JP2002202662A - Wet developing device and wet image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wet printer where a gravure roller 104 on the surface of which the very small recessed part is formed and a developing roller 106 are respectively moved in terms of surface in a reverse direction at their contact position and in which the irregular density and the roughness of a developed image caused by reflecting a very small projecting part corresponding to the very small recessed part on a developer thin layer on the developing roller are restrained. SOLUTION: The maximum contact pressure (p) between the gravure roller 104 and the developing roller 106 is set to >=0.12 [Mpa].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet developing apparatus for rotating a developing roller and a coating roller which rotate while contacting each other so as to move the surfaces in opposite directions at respective contact positions, and a wet image forming apparatus having the same. It is about.

[0002]

2. Description of the Related Art Conventionally, in a wet developing apparatus using a liquid developer in which a toner is dispersed in an insulating liquid carrier, a latent image formed on a latent image carrier such as a photoreceptor is processed by the following process. Is known. That is, first, after the liquid developer is pumped up by the application roller, the amount of the liquid developer on the application roller is regulated by a doctor blade as a regulating member that comes into contact with the liquid developer. Then
The regulated liquid developer is applied to a rotating developing roller while forming an application nip by contacting the applying roller to form a thin developer layer. Then, the thin developer layer on the developing roller is transported to a developing nip where the developing roller and the latent image carrier are in contact with each other, and the charged toner in the thin developer layer is transferred to the electrostatic latent on the latent image carrier. Electrophorese towards the image and attach.
This adhesion develops the electrostatic latent image into a toner image.

In such a process, 50 to 1000
When a high-viscosity liquid developer such as 0 [mPa · s] is used, the toner migration speed in the developing nip is lower than when a low-viscosity liquid developer is used.
In order to obtain a desired development density without lowering the development speed as much as possible despite such an electrophoretic speed,
It is necessary to form a very thin developer thin layer, such as a micron unit, on the developing roller so as to minimize the migration distance of the toner.

However, the viscosity of the liquid developer changes subtly depending on the temperature, and the amount of the liquid developer pumped up by the application roller also changes subtly according to the temperature change. As a result, a thin developer layer having a stable thickness could not be applied on the developing roller in the application nip, and it was easy to cause unevenness in density and unevenness in a developed image.

If the developing roller and the coating roller are rotated so as to move the surface in the forward direction at the coating nip, density unevenness and blurring may occur for the following two reasons. It was easy.

That is, the first reason is that cavitation occurs. Specifically, at the exit of the application nip where both rollers move in the forward direction, as shown in FIG. 5, the liquid developer 60 in the nip moves to the surface of the developing roller 106 and the surface of the application roller 113 , And each moves away from the separation point P1. Such a movement tends to cause a phenomenon called cavitation at the separation point P1. The cavitation is a phenomenon in which air bubbles such as air bubbles are generated at the separation point P1 due to the negative pressure, and when this occurs, the developer thin layer on the developing roller 106 has a patchy thickness unevenness (void).
Or stripe-shaped uneven thickness extending in the circumferential direction. As a result, uneven density and blurring occur in the developed image.

[0007] The second reason is that uneven thickness of the developer thin layer on the developing roller easily occurs due to uneven pressure of the coating nip. Specifically, the developing roller and the application roller are skewed in the axis line due to assembly errors and dimensional errors during manufacture, etc. Causes slight pressure unevenness. In the apparatus shown in FIG. 5, the position where the thickness of the developer thin layer on the developing roller 106 is regulated to be the thinnest is the point where the pressure becomes maximum in the coating nip. If there is no skew in both rollers and the respective rotation trajectories are perfect circles, the pressure in the application nip becomes highest at the intermediate point P2, so that the thickness is determined at this position. Since the rotation trajectories of both rollers are perfect circles, the pressure at the intermediate point P2 is constant and maximum irrespective of the rotation angle of both rollers, and since the skew does not occur in both rollers, the pressure at the intermediate point P2 is It becomes uniform in the axial direction. Therefore, the thickness of the developer thin layer is regulated to be constant in the roller axis direction at the intermediate point P2 regardless of the rotation angle of both rollers, and a developer thin layer without thickness unevenness is formed. However, for example, when the application roller 113 is eccentric, the pressure maximum point deviates from the intermediate point P2 due to the rotation angle of the application roller 113. There is no problem if it is only shifted, but since the maximum pressure also changes, uneven thickness occurs in the thin developer layer.

Therefore, a gravure roller (also referred to as an anilox roller) having a plurality of sculpture-shaped fine concave portions formed on the surface thereof is used as an application roller, and the surface of the gravure roller and the developing roller are moved in opposite directions by an application nip. A known wet developing device is known.

In such a wet developing device, after the liquid developer is accommodated in the minute concave portion on the surface of the gravure roller, excess liquid developer is scraped off with a doctor blade to remove the liquid developer regardless of its viscosity. It can measure accurately. Therefore, a predetermined amount of the liquid developer can be supplied to the coating nip regardless of the viscosity of the liquid developer.

Further, as shown in FIG. 6, at the outlet of the coating nip, the liquid developer
0 away from the separation point P1, while the gravure roller 1
Since the liquid developer on 04 is supplied close to the separation point P1, a negative pressure is hardly generated at the separation point P1. Thus, the occurrence of cavitation can be suppressed.

Further, in the apparatus shown in FIG. 6, the liquid developer 60 which tries to follow the developing roller 106 in the application nip and the liquid developer 60 (supply developer) which tries to follow the application roller 113 are formed. To move in the opposite direction,
A new liquid developer is supplied to the former liquid developer that has passed the pressure maximum point. When the liquid developer is supplied in this way, even if an error occurs in the regulation thickness due to the fluctuation of the maximum pressure,
The error is somewhat absorbed by the supply of liquid developer.
For this reason, thickness unevenness of the developer thin layer due to unevenness in pressure of the coating nip can be suppressed.

[0012]

However, even in the apparatus shown in FIG. 6, the shape of the minute concave portion (not shown) of the gravure roller 104 appears as a minute convex portion on the developer thin layer on the developing roller 106. This sometimes caused uneven thickness of the developer thin layer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has a wet developing apparatus and a wet developing apparatus in which a coating roller, such as a gravure roller, in which minute concave portions are formed, and a developing roller are surface-moved in opposite directions at contact positions. In a wet image forming apparatus having the same, a wet developing device capable of suppressing unevenness in density and unevenness of a developed image due to a minute convex portion corresponding to the minute concave portion being reflected on a thin developer layer on a developing roller. And a wet image forming apparatus.

