JPS62242946A - Photomechanical process - Google Patents

Abstract

PURPOSE:To prevent the ground stain of a lithographic printing plate and to improve the sensitizability of the image part by applying an aqueous soln. contg. starch or saccharide to the printing plate after development and by burning the printing plate. CONSTITUTION:A photosensitive lithographic printing plate is imagewise exposed and developed. An aqueous soln. contg. one or more kinds of substances selected among starch derivs., oxidized starch, pullulan, pullulan derivs., cyclodextrin and saccharides is then applied to the printing plate. After the soln. is dried, the printing plate is burned. Esterified starch and cyclodextrin are preferably used as the substances. By this method, affinitizing after burning is not required and a lithographic printing plate having superior printing resistance is obtd. The non-image area of the printing plate is not stained and the printing area has high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a plate-making method using a photosensitive lithographic printing plate. In particular, after imagewise exposure and development of a photosensitive lithographic printing plate using a metal as a support, This relates to a plate-making method when used by burning.

[Prior art]

Lithographic printing is a printing method that skillfully takes advantage of the property that water and oil essentially do not mix.The printing plate surface has two areas: one area that accepts water and repels oil-based ink, and the other area that repels water and accepts oil-based ink. The former is a non-image area and the latter is an image area. Therefore, the photosensitive composition used for preparing a lithographic printing plate is required to have the property of repelling water and accepting oil-based ink after image formation.

There are two types of photosensitive compositions used to create lithographic printing plates: positive type and negative type.
Those made of quinonediazide compounds are widely used.

A positive-working photosensitive lithographic printing plate is one in which an O-quinonediazide compound alone or mixed with an alkali-soluble resin such as a novolac type phenol resin or a cresol resin is coated on a suitable support such as metal or plastic.
When exposed to actinic light through a transparency, the 0-quinonediazide compound in the exposed areas decomposes and becomes alkali-soluble, so it is easily removed by an aqueous alkaline solution to give a positive image. Therefore, when a support having a hydrophilic surface is used, the hydrophilic surface of the support is exposed in the area removed by the alkaline aqueous solution, and this area accepts water and repels ink. On the other hand, the portion that remains as an image is lipophilic and will absorb ink.

On the other hand, many negative photosensitive compositions use diazonium salts, azide compounds, or photopolymerizable compounds. It will be painted on. When a support with a hydrophilic surface is used, the unexposed areas are removed by a developer to expose the hydrophilic surface of the support, which receives water and repels ink. On the other hand, the portion that is cured by exposure and remains as an image during development is oleophilic and accepts ink.

When the lithographic printing plate created in this way is printed on an offset printing machine, beautiful printed matter can be obtained. Planographic printing plates made from such photosensitive planographic printing plates can produce tens of thousands of beautiful prints by appropriately selecting the composition of the support and the photosensitive layer coated thereon.
In particular, by using a grained and anodized aluminum plate as a support, it is possible to obtain as many as 100,000 beautiful prints.

However, there is also a desire to print more than just one printed version. In such cases, a method is to strengthen the image area by exposing and developing a photosensitive lithographic printing plate using a metal plate such as aluminum or zinc as a support in the usual way, and then heating it at a high temperature (so-called burning treatment). is valid.

That is, by performing the burning process, the number of printed matter obtained from one lithographic printing plate can be increased several times compared to the case where the burning process is not performed.

Furthermore, when printing with special printing inks such as ultraviolet curing inks or low-temperature drying inks that contain a large amount of components that dissolve images on printing plates, printing plates made using normal methods that do not undergo burning treatment may cause the image areas to dissolve. However, when the burning process is applied, the solvent resistance of the image area is greatly improved, so even with the special printing inks mentioned above, A sufficient number of printed materials can be obtained.

However, the non-image area of the printing plate (i.e., the area where the hydrophilic support surface is exposed by development), which was hydrophilic before the treatment, loses its hydrophilicity and becomes receptive to printing ink due to the burning treatment. As a result, stains (so-called background stains) occur in the background of printed matter. Heating to an extent that does not cause such background smearing does not produce a burning effect, and image reinforcement is not achieved. Therefore, it is necessary to carry out a surface preparation process to prevent staining of the non-image area caused by the burning process. Various proposals have been made in the past as a surface smoothing treatment used before and/or after this burning treatment step.

For example, after the burning process, a fluoride aqueous solution such as hydrofluoric acid, borohydrofluoric acid, silicohydrofluoric acid, etc. However, these fluorides are classified as poisonous and deleterious substances and pose many problems in terms of pollution control.

Furthermore, when this surface smoothing treatment is applied, the metal surface of the support corrodes, making the surface more susceptible to scratches and becoming more susceptible to abrasion. ) is lost, background smearing occurs, and further printing is no longer possible.

In addition, as a processing method to prevent the hydrophilicity of the non-image area from decreasing before the burning process, Japanese Patent Laid-Open No. 51
Publication No. 34001 discloses treatment with an aqueous solution of an organic sulfonic acid salt such as alkylnaphthalene sulfonic acid sorter, alkyldiphenyl ether sodium sulfonate, and lithium nitrate before burning. Among these, aqueous solutions of organic sulfonic acid salts such as sodium alkylnaphthalene sulfonate and sodium alkyl diphenyl ether sulfonate have extremely high foaming properties.
It is unsuitable for use in the spray circulation type processors that are currently widely used, and has the drawback that it cannot automate the plate-making process. Furthermore, when treated with a solution containing lithium nitrate and burned, the prevention of scumming was not sufficient. Furthermore, Japanese Patent Publication No. 55-28062 discloses a method of treating with an aqueous solution containing sublimable boric acid and its salts before burning, and then performing burning in the presence of the compound. Prevention of scumming was not sufficient. In particular, scumming may occur due to conditions such as washing with water and gumming after burning treatment, i.e., if washing with water is insufficient or if a dextrin-based gum solution with weak hydrophilicity is used as the desensitized gum solution. The drawback was that it was easy to occur. Furthermore, JP-A No. 52-6205 discloses that water-soluble organic substances such as gum arabic, dextrin, cellulose ether, and polyacrylic acid, and/or borates, phosphates, sulfates, alkali metals, and alkaline earths are added before the burning process. Treatment with an aqueous solution of water-soluble inorganic salts such as halides of similar metals has been shown, but even with this method, it is not always possible to completely prevent background stains, and in particular, it is not possible to completely prevent background stains. When using an aqueous solution of a water-soluble polymer such as, there is a drawback that it becomes difficult for the image area to receive ink during printing, resulting in so-called inking failure. Furthermore, JP-A-57-5205
No. 7 discloses a method of treating with an aqueous solution containing a carboxyl group-containing amine or a salt thereof, such as ethylenediaminetetraacetic acid or hydroxyalkylethylenediaminetriacetic acid, before the burning treatment. However, this method could not be said to be sufficiently effective in preventing background stains.

[Purpose of the invention]

An object of the present invention is to provide an improved plate-making method that includes a burning process. More specifically, it is an object of the present invention to provide a plate-making method including a burning process, which can produce a lithographic printing plate that is free from scumming and has excellent oil sensitivity in image areas.

Another object of the present invention is to provide a plate-making method including a burning process that can be automated by using a spray circulation type processing machine or the like.

A further object of the present invention is to provide a plate-making method capable of obtaining a lithographic printing plate that does not cause background stains in non-image areas even when printing is started after printing without desensitizing treatment after burning treatment. The goal is to provide the following.

[Structure of the invention]

The present inventor has proposed that starch derivatives, oxidized starch, pullulan and its derivatives,
It has been found that the above objectives can be achieved by using an aqueous solution containing at least one compound selected from the group consisting of cyclodextrins and saccharides.

The starch derivatives used in the present invention are those in which various highly reactive functional groups are bonded to the hydroxyl group of the glucose residue of starch, such as carboxyalkyl starch, hydroxyalkyl starch, sulfoalkyl starch, cyanoethyl starch, Etherified starches such as allyl starch, benzyl starch, vinyl starch, carbamylethyl starch, and dialkylaminoalkyl starch; esterified starches such as phosphate starch, fatty acid starch, sulfate starch, nitrate starch, xanthate starch, and carbamic acid starch; Crosslinked starches such as methylol crosslinked starch, hydroxyalkyl crosslinked starch, phosphoric acid crosslinked starch, dicarboxylic acid crosslinked starch, acrylamide grafted starch, acrylic acid grafted starch, vinyl acetate grafted starch, acrylonitrile grafted starch, acrylic acid ester grafted starch, vinyl grafted starch , styrene-maleic acid grafted starch, ethylene oxide grafted starch, and other grafted starches. The oxidized starch used in the present invention is obtained by oxidizing starch with an oxidizing agent, and includes hypochlorous acid oxidized starch, dialdehyde starch, and the like. The pullulan used in the present invention is a linear polymer in which maltotriose, which is a trimer of glucose, is repeatedly bonded through α-1,6 bonds.

Furthermore, in the present invention, pullulan derivatives into which an alkyl group, hydroxyalkyl group, carboxyalkyl group, sulfone group, or amino group, etc. have been introduced can also be used within the range of easy water solubility.

The cyclodextrin used in the present invention is an oligosaccharide in which glucose residues are connected in a cyclic manner through α-1,4-glucoside bonds; α-cyclodextrin has 6 glucose units, β-cyclodextrin has 7 glucose units, and β-cyclodextrin has 8 glucose units. T-cyclodextrins are well known, and any of them can be used in the present invention. These compounds are available as commercial products, for example, from Toyo Jozo Co., Ltd. under the name Toyozolin-P.

Furthermore, in the present invention, sugars such as sucrose, glucose, fructose, maltose, lactose, starch syrup, and powdered candy can be used.

The present invention uses at least one of the above compounds, and among these compounds, esterified starch and cyclodextrin are particularly preferred.

The above compounds can be used alone or in combination of two or more, and are 0.1 to 30% by weight, more preferably 0.1 to 30% by weight, based on the total weight of the burning pretreatment liquid according to the present invention.
．． It is contained in a range of 5 to 20% by weight.

The burning pretreatment liquid used in the present invention may further contain various additives.

Examples of such additives include surfactants, various salts, acids, alkalis, and the like.

The surfactant helps the pre-burning treatment liquid used in the present invention to be uniformly applied to the surface of the lithographic printing plate, and also partially suppresses the occurrence of non-image stains caused by the burning process. There is. Preferred surfactants are anionic surfactants, especially those containing sulfonic acid groups such as alkylbenzene sulfonates, alkyldiphenyl ether disulfonates, alkylnaphthalene sulfonates, aldehyde condensates of alkylnaphthalene sulfonates, and α-olefin sulfonates. Particularly preferred are surfactants and sulfate-based surfactants such as lauryl sulfate, polyoxyethylene alkyl ether sulfate, and polyoxyethylene alkyl phenyl ether sulfate. The surfactant is suitably contained in the burning pretreatment liquid in an amount of about 0.05% to about 10% by weight, preferably 0.1 to 5% by weight.

Furthermore, an acid, alkali or salt can be used for pH adjustment in the burning pretreatment liquid used in the present invention, if necessary. As acids it is possible to use mineral acids and organic acids. Mineral acids such as nitric, sulfuric and phosphoric acids; organic acids such as citric, succinic, oxalic, tartaric, acetic and malic acids; potassium, lithium, sodium or ammonium salts of these acids; Examples include alkali metal hydroxides, carbonates, and hydrogen carbonates.

These acids, salts, and alkalis adjust the pH of the burning pretreatment liquid used in the present invention from 2 to 10, preferably from 3 to 8.
It can be contained in an amount within the range of.

Furthermore, the burning pretreatment liquid used in the present invention contains water-soluble polymers such as gum arabic, dextrin, carboxymethyl cellulose, and polyacrylic acid, polymethacrylic acid, and salts thereof (for example, salts of IJ, etc.). Substances, dyes, defoamers, preservatives, etc. may also be added.

In the present invention, the burning pretreatment liquid is used to image-expose a photosensitive lithographic printing plate, develop it, wash it with water if necessary, and then remove unnecessary portions for printing with a correction agent. After it is created, it is dried if necessary and applied before the burning process. Methods for this include coating the planographic printing plate with a sponge or absorbent cotton impregnated with the pretreatment liquid, coating the printing plate by immersing it in a vat filled with the treatment liquid, and applying it automatically. Application with a coater etc. is applied. Also, after applying, use a squeegee or
To make the amount of application uniform with a squeegee roller,
Gives more favorable results.

The lithographic printing plate coated with the burning pretreatment liquid is dried if necessary, and then heated to a high temperature using a burning processor (for example, Burning Processor 1300 sold by Fuji Photo Film ■). The heating temperature and time in this case are preferably in the range of 180 to 300° C. for 1 to 20 minutes, although it depends on the type of component forming the image.

The burn-treated lithographic printing plate can be subjected to conventional treatments such as water washing and gumming, as necessary. However, when the burning pre-treatment liquid of the present invention is used, the burn So-called desensitizing treatment such as post-gumming can be omitted.

The plate making method according to the present invention can be applied to various photosensitive planographic printing plates, but in particular, photosensitive planographic printing plates (printing plates to which photosensitization has been imparted in advance) using an aluminum plate as a support, PS
called a version. ) can be suitably used. Such P
A preferred S version is, for example, British Patent No. 1.350.
Diazo resin (p-
British Patent No. 1.460, in which a photosensitive layer consisting of a mixture of shellac and a salt of a condensate of diazodiphenylamine and paraformaldehyde is provided on an aluminum plate.
No. 978 and No. 1.505.739, the photosensitive layer is made of a mixture of a diazo resin and a polymer having hydroxyethyl methacrylate units or hydroxyethyl acrylate potential as a main repeating unit. A negative PS plate such as one provided on an aluminum plate, and a photosensitive layer made of a mixture of an 0-quinonediazide photosensitive material and a novolac type phenol resin as described in JP-A-50-125806 are placed on an aluminum plate. Includes the positive PS plate provided above.

Furthermore, a PS plate in which a photosensitive layer of a photocrosslinkable photopolymer is provided on an aluminum plate as specifically shown in U.S. Pat. No. 3,860,426, and U.S. Pat.
, No. 072.528 and No. 4.072.527, a PS plate in which a photosensitive layer of a photopolymerizable photopolymer composition is provided on an aluminum plate, as described in British Patent No. 1. 235.281 and 1.495.
Also preferred is a PS plate in which a photosensitive layer made of a mixture of azide and a water-soluble polymer is provided on an aluminum plate as described in each specification of No. 861. Among these PS plates, a particularly preferred PS plate to be used in the plate making method of the present invention is a positive PS plate having a photosensitive layer consisting of an 0-naphthoquinonediazide compound and a novolak resin, and is disclosed in U.S. Pat. No. 4.259. .434 Specification, column 3, lines 2 to 6 from the bottom
This is explained in detail in column 14.

〔Effect of the invention〕

According to the plate making method of the present invention, there is no need to perform a surface smoothing treatment after the burning treatment. Despite this, a lithographic printing plate with excellent printing durability and high oil sensitivity in the image area without staining in the non-image area can be obtained. Moreover, since the burning pretreatment liquid used in the present invention has a low foaming property, it can be applied to planographic printing plates using a spray circulation type processing machine, which has great advantages such as automation of plate making work.

Moreover, according to the plate making method of the present invention, desensitization treatment after burning can be omitted. After the burning process, it not only has the excellent effect of not causing background smudges even after being placed on the plate for a long time, but also has the effect of preventing scratches from forming on the plate surface, thus making it difficult for scratches and stains to occur. .

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Naphthoquinone-(1) of 1.5-dihydroxynaphthalene
, 2)-Diazide (2)-5-sulfonic acid ester (2 parts by weight) and 4 parts by weight of novolac type cresol-formaldehyde resin were dissolved in 100 parts by weight of ethylene glycol monomethyl ether. Next, this solution was applied onto a grained aluminum plate having a thickness of 0.24 mm so that the weight after drying was 2.5 g/mr. The positive-working photosensitive lithographic printing plate thus prepared was brought into close contact with the transparency and exposed for 30 seconds from a distance of 1 meter using a 3KW metal halide lamp, and then exposed to a 5% by weight aqueous solution of IJium silicate for about 1 minute. It was immersed and developed. Next, after washing with water, a burning pretreatment liquid having the following composition was applied and dried.

phosphoric acid
1 g pure
□ 850 g of water The printing plate thus treated was heated in a commercially available burning processor at a temperature of 260° C. for 6 minutes.

After cooling, it was gummed, and when this printing plate was attached to an offset printing machine and printed, beautiful prints were obtained after just a few sheets, and when printing was continued, 150,000 beautiful prints were obtained.

Comparative Example 1 A lithographic printing plate treated under exactly the same conditions as in Example 1 up to development was treated with a 4% by weight ammonium borate aqueous solution instead of the burning pretreatment liquid used in Example 1, and subjected to the same burning treatment. and pulled gum. When this lithographic printing plate was used for printing, smearing occurred in the halftone dot image in a portion of the shadow from the beginning of printing, and it was necessary to remove the dirt from the smeared area with a plate cleaner.

Example 2 Examples 1 and 2 were deposited on a 0.3 mm thick aluminum plate that had been grained and anodized (anodized in 15 wt% sulfuric acid at a current density of 1.6 amperes/dm' for 2 minutes). A positive photosensitive lithographic printing plate was prepared by applying the same photosensitive solution.

A transparent positive was attached to this and exposed for 40 seconds with a 3KW metal halide lamp from a distance of 1 m, and then developed by immersing it in a 7% by weight aqueous sodium silicate solution for about 1 minute.

This lithographic printing plate is processed using an automatic through-type burning processor [
Made of process materials ■, applying pre-burning treatment liquid, burning, and gumming are performed continuously. ] was continuously processed. Here, the burning temperature was set as 150° C. for preheating, 240° C. for postheating, and a passing time of about 3 minutes through the furnace, and the following composition of the burning pretreatment liquid was used.

Sodium hexametaphosphate □ 5g pure water
□ When the lithographic printing plate obtained by the 800g burning process was directly attached to an offset printing machine and printed, beautiful prints were obtained in just a few prints, and 300,000 prints were obtained by continuing the printing process. .

Example 3 In the same manner as in Example 1, however, an aqueous solution having the following composition was used as the burning pretreatment liquid, and the same results as in Example 1 were obtained.

Cane sugar □ 1
10g pure water
□ 887 g Example 4 Polyhydroxyphenyl and naphthoquinone-1,2 obtained by polycondensation of acetone and pyrogallol as described in Example 1 of U.S. Pat. No. 3,635,709
- 4 parts by weight of diazide (2)-5-sulfonic acid ester and 4 parts by weight of novolac type cresol formaldehyde resin were dissolved in 100 parts by weight of ethylene glycol monomethyl ether, and the mixture was subjected to the graining and anodizing treatment used in Example 2. Aluminum plate with dry weight of 2.5 g/
A positive photosensitive lithographic printing plate was prepared by coating the film in an amount of m'.

After this positive photosensitive lithographic printing plate was exposed, developed and washed with water under the same conditions as in Example 1, a burning pretreatment liquid having the following composition was applied, and then a burning treatment was performed at 260° C. for 5 minutes.

phosphoric acid
1 g pure
Water □ 885 g (When I attached the lithographic printing plate that was asked to it without gumming it to an offset printing machine and printed it, beautiful prints were obtained in just a few sheets, and I continued to print 200,000 sheets. I was able to do it.

Example 5 A solution was prepared by dissolving 20 parts by weight of shellac and 3 parts by weight of a diazo resin obtained by condensing p-)luenesulfonate of p-diazodiphenylamine with formaldehyde in 80 parts by weight of dimethylformamide. On the other hand, a grained aluminum plate was heated to 80°C with 0.2% potassium zirconium fluoride.
After being immersed in an aqueous solution for 3 minutes to make it hydrophilic,
Wash with water, dry, and add the above prepared solution to a weight of 2.0 after drying.
g/m'.

The negative photosensitive lithographic printing plate thus obtained was exposed through a transparent negative for 30 seconds from a distance of 1 m using a 3KW metal halide lamp, immersed in an aqueous solution of 20% by weight of isopropyl alcohol for about 1 minute, and then surfaced with absorbent cotton. When rubbed lightly, only the unexposed areas were peeled off and removed, exposing the surface of the support.

After washing with water, apply the burning pretreatment liquid used in Example 1,
After drying and performing a burning process under the same conditions as in Example 1, it was installed on an offset printing machine and printed. Beautiful prints were obtained in about 10 sheets from the beginning of printing, and when printing continued as it was, the results were as follows. We were able to obtain 150,000 pieces of printed matter with almost no change in condition.

Example 6 Graining with pumice/water slurry and a nylon brush, anodizing treatment (anodizing in 20% sulfuric acid at 2A/dm for 2 minutes), followed by a 2.5% by weight aqueous solution of sodium silicate at 70°C. An aluminum plate with a thickness of 0.3 mm was prepared by treating it for 1 minute.

A photosensitive liquid having the following composition was applied to this aluminum plate so that the weight after drying was 2.0 g/m'.

Victoria Pure Blue BOH (manufactured by Odogaya Chemical Co., Ltd.) 0.1 g Methyl cellosolve 95rIJ1 water

5-The negative photosensitive lithographic print thus obtained was passed through a transparent negative using a 3 Kl metal halide lamp.
The film was exposed to light for 30 seconds from a distance of m, and developed using the following developer.

Benzyl alcohol 30ml Diethanolamine 10g Sodium sulfite 5g Water 11
After washing with water, apply the burning pretreatment liquid used in Example 2,
After drying and performing burning treatment under the same conditions as in Example 2, I attached it to an offset printing machine and printed it, and a few sheets of beautiful prints were obtained from the beginning of printing, and when I continued printing as it was, it was almost the same as the beginning of printing. We were able to obtain 200,000 copies of printed matter that remained in good condition.

Example 7 The following photosensitive solution was applied to a plate that had been grained, anodized, and treated with sodium silicate in the same manner as in Example 6 to a dry weight of 3.
It was coated at a weight of 0 g/m' and dried at 100°C for 2 minutes.

3-Methyl-2-benzoylmethylenenaphtho(1-2-d) thiazole 5 g Phthalocyanine blue 3 g Ethylene dichloride 500 g 2-methoxyethyl acetate 500 g After drying, 3 g of polyvinyl alcohol
An aqueous solution of 15% by dry weight was applied to the surface of the photosensitive layer.
g/m'' and dried.

This plate was exposed and developed in the same manner as in Example 6.

After washing with water, the pre-burning treatment liquid used in Example 4 was applied, and after performing the burning treatment under the same conditions, the product was attached to an offset printing machine and printed, and beautiful printed matter was obtained in just a few sheets after printing. .

Example 8 A burning pretreatment liquid having the following composition was prepared.

phosphoric acid
□ 1g pure water
□ 894 g Example 1 except that the above liquid was used instead of the burning pretreatment liquid in Example 1.
When we made printing plates using exactly the same method as above and evaluated the printing, we were able to obtain beautiful prints after just a few prints.

Example 9 When the following liquid was used in place of the burning pretreatment liquid of Example 1, the same results as in Example 1 were obtained.

Pullulan PF-7 (made by Hayashibara ■) -100g pure
Water □ 900
g Example 10 When the following liquid was used in place of the burning pretreatment liquid in Example 2, the same results as in Example 2 were obtained.

Claims (1)

[Claims] In a plate-making method in which a photosensitive lithographic printing plate is subjected to image exposure and development and then subjected to a burning treatment, after development and before the burning treatment, a starch derivative selected from the group consisting of starch derivatives, oxidized starch, pullulan and its derivatives, cyclodextrins and saccharides is used. applying an aqueous solution containing at least one compound;
A plate-making method characterized by carrying out a burning treatment in the presence of the compound.