JPS6146826B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lithographic printing plate using a silver complex diffusion transfer method and a method for manufacturing the same. A lithographic printing plate consists of an oleophilic image area that accepts oil-based ink and an oil-repellent non-image area that does not accept ink, and the non-image area generally consists of a hydrophilic area that accepts water. has been done. In normal lithography, therefore, both water and ink are supplied to the print, and colored ink is applied to the printing area.
The non-image areas are created by selectively accepting water and transferring the ink on the image 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 is It is necessary that a sufficient amount of ink be accepted, and that the non-image area should not receive any ink. Disadvantages associated with lithographic printing plates made by the silver complex diffusion transfer method (DTR method) include, for example, insufficient resistance to mechanical abrasion, lack of hydrophobic areas that carry the ink image, and Alternatively, it may gradually lose its ink receptivity, resulting in a decrease in printing durability. Furthermore, the hydrophilic areas gradually become hydrophobic, so that the non-imaged areas or areas become smeared with ink. Furthermore, the uniform greasy ink receptivity in the hydrophobic image areas is compromised, which causes variations in the ink receptivity in said image areas, and thus the printed area is unable to accept a uniform amount of ink. . Printing plates that apply the DTR method and utilize the formed metal-silver complex pattern as ink receptivity are already known (for example, U.S. Pat. No. 3,220,837, U.S. Pat. No. 3,721,559).
No., Special Publication No. 16725, No. 16725, No. 30562, Special Publication No. 1973
4482, 1972-21602, etc.), although some of them have been realized, they still have the above-mentioned drawbacks. As with other lithographic printing plates,
Even in planographic printing plates to which the DTR method is applied, it is required to increase the printing durability by changing the composition of the plate material, the composition of the processing liquid, printing conditions, etc., and many attempts have been proposed so far. In such printing plates, in addition to ensuring that the transferred silver particles have good ink receptivity, one important factor that determines printing durability is that the transferred silver in the fine line areas does not come off during printing. be. One of the factors that governs the resistance of transferred silver to mechanical abrasion is the type of silver halide solvent.
55-146452, Showa 56-1057, Showa 56-6237, Showa
It was proposed in 1986-8145, 1984-9749, 1984-9750, etc. Another method is to sufficiently harden the silver halide emulsion layer or undercoat layer provided below the physical development nucleus layer with a hardening agent such as formalin. As is well known, the hardening of gelatin depends on the pH
As the value increases, a higher level can be obtained, and the required level of hardening can be obtained in a short period of time. The above-mentioned patent specifications disclose that after coating an undercoat layer containing formalin and a silver halide emulsion layer, the coating is cured by heating at 40° C. for 3 days. Generally, it is possible to obtain the level of curing required for the lithographic printing plate in such a short period of time. However, such methods have the drawback that, although the required level of curing is achieved, the transferred silver in the fine line areas often comes off during printing, resulting in failures that can no longer be used for printing. It became clear that it was. Naturally, as the amount of silver per unit area is reduced, for example silver halide corresponding to less than 0.8 mmol of silver per square meter, the above-mentioned disadvantages become more severe. Further, as described above, printing durability is also reduced by ink staining due to decreased hydrophilicity of non-image areas. Therefore, it is a matter of course that the lithographic printing plate must be free from image skipping and background smearing and can withstand long printing times. Although it is generally difficult to maintain both lipophilicity and hydrophilicity at a satisfactory level during long printing periods due to their contradictory properties, it is difficult to maintain both lipophilicity and hydrophilicity at a satisfactory level during long printing periods. Development is desired. An object of the present invention is to provide a lithographic printing plate using a silver complex diffusion transfer method with improved printing durability and a method for manufacturing the same. Another object of the present invention is to provide a lithographic printing plate using a silver complex diffusion transfer method that has a low silver content and improved printing durability, and a method for producing the same. Further objects and advantages of the present invention will be understood from the following description of the specification. The present invention provides at least one layer under the physical development nucleus layer.
