JPH0588587A - Image forming device - Google Patents

Abstract

PURPOSE:To provide the image forming device where the generation of ozone causing environmental pollution can be suppressed to the minimum, with high image quality, low cost, and which is compact. CONSTITUTION:The image forming device is provided with a seamless belt-like conductive substrate 1a of <=320mm periphery length, corotron electrifying devices 2 and 5 (for exposure and transferring) carrying out positive corona discharging, a semi-conductive laser exposure part 3 written with image density of >=400dpi, a one-component developing device 4 carrying out developing with negatively charged toner are provided in the periphery of a positive charge type OPD photosensitive belt 1 consisting of an electric charge movement layer 1b, an electric charge generating layer 1c, and a surface protection layer 1d formed in this order over the first mentioned conductive substrate 1a and each containing a binder resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly, to an image forming apparatus that reduces ozone (O ₃ ) generation.

[0002]

2. Description of the Related Art Conventionally, each unit around a photosensitive drum of an electrophotographic digital copying machine generally has an arrangement configuration shown in FIG. In the figure, the photosensitive drum 11 is a negative charging type OPC. First, a photoconductor drum 1 is charged with a scorotron charger that performs negative corona discharge (hereinafter referred to as a negative corona corotron charger or scoroton charger).
1 surface is uniformly charged, the laser beam 13 is scanned to expose the image, and a dry two-component developer (negatively charged toner) is used to perform reversal development by a developing device 14 to form a toner image on the photosensitive drum 11. When the toner is formed and passed through a transfer sheet, a corotron charger 15 (hereinafter referred to as a positive corona corotron charger or a corotron charger) that performs positive corona discharge from the back surface side, and then an AC corona charger 16 charges the toner. Image transfer and charge separation of transfer paper are performed. After that, an AC corona charger (PCC) 17 applies a negative DC bias AC corona to the surface of the photoconductor drum 11 having the transfer paper toner to temporarily negatively charge the photoconductor drum 11 and the transfer residual toner. Cleaning by the cleaning blade 18 and quenching by the LED 19 are performed smoothly.

By such an image forming process, the ozone concentration immediately below each charger around the photosensitive drum 1 when one copy of A4 size transfer paper is obtained is determined by corona discharge of each charger and the subsequent process. When measured according to time, as shown in FIG. 5, the negative corona corotron charger 2 and the AC corona chargers 5 and 6 show high ozone concentrations, and in recent years, ozone (O ₃ ) emitted from a copying machine has been increased. Can understand why is a pollution problem.

By the way, the positive corona during charging is shown in FIG.
As shown in (b), the wire is uniformly discharged, whereas in the negative corona, the discharge is point-like and non-uniform as shown in FIG. Therefore, in the case of negative corona, a scorotron charger is used to uniformly charge the photosensitive drum 1.

Then, the photosensitive drum 1 is kept at a constant potential (80
For uniform charging to 0 V), the scorotron charger and the positive corona corotron charger are respectively shown in FIG. 7 (a).
It is necessary that the discharge conditions shown in (b) and (b) are satisfied.
Further, when the ozone concentration in the scorotron charger and the corotron charger is measured, as shown in FIG. 8, both the positive corona A and the negative corona B have a higher ozone concentration in proportion to the discharge current. The scorotron charger is calculated to generate 27 times more ozone than the positive corona coroton charger.

[0006]

As described above, ozone generated by corona discharge by the negative corona corotron and AC corona charger deteriorates members inside the copying machine and leaks out of the apparatus through the exhaust port and the like. However, there is a problem of causing environmental pollution.

Therefore, in order to reduce the ozone concentration in the copying machine, the negative corona corotron and the AC corona charger are not used, and the minimum necessary charger (used for charging and transfer) is charged by the positive corona corotron. The image forming apparatus may be designed as a container.

Therefore, instead of the non-contact charging method in which a high voltage is applied to a wire to perform corona discharge, a contact charging method in which a low voltage is applied to a brush or a roller has been studied.
For example, in Japanese Patent Application Laid-Open No. 1-204081, a roller-shaped charging member is formed of a conductive rubber layer, and at least outside the charging member, a member to be charged (released at a portion contacting the photosensitive drum) is released. By forming a conductive coating,
There is disclosed a charger that prevents defective charging, uneven charging, and ozone generation.

However, in the above-mentioned conventional method, there are still insufficient points in terms of uniform charging of the photosensitive member and prevention of ozone generation.

Therefore, the present invention eliminates the above-mentioned conventional problems and suppresses the generation of ozone as much as possible.
An object is to provide an image forming apparatus that achieves high image quality, low cost, and compactness.

[0011]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a photosensitive belt and a periphery of the photosensitive belt.
At least each charger for exposure and transfer, pixel density 40
In an image forming apparatus provided with a semiconductor laser exposure unit for writing at 0 dpi or more and a one-component developing device for developing with negatively charged toner, each of the chargers is a corotron charger for performing positive corona discharge, and the photosensitive member. The belt is a seamless belt-shaped conductive substrate having a circumference of 320 mm or less,
A charge transfer layer (CTL) and a charge generation layer (CG) which are formed in this order on the conductive substrate and each contain a binder resin.
L) and a surface protection layer (OCL) are positive charging type OPC photoconductors.

[0012]

Therefore, the photoreceptor belt is composed of a seamless belt-shaped conductive substrate, a charge transfer layer containing a binder resin, a charge generation layer, and a surface protection layer, and is a positive charge type OPC.
Since it is a photoconductor, only the corotron charger that performs positive corona discharge is used (AC corona and negative corona corotron charger are not used), and the generation of ozone can be suppressed as much as possible.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a photoconductor belt having a circumference of 32.
It is a positive charging type OPC photosensitive member having a seamless belt shape of 0 mm or less. A positive corona corotron charger 2 (total corona current 200 μA) 2 uniformly charges the photoconductor belt 1 to 800V. Reference numeral 3 denotes an exposure portion, which is scanned with a semiconductor laser beam (beam diameter of about 90 μ) to perform background exposure (non-image portion potential 1).
00V). A developing device 4 performs one-component development using negatively charged magnetic toner. 5 is a positive corona corotron charger for transfer (total corona current 180 μA), transfer rate 80
It is 0% or more. Denoted at 6 is a separating portion, which peels off the transfer paper by utilizing the curvature of the photosensitive belt 1. 7 is a cleaning blade. Reference numeral 8 is a quenching (LED), and since the residual potential of the photosensitive belt 1 is always positive, it is photo-erased.

By the way, regarding the photosensitive belt 1,
Selenium drums were mainly used as electrophotographic photoconductors, but they are advantageous in terms of pollution, spectral sensitivity (no sensitivity to semiconductor laser light), and manufacturing cost.
Most of the OPC photoconductors in which the photoconductor is used are negatively charged with the layer structure shown in FIG. 2A, which causes environmental pollution due to ozone generation. Therefore,
The OPC photosensitive member used in this example is a positive charging type, has a layer structure shown in FIG. 1B, and is made of an organic substance containing a binder resin on the seamless belt-shaped conductive substrate 1a. Charge transfer layer (CTL) 1b, charge generation layer (C
GL) 1c and surface protection layer (OCL) 1d are formed in this order. The reason why the belt-shaped OPC photoconductor is adopted is that the curvature separation method (the photoconductor naturally peels off because the transfer paper cannot follow the surface having a relatively high curvature) and the AC corona for separation is used. This is because a charger (which causes ozone generation) is unnecessary. Further, in the case of the conventional jointed photosensitive belt, cleaning by the blade 7 is impossible, and the belt circumference is required to be 420 mm or more for A3 size, which hinders the compactness of the apparatus. In the example, the photosensitive belt 1 of seamless belt is adopted.

Now, a method for producing the photosensitive belt 1 used in this embodiment will be described. Perimeter about 250 created by electroforming
A mm seamless Ni seamless belt (thickness: 50 μm) is held by a concentric cylindrical drum, and the CTL, CGL, and OCL containing a binder resin are sequentially applied by a depping method. This CTL consists of 1 part by weight of hydrazone (CTM) and 1 part by weight of polycarbonate resin, and has a film thickness of 2
The film thickness is 5 μm, the film thickness of CGL is 0.5 μm with 2 parts by weight of trisazo pigment and 1 part by weight of polyvinyl butyral resin, and OCL is polyester resin with a film thickness of 1.5 μm. In this embodiment, the photosensitive belt 1 has a linear velocity of 90.
Rotate at mm / sec.

The exposed portion 3 is scanned with a semiconductor laser beam (diameter of about 90 μ) to generate a non-image portion potential 100.
Background exposure with V. Conventionally, in the formation of a latent image by a laser beam, image exposure (P is a bit pitch, D is a beam diameter) as shown in FIG. 3 (a) has more unevenness of an image edge than background exposure shown in FIG. 3 (b). It has been widely used because it has a low degree, but as the pixel density increases, the difference disappears, and in this embodiment in which the pixel density is 400 dpi or more, it is almost impossible to discriminate.

Regarding the developing system of the developing device 4, the two-component developer using the resin-coated carrier has a high resistance, so that there is no problem even if a high developing bias is applied in the reversal development. Since the one-component developer has a low resistance and a bias potential leak becomes a problem, regular development is rather suitable.

When an example of the image forming apparatus having the above-mentioned configuration is tested, the ozone concentration around the corotron chargers 2 and 5 is 1.0 PPm, and 0.05 ppm near the exhaust gas of the apparatus body. The number of occurrences is drastically reduced to 1/20 to 1/30 of conventional copying machines.

[0019]

As described above, according to the present invention, since only the corotron charger that performs positive corona discharge is used as the charger, the amount of ozone generated during corona discharge is extremely small ( 1/20 to 1/30)
Can be suppressed to. In addition, the photoreceptor belt is composed of a conductive substrate having a seamless belt shape and a charge transfer layer (CT).
L), a charge generation layer (CGL), and a surface protection layer (OCL) are used, a positive charge type OPC photoreceptor is used, so that the belt circumference is short (320 mm or less), and blade cleaning is possible. As a result, the device can be made compact and the cost can be reduced. Further, since the transfer paper is flexible, it is possible to separate the curvature of the transfer paper, and the AC corona charger for the separation is not required. For this reason, the ozone generation can be reduced, the device can be made compact, and the cost can be reduced. ..

The pixel density of the semiconductor laser exposure portion is 4
Since it is greater than or equal to 00 dpi, the degree of unevenness of the image edge does not pose a problem even with background exposure as compared with image exposure. Further, each layer of the photoconductor belt can be formed by forming a coating solution using a solvent and applying the solution by a dipping method or a spray method, so that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2A and FIG. 2B are cross-sectional configuration diagrams of a photoconductor belt according to the related art and this embodiment.

3A and 3B are explanatory diagrams showing image exposure and background exposure.

FIG. 4 is a configuration diagram showing a conventional image forming apparatus.

FIG. 5 is a characteristic diagram showing the concentration of ozone generated from each charger.

6 (a) and 6 (b) are discharge characteristic diagrams on a wire having a positive corona and a negative corona.

7A and 7B are explanatory diagrams showing discharge conditions of a negative corona corotron and a positive corona corotron charger.

FIG. 8 is a characteristic diagram of ozone generation in a positive corona and a negative corona.

[Explanation of symbols]

 1 Photoreceptor Belt 2.5 Positive Corona Corotron Charger 3 Exposure Part 4 Developing Device 1a Seamless Conductive Substrate 1b Charge Transfer Layer 1c Charge Generation Layer 1d Surface Protective Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // G03G 5/147 6956-2H

Claims (1)

[Claims] 1. A photosensitive belt, a charging device for at least exposure and transfer around the photosensitive belt, a semiconductor laser exposure section for writing at a pixel density of 400 dpi or more, and one-component development for developing with negatively charged toner. In the image forming apparatus including a device, each of the chargers is a corotron charger that performs positive corona discharge, and the photosensitive belt is a seamless belt-shaped conductive substrate having a peripheral length of 320 mm or less, and the conductive material. A positive charging type OPC photosensitive member which is formed in order on a substrate and comprises a charge transfer layer (CTL) containing a binder resin, a charge generation layer (CGL), and a surface protective layer (OCL). Image forming apparatus.