JPS6025777B2 - Method for manufacturing a reversed reading image of a direct reading original - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a reversal positive image of a straight read original and its use as an intermediate copy in the production of lithographic printing plates.

Transparent line and/or halftone images used to make lithographic plates, especially presensitized plates for offset printing, are supported in contact with the light-sensitive side of the plate for maximum resolution and sharpness. It is known that one side must be subjected to the exposure process. Furthermore, when performing lithography using the offset method, the plate must be read directly or authentically.
The line and/or halftone images used for the desired contact exposure must be reversed or read in reverse. Therefore, depending on the type of plate used, whether a positive or negative working plate, the line and halftone or screened intermediate copy used should be a reverse read positive or negative image of the original. When used with conventional graphic arts materials, reversal-task positive line and/or halftone images for use as intermediate copies in the exposure of positive-working lithographic plates first form a correct reading negative and then This is obtained by copying this negative to form an inverted positive.
This involves two exposure and processing steps. Starting with a continuous tone original, a correct resolution negative is formed by exposing an emulsion layer of negative film material through a screen and then processing by a camera with a reversing mirror or prism, whereas a reversing resolution is A read positive image is formed by exposing and processing a second negative film material in contact with the correct read negative. Apart from long processing times, this method of forming a reversal read positive image involves the use of expensive processing equipment as well as the use of expensive cameras with reversing mirrors or prisms.

Furthermore, exposure using an optical inversion device reduces image quality when compared to direct exposure due to large light scattering. Correct resolution negative images can also be obtained with cameras without a reversing device, i.e. by exposing the silver halide emulsion of the negative film material to the original through a film support instead of directly. It is known. In this exposure method, exposure is usually carried out through an antihalation coating applied to the back side of the support which absorbs the exposure light and thus reduces sensitivity, but this can be compensated for by slightly increasing the exposure time. can.
Nevertheless, exposure through the support reduces the sharpness of the screen points. High quality line and/or halftone images can be produced very rapidly by the peel diffusion transfer reversal (DTR) process.

In this method, a suitable high contrast negative light-sensitive silver halide material is applied to the original by electronic reproduction (reproduction) using a screen, for example when the original is a continuous tone original.
The negative material is then developed while in contact with the receiving material. When the image-receiving material is peeled off from the negative silver halide material, the latter carries a negative image of the original, and the former shows a positive image of the original.
A complete explanation of the silver halide diffusion transfer reversal law (DTR method) is well known to those skilled in the art and is not considered necessary here, but details can be found in The Focal Press, London-New York, 1972. , "Photographic Silver Halide Diffusion Processes" by A. Lott and E. Wide. Light-sensitive negative silver halide materials and non-light-sensitive image-receiving materials for producing line and/or halftone images by silver halide diffusion transfer methods are available from Agfa Gewert.
It is marketed by N.V. under the trade name Copy Proof.

These diffusion transfer materials offer the advantage of rapidly producing line and/or halftone images with simple equipment. However, for the formation of inverted readout positive lines and/or halftone images, expensive cameras with inverted mirrors or prisms must be used. By actually exposing a negative material consisting of a high-contrast negative halide emulsion on a polyethylene-coated paper support with a camera without a reversing device, and then bringing it into close contact with an image-receiving material having a transparent film support for diffusion transfer processing. A direct draft positive can be obtained, but this is not suitable for obtaining a correct draft offset printing plate by the desired contact exposure of a positive working presensitized offset plate as described above. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a positive line and/or halftone image of a correctly read original by a silver halide diffusion transfer method without using a processing camera with an expensive reversing device. .

According to the present invention, there is provided a method for producing reversal read positive line and/or halftone images on a transparent film support, which method comprises applying a '11 photographic negative-working silver halide emulsion material to an original image. This exposure is carried out through a screen when the original is a continuous tone original, and the emulsion layer side of the photographic material is brought into contact with an image-receiving material having an image-receiving layer containing development nuclei on a transparent support. The transfer of silver halide from the photographic material to the image-receiving layer is effected by placing the silver halide in the presence of a developer and an aqueous alkaline liquid and in the presence of a silver halide converting agent which causes development of the exposed silver halide. A process for separating an exposed photographic material from an image-receiving material, carried out by diffusion of rust salts to form a visible silver image therein, in which the photographic material comprises a negative-working silver halide emulsion layer on a transparent film support; and an antihalation layer between the emulsion layer and the film support or on the side of said support opposite to the side carrying the emulsion layer, and the exposure of the silver halide emulsion is supported by a reversing mirror or a camera without a prism. It is characterized in that it is carried out through the body and an antihalation layer.

"Negative-working silver halide emulsion material" is understood as a material which, upon exposure and development, corresponds to the exposed areas and causes development.

The advantage of the diffusion transfer reversal method of the present invention is therefore that the support for the negative material is a transparent film support and that the emulsion layer is exposed to light through the support and the antihalation layer.

Preferably, the antihalation layer is located between the emulsion layer and the support.

Lines and/or halves created by the negative-positive method of traditional photography
In graphic arts materials for foottone imaging, antihalation layers are usually applied to the emulsion of the support to facilitate the removal of antihalation dyes during processing and to minimize the effect of these dyes on the emulsion properties. coated on the side opposite to the side that carries it.

Although any antihalation dye can be used in the negative diffusion transfer materials used in accordance with the invention, it is preferred to use highly light-absorbing carbon black in the antihalation layer.

This is possible because the antihalation layer does not need to be discolored during processing, as is the case with the antihalation layer of the graphic arts negative materials described above. The use of an antihalation layer coated between the emulsion layer and the support provides better sharpness and higher quality clean screen points than when coated on the back side of the support. When using carbon black, there is no risk of an adverse effect of the antihalation layer on the sensitometric properties of the emulsion. The use of carbon black in the antihalation layer is disclosed in British Patent No. 1, for example.
It is known from No. 541303.

Since according to the invention the exposure of the silver halide emulsion layer must be carried out through the antihalation layer, its optical density is such that exposure of the silver halide emulsion layer with an electrophotographic camera having a normal light source is suitable. Preferably, this is still possible within the exposure time. Therefore, the optical density of the antihalation layer is preferably not greater than 0.9, and for sufficient absorption preferably not less than 0.3. Optical densities in the range 0.6-0.5 give very advantageous results.

As previously pointed out, the antihalation layer preferably contains a non-bleaching carbon black, such as lamp black, preferably having an average particle size in the range of 10 to 2 microns, and a hydrophilic colloid binder. It is preferably used in an amount of 3 to 50% by weight based on gelatin (preferably gelatin).

The support of the photographic material can be a customary transparent hydrophobic resin film made, for example, from cellulose esters or polyesters (eg polyethylene terephthalate).

These supports in the present invention are preferably provided with a subbing layer on both sides to improve the adhesion of the hydrophilic colloid coating.

The thickness of the transparent support is preferably in the range of 0.05 to 0.2 willow.

The silver halide of the emulsion used in this invention can be any conventional silver halide, but preferably consists essentially of silver chloride, eg at least 70 mole percent of the silver halide is silver chloride. Preferably, the remainder consists of silver bromide.

Average particle size usually ranges from 200 to 30 grains. To obtain spectral sensitivity in the visible spectral range (orthochrome or panchrome sensitivity), the silver halide is spectrally sensitized with one or more of the known methine dyes. The amount of spectral sensitizing dye may be, for example, 0.
It is 9 on a scale of 10 to 60. The hydrophilic colloid used as a binder for the silver halide is preferably gelatin.

The preferred coverage of silver halide, expressed in units of silver nitrate per 1 ta, is in the range from 1 to 5 units per unit.

The image-receiving material used according to the invention must contain a transparent support, which can be the same as described for the photosensitive film material.