In a lithographic printing plate having two gelatin-containing layers, all of the gelatin-containing layers have a pH value below the isoelectric point of the gelatin, and at least one of the gelatin-containing layers contains photographic gelatin and low molecular weight gelatin. This was basically achieved by In particular, it is a preferred embodiment of the present invention to use photographic gelatin and low molecular weight gelatin in the undercoat layer.
Furthermore, it is a preferred embodiment to use photographic gelatin and low molecular weight gelatin in the emulsion layer. An example of the method for producing the lithographic printing plate of the present invention is to place the above two types of gelatin on a support that has been subjected to a hydrophilic treatment or a subbing treatment, the pH value of which is adjusted to be lower than the isoelectric point of the gelatin. A subbing layer containing gelatin is applied along with carbon black for antihalation. This undercoat layer contains a curing agent. Furthermore, the isoelectric point of the gelatin on top of the above-mentioned subbing layer is lower than that of the gelatin. A gelatin/silver halide emulsion layer adjusted to the desired pH value is applied. This emulsion layer also contains a hardening agent. This sample is cured by a heating process at 40°C. The number of days of heating is determined by heating a sample prepared in the same manner as above, except that the pH value of the undercoat layer and emulsion layer in the above sample is adjusted to be above the isoelectric point of the gelatin, for example, to about PH 6.0, for example, for 3 days. In order to achieve the same degree of cure as the level of cure obtained, it is preferred to heat for 3 to 8 times longer than 3 days. It can be shortened to some extent by increasing the amount of curing agent. The level of hardening can be measured by known methods that measure mechanical resistance, such as ball point stylus loading. A known physical development nucleus coating liquid is applied onto each of the above samples having the same degree of curing by varying the number of days of heating, thereby forming a lithographic printing material. After storing these lithographic printing materials, they are image-exposed, plate-made by the known DTR method, and printed.
There was no visually significant difference in the transfer silver produced in the core layer of the two printing plates, and there was no significant difference in printing, at least up to a considerable number of prints, indicating that good prints were produced. can. However, with more printing, the comparative printing plate loses the transferred silver, especially in the thin line areas, and ink stains occur in the non-image areas, making further printing impossible.
The lithographic printing plate of the present invention does not remove transferred silver in fine line areas even after printing a larger number of sheets than the comparative printing plate.
Furthermore, it was confirmed that no ink stains occurred in the non-image areas, and that good printing was possible. In Japanese Patent Application No. 56-13829 (see Japanese Patent Application Laid-open No. 58-39495), it was proposed to use low molecular weight gelatin. However, subsequent research has shown that if longer heating times or increased amounts of curing agent are used to achieve even higher levels of curing, scumming occurs in non-image areas during storage of printing materials. It turns out that there are still shortcomings. By using such low-molecular-weight gelatin and lowering the layer PH value, lithographic printing with high printing durability without scumming in non-image areas and no transfer silver scattering even after long-term storage of printing materials. This version was successfully developed. Gelatin includes alkali-treated gelatin, acid-treated gelatin, and gelatin derivatives treated and modified by various methods, and usually has an average molecular weight of tens of thousands or hundreds of thousands. Methods known for measuring molecular weight include terminal group analysis, amino acid composition analysis, light scattering method, gel filtration method, ultracentrifugation, and surface pressure. As is well known, the gelatin-containing layer is applied by utilizing a phenomenon in which gelatin gels (referred to as setting) after applying a gelatin coating solution. Gelatin gelation is said to be observed when the average molecular weight is around 30,000, but gelatin commonly used for photography has an average molecular weight of around 100,000, and generally around 70,000. It has an average molecular weight of from about 150,000 to about 150,000. As used herein, the term photographic gelatin refers to gelatin that has sufficient gelling properties and is customary for photographic purposes. In other words, gelatin with an average molecular weight of about 30,000 or less has no setting phenomenon, or even if it does, it is very weak, and it is difficult to form a good photographic layer with a coating solution containing gelatin alone.
Not normally used for photography. As used herein, the term low molecular weight gelatin refers to
It refers to gelatin that has the above-mentioned properties that are different from conventional photographic gelatin. The typical average molecular weight of low molecular weight gelatin is approximately
3,000 to 30,000, preferably about 5,000 to 30,000
20000. Although photographic gelatin necessarily contains some low molecular weight gelatin, the low molecular weight gelatin of the present invention is distinguished from this. The low molecular weight gelatin is preferably used in an amount of about 3 to about 30 parts by weight per 100 parts by weight of photographic gelatin. When used in an excessively large proportion, there is a risk that a gelatin-containing layer cannot be formed well, and the printing durability of the lithographic printing plate becomes poor. Low molecular weight gelatin is produced by, for example, enzymatically decomposing ordinary photographic gelatin. The gelatin-containing layer of the present invention is preferably a subbing layer and may also be a silver halide emulsion layer. The photographic gelatin in the gelatin-containing layer of the present invention partially contains starch, albumin, sodium alginate, hydroxyethylcellulose, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, polyacrylamide, styrene-maleic anhydride copolymer. It is also possible to substitute with one or more hydrophilic polymer binders such as a polyvinyl methyl ether-maleic anhydride copolymer. Furthermore, an aqueous vinyl polymer dispersion (latex) can also be used. The polymeric binder in the undercoat layer is generally 0.5 to 10 g/
m ² , preferably 1 to 6 g/m ² . The undercoat layer may also contain coating materials, dyes, etc. for the purpose of preventing halation. In addition, the undercoat layer is
-100203, may be as described in 1972-16507. As the silver halide emulsion layer, all known photographic materials can be used. Preferred silver halide emulsions are those described in JP-A-49-55402. There are no restrictions on the type and amount of hardening agent used in the gelatin-containing layer of the present invention. For example, aldehydes such as formaldehyde, glyogysar, glutaraldehyde, mucochloric acid, 2,
Aldehyde green compounds such as 3-dihydroxy-1,4-dioxane, nitrogen-containing six-membered heterocyclic compounds having two or more active halogens, compounds having active vinyl groups, compounds having vinyl sulfone groups, ethyleneimino groups, etc. Compounds having an epoxy group, compounds having an N-methylol group, chromium alum, dialdehyde starch as a polymer hardening agent, and other compounds known as gelatin hardening agents can be used alone or in combination of two or more. can. The PH value of the gelatin-containing layer is less than the isoelectric point of gelatin (when using two or more types of gelatin, the smallest isoelectric point), and preferably at least 0.3 or more smaller than the isoelectric point of the gelatin. It is PH value. As the gelatin, ordinary lime-treated gelatin is preferably used. As the acid for adjusting the pH value below the isoelectric point of gelatin, any inorganic or organic acid such as sulfuric acid or citric acid can be used. The silver halide emulsion consists of silver halides, such as silver chloride, silver bromide, silver chlorobromide, and those containing iodide, dispersed in the above-mentioned hydrophilic colloid. Silver halide emulsions can be sensitized in a variety of ways, either as they are manufactured or as they are coated. It may be chemically sensitized by methods well known in the art, for example with sodium thiosulfate, alkylthioureas, or with gold compounds such as rhodan gold, gold chloride, or a combination of both. good. The emulsion is further sensitized, usually to a range of about 530 to about 560 mm, but can also be panchromatically sensitized. The weight ratio of hydrophilic colloid to silver halide is generally between 2 and 0.3.
It is preferable that As already mentioned, the invention is particularly effective when the amount of silver halide is less than the equivalent of 0.8 mmol of silver per square meter. Physical development nuclei include antimony, bismuth,
cadmium, cobalt, palladium, nickel,
Known metals such as silver, lead, and zinc and their sulfides can be used. The image-receiving layer does not need to contain hydrophilic colloids, and may include gelatin, carboxymethylcellulose, gum arabic, sodium alginate, hydroxyethyl starch, dextrin, hydroxyethylcellulose, polystyrene sulfonic acid, a copolymer of vinylimidazole and acrylamide, Hydrophilic colloids such as polyvinyl alcohol may also be included. Hygroscopic substances such as humectants such as sorbitol, glycerol, etc. may be present in the image-receiving layer. Furthermore, the image-receiving layer may also contain pigments for preventing scumming such as barium sulfate, titanium dioxide, china clay, and silver, developing agents such as hydroquinone, and hardening agents such as formaldehyde. The support may be, for example, paper, film, such as cellulose acetate film, polyvinyl acetal film, polystyrene film, polypropylene film, polyethylene terephthalate film, or a composite film in which polyester, polypropylene, or polystyrene film is coated with polyethylene film, metal, or metallized paper. Or it can be a support for a metal/paper laminate. Paper supports coated on one or both sides with an α-olefin polymer, such as polyethylene, are also useful. These supports may also contain antihalation dyes or pigments. The DTR processing solution used in the present invention contains alkaline substances such as sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate, etc., sulfites as preservatives, silver halide solvents such as thiosulfate, etc. , thiocyanates, cyclic imides, thiosalicylic acid, amines, etc., thickening agents such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants such as potassium bromide, 1-
Phenyl-5-mercaptotetrazole, JP-A-Sho
Compounds and developers described in 47-26201, such as hydroquinone, 1-phenyl-3-pyrazolidone,
Development modifiers such as polyoxyalkylene compounds,
It can contain onium compounds and the like. In carrying out the silver complex diffusion transfer method, for example, British Patent No. 1000115, British Patent No. 1012476, British Patent No.
As described in specifications such as No. 1017273 and No. 1042477, a developer is mixed into the silver halide emulsion layer and/or the image-receiving layer or other water-permeable layer in contact therewith. . Therefore, for such materials, the processing liquid used in the development step may be a so-called "alkaline activating liquid" which does not contain a developer. The ink receptivity of the lithographic printing plate produced according to the present invention can be changed or enhanced with compounds such as those described in Japanese Patent Publication No. 48-29723 and US Pat. No. 3,721,539. The printing method, the desensitizing liquid, the wetting liquid, etc. used can be any commonly known method. The present invention will be explained below with reference to Examples, but of course it is not limited thereto. Example 1 A matting layer containing silica particles with an average particle size of 5 μm was provided on one side of a 135 g/m ² double-sided polyethylene-coated paper, and the opposite side was subjected to corona discharge machining.
An undercoat layer for preventing volatility (PH4.0) containing carbon black and 20% by weight of silica powder with an average particle size of 7 μm based on photographic gelatin with an isoelectric point of 4.8.
An ortho-sensitized high-sensitivity silver chloride emulsion containing silica powder with an average particle size of 7 μm at a ratio of 5% by weight to photographic gelatin with an isoelectric point of 4.8 after being chemically sensitized at pH 6.0 layer (adjusted to PH4.0). Gelatin for the undercoat layer was coated at a rate of 3.0 g/ ^m2 , gelatin for the emulsion layer was coated at a rate of 1.0 g/ ^m2 , and silver halide was coated at a rate of 1.0 g/ ^m2 in terms of silver sulfate. The undercoat layer and emulsion layer contain formalin as a hardening agent in an amount of 5.0 mg/g gelatin. After drying and heating at 40℃ for 14 days, on top of this emulsion layer,
The core coating liquid described in Example 2 of JP-A-53-21602 (polymer is No. 3 copolymer of acrylamide and imidazole, hydroquinone is 0.8 g/m ²
Comparative lithographic printing plate A was prepared by coating and drying the lithographic printing plate A. Furthermore, a lithographic printing plate was produced in exactly the same manner as above, except that the PH value of the undercoat layer and the low molecular weight gelatin were changed as shown in the table below.

【table】

[Table] The lithographic printing plate obtained in this way was heated to 7°C at 40℃.
Each original plate, which had been heated for several days, was subjected to image exposure using a letterpress camera having an image reversal mechanism, and developed at 30° C. for 1 minute using the following silver complex salt diffusion transfer developer. <Transfer developer> Water 700ml Potassium hydroxide 20g Anhydrous sodium sulfite 50g 2-Mercaptobenzoic acid 1.5g 2-Methylaminoethanol 15g Adjust to 1 with water. After the development process, the original plate was passed between two squeezing rollers to remove excess developer, and immediately treated with a neutralizing solution having the following composition at 25°C for 20 seconds, and the excess liquid was removed using a squeezing roller. , dried at room temperature. <Neutralizing solution> Water 600ml Citric acid 10g Sodium citrate 35g Colloidal silica (20% liquid) 5ml Ethylene glycol 5ml Add water to bring the total volume to 1. The lithographic printing plate prepared by the above procedure was mounted on an offset printing machine, the following desensitizing liquid was applied all over the print, and printing was carried out using the following dampening liquid. <Degreasing liquid> Water 600ml Isopropyl alcohol 400ml Ethylene glycol 50g 3-mercapto-4-acetamide-5-n-
Heptyl-1,2,4-triazole 1g <Moisturizing liquid> O-phosphoric acid 10g Nickel nitrate 5g Sodium sulfite 5g Ethylene glycol 100g Colloidal silica (20% liquid) 28g Add water to make 2. The printing machine is AB Deitsku 350CD (A.
Judging based on the following evaluation criteria based on the number of sheets printed when using a B.Dick offset printing machine (trademark), the image becomes unusable due to background smudges in non-image areas and missing silver images. did. ◎ 10,000 sheets or more 〇 8,000 sheets to 10,000 sheets △ 5,000 sheets to 8,000 sheets x 5,000 sheets or less The results are shown in Table 1 below.

[Table] From the above results, it can be seen that when the PH value of the undercoat layer and the combination of low molecular weight gelatin are all satisfied, a lithographic printing plate with high printing durability can be obtained even during long-term storage. Example 2 A lithographic printing plate was produced in the same manner as in Comparative Sample A of Example 1 except that 10% of the photographic gelatin in the emulsion layer was replaced with the low molecular weight gelatin used in Example 1. It was confirmed that it would be improved. From the results of Examples 1 and 2, it is thought that background smudge is caused by over-hardening of the undercoat layer and emulsion layer due to long-term storage of the printing plate, but it can be solved by controlling over-hardening of either layer. I know it's possible. However, depending on the degree of overcuring,
It is often difficult to always control with the emulsion layer alone, and it is preferable to control with the undercoat layer, which has a large amount of gelatin coated. Example 3 Comparative printing plate F was prepared in the same manner as in Comparative Sample A of Example 1, except that the PH value of the undercoat layer was adjusted to 4.4. In the printing plate of Comparative F, which was heated at 40° C. for 2 weeks, scumming occurred after 5000 sheets or less were printed. Lithographic printing plates were prepared in the same manner as Comparative F except that 5, 10 or 20% of the photographic gelatin in the undercoat layer was replaced with low molecular weight gelatin having an average molecular weight of about 15,000. In both cases, background stains have been greatly improved, and there is no silver scattering.
It became possible to print more than 10,000 sheets. Example 4 1-Phenyl-3 in the anti-halation undercoat layer
- Pyrazolidone 0.2g/m ² , palladium sulfide core layer containing hydroquinone in an amount of 0.5g/m ² , undercoat layer and emulsion layer formalin 100mg/g
Gelatin and dimethylolethylene urea 100mg/
A lithographic printing plate was prepared in exactly the same manner as Example 1 and the present invention sample, except for the above changes, including the addition of gelatin in an amount of 1.5 g gelatin, and the use of low molecular weight gelatin with an average molecular weight of approximately 18,000 in the undercoat layer. did.
Good printing was possible for more than 10,000 sheets without background smudges in non-image areas or scattering of transferred silver.

Claims (1)

[Claims] 1. A method for producing a lithographic printing plate having at least one gelatin-containing layer below the physical development nucleus layer, wherein all of the gelatin-containing layers have a pH value below the isoelectric point of the gelatin, and Photographic gelatin and low molecular weight gelatin having an average molecular weight of about 3,000 to 30,000 at a ratio of about 3 to about 30 parts by weight per 100 parts by weight of the photographic gelatin are mixed and used in at least one of the above. Production method.