[0014]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the minute projections formed on the thin developer layer on the developing roller 106, and found that the maximum contact between the developing roller 106 and the gravure roller 104 was obtained. It has been found that when the pressure p is set too low, this easily occurs. For the maximum contact pressure p, Ea / Ea /
It can be obtained by calculating 4R. In this equation, each symbol is as follows. 1 / E = (1-ν 1 2) / E 1 + (1-ν 2 2) / E 2 1 / R = 1 / r 1 + 1 / r 2 E 1: longitudinal coefficient of the developing roller 106 [Mpa] ν ₁ : Poisson's ratio of the developing roller 106 r ₁ : Radius [mm] of the developing roller 106 E ₂ : Longitudinal coefficient [Mpa] of the gravure roller 104 (coating roller) ν ₂ : Poisson's ratio of the gravure roller 104 r ₂ : gravure Roller 104 radius [mm] a: coating nip width (contact length of both rollers in the circumferential direction) [mm]

Therefore, the present inventors have examined the relationship between the maximum contact pressure p and the state of occurrence of the minute projections. Specifically, as shown in the following Table 1, the developer thin layer formed on the developing roller 106 is changed while changing the maximum contact pressure p by changing the developing roller 106 to one having a different hardness and diameter. A test for measuring the thickness of the sample was conducted.

[Table 1]

The basic configuration of the developing roller 106 used in the test is as follows. Base material: conductive urethane rubber Surface coating material: conductive PFA tube

The gravure roller 104 having the following conditions was used. Material: A plurality of fine concave portions are hardened by chromium plating on a base material made of low carbon steel (S25C). Longitudinal coefficient E ₂ : 20,000 [MPa] Poisson's ratio ν ₂ : 0.3 Radius r ₂ : 10 [mm] ]

The test was conducted under the following conditions. Test location: Laboratory with air conditioning Temperature: 24 [° C] Humidity: 50-60 [%] Liquid developer: Disperse toner at a concentration of 15 [wt%] in silicone oil with a viscosity of 100 [mPa · s] To a total viscosity of 1000 [mPa · s] (B-type viscometer 6 rpm
m) Developing roller linear speed: 300 [mm / sec] Gravure roller linear speed: 400 [mm / sec] Surface movement direction of both rollers in coating nip: counter direction Thickness measurement of developer thin layer: gravimetric method ( The liquid developer on the developing roller is wiped off using a mask with a fixed area, and the thickness per unit area is calculated from the change in weight.)

In this test, the results shown in the graph of FIG. 1 were obtained. When the maximum contact pressure p was set to less than 0.12 [Mpa], the thickness unevenness of the developer thin layer caused by the minute projections was determined. Suddenly began to occur.

Also, the present inventors set the linear rotation speed of the gravure roller 104 too slow with respect to the rotation linear speed of the developing roller 106, so that the minute convexities on the developer thin layer on the developing roller 106 can be reduced. Have been found to easily occur. Specifically, the rotational linear velocity V ₂ of the gravure roller 104
The relationship between the above and the state of occurrence of the minute projections was tested. Then, the results shown in the graph of FIG. 2 is obtained and set slower than the rotation linear velocity V ₁ of the developing roller 106 rotating linear velocity V ₂ of the gravure roller 104, the developer thin due to the fine convex portions It was found that the thickness unevenness of the layer began to be rapidly generated. Further, as shown in FIG.
A rotational linear velocity _{V 2} of 04 of the developing roller 106 rotating linear velocity _{V 1}
It was also found that when the setting was faster than twice, the application amount of the liquid developer started to fluctuate rapidly, and the fluctuation error reached 10% or more.

Therefore, the invention of claim 1 carries a liquid developer containing a toner and a liquid carrier, and attaches the liquid developer to a latent image formed on a latent image carrier of a wet image forming apparatus to form the latent image. A developing roller that develops an image, an application roller that applies the liquid developer carried on the surface on which the plurality of minute recesses are formed to the development roller, and an amount of the liquid developer that is in contact with the application roller before application. And a regulating member for regulating the rotation of the rollers so that the surfaces of the rollers are moved in opposite directions at the contact positions of the rollers to which the liquid developer is applied. The value of a certain p is 0.1
It is characterized by being set to 2 [Mpa] or more. However, "1 / E = (1-ν 1 2) / E 1 + (1-ν
₂ ² ) / E ₂ ”and“ 1 / R = 1 / r ₁ + 1 / r ₂ ”, and E ₁ , ν ₁ , r ₁ , E ₂ , ν ₂ , r ₂ , and a are the respective values of the developing roller. Longitudinal modulus of elasticity [Mpa], Poisson's ratio,
Radius [mm], longitudinal elastic coefficient E ₂ [Mp
a], Poisson's ratio, and r ₂ [mm] indicate the contact length [mm] in the rotation direction of both rollers.

In this wet developing apparatus, since the maximum contact pressure p of both rollers is set to 3.0 [Mpa] or more, as shown in the graph of FIG. This can suppress the minute projections of the developer thin layer caused by the above. Therefore, it is possible to suppress density unevenness and blurring of the developed image due to the minute projections.

According to a second aspect of the present invention, a liquid developer containing a toner and a liquid carrier is carried, and the liquid developer is attached to a latent image formed on a latent image carrier of a wet image forming apparatus, and the latent image is formed. A developing roller for developing, an application roller for applying the liquid developer carried on the surface having the plurality of minute recesses formed thereon to the developing roller, and abutting on the application roller to regulate the amount of the liquid developer before application. and a regulating member, the wet developing device for rotating the two rollers so that the liquid developer to move the mutual surface in opposite directions at the contact position of both rollers applied, the coating roller rotation linear velocity V ₂ it is characterized in that set faster than the rotational linear velocity V ₁ of the developing roller.

[0024] In this wet developing apparatus, since the set faster than the rotational linear velocity V ₁ of the rotation linear velocity V ₂ of the application roller the developing roller, as shown in the graph of FIG. 2, the minute of the application roller It is possible to suppress the minute projections of the developer thin layer generated by the projection of the depressions. Therefore, it is possible to suppress density unevenness and blurring of the developed image due to the minute projections.

The invention of claim 3 is the wet developing apparatus according to claim 2, 2 the rotational linear velocity V ₂ of the rotational linear velocity V ₁
It is characterized by being set to twice or less.

