JP2002283764A - Plate surface cleaning agent for planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate surface cleaning agent having a superior cleaning and desensitization effects without exerting adverse influences on a silver image, in the planographic printing plate wherein an image silver is utilized as an ink receptivity. SOLUTION: The plate cleaning agent is characterized by that the cleaning agent contains at least one of organic phosphate compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate cleaning agent used in a lithographic printing plate in which image silver is used as ink receptivity, and more particularly to an anodized aluminum support and a silver halide emulsion layer. The present invention relates to a plate surface cleaning agent suitable for a lithographic printing plate using a silver complex salt diffusion transfer method having the following.

[0002]

2. Description of the Related Art A lithographic printing plate in which a transferred silver image obtained by a silver complex salt diffusion transfer method (DTR method) can be immediately used as ink acceptability is already known. Part 1
One type is a lithographic printing plate having, in this order, at least a silver halide emulsion layer and a physical development nucleus layer on a support (eg, a paper base coated with a polyethylene resin, a polyethylene terephthalate base, etc.), for example, US Pat. No. 3,721,559. No. 3490905, No. 33
No. 85701, No. 3814603, No. 34543
No. 98, No. 3764323, No. 3099209
No., JP-B-44-27242, 48-30562
No., JP-A-53-9603, JP-A-53-21602,
Nos. 54-103104 and 56-9750.

The above lithographic printing plate has a physical development nucleus on the surface of the emulsion layer using gelatin as a binder, and the silver halide crystals in the exposed emulsion layer undergo chemical development by DTR development to become black silver. To form a hydrophilic non-image portion mainly composed of gelatin. On the other hand, unexposed silver halide crystals are converted into a silver salt complex by the silver salt complexing agent in the developing solution and diffused to the physical development nucleus layer on the surface. An image portion mainly composed of physically developed silver is formed. Here, the silver image part is used as ink acceptability.
The gelatin surface in the non-image area is subjected to printing as ink repellency.

Another type is a monosheet type lithographic printing plate using an aluminum plate as a support and utilizing a silver complex salt diffusion transfer method (hereinafter referred to as an aluminum lithographic printing plate). No. 57-1
58844, 63-260491, JP-A-3-1
No. 16151, 4-282295, U.S. Pat.
Nos. 5,567,131 and 5,427,889.

[0005] The aluminum lithographic printing plate has a structure in which a physical development nucleus is supported on a roughened and anodized aluminum support, and a silver halide emulsion layer is further provided thereon. The general method of making a lithographic printing plate is
After exposure, the process includes development, washing (wash-off: removal of the silver halide emulsion layer), and finishing.

More specifically, a metal silver image portion is formed on a physical development nucleus by a development process, and a silver halide emulsion layer is removed by a subsequent washing process to form a metal silver image portion (hereinafter referred to as silver) on an aluminum support. Image portion) is exposed. At the same time, the anodized aluminum surface itself is exposed as a non-image area.

The exposed silver image area and the non-image area are coated with a finishing solution containing a protective colloid such as gum arabic, dextrin, carboxymethylcellulose, polystyrene sulfonic acid and the like for protection. A so-called gumming process is performed. This finishing solution is also called a fixing solution or a finishing solution, and generally contains a compound (for example, a nitrogen-containing heterocyclic compound having a mercapto group or a thione group) that renders a silver image portion lipophilic.

[0008] In normal lithographic printing, both water (humidifying liquid) and ink are supplied to the plate surface, and the image portion selectively receives color ink, the non-image portion selectively receives water, and the ink on the image is selectively received. For example, the transfer is performed by transferring to a substrate such as paper. In these types of printing, if the hydrophilic non-image area deteriorates for some reason, the oily ink adheres to the area and causes soiling. Therefore, it is necessary to remove the attached ink and restore the hydrophilicity of the area.

[0009] However, the cleaning operation at the time of printing is usually performed by including a cleaning agent in a sponge or the like and wiping the entire plate surface of the printing plate. Therefore, since the cleaning agent is applied not only to the non-image portion where the stain has occurred but also to the image portion, it is necessary not to affect the image portion.

When a commercially available plate surface cleaning agent is used for the lithographic printing plate of the present invention, the ability of the non-image portion to recover the hydrophilicity of the ink stained portion is insufficient, or the hydrophilicity of the non-image portion of the ink stained portion is insufficient. Even if the recovery ability of the printing plate was sufficient, the silver image portion was melted or abraded by the plate surface cleaning work, thereby causing poor ink deposition and poor printing durability.

JP-A-6-344680 discloses a plate cleaning agent for a lithographic printing plate to which the present invention is directed and discloses the use of glycol ethers. This cleaning agent did not sufficiently satisfy the effects of cleaning and desensitization, and was insufficient particularly for aluminum lithographic printing plates.

In an aluminum lithographic printing plate, if the non-image portion deteriorates due to corrosion of the plate surface such as etch pits of anodized aluminum, ink adheres to the non-image portion to cause background contamination, or the non-image portion remains in the air for a long time. When exposed to water, there is a problem peculiar to aluminum lithographic printing plates that generates spot-like ink stains called oxidation stains.

Japanese Unexamined Patent Publication No. 2000-158841 discloses a plate cleaning agent for a lithographic printing plate having an aluminum support. When this cleaning agent is left for a few days after the plate surface cleaning, the silver image is corroded and dissolved to form an ink. It has been found that the wall thickness is reduced and printing durability is poor. In particular, when the amount of anodized aluminum support is small, for example, 3.5
g / m ² or less, and more remarkable at 3 g / m ² or less.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plate cleaning agent which does not adversely affect the silver image of a lithographic printing plate utilizing image silver as ink receptivity and has excellent cleaning and desensitizing effects. To provide. In particular, the present invention provides a lithographic printing plate having an aluminum support, which does not adversely affect printability even after being stored for several days after the plate surface cleaning operation even when the amount of anodized aluminum is small. With the goal.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This has been attained by a plate surface cleaner characterized by containing at least one organic phosphonic acid compound.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Organic phosphonic acid compounds used in the plate surface cleaning agent of the present invention include, for example, aminotrimethylenephosphonate, 1-hydroxyethylidene-1-diphosphonate, ethylenediaminetetramethylenephosphonate, diethylenetriaminepentamethylenephosphonate, Methylenediaminetetramethylenephosphonate, N-carboxymethyl N, N-dimethylenephosphonate, N, N-dicarboxymethyl-N-methylenephosphonate, 2-phosphonobutane-1,2,4-tricarboxylate And the like, but are not limited thereto. In addition, these compounds are already marketed by each manufacturer, and can be easily obtained, for example, as `` Dequests '' of a registration certificate of Sorcia Japan Co., Ltd., and `` Donsums '' of a registration certificate of Sakai Chemical Industry Co., Ltd. Can be.

These organic phosphonic acid compounds can be used alone or in combination of two or more kinds, and the addition amount thereof can be used at 0.01 to 1.0 mol / l, preferably 0.05 to 0.5 mol / l. It is.

Further, as the alkaline earth metal used in the present invention, calcium, strontium, barium, beryllium and magnesium can be used. Magnesium and calcium are preferred, and magnesium is more preferred.

When the alkaline earth metal is added to the detergent, it may be added as the following compound. For example, calcium bromide, calcium carbonate, calcium chloride, calcium citrate, calcium gluconate, calcium hydroxide, calcium iodide, calcium nitrate, calcium nitrite, calcium oxalate, calcium stearate, calcium sulfate, calcium tartrate, bromide Barium, barium nitrate, barium sulfate, barium thiosulfate, barium nitrite, beryllium chloride, beryllium bromide, beryllium iodide, beryllium nitrate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium nitrate, magnesium stearate Strontium chloride, strontium bromide, strontium nitrate, strontium sulfate, and the like. In particular, it is preferable to use it in the form of nitrate.

The amount of the alkaline earth metal added is 0.05
To 5 mol / l, preferably 0.1 to 3 mol / l, more preferably 0.2 to 2 mol / l. These alkaline earth metals can be used alone or in combination of two or more.

In the cleaning agent of the present invention, in addition to the above compounds,
It is preferable to include an organic solvent having an action of dissolving the ink. As the organic solvent, a hydrocarbon fraction and a petroleum fraction having a boiling point in the range of 120 to 350 ° C. are preferable. For example, cyclohexane, benzyl alcohol, limonene,
Alkylbenzene, K Solvent manufactured by Nippon Oil Co., Ltd.
No. 3 solvent, No. 5 solvent and the like can be mentioned, and among them, limonene is preferable. The hydrocarbon solvent is preferably used in the range of 10 to 60% by weight of the detergent.
In this case, if an alcohol-based solvent or a glycol-based ether compound is added, the ink solubility can be further increased.

