JP2000112203A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negatively electrifying color printer adequate to high- speed color printing with high performance. SOLUTION: As to this tandem type electrophotographic system image forming device 18; an image forming element 7 in which a photoreceptor 8, a corona electrifying device 9 imparting a negative charge on the surface of the photoreceptor 8 a developing machine 12, a transfer device 14, a cleaning means 15 and a discharge means 16 are disposed, is arrayed, the photoreceptor mounted on at least one image forming element is constituted of an a-Si photoconductive layer in which intensity Ia in wave number 2000 cm-1 and intensity Ib in wave number 2100 cm1 satisfy the relational expression of 0.22<=Ib/(Ia+Ib)<=0.35 in an infrared ray absorbing spectrum, and a process speed is >=200 mm/second.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type electrophotographic image forming apparatus which is mounted on a negatively charged photoreceptor made of an amorphous silicon photoconductive layer and is applied to high-speed copying.

[0002]

2. Description of the Related Art As a color printer which has already been commercialized, there is an image forming apparatus of a tandem type electrophotographic system, and a photosensitive member mounted thereon is constituted by a negative charging type OPC. The charging ability of this OPC photoreceptor is -8.
Since the voltage can be increased to about 00 V, the adhesion of the color toner becomes easy (see JP-A-4-287070 and JP-A-7-306624).

On the other hand, an amorphous silicon photosensitive member is used for high-speed copying, and a process speed of 180 m
An image forming apparatus for positive charging achieving m / sec or more has been proposed (see Japanese Patent No. 2622966).

[0004]

However, the above O
When an image forming apparatus equipped with a PC photoreceptor is applied to high-speed color printing, the OPC photoreceptor is not suitable because of poor abrasion and durability.

In view of the above, at least a photoconductor using a black toner image is replaced by an amorphous silicon photoconductor (hereafter, amorphous silicon is abbreviated as a-Si) instead of the OPC photoconductor. But,
The charging ability and light sensitivity were lower than those of the OPC photoreceptor, and satisfactory printing performance could not be achieved. Hereinafter, the reason will be described.

The a-Si photoreceptor is suitable for positive charging,
This is a layer configuration in which an a-Si charge injection blocking layer and an a-Si photoconductive layer are sequentially laminated on a conductive substrate by a glow discharge decomposition method. Then, the a-Si charge injection blocking layer is provided in the periodic table II.
By doping with the Group Ia element, a potential barrier against electrons was formed, thereby preventing injection of electrons from the conductive substrate and making it possible to obtain an electrophotographic photosensitive member for positive charging.

On the other hand, a potential barrier for holes is formed by doping the a-Si charge injection blocking layer with a Group Va element of the Periodic Table instead of the Group IIIa element of the Periodic Table. Electrophotographic photoconductors for negative charging are expected to replace the conventional OPC photoconductor by preventing injection of holes from the substrate, but have not yet been put to practical use.

The inventor of the present invention has conducted various investigations on such problems that have not been put into practical use. If the doping of the charge injection blocking layer with the element (abbreviated as element) is merely replaced with a group Va element of the periodic table (hereinafter abbreviated as group Va element), the layer is charged negatively, Was also found to be charged.

Therefore, when such an electrophotographic photosensitive member is mounted on a printer (image forming apparatus) and an image is to be formed using a toner for negative charging, when the toner is transferred to paper, the above-mentioned positive charging property is obtained. For this reason, the transfer bias voltage was canceled, and the image characteristics deteriorated.

In addition, phosphine (PH ₃ ), which is a typical gas used for doping a Va group element, is highly toxic and has a bad effect on the human body even at a low concentration. And there is also a problem that the cost increases accordingly. Furthermore, in order to use such a doping gas with high precision as required and thereby reduce the variation in electrophotographic characteristics, it is necessary to considerably increase production control, which also increased production costs. .

Generally, in the case of a color printer in which a plurality of photoconductors are arranged for one image forming apparatus,
When photoconductors having different photoconductive layers are provided, there is also a problem that a required coloring cannot be obtained due to a difference in performance between the photoconductors.

In view of the above circumstances, the present inventor has made intensive studies and found that in a tandem type electrophotographic color printer, the photosensitive member mounted on the image forming element was a-Si.
By increasing the film quality by defining the relationship between the intensity Ia at a wave number of 2000 cm ⁻¹ and the intensity Ib at a wave number of 2100 cm ⁻¹ in the infrared absorption spectrum of the a-Si photoconductive layer, , Process speed 2
00 mm / sec or more, and as a result, high-speed copying can be obtained with excellent negative chargeability. Furthermore, even when an image forming element equipped with an OPC photoreceptor is used, there is a difference in charging and sensitivity characteristics between them. It has been found that an image forming apparatus which is sufficiently practical as a color printer even when a different kind of photoconductor is mounted is obtained by reducing the size and increasing the light sensitivity. In addition, it has been found that even if the a-Si charge injection blocking layer is not doped with a Va group element, the negative charge can be satisfactorily charged, thereby reducing the production cost by not using a phosphine gas or the like.

Accordingly, the present invention has been accomplished based on the above findings, and an object of the present invention is to provide an image forming apparatus for negative charging suitable for high-speed color printing.

Another object of the present invention is to provide an image forming apparatus in which the production cost can be reduced by not using phosphine gas or the like.

Still another object of the present invention is to provide a long-term reliable image forming apparatus having improved durability.

[0016]

The tandem type electrophotographic image forming apparatus of the present invention has a configuration in which a plurality of image forming elements are arranged, and each image forming element has a photosensitive member and a negative electrode on the surface of the photosensitive member. A charging unit for applying a charge; and an exposure unit for irradiating the charged area of the photoreceptor with light. The charging unit and the exposure unit form an electrostatic latent image on the surface of the photoreceptor. Developing means for forming a colored toner image corresponding to the image on the surface of the photoreceptor; transfer means for transferring the colored toner image to a transfer material; cleaning means for removing residual toner on the photoreceptor surface after transfer; A static eliminator for removing a residual electrostatic latent image is provided, and the photoreceptor mounted on at least one image forming element is provided with an intensity Ia at a wave number of 2000 cm ^-1 in an infrared absorption spectrum.
And the intensity Ib at a wave number of 2100 cm ^-1 is 0.22 ≦ I
a−S that satisfies the relational expression of b / (Ia + Ib) ≦ 0.35
i photoconductive layer to increase the process speed by 200
mm / sec or more.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Photoreceptor Configuration FIG. 2 shows a layer configuration of a photoreceptor 1 relating to an image forming element for forming a black toner image according to the present invention.
The photosensitive layer 3 made of -Si or the like is formed by vacuum evaporation, active reactive evaporation, ion plating, RF sputtering, DC sputtering, RF magnetron sputtering, DC magnetron sputtering, or thermal CV.
A film is formed by a D method, a plasma CVD method, or the like. The photosensitive layer 3 is formed by sequentially laminating, for example, a charge injection blocking layer 4, a photoconductive layer 5, and a surface protective layer 6.

The substrate 2 is made of copper, brass, SUS, Al, N
i. A material made of a metal conductor such as i, or an insulator such as glass or ceramic coated with a conductive thin film. The substrate 2 may be a sheet-shaped, belt-shaped or web-shaped flexible conductive sheet. Such a sheet may be a metal sheet such as SUS, Al, Ni, or a polymer resin film such as polyester, nylon, or polyimide. Metal such as Al, Ni or tin oxide,
A transparent conductive material such as indium tin oxide (ITO) or an organic conductive material coated by vapor deposition or the like and subjected to a conductive treatment is used.

The charge injection blocking layer 4 contains a group IIIa element as a valence electron controlling impurity and / or
Alternatively, even if such a non-doped element is not doped with the Va group element, the intensity Ia at a wave number of 2000 cm ⁻¹ and the intensity Ib at a wave number of 2100 cm ⁻¹ in the infrared absorption spectrum of the photoconductive layer 5 are set to 0. .22 ≦ Ib /
By setting so as to satisfy the relational expression of (Ia + Ib) ≦ 0.35, excellent negative charging ability was obtained.

That is, in the present invention, non-doped a-Si exhibits a weak n-type due to a structural defect of a bonding network formed during film formation, so that phosphine (PH ₃ ) gas or the like is used. It was an unexpected effect that excellent negative charging ability could be obtained by defining the film quality of the photoconductive layer 5 without doping P.

