JPH0213295B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve the practical characteristics of a negative planographic printing plate that does not require dampening water and uses a silicone rubber layer as an ink repellent layer, particularly to improve printing durability and solvent resistance during printing. This relates to a fixing method.

In conventional planographic printing using the offset method, two types of surfaces with different surface chemical properties configured in the image shape are given the functions of an image area (new oil-based) and a non-image area (new water-based). By supplying dampening water to the non-image area and forming a water film, it becomes an ink repellent layer. This lithographic offset printing plate is the most widely used in practice because it has the advantage of being relatively easy to make, low cost, and capable of producing high-quality printed matter. However, since the use of dampening water is an unavoidable requirement, there are problems caused by this. For example, (a) Adjusting the balance between water and ink is difficult and requires skill. It becomes an obstacle to labor saving and automation.

(b) When printing starts (the same applies when restarting after a pause), a large number of sheets are printed until the balance of water and ink stabilizes, resulting in a high paper waste rate.

(c) The paper expands and contracts due to water, which tends to cause misregistration.

(d) The emulsification of the ink distorts the shape of the halftone dots, making it difficult for the ink to stick to them, causing problems in the reproducibility of the halftone dots, and at the same time causing fluctuations in printed color.

(E) The printing press requires a dampening water device, which increases the size of the machine.

etc.

In order to fundamentally solve these problems,
About ten years ago, research began on plates that use silicone rubber as an ink-repellent layer for lithographic printing without the use of dampening water. Japanese Patent Publication No. 44-23042 was the first technology to show the use of silicone rubber as an ink repellent layer, and patent applications for lithographic printing without dampening water have been filed since then with various configurations. Among such lithographic printing plates that do not require dampening water, in order to achieve negative working in silicone-top layer type lithographic printing plates that do not require dampening water and are constructed by providing a photosensitive layer and a silicone layer in this order on a support, it is necessary to For the layer, it is necessary to select a photo-solubilizable photosensitive substance. An example of a lithographic printing plate that does not require dampening water and has such a structure is shown in Japanese Patent Publication No. 16044/1983. In this plate configuration, the photosensitive layer in the exposed area is photodecomposed, becomes soluble in the developer, and is removed together with the upper silicone rubber layer, so the exposed area becomes the image area, making it a negative working lithographic printing plate that does not require dampening water. Become. However, the photo-solubilized photosensitive material that retains the silicone layer, which is the unexposed area and the non-image area, maintains its photosensitivity even after development, and remains sensitized by sunlight or indoor fluorescent light. and change. On the other hand, printing plates may come into contact with organic solvents similar to developing solvents during plate washing during the printing process or contact with printing ink, and in this case, no matter how good the image reproduction is obtained up to the developing process, After that, the photosensitive layer is re-exposed and becomes solubilized, so it is attacked by the organic solvent and falls off together with the silicone layer that forms the non-image area.
It has a fatal flaw in that the development reproducibility on the printing plate cannot be maintained.

In order to solve this problem, the present inventors
Previously, JP-A No. 55-60947 disclosed a method of exposing, developing, and heat-fixing a negative planographic printing plate that does not require dampening water. However, there are problems such as practical limitations such as difficult heat treatment operations and economic burden.

The present inventors have conducted intensive studies on a method for fixing after exposure and development in a negative-working lithographic printing plate that does not require dampening water and has a structure in which a photosensitive layer and a silicone layer are coated on a support in this order. The invention has been achieved.

That is, the present invention is characterized in that a negative-working lithographic printing plate that does not require dampening water, which is formed by coating a photosensitive layer containing an orthoquinonediazide compound and a silicone rubber layer in this order on a support, is treated with an organic base after exposure and development. The present invention relates to a method for fixing the printing plate.

A feature of the fixing method of the present invention is that the printing plate after development is treated with an organic group. The base mentioned here is
means a base used in the ordinary chemical field,
It is defined as a proton acceptor or an electron donor.

Examples of the organic base include amines, alkali metal alcoholates, and alkali metal amides. For example, amines include aliphatic chain amines, aliphatic cyclic amines, aromatic amines, heterocyclic amines, primary, secondary, and tertiary amines, and polyamines such as monoamines, diamines, triamines, and tetraamines. Yes, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine,
triethylamine, n- or iso-propylamine, dipropylamine, tripropylamine,
Butylamine, dibutylamine, tributylamine, amylamine, diamylamine, methyldiethylamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, ethanolamine, diethanolamine, triethanolamine, benzylamine, dimethylbenzylamine,
Diethylbenzylamine, dipropylbenzylamine, o- or m- or p-methoxy or methylbenzylamine, N,N-dimethoxybenzylamine, β-phenylethylamine, ε, δ
-Phenylamylamine, γ-phenylpropylamine, cyclohexylamine, aniline, monomethylaniline, dimethylaniline, toluidine, benzidine, naphthylamine, phenylenediamine, pyrrolidine, piperidine, piperazine,
Morpholine, urothrobin, pyrrole, pyridine, quinoline, hydrazine, phenylhydrazine, N,N'-diphenylhydrazine, hydroxylamine, urea, glycine, alanine, phenylalanine, lysine, histidine, quinine, brucine, tetraalkal hydroxide Ammonium etc. are used.

As alkali metal alcoholates and amides,
Methylates of sodium, potassium and lithium,
Ethylate, propylate, sodium, potassium, lithium amides, diethylamide, dipropylamide, etc. are used.

These organic bases may be used alone or in a mixture, in liquid or gas phase. In the case of a liquid, it is used, for example, as an organic base itself or in the form of a solution. When used as a solution, the solvent may be water, an organic solvent, or a mixture of both. When processing in a liquid state, it is sufficient to wet the printing plate with an organic base or an organic base solution, and when processing in a gas phase, it is sufficient to expose the printing plate to a gaseous phase containing the organic base.

Regardless of whether the treatment is carried out in the gas or liquid phase, the effect is only slightly dependent on the concentration of the organic base; if the base is concentrated, the treatment may be carried out in a short time, and if the base is weak, the treatment may be carried out over a long period of time. However, from the viewpoint of ease of operation, safety and practical processing time, in the gas phase it is less than 50% 0.01
or more, preferably 30-40% or more, 0.1% or more, 100% or less in liquid phase, 0.01% or more, preferably 50% or less
It is carried out in a concentration range of 0.1% or more.

The treatment time can be appropriately selected depending on the concentration of the organic base as described above, but is usually about 1 to 30 minutes. Further, during processing, if the fixing progresses beyond a certain level, the effect will be the same even if the processing takes longer than that.

Orthoquinone diazide compounds used in the photosensitive layer of printing plates are usually used in positive-working PS plates, Wipon plates,
Orthoquinone diazides used in photoresists etc. have a 1,2-quinone diazide or 1,2-naphthoquinone diazide structure in the molecule, and are usually in the form of sulfonic acid derivatives such as esters and amides. used in

The photosensitive layer of the present invention is, for example, disclosed in Japanese Patent Application Laid-Open No. 55-59466.
A photo-solubilizable photosensitive layer or a photosensitive layer as shown in
No. 54-156871 (see Japanese Patent Application Laid-open No. 56-80046). Particularly preferred as the photo-solubilized photosensitive layer are novolak resin, pyrogallol acetone resin, and naphthoquinone of polyhydroxystyrene.
It is a partially esterified product of 1,2-diazido-5-sulfonic acid. The novolak resin referred to herein is a novolak type phenolic resin obtained by condensing phenol or m-cresol with formaldehyde.

Particularly preferable photosensitive layers include:
It is obtained by crosslinking or modifying the above partially esterified product with a polyfunctional or monofunctional compound. The thickness of the photosensitive layer is about 0.1-100μ, preferably about
A suitable thickness is 0.5 to 10μ; if it is too thin, defects such as pinholes are likely to occur during coating, while if it is too thick, it is disadvantageous from an economic standpoint.

