JPH08108663A - Protecting agent for lithographic printing plate - Google Patents

Abstract

PURPOSE: To obtain a plate surface-protecting agent that has sufficient desensitizing properties, prevents missing of printing of a desensitized plate, prevents deterioration of a plate wear, and can be easily applied on/removed from a plate. CONSTITUTION: This protecting agent contains a compound represented by a general formula [I] or a general formula [II], a water-soluble polymer compound, and a nonionic surface active agent or an organic solvent having a boiling point of 130 deg.C or higher (in the formulas, R<1> -R<10> represent a hydrogen atom, an alkyl group, a ring alkyl group, a hydroxyalkyl group, a benzylalkyl group, and a phenyl group; Z1 -Z3 represents N<+> , P<+> , or B<-> ; X<1> -X<3> represent each an anion when Z1 -Z3 are N<+> or P<+> and cation when Z1 -Z3 are B<+> , and (n) represents an integer of 1-5, but none of R<1> -R<4> , R<5> -R<7> , and R<8> -R<10> are two or more hydrogen atoms.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plate surface protective agent for a lithographic printing plate.

[0002]

2. Description of the Related Art When making a lithographic printing plate, a plate surface protective agent, a so-called gum solution, is applied in the final step. The purpose of applying the plate surface protective agent is not only to protect the hydrophilicity of the non-image area, but also to correct the image area by adding or erasing the image area, storing the image after platemaking for a period of time before printing or for reuse, and for printing machines. This is a so-called desensitizing treatment such as prevention of stains caused by adhesion of fingerprints, oils and fats, dusts, etc. during mounting and handling and protection from scratches, and further suppression of generation of oxidative stains. Conventionally, gum arabic, cellulose gum or an aqueous solution of a water-soluble polymer having a carboxyl group in the molecule has been generally used as a plate surface protective agent for a lithographic printing plate. However, these plate protectors are
Although it has desensitizing power, it has the following problems. That is, in the final finishing step of a normal printing plate, a plate surface protective agent is poured on the plate and spread over the entire plate surface with a sponge, a cotton tampon, or the like, and further rubbed with a wiping cloth until the plate surface is dry. The water-soluble polymer substance is partially applied thickly to the ink receiving area). The image portion of the thickly coated portion has poor ink receptivity in the printing process and requires a considerable number of printed sheets before a printed matter having a desired ink density is obtained. This development is generally referred to as print omission (so-called defective ink deposition). In particular, printing defects are likely to occur when the plate coated with the plate surface protective agent is stored for a long period of time because the oil sensitivity of the image area is lowered. When the above-mentioned development occurs, in order to reproduce the missing image part, in order to protect the oil sensitivity of the image part, the image part is coated with oil or fat before gumming, or
Alternatively, it is necessary to wash the plate with water or a weakly acidic solution to remove the hydrophilic colloid adsorbed on the image area.

However, the above steps are not preferable because they are complicated, workability is deteriorated, and waste liquid is contaminated and health problems occur. On the other hand, it has been attempted to prevent printing loss by using the following water-soluble organic polymer compound as a plate surface protective agent instead of gum arabic which has the above problems. For example, JP-A-52-56603 and JP-A-54-97102.
No. 2, West German Patent No. 2,504,594, Soviet Patent No. 62
No. 3,755, dextrin, pullulan and pullulan derivatives, carboxy-containing polyacrylamide derivatives, methyl (meth) acrylate graft polyacrylamide copolymers, and starch-modified compounds such as carboxymethylated modified starch and cyclodextrin are used as plate surface protective agents. Is proposed to be used as. However, none of these have sufficient desensitizing power in the non-image area.

In order to prevent deterioration of ink receptivity in the image area, a method of imparting oil sensitivity to the image area is described.
Several methods have been proposed. Typical examples are water-insoluble and highly oil-sensitive castor oil, oleic acid, petroleum fractions, emulsification type solvents emulsifying plasticizers, etc. or plate surface protective agents containing surfactants (especially nonionic surfactants). is there. Many of these compounds are high-boiling compounds. However, the plate surface protective agent containing a nonionic surfactant or a solvent is excellent in preventing deterioration of the oil sensitivity, but the nonionic surfactant or solvent dissolves or swells the surface of the image area, or It permeates and adversely affects the adhesion of the image area to the support, which causes deterioration of printing durability.

