JPH0481790B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic lithographic printing plate material. More specifically, the present invention relates to an improved electrophotographic lithographic printing plate material that exhibits less deterioration in image quality due to changes over time, less plate elongation, and excellent printing durability. [Prior art] In recent years, the development of small offset printing machines and
With the development of automated printing equipment, the mainstream of light printing has become
It is becoming dominated by offset printing. A large amount of research and development has been carried out regarding such printing plate materials for offset printing, and various materials have been proposed and are being put into practical use. These offset printing plate materials have a support and a photoconductive layer, and in particular, electrophotographic lithographic printing plate materials having a photoconductive layer using zinc oxide as the main component of the photoconductive pigment are inexpensive. It is the most popular light printing plate material because it has a simple plate-making process. To prepare an electrophotographic lithographic printing plate from its printing plate material, the printing plate material is subjected to corona charging, exposure, development and fixing processes in a desired pattern using a plate making machine to form a photoconductive layer of the printing plate material. A visible image of the desired pattern is formed. Generally, the above-mentioned developing process includes a dry developing method using a mixture of toner and a carrier such as iron powder as a developer, and a wet developing method using a developer in which toner is dispersed in an organic solvent such as Isopar. The above-mentioned wet development method has advantages such as good midtone reproducibility, excellent resolution, short platemaking time, and no correction process required in the resulting printed matter. There is. For this reason, wet development is the most widely used method for producing electrophotographic lithographic printing plates. Electrophotographic printing plate materials are required to be compatible with the above-mentioned printing plate manufacturing process and to exhibit high quality in the resulting images; It was also required that the plates have excellent printing properties. For example, a lithographic printing plate produced through a development process must be capable of desensitizing its non-image areas. In addition, lithographic printing plate materials can be made hydrophilic in non-image areas by treating the surface of the exposed photoconductive layer with an etching solution; Since it comes into contact with dampening water, it is necessary to have excellent water resistance. In view of the above requirements, it is known to provide an intermediate layer between the support and the photoconductive layer in order to improve water resistance. Generally, the intermediate layer of electrophotographic printing plate materials includes:
It is required to have the following characteristics. (1) Good barrier properties. (2) Excellent solvent resistance. (It must not be damaged by the solvent of the photoconductive layer paint.) (3) It must have excellent water resistance. (4) Appropriate electrical resistance value (1 at 20℃, 65RH)
×10 ⁹ to 9 × 10 ¹¹ Ω-cm). However, solvent resistance and water resistance are mutually contradictory properties, and it is therefore important to maintain a balance between them.With this point in mind, various improvements have been made to the structure of the intermediate layer. There is. For example, synthetic resin emulsion, hydrophilic polymer,
Also known is an intermediate layer using a waterproofing agent (glyoxal, urea resin, melamine resin, etc.) (Japanese Patent Publication No. 11902/1982). However, such intermediate layers are unsatisfactory in terms of water resistance. Furthermore, formalin or glyoxal contained in the water-resisting agent is liberated from the intermediate layer over time, adsorbs to the surface of the zinc oxide particles in the photoconductive layer, and deteriorates the photoconductive layer. There were problems such as interfering with oxygen reabsorption of the pigment after irradiation with light and worsening the exposure property. Therefore, the present inventor has already proposed the use of a specific silane coupling agent as a useful waterproofing agent for the intermediate layer. Conventionally, binders for intermediate layers that satisfy the above-mentioned properties have generally been water-soluble polymers such as polyvinyl alcohol, casein, starch, etc., or water-resistant agents such as amino resin condensates of these water-soluble polymers. crosslinking reaction products with are widely used. It is also known to mix synthetic resin emulsions and the like with these binders. However, when using the above-mentioned crosslinking reaction product, if the crosslinking reaction is carried out in the paint before being applied to the support, the paint will thicken and gel, making it practically impossible to coat. In addition, in order to cause a crosslinking reaction during or after coating, it is necessary to heat the coating at a temperature of at least 150° C. for 5 minutes or more.
