plexes, which have the following general formula, one

mole of metallic dialkyldithiocarbamate is combined with one mole of amine:

Me--Am R RlNCSS wherein R R R and R are lower alkyl radicals, Me is a metal (zinc, cadmium or tellurium) and Am is an organic amine. Among the alkyl radicals which R R R and R represent are methyl, ethyl, propyl, butyl, isobutyl and amyl radicals.

The organic amine, Am, can be any of a wide variety of non-aromatic amines containing 4 to 10 carbon atoms, inclusive. Primary aliphatic amines such as methylamine, ethylamine, n-butylamine, t-butylamine, hexylamine and decylamine are operative. Secondary aliphatic amines such as dimethylamine, methylethylamine, methyl-n-butylamine, and di-n-butylamine are also included in this group. Tertiary aliphatic amines which are operative include trimethylamine, triethylamine and the like.

The organic amine, Am, can also include alicyclic amines such as cyclohexylamine, N-methylcyclohexylamine, N-isopropylcyclohexylamine, N-butylcyclohexyL amine, N (2 cyanoethyl)cyclohexylamine, cyclobutylamine, N-methylcyclobutylamine, cyclopentylamine, N- ethylcyclopentylamine, :cycloheptylamine, cyclooctylamine and related amines.

Hydroxyamines such as N (2 hydroxyethyl)cyclohexylamine and N-(Z-hydroxypropyl)cyclohexylamine are useful in this invention, as are diamines such as N (2 aminoethyl)cyclohexylamine and N-(3-aminopropyl)cyclohexylamine. When diamines are combined with the metallic dialkyldithiocarbamate, they form complexes with both one mole and two moles of the metallic salts.

One important characteristic which determines the suitability of a particular amine as an alkaline donor when combined as a complex with a metallic dialkyldithiocarbamate is the pH of the complex in 10% aqueous mixture. Suitable amines form complexes which produce pH values not greater than 8.

The preferred amines in this invention are cyclohexylamine, t-butylamine and derivatives of cyclohexylamine such as N (2 cyanoethyl)cyclohexylamine, N-(2- hydroxyethyl)cyclohexylarnine and N isopropylcyclohexylamine.

The complexes are readily produced by treating a slurry of a metallic dialkyldithiocarbamate in an inert solvent, such as benzene or other hydrocarbon liquid, with an equivalent quantity of the organic am ne in the same solvent. The complex is insoluble in hydrocarbon solvents and can be readily isolated by filtration.

The metallic dialkyldithiocarbamate-amine complexes are dispersed in an inert solvent, such as toluene, in any conventional dispersion mill and applied directly to the substrate (e.g., paper) by roller coating or similar techniques in conjunction with an air knife or other suitable doctoring means. The alkaline donor coating can be applied as a precoat to the photosensitive coating or it can be applied over an existing photosensitive layer.

The metallic dialkyldithiocarbamate-amine complexes are water-insoluble, are stable at room temperature and dissociate in the temperature range from to C., releasing the amine. The latter raises the pH of the diazotype material and creates an environment in which the diazo compound can react with the coupling component to form an azo dye.

The light-sensitive diazo compounds which are useful in two-component diazotype systems can also be used to a advantage in thermally responsive diazotype materials. Examples of such compounds are the diazonium salts ob tained by the diazotization of the following amines:

The preferred diazo compound is the zinc chloride double salt of 4-morpholinobenzenediazonium chloride.

Generally, a number of coupling components may be employed. The preferred coupling component that may be employed to produce the dye image is 2,4-dihydroxynaphthalene-6-sulfonic acid. Other known couplers may be employed such as resorcinol, acetoacetanilide, 4-chlororesorcinol and diacetoacetylethylenediamine. It is, of course, desirable to select coupling components which have little tendency to react with the diazo compounds until the alkaline donor developer has released the amine upon being heated above about 100 C.

To prevent precoupling and premature dye formation, there can be added an acid component to keep the pH below the level required for coupling. Sulfonic acid derivatives, such as m-benzenedisulfonic acid, are employed as the preferred acid components. Other acids may be used to produce the desired pH such as:

oxalic acid citric acid tartaric acid lactic acid maleic acid malonic acid ethanesulfonic acid benzenesulfonic acid 'of diazo compound and coupling component.

The complexes of this invention, when exposed to heat, undergo dissociation to yield the corresponding amines which react with the free acid in the diazotype formulation. It is seen that the alkaline donors of this invention tend to lower the temperature to which the diazotype materials are subjected, simplify the equipment, produce more intense copy since the high temperatures which would degrade the diazo salts are avoided and increase the shelf life of diazotype materials.

