JPH0443362A - Plate making method - Google Patents

Abstract

PURPOSE:To enable plate making including an improved burning pretreatment without generating surface stains and without attacking image parts by incorporating 0.01 to 0.5wt.% methyl cellulose into a burning pretreating agent. CONSTITUTION:The methyl cellulose is incorporated at 0.01 to 0.5wt.% into the burning pretreating agent at the time of making the planographic printing plate by subjecting the photosensitive planographic printing plate having a photosensitive layer contg. an O-quinonediazide compd. and a novolak resin to image exposing and developing, then applying the burning pretreating agent thereon and subjecting the plate to the burning treatment. The methyl cellulose to be used is formed by substituting the hydroxyl group of cellulose with a methoxy group and the substitution rate thereof is preferably >=0.5. The need for subjected the plate to a surface conditioning treatment after the burning treatment is eliminated in this way and the generation of stains in non-image parts is nevertheless prevented.

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, and in particular, after imagewise exposure and development of a photosensitive lithographic printing plate using a metal as a support, burning is performed. This relates to a plate-making method when used as a plate.

[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 for making lithographic printing plates), positive type and negative type.
- Quinone diand 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 attracts water and repels ink. On the other hand, the portion that is cured by exposure and remains as an image upon development is lipophilic 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 obtain a larger number of prints from a single printing plate. 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 -1 planographic 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 dramatically improved, so the special printing mentioned above is possible. Even with ink, a sufficient number of prints 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 smudges occur, 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 a salt of an organic sulfonic acid, such as sodium alkylnaphthalene sulfonate, sodium alkyldiphenyl ether sulfonate, or lithium nitrate, before burning. Among these, aqueous solutions of organic sulfonic acid salts such as sodium alkylnaphthalene sulfonate and alkyldiphenyl ether sulfonic acid sortanate 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 the burning treatment, and then performing the burning treatment in the presence of the compound. An aqueous solution containing the salt has poor wettability on a lipophilic image and is difficult to apply uniformly.As a result, the image may be eroded in the form of droplets during burning, making automatic processing difficult. In addition, Japanese Patent Application Publication No. 5
Publication No. 2-6205 discloses that treatment is performed with an aqueous solution of a water-soluble organic substance such as gum arabic, dextrin, cellulose ether, or polyacrylic acid before the burning process, but in this case, in order to prevent scumming, The concentration of water-soluble organic substances in the processing liquid must be high enough to form a continuous film on the surface, and such processing liquids have a high viscosity that makes them difficult to handle automatically, such as by roller application. It wasn't suitable.

Furthermore, JP-A-57-52057 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. .

JP-A-60-138551 describes malic acid and its salts; JP-A-60-212395 describes combinations of hydrophilic polymers with organic acids such as benzenecarboxylic acid, benzenesulfonic acid, and alkanephosphonic acids; 62-1
Although Japanese Patent No. 16938 discloses a method of processing with a water-soluble polymer having a sulfonate group, all of the processing liquids had poor wettability on lipophilic images and were not suitable for automatic processing.

[Problem to be solved by the invention]

An object of the present invention is to provide an improved plate-making method for burning lithographic printing plates.

More specifically, it is an object of the present invention to provide a plate-making method suitable for processing using an automatic processing machine that is automatically conveyed and applies a burning pre-treatment liquid.

Yet another object of the present invention is to provide an improved plate-making method that includes an improved pre-burning treatment that is free from scumming and does not attack image areas.

[Means to solve the problem]

The present inventor has discovered that burning stains can be prevented by using an aqueous solution of boric acid and its salts as a burning pretreatment liquid. The inventors have discovered that the compatibility of lithographic printing plates with lipophilic images containing novolac resins is specifically improved, leading to the present invention.

That is, the present invention provides a method for making a lithographic printing plate, in which a photosensitive lithographic printing plate having a photosensitive layer containing a ○-quinonediazide compound and a novolac resin is subjected to image exposure and development, and then coated with a burning pretreatment agent and then subjected to burning treatment. In this case, the burning pretreatment agent contains methyl cellulose at a concentration of 0.0
This is a plate-making method characterized by containing 1 to 0.5% by weight.

In the methylcellulose used in the present invention, the hydroxyl groups of cellulose are substituted with methoxyl groups, and the substitution ratio is preferably 0.5 or more. This refers to the average number of methoxyl groups substituted. The methyl cellulose used in the present invention may further have other substituents, examples of which include hydroquine ethyl methyl cellulose and hydroquine propyl methyl cellulose. Furthermore, products obtained by adding glyoxal to these methylcelluloses, such as cryoxal-added methylcellulose, glyoxal-added hydroxyethylmethylcellulose, and glyoxal-added hydroxypropylmethylcellulose, are used. The above methylcelluloses can be used alone or in combination of two or more.

As mentioned above, methylcellulose is added to improve the affinity with the image area of the lithographic printing plate, and is not required to have the effect of preventing scumming caused by burning.

Therefore, the preferred range of the amount of methylcellulose added is 0.5% by weight based on the total weight of the burning pretreatment liquid.
or less, more preferably 0.05 to 0.5% by weight
is within the range of If the amount is less than this range, the affinity to the image area will be insufficient and the pre-burning treatment liquid will not be uniformly applied. On the other hand, if the amount exceeds this range, the pretreatment liquid becomes viscous, making it unsuitable for roller coating, and at the same time, it causes so-called inking failure, in which ink is difficult to adhere to the image area at the start of printing after plate making.

It is necessary to separately add a compound that prevents burning stains to the burning pretreatment agent of the present invention.

Examples of such compounds include boric acid and its salts described in Japanese Patent Publication No. 55-28062, Japanese Patent Publication No. 61-159'
Polystyrene sulfonic acid and its salts described in No. 655,
Condensation resin of aromatic sulfonic acid or its salt and aldehyde described in JP-A-62-242925, JP-A-62-2
Starch derivatives, oxidized starch, pullulan and its derivatives, cyclodextrin and saccharides as described in No. 42946, phytic acid, hexametaphosphoric acid and their salts as described in JP-A-60-138552, carboxyl groups as described in JP-A-57-52057 Amines or their salts containing
Ammonium sulfate described in No. 7-66437, JP-A-52
Natural or synthetic water-soluble polymers such as gum arabic, dextrin, polyvinyl alcohol (PVA), carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid and polymethacrylic acid as described in No. 6205, malic acid as described in JP-A-60-138551 boric acid and its salts, and surfactants such as sodium dodecylphenoxybenzenedisulfonate described in JP-A No. 51-34001 are used. Of these, boric acid and its salts are effective against burning stains and foaming (and methyl cellulose). The most preferred boric acid and its salts include boric acid, ammonium borate, boric acid, potassium borate, and lithium borate. The preferred amount added is 1 to 10% by weight, more preferably 2 to 7% by weight. If the amount added is less than this range, the effect of preventing burning stains will be insufficient, and if it is too much, it will become supersaturated at low temperatures and crystals will easily precipitate.

The burning pretreatment liquid used in the present invention may further contain various additives as long as they do not affect the coating properties. Examples of such additives include surfactants,
Includes various salts, acids, alkalis, etc.

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. Surfactants and sulfate ester surfactants such as lauryl sulfate ester polyoxyethylene alkyl ether sulfate and polyoxyethylene alkylphenyl ether sulfate M are particularly preferred. 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.
is within the range of

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 gum arabic, dextrin, carboxymethyl cellulose, water-soluble polymer substances such as polyacrylic acid, polymethacrylic acid, and salts thereof (such as sodium salts), and pigments. , antifoaming agents, 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, immersing the printing plate in a vat filled with the treatment liquid, and applying the coating automatically. Application using a coater is applicable, but application using an automatic coater is particularly preferred in order to bring out the features of the pretreatment liquid of the present invention. Application methods using a coater include supplying the liquid by spraying or dipping, and then metering it using a wire bar or a pair of rubber rollers, or using a curtain coater, which supplies a pre-measured amount of liquid to ensure the required coating amount. There are several methods to do this, but the former method, a roller coater, is preferred because it has a simple structure.

Conventional burning pretreatment liquids have insufficient wettability, and after passing through the coater, the pretreatment liquid forms droplets on the image, which often results in erosion of the image during burning. In contrast, in the case of the pretreatment liquid of the present invention, the pretreatment liquid is uniformly retained on the image, so the image is not damaged, and the pretreatment liquid can be applied thickly, so printing stains caused by the burning process are avoided. Greatly improved. In this case, the preferred coating amount is 0.5 to 10 cc/m', more preferably 1.0 to 5.0 cc/rn'.

The lithographic printing plate coated with the burning pretreatment liquid is dried if necessary, and then heated to a high temperature in a burning processor. In the plate-making method of the present invention, an automatic conveyance type burning processor connected to an automatic coater for a burning pretreatment liquid is suitably used. The burning process is performed at 180 to 300 degrees Celsius, depending on the type of components forming the image.
It is preferable to heat in the range of 1 to 20 minutes.

The plate-making method according to the present invention can be applied to various photosensitive planographic printing plates (photosensitivity is imparted in advance, and a planographic printing plate is obtained by exposure and development; called a PS plate).
In particular, it can be suitably used for photosensitive planographic printing plates having metals such as aluminum as supports.

Preferred such PS versions include, for example, British Patent No. 1.
350. ．． British Patent No. 1, in which a photosensitive layer made of a mixture of a diazo resin (salt of a condensate of p-diazodiphenylamine and paraformaldehyde) and shellac as described in the specification of No. 121 is provided on an aluminum plate. ．．
Consisting of a mixture of a diazo resin and a polymer having hydroxyethyl methacrylate units or hydroquinethyl acrylate units as the main repeating unit as described in the specifications of No. 460.978 and No. 1, 505.738. Negative PS plates such as those in which a photosensitive layer is provided on an aluminum plate, and JP-A-1258-1989
This includes a positive PS plate in which a photosensitive layer made of a mixture of an 0-quinonediazide photosensitive material and a novolak type phenol resin is provided on an aluminum plate as described in Japanese Patent No. 06. Further, 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. 4,072.528. No. 4.072.527
PS plate in which a photosensitive layer of a photopolymerizable photopolymer composition as described in each specification of the British Patent Nos. 1.235.281 and 1.49
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 the specifications of No. 5.861.

Since the methylcellulose contained in the burning pretreatment agent of the present invention has particularly high affinity with novolac resin, among the above PS plates, a PS plate having a photosensitive layer containing an 0-naphthoquinone diazide compound and a novolac resin is particularly preferable. . Particularly preferred is a PS plate having a photosensitive layer containing 20% by weight or more of novolac resin.

〔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, stains do not occur in non-image areas. Furthermore, the plate making method of the present invention is suitable for automatic processing and can be applied uniformly and thickly onto a planographic printing plate without damaging the image area, so that a planographic printing plate without burning stains can be stably obtained.

〔Example〕

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

Example 1 ■,5-Dihydro-bovine sinusaphthalene phthoquinone-(1
, 2)-diazide (2)-5-sulfonic acid ester (2 parts by weight) and 4 parts by weight of novolak-type resol-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 and 7 m 2 . The positive-working photosensitive lithographic printing plate thus prepared was placed in close contact with the transparency and exposed for 30 seconds from a distance of 1 m using a 3KW metal halide lamp, and then immersed in a 5% by weight aqueous sodium silicate solution for about 1 minute. Developed and washed with water.

Next, a burning pretreatment liquid A having the following composition was prepared.

Ammonium borate 60g Methyl cellulose (trade name Metrose 1g90SH100
000: Shin-Etsu Chemical @J'A) Pure water 9
40 g of the second pretreatment liquid was charged into an automatic processing machine having an automatic conveyance type pretreatment section and a subsequent burning device, and the lithographic printing plate that had been developed and washed with water was processed.

(The pretreatment section of this automatic treatment machine consists of a pretreatment liquid tank, a liquid circulation pump, a spray conveyance roller, and finally a pair of silicone rubber squeezing rollers, and the amount of pretreatment liquid applied is 2.5 cc. / m'.

