JP2003098833A - Liquid development apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid development apparatus which is provided with a developer-holding element for suppressing abrasion, having proper surface smoothness and not swollen by insulative liquid of a liquid developer. SOLUTION: The liquid development apparatus 4 is provided with a developer accommodating tank 401 for accommodating the liquid developer, an application member 404 for rotating and holding a predetermined quantity of the liquid developer D drawn from the developer-accommodating tank 401 on a surface, the developer-holding element 402 for applying the liquid developer D held on the surface to the electrostatic latent image on an image-holding element 1 and developing, and an intermediate applying member 405 for carrying the liquid developer D from the surface of the applying member 404 to the surface of the developer holding element 402. An elastic layer 402b is formed on a core metal 402a of the developer-holding element 402, and a coating layer 402c is provided on the surface of the elastic layer 402b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a coating member that carries a predetermined amount of liquid developer on its surface and rotates, and applies the liquid developer carried on the surface of the coating member to the surface of a member to be coated. The present invention relates to a liquid developing device which visualizes an electrostatic latent image formed on an image bearing member with a liquid developer which is applied to a developer bearing member as a member to be coated.

[0002]

2. Description of the Related Art As an image forming apparatus, there is known an image forming apparatus which visualizes an electrostatic latent image formed on a surface of an image bearing member by using a high-viscosity, high-concentration liquid developer. For example, JP-A-7-152254 and JP-A-7-209.
922, JP-A-7-219355, etc.). In this type of image forming apparatus, first, the surface of a photoconductor as an image carrier is uniformly charged by a charging unit, and then the surface of the photoconductor is exposed according to image data by an optical writing unit. , Forms an electrostatic latent image on the surface of the photoconductor. Then, the electrostatic latent image formed on the surface of the photoconductor is developed by a developing device to be visualized.

The above-mentioned developing device is a liquid developer for applying a liquid developer stored in a storage tank in a thin layer on a surface of a developer carrier including a developing roller and a developing belt. Equipped with a coating device. The developer carrying member is arranged close to the surface of the photoconductor. Then, in the developing area, which is the vicinity of the developer carrying member and the photosensitive member, the liquid developer applied to the surface of the developer carrying member by the application device comes into contact with the surface of the photosensitive member. As a result, the toner in the thin layer of the liquid developer visualizes the electrostatic latent image on the photoconductor to form a toner image on the photoconductor. The liquid developer remaining on the developer carrier after passing through the developing area is removed by a cleaning member such as a blade and collected in a storage tank.

In this way, the toner image formed on the photoconductor is transferred onto a transfer material such as a transfer paper or an OHP sheet. Thereafter, the toner image is fixed on the transfer material by the fixing device, so that an image is formed on the transfer material. The toner remaining on the photoconductor during the transfer of the toner image onto the transfer material is removed by the photoconductor cleaning means.

As the liquid developer, a carrier liquid which is an insulating liquid in which a solid content consisting of a resin and a pigment is dispersed, for example, in a developer solvent which is an insulating liquid such as dimethylpolysiloxane oil. , 10000 mPa · s in which the toner, which is a visualization particle, is dispersed in a high concentration.
The high viscosity liquid developer is used. When the liquid developer comes into contact with the surface of the photoconductor, the charged toner in the liquid developer moves in the insulating liquid by the force of static electricity to develop the electrostatic latent image on the photoconductor. Therefore, as the liquid developer, the shorter the moving distance of the toner, the higher the developing efficiency. Therefore, it is desirable to form a thin layer of liquid developer on the developer carrying member in a unit of micron, and bring the thinned liquid developer into contact with the photoconductor to develop the electrostatic latent image. . This is especially in the range of 50 to 10,000
This is more remarkable when a high-viscosity liquid developer of mPa · s is used.

As described above, when the electrostatic latent image on the image carrier is developed with a thin layer of liquid developer, the toner concentration is determined by the thickness of the thin layer. Therefore, in the developing device, it is important to form a uniform thin layer of the liquid developer on the developer carrier. Therefore, in the developing device of this type, as a coating member for coating the liquid developer on the developer carrying member, for example, Japanese Patent Laid-Open No. 11-2
As disclosed in Japanese Patent No. 65122, a coating roller (anilox roller) having regular recesses formed on its surface.
Is used. In the coating device including the coating roller, first, the liquid developer is carried on the surface of the coating roller. The excess liquid developer carried on the surface of the application roller comes into contact with the surface of the application roller to control the application amount of the liquid developer carried on the surface of the application roller. Removed by blade. As a result, the amount of liquid developer carried on the surface of the coating roller is measured. The liquid developer measured in this way is directly transferred and applied onto the developer carrier to form a uniform liquid developer thin layer of the liquid developer on the developer carrier of the developing device. Become so.

However, in the developing device using the above coating device, the contact roller between the coating roller and the developer carrying member rotates the surface of the developer carrying member due to the regular unevenness on the surface of the applying roller. It is easily scraped, and the developer carrying member is significantly consumed and damaged. Therefore, for a developing roller or a developing belt as a developer bearing member in a developing device using this type of coating device, (1) a low hardness one capable of forming a predetermined developing nip by contact with the photoconductor. To be. (2) At least the surface is made of a conductive material capable of applying a bias. (3) At least the surface has mechanical strength with high abrasion resistance due to rubbing against the coating roller. (4) At least the surface has mechanical strength with high abrasion resistance due to rubbing against the cleaning blade. (5) It has smoothness so that the liquid developer can be uniformly applied to the photoreceptor. Such characteristics are required. Also, the swelling of the roller due to the insulating liquid of the liquid developer must be taken into consideration.

As described above, in the developing device using the coating device, since the specifications required for the developing roller and the developing belt as the developer carrying member are strict, the range of selection of the developing roller and the developing belt is wide. However, it was difficult to make a highly durable developer carrier. In particular, among the above-mentioned required characteristics of the developer carrying member, the items (3) and (4) relate to the durability of the material of the developer carrying member and determine the life of the developer carrying member. . However, in the conventional developer bearing member, for example, even when the surface of the developing roller is coated with the conductive PFA tube, the durable life thereof is about 50,000 sheets.

[0009]

Therefore, in order to reduce the hazard due to the contact member with the developing roller, there has been proposed a structure of a liquid developing apparatus in which an intermediate roller is provided between the coating roller and the developing roller. In this liquid developer device, a predetermined amount of liquid developer is carried on the surface of the application roller by the rotation of an application roller (or an application belt) as an application member. The liquid developer carried on the surface of the coating roller is in contact with the surface of the coating roller, and the contact surface moves in the same direction as the surface of the coating roller and at a constant speed. May be applied). The liquid developer applied to the surface of the intermediate roller is applied to the surface of the developing roller or the developing belt as a member to be applied. Here, the contact surface of the intermediate roller with the surface of the developing roller or the developing belt moves in the direction opposite to the surface of the developing roller or the developing belt. Thus, in the coating method, the liquid developer carried on the surface of the coating roller is coated on the developing roller or the like via the intermediate roller. Therefore, since the coating roller does not come into direct contact with the developing roller or the like, consumption and damage of the developing roller or the like due to contact rotation between the coating roller and the developing roller or the like can be avoided.