As described above, the plate surface protective agent for a lithographic printing plate is required to have a contradictory effect of giving good hydrophilicity in the non-image area and preventing deterioration of the oil sensitivity in the image area. It is required not to deteriorate the printing durability of the image area.

[0006]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to sufficiently desensitize the non-image areas of a lithographic printing plate, and to prevent printing defects even when the desensitized plate is stored for a long period of time. An object is to provide a plate surface protective agent that does not cause deterioration in printing durability. Yet another object of the present invention is a sponge, cotton tampon,
To provide a plate surface protective agent which can be easily applied on a plate even by using an automatic gum coater or the like, and which can be easily removed from a lithographic printing plate by washing with water or contact with a humidifying roller of a printing machine. Is.

[0007]

The present inventors have completed the present invention as a result of earnest research to achieve the above object. That is, the present invention includes a compound represented by the following general formula [I] or general formula [II], a water-soluble polymer compound having a film-forming property and a nonionic surfactant or a boiling point of 13
It can be achieved by a plate surface protective agent for a lithographic printing plate, which is an aqueous solution containing an organic solvent at 0 ° C. or higher.

[0008]

Embedded image

In the formula, R ^{1 to} R ¹⁰ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxyalkyl group, a benzylalkyl group, a substituted or unsubstituted phenyl group, Z _{1 to} Z ₃ are N ⁺ , P ⁺
Or B ⁻ and Z _{1 to} Z ₃ are N ⁺ or P ⁺ , X ¹
To X ³ represent anions, and when Z _{1 to} Z ₃ are B ⁻ , X ¹
To X ³ represents a cation, n represents an integer of 1-5. However, each of R ^{1 to} R ⁴ , R ^{5 to} R ^7, and R ^{8 to} R ¹⁰ does not have two or more hydrogen atoms.

According to the present invention, as described above, the compound represented by the general formula [I] or the general formula [II], a water-soluble polymer compound having a film-forming property, a nonionic surfactant or a boiling point of 130 ° C. or higher. By containing the above organic solvent, the hydrophilicity of the non-image area and the oil sensitivity of the image area as well as the printing durability can be improved. That is, when a nonionic surfactant or an organic solvent is contained as in the past, these components adversely affect the photosensitive layer (probably penetrating into the photosensitive layer) and the image area of the printing plate deteriorates. However, the printing durability is deteriorated, but the above general formulas [I] and [II]
By containing at least one compound represented by the formula (1), it is possible to prevent deterioration of the image area surprisingly.

Examples of the water-soluble polymer compound having a film-forming property of the present invention include gum arabic, fibrin derivatives (eg, carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose) and their modified products, polyvinyl alcohol. And derivatives thereof, polyvinylpyrrolidone, polyacrylamide and copolymers thereof, vinyl methyl ether / maleic anhydride copolymer, vinyl acetate / maleic anhydride copolymer styrene / maleic anhydride copolymer, water-soluble soybean polysaccharide, Examples thereof include starch derivatives (eg, dextrin, enzymatically-degraded dextrin, hydroxypropylated starch, enzymatically-degraded dextrin, carboxymethylated starch, and phosphorylated starch). The content of these water-soluble polymers is preferably 0.
5% to 50% by weight, more preferably 1.0 to 40% by weight
Is. Two or more kinds of these water-soluble polymers may be mixed and used.

The nonionic surfactants used in the present invention include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers and glycerin fatty acid. Partial esters, sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol monofatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid Esters, polyglycerin fatty acid partial esters, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial Ester, fatty acid diethanol amides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, molecular weight of polypropylene glycol 200 and 500
0, trimethylol propane, polyoxyethylene or polyoxypropylene adduct of glycerin or sorbitol, acetylene glycol type, and the like.

Of these, polyoxyethylene alkylphenyl ethers and polyoxyethylene / polyoxypropylene block polymers are preferably used. or,
Fluorine-based and silicon-based nonionic surfactants can be used as well. Two or more of these nonionic surfactants can be used in combination. The amount of the nonionic surfactant used is not particularly limited, but is preferably 0.01 to 20% by weight of the plate surface protective agent.

