JP2733496B2 - Desensitizing solution for lithographic printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desensitizing solution for lithographic printing, and more particularly to a desensitizing solution for lithographic printing of an electrophotographic planographic printing plate, a silver salt printing plate, a PS plate, etc. It is about.

[0002]

2. Description of the Related Art In lithographic printing, ie, offset printing, a lipophilic image area is formed by applying a desensitizing solution onto a printing original plate on which an image area has been formed by plate making to form a hydrophilic layer on the non-image area. Is a printing method in which an oil-based ink is adhered to transfer the ink in the image area to paper. Among the printing original plates used in this printing method, an electrophotographic lithographic printing original plate in which a photosensitive layer in which a photoconductive powder such as zinc oxide is dispersed in an adhesive resin is coated on a support such as paper, The plate is made by electrophotography consisting of a process of charging, exposure and development, and lipophilic toner particles in a developer are attached to form an image portion on the plate surface,
Then, a hydrophilic substance is formed by the desensitizing agent in the processing liquid and the photoconductive powder in the surface layer by applying the desensitizing processing liquid to form a hydrophilic layer on the non-image portion of the original plate.
Thus, the original plate having the lipophilic portion and the hydrophilic layer is supplied to a printing press and used for lithographic printing.

The main components of the conventional desensitizing solution are roughly divided into cyan-based substances and non-cyan-based substances. Cyanide-based substances are those in which cyan ions are present in the molecule as an inorganic complex, and ferrocyanides and ferricyanates are widely used. These have strong desensitizing power and satisfy printing characteristics comprehensively. However, these cyanide substances are unstable to light and heat, discoloring and sedimenting, and desensitizing power decreases with time.Also, although they are stable and harmless to the human body, ultraviolet rays and It is feared that it is decomposed by various environmental conditions such as irradiation of radiation, and harmful cyanide alone is released to cause pollution. In addition, printing on neutral paper or printing with a quick-drying color ink tends to cause phenomena such as stains on printed matter and emulsification of the ink, which poses a practical problem.

On the other hand, some non-cyanide substances use inorganic acid salts, but phytic acid, which is an organic acid, and salts thereof are widely used. Phytic acid or a salt thereof is excellent in environmental safety and workability, but has a problem in that it is difficult to set conditions at the time of printing due to weak desensitizing power alone, and the printed matter is easily stained. In order to solve such problems of phytic acid, a combination with a metal complex of aminocarboxylic acid or the like (Japanese Patent Publication No. 2-39397) or a combination with a hexametaphosphate (Japanese Patent Publication No. 62-7597) has been tried. However, no satisfactory effect has been obtained yet.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a desensitizing solution for lithographic printing which has a good desensitizing power and has no environmental problems. It is.

[0006]

The present invention is characterized in that a desensitizing solution for lithographic printing mainly containing phytic acid or a salt thereof contains a polyamine derivative represented by the following general formula. It is a desensitizing solution for lithographic printing.

Embedded image (Wherein, X represents a halogen element, and k and m are 2 to 2)
6, and n is 3-2000. )

The polyamine derivative represented by the above general formula used in the present invention is a polymer having high cationicity and a chemical structure containing a quaternary amino group. Such a compound exhibits a remarkable action and effect that the desensitizing ability can be greatly improved by reacting with phytic acid or a salt thereof. In the present invention, the colloid equivalent value as a measure of cationic is pH
A polyamine derivative having 3 or more in the range of 3 to 10 is preferably used because it has good reactivity with phytic acid or a salt thereof and can obtain more excellent desensitizing property.

The polyamine derivative as described above is a water-soluble compound obtained by copolymerizing a compound having an epoxy ring such as epichlorohydrin with an alkyleneimine. The polyamine derivative in the present invention is a copolymer of an alkylene imine having a lower alkylene group and epichlorohydrin, particularly, a water-soluble polymer in which k and m in the above general formula are 2 to 3 and X is Cl. Is preferred, and good desensitizing properties are achieved with good reactivity with phytic acid or a salt thereof. The molecular weight is 1000 to 10
About 100,000 is used, and preferably 50,000 to 1,000,000.

The phytic acid and its salt used in the present invention are also known as inosit hexaphosphate,
Conventionally used ones are generally used. Since these compounds are acidic and form a salt with a metal, they can be used as a desensitizing agent. In addition, as a phytate, an alkali metal salt, an ammonium salt, an amine salt, etc. are mentioned. The amount of phytic acid or a salt thereof in the desensitizing solution of the present invention is 1 to 200 g / liter, and the amount of polyamine derivative is 0.01 to 20 g / liter.
More preferably, it is 0.1 to 5.0 g / liter.

In the present invention, phytic acid or a salt thereof and a polyamine derivative may be combined with each other to form a water-insoluble compound, so that a buffer may be added as necessary. Examples of the buffer used include sulfonic acid compounds such as ammonium sulfate, methanesulfonic acid or a salt thereof, ethanesulfonic acid or a salt thereof, benzenesulfonic acid or a salt thereof, toluenesulfonic acid or a salt thereof, xylenesulfonic acid or a salt thereof, and the like. Is mentioned.

Further, the desensitizing solution of the present invention may contain additives such as a pH adjuster, a pH buffer, a lubricant, a wetting agent and a preservative, such as the following components. That is, p
Inorganic acids, organic acids and salts thereof are used alone or as a mixture as an H adjustor or a pH buffer. Inorganic acids include phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, and the like.Organic acids include formic acid, acetic acid, butyric acid, valeric acid, lactic acid, tartaric acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, and maleic acid. , Phthalic acid, citraconic acid, itaconic acid, fumaric acid, tricarbalic acid, glycolic acid, propionic acid, thioglycolic acid, malic acid, citric acid, gluconic acid, pyruvic acid, glycolic acid, salicylic acid, adipic acid, hydroacrylic acid Glyceric acid, P-toluenesulfonic acid and the like. These salts include alkali metal salts, ammonium salts, amine salts and the like.

Also, as a wetting agent, wetting agents such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, gum arabic, carboxymethyl cellulose, acrylic polymer, methanol, ethanol, iso and normal propyl alcohol, triethanolamine, etc. Can be. In addition, salicylic acid, phenol,
Phenol butyl parabenzoate, sodium dehydroacetate, 4-isothiazolone-3-one compound and the like can be added. In addition, EDTA, sodium nitrite, dicyclohexylammonium nitrite and the like can be added as a rust preventive.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5 After blending with the composition shown in Table 1 and thoroughly mixing and dissolving, an aqueous ammonia solution (50%) was added to adjust the pH to 4.0 to prepare a desensitizing solution of the present invention.

[Table 1]

COMPARATIVE EXAMPLES 1-4 Compounds were mixed according to the composition shown in Table 2 and thoroughly mixed and dissolved. Aqueous ammonia solution (50%) was added to adjust the pH to 4.0, and a desensitizing solution for comparison was used. Was prepared.

[Table 2]

An electrophotographic lithographic printing plate precursor of a commercially available zinc oxide-resin dispersion system is made by electrophotography, and the desensitizing solution of Examples 1 to 5 and Comparative Examples 1 to 4 is used to prepare an automatic plate made by Ricoh. This original plate was etched by an etching apparatus to obtain a printing plate for offset printing. Further, a fountain solution obtained by diluting the desensitizing solution used for etching by 5 times with water was supplied to a Ryobi thin flow lithographic printing press, and printing was performed by the printing press. At this time, a quick-drying color ink (F gloss ultramarine, manufactured by Dainippon Ink and Chemicals, Inc.) was used as the ink, and neutral paper (TomoEliver, manufactured by Tomagawa Paper) was used as the printing paper.

In the printing test, continuous printing of 3,000 sheets was performed, and the inking property, resolution, background contamination,
Confirmation of dot blur, emulsification on the roller of the printing press, and occurrence of roller strip were observed, and the results are shown in Table 3.

[Table 3]

The evaluation method of the printing test is as follows. <Adhesiveness> The density of the solid portion of the ink transfer portion of the printed matter was measured with a Macbeth densitometer RD-914. <Resolution> The reproducibility of the resolution test chart of the printed matter was visually evaluated using a loupe in each of the vertical direction and the horizontal direction, and represented by a numerical value of the resolution (the number of lines per 1 mm). The larger the numerical value, the higher the resolution. <Background Soil> As a desensitizing property, the stain of the printed matter with the ink in the untransferred portion of the ink was visually evaluated. ：: no stains Δ: slight stains X: considerable stains <dot blur> The reproducibility of halftone dots corresponding to an area ratio of 80% of the dot test chart of the printed matter was observed using a loupe. ：: good ×: bad <Emulsification> The occurrence of abnormal emulsification at the roller portion of the printing machine was visually evaluated. ：: No occurrence Δ: Slight occurrence X: Considerable occurrence <Roller strip> The ink stripping phenomenon at the roller portion of the printing press was visually evaluated. ○: No occurrence ×: Occurrence

As is clear from Table 3, when the desensitizing solution according to the present invention is used, the ink has good inking properties even after continuous printing of 3000 sheets, the printed matter has no background stain, and other printing characteristics. Was also confirmed to be good. In addition, no emulsification or roller strip occurred in the printing machine. On the other hand, the desensitizing treatment liquids for comparison all had poor background soiling, and furthermore caused emulsification and roller stripping in the printing machine, so that satisfactory printing characteristics could not be obtained.

[0019]

The desensitizing solution for lithographic printing of the present invention comprises:
Since it is a non-cyanic treatment liquid, it has no problem of environmental pollution and has good desensitization characteristics, so that practically good printing characteristics can be obtained and excellent printed matter can be provided.

Claims (1)

(57) [Claims] 1. A desensitizing solution for lithographic printing comprising phytic acid or a salt thereof as a main component, comprising a polyamine derivative represented by the following general formula: . Embedded image (Wherein, X represents a halogen element, and k and m are 2 to 2)
6, and n is 3-2000. )