JPH0414046A - Planographic printing plate having improved water retention - Google Patents

Abstract

PURPOSE:To obviate the staining printing of the planographic printing plate and to enhance the ink receptivity and plate wear of this plate by providing a thin layer consisting of a prescribed hydrophilic matrix on an emulsion layer. CONSTITUTION:The material of the printing plate is formed by laminating the silver halide emulsion layer and the thin layer consisting of the hydrophilic matrix consisting of a high-polymer gel having high water absorptivity via a primer layer on polyethylene-coated paper. A copolymer consisting of 4 components; vinyl alcohol, vinyl acetate, sodium acrylate, and methyl acrylate, etc., are usable as the high-copolymer material forming this thin layer. Sodium polyacrylate maybe added thereto. After this material is exposed and developed, the undeveloped silver halide existing in unexposed parts is processed in the presence of a prescribed compd., etc., by which the ink receptivity is imparted to the surfaces of the unexposed parts.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to lithographic printing plates produced in a novel manner from photographic silver halide materials. Furthermore, the present invention significantly improves the control of printing smudges by increasing water retention in lithographic printing plates and their manufacturing methods in which photographically formed silver halide images are applied as oleophilic and ink receptive. Regarding how to improve.

(B) Prior art and its problems A lithographic printing plate consists of an oleophilic image area that accepts oil-based ink and an oleophilic non-image area that does not accept ink, and generally the non-image area The part is composed of a hydrophilic part that receives and absorbs water.

In normal lithographic printing, therefore, both water and ink are supplied to the plate surface, and colored ink is selectively received in the image area and water is selectively received in the non-image area, and the ink on the image line is, for example, This is done by transferring it to a substrate such as paper. Therefore, in order to obtain good printed matter, the difference in lipophilicity and hydrophilicity between the surface of the printed area and the background non-printed area must be sufficiently large, so that when water and ink are applied, the printed area has a sufficient amount. It is necessary to apply ink to the non-image areas, and not to apply any ink to the non-image areas.

Generally, it is well known in the art that the occurrence of printing stains in lithographic printing is not caused by a single cause, but is caused by a combination of various factors. For example, it may be due to the inherent properties of the plate material, or it may be due to the printing ink, dampening water, printing paper, or even the condition of the printing press or the temperature at the time of printing. , the influence of environmental conditions such as humidity, etc. When printing, it is important to properly maintain these conditions and environment. However, from a practical point of view, materials that can be printed under as wide conditions as possible are required.

The same is true for the materials basically described in Japanese Patent Publication No. 57-3939; the tolerance level is narrow for various commercially available inks, and the printing characteristics tend to change over time before and after plate making. However, there are drawbacks such as smudges that easily occur during long printing runs, and improvements to these problems are desired.

In particular, the treatment is carried out in the presence of an organic compound that reacts with silver ions to form a poorly soluble compound.
In the lithographic printing plate described in -3939, even in the exposed areas where almost no undeveloped silver halide is present, trace amounts of organic compounds such as these adhere to the plate and show a tendency to become oleophilic, and special treatment (
If it is not washed with water, etc., it has the disadvantage that ink stains are likely to appear, and improvement of this problem is strongly desired.

(C) Object of the invention The object of the present invention is to provide an ink-receptive method which does not have the above disadvantages.
It is an object of the present invention to provide a lithographic printing material which has excellent properties required for a printing plate such as printing smudge, printing durability, and image reproducibility, is particularly excellent in preventing printing smear, and has excellent stability over time.

(D) Structure of the Invention The present invention discloses that after a photographic light-sensitive material having at least one silver halide emulsion layer is image-wise exposed and subjected to ordinary photographic development processing, the portion that is not reduced by development, that is, remains. The silver halide portion is treated in the presence of an organic compound and a silver halide solvent that can react with silver ions to convert it into a sparingly soluble silver salt with lower solubility (small solubility product) to make the surface of the unexposed area more philic. In a method for producing an oil-based lithographic printing plate, a lithographic printing plate with enhanced water retention is provided by forming a thin layer of a hydrophilic matrix made of a highly water-absorbing polymer gel on the top layer. This achieves the above objectives.

In order to achieve the objects of the present invention, particularly desirable hydrophilic matrix forming agents include water-soluble synthetic polymers having the following structural units.

D: 6CH2-CchiC=0 R3 A: GoCH2-Cu-ff B: -fCH2-Cday-C-R2 R3 C: 6CH2-CchiC=0 (A+B): (C+D) Molar ratio is 90:10-1
0:90 is preferable, more preferably 50:50
A range of 10:90 to 10:90 is valid. The above copolymer is a copolymer of vinyl ester and ethylenically unsaturated carboxylic acid or its derivative described in Japanese Patent Publication No. 57-41298, which is prepared by adding an alkali catalyst in a suitable solvent, preferably alcohol water or an alcohol-water mixture. It can be obtained by saponifying using acrylic acid, or it can be made by performing radical polymerization of acrylic acid, which can be radically polymerized, in the presence of a PVA polymer having a mercapto group at the end, as described in JP-A-59-189113. This includes an acrylic acid block copolymer containing a PVA-based polymer as one component. Furthermore, monomers that can be copolymerized with these vinyl esters can also be copolymerized.

The aqueous solution containing the copolymer of the present invention is adjusted to pH=1 to 6, preferably 2 to 4, and dried until the water content is 100% by weight, preferably 50% by weight or less, or impregnated into a substrate or After coating, it is possible to crosslink and form a super absorbent gel layer by post-curing.

(The term "superabsorbent gel layer" here refers to a layer that has a water absorption capacity of several tens to hundreds of times its own weight, and whose water-holding capacity does not decrease easily due to pressure or contact with other water-absorbing substances.) To tell).

Alternatively, a polyfunctional compound capable of reacting with a hydroxyl group or a carboxyl group, such as a dialdehyde compound, an epihalohydrin compound, a di(tri)epoxy compound, a diisocyanate compound, etc., is added to the aqueous solution containing the copolymer of the present invention. There is also a method of crosslinking.

The degree of polymerization of the copolymer of the present invention is not particularly limited, but if it is too low, the strength of the superabsorbent gel layer formed will be weak, and if it is too high, the coating properties will be impaired, causing problems as a lithographic printing plate.

Preferably, the degree of polymerization is in the range of 700 to 3,500.

The copolymer of the present invention can be used in combination with various water-soluble polymers. In particular, polyacrylic acid (soda) and polyacrylamide can be mentioned as water-soluble polymers that can be used in combination to enhance the effect. Polyacrylic acid (
Although there is no particular restriction on the degree of polymerization of (soda) and polyacrylamide, a degree of polymerization of 600 to 6,000 is preferred.

The level of the coating amount of the copolymer of the present invention and the sodium polyacrylate and polyacrylamide used in combination is the amount of the binder layer such as gelatin and the hardening agent contained in the silver halide emulsion layer and/or its adjacent layer. Generally, amounts of up to 0.1 g/m2 are used, more preferably from 0.01 to 0.05 g/m2, depending on the amount of paint applied. If the coating amount of the uppermost hydrophilic matrix layer becomes too large, the lipophilicity of the surface of the unexposed area decreases, resulting in a decrease in ink receptivity.

In the present invention, as detailed in the above-mentioned Japanese Patent Publication No. 57-3939, there is a wide range of combinations of organic compounds and silver halide solvents that make the unexposed surface oleophilic, but particularly preferred are silver halide solvents. The solvent (converting agent) is iodide, which is supplied in the form of sodium, potassium, and ammonium salts.

As the organic compound, those represented by the following general formula are preferred.

General formula (I), Z-.
Among the compounds represented by formulas (n) and (m), those represented by formulas (n) and (m) are particularly preferred.

General formula (II) /\ R, -CC-3H N General formula (III) H-R3 /\ R2-CC-3H -N (wherein R+ and R2 are hydrogen, an alkyl group, an aryl group,
Indicates an aralkyl group. R3 represents hydrogen, acyl, or arylsulfonyl group. ) Typical compounds represented by the general formulas (II) and (I[) will be specifically exemplified.

3゜NHCOCHa 4゜NHCOC5HI Although the amount of iodide effective for the purpose of the present invention is not uniform depending on the halogen composition of the silver halide emulsion, 10-
It is within the range of 2 mol/l-1 mol/l. The amount of the organic compound is not necessarily uniform for each compound, but 1
It is used in concentrations of 0-3 mol/l-10 mol/l.

The processing composition liquid (conversion liquid) containing an organic compound and a silver halide solvent for lipophilization is made of methanol, ethanol, propatool, etc. in order to improve the solubility of the organic compound.
It may contain water-miscible organic solvents such as ethylene glycol and diethylene glycol. Further, it is preferable that the conversion liquid is buffered to a pH of 4 to 8. The pH buffering agent can be selected from acids such as acetic acid, citric acid, phosphoric acid, and salts thereof. Further, the conversion liquid may contain various other components. For example, it may contain water-soluble polymers such as hydroxyethyl cellulose, surface hydrophilic agents such as colloidal silica, and the like.

According to the method according to the invention, the areas of the photographic material which correspond to the silver metal images, but not the areas containing undeveloped silver halide, are made to receive ink. Therefore, a negative-type silver halide material is imagewise exposed and, after development,
Positive-working printing plates are obtained by treatment with the conversion liquid according to the invention. Also, negative-working printing plates can be obtained from directly positive-type silver halide materials.

Furthermore, according to another embodiment, the silver halide light-sensitive material is developed and then fixed, or the silver image remaining after bath development and fixing is oxidized and rehalogenated, and by the method according to the invention, The silver halide image areas can be made ink receptive.

In the method according to the invention for producing the lithographic printing plate of the invention, the photographic material consisting of a silver halide emulsion may contain iodide of silver chloride, silver chlorobromide or silver bromide. The binder for the photosensitive material is preferably gelatin. However, part or all of it may be substituted with other colloidal substances such as albumin, casein, polyvinyl alcohol, polyvinyl alcohol-maleic anhydride, polyvinyl alcohol-styrene maleic anhydride, alginates, cellulose derivatives, etc. good.

The weight ratio of binder, preferably gelatin, to silver halide and the absolute amount of binder are important factors in determining the quality of the printing plates of the present invention.

The amount of binder is preferably between 0.3 and 2.0 when the amount of silver halide expressed as silver nitrate is 1. If the ratio of the binder is less than 0.3, the film strength as an emulsion layer tends to decrease, and unfavorable printing characteristics tend to occur. On the other hand, when the ratio of binder increases, the ink acceptance ability may decrease. The silver halide emulsion layer has a silver nitrate content of 0. 6~1g1rd Converting to the amount of binder, it is 0゜5~2.5g/rr? Preferably, the coating is applied with

Another important factor in the production of the printing plates of this invention is the hardening of the light-sensitive silver halide emulsion layer.

It must be sufficiently cured at least before printing ink is applied. A hardening agent may be added to the photographic emulsion coating solution in the same manner as in the conventional hardening method for photographic emulsion layers, or
It may be hardened by a method such as heat treatment before or after development and plate-making processing. In order to obtain stable curing characteristics, it is preferable to apply and dry a silver halide emulsion containing a curing agent and then subject it to an appropriate heating treatment. This heating process is
This is a treatment to obtain a good degree of hardening, for example 80
~150℃ for several or several tens of minutes, or 30-
The treatment may be performed at 50° C. for several days (about 1 to 20 days).

As the hardening agent, compounds commonly used as hardening agents for photographic emulsion layers can be used. For example, alkyl curing agents such as formalin, glyoxal, geltaraldehyde, and mucochromic acid, as well as urea-formalin condensates, are also effective, and organic curing agents such as epoxy, aziridine, active olefins, and isocyanate compounds are also effective. Known compounds as hardening agents for photographic emulsion layers, such as salts of inorganic polyvalent metals such as chromium, aluminum, and zirconium, can be used alone or in combination.

In addition, the silver halide photographic emulsion layer preferably contains fine particles having a diameter of about 2 to 10 μm in order to prevent colloid wear during printing, and the fine particles include silica, clay, etc. , talc, gicrite, rice starch, etc. can be used, but silica, which is an oxide of silicon, is particularly preferred.

Silica is added to the silver halide emulsion coating solution at 0.01 to 1.0 grams per square meter. If the silica particle density becomes too high, it becomes difficult to increase the ink density during printing, or a scumming phenomenon occurs. For the purpose of improving the photographic sharpness and ultimately the resolution and sharpness of the printed matter, it is preferred to apply so-called antireflection dyes or pigments. These are in the photographic silver halide emulsion layer, in the so-called antireflection layer between the support and the silver halide emulsion layer, in the support, or on the side opposite to the silver halide emulsion layer across the support. The objective is achieved by applying it in a layer of . The object can also be achieved by using a light-reflecting pigment such as a white pigment such as titanium oxide, barium sulfate, or magnesium oxide, or a yellow organic pigment in combination with a light-absorbing dye or pigment.

The most preferred embodiment of the photographic light-sensitive material in the method for producing a printing plate of the present invention is to have a colloidal undercoat layer containing an antireflection dye or pigment on the support, and a photosensitive silver halide emulsion on the support. It has layers.

The colloidal subbing layer with anti-reflective dye or pigment preferably comprises gelatin and has a particle size of 2.
Contains particles of ~10μ.

A preferred particulate is silica. Gelatin is a binding agent,
0.0 per square meter. 5 grams to 2.5 grams should harden well as well as the silver halide emulsion layer. Silica is also applied at between 0.1 and 20 grams per square meter.

The subbing layer containing particulates, as in this configuration, has a cure that improves the abrasion of the colloid during printing and thus improves printing durability. In this case, fine particle silica is not necessarily required in the emulsion layer.

The support for the light-sensitive silver halide emulsion can be any support commonly used in the art. For example, the support may be paper, resin film, or metal sheet. The paper support is preferably coated on both sides with a resin coating, for example polyethylene. These supports are previously subjected to corona discharge machining, hydrophilic undercoating, etc. for the purpose of improving adhesion between coating layers mainly composed of gelatin.

Above, the lithographic printing plate of the present invention and its manufacturing method have been basically described, but in addition to the photosensitive silver halide material, for example, a surfactant for improving coating properties, a stabilizer for maintaining photographic sensitivity characteristics, Antifoggants, spectral sensitizers, developers and development accelerators, and dyes, pigments, and the like may optionally be included for the purpose of coloring the photographic emulsion layer.

In a modified embodiment of the present invention, part or all of an organic thiol compound or thione compound or other organic heterocyclic compound that imparts ink receptivity may be added in advance to the material having the silver halide emulsion layer. . It may be a layer other than the photosensitive silver halide emulsion layer. Alternatively, the organic compound may be added by dissolving it in an oil agent and dispersing it onto minute oil droplets.

Exposure of the material having a silver halide emulsion layer can be carried out by conventional methods such as contact, reflection, and projection methods.

Materials with exposed silver halide emulsion layers can be developed with conventional photographic developers based on para-dihydroxybenzene-based developing agents, and also with lithium-type developer compositions containing only small amounts of so-called sulfites. can.

It is also possible to incorporate a developer into the photosensitive material and treat it with an activating solution consisting essentially of an alkaline solution.

In a preferred embodiment, the exposed and developed material is subsequently treated with a conversion liquid according to the invention.

The printing plate thus produced can be immediately mounted on a printing press, and after ink can be applied, printing can be performed. They can also be stored for long periods of time without inking.

In another embodiment, after the development process, the printing plate is treated with an acidic stop bath such as that used in the processing of conventional silver halide photographic materials, and then the conversion liquid according to the invention is applied to the printing plate, for example on a printing press. It can be applied on top and printed.

The most useful processing method is to use fully automated exposure processing equipment. For example, Silver Master System CP-404 fully automatic plate making machine (trade name of Mitsubishi Paper Industries) can be used.

In this apparatus, the material is supplied in a roll, exposed, cut to any length, developed in a first bath, and subsequently processed in a second conversion bath according to the invention.

Development in the first bath is usually carried out at a temperature of 20°C to 35°C, but may be performed at a higher temperature. The processing time depends on the temperature of development, but 15 seconds at 30° C. is usually sufficient. The conversion bath treatment in the second bath is usually carried out at room temperature (18°C to 25°C). The processing time for this layer has little effect on printing properties, and a processing time of 5 seconds to 20 seconds is sufficient.

The treated printing plate is then squeezed out of excess liquid by a rubber roller and left as is.
It can be attached to a printing machine and printed. Another advantage of the printing plate of the present invention is that the image can be easily modified and erased.

The liquid composition shown in Japanese Patent Publication No. 51-15761 and Japanese Patent Application Laid-Open No. 51-21901, that is, a liquid composition containing an organic compound having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule, is used for the purpose. Can be used for

The present invention will be specifically described below with reference to Examples, but it is not necessarily limited thereto.

(E) Example (I) Preparation of lithographic printing material A gelatin undercoating solution containing silica particles (average size 5 μm) and carbon black was coated onto corona discharge machined polyethylene coated paper. Further, formalin and dimethylol urea were added as colloid hardening agents. The amounts of gelatin and silica deposited were 1.2 grams and 0.7 grams per square meter, respectively. In addition, the core layer showed a reflection density of 0.9.

Subsequently, an ortho-sensitized, high-contrast silver halide emulsion containing formalin and dimethylol urea as colloidal hardeners was coated onto the undercoat layer.

The emulsion layer had the following structure.

After heating the photosensitive silver halide emulsion-containing photographic material at 40°C for 3 days, a lithographic printing material was prepared by applying an aqueous solution containing a water-soluble synthetic polymer substance of the following formulation to 15 mA'/i. did.

Different water-soluble synthetic polymers of the present invention and sodium polyacrylate (from Wako Pure Chemical Industries, Ltd., K, reagent, degree of polymerization 2°700~
7,500) and polyacrylamide (degree of polymerization 1,3
00 to 2.700) were added in amounts shown in Table 2. In addition, a coating liquid containing no polymer at all was prepared as a blank, and a coating liquid containing polyvinyl alcohol and hydroxyethyl cellulose was also prepared for comparison.

The sample was subjected to forced heating at 50°C and 80% for 3 days and 9 days.

(Margin below) (Unit: 2 mole percent) Here, the BSD component contains 5 mol% and R,=H.

R2, R,=CH3, M=N.

As described above, after applying coating liquids containing various water-soluble polymers and drying them by heating, the photosensitive material was subjected to each (II) treatment in order to observe the deterioration of the printing properties of the printing plate material due to natural aging, especially the deterioration of printing stains. After imagewise exposure, it was developed by immersion in a 1:1 dilution of Kogutsklov 2 developer at 25° C. for 30 seconds, and excess developer was squeezed out. Subsequently, it was eroded in a conversion liquid having the following composition at 30° C. for 20 seconds, squeezed, and dried to obtain a printing plate.

(m) Printing method The printing plate thus obtained was printed on an offset printing machine NieB-DiCk350CD (A-B-DiCk350CD).
(product name) and the plate surface with etching liquid (SLM-OH).
Printing was performed after wiping with liquid (manufactured by Mitsubishi Paper Industries). The printing room was at 22° C. and 60% humidity.

Ordinary water was used as a wetting liquid, and F-Gloss Sumi B and F-Gloss Navy Ai manufactured by Dainippon Ink were used as printing inks. F gloss navy blue was one of the inks that easily smeared on the offset printing plate prior to the present invention. Ink acceptance characteristics and ease of staining were determined by the following methods.

1) Ink receptivity: Using F gloss ink as ink, starting paper feeding at the same time as the inked roller contacts the plate surface, the number of prints until a print with good image density is obtained.

2) Evaluation of stains: Using F gloss navy indigo ink, 1.
000 sheets were printed, and the following three levels were evaluated based on the degree of staining of the printed matter.

O No stains occur at all.

Δ Partial or thin dirt.

× Deep stains all over.

3) Printing durability: 1,000 or more sheets were printed, and evaluation was made according to the number of sheets printed at the time when ink starts to appear in the image area, according to the following standards.

03,000 pieces or more △　1,000-3,000 sheets Xi, 000 pieces or less The results obtained here are shown in Table 3 below.

(Hereinafter referred to as margins) From the above results, it was confirmed that the use of the water-soluble synthetic polymer of the present invention has excellent printing properties, especially excellent printing stains, and excellent stability over time.

(F) Effects of the Invention The lithographic printing material of the present invention has the following effects by containing at least one water-soluble synthetic polymer in the uppermost layer, which is crosslinked by heat drying and curing to form a highly absorbent gel layer. It worked.

In other words, it is a planographic printing plate that has a wide tolerance for the amount used, has excellent properties as a printing plate such as ink receptivity, printing smear, printing durability, and image reproducibility, and is especially stable without increasing printing smear due to natural aging. material can be provided.

In addition, it is a lithographic printing material that is stable over time (plate placement) after platemaking processing, has excellent printing properties, and does not particularly cause an increase in printing stains.

Claims (1)

[Claims] After a photographic light-sensitive material having at least one silver halide emulsion layer is imagewise exposed and developed, the undeveloped silver halide remaining in the unexposed areas is reacted with silver ions and has a lower solubility (solubility product). In the process of manufacturing lithographic printing plates in which the surface of the unexposed area is treated in the presence of an organic compound that can be converted into a silver salt (small) and a silver halide solvent, the highly water-absorbing top layer is A lithographic printing plate characterized by enhanced water retention by forming a thin layer of a hydrophilic matrix made of polymer gel.