When the metallic dialkyldithiocarbamate-amine complexes are applied to sheet materials in the production of diazotype materials, they are dispersed in fine particulate form in an organic solvent such as a hydrocarbon liquid (e.g., toluene) and the resulting suspension applied to the sheet material by conventional coating procedures. The complexes are usually present in the suspensions or dispersions at concentrations of 1% to 10% by weight, the range from 2% to 5% being preferred. The donor coating should be applied at a rate sufficient to afiord in the range of 0.075 to 0.250 gram of complex per square foot of substrate, the preferred concentration being in the range of 0.1 to 0.125 gram of complex per square foot on a dry basis. After the solvent evaporates, the complexes form a thin coating of fine particles which can release an organic amine when activated by heat. It was found that the alkaline donor should be crystalline in form so that itmay be dispersed as particulate material in a solvent vehicle and deposited on the substrate as distinct particles.

In the photosensitive coating formulations for sheet materials, the amount of diazo compound is usually convention. It generally constitutes 2% to 6% of the formulation with 4% being preferred. Equivalent quantities of coupling reagent are employed, following conventional practice. The coating formulations are applied in amounts which will provide about 15 grams of diazo compound for 3,000 square feet of surface on a dry basis.

The base or substrate for the diazotype material can be paper or any other web or film material which is stable at 100150 C. Polyester films such as sold under the trade names Mylar and Kodar are suitable film mate- Example 1 Three moles of zinc dimethyldithiocarbamate (917 grams) are mixed with 5 liters of benzene. The mixture is stirred for several hours forming a slurry. To the slurry there are gradually added 3 moles (297 grams) of cyclohexylarnine in 350 milliliters of benzene which result in the formation of the zinc dimethyldithiocarbamatecyclohexylamine complex. The complex is filtered off under suction and washed with lbetnzene to remove unreacted amine. The yield was of product 'having a melting point in the range of 153 to 155 C. and a pH of a 10% complex-Water mixture of 8.0.

The complex obtained from the above procedure is used by applying it as a separate donor precoat to the base support for the thermal diazo sheet. A typical donor coating formulation is as follows:

Parts by weight The amine metallic alkyl dithiocarbamate complex 2.5 Toluene The complex is dispersed in the toluene by any conventional dispersion type will equipment and applied directly to a paper substrate by the use of roller coating techniques in conjunction with an air knife.

On top of the donor coating there is applied photosensitive coating of which the following is a typical formula:

Ingredient: Parts by weight Water 100 Citric acid 2 Thiourea 4 2,3-dihydroxynaphthalene-6-sulfonic acid 6 Zinc sulfate 4 p-Diazo-N-ethyl-N-hydroxyethylaniline 1 Silica particles (finely divided) 5 Rice starch 3 Polyvinyl acetate emulsion 8 This diazotype paper is stable in storm has a long shelf life and can be developed at relatively low temperature (HO- C.).

Example 2 Three moles of cadmium dibutyldi-thiocalibamate suspended in 5 liters of toluene are treated with 3 moles of N-(Z-hydroxyethyl)cyclohexylamine according to the procedure of Example 1. The resulting complex is collected on a filter, washed with toluene and dried. It is dispersed in toluene (5 parts in 100 parts of toluene) and the dispersion is coated on a dry diazotype paper coated with the photosensitive coating shown in Example 1. The resulting diaz otype paper is stable in storage and can be developed at 115130 C.

Example 3 Other metallic dialkyldithiocanba-mate-amine complexes which are suitable in diazotype materials such as that described in Example 1 are listed below. These are prepared by the method of Example 1 by reacting a mole of the metallic dialkyldithiocarbamate with a mole of amine in an inert solvent such as benzene or toluene. In the case of diamines, two moles of the carbamate are reacted with one mole of the diamine. Each of these complexes dissociates at the temperature listed in (the table below under developing temperature and releases amine which induces coupling of the diazo compound and the coupling component to form a dye which has the dye density listed in the table. In the table the developing temperature is measured on a hotplate device and represents the temperature at which the amine is released.

Dye Devel- Density oping Temp, C.

