JPS60200256A - Treatment of photosensitive lithographic plate - Google Patents

Abstract

PURPOSE:To favorably erase unnecessary image parts by using an erasing soln. contg. an aliphatic multivalent carboxylic acid or aliphatic oxycarboxylic acid as an erasing soln. for erasing unnecessary image parts of a printout image. CONSTITUTION:A photosensitive lithographic plate obtained by forming a photosensitive layer contg. an o-quinonediazide compd. or the like on a support is imagewise exposed to form a printout image. A good image freed of unnecessary image parts is obtained by spreading an erasing soln. contg. an aliphatic multivalent carboxylic acid, such as malonic or succinic acid, or aliphatic oxycarboxylic acid, such as lactic or citric acid, in an amt. of 0.1-10wt% on unnecessary image parts, such as register marks, and developing them with a developing soln., such as an aq. soln. of NaOH or monoethanolamine.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a photosensitive lithographic printing plate (hereinafter referred to as a PS plate).
In particular, the present invention relates to a method for processing a PS plate, which is characterized in that after the PS plate is imagewise exposed, an erasing liquid is applied to unnecessary image areas, and then developed with a developer.

[Prior art]

Conventionally, when processing a 28-plate, especially a positive 18-plate, after exposing it to the original film and developing it with a developer, and then washing with water, unnecessary gaps (adhered to the film or the glass of the printing frame) are removed. An erasing liquid was applied to the dirt (dust, film edge marks, register marks, etc.), washed with water, and then gummed before printing.

Incidentally, in recent years, systems that omit the post-development washing step have been developed for the purpose of low cost and low pollution.

For example, Japanese Unexamined Patent Application Publication No. 1997-01000 discloses a plate-making method in which an image-exposed PS plate is developed and immediately gummed without washing with water. Furthermore, Tokukai Akira! j-／／
Publication j04Aj discloses a plate-making method in which images are exposed, washed with water, and then gummed.

However, even in this system, when erasing is required, the steps of applying an erasing liquid, washing with water, and gumming are required after the rinsing treatment, resulting in an increase in the number of work steps.

The present inventor has previously discovered that the plate-making process can be simplified, resulting in cost savings and
As a new labor-saving processing method for 28 plates, unnecessary image areas are detected by examining the printed image that appears after image exposure, and after applying erasing liquid to these areas, this erasing liquid is removed by washing with water. Regarding the method of processing with a developing solution, and the erasing solution used therein, it is preferable to use an erasing solution that contains an alkali-soluble acidic substance (especially phosphoric acid) and has a viscosity of λθOcp or less. (See Japanese Patent Application No. 27J).

By the way, in the above-mentioned external processing method using a positive type 28 plate, if an alkali-soluble eraser that does not contain acidic substances is applied to unnecessary image areas and developed, the eraser must be dissolved once before development. During this phenomenon, the photosensitive layer that had been exposed to the photosensitive layer is re-adsorbed onto the surface of the support. Furthermore, it is difficult to apply the erasing liquid only to unnecessary image areas (this is the unexposed area), and the erasing liquid also applies to the surrounding non-image area (this is the exposed area). Because of this, both the photodecomposed diazo compound in the exposed area and the undecomposed diazo compound in the unexposed area are dissolved and mixed by the erasing solution, and when an alkaline developer is applied thereto, an alkali-insoluble diazo cup is formed. A ring product is formed which inhibits the development removal of the exposed portions of the photosensitive layer as well as the unwanted image areas. On the other hand, when using an erasing liquid containing an alkali-soluble acidic substance,
It is possible to prevent the photosensitive layer dissolved by the erasing liquid from re-adhering to the support surface during development, and to remove the diazo coupling product from the support surface before the diazo coupling product is generated and the development is inhibited. Therefore, desired unnecessary image areas and non-image areas can be removed using a developer. In particular, when phosphoric acid is used as an alkali-soluble acidic substance, especially in the case of a positive 28 plate using an aluminum support, the phosphoric acid may etch the aluminum surface to some extent, resulting in unwanted images from the surface of the aluminum support. This makes it easier to develop and remove parts.

