JPH07334003A - Liquid crystal developing device for electrostatic latent image - Google Patents

Abstract

PURPOSE:To provide a liquid developing device for an electrostatic latent image capable of uniformly supplying liquid developer to the latent image surface of an image supporting body by uniformly applying high concentration and high viscosity liquid developer on a developer supporting body. CONSTITUTION:As for the liquid developing device for developing the electrostatic latent image formed on a photoreceptor by toner, the device is provided with a developing belt 510 formed of a flexible belt-like member and for supplying the high concentration and high viscosity liquid developer to the latent image surface of the photoreceptor, applying devices 52a to 52d equipped with an applying roller 522a for applying the liquid developer on the developing belt 510 and a supporting roller 516 formed of an elastic member and brought into contact with the applying roller 522a through the developing belt 510.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electrophotography, electrostatic recording,
The present invention relates to a liquid developing device for an electrostatic latent image that visualizes an electrostatic latent image formed by a method such as ionography using a liquid developer.

[0002]

2. Description of the Related Art Conventionally, in a liquid developing apparatus for an electrostatic latent image, as a method for supplying a liquid developer to a latent image surface on an image support, unevenness is provided on the surface of a developing roller which is a developer support. A method of holding a liquid developer in a concave portion and supplying it to an image support, using a sponge roller as the developer support, and pressing the sponge roller against the image support to image the liquid developer absorbed by the sponge roller. A method of supplying to the support, or a method of directly supplying the liquid developer to the image support without using the developer support by immersing the image support in a developer tank in which the liquid developer is stored, etc. It is used.

[0003]

However, in the conventional large-sized electrostatic recording apparatus and the like, Isop which is an organic solvent is generally used.
arG (registered trademark: manufactured by Exxon) is used as a low-viscosity liquid developer in which a toner is mixed at a ratio of about 1 to 2%. Therefore, when a highly viscous liquid developer in which toner is dispersed in an insulating liquid at a high concentration is used, which method is preferable as a method for supplying the liquid developer to the latent image surface of the image support. Not clear.

[0004]

[Purpose] The present invention has been made based on the above circumstances, and a liquid developer having a high concentration and a high viscosity is uniformly coated on a developer support to form a liquid developer on the latent image surface of the image support. An object of the present invention is to provide a liquid developing device for an electrostatic latent image that can be uniformly supplied.

[0005]

In order to achieve the above-mentioned object, a liquid developing apparatus for an electrostatic latent image according to the present invention described in claim 1 charges an electrostatic latent image formed on an image support. Is a liquid developing device for an electrostatic latent image, which is developed with a toner that is a visualized particle, and a high-viscosity liquid developer of 100 to 10000 mPa · s in which a toner is dispersed in an insulating liquid at a high concentration, A developer support formed of a flexible belt-shaped member for supplying to the latent image surface of the image support, an application roller for applying the liquid developer on the developer support, and the developer It is characterized in that it comprises a pressing means that comes into contact with the applying roller via a support, and at least one of the applying roller and the pressing means is formed of an elastic member.

According to a second aspect of the present invention, there is provided an electrostatic latent image liquid developing device according to the first aspect, wherein the pressing means is formed in a roller shape.

According to a third aspect of the present invention, there is provided an electrostatic latent image liquid developing device according to the first or second aspect, wherein the insulating liquid of the liquid developer has a viscosity of 0.5 to 1000 m.
Pa · s, electric resistance 10 ¹² Ωcm or more, surface tension 2
It is characterized in that the boiling point is 1 dyne / cm or less and the boiling point is 100 ° C. or more.

According to a fourth aspect of the invention, there is provided an electrostatic latent image liquid developing apparatus according to the third aspect, wherein the liquid developer utilizes silicon oil as an insulating liquid. It is what

According to a fifth aspect of the present invention, there is provided an electrostatic latent image liquid developing apparatus according to the first, second, third or fourth aspect, wherein the liquid developer has an average particle size of 0.1 to 5 μm. The toner is characterized by containing toner at a concentration of 5 to 40%.

[0010]

According to another aspect of the invention, there is provided a liquid developing device for an electrostatic latent image, comprising: a coating roller for coating the liquid developer on the developer support; and a pressing means for contacting the coating roller via the developer support. By providing at least one of the applying roller and the pressing means with an elastic member, the applying roller can be brought into contact with the developer support with an appropriate pressing force. Therefore, the liquid developer layer formed on the coating roller with a constant layer thickness can be supplied onto the developer support without being crushed at the contact portion between the coating roller and the developer support. As a result, the liquid developer can be uniformly coated on the developer support, and thus the high-concentration and high-viscosity liquid developer can be uniformly supplied to the latent image surface of the image support. Further, since the liquid developer in which the toner is dispersed in a high concentration is used, the liquid amount can be much smaller than that of the conventional low concentration liquid developer. Also,
When the viscosity of the liquid developer is 10,000 mPa · s or more, it becomes difficult to stir the insulating liquid and the toner, and a problem is how to make the liquid developer. Therefore, a liquid developer of 10,000 mPa · s or more becomes unrealistic in terms of cost and becomes unrealistic. On the other hand, 100m
If it is less than Pa · s, the toner density will be low and the dispersibility of the toner will be poor, so that the developer cannot be made into a thin layer for development.

In the electrostatic latent image liquid developing device according to the second aspect, the pressing means is formed in a roller shape, so that the same operation as the invention according to the first aspect is achieved.

According to a third aspect of the present invention, there is provided an electrostatic latent image liquid developing apparatus, wherein an insulating liquid having the above characteristics is used.
A high-viscosity liquid developer can be obtained. Since the liquid developer formed on the developer support is formed in a thin layer,
Since the amount of insulating liquid contained in the liquid developer layer is extremely small, the amount of insulating liquid contained in the liquid developer supplied to the latent image surface of the image support is also very small. Therefore, the amount of the insulating liquid absorbed on the paper or the like at the time of transfer is extremely small, so that the problem of the insulating liquid adhering to the paper or the like does not occur if the viscosity is 1000 mPa · s or less. However, if the viscosity is 0.5 mPa · s or less, the volatility becomes high and it is not suitable as a hazardous material. When the boiling point of the insulating liquid is 100 ° C. or less, the amount of evaporation is large, so that there is a problem in the method of storing the developer, the entire device must have a closed structure, and it is difficult to improve the working environment. . When the electric resistance is 10 ¹² Ωcm or less, the insulating property is deteriorated, and the toner has a problem of conductivity and cannot be used as a developer. Therefore, it is desirable that the electric resistance be as high as possible. When the surface tension is 21 dyne / cm or more, the wettability becomes poor. Therefore, it is desirable that the surface tension be as low as possible.

In the electrostatic latent image liquid developing device according to the fourth aspect, since the insulating liquid contains silicon oil as a main component, the insulating liquid having the characteristics according to the fifth aspect can be obtained. it can.

According to a fifth aspect of the present invention, there is provided a liquid developing device for an electrostatic latent image, wherein the liquid developer comprises a toner having an average particle diameter of 0.1 to 5 μm.
By containing it at a concentration of -40%, it is possible to obtain a liquid developer in which the toner is dispersed in the insulating liquid at a high concentration. In addition, the resolution is improved in almost inverse proportion to the particle size of the toner. Usually, the toner is present as a mass of about 5 to 10 pieces on the printed paper, so that when the average particle diameter of the toner becomes 5 μm or more,
The resolution is poor. On the other hand, the average particle size of the toner is 0.1μ
When it is less than m, the physical adhesive strength becomes large and it becomes difficult to peel off the toner during transfer.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 6 and 16. FIG. 1 is a schematic configuration diagram of an electrostatic latent image liquid developing apparatus which is an embodiment of the present invention, and FIG.
3 is a schematic front view of the developing device used in the liquid developing device for electrostatic latent image shown in FIG. 3, FIG. 3 is a right side view of the developing device shown in FIG. 2, and FIG. 4 is an operation of the coating section of the developing device shown in FIG. FIG. 5 is a diagram for explaining a contact method of adjacent rollers of the coating unit shown in FIG. 4, and FIG. 6 is a diagram for explaining the operation of the electrostatic latent image liquid developing device shown in FIG. FIG. 16 and FIG. 16 are views for explaining a state in which the support roller comes into contact with the application roller via the developing belt.

As shown in FIG. 1, an electrostatic latent image liquid developing apparatus 1 according to an embodiment of the present invention applies a photoconductor 10 as an image support and a prewetting liquid on the photoconductor 10. A pre-wetting device 20, a charging device 30 that charges the photoconductor 10, and an exposure device 40 that exposes an image on the photoconductor 10.
And a developing device 50 that visualizes the electrostatic latent image by supplying toner to the portion of the photoconductor 10 on which the electrostatic latent image is formed.
A transfer device 60 for transferring and fixing the toner on the photoconductor 10 to a predetermined paper P, a cleaning device 70 for removing the toner remaining on the photoconductor 10, and a charged photoconductor (not shown). A static eliminator for static erasing 10 is provided.

For the charging device 30, the exposure device 40, the cleaning device 70, and the static eliminator, the conventional technique used in the conventional electrophotographic printer can be used in most cases. Therefore, in the present embodiment, the description of each of the above devices will be omitted, and the pre-wetting device 20, the developing device 50, and the transfer device 60, which are the main parts of the present invention, will be described.

The function required of the pre-wetting device 20 of this embodiment is to apply a uniform amount of the pre-wetting liquid onto the photoconductor 10 uniformly. For that purpose, a method of applying the pre-wetting liquid with a sponge-like material,
A coating method for other purposes such as a method of ejecting the pre-wet liquid from a plurality of nozzles arranged in the width direction of the photoconductor 10 or a method of applying with a sponge roller can be used. The inventors of the present invention tried various methods and confirmed that the above method was possible. The most convenient and best-performing method was to use a pre-wetting liquid using BELITA (registered trademark: Kanebo Co., Ltd.). Was the method of applying. Bell eater is a continuous porous sponge having a three-dimensional network structure in which the pores are continuous, can hold the pre-wet liquid by the volume of the pores, and when the pre-wet liquid exceeding the volume of the pores is supplied, The pre-wetting liquid can be uniformly discharged from the surface. The bell eater used in the present embodiment had a substantially semi-cylindrical contact surface with the photoconductor 10.

As shown in FIGS. 2 and 3, the developing device 50 comprises a developing section 51 and a coating section 52.
The developing section 51 includes a developing belt 510 that is a developer support.
Drive rollers 512a and 512b for rotating and driving the developing belt 510 and holding a portion of the developing belt 510 in contact with the photoconductor 10, and the developing belt 51.
Scraping blade 5 for removing the liquid developer remaining at 0
14 and a supporting roller 516 which is a pressing unit.
The coating unit 52 includes coating devices 52a, 52b, 52c, and 52d that coat the surface of the developing belt 510 with the liquid developer.

The coating devices 52a to 52d include a bellows pump 520 for storing and discharging the liquid developer, and a coating roller 52 for coating the liquid developer on the developing belt 510.
2a and a transport roller 522 that transports the liquid developer discharged by the bellows pump 520 to the coating roller 522a.
b, 522c, adjusting roller 522d, coating roller 5
And a separating / connecting device 524 that separates / separates 22a from the developing belt 510. Liquid developer containing yellow toner is applied to the bellows pump 520a of the coating device 52a.
The liquid developer containing magenta toner is applied to the bellows pump 520b of FIG.
0c is a liquid developer containing cyan toner, and
A liquid developer containing black toner is stored in the bellows pump 520d of the coating device 52d.

The coating roller 522a is a conveying roller 522b.
The transport roller 522b is configured to come into contact with the transport roller 5
22c so that it abuts against the transport roller 522c.
Are provided so as to contact the adjusting roller 522d. The coating roller 522 a is in the direction in which it is driven by the developing belt 510, and the transport roller 522 b is the coating roller 522.
a in the direction to be driven, the transport roller 522c is in the direction to be driven by the transport roller 522b, and the adjusting roller 522
Each of d rotates in the direction in which it is driven by the transport roller 522c.

Application roller 522a and transport roller 522
A hard roller having a hardness of 60 ° (JIS A) or more is used for c, and a soft roller having a hardness of 60 ° (JIS A) or less is used for the conveying roller 522b and the adjusting roller 522d. Hard rollers with a hardness of 60 ° (JIS A) or more and soft rollers with a hardness of 60 ° (JIS A) or less were alternately contacted and arranged, as shown in FIG. This is to form the nip width t at the contact portion with the adjacent hard roller. The harder the hard roller, the better for elastically deforming the soft roller. Therefore, the hardness of the hard roller is preferably 90 ° (JIS A) or more. As a roller having a hardness of 90 ° (JIS A) or more, ULTRA-S made by urea resin (made by Miyagawa Roller Co., Ltd.), a ceramic roller made by ceramics containing alumina as a main component (made by Nippon Steel Co., Ltd.) ), And a resin roller such as a roller formed of ebonite. Further, when the pressing force of the soft roller to the hard roller is strong, a high torque is required to rotate each roller. Therefore, it is preferable that the soft roller is elastically deformed by a weak pressing force. Therefore, the hardness of the soft roller is preferably 40 ° (JIS A) or less. However, when the hardness is 15 ° (JIS A) or less, it becomes impossible to maintain a constant shape, and thus it becomes difficult to form a constant nip width at the contact portion with the hard roller. As a roller having a hardness of 15 ° to 40 ° (JIS A), BEET (manufactured by Miyagawa Roller Co., Ltd.) made of synthetic resin, NB
There is a roller formed of R (acrylonitrile-butadiene rubber). The coating roller 522a and the transport rollers 522b and 522c are required to thinly and uniformly coat a liquid developer having a high concentration and a high viscosity, which will be described later, on their surfaces.
Those with good lipophilicity are desirable.

As shown in FIG. 5, a disk wheel 526a having the same outer diameter as the outer diameter of the applying roller 522a is provided on both sides of the applying roller 522a, and an outer diameter same as the outer diameter of the carrying roller 522c is provided on both sides of the carrying roller 522c. Disc wheels 526a each having a diameter are provided. A disk wheel 526b having an outer diameter slightly smaller than the outer diameter of the transfer roller 522b is provided on both sides of the transfer roller 522b, and a disk wheel 526b having an outer diameter slightly smaller than the outer diameter of the adjustment roller 522d is provided on both sides of the adjustment roller 522d. Are provided respectively. And the adjacent disc wheels 526
By bringing a and the disk wheel 526b into contact with each other, the axial distance between the coating roller 522a and the conveying roller 522b is made shorter than the total radius of the coating roller 522a and the conveying roller 522b, and the conveying roller 522b and the conveying roller 522c are made.
The distance between the axes of the transfer rollers 522b and 522c
Shorter than the total radius of the
And the distance between the axes of the adjusting roller 522d and the conveying roller 522c.
And the radius of the adjusting roller 522d is shorter than the total.
As a result, the applying roller 522a and the conveying roller 522
b, the carrying roller 522b and the carrying roller 522c, and the carrying roller 522c and the adjusting roller 522d contact each other with a constant pressing force. In this embodiment, the coating roller 522
a, conveying rollers 522b and 522c, and adjusting roller 52
2d has an outer diameter of 20 mm, disc wheel 526a has an outer diameter of 20 mm, and disc wheel 526b has an outer diameter of 1 mm.
A 9 mm one was used. The disc wheel may be a cylindrical roller.

The separating / connecting device 524 includes arms 524a, 52a.
4a. A coating roller 522a and a conveying roller 522b are fixed to the arms 524a and 524a. The arms 524a and 524a rotate about the shaft of the transport roller 522b as an axis by a driving device (not shown). As a result, the applying roller 522a is moved to the developing belt 51.
Separate from and touch 0.

The developing belt 510 includes a driving roller 512.
It is rotationally driven in the direction in which the photoconductor 10 is driven by a and 512b. As the developing belt 510, a flexible belt member such as a seamless nickel belt or a resin belt such as a polyimide belt is used. The developing belt 510 must be capable of applying a developing bias. Therefore, when a resin belt is used, conductive particles are added to reduce the electric resistance value, or
It is necessary to apply conductive processing to the surface of the belt.

The support roller 516 is a coating roller 522a.
Is applied to the developing belt 510 when the applying roller 522a
Is installed so as to be supported from the back surface of the developing belt 510, and rotates in a direction that follows the developing belt 510.
For the support roller 516, an elastic member such as sponge and felt is used. As a result, the coating roller 522a is
As shown in FIG. 16, the developing belt 510 is contacted with an appropriate pressing force.

The transfer device 60 includes an intermediate transfer belt 610, which is an intermediate transfer member, and a drive roller that rotates and drives the intermediate transfer belt 610 and holds a part of the intermediate transfer belt 610 so as to contact the photosensitive member 10. 612a, 61
2b and 612c, and a secondary transfer roller 6 that is a secondary transfer member installed so as to be in contact with the intermediate transfer belt 610.
14 and a scraping blade 616 for removing the toner remaining on the intermediate transfer belt 610.

The intermediate transfer belt 610 includes a driving roller 61.
2a, 612b, 612c are driven to rotate in the direction in which the photoconductor 10 is driven. The secondary transfer roller 614 is pressed against the intermediate transfer belt 610 via the paper P. The fixing heater 6 for heating the paper P is provided inside the driving roller 612c.
18 is provided.

Next, the image forming material used in one embodiment of the present invention will be described. The liquid developer used in this example includes a resin that serves as a binder such as epoxy, a charge control agent that gives a predetermined charge to the toner, a color pigment, a toner that includes a dispersant that uniformly disperses the toner, and a carrier liquid. Consists of. The toner composition is basically similar to that used in conventional liquid developers, but their formulation has been modified to be compatible with silicone oils for adjusting charging characteristics and dispersibility. The smaller the average particle size of the toner is, the better the resolution is. However, the smaller the particle size is, the larger the physical adhesive force is, and the more difficult it is to remove when transferring. Therefore, in this embodiment, the average particle diameter of the toner is adjusted so that the center is around 2 to 4 μm for the purpose of improving transferability.

The viscosity of the liquid developer depends on the carrier liquid used,
It depends on the resin, color pigment, charge control agent, etc. and their concentrations. In this example, the viscosity is 50 to 6000 m.
An experiment was conducted by changing the Pa · s and the toner concentration within the range of 5 to 40%.

As the carrier liquid, one having a low viscosity such as dimethylpolysiloxane oil or cyclic polydimethylsiloxane oil exhibiting high electric resistance is used. Incidentally, the developing belt 510
Since the liquid developer layer formed thereon is formed in a thin layer, the carrier liquid contained in the liquid developer layer is extremely small. Therefore, the amount of carrier liquid contained in the liquid developer supplied to the latent image surface of the photoconductor 10 is also extremely small, so that the amount of carrier liquid absorbed by the paper or the like during transfer is extremely small. Therefore, the viscosity is 1000 mPas
If it is below, almost no carrier liquid remains after fixing.

According to the experiments conducted by the present inventors, when the image output experiment was conducted using DC344 of Dow Corning Co., USA having a viscosity of 2.5 mPa · s as the carrier liquid, the carrier remaining on the paper after fixing was determined. No liquid was seen. But,
Due to its high volatility, it was necessary to make the developing device a closed structure. In addition, when the image output experiment was conducted using DC345 of Dow Corning Co., USA, which has a viscosity of 6.5 mPa · s as the carrier liquid, it was fixed on paper after fixing similarly to the case where the image output experiment was conducted using DC344. No carrier liquid remained in the. However, since the volatility is high, it is necessary to make the developing device have a closed structure. Furthermore, the carrier liquid has a viscosity of 20 mPas, Shin-Etsu Silicon KF-96
When the image output experiment was carried out using -20, no carrier liquid remained on the paper after fixing. Further, since the volatility is not so high, it is not necessary to make the developing device have a closed structure. DC344, DC345 and KF-
96-20 is generally used for cosmetics and has high safety such as toxicity. There are many kinds of carrier liquids such as KF9937 manufactured by Shin-Etsu Silicon Co., Ltd., and any one may be selected as long as the electric resistance, the evaporation property, the surface tension, the safety and the like are satisfied.

Further, in an experiment conducted by the present inventors, when the surface tension is large, fogging or a lump of toner occurs on the photoreceptor 10.
21 dyne / cm experimentally
From the above, it was found that the problem of image quality is likely to occur.

The electric resistance value is preferably 10 ¹⁴ Ωcm or more because of the problem of toner charging stability. At least 1
0 ¹² Ωcm or more is necessary. In the description of the present embodiment, in view of these experimental results, the DC3 is low in price and easily available.
An example using 45 is shown.

The pre-wetting liquid easily evaporates during fixing without disturbing the electrostatic latent image formed on the photoconductor 10,
It is required that the fog and the lump of toner do not adhere to the photoconductor 10. As an example, DC344, DC200-0.65, -1.0,-, manufactured by Dow Corning, USA
2.0, Shin-Etsu Silicon KF96L-1, KF993
7 etc. are mentioned. Generally, it is necessary to select a highly evaporative silicone oil.

In the experiment conducted by the present inventors, the liquid was dried by development, transfer and fixing without any problem when the liquid viscosity was in the range of 0.5 to 3 mPa · s, but from 5 mPa · s to 6 m
At about Pa · s, there was a tendency that a time and a temperature were required for drying the liquid at the time of fixing. If it is 10 mPa · s, the energy required for drying becomes too large, which is not general. Further, if it is 0.5 mPa · s or less, the volatility becomes high, so that it is regarded as a hazardous material and is not suitable. In addition, the boiling point needs to be 250 ° C. or lower because of the effect of heating the paper.

The surface tension eliminates the adhesive force between the liquid developer and the photoconductor 10 and improves the releasability to prevent image stains and fogging, and also improves the resolution of image quality and fogging.
It should be as low as possible. According to experiments conducted by the present inventors, the limit is about 20 to 21 dyne / cm, and it is necessary to select one lower than this.

When the electric resistance is low, the insulating property deteriorates and electric charges are leaked. Therefore, it is necessary to use the highest possible one. Experimentally, about 10 ¹⁴ Ωcm or more is desirable. A minimum of 10 ¹² Ωcm is required.

Next, the operation of the electrostatic latent image developing device according to the first embodiment of the present invention will be described. First, FIG. 6 (A)
As shown in, the charging device 30 charges the photoconductor 10. Generally, a corona discharger is used for the charging device 30. Next, the image is exposed on the charged photoreceptor 10. For example, the image is exposed by a laser scanner to expose the photoreceptor 10.
To form an electrostatic latent image on the surface of. As shown in FIG. 6B, the portion of the laser scanner exposed to the light becomes conductive, so that the electric charge disappears, and the portion not exposed to the light remains as an electrostatic latent image which is an image of the electric charge.

Next, as shown in FIG. 6C, the above-mentioned pre-wetting liquid is applied onto the photoconductor 10 by the pre-wetting device 20.

Next, the electrostatic latent image is visualized by the developing device 50. As shown in FIG. 4, the liquid developer discharged by the bellows pump 520 to the contact start position of the adjusting roller 522d and the conveying roller 522c is a nip (elasticity) formed at the contact portion of the adjusting roller 522d and the conveying roller 522c. It is regulated to have a uniform thickness by the deformed portion) and is thinly applied onto the transport roller 522c. The liquid developer applied onto the carrying roller 522c is regulated to have a more uniform thickness by the nip formed at the contact portion between the carrying roller 522c and the carrying roller 522b, and is thinly applied onto the carrying roller 522b. The liquid developer applied on the carrying roller 522b is regulated to have a more uniform thickness by a nip formed at the contact portion between the carrying roller 522b and the applying roller 522a, and is thinly applied on the applying roller 522a. As shown in FIG. 16, the liquid developer thinly applied to the application roller 522a with a uniform thickness is such that the application roller 522a is brought into contact with the developing belt 510 by the support roller 516 with an appropriate pressing force. As a result, the toner is applied to the surface of the developing belt 510 without being crushed at the contact portion between the applying roller 522a and the developing belt 510, and thus without forming a liquid pool in the front and rear. Thereby, a thin layer of the liquid developer can be formed on the developing belt 510. The thickness of the thin layer formed on the developing belt 510 can be adjusted by changing the nip width t. The developing device 50 causes any of the coating devices 52 a to 52 d to come into contact with the developing belt 510 by the separation / contact device 524. As a result, the liquid developer containing the toner of any one of yellow, magenta, cyan, and black can be thinly and evenly applied onto the developing belt 510.

Next, the liquid developer layer formed on the developing belt 510 is brought close to the electrostatic latent image formed on the surface of the photoconductor 10 as shown in FIG. Thus, the charged toner is moved onto the photoconductor 10. As a result, a toner image is formed on the photoconductor 10.

Next, as shown in FIG. 6E, the toner image formed on the photoconductor 10 by the transfer device 60 is primarily transferred onto the intermediate transfer belt 610. On the other hand, the photoconductor 10
The liquid developer remaining on the photoconductor 10 is removed by the cleaning device 70, and then the charge is removed by a charge removing device (not shown). Then, the coating devices 52a to 52 that come into contact with the developing belt 510 by the separating / connecting means 524.
After switching d, the above-described cycle from charging to static elimination is repeated again, so that yellow, magenta, cyan, and black toner images are transferred one after another onto the intermediate transfer belt 610. As a result, the intermediate transfer belt 6
A toner image corresponding to colorization is formed on 10.

Next, as shown in FIG. 6 (F), the toner image corresponding to the color formed on the intermediate transfer belt 610 by the transfer device 60 is secondarily transferred to the paper P which is a recording medium and fixed at the same time. Let The toner image corresponding to the color formed on the intermediate transfer belt 610 moves onto the paper P and is secondarily transferred by the pressing force of the secondary transfer roller 614 to the intermediate transfer belt 610 and the heat from the fixing heater 618. At the same time, it is thermally melted and fixed. As a result, the paper P
A color image can be formed on it.

7 to 11 are views for explaining the developing process in one embodiment of the present invention in detail, FIG. 7 is a diagram for explaining the whole developing process, and FIG. 8 is a state of the approaching process. FIG. 9, FIG. 9 is a diagram showing a state of a toner moving process, FIG. 10 is a diagram showing a state of a non-image portion separating process, and FIG. 11 is a diagram showing a state of an image portion separating process. Unlike the conventional developing process, the developing process of this embodiment is as shown in FIG.
An approaching process in which the developing belt 510 approaches the photoconductor 10 and the liquid developer approaches the surface of the photoconductor 10, and a toner moving process in which the liquid developer layer and the pre-wet liquid layer are in soft contact to move the toner. It is considered that the developing belt 510 is made up of three processes, that is, the process of separating the developing belt 510 from the photoconductor 10 and adhering to the developing belt 510 and separating the toner to the photoconductor 10.

In the approaching process, since the developing belt 510 is made of a flexible belt member, as shown in FIG. 8, the liquid developer layer on the developing belt 510 and the photosensitive member 1 are formed.
The contact pressure at the time of contact with the pre-wet layer above 0 is dispersed, and the high-viscosity liquid developer consisting of the carrier liquid and the toner is soft-contacted with the pre-wet liquid. As a result, the pre-wet liquid having a low viscosity is slightly pushed back and forth, and a liquid pool of the pre-wet liquid is generated.

In the toner moving process, as shown in FIG. 9, in the image portion, the toner on the developing belt 510 is mainly caused by the Coulomb force due to the electric field formed between the charges on the photoconductor 10 and the developing belt 510. It passes through the pre-wet liquid layer and moves to the latent image surface. On the other hand, in the non-image portion, the toner on the developing belt 510 has the surface of the photoconductor 10 and the liquid developer layer separated by the pre-wet liquid layer.
It does not move to the surface of the photoconductor 10.

In the separation process, in the non-image part, as shown in FIG.
As shown in 0, the liquid developer remains on the developing belt 510. At the interface between the pre-wet liquid layer and the liquid developer layer, when the two layers are separated, a part of the pre-wet liquid layer having a low viscosity is transferred to the liquid developer layer and separated. Therefore, the separation point of the two layers is considered to be inside the pre-wet liquid layer. On the other hand, in the image area, as shown in FIG. 11, the toner that has moved to the surface of the photoconductor 10 pushes away the pre-wet liquid layer, so that the pre-wet liquid layer is located above the toner layer, and both are in the pre-wet liquid layer. Separate inside. On the developing belt 510, a part of the carrier liquid remaining after the toner is moved and a part of the pre-wetting liquid form a layer.

FIG. 12 is a diagram for explaining the significance of thinning the liquid developer. If the liquid developer layer applied on the developing belt 510 is too thick, the viscosity of the liquid developer is high, so that the electrostatic force can cause the developing belt 510 to move to the photoreceptor 1.
The toner group that is about to move to the surface of 0 forms a cluster without breaking the viscosity of the toner located around it and moves to the surface of the photoconductor 10. For this reason, the toner excessively moves, the toner image formed on the photoconductor 10 is disturbed, and image noise occurs. In order to suppress the generation of these clusters, it is necessary to control the layer thickness of the liquid developer layer to a minimum value that allows sufficient development.

FIG. 13 is a view showing a state in which the developing roller formed of a rigid body which is a developing support and the photoconductor 10 are in hard contact, and FIG. 14 is a diagram for explaining the soft contact of this embodiment. Is. As described above, the function of the pre-wet liquid layer for image formation is important in the developing process of this embodiment. Therefore, the important requirements in the development process are the prewetting liquid layer and the liquid developer layer.
It is to maintain the state of layers. As shown in FIG. 13, when the developing roller and the photoconductor are in hard contact, the two-layer state cannot be maintained. Therefore, in this embodiment, as shown in FIG. By using the developing belt 510 including the belt member having the prewetting liquid layer, the prewetting liquid layer on the photoconductor 10 and the liquid developer layer on the developing belt 510 are dispersed by the contact pressure being dispersed. The two layers of the liquid developer layer and the liquid developer layer are maintained.

Next, the layer thickness of the liquid developer layer on the developing belt 510 and the layer thickness of the pre-wet liquid layer on the photoconductor 10 will be described. The layer thickness of the liquid developer layer on the developing belt 510 needs to be thin when the viscosity of the liquid developer is 50 to 100 mPa · s or more, particularly 500 mPa · s or more. Ideally, the layer thickness is slightly thicker than the layer thickness that satisfies the toner development amount (that is, the density when solid black is produced) required at the time of development. This is because when a high-viscosity liquid developer is used, the electrostatically selected toner moves to the photoconductor 10 along with the extra toner due to the viscosity of the liquid during development.
This is because the toner image formed on the image surface 0 is disturbed.
In an experiment conducted by the inventors, a good image was obtained with a layer thickness of about 5 μm for a liquid developer having a high toner concentration and with a layer thickness of about 40 μm for a liquid developer having a low toner concentration. In particular, when a liquid developer having a toner concentration of 20 to 30% was used, good image quality was obtained when the layer thickness of the liquid developer was about 20 μm.

The layer thickness of the pre-wet liquid layer on the photoconductor 10 has an optimum value depending on the viscosity and surface tension of the selected pre-wet liquid. If it is too thin, the development belt 51
The toner on 0 moves irregularly on the photoconductor 10 and disturbs the toner image formed on the photoconductor 10. As the amount of the pre-wet liquid is increased, the disorder of the toner image is improved, and the optimum value is confirmed. When the amount is further increased, the toner on the photoconductor 10 flows and the toner image on the photoconductor 10 tends to be blurred. In the experiment using DC344, good results were obtained with a thickness of 5 to 30 μm. For those with a lower viscosity, a thinner or thicker result can be obtained. However, for high viscosity ones, the optimum value tends to have a narrow range.

As a result of conducting an image development experiment under the above-mentioned conditions, the optimum range of the liquid developer and the viscosity of the pre-wet liquid for the electrostatic latent image liquid developing apparatus of this embodiment is 100 mPa for the liquid developer. -S to 6000 mPa-s, and the pre-wet liquid was found to be between 0.5 mPa-s and 5 mPa-s. The silicone oil of the pre-wet liquid is DC200 series manufactured by Dow Corning, and the carrier liquid of the developer is DC34 manufactured by the same company.
5 was used.

According to the present embodiment, by providing the support roller 516 formed of an elastic member that is in contact with the application roller 522a through the developing belt 510 formed of a flexible belt-shaped member, the application is performed. Since the roller 522a and the developing belt 510 can be brought into contact with each other with an appropriate pressing force, the liquid developer layer formed with a constant layer thickness on the applying roller 522a is applied to the applying roller 522a and the developing belt 51.
The toner can be supplied onto the developing belt 510 without being crushed at the contact portion with 0, and therefore without forming a liquid pool in the front and rear. As a result, the developing belt 51
Liquid developer can be evenly and evenly coated on the surface of the photosensitive member 1.
It can be uniformly supplied to the latent image surface of 0.

Furthermore, according to the present embodiment, since silicon oil is used as the carrier liquid for the liquid developer,
It has the following advantages over conventional ones.

Conventional liquid developers generally use IsoparG (registered trademark: manufactured by Exxon) as a carrier liquid.
Since this Isopar has a resistance value not as high as that of silicone oil, when the toner concentration is increased, that is, when the distance between particles is reduced, the chargeability of the toner is deteriorated. Therefore, Isop
In the case of ar, the toner density is limited. On the contrary,
Since the silicone oil used in this embodiment has a sufficiently large resistance value, the toner concentration can be increased. Also,
Generally, in the case of Isopar, the toner is well dispersed, and therefore even if the toner concentration is 1 to 2%, the toners repel each other, so that the toner is uniformly dispersed. On the other hand, silicone oil has a toner concentration of 1 to 2%,
The dispersibility is not good and it will precipitate soon. However, when the toner concentration is set to 5 to 40%, the toner is densely packed and stably dispersed. Therefore, in this embodiment, a high-viscosity liquid developer in which toner is dispersed at high density is used. As a result, the amount of the developer can be significantly reduced as compared with the conventional low-concentration liquid developer, and the device can be downsized. Furthermore, since the liquid developer of this embodiment is a high-viscosity liquid, it is easier to store and handle than the conventional low-viscosity liquid developer or powder developer.

Isopar used in the conventional liquid developer is
As mentioned above, it is highly volatile and emits a foul odor,
There is a problem that it not only deteriorates the work environment but also causes pollution. On the other hand, the silicone oil used in this example is a safe liquid and is odorless, as is clear from the fact that it is used for cosmetics. The environment can be improved and pollution problems do not occur.

The present invention is not limited to this embodiment, and various modifications can be made within the scope of the invention. For example, in the present embodiment, the hard roller that is a rigid body is used as the application roller 522a, and the elastic body is used as the support roller 516, but the present invention is not limited to this, and the application roller and the support roller 516 are not limited thereto. It is sufficient that at least one of the rollers uses an elastic body.

In this embodiment, the support roller 516 formed in a roller shape is used as the pressing means, but the present invention is not limited to this, and the developing belt 510 is used as the pressing means. Through application roller 5
It may be formed of an elastic member that comes into contact with 22a. For example, the contact surface with the developing belt 510 formed of felt, sponge, or the like may have a substantially semi-cylindrical shape or a flat shape.

Further, in this embodiment, the coating roller 522 is used.
A disk wheel 526a having the same outer diameter as the roller outer diameter is provided on both sides of a and the transport roller 522c, and disk wheels 526b having an outer diameter slightly smaller than the roller outer diameter are provided on both sides of the transport roller 522b and the adjusting roller 522d, respectively. Adjacent disk cars 526
Although the case where a and the disk wheel 526b are brought into contact with each other has been described, the present invention is not limited to this, and the axial distance between the adjacent hard roller and the soft roller is the radius of the adjacent hard roller and the soft roller. What is necessary is just to make it shorter than the total of. For example, as shown in FIG.
A disk wheel 526c having an outer diameter slightly smaller than the roller outer diameter may be provided on both sides of the soft roller, and the disk wheel 526c may be brought into contact with the surface of an adjacent hard roller.

Further, in this embodiment, a coating device 52a for coating the developing belt 510 with a liquid developer containing yellow toner, and a coating device 52b for coating the developing belt 510 with a liquid developer containing magenta toner. The application device 52c for applying the liquid developer containing cyan toner to the developing belt 510 and the application device 52d for applying the liquid developer containing black toner to the developing belt 510 have been described. It is not limited to this. It suffices if at least one coating device provided with a coating roller that coats the liquid developer containing the toner of a desired color on the developing belt is provided as needed.

Further, in the present embodiment, the case where the liquid developer is applied onto the applying roller 522a via the plurality of conveying rollers 522b and 522c has been described, but the present invention is not limited to this, and the applying method is not limited thereto. It is sufficient if the liquid developer can be applied thinly and evenly on the roller 522a.

Further, in this embodiment, as the image support,
Although the case where the organic photoreceptor 10 is used has been described, the present invention is not limited to this. The image support may be various photoconductors used in the Carlson method, those in which an insulating layer is formed on a conductor that directly forms an electrostatic latent image such as ionography, or electrostatic recording paper such as an electrostatic plotter.

Further, in this embodiment, as the transfer device,
After the toner image formed on the photoconductor 10 is primarily transferred onto the intermediate transfer belt 610 which is an intermediate transfer member, the toner image primarily transferred onto the intermediate transfer belt 610 is secondarily transferred onto the paper P. Although the description has been given of the case where the image is formed on the paper P, the present invention is not limited to this, and the transfer device can transfer the toner image formed on the image support to the recording medium. Anything will do. For example, in a monochrome liquid developing device, the toner image formed on the image support may be directly transferred onto a recording medium without primary transfer onto the intermediate transfer member.

In this embodiment, the image was exposed on the image support charged by the exposure device 40, and then the pre-wet liquid was applied on the image support by the pre-wet device 20. The present invention is not limited to this, and the application of the pre-wet liquid may be performed before the developing step.

The present invention is not limited to the above-mentioned respective embodiments, and a pre-wet liquid layer is formed, and
If the layer thickness of the liquid developer is 5 to 40 μm, the viscosity of the high viscosity developer may be 10,000 mPa · s. At present, a developer with a high viscosity of 6000 mPa · s or more is difficult to agitate between the carrier liquid and the toner, so it is thought to be costly. Good. Viscosity 100
Those exceeding 00 mPa · s become unrealistic. The pre-wetting liquid has a viscosity of 0.5 to 5 mPa · s,
Electric resistance is 10 ¹² Ωcm or more, boiling point is 100 to 250
Silicone oil may not be the main component as long as the temperature and the surface tension are 21 dyne / cm or less. Furthermore, the carrier liquid of the liquid developer is not limited to silicone oil.

Further, in each of the above-mentioned embodiments, the liquid developing method of the electrostatic latent image having the pre-wet process has been described, but the present invention is not limited to this. For example, if the surface of the image support is coated with a material having releasability, the pre-wetting step is not particularly required.

[0068]

As described above, according to the invention of the first aspect, the application roller can be brought into contact with the developer support by the pressing means with an appropriate pressing force. Therefore, it is possible to supply the liquid developer layer formed on the coating roller with a constant layer thickness onto the developer support without being crushed at the contact portion between the coating roller and the developer support. The liquid developer can be evenly and evenly coated on the developer support, so that the high-concentration and high-viscosity liquid developer can be uniformly supplied to the latent image surface of the image support, and the toner can be used. A high-resolution liquid developer for electrostatic latent images that is easy to downsize and has low pollution by developing a high-viscosity liquid developer dispersed in high concentration in a thin layer can do.

According to the second aspect of the present invention, by virtue of the above construction, it is possible to provide the electrostatic latent image liquid developing device having the same effect as that of the first aspect of the invention.

According to the invention of claim 3, by virtue of the above-mentioned constitution, in addition to the effect of the invention of claim 1, there is provided a liquid developing device for an electrostatic latent image having good wettability of the liquid developer. Can be provided.

According to the invention described in claim 4, by virtue of the above-mentioned constitution, in addition to the effect of the invention described in claim 3, there is little pollution and an electrostatic latent image capable of improving the working environment. It is possible to provide the liquid developing device.

According to the invention described in claim 5, in addition to the effect of the invention described in claim 1, with the above structure, the liquid developing device for an electrostatic latent image in which toner is easily peeled off at the time of transfer Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid developing device for an electrostatic latent image that is an embodiment of the present invention.

FIG. 2 is a schematic front view of a developing device used in the electrostatic latent image liquid developing device shown in FIG.

FIG. 3 is a right side view of the developing device shown in FIG.

FIG. 4 is a diagram for explaining an operation of a coating unit of the developing device shown in FIG.

FIG. 5 is a diagram for explaining a method of contacting adjacent rollers of the coating unit shown in FIG.

6A and 6B are diagrams for explaining the operation of the liquid developing device for the electrostatic latent image shown in FIG.

FIG. 7 is a diagram for explaining the entire developing process.

FIG. 8 is a diagram for explaining a state of an approaching process.

FIG. 9 is a diagram for explaining a state of a toner movement process.

FIG. 10 is a diagram for explaining a separation process of a non-image portion.

FIG. 11 is a diagram for explaining a separation process of an image portion.

FIG. 12 is a diagram for explaining the significance of thinning the liquid developer.

FIG. 13 is a diagram showing a state in which a developing roller and a photoconductor are in hard contact with each other.

FIG. 14 is a diagram for explaining soft contacts of the electrostatic latent image liquid developing apparatus according to the present embodiment.

FIG. 15 is a diagram for explaining a modified example of the contacting method of the adjacent rollers of the coating unit shown in FIG.

FIG. 16 is a diagram for explaining a state in which a support roller comes into contact with an application roller via a developing belt.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Photoconductor 20 Pre-wetting device 30 Charging device 40 Exposure device 50 Developing device 51 Developing part 52 Coating part 52a, 52b, 52c, 52d Coating device 60 Transfer device 70 Cleaning device 510 Developing belt 512a, 512b, 612a, 612b, 612c
Drive roller 514, 616 Scraping blade 516 Support roller 520 Bellows pump 522a Coating roller 522b, 522c Conveying roller 522d Adjusting roller 524 Contacting device 524a Arm 526a, 526b, 526c Disc wheel 614 Secondary transfer roller 618 Heater

Claims (5)

[Claims] 1. A liquid developing device for an electrostatic latent image, which develops an electrostatic latent image formed on an image support with toner, which is a charged developing particle, wherein the toner is high in an insulating liquid. 100 to 1 dispersed in concentration
A high-viscosity liquid developer of 0000 mPa · s, a developer support formed of a flexible belt-like member for supplying the latent image surface of the image support, and the liquid on the developer support. It is provided with an application roller for applying a developer, and a pressing means for contacting the application roller via the developer support, and at least one of the application roller and the pressing means is formed of an elastic member. Liquid developing device for electrostatic latent image. 2. The electrostatic latent image liquid developing device according to claim 1, wherein the pressing means is formed in a roller shape. 3. The liquid developer, wherein the insulating liquid has a viscosity of 0.5 to 1000 mPa · s and an electric resistance of 10 ¹² Ωcm.
Above, surface tension is 21 dyne / cm or less and boiling point is 10.
The liquid developing device for an electrostatic latent image according to claim 1 or 2, wherein the temperature is 0 ° C or higher. 4. The liquid latent electrostatic image developing device according to claim 3, wherein the liquid developer uses silicon oil as an insulating liquid. 5. The liquid developer has an average particle size of 0.1 to 5
5. The electrostatic latent image liquid developing device according to claim 1, wherein the toner contains .mu.m toner at a concentration of 5 to 40%.