JPH0431588B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a liquid developer for developing electrostatic latent images in electrophotography, electrostatic recording, etc.
The present invention relates to a liquid developer that has excellent stability and fixing properties, and can particularly achieve high image quality. (Prior Art) Many types of electrostatic latent image liquid developers are already known. For example, coloring pigments or dyes such as carbon black, cyanine blue, nigrosine, oil dyes, etc. are placed in a highly insulating solvent together with resins such as rosin, alkyd resin, acrylic resin, synthetic rubber, etc., and machined using a ball mill, attritor, Vomodiniger, etc. The most common method was to disperse the dispersion and then add metal particles, amines, higher fatty acids, etc. to stably impart an electric charge to the dispersed particles of the dispersion. However, since the liquid developer obtained by this method has a large particle size distribution of dispersed particles as a developer, it is difficult to obtain stable images due to the occurrence of a large amount of precipitates and poor charge stability and manufacturing stability. It had the following drawback. As described in Japanese Patent Publications Nos. 53-54029 and 57-12985, a vinyl group that can be polymerized by a polymer reaction is introduced into a precursor polymer in advance, and monomers are polymerized in the presence of this group to graft it. There is a method of obtaining a liquid developer by producing a polymer and coloring it with a dye. Although this method can be said to be an excellent method, there are problems in the control and reproducibility of the introduction of vinyl groups, and it is often accompanied by gel formation, and it is difficult to form dispersed particles stably. The following minute particles may be generated, which is not practical. Furthermore, JP-A-59-83174, JP-A No. 59-177572,
No. 59-212850, No. 59-212851, No. 60-164757
No. 60-179751, No. 60-185962, No. 60-
185963, etc., in the presence of a polymer soluble in a highly insulating medium, monomers that are soluble in the solvent but become insoluble when formed into a polymer are polymerized, and the resulting resin dispersion is liquid developed. It has been mentioned that it is used as a drug. This method has excellent industrial production stability and dispersion stability. However, when a liquid developer using a resin obtained by this method is used to form an image on an electrostatic recording material using Coulomba, electrostatic mutual repulsion due to Coulomba of the dispersed particles and the concentration of the dispersion stabilizing polymer increase. This results in a volume exclusion effect where the particles repel each other. For this reason, when the effective surface potential of the electrostatic recording material decreases, it has the disadvantage that a bleeding-like ghost is likely to occur around the image area. In addition, if a liquid developer using a resin obtained by this method is used continuously while actually being replenished, the solvent-soluble resin will accumulate, and depending on the type of soluble resin used, the amount of charge on the dispersed particles will decrease. It also had the disadvantage of having an impact. (Object of the Invention) The object of the present invention is to provide a liquid developer that improves the conventional drawbacks listed above, and in particular, a liquid developer that has excellent particle uniformity, image reproducibility, and charge stability. The goal is to provide the following. Another object of the present invention is to provide a liquid developer that provides excellent print quality as a developer for offset lithographic printing plates using zinc oxide or organic semiconductors as photoreceptors. Still another object of the present invention is to provide a liquid developer which can be used in any system in which a liquid developer can be used, such as inkjet recording, cathode ray tube recording, and recording of various change processes such as pressure changes or electrostatic changes. It is to be. (Structure of the Invention) The present invention provides an electrostatographic liquid developer containing at least resin particles dispersed in a highly insulating hydrocarbon solvent, in which the resin polymerizes in the solvent to form a soluble polymer. Polymerize in the solvent to form an insoluble polymer in the solvent-insoluble polymer p obtained by copolymerizing monomer A and monomer B that polymerizes in the solvent to form an insoluble polymer. This liquid developer for electrostatic photography is characterized in that it is a resin obtained by polymerizing one or more types of monomer C. Highly insulating hydrocarbon solvents used in the present invention include normal paraffinic hydrocarbons, isoparaffinic hydrocarbons, alicyclic hydrocarbons, halogenated aliphatic hydrocarbons, etc. From this point of view, isoparaffinic hydrocarbon solvents are practically preferred. Ciel Sol 7 ₁ (manufactured by Ciel Sekiyu)
Isopar O, Isopar H, Isopar K, Isopar L, Isopar G (Isopar is a trade name of Exoni), IP Solvent (manufactured by Idemitsu Petrochemical), Amsco OMS, Amsco 460 solvent (manufactured by Spirits), etc. can be used. Structure of the resin used in the liquid developer of the present invention The monomer A that polymerizes in the petroleum hydrocarbon solvent to form a soluble polymer is an acrylic resin having a long alkyl chain, particularly an alkyl chain having 8 or more carbon atoms. Acid esters, methacrylic esters, vinyl compounds, etc. given by the general formula (). General formula <1> In formula (1), R represents an aliphatic group having 8 or more carbon atoms.
A is -COO-, -CONH-,

[Formula] (R' represents an aliphatic group), -OCO-, -CH ₂ OCO-,
or -O-, Z ₁ and Z ₂ may be the same or different and represent a hydrogen atom, an alkyl group, -COOR'' or
CH ₂ COOR''(R'' represents an aliphatic group). For example, acrylic acid, methacrylic acid, crotonic acid,
Esters of unsaturated carboxylic acids such as maleic acid and itaconic acid (as aliphatic groups, decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, docosanyl, dodecenyl, hexadecenyl, oleyl, linoleyl group, docosenyl group, etc.), amides of the unsaturated carboxylic acids (aliphatic groups are the same as those shown for esters), vinyl esters, allyl esters, or allyl esters of higher fatty acids (as higher fatty acids, For example, lauric acid,
myristic acid, stearic acid, oleic acid, linoleic acid, behenic acid, etc.) or vinyl ethers substituted with higher aliphatic groups (the aliphatic group represents the same range as the aliphatic group of the unsaturated carboxylic acid mentioned above). can be mentioned. Monomer B, which is copolymerized with monomer A and forms an insoluble polymer by polymerization in a petroleum-based hydrocarbon solvent, has a hydroxyl group, a carboxyl group, a sulfonic acid group, a methylol group, a cyano group, or a ketonimide bond. , it is desirable to contain at least one kind of monomer having strong hydrogen bonding properties. Examples of monomer B include unsaturated carboxylic acids such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, and itaconic acid, or their anhydrides, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate,
Hydroxypropyl acrylate, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, acrylonitrile, N-vinylpyrrolidone and the like can be mentioned. Examples of monomer C that forms an insoluble polymer by polymerization in petroleum-based hydrocarbon solvents include, for example, in addition to those listed as monomer B, vinyl acetate, vinyl propionate, styrene, vinyltoluene, propyl methacrylate, and ethyl methacrylate. Methacrylate, methyl methacrylate, propyl acrylate, ethyl acrylate, methyl acrylate, methoxyethyl methacrylate, methoxyethyl methacrylate,
Glycidyl methacrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, carbitol acrylate, carbitol methacrylate, benzyl methacrylate, benzyl acrylate, N-vinyloxazolidone, N-vinylsuccinimide, N-methyl, N-vinylformamide, Examples include t-butylacrylamide, NN-dimethylmethacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, butoxymethylacrylamide, methoxymethylmethacrylamide, ethoxymethylmethacrylamide, butoxymethylmethacrylamide, and the like. Two steps are required to produce the dispersion resin used in the present invention as described above. In the first step, polymer P is produced. A petroleum hydrocarbon solvent and a mixed solvent of low boiling point solvents such as tetrahydrofuran, ethyl alcohol, isopropyl alcohol, methyl ethyl ketone and the like which are soluble in the above petroleum hydrocarbon solvent are used as an auxiliary solvent, and benzoyl peroxide and azobis are used as a solvent. Polymer P is obtained by heating and polymerizing monomer A and monomer B in the presence of a polymerization initiator such as sobutyronitrile. The polymer P obtained here is insoluble in the highly insulating solvent and is dissolved in the auxiliary solvent. Next, in the presence of the formed polymer P, monomer C is added to the polymerization initiator,
Monomer C is polymerized by heating, and the final reaction monomer and cosolvent are removed to complete the production. When producing the polymer P, the auxiliary solvent preferably accounts for 5 to 40% by weight of the solvent, depending on the solvent and polymer used. Regarding the composition of monomer A and monomer B, it is desirable that monomer B accounts for 5 to 50% by weight of the total monomers. Monomer C is added in an amount of 50 to 20 parts by weight of polymer P.