Further, if necessary, if mixed with an anionic surfactant, the inking property or coater coatability may be improved. Specific examples of anionic surfactants that can be used in the present invention include, for example, anionic surfactants such as fatty acid salts, abietic acid salts, hydroxyalkanesulfonic acid salts, alkanesulfonic acid salts, dialkylsulfosuccinic acid salts, Linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium, N-alkylsulfosuccinic acid monoamide disodium salts, petroleum sulfonates, sulfated castor oil, sulfated tallow oil, sulfate ester salts of fatty acid alkyl esters,
Alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, fatty acid monoglyceride sulfate ester salts, polyoxyethylene alkylphenyl ether sulfate ester salts, polyoxyethylene styryl phenyl ether sulfate ester salts, alkyl phosphate ester salts, polyoxyethylene alkyl ether Phosphate ester salts, polyoxyethylene alkylphenyl ether phosphate ester salts, partially saponified products of styrene-maleic anhydride copolymers, partially saponified products of olefin-maleic anhydride copolymers, naphthalene sulfonate formalin condensates Etc. Among these, dialkyl sulfosuccinates, alkyl sulfate ester salts and alkyl naphthalene sulfonates are particularly preferably used.

These nonionic surfactants and anionic surfactants are effective in making the coating uniform on the printing plate surface and preventing the deterioration of the oil sensitivity in the image area, and contribute to the improvement of the ink receptivity. To do.

The organic solvent having a boiling point of 130 ° C. or higher used in the present invention effectively contributes to the protection of the oil sensitivity of the image area, while it adheres to the fine grains of the aluminum plate in the non-image area. It works to remove the trace amount of the photosensitive film and increase the hydrophilicity of the non-image area. Specific examples of the organic solvent having a boiling point of 130 ° C. or higher used in the present invention include alcohols such as n-hexanol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, and 2-octanol. 2-ethylhexanol, 3,5,5-trimethylhexanol,
Nonanol, n-decanol, udecanol, n-dodecanol, trimethylnonyl alcohol, cyclohexanol, benzyl alcohol, tetrahydrofurfuryl alcohol and the like can be mentioned. Methyl as a ketone
Examples thereof include n-amyl ketone, methyl-n-hexyl ketone, ethyl-n-butyl ketone, di-n-propyl ketone, diacetone alcohol, aurone and cyclohexanone. Examples of the esters include acetic acid-n-amyl acetate, isoamyl acetate, methyl isoamyl acetate, methoxybutyl acetate, benzyl acetate, ethyl lactate, butyl lactate, lactate-n.
-Amyl, methyl benzoate, ethyl benzoate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate and the like. Polyhydric alcohols and their derivatives include ethylene glycol mome methyl ether acetate,
Ethylene glycol monoethyl ether acetate, ethylene glycol butyl ether, ethylene glycol dibutyl ether, ethylene glycol isoamyl ether, ethylene glycol monophenyl ether, ethylene glycol monophenyl ether acetate, ethylene glycol benzyl ether, ethylene glycol monohexyl ether, methoxy, methoxy ethanol, Diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethyl Glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol, propylene glycol, propylene glycol, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 1-butoxyethoxy propanol, dipropylene glycol, dipropylene glycol Examples thereof include monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol, monomethyl ether, tripropylene glycol monobutyl ether, octylene glycol, glycerin, glycerin monoacetate and glycerin triacetate.

Among these, 2-ethylhexanol,
Benzyl alcohol, tetrahydrofurfuryl alcohol, cyclohexanone, ethylene glycol monobutyl ether, ethylene glycol, monophenyl ether, propylene glycol monobutyl ether and the like are particularly preferably used. The preferred range of use is 0.1
˜15.0% by weight, more preferably 1 to 10% by weight. Further, the above compounds may be used as a mixture of two or more kinds.

The compound represented by the general formula [I] or [II] used in the present invention is as follows.

[0019]

Embedded image

R in the formula¹~ R^TenAre independent hydrogen
Child, alkyl having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms
Group (for example, methyl group, ethyl group, n-propyl group, n-
Butyl group), cyclic alkyl group (eg cyclohexyl)
Group, 3-methylcyclohexyl group), hydroxyalk
Group (eg hydroxymethyl group, hydroxyethyl group
Group), benzylalkyl group (eg benzyl group, isoprene group)
Ropylbenzyl group), substituted or unsubstituted phenyl group (eg
For example, 2-methoxyphenyl group, 3,5-dichlorophenyl
Group), Z₁~ Z₃Is N⁺, P⁺Or B^-Indicates that
Z₁~ Z₃Is N⁺Or P⁺In case of X¹~ X³Is an anion
For example, halogen ions, nitrate ions, sulfate ions
Ion, phosphate ion, hydroxide ion, PF₆ ^-Or BF_Four ^-Such
, And Z₁~ Z₃Is B^-In case of X¹~ X³Is
Thione, for example Li⁺, Na⁺, K ⁺Or NH_Four ⁺But
And n represents an integer of 1 to 5, preferably 1 to 3.
You. Where R¹~ R^Four, R^Five~ R⁷And R⁸~ R^TenThat
There can be no more than two hydrogen atoms in each.

