JPH0450950A - Electrophotographic planographic printing plate material - Google Patents

Abstract

PURPOSE:To prevent occurrence of uneven scanning by adding a mixture of 2 kinds of specified sensitizing dyes to an electrophotographic sensitive layer containing zinc oxide as a photoconductor. CONSTITUTION:The electrophotographic sensitive layer containing photoconductive zinc oxide, a binder resin, a chemical sensitizer, and the sensitizing dyes is formed on a water-resistant conductive substrate. The sensitizing dyes are composed of the one having a light absorption peak in the wavelength region of 400-700 nm and contained in an amount of 0.03-0.3 wt.% of the solid of the photosensitive layer and th one having a light absorption peak in the 760-820 nm and contained in an amount of 0.003-0.05 wt.% of the solid of the photosensitive layer, thus permitting uneven scanning to be reduced by adding a large amount of sensitizing dye absorbing short wavelength lights.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic lithographic printing plate material suitable for electrophotographic engraving using a semiconductor laser light source.

[Conventional technology]

A lithographic printing plate material using zinc oxide as a photoconductor, a so-called zinc oxide offset master, is widely used in the light printing industry because it is inexpensive and the plate-making process is simple.

Conventionally, in the plate making of this type of printing plate material, a so-called camera-based plate making method has been used, in which visible light from a halogen lamp or the like is used as an exposure light source, and the reflected light from the original is irradiated onto the plate surface. However, in recent years, with the development of recording equipment and the spread of data digitization, the so-called computer-to-plate method, in which the plate surface is scanned and exposed using a laser beam driven according to computer data, is sometimes used. It's becoming more common.

Among laser beams, semiconductor laser beams, which have a compact generator and can be directly modulated, are particularly useful.

As a zinc oxide offset master material that can be used for semiconductor laser light, a lithographic printing material that is spectrally sensitized with a sensitizing dye and has the highest sensitivity to light at a wavelength of around 780 nm of semiconductor laser light is used.

In this type of lithographic printing material, scanning unevenness is a particular problem in practical use. That is, in the conventional camera-based plate making method, non-image areas are exposed simultaneously and uniformly, so unevenness in illuminance is less likely to occur. However, in scanning exposure using laser light, uneven illuminance inevitably occurs due to gaps or overlapping of scanning lines. For this reason, density unevenness in the form of fine horizontal stripes parallel to the scanning line may occur even in the non-image area of the developed plate. This density unevenness not only deteriorates the appearance of the developed plate, but also may actually lead to printing stains, posing a major problem in terms of plate quality. In order to solve this problem, various researches have been made in terms of sensitizing dyes and binder resins, but a sufficient solution has not yet been found.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic lithographic printing plate material that can be used in an electrophotographic process using semiconductor laser light and does not cause scanning unevenness.

(Means for Solving the Problems) As a result of intensive research into electrophotographic printing plate materials that do not have the problem of scan unevenness and can be used with semiconductor laser light, the inventors found that 400 to 70
A mixture of a predetermined amount of a sensitizing dye compound having an absorbance peak at a wavelength of 0r+a+ and a predetermined amount of a sensitizing dye compound having an absorbance peak at a wavelength of 760 to 830n11+ is added to an electronic compound containing zinc oxide as a photoconductive material. It has been discovered that the above object can be achieved by adding it to a photographic light-sensitive layer.

That is, the electrophotographic lithographic printing plate material of the present invention includes a support having conductivity and water resistance, a photoconductive zinc oxide, a resin binder, and a chemical enhancer formed on one surface of the support. an electrophotographic photosensitive layer containing a sensitizer and a sensitizing dye, the sensitizing dye has an absorbance peak within a wavelength range of 400 to 700r+n+, and the solid content weight of the electrophotographic photosensitive layer 0.03 to 0.3% of the sensitizing dye compound, having an absorbance peak within the wavelength range of 760 to 820 nm, and 0.003 to 0.0% of the solid content of the electrophotographic photosensitive layer. .05% of a sensitizing dye compound.

In order to spectrally sensitize zinc oxide to semiconductor laser light, a sensitizing dye having an absorbance peak within a wavelength range of 760 to 830 nm is added at a rate of 0.00% relative to the solid weight of the electrophotographic photosensitive layer.
It is known that the compound is added to an electrophotographic photosensitive layer together with a chemical sensitizer in an amount of 0.003 to 0.05%.