Specifically, when the photoconductive layer 5 is formed by the plasma CVD method, the bonding state of Si atoms and H atoms is obtained by changing the value of the applied high-frequency power or changing the film forming speed. [SiH bond] and [(SiH ₂ ) _n bond]
Can be defined, but when it is represented by an infrared absorption spectrum, the intensity Ia at a wave number of 2000 cm ^-1 is obtained.
Showing the relationship between the intensity and the intensity Ib at a wave number of 2100 cm ^-1
When the R ratio is represented by Ib / (Ia + Ib), 0.22 ≦ IR
When the relational expression of ratio ≦ 0.35, preferably 0.25 ≦ IR ratio ≦ 0.34 is satisfied, excellent negative charging ability can be obtained.
The difference in charging and sensitivity characteristics from other image forming elements equipped with a PC photoreceptor was reduced, and the light sensitivity was increased, thereby making it suitable for high-speed color printing at a process speed of 200 mm / sec or more. Further, from short wavelength visible light to near infrared light (long wavelength light), that is, the wavelength peak 52
The light sensitivity to irradiation light of 0 to 820 nm was improved. As a result, various light sources having a wide wavelength peak in laser light, LED, and the like can be used for the printer.

In addition, oxygen and nitrogen are contained in the charge injection blocking layer 4 to increase the forbidden band width, thereby increasing the function of preventing charge injection and increasing the barrier. This increases the adhesion to the substrate. However, oxygen alone can easily react with silane gas and cause an explosion.
Actually, nitrogen monoxide (NO) gas or the like is used.

The surface protective layer 6 is made of a-Si, amorphous silicon carbide, amorphous silicon nitride, amorphous silicon oxide, selenium, etc. by glow discharge decomposition, vacuum deposition, active reactive deposition, ion plating, RF sputtering. Method, DC sputtering method, RF magnetron sputtering method, DC
A film is formed by a magnetron sputtering method, a thermal CVD method, or the like. When an organic material is used, a film is formed by coating or the like.

As described above, according to the photoreceptor 1, the film quality is improved by defining the IR ratio of the photoconductive layer 5 as described above, thereby providing excellent negative chargeability and a process speed of 200 mm / sec or more. It is suitable for high-speed color printing, and the difference in charging and sensitivity characteristics from other image forming elements equipped with an OPC photoreceptor is reduced, and by increasing the light sensitivity, different types of photoreceptors can be mounted. Thus, the image forming apparatus was sufficiently practical as a color printer. In addition, even if the a-Si charge injection blocking layer was not doped with a Va group element, the negative polarity could be satisfactorily charged, and the production cost could be reduced by not using a phosphine gas or the like.

The diagram 1 of an image forming apparatus is an image forming apparatus of the present invention, firstly showing the principle of the imaging element 7 of the printer manner according to the present invention in FIG.
Reference numeral 8 denotes a photoconductor, a corona charger 9 serving as a charging unit that applies a negative charge to the peripheral surface of the photoconductor 8, an LED head 10 serving as an exposure unit that irradiates light after the charging, and a photoconductor. A developing device 12 provided with a toner 11 for forming the toner image on the surface of the transfer member 8; a transfer device 14 serving as a transfer device for transferring the toner image to a transfer material 13; In this configuration, a cleaning unit 15 for removing the toner and a charge removing unit 16 for removing the residual electrostatic latent image after the transfer are provided. Reference numeral 17 denotes a fixing device for fixing the toner image transferred to the transfer material 13 by heat or pressure.

In the Carlson method, the following processes (1) to (3) are repeated. The peripheral surface of the photoconductor 8 is negatively charged by the corona charger 9. An image is exposed by the LED head 10 to form an electrostatic latent image as a potential contrast on the surface of the photoconductor 8. This electrostatic latent image is developed by the developing machine 12. By this development, the colored toner adheres to the surface of the photoreceptor by electrostatic attraction with the electrostatic latent image and is visualized. The toner image on the surface of the photoreceptor is electrostatically transferred from the back surface of the transfer material 13 such as paper by applying an electric field having a polarity opposite to that of the toner, whereby an image is obtained on the transfer material 13. The cleaning unit 15 mechanically removes residual toner on the surface of the photoconductor. The entire surface of the photoconductor is exposed to intense light, and the remaining electrostatic latent image is removed by the charge removing means 16.

Next, in the image forming apparatus 18 shown in FIG.
7a is an image forming element for black (indicated by K in the figure), 7b is an image forming element for yellow (indicated by Y in the figure), and 7c is an image forming element for cyan (indicated by C in the figure). , 7d are magenta image forming elements (indicated by M in the figure). Then, the photoconductor 1 is mounted on the image forming element 7a (K), and the other image forming elements 7b (Y),
A known OPC photoconductor is mounted on 7c (C) and 7d (M). Further, a sheet as the material to be transferred 13 is placed on the transport belt 19 and is moved in the direction of the arrow.

