JP2009251087A - Wet developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet developer, in which chargeability of toner particles can be controlled while assuring storage stability and fixability. <P>SOLUTION: The wet developer is prepared by dispersing toner particles comprising at least a colorant and a binder resin in a nonvolatile carrier liquid by using a dispersant. A polymer dispersant having a basic group is used for the dispersant; and the carrier liquid used contains a nonionic surfactant. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wet developer used in an image forming apparatus using a wet electrophotographic system such as a copying machine, a printer, a digital printing machine, etc.

  In electrophotographic image formation, generally, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductor by image exposure according to a document image or image data. The electrostatic latent image is developed into a visible toner image, and the toner image is transferred and fixed on a recording material to obtain a target image.

  Development methods can be divided into dry development methods and wet development methods. In the dry development method, a toner or a toner added with a carrier having magnetism or the like is used as a developer. The dry toner usually uses a pigment and a binder resin as main components, and a charge control agent, a conductivity control agent, a plasticizer, a release agent and the like are added or added as necessary. On the other hand, in the wet development method, a liquid developer in which toner particles mainly composed of a pigment and a binder resin, a charge control agent, a dispersion stabilizer and the like are dispersed in an electrically insulating dispersion medium (carrier liquid) is used. ing. The toner particles used in the wet developer can be made fine because there is no fear of escaping into the atmosphere, and those having an average particle size of submicron are also practical. Therefore, there are advantages such that an image having high resolution can be obtained and the toner image can be easily fixed.

In the wet development method, development is performed by electrostatically adhering charged toner particles to the electrostatic latent image on the electrostatic latent image carrier. In order to control the chargeability of toner particles, conventionally, a method of adding a charge adjusting agent such as a metal soap or a fatty acid is known. (For example, patent document 1).
Special table 2007-505953 gazette

  However, if it is attempted to control the chargeability of toner particles using only the charge control agent, the amount of charge control agent added increases and the fixability decreases. On the other hand, the dispersant is added to ensure the storage stability of the developer. However, since the charge amount of the toner particles increases when the addition amount is increased, the amount of the toner particles can also be changed by changing the addition amount of the dispersant. It is possible to control the charging property. However, when the dispersant is added excessively, the carrier liquid is easily held in the toner particles, and there is a problem that the fixing property is lowered. Further, when the charge amount is increased, toner particles are firmly attached to a toner carrier such as a photoconductor, so that there is a problem that the cleaning performance with respect to the toner carrier is lowered and the residual toner is increased even after cleaning. . Therefore, it is difficult to adjust the chargeability of the toner particles while ensuring storage stability and fixability.

  Accordingly, an object of the present invention is to provide a wet developer capable of adjusting the chargeability of toner particles while solving the above-described problems and ensuring storage stability and fixability.

  In order to solve the above problems, the wet developer of the present invention is a wet developer obtained by dispersing toner particles composed of at least a colorant and a binder resin in a non-volatile carrier liquid using a dispersant. The dispersant is a polymer dispersant having a basic group, and the carrier liquid contains a nonionic surfactant.

  In the present invention, the HLB of the nonionic surfactant is preferably 8 or less.

  The polymer dispersant preferably has at least one basic group selected from the group consisting of an amide group, a methylol group, a pyridine group, a pyrrolidone group, an imidazole group, an imine group, and an amino group.

  Moreover, it is preferable that binder resin is a polyester resin.

  According to the present invention, a polymer dispersant having a basic group is used as a dispersant, and the carrier liquid contains a nonionic surfactant, so that toner particles can be secured while ensuring storage stability and fixability. It is possible to adjust the charging property. The polymer dispersant having a basic group can ensure storage stability even when added in a small amount, and the nonionic surfactant can adjust the chargeability of toner particles without affecting the fixability. it is conceivable that.

Hereinafter, embodiments of the present invention will be described in detail.
The wet developer of the present invention is a wet developer in which toner particles composed of at least a colorant and a binder resin are dispersed in a nonvolatile carrier liquid using a dispersant, and the dispersant has a basic group. It is a polymer dispersant, and the carrier liquid contains a nonionic surfactant.

The wet developer according to the present invention contains at least a carrier liquid, toner particles, and a dispersant.
(Carrier liquid)
As the carrier liquid, a non-volatile solvent having a high dielectric constant with a dielectric constant of 3 or less can be used. For example, liquid paraffin, silicon oil, animal and vegetable oils, mineral oil, and the like can be used from the viewpoint of odor, pollution-free property, and cost, but liquid paraffin is preferable. In the present invention, the non-volatile solvent is a solvent having a flash point of 70 ° C. or higher unless otherwise specified.

(Toner particles)
The toner particles used in the present invention contain at least a colorant and a binder resin.
The binder resin is a thermoplastic resin and is not particularly limited as long as it does not substantially dissolve in the carrier liquid. A polyester resin is particularly preferable. The polyester resin has sharp melt properties, and it is possible to achieve both storage stability and fixability.

  Specifically, the polyester resin means a resin obtained by polycondensation of a polybasic acid and a polyhydric alcohol. As polybasic acids, isophthalic acid, terephthalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid and its acid anhydride, trimellitic acid, trimesic acid, pyromellitic An acid etc. can be mentioned. Isophthalic acid, terephthalic acid, and trimellitic acid are preferable.

  As the polyhydric alcohol, the polyhydric alcohol is not limited to these, but propylene glycol such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,4- Butanediols such as butanediol, neopentyl glycol, alkylene glycols (aliphatic glycols) such as 1,6-hexanediol and their alkylene oxide adducts, bisphenols such as bisphenol A and hydrogenated bisphenol, and their addition of alkylene oxides Phenolic glycols of the product, alicyclics such as monocyclic or polycyclic diols, and aromatic diols, triols such as glycerin and trimethylolpropane, and the like. These can be used alone or in admixture of two or more.

  A desired polyester resin can be obtained by polycondensation of the above polybasic acid and polyhydric alcohol. A conventionally known polycondensation method can be used as the polycondensation method. Although it varies depending on the type of raw material monomer, it is generally carried out at a temperature of about 150 ° C to 300 ° C.

  Moreover, it can carry out on arbitrary conditions, such as using inert gas as atmospheric gas, using various solvents, or making the reaction container internal pressure normal pressure or pressure reduction. An esterification catalyst may be used to promote the reaction. As the esterification catalyst, metal organic compounds such as tetrabutyl zirconate, zirconium naphthenate, tetrabutyl titanate, tetraoctyl titanate, 3/1 stannous oxalate / sodium acetate, etc. can be used, but they are products. Those that do not color the ester are preferred. Moreover, you may use an alkyl phosphate, an allyl phosphate, etc. as a catalyst or a hue regulator.

In order to control the molecular weight of the product polyester resin, the polymerization temperature, reaction system pressure, reaction time, etc. may be adjusted. The acid value can be controlled by the molar ratio of the carboxylic acid to be reacted and the alcohol, the molecular weight of the polymer, and the like. The molecular weight is preferably a weight average molecular weight (Mw) of 3000 to 100,000. If the lower limit is not reached, the storage property is deteriorated, and if the upper limit is exceeded, melting by heat becomes difficult.

  The acid value of the polyester resin is preferably 20 mgKOH / g or more. More preferably, it is 20-80 mgKOH / g. This is because a polyester resin having an acid value of 20 mgKOH / g or more can improve storage stability and fixability when used with a polymer dispersant having a pyrrolidone group.

  In addition to polyester resin, binder resin may be styrene-acrylic copolymer resin, styrene-acrylic modified polyester resin, polyolefin copolymer (especially ethylene copolymer), rosin modified phenolic resin, rosin modified as required. An appropriate amount of maleic resin, paraffin wax, etc. can be mixed within a range of 30% by weight or less of the total weight.

As the colorant used in the developer of the present invention, known pigments and dyes can be used.
Specifically, furnace black, lamp black, acetylene black, channel black, C.I. I. Pigment Black, Orthoaniline Black, Toluidine Orange, Permanent Carmine FB, First Yellow AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmine 6B, Phthalocyanine Blue, Quinacridone Red, C.I. I. Pigment blue, C.I. I. Pigment Red, C.I. I. Pigment Yellow, Dioxane Violet, Pictoria Pure Blue, Alkali Blue Toner, Alkali Blue R Toner, First Yellow 10G, Ortho Nitroaniline Orange, Toluidine Red, Barium Red 2B, Calcium Red 2B, Pigment Scar Red 3B Lake, Anthosine 3B Lake, Rhodamine 6B lake, methyl violet lake, basic blue 6B lake, first sky blue, reflex blue G, brilliant green lake, phthalocyanine green G, bitumen, ultramarine blue, iron oxide powder, zinc white, calcium carbonate, clay, barium sulfate, alumina Examples thereof include white, aluminum powder, daylight fluorescent pigment, and pearl pigment.

