GB1588497A

GB1588497A - Method of developing a diazo recording material

Info

Publication number: GB1588497A
Application number: GB2220078A
Authority: GB
Original assignee: Meteor Siegen Apparatebau Paul Schmeck GmbH
Current assignee: Meteor Siegen Apparatebau Paul Schmeck GmbH
Priority date: 1977-05-24
Filing date: 1978-05-24
Publication date: 1981-04-23
Also published as: DE2723249A1; DE2723249C2

Description

(54) METHOD OF DEVELOPING A DIAZO RECORDING MATERIAL (71) We, METEOR-SIEGEN APPARATEBAU PAUL SCHMECK GmbH, a German Body Corporate, of D-5900 Siegen, 1, Frankfurter Strasse 27, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment The present invention is concerned with a method of developing a diazo recording material.

Exposed diazo recording materials are conventionally developed by passing them through an atmosphere containing ammonia gas. There is inevitably some escape of ammonia from the developing apparatus, which is both hazardous and inconvenient for operating personnel.

There is also known a semi-wet developing method, in which the developer -supplies- the coupling agent. In this method, it is necessary to employ a special diazo recording material which includes a layer which releases a developing gas when the recording material is heated. This method has a number of disadvantages, among which are the necessity of using a special material, and the fact that the recording material must be stored at an extremely low temperature in order to avoid partial pre-development during storage.

We have now found a method of developing a diazo recording material in which the above disadvantages are at least partially alleviated.

According to the invention, there is provided a method of developing a latent image on an imagewise exposed diazo recording material comprising an ammonia-developable diazo recording layer on a substrate, which method comprises applying to the recording layer or to a gas-pervious layer in or on the recording material, there being no intervening gas-impervious layer between such a gas-pervious layer and the recording layer, a solution or suspension of a salt which is thermally decomposable to generate ammonia, the solution or suspension being applied so as to form a layer containing the requisite amount of salt for development of the latent image; and uniformly heating the recording material so as to cause development of the latent image solely by means of ammonia generated on decomposition of the salt.

When the suspension or solution is applied directly to the recording layer, gas-impervious substrates (for example, plastics -films) may be used, if desired, instead of the conventional paper substrates, which are gas-pervious. When the suspension or solution is applied to a gas-pervious layer, this layer is preferably the back surface of a paper substrate.

The solution or suspension is preferably applied to the appropriate layer of the recording material in atomized form; this can be carried out without external pressure (that is, by passing the recording material through a chamber containing the atomized solution ar suspension).

The salt is preferably an ammonium salt such as, for example, ammonium salts of carbonic acid or derivatives thereof, such as ammonium carbonate, ammonium bicarbonate or ammonium carbamate. Because ammonium bicarbonate has a lower ammonium content, a relatively large amount thereof is necessary. When ammonium carbamate is used, allowance should be made for the fact that it decomposes at room temperature; it should therefore be stored in sealed containers until required.

When the salt is in solution, suitable solvents therefor include water, glycerine ethylene glycol and mixtures thereof. When water is used, care should be taken to ensure that the recording layer is not stripped from the substrate. A preferred solvent is ethylene glycol.

When the salt is in suspension, it is preferably in finely ground form and suspended in an inert carrier liquid, such as an aliphatic hydrocarbon. The viscosity of the suspension is preferably increased by the addition of a thixotropic agent; this ensures that the suspension has a long storage life.

In order that the invention may be more fully understood, the following Example is given by way of illustration only: EXAMPLE A conventional diazo printing paper was imagewise exposed and then a solution of ammonium carbonate in a mixed solvent consisting of 50% glycerine and 50% water was applied to the diazo layer in an amount of 2 grams per square metre.

The printing paper was immediately uniformly heated at a temperature of 80 to 100or while the coated diazo layer was guided along a gas-impervious wall (so that ammonia liberated could not escape).

Satisfactory prints were obtained.

WHAT WE CLAIM IS:- 1. A method of developing a latent image on an imagewise exposed diazo recording material comprising an ammoniadevelopable diazo recording layer on a substrate, which method comprises applying to the recording layer or to a gas-pervious layer in or on the recording material, there being no intervening gas-impervious layer between such a gas pervious layer and the recording layer, a solution or suspension of a salt which is thermally decomposable to generate ammonia, the solution or suspension being applied so as to form a layer containing the requisite amount of salt for development of the latent image; and uniformly heating the recording material so as to cause development of the latent image solely by means of ammonia generated on decomposition of the salt.

2. A method according to claim 1, in which the solution or suspension is applied in atomized form.

3. A method according to claim 2, in which the atomized solution or suspension is applied by passing the recording material through a chamber containing the atomized solution or suspension.

4. A method according to any of claims 1 to 3, in which the salt is ammonium carbonate or ammonium carbamate.

5. A method according to any of claims 1 to 4, in which the solvent for the solution is one or more of water, glycerine and ethylene glycol.

6. A method according to any of claims 1 to 4, in which the suspension comprises an aliphatic hydrocarbon having the salt dispersed therein, the salt being finely ground, and a thixotropic agent.

7. A method according to any of claims 1 to 6, in which, during heating, the recording layer is in contact with a gas-impervious wall.

8. A method of developing an imagewise exposed diazo recording material, substantially as herein described in the Example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. EXAMPLE A conventional diazo printing paper was imagewise exposed and then a solution of ammonium carbonate in a mixed solvent consisting of 50% glycerine and 50% water was applied to the diazo layer in an amount of 2 grams per square metre. The printing paper was immediately uniformly heated at a temperature of 80 to 100or while the coated diazo layer was guided along a gas-impervious wall (so that ammonia liberated could not escape). Satisfactory prints were obtained. WHAT WE CLAIM IS:-

1. A method of developing a latent image on an imagewise exposed diazo recording material comprising an ammoniadevelopable diazo recording layer on a substrate, which method comprises applying to the recording layer or to a gas-pervious layer in or on the recording material, there being no intervening gas-impervious layer between such a gas pervious layer and the recording layer, a solution or suspension of a salt which is thermally decomposable to generate ammonia, the solution or suspension being applied so as to form a layer containing the requisite amount of salt for development of the latent image; and uniformly heating the recording material so as to cause development of the latent image solely by means of ammonia generated on decomposition of the salt.