JP2622966B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic recording process, such as an electrostatic copying machine and the same printer.

(Prior Art and Problems to be Solved) A photoconductive layer (referred to as a photosensitive layer) is formed on the surface of a conductive substrate, and a charged toner is supplied to an electrostatic latent image formed thereon to form a toner image. An image forming apparatus configured to transfer a toner image onto a transfer material such as paper is conventionally known.

In such an image forming apparatus, as the photosensitive layer, Cd
Various materials such as S-resin dispersion system, ZnO-resin dispersion system, Se system, OPC system, and amorphous silicon are used.Amorphous silicon has high hardness, excellent abrasion resistance, and performance in environmental changes. Has high stability, but on the other hand, it is difficult to increase the thickness of the photosensitive layer (for example, 50-60μ of Se-based photosensitive layer,
25-30μ), and the dielectric breakdown voltage is, for example, 5KV or more for the OPC type photosensitive layer and 3KV or more for the Se type, while amorphous silicon type has a low defect of about 2.0-2.6KV. ing.

Furthermore, the amorphous silicon type has a large capacity due to low charging ability, requires a large current for charging, and increases a printing voltage to a discharge wire of a charger in a transfer process, thereby contaminating the wire. Due to vibration, etc., spark discharge easily occurs between the discharge wire of the charger and the grid, and the spark may cross the grid and reach the photosensitive layer. In this case, as described above, the counter pressure of the photosensitive layer Is broken down into a pinhole shape, and spots (white spots in a full black image, black spots in a full white image) are formed in the running direction of the transfer material, resulting in marked deterioration in image quality.

Further, in the case where a separation charger is used in the separation step, since the applied voltage is mainly of alternating current, it is easy to induce vibration, thereby generating a spark discharge. It is easy to cause inconvenience.

The present invention has been made in order to cope with the above situation, and even in an image forming apparatus using a photosensitive layer made of amorphous silicon, this kind of photosensitive layer can be formed without causing the above-described inconvenience. An object of the present invention is to provide an image forming apparatus capable of stably obtaining a good quality image by effectively utilizing the image forming apparatus.

(2) Configuration of the Invention (Means for Solving the Problems and Their Functions) In order to achieve the above object, the present invention provides a positive withstand voltage value.
A photosensitive member provided with an amorphous silicon photosensitive layer having a negative withstand voltage lower than the positive withstand voltage value of 2.0 to 2.6 kV, a charger for positively charging the photosensitive member, and a transfer roller contacting the photosensitive member; An image forming apparatus having a transfer roller for transferring a toner image from the photoconductor to a transfer material sent between the photoconductor and the transfer roller, wherein the process speed of the photoconductor is 180 mm / sec or more. The image forming apparatus is characterized in that the transfer roller has a rubber hardness of 15 ° to 60 ° (JIS) and a negative voltage lower than the negative withstand voltage is applied.

With such a configuration, it is possible to reliably prevent the occurrence of spark discharge and to lower the transfer potential, thereby making it easy to separate and eliminate the need for a separate charger. , High quality images,
The configuration of the transfer and separation sites can be made compact and compact.

DESCRIPTION OF EMBODIMENTS The accompanying drawings are main part side views showing an embodiment in which the present invention is applied to a copying machine having a rotating cylindrical photoreceptor extending in a direction perpendicular to the plane of the paper. Extending photoreceptor 1
Has an amorphous silicon photosensitive layer comprising a charge injection blocking layer (thickness 3μ), a photoconductive layer (24μ), and a surface protection layer (0.5μ) laminated on the surface of an animinum substrate, withstand voltage of + 2.6KV. , -0.8 KV.

The charging roller 2 applies a DC voltage of +1.3 KV to charge the toner, forms a latent image by the image signal applying means 3, and supplies a negatively charged toner by the developing device 4 to visualize the latent image.

It is assumed that the toner image is transferred in contact with a transfer material (not shown) conveyed by the conveyance path 6 at a transfer portion where the transfer roller 5 comes into contact with the photoconductor at a timing.

The transfer roller 5 is made of stainless steel with a diameter of 8 mm and EPDM.
Using a conductive roller formed by winding a rubber and a conductive rack skin CF5700 on it and forming it to a diameter of 18 mm, DC + 1.1 KV was applied and transfer was performed. Obtained. According to experiments, this applied voltage is DC + 1.
It has been confirmed that 0 to 1.5 KV is suitable.

The transfer roller 5 has a hardness of 15 to 60 degrees (JIS H
s), the electrical resistance shall be in the range of 10 ⁴ to 10 ⁶ Ω.

The transferred transfer material is then separated from the photoreceptor by its own stiffness and its own weight, and is conveyed to the next step by the conveying means 9.

Reference numeral 7 denotes a separation claw for separating the transfer material from the photoreceptor. However, since the voltage applied to the transfer roller 5 is relatively low, there is no need for the separation claw except for thin paper which is particularly weak.

With the above equipment, in an environment of 15 ° C and 10% RH,
A 100,000 sheet passing test was performed. As a result, no spark discharge occurred between the photoreceptor 1 and the transfer roller 5, and no perforated white spot array was observed in the entire black image.

On the other hand, using a known corona charger without cleaning
When a 100,000-sheet feed test is performed, φ0.3
Twelve white spots of about mm were observed.

Further, a negative voltage was applied to the transfer roller by an image forming apparatus that performs reversal development using a laser exposure system, and transfer was performed using positively charged toner.
A transfer rate of 80% was obtained with V.

Although this transfer voltage is close to the above-mentioned withstand voltage limit value, the dielectric breakdown due to the + voltage causes the breakdown to be slow, 0.1 to 0.5
Since it is destroyed after c, it is enough to be practically used for medium and high speed machines with a process speed of 180 mm / sec or more.

To further explain the above points, in the case of the amorphous silicon photoreceptor having a low charging ability as described above, dielectric breakdown hardly occurs by combining this with a transfer member that contacts the opposite side of the transfer material. Further, when the transfer bias applied to the transfer member is a negative voltage, the amorphous silicon photoreceptor has a lower withstand voltage than the positive, but on the other hand, in the case of the negative voltage, it takes a longer time to cause dielectric breakdown. By setting the process speed of the photoconductor to 180 mm / sec or more, dielectric breakdown can be substantially prevented.

When a 50,000-sheet passing test was performed using this apparatus in an environment of 15 ° C. and 10% RH, no perforated black spot arrays were found.

As described above, since the present device does not use a transfer charger, the generation of spark discharge can be sufficiently suppressed, and the advantages of the amorphous silicon photosensitive layer having a low dielectric strength and a large mechanical strength can be fully utilized.

Also, since the voltage applied to the transfer roller is low, the tendency of the transfer material to be attracted to the photoreceptor after the transfer is weak, and since there is usually no need for a separating means other than thin paper having a particularly low stiffness,
This is effective for downsizing the device.

In addition, it is of course possible to use the same conductive roller as the above-described transfer roller also in the primary charging portion, and thus a special high-voltage power supply is not required by this configuration. This contributes to downsizing of the device.

The case where the present invention is applied to a copying machine has been described above, but it can be easily understood that the present invention is not limited to this, and can be applied to other types of image forming apparatuses.

(3) Effects of the Invention As described above, according to the present invention, in an image forming apparatus provided with an amorphous silicon photoreceptor, a transfer member is provided in contact with the same, and a negative voltage is applied to the transfer member. When the process speed at this time is 180 mm / sec or more, dielectric breakdown of the amorphous silicon photosensitive layer can be effectively prevented, so that the mechanical strength of amorphous silicon is large. In addition, it is possible to provide an image forming apparatus that can perform transfer with high efficiency stably for a long period of time and obtain high-quality images in combination with an advantage that stability can be maintained even under environmental changes.

[Brief description of the drawings]

The attached drawing is a side view of a main part of an embodiment in which the present invention is applied to a copying machine. 1 ... Photoconductor, 2 ... Charge roller, 5 ... Transfer roller,
7 Separating claws.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-281260 (JP, A) JP-A-53-77533 (JP, A) JP-A-62-175779 (JP, A) 66254 (JP, U)

Claims (1)

(57) [Claims] A photosensitive member having an amorphous silicon photosensitive layer having a positive withstand voltage of 2.0 to 2.6 kV and a negative withstand voltage lower than the positive withstand voltage; a charger for positively charging the photosensitive member; An image forming apparatus, comprising: a transfer roller that contacts the photosensitive member; and a transfer roller that transfers a toner image from the photosensitive member to a transfer material sent between the photosensitive member and the transfer roller. An image wherein the process speed of the body is 180 mm / sec or more, the transfer roller has a rubber hardness of 15 ° to 60 ° (JIS), and a negative voltage lower than the negative withstand voltage value is applied. Forming equipment.