JPH06266114A - Retouching agent for printing plate - Google Patents

Abstract

PURPOSE:To provide a retouching agent for the printing plate, by using which the retouched part and its peripheral part can be provided with ink receptivity so as not to generate greasing in these parts by adding iodine and a soluble bromide and/or a soluble iodide and a specific compound to the retouching agent. CONSTITUTION:The retouching agent contains iodine and a soluble bromide and/or a soluble iodide and a compound contg. at least one mercapto or thionic group and at least one hydrophilic group in the same molecule. Examples of the water soluble bromide or iodide are sodium bromide, sodium iodide, etc., and the required amount of any one of these salts is at least 0.3mol, preferably from 0.5mol per liter of the retouching agent to the solublity limit. Examples of the compounds contg. at least one mercapto or thionic group and at least one hydrophilic group in the same molecule are 2-mercaptoethanol, alpha- thioglycerol, thioglycolic acid and alpha-mercaptopropionic acid, etc. The amount of this compound to be added to the retouching agent of 0.1 to 10g per 100ml of the retouching agent is sufficient and that of 0.5 to 5g per 100ml of the retouching agent is preferred.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset printing plate that utilizes a silver image as an ink-receptive material, and a silver image correcting agent formed on the printing plate. By appropriately surface-treating unnecessary portions on the offset printing plate formed by a conventional method with a specific treating agent at any stage in the printing process, there is no particular problem with printing characteristics, equipment, etc. The present invention relates to completely hydrophilizing and eliminating ink acceptability. Usually, in the printing field, such a process is called "correction", and the present inventors will follow it. Further, the processing agent used for the correction operation will be referred to as "correction agent".

[0002]

2. Description of the Related Art In general, a printing original plate produced by a photoengraving method needs to be corrected in such a manner that it already exists in a copy original, that which occurs during exposure, and other uneven development processing steps. There are things caused by.

That is, for example, an unnecessary image is generated in a copy original, or when an original made by pasting various originals is used, a shadow is projected at the time of exposure. In order to obtain a good printed matter, all of these areas must be corrected at the stage of plate making and printing. Generally speaking, the correction operation is indispensable, and it is desirable that the necessary correction can be performed at any stage of the plate making and printing process.

Further, stability of the liquid over time is also required. The stability with time is required to be that before the correction agent is applied to the printing plate and that after the correction agent is applied. The stability after coating is required to be stable with time until printing, and that the initial erasability is not lost even if printing is started and then interrupted and printing is restarted.

Many attempts have been made as a method of correcting unwanted images in offset printing plates which utilize a silver image as the ink receptivity. For example, JP-A-48-92101 and JP-A-51
21901, 54-53002, 59-96
The compounds having a mercapto or thione group and a hydrophilic group described in 61, etc. can surely and almost instantaneously hydrophilize a silver image. However, these compounds have drawbacks such as a strong acid effect on the human body and lack of stability over time which is considered to be mainly caused by oxidation. Further, JP-A-58-134639 and JP-A-63-1
15171 also describes a corrector using iodine and soluble bromide and / or soluble iodide ion.
However, these correction agents gradually recover the ink acceptability due to printing after correction and cause background stains, or
When a long time elapses after the correction, the repaired portion becomes ink-receptive, and there is a defect that scumming occurs and there is a demand for improvement.

[0006]

DISCLOSURE OF THE INVENTION It is an object of the present invention to have drawbacks of a corrector using iodine and soluble bromide and / or soluble iodide ion, which is used for a lithographic printing plate utilizing a silver image as an ink receiving property. That is, it is an object of the present invention to provide a correction agent that improves the ink acceptability of the repaired portion due to the passage of time after repairing, or that the repaired portion and its surroundings become ink-receptive and cause smearing.

[0007]

The above object of the present invention is to provide iodine and soluble bromide and / or soluble iodide and a compound having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule. Was added to the corrector.

The amount of iodine used is preferably 1 to 20% by weight.

Soluble bromide and soluble iodide mean bromide and iodide which are soluble in the solvent of the corrector solution. Usually, water is used as a part or all of the solvent, so that a water-soluble bromide or iodide such as sodium bromide, potassium bromide, ammonium bromide, sodium iodide, potassium iodide, or ammonium iodide is used. As a specific example. The amount of soluble bromide or soluble iodide must be 0.3 mol or more per liter of the correction agent solution, and preferably 0.5 mol to a soluble amount. You may combine 2 or more types.

The compound having a mercapto group or thione group and at least one hydrophilic group in the same molecule is
The following compounds may be mentioned. 2-mercaptoethanol, hydroxymercaptan such as α-thioglycerol, thioglycolic acid, α-mercaptopropionic acid, β-mercaptopropionic acid, α-mercaptobutyric acid, β-mercaptobutyric acid, γ-mercaptobutyric acid, α-mercaptocaproic acid , Mercaptoalkylcarboxylic acids such as cysteine and derivatives thereof, 2-mercaptoethylsulfonic acid, mercaptopropylsulfonic acid, 2,3-
A mercaptoalkyl sulfonic acid such as dimercaptopropene sulfonic acid and a compound further containing an aromatic ring or a heterocycle are also effective. For example, p-mercaptobenzoic acid,
p-mercaptobenzenesulfonic acid, 2-mercaptobenzimidazole-5-sulfonic acid, 2-mercaptobenzothiazole-5-sulfonic acid, 2-mercapto-3
-Methylbenzothiazole-5-sulfonic acid, 2-mercaptobenzoxazole-5-sulfonic acid, 2-carboxymethylmercapto-5-mercapto-1,3,4
-Thiadiazole, etc.

The amount of the above compound added to the correction agent of the present invention is 0.1 to 10 g per 100 ml, and preferably 0.5 to 5 g.

The correcting agent of the present invention can be used as a correcting agent using water, various alcohols or a mixed solvent thereof. Further, an element for making the liquid viscous such as carboxymethyl cellulose, polyvinyl alcohol, glycerin, etc., or a dye, an organic or inorganic pigment, etc. can be contained as an element for coloring the liquid, but these are essential. Is not an element of.

Further, a fine particle powder as described in JP-A-51-21901 can be contained.

[0014]

【Example】

Example 1 In the same manner as in Example 1 of JP-A-53-21602, except that the physical development nucleus layer of the offset printing plate (plate No. 3) contained 1.0 g / m 2 of hydroquinone. A lithographic printing material was prepared. The lithographic printing material was imagewise exposed and then developed with the following silver complex salt diffusion transfer developer at 30 ° C. for 30 seconds.

<Transfer Developer> 700 ml of water 20 g of potassium hydroxide 50 g of anhydrous sodium sulfite 50 g 2-mercaptobenzoic acid 1.5 g 2-methylaminoethanol 15 g Water is added to make 1 liter.

After the development treatment, the original plate is passed between two squeezing rollers to remove excess developer, and immediately treated with a neutralizing solution having the following composition at 25 ° C. for 20 seconds, and the squeeze roller is used to remove the excess liquid. Removed and dried at room temperature.

<Neutralization liquid> Water 600 ml Citric acid 10 g Sodium citrate 35 g Colloidal silica (20% liquid) 5 ml Ethylene glycol 5 ml Water is added to make 1 liter.

A correction liquid was prepared by using the compounds and amounts shown in the following correction liquid as a correction agent, and the portion to be corrected of the lithographic printing plate was wiped with the correction liquid shown in Table 1 below.

[0019]

[Table 1]

The printing plate thus obtained is subjected to an offset printing machine ABDick 350CD.
The plate surface was wiped with an oil-sensitizing solution having the following formulation, and printing was performed on 500 sheets. After that, the ink on the plate surface was dropped, and after 1 hour, the plate surface was wiped again with an oil-sensitizing solution to print 500 sheets. The printing room had a temperature of 22 ° C. and a humidity of 60%.

<Sensitizer> Water 400 ml Citric acid 1 g Sodium citrate 3.5 g 2-Mercapto-5-heptyl-1,3,5-oxadiazole 0.5 g Ethylene glycol 50 ml

The results of the correctability are shown in Table 2.

[0023]

[Table 2] The modified evaluation shows that 5 indicates complete erasability and 1 indicates almost no erasability. A value of 3 or more means that the product can withstand.

As can be seen from Table 2, the corrective agent A of the present invention,
It can be seen that D shows sufficient erasability at the initial stage and even after 1 hour, but B and C cannot obtain sufficient erasability. Example 2

Example 1 was followed except that the correction liquid of Example 1 was filled in a felt pen and used. The result was excellent as in Example 1.

Example 3 Example 1 was followed except that potassium bromide was used in place of the potassium iodide of Example 1. The result was excellent as in Example 1.

[0027]

The corrective agent of the present invention enables rapid and reliable correction, has a long-lasting effect, and is excellent in liquid stability.

Claims (1)

[Claims] 1. A correction agent for an offset printing plate, which utilizes a silver image as an ink receiving property, comprising iodine and soluble bromide and / or soluble iodide and at least one mercapto group or thione group and at least one hydrophilic group in the same molecule. A correction agent for a printing plate comprising a compound having a functional group.