It is preferable that the detergent further contains a surfactant. As the surfactant, JP-A-6-32
No. 081, anionic and nonionic surfactants. In particular, a nonionic surfactant having a polyethyleneoxy group is preferred. For example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, and polyoxyethylene adducts of acetylenol are included.

In addition, a water-soluble polymer can be contained. For example, gum arabic, starch derivatives such as dextrin, alginic acid, carboxymethyl cellulose,
Examples include polyethylene glycol, polyvinyl alcohol, polystyrene sulfonic acid, and polyacrylic acid.

The washing agent may further contain commonly used buffers, preservatives, preservatives, wetting agents and the like, if necessary. Examples thereof include inorganic acids such as phosphoric acid and sulfuric acid, organic acids such as succinic acid and propionic acid, and complexing agents such as iminodiacetic acid and ethylenediaminetetraacetic acid. Further, colloidal silica, alumina sol and the like can be contained.

The pH of the cleaning agent of the present invention is preferably in the range of 3-6. When the pH is lower than 3, the silver image portion dissolves and the printing durability decreases, and when the pH is higher than 6, the stain on the non-image portion is difficult to remove.

The silver halide emulsions used in the lithographic printing plate of the present invention include silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodobromide, and silver iodobromide. Although silver chloride is mainly used (meaning silver chloride of 50 mol% or more) is preferable. The emulsion type may be either a negative type or a positive type. These silver halide emulsions can be chemically or spectrally sensitized as necessary.

Gelatin is preferably used as the hydrophilic colloid in the silver halide emulsion layer when preparing silver halide grains. Various gelatins such as acid-treated gelatin and alkali-treated gelatin can be used as the gelatin.
Further, those modified gelatins (for example, phthalated gelatin, amidated gelatin, etc.) can also be used. Further, hydrophilic polymer compounds such as polyvinylpyrrolidone, various starches, albumin, polyvinyl alcohol, gum arabic, and hydroxyethyl cellulose can be contained.

The aluminum support used in the present invention is a roughened and anodized aluminum plate, preferably the one described in US Pat. No. 5,427,889 is used. When the amount of the anodic oxide film is small, for example, 3.5 g / m ² or less,
g / m ² or less.

The physical development nucleus of the physical development nucleus layer used in the present invention may be one used in a known silver complex salt diffusion transfer method, for example, a colloid such as gold or silver, or a water-soluble salt such as palladium or zinc. Metal sulfide mixed with sulfide can be used. Various hydrophilic colloids can be used as the protective colloid. For details and manufacturing method,
For example, Focal Press, London New York (1972), Andre Lott and Edith
See Weide, "Photographic Silver Halide Diffusion Processes".

In the present invention, a water-swellable intermediate layer described in JP-A-3-116151 and a hydrophobic polymer described in JP-A-4-282295 are provided between a physical development nucleus layer and a silver halide emulsion layer. An intermediate layer containing beads may be provided.

[0031]

EXAMPLES The present invention will be described below with reference to examples, but is of course not limited thereto.

Example 1 An A1050 type aluminum plate strip having a width of 1030 mm and a thickness of 0.24 mm was moved at a processing speed of 13 m / min.
Immersed in a 4% aqueous solution of sodium hydroxide for 10 seconds, rinsed with water, immersed in an indirect power supply type electrolytic cell filled with 1.5% hydrochloric acid and 2% acetic acid at 30 ° C.
/ Dm ² , 50 Hz single-phase alternating current is passed for 30 seconds,
The surface was subjected to AC electrolytic surface roughening, washed with water, and then immersed in a 6% nitric acid aqueous solution at 70 ° C. for 10 seconds, desmutted, washed with water, and dried. Furthermore, the resultant was passed through 25% sulfuric acid and 20% sulfuric acid to carry out anodization, thereby obtaining an aluminum support having an anodized aluminum amount of 2.0 g / m ² .

A palladium sulfide nucleus solution was applied to these aluminum supports and then dried. The amount of nuclei contained in the physical development nucleus layer was 3 mg / m ² .

As a silver halide emulsion, alkali-treated gelatin was used as a protective colloid, and potassium hexachloroiridate (III) having an average particle size of 0.2 μm was added in an amount of 0.006 per mol of silver by a control double jet method.
mmol-doped silver chloroiodobromide emulsion (AgBr20
Mol%, AgI 0.4 mol%). Further, this emulsion was subjected to sulfur gold sensitization, and a red sensitizing dye was added in an amount of 3 per gram of silver.
mg was used for spectral sensitization.

A surfactant is added to the silver halide emulsion thus prepared, and the silver amount is 2 g / m ² (the gelatin amount is 2.3) on the aluminum support coated with the physical development nuclei.
g / m ² ) and dried to obtain a lithographic printing material.

A 633 nm red LD
An image was output by an output device using a laser as a light source, and then processed by a plate-making processor (SLT-85N automatic developing machine manufactured by DuPont) to prepare a lithographic printing plate. The plate-making processor includes a developing step (immersion at 21 ° C. for 10 seconds), a washing step (separating the emulsion layer with a scrub roller while spraying a washing liquid at 33 ° C. for 10 seconds), and a finishing step (21 ° C. 5 seconds shower) and a drying step. The water washing process of the plate making processor is carried out through a tank for storing 30 liters of the washing liquid, a unit for supplying the lithographic printing material from the tank to the lithographic printing material via a pump and peeling and removing the emulsion layer, and a filtration filter arranged outside the system from the tank. It is composed of a unit that circulates washing water.
As the filtration filter, a cylindrical 5 μm filter was used.

The following developing solution, washing solution and finishing solution were used. <Developer> Sodium hydroxide 30 g Polystyrene sulfonic acid and maleic anhydride copolymer (average molecular weight 500,000) 10 g Hydroquinone 15 g 1-Phenyl-3-pyrazolidinone 3 g Sodium sulfite 100 g Monomethylethanolamine 50 g 2-Mercapto-5-n-heptyloxa Sia sol 0.1 g 5 Mercapto 1 phenyltetrazole 0.8 g 5 Methylbenzotriazole 0.2 g Sodium thiosulfate 20 g Amino trimethylene phosphonic acid 7 g Calcium sulfate 1 g Water is added to adjust the total volume to 1 liter. The pH was adjusted to 13.3.

<Washing solution> 2-mercapto-5-n-heptyloxasiasol 0.5 g triethanolamine 20 g potassium bisulfite 6 g aminotrimethylenephosphonic acid 20 g proteinase 1 g Water is added to adjust the total amount to 1000 cc. The pH was adjusted to 7.4. Bioprolase AL-15 (bacterial proteinase, manufactured by Nagase Sangyo Co., Ltd.) was used as a protease.

<Finishing Solution> Phosphoric acid 100 g N-methylethanolamine 30 g 2-mercapto-5-n-hexyloxasitol 0.5 g polyphenylene glycol alcohol ether 90 g sodium nitrate 20 g arabic gum 50 g ethylenediamine tetraacetic acid 0.5 g proteinase 1 g Make up to 1000 ml with deionized water. The pH was adjusted to 5.4.

The printing plate prepared by the above operation was heated at 50 ° C. for 5 days by forcibly attaching a fingerprint to a non-image portion of the printing plate so as to easily cause printing stains. This printing plate was attached to a printing machine (Heidelberg MO: Alcolor water supply device; manufactured by Heidelberg), and printing was performed using New Champion Boku H ink manufactured by Dainippon Ink Co., Ltd. and a commercially available humidifier for PS plates. As a result, fingerprint-like ink stains occurred on the non-image area. Printing was interrupted, and the plate surface was wiped with a sponge containing the following cleaning agent. After that, printing was started again, and non-image areas were evaluated for ink stains. Table 1 shows the evaluation results.
Shown in

The ink stain was evaluated according to the following criteria based on the number of printed sheets where the ink stain occurred. ○: No ink stain is generated even when printing 10,000 sheets or more. Δ: Ink stain occurs on about 5,000 sheets. ×: Ink stain occurs on 1,000 sheets or less.

<Plate Cleaning Agent> 50 g of gum arabic 50 g of compound A 30 g of phosphoric acid (85% solution) 5 g of polyoxyethylene polyoxyfluorophenyl phenol polymer 50 g of butyltriglycol 60 g of limonene 100 g of 2-phenoxyethanol 50 g of sodium polyacrylate 10 g of water Adjust so that pH adjusted to 4.5.

