JP2009036814A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having high transfer efficiency in transfer of an image on an image carrier onto a recording medium and capable of forming an image having sufficient fixing strength, with respect to an image forming apparatus using a nonvolatile liquid developer. <P>SOLUTION: The image forming apparatus using a liquid developer includes: a developing means for performing development with the liquid developer including a nonvolatile carrier liquid, charged pigment fine particles dispersed in the carrier liquid, and thermoplastic resin fine particles dispersed in the carrier liquid; a carrier liquid removing means for partially removing the carrier liquid in a layer of the liquid developer on an image carrier which carries an image developed by the developing means; and a transfer means for transferring the image on the image carrier onto a recording medium after partially removing the carrier liquid by the carrier liquid removing means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using a liquid developer.

  An electrophotographic image forming apparatus that forms an electrostatic latent image on a photoconductor (photosensitive drum), attaches toner to the photoconductor, and transfers and fixes the image onto paper or the like is a copying machine, an MFP (multifunctional printer), Used for FAX, printer, etc. In these image forming apparatuses, in general, a dry type using powder toner is widely used.

  However, the powder toner has a problem that the toner is scattered, and also has a problem in image quality that the resolution is poor because the toner particles are as large as 7 to 10 μm.

  Therefore, in image forming apparatuses that require higher image quality and higher resolution, such as office printers for mass printing and on-demand printing apparatuses, liquid development in which toner is dispersed in a nonpolar organic solvent such as liquid paraffin A wet development method using an agent is used. This is because the liquid developer has toner particles as small as about 1 μm, and the charge amount is large, so that the toner image is hardly disturbed and high resolution can be realized.

  In a conventional wet image forming apparatus, a low-viscosity liquid developer obtained by mixing a toner in an organic solvent as a carrier liquid at a ratio of 1 to 2% is used as a liquid developer. However, since such a developer has a low toner concentration (hereinafter, also referred to as developer concentration or simply concentration), it is necessary to deposit a large amount on the paper and dry it at the time of fixing, and a large amount of vapor is generated. It had a big environmental problem. Moreover, since only a low boiling point carrier liquid can be used for volatilization, there is a big problem in safety such as a low flash point.

  Against this background, high-viscosity, high-concentration liquid development is achieved by dispersing toner as a solid component consisting of resin and pigment in a non-volatile carrier liquid such as silicone oil at a high concentration. An image forming apparatus using an agent has been proposed. When this liquid developer is used, the above-described problems can be prevented and the toner concentration is high, so that there is an advantage that it is not necessary to use a large amount of liquid developer.

  When developing with this liquid developer, the charged toner moves in the insulating liquid by electrostatic force to develop the electrostatic latent image. The developing efficiency is improved as the moving distance is shorter. For this purpose, a thin layer of a micron unit of developer is formed on a developer carrying member such as a developing roller, and development is performed by bringing the thinned developer into contact with the photoreceptor.

  The toner image formed on the photosensitive member by development is directly transferred to the recording material, or is primarily transferred to the intermediate transfer member and then secondarily transferred to the recording material.

  The transfer from the intermediate transfer member to the recording medium is performed by electrostatic transfer by applying a voltage. However, since electrostatic transfer is affected by the electrical resistance of the recording medium, it is not affected by environmental factors such as ambient temperature and humidity. There is a problem that the dependency is high and it is difficult to obtain a stable image.

  In order to solve this problem, a melt transfer fixing method is used in which toner is melted to generate an adhesive force and transferred to a recording medium. Normally, the melt transfer fixing method can be less dependent on environmental factors, but the transfer pressure needs to be excessive because the toner is transferred to the recording medium with the adhesive force of the toner. Therefore, vibration occurs when the recording medium bites into the contact portion of the intermediate transfer member, causing image noise.

  In addition, the toner remaining on the intermediate transfer member, which is not transferred to the recording medium during transfer of the toner image, is stuck on the surface of the intermediate transfer member due to excessive pressure, and it is difficult to remove the residual toner with a cleaning device. There was also a problem of becoming.

In order to solve such a problem, in Patent Document 1, the liquid developer on the image support is heated to a temperature higher than the glass transition temperature of the toner and lower than the melting point before transfer to the recording medium. A method has been proposed in which the solid content ratio of the toner is adjusted to 50% to 90% with the carrier liquid removing roller, so that the transfer efficiency to the transfer medium is good and strong fixing strength can be obtained even at a slight pressure. .
JP 2003-323053 A

  However, even with the technique of Patent Document 1, the carrier liquid is transferred to the recording medium together with the toner image. Since the transferred carrier liquid is interposed between the recording medium and the toner, there is a problem that sufficient fixing strength cannot be obtained.

  An object of the present invention is to form an image with high transfer efficiency and sufficient fixing strength when transferring an image on an image carrier to a recording medium in an image forming apparatus using a non-volatile liquid developer. An image forming apparatus is provided.

  In order to solve the above problems, the present invention has the following features.

1.
In an image forming apparatus for transferring an image developed using a liquid developer to a recording medium,
Developing means for developing an electrostatic latent image using a liquid developer comprising a non-volatile carrier liquid, pigment fine particles dispersed in the carrier liquid, and thermoplastic resin fine particles dispersed in the carrier liquid;
A carrier liquid removing means for removing a part of the carrier liquid in the layer of the liquid developer on the image carrier that carries the image visualized by the developing means;
An image forming apparatus comprising: transfer means for transferring an image on the image carrier after removing a part of the carrier liquid by the carrier liquid removing means to a recording medium.

2.
2. The image forming apparatus according to 1, wherein the resin fine particles have a volume average particle diameter in the carrier liquid of 10 nm or more and 500 nm or less.

3.
The image forming apparatus according to 1 or 2, wherein the pigment fine particles have a volume average particle diameter in the carrier liquid of 30 nm or more and 500 nm or less.

4).
The carrier liquid removing means is a sliding body that is in contact with a liquid developer layer on the image carrier and to which a voltage having the same polarity as the charged polarity of the pigment fine particles is applied. The image forming apparatus according to claim 1.

5).
5. The image forming apparatus according to claim 1, wherein the transfer unit is a heating roller having a heater.

6).
After the carrier liquid in the liquid developer layer on the image carrier is removed by the carrier liquid removing unit, the liquid developer layer on the image carrier is transferred from the carrier liquid to the recording medium by the transfer unit. The image forming apparatus according to any one of 1 to 5, further comprising a heating unit that heats the substrate.

  According to the present invention, in an image forming apparatus for transferring an image developed using a liquid developer onto a recording medium, a non-volatile carrier liquid, pigment fine particles dispersed in the carrier liquid, and the carrier liquid are dispersed. Developing means for developing an electrostatic latent image using a liquid developer containing fine thermoplastic resin particles, and a carrier for a liquid developer layer on an image carrier for carrying an image visualized by the developing means Carrier liquid removing means for removing a part of the liquid, and transfer means for transferring an image on the image carrier after removing a part of the carrier liquid by the carrier liquid removing means to a recording medium. . In this way, when the image on the image carrier is transferred to the recording medium, the content of the carrier liquid contained in the transferred image can be reduced, and thus the image on the image carrier can be reduced. It is possible to provide an image forming apparatus that can form an image with high transfer efficiency and sufficient fixing strength when transferred to a recording medium.

Embodiments according to the present invention will be described with reference to the drawings.
(Example of overall configuration and operation of image forming apparatus according to this embodiment)
FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus of the present invention. Around the drum-shaped photoconductor 201, a charging device 203, an exposure device 204, a developing roller 103, an intermediate transfer body 301, and a photoconductor cleaning blade 202 are arranged in this order in the rotation direction indicated by the arrows. A primary transfer roller 302, a squeeze roller 303, a squeeze roller cleaning blade 304, a secondary transfer roller 307, a tension roller 308, and a halogen heater 309 are disposed around 301.

