JPH01297245A - Preparation of planographic printing plate - Google Patents

Abstract

PURPOSE:To obtain high image quality and high printing durability, by forming an exposed image, which is composed of photoconductive toner consisting of an electric insulating non-polar liquid, zinc oxide, a spectrally sensitizing cyanine dye having sensitivity to near infrared rays and a binder resin, on a conductive substrate hydrophilic or susceptible to hydrophilic treatment. CONSTITUTION:A photoconductive toner layer is provided between conductive substrates hydrophilic or susceptible to hydrophilic treatment and voltage is applied between both electrodes to attract toner particles toward the transparent electrode and imagewise exposure is applied on the side of the transparent electrode to move the toner particles of the exposed part to the opposed electrode by electrophoresis. Both electrodes are separated and the toner particles on the opposed electrode are fixed by a heat source. The photoconductive toner is based on a non-polar liquid, zinc oxide, a sensitizing dye and a binder resin and, as the non-polar liquid, a carrier liquid generally used as a liquid developer for electrophotography is used. A cyanine dye for spectrally sensitizing zinc oxide and having sensitivity to near infrared rays has high adsorbing capacity to zinc oxide and relatively high stability to heat.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing a lithographic printing plate, in which a photoconductive material containing zinc oxide dye-sensitized to the near-infrared light region of a semiconductor laser, etc. The present invention relates to a method for producing a lithographic printing plate in which a photoelectrophoretic image is formed using toner.

<Prior art> Plates for lithographic printing include: ■ A so-called PS plate, which is a grained aluminum sheet coated with a photosensitive resin, is imagewise exposed and developed, ■ Zinc oxide powder and binder resin, etc. Corona charging, image exposure,
The so-called electrofuchs method involves manufacturing a lithographic printing plate by performing an image forming process such as toner development and then hydrophilizing the non-image area. This is an application of the electrophotographic method to After performing a series of electrophotographic image forming processes such as exposure and toner development, the toner image is used as a resist and the photoconductive compound layer other than the image area is etched away using an alkaline water-soluble etching solution to produce a lithographic printing plate. Examples include methods.

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 through a simple process of exposure and development, but its photosensitivity and sensitive wavelength range are limited. This requires close contact or projection exposure using ultraviolet light from a mercury lamp or the like, making scanning exposure using digital signals impossible.Additionally, the plate material is relatively expensive.

Lithographic printing plates produced by the electrofuchs method using method (2) are suitable for office use and light printing of small numbers of copies, and have been widely used in recent years because they can be manufactured in tubes and the plate materials are relatively inexpensive. This method also has narrow exposure conditions, in that it can only use a light source with a limited wavelength range, such as a halogen lamp, and is mainly exposed to light reflected from the document. Method (2) improves the photosensitivity and sensitive wavelength range of (2), and enables not only exposure using reflected light from the document but also scanning exposure using Ar lasers, He-Ne lasers, and in recent years, semiconductor lasers.
Although progress is being made toward so-called direct plate making, in which laser light is modulated using image data from a word processor, etc., and exposed.
The printing plate manufacturing process is complicated.

That is, after charging, exposure, and development, an etching solution is required, which increases the processing time and requires a large-scale apparatus. In addition, not only do two types of processing solutions become necessary, but the etching process uses the toner image as a resist. However, it has the disadvantage that it deteriorates and it is difficult to reproduce fine patterns. There was also the problem that the printing materials were expensive.

Also, JP-A-59-116759, JP-A-59-1
A lithographic printing plate made of zinc oxide, phthalocyanine pigment, and binder resin, which is an improved version of the electrofuchs method described in Publication No.
It is possible to print and direct plate making using semiconductor laser scanning exposure is possible, but since the base is paper, it is suitable for printing in small quantities, the hydrophilicity is poorer than AI board due to grainy grain, and the plate material is also expensive (spray printing). It was in quantity.

<Problems to be Solved by the Invention> The present invention provides a lithographic printing plate for a large number of copies, which is capable of direct plate making using semiconductor laser scanning exposure, can print with high image quality and high rigidity, and has low running costs. The purpose is to provide a manufacturing method.