In order to reduce scan unevenness, it is effective to increase the amount of sensitizing dye added, but if the amount is increased too much, the sensitivity will increase excessively, resulting in the problem of decreasing exposure latitude and making it easier for fine lines to fly out. 0 The inventor of the present invention did not increase the amount of the sensitizing dye that absorbs semiconductor laser light (but added a large amount of sensitizing dye compound that absorbs visible light with a shorter wavelength to such a sensitizing dye compound). The present invention was completed by discovering that the desired effect, that is, reduction of scan unevenness, can be obtained by adding a visible light absorbing dye compound to a semiconductor laser. It was discovered that the other properties necessary for a lithographic material, such as electrical properties and plate-making properties, were not adversely affected, and the performance could therefore be further improved.

A secondary effect of this invention is that this lithographic material can also be used for camera-based plate making using visible light. This not only provides printers with the convenience of simplified material procurement, but also has the advantage of increased flexibility in the platemaking process.

As the sensitizing dye compound having an absorbance peak in the wavelength range of 760 to 830 nm, polymethine-based cyanine dye compounds are suitable for use in the present invention, such as those of the following formula (
I) and compounds of formula (n). However, it is not limited to these.

If the amount of the sensitizing dye compound having an absorbance peak in the wavelength range of 760 to 830 nm is less than 0.003%, sufficient sensitivity to semiconductor laser light cannot be obtained;
If it exceeds 5%, the exposure latitude will decrease.

Examples of the sensitizing dye compound having an absorbance peak at a wavelength of 400 to 700 nm that can be used in the present invention include Eva, rose bengal, phthalocyanine, rhodamine B, fluorescein, methylene blue, etc.
It is not limited to these. If the amount of these sensitizing dyes added is less than 0.03%, the effect of reducing scan unevenness will be small, and if it is more than 0.3%, the electrical properties of the lithographic printing material will deteriorate.

Examples of the chemical sensitizer used in the present invention include cyclic acid anhydrides such as phthalic anhydride, maleic anhydride, dichloromaleic anhydride, pyromellitic anhydride, and trimellitic anhydride. It is not limited to.

The zinc oxide used in the electrophotographic photosensitive layer has photoconductivity, and the -S used is a fine powder having a particle size of 0.1 to 0.5 .mu.m.

The insulating bonding resin used in the electrophotographic photosensitive layer may be a single resin or a mixture of two or more resins. Such a binding resin has film-forming properties that bind the zinc oxide fine powder and other components, appropriate dielectricity, and does not impair photoconductivity. Although there are no particular limitations on the type, it is generally preferable to use an oil-soluble acrylic resin. As such oil-soluble acrylic resin, for example, L manufactured by Mitsubishi Rayon Co., Ltd.
I? 188 (trademark), Acridic A405 (trademark) manufactured by Dainippon Ink and Chemicals, and the like.

The solid content of the binder resin contained in the electrophotographic photosensitive layer is preferably 10 to 30%, more preferably 15 to 25%, based on the weight of zinc oxide.

Toluene, 2-butanone, butyl acetate, etc. can be used as a solvent to dissolve each of the above components to prepare a coating solution, but they must have an appropriate evaporation rate and have a relatively low odor. Toluene is often selected because of its low content.

The support for the lithographic printing plate material of the present invention is electrically conductive and water resistant, and includes paper, a laminate of paper and aluminum foil, or a polymer film treated to be electrically conductive, and a vapor-deposited metal layer. You can choose from paper with

The thickness of the support is generally preferably 100 to 170 nm. In addition, the thickness of the entire printing plate material is 130 to 200 mm.
Preferably it is 1M.

In order to improve the water resistance of the printing plate material, an intermediate layer may be formed between the support and the photoconductive layer. Components forming such an intermediate layer generally include water-soluble molecules such as polyvinyl alcohol, casein, and starch, acrylic ester copolymers, and SBR.
A polymer material selected from synthetic resin emulsions such as
A mixture of melamine-formaldehyde resin, glyoxal, and a water-resistant agent such as a silane coupling agent is used. The weight of the intermediate layer is generally preferably 5 to 10 g/h (dry weight).

To produce the electrophotographic printing plate material of the present invention, first, predetermined amounts of zinc oxide, a sensitizing dye compound for laser light, a sensitizing dye compound for visible light, a chemical sensitizer, and a binder resin are mixed with toluene, etc. A coating solution is prepared by mixing the mixture into a solvent and dispersing it using a mixing and dispersing machine such as a ball mill, sand glider 2, or paint shaker.

Next, the obtained coating liquid is applied onto one side of the support via an intermediate layer or directly, and is dried to form an electrophotographic photosensitive layer. The thickness of the photosensitive layer in this case affects the electrophotographic properties, and is usually 5 to 25 mm thick.
It is preferable that it is Ins, and it is more preferable that it is in the range of 10 to 20 trm.

