JPH0257034B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a lithographic printing original plate, and more specifically, to a lithographic printing original plate with excellent printing durability. Prior Art In general, a lithographic printing original plate consists of a supporting substrate and a
It has an intermediate layer formed on the surface and an image receiving layer formed on the intermediate layer. The intermediate layer is for firmly bonding the supporting substrate and the image-receiving layer, and is required to have the following properties. (1) Excellent water resistance, and the image-receiving layer should not peel off when water is applied. (2) Located between the supporting substrate and the image-receiving layer, both layers should be firmly adhered, and the image-receiving layer should not peel off due to external physical forces such as sticking or bending. (3) When coating the image-receiving layer, water or organic solvent as a solvent in the coating solution, or adhesive components in the coating solution should not penetrate into the supporting substrate through the intermediate layer. (4) Particularly in the case of electrophotographic planography, there are the following problems. That is, the intermediate layer is electrically conductive in order to prevent contrast deterioration such as a decrease in image density and an increase in fog during image creation. For this purpose, inorganic salts, anionic polymer conductive agents, quaternary ammonium polymer conductive agents, and the like have been used. All of the above-mentioned conductive agents are hydrophilic substances that easily dissolve in water, so if water adheres to an electrophotographic material having a support coated with a conductive treatment agent containing such a conductive agent, the photosensitive material will deteriorate. The layer is destroyed. It is therefore necessary to provide the intermediate layer with water resistance, especially when using this material as a master for offset printing. Conventionally, the intermediate layer to satisfy these characteristics has generally been made of water-soluble polymers such as polyvinyl alcohol, casein, starch, etc., or cross-linked between these water-soluble polymers and a water-resistant agent such as an amino resin condensate. Reaction products are widely used. It is also known to incorporate synthetic resin emulsions and the like into these systems. However, when using a crosslinking reaction product, if the crosslinking reaction is carried out in the state of the paint before being applied to the supporting substrate, 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 product at a temperature of at least 150°C for 5 minutes or more, but such conditions are not suitable for productivity on an industrial scale. , it is impossible to adopt this method considering profitability. Furthermore, if the supporting substrate is exposed to such high temperatures for a long period of time, the supporting substrate becomes brittle, making it impossible to obtain a lithographic printing original plate having the required physical strength. Therefore, conventional interlayers are completely insufficient to complete the crosslinking reaction at the temperature and time expected from commonly used coating conditions, and when such an interlayer is used, it is difficult to achieve the desired purpose. It is not possible to obtain sufficient water resistance, and only a printing original plate with extremely low printing durability can be obtained. Furthermore, since a hydrophilic substance is used in the intermediate layer of the electrophotographic planographic original plate, the adhesion between the intermediate layer and the lipophilic adhesive in the photoconductive layer is not sufficient. For this reason, it is also known to use a paint consisting of a vinyl resin and an amino resin having a functional monomer (hydroxyethyl acrylate) in the intermediate layer (Japanese Patent Publication No. 47-47610), but in this case,
The reaction between the functional group and the amino resin is slow, water resistance is low, and light attenuation during image formation is poor, resulting in images with a lot of fog and poor contrast. In view of the above-mentioned current situation, the inventors of the present invention have conducted intensive research in order to eliminate the drawbacks of the conventional technology, and as a result, have developed an intermediate layer mainly composed of amphoteric ionic synthetic polymer copolymer latex and pigment. The present invention was achieved by discovering that an original plate with good water resistance can be obtained by using the above method. OBJECT OF THE INVENTION An object of the present invention is to provide a lithographic printing original plate having good water resistance and excellent printing durability. Structure of the Invention The lithographic printing original plate of the present invention which achieves the above-mentioned object includes at least one zwitterionic synthetic polymer copolymer latex between the supporting substrate and the image-receiving layer or the photoconductive layer. It is characterized by the provision of an intermediate layer. DETAILED DESCRIPTION OF THE INVENTION The amphoteric polymer latex used in the present invention is a synthetic rubber polymer latex having both anionic and cationic functional groups. It can be manufactured by the method described in Japanese Patent No. 3671472. The copolymerization main components of the zwitterionic polymer copolymer latex include aliphatic conjugated diolefin monomers such as 1,3-butadiene and 2-methyl-1,3-butadiene; and styrene and α-methylstyrene. , monochlorostyrene, aromatic vinyl compounds such as vinyltoluene, methyl acrylate,
Monoolefin monomers including alkyl esters of acrylic acid and methacrylic acid such as methyl methacrylate, ethyl acrylate, and butyl acrylate, and ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile. etc. are used. Furthermore, acrylic acid-
β-hydroxyethyl, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate, acrylamide, methacrylamide, N-
It may contain hydrophilic monomers such as methylol acrylamide, diacetone acrylamide, glycidyl acrylate, glycidyl methacrylate, acrolein, and allyl alcohol. The anionic copolymer components of the zwitterionic synthetic polymer copolymer latex include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid. ; Monoalkyl esters of unsaturated dicarboxylic acids such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester; sulfoethyl acrylate sodium salt, sulfopropyl methacrylate sodium salt, acrylamide propane sulfonic acid, etc. ethylenically unsaturated acid monomers such as unsaturated sulfonic acids or alkali salts thereof, and the like. In addition, as the cationic copolymer component of the zwitterionic synthetic polymer copolymer latex, unsaturated amines can be used with the general formula (In the formula, R ₁ is H or a methyl group, R ₂ is a C _2-12 alkylene group, R ₃ and R ₄ are H or a C _1-12 alkyl group, A is

【formula】

[Formula] or -O-), for example, methylaminoethyl (meth)acrylate,
t-Butylaminoethyl (meth)acrylate, dimethyl-aminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminoethyl (meth)acrylate, or dibutylaminoethyl (meth)acrylate
Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as acrylates; aminoalkylamides of ethylenically unsaturated carboxylic acids such as methylaminoethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide; Aminoalkyl vinyl ethers such as aminoethyl vinyl ether, methylaminoethyl vinyl ether, dimethylaminoethyl vinyl ether, etc., and 2-vinylpyridine, 4-vinylpyridine,
Ethylenically unsaturated amine monomers such as vinylpyridines such as 2-methyl-5-vinylpyridine and 2,4-diethyl-5-vinylpyridine can be used. A typical zwitterionic synthetic polymer copolymer latex that can be used in the present invention includes 20 to 50% by weight of aliphatic conjugated diolefin monomer and 0.5 to 20% by weight of ethylenically unsaturated acid monomer (anionic component). weight%,
There is a copolymer containing 0.5 to 20% by weight of an ethylenically unsaturated amine monomer (cationic component) and 10 to 74% by weight of a monoolefin compound monomer.
Such zwitterionic synthetic polymer copolymer latexes can be prepared by conventional emulsion polymerization techniques. During polymerization, it is important to prevent the formation of coagulated substances, and for this purpose, it is necessary to ensure that the ethylenically unsaturated acid monomer and the ethylenically unsaturated amine monomer do not exist simultaneously in the polymerization system. It is preferable to For this purpose, first, in the first polymerization step, a copolymer consisting of an aliphatic conjugated diolefin monomer, an ethylenically unsaturated acid monomer, and a monoolefin monomer is produced, and an ethylenically unsaturated acid After the monomer is exhausted, the ethylenically unsaturated amine monomer alone or an additional amount of aliphatic conjugated diolefin monomer and monoolefin monomer are added to the polymerization system in the second polymerization step. It is preferable to continue the polymerization. At this time, favorable results can be obtained by adjusting the pH of the polymerization system to 7 or more, preferably 9 or more after the first polymerization step is completed. As mentioned above, the ethylenically unsaturated acid monomer and ethylenically unsaturated amine monomer in the amphoteric copolymer are used as an anionic component and a cationic component, respectively, in the resulting amphoteric synthetic polymer. It is an essential component for adjusting the isoelectric point of polymer latex. Both components are used in a ratio of 0.5 to 20% by weight, preferably 1 to 10% by weight, and the amount of each used is determined so that the resulting zwitterionic synthetic polymer copolymer latex has a desired isoelectric point. adjusted to give Generally, the isoelectric point of the zwitterionic synthetic polymer copolymer latex of the present invention is preferably within the range of PH3.5 to 8.5. In the zwitterionic synthetic polymer copolymer latex used in the present invention, its isoelectric point PH is 3.5.
If it is on the lower acidic side, it is difficult to achieve the desired purpose because the PH in the color of the coating layer is not sufficiently lowered when drying the intermediate layer, and strong ionic bonds cannot be obtained. It may become. In addition, the isoelectric point of zwitterionic synthetic polymer copolymers
When the pH is higher than 8.5 and on the alkaline side, the dispersion state of the paint liquid components may become unstable. Therefore, it is necessary to synthesize a zwitterionic synthetic polymer copolymer so that its isoelectric point PH is 3.5 to 8.5. In order to produce the lithographic printing original plate of the present invention, when coating a coating solution containing a pigment and a binder on a support substrate, an aqueous solution containing an alkali such as ammonia is used to adjust the pH of the coating solution. Adjust the pH so that it is higher than the isoelectric point of the zwitterionic synthetic polymer copolymer latex in the working solution. Then, the particle surfaces in the coating liquid exhibit anionic properties, and the pigment can be stably dispersed in the coating liquid. When such a coating solution is applied to the surface of a supporting substrate and ammonia and water are permeated, volatilized, and evaporated, the pH of the coating solution gradually decreases, and eventually the zwitterionic synthetic polymer copolymer latex etc. Closer to its electrical point, the zwitterionic synthetic polymer copolymer latex also exhibits positive properties, allowing it to interact electrostatically with pigment molecules that have a negative surface charge or with other zwitterionic synthetic polymer copolymer latexes. form ionic bonds,
A more effective weld point can be created than with conventional anionic or nonionic latexes. Therefore, since it is in an electrically neutralized form due to the above-mentioned bonds, the resulting intermediate layer is considered to exhibit stronger water resistance than when ordinary anionic latex is used. In addition, because they are bonded by ionic bonds, the coating and drying temperatures are particularly high at 150°C.
does not require high temperatures. However, there is no problem with drying at high temperatures. The solid content of the zwitterionic synthetic polymer copolymer latex is preferably 5 to 90% of the weight of the intermediate layer. If the amount of the zwitterionic synthetic polymer copolymer latex is less than 5%, it becomes difficult to obtain an intermediate layer with sufficient water resistance;
If it exceeds 90%, it may be difficult to obtain the desired coated paper due to problems such as adhesion between the front and back sides of the paper (so-called blocking phenomenon) during winding after coating the intermediate layer. The solid content weight of the zwitterionic synthetic polymer copolymer latex is
More preferably, it is 10 to 80%. In addition, in forming the intermediate layer, various natural binders such as starch, Neil gum, and casein, or polyvinyl alcohol,
Various synthetic binders such as hydroxyethyl cellulose and carboxymethyl cellulose may be added in appropriate amounts for the purpose of improving fluidity. or,
It is also possible to mix a water-resistant synthetic latex or plastic pigment with the zwitterionic synthetic polymer latex, as long as the properties of the zwitterionic synthetic polymer latex are not lost. (preferably less than half). In the present invention, the pigments contained in the intermediate layer paint include various clays, calcium carbonate, aluminum hydroxide, and mixtures thereof, or various pigments such as titanium oxide, zinc oxide, barium sulfate, and plastic pigments. A mixture can be used. In addition to the pigment and the zwitterionic synthetic polymer copolymer described above, the intermediate layer of the lithographic printing original plate of the present invention may contain any additives, such as a pigment dispersant, as long as they do not impede the purpose of the present invention. , viscosity modifier, water retention agent,
Contains one or more of antifoaming agents, ultraviolet absorbers, antioxidants, fluorescent dyes (pigments), dyes (pigments), lubricants, PH regulators, waterproofing agents, conductive agents, and other surfactants. It may be In order to form the intermediate layer in the lithographic printing original plate of the present invention, a liquid material containing a pigment, a zwitterionic synthetic polymer copolymer latex, and optionally additives that do not affect the properties of the latex is used. ,
Coat on the surface of the supporting substrate and dry. In this case, the coating can be dried by a conventional method. The coating amount (dry weight) when forming the intermediate layer may be within the range necessary to suit the purpose of the present invention and impart water resistance, and is usually 1 to 20 g/m ² , preferably It is 5 to 15 g/ ^m2 . In addition, the basic structure of the lithographic printing original plate of the present invention, the material of the supporting substrate and the image-receiving layer,
The material, formation method, etc. of the photoconductive layer may be as described below. The basic structure of a lithographic printing original plate is to provide an image-receiving layer or a photoconductive layer on a supporting substrate such as paper or plastic film, which itself is water-resistant. A coating amount may be set in order to maintain a corresponding function. The coating layer or intermediate layer on the surface of the supporting substrate is
The coating layer on the back side of the supporting substrate is used for the purpose of improving printing durability by imparting water resistance or increasing the adhesion between the supporting substrate and the image-receiving layer. In particular, the purpose is to obtain a good image in an original plate for electrophotographic planographic printing. For this reason, a low-resistance back coat layer containing a conductive component or an absorbent substance is usually provided on the back surface of the supporting substrate. In the case of direct drawing planography, the image-receiving layer uses polyvinyl alcohol, acrylic acid ester copolymer, or other hydrophilic resin as a binder and disperses pigments, etc. In the case of electrophotographic planography, a photoconductive layer is used. A common method is to apply pigment particles such as zinc oxide, cadmium sulfide, titanium oxide, etc. dispersed in acrylic resin, silicone resin, or vinyl acetate resin. Further, in order to improve image quality, an image improving layer may be further coated between the image receiving layer and the intermediate layer. That is, by providing a solvent-resistant layer consisting of various pigments, a water-soluble binder such as starch, casein, polyvinyl alcohol, synthetic latex, and a crosslinking agent, organic solvents contained in the image-receiving layer, magic, developer, etc. By preventing the infiltration of the toner into the supporting substrate, it is possible to form even better images. Even in such a structure, by using the intermediate layer of the present invention, water resistance can be improved, water can be prevented from penetrating into the supporting substrate (base paper), and printing durability can be improved. The actual planographic printing (offset printing) will be explained below. In the case of a direct drawing lithographic printing plate, the image is formed by printing on the image-receiving layer with a typewriter or the like, or by handwriting with an oil-based marker, ballpoint pen, or the like. Alternatively, a method is also possible in which an image formed by a xerographic method is transferred onto the above-mentioned receiving layer and then thermally fixed. On the other hand, for electrophotographic planographic original plates, the photoconductive layer is uniformly charged with corona, exposed to light through the original image of the desired image, and then an image is formed by dry or wet development. be able to. Next, the plate surface of the direct drawing lithographic original plate or the electrophotographic lithographic original plate on which the image has been formed is treated with a desensitizing liquid (etching liquid). As a result, the non-image areas are rendered fat-insensitive and become hydrophilic. However, the image area itself is lipophilic, so oil-based ink
Since the image-receiving layer is coated with toner or the like, the action of the etchant is prevented from reaching the image-receiving layer. Therefore, the image area maintains lipophilicity. When a lithographic printing original plate that has been desensitized in this manner is used for offset printing, oil-based ink will adhere only to the image area, and by transferring this to the intended paper, a printed matter is obtained. When desensitizing is performed, the plate surface is generally treated with an aqueous solution containing components such as sodium ferrocyanide, ammonium phosphate, citric acid, and phytic acid. This liquid can also be used as a dampening solution to moisten the plate surface during printing by diluting it with water to an appropriate ratio. Next, the present invention will be explained by examples, but the present invention is not limited thereto. Note that the middle part of the example represents parts by weight. Example 1 Synthesis of Zwitterionic Synthetic Copolymer Latex A polymerization mixture consisting of 1,3-butadiene, 36.5 parts by weight, styrene, 56.7 parts, methacrylic acid, 4.8 parts, and dimethylaminoethyl methacrylate, 2.0 parts, was prepared as described in JP-A-54-30910. A copolymer was produced by polymerization according to the method described in . The resulting zwitterionic synthetic polymer copolymer latex had an isoelectric point of PH 5.6 and a solid content concentration of 50%. Manufacture of a lithographic printing original plate A lithographic printing original plate was prepared as follows using the thus obtained amphoteric synthetic polymer latex. Surface sized with polyvinyl alcohol
Using a 120g/ ^m2 base paper as a support base, an intermediate layer coating solution having the following composition was applied to the surface of the base paper so that the coating amount (solid weight) was 5g/ ^m2 , and the mixture was heated at 140℃ for 30 minutes.
Dry for seconds. Zwitterionic synthetic polymer copolymer latex
50 parts Clay 45 Starch 5 An image-receiving layer (7 g/m ² ) was further formed on this intermediate layer using a coating solution having the following composition and dried at 150° C. for 1 minute. Calcium carbonate 35 parts Clay 15 parts Acrylic ester copolymer emulsion (Primal B18 manufactured by Nippon Acrylic Co., Ltd.) 50 parts After printing on the planographic printing master plate thus obtained using a commercially available typewriter, an image The paper is treated with an insensitizing liquid and then printed using an offset printing machine (Ryobi).