Such heating conditions cannot be adopted in terms of productivity and profitability on an industrial scale. In addition, if the support is exposed to such high temperatures for a long time, the support becomes brittle, making it impossible to obtain a lithographic printing original plate having the necessary physical strength. Therefore, the temperature and time expected from the commonly used coating conditions are completely insufficient to complete the crosslinking reaction, and the desired desired water resistance cannot be obtained. The printing plate precursor has extremely low printing durability. Furthermore, when a hydrophilic substance is used as an intermediate layer of an electrophotographic original plate, the adhesion between the intermediate layer and the lipophilic adhesive in the photoconductive layer becomes insufficient. In addition, it is conventionally known to use a paint consisting of a vinyl resin and an amino resin containing a functional monomer (hydroxyethyl acrylate) in the intermediate layer (Japanese Patent Publication No. 47-47610); The reaction between the group and the amino resin is slow, the resulting printing plate precursor has low water resistance, and light attenuation during image formation is poor, resulting in images with a lot of capri and poor contrast. It is also known to coat a synthetic polymer resin infiltrated or swollen with a photoconductive coating solvent between the hydrophilic polymer coating layer and the photoconductive coating applied to the surface of the support (particularly Publication No. 40-7332), but in this method, one more step is added in order to add one more lipophilic layer between the hydrophilic polymer layer and the photoconductive layer, which also causes high costs. In addition, this oleophilic layer has the disadvantage of having a negative effect on the light attenuation of the photoconductive layer. The present inventors have proposed that, as a means to eliminate or reduce the above-mentioned problems caused by providing an intermediate layer, the intermediate layer already contains wet-milled fine muscovite powder together with a binder. However, it has been desired to further improve its effects, particularly to increase the solvent resistance of the intermediate layer and the strength of the coating film, and to improve the printing durability and image density of the resulting printing plate. [Problems to be Solved by the Invention] The present invention seeks to solve problems in conventional electrophotographic printing plate materials, such as deterioration of image quality due to changes over time, low printing durability, and plate elongation. be. [Means for solving the problems and their effects] The electrophotographic lithographic printing plate material of the present invention comprises a support, a photoconductive pigment formed on one surface of the support, and a photoconductive pigment and an insulating binder. a photoconductive layer comprising: a wet-milled muscovite powder formed between the support and the photoconductive layer and having an average particle size of 5 to 50 μm; a binder; and a water-resisting agent. The waterproofing agent in the intermediate layer has the following general formula (1): R _o SiX _4-o (1) [However, in the above formula, R has 1 to 30 carbon atoms. represents one member selected from aliphatic, cycloaliphatic, aromatic, and heterocyclic organic substituents, at least one of the organic substituents represented by R is a chemically active group, and n is represents one or two integers,
X represents a hydrolyzable substituent; and the binder in the intermediate layer is an acrylic ester and a methacrylic ester. It is characterized by containing as a main component a copolymer of an ester component consisting of at least one selected from the following and a nitrile component consisting of at least one selected from acrylonitrile and methacrylonitrile. The support used in the present invention is formed from paper, laminated paper made by laminating aluminum foil or polyethylene film on paper, synthetic paper, etc.
Generally, it has a thickness of about 100 to 170 μm, for example. The photoconductive layer contains a photoconductive pigment and an insulating binder. Zinc oxide, titanium oxide, etc. are used as the photoconductive pigment. As insulating binders, acrylic ester copolymers with good hydrophilicity,
Methacrylic acid ester copolymers, vinyl acetate copolymers, silicone resins, gutilal resins, and the like are used. In each of the above copolymers and resins, acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc. form functional groups in the polymer to improve image quality, paint properties, and mechanical strength of the coating film. It is used as a copolymerization component. The photoconductive layer may contain a sensitizing dye. The intermediate layer of the printing plate material of the present invention is formed between the support and the photoconductive layer and is a wet-milled layer having an average particle size of 5 to 50 μm, preferably 5 to 40 μm, more preferably 10 to 40 μm. It contains muscovite powder, a specific water resistant agent, and a specific binder. The average particle diameter of the muscovite powder used in the present invention was measured using a light transmission particle size analyzer model SKN-1000 manufactured by Seishin Enterprise Co., Ltd. The intermediate layer according to the present invention is effective in enhancing the image quality of the resulting printing plate material, improving the printing durability, and reducing plate elongation. The chemical composition of the muscovite powder used in the present invention is represented by the general formula: K _{2 O.3Al 2} O _3.6SiO 2.2H ₂ O. A pigment similar to the muscovite of the present invention is sericite clay. Sericite is called sericite because it has a silky luster when wet with water. The chemical compositions of muscovite and sericite clay are as follows.

【table】

[However, in the above formula, R represents one member selected from aliphatic, cycloaliphatic, aromatic, and heterocyclic organic substituents having 1 to 30 carbon atoms, and At least one is a chemically active group, n represents an integer of 1 or 2, and X represents a hydrolyzable substituent]

A compound containing at least one organic silane compound represented by the following is used. The chemically active group represented by R in the above general formula (1) is, for example, a vinyl group, a glycidyl group,
It can be chosen from mercapto groups, amino groups, epoxy groups, halogen groups, and ester groups, and substituted alkyl groups containing the groups or atoms mentioned above.
Examples of other organic substituents represented by R include aliphatic substituents such as N-β (aminoethyl)-γ-aminopropyl group and γ-methacryloxypropyl group; cyclic aliphatic substituents such as γ-anilinopropyl group; group substituents; aromatic substituents such as N-β-(N-vinylbenzylaminoethyl-γ-aminopropyl group); and heterocyclic substituents such as octadecyldimethylammonium chloride. Examples of the hydrolyzable substituent represented by X in 1) include a halogen atom, an amino group, a hydroxy group, and 1-
Examples include alkoxy groups having 4 carbon atoms. The amount of waterproofing agent contained in the intermediate layer is preferably in the range of 1 to 15% by weight, preferably 5 to 10% by weight.
It is more preferable that it is within the range of . In the intermediate layer of the present invention, the organic silane compound of general formula (1) described above is effective as a water resistance agent and a solvent resistance agent. It is a chemically active group in a silane compound, such as an amino group, a vinyl group, an epoxy group, a mercapto group, that is
Alternatively, a halogen atom can undergo a crosslinking reaction to make the intermediate layer water resistant, and a hydrolyzable substituent in the silane compound, such as a methoxy group or an ethoxy group,
etc. are hydrolyzed and modified into silanol groups, and the modified silanol compounds undergo a condensation reaction to crosslink the synthetic resin and hydrophilic polymer. Through the crosslinking reaction as described above, the resulting intermediate layer can exhibit excellent water resistance and solvent resistance. In the intermediate layer of the invention, binders include acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate and diacrylic acid.
- an ester component consisting of at least one selected from ethylhexyl, etc. and methacrylic acid esters, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and glycidyl methacrylate; and an ester component selected from acrylonitrile and methacrylonitrile. It contains as a main component a copolymer with at least one nitrile component. The content of the copolymer in this binder is preferably 20 to 100% by weight, more preferably 30 to 100% by weight. By using the above-mentioned specific copolymer, the solvent resistance of the resulting intermediate layer is improved, and the strength of the intermediate layer coating is improved, resulting in improved printing durability of the resulting printing plate and density of the resulting image. will improve. In the binder for the intermediate layer according to the present invention, the copolymerization molar ratio of the ester component and the nitrile component in the copolymer is preferably in the range of 20:80 to 80:20. If the amount of the nitrile component exceeds 80 mol%, the resulting copolymer may have insufficient film-forming properties, and its solvent resistance may be too high, resulting in poor adhesion between the resulting intermediate layer and photoconductive layer. This may result in insufficient properties and reduce printing durability. Furthermore, if the amount of the nitrile component is less than 20 mol %, solvent resistance may deteriorate, and solvent may remain during coating of the photosensitive layer or coating properties may deteriorate. The amount of binder contained in the intermediate layer is 20-60% by weight
It is preferable that it is within the range of . In addition to the above copolymer, the binder contains 20% by weight or less of other polymers, such as polyacrylic ester, polymethacrylic ester, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyurethane, and polyacrylonitrile. , polymethacrylonitrile, polybutadiene, polystyrene,
It may also contain polymers such as. In addition to the above-mentioned muscovite powder, water-resistant agent, and binder, the intermediate layer also contains inorganic fillers such as clay, talc, calcium carbonate, and silica, and water-soluble polymer compounds such as starch, Alternatively, derivatives thereof, cellulose derivatives, polyvinyl alcohol, casein, vinyl acetate-maleic anhydride copolymers, etc. may be contained in a content of 20% by weight or less. The weight of the intermediate layer according to the present invention is 5 g/m ² to 15
It is preferably in the range of g/m ² , and 5 g/m ² to
More preferably, it is within the range of 10 g/m ² . In the electrophotographic printing plate material of the present invention,
A conductive layer may be formed on the back surface of the photoconductive layer. The conductive layer is made of a conductive material, such as polydiallyldimethylammonium chloride, and a quaternary material such as polyvinyldimethylammonium chloride.
A binder is made of a class ammonium type polymer compound, sodium polyacrylate, sodium polystyrene sulfonate, ammonium polystyrene sulfonate, etc., and a binder such as polyvinyl alcohol, vinyl acetate resin, acrylic resin, styrene-butadiene resin, etc. It includes. The weight of the conductive layer is 5
It is preferably within the range of ~15 g/ ^m2 . In order to produce the printing plate material of the present invention, an intermediate layer coating containing the necessary components and a solvent is coated on one surface of the support and dried, and further the necessary components and a solvent (for example, ethyl acetate, butyl acetate, A photoconductive layer coating containing (toluene or xylene) may be applied and dried. At this time, the binder used for forming the intermediate layer is mixed with other components in the form of an emulsion.
Formed with intermediate layer paint. [Example] The present invention will be further explained below with reference to Examples. Example 1 An electrophotographic lithographic printing plate material was prepared by the steps described below, a printing plate was made from it, and its properties were measured and evaluated. (1) A barrier layer of the following composition is applied on one side of base paper with a basis weight of 100 g/m ² by size and press treatment.
m ² (dry coating weight). Polyvinyl alcohol 80 parts (solid weight) Sodium polyacrylate 20 parts (solid weight) (2) Press-treated base paper of the above size (thickness)
An intermediate layer paint having the following composition was applied to the surface of the barrier layer (110 μm) and dried to form an intermediate layer with a dry coating weight of 10 g/m ² . Muscovite powder ^*1 40 parts by weight Copolymer emulsion ^*2 40 parts by weight Casein aqueous solution (10%) 10 parts by weight Silane coupling agent ^*3 10 parts by weight Note: *1 - Manufactured by Yamaguchi Mica Co., Ltd., average particle diameter :20μm *2-Butyl methacrylate (20 mol%)-
45% emulsion of butyl acrylate (20 mol%) - acrylonitrile (60 mol%) copolymer *3 - Trademark: SH6040, manufactured by Toray Silicone Co., Ltd. (3) On the surface of the intermediate layer, a photoconductive layer coating with the following composition was applied. It was coated and dried to form a photoconductive layer with a dry coating weight of 25 g/m ² . Photoconductive zinc oxide ^*4 100 parts (weight) Silicone resin ^*5 30 parts (weight) Rose Bengal 0.1 part (weight) Toluene 150 parts (weight) Note *4...Trademark: SAZEX2000, manufactured by Sakai Chemical *5...Trademark: KR-211, manufactured by Shin-Etsu Chemical (4) A conductive layer paint having the following composition was applied and dried on the back surface of the photoconductive layer to form a conductive layer with a dry coating weight of 8 g/m ² . Polyvinyl alcohol ^*6 30 parts (weight) Vinyl acetate resin ^*7 50 parts (weight) Quaternary ammonium type polymer conductive agent ^*8
20 parts (weight) Note *6...Trademark: T-330, manufactured by Nippon Gosei *7...Trademark: Cevian A-522, manufactured by Daicel *8...Trademark: Chemistat 5500, manufactured by Sanyo Chemical (5) Obtained printing plate The material was acclimatized for 24 hours in a dark room atmosphere at 50% RH and 25°C, and then
A printing plate having a predetermined pattern was created using a 175-type electronic plate making machine. (6) Evaluation of the deterioration of image quality due to changes over time was performed as follows. The obtained printing plate material was placed in a black polyvinyl chloride bag, the bag was sealed, and the bag was left for one month at a temperature of 35°C. This was pre-exposed to 1000 lux for 10 seconds, and the charging characteristics of the photoconductive layer were measured using EPA (manufactured by Kawaguchi Electric). Thereafter, this printing plate material was made into a printing plate using an ITEC 175 plate making machine.
The pre-exposure properties of the printing plate materials before and after the aging test were compared based on the EPA measurement value. The results are shown in Table 1. (7) The printing test of the obtained printing plate was carried out by first desensitizing the printing plate with an etching liquid (manufactured by ITETICS Co., Ltd.), using an offset printing machine (Hamada Star 500), and using New Champion F as the ink. A printing durability test (picking evaluation) and plate elongation test were conducted using gloss (black). The results are shown in Table 1. Example 2 The same operation as in Example 1 was performed. However, the composition of the intermediate layer paint was as follows. Muscovite powder ^*9 40 parts by weight Copolymer emulsion ^*10 40 parts by weight Cezein aqueous solution (10%) 10 parts by weight Silane coupling agent ^*11 10 parts by weight Note *9...Manufactured by Yamaguchi Mica Co., Ltd., average particle diameter: 10 μm *10...45% emulsion of methyl methacrylate (30 mol%)-ethyl acrylate (30 mol%)-acrylonitrile (40 mol%) copolymer *11...Trademark: SH6040, manufactured by Toray Silicone Co., Ltd. Comparative Example 1 Example 1 I performed the same operation. However, in the intermediate layer paint, Zeeklite clay (manufactured by Zeeklite Industries Co., Ltd., 35% sericite) is used instead of muscovite powder.
) was used. The results of the pre-exposure plate elongation and printing durability tests are shown in Table 1. Comparative Example 2 The same operation as in Example 1 was performed. However, the composition of the intermediate layer paint was as follows. Muscovite 40 parts (weight ratio) Copolymer emulsion (same as Example 1)
40 parts (weight ratio) Casein aqueous solution (10%) 10 parts (weight ratio) Glyoxal (manufactured by Daicel Chemical Co., Ltd.)
10 parts (weight ratio) Table 1 shows the test results for pre-exposure properties, plate elongation, and printing durability. Comparative Example 3 The same operation as in Example 1 was performed. However, the composition of the intermediate layer paint was as follows. Muscovite 40 parts by weight Polyacrylic acid ester emulsion ^*12
40 parts by weight Casein aqueous solution (45%) 10 parts by weight Silane coupling agent 10 parts by weight Note * 45% of 2-methyl methacrylate (60 mol%)-butyl acrylate (40 mol%) copolymer
Table 1 shows the test results for emulsion pre-exposure, plate elongation and printing durability. Comparative Example 4 The same operation as in Example 1 was performed. However, the composition of the intermediate layer paint was as follows. Muscovite 40 parts by weight Polyacrylonitrile emulsion (45%)
40 parts by weight Casein aqueous solution (10%) 10 parts by weight Silane coupling agent 10 parts by weight Test results for pre-exposure, plate elongation and printing durability are shown in Table 1.

〔Effect of the invention〕

In the present invention, by using a specific copolymer as a binder in the intermediate layer, a printing plate with excellent water resistance and solvent resistance, less deterioration of image quality due to changes over time, and extremely low plate elongation can be created. Obtained. Moreover, the printing durability of this printing plate was excellent.

Claims (1)

[Scope of Claims] 1. A support, formed on one surface of the support,
and a photoconductive layer containing a photoconductive pigment and an insulating binder, and a wet-milled muscovite powder formed between the support and the photoconductive layer and having an average particle size of 5 to 50 μm. , a binder, and an intermediate layer containing a waterproofing agent, and the waterproofing agent in the intermediate layer has the following general formula (1): R _o SiX _4-o (1) [However, the above formula where R represents one member selected from aliphatic, cycloaliphatic aromatic, and heterocyclic organic substituents having 1 to 30 carbon atoms, and at least one of the organic substituents represented by R is a chemical is an active group, n represents 1 or 2 integers, and
represents a hydrolyzable substituent], and the binder in the intermediate layer is selected from acrylic esters and methacrylic esters. An electrophotographic lithographic printing plate material, characterized in that it contains as a main component a copolymer of an ester component consisting of at least one type selected from acrylonitrile and a nitrile component consisting of at least one type selected from acrylonitrile and methacrylonitrile. 2. Claim 1, wherein the copolymerization molar ratio of the ester component and nitrile component in the copolymer contained in the binder of the intermediate layer is within the range of 20:80 to 80:20. Printing plate material listed. 3. The printing plate material according to claim 1, wherein the content of the copolymer in the intermediate layer binder is in the range of 20 to 100% by weight. 4. The material according to claim 1, wherein the weight of the intermediate layer is within the range of 5 to 15 g/ ^m2 . 5. The printing plate material according to claim 1, wherein the muscovite powder content in the intermediate layer is within the range of 30 to 70% by weight. 6 In the general formula (1) representing the organosilane compound, the chemically active organic substituent represented by R is a vinyl group, a glycidyl group, a mercapto group,
The hydrolyzable substituent represented by and alkoxy groups having 1 to 4 carbon atoms. 7. The printing plate material according to claim 1, wherein the content of the silane compound in the intermediate layer is 1 to 15% by weight.