JPH0222096A - Method for making planographic printing plate - Google Patents

Abstract

PURPOSE:To obtain a planographic printing plate generating no background staining and having no filling-up in a dot image part, especially, in a shadow part by containing a water-soluble high-molecular compound and water in a desensitizing solution of a planographic printing plate and making said solution alkaline. CONSTITUTION:A photosensitive planographic printing plate especially having a metal as a support is imagewise exposed to be developed and subsequently subjected to burning treatment to prepare a planographic printing plate. Thereafter, a desensitizing solution is applied to said printing plate but this solution is alkaline and contains a water-soluble high-molecular compound such as starch, cellulose or polyvinyl alcohol and water. Whereupon, the compound causing a contaminant scattered from an image part by burning treatment to be bonded to a non-image part is made easy to remove from the non-image part at the time of printing and no background staining is generated and filling-up in a dot image part, especially, in a shadow part is eliminated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing a lithographic printing plate from a photosensitive lithographic printing plate, and in particular, it relates to a method for manufacturing a lithographic printing plate from a photosensitive lithographic printing plate, and in particular, a photosensitive lithographic printing plate having a metal support is subjected to image exposure and The present invention relates to a method of manufacturing a lithographic printing plate by performing a burning treatment after development.

[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.

Positive-working photosensitive lithographic printing plates are made by coating an 0-quinonediazide compound alone or with an alkali-soluble resin such as a novolac type phenol resin or cresol resin on a suitable support such as metal or plastic, and are transparent. When a positive image is exposed to actinic light, the 0-quinonediazide compound in the exposed area 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, and these photosensitive compositions are used alone or mixed with additives such as suitable resins to support It is painted on the body. 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 hardens upon exposure and remains as an image upon development is lipophilic and receptive to 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). It 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 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. If heating is performed to a level that does not cause background smearing, no burning effect will be obtained and image reinforcement will not be achieved.

In order to prevent staining of non-image areas caused by this burning process, a surface smoothing process is performed before and/or after the burning process. Various proposals have been made in the past as this surface treatment liquid.

For example, after the burning process, a fluoride aqueous solution such as hydrofluoric acid, borohydrofluoric acid, silicohydrofluoric acid, etc. is used.

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
Japanese Patent Publication No. 34001 discloses treatment with an aqueous solution of organic sulfonic acid salts, such as sodium alkylnaphthalene sulfonate, sodium alkyldiphenyl ether sulfonate, and lithium nitrate before burning, and Japanese Patent Publication No. 5228062 discloses that , discloses a method in which the material is treated with an aqueous solution containing sublimable boric acid and its salts before the burning treatment, and the burning treatment is performed in the presence of the compound.

Furthermore, JP-A No. 52-6205 discloses that water-soluble organic substances such as gum arabic, cellulose ether, and polyacrylic acid, and/or borates, phosphates, sulfates, alkali metals, and alkaline earth metals are added before burning. Treatment with aqueous solutions of water-soluble inorganic salts such as halides has been shown.

After the burning process, which includes surface preparation before and/or after burning, a desensitizing liquid is applied (so-called gumming) in order to increase the hydrophilicity of non-image areas and prevent background smearing. is normally done.

The desensitizing liquid is an aqueous solution of a water-soluble resin such as gum arabic, dextrin, polyacrylic acid, hydroxymethylcellulose, mineral acid such as phosphoric acid or nitric acid, citric acid,
Those added with an organic acid such as p-toluenesulfonic acid to make the acidic region are used.

Despite surface treatment and gumming before and/or after burning, the effect of preventing scumming is not sufficient, and in order to increase the number of sheets that can be printed, it is necessary to increase the burning time or increase the temperature. When the height was set higher, smearing occurred.

In addition, stains in the halftone image area, especially in the shadow area (hereinafter referred to as smudge), are more pronounced compared to lithographic printing plates that do not undergo burning treatment.
Burning treated products were much more likely to cause this.

[Problem to be solved by the invention]

An object of the present invention is to provide an improved plate-making method that includes a burning process. More specifically, there is no background smudge, and there is no color in the halftone image area, especially in the shadow area.
An object of the present invention is to provide a plate-making method including a burning process.

[Means to solve the problem]

The present invention provides a plate-making method in which a photosensitive lithographic printing plate is subjected to image exposure and development, then subjected to a burning treatment, and then a desensitizing liquid is applied, in which the desensitizing liquid contains (a) a water-soluble polymer compound; ([1) A method for making a lithographic printing plate characterized by containing water and being alkaline is provided.

The present invention will be explained in detail below.

The present invention is characterized in that the desensitizing liquid applied to the lithographic printing plate after the burning treatment is alkaline.

At present, it is unclear why the use of such an alkaline desensitizing liquid makes background smear and halftone dot image areas significantly less likely to occur.

However, it is speculated that the reason for this is that the alkaline desensitizing liquid makes it easier to remove stain-causing compounds from the non-image areas during printing, which are scattered from the image areas and attached to the non-image areas during the burning process. Ru.

i) Water-soluble polymer compounds Examples of water-soluble polymer compounds that can be used in the present invention include the following.

For example, natural polymer compounds include starches such as apricot starch, potato starch, tapioca starch, wheat starch and corn starch, algae such as carrageenan, laminaran, seaweed mannan, funori, Irish moss, agar, and alginate. What can be obtained, trolo mallow, mannan, quince seed, pectin, tragacanth gum, karaya gum, xanthine gum, guarbing gum,
Vegetable mucilages such as locust bingham, gum arabic, calopkaum and pagein gum, microbial mucilage such as homopolysaccharides such as dextran, glucan and levan, and heteropolysaccharides such as succinoglucan and xanthan gum, glue, gelatin, casein and collagen. Examples include proteins such as

In addition to alginate propylene glycol ester, semi-natural products (semi-synthetic products) include viscose, methylcellulose, ethylcellulose, methylethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxypropylethylcellulose, and hydroxyl. Examples include cellulose derivatives such as propyl methyl cellulose phthalate and modified starch.

Processed starches include roasted starches such as white dextrin, yellow dextrin, and British gum, enzyme-modified dextrins such as enzyme dextrin and Schardinger dextrin, acid-decomposed starches as shown in solubilized starch, oxidized starches as shown in dialdehyde starch, and modified starches. Pregelatinized starch such as pregelatinized starch and unmodified pregelatinized starch, esterified starch such as phosphate starch, fatty starch, sulfate starch, nitrate starch, xanthate starch and carbamic acid starch,
Carboxylalkyl starch, hydroxyalkyl starch,
Etherified starches, methylol cross-linked starches, such as sulfoalkyl starch, cyanoethyl starch, allyl starch, benzyl starch, carbamylethyl starch and dialkylamino starch,
Crosslinked starch such as hydroxyalkyl crosslinked starch, phosphoric acid crosslinked starch and dicarboxylic acid crosslinked starch, starch polyacrylamide copolymer, starch polyacrylic acid copolymer, starch polyvinyl acetate copolymer, starch polyacrylonitrile copolymer, cationic starch polyacrylate copolymer,
Examples include starch kraft copolymers such as cationic starch vinyl polymer copolymers, starch polystyrene maleic acid copolymers, and starch polyethylene oxide copolymers.

In addition to polyvinyl alcohol, synthetic products include partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, modified polyvinyl alcohol such as polyvinyl methyl ether, polyvinylethyl ether, and polyvinyl isobutyl ether, sodium polyacrylate, and partially saponified polyacrylic esters. , partially saponified polyacrylic acid ester copolymers, polyacrylic acid derivatives and polymethacrylic acid derivatives such as polymethacrylates and polyacrylamide, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone,
Copolymer of polyvinylpyrrolidone and vinyl acetate,
These include carboxyvinyl polymer, styrene maleic acid copolymer, and styrene crotonic acid copolymer.