Thus, according to the image forming apparatus 18 having the above-described configuration, the charging of the photosensitive member A of the image forming element 7a (K) is
As compared with the C photoreceptor, a charging difference of 200 V or less was obtained, printing unevenness was not generated, and a color image forming apparatus capable of obtaining a clear color image could be provided. Moreover, by improving the durability performance of the photoconductor A of the image forming element 7a (K),
High-speed color printing with a process speed of 200 mm / sec or more was possible, and the quality as a whole could be maintained for a long period of time, even if color printing and monochrome printing were properly used.

In the image forming apparatus 18, each of the image forming elements 7a (K), 7b (Y), 7c (C), 7d
The a-Si photoreceptor 1 may be mounted on all of (M), so that it is not necessary to change the drum current for each photoreceptor, and the circuit design for it is not necessary. Moreover, there is no charge difference, and the sensitivity characteristics are the same,
Therefore, there is no difference in density between the photoconductors, which is suitable for high-speed color printing.

[0030]

(Example 1) Photoconductor 1 of image forming element 7a (K)
Was prepared as follows. Cylindrical substrate 2 made of 99.9% pure Al (outer diameter 180 mm, length 372 mm)
A photosensitive layer 3 is formed by a plasma CVD method. The photosensitive layer 3 has a configuration in which a charge injection blocking layer 4, a photoconductive layer 5, and a surface protective layer 6 are sequentially laminated under the film forming conditions shown in Table 1. As for the surface protective layer 6, the flow rates of SiH ₄ and CH ₄ from the start to the end of the film formation are gradually changed, and the film formation rate is also changed accordingly.

[0031]

[Table 1]

As for the other OPC photosensitive member, an undercoat layer (intermediate layer) and a 1 μm-thick film were formed on a cylindrical substrate made of Al.
m or less, and a carrier transport layer having a thickness of 15 to 40 μm, which is sequentially laminated, wherein the undercoat layer is a water-soluble or alcohol-soluble resin, a thermosetting or photocurable resin, The carrier generating layer is composed of a resin binder in which fine-particle pigments are dispersed, and the carrier transporting layer has a large electron mobility of hole mobility, and is a layer in which a carrier transporting material is dispersed and dissolved in the resin binder. It is.

When the photoconductive layer 5 was formed, by changing the high frequency power as shown in Table 2, various IR ratios [Ib / (Ia + Ib)] were obtained, and each photoconductor was subjected to image formation. The image forming apparatus 18 having various configurations was mounted on the forming element 7.

[0034]

[Table 2]

The print quality is classified into "O" and "X". The "O" mark indicates that excellent print quality without practical problems was obtained at a process speed of 200 mm / sec, and the "X" mark indicates that print defects were observed. is there.

As is evident from the results shown in Table 2, in Samples C to F of the present invention, no printing failure occurred at all, and excellent image characteristics were obtained. Incidentally, the charging of the photoconductor A of these image forming elements 7a (K) was around -620V, the charging of the OPC photoconductor was -800V, and the charging difference between the two was about 180V.

On the other hand, since the high-frequency power is low in the samples A and B, the discharge does not spread uniformly in the film forming apparatus, and the films near the upper and lower ends become thinner. This resulted in poor adhesion of the film at both ends and peeling in some cases. Further, in the sample G, a thin black solid was generally generated, and in the sample H, the black solid was blurred.

(Example 2) Next, using the image forming apparatus 18 equipped with each of the photoconductors of the samples C to F of the present invention, the process speed of the image forming element 7a (K) was 200 mm.
Per second, a printing test (500,000 sheets) was performed. As a result, scratches and the like did not occur at all, and high quality image quality was obtained. On the other hand, when a conventional OPC photoreceptor is used as the photoreceptor of the image forming element 7a (K), the surface of the photoreceptor is scratched, and black streaks are generated on a white background in terms of image quality.

Example 3 In this example, the print quality was evaluated by changing the process speed for the image forming apparatus 18 equipped with the photosensitive member of Sample C, and the results shown in Table 3 were obtained. Was done. The mark ○ indicates that the image quality was good in terms of density, fogging, flaws, etc., and the mark Δ indicates the case where some fog occurred due to a decrease in the charging ability with respect to the dark decay characteristics. Is the case where the charging ability further decreases, fogging occurs on the entire surface, and a sufficient density cannot be obtained.

[0040]

[Table 3]

As is clear from the results shown in Table 3, by increasing the process speed to 200 mm / sec or more, the print density was excellent, no scratches or fogging occurred, and good image quality was obtained.

