JP2003280397A - Method and apparatus for wet electrophotographic printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for wet electrophotographic printing which avoids direct transfer from a developer from a photosensitive body to a recording medium accompanied by difficulties due to various factors, uses an intermediate transfer body capable of high-pressure transfer without heating causing deterioration, and uses a liquid developer free of an image blur (image run) even on coat paper and element absence even on high-quality paper. <P>SOLUTION: The intermediate transfer body is used and a recording medium is pressed against the intermediate transfer body under pressure of 1 to 13 [kg/cm<SP>2</SP>]; and the viscosity of the liquid crystal is set to 1,000 to 50,000 [mPas] and the developer film thickness on the intermediate transfer body is set to 1 to 6 [μm], thereby transferring an excellent image which is free of an image run and element absence from the intermediate transfer body to coat paper and high-quality paper only with an electric field and pressure. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet electrophotographic printing method and apparatus using a liquid developer and an intermediate transfer member, and in particular, to coated paper and high-quality paper, image bleeding due to an increase in dot gain ( The present invention relates to a wet electrophotographic printing method and apparatus using a liquid developer and an intermediate transfer member capable of forming a good image without causing blank defects due to image deletion) or transfer failure.

[0002]

2. Description of the Related Art An electrophotographic apparatus using a liquid developer is economical because it can realize high image quality equivalent to offset printing by using a fine toner and can obtain a sufficient image density with a small amount of toner. Have advantages.

However, the conventional wet electrophotographic printing apparatus has a weak point that it is easily affected by the material of the medium for recording the developer image formed on the photoconductor and the image quality of the transferred image is easily changed. . For example, even if a developer image with the same film thickness is formed on the photoconductor, image bleeding (image deletion) occurs due to an increase in dot gain at the transfer nip on coated paper with low liquid absorption and high smoothness. On the other hand, there is a problem that a fine paper having a high liquid absorbing property and a low smoothness causes a transfer failure (blank void) in which the toner does not reach the concave portion of the high quality paper.

In order to solve such a problem, the developer image on the photoreceptor is once transferred to an intermediate transfer member by an electric field, and then the developer image is heated and melted by pressure and heat to form a film, which is a recording medium. An apparatus that melt-transfers at the same time as transfer to U.S. Pat. Nos. 4,518,976 and 4,70.
8,460, 5,148,222, 5,16
No. 6,734, 5,208,637 and the like. Further, in Japanese Patent Publication No. 46-41679 and Japanese Patent Laid-Open No. 62-280882, an apparatus using pressure and heat for both transfer to an intermediate transfer member and transfer to a recording medium without using electric field transfer. Is disclosed. The intermediate transfer member is relatively easy to be made of a material having a smooth surface and less variation or fluctuation in electric resistance, and since transfer can be performed with high pressure, electric field transfer is directly performed from the photosensitive member to the recording medium. Compared with the case, the image quality deterioration due to transfer is dramatically improved.

However, in these apparatuses, a heating system for the intermediate transfer member and a system for cooling the photosensitive member before contacting the intermediate transfer member in order to prevent deterioration of the characteristics of the photosensitive member due to heat from the intermediate transfer member. Are required, the process is complicated, and the image quality changes due to deterioration of the intermediate transfer member due to heating, resulting in a decrease in system reliability.

[0006]

Therefore, in the present invention, it is possible to avoid the direct transfer of the developer image from the photoconductor to the recording medium, which is difficult due to the various factors described above, and to perform the transfer with high pressure. A wet electrophotographic printing method and apparatus using a liquid developer that does not cause image bleeding (image deletion) even on coated paper and does not cause blank drop even on high-quality paper The task is to do so.

[0007]

Therefore, claim 1 of the present invention is a method invention, in which a latent image formed on a photoconductor by an electrophotographic system is developed by a liquid developer held on a developing roller to form a latent image. In the wet electrophotographic printing method in which the formed developer image is transferred to an intermediate transfer member and then transferred to a recording medium, 30 to 50 [wt%] of toner having an average particle diameter of 0.1 to 6 [μm] is applied to the developing roller. And a viscosity of the liquid developer is controlled to a range of 1000 to 50,000 [mPas] in a thickness of 2 to 7 [μm], and a latent image on the photoconductor is developed. The second step of developing with a liquid developer on a roller to form a developer image, and the intermediate transfer member being composed of a conductive roller or belt, the transfer efficiency by the intermediate transfer bias is increased and the intermediate transfer member is improved. Membrane on top The third step of transferring the developer image on the photosensitive member so that the thickness becomes 1 to 6 [μm], and a transfer bias larger than the intermediate transfer bias is applied to the recording medium side to develop the developer from the intermediate transfer member. It is characterized in that the developer image can be transferred by the fourth step of transferring the image to coated paper or high-quality paper.

The invention according to claim 3, which is an apparatus invention for carrying out the method invention, has means for forming a latent image on a photoreceptor by an electrophotographic method, and the latent image is developed with a liquid developer. And a developing means for forming a developer image, and an intermediate transfer member for transferring the developer image by an intermediate transfer bias,
In a wet type electrophotographic printing apparatus provided with a transfer means for transferring the developer image transferred to the intermediate transfer member to a recording medium, toner having an average particle diameter of 0.1 to 6 [μm] is used in an amount of 30 to 5
Included in the concentration of 0 [wt%] to increase the viscosity to 1000 to 500
The developer on the photoconductor is constituted by the developing roller in the developing means, which carries the liquid developer controlled in the range of 00 [mPas] to a thickness of 2 to 7 [μm], and a conductive roller or belt. The image forming apparatus has the intermediate transfer member capable of transferring images in a range of 1 to 6 [μm] by increasing transfer efficiency of images and a unit for applying a transfer bias larger than the intermediate transfer bias to the transfer unit. The developer image formed by the developer carried by the developing roller is transferred to the coated paper or the high-quality paper by the transfer means via the intermediate transfer body.

As described above, the liquid developer containing the toner having the average particle diameter of 0.1 to 6 [μm] in the concentration of 30 to 50 [wt%] and the viscosity of 1000 to 50,000 [mPas] is used, and , The intermediate transfer member is composed of a roller or belt formed of conductive rubber or resin to increase the transfer efficiency of the developer image from the photosensitive member by the intermediate transfer bias,
By controlling the developer film thickness on the intermediate transfer member to be 1 to 6 [μm], it is possible to prevent image bleeding (image deletion) due to an increase in dot gain when the developer image is transferred onto the coated paper, In addition, it is possible to obtain a good image without causing blank defects due to defective transfer when the developer image is transferred onto the high-quality paper.

The pressing force of the recording medium on the intermediate transfer member by the transfer means is as described in claims 2 and 4.
In the fourth step, recording media 1 to 13
It is characterized in that a transfer bias is applied while pressing the intermediate transfer member with [kg / cm ² ]. The transfer means includes means for applying a transfer bias while pressing the recording medium at 1 to 13 [kg / cm ² ] against the intermediate transfer body.

By thus regulating the pressing force of the recording medium to the intermediate transfer body, it is possible to prevent image bleeding (image deletion) due to an increase in dot gain when the developer image is transferred onto the coated paper. A good image can be obtained.

According to a fifth aspect of the present invention, the intermediate transfer member is provided with a release agent applying means for applying a release agent to the intermediate transfer member upstream of the transfer position of the developer image on the photosensitive member. In addition to facilitating the transfer of the developer image to the recording medium by the release agent, the cleaning device for cleaning the residual developer on the intermediate transfer member is provided on the downstream side of the transfer position of the developer image to the recording medium. Characterize.

By thus providing the releasing agent applying means and the cleaning means, most of the developer image transferred to the intermediate transfer body is transferred to the coated paper or the high-quality paper, and the residual developer still remained. Is not cleaned by a cleaning device and does not affect the next image formation, and a good image can always be formed.

Further, the release agent applying means is defined in claims 6 and 7.
As described above, the release agent applying means is composed of a rotating body that comes into contact with the intermediate transfer body with a peripheral speed difference. The release agent applying unit may rotate in the same direction as the rotation direction of the intermediate transfer member or in the opposite direction at a slower speed than the intermediate transfer member.

In this way, the release agent applying means is composed of a rotating body which comes into contact with the intermediate transfer body at a peripheral speed difference, and
Rotate in the same direction as the rotation direction of the intermediate transfer member (for example, if the intermediate transfer member is rotating in the counterclockwise direction, the rotating member is also rotated in the counterclockwise direction), or in the opposite direction to the intermediate transfer member. It is possible to efficiently apply the release agent to the intermediate transfer member by rotating the rotating member at a speed lower than the rotation speed of (for example, when the intermediate transfer member is rotating in the counterclockwise direction, rotating the rotating member in the clockwise direction). .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the constituent parts described in this embodiment are not intended to limit the scope of the present invention thereto, unless otherwise specified, and are merely It is only an example.

FIG. 1 is a schematic structure of a wet electrophotographic printing apparatus according to the present invention, and FIG. 2 shows a pressing force and an image (developer image) viscosity when a developer image is transferred from an intermediate transfer member to a recording medium. FIG. 3 is a graph showing the relationship between the dot gains, and FIG. 3 shows the relationship between the image flow of the transferred image and the voids depending on the image (developer image) viscosity and the film thickness when the developer image is transferred from the intermediate transfer body to the recording medium. It is a graph.

In the figure, 1 is amorphous silicon (a-S).
i), or a photoconductor drum composed of an organic photoconductor (OPC) or the like, having a diameter of about 240 mm,
It rotates at a peripheral speed of about 1 m / sec. 2 is an intermediate transfer member,
For example, the photosensitive drum 1 is made of a known material such as silicon-based conductive rubber or conductive resin, and is 240 m in length like the photosensitive drum 1.
It has a diameter of about m and rotates in the same direction as the photosensitive drum 1 at a peripheral speed of about 1 m / sec, and an intermediate transfer bias of about -1000V is applied. The intermediate transfer member 2 is shown in FIG.
In the above, the drum shape is shown, but a belt shape may be used, and by using a roller or belt formed of such conductive rubber or resin, the photosensitive drum 1
The transfer efficiency of the developer image from the intermediate transfer bias can be increased. When the intermediate transfer member 2 is composed of a belt, a backup roller or the like is provided at the contact point with the photosensitive drum 1 and the contact point with the backup roller 18. 3 is a developing roller, which is 20 in JIS-A.
It is composed of a conductive rubber roller having a hardness of 60 to 60 degrees, and has a resistance of, for example, 10 ^{4 to} 10 ¹⁰ Ωcm and 20
A bias of 0 to 400 V is applied to the photosensitive drum 1
Rotates in the same direction as and at the same peripheral speed. Reference numeral 4 denotes an original roller composed of a metal roller, which has a diameter similar to that of the developing roller 3 and rotates in the same direction at a peripheral speed of 1/30 to 1/2 of that of the developing roller 3.

5 is a developer container, 6 is a silicon-based solvent, the solid content concentration is 30 to 50 [wt%], the viscosity is 1000 to 50000 [mPas], and the average particle size is 0.1 to 6 [μ].
m] is the developer liquid, 7 is reverse to the developing roller 3,
Alternatively, a cleaning device that has a cleaning roller 8 that swings while rotating in the reverse direction and uses a solvent 9 to clean the developer remaining on the developing roller 3 to prevent a history phenomenon,
Reference numeral 10 is an exposure device that forms an image on the photosensitive drum 1 by an image signal sent from a control device of a wet electrophotographic printing device (not shown), 11 is a corotron that charges the photosensitive drum 1 to, for example, about 500V, or A charging device using a scoroton or the like, 12 is a static eliminator for removing the residual charge remaining on the photosensitive drum 1, 13 is a cleaning blade for scraping off the residual developer also remaining on the photosensitive drum 1, 14 is a cleaning device for the residual developer remaining on the intermediate transfer body 2 without being transferred, 15 is a blade for scraping off the developer on the cleaning device, 16 is a release agent coating device composed of a rotating body, This rotating body is rotated in the same direction as the intermediate transfer body 2 (for example, when the intermediate transfer body 2 is rotating counterclockwise, the rotating body is also rotated counterclockwise). A mold agent is applied to the intermediate transfer member 2 or is rotated in the reverse direction at a speed lower than the peripheral speed of the intermediate transfer member 2 (for example, when the intermediate transfer member 2 is rotating in the counterclockwise direction, the rotating member is rotated in the clockwise direction). Rotate). Reference numeral 17 is a container for containing a release agent such as silicon, and 18 is a backup roller for transferring the developer image on the intermediate transfer body 2 to the recording medium 19, and a transfer bias of, for example, about -2000 V is applied. Reference numeral 20 is a heat fixing device. It should be noted that the respective constituent elements described above and the numerical values related to the respective constituent elements described below do not limit the present invention and are merely examples.

The developer liquid 6 in the developer container 5 rotates in the direction opposite to that of the developing roller 3 (for example, when the developing roller 3 rotates in the counterclockwise direction, the original roller 4 rotates in the clockwise direction). The roller 4 has an outlet film thickness of about 30 [μm] and is conveyed to the developing roller 3 side. The peripheral speed of the original roller 4 is 1/30 to 1/2 of that of the developing roller 3 as described above.
The developer layer having a thickness of 2 to 7 [μm] is formed on the developing roller 3 due to the slip caused by the difference in peripheral speed. Hereinafter, the operation of the wet electrophotographic printing apparatus configured as described above will be described by way of example in the case of reversal development using positively charged toner, but the present invention is not limited to the case of positively charged toner, It is obvious that the negatively charged toner can be similarly configured.

In forming an image, first, when the photoconductor drum 1 is uniformly charged by the charger 11 to, for example, 500 V and an image is drawn by the exposure device 10, the electric charge in the exposed portion escapes to about 50 V. , A latent image is formed. When the latent image reaches the position of the developing roller 3, since a voltage of 200 to 400 V is applied to the developing roller 3, the liquid developer on the developing roller 3 is transferred to the latent image portion and developed. A developer image is formed. Then, the developer image is transferred to the intermediate transfer body 2 to which an intermediate transfer bias of about -1000V is applied. Since the intermediate transfer body 2 is composed of a conductive roller or belt, transfer by the intermediate transfer bias is performed. It has become possible to increase efficiency. Further, the intermediate transfer member 2 is coated with a release agent composed of silicon or the like by the release agent application device 16, so that a transfer bias of about -2000 V is applied and 1 to 13 [kg / cm 2]. ² ] The backup roller 18 that is in contact with the intermediate transfer member 2 under the pressure
As a result, most of them are transferred to the recording medium 19, fixed by the thermal fixing device 20, and discharged.

The developer remaining without being transferred to the recording medium 19 on the intermediate transfer body 2 rotates in the same direction as the intermediate transfer body 2 (for example, when the intermediate transfer body 2 rotates counterclockwise). The cleaning device 14 is also rotated counterclockwise) and is scraped by the cleaning device 14, and the scraped developer is scraped by the blade 15 and discarded. Further, the residual developer remaining on the photosensitive drum 1 is scraped off by the cleaning blade 13 and discarded. Further, the developer remaining on the developing roller 3 is removed by the cleaning roller 8 into a solvent 9
And the development history on the developing roller 3 is prevented.

In the wet electrophotographic printing apparatus having the above-described structure, the pressing force (printing pressure) and the image (developer image) viscosity at the time of transferring the developer image from the intermediate transfer member 2 to the recording medium 19 are variously changed. Then, Table 1 shows whether the dot gain of the image on the recording medium 19 is good or bad, and FIG. 2 shows it as a graph. In Table 1, 1000 to 50000 [mPas] in the horizontal column represents the viscosity of the developer image (image), and 0.5 to 19.4 in the vertical column.
0 [kg / cm ² ] represents printing pressure. In FIG. 2, the horizontal axis represents the image (developer image) viscosity in logarithm,
The vertical axis represents the pressing force (printing pressure). In Table 1 and FIG. 2, ○ indicates a good dot gain state, □ indicates a poor dot gain state, and Δ indicates a poor transfer state. Shows.

[0024]

[Table 1]

As is clear from Table 1 and FIG.
First, when the printing pressure is 0.5 [kg / cm ² ] or less, transfer failure occurs, but in the range of 1 to 13 [kg / cm ² ], good dot gain was exhibited at all image viscosities investigated. Therefore, the developer image is transferred from the intermediate transfer member 2 to the recording medium 1.
It can be seen that a good dot gain can be obtained by setting the pressing force (printing pressure) of the backup roller 18 at the time of transferring to 9 to 1 to 13 [kg / cm ² ].

On the other hand, FIG. 3 shows the transferred image on the coated paper by the image (developer image) viscosity (vertical axis) and the film thickness (horizontal axis) when the developer image is transferred from the intermediate transfer member 2 to the recording medium 19. 5 is a graph showing the relationship between the image flow of No. 3 and the blank image on high-quality paper. In the graph of FIG. 3, the case where a good image without blank is obtained on the high-quality paper is indicated by ●,
The case where there is no image bleeding (image deletion) due to an increase in the dot gain on the coated paper is indicated by ▪, and the case where it is present is indicated by ▲.

Generally, as the film thickness increases, the amount of increase in dot gain increases, image flow increases, and consequent dropouts decrease. Further, as the image viscosity increases, the increase amount of the dot gain decreases, the image deletion decreases, and the dropout increases. Therefore, as is clear from FIG. 3, first, regarding the image deletion of the coated paper, when the film thickness becomes 6 [μm], it is 10
Image deletion occurs at 00 [mPas], but does not occur at 4 [μm] or less, and the viscosity is 2200 [m] even with the same film thickness 6 [μm].
It can be seen that it does not occur when the pressure exceeds about Pas], and the image deletion is reduced by increasing the viscosity.
In addition, when the film thickness is 1 [μm], the blank does not occur at a viscosity of about 22000 [mPas], and when the viscosity is about 43000 [mPas], the film thickness needs to be about 2 [μm]. However, the film thickness is thicker and the viscosity is 43000.
If it is about [mPas] or less, almost no void occurs.

Therefore, the range shown in FIG. 3 as "no flow of coated paper image, no omission of fine paper", that is, the viscosity is 1000 to 50000 [mPas], and the developer film thickness on the intermediate transfer member is 1 to 1. It can be seen that in the range of 6 [μm], the image deletion does not occur on the coated paper and the blank image does not occur even on the high-quality paper. Therefore, if the developer viscosity is controlled so as to satisfy the above conditions, and the transfer bias is controlled so that the image film thickness on the intermediate transfer member is in the range of 1 to 6 [μm], coated paper or fine paper A wet electrophotographic printing apparatus using a liquid developer capable of transferring a good image can be configured.

Therefore, in the present invention, as described above, the average particle diameter is 0.1 to 6 [μ] in the silicon-based solvent.
The developer liquid 6 was used in which the solid content of m] was contained in a concentration of 30 to 50 wt% and the viscosity was 1000 to 50,000 [mPas]. Further, in order to form a developer film thickness of 1 to 6 [μm] on the intermediate transfer member 2, 95 to 100% of the developer liquid 6 on the developing roller 3 is transferred to the photosensitive member 1, and The transferred developer is also transferred to the intermediate transfer member 2 by 95 to 1
In the case of the transfer of 00%, it is necessary to form a developer film thickness of about 2 to 7 [μm] on the developing roller 3. Therefore, the intermediate transfer member 2 is formed of a conductive roller or belt so that the transfer efficiency by the intermediate transfer bias can be increased.

Therefore, the original roller 4 for supplying the developer liquid 6 in the developer container 5 to the developing roller 3 rotates in the opposite direction to the developing roller 3, and the developer film thickness at the outlet becomes about 30 [μm]. Further, the original roller 4 has a peripheral speed of about 1/30 to 1/2 of that of the developing roller 3 as described above, and the slip caused by this peripheral speed difference causes the developing roller 3 to rotate.
A developer layer having a thickness of about 2 to 7 [μm] is formed on the top.

By doing so, the latent image formed on the photosensitive drum 1 is developed by the developing roller 3,
When the developer corresponding to the image adheres to the latent image on the photosensitive drum 1 to form a developer image, which is further transferred to the intermediate transfer body 2, as described above, the intermediate transfer bias is controlled to 1 A developer film thickness of 6 [μm] is formed. Therefore, as described in Table 1, FIG. 2 and FIG. 3, the pressing force (printing pressure) of the backup roller 18 at the time of transferring the developer image from the intermediate transfer body 2 to the recording medium 19.
Is 1 to 13 [kg / cm ² ], and the viscosity of the developer is 10
By setting the developer film thickness on the intermediate transfer member in the range of 0 to 50000 [mPas] and 1 to 6 [μm], a high-quality image free from image deletion and blank can be obtained even on coated paper and high-quality paper. be able to.

In the above description, the wet electrophotographic printing apparatus of the present invention shown in FIG. 1 has been described as an example of a single color. However, a plurality of chargers, an exposure device and a developing device are prepared, and a plurality of colors are prepared. May be formed at one time.

[0033]

As described above, according to the present invention as set forth in claims 1 and 4, it is possible to avoid a direct transfer of a developer image from a photoconductor onto a recording medium, which is difficult due to various factors, and a high pressure is applied. A transferable intermediate transfer member is used without heating that causes deterioration, and toner having an average particle size of 0.1 to 6 [μm] is used.
To 50 [wt%] and a viscosity of 1000 to 50000 [mPas] is used, and the intermediate transfer member is composed of a roller or belt formed of conductive rubber or resin. By increasing the transfer efficiency of the developer image from the photosensitive member by the intermediate transfer bias and controlling the developer film thickness on the intermediate transfer member to be 1 to 6 [μm], the developer image on the coated paper can be formed. Image bleeding (image deletion) due to an increase in dot gain can be prevented during transfer, and a good image can be obtained without causing blank defects due to transfer failure when transferring a developer image onto high-quality paper.

According to the present invention as set forth in claims 2 and 4, the pressing force of the coated paper or the high-quality paper on the intermediate transfer member is regulated to 1 to 13 [kg / cm ² ], whereby the above-mentioned coating is performed. When a developer image is transferred onto paper, image bleeding (image deletion) due to an increase in dot gain can be prevented, and a good image can be obtained.

According to the present invention as set forth in claim 5, most of the developer image transferred to the intermediate transfer member is coated paper by providing the intermediate transfer member with the releasing agent applying means and the cleaning means. Alternatively, the residual developer that has been transferred to the high-quality paper and still remains is cleaned by the cleaning device and does not affect the next image formation, and a good image can always be formed.

According to the present invention as set forth in claims 6 and 7, the releasing agent applying means is composed of a rotating member which comes into contact with the intermediate transfer member at a peripheral speed difference, and Rotate in the same direction as the rotation direction (for example, if the intermediate transfer member is rotating in the counterclockwise direction, the rotating member also rotates in the counterclockwise direction)
Or by rotating it in the opposite direction to the intermediate transfer member at a slower speed than the rotation speed of the intermediate transfer member (for example, if the intermediate transfer member is rotating in the counterclockwise direction, rotate the rotating member in the clockwise direction). A release agent can be applied to the intermediate transfer member.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a wet electrophotographic printing apparatus according to the present invention.

FIG. 2 is a graph showing a relationship between a pressing force, an image (developer image) viscosity, and a dot gain when a developer image is transferred from an intermediate transfer body to a recording medium.

FIG. 3 is a graph showing the relationship between the image flow of a transferred image and the voids depending on the image (developer image) viscosity and the film thickness when a developer image is transferred from an intermediate transfer member to a recording medium.

[Explanation of symbols]

1 photoconductor drum 2 Intermediate transfer body 3 developing roller 4 original roller 5 developer container 6 developer liquid 7 Cleaning device 8 cleaning roller 9 solvent 10 Exposure equipment 11 charger 12 Static eliminator 13 Cleaning blade 14 Cleaning device 15 blades 16 Release agent coating device 17 Container for release agent 18 Backup roller 19 recording media 20 heat fixing device

Continued front page    F-term (reference) 2H069 DA03 DA06 DA08                 2H074 AA03 AA09 EE07 EE09                 2H171 FA04 FA09 FA10 FA13 FA14                       FA15 FA22 FA24 GA01 LA04                       QA02 QA08 QA18 QA23 QA28                       QB02 QB14 QB32 QB40 QB54                       QC03 QC23 TA07 TA08                 2H200 FA17 FA19 GA04 GA16 GA18                       GA23 GA34 GA43 GA49 GA56                       GA59 GB02 GB12 GB25 HA12                       HA28 HB03 HB12 HB22 HB48                       JA02 JA08 JA21 JA28 JC02                       JC03 JC09 JC12 JC15 JC16                       JC18 LA12 LA18 LB02 LB13                       MA03 MB01 NA02 NA09

Claims (7)

[Claims] 1. A latent image formed on a photoconductor by an electrophotographic method is developed by a liquid developer held on a developing roller, and the formed developer image is transferred to an intermediate transfer member and then transferred to a recording medium. In the wet electrophotographic printing method, the developing roller is made to contain a toner having an average particle diameter of 0.1 to 6 [μm] at a concentration of 30 to 50 [wt%] and a viscosity of 100.
A first step of carrying a liquid developer controlled to a range of 0 to 50,000 [mPas] to a thickness of 2 to 7 [μm], and developing the latent image on the photoconductor with the liquid developer on a developing roller. And a second step of forming a developer image, and by forming the intermediate transfer member with a conductive roller or belt, the transfer efficiency by the intermediate transfer bias is increased and the film thickness on the intermediate transfer member is 1 to 6 The third step of transferring the developer image on the photoconductor so as to be [μm], and applying a transfer bias larger than the intermediate transfer bias to the recording medium side to transfer the developer image from the intermediate transfer body to a coated paper or A wet electrophotographic printing method characterized in that a developer image can be transferred by a fourth step of transferring onto high-quality paper. 2. The wet electrophotography according to claim 1, wherein in the fourth step, a transfer bias is applied while pressing the recording medium at 1 to 13 [kg / cm ² ] against the intermediate transfer member. Printing method. 3. A means for forming a latent image on a photoconductor by an electrophotographic method, a developing means for developing the latent image with a liquid developer to form a developer image, and an intermediate transfer bias for the developer image. In the wet electrophotographic printing apparatus provided with an intermediate transfer member for transferring the image on the recording medium and a transfer unit for transferring the developer image transferred on the intermediate transfer member to a recording medium, an average particle size of 0.1 to 6 [μm] 30 to 50 toner
Viscosity of 1000 to 5000 when added at a concentration of [wt%]
The liquid developer controlled in the range of 0 [mPas] is 2 to 7
The developing means has a thickness of [μm], and is composed of a developing roller in the developing means and a conductive roller or belt to increase the transfer efficiency of the developer image on the photoconductor to increase the developer image thickness to 1
To 6 [μm], the developer having the intermediate transfer body capable of transferring and a means for applying a transfer bias larger than the intermediate transfer bias to the transfer means, the developer being carried by the developing roller. A wet electrophotographic printing apparatus characterized in that an image is transferred onto a coated paper or a high-quality paper by a transfer means via an intermediate transfer body. 4. The transfer means comprises a recording medium 1 to 13.
The wet electrophotographic printing apparatus according to claim 3, further comprising means for applying a transfer bias while pressing the intermediate transfer member with [kg / cm ² ]. 5. A release agent applying unit for applying a release agent to the intermediate transfer body is provided on the intermediate transfer body on the upstream side of the transfer position of the developer image on the photoreceptor, and the developer is released by the release agent. 4. The cleaning device for cleaning the residual developer on the intermediate transfer member, which facilitates the transfer of the image onto the recording medium and is provided downstream of the transfer position of the developer image onto the recording medium. Wet electrophotographic printer. 6. The wet electrophotographic printing apparatus according to claim 5, wherein the release agent applying means is composed of a rotating body that comes into contact with the intermediate transfer body with a peripheral speed difference. 7. The release agent applying device rotates in the same direction as the rotation direction of the intermediate transfer member or in the opposite direction at a slower speed than the intermediate transfer member. The wet electrophotographic printing device described.