JP2000089575A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus capable of sufficiently expressing gradation by a high-definition image using fine dots and stably forming a solid image. A photosensitive drum (102) and a photosensitive drum (1)
02, a developer holding member 103 arranged to rotate in conjunction with the surface of the photosensitive drum 102, a charger 106 for uniformly charging the surface of the photosensitive drum 102, and selectively exposing based on image information. Selective exposure means 107 as exposure means
And the liquid developer 13 formed on the photosensitive drum 102
Transfer roller 109 for transferring an image based on 0 to the recording paper PP
And a second unit 200 having a similar configuration.
The diameters of the dots constituting the image are controlled by changing the outputs of 6,206, and an image is formed by a unit that forms an image with a small dot diameter and a unit that forms an image with a large dot diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming and developing a high-gradation image at high speed using a liquid developer.

[0002]

2. Description of the Related Art In a conventional image forming apparatus using a liquid developer, toner fine particles dispersed in an insulating liquid carrier such as an aliphatic saturated hydrocarbon are deposited on a dielectric surface on which an electrostatic latent image is formed. The method of selectively attaching by electrophoresis 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 undesired odor, may cause a fire, and needs to be dried after image formation, and thus is not suitable for use in offices and homes. .

On the other hand, in Japanese Patent Publication No. 55-18906, a water-soluble developer is held in fine holes of a developer holding member without wetting the entire surface of the latent image forming member with a liquid developer. There has been proposed an apparatus using a method in which a developer is adhered to an electrostatic latent image surface in close proximity and a developer is selectively attached to perform development. With this apparatus, there is no odor and there is no need to dry after image formation.

In such an image forming method, the formed electrostatic latent image is not allowed to adhere to the liquid developer held by the developer holding member having the fine holes in order to develop the electrostatic latent image. Therefore, the definition of an image that can be formed depends on the fine pitch of the arrangement of the fine holes. Therefore, when a coarse mesh is used, only an image whose gradation cannot be sufficiently expressed can be formed. In order to form an image with a high-definition dot pitch so that gradation can be expressed, it was necessary to provide a developer holding member having a fine hole with a fine pitch corresponding to this to perform development. .

[0005]

However, if micro holes having an extremely fine pitch are used in order to obtain a gradation of an image, the opening area of the micro holes becomes small. Therefore, the amount of the liquid developer that can be held in the fine holes is also reduced. for that reason,
The liquid developer, which has no continuous blank portion and can form a so-called solid image stably, cannot be held in the fine holes, and the sufficient liquid developer cannot be adhered to the image carrier. There is a problem that a solid image cannot be formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to sufficiently express gradation by using a high-definition image formed by fine dots, but to obtain a solid image in which a liquid developer is sufficiently adhered. It is an object of the present invention to provide an image forming apparatus capable of stably forming an image and thereby forming a high-quality image.

[0007]

In order to achieve this object, an image forming apparatus according to the first aspect of the present invention comprises an exposing means for selectively exposing to form an electrostatic latent image. A developer holding member for holding a liquid developer in which a coloring component such as a dye or a pigment is dissolved or dispersed in a liquid and a plurality of fine holes are penetrated, and the developer holding member is disposed to face the developer holding member; Forming an electrostatic latent image capable of adhering the liquid developer selectively to the surface by being exposed to the liquid developer; and applying the liquid developer held in the corresponding fine holes of the developer holding member to the electrostatic latent image. An image comprising: an image carrier that adheres to form an image clarified from an electrostatic latent image and carries the image; and a charger that charges the image carrier prior to formation of the electrostatic latent image on the image carrier. A plurality of forming units, wherein the plurality of units are: Characterized in that it is configured to form an image by dots of different diameters for each unit.

In the image forming apparatus having the above-described configuration, the diameters of dots forming an image formed by a plurality of image forming units can be different. Therefore, when a final image is formed using a plurality of units that form an image using dots of different diameters, a high-quality image having dot gradation can be formed.

Also, by using dots of different diameters,
With a small dot diameter, it is possible to express an intermediate tone without interference between adjacent liquid developers. On the other hand,
A large dot diameter where the amount of liquid developer per attached area is large and where the liquid developer cannot adhere to the electrostatic latent image;
A so-called solid image without dropping can also be expressed, and an image having gradation and good tightness can be obtained.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, the charging units of the plurality of units charge the image carrier to different potentials for each unit. It is characterized by having been constituted as follows.

In the image forming apparatus having the above-described configuration, the charging potential of the charger for charging the image carrier before the formation of the electrostatic latent image on the image carrier is different. The potentials of the latent images can be different. Therefore, the amount of liquid developer attached to the electrostatic latent image during development can be made different, and the diameter of dots formed by a plurality of image forming units can be controlled based on the difference in the amount of liquid developer attached. it can. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tightness.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the exposure means of the plurality of units includes an electrostatic latent image formed on the image carrier. It is characterized in that the dot area to be formed is different for each unit.

In the image forming apparatus having the above configuration, when an electrostatic latent image is formed by the exposure unit, the area of the electrostatic latent image can be different. Therefore, the charge amount per dot can be changed to make the amount of the liquid developer adhered to the electrostatic latent image at the time of development different, and from the difference in the amount of the liquid developer adhered, a plurality of image forming units can be formed. Dot diameter can be controlled. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tightness.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the developer holding members of the plurality of units may be configured such that the fine particles penetrated by the developer holding members. The arrangement pitch of the holes is configured to be different for each unit.

In the image forming apparatus having the above-described configuration, by making the arrangement pitch of the fine holes penetrated through the developer holding member different, dots having a small diameter are formed by the developer holding member having a fine pitch. The dot diameter can be controlled so that a large-diameter dot is formed by a coarse developer holding member. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tightness.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the developer holding members of the plurality of units may be configured such that the fine particles penetrated by the developer holding members. The opening area of the hole is configured to be different for each unit.

In the image forming apparatus having the above-described configuration, by making the opening areas of the fine holes penetrated through the developer holding member different, dots having a small diameter are formed by the developer holding member having a fine pitch. The dot diameter can be controlled so that a large-diameter dot is formed by a coarse developer holding member. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tightness.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the developer holding members of the plurality of units may be configured such that the fine particles penetrate the developer holding members. The wall surface of the hole is configured to have a different shape for each unit so that the distance between the liquid surface of the liquid developer held in the microhole and the surface of the image carrier during development is different. It is characterized by.

In the image forming apparatus having the above structure, the shape of the wall surface of the fine hole is changed, and the angle of the wall surface is changed, so that the position of the liquid surface of the liquid developer which is maintained at an energy stable position can be adjusted. Can be controlled. Therefore, even if an electrostatic latent image under the same conditions is formed on the image carrier during development, the distance between the liquid surface and the image carrier is different, so that the amount of the liquid developer attached can be made different. Further, the size of the dot diameter can be controlled by the difference. Therefore,
From the difference in the dot diameter, it is possible to obtain an image having a gradation and a good compactness.

According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the developer holding members of the plurality of units may be configured such that the fine particles penetrated by the developer holding members. The water repellency of the wall surface of the hole is configured to be different for each unit.

In the image forming apparatus having the above structure, the material of the wall surface of the fine holes is made different, or the water repellency is changed by applying a coating, so that the liquid level of the liquid developer which is held at a stable position in terms of energy can be maintained. Can be controlled. Therefore, even if an electrostatic latent image under the same conditions is formed on the image carrier during development, the distance between the liquid surface and the image carrier is different, so that the amount of the liquid developer attached can be made different. Further, the size of the dot diameter can be controlled by the difference. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tightness.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus 1 according to a preferred embodiment of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a schematic diagram schematically illustrating the configuration of the image forming apparatus 1 according to the present embodiment. The outline of the configuration of the image forming apparatus 1 of the present embodiment will be described with reference to FIG.

