JPH08262877A - Liquid developing device - Google Patents

Abstract

PURPOSE: To provide a liquid developing device which is reduced in the quantity of medium liquid mechanically stuck to a latent image carrier. CONSTITUTION: A voltage is applied between a developing roller 202 dipped in a liquid developer stored in a developing tank 208 and a thin layer forming electrode 201 provided on the top end of the developer tank 208, a thin layer of toner is formed on the developing roller 202 and the layer of the medium liquid in which the toner hardly exists is formed on the thin layer. Air is sucked from an air sucking port 212, the upper part of a liquid recovering tank 209 in a developing head 200 becomes an evacuated state and the flow of the air at a high speed is generated in a part (liquid draining part) (g) where the top end of a cover 214 provided in the upper part of the developing head 200 faces the developing roller 202. A liquid developer layer is carried to the liquid draining part, (g) by the rotation of the roller 202 and a part of the medium liquid top layer is scraped by the flow of the air generated in the liquid draining part (g). After the liquid developer passes through the liquid draining part (g), the liquid developer comes into contact with the surface of a photoreceptor drum 1, to develop an electrostatic latent image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus for developing an electrostatic latent image carried on a latent image carrier with a liquid developer.

[0002]

2. Description of the Related Art An electrophotographic method, which is an image forming method for developing an electrostatic latent image formed on a latent image bearing member such as a photoconductor with a charged toner, is roughly classified into powder toner. There are a dry developing method used directly and a wet developing method using a liquid developer in which a toner is dispersed in a medium liquid.

Among them, the wet developing method is to develop an electrostatic latent image on the photosensitive surface by bringing a liquid developer into contact with the photosensitive surface. Usually, in the wet development method, a toner having a particle diameter smaller than that of the toner used in the dry development method is used, and therefore it is promising in terms of high image quality.

In the image forming apparatus equipped with the liquid developing device for developing by the wet developing method, it is inevitable that the medium liquid adheres to the latent image carrier together with the toner during the development. Normally, the image formed on the latent image carrier is transferred to a recording medium such as copy paper, but the recording medium is wetted by the medium liquid contained in the image at the time of transfer, so the recording medium Will need to be dried.

In order to reduce the load required for drying, a so-called squeeze mechanism for squeezing the medium liquid from the image formed on the surface of the latent image carrier is often provided near the latent image carrier. For example, a roller is provided facing the latent image carrier, and the roller is pressed against the image on the latent image carrier to squeeze the medium liquid from the image formed on the surface of the latent image carrier.

[0006]

However, as described above, the one that squeezes the medium liquid from the image formed on the surface of the latent image bearing member causes the image disturbance or the photoconductor which is the latent image bearing member. There was a risk of causing problems such as scratches. This problem was particularly noticeable when the amount of medium liquid to be squeezed out was large.

In order to prevent such a problem, the amount of the medium liquid in the liquid developer used for the development is reduced so that the amount of the medium liquid attached to the surface of the latent image carrier is reduced. Has been proposed, but the one with sufficient performance has not been obtained.

The present invention has been made in view of the above problems, and the amount of the medium liquid contained in the liquid developer carried by the developer carrying body carrying the liquid developer to the latent image carrying body is sufficient. It is an object of the present invention to provide a liquid developing device that can reduce the amount of the medium liquid that adheres to the latent image bearing member.

[0009]

In order to achieve the above object, the present invention provides a liquid developer in which charged toner is dispersed in a medium liquid at a developing position for an electrostatic latent image formed on the surface of a latent image carrier. In a liquid developing device that makes contact and develops, a developer transport body that transports the liquid developer from the developer supply position to the development position, and a supply unit that supplies the liquid developer to the developer transport body at the developer supply position, Electrodeposition means for electrodepositing toner particles in the liquid developer supplied by the supply means onto the developer transport body, and liquid on the developer transport body in a region between the developer supply position and the development position. And a regulation means for regulating the developer to a predetermined thickness.

[0010]

In the present invention, first, the supply means supplies the liquid developer to the developer transport body at the developer supply position.
Next, the toner particles contained in the supplied liquid developer are
It is electrodeposited on the developer transport body by the electrodeposition means. The developer transporter thus carries the liquid developer on its surface and transports it toward the developing position. The liquid developer on the developer transport body is regulated to have a predetermined thickness by the regulation means in a region between the developer supply position and the development position. Then, at the developing position, the liquid developer comes into contact with the latent image carrier to develop the electrostatic latent image on the latent image carrier.

[0011]

The present invention will be described in detail below with reference to examples. <Apparatus Configuration> FIG. 1 is a sectional view of an electrophotographic printer 100 incorporating a liquid developing apparatus to which the present invention is applied. As shown in FIG. 1, inside the printer 100, a cylindrical photosensitive drum 1 on which an electrostatic latent image is formed.
Is rotatably provided in the direction of arrow a shown in the figure. Around the photosensitive drum 1, a laser generator 10 that generates a laser beam based on image data sent from a host computer (not shown), a liquid developing device 20 that is a process device for image formation, and a squeeze roller 2 , Transfer roller 4, cleaner 7, eraser lamp 8,
The charging charger 9 is sequentially arranged. Further, on the side portion of the printer 100, a paper storage cassette 11 having paper stored therein, a fixing device 5 for fixing a toner image formed on the paper, and a paper discharged from the inside of the printer are mounted. A paper discharge tray 12 to be placed is provided.

The printing operation of the printer 100 is performed as follows. The photosensitive drum 1 starts rotating at a predetermined speed in the direction of the arrow a, is uniformly charged by the charging charger 9, and is irradiated with a laser beam by the laser generator 10, so that the surface of the photosensitive drum 1 is electrostatically latent. An image is formed. This electrostatic latent image is visualized by the liquid developing device 20 using a liquid developer, and then the squeeze roller 2 squeezes out the excessively adhered medium liquid.

On the other hand, the paper feed roller 3 provided near the paper storage cassette 11 also starts to rotate, and the paper storage cassette 1
The paper is conveyed from 1 to the inside of the printer. Then, the timing roller 13 feeds the paper toward the facing portion of the photoconductor drum 1 and the transfer roller 4 in synchronization with the toner image formed on the photoconductor drum 1. The transfer roller 4 to which a reverse polarity voltage is applied transfers the toner image on the photosensitive drum 1 onto the sheet. The transfer-finished paper is dried by the fixing device 5, and the transferred toner image is fixed on the surface of the paper.
The sheet is discharged onto the sheet discharge tray 12 by the sheet discharge roller 6.

After the transfer of the toner image is completed on the photosensitive drum 1, the developer remaining on the surface is removed by the cleaner 7 in preparation for the next printing, and the electric charge remaining on the surface is removed by the eraser lamp 8. In this way, a series of printing operations is completed.

The liquid developing device 20, as shown in FIG.
A developer storage tank 23 for storing the liquid developer, a liquid supply device 21 for pumping the liquid developer in the developer storage tank 23, and a liquid developer supplied by the liquid supply device 21 facing the photoconductor drum 1. By the developing head 200 for developing the electrostatic latent image on the photosensitive drum 1, and the developing head 2
Liquid recovery device 22 and a residual liquid recovery device 24 for returning the liquid developer in 00 to the developer storage tank 23, and a part of the liquid developer returned to the developer storage tank 23 by the liquid recovery device 22 for cleaning liquid. Cleaning liquid supply device 25 for supplying to the developing head 200 as a
And an air suction device 30 for sucking air in the inside. The liquid developer in the developing solution storage tank 23 is kept replenished with toner and medium liquid by a toner replenishing device (not shown) at a substantially constant toner concentration and liquid amount.

FIG. 2 is an enlarged view of the vicinity of the developing head 200. As shown in FIG. 2, the developing head 200 includes a developing roller 202 for supporting the liquid developer on its surface, a frame 206 for supporting the developing roller 202, and a developer tank 208 for storing the liquid developer. And developer tank 208
A liquid recovery tank 209 for collecting the liquid developer overflowing from the cleaning roller, a cleaning blade 205 for scraping off the liquid developer remaining on the developing roller 202, and a residue for recovering the liquid developer scraped off by the cleaning blade 205. The liquid recovery tank 213 includes an air suction port 212 that sucks air in the developing head 200, and a nozzle 211 that sprays the cleaning liquid onto the developing roller 202. The shaded area represents the liquid developer.

In the present embodiment, as will be described later, the air suction port 212 constitutes a part of the regulation means for regulating the liquid developer on the developing roller 202 to a predetermined thickness, and the air is suctioned from the air suction port 212. Then, a flow of air is generated along the developing roller 202, thereby regulating the thickness of the liquid developer.

The developing roller 202 is a columnar member made of a conductive material and is arranged parallel to the longitudinal direction of the photoconductor drum 1. The frame 206 allows the frame 206 to move in the direction of arrow b in FIG. It is supported rotatably in the same direction as the direction (arrow a) in which the photosensitive drum 1 rotates at a portion c facing the drum 1 (hereinafter referred to as a developing portion c).

The distance between the photosensitive drum 1 and the developing roller 202 in the developing section c (hereinafter referred to as the developing gap) is
It can be arbitrarily set within the range of 0 to 2 mm.

The developer tank 208 is provided below the developing roller 202. A liquid supply port 203 connected to the liquid supply device 21 shown in FIG. 1 is formed at the bottom of the developer tank 208, and when developing, liquid development from the liquid supply port 203 to the developer tank 208 is performed. The developer is supplied, and the lower portion of the developing roller 202 is dipped in the liquid developer in the developer tank 208 as shown in FIG.

A part of the upper end of the wall surface forming the developer tank 208 is an edge portion f adjacent to the lower portion of the developing roller 202 and extending parallel to the longitudinal direction of the developing roller. After the developer tank 208 is filled with the liquid developer, the excess liquid developer overflows from the edge portion f.

The inner wall surface of the developer tank 208 from the edge portion f to the portion facing the lowermost point of the developing roller 202 is a circumferential surface 201 which is kept at a predetermined distance from the developing roller 202. The circumferential surface 201 serves as an electrode (hereinafter referred to as a thin layer forming electrode) for adhering toner to the surface of the developing roller 202 by applying a voltage between the circumferential surface 201 and the developing roller 202.

The gap d between the thin layer forming electrode 201 and the developing roller 202 (hereinafter referred to as the thin layer forming portion d) is filled with the liquid developer, and then a voltage is applied, whereby When the charged toner particles move to the developing roller 202 side by receiving an electrostatic force, a thin layer of toner (a thin layer of extremely high-concentration liquid developer) is formed on the surface of the developing roller 202. A layer of medium liquid is formed on top of which there is almost no toner.

The voltage applied between the thin layer forming electrode 201 and the developing roller 202 may be direct current, direct current with alternating current superimposed, direct current with pulsed voltage superimposed, or the like. The DC component is 100 to 2000V, preferably 200 to 1500V. When the AC component is superimposed, the peak-to-peak voltage is 200 to 4000 V, preferably 400 to 3000 V, and the frequency is 10 to 10000 Hz.

The length of the thin layer forming portion d (arrow e in FIG. 2).
3) to 80 mm, preferably 5 to 50 mm
When set to 1, the toner transfer time required for forming a thin layer can be sufficiently taken, and a high-concentration liquid developer thin layer can be formed.

The distance between the thin layer forming electrode 201 and the developing roller 202 (hereinafter referred to as the thin layer forming gap) is 0.1 to 1.
When the thickness is set to 0 mm, preferably 0.3 to 3 mm, the liquid developer layer composed of the toner thin layer and the medium liquid layer can be formed while allowing the liquid developer to flow well to the thin layer forming portion d. it can.

The liquid recovery tank 209 is provided adjacent to the edge f, and the liquid developer flows from the developer tank 208 over the edge f into the liquid recovery tank 209. A liquid recovery port 204 connected to the liquid recovery device 22 shown in FIG. 1 is formed at the bottom of the liquid recovery tank 209.
The liquid developer that has flowed into the liquid developer 9 is recovered from the liquid recovery port 204 and returned to the developer storage tank 23 shown in FIG.

The air suction port 212 is provided above the liquid recovery tank 209 and is connected to the air suction device 30 shown in FIG. Further, a cover 214 is provided at the uppermost part of the frame 206 so as to face the liquid recovery tank 209. The cover 214 is a thick member extending from the frame 206 toward the developing roller 202, and its tip end portion is a circumferential surface along the developing roller 202.

The space above the liquid recovery tank 209 in the developing head 200 is covered by the cover 214, the developing roller 202 and the frame 206. Therefore, when air is sucked from the air suction port 212, a facing portion g between the circumferential surface and the developing roller 202 (hereinafter referred to as a liquid draining portion g).
High-speed air flow is generated. When the liquid developer carried on the surface of the developing roller 202 is conveyed to the liquid draining section g,
The upper layer is scraped off by the air flow described above,
The liquid developer on the developing roller 202 is regulated to have a predetermined thickness.

The distance between the circumferential surface and the developing roller 202 (hereinafter referred to as the liquid draining gap) is 0.1 mm to 5 m.
m, preferably 0.2 mm to 2 mm. If the drainage gap is less than 0.1 mm, high working precision is required to form the gap, and clogging due to agglomerated toner or the like may occur. If it exceeds 5 mm, the developer may not be sufficiently scraped off. The length of the drainage part g is 50 mm or less, preferably 20 mm or less. When the length of the liquid draining portion g exceeds 50 mm, the pressure loss is large and the effect of scraping off the developer may be insufficient as compared with the capacity of the air suction device. The flow rate of air flowing through the drainage part g is
0.5 cc / s to 2.5 liter / s, preferably 10
cc / s to 0.5 liter / s. Air flow rate is 0.
If it is less than 5 cc / s, the developer may not be sufficiently scraped off, and if it exceeds 2.5 liters / s, the electrodeposited toner layer may be scraped off.

The liquid draining portion g does not necessarily have to form a uniform gap, and for example, the inlet portion or the outlet portion may be widened.

As described above, in the present embodiment, since the liquid developer is scraped off by the air flow generated in the liquid draining portion g, clogging of the liquid draining portion g due to agglomerated toner or the like is prevented. Can be prevented. Further, since high precision is not required for forming the gap in the liquid draining portion g, there is an advantage that the device can be easily manufactured.

The residual liquid recovery tank 213 is provided on the opposite side of the liquid recovery tank 209 and adjacent to the developing solution tank 208. At the bottom of the residual liquid recovery tank 213, a residual liquid recovery port 210 connected to the residual liquid recovery device 24 shown in FIG. 1 is formed, and the liquid developer flowing into the residual liquid recovery tank 213 is recovered by this residual liquid recovery port 213. Mouth 2
It is collected from the cartridge 10 and returned to the developer storage tank 23 shown in FIG.

A partition plate 216 is attached to the upper end of the inner wall surface of the residual liquid recovery tank 213. The partition plate 216 extends upward to form a boundary between the developer tank 208 and the residual liquid collecting tank 213. The partition plate 216 does not necessarily completely prevent the flow of the liquid, and the amount of the liquid leaked from the residual liquid recovery tank 213 to the developer tank 208 is the liquid supply amount from the liquid supply port 203. It may be negligible compared to. Specifically, there is no problem if the ratio of the leak amount to the liquid supply amount is 1/10 or less, more preferably 1/30 or less.

The cleaning blade 205 is made of polyurethane rubber and is attached to the tip of the partition plate 216. The tip of the cleaning blade 205 is in contact with the surface of the developing roller 202 so as to face the surface of the developing roller 202 in the roller rotation direction, and scrapes off the liquid developer remaining on the developing roller 202. The liquid developer scraped off is guided to the residual liquid recovery tank 213 through the cleaning blade 205 and the partition plate 216.

When the developing roller 202 is made of a hard material such as metal or high hardness resin, the cleaning blade may be made of a flexible material such as a rubber blade. Particularly, a polyurethane rubber blade is preferable. When the developing roller is made of a soft material such as NBR (nitrile rubber) roller, the cleaning blade is a metal blade,
A resin blade, a ceramic blade or the like made of a hard material may be used.

The nozzle 211 is provided above the residual liquid recovery tank 213 and is connected to the cleaning liquid supply device 25 shown in FIG. The tip portion of the nozzle 211 extends in the longitudinal direction of the developing roller 202 and is provided with a plurality of ejection ports.

A cover 215 is provided above the nozzle 211 so as to trap the cleaning liquid ejected from the nozzle 211 and the liquid developer that has been wound up when the cleaning blade 205 scrapes the developer and prevent the liquid developer from being scattered outside. Is provided.

Next, the operation of the liquid developing device 20 will be described in detail. First, the liquid supply device 21 operates to supply the liquid developer from the liquid supply port 203 to the developer tank 208.
The liquid developer passes through the thin layer forming section d and the liquid recovery tank 209, is recovered from the liquid recovery port 204 by the liquid recovery device 22 into the developer storage tank 23, and then is again supplied to the liquid supply device 2.
1 to the developing head 200. Thus, the liquid developer circulates in the developing device 20 during development.

In the developing device 20, the liquid recovery device 22
The liquid recovery capability of the liquid supply device 21 is larger than the liquid supply capability of the liquid supply device 21. Therefore, as shown in FIG. 2, the liquid level of the liquid developer in the developing head 200 is set to the highest level at a position slightly above the edge f of the developer tank 208 (that is, the upper end of the thin layer forming electrode 201). It becomes almost constant.

On the other hand, the developing roller 202 also starts to rotate in the direction of arrow b. Further, a predetermined voltage is applied between the thin layer forming electrode 201 and the developing roller 202, and while the liquid developer passes through the thin layer forming portion d, the charged toner particles in the liquid developer are electrostatically charged. By receiving the force and moving to the developing roller 202 side, a thin layer of toner is formed on the surface of the developing roller 202, and a medium liquid layer containing almost no toner is further formed thereon.

The air suction device 30 is also started to suck air from the air suction port 212. As a result, the upper portion of the liquid recovery tank 209 inside the developing head 200 is maintained in a depressurized state, and a high-speed air flow toward the inside of the developing head 200 is generated in the liquid draining portion g.

When the liquid developer layer composed of the thin toner layer and the medium liquid layer is conveyed to the liquid draining portion g by the rotation of the developing roller 202, the air flow generated in the liquid draining portion g causes
The upper portion of the liquid developer on the developing roller 202, that is, the medium liquid layer is mainly scraped off. At the same time, the developing roller 2
The liquid developer on 02 is evened out. In this way, the medium liquid is removed from the liquid developer on the developing roller 202.

After passing through the liquid draining portion g, the liquid developer is further carried to the developing portion c by the rotation of the developing roller 202 and comes into contact with the surface of the photosensitive drum 1. Developing roller 202
A predetermined developing bias is applied to the electrostatic latent image on the photosensitive drum 1 by the Coulomb force of the toner due to the electric field generated by the electrostatic latent image on the photosensitive drum 1. Is developed.

After passing through the developing section c, the developing roller 202
The cleaning liquid is sprayed from the nozzle 211 to the nozzle. As a result, it is possible to prevent an unwiped portion from remaining on the developing roller 202 and prevent the rotation torque of the developing roller 202 from increasing.

After this, the developer remaining on the developing roller 202 is scraped off by the cleaning blade 205. It should be noted that the developer tank 2 is directly subjected to no special recovery process.
It may be soaked in the liquid developer in 08 and passed again through the thin layer forming portion d.

The liquid developer that has flowed into the residual liquid recovery tank 213 is recovered from the residual liquid recovery port 210 and returned to the developer storage tank 23 by the residual liquid recovery device 24.

When the development is completed in this way, the voltage application is stopped, and the liquid supply device 21, the liquid recovery device 22, and the developing roller 202 are stopped. Due to its own weight, the liquid developer in the developer tank 208 has a liquid supply port 203 and a liquid recovery port 2.
From 04, it immediately drops toward the developer storage tank 23.

Most preferably, the rotation speed of the developing roller 202 is substantially the same as the rotation speed of the photosensitive drum 1. In this case, since the shearing force does not act on the toner that is about to adhere to the photosensitive drum 1, the image disturbance can be minimized. If desired, the rotational speeds of the two may be different, and the developing roller 202 may be replaced by the photosensitive drum 1.
If the toner is rotated faster, the toner supply amount to the photoconductor drum 1 can be increased, and if the toner is rotated slower than the photoconductor drum 1, the toner supply amount to the photoconductor drum 1 can be decreased. Further, the developing roller 202 may be rotated at the portion facing the photosensitive drum 1 so as to be opposite to the rotating direction of the photosensitive drum 1. This way,
The amount of liquid adhering to the photoconductor drum 1 can be reduced.

The surface roughness of the developing roller 202 is a ten-point average roughness of 5 μm or less. By doing so, image disturbance due to non-uniform contact between the photosensitive drum 1 and the developing roller 202, destruction of the toner thin layer due to contact between the developing roller 202 and the thin layer forming electrode 201, and electric field in the developing portion c. It is possible to prevent uneven development due to unevenness, unevenness of the toner thin layer due to uneven electric field in the thin layer forming portion d, and cleaning unevenness due to the cleaning blade 205.
The ten-point average roughness is defined in JIS standard B0601.

As described above, in this embodiment, the thin layer forming electrode 201 is provided so as to form the facing portion of a predetermined length between the thin roller forming electrode 2 and the developing roller 202.
01 and the developing roller 202 are electro-deposited, a liquid developer layer composed of a thin layer of the liquid developer having a high toner concentration and a medium liquid layer containing almost no toner is formed on the developing roller 202. Can be formed. As a result, the medium liquid is effectively removed from the liquid developer layer carried on the surface of the developing roller 202 at the liquid draining portion g, and the amount of the medium liquid attached to the photosensitive drum 1 at the developing portion c is extremely reduced. Therefore, the load on the fixing device 5 can be greatly reduced, and the drying time of the paper can be shortened. Further, since the load on the squeeze roller 2 is greatly reduced, it is possible to prevent the image from being disturbed and the surface of the photosensitive drum 1 from being scratched, and the squeeze roller is not necessarily provided.

In this embodiment, an example in which electrodeposition is carried out using an electrode having a circumferential surface along the developing roller which is the developer carrier is shown, but the present invention is not limited to this. However, the configuration is not limited to this, and any configuration can be arbitrarily changed as long as the toner can be electrodeposited on the developer transport body.

The means for adhering the toner particles onto the developer carrier is not limited to the electrostatic force described above. For example, when the toner is magnetic, it is formed by the action of a magnetic field. It is also possible.

Next, a modified example will be described. The developing head 300 shown in FIG. 3 is an example in which a roller member is provided so as to face the developing roller, and the liquid developer is scraped by the roller member.

As shown in FIG. 3, in the direction of rotation of the developing roller 302 (direction of arrow b), upstream of the developing section c,
A diaphragm roller 318 is provided so as to face the developing roller 302. The squeeze roller 318 rotates in the direction of the arrow h shown in the figure, that is, in the portion opposite to the developing roller 302, in the direction opposite to the rotating direction of the developing roller 302 (the direction of the arrow b), the excess roller on the developing roller 302 is removed. Scrap the liquid developer.

The scraper 3 is adjacent to the squeezing roller 318.
19 is provided so that the developer adhering to the aperture roller 318 is removed and dropped into the liquid recovery tank 309 below. The thin layer forming electrode 301, the developing roller 302, the liquid supply port 303, the liquid recovery port 304, the cleaning blade 305, the frame 306, the developing solution tank 308, and the liquid recovery tank 3
09, residual liquid recovery port 310, nozzle 311, residual liquid recovery tank 3
13, the cover 315 and the partition plate 316 are the same as those shown in FIG.

The rotation speed of the squeezing roller 318 is preferably the same as or higher than that of the developing roller 302. Also,
The distance between the aperture roller 318 and the developing roller 302 is 10 to 10.
The thickness is 500 μm, preferably 40 to 300 μm. In the above embodiment, the rotation direction of the aperture roller is opposite to the liquid developer feed direction, but the roller rotation direction is the forward direction with respect to the liquid developer feed direction. It may be.

As described above, by using the roller member, it is possible to scrape a sufficient amount of liquid with a relatively simple structure.

The developing head 400 shown in FIG. 4 shows an example in which a plate member is provided so as to face the developing roller, and the liquid developer is scraped off by this plate member.

As shown in FIG. 4, a supporting member 414 is provided on the upstream side of the developing portion c with respect to the rotating direction of the developing roller 402 (direction of arrow b), and the blade 4 is mounted on this supporting member 414.
21 is provided. The blade 421 is opposed to the developing roller 402 with a predetermined gap, and the excess medium liquid is scraped from the liquid developer on the developing roller 402 by passing between the blade 421 and the developing roller 402. The distance between the blade 421 and the developing roller 402 is 10
To 300 μm, preferably 40 to 200 μm.

The thin layer forming electrode 401 and the developing roller 4
02, liquid supply port 403, liquid recovery port 404, cleaning blade 405, frame 406, developer tank 408, liquid recovery tank 409, residual liquid recovery port 410, nozzle 411, residual liquid recovery tank 413, cover 415 and partition plate 416. Is equivalent to that of FIG.

As described above, by using the blade, the thickness of the liquid developer on the developing roller can be regulated with an extremely simple structure.

The developing head 500 shown in FIG. 5 shows an example of removing the excess liquid on the developing roller by corona discharge. As shown in FIG. 5, a corona discharger 520 is provided on the upstream side of the photosensitive drum 1 with respect to the rotation direction of the developing roller 502 (direction of arrow b). Corona discharger 52
0 is for performing corona discharge having the same polarity as the electric charge of the toner. The surface layer of the medium liquid is charged by the corona discharge of the corona discharger 520, and the medium liquid moves to a position away from the portion facing the corona discharger 520 by electrical repulsion. In this way, the medium liquid is removed from the developing roller.

The thin layer forming electrode 501 and the developing roller 5
02, liquid supply port 503, liquid recovery port 504, cleaning blade 505, frame 506, developer tank 508, liquid recovery tank 509, residual liquid recovery port 510, nozzle 511, residual liquid recovery tank 513, cover 515 and partition plate 516. Is equivalent to that of FIG.

<Composition of Liquid Developer> The liquid developer used in the image forming apparatus of the present invention contains at least a medium liquid used as a medium liquid and toner particles. Further, in addition to this, a function-imparting agent such as a charge control agent, a dispersant, or a dispersion stabilizer may be contained.

The volume average particle diameter of the toner particles is 0.5 μm.
It is desirable to adjust to m to 5 μm. Further, it is desirable to adjust so that 80% by volume of the total amount of the toner particles exists within the range of ± 1 μm, preferably ± 0.5 μm of the volume average particle size. In the present invention, the volume average particle size and particle size distribution are measured by a particle size distribution measuring device (SALD-110
0: manufactured by Shimadzu Corporation).

As the toner particles, polymer fine particles obtained by a dry manufacturing method and a wet manufacturing method can be used. The dry manufacturing method includes dry grinding method, spray drying method and the like, and the wet manufacturing method means grinding method in solution, suspension polymerization method, emulsion polymerization method, non-aqueous dispersion polymerization method, seed polymerization method and It includes an emulsion dispersion granulation method and the like. In particular, it is preferable to use polymer fine particles prepared by an emulsion dispersion granulation method or a spray drying method in view of the number of kinds of resins used, the ease of adjusting the molecular weight, the resin blending property, the sharpness of the particle size distribution, and the like. The in-solution pulverization method is preferable from the viewpoint of inexpensively producing toner particles.

In the emulsification dispersion granulation method, a polymer solution obtained by dissolving a polymer in a non-water-soluble organic solvent is emulsified and dispersed in an aqueous dispersion to form an O / W type emulsion, and the O / W type emulsion is stirred while stirring. Polymer fine particles are produced by applying heat to an emulsion to evaporate an organic solvent and deposit polymer particles.

In the spray drying method, a polymer solution is prepared by dissolving a polymer in an organic solvent and dispersing components such as a colorant, and spraying the polymer solution from a nozzle to heat the solution to evaporate the organic solvent. To produce fine polymer particles.

When such polymer fine particles are used as toner particles of a liquid developer, the polymer fine particles are washed and dried, and if necessary, known additives such as a charge control agent, a dispersion aid and a resin are added. Then, it may be dispersed in an electrically insulating medium liquid using an ultrasonic disperser or the like.

As the resin constituting the polymer fine particles,
Resins such as polyester resin, styrene-acrylic copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polymethacrylic acid ester, polyacrylic acid ester, epoxy resin, polyethylene, polyurethane, polyamide, and paraffin wax are not particularly limited. These are used alone or as a blend.

If necessary, components such as a colorant, a charge control agent, an offset preventive agent may be added to the polymer fine particles.

As the colorant, various color pigments and dyes such as carbon black and phthalocyanine can be used, but it is not necessary to add them when the resin itself is colored.

As the medium liquid used in the liquid developer according to the present invention, an electrically insulating organic substance is used, and it may be in a state at room temperature as long as it is liquid at the time of development. For example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be used, but in view of harmlessness, odor, cost, etc., normal paraffin-based or isoparaffin-based It is desirable to use the above solvent.

Specifically, Isopar G, Isopar H, Isopar L, Isopar K (manufactured by Esso), Shellsol 71 (manufactured by Shell Petrochemical Co., Ltd.), IP Solvent 1620, IP Solvent 2028 (manufactured by Idemitsu Petrochemical Co., Ltd.) Is particularly preferably used. Waxes, paraffins, and the like can be used as substances that are solid at room temperature.

If necessary, a charge control agent, a dispersant, a dispersion stabilizer, etc. may be added to the medium liquid of the liquid developer according to the present invention.

As the charge control agent, known ones can be used. To charge the toner particles in a positive polarity, for example, a metal salt of a fatty acid such as stearic acid, a metal salt of a sulfosuccinate ester, or abietin is used. Examples thereof include metal salts of organic acids such as metal salts of acids, or soluble polymers such as alkyd resins that are adsorbed to particles. For negatively charged, for example, surfactants such as lecithin and nitrogen-containing compounds. Alternatively, a soluble polymer such as a polyamide resin that is adsorbed on the particles may be used. These charge control agents are contained in the medium liquid in an amount of 0.0001 to 10% by weight, preferably 0.001.
It is desirable to add about 3% by weight.

In addition to the above, a metal oxide such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , or ZnO may be added as a charge assistant in the same amount as the charge control agent.

As the dispersant and dispersion stabilizer for stabilizing the dispersion of toner particles in the liquid developer, the above-mentioned various surfactants and soluble polymers can be used.

Examples of the soluble polymer include, but are not limited to, polyolefin petroleum resin, linseed oil, polyalkylmethacrylate, and the like. Further, in order to enhance the affinity with polymer particles, methacrylic acid, acrylic resin, etc. A small amount of a monomer having a polar group such as acid or alkylaminoethyl methacrylate may be copolymerized. The soluble polymer is added in an amount of 0.01 to 20% by weight, preferably 0.1 to 10% by weight, with respect to the medium liquid, from the viewpoint of improving dispersibility and preventing the viscosity increase of the medium liquid by the addition thereof.
It is desirable to set the degree.

As the surface active agent, a natural surface active agent such as saponin, a nonionic surface active agent such as alkylene oxide type, glycerin type or glycidol type surfactant,
Examples thereof include anionic surfactants containing an acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group and phosphoric acid ester group.

In the liquid developer used in the present invention, the ratio of the total weight of solid components such as toner and dispersant (solid content ratio) to the total weight of the liquid developer is 1 to 90% by weight. The solid content ratio is preferably 2 to 50% by weight in order to reduce the total amount of the liquid developer used and to facilitate the handling.

Next, the composition of the liquid developer used in this embodiment will be specifically described. In the following, "part"
“Parts by weight” means “parts by weight”.

<Production Method of Toner A> 100 parts of a low molecular weight polyester resin (MW: 15000, Mn: 6000) was completely dissolved in methylene chloride so that the concentration became 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution.

The resin solution obtained as described above was added to a homomixer (made by Tokushu Kika Kogyo Co., Ltd.) in an aqueous dispersion of 1% of Metroze 65SH-50 (made by Shin-Etsu Chemical Co., Ltd.) and 1% of sodium lauryl sulfate. ) Was used to emulsify and disperse at 8,000 rpm for 30 minutes at room temperature to obtain an O / W type emulsion. Next, replace with 4 stirring blades
Methylene chloride was distilled off while stirring at 5 ° C. for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having a volume average particle diameter of 2 μm.

From the obtained aqueous suspension of fine polymer particles for toner, the solid content is taken out by a centrifuge, washed well with water, filtered, and dried to obtain fine polymer particles for toner having a volume average particle diameter of 2 μm. Got

<Manufacturing Method of Developer A> 80.0 parts of Toner A,
Lauryl methacrylate-methacrylic acid copolymer 2
6.7 parts and n-hexyltrimethoxysilane 13.
Liquid developer A was obtained by adding 3 parts to 880 parts of electrically insulating isoparaffin solvent IP solvent 1620 (manufactured by Idemitsu Petrochemical Co., Ltd.) and mixing and dispersing this for 20 minutes with an ultrasonic disperser. .

<Experimental Example> Using the electrophotographic printer 100 shown in FIGS. 1 and 2, the developer A is subjected to reversal development under the following conditions to obtain a good image. It is possible to sufficiently reduce the amount of medium liquid adhering to the surface of the photosensitive drum.

10 point average roughness of developing roller 2 μm developing gap 200 μm developing roller applied voltage +550 V thin layer forming gap 1 mm thin layer forming electrode applied voltage +1550 V (thin layer forming gap applied voltage 1000 V) liquid flow rate 200 cc / Min-The length of the developing area in the longitudinal direction of the developing roller 320 mm-Photoconductor rotation speed 20 cm / s-Development roller rotation speed 20 cm / s-Photoconductor surface potential of unexposed area +750 V-Photoconductor surface potential of exposed area +50 V-Development Roller diameter 30mmφ ・ Drainage gap 0.7mm ・ Drainage length 5mm ・ Air suction rate 14 liters / min

[0090]

According to the present invention, the toner particles contained in the liquid developer are electrodeposited on the developer carrier, and then the thickness of the liquid developer carried on the developer carrier is regulated by the regulating means. Therefore, the amount of the medium liquid contained in the liquid developer on the developer carrier can be sufficiently reduced,
This makes it possible to sufficiently reduce the amount of the medium liquid adhering to the latent image carrier.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophotographic printer 100 incorporating a liquid developing device to which the present invention is applied.

2 is an enlarged view of the vicinity of the developing head 200 of the liquid developing device 20. FIG.

FIG. 3 is a diagram showing a developing head 300 according to another embodiment.

FIG. 4 is a diagram showing a developing head 400 according to still another embodiment.

FIG. 5 is a diagram showing a developing head 500 which is still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum c Developing part d Thin layer forming part g Liquid draining part 20 Liquid developing device 200 Developing head 201 Thin layer forming electrode 202 Developing roller 208 Developer tank 212 Air suction port 214 Cover

Front page continuation (72) Inventor Ryuji Kurita 2-3-13 Azuchi-cho, Chuo-ku, Osaka Osaka International Building Minolta Co., Ltd.

Claims (5)

[Claims] 1. A liquid developing apparatus for developing an electrostatic latent image formed on the surface of a latent image bearing member by contacting with a liquid developer formed by dispersing charged toner in a medium liquid at a developing position. From a developing position to a developing position, a developer conveying body for conveying the liquid developer to the developing position, a supplying means for supplying the liquid developer to the developer conveying body at the developer supplying position, and a toner particle in the liquid developer supplied by the supplying means. Electrodeposition means for electrodeposition on the developer transport body, and regulation means for regulating the liquid developer on the developer transport body to a predetermined thickness in a region between the developer supply position and the development position. A liquid developing device characterized by being provided. 2. The liquid developing apparatus according to claim 1, wherein the regulating means includes an air flow generating means for generating an air flow along the developer transport body. 3. The rotating member, wherein the regulating means is provided at a predetermined distance from the developer carrying body.
Liquid developing device. 4. The plate member, wherein the regulating means is provided at a predetermined distance from the developer transport body.
Liquid developing device. 5. The liquid developing apparatus according to claim 1, wherein the regulating means is a corona discharger provided so as to face the developer transport body.