Specific examples of the above compounds include tetraphenylphosphonium iodide, tetraphenylphosphonium bromide, tetraphenylphosphonium chloride, tetraphenylphosphonium sulfate, tetraphenylphosphonium nitrate, tetraphenylboron sodium, tetra-n-butylphosphonium iodide. , Tetra-n-butylphosphonium bromide, tetra-n-butylphosphonium chloride, tetra-n-butylphosphonium sulfate, tetra-n-butylphosphonium nitrate, tetrabutylammonium sulfate, tetrabutylammonium nitrate, ethyltriphenylphosphonium bromide, benzyltriphenyl Phosphonium chloride, tetrabutylphosphonium hydroxide, tetrabutylphosphonium chloride Acid salt, ethyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetratolylphosphonium bromide, triethylbenzylammonium chloride, triethylammonium bromide, triethylbenzylammonium iodide, octyldimethylbenzylammonium chloride, octyldimethylammonium Examples thereof include bromide, lauryl dimethyl ammonium chloride, lauryl dimethyl ammonium bromide, and 1,2-bis (diphenylphosphino) ethane bromide.

Among the above, tetrabutylphosphonium chloride, tetraphenylphosphonium bromide and the like are preferable. One or two of these compounds
It is also possible to use together more than one species. The preferred range of use is 0.01% to 10% by weight, preferably 0.1 to 8% by weight, and more preferably 1 to 5% by weight.

The plate surface protective agent of the present invention is generally advantageously used in the acidic region of pH 3 to 6. In order to adjust the pH to 3 to 6, mineral acid is generally added to the plate surface protective agent,
Adjust by adding an organic acid or an inorganic salt. The amount added is 0.01 to 2% by weight. For example, nitric acid as the mineral acid,
Examples thereof include sulfuric acid, phosphoric acid and metaphosphoric acid. Examples of the organic acid include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid, levulinic acid, phytic acid, and organic phosphonic acid. Examples of the inorganic salt include magnesium nitrate, monobasic sodium phosphate, dibasic sodium phosphate, nickel sulfate, sodium hexametaphosphate and sodium tripolyphosphate. You may use together at least 1 type, or 2 or more types, such as a mineral acid, an organic acid, or an inorganic salt.

In addition to the above components, a chelate compound may be added if necessary. Usually, the plate surface protective agent is commercially available as a concentrated solution, and is diluted with tap water, well water, etc. before use. The calcium ions and the like contained in the diluted tap water or well water adversely affect the printing, and may cause the printed matter to be easily stained. . Preferred chelate compounds include, for example, ethylenediaminetetraacetic acid, its potassium salt, its sodium salt; diethylenetriaminepentaacetic acid, its potassium salt, its sodium salt; triethylenetetraminehexaacetic acid, its potassium salt, its sodium salt, hydroxyethylethylenediaminetriacetic acid. Acetic acid, its potassium salt, its sodium salt; nitrilotriacetic acid, its sodium salt; 1-hydroxyethane-1,1-diphosphonic acid, its potassium salt, its sodium salt; aminotri (methylenephosphonic acid), its potassium salt, its Examples thereof include organic phosphonic acids such as sodium salts and phosphonoalkane tricarboxylic acids. Organic amine salts are also effective in place of the sodium and potassium salts of the above chelating agents. As these chelating agents, those which are stably present in the plate surface protective composition and which do not impair the printability are selected. An appropriate amount of addition is 0.001 to 1.0% by weight based on the plate surface protective agent at the time of use.

Further, an antiseptic agent, an antifoaming agent and the like can be added to the plate surface protective agent of the present invention. For example, as a preservative, phenol or its derivative, formalin, imidazole derivative, sodium dehydroacetate, 4-isothiazolin-3-one derivative, benzisothiazolin-3-one,
Benztriazole derivatives, amidising anidine derivatives, quaternary ammonium salts, pyridine, quinoline, guanidine and other derivatives, diazines, triazole derivatives,
Examples thereof include oxazole and oxazine derivatives. The preferable addition amount is an amount that exerts a stable effect on bacteria, molds, yeasts and the like, and although it varies depending on the types of bacteria, molds, yeasts, it is 0.01 for the plate surface protective agent at the time of use.
The range of 4 to 4% by weight is preferable, and it is preferable to use two or more kinds of preservatives together so as to be effective against various molds and sterilization. In addition, a silicone antifoaming agent is preferable as the antifoaming agent. Among them, any of emulsification dispersion type and solubilization can be used. The optimum range is 0.001 to 1.0% by weight based on the plate surface protective agent at the time of use.

The plate surface protective agent of the present invention may be emulsified and dispersed, and an organic solvent may be used as an oil phase thereof, or may be solubilized with the aid of a solubilizing agent. The plate surface protective agent of the present invention can be easily provided in a solution type, an emulsion type or the like according to the characteristics of the photosensitive lithographic printing plate, and exhibits excellent effects in protecting the image area oil sensitivity and the non-image area hydrophilicity. To do.

The plate surface protective agent of the present invention is a positive type lithographic printing plate,
It can be used for any of the negative type lithographic printing plates. Further, it is possible to apply evenly by using an automatic gum filling machine or the like. The treatment with the plate surface protective agent of the present invention can be carried out immediately after the development treatment step by anhydrous washing, or after the development treatment (including a washing step, running water circulation washing or a small amount of water washing) or containing a surfactant. Alternatively, the treatment can be performed after the treatment with the rinse solution. At the time of printing, it is possible to obtain a sufficiently satisfactory clear printed matter immediately after printing without producing a large number of defective printed matter as in the conventional case.

[0028]

The present invention will be described in more detail with reference to the following examples, but the invention is not limited thereto. Example 1 616.3 parts by weight of pure water and 100 parts of cream dextrin.
Parts by weight, hydroxypropylated enzyme-degraded dextrin 1
A solution in which 00 parts by weight was dissolved was mixed with 150 parts by weight of gum arabic having a concentration of 14 ° Be. (About 250 parts by weight of water-soluble high molecular weight) 12 parts by weight of polyoxyethylene nonylphenol ether (trade name: Ribonox NC-60 HLB11, manufactured by Lion Corporation) as a nonionic surfactant in the aqueous solution, and acetylene glycol oxyethylene adduct ( Trade name Surfynol 465 Nissin Chemical Industry Co., Ltd. 4 parts by weight, benzyl alcohol 8 as solvent
Parts by weight were mixed.

0.5 parts by weight of tetraphenylphosphonium bromide, 0.2 parts by weight of methyl benzoate,
An isothiazolin-3-one derivative (1.0 parts by weight), phosphoric acid (85%) (3.0 parts by weight) and magnesium sulfate (5.0 parts by weight) were added and dissolved to prepare a plate surface protective agent.

Example 2 A plate surface protective agent was prepared in the same manner as in Example 1 using the following components. Pure water 620.3 parts by weight Cream dextrin 200 parts by weight Gum arabic (14 ° Be) 150 parts by weight Ribonox NC60 (HLB11) 15 parts (Polyoxyethylene nonylphenol ether (manufactured by Lion Corporation) Lapizole B-80 5 parts (dialkyl) Sodium sulfosuccinate (Nippon Oil & Fats Co., Ltd.) Octylene glycol 5 parts Tetrabutylammonium bromide 0.5 part Methyl benzoate 0.2 parts 4-Isothiazolin-3-one derivative 1.0 parts Phosphoric acid (85%) 3 0.0 parts Sodium hexametaphosphate 5.0 parts These plate surface protective agents were diluted 1: 1 with water to prepare a working solution, while used as a lithographic printing plate (FPS Fuji Photo Film Co., Ltd. anodized multi-grain type positive Type PS plate) is imagewise exposed, and the PS automatic processor 900D After development with a positive developer having the following composition, a plate surface protective agent was applied to the plate surface, and another plate surface after development was treated with a burning surface-adjusting solution BC-3 manufactured by Fuji Photo Film Co., Ltd. Temperature 25
Burning was carried out at 0 ° C. for 2 minutes, and then the plate surface protective agent of the present invention was applied. For comparison, the same experiment was performed using the plate surface protective agents of Comparative Examples 1 and 2 in Table 1. (Developer): Sodium silicate (SiO ₂ / Na ₂ O molar ratio of 1.2) 2 g: sodium ethylenediamine tetraacetate 4H ₂ O 0.1 g: water 97.9g

Comparative Examples 1 and 2 A plate surface protective agent was prepared in the same manner as in Example 1 except that the conditions shown in Table 1 below were used.

[0032]

[Table 1]

The lithographic printing plates, on which the plate surface protective agents of Examples 1 and 2 and Comparative Examples 1 and 2 were applied and the plate making was completed, were printed using a Heidel SOR printer, and the performance evaluation method shown in Table 2 The performance was evaluated. The results are shown in Table 3.

[0034]

[Table 2]

[0035]

[Table 3]

Evaluation of Table 3: ◯ Good, Δ Slightly inferior, × Inferior As shown in Table 3, Examples 1 and 2 were superior to Comparative Examples 1 and 2 as a plate surface protective agent in any item. . The plate coated with the desensitizing solution after development had good other evaluation items, namely, ink receptivity, blanket stain, and scratch stain.

Example 3 Water-soluble soybean polysaccharide (Soya Five S manufactured by Fuji Oil Co., Ltd.)
-LN) 80 parts by weight and cream dextrin 170 parts by weight were dissolved in pure water 673.5 parts by weight. 0.3 parts by weight of triethylbenzylammonium fluoride, 5 parts by weight of ammonium phosphate, 3 parts by weight of phosphoric acid, 0.2 parts by weight of methyl benzoate, 4-isothiazoline-3-
1.0 part by weight of the on derivative was added and dissolved to prepare an aqueous phase.

10 parts by weight of DOP (dioctyl phthalate), 5.0 parts by weight of benzyl alcohol, 25 parts by weight of di (2-ethylhexyl) sulfosuccinate (rapizole B-80 NOF CORPORATION) as a surfactant, poly Oxyethylene nonylphenol ether (Emulgen # 9
03 Kao Co., Ltd., HLB = 7.8) 12 parts by weight and sorbitan monooleate (Nonion OP-80 NOF CORPORATION) 3 parts by weight were mixed and dissolved to prepare an oil phase. The water phase was added to 500 r. p. m. ~ 600r. p. m. After stirring, the oil phase was dropped little by little, and after completion of the dropping, the mixture was passed through a homogenizer to obtain an emulsion type plate surface protective agent.

On the other hand, for comparison, the plate surface protective agents of Comparative Examples 3 and 4 shown in Table 4 were prepared. A printing test was carried out in the same manner as in Example 1. Emulsion stability was measured after storage at room temperature (25 ° C, 72 hours) and after freeze-thawing (-15 ° C, 72 hours).
The appearance of (time-freezing) was observed. The results are shown in Table 5.

[0040]

[Table 4]

[0041]

[Table 5]

As shown in the above table, the plate surface protective agent of the present invention had extremely satisfactory performance as compared with the comparative example.
The plate coated with the desensitizing solution after development had good other evaluation items, namely, ink receptivity, blanket stain, and scratch stain.

[0043]

INDUSTRIAL APPLICABILITY According to the present invention, the non-image area of a lithographic printing plate is desensitized, and at the same time, even if the desensitized plate is stored for a long period of time, printing defects do not occur and printing plate deterioration does not occur. An agent can be provided. Further, the present invention provides a sponge,
A plate surface protective agent that can be easily applied to the plate using a cotton tampon, an automatic gum coater, etc. and that can be easily removed from the lithographic printing plate by washing with water or by contact with the humidifying roller of the printing machine. Can be provided.

Claims (1)

[Claims] 1. The following general formula [I] or general formula [I
I], a water-soluble polymer compound having a film-forming property and a nonionic surfactant or a boiling point of 130 ° C.
A plate surface protective agent for a lithographic printing plate, which is an aqueous solution containing the above organic solvent. Embedded image In the formula, R ^{1 to} R ¹⁰ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxyalkyl group, a benzylalkyl group, a substituted or unsubstituted phenyl group, and Z ₁ to Z ₃ is N ^+, P ⁺ or B ^- are shown, Z ₁ to Z ₃ If is N ⁺ or P ⁺ X ¹ to X ³ represents an anion, and the Z ₁ to Z ₃ B ^- when X ¹ to X ³ represents a cation, n represents an integer of 1-5. However, R ¹ ~
Each of R ⁴ , R ^{5 to} R ⁷ and R ^{8 to} R ¹⁰ does not have two or more hydrogen atoms.