[0043]

[Table 1] ────────────────────────────── Cleaning compound A fingerprint ink stain Remarks ──────── ────────────────────── 1. None × Comparison 2. Amino trimethylene phosphonic acid ○ The present invention 3. 2-phosphonopentane-1,2,4 ○ The present invention-tricarboxylic acid ──────────────────────────────

As shown by the above results, it can be seen that the present invention is clearly superior to the comparison in removing fingerprint stains.

Example 2 A printing plate produced in the same manner as in Example 1 was stopped during printing,
Leave it for one hour. When reprinting is started, spot-like ink stains called so-called oxidation stains occur. After the surface of the printing plate on which the oxidized stain was generated was wiped with a cleaning agent, reprinting was performed, and the removability of the oxidized stain was evaluated.

The cleaning agents used are shown below. <Sheet cleaning agent> 50 g of gum arabic 50 g of compound B 20 g of aminotrimethylenephosphonic acid 30 g of phosphoric acid (85% solution) 5 g of polyoxyethylene polyoxyfluorophenol perfluoropolymer 50 g of butyl triglycol 60 g of limonene 100 g of 2-phenoxyethanol 50 g of sodium polyacrylate 10 g of water Adjust to 1000 g with. pH adjusted to 4.5.

The evaluation criteria for the oxidized soil removal property are shown below.
Table 2 shows the evaluation results. ○: Oxidized dirt can be completely removed △: Oxidized dirt can be partially removed ×: Oxidized dirt cannot be removed

[0048]

[Table 2] 洗浄 Detergent Compound B Oxidized dirt removal ────────────────── ─── 1. None × 2. Magnesium sulfate △ 3. Magnesium nitrate ○ 4. Calcium nitrate ○ 5. Sodium nitrate △ ─────────────────────

From the above results, it is clearly advantageous to use an alkaline earth metal in combination with respect to the removability of oxidized soil, and it is preferable to use nitrate.

Embodiment 3 Using a printing plate prepared in the same manner as in Embodiment 1, Embodiment 2
The printing plate whose surface was wiped with the cleaning agent 4 described in 1) was placed for one week, and after printing, 100,000 sheets were reprinted, and the ink stain and printing durability were evaluated. As a result, no ink stain and poor printing durability occurred even in a one-week printing plate.

Example 4 The pH of the solution of the plate surface cleaning agent 4 used in Example 2 was adjusted to 2 to 8 using caustic soda and sulfuric acid, and the oxidized soil removal property was tested in the same manner as in Example 2. With respect to printing durability, the number of prints until good printing could not be performed was evaluated. Table 3 shows the results.

[0052]

[Table 3] ────────────────────────────── Detergent Liquid pH Oxidized dirt-removing property Printing durability ───── ───────────────────────── 1. 2.0 ○ 50,000 sheets 3.0 ○ 100,000 sheets or more 4.0 ○ 100,000 sheets or more 5.0 ○ 100,000 sheets or more 6.0 ○ 100,000 sheets or more 7.0 △ 100,000 sheets or more ──────────────────────────────

The above results show that the pH of the plate surface washing solution is preferably in the range of 3 to 6.

[0054]

According to the present invention, a silver image of a lithographic printing plate utilizing image silver as ink acceptability is not adversely affected.
In addition, a plate surface cleaning agent excellent in cleaning effect and desensitizing effect on oxidized dirt and corrosive dirt peculiar to aluminum lithographic printing plates can be provided. In addition, it has become possible to provide a method that does not adversely affect printability even in a plate placed for several days after the plate surface cleaning operation, which has been eagerly desired in the present invention.

Claims (5)

[Claims] 1. A plate cleaning solution for a lithographic printing plate utilizing image silver as ink receptivity, comprising at least one organic phosphonic acid compound. 2. The plate surface cleaner according to claim 1, which is used for a lithographic printing plate utilizing a silver complex salt diffusion transfer method having at least a silver halide emulsion layer on an anodized aluminum support. 3. The plate surface cleaning agent according to claim 1, further comprising an alkaline earth metal. 4. The plate surface cleaning agent according to claim 1, wherein the alkaline earth metal is magnesium or calcium. 5. The plate surface cleaning agent according to claim 1, which further has a pH of 3 to 6.