JPS6089395A - Original plate for lithographic printing - Google Patents

Abstract

PURPOSE:To improve the water resistance and printability by providing an intermediate layer mainly composed of amphoion synthetic high molecular copolymer latex and a pigment. CONSTITUTION:An intermediate layer containing an ampho-ion synthetic high molecular copolymer latex is provided between a support substrate and an image receiving layer or a photoconducitive layer. To form the intermediate layer, a liquid body in which a pigment and the ampho-ion synthetic high molecular copolyer latex are mixed with an additive and the like as required as far as the characteristic of the latex will not lose is coated onto the surface of the support substrate and dried. It should be noted that the printability is improved by imparting a water resistance to the intermediate layer or increasing the adhesivity between the support substrate and the image receiving layer.

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 Generally, a lithographic printing original plate has a supporting substrate, an intermediate layer formed on one surface thereof, and an image-receiving layer formed on the intermediate layer. The intermediate layer is used to firmly bond 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 be separated by application of water.

2) Located between the supporting substrate and the image-receiving layer, the two layers should be firmly adhered, and the image-receiving layer should not be peeled off by physical external forces such as scratching or bending.

3) When coating the image-receiving layer, water or organic solvent as a mulch agent 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 lithography, 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 conventionally used.

All of the above-mentioned conductive agents are hydrophilic substances that easily dissolve in water, so if water adheres to an electrophotographic substrate material that has a support coated with a conductive treatment agent containing such a conductive agent, the The photosensitive layer is destroyed. Therefore, especially when using this material as a master for offset printing, it is necessary to provide the intermediate layer with water resistance.

Conventionally, the intermediate layer that satisfies these properties has generally been made of water-soluble polymers such as polyvinyl alcohol, starch, starch, etc., or water-resistant agents such as amino resin condensates of these water-soluble polymers. crosslinking reaction products are widely used. It is also known to blend 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. Also,
In order to cause a crosslinking reaction during or after coating, it is necessary to heat at a temperature of at least 150°C for 5 minutes or more, but such conditions are difficult to achieve on an industrial scale due to productivity and profitability. Considering the gender, it is not possible to adopt the basolateral position.

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 intermediate layers are completely insufficient to complete the crosslinking reaction at the temperature and time expected from the commonly used coating conditions, and when using such an intermediate layer, it is difficult to achieve the intended purpose. However, sufficient water resistance cannot be obtained, 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 having a functional monomer (hydroxyethyl acrylate) and an amino resin in the intermediate layer (Japanese Patent Publication No. 47-47610); The reaction between the resin and the amino resin is slow, the water resistance is low, and the light attenuation during image formation is poor, resulting in an image with a lot of capri and poor contrast.

In view of the above-mentioned current situation, the inventors of the present invention have conducted extensive research in order to eliminate the drawbacks of the conventional technology, and as a result, have developed an intermediate layer mainly composed of zwitterionic 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.

OBJECTS 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.

The lithographic printing original plate of the present invention which achieves the N-axis structure of the invention comprises 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 providing an intermediate layer containing the material.

3. Detailed Description of the Invention The amphoteric polymer latex used in the present invention is a latex of synthetic rubber 1Jmer having both anionic and cationic functional groups, and is disclosed in, for example, JP-A-54-30910. and U.S. Patent No. 3.671.47
It can be manufactured by the method described in No. 2.

The main copolymer components of the zwitterionic polymer copolymer latex include 1,3-butadiene and 2-methyl-1,3-
Aliphatic conjugated diolefin monomers such as butadiene; and aromatic vinyl compounds such as styrene, α-methylstyrene, monochlorostyrene, vinyltoluene, methyl acrylate, methyl methacrylate, ethyl acrylate,
Monoolefinic monomers including alkyl esters of acrylic acid and methacrylic acid such as butyl acrylate, and ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile are used. Furthermore, copolymerization components of the zwitterionic synthetic polymer copolymer latex used together with the monoolefin monomer used as the main component include acrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxyethyl Hydrophilic single ions such as propyl, β-hydroxyethyl methacrylate, acrylabad, methacrylazido, N-methylolacrylamide, diacetone acrylamide, glycidyl acrylate, glycidyl methacrylate, acrolein, and allyl alcohol. Polymerization components include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid; itaconic acid monoethyl ester, fumaric acid monobutyl ester , and monoalkyl esters of unsaturated dicarboxylic acids such as monobutyl hismaleate: sulfonityl acrylate Na
The cationic copolymerization component of unsaturated sulfonic acids such as Na salt, sulfobropyl methacrylate, acrylamide propane sulfonic acid, or its alkali salts can be used as an unsaturated amine with the general formula (in the formula, R1 is H or a methyl group). , R2 is an alkylene group of 02-1!, R5 and R4 are H or flC, ~12 (7)
7 represents monomers such as methylamine ethyl (meth)acrylate, 1-methylamine ethyl (meth)acrylate, dimethyl-amine ethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminoethyl ( Meta)
Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as acrylate or diptylaminoethyl (meth)acrylate fi; methylabanoethyl (meth)ac 1-noramide, dimethylaminoethyl (meth)ac 1-noramide, dimethylaminopropyl (meth) ) achanoalkylamides of ethylenically unsaturated carboxylic acids such as ac-1-noramide; ainoalkyl vinyl ethers such as aminoethyl vinyl ether, methylaminoethyl vinyl ether, dimethylabanoethyl vinyl ether, and @2-vinyl Pyridine, 4-vinylpyridine, 2-methy/I/-5-vinylpyridine, 2,4-diethyl-
Ethylenically unsaturated aban monomers such as vinylpyridines such as 5-vinylpyridine can be used.

