JPS63179368A - Liquid developer for electrostatic photography - Google Patents

Abstract

PURPOSE:To prevent generation of excluded volume effect of dispersed particles themselves of a resin for liquid developer for electrostatic photography and to obtain satisfactory picture image by forming the resin from a polymer being insoluble in a solvent and having amide groups, a monomer being soluble in the solvent but insolubilized by the polymer, and a monomer being soluble in the solvent but forming a polymer after polymn. CONSTITUTION:A liquid developer for electrostatic photography is used after polymerizing a monomer A and a monomer B with the developer contg. resin particles dispersed in a hydrocarbon solvent having high electric insulation in the presence of a polymer S being insoluble in the solvent but having amide groups. The monomer A is selected from monomers being soluble in the solvent but forming insoluble polymer after polymn., and the monomer B is selected from monomers being soluble in the solvent and forming also soluble polymer after polymn. Thus, electrostatic mutual repulsive effect due to the Coulomb's force attributed to the dispersed particles themselves and the excluded volume effect due to the mutual repulsion of elevated stabilizing dispersed polymer are eliminated, and the lowering of effective surface potential of the electrostatic material is prevented, the disturbance of picture image due to ghost in the neighbourhood of picture image is eliminated, displaying a distinct picture image.

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., and has excellent storage stability, stability, and fixing properties. In particular, the present invention relates to a liquid developer that can achieve high image quality.

(Prior Art) Many types of electrostatic latent image liquid developers are already known. For example, colorant pigments or dyes such as carbon black, cyanine blue, nigrosine, and oil dyes are placed in a highly insulating medium together with resins such as rosin, alkyd resins, acrylic resins, and synthetic rubbers, and mechanically processed using a ball mill, attritor, homogenizer, etc. The most common method was to disperse particles in the dispersion and further add metal soap, 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 diameter of the dispersed particles as a developer, it tends to generate a lot of precipitates, has poor charge stability and manufacturing stability, and cannot produce stable images. It had the disadvantage of being difficult to obtain.

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 form a graft. There is a method of obtaining a liquid developer by producing a copolymer 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, often accompanied by the formation of gels, and in some cases it is difficult to form dispersed particles stably.
Coarse particles of 1 μm or more and fine particles of 0.1 μm or less may be produced, which is undesirable from a practical standpoint.

In addition, Machimon Sho 59-83174 Tan, Sho 59-177572
No. 59-212850, No. 5-1 212851, No. 60-164757, No. 60-179751,
No. 60-185962, No. 60-185963@, No. 60-252367, No. 61-116364, No. 6
1-116365 etc., in the presence of a polymer soluble in a highly insulating medium, a monomer that is soluble in the solvent but becomes insoluble when a polymer is formed is polymerized, and the resulting resin dispersion is made into a liquid. It is mentioned that it is used as a developer.

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 Coulomb force, electrostatic mutual repulsion due to Coulomb force of the dispersed particle whites and the concentration of the dispersion stabilizing polymer occur. A volume exclusion effect occurs in which the particles rise and repel each other. For this reason, when the effective surface potential of the electrostatic recording material decreases, it has the disadvantage that a smear-like goose tends to occur around the image. Furthermore, if a liquid developer using the resin obtained by this method is used continuously while being actually replenished, the solvent-soluble resin will accumulate, and depending on the type of soluble resin used, it will affect the amount of charge on the dispersed particles. It also had the disadvantage of giving.

(Objective of the Invention) The object of the present invention is to provide a liquid developer which improves the conventional drawbacks mentioned above, and which provides a clear image with no bleeding ghost in the image periphery, and which has a long lifespan. It is an object of the present invention to provide a liquid developer that exhibits little image deterioration even when used continuously for many years.

Another object of the present invention is to provide a liquid developer that provides excellent printing quality as a developer for offset lithographic printing plates using zinc oxide or organic semiconductors as photoreceptors.

(Structure of the Invention) The present invention provides an electrostatographic liquid developer comprising at least resin particles dispersed in a highly insulating hydrocarbon medium, in which the resin is in the presence of the following polymer (S): This is a liquid developer for electrostatic photography characterized by being a resin obtained by polymerizing the following monomer (A>) and monomer (B).

Polymer (S): A polymer that is insoluble in the medium and has an amide group.

Monomer (A): 0 monomers that are soluble in the medium and become insolubilized by polymerization Monomer (B): 0 monomers that are soluble in the medium and form a polymer that is soluble even when polymerized Highly insulating properties used in the present invention The hydrocarbon medium includes normal paraffinic hydrocarbons, isoparaffinic hydrocarbons, alicyclic hydrocarbons, halogenated aliphatic hydrocarbons, etc., but isoparaffinic hydrocarbons are practically preferred in terms of safety and volatility. Hydrogen solvent Shell Silua 1 (Shell Oil Co., Ltd.), Isopar 01 Isopar H1 Isopar 1
Isopar L1 Isopar G (Isopar is a trade name of Exxon), Ivy Solvent (manufactured by Idemitsu Petrochemical), etc. can be used.

The structure of the resin used in the liquid developer of the present invention and the formation mechanism of the resin dispersion (hereinafter referred to as emulsion) will be explained. The polymer (S) that is insoluble in the solvent and has an amide group used in the present invention is referred to as a shell polymer. Further, a polymer of monomer (A) that is soluble in the solvent and becomes insolubilized when polymerized is referred to as P1 polymer, and a polymer of monomer (B) that is soluble in the solvent and is soluble even when polymerized is referred to as P2 polymer. do. The most common embodiment of the emulsion used in the present invention before the start of polymerization is the solvent, shell polymer, monomer (
A> and monomer (B). (In order to control the physical properties such as Tm and Tg of the obtained emulsion particles, two or more of these materials may be used depending on the case.Also, to control the heat generation during polymerization, the monomers used may be divided. It may be added after.

The formation mechanism of emulsion particles can be broadly classified into two types. The first case is that the state before the start of the polymerization is homogeneous. In this case, the fact that the shell polymer becomes homogeneous even though it is originally insoluble in the solvent is because it dissolves in the monomer (A>) or the monomer (B).

By heating the aqueous system and adding a polymerization initiator, radicals are generated and polymerization starts. Since the P1 polymer component produced from the monomer (A>) is insoluble in the solvent, the P2 polymer component soluble in the solvent is used as a protective colloid to form particles and become cloudy to produce an emulsion.

The particle size depends on the amount of P2 polymer component, that is, the charged monomer (
B) It can be changed relatively freely depending on the amount. The monomer (A)/monomer (B) ratio depends, of course, on the solubility and cohesiveness of the resulting polymer in the solvent, but a relatively stable emulsion can be obtained in the weight range of 98/2 to 20/80. However, a range of about 95/5 to 50/50 is suitable.

Furthermore, since the particle size most depends on the solubility parameters of the solvent and the polymer to be produced, the particle size can be controlled by selecting these factors.

As the polymerization progresses, the shell polymer cannot be uniformly dissolved in the system because the monomer to be solubilized is consumed as a polymer. Therefore, it becomes insolubilized, but actually it is deposited on the surface of the emulsion particles formed by the P1 polymer.

The sedimentation stability and particle size of the emulsion also depend on the type and amount of shell polymer, and if there is too much shell polymer, sedimentation tends to occur. However, in this case, dispersion stability can be improved by increasing the amount of upper layer (B).

As mentioned above, the amount of shell polymer depends on the type and amount of monomer (A) and monomer (B) and the type of shell polymer, but it is 1% to 50% (by weight) of monomer (A>), preferably 3%. ~25% is preferred.

Therefore, the formed emulsion particles have a core layer consisting mainly of P1 polymer inside, a shell layer consisting of shell polymer deposited on the outside, and an outermost layer mainly consisting of P2 polymer which stabilizes the particles in the solvent. 3 of the distributed layer
It is thought that they form an @ structure. Of course, as can be seen from the particle formation mechanism, there are no clear interfaces between the layers, and it is presumed that each component is more localized in a three-layered state.

The second formation mechanism of emulsion particles is a case where the state before the start of polymerization is heterogeneous. In this case, the polymerization may be started as is, but it is preferable to add an auxiliary solvent having a relatively low boiling point to make the system homogeneous. When polymerization is started in the same way as in the first formation mechanism, a cloudy emulsion mainly composed of the P1 polymer component is produced by using the P2 polymer component as a protective colloid. After the polymerization is completed, the co-solvent is removed and the shell polymer is deposited on the surface of the emulsion particles. If too much co-solvent is required, a uniform emulsion may not be produced.

Examples of the auxiliary solvent include tetrahydrofuran, ethyl alcohol, isopropyl alcohol, methyl ethyl ketone, and ethyl acetate.

The shell polymer used in the present invention has an amide group, is insoluble in a highly insulating hydrocarbon medium, and must have the property of being soluble in a monomer that becomes insolubilized in the solvent upon polymerization. It's going to change. Moreover, the most desirable final emulsion embodiment is that the shell polymer is localized on the surface of the resulting emulsion particles.

From a different perspective, it means modifying the particle surface with a polymer having an amide group.

Polymers exhibiting such properties are, for example, those of the general formula (I
) and, for example, a copolymer of a monomer represented by general formula (II).

General formula (I) CH21=CZz C0NR1R2 (Zl and Zl represent H or an alkyl group, and RlRz represents an aliphatic group that may have a substituent.) General formula (II) (R1 and Rz are H, Alkyl group, -COOR4, -CH
z represents COOR5, and R3, R4, and R5 represent an aliphatic group which may have a substituent. ) Monomers represented by general formula (I) include, for example, acrylamide, methacrylamide, N-isopropylacrylamide, N-te
Examples include rt-butylacrylamide, N,N-dimethylacrylamide, and the like. Furthermore, as monomers having an amide group, acrylpiperidine, acrylmorpholine, acrylpyrrolidine, phenylmethacrylamide, N-anisylmethacrylamide, N-tolylmethacrylamide, N-chlorophenylacrylamide, N-
-nitrophenylmethacrylamide, /N-methacryl-α-aminoketone, N-medyrolmethacrylamide and its esters, N-β-cyanoethylmethacrylamide, diacetone acrylamide, and the like.

Furthermore, monomers with amide groups are described in "Synthetic Polymers" (published by Choji Shoten) and "Kyomunshi Data Handbook" (published by Baifukan).
etc. are listed. Since it is important for the shell polymer to have an amide group, the monomers that can be used are not limited to general formula (I).

The monomer represented by the general formula (n) is an esterified product of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, etc. If it is an ester of an aliphatic group, for example, methyl, ethyl, Propyl, butyl, amyl, hexyl, ethylhexyl, dodecyl, tridecyl, hexadecyl, docosanyl, hexadecenyl, oleyl, and the like. These are halogen atoms,
It may be substituted with an amino group, an alkoxy group, etc., or may be bonded with atoms such as nitrogen, oxygen, sulfur, etc.

Further, in order to adjust the physical properties of the shell polymer, a copolymerizable monomer may be copolymerized as a third component. Furthermore, a plurality of polymers may be used as the shell polymer.

Polymerization of shell polymers can be obtained by known polymerization methods, but in order to synthesize emulsions using shell polymers as raw materials, they can be obtained by solution polymerization in a medium that is the same as or mixed well with the solvent used during emulsion synthesis. is most preferred. Furthermore, it is not very desirable that the shell polymer has the property of being dissolved in the solvent at high temperatures.

This is because the properties of the liquid developer depend on temperature, and particularly when the temperature rises, there is a risk that the shell polymer will be desorbed from the particles and change the physical properties of the toner particles.

Examples of copolymers of the shell polymer used in the present invention will be listed below, but the present invention is not limited thereto. Figures in parentheses are weight ratios.

(a) n-hexyl methacrylate-acrylamide (94/6) (b) stearyl methacrylate-methacrylamide (9515) (c) stearyl methacrylate-N,N-dimethylacrylamide (90/10) (d) lauryl Methacrylate-phenylacrylamide (9515) (e) N-hexyl acrylate-diacetone acrylamide (92/8) (f) Stearyl methacrylate-N-isopropylacrylamide (85/15) Compatible with the solvent used in the present invention Examples of the monomer (A) that provides a polymer that becomes insolubilized when polymerized in solution include acetic acid,
Vinyl esters and allyl esters such as propionic acid and acetic acid. Alkyl esters such as itaconic acid, maleic acid, and crotonic acid (however, long-chain alkyl polymers are solubilized, so up to 4 carbon atoms), and even those with substituents such as acrylic acid and methacrylic acid. Good lower alkyl esters and amides. Styrene, methylstyrene, vinyltoluene and other styrene derivatives, N-vinylpyrrolidone, N
Examples include those having a heterocycle such as -vinyloxazolidone. In order to adjust the physical properties of the obtained emulsion particles, a copolymerizable second component such as a basic monomer or a heptamer having an ether bond may be copolymerized.

The monomer (B) used in the present invention that gives a polymer that is soluble in the solvent and soluble even when polymerized is, for example, the following general formula CI)
It is indicated by.

General formula (I[I) In general formula (1), R represents an aliphatic group having 8 or more carbon atoms,
B is an ester group or an amide group, Ql, Ql are hydrogen atoms,
An alkyl group, -COOR=, -CH2COOR'' is represented. R-R'' represents an aliphatic group.

Examples of the monomer (8) include esters and amides of acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid; for example, in the case of aliphatic groups, decyl, dodecyl, tridecyl, hexadecyl, docosanyl,
Examples include hexadecenyl and oleyl.

These may be substituted with a halogen atom, an amine group, an alkoxy group, a hydroxy group, etc., or may be bonded with atoms such as nitrogen, oxygen, sulfur, etc.

The necessary properties of the monomers (A) and (B) are that, although it is preferable that each monomer dissolves the shell polymer, it is not necessary that each monomer dissolve the shell polymer;
There is no problem if the shell polymer and monomers (A> and (B) are mixed to form a substantially homogeneous system.Also, if the solubility is poor and a heterogeneous system results, use a co-solvent with a relatively low boiling point. After the polymerization is completed, it can be drained.

In order to use the emulsion obtained in the present invention as a liquid developer for electrostatic photography, the dispersed resin particles may be colored and charged. As the colorant for the dispersed particles, any colorant generally known as a colorant for liquid developers can be used. For example, oil-soluble dyes such as oil black and oil red, basic azo dyes such as Bismarck brown and chrysoidine, wool black, amide black green, and blue black H.
Acidic azo dyes such as F, direct dyes such as Congo red, anthraquinone dyes such as Sudan violet and acid blue, carbonium dyes such as auramine, malachite green, crystal violet, and Victoria blue, rhodamine dyes such as Rhodamine B, safranin,
Examples include dyes such as quinone imine dyes such as nigrosine and methylene blue. As a pigment, carbon black,
Examples include phthalocyanine blue, phthalocyanine green, washing red, and benzidine yellow.

Also, surface-treated pigments such as carbon black dyed with nigrosine, grafted carbon, silicon oxide fine powder dyed with rhodamine H, microlith blue, etc. can be used.

The simplest method for coloring the dispersed particles is to dissolve the colorant to be used in advance in a solvent, and then dropwise add and stir this colorant solution into the emulsion. In particular, coloring can be achieved well by dissolving the oil dye in an aromatic solvent such as toluene or xylene and adding it dropwise with stirring. Since the used solvent is mixed with the toner solvent, there is no need to remove it unless there is an adverse effect on quality. Alternatively, the solvent may be removed later by using a solvent system as disclosed in JP-A-57-48738.

Furthermore, as another coloring method, the obtained emulsion and coloring agent may be added to a dispersing machine such as a colloid mill, a ball mill, or a turbulence mill, and then colored by applying mechanical motion.

For the liquid developer of the present invention, by selecting a charge control agent, a colorant, etc., it is possible to freely produce a toner having a positive charge or a toner having a negative charge.

The charge control agent used in the liquid developer of the present invention includes:
Examples include copper oleate, cobalt naphthenate, zinc naphthenate, manganese naphthenate, cobalt octylate, lecithin, sodium dioctyl sulfosuccinate, and aluminum salt of steverite resin.

Also, Special Publication No. 49-26594, No. 49-26595
No., JP-A-60-173558, JP-A No. 60-17506
No. 0, No. 60-179750, No. 60-182447
No. 60-218662, patent application No. 60-78062
The charge control agents listed in No. 1, etc. can also be used.

The liquid developer obtained by the present invention is disclosed in Japanese Patent Publication No. 37-17162.
No. 38-6961, No. 41-2426, No. 46
-39405, JP-A-50-195098, JP-A-50-
No. 19510, No. 54-145538, No. 54-89
No. 801, No. 54-134632, No. 54-1980
No. 3, No. 55-105244, No. 57-16”186
3@, 58-76843@, 58-76844,
No. 58-122897, No. 58-118658, No. 59-170862, No. 60-194467, No. 6
No. 1-32861, No. 61-49895, No. 61-6
It can also be used for lithographic printing plates such as those described in No. 7869 and No. 61-149399. When used for these lithographic printing plates, it must have resistivity to alkaline eluents. The liquid developer obtained according to the invention gives particularly good printing plates when eluted with an inorganic alkaline eluent without a penetrant such as benzyl alcohol.

Synthesis Example 1 (Synthesis of emulsion of the present invention) An n-hexyl methacrylate-acrylamide copolymer was prepared by a known solution polymerization method.
% xylene solution was obtained.

11! 30g of this solution! When added to hexane, a copolymer precipitate was obtained as a slurry.

The slurry was washed several times with hexane and decanted.
11 equipped with NZ gas inlet pipe, thermometer, stirrer, and cooling pipe
450 g of IP solvent (manufactured by Idemitsu Petrochemical Co., Ltd.) was added to the 450 g of IP solvent (manufactured by Idemitsu Petrochemical Company).

At this stage, even if well stirred, the copolymer remains precipitated without being dissolved in the IP solvent at all.

Next, 1303 vinyl acetate (corresponding to monomer (A>)
When 25V of lauryl methacrylate (corresponding to monomer (B)) was added and stirred well, a uniform transparent solution was obtained. After purging with NZ gas at 80°C, 1g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and polymerization started. After about 40 minutes, the mixture began to become cloudy and the internal temperature reached 1'IO.
It rose to 'C. After the internal temperature dropped to 80'C, heating was continued for an additional 2 hours. In order to remove the remaining vinyl acetate monomer, the internal pressure was reduced and distillation was performed to obtain about 33 distillates. The resulting white emulsion had no precipitates and almost no monomer odor.

When the particle size was measured using an electron microscope, the particle size was 0.22μ and there was almost no particle size distribution.

Synthesis Examples 2 to 8 Emulsions with the compositions shown in the table below were synthesized by the same method as in Synthesis Example 1. Shell polymer is abbreviated as S.
The amount is expressed as solid content.

Monomer (A) and monomer (B) are each abbreviated as AlB. Note that in Synthesis Examples 3 and 6, methyl ethyl ketone 209 was used as an auxiliary solvent.

(Margins below) The emulsion obtained in this synthesis example had almost no precipitates and was stable without increasing the amount of precipitates even after being stored naturally for several months. The particle size of the emulsion was measured using an electron microscope and was about 0.15 to 0.3 μm, although it varied depending on the type of emulsion. However, each emulsion showed an almost monodisperse particle size distribution, and no coarse particles or fine particles were observed, and the particle sizes were extremely uniform. Incidentally, particles that could not be observed due to fusion at the lowest temperatures were measured using the replica method.

Comparative Synthesis Example 1 (Synthesis of Comparative Emulsion) A 40% hexane solution of stearyl methacrylate methacrylic acid copolymer (weight: 98/2) was obtained by a known solution polymerization method. When 70 g of this polymer solution was added to a 4-tube flask together with 4509 IP solvent in the same manner as in Example 1, a homogeneous and transparent solution was obtained. (This polymer is not a shell polymer, but corresponds to a soluble polymer used in the prior art.) Monomers were added and polymerization was carried out in exactly the same manner as in Synthesis Example 1, and the internal temperature rose to 105°C. There is no precipitate in the white emulsion after distilling off the remaining monomer.
There was almost no monomer odor. The particle size was 0.2μ and there was no particle size distribution.

Example 1 (Production Example of Positively Chargeable Liquid Developer) Into 250 g of the emulsion obtained in Synthesis Example 1, 5 g of oil black HBB (manufactured by Orient Chemical Co., Ltd.) dissolved in 40 Ij of xylene was added while applying ultrasound. It was added dropwise to color the emulsion particles.

Next, 8 g of a xylene solution of 1% aluminum salt of steverite resin was added as a charge control agent to obtain a condensed toner.

The total of this conctner is 10Il with Isopar G.
A positively chargeable liquid developer (P-1 toner) was obtained.

Example 2 (Example of manufacturing a negatively chargeable liquid developer) The procedure up to the coloring of the emulsion particles was carried out in exactly the same manner as in Example 1, and 0.33% of sodium salt of dioctyl sulfosuccinate was added as a negatively chargeable charge control agent. , got a conctner.

The obtained conctonner is used in Isopar G for a total of 10
1 to obtain a negatively chargeable liquid developer (N-1 toner).

Example 3 The emulsions obtained in Synthesis Examples 2 to 8 were produced in the same manner as in Example 1 in order to make positively chargeable developers. Although the particle charging ability was slightly different, a good positively chargeable liquid developer was obtained. A drug was obtained. (P-2 to P-8 toner).

Example 4 The emulsions obtained in Synthesis Examples 2 to 8 were produced in the same manner as in Example 2 in order to produce a negatively chargeable developer, and although the particle charging ability was slightly different, a good negatively chargeable liquid developer was obtained. (Toners N-2 to N-8) were obtained.

Comparative Example 1 (Manufacture of Comparative Liquid Developer) Using the emulsion synthesized in Comparative Synthesis Example 1, the emulsion was prepared in exactly the same manner as in Example 1 for positive chargeability, and in the same manner as in Example 2 for negative chargeability. Liquid developers were obtained by a method (Comparative P-1 toner, Comparative N-1 toner).

Example 5 Using the P-1 toner obtained in Example 1 and the P-2 to 'P-8 toners obtained in Example 3 as liquid developers, EP1
2 (Mitsubishi Paper Mills (11 model direct plate making machine) was used to make the electrophotographic direct printing plate LOM-IIB, and images with firm etching were obtained in all cases, and the printed matter using this printing plate also had a beautiful finish. For comparison, in the case of comparative toner P-1 obtained in Comparative Example 1, a smudge-like ghost appeared around the image area.The image also appeared to be a little distorted, which caused problems. This was not possible because a pattern of image failure appeared on the printed matter.

Example 6 An ε-type copper phthalocyanine pigment dispersed in an acrylic resin with a high acid value was coated on an aluminum plate that had been subjected to a hydrophilic treatment and dried to prepare a printing original plate (binder/pigment ratio -7).
5/25>. After the original plate was positively charged by corona charging in a dark place, image exposure was performed.

After forming a solid image with the N-2 toner obtained in Example 4, it was heat-fixed. After cooling, it was immersed for 10 seconds in a solution prepared by diluting DP-4 (Fuji Photo Film ■PS plate developer) ten times with water, and then washed with water. A printing plate was created in which only the toner image area remained as a beautiful image, and the non-image area was completely eluted.

On the other hand, when developed with the Comparative N-1 toner obtained in Comparative Example 1, a smudge-like post was generated around the image area.
The pattern remained even after the non-image area was eluted with DP-4. Also, good printing plates were obtained when using N-3 to N-8 toners, and the printed matter was sharp, or only the comparison N-1 toner had a beautiful finish due to ghosts around the image area. It didn't happen.

Furthermore, when continuous processing was performed on the original B-4 plate using 11 each of the N-2 toner and the comparison N-1 toner, ghosting occurred so much in the case of the 20 plate l1 comparison N-1 toner that it became unusable. However, the N-2 toner showed no abnormality even after being processed for 100 plates.

The above examples show that when a liquid developer containing the emulsion of the present invention is used, good printing plates and printed matter with a beautiful finish can be obtained.

Claims (1)

[Scope of Claims] An electrostatographic liquid developer comprising at least resin particles dispersed in a highly insulating hydrocarbon medium, wherein the resin contains the following monomer in the presence of the following polymer (S). A liquid developer for electrostatic photography, characterized in that it is a resin obtained by polymerizing (A) and a monomer (B). Polymer (S): A polymer that is insoluble in the medium and has an amide group. Monomer (A): A monomer that is soluble in the medium and becomes insolubilized by polymerization. Monomer (B): A monomer that is soluble in the medium and forms a soluble polymer upon polymerization.