150 parts by weight is preferred. Removal of the co-solvent is suitably carried out under reduced pressure at a temperature below 90°C. As described above, the dispersion resin produced according to the present invention has excellent dispersion stability and exists as fine particles with a narrow and uniform particle size distribution. Furthermore, since the polymer P is insoluble in petroleum-based hydrocarbon solvents, it exists in a strongly bound manner near the particles. In the present invention, a coloring agent may be used if necessary, and the coloring agent is not particularly specified, and various conventionally known pigments or dyes can be used. The liquid developer of the present invention requires a charge control agent to charge the dispersed particles. For example, copper oleate, cobalt naphthenate, zinc naphthenate,
Manganese naphthenate, cobalt octylate, aluminum salt of steverite resin, etc.
No. 26594, No. 49-26595, JP-A-60-173558,
No. 60-175060, No. 60-179750, No. 60-182447
Charge control agents listed in Japanese Patent Application No. 60-218662, Japanese Patent Application No. 60-78062, etc. can also be used. Furthermore, in order to have negative chargeability, it is necessary to combine polymers that are soluble in petroleum hydrocarbon solvents and have a base (for example, a copolymer of lauryl methacrylate and dimethylaminoethyl methacrylate) with pyromellitic acid, trimellitic acid, trimesic acid, Acids insoluble in the solvent can be used in combination, such as, but not limited to, benzoic acid. The liquid developer obtained by the present invention is
No. 17162, No. 38-6961, No. 41-2426, No. 46-
39405, Japanese Patent Publication No. 50-19509, Japanese Patent Publication No. 50-19510,
No. 54-145538, No. 54-89801, No. 54-134632
No. 54-19803, No. 55-105244, No. 57-
No. 161863, No. 58-76843, No. 58-76844, No. 58
It can also be used for lithographic printing plates such as those described in No.-122897. When used in these lithographic printing plates, it must have resistance to alkaline eluents. The liquid developer obtained according to the invention gives particularly good printing plates when eluted with an inorganic alkaline eluent without using a penetrant such as benzyl alcohol. Examples of the present invention are shown below, but the content of the present invention is not limited thereto. Production example of polymer P-1 Lauryl methacrylate 180 in a polymerization flask
parts by weight, 20 parts by weight of hydroxyethyl methacrylate and IP Solvent 1620, 150 as a solvent.
parts by weight, and 50 parts by weight of isopropyl alcohol and azobisisobutylonitrile as a polymerization initiator.
After adding 1.5g parts by weight and thoroughly purging with nitrogen,
Heated to 80°C. 1.5 hours after the start of polymerization, 0.5 g part by weight of azobisisobutyronitrile was added,
The mixture was further heated for 3 hours and finally 200 parts by weight of IP Solvent-1620 was added to obtain a transparent, colorless and viscous solution. Production Example of Polymer P-2 95 parts by weight of lauryl methacrylate and 100 parts by weight of IP Solvent-1620 were placed in a polymerization flask, 0.75 parts by weight of azobisisobutyronitrile was added, and the mixture was thoroughly purged with nitrogen and heated to 80°C. . Furthermore, 5 parts by weight of N-methylolacrylamide dissolved in 40 parts by weight of tetrahydrofuran, 40 parts by weight of ethanol, and 100 parts by weight of methyl ethyl ketone was added to the flask over 40 minutes. Two hours after the start of polymerization, 0.25 parts by weight of azobisisobutyronitrile was added, and the mixture was heated for an additional 3 hours to obtain a transparent, colorless and viscous solution. Production example of polymer P-3 Lauryl methacrylate was added to the polymerization flask.
180 parts by weight and 20 parts by weight of methacrylic acid, 200 parts by weight of IP Solvent-1620 as a solvent and 40 parts by weight of isobutyl alcohol were added, 1.5 parts by weight of azobisisobutyronitrile were added, and after thorough nitrogen substitution, 80 parts by weight of methacrylic acid was added. 0.5 parts by weight of azobisisobutyronitrile was added 1.5 hours after the start of polymerization, heated to ℃.
After further heating for 3 hours, 230 parts by weight of Isopar 1620 was added. A clear, colorless and highly viscous solution was obtained. Resin Production Example-1 60 parts by weight of the solution obtained in Production Example 1 of Polymer P was placed in a polymerization flask, and IP Solvent 1620 was added.
When 200 parts by weight of Polymer P was added, Polymer P precipitated.
Further, when 60 parts by weight of methoxyethyl acrylate and 20 parts by weight of hydroxyethyl acrylate were added, the precipitate was dissolved in the monomer to form a homogeneous system. After adding 0.64 parts by weight of azobisisobutyronitrile and thoroughly purging with nitrogen, the mixture was heated to 80°C. After 3 hours, the pressure inside the flask was reduced and the auxiliary solvent was removed to obtain a milky white resin dispersion. The average particle size of the particles was 0.17 μm. Resin Production Example-2 80 parts by weight of the solution obtained in Production Example 2 of Polymer P was placed in a polymerization flask, and
When 200 parts by weight of 1620 was added, the polymer precipitated. Furthermore, when 80 parts by weight of vinyl acetate and 40 parts by weight of methyl ethyl ketone were added as an auxiliary solvent, the polymer was dissolved and a homogeneous system was obtained.0.64 parts by weight of azobisisobutyronitrile
After adding parts by weight and thoroughly purging with nitrogen, heat to 80°C.
heated to. After 3 hours, the pressure inside the flask was reduced to remove residual monomers and auxiliary solvents to obtain a milky white resin dispersion. The average particle size of the particles was 0.15 μm. Resin Production Example-3 65 parts by weight of the solution obtained in Production Example 3 of Polymer P was placed in a polymerization flask and added with IP Solvent 1620.
When 200 parts by weight of was added, the polymer precipitated. Further, when 80 parts by weight of vinyl acetate and 40 parts by weight of isobutyl alcohol were added as an auxiliary solvent, the polymer was dissolved to form a homogeneous system. Azobisisobutyronitrile
After adding 0.64 parts by weight and thoroughly purging with nitrogen, the mixture was heated to 80°C. After 3 hours, the pressure inside the flask was reduced to remove residual monomers and auxiliary solvents to obtain a milky white resin dispersion, with an average particle size of 0.15 μm.
It was hot. Comparative Example-1 Lauryl methacrylate 20 in a polymerization flask
Parts by weight of vinyl acetate, 80 parts by weight of vinyl acetate, and 220 parts by weight of IP Solvent-1620 were taken, and 0.8 parts by weight of azobisisobutyronitrile was added thereto, and after thorough nitrogen substitution, the mixture was heated to 80°C. After 4 hours, heating was terminated to obtain a milky white resin dispersion. The average particle size of the particles was 0.16 μm. Comparative Example-2 Lauryl methacrylate 20 was added to the polymerization flask.
Take 20 parts by weight of IP Solvent 1620, add 0.16 parts by weight of azoisobutyronitrile, and after sufficiently purging with nitrogen, heat to 80°C. 0.05 parts by weight of azobisisobutyronitrile was added and further heated for 2 hours. After 3 hours, the mixture was cooled, 80 parts by weight of vinyl acetate and 200 parts by weight of IP-1620 were added, and 0.64 g of azobisisobutyronitrile was added, and the mixture was again thoroughly purged with nitrogen, and then heated to 80°C. . Heating was terminated after 3 hours, and a milky white resin dispersion was obtained. The average particle size of the particles was 0.16 μm. Example 1 Resin Production Examples 1 to 3 and Comparative Examples 1 and 2 were colored black using oil black dye, and particles were positively charged using aluminum salt of steverite resin. A positively charged liquid developer was obtained. Z ₁₁ O
An image was formed on the master LOMB using a plate making machine EP-12 (all manufactured by Mitsubishi Paper Industries), and the following results were obtained.

[Table] Image reproducibility (×) is a practical problem as the edges of the image are not sharp and blur-like ghosts occur. Regarding charge stability (△), particle charge slightly changed when the liquid developer was used for a long time (about 3 months). (○) shows no change in particle chargeability after 3 months of use. Dispersion stability (○) is at a level where no precipitates or aggregates form at all after 3 months as a liquid developer. Example 2 Five types of developers were obtained in the same manner as in Example 1, except that sodium salt of dioctyl sulfosuccinate was used as a negatively charged liquid developer. A molded copper phthalocyanine pigment dispersed in an acrylic resin with a high acid value was coated on an aluminum plate that had been treated to make it hydrophilic and dried to create a printing plate. After the original plate was positively charged by corona charging, it was imagewise exposed, developed with the five types of developer described above, and heat-fixed. The sample was immersed for 10 seconds in a solution prepared by diluting DP-4 (Fuji Photo Film Co., Ltd., PS plate developer) 10 times with water, and then washed with water. Only the developers obtained from Resin Production Examples 1 to 3 produced beautiful images, and Comparative Examples 1 and 2
When the developer obtained in the above was used, a smudge-like ghost appeared at the interface between the image area and the non-image area, and a good printing plate could not be obtained. Also, when the comparative example resin was used for printed matter using this printing plate, the edges of the image area were not sharp and the finish was not good, but the developer obtained in Production Examples 1 to 3 produced a beautiful finish. A print was obtained.

Claims (1)

[Claims] 1. A liquid developer for electrophotography containing at least resin particles dispersed in a highly insulating hydrocarbon solvent, wherein the resin polymerizes to form a polymer soluble in the solvent. Polymerized in the presence of a polymer P insoluble in the solvent obtained by copolymerizing the following monomer A and the following monomer B that polymerizes to form a polymer insoluble in the solvent. It is a resin obtained by polymerizing the following monomer C that forms a polymer, and monomer B is 5 to 50% by weight of the total monomers used for copolymerization of polymer P, and monomer C is 50% by weight based on 20 parts by weight of polymer P. 1. A liquid developer for electrostatic photography, characterized in that the amount is used in a range of 150 parts by weight. Monomer A: A monomer represented by the following general formula (1). General formula (1) [R in formula (1) represents an aliphatic group having 8 or more carbon atoms. A is -COO-, -CONH-, [Formula] (R' represents an aliphatic group), -OCO-, -CH ₂ OCO-,
or Z ₁ and Z ₂ representing -O- may be the same or different and represent a hydrogen atom, an alkyl group, -COOR'' or -
CH ₂ COOR''(R'' represents an aliphatic group). Monomer B: unsaturated carboxylic acid or anhydride thereof such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, methacrylamide, N-methylol acrylamide, N
- A monomer selected from methylolmethacrylamide, acrylonitrile, and N-vinylpyrrolidone. Monomer C: unsaturated carboxylic acid or anhydride thereof such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, methacrylamide, N-methylol acrylamide, N
- Methylolmethacrylamide, acrylonitrile, N-vinylpyrrolidone, vinyl acetate, vinyl propionate, styrene, vinyltoluene, propyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl acrylate, ethyl acrylate, methyl acrylate, methoxyethyl methacrylate, methoxyethyl methacrylate, Glycidyl methacrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, carbitol acrylate, carbitol methacrylate, benzyl methacrylate, benzyl acrylate, N-vinyloxazolidone, N
-vinyl succinimide, N-methyl, N-vinylformamide, t-butylacrylamide,
A monomer selected from N,N-dimethylmethacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, butoxymethylacrylamide, methoxymethylmethacrylamide, ethoxymethylmethacrylamide, butoxymethylmethacrylamide.