JPH0962039A - Electrophotographic planographic printing plate material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive electrophotographic planographic printing plate material having excellent dimensional stability and little fog in a printed plate under low moisture condition. SOLUTION: An intermediate layer and a photoconductive layer are successively formed on a water-resistant supporting body, and a back layer containing a conducting agent is formed on the other surface of the water-resistant supporting body to constitute an electrophotographic planographic printing plate material. The Young's modulus in the transverse direction calculated from the stress-strain curve obtd. from a wet tensile strength test for 10min dipping time according to JIS P 8135 is specified to >=1500kN/m<2> .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrophotographic lithographic printing plate material, and more specifically, it is excellent in dimensional stability, does not cause image fog at low humidity in a plate-making product, and is inexpensive electrophotographic lithographic printing plate. It concerns printing materials.

[0002]

2. Description of the Related Art In recent years, the development of small offset printing machines,
And with the development of automatic printing machines, the mainstream of light printing is shifting to offset printing. Many researches and developments have been made on such offset printing plate materials, and various offset printing plate materials have been put to practical use. Among these offset printing plate materials, the electrophotographic lithographic printing plate material having a photoconductive layer containing zinc oxide as a main component is inexpensive,
Moreover, it is the mainstream of light printing plate materials because the plate making process is simple.

The electrophotographic lithographic printing plate material is usually a corona electrified in a desired pattern by using a plate making machine as the printing plate material.
It is obtained by exposing, developing and fixing processes to form a visible image of a desired pattern on the photoconductive layer. In the developing step, there are a dry developing method using a mixture of toner and a carrier such as iron powder, and a wet developing method using a developing solution in which the toner is dispersed in an organic solvent such as Isopar.

In the case of plate making using the wet development method,
It has advantages such as good halftone reproducibility, excellent resolution, short plate-making time, and no need for correction.
Therefore, electrophotographic lithographic printing plate materials prepared by the wet development method are widely used.

In recent years, computers have been remarkably used in the printing industry, and a plate making method is shifting from an analog method to a digital method. The electrophotographic lithographic printing plate material compatible with this digital system is 780 as a sensitizing dye for the photoconductive layer.
The so-called computer-to-plate method, in which computer data is directly exposed to semiconductor laser light with an oscillation wavelength of 780 nm by blending a cyanine dye that sensitizes in the vicinity of nm, has become widely used. .

The electrophotographic lithographic printing plate material is required as a lithographic printing plate material in addition to image characteristics such as image density, fog, sharpness, image uniformity and printing background stain generally required as an electrophotographic copying material. It is necessary to have various characteristics such that the non-image area of the printing plate that has undergone the developing process can be desensitized. Further, as a printing plate material, it is necessary that the plate elongation is small and the dimensional accuracy is high.

Various methods have been proposed to improve the image characteristics and dimensional stability as described above. JP 58
JP-A-96594 attempts to improve plate elongation by including a water-soluble resin and a melamine resin in the intermediate layer and crosslinking and curing the resin with an acid catalyst. JP-A-60-
JP-A-83043 attempts to improve plate elongation by crosslinking and curing the intermediate layer with an unsaturated carboxylic acid alkali metal salt.

However, in these conventional techniques, 1000
The limit is to keep the plate elongation at the time of sheet printing to about 0.8%. At present, in the field of light printing, the colorization of form printing has become widespread, and higher dimensional stability is required. It is necessary to reduce the plate elongation at the time of printing 1,000 sheets to 0.5% or less. .

[0009]

SUMMARY OF THE INVENTION The present invention solves the drawbacks of the prior art, provides an inexpensive electrophotographic lithographic printing plate material having excellent dimensional stability, no image fog even in a platemaking product at low humidity. Especially.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to solve the above problems, and as a result, formed an intermediate layer and a photoconductive layer on one surface of a water-resistant support successively, An electrophotographic lithographic printing plate material comprising a back layer containing a conductive agent formed on the other surface of a water resistant support according to JIS
It is possible to solve this problem by setting the Young's modulus in the lateral direction calculated from the stress-strain curve obtained from the wet tensile strength test measured with a water immersion time of 10 minutes based on P8135 to 1500 kN / m ² or more. Heading, completes the present invention.

It has been found that the plate elongation is rolled by the etchant, the water elongation caused by the penetration of dampening water into the water resistant support, and the nip pressure between the plate cylinder and the blanket cylinder. In other words, as a result of intensive research conducted by paying attention to the strength of the printing plate in a wet state wet with water, it was found that the plate elongation greatly depends on the wet tensile strength property, and the present invention was completed.

According to JIS P 8135, the Young's modulus in the transverse direction calculated from the stress-strain curve measured by a wet tensile strength test at a water immersion time of 10 minutes is 1500 kN / m.
^Although any method may be used to obtain ² or more, the conductive agent used in the back layer is a needle-shaped conductive pigment having a major axis diameter of 2 to 30 μm or a conductive pigment having a particle diameter of 3 to 20 μm. Is the most effective.

The acicular conductive pigments include potassium titanate, aluminum borate, zinc oxide, titanium oxide,
Alumina, boron nitride, titanium nitride, alumina, magnesium hydrogensulfate, barium sulfate, etc. are used to form a tin oxide on the needle-shaped crystal pigment surface having a major axis diameter of 2 to 30 μm and a minor axis diameter of 0.2 to 1.2 μm. Those coated with a metal oxide such as the above or a conductive substance such as carbon can be used. Examples of the conductive pigment include potassium titanate, aluminum borate, zinc oxide, titanium oxide, aluminum nitride, boron nitride, titanium nitride, alumina, magnesium hydrogensulfate, barium sulfate, etc., and pigments having a particle size of 3 to 20 μm. It is possible to use a material whose surface is coated with a metal oxide such as tin oxide or a conductive material such as carbon.

BEST MODE FOR CARRYING OUT THE INVENTION

The back layer of the present invention comprises a conductive agent such as synthetic hectorite disclosed by the present inventors in Japanese Patent Application No. 6-309070, a binder resin, and an auxiliary additive component which can be added if necessary. Become. In the present invention, the purpose of containing a conductive agent in the back layer is to prevent image fog in plate making under low humidity conditions, and the surface electric resistance value of the back layer is 1.0 × 10 ⁷ Ω / □ to 1. 0 × 10 ¹² Ω /
This is because of □.

Examples of pigments usable in the back layer of the present invention include inorganic substances such as calcium carbonate, magnesium carbonate, kaolin, talc, calcined clay, silica, diatomaceous earth, mica, synthetic aluminum silicate, aluminum hydroxide and barium sulfate. Examples thereof include pigments.
The compounding ratio of the pigment is 10 to 80 of the solid content of the paint in the back layer.
It is preferably used in the range of weight%.

The binder resin used in the back layer of the present invention may be a water-dispersible hydrophobic resin and / or a water-soluble resin. It is preferable to use the compounding ratio of the water-dispersed hydrophobic resin in the range of 10 to 80% by weight based on the solid coating weight of the back layer, and the mixing ratio of the water-soluble resin to 10% by weight or less of the solid coating weight of the back layer.

Examples of the water-dispersible hydrophobic resin include styrene-butadiene latex, acrylic emulsion, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, and methacrylic acid ester copolymer. Polymer emulsions and acrylic ester copolymer emulsions can be used. As the water-soluble resin, for example, polyvinyl alcohol, oxidized starch, modified starch, gum arabic, gelatin, casein, chitosan and the like can be used.

To form the back layer in the present invention,
An aqueous coating material for the back layer is applied to the other surface of the water resistant support, and the applied layer is dried and solidified to form a film. As a method of applying the back layer coating material, a Meyer bar method, an air knife method, a blade method, a reverse roll method, a slit die method, or the like can be used, and the method is not limited to these. The coating amount after drying the back layer is 5
It is preferably in the range of ˜30 g / m ² .

The water-resistant support used to form the electrophotographic lithographic printing plate material of the present invention is a paper substrate that has been subjected to a water-proof treatment such as a size press. However, a laminated paper in which aluminum or polyethylene is attached to a paper substrate, a synthetic paper, or the like becomes expensive, so that an inexpensive printing plate material cannot be provided and is not used.

The components of the intermediate layer of the present invention are pigments, binder resins and the like. Further, if necessary, auxiliary additive components such as a dispersant, a conductive agent, and a water resistant agent for strengthening water resistance may be added to the intermediate layer. As the pigment, binder resin and the like that can be used in the intermediate layer of the present invention, those similar to the back layer can be used.