However, as a result of further studies, it was discovered that the following new problems occur when phosphoric acid is used.

In other words, if there are a large number of erased areas, the time required for erasing will be long (but if phosphoric acid is used, the components of the photosensitive layer, especially the areas coated with the erasing liquid, will be removed after being left for a long time of about io minutes or more). It was found that the desired erasure was not achieved because the dye was adsorbed onto the aluminum surface and the diazo coupling product was stuck. This occurred noticeably in the case of type 28 edition.

゛ Contamination of non-image areas by dyes like this occurs even more prominently in positive-working 82 plates that use a support made of anodized aluminum plate undercoated with a water-soluble polymer such as carboxymethyl cellulose. This unexpected result was obtained.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide an improved erasing liquid that can be used in a processing method in which after imagewise exposing an H1ps plate to form a printout image, the erasing liquid is applied to unnecessary image areas and then developed. It's about doing.

Another object of the present invention is to prevent dyes, photosensitive compositions, diazo coupling products, etc. from adhering to the surface of the support in the erasing section (to prevent dyes, photosensitive compositions, diazo coupling products, etc. The goal is to provide liquid.

Furthermore, another object of the present invention is that even if the erasing solution applied to the unnecessary image area is left to stand for a long time and then developed, the dye, photosensitive composition, and vocal diazo coupling product are removed. It is an object of the present invention to provide an erasing liquid suitable for the above-mentioned processing method, which does not adhere to the surface of the support in the erased area.

As a result of various studies, the inventors of the present invention have found that the present invention can be achieved by using an erasing liquid containing at least seven carboxylic acids selected from the group consisting of aliphatic polycarboxylic acids and aliphatic oxycarboxylic acids as alkali-soluble acidic substances. I found that the purpose was achieved.

The method for processing plate 28 according to the present invention and the erasing liquid used therein will be explained in detail below.

As the PS plate used in the present invention, one commercially available as a normal positive PS plate can be used, but since it is necessary to detect unnecessary image areas after exposure, it is necessary to detect discoloration or color cumulative density change due to exposure. It is advantageous that the value is large. Suitable for positive type 28 plates, which inevitably have many erased areas. The 0-quinone diazide compound used as the photosensitive layer of positive-type 28 plates originally has a pale yellow color and becomes colorless when exposed to light, but this is extremely weak, so in recent years many positive-type 28 plates have been It is made to show a change in color or color density, allowing unnecessary image areas to be detected immediately after image exposure. Specifically, Fuji Photo Film PS version, FPD, FPD-V, FPS, PP
P, etc., Konishi Roku Kogyo's SLP%SMP, SXP, Curry's P7S, P3S, Hawthorn Alpha's Arinbik, Polychrome's GP''-, s, GP-j, and many others. Most of these plates are made by coating a positive photosensitive material containing 0-quinonediazide on an aluminum support that has been grained and then anodized. It is also possible to use materials that have been immersed or coated with a water-soluble polymer such as carboxymethyl cellulose.

These plate materials are first brought into complete contact with the film and then exposed to an ultraviolet light source.

An erasing liquid is applied to unnecessary image areas (dust-covered areas, film edges, register marks, etc.) on the exposed plate material to erase them. After erasing, development is carried out with a developer without removing the erasing solution or after removing it by washing with water if necessary.

The developer is usually a developer commercially available as a developer for positive PS plates or a developer containing sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate, dibasic sodium phosphate, or Inorganic alkaline agents such as ammonium triphosphate, ammonium diphosphate, sodium metasilicate, sodium bicarbonate, aqueous ammonia, etc., aqueous solutions of organic alkaline agents such as yamonoethanolamine or jetanolamine, etc. can be used.

The developing method may be an automatic developing machine having both a developing part and a gum part, a normal automatic developing machine having a water washing part, dish developing, or manual developing.
In order to fully utilize the effects of the present invention, the best method is to perform direct development without removing the erasing liquid using an automatic developing machine, especially a developing machine that has both a developing and a gum section, and to remove the erasing liquid using the developing solution. .

The erasing liquid used in the present invention contains at least one carboxylic acid selected from aliphatic polycarboxylic acids and aliphatic dicarboxylic acids. Preferred aliphatic polycarboxylic acids include, for example, malonic acid, succinic acid, etc.
Further, preferable aliphatic Φ dicarboxylic acids include lactic acid,
These acids include glyceric acid, gluconic acid, malic acid, tartaric acid, mucic acid, (citric acid, etc.). Neutralized versions of these carboxylic acids can also be used.
It is suitable to contain -10 deuterons, and 0.3 to 1
% by weight is more preferred.

The viscosity of the erasing liquid used in the present invention is preferably less than or equal to cooc,p.

That is, an erasing liquid having a viscosity higher than 00c;p is
When the photosensitive layer of a PS plate is coated on a desired part and then passed through an automatic processor without being removed, the eraser is compressed and spread by the first roller of the automatic processor, and erased in the developing direction. In contrast to poor development, especially in the later parts, if the viscosity is less than 00t,p, the spread eraser can be easily removed by a developer. However, if the viscosity is higher than 200 cp, it will be difficult to remove, so it will be necessary to wash it off with water before development.

One form of the erasing liquid in the present invention contains the above-mentioned carboxylic acid and is composed of a water-soluble solvent, and the other form contains the above-mentioned carboxylic acid and is insoluble in water. A solvent made by emulsifying or dispersing or solubilizing a solvent in water can be used.

When erasing with the present invention, it is sufficient to dissolve the unnecessary image with a solvent and then replace it with a developer. However, if it is difficult to replace the image, that is, if the image is made of a water-insoluble solvent, the part that has been spread out with a roller may be removed. The solvent delays development, resulting in poor development, and in addition, in the erased area, the developer-insoluble components that were once dissolved are re-allocated. Since it is easily adsorbed onto the surface of the nium support, it is easy to cause defective erasing. Therefore, as methods for easily replacing the developer, one is to use a water-soluble solvent, and the other is to emulsify or solubilize a water-insoluble solvent in water. is to use.

As water-soluble solvents, those that dissolve the photosensitive layer can be used, including alcohols, ketones, glycols, lactones,
Esters and others include methanol, ethanol, acetone, methyl ethyl ketone, ethylene glycol monomethyl ether, r-butyrolactone, dimethyl formamide, and the like. These solvents can be used alone or in combination of two or more, but the effect of adding carboxylic acid can be improved by adding 1-21% by weight of water based on the total solvent content of the erasing solution. I can do it.

Similarly, it is necessary to dissolve the photosensitive layer for water-insoluble pigments.
Examples of the medium include cyclohexanone, butyl acetate, benzyl alcohol '7C, etc., and these can be used as anionic surfactants or nonionic surfactants. Dicarboxylic acid salts, primary higher alcohol sulfate ester salts, primary higher alcohol sulfate ester salts, primary alcohol sulfate salts,
Sulfonates, λ-class alkyl disulfonates, higher alkyl disulfonates, sulfonated fats and fatty acid salts, sulfonated higher fatty acid salts, higher alkyl phosphate ester salts, glycerin esters of higher fatty acids, glycols of higher fatty acids - Emulsifying and dispersing or solubilizing esters, hantaerythritol esters of higher fatty acids, sucrose esters of higher fatty acids, sorbitan and mannitan esters of higher fatty acids, etc. can be performed in an aqueous solution. The water-insoluble solvent should be between 20
It is preferable to include 10% by weight of the surfactant and ij/-10% by weight of the surfactant. These solvents, surfactants, and acidic substances can be used alone or in combination.

Various compounds and dispersants can be dissolved or dispersed in these erasing liquids as necessary. For example, dyes and pigments for coloring purposes, surfactants (e.g. fluorine surfactants) for coating on plates, prevention of spreading, prevention of drying, polymerized compounds, fine particles of silicon dioxide, etc. There is.

Such erasing liquid can be applied onto the plate 1c using a brush or IT brush, or it can be stored in a felt container for marking and applied. Further, it may be removed by washing with water before the development, or may be removed at the same time as development without being removed.

It is preferable that the plate material developed as described above is made into a printing plate by gumming after washing with water or by gumming immediately after development, but gumming may be omitted if desired. You can also do it. Commercially available gum liquids can be used. If you want to gum up the developing machine immediately, use JP-A-1-IOjt! rI issue and the same zt-17Jt9! The plate surface protective agent described in the above issue is preferred, and can be processed using an automatic developing machine that does not require a water washing step. In addition, in the case of burning processing, Tokukai Sho! ! -//! 0 hiro! After development, it is treated with an aqueous solution of a surfactant as described in the issue, or after washing with water, it is treated with a burning surface preparation solution as described in JP-A-Shozt-3aooi@, followed by burning and printing. You can also do that.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that *ti indicates weight tlj unless otherwise specified.

Examples 1 to 4 and Comparative Examples a''i Eraser liquids 1 to 4 (Examples) and a to i (Comparative Examples) having the following compositions were prepared.

Erasing liquid l Erasing liquid 2 (citric acid) (tartaric acid) ■ OOH Erasing liquid 3 Erasing liquid 4 (di-malic acid) (malonic acid) ■ OOH Erasing liquid a Erasing liquid b (phosphoric acid (1j aqueous solution)) (acetic acid) )13PO4ct-t3COOH Eraser C Eraser d (Trichloroacetic acid) (Propionic acid) CC/! 3CO
OHCH3CN 2COOH Erasing liquid e Erasing liquid f (phthalic acid) (Salicylic acid) Erasing liquid g Erasing liquid h (Gallic acid) (Levulinic acid) Erasing liquid l (No addition) 0.3mm thick aluminum plate <Material 1ozO) After dyeing with Triclean and degreasing, use a nylon brush and ≠00
The surface of this board was sand-grained using a mesh water suspension and thoroughly washed with water.
Etching was carried out by immersing it in an aqueous sodium hydroxide solution for 2 seconds, washing with water, and then immersing it in 20% nitric acid for 20 seconds and washing with water. The amount of etching on the grained surface at this time is approximately 3
After forming a 97nh'' oxide film, it was washed with water and dried (Support A).

Moreover, 0.3! %
After applying the aqueous solution with a roll coater, it was air-dried. At this time, the solid content t after dry application is approximately /! In9/m2 (Support B). Apply the following photosensitive solution to each of the supports A and B that have been treated in this way! 1.1000
A positive type Ps plate and B were obtained by drying the C plate for a minute. The coating amount after drying is J, 41~J, jJil/m2
Met.

Photosensitive liquid Naft life non-/, Codiazide number one! - ester compound of sulfonyl chloride and pyrogallol-acetone resin (as described in Example 1 of U.S. Pat. No. 3, tJ!, 702). y Cresol-Formaldehyde Resin J, 009 t-Phthylphenol e-Formaldehyde Resin (U.S. Patent No. μ).

3. o, o, tg Naphthogyf non-7, cordiazide 1 μm sulfonyl chloride)" 0,0217 Co (P
-methoxystyryl)-da,bu-bis(trichloromethyl)-8-triazine. , 039 Oil Blue #403 (Oil-soluble blue dye made by Orient Chemical Industries) 0.0g Methyl ethyl ketone rg λ-methoxyethyl acetate) /j fl 30 amperes when these positive type 28 plates are in close contact with the film original. Exposure was performed using a carbon arc lamp from a distance of 70 cm. Discoloration occurred in the exposed areas (non-image areas) of the photosensitive layer, and the difference in optical density from the unexposed areas was 1fJO020. Apply each erasing solution shown above to the unnecessary image area of this plate, and without washing it with water, add developer DP-J (diluted with water/t) to a PS processor rooE manufactured by Fuji Photo Film ■. Gum FP (diluted with water) was charged and a development-gumming process was performed. At this time, the developing solution should be a new developer with less processing fatigue, and an over-replenished fatigued solution that tends to cause diazo coupling (replenisher DP-JR (replenisher DP-JR with water to maintain sensitivity).
After processing a 1 m2/l plate while replenishing the diluted solution, the difference in optical density was 0.1 compared to the fresh solution! DP-3 to increase the sensitivity of the step tablet by one step
Rt supplemented solution]. Furthermore, since there were many erased areas, it took 20 minutes to erase, but immediately after erasing and in the areas left for 20 minutes, contamination with the dye in the erased areas and occurrence of fixation of the diazo coupling product were visually judged. It is often difficult to distinguish between the two as they can occur at the same time, but the former is colored blue and the latter colored red, so we used these colors to distinguish them.

In the case of poly(), there was dye staining and fixation of the coupling product in the area where the unnecessary image area was, but if phosphoric acid was used and the area was left for more than 20 minutes, the erasing liquid was not applied. Dye staining occurred in both the unnecessary image area and the surrounding non-image area.Table 1 summarizes these results.

In the amount of erasing liquid to which no acid was added, dye generation and coupling product fixation occurred. This is thought to be the result of a combination of various causes, such as re-adsorption of the photosensitive composition in the photosensitive layer coated with the eraser onto the aluminum surface, and coupling products inhibiting developability. .

When using phosphoric acid, if the erasing solution was left on an unundercoated A plate for 20 minutes and developed with an over-replenished developer [a slight sticking of the coupling product occurred, but other than that the erasing was good. I got sex.

However, if the eraser was left for a long time, the entire area where the eraser was applied became stained with blue dye. This is thought to be because the phosphoric acid etched the surface of the aluminum support by allowing it to stand for a long time, and as a result, the dye became more easily absorbed.

On the other hand, erasing solutions 1 to 4 using aliphatic oxycarboxylic acids or aliphatic polyhydric carboxylic acids do not cause dye staining in the erasing area, and when phosphoric acid is used, coupling products do not occur. Good erasability was exhibited without any coupling product sticking even under conditions where sticking occurred.

In addition, erasing solutions b-d using an alkali-soluble acidic substance having only one carboxylic acid group are erasing solutions i without addition of acid.
Eraser E using aromatic polyhydric carboxylic acid and Eraser F and G using aromatic oxycarboxylic acid are more effective than Eraser I, but are insufficient. Eraser liquid hH, which is an acid, had little effect.

Using a lithographic printing plate created using erasers 1 to 4,
When printed with an offset printing machine, no ink adhered to the erased unnecessary image area, and a good printed product without stains was obtained.

Example 5 In 10fi of pure water (tripotassium citrate 7g, phosphoric acid (1j%)
)/9, Megafuck F-/7zo7,, after dissolving I, r
- When butyrolactone rs'g-iz was added and stirred,
A white precipitate formed.

The pH of the solution from which this white precipitate was separated was determined by μ
, O. When a printing plate was prepared using this erasing liquid in the same manner as in Example 1, good results similar to those in Example 1 were obtained. Potassium phosphate 1g gold water iogy
c (After B solution, when γ-butyrolactone rtg@ was added, it became cloudy and precipitated, and (when citric acid-potassium/l was used, it became cloudy and the pH showed j, 3, and (when citric acid was used) Since the pHU of Example 1 is It turns out that there is.

Examples 6 to 9 Good results were obtained when the same tests as in Example 1 were conducted using Eraser Solutions 6 to 9 in which γ-butyrolactone was replaced with the same amount of ethylene glycol monomethyl ether. .

Example 1O Eraser liquid 10 was prepared by emulsifying and dispersing the following composition.

Cyclohexanone sty Slex NBL (Chigi solution of sodium alkylnaphthalene sulfonate 3 manufactured by Kako Atlas ■) 3 oy 1 g of water 3 g of citric acid Using this erasing solution, the same test as in Example 1 was conducted and good results were obtained. .

Claims (1)

[Scope of Claims] 1) A photosensitive lithographic printing plate in which a photosensitive lithographic printing plate is imagewise exposed to form a printout image, and then an erasing liquid is applied to unnecessary image areas, and then developed with a developer. A method for processing a printing plate, characterized in that the erasing liquid contains at least one carboxylic acid selected from the group consisting of aliphatic polycarboxylic acids and aliphatic oxycarboxylic acids. 2) The method for processing a photosensitive lithographic printing plate according to claim 1, wherein the erasing liquid contains the carboxylic acid in an amount of t-0,/-10 by weight.