Diazotype materials which can be developed by heat and contain a

Details Diazotype materials which can be developed by heat and contain a Diazotype materials which can be developed by heat and contain a

1984-11-21

1986-04-22

Bowers, Jr., Charles L.

Radiation imagery chemistry: process, composition, or product th

Diazo reproduction, process, composition, or product

Composition or product which contains radiation sensitive...

430151, 430158, 430161, 430162, 430178, 430179, G03C 160

Patent

active

045842566

DESCRIPTION:

BRIEF SUMMARY
The present invention relates, by way of new industrial products, to diazotype products which can be developed by heat and of which the sensitive layer contains an activator precursor for the coupling reaction. The present invention also relates to a thermal diazo copying process characterised by the use of the diazotype products of the invention.
Diazotype products are already known which can be developed by heat and of which the sensitive layer, which is generally a two-component layer and which thus contains a diazonium salt and a coupler, contains an activator precursor for the coupling reaction, the activator precursor also being commonly referred to as a base generator. In fact, the activator precursor generally releases a basic compound, such as ammonia or a nitrogen-containing organic base, under the action of heat.
Thus, British Pat. No. 998,949 (KODAK, U.S. Priority of 27.06.1960) describes diazotype materials of which the sensitive layer contains a colloidal binder, a diazonium salt, a coupler and at least one thermolabile salt of an organic carboxylic acid and an organic base. After exposure, developing is ensured by heating to a temperature between 60.degree. and 130.degree. C. during which time the salt is decomposed into carbon dioxide and a basic compound, the latter activating the coupling reaction. As a general rule, the thermolabile salt consists of a trihalogenoacetate of a nitrogen-containing organic base, such as piperidinium trichloroacetate, which releases carbon dioxide, a halogenoform (chloroform) and a nitrogen-containing organic base (piperidine) on heating. Volatile compounds are therefore evolved from these activator precursors, and these volatile compounds can form undesirable bubbles in the developed diazotype material, which is of course a disadvantage. It is also known that the halogenoform released combines with the diazotype printing products to give a yellow background on developing, which intensifies during storage.
U.S. Pat. No. 3,625,693 of RICOH (Japanese Priority of 9.11.1966) describes a diazotype material of which the sensitive layer contains an aryldiazonium salt carrying a free carboxyl group in the ortho-position to the diazonium group, a coupler, and a base generator which, under the action of heat, releases a base which initiates and completes the coupling reaction. The activator precursor, also referred to as a base generator, can be urea, thiourea or their derivatives, guanidine or its derivatives, amides, or alternatively salts of trichloroacetic acid and a basic compound such as ammonia, an amine a guanidine or an inorganic base.
According to U.S. Pat. No. 3,625,693, the process makes it possible to obtain diazotype materials which are stable on storage, by virtue of the particular choice of the diazonium compound. However, this is a disadvantage because it considerably limits the possible choice of the diazonium compound.
This U.S. Pat. No. 3,625,693 indeed emphasises the difficulties which are encountered in practice if it is desired to prepare a two-component diazotype material of which the sensitive layer contains a base generator in addition to the diazonium salt and the coupler. It is in fact stipulated that these diazotype materials generally have a low storage stability, which simultaneously results in an increase in the background and a weakening of the coloured images.
French Pat. No. 2,056,231 of RICOH (French Application No. 70/20,228) describes diazotype materials which make it possible to obtain an intense black azo image by virtue of the particular choice of the coupler (a phenol carrying carboxyl groups) and of specific mixtures of diazonium salts carrying carboxyl groups. Furthermore, it is indicated on page 8 that the storage properties of the diazotype material are only obtained if the photosensitive layer does not contain alkali generator.
French Pat. No. 2,360,909 (National Registration No. 77/24,157) describes activator precursors comprising an acid part and a basic part, the acid part being an .alpha.-sulphonylacetate group. These

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patent: 4088496 (1978-05-01), Merkel
Kosar, J., Photo. Sci. & Eng., vol. 5, No. 4, 7/8/1961, pp. 239-243.

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