JPH0623865B2 - Liquid developer for electrostatic photography - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a developer for an electrostatic latent image. More specifically, the electrostatic latent image is visualized in an electrophotographic process or an electrostatic recording process. To an improved liquid developer for conversion into This improved developer is particularly suitable for developing electrostatic latent images on insulating surfaces with positively charged toner particles.

(Prior Art) In the process of electrophotography, for example, first, a surface of a recording material such as a photosensitive layer made of photoconductive zinc oxide provided on a support having relatively high conductivity is uniformly formed in a dark place. Is charged negatively. Then, by projecting the optical image of the original image of the subject on the charged photosensitive layer, a uniform partial discharge of the charged surface is generated according to the intensity of the irradiated light, and the electrostatic latent image is generated. To form.

A visible image is formed by causing electroscopic toner particles to act on the electrostatic latent image. This visible image is fixed directly to the photoconductive surface in the electrochromic process.
Alternatively, the electrostatic latent image or the visible image is transferred and fixed on a desired support surface through a transfer process such as charge transfer, pressure transfer, magnetic transfer.

Further, in the case of ordinary copying, it is required to obtain a positive copy from the positive original plate. Therefore, when the surface of the photosensitive layer is used while being negatively charged, the electroscopic toner particles are required to have a strong and stable positive charge. A liquid developer containing toner particles having a positive charge is
Many kinds are already on the market.

However, all of these commercially available developers are designed for copying original line images or original halftone dot images and are not suitable for continuous tone image reproduction. That is, when a continuous tone image is copied using these developers, a sufficient image density cannot be obtained, and a flow-like defect (so-called streak) is liable to occur in the image, and further, a non-image portion is not affected. It was found that toner precipitation (fogging) is likely to occur.

As a developer capable of improving these problems and obtaining a good continuous tone image, it is preferred to use a half-alkylamide compound of diisobutylene-maleic acid copolymer as a charge control agent (Japanese Patent Publication No. 49-26594). US Patent 406
No. 2789).

However, according to the experimental results of the present inventors, the positive charge retention of the toner particles in the developer is strong and does not cause the polarity to be changed. It was found that the sharpness of the copied image gradually lost when it was repeatedly used more than once and many times. This is also a problem in that the amount of toner particles adhering to the image surface is reduced, the above-mentioned defects occur, and the strength of the formed image after fixing is not sufficient. Therefore, when an image was formed on a zinc oxide photosensitive paper using these developers and used as an offset printing plate, there was a problem that the sensitivity to printing ink and the number of printing sheets became insufficient. . In addition, the image quality of the copied image obtained through the transfer process was significantly deteriorated.

(Object of the Invention) The present invention solves the above problems of the conventional liquid developer.

An object of the present invention is to provide an excellent liquid developer which gives excellent image quality of a good continuous tone image and does not cause image quality deterioration such as density decrease, thin line lacking, and fog increase even after continuous use for a long time. Is to provide.

Another object of the present invention is to provide a liquid developer which enables continuous production of a very large number of offset printing original plates by electrophotography having excellent printing ink oil sensitivity and printing durability. .

Another object of the present invention is to provide a liquid developer suitable for various types of electrostatic photography and various types of transfer such as charge transfer, in addition to the above applications.

(Structure of the Invention) The present invention relates to a liquid for electrostatic photography in which a toner containing at least a resin as a main component is dispersed in a non-aqueous solvent having an electric resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.5 or less. In the developer,
The resin is a copolymer having at least one or more monomers capable of being polymerized to make the resin soluble in the non-aqueous solvent and maleic anhydride as constituent units, and a primary amino compound or primary amino compound. A high-molecular compound obtained by reaction with a compound and a secondary amino compound, and the resin is a high-molecular compound having a half-maleic acid amide component and a maleinimide component as repeating units. It is a liquid developer for photography.

