JPH10171256A - Method and device for wet system image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the uniform electrification, and to form a uniform pre-wet liquid layer by performing simultaneously the pre-wet processing and the electrification processing. SOLUTION: This device is capable of simultaneously performing the pre-wet and the electrification by adopting the constitution integrating the applying device of a releasing agent (pre-wet liquid) and a contact electrifying device into one body. Namely, an electrification of copying machine and pre-wet application device 20 applies the pre-wet liquid 4 which is saved in an oil sump (pre-wet liquid pan) 20a, drawn up by a draw up roller 21, and extended on plural rollers 22 and 23, onto a photoreceptor 2. Moreover, an applying roller 23 directly facing the photoreceptor 2 composed of a conductive material, is capable of electrifying the photoreceptor 2 while applying the pre-wet liquid thereon by applying a voltage on its core bar by a power source 24. In such a way, by simultaneously executing the electrocution processing and the pre-wet processing of the image carrier, the result of the processing executed earlier is prevented from being disturbed by the processing executed later, therefore uniformity of both can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, and a printing machine, and more particularly, to a wet image forming method including a step of performing development using a developer and an apparatus therefor. Things.

[0002]

2. Description of the Related Art In this type of wet image forming apparatus, a developing device is used which develops an electrostatic latent image formed on a latent image carrier such as a photoreceptor with toner as charged particles. In order to reduce the size of the developing device, it has been proposed to use a high-concentration and high-viscosity developer in which the toner concentration of a developer in which toner is dispersed in an insulating liquid is set to be higher. For example, Japanese Patent Application Laid-Open No. 7-209922 discloses a liquid development method for an electrostatic latent image formed by developing an electrostatic latent image formed on an image support with toner, which is a charged visualized particle, The toner is dispersed at a high concentration in an insulating liquid applied on a conductive developer support.
An electrostatic latent image comprising a developing step of supplying the liquid developer to a latent image surface of the image support by bringing a liquid developer having a high viscosity of 10,000 mPa · s into contact with the image support. Liquid development method. Has been proposed.

[0003] Further, in the same publication, the above-mentioned liquid developing method is characterized in that, prior to the above-mentioned developing step, a pre-wet, which is a release liquid and a chemically inert dielectric liquid, is formed on the image support. A liquid developing method for an electrostatic latent image, characterized by comprising a pre-wetting step of applying a liquid.
This pre-wet step is performed by separating the layer of the liquid developer supplied to the image support from the surface of the image support by a pre-wet liquid layer, thereby preventing unnecessary toner from adhering to the image support surface. This is for preventing image disturbance due to toner adhesion to non-image portions.

[0004]

In a wet electrophotographic apparatus in which the pre-wet liquid is used to prevent the above-mentioned background contamination as image disturbance, when a general corona charger is used as a charging device for a photoreceptor, a pre-wetting liquid is required. If the wetting agent is a volatile liquid, the components of the pre-wetting liquid crystallize due to ozone generated by the corona charger and adhere to the corona charger wires, which may cause unevenness in image density due to uneven charging. is there. Therefore, it is desirable to use a technology such as a charging roller that generates less ozone as the charging device.

FIG. 5 shows an apparatus for carrying out a liquid developing method for an electrostatic latent image including the above-mentioned pre-wet process, which is an example of an apparatus using a charging roller as a charging device for a photosensitive member. In FIG. 5, in this apparatus, a pre-wet liquid (which is sufficiently uniformly spread by a combination of several rollers 3) is applied to a photoconductor 2 as a latent image carrier charged by a charging roller 1 as a charging device. For example, the main component is silicon, and the viscosity is 0.5 to 1000 mPa · s.
Of about 10 ¹² Ωcm or more). The photosensitive member 2 is irradiated with light from an exposure device (not shown) to form an electrostatic latent image. This electrostatic latent image is developed by the developing device 5. Specifically, a high-viscosity developer applied uniformly on the developing belt 6 as a developer carrier of the developing device 5 is brought into contact with the surface of the photoreceptor 2 on which the electrostatic latent image is formed, and The toner is transferred to the latent image on the photoconductor 2 and developed. The toner image formed on the photoreceptor 2 formed by this development is electrically hardened by a set roller 7 to which a predetermined voltage is applied, and is transferred onto a transfer paper 8 sent from a paper feeder (not shown). The image is transferred by the transfer roller 9. And
After the transfer, the surface of the photoreceptor 2 is cleaned of residual toner by a cleaning blade 10 of a cleaning device, and the residual charge is removed by a discharging lamp 11 as a discharging device to prepare for the next image formation. On the other hand, the transfer paper 8 onto which the toner image has been transferred is separated from the photoreceptor 2 by a separation device (not shown), and is discharged from the device after being subjected to a fixing process by a fixing device (not shown).

