JPH08137109A - Planographic printing plate - Google Patents

Abstract

PURPOSE: To provide a planographic printing plate which uses a silver complex salt diffusion transfer method and has excellent scratching resistance, contamination resistance and picture qualities of printing. CONSTITUTION: This planographic printing plate is produced by successively forming at least one under coating layer and a silver halide emulsion layer and a physical development nucleus layer on a supporting body. Features of this printing plate are that (a) the center line average roughness Ra of the planographic printing plate is <=0.6, (b) the total amt. of the binder in the emulsion layer side of the printing plate is <=8.0g/m<2> , and (c) a matting agent included in the base coating layer is >=2.0g/m<2> .

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lithographic printing plate to which a silver complex salt diffusion transfer method is applied.

[0002]

2. Description of the Related Art A lithographic printing plate is composed of an oleophilic image-forming portion that accepts oil-based ink and an oil-repellent non-image-forming portion that does not receive ink. It is composed of sex parts. In ordinary lithographic printing, both water and ink are supplied to the plate surface, the image area selectively receives the coloring ink, and the non-image area selectively receives water, and the ink on the image area, such as paper Printing is performed by transferring it to a printing medium. Therefore, in order to obtain a good printed matter, the difference in lipophilicity and hydrophilicity between the image area and the non-image area is sufficiently large, and when water and ink are supplied to the plate surface,
It is necessary that the image area receives a sufficient amount of ink and the non-image area does not receive ink at all.

A lithographic printing plate using a silver complex salt diffusion transfer method (DTR method), particularly a lithographic printing plate having a physical development nucleus layer on a silver halide emulsion layer is disclosed in, for example, US Pat.
No. 8,114, No. 4,134,769, No. 4,1
No. 60,670, No. 4,336,321, No. 4,
No. 501,811, No. 4,510,228, No. 4,621,041 and the like. The exposed silver halide crystals cause chemical development by DTR development to give a black color. It becomes silver and forms a hydrophilic non-image area, while unexposed silver halide crystals become a silver salt complex by the silver salt complexing agent in the developing solution and diffuse to the physical development nucleus layer on the surface to form nuclei. In the presence of the above, physical development is caused to form an image area mainly composed of ink-receptive physically developed silver.

The influence of the surface irregularities of the lithographic printing plate on the printability is well known in the field of PS plates, but it is also an important factor in the lithographic printing plate using the silver complex salt diffusion transfer method of the present invention. It is known. In particular, in a lithographic printing plate using the silver complex salt diffusion transfer method, the non-image area is mainly composed of a gelatin film, and although it is originally highly hydrophilic, it is used to improve the printing durability of the image area. It was general that the agent is designed to have a large matte surface (large unevenness on the surface). Japanese Unexamined Patent Application Publication No. 5-66564, No. 5-80517, No. 5-80518, No. 5-805.
20, Dohei 5-80519, Dohei 5-100430, and U.S. Pat. No. 5,281,509, it is disclosed that there is a correlation between the matteness of the surface and the print stain, and the surface is smoothed. Disclose that the print stain on the non-image area can be significantly reduced.

However, although smoothing the surface was effective in improving printing stains, the polyester film support was more automatic than the support such as RC paper in the developing process during plate making. The processing by the developing machine easily caused scratches on the plate surface. Since the scratches appear overlapping the image portion, they are serious defects in practical use. Further, recently, due to the diversification of automatic developing machines and the like, they are subjected to more severe handling than conventionally performed, and scratches are more likely to occur. Further, in recent years, while demands for high image quality and high definition printing have increased more than ever, the same demands have been made for lithographic printing plates using the silver complex salt diffusion transfer method. Particularly, in order to improve the printing image quality of the planographic printing plate, it is important to reduce the surface roughness, and therefore smoothing has become an essential condition. Therefore, there is a demand for a lithographic printing plate using a silver complex salt diffusion transfer method that has excellent scratch resistance and is capable of sufficiently enduring under such practically necessary processing conditions.

