JPS585799B2 - Desensitizing liquid for offset printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment liquid for offset printing plates, and more particularly to a desensitization treatment liquid used when an electrophotographic copying material on which an image is formed by electrophotography is used as an offset printing original plate.

An electrophotographic offset printing original plate (hereinafter referred to as a master), which has a photoconductive layer such as a photoconductive powder such as oxidation powder and a resin binder (hereinafter referred to as a master), is used to create a lipophilic image by performing charging, exposure, development, and fixing operations on the surface of the photosensitive layer. It is made by forming and treating with a desensitizing treatment liquid.

Generally, in offset printing, a treatment liquid is applied to the surface of the master to form a hydrophilic coating on the non-image areas to prevent oil-based ink from adhering, while oil-based ink is applied to the image areas, and the image formed with this ink is It is well known that this is a printing method that transfers images onto paper.

Hitherto, as such desensitizing treatment liquids, those containing ferrocyanic compounds and ferricyanide compounds as main components have been known, and these treatment liquids have strong desensitizing power and are effective. And Felician ions are unstable to heat and light, and since they contain cyanide ions, they are detected as free cyanide, which poses various problems in terms of pollution.

However, the present invention provides an excellent desensitization treatment liquid that does not contain ferrocyan compounds and ferricyan compounds, which cause pollution problems and deteriorate due to heat and light, and which contains only harmless substances as constituent components.

In other words, the present invention is characterized in that (A) an ionic complex of an aminocarboxylic acid, an aminocarboxylic acid complex, or a salt thereof, a water-soluble cationic polymer, and an inositic hexaphosphate or a derivative thereof is used as an active ingredient. This is a desensitizing liquid for offset printing.

Conventionally, it is well known that aminocarboxylic acids, aminocarboxylic acid complexes, or salts thereof (hereinafter referred to as aminocarboxylic acids) form chelate compounds with metals, but even if they are used alone as a desensitizing treatment liquid for offset printing. It has only a weak desensitizing power and has insufficient water retention in non-image areas, resulting in poor separation of printing ink and causing stains.

The treatment liquid of the present invention uses the above-mentioned aminocarboxylic acids together with a water-soluble cationic polymer and inosit hexaphosphate or its derivative, and is produced by the water-soluble cationic polymer and inosit hexaphosphate or its derivative. This makes effective use of ion complexes.

The generated ion complex has the ability to form a hydrophilic film, and reacts with metal ions to create extremely strongly bound chelate compounds, which when used in combination with aminocarboxylic acids to form a desensitized film that is poorly soluble in water. It has been found that water retention is significantly improved compared to conventional methods.

Each of the above three components is a non-toxic substance that is stable against heat and light, and does not change over time.

Examples of aminocarboxylic acids used in this treatment liquid include the following.

NH2CH2COOH, HOOC (C Tsuru) 2CH (NH
2) COOH, CH3CH (NH2) COOH, HOO
CCH2CH(NH2)COOH,NH2C(NH2)
NH(CH2)3CH(NH2)COOH,HSCH2
CI{(NH2)COOH,H00CCH(NH2)C
H2SSCH2CH(NH2)C00H, [CO(NH
2CH2COO)3], KCCO(C204)(NH,
CH2■0)3], Na(CO(C204)(NI{
2CI {2αli)]BaCCo(C204)2(NH2
CH2COO)3], [CO(NH2CH2COO)(
C6H8N2)]I2, [co(CO3)(NH2C
H2COO)(NH3)2], [Co(NH2CH2C
00) (C6H18N4)] I2 , CNi (NH2
CH2COO)2(H202)), (Ni(NH
2CH2COO)2(NHs)2),K
(Ni(NH2CH2COO)a)
, (Co(CsI{6NH2)a) −(
Co (L C3H6NO2) (C2H3N2
)2:) I2, and water-soluble cationic polymers include polyvinylbenzyltrimethyl chloride polyamide polyamine-epichlorohydrin resin, melamine-formaldehyde resin, polyamide-epichlorohydrin resin, acetoguanamine-formaldehyde resin,
Polyamide epoxy resin, benzoguanamine-formaldehyde resin, etc.

Furthermore, inositic hexaphosphates and their derivatives include phytic acid and monophytate such as sodium phytate, potassium phytate, calcium phytate, etc.
Mention may be made of water-soluble salts of valent or divalent metals.

The amounts of the above-mentioned substances used in this treatment liquid are 2 to 7% by weight for aminocarboxylic acids and 0.0% by weight for water-soluble cationic polymers.
The preferred concentration is 0.04 to 0.2% by weight, and the concentration of inosit hexaphosphate and its derivatives is 1.6 to 4.0% by weight.

Furthermore, in addition to the above three components, this treatment solution contains NaBr + NaclwLi as an ion complex stabilizer.
Inorganic electrolytes such as Cl, etc., organic acids such as citric acid, malonic acid, malic acid, tartaric acid, tannic acid, glycolic acid, etc., or phosphoric acid as pH adjusters. Inorganic acids such as , nitric acid, sulfuric acid, etc.
pH buffers such as sodium, potassium and ammonium salts of phosphoric acid; humectants such as ethylene glycol, sorbitol, glycerin and their derivatives; preservatives such as salicylic acid and dihydroacetic acid; rust preventives Appropriate amounts of triethanolamine, triethyleneamine, EDTA, etc. can be added for use.

When implementing this treatment liquid, the appropriate pH value of the treatment liquid is in the range of 4 to 6, and the desensitizing ability is best exhibited.

Further, this treatment liquid can be diluted 2 to 5 times with water and used as dampening water during printing.

The present invention will be specifically explained below using examples of actual persimmons.

Example 1 was sufficiently dissolved and the pH was adjusted to 5.0 with trisodium phosphate.

Example 2 was sufficiently dissolved and adjusted to pH=5.0 with trisodium phosphate.

Example 3 was sufficiently dissolved and adjusted to pH=5.0 with triammonium phosphate.

Example 4 was sufficiently dissolved and adjusted to pH=5 with trisodium phosphate.

Example 5 was sufficiently dissolved and adjusted to pH=5 with potassium phosphate.

Comparative Example 1 was sufficiently dissolved and adjusted to pH=5 with trisodium phosphate. 0
And so.

Comparative Example 2 was sufficiently dissolved and adjusted to pH=5 with trisodium phosphate. 0
And so.

After forming an image on a commercially available zinc oxide/resin dispersion electrophotographic material using a conventional method, absorbent cotton is soaked with each of the processing solutions mentioned above, and the photosensitive layer is etched by hand or using an automatic etching device (Ricoh Processor). An offset printing original plate was prepared by performing automatic etching treatment, and offset printing was performed using a dampening solution diluted 5 times with water for each treatment solution.

The results are shown in the table.

As shown in the table, in Examples 1 to 5, no matter which etching method was used, clear prints with good ink receptivity were obtained without background stains on the master and prints after printing 4,000 sheets.

However, in Comparative Examples 1 and 2, when an automatic etching device was used, background smear occurred and the ink separation property was also poor, making printing impossible.

Claims (1)

[Scope of Claims] 1. A desensitizing liquid for offset printing, characterized by containing the following (support) and (B) as active ingredients. (A): Aminocarboxylic acid or aminocarboxylic acid complex or salt thereof. Old): Ionization of water-soluble cationic polymer and inositic hexaphosphate or its derivatives.