A typical zwitterionic synthetic polymer copolymer latex that can be used in the present invention includes an aliphatic conjugated diolefin monomer of 20 to 50% by weight, an ethylenically unsaturated acid monomer (
Anionic component) 025 to 20% by weight, ethylenically unsaturated aban monomer (cationic component) 0.5 to 20% by weight, and monoolefin compound monomer 10 to 74% by weight
There are copolymers containing This/Such I Zwitterionic W
Molecular copolymer latexes can be prepared by conventional emulsion polymerization methods. During polymerization, it is important to prevent the formation of coagulum, and for this purpose it is necessary to ensure that the ethylenically unsaturated acid monomer and the ethylenically unsaturated aban monomer are simultaneously present in the polymerization system. It is preferable not to do so.

To this end, 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 the ethylenically unsaturated After the acid monomer is exhausted, the ethylenically unsaturated amine monomer alone or an additional amount of aliphatic conjugated diolefin monomer and monomer are added to the polymerization system in the second polymerization step. It is preferable to continue the polymerization by adding an olefinic monomer. At this time, favorable results can be obtained by adjusting C 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 aban monomer in the amphoteric copolymer are used as an anionic component and a cationic component, respectively, to form the resulting zwitterionic synthetic polymer. It is an essential component for adjusting the isoelectric point of molecular copolymer latex. Both components are used at a weight ratio of 0.5 to 20, respectively, and a weight ratio of 1 to 10. Adjusted to give the isoelectric point. Generally, the isoelectric point 1-I, pH 3 of the zwitterionic synthetic polymer copolymer latex of the present invention
, 5 to 8.5.

When the isoelectric point pH of the zwitterionic interpolated molecular copolymer latex used in the present invention is on the acidic side, lower than 3.5, when the intermediate layer is coated and dried, the color of the coated layer is If the pH is not lowered enough and strong ionic bonds are obtained.
Because there is no "L", it may be difficult to achieve the intended purpose.

Also, the isoelectric point of the zwitterionic synthetic polymer copolymer is 8.
When it is higher than 5 and on the alkaline side, the dispersion state of the coating liquid components may become unstable.

Therefore, it is necessary to synthesize a zwitterionic synthetic polymer copolymer so that its isoelectric point is from 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 supporting substrate, an aqueous solution containing an alkali such as ammonia is used to coat the coating solution's p.
H is adjusted to be higher than the isoelectric point of the zwitterionic synthetic polymer copolymer latex in the coating 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 the electrical point, the zwitterionic synthetic polymer copolymer latex also exhibits positive properties, and is electrostatically sensitive to pigment molecules with negative surface charges or to other zwitterionic synthetic polymer copolymer latexes. Since it forms ionic bonds more effectively than conventional anionic/one-ionic latexes or nonionic latexes, more effective welding points can be created. Therefore, since it is in a 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. Furthermore, since the bonding occurs through ionic bonds, high temperatures of up to 150C are not required during coating and drying. However, there is no problem with drying at high temperatures.

The solid weight 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 parts, it will be difficult to obtain an intermediate layer with optical water resistance, and if it exceeds 90 parts, it will be difficult to obtain an intermediate layer with optical water resistance. 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). The solid content weight of the zwitterionic synthetic polymer copolymer latex is 10 to 8% relative to the weight of the intermediate layer.
More preferably, it is 0%.

