JPH0584515B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial field of application: The present invention provides a new resin dispersion useful for an electrophotographic liquid developer for offset masters, which has particularly excellent dispersion stability, no bleeding or scumming, and has a long printing life. The present invention relates to a novel resin dispersion that provides a liquid developer that forms images with excellent properties. Conventional technology: Conventionally, resin dispersions for electrophotographic liquid developers have been prepared by mixing polymers that are soluble in organic solvents (hereinafter referred to as "solvents") with a low dielectric constant and high electrical insulation properties, and polymers that are insoluble in the solvents. There have been resin dispersions obtained by graft polymerization of monomers that produce polymers (e.g., JP-A-53-54029), but such resin dispersions are complicated to manufacture; Moreover, there were problems such as gel formation often occurring in the developer, making it difficult to obtain a stable developer. Attempts have been made in recent years to improve the drawbacks of such graft copolymer resin dispersions, which consist of a solvent-soluble polymer and a solvent-insoluble polymer, and both of these polymers contain -COOH, -. _SO3H ,
Alternatively, there is a technology that improves the stability of a resin dispersion by incorporating a polar functional group such as -COOCH ₃ by utilizing the adsorption between the polar functional group of a soluble polymer and the polar functional group of an insoluble polymer. It has been disclosed (e.g., Japanese Patent Application Laid-Open No. 59-83174). Problems to be Solved by the Invention: However, as described above, in a resin dispersion in which a soluble polymer and an insoluble polymer are simply provided with polar functional groups, the stability is improved to some extent, but image bleeding ( It has been found that problems such as blurring of outlines) and scumming frequently occur, and printing durability is not always sufficient, especially when used as an electrophotographic liquid developer for offset masters. The present invention solves the above-mentioned problems of the prior art and provides a resin dispersion for electrophotographic liquid developers that has good stability, no image bleeding or background smudge, and has extremely excellent printing durability. It is something to do. Here, background smudge refers to a phenomenon in which printing ink adheres to non-image areas during offset printing, causing stains. In addition, in offset printing,
As the number of printing increases, the offset master becomes immersed in the solvent of the printing ink, which causes the printing ink to adhere to the image area and disappear. Printing durability refers to the property that this phenomenon does not occur. Means for solving the problem: According to the invention, in a highly insulating hydrocarbon medium (A) b) 20-99.5% by weight of vinyl acetate, preferably 50-99.5% by weight, most preferably 70-99.5% by weight of vinyl acetate; Weight%, b) Formula

[ka] [Here, R is

【formula】

【formula】

[expression] or

[Formula], and R ₁ , R ₂ and R ₄ each independently represent hydrogen, C _1-6 alkyl, or alkoxyalkyl having 1 to 4 carbon atoms in each alkyl moiety, and R ₃ and R ₃ ' independently represents C _1-4 alkylene, X represents hydrogen or methyl] 0.5 to 12% by weight, preferably 2 to 12% by weight, most preferably 2 to 6% by weight, and c) C _1-20 alkyl ester and/or C _3-8 cycloalkyl ester of acrylic acid or methacrylic acid 0
~79.5% by weight, preferably 2-48% by weight, most preferably 5-28% by weight (a), b)
and c), the total of which is 100% by weight), and at least a part of the monomer of formula () has its amino group converted to quaternary ammonium using a quaternary ammonium forming agent. A copolymer substantially insoluble in the medium, (B) D)

[Here, X has the above meaning, Y represents _-COOR5 , _-OCOR5 or _-OR5 , and _R5 represents _C4-20 alkyl]

95-15% by weight of monomers, preferably 80-40% by weight,
Most preferably 75 to 65% by weight, E) formula

[Here, X has the above meaning, and R ₆ represents a C _3-8 cycloalkyl or an aralkyl having 1 to 3 carbon atoms in the alkyl moiety]

5 to 85% by weight of monomers, preferably 20 to 60% by weight,
Most preferably 25 to 35% by weight (however, the sum of d) and e) above is 100% by weight) and f) an organic mercaptan having at least one thiol group with a sulfur content of 0 to 2% by weight. , preferably 0.03~
2% by weight, most preferably 0.1-1% by weight, especially
A copolymer substantially soluble in the medium containing 0.2 to 0.3% by weight (however, the sulfur content per soluble copolymer shown below is expressed in weight%). A resin dispersion suitable for an electrophotographic liquid developer for offset masters is provided. Examples of the monomer of formula (b) contained in the above insoluble copolymer include methacrylic acid or esters of acrylic acid and the following alcohols; mono- or dimethylaminoethyl alcohol, mono- or dimethylaminoethyl alcohol; Diethylaminoethyl alcohol, mono or dimethylaminopropyl alcohol, mono or diethylaminopropyl alcohol, mono or diphenylaminomethyl alcohol, mono or diphenylethyl alcohol, dimethoxyaminoethyl alcohol, diethoxyaminoethyl alcohol, mono or dimethylaminopropylaminoethyl Alcohol, mono- or diethylaminopropylaminoethyl alcohol. Among the monomers of the above formula (), dialkylaminoalkyl esters of methacrylic acid are preferred, and dimethylaminoethyl ester and diethylaminoethyl ester of methacrylic acid are particularly preferred. Furthermore, monomers of formula () in b) include acid amides of methacrylic acid or acrylic acid and the following amines; mono- or dimethylamine, mono- or diethylamine, mono- or dipropylamine, mono- or dipropylamine; Dimethylaminoethylamine, mono- or diethylaminoethylamine, mono- or dimethylaminopropylamine and mono- or diethylaminopropylamine.
Among the monomers of formula (), acid amides of methacrylic acid or acrylic acid and dialkylamine or dialkylaminoalkylamine, especially acid amides of dimethylamine, diethylamine or dimethylaminopropylamine, are preferred. The insoluble copolymer may contain one or more monomers of formula (), and if the content exceeds 12% by weight, the hydrophilicity of the image may deteriorate. This is undesirable because it increases the ink receptivity during offset printing, and
If the amount is too small, such as less than 0.5% by weight, printing durability will decrease, which is not preferable. Also, the formula () contained in the insoluble copolymer
At least a part of the monomer (particularly the monomer contained on or near the surface of the dispersed particles) has its amino group converted into a quaternary ammonium using a quaternary ammonium forming agent. The amount of ammonium forming agent used is 0.1 to 5 per monomer of formula ().
Preferably an insoluble copolymer with a mole % of 0.5
More preferred are insoluble copolymers that are ˜2 mol %. If the amount of the quaternary ammonium-forming agent used is too large, exceeding 5 mol%, the image density will decrease and the hydrophilicity will become stronger, so the affinity with the offset ink after plate making will decrease, which is not preferable. If the amount is too small, such as less than 0.1 mol%, printing durability will decrease, which is not preferable. The quaternary ammonium forming agent used is an organic compound exhibiting acidity, examples of which include aliphatic or aromatic carboxylic acids, aliphatic or aromatic halides, aliphatic or aromatic sulfonic acids, etc. Examples include dimethyl sulfate, methyl chloride, and ethyl chloride. Dimethyl sulfate, methyl chloride and the like are preferably used. Examples of the _C1-20 alkyl ester of acrylic acid or methacrylic acid contained in the insoluble copolymer include esters of methacrylic acid or acrylic acid and the following alcohols; n
-butanol, isobutanol, n-hexyl alcohol, 2-ethylhexyl alcohol, n-
Octanol, n-nonyl alcohol, iso-nonyl alcohol, n-decyl alcohol, iso-
Decyl alcohol, n-dodecyl alcohol, n
-tridecyl alcohol, n-octadecyl alcohol, n-propanol, iso-propanol, ethanol, methanol. Among them, C _4-12 alkyl esters of methacrylic acid are preferred;
Particularly preferred is n-octyl ester or 2-ethylhexyl ester. Examples of the _C3-8 cycloalkyl ester of acrylic acid or methacrylic acid contained in the insoluble copolymer include esters of methacrylic acid or acrylic acid and the following alcohols: cyclopropyl alcohol, cycloheptyl Alcohol, cyclohexyl alcohol, cyclopentyl alcohol and cyclooctyl alcohol. Among them, cyclohexyl ester of methacrylic acid is preferred. The C _1-20 alkyl ester and/or C _3-8 cycloalkyl ester of acrylic acid or methacrylic acid contained in the insoluble copolymer is 1
A type or two or more types may be contained,
Preferably the content is 2 to 48% by weight, but 48% by weight
If the amount exceeds 2% by weight, it is undesirable because the image density decreases and printing durability deteriorates, and if it is too small (less than 2% by weight), the particle size increases and sedimentation stability deteriorates, which is undesirable. Insoluble copolymer vinyl acetate, formula ()
monomers of acrylic acid or methacrylic acid
Components other than C _1-20 alkyl esters and/or C _3-8 cycloalkyl esters may be contained as necessary within the range that does not adversely affect various properties such as stability, scumming, and printing durability. . Formula (d) contained in the soluble copolymer ()
The monomers include n-butyl ester, iso-butyl ester, n-hexyl ester, n-octyl ester, 2-ethylhexyl ester, n-dodecyl ester, n-tridecyl ester, n- - Methacrylate or acrylate such as octadecyl ester, n-nonyl ester, iso-nonyl ester, n-decyl ester, iso-decyl ester, fatty acid vinyl and vinyl n-butyl ether such as vinyl propionate, vinyl butyrate, vinyl versatate, vinyl Examples include vinyl ethers such as isobutyl ether. Preferred monomers of formula () are of formula

