JPH08142533A - Plate surface protecting agent for planographic printing plate - Google Patents

Abstract

PURPOSE: To provide sufficient plate surface protecting capacity without damaging the sensitivity of an image part by adding a compd. having at least one amino group and at least one group selected from a carboxyl group, a sulfo group and a phosphono group or a salt thereof. CONSTITUTION: A compd. containing at least one amino group such as aminoacetic acid or lysine and at least one group selected from a carboxyl group, a sulfo group and a phosphono group or a salt thereof is added to a plate surface protecting agent in an amt. of 0.5-5wt.% per the total wit. of the plate surface protecting agent. The mol.wt. of the compd. is pref. 1000 or less. Sufficient plate surface protecting capacity can be obtained by the plate surface protecting agent for a planographic printing plate without damaging the sensitivity of an image part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate surface protective agent (usually called "gum solution") used for desensitizing a lithographic printing plate.

[0002]

2. Description of the Related Art Conventionally, when making a lithographic printing plate, a gumming step of applying a so-called gum solution, which is a plate surface protective agent, is performed in the final step. This is done to prevent stains from adhering to the plate surface after printing until it is applied to the printing machine after printing, and also to prevent scratches if it is stored in piles or hits foreign matter. It is what is done. The most important function is to prevent the deterioration of the desensitizing property of the non-image area due to an oxidation phenomenon or the like by exposing the plate surface directly to the air, and to bring about the effect of increasing the desensitizing property. From this point of view, gumming is indispensable in the plate making process.

As a gum solution, it has been about
Aqueous solutions of 15-30% by weight have been used. Also,
62-25119 discloses a metal salt of phytic acid, pH 3-6.
There is disclosed a processing solution for a lithographic printing plate containing a nitrogen-containing compound and an amino compound having a hydroxyl group capable of forming a 5-membered to 6-membered chelate compound having a stability constant smaller than that of phytic acid. The planographic printing plate treatment liquid and gum arabic are excellent as plate surface protective agents in terms of desensitizing action, film forming property, solubility and the like.

[0004]

On the other hand, however, the processing solutions for lithographic printing plates and gum arabic, which have a strong desensitizing effect, often reduce the oil sensitivity of the image area when used as a plate surface protective agent. In this case, a large number of defective printed materials are produced until a printed material having a satisfactory ink density is obtained in printing. In order to prevent this, the image area is often covered with oils and fats before gumming, but this is not preferable because it complicates the process, lowers workability, and causes contamination of waste liquid and health problems.

Therefore, an object of the present invention is to provide a plate surface protective agent having a sufficient plate surface protection ability without impairing the oil sensitivity of the image area.

[0006]

The constitutions of the present invention for achieving the above object are the following (1) to (4).

(1) A plate surface protective agent for a lithographic printing plate containing a compound having at least one amino group and at least one group selected from a carboxyl group, a sulfo group and a phosphono group, or a salt thereof. .

(2) The plate surface protective agent for a lithographic printing plate as described in (1) above, wherein the compound has a molecular weight of 1,000 or less.

(3) A plate surface protective agent for a lithographic printing plate containing an alkane having at least one amino group or a salt thereof.

(4) The plate surface protective agent for a lithographic printing plate as described in (3) above, wherein the alkane having at least one amino group or a salt thereof has a molecular weight of 1,000 or less.

The present invention will be described in detail below.

At least one amino group used in the plate surface protective agent of the invention according to claim 1 or 2 (hereinafter referred to as "plate surface protective agent A") and at least one selected from a carboxyl group, a sulfo group and a phosphono group. Examples of the compound having a group or a salt thereof include amino acids such as aminoacetic acid, lysine, threonine, serine, aspartic acid, parahydroxyphenylglycine, dihydroxyethylglycine, anthranilic acid, tryptophan, and arginine; sulfamic acid, cyclohexylsulfamic acid, and the like. Hydrochloric acid, oxalate, phosphate, formate, or 1-aminoethane-1,1-diphosphonic acid, 1-amino-1-phenylmethane-1,1-diphosphonic acid of aliphatic aminosulfonic acids or these compounds, 1-
Dimethylaminoethane-1,1-diphosphonic acid, 1-dimethylaminobutane-1,1-diphosphonic acid, 1-dimethylaminomethane-1,1-diphosphonic acid, 1-propylaminoethane-1,1-
Diphosphonic acid, 1-butylaminomethane-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminopentamethylenephosphonic acid, ethylenediaminotetramethylenephosphonic acid, diethylenetriaminopentamethylenephosphonic acid, aminotri (2-propylene-2 -Phosphonic acid) and their alkali metal salts (sodium, potassium, ammonium salts, lower alkanolamine salts, etc.). The above compound is preferably 0.05 to 10% by weight, more preferably 0.5 to 5% by weight based on the total weight of the plate surface protective agent.
Used in the range of weight percent.

The alkane having at least one amino group or a salt thereof used in the plate surface protective agent of the invention according to claim 3 or 4 (hereinafter referred to as "plate surface protective agent B") is
1-aminopropane, 2-aminopropane, 1-aminobutane, 2-aminobutane, 1-aminopentane, 2-aminopentane, 1-aminohexane, 1-aminoheptane, 1-aminooctane, 1-amino-2-methyl Propane, 2-amino-2-
Methylpropane, 2-amino-2-methylbutane, 1-amino-
3-methylbutane, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,2-diaminopropane, 1,
2-diamino-2-methylpropane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,
2-diaminocyclohexane, 1,8-diaminooctane, 1,
9-diaminononane or their hydrochlorides, phosphates, phosphites, sulfates, nitrates and the like. The above compound is used in an amount of preferably 0.05 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total weight of the plate surface protective agent.

A compound having at least one amino group and at least one group selected from a carboxyl group, a sulfo group and a phosphono group or a salt thereof, and an alkane having at least one amino group or a salt thereof have a molecular weight of 1000. The following are suitable:

The plate surface protective agents A and B (hereinafter referred to as the "plate surface protective agent of the present invention") may contain various water-soluble polymer compounds in addition to the above components for the purpose of improving the film forming property. . As such a high molecular compound, any compound that can be used as a conventional plate surface protective agent can be preferably used. For example, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, starch derivatives such as pregelatinized starch, dextrin, dialdehyde starch, alginate, roast bean gum, structan, stellabic, pullulan, etc. Examples thereof include molecular compounds, polyvinyl alcohol, polyacrylamide, synthetic polymer compounds such as a copolymer of vinyl methyl ether and maleic anhydride, gum arabic and the like. These water-soluble polymer compounds are 1 to the total weight of the plate surface protective agent of the present invention.
Used in the range of 40% by weight.

The preferred pH of the plate surface protective agent of the present invention is 1 to
7, more preferably 2 to 5, and may contain an acid or a buffer for pH adjustment. Such acids and buffers include acetic acid, oxalic acid, tartaric acid, benzoic acid, molybdic acid, boric acid, nitric acid, sulfuric acid, phosphoric acid, and polyphosphoric acid, and their water-soluble alkali metal salts and ammonium salts,
For example, ammonium acetate, sodium acetate, potassium acetate, sodium molybdate, sodium borate, lithium nitrate, monobasic sodium phosphate, dibasic sodium phosphate,
Examples thereof include sodium polyphosphate. 2 for acid and buffer
You may use together 1 or more types.

By adding a surfactant to the plate surface protective agent of the present invention, the surface condition of the coating film is improved. Surfactants that can be used include anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. Examples of the anionic surfactant include aliphatic alcohol sulfate ester salts, aliphatic alcohol phosphate ester salts, dibasic aliphatic ester sulfonates, aliphatic amide sulfonates, alkylaryl sulfonates, formaldehyde-condensed naphthalene sulfonate. Salts and the like are used. As the cationic surfactant, alkylamine salts, quaternary ammonium salts and the like are used. As the amphoteric surfactant, alkyl carboxy betaines, alkyl imidazolines and the like are used. As the nonionic surfactant, polyethylene glycol alkyl ether, polyethylene glycol alkyl ester, sorbitan alkyl ester, polyoxypropylene polyoxyethylene ether, etc. are used. Two or more of these surfactants can be used in combination. The amount used is not particularly limited, but the preferred range is 0.01 to 10% by weight of the plate surface protective agent.

In the plate surface protective agent of the present invention, a lower polyhydric alcohol such as glycerin, ethylene glycol or triethylene glycol may be used as a lubricant, if necessary, in addition to the above components. The content of these lubricants in the composition is preferably 0.1 to 5.0% by weight, more preferably 0.5 to 3.0% by weight. In addition to the above, the plate surface protective agent of the present invention,
Preservatives, bactericides and the like can be added. For example, benzoic acid and its derivatives, phenol, formalin, sodium dehydroacetate, isothiazolone compounds, etc.
It can be added in the range of 005 to 2.0% by weight.

The plate surface protective agent of the present invention can be used for various lithographic printing plates. In particular, a photosensitive lithographic printing plate having an aluminum plate as a support and a photosensitive layer thereon (previously It is suitable for the planographic printing plate obtained by imagewise exposing and developing a printing plate having PS. The preferred PS plate is, for example, a photosensitive layer comprising a mixture of a diazo resin (a salt of a condensate of p-diazodiphenylamine and paraformaldehyde) as described in British Patent 1,350,521 and a shellac. Which is provided on the aluminum plate,
Aluminum as a photosensitive layer comprising a mixture of a diazo resin as described in British Patent Nos. 1,460,978 and 1,505,739 and a polymer having a hydroxyethyl methacrylate unit or a hydroxyethyl acrylate unit as a main repeating unit. A negative PS plate such as one provided on a plate, and a photosensitive layer composed of a mixture of an o-quinonediazide photosensitive material and a novolak type phenolic resin as described in JP-A-50-125806 are provided on an aluminum plate. The positive PS plate provided in 1. is included. Further US patent
A PS plate having a light-sensitive layer of a photocrosslinkable photopolymer as illustrated in US Pat. No. 3,860,426 on an aluminum plate, US Pat. Nos. 4,072,528 and 4,072,5.
PS provided with a photosensitive layer of a photopolymerizable photopolymer composition as described in each specification of No. 27 on an aluminum plate
PS, a photosensitive layer comprising a mixture of an azide and a water-soluble polymer as described in the specifications of U.S. Pat. Nos. 1,235,281 and 1,495,861 is provided on an aluminum plate.
Plates are also preferred.

Next, an example of the use of the plate surface protective agent of the present invention when a PS plate is used will be described.

First, the PS plate is imagewise exposed and then developed to prepare a lithographic printing plate. This lithographic printing plate is washed with water and squeezed with water on the plate surface, then an appropriate amount of the plate surface protective agent of the present invention is poured onto the plate surface, and the plate surface is rubbed with a sponge so as to coat the entire surface. This protects the non-image areas on the plate,
The planographic printing plate can be stored. When printing is started, the gum on the printing plate is washed off with water, and then printing is performed according to a normal procedure. Further, even if an automatic gum coater is used, the application can be performed uniformly.

In addition, the plate surface protective agent of the present invention contains a post-development surfactant when the plate surface protective agent is applied to the entire plate surface immediately after development using an automatic processor without washing with water. Immediately after rinsing with an aqueous solution, or after washing with water, when applied to the plate surface, after development, after washing with circulating washing water,
It is preferably used in any case, such as when it is supplied and applied to the plate surface, or when it is washed with circulating washing water after development and treated with an aqueous solution containing a surfactant and then applied to the plate surface.

Further, it is also suitable as a plate surface protective agent after baking the lithographic printing plate for strengthening the image area, and as a plate surface protective agent used for plate placement on a printing machine.

Further, it is also preferably used as a plate surface protective agent when the above-mentioned negative-type and bodi-type PS plates are treated with a common developing 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. An example will be described below.

[0025]

【Example】

 Examples 1 to 3 A plate surface protective agent having the following composition was prepared.

(Composition of the plate surface protective agent of Example 1) Lysine / hydrochloride 5 parts by weight Carboxymethyl cellulose sodium salt 0.45 parts by weight Modified dextrin (Penon JE-66, manufactured by Nippon Starch Chemical Co., Ltd.) 10 parts by weight Phosphoric acid (85 %) 0.25 parts by weight Polyethylene oxide (average addition number of ethylene oxide: 20) Nonyl phenyl ether 0.1 parts by weight Water 90 parts by weight (Composition of plate surface protective agent of Example 2) Sulfamic acid 3.5 parts by weight Carboxymethyl cellulose sodium salt 0.45 parts by weight Modification Dextrin (Penon JE-66, manufactured by Nitto Kagaku Co., Ltd.) 9 parts by weight Phosphoric acid (85%) 0.2 parts by weight Polyethylene oxide (ethylene oxide average addition mole number 15) Nonyl phenyl ether 0.1 parts by weight Di (2-ethylhexyl) sulfosuccine Sodium acid salt 0.12 parts by weight Water 90 parts by weight (Composition of plate surface protective agent of Example 3) Phosphonic acid) 5Na salt 4 parts by weight Carboxymethyl cellulose sodium salt 0.45 parts by weight Modified dextrin (Penone JE-66, manufactured by Nitto Kagaku Co., Ltd.) 10 parts by weight Phosphoric acid (85%) 0.25 parts by weight Polyethylene oxide (average addition mole of ethylene oxide) Formula 19) Nonylphenyl ether 0.08 parts by weight Sodium dehydroacetate 0.25 parts by weight Water 90 parts by weight Example 4 Plate surface protection having the same composition as in Example 1 except that the lysine hydrochloride of Example 1 was changed to 1-aminopropane. The agent was prepared.

Example 5 A plate surface protective agent having the same composition as in Example 2 was prepared except that 1,5-diaminopentane was used instead of sulfamic acid in Example 2.

Comparative Example 1 A plate surface protective agent having the same composition as in Example 1 except that lysine / hydrochloride was not added in Example 1 was prepared.

Comparative Example 2 A plate surface protective agent having the same composition as in Example 5 except that 1,5-diaminopentane was not added was prepared.

Comparative Example 3 A plate surface protective agent having the same composition as in Example 1 was prepared except that lysine hydrochloride of Example 1 was changed to triethanolamine.

Comparative Examples 4 and 5 A plate surface protective agent having the following composition was prepared.

(Composition of plate surface protective agent of Comparative Example 4) Hexa sodium phytate 5 parts by weight Iminodiacetic acid 1 part by weight Tetrakis (β-hydroxyethyl) ammonium hydroxide 0.3 parts by weight Phosphoric acid (85%) 0.25 parts by weight Water 94 Parts by weight (composition of the plate surface protective agent of Comparative Example 5) gum arabic 25 parts by weight phosphoric acid (85%) 0.2 parts by weight sodium sulfonate (35% aqueous solution) 0.5 parts by weight sodium dehydroacetate 0.15 parts by weight water 75 parts by weight A 0.24 mm thick grained aluminum plate was anodized in sulfuric acid to form an oxide film of about 2 g / m ² , washed well, immersed in an aqueous sodium silicate solution, thoroughly washed with water, and then dried.

2.0 parts by weight of 2-hydroxyethyl methacrylate copolymer (synthesized by the method of Example 1 of British Patent No. 1,505,739), 2-methoxy-4, a condensate of p-diazodiphenylamine and paraformaldehyde. -Hydroxy-5-benzoylbenzenesulfonate 0.12 parts by weight, Oil Blue # 603 (manufactured by Orient Chemical Industry Co., Ltd.)
0.03 parts by weight, 15 parts by weight of 2-methoxyethanol, 10 parts by weight of methanol and 5.0 parts by weight of ethylene chloride are applied to the above support, and the dry weight of the photosensitive layer is applied.
A 1.8 g / m ² photosensitive lithographic printing plate was obtained. This printing plate was exposed using a halftone negative film and sodium sulfite 3.0
Parts by weight, benzyl alcohol 30.0 parts by weight, triethanolamine 20.0 parts by weight, monoethanolamine 5 parts by weight,
After development with an aqueous developer containing 10 parts by weight of sodium t-butylnaphthalenesulfonate and 1000 parts by weight of pure water, the product was washed with water and dried. On the surface of the lithographic printing plate thus prepared, the above-mentioned plate surface protective agent sample was applied by being included in a sponge, and the excess was wiped off with a cloth to obtain a printing plate sample.

In order to evaluate the ink receptivity and desensitizing power of these printing plate samples, the samples were left in advance at 35 ° C. and 85% for 3 days. The samples were mounted on a printing machine Hamaster Star 900 CD-X offset printing machine and printing was started according to a usual method. The number of prints until the ink adhered to the image area at that time and a good printed matter was obtained is shown in the column of ink receptivity in Table 1. After further printing 1000 sheets,
The supply of dampening water and printing paper was stopped, and ink was made to adhere to the entire surface of the printing plate sample. The desensitizing power at this time was evaluated by the ease of ink ejection and is shown in Table 1. According to this evaluation method, in the printing plate samples in the case of using the plate surface protective agent of Japanese Patent Publication No. 62-25119 of Comparative Example 5 and Comparative Example 4 using a plate surface protective agent having a strong desensitizing power such as gum arabic. The ink on the non-image areas was immediately dispelled (ie, removed) and good prints were obtained. However, in Comparative Examples 1, 2, and 3, it was difficult to remove the ink on the non-image area, and it took 30 sheets of printing before a good printed material was obtained. On the other hand, the ink receptivity of gum arabic was greatly inferior, and 45 sheets of printing were required to obtain a good printed matter. On the other hand, Examples 1 to 5 were excellent in ink receptivity and were also good in desensitizing power.

[0035]

[Table 1]

[0036]

Since the conventional desensitizing solution for lithographic printing plates has a strong desensitizing action, when used as a plate surface protective agent, the oil sensitivity of the image area is often lowered, and a satisfactory ink for printing is obtained. Although a large number of defective prints are produced until a print having a density is obtained, the present invention provides a plate surface protective agent having a sufficient plate surface protecting ability without impairing the oil sensitivity of the image area.

Claims (4)

[Claims] 1. A plate surface protective agent for a lithographic printing plate, comprising a compound having at least one amino group and at least one group selected from a carboxyl group, a sulfo group and a phosphono group, or a salt thereof. 2. The plate surface protective agent for a lithographic printing plate according to claim 1, wherein the compound has a molecular weight of 1,000 or less. 3. A plate surface protective agent for a lithographic printing plate comprising an alkane having at least one amino group or a salt thereof. 4. The plate surface protective agent for a lithographic printing plate as claimed in claim 3, wherein the alkane having at least one amino group or a salt thereof has a molecular weight of 1,000 or less.