The image forming apparatus 1 performs two image forming processes of a first image forming unit 100 (hereinafter, referred to as a first unit 100) and a second image forming unit 200 (hereinafter, referred to as a second unit 200). (Hereinafter referred to as a unit). These units 100 and 200 have a common basic configuration, and differ only in a part of the structure so as to form dots having different diameters. Specifically, in the image forming apparatus 1 of the present embodiment, only the charging potential of the charger is different, and the other parts have the same configuration. The basic configuration will be described.

The first unit 100 is arranged at a position facing the photosensitive drum 102 and a photosensitive drum (image carrier) 102 capable of carrying an electrostatic latent image.
A developer holding member 103 disposed so as to rotate in conjunction with the surface of the developer holding member 103; a developer supply foaming member 104 disposed inside the developer holding member 103; The foam material 1 which is disposed inside the member 104 and in which the liquid developer 130 is permeated and held in order to supply the liquid developer 130 to the developer supply foam member 104
And a charger 106 disposed in close proximity to the photosensitive drum 102 for uniformly charging the surface thereof, and selectively charging the surface of the photosensitive drum 102 based on image information. Selective exposure means 1 as exposure means for exposing
07 and a transfer roller 1 for transferring an image formed by the liquid developer 130 formed on the photosensitive drum 102 onto the recording paper PP.
09 and a cleaning roller 110 that removes the liquid developer 130 remaining without being transferred to the recording paper PP and cleans the surface of the photosensitive drum 102 as main components.

In the first unit 100 of the image forming apparatus 1 of the present embodiment, a solution containing water as a main component can be used as the liquid developer 130, and the liquid developer 130 contains an aliphatic saturated hydrocarbon as a main component. Compared with conventional liquid developers, they are advantageous in environmental aspects such as less odor, industrial aspects due to lower material costs, and safety aspects such as less risk of ignition. In addition, compared to the conventional electrophotographic method using a powder toner, a heat fixing unit is not required, which is advantageous in power saving and space saving, and since the liquid developer 130 is used, the image quality of a natural image is reduced. This is advantageous in that a good gradation can be obtained.

Next, FIG.
Each component will be described in detail using the first unit 100 shown in FIG. 7 as an example.

As the liquid developer 130 used in the first unit 100 of the present embodiment, an aqueous and conductive liquid in which coloring components such as dyes and pigments are dissolved or dispersed in pure water can be used. The conductivity of the liquid developer 130 is 10 8
What is necessary is just about the square ohm centimeter or less. Although it is not necessary to limit the aqueous developer from the specifications of the apparatus, an aqueous liquid developer is more preferable in consideration of environmental problems and manufacturing costs.

The photosensitive drum 102 can hold the electrostatic latent image 120 on its surface 121, and the wettability of the surface 121 with respect to the liquid developer 130 is greater than the wettability of the developer holding member 103. A high material is desirable. However, if the wettability is too high, the liquid developer 130
When the particles adhere, the droplets 122 are spread and the image is disturbed. Therefore, it is suitable that the contact angle G is about 30 ° to 80 °. As a material for forming the photosensitive drum 102, an organic photoconductor (OPC) material generally used for a laser printer is used. Organic photoconductors have a negative charge type laminated OPC
There is a single-layer OPC of the positive charging type, and the former is generally used in a relatively large amount. In the present embodiment, the latter positive charging OPC is adopted. This is composed of a single-layer OPC based on a polycarbonate resin and a perylenetetracarboxylic diimide derivative (perylene pigment) dispersed therein as a charge generation material (CGM).

FIG. 2 is an enlarged view of the appearance of the developer holding member 103 of the first unit 100 and a part of the surface thereof. The developer holding member 103 is provided for selectively supplying the liquid developer 130 to the surface 121 of the photosensitive drum 102 as shown in FIG. 1, and as shown in FIG.
The developer holding member 103 is formed by forming a metal thin plate made of a mesh-like nickel material or the like, on which a large number of fine holes 111 are provided so as to vertically penetrate the surface thereof, into a roller-shaped drum. is there. The developer holding member 103 can be formed by, for example, forming a sheet-like mesh 112 having a fine pitch into a roll shape. In addition,
The shape of the developer holding member 103 is not limited to the roller shape, but may be, for example, a belt shape. Further, the mesh 112 can be used for high-definition screen printing, and a mesh having 200 lines or more per inch is suitable for forming a high-definition image.

Further, electroforming (electroforming)
The metal mesh prepared in step (1) has no weave and can form a uniform, high-definition and high aperture ratio mesh of 2000 lines or more per inch, which is suitable for forming the developer holding member 103. Copper, nickel, or the like is used as a material forming the mesh. In addition, mesh 11
The sectional shape of the liquid developer 130 and the fine holes 1
Since the contact angle differs depending on the wall surface of the eleventh wall, various shapes are adopted. In the present embodiment, a bone having a substantially circular cross-sectional shape is used.

A method for producing the fine mesh 112 by such electroforming is described in, for example,
As described in detail in Japanese Patent No. 20740 or the like, a method of manufacturing the mesh 112 used for the developer holding member 103 of the present embodiment will be specifically described below.

FIGS. 6A to 6E show an example of a method of manufacturing the developer holding member 103 shown in FIG. 1 according to the present embodiment using a mesh 112 having a substantially circular bone section. is there. Hereinafter, the manufacturing method will be described with reference to FIGS. First, as shown in FIG. 6A, a liquid or sheet-shaped light-curable negative type resist 52 is applied as a photoresist to a base material (plating substrate) 51 made of, for example, stainless steel, nickel, or the like, or by thermocompression bonding. Then, a resist layer 52 is formed.

Next, as shown in FIG.
A light-shielding mask 53 is formed at a location corresponding to the twelve bones and exposed. Since the negative type resist 52 at the portion where the mask 53 is formed is removed by the exposure, plating is performed to form the mesh 112. Prior to the plating process, a release process may be performed as necessary so that the formed mesh 112 is easily detached from the base material 51. The release treatment is performed, for example, by forming an oxide film. After the release treatment, electric nickel plating is performed in a plating tank. For example, in the present embodiment, nickel sulfate or nickel sulfamate is added as an ion source in a nickel sulfamate bath.

As shown in FIG. 6 (C), a plating process forms a plating layer 55 on the exposed portion of the base material 51. When the plating layer 55 has a predetermined thickness, it is washed with water and the resist 52 is removed. The plating layer 55 is peeled off from the base material 51.

The bone portion of the mesh 112 peeled off here has a rectangular cross section as shown in FIG.
In order to make it round here, only the mesh 112 is again subjected to a plating bath, and a plating layer is adhered to the surroundings.
A substantially circular final shape as shown in (E) is obtained.

When the developer holding member 103 formed of such a mesh is used, the liquid developer 130 corresponding to one dot image is held in each of the fine holes 111 of the mesh. Conventionally, the liquid developer 130 held in the fine holes 111 is attached to the electrostatic latent image 120,
Alternatively, it was either not attached at all, and the amount of attachment could not be adjusted. Therefore, the finer the pitch of the mesh 112, the higher the definition of the image. Therefore, it is necessary to make the mesh pitch finer in order to increase the image quality by giving gradation to the image.

However, if the pitch of the fine holes 111 of the mesh 112 is made fine, a fine gradation can be expressed, but the diameter of the fine holes 111 becomes small. The fine holes 111 hold the liquid developer 130 as described later, and have a configuration in which the liquid developer 130 is attached to the electrostatic latent image 120 by the attraction force of the static electricity of the electrostatic latent image 120 in the vicinity thereof. Therefore, if the amount of the liquid developer 130 that can be held here is small, the liquid developer 130 cannot be sufficiently supplied to a solid screen that uses a large amount of the liquid developer 130, and a blank portion, that is, a so-called missing portion is generated. Will happen. Therefore, if only the mesh 112 having an extremely fine pitch capable of expressing a fine image is used, there is a possibility that an image having no so-called tightness is obtained. Therefore, in the present invention, such a disadvantage is solved by using a plurality of units.