[Here, R' represents _C4-12 alkyl]

2-ethylhexyl methacrylate and n-octyl methacrylate are particularly preferred. If the monomer of formula () is too large, exceeding 95%,
This is not preferable because it causes blurring of images and a decrease in printing durability, and if it is too small (less than 15% by weight), it is not preferable because sedimentation stability decreases. Formula () of e) contained in the soluble copolymer
Examples of monomers include _C3-8 cycloalkyl esters of acrylic acid or methacrylic acid, and γ-phenylpropyl ester and β-phenylethyl of acrylic acid or methacrylic acid, as exemplified as monomers in c). Examples include esters and benzyl esters. Preferred monomers of formula () are C _3-8 cycloalkyl methacrylates or C _3-8 cycloalkyl acrylates, particularly cyclohexyl methacrylate or cyclohexyl acrylate. If the monomer of formula () is too large, exceeding 85% by weight, the solubility will decrease and the stability of the dispersion will decrease, which is undesirable, while if it is too small, below 5% by weight, the image will bleed and printing durability will be affected. This is not preferable because it lowers the temperature. The organic mercaptan containing at least one thiol group of f) contained in the soluble copolymer has from 1 to about 4 thiol groups per molecule and from 1 to about 12 carbon atoms per thiol group, preferably Contains 2 to 8 carbon atoms. These organic mercaptans can contain other substituents in addition to the hydrocarbon group, such substituents include carboxylic acid groups, hydroxyl groups, ether groups, ester groups,
Includes sulfide, amine and amide groups. Examples of useful mercaptans include methyl mercaptan, ethyl mercaptan, butyl mercaptan, octyl mercaptan, lauryl mercaptan, mercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptoacetic acid,
Mercaptopropionic acid, thiomalic acid, benzyl mercaptan, phenyl mercaptan, cyclohexyl mercaptan, 1-thioglycerol,
2,2'-dimercapto diethyl ether, 2,
2'-dimercaptodipropyl ether, 2,2'-
Dimercapto diisopropyl ether, 3,3'-
Dimercapto dipropyl ether, 2,2'-dimercapto diethyl sulfide, _3,3'- dimercapto dipropyl sulfide, 1,11-dimercapto-3,9-dioxa-6-thiaundecane, bis(β -mercaptoethoxy)methane, bis(β
-mercaptoethylthio)methane, ethanedithio-1,2, propanedithiol-1,2, butanedithiol-1,4, 3,4-dimercaptobutanol-1, trimethylolethane tri(3-mercaptopropionate), Included are pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane trithioglycolate and pentaerythritol tetrathioglycolate. Examples of suitable organic mercaptans are butyl mercaptan, octyl mercaptan, lauryl mercaptan, mercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptoacetic acid, mercaptopropionic acid, benzyl mercaptan, phenyl mercaptan, etc., especially lauryl mercaptan, mercapto ethanol, mercaptopropanol, mercaptobutanol,
Mercaptoacetic acid and mercaptopropionic acid are preferred. The content of the above-mentioned organic mercaptan per soluble copolymer is preferably 0.03 to 2% by weight in terms of S content, and if it exceeds 2% by weight, it is not preferable because the sedimentation stability of the dispersion will decrease. If the amount is too small, such as less than 0.03% by weight, it is not preferable because the dilution stability of the dispersion liquid and background smearing of the developed product may occur. The soluble copolymer must contain components other than the monomer of formula (), the monomer of formula (), and organic mercaptan to the extent that it does not adversely affect various properties such as stability, scumming, and printing durability. It can be included depending on the situation. The soluble polymer used in the present invention is preferably
It has a molecular weight of 50,000 or less, more preferably 3,000 to 30,000, most preferably 5,000 to 25,000. If the molecular weight is too high, exceeding 50,000, it is undesirable because the dilution stability of the dispersion liquid tends to decrease and background smearing of the developed product tends to occur, and if the molecular weight is too low, the stability of the dispersion liquid deteriorates. So I don't like it. The ratio of the soluble copolymer (B) to the insoluble polymer (A) in the resin dispersion of the present invention is not particularly limited, but the soluble copolymer is 20 to 50%, preferably 30 to 50%. A proportion of 40% by weight and 80-50% by weight of insoluble polymer, preferably 70-60% by weight, is used. If the amount of soluble copolymer is too small (less than 20% by weight), the stability of the dispersion resin liquid will decrease, which is undesirable.
If the amount exceeds 50% by weight, it is not preferable because the image may bleed, the density may become thinner, and printing durability may be reduced. The particle size distribution of the dispersed particles of the resin dispersion of the present invention is
The proportion of particles of 0.5μ or less is 70% or more, preferably 90% or more. The highly insulating hydrocarbon medium contained in the resin dispersion of the present invention is an organic solvent with a low dielectric constant and high electrical insulation properties, and such organic solvents include normal paraffinic hydrocarbons, isoparaffinic hydrocarbons, Examples include hydrocarbons, alicyclic hydrocarbons, halogenated aliphatic hydrocarbons, etc., but paraffinic or alicyclic hydrocarbons with a boiling point of 150 to 200°C are preferred from the viewpoint of odor, safety, drying properties, etc. Hydrocarbon-based media are preferably used. The resin dispersion of the present invention can generally be easily produced by polymerizing an insoluble polymer in a solution of a soluble copolymer in a medium; It can also be suitably produced by a method such as separately producing a combination, dissolving both polymers in a common solvent for both polymers, and then dropping the mixture into a hydrocarbon medium with stirring. The particle size distribution of the resin dispersion can be adjusted by changing the ratio of the soluble copolymer to the insoluble copolymer.
It can also be adjusted by changing the amount of _C1-20 alkyl methacrylate or acrylate. In addition, in order to convert at least a part of the monomer of formula () contained in the insoluble polymer into quaternary ammonium, after preparing the resin dispersion, dimethyl sulfate etc.
The monomer () is converted into a quaternary ammonium by a conventional method using a quaternary ammonium-forming agent, but as a modified method, the monomer () is converted into a quaternary ammonium by a conventional method using dimethyl sulfuric acid, methyl chloride, etc. prior to the above polymerization reaction. You can leave it there. In order to produce an electrophotographic liquid developer from the resin dispersion of the present invention, the dispersed particles may be colored and charged if necessary. A charge control agent is used to impart charge to the resin dispersion of the present invention, and such charge control agents include zinc naphthenate, manganese naphthenate,
Copper oleate, cobalt octylate, lecithin,
Examples include sodium dioctyl sulfosuccinate and aluminum salt of steverytrozin. For coloring the resin dispersion of the present invention, nigrosine dyes, phthalocyanine pigments, oil black,
