JP2003223056A - Full color electrophotographic device using nonvolatile high-viscosity, high concentration liquid toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of a heat damage to a photoreceptor by dispensing with cooling of an intermediate transfer body before it is brought into contact with the photoreceptor. <P>SOLUTION: This full color electrophotographic device forms a toner image on the intermediate transfer body. In this case, the intermediate transfer body is heated up to a temperature at which softening of resin of a liquid toner is started or above and to a heat resistant temperature of the photoreceptor or below. A carrier removal roller to which a bias can be applied is abutted on the intermediate transfer body and removes a carrier while pressing and hardening the softened toner by force of an electric field generated by the bias. In a transfer part to a printing medium, the printing medium is pressurized on the intermediate transfer body by a backup roller and the toner image of the intermediate toner image is transferred to the printing medium. The printing medium is heated before it is pressurized on the toner image of the intermediate transfer body. The bias is applied to the backup roller, the toner image on the intermediate transfer body is attracted onto the printing medium by the electric field and transfer is supported. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-volatile, high-viscosity, high-viscosity non-volatile material that melts and transfers a full-color image onto a printing medium after forming a full-color image by sequentially superposing color toners of a plurality of colors on an intermediate transfer member. The present invention relates to a full-color electrophotographic apparatus using a concentrated liquid toner.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus using a liquid toner, a volatile or non-volatile carrier liquid has been used as a carrier liquid for the liquid toner. When a volatile carrier liquid is used, it is volatilized and removed from the toner image by heating at the time of fixing, but since a hydrocarbon solvent is usually used as this volatile carrier liquid, considering the influence on the human body, It is necessary to collect the volatilized carrier liquid so as not to go out of the device, and a large-scale recovery device is required.

On the other hand, in a liquid developing apparatus using a non-volatile carrier liquid, it is effective to heat the toner image formed on the intermediate transfer member (intermediate transfer belt) to remove the carrier liquid. In addition, it is possible to remove the non-volatile carrier liquid, which makes it possible to transfer and fix the toner image to the print medium while preventing the wetting of the print medium by the carrier liquid and the fixing failure. However, in order to reduce heat damage to the photoconductor, it is necessary to cool the intermediate transfer member before contacting the photoconductor, which requires a large amount of energy (Japanese Patent Laid-Open No. 2001-22186, Japanese Patent Laid-Open No. 2-22186).
001-305886).

This is because the intermediate transfer member is heated until the toner is sufficiently melted, so that the photosensitive member is heated when the intermediate transfer member comes into contact with the photosensitive member again. It was necessary to cool the intermediate transfer member after the transfer to. In order to enable this heating / cooling cycle, it is necessary to make the intermediate transfer member sufficiently large to allow time for cooling, and the apparatus becomes large.
Moreover, since heating and cooling are repeated, a large amount of energy is required.

[0005]

SUMMARY OF THE INVENTION The present invention uses a non-volatile carrier liquid to effectively remove the carrier liquid without the need for a large-scale recovery device and to effectively produce a full-color image. It is an object of the present invention to provide a full-color electrophotographic apparatus capable of being transferred to a print medium.

Another object of the present invention is to prevent the intermediate transfer member from being cooled before it comes into contact with the photosensitive member, so that thermal damage to the photosensitive member does not occur.

[0007]

The present invention can be achieved at a temperature for melt-transferring a toner image onto a print medium lower than a temperature for fixing, and carrier removal at a lower temperature is sufficient. It is based on the evaluation that it can be achieved at various levels. According to the present invention, the toner image on the intermediate transfer member is heated above the softening start temperature of the toner resin and below the heat resistant temperature of the photosensitive member, and the biased carrier removing roller is brought into contact with the toner image on the intermediate transfer member. The carrier is removed by rotating and pressing the toner solids against the intermediate transfer member by the force of the electric field. Here, the softening start temperature of the resin means the temperature at which the needle starts moving when measured by TMA, and the temperature at which the movement of the needle becomes constant when the melting temperature of the resin is measured by TMA. Further, as the heat resistant temperature of the photoconductor, the glass transition point of the binder resin used for the photoconductor or the temperature at which the resin is mechanically deformed can be used. TMA (Thermal mechanical analy
sis: Thermo-mechanical analyzer is a general measuring device that measures the mechanical strength of materials (mainly resins) against heat.
The sample is heated and the mechanical strength of the sample is measured from the displacement of the probe.

The full-color electrophotographic apparatus of the present invention forms a toner image on the intermediate transfer member. At this time, the intermediate transfer member is heated above the softening start temperature of the resin of the liquid toner and below the heat resistant temperature of the photosensitive member. A carrier removing roller to which a bias can be applied is in contact with the intermediate transfer member, and the carrier is removed while pressing the softened toner by the force of the electric field due to the bias. In the transfer portion to the print medium, the print medium is pressed against the intermediate transfer body by the backup roller, and the toner image on the intermediate transfer body is transferred to the print medium. The print medium is heated before being pressed against the toner image on the intermediate transfer member. A bias is applied to the backup roller, and the toner image on the intermediate transfer member is attracted to the print medium by an electric field to assist the transfer.

To obtain the final fixing strength, the toner image transferred to the print medium is heated and fixed by the fixing device.

[0010]

FIG. 1 is a diagram illustrating the configuration of a full-color electrophotographic apparatus embodying the present invention. The non-volatile liquid toner used in this device uses non-volatile silicone oil as a carrier and has a viscosity of 10 cSt to 2
00cSt, preferably 50cSt-100cSt is used.
Particle size of resin and pigment in this silicone oil
Toner particles of about 2 μm are dispersed at a ratio of about 10 to 30%, preferably 10 to 20%.

The intermediate transfer member may have either a drum structure or a belt structure, but in the illustrated apparatus, a drum shape is formed in consideration of stability of color superimposition, and a yellow color is formed around the drum.
A tandem type full-color electrophotographic apparatus is provided in which photosensitive drums (photosensitive members) are arranged in contact with each other for magenta, cyan, and black colors. 1 intermediate transfer drum
While rotating, the intermediate transfer drum contacts the photoconductor corresponding to each color, and the images are sequentially superimposed on the intermediate transfer drum to form a color image.

Each photosensitive drum is provided with a charging device for charging the photosensitive drum, an exposure unit, a blade for scraping off the residual toner after transfer to the intermediate transfer drum, and the developing roller is in contact therewith. ing.

The charger is for charging the photosensitive drum to about 700 V, and the exposure unit is operated by using a laser beam having a wavelength of 780 nm, for example, on the charged photosensitive drum based on image data. by this,
An electrostatic latent image is formed on the photosensitive drum so that the potential of the exposed portion is about 100V. Further, a charge eliminating device (not shown) is provided to eliminate the residual potential on the photosensitive drum.

The developing roller is biased to a predetermined voltage such as about 400V to 600V, and supplies the positively charged toner to the photosensitive drum according to the electric field between the developing roller and the photosensitive drum. As a result, toner is attached to the exposed portion on the photosensitive drum that is charged to about 100 V, the electrostatic latent image on the photosensitive drum is developed, and an image is formed. The toner supply roller is composed of one or a plurality of rollers for each color toner, and a non-volatile, high-concentration, high-viscosity liquid toner having a toner particle content of 10 to 20% is formed on the developing roller in an amount of 5 to 30.
It is applied in a thickness of μm, preferably 5 to 10 μm. As a toner supply roller for uniformly and stably applying a toner layer on the developing roller, a pattern roller (a roller known per se having a large number of fine grooves formed on the surface) which is driven by the developing roller is used to form the pattern. The liquid toner can be transferred and applied to a predetermined toner layer thickness while measuring a predetermined amount of the liquid toner using the groove.

The toner layer formed on the developing roller is provided with a conductive blade which comes into contact with the toner layer on the developing roller before the developing roller rotates and comes into contact with the photosensitive drum. By applying the toner particles, the toner particles are aggregated so that the carrier oil can be present on the surface of the toner layer. By developing in such a state, a high-quality image without fog can be formed. Further, the developing roller is provided with a blade or the like that comes into contact with the developing roller to scrape off the residual toner after development.

The intermediate transfer drum transfers the toner attached to the photosensitive drums according to the electric field between each of the photosensitive drums. Further, in order to set the optimum transfer bias for each color, the shaft of the intermediate transfer drum is grounded while the optimum transfer bias of each color is applied to the shaft of each photoconductor.

FIG. 2 is a diagram showing the relationship between the biases. The transfer bias is independently applied to the photosensitive drums of the respective colors to the intermediate transfer drum having the ground potential so that the transfer bias becomes optimum. Also, based on the transfer bias applied to the photosensitive drum shaft,
If a charging potential (grid bias) relating to image formation on each photosensitive drum, a developing bias, and a bias blade for aggregating the toner layer on the developing roller are provided, this blade bias is set.

To the intermediate transfer drum, for example, first, the yellow toner attached to the first photosensitive drum is transferred, and then the magenta transfer portion, which is the second toner, is transferred to the second photosensitive drum. Transfer the magenta toner adhering to the drum, then transfer the cyan toner adhering to the third photosensitive drum, and finally transfer the black toner adhering to the fourth photosensitive drum. Will be done.
In this way, the four developed on the first to fourth photosensitive drums
The color toner images are sequentially superimposed on the intermediate transfer drum during one rotation of the intermediate transfer drum to form a color image.

In this way, the toner image developed on the photosensitive drum contacts the intermediate transfer drum by the rotation of the photosensitive drum and is transferred to the intermediate transfer drum by the force of the electric field. The color toner image formed on the intermediate transfer drum has a non-volatile carrier, but if it is directly transferred to the print medium, fixing failure occurs. Therefore, the carrier is removed before being transferred to the print medium.

The intermediate transfer drum is heated and maintained at a temperature above the softening start temperature of the resin of the liquid toner and below the heat resistant temperature of the photoreceptor by the heater provided inside. The carrier removing roller is provided on the intermediate transfer drum at the downstream side corresponding to each photosensitive drum, and a bias having the same polarity as the toner particles is applied every time a toner image of each color is transferred to the intermediate transfer drum. The carrier removing roller is rotated in contact with the toner image on the intermediate transfer drum to remove the carrier while compacting the softened toner by the force of the electric field due to the bias.

In this way, the four-color image on the intermediate transfer drum, which has been superposed and carrier-removed, is heated by the intermediate transfer drum and the backup roller with a built-in heater in the transfer portion to the print medium. It is heated and melted, pressed against the print medium, and transferred.

A bias is applied to the backup roller so that the toner image is attracted to the print medium by the electric field when the toner image is transferred from the intermediate transfer drum to the print medium. After that, the toner image is fixed by pressing the print medium by the two heat rollers in the fixing device. As a result, the color image transferred to the print medium is subjected to higher heating and higher pressure by the heat roller after the melt transfer in order to secure the fixing strength, thereby securing the fixing strength. In this way, since the fixing unit that generates a large amount of heat is separated from the transfer unit, the heat generated in the transfer unit can be suppressed to a low level. With such a heat fixing mechanism, the toner image transferred onto the print medium can be sufficiently heated and fixed by applying heat and pressure by the backup roller.

Further, a pre-heater for preheating the print medium at a temperature above the temperature at which the resin of the toner is sufficiently melted is provided at a position before the print medium contacts the intermediate transfer drum.
When the toner image formed on the intermediate transfer drum is transferred to the print medium, the print medium needs to be heated to the melting temperature of the toner in the transfer section. It was experimentally confirmed that it is desirable that the medium temperature is heated to about 100 ° C. The illustrated apparatus is equipped with a heat roller controlled at 150 ° C. to heat the media prior to melt transfer.
At this time, since the heated medium maintains the temperature between the nip formed by the intermediate transfer drum and the backup roller in the melt transfer section, the backup roller also has a heat resistance temperature of the photoconductor above the softening start temperature of the toner resin. It is heated and maintained below. Alternatively, the backup roller is heated to the melting temperature of the toner or higher, and the backup roller is separated from the intermediate transfer member except during printing so that the intermediate transfer drum is not heated by the heat of the backup roller, and the print medium is conveyed. The intermediate transfer member may be contacted via the print medium only when the medium is heated, and the medium may be heated to a temperature required for melt transfer.

Further, a bias is applied to the backup roller, and when the toner image is transferred from the intermediate transfer drum to the print medium, it is attracted to the print medium by the electric field to assist the melt transfer. This bias assists melt transfer, and if the print medium is not heated sufficiently, the adhesion of the toner to the medium will be weak and the transfer will not be sufficient because it is firmly attached to the intermediate transfer drum. .

[0025]

INDUSTRIAL APPLICABILITY By using a non-volatile carrier liquid, the present invention not only effectively removes the carrier liquid without requiring a large-scale recovery device, but also effectively produces a full-color image on a print medium. In addition to being capable of transferring, it has an effect that the intermediate transfer member does not need to be cooled before coming into contact with the photosensitive member, and thus thermal damage to the photosensitive member does not occur.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the configuration of a full-color electrophotographic apparatus embodying the present invention.

FIG. 2 is a diagram showing a mutual relationship between biases.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiko Kishimoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Masanobu Motoe             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Shigenori Uesugi             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Yoshiro Kawamoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor, Yasuichi Takeda             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Koichi Yoshida             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Yoshiaki Fujimoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Moriki             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. F-term (reference) 2H030 AB02 AD01 AD03 AD04 AD18                       BB02 BB22 BB27 BB42 BB46                       BB52                 2H069 EA02                 2H074 AA03 AA07 AA41 BB44                 2H200 FA15 GA12 GA23 GA43 GA47                       GA56 GB12 GB22 GB43 HA02                       HB12 HB22 JA02 JA07 JA12                       JA21 JB10 JC02 LA31

Claims (8)

[Claims] 1. A non-volatile, high-viscosity, high-concentration liquid toner is used, in which color toner images of a plurality of colors are sequentially superposed on an intermediate transfer member to form a full-color image, and then the full-color image is heated and melt-transferred onto a print medium. In the full-color electrophotographic apparatus, the intermediate transfer member is heated and maintained below the heat-resistant temperature of the photosensitive member above the softening start temperature of the resin of the liquid toner, and the carrier is removed every time the toner image of each color is transferred to the intermediate transfer member. A carrier removing mechanism is provided on the intermediate transfer member. The carrier removing mechanism is configured such that a carrier removing roller to which a bias having the same polarity as the toner particles on the intermediate transfer member is applied is rotated in contact with the toner image on the intermediate transfer member. The softened toner is configured to remove the carrier while being pressed by the force of the electric field due to the bias, and the toner image from which the carrier is removed is transferred to the print medium. A full-color electrophotographic apparatus that prints a color image on a print medium by pressing and transferring the print medium with a backup roller. 2. The full-color electrophotographic apparatus according to claim 1, further comprising a mechanism for heating the print medium to a temperature at which the resin of the toner is sufficiently melted at a position before the print medium comes into contact with the intermediate transfer member. 3. The full-color electrophotographic apparatus according to claim 2, wherein the backup roller is also provided with a mechanism for heating and maintaining the temperature above the softening start temperature of the resin of the toner and below the heat resistant temperature of the photoconductor. 4. The full-color electrophotography according to claim 1, wherein the backup roller is heated to a temperature higher than a melting temperature of the toner so as to contact the intermediate transfer body through the print medium only when the print medium is conveyed. apparatus. 5. The bias voltage is applied to the backup roller so that the toner image is attracted to the print medium by an electric field when the toner image is transferred from the intermediate transfer member to the print medium. Full-color electrophotographic device. 6. The intermediate transfer member is drum-shaped, and a photosensitive member unit and a developing unit corresponding to each color and a carrier removing roller corresponding to each color are arranged around the intermediate transfer drum. Full-color electrophotographic device. 7. The intermediate transfer drum is grounded, a bias is independently applied to each photoconductor of each color so as to obtain an optimum transfer bias, and a developing bias and a charging bias of each color are applied to the photoconductor. 7. The full-color electrophotographic apparatus according to claim 6, wherein the transfer bias is applied on the basis of the reference. 8. After transferring the toner image onto the print medium,
The full-color electrophotographic apparatus according to claim 1, further comprising a heating and fixing mechanism for sufficiently heating and fixing.