Next, the state of the liquid developer 130 held by the developer holding member 103 shown in FIG. 3 will be described.

In the present embodiment, the developer holding member 103
The liquid developer 130 is held in each of the micro holes 111. The photosensitive drum 1 of the developer holding member 103
02 on the opposite side (inner side) from the liquid developer 130
Is adhered by its own adhesive force, and the liquid surface is free from pressure. The liquid developer 130 held in each of the micro holes 111 is connected by the liquid developer 130 attached to the inner surface, and the liquid developer 130 held by the developer holding member 103 is integrated. ing.

When the diameter and the film thickness of the fine holes 111 are on the order of several tens of μm, there is almost no need to consider the effect of gravity, and the behavior of the liquid is governed by the surface tension. Therefore, the liquid surfaces 131 and 132 are stabilized in a state where the overall surface energy is minimized.

When considering the liquid developer 130 in the fine hole 111 which forms the free surface by connecting the liquid developer 130 on the rear side as shown in FIG.
In No. 2, the surface energy of the liquid surface is always constant. Therefore, the change in the surface energy needs to be considered only with respect to the liquid surface 131 of the liquid developer 130 in front (on the photosensitive drum 2 side). Here, the liquid surface 131 is always flat so that the surface energy is minimized. If the angle θ between the liquid surface 131 and the surface of the fine holes 111 (see FIG. 4) is
When the contact angle G is smaller than the contact angle G determined by the relation of the Dupre equation, the liquid developer 130 gradually advances into the fine holes 111.

It should be noted that the contact angle usually has an advancing contact angle when the liquid developer 130 advances along the surface and a receding contact angle when the liquid developer 130 recedes. Micropore 1
When the surface of the eleventh surface is once wet, its contact angle becomes equal to the receding contact angle, so that the contact angle G is suitably set as the receding contact angle. Hereinafter, unless otherwise specified, the contact angle G refers to a receding contact angle.

Here, the sectional shape of the fine holes 111 and the liquid level 1
The relationship between the 31 positions will be described using the case of FIG. 3 as a specific example.

FIG. 3 shows a case in which a mesh 112 having a substantially circular cross-sectional bone is used to form a fine hole 111 having a shape obtained by combining two trumpet shapes.
The enlarged view of the fine hole 111 holding 0 is shown. The inner liquid surface 132 on the opposite side to the photosensitive drum 102 is supplied with the liquid developer 130 abundantly and continuously with the liquid developer 130 held in the large number of fine holes 111, so that the liquid developer 130, the developer holding member 10
The liquid developer 130 held in the fine holes 11 is attached through the liquid developer 130 attached to the inside of the developer holding member 3 so as to substantially cover the inside of the developer holding member 3.
Are combined. Further, in the present embodiment, the developer holding member 103 and the developer supply foam
4, a gap is provided in a non-contact state, and since the liquid developer 130 is supplied abundantly in the gap (see FIG. 8), the inner liquid surface 132 of the liquid developer 130 of the developer holding member 103 is formed. Is in a state where it does not receive any special pressure. Therefore, the inner liquid surface 132 of the liquid developer 130 held by the developer holding member 103 is substantially free from pressure.

On the other hand, the photosensitive drum 1 of the liquid developer 130
Since the inner liquid surface 132 is in a pressure free state as described above, the photosensitive drum 102
The side liquid surface 131 is also substantially free in pressure and tries to form a flat surface. In addition, as described above, the position is the fine hole 111.
Cross section and wall surface of the fine hole 111 and the liquid developer 130
Is determined by the contact angle G with

Further, the position of the liquid surface 131 of the liquid developer 130 on the photosensitive drum 102 side will be described in detail. Here, FIG. 4 shows an arbitrary position P11 on the wall surface of the fine hole 111 having a shape obtained by combining the two trumpet shapes shown in FIG.
To angle P1 between the cross section perpendicular to the penetrating direction at P15 and the wall surface of the fine hole 111 on the opposite side to the photosensitive drum 102
It is a figure showing 1- (theta) 15. When the cross-sectional shape of the bone of the fine hole 111 is substantially circular as shown in FIG.
The liquid surface 131 is fixed at a point P at which an angle θ formed by the wall surface of the liquid developer becomes equal to a contact angle (particularly, a receding contact angle) G determined by the wettability between the wall surface of the fine hole 111 and the liquid developer 130. That is, in the case of the present embodiment, assuming that the contact angle G is approximately 80 °, the angle θ14 matches the contact angle G at the position P14 as can be seen from FIG. Therefore, when the liquid surface 131 reaches the position of P14, the liquid surface 131 of the liquid developer 130 having the contact angle G becomes flat, and the liquid surface is most stable in terms of energy.

As described above, the liquid surface 131 can be controlled to a desired position by adjusting the angle θ by changing the cross-sectional shape of the fine hole 111 in accordance with the contact angle G. As a result, the surface 121 on the photosensitive drum 102
, The distance S between the electrostatic latent image 120 and the liquid surface 131 can be made constant, and the effect of the electric field by the electrostatic latent image 120 on the liquid surface 131 is made constant (see FIG. 7).

The developer supply foam member 104 is provided with a roller-shaped sponge, and the liquid developer 130 is permeated and held. The liquid developer 130 is supplied into the fine holes 111 by contacting or approaching the developer holding member 103. The developer container 105 is disposed inside the developer supply foam member 104, and is preferably airtight except for a part in contact with the developer supply foam member 104. Further, the developer container 105 includes a foam material 148 therein, and the liquid developer 130 is configured to penetrate and be held in the foam material 148.

Here, the supply of the liquid developer 130 will be described. FIG. 8 is a schematic sectional view showing an apparatus for supplying the liquid developer 130. The liquid developer 130 is stored in the developer container 105 inside the developing roller core 141.

The developer supply foam member 104 is adhered and held to the outer peripheral portion of the central portion of the developing roller core 141 where the outer shape is reduced, and a part of the end is provided in the developer container 1.
The liquid developer 130 impregnated with the foaming agent 148 in the liquid developer 05 contacts the contact part 147. The liquid developer 130 is in contact with the contacting portion 147 of the developer supply foam member 104.
And is supplied to the whole.

At the start of use, the liquid developer 130 is supplied from the supply pipe 143 so that the liquid developer 130 is sufficiently supplied between the developer supply foaming member 104 and the developer holding member 103. After that, the stopper 144 is closed and sealed. The supply of the liquid developer 130 after the start of use is performed from the central supply pipe 145, and the cap 146 is attached after the supply.

The portion of the mesh 112 of the developer holding member 103 is attached to the portion of the developing roller core 141 where the outer diameters of both ends are large, and the portion between the portion of the mesh 112 and the developer supply foaming member 104 is formed. Is provided with a gap, and the gap is always constant.

Next, as the charger 106, a scorotron charger used in an ordinary laser printer can be used. The outline of the configuration is as follows.
In this configuration, a tungsten wire of μm is shielded by a metal such as aluminum having a U-shaped cross section at a distance of about 1 cm, and several wires or meshes are arranged as grid electrodes insulated from the shield electrode on the opening surface. A bias voltage is applied to the grid electrode with the opening surface of the scorotron facing the photosensitive drum 102. In the charger 106 using this scorotron charger, the charging potential is regulated by the voltage applied to the grid electrode even when the charging time is long, and the surface potential is saturated. Therefore, the photosensitive drum 102
Can be uniformly charged. Further, by changing the charging voltage and the bias voltage, the charging potentials of the photosensitive drums 102 and 202 can be made different. The charging potential can be set to about 400 to 600V.

In the image forming apparatus 1 of the present embodiment, the difference in the configuration of the chargers 106 and 206 is a difference in the configuration of the first unit 100 and the second unit 200.

Next, the selective exposure means 107 will be described. Here, FIG. 9 schematically shows the configuration of the selective exposure means 107 using the LD (semiconductor laser) scanner 161 of the present embodiment. This will be described below with reference to FIG.

The selective exposure means 107 is provided for the developer holding member 1.
An LD scanner 161 for irradiating the photosensitive drum 102 arranged to rotate with the LD scanner 16;
1 is configured by a control unit 70 for controlling the control unit 1. The control unit 70 includes the image forming units 100 and 200
Scanners 161 and 261 used for
Is a unit that controls both. That is, the RAM 7
The CPU 71 expands the image data input to the printer 2 into bitmap print data. In this case, for the solid image portion where the dots are continuous, the second unit 200 having a larger dot is used to form a gap between the dots. In the location of the intermediate tone having a color, the ON / OFF timing control unit 75 drives the LD current supply unit 176 so that the first unit 100 forms an image, distributes data to the LD scanner 161 and the LD scanner 261, and outputs the final image. Form. The LD scanner 261 is attached to the second unit 200.
ON / OFF by providing LD current supply unit 276 for
The control signal is transmitted to the second unit 200 by the timing control unit 75.
It may be configured to send to In the present embodiment, the LD power control unit 74 for modulating the output of the LD is not always necessary. However, by using this LD power control unit 74, it is possible to output more tones. In the following description, the selective exposure unit 107 of the first unit 100 will be described as an example.

An LD 163 for outputting a laser beam is provided on the left rear portion (lower left in FIG. 9) of the housing 162 of the LD scanner 161.
And the collimating lens (Coll
imate lens) 164, and a polygon mirror 165 in the traveling direction of the laser light. Also, housing 1
A BD mirror (horizontal periodic mirror) 16 is provided at the left front of 62.
7, a BD sensor 168 is provided behind the BD mirror 167.
Is arranged. An fθ lens 166 is arranged in front of the polygon mirror 165. A control unit 70 electrically connected to the LD scanner 161 is provided at a different position from the LD scanner 161. The CPU 71 that controls the entire LD scanners 161 and 261 provides the original image data and the print data obtained by developing the original image data. An on / off timing control unit 75 for controlling blinking of a RAM 72 storing data, a ROM 73 storing a control program, an LD 163, an LD 1
An LD power control unit 74 for controlling the amount of light 63 is connected via a bus. Further, the CPU 71 is connected to a polygon mirror control unit 78 and a photosensitive drum control unit 79, and these are connected to a polygon mirror (not shown) and an LF motor (Line Feed motor, a paper conveyance drive motor) via a driver (not shown). Drive these motors. The BD signal receiving unit 77 electrically connected to the BD sensor 168 is connected to the ON / OFF timing control unit 75.

Note that the second unit 200 has L
An LD scanner 262 (not shown) having the same configuration as the D scanner 161 is provided, and an LD current supply unit 276 for supplying a drive current is electrically connected to the LD scanner 262. The LD current supply unit 276 is a control unit 7 which is a common control device for the image forming units 100 and 200.
The ON / OFF timing control unit 75 and the LD power control unit 74 are controlled to supply a current to the LD 263 so as to receive a part of the image data and form an image as described above.

Further, the operation of the selective exposure means 107 will be described in detail. First, a laser beam is output from the LD 163 which emits light under the control of the control unit 70. In addition, various laser devices such as a gas laser are used for the laser light emitter in addition to the semiconductor laser as in this embodiment. Here, the apparatus is made compact and the photosensitive drum 10
The semiconductor laser is used in consideration of the sensitivity of (2). The outputted laser light is condensed by the collimator lens 164, the optical axis thereof is aligned, and is incident on the polygon mirror 165.
In the present embodiment, the polygon mirror 165 has a hexagonal prism shape and rotates at a constant speed in the clockwise direction in the figure.

The laser light incident on the polygon mirror 165 is first scanned by B light before scanning on the photosensitive drum 102.
The light is reflected in the direction of the D mirror 167, and
7 is reflected and enters the direction of the BD sensor 168. In the BD sensor 168, a current is generated by the incidence of light, and a signal based on this current is received by the BD signal receiving unit 77. The BD signal receiving unit 77 turns on the pulse signal using the change in the voltage as a control signal. / OFF timing control unit 75. The ON / OFF timing control unit 75 that has received this signal counts the clock from the time when this signal is received as a reference time and uses the reference clock inside the CPU 71, and based on the image information, turns on the LD 163 at a predetermined timing. The switching operation is performed by determining the light emission timing.

Since the polygon mirror 165 is rotating at a constant speed, the laser beam incident on the polygon mirror 165 is applied to the surface of the photosensitive drum 102 made of OPC after a predetermined time after the incidence on the BD mirror 167. Reflected toward. At this time, the laser light reflected in the direction of the photosensitive drum 102 passes through the fθ lens 166, so that the linear velocity of the laser light is substantially constant on the surface 121 of the photosensitive drum 102 by the fθ lens 166. The light is adjusted and incident, and scans the photosensitive drum 102 at a constant speed. The laser beam that scans the photosensitive drum 102 blinks and is modulated at a predetermined position based on the image information stored in the RAM 72 to form an electrostatic latent image at a predetermined position. The predetermined position to be irradiated with the laser light is based on the clock position at which the irradiation position moved by the rotation of the polygon mirror 165 is detected by the above-described BD sensor 168 and becomes the origin, and the counting is started based on this position. From the angular velocity of the polygon mirror 165
The distance from a reference point (not shown) on 02 is calculated and controlled.

Here, the LD 163 is connected to the LD current supply unit 1.
Current is supplied from 76 to emit light. LD current supply unit 1
An ON / OFF timing control unit 75 that controls the blinking of the LD 163 and an LD power control unit 74 that adjusts the amount of current to adjust the amount of exposure are connected to 76, and the amount of light is increased or decreased at each light emission timing of the LD 163. It is controlled to emit light.

According to the configuration of the present embodiment, CPU 7
1. An LF motor (not shown) is controlled to control the photosensitive drum 10
A photosensitive drum controller 79 for controlling the rotation of the polygon mirror 2, a polygon mirror controller 78 for controlling the rotation of the polygon mirror 165, and an ON / OFF timing controller 75 for changing the light emission timing of the LD 163. The exposure position in the rotation direction (sub-scanning direction) and the main scanning direction on the photosensitive drum 102 can be moved by a distance corresponding to, for example, １ ／ of the pitch of the mesh 112.

As shown in FIG. 1, the transfer roller 109 can be a silicone rubber roller or a rubber roller formed of urethane rubber or the like. It is also possible to improve the conductivity by adding carbon to these rubbers, and to promote the transfer by applying a bias voltage.

The cleaning roller 110 removes the liquid developer 13 remaining on the surface of the photosensitive drum 102 after the transfer.
A sponge roller that absorbs and removes 0 and can easily absorb the liquid developer 130 can be used.

Next, in the first unit 100 of the image forming apparatus 1 configured as described above, as shown in FIG.
The principle that the liquid developer 130 selectively adheres to the electrostatic latent image 120 formed on 21 will be described with reference to FIG. As shown in FIG. 7A, the liquid developer 130 has a liquid surface 131 inside the fine holes 111 of the metal mesh 112 grounded by the grounding portion 113 so as to be inside the surface 114 of the developer holding member 103. Is held so that Here, when the photosensitive drum 102 and the developer holding member 103 rotate, the distance between the liquid developer 130 held in the fine holes 111 and the electrostatic latent image 120 formed on the photosensitive drum 102 gradually decreases, As shown in FIG. 7B, the surface 114 of the developer holding member 103 and the surface 121 of the photosensitive drum 102 are in contact with each other. The distance between the liquid surface 131 of the liquid developer 130 that has not been sucked and the surface 121 of the photosensitive drum 102 at the time of the closest approach is about several μm.
This distance depends on the sectional shape of the fine hole 111 and the contact angle G between the liquid developer 130 and the surface of the fine hole 111 as described above.
The variation between the fine holes 111 and the variation with time are small. Here, the liquid developer 130 in the vicinity of the region where the charge of the electrostatic latent image 120 exists is attracted by the electrostatic force and contacts the surface 121 of the photosensitive drum 102.

Since the surface 121 of the photosensitive drum 102 is formed of a material having better wettability with respect to the liquid developer 130 than the fine holes 111, the surface 114 of the developer holding member 103 When the liquid developer 130 is separated from the surface 121 of the photosensitive drum 102, the liquid developer 130 remains as a droplet 122 while adhering to the photosensitive drum 102, as shown in FIG. On the other hand, the liquid developer 130 in the vicinity of the region where no electric charge exists is not affected by the electrostatic force and does not contact the photosensitive drum 102 at all. Thus, in the non-image part 123,
Since the liquid developer 130 does not contact, dirt and fogging hardly occur. As can be seen from the above description, the fine holes 111
The retained liquid developer 130 contains the electrostatic latent image 12
0 to form a visible image on the photosensitive drum 102.

Here, the principle of forming an image having a gradation in the image forming apparatus 1 of the present embodiment will be described. The image forming apparatus 1 of the present embodiment includes the first unit 100 described above and the second unit 200 having basically the same configuration as the first unit 100 described above.
As shown in (1), the first unit 100 first forms an image on the recording paper PP, and then the second unit 200 forms an image to obtain a final image. Hereinafter, the components of the first unit 100 are represented by reference numerals using 100 numbers, and the components of the second unit 200 are 2
It is represented by a code using 00 numbers. Here, components having the same last two digits are the same in principle, unless otherwise specified.

Here, the first unit 100 and the second unit 200 have different charging potentials of the chargers 106 and 206. That is, the charger 106 of the first unit 100 applies a voltage of 400 V, and the charger 206 of the second unit 200 applies a voltage of 600 V. As a result, there is a difference between the charged potentials of the photosensitive drums 102 and 202, and the photosensitive drum 202 is charged to a higher potential than the photosensitive drum 102. Therefore, the LD scanner 16
If an electrostatic latent image is formed by performing exposure in steps 1 and 261, an electrostatic latent image having a higher potential is formed in the second unit 200, so that the second unit 200 adheres to the electrostatic latent images 120 and 220. Comparing the amounts of the liquid developers 130 and 230, the second unit 200 adheres more, and the dots of the image formed there are also larger in the second unit.

FIG. 10 is a schematic cross-sectional view showing the state of development in the second unit 200 of the present embodiment. On the other hand, FIG. 11 shows the first unit 1 of the present embodiment.
FIG. 9 is a schematic cross-sectional view showing a state of development at 00.

The graph shown in the upper part of FIG. 10A is a graph showing the charged potential of the surface 221 of the photosensitive drum 202. E indicates the surface potential, and the level of “max” is
The potential in the state charged by the charger 206 is shown. or,
A level of “0” indicates a state where the potential has been completely reduced by exposure. Hereinafter, the same applies to FIGS. 11 to 15.

Here, the location 220 is where the electrostatic latent image is formed without exposure. Further, the non-image portion 22 in which both sides of 220 are exposed and the potential is lowered.
3. In the state of FIG. 10A, the fine holes 2 of the mesh 212 are still in a state where the developer holding member 203 is separated.
The liquid surface 231 of the liquid developer 230 held at 11 is not affected by the electric field of the electrostatic latent image 220, and the liquid surface is a horizontal plane.

FIG. 10B shows the state of the photosensitive drum 20.
2 and the developer holding member 203 are rotated, and the minute holes 211 are closest to the electrostatic latent image 220. In this state,
The liquid surface 231 is attracted by the electric field of the electrostatic latent image 220 and is attracted to the electrostatic latent image 220, and the liquid developer 230 adheres.

FIG. 10C shows again the electrostatic latent image 22.
At this time, the droplet 222 adheres in a state where the fine hole 211 is separated from 0.

On the other hand, in FIG. 11A, the first unit 1
00 is applied to the second unit 2
Since the voltage applied from the charger 206 is low, the charging potential of the photosensitive drum 102 is low.
Therefore, the potential of the electrostatic latent image 120 formed here is also low.

Therefore, as shown in FIG. 11B, even if the minute hole 111 approaches, the liquid surface 131 rises less than the electrostatic latent image 220 described above because the attraction force due to static electricity is smaller than that of the second unit. And the area of the liquid developer 130 adhering thereto is also small.

Accordingly, when the fine holes 111 are separated, the area of the liquid droplets 122 formed here is small, and the amount of the liquid developer 130 that can be adhered to the droplets 122 is smaller than the amount of the liquid developing agent 221 on the surface of the photosensitive drum 102. The amount of the liquid developer 130 that can be held in the droplet 122 is reduced because it is determined by the contact angle formed with the agent 130. Therefore, the dots of the image formed here are smaller than in the case of the second unit 200 described above.

For the reasons described above, the dots of the image formed by the first unit 100 are small, interference between adjacent dots is unlikely to occur, and small dots suitable for expressing an intermediate tone are used. It becomes an image forming unit.

On the other hand, since the dots of the image formed by the second unit 200 can hold a large and sufficient amount of the liquid developer 230, they are continuous images requiring a large amount of the liquid developer 230, so-called solid images. However, the liquid developer 23
A dark and tight image can be formed without causing a place where so-called "0" is insufficient and cannot be attached, that is, a so-called dropping.

Therefore, the image forming apparatus 1 according to the present embodiment has the first unit 100 and the second unit 200, each of which forms an image by sharing a small-diameter dot and a large-diameter dot. Therefore, while it is possible to express finely without crushing the image, it is also possible to form a powerful image with a dark color and no dropout.

Next, a modified example of this embodiment will be described.

The configuration of the first modification is that, in the present embodiment, the charging potentials of the chargers 106 and 206 are changed,
The second unit 200 controls the size of the electrostatic latent image instead of the first unit 100, while controlling the dot size of the image. An image forming unit 300 (hereinafter, referred to as a third unit 300) is used. This third unit 30
0, the charger 306 (not shown) is connected to the second unit 2
The same potential as that of the charging by the charger 206 of 00 is used.

The third unit 300 changes the light emission timing of an unillustrated LD scanner to change the electrostatic latent image 320 formed at the time of exposure to light.
The dot diameter of the formed image is controlled to be smaller by making the area smaller than that of the electrostatic latent image 220 formed by. Specifically, the following method is used.

FIG. 12 is a cross-sectional view schematically showing a state in which an exposure area corresponding to the fine hole 311 is divided into an exposed portion and an unexposed portion to form an electrostatic latent image 320. In this modification, the blinking timing of the exposure is
One third of the pitch of the mesh 312. Therefore, the minimum exposure unit 25 that can be exposed at one timing is ３ of the exposure area (see FIG. 18).

The upper graph of FIG. 12A is a graph showing the potential of the electrostatic latent image 320 formed on the surface 321 of the photosensitive drum 302, where E represents the surface potential and m represents the surface potential.
The portion where the exposure has been increased to the level of ax has not been exposed at all, and the electrostatic latent image 320 having the highest potential is formed. In addition, at the level of 0 which is the lowest, the potential is low in the portion exposed with the maximum light amount, and there is almost no suction force. As can be seen from the figure, in this example, since the exposure area corresponding to the fine hole 311 can be exposed in three parts, the second unit 200 does not expose all portions of the electrostatic latent image 220, and the potential becomes high as a whole. On the other hand, in the case of the electrostatic latent image 320 of the third unit 300, only the central portion of the minimum exposure unit in the exposure region divided into three in the main scanning direction is not exposed, and only the potential of this portion is exposed. It can be seen that both sides are not charged similarly to the non-image portion 323.

