JPH05158391A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent the degradation in a resolving power and the generation of an image blur by printing resistance by controlling the exposure for destaticization of a photosensitive body having an amorphous carbon film formed by a plasma polymn. method. CONSTITUTION:The photosensitive body is electrified by an electrifier 1 and is exposed in an exposing part 2 and the image is transferred by a developing device 4 to a transfer paper. Residual toners are removed by a cleaner 5 and the exposing for the purpose of destaticization of the photosensitive body 8 is executed by an elaser 6. The exposing for the purpose of destaticization is required to be so set that the condition equation 0<=R/S<=1.8 holds where the total sum of the light quantity of the exposing part is designated as R(lux sea) and the system speed as S(cm/sec) when the surface protective layer of the photosensitive body 8 is constituted of the amorphous carbon film produced by the plasma polymn. method. The resolving power of the image forming system is too much degraded and such degradation is undesirable if the R/S exceeds 1.8. More particularly preferably, the R/S is 0 to 50lux.sec. The system speed is 20 to 50cm/sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a photoreceptor provided with an amorphous carbon film obtained by a plasma polymerization method as a surface protective layer of a photosensitive layer.

[0002]

2. Description of the Related Art In recent years, various photosensitive layers used in electrophotographic photoreceptors have been proposed which are made of an inorganic photoconductive material such as selenium or an organic photoconductive material. In general, a photosensitive layer with a low hardness, the photoreceptor is scraped by friction of transfer paper, a cleaning member, a developer, etc. during repeated use,
It is easily scratched. In order to solve such a problem, a technique has been proposed in which a surface protective layer is provided on the surface of a photoreceptor having insufficient hardness.

An amorphous carbon film (hereinafter referred to as a PAC film) produced by a plasma polymerization method is used as a kind of such a surface protective layer. The photoreceptor having such a film has excellent durability as compared with a photoreceptor having no protective layer, and has sufficient strength for long-term use at room temperature and normal humidity, but has a reduced resolution and resistance to abrasion. The resistance of the photoconductor decreases with printing, and blurring or flow of the copied image occurs.
The cause of the decrease in resistance due to the shape of the PAC surface protective layer has not been clarified yet.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming method capable of preventing a reduction in resolution due to a PAC film and causing no image blur due to printing durability.

[0005]

The above-mentioned object can be achieved by adjusting the total amount of light in the charge-exposed exposed portion during development of the photosensitive member.

That is, the present invention provides a system in which the total amount of light at the exposed portion that neutralizes the surface of the photoconductor in the image forming process using the photoconductor overcoated with the PAC film is R (lux.sec.). Speed S (cm / sec.)
In this case, the image forming method is performed under the condition that the following conditional expression (I): 0 ≦ R / S ≦ 1.8 (I) is satisfied.

In the electrophotographic process, the photosensitive member is generally used in the structure as shown in FIG. That is, charging is performed by the charging device (1), exposed by the exposure unit (2), developed by the developing device (3), and then transferred to the transfer paper by the transfer separator (4).
After that, the cleaner (5) removes the residual toner, the eraser (6) exposes the photosensitive member to remove electric charge, and the process proceeds to the next step. At this time, in order to improve the transfer efficiency, an eraser (7) may be installed before the transfer to perform static elimination exposure before the transfer.

In the present invention, the total amount of light in the static elimination exposure section is
The total amount of light of the other static elimination exposure sections (6) and (7) not including the image exposure section ((2) in FIG. 1) is shown.
The exposure amount of the image exposure (2) is generally smaller than the exposure amount of the static elimination exposure by an order of magnitude, so that the influence thereof is hardly a problem as compared with the static elimination exposure. By adjusting the sum of the light amounts of the static elimination exposure units (6) and (7), image blurring, image deletion, etc. are avoided. This mechanism is not clear at present, but it is presumed as follows.

The PAC film produced by P-CVD (plasma chemical vapor deposition) has many trap sites in the film.
Therefore, when the photoconductor is excessively irradiated with light, many carriers are trapped in the film and the resistance of the film decreases. When a latent image is formed on this film, the trapped carriers are moved by the electric field, which reduces the definition of the latent image.
Therefore, it is considered that by reducing the exposure amount as compared with the conventional case, the decrease in the resistance of the film as described above is reduced and the image blur is avoided.

The system speed referred to in the present invention is the peripheral speed of the photoconductor. Mobility of PAC film is usually 10 ^-8 to 10
^Since it is about ^-7 (cm ² / (Volt · sec.)), It is considered that the slower the system speed, the more easily it is affected by the resistance decrease.

From the above, the static elimination exposure amount is set to R (lux.se
c.), assuming that the system speed is S (cm / sec.), it is considered that the reduction in resolution of this image forming system is proportional to R / S. As a result of the research conducted by the present inventors paying attention to this point, when the exposure amount and system speed are controlled so that 0 ≦ R / S ≦ 1.8, preferable image stability can be obtained. all right.

If the R / S exceeds 1.8, the image deterioration speed due to the reduction in the resistance of the PAC film of the resolution of the image forming system becomes too large as compared with the exposure and development time, which is not preferable. The exposure amount R is 0 to 100 lux · sec., And particularly preferably 0 to 50 lux · sec. Further, as shown in the above equation, R / S = 0, that is, a system in which no static elimination exposure is performed is also included in the present invention. The system speed S is 20 to 50 cm / sec.

In the case of controlling the exposure amount, if the static elimination exposure amount is simply decreased or the static elimination exposure step is omitted, static elimination is not completely performed and an image memory is generated. Further, in the conventional image forming apparatus, since the deterioration of the lamps should be set in consideration of the deterioration, for example, a sufficient charge removal exposure amount of 10 lux · sec. Is set to 20 lux · sec in anticipation of the deterioration of the lamp. As described above, it is necessary to initialize the exposure amount more than that required for the static elimination.

There are two conceivable methods for controlling the exposure amount in order to satisfy these requirements and to satisfy the conditional expressions of the present invention: to install a light amount feedback mechanism and to combine with a charge eliminating charger.

The light amount feedback mechanism detects a decrease in the light amount due to the deterioration of the lamp and automatically increases the output of the lamp when the decrease is detected. As a result, it is possible to always set the required minimum exposure amount without performing excessive exposure due to deterioration of the lamp.

Further, the total amount of light necessary for removing the charge on the photoconductor can be greatly reduced by combining it with a charge removing charger. That is, the charge removal is not performed only by exposure, but a charge charger (CHG) and a charge removal charger that performs reverse charging are used in combination. The static eliminator usually has a reverse charge component (DC component).
An alternating current (AC component) is superimposed on and used. As a result, the static elimination exposure amount can be reduced significantly or entirely.

The photoreceptor used in the present invention has a PAC film as a surface protective film for the photosensitive layer. This PA
The C film is a conventionally known plasma polymerization device (for example, JP-A-63 / 1988).
-97962). A typical PAC film is produced using butadiene gas as a source gas and hydrogen as a carrier gas. Further, if necessary, impurities such as oxygen, nitrogen, group III atom, group IV atom, group V atom, etc. of the periodic table may be contained. This PA
The C film thickness is preferably 0.01 to 5 μm.

The amorphous carbon film produced in this manner is a film having the following features (when butadiene is used as the source gas). (I) Hole mobility 10 ⁻⁷ to 10 ⁻¹⁰ [cm
² / V / sec.] (Ii) Electronic mobility 10 ⁻⁷ to 10 ⁻¹⁰ [1
0 cm ² / V / sec.] (Iii) Ionization potential 5.0 to 5.8 [e
V] (iv) Optical band gap 2.0 to 2.8 [eV] (v) Relative permittivity 2.4 to 3.0 (vi) Visible light absorption coefficient 200 to 4000 [1
/ cm] (vii) Spin density 2.0 × 10 ^{18 to} 9.0
× 10 ¹⁹ [1 / cm] (viii) Refractive index 1.5 to 1.7 (ix) Vickers hardness 200 to 1000

The photosensitive layer used in the present invention is not only a so-called function-separated type organic photosensitive layer (OPC) but also a so-called anti-stack type photosensitive layer having a charge generation layer provided on a charge transport layer. It may be a photosensitive layer having a so-called single layer structure having both a charge transporting function and a charge transporting function. Known materials may be appropriately selected as the charge generating material, the charge transporting material, the binder resin, and the like.

Further, not only the organic photosensitive layer but also inorganic materials such as zinc oxide, cadmium sulfide, selenium alloy, and amorphous silicon alloy may be used. The substrate material used in the present invention is not particularly limited as long as it has a conductive surface, and may have a flat plate shape or a belt shape other than the cylindrical shape. The surface of the substrate may be roughened, oxidized, or colored. Further, the photoconductor that can be used in the present invention,
An undercoat layer may be provided in order to improve adhesiveness and the like. As the material of the undercoat layer, a resin such as an ultraviolet curable resin, a room temperature curable resin, a thermosetting resin, a mixed resin in which a resistance adjusting material is dispersed in the resin, a metal oxide,
It is possible to use a vacuum thin film material obtained by thinning a metal sulfide or the like in a vacuum by an evaporation method or an ion plating method, an amorphous carbon film produced by using a plasma polymerization method, an amorphous silicon carbide film, etc. ..

[0021]

EXAMPLE An amorphous carbon film formed by a plasma decomposition reaction from a hydrocarbon-based gas was formed on a function-separated organic photosensitive layer (OPC) for negative charging, which has a good sensitivity in a relative visual sensitivity range. A photoconductor provided as a surface protective layer was produced by the following method and subjected to an evaluation test for image blur and the like.

Preparation of Charge Generation Layer Structural Formula I

[Chemical 1] 0.45 part by weight of an azo compound represented by, polyester resin (Byron 200: manufactured by Toyobo Co., Ltd.) 0.45 part by weight,
And 50 parts by weight of cyclohexanone were placed in a sand grinder and dispersed for 24 hours to obtain a photosensitive coating liquid. At this time, the viscosity of the photosensitive coating liquid was 20 cp at 20 ° C.

This coating solution was applied to an outer diameter of 80 mm and a length of 340 m.
It was applied to the surface of an aluminum cylindrical substrate having a thickness of 2 mm and a thickness of 2 mm by dipping to form a charge generation layer having a thickness of 0.3 μm after drying. The cylindrical substrate used here is an aluminum alloy containing 0.7% by weight of magnesium and 0.4% by weight of silicon. The drying condition was 30 minutes in circulating air at 20 ° C.

Preparation of Charge Transport Layer On the above charge generation layer, structural formula II

[Chemical 2] And a polycarbonate resin (Panlite K-1300: manufactured by Teijin Chemicals Ltd.) in an amount of 40 parts by weight of 1,4-dioxane in a solvent. Apply using 1
It was dried in circulating air at 00 ° C for 30 minutes.

As described above, a photosensitive layer in which a charge generation layer and a charge transport layer were sequentially laminated on a conductive substrate was prepared.

Preparation of Surface Protective Layer An amorphous carbon film was provided on the above-mentioned laminated type photosensitive layer by plasma polymerization under the following conditions to complete the photoreceptor. Raw material gas Butadiene 150 sccm Carrier gas Hydrogen 300 sccm Vacuum degree 1 Torr Electrode distance 38 mm Drum rotation speed 5 rpm Electric power 150 W Power supply frequency 100 kHz Drum temperature 50 ° C. Film formation time 3 minutes Film thickness 0.11 μm

This photoconductor is mounted on a copying machine in which the static elimination exposure amount and system speed are variable, and the total light amount is 30 to 120.
The effect on image blur after printing 10,000 sheets was examined under conditions of 25 ° C. and 60% while varying the lux · sec. and system speed from 18 to 55 cm / sec. Image blur was evaluated by whether or not 5.0 lines per 1 mm (lines having a pitch of 100 μm) can be reproduced, and ranked as follows.

No: 100 μm pitch line can be reproduced Yes: 100 μm pitch line cannot be reproduced Results are shown in Table 1.

[0028]

[Table 1]

[0029]

EFFECTS OF THE INVENTION In an image forming process using a photoconductor having an amorphous carbon film produced by a plasma polymerization method, a reduction in resolution and a blur of an image due to printing endurance are prevented by controlling a charge-removing exposure amount of the photoconductor. It was possible to obtain a stable and clear image for a long time.

[Brief description of drawings]

FIG. 1 is a structural example of a method of using a photoconductor.

[Explanation of symbols]

1: Charger, 2: Development exposure, 3: Development device, 4: Transfer separator, 5: Cleaner, 6, 7: Eraser (charge elimination exposure part), 8: Photoconductor

Claims (1)

[Claims] 1. The total amount of light at an exposed portion for eliminating charge in an image forming process using a photoreceptor overcoated with an amorphous carbon film obtained by a plasma polymerization method is R (lux. sec.) and the system speed is S (cm / sec.), the following conditional expression (I): 0 ≦ R / S ≦ 1.8 (I) is satisfied. Image forming method.