  The surface of the photoconductor 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 photoconductor 201. Next, the electrostatic latent image on the photoconductor 201 is developed by the developing roller 103 carrying the liquid developer 104 in the developer tank 102, and a toner image is formed on the surface of the photoconductor 201. At this time, the liquid developer on the developing roller 103 is charged by the corotron charging device 105. Further, the liquid developer on the developing roller 103 after development is scraped off by the cleaning blade 101.

  The liquid developer contains pigment fine particles as a toner, thermoplastic resin fine particles, and a carrier liquid that is a non-volatile liquid having a vapor pressure at 20 ° C. of 200 Pa or less. The pigment fine particles and the resin fine particles are charged to the same polarity by the corotron charging device 105.

  In addition, the toner image developed on the photoconductor 201 is attached to the photoconductor 201 in a state of containing a large amount of carrier liquid as well as toner.

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

  The intermediate transfer member 301 may have a belt shape as shown in FIG. 1, or a drum-like intermediate transfer member 301 as shown in FIG. When the drum-shaped intermediate transfer member 301 is used, the positional accuracy is easily obtained and the drive system can be simplified.

In the case where the intermediate transfer member 301 is a belt, the belt material is a resin or an elastic body, and an elastic body is desirable in view of transferability to rough paper, and a material having heat resistance is desirable. Desirably, the thickness is 50 μm or more and 1 mm or less, the volume resistivity is 10 ⁶ or more and 10 ¹² Ωcm or less, and the surface resistivity is 10 ⁶ or more and 10 ¹² Ω / □ or less. 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 is desired to have high releasability. Therefore, it is preferable that the surface layer is provided with a low surface energy polymer such as fluorine-based or silicon-based or a hard layer of 1 μm or less by plasma treatment or the like.

  In the liquid developer containing the image transferred to the intermediate transfer member 301, as a step of removing a part of the carrier liquid, the squeeze roller 303 which is a carrier liquid removing means for the carrier liquid removes the carrier liquid in the liquid developer layer. Part is removed. The squeeze roller 303 is a sliding body that is in contact with the liquid developer layer on the intermediate transfer body 301 and to which a voltage having the same polarity as the charged polarity of the pigment fine particles is applied. By applying a voltage having the same polarity as the pigment fine particles to the squeeze roller 303, the pigment fine particles can be prevented from moving to the squeeze roller 303. Therefore, the carrier liquid moves to the squeeze roller 303 side, and the amount of carrier liquid on the intermediate transfer member 301 decreases after passing through the squeeze roller 303. The carrier liquid that has moved to the squeeze roller 303 side is cleaned by the cleaning blade 304.

  The carrier liquid amount of the liquid developer on the intermediate transfer member 301 as an image carrier is reduced before being transferred to the recording medium P by such means. By reducing the amount of the carrier liquid, the toner particles in the liquid developer come into contact with each other and are further closely adhered to form a film. The situation at this time will be described with reference to FIGS. 3A and 3B, comparing the case where the conventional liquid developer is used (a) and the case where the liquid developer of the present invention is used (b). To do.

  Conventional toner particles use particles in which a pigment is dispersed in a binder resin, and have a relatively large particle size. When the carrier is removed by the squeeze roller 303, as can be seen from FIG. 3A, in the conventional toner image that has been visualized, a large amount of carrier liquid remains between the particles. In contrast, the liquid developer of the present invention uses pigment fine particles themselves as a toner as shown in FIG. 3B, so that they adhere closely to the image carrier and also disperse the thermoplastic resin fine particles. As a result, resin fine particles enter between the pigment fine particles. For this reason, the amount of the carrier liquid between the particles is further reduced, and the solid content ratio of the toner image can be reduced. Further, when the pigment fine particles and the resin fine particles are brought into close contact with each other, an adhesive force is generated and a film is formed.

  In this state, the image on the intermediate transfer member 301 is heated by a halogen heater 309 as a heating unit. The resin fine particles are softened or melted by heating, and the process proceeds to the next transfer step.

  In the process of transferring to the recording medium, the toner image is melted and transferred to the recording member P using a transfer roller 307 and a backup roller 306 which are heating rollers incorporating a heater as a transfer means. The transfer efficiency at this time is almost 100%, the fixing performance after transfer is improved, and an image having a high fixing strength can be formed.

  The squeeze roller 303 preferably has a heating means inside, and heats the liquid developer on the intermediate transfer member 301. The backup roller 305 may also have a heating unit.

  The squeeze roller 303 is an elastic body having an Asker A hardness of 20 degrees to 90 degrees. As the elastic body, silicon rubber, fluorine rubber, EPDM, urethane rubber, nitrile rubber, and the like can be disclosed, but not limited thereto. When the squeeze roller 303 is heated, it may be heated from about 80 ° C. to about 200 ° C. Further, a plurality of such squeeze rollers 303 may be arranged before transferring to the recording medium P. Further, a means for heating the intermediate transfer member 301 before transfer to the recording medium P, such as the halogen heater 309, may be omitted.

  Thus, by heating the toner image on the intermediate transfer body 301 before transferring to the recording member P, the toner image becomes a film, and the transfer efficiency can approach 100%.

  As the transfer means, thermal transfer is used, but electric transfer or shear transfer may be used. There is no particular limitation, but thermal transfer is preferable. When thermal transfer is used, the transfer roller 307 and the backup roller 306 have heating means. In this case, the heating temperature is preferably 80 ° C. or higher and 200 ° C. or lower. The backup roller 307 is an elastic body having an Asker A hardness of 20 ° C. or higher and 90 ° C. or lower. As the elastic body, silicon rubber, fluorine rubber, EPDM, urethane rubber, nitrile rubber, or the like can be disclosed, but not limited thereto.

  After the transfer to the recording medium P, it is desirable that the intermediate transfer member 301 has a cooling process like the cooling member 310. As the cooling member 310, a cooling fan or the like can be used. By cooling the intermediate transfer member 301 using the cooling member 310, heat is prevented from being transmitted to the photosensitive member 201, and the durability of the photosensitive member 201 can be improved.

In the above embodiment, the intermediate transfer member 301 is used as the image carrier. However, the image on the photosensitive member 201 may be directly transferred to the recording medium P without using the intermediate transfer member 301. good. In this case, the image carrier is the photosensitive member 201.
(Configuration of liquid developer)
The liquid developer is composed of at least a carrier liquid, pigment fine particles, a dispersant, and resin fine particles.

  The carrier liquid is non-volatile, has a vapor pressure at 20 ° C. of 200 Pa or less, a low dielectric constant of 3 or less, and a high electrical insulation property. For example, it is selected from hydrocarbons (liquid paraffin), silicon oil, animal and vegetable oils, mineral oils, and the like.

  Examples of the pigment fine particles of the present invention include 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 rake, methyl violet rake, basic blue 6B rake, first sky blue, reflex blue G, brilliant green rake, copper phthalocyanine, phthalocyanine green G, bitumen, ultramarine, iron oxide powder, zinc white, calcium carbonate, clay, sulfuric acid Examples include barium, alumina white, aluminum powder, daylight fluorescent pigment, and pearl pigment.

  In order to improve the dispersibility of the pigment fine particles, a pigment derivative may be used. A pigment derivative having a desired functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group, or an amide group can be used.

  The pigment fine particles are dispersed in the carrier liquid, and the secondary particle size thereof is preferably 30 nm or more and 500 nm or less, more preferably 50 nm or more and 300 nm or less. By setting it as such a particle size, the clearance gap between pigment fine particles can be decreased. If the thickness is less than 30 nm, the developability on the photosensitive member 201 tends to be reduced as in the case of the resin fine particles. On the other hand, if it exceeds 500 nm, the effect of removing the carrier liquid in the carrier liquid removing means described above tends to decrease.

  The blending amount of the pigment fine particles is preferably 3% by mass or more and 30% by mass or less with respect to the carrier liquid amount. If it is 3% by mass or less, the desired concentration cannot be obtained, and if it is 30% by mass or more, the dispersibility may be impaired.

  The dispersant for the pigment fine particles includes hydroxyl group-containing carboxylic acid ester, long chain polyaminoamide and high molecular weight acid ester salt, high molecular weight polycarboxylic acid salt, long chain polyaminoamide and polar acid ester salt, high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Nonylphenyl ether, polyester polyamine, stearylamine acetate and the like can be used.

  The amount of the pigment fine particle dispersant is preferably 10% by mass or more and 200% by mass or less based on the pigment fine particles.

  The amount of dispersant required varies depending on the particle size of the pigment fine particles, and it is desirable to add a large amount if a small particle size is desired. If it is 10% by mass or less, the dispersibility is impaired, and if it is 200% by mass or more, the conductivity of the liquid increases and the chargeability may be impaired.

  The pigment fine particle dispersant is preferably a polymer pigment dispersant. The polymer pigment dispersant has a long-chain alkyl group for increasing compatibility with an organic solvent and an acid or basic functional group for adsorption of the pigment. A preferable dispersant varies depending on the pigment, and it is preferable to select a pigment dispersant having an acid or basicity opposite to the acid or basicity of the pigment.

  The resin fine particles are thermoplastic and preferably have a glass transition point of −10 ° C. or higher and 60 ° C. or lower.

  The resin fine particles are dispersed in the carrier liquid, and the secondary particle size thereof is preferably 10 nm or more and 500 nm or less, and more preferably 50 nm or more and 300 nm or less. By setting it as such a particle diameter, it becomes easy to fill between pigment fine particles, and can remove a carrier liquid more. If the thickness is less than 10 nm, it is difficult to obtain in production, and the mobility of fine particles due to the electric field is restricted, and the developability to the photosensitive member 201 tends to be lowered. On the other hand, when the particle diameter exceeds 500 nm, the fine particles tend to aggregate and the effect of removing the carrier liquid in the carrier liquid removing means described above tends to decrease.

  Commercially available resin fine particles can be used as the resin fine particles. Further, a non-aqueous dispersion (NAD) in which resin fine particles are dispersed in a poor solvent can be used by mixing with a carrier liquid.

  NAD is composed of a resin dispersed phase unnecessary for a solvent and a polymer dispersion stabilizer. As an example of the resin dispersed phase, a radical polymerized acrylic polymer can be presented. The polymer dispersion stabilizer of NAD is a polymer having a number average molecular weight of 1000 or more, and the polymer dispersant has a binding active point with the resin dispersed phase and has a functional group necessary for crosslinking and adhesion. As the NAD polymer dispersant, an acrylic resin, a polyester resin, an alkyd resin, a melamine resin, a cellulose derivative, or the like into which a functional group such as a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, or an amide group is introduced is preferable. The glass transition point of the resin dispersed phase is desirably -10 ° C or higher and 60 ° C or lower. If it is −10 ° C. or lower, the storage stability is deteriorated, and if it is 60 ° C. or higher, there is a possibility that a problem occurs in the fixing property. A dispersed phase having a small diameter and a large number of polar groups, such as an NAD dispersed phase, has higher stability in a liquid state and can have a lower Tg than a general liquid developer such as the preceding example. Easy to fix at low temperature. Further, the NAD dispersed phase may have a reactive functional group so that the particles or the inside of the particles react as necessary.

  The blending amount of the resin fine particles (solid content) is preferably 0.5 to 20 times the pigment fine particles. If it is 0.5 times or less, the fixability is impaired, and if it exceeds 20 times, the viscosity increases and the developability may be impaired.

  As a method for producing a liquid developer, a dispersion in which pigment fine particles are dispersed in a solvent and a dispersion in which resin fine particles are dispersed in a solvent may be separately prepared and mixed, or the resin fine particles are polymerized in the presence of the pigment fine particles. However, it may be a dispersion.

1. Production of liquid developer A (dispersion adjustment of pigment in carrier liquid)
Pigment: Acid-treated copper phthalocyanine derivative 12 parts by weight Dispersant: Basic pigment dispersant Solspers 13940 (manufactured by Avicia) 5 parts by weight Carrier liquid: Liquid paraffin (vapor pressure about 30 Pa, flash point 144 ° C.) 100 parts by weight are mixed Then, the mixture was stirred with a paint conditioner for 24 hours together with 100 parts by mass of zirconia beads, and the beads were removed to obtain pigment dispersion 1. When the particle size of the pigment fine particles of the pigment dispersion 1 was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), the volume average particle size was 120 nm.
(Dispersion adjustment of resin fine particles in carrier liquid)
First, a dispersant A for resin fine particles was prepared as follows.

  In a four-necked flask equipped with a stirrer, thermometer, reaction product removal apparatus and nitrogen gas introduction tube, 100 parts by mass of liquid paraffin and AIBN 1 part by mass, which are the same as the carrier liquid, are charged and heated to 120 ° C. 25 parts by mass of methyl methacrylate, 55 parts by mass of lauryl methacrylate, 19 parts by mass of hydroxyethyl methacrylate and 1 part by mass of acrylic acid were added, and this mixture was added dropwise over 4 hours. This was distilled under reduced pressure to obtain Dispersant A having a nonvolatile content of 40%.

  Next, using this dispersant A, a resin fine particle dispersion 1 dispersed in a carrier liquid was prepared as follows.

As raw materials for the resin fine particles, 35 parts by mass of methyl methacrylate, 12 parts by mass of hydroxyethyl methacrylate, 2 parts by mass of glycidyl methacrylate and 1 part by mass of acrylic acid were added, and further 1 part by mass of AIBN was added to obtain a mixture. 30 parts by mass of dispersant A and 70 parts by mass of liquid paraffin as a carrier liquid were added to this mixture, and the mixture was added dropwise to a four-necked flask heated to 100 ° C. over 4 hours. Further, a mixture of 0.5 parts by weight of AIBN and 8 parts by weight of liquid paraffin was added to the flask and distilled under reduced pressure to obtain a resin fine particle dispersion 1 having a solid content of 50% and becoming cloudy. When the particle size of the resin fine particles was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), the volume average particle size was 100 nm.
(Adjustment of liquid developer A)
100 parts by mass of the pigment dispersion 1 and 50 parts by mass of the resin fine particle dispersion 1 were mixed to obtain a liquid developer A.
2. Production of liquid developer B (dispersion adjustment of pigment in carrier liquid)
Pigment: Derivative of copper phthalocyanine treated with a basic treatment 8 parts by weight Dispersant: Acid pigment dispersant Solspers 3000 (manufactured by Avicia) 5 parts by weight Carrier liquid: Liquid paraffin (vapor pressure about 10 Pa, flash point 144 ° C.) 100 parts by weight are mixed Then, the mixture was stirred for 24 hours with a paint conditioner together with 100 parts by mass of zirconia beads, and the beads were removed to obtain a pigment dispersion 2. When the particle size of the pigment fine particles of the pigment dispersion 2 was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), the volume average particle size was 300 nm.
(Dispersion adjustment of resin fine particles in carrier liquid)
The resin fine particle dispersion 1 used in the liquid developer A was used.
(Adjustment of liquid developer B)
100 parts by mass of the pigment dispersion 2 and 40 parts by mass of the resin fine particle dispersion 1 were mixed to obtain a liquid developer B.
3. Production of liquid developer C (dispersion adjustment of pigment in carrier liquid)
Pigment: Carbon black (MA-100, Mitsubishi Chemical) 8 parts by mass Dispersant: Basic pigment dispersant Solspers 13940 (manufactured by Abyssia) 4 parts by mass Carrier liquid: Liquid paraffin (vapor pressure about 10 Pa, flash point 144 ° C.) 100 parts by mass Parts were mixed and stirred with a paint conditioner for 24 hours together with 100 parts by mass of zirconia beads, and the beads were removed to obtain pigment dispersion 3. When the particle size of the pigment fine particles of the pigment dispersion 3 was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), the volume average particle size was 80 nm.
(Dispersion adjustment of resin fine particles in carrier liquid)
A resin fine particle dispersion 3 was prepared using a commercially available resin dispersion (Acridic YL-431, Dainippon Ink) in which 40 parts by mass of acrylic resin fine particles were dispersed in 60 parts by mass of liquid paraffin as a carrier liquid. When the particle size of the resin fine particles was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), the volume average particle size was 50 nm.
(Adjustment of liquid developer C)
100 parts by mass of the pigment dispersion 3 and 40 parts by mass of the resin fine particle dispersion 3 were mixed to obtain a liquid developer C.
4). Production of liquid developer D In the production of liquid developer C, liquid developer D was prepared in the same manner as liquid developer C except that a commercially available resin dispersion was used as Nisset U3611 (manufactured by Nippon Carbide). . The particle size of the resin fine particles was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), and the volume average particle size was 300 μm.
5). Production of liquid developer E Liquid developer E was prepared in the same manner as liquid developer A except that S13940 of the dispersant was changed to 2.5 parts by mass in the production of liquid developer A. The particle size of the pigment fine particles at this time was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), and the volume average particle size was 1.5 μm.
6). Production of liquid developer F 100 parts by mass of styrene acrylic copolymer (styrene: butyl methacrylate: methyl methacrylate = 70: 25: 5, Mn = 5300, Mw = 23500) and 10 parts by mass of copper phthalocyanine were mixed into a Henschel mixer. The mixture was melted and mixed with a twin screw extruder kneader, cooled, then coarsely pulverized, and finely pulverized to a volume average particle diameter of 10 μm with a jet pulverizer to obtain pigment resin fine particles.

20 parts by mass of the pigment resin fine particles, 3 parts by mass of Solspers S13940 as a dispersant, 100 parts by mass of liquid paraffin as a carrier liquid (vapor pressure of about 5 Pa, flash point 200 ° C.), and 100 parts by mass of zirconia beads are mixed in a sand mill. For 120 hours to obtain a liquid developer F. The particle diameter of the pigment resin fine particles was measured with a particle size distribution meter (SALD-2200, manufactured by Shimadzu Corporation), and the volume average particle diameter was 2 μm.
Example 1
The image forming apparatus shown in FIG. 1 was used to evaluate the fixability. The photoconductor 201 is formed by forming an organic photoconductor film (film thickness: 35 μm) on an aluminum drum having a diameter of 100 mm, and the rotational peripheral speed was set to 200 mm / sec. The liquid developer is positively charged on the developing roller 103 by the discharge from the charge wire applied to 5 kV by the corotron charging device 105. The charging device 203 was a scorotron charger, and the surface potential of the photoconductor 201 was set to 600V. The exposure device 204 was set so that the surface potential of the photosensitive member 201 was 100 V when the image portion was exposed with a semiconductor laser, and a 400 V voltage was applied to the developing roller 103.

Developer A was used as the liquid developer, and a solid pattern (100 solids) was printed as an image pattern. At this time, the developer amount on the developing roller 103 was adjusted to 7.5 g / m ² . (Solid content 20%)
A voltage of −800 V was applied to the primary transfer roller 302.

As the intermediate transfer member 301, a multi-layer structure having a silicon rubber with a thickness of 500 μm on a polyimide resin with a thickness of 100 μm was used. The amount of developer on 301 immediately after the primary transfer roller 302 was 5 g / m ² (solid content 30%). The squeeze roller 303 is a silicon roller having a diameter of 30 mm and an Asker A hardness of 40 ° C. Here, the squeeze efficiency is improved by installing a heater in the squeeze roller 303 and melting the resin component in the liquid developer. The heating temperature is heated so that the surface temperature of the squeeze roller 303 is 120 ° C. In addition, a voltage of 1000 V is applied to the squeeze roller 303. The carrier liquid removal blade 304 is a metal blade, and the carrier liquid collected by the squeeze roller 303 is removed by the carrier liquid removal blade 304. The developer amount after passing through the squeeze roller 303 was 1.8 g / m ² (solid content 83%).

The heating unit 309 heats the surface of the intermediate transfer member 301 and melts the resin component in the developer on the intermediate transfer member 301. The secondary transfer roller 307 is a silicon rubber roller having a temperature of 140 ° C. and an Asker A hardness of 40 degrees. Using the secondary transfer roller 307, the developer was transferred and fixed on OK top coat paper manufactured by Oji Paper Co. as the recording medium P.
(Examples 2 to 5)
In Examples 2 to 5, evaluation was performed in the same manner as in Example 1 except that Developers B to E were used instead of Developer A of Example 1.
(Comparative Example 1)
In Comparative Example 1, evaluation was performed in the same manner as in Example 1 except that Developer F was used instead of Developer A in Example 1.

The amount of the developer after passing through the squeeze roller 303 was 3 g / m ² (solid content: 67%).
(Evaluation)
Transfer efficiency: Visual observation of the toner on the intermediate transfer member after transfer, ○ that is not recognized at all, △ that is slightly recognized but not causing a problem, that can be clearly confirmed, and that has a problem level Was marked with x.

Fixability evaluation: A tape peel test of a fixed image was performed. As the tape, a Scotch mending tape (manufactured by Sumitomo 3M) was used. The reflection density before and after the tape peeling was measured, and the density ratio before and after the tape was 90% or more, ○ was 80% or more and less than 90%, Δ was less than 80%, and Δ or more was passed. (Measurement uses X-Rite densitometer)
The evaluation results are shown in Table 1.

  From the results in Table 1, the fixing strengths of Examples 1 to 5 are improved compared to Comparative Example 1 in the image forming apparatus according to the present invention, in which the liquid developer is a non-volatile liquid carrier liquid, The liquid developer on the image carrier is provided with a carrier liquid removing means for removing the carrier liquid in the liquid developer layer on the image carrier, the pigment fine particles and the thermoplastic resin fine particles. It can be seen that the liquid developer layer on the image carrier is transferred to the recording medium after the carrier liquid in the agent layer is removed. Further, the fixing strength in Example 5 is slightly lower than in Examples 1 to 4, because the particle size of the pigment fine particles in Example 5 is as large as 1500 nm, and the carrier liquid is removed by the carrier liquid removing means. It is thought that the effect decreased.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the whole structure of the image forming apparatus in another embodiment of this invention. It is a schematic diagram showing a toner image on the image carrier from which the carrier liquid has been removed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Cleaning blade 102 Developer tank 103 Developing roller 104 Liquid developer 105 Corotron charging device 201 Photoconductor 202 Photoconductor cleaning blade 203 Charging device 204 Exposure device 301 Intermediate transfer body 302 Primary transfer roller 303 Squeeze roller 304 Cleaning blades 305 and 306 Backup roller 307 Transfer roller 308 Tension roller 309 Halogen heater 310 Cooling member P Recording medium

Claims (6)

In an image forming apparatus for transferring an image developed using a liquid developer to a recording medium,
Developing means for developing an electrostatic latent image using a liquid developer comprising a non-volatile carrier liquid, pigment fine particles dispersed in the carrier liquid, and thermoplastic resin fine particles dispersed in the carrier liquid;
A carrier liquid removing means for removing a part of the carrier liquid in the layer of the liquid developer on the image carrier that carries the image visualized by the developing means;
An image forming apparatus comprising: transfer means for transferring an image on the image carrier after removing a part of the carrier liquid by the carrier liquid removing means to a recording medium. The image forming apparatus according to claim 1, wherein the resin fine particles have a volume average particle diameter in the carrier liquid of 10 nm to 500 nm. 3. The image forming apparatus according to claim 1, wherein the pigment fine particles have a volume average particle diameter in the carrier liquid of 30 nm or more and 500 nm or less. 2. The carrier liquid removing unit according to claim 1, wherein the carrier liquid removing means is a sliding body that is in contact with a liquid developer layer on the image carrier and to which a voltage having the same polarity as the charged polarity of the pigment fine particles is applied. 4. The image forming apparatus according to any one of items 3. The image forming apparatus according to claim 1, wherein the transfer unit is a heating roller having a heater. After the carrier liquid in the liquid developer layer on the image carrier is removed by the carrier liquid removing unit, the liquid developer layer on the image carrier is transferred from the carrier liquid to the recording medium by the transfer unit. The image forming apparatus according to claim 1, further comprising a heating unit that heats the image forming apparatus.

Images