Zinc dimethyldithiocarbamate cyclohexylamine." 1.1 115 Zinc diethyldithiocarbamate cyel0hexylamine .83 105 Zinc dibutyldithiocarbamate cyclohexylamine 1. 1 115 Zinc diethyldithioearbamate tort-butylamine 1. 04 115 Zinc diethyldithiocarbamate N-(2-hydr0xyethyl) cyelohexylamine 1. 02 130 Zinc diethyldithiocarbamate N-(Z-cyanoethyl) cyclohexylamine 1. 30 138 Zinc diethyldithiocarbarnate N-isopropylcyclohexylarnine 87 138 Zinc dimethyldithiocarbamate N-(Z-hydroxyethyl) cyelohexylamine 90 140 Zinc dimethyldithiocarbamate tert-butylamine .90 145 Zinc dimethyldithioearbamate N-(2-cyanoethy1) cyelohexylamine 90 152 Zinc dibutyldithiocarbamate N-(Z-cyanoethyl) eyelohexylamine 73 125 Zinc dimethyldithiocarbamate N-isopropylcyelohexylamine 85 145 Zinc dimethyldithiocarbamate N -ethyleyclohexylamine 75 145 Zinc dimethyldithiocarbamate N-(3-aminopropy1) cyelohexylamine 79 145 Dilzinc dunethyldithiocarbamate] N-(3-aminopropyl) cyelohexylamine 82 145 Zinc dibutyldithiocarbamate N-isopropyleyclohexyhmina 43 138 Cadmium diethyldithiocarbamate cyclohexylamine 8 105 Cadmium dimethyldithioearbamate eyclohexylamin 1. O 125 Tellurium diethyldithioearbamate eyelohexylamine 1. O4 115 I claim:

1. A heat-sensitive diazotyp'e material comprising a base sheet coated with a diaz-o compound, a coupling component and an alkaline donor metallic dialkyldithiocanbamate-amine complex, wherein the metal is selected from the group consisting of zinc, cadmium and telluriurn, the alkyl radicals contain 1 to 5 carbon atoms, inclusive, and the amine is selected from the gnoup consisting ctf aliphatic and alicyclicamines containing 4 to 10 carbon atoms, inclusive.

2. A heat-sensitive diazotyipe material comprising a base sheet coated with a diazo compound, a coupling component and an alkaline donor metallic dialkyldithiocarbamate-amine complex as defined by claim 1 wherein the amine is an aliphatic amine containing 4 to 10 carbon atoms, inclusive.

3. A heat-sensitive diazotype material comprising a base sheet coated with a diazo compound, a coupling component and an alkaline donor metallic dialkyldithiocarbamate-amine complex as defined by claim 1 wherein the amine is an alicyclic amine containing 4 to 10 carbon atoms, inclusive.

4. A heat-sensitive diazoty-pe material comprising a base sheet coated with a diazo compound, a coupling component and an alkaline donor zinc dialkyldithi-ocarb-amatecyclohexylamine complex, wherein the alkyl radicals contain 1 to 5 carbon atoms, inclusive.

5. A heat-sensitive diazotype material comprising a base sheet coated with a diazo compound, a coupling component and an alkaline donor zinc dimethyldithocarbamate-cyclohexylamine complex.

References Cited by the Examiner UNITED STATES PATENTS 2,732,299 1/1956 Morrison 11736.-8 2,967,784 1/1961 Newman et al. 11736.8 2,995,465 8/1961 Richey 11736.8 2,999,035 9/1961 Sahler 11736.8 3,057,895 10/1962 Marblehead et al. 260-4299 3,076,707 2/ 1963 Lawton et al. 11736.8 3,149,990 9/1964 Coles et al. 11736.8 3,157,526 11/1964 Johnson et al. 11736.8 3,177,233 4/1965 Calhoun 260--429.9 3,185,585 5/1965 Baumann et al 11736.8 3,191,030 6/1965 Huett et. al. 117-36.8

OTHER REFERENCES Kosar: Thermal Development of Diazotype Papers, Photographic Science and Enginering, vol. 5, No. 4, July-August 1961, pp. 239-243.

MURRAY KATZ, Primary Examiner.

Claims

1. A HEAT-SENSITIVE DIAZOTYPE MATERIAL COMPRISING A BASE SHEET COATED WITH A DIAZO COMPOUND, A COUPLING COMPONENT AND AN ALKALINE DONOR METALLIC DIALKYLDITHIOCARBAMATE-AMINE COMPLEX, WHEREIN THE METAL IS SELECTED FROM THE GROUP CONSISTING OF ZINC, CADMIUM AND TELLURIUM, THE ALKYL RADICALS CONTAIN 1 TO 5 CARBON ATOMS, INCLUSIVE AND THE AMINE IS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC AND ALICYCLICAMINES CONTAINING 4 TO 10 CARBON ATOMS, INCLUSIVE.