In addition, other components may be added to the photosensitive layer for the purpose of improving coating film formation properties and adhesion to the support within a range that does not impair the effects of the present invention, or to make images visible during development or exposure. It is possible to add dyes etc.

The silicone rubber layer used in the present invention is mainly composed of a linear organic polysiloxane having a molecular weight of several thousand to several hundred thousand and having the following repeating units.

Here, n is an integer of 1 or more, R is an alkyl group, alkenyl group, or phenyl group having 1 to 10 carbon atoms, and preferably 60% or more of R is a methyl group. Such linear organic polysiloxanes can be made by adding organic peroxides and subjecting them to heat treatment, etc.
It is also possible to form a silicone rubber by sparsely crosslinking.

A crosslinking agent is also added to the linear organopolysiloxane. Crosslinking agents used in so-called room temperature (low temperature) curing silicone rubber include acetoxysilane, ketoxime silane, alkoxysilane, aminosilane, amidosilane, etc., and are usually linear organic polysiloxanes with hydroxyl groups at the ends. When combined, they become deaceticated, oxime-free, alcohol-dealt, deamined, and deamidated silicone rubbers. Generally, a small amount of an organic tin compound or the like is further added as a catalyst to these silicone rubbers.

The appropriate thickness of the silicone rubber layer is approximately 0.5 to 100μ, preferably approximately 0.5 to 10μ; if it is too thin, it may cause problems in terms of printing durability, while if it is too thick, it is economically disadvantageous. Not only is
It becomes difficult to remove the silicone rubber layer during development, resulting in a decrease in image reproducibility.

In the lithographic printing plate of the present invention, adhesion between the support and the photosensitive layer, and between the photosensitive layer and the silicone rubber layer is very important for basic plate performance such as image reproducibility and printing durability, so it is necessary to Accordingly, it is possible to provide an adhesive layer between each layer or to add an adhesion-improving component to each layer. In particular, for adhesion between the photosensitive layer and the silicone rubber layer, it is effective to provide a known silicone primer or silane coupling agent layer between the layers, or to add a silicone primer or silane coupling agent to the silicone rubber layer or photosensitive layer. .

The support must be flexible enough to be set in a normal lithographic printing machine and capable of withstanding the load applied during printing. Typical examples include metal plates such as aluminum, copper, and steel, plastic films such as polyethylene terephthalate, and coated paper. It is also possible to provide a support by further applying a coating to these sheets for antihalation and other purposes.

For the purpose of protecting the silicone rubber layer forming the surface of the planographic printing plate that does not require dampening water and constructed as described above, a thin protective film may be laminated on the surface of the silicone rubber layer.

The lithographic printing plate that does not require dampening water as described above is manufactured, for example, as follows. First, a composition solution to form a photosensitive layer is applied onto a support using a normal coater such as a reverse roll coater, an air knife coater, a Meyer bar coater, or a rotary coater such as a Whaler, and then dried and coated as necessary. After heat curing, if necessary, apply an adhesive layer on the photosensitive layer in the same manner, and after drying, apply a silicone gum solution on the adhesive layer in the same manner, and cure several times at a temperature of usually 100 to 120°C. Heat treated for a minute,
Fully cure to form a silicone rubber layer. If necessary, cover the silicone rubber layer with a protective film using a laminator or the like.

The thus produced lithographic printing plate, which does not require dampening water, is exposed to actinic light through, for example, a negative film sealed in vacuum. The light source used in this exposure process is one that generates abundant ultraviolet light, and can be a mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, or the like.

After exposure, remove the protective film from the exposed printing plate if necessary, immerse it in a developer, and lightly rub the surface with a soft developing pad such as Sofpad.

In the case of a photo-solubilizable photosensitive layer, the photosensitive layer in the exposed area is dissolved and the upper silicone rubber layer is easily peeled off to expose the support.

In the case of a light-peelable photosensitive layer, only the silicone rubber layer in the exposed areas is removed, exposing the photosensitive layer.

The developing solution used is aliphatic hydrocarbons (hexane, heptane, gasoline, kerosene, etc.), aromatic hydrocarbons (toluene, xylene, etc.), or halogenated hydrocarbons (triclene, etc.) that can swell silicone rubber. It is preferable to add the following polar solvent to the above.

Alcohols (methanol, ethanol, etc.) Ethers (ethyl cellosolve, dioxane, etc.) Ketones (acetone, methyl ethyl ketone, etc.) Esters (ethyl acetate, cellosolve acetate, etc.) Printing plates developed in this way are organic as described above. The base treatment fixes the photosensitive layer, and even if it is re-exposed, the photosensitive layer will not be attacked by an organic solvent such as a developer.

Although the mechanism by which the fixing effect is obtained by the organic base treatment is not necessarily clear, it is presumed that the organic base and the orthoquinone diazide compound react to crosslink the photosensitive layer.

The effects obtained by the present invention include the following.

(1) Increased solvent resistance of the photosensitive layer (2) Increased adhesive strength between the photosensitive layer and the silicone rubber layer The above effects dramatically increase the printing durability and solvent resistance of the printing plate.

The present invention will be explained in detail by giving examples below.

Example 1, Comparative Example 1 A 7% by weight dioxane solution of naphthoquinone-1,2-diazide-5-sulfonic acid ester of phenol novolak resin with a degree of esterification of 44% was applied to a chemical conversion treated aluminum plate (manufactured by Sumitomo Light Metal) using a Whaler. After spin coating, it was dried at 60°C for 3 minutes. On top of this, 0.5% by weight of γ-aminopropyltriethoxysilane (manufactured by Union Carbide, "A1100)""IsoperE"
Spin coat the solution (manufactured by Etsuso) with a Whaler, leave it for one day, dilute RTV silicone "YE3085" manufactured by Toshiba Silicone with Isopar E, and apply it with a Whaler for 10 minutes.
After spin coating for a minute, the coating was cured by heating at 120° C. for 4 minutes to form a silicone rubber layer with a thickness of 2 μm, which was used as a printing original plate.

The obtained printing original plate was passed through a negative film and irradiated for 60 seconds from a distance of 1 m using a metal halide lamp. Coat the plate with ethanol (9 parts)/Isopar E
(1 part) of the mixed solvent and lightly rubbed with a developing pad, the exposed areas were easily removed and the aluminum surface was exposed in a pattern.

Fixing was carried out by treating the plate with an ethanol solution containing 1% benzylamine for 5 minutes. The entire surface was reexposed with a metal halide lamp, and the plate surface was rubbed with ethanol and butyl acetate, but the plate surface was not damaged at all.

As a comparative example, a printing plate that was not treated with an organic base showed peeling of the silicone rubber layer in the non-image area in the same test.

Example 2 Naphthoquinone-1,2-diazide-5-sulfonic acid ester (ethanol soluble component: 9.7 A 3 wt % dioxysan solution (wt%, degree of esterification determined from IR spectrum) was spin-coated using a Whaler and dried to 1.2μ.
A photosensitive layer was formed. On top of this, add a 7% Isopar E solution of a silicone gum composition having the following composition:
4% by weight of γ-aminopropyltriethoxysilane (manufactured by UCC: A1100) was added to the silicone composition, stirred uniformly, and then spin-coated using a Whaler.
After drying, it was cured by heating at 120°C for 4 minutes to obtain a 2.2μ silicone rubber layer.

(a) Dimethylpolysiloxane (molecular weight approximately 80,000, unterminated OH groups) 100 parts (b) Ethyltriacetoxysilane 5 parts (c) Dibutyltin diacetate 0.2 parts The original printing plate obtained as above was vacuum-adhered. The film was irradiated for 60 seconds from a distance of 1 m using a metal halide lamp (Idolfin 2000 manufactured by Iwasaki Electric) through a negative film having a halftone image of 150 lines. The exposed plate was washed with 8 parts isopar of ethanol.
When development was carried out through an automatic developing machine at a transport speed of 30 cm/min using a developer consisting of E2 parts, the exposed areas were easily removed and the chemical conversion treated aluminum surface was exposed, while the unexposed areas had a silicone rubber layer. It remained strong and an image that faithfully reproduced the negative film was obtained.

This printing plate was immersed in a 5% ethanolamine water/alcohol mixed solution for 10 minutes, washed with water, and dried. This printing plate was attached to an offset printing machine (Komori Sprint 2 Color) and printed using Toyo Ink's "Aquares ST Indigo" without using dampening water, resulting in a 150-line halftone dot of 5 to 95%.
A printed matter with an extremely good image in which the images were reproduced was obtained. Even after printing 50,000 copies, no scumming or damage to the plate surface was observed, and printing could continue. The image reproducibility of the printed matter did not change at all throughout the printing period.

Example 3, Comparative Example 2 A 0.24 mm thick aluminum plate (manufactured by Sumitomo Light Metals) was coated with resol resin (Sumilight Resin PC-1, manufactured by Sumitomo Durez) to a thickness of 2μ, cured at 180°C for 3 minutes, and supported. As a body. On this support, the following photosensitive layer composition was spin-coated and cured by heating at 120° C. for 2 minutes to form a photosensitive layer having a thickness of 2.4 μm.

(a) Naphthoquinone in phenolic novolak resin
1,2-Diazide-5-sulfonic acid ester (from Example 1) 100 parts (b) 2,6-toluene diisocyanate 20 parts (c) Dibutyltin dilaurate 0.2 parts (d) Dioxane 2000 parts On top of this Spin coat a silicone rubber composition liquid with the following composition and heat cure it at 120℃ for 2 minutes.
A 2.1μ silicone rubber layer was provided.

(a) Dimethylpolysiloxane (molecular weight approximately 80,000, terminal hydroxyl group) 100 parts (b) Vinyltri(methylethylketoxime) silane 8 parts (c) Dibutyltin diacetate 0.2 parts (d) γ-[N-(β-aminoethyl)amino ] Propyltrimethoxysilane 1.0 part (e) Isopar E 1800 parts A negative film with a halftone image of 150 lines is passed through a negative film with a halftone image of 150 lines, which is vacuum-adhered to the printing original plate obtained as above, from a distance of 60 m from a distance of 1 m using a metal halide lamp.
Second exposure. When the plate surface is immersed in a developer (Isopar E/ethanol = 9/1) and rubbed lightly with a developer pad, only the exposed silicone rubber layer is removed, resulting in a printing plate with an exposed photosensitive layer that faithfully reproduces the negative film image. was gotten.

This plate is fixed by wetting it for 3 minutes with a mixed solution of 5% sodium ethylate in water/ethyl cellosolve. Apply a load of 10 g/cm ² to the fixed printing plate,
When we conducted a scratch test using a polishing tester equipped with a head of "Sofpad" (manufactured by Dainippon Screen) immersed in roller cleaning oil (manufactured by Dainippon Ink) for the UV ink "Daikyure", we found that In the rubbing test, no peeling of the silicone rubber layer was observed. However, printing plates without fixing treatment
Peeling of the silicone rubber layer was observed after 100 to 300 reciprocations.

Example 4 The plate developed in Example 3 was exposed to ethylamine vapor in a closed container for 3 minutes and then subjected to a similar scratch test, but no peeling of the silicone layer was observed even after 500 rubs.

Claims (1)

[Claims] 1. A negative-working lithographic printing plate that does not require dampening water and is prepared by coating a photosensitive layer containing an orthoquinone diazide compound and a silicone rubber layer on a support in this order, is treated with an organic base after exposure and development. How to fix printing plates.