In addition, when forming the intermediate layer, use fc# as long as the properties of the zwitterionic synthetic polymer copolymer latex are not lost.
Various natural binders such as powder, Neil gum, casein, etc. 1.
Alternatively, various synthetic binders such as polyvinyl alcohol hydroxyethyl cellulose and carboxymethyl cellulose may be added in appropriate amounts for the purpose of improving fluidity. 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 the amount of latex).

In the present invention, the pigments contained in the intermediate layer paint include various clays, calcium carbonate, albanium hydroxide, and mixtures thereof, or titanium oxide, zinc oxide, barium sulfate, plastic pigments, etc. A mixture of various pigments 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, antifoaming agent, ultraviolet absorber, antioxidant, fluorescent dye (pigment), dye (pigment), lubricant, pH adjuster, water resistant agent, conductive agent, other interfaces It may also contain one or more activators and the like.

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 lose the properties of this latex is used. , coated on the surface of the supporting substrate and dried. In this case, coating and drying can be carried out by conventional methods. 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 P/m', preferably 5 to i55'/m'.

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 layer may be provided to maintain appropriate functions. The coating layer on the surface of the supporting substrate, that is, the intermediate layer, imparts water resistance and improves printing durability, or
Or, the purpose is to increase the adhesion between the supporting substrate and the image-receiving layer to improve printing durability, and the coating layer on the back side of the supporting substrate is used to obtain a good image, especially in an electrophotographic lithographic printing original plate. The purpose is to For this reason, a low-resistance backcoat layer containing a conductive component or a dielectric material is usually provided on the back surface of the supporting substrate.

For the image-receiving layer, in the case of direct-plating lithography, a material in which pigments are dispersed using polyvinyl alcohol, acrylic acid ester copolymer, or other hydrophilic resin as a binder is used, and in the case of electrophotographic lithography, an oxidized material with a photoconductive layer is used. A common method is to apply pigment particles such as zinc, 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 entirely coated between the image receiving layer and the intermediate layer. In other words, 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, it is possible to remove the organic compounds contained in the image-receiving layer, marker, developer, etc. By preventing the solvent from penetrating 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 straight-to-horizontal 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 pen, 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. I can do it. The surface of the direct-lift lithographic original plate or electrophotographic lithographic original plate on which the image has been formed is then treated with a desensitizing liquid (etching liquid). As a result, the non-image areas are desensitized -i1. Becomes 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 performing fat desensitization treatment,
It can also be used by treating the plate surface with an aqueous solution containing ingredients such as sodium ferrocyanide, ammonium phosphate, citric acid, and phytic acid.

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 polymer copolymer latex1.
3-Butadiene 36.5 parts by weight Styrene 56.7 7 Methacrylic acid 4.81 Dimethelanoethyl 2. A polymerization mixture consisting of O# methacrylate was polymerized according to the method described in JP-A-54-30910 to produce a copolymer.

The obtained zwitterionic synthetic polymer latex is
It had an isoelectric point pH of 5.6 and a solid content concentration of 50%.

Manufacture of a lithographic printing original plate A lithographic printing original plate was prepared using the thus obtained amphoteric synthetic polymer latex in the following manner.

1205 with surface size made of polyvinyl alcohol
'/i base paper is used as a support base, and an intermediate layer coating liquid having the following composition is applied to the surface of the base paper in a coating amount (solid weight) of 57. It was coated in a tacky pattern and dried at 140°C for 30 seconds.

On top of this intermediate layer, a coating liquid having the following composition is further applied to form an image-receiving layer (7)/W? ) and dried at 150°C for 1 minute.

Calcium carbonate: 35 parts Clay: 15 parts Nippon Acrylic Co., Ltd.) After printing on the planographic printing master plate obtained in this way using a commercially available typewriter, the image was treated with an insensitizing liquid, and then printed on an offset printing machine (Remy Beam Co., Ltd.). 2800), no damage was observed in the condition of the plate even after printing 500 sheets in one row.

Comparative Example 1 Next, as a comparative example, an intermediate layer composed of the following composition was prepared by using a latex having zwitterionic properties, that is, having 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 steps, peeling of the image-receiving layer occurred after printing 200 sheets.

Intermediate Jla coating liquid In addition, the size degree (10 minute value Ta) of COb of each intermediate layer
pp i'), and there was a clear difference between the two.

An intermediate layer coating solution having the following composition was coated on a base paper having a weighing value of too P/m' as a supporting substrate, and the mixture was heated at 140°C for 30 minutes.
Dry for 0 seconds.

Clay 30〃 Starch 5〃 Casein 5# Next, apply a conductive paint of the following composition to the back of the base paper 107/n?
Coated.