In this wet image forming apparatus, as shown in the graph of FIG. 2, a coating roller (gravure roller)
It is possible to suppress variations in coating amount of the liquid developer due to the set too fast rotational linear velocity V _2. Therefore,
Density unevenness and blurring of a developed image due to a variation in the amount of coating can be suppressed.

According to a fourth aspect of the present invention, in the wet developing device according to the first, second or third aspect, a minute groove extending continuously from one end of the coating roller to the other end is provided as the minute concave portion. It is assumed that.

The coating roller of this wet developing device has minute grooves extending in the axial direction of the roller as minute concave portions. For the following reason, a plurality of minute microcells arranged side by side in the axial direction of the roller are provided. It is possible to suppress unevenness in the thickness of the thin developer layer on the developing roller and to improve the coating efficiency as compared with a developer having a concave portion. That is, while only a small amount of the liquid developer adhering to the roller surface exists between the concave portions (between the minute concave portions) of the application roller, a larger amount of the liquid developer is present in the minute concave portions. Is stored, there is a difference in the amount of liquid developer applied between the concave portions and the minute concave portions. Between the recesses, there are a roller formed in the roller circumferential direction and a roller formed in the roller axis direction. Of these, even if there is a difference in the amount of application between the concave portion formed in the roller circumferential direction and the minute concave portion, when both rollers move in the opposite direction to each other at the application nip, the developer due to the concave portion is applied to the developing roller. The liquid developer is further applied to the application area by the minute concave portion. For this reason, even if there is a space between the concave portions formed in the roller circumferential direction, uneven thickness of the developer thin layer in the roller circumferential direction hardly occurs. However, when there is a gap between the recesses formed in the roller axis direction, even if both rollers move in the opposite direction at the application nip, the liquid developer is further reduced by the minute recesses with respect to the developer application area between the recesses. Is not applied. For this reason, thickness unevenness of the developer thin layer in the roller axis direction is likely to occur. The coating roller of the present wet developing device has minute grooves that are continuous in the axial direction of the roller as minute concaves, and do not form gaps between the concaves in the roller axial direction. Therefore, the thickness of the developer thin layer can be made more uniform than that in which the space between the concave portions is formed in the roller axis direction by the cell-shaped minute concave portions. In addition, the side wall of the minute concave portion inhibits the liquid developer from coming out of the concave portion by contact with the liquid developer, and causes the liquid developer to adhere to the surface thereof. For this reason, no partition wall is formed in the roller axis direction, and in the minute groove that allows the internal liquid developer to smoothly transfer to the developing roller surface, the partition wall (between the concave portions) is formed in the internal liquid roller axis direction. The application efficiency of the liquid developer can be improved as compared with the case where a large number of cell-shaped minute concave portions are formed.

According to a fifth aspect of the present invention, in the wet developing apparatus of the first, second, third or fourth aspect, the minute concave portion is formed on a surface of a roller base material having a Vickers hardness of 200 [degrees] or less as the application roller. Thereafter, a material subjected to a surface hardening treatment is used.

In this wet developing apparatus, a plurality of minute concave portions are formed in a roller base material having a Vickers hardness of 200 [degrees] or less. In the formation of such a minute concave portion, 200
Even a material having a high hardness exceeding [degree] can form a minute concave portion, and can use a simple rolling method without using a laborious and costly cutting method. Further, even if a relatively low hardness roller base material such as 200 [degrees] or less is used, the hardness of the application roller is reduced to a level suitable for actual use by performing a surface hardening treatment on the roller base material after forming the minute concave portions. It is possible to increase. Therefore, even if the hardness of the application roller is increased to a level suitable for actual use, a simple rolling method can be used as a method for forming the minute concave portions of the application roller.

According to a sixth aspect of the present invention, in the wet developing device of the fifth aspect, the regulating member has a hardness lower than the surface hardness of the coating roller.

In this wet type developing device, it is possible to suppress the wear of the application roller due to the rubbing with the regulating member, and to suppress the temporal change in the application amount of the liquid developer due to the wear. Further, in general, the application roller is more expensive than the regulating member and requires more labor for replacement. Therefore, by suppressing the wear of the application roller, the running cost can be reduced and the maintenance labor can be reduced.

[0033] The invention of claim 7 is based on claims 1, 2, 3,
4, 5 or 6, wherein the supporting member of the coating roller and the supporting member of the regulating member are respectively insulated from the ground.

In this wet developing apparatus, even if the coating roller and the regulating member are made of a conductive material, the developing bias applied to the developing roller leaks from the supporting member of the coating roller and the regulating member to the ground. There will be no such a situation as being caused to occur. Therefore, it is possible to avoid a voltage drop of the developing bias due to such a leak.

According to an eighth aspect of the present invention, in the wet developing device of the seventh aspect, a conductive regulating blade is used as the regulating member, and the developing roller and the applying roller each have a conductive surface. It is characterized in that a developing bias is applied from the regulating blade to the surface of the developing roller via the coating roller.

In this wet developing apparatus, for the reason described below, compared with a case where a developing roller is provided with a cored bar and a developing bias is applied thereto, conduction failure of the developing bias is suppressed, and A desired elasticity can be easily exerted on the roller. That is, when a developing bias is applied to the cored bar to the developing roller, generally, a needle electrode connected to a power source is brought into contact with a metal roller shaft provided on the cored bar. However, in such a configuration, the contact area between the tip of the needle electrode and the metal roller shaft is relatively small. Easily occur. On the other hand, in the present wet developing device, the regulating blade plays the role of a needle electrode, and the contact area between the regulating blade and the coating roller is much larger than the contact area between the needle electrode and the metal roller shaft. Become larger. For this reason, even if the above-described insulating film is formed to some extent, the developing bias can be guided to the surface of the developing roller, and conduction failure of the developing bias can be suppressed. In a general wet developing device, the width (length in the circumferential direction) of a developing nip formed by contact between a developing roller and a latent image carrier such as a photoreceptor is secured to a certain extent to obtain a desired developing performance. The roller portion of the developing roller is made of an elastic material, and a conductive material such as carbon is added to the elastic material to realize conduction of the developing bias from the metal core to the roller surface. However, since the addition of the conductive material increases the hardness of the elastic material, when the electric resistance of the roller portion is reduced to a target value, the desired elasticity may not be exerted on the roller portion in some cases. . On the other hand, in the present wet developing device, a developing bias is applied to the developing roller not from the core metal but from the roller surface. In such a configuration, if the surface of the elastic material used for the roller portion is coated with a thin conductive film, the developing bias can be conducted to the surface of the developing roller without adding a conductive material to the elastic material. Therefore, the situation where the elastic material is hardened by the addition of the conductive material is eliminated, and the desired elasticity can be easily exerted on the developing roller.

According to a ninth aspect of the present invention, there is provided a wet image forming apparatus comprising: a latent image carrier for carrying a latent image; and a wet developing device for developing the latent image using a liquid developer containing a toner and a liquid carrier. In the apparatus, the wet developing device according to claim 1, 2, 3, 4, 5, 6, 7, or 8 is used.

In this wet image forming apparatus, the minute projections corresponding to the minute recesses of the application roller are imaged on the developer thin layer on the development roller by the same operation as the wet development apparatus of claim 1 or 2. It is possible to suppress unevenness and blurring of the density of the developed image due to this.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic wet printer (hereinafter simply referred to as a printer) which is a wet image forming apparatus will be described below.

First, the basic configuration of the printer will be described. FIG. 3 is a schematic configuration diagram of a main part of the printer according to the present embodiment. In the figure, the printer includes a charger 2 around a photosensitive drum 1 as a latent image carrier.
0, an exposure device (not shown) for irradiating the photosensitive drum 1 with the exposure L, a wet developing device 100, a transfer device including an intermediate transfer belt 31, a transfer roller 32, and the like, a static elimination lamp 40, a drum cleaning device 50, and the like. I have.

The surface of the photosensitive drum 1 is formed of amorphous silicon (a-Si), and is driven to rotate in a direction indicated by an arrow in FIG.

The charger 20 uniformly charges the surface of the rotating photosensitive drum 1 in the dark by corona discharge. In addition, as the charger 20, in addition to the one that realizes the charging by corona discharge, the photosensitive drum 1 is also used.
A type in which a predetermined charging bias is applied to a charging member such as a charging roller brought into contact with a member may be used.

The exposure apparatus has a scanning optical system, and the photosensitive drum 1 uniformly charged by the charger 20.
Is exposed by LED light or laser light based on image information to carry an electrostatic latent image.

The wet developing device (hereinafter simply referred to as a developing device) 100 causes a charged toner to adhere to the electrostatic latent image and develops the electrostatic latent image. As a result, a toner image is formed on the photosensitive drum 1.

The transfer device includes, in addition to the intermediate transfer belt 31 shown in FIG. 3, a transfer roller 32 that stretches the belt, a plurality of stretch rollers 33, and a transfer roller 32 having a polarity opposite to the charging polarity of the toner. A power source (not shown) for applying a transfer bias is provided, and during printing, the intermediate transfer belt 31 is moved endlessly in the direction of the arrow in the figure. Further, the intermediate transfer belt 41 is pressed by the transfer roller 32 toward the photosensitive drum 1 to perform a transfer nip. In this transfer nip,
A transfer electric field is formed by a potential difference between the transfer roller 32 to which the transfer bias is applied and the surface of the photosensitive drum 1. The toner image that has entered the transfer nip with the rotation of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 31 under the action of the transfer electric field and the nip pressure. As the transfer device, in addition to the transfer device using such a transfer roller, a transfer device that transfers a toner image by corona discharge, adhesion, heat, or the like can be used.

The toner image primary-transferred in this manner is secondarily transferred to a transfer sheet in a region (not shown), and then fixed by a fixing device using a fixing method such as heat and pressure fixing, solvent fixing, or UV fixing. It is established. The transfer paper on which the toner image has been fixed is discharged from the fixing device to the outside of the apparatus via a paper discharge path.

The charge removing lamp 40 removes charges remaining on the surface of the photosensitive drum 1 that has passed through the transfer nip.

The drum cleaning device 50 removes the liquid developer remaining on the surface of the photosensitive drum 1 from which the charge has been removed by the charge removing lamp 40 to remove the developer from the cleaning blade 51.
To remove. By this removal, the surface of the photosensitive drum 1 is initialized, and the next image formation can be realized.

Next, the structure of the developing device 100 will be described. The developing device 100 includes a developing unit 109 and a sweep unit 112. This developing unit 109
Is a tank unit 101, stirring screws 102, 103,
Gravure roller 104, doctor blade 105, developing roller 106, cleaning blade 107, return unit 1
08 and the like. Further, the sweep unit 112 includes:
A sweep roller 110, a cleaning blade 111 and the like are provided.

The liquid developer 60 containing the toner and the liquid carrier is stored in the tank 101.
The liquid developer 60 has a high viscosity and a high concentration, not a low viscosity and a low concentration widely used in a general wet developing apparatus. The low-viscosity, low-concentration liquid developer is, for example, an iso-form which is widely marketed.
par (trade name: manufactured by Exxon) is a liquid developer having a viscosity of about 1 [mPa · s] containing a toner of about 1 [wt%] in an insulating liquid carrier.
The high-viscosity, high-concentration liquid developer is, for example, 5 to 40 wt% in an insulating liquid carrier such as silicone oil, normal paraffin, IsoparM (trade name: manufactured by Exxon), vegetable oil, or mineral oil. ] Is a liquid developer having a viscosity of about 50 to 10000 [mPa · s] containing a toner of about a concentration. The volatility or non-volatility of such a high-viscosity, high-concentration liquid developer 60 used in the developing device 100 is adjusted according to the developing performance of the developing device 100 and the image forming performance of the printer. Also,
The particle size of the toner in the liquid developer 60 may be from submicron to 6 in accordance with the developing performance and image forming performance.
It is adjusted in a range up to about [μm].

The stirring screws 102 and 103 are disposed in parallel with each other so as to be immersed in the liquid developer 60 in the tank 101, and are rotated in opposite directions by driving means (not shown) as shown by arrows in the figure. Driven. When the developing device 100 starts a developing operation, the screws 102 and 103 rotate in the opposite directions as described above, and the liquid developer 60 in the tank 101 is stirred. By this stirring, the toner concentration and viscosity of the liquid developer 60 are made uniform. When the screws 102 and 103 rotate in opposite directions to each other, the liquid surface of the liquid developer 60 rises between the two as shown in the figure, and adheres to the gravure roller 104 disposed above the liquid developer 60.

The above gravure roller 1 as a coating roller
The liquid developer 60 is pumped up by the liquid developer 60 thus attached while being rotationally driven in a direction indicated by an arrow in the figure by a driving unit (not shown). On the peripheral surface of the gravure roller 104, a sculpture 104a as shown in FIG. 4A is formed, thereby forming a pyramid as shown in FIG. Lattice type, Fig. 4 (d)
A plurality of concave portions 104b are formed in a shape such as an inclined type shown in FIG. Part of the liquid developer 60 pumped up by the gravure roller 104 is accommodated in these recesses 104b.

The doctor blade 105 as a regulating blade is made of metal such as stainless steel, and scrapes the liquid developer 60 on the gravure roller 104 by contacting the rotating gravure roller 104. By this scraping, the amount of the liquid developer 60 on the gravure roller 104 is accurately measured to a value corresponding to the capacity of the plurality of recesses 104b.

As shown in FIG. 3, the developing roller 106 comes into contact with the surface of the gravure roller 104 that has passed through the contact portion with the doctor blade 105, and the surface of the developing roller 106 is directed in the opposite direction to the gravure roller 104 at the contact portion. Rotate to move to.

The developing roller 106 and the gravure roller 104
In the application nip, which is the contact position with the roller, the two rollers come into contact with each other while moving in the counter direction, and the liquid developer 60 on the gravure roller 104 is accurately measured regardless of the viscosity. A thin developer layer having a uniform thickness can be formed on the roller 106.

Further, while the liquid developer transferred onto the developing roller 106 is kept away from the outlet of the coating nip, the liquid developer on the gravure roller 104 is supplied close to the outlet of the coating nip. Cavitation can be suppressed by making it difficult to generate a negative pressure.

Further, at the exit side of the coating nip, the developing roller 1
While the supply of the liquid developer to 06 is started, the liquid developer transferred onto the developing roller 106 moves in a direction opposite to the supply direction. In such a configuration, if the maximum pressure in the application nip is equal to or more than a certain value, the thickness of the thin developer layer on the developing roller 106 does not depend on the value of the maximum pressure. For this reason, it is also possible to suppress thickness unevenness of the developer thin layer due to pressure unevenness in the coating nip.

As a result, a thin developer layer of the liquid developer 60 having a uniform thickness is formed on the surface of the developing roller 106 by such application.

The developing roller 106 is provided with a conductive elastic layer made of conductive urethane rubber or the like on its peripheral surface.
The developing nip is formed in contact with the photosensitive drum 1 while rotating at a constant speed. A developing electric field is formed in the developing nip by a potential difference between the developing roller 106 to which a developing bias having the same polarity as the toner charging polarity is applied from a power supply (not shown) and the photosensitive drum 1. Specifically, in the developing nip, the developing roller 106, the background portion of the photosensitive drum 1 and the electrostatic latent image each have a potential of the same polarity as the toner, and the value is the background portion, the developing roller 106, and the electrostatic latent image. The order is lower. For this reason, an electric field is formed between the background portion and the developing roller 106 so as to electrostatically move the toner toward the developing roller 106 having a lower potential. Further, between the developing roller 106 and the electrostatic latent image,
An electric field is created that moves the toner toward the lower potential electrostatic latent image. In the developing nip where such a developing electric field is formed, the toner in the developer thin layer electrophoreses and concentrates between the developing roller 106 and the background portion toward the surface of the developing roller 106, Electrophoresis is performed between the developing roller 106 and the electrostatic latent image toward the electrostatic latent image and adheres. Due to this adhesion, the electrostatic latent image is developed into a toner image.

The cleaning blade 107 is made of a member such as metal or rubber, and comes into contact with the surface of the developing roller 106 after passing through the developing nip, thereby scraping and removing the residual developer from the surface. By this removal, the surface of the developing roller 106 is initialized. The removed residual developer returns to the tank unit 101 via the return unit 108.

The developing section 109 is configured to develop the electrostatic latent image on the photosensitive drum 1 in this manner.

In the development nip, it is necessary to secure a development time (time required for the nip to pass through the thin developer layer) so that the toner can be sufficiently electrophoresed. The developing time depends on the width of the developing nip and the process linear speed which is the peripheral speed of the photosensitive drum 1 and the developing roller 106.
In the printer according to this embodiment, the development time is secured by setting the width of the development nip to a value obtained by multiplying the process linear velocity by the development time constant. This development time constant is the time required until the development amount is saturated,
This is a value obtained by dividing the process linear velocity by the minimum development nip width required for saturation of the development amount. For example, if the process linear velocity is 300
[Mm / sec] and the development time constant is 10 [msec]
Then, the width of the development nip is 3 [mm]. In addition,
The width of the removal nip described later is set similarly.

As described above, the developing roller 1 of the developing nip
06 and the background portion, the toner in the developer thin layer is electrophoresed toward the surface of the developing roller 106 and aggregates, and thus does not theoretically adhere to the background portion. However, there is a case where a toner having a smaller amount of charge than usual is electrophoresed later than other toners, adheres to a background portion, and causes a phenomenon of so-called fog (also referred to as background fouling).

The sweep section 112 removes the fogging toner that has caused such fogging from the photosensitive drum 1. Specifically, the sweep roller 110 of the sweep section 112 has a conductive elastic layer made of conductive urethane rubber or the like on its peripheral surface, and contacts the photosensitive drum 1 while rotating at a constant speed. To form a removal nip. In the removal nip, a sweep electric field is formed by a potential difference between the sweep roller 110 to which a removal bias having the same polarity as the toner charging polarity is applied from a power supply (not shown) and the photosensitive drum 1. In particular,
In this removal nip, the sweep roller 110, the background portion, and the electrostatic latent image each have a potential of the same polarity as the toner, and the value decreases in the order of the background portion, the sweep roller 110, and the electrostatic latent image. For this reason, the fog toner that has not been collected on the surface of the developing roller 106 at the developing nip is removed from the photosensitive drum 1 by electrophoresis between the background portion and the sweep roller 110 toward the sweep roller 110. You.

The cleaning blade 111 is formed of a member such as metal or rubber, and is brought into contact with the surface of the sweep roller 110 after passing through the removal nip,
The residual developer is scraped off from this surface. By this removal, the surface of the sweep roller 110 is initialized.

The surface of each of the developing roller 106 and the sweep roller 110 is coated with a conductive coating or covered with a conductive tube to have a smoothness of 3 μm or less in Rz. It is desirable to be configured so as to exert it. This is because, in order to carry a thin developer layer having a uniform thickness of about 3 to 10 [μm] on the developing roller 106 and the sweep roller 110, it is necessary to exhibit such smoothness.

The material of the conductive elastic layer of the developing roller 106 and the sweep roller 110 is JIS-A
It is desirable to use one having a hardness of 50 [degrees] or less.
While the surface of the photosensitive drum 1 is formed of a-Si having high hardness, in order to secure the developing nip and the removing nip having a desired width, the conductive elastic layer is formed with a hardness of 50 [degree] or less. It is necessary to freely deform. The material of the conductive elastic layer is not limited to the above-described conductive urethane rubber, but may be any material that exhibits conductivity and is not likely to be swollen or dissolved by the liquid carrier.

Next, the characteristic configuration of the printer will be described. In this printer, the developing roller 106 and the gravure roller 104 are configured as follows. The longitudinal elastic modulus E ₁ of the developing roller 106 is 1.7 [Mp
a] Poisson's ratio ν _{1 of} developing roller 106: 0.5 Radius r ₁ of developing roller 106: 12 [mm] Longitudinal elastic coefficient E ₂ of gravure roller 104: 20000
[Mpa] Poisson's ratio ν _{2 of} gravure roller 104: 0.3 Radius r ₂ of gravure roller 104: 10 [mm] Coating nip width (length of coating nip in the circumferential direction)
a: 1.7 [mm]

Each of these parameters is defined as the maximum contact pressure p
= Ea / 4R, the maximum contact pressure p of both rollers is 0.18 [MPa], and 0.12 ≦
conditions are provided that p (1 / E = (1 -ν 1 2) /
_{E 1 + (1-ν 2} 2) / E 2, 1 / R = 1 / r 1 + 1 /
r ₂ ). In such a configuration, as shown in the graph of FIG. 1, the concave contact pattern of the gravure roller 104 is used as a convex pattern because the maximum contact pressure p is set too low. It is possible to suppress such a situation that the image is copied to the camera. Therefore, it is possible to suppress density unevenness and looseness of the developed image due to the minute projections.

In the case of a configuration in which the surfaces of both rollers are rubbed while being moved in the opposite direction by the coating nip as in this printer, if the maximum contact pressure p is set too large, the load of the drive motor for driving the rollers is increased. Is excessively increased to generate chatter called banding, and the thickness of the thin developer layer may be rather uneven. Therefore, it is desirable to set the maximum contact pressure p to an upper limit such that the load on the drive motor is lower than its rated torque. In this printer,
When the maximum contact pressure p is set to 0.8 [Mpa], the load applied to the drive motor is 15691 [N · m] (16 kg).
f · cm) has been confirmed by experiments. If the load becomes larger than this, the rated torque of the drive motor will be exceeded. Therefore, in this printer, it is desirable to set the maximum contact pressure p to 0.8 [Mpa] or less.

Even if the load applied to the drive motor is set to the maximum contact pressure p so as to be equal to or less than the rated torque, the elastic surface of the developing roller 106 may be damaged or permanently deformed. In such a case, it is desirable to further reduce the maximum contact pressure p to a level that does not cause permanent deformation or damage to the elastic surface.

[0072] In this printer, the rotational linear velocity _{V 1} of the developing roller 106, the a rotational linear velocity _{V 2} of the gravure roller 104 is set so as to include a condition that _"V 1 <V". In such a configuration, as shown in the graph of FIG. 2, the developing roller recess pattern of the gravure roller 104 due to set too slow rotational linear velocity V ₂ relative to the rotational linear velocity V ₁ as protrusions pattern It is possible to suppress a situation in which the developer 106 is transferred to the thin layer of the developer. In this way, density unevenness and blurring of the developed image can be suppressed.

Further, in this printer, “V ₂ ≦ V ₁ ×
2 ”. In such a configuration, as shown in the graph of FIG. 2, situation due to the set too fast rotational linear velocity V ₂ greatly fluctuated the coating amount of the liquid developer with respect to the rotational linear velocity V ₁ Can also be suppressed. And by this,
Density unevenness and blurring of a developed image can be suppressed.

According to experiments by the present inventors, “V ₁ <V ₂ ” and “V ₁ <V ₂ ” depend on the properties of the liquid developer used.
_Even if the condition of ₂ ≦ V ₁ × 2 ”is satisfied, the above-mentioned minute projections may be formed, and“ V ₁ × 1.2 <
Within the range of “V ₂ ≦ V ₁ × 1.5”, the formation of minute projections could be suppressed regardless of the properties of the liquid developer. Therefore, desirably preferable to set the rotation linear velocity V ₁ and V ₂ within this range. In this printer, V1 = 300 [mm / s]
ec] and V2 = 400 [mm / sec],
Such a setting is realized.

As shown in FIGS. 4B to 4C,
The concave portion 104b is provided with a shape processed into a pyramid type, a lattice type, or an inclined type. However, pyramid-shaped (FIG. 4B) or lattice-shaped (FIG. 4C) concave portions 104
In FIG. 4B, each recess 104b is partitioned in the roller axis direction, whereas in the inclined type (FIG. 4D), no partition wall is formed in the roller axis direction. For this reason, in the inclined type, contact of the liquid developer with the partition wall formed in the roller axis direction prevents the liquid developer from being removed from the concave portion 104b, or the liquid developer adheres to the partition wall. And the liquid developer can be smoothly transferred onto the developing roller 106. Further, there is no occurrence of thickness unevenness in the roller axis direction in the thin developer layer on the developing roller 106 due to the difference in the application amount between the partition wall portion and the concave portion 104b. Therefore, in the inclined type, the thickness unevenness of the liquid developer can be suppressed and the coating efficiency can be improved as compared with the pyramid type or the lattice type.

Further, the inclined concave portion 104b is formed as shown in FIG.
The liquid developer in the concave portion 104b moves not only in the rotational direction but also in the axial direction of the roller with the rotation of the gravure roller 104b because of the spiral micro groove structure as shown in FIG. For this reason, the coating thickness unevenness in the roller axis direction can be suppressed. Therefore, the inclined concave portion 104b
Is provided, the unevenness of the coating thickness in the axial direction of the roller can also be suppressed, so that the unevenness in density and unevenness of the developed image can be suppressed.

Further, in the inclined concave portion, it is possible to suppress density unevenness and blurring of the developed image for the following reason. That is, the capacity of the concave portion 104b can be adjusted by the depth of the concave portion 104b. However, if the depth is too large, uneven thickness tends to be caused in the developer thin layer. Further, regarding the capacity of the concave portion 104b,
Although it can be adjusted by the opening area of the developing roller 04b, even if the width of the concave portion in the roller circumferential direction is too long to secure a large opening area, the thickness of the developer thin layer on the developing roller 106 may be uneven. I will. If the width of the concave portion is too long, the liquid developer is not properly pumped up by the concave portion 104b, so that unevenness in coating thickness is likely to occur.
As a result, it is necessary to set the depth of the recess 104b and the width of the recess in the roller circumferential direction within a predetermined range. With such a setting, the inclination type developer accommodating efficiency in which no partition wall is formed in the roller axis direction is the best.
In order to obtain the same developer accommodating efficiency as the inclined type in the pyramid type or the lattice type, it is necessary to make the concave portion 104b deeper or to reduce the distance between the concave portions in the roller circumferential direction, as compared with the inclined type. Only the developer thin layer tends to have uneven thickness. Therefore, in the case of the inclined type, it is possible to suppress unevenness in density and blur of the developed image by improving the developer accommodating efficiency as compared with those of other shapes.

Further, if the width of the concave portion is increased in order to increase the developer accommodating efficiency, the distance between the concave portions in the roller circumferential direction is reduced, so that the contact pressure per unit area between the doctor blade 105 and the gravure roller 104 is increased. There is a possibility that a situation where both wears are accelerated may be caused. Therefore, in the case of the inclined type, the developer accommodating efficiency is improved as compared with those of other shapes, so that it is possible to increase the distance between the concave portions and suppress the wear of both.

According to the experiments by the present inventors, the transfer rate of the liquid developer was improved by about 30 to 50% in the lattice type as compared with the pyramid type. This is presumably because the grid type has better developer accommodation efficiency than the pyramid type because the bottom is not sharp.

The gravure roller 104 is more expensive than the doctor blade 105, and requires much time and labor for replacement. Therefore, it is desirable to make the hardness of the gravure roller 104 higher than the hardness of the doctor blade 105 so that the doctor blade 105 is mainly worn.

Further, regarding the gravure roller 104,
After forming a plurality of recesses 104b in a roller base material having a Vickers hardness of 200 [degrees] or less, it is desirable to use a roller subjected to a surface hardening treatment. Vickers hardness 200 [degree]
In the following materials, as the method for forming the concave portion 104b, a rolling process in which a member having a convex portion pattern corresponding to the concave portion pattern is pressed into contact can be used. By using such a rolling method, it is possible to reduce the labor and work cost as compared with a cutting method using a laser or the like. Even if a roller base material having a relatively low hardness of Vickers hardness of 200 [degrees] or less is used,
By performing the surface hardening treatment after the formation of the gravure roller 104b, the hardness of the gravure roller 104 can be increased to a level suitable for actual use and superior to the doctor blade 105.

Examples of the combination of the gravure roller 104 and the doctor blade 105 include those shown in Table 2 below.

[Table 2]

As a roller base material that achieves a Vickers hardness of 200 [degrees] or less, in addition to S25C shown in Table 2,
SUS XM7, aluminum alloy and the like.

The developing roller 106 includes a lower layer made of a metal core, an intermediate layer made of an elastic material such as rubber, and a conductive surface layer made of a conductive tube or the like. As the gravure roller 104 and the doctor blade 105, those exhibiting conductivity at least on the surface are used.

A developing bias power source (not shown) is connected to the doctor blade 105.
The voltage is applied to the surface of the developing roller 106 via the doctor blade 105 and the gravure roller 104. In such a configuration, the doctor blade 105 and the gravure roller 10 are larger than the contact area between the needle electrode and the roller shaft when the developing bias is applied by bringing the needle electrode into contact with the roller shaft of the developing roller 106.
4 is much larger in contact area. For this reason, poor conduction of the developing bias due to the formation of the insulating film at the contact portion can be suppressed. In addition, even without adding a conductive material to an elastic material such as rubber to cause the middle layer to exhibit conductivity, a developing bias can be introduced to the surface of the developing roller 106. There is no case where the elastic material is hardened to make it difficult to adjust the elasticity. Therefore, the elasticity of the middle layer can be easily adjusted depending on the type of the elastic material, and the desired elasticity can be easily exerted on the developing roller 106.

However, in such a configuration, the gravure roller 1
It is necessary to electrically float the support member 04 and the support member of the doctor blade 105 so as to prevent leakage of the developing bias from these support members to the ground. If such a leak occurs, the value of the developing bias at the developing nip becomes unstable, causing unevenness in the developing density.

Although the printer which performs the secondary transfer of the toner image to the transfer paper via the intermediate transfer belt 31 has been described above, the toner image is directly transferred from the latent image carrier such as the photosensitive drum 1 to the transfer body such as the transfer paper. The present invention is also applicable to a wet image forming apparatus in which transfer is performed.

[0088]

According to the first, second, third, fourth, fifth, sixth, seventh or eighth aspect of the present invention, the minute convex portions corresponding to the minute concave portions of the application roller are reflected on the developer thin layer on the developing roller. Thus, there is an excellent effect that density unevenness and blurring of a developed image due to the above can be suppressed.

In particular, according to the first aspect of the present invention, there is an excellent effect that it is possible to suppress the minute projections of the developer thin layer caused by the inappropriate maximum contact pressure p between the developing roller and the application roller.

[0090] Particularly, according to the second aspect of the invention, an excellent effect that it is possible to suppress the fine recesses of the thin developer layer caused by set too slow rotational speed V ₂ of the application roller.

[0091] Particularly, according to the third aspect of the present invention, uneven density and Bosotsuki developed image by bringing set too fast rotational linear velocity V ₂ of the application roller fluctuated the coating amount of the liquid developer Can be suppressed.

In particular, according to the invention of claim 4, the thickness unevenness of the developer thin layer on the developing roller is suppressed as compared with the case where an application roller in which a plurality of cell-shaped minute concave portions are arranged in the roller axis direction is provided. In addition, there is an excellent effect that the coating efficiency can be improved. Further, by improving the coating efficiency, it is possible to avoid a situation in which the minute convex portions are easily formed in the thin developer layer due to the increase in the capacity of each minute concave portion for improving the coating efficiency. There is an excellent effect that it becomes possible.

In particular, according to the fifth aspect of the present invention, even if the hardness of the application roller is increased to a level suitable for actual use, it is possible to use a simple rolling method as a method for forming minute concave portions of the application roller. There is an excellent effect that it can be done.

In particular, according to the invention of claim 6, since the change in the applied amount of the liquid developer over time due to the wear of the application roller due to the rubbing with the regulating member is suppressed, the development density of the developer over time is reduced. There is an excellent effect that a significant change can be suppressed. Also, there is an excellent effect that running costs can be reduced and maintenance work can be reduced.

In particular, according to the seventh aspect of the present invention, it is possible to avoid a voltage drop of the developing bias caused by leaking the developing bias from the coating roller and the supporting member of the regulating member to the ground. Has an effect.

In particular, according to the invention of the eighth aspect, compared with the case where a developing roller is provided with a metal core and a developing bias is applied thereto, conduction failure of the developing bias can be suppressed, and On the other hand, there is an excellent effect that desired elasticity can be easily exerted.

According to the ninth aspect of the present invention, unevenness and blurring of the density of a developed image due to the fact that the minute projections corresponding to the minute recesses of the application roller appear on the thin developer layer on the development roller are suppressed. Thus, there is an excellent effect that deterioration of the image quality of the formed image due to these can be suppressed.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a maximum contact pressure p between a gravure roller and a developing roller and a thickness unevenness of a thin developer layer.

FIG. 2 is a graph showing a relationship between a linear velocity ratio between a gravure roller and a developing roller and thickness unevenness of a thin developer layer.

FIG. 3 is a schematic configuration diagram illustrating a printer according to the embodiment.

FIG. 4A is a plan view showing a gravure roller of the printer. (B) to (d) are schematic diagrams each showing a concave portion of the gravure roller.

FIG. 5 is a configuration diagram showing a conventional developing roller and a coating roller which rotate while contacting each other and move the surface in the forward direction at a contact portion.

FIG. 6 is a configuration diagram showing a conventional developing roller and a gravure roller that rotate while contacting each other and move surfaces in opposite directions at a contact portion.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum (latent image carrier) 20 charger 31 intermediate transfer belt 32 transfer roller 33 tension roller 40 static elimination lamp 50 drum cleaning device 51 cleaning blade 60 liquid developer 100 developing device (wet developing device) 101 tank unit 102 , 103 Stirring Screw 104 Anilox Roller (Developer Coated Body) 105 Doctor Blade (Regulator) 106 Developing Roller (Developer Carrier) 107 Cleaning Blade 108 Return Section 109 Developing Section 110 Sweep Roller 111 Cleaning Blade

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] January 12, 2001 (2001.1.1)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0070

[Correction method] Change

[Correction contents]

In a configuration in which the surfaces of both rollers are rubbed while being moved in the opposite direction by the coating nip as in the case of the present printer, if the maximum contact pressure p is set too large, the load of the drive motor for driving the rollers is increased. Is excessively increased to generate chatter called banding, and thus the thickness of the thin developer layer may be rather uneven. Therefore, it is desirable to set the maximum contact pressure p to an upper limit such that the load on the drive motor is lower than its rated torque. In this printer,
When the maximum contact pressure p is set to 0.8 [Mpa], the load applied to the drive motor is 1.5691 [N · m] (16 k
gf · cm) has been confirmed by experiments. If the load becomes larger than this, the rated torque of the drive motor will be exceeded. Therefore, in this printer, it is desirable to set the maximum contact pressure p to 0.8 [Mpa] or less.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yusuke Takeda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Tsutomu Sasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Tsuneo Kurotori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Toru Nakano 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. F-term (reference) 2H074 AA03 AA07 AA41 BB50 CC26

Claims (9)

[Claims] A developing roller for carrying a liquid developer containing a toner and a liquid carrier, attaching the liquid developer to a latent image formed on a latent image carrier of a wet image forming apparatus, and developing the latent image. A coating roller for applying the liquid developer carried on the surface on which the plurality of minute concave portions are formed to the developing roller; and a regulating member that contacts the coating roller and regulates the amount of the liquid developer before application. In a wet developing device in which both rollers are rotated so that their surfaces are moved in opposite directions at the contact position between the rollers to which the liquid developer is applied, the value of p defined by the following equation 1 is set to 0.12. [Mpa] A wet developing apparatus characterized by being set to not less than [Mpa]. [Number 1] p = Ea / 4R However, 1 / E = (1- ν 1 2) / E 1 + (1-ν 2 2)
/ E ₂ 1 / R = 1 / r ₁ + 1 / r ₂ , and E ₁ , ν ₁ , r ₁ , E ₂ , ν ₂ , r ₂ , and a are respectively the longitudinal elastic modulus [Mpa] of the developing roller, Poisson's ratio, the radius [mm], the modulus of longitudinal elasticity _E 2 [Mpa] of the coating roller, Poisson's _ratio, r 2 [mm] both roller contact length in the rotation direction of showing a [mm]. 2. A developing roller for carrying a liquid developer containing a toner and a liquid carrier, attaching the liquid developer to a latent image formed on a latent image carrier of a wet image forming apparatus, and developing the latent image. A coating roller for applying the liquid developer carried on the surface on which the plurality of minute concave portions are formed to the developing roller; and a regulating member that contacts the coating roller and regulates the amount of the liquid developer before application. , in the wet developing device for rotating the two rollers so that the liquid developer to move the mutual surface contact position of both rollers applied in the reverse direction, rotating the rotating linear velocity V ₂ of the coating roller of the developing roller wet development apparatus being characterized in that set faster than the linear velocity V _1. 3. A wet developing apparatus according to claim 2, wet development apparatus, characterized in that the rotational linear velocity V ₂ is set to less than 2 times the rotational linear velocity V _1. 4. The wet developing device according to claim 1, wherein the minute concave portion is provided with a minute groove extending continuously from one end of the coating roller to the other end. . 5. The wet developing device according to claim 1, wherein the coating roller is formed with the fine concave portions on the surface of a roller base material having a Vickers hardness of 200 [degrees] or less, and then subjected to a surface hardening treatment. A wet developing device characterized by using the above. 6. The wet developing device according to claim 5, wherein the regulating member has a hardness lower than the surface hardness of the application roller. 7. The wet developing device according to claim 1, wherein the supporting member of the coating roller and the supporting member of the regulating member are respectively insulated from ground. Wet developing device. 8. The wet developing device according to claim 7, wherein a conductive regulating blade is used as the regulating member, and the developing roller and the applying roller each having a conductive surface are used. A wet developing device, wherein a developing bias is applied to a surface of the developing roller via an application roller. 9. A wet image forming apparatus comprising: a latent image carrier for carrying a latent image; and a wet developing device for developing the latent image using a liquid developer containing a toner and a liquid carrier. Claims 1, 2, 3, 4, as a developing device.
A wet image forming apparatus, comprising the wet developing apparatus of any one of 5, 6, 7 and 8.