Carbon black or the like is used. Effects of the invention: The resin dispersion of the present invention has extremely excellent stability, so the electrophotographic liquid developer for offset masters using the resin dispersion of the present invention can be diluted approximately 160 times to prepare a developing bath. It is extremely stable even when printed, and does not cause phenomena such as the formation of large amounts of sediment or gel-like aggregates, and there is no image blurring (blurred outlines) or background smearing when offset printing is performed. , and has excellent printing durability such that the desired clear image can be obtained even after 5000 printings. Example 1 120 g of n-heptane, 40 g of toluene, and 4 g of azobisisobutyronitrile were placed in a reactor equipped with a stirrer, a reflux device, and a dropping device, and heated to reflux to dissolve 130 g of n-octyl methacrylate and cyclohexyl. A mixture of 70 g of methacrylate and 2 g of azobisisobutyronitrile was added dropwise over 1 hour, and after reacting for 1 hour, a mixture of 40 g of toluene and 1.5 g of azobisisobutyronitrile was added dropwise over 30 minutes.
Allowed time to react. Next, a mixture of 300 g of vinyl acetate and 3 g of benzoyl peroxide was added dropwise over 2.5 hours, and after reacting for 30 minutes, a mixture of 200 g of n-heptane and 2 g of Perloyl L (manufactured by NOF Corporation) was added dropwise over 30 minutes, and after reacting for 20 minutes, diethylaminoethyl A mixture of 12 g of methacrylate, 4 g of n-heptane, and 1 g of Perloyl L was added, and after reacting for 1 hour, 1 g of Perloyl L was added and the mixture was further reacted for 2 hours to form a mixture of 100 g of Isopar G and dimethyl sulfate.
0.2 g was added and cooled to obtain a milky white stable dispersion. 20 g of this resin dispersion, 1.6 g of Bontron N-04 (manufactured by Orient Chemical Industry Co., Ltd.), 80 g of Isopar G, and 1 g of zinc naphthenate were kneaded at room temperature in a sand mill for 11 hours to obtain a concentrated developer, which was then increased in volume by 10 times. A developer solution diluted with Isopar G was used. Example 2 In the same reactor as in Example 1, 125 g of n-octyl methacrylate and cyclohexyl methacrylate were added.
Add 75g of n-heptane and 2g of mercaptoethanol, stir while sending a small amount of air to the liquid surface, hold at 80℃ for 16 hours, turn off the air, add 35g of n-heptane, heat, and add 40g of toluene and azobis under reflux. A mixture of 1.5 g of isobutyronitrile was added dropwise over 3 hours,
The reaction continued for hours. The molecular weight of the obtained copolymer was approximately 15,000. Next, 70 g of n-heptane was added, and under reflux, 2 g of a mixture of 150 g of vinyl acetate, 25 g of n-octyl methacrylate, and 4 g of benzoyl peroxide was added.
Add vinyl acetate for 1 hour and react for 1 hour.
A mixture of 150g, n-heptane 40g and benzoyl peroxide was added dropwise over 1 hour and reacted for 30 minutes, then a mixture of 10g dimethylaminoethyl methacrylate, ethyl acrylate 15g and benzoyl peroxide 1g was added and reacted for 30 minutes. Furthermore, pearloil L1g and n
- A mixture of 5 g of heptane was added and reacted for 1.5 hours. After that, 130 g of Isopar G was added, the mixture was cooled to below 10°C, and further 0.1 g of ethyl chloride was added. The resulting dispersion was a slightly transparent, slightly yellowish and very stable emulsion. 5.5 g of surface-treated phthalocyanine blue, 314 g of Isopar G, and 4 g of zinc stearate were added to 50 g of the resulting resin dispersion, and kneaded in a ball mill for 24 hours to obtain a concentrated developer. This concentrated developer was diluted 10 times with Isopar G to prepare a developer. Example 3 In the reactor of Example 1, 140 g of 2-ethylhexyl methacrylate, 60 parts of benzyl methacrylate,
0.4 g of azobisisobutyronitrile, 3 g of mercaptoacetic acid and 5 g of n-hexane were added and heated until reflux. After reacting under reflux for 2 hours, a mixture of 10 g of toluene and 0.3 g of azobisisobutyronitrile was added dropwise over 2 hours, and the reaction was continued for an additional 2 hours to obtain a copolymer solution with a molecular weight of about 11,000. Next, add 346 g of vinyl acetate, 50 g of 2-ethylhexyl acrylate, and Perbutyl O (manufactured by NOF)
A mixture of 8g of n-heptane and 50g of n-heptane was added dropwise over 4 hours, and after reacting for 1 hour, 4g of perbutyl O was added dropwise over 30 minutes.
After 20 minutes, a mixture of 4 g of dimethylacrylamide, 5 g of n-heptane, and 1 g of perbutyl O was added, and after 30 minutes, 1 g of perbutyl O was added, and the mixture was reacted for 2 hours. 100 g of Isopar G was added, and after cooling, 0.05 g of dimethyl sulfate was added.
added. The resulting dispersion was a slightly transparent light brown emulsion with an average particle size of 0.2 μm. Add 150g of Iisopar G to 100g of this generated resin dispersion.
A mixture of 5 g of oil black HBB and 20 g of xylene was added dropwise with stirring, 1 g of aluminum stearate was added, and 10 g of Isopar G was added to prepare a developer. Example 4 70 g of n-hexane, 130 g of Isopar G, 227 g of vinyl acetate, and n-octyl methacrylate were added to the copolymer solution of n-octyl methacrylate and cyclohexyl methacrylate obtained in Example 2.
35 g of cyclohexyl methacrylate, 21 g of benzoyl peroxide, and 6 g of benzoyl peroxide were added and reacted under reflux, resulting in whitening after 3 hours.Furthermore, a mixed solution of 45 g of n-heptane and 2 g of benzoyl peroxide was added, and the mixture was reacted for 1 hour. Next, 24 g of N,N dimethylaminopropylacrylamide, 30 g of methyl acrylate, 0.4 g of dimethylaminoethyl methacrylate methyl chloride salt, and 1 g of benzoyl peroxide were added and reacted for 1 hour, and then 1 g of benzoyl peroxide was added and reacted for 2 hours. A slightly transparent, pale brown emulsion was obtained. A developer was prepared from this resin dispersion in the same manner as in Example 2. Comparative Example 1 A developer was prepared in the same manner as in Example 1 except that stearyl methacrylate was used instead of cyclohexyl methacrylate. Comparative Example 2 A developer was prepared in the same manner as in Example 1, but
When polymerizing the dispersion, 12 g of diethylaminoethyl methacrylate, 4 g of n-heptane, perloyl
No addition of L1g of mixture was made. Comparative Example 3 A developer was prepared in the same manner as in Example 2, but
The amount of dimethyl sulfate after dispersion polymerization was changed from 0.1 g to 1 g. Comparative Example 4 A developer was prepared in the same manner as in Example 3, but
No dimethyl sulfate was added after dispersion polymerization. Using the developer obtained as described above, an image was formed on offset master electrostatic recording paper coated with zinc oxide, and after performing an etching process, printing was performed using a commercially available offset ink. The compositions of the resin dispersions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1, and the results of the printing tests are shown in Table 2:

【table】

[Table] 1) Using Example 1 as standard (3), the number was increased as the concentration increased. 2) Image bleeding was determined using the following 5-point method: 5: No image bleeding at all 4: Slightly observed 3: Slightly present 2: Yes 1: Major 3) The etched image was used as the original plate. The results were evaluated by printing on high-quality paper using commercially available offset ink, and determining the number of prints until the fine dot images disappeared. 5: 5,000 sheets or more 4: 4,000 to 5,000 sheets 3: 3,000 to 4,000 sheets 2: 2,000 to 3,000 sheets 1: 2,000 sheets or less 4) The density of the printing paper obtained from the printing durability test, bleeding at the edge of the image area, Evaluation was made based on the clarity of fine dots. 5: High density, no image blurring, and fine dots are clear. 4: Slight bleeding is observed in the dark printed area. 3: Slight bleeding is observed at the edges of the printed area. 2: The image is blurred in general and the fine points are slightly unclear. 1: The image is blurred or faded. Or, the fine dots are scratched, resulting in solid black printing5) Stack the 5 sheets of printed paper obtained as a printing durability test with the image area aligned, and compare the non-image area and the same number of unprinted sheets side by side. , the dirt status was determined. 5: No difference observed even after repeated applications 4: Slight difference observed 3: Slight difference observed 2: Difference observed 1: Very large difference observed

Claims (1)

[Claims] 1. In a highly insulating hydrocarbon medium, (A) a) 20 to 99.5% by weight of vinyl acetate, b) the formula [formula] [where R is [formula] [formula] [formula] or [Formula], and R ₁ , R ₂ and R ₄ each independently represent hydrogen, C _1-6 alkyl, or alkoxyalkyl having 1 to 4 carbon atoms in each alkyl moiety, and R ₂ and R ₃ ′ is independently C ₁ ~
C ₄ alkylene, X represents hydrogen or methyl] 0.5 to 12% by weight of the monomer and c) C _{1 to 20} alkyl ester and/or C _{3 to 80} cycloalkyl ester of acrylic acid or methacrylic acid 0~79.5
% by weight (however, the sum of a), b) and c) above is 100% by weight), and has the formula ()
A copolymer substantially insoluble in the medium, in which at least a portion of the monomers thereof have been quaternary ammoniumated with a quaternary ammoniumating agent; , X has the meaning given above and Y also -
COOR ₅ , -OCOR ₅ or -OR ₅ , R ₅ represents C _4-20 alkyl] 95-15% by weight of the monomer of the formula [formula] [where X is the meaning described above] and R ₆ is C _3-8 cycloalkyl or the alkyl moiety has 1 carbon number.
5 to 85% by weight of the monomer (representing an aralkyl of ~3) (however, the total of the above d) and e) is 100% by weight) and f), a sulfur-containing organic mercaptan having at least one thiol group. A copolymer substantially soluble in the medium containing 0 to 2% by weight (however, the sulfur content per soluble copolymer shown below is expressed in weight%). A resin dispersion suitable for an electrophotographic liquid developer for offset masters. 2. The resin dispersion according to claim 1, wherein the soluble copolymer contains the organic mercaptan in a sulfur content of 0.03 to 2% by weight. 3 The amount of the quaternary ammonium forming agent used is expressed by the formula ()
The resin dispersion according to claim 1, wherein the resin dispersion is 0.1 to 5 mol% per monomer. 4. The resin dispersion according to any one of claims 1 to 3, wherein the soluble copolymer has a molecular weight of 50,000 or less.