JPH02235634A - Planographic printing plate and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a planographic printing plate capable of direct plate making form an electric signal, requiring no developing process and capable of performing printing requiring no damping water by incorporating a powder imparting conductivity in a conductive resin layer and incorporating silicone rubber in an ink repelling layer. CONSTITUTION:A planographic printing plate is formed by successively laminating a conductive resin layer and an ink repelling layer to a support substrate. As the support substrate, paper, a plastic plate and a metal plate composed of brass can be used. A resin layer having a powder imparting conductivity such as carbon dispersed therein can be adapted to the conductive layer and, as the powder, a metal powder or a carbon black powder can be used but the carbon black powder easy to obtain and easy to disperse is pref. As a resin, one bondable to the room temp. curable silicone rubber of an upper layer and showing ink receptivity after discharge breakdown is pref. and, concretely, a polyester resin is designated. As the silicone rubber of the ink repelling layer, one wherein an organosilicon compound having the three or more easily hydrolyzable functional groups, for example, alkoxy groups are contained in polyorganosiloxane having the hydroxyl group bonded to a silicon as a crosslinking agent is used.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a lithographic printing plate used in offset printing. Prior Art> Plates for lithographic printing include: ■ A so-called PS plate, which is a grained aluminum sheet coated with a photosensitive resin, is image-wise exposed and developed. ■After performing image forming processes such as corona charging, image exposure, and toner development on a plate material with a photosensitive layer made of zinc oxide powder, binder resin, etc. on the base, compatibility treatment of non-surface image areas is performed. The so-called electrofax method is used to produce lithographic printing plates. ■The printing plate material described in Japanese Patent Publication No. 37-17162, etc., in which a layer of an alkali-soluble organic photoconductive compound is coated on a conductive substrate, is subjected to a series of processes such as corona charging, image exposure, and toner development. Examples include a method of making a lithographic printing plate by performing an electrophotographic image forming process and then etching away the photoconductive compound layer other than the surface image area using an alkaline water-soluble etching solution using the toner layer as a resist. The PS plate produced by method (2) is used as a normal lithographic printing plate suitable for most types of printing, and can be manufactured using a simple process of exposure and development, but due to its sensitivity and sensitive wavelength range, it is not suitable for mercury lamps. This method requires close contact or projection exposure using ultraviolet rays such as UV rays, making scanning exposure using digital signals impossible, and in addition, the plate material is relatively expensive.

The lithographic printing plate produced by the electrofax method according to method (2) is suitable for office use and light printing of small quantities and can be easily manufactured, and the plate material is relatively inexpensive, so it has been widely used in recent years. In addition to being able to use only a light source with a limited wavelength range, such as a halogen lamp, the exposure conditions are narrow in that the original is mainly exposed to reflected light.

Method (2) improves the photosensitivity and sensitive wavelength range of (2), so it is possible to perform not only exposure using reflected light from the original, but also scanning exposure using lasers, He-Ne lasers, and in recent years, semiconductor lasers. Progress is being made in so-called direct plate making, in which laser light is modulated and exposed using image data, but the plate manufacturing process is complex, requiring an additional etching process after charging, exposure, and development, resulting in longer processing times. Not only does it take a long time, the equipment is large, and two types of processing solutions are required, but the toner image is used as a resist for etching, which deteriorates the image and makes it difficult to reproduce fine patterns. ．． There was also the problem that the plate material was expensive.

Also, JP-A-59-116759, JP-A-59-116759,
A lithographic printing plate with a photosensitive layer consisting of zinc oxide, cyanine pigment, and binder resin, which is an improved version of the electrofax method described in Publication No. 116760, can be developed and printed in the same manner as ordinary zinc oxide plates. Moreover, direct plate making using semiconductor laser scanning exposure is possible. However, all of the above-mentioned printing plates are offset printing plates that use water, and the balance between ink and water has to be adjusted. There were various problems caused by water, such as ink emulsification and temperature effects, so waterless printing was expected. However, currently only P5 plates made of a combination of photosensitive resin and silicone resin are in use, and there are currently no waterless printing plates that can be printed directly from digital data. In addition, graft polymerization was carried out between the conductive resin layer of Japanese Patent Application No. 63-237167 and an ink repellent layer containing reactive silicone oil laminated thereon to modify the surface of the plate material to be ink repellent. The lithographic printing plate uses the discharge breakdown recording method in the plate making method, making it possible to create valleys and waterless lithographic printing by directly making the plate from digital data. However, this printing plate has the disadvantage that it requires a dissolution treatment with a solvent to remove the unpolymerized portion after graft polymerization or the homopolymer of silicone oil during production, which takes time and effort. <The invention is about to be defeated! lrs> The object of the present invention is to provide a high-quality, high-durability lithographic printing plate that enables direct plate making from electrical signals, eliminates the need for a developing process, and enables printing without the need for dampening water. An object of the present invention is to provide a manufacturing method thereof.

<Means for Solving the Problems> The present invention, which achieves the above objects, provides a lithographic printing plate in which at least a conductive resin layer and an ink anti-tn layer are successively laminated on a support substrate. This is a lithographic printing plate characterized by containing powder that imparts conductivity to the layer and silicone rubber in the ink repellent layer. A conductive resin layer is formed by separating powder that imparts conductivity to the surface, and an ink repellent layer containing silicone rubber is laminated thereon.A voltage is applied to the surface image area to cause the ink to break down due to electrical discharge. Remove the repellent layer on the image to expose the conductive resin layer,
A method for producing a lithographic printing plate characterized by forming an ink-receptive image.

<Function> In this printing plate, both the conductive resin layer and the ink layer can be easily formed using a general coating method. In addition, the ink repellent layer is made by adjusting the solid content ratio of silicone rubber.
It is possible to form a ff film, which causes discharge damage to occur easily. In addition, silicone rubber is selected to have polar groups, so it exhibits excellent adhesion, so it does not peel off easily and has strong rigidity. In addition, since the plate-making method uses the discharge breakdown recording method, the plate can be made directly from digital data, and it does not involve wet processes such as development. Moreover, since the surface tension of the silicone rubber layer is extremely low,
The exposed part of the conductive resin layer that has been destroyed by discharge attracts ink, and the silicone rubber layer that remains without being destroyed by discharge has the property of absorbing ink. Printing is now possible. The present invention will be explained in detail below. The lithographic printing plate of the present invention is generally one in which a conductive resin layer and an ink repellent layer are sequentially laminated on a supporting substrate. The supporting substrate can be paper, plastic, a polymer film such as polyvinyl chloride, or metal such as brass, copper, stainless steel, aluminum, or treated steel, and glass. The conductive resin layer can be a resin layer in which conductive powder such as carbon is dispersed. Metal powder and carbon black can be used as the powder that imparts conductivity, but carbon black is preferred because it is easily available and easily dispersed.
Examples of carbon plaque include Ferne black, Ke7chen black, and acetylene black. The resin is preferably one that can adhere to the room-temperature curable silicone rubber of the upper layer and exhibits ink receptivity after discharge breakdown, specifically polyester resins, acrylic resins, epoxy resins, polyamide resins, phenolic resins, melamine resins, Examples include acetal resin, urethane resin, silicone resin, etc. The content of carbon black is preferably 5 to 25% by weight based on the resin. Dispersion methods include ball mill, paint shaker, and sonic homogenizer.
A sand mill etc. can be applied. The thickness of the conductive resin layer can be set arbitrarily, but it is 5 μm or more, preferably 10 to 100 μm.
μm is preferable. This conductive resin layer can be formed using an applicator, spray coater, bar coater, dip coater, doctor blade, etc. After application, it is dried, but at this time it is dried with hot air of 100℃ or higher for 2 hours.
It is recommended to heat for at least 1 minute. In addition, this conductive resin layer can be used by itself without imparting conductivity if the resin itself is conductive, such as polyaniline. Regarding the silicone rubber of the ink repellent layer, the formula is as follows■
A polyorganosiloxane having a water M group bonded to a silicon atom represented by the formula contains an organosilicon compound having three or more hydrolyzable functional groups such as an alkoxy group, an oxime group, an acetoxy group, etc. as a crosslinking agent. However, in particular, silicone rubber containing a cross-linked compound represented by the formula (■) below has excellent adhesive properties and is easy to work with during coating, but it is irritating because the oxime group is released during the curing process. It is suitable without any problems. Formula I Me ~ O -Si) -OR Me Formula ■ CHs -Si (ON-χ), Silicone rubbers are classified into addition reaction type and condensation reaction type based on their curing reaction, but the silicone rubber used here is of the condensation reaction type. Especially excellent in adhesive properties. This silicone rubber may be used alone, but it may also be used in combination with other room temperature curable silicone rubbers. Of course, if there is a silicone rubber that cures at room temperature other than those listed here and has excellent adhesive properties, you may use it. The ink-repellent layer is formed by coating the silicone rubber diluted in a solvent if necessary. In this case, the solid content ratio is 25
~40% by weight is suitable. For application, applicators, spray coaters, bar coaters, temper coaters, doctor blades, etc. can be used. After coating, drying may be performed if necessary, but it is preferable to heat with hot air at 80°C for 30 minutes or more. Regarding the layer structure of these printing plates, there is no particular restriction on the thickness of the supporting substrate, and the thickness of the conductive resin layer is preferably 5 μm or more, and suitably 10 μm or more. If the ink anti-tB layer is too thin, the ink repellency will be poor. If it is too thick, discharge breakdown will not occur, so a thickness of 0.5 μm or more and 20 μm or less is suitable, and in particular, from the viewpoint of image quality such as resolution, 0.5 μm or more and 10 μm or more.
Preferably less than μm. The surface of the plate material thus obtained has a silicon layer with a lower surface tension than that of lithographic printing ink, and has excellent ink reversibility. In order to form an image on the plate material, the silicon layer in the surface image area is destroyed by discharge destruction.
The conductive resin layer may be exposed to form an ink-receptive image area. That is, by scanning, a voltage is applied to a bottle electrode etc. according to the image information, and the surface image portion is written on the plate material. Applied voltage is 60-80V
The recording speed is preferably IOCIm/sec or less. Air pressure may be applied to the plate surface to remove silicon debris generated by discharge breakdown during image formation. For printing using the printing plate thus obtained, a normal offset printing machine can be used, and waterless printing can be performed as long as dampening water is not supplied.

In addition, ordinary offset printing machines require numerous rollers and controls because the balance of ink and water subtly changes the printing condition, but waterless offset printing using the plate of the present invention can be used in principle. The number of rollers and control points should also be reduced.

In the present invention, during digital plate making using pin electrodes, image data taken from a scanner or the like and separated for each color plate of yellow, magenta, cyan, and black plates can be used as a modulation signal to the electrode voltage. It is possible to easily produce lithographic printing plates for each color used in color printing. By printing these lithographic printing plates of each color in register, color printed matter can be obtained.

<Examples> The present invention will be explained in more detail below using examples. (Example 1) Epoxy resin (Epicor 1-80
7, manufactured by Shell Chemical Co., Ltd.) 195g, 10g of dimethyldodecyalamine as a catalyst, 1 carbon black (COND
UC EX, SC, : ] Cl 30g (manufactured by Nbip Carbon Co., Ltd.) was placed in a glass bottle with 150g of glass beads, and in a paint shaker (manufactured by Red Devil Co., Ltd.)
Disperse for 1 minute, form a coating film of 120 lum using a Heber Coater on base paper with a basis weight of HOg/rrr, which is a supporting substrate.
'C Dry for 2 hours. In addition, room-temperature curable silicone rubber (KE45TS manufactured by Shin-Etsu Silicone Co., Ltd.) (oxime-free type) is applied to the Q surface.
150g and 100g of toluene using a bar coater
After coating to a film thickness of μm, dry at 80°C1 with an electric dryer.
After drying for several hours, 32 pieces per plate were printed at a recording speed of 8 ell/sec using bottle III with an applied voltage of 80 μm to the plate material.
An image was formed at an image density of (2) to obtain a lithographic printing plate.

This is a commercially available offset printing machine (Ryobi Printing Machine AD
-80) and printed without dampening water using Toyo Ink Co., Ltd.'s Aquares ■. As a result, the area rate of background stains at the beginning of printing was 0.
1% or less (Viewback manufactured by Toyo Ink Co., Ltd.) and 50
Very high quality printed matter was obtained, with a printed image density of 1.2 or more (Macbeth reflection densitometer RD-914) after printing 00 sheets.

(Example 2) A lithographic printing plate was prepared in the same manner as in Example 1, except that acrylic resin (Dianal Lli-637 manufactured by Mitsubishi Rayon Co., Ltd.) was used as the resin for the conductive resin layer, and printing was carried out in the same manner. When I went there, the printed image density after printing 5000 sheets was 1.
1 or higher, and a high-quality printed matter similar to that of Example 1 was obtained. (Example 3) A lithographic printing plate was prepared in the same manner as in Example 1, except that room temperature curing silicone rubber (XE42TS, manufactured by Shin-Etsu Silicone Co., Ltd.) (acetic acid-removed type) was used as the silicone rubber. Although it had a pungent odor of vinegar, a lithographic printing plate that could be made into plates could be created. Then, when printing was carried out in the same manner, the print density of the 5000th sheet was 1.2 or more, and a sharp, high-quality printed image without background smudge was obtained. (Example 4) Polyester resin (Vylon-200 manufactured by Toyobo Co., Ltd.) was used as the resin of the conductive resin layer, and room temperature curable silicone rubber (KE471W manufactured by Shin-Etsu Silicone Co., Ltd.) was used as the silicone rubber.
(Dealcoholization type) A lithographic printing plate was prepared in the same manner as in Example 1 except that 60 g was used, and printing was performed in the same manner. After printing 5000 sheets, the printed image density was 1.
．． 2 or higher, and a high-quality printed matter similar to that of Example 1 was obtained. (Comparative Example 1) A lithographic printing plate was prepared in the same manner as in Example 1 except that the ink repellent layer of 10 μm was changed to 0.2 μm. When I printed in the same way, I could only obtain low-quality prints with severe background smudges in the non-image areas. (Comparative Example 2) When a lithographic printing plate was prepared in the same manner as in Example 1 except that the ink repellent layer was changed from 10 μm to 32 μm, no discharge damage occurred and no image was formed. Effects> As explained above, according to the lithographic printing plate and the method for manufacturing a lithographic printing plate of the present invention, direct plate making is possible, and there is no developing step, and a good lithographic printing plate can be produced easily and in a shorter time than the conventional method. was gotten. Furthermore, the surface of the printing plate has high ink repellency, making it possible to create a waterless plate that does not require etching before printing or dampening water during printing, and also produces high-quality, highly durable printed matter with little background smearing. Patent application: Kazuo Suzuki, Representative of Toppan Printing Co., Ltd.

Claims (2)

[Claims] (1) In a lithographic printing plate formed by sequentially laminating at least a conductive resin layer and an ink repellent layer on a support substrate, the conductive resin layer contains powder that imparts conductivity, and the ink repellent layer contains a powder that imparts conductivity. A lithographic printing plate characterized by containing silicone rubber. (2) A conductive resin layer made by dispersing powder that imparts conductivity in the resin is provided on the supporting substrate, and an ink repellent layer containing silicone rubber is laminated thereon, and then a voltage is applied to the surface image area. 1. A method for producing a lithographic printing plate, which comprises applying a voltage to remove the ink-repellent layer in an imagewise manner by discharge destruction, exposing the conductive resin layer, and forming an ink-receptive surface image area.