JP2009251438A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device stably supplying a magnetic latent image holder with a sufficient amount of magnetic toner for development of a magnetic latent image holder, and also to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device 14 comprises: a developer storage unit 20 for storing liquid developer 26; and the developing device 14. The magnetic roll 22A and developing sleeve 22 of the developing device 14 are rotated in opposite directions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus.

  2. Description of the Related Art A magnetic printing apparatus that can print a required number of copies by forming a latent image once is known. In this magnetic printing apparatus, a magnetic latent image magnetically formed is held on a magnetic recording medium (magnetic latent image holder), and a magnetic material is supplied to the magnetic recording medium in a development area to reveal the magnetic latent image. By pressing a recording medium such as paper against the magnetic recording medium in the transfer area, transferring the visualized image to the recording medium, and further transporting the transferred recording medium to the fixing area for fixing processing. Complete the print.

As a technique related to the magnetic printing apparatus, for example, a developer in which resin particles containing a ferromagnetic material are dispersed in liquid ink is supplied from a developing device to a magnetic drum (magnetic latent image holding member), and a magnetic material on the drum is supplied. There is a technology in which a latent image is visualized with a developer, and the visualized image is pressed onto a recording medium, whereby only liquid ink is transferred to the recording medium and an image is formed on the recording medium with the liquid ink. It has been proposed (see, for example, Patent Document 1).
In the technique of Patent Document 1, a developing device that supplies a developer to a magnetic drum is provided with a developing roll provided so that a part of the developing device is immersed in a developer stored in a developer storage container that stores the developer. Offering. The developing roll is magnetically moved in the developer storage container by rotating together a pre-magnetized aluminum drum and a solvent-resistant layer provided on the peripheral surface of the aluminum drum. The developer containing the resin particles that have reached the developing roll by the migration is held, and the held developer is supplied to the magnetic drum.
JP 11-38671 A

  An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus capable of stably supplying a sufficient amount of magnetic toner for developing a magnetic latent image holding member to the magnetic latent image holding member. To do.

  The invention according to claim 1 is a developer storing means for storing a liquid developer containing magnetic toner and an aqueous medium, a magnetic roll in which a plurality of magnetic poles are arranged in the circumferential direction and rotated in the circumferential direction, A rotating shaft is provided on the outer periphery of the magnetic roll so as to be coaxial with the rotating shaft of the magnetic roll, and is provided so that a part of the outer periphery is immersed in the liquid developer and rotated in the opposite direction to the magnetic roll. And a developing sleeve having a developing sleeve for holding the liquid developer on the surface and supplying the magnetic toner to a magnetic latent image holding member having a water-repellent surface.

  The invention according to claim 2 is the developing device according to claim 1, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity.

  According to a third aspect of the present invention, there is provided a magnetic latent image holder having a water-repellent surface, developer storage means for storing a liquid developer containing magnetic toner and an aqueous medium, and a plurality of magnetic poles arranged in the circumferential direction. A magnetic roll that is rotated in the circumferential direction, and a rotation axis is provided on the outer periphery of the magnetic roll so that the rotation axis is coaxial with the rotation axis of the magnetic roll and a part of the outer periphery is immersed in the liquid developer. And a developing sleeve that holds the liquid developer on the surface by being rotated in the opposite direction to the magnetic roll and supplies the magnetic toner to the magnetic latent image holding member, A process cartridge is provided.

  The invention according to claim 4 is the process cartridge according to claim 3, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity.

  The invention according to claim 5 is the process cartridge according to claim 3 or 4, wherein a contact angle of the surface of the magnetic latent image holding member with pure water is 70 ° or more.

  The invention according to claim 6 includes a magnetic latent image holder having a water-repellent surface, magnetic latent image forming means for forming a magnetic latent image on the magnetic latent image holder, magnetic toner and an aqueous medium. Developer storing means for storing a liquid developer, a magnetic roll in which a plurality of magnetic poles are arranged in the circumferential direction and rotated in the circumferential direction, and a rotation axis on the outer circumference of the magnetic roll is coaxial with a rotation axis of the magnetic roll And is provided so that a part of the outer periphery is immersed in the liquid developer and rotated in the opposite direction to the magnetic roll to hold the liquid developer on the surface and A developer holding unit having a developing sleeve to be supplied to the magnetic latent image holding member, and a toner image corresponding to the magnetic latent image formed by supplying the liquid developer by the developer holding unit is recorded. Transfer to media A shooting unit, an image forming apparatus characterized by comprising a, a degaussing means for degaussing the magnetic latent image on the magnetic latent image holding member.

  A seventh aspect of the present invention is the image forming apparatus according to the sixth aspect, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity.

  The invention according to claim 8 is the image forming apparatus according to claim 6 or 7, wherein a contact angle of the surface of the magnetic latent image holding member with pure water is 70 ° or more.

  According to the developing device of the first aspect, the magnetic latent image is held as compared with the case where only one of the magnetic roll and the developing sleeve is rotated or the case where the magnetic roll and the developing sleeve are rotated in the same direction. There is an effect that a sufficient amount of magnetic toner for developing the body is stably supplied to the magnetic latent image holding body.

  According to the developing device of the second aspect, there is an effect that the magnetic toner in the liquid developer is efficiently and stably supplied to the magnetic latent image holding member.

  According to the process cartridge of the third aspect, there is an effect that a sufficient amount of magnetic toner for developing the magnetic latent image holding member is stably supplied to the magnetic latent image holding member.

  According to the process cartridge of the fourth aspect, the magnetic toner in the liquid developer is efficiently and stably supplied to the magnetic latent image holding member.

  According to the process cartridge of claim 5, the process cartridge capable of further reducing the occurrence of residual liquid and image fog on the magnetic latent image holding member after development without being subjected to fluctuations in the surface tension of the liquid developer. Is provided.

  According to the image forming apparatus of claim 6, the magnetic latent image is compared with a case where only one of the magnetic roll and the developing sleeve is rotated or a case where the magnetic roll and the developing sleeve are rotated in the same direction. There is an effect that a sufficient amount of magnetic toner for developing the holding member is stably supplied to the magnetic latent image holding member, and the speed of image formation can be increased.

  According to the image forming apparatus of the seventh aspect, there is an effect that the magnetic toner in the liquid developer is efficiently and stably supplied to the magnetic latent image holding member.

