JPS62253174A - Photoengraving method - Google Patents

Abstract

PURPOSE:To permit a burning treatment which obviates scumming, provides an excellent sensitization characteristic to an image part and can be automated by coating an aq. soln. contg. a specific compd. on a plate prior to the burning treatment after development and subjecting the plate to the burning treatment in the presence of said compd. CONSTITUTION:The aq. soln. contg. at least one kind of the ocmpd. selected from the group consisting of nitrious acid and the alkali metal salt thereof, ammonium salt, phosphorous acid, thiosulfuric acid and ammonium salt of peroxysulfuric acid is coated on the photosensitive lithographic printing plate prior to the burning treatment after image exposure and development, then the plate is subjected to the burning treatment in the presence of said compd. The compd. is incorporated into the processing soln. at 0.1-30wt%, more preferably 5-20wt% based on the total weight thereof. A surface active agent, various salts, acids, alkakis, etc. may be added to the processing soln. Further, gum arabic, water-soluble high-polymer such as dextrin, dyes, defoaming agents, antiseptics, etc. may be added to the processing soln.

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.
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 portion removed by the alkaline aqueous solution, and this portion receives 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 using a support with a hydrophilic surface, 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 many more printed sheets 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 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 salts of organic sulfonic acids 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. 51-6205 discloses that water-soluble organic substances such as gum arabic, cellulose ether, polyacrylic acid, and/or borates, phosphates, sulfates, alkali metals, and alkaline earth metals are added before the burning process. It has been shown that treatment with an aqueous solution of water-soluble inorganic salts such as halides such as When an aqueous solution of a water-soluble polymer is used, there is a drawback that it becomes difficult for the image area to receive ink during printing, resulting in so-called inking failure. Furthermore, in Japanese Patent Application Laid-Open No. 57-52057,
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, is disclosed 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.

[Structure of the invention]

The present inventor has discovered that nitrous acid and its alkali metal salts, ammonium salts, phosphorous acid, thiosulfuric acid, and 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 ammonium salts of peroxysulfuric acid.

The compound used in the present invention is the above acid or a salt thereof.

Among these, examples of alkali metal salts include sodium salts, potassium salts, and lithium salts.

The above compounds can be used alone or in combination of two or more, and are 0.1 to 30% by weight, more preferably 0.5 to 2% by weight, based on the total weight of the burning pretreatment liquid according to the present invention.
It is contained in a range of 0% 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 burning pretreatment 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 stains in non-image areas due to 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. For example, mineral acids such as nitric acid, sulfuric acid, phosphoric acid, organic acids such as citric acid, cono-phosphoric acid, oxalic acid, tartaric acid, acetic acid, malic acid, potassium salts, lithium salts, sodium salts or ammonium salts of these acids. , or alkali metal hydroxides, carbonates, hydrogen carbonates, and the like.

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, immersing the printing plate in a vat filled with the treatment liquid, and applying the coating 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 washing with water and gumming, if necessary. It is possible to omit so-called desensitization treatment such as.

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.
521, a photosensitive layer made of a mixture of a diazo resin (salt of a condensate of p-diazodiphenylamine and paraformaldehyde) and shellac is provided on an aluminum plate, British Patent No. 1 .460.9
No. 78 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 units as main repeating units. 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 28 positive plates shown above. 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. 4,07
2.528 and 4.072.527, a PS plate in which a photosensitive layer of a photopolymerizable photopolymer composition is provided on an aluminum plate, British Patent No. 1.235 .281 and 1.495.861
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 the above-mentioned publications. Among these PS plates, a particularly preferred PS plate to be used in the plate making method of the present invention is a positive-working PS plate having a photosensitive layer consisting of an O-naphthoquinone diazide compound and a novolac resin, and is disclosed in US Pat. No. 4.2.
59.434 Specification, Column 3, Line 2 from the bottom to Column 6, No. 1
It is explained in detail in 4 lines.

〔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>-2>-2 parts by weight of -5-sulfonic acid ester and 4 parts by weight of novolak type cresol-formaldehyde resin were dissolved in 100 parts by weight of ethylene glycol monomethyl ether. Then, a solution of 0.24 mm thick was dissolved in 100 parts by weight of ethylene glycol monomethyl ether. This solution was coated on a grained aluminum plate to give a weight after drying of 2.5 g/m'.The positive-working photosensitive lithographic printing plate thus prepared was brought into close contact with a transparency. After exposure for 30 seconds with a 3 KW metal halide lamp from a distance of 1 m, the film was developed by immersing it in a 5% by weight sodium silicate aqueous solution for about 1 minute.After washing with water, a burning pretreatment solution with the following composition was applied. was applied and dried.

Sodium nitrite □150g Pure water
□ 850 g of the printing plates thus treated were 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 Graining and anodizing (anodizing in 15% by weight sulfuric acid at a current density of 1.6 amperes/d m' for 2 minutes.

) A photosensitive liquid similar to that in Example 1 was applied onto an aluminum plate having a thickness of 0.3 mm to prepare a positive photosensitive lithographic printing plate.

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 solution of IJium silicate for about 1 minute. This lithographic printing plate was processed using an automatic through-type burning processor [manufactured by Process Materials Co., Ltd., which continuously performs the application of a burning pretreatment liquid, burning, and gumming. ] was continuously processed. Here, the burning temperature was preheated at 150°C, postheated at 240°C, and the time required for passage through the filtration was about 3 minutes, and the burner pretreatment liquid used had the following composition.

Ammonium thiosulfate □115g Hexametaphosphoric acid □5g Pure water
□ When the lithographic printing plate obtained by the 880 g 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 process.

Comparative Example 2 The development process was carried out in the same manner as in Example 2, and the treatment liquid in the nozzling processor was changed to an aqueous solution of 8% by weight of sodium alkyl diphenyl ether sulfonate. As a result, significant foaming occurred from the spray pipe in the area where the treatment liquid was applied and its tank, and the liquid overflowed from the tank, necessitating the operation of the automatic treatment machine to be stopped.

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.

Ammonium phosphite □123g Sodium dodecylbenzenesulfonate 5g Phosphoric acid (85%) 2g pure
Water □ 870 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. 3,365,709
-Diazide (4 parts by weight of 2i5-sulfonic acid ester and 4 parts by weight of novolac type cresol-formaldehyde resin were dissolved in 96 parts by weight of ethylene glycol monomethyl ether, and the solution was treated with the grain chamber used in Example 2 and anodized. Dry weight on aluminum plate 2.8 g/m
A positive photosensitive lithographic printing plate was prepared.

After this positive photosensitive lithographic printing plate was exposed to light, 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 250° C. for 6 minutes.

Ammonium peroxysulfate salt □130g Sodium dodecylbenzenesulfonate □20g Pure water
□ When the obtained lithographic printing plate weighing 850 g was mounted on an offset printing machine without gumming and printed, beautiful prints were obtained in just a few sheets from the start of printing, and it was possible to print 250,000 sheets by continuing to print. done.

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, nitrous acid and its alkali metal salts, ammonium salts, phosphorous acid, thiosulfuric acid, and peroxysulfuric acid are added after development and before the burning treatment. 1. A plate-making method comprising applying an aqueous solution containing at least one compound selected from the group consisting of ammonium salts and performing a burning treatment in the presence of the compound.