2800), no damage was observed in the condition of the plate even after printing 500 sheets. Comparative Example 1 Next, as a comparative example, an intermediate layer composed of the following composition was created using a latex with zwitterionic properties, that is, no isoelectric point, in place of the above zwitterionic synthetic polymer copolymer. When a printing test was conducted using a lithographic printing original plate prepared in the same manner as in Example 1 except for the above, peeling of the image-receiving layer occurred after printing 200 sheets. Intermediate layer coating liquid JSK0610 (Lattetsux manufactured by Japan Synthetic Rubber Co., Ltd.)
50 parts Clay 45〃 Starch 5〃 Cobb size degree (10 minute value) of each intermediate layer
Tappi) was 8 g/m ² in Example 1 and 30 g/m ² in Comparative Example 1, and there was a clear difference between the two. Example 2 10 g/m ² of an intermediate layer coating solution having the following composition was applied to a base paper weighing 100 g/m ² as a supporting substrate, and the mixture was heated at 140°C for 30 minutes.
Dry for seconds. Zwitterionic synthetic polymer copolymer latex described in Example 1 60 parts Clay 30 Starch 5 Casein 5 Next, 10 parts of conductive paint having the following composition was applied to the back side of the stock solution.
g/m ² coated. Clay 40 parts Vinyl acetate resin (Sevian A-522, manufactured by Daicel) 50〃 Conductive agent (Oligo Z: manufactured by Tomogawa) 10〃 Then, on the intermediate layer, photoconductive zinc oxide with the following composition (Sazex 2000, Sakai) (manufactured by Kagaku Co., Ltd.) 100 parts Acrylic resin (LR-188, manufactured by Mitsubishi Rayon Co., Ltd.)
A coating material containing 30 parts Rose Bengal, 0.1 parts, and 120 parts of toluene was applied as a dry coating amount of 25 g/m ² to form a photoconductive layer. Next, do this in a dark place under an atmosphere of 50%RH 25℃.
After conditioning the humidity for 24 hours, plate making was performed using an ITEC 175 electronic plate making machine. When this was desensitized with etching solution (Itek Co., Ltd.) and printed on an offset printing machine (Ryobi 2800), the condition of the plate was still good even after printing 5000 sheets, with no wrinkles or peeling of the plate surface. I couldn't help it. Comparative Example 2 A latex with zwitterionic properties, that is, no isoelectric point, was used in place of the zwitterionic synthetic polymer copolymer described in Example 1, and an intermediate layer with the following composition was provided. A lithographic printing original plate was created in the same manner as Example 2, and this was used for printing.
Peeling of the plate surface occurred after 2000 sheets. PL-752 (latex manufactured by Mitsui Toatsu Co., Ltd.) 60 parts Clay 30〃 Starch 5〃 Casein 5〃 Also, the size degree of Cobb in the middle layer is: Example 2: 10 g/m ² Comparative Example 2: 35 g/m ² , Example 2 was clearly superior. Example 3 Preparation of a zwitterionic synthetic polymer copolymer latex A zwitterionic synthetic polymer copolymer latex having the following composition was prepared by the method described in JP-A-54-30910. 1,3-Butadiene 36.5 parts Styrene 57.1 Itaconic acid 2.4 Dimethylaminoethyl methacrylate 2.0 β-hydroxyethyl acrylate 2.0 The isoelectric point of the obtained latex was PH5.0. Manufacture of original printing plate As a supporting substrate, 10 g/m ² of an intermediate layer coating solution of the following composition was applied to a base paper weighing 100 g/m ² and heated at 140°C for 30 minutes.
Dry for seconds. 30 parts of the zwitterionic synthetic polymer copolymer latex described in Example 1 30 parts of the zwitterionic synthetic polymer copolymer latex of this example 35 parts of clay 5 parts of starch Next, an image of the following composition was placed on the intermediate layer. improvement layer,
2 g/m ² was applied. Casein: 45 parts by weight Clay: 45 Glyoxal: 10 Next, in the same manner as in Example 2, a back conductive layer and an image-receiving layer were formed, and a lithographic printing original plate was produced. When printing was carried out in the same manner as in Example 1 using this original plate, good images and printed matter were obtained.
