JP2000075587A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance color printer suitable for high-speed color printing. SOLUTION: In the electrophotographic image forming device 18 of a tandem type, image forming elements 7a, 7b, 7c, and 7d are arranged. Disposed in each element are a developing machine 12 for forming an electrostatic latent image onto the surface of a photoreceptor 8 and also forming a color toner image corresponding to the electrostatic latent image onto the surface of the photoreceptor 8, a transfer unit 14 for transferring the toner image to a material 13 to be subjected to the transfer, a cleaning means 15 for removing residual toner on the surface of the photoreceptor 8 after the transfer, and a destaticization means 16 for removing the residual electrostatic latent image after the transfer. Also, the photoreceptor A mounted in the image forming element 7, which forms the black toner image, is composed of an a-Si photoconductive layer in which strength Ia in a wave number of 2000 cm-1 and strength Ib in a wave number of 2100 cm-1 in an infrared absorption spectrum satisfy the relational expression of 0.22<=Ib/(Ia+Ib)<=0.35.

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 equipped with a negatively charged photoreceptor comprising an amorphous silicon photoconductive layer.

[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).

[0003]

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.

[0004] At least for a photoreceptor using a black toner image, an already commercialized amorphous silicon photoreceptor (hereinafter, amorphous silicon is abbreviated as a-Si) is used in place of the OPC photoreceptor. 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.
Doping with the Group Ia element forms a potential barrier for electrons, thereby preventing injection of electrons from the conductive substrate and obtaining a positively charged electrophotographic photosensitive member.

On the other hand, by doping the charge injection blocking layer with a Group Va element of the Periodic Table instead of the Group IIIa element of the Periodic Table, a potential barrier against holes is formed. Electrostatic photoreceptors for negative charging have been expected to replace the conventional OPC photoreceptor by preventing the injection of holes, but have not yet been put to practical use.

The inventor of the present invention has conducted various studies on such problems which have not been put to practical use. As a result, an element belonging to Group IIIa of the Periodic Table (hereinafter referred to as Group IIIa) was added to an existing electrophotographic photosensitive member for positive charging. 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-described positive charging property is obtained. For this reason, the transfer bias voltage was canceled, and the image characteristics deteriorated.

Furthermore, 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. .

In general, in the case of a color printer in which a plurality of photoconductors are arranged for one image forming apparatus, if photoconductors having different photoconductive layers are arranged, the required performance may be different depending on the performance. There is a problem that the desired coloring cannot be obtained.

In view of the above circumstances, the inventor of the present invention has intensively studied and found that a tandem-type electrophotographic color printer not only actually performs color printing but also performs color printing.
Attention is paid to the fact that monochrome (black) printing is frequently performed, and monochrome printing is often used more frequently than color printing. Therefore, it is mounted on an image forming element that forms a black toner image. The photoreceptor is composed of an a-Si photoconductive layer, and further defines 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 an infrared absorption spectrum of the a-Si photoconductive layer. The film quality is improved by this, and excellent negative charging property is obtained,
Further, in order to form a colored toner image other than the black toner image, O
The difference in charging and sensitivity characteristics between the image forming element equipped with a PC photoreceptor is reduced, and the photosensitivity is increased. Therefore, even if a different type of photoreceptor is mounted, it is sufficiently practical as a color printer. It has been found that a certain image forming apparatus can be obtained.

In addition, even if the a-Si charge injection blocking layer is not doped with a Va group element, it can be favorably charged to a negative polarity,
By not using phosphine gas etc. by this,
They also found that production costs could be reduced.

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

Another object of the present invention is to improve the durability against monochrome printing, so that the overall printing performance can be maintained for a long period of time even when used properly for color printing. To provide an image forming apparatus.

Still another object of the present invention is to provide an image forming apparatus which can reduce production cost by not using phosphine gas or the like.

[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; and charge removing means for removing the residual electrostatic latent image is disposed, and the intensity Ia at wavenumber 2000 cm ^-1 in the infrared absorption spectrum of the photosensitive member to be mounted on an image forming element for forming a black toner image, wavenumber 21 And intensity Ib in 0 cm ^-1 is 0.22
A that satisfies the relational expression of ≦ Ib / (Ia + Ib) ≦ 0.35
-Si photoconductive layer.

[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 is made of aS
i is not doped with a Group IIIa element and / or a Group Va element as a valence electron controlling impurity, and even if it is non-doped, it has a wave number of 2000 cm ^-1 in the infrared absorption spectrum of the photoconductive layer 5. Strength Ia
And the intensity Ib at a wave number of 2100 cm ^-1 is 0.22 ≦ I
By setting so as to satisfy the relational expression of b / (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 satisfying the relationship of ≦ 0.35, preferably 0.25 ≦ IR ratio ≦ 0.34 is satisfied, excellent negative charging ability is obtained. In addition, the OPC is performed to form a colored toner image other than a black toner image. The difference in charging and sensitivity characteristics between the photosensitive member and the image forming element on which the photosensitive member was mounted was reduced, and the light sensitivity was increased, thereby making it suitable for high speed color printing. Further, from short wavelength visible light to near infrared light (long wavelength light), that is, a wavelength peak 5
The light sensitivity to irradiation light of 20 to 820 nm is 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, if only oxygen is used, it reacts with the silane gas to easily cause an explosion. Therefore, it is preferable to use inert nitrogen together. In practice, 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 or the like.
Glow discharge decomposition method, vacuum deposition method, active reaction deposition method, ion plating method, RF sputtering method, DC sputtering method, RF magnetron sputtering method, D
A film is formed by a C 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.

According to the photoconductor 1 having the above structure, the photoconductive layer 5
As described above, the IR ratio is specified as described above to improve the film quality, thereby obtaining excellent negative chargeability. Further, an image forming element equipped with an OPC photoreceptor for forming a colored toner image other than a black toner image The difference in the charging and sensitivity characteristics between the photoconductors and the photosensitivity of the photoconductors has been increased, so that the image forming apparatus has sufficient practicality as a color printer even when different types of photoconductors are mounted.

In addition, even if the a-Si charge injection blocking layer is not doped with a Va group element, it can be favorably charged to a negative polarity,
By not using phosphine gas etc. by this,
They also found that production costs could be reduced.

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 photoreceptor, and a corona charger 9 serving as charging means on the peripheral surface of the photoreceptor 8, an LED head 10 serving as an exposure means for irradiating light after the charging, and a toner image formed on the surface of the photoreceptor 8. , A transfer device for transferring the toner image to a transfer material 13, and cleaning for removing residual toner on the surface of the photoconductor after the transfer. This is a configuration in which means 15 and static elimination means 16 for removing a 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 (4) are repeated. The peripheral surface of the photoconductor 8 is charged by the corona charger 9. By exposing the image with the LED head 10,
An electrostatic latent image as a potential contrast is formed 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 was possible, and the quality as a whole could be maintained for a long period of time, even if the printing was switched between color printing and monochrome printing.

[0030]

(Example 1) Photoconductor 1 of image forming element 7a (K)
Was prepared as follows. Cylindrical substrate 1 made of 99.9% pure Al (outer diameter 180 mm, length 372 mm)
The photosensitive layer 2 is formed by a plasma CVD method. In the photosensitive layer 2, a charge injection blocking layer 4, a photoconductive layer 5, and a surface protective layer 6 were 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 and a carrier transporting layer having a thickness of 15 to 40 μm, which are sequentially laminated, and the undercoat layer is made of a water-soluble or alcohol-soluble resin, a thermosetting resin or a photo-setting resin. The carrier generation layer is composed of a resin binder in which fine-particle pigments are dispersed, and the carrier transport layer has an electron-donating property having a large hole mobility, and the carrier transport material is dispersed in the resin binder. It is a dissolved layer.

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. Various image forming devices 18 were mounted on the forming element 7.

[0034]

[Table 2]

The print quality is classified into "O" and "X". The "O" mark indicates a case where excellent print quality which does not hinder practical use was obtained, and the "X" mark indicates a case where a print defect was recognized.

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. When color printing was performed on Samples C to F of the present invention, excellent color images were obtained at a printing speed of 12 sheets / minute.

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. occured. In addition, the adhesiveness of the film at both ends was poor, and the film was sometimes peeled off. 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, a printing durability test (500,000 sheets) was performed using the image forming apparatus 18 equipped with the photoconductors of the samples C to F of the present invention. As a result, no scratches or the like were generated at all, and good image quality was obtained. On the other hand, when a conventional OPC photoconductor was used as the photoconductor of the image forming element 7a (K), the surface of the photoconductor was damaged, and black streaks were generated on a white background in terms of image quality.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may 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 photoreceptor mounted on the image forming element for forming a black toner image has a wave number of 200 in the infrared absorption spectrum.
And intensity Ia at 0 cm ^-1, by the intensity Ib at wavenumber 2100 cm ^-1 was composed of 0.22 ≦ Ib / (Ia + Ib ) satisfy ≦ 0.35 relation a-Si photoconductive layer, black OP to form colored toner image other than toner image
20 times less than the charging of the image forming element on which the C photoconductor is mounted.
A charge difference of 0 V or less can be achieved, and light sensitivity can be further increased. As a result, a high-performance color printer suitable for high-speed color printing can be provided.

Further, according to the present invention, by increasing the durability against monochrome printing, it is possible to sufficiently use it for color printing, and to obtain a long-term reliable image capable of maintaining the overall printing performance for a long time. A forming device could be provided.

Furthermore, 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.

[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 Substrate 2 Photosensitive layer 4 Photoconductive layer 5 Light absorption 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 Developing machine 13 Transfer material Reference Signs List 14 transfer unit 15 cleaning means 16 static elimination means 18 image forming apparatus 19 transport 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; A plurality of image forming elements provided with cleaning means for removing residual toner on the photoreceptor surface after the transfer and charge removing means for removing a residual electrostatic latent image after the transfer are arranged in a plurality, and one image forming element is For black toner image formation,
The photoreceptor mounted on the image forming element for forming the black toner image has a wave number of 2,000 c in an infrared absorption spectrum.
The intensity Ia at m ^-1 and the intensity Ib at a wavenumber of 2100 cm ^-1
Tandem type electrophotographic image forming apparatus, characterized by comprising an amorphous silicon photoconductive layer satisfying a relational expression of 0.22 ≦ Ib / (Ia + Ib) ≦ 0.35.