Monomers capable of forming a polymer soluble in a non-aqueous solvent that constitutes the copolymer of the present invention include polymerizable alkenes, cycloalkenes, styrenes, vinyl ethers, allyl ethers, carboxylic acids. Examples thereof include vinyl esters or allyl esters, and esters of methacrylic acid or acrylic acid. To further explain, the monomer has a total carbon number of 3 to
40 optionally substituted alkenes (eg, propenylene, butene, vinylidene chloride, ω-phenyl-1-propene, allyl alcohol, hexene, octene, 2-
Ethylhexene, decene, dodecene, tetradecene, hexadecene, octadecene, docosene, eicosene, 1
0-hexene hexylate, etc.), cycloalkenes having a total carbon number of 5 to 40 (for example, cyclopentene, cyclohexene, bicyclo [2,2,1] -heptene-2,5-cyanobicyclo [2,2,1]-). Heptene-2, etc.), styrenes having a total carbon number of 8 to 40, which may be substituted (for example, styrene, 4-methylstyrene, 4-n octylstyrene, 4-hexyloxystyrene, etc.), and a total carbon number of 1 to 4
0 aliphatic group-substituted vinyl ethers or allyl ethers [as an aliphatic group, an alkyl group which may be substituted (for example, a methyl group, an ethyl group, a butyl group, a hexyl group,
Octyl group, decyl group, dodecyl group, hexadecyl group,
Octadecyl group, docosanyl group, chloroethyl group, 2-
Ethylhexyl group, 4-methoxybutyl group, etc.), optionally substituted aralkyl group (eg benzyl group, phenethyl group etc.), optionally substituted cycloalkyl group (eg cyclopentyl group, cyclohexyl group etc.) or substituted Optionally an alkenyl group (eg, 2-pentenyl group,
4-propyl-2-pentenyl group, oleyl group, linoleyl group, etc.), aromatic group-substituted vinyl ether or allyl ether having a total carbon number of 6 to 40 [as aromatic group, for example, phenyl group, 4- Butoxyphenyl group, 4-octylphenyl group, etc.], total carbon number 2-40
Vinyl esters or allyl esters of optionally substituted aliphatic carboxylic acids (eg, acetic acid, valeric acid, caproic acid, capric acid, lauric acid, myristic acid, palminanoic acid, stearic acid, oleic acid, sorbic acid, linoleic acid) Etc.), vinyl esters or allyl esters of aromatic carboxylic acids having a total carbon number of 6 or more (for example, esters of benzoic acid, 4-butylbenzoic acid, 2,4-butylbenzoic acid, 4-hexyloxybenzoic acid). Etc.) or unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, crotonic acid, etc., which may have a total carbon number of 1 to 32 and which may be substituted (eg, methyl group, ethyl group, propyl ester) Group, hexyl group, decyl group, 2
-Hydroxyethyl group, N, N-dimethylaminoethyl group, etc.) and the like.

The copolymers of these monomers and maleic anhydride will be illustrated more specifically, but the invention is not limited to the following compound examples.

(1) (2) (3) (4) (5) (6) (7) (8) (9) (Ten) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (twenty one) (twenty two) The above-described copolymer containing maleic anhydride can be produced by a conventionally known method. For example, Ryohei Oda, “Modern Industrial Chemistry Vol. 16, Polymer Industrial Chemistry I”
281 (published by Asakura Shoten), J. Brandrup et al., "Polymer
Hand book 2nd, Edition, John Wiley & Sons, New York,
It is described in detail in the publicly known documents of the review literature such as Chapter 2.

The novel compound provided in the present invention is a reaction product of the copolymer containing maleic anhydride and an amino compound,
As the amino compound, a primary amino compound represented by the following general formula (I), or a primary amino compound represented by the general formula (I) and a secondary amino compound represented by the general formula (II) are used.

General formula (I) R ₁ NH ₂ General formula (II) In the formula, R ₁ and R ₂ represent an aliphatic group, an alicyclic hydrocarbon group, an aromatic group or a heterocyclic group, and R ₁ and R in the general formula (II)
_Two may be the same or different. Preferably, the carbon number is 1 to
32 optionally substituted alkyl groups (eg, methyl group,
Ethyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, docosanyl group, chloroethyl group, cyanoethyl group, 4-butoxypropyl group, 2-
Ethylhexyl group, N, N-butylaminopropyl group, etc.), alkenyl group having 3 to 32 carbon atoms which may be substituted (eg allyl group, 2-pentenyl group, 4-propyl-
2-pentenyl group, decenyl group, oleyl group, linoleyl group, etc.), optionally substituted aralkyl group having 7 to 36 carbon atoms (eg, benzyl group, phenethyl group, etc.), carbon number 5
To 32 optionally substituted alicyclic hydrocarbon groups (eg, cyclopentyl group, cyclohexyl group, bicyclo [2,2
2,1] -heptyl group, cyclohexenyl group and the like), aryl group having 6 to 38 carbon atoms which may be substituted (for example, phenyl group, tolyl group, 4-butylphenyl group, 4-decylphenyl group, 4-butoxyphenyl group, Etc.) or a heterocyclic group having 5 or more atoms (eg, furyl group, thienyl group, etc.). In the case of the general formula (II), R ₁ and R ₂ may be ring-closed with a carbon atom or may contain a hetero atom in the ring (eg, morpholyl group).

Specific examples of preferred amino compounds used in the present invention include ethylamine, propylamine, butylamine,
Pentylamine, hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, stearylamine, docosanylamine, 2-ethylhexylamine, 3,3-dimethylpentylamine, allylamine, hexenylamine, dodecenylamine, tetradecenyl. Examples thereof include ruamine, hexadecenylamine, octadecenylamine, 2-nonyl-2-butenylamine, allylamine, cyclohexylamine, benzylamine and 4-n-octylaniline.

The polymer compound which is a reactant with the amino compound of the present invention is characterized by containing a half-maleic acid amide component and a maleinimide component, but the compound of the present invention is a maleic anhydride component in the polymer compound. It can be easily produced by converting a part of the half-maleic acid amide component into a maleinimide component by performing a dehydration ring-closing reaction by forming a half-maleic acid amide copolymer by a high-molecular reaction between cis and a primary amino compound. it can.

That is, in an organic solvent that does not react with a carboxylic acid anhydride and an amino compound and can dissolve both at the following reaction temperatures [for example, hydrocarbons (for example, decane, isopa-G, isopa-H, shell sol 71, Cyclohexane, benzene, toluene, xylene etc.), ketones (eg methyl ethyl ketone, methyl isobutyl ketone etc.), ethers (eg dioxane, tetrahydrofuran, anisole etc.), halogenated hydrocarbons (chloroform, dichloroethylene, methyl chloroform etc.), dimethylformamide Or dimethyl sulfoxide, etc., which may be used alone or in combination], and the compounds are mixed at a temperature of 60 ° C. to 200 ° C., preferably 10 ° C.
0 to 180 ° C., 1 to 80 hours, preferably 3 to
Incubate for 15 hours. In this reaction, the use of an organic base (eg, triethylamine, dimethylaniline, pyridine, morpholine, etc.) or an inorganic or organic acid (eg, sulfuric acid, methanesulfonic acid, benzenesulfonic acid, etc.) in a catalytic amount promotes the reaction. Alternatively, an ordinary dehydrating agent (for example, phosphorus pentoxide, dicyclocarboxydiimide, etc.) may be used in combination.

As described above, the reactant obtained by this reaction is a polymer compound containing a half-maleic acid amide compound and a maleic amide compound in the polymer compound. The ratio is 10:90 to 90:
10 and preferably 30:70 to 70:30. The weight ratio of the monomer portion capable of forming a polymer soluble in a non-aqueous solvent and the maleic anhydride portion constituting the polymer compound is 10:90 to 99.5: 0.5, and preferably Is from 70:30 to 30:70. The molecular weight of the polymer compound is 1,000 to 500,000, preferably 50.
It is from 00 to 50,000.

Compared with the semi-alkylamide compound of the diisobutylene-maleic acid copolymer described in JP-B-49-26594, the liquid developer using the compounds of the present invention has a significantly higher number of development uses. It has been found that there is almost no change in performance even after long-term storage.

The non-aqueous solvent used in the present invention having an electric resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.5 or less, preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic Hydrocarbons or halogenated hydrocarbons can be used. From the viewpoint of volatility, stability, toxicity, odor, etc., octane, isooctane, decane, isodecane,
Nonane, dodecane, isododecane, decalin, isoparaffin-based petroleum solvent, Isopa-E, Isopa
G, Isopa-H, Isopa-L (trade name of Exxon), Cielsol 71 (tradename of Ciel), Amsco O
MS, Amsco 460 (trade name of Spirits Inc.) and the like are used alone or in combination.

The toner particles used in the present invention are not particularly specified, and conventionally known particles can be used. For example, the resin that is the main constituent part of the toner particles may be a resin that is not substantially insoluble in the organic solvent, such as an acrylic resin, an ester resin, an amide resin, an alkylene resin, a phenol-modified alkyd resin, or an epoxy resin. Examples thereof include synthetic resins such as resins, rosins and synthetic rubbers, and natural resins. The resin dispersion that can be used for the liquid developer can be prepared by a method known to those skilled in the art.

For example, there is a method in which a desired resin is dispersed in a nonpolar solvent and kneaded with a ball mill or a high-speed stirrer to produce the resin.
As for the monomer, a so-called polymerization granulation method is known, in which a monomer that is insoluble in a solvent when it is dissolved in a nonpolar solvent and polymerized into a resin is polymerized to obtain a resin dispersed in the solvent. Has been. For example, K. E. J. Barrett, `` Dispersion Polyme
rization in Organic Media '' John Willey and Sons, Lo
ndon, 1974, US Pat. No. 3,637,569, US Pat. No. 3,753,760, and the like.

The particle size of the obtained dispersed resin is preferably 5 μm or less, particularly 2 μm or less in order to obtain a continuous tone image.

The colorant which is the other main constituent of the toner particles is not particularly specified, and various conventionally known pigments or dyes can be used. The colorant may be used alone by dispersing it in the non-aqueous solvent in combination with a dispersion accelerator or the like, or may be a graft type particle (for example, graft carbon) in which a polymer is chemically bonded to the surface of the colorant. : Mitsubishi gas chemical product name) may be used. Further, a colorant may be contained in the above resin for use.

As a method for coloring the dispersed resin, for example, JP-A-48-7
There is a method of physically dispersing in a resin using a well-known dispersing machine such as 5242 (paint shaker, colloid mill, vibration mill, ball mill, etc.), and the pigments and dyes used are very well known. ing. Examples include magnetic iron oxide iron powder, carbon black, nigrosine, alkali blue, Hansa yellow quinacridone red, phthalocyanine blue, phthalocyanine black, and benzidine yellow.

As another coloring method, there is a method of heating and dyeing a dispersed resin material with a preferable dye as described in JP-A-57-48738.

Examples thereof include Hansa Yellow Crystal Violet, Victoria Blue, Malachite Green, Seriton Hua Streddo, Desperce Yellow, Desperce Red, Desperce Blue, Solvent Red, and the like.

Still another coloring method is a method of chemically bonding a dispersion resin and a dye. For example, JP-A-53-54029
Etc., a method of reacting a resin with a dye or a method of previously binding a dye to a monomer of a resin which is insoluble and dispersible by polymerization in JP-B-44-22955 is known. Can be used.

In order to stably disperse the above-mentioned resin or colorant in the non-aqueous solvent, a conventionally known dispersion stabilizer can be used. That is, various synthetic resins or natural resins can be used alone or in combination of two or more kinds. For example, an alkyl chain having a total carbon number of 4 to 30 [halogen atom,
Acrylic acid or methacrylic acid which may contain a substituent such as a hydroxyl group, an amino group or an alkoxy group, or may have a carbon-carbon atom bond in the main chain through a hetero atom such as an oxygen atom may be present. Alkyl ester, vinyl ester of fatty acid, polymer of vinyl alkyl ether or monomer such as olefin such as butadiene, isoprene and diisobutylene, copolymer of two or more kinds thereof, and further aliphatic group as described above. A copolymer of a monomer that forms a polymer soluble in a hydrocarbon solvent and one or more kinds of various monomers described below can be used.

For example, vinyl acetate, acrylic acid, or methacrylic acid,
Crotonic acid methyl, ethyl, n-propyl or i
so-propyl ester, styrene, vinyltoluene,
Styrene derivatives such as α-methylstyrene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid or anhydrides thereof, hydroxyethyl acrylate, diethylaminoethyl methacrylate, N-vinylpyrrolidone, acrylamide, Acrylonitrile, 2-chloroethyl methacrylate, 2,
To mention monomers such as 2,2-trifluoroethylmethacrylate containing various polar groups such as hydroxy group, amino group, amide group, cyano group, sulfonic acid group, carbonyl group, halogen atom and hetero ring. You can

Alternatively, in addition to the above synthetic resins, resins such as alkyd resins, alkyd resins modified with various fatty acids, and linseed oil-modified polyurethane resins can be used.

The amount of each main component of the liquid developer of the present invention will be described below.

The toner particles containing a resin and a colorant as main components are preferably 0.5 to 50 parts by weight with respect to 1000 parts by weight of the carrier liquid. When the amount is 0.5 parts by weight or less, the image density is insufficient, and when the amount is 50 parts by weight or more, fog easily occurs on the non-image part. A carrier liquid-soluble resin such as the above-mentioned dispersion stabilizer is also used if necessary, and can be added in an amount of about 0.5 to 100 parts by weight with respect to 1000 parts by weight of the carrier liquid.
The novel compound of the present invention, which is a charge control agent, produces a remarkable effect with a very small amount on the carrier liquid, and the best amount is from 0.001 to 0.5 part by weight to 1000 parts by weight of the carrier liquid.

Below this lower limit, the positive charge retention of the toner particles becomes unstable, and above the upper limit, the electrical resistance of the developer decreases and the image density obtained is lowered.

In addition, various additives may be added as required. Specific examples are given in Yuuji Harazaki, “Electrophotography”, Vol. 16, No. 2, page 44.

The upper limit of the total amount of the liquid developer additives as described above is restricted by the electric resistance of the developer. That is, if the electric resistance of the liquid developer with the toner particles removed is less than 10 ⁹ Ω · cm, it becomes difficult to obtain a continuous tone image of good quality. Therefore, each addition amount of each additive is controlled within this limit. It is necessary to.

Examples of the present invention will be presented below, but the invention is not limited thereto.

Intermediate Production Example 1: Specific Example of Intermediate (2) A mixture of 98 g of maleic anhydride, 252 g of 1-dodecene and 816 g of toluene was heated to a temperature of 85 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 6.0 g of an initiator: benzoyl peroxide was added and stirred for 3 hours, and further 6.0 g of benzoyl peroxide was added and stirred for 4 hours.

The solid content of the obtained polymer solution was 22.5%.

Intermediate Production Example 2: Specific Example of Intermediate (5) A mixture of 98 g of maleic anhydride, 378 g of 1-octadecene and 1850 g of toluene was heated to 90 ° C. while stirring under a nitrogen atmosphere.

At that temperature, 7.0 g of an initiator: benzoyl peroxide was added and stirred for 3 hours, and then 7.0 g of benzoyl peroxide was added and stirred for 5 hours.

The solid content of the obtained polymer solution was 14.8%.

Intermediate Production Example 3: Specific Example of Intermediate (15) A mixture of 49 g of maleic anhydride, 135 g of vinyl laurate and 430 g of methyl isobutyl ketone was heated to a temperature of 80 ° C. with stirring under a nitrogen atmosphere. At that temperature, 2.4 g of benzoyl peroxide was added and stirred for 3 hours, and then 2.4 g of benzoyl peroxide was added and stirred for 5 hours. After cooling, the above reaction solution was added over 10 minutes with stirring to 3.0 of acetonitrile, and the mixture was added to 30 minutes as it was.
Stir for minutes. The precipitated solid was collected and dried under reduced pressure to obtain 185 g of a white solid.

Intermediate Production Example 4: Specific Example of Intermediate (16) A mixture of 49 g of maleic anhydride, 186 g of vinyl stearate and 550 g of toluene was heated to a temperature of 85 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 4.0 g of benzoyl peroxide was added and stirred for 3 hours, then 4.0 g of benzoyl peroxide was further added and stirred for 4 hours.

After cooling, the above reaction solution was added to 3.0 mL of acetonitrile with stirring over 10 minutes, and stirred as it was for 30 minutes.

The precipitated solid is collected and dried under reduced pressure to give a white solid (165 g)
Got

Intermediate Production Example 5: Specific Example of Intermediate (12) A mixture of 49 g of maleic anhydride, 178 g of n-octadecyl vinyl ether and 835 g of toluene was heated to 70 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 2.1 g of 2,2'-azobisisobutyronitrile was added and stirred for 3 hours, and then 2,2'-
2.1 g of azobis isobutyronitrile was added, the temperature was raised to 85 ° C., and the mixture was stirred for 4 hours. After cooling, the reaction solution is
It was added to acetonitrile 5.0 with stirring for 10 minutes, and the mixture was stirred for 30 minutes as it was. Collect the precipitated solids
After drying under reduced pressure, 167 g of a white solid was obtained.

Compound Production Example 1 A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 1, 23.2 g of n-octadecylamine and 2 g of pyridine was stirred at a temperature of 100 ° C. for 8 hours. After cooling, the reaction solution was added to 800 m of methanol with stirring for 15 minutes,
The mixture was stirred as it was for 1 hour.

The precipitated solid is collected and dried under reduced pressure to give a pale yellowish white solid 37g.
Got The molecular weight measured by high performance liquid chromatography was 11,000. Moreover, the ratio of the half-maleic acid amide component and the maleinimide component was 6: 4 from the result of neutralization titration with an ethanol solution of potassium hydroxide.

Compound Production Example 2 A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 2, 11.6 g of n-hexadecylamine and 1.0 g of pyridine was heated and stirred under reflux of the solvent for 6 hours. After cooling, the solution was stirred in 600 m of methanol with stirring 15
It was added in minutes and stirred as it was. The precipitated solid was collected and dried under reduced pressure to obtain 22.6 g of a pale white-yellow solid.

The molecular weight measured by high performance liquid chromatography is 7,000.
It was. From the result of the neutralization titration, the ratio of the half-maleic acid amide component and the maleinimide component was 50:50.

Compound Production Example 3 100 g of the polymer solution obtained in Intermediate Production Example 2, 4.0 g of N-methyl-octadecylamine and 1.5 g of pyridine.
The mixture was heated to 100 ° C. and stirred for 10 hours.
Then, 1.8 g of n-hexylamine was added, and the mixture was stirred at the same temperature for 8 hours. After cooling, this solution was added to methanol 1
The mixture was stirred for 15 minutes, and the mixture was stirred for 1 hour. The precipitated solids were collected and dried under reduced pressure to obtain 17.5 g of a pale yellow solid.

The molecular weight measured by high performance liquid chromatography is 7,000.
It was. From the result of the neutralization titration, the ratio of the half-maleic acid amide component and the maleinimide component was 7: 3.

Compound Production Example 4 27 g of the white solid obtained in Intermediate Production Example 4, 13 g of n-octylamine, 0.8 g of pyridine and 100 of dioxane.
The mixture of g was stirred at a temperature of 110 ° C. for 6 hours. After cooling, the mixture was added to methanol 1 for 15 minutes with stirring and the mixture was further stirred as it was for 1 hour.

The precipitated solids were collected and dried under reduced pressure to give a pale white yellow solid 3
4 g was obtained. The molecular weight measured by high performance liquid chromatography was 17,000. From the result of the neutralization titration, the ratio of the half-maleic acid amide component and the maleinimide component is
It was 7: 3.

Compound Production Example 5 39.4 g of the solid obtained in Intermediate Production Example 5, 26.9 g of n-octadecylamine, 2.3 g of pyridine and xylene 1
00 g of the mixture was stirred at a temperature of 120 ° C. for 5 hours. After cooling, the mixture was put into 1.0 of methanol with stirring for 15 minutes, and further stirred for 1 hour. The precipitated solid was collected and dried under reduced pressure to obtain 57 g of a pale yellowish white solid.

The molecular weight measured by high performance liquid chromatography is 1900.
It was 0. The neutralization titration result showed that the ratio of the half-maleic acid amide component and the maleinimide component was 4: 6.

Example 1 14 g of poly (lauryl methacrylate), 1 vinyl acetate
A mixed solution of 00 g and 385 g of isododecane was heated to 70 ° C. while stirring under a nitrogen stream. 2,2'-
1.7 g of azobis (isobutyl nitrile) was added and reacted for 4 hours, then cooled and passed through a 200 mesh nylon cloth.

A white resin dispersion having a polymerization rate of 83% and an average particle size of 0.18 μm was obtained.

Poly (lauryl methacrylate) 10g, Nigrosine 1
0 g and isododecane (30 g) were put together with glass beads in a paint shaker and dispersed for 2 hours to obtain a fine dispersion of nigrosine.

32 g of the above-mentioned white resin dispersion, 2, 5 g of the above-mentioned nigrosine dispersion, and the polymer 0.0 obtained in Compound Production Example 1
A liquid developer for electrostatic photography was prepared by dispersing 3 g in isododecane 1.

The liquid developer obtained is used as a Fuji fully automatic plate-making machine ELP280.
(Fuji Photo Film Co., Ltd.) developer and ELP master (Fuji Photo Film Co., Ltd.) as an electrophotographic photosensitive material for printing master, using a positive tone original having continuous gradation to form an image on the ELP master. To form a master plate. The image of the obtained master plate was a good continuous tone image, and the maximum optical density of the image was 1.51 and the minimum (fog) was 0.06. The color tone of the image was temperature control. Similarly, ELP master 2
When 000 sheets were processed and the optical density of the image of the 2000th master plate was examined, the maximum was 1.48,
There was little decrease in concentration, and the minimum was 0.06, which was unchanged. Further, when the images of the first processed image and the 2000th image were observed, both were very clear images.

Next, the non-image areas of the first and 2000th master plates were desensitized to make printing plates, and 3000 sheets were printed. In all of the plates printed, the 3000th printed matter was clear, there were no fine line breaks, and there was no fog.

Examples 2 to 6 In the same manner as in Example 1, except that the polymer shown in Table 1 was used in place of the polymer [charge control agent] of the compound production example 1 of the present invention in the preparation of the liquid developer of Example 1. A liquid developer for electrostatic photography was prepared. For comparison, a known charge control agent, diisobutylene-maleic acid half-octadecylamide copolymer, was also prepared. The obtained liquid developer was tested in the same manner as in Example 1, and the maximum density of the image of the first master plate and the maximum density of the 2000th master plate in the same image area were measured. The change rate was calculated by the following formula.

Next, the 1st and 2000th master plates were used as printing plates in the same manner as in Example 1 to print 3000 sheets, and the image of the printed matter was observed. The results are shown in Table 1.

As is clear from Table 1, in Examples 2 to 5 using the polymer of the present invention, the maximum image density of the obtained master plate was high, and the density decrease was low even after processing 2000 sheets. However, in Example 6 performed for comparison, the master density of the first sheet is high, but the density of the 2000th sheet is greatly reduced, and the printed matter printed using this has a conspicuous cut of fine lines in the printed image. Fog was seen in the image area (20
The density of the non-image area of the 00th master plate is 0.1
There was 0 and it was more than the first one).

Example 7 To 100 g of the white resin dispersion obtained in Example 1, 5 g of finely pulverized Sumikaron Navy Blue (manufactured by Sumitomo Chemical Co., Ltd.)
Was added and the mixture was stirred at a temperature of 100 ° C. for 5 hours. After cooling, 2
A blue resin dispersion was obtained by passing through a 00 mesh nylon cloth. This was a resin having an average particle size of 0.18 μm.

A liquid developer was prepared by dispersing 35 g of the above blue resin dispersion and 0.035 g of the polymer obtained in Compound Production Example 5 in Isodecane 1. Using this liquid developer, the method described in Example 1 was tested.

The images obtained from both the first master plate and the 2,000th master plate were good continuous tone images, and the maximum optical density of the images was 1.40 each.
And 1.38. The minimum (fog) was 0.06 in both cases.

After printing 3000 sheets of each of the first and 2000th master plates according to a conventional method, clear printed matter could be obtained even after printing 3000 sheets.

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Claims (1)

[Claims] 1. A liquid developer for electrostatic photography in which at least a toner containing a resin as a main component is dispersed in a non-aqueous solvent having an electric resistance of 10 ⁹ Ω · or more and a dielectric constant of 3.5 or less. A primary amino compound or a primary amino compound or a copolymer having at least one monomer capable of being polymerized to make the resin soluble in the non-aqueous solvent and maleic anhydride as constituent units; A high molecular compound obtained by reaction with a secondary amino compound, and the resin is a high molecular compound having a half-maleic acid amide component and a maleinimide component as repeating units, for electrostatic photography. Liquid developer.