Furthermore, the burning was performed at a temperature of 150 tons for preheating and 275° C. for postheating for 2 minutes and 45 seconds).

When the lithographic printing plate that had been burnt in this way was cooled, washed with water and gummed, and then mounted on an offset printing machine and printed, beautiful prints were obtained after just a few sheets, and five consecutive prints were made. As a result, 250,000 beautiful prints were obtained.

Comparative Example 1 A lithographic printing plate was prepared under exactly the same conditions as in Example 1, except that the following burning pretreatment liquid was used.

Burning pre-treatment liquid B Ammonium borate 60g Pure water
940 g The pretreatment liquid could not be applied uniformly on the image area of the printing plate prepared under these conditions, and in the thickly coated area, the image area was attacked and numerous pinholes were generated. Furthermore, when this printing plate was used for printing, printing stains occurred in the halftone dot images in the shadow areas from the beginning of printing, and no clean prints were obtained.

Example 2 The same as in Example 1 was deposited on a 0.3 mm thick aluminum plate that had been grained and anodized (anodized in 15% by weight sulfuric acid at a current density of 1.6 ampere/dm2 for 2 minutes). A positive photosensitive lithographic printing plate was prepared by coating the photosensitive liquid.

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 penetrating type Hahnink processor.
Process 'R material@m, application of panning pretreatment liquid, burning, and gumming are performed continuously. ] was continuously processed. Here, the settings for the burning treatment are pre-heating at 150°C, post-heating at 240°C, and passing time through the furnace for approximately 3 minutes.The burning pre-treatment liquid used has the following composition. A pair of silicone rubber rollers with a hardness of 35 degrees were used as the rollers.

The amount of pretreatment liquid applied was 2.8 cc/m'.

Pretreatment liquid C Potassium hydroxide (48%) 0.1 Ammonium borate 55 g Pure water
When the planographic printing plate obtained by the 945g burning process was gummed, attached to an offset printing machine, and printed, beautiful prints were obtained in just a few prints, and continued as it was for three times.
We were able to obtain 00,000 prints.

Comparative Example 2 A printing plate made under the same conditions as Example 2 except for using the pretreatment liquid shown below had numerous pinholes in the image area as in Comparative Example 1, and also had problems in the shadow area during printing. Printing stains occurred.

Pre-treatment liquid Riken ammonium lunate 55g pure water
945g Comparative Example 3 A printing plate prepared under the same conditions as in Example 2 except that the following pretreatment liquid E was used could be coated uniformly on the image, but scumming occurred in the non-image area from the start of printing. (Karamy was noticeable especially in the shadow areas).

Pretreatment liquid E Pure water 945g Example 3 Burning pretreatment liquid F was prepared.

Pretreatment liquid F d, f-Sodium malate 80g Sodium phytate 20g Pure water
900 g Printing was performed using a printing plate prepared under the same conditions as in Example 2, except that pretreatment liquid F was used instead of pretreatment liquid C. As in Example 2, 200,000 beautiful prints were obtained.

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)-4-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. A positive photosensitive lithographic printing plate was prepared by coating an aluminum plate with a dry weight of 2.5 g/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 G having the following composition was applied, and then a burning treatment was performed at 260° C. for 5 minutes.

Pre-treatment liquid G Boric acid 40g Pure water 960g After washing and gumming the obtained lithographic printing plate, we installed it in an off-cent printing machine and printed it.Beautiful prints were obtained in just a few pages after printing, and we continued to print 200,000 copies. I was able to obtain a printed copy of this.

Potassium hydroxide (48%) 0.1g

Claims (1)

[Claims] In a method for making a lithographic printing plate, in which a photosensitive lithographic printing plate having a photosensitive layer containing an o-quinonediazide compound and a novolac resin is subjected to image exposure and development, a burning pretreatment agent is applied, and then a burning treatment is performed. A plate-making method characterized in that the processing agent contains 0.01 to 0.5% by weight of methylcellulose.