The binder of the image-receiving layer containing the development nuclei in a dispersed state can be a hydrophilic binder conventional in the art, such as gelatin.

Although it is preferred to use silver sulfide nuclei, other development nuclei can be used as well, such as sulfides of heavy metals, such as sulfides of antimony, bismuth, cadmium, cobalt, lead, nickel and zinc.

Further information on the composition of the image receiving layer can be found in The Focal. King Press (London and New York) 1972, by Andre Lott and Edith Wade.
Photographic Silver Halide Diffusion Processes, pages 50-65.

In carrying out the silver-lead salt diffusion transfer process, it is common practice to incorporate a developer into the light-sensitive silver halide emulsion layer and/or image-receiving layer, or other water-permeable layer adjacent thereto. ing. Therefore, the DTR processing liquid used in the present invention is preferably an alkaline liquid containing no developer. Suitable developers for exposed silver halide are, for example, hydroquinone and 1-phenyl-3-pyrazolidinone type developers and also p-monomethylaminophenol. The developing or activating solution contains a silver halide solvent such as an alkali metal or ammonium thiosulfate or thiocyanate, or an armoring compound such as ammonia in a method for forming a silver image by silver rust salt diffusion transfer. Alternatively or additionally such a keying compound may be present in the image receiving layer. The inverted read-out positive image obtained by the method of the invention is used for contact exposure of positive-working lithographic printing plates.

Such plates contain, for example, a photosensitive layer of a positive-working photoresist composition. Such photoresist compositions become more soluble in exposed areas. Suitable positive-working photoresist compositions are described, for example, in Photoresist Materials and Processes, by W. S. DeFoorest, published by McGraw-Hill Book Company, 1973. In the preparation of positive-working photoresist layers suitable for use with the inverted positive images made in accordance with the present invention, photosensitive compounds are used which provide improved alkaline solubility when exposed to light. is preferred.

For this purpose, photosensitive o-quinonediazides are preferred. Such compounds are described, for example, in published German patent applications (DE
-OS) No. 2810463 and U.S. Patent No. 3201
No. 239, which also describes the production of positive-working lithographic printing plates, and should therefore be read in the context of the present invention. In the production of photosensitive materials for producing lithographic printing plates,
A positive-working photoresist composition is applied to a lithographic support material.

The lithographic support material can be any of those well known to those skilled in the art;
For example, zinc, anodized aluminum, granular aluminum, copper and specially made metal grade supports, partially hydrolyzed cellulose ester films, polymeric supports such as polyolefin, polyester, polyamide supports. . The photosensitive resist layer is exposed to actinic radiation (
This can be exposed in the usual manner to ultraviolet light (preferably ultraviolet light).

The exposed material is then washed, soaked, rubbed, or otherwise treated with a solvent or solvent system that acts on the exposed or unexposed areas to remove material that has not been insolubilized by the action of the light. and develop. These developing solvents can be organic or aqueous and will vary depending on the composition of the photosensitive layer being developed. Examples of developing solvents include water,
aqueous acids and alkalis, lower alcohols and ketones,
and aqueous solutions of lower alcohols and ketones. The image formed can be processed in known manner depending on the intended end use. The method for producing a lithographic printing plate according to the invention comprises: (1) a positive effect imparted to a lithographic support via an image-receiving material containing an inverted positive line and/or a halftone image made according to the invention; {2} intimately exposing a photosensitive resist layer with the copper image-bearing side of the image-receiving material in contact with said positive-working photosensitive resist layer; {2} selectively removing the exposed areas with a solvent for the exposed areas; This is done by developing the resist layer as described above and exposing the lithographic support in these areas.

In the examples, all percentages and ratios are by weight unless otherwise specified.

Examples Preparation of photosensitive film material A having an antihalation layer on the back side of a transparent support A washed gelatin silver chloride bromide emulsion (silver chloride 98.2 mol%, silver bromide 1.8 mol%) was coated with orthochrome sensitivity. A special sensitizer, a common stabilizer, and hydroquinone and 1-phenyl-4-methyl-3-pyrazolidinone as developers were added to give .