The content of the water-soluble polymer compound is preferably 1 to 30% by weight, more preferably 3 to 25% by weight. Content rate is 1
As it becomes less than 30% by weight, the effect of using it decreases, and as it becomes more than 30% by weight, it begins to reduce the oil sensitivity of the image area, and the printed matter has a satisfactory ink density at the start of printing. You will have to print many copies before you can get it.

These water-soluble polymer compounds may be used alone,
Also, two or more types can be used in combination.

ii) Alkalinity The desensitizing liquid of the present invention is alkaline, preferably having a pH of 9.5 or higher at 25°C, more preferably 12 or higher.

In order to make the desensitizing liquid alkaline, it is necessary to use a basic compound. Various inorganic compounds and organic compounds can be used as the basic compound. Examples of inorganic compounds include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, sodium acetate, potassium borate, sodium silicate, potassium silicate, tribasic potassium phosphate, sodium bicarbonate, lithium molybdate. Examples include alkali metal hydroxides such as alkali metal hydroxides and alkali metal weak acid salts. Examples of organic compounds include amines such as triethanolamine, triethylamine, jetanolamine, and monoethanolamine, and quaternary ammonium compounds such as tetramethylammonium hydroxide and tetraethylammonium hydroxide.

The amount of these basic compounds added is such that the pH of the desensitizing liquid in the present invention becomes 9.5 or more, and varies depending on the base strength of the basic compound used.

111) Surfactant In addition, the desensitizing liquid for lithographic printing plates of the present invention may contain various known components as necessary.

For example, by adding a surfactant to the desensitizing liquid of the present invention, the surface condition of the coating layer is improved.

Surfactants that can be used include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants.

For example, anionic surfactants include fatty acid salts, alkylbenzene sulfonates, linear alkylbenzene sulfonates, alkyl sulfates, α-olefin sulfonates, alkyl phosphate ester salts, dialkyl sulfosuccinate ester salts, polyoxyethylene alkyl ether, Sulfates, polyoxyethylene alkyl ether phosphates, alkylnaphthalene sulfonates,
Examples include N-lauroylsarcosine salts, sulfonic acids of naphthalene-pormarine condensates, and diphenyl ether disulfonates. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene, polyoxypropylene flock polymers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, and polyethylene glycol fatty acids. These include esters, polyoxyethylene fatty acid amines, fatty acid monoglycerides, sorbitan fatty acid esters, pentaerythritol fatty acid esters, sucrose fatty acid esters, and amine oxides.

Examples of amphoteric surfactants include alkylcarboxybetaine types, alkylaminocarboxylic acid types, and alkylimidacillin types. Examples of cationic surfactants include tetraalkylammonium salts, trialkylbenzylammonium salts, and alkylimidazolinium salts.

Other examples include fluorine-based surfactants and silicone-based surfactants.

Among the surfactants, anionic surfactants and/or nonionic surfactants are particularly effective. Two or more of these surfactants can also be used in combination.

The amount used is not particularly limited, but the preferred range is 0.01 to 10% by weight of the desensitizing solution.

iv) Water Water functions as a solvent for the desensitizing liquid. Water includes distilled water, deionized water, water with solids removed by filtration,
Tap water, etc. can be used.

Water occupies the remaining amount of other components, and the range of its content is not specified, but generally 40%
It is preferably used in a range of 95% by weight.

■) Plate-making method The desensitizing liquid of the present invention can be used for various lithographic printing plates, but in particular, it can be used for offset printing plates printed on metal sheets using ultraviolet curing ink on a flatbed offset printing device. It can be suitably used for.

The plate making method for such an offset printing plate was disclosed in Japanese Patent Application Laid-open No. 53
-100002, 54-100005, 54-
It is described in detail in the publications No. 53004 and No. 56-2168.

In the plate-making method of the present invention, in order to further reduce the occurrence of background smearing, surface shaping treatment can be performed after the photosensitive lithographic printing plate has been subjected to image exposure and development, and before and/or after the burning treatment. As the surface preparation liquid before and/or after burning, the above-mentioned known liquids can be used.

Methods for applying the desensitizing liquid include pouring an appropriate amount of the desensitizing liquid onto the surface of the lithographic printing plate, rubbing it with a sponge or the like to coat the entire surface of the plate, and then drying it, or using an automatic coating device. (Generally called a gum coater)
There are methods for automatically applying and drying.

