JP2001147541A - Corrector for planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrector for a planographic printing plate which can quickly erase an image area and does not cause the printing stain of the erased area. SOLUTION: The corrector for a planographic printing plate contains an organic solvent and an alkali agent having a quaternary ammonium group and miscible with the organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate modifier (also referred to as an erasing liquid) capable of rapidly erasing an image area (a region for receiving printing ink), and more particularly to a positive photosensitive lithographic plate. The present invention relates to a lithographic printing plate modifier which is suitable for erasing an image portion of a lithographic printing plate obtained by imagewise exposing and developing a printing plate.

[0002]

2. Description of the Related Art As a correcting agent for erasing unnecessary image portions of a lithographic printing plate prepared from a photosensitive lithographic printing plate (also called a PS plate), a correcting agent containing a lactone having 3 to 6 carbon atoms is used. The agent is disclosed in JP-B-51-33442. In addition, Japanese Patent Publication No. 46-16047 discloses that
As a lithographic printing plate modifier, a modifier containing an acidic substance and an organic solvent that dissolves or swells the image area is disclosed.

[0003]

However, these correcting agents have a disadvantage that the erasing speed of the image area is low. For this reason, with the recent increase in printing durability and enhancement of the image area of the lithographic printing plate, there is a problem that it takes a long time to erase the image area, and a problem that print smear occurs on the erase area due to insufficient erasure of the image area. Had occurred.

[0004] US Pat. No. 4,351,895 discloses a modifying agent having improved erasing speed in an image area, which comprises a primary to tertiary amine (primary to tertiary amine) and an organic solvent. Is disclosed. This correcting agent has an improved erasing speed as compared with a correcting agent containing an acidic substance such as phosphoric acid. However, the problem of the erasing speed and the problem of the print stain on the erased portion cannot be said to be sufficient, and further improvement in the erasing speed has been desired.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a lithographic printing plate modifier which can quickly erase an image area and does not cause print stains on the erased area.

[0006]

The lithographic printing plate modifier of the present invention comprises an organic solvent and an alkali agent having a quaternary ammonium group miscible with the organic solvent. The alkaline agent having a quaternary ammonium group is preferably a compound represented by the following general formula (I). (Wherein, R ^{1 to} R ⁴ are each a hydrogen atom,
Represents an alkyl group having 1 to 10 carbon atoms, a benzylalkyl group, or a substituted or unsubstituted phenyl group. )

[0007]

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[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Quaternary ammonium group in the present invention is a (quaternary ammonium bases, such as also referred to quaternary ammonium groups), the general formula, -N ⁺ R ₃ X ^- (wherein, each R is an alkyl group, a hydrocarbon such as an aryl group X represents a group or a hydrogen atom;
Represents a halogen atom, OH, SO ₄ or the like).

[0009] alkali agent having a quaternary ammonium group in the present invention may be those which can be miscible in the organic solvent, examples of such an alkali agent, quaternary ammonium compounds ^{_{([R 4 N +] X}} -, Quaternary ammonium salts and quaternary ammonium compounds). Other examples of the alkaline agent having a quaternary ammonium group include a quaternary alkyl ammonium type resin having a quaternary alkyl ammonium group in the side chain, and a quaternary alkanol ammonium type resin having a quaternary alkanol ammonium group in the side chain. A quaternary ammonium type resin and the like can be mentioned. The term “mixing” in the present invention refers to a state of being dissolved, dispersed or solubilized in an organic solvent.

As the quaternary ammonium compound, for example, quaternary ammonium fluoride, quaternary ammonium chloride, quaternary ammonium bromide, quaternary ammonium iodide,
Examples include quaternary ammonium hydroxide and quaternary ammonium sulfate. Among them, strong alkaline hydroxide
Ammonium can be preferably used because it has an excellent effect of increasing the erasing speed of the lithographic printing plate modifier.

The quaternary ammonium compounds include, for example, ammonium, methyl ammonium, dimethyl ammonium, trimethyl ammonium, tetramethyl ammonium, ethyl ammonium, diethyl ammonium, triethyl ammonium, tetraethyl ammonium, tetra n-propyl ammonium, tetra n-butyl ammonium , Trimethylethyl ammonium, trimethyl vinyl ammonium, trimethyl stearyl ammonium, dimethyl cetyl ethyl ammonium, triethyl cetyl ammonium, dimethyl benzyl cetyl ammonium, trimethyl phenyl ammonium, triethyl phenyl ammonium, dimethyl ethyl benzyl ammonium, trimethyl benzyl ammonium, triethyl benzyl ammonium , Anilinium, fluorides such N- methylpyridinium chloride, bromide, iodide,
Hydroxide, sulfate and the like. Among these,
Since quaternary ammonium hydroxide represented by the following general formula (I) has an excellent effect of particularly increasing the erasing speed of the lithographic printing plate modifier, it can be suitably used as the alkali agent in the present invention. (In the formula, R ^{1 to} R ⁴ each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a benzylalkyl group, or a substituted or unsubstituted phenyl group.)

[0012]

Embedded image

These alkali agents having a quaternary ammonium group can be used alone or in combination of two or more. The content of the alkali agent having a quaternary ammonium group is preferably 0.1 to 20.0% by weight, more preferably 1 to 10% by weight, based on the lithographic printing plate modifier.

The organic solvent in the present invention is for dissolving or swelling the image area. Examples of such an organic solvent include alcohols, ketones, glycol ethers, lactones, cyclic imides, and the like. Esters, hydrocarbon solvents, and the like.

The alcohols include, for example, methanol, ethanol, n-butanol, n-hexanol,
Examples thereof include 2-ethylbutanol, n-heptanol, n-octanol, 2-ethylhexanol, nonanol, cyclohexanol, 2-methylhexanol, benzyl alcohol, and tetrahydrofurfuryl alcohol.

Examples of ketones include dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, diethyl ketone, methyl butyl ketone, methyl isobutyl ketone, ethyl butyl ketone, butyrone, methyl amyl ketone, methyl hexyl ketone, valerone, mesityl Oxide, diacetone alcohol, cyclohexanone, methylcyclohexanone, acetophenone, isophorone, acetylacetone, acetonylacetone and the like can be mentioned.

As glycol ethers, for example,
2-methoxyethanol (methyl cellosolve), 2-ethoxyethanol, 2-isopropoxyethanol, 2
Glycol monoalkyl ethers such as butoxyethanol; glycol monoaryl ethers such as 2-phenoxyethanol; diethylene glycol monomethyl ether, diethylene glycol monoethyl ether;
Diethylene glycol monoalkyl ethers such as diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoisobutyl ether; triethylene glycol monoalkyl ethers such as triethylene glycol monomethyl ether, triethylene glycol monoether, and triethylene glycol monobutyl ether; Ethylene diglycol dialkyl ethers such as ethylene glycol methyl ether; diethylene glycol dialkyl ethers such as diethylene glycol dimethyl ether (diglyme) and diethylene glycol diethyl ether;

Examples of the lactones include γ-butyrolactone, γ-valerolactone, γ-caprolactone,
γ-laurolactone, δ-valerolactone, hexanolactone and the like. As cyclic imides, for example, 2-pyrrolidone, N-methyl-2-pyrrolidone (N
-Methylpyrrolidone), N-ethyl-2-pyrrolidone (N-ethylpyrrolidone) and the like.

Examples of the esters include amyl acetate, isoamyl acetate, methyl isoamyl acetate,
Hexyl, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, benzyl acetate, butyl propionate, isoamyl propionate, butyl butyrate, isobutyl butyrate, isoamyl butyrate, butyl lactate, amyl lactate, isoamyl lactate Is mentioned. Examples of the hydrocarbon solvent include, for example, toluene, xylene, ethylbenzene, diethylbenzene,
Examples thereof include a petroleum fraction having a boiling point of about 120 ° C to 300 ° C, methylnaphthalene, and the like.

Other organic solvents include, for example, N,
N-dimethylformamide (DMF), acetamide,
Dimethyl sulfoxide, polyethylene glycol and polypropylene glycol having a molecular weight of 200 to 1000,
Monomethyl ether, monoethyl ether, monopropyl ether, isopropyl ether of those compounds,
Monobutyl ether and the like. These organic solvents can be used alone or in combination of two or more. The content of the organic solvent is usually 50 to 90% by weight, preferably 60 to 90% by weight based on the lithographic printing plate modifier.
It is in the range of 80% by weight.

The correction liquid for a lithographic printing plate of the present invention can contain water, a water-soluble polymer compound, a surfactant, a coloring agent, a viscosity modifier and the like, if necessary. Water promotes dissolution of the water-soluble polymer compound and enhances the activity of the alkaline agent. The content of water is usually in the range of 1 to 30% by weight, preferably 5 to 20% by weight, based on the lithographic printing plate modifier.

The water-soluble polymer imparts properties such as ease of spreading and prevention of bleeding to the lithographic printing plate modifier when the lithographic printing plate modifier is applied onto the lithographic printing plate using a brush. It is. Examples of the water-soluble polymer compound include modified cellulose such as methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose / Na salt; gum arabic;
High molecular compounds such as structan, polyvinylpyrrolidone, polyvinyl methyl ether, polyethylene glycol, polypropylene glycol, vinyl methyl ether-maleic anhydride copolymer, and vinyl acetate-maleic anhydride copolymer are exemplified. Among them, modified cellulose, polyvinylpyrrolidone, vinyl methyl ether maleic anhydride copolymer, structan and the like are preferably used. These water-soluble polymer compounds can be used alone or in combination of two or more. The content of the water-soluble polymer compound is usually 0.1 to 0.1 with respect to the lithographic printing plate modifier.
It is in the range of 1 to 10% by weight, preferably 1 to 5% by weight.

The surfactant promotes better penetration of the components contained in the lithographic printing plate modifier of the present invention into the image area of the lithographic printing plate. This is effective in that the contained components can be mixed well to form a stable solution. As surfactants, polyoxyethylene alkyl ethers,
Polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ether, polyoxyethylene polyoxypropylene alkyl ether,
Glycerin fatty acid partial ester, sorbitan fatty acid partial ester, pentaerythritol fatty acid partial ester, propylene glycol monofatty acid ester, sucrose fatty acid partial ester, oxyethylene oxypropylene block copolymer, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene Sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, polyoxyethylated castor oil, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N, N-bis-2-hydroxyalkyl Nonionic fields such as amines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, and trialkylamine oxides Active agent;

Fatty acid salts, avicenates, hydroxyalkanesulfonates, alkanesulfonates,
Dialkyl sulfosuccinates, linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl- N-oleyltaurine sodium, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonate, sulfated castor oil, sulfated cow leg oil, sulfate ester of fatty acid alkyl ester, alkyl sulfate ester salt, polyoxyethylene alkyl Ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene styryl phenylate Sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, partially saponified styrene-maleic anhydride copolymers, olefins-maleic anhydride Anionic surfactants such as partially saponified acid copolymers and naphthalene sulfonate formalin condensates;

Cationic surfactants such as alkylamine salts, polyoxyethylene alkylamine salts, and polyethylenepolyamine derivatives; amphoteric surfactants such as carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfates, and imidazolines. , Fluorine-based surfactants, silicon-based surfactants and the like. Among the surfactants mentioned above, the term "polyoxyethylene" can be read as a polyoxyalkylene such as polyoxymethylene, polyoxypropylene, or polyoxybutylene.

Of these, nonionic surfactants and anionic surfactants are preferable, and since the components contained in the lithographic printing plate modifier are well mixed, a surfactant having an HLB of 9 or more is preferably used. More preferred. Furthermore, polyoxyethylene alkyl phenyl ethers, oxyethylene oxypropylene block copolymer, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester, polyerythylene glycol fatty acid ester, polyglycerin fatty acid partial ester, It is particularly preferable to improve the effect of eliminating the image portion of the erasing liquid. Among these, the most preferred is an oxyethyleneoxypropylene block copolymer. These surfactants can be used alone or in combination of two or more. The content of the surfactant is usually 0.1 to 2 with respect to the lithographic printing plate modifier.
0% by weight, preferably in the range of 3 to 15% by weight.

The colorant can be contained when contrast is desired visually. Examples of the coloring agent include crystal violet, safranin, brilliant blue, malachite green, and acid rhodamine B.
And the like, inorganic pigments, organic pigments and the like. The content of the coloring agent is usually 0.1 to 0.1 with respect to the lithographic printing plate modifier.
001 to 0.1% by weight, preferably 0.005 to 0.0%
It is in the range of 5% by weight.

The viscosity modifier has better writability, for example, when the lithographic printing plate modifier is applied to the image portion of the lithographic printing plate using a brush, the modifier may drip off the brush. Such a property is imparted to the lithographic printing plate modifier so as not to cause any inconvenience. Examples of the viscosity modifier include fine silica powder, colloidal silica, zeolite, and the like. The content of the acidic substance is usually in the range of 0 to 10% by weight, preferably 3 to 6% by weight, based on the lithographic printing plate modifier.

The lithographic printing plate modifier of the present invention can be applied to lithographic printing plates prepared from positive-working and negative-working photosensitive lithographic printing plates, and in particular, a positive working plate having a positive photosensitive layer provided on a support. When erasing the image portion of a lithographic printing plate obtained by making a plate from a photosensitive lithographic printing plate, excellent erasability (erasing speed of the image portion, prevention of printing stain of the erasing portion) can be exhibited. Among such positive photosensitive lithographic printing plates, the present invention is particularly advantageous for a positive photosensitive lithographic printing plate having a support on which a photosensitive layer containing an o-quinonediazide compound as a photosensitive component is provided.

As the support, for example, aluminum,
Metal plate of zinc, copper, stainless steel, iron, etc .; plastic film of polyethylene terephthalate, polycarbonate, polyvinyl acetal, polyethylene, etc .; paper on which synthetic resin is melt-coated or synthetic resin solution coated, vacuum-depositing and laminating metal layer on plastic film And other materials used as a support for a printing plate. Among these supports, aluminum is particularly preferably used because it has excellent dimensional stability and is inexpensive.

In the case of a support having a metal surface, particularly an aluminum surface, it is preferable that a surface treatment such as graining treatment, anodic oxidation treatment, and hydrophilic treatment is performed.
In the hydrophilization treatment, a support made of grained aluminum and anodized aluminum is treated with sodium silicate, potassium fluoride zirconate, phosphate, alkali salt of condensed aryl sulfonic acid, amino acid or salts thereof, and hydroxyl group. It is carried out by treating with an amine or a salt thereof.

The o-quinonediazide compound is preferably an o-naphthoquinonediazide compound. Examples of the o-naphthoquinonediazide compound include, for example, U.S. Pat. No. 3,046,110 and U.S. Pat.
No. 1, U.S. Pat. No. 3,046,121, U.S. Pat. No. 3,046,115, U.S. Pat. No. 3,046,118
No. 3,046,119; U.S. Pat.
046,120, U.S. Patent No. 3,046,122,
U.S. Pat. No. 3,046,123, U.S. Pat.
No. 1,430, U.S. Pat. No. 3,102,809, U.S. Pat. No. 3,106,465, U.S. Pat.
No. 707 and U.S. Pat. No. 3,647,443.

Among the o-naphthoquinonediazide compounds, o-naphthoquinonediazidesulfonic acid ester or o-naphthoquinonediazidecarboxylic acid ester of an aromatic hydroxy compound and o-naphthoquinonediazidecarboxylic acid ester of an aromatic amino compound
Naphthoquinonediazidosulfonamide or o-naphthoquinonediazidocarboxylic acid amide is preferred, particularly,
1,2-described in JP-A-56-1044
An ester of diazobenzoquinonesulfonic acid chloride and polyhydroxyphenyl or an ester of 1,2-diazonaphthoquinonesulfonic acid chloride and a resorcinol-benzoaldehyde resin is preferred.

For the purpose of forming a photosensitive layer containing these photosensitive components and for improving the physical properties of the photosensitive layer, it is preferable to mix a resin or the like into the carrier of the photosensitive layer. As the resin, for example, an alkali-soluble resin such as a phenol formaldehyde resin, a cresol formaldehyde resin, a p-tert-butylphenol resin, and a phenol-modified xylene resin is preferably used. Further, additives such as a dye, a plasticizer, and a component for giving printout performance can be further added to the photosensitive layer. The photosensitive layer having such a composition is coated on a support using an appropriate solvent solution. The coating amount of the photosensitive layer is 0.1 to 7 g / m ² , preferably 0.5 to 3 g / m ² .

Next, the method of using the lithographic printing plate modifier of the present invention will be described. First, a photosensitive lithographic printing plate is exposed through a film original drawing and then developed with an alkaline aqueous solution to obtain a lithographic printing plate having an image area formed thereon. If the lithographic printing plate after the development processing has an unnecessary image portion, the lithographic printing plate modifier of the present invention is applied on the image portion, and the image portion is erased.

When the lithographic printing plate modifier of the present invention is applied to an image area of the lithographic printing plate, it is preferable that the lithographic printing plate be washed with water after development, and then squeezed with the washing water before coating. As a specific method of erasing the image portion of the lithographic printing plate, a correction agent for lithographic printing plate is included in a brush, and the brush is applied to the image portion and left for 10 seconds to several minutes. After rubbing, a general method is to wash off the erase float by washing with water. The lithographic printing plate from which the image of the unnecessary portion has been erased in this way is subjected to normal gumming and other processing steps, and then subjected to printing.

Such a lithographic printing plate modifier contains an alkaline agent having a quaternary ammonium group which is more alkaline than the primary to tertiary amines. Faster erasure than amine-containing modifiers. Further, the image portion is completely erased, and no print stain is generated in the erased portion during printing. Also, the fourth
An alkaline agent having an ammonium group is more easily miscible with an organic solvent than an alkali metal hydroxide, so that when contained in a lithographic printing plate modifier, the activity as an alkaline substance is maximized and erased. The effect of sex can be fully exhibited.

[0038]

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by these examples. In addition,% in an Example shows a weight% unless there is particular notice.

The evaluation method in this embodiment is as follows. (Evaluation planographic printing plate) Positive photosensitive planographic printing plate (Product name: RP, Kodak Polychrome Graphics Co., Ltd.)
Manufactured by Dainippon Screen Co., Ltd. using a 2 kW metal halide lamp and exposing for 60 seconds at 8 mW / cm ^2.
2. Use Kodak Polychrome Graphics Co., Ltd. developer PD-1 (developer: water = 1: 8) at 30 ° C.
A development process was performed for 2 seconds to obtain a lithographic printing plate for evaluation on which an image portion was formed.

(Erasing Speed) In the erasing operation of applying a lithographic printing plate modifying agent to the image area of the lithographic printing plate for evaluation, leaving it for a certain period of time, and then removing the modifying agent with water, the leaving time is 5 to 5 minutes.
The erasing operation was completed within 90 seconds at intervals of 5 seconds, and the number of seconds required to complete the erasing operation was measured. (Print Smear of Erased Area) After the lithographic printing plate from which the image area had been erased was gummed, it was visually determined whether or not any stain had occurred on the erased marks when mounted on an offset printing machine and printed 10,000 sheets. The criterion is: 印刷: no print stain occurs on the erased mark,
Δ: erasure trace stains generated when printing 5000 to 10,000 sheets
×: Occurrence of stains on erased marks during printing of 0 to less than 5000 sheets.

Example 1 First, 2 parts by weight of HPC-L (hydroxypropylcellulose, manufactured by Nippon Soda Co., Ltd.), 71 parts by weight of N-methylpyrrolidone, and Pluronic P-
85 (oxyethylene oxypropylene block copolymer, manufactured by Asahi Denka Co., Ltd.) was dispersed in 5 parts by weight, and 20 parts by weight of water was added to the dispersion to dissolve HPC-L and Pluronic P-85. Then, 2 parts by weight of tetramethylammonium hydroxide was added, and sufficiently stirred to obtain a lithographic printing plate modifier. The lithographic printing plate modifier was a homogeneous solution without insolubles. Using this lithographic printing plate modifier, the erasing speed and the printing stain on the erased portion were evaluated. Table 2 shows the results.

Example 2 First, 35 parts by weight of N-methylpyrrolidone, 20 parts by weight of methyl cellosolve, DMF16
2 parts by weight of HPC-L (hydroxypropylcellulose, manufactured by Nippon Soda Co., Ltd.) and 5 parts by weight of Pluronic P-85 (oxyethyleneoxypropylene block copolymer, manufactured by Asahi Denka Co., Ltd.) Was dispersed, and 20 parts by weight of water was added to the dispersion to dissolve HPC-L and Pluronic P-85. Then, 2 parts by weight of tetramethylammonium hydroxide was added, and sufficiently stirred to obtain a lithographic printing plate modifier. The lithographic printing plate modifier was a homogeneous solution without insolubles. Using this lithographic printing plate modifier, the erasing speed and the printing stain on the erased portion were evaluated. Table 2 shows the results.

Example 3 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 1 except that tetramethylammonium hydroxide was changed to tetraethylammonium hydroxide. Table 2 shows the results.

Example 4 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 2 except that tetramethylammonium hydroxide was changed to tetraethylammonium hydroxide. Table 2 shows the results.

Example 5 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 1 except that tetramethylammonium hydroxide was changed to tetra-n-butylammonium hydroxide. Table 2 shows the results.

Example 6 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 2 except that tetramethylammonium hydroxide was changed to tetra-n-butylammonium hydroxide. Table 2 shows the results.

Example 7 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 1 except that tetramethylammonium hydroxide was changed to trimethylbenzylammonium hydroxide. Table 2 shows the results.

Example 8 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 2 except that tetramethylammonium hydroxide was changed to trimethylbenzylammonium hydroxide. Table 2 shows the results.

Comparative Example 1 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 1 except that tetramethylammonium hydroxide was changed to monoethanolamine and the composition was changed as shown in Table 1. Was done. Table 2 shows the results.

Comparative Example 2 A lithographic printing plate modifier was prepared and evaluated in the same manner as in Example 2 except that tetramethylammonium hydroxide was changed to monoethanolamine and the composition was changed as shown in Table 1. Was done. Table 2 shows the results.

Comparative Example 3 A lithographic printing plate modifier was prepared in the same manner as in Example 1 except that tetramethylammonium hydroxide was changed to phosphoric acid (85%) and the composition was changed as shown in Table 1. And evaluated. Table 2 shows the results.

Comparative Example 4 A lithographic printing plate modifier was prepared in the same manner as in Example 2 except that tetramethylammonium hydroxide was changed to phosphoric acid (85%) and the composition was changed as shown in Table 1. And evaluated. Table 2 shows the results.

[0053]

[Table 1]

[0054]

[Table 2]

The lithographic printing plate modifiers of Examples 1 to 8 using an alkaline agent having a quaternary ammonium group have a higher erasing speed than that of the comparative example, and also cause the occurrence of printing stains in the erasing portion. There was no.

[0056]

As described above, since the lithographic printing plate modifier of the present invention contains an organic solvent and an alkali agent having a quaternary ammonium group miscible with the organic solvent, the image area is improved. Erasing can be performed quickly, and no print stains occur on the erasing portion. Further, when the alkaline agent having a quaternary ammonium group is a compound represented by the general formula (I), the erasing speed of the image area can be further improved.

Claims (2)

[Claims] 1. A lithographic printing plate modifier comprising: an organic solvent; and an alkaline agent having a quaternary ammonium group miscible with the organic solvent. 2. The lithographic printing plate modifier according to claim 1, wherein the alkaline agent having a quaternary ammonium group is a compound represented by the following general formula (I). Embedded image (Wherein, R ^{1 to} R ⁴ each represent a hydrogen atom,
0 represents an alkyl group, a benzylalkyl group, or a substituted or unsubstituted phenyl group. )