Coating of the emulsion onto a transparent polyethylene terephthalate support subbed on both sides was carried out in such a way that the halogenated line gave a coverage equal to 2.5 of silver nitrate per first line.
The weight ratio of gelatin to silver halide expressed as silver nitrate was 1.2. Hydroquinone and 1-phenyl-4-methyl-3-pyrazolidinone each have 1
It was present at a coverage of 0.90 and 0.25 night for each eye. An antihalation layer based on gelatin and carbon black was applied. This layer was applied in such a way that, after drying, the optical density for visible filtered light was 0.6, as measured with a Macbeth® TDI02 densitometer. "Visible filtered light" is light that has a spectral range distribution characteristic relative to the sensitivity of the human eye. The weight ratio of gelatin to carbon black was 32:1. Preparation of photosensitive film material B having an antihalation layer between the silver halide emulsion layer and the transparent support The preparation of material B was carried out in the same manner as described for the preparation of material A, except that the emulsion was added to the antihalation layer. The difference is that no further antihalation layer was applied.

Image Receiving Material The image receiving material used in connection with the photosensitive film materials described above for the diffusion transfer reversal (DTR) process consisted of a primed polyethylene terephthalate film support with a 11%
gelatin and an aqueous colloidal dispersion containing 0.2% silver sulfide development nuclei.

The resulting dispersion was coated with a gelatin coverage of 1 to 2.5 coats and dried. Exposure and Processing Photographic materials A and B were exposed to continuous tone black and white originals for direct screening using a contact screen using a vertical darkroom camera without a reversing mirror.

Exposure was carried out on the emulsion side away from the camera lens, thus through the support and antihalation layer. With DTR processing, this resulted in a properly processed negative on the photosensitive film material and a reverse processed positive print on the receiver material. After exposure, materials A and B were introduced together with the image-receiving material into a diffusion transfer plate containing a liquid having the following composition. water 80
0 [tribasic sodium phosphate 12 L0 7
5 Sodium sulfite in evening rice bran water 40 Potassium bromide 0.5 t Sodium thiosulfate anhydride 20 In 1-phenyl-5-mercaptotetrazole 70 in evening water
It was set at 1000'.

As each sandwich of photosensitive material and image-receiving material exited the squeeze roller of the diffusion transfer device, each material was brought into close contact for an additional 6 days and then separated from each other. The screen dots of the inverted positive print obtained on the receiver material using photosensitive film material A have a sharpness inferior to that of the screen dots obtained using film material B. Ta.

Both prints were used in the production of positive direct resolution lithographic offset printing plates. Materials A and B and the image-receiving materials described above were likewise perfectly suitable for the reproduction of line originals reproduced without screening exposure.

Claims (1)

[Claims] 1 (1) exposing a photographic negative-working silver halide emulsion material to an original, said exposure being through a screen when the original is a continuous tone original; (2) exposing the emulsion layer side of the photographic material to a transparent support. placed in contact with an image-receiving material having an image-receiving layer containing development nuclei thereon, in the presence of a developer and an aqueous alkaline liquid and in the presence of a silver halide complexing agent, which causes development of the exposed silver halide; (3) separating the exposed photographic material from the image-receiving material; and (3) separating the exposed photographic material from the image-receiving material. A method for producing a reversal read positive line and/or halftone image on a transparent film support comprising a photographic material comprising a negative-working silver halide emulsion layer on the transparent film support and between the emulsion layer and the film support. or 0.9 on the side opposite to the side carrying the emulsion layer of the support.
A process characterized in that it comprises an antihalation layer having an optical density not greater than that of the antihalation layer, and that the exposure of the silver halide emulsion layer is carried out through the support and the antihalation layer using a reversing mirror or a camera without a prism. .