The print quality of each of the image forming apparatuses 18 on which the photosensitive members of Sample D, Sample E, and Sample E were mounted was evaluated by changing the process speed in the same manner. Became the same as

(Example 4) Image forming elements 7a (K), 7b
An a-Si photosensitive member was used in which all of the photosensitive members mounted on (Y), 7c (C), and 7d (M) were used in (Example 1). For each of these photoconductors, a sample C is used, a sample D is used, a sample E is used, and a sample F is used. When the print quality was evaluated by changing the process speed in the same manner as in (Example 3), the results were the same as those shown in Table 3.

Further, when all are constituted by the a-Si photoreceptor as in this embodiment, compared with the image forming apparatus of (Example 1),
Machine settings (drum flow current and exposure light amount) because there is no difference in charging ability and photosensitivity characteristics for each photoconductor
And the density difference between the respective photoconductors disappeared, so that the photoconductor became more suitable for high-speed color printing. When a printing test (500,000 sheets) was performed at a process speed of 200 mm / sec, the number of color prints increased, and even if the frequency of use of each of the cyan, aagenta, and yellow photoconductors increased, scratches and the like occurred. And excellent color display could be printed over a long period of time, and good durability was obtained.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements can be made without departing from the scope of the present invention. For example, in this embodiment, an LED head is used as the exposure means.

Gen light or the like may be used.

As described above, according to the image forming apparatus of the present invention, the intensity of the photoreceptor mounted on the image forming element at a wave number of 2000 cm ^-1 in the infrared absorption spectrum is as follows.
And the intensity Ib at a wave number of 2100 cm ^-1 is 0.22 ≦ I
a−S that satisfies the relational expression of b / (Ia + Ib) ≦ 0.35
With the i-photoconductive layer, the charge difference can be reduced or eliminated even between the photoconductors, and the photosensitivity can be further increased, whereby printing unevenness does not occur and a clear color image can be obtained. An image forming apparatus for color was provided. In addition, high-speed color printing at a process speed of 200 mm / sec or more can be performed, and the quality as a whole can be maintained for a long period of time even if the printing is selectively performed between color printing and monochrome printing.

Further, according to the present invention, by increasing the durability for monochrome printing, it is possible to sufficiently use the same for color printing and to maintain long-term reliability of the image for a long time. A forming device could be provided.

Further, according to the present invention, even if the a-Si charge injection blocking layer is not doped with a Va group element, the negative polarity can be satisfactorily charged, thereby reducing the production cost by not using a phosphine gas or the like. I was able to.

Further, when all are made of a-Si photoreceptors, there is no difference in charging ability and photosensitivity characteristics between the respective photoreceptors, so that machine setting is facilitated, thereby providing high quality and high durability. In addition, cost reduction was achieved. Even when the frequency of use of each of the cyan, aagenta, and yellow photoconductors in color printing increased, excellent color display could be printed over a long period of time, and good durability was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus of the present invention.

FIG. 2 is a partial cross-sectional view illustrating a layer configuration of a photoreceptor according to the embodiment of the present invention.

FIG. 3 is a schematic diagram of an image forming element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Substrate 3 Photosensitive layer 4 Charge injection blocking layer 5 Photoconductive layer 6 Surface protective layer 7, 7a, 7b, 7c, 7d Image forming element A, 8 Photoreceptor 9 Corona charger 10 LED head 11 Toner 12 Developer DESCRIPTION OF SYMBOLS 13 To-be-transferred material 14 Transfer device 15 Cleaning means 16 Static elimination means 18 Image forming apparatus 19 Conveying belt

Claims (1)

[Claims] 1. A photoreceptor, a charging means for imparting a negative charge to the surface of the photoreceptor, and an exposure means for irradiating a charged area of the photoreceptor with light. Developing means for forming a colored toner image corresponding to the electrostatic latent image on the surface of the photoreceptor, and a transfer means for transferring the colored toner image to a material to be transferred; At least one image forming element comprising a plurality of image forming elements provided with cleaning means for removing residual toner on the surface of the photoreceptor after the transfer and charge removing means for removing a residual electrostatic latent image after the transfer. The photoreceptor to be mounted on the surface is set to have a wave number of 2000 cm ^-1 in the infrared absorption spectrum.
And an intensity Ib at a wave number of 2100 cm ^-1 satisfying a relational expression of 0.22 ≦ Ib / (Ia + Ib) ≦ 0.35 by an amorphous silicon photoconductive layer,
An image forming apparatus of a tandem type electrophotographic system, wherein a process speed is set to 200 mm / sec or more.