JPH0256232B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic offset printing plate surface treatment liquid, and more particularly to a desensitization treatment liquid for cyan-free offset printing, which does not contain any cyan compounds. An electrophotographic offset printing original plate (hereinafter referred to as a master) has a photosensitive layer in which photoconductive fine powder such as zinc oxide is dispersed in a resin binder, and a normal electrophotographic operation is performed on this layer. , obtained by forming a lipophilic image. Generally, in offset printing, a plate is used that consists of a non-image area that is easily wetted by water (hydrophilic area) and an image area that is difficult to wet (oleophilic area), but electrophotographic offset printing original plates are Since the image area is made of a hydrophobic photoconductive layer, if printing is performed as is, the printing ink will adhere to the non-image area and normal printing will not be possible. Therefore, prior to printing, it is necessary to desensitize the non-image areas of the printing plate to impart hydrophilic properties. Conventionally, this type of desensitizing treatment liquid includes ferrocyanate, a cyanide compound-containing treatment liquid containing ferricyanide as a main component, and a cyanide-free treatment liquid containing ammine cobalt base, phytic acid and its derivatives, and guanidine derivatives as main components. has been raised. However, these processing solutions cannot be said to be fully satisfactory processing solutions. That is, in the case of the former ferrocyan salt and ferricyan salt-containing treatment solution, the desensitizing power is strong and the ability to form a strong hydrophilic film is strong.
Although they have the advantage of fast film formation speed, on the other hand, ferrocyan ions and ferricyan ions are unstable to heat and light, and when exposed to light they become colored and precipitate, weakening their desensitizing power. ), which is detected as free cyanide, which poses various problems in terms of pollution, such as drainage. On the other hand, in consideration of these points, cyan-free processing liquids containing a desensitizing agent as the main component have been proposed, but even with these, it is still not possible to obtain a sufficiently satisfactory lithographic printing original plate. I can't say that. Specifically, the film formation speed is slower than the former, and the etching method using a processor cannot form a hydrophilic film with high physical strength that can be immediately printed in one pass, resulting in background smudges and halftone gradation. It has the disadvantage of causing It is well known that inositohexalic acid esters and their metal derivatives form chelate compounds with metals, and various types of desensitizing agents for offset printing original plates have been provided. However, these methods all have slow film formation speeds, and do not form a printable hydrophilic film with a single processor treatment, resulting in poor ink separation and disadvantages of background smudges and collapsed halftone gradations. be. The present inventors previously reported in Japanese Patent Publication No. 58-5799 that an ionic complex of monovalent and divalent metal salts such as sodium phytate, potassium phytate, and calcium phytate of inositohexalic acid ester and an aqueous cationic polymer was developed. Although this method improved water retention, it had the disadvantage that a satisfactory etching speed could not be obtained. As a way to improve these shortcomings, further research revealed that a specific electrolyte was added to the ionic complex of inositohexalic acid ester, its derivatives, an anionic polymer capable of forming a chelate with zinc ions, and an aqueous cation. The present invention was completed by discovering that the etching speed could be increased by adding a compound. That is, the present invention provides (a): an anionic compound other than an ammonium salt or an amine salt of inositohexalic acid ester, which has a molecular weight of about 500 or more and has the ability to form a chelate with zinc ions, (b): a water-soluble cationic polymer, and (c) ): At least one electrolyte selected from alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts of formic acid, oxalic acid, sulfuric acid, nitric acid, sulfamic acid, or carbonic acid and having a solubility in water of 10% by weight or more at room temperature. This is a desensitizing treatment liquid for offset printing consisting of a compound. Examples of anionic compounds having a molecular weight of about 500 or more and having the ability to form a chelate with zinc ions that can be used in the treatment solution of the present invention include JP-A-57-199694 and JP-B-Sho.45.
Phytic acid or its metal salts described in JP-A-24609, JP-A-51-103501 and JP-A-54-10003, JP-A-53-83806, JP-A-Sho Specification No. 53-83807, JP-A-53-
109701 specification, JP-A-53-127002, JP-A-5-127003 and JP-A-54-44901, the hydroxyl group at the 1st and/or 4th position is inactive. Inositohexaphosphate derivatives, vinylphosphonic acid (salt) polymers or copolymers, cellulose phosphate (salts), 2-hydroxyethyl (meth)acrylic acid ester polymers or copolymers Acid ester (salt), phosphate ester (salt) of 2-hydroxypropyl (meth)acrylic acid ester polymer or copolymer, polyacrylic acid (salt), polymethacrylic acid (salt), polystyrene sulfonic acid (salt) , polyvinyl alcohol sulfate, polyglutamic acid (salt), alginic acid (salt), carboxymethylcellulose, 2-acrylamide-2-methylpropanesulfonic acid polymer (salt) or copolymer (salt), etc. Among these, phosphoric acid esters of polyhydroxy compounds or salts thereof are particularly preferred. The water-soluble cationic polymer used in the treatment liquid of the present invention is preferably a water-soluble compound having a molecular weight of about 500 to 100,000. Specifically, aniline resin hydrochloride, polythiourea hydrochloride, cationized amino resin, polyvinylpyridine hydrochloride, polyacrylamide cation-modified product (vinylamine polymer obtained by Hofmann decomposition of polyacrylamide, polyacrylamide with formalin and secondary amine) Mannitz reaction and quaternary ammonium salt with dimethyl sulfate), polvinylbenzyl chloride with tertiary amine as quaternary ammonium salt, poly(N-vinyl-2-methylimidazolium) methyl sulfate), dimethylaminoethyl (meth)acrylate polymer and its quaternary ammonium group, amino group-containing (meth)acrylate polymer (diethylaminoethyl (meth)acrylate polymer and its quaternary ammonium salt), especially A polyalkylimine compound in which a part or all of the amino groups of a polymer containing an aliphatic amino group in the repeating unit are changed into a salt or a quaternary ammonium salt, as described in the specification of Publication No. 45-24609, Alternatively, examples include, but are not limited to, quaternary ammonium salts such as amine adducts of epoxy resins, amine adducts of maleated polymers, amino group-containing polyamide resins, polyamide-epoxy resins, and polyamide-epichlorohydrin resins. . Further, the electrolyte compounds having a solubility in water of 10% by weight or more used in the treatment liquid of the present invention include alkali metal salts, alkaline earth metal salts, ammonium salts, or amines of formic acid, oxalic acid, sulfuric acid, nitric acid, sulfamic acid, or carbonic acid. It's salt. Specifically, _AgNO3 ,
Ba( _NO3 ) ₂ , Ba( _{SO3NH2 ) 2} , Ca( _NO3 ) ₂ , Ca
( _SO3NH2 ) _{2 , KHCO3} , _KHSO4 , _KNO3 ,
K ₂ SO ₄ , LiNO ₃ , MgCO ₃ , MgSO ₄ , NH ₄ NO ₃ ,
(NH ₄ ) ₂ SO ₄ , NH ₄ SO ₃ NH ₂ , Na ₂ CO ₃ , NaNO ₃ ,
_NaSO3NH2 , _HCOONa , HCOOK,
Examples include NaOOCCOONa, KOOCCOONa, guanidine carbonate, and ammonium carbonate.
In addition, reducing salts such as nitrites and sulfites are also included if they are oxidized and turn into nitrates or sulfates. The solubility of these electrolyte compounds in water is
If it is less than 10% by weight, crystals will form if left for a long time when used as a processing solution, which is not preferable. Preferably, the solubility in water is 20% by weight or more. The present invention has discovered a processing solution with a high etching speed by adding an electrolyte compound consisting of a salt of a specific acid to an ion complex of an anionic compound and a cationic compound. Even if a phosphate added to the solution is used in place of the electrolyte compound of the present invention, the etching speed is low and sufficient desensitizing power cannot be obtained.
Furthermore, salts of halogenated acids such as NaCl, NH ₄ Cl, KBr, etc. are highly corrosive to metals and are therefore unsuitable as the electrolyte compound of the present invention. The amount of the above substances constituting the treatment solution of the present invention is 10 to 200 parts by weight of an anionic compound having the ability to form a chelate with zinc ions in 1000 parts by weight of the treatment agent;
More preferably 40 to 75 parts by weight, 20 to 20 parts by weight of electrolyte compound
150 parts by weight, more preferably 40 to 100 parts by weight, and 0.2 to 20 parts by weight, more preferably 1 to 10 parts by weight of the water-soluble cationic polymer. These compounds are dissolved in ion-exchanged water or tap water to prepare the main treatment liquid. Although the order of dissolution is not particularly limited, preferably, after dissolving zinc ions and an anionic compound having chelate-forming ability in water, the electrolyte compound is added, and then the cationic polymer aqueous solution is added. In addition to the above ingredients, the processing solution
Organic or inorganic acids, basic hydroxides such as calcium hydroxide and sodium hydroxide as pH adjusters, ethylene glycol, sorbitol, glycerin, gum arabic, surfactants, etc. as wetting agents, salicylic acid and phenol paralysis as preservatives. Butyl benzoate, sodium dehydroacetate, 4-isothiazolin-3-one compounds, etc. as rust inhibitors
It can be used by adding appropriate amounts of EDTA, amines, etc. When performing the treatment liquid, the PH value of the treatment liquid is 3.
It is preferable to set it in the range of ~6. It can also be used as a dampening solution by diluting it with water. As mentioned above, the treatment liquid of the present invention poses a problem in terms of pollution, and also contains ferrocyan, which deteriorates due to light and heat.
It does not contain ferricyanide compounds, is stable even under long-term storage, does not discolor or precipitate, is less affected by the printing environment than conventional cyanide-free processing liquids, and has a significantly faster film formation rate, allowing for high-speed etching processing. It is an excellent cyan-free processing liquid that allows you to obtain an offset printing original plate without background smear or halftone gradation. The present invention will be explained below with reference to Examples and Comparative Examples. Example 1 Water 1000 parts by weight Potassium phytate salt (50% aqueous solution)
100 〃 Quaternized polyamide-epichlorohydrin resin (30% aqueous solution) 7 〃 Glycerin 100 〃 (NH ₄ ) ₂ SO ₄ (electrolyte compound) 80 parts by weight Armogen (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.: Amphoteric surfactant 0.1 〃 Salicylic acid 1.0 〃 1,2-Benzisothiazolone-3-one
0.5 〃 was sufficiently dissolved, and glycolic acid was added to adjust the pH to 4.5. On the other hand, after forming an image on an electrophotographic light-sensitive material containing zinc oxide and a resin dispersion according to a conventional method, it was subjected to high-speed etching treatment with the above-mentioned processing solution to obtain an offset master original plate, and the above-mentioned processing solution was added to dampening solution with water. Offset printing was performed using a 5-fold dilution.
The results are shown in Table-1. Examples 2 to 9, Comparative Examples 1 to 7 Offset printing was performed in the same manner as in Example 1 using the compounds shown in Table 1 as electrolyte compounds. The results are shown in Table-1.

[Table] In Comparative Examples 5 to 7, a printing test was not conducted because precipitation occurred in the processing liquid. As can be seen from Table 1, in Examples 1 to 9, even after high-speed etching, there was no scuffing on the master or printed matter after 4000 sheets were printed, the ink adhesion was good, and the printed matter was clear with no halftone gradation. In addition, there was no precipitate in the treatment agent itself, and no corrosion was observed on the aluminum plate. Example 10 Water 1000 parts by weight Phytic acid (50% aqueous solution) 100 〃 NaOH (50% aqueous solution) 70 〃 Polyethyleneimine quaternized with dimethyl sulfate
7 Glycerin 100 (NH ₄ ) ₂ SO ₄ 80 Glycolic acid was added to adjust the pH to 4.0. An offset master printing plate was prepared by high-speed etching in the same manner as in Example 1, and printed using a 5-fold dilution of the treatment solution of Example 1 with water as a dampening solution to remove background stains on more than 4000 sheets. Got no prints. Example 11 Water 1000 parts by weight Sodium polyvinylphosphonate 40 Quaternized polyamide-epichlorohydrin resin (30% aqueous solution) 100 Glycerin 100 Na ₂ SO ₄ 50 Sodium formate 50 Add glycolic acid to adjust pH to 4.0 did. An offset master printing plate was prepared by high-speed etching in the same manner as in Example 1, and printed using a 5-fold dilution of the treatment solution of Example 1 with water as a dampening solution to remove background stains on more than 4,000 sheets. Got no prints.

Claims (1)

[Claims] 1. A desensitizing treatment liquid for cyan-free offset printing, characterized by containing the following (a), (b) and (c) as active ingredients. (a): Anionic compound other than ammonium salt or amine salt of inositohexaphosphate ester with a molecular weight of about 500 or more and capable of forming a chelate with zinc ions, (b): Water-soluble cationic polymer, (c): Formic acid, oxalic acid, Alkali metal salts, alkaline earth metal salts of sulfuric acid, nitric acid, sulfamic acid or carbonic acid,
The solubility of at least one selected from ammonium salts and amine salts in water at room temperature is
More than 10% by weight of electrolyte compounds.