As a means for adjusting the center line average roughness by smoothing the surface roughness of a lithographic printing plate using the silver complex salt diffusion transfer method, silica having a relatively small particle size is filled. Although it was also disclosed in 107765 and was general,
The smaller the particle size of silica, the lower the dispersion performance, so there was a limit to the particle size and addition amount. In particular, silica having an average particle size of 3 microns or less causes a large decrease in dispersion performance, and thus has problems such as aggregation. To adjust the surface properties of a lithographic printing plate, a large amount of matting agent relative to the amount of binder is added. Since it is necessary, it is particularly difficult to use, and a system in which fine silica is applied to adjust the surface roughness has many problems and is not suitable for practical use.

[0007] In recent years, the development of fine silica having extremely excellent dispersibility has made great progress, and it has become possible to adjust the surface roughness using such fine silica. Paying attention to this point,
A matting agent having a small average particle diameter is densely filled in the undercoat layer of the lithographic printing plate, and the center line average roughness R of the lithographic printing plate is
It has been clarified that maintaining the reduction of the a value is effective in improving the high print image quality and the scratch resistance without lowering the stain resistance.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithographic printing plate using a silver complex salt diffusion transfer method, which is excellent in scratch resistance, stain resistance and printing image quality.

[0009]

A lithographic printing plate comprising at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer, which are successively coated on a support. The centerline average roughness Ra value is 0.6 or less, and b) the total binder amount on the emulsion layer side of the planographic printing plate is 8.0 g.
/ M ² or less and c) the matting agent contained in the undercoat layer is adjusted to 2.0 g / m ² or more. More preferably, the average particle diameter of the matting agent is 3 μm or less, and the amount of the matting agent contained in the undercoat layer of the lithographic printing plate is adjusted to 1.5 or more relative to 1 of gelatin. .

In the present invention, the center line average roughness Ra value of the lithographic printing plate can be measured by using a surface roughness profile measuring device, for example, Surfcom 500B manufactured by Tokyo Seimitsu Co., Ltd. From the roughness curve, a portion of the measurement length l is extracted in the direction of the center line, and the center line of the extracted portion is the X axis,
When the direction of longitudinal magnification is taken as the Y axis and the roughness curve is represented by y = f (x), the centerline average roughness Ra value is expressed in units of micrometers and can be calculated by the formula (1).

[0011]

[Equation 1]

In the present invention, the centerline average roughness Ra value of the planographic printing plate must be 0.6 or less. When the center line average roughness Ra value of the planographic printing plate is larger than 0.6, the print image quality deteriorates.

In the present invention, it is necessary that the total binder amount on the emulsion layer side is 8.0 g / m ² or less. If the total amount of binder on the emulsion layer side is 8.0 g / m ² or more, the scratch resistance decreases.

The binder used in the present invention is
Gelatin, water-soluble gelatin, starch, dextrin, albumin, sodium alginate, hydroxyethyl cellulose, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, polyacrylamide, styrene-maleic anhydride copolymer, polyvinyl methyl ether-maleic anhydride copolymer It is also possible to substitute one or more hydrophilic polymers such as polymers. Further, it is an aqueous dispersion of a vinyl polymer (latex such as styrene-butadiene copolymer).

The matting agent used in the present invention has an average particle size of 5
Solid powder of micron or less, for example, silica particles,
Examples include organic particles such as styrene. In the present invention, silica particles having an average particle diameter of 3.0 μm or less are particularly preferable. Specific examples of silica particles include Carplex (average particle size: 1.2 microns) manufactured by Shionogi Pharmaceutical Co., Ltd.

In the present invention, the matting agent is contained in the subbing layer between the support and the silver halide emulsion layer. The amount of the matting agent added varies depending on various conditions, but 1.
It is in the range of 0 to 5.0 g / m ² , preferably 2.2.
It is in the range of 3.5 g / m ² .

US Pat. No. 5,281,509 describes a lithographic printing plate having a centerline surface roughness of 0.6 or less, and a matting agent of 2.0 g / m ² or more. However, from the technology at the time, if the total amount of binder on the emulsion layer side is 8.0 g / m ² or less and a matting agent of 2.0 g / m ² or more is used, the center line surface roughness will be 0. It was impossible to obtain a lithographic printing plate of 6 or less. By using the silica particles having good dispersibility of the fine particles in the present invention, even if the total binder amount on the emulsion layer side is 8.0 g / m ² or less, a matting agent of 2.0 g / m ² or more is used. In particular, it became easy to obtain a lithographic printing plate having a center line surface roughness of 0.6 or less.

The mechanism of action of the present invention is presumed as follows. By reducing the center line average roughness Ra value for the purpose of improving the stain resistance performance and the print image quality, it is possible to perform processing especially in an automatic developing machine (hereinafter abbreviated as an automatic processor) in the development processing step during plate making. At that time, scratches were likely to occur. This is because, for example, when the lithographic printing plate being conveyed during the development process comes into contact with the guide plate inside the developing machine, the function of dispersing the force applied to the plate surface improves the smoothness of the lithographic printing plate. I think that it has declined as a result. In particular, the tendency of the support of the polyester film became remarkable because the function of dispersing the force applied to the plate surface, that is, the stress relaxation property was further deteriorated because the hardness of the support was higher than that of RC, It is expected that this will lead to scratches. In the present invention, in order to improve the stress relaxation property and maintain the smoothness of the surface roughness, it is necessary to densely fill the undercoat layer with a fine matting agent to improve scratch resistance, stain resistance and print image quality. Proved to be effective.

The lithographic printing plate which is the object of the present invention contains gelatin, and the containing layer may be an undercoat layer, an emulsion layer or a physical development nucleus layer. These gelatin-containing layers can be hardened with a gelatin hardener.
Examples of the gelatin hardener include inorganic compounds such as chromium alum, aldehydes such as formalin, glyoxal, malealdehyde and glutaraldehyde, N-methylol compounds such as urea and ethyleneurea, mucochloric acid, 2,3. Aldehydes such as dihydroxy-1,4-dioxane, 2,4-dichloro-6-hydroxy-
Compounds having an active halogen such as S-triazine salts and 2,4-dihydroxy-6-chloro-S-triazine salts, divinyl sulfone, divinyl ketone and N, N, N
-Triacroylhexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups or epoxy groups in the molecule, one of various compounds such as dialdehyde starch as a polymer hardener, or Two or more kinds can be used.

The hardener can be added to all layers or to some or only one layer.
Of course, in the case of two-layer simultaneous application, the diffusible hardener can be added to only one of the layers. As an addition method, it may be added at the time of emulsion production or in-line at the time of coating.

The undercoat layer may contain pigments such as carbon black and dyes for the purpose of preventing halation. Further, photographic additives such as developing agents can be included. Further, the undercoat layer is disclosed in JP-A-48-5503 and JP-A-48-10020.
3, such as those described in JP-A-49-16507.

The silver halide emulsion layer is, for example, silver chloride,
It comprises silver bromide, silver chlorobromide, and those containing silver iodide. The silver halide crystal may contain a heavy metal salt such as a rhodium salt, an iridium salt, a palladium salt, a ruthenium salt, a nickel salt and a platinum salt, and the addition amount is from 10 ^-8 to 10 ^-3 per mol of silver halide. It is a mole. The crystal form of silver halide is not particularly limited, and may be cubic or tetradecahedral grains, or core-shell type or tabular grains. The silver halide crystal may be a monodisperse or polydisperse crystal,
The average particle size is in the range of 0.2 to 0.8 μm. One preferable example is a monodisperse or polydisperse crystal containing rhodium salt or iridium salt and having a silver chloride content of 80 mol% or more.

The silver halide emulsion can be sensitized in various ways as it is manufactured or coated. It is preferable to chemically sensitize by methods well known in the art, for example, with sodium thiosulfate, alkyl thiourea, or with a gold compound such as gold rhodanide, gold chloride, or a combination of both. The silver halide emulsions can also be sensitized or desensitized positively or negatively with dyes such as cyanines, merocyanines. There is no particular limitation on the wavelength range that can be sensitized or desensitized. Therefore, ortho sensitization, panchromatic sensitization, helium-neon laser sensitization, argon laser sensitization, LED sensitization, semiconductor laser sensitization can be performed, and UV sensitization and visible light desensitization for bright rooms. I can feel it.

The surface layer present on top of the emulsion layer contains physical development nuclei. Physical development nuclei include fine particles of metal colloid such as silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium, gold and platinum, and sulfides, polysulfides, selenides of these metals, or those. It may be a mixture or a mixed crystal. Physical development nuclei may or may not contain a hydrophilic binder, but gelatin, starch, dialdehyde starch, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl cellulose, polystyrene sulfonic acid, sodium polyacrylate, vinyl It may contain a copolymer of imidazole and acrylamide, a copolymer of acrylic acid and acrylamide, a hydrophilic polymer such as polyvinyl alcohol or an oligomer thereof, and the content thereof is 0.5 g / m.
It is preferably ² or less. Further, the physical development nucleus layer may contain a developing agent such as hydroquinone, methylhydroquinone and catechol, and a known hardener such as formalin and dichloro-s-triazine.

Each of the coating layers such as the undercoat layer, the silver halide emulsion layer and the physical development nucleus layer may contain some of anionic, cationic or neutral surfactants as coating aids. , Antifoggants, matting agents, thickeners, antistatic agents and the like.

The support for the lithographic printing plate of the present invention includes:
Paper or a synthetic or semi-synthetic polymer film, a metal plate such as aluminum or iron, and the like can be used as long as they can withstand lithographic printing. The surface of the support may be coated on one side or both sides with one or more polymer films or metal thin films. The surface of these supports can be surface-treated in order to improve the adhesion with the coating layer.

Particularly preferably used supports are paper having both surfaces or one surface coated with a polyolefin polymer, a polyester film, a polyester film having a hydrophilic surface, a surface-treated aluminum plate, and the like.
These supports may contain pigments for preventing halation and solid fine particles for improving surface properties. The support may also be light transmissive so that backside exposure is possible.

The developing solution used in the present invention contains an alkaline substance such as sodium hydroxide or potassium hydroxide,
Lithium hydroxide, sodium triphosphate, etc., sulfites as preservatives, silver halide solvents, such as thiosulfates,
Thiocyanates, cyclic imides, 2-mercaptobenzoic acid, amines, thickeners such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants,
For example, potassium bromide, the compounds described in JP-A-47-26201, developers, such as hydroquinones, catechol, 1-phenyl-3-pyrazolidone, development modifiers,
For example, a polyoxyalkylene compound and an onium compound can be included. Further, compounds such as those described in U.S. Pat. No. 3,776,728, which improve ink transfer of the surface silver layer, can be used in the developing solution.

The surface silver layer after development of the lithographic printing plate of the present invention can be converted into ink receptivity or the receptivity can be enhanced with any known surface treatment agent. Examples of such treatment liquid include Japanese Patent Publication No. 48-29723 and U.S. Pat. No. 3,7.
21, 559 and the like. The printing method, or the desensitizing liquid, the dampening liquid, or the like to be used may be a commonly known method.

[0030]

EXAMPLES The present invention will be explained below with reference to examples, but of course the present invention is not limited thereto.

Example 1 An undercoat layer was formed on a polyester film support which had been subjected to an aqueous undercoating treatment with an undercoating composition containing an epoxy compound disclosed in JP-A-60-213942 for the purpose of hydrophilization. Apply.

<Undercoating liquid> Gelatin 15 g Water 200 g Shionogi Pharmaceutical Co., Ltd. Carplex (FPS-101) Xg Water 160 g Carbon black dispersion liquid (solid content 32%) 8 g Formaldehyde (30% aqueous solution) 2 g Gliogizar (30) % Aqueous solution) 4 g Surfactant 6 ml Water is added to bring the total amount to 600 g.

The amount of gelatin and the amount of silica are shown in Table 1. The coating amount was 60 g / m ² in terms of moisture coating amount. An ortho-sensitized high-contrast silver chloride emulsion was coated on the undercoat layer in an amount of 1.5 g / m ² in terms of silver nitrate.
After drying, the mixture is heated at 50 ° C. for 2 days, and then, disclosed in JP-A-58-21602
In the core coating solution described in Example 2 (containing a copolymer of acrylamide and imidazole of No. 3 as a polymer and containing hydroquinone as a developing agent at a rate of 0.8 g / m ² ), sodium polyacrylate ( Average molecular weight 26,000
0) was added in an amount of 0.04 g / m ² to prepare and apply the solution in the same manner. (Samples 1, 2, 3, 4)

For comparison, comparative samples were prepared in the same manner except that the amount of gelatin and the amount of silica in the undercoating liquid were shown in Table 1 (Comparison a to c).

Each of the planographic printing plates was subjected to image exposure and development processing using a plate-making camera processor CP-550II manufactured by Mitsubishi Paper Mills. The development was carried out with the following diffusion transfer developer at 30 ° C. for 20 tons. Stabilization was carried out by treating with a stabilizing solution having the following composition at 25 ° C. for 20 seconds and drying.

<Diffusion Transfer Developer> Water 700 g Sodium hydroxide 18 g Potassium hydroxide 7 g Anhydrous sodium sulfite 50 g 2-Mercaptobenzoic acid 1 g Uracil 10 g 2-Methylaminoethanol 30 g 5-Phenyl-2-mercapto-1,3,4 -Oxadiazole 0.1 g Potassium bromide 1 g Water is added to bring the total volume to 1,000 ml.

<Stabilizing Solution> Water 600 g Citric acid 10 g Sodium citrate 35 g Colloidal silica (20%) 5 g Ethylene glycol 5 g Water is added to bring the total volume to 1,000 ml.

The printing evaluation is AB Dick 350.
CD (trademark of AB Dick offset printing machine)
It was used. In order to check the stain resistance of the non-image area, F gloss purple 68S made by Dainippon Ink is used as the ink, and 2.5% aqueous solution of KPS # 500 made by ROSOS Co., Ltd. is used as the moisturizing liquid. The number of prints when stains occurred and printing was stopped, and the evaluation was made according to the following evaluation criteria. (A) 3000 sheets or more (B) 1000 to 3000 sheets (C) 500 to 1000 sheets (D) 100 to 500 sheets (E) Less than 100 sheets The printing results are shown in Table 1.

The scratch resistance was evaluated on the basis of the level of scratches generated on the plate surface after the development processing was carried out by the processor. (A) There are no scratches on the printing plate. (B) Although there are very thin scratches, there is no problem in practical use. (C) Although inferior to the level of (B), there is no practical problem. (D) It is inferior to the level of (C), and a scar is seen thinly during printing, which is a problem in practical use. (E) There are scratches and there are practical problems. The scratch resistance results are shown in Table 1.

The print image quality was evaluated by evaluating the image quality of the printed matter. (A) Excellent (B) Somewhat excellent (C) Somewhat inferior (D) Inferior

[0041]

[Table 1]

As is clear from Table 1, the samples of the present invention were found to be superior in stain resistance and scratch resistance as compared with Comparative samples a, b and c.

Example 2 In the undercoating liquid of Example 1, a sample was prepared in the same manner as in Example 1 except that the particle size of silica was as shown in Table 2, and the printing evaluation was performed. The results are shown in Table 2.

[0044]

[Table 2]

As is clear from Table 2, the samples of the present invention are superior in scratch resistance, stain resistance and print image quality as compared with Comparative Examples d, e and f.

Example 3 A sample was prepared in the same manner as in Example 1 except that the amount of gelatin and the amount of silica added in the undercoating liquid of Example 1 were as shown in Table 3, and printing evaluation was performed. The results are shown in Table 3.

[0047]

[Table 3]

As is clear from Table 3, the samples of the present invention are excellent in scratch resistance, stain resistance and print image quality as compared with Comparative g and h.

[0049]

By using the present invention, it is possible to provide a lithographic printing plate excellent in scratch resistance, stain resistance and printing image quality.

Claims (3)

[Claims] 1. A lithographic printing plate comprising at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer, which are successively coated on a support, comprising: a) a center line average roughness of the lithographic printing plate. Ra value is 0.6 or less, and b) the total amount of binder on the emulsion layer side of the planographic printing plate is 8.0 g.
/ M ² or less, and c) the matting agent contained in the undercoat layer is 2.0 g / m ² or more, a lithographic printing plate. 2. The lithographic printing plate as claimed in claim 1, wherein the matting agent has an average particle size of 3 μm or less. 3. The lithographic printing plate as claimed in claim 1, wherein the amount of the matting agent contained in the undercoat layer of the lithographic printing plate is 1.5 or more relative to 1 of gelatin.