Even after printing 5000 sheets, the condition of the plate remained good, with no wrinkles or peeling of the plate surface observed. Comparative Example 3 A lithographic plate was prepared in exactly the same manner as in Example 3, except that instead of the amphoteric ionic synthetic polymer copolymer latex described in Example 3, the above JSR0610 was used to coat an intermediate layer having the following composition. A printing plate was produced.
When this original plate was used for printing, the plate surface peeled off after 3,000 copies. JSR0610 (latex manufactured by Japan Synthetic Rubber Co., Ltd.) 60 parts Clay 35 Starch 5 Also, the size degree of Cobb in the intermediate layer is: Example 3: 5 g/m ² Comparative Example 3: 30 g/m ² , and Example 3 is better. It was excellent. Example 4 A base paper having a basis weight of 100 g/m ² was coated with an intermediate layer having the following composition at 10 g/m ² as a supporting substrate, and dried at 140° for 30 seconds. Zwitterionic synthetic polymer copolymer latex described in Example 1 40 Clay 30 Acrylic resin [highly water resistant synthesized in JP-A-57-38194] 25 Starch 5 Example 3 was applied on this intermediate layer. An image quality improving layer, a back conductive layer, and an image-receiving photosensitive layer similar to those described above were coated to prepare a lithographic printing original plate. Using this original plate, plate making and printing were carried out in the same manner as in Example 2, and a good image was obtained, and no wrinkles or peeling of the plate surface was observed even after printing 5000 sheets. Comparative Example 4 Instead of zwitterionic synthetic polymer latex,
When printing was performed using a lithographic printing original plate prepared in the same manner as in Example 4 except that JSR0610 was used and an intermediate layer having the composition shown below was provided, the plate surface peeled off after 3000 sheets. JSR0610 (latex manufactured by Japan Synthetic Rubber Co., Ltd.) 40 Acrylic resin [highly water resistant synthesized in JP-A-57-38194] 25 Clay 30 Starch 5 The size of Cobb in the intermediate layer is Example 4 5 g/m ² Comparative Example 4 It was 25 g/m ² . Effects of the Invention As described above, the present invention achieves good water resistance, printing durability, electrical properties, and image forming properties by using 5 to 90% of a zwitterionic synthetic polymer copolymer to form the intermediate layer. The present invention provides a lithographic printing original plate having the following characteristics, and is extremely useful industrially.

Claims (1)

[Scope of Claims] 1. A supporting substrate, an intermediate layer formed on one surface thereof, and an image-receiving layer formed on the intermediate layer, wherein the intermediate layer contains at least one type of zwitterion. A lithographic printing original plate characterized by containing a synthetic polymer copolymer. 2. The lithographic printing original plate according to claim 1, wherein the weight of the intermediate layer is 1 to 20 g/m ² . 3. The lithographic printing original plate according to claim 1, wherein the weight of the zwitterionic synthetic polymer copolymer contained in the intermediate layer is 5 to 90% of the total weight of the intermediate layer. 4 The zwitterionic synthetic polymer copolymer is (a)
at least one olefin monomer selected from aliphatic conjugated diolefin monomers and monoolefin monomers; and (b) unsaturated carboxylic acid, unsaturated dicarboxylic acid monoalkyl ester, and unsaturated diolefin monomer; At least one ethylenically unsaturated acid monomer selected from saturated sulfonic acids and alkali salts thereof, and (c) aminoalkyl esters, aminoalkylamides, and aminoalkyls of ethylenically unsaturated carboxylic acids. The lithographic printing original plate according to claim 1, which is a copolymer of vinyl ether and at least one ethylenically unsaturated amine monomer selected from vinylpyridine compounds. 5 The zwitterionic synthetic polymer copolymer is 20
~50% by weight of aliphatic conjugated diolefin monomer;
10-74% by weight of monoolefin monomer and 0.5
~20% by weight ethylenically unsaturated acid monomer and 0.5
The lithographic printing original plate according to claim 4, which is a copolymer with ~20% by weight of an ethylenically unsaturated amine monomer. 6. The intermediate layer is obtained by applying a coating solution containing a latex of the amphoteric ionic synthetic polymer copolymer onto the supporting substrate surface and drying it.
A lithographic printing original plate according to claim 1. 7. The lithographic printing original plate according to claim 1, wherein the copolymer has an isoelectric point of PH3.5 to 8.5.