Then, a paint having the following composition of 0.1 parts of rose bengal and 120 parts of toluene was applied onto the intermediate layer at a dry coating weight of 25 P/m' to form a photoconductive layer.

Next, this was heated for 50 seconds in an atmosphere of RH 25℃ (excluding the dark).
It was desensitized using an offset printing machine (Ryobi 2800).
), the condition of the plate was still good even after printing 5000 sheets, and no wrinkles or peeling of the plate surface were observed.

Comparative Example 2 A latex having 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 having the following composition was provided. A lithographic printing original plate was prepared in the same manner as in Example 2, and when printing was performed using this, the plate surface peeled off after 2000 sheets.

Also, the size of Cobb in the middle layer is Therefore, 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.

The constant point of the obtained latex was pH 5.Q.

Manufacture of original printing plate As a supporting substrate, 10 b/arm of an intermediate layer coating solution having the following composition was coated on P@100g base paper and dried at 140°C for 30 seconds.

Next, an image improving layer having the following composition was coated on the intermediate layer (27/I).

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 manufactured. Using this original plate, printing was performed in the same manner as in Example 1, and good images and printed matter were obtained.Even after printing 5000 sheets, the condition of the plate was good, and no wrinkles or peeling of the plate surface was 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 JSR0610 was used to coat an intermediate layer having the following composition. The original printing plate was produced.

When this original plate was used for printing, peeling of the plate surface occurred after 3,000 copies were printed.

Also, the CobbO size degree of the intermediate layer is Therefore, Example 3 was better.

Example 4 An intermediate layer having the following composition was coated on a base paper having a basis weight of 100 P/i as a support base (1/m') and dried at 140° for 30 seconds.

On this intermediate layer, an image quality improving layer, a back conductive layer, and an image-receiving photosensitive layer similar to those in Example 3 were coated to prepare a lithographic printing original plate. When plate making and printing were carried out in the same manner as in Example 2 using this original plate, good images were obtained, and no wrinkles or peeling of the plate surface was observed even after printing 5,000 sheets.

Comparative Example 4 JSR0 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 an intermediate layer having the following composition was used and an intermediate layer having the following composition was used, the plate surface peeled off after 3000 sheets.

The size of Cobb in the sentence middle layer is Met.

Effects of the Invention As described above, the present invention uses 5 to 90% of a zwitterionic synthetic polymer copolymer to form the intermediate layer, thereby achieving good water resistance, printing durability, electrical properties, and image forming properties. The present invention provides a lithographic printing original plate having the following characteristics, and is extremely useful industrially.

patent applicant Oji Paper Co., Ltd. Nippon Zeon Co., Ltd. patent application agent Patent attorney Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Akira Yamaguchi Patent attorney Masaya Nishiyama

Claims (1)

[Claims] 1. A support base, and an intermediate layer formed on its surface. and an image-receiving layer formed on the intermediate layer, wherein the intermediate layer contains at least one zwitterionic synthetic polymer copolymer. 2. The lithographic printing original plate according to claim 1, wherein the weight of the intermediate layer is 1 to 201. 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 inches based on the total weight of the intermediate layer. 4. The zwitterionic synthetic polymer copolymer contains (a) at least one olefin monomer selected from aliphatic conjugated diolefin monomers and monoolefin monomers; b) at least one ethylenically unsaturated acid monomer selected from unsaturated carboxylic acids, unsaturated dicarboxylic acid monoalkyl esters, unsaturated sulfonic acids, and alkali salts thereof, and (C ) A copolymer of at least one ethylenically unsaturated aban monomer selected from aminoalkyl esters, aminoalkyl abads and aminoalkyl vinyl ethers of ethylenically unsaturated carboxylic acids, and vinylpyridine compounds. The lithographic printing original plate according to claim 1. 5. The zwitterionic synthetic polymer copolymer is 20 to 5
0% by weight of aliphatic conjugated diolefin monomer and 10-7
Copolymer of 4% by weight of monoolefinic monomer, 0.5-20% by weight of ethylenically unsaturated acid monomer, and 0.5-20% by weight of ethylenically unsaturated amine monomer. is,
The lithographic printing original plate according to claim 4. 6. Claim 1, wherein the intermediate layer is obtained by applying a coating solution containing a latex of the amphoteric ionic synthetic polymer copolymer to the surface of the supporting substrate and drying it.
Original plate for lithographic printing described in Section 1. 7. The lithographic printing original plate according to claim 1, wherein the copolymer has an isoelectric point of pH 3.5 to 8.5.