FIG. 12B shows the photosensitive drum 302 and
The state in which the developer holding member rotates and comes closest is shown.
Since the electrostatic latent image 320 has a high potential only at the central portion, the suction force also acts only at the central portion.
Since the small holes 311 are raised in a hill shape so as to form a spherical surface as a whole, the electrostatic latent image 22 of the second unit 200 is formed.
Since the suction force as a whole is weaker than 0, the small liquid surface 331 rises, and the liquid developer 330 contacts the photosensitive drum surface 321 with a small area.

FIG. 12C shows that the liquid developer 330 adheres to the electrostatic latent image 320 in FIG.
22 shows a state in which 22 is formed. Droplets 32 attached here
It can be seen that No. 2 has a smaller liquid amount than the liquid droplet 222 attached in the second unit 200 shown in FIG. Therefore, the dots of the image formed by the liquid developer 330 are also small. In this way, the diameter of a dot for forming an image in the third unit 300 is controlled.

Here, FIG. 18 shows this one fine hole 31.
FIG. 3 is a view of an exposure area on the photosensitive drum 302 corresponding to No. 1 when viewed in a rotation axis direction. The width of this exposure area is L
The width corresponds to three times the shortest exposure interval by the D scanner 361 (not shown). The pitch of the fine holes 311 is three times the pitch of the paper feed of a paper feed mechanism (not shown). Conversely, the exposure timing by the LD scanner 361 is １ ／ of the pitch of the fine holes 311. Also, the minimum paper feed unit is １ ／ of the pitch of the fine holes 311. Therefore, assuming that the smallest exposure range in this embodiment is the minimum exposure unit 25, the exposure area is exposed in the minimum exposure unit 25 in three rows and three rows. And
In this case, the main scanning direction is such that the exposure light scans the surface 321 of the photosensitive drum 302, which is the surface to be exposed, rightward in FIG. 18 and the sub-scanning direction is the downward direction in FIG. Here, each exposure unit of the exposure area is set as a matrix, and the minimum exposure unit 25 is defined as (1, a), (1, b), (1, c) from the upper left of the figure to the right in the second row. Are referred to as (2, a), (2, b), (2, c), and the third row is referred to as (3, a), (3, b), (3, c). The hatched portion in the figure indicates the place where the electrostatic latent image 320 is formed.

As shown in FIG. 18, in the third unit 300 of this modification, the ON / OFF timing control unit 7
5, the light emission of the LD 363 is controlled, only the portion (2, b) is not exposed, and the range of the other minimum exposure unit 25 indicates the exposed state. Therefore, only the portion (2, b) of the electrostatic latent image 320 is formed. In this case, the area that has not been exposed is 1/9 of the area of the exposure area 24. This state corresponds to FIG. 12 described above.

As described with reference to FIG. 12A, since the electrostatic latent image is formed only on the portion (2, b),
Also in 2 (C), the liquid developer 330 adheres only to the central portion, and an image is formed only in the minimum exposure unit at the central portion of the exposure region.

In this way, by dividing the exposure area into a portion where an image is formed and a portion where no image is formed, the dot diameter for forming an image can be controlled.

Next, instead of the first unit 100, a fourth image forming unit 400 having a small opening area
A second modified example of the present embodiment using (hereinafter, referred to as a fourth unit 400) will be described.

First, FIG. 16 shows the second unit 20.
It is the figure which expanded the mesh 212 used for 0. On the other hand, FIG. 17 is an enlarged view of the mesh 412 used in the fourth unit 400 of the present modification. As can be seen from the comparison between FIG. 16 and FIG. 17, although the mesh pitch itself is the same,
Of the mesh 412 of the fourth unit 400 is smaller than the mesh 212 of the second unit 200.

FIG. 13 is a schematic diagram showing a state of development in the fourth unit 400. As shown in FIG. 13A, an electrostatic latent image 420 formed on the photosensitive drum 402
Has the same potential and area as the second unit 200. However, as shown in FIG. 17, the opening area of the fine holes 411 in the mesh 412 used for the fourth unit 400 is smaller than that of the second unit 200, and therefore, FIG.
As shown in the figure, the rise of the liquid level 431 becomes small. Therefore, as shown in FIG.
The amount of the liquid developer 430 attached to 0 is small, and the droplet 422 formed here is also small. Accordingly, it can be seen that even if the charging potential, the area of the electrostatic latent image 420, the pitch of the mesh 412, and the like are the same as those of the second unit 200, the dot diameter for forming an image is small. That is, by adjusting the opening area of the fine holes, the diameter of the dots forming the image can be controlled.

Next, the first unit 100 of the present embodiment
Instead, a fifth image forming unit 500 having a different mesh dot pitch (hereinafter referred to as a fifth unit 500)
A third modified example using the method will be described.

FIG. 14A is a schematic diagram showing the state of development by the fifth unit 500 of the third modification. The pitch P of the mesh 512 used for the fifth unit 500 is smaller than the pitch P of the mesh 212 used for the second unit 200. In this case, if the bones of the mesh 512 and the bones of the mesh 212 have the same shape and the same thickness, the smaller the pitch, the smaller the fine holes 511. Therefore, FIG.
As shown in the figure, the rising of the liquid level 531 is smaller than that of the second unit 200. Therefore, as shown in FIG. 14C, the liquid developer 53 adhered to the electrostatic latent image 520
The attached amount of 0 is small, and the droplet 522 formed here is also small. Accordingly, it can be seen that the dot diameter for forming an image is small even if the charging potential, the area of the electrostatic latent image 220, the shape of the bone of the mesh 212, and the like are the same as those of the second unit 200. That is, by adjusting the pitch P of the mesh 512, it is possible to control the diameter of the dots forming the image.

Next, the first unit 100 of the present embodiment
Instead, a fourth image forming unit 600 (hereinafter, referred to as a sixth unit 600) using a sixth image forming unit 600 in which the distance between the liquid developer and the electrostatic latent image is changed by changing the shape of the mesh bone portion. A modified example will be described.

As described above, the liquid level 6 of the liquid developer 630 is
The position of 31 is determined by the contact angle determined by the liquid developer 630 and the fine holes 611. Therefore, even if the conditions such as the charging potential, the area of the electrostatic latent image 220, the pitch of the liquid developer 230 and the pitch of the mesh 212, and the opening area of the fine holes 211 are the same in the second unit 200, the wall surface of the fine holes 611 The position of the liquid level 631 can be changed by changing the shape of.

FIG. 15 is a schematic view showing the state of development by the sixth unit 600. As shown in FIG. 15 (A), the cross-sectional shape of the bone of the mesh 212 of the second unit 200 is substantially circular, whereas the bone of the mesh 612 of the sixth unit 600 of the present modified example has a square shape. It has a round, generally triangular cross-sectional shape. Therefore, the angle formed between the wall surface of the fine hole 611 and the cross section of the fine hole 611 in the penetrating direction on the opposite side with respect to the photosensitive drum 602 depends on the liquid developer 63 in this case.
The point at which the contact angle between 0 and the wall surface of the fine hole 611 becomes equal is
The liquid level 631 and the photosensitive drum 60 are compared with the distance from the surface 221 of the photosensitive drum 202 in the second unit 200.
The liquid level 631 of the sixth unit 600 is stabilized at a position where the distance from the second surface 621 is larger. Therefore, FIG.
As shown in FIG. 5B, even when the photoconductor drum 602 and the fine hole 611 of the developer holding member 603 are closest to each other, since the distance is larger than the distance in the second unit 200, the electrostatic latent image 620 It is hardly affected by the electric field and the suction force is small. Therefore, the rise of the liquid level 631 is
It is smaller than the second unit 200. Therefore, FIG.
As shown in FIG. 5C, the amount of the liquid developer 630 attached to the electrostatic latent image 620 is small, and the droplet 622 formed here is also small. Accordingly, even if the charging potential, the area of the electrostatic latent image 220, the pitch of the liquid developer 230, the mesh 212, the opening area of the fine holes 211, and the like are the same as those of the second unit 200, the dot diameter for forming an image is small. I understand. That is, by changing the shape of the bones of the mesh 612, the liquid level 631 can be adjusted, and the diameter of the dots forming the image can be controlled.

Next, the first unit 100 of the present embodiment
Instead, a fifth image forming unit 700 (hereinafter referred to as a seventh unit 700) using a seventh image forming unit 700 in which the distance between the liquid developer and the electrostatic latent image is changed by changing the water repellency of the microporous wall surface. A modified example will be described. Seventh unit 70
0 is not illustrated because the configuration is the same as that of the second unit 200 and the mesh shape, pitch, etc., and the description is made by replacing the 200 numbers in FIG. 10 with the 700 numbers. The second unit 200 is different from the second unit 200 in that a highly water-repellent coating is applied to the wall surfaces of the micro holes 711. By increasing the water repellency of the fine holes 711, the contact angle between the liquid developer 730 and the wall surface of the fine holes 711 is changed. Therefore, as described above, the angle formed between the wall surface of the fine hole 711 and the cross section of the fine hole 711 in the penetrating direction on the opposite side to the photosensitive drum 702 depends on the liquid developer 730 in this case.
The point at which the contact angle between the surface of the photoconductor drum 202 of the second unit 200 is
21, the liquid level 731 and the photosensitive drum 702
The liquid level 731 of the seventh unit 700 is stabilized at a position where the distance from the surface 721 is larger. As a result, the liquid level 731 becomes flat, and the liquid level 731 of the liquid developer 730 is changed.
From the liquid surface 231 of the second unit 200 to the photosensitive drum 7
The liquid level 731 moves in the opposite direction to the liquid level 02. By moving the liquid level 731 away from the photoconductor drum 702, as in the fourth modified example, even when the photoconductor drum 702 and the fine hole 711 of the developer holding member 703 are closest to each other, the second Since the distance is larger than the distance in the unit 200, the suction force is less likely to be affected by the electric field of the electrostatic latent image 720. Therefore, the swelling of the liquid level 731 is smaller than the second unit 200. Therefore, although not shown, the amount of the liquid developer 730 that adheres to the electrostatic latent image 720 is small, and the droplets 72 formed there are small.
2 will also be smaller. Therefore, the second unit 20
0 and charging potential, area of electrostatic latent image 220, liquid developer 23
It can be seen that the dot diameter for forming an image is small even if the pitch, shape, and opening area of the fine holes 211 are the same. That is, by changing the shape of the bones of the mesh 712, the liquid level 731 can be adjusted, and the diameter of the dots forming the image can be controlled.

By using liquid developers having different contact angles for image forming units having the same structure, the contact angle can be adjusted to control the dot diameter of the image,
It is also possible to use a liquid developer in which the concentration of a dye or the like is changed, so as to produce gradation.

In the present embodiment and the modified example, an image is formed by using two image forming units. However, by using three or more image forming units, a finer and more compact image can be formed. May be formed.

Further, although an LD scanner has been described as an example of the exposure means, an exposure means using an LED array may be employed.

Next, the operation of the image forming apparatus 1 according to the present embodiment having the above-described configuration will be described with reference to FIGS. The liquid developer 130 used in the image forming units 100 and 200 of the image forming apparatus 1 according to the present embodiment,
Reference numeral 230 is always stored in the developer containers 105 and 205. The foam material 148 inside the developer containers 105 and 205,
248 is a developer supply foam member 10 through a slit.
4,204, and supplies the liquid developers 130, 230 appropriately. The supply amount is the developer container 105, 2
It can be adjusted by appropriately setting the balance between the foaming ratio of the foaming materials 148 and 248 inside the foaming member 05 and the foaming ratio of the developer supply foaming members 104 and 204.

The developer supply foam members 104 and 204 are
The liquid developer 130 and 230 are supplied to the fine holes 111 and 211 formed in the developer holding members 103 and 203 by rotating while being in contact with the developer holding members 103 and 203.

The liquid developers 130 and 230 held in the fine holes 111 and 211 have the liquid surfaces 131 and 231 held at fixed positions in accordance with the principle described above.

The exposure positions are adjusted, and the electrostatic latent images 120 and 220 formed on the photosensitive drums 102 and 202 are adjusted.
And the liquid developers 130 and 2 for developing the
It is desirable that the positions of the fine holes 111 and 211 holding the holes 30 coincide with each other at the time of development.

The photosensitive drums 102 and 202 are connected to the charger 1
06,206 charges the surfaces 121,221 uniformly. Here, the voltages applied to the chargers 106 and 206 are different, and the charging potential of the photosensitive drum 202 is higher in the case of the charging unit 206 than in the case of the charger 206.

Thereafter, the exposure is selectively performed by the selective exposure means 107 and 207, and the potential of the exposed portion is lowered.
20, 220 are formed.

The photosensitive drums 102 and 202 and the developer holding members 103 and 203 are rotated while being in contact with each other, so that the electrostatic latent images 120 and 22 are rotated as described above.
The liquid developers 130 and 230 are selectively adhered on the zero.
As a result, an image is formed on the photosensitive drums 102 and 202 using the liquid developers 130 and 230. Further, the recording paper PP is conveyed to a nip portion which is a contact surface between the photosensitive drums 102 and 202 and the transfer rollers 109 and 209 by a conveying unit (not shown). In this nip portion, the liquid developers 130 and 23 on the photosensitive drums 102 and 202
0 is transferred to the recording paper PP, and a final image is formed. Further, the liquid developer 1 remaining without being transferred to the recording paper PP
30 and 230 are removed by the cleaning rollers 110 and 210, and the surface 12 of the photosensitive drums 102 and 202 is removed.
1, 221 return to the initial state.

By repeating a series of these operations, a desired image is formed on the recording paper PP, and the recording paper PP is discharged out of the apparatus.

As described above, the diameter of a dot forming an image can be controlled by various methods. By forming an image with dots of different diameters controlled by a plurality of image forming units, the gradation can be sufficiently expressed by a high-definition image of fine dots, while the liquid developer is sufficiently adhered. A solid image can also be formed stably, so that a high quality image can be formed.

As described above, the preferred 1 of the invention according to the present application is as follows.
Although one embodiment and its modifications have been described, it is needless to say that the present invention is not limited to the above-described embodiments without departing from the scope of the claims. It can be easily inferred.

[0114]

As is apparent from the above description,
An image forming apparatus according to a first aspect of the present invention is an image forming apparatus, comprising: an exposure unit for forming an electrostatic latent image; a developer holding member having a plurality of fine holes for holding a liquid developer; An image carrier for forming an electrostatic latent image capable of adhering a liquid developer to a surface portion thereof and adhering and developing a liquid developer held in corresponding fine holes; and an electrostatic latent image on the image carrier. A plurality of image forming units each including a charger for charging the image carrier prior to image formation, wherein each unit is configured to form an image with a dot having a different diameter. There is an effect that the diameters of dots forming an image formed by a plurality of image forming units can be different. Therefore, there is an effect that a high-quality image having a dot gradation can be formed by selectively using a plurality of units for forming an image with dots having different diameters. In addition, the use of dots of different diameters has the effect of being able to express an intermediate tone without interference between adjacent liquid developers with a small dot diameter, while at the same time, the liquid development per attached area A large amount of the agent and a large dot diameter, so that a portion where the liquid developer cannot be adhered to the electrostatic latent image, that is, a solid image without so-called dropping can be expressed, and it is possible to obtain an image having a gradation and a good tightness. This has the effect of becoming

According to a second aspect of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the charging units of a plurality of units charge the image carrier to a different potential for each unit. Since the charging potential of the charger for charging the image carrier is different prior to the formation of the electrostatic latent image on the image carrier, the image forming unit is formed in a plurality of image forming units. There is an effect that the potential of the electrostatic latent image can be different.
Therefore, the amount of liquid developer attached to the electrostatic latent image during development can be made different, and the diameter of dots formed by a plurality of image forming units can be controlled based on the difference in the amount of liquid developer attached. it can. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

According to a third aspect of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the exposure means of the plurality of units includes an electrostatic latent image formed on the image carrier. Is formed so that the area of the dot forming the image is different for each unit. Therefore, when an electrostatic latent image is formed by the exposure unit, the area can be made different. . Therefore, the charge amount per dot can be changed to make the amount of the liquid developer adhered to the electrostatic latent image at the time of development different, and from the difference in the amount of the liquid developer adhered, a plurality of image forming units can be formed. Dot diameter can be controlled. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

According to the image forming apparatus of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the developer holding members of the plurality of units are finely divided through the developer holding members. Since the arrangement pitch of the holes is configured to be different for each unit, the arrangement pitch of the fine holes penetrated through the developer holding member is made different so that the developer holding member having a fine pitch can be formed. Thus, there is an effect that the dot diameter can be controlled so that a dot having a smaller diameter is formed and a dot having a larger diameter is formed by a developer holding member having a coarse pitch. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

According to the image forming apparatus of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the developer holding members of the plurality of units are finely divided through the developer holding members. Since the opening area of the hole is different for each unit, the opening area of the fine hole penetrated by the developer holding member is made different so that the fine pitch developer holding member can be formed. Thus, there is an effect that the dot diameter can be controlled so that a dot having a smaller diameter is formed and a dot having a larger diameter is formed by a developer holding member having a coarse pitch. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

According to the image forming apparatus of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the developer holding members of the plurality of units have fine holes formed through the developer holding members. The wall surface is configured to have a different shape for each unit so that the distance between the liquid surface of the liquid developer held in the micropores and the surface of the image carrier during development is different. Therefore, by changing the shape of the wall surface of the fine hole and changing the angle of the wall surface, there is an effect that the position of the liquid surface of the liquid developer held at a position stable in terms of energy can be controlled. . Therefore, even if an electrostatic latent image under the same conditions is formed on the image carrier during development, the distance between the liquid surface and the image carrier is different, so that the amount of the liquid developer attached can be made different. Further, the size of the dot diameter can be controlled by the difference. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

According to the image forming apparatus of the present invention, in addition to the effects of the image forming apparatus of the first aspect, the developer holding members of the plurality of units are finely divided through the developer holding members. The water repellency of the wall surface of each hole is different for each unit, so that the material of the wall surface of the fine hole can be made different, and the water repellency can be changed by applying a coating. There is an effect that the position of the liquid level of the liquid developer held at the set position can be controlled. Therefore, even if an electrostatic latent image under the same conditions is formed on the image carrier during development, the distance between the liquid surface and the image carrier is different, so that the amount of the liquid developer attached can be made different. Further, the size of the dot diameter can be controlled by the difference. Therefore, from the difference in the dot diameter, it is possible to obtain an image having a gradation and a tight pattern.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an outline of a configuration of an image forming apparatus 1 according to an embodiment.

FIG. 2 is an enlarged view of an appearance of a developer holding member 103 and a part of a surface thereof.

FIG. 3 is a diagram illustrating a fine hole 111 having a shape obtained by combining two trumpet shapes.

FIG. 4 shows the wall surface of the fine hole 111 and the fine hole 111 shown in FIG.
FIG. 6 is a diagram showing a relationship between an angle θ formed by a cross section perpendicular to the penetration direction of the micro holes 111 and a position of the micro holes 111 in the penetration direction.

FIG. 5 is a graph showing the relationship shown in FIG. 4;

FIG. 6 is a diagram showing a fine hole 1 in which two trumpet shapes are combined.
FIG. 9 is a process diagram illustrating a procedure of a method of manufacturing a mesh 112 for forming the mesh 11.

FIG. 7 illustrates a state in which the developer holding member 103 is moved to the photosensitive drum 102.
FIG. 3 is a schematic diagram illustrating a principle that a liquid developer 130 selectively adheres to an electrostatic latent image 120 formed thereon.

FIG. 8 is a schematic sectional view showing an apparatus for supplying a liquid developer 130.

FIG. 9 is a schematic diagram showing an outline of a configuration of a selective exposure unit 107 of the present embodiment.

FIG. 10 is a schematic cross-sectional view showing a state of development in the second unit 200 of the present embodiment.

FIG. 11 is a schematic cross-sectional view illustrating a state of development in the first unit 100 of the present embodiment.

FIG. 12 is a schematic cross-sectional view illustrating a state of development in a third unit 300 of the present embodiment.

FIG. 13 is a schematic cross-sectional view illustrating a state of development in a fourth unit 400 of the present embodiment.

FIG. 14 is a schematic cross-sectional view showing a state of development in a fifth unit 500 of the present embodiment.

FIG. 15 is a schematic sectional view showing a state of development in a sixth unit 600 of the present embodiment.

FIG. 16 is an enlarged view of a mesh 212 used in the second unit 200 according to the present embodiment.

FIG. 17 is an enlarged view of a mesh 412 used in the fourth unit 400 according to the present embodiment.

FIG. 18 is a diagram illustrating formation of an electrostatic latent image 320 of the third unit 300 according to the present embodiment.

[Explanation of symbols]

1 Image Forming Apparatus 100, 200 Image Forming Unit 102, 202 Photoconductor Drum (Image Carrier) 103, 203 Developer Holding Member 104, 204 Developer Supply Foaming Member (Supply Roller) 105, 205 Developer Container 106, 206 Charger 107, 207 Selective exposure means (exposure means) 109, 209 Transfer roller 110, 210 Cleaning roller 111, 211 Micropore 112, 212 Mesh 120, 220 Electrostatic latent image 130, 230 Liquid developer 161, 261 LD scanner 70 Control unit 71 CPU 74 LD power control unit (exposure amount modulation unit) 75 ON / OFF timing control unit (exposure blinking unit) 78 Polygon mirror control unit 79 Photoconductor drum control unit

Claims (7)

[Claims] 1. An exposure means for selectively exposing to form an electrostatic latent image, and a liquid developer in which a number of fine holes are penetrated to dissolve or disperse a coloring component such as a dye or pigment in a liquid. A developer holding member that holds the liquid developer, is arranged to face the developer holding member, and forms an electrostatic latent image that is selectively exposed by the exposure unit and that can adhere the liquid developer to a surface portion thereof. An image carrier that adheres a liquid developer held in a corresponding fine hole of the developer holding member to the electrostatic latent image to form and carry an image that is made visible from the electrostatic latent image; A plurality of image forming units each including a charger for charging the image carrier before forming an electrostatic latent image on the body, wherein the plurality of units form an image with dots of different diameters for each unit. Characterized in that Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the chargers of the plurality of units are configured to charge the image carrier to a different potential for each unit. 3. The exposure means of the plurality of units, wherein an area of a dot forming an electrostatic latent image formed on the image carrier is different for each unit. An image forming apparatus according to claim 1. 4. The developer holding member of the plurality of units, wherein the arrangement pitch of the fine holes penetrated by the developer holding member is different for each unit. The image forming apparatus as described in the above. 5. The developer holding member of the plurality of units, wherein the opening area of the fine hole penetrated by the developer holding member is different for each unit. The image forming apparatus as described in the above. 6. The developer holding member of the plurality of units, wherein a wall surface of the fine hole penetrated by the developer holding member is
The shape is different for each unit so that the distance between the liquid surface of the liquid developer held in the micropores and the surface of the image carrier during development is different. Item 2. The image forming apparatus according to Item 1. 7. The developer holding member of the plurality of units, wherein a water repellency of a wall surface of the fine hole penetrated by the developer holding member is different for each unit. 2. The image forming apparatus according to 1.