<Means for Solving the Problems> In other words, the present invention provides a method of applying at least an electrically insulating non-polar liquid, zinc oxide, and a spectral sensitizer sensitive to near-infrared light onto a hydrophilic or hydrophilically treatable conductive substrate. This is a method for producing a lithographic printing plate, which comprises forming an exposed image using a photoconductive toner composed of a cyanine dye and a binder resin, and then fixing the image.

<Function> The photoconductive toner used in the present invention has high electrophotographic sensitivity and has a spectral sensitivity in the range of 700 to 900 nm, so that scanning exposure using a semiconductor laser is possible. Also,
Since it is a liquid toner, it can be sufficiently dispersed, and in principle it can resolve up to a primary particle size of zinc oxide of 0.2 to 0.5 μm, resulting in a high-resolution image. In addition, by using the ^l plate as the counter electrode and the base of the lithographic printing plate, a lithographic printing plate for large numbers of copies with excellent hydrophilicity in non-image areas, high quality with no expansion and contraction, and high stiffness resistance can be obtained. It will be done.

Further, after image formation, the toner in the non-image area can be collected and the collected toner can be reused, so that the only consumables are the substrate and the photoconductor toner in the image area, and running costs are extremely low.

<Detailed Description of the Invention> The present invention will be described in detail below. First, each constituent material will be explained, and then a method for producing a photoconductive toner and a method for producing a lithographic printing plate will be described.

As the non-polar liquid, a carrier liquid generally used for electrophotographic liquid developers can be used.

Particularly preferred is an organic solvent having an electrical resistance of 10'Ωcm or more and a dielectric constant of 3 or less. Examples include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons, but isoparaffinic solvents are preferred in terms of odor and toxicity.

Specific examples include Shell Silua 1 (made by Shell Chemical Co., Ltd.), Isopar G1, Isopar H, Isopar L (all made by Exxon Chemical Co., Ltd.), etc. Zinc hexaoxide is not particularly limited, but has an average particle size of 0.2 to 0. It is preferable to use powdered materials, which are most commonly used for electrophotography with a diameter of about 5 μm.

As the binder resin, methacrylic acid or higher alkyl acrylic acid that is soluble in non-polar liquids (e.g. lauryl, tridecyl, 2-ethylhexyl, stearyl, etc.)
An example is an ester polymer. Although these monomers can be used alone, a copolymer of two or more monomers can also be used. In this case, it is also possible to copolymerize a compound that is insoluble in a nonpolar liquid. However, this inclusion [1 is 30
% or less is preferable. Examples of the insoluble compound include glycidyl methacrylate and lower alkyl (eg, methyl, ethylhydroxyethyl, etc.) esters of methacrylic acid or acrylic acid.

In addition, alkyd resins modified with soybean oil, linseed oil, etc.
Resins that exhibit good dispersibility in nonpolar liquids, such as natural rubber, synthetic rubber, and various modified rubbers, can also be used. These resins have the function of controlling dispersion stability and fixing properties.

Regarding cyanine dyes sensitive to near-infrared light, which are used for spectral sensitization of zinc oxide, for example, the dyes represented by formulas I and (■) below have electronic structures that are compatible with dye sensitization of zinc oxide. In addition to its high adsorption capacity to zinc oxide, its stability against heat is also relatively high, from 700 to 11,000 nm.
It is suitable as a spectral sensitizer because it has spectral absorption and does not inhibit the chargeability of photoconductive toner in the dark. This dye may be used alone, but it may also be used in combination with other cyanine dyes. Of course, if there are cyanine dyes other than those listed here that have excellent spectral sensitization, you can also use them. There is no problem, the blending amount is based on zinc oxide.
0.01-0.1% by weight is suitable.

If the amount of cyanine dye blended with respect to zinc oxide is small, sufficient sensitivity cannot be obtained, and if it is too large, the dark current increases.
Sufficient contrast cannot be obtained by exposure.

formula! (However, R is C, lHz, n-1,2X Lt
(Halogen element, A- is an acid anion) Formula ■ (However, R is C, Hz, 1.I, n"l, 2X is a halogen element, A- is an acid anion.

In addition to the above main components, electron-affinity substances may be added, such as acid anhydrides such as phthalic anhydride, maleic anhydride, benzoic anhydride, tetracyanoquinodimethane, etc., and the spectral increase of zinc oxide. Known sensitizers for improving chargeability can be used. The blending amount is 0.001 to 0.00% relative to zinc oxide.
1% by weight is suitable. If it is less than 0.001% by weight, there is almost no effect, and if it is more than 0.1% by weight, the dark current becomes thick and sufficient image contrast cannot be obtained.

The photoconductive toner is mainly composed of the above-mentioned non-polar liquid, zinc oxide, sensitizing dye, and binder resin, and has a composition ratio of 1 to 80% by weight of binder resin as solid content,
20-99% by weight of zinc oxide is suitable. Solid content ratio is 0
．． 5-20% by weight is suitable.

If the amount of binder resin is too small, the fixing properties and dispersion stability will be poor, and if it is too large, the sensitivity and migration properties upon irradiation with light will be poor.

If the amount of zinc oxide is too low, the amount of adhesion in the image area will be small and the contrast of the printed image will be lost, and if it is too high, the electrophoresis will be poor.

The conductive substrate is a metal plate such as a zinc plate or an aluminum plate that has been grained by known means or made hydrophilic by chemical treatment, and the above metal plate is coated with polyvinyl alcohol, casein, starch derivatives, or cellulose. A film made of a hydrophilic resin such as a derivative and a conductive agent such as a polymer electrolyte, an inorganic salt, or a metal powder may be added thereto to make it conductive, and the film may be coated or impregnated onto paper, synthetic paper, or plastic sheet.

Further, as the transparent electrode disposed opposite to the conductive substrate, optically transparent NESA coated with transparent mN of tin oxide or the like can be used.

The method for producing the photoconductive toner of the present invention includes mixing a dye and zinc oxide dissolved in a solvent using a carrier wave, a ball mill, a vibration mill, or a
You can add a non-polar liquid and a binder resin to the sensitized zinc oxide obtained by dispersing and adsorbing it in a sand mill or the like, then evaporate the solvent, and then disperse it with the above dispersing machine, or you can mix each substance at once. , may be dispersed.

A method for producing a lithographic printing plate using the photoconductive toner thus obtained will be described below.

As shown in FIG. 1, as a manufacturing process of a lithographic printing plate, (1) a photoconductive toner layer is provided between a transparent electrode and a counter electrode (a hydrophilic or hydrophilically treatable conductive substrate).

(2) A voltage is applied between both electrodes to attract the toner particles to the transparent electrode side.

(3) Image exposure is performed from the transparent electrode side, and the toner particles in the exposed area are moved onto the counter electrode by electrophoresis.

(4) Separate both electrodes.

(5) Fixing the toner particles on the counter electrode using a heat source such as a heater.

There are various stages.

As a means for (1), there is a method of dropping photopolar toner from above the counter electrode 2 in a dark place and covering the photopolar toner with the transparent electrode 3;
The thickness of the photoconductive toner layer, which may be provided with a dielectric layer such as ET or polyethylene, should be approximately 5 to 50 ml, as too thin will result in poor rigidity in a lithographic printing plate, and too thick will result in a decrease in sensitivity.
Approximately 500 μm is appropriate, but preferably 10 to 500 μm.
It is 100 μm.

In (2), switch 5 is closed and voltage is applied. As a result, the negatively charged toner particles between the two electrodes are attracted toward the transparent electrode. The applied voltage is 20
It is preferable that the voltage is about 0 to 1000 V, the electric field strength is 10'V/Ω or more, and the application time is 0.01 to 20 seconds.

In step (3), image exposure such as scanning exposure using a white lamp or semiconductor laser light is performed in a dark place. Then, hole-electron pairs of charge carriers are generated within the particles in the exposed portion, and the negative carriers of these hole-electron pairs move toward the transparent conductive layer 3 . Toner particles containing only holes become positively charged, are repelled by the transparent conductive layer 3, and move toward the conductive substrate 2, forming a photoelectrophoretic image on the conductive substrate. A suitable exposure amount is 1 to 1000 μJ/d.

Preferably it is 10 to 500 μJ/cd.

In (4), both electrodes are separated. At this time, it is necessary to do this so as not to destroy the image formed on the counter electrode.

For fixing (5), heat fixing using a panel heater, hot air, heat roll, etc., solvent fixing, pressure fixing, etc. can be used.

Further, there are other manufacturing methods as described below.

That is, as shown in FIG. 2, a cylindrical counter electrode 2 made of a conductive substrate that is hydrophilic or monohydrophilic is placed on the transparent electrode 3 on which the photoconductive toner is placed, and is placed at a constant distance from the transparent electrode. There is a method in which an exposed image of toner particles is formed on the counter electrode by applying a voltage between both electrodes at the same time while maintaining a distance and performing imagewise exposure from the transparent electrode side, as shown in FIG. 3. A cylindrical transparent electrode 3, which can be exposed from the inside, is rolled over the counter electrode 2 on which toner is placed, while maintaining a constant distance from the counter electrode, and at the same time, a voltage is applied between both electrodes, and the transparent There is a method in which an exposed image of toner particles is formed on the counter electrode by performing imagewise exposure from inside the electrode.

According to the methods shown in FIGS. 2 and 3, steps (1) to (4) in the above-mentioned manufacturing method can be performed simultaneously, and then a fixing process is applied to the exposed image by toner particles on the counter electrode. By applying this, a lithographic printing plate can be produced.

The lithographic printing plate obtained as described above can be subjected to an etching treatment (a aqueous treatment) prior to printing. As the etching solution, a known solution prepared by adding a colloidal substance to a weak acid such as phosphoric acid or tannic acid can be used.

In the present invention, when performing scanning exposure using a semiconductor laser, image data taken from a color scanner or the like and separated into each color version of yellow, magenta, cyan, and black can be used as a modulation signal for the semiconductor laser. For example, it is possible to easily produce lithographic printing plates of each color used in color printing. Color printed matter can be obtained by printing the lithographic printing plates of each color while adjusting the register.

<Example> Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example 1) 2 0.02 g of the cyanine dye represented by the above formula 2 was dissolved in 200 g of methyl alcohol, 80 g of zinc oxide (5AZI! After dispersing for a minute, the solvent was removed using a rotary evaporator to obtain dye-sensitized zinc oxide.

Add to this 190g of shell silua, dodecyl methacrylate.
Glycidyl methacrylate copolymer resin (weight ratio 3:1)
A photoconductive toner was obtained by adding 34 g of the solution and dispersing it in a glass bottle together with 1.0 g of glass peas in a paint shaker (manufactured by Left Devil Co., Ltd.) for 1 hour.

This toner was injected to a thickness of about 10 μm between the opposite electrode made of a grained AI plate and the transparent electrode, and a voltage of 1500 V was applied to the transparent electrode side using a power source (Trek 610B) in a dark place. 780 μm to the white light.
Using a light source equipped with an interference filter (manufactured by Toshiba Glass), the light fio is 3mJ/a! Image exposure was performed. Thereafter, both electrodes were separated, and the exposed image formed on the AI plate was heat-fixed using a dryer to obtain a lithographic printing plate.

Add this to a commercially available plate etch solution (Fuji Film - EV).
-1), and then printed using a commercially available light offset printing machine (Ryobi Printing Co., Ltd. AD-80). The result is 50
The printed image density after printing 00 sheets was 1.2 or more (Macbeth reflection densitometer RD-914), and very high quality printed matter was obtained.

(Example 2) 2) A photoconductive toner was prepared in the same manner as in Example 1, except that 0.03 g of the dye represented by the above formula (2) was used. In the printing plate manufacturing method, as shown in FIG.
A counter electrode 2 made of a roller-shaped grained plate with photoconductive toner 1 placed thereon is spaced from the transparent electrode 3 by 3.
While keeping it at 0 μm, it is rolled at a speed of 10 ma+/sec without slipping, and at the same time it is transparent. Ti
A voltage of -500 V was applied to the transparent electrode side, and image exposure was performed from the transparent electrode side using the same light source as in Example 1.

As a result, an exposed image of toner particles was formed on the AI analysis plate, and this was fixed by heating at 120"C for 2 minutes to obtain a lithographic printing plate. Using this printing plate, printing was carried out in the same manner as in Example 1. As a result, good printed matter was obtained.

(Example 3) A lithographic printing plate was prepared using the photoconductive toner of Example 1 by the method shown in FIG.

A photoconductive toner 1 is placed on a counter electrode 2 made of a grained Al plate, and a roller-shaped transparent electrode 3 having an internal light source similar to that in Example 1 and capable of image exposure from the inside is placed between both electrodes. Roll it without slipping while maintaining the interval of 35 μm. At the same time, when 1600 V was applied to the transparent electrode side and image exposure was performed from the inside of the transparent electrode, an exposed image of toner particles was formed on the Al plate. This At plate is 120°
A lithographic printing plate was obtained by heating and fixing at C for 5 minutes. When printing was carried out in the same manner as in Example 1 using this printing plate, good printed matter was obtained.

(Comparative Example 1) Except for using 0.02g of rose bengal as the pigment,
A photoconductive toner was produced in the same manner as in Example 1. Using this toner, imagewise exposure was carried out using the same apparatus and light source as in Example 1, but no exposed image of toner particles was formed on the Al plate. 1. With a white light as a light source.
When exposure was carried out under the conditions of 2IIJ/cffl, a good lithographic printing device was obtained.

(Comparative Example 2) In Example 1, cyanine dye 0.02 g '1.
A lithographic printing plate was prepared in the same manner from a photoconductive toner weighing 0.008 g. When similarly printed, toner adhesion was not sufficient to sufficiently reproduce the printed image density due to insufficient toner sensitivity, and the printed image density of the 50th sheet was 0.3 or less.

(Comparative Example 3) 0.2 g of cyanine dye 0.02 g in Example 1
A lithographic printing plate was prepared using the same photoconductive toner. When similarly printed, the image density of the 50th print was 0.5 or less, resulting in a low-quality print.

I could only get it.

<Effects> As explained above, according to the method of the present invention, a photoconductive toner whose pigment has been enhanced to near-infrared light such as a semiconductor laser is used, and direct plate making using semiconductor laser scanning exposure is possible. A good lithographic printing plate could be obtained more easily and in a shorter time than the conventional direct plate making method.

Furthermore, by using a hydrophilic conductive substrate such as graining a metal plate such as aluminum as the base material of the lithographic printing plate, a printing plate with less background staining and high stiffness resistance was obtained.

In addition, after image formation by image exposure, toner in non-image areas can be collected and reused, so printing plates can be produced at low cost.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are explanatory diagrams showing a method for manufacturing a lithographic printing plate according to the present invention. 1... Photoconductive toner 2... Counter electrode 3...
Transparent electrode 4...Glass 5...Switch
6... Photoelectrophoresis image 7... Heat source for fixing (yam) Figure 1

Claims (4)

[Claims] (1) At least an electrically insulating non-polar liquid, zinc oxide,
cyanine dye for spectral sensitization that has absorption sensitivity to near-infrared light;
A photoconductive toner layer composed of a binder resin and a transparent electrode is provided between a transparent electrode and an opposing electrode composed of a hydrophilic or hydrophilically treatable conductive substrate, a voltage is applied between both electrodes, and an image is imaged through the transparent electrode. A method for producing a lithographic printing plate, which comprises performing exposure to form a photoelectrophoretic image of toner particles on a counter electrode, then separating both electrodes, and fixing the toner particles on the counter electrode. (2) Roll a cylindrical counter electrode made of a hydrophilic or hydrophilically treatable conductive substrate over the transparent electrode on which the photoconductive toner is placed, while keeping the transparent electrode at a constant distance, and simultaneously roll the transparent electrode between the two electrodes. A method for producing a lithographic printing plate, comprising forming an exposed image of toner particles on the counter electrode by applying a voltage to the electrode and performing imagewise exposure from the transparent electrode side, and then fixing the exposed image. (3) At the same time, a cylindrical transparent electrode that can be exposed from the inside is rolled over a counter electrode made of a hydrophilic or hydrophilic conductive substrate on which the photoconductive toner is placed, while maintaining a constant distance from the counter electrode. A method for producing a lithographic printing plate, comprising forming an exposed image of toner particles on the counter electrode by applying a voltage between both electrodes and performing imagewise exposure from inside the transparent electrode, and then fixing the exposed image. . (4) The method for producing a lithographic printing plate according to any one of claims 1 to 3, wherein the ratio of the sensitizing dye to zinc oxide in the photoconductive toner is 0.01 to 0.1% by weight.