JP3363916B2 - Wet developing device - Google Patents

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] A wet developing device applied to an image forming apparatus such as a copying machine, a facsimile, and a printer.
More specifically, the present invention relates to the improvement of the surface structure of a developer carrier in a wet developing device using a one-component liquid developer.

[0002]

2. Description of the Related Art Conventionally, dry developing devices and wet developing devices are known as developing devices used in image forming apparatuses. Further, the wet developing device using the liquid developer has an advantage that high resolution can be obtained because the toner particles are finer than the wet developing. As a wet developing device, for example, an oil-based developer in which a toner made of carbon black coated with a resin is dispersed in a liquid carrier made of a petroleum solvent such as Isopar (trade name) is used to form a latent electrostatic latent image. By flowing between the surface of the image bearing member and the counter electrode arranged at a constant interval on the surface to bring the oily developer into contact with the surface of the latent image bearing member, the electrophoretic phenomenon of the toner charged by the liquid carrier is utilized. A device that develops an electrostatic latent image is generally used. This oil-based developer is called a two-component liquid developer because it uses a liquid carrier for toner charging and toner transfer.

However, in a wet type developing device using a two-component liquid developer, the developer is brought into contact not only with the electrostatic latent image but also with the non-charged portion, so that the developer adhered to the latent image carrier is taken out. Since the amount is large, a means for removing the excess developer on the surface of the latent image carrier is required. Further, since the developer also contacts the non-charged portion, the residual charge of the non-charged portion causes the toner to adhere to the non-charged portion, which may cause a background stain on the image. Further, when the toner on the latent image carrier is transferred to a transfer material such as a transfer to obtain a final image, the developer adhered to the latent image carrier is transferred to the transfer material regardless of the image area and the non-image area. Therefore, the transfer material immediately after the transfer of the toner image is in a wet state with the developer, and it is necessary to evaporate the solvent before it is discharged out of the apparatus. The amount of heat for evaporating the solvent not only occupies a large part of the amount of heat used in the image forming apparatus, but also the vapor concentration of the organic liquid evaporated by drying becomes high around the image forming apparatus, which may cause discomfort. is there.

As a wet developing device for solving the above problems, a developing device using a developer in which a coloring material is dispersed or dissolved in a liquid has been proposed. This developer is called a one-component liquid developer because the color material does not move in the liquid, the entire liquid behaves as a toner, and there is no equivalent to a liquid carrier in a two-component liquid developer. There is. For example, in U.S. Pat. No. 30,840,43, a conductive liquid ink as a one-component liquid developer is supplied to a developing roller having a fine uneven surface, and ink at the apex of the convex portion is bladed to prevent background stain. By squeezing the ink, the developing roller is brought into contact with the surface of the latent image bearing member by uniformly holding the ink only in the concave portions, and the ink in which the opposite polarity charge is induced by the latent image charge is applied to the apex portion by the electrocapillary phenomenon. There is disclosed a wet type developing device which develops by attracting latent image charges via the latent image charges.

[0005]

However, in the developing device disclosed in US Pat. No. 30,840,43, the pitch of the concavities and convexities determines the resolving power, and the finer the pitch, the higher the resolving power. There is a technical limit, and the cost becomes higher as it becomes finer. In order to reduce the cost of processing for forming such fine pitch irregularities on the surface, it is desirable to use, as the material of the developing roller, a material that is rich in malleability and ductility and is easy to process, such as aluminum. However, with a developing roller made of such a material that can be easily processed, for example, when the developing roller is taken out for maintenance and inspection, it is easy to accidentally hit the peripheral member by scratching the apex of the convex portion, and the squeeze of the blade or the like is likely to occur. In the case of abutting members, this abrading easily causes wear. If such scratches or abrasion occur on the top of the convex portion, the amount of the one-component liquid developer that can be held on the surface of the developing roller decreases, and the amount of the one-component liquid developer supplied to the surface of the latent image carrier is insufficient. However, there is a problem in that a partial or general reduction in image density occurs.
In addition, since the area of the top of the convex portion is enlarged due to abrasion, squeeze failure due to a squeeze member such as a blade is likely to occur, and the one-component liquid developer left unsqueezed here is the latent image carrier surface. There is also a problem that it adheres to the surface and causes dirt.