However, in the apparatus shown in FIG. 5, since the pre-wet liquid is contact-applied by the roller 3 after being charged by the charging roller 1, uniform charging may be disturbed by the application of the pre-wet. If uniform charging is disturbed, density unevenness or unevenness occurs in an image. Contrary to the apparatus shown in FIG. 5, if the pre-wet liquid is applied and then contact-charged by the charging roller 1, the charging roller 1 may break down the uniform pre-wet liquid film. When the pre-wet liquid film is destroyed, the above-mentioned background contamination occurs at the broken portion of the pre-wet liquid film. Furthermore, even if charging is performed before and after the application of the pre-wet liquid using two charging rollers, the pre-wet liquid film may be destroyed by the final-stage charging roller, and the above-described background contamination may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a wet image forming method and a device which can form a uniform pre-wet liquid film while uniformly charging. That is.

[0008]

In order to achieve the above object, the present invention is directed to a pre-wetting step of applying a predetermined pre-wet liquid to the surface of a latent image carrier, A charging step of charging the latent image carrier to form a latent image, and developing a latent image by applying a developing solution to the latent image carrier on which the pre-wet liquid is applied and the latent image is formed And a developing step, wherein the pre-wet step and the charging step are performed simultaneously.

Further, the invention according to claim 2 is a pre-wet means for applying a predetermined pre-wet liquid to the surface of the latent image carrier, and the latent image carrier for forming a latent image on the latent image carrier. And a developing means for applying a developing solution to the latent image carrier on which the pre-wet liquid is applied and the latent image is formed to develop the latent image. , The pre-wet means and the charging means,
It is characterized in that the application of the prewetting liquid and the charging are performed simultaneously.

According to a third aspect of the present invention, in the wet image forming apparatus of the second aspect, the prewetting means and the charging means use a common opposing member which opposes the surface of the latent image carrier. The coating and charging are performed.

According to a fourth aspect of the present invention, in the wet image forming apparatus of the third aspect, the opposed member is a conductive member to which a predetermined voltage is applied, and a pre-wet liquid is applied to the surface of the opposed member. And a pre-wet liquid supply means for supplying the liquid.

According to a fifth aspect of the present invention, in the wet image forming apparatus of the third aspect, the opposing member is a dielectric member capable of accumulating electric charges, and charging means for applying an electric charge to the opposing member for charging. And a pre-wet liquid supply means for supplying a pre-wet liquid to the surface of the facing member.

According to a sixth aspect of the present invention, in the wet image forming apparatus of the fourth or fifth aspect, the prewetting liquid supply means is constituted by using a coating member for applying a prewetting liquid to the facing member. The coating member is formed of an insulating material or is attached to the apparatus body in an insulated state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a wet electrophotographic copying machine as a wet image forming apparatus will be described below. FIG. 1A is a front view showing a schematic configuration of a copying machine according to the present embodiment. This copier employs a configuration in which a coating device for a release agent (pre-wet liquid) and a contact charging device are integrated, and by performing pre-wet and charging simultaneously, pre-wet without disturbing the uniformity of each other. Coating and charging are performed. The configuration of the apparatus other than the application and charging of the pre-wet liquid is the same as that of the above-described apparatus of FIG. 5, and the description thereof will be omitted.

FIG. 1B is an enlarged view of the charging and pre-wet coating device 20 of the copying machine shown in FIG. In FIG. 1 (b), this apparatus draws up a pre-wet liquid 4 stored in an oil sump (a pre-wet liquid receiver) 20a with a pump-up roller 21 and spreads the pre-wet liquid 4 with a plurality of rollers 22 and 23. Is applied as a uniform film. The application roller 23 that directly faces the photoconductor 2 is made of a conductive material, and charges the photoconductor 2 while applying a pre-wet liquid by applying a voltage from a power source 24 to the metal core.

The coating roller 23 can be a roller having a metal core such as sus as a shaft and a surface layer made of a conductive material such as hydrin rubber formed thereon. For example, a roller having a volume resistance of 10 ⁸ Ωcm and a hardness of 30 to 70 degrees is suitable. As a material of the supply roller 22 for supplying the pre-wet liquid to the conductive application roller 23, it is desirable to use a non-conductive material in order to avoid electric leakage. When a conductive material is used, it is desirable to insulate between the shaft made of the cored bar and the device side plate.

FIGS. 2 (a) and 2 (b) show an example of a structure for insulating the shaft and the side plates 30 of the apparatus when the conductive supply roller 22 is used. 2 (a)
Is a perspective view thereof, and FIG. 2 (b) is a front view thereof. In each of the drawings, the oil sump 20a, the application roller 23, and the pumping roller 21 are not shown. In this configuration example, the shaft 22a of the supply roller 22 is held by a roller holding stay 22c made of insulating resin via a bearing 22b made of a bearing or the like. Then, the roller holding stay 22c is connected to the pre-wet coating device 20.
Is fixedly attached to the coating device frame pair 20b which also serves as the casing 20b. The frame pair 20b is attached to both side plates 30 with positioning pins 20c and the like. According to this, since the roller holding stay 22c made of an insulating resin is interposed between the shaft 22a of the supply roller 22 and the both side plates 30, the both are insulated. Note that FIG.
As shown in (b), the end 22d of the supply roller shaft 22a
It is advantageous to keep the distance between the side plate 30 and the side plate 30 at least about 10 mm in order to prevent discharge at this distance.

When the non-conductive supply roller 22 is used, the supply roller 22 is always in contact with the high-voltage conductive roller 23, and may be charged. In order to prevent this charging, for example, as shown by a two-dot chain line in FIG.
5 and the surface is neutralized. This ensures electrical safety. However, since the conductive roller 23 to which a high voltage is applied is still contained in the charging and pre-wetting coating device, it is desirable to pay sufficient attention to abnormal discharge and leakage. Specifically, the application roller 2
It is desirable to design so that the conductive member does not approach the vicinity of 3 as much as possible. Although one supply roller 22 which is an intermediate roller is used in the illustrated example, two or more supply rollers 22 may be used. Conversely, the intermediate roller 22 is omitted, and the pumping roller 21 and the application roller 23 are directly contacted and disposed. Alternatively, the intermediate roller 22 and the application roller 23 are omitted, and the application roller 23 is directly connected to the oil sump 2.
0a.

[Embodiment] In the apparatus shown in FIGS. 1A and 1B, as a developing solution, DC345 (trade name) manufactured by Dow Corning Co., USA, which is a cyclic polydimethylsiloxane oil having a viscosity of 20 mPa · s, was wet-processed. Toner dispersed (toner concentration (pigment content)) 20%, viscosity 200 to 3000
mPa · s (viscosity varies depending on the type of pigment corresponding to the toner color) was used. As a pre-wet liquid, DC344 manufactured by Dow Corning Co., USA, which is a cyclic polydimethylsiloxane oil having a viscosity of 2.5 mPa · s.
(Trade name) was used.

FIG. 4 is a graph showing the relationship between the voltage applied to the metal core of the application roller 23 and the surface potential of the charged photosensitive member 2 in the apparatus according to the above embodiment. The characteristic line a is a measurement result when a relatively large amount of prewetting liquid is applied, the characteristic line b is a measurement result when a relatively small amount of prewetting liquid is applied, and the characteristic line c is a measurement result when no prewetting liquid is applied. As can be seen from this graph, when the application amount of the pre-wet liquid increases, the charging potential of the photoconductor when the same voltage is applied to the core metal tends to decrease.
By setting the applied voltage, a desired photoconductor charging potential can be sufficiently obtained. Regarding the uniformity of charging, there was no change in the charging and uniformity when no liquid was present, but rather, the uniformity of charging in the circumferential direction of the photoconductor tended to be improved. Also,
Regarding the uniformity of the film thickness of the pre-wet liquid, the adverse effect of increasing the ribs generated in the liquid film on the application roller 23 by applying the voltage while applying the voltage is not particularly observed, and is sufficient even on the photoreceptor. It was possible to obtain a uniform film thickness.

FIG. 3A is a schematic configuration diagram of a charging and pre-wet coating apparatus according to a modification. In this apparatus, the coating roller 23 is made of a material having a high dielectric constant so that the surface can be charged. And this application roller 23
Is charged first, and the photosensitive member 2 is charged by the charged coating roller 23, that is, indirect charging is performed. In the illustrated example, the application roller 23 is charged by the supply roller 22 which also serves as a charger. Specifically, the supply roller 22 that is in contact with the application roller 23 is formed of a conductive member, and a voltage is applied to the core. Alternatively, as shown in FIG. 3B, a dedicated charging member 26 made of a conductor to which a voltage is applied by the power supply 25 may be brought into contact with the surface of the application roller 23.

The coating roller 23 of this embodiment is made of an electrically grounded conductive metal core and a dielectric material having a thickness of about 50 μm to 1 mm on its surface layer, and has a charge density of about 1 × 10 ⁸ C / mm ^2. And can be charged. By the way, 2.10 ⁹
The photoreceptor can be charged to about 600 V with a charge density of about C / mm ² . The surface of the application roller 23 is charged so that the potential difference between the application roller 23 and the photosensitive member 2 is equal to or higher than the discharge starting voltage and the potential difference can charge the photosensitive member 2 to a desired target potential. When brought into contact with the body 2, the photoconductor 2 can be charged to a target potential. The advantage of this indirect charging is that no charge higher than the charge given to the dielectric layer of the coating roller 23 is supplied to the photosensitive member 2, and therefore, the conductive coating roller 23 connected to the power supply is applied to the photosensitive member 2. Unlike the case of contact, the photoconductor is less likely to be damaged by abnormal discharge or the like.

The developing belt 6 serving as a developer carrier of the above-described developing device is made of a metal material or an elastic material, and the surface on which the thin developer layer is formed is a resin material and the other surface is a conductive material. A configuration in which processing is performed may be used. Further, a developing roller may be used instead of the developing belt.

[0024]

According to the first to sixth aspects of the present invention, the charging step of the latent image carrier and the pre-wetting step are performed at the same time. The uniformity of both charging and pre-wetting can be maintained without disturbing the results of the repeated steps.

In particular, according to the third aspect of the present invention, the common opposing member is used for both application and charging of the pre-wet liquid, so that space and cost can be reduced due to a decrease in the number of parts.

According to the fourth aspect of the present invention, there is provided a simple structure in which a predetermined voltage is applied to the conductive opposing member to which the pre-wet liquid is supplied by the pre-wet liquid supply means.
Prewet liquid application and charging can be performed.

According to the fifth aspect of the present invention, since the latent image carrier is charged by the opposing member made of a dielectric member charged with the electric charge by the charging means, the electric charge more than the electric charge applied by the charging means is charged. It does not flow to the latent image carrier side. Therefore, it is possible to prevent the latent image carrier from being damaged due to an excessive current flowing toward the latent image carrier.

According to the sixth aspect of the present invention, since the coating member for applying the pre-wet liquid to the facing member is formed of an insulating material or attached to the apparatus body in an insulated state, a high voltage is applied. Even if the coating member is brought into contact with the facing member whose surface is charged to a predetermined potential, abnormal discharge or the like between the two members can be prevented.

[Brief description of the drawings]

FIG. 1A is a schematic configuration diagram of a copying machine according to an embodiment.
(B) is a partially enlarged view of the copying machine.

FIG. 2A is a perspective view of a charging and coating apparatus according to a modification. (B) is a front view of the charging and coating device according to the modification.

FIG. 3A is an explanatory diagram of a charging and coating device according to another modification. (B) is explanatory drawing of the charging and coating device which concerns on another modification.

FIG. 4 is a graph showing an experimental result using the copying machine.

FIG. 5 is a schematic configuration diagram of an example of a copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging roller 2 Photoreceptor 4 Pre-wet liquid 5 Developing device 6 Developing belt 20 Charging and pre-wet coating device 20a Oil sump 21 Pump-up roller 22 Supply roller 23 Coating roller 24 Power supply 25 Static electricity removing conductive member 26 Charging power supply 27 Charging member

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[Procedure amendment]

[Submission date] April 10, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2 is an explanatory diagram of a charging and coating device according to a modification.

Claims (6)

[Claims] A pre-wetting step of applying a predetermined pre-wetting liquid to the surface of the latent image carrier; a charging step of charging the latent image carrier to form a latent image on the latent image carrier; A developing step of applying a developing solution to the latent image carrier on which the prewetting liquid is applied and the latent image is formed to develop the latent image, wherein the prewetting step and the charging A wet image forming method, wherein the steps are performed simultaneously. A pre-wet means for applying a predetermined pre-wet liquid to the surface of the latent image carrier; a charging means for charging the latent image carrier to form a latent image on the latent image carrier; A developing means for applying a developing solution to the latent image carrier on which the latent image is formed on which the prewetting liquid is applied and developing the latent image; A wet image forming apparatus, wherein the charging means is configured to simultaneously perform application of a prewetting liquid and charging. 3. A wet image forming apparatus according to claim 2, wherein said prewetting means and said charging means apply and charge a prewetting liquid by using a common opposing member opposing the surface of the latent image carrier. A wet image forming apparatus. 4. A wet image forming apparatus according to claim 3, wherein said opposing member is a conductive member to which a predetermined voltage is applied, and a prewetting liquid supply for supplying a prewetting liquid to a surface of said opposing member. And a wet image forming apparatus. 5. A wet image forming apparatus according to claim 3, wherein said opposing member is a dielectric member capable of accumulating electric charges, and charging means for applying electric charges to said opposing member for charging. And a pre-wet liquid supplying means for supplying a pre-wet liquid to the surface of the liquid image forming apparatus. 6. The wet-type image forming apparatus according to claim 4, wherein said prewetting liquid supply means is constituted by using a coating member for applying a prewetting liquid to said opposed member, and said coating member is provided. A wet-type image forming apparatus characterized in that is formed of an insulating material or is attached to the apparatus body in an insulated state.