As the conductive agent used in the intermediate layer of the present invention, for example, a cationic conductive resin such as polyvinylbenzyl trimethyl ammonium chloride, polydimethyl diallyl ammonium chloride, styrene acrylic acid trimethylaminoethyl chloride copolymer, polystyrene sulfone, etc. Examples thereof include anionic conductive resins such as acid salts, polyacrylates and polyvinyl sulfonates, and conductive pigments such as carbon black and needle-shaped conductive pigments.

The coating amount of the intermediate layer after drying is 3 to 30 g /
It is in the range of m ² , and preferably 5 to 20 g / m ² . As the method for applying the intermediate layer paint, for example, the same method as for the back layer can be used.

The photoconductive layer of the present invention comprises zinc oxide, titanium oxide or the like as a photoconductive pigment, a binder resin, a sensitizing dye,
A coating material consisting of a solvent and a solvent is applied onto the intermediate layer and dried to form the coating. The coating amount of the photoconductive layer after drying is 20 to 30.
It is in the range of g / m ² . If it is less than 20 g / m ² , the image density will be low, and if it is more than 30 g / m ² , the charging potential will reach saturation and the image density will not be improved and the cost will be high. As the method for applying the photoconductive layer coating material, the same method as for the back layer can be used.

Examples of the binder resin used in the photoconductive layer of the present invention generally include hydrophilic acrylic acid ester copolymers, methacrylic acid ester copolymers, vinyl acetate copolymers, silicone resins and butyral resins. be able to. There is no problem with copolymerizing a monomer having a functional group such as acrylic acid, methacrylic acid or maleic acid with these binder resins for the purpose of improving image quality and the like. The binder resin contained in the photoconductive layer is
10 to 30% by weight is preferable with respect to the photoconductive pigment, and 1
More preferably, it is in the range of 5 to 20% by weight.

Examples of the sensitizing dye used in the photoconductive layer of the present invention include rose bengal, uranine, BPB (bromphenol blue), nigrosine and cyanine.
Various sensitizations such as photosensitive materials, electron-accepting substances, and compounds having a maximum absorption wavelength for light in the wavelength range of 700 to 1000 nm for sensitivity to light having an oscillation wavelength of a semiconductor laser, which have been conventionally used. Agents can be used.

If necessary, an auxiliary additive component such as a sensitizing aid may be added to the photoconductive layer of the present invention. Examples of the sensitization aid include maleic anhydride, phthalic anhydride, cobalt salt, manganese salt and the like.

[0027]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these. In each example, "part" represents "dry weight part".

Example 1 An electrophotographic lithographic printing plate material was prepared by the method described below and its characteristics were evaluated. (1) A surface sizing agent having the following composition was formed on the surface of a paper substrate having a basis weight of 100 g / m ² by a size press treatment at a coating amount of 2 g / m ² after drying to obtain a water resistant support. Surface sizing agent Polyvinyl alcohol 80 parts Sodium polyacrylate 20 parts

(2) Next, the following intermediate layer coating material was applied to one surface of the water resistant support so that the coating amount after drying was 20 g / m ² . Intermediate layer paint Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 30 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 30 parts Urethane emulsion (trademark: Vylok RL-3, manufactured by Kanebo NSC) 35 parts Poly Sodium acrylate (trademark: Primal 850, made by Japan Acrylic) 5 parts

(3) The following back layer coating material was applied on the water-resistant support on the opposite side provided with the intermediate layer, and the coating amount after drying was 10 g.
It was applied so as to be / m ² . Back layer material Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 47 parts Needle-like conductive pigment (conductive potassium titanate, trademark: Dentol WK-200B major axis diameter 10 to 20 μm, minor axis diameter 0.4 μm, Otsuka Chemical Co., Ltd.) 8 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 20 parts Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts On the back surface of the printing plate obtained as described above The surface electric resistance was measured at 20 ° C. and 30% RH.

(4) Further, the following photoconductive layer coating material was applied onto the intermediate layer so that the coating amount after drying was 25 g / m ² . Photoconductive layer paint Photoconductive zinc oxide (trademark: Sazex 2000, manufactured by Sakai Chemical) 85 parts Silicone resin (trademark: KR-211, manufactured by Shin-Etsu Chemical) 15 parts Rose Bengal 0.1 part

A plate for printing in which the length of a straight line of 200 mm was accurately entered was prepared, immersed in a flat container containing water for 15 minutes, and then the length of the straight line was measured (the first sheet was printed. length). In addition, a printing plate made with an Itek 275 type electronic plate making machine is treated with an etching solution (made by Itek Co.) as a desensitizing resin, and the solution obtained by diluting the etching solution 7 times with water is used as dampening water. After printing 3000 sheets with an offset printing machine (Ryobi 2800CD), the length of the straight line was measured (300
(Print length of 0th sheet). Table 1 shows the results of plate elongation calculated from the following formula (1). (Plate elongation) = {(printing length of 3000th sheet)-(printing length of 1st sheet)} / (printing length of 1st sheet) x 100 [%] (1)

1 to pure water based on JIS P 8135
Immerse for 0 minutes, then TENSILON (TOYO BALD
A stress-strain curve was obtained from a wet tensile strength test using WIN) and Young's modulus was calculated.

Example 2 An electrophotographic lithographic printing plate material was prepared in the same manner as in Example 1 except that the back layer coating composition was changed to the following composition, and its characteristics were evaluated. The results are shown in Table 1. Back layer paint Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 20 parts Needle-like conductive pigment (needle-like conductive titanium oxide, trademark: FT-2000, major axis diameter 2.9 μm, minor axis diameter 0.2 μm , Ishihara Sangyo) 35 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 20 parts Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts

Example 3 An electrophotographic lithographic printing plate material was prepared in the same manner as in Example 1 except that the back layer coating composition was changed to the following composition, and its characteristics were evaluated. The results are shown in Table 1. Back layer paint Kaolinite clay (Trademark: Hydrogloss 90, manufactured by Huber) 35 parts Plate-like conductive pigment (conductive barium sulfate, trademark: Pastran TYPE-IV, particle size 7 μm, manufactured by Mitsui Metal Co., Ltd.) 20 parts Acrylic emulsion (trademark) : A-104, manufactured by Toagosei) 20 parts Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts

Comparative Example 1 An electrophotographic lithographic printing plate material was prepared in the same manner as in Example 1 except that the back layer coating composition was changed to the following composition, and its characteristics were evaluated. The results are shown in Table 1. Back layer paint Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 10 parts Conductive pigment (granular conductive titanium oxide, trademark: ET-500W, particle size 0.2 to 0.3 μm, manufactured by Ishihara Sangyo) 45 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 20 parts Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts

Comparative Example 2 An electrophotographic lithographic printing plate material was prepared in the same manner as in Example 1 except that the back layer coating composition was changed to the following composition, and its characteristics were evaluated. The results are shown in Table 1. Back layer coating carbon black aqueous dispersion (trademark: LKB-100, manufactured by Hoechst Synthetic) 5 parts Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 50 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 20 Part Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts

Comparative Example 3 An electrophotographic lithographic printing plate material was prepared in the same manner as in Example 1 except that the back layer coating composition was changed to the following composition, and its characteristics were evaluated. The results are shown in Table 1. Back layer paint Kaolinite clay (trademark: Hydrogloss 90, manufactured by Huber) 50 parts Sodium polyacrylate (trademark: Primal 850, manufactured by Nippon Acrylic) 5 parts Acrylic emulsion (trademark: A-104, manufactured by Toagosei) 20 parts Styrene-butadiene latex (trademark: L-1537A, manufactured by Asahi Kasei) 25 parts

[0039]

[Table 1]

[0040]

According to the present invention, even in low humidity plate making,
It is possible to produce an electrophotographic lithographic printing plate material that is free from image fog, has good dimensional stability, and is excellent in image quality, and is extremely useful industrially.

Claims (1)

[Claims] 1. An electrophotographic lithographic plate comprising an intermediate layer and a photoconductive layer which are sequentially formed on one surface of a water resistant support and a back layer containing a conductive agent which is formed on the other surface of the water resistant support. In the printing plate material, the Young's modulus in the lateral direction calculated from the stress-strain curve obtained from the wet tensile strength test measured at a water immersion time of 10 minutes according to JIS P 8135 was 150.
An electrophotographic lithographic printing plate material characterized by being 0 kN / m ² or more.