As described above, by using the intermediate roller, the abrasion and damage of the developing roller can be surely reduced, and the durable life of the image forming apparatus can be remarkably improved. Further, in order to further improve the durable life of the image forming apparatus and continuously obtain a good image, the developing roller has a structure capable of further reducing the hazards to the intermediate roller and the photoconductor, and has a static electricity on the photoconductor. It is required that the latent image be faithfully developed. The necessary items and problems for that are as follows. (1) The developing roller has a low hardness that can reduce the hazard to the intermediate roller and has a small surface friction coefficient,
The surface of the developing roller itself must have excellent wear resistance. (2) If the surface of the developing roller is not even, the thin toner layer on the developing roller becomes uneven, which causes uneven density in the image. Therefore, smoothness is required. (3) Abrasion, torque increase, vibration, abnormal noise, and heat generation occur due to rubbing against the photoconductor and the intermediate roller. (4) The material forming the developing roller should not swell more than necessary with respect to the insulating liquid of the liquid developer. (5) It is necessary that a predetermined developing nip can be formed by contact with the photoconductor and that the hardness is low so that the hazard to the photoconductor can be reduced. (6) It is necessary to have a conductivity that enables development that is faithful to the electrostatic latent image.

In view of the above problems, the present invention provides a liquid developing device having a developer carrier which suppresses abrasion, has good surface smoothness, and does not swell into an insulating liquid of a liquid developer. The challenge is to provide. Further, it is an object of the present invention to provide an image forming apparatus that includes the liquid developing device and stably gives a good image and has high durability.

[0012]

In order to solve the above problems, a first aspect of the present invention is directed to a developer storage tank for storing a liquid developer, and a predetermined amount of liquid drawn from the developer storage tank. A coating member that carries a developer on its surface and rotates, a developer carrier that coats and develops a liquid developer carried on the surface on an electrostatic latent image on an image carrier, and a coating member from the surface of the coating member. In a liquid developing device including an intermediate coating member for transferring a liquid developer to the surface of a developer carrier, the developer carrier has an elastic layer formed on a core metal and a coating layer provided on the surface thereof. And a liquid developing device. According to a second aspect of the present invention, in the liquid developing apparatus according to the first aspect, the developer carrier has the coating layer of P.
A liquid developing device in which TFE particles are dispersed is used.

The invention described in claim 3 is the invention according to claim 1 or 2.
In the liquid developing device according to the item (1), the elastic layer of the developer carrier is made of rubber having polarity, and the liquid developer is a carrier liquid that is an insulating liquid in which a toner made of a resin and a pigment is dispersed. Liquid developing device. According to a fourth aspect of the present invention, in the liquid developing apparatus according to any one of the first to third aspects, the solubility index (SP value) of the polymer material forming the elastic layer of the developer carrier is the development value. The liquid developing device has a difference of 2 or more from the solubility index (SP value) of the carrier liquid of the agent. The invention according to claim 5 is the liquid developing device according to any one of claims 1 to 4, wherein the elastic layer of the developer carrying member has a JIS-A hardness of 20 to 50 degrees. To do.

According to a sixth aspect of the present invention, in the liquid developing apparatus according to any of the first to fifth aspects, the developer carrier has a surface roughness Rz of the coating layer of the toner in the developer. The liquid developing device has an average particle size or less. According to a seventh aspect of the present invention, in the liquid developing apparatus according to any one of the first to sixth aspects, the developer carrying member has a coating layer having a film thickness of 10 to 30 μm. The invention according to claim 8 is the liquid developing apparatus according to any one of claims 1 to 7,
The developer carrier is a liquid developing device having a maximum static friction coefficient of 0.2 or less.

According to a ninth aspect of the present invention, in the liquid developing apparatus according to any one of the first to eighth aspects, the developer carrying member has an electric resistance in the volume direction of 10 ³ to 10 ¹² Ω.
The liquid developing device is According to a tenth aspect of the present invention, in the liquid developing apparatus according to any one of the first to ninth aspects, the developer carrying member has a surface direction electric resistance of 3.0 × 10 ⁴ Ω or more. The device.

An eleventh aspect of the present invention is an image forming apparatus including the liquid developing device according to any one of the first to tenth aspects.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an image forming unit of an image forming apparatus according to the present invention. This image forming apparatus includes a photoconductor 1 as an image carrier.
An image forming unit including a charger 2, an exposure device 3, a developing device 4, a transfer device 5, and a photoconductor cleaning device 6 is arranged around the photoconductor 1. The material of the photoconductor 1 is a-Si (amorphous silicon), OPC
Etc. can be used. The charger 2 may be in the form of a roller or a charger. As the exposure device 3,
An LED, a laser scanning optical system, etc. can be used.

Next, the developing device 4 will be described in detail. As shown in FIG. 1, the developing device 4 has a developer accommodating tank 401 for accommodating the liquid developer D therein, and as a developer carrier rotatably disposed in the developer accommodating tank 401. The developing roller 402 is provided. In addition, a sweep roller 403 rotatably arranged inside the casing 410 is provided. Further, a coating device for coating the liquid developer D on the developing roller 402 as a member to be coated is provided. The coating device mainly includes a coating roller 404 serving as a coating member and a liquid developer D on the developing roller 402.
The intermediate roller 405 serves as an intermediate coating member for coating the liquid developer, the stirring / transport screw 406 serves as a stirring / transporting means for the liquid developer D, and the like.

FIG. 2 is a sectional view showing the structure of the developing roller 402. The developing roller 402, as shown in FIG.
Elastic layer 402b made of an elastic material on the outer peripheral surface of the core metal 402a.
And a coating layer 402c is further provided on the outer peripheral surface of the elastic layer 402b. The material of the elastic layer 402b may be any material that does not swell or dissolve in the carrier liquid of the developer, and various polymer materials can be used. For example, polar rubbers such as epichlorohydrin rubber, acrylonitrile butadiene rubber, urethane rubber and chloroprene rubber are preferable. Furthermore, in order to prevent the elastic layer 402b from swelling or dissolving with the carrier liquid, the solubility index (SP value) of the polymer material forming the elastic layer 402b and the solubility index (SP value) of the carrier liquid are used. Preferably has a difference of 2 or more. This is because if the difference in solubility index (SP value) between the polymer material forming the elastic layer 402b and the carrier liquid is smaller than 2, the elastic layer 405b will be dissolved or swelled. The solubility index (SP value) is the square root of the cohesive energy density, and is a value determined by the heat of evaporation, surface tension, and solubility.

The developing roller 402 has a rubber hardness of
The JIS-A hardness is preferably 20 to 50 degrees.
In order to efficiently form the developing nip with the photoconductor 1, the rubber hardness of the elastic layer 402b is set according to JIS.
-A hardness is preferably 50 degrees or less. If the elastic layer 402b has a low JIS-A hardness of less than 20 degrees, the toner cannot be stably moved onto the photoconductor 1, so that the JIS-A hardness is 20 degrees or more. Is preferred.

The direct contact of the elastic layer 402b of the developing roller 402 having the JIS-A hardness with the photoconductor 1 or the intermediate roller 405 produces a very large frictional resistance, so that the photoconductor 1 and the intermediate roller 405 have a large frictional resistance. This causes a load on the drive system (torque increase), generation of abnormal noise, heat generation, and vibration, which significantly shortens the life of the photoconductor 1 and the intermediate roller 405. Therefore, in the liquid developing apparatus of the present invention, the coating layer 402c made of a low friction member is provided on the surface of the elastic layer 402b of the developing roller 402. Examples of the material of the coating layer 402c include PTFE and PF
A fluororesin such as A or ETFE can be used. In particular, PTFE is suitable for reducing the frictional resistance with the developing roller 402. When these fluororesins are melted and coated on the outer peripheral surface of the elastic layer 402b, the melting temperature of the fluororesin is high, so that the elastic layer 402b is damaged, which is not preferable. Therefore, it is preferable to disperse and coat the fluororesin particles in another low melting temperature resin.

