JPH11212286A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Problem] To provide an electrophotographic photosensitive member for negative charging. A photoconductor (1) in which a charge injection blocking layer (3) made of a-Si: H and a photoconductive layer (4) made of a-Si: H are sequentially laminated on a conductive substrate (2). 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 No. 4 were 0.2
It is used for negative charging so as to satisfy the relational expression of 2 ≦ 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 an electrophotographic photosensitive member having a hydrogenated amorphous silicon photoconductive layer.

[0002]

2. Description of the Related Art A photoreceptor using amorphous silicon (hereinafter, amorphous silicon is abbreviated as a-Si) as a photoconductive layer has already been commercialized, but this a-Si photoreceptor is used for positive charging. A charge injection blocking layer made of hydrogenated amorphous silicon (hereinafter abbreviated as a-Si: H) and an a-Si: H photoconductive layer formed on a conductive substrate by a glow discharge decomposition method. This is a layer configuration in which layers are sequentially stacked. A potential barrier for electrons is formed by doping the a-Si: H charge injection blocking layer with a Group IIIa element of the periodic table, thereby preventing injection of electrons from the conductive substrate and providing positive charging. An electrophotographic photoreceptor is obtained.

On the other hand, a potential barrier for holes is formed by doping the charge injection blocking layer with a group Va element of the periodic table in place of the group IIIa element of the periodic table, thereby forming a potential barrier against the conductive substrate. An electrophotographic photoconductor for negative charging is expected to replace the conventional OPC photoconductor by preventing the injection of holes, but has not yet been put to practical use.

[0004]

The inventor of the present invention has conducted various investigations on the problems which have not been put into practical use. The doping of the charge injection blocking layer (hereinafter abbreviated as IIIa element) into the charge injection blocking layer is performed simply by adding
It was found that if only a group a element (hereinafter abbreviated as a group Va element) was used, the element was charged negatively, but also charged positively.

Therefore, when such an electrophotographic photosensitive member is mounted on an electrophotographic apparatus such as a copying machine or a printer and an image is to be formed using a toner for negative charging, when the toner is transferred to paper, Due to the chargeability, the transfer bias voltage was canceled, and the image characteristics deteriorated.

Further, the electrophotographic photoreceptor for negative charging has a problem in that the photosensitivity to short-wavelength visible light is inferior, so that the exposure wavelength of the light source is limited.

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 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 the production cost. .

In view of the above circumstances, the present inventor has made intensive studies, and as a result, the film formation conditions under which the a-Si: H charge injection blocking layer can be favorably charged to a negative polarