JPH0451023B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application of the Invention) The present invention relates to a liquid developer for electrostatography, and more particularly to a liquid developer useful for converting an electrostatic latent image into a visible image in an electrophotographic process or an electrostatic recording process. , relates to an improved liquid developer containing a novel charge control agent. 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, the surface of a recording material, such as one in which a photosensitive layer made of photoconductive zinc oxide is provided on a relatively highly conductive support, is uniformly coated in a dark place. is negatively charged. By projecting the optical image of the original document onto the charged photosensitive layer, a uniform partial discharge of the charged surface occurs depending on the intensity of the irradiated light, and the electrostatic latent image is created. Let it form. A visible image is created by applying electroscopic toner particles to this electrostatic latent image. This visible image is
In the electrophoretic method, it is fixed directly to the photoconductive surface. Alternatively, the electrostatic latent image or visible image is transferred and fixed onto the surface of a desired support through a transfer process such as charge transfer, pressure transfer, or magnetic transfer. Further, in normal copying, it is required to obtain a positive copy from a positive original. Therefore, when the surface of the photosensitive layer is used with a negative charge, the electrodetectable toner particles are required to have a strong and stable positive charge. Many types of liquid developers containing positively charged toner particles are already commercially available. However, all of these commercially available developers are designed for copying line or halftone image originals and are not suitable for continuous tone image reproduction. In other words, when a continuous tone image is copied using these developers, sufficient image density cannot be obtained, running defects (so-called streaks) are likely to occur in the image, and furthermore, non-image areas may be affected. It was found that toner deposition (fogging) was likely to occur. Japanese Patent Publication No. 49-26594 discloses a developer that uses a semi-alkylamide compound of diisobutylene-maleic acid copolymer as a charge control agent as a developer that improves these problems and provides good continuous tone images. (US Pat. No. 4,062,789). However, according to the experimental results of the present inventors, the positive charge of the toner particles in the developer is strongly maintained and the polarity does not change. It has been found that when the developer is used repeatedly, for example, over 1,000 times, while replenishing the developer at will, the sharpness of the resulting copied images gradually decreases. This resulted in the problem that the amount of toner particles adhering to the image surface decreased, causing the above-mentioned drawbacks, and that the strength of the formed image after fixing was not sufficient. Therefore, when these developers are used to form an image on zinc oxide photosensitive paper and used as an offset printing plate, problems arise such as insufficient oil sensitivity to printing ink and insufficient number of printing sheets. .
Furthermore, the quality of the copied image obtained through the transfer process was also significantly degraded. (Objective of the Invention) The present invention is intended to improve the problems of conventional liquid developers as described above. An object of the present invention is to provide an excellent liquid developer that provides excellent image quality with good continuous tone images and does not cause image quality deterioration such as a decrease in density, lack of thin lines, or increase in fog even when used continuously for a long time. The goal is to provide the following. Another object of the present invention is to provide a liquid developer that can continuously produce a large number of cuffset printing original plates having excellent printing ink sensitivity and printing durability by electrophotography. 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-mentioned uses. (Structure of the Invention) The present invention is characterized in that resin particles produced by a polymerization granulation method in a non-aqueous solvent are contained in a non-aqueous solvent having an electrical resistance of 10 ⁹ Ω·cm or more and a dielectric constant of 3.5 or less. An electrostatographic liquid developer containing a toner dispersed therein and a charge control agent, wherein the charge control agent comprises at least one of monomers A capable of forming a polymer soluble in the non-aqueous solvent. Type 1 and the following general formula ()
The above-mentioned non-aqueous solvent soluble copolymer is composed of at least one monomer B represented by the following general formula () or monomer C represented by the following general formula (), wherein monomer A and monomer B or the monomer Composition weight ratio with body C is 30:70 to 90:10
and the charge control agent is added to the non-aqueous solvent at 100%
This is a liquid developer for electrostatic photography, characterized in that the content is 0.001 to 0.5 parts by weight. General formula () General formula () In formula (), R ₁ and R ₂ may be the same or different, and represent a hydrogen atom, an alkyl group, -COOH or -COOL (L represents a hydrocarbon group), and X ₁ is
The atomic group connecting the unsaturated bond group and -CONH- is
Further, Y ₁ each represents a group that connects -CONH- and -COOH with the number of atoms being 6 or less. Moreover, -CONH-Y ₁ -COOH may be directly bonded to the unsaturated bonding group without going through X ₁ . In formula (), R ₃ and R ₄ are R ₁ and R 4 in formula ()
Synonymous with R ₂ , X ₂ is an unsaturated bond group and −NHCO
-, and Y ₂ is -NHCO- and -
Each represents a group that connects COOH with 5 or less atoms. Also, −NHCO−Y ₂ − without going through X ₂
COOH may be directly bonded to the unsaturated bond group. The monomer A that can form a polymer soluble in a non-aqueous solvent constituting the copolymer that is the charge control agent of the present invention includes polymerizable alkenes, cycloalkenes,
These include styrenes, vinyl ethers, allyl ethers, vinyl esters or allyl esters of carboxylates, and esters of unsaturated carboxylic acids such as methacrylic acid, acrylic acid, itaconic acid, and maleic acid. To explain further, monomer A includes optionally substituted alkenes having a total number of carbon atoms of 6 to 40 (for example, hexene, octene, 2-ethylhexene,
Decene, dodecene, tetradecene, hexadecene, octadecene, docosene, eicosene, 10−
hexyl undecenoate, ω-phenyl-1-propane, etc.), optionally substituted cycloalkenes having a total of 5 to 40 carbon atoms (e.g., cyclopentene, cyclohexane, bicyclo[2,2,1]-heptene-
2,5-cyanobicyclo[2,2,1]-heptene-2, etc.), optionally substituted styrenes having a total of 8 to 40 carbon atoms (e.g., styrene, 4-methylstyrene, 4-n octylstyrene, 4 -hexyloxystyrene, etc.), aliphatic group-substituted vinyl ethers or allyl ethers having a total carbon number of 6 to 40 [optionally substituted alkyl groups (e.g. methyl group, ethyl group, butyl group, 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 (e.g. benzyl group, phenethyl group, etc.) ), an optionally substituted cycloalkyl group (e.g. cyclopentyl group, cyclohexyl group, etc.), or an optionally substituted alkenyl group (e.g. 2-pentenyl group, 4-pentenyl group, etc.)
-propyl-2-pentenyl group, oleyl group, linoleyl group, etc.], total carbon number 6 to
40 aromatic group-substituted vinyl ethers or allyl ethers [aromatic groups such as phenyl group, 4-butoxyphenyl group, 4-octylphenyl group, etc.], optionally substituted aliphatic carbon atoms having a total number of carbon atoms of 6 to 40 Vinyl or allyl esters of acids (e.g. caproic acid, capric acid,
esters of lauric acid, myristic acid, palminic acid, stearic acid, oleic acid, sorbic acid, linoleic acid, etc.), vinyl esters or allyl esters of optionally substituted aromatic carboxylic acids having a total of 6 to 40 carbon atoms ( For example, esters of benzoic acid, 4-butylbenzoic acid, 2,4-dibutylbenzoic acid, 4-hexyloxybenzoic acid, etc.), or unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, crotonic acid, etc. C6-40 optionally substituted aliphatic group esters [aliphatic groups include methyl group, ethyl group, propyl group, hexyl group, decyl group, 2-hydroxyethyl group, N,N
-dibutylamino] and the like. Next, the monomer B represented by the general formula () copolymerized with these monomers A will be explained. In the general formula (), R ₁ and R ₂ may be the same or different and may be a hydrogen atom, an alkyl group (such as a methyl group), -COOH or -COOL (L is a hydrocarbon group such as a methyl group, an ethyl group, a butyl group, etc.). group, hexyl group, decyl group, phenyl group, cyclohexyl group,
(represents a benzyl group, phenethyl group, etc.). X ₁ represents a group that bonds an unsaturated bonding group and -CONH- with at least one atom selected from a carbon atom or a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom; To name a few,

[Formula] (R, R' represent a hydrogen atom, an alkyl group, a halogen atom, etc.), -CH=CH-,

【formula】

[Formula] −COO−, −NHCO−, −NHSO ₂ −, −NHCONH−, −
NHCOO-, _-SO2- , -CO-, -O-, -S-,

[Formula] (R'' represents a hydrogen atom, an alkyl group, etc.) or any combination thereof. In addition, Y ₁ is a combination of -CONH- and -COOH. Represents a group connected by a chain of up to six atoms selected from atoms or heteroatoms such _as oxygen atoms, nitrogen atoms, and ionic atoms.
CONH−Y ₁ −COOH] may be directly bonded to the unsaturated bond group. Furthermore, to explain the monomer C represented by the general formula () that copolymerizes with the above-mentioned soluble monomer A, the general formula (), R ₃ and R ₄ are R ₁ of the formula ()
and R ₂ have the same meaning, and X ₂ connects the unsaturated bond group and -NHCO- with at least one atom selected from a carbon atom or a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. Specifically, it represents a group similar to that explained for X ₁ in formula (). _Y2 represents a group that connects -NHCO- and -COOH with a chain of five or less atoms selected from carbon atoms or heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. Moreover, [-NHCO- _Y2 -COOH] may be directly bonded to the unsaturated bonding group without passing through _X2 . More specific examples of each monomer represented by general formula () and general formula () are given below, but the present invention is not limited to the following compound examples. In order to produce the above-mentioned non-aqueous solvent-soluble copolymer resin which is a charge control agent used in the present invention, monomer A and monomer B or monomer C as described above are generally combined. in an organic solvent in the presence of a polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, butyl lithium, at a reaction temperature of 40 to 150°C.
The reaction may be carried out at a temperature of 2 to 15 hours. In the present invention, a ternary or more copolymer can be obtained by further adding other monomers to the reaction system and performing a polymerization reaction. In any case, monomer A
The composition ratio of monomer B or monomer C is 30:
70 to 90:10 (weight ratio) is preferred. Further, the molecular weight of the copolymer is 1,000 to 1,000,000, preferably 5,000 to 1,000,000.
500,000. Specific examples of the charge control agent used in the present invention are shown below, but the present invention is not limited to these specific examples. It has been found that the charge control agent of the present invention described above can control the electrodetectable toner particles in the liquid developer to have a strong and stable positive charge. Furthermore, compared to the diisobutylene-maleic acid semi-alkylamide compound described in Japanese Patent Publication No. 49-26596,
The liquid developer using the charge control agent of the present invention can dramatically increase the number of times it can be used for development, and
It was found that there was almost no change in performance even after long-term storage. The nonaqueous solvent having an electrical resistance of 10 ⁹ Ω·cm or more and a dielectric constant of 3.5 or less used in the present invention is preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, or Halogenated hydrocarbons and the like can be used. From the viewpoint of volatility, stability, toxicity, odor, etc., octane,
Isooctane, decane, isodenka, nonane, dodecane, isododecane, decalin, isoparaffin-based petroleum solvents Isopa-E, Isopa-
G, Isopa-H, Isopa-L (trade name of Exxon Corporation), Ciel Sol 71 (trade name of Ciel Corporation), Amsco OMS, Amsco 460 (trade name of Spirits Corporation), etc. are used alone or in combination. The resin particles, which are the main components of the toner particles used in the present invention, are made by polymerizing monomers that are soluble in non-aqueous solvents, but become insoluble in the solvents when polymerized to become resins. It is manufactured by the so-called polymerization granulation method, which obtains resin particles dispersed therein. Specifically, for example, KEJ Barrett, “Dispersion
Polymerization in Organic Media”John
Willey and Sons, London, 1974, U.S. Patent No.
It can be produced according to the method described in No. 3637569, US Patent No. 3753760, etc. The particle size of the resulting dispersed resin particles is desirably 5 microns or more, particularly 2 microns or less, in order to obtain a continuous tone image. The colorant, which is another component of the toner particles, is not particularly limited, and various conventionally known pigments or dyes can be used. The colorant may be used alone by being dispersed in the non-aqueous solvent in combination with a dispersion accelerator or the like, or it may be used as a graft-type particle (for example, grafted carbon) in which a polymer is chemically bonded to the surface of the colorant. : Mitsubishi Gas Chemical product name) may be used. Further, a coloring agent may be contained in the resin particles described above. As a coloring method, for example, JP-A-48-
As is known from Publication No. 75242, pigments and dyes are physically dispersed in a resin using a dispersion machine (paint shaker, colloid mill, vibration mill, ball mill, etc.), and this dispersion is mixed with the above-mentioned resin particles. There are many methods of mixing, and a large number of pigments and dyes are known. Examples include magnetic iron oxide powder, carbon black, nigrosine, alkali blue, Hansa yellow, quinacridone red, phthalocyanine blue, phthalocyanine black, and benzidine yellow. Another method of coloring is a method of heating and dyeing dispersed resin particles with a preferred dye, as described in JP-A No. 57-48738. Examples include Hansa Yellow Crystal Violet, Victoria Blue, Malachite Green, Seriton Fast Red, Despers Yellow, Despers Red, Despers Blue, and Solvent Red. Still another method of coloring is a method of chemically bonding dispersed resin particles and a dye. For example, JP-A No. 53-54029 discloses a method of reacting a resin with a dye, or JP-A No. 44-22955 discloses a method in which a dye is bonded in advance to monomers of resin particles that can be made insolubilized and dispersed through polymerization. Methods are known and 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. For example, total carbon number 4 to 30
Alkyl chain [halogen atom, hydroxyl group,
an alkyl ester of acrylic acid or methacrylic acid, which may contain a substituent such as an amino group or an alkoxy group, or may have a carbon-carbon bond in the main chain via a hetero atom such as an oxygen atom; Polymers of monomers such as vinyl esters of fatty acids, vinyl alkyl ethers, or olefins such as butadiene, isoprene, diisobutylene, or 2
A copolymer formed by a combination of two or more species, and further a copolymer formed by a monomer forming a polymer soluble in an aliphatic hydrocarbon solvent as described above and one or more of the following various monomers. Polymers can be used. For example, methyl, ethyl, n-propyl or iso-propyl esters of vinyl acetate, acrylic acid, methacrylic acid or crotonic acid, styrene, styrene derivatives such as vinyltoluene or α-methylstyrene, acrylic acid, methacrylic acid, crotonic acid, Unsaturated carboxylic acids such as maleic acid or itaconic acid or their anhydrides, hydroxyethyl acrylate, diethylaminoethyl methacrylate, N-vinylpyrrolidone, acrylamide, acrylonitrile, 2-chloroethyl methacrylate or 2,2,2-trifluoroethyl methacrylate. Examples include monomers containing various polar groups such as a hydroxy group, an amino group, an amide group, a cyano group, a sulfonic acid group, a carboxyl group, a halogen atom, or a heterocycle. Alternatively, in addition to the above synthetic resins, alkyd resins, alkyd resins modified with various fatty acids,
Resins such as linseed oil modified polyurethane resins can also be used. The amounts of each main component of the liquid developer of the present invention are explained below. The toner particles containing resin as a main component are preferably 0.5 parts by weight to 50 parts by weight based on 1000 parts by weight of the carrier liquid. If it is less than 0.5 parts by weight, the image density will be insufficient, and if it is more than 50 parts by weight, fogging will tend to occur in non-image areas. A carrier liquid soluble resin such as the above-mentioned dispersion stabilizer may also be used if necessary, and can be added in an amount of about 0.5 to 100 parts by weight per 1000 parts by weight of the carrier liquid. The copolymer of the present invention, which is a charge control agent, has a remarkable effect in a very small amount on the carrier liquid, and is 0.001 to 0.5 parts by weight per 1000 parts by weight of the carrier liquid.
Particularly good results are obtained at 0.001 to 0.1 parts by weight. 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 resulting image density decreases. Various other additives may be added as necessary.
For example, Yuji Harasaki, “Electronic Photography” Vol. 16 No. 2 44
Specific examples are given on the page. The upper limit of the total amount of additives in the liquid developer as described above is regulated by the electrical resistance of the developer. In other words, if the electrical resistance of the liquid developer with toner particles removed is less than 10 ⁹ Ωcm, it will be difficult to obtain a high-quality continuous tone image, so the amount of each additive added should be controlled within this limit. It is necessary. Examples of the present invention are presented below, but the present invention is not limited thereto. Charge control agent production example 1: Production of specific example (a) 30.6 g of stearyl methacrylate, 8.6 g of N-carboxymethyl methacrylamide, 80 g of toluene
A mixture of 20 g of methanol and 20 g of methanol was heated to a temperature of 70° C. with stirring under a nitrogen atmosphere. At that temperature,
3 by adding 0.8g of azobisisobutyronitrile
Stir for an hour and add azobisisobutyronitrile
0.4 g was added and stirred for 3 hours. After cooling, the reaction solution was added to 500 ml of methanol with stirring over 30 minutes, and the mixture was further stirred for 1 hour. The precipitate was collected and dried to obtain 31 g of a white solid. The weight average molecular weight measured by high performance liquid chromatography was 4.3×10 ⁴ . Soluble resin production example 2: Production of specific example (c) 30.6 g of stearyl methacrylate, N-(2-
carboxyphenyl) methacrylamide 12.3g,
A mixture of 100 g of toluene and 30 g of methanol was heated to a temperature of 75° C. with stirring under a nitrogen atmosphere. At that temperature, 0.6 g of benzoyl peroxide was added and stirred for 3 hours, and further, 0.3 g of benzoyl peroxide was added and stirred for 4 hours. After cooling, the reaction solution was added to 500 ml of methanol while stirring for 30 minutes, and the mixture was further stirred for 1 hour. The precipitate was collected and dried to obtain 33 g of a white solid. The weight average molecular weight measured in the same manner as in Production Example 1 was 4.5×10 ⁴ . Example 1 A mixed solution of 14 g of poly(lauryl methacrylate), 100 g of vinyl acetate, and 385 g of isododecane,
The mixture was heated to 70°C while stirring under a nitrogen stream.
2,2'-azobis(isobutylnitrile) 1.7g
was added and reacted for 4 hours, then cooled and passed through a 200 mesh nylon cloth. A white resin particle dispersion with a polymerization rate of 83% and an average particle size of 0.18 μm was obtained. 10 g of poly(lauryl methacrylate), 10 g of nigrosine and 30 g of isododecane were placed in a paint shaker together with glass beads and dispersed for 2 hours to obtain a fine dispersion of nigrosine. 32 g of the above white resin dispersion, 2.5 g of the above nigrosine dispersion, and 0.06 g of the charge control agent a polymer obtained in Production Example 1 of the charge control agent were added to 1 part of isododecane.
A liquid developer for electrostatic photography was prepared by dispersing the mixture in The obtained liquid developer is transferred to the Fuji fully automatic plate making machine.
Used as a developer for ELP280 (manufactured by Fuji Photo Film Co., Ltd.) and used as an electrophotographic photosensitive material for printing master ELP Master (manufactured by Fuji Photo Film Co., Ltd.)
ELP from positive manuscript with continuous tone using
A master plate was obtained by forming an image on the master. The obtained master plate image is a good continuous tone image, and the maximum optical density of the image is 1.51.
The minimum (fog) was 0.06. The color tone of the image was warm. Similarly, ELP master
When 2,000 sheets were processed and the optical density of the 2,000th master plate image was examined, the maximum was 1.48, indicating a small decrease in density, and the minimum was 0.06, with no change. Furthermore, when I observed the first processed image and the 2000th image, both were very clear. Next, the non-image areas of the first and 2000th master plate were desensitized, and each was used as a printing plate, and 3000 sheets were printed. No matter which version was used, the 3,000th print was clear, with no broken lines, and no fog. Comparative Example A In the preparation of the liquid developer of Example 1, the following polymer A was used instead of the charge control agent a of the present invention.
An electrostatic photographic liquid developer was prepared in the same manner as in Example 1, except that . Polymer A Copolymerization composition ratio: 7/3 (mole ratio) The obtained liquid developer was tested in the same manner as in Example 1, and when the image on the first master plate was observed, it was found that solid areas and image areas could be distinguished. was impossible. This was due to the fact that the toner particles in the liquid developer used had no electrodetection properties. From the above results, in order to maintain a positive charge in the toner particles, it is necessary that [-CONH-] and [-COOH] be close to each other within 6 atoms, as in the compound of the present invention. be. Examples 2 to 5 and Comparative Examples B to C The liquid developer of Example 1 was prepared in the same manner as in Example 1, except that the charge control agent shown in Table 1 was used instead of the charge control agent a of the present invention. A liquid developer for electrostatic photography was prepared. For comparison, a sample using diisobutyl-maleic acid half-octadecylamide copolymer, which is a high-altitude charge control agent, was also prepared (Comparative Example B). Furthermore, a liquid developer was prepared according to the description in Example 2 of Japanese Patent Application Laid-Open No. 58-38960 (Comparative Example C). The obtained liquid developer was tested in the same manner as in Example 1, and the maximum density of the image on the first master plate and the maximum density of the 2000th master plate in the same image area were measured. The rate of change was determined using the following formula. Rate of change (%) = 100 - [2000th image density/1st image density] x 100 As is clear from the results in Table 1, in Examples 2 to 5 using the charge control agent of the present invention, , the maximum image density of the obtained master plate is high and 2000
There is little decrease in density even after processing sheets. However, in Comparative Example B using a known charge control agent, the master density was high on the first sheet, but the density decreased significantly on the 2000th sheet, and the printed matter printed using this had noticeable breaks in fine lines in the printed image. , fog was observed in the non-image area (the density of the non-image area of the 2000th master plate was 0.10, which was higher than that of the first master plate). On the other hand, in Comparative Example C, the change in the image density of the master plate was small even after the 2000th sheet.
However, when the copied image was visually evaluated, image deletion occurred in the image area, and this phenomenon was particularly noticeable in the solid area. This indicates that although sufficient charge is imparted, there is a problem in the faithful reproducibility of actual copied images. Furthermore, when this master plate after plate making was subjected to a desensitization treatment in the same manner as in Example 1 and printed as a printing master plate, image portions immediately appeared missing from the printed matter. This is considered to be due to the fact that the fixing properties of the toner image area of the developer are significantly insufficient.

[Table] Example 6 To 100 g of the white resin particle dispersion obtained in Example 1,
5 g of finely pulverized Sumikalon Navy Blue (manufactured by Sumitomo Chemical Co., Ltd.) was added and stirred at a temperature of 100° C. for 5 hours. After cooling, a blue resin particle dispersant was obtained by passing it through a 200 mesh nylon cloth. This material was resin particles with an average particle size of 0.18 μm. A liquid developer was prepared by dispersing 35 g of the blue resin particle dispersion described above and 0.045 g of the charge control agent c obtained in Production Example 2 of Charge Control Agent in Isodecane 1. Using this liquid developer, a test was conducted according to the method described in Example 1. The images obtained from the first master plate and the 2000th master plate are good continuous tone images, and the maximum optical density of the images is:
They were 1.40 and 1.38, respectively. The minimum (fog) was 0.06 for both. After printing 3000 sheets each using the above 1st and 2000th master plate according to the usual method,
Even after printing 3000 sheets, we were able to obtain clear prints.

Claims (1)

[Scope of Claims] 1. A toner containing resin particles as a main component produced by a polymerization granulation method in a non-aqueous solvent having an electrical resistance of 10 ⁹ Ω·cm or more and a dielectric constant of 3.5 or less. In the electrostatographic liquid developer, the charge control agent is at least one monomer A capable of forming a polymer soluble in the non-aqueous solvent. and at least one of monomer B represented by the following general formula () or monomer C represented by the following general formula (), and monomer A and at least one monomer C represented by the following general formula (). The composition weight ratio with monomer B or monomer C is 30:70 to 90:10, and the charge control agent is contained in 0.001 to 0.5 parts by weight per 1000 parts by weight of the nonaqueous solvent. A liquid developer for electrostatic photography. General formula () General formula () In formula (), R ₁ and R ₂ may be the same or different and represent a hydrogen atom, an alkyl group, -COOH or -
COOL (L represents a hydrocarbon group), X ₁ represents an atomic group connecting the unsaturated bond group and -CONH-,
Further, Y ₁ each represents a group that connects -CONH- and -COOH with the number of atoms being 6 or less. Moreover, -CONH-Y ₁ -COOH may be directly bonded to the unsaturated bonding group without going through X ₁ . In formula (), R ₃ and R ₄ are R ₁ and R 4 in formula ()
Synonymous with R ₂ , X ₂ is an unsaturated bond group and −NHCO
Y2 represents an atomic group connecting -, and _Y2 represents a group connecting -NHCO- and -COOH within 5 atoms. Also, −NHCO−Y ₂ without going through X ₂
-COOH may be directly bonded to the unsaturated bond group.