The surface roughness Rz of the coating layer 402c is preferably equal to or smaller than the average particle size of the toner in the developer. Surface roughness Rz of coating layer 402c
This is because when the value is larger than the average particle diameter of the toner, the toner in the developer applied to the developing roller 402 enters the dents on the surface of the coating layer 402c, and toner adhesion occurs.

Further, the coating layer 402c preferably has a thickness of 10 to 30 μm. This is because if the film thickness of the coating layer 402c is less than 10 μm, the surface roughness Rz of the coating layer 402c reflects the surface roughness of the elastic layer 402b, and it is difficult to make it equal to or smaller than the average particle diameter of the toner. . In addition, the coating layer 405
If the film thickness of c exceeds 30 μm, the coating layer 402
This is not preferable because a large undulation occurs in c, and the electrostatic latent image on the photoconductor 1 cannot be uniformly developed.

Developing roller 40 obtained as described above
No. 2 preferably has a maximum static friction coefficient of 0.2 or less. When the maximum static friction coefficient of the developing roller 402 is larger than 0.2, the friction (rubbing up) of the drive system, the generation of abnormal noise, the heat generation,
This is because vibration is generated and the life of the photoconductor 1 and the developing roller 402 is shortened. The maximum static friction coefficient can be calculated as follows. FIG. 7 is a block diagram of a measuring apparatus (Euler method) for measuring the maximum static friction coefficient. As shown in FIG. 7, PET film (t = 0.1)
14 on the roller 11 and 0.98N (100
g) and pull the PET film 14 with the digital push-pull gauge 13 from the other side,
Read the gauge value when the ET film 14 starts moving.
If the value at this time is F (N), the maximum coefficient of static friction μ is
It is derived by the following Equation 1. μ = [ln (F / 0.98)] / (π / 2) (Equation 1)

Next, the sweep roller 403 will be described. As shown in FIG. 3, in the sweep roller 403, an elastic layer 403b made of an elastic body is provided on the outer peripheral surface of a core metal 403a, and a conductive layer 403 is further provided on the outer peripheral surface of the elastic layer 403b.
c is provided. Here, the elastic layer 40
Urethane rubber can be used as the material of 3b. Further, in order to efficiently form the removal nip between the sweep roller 403 and the photoconductor 1, the elastic layer 403b preferably has a JIS-A hardness of 50 degrees or less. The material of the elastic layer 403b of the sweep roller 403 may be any material that does not swell or dissolve in the carrier liquid of the developer. Alternatively, the material of the conductive layer 403c formed on the elastic layer 403b is
The elastic layer 403, which is a material that does not swell or dissolve in the carrier liquid of the liquid developer, and has the structure of the inner layer
If the structure is such that the carrier liquid of the liquid developer does not come into contact with b, the material of the elastic layer 403b can be used without restrictions such as swelling and dissolution. Here, the elastic layer 40
When 3b is an insulator, it is necessary to apply the sweep bias voltage from the surface of each core metal 403a of the sweep roller 403 rather than from each core metal 403a.

In FIG. 1, when the developing roller 402 and the sweep roller 403 are brought into contact with the photosensitive member 1 at appropriate pressures, the elastic layers 402b and 403b of the developing roller 402 and the sweep roller 403 are elastically deformed. , A development nip and a removal nip are formed between the photoconductor 1 and the photoconductor 1. In particular, because the development nip is formed,
A certain developing time is ensured for the toner in the liquid developer to move and adhere to the photoconductor 1 due to the developing electric field in the developing area A. Further, by adjusting the contact pressure between the developing roller 402 and the sweep roller 403 and the photoconductor 1, the nip width, which is the width in the surface movement direction at each nip portion, can be adjusted. These nip widths are set to be larger than the product of the linear velocity of the developing roller 402 and the sweep roller 403 and the developing time constant.
Here, the development time constant is the time required until the amount of development is saturated, and is the required minimum nip width divided by the process speed. For example, if the required minimum nip width is 3 mm and the process speed is 300 mm / s, the development time constant is 10 msec.

The liquid developer used in the liquid developing apparatus of the present invention is conventionally commercially available and used as Is.
This is not a low-viscosity (about 1 cSt), low-concentration (about 1%) liquid developer using opar (manufactured by Exxon) as a carrier liquid, but a high-viscosity high-concentration liquid developer. The range of the viscosity and the concentration of the liquid developer is, for example, a viscosity of 50.
It is preferable to use one having a concentration of 1 to 10,000 mPa · s and a concentration of 5% to 40%. As the carrier liquid, silicone oil, normal paraffin, IsoparM
(Made by Exxon), vegetable oil, mineral oil, or the like having high insulating properties can be used. As the liquid developer, a volatile one or a non-volatile one can be selected and used according to the purpose. Further, the toner contained in the liquid developer is a toner composed of a resin and a pigment, and has a particle size of submicron to about 6 μm.
It can be selected according to the purpose.

Next, the developing roller 40 as a member to be coated.
An application device for applying the liquid developer D to No. 2 will be described. This coating apparatus includes a coating roller 404 having a uniform pattern engraved on the surface as a coating member, an intermediate roller 405 serving as an intermediate coating member for coating the developing roller 402 with the liquid developer D, and stirring of the liquid developer D. Mainly composed of an agitating / conveying screw 406 as a conveying means. Further, the intermediate roller 405 and the sweep roller 403 are provided with cleaning members 408 and 411 made of metal blades or rubber blades, respectively. The cleaning members 408 and 411 are
A roller type may be used instead of the blade type. In the coating device, the intermediate roller 405 is
It also functions as a doctor roller that comes into contact with the surface of the coating roller 404 and removes the excess liquid developer on the surface to regulate the amount of the developer carried on the surface of the coating roller 404. Then, on the surface of the intermediate roller 405, the liquid developer which is applied to the application roller 404 and measured by the doctor blade 409 as a coating amount regulating member is transferred.

The coating roller 404 will be described. Figure 4
FIG. 4 is a diagram showing a configuration of an application roller. As shown in FIG. 4, the coating roller 404 is an anilox roller having concave portions 404a having a uniform pattern formed on its surface. Anilox rollers are also called gravure rollers because they are used for gravure printing. FIG. 5 shows the coating roller 4
It is a figure which shows the recessed part shape of the surface of 04. For example, in FIG.
Examples include a diagonal type shown in (a), a pyramid type shown in FIG. 5 (b), and a lattice type shown in FIG. 5 (c). In the liquid developing device according to the present embodiment, the coating roller 404 having the hatched concave portion 404a is used for reasons such as good transferability. As described above, by using the anilox roller as the application roller 404, the surplus amount of the liquid developer carried on the surface is squeezed out at the contact portion with the intermediate roller 405 which also serves as the application amount regulating member. As a result, a predetermined amount of the liquid developer accurately measured by the recess 404a is carried on the surface of the coating roller 404.

By the way, the coating roller 404 having the concave portion 404a formed on the surface such as the above anilox roller is brought into direct contact with the developing roller 402 to form the coating roller 40.
The liquid developer applied to the surface of
When the coating is applied to the surface of the developing roller 402,
The surface of the developing roller 402 is rubbed, and the surface of the developing roller 402 is worn and damaged. That is, in the case of such a configuration, the surface of the developing roller 402 and the surface of the coating roller 404 move in different directions from each other, so that there is always a large linear velocity difference with the concave portion 404a on the surface of the coating roller 404. Contact. As a result, the surface of the developing roller 402 is damaged by friction due to the difference in linear velocity. Therefore, in the coating device having such a configuration, the developing roller 4
There was a problem that the life of 02 was remarkably shortened.

On the other hand, in the liquid developing apparatus according to the present invention, as described above, the liquid developer applied to the surface of the applying roller 404 is applied to the surface of the developing roller 402 via the intermediate roller 405. Is configured to. As a result, the developing roller 402 and the applying roller 404
And the surface of the developing roller 402 is not worn or damaged by the recess 404a on the surface of the coating roller 404. In addition, the intermediate roller 4
Reference numeral 05 makes contact with the developing roller 402 while rotating in the opposite direction, but since the surface of the intermediate roller 405 has no unevenness, it does not damage the surface of the developing roller 402. Therefore, in the liquid developing apparatus according to the present invention, the mechanical stress applied to the developing roller 402 is reduced, and the life of the developing roller 402 can be extended. Although the intermediate roller 405 is in contact with the coating roller 404, the surface of the intermediate roller 405 and the coating roller 40
Since the surface of No. 4 and the surface of No. 4 rotate at the same speed in the same direction, there is no difference in peripheral speed at the contact portion with the coating roller 404. Therefore, the intermediate roller 405 receives a small mechanical stress from the application roller 404, and the surface of the intermediate roller 405 is not worn or damaged by the recess 404a on the surface of the application roller 404.

Next, the structure of the intermediate roller will be described. FIG. 6 is a sectional view showing the structure of the intermediate roller. As shown in FIG. 6, the intermediate roller 405 has a structure in which an elastic layer 405b made of an elastic material is provided on the outer peripheral surface of a core metal 405a, and a slipping layer 405c is further provided on the outer peripheral surface of the elastic layer 405b. There is. As the material of the elastic layer 405b,
As long as the material does not swell or dissolve in the carrier liquid of the liquid developer, various polymer materials can be used. Preferred materials are polar rubbers such as epichlorohydrin rubber, acrylonitrile butadiene rubber, urethane rubber and chloroprene rubber.
In order to prevent the elastic layer 405b from swelling or dissolving with the carrier liquid, the solubility index (SP value) of the polymer material forming the elastic layer 405b and the solubility index (SP value) of the carrier liquid are used. Preferably has a difference of 2 or more. When the difference in solubility index (SP value) between the polymer material forming the elastic layer 405b and the carrier liquid is less than 2,
This is because the elastic layer 405b is dissolved or swollen. The solubility index (SP value) is the square root of the cohesive energy density, and is a value determined by the heat of evaporation, surface tension, and solubility.

The elastic layer 405b has a rubber hardness of JI.
The S-A hardness is preferably 30 to 70 degrees. The coating roller 404 and the intermediate roller 405 are ideally rollers having a perfect circle in cross section and free from rotational shake, but this is difficult due to the limit of mechanical accuracy. Therefore, it is preferable that the elastic layer 405b of the intermediate roller 405 be configured to absorb the rotational shake so that the outer peripheral surface of the intermediate roller 405 is always in stable contact with the outer peripheral surface of the coating roller 404. . Therefore, the rubber hardness of the elastic layer 405b of the intermediate roller 405 is set to JIS-A hardness 70 degrees or less. The rubber hardness of the elastic layer 405b is 70
This is because it is difficult to bring the surface of the intermediate roller 405 into uniform contact with the surface of the coating roller 404 when the surface area is larger than the degree. In addition, the elastic layer 405b according to JIS
If the -A hardness is a low hardness of less than 30 degrees, it is difficult to obtain the contact pressure required for the intermediate roller 405 to have a function as a coating amount regulation member, and thus it is difficult to obtain the JI.
It is preferable that the S-A hardness is 30 degrees or more.

The direct contact of the elastic layer 405b of the intermediate roller having the above JIS-A hardness with the developing roller 402 produces a very large frictional resistance, and therefore the intermediate roller 4
05, the load on the drive system of the developing roller 402 (torque increase), generation of abnormal noise, heat generation, and vibration are generated, and the life of the intermediate roller 405 and the developing roller 402 is significantly reduced. Therefore, a coating layer 405c made of a low friction member is provided on the surface of the elastic layer 405b of the intermediate roller 405. As the material of the coating layer 405c, for example, a fluororesin such as PTFE, PFA or ETFE can be used. In particular, PTFE is suitable for reducing the frictional resistance with the developing roller 402. When these fluororesins are melted and coated on the outer peripheral surface of the elastic layer 405b, since the melting temperature of the fluororesin is high,
The elastic layer 405b is damaged, which is not preferable. Therefore, other low melting temperature resins such as fluororesin, especially PTFE
It is preferable to disperse and coat the particles.

The contact pressure between the intermediate roller 405 and the coating roller 404 is as follows. The intermediate roller 405 is provided with the elastic layer 405b, so that the intermediate roller 405 is uniformly contacted along the rotation axis direction of the coating roller 404. Further, by abutting at a certain constant pressure, the amount of the developer carried in the recess 404a of the applying roller 404 is regulated to apply the developer to the developing roller 402. Here, if the contact pressure of the intermediate roller 405 with respect to the coating roller 404 is insufficient, the liquid developer may pass through between the surface of the coating roller 404 other than the concave portion 404a and the surface of the intermediate roller 405. Therefore, the coating roller 4
The application amount of the liquid developer applied to 04 is the application roller 4
The coating amount is not determined by the volume of the concave portion 404a of No. 04, and an image having an appropriate density cannot be formed. Although such a phenomenon changes depending on the linear velocity of the intermediate roller 405 and the coating roller 404, the viscosity of the liquid developer, etc., the higher the viscosity of the liquid developer used in the liquid developing apparatus of the present invention, the more the liquid developer. The passing through becomes noticeable.
Therefore, there is concern that the amount of the liquid developer applied to the application roller 404 may vary due to the change in the viscosity of the liquid developer due to the temperature change of the image forming environment, and therefore, the application roller of the intermediate roller 405. The contact pressure on 404 is set to 0.2 MPa. In this way, the intermediate roller 405 has a function as a regulating member (doctor roller) for efficiently regulating the contact pressure of the intermediate roller 405 with respect to the coating roller 404 to efficiently regulate the amount of the developer coated on the coating roller 404. I am holding it.

The application amount of the liquid developer to the developing roller 402 is the cell volume (cell volume capacity per unit area) of the recess 404a formed on the surface of the applying roller 404, and the applying roller 404 to the developing roller 40.
It depends on the transfer rate of the liquid developer to 2. Therefore, in the liquid developing apparatus of the present invention, in order to obtain a toner image having a target image density on the photoconductor 1, an anilox roller having an appropriate cell volume is selected as the application roller 404, and the intermediate roller 405 is applied with sufficient pressure. To contact the developing roller 40
The application amount of the liquid developer with respect to No. 2 does not change. In this way, from the application roller 404 to the developing roller 4
The transfer rate of the liquid developer to 02 shows a substantially constant value if the physical properties of the liquid developer are determined. However, if the viscosity of the liquid developer changes due to changes in the environmental temperature, the transfer rate of the liquid developer changes. As a result, the toner image on which the electrostatic latent image on the photoconductor 1 has been developed has a different image density as compared with that before the change in the environmental temperature. When controlling the image density by controlling the developing electric field, there is no problem when the developing electric field is increased to output a high density image, but when the developing electric field is weakened to output a low density image. Causes fine non-uniformity in the liquid developer layer after development. That is, since the behavior of the solid content of the liquid developer cannot be controlled under a low electric field, when the surface of the photoconductor 1 and the surface of the developing roller 402 are separated and the liquid developer is separated, each surface has the above solid content. Are attracted to each other, and the traces of this attraction become fine non-uniformity and remain in the liquid developer layer after development. This nonuniformity becomes conspicuous unless the development rate is 90% or more.

Therefore, in order to prevent uneven image density caused by a low developing electric field, the electric resistance in the volume direction of the developing roller 402 is set in the range of 10 ³ to 10 ¹² Ω. It is preferably 10 ³ to 10 ⁸ Ω. By setting the electric resistance in the volume direction of the developing roller 402 within the above range, the developing rate can be stabilized at 90% or more even in the low developing electric field region, and nonuniform image density can be prevented.

It is possible to reduce the electric resistance in the volume direction of the developing roller 402 by lowering the electric resistance of the coating layer 402c, but the electric resistance in the surface direction is lower than necessary. In the case of resistance, surface leakage may occur due to the developing electric field, and when the surface leakage occurs, the developing roller 402 and the photoconductor 1 are destroyed or damaged. Further, when the developing roller 402 and the photoconductor 1 are damaged or damaged, an abnormal image (white spot etc.) occurs. Therefore, in order to prevent the surface leak of the developing roller 402, the electric resistance in the surface direction is 3.0 × 10 ^4.
It is preferably Ω or more. The electrical resistance in the volume direction and the electrical resistance in the surface direction of the developing roller were measured with a resistance meter R8340A (manufactured by Advantest) with an applied voltage of 100 V and an application time of 30 seconds.

Hereinafter, the present invention will be described in more detail with reference to examples. First, the image forming operation of the image forming apparatus shown in FIG. 1 will be described. The photoconductor 1 is rotationally driven in the arrow direction at a constant speed during image formation by a driving unit such as a motor (not shown). Then, first, the surface of the photoconductor 1 is uniformly charged by the charger 2 in the dark. Next, the exposure device 3 irradiates and forms a document light image on the surface of the photoconductor 1. As a result, an electrostatic latent image is formed on the surface of the photoconductor 1. After that, when the electrostatic latent image passes through the developing area A,
The electrostatic latent image is visualized (developed) by the developing device 4,
A toner image is formed on the surface of the photoconductor 1.

The developing operation by the developing device 4 is as follows.
is there. On the surface of the developing roller 402,
Liquid developer by the roller 404 and the intermediate roller 405.
To form an electrostatic latent image on the photoconductor 1.
develop. Here, the liquid applied on the developing roller 402
The thickness of the body developer is 1 cm on the surface of the developing roller 402.^Two
The content of pigment in the toner carried per hit is 3 μg or more
It was set to be 60 μg or less. That is, the development
Layer of developer having a thickness of 3 to 10 μm on the surface of the roller 402.
Was applied. The reason for this is that the developing roller 402
The thickness of the liquid developer applied to the surface of the
402 surface 1 cm ^TwoFace in toner carried per hit
A thickness such that the content of ingredients is less than 3 μg is sufficient.
Of pigment to the image area formed on the photoreceptor 1.
The image density in the image area may be reduced.
It 1 cm of the surface of the developing roller 402^TwoPer hit
The pigment content in the carried toner is greater than 60 μg
With such a thickness, the electrostatic latent image formed on the photoconductor 1
Toner remaining on the background of the photoconductor 1 after developing the toner
Of the excess toner due to the sweep roller 403
This is because the removal may be incomplete.

The specified amount of the liquid developer is precisely measured and carried on the surface of the coating roller 404, and the liquid developer is transferred to the surface of the developing roller 402 through the intermediate roller 405. , Applied on the developing roller 402. Here, the intermediate roller 405 is the coating roller 4
In the contact portion with 04, the coating roller 404 rotates so as to be equal to the peripheral speed of the application roller 404 and in the same moving direction, and in the contact portion with the developing roller 402, in the reverse direction opposite to the rotating direction of the developing roller 402. Rotate. by this,
A thin layer of liquid developer having a uniform thickness is formed on the surface of the developing roller 402. That is, the thin layer of the liquid developer immediately after being transferred from the coating roller 404 to the intermediate roller 405 is
The pattern of the recesses 404a on the surface of the coating roller 404 is transferred as it is. Therefore, the intermediate roller 40
5 and the developing roller 402, the developing roller 40
The intermediate roller 405 is rotated in a direction opposite to the rotation direction of 2. As a result, the intermediate roller 405 and the developing roller 402
Due to the linear velocity difference between the developing roller 402 and the developing roller 402, the thin developer layer transferred to the surface of the developing roller 402 is evenly stretched, and a thin developer layer having a uniform thickness is formed on the surface of the developing roller 402.

The thin developer layer formed on the surface of the developing roller 402 in this manner is the photosensitive member 1 and the developing roller 402.
When it passes through the developing nip formed by and, it comes into contact with the surface of the photoconductor 1. As a result, the toner in the thin developer layer forms an electrostatic latent image (image portion) on the surface of the photoconductor 1.
To develop the electrostatic latent image. On the other hand, in the background portion (non-image portion) of the photoconductor 1, the toner is transferred to the surface of the developing roller 402 by the electric field formed by the developing bias potential and the photoconductor potential, and the toner is transferred to the background portion of the photoconductor 1. Will not adhere. However, if a part of the toner adhered to the background portion of the photoconductor 1 cannot be moved to the surface of the developing roller 402 and remains on the photoconductor 1, fog occurs in the image formed on the photoconductor 1. Therefore, the sweep roller 403 removes the toner (hereinafter, referred to as “fogging toner”) that causes such image fogging. As shown in FIG. 1, the sweep roller 403 has a toner image (developer layer) developed on the photosensitive member 1 by the developing roller 402 at a position downstream of the developing roller 402 in the rotation direction of the photosensitive member 1. The photoconductor 1 is pressed against the photoconductor 1 so as to sandwich it. Then, the surface of the sweep roller 403 moves in contact with the surface of the photoconductor 1 at a substantially constant speed, so that the fog toner on the background portion of the photoconductor 1 is removed. The liquid developer removed by the sweep roller 403 is removed by a cleaning member 408 including a blade in order to maintain the sweep (cleaning) performance of the sweep roller 403.

The residual toner remaining on the surface of the developing roller 402 after development is removed by the surface of the intermediate roller 405 which rotates in contact with the surface of the developing roller 402 in the opposite direction to prevent ghost. Intermediate roller 405
The residual toner removed from the surface of the developing roller 402 by the above adheres to the surface of the intermediate roller 405. Then, the residual toner adhering to the surface of the intermediate roller 405 is removed from the surface of the intermediate roller 405 by a cleaning member 411 composed of a blade that is disposed in contact with the intermediate roller 405.

As described above, the developing roller 402, sweep roller 403, coating roller 404, intermediate roller 4
The liquid developer removed from 05 is stored in the developer storage tank 4
01 is temporarily collected in a temporary storage unit 412. The liquid developer collected in the temporary storage unit 412 is sent to a concentration adjusting unit (not shown) by the conveying screw 413, and after the developer concentration is adjusted in the concentration adjusting unit, the liquid developer is returned to the developer containing tank 401. And then reused. The temporary storage unit 412 is provided with a stirring unit 413, a concentration detection unit (not shown), a liquid amount detection unit (not shown), and the like, and stores the liquid developer collected in the temporary storage unit 412. The concentration and liquid volume are detected. Based on the detection result, the concentration adjusting unit replenishes a new liquid developer or a carrier and adjusts the concentration of the collected liquid developer to be uniform. Here, the supply amount of the liquid developer into the developer storage tank 401 is set to be slightly larger than the consumption amount of the liquid developer. As a result, the liquid developer overflowing from the developer storage tank 401 is returned to the temporary storage section 412. In this way, the liquid developer is constantly circulated.

The toner image on the photoconductor 1 developed by the developing device 4 is transferred in the transfer area B by the transfer bias applied through the transfer roller 501 of the transfer device 5 to the intermediate transfer member (belt) of the transfer device 5. The image is primarily transferred onto 502. The toner image primarily transferred onto the intermediate transfer member 502 is
In a secondary transfer area (not shown), secondary transfer is performed by a secondary transfer means (not shown) onto a transfer material such as a copy sheet or an OHP sheet. Then, the transfer material on which the toner image is secondarily transferred is discharged to the outside of the machine after the toner image is fixed by a fixing device (not shown). On the other hand, after the primary transfer, the residual potential remaining on the photoconductor 1 is removed by the static elimination lamp 7. Further, the residual toner remaining on the photoconductor 1 is removed by the photoconductor cleaning device 6 and prepared for the next image formation.

[0046]

EXAMPLE A method for producing an elastic layer of a developing roller will be described. (Elastic layer A) φ14 mm SUS core shaft coated with adhesive
A foam layer having the following composition A1 is press-formed (150
Φ × 15min), and then φ2 by outer diameter grinding.
It was adjusted to 4.0 mm. Then, non-foaming of the following composition A2
A layer is extruded around the foam layer and pressureless vulcanized (1
It was vulcanized and adhered at 60 ° C. × 1 hr). Then outer diameter
It was adjusted to φ24.1 mm by grinding.Composition A1 (foam layer) Epichlorohydrin rubber: 100 parts by weight Calcium carbonate: 30 parts by weight Carbon black: 10 parts by weight Foaming agent / foaming aid: 3 parts by weight each Vulcanization accelerator: 3 parts by weight Sulfur: 1 part by weightComposition A2 (non-foamed layer) Epichlorohydrin rubber: 100 parts by weight Calcium carbonate: 30 parts by weight Carbon black: 10 parts by weight Foaming agent / foaming aid: None added Vulcanization accelerator: 3 parts by weight Sulfur: 1 part by weight The produced elastic layer A has an electric resistance of 10 in the volume direction.
⁶Ω, JIS-A hardness of 37 degrees, surface roughness Rz of 4 μm
Met.

(Elastic layer B) φ14 mm coated with adhesive
An elastic layer of urethane elastomer was formed around the SUS core shaft by a one-shot method using a polyol resin and an isocyanate resin in which carbon black was dispersed. After that, by outer diameter grinding, φ24.1mm and φ24.0mm
Adjusted to. The produced elastic layer B had an electric resistance in the volume direction of 6.0 × 10 ³ Ω, a JIS-A hardness of 30 degrees, and a surface roughness Rz of 5 μm.

(Elastic layer C) φ14 mm coated with adhesive
An elastic layer of the following composition C is press-formed around the SUS core shaft of
It was made by a shape (150 ° C x 30 min). afterwards,
The outer diameter was adjusted to φ24.1 mm.Composition C Epichlorohydrin rubber: 100 parts by weight Calcium carbonate: 30 parts by weight Vulcanization accelerator: 3 parts by weight Sulfur: 1 part by weight The produced elastic layer C has an electric resistance of 5.0 × in the volume direction.
10⁶Ω, JIS-A hardness 53 degrees, surface roughness Rz 3
was μm.

(Elastic layer D) φ14 mm coated with adhesive
An elastic layer of the following composition D is press-formed around the SUS core shaft of
Formed (160 ℃ × 20min), pressureless vulcanization
(200 ° C. × 4 hours). After that, by outer diameter grinding,
The diameter was adjusted to 24.1 mm.Composition D Conductive silicone rubber D1: 80 parts by weight Conductive silicone rubber D2: 20 parts by weight Organic peroxide (vulcanizing agent): 2 parts by weight The produced elastic layer D has an electric resistance of 10 in the volume direction.
^ThreeΩ, JIS-A hardness of 40 degrees, surface roughness Rz of 4 μm
Met.

Next, a method for producing the coating layer will be described. (Coating layer 1): Urethane resin (containing PTFE) A coating layer 1 to which a silane coupling type curing agent is added is formed around the elastic layer by a spray coating method,
It was baked at 130 ° C. for 1 hr.

(Coating layer 2): Urethane resin (polycarbonate type) + PTFE particles (average particle size 0.3 μm)
m) A coating layer 2 containing a silane coupling type curing agent is formed around the elastic layer by a spray coating method,
It was baked at 130 ° C. for 1 hr.

(Coating layer 3): Conductive urethane resin (containing PTFE) A coating layer 3 containing a silane coupling curing agent is formed around the elastic layer by a spray coating method.
It was baked at 130 ° C. for 1 hr.

(Coating layer 4): An insulating primer was applied around the elastic layer of the conductive PFA tube having a thickness of 50 μm, and the coating layer 4 was press-fitted and adhered around the insulating primer.

(Coating layer 5): A coating layer 5 using MEK / butyl acetate as a solvent was formed around the fluororesin elastic layer by a spray coating method to form 130
It was baked at ℃ × 1 hr.

(Coating layer 6): A coating layer 6 using toluene / xylene as a solvent is formed around the fluororesin elastic layer by a spray coating method to form 130
It was baked at ℃ × 1 hr.

(Coating layer 7): Conductive urethane resin (containing PTFE) A coating layer 7 containing a silane coupling type curing agent is formed around the elastic layer by a spray coating method.
It was baked at 130 ° C. for 1 hr.

The elastic layers A to D and the coating layers 1 to 7
And the combination shown in Table 1 to prepare a developing roller, and
The continuous copying test was conducted on up to 500,000 sheets of plain paper by the image forming apparatus incorporated in the liquid developing apparatus of No. still,
As the intermediate roller, a roller in which the elastic layer C and the coating layer 1 are combined is used.

[Table 1]

[0058]Example 1 <Combination of elastic layer A and coating layer 1> Elastic layer is polar
It is formed from epichlorohydrin rubber, which is currently
The solubility index (SP value) of the carrier liquid that constitutes the image agent is 2
Since they are far apart, swelling and dissolution are at a problematic level.
There is no. The coating layer contains PTFE particles
And the maximum coefficient of static friction is 0.17, so wear,
There is no torque increase, vibration, or abnormal noise. JIS-A
The hardness is 37 degrees and the thickness of the coating layer is 20 μm
And the surface roughness R is less than the average particle diameter of the toner in the developer.
z4 μm, electric resistance in the volume direction is 1.9 × 10⁹
Ω, the electric resistance in the surface direction is 4.0 × 10¹⁰In Ω
Therefore, even on the 500,000th sheet, a good image (density
It was possible to obtain non-uniformity and streak images). Communicating
After continuous copy test, observe the surface of developing roller and intermediate roller
However, there are about 10 or less shallow streaky scratches.
It was just

[0059]Example 2 <Combination of elastic layer A and coating layer 2> The elastic layer is polar
It is formed from epichlorohydrin rubber, which is currently
The solubility index (SP value) of the carrier liquid that constitutes the image agent is 2
Since they are far apart, swelling and dissolution are at a problematic level.
There is no. PTFE particles are dispersed in the coating layer.
Therefore, the maximum coefficient of static friction is 0.16.
There is no look-up, vibration or noise. JIS-A hard
The degree is 37 degrees, and the thickness of the coating layer is 20 μm.
Yes, the surface roughness is Rz less than the average particle diameter of the toner in the developer.
4 μm, electric resistance in the volume direction is 8.3 × 10⁹Ω
And the electric resistance in the surface direction is 1.6 × 10 ¹¹In Ω
Therefore, even with the 500,000th sheet, a good image (density
La and streak images have not been generated). Continuous
After the copy test, observe the surface of the developing roller and the intermediate roller.
However, there are about 10 or less shallow streaky scratches.
Was only.

[0060]Example 3 <Combination of elastic layer A and coating layer 3> Elastic layer is polar
It is formed from epichlorohydrin rubber, which is currently
The solubility index (SP value) of the carrier liquid that constitutes the image agent is 2
Since they are far apart, swelling and dissolution are at a problematic level.
There is no. The coating layer contains PTFE particles
And the maximum static friction coefficient is 0.18, wear,
There is no torque increase, vibration, or abnormal noise. JIS-A
The hardness is 37 degrees and the thickness of the coating layer is 20 μm
And the surface roughness R is less than the average particle diameter of the toner in the developer.
z4 μm, electric resistance in the volume direction is 2.0 × 10⁷
Ω, electric resistance in the surface direction is 5.0 × 10⁷In Ω
Therefore, even with the 500,000th sheet, a good image (density
La and streak images have not been generated). Continuous
After the copy test, observe the surface of the developing roller and the intermediate roller.
However, there are about 10 or less shallow streaky scratches.
Was only.

[0061]Example 4 <Combination of elastic layer B and coating layer 1> The elastic layer is polar.
It is made of polyurethane rubber, which is used as a developer.
The solubility index (SP value) of the constituent carrier liquids is 2 or more.
Therefore, swelling or dissolution is not a problematic level.
Yes. The coating layer contains PTFE particles
Therefore, the maximum coefficient of static friction is 0.17.
There is no look-up, vibration or noise. JIS-A hard
The degree is 30 degrees, and the thickness of the coating layer is 20 μm.
Yes, the surface roughness is Rz less than the average particle diameter of the toner in the developer.
4 μm, electric resistance in the volume direction is 5.0 × 10⁶Ω
And the electric resistance in the surface direction is 10¹⁰Since it is Ω,
Even on the 500,000th sheet, a good image (density unevenness and stripes)
Images, etc. have not been generated). Continuous copy trial
After the test, the surfaces of the developing roller and the intermediate roller were observed.
Only 10 or less streaky scratches have occurred.
It was

[0062]Example 5 <Combination of elastic layer B and coating layer 2> The elastic layer is polar.
It is made of polyurethane rubber, which is used as a developer.
The solubility index (SP value) of the constituent carrier liquids is 2 or more.
Therefore, swelling or dissolution is not a problematic level.
Yes. PTFE particles are dispersed in the coating layer,
Wear and torque as the maximum static friction coefficient is 0.16
No ups, vibrations, or abnormal noises have occurred. JIS-A hardness is
30 degrees and the thickness of the coating layer is 20 μm
The surface roughness is Rz4 which is equal to or smaller than the average particle diameter of the toner in the developer.
μm, electric resistance in the volume direction is 1.2 × 10⁷In Ω
Yes, the electrical resistance in the surface direction is 7.3 × 10¹⁰Is Ω
Therefore, even on the 500,000th sheet, a good image (density unevenness)
And streak images etc. have not been generated). Continuous
After the pee test, the surfaces of the developing roller and the intermediate roller were observed.
However, there are about 10 or less shallow streaky scratches.
I was injured.

[0063]Example 6 <Combination of elastic layer B and coating layer 3> The elastic layer is polar.
It is made of polyurethane rubber, which is used as a developer.
The solubility index (SP value) of the constituent carrier liquids is 2 or more.
Therefore, swelling or dissolution is not a problematic level.
Yes. The coating layer contains PTFE particles
Therefore, the maximum coefficient of static friction is 0.18.
There is no look-up, vibration or noise. JIS-A hard
The degree is 30 degrees, and the thickness of the coating layer is 20 μm.
Yes, the surface roughness is Rz less than the average particle diameter of the toner in the developer.
4 μm, electric resistance in the volume direction is 6.8 × 10⁵Ω
And the electric resistance in the surface direction is 1.2 × 10⁷Is Ω
Therefore, even on the 500,000th sheet, a good image (density unevenness)
And streak images etc. have not been generated). Continuous
After the pee test, the surfaces of the developing roller and the intermediate roller were observed.
However, there are about 10 or less shallow streaky scratches.
I was injured.

[0064]Comparative Example 1 <Combination of elastic layer A and coating layer 5> Coating
The layer does not contain PTFE particles, maximum static friction
Since the coefficient is as high as 1.15, it slides with the photoconductor and the intermediate roller.
The generation of vibration and abnormal noise due to rubbing is remarkable from the beginning, and continuous
I couldn't do the Pea test. The elastic layer is polar.
It is formed from epichlorohydrin rubber which is a rubber
The solubility index (SP value) of the carrier liquid that constitutes the developer is
Two or more apart, so swelling or dissolution is a problem level
is not. The JIS-A hardness is 37 degrees,
The coating layer has a thickness of 20 μm and the surface roughness is
Rz 4 μm, which is less than the average toner particle diameter,
Electrical resistance of 1.4 × 10⁹Ω and electricity in the surface direction
Resistance is 1.4 × 10¹⁰Ω, and problems other than the above are
Not seen.

[0065]Comparative example 2 <Combination of elastic layer A and coating layer 6> Coating
The layer does not contain PTFE particles, maximum static friction
Coefficient is 0.55, which is rather high, so
It was confirmed from the beginning that vibration and abnormal noise were generated due to the rubbing of the
However, it is not at a level where a continuous copy test cannot be performed.
won. However, about 20,000 sheets, vibration and abnormal noise are remarkable
It becomes impossible to continue the continuous copy test
It was The electric resistance in the volume direction is 1.2 × 10.¹²In Ω
In the low developing electric field, the image had uneven density. Na
The elastic layer is made of a polar rubber, epichlorohydrin rubber.
And the solubility of the carrier liquid that makes up the developer.
Since the numbers (SP values) are 2 or more apart, swelling and dissolution do not matter.
It's not at the level of the subject. The JIS-A hardness is 37.
And the thickness of the coating layer is 20 μm.
The surface roughness is Rz 4 μm, which is less than the average particle diameter of the toner in the developer.
Yes, the electrical resistance in the surface direction is 2.8 × 10¹²In Ω
No other problems have been observed.

[0066]Comparative Example 3 <Combination of elastic layer A and coating layer 7>
Qi resistance is 2.2 × 10^ThreeIt has a low resistance of Ω and can be removed from the surface.
Cause damage to the developing roller and photoconductor
I made it. Moreover, the abnormal image (white spot) due to it
confirmed. The elastic layer is made of polar rubber epichlorohydride.
A carrier that is made of phosphorus rubber and constitutes the developer.
Since the solubility index (SP value) of the liquid is 2 or more apart,
Swelling and dissolution are not problematic levels. coating
The layer contains PTFE particles and has a maximum static friction coefficient.
Since the number is 0.19, wear, torque increase, vibration,
There is no unusual noise. The JIS-A hardness is 37 degrees.
Yes, the coating layer thickness is 20 μm,
Is Rz 4 μm, which is less than the average particle size of the toner in the developer.
And the electrical resistance in the volume direction is 1.8 × 10⁵Ω and above
No other problems than the above have been observed.

[0067]Comparative Example 4 <Combination of elastic layer B and coating layer 4> Intermediate roller
With conventional technology not used, it has a durable life of about 50,000 sheets
It has a different structure. The coating layer is PFA tube
The maximum static friction coefficient was 0.22, which was slightly high.
Therefore, after passing the continuous copy test of 20,000 sheets,
Ringing layer (damaged streaks in the circumferential direction)
The image occurred. However, torque increase, vibration, abnormal noise
Has not occurred. The coating layer has a thickness of 50 μm.
Since it is a tube, uneven image density due to tube deviation
It became visible. The elastic layer is made of polar rubber.
It is made of urethane rubber and is a key component of the developer.
The solubility index (SP value) of the carrier solution is 2 or more apart.
Therefore, swelling and dissolution are not problematic levels. Also, J
The IS-A hardness is 42 degrees, and the surface roughness is
The average particle size is less than Rz 2 μm
Resistance is 9.5 × 10¹¹Ω, electrical resistance in the surface direction
Is 3.4 × 10^FourΩ.
Absent.

[0068]Comparative Example 5 <Combination of elastic layer C and coating layer 1> JIS-A hard
Since the degree is as high as 53 degrees, take a sufficient nip width with the photoconductor
Cannot form a uniform thin toner layer on the photoconductor
I couldn't. Therefore, uneven density is seen in the image
It was It is also possible to have a sufficient nip width with the intermediate roller.
Scratches, residual toner and high-concentration liquid developer cleaner
Becomes insufficient and ghost images become apparent over time.
It was The elastic layer is made of polar rubber, epichlorohydrin rubber.
It is formed from the solution of the carrier liquid that constitutes the developer.
Since the resolution index (SP value) is 2 or more apart, swelling or dissolution
The solution is not at a problematic level. P for the coating layer
It contains TFE particles and has a maximum static friction coefficient of 0.
Since it is 17, wear, torque increase, vibration, and abnormal noise are
I haven't. The film thickness of the coating layer is 20 μm,
The surface roughness is Rz 4 μm, which is equal to or smaller than the average particle diameter of the toner in the developer.
And the electric resistance in the volume direction is 1.9 × 10.⁹In Ω
And the electrical resistance in the surface direction is 4.0 × 10¹⁰Ω,
No defects other than the above have been observed.

[0069]Comparative Example 6 <Combination of elastic layer D and coating layer 1> Elastic layer is non-polar
Silicone rubber (SP value 7.5), which is a rubber
Solubility index of carrier liquid (SP value 5.5)
Because they are not more than 2 apart, they swell and coat
A crack was seen in the ring layer. Therefore, the image shows
Color loss was seen corresponding to the table. The coating layer
Contains PTFE particles, the maximum static friction coefficient
Is 0.17, so wear, torque increase, vibration,
No sound is produced. The JIS-A hardness is 40 degrees.
The coating layer thickness is 20 μm, and the surface roughness
Is Rz 4 μm, which is equal to or smaller than the average particle diameter of the toner in the developer,
The electrical resistance in the volume direction is 10⁶Ω and electricity in the surface direction
Resistance is 6.8 × 10⁹Ω.
I can't.

[0070]Comparative Example 7 In Example 4, when the thickness of the coating layer was 8 μm.
If the surface roughness Rz of the elastic layer is 5 μm,
Surface roughness, the surface roughness can be adjusted to the average toner particle size (3 to 5 μm).
m) cannot be less than or equal to Also, the film thickness is 30 μm
If it exceeds, the swell of the coating layer itself will increase.
In each case, a uniform thin toner layer is formed on the photoreceptor.
I couldn't do it. Therefore, the density unevenness in the image
I was seen.

[0071]Comparative Example 8 In Example 4, the surface roughness of the coating layer was Rz 7 μm.
If the average particle size of the toner is 3 to 5 μm, the development
Toner enters the dents on the
Transfer is insufficient (development rate 90% or less), and the image is dark
There was unevenness. In addition, the cleaner
Is also inferior in terms of ringing property, and as time passes
Has stuck. Therefore, a ghost image occurs
Oops.

[0072]

As described above, according to the present invention, the maximum static friction coefficient of the developer carrier can be improved by forming the coating layer in which the PTFE particles are dispersed on the surface of the elastic layer of the developer carrier. It is possible to provide a liquid developing device which is lowered to prevent abrasion, torque increase, vibration, and abnormal noise in the nip between the image carrier and the intermediate coating member. With the liquid developing apparatus of the present invention, not only the developer carrying member but also the intermediate coating member can have a long useful life, and thus the image forming apparatus itself can have a long useful life. Further, by setting the electric resistance in the volume direction of the developing roller in the range of 10 ³ to 10 ¹² Ω and the electric resistance in the surface direction to 3.0 × 10 ⁴ Ω or more, the image density is made uniform even in a low developing electric field. The liquid developing device can be maintained. Furthermore, by providing the liquid developing device, it is possible to provide a stable and good image, and to provide an image forming apparatus having high durability.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming unit of an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a developing roller.

FIG. 3 is a sectional view showing a configuration of a sweep roller.

FIG. 4 is a diagram showing a configuration of a coating roller.

FIG. 5 is a diagram showing a concave shape on the surface of the coating roller.

FIG. 6 is a cross-sectional view showing a configuration of an intermediate roller.

FIG. 7 is a configuration diagram of a maximum static friction coefficient measuring device (Euler method).

[Explanation of symbols]

1 photoconductor (image carrier) 4 Liquid developing device 401 developer storage tank 402 developer carrier 402a core metal 402b Elastic layer 402c coating layer 404 Coating member 405 Intermediate coating member D liquid developer

Claims (11)

[Claims] 1. A developer accommodating tank for accommodating a liquid developer, a coating member for supporting and rotating a predetermined amount of liquid developer drawn up from the developer accommodating tank, and a liquid developer carried on the surface. A developer carrier for applying an agent to the electrostatic latent image on the image carrier to develop it, and an intermediate coating member for transferring the liquid developer from the surface of the coating member to the surface of the developer carrier. In the liquid developing device, the developer carrying member comprises an elastic layer formed on a cored bar, and a coating layer provided on the surface thereof. 2. The liquid developing apparatus according to claim 1, wherein the developer carrying member has the coating layer in which PTFE particles are dispersed. 3. The liquid developing apparatus according to claim 1, wherein the elastic layer of the developer carrier is made of rubber having polarity, and the liquid developer is contained in a carrier liquid that is an insulating liquid. ,
A liquid developing apparatus, wherein a toner composed of a resin and a pigment is dispersed. 4. The liquid developing apparatus according to claim 1, wherein the solubility index (SP value) of the polymer material forming the elastic layer of the developer carrier is the carrier liquid of the developer. And a solubility index (SP value) of 2 or more. 5. The liquid developing device according to claim 1, wherein the elastic layer of the developer bearing member has a JIS-A hardness of 20 to 20.
A liquid developing device having a temperature of 50 degrees. 6. The liquid developing apparatus according to claim 1, wherein the developer carrier has a surface roughness R of the coating layer.
A liquid developing device, wherein z is equal to or less than the average particle diameter of the toner in the developer. 7. The liquid developing apparatus according to claim 1, wherein the developer carrying member has a coating layer thickness of 10 or less.
A liquid developing device having a thickness of about 30 μm. 8. The liquid developing apparatus according to claim 1, wherein the developer carrier has a maximum static friction coefficient of 0.2 or less. 9. The liquid developing apparatus according to claim 1, wherein the developer carrying member has an electric resistance in the volume direction of 10 ³ to 1.
A liquid developing device having a resistance of 0 ¹² Ω. 10. The liquid developing apparatus according to claim 1, wherein the developer carrying member has an electric resistance of 3.0 × 1 in a surface direction.
A liquid developing device having a resistance of 0 ⁴ Ω or more. 11. An image forming apparatus comprising the liquid developing device according to claim 1. Description: