JPH112965A - Liquid developing device - Google Patents

Abstract

(57) [Problem] To provide a high-definition liquid developing apparatus that can use an aqueous liquid developer and has little fogging and background fouling. SOLUTION: The receding contact angle β of the liquid developer 10 in the non-electrostatic latent image portion on the surface of the photosensitive drum 2 is set to be larger than the receding contact angle α of the liquid developer 10 in the electrostatic latent image portion. The liquid developer 10 adheres only to the electrostatic latent image portion, and a high-definition image with little fog and background smear can be obtained.

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 a high-definition image using a liquid developer.

[0002]

2. Description of the Related Art In a conventional liquid developing apparatus, toner fine particles dispersed in an insulating liquid carrier such as an aliphatic saturated hydrocarbon are selectively electrophoretically transferred onto a dielectric surface on which an electrostatic latent image is formed. The method of attaching to the mainstream was the mainstream. This method is suitable for obtaining a high-resolution image because the toner particles can be set smaller than a developing device using a powder toner. Further, the liquid toner has an advantage that the energy required for fixing is smaller than that of the powder toner. However, the aliphatic saturated hydrocarbon used as the liquid carrier generates an unpleasant odor, and is not suitable for use in offices and homes. In contrast, Shoko 4
As shown in JP-A-6-41349, a liquid developing apparatus using a selective wet development method using a liquid developer containing water as a main component has been devised. A liquid developing device using an aqueous liquid developer like this liquid developing device can solve the problem of odor, and is an inexpensive material, which is advantageous in cost.

[0003]

However, in the liquid developing apparatus using the conventional selective wet developing method, the change in wettability between the liquid developer and the surface of the photoreceptor is utilized. And no clear criteria were given for their definitions. Therefore, the developer remains even in a region having poor wettability, and the developer adheres to the non-image portion, which is a main factor of image deterioration such as bleeding and fogging. Conversely, in the lyophilic region, the amount of the developer adhered may become insufficient, and image deterioration such as white spots may occur in the image area.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and clarifies the lyophilic and lyophobic standards in the selective wet development method, thereby preventing image deterioration and preventing water deterioration. It is an object of the present invention to provide a high-quality liquid developing apparatus that can use the liquid developer of the present invention.

[0005]

In order to achieve this object, a liquid developing apparatus according to the first aspect of the present invention comprises a liquid developer in which a coloring component such as a dye or pigment is dissolved or dispersed in a liquid. An image carrier capable of forming a latent image to which the liquid developer can be attached on a surface portion, and forming an image by attaching the liquid developer to a portion where the latent image is formed. In particular, the receding contact angle of the liquid developer in the non-latent image portion of the image carrier surface is larger than the receding contact angle of the liquid developer in the latent image portion of the image carrier surface. It is configured to be. Therefore, the liquid developer is easy to peel off at the non-latent image portion on the surface of the image carrier, and has high adhesion at the latent image portion on the surface of the image carrier. Image can be formed.

[0006] The liquid developing device according to claim 2 is
The receding contact angle of the liquid developer at a non-latent image portion on the surface of the image carrier is configured to be about 60 degrees or more and less than 180 degrees. Therefore, the residual ratio of the liquid developer adhered to the non-latent image portion of the image carrier can be set to 1% or less, and the occurrence of fogging and background contamination can be prevented.

[0007] The liquid developing apparatus according to claim 3 is
The receding contact angle of the liquid developer at the latent image portion on the surface of the image carrier is configured to be 0 degree or more and about 30 degrees or less. Therefore, the amount of the liquid developer adhering to the latent image portion of the image carrier can be sufficiently increased, so that an image having high density and excellent contrast can be formed.

The liquid developing device according to claim 4 is
The surface portion of the image carrier is made of a material capable of forming the latent image by changing the surface tension by light irradiation or heating. Therefore, the latent image portion and the non-latent image portion can be formed by selectively irradiating or heating the surface of the image carrier with light to change the surface tension.

Further, the liquid developing device according to the present invention is characterized in that:
A surface portion of the image carrier is made of a material capable of forming the latent image by changing a surface tension by a surface charge. Therefore, the latent image portion and the non-latent image portion can be formed by selectively applying a surface charge to the surface of the image carrier to change the surface tension.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the liquid developing device of the present embodiment will be described with reference to FIG.

A liquid developing device 1 according to the present embodiment includes a photosensitive drum 2 having a photoconductive material applied to a surface thereof, and a developing roller disposed close to or in contact with the photosensitive drum 2 at a position facing the photosensitive drum 2. 3, a supply roller 4 that is arranged to rotate while being in contact with the developing roller 3, and is arranged to rotate while being in contact with the developing roller 3; The main component is a doctor roller 5 that adjusts the amount of the agent 10 to an appropriate amount.
The liquid developing device according to the present embodiment can use a solution containing water as a main component as the liquid developer 10, and has a higher odor than a conventional liquid developer containing an aliphatic saturated hydrocarbon as a main component. This is advantageous in terms of the environment such as the above, or the industrial aspect due to the low material cost. Incidentally, the photosensitive drum 2
Is a component of the image carrier of the present invention.

As a photoconductor material used for the photoconductor drum 2, an organic photoconductor generally called OPC can be used. In the liquid developing device of the present embodiment, the wettability is set by adjusting the receding contact angle between the developer 10 and the surface of the photosensitive drum 2. The receding contact angle refers to a contact angle measured after gently removing a part of the droplet adhered on the solid surface with a syringe or the like.

The receding contact angle can be set by, for example, selecting an appropriate binder resin for the photoconductor or dispersing a fluorine resin or a silicone resin in the photoconductor.
It can be performed by adjusting the surface tension of the photoconductor. The receding contact angle can also be adjusted by thinly coating the surface of the photoreceptor with a resin layer also serving as a protective layer.

On the surface of the photosensitive drum 2 on which the photoconductive material is applied, a desired electrostatic latent image, that is, a potential higher than the surroundings (or a potential) is provided by a charger (not shown) and selective exposure means. (Low) region is created and retained. When the liquid developer 10 is supplied to the surface of the photosensitive drum 2, the liquid developer 10 adheres only to the area where the electrostatic latent image is formed.

FIG. 2 shows the receding contact angles of the electrostatic latent image portion on the surface of the photosensitive drum 2 and other portions (non-electrostatic latent image portion) when the liquid developer 10 is applied. FIG. Receding contact angle α in the electrostatic latent image portion
And the receding contact angle β in the non-electrostatic latent image portion, β> α
It is set to satisfy the relationship. Incidentally, the electrostatic latent image is a latent image to which the liquid developer can be attached in the present invention,
The electrostatic latent image portion corresponds to a latent image portion, and the non-electrostatic latent image portion corresponds to a non-latent image portion.

Here, the phenomenon that the liquid developer 10 adheres only to the area of the surface of the photosensitive drum 2 where the electrostatic latent image is formed will be described.

The liquid developer 10 is applied to the photosensitive drum 2
When dropped on the surface, a so-called wetting phenomenon occurs in which the developer 10 occupies a certain area on the surface of the photosensitive drum 2 and adheres. This wetting phenomenon is related to the surface tension of the liquid and the contact angle between the liquid and the solid. When the contact angle is small, the degree of adhesion of the liquid is large, while when the contact angle is large. Has a relationship that the degree of adhesion of the liquid is small. At this time, the amount of adhesion remaining when removing the developer once contacted has a stronger relationship with the receding contact angle than with the advancing contact angle. Usually, when simply referred to as a contact angle, it often indicates an advancing contact angle, which is a contact angle measured with a droplet attached. On the other hand, the receding contact angle is
As described above, this is a contact angle measured after a part of the attached droplet is gently removed with a syringe or the like. The larger the receding contact angle, the easier the droplet is to remove, and the smaller the amount of the droplet remaining. The receding contact angle differs depending on the combination of the developer 10 and the surface of the photosensitive drum 2 as in the case of the advancing contact angle.

FIG. 3 shows that the developer 10 is once adhered to the surface of the photosensitive drum 2 and then the developer 10 is removed.
An experiment was performed in which the measurement was performed while changing the receding contact angle by changing the combination with the surface, and the relationship between the receding contact angle and the residual adhesion rate (the ratio of the remaining amount of the developer to the amount of the adhered developer) was determined. It is a graph which shows a result.

According to this graph, the receding contact angle is about 60
Above the degree, the residual adhesion ratio was 1% or less, and it was found that almost no residue remained. Then, as the receding contact angle approaches 180 degrees, the shape of the droplet becomes closer to a sphere, and the residual adhesion rate approaches 0%. However, a receding contact angle of 180 degrees cannot be realized in practice because it means that the liquid droplets float above the solid surface.

On the other hand, when the receding contact angle was about 30 degrees or less, the adhesion residual ratio was 50% or more, and a sufficient image density could be obtained. Then, as the receding contact angle approaches 0 degree, the shape of the droplet becomes flatter, and the residual adhesion ratio becomes 100%.
Will approach. Note that the receding contact angle of 0 degrees means that the solid surface is completely wet.

Therefore, in the non-electrostatic latent image portion, which is a non-image portion, the receding contact angle is set to about 60 degrees or more and less than 180 degrees,
By setting the receding contact angle in the electrostatic latent image portion, which is the image portion, to 0 degree or more and about 30 degrees or less, it is possible to form an image with sufficient density without fogging or contamination.

Experiments have also shown that the receding contact angle varies depending on the surface potential of the solid. FIG. 4 shows the receding contact angle when an aqueous liquid developer is dropped on the surface of the organic photoconductor using the organic photoconductor material used for the photoconductor drum 2 as a solid, and the surface potential of the organic photoconductor. 6 is a graph showing a result of an experiment in which measurement is performed while changing the measurement, and is a graph showing a relationship between a surface potential of the organic photoconductor material and a receding contact angle of the liquid developer. According to the experimental results, when the surface potential was changed from 0 V to 600 V, the receding contact angle changed from about 60 degrees to about 30 degrees, and the degree of the residual adhesion amount was found to be large. It should be noted that this change in the receding contact angle is not related to the polarity of charging, as is clear from the fact that the receding contact angle also changes when the surface potential is negative.

In this experiment, the organic photoreceptor material was adjusted by the above-mentioned means so that the receding contact angle with the liquid developer was 60 degrees or more when not charged, that is, at a surface potential of 0 V. Further, the receding contact angle is set to be reduced by about 30 degrees due to the charging of about 600 V, so that the receding contact angle becomes 30 degrees. As described above, the degree of adhesion of the liquid developer 10 on the photosensitive drum 2 can be controlled by the surface potential.
Therefore, an electrostatic latent image is formed on the surface of the photosensitive drum 2, and the liquid developer 10 can be adhered to a region where the electrostatic latent image is formed.

The developing roller 3 is provided to supply an appropriate amount of the liquid developer 10 to the surface of the photosensitive drum 2, and the surface of the developing roller 3 is provided with a large number of fine holes 6 as shown in FIG. Is formed like a minute pocket for holding FIG. 6 is an enlarged sectional view of the surface of the developing roller 3. Here, when the aqueous liquid developer 10 is used, the surface portion 7 of the fine hole 6 is hydrophilic, and the surface portion 8 of the developing roller other than the fine hole 6 is hydrophobic. With this configuration, the liquid developer 10 is satisfactorily held in the fine holes 6, and the liquid developer 10 does not adhere to the developing roller surface 8 other than the fine holes 6. For this reason, the liquid developer 10 is divided by the fine holes 6, and the liquid developers 10 in each of the fine holes 6 independently contact the photosensitive drum 2. Therefore, the liquid developer 10 in each of the fine holes 6 is not affected by the liquid developer 10 in each of the other fine holes 6, and the liquid developer 10 is selected in a region having good wettability formed by the electrostatic latent image. Can be adhered. Further, since the excess liquid developer 10 does not adhere to the surface 8, the developer does not adhere to the surface of the photosensitive drum 2 other than the image portion, and the background portion can be prevented from being stained or blurred.

In the above description, the adhesion of the liquid developer 10 to the portion of the electrostatic latent image has been described by the phenomenon of wetting. However, the liquid developer 10 is attracted by the electrostatic force of the electrostatic latent image. Act on. That is, the liquid developer 10 is divided and held in each of the fine holes 6 of the developing roller 3, so that the liquid developer 10 can be easily attracted by electrostatic force.

For the above reasons, according to this structure, the resolution can be set very high. That is, it is understood that the smaller the pitch of the fine holes 6, the higher the image resolution. In general, in order to print character data and image data as a printer, it is desirable that at least the diameter of the fine hole 6 is about 100 μm or less. Also, the fine holes 6
In consideration of the fact that has a function of holding the liquid developer 10, a sufficient amount of the liquid developer 10 cannot be held unless its diameter is about 1 μm or more. Similarly, in order to make the amount of the liquid developer 10 held in the fine holes an appropriate amount, the depth of the fine holes 6 is desirably about 1 μm to about 100 μm. That is, when the depth is about 100 μm or more, 1
The amount of the liquid developer 10 per dot becomes too large, and the possibility of occurrence of bleeding increases, leading to degradation of resolution. Conversely, if the depth of the fine holes 6 is about 1 μm or less, a sufficient amount of the liquid developer 10 cannot be held.

Next, a method of forming the fine holes 6 on the developing roller 3 will be described. As described above, the surface portion 7 of the fine hole 6 is hydrophilic, and the surface portion 8 of the developing roller other than the fine hole 6 is formed.
Is made to be hydrophobic. Several methods are conceivable as a method for producing this shape.

The first method is a method of manufacturing by photoelectroforming. Photoelectroforming is a method of applying a photoresist, exposing the photoresist using a mask, selectively removing the exposed photoresist, and selectively plating only the areas where the photoresist has been removed. It is. By this manufacturing method, except for the fine holes 6 only, if other portions are plated with a hydrophilic metal, the fine holes can be formed with high accuracy. A desired shape can be formed by forming a fine hole by plating, coating a hydrophobic resin such as a fluorine resin or a silicon resin, and then removing the remaining photoresist. That is, the surface 7 of the fine holes is a hydrophilic metal surface, and the developing roller surface 8 other than the fine holes is formed of a hydrophobic resin. In this manufacturing method, it is possible to plate directly on the developing roller 3, but it is also possible to fix the sheet-like metal having the fine holes 6 formed on the surface of the developing roller 3.

The second method is to form fine holes 6 by etching.
It is a method of forming. In this method, the base material of the developing roller 3 is formed of a hydrophilic metal, and the metal surface is selectively etched to form the fine holes 6. Further, after filling a fine hole by applying a photoresist, polishing is performed until a metal surface other than the fine hole is uniformly exposed. In addition, after coating a hydrophobic resin such as fluororesin or silicone resin, by removing the remaining photoresist,
A desired shape can be produced. That is, the surface 7 of the fine holes is a hydrophilic metal surface, and the developing roller surface 8 other than the fine holes is formed of a hydrophobic resin. In this manufacturing method, it is possible to plate directly on the developing roller, but it is also possible to fix the sheet-like metal having the fine holes 6 formed on the surface of the developing roller.

By the above-described method, the developing roller 3 having the desired size of the fine holes 6 can be manufactured.

The supply roller 4 is installed so that a part thereof is inserted into the liquid developer 10 stored in the developer container 9. The supply roller 4 has a surface made of a water-absorbing material such as a foam material so as to hold the liquid developer 10 and sufficiently supply the liquid developer 10 to the surface of the developing roller 3. With this configuration, the supply roller 4 absorbs the liquid developer 10 in the developer container 9 and then fills the liquid developer 10 so as to fill all the fine holes 6 on the surface of the developing roller 3 rotating while being in contact with each other. Supply 10

The doctor roller 5 has a surface formed of a material having a higher hydrophobicity than the surface 7 of the fine holes 6 and a higher hydrophilicity than the surface 8 other than the fine holes 6, and rotates while contacting the developing roller 3. I have. Here, the linear velocity on the surface of the doctor roller 5 is set to a value different from the linear velocity on the surface of the developing roller. With this configuration, the doctor roller 5 can remove only the liquid developer 10 on the surface 8 of the developing roller 3 while leaving only the liquid developer 10 in the fine holes 6 of the developing roller 3. Thereby, the developing roller 3 is provided only in the fine holes 6,
The divided developer 10 is held.

Next, the operation of the liquid developing apparatus 1 of the present invention will be described in order.

First, the photosensitive drum 2 is uniformly charged to a potential of about 600 V by a charger (not shown), for example, a scorotron charger. Next, exposure is selectively performed by an exposure device (not shown), for example, an optical scanning device including a semiconductor laser and a polygon scanner. The exposed area of the surface of the photoreceptor drum 2 loses electric charge and has a potential of 0
V to about 100V. Here, since the receding contact angle is small in the region where the potential is high on the surface of the photosensitive drum 2 and the receding contact angle is large in the region where the potential is low, the liquid developer 10 can be attached only to the region where the potential is high. In parallel with this operation, the supply roller 4 supplies the liquid developer 10 in the developer container 9 to the surface of the developing roller 3. The developing roller 3 is in a state in which the fine holes 6 are sufficiently filled with the liquid developer 10 and the surplus liquid developer 10 is also applied to the surface 8. Thereafter, the doctor roller 5 rotates in contact with the developing roller 3, thereby removing the excess liquid developer 10.

Next, the developing roller 3 holding only an appropriate amount of the liquid developer 10 comes into contact with the photosensitive drum 2 so that
Liquid developer 1 only in the region where the potential is high and the receding contact angle is small
0 selectively adheres. Further, in the region where the potential is low and the receding contact angle is large, the liquid developer 10 hardly adheres as described above, so that fogging and background contamination are hardly generated. Through the above-described series of operations, the electrostatic latent image on the photosensitive drum 2 is developed by the liquid developer 10. The image developed on the photoreceptor drum 2 is transferred to a desired recording sheet, thereby becoming a final recorded image.

As is clear from the above description, in the liquid developing apparatus of the present embodiment, the wettability is clearly set by the index of the receding contact angle, and the design and selection of the photosensitive material and the liquid developer are performed. Therefore, a highly reliable liquid developing device can be supplied.

The present invention is not limited to the embodiment described in detail above, and various modifications can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the development process using the photosensitive drum 2 has been described. However, a recording medium in which the above-described photoconductive material is applied to a sheet may be used. In this case, transfer is not required, and the image on the recording medium can be the final recorded image.

Further, in the above-described embodiment, a region having a small receding contact angle is formed by an electrostatic latent image. However, the receding contact angle changes only by light irradiation as an image carrier (ie, the wettability is improved). A similar effect can be obtained by using a material which is worse or worse). As such a material, for example, a spiropyran compound which is photoisomerized as described in JP-B-62-7930 is known. By applying such a material to the surface of the drum, a region having a small receding contact angle can be selectively formed only by light irradiation, and the liquid developer 10 can be adhered to the region and developed. According to this method, since there is no need to perform charging in advance, there is an advantage that a charger and a high-voltage power supply are not required.

It is also possible to use a material whose receding contact angle changes with temperature as the image carrier. In this method, a material having a small receding contact angle can be produced by applying a material whose wettability changes depending on the temperature to the drum surface and selectively heating the material with a thermal head. This method does not require a charger and an exposure device, but instead requires a selective heating device such as a thermal head.

It is also possible to use a magnetic material whose receding contact angle changes depending on the direction of the magnetic moment as the image carrier. In this method, a magnetic material whose receding contact angle changes according to the direction of the magnetic moment is applied to the drum surface, and the direction is selectively changed by a magnetic head, whereby a region having a small receding contact angle can be produced. In this scheme,
Although a device for selectively generating a magnetic field such as a magnetic head is required, a charger and an exposure device are not required.

In the above embodiment, the photosensitive drum 2
Although the electrostatic latent image is formed by charging the surface with a charger and selectively performing exposure, the electrostatic latent image is formed directly on the dielectric drum by an ion flow head or the like. It is also possible.