When starting printing, it is generally possible to wash the gum on the plate surface with water (so-called gum removal), and then print according to the normal procedure, or printing can be started immediately without so-called gum removal. can.

〔Effect of the invention〕

According to the plate making method of the present invention, it is possible to obtain a lithographic printing plate that is free from background smudges and free from smudges in the halftone image areas, particularly in the shadow areas.

〔Example〕

This will be explained below using examples. Note that % does not indicate weight % unless otherwise specified.

Example 1 Naphthoquinone-(1) of 1.5-dihydroxynaphthalene
,2)-Diazide(2)-5-sulfonic acid Nisdel 2 parts by weight and novolac type cresol formaldehyde resin 4
parts by weight 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/m'. The positive photosensitive lithographic printing plate thus prepared was brought into close contact with the transparent positive image and exposed for 30 seconds from a distance of 1 m using a 3KW metal halide lamp, followed by silicic acid treatment).
It was developed by immersing it in a wt% aqueous solution for about 1 minute. Next, after washing with water, a burning pretreatment liquid having the following composition was applied and dried. The coating amount was 0.4 g/m' (dry weight).

980 parts by weight of pure water
) for 7 minutes at a temperature of 280°C.

After cooling, the following desensitizing liquid [■] was applied, the excess was wiped off with a cloth, and the film was allowed to dry naturally. The coating weight was 0.3 g/m' (dry weight).

Desensitizing liquid [I] Water-soluble hydroxypropyl etherified starch (degree of substitution 0
．． 05) 60 parts by weight was dissolved in 914 parts by weight of pure water. 18 parts by weight of IK potassium silicate solution (20t52Be') was added to the aqueous solution, and 8 parts of KOH (48.5% aqueous solution) was added thereto.
A desensitizing liquid of the present invention was prepared by adding parts by weight. 25℃
The pH at was 12.5.

When this lithographic printing plate was attached to a Hamada Star 900CI)-X printing machine and printed, beautiful prints were obtained in just a few sheets after printing, and 150,000 beautiful prints were obtained after printing.

Comparative Example 1 The following desensitizing liquid [■] was applied to a lithographic printing plate obtained by processing under exactly the same conditions as in Example 1 up to the burning treatment in Example 1.
It was applied in the same manner as above and allowed to dry. The application amount is 0.3
g/m' (dry weight).

Desensitizing liquid [Ir] Water-soluble hydroxypropyl etherified starch (degree of substitution 0
．． 05) 6.0 parts by weight was dissolved in 914 parts by weight of pure water.

The pH at 25° C. was 7.0. When this lithographic printing plate was printed in the same manner as in Example 1, scumming occurred, and the printing press had to be stopped and the stains had to be removed with a plate cleaner.

Comparative Example 2 A lithographic printing plate obtained under exactly the same conditions as in Example 1'' up to the burning treatment was coated with the following desensitizing liquid [I] and dried in the same manner as in Example 1.The amount of coating was 0.3 g. /m' (dry weight).

Desensitizing liquid [II] Water-soluble hydroxypropyl ether starch (degree of substitution 0.
05) 60 parts by weight was dissolved in 914 parts by weight of pure water. 1.7 parts by weight of 85% phosphoric acid was added to the aqueous solution. 25
The pH at °C was 3.6.

When this lithographic printing was performed in the same manner as in Example 1, no background staining occurred, but smearing occurred in the halftone image area from the beginning of printing, and even after several hundred copies were printed, a clean print could not be obtained. .

Comparative Example 3 A lithographic printing plate obtained under exactly the same conditions as in Example 1 up to the burning process was diluted with GU-7 (trade name, desensitizing liquid manufactured by Fuji Photo Film ■) (diluted with the same volume of water). was applied in the same manner. The PL of the GU-7 dilution at 25°C was 3.6
The coating amount was 0.35 g/m' (dry weight).

When this lithographic printing plate was printed in the same manner as in Example 1, some smearing occurred in the shadow area of the halftone image area from the start of printing, and the printing press had to be stopped and the smearing removed using a plate cleaner. There wasn't.

Example 2 A photosensitive lithographic printing plate prepared in the same manner as in Example 1 was
The transparencies were brought into close contact and exposed for 40 seconds using a 3KW metal halide lamp from a distance of 1 m, and then developed by immersing them in a 7% by weight aqueous sodium silicate solution for about 1 minute. This lithographic printing plate is processed by an automatic through-type burning processor (manufactured by Flosses Materials Co., Ltd., which applies a pre-burning treatment liquid, burns,
Perform gum bowing continuously. It has a pre-heating chamber and a post-heating chamber. ] was continuously processed. Here, the burning temperature was set such that the pre-heating chamber temperature was 150° C., the post-heating chamber temperature was 240° C., and the heating chamber passage time was about 3 minutes, and no pre-burning treatment liquid was used.

The following desensitizing liquid (■) was applied to the planographic printing plate obtained by the burning process using G-800H (Gum coater manufactured by Fuji Photo Film L-@) and dried. Desensitizing liquid [IV] 25
The pH at °C was 13.1, and the coating amount was 0.4 g/m' (dry weight).

Desensitizing liquid [■] Roasted dextrin (trade name Amicol 6H: Nippon Deka Chemical ■
100 parts by weight of (manufactured by) was dissolved in 740 parts by weight of pure water. To the aqueous solution, 7 parts by weight of sodium hydroxide, 5 parts by weight of a 35% aqueous solution of sodium isopropylnaphthalene sulfonate, an anionic surfactant, and 0 parts by weight of sodium dehydroacetate.
．． 3 parts by weight were dissolved.

When this lithographic printing plate was attached to a Huff Duster 900CD-X printing machine and printed, beautiful prints were obtained in just a few sheets from the start of printing, and 200,000 beautiful prints were obtained after printing.

Comparative Examples 4, 5.6 In place of the desensitizing liquid [■] in Example 2, the following desensitizing liquid [■] (Comparative Example 4) and desensitizing liquid [VI] (Comparative Example 5) were used.
) and desensitizing liquid [■] (Comparative Example 6) were prepared. The amount of desensitizing liquid applied was 0.4 g/m' (dry weight) in each case.

Desensitizing liquid [■] Desensitizing liquid [Produced in the preparation of rVI without adding only sodium hydroxide. The pit at 25°C was 6.8.

Desensitizing liquid CVI) In preparing the desensitizing liquid [■], 2.0 parts by weight of 85% phosphoric acid was added instead of sodium hydroxide. 25℃
The pH at that time was 3.5.

Desensitizing liquid [■] In the preparation of the desensitizing liquid [■], 3.5 parts by weight of 85% phosphoric acid was added in place of IJ ram (which is hydroxylated). 25
The pH at °C was 1.1.

When these lithographic printing plates were printed in the same manner as in Example 2, in the case of the desensitizing liquid [■] (Comparative Example 4), background smear occurred along with coloring of the halftone dots, and the desensitizing liquid [■] In the case of (Comparative Example 5), no scumming occurred, but smear occurred in the halftone image area, and in the case of the desensitizing liquid [■] (Comparative Example 6), the desensitizing liquid [VI] Although the degree of karami was small, some karami occurred in the shadow area. Furthermore, with the desensitizing liquid [■], the inking property at the beginning of printing was poor, and it was necessary to print several dozen sheets until the ink was completely covered in the image area. Desensitizing liquid [V:], [VI:], [
■ Even after printing several hundred copies, I could not get clean prints, so I had to stop the printing machine and use a plate cleaner to remove the background dirt and smudges.

Claims (1)

[Scope of Claims] In a plate-making method in which a photosensitive lithographic printing plate is imagewise exposed and developed, subjected to a burning treatment, and then a desensitizing liquid is applied, the desensitizing liquid is (a) a water-soluble polymer compound. , and (b) a method for making a lithographic printing plate characterized by containing water and being alkaline.