JP2002333776A - Liquid developing electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developing electrophotographic device which removes carrier liquid more effectively and stably. SOLUTION: An electrostatic latent image which is formed on a picture substrate by using a liquid toner is developed and, thereafter, the toner picture is transferred on an intermediate transfer body. The toner picture which is transferred on the intermediate transfer body is fused and transferred on a printed medium. In order to remove the excessive carrier from a toner layer which forms the toner picture on the intermediate transfer body, a carrier removing roller which is in contact with the intermediate body and is rotated and a bias applying means which applies a bias voltage between the intermediate transfer body and the carrier removing roller in the direction of pressing toner particles against the intermediate transfer body are disposed. The bias applying means applies an AC bias as the bias voltage. Otherwise, the bias applying means applies a DC bias in addition to the AC bias.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing electrophotographic apparatus provided with a surplus carrier removing mechanism for removing surplus oil from a toner layer for forming an image on an intermediate transfer member.

[0002]

2. Description of the Related Art FIG. 8 shows the overall configuration of a conventionally known liquid developing type electrophotographic apparatus (for example, Japanese Patent Application Laid-Open No.
0-055655). After being charged by the charging device 21, the photosensitive drum 10 is exposed by the exposure device 22 to form an electrostatic latent image. The pre-wetting device 23 is, for example, a silicone oil
0 surface. In the drawing, reference numeral 26 denotes a blade for scraping residual toner, and 27 denotes a static eliminator.

The developing device 24 is provided in association with yellow / magenta / cyan / black, and uses a non-volatile, high-viscosity, high-density liquid toner as a developer. The developing roller supplies the developer onto the photosensitive drum 10 and causes toner particles of the developer to adhere to the photosensitive drum 10 according to an electric field generated between the developing roller and the photosensitive drum 10.

The intermediate transfer roller 15 transfers the color toner adhered to the photosensitive drum 10 one by one according to an electric field between the intermediate transfer roller 15 and the photosensitive drum 10. When the intermediate transfer roller 15 transfers toner particles adhered to the photosensitive drum 10 in accordance with an electric field between the intermediate transfer roller 15 and the photosensitive drum 10, excessive pre-wet and development that move from the photosensitive drum 10 to the intermediate transfer roller 15 together with the toner particles It is necessary to remove the oil consisting of the carrier in the toner layer. Therefore, in the illustrated apparatus, an oil removing roller 25 is provided on the intermediate transfer roller 15.

The heating device 28 heats the surface of the intermediate transfer roller 15 to melt the toner attached to the intermediate transfer roller 15. The heating by the heating device 28 is performed after all the color toners have been transferred. The pressure roller 19 fixes the toner on the intermediate transfer roller 15 melted by the heating device 28 to the print medium.

[0006] The carrier liquid in the liquid development has a function of preventing the toner particles of about 1 µm from being scattered and of charging the particles to make them uniformly dispersed. Also plays a role like a “bridge” to move easily by electric field action.

[0007] The carrier liquid in the liquid developing printer process is a necessary component for toner storage, toner transport / layer formation, development, and electrostatic transfer. However, the carrier liquid is not necessary after the fixing process on the paper medium due to image quality and the like. In the case of a liquid developing toner using a non-volatile carrier liquid, the carrier liquid cannot volatilize the toner when heated and melted,
In particular, when the toner is fixed or when the toner image is melt-transferred, the adhesion of the molten toner to the paper medium is hindered, and the image quality and the adhesive strength to the paper medium may not be sufficiently satisfied.

For this reason, conventionally, a direct current bias has been applied to remove excess carrier liquid. As shown in FIG. 7, the carrier removing roller CR removes the carrier from the image toner on the intermediate transfer member IMR.
Is used. At this time, a DC bias is applied between the intermediate transfer member IMR and the carrier removing roller CR by utilizing the characteristic of + charge of the toner particles to restrict the toner particles to the intermediate transfer member IMR side by an electric force. While removing the carrier roller
The carrier is removed by CR.

Thus, even when the toner particles come into contact with the carrier removing roller CR and receive a force, it is possible to create a state in which image collapse is suppressed. However, even with such a carrier removal technique, it cannot be said that the removal of the carrier liquid filling the voids between the toner particles is sufficient.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to further improve the conventional carrier removing method and to remove the carrier liquid more effectively and stably.

[0011]

A liquid developing electrophotographic apparatus according to the present invention develops an electrostatic latent image formed on an image support using a liquid toner, and transfers the developed toner image to an intermediate transfer member. The toner image transferred onto the intermediate transfer member is melt-transferred onto a print medium. A carrier removing roller that rotates in contact with the intermediate transfer member to remove excess carrier from a toner layer forming a toner image on the intermediate transfer member; and a carrier removing roller that rotates in a direction of pressing toner particles onto the intermediate transfer member. There is provided bias applying means for applying a bias voltage between the intermediate transfer member and the carrier removing roller.
The bias applying means applies an AC bias in addition to an AC bias or a DC bias as a bias voltage.

Further, the liquid developing electrophotographic apparatus of the present invention comprises:
A carrier removing roller that rotates in contact with the intermediate transfer member to remove excess carrier from a toner layer that forms a toner image on the intermediate transfer member; and a carrier removing roller that rotates in a direction of pressing toner particles onto the intermediate transfer member. There is provided bias applying means for applying a bias voltage between the intermediate transfer member and the carrier removing roller. And the carrier removal roller is
Rotation is performed in such a direction that both contact surfaces move in opposite directions at a contact portion with the intermediate transfer member.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail according to embodiments. The present invention can be applied to an electrophotographic apparatus using a general liquid toner as described above with reference to FIG. FIG. 1 is a diagram for explaining a surplus carrier removing mechanism which is a feature of the present invention. As shown, a carrier removing roller CR is used to remove the carrier from the image toner on the intermediate transfer member IMR. Then, by utilizing the characteristic of + charge of the toner particles, between the intermediate transfer member IMR and the carrier removing roller CR, the toner particles are constrained to the intermediate transfer member IMR side by the electric force while the carrier removing roller CR is used. A bias is applied to remove carriers. For the bias, the central portion of the intermediate transfer member IMR or the carrier removing roller CR is constituted by a drum made of a conductive material such as metal, and the central drum can be electrically connected from a bias power supply. As the bias, an AC bias is applied in addition to the AC bias or the DC bias. Thereby, even when the toner particles come into contact with the carrier removing roller CR and receive a force, a state in which image collapse is suppressed can be created. Note that A
Even when only the C bias is used, a sufficient effect is produced as described later with reference to FIG. 3. However, at the time of the lowest AC bias, that is, at the time of the negative half-wave of the AC, a reverse bias is applied to the intermediate transfer. There is a possibility that the toner particles lose their holding power on the surface of the body IMR, causing image collapse. In consideration of this, it is more desirable to maintain the center value of the AC bias at a positive bias equal to or higher than a certain value.

As a result, as shown in FIG. 2, the carrier and the toner particles are completely separated into two layers. Thus, the carrier removing roller takes only the pure carrier. At this time, the carrier can be collected by applying pressure to the carrier removing roller to extrude only the carrier.

FIG. 3 is a table of experimental data showing the relationship between the applied bias type and the carrier removal effect, and FIG. 4 is a graph of the experimental result. Each time the carrier removal (CR) is performed, the applied bias
DC 2kv, DC 3kv, AC bias 2kv (40kHz),
The solid content ratio was obtained as a percentage in the case of DC 500v + AC bias 2kv (40kHz). The toner on the rotating intermediate transfer member is configured to rotate once in contact with the carrier removing roller each time the toner is rotated. Therefore, the number of times of carrier removal is equal to the rotation speed of the intermediate transfer member. The solid content ratio was determined by collecting the residual toner on the intermediate transfer member after removing the carrier, measuring the mass (carrier + solid content), removing the carrier in the toner, collecting only the solid content, and measuring the mass. It is obtained by measuring (solid content) and determining the ratio of both.

As shown in FIG. 4, which is a graph of the experimental results, the effect of applying an AC bias is remarkable when the number of removals is small. In addition, AC
By applying a DC bias to the bias and keeping the center value of the AC bias on the + side (500 V), the efficiency can be further improved.

FIG. 5 is a table of experimental data showing the relationship between the rotation direction of the carrier removing roller and the carrier removing effect, and FIG. 6 is a graph of the experimental result. Under the same conditions with all DC bias applied, if the carrier removal roller is in the same direction for each number of carrier removals (both surfaces move in the same direction at the contact surface with the intermediate transfer member), the surface movement speed is the same In the counter direction in which the moving direction is reversed, the surface moving speed of the carrier removing roller is twice the surface moving speed of the intermediate transfer member, and the solid content ratio is calculated as a percentage in each of the counter directions. It is.

As shown in FIG. 6, which is a graph of the experimental results, the carrier removal can be efficiently performed by rotating the carrier removal roller in the counter direction. Further, as the relative speed between the intermediate transfer member and the carrier removing roller is increased, the efficiency can be further improved, and the carrier scraping efficiency can be improved. However, although there is a limitation on the mechanism for rotating the carrier removing roller, at least the rotational speed of the carrier removing roller in the counter direction is
It is desirable that the speed be higher than the speed of the intermediate transfer member. Further, in order to increase the relative speed, the speed of the intermediate transfer member is made lower than the steady process speed, so that the carrier scraping efficiency can be improved.

Further, the technique of rotating the carrier removing roller in the counter direction can further improve the efficiency by combining with the above-described AC bias applying technique.

As described above, when the intermediate transfer member and the carrier removing roller are rotated in the reverse direction to remove the carrier, if the intermediate transfer member and the carrier removing roller slide well, only the carrier can be collected at one time. In order to improve the slip, the carrier removing roller and the intermediate transfer member surface sheet may be made of a fluorine resin material having an extremely low operating friction coefficient and good abrasion resistance. further,
As the carrier removing roller, for example, a sponge-based material that is collected while sucking the carrier is used.

[0021]

According to the present invention, an AC bias is applied in addition to an AC bias or a DC bias as a bias voltage for removing excess carriers, or the carrier removing roller is moved in a direction opposite to the intermediate transfer member. By rotating in the direction in which the toner particles move, the toner particles come into contact with the carrier removing roller, and even when subjected to a force, it is possible to create a state in which image collapse is suppressed, and the carrier liquid is more effectively and , Can be removed stably.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a surplus carrier removing mechanism which is a feature of the present invention.

FIG. 2 is a diagram for explaining an effect of a carrier and toner particles being completely separated into two layers by application of a bias.

FIG. 3 is a table of experimental data showing the relationship between the applied bias type and the carrier removal effect.

FIG. 4 is a graph of the experimental result shown in FIG.

FIG. 5 is a table of experimental data showing a relationship between a rotation direction of a carrier removing roller and a carrier removing effect.

6 is a graph showing the experimental data shown in FIG.

FIG. 7 is a diagram showing a conventional surplus carrier removing mechanism.

FIG. 8 is a view showing the overall configuration of a conventionally known liquid developing type electrophotographic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Photosensitive drum 15 Intermediate transfer roller 19 Pressure roller 21 Charging device 23 Pre-wet device 24 Developing device 25 Oil removing roller 26 Blade 27 Static elimination device 28 Heating device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironaga Honkawa 98 Uno-nu, Unoki-cho, Kawakita-gun, Ishikawa Pref. 2 Inside PFU Co., Ltd. (72) Isao Nagata Unoki, Unoki-cho, Kawakita-gun, Ishikawa 98 No. 2 in PFU Co., Ltd. (72) Inventor Shigeharu Okano Character of Unoki-cho, Kawakita-gun, Ishikawa Pref. No. 98 No. 2 Inside PFU Co., Ltd. (72) Inventor Tadashi Nishikawa Unoki-cho, Kawakita-gun, Ishikawa Prefecture No. 98 No. 2 Pfuyu Co., Ltd. (72) Inventor Akihiko Inamoto Unoki-cho, Unoki-cho, Kawakita-gun, Ishikawa Prefecture No. 98 No. 2 PFU Co., Ltd. (72) Inventor Satoshi Miyamoto Unoki 98, Unoki-cho, Kawakita-gun, Ishikawa Prefecture 2 Co., Ltd. Piefuyu in the F-term (Reference) 2H074 AA03 BB42 BB60 BB72 EE07 2H200 FA20 GA23 GA43 GA45 GA47 GA50 GA51 GB40 JA07 JA08 JC02 JC12 JC15 JC17 JC18 JC19 LA31 LB02 LB08 LB15 LB38 MA02 MC05 NA03 NA06 PA11

Claims (9)

[Claims] An electrostatic latent image formed on an image support is developed using a liquid toner, and the developed toner image is transferred onto an intermediate transfer member, and is transferred onto the intermediate transfer member. A liquid developing electrophotographic apparatus that melt-transfers a toner image onto a print medium, wherein a carrier that rotates in contact with the intermediate transfer body to remove excess carrier from a toner layer that forms a toner image on the intermediate transfer body A removing roller, and a bias applying unit that applies a bias voltage between the intermediate transfer body and the carrier removing roller in a direction in which the toner particles are pressed onto the intermediate transfer body, wherein the bias applying unit is configured as a bias voltage. Applying a AC bias to the liquid developed electrophotographic apparatus. 2. The liquid developing electrophotographic apparatus according to claim 1, wherein the bias applying unit applies an AC bias as a bias voltage in addition to the DC bias. 3. The liquid developing electrophotographic apparatus according to claim 1, wherein the carrier removing roller applies pressure in the direction of the intermediate transfer member to extrude only the carrier to perform sampling. 4. An electrostatic latent image formed on an image support is developed using a liquid toner, and the developed toner image is transferred onto an intermediate transfer member, and is transferred onto the intermediate transfer member. A liquid developing electrophotographic apparatus that melt-transfers a toner image onto a print medium, wherein a carrier that rotates in contact with the intermediate transfer body to remove excess carrier from a toner layer that forms a toner image on the intermediate transfer body A removing roller, and bias applying means for applying a bias voltage between the intermediate transfer member and the carrier removing roller in a direction of pressing the toner particles onto the intermediate transfer member, wherein the carrier removing roller includes an intermediate transfer member. A liquid developing electrophotographic apparatus comprising: rotating in a direction in which both contact surfaces move in opposite directions at a contact portion with the liquid developing device. 5. A fluororesin-based material having a very low operating friction coefficient and good abrasion resistance for improving the slip is used as the surface material of the carrier removing roller and the intermediate transfer member. The liquid developing electrophotographic apparatus according to claim 4. 6. The liquid developing electrophotographic apparatus according to claim 4, wherein the speed of the carrier removing roller is increased to be higher than the speed of the intermediate transfer member. 7. The liquid developing electrophotographic apparatus according to claim 4, wherein the speed of the intermediate transfer member is lower than a steady speed. 8. The liquid developing electrophotographic apparatus according to claim 4, wherein the carrier removing roller is made of a material that is collected while sucking the carrier. 9. The liquid developing electrophotographic apparatus according to claim 4, wherein said bias applying means applies an AC bias in addition to an AC bias or a DC bias.