In the above-described embodiment, the aqueous liquid developer 10 which is more desirable in terms of environment is used. However, the present invention is not limited to this, and a liquid developer mainly containing an organic solvent can be used. is there.

[0044]

As is apparent from the above description,
The liquid developing device according to claim 1, wherein the receding contact angle of the liquid developer on the non-latent image portion on the surface of the image carrier is such that the receding contact angle of the liquid developer on the latent image portion on the surface of the image carrier is reduced. Because it is configured to be larger than the corner,
The liquid developer is easy to peel off at the non-latent image portion on the surface of the image carrier, and has high adhesion at the latent image portion on the surface of the image carrier. Can be formed.

Further, the liquid developing device according to claim 2 is
Since the receding contact angle of the liquid developer in the non-latent image portion on the surface of the image carrier is configured to be approximately 60 degrees or more and less than 180 degrees, the liquid in the non-latent image portion of the image carrier is The adhesion residual ratio of the developer can be set to 1% or less, and generation of fogging and background stain can be prevented.

The liquid developing device according to claim 3 is
Since the receding contact angle of the liquid developer at the latent image portion on the surface of the image carrier is configured to be 0 degree or more and about 30 degrees or less, the liquid developer at the latent image portion of the image carrier is Can be sufficiently increased, and an image having a high density and excellent contrast can be formed.

The liquid developing device according to claim 4 is
Since the surface portion of the image carrier is formed of a material capable of forming the latent image by changing the surface tension by light irradiation or heating, the surface of the image carrier is selectively irradiated with light. Alternatively, the latent image portion and the non-latent image portion can be formed by changing the surface tension by heating. In addition, since it is not necessary to use a charger or a high-voltage power supply, the entire apparatus can have a simple configuration.

The liquid developing device according to claim 5 is
Since the image carrier has a surface portion made of a material capable of forming the latent image by changing a surface tension by a surface charge, the surface portion is selectively provided with a surface charge on the surface of the image carrier. The latent image portion and the non-latent image portion can be formed by changing the tension. In addition, using the conventional electrophotographic method, easily and efficiently,
In addition, a highly reliable liquid developing apparatus capable of reversibly controlling the receding contact angle can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid developing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating receding contact angles in an electrostatic latent image portion and a non-electrostatic latent image portion.

FIG. 3 is a graph showing the relationship between the receding contact angle and the amount of developer attached.

FIG. 4 is a graph showing a relationship between a surface potential and a contact angle.

FIG. 5 is a perspective view illustrating a schematic configuration of a developing roller.

FIG. 6 is an enlarged sectional view of the surface of a developing roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid developing device 2 Photoreceptor drum 3 Developing roller 6 Micropore 7 Micropore surface 8 Developing roller surface 10 Liquid developer

Claims (5)

[Claims] 1. A liquid developer in which a coloring component such as a dye or a pigment is dissolved or dispersed in a liquid, and an image carrier capable of forming a latent image to which the liquid developer can be attached on a surface portion. A liquid developer that adheres the liquid developer to a portion where the latent image is formed to form an image, wherein a receding contact angle of the liquid developer in a non-latent image portion on the surface of the image carrier is Wherein the liquid developer is configured to be larger than a receding contact angle of the liquid developer at a latent image portion on the surface of the image carrier. 2. The liquid developer according to claim 1, wherein a receding contact angle of the liquid developer at a non-latent image portion on the surface of the image carrier is about 60 degrees or more and less than 180 degrees. The liquid developing device according to claim 1. 3. The liquid developer according to claim 1, wherein a receding contact angle of the liquid developer at a latent image portion on the surface of the image carrier is not less than 0 degrees and not more than about 30 degrees. The liquid developing device according to item 1. 4. The image carrier according to claim 1, wherein a surface portion of the image carrier is formed of a material capable of forming the latent image by changing surface tension by light irradiation or heating. 4. The liquid developing device according to any one of 3. 5. The image carrier according to claim 1, wherein a surface portion is formed of a material capable of forming the latent image by changing a surface tension by a surface charge. A liquid developing device according to any one of the above.