JPH10171186A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To faithfully reproduce an electrostatic latent image on an electrostatic latent image carrier even for the fine image of a line-image or the like having high contrast by making the dielectric constant of a body to be developed in the direction of thickness higher than that in a facial direction. SOLUTION: The dielectric constant in the direction of the thickness is made higher than that in the facial direction in addition to translucency and heat resistance necessitated for a conventional body to be developed at the body to be developed 102. In this case, when the body 102 generates dielectric polarization or electrostatic induction and the electrostatic latent image corresponding to the electrostatic latent image on the electrostatic latent image carrier 101 is formed on the body 102, the body 102 hardly generates the dielectric polarization or the electrostatic induction in the facial direction. Thus, the rising of potential is maintained so as to be steep without diffusing an electric charge in the facial direction at the boundary part of a latent image. Thus, the electrostatic latent image on the electrostatic latent image carrier 101 is faithfully reproduced on the body 102.

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 used for a printer, a copying machine, and the like.

[0002]

2. Description of the Related Art An image forming apparatus as shown in Japanese Utility Model Laid-Open No. 3-103463 is known. A schematic diagram of this device is shown in FIG. A drum-shaped electrostatic latent image carrier 101 having a photoconductive layer 101b formed on a conductive support 101a is disposed so as to be driven to rotate in the direction of the arrow. On the peripheral surface of the electrostatic latent image carrier 101, an endless developing object 102 is stretched by the electrostatic latent image carrier 101, the pressing roll 103 and the pulling roll 111, and the electrostatic latent image It moves in the direction of the arrow due to the frictional force with the carrier. The object to be developed 102 is required to have translucency adapted to the wavelength of the light source at the time of exposure, insulation at the time of development, and heat resistance at the time of transfer and fixing.

The image forming process of this image forming apparatus will be described below. First, the electrostatic latent image carrier 101 is uniformly charged by the charging device 104. Next, the electrostatic latent image carrier 101 is brought into close contact with the object to be developed 102, and charges are generated on the object to be developed 102 by dielectric polarization. Next, light corresponding to the image signal is emitted by the exposure device 105 to the developing object 10.
The light is transmitted to the electrostatic latent image carrier 101 through the laser beam 2. By this exposure process, an electrostatic latent image is formed on the electrostatic latent image carrier 101, and an electrostatic latent image is formed on the developing object 102 accordingly. Then, the electrostatic latent image on the developing object 102 is developed by the developing device 106 to form a toner image.

Next, the electrostatic latent image carrier 101 and the developing object 10
In this case, the AC corona charger 112 removes the electric charge on the developing member 102, thereby preventing the toner image from being disturbed by the electric discharge at the time of separation. After the separation, the developing member 102 includes the pressure roll 103 and the heating roll 1.
It is conveyed to the transfer / fixing unit 13.

On the other hand, the final recording support 114 accommodated in the paper cassette 120 is taken out by the paper feed roll 115, skew is corrected by the paper feed roll 116, and then conveyed to the transfer / fixing section. And the final recording support 1
14 is superimposed on the developing object 102 on which the toner image is formed, and is heated and pressurized, and the toner image on the developing object 102 is melted and fixed. Final recording support 114 on which toner image is fixed
Is discharged to the outside of the apparatus by a discharge roll 117.

Although a small amount of toner 108 may remain on the developing member 102 after transfer and fixing, the pressure roller 1
03 and a fixing cleaner 118 provided so as to press against
To be removed. At this time, since the toner 108 is still in the molten state in the fixing unit, the residual toner can be easily removed.

After the electrostatic latent image carrier 101 is separated from the developing object 102 after the developing process, the entire surface of the electrostatic latent image carrier 101 is irradiated with light by a neutralization lamp 119 to remove residual charges. Thus, the electrostatic latent image carrier 101 is repeatedly used.

[0008]

However, in the conventional image forming apparatus, an electrostatic latent image corresponding to the electrostatic latent image on the electrostatic latent image carrier is formed by the dielectric polarization of the developed object. Although it is generated on the surface, the dielectric polarization is slightly diffused in the plane direction of the developing object, so that the contrast at the boundary portion of the latent image is reduced, and particularly for high contrast and dense images such as line images. Problem with reproduction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus using a developing object capable of faithfully reproducing an electrostatic latent image on an electrostatic latent image carrier on the developing object.

[0010]

In order to achieve the above object, an image forming apparatus according to the present invention is arranged so as to surround an electrostatic latent image carrier and partially contact the electrostatic latent image carrier. In an image forming apparatus for developing an electrostatic latent image formed on an endless sheet made of an endless sheet by a developing device arranged opposite to the contact area, the object to be developed is a dielectric material in a thickness direction. It is characterized in that the resistivity is higher than the dielectric constant in the plane direction, or the developed body has a resistivity in the thickness direction lower than that in the plane direction.

In this way, dielectric polarization or electrostatic induction diffusion in the surface direction of the developing object at the boundary portion of the electrostatic latent image is suppressed, and the electrostatic latent image on the electrostatic latent image carrier is faithfully reproduced. Thus, even a high-contrast and dense image such as a line image can be faithfully reproduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image forming apparatus of the present invention is as follows.
Developing object 102 in conventional image forming apparatus shown in FIG.
Is basically the same except that the object to be developed in the present invention is replaced, and a schematic configuration diagram will be described with reference to FIG.

The drum-shaped electrostatic latent image carrier 101 is rotated at a constant peripheral speed in the direction of the arrow by a driving means (not shown). This electrostatic latent image carrier 101 is a conductive support 101
The photoconductive layer 101b is provided on the substrate a, and any of a selenium photoconductor, an organic photoconductor, a zinc oxide photoconductor, and an amorphous silicon photoconductor can be used. In the present embodiment, a negatively charged organic photoconductor in which a charge generation layer and a charge transport layer are sequentially laminated on the conductive support 101a as the photoconductive layer 101b is used.

An endless developing object 102 is stretched around an electrostatic latent image carrier 101, a pressure roll 103 and a pulling roll 111, and moves in the direction of the arrow due to a frictional force with the electrostatic latent image carrier 101. . The developing object 10 is attached to the pulling roll 111.
2 is provided with a tension mechanism for giving an appropriate tension.

Next, the image forming process will be described. First, the electrostatic latent image carrier 101 is uniformly charged by the charging device 104. As the charging device 104, a corona charger as generally illustrated is used, but a brush charger or the like can also be used. The developing member 102 comes into close contact with the electrostatic latent image carrier 101 between the charging process and the next exposure process. In the exposure process, the exposure apparatus 1
In step 05, light corresponding to the image signal is transmitted through the developing member 102 and irradiated on the electrostatic latent image carrier 101 to form an electrostatic latent image. The exposure apparatus 105 uses the LE used here.
In addition to the combination of the D array and the Selfoc lens (trade name), any combination such as a combination of a laser and an image forming optical system can be used. Further, if the transparent conductive support 101a is used, the electrostatic latent image support 1
An exposure apparatus can be provided inside the device 01.

A developing device 106 is provided so as to be opposed to the developing object 102 which is in close contact with the electrostatic latent image carrier 101. The developing device 106 adsorbs the toner 108 onto the toner carrier 107 and The developer 102 is conveyed in the direction of the arrow shown in the figure, and is developed on the electrostatic latent image formed on the electrostatic latent image carrier 101. In this embodiment, reversal development is used, and a bias voltage is applied between the conductive support 101 a of the electrostatic latent image carrier 101 and the toner carrier 107.

In the above configuration, in the space between the toner carrier 107 and the developing member 102, the lines of electric force associated with the electrostatic latent image formed on the electrostatic latent image supporting member 101 move the developing member 102. It occurs through. Therefore, the charged toner 108 on the toner carrier 107 adheres to the developing object 102 by electrostatic force, and is developed to form a toner image. As the developing device 106, any of a two-component magnetic brush developing device, a one-component magnetic brush developing device, and a one-component non-magnetic developing device can be used.

When the electrostatic latent image carrier 101 and the developing member 102 are separated from each other, the charge on the developing member 102 is removed by the AC corona charger 112, and the toner image is disturbed by the discharge when separating. Is prevented.

Thereafter, the developing member 102 separated from the electrostatic latent image carrier 101 is provided with a pressure roller 103 and a heat roller 113.
And transferred to the transfer / fixing section composed of

On the other hand, the final recording support 114 (generally paper is used) accommodated in the paper cassette 120 is taken out by the paper feed roll 115 and sent to the paper feed roll 116 whose rotation has been stopped to be subjected to the final recording. The skew of the support 114 is corrected. Here, the paper feed roll 116 is activated,
The final recording support 114 is sent to a transfer / fixing unit, where it is superposed and heated / pressed on the developing object 102 on which the toner image is formed. Then, the heat of the heating roll 113 is transmitted to the final recording support 114 to melt the toner on the developing object 102,
The fiber penetrates between the fibers of the final recording support 114 by a pressurizing action, and transfer and fixing to the final recording support 114 are performed simultaneously. The transferred and fixed final recording support 114 is sent out to the outside by a discharge roll 117.

On the other hand, a small amount of toner 108 may remain on the developing member 102 after the transfer and fixing, but a fixing cleaner provided so as to press the developing member 102 on the pressure roller 103 in pressure. Removed by 118. At this time, the toner 108 can be easily removed because the molten state in the fixing portion is still continued.

Further, the electrostatic latent image carrier 101 is separated from the object to be developed 102 after the developing process, and the entire surface is irradiated with light by a static elimination lamp 119 serving as a static eliminator. Is removed. Thus, the electrostatic latent image carrier 101 is used repeatedly.

Next, the developing object 102 which is a feature of the present invention is described.
Will be described. In the developing object of the present invention, in addition to the light transmittance and heat resistance required for the conventional developing object, the dielectric constant in the thickness direction is higher than the dielectric constant in the plane direction, or the resistivity in the thickness direction. Is lower than the resistivity in the surface direction. It is preferable that both the dielectric constant and the resistivity have a large difference between the thickness direction and the plane direction.

In this way, the developing member 102 causes dielectric polarization or electrostatic induction, and the electrostatic latent image carrier 101
When an electrostatic latent image corresponding to the above electrostatic latent image is formed on the object to be developed 102, the object to be developed 102 is unlikely to cause dielectric polarization or electrostatic induction in a plane direction. Charges can be maintained in a steep rise of potential without diffusion of charges in the plane direction. Therefore, the electrostatic latent image on the electrostatic latent image carrier 101 can be faithfully reproduced on the developing object 102, and therefore, even a high-contrast, dense image such as a line image can be faithfully reproduced. .

The development of the developing member 102 having different dielectric constants in the thickness direction and the plane direction is performed as follows. Fine powder of ferroelectric substance such as barium titanate, lead titanate, titanium and lead zirconate is mixed with molten resin such as polyester, polyimide, polyetherimide, polyethersulfone, polyetheretherketone and pressed by hot roll. Then, the sheet is formed by applying a voltage from both sides of the sheet with the sheet temperature raised. The control of the anisotropy of the dielectric constant is performed by changing the magnitude of the applied voltage.

The development of the developing member 102 having different resistivity in the thickness direction and the surface direction is performed as follows. Small conductive fiber pieces such as carbon fiber, tungsten, nickel, iron, etc. are electrostatically planted at predetermined intervals on a metal substrate or the like, and polyester, polyimide,
This is performed by forming a dielectric layer of polyetherimide, polyethersulfone, polyetheretherketone, or the like, and then peeling it off from the metal substrate. The control of the anisotropy of the resistivity is performed by changing the density of the minute conductive fiber pieces to be planted.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a line reproduction state in the image forming apparatus of the present invention will be described below, and the superiority of the present invention will be clarified with reference to a comparative example.

Example 1 In the image forming apparatus shown in FIG. 1, an organic photosensitive layer having a thickness of 20 μm and a relative dielectric constant of 3.3 was used as the photosensitive layer 101b. As the object to be developed 102, fine powder of barium titanate was added to a molten resin of polyester.
wt.%, and a sheet having a thickness of 50 μm was formed by a hot press. Then, a direct current electric field of 150 kV / cm was applied at 120 ° C. for 15 hours, and then cooled to room temperature while applying the electric field as it was. In this way, the barium titanate in the resin is oriented so that the dielectric constant in the thickness direction is higher than the dielectric constant in the plane direction.

First, the charging device 10 is placed on the developing object 102.
4, several charge images having a width of 50 μm are formed on the photosensitive layer at intervals of 50 μm. Then, the conductive support 101a
The developing object 102 is overlaid on the photosensitive layer 101b with the rotation of, and electric charges are induced on the surface of the developing object 102. A voltage of -350 V is applied to the developing sleeve, and negatively charged toner is formed in a thin layer on the surface. In the developing region, the toner adheres to a portion of the developing object 102 where no charge exists. Therefore, the toner adheres so as to form a line having a width of 50 μm. Thereafter, the toner image is transferred and fixed to the paper in the transfer and fixing section.

FIG. 2 shows the distribution of the amount of adhesion of the obtained fixing line image in the transverse direction.

(Comparative Example 1) A developing member 102 was prepared in the same manner as in Example 1 except that barium titanate was not added and a DC electric field was not applied, and a developing member having an isotropic dielectric constant was prepared. The body 102 was obtained.

A fixing line image was formed in the same manner as in Example 1. FIG. 3 shows the distribution of the amount of adhesion of the obtained fixing line image in the transverse direction.

(Comparative Example 2) A developing member 102 was prepared in the same manner as in Example 1 except that no DC voltage was applied.
The developing object 102 having an isotropic dielectric constant was obtained.

A fixing line image was formed in the same manner as in Example 1. FIG. 4 shows the distribution of the amount of adhesion of the obtained fixing line image in the transverse direction.

Example 2 A carbon fiber having a diameter of 7 to 10 μm (volume resistance of 1 × 10 ⁻³ Ω · cm) was used for 800 to
Hair was implanted at a density of 1,000 fibers / mm, and a polyester resin film was formed by embedding the hairs. Thus, a development target 102 having a thickness of 50 μm was produced.

A fixing line image was formed in the same manner as in Example 1. FIG. 5 shows the distribution of the amount of adhesion of the obtained fixing line image in the transverse direction.

As can be seen from these results, the higher the permittivity in the thickness direction of the object to be developed is higher than the permittivity in the plane direction,
Alternatively, an image having better line reproducibility was obtained as the resistivity in the thickness direction was lower than the dielectric constant in the plane direction.

[0038]

As described above, the image forming apparatus of the present invention comprises an endless sheet which surrounds the electrostatic latent image carrier and is arranged so as to be in partial contact with the electrostatic latent image carrier. In an image forming apparatus for developing an electrostatic latent image formed on a developing object by a developing device arranged opposite to the contact area, the developing object has a dielectric constant in a thickness direction which is a dielectric constant in a plane direction. Or the resistivity of the developing object in the thickness direction is lower than the resistivity in the surface direction.

For this reason, at the boundary portion of the electrostatic latent image, dielectric polarization or diffusion of electrostatic induction in the surface direction of the developing object is suppressed, and the electrostatic latent image on the electrostatic latent image carrier is faithfully developed. It can be reproduced on the body, and can be faithfully reproduced even in a high-contrast and dense image such as a line image.

[Brief description of the drawings]

FIG. 1 is a schematic view of an image forming apparatus of the related art and the present invention.

FIG. 2 is a diagram illustrating line reproducibility in the image forming apparatus of the present invention.

FIG. 3 is a diagram illustrating line reproducibility in a conventional image forming apparatus.

FIG. 4 is a diagram illustrating line reproducibility in a conventional image forming apparatus.

FIG. 5 is a diagram illustrating line reproducibility in another embodiment of the image forming apparatus of the present invention.

[Description of Signs] 101: electrostatic latent image carrier, 102: object to be developed, 106:
Developing device

Claims (4)

[Claims] 1. An electrostatic latent image formed on an object to be developed comprising an endless sheet that surrounds the electrostatic latent image carrier and is arranged to be in partial contact with the electrostatic latent image carrier. An image forming apparatus that develops the object with a developing device arranged to face the contact area, wherein the developing object has a higher dielectric constant in a thickness direction than a dielectric constant in a plane direction. 2. The image forming apparatus according to claim 1, wherein the developing member has a ferroelectric substance dispersed and oriented in a resin. 3. An electrostatic latent image formed on an object to be developed comprising an endless sheet that surrounds the electrostatic latent image carrier and is arranged to be in partial contact with the electrostatic latent image carrier. An image forming apparatus which develops the image by using a developing device arranged opposite to the contact area, wherein the object to be developed has a resistivity in a thickness direction lower than a resistivity in a surface direction. 4. The image forming apparatus according to claim 3, wherein the object to be developed has conductive needle-shaped members dispersed and oriented in a resin in the thickness direction.