JPH01259995A - Desensitized composition for lithographic printing plate - Google Patents

Abstract

PURPOSE:To prevent a lithographic printing plate particularly having zinc oxide- containing photosensitive layer from adhering to a printer cylinder by adding alkaline metal compound component further to phytic acid component and bivalent metallic compound component in desensitizing solution. CONSTITUTION:Desensitizing composition for a lithographic printing plate contains aqueous solution including 0.4-20wt.% of phytic acid, at least one type of phytic acid component selected from its functional derivatives, 0.1-10wt.% of at least one type of amino compound, 1-10moles of bivalent metal compound component of MXm to 1mole of phytic acid component, and 0.1-10wt.% of at least one type of alkaline metal compound selected from compounds of a formula AnY. In the formulae I, II, M is bivalent metal atoms, A is alkaline metal atoms, X, Y are univalent or bivalent anionic atom or atom group, and (m), (n) are integer number of 1 or 2. Thus, the adhesive operation of the phytic acid and chelate of phytic acid and metal salt is reduced, and the adherence of a printing plate to a cylinder is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a desensitizing solution for lithographic printing plates. To explain in more detail, what is the present invention? By adding an alkali metal salt to a desensitizing composition containing itinic acid or its functional derivative as a main component, it is possible to eliminate adhesion between the plate cylinder of the printing press and the lithographic printing plate, and to use an automatic plate discharge printing machine. The present invention relates to a desensitizing treatment solution that attempts to eliminate troubles during plate discharge when printing.

[Conventional technology]

An offset lithographic printing original plate that uses electrophotography as the basic plate-making principle consists of a sheet base material and a photoconductive photosensitive layer formed thereon, the main component of which is a photoconductive substance such as zinc oxide. A lithographic printing plate having a toner image can be produced by subjecting a Yuko original plate to a photosensitive treatment in a desired pattern and developing it with an oil-sensitive developer.

Another method for producing an offset lithographic printing plate is to create an original plate consisting of a sheet-like base material and an image-receiving layer formed thereon and containing a binder and an inorganic pigment. Methods of transferring electrophotographic images to form printing plates are also known.

Another method for producing offset lithographic printing plates is
A so-called direct image offset master (straight groove master) manufacturing method is also known, in which a printing plate is obtained by directly applying writing or type printing using oil-based ink to an original plate having an image-receiving layer.

When performing offset lithographic printing using a conventional printing plate as described above, in order to make the non-image area on the plate hydrophilic, it is necessary to subject this area to an anti-fat treatment. In particular, when using a lithographic printing original plate having a photoconductive photosensitive layer, the majority of the non-image areas, which should originally be hydrophilic, exhibit considerable lipophilicity, so it is necessary to subject these areas to a degreasing treatment. is important. If this treatment is insufficient, stains will occur on the non-image areas of the printing plate during printing, which can easily cause stains on the printed matter.Especially when printing is continued for a long period of time, it will be difficult to maintain clear prints without background stains. You won't be able to get it.

Currently, this desensitization treatment liquid, ie, etch liquid, is
Broadly divided, the following types are known.

(I) Those whose main components are organic acids, inorganic acids, salts thereof, etc. (For example, Special Publication No. 43-28404) (2)
Ferrocyan salt or ferricyan salt as the main ingredient. (For example, Japanese Patent Publication No. 39-8416) (3) Those using phytic acid as the main component (Japanese Patent Publication No. 45-2460)
(No. 9) However, the above-mentioned known desensitizing treatment liquid (I) has a low desensitizing efficiency, and as a result, the background stains that occur on printed matter during printing are significant, making it difficult to stably obtain clear printed matter over a long period of time. I have a bad memory.

Further, the above-mentioned known desensitizing liquid (2) has a considerably higher desensitizing effect compared to the above-mentioned known desensitizing liquid (I), but the effect itself is not necessarily sufficient. Furthermore, it has the disadvantage of being unstable to light and heat, so when printing on acid-free paper that generates a lot of paper dust, or when the printing pressure is high during printing, printing stains may occur on printed matter. The problem is that it is easy to occur.

Furthermore, the known desensitizing solution (2) has a serious problem in that it contains cyanide ions (CN-), which are toxic to the human body.
) is said to be stable in itself and harmless to the human body, but depending on the environmental conditions in which it is used, there is a risk that it may decompose and generate cyanide ions, so care should be taken when using it. Caution must be taken.

In view of the problems with the conventional fat-free treatment liquids mentioned above, we have developed a treatment liquid that uses safe natural products, taking work safety into consideration.
That is, a desensitizing treatment liquid (3) using phytic acid has been proposed.