  In order to improve the dispersibility of the colorant, a colorant having a functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group, or an amide group on the surface by surface treatment or surface modification can be used. .

  The blending amount of the colorant is 3 to 50 parts by weight, preferably 5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. This is because if it is less than 3 parts by weight, the desired concentration cannot be obtained, and if it exceeds 50 parts by weight, the dispersibility and fixability in the binder resin may be impaired.

(Dispersant)
In the present invention, a polymer dispersant having a basic group is used as the dispersant. Basic groups include aromatic amino groups, aliphatic amino groups, heterocyclic nitrogen-containing groups, heterocyclic oxygen-containing groups, and heterocyclic sulfur-containing groups. Specifically, a polymer dispersant having at least one basic group selected from the group consisting of an amino group, an imino group, an amide group, and a pyrrolidone group can be used. For example, a polyalkylene polyamine, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a polyaminoamide and a polar acid ester, a modified polyurethane, a polyester polyamine, a polyester polyimine, polyvinyl pyrrolidone, or the like can be used. Polyester polyamine, polyester polyimine, and polyvinyl pyrrolidone are preferable.

  Specific examples include BY-Chemie's Anti-Terra-U (polyaminoamide and acid polymer salt), Anti-Terra-204 (polyaminoamide and polycarboxylic acid salt), Disperbyk-101 (polyaminoamide and polar acid). Ester salt), Disperbyk-130 (unsaturated polycarboxylic acid polyaminoamide), Disperbyk-109 (alkylol aminoamide), Solspurs 19000 (polyester polyamine), Solspurs 13940 (polyester polyimine), Solspurs 11200 manufactured by Lubrizol. (Polyester polyimine), V-216, V-220 (polyvinylpyrrolidone) manufactured by ISP, and the like can be mentioned.

  The polymer dispersant can be added in an amount of 1 to 100 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the toner particles. When the amount is less than 1 part by weight, the dispersibility is lowered. When the amount is more than 100 parts by weight, the carrier liquid is easily held by the toner particles, and the fixability is lowered.

(Nonionic surfactant)
The nonionic surfactant is not particularly limited, and known ones such as an ether type, an ester type, an ester / ether type, and an alkanolamide type can be used. For example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, ether type such as polyoxyethylene polyoxypropylene glycol, ester type such as sucrose fatty acid ester, sorbitan fatty acid ester, glycerol fatty acid ester, polyoxyethylene fatty acid ester and poly Examples include ester / ether types such as oxyethylene sorbitan fatty acid esters, and alkanolamide types such as aliphatic alkanolamides. Preferably, the HLB is 8 or less. This is because if the HLB is larger than 8, it is difficult to dissolve in the carrier liquid. More preferred are sucrose fatty acid ester, sorbitan fatty acid ester, glycerol fatty acid ester, polyoxyethylene fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. This is because these nonionic surfactants have little influence on the dispersibility of the toner particles. Among these, sorbitan fatty acid ester, glycerol fatty acid ester, and polyoxyethylene fatty acid ester are more preferable.

  Examples of sorbitan fatty acid esters include sorbitan monostearate (HLB4.7), sorbitan monooleate (HLB4.3), sorbitan monopalmitate (HLB6.7), sorbitan monostearate (HLB4.7), sorbitan tristearate (HLB2.1), sorbitan monooleate (HLB4.3), sorbitan trioleate (HLB1.8) and the like can be mentioned, but sorbitan monostearate or sorbitan trioleate is preferable.

  As glycerol fatty acid esters, glycerol monostearate (HLB4.3), glycerol monopalmitate (HLB4.3), glycerol monobehenate (HLB4.2), glycerol monooleate (HLB4.3), glycerol monocapry Examples thereof include rate (HLB7.0), glycerol monocaprate (HLB6.8), glycerol monolaurate (HLB5.4), and glycerol monostearate is preferable.

  Examples of the polyoxyethylene fatty acid ester include polyethylene glycol dilaurate (HLB 6.6), polyethylene glycol distearate (HLB 7.3), polyethylene glycol dioleate (HLB 8.0), and the like. Glycol is preferred.

One or more of the above nonionic surfactants are added in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the developer. This is because if the amount is less than 0.01 parts by weight, the cleaning property is lowered, and if it is more than 10 parts by weight, the charging property is deteriorated.
In addition to the nonionic surfactant, a metal soap may be added as necessary.

(Manufacture of developer)
A colored kneaded material composed of the binder resin and the colorant is coarsely pulverized using a cutter mill, a jet mill or the like, and the colorant is dispersed in a secondary particle size of 50 nm to 1 μm, preferably 50 nm to 300 nm. A coarsely pulverized toner is obtained. The coarsely pulverized toner is further wet pulverized in a carrier liquid containing a polymer dispersant, and the toner particles are finely adjusted until the volume average particle size of the toner particles is about 0.1 to 10 μm, preferably about 0.5 to 5 μm. Grind to obtain a concentrated liquid developer. The concentrated liquid developer thus obtained is subjected to dilution / dispersion treatment to obtain an appropriate concentration with a carrier liquid containing additives such as a charge control agent, if necessary, to obtain a liquid developer.

  The present invention will be specifically described by the following examples, but the present invention is not limited to these examples. In the following examples, “part” means “part by weight” unless otherwise specified, “Mw” means “weight average molecular weight”, and “Mn” means “number average”. "Molecular weight", and "Tg" represents "glass transition temperature".

  In the following examples, Mw and Mn were calculated from the results of gel permeation chromatography, respectively. Gel permeation chromatography is a high performance liquid chromatograph pump TRI ROTAR-V type (manufactured by JASCO Corp.), UV spectroscopic detector UVIDEC-100-V type (manufactured by JASCO Corp.), 50 cm long column Shodex GPC A- 803 (manufactured by Showa Denko KK) was used, and the molecular weight of the test sample was determined as Mw and Mn in terms of polystyrene from the chromatographic results. The test sample used was 0.05 g of binder resin dissolved in 20 ml of tetrahydrofuran (THF).

  Tg was measured using a differential scanning calorimeter DSC-20 (manufactured by Seiko Denshi Kogyo Co., Ltd.) under the conditions of a sample amount of 35 mg and a heating rate of 10 ° C./min. The acid value was measured based on JIS K5400 method.

(Manufacture of polyester resin)
Production Example 1
1600 parts of propylene oxide adduct of bisphenol A, 790 parts of terephthalic acid, 100 parts of trimellitic acid in a round bottom flask equipped with a reflux condenser, water / alcohol separator, nitrogen gas inlet tube, thermometer and stirrer Then, nitrogen gas was introduced with stirring, and dehydration polycondensation or dealcoholization polycondensation was performed at a temperature of 200 to 240 ° C. When the acid value of the produced polyester resin or the viscosity of the reaction solution reached a predetermined value, the temperature of the reaction system was lowered to 100 ° C. or less to stop polycondensation. Thus, a thermoplastic polyester resin A was obtained.

  The obtained polyester resin A had Mw = 7000, Mn = 2200, Tg = 68.3 ° C., and acid value = 27.0 mgKOH / g.

Production Example 2
1600 parts of propylene oxide adduct of bisphenol A, 320 parts of bisphenol A ethylene oxide adduct and terephthalic acid in a round bottom flask equipped with a reflux condenser, water / alcohol separator, nitrogen gas inlet tube, thermometer and stirrer 790 parts and trimellitic acid 200 parts were added, nitrogen gas was introduced while stirring, and dehydration polycondensation or dealcoholization polycondensation was performed at a temperature of 200 to 240 ° C. When the acid value of the produced polyester resin or the viscosity of the reaction solution reached a predetermined value, the temperature of the reaction system was lowered to 100 ° C. or less to stop polycondensation. Thus, a thermoplastic polyester resin B was obtained.

  The obtained polyester resin B had Mw = 12000, Mn = 3200, Tg = 78.3 ° C., and acid value = 47.0 mgKOH / g.

(Manufacture of developer)
Example 1
100 parts by weight of polyester resin A and 15 parts by weight of copper phthalocyanine were mixed, thoroughly mixed with a Henschel mixer, melt-mixed with a twin-screw extrusion kneader, cooled, and then coarsely pulverized. By finely pulverizing with a jet pulverizer, toner particles having an average particle diameter of 6 μm were obtained.

  1 part by weight of V-216 (manufactured by ISP, polyvinylpyrrolidone), 0.5 part by weight of sorbitan monostearate (HLB4.3), and 75 parts by weight of liquid paraffin are added to 25 parts by weight of the toner particles. Part (flash point 200 ° C.) and 100 parts by weight of zirconia beads were mixed and stirred for 120 hours in a sand mill to obtain a developer. The average particle size of the toner particles in the developer was 2.6 μm.

Example 2
100 parts by weight of polyester resin B and 10 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Kasei Co., Ltd.) are mixed, thoroughly mixed with a Henschel mixer, melt-mixed with a twin screw extruder kneader, cooled, and then coarsely mixed. Crushed. By finely pulverizing with a jet pulverizer, toner particles having an average particle diameter of 6 μm were obtained.

  2 parts by weight of Solsperse 11200 (manufactured by Lubrizol) as a polymer dispersant, 0.3 part by weight of sorbitan trioleate (HLB1.8) and 75 parts by weight of liquid paraffin (to 25 parts by weight of the toner particles) Flash point 200 ° C.) and 100 parts by weight of zirconia beads were mixed and stirred in a sand mill for 120 hours to obtain a developer. The average particle size of the toner particles in the developer was 2.9 μm.

Example 3
100 parts by weight of polyester resin B and 20 parts by weight of quinacridone were mixed, sufficiently mixed with a Henschel mixer, melt-mixed with a twin-screw extrusion kneader, cooled, and then coarsely pulverized. By finely pulverizing with a jet pulverizer, toner particles having an average particle diameter of 6 μm were obtained.

  25 parts by weight of the toner particles, 6 parts by weight of Solsperse 13940 as a polymer dispersant, 1 part by weight of glycerol monostearate (HLB 6.6), 75 parts by weight of liquid paraffin (flash point 140 ° C.), and 100 of zirconia beads Part by weight was mixed and stirred in a sand mill for 120 hours to obtain a developer. The average particle size of the toner particles in the developer was 3.1 μm.

Example 4
A developer was produced in the same manner as in Example 1 except that polyethylene glycol distearate (HLB 7.3) was used instead of sorbitan monostearate. The average particle size of the toner particles in the developer was 2.6 μm.

Example 5
A developer was produced in the same manner as in Example 2 except that dioleate polyethylene glycol (HLB 8.0) was used instead of sorbitan trioleate. The average particle size of the toner particles in the developer was 2.7 μm.

Comparative Example 1
A developer was produced in the same manner as in Example 1 except that the polymer dispersant V-216 was not added. The average particle size of the toner particles in the developer was 7.3 μm.

Comparative Example 2
A developer was produced in the same manner as in Example 1 except that sorbitan monostearate was not added.

Comparative Example 3
A developer was produced in the same manner as in Example 1 except that 10 parts by weight of the polymer dispersant V-216 was added.

  About the manufactured said developer, the fixing property and the heat-resistant storage stability were evaluated by conducting a real-photo test using the experimental machine of the wet image forming apparatus.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of an experimental machine of a wet image forming apparatus. Around the drum-shaped image carrier 201, a charging device 203, an exposure device 204, a developing roller 103, an intermediate transfer member 301, and an image carrier cleaning blade 204 are arranged in order in the rotation direction indicated by the arrows. Around the transfer body 301, a primary transfer roller 302, a belt conveyance roller 305, a counter roller 306, a secondary transfer roller 307, and a tension roller 308 are disposed.

  The surface of the image carrier 201 is uniformly charged to a predetermined surface potential by the charging device 203, and then image information is exposed by the exposure device 204 to form an electrostatic latent image on the surface of the image carrier 201. . Next, the electrostatic latent image on the image carrier 201 is developed by a developing roller 103 in a developing tank 100 containing a developer 102 containing toner particles and a carrier liquid, and a toner image is formed on the surface of the image carrier 201. . At this time, not only the toner particles but also the carrier liquid adheres to the surface of the image carrier 201. Note that the developer coating layer on the surface of the developing roller 103 is held at a constant thickness by the regulating blade 101.

  Next, the toner image on the image carrier 201 is transferred to the intermediate transfer member 301 by applying a predetermined voltage to 302. A voltage having a polarity opposite to that of the toner particles is applied to 302. At this time, the potential difference from the image carrier is 300 V to 3 kV.

As the intermediate transfer member 301, the belt shown in FIG. 1 or the roller shown in FIG. 2 can be used.
When the intermediate transfer member is a belt, the belt material is a resin or an elastic member, and an elastic member is preferable in view of transferability to rough paper, and one having heat resistance is preferable. The thickness is preferably 50 μm to 1 mm, the volume resistivity is 10 ⁶ to 10 ¹² Ωcm, and the surface resistivity is preferably 10 ⁶ to 10 ¹² Ω / □. Examples of the resin include polyester, polypropylene, polyamide, polyimide, fluorine-based resin, polyphenyl sulfate, and the like, and examples of the elastic body include silicon rubber, fluorine rubber, EPDM, urethane rubber, and nitrile rubber, but are not limited thereto. Considering the stability of conveyance, a multilayer belt having an elastic body on a resin substrate is desirable. In this case, the thickness of the resin substrate is desirably 50 to 200 μm, and the thickness of the elastic body is desirably 200 μm to 1 mm. Further, the outermost layer preferably has a high releasability. Therefore, the surface layer is provided with a hard layer having a thickness of 1 μm or less by using a low surface energy polymer such as fluorine or silicon or by plasma treatment or the like. It is preferable.

  The developer transferred to the intermediate transfer member is transferred to the print medium at the secondary transfer portion (306, 307). A voltage having a polarity opposite to that of the toner is applied to 307. Reference numerals 309 and 310 denote heat rollers on which toner is fixed.

(Storage stability evaluation)
The developer was put in a glass bottle, stored at 50 ° C. for 24 hours, and the particle size before and after storage was measured using SALD-2200 manufactured by Shimadzu Corporation. A particle size change rate (average particle size after storage / particle size before storage) of 1.2 or less was rated as ○, and those exceeding 1.2 were rated as x.

(Fixability evaluation)
The developer to be evaluated was placed in the developing tank 102, and the solid image was developed and the transfer conditions were adjusted so that the toner amount on the medium was 3 g / m ² . An image sample was obtained under the conditions that the system speed was 180 mm / sec, the temperature of the heat roller was 180 ° C., and the NIP passage time was 40 msec.

  Fixability was evaluated by a tape peel test (tape; 3M mending tape), and the density of the peeled tape was measured to determine the fixability. The reflection density before and after tape peeling was measured using an X-Rite densitometer (Model No. 310). The density ratio before and after the tape was 95% or more, ◎, and 90% or more and less than 95%. Those less than were marked with x.

(Cleanability evaluation)
When a developer thin layer of 10 g / m ^{2 is} formed on the developing roller 103 and the urethane rubber cleaning blade 101 is pressed at 20 N / m, the cleaning property is visually evaluated. The case where there was no cleaning residue was marked as ◯.

  As described above, in Comparative Example 1 containing no polymer dispersant, the storage stability and the cleaning property were deteriorated. Further, in Comparative Example 2 which did not contain a nonionic surfactant, the cleaning property was deteriorated.

It is a schematic diagram which shows an example of a structure of a wet image forming apparatus. It is a schematic diagram which shows another example of a structure of a wet image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Developing tank 101 Control blade 102 Developer solution 103 Developing roller 201 Image carrier 202 Cleaning blade 203 Charging device 204 Exposure device 301 Intermediate transfer body 302 Primary transfer roller 305 Belt transport roller 306 Opposed roller 307 Secondary transfer roller 308 Tension roller 309 Heat roller 310 Heat roller

Claims (4)

A wet developer in which toner particles comprising at least a colorant and a binder resin are dispersed in a non-volatile carrier liquid using a dispersant,
The dispersant is a polymer dispersant having a basic group, and the carrier liquid contains a nonionic surfactant.   The wet developer according to claim 1, wherein the nonionic surfactant has an HLB of 8 or less.   The polymer dispersing agent has at least one basic group selected from the group consisting of an amide group, a methylol group, a pyridine group, a pyrrolidone group, an imidazole group, an imine group, and an amino group. Wet developer.   The wet developer according to any one of claims 1 to 3, wherein the binder resin is a polyester resin.

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