JPH01259994A - Desensitized composition for lithographic printing plate - Google Patents

Abstract

PURPOSE:To sufficiently perform the desensitization effect of a lithographic printing plate particularly having zinc oxide containing photosensitive amount, to reduce the stickness of desensitizer, and to prevent the plate from adhering to a cylinder by adding specific alkaline metal compound in desensitizing solution containing phytic acid component and amino compound component. CONSTITUTION:Desensitizing composition for a lithographic printing plate contains aqueous solution including 0.4-20wt.% of phytic acid, at least one type selected from its functional derivatives, 0.1-10wt.% of at least one type of amino compound, and 0.1-10wt.% of at least one type selected from alkaline metal compounds of formula MnX, where, in the formula, M is alkaline metal atoms, X is univalent or bivalent anionic atom or atom group, and n is integer number of 1 or 2. Thus, the viscous operation of the phytic acid is reduced, and the adherence of a master printing plate to a cylinder is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a lithographic printing plate desensitization treatment composition. More specifically, the present invention provides a desensitizing treatment for a lithographic printing plate that can prevent the lithographic printing plate from adhering to the plate cylinder of a printing press, and therefore facilitate automatic discharge of the lithographic printing plate from the printing press. The present invention relates to a composition.

- [Prior Art] An offset lithographic printing original plate using electrophotography as the basic plate-making principle consists of a sheet base material and a photosensitive material formed on the sheet base material and mainly composed of a photoconductive substance such as zinc oxide. It consists of a conductive photosensitive layer. A lithographic printing plate having a toner image can be produced by subjecting this original plate to 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 (direct-printing 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 offset lithographic printing is performed using a conventional printing plate as described above, in order to make the non-image area on the plate hydrophilic, it is necessary to apply a desensitizing treatment to this area. In particular, when using a lithographic printing original plate having a photoconductive photosensitive layer, the non-image area, which should originally be hydrophilic, usually exhibits considerable lipophilicity, so it is necessary to apply desensitization treatment to this area. is necessary. If this treatment is insufficient, the non-image areas of the printing plate will become smeared during printing, which can easily cause stains on the printed matter. Especially when printing is continued for a long period of time, it is difficult to maintain clear printed matter without background smudges. You won't be able to get it.

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

(1) Products whose main components are organic acids, inorganic acids, salts thereof, etc. (For example, Special Publication No. 43-28404) (2
) Ferrocyan salt or those whose main component is ferricyan salt. (For example, Japanese Patent Publication No. 39-8416) (3) Those using phytic acid as the main component (Japanese Patent Publication No. 45-246)
(No. 09) However, the above-mentioned known desensitizing treatment liquid (1) has a low desensitizing effect, 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. Have difficulty.

Furthermore, the above known desensitizing liquid (2) has a considerably higher desensitizing effect compared to the known desensitizing liquid (1), but the effect itself is not necessarily sufficient. Furthermore, it has the disadvantage of being unstable to light and heat, so when printing on neutral paper, which generates a lot of paper dust, or when printing pressure is high, printing stains may occur on printed matter. There is a problem that this is likely 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.
``''4) 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. requires careful attention.

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

Initially, this known desensitizing treatment liquid (3) had extremely low chelating power, and therefore its desensitizing effect was not practical.

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
In No. 5257, it 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 strong hydrophilic film on the non-printing area of the printing plate. We proposed a desensitizing solution that can produce clear printed matter.

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. Furthermore, in JP-A-56-2189, a desensitizing composition comprising phytic acid, a polyvalent amino compound, and an alcohol amine was proposed, but this also had the problem of cylinder adhesion. Generally, desensitization treatment is carried out by running the printing plate through a desensitizing treatment solution for several seconds using a circular cutting processor, and the excess treatment solution adhering to the master plate surface is removed. However, for this process, the printing plate passes through an etching processor, and at this time, the desensitizing liquid also adheres to the back side of the plate. .

In other words, it is unavoidable that more or less of the desensitizing liquid will adhere to the back surface of the master, resulting in the problem that the back surface of the master printing plate will adhere to the cylinder after printing, making it difficult to remove it. . This phenomenon may pose a serious problem in usability. especially,
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 solves the above-mentioned drawbacks in the conventional lithographic printing plate desensitization treatment liquid which is mainly composed of phytic acid and an amino compound and has a sufficient desensitization effect. This is an attempt to solve the problem of adhesion to the parts.

[Means to solve the problem]

The lithographic printing plate desensitization treatment composition of the present invention has a
0% by weight of at least one selected from phytic acid and its functional derivatives, 0.1-10% by weight of at least one amino compound, and 0.1-10% by weight of the following general formula ( (2): M, X (I) [However, M represents an alkali metal atom, X represents a monovalent or divalent anionic atom or atomic group, and n represents an integer of 1 or 2. ] At least one selected from the alkali metal compounds of
It is characterized by consisting of an aqueous solution containing.

Although the phytic acid used in the desensitizing treatment liquid has the disadvantage of causing cylinder adhesion, we focused on the property that it does not contain cyanide compounds and is non-polluting, and we aimed to prevent cylinder adhesion. He studied law extensively. As a result, phytic acid itself is sticky, so when the processing liquid on the back side of the master printing plate dries to form a film, its sticky action increases and the cylinder It was found that the surface and the back of the master printing plate adhered. It has also been found that as the content of phytic acid in the desensitizing solution increases, its adhesive effect increases. Therefore, in the desensitizing treatment liquid of the present invention, the compound of general formula (I) is added to reduce the adhesive action of phytic acid and prevent the master printing plate from adhering to the cylinder.

In addition, when the desensitization treatment liquid of the present invention is used, the master printing plate does not cause cylinder adhesion, has a high desensitization effect, and quickly forms a strong hydrophilic coating on the non-image areas of the printing plate surface. can be formed. Furthermore, the desensitizing composition of the present invention does not reduce its desensitizing ability even when exposed to heat or light, and provides a desensitizing solution for planographic printing plates that is harmless to the human body. be.

In the desensitizing solution of the present invention, phytic acid or a functional derivative of phytic acid is used as the main component.

Functional derivatives of phytic acid include monovalent or monovalent metal water-soluble salts of phytic acid, such as sodium phytate, potassium phytate, and calcium phytate;
You can choose from. The content of phytic acid or a functional derivative of phytic acid in the desensitizing solution is 0 when the total amount of the desensitizing solution is 100 parts by weight.
．． The amount is 4 to 20 parts by weight, preferably 1 to 10 parts by weight. If the content of the phytic acid component is less than 0.4% by weight, the desensitizing effect of the resulting composition will be unsatisfactory, and if it is more than 20% by weight, the hydrophilicity of the printing plate obtained will be This results in an inconvenience in that the printing quality becomes excessively high and the printing durability becomes insufficient.

In the desensitizing solution of the present invention, the amino compounds effective in desensitizing include monoamines such as propylamine and diethylamine, ethylenediamine, propylenediamine, trimethylenediamine, tetrame, ethylenediamine, and p-phenylenediamine. It is selected from polyamines such as diamine, diethylenetriamine, and tetraethylenepentamine, and alcoholamines such as monoethanolamine. In addition, the content of amino compounds is
When the total amount of desensitization treatment liquid is 100 parts by weight, 0,
The amount is 1 to 10 parts by weight, preferably 0.5 to 4 parts by weight. If the content of the amino compound is less than 0.1% by weight, there will be an inconvenience that scumming will occur on the printed matter, and if it is more than 10% by weight, there will be no particular improvement in the effect, and the resulting printing plate will deteriorate. This results in the inconvenience of reduced printing durability.

In the desensitizing treatment liquid of the present invention, the compound of general formula (I) that is effective in preventing cylinder adhesion of the master printing plate is M, X (I) [where M represents an alkali metal atom and X is It represents a monovalent or divalent anionic atom or atomic group, and n represents an integer of 1 or 2. ] It is a compound. In general formula (I), the alkali metal atom represented by M is preferably a sodium or potassium atom. The anionic atom or atomic group represented by X is preferably a halogen ion, sulfate ion, acetate ion, phosphate-hydrogen ion, or dihydrogen phosphate ion.

Further, the content of the compound of general formula (I) in the desensitizing treatment liquid is as follows, when the total amount of the desensitizing treatment liquid is 100 parts by weight.
The amount is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. The content of this metal compound is 0.1% by weight
When the content is less than 10% by weight, the anti-adhesion promoting effect of the resulting composition becomes unsatisfactory, and when the content is more than 10% by weight, there is a disadvantage that scumming tends to occur on printed matter.

The desensitizing treatment composition of the present invention contains a phytic acid component, an amino compound component, and a compound component of the general formula (I) as essential components, but in addition to these,
In order to improve the desensitizing effect, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, etc. are used as additives. Solvents, polyacrylic acid, modified polyacrylic acid, polyacrylic acid copolymers and their metal salts, wood-loving polymers such as polyethylene glycol, organic acids such as citric acid, tartaric acid, malonic acid, malic acid, adipic acid, etc. use be able to. In addition, sodium dehydroacetate, salicylic acid, etc. may be added as preservatives, and surfactants and the like may be added as wetting agents to the composition of the present invention.

[For production]

By adding the alkali metal compound of the general formula (I) to the desensitizing treatment solution containing a phytic acid component and an amino compound component of the present invention, a lithographic printing plate, particularly a lithographic printing plate having a zinc oxide-containing photosensitivity, can be used. It has become possible to sufficiently achieve the desensitizing effect of the plate and to reduce the tackiness of the desensitizing liquid, thereby preventing the printing plate from adhering to the 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" right and "%" in the examples are as follows, unless otherwise specified.
Represents parts by weight and % by weight.

Example 1 The following ingredients were composed as follows: Phytic acid 50 parts Ethylene diamine 10 parts Polyethylene glycol
20 parts (molecular weight 200) Sodium polyacrylate 10 parts Ethylene glycol monobutyl ether 16 parts Na1l! 50 parts water
The pH of the liquid composition obtained by mixing 844 parts was adjusted to pH 3.7 with a 20% NaOH aqueous solution to produce a desensitizing treatment liquid.

Next, an image is formed on a commercially available electrophotographic material containing a zinc oxide/resin dispersion system using an electrophotographic engraving machine, and the surface of the photosensitive layer is coated with the desensitizing solution described above using an automatic etching device (Ricoh Etching Processor). An offset printing plate was created by performing an etching process. As dampening water,
A 20-fold dilution of the above desensitizing solution was used. Offset printing was performed using this printing plate. The results are shown in Table 1.

As shown in Table 1, when the desensitizing treatment liquid of this example was used, clear prints with no stains were obtained after printing 5,000 sheets, and after printing an additional 5,000 sheets. It was also confirmed that there was no adhesion to the cylinder of the master printing plate.

Examples 2 and 3 In each of Examples 2 and 3, desensitizing treatment solutions were prepared in the same manner as in Example 1, except that the amounts of NaCR added were 20 parts and 5 parts, respectively. As shown in Table 1, good printing test results similar to those of Example 1 were obtained.

Example 4 The following ingredients were composed as follows: Phytic acid 75 parts Tetramethylenediamine 15 parts Glycerin
15 parts ethylene glycol monobutyl ether 1
0 parts NaC, 150 parts, and 835 parts water were mixed, and the pH of the resulting composition was adjusted to 3.6 to prepare a desensitizing treatment liquid. As shown in Table 1,
Similar to Example 1, good printing test results were obtained.

Example 5 The following ingredients were made into the following composition: Phytic acid 40 parts Ethylenediamine 20 parts Polyethylene glycol
80'l (molecular weight 600) Anionic modified sodium polyacrylate 20 parts Ethylene glycol monomethyl ether 30 parts KCl 40 parts Water
770 parts were mixed, the pH of the resulting composition was adjusted to 3.9, and a desensitizing treatment liquid was prepared. As shown in Table 1, Example 1
Similar good printing test results were obtained.

Example 6 The following components were composed as follows: Phytic acid 70 parts Citraconic acid 10 parts p-) Sodium luenesulfonate 20 parts Diethylenetriamine 20 parts
50 parts of ethylene glycol monomethyl ether, 50 parts of NaCR, and 780 parts of water, and the pH of the resulting composition was adjusted to 4.0 to prepare a desensitizing treatment solution. As shown in Table 1, good printing test results similar to those of Example 1 were obtained.

Comparative Example 1 The following components were composed as follows: Phytic acid 50 parts Ethylenediamine 10 parts Polyethylene glycol
201 (molecular weight 200) 10 parts of sodium polyacrylate 16 parts of ethylene glycol monobutyl ether 894 parts of water were mixed, and the pH of the obtained liquid composition was adjusted to 3.7 with a 20% NaOH aqueous solution, and comparative desensitization treatment was performed. A liquid was prepared.

An image was formed on an electrophotographic light-sensitive material containing a zinc oxide/resin dispersion system using an electrophotographic engraving machine, and the comparative printing plate obtained was subjected to an etching process using a comparative desensitizing treatment liquid using a Ricoh etching processor to obtain a comparative offset. A printed version was created. Offset printing was carried out using a 20-fold dilution of the comparative desensitizing treatment liquid as the dampening solution.

The results were as shown in Table 1. That is, after printing 5,000 sheets, clear prints without stains were obtained, but as shown in Table 1, 5.0
After printing 00 sheets, the printing plate started to stick to the cylinder.

Comparative Example 2 The following components were composed as follows: Phytic acid 75 parts Tetramethylenediamine 15 parts Glycerin
15 parts ethylene glycol monobutyl ether 10 parts
885 parts of water were mixed, and the pH of the resulting composition was adjusted to 3.8 to obtain a comparative desensitization treatment solution. As shown in Table 1, the results of the printing test showed that the printing plate adhered to the cylinder.

Comparative Example 3 The following components were composed as follows: Phytic acid 40 parts Ethylenediamine 20 parts Polyethylene glycol
81 (molecular weight 600) 20 parts of anionic modified sodium polyacrylate, 30 parts of ethylene glycol monomethyl ether, and 810 parts of water were mixed, and the pH of the resulting composition was adjusted to 3.8 to prepare a comparative desensitization treatment solution. did. As a result of the printing test, as shown in Table 1, adhesion of the printing plate to the cylinder was observed.

Comparative Example 4 The following components were composed as follows: phytic acid 70 parts citraconic acid 10 parts p-toluenesulfonic acid sorter 20 g'B ethylenediamine 20
50 parts of ethylene glycol monomethyl ether and 830 parts of water were mixed, and the pH of the resulting composition was adjusted to 3.8 to prepare a comparative desensitization treatment solution.

As a result of the printing test, as shown in Table 1, adhesion of the printing plate to the cylinder was observed.

Table 1 [Effects of the Invention] Desensitization treatment composition of the present invention 1. :More, faster, safer,
In addition, it has become possible to effectively desensitize a lithographic printing plate and to prevent the printing plate from adhering to the cylinder.

Claims (1)

[Scope of Claims] 1. 0.4 to 20% by weight of at least one selected from phytic acid and its functional derivatives;
% by weight of at least one amino compound and from 0.1 to
10% by weight of the following general formula: M_nX(I) [In the above formula, M represents an alkali metal atom, X represents a monovalent or divalent anionic atom or atomic group, and n is an integer of 1 or 2. At least one selected from the alkali metal compounds representing
A lithographic printing plate desensitization treatment composition comprising an aqueous solution containing.