Initially, this known desensitizing solution (3) had an extremely low chelating power, and therefore its desensitizing effect was not of a practical level.

However, due to the results of research focused on the safety of phytic acid, it has become possible to exert a sufficient desensitizing effect by using it in combination with various additives. The inventors of the present invention
No. 5257, which contains phytic acid, a divalent metal compound, and ethylene glycol mono- or di-alkyl ether as main components, has a high desensitizing effect and quickly forms a tough hydrophilic film on the non-printing area of the printing plate. We have proposed a desensitizing solution that can be used to form clear prints.

However, this desensitizing liquid has the disadvantage that if the etching processor is insufficiently squeezed, the master plate will adhere to the cylinder of the printing press during printing and will not be peeled off. Generally, desensitization is carried out by running the printing plate through a desensitizing solution for several seconds using an etching processor, and the excess processing solution adhering to the master plate surface is squeezed out by an outlet roll. It looks like this. However, for this treatment, the printing plate passes through an etching processor, and at this time, the desensitizing liquid also adheres to the back side of the plate. That is, it is unavoidable that the desensitizing liquid adheres to the back surface of the master to some extent, resulting in the problem that the master printing plate adheres to the cylinder after printing, making it difficult to remove it. This phenomenon may pose a serious problem during use. In particular, when using an automatic plate discharge printing machine, a problem arises in that the master cannot be discharged when the master plate is discharged.

[Problem to be solved by the invention]

The present invention overcomes the above-mentioned drawbacks of conventional lithographic printing plate desensitizing liquids containing phytic acid and divalent metal compounds such as Ni and Co as main components, that is, has a sufficient desensitizing effect. , however, attempts to solve the problem of promoting adhesion between the master printing plate and the printing press cylinder.

[Means to solve the problem]

The desensitization treatment composition for lithographic printing plates of the present invention has a composition of 0.4 to
20% of a phytic acid component consisting of at least one selected from phytic acid and its functional derivatives; and 1 to 10 mol of the following general formula (I): MXm per 1 mol of the phytic acid component. (I) [In the above formula, M represents a divalent metal atom, X is monovalent,
or represents a divalent anionic atom or atomic group,
m represents an integer of 1 or 2], and 0.1 to IO weight % of the following general formula (II): AnY
(If) [In the above formula, A represents an alkali metal atom, Y represents a monovalent or divalent anionic atom or atomic group,
n represents an integer of 1 or 2]; and an aqueous solution containing:

The present inventors have solved the problem that the phytic acid used in the desensitization treatment liquid causes the printing plate to stick to the printing press cylinder, but it does not contain cyan compounds and is non-polluting. Focusing on this characteristic, we conducted intensive research on ways to improve it after treatment. As a result, phytic acid itself is sticky, so when the desensitizing solution applied to the printing plate dries, it forms a sticky film on the master printing plate surface. It was found that this caused the cylinder surface and the back surface of the master that was in contact with the cylinder surface to adhere to each other. The greater the content of phytic acid in the desensitizing solution, the greater the adhesive strength of the dried film. In addition, Ni and Go are added to the treatment solution for the purpose of increasing the desensitization treatment effect.

It has been proposed to add metal salts such as Cu and Mg. However, it has been found that in this case chelates of phytic acid and metal salts are formed, which significantly increases the adhesive action of the dried film. Therefore, in the nonfatting treatment liquid of the present invention, by adding the alkali metal compound component of the general formula (II), the adhesive action of phytic acid and the chelate of phytic acid and metal salts is reduced, thereby printing This prevents the plate from sticking to the cylinder.

In other words, the anti-lipidizing treatment composition of the present invention has a strong desensitizing effect, can quickly form a strong hydrophilic film, and reduces its desensitizing ability even when exposed to heat or light. It is harmless to the human body, and does not cause the printing plate to which it is applied to adhere (adhesion) to the printing press cylinder, making it difficult to remove it.

In the desensitizing treatment solution of the present invention, phytic acid or a functional derivative of phytic acid is used as the phytic acid component. Functional derivatives of phytic acid can be selected from water-soluble salts of phytic acid with monovalent or divalent metals, such as sodium phytate, potassium phytate, and calcium phytate. Further, the content of the phytic acid component in the desensitizing treatment composition is 0.4 to 2
0% by weight, preferably 1 to 10% by weight.

When the content of the phytic acid component is lower than 0.4% by weight, the fat-repelling effect is insufficient, and when it is higher than 20% by weight, there is a disadvantage that the rigidity resistance is lowered.

In the desensitizing treatment liquid of the present invention, the divalent metal compound component effective in desensitizing has the general formula (I) MXm(I) [where M represents a divalent metal atom and X is monovalent or divalent Represents a valent anionic atom or atomic group, m is 1 or 2
represents an integer. ] It consists of a compound consisting of: In general formula (I), the divalent metal atom represented by M is selected from nickel, manganese, magnesium, cobalt, copper (If), and the like. In addition, the anionic atoms or atomic groups represented by Preferably, it is selected from the group (root). Moreover, the content of the divalent metal compound component is 1 to 10 mol, preferably 4 to 6 mol, per 1 mol of the phytic acid component. The content of the divalent metal compound component is phytic acid component 1
If it is less than 1 mol, the resulting composition will have an unsatisfactory desensitizing effect, and if it is more than 10 mol, the stiffness resistance of the resulting printing plate will decrease, Further, there is a problem in that precipitates are likely to be generated in the desensitizing (etching) treatment solution.

In the non-greasing treatment composition of the present invention, the alkali metal compound component effective in preventing cylinder adhesion is contained in one vessel type' (
Compound II): AnY (■) [However, A represents an alkali metal atom, and Y represents a monovalent or divalent anionic atom or atomic group.

n represents an integer of 1 or 2.] In general formula (n), the alkali metal atom represented by A is preferably selected from sodium and potassium. In addition, the anionic atom or atomic group represented by Y is a halogen atom, a sulfate group (
(root), acetate group (root), phosphate-hydrogen group (root) and dihydrogen phosphate group (root). Also,
The content of the alkali metal compound component in the fat-free treatment composition is 0.1 to 10% by weight, preferably 0.5 to 5% by weight, and the content of the alkali metal compound component is 0. If the amount is less than .1% by weight, the adhesiveness of the resulting coated and dried film will not be reduced sufficiently, and if it is more than 10% by weight, there will be a disadvantage that scumming will easily occur on the printed matter.

The desensitizing treatment composition of the present invention contains the above-mentioned phytic acid component, divalent metal compound component, and alkali metal compound component as essential components, but in addition to these, additives are added to improve the desensitization treatment effect. As agents, solvents for glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether, polyacrylic acid, modified polyacrylic acid, and It may contain small amounts of acrylic acid copolymers and their metal salts, hydrophilic polymers such as polyethylene glycol, and organic acids such as citric acid, tartaric acid, malonic acid, malic acid, and adipic acid.

Further, sodium dehydroacetate, salicylic acid, etc. may be added as a preservative, and a surfactant, etc. may be added as a wetting agent to the fat-free treatment composition of the present invention.

[For production]

By further adding an alkali metal compound component to the phytic acid component and the divalent metal compound component in the degreasing treatment liquid of the present invention, it is possible to improve the lithographic printing plate, especially the lithographic printing plate having a zinc oxide-containing photosensitive layer. , it is possible to reduce the tackiness of the applied and dried coating while providing a sufficient degreasing treatment effect, thereby preventing the printing plate from adhering to the printing press cylinder.

〔Example〕

The present invention will be further explained below with reference to Examples, but these are not intended to limit the scope of the present invention. In addition, "part" and "%" in the examples are unless otherwise specified.
Represents coulometric parts and weight %.

The composition of the following ingredients is as follows: Phytic acid 50 parts Nickel chloride hexahydrate 4 parts Polyethylene glycol 20 parts (molecular weight 200) Sodium polyacrylate 10 parts Ethylene glycol monobutyl ether 16 parts NaC150
Department water
850 parts, and the pH of the obtained liquid composition was adjusted to 20.
% was adjusted to 3.7 with an aqueous NaOH solution to prepare a desensitizing treatment solution.

An image was formed on a commercially available zinc oxide/resin dispersion electrophotographic material using an electrophotographic engraving machine, and the printing surface of the printing plate was etched with the above desensitizing solution using an automatic etching device (Ricoh etching processor). An offset printing plate was prepared, and offset printing was performed using a 20-fold dilution of this desensitizing solution as a dampening solution.

As a result, after continuous printing of 5000 sheets, clear printed matter without stains was obtained, and it was confirmed that there was no adhesion between the printing plate and the printing area cylinder after continuous printing of 5000 sheets. The results are shown in Table 1.

Disaster Treatment 11 In Main Example 2.3, a fat-unfattening treatment solution was prepared in the same manner as in Example 1, except that the amounts of NaCl added were changed to 20 parts and 5 parts, respectively. The results of the 5000-sheet printing test are shown in Table 1.

The composition of the following ingredients is as follows: Phytic acid 75 parts Nickel chloride hexahydrate 4 parts Polyethylene glycol 20 parts (molecular weight 200) Sodium polyacrylate 10 parts Ethylene glycol monobutyl ether 16 parts NaC 150
Department water
825 parts were mixed, the pi of the resulting composition was adjusted to 3.6, and a fat-unfavorable treatment liquid was prepared. Table 1 shows the results of the 5000-sheet printing test.

The composition of the following ingredients is as follows: Phytic acid 40 parts Nickel acetate 10 parts Polyethylene glycol 80 parts (molecular weight 600) Anionic modified sodium polyacrylate 20 parts Ethylene glycol monomethyl ether 30 parts KCI
40 parts water
The pH of the resulting composition was adjusted to 3.9 to prepare a desensitizing solution. Table 1 shows the results of the 5000-sheet printing test.

1 process The following ingredients are composed as follows: Phytic acid 70 parts Cobalt chloride 20 parts Citraconic acid IO part P-) Luenesulfonic acid sorter 20 parts Ethylene glycol monomethyl ether 50 parts NaC
150 parts water 7
The pH of the resulting composition was adjusted to 4.0 to prepare a desensitizing solution. Table 1 shows the results of the 5000-sheet printing test.

The composition of the following ingredients is as follows: Phytic acid 50 parts Nickel chloride hexahydrate 4 parts Polyethylene glycol 20 parts (molecules! 200) Sodium polyacrylate 10 parts Ethylene glycol monobutyl ethyl 16 parts Water
The pn of the liquid composition obtained by mixing 900 parts was 20%.

It was adjusted to 3.7 with an aqueous NaOH solution to prepare a desensitizing treatment solution. Table 1 shows the results of the 5000-sheet printing test.

Comparison 1 The following ingredients are composed of: Phytic acid 75 parts Nickel chloride hexahydrate 4 parts Polyethylene glycol 2061S (molecule fi200
) Sodium polyacrylate 10 parts Ethylene glycol monobutyl ether 16 parts Water
875 parts were mixed, and the pH of the resulting composition was adjusted to 3.6 to prepare a fat-unfavorable treatment liquid. Table 1 shows the results of the 5000-sheet printing test.

Stop test 1 The following ingredients are composed as follows: Phytic acid 40 parts Nickel acetate 10 parts Polyethylene glycol 80 parts (molecule 1600) Anionic modified sodium polyacrylate 20 parts Ethylene glycol monomethyl ether 10 parts Water
The pH of the resulting composition was adjusted to 3.8 to prepare a desensitizing solution. Table 1 shows the results of the 5000-sheet printing test.

Phytic acid 70 parts Cobalt chloride 20 parts Citraconic acid 10 parts p-Toluenesulfonic acid sorter 20 parts Ethylene glycol monomethyl ether 50 parts Water
830
The pH of the resulting composition was adjusted to 3.8 to prepare a desensitizing treatment solution. Table 1 shows the results of the 5000-sheet printing test.

As clearly shown in Table 1-1, all of the desensitizing compositions of the present invention (Examples 1 to 6) exhibit good printing stain prevention effects, and also It showed excellent effectiveness in preventing adhesion to cylinders. However, although the comparative desensitized compositions (Comparative Examples 1 to 4) eventually showed good printing smudge prevention effects, they resulted in the printing plate sticking to the printing press cylinder.

〔Effect of the invention〕

The desensitization treatment composition of the present invention enables rapid, safe, and effective desensitization treatment of lithographic printing plates, and imparts good printing properties to the printing plates. possible, and also prevents the printing plate from adhering to the printing press cylinder (
This can prevent the occurrence of adhesion.

Claims (1)

[Scope of Claims] 1. 0.4 to 20% by weight of a phytic acid component consisting of at least one selected from phytic acid and its functional derivatives, and 1 to 10% by weight per mole of the phytic acid component. molar, the following general formula (I): MXm(I) [In the above formula, M represents a divalent metal atom, X is a monovalent,
or represents a divalent anionic atom or atomic group,
m represents an integer of 1 or 2], and 0.1 to 10% by weight of the following general formula (II): AnY(I
I) [In the above formula, A represents an alkali metal atom, Y represents a monovalent or divalent anionic atom or atomic group,
1. A desensitizing treatment composition for a lithographic printing plate, comprising an alkali metal compound component consisting of at least one compound selected from the compounds [n represents an integer of 1 or 2], and an aqueous solution containing the following.