JPH046943B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Field of Application The present invention provides an offset printing plate in which a silver image is used as ink receptive, by converting unnecessary portions of the silver image formed on the printing plate into hydrophilic ones. The present invention relates to an image modifying agent for offset printing plates that eliminates ink receptivity, and more specifically, it is an image modifying agent for eliminating ink receptivity for offset printing plates. It is concerned with making the surface completely hydrophilic and eliminating ink receptivity without causing any damage to the printing properties, base material, etc., by appropriately treating the surface with a specific treatment agent. Since such processing is usually called "correction" in the printing field, the present inventors will follow this term hereinafter. Furthermore, the processing agent used in the correction operation will be referred to as a "correction agent." (B) Prior art and its problems In general, areas that require correction that occur in printing original plates manufactured by photolithography include those that already exist in the copied original, those that occur during exposure,
and others caused by non-uniform development processing. This means, for example, if there are unwanted images in the reproduced original, if there are dust and dirt particles, fingerprints or other stains, or if the original is made by gluing together different originals, Shadows may appear during exposure. In order to obtain good printed matter, all of these points must be corrected during the plate-making and printing stages. Generally speaking, correction operations are essential, and it is desirable to be able to make necessary corrections at any stage of the plate-making and printing processes. A number of attempts have been made to correct unwanted images in offset printing plates by utilizing the silver image as an ink receptivity. For example, JP-A-48-92101, JP-A-51-21901,
Compounds having a mercapto or thione group and a hydrophilic group described in 54-53002 and 1982-9661 are capable of making silver images hydrophilic with a reliable and almost instantaneous reaction. However, it has drawbacks such as having a strong odor, having an adverse effect on the human body due to its strong acidity, and lacking in storage stability, and improvements are desired. In addition, the correction agent containing red blood salt or FDTA metal salt and thiocyanate described in JP-A No. 48-41808 has problems with pollution, and the correction agent may be gradually removed by printing after correction. It has drawbacks such as recovery of ink receptivity, resulting in scumming, and lack of storage stability. (C) Purpose of the invention The purpose of the present invention is to have no adverse effects on the human body or the environment;
To provide a correcting agent for offset printing plates that can be quickly and reliably corrected, can maintain hydrophilicity for a long period of time after correction, and has excellent storage stability of the correcting agent solution. (D) Structure of the Invention The above object of the present invention is to provide organic acid ferric complex salts and
This was achieved with a modifier consisting of soluble bromide or/and soluble iodide in an amount of 0.3 moles or more per mole. A preferred example of the organic acid ferric complex salt is an aminopolycarboxylic acid ferric salt, but phosphonic acid ferric salts and the like can also be used. Organic acid ferric complex salts are usually used in the form of complex salts, but ferric salts such as ferric sulfate, ferric chloride, ferric nitrate, ferric ammonium sulfate, and ferric phosphate A ferric ion complex salt may be formed in a solution using diiron or the like and an organic acid. The aminopolycarboxylic acid second complex salt is a complex of ferric ion and aminopolycarboxylic acid or a salt thereof. Typical examples of aminopolycarboxylic acids and their salts include ethylenediaminetetraacetic acid (EDTA),
EDTA disodium salt, EDTA diammonium salt, EDTA tetra (trimethylammonium)
salt, EDTA tetrapotassium salt, EDTA tetrasodium salt, EDTA trisodium salt, diethylenetriaminepentaacetic acid, diethylenetriaminepentaacetic acid pentasodium salt, ethylenediamine-N-(β-oxyethyl)-N,N',N'-
Triacetic acid, ethylenediamine-N-(β-oxyethyl)-N,N',N'-triammonium salt of triacetate, propylenediaminetetraacetic acid, propylenediaminetetraacetic acid disodium salt, nitrilotriacetic acid, nitrilotriacetic acid trisodium salt,
Examples include cyclohexanediaminetetraacetic acid, cyclohexanediaminetetraacetic acid disodium salt, iminodiacetic acid, dihydroxyethylglycine, ethyl etherdiaminetetraacetic acid, ethylenediaminetetrapropionic acid, and the like. Typical examples of phosphonic acids or salts thereof include diethylenetriaminepentamethylenephosphonic acid, cyclohexanediaminetetramethylenephosphonic acid, triethylenetetraminehexamethylenephosphonic acid, glycol ether diaminetetramethylenephosphonic acid, and 1,2-diaminopropanetetramethylene. Phosphonic acid, methylimino dimethylene phosphonic acid, 1,3-diaminopropane-
