JPH09319228A - Liquid developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the missing of dots and surface staining by providing a developing roller whose surface has a plurality of recesses and protrusions and which holds the supplied developer in the recesses to carry the supplied developer. SOLUTION: On the surface of the developing roller 9, a large number of recesses 9a arrayed at predetermined pitches (p) from each other and protrusions 9b except the recesses 9a are formed. The diameter (r) of the recess 9a corresponds to that of one dot of a developer used for developing by this liquid developing device. Then, at a position where the developer is supplied, the developer is supplied to the surface of the developing roller 9 from a developer supplying roller arranged to face the developing roller 9. This roller 9 holds the supplied developer in the recesses 9a, to carry the supplied developer up to a developing position and supply the developer to a photoreceptor drum arranged oppositely at the developing position. Thus, the developer supplied to the roller 9 is surely supplied thereto and surely held in the recesses 9a. Further, the developer does not remain in the protrusions 9b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus for developing an electrostatic latent image using a liquid developer, which is used by being incorporated in an electrophotographic copying machine or printer.

[0002]

2. Description of the Related Art Conventionally, as a developing method of an electrostatic latent image in an electrophotographic image forming apparatus, a dry developing method using a powder developer and a wet developing method using a liquid developer are known. Both the dry development method and the wet development method have advantages and disadvantages,
Although the wet developing method has a drawback that the structure of the developing device is more complicated than the dry developing method, the wet developing method can use finer toner particles than the dry developing method and thus is suitable for high-resolution image formation. In addition, there is also an advantage that the fixing process can be simplified or unnecessary.

There are many methods among the wet development methods,
One of them is a developer solution in which toner particles charged to the opposite polarity of the latent image charge are dispersed in a highly insulating organic solvent, and this developer solution is brought into contact with the surface of the electrostatic latent image carrier. Then, there is a method of visualizing the electrostatic latent image by causing the toner particles in the developing solution to adhere to the electrostatic latent image by electrophoresis. However, in this method, the surface of the electrostatic latent image bearing member is wet with the developer,
Background stains are likely to occur in a non-image area on the electrostatic latent image carrier, which may deteriorate the image quality. Further, since a highly flammable and highly volatile organic solvent is used as a solvent, it is necessary to install a special processing device for safety and hygiene and environmental protection, and there is also a problem that the cost of the image forming apparatus tends to increase. .

In order to solve such a problem, a wet developing method using a developing solution in which a coloring material is dispersed in a liquid has been proposed. In this developing solution, the coloring material does not move in the liquid, but the entire developing solution in which the coloring material and the dispersion medium are integrated behaves as a toner. As one of the developing methods, US Pat.
There is a polar liquid development method disclosed in 084043. The outline of this developing method is as follows. A developing roller having regular fine irregularities on its surface is prepared. A conductive developing solution is held in the concave portion of the developing roller by a capillary force, and the convex portion of the developing roller is brought into contact with an electrostatic latent image carrier that carries an electrostatic latent image, thereby The developer held in the concave portion induces the opposite polarity charge due to the latent image charge of the electrostatic latent image. Due to the electrocapillary phenomenon based on the latent image charge of the electrostatic latent image and the opposite polarity charge of the developer, the developer is attracted to the electrostatic latent image on the electrostatic latent image carrier along the side wall of the convex portion of the developing roller. Develop the electrostatic latent image.

In this polar liquid developing method, the electrostatic latent image bearing member and the developing roller are brought into contact with each other. Therefore, the developer adhering to the convex portion of the developing roller adheres to the surface of the electrostatic latent image bearing member. There is a problem that it is easy to cause dirt on the ground. Therefore, as a countermeasure, a method of forcibly removing the developer adhering to the convex portion of the developing roller by using a developing scraping member formed of an elastic material, or a method of coating the concave and convex portion of the developing roller with a liquid repellent material is used. A method for developing a electrostatic latent image by using a developing roller covered with the above method, preventing the developer from adhering to the convex part of the developing roller, holding the developer in the concave part, and developing the electrostatic latent image with the developer held in the concave part. Have been proposed.

For example, in Japanese Patent Publication No. 55-28067, a developing solution coating member is used to coat the surface of a developing roller with a developing solution, and then a squeezing member is used to coat the surface of the developing roller. The excess developer and a part of the developer in the concave portion of the developing roller are squeezed out to keep the amount of developer in the concave portion constant, and then the developer adhering to the convex portion using a developer scraping member. A method of removing the liquid is disclosed.

Further, in JP-A-5-142950, there is used a developing roller in which uneven portions on the surface of the developing roller are coated with a film of a liquid repellent material, and the developing roller is rotated while being immersed in the developing solution. After supplying the developer into the recess,
A method is disclosed in which a developer scraping member is used to remove excess developer in the concave portion of the developing roller and the developer adhering to the convex portion.

[0008]

However, none of the methods described above is a complete solution. That is, in the developing method disclosed in the above Japanese Patent Publication No. 55-28067, even if an appropriate amount of the developing solution is held in the concave portion by the developing solution applying member and the squeezing member, the following developing solution scratching is performed. It is expected that the developer on the convex portion scraped off by the removing member will enter the concave portion and change the amount of the developer in the concave portion of the developing roller. As a result, the capillary phenomenon may occur due to this, and the developer may ooze out from the concave portion to the convex portion, causing the occurrence of background stain.

Further, in the developing method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-142950, since the uneven portion of the developing roller is covered with the film of the liquid repellent material, the contact angle with respect to the developing solution is large, and the development in the concave section is performed. There is a possibility that the liquid cannot enter and the developer cannot be retained in a sufficient amount in the recess. Even if the developer enters the concave portion, since the holding force due to the capillary force is weak, the developer in the concave portion is likely to seep out when the developer adhering to the convex portion is squeezed out by the squeezing member. ,
There is a possibility that the developer in the recess may be insufficient.

Generally, in such a liquid developing apparatus for developing an electrostatic latent image with the developing solution in the concave portion of the developing roller having the unevenness on the surface, the concave portion of the developing roller may be fine in size and pitch. The higher the number, the higher the quality of the image that can be obtained, but on the other hand, it becomes difficult to supply and hold the developer in the recesses of the developing roller and scrape off the excess developer.

FIG. 14 is a view showing a state where the developing solution is held in the concave portion of the developing roller having the uneven surface. As shown in FIG. 14, among the plurality of concave portions of the developing roller 100 having the uneven surface, the concave portion 1 that holds an appropriate amount of the developing solution 8 is used.
If there is also 01a, the concave portion 10 with an insufficient holding amount of the developer 8
There is also 2a. Further, among the plurality of convex portions of the developing roller 100, there are a convex portion 102b where the developing solution 8a remains on the surface and a convex portion 101b where the residual developing solution does not exist. As described above, when the concave portion 102a having an insufficient amount of the developer 8 is present, a dot omission occurs at a position corresponding to the concave portion 102a in the developed image, and the developer 8a is convex 102b.
If left on the surface, the developed image will have background stains at the positions corresponding to the convex portions 102b, which both cause deterioration in image quality.

In view of the above circumstances, it is an object of the present invention to provide a liquid developing device in which dot omission and background stain are prevented.

[0013]

A liquid developing device of the present invention which achieves the above object is a liquid developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier with a developing solution. Has a plurality of concave portions and convex portions, the developing solution is supplied at a predetermined developing solution supply position, the supplied developing solution is conveyed to a predetermined developing position, and the electrostatic latent image carrier is contacted at the developing position. And a developing solution supplying means for supplying the developing solution to the developing roller at the developing solution supplying position, and a bias voltage is applied to the developing roller when the developing solution is supplied to the developing roller by the developing solution supplying means. And a bias voltage applying unit.

Here, it is preferable that the developing roller has a concave surface and a convex surface which are relatively lyophilic and liquid repellent, respectively. Further, the developing roller comprises a conductive substrate and a surface layer made of an insulating material coated on the conductive substrate.
It is also a preferable embodiment that the surface of the developing roller is provided with a charge applying means for applying an electric charge.

Further, the developing roller is formed by coating a conductive base material only on the inner surface of the recess with an insulating material, and the liquid developing device further imparts an electric charge to the surface of the developing roller. It is also a preferable embodiment to have a means for providing electric charge. Further, the developing roller has a surface layer made of an insulating material on an inner surface of the concave portion and a photoconductive material on a surface of the convex portion on a conductive base, and the liquid developing apparatus further comprises: It is also one of preferred embodiments that it is provided with a charge applying means for applying an electric charge to the surface of the developing roller and a light irradiating means for irradiating the surface of the developing roller charged by the charge applying means with light. Is.

A corotron is preferably used as the charge applying means.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic view of an embodiment in which the liquid developing device of the present invention is incorporated as a developing unit of a wet image forming apparatus. As shown in FIG. 1, the wet image forming apparatus includes a photosensitive drum 1 which is an electrostatic latent image carrier, a charger 2 arranged around the photosensitive drum 1, an exposure device 3, and a liquid developing device 4. , Transfer device 5, cleaning device 6, and static eliminator 7
And are provided.

The photosensitive drum 1 is driven by a driving means (not shown) to rotate in the direction of arrow A. The photosensitive drum 1
First, the photoconductive layer on the surface of the photosensitive drum 1 is uniformly charged by the charger 2. The charged photoconductor drum 1 is exposed by the exposure device 3 to form an electrostatic latent image on the surface. The electrostatic latent image formed on the photosensitive drum 1 is the liquid developing device 4
Is developed and visualized by the developing solution 8. As the electrostatic latent image carrier, a belt-shaped photoreceptor may be used instead of the photoreceptor drum 1 as shown in FIG.

As the developing solution 8, any one-component developing solution can be used. For example, a liquid developer formed by mixing a pigment or a dye in an aqueous solution and, if necessary, mixing a surface tension adjusting agent, a viscosity adjusting agent or the like can be used. As shown in FIG. 1, the liquid developing device 4 includes a developing roller 9 that rotates in the direction of arrow B, and a roll-type developing solution supply roller 10 that supplies the developing solution 8 to the developing roller 9 and that rotates in the direction of arrow C. A developing solution removing blade 11 for removing excess developing solution on the surface of the developing roller 9, a developing solution tank 13 for containing the developing solution 8, a developing solution collecting roller 12 for collecting the developing solution 8 after development, and a developing roller 9 Bias voltage applying means 14 for applying a bias voltage to the surface is provided.
The bias voltage applying means 14 will be described later.

FIG. 2 is a plan view showing the surface structure of the developing roller used in this embodiment and a sectional view taken along the line AA. As shown in FIGS. 2A and 2B, on the surface of the developing roller 9, a large number of concave portions 9a arranged at a predetermined pitch p from each other and convex portions 9b other than the concave portions are formed. Has been done. The diameter r of the recess 9a corresponds to the diameter of one dot of the developed image developed by the liquid developing device 4.

As shown in FIG. 1, the developing solution 8 is supplied to the surface of the developing roller 9 from the developing solution supply roller 10 arranged so as to face the developing roller 9 at the developing solution supply position P1.
The developing roller 9 holds the supplied developer 8 in a recess 9a (see FIG. 2).
(Refer to FIG. 1) and convey it to the developing position P2 (refer to FIG. 1). The developing roller 9 supplies the developing solution 8 to the photoconductor drum 1 which is arranged to face the developing position P2.

FIG. 3 is a schematic view showing how the developing solution is supplied from the developing solution supply roller to the developing roller in this embodiment. As shown in FIG. 3, the developer supply roller 10
Are arranged in contact with or close to the developing roller 9 at the developing solution supply position P1 so as to face each other. Further, a part of the developer supply roller 10 is rotated in the direction of arrow C by a driving means (not shown) while being immersed in the developer 8 in the developer tank 13, and the developer 8 is pumped up from the developer tank 13 to develop. Supply to the roller 9. The developing roller 9 rotating in the direction of the arrow B receives the supply of the developing solution 8 at the developing solution supply position P1 and holds the developing solution 8 in the recess 9a.

FIG. 4 is a schematic diagram showing how the developing solution removing blade in this embodiment removes the developing solution from the developing roller. The developer removing blade 11 is arranged above the developing roller 9 as shown in FIG. Then, as shown in FIG. 4, the developing roller 9 causes the convex portion 9b to come into contact with the tip portion of the developer removing blade 11 while the arrow B
Is moving in the direction. The developer removing blade 11 removes the unnecessary developer 8 adhering to the convex portion 9b on the surface of the developing roller 9 and scoops out a part of the upper portion of the developer 8 in the concave portion 9a to develop an appropriate amount in the concave portion 9a. While leaving the liquid 8, the excess developing liquid 18 excessively supplied to the developing roller 9 is scraped off. The scraped off excess developer 18 falls along the developing roller 9 and returns to the developer supplying roller 10. The member for removing the excess developer on the developing roller 9 is not limited to the blade-shaped member shown in FIG.
Various methods such as a method in which a roll-shaped member is disposed in contact with the developing roller 9 and the excess developer 18 is squeezed while rotating in the reverse direction can be used.

As shown in FIG. 1, the developing solution collecting roller 12 is arranged below the developing position P2 formed by the photosensitive drum 1 and the developing roller 9, and is brought into contact with the developing roller 9 by a driving means (not shown). It is driven to rotate in the direction of arrow D and scrapes off the residual developing solution on the developing roller 9. Although FIG. 1 shows a squeeze roller type developer collecting roller 12, the developer collecting roller is not limited to this type,
For example, a rotating brush type or a type in which a developing solution is sucked by a porous member such as a sponge can be used.

When the developing solution 9 supplied to the concave portion 9a of the developing roller 9 is conveyed to the developing position P2 by the rotation of the developing roller 9 thus constructed, it is held in the concave portion 9a of the developing roller 9 at the developing position P2. The developed developer 8 is the photosensitive drum 1.
Development is performed by contacting the electrostatic latent image on the top. Next, regarding the principle of this development, there are a contact type in which development is performed in a state where the photosensitive drum 1 and the developing roller 9 are in contact with each other, and a non-contact type in which development is performed in a state where these are not in contact with each other. Will be described with reference to the drawings.

FIG. 5 is a schematic diagram for explaining the developing principle in the case of the contact type. As shown in FIG. 5A, when the photosensitive drum 1 on which the electrostatic latent image is formed and the developing roller 9 holding the developing solution 8 in the recess 9a approach each other, the electrostatic charge on the photosensitive drum 1 is reduced. The latent image charge 1a induces a charge having a polarity opposite to that of the electrostatic latent image charge 1a in the developer 8 in the recess 9a. In the case of the contact type shown in FIG. 5, the developer near the wall of the concave portion 9a of the developing roller 9 closest to the electrostatic latent image charge 1a is first induced, and the induced developer is electrostatically transferred along the wall by the electrostatic capillary phenomenon. It starts moving toward the latent image (see FIG. 5B), reaches the electrostatic latent image, and contacts the electrostatic latent image charge 1a (see FIG. 5).
(C) and FIG. 5 (d)), the electrostatic latent image is developed. As a result, the electrostatic latent image charge 1a disappears and the development ends.

Next, the non-contact type will be described. In the case of the non-contact type, the developing solution in the concave portion 9a of the developing roller 9 is held depending on whether it is held in a concave shape or a convex shape. Since the method of induction is different, the non-contact type will be further described by being divided into two types, A type (concave surface) and B type (convex surface). FIG. 6 is a schematic diagram for explaining the developing principle in the case of the non-contact type A type.

In the case of the non-contact type A type, the developing roller 9
Since the inner wall surface of the recess 9a is lyophilic with respect to the developing solution, the liquid surface of the developing solution 8 in the recess 9a exhibits a concave surface as shown in FIG. 5A, as shown in FIG. The developing solution near the wall of the recess 9a is induced by the photosensitive drum 1, and the induced developing solution is attracted by the electrostatic latent image charge 1a and extends in a columnar shape toward the electrostatic latent image to form the electrostatic latent image. (See FIG. 6B), the electrostatic latent image is developed by coming into contact with the electrostatic latent image charge 1a (see FIG. 6C).

FIG. 7 is a schematic view for explaining the developing principle in the case of the non-contact type B type. In the case of the non-contact type B type, since the inner wall surface of the recess 9a of the developing roller 9 is liquid repellent to the developer, the liquid level of the developer 8 in the recess 9a is as shown in FIG. The developer at the center of the concave portion 9a is induced by the photosensitive drum 1, and the induced developer is attracted by the electrostatic latent image charge 1a and extends in a columnar shape toward the electrostatic latent image. The electrostatic latent image is developed by reaching the electrostatic latent image (see FIG. 7B) and coming into contact with the electrostatic latent image charge 1a (see FIG. 7C).

Generally, in the non-contact type developing method, since the developing distance between the electrostatic latent image charge 1a and the developer 8 in the recess 9a of the developing roller 9 is long, a developing bias is applied to the developing roller 9. Often need to do. In the present embodiment as well, a developing bias for that purpose is applied to the developing roller 9. However, in the present embodiment, the developing bias is attracted to the concave portion 9a of the developing roller 9 and the developing bias is securely held in the concave portion 9a. It is also used as a bias voltage for sucking the developing solution.

FIG. 8 is an explanatory view of a bias voltage applying means for applying a developing bias / developing liquid attracting bias voltage to the developing roller. In the developing roller 9 of the present embodiment, the base is made of a conductive material, and the surface of the base is coated with an insulating material. The bias voltage applying means 14 applies the developing bias / developing liquid attracting bias voltage to the substrate. The bias voltage is applied at the same time that the developing solution is supplied from the developing solution supply roller 10 to the developing roller 9, and the electrostatic latent image on the photosensitive drum 1 is at the developing position P2 with the developing roller 9. The bias voltage is applied before entering the. In this embodiment, the bias voltage applied to the developing roller 9 is set to −
It is set to 300v. This voltage is applied to the developer supply roller 10
The developer 8 (see FIG. 7) supplied from the developing roller 9 to the developing roller 9 is induced to the recess 8a (see FIG. 7) of the developing roller 9.
Is a bias voltage required to attract the toner, and below this, a sufficient developer suction effect cannot be obtained.

In the present embodiment, the bias voltage applied to the developing roller 9 also serves as the developing bias as described above, and the electrostatic latent image is selectively developed by the potential difference between the electrostatic latent image charge and the developing bias. To do. The above bias voltage is applied to the developer 8 in the recess 9a of the developing roller 9 under the experimental conditions.
(See FIG. 7) This is a bias voltage required for inducing the electrostatic latent image on the photoconductor drum 1 because the developing condition changes depending on the physical properties of the developer 8 and the electrostatic latent image charge on the photoconductor drum 1. Problems such as fogging may occur depending on the amount of image charge and background charge. As a solution in that case, there is a method of applying a bias to the developing solution supply roller 10 side to accelerate the movement of the developing solution to the developing roller 9.

In this way, the developing solution 8 (see FIG. 7) supplied from the developing solution supply roller 10 is accurately supplied and held in the recess 9a (see FIG. 7) on the surface of the developing roller 9, and the surface of the developing roller 9 is maintained. The unnecessary developer on the convex portion 9b is surely removed. The developing roller 9 in such a state moves to the developing position P2 (see FIG. 1), and the electrostatic latent image on the photosensitive drum 1 is developed at the developing position P2. A developed image with no background stain and no missing dots can be obtained. The developed image is carried on the photosensitive drum 1 and conveyed to the transfer position P3, and the transfer medium 1 such as paper inserted between the transfer device 5 and the photosensitive drum 1 at the transfer position P3.
Transferred to 7. The transfer is performed by the developer on the photosensitive drum 1 contacting the transfer medium 17 and permeating the transfer medium 17. The transfer medium 17 is output after being dried by a drying unit (not shown) if necessary. After the transfer is completed, the developing device 6 removes the developer adhering to the surface of the photoconductor drum 1 and the static eliminator 7 removes the charge on the surface, and then proceeds to the next image formation.

Next, a second embodiment of the liquid developing apparatus of the present invention will be described. In the second embodiment, as shown in FIGS. 3 and 4, the developing roller 9 has a lyophilic concave portion 9a surface and a lyophobic convex portion 9b surface. Therefore, the developer 8 is easily held in the concave portion 9a, and the convex portion 9b
The developer 8 is unlikely to remain in the. Therefore, as shown in FIG. 3, the supply of the developing solution 8 from the developing solution supply roller 10 to the developing roller 9 and the holding of the developing solution 8 in the recess 9a are reliably performed, and as shown in FIG. Developer removing blade 11
It is possible to prevent the developing solution from remaining on the convex portion of the developing roller 9 when the excessive developing solution is removed from the surface of the developing roller 9 by.

In order to make the surface of the convex portion 9b liquid repellent, a coating film made of a silicone liquid repellent material or a fluorine liquid repellent material is used. As a silicone-based liquid repellent material,
Examples thereof include silicone release agents, coatings of silicone oil, silicone sealant coupling agents, and the like. Examples of the fluorine-based liquid repellent materials include coatings of fluororesins and fluorine oils. . These lyophobic materials are coated on a developing roll base made of a lyophilic material with a uniform thickness, and then irregularities are formed on the surface by mechanical processing or laser processing as shown in FIG. .

In order to make the surface of the recess 9a lyophilic, the base of the developing roller 9 is made of a metal material. As the metal material, aluminum or stainless steel is preferable from the viewpoints of workability and finished dimensional accuracy of the developing roll. Next, a third embodiment of the liquid developing apparatus of the present invention will be described. FIG. 9 is a diagram showing a configuration in which a developing roller is provided with a corotron in the third embodiment, and FIG.
FIG. 6 is a diagram showing how the surface of the developing roller is charged.

The third embodiment is a modification of the first embodiment described above and further improved so that the developing solution can be easily retained in the recess of the developing roller. That is, as shown in FIGS. 9 and 10, in the third embodiment, the developing roller 9 comprises a conductive substrate 9d and a surface layer 9c made of an insulating material coated thereon. There is provided a charge applying means for applying an electric charge to the surface of the developing roller 9. A corotron 15 and a power supply 15a for the corotron 15 are provided below the developing solution supply roller 10 as charge applying means. The surface layer 9c of the developing roller 9 by the corotron 15
Is charged to the developing roller 9, and the developer is attracted to and held by the developing roller 9. The charge is applied before the developing solution is supplied from the developing solution supply roller 10 to the developing roller 9. The voltage applied to the corotron 15 is adjusted so that the surface potential of the developing roller 9 becomes 300 V or more. Under the experimental conditions of this embodiment, the developing roller 9
When the surface potential is less than 300 V, sufficient induction of the developing solution does not occur and the developing solution is not sufficiently sucked to the developing roller 9. Therefore, the surface potential of the developing roller 9 is preferably 300 V or more.

FIG. 11 is a schematic diagram showing how the developing solution is supplied from the developing solution supply roller to the developing roller in the third embodiment. Before the developing solution 8 is supplied from the developing solution supply roller 10 to the developing roller 9, the surface of the developing roller 9 is charged, and the surface of the developing roller 9 is negatively charged (FIG. 11A). The developing solution 8 attached to the developing solution supply roller 10 is instantly induced between the developing roller 9 and the developing solution supply roller 10 and sucked to the developing roller 9 side (FIG. 11).
(B)) It is held in the recess 9a of the developing roller 9 (FIG. 11 (c)). At the same time when the developing solution 8 comes into contact with the developing roller 9, the charge on the surface of the developing roller 9 disappears and the supply of the developing solution is completed. The developer 8 is held by the capillary force of the recess 9a of the developing roller 9 (FIG. 11 (d)).

Next, a fourth embodiment of the liquid developing apparatus of the present invention will be described. The fourth embodiment is a modification of the above-described third embodiment and further improved so that the developer can be easily held in the concave portion of the developing roller. In other words, in the fourth embodiment, the developing roller is formed by coating the conductive substrate only on the inner surface of the concave portion with an insulating material. An imparting means is provided.

FIG. 12 is a diagram showing how the developing roller surface is charged in the fourth embodiment. As shown in FIG. 12, the developing roller 9 is formed on the conductive substrate 9d with only the inner surface of the recess 9a covered with an insulating material. The surface layer 9c of the developing roller 9 configured as described above
Then, the electric charge is applied by the corotron 15 and the power source 15a that apply the electric charge. Even if electric charge is applied to the entire surface layer 9c by the electric charge applying means, the applied electric charge is lost immediately because the conductive convex portion 9b is grounded, and the electric charge is retained only in the insulating concave portion 9a. The timing of charge application and the charging potential of the recess 9a are the same as in the third embodiment.

The developing solution supplied from the developing solution supply roller 10 as described above is induced between the charge of the recess 9a of the developing roller 9 and the developing solution supply roller 10 as in the third embodiment. , And is attracted into the recess 9a of the developing roller 9 having an electric charge, and is held by the capillary force of the recess 9a of the developing roller 9. At the same time when the developing solution comes into contact with the developing roller 9, the charge on the surface of the developing roller 9 disappears and the supply of the developing solution ends.

Next, a fifth embodiment of the liquid developing apparatus of the present invention will be described. FIG. 13 is a diagram showing how the developing roller surface is charged and discharged in the fifth embodiment. Since the fifth embodiment is similar to the above-described fourth embodiment, differences from the fourth embodiment will be described below. In the fourth embodiment, when an electric charge is applied to the surface layer 9c of the developing roller 9 by the electric charge applying means 15,
Since the conductive protrusion 9b is grounded, most of the charge escapes through the protrusion 9b, and it may be difficult for the charge to accumulate in the insulating recess 9a.

In the fifth embodiment, the electric charges are easily accumulated in the recesses as follows. That is, as shown in FIG. 13, the developing roller 9 has a conductive base 9d and a surface layer 9c in which the inner surface of the recess 9a is made of an insulating material and the surface of the projection 9b 'is made of a photoconductive material. Therefore, in the fifth embodiment, a charge applying unit that applies an electric charge to the surface of the developing roller 9 and a light irradiating unit that irradiates the developing roller surface layer 9c charged by the charge applying unit with light. And are provided. The charge application by the charge application means (corotron 15 and power supply 15a) is the same as in the third and fourth embodiments (see FIGS. 9 to 12) described above, but the fifth embodiment includes The difference is that a static elimination lamp 16 is provided as a light irradiation means. Electric charges are uniformly applied to the concave portions 9a and the convex portions 9b 'of the developing roller 9 moving in the direction of the arrow B by the corotron 15, but when the static elimination lamp 16 arranged on the downstream side of the corotron 15 receives light irradiation. , The surface of the convex portion 9b 'made of a photoconductive material becomes conductive and the convex portion 9b'
The surface is neutralized. The recess 9a formed of an insulating material does not change its insulating property even when it is irradiated with light, and thus retains electric charges. The timing of charge application by the corotron 15 and light irradiation by the static elimination lamp 16 is determined by the developer supply roller 1
This is performed before the developer is supplied to the developing roller 9 from 0. In this way, after the light is irradiated and only the recess 9a holds the electric charge, the developing solution supply roller to the developing roller 9
The developing solution is supplied to. The developer is the recess 9 of the developing roller 9.
It is instantly induced between the electric charge of a and the developing solution supply roller, sucked into the concave portion 9a, and held by the capillary force of the concave portion of the developing roller 9. At the same time when the developing solution comes into contact with the electric charge in the recess 9a, the electric charge in the recess 9a disappears and the supply of the developing solution ends. The irradiation time of the static elimination lamp 16 is the same as the projection 9 after the light irradiation.
The irradiation time of the static elimination lamp 16 is adjusted so that the charge of b ′ becomes 0 v. The charging potential of the recess 9a is the same as in the third and fourth embodiments.

Although the roller type developing solution supplying means is used as the developing solution supplying means in each of the above-described embodiments, the developing solution supplying means is not limited to the roller type, and the slits are not limited to the roller type. Various types such as a mold and a nozzle type can be used. Further, as the charge applying means, a corona discharge type such as corotron is generally used and the constitution is easy, and it is preferable to use this, but it is not necessarily limited to only the corotron. For example, a corona discharge type using an ion flow, a solid state discharge, a dicorotron, a scorotron, a conductive brush or the like can be used as the non-contact type charge giving means. As the contact-type charge applying means, various methods such as a corona discharge type using a conductive roller, an injection charging type using a conductive brush, and a friction charging type using an insulating brush can be used.

[0045]

As described above, according to the liquid developing apparatus of the present invention, the developing solution supplying means for supplying the developing solution to the developing roller and the developing apparatus having a plurality of concave and convex portions on the surface thereof are supplied. Since the developing roller that holds and conveys the liquid in the concave portion and the bias voltage applying unit that applies the bias voltage to the developing roller are provided, the developing liquid supplied to the developing roller is reliably supplied to the developing roller, and the concave portion Securely held in
Further, the developer does not remain on the convex portion on the surface of the developing roller.
Therefore, it is possible to obtain a developed image without missing dots or background stains on the electrostatic latent image carrier after development.

When a developing roller having a concave surface and a convex surface which are relatively lyophilic and liquid repellent, respectively, is used, the developing solution easily enters and is retained in the concave due to the capillary phenomenon. The developing solution adhering to the convex portions is easily removed by the developing solution removing means, and the developing solution is prevented from remaining on the convex portions, so that a developed image without missing dots or background stains can be obtained.

A developing roller comprising a conductive substrate and a surface layer made of an insulating material coated thereon is used, and
When the surface layer of the developing roller is provided with a charge applying means for applying an electric charge, the charge applying means can be configured by a simple method by the conventional charging technique, and it is effective for holding the developer in the concave portion. Further, a developing roller is used, in which only the inner surface of the recess is covered with an insulating material on a conductive substrate, and the charge is applied by the charge applying means before the developing solution is supplied from the developing solution supply roller to the developing roller. When given, the electric charge is easily retained in the concave portion, and the electric charge allows the developer to be electrically drawn into the concave portion of the developing roller. Since the defective supply of the developing solution to the concave portion of the developing roller and the defective holding due to the defective holding can be prevented, a developed image without missing dots or background stain can be obtained.

Further, a developing roller having a surface layer having an inner surface of a concave portion made of an insulating material and a surface of the convex portion made of a photoconductive material on a conductive substrate is used, and an electric charge is applied to the surface layer of the developing roller. In the case where the charging roller is provided with an electric charge applying means for irradiating the developing roller surface layer to which the electric charge is applied by the electric charge applying means, light is uniformly applied to the developing roller surface, Since the charges are removed and only the charges in the recesses act on the developer, the supply and retention of the developer in the recesses are more reliable, and a developed image free from missing dots and background stains can be obtained.

When the charge applying means is constituted by a corotron having a simple structure, the charge applying means can be simply constructed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment in which a liquid developing apparatus of the present invention is incorporated as a developing unit of a wet image forming apparatus.

FIG. 2 is a plan view showing a surface structure of a developing roller used in this embodiment and a sectional view taken along the line AA.

FIG. 3 is a schematic diagram showing how the developing solution is supplied from the developing solution supply roller to the developing roller in the present embodiment.

FIG. 4 is a schematic diagram showing a state in which the developing solution on the developing roller is removed by the developing solution removal blade in the present embodiment.

FIG. 5 is a schematic diagram for explaining a developing principle in the case of a contact type.

FIG. 6 is a schematic diagram for explaining a developing principle in the case of a non-contact type A type.

FIG. 7 is a schematic diagram for explaining a developing principle in the case of a non-contact type B type.

FIG. 8 is an explanatory diagram of a bias voltage applying unit that applies a developing bias / developing solution suction bias voltage to the developing roller.

FIG. 9 is a diagram showing a configuration in which a developing roller is provided with a corotron in the third embodiment.

FIG. 10 is a diagram showing how the surface of the developing roller is charged.

FIG. 11 is a schematic diagram showing how the developing solution is supplied from the developing solution supply roller to the developing roller in the third embodiment.

FIG. 12 is a diagram showing how the developing roller surface is charged in the fourth embodiment.

FIG. 13 is a diagram showing how the developing roller surface in the fifth embodiment is charged and discharged.

FIG. 14 is a diagram showing a state in which a developing solution is held in a concave portion of a developing roller having an uneven surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 1a Electrostatic latent image charge 2 Charging device 3 Exposure device 4 Liquid developing device 6 Cleaning device 7 Static eliminator 8 Developer 9 Developing roller 9a Recesses 9b and 9b 'Convex portion 9c Surface layer 9d Substrate 10 Developer supplying roller 14 bias voltage applying means 15 corotron 15a power supply 16 static elimination lamp

Claims (6)

[Claims] 1. A liquid developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier with a developing solution, the surface having a plurality of recesses and protrusions at a predetermined developing solution supply position. A developing roller is supplied and the supplied developing solution is conveyed to a predetermined developing position and comes into contact with the electrostatic latent image carrier at the developing position; and the developing roller is provided with the developing solution at the developing solution supplying position. A liquid developing apparatus comprising: a developing solution supplying unit that supplies the developing roller; and a bias voltage applying unit that applies a bias voltage to the developing roller when the developing solution is supplied to the developing roller by the developing solution supplying unit. 2. The liquid developing apparatus according to claim 1, wherein the developing roller has a concave surface and a convex surface, which are relatively lyophilic and liquid repellent, respectively. 3. The developing roller comprises a conductive base material and a surface layer made of an insulating material coated on the conductive base material, and is provided with a charge applying means for applying an electric charge to the surface of the developing roller. The liquid developing device according to claim 1, wherein 4. The developing roller is composed of a conductive substrate and only the inner surface of the recess is covered with an insulating material. The developing roller is provided with a charge applying means for applying an electric charge to the surface of the developing roller. The liquid developing device according to claim 1, wherein 5. The developing roller comprises a conductive substrate and a surface layer having an inner surface of the concave portion made of an insulating material and a surface of the convex portion made of a photoconductive material on a conductive base. 2. The liquid developing apparatus according to claim 1, further comprising: a charge applying unit for applying a charge to the surface, and a light irradiating unit for irradiating the surface of the developing roller, to which the charge is applied by the charge applying unit, with light. apparatus. 6. The liquid developing apparatus according to claim 3, wherein the charge applying unit is a corotron.