The present invention has been made in view of the above problems, and an object of the present invention is to consume a small amount of a liquid developer and to prevent an unnecessary liquid developer from adhering to a latent image carrier. Another object of the present invention is to provide an inexpensive wet developing apparatus capable of stably forming an image of high density and high resolution with little background stain on the image for a long period of time.

[0007]

In order to achieve the above object, the invention of claim 1 supplies a one-component liquid developer facing a latent image bearing member with a developing roller having an uneven surface. In a wet developing device for developing a latent image on a latent image carrier, the developing roller is made of metal and has a groove on the surface in an iris shape.
The Vickers hardness is 500 H on the surface of the roller base material having the concave portion having a cut shape and the convex portion having a sharp cross section.
It is characterized by using a cured film having a thickness of v or more.

According to a second aspect of the present invention, in the wet developing apparatus according to the first aspect, the cured film is a film formed by anodic oxidation.

According to a third aspect of the present invention, in the wet developing apparatus according to the first aspect, the cured film is a film formed by nickel-phosphorus alloy plating treatment in which plating is continuously promoted by an autocatalytic action of nickel. is there.

According to a fourth aspect of the present invention, in the wet developing apparatus of the first aspect, the cured film is a composite plating film in which fine particles of fluororesin are uniformly dispersed and deposited in an electroless nickel phosphorus alloy film. It is a feature.

According to a fifth aspect of the present invention, in the wet developing apparatus according to the fourth aspect, the cured film has a thickness of 10 to 30 μm.

According to a sixth aspect of the present invention, in the wet developing apparatus according to the fourth aspect, the variation in the thickness of the cured film is ± 10%.
It is characterized by being within.

[0013]

According to a seventh aspect of the present invention, in the wet developing apparatus according to the fourth aspect, the contact angle of the one-component liquid developer with respect to the cured film is 60 to 80 degrees.

[0015]

According to an eighth aspect of the present invention, the one-component liquid developer is supplied onto the developing roller having an uneven surface, and excess developer on the developing roller is removed by a squeeze member contacting the developing roller. In a wet type developing device which supplies a latent image on the latent image carrier by supplying it to a portion facing the image carrier, the developing roller is made of metal and cuts grooves in a iris shape on the surface.
Using a roller base material having a concave shape and a convex shape having a pointed cross-section with a cured coating having a Vickers hardness of 500 Hv or more, at least with the developing roller of the squeeze member. A cured film having substantially the same hardness as that of the developing roller is formed on the contact portion.

According to a ninth aspect of the present invention, in the wet developing apparatus according to the eighth aspect , the cured film is a composite plating film in which fine particles of silicon carbide are uniformly dispersed and deposited in an electroless nickel phosphorus alloy film. It is a feature.

[0018] The invention of claim 1 0, in the wet developing apparatus according to claim 9, Vickers hardness of the cured film is 800
It is characterized by being Hv or more.

[0019]

The wet developing apparatus of the present invention develops the latent image on the latent image bearing member by supplying the one-component liquid developer facing the latent image bearing member with the developing roller having the uneven surface. Further, by providing a cured film on the surface of the developing roller, even if a material having high malleability and ductility such as aluminum, which is easy to make unevenness on the surface, is used as the material of the developing roller base, the top of the convex portion is Even if the squeeze member is brought into contact with the developer to remove the excess developer, the wear can be reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a wet developing device for an electrophotographic copying machine will be described. Figure 1 (a)
FIG. 3 is a front view showing a main part of the wet developing device according to the embodiment. In FIG. 1A, the photosensitive drum 1, which is a latent image carrier, is rotationally driven in the clockwise direction by an arrow by a driving unit (not shown). On the peripheral surface of the photosensitive drum 1, in addition to the wet developing device, not shown for executing an electrophotographic process,
A uniform charger, an optical system for forming and irradiating a light image of a document, a transfer device for transferring a developed image on the photosensitive drum 1 onto a transfer paper, a cleaning device for cleaning the surface of the photosensitive drum 1 after transfer, A static eliminator or the like is provided. In addition,
A belt-shaped photoreceptor may be used instead of the drum-shaped photoreceptor as described above.

The wet developing device of this embodiment develops the electrostatic latent image on the photosensitive drum 1 formed by the above optical system, using a one-component liquid developer (hereinafter referred to as a developer). . This developing solution comprises an oily or aqueous solvent mixed with a binder and a pigment or dye. If necessary, various special agents may be added to exert a special function. For example, a viscosity control additive or a surface tension modifier that contributes to fixing the pigment on the transfer paper can be used. The viscosity is preferably 500 cp or less. This developer has a volume resistance value of about 10 ⁵ Ωcm to 10
It may be charged or uncharged as long as it is in the range of ¹⁴ Ωcm.

The wet type developing device of this example is a developing roller 2 which is a developer carrying member having an uneven shape formed on its surface, and a squeeze member for removing the developing solution on the top of the convex portion on the surface of the developing roller 2. A regulation roller 3 and a developer container 4 for containing a developer are provided. The developing roller 2 is arranged so that a part of the surface thereof is submerged in the developing solution in the developing solution container 4, and is driven to rotate counterclockwise by an unillustrated driving means. The surface shape and surface treatment of the developing roller 2 will be described in detail later. The developing roller 2 may be arranged such that the top of the recess is in contact with the surface of the photosensitive drum 1, or may be arranged so as not to be in contact with the surface of the photosensitive drum 1. The regulation roller 3 is arranged at a height that does not allow it to be immersed in the developing solution in the developing solution container 4, and is rotationally driven in the same direction as the developing roller 2 so that the surfaces of the two rollers 2 and 2 facing each other face each other. By moving in the opposite direction, the developer on the top of the concave portion on the surface of the developing roller 2 can be efficiently wiped off. The regulation roller 3 which is the squeeze member
The rotation direction is not limited to this, and instead of the regulation roller 3, a rotating belt-shaped squeeze member, a blade-shaped squeeze member, or the like may be used. Since the developing roller 2 is rotating, the squeeze member can be squeezed even if the squeeze member is not in contact with the surface of the developing roller 3. However, when the squeeze member is fixedly arranged like the squeeze member on the blade, the squeeze member is squeezed. In order to bring out the effect well, it is desirable to contact the surface of the developing roller 3.

In the above structure, the developing solution in the developing solution container 4 is held in the concave portion on the surface of the developing roller 2 by the rotation of the developing roller 2 and pumped up, and as shown in FIG. The developer on the top portion 2a of the convex portion is removed at the facing portion, and is supplied to the developing area, which is the facing portion to the surface of the photosensitive drum 1, as shown in FIG. In this developing area, the developing solution held in the concave portion on the surface of the developing roller 2 adheres to the electrostatic latent image on the photoconductor drum 1, thereby developing the electrostatic latent image.

The adhesion of the developing solution to the electrostatic latent image is caused by the following principle. In FIG. 1C, an equivalent circuit between the photosensitive drum 1 and the developing roller 2 in the vicinity of the developing area is the conductive base 1a of the photosensitive drum 1 (1b in the drawing indicates a photosensitive layer) and the developing roller. 2 is connected via a DC power source 5 and a switch 6. The DC power source 5 corresponds to a power source for a developing bias in a normal wet developing device. The developing solution is held in a concave portion on the peripheral surface of the developing roller 2, and the tip of the apex 2a of the convex portion on the peripheral surface of the developing roller from which the developing solution has been removed by the regulating roller 3 comes close to or in contact with the surface of the photosensitive drum 1. There is. The state in which the developer held in the concave portion on the peripheral surface of the developing roller 2 faces the photosensitive drum 1 corresponds to the state in which the switch 6 in the equivalent circuit is closed. In this state, in this example, the conductive base 1a
A DC voltage is applied between the conductive base 1a and the developer carrying member 1 by the DC power supply 5 so that the voltage becomes a positive potential. When an uncharged developer is used, such a bias induces an equal amount of charge of the opposite sign in the developer with the charge on the electrostatic latent image. In this example, the developer is negatively induced. The developer may be charged. Due to the electrostatic attraction force that acts between the dielectric charge of the developing solution and the charge of the electrostatic latent image, the developing solution adheres only to the charged portion of the electrostatic latent image on the photosensitive drum 1. Contrary to this example, an electrostatic latent image of negative charge is formed on the photosensitive drum 1, and the conductive base 1a and the developing roller are arranged so that the conductive base 1a of the photosensitive drum 1 has a negative potential. Similarly, when a DC voltage is applied between the two and a positively charged developer or an uncharged developer is used, the developer is similarly attached only to the charged portion of the electrostatic latent image. You can In this example, the photosensitive layer 1b and the conductive substrate 1a, which is the counter electrode, are integrally combined to form the photosensitive drum 1, but instead of this,
The photosensitive layer 1b and the counter electrode may be provided separately.

After the electrostatic latent image is developed as described above, the developing solution which is not attached to the surface of the photosensitive drum 1 but is held in the concave portion of the surface of the developing roller 2 is rotated by the rotation of the developing roller 2. It is collected in the storage container 4.

Here, the surface shape and surface treatment of the developing roller 2 will be described. In this embodiment, the roller-shaped substrate of the developing roller 2 is made of a material that can be easily processed, such as a metal such as aluminum. Irregularities are provided on this surface so that the developer can be held. Further, a cured film is formed to increase the hardness of the surface.

First, the uneven shape formed on the surface of the roller-shaped substrate will be described. The uneven shape of the surface of the developing roller 2 is for holding the developing solution and supplying it to the photoconductor drum 1 as described above. And the like affect the quality of the developed image. As the concavo-convex shape capable of holding the developing solution and easily processed, for example, a screw-shaped concavo-convex shape as shown in FIG. 2A, or a large number in the developing roller axial direction as shown in FIG. 2B. 2C, a shape having a large number of grooves in the developing roller axial direction and a large number of grooves in the developing roller rotating direction as shown in FIG. 2C, and a developing roller rotating direction as shown in FIG. 2D. On the other hand, it is conceivable that the iris has a grooved shape.

In the shape of FIG. 2A, the groove in the direction of rotation of the developing roller makes it easy to remove the developing solution from the top of the recess, but the groove holding the developing solution rotates in the developing roller. Since they are continuous in the direction, the latent image portions formed at minute intervals in the rotation direction of the photosensitive drum 1 may be connected and developed. In the shape of FIG. 2B, since the groove holding the developing solution is continuous in the axial direction of the developing roller, the latent image portions formed at minute intervals in the axial direction of the photosensitive drum 1 are connected. On the other hand, the line latent image in the rotation direction of the photosensitive drum 1 may not be developed to a uniform density. Further, since the groove is formed in the axial direction of the developing roller, there is a risk of squeeze failure in which the developing solution remains on the wall surface on the downstream side in the developing roller rotation direction at the top of the recess. In the shape of FIG. 2C as well, since there are continuous grooves in the developing roller rotation direction, there is a risk that latent image portions formed at minute intervals in the rotation direction of the photosensitive drum 1 will be connected and developed. is there. In the shape of FIG. 2D, since the groove has an iris shape having a predetermined inclination in the developing roller rotation direction,
Even if the developing roller 2 rotates, the grooves do not become continuous, so that it is possible to satisfactorily develop both the dot-shaped and line-shaped latent image portions, which is the most suitable surface shape for the developing roller 2 of the apparatus of this embodiment. is there.

As for the cross-sectional shape of the unevenness,
A trapezoidal shape as shown in FIG. 3A, a trapezoidal shape close to a rectangle as shown in FIG. 3B, or a cross-sectional shape having a mountain shape with a sharp tip as shown in FIG. 3C is considered. .

Among them, regarding the cross-sectional shape of FIG. 3A, since the area of the top of the convex portion contacting the surface of the photosensitive drum 1 is relatively large, there is a possibility that the squeeze defect causes the background stain of the image. . In the shape of FIG. 3B in which the width of the convex portion is narrowed and the interval between the convex portions is also narrow, it is difficult for the developing solution to enter the concave section and for the developing solution that once enters the concave section to escape from here. Therefore, the image density may be insufficient. With respect to the shape of FIG. 3C, the developer does not adhere to the background portion of the surface of the photosensitive drum 1 because the tip of the top of the convex portion is dot-shaped, and the space between the wall surfaces of adjacent concave portions is small. Since the distance is relatively large, it is possible to favorably move the developing solution in and out of the concave portion while ensuring the concave portion volume for holding the developing solution to the extent that the image density is not insufficient. Therefore, it is optimal when the pitch of the unevenness is set finely to obtain a large resolving power.

Next, the surface treatment of the developing roller 2 will be described. As described above, the material of the base roller of the developing roller 2 is, for example, a metal such as aluminum that is easy to process. However, the base roller made of such a material that is easy to process has low surface hardness and is easily worn. It has the drawback of being vulnerable to damage. For example, aluminum has a specific gravity of 2.7.
It is light and has excellent electrical conductivity and heat conductivity, and also has excellent malleability and ductility, so it has the advantage of being easy to mold.
Although it is easy to process the surface shape as described above, the surface hardness is low and it is weak against abrasion and damage. Since this aluminum forms a thin and dense transparent oxide film on the surface in the air, it is generally said that it has good corrosion resistance, but it easily rusts in a humid place or in an acid / alkali atmosphere. Surface treatment is required. Therefore, in this embodiment, the surface of the developing roller 2 is hardened to form a hardened film. This hardening treatment includes anodic oxidation, nickel-phosphorus alloy plating in which plating is continuously promoted by the autocatalytic action of nickel, and a composite in which fine particles such as fluororesin or silicon carbide are uniformly dispersed and deposited in an electroless nickel-phosphorus alloy film. Plating or the like is suitable.

Here, the aluminum anodic oxidation method will be described. Add 0.5% of surfactant to a degreasing solution of 5 to 10% sodium hydroxide, sulfuric acid, etc.
After degreasing by immersing it in the liquid of ° C for 3 to 200 seconds,
Mechanical pretreatment such as buffing and blasting, and chemical pretreatment with phosphoric acid + nitric acid chemical polishing liquid. If degreasing of aluminum products is incomplete, dyeing after anodic oxidation may cause uneven coloring. Next, an anodic oxidation process is performed.
A method using an electrolytic solution of sulfuric acid, oxalic acid, chromic acid or the like is representative, and here, a sulfuric acid direct current method with an industrial utilization rate of 90% or more is shown. Current density 0.8 to 1.2 A / d
Electrolysis is carried out for 20 to 60 minutes at a liquid temperature of -5 to 22 ° C. at m ² to form a film of 5 to 20 μm. The gas generated from the cathode and the anode during anodization is harmful to hygiene because it produces droplets accompanied by the electrolytic solution when it goes out of the electrolytic solution.
Further, since it corrodes equipment and devices, it is necessary to add a surfactant to the electrolytic solution to prevent it. Further, it is convenient to add a surfactant to the electrolytic solution because a small amount of oil and fat adhering to aluminum is removed.

FIG. 4 shows the relationship between the electrolysis time and the coating thickness when the current density is 6 A / dm ² , 4 A / dm ² , 2 A / dm.
^It shows the case of ² . As can be seen from this figure, the thickness of the coating is proportional to the current density and the electrolysis time, and the higher the current density, the faster the formation of the coating. However, if the current density is excessively increased, problems such as the occurrence of burning due to the non-uniform formation of the film will occur, which is not preferable.
The surface hardness can be increased by forming a film by the above anodic oxidation. FIG. 5 shows the relationship between the film thickness and Vickers hardness. As can be seen from this figure, the hardness decreases as the film thickness increases. The hardness of the coating on the base aluminum side is the highest,
It grows softer as it grows. That is, it is considered that the film is a hard film immediately after the film is formed, but if it is exposed to the electrolytic solution for a long time, some of the pores are dissolved and become soft. However, if it is 20 μm or less, the hardness is not particularly lowered and there is no problem. The harder the coating, the better the abrasion resistance.

Next, a method of nickel-phosphorus alloy plating in which plating is continuously promoted by the autocatalytic action of nickel will be described. After the pretreatment steps such as alkali degreasing, pickling and electrolytic degreasing, plating is performed. In plating, when the hypophosphite anion comes into contact with the eighth metal of the periodic table under certain specific conditions, the metal acts as a catalyst to cause dehydrogenation decomposition as shown in the following formula. The hydrogen atom thus generated is adsorbed on the surface of the catalytic metal and activated, and when it contacts the nickel cation in the plating solution, the nickel cation is reduced to a metal and deposited on the surface of the catalytic metal as shown in the following formula. Further, the activated hydrogen atoms on the surface of the catalytic metal react with the hypophosphite anion in the liquid to reduce the contained phosphorus as shown in the following formula, thereby forming an alloy with nickel. The nickel thus deposited serves as a catalyst, and the same nickel reduction plating reaction as that described above continues to proceed. That is, the feature of this plating reaction is that the plating continues to proceed due to the autocatalytic action of nickel, which is completely different from the so-called electroless plating of metals other than the eighth metal. As described above, this plating is performed by the catalytic action of the eighth metal. Namely iron, cobalt, nickel, ruthenium, rhodium,
In addition to palladium, osmium, iridium, platinum, etc., it is possible to plate copper, silver, gold, beryllium, germanium, aluminum, magnesium, carbon, vanadium, molybdenum, chromium, selenium, titanium, uranium, etc. other than catalytic metals. is there. However, this plating cannot be applied to bismuth, cadmium, antimony, tin, lead, zinc, etc. This is because they interfere with the catalytic action. Further, non-metals such as resin plastics, ceramics, and glass can be plated by special pretreatment. The nickel-phosphorus alloy plating becomes thicker in proportion to the immersion time in the plating solution. Its chemical composition is 90-92% nickel, 8-10% phosphorus, and a Vickers hardness of 5
1000Hv for heat treatment at 00Hv, 400 ℃ for 1 hour
Is. As long as it has such hardness, it is hardly worn even by squeezing with a regulation roller or the like. The hardness can be adjusted by the temperature and time of such heat treatment. It is also characterized by complete coverage and uniform film thickness, with an accuracy of ± 10% of the required thickness.
Within. Therefore, even when a pyramid-shaped or sword-shaped convex portion is formed on the surface of the base roller of the developing roller 2 that is made of a soft metal that is easy to process, plating is performed to form a film, the convex portion is also formed. It is possible to form a film with a uniform thickness. The film thickness of 30 μm is sufficient in terms of corrosion resistance and wear resistance. Its corrosion resistance is superior to that of pure nickel, because it is an alloy, but it is not attacked by most organic solvents and has a high corrosion resistance to organic acids, salts, caustic alkali and dilute mineral acids. Have. Therefore, it is less likely to be affected by the solvent that constitutes the developing solution, and the range of solvent selection can be expanded.

Next, among such nickel-phosphorus alloy plating, composite plating for uniformly dispersing and depositing fine particles of fluororesin in the electroless nickel-phosphorus alloy coating will be described. Since this plating contains a fluororesin in the plating film, it is characterized in that it is excellent in self-lubricating property, non-adhesive property, and releasing property. Further, there is also a characteristic that the coefficient of friction is low, and when the regulating roller 3 is brought into contact with the surface of the developing roller 2 to squeeze, the mutual friction amount can be reduced. It is also excellent in wear resistance, damage resistance and mechanical strength. Similar to the above nickel-phosphorus alloy plating, the film thickness uniformity, high dimensional accuracy, etc. are the most suitable features for dealing with fine irregularities. In particular, this plating is as excellent in water repellency and oil repellency as the Teflon coating. This is advantageous in contacting the regulation roller 3 with the surface of the developing roller 2 and squeezing. As a result, the top of the convex portion on the surface of the developing roller 2 can be squeezed cleanly, so that the developer can be prevented from adhering to the background portion of the electrostatic latent image. Further, the developer held in the recess of the developing roller 2 and facing the surface of the photosensitive drum 1 is not wasted due to the water and oil repellency of the recess.
It moves to the surface of the photoconductor drum 1 to obtain a high image density. This plating method is superior in that it is easier and cheaper than the method of covering the surface of the developing roller with a Teflon tube.

Next, of the above nickel-phosphorus alloy plating, the composite plating for uniformly dispersing and depositing fine particles of silicon carbide in the electroless nickel-phosphorus alloy coating will be described.
This plating is a surface treatment method in which an appropriate amount of silicon carbide is added to the plating film and these fine particles are simultaneously deposited in the film simultaneously with nickel phosphorus coating. Since this plating contains silicon carbide in the plating film, the Vickers hardness is approximately 75
0 Hv is obtained. It is possible to further increase the hardness by performing heat treatment. For example, a heat treatment at 300 ° C. gives a hardness of about 1400 Hv. The thicker the coating, the better the abrasion resistance, but the longer the reaction time. Therefore, considering the simplicity, if the thickness of the coating is 10 μm, the surface of the developing roller 2 or the surface of the regulating roller 3 described later will be used. Is sufficient as a film. The hardness can be adjusted by the temperature and time of such heat treatment. Also, the hardness can be adjusted by fine particles to be deposited. The amount of wear is significantly smaller than that of surface hardening methods such as alumite and hard chrome plating. By heat treatment, the wear resistance can be further improved and the coefficient of friction is also extremely low. And has a characteristic that slidability is improved. Due to the above features, the regulation roller 3
Even when the developer is squeezed on the top of the surface convex portion due to, the amount of wear of each of the regulation roller 3 and the developing roller 2 can be reduced. It is also excellent in wear resistance, damage resistance and mechanical strength. Similar to the above nickel-phosphorus alloy plating, the film thickness uniformity, high dimensional accuracy, etc. are the most suitable features for dealing with fine irregularities. As the fine particles to be deposited, instead of the above silicon carbide, tungsten carbide,
Boron carbide, aluminum oxide, titanium carbide, molybdenum boron, chromium carbide, silicon carbide or the like may be used.

When the above-described hardening treatment is applied to the surface of the developing roller 2, a coating having extremely high hardness such as a composite plating in which fine particles of silicon carbide are uniformly dispersed and deposited in the electroless nickel-phosphorus alloy coating. If the amount of wear of the surface of the regulation roller 3 that comes into contact with this surface increases when the treatment for forming the above is performed, it is desirable that the surface of the regulation roller 3 also be cured. In particular, it is desirable to carry out a curing treatment that produces a cured film having substantially the same hardness as the surface of the developing roller 2. As a result, the amount of wear of both the developing roller 2 and the regulation roller 3 can be reduced. In order to form cured films having the same hardness as each other, the same curing treatment may be performed or different curing treatments may be performed. In the latter case, the processing conditions are set so that a cured film having the same hardness can be produced. For example, one side is plated with phosphorus-nickel alloy and 35
When heat-treated at 0 ° C. for 1 hour and treated with nickel-phosphorus alloy plating having silicon carbide deposited on the other side, both have a Pickers hardness of about 850 Hv. Further, when one is plated with a phosphorus-nickel alloy and heat-treated at 400 ° C. for 1 hour, and the other is treated with a nickel-phosphorus alloy plated with boron carbide deposited, both have a Pickers hardness of about 1000 Hv.

The electrostatic latent image developed by the above wet developing device and having the developing solution attached only to the image portion is transferred to a transfer body such as paper to form a copy. This transfer is performed by contacting the electrostatic latent image with the developing solution with the transfer body, and the developing solution permeating into the transfer body. Therefore, it is necessary to use corona discharge, which is used in conventional copying machines. Copying is completed with a simple mechanism. Further, by applying pressure from the back side of the transfer body with a roller or the like in a state where the transfer body is superposed on the surface of the photosensitive drum 4, it is possible to transfer the developed image more reliably. Further, since only the developing solution that has adhered to the charged portion of the electrostatic latent image adheres to the transfer body, there is no particular need for a fixing step,
When transfer paper is used as the transfer body, its smoothness is 2
If it is less than 00 Sec (using Beck's smoothness tester), there is no problem in transfer and fixing. In particular, if the transfer paper has a smoothness of 150 Sec or less, as shown in FIG. 6, after 5 seconds from copying, the developer does not get on the hand by rubbing with a finger.
It showed good fixability that was the same as when more than a minute had passed.
Here, FIG. 6 shows the reflection density (Smea) of the toner adhered to the finger when the toner image on the transfer paper after transfer is rubbed with the finger on the vertical axis.
r, smear) and the elapsed time after transfer on the horizontal axis, and image density (ID) 1. on the surface (face, smoothness 200Sec) of PPC paper type 1000 manufactured by Ricoh Co., Ltd.
15 toner images, I on the back surface (back, smoothness 150 Sec)
6 is a graph showing the results of smear measurement by forming a toner image of D1.10. As a result, unlike conventional wet copiers, there is no need to apply heat at high temperatures, so the total heat consumption of the copier is small, and the concentration of solvent gas in the air increases due to solvent evaporation, which causes discomfort. Nothing.

[0039]

Effects of the Invention According to the invention of claims 1 to 1 0, by providing the cured film on the surface of the developing roller having a rough surface, as a material of the developing roller base, easier to roughened surface Even if a material having high malleability and ductility such as aluminum is used, the top of the convex portion is not easily damaged, and wear can be reduced even in a case where a squeeze member is abutted to remove excess developer. Therefore, the consumption of the liquid developer is small, the unnecessary liquid developer does not adhere to the latent image carrier, and the image has almost no background stain, and a high-density and high-resolution image can be stably obtained for a long period of time. An inexpensive wet developing device that can be formed can be provided.

In particular, according to the invention of claim 3, 4, 6 or 9 , a uniform cured film is formed according to the surface shape of the surface of the base roller of the developing roller in which the cured film is processed into an uneven shape. Therefore, it is possible to provide a wet developing device capable of exhibiting desired developing solution holding performance and developing characteristics.

Further, according to the invention of claim 4 or 7, since the cured film has a property of repelling the developer, the one-component liquid developer held in the concave portion of the surface of the developing roller is subjected to the electrostatic latent image. According to the above, it is possible to satisfactorily adhere to the surface of the electrostatic latent image bearing member, and it is possible to provide a wet developing device capable of obtaining a high-density image. Further, when the developer held in the concave portion of the developing roller surface is supplied to the electrostatic latent image carrier surface after removing the one-component liquid developer on the top of the convex portion of the developing roller surface, the convex portion Since the developer can be satisfactorily removed from the top of the image forming apparatus, it is possible to provide a wet image forming apparatus capable of particularly effectively preventing the background stain of the image.

Further, according to the invention of claim 5 or 1 0,
It is possible to provide a wet developing apparatus having a developing roller that does not spend a lot of time for forming the above-mentioned cured film and has practically sufficient abrasion resistance and corrosion resistance.

[0043]

Further, according to the invention of claim 8 , a hardened film having substantially the same hardness is formed on the surface of the developing roller having irregularities on the surface thereof and on at least the contact portion of the squeeze member with the developing roller. It is possible to provide a wet developing device which can reduce wear on both the developing roller surface and the squeeze member surface and can obtain a good image for a long period of time.

[Brief description of drawings]

FIG. 1A is a front view of a main part of a wet developing apparatus according to an embodiment, and FIGS. 1B and 1C are explanatory views for explaining a developing principle of the wet developing apparatus.

FIGS. 2A, 2B, 2C, and 2D are views for explaining a configuration example of a surface shape of a developing roller of the wet developing apparatus.

FIGS. 3A, 3B, and 3C are views for explaining a configuration example of a cross-sectional shape of a concavo-convex portion on a surface of a developing roller of the wet developing apparatus.

FIG. 4 is a graph showing the relationship between anodizing time and film thickness.

FIG. 5 is a graph showing the relationship between film thickness and Vickers hardness.

FIG. 6 is a graph showing the fixability when a developed image developed by the wet developing apparatus according to the example is transferred to a transfer paper.

[Explanation of symbols]

1 photoconductor drum, 2 developing roller 3, regulating roller, 4 developer container

Claims (10)

(57) [Claims] 1. A wet developing device for developing a latent image on a latent image bearing member by supplying a one-component liquid developer facing a latent image bearing member with a developing roller having an uneven surface. As a iris on the surface made of metal
A Vickers hardness of 500 is applied to the surface of a roller base material having a groove-shaped concave portion and a cross-sectionally pointed convex portion.
A wet developing device using a cured film having a Hv or higher. 2. The wet developing apparatus according to claim 1, wherein the cured film is a film formed by anodic oxidation. 3. The wet developing apparatus according to claim 1, wherein the cured film is a film formed by nickel-phosphorus alloy plating treatment in which plating is continuously promoted by an autocatalytic action of nickel. 4. The wet developing apparatus according to claim 1, wherein the cured film is a composite plating film in which fine particles of fluororesin are uniformly dispersed and deposited in an electroless nickel phosphorus alloy film. 5. The wet developing apparatus according to claim 4, wherein the cured film has a thickness of 10 to 30 μm. 6. The thickness variation of the cured film is ± 10%.
5. The wet developing device according to claim 4, wherein 7. The wet developing apparatus according to claim 4, wherein the contact angle of the one-component liquid developer with respect to the cured film is 60 to 80 degrees. 8. A single component on a developing roller having an uneven surface.
Supply the liquid developer to remove excess developer on the developing roller.
Latent image bearing after removal with a squeeze member that contacts the image roller
It is supplied to the portion facing the bearing member, to develop the latent image on the latent image bearing member
In the wet developing device, the developing roller is made of metal and has an iris shape on the surface.
The concave part with the groove cut and the convex part with the sharp tip in cross section
The Vickers hardness is 500 on the surface of the roller base material having
A squeeze member that comes in contact with at least the developing roller is used, which has a cured coating of Hv or more.
Hardened skin with almost the same hardness as the hardened film on the developing roller
A wet developing device having a film formed thereon. 9. The cured film is an electroless nickel-phosphorus alloy film.
A composite mesh in which fine particles of silicon carbide are uniformly dispersed and deposited.
9. A wet developing apparatus according to claim 8, which is a coating film.
Place 10. The Vickers hardness of the cured film is 800.
The wet developing device according to claim 9, wherein the wet developing device is Hv or more.
Place