JPH07168360A - Planographic printing plate - Google Patents

Abstract

PURPOSE:To improve staining resistance and scratching resistance by using a silver complex salt diffusion transfer method by incorporating silica particles having a specific oil absorption rate into constituting layers and specifying center line average height of a planographic printing plate. CONSTITUTION:A primer coating layer, silver halide emulsion layers and physical development nuclei layers are successively applied on a base. The silica particles which are<=150 in the oil absorption rate by the testing method stipulated in JIS(Japanese Industrial Standards) are incorporated in these constituting layers and the center line average height Ra value of the planographic printing plate is adjusted to <=1.2. Namely, a matting agent to be used is silica powder having the oil absorption rate of <=150 and <=10 mircon average grain size and is more particularly preferably the silica particles having 0.5 to 5 micron average grain sizes. The center line average height Ra value of the planographic printing plate is measured by using a surface roughness shape measuring machine. The dispersibility in an aq. soln. is better with the silica having the lower oil absorption rate. The decrease of the necessary amt. of the dispersing water is thus possible.

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 the image area is sufficient when water and ink are supplied to the plate surface. It is necessary to accept a certain amount of ink and not to accept ink in the non-image area.

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 described in, for example, US Pat. No. 3,72.
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 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 was revealed. Particularly, 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 Patent Application Nos. 3-259655, 3-268864, 3-268765, 3-2
68767, Dohei 3-268766, Dohei 3-2856
23, it was disclosed that there is a correlation between the matteness of the surface and the print stain, and it was disclosed that the print stain of the non-image area can be significantly reduced by smoothing the surface.

However, although smoothing the surface was effective in improving print stains, scratches were likely to occur on the plate surface during development processing during plate making, especially during processing by an automatic processor. Since the scratches appear overlapping the image portion, they are serious defects in practical use. Further, recently, due to the expansion of processing methods and the diversification of automatic developing machines, the handling is more severe than in the past, and scratches are more likely to occur. 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.

In order to overcome this drawback, it is necessary to densely fill the constituent layers with silica having a small average particle size and to keep the center line average roughness Ra value reduced, which leads to deterioration of the stain resistance performance. Although it has been clarified that it is effective for improving scratch resistance, it is conventionally necessary to densely fill such a constituent layer of such fine silica with a large amount of dispersed water in the dispersion process of silica. In addition, since the silica itself has low dispersibility, it tends to aggregate when added to the gelatin aqueous solution. As a result, the center line average roughness Ra value increases, and the stain resistance performance deteriorates, which is a problem.

[0008]

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 stain resistance and scratch resistance.

[0009]

In a lithographic printing plate having at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer, which are successively coated on a support, the constituent layers are
This was achieved by containing silica particles having an oil absorption of 150 or less according to the JIS K5101 test method and adjusting the center line average roughness Ra value of the lithographic printing plate to 1.2 or less.

The matting agent used in the present invention has an oil absorption of 15
It is a silica powder having an average particle size of 0 or less and an average particle size of 10 microns or less, and particularly preferably silica particles having an average particle size of 0.5 to 5 μm in the present invention. Specific examples of silica particles include Carplex manufactured by Shionogi Pharmaceutical Co., Ltd. The amount of matting agent added varies depending on various conditions, but is 1 m.
It is in the range of 0.1 g to 5 g per ² .

In the present invention, the centerline average roughness Ra value of the planographic 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).

[0012]

[Equation 1]

In the present invention, the center line average roughness Ra value of the planographic printing plate must be 1.2 or less. When the center line average roughness Ra value of the planographic printing plate is larger than 1.2, printing stains are likely to occur.

The mechanism of action of the present invention is presumed as follows. The smaller the oil absorption, the better the dispersibility in an aqueous system. Therefore, it is generally necessary to increase the amount of dispersed water when densely packing fine particle silica into the constituent layer, but it is possible to reduce the amount of dispersed water required for silica with a small oil absorption amount. Is. Therefore, it is possible to obtain a good dispersion state with a smaller amount of dispersed water compared to silica, which has a large oil absorption amount, so that it is possible to maintain close packing and good dispersibility in the constituent layers during the manufacturing process. Therefore, an increase in the average line center roughness Ra value can be suppressed. It is considered that the dense packing of the fine particles in the constituent layer is effective for the scratch resistance because the function of dispersing the force applied to the plate surface at the time of contact, which is the cause of the scratch, is improved. It is considered that the results are excellent in relaxation characteristics.

The lithographic printing plate which is the object of the present invention contains gelatin, and its 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
-Triacryloylhexahydrotriazine, compounds having two or more ethyleneimino groups or epoxy groups in the molecule, which are active three-membered rings, 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, the diffusible hardener can be added to only one layer in the case of simultaneous coating of two layers. As an addition method, it may be added at the time of emulsion production or in-line at the time of coating.

Gelatin in the gelatin-containing layer of the present invention comprises a part of water-soluble gelatin, starch, dextrin, albumin, sodium alginate, hydroxyethyl cellulose, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, polyacrylamide, styrene. It may be substituted with one or more hydrophilic polymers such as a maleic anhydride copolymer and a polyvinyl methyl ether-maleic anhydride copolymer. Further, an aqueous vinyl polymer dispersion (latex) can be added to the gelatin layer.

The polymeric binder of the subbing layer is generally 0.5.
It is preferably from 1 to 6 g / m ^2, more preferably from 10 to 10 g / m ² .
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, 48-100203 and 49-49.
It may be as described in 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. The physical development nucleus 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, the content of which is 0.5 g / m 2.
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 papers whose both surfaces or one surface is coated with a polyolefin polymer, polyester films, polyester films whose surfaces have been hydrophilized, and surface-treated aluminum plates.
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 treating 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.

[0027]

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.

<Undercoat liquid> Gelatin 55 g Water 200 g Shionogi Pharmaceutical Co., Ltd. Carplex (FPS-101) 40 g 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 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. (Sample 1)

For comparison, comparative samples were prepared in the same manner except that silica having different oil absorption was added to the undercoating liquid (comparisons 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 by the level of the scratches 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.

[0037]

[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. Further, Comparative a has a tendency to aggregate, but has a relatively small Ra value because of its small particle size, and has good stain resistance but poor scratch resistance. Regarding Comparative b, the scratch resistance is good but Ra
Since the value is large, the stain resistance is poor. Regarding Comparative c, the dispersibility of the silica particles was good, but the stain resistance performance deteriorated as the Ra value increased with this silica usage amount because the particle size was relatively large.

Example 2 A sample was prepared in the same manner as in Example 1 except that the amount of silica used in the undercoating liquid of Example 1 was half that of Example 1 and the particle size was as shown in Table 2. , Printing evaluation was performed. The results are shown in Table 2.

[0040]

[Table 2]

As is clear from Table 2, the samples of the present invention are superior in stain resistance and scratch resistance as compared with Comparative Examples d, e and f.
Regarding the comparisons d and e, the Ra value is 1.2 or less and the stain resistance is excellent, but the scratch resistance is inferior. In Comparative Example f, since the amount of silica particles supplied was small, the dispersibility was good and the scratch resistance was excellent, but the Ra value was 1.2 or more and the stain resistance was poor.

[0042]

EFFECT OF THE INVENTION By using the present invention, it is possible to provide a lithographic printing plate excellent in stain resistance and scratch resistance.

Claims (1)

[Claims] 1. A lithographic printing plate obtained by sequentially coating at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer on a support, wherein the constituent layers have an oil absorption by JIS K5101 test method. A planographic printing plate comprising silica particles in an amount of 150 or less and having a center line average roughness Ra value of 1.2 or less.