Examples include 2-oltetramethylenephosphonic acid and ethylenediaminetetramethylenephosphonic acid. Any combination of these organic acids and the above-mentioned ferric salts can be used as an organic acid ferric complex salt. Organic acid ferric complex salts are used to oxidize silver images used for ink receptivity, and generally oxidize silver images to which mercapto compounds, etc., which are used to enhance lipophilicity, are strongly adsorbed. It is recommended to use a relatively large amount. Generally 0.05 to 1.0 mol, preferably 0.1 to 1.0 mol per corrector solution
A range of 0.5 mol is preferable, and two or more types may be combined. Soluble bromide, soluble iodide means bromide and iodide that are soluble in the solvent of the corrector solution. Usually, water is used as part or all of the solvent, so water-soluble bromides or iodides such as potassium bromide, sodium bromide, ammonium bromide, potassium iodide, and ammonium iodide are specific examples. Can be mentioned. It is thought that these bromides and iodides react with the silver image (which has become silver ions) oxidized with an organic acid ferric complex salt, change into silver halide, and become hydrophilic. However, the effect of the present invention is not observed with water-soluble chlorides (eg, sodium chloride). Particularly preferred are water-soluble bromides. The amount of soluble bromide or soluble iodide is required to be 0.3 mol or more per modifier solution, preferably 0.5 mol or more, which is the amount that can be dissolved.
Two or more types may be combined. The correction agent of the present invention can be used as a correction fluid using water, various alcohols, or a mixed solvent thereof. It is also possible to use a so-called correction pen method. The concentration of the modifier ranges from about 5 to about 50%, preferably from about 10 to about 40% by weight of the organic acid ferric complex salt and soluble bromide and/or iodide. In addition, elements for making the liquid viscous, such as carboxymethyl cellulose, polyvinyl alcohol, and glycerin, and elements for coloring the liquid, such as dyes, organic or inorganic pigments, can be included, but these are essential elements. isn't it. Furthermore, fine particle powder as described in JP-A-51-21901 may also be included. The modifier of the present invention is stable and odorless. In addition, it can be corrected quickly and completely, and even if it is rubbed strongly after correction, ink will not get on the correction area.
Therefore, a larger number of sheets can be printed. As an offset printing plate using the silver image of the present invention for ink receptivity, Japanese Patent Publication No. 48-30562,
Japanese Patent Application Publication No. 53-21602, U.S. Patent No. 3721559,
In addition to No. 3,490,905, offset printing plates having silver halide images that are ink receptive are included, such as those disclosed in U.S. Pat. (E) Examples Example 1 Other than containing 1.0 g/m ² of hydroquinone in the physical development nucleus layer of the offset printing plate (Plate No. 3) described in Example 1 of JP-A-53-21602. A lithographic printing material was prepared in the same manner. After image-wise exposure of the lithographic printing material, transfer development was carried out by immersing it in a transfer developer having the following formulation at 30°C for 30 seconds, and subsequently in a stop solution having the following formulation for 30 seconds (at 25°C ), the excess liquid was removed by immersion and squeezing, and the material was dried under atmospheric conditions. A correction solution was prepared using the compounds and amounts shown in Table 1 below as a correction agent, and the portions of the lithographic printing plate to be corrected were wiped with the correction solution soaked in absorbent cotton. [Transfer developer] Water 700ml Potassium hydroxide 20g Anhydrous sodium sulfite 60g Potassium bromide 0.5g 2-mercaptobenzoic acid 10 mmol 3-mercapto-4-acetamide-5-n-
Heptyl-1,2,4-triazole 0.15g 2-methyl-2-amino-1-propanol
Add 10g water to make 1. [Stopping liquid] Water 2 Citric acid 10g Sodium citrate 35g The printing plate thus obtained was mounted on an offset printing machine ABC 350CD (trade name ABDick350CD), and the plate surface was wiped with a liquid called prescription (E). Post-printing was done. The temperature in the printing room was 22°C and 60% humidity. [E] Water 400ml Citric acid 1g Sodium citrate 3.5g 2-Mercapto-5-heptyl-1,3,5oxadiazole 0.5g Ethylene glycol 50ml Corrections for printing the 20th, 2000th and 5000th sheets The ink receptivity (background staining) was evaluated and the results are shown in Table 2.

【table】

【table】

[Table] Example 2 Example 1 was followed except that the correction fluid of Example 1 was filled into a felt tip pen. The results were the same as in Example 1. Example 3 Example 2 was repeated using the correction fluids in Table 3 below.

【table】 The results are shown in Table 4.

[Table] (F) Effects of the Invention The correction agent of the present invention is safe, allows quick and reliable correction, has a long-lasting effect, and has excellent liquid stability.

Claims (1)

[Claims] 1. A printing plate comprising a correcting agent for an offset printing plate that utilizes a silver image as ink receptivity, comprising an organic acid ferric complex salt and 0.3 mol or more of soluble bromide and/or soluble iodide per unit. correction agent.