JPH06266224A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a high-density image having a good transfer property with a normal paper by specifying the resistance value of the latent image carrying layer of an image carrier at a latent image forming portion and a latent image nonforming portion respectively at the time of latent image formation. CONSTITUTION:When a photoreceptor 1 is exposed from the inner face side by an LED head array 7 while the photoreceptor 1 laminated with a transparent electrode and a photoconductive layer on the outer periphery of a translucent cylinder made of a cylindrical glass raw tube, the surface potential is made zero at only the exposed portion, and a well type potential is formed. Negatively charged insulating nonmagnetic toners in a developer mixed with insulating nonmagnetic toners and conducting magnetic toners are stuck to the low potential section of the well type potential. The photoconductive film of the photoreceptor 1 has the resistance value of 10<8>OMEGA.cm or below at the exposed portion and the resistance value of 10<10>OMEGA.cm or above at the unexposed portion, a toner image made of only insulating nonmagnetic toners is formed at the exposed portion, and it is electrostatically attracted on the recording paper 9 by a transferring means 8.

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 such as an LED printer, a laser printer, a fluorescent tube printer, a digital copying machine incorporating them, a plain paper facsimile or the like.

[0002]

2. Description of the Related Art Generally, the electrophotographic system by the Carson process is widely used as a copying machine or a printer. This Carlson process has steps of charging, exposing, developing, transferring, discharging, and cleaning, and a corona discharger is used for charging and transferring. Since the corona discharger is configured to apply a high voltage of several kv to the corona wire, it requires a high-voltage power supply, is easily affected by humidity and dust, and has the problem of generating ozone, which is harmful to the body. ing.

In order to solve such a problem, there has already been proposed a method in which exposure and development are performed almost simultaneously without using a corona discharger to simplify the process. For example, Japanese Patent Laid-Open No. Sho 62
No. 280772, a charging device, a charge eliminator, and a cleaning device are not required by charging, exposing, and developing in a developing nip using a conductive magnetic toner, thereby reducing the size of the apparatus.
It enables price reduction. Also, JP-A-63-135
In 956, a similar composition is adopted by using a mixture of a conductive toner and an insulating toner as a developer.

[0004]

However, the former method has a problem in that the transferability of the conductive toner to the plain paper is poor, and a high resistance paper must be used to obtain a high density. In the latter method, conductive toner and insulating toner are used.
Is transferred and consumed on the recording paper, so if the mixing ratio changes due to environmental changes, etc., stable toner
There arises a problem that supply becomes difficult.

[0005]

SUMMARY OF THE INVENTION The present invention provides a latent image-bearing layer while forming a latent image while applying a voltage while supplying conductive particles and an insulating toner to the image-bearing member. An image forming apparatus for forming a toner image by adsorbing an insulating toner to a latent image forming part of the latent image forming layer of the image carrier in order to solve the above problems. 10 ⁸ Ω · cm or less at the formation site and 10 ^{10 at the} non-latent image formation site
It is characterized by exhibiting a resistance value of Ω · cm or more.

The latent image bearing layer of the image bearing member is preferably 10 ⁶ Ω · c at the latent image forming portion during latent image formation.
m or less, and a resistance value of 10 ¹¹ Ω · cm or more in the non-latent image forming portion.

[0007]

As described above, the latent image bearing layer of the image bearing member exhibits a resistance value of 10 ⁸ Ω · cm or less at the latent image forming portion and 10 ¹⁰ Ω · cm or more at the non-latent image forming portion, and preferably a latent image forming layer. By exhibiting a resistance value of 10 ⁶ Ω · cm or less at the image forming portion and 10 ¹¹ Ω · cm or more at the non-latent image forming portion, only the insulating toner is developed in the latent image forming portion.

Therefore, according to the present invention, the transfer onto the plain paper can be performed well, and the toner that is transferred and consumed is only the insulating toner, so that the toner can be easily replenished.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming apparatus of the present invention will be described below by taking an electrophotographic image forming apparatus for forming a latent image on a photosensitive member as an image bearing member by selective exposure.

FIG. 1 is a schematic view of an embodiment of the image forming apparatus of the present invention. As shown in FIG. 2, the photosensitive member 1 has a transparent electrode on the outer periphery of a light-transmissive cylinder 1a made of a cylindrical glass tube. 1b and the photoconductive layer 1c are laminated to have a predetermined thickness. The developing device 2 has an opening at the lower end of the toner box 3,
A magnetic roller 4 having S poles and N poles formed alternately is arranged on the peripheral surface, and a non-magnetic developing sleeve 5 rotatably covers the outer periphery thereof. A bias voltage (eg, negative) is applied to the developing sleeve 5 by a bias power source 6.

The developer is a conductive particle composed of an insulating non-magnetic toner and a conductive magnetic toner or a conductive carrier. In this embodiment, the conductive magnetic toner is mixed in the toner.
The insulating non-magnetic toner housed in the box 3 is charged with, for example, a negative charge. The conductive magnetic toner forms a magnetic brush by the magnetic force of the magnetic roller 4, and moves with the rotation of the developing sleeve 5. At this time, the insulating nonmagnetic toner also moves as the magnetic brush rotates.

A conductive path is formed by a conductive magnetic toner on the magnetic brush, and charges are injected onto the surface of the photosensitive member 1 until the potential becomes the same as the developing bias voltage while being in contact with the magnetic brush. Done. As a result, the surface of the photoconductor 1 and the developing sleeve 5 have the same potential and the same polarity, and the Coulomb force acting on the conductive magnetic toner and the insulating non-magnetic toner becomes zero.

Under such a charged state of the photoconductor 1, as a result of performing the exposure from the inner surface side of the photoconductor 1 using the LED head array 7, the surface potential of the photoconductor 1 becomes zero only in the exposed portion. A well-type potential is formed. At this time, since the insulating nonmagnetic toner is negatively charged, it is electrostatically attached to the low potential portion of the well type potential.

In the past, conductive toner was also attached to the low-potential portion at the same time, leading to transfer failure. However, the present inventor has found that the attachment of the conductive toner and the electrostatic latent image-bearing layer of the photoconductor 1 make it possible. By optimizing the resistance value of a certain photoconductive film 1c during exposure and during non-exposure, it was found that such a conductive toner does not adhere to the exposed portion. That is, according to the experiment of the present inventor,
In the exposed portion where the photoconductive film 1c is a latent image forming portion, 10
^It exhibits a resistance value of ⁸ Ω · cm or less, a resistance value of 10 ¹⁰ Ω · cm or more in the non-latent image forming portion (non-exposed portion), and preferably 10 ⁶ Ω · cm or less in the latent image forming portion and 10 in the non-latent image forming portion. By exhibiting a resistance value of ¹¹ Ω · cm or more, only the insulating toner is developed in the latent image forming portion,
The result was obtained. As a result, a toner image of only the insulating nonmagnetic toner is obtained in the exposed portion.

This toner image is formed by applying a charge having a polarity (positive electrode) opposite to the charging polarity (negative electrode) of the insulating non-magnetic toner to the transfer means 8 such as a transfer roller or a corona discharger. It is electrostatically adsorbed on the recording paper 9. The transferred toner image is fixed by a fixing unit (not shown) to become a permanent image.

After the transfer is completed, the insulating non-magnetic toner on the surface of the photoconductor 1 which has not been transferred is mechanically returned to the developing sleeve 5 side during the next passage of the magnetic brush, and is again used as a developer. Function.

The residual potential of the electrostatic latent image is smoothed by the injection of charges from the conductive magnetic toner while passing through the magnetic brush, and as a result, the insulating non-magnetic toner remaining on the photosensitive member 1 is left. The adhesion to the photoconductor 1 with respect to − is weakened, and the collection to the developing device 2 is promoted.

FIG. 3 shows the results of measurement of the mixing ratio (weight ratio of insulating non-magnetic toner) of toner deposited on the photosensitive member 1 by development. The horizontal axis represents the resistance of the photosensitive member in the exposed area and the vertical axis represents the development. The mixing ratio on the photoconductor after is shown. The developer is a conductive magnetic toner having a particle size of 9 μm, a resistivity of 10 ² Ω · cm, and a particle size of 11 μm.
A mixture of insulating non-magnetic toner having m and a resistivity of 10 ¹⁴ Ω · cm was used, and the mixture ratio was 20%. The experimental apparatus has the same configuration as that shown in FIG. The bias applied to the developing sleeve was -100 v, the peripheral speed of the photosensitive member was 25 mm / sec, and the peripheral speed of the developing sleeve was 200 m.
m / sec. Here, the mixing ratio of the toner adhered to the photoconductor by development is such that the photoconductor resistance of the exposed portion is 10 ⁸ Ω.
When it is smaller than cm, it shows about 100%, which means that there is no adhesion of the conductive magnetic toner.

Although the embodiments of the present invention have been described above, it is obvious that the above embodiments are merely examples and should not be construed as limitations.

Further, instead of the photoconductor and the exposing means of the present invention, the resistance of the image forming portion and the non-image forming portion is 10 ⁸ Ω.
It is clear that the same effect as that of the present invention is exhibited if the combination of the image bearing member and the latent image bearing layer is such that it is less than or equal to cm and less than or equal to 10 ¹⁰ Ωcm.

[0021]

According to the present invention, since only the insulating toner is developed, the transferability is good and a high density image can be obtained even when plain paper is used, and the toner density control is easy. You can do it.

Further, since the charging, exposing and developing are performed in the developing nip, the process is simplified, and since the charger, the static eliminator and the cleaning are not required, the apparatus can be downsized and the cost can be reduced. .

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a photoconductor of the present invention.

FIG. 3 is a graph showing a mixing ratio of toner deposited on a photoconductor after development.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Developing device 3 ... Toner box 4 ... Magnetic roller 5 ... Development sleeve 6 ... Power supply 7 ... LED array head 8 ... .Transfer means 9: recording paper

Claims (4)

[Claims] 1. An insulating toner is formed on a latent image forming portion of the image bearing member while a latent image is formed on the latent image bearing layer while applying a voltage while supplying conductive particles and an insulating toner to the image bearing member. An image forming apparatus for adsorbing − to form a toner image, wherein the latent image bearing layer of the image bearing member is 10 ⁸ Ω · cm or less at a latent image forming portion during latent image formation, and a non-latent image forming portion. An image forming apparatus having a resistance value of 10 ¹⁰ Ω · cm or more. 2. The latent image bearing layer of the image bearing member exhibits a resistance value of 10 ⁶ Ω · cm or less at a latent image forming portion and 10 ¹¹ Ω · cm or more at a non-latent image forming portion during latent image formation. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 1, wherein the conductive particles are conductive toner. 4. The image forming apparatus according to claim 1, wherein the conductive particles are conductive carriers.