JP2549782B2 - Lithographic printing plate - Google Patents

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.

As described above, in the planographic printing plate, gelatin-
Since the silver image deposited on the physical development nucleus layer on the silver halide emulsion layer is used as the ink-receptive image area, the image area is larger than that of a general lithographic printing plate (eg PS plate). There is a defect that the resistance to mechanical abrasion of the image part is insufficient, the image part is missing, and the ink receiving property of the image part is gradually lost.

In order to overcome this drawback, if the hardness of gelatin is increased or the amount of physical development nuclei is increased, scumming occurs and the printing durability of the lithographic printing plate remarkably decreases.
Further, there are drawbacks such as background stain and deterioration of ink receptivity due to storage for a long period from the production of the lithographic printing plate to the production of the lithographic printing plate, and improvement is desired.

The effect of surface irregularities of the lithographic printing plate on printability is well known in the field of PS plates, but it is an important factor even in the lithographic printing plate using the silver complex salt diffusion transfer method of the present invention. It was revealed. 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). The present inventors have examined the correlation between the matting property of the surface and the printing stain, and in the present invention, in the lithographic printing plate containing a matting agent and titanium oxide in the undercoat layer, the lithographic printing plate It has been found that by specifying the center line average roughness Ra value of No. 1, the print stain in the non-image area can be significantly reduced.

[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 printing durability and water retention.

[0009]

The above object of the present invention is to provide a lithographic printing plate comprising a support and at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer, which are sequentially coated on the support. A matting agent and titanium oxide are contained in the undercoat layer, and the center line average roughness Ra value (CUT OFF value:
0.08mm, TRAVERSING LENGTH: 0.8mm) was adjusted to 1.2 or less.

The matting agent used in the present invention has an average particle size of 1 to
10 micron solid powder, eg silica particles,
There are talc and clay. In the present invention, silica particles having an average particle size of 1 to 5 μm are preferable. In particular, silica particles whose surface is treated with hydrogen fluoride have excellent dispersion stability and are preferred. Specific examples of silica particles include Syloid manufactured by Fuji Divison Chemical Co., Ltd. The amount of the matting agent added varies depending on various conditions, but is in the range of 0.1 to 4 g per 1 m ² .

The titanium oxide used in the present invention may be of any type such as anatase type and rutile type, and may be surface-treated for the purpose of dispersion stability and the like. In the present invention, titanium oxide particles having an average particle diameter of 0.01 to 0.8 micron are preferable. Titanium oxide is usually dispersed in water,
It is added during makeup before application, but not always
It is not limited to this. The amount of titanium oxide added varies depending on various conditions, but is in the range of 1 to ²⁰ g per 1 m ² .

In the present invention, the center line average roughness Ra value of the planographic printing plate can be measured by using a surface roughness profile measuring instrument, 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).

[0013]

[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 matting agent added for the purpose of improving printing durability has a tendency to aggregate, which increases the matteness of the surface and makes it easier for ink to accumulate in the recesses on the surface of the non-image area, resulting in printing. Contamination will occur. A combination of matting agents having different particle diameters also tends to agglomerate, which easily causes print stains. To reduce the agglomeration of this matting agent, use titanium oxide fine particles with excellent dispersibility,
By entering between the matting agent and interfering with the aggregation of the matting agent, the matting property of the surface is reduced,
As a result, ink is less likely to be accumulated in the non-image area, and print stains are less likely to occur. The effect of titanium oxide that disperses the matting agent depends on the average size of the matting agent and the amount of binder. The center line average roughness Ra value correlates with the matteness of this surface, and this value can specify the range of combined use of the matting agent and titanium oxide.

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 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. The undercoat layer is disclosed in JP-A-4.
8-5503, 48-100203, 49-1
It may be as described in 6507.

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 above 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 an anion, a cation or a neutral surfactant as a coating aid. , 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 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.

[0028]

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 55 g Water 200 g Titanium oxide (SR-1 manufactured by Sakai Chemical Co., Ltd.) 50 g Water 100 g Syroid (No. 978) 15 g manufactured by Fuji Divison Co., Ltd. 15 g Carbon black dispersion liquid (solid content 32%) 8 g Formaldehyde ( It was added a 30% aqueous solution) 2 g glyoxal hexa Lumpur (30% aqueous solution) 4g surfactant 6ml water to a total volume of 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, a comparative sample was prepared in the same manner except that titanium oxide (TR-1 manufactured by Sakai Chemical Co., Ltd.) was not added to the undercoating liquid ( Comparison a). In addition, as a comparison, the undercoating liquid was made by Fuji Divison's Syroid (N
o. A comparative sample was prepared in the same manner except that ( 978: average particle size 2.5 μm) was not added ( Comparison b).
Next, as a comparison, a primer coating liquid of Fuji Divison Co. Syloid: the amount of (Nanba978 mean particle size 2.5 microns), except that the 50 g, was prepared the ratio較試charges in a similar manner ( Comparison c).

Each of the above lithographic 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. Regarding the printing durability, each lithographic printing plate was treated with the following desensitizing liquid, and then the following dampening liquid was used to print using New Champion Ink N manufactured by Dainippon Ink and Co., Ltd. Used and used as ink F by Dainippon Ink
Using gloss black, the number of prints when the image was skipped due to the missing of the silver image portion and the image could not be printed was judged according to the following evaluation criteria. (A) 20,000 sheets or more (B) 10,000 to 20,000 sheets (C) 5,000 to 10,000 sheets (D) 2,000 to 5,000 sheets (E) Less than 2,000 sheets The results are shown in Table 1.

<Desensitizing Solution> Water 600 g Isopropyl alcohol 400 g Ethylene glycol 50 g 3-Mercapto-4-acetamido-5-n-heptyl-1,2,4-triazole 1 g

<Moistening liquid> O-phosphoric acid 10 g Nickel nitrate 5 g Sodium nitrite 5 g Ethylene glycol 100 g Colloidal silica (20% liquid) 28 g Water is added to make 2,000 ml.

On the other hand, in order to see the water retention (background stain) of the non-image area, the ink is F Gloss Purple 68S made by Dainippon Ink.
Was used, and 2.5% KPS # 500 aqueous solution manufactured by Rossos Co., Ltd. was used as a moisturizing liquid, and the number of printed sheets when AB Dick350CD became dirty and could not be used for printing was judged by 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.

[0040]

[Table 1]

As is clear from Table 1, Syloid 97
In Comparative c with a large addition amount of 8 and Comparative a containing no titanium oxide, the center line average roughness exceeds 1.2,
These have poor water retention, while Syloid 978
In Comparative b which does not include, the center line average roughness is 1.2 or less, but this is inferior in printing durability. On the other hand, the sample 1 of the present invention was found to be excellent in water retention and printing durability because it contained Syloid 978 and titanium oxide and had a center line average roughness of 1.2 or less. did.

Example 2 In the undercoating liquid of Example 1, gelatin, siloid,
Also, the amount of titanium oxide added and the grade of siloid (N
o. 65: Average particle size 3.5 μm, NO. 308: Average particle size 3.5 μm, NO. 150: Average particle size 1.4
(Micron) as shown in Table 2, a sample was prepared in the same manner as in Example 1, and printing evaluation was performed. The results are shown in Table 2.

[0043]

[Table 2]

As is clear from Table 2, Samples 2 of the present invention
No. 5 has a center line average roughness Ra value of 1.2 or less and is excellent in water retention and printing durability, while in comparisons d to e, the center line average roughness Ra value exceeds 1.2. And has poor water retention.

[0045]

INDUSTRIAL APPLICABILITY By using the present invention, it is possible to provide a lithographic printing plate excellent in water retention and printing durability.

Claims (1)

(57) [Claims] 1. A lithographic printing plate comprising a support, on which at least one undercoat layer, a silver halide emulsion layer and a physical development nucleus layer are successively coated, wherein a matting agent and an oxidation agent are contained in the undercoat layer. A lithographic printing plate containing titanium and having a center line average roughness Ra value of 1.2 or less.