There are two methods for plate making using the lithographic printing material of the present invention. First, when using a semiconductor laser light source,
An electrostatic latent image is formed on the photosensitive layer of the lithographic printing plate material by scanning exposure using semiconductor laser light according to digital data, and then this latent image is usually developed with a liquid developer to form an image. Heat and fix.

In addition, when using a visible light source such as a halogen lamp,
Using a camera-type plate-making machine, the plate surface is irradiated with reflected light from an image to be used as a master plate for a predetermined period of time. The electrostatic latent image thus obtained is developed and fixed in the same manner as above.

Furthermore, one printing plate can be made using both light sources. That is, for example, first, the lithographic printing material according to the present invention is subjected to primary plate making using a camera-type plate making machine that uses a visible light source, and then the obtained plate-made product is supplied to a laser light plate making machine. Make the second plate. In such a method, for example, an illustration image can be formed using a camera type plate making machine, and then a character image can be created on a single printing plate using a laser plate making machine.

To perform offset printing using a printing plate obtained by any of the above methods, the surface of the plate-made printing plate is treated with a so-called etching liquid containing potassium ferrocyanide etc. to make the non-image area hydrophilic. Thereafter, it may be attached to an offset printing machine and printing operations may be performed in a conventional manner.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

However, these are not intended to limit the scope of the invention.

In addition, "parts" and "%" in the examples represent "parts by weight" and "% by weight", respectively, unless otherwise specified.

S11''1 The following coating liquid components were added to a rotary stirrer in the order listed and mixed.

Toluene methanol zinc oxide 5AZBX#2000 manufactured by Sakai Chemicals
A coating solution was prepared by dispersing the mixed solution of 80 and 2 using a sand grinder.

As a support, a composite sheet obtained by laminating 10 layers of aluminum foil on conductive-treated paper with a basis weight of 80 g/rrf was used.

The photosensitive layer coating solution was applied onto the aluminum foil layer of the support and dried to form a photosensitive layer having a basis weight of 25 g/rrf to obtain a lithographic printing plate material.

The obtained printing plate material was plate-made by a conventional method using a laser plate-making machine manufactured by Toppan Printing Co., Ltd. to form an image of a test pattern. The properties of this plate are shown in Table 1.

The resulting printing plate had a clear image, and when it was treated with an etchant and subjected to offset printing, clear printed matter was obtained without any problems.

Implementation The same operation as in Example 1 was performed. However, in the plate-making process, a camera-type ITek 235 plate-making machine was used to obtain a lithographic printing plate. The resulting printing plate had a clear image, and when it was treated with an etchant and subjected to offset printing, clear printed matter was obtained without any problems.

The lithographic printing plate material obtained in Main Example 1 was subjected to camera method I
The plate was supplied to a tek235 plate making machine, and a primary plate was made using the illustration image as a base plate to obtain a plate. The plate-made product thus obtained was immediately supplied to a laser plate-making machine manufactured by Toppan Printing Co., Ltd., and second plate-making was performed using computer character data.

When the resulting printing plate was treated with an etchant and offset printed, clear printed matter with illustrated text could be obtained.

The same operation as in Example 1 was performed. However, rose bengal and fluorescein were not added to the photosensitive layer coating solution.

The obtained lithographic printing plate material was subjected to plate making using a laser plate making machine manufactured by Toppan Printing Co., Ltd. using the same laser output as in Example 1. The results of measuring the optical/electrical properties of the obtained plate were measured in the first
Shown in the table.

Table 1 [Effects of the Invention] According to the present invention, it has become possible to use an electrophotographic lithographic printing plate material for semiconductor laser light, which is free from scanning unevenness and is used for plate making of lithographic printing plates. Further, the present invention provides an electrophotographic lithographic printing material that can be used for both a semiconductor laser light source and a visible light source.

Claims (1)

[Scope of Claims] 1. A support having conductivity and water resistance, and a photoconductive zinc oxide formed on one surface of the support, a resin binder, a chemical sensitizer, and a sensitizer. and an electrophotographic photosensitive layer containing a sensitizing dye, wherein the sensitizing dye has an absorbance peak within a wavelength range of 400 to 700 nm, and the electrophotographic photosensitive layer has an absorbance peak of 0.000 nm relative to the solid content weight of the electrophotographic photosensitive layer. 03 to 0.3% of a sensitizing dye compound, and 7
It has a peak of absorbance within a wavelength range of 60 to 820 nm, and has an absorbance peak of 0.000 nm relative to the solid content weight % of the electrophotographic photosensitive layer.
An electrophotographic lithographic printing material characterized in that it consists of a mixture with 0.003 to 0.05% of a sensitizing dye compound.