  According to the image forming apparatus of the present invention, an image that can further reduce the occurrence of residual liquid and image fog on the magnetic latent image holding member after development without being subjected to fluctuations in the surface tension of the liquid developer. There is an effect that a forming apparatus is provided.

  Hereinafter, the image forming apparatus according to the present embodiment will be described with reference to the drawings.

  As shown in FIG. 1 (enlarged view of the development region in FIG. 1), the image forming apparatus 10 of the present embodiment includes a water-repellent magnetic drum (magnetic latent image holder) 11 as shown in FIG. And is rotatably supported with respect to the apparatus main body. Around the magnetic drum 11, a magnetic head 12, a developing device 14, a transfer device 16, and a demagnetizing device 18 are sequentially provided along the rotation direction of the magnetic drum 11. For example, the magnetic drum 11 and the developing device 14 constitute a process cartridge 15 that is detachably provided to the main body of the image forming apparatus 10).

  The magnetic drum 11 has its surface magnetized by causing a leakage magnetic flux from the magnetic pole tip of the magnetic head 12 when a current flows through the coil of each channel of the magnetic head 12. As a result, a magnetic latent image (magnetic latent image portion (hatching portion) 34) is formed on the surface of the magnetic drum 11.

  The developing device 14 is roughly divided into a developer storage unit 20 and a developer holding unit 22, and a developer storage tank 21 is provided in the developer storage unit 20, and the magnetic toner 24 is dispersed in the aqueous medium 23. A liquid developer 26 is stored.

  Although details will be described later, the developer holding unit 22 holds the liquid developer 26 stored in the developer storage unit 20 and transports it to a region facing the developer holding unit 22. The magnetic toner 24 in the liquid developer 26 that has reached this facing area develops the magnetic latent image portion 34 on the surface of the magnetic drum 11, and a toner image 28 corresponding to the magnetic latent image portion 34 is formed on the magnetic drum 11. It is formed. The aqueous medium 23 in the liquid developer 26 has a higher water repellency on the surface of the developer holding unit 22 than the surface of the developer holding unit 22, so that it is difficult to move to the magnetic drum 11 side. Is returned to the developer storage section 20 again.

  The transfer device 16 includes a transfer fixing roll 38 and is arranged so as to form a nip with respect to the magnetic drum 11. Then, the paper 40 is fed between the magnetic drum 11 and the transfer fixing roll 38 in synchronization with the toner image 28 on the magnetic drum 11. By pressing the paper 40 toward the magnetic drum 11, the toner image on the magnetic drum 11 is transferred to the paper 40 and fixed.

  When forming a new image, the magnetic latent image on the magnetic drum 11 is formed by the degaussing device 18 disposed between the magnetic head 12 and the transfer device 16 before the magnetic latent image is formed by the magnetic head 12. Is erased.

  Here, when the transfer efficiency of the toner image from the magnetic drum 11 to the paper 40 is less than 100%, a part of the toner image 28 remains on the magnetic drum 11 after the transfer. Therefore, in this case, a cleaner for removing the toner image 28 remaining on the magnetic drum 11 is disposed on the upstream side of the demagnetizer 18 in the rotation direction of the magnetic drum 11.

  Next, each configuration of the image forming apparatus of the present embodiment will be described sequentially.

(Magnetic latent image holder)
The structure of the magnetic drum (magnetic latent image holding member) 10 is such that, for example, an underlayer such as Ni or Ni-P is formed on a drum made of a metal such as aluminum with a thickness of about 1 μm to 30 μm. A magnetic recording layer of Co—Ni, Co—P, Co—Ni—P, Co—Zn—P, Co—Ni—Zn—P, etc. is formed to a thickness of about 0.1 μm to 10 μm. A protective layer such as Ni-P is formed with a thickness of about 0.1 μm to 5 μm. If there is a defect such as a pinhole in the plating of the underlayer, a defect is also formed in the magnetic recording layer. Therefore, it is preferable to carry out fine and uniform plating.

  In addition to plating, there are also methods such as sputtering and vapor deposition. Furthermore, the underlayer and the protective layer are preferably nonmagnetic. Maintaining the surface accuracy of the surface of each layer by tape polishing or the like is suitable for maintaining the gap with the magnetic head 12 forming the magnetic latent image with high accuracy.

  The film thickness of the magnetic recording layer is preferably in the range of 0.1 μm to 10 μm, and the magnetic characteristics of the magnetic recording layer are such that the coercive force is 16000 A / m or more and 80000 A / m or less (200 Oersted or more and 1000 Oersted (Oe) or less. The residual magnetic flux density is preferably about 100 mT to 200 mT (1000 gauss to 2000 gauss (G)).

  The above is the configuration of the magnetic drum in the case of the horizontal magnetic recording type, but in the case of the vertical magnetic recording type, a configuration in which a recording layer such as Co—Ni—P is provided on the nonmagnetic layer, A configuration in which a soft magnetic layer having a high magnetic permeability is provided below the recording layer may be employed, and the present invention is not limited to any one. Further, the magnetic latent image holding member is not limited to the drum shape in the present embodiment, but may be a belt shape.

  In this embodiment, the magnetic drum 11 having water repellency is used. Here, water repellency means the property of repelling water, and specifically means that the contact angle with pure water is 70 degrees or more. In the present embodiment, the contact angle of the magnetic drum 11 with respect to pure water is desirably 70 degrees or more, and more desirably 100 degrees or more. If the contact angle is less than 70 degrees, liquid may remain on the magnetic drum 11 or image fogging may occur after development with the liquid developer 26 using an aqueous medium described later. .

  The contact angle of the surface of the magnetic drum 11 was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd .: CA-X) and pure water was added to the surface of the magnetic drum 11 in an environment of 25 ° C. and 50% RH. 3.1 μl was added dropwise to the tube, and the contact angle after 15 seconds was determined. Measurement was made at four points in the circumferential direction at the end and center, and the average value of these was taken as the contact angle.

  In order to make the surface of the magnetic drum 11 have the above-mentioned preferable contact angle, it is desirable to coat the surface of the magnetic drum 11 configured as described above. Examples of the surface coat include fluorine lubrication plating and coating using a polymer containing fluorine atoms or silicon atoms. Fluorine lubrication plating is a functional plating in which fluorine resin (polytetrafluoroethylene: PTFE) is combined and co-deposited with electroless nickel plating, and PTFE particles are uniformly deposited in the formed film. Combines the characteristics of electroless nickel plating and PTFE resin.

  Examples of the coating using a polymer containing a fluorine atom or a silicon atom include, for example, a polymer having a fluorine-containing cyclic structure, a copolymer of fluoroolefin and vinyl ether, a photopolymerizable fluororesin composition, and the like. It may be applied to the surface of the layer, or may be coated on the entire surface by sputtering a fluorine atom-containing polymer on the surface of the protective layer.

  Of these, fluorine lubrication plating is preferable from the viewpoint of adhesion to the lower plating layer, durability, and the like. The fluorine lubrication plating or fluororesin coating may be performed after forming the protective layer, or a layer formed by fluorine lubrication plating or the like may be used as it is.

  The film thickness of the surface layer formed by the surface coating is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.3 μm or more and 3 μm or less.

(Magnetic latent image forming means)
The magnetic latent image forming device (magnetic latent image forming means) 13 includes a magnetic head 12 and its drive circuit (not shown). The magnetic head 12 mainly includes a full-line type magnetic head and a multi-channel type magnetic head. In the case of a full-line type magnetic head, it is not necessary to scan the magnetic head 12, but in the case of a multi-channel type magnetic head, It is necessary to scan the magnetic head 12 with respect to the magnetic drum 11. The scanning method includes serial scanning and helical scanning. In the helical scanning, the recording speed can be increased by changing the rotation speed of the magnetic drum 11 only in the latent image forming process.

  On the other hand, in the case of a full-line magnetic head, for example, if the resolution is 600 dpi, a head of about 500 channels is required to cover the recording width in the width direction of A4 size paper. If they are arranged side by side to form a full line, it is not necessary to scan the head, and extremely high-speed recording becomes possible. In order to achieve the above full line, it is necessary to superimpose the head core and the head core. However, as the resolution is increased, the track pitch becomes narrower. A sheet coil is used.

  Here, leakage magnetic flux is generated from the magnetic pole tip of the magnetic head 12 to magnetize the magnetic drum 11 and form a magnetic latent image. The output from the magnetic head 12 is output from the magnetic recording layer of the magnetic drum 11. It is necessary to be not less than 2 times and not more than 3 times the coercivity. The magnetic latent image formed here does not disappear unless erased by the demagnetizer 18 and has a function of copying a large number of sheets by repeating the steps of development, transfer, fixing, and cleaning. In addition, since the magnetic latent image is less susceptible to humidity, it has better environmental stability than the electrostatic type.

(Developer)
As described above, the developing device 14 includes the developer storage unit 20 and the developer holding unit 22.

  The developer storage unit 20 includes a developer storage tank 21. A liquid developer 26 containing magnetic toner 24 and aqueous medium 23 is stored in the developer storage tank 21. In addition, it is desirable that a stirring member 25 is disposed at a corner in the developer storage tank 21. As the stirring member 25 continues to stir the liquid developer 26 at a predetermined rotation speed, variations in the density of the magnetic toner 24 in the liquid developer 26 are reduced.

  The developer storage tank 21 may have a configuration in which a toner concentration detection device (not shown) is provided. This toner concentration detection device is connected to a control device (not shown) and may be configured so that the toner concentration of the liquid developer 26 is managed within a predetermined range.

  The developer holding unit 22 includes a cylindrical magnetic roll 22A that is rotatably provided, a developing sleeve 22B that is provided on the outer periphery of the magnetic roll 22A so that the rotation axis is coaxial with the magnetic roll 22A, and the like. The magnetic roll 22A and the drive unit 22C for rotationally driving the magnetic roll 22A are included.

  On the other hand, the magnetic roll 22A provided in the developer holding unit 22 is provided so as to be rotatable in the circumferential direction around the rotation axis, and a plurality of S poles and N poles are circumferentially provided on the surface of the magnetic roll 22A. Are arranged alternately.

  For example, when adjacent magnets have the same polarity, magnetic force lines are formed in a direction away from the magnetic roll 22A in areas where they repel each other, and the magnetic toner 24 does not adhere to the developing sleeve 22B. However, by making adjacent magnets different from each other, magnetic lines of force are formed so as to exit from the N pole of the magnetic roll 22A and return to the S pole, so that the magnetic toner 24 is spread over the outer circumference of the magnetic roll 22A over a larger area. Is adsorbed to the developing sleeve 22B.

  The developing sleeve 22B is a cylindrical and non-magnetic member provided on the outer periphery of the magnetic roll 22A so that the rotation axis is coaxial with the magnetic roll 22A. It is rotated in the opposite direction.

  The developing sleeve 22 </ b> B is provided such that a part of the outer periphery is immersed in the liquid developer 26 stored in the developer storage tank 21. In the present embodiment, the part of the outer periphery of the developing sleeve 22B is a part of the entire outer surface of the cylindrical developing sleeve 22B in the circumferential direction and from one end to the other end in the rotation axis direction. It shows the crossing area.

  Due to the developing magnetic field formed on the developing sleeve 22B by the magnetic roll 22A, the magnetic toner 24 in the liquid developer 26 stored in the developer storage tank 21 is magnetized and reaches the developing sleeve 22B. The liquid developer 26 is adsorbed on 22B. The liquid developer 26 adsorbed on the developing sleeve 22B is held on the developing sleeve 22B by its surface tension, moves with the rotation of the developing sleeve 22B, and reaches the developing region 30.

  Here, in the developer holding part 22 of the developing device 14 of the present embodiment, the magnetic roll 22A and the developing sleeve 22B are coaxially rotated in the opposite direction. For example, as shown in FIG. 1, the magnetic roll 22A is rotated in the direction of arrow B in FIG. 1, and the developing sleeve 22B is rotated in the direction of arrow C in FIG. Further, in the developing device 14 of the present embodiment, the magnetic developer 24 holds the liquid developer 26 dispersed in the aqueous medium 23 on the surface. For this reason, the liquid developer 26 held on the developing sleeve 22B by the magnetic force of the magnetic roll 22A accumulates in a region where a developing magnetic field is formed between the north and south poles of the magnetic roll 22A, and the liquid pool 26A. Is formed.

  Specifically, as shown in FIG. 1, the liquid developer 26 adsorbed on the developing sleeve 22B is held so as to exist between the magnetic poles of the magnetic roll 22A, and a magnetic force is applied to a region corresponding to the gap between the magnetic poles. As the magnetic toner 24 activated by the stagnation stays, a liquid reservoir 26A is formed in the developing region 30 which is a facing region between the developing sleeve 22B and the magnetic drum 11, and is formed by the liquid developer 26. Become.

  For this reason, compared to the case where the magnetic roll 22A and the developing sleeve 22B rotate in the same direction, or the mechanism in which the magnetic roll 22A does not rotate and only the developing sleeve 22B rotates, the liquid development accumulated in the developing region 30 is increased. The amount of the agent 26 increases. For this reason, the magnetic roll 22A and the developing sleeve 22B are provided with a liquid reservoir 26A of the liquid developer 26 containing a sufficient amount of magnetic toner 24 for developing the magnetic latent image portion 34 on the surface of the magnetic drum 11. 30.

  From the viewpoint of forming the liquid pool 26A in the same region in the circumferential direction of the developing sleeve 22B, it is desirable that the angular velocities in rotation of the magnetic roll 22A and the developing sleeve 22B are the same.

  In order to rotate the magnetic roll 22A and the developing sleeve 22B so that the magnetic roll 22A and the developing sleeve 22B are rotated in the opposite directions, the magnetic roll 22A and the developing sleeve 22B are illustrated by the driving unit 22C. This is realized by controlling the omitted driving mechanism. Similarly, in order to adjust each of the magnetic roll 22A and the developing sleeve 22B so that the angular velocities in the rotation of the magnetic roll 22A and the developing sleeve 22B are the same, the magnetic roll 22A and the developing sleeve 22B are driven by the driving unit 22C. What is necessary is just to control the drive mechanism which abbreviate | omits each illustration.

(Liquid developer)
As shown in FIG. 1, in the present embodiment, a liquid developer 26 in which a magnetic toner 24 is dispersed in an aqueous medium is used as a developer for magnetic development. Is a solvent containing 50% by mass or more. “Water” means purified water such as distilled water, ion exchange water, ultrapure water, and the like.

  In so-called liquid magnetography using the liquid developer 26, since the toner image on the image carrier immediately after development usually contains a large amount of excess developer, the toner image is transferred to a recording medium such as paper. In some cases, it is necessary to previously provide a drying step to remove excess developer.

  However, in the present embodiment, since an aqueous medium is used as a dispersion medium in the liquid developer 26, water has a large surface tension due to hydrogen bonding. Therefore, in combination with the water-repellent magnetic drum 11, liquid development can be performed. Even if the agent 26 comes into contact with the magnetic drum 11, the liquid as the dispersion medium is difficult to transfer to the magnetic drum 11, and the toner image can be transferred to the paper 40 without leaving the liquid on the magnetic drum 11. Therefore, a squeeze roll or the like for removing the residual solvent on the magnetic drum 11 is not necessary, and the paper 40 on which the toner image is transferred hardly needs to be dried.

  Further, during development, an aqueous medium having a large surface tension hardly wets and spreads on the surface of the magnetic drum 11, while the magnetic toner 24 having high mobility and uniformly dispersed in the developer is Simultaneously with the contact with the magnetic drum 11, only the magnetic latent image portion 34 is transferred by magnetic force, so that a developing environment in which image fog hardly occurs is created.

  In the present specification, “uniform” with respect to the dispersion and the like means that there is no aggregate having a size such that more than ten primary particles such as magnetic powder and polymer particles are collected in the system. . The same applies to the following.

  The image forming process applied to the present embodiment includes a so-called electrophotographic process, a process of forming an electrostatic latent image with ions or the like (ionography) on a dielectric, and image information by heat of a thermal head on a charged dielectric. It is a process that forms a toner image by forming a magnetic latent image on an image carrier, not using an electrostatic latent image, such as a process of forming an electrostatic latent image according to There is no particular limitation other than using a liquid developer containing an aqueous medium as an agent and an image carrier having water repellency as an image carrier.

  On the other hand, as the magnetic toner, magnetic polymer particles containing a magnetic powder in a polymer compound are generally used. The magnetic polymer particles are composed of magnetic powder dispersed particles in which magnetic powder is dispersed in a polymer.

-Polymer compound-
As the polymer compound, a resin conventionally used in a magnetic recording apparatus can be used. Specifically, homopolymers of styrene and its substituted products and copolymer resins thereof, copolymer resins of styrene and (meth) acrylate, styrene and (meth) acrylate and other vinyl series Multi-component copolymer resins with monomers, styrene copolymer resins of styrene and other vinyl monomers, and those obtained by crosslinking a part of each of the above resins can be used. Furthermore, polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate resin, polyester resin, epoxy resin, polyamide resin, polyolefin resin, silicone resin, polybutyral resin, polyvinyl alcohol resin, polyacrylic acid resin, phenol resin, aliphatic or finger ring Examples thereof include aromatic hydrocarbon resins, petroleum resins, styrene-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, wax resins, and the like, or a mixture thereof.

  As described above, the magnetic polymer particles as a magnetic toner are dispersed in an aqueous medium. However, uniform and stable dispersion of the magnetic polymer particles in an aqueous dispersion medium means that the polymer compound is hydrophobic. In addition, since the surface of the magnetic polymer particles has characteristics different from those of normal polymer particles, it may not be easily achieved with the configuration of normal polymer particles.

  In the present embodiment, from the above viewpoint, by using a polymer compound obtained by controlling the monomer species and composition constituting the polymer as described below, the magnetic polymer particles are excellent in the aqueous medium. Dispersibility is obtained, and better developability and the like are exhibited with respect to the magnetic latent image holding member having water repellency. Hereinafter, the structure of the high molecular compound used suitably for this embodiment is demonstrated.

  The polymer compound includes a polymer of an ethylenically unsaturated monomer, the ethylenically unsaturated monomer includes a monomer having a hydroxyl group and a hydrophobic monomer, and It is desirable to use those having a hydroxyl group content of 0.1 mmol / g or more and 5.0 mmol / g or less.

  The liquid developer in the present embodiment is configured by dispersing magnetic toner particles (magnetic polymer particles) in an aqueous medium as described above. Therefore, in order to obtain good dispersibility in the aqueous medium while maintaining a certain level of magnetic force as the magnetic toner particles, it is effective to have a hydroxyl group on the particle surface. For this purpose, it is desirable that the constituent components of the polymer constituting the particles have a hydroxyl group.

  The polymer of an ethylenically unsaturated monomer suitably used as the polymer compound in the present embodiment has a dispersibility in an aqueous medium depending on a copolymerization ratio of a hydrophilic monomer having a hydroxyl group and a hydrophobic monomer. From the viewpoint of the stability of the polymer particles and the relationship with the content of the magnetic powder contained in the polymer particles in a certain amount, the hydroxyl group amount of the polymer is set to the optimum range.

  Since the amount of hydroxyl group varies depending on the content of magnetic powder, it is defined as the amount of hydroxyl group of the polymer component excluding the magnetic powder, and is preferably 0.1 mmol / g or more and 5.0 mmol / g or less. 0.2 mmol / g or more and 4.0 mmol / g or less is more desirable, and 0.3 mmol / g or more and 3.0 mmol / g or less is more preferable.

  If the amount of hydroxyl groups is less than 0.1 mmol / g, the dispersibility of polymer particles in an aqueous medium may be deteriorated. If it exceeds 5.0 mmol / g, the swellability of the polymer particles in water increases and the operability may deteriorate.

  The amount of hydroxyl group can be determined by a general titration method. For example, a certain amount of a reagent such as pyridine solution of acetic anhydride is added to the above polymer, heated, hydrolyzed by adding water, separated into particles and supernatant by a centrifuge, and the supernatant is used as an indicator such as phenolphthalein. The amount of hydroxyl groups can be determined by titrating with an ethanolic potassium hydroxide solution or the like.

  The said ethylenically unsaturated monomer means the monomer which has ethylenically unsaturated groups, such as a vinyl group. The following hydrophilic monomer and hydrophobic monomer are both included in the ethylenically unsaturated monomer in this embodiment.

  Examples of the hydrophilic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, glycerin di (meth) acrylate, 1, Examples include 6-bis (3-acryloxy-2-hydroxypropyl) -hexyl ether, pentaerythritol tri (meth) acrylate, tris- (2-hydroxyethyl) isocyanurate (meth) acrylate, polyethylene glycol (meth) acrylate, and the like. be able to.

  In addition, the said (meth) acrylate is an expression showing an acrylate or a methacrylate here, and applies to this in the following.

  Among these, it is possible to use at least one selected from 2-hydroxyethyl (meth) acrylate and polyethylene glycol (meth) acrylate, to control the copolymerization ratio with the hydrophobic monomer described later, and to control the polymerization reaction From the viewpoint of properties and the like.

  Moreover, it is desirable that the magnetic polymer particles of this embodiment have a carboxyl group in addition to the hydroxyl group in the polymer. In this case, it is desirable to use a monomer having a carboxyl group as the ethylenically unsaturated monomer.

  Examples of the monomer having a carboxyl group used in the present embodiment include acrylic acid, methacrylic acid, methacryloyloxyethyl monophthalate, methacryloyloxyethyl monohexahydrophthalate, methacryloyloxyethyl monomaleate, and methacryloyloxyethyl monosuccinate. And so on.

  Among these, it is preferable to use methacryloyloxyethyl monophthalate from the viewpoints of control of the copolymerization ratio with the hydrophobic monomer described later, dispersion of magnetic powder in the polymer particles, controllability of the polymerization reaction, and the like. .

  Examples of the hydrophobic ethylenically unsaturated monomer include aromatic vinyl monomers such as styrene and α-methylstyrene; alkyl having 1 to 18 carbon atoms (more preferably 2 to 16 carbon atoms). (Meth) acrylic acid alkyl ester having a group or an aralkyl group (for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, etc.); (meth) acrylic acid alkoxyalkyl ester having an alkylene group having 1 to 12 carbon atoms (more preferably 2 to 10 carbon atoms) (for example, , Methoxymethyl (meth) acrylate, methoxy Til (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, ethoxybutyl (meth) acrylate, n-butoxymethyl (meth) acrylate, n-butoxyethyl (meth) acrylate, etc.); amino group-containing (Meth) acrylic acid esters (for example, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, etc.); acrylonitrile, ethylene, vinyl chloride, vinyl acetate and the like can be mentioned.

  Among these, styrene, methyl (meth) acrylate, butyl (meth) acrylate 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, ethoxybutyl (meth) acrylate, benzyl (meth) acrylate, diethylaminoethyl (meth) acrylate Further, styrene, methyl (meth) acrylate, and butyl (meth) acrylate are particularly preferable.

  The content of the hydrophobic monomer copolymerizable with the hydrophilic monomer is preferably 1% by mass or more and 99% by mass or less, and preferably 5% by mass or more and 95% by mass in all monomer components. More preferably, it is as follows. In particular, when using a monomer having a carboxyl group such as methacryloxyethyl monophthalate in addition to the monomer having a hydroxyl group as an ethylenically unsaturated monomer, the content of the hydrophobic monomer is Of all the monomer components, the content is preferably 20% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 90% by mass or less.

  When the content is less than 1% by mass, the amount of hydroxyl groups in the polymer becomes too large, and there are cases where uniform polymerization cannot be performed during the production of the polymer. Sexual effects may not be obtained.

  As the other monomer, a reactive mixture (containing the ethylenically unsaturated monomer and the like) dispersed in an aqueous medium described later can be mixed with a crosslinking agent as necessary. By adding a crosslinking agent to the monomer mixture, aggregation during polymerization is suppressed, and dispersion stability is ensured.

  As the crosslinking agent to be used, a known crosslinking agent can be selected and used. Examples of suitable crosslinking agents include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, methylene bis (meth) acrylamide, Examples thereof include glycidyl (meth) acrylate and 2-([1′-methylpropylideneamino] carboxyamino) ethyl methacrylate. Among these, divinylbenzene, ethylene glycol di (meth) acrylate, and diethylene glycol di (meth) acrylate are more preferable, and divinylbenzene is particularly preferable.

  Further, the polymer compound in the present embodiment can contain a non-crosslinked resin from the viewpoint of improving the fixability. The non-crosslinked resin is not particularly limited as long as it is a polymer that fixes particles on a medium to be fixed such as paper, film by external energy such as heat, ultraviolet rays, and electron beams, solvent vapor, solvent volatilization from the polymer, and the like. .

  Specifically, for example, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Examples of homopolymers or copolymers include: vinyl ethers such as methyl ether, vinyl ethyl ether, and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone; .

-Magnetic powder-
On the other hand, as the magnetic powder, magnetite, ferrite or the like represented by a general formula of MO · Fe ₂ O ₃ or M · Fe ₂ O ₄ exhibiting magnetism can be preferably used. Here, M is a divalent or monovalent metal ion (Mn, Fe, Ni, Co, Cu, Mg, Zn, Cd, Li, etc.), and M can be a single metal or a plurality of metals. Examples thereof include iron-based oxides such as magnetite, γ iron oxide, Mn—Zn-based ferrite, Ni—Zn-based ferrite, Mn—Mg-based ferrite, Li-based ferrite, and Cu—Zn-based ferrite. Among these, inexpensive magnetite can be used more preferably.

Other metal oxides include Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, and Sn. Nonmagnetic metal oxides using a single metal or a plurality of metals such as Ba, Pb, and the like, and metal oxides exhibiting the above magnetism can be used. For example, as non-magnetic metal oxides, Al ₂ O ₃ , SiO ₂ , CaO, TiO ₂ , V ₂ O ₅ , CrO ₂ , MnO ₂ , Fe ₂ O ₃ , CoO, NiO, CuO, ZnO, SrO, Y ₂ O ₃ , ZrO _{2 and the} like can be used.

  The average primary particle size of the magnetic powder before the hydrophobization treatment described later is preferably in the range of 0.02 μm to 2.0 μm. If the average primary particle diameter of the magnetic powder is not within the above range, the magnetic powder tends to aggregate and it may be difficult to uniformly disperse it in the polymerizable monomer.

  The surface of the magnetic powder is preferably subjected to a hydrophobic treatment. The method for the hydrophobizing treatment is not particularly limited, and can be performed by coating the surface of the magnetic powder with a hydrophobizing agent such as various coupling agents, silicone oils, and resins. It is preferable to perform a surface coating treatment with an agent.

  Since the surface of the magnetic powder is basically hydrophilic, the affinity for the hydrophobic monomer can be increased by carrying out a hydrophobizing treatment. As the compatibility of the monomers improves, the dispersion uniformity in the magnetic powder particles can be improved.

  The content of the magnetic powder is determined by the required magnetic force, but in the present embodiment, it is preferably 2% by mass or more and 50% by mass or less based on the total amount of the magnetic polymer particle constituent components. It is more preferable that the content is not less than 30% by mass and not more than 30% by mass. By setting the content in the above range, a sufficient magnetic force can be obtained, and the dispersion stability of the polymer particles in an aqueous medium can be enhanced.

-Other ingredients-
The magnetic polymer particles of the present embodiment can further contain a dye for the purpose of coloring the polymer, an organic pigment, carbon black, titanium oxide, and the like. In that case, each of the additives can be directly mixed in a mixture of the monomer and the like in which the magnetic powder is dispersed. For example, when mixing a pigment such as an organic pigment, carbon black, or titanium oxide. For example, it is desirable that the non-crosslinked resin is mixed and dispersed in advance by a known method such as a roll mill, a kneader, or an extruder, and this is mixed with a mixture of the polymerizable monomer or the like.

  As a method for producing magnetic polymer particles containing the above monomers, etc., for example, first, the ethylenically unsaturated monomer, the polymerization initiator and other necessary components are mixed to prepare monomers, etc. A mixed solution is prepared. The mixing method is not particularly limited.

  Moreover, a well-known method is applicable to dispersion | distribution of the magnetic powder to the said liquid mixture. That is, for example, a dispersing machine such as a ball mill, a sand mill, an attritor, or a roll mill can be used. In the case where the monomer component is separately polymerized in advance and the magnetic powder is dispersed in the obtained polymer, a kneader such as a roll mill, a kneader, a Banbury mixer, or an extruder can be used.

  In order to obtain magnetic polymer particles suitably used in the present embodiment, a known method can be used. For example, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, a seed polymerization method and the like are preferably used. Furthermore, suspension polymerization can be performed using an emulsification method known as a membrane emulsification method.

  The magnetic polymer particles thus obtained preferably have a number average particle size of 0.1 μm or more and 20 μm or less, and more preferably 1.0 μm or more and 8.0 μm or less. If the number average particle size is less than 0.5 μm, the particle size may be too small to be handled, and if it exceeds 5 μm, high image quality may not be obtained when used as an image forming material.

  Moreover, when the said high molecular compound has a carboxyl group, it is desirable that the amount of carboxyl groups is 0.005 mmol / g or more and 0.5 mmol / g or less. When the amount of carboxyl groups is in the above range, even if the number of functional groups is smaller than that of hydroxyl groups, good dispersibility in an aqueous medium and swelling suppression effect can be obtained, with respect to fluctuations when other functional groups are present. Can maintain these characteristics.

  The amount of carboxyl groups is more preferably 0.008 mmol / g or more and 0.3 mmol / g or less, and further preferably 0.01 mmol / g or more and 0.1 mmol / g or less.

  The amount of the carboxyl group can be determined by a general titration method. For example, a neutralization reaction is carried out by adding a reagent such as an ethanol solution of potassium hydroxide to the above polymer compound, and the supernatant containing excess potassium hydroxide is automatically titrated by separating it into particles and supernatant using a centrifuge. The amount of the carboxyl group can be determined by titrating with an isopropanol hydrochloric acid solution or the like.

  The liquid developer in the present embodiment is a particle dispersion in which the magnetic polymer particles are dispersed in an aqueous medium such as water.

  As the aqueous medium, water or water added with a water-soluble organic solvent such as methanol or ethanol is suitably used. Among these, water alone is particularly preferable. The amount of water-soluble organic solvent added is preferably 30% by mass or less, more preferably 10% by mass or less based on the total amount of the solvent, although it depends on the properties of the suspended monomer.

  In the production of a liquid developer, various auxiliary materials that can be used in ordinary aqueous particle dispersions, such as dispersants, emulsifiers, surfactants, stabilizers, wetting agents, thickeners, foaming agents. Antifoaming agent, coagulant, gelling agent, anti-settling agent, charge control agent, antistatic agent, anti-aging agent, softening agent, plasticizer, filler, coloring agent, flavoring agent, anti-adhesive agent, mold release An agent or the like may be used in combination.

  Specifically, as the surfactant, any known surfactant such as an anionic surfactant, a nonionic surfactant, and a cationic surfactant can be used. In addition, silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, oxyethylene perfluoroalkyl ethers; splicrisporic acid and rhamnolipid, And biosurfactants such as lysolecithin.

  As the dispersant, any polymer having a hydrophilic structure portion and a hydrophobic structure portion can be used effectively. For example, styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer. Polymer, vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester -Acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer, etc., and these copolymers are random, block and graft copolymer Coalescence It may be in any of the structure.

  In the present embodiment, a water-soluble organic solvent can be used for the purpose of controlling evaporation and interface characteristics. The water-soluble organic solvent is an organic solvent that does not separate into two phases when added to water, and examples thereof include mono- or polyhydric alcohols, nitrogen-containing solvents, sulfur-containing solvents, and other derivatives thereof.

  Furthermore, for the purpose of adjusting the conductivity and pH of the ink in an aqueous medium, compounds of alkali metals such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine, Nitrogen-containing compounds such as 2-amino-2-methyl-1-propanol, alkaline earth metal compounds such as calcium hydroxide, acids such as sulfuric acid, hydrochloric acid and nitric acid, strong acid and weak alkali salts such as ammonium sulfate, etc. Addition is possible.

  In addition, benzoic acid, dichlorophen, hexachlorophene, sorbic acid, and the like may be added as necessary for the purpose of mold prevention, antiseptic, rust prevention, and the like. Moreover, you may add antioxidant, a viscosity modifier, a electrically conductive agent, a ultraviolet absorber, a chelating agent, etc.

  In this embodiment, the dispersed particle diameter of the magnetic polymer particles in the liquid developer is preferably 0.1 μm or more and 20 μm or less in terms of average particle diameter, and is preferably in the range of 1 μm or more and 8 μm or less. The dispersion average particle size of the magnetic polymer particles is a volume average particle size determined by Coulter Counter Multisizer 3 (Beckman Coulter, Inc.).

  When magnetic polymer particles suitably designed for the present embodiment are used as the magnetic toner in the liquid developer, the magnetic powder is uniformly dispersed in the particles as described above. There is almost no magnetic powder on the particle surface. Moreover, since it has a hydroxyl group on the particle surface, it exhibits good dispersibility in an aqueous medium.

  For this reason, when the above liquid developer is used, there is no variation in micro surface tension in the liquid, and the mobility of the particles with respect to the magnetic force during development is small among the particles. Adhesion of liquid on the magnetic drum after development based on the water repellency of the surface and occurrence of image fog are more efficiently reduced.

  The liquid developer can be manufactured by the following procedure, but is not limited thereto.

  First, a dispersion medium containing water as a main solvent and the respective additives is prepared using a magnetic stirrer or the like, and the magnetic polymer particles are dispersed in the dispersion medium. A known method can be applied to the dispersion. That is, a dispersing machine such as a ball mill, a sand mill, an attritor, or a roll mill can be used. Further, as a mixer, a method of rotating a special stirring blade at high speed to disperse, a method of dispersing by the shearing force of a rotor / stator known as a homogenizer, a method of dispersing by ultrasonic waves, and the like can be mentioned.

  It was confirmed by microscopic observation of the dispersion liquid that the magnetic polymer particles were in a single dispersion state in the liquid, and then it was confirmed that the additive was dissolved by adding additives such as preservatives. Thereafter, the obtained dispersion liquid is filtered using, for example, a membrane filter having a pore diameter of 100 μm, and dust and coarse particles are removed to obtain a liquid developer as an image forming recording liquid.

  The viscosity of the liquid developer in the exemplary embodiment is preferably 1 mPa · s or more and 500 mPa · s or less, although it depends on the image forming system used. When the viscosity of the liquid developer is less than 1 mPa · s, a sufficient image density may not be obtained because the amount of the magnetic polymer particles and the amount of the additive are not sufficient. On the other hand, when the viscosity of the liquid developer is greater than 500 mPa · s, handling may be difficult or developability may be deteriorated because the viscosity is too high.

(Transfer device)
As the transfer method, there are generally an electrostatic transfer method, a pressure transfer method, and an electrostatic pressure method using both of them. However, as described above, in this embodiment, the toner particles do not have an electric charge. The transfer method and electrostatic pressure method cannot be used. On the other hand, the pressure transfer system usually transfers and attaches a toner image to the surface of the transfer medium while being plastically deformed by the pressure between the magnetic drum 11 and the transfer medium, and can be used in combination with shearing transfer.

  On the opposite side of the developing device 14 across the magnetic drum 11 in FIG. 1, a transfer fixing roll 38 is disposed so as to form a nip with respect to the magnetic drum 11, and timing is applied to the toner image 28 on the magnetic drum 11. In addition, the paper 40 is fed to the nip between the magnetic drum 11 and the transfer fixing roll 38.

  The transfer fixing roll 38 is made of, for example, a stainless steel substrate, a silicone rubber layer, and a fluororubber layer. By pressing the paper 40 that passes through the nip against the magnetic drum 11, the toner image on the magnetic drum 11 is transferred to the paper 40. Is transcribed.

  In this embodiment, the toner image 28 is transferred from the magnetic drum 11 to the paper 40, and at the same time, the toner image 28 is fixed to the paper 40. That is, when the paper 40 passes through the nip region between the transfer fixing roll 38 and the magnetic drum 11, the paper 40 is pressed from the magnetic drum 11 by the transfer fixing roll 38, and the toner image is transferred to the paper 40. The toner particles constituting the toner image soften and infiltrate into the fibers of the paper 40.

  Depending on the toner particles to be used, the toner can be fixed to the paper 40 even in this state. However, if the fixing is not sufficient, the transfer fixing roll 38 is provided with a heating means, and the transfer fixing roll 38 is heated to thereby fix the toner. The image melts and enters into the fibers of the paper 40 and is fixed to form a fixed image 41. In this state, the fixed image 41 does not peel off even if the paper 40 is bent or peeled off after the adhesive tape is applied.

  In this embodiment, the fixing is performed simultaneously with the transfer to the paper 40. However, the transfer process and the fixing process may be performed separately, and the fixing may be performed after the transfer.

(Demagnetizer)
There are two types of demagnetizers, a permanent magnet type and an electromagnet type. In the case of the permanent magnet type, it is magnetized in the circumferential direction of the magnetic drum 11 so that the magnetic flux does not leak locally, and energy such as electric power is unnecessary and inexpensive. However, when the magnetic latent image is not erased, it is necessary to move the degaussing device 18 relative to the magnetic drum 11 to increase the magnetic distance and weaken the erasing magnetic field.

  On the other hand, the electromagnet type is composed of a yoke and a coil, and it is necessary to pass a current. However, when it is not necessary to erase the magnetic latent image, the erasing magnetic field becomes zero by turning off the current, so that the control is relatively easy. Be free.

  In the present embodiment, both the permanent magnet type and the electromagnet type can be used.

(Action / Effect)
First, the operation of the image forming apparatus 10 will be briefly described.

  A magnetic head 12 shown in FIG. 1 is connected to an information device (not shown), for example, and receives binarized image data sent from the information device. The magnetic head 12 forms a magnetic latent image portion 34 on the magnetic drum 11 by emitting lines of magnetic force while scanning the side surface of the magnetic drum 11. In FIG. 1, the magnetic latent image portion 34 is indicated by a hatched portion in the magnetic drum 11.

  Next, in the developing device 14, the magnetic roll 22A and the developing sleeve 22B rotate in the opposite directions as described above, whereby the liquid reservoir 26A of the liquid developer 26 held on the developing sleeve 22B is transferred to the developing region 30. The magnetic toner 24 in the liquid developer 26 is supplied to the magnetic latent image portion 34 on the magnetic drum 11 when the outer periphery of the magnetic drum 11 contacts and passes through the liquid reservoir 26A. As a result, the magnetic latent image portion 34 is visualized and becomes a toner image 28.

  The developed toner image 28 is conveyed by the magnetic drum 11 rotating in the circumferential direction (the direction of arrow A in FIG. 1), transferred to the paper 40 at the contact position with the transfer fixing roll 38, and fixed at the same time.

  On the other hand, when a new image is formed, the demagnetizer 18 erases the magnetic latent image portion 34 formed on the magnetic drum 11. The degaussing device 18 returns the magnetic drum 11 to a state in which there is no variation in the magnetization state of the magnetic layer before image formation.

  By repeating the above operation, images successively sent from the information device are continuously formed in a short time. The magnetic head 12, the developing device 14, the transfer fixing roll 38, and the demagnetizing device 18 provided in the image forming apparatus 10 all operate in synchronization with the rotational speed of the magnetic drum 11.

  The rotating direction of the magnetic drum 11 is preferably opposite to the developing sleeve 22B for the reason of stable supply of magnetic toner.

  Further, it has been described above that the angular velocity of the magnetic roll 22A and the developing sleeve 22B is preferably the same, but the angular velocity of the magnetic roll 22A and the developing sleeve 22B and the magnetic drum 11 may be the same. And it may be different. In the case of the developing device 14 having the configuration of the present embodiment, a liquid pool 26A is formed in the developing region 30 as described above. For this reason, even when the angular velocity of the magnetic drum 11 is larger than the angular velocity of the magnetic roll 22A and the developing sleeve 22B, the liquid developer 26 containing a sufficient amount of magnetic toner 24 for developing the magnetic latent image portion 34. Is held in the development area 30. For this reason, the magnetic drum 11 can be rotated at a high speed.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Magnetic drum 12 Magnetic head 14 Developing apparatus 15 Process cartridge 16 Transfer apparatus 18 Demagnetizing apparatus 20 Developer storage part 22 Developer holding part 22A Magnetic roll 22B Developing sleeve 22C Drive part 23 Aqueous medium 24 Magnetic toner 26 Liquid development Agent 34 Magnetic Latent Image Portion 38 Transfer Fixing Roll

Claims (8)

Developer storage means for storing a liquid developer containing magnetic toner and an aqueous medium;
A magnetic roll having a plurality of magnetic poles arranged in the circumferential direction, and a rotating shaft provided on the outer periphery of the magnetic roll so as to be coaxial with the rotating shaft of the magnetic roll, and the liquid developer The magnetic toner is supplied to a magnetic latent image holding body that is provided so that a part of the outer periphery is immersed and is rotated in the opposite direction to the magnetic roll to hold the liquid developer on the surface and the surface has water repellency. A developer holding means comprising: a developing sleeve;
A developing device comprising:   The developing device according to claim 1, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity. A magnetic latent image carrier having a water-repellent surface;
Developer storage means for storing a liquid developer containing magnetic toner and an aqueous medium;
A magnetic roll having a plurality of magnetic poles arranged in a circumferential direction, and a rotating shaft provided on an outer periphery of the magnetic roll so that a rotating shaft is coaxial with a rotating shaft of the magnetic roll, and the liquid developer A developing sleeve that is provided so that a part of the outer periphery is immersed and is rotated in a direction opposite to the magnetic roll to hold the liquid developer on the surface and supply the magnetic toner to the magnetic latent image holder; Developer holding means comprising:
A process cartridge comprising:   The process cartridge according to claim 3, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity.   The process cartridge according to claim 3 or 4, wherein a contact angle of the surface of the magnetic latent image holding member with pure water is 70 ° or more. A magnetic latent image carrier having a water-repellent surface;
Magnetic latent image forming means for forming a magnetic latent image on the magnetic latent image holding member;
Developer storage means for storing a liquid developer containing magnetic toner and an aqueous medium;
A magnetic roll having a plurality of magnetic poles arranged in the circumferential direction, and a rotating shaft provided on the outer periphery of the magnetic roll so as to be coaxial with the rotating shaft of the magnetic roll, and the liquid developer A developing sleeve provided so that a part of the outer periphery is immersed and rotated in the opposite direction to the magnetic roll to hold the liquid developer on the surface and supply the magnetic toner to the magnetic latent image holder; Developer holding means having
Transfer means for transferring a toner image corresponding to the magnetic latent image formed by supplying the liquid developer by the developer holding means to a recording medium;
A degaussing means for degaussing the magnetic latent image on the magnetic latent image holder;
An image forming apparatus comprising:   The image forming apparatus according to claim 6, wherein the magnetic roll and the developing sleeve are rotated at the same angular velocity.   The image forming apparatus according to claim 6 or 7, wherein a contact angle of the surface of the magnetic latent image holding member with pure water is 70 ° or more.

Images