JP2003098835A - Liquid development apparatus and image forming apparatus - Google Patents

Abstract

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

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.

However, the intermediate coating member including the intermediate roller has the following problems. (1) Abrasion and scratches are generated on the surface of the intermediate coating member, causing streaks in the toner layer on the developing roller, which causes streaks in the image. (2) Due to the surface properties (surface roughness, waviness) of the intermediate coating member, the toner having a small particle size in the liquid developer adheres to the irregularities on the surface and cannot be completely cleaned. Further, smoothness is required to uniformly apply the liquid developer to the developing roller. (3) Coating Torque increase, vibration, sound, and heat generation are caused by sliding friction between the coating member, the developer carrying member, and the cleaning blade. (4) It is necessary that the material forming the intermediate coating member does not swell in the insulating liquid of the liquid developer.

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

[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 provided with an intermediate coating member for transferring a liquid developer to the surface of a developer carrier, the intermediate coating member has an elastic layer formed on a core metal, and a coating layer is provided on the surface of the elastic layer. Liquid developing device. According to a second aspect of the present invention, in the liquid developing apparatus according to the first aspect, the intermediate coating member 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 apparatus described in the paragraph 1, the elastic layer of the intermediate coating member is made of rubber having polarity, and the liquid developer is a carrier liquid that is an insulating liquid in which toner made of resin and pigment is dispersed. Liquid developing device. According to a fourth aspect of the invention, in the liquid developing apparatus according to any of the first to third aspects, the solubility index (SP value) of the polymer material forming the elastic layer of the intermediate coating member is the developer. The liquid developing device has a difference of 2 or more from the solubility index (SP value) of the carrier liquid. 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 intermediate coating member has a JIS-A hardness of 30 to 70 degrees. .

According to a sixth aspect of the present invention, in the liquid developing apparatus according to any one of the first to fifth aspects, in the intermediate coating member, the surface roughness Rz of the coating layer is the average of the toner in the developer. The liquid developing device has a particle size or less. According to a seventh aspect of the invention, in the liquid developing apparatus according to any one of the first to sixth aspects, the intermediate coating member is a liquid developing apparatus in which the coating layer has 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 intermediate coating member 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, there is provided an image forming apparatus including the liquid developing device according to any one of the first to eighth aspects.

[0016]

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. FIG. 2 is a cross-sectional view showing the configurations of the developing roller 402 and the sweep roller 403. As shown in FIG. 2, elastic layers 402b and 403b made of an elastic body are provided on the outer peripheral surfaces of the cored bars 402a and 403a, and the conductive layer 402 is further provided on the outer peripheral surfaces of the elastic layers 402b and 403b.
c and 403c are provided.

Urethane rubber can be used as the material of the elastic layers 402b and 403b. Further, in order that the developing roller 402 and the sweep roller 403 can efficiently form the developing nip and the removing nip with the photoconductor 1, the rubber hardness of the elastic layers 402b and 403b is JIS-A hardness. , 50 degrees or less is desirable. The material of the elastic layers 402b and 403b of the developing roller 402 and the sweep roller 403 is not limited to urethane rubber, and may be any material that does not swell or dissolve in the carrier liquid of the liquid developer. Alternatively, conductive layers 402c, 4 formed on the elastic layers 402b, 403b.
03c is a material that does not swell or dissolve with the carrier liquid of the liquid developer, and its configuration is such that the carrier liquid of the liquid developer does not contact the inner elastic layers 402b and 403b. If so, the elastic layer 40
The materials of 2b and 403b can be used without restrictions such as swelling and dissolution. Here, the elastic layers 402b and 403b
Is an insulator, it is necessary to apply the developing bias voltage / sweep bias voltage not from the cores 402a and 403a of the developing roller 402 and the sweep roller 403, but from the surface thereof.

As another method for efficiently forming the developing nip and the removing nip between the developing roller 402 and the sweep roller 403 and the photosensitive member 1, the developing roller 40 can be used.
2 and the sweep roller 403 may be a rigid body and an elastic layer may be formed on the photoconductor 1 side. Further, as another method of giving elasticity to the photoreceptor 1 side as described above, the photoreceptor 1
May be composed of an endless belt member. Further, the surfaces of the developing roller 402 and the sweep roller 403 are rounded.
Coating or tube coating is applied so that the surface has a smoothness of 3 μm or less.

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.

Further, the developing device 4 is equipped with a coating device for coating the liquid developer D on the developing roller 402 as a member to be coated. 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. The intermediate roller 405 and the sweep roller 403 have cleaning members 408, 4 made of metal blades or rubber blades, respectively.
11 is provided. This cleaning member 408,
A roller type 411 may be used instead of the blade type. In the above coating apparatus, the intermediate roller 405 serves as a doctor roller that comes into contact with the surface of the coating roller 404 to remove excess liquid developer on the surface and regulates the amount of developer carried on the surface of the coating roller 404. Also has the role of. 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 3
FIG. 4 is a diagram showing a configuration of an application roller. As shown in FIG. 3, the coating roller 404 is an anilox roller having concave portions 404a having a uniform pattern formed on the surface thereof. Anilox rollers are also called gravure rollers because they are used for gravure printing. FIG. 4 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. 4 (b), and a lattice type shown in FIG. 4 (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 a concave portion 404a formed on the surface such as the anilox roller and the developing roller 402 are brought into direct contact with each other 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 device 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. 5 is a sectional view showing the structure of the intermediate roller. As shown in FIG. 5, the intermediate roller 405 has a structure in which an elastic layer 405b made of an elastic body 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. Preferable materials are polar rubbers such as epichlorohydrin rubber, NBR, urethane rubber and acrylic rubber. Further, in order to prevent the elastic layer 405b from swelling or dissolving with the carrier liquid, the elastic layer 4
Solubility index (SP value) of the polymer material constituting 05b
And the solubility index (SP value) of the carrier liquid preferably have 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 405b and the carrier liquid is smaller than 2, the elastic layer 405b will be dissolved or swelled. The solubility index (SP value) is
It is a square root of cohesive energy density and is a value obtained by heat of vaporization, 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, in the liquid developing apparatus of the present invention, the coating layer 405c made of a low friction member is provided on the surface of the elastic layer 405b of the intermediate roller 405. Coating layer 4
As the material of 05c, for example, PTFE, PFA, E
A fluororesin such as TFE can be used. In particular, PTFE is suitable for reducing the frictional resistance with the developing roller 402. These fluororesins are used in the elastic layer 4
If the outer peripheral surface of 05b is melted and coated, since the melting temperature of the fluororesin is high, the elastic layer 405b 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 405c is preferably equal to or smaller than the average particle size of the toner in the developer. Surface roughness Rz of coating layer 405c
Is larger than the average particle diameter of the toner, the toner in the developer applied to the intermediate roller 405 will enter the dents on the surface of the coating layer 405c, and toner adhesion will occur.

Further, the coating layer 405c preferably has a thickness of 10 to 30 μm. This is because if the thickness of the coating layer 405c is less than 10 μm, the surface roughness Rz of the coating layer 405c reflects the surface roughness of the elastic layer 405b, 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
When the film thickness of c exceeds 30 μm, the coating layer 405
A large undulation occurs in c, and a uniform developer layer cannot be formed on the developing roller 402, which is not preferable.

The intermediate transfer roller 405 obtained as described above preferably has a maximum static friction coefficient of 0.2 or less. If the maximum coefficient of static friction of the intermediate transfer roller 405 is larger than 0.2, the drive system of the intermediate roller 405 and the developing roller 402 is burdened (torque up), abnormal noise is generated, heat is generated, and vibration is generated. Also, the life of the developing roller 402 is shortened.
The maximum static friction coefficient can be calculated as follows. FIG. 6 is a configuration diagram of a maximum static friction coefficient measuring device (Euler method). As shown in FIG. 6, a PET film (t = 0.1) is placed on the roller 11 and 0.9 is applied on one side.
Attach a weight 12 of 8 N (100 g weight), pull the PET film from the other side with a digital push-pull gauge 13, and read the value of the gauge when the PET film starts moving. If the value at this time is F (N), the maximum static friction coefficient μ
Is derived by Equation 1 below. μ = [ln (F / 0.98)] / (π / 2) (Equation 1)

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.

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 liquid developer of the above specified amount is accurately weighed 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 thus formed on the surface of the developing roller 402 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, the sweep roller 403, the coating roller 404, and the 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.

[0040]

Example An intermediate roller was manufactured by the following procedure. First, elastic layers having the following compositions A and B were formed around the SUS core shaft having a diameter of 16 mm coated with an adhesive by press forming. Then, by adjusting the outer diameter by φ24 mm, an elastic layer having a thickness of 4 mm was obtained. (Composition A) Epichlorohydrin rubber 100 parts by weight Calcium carbonate 30 parts by weight Vulcanization accelerator 3 parts by weight Sulfur 1 part by weight (Composition B) NBR 100 parts by weight Zinc oxide 20 parts by weight Vulcanization accelerator 1 part by weight Stearic acid 1 part by weight Sulfur 1.5 parts by weight

In Examples 1 and 2, a coating layer having the composition shown in Table 1 below was formed on the elastic layer of the above formulation A by the spray coating method. In addition, in Example 3, a coating layer having the composition shown in Table 1 was formed on the elastic layer having the composition B by the spray coating method. Further, in Comparative Example 1, conductive urethane rubber (JIS-A hardness 60 degrees) was used as an elastic layer, and a conductive PFA tube was adhered to the surface of the elastic layer for coating. In Comparative Examples 2 and 3, a coating layer having the composition shown in Table 1 below was formed on the elastic layer of the above-mentioned formulation A by the spray coating method.

The intermediate roller produced as described above was incorporated into the image forming apparatus shown in FIG. 1 and a continuous copy test was conducted to evaluate the durability of 200,000 plain paper sheets at the end of copying. However, in the initial stage, NG products were not evaluated further. In this example, dimethylsiloxane oil was used as a carrier liquid, and a liquid developer containing toner having an average particle diameter of 3 to 5 μm was used. The evaluation results are shown in Table 1.

[0043]

[Table 1]

As shown in Table 1, the PTFs of Examples 1 to 3 were obtained.
Each of the intermediate rollers according to the present invention obtained by coating the urethane resin containing E particles on the elastic layer has a low maximum static friction coefficient of 0.2 or less, which reduces friction with the developing roller and causes vibration. And was preventing abnormal noise. Also, plain paper 2
A good image without density unevenness and streak images was able to be obtained even after making a copy of 0,000 sheets. Further, when the surface of the intermediate roller was observed after the test, there were only 10 or less shallow streak-like scratches. On the other hand, in Comparative Example 2 in which the fluororesin was melted and coated on the elastic layer, the maximum static friction coefficient was as high as 1.15 because the coating layer did not contain the PTFE particles, and thus the photoreceptor and the intermediate roller were not affected. Due to the rubbing, the generation of vibration and abnormal noise was remarkable from the beginning, and the continuous copy test could not be performed. Also, in Comparative Example 3 in which the fluorine-based resin was melted and coated on the elastic layer, the maximum static friction coefficient was slightly high at 0.55 because the coating layer did not contain PTFE particles, and the photoreceptor and the intermediate roller It was confirmed from the beginning that vibration and abnormal noise were generated due to the rubbing against. It was not at a level where continuous copy test could not be performed, but it was 20,000
Vibration and abnormal noise became noticeable after about one sheet, making it impossible to continue the continuous copy test. Further, in Comparative Example 1 in which the conductive PFA tube was attached on the elastic layer, the maximum static friction coefficient was 0.22, which was slightly high. Therefore, after the continuous copying test of 20,000 sheets, the coating layer of the intermediate roller was It was damaged (streak-like scratches were generated in the circumferential direction), and streak images were generated. However, torque up, vibration, and abnormal noise did not occur.

[0045]

As described above, according to the present invention, the maximum static friction coefficient of the intermediate roller is lowered by forming the coating layer in which the PTFE particles are dispersed on the surface of the elastic layer of the intermediate coating member. It is possible to provide a liquid developing apparatus that includes an intermediate coating member that suppresses abrasion and has good surface smoothness. Further, the elastic layer of the intermediate coating member is made of rubber having polarity, and the material is selected so that its solubility index has a difference of 2 or more with the solubility index of the carrier liquid of the liquid developer. The liquid developing device may include an intermediate coating member that does not swell in the carrier liquid of the liquid developer. Furthermore, by providing the above-mentioned liquid developing device, it is possible to provide an image forming apparatus which gives a stable and good image.

[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 configurations of a developing roller and a sweep roller.

FIG. 3 is a diagram showing a configuration of a coating roller.

FIG. 4 is a view showing a shape of a concave portion on the surface of a coating roller.

FIG. 5 is a cross-sectional view showing a configuration of an intermediate roller.

FIG. 6 is a configuration diagram of an apparatus for measuring the maximum static friction coefficient (Euler method).

[Explanation of symbols]

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

Claims (9)

[Claims] 1. A developer accommodating tank for accommodating a liquid developer, a coating member for supporting and rotating a predetermined amount of liquid developer pumped 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 intermediate coating member is formed by forming an elastic layer on a cored bar and providing a coating layer on the surface thereof. 2. The liquid developing apparatus according to claim 1, wherein the intermediate coating 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 intermediate coating member is made of polar rubber, 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 intermediate coating member is equal to that of the carrier liquid of the developer. A liquid developing apparatus having a solubility index (SP value) and a difference of 2 or more. 5. The liquid developing apparatus according to claim 1, wherein the elastic layer of the intermediate coating member has a JIS-A hardness of 30 to 30.
A liquid developing device having a temperature of 70 degrees. 6. The liquid developing apparatus according to claim 1, wherein the intermediate coating member 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 intermediate coating member has a coating layer having a 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 intermediate coating member has a maximum static friction coefficient of 0.2 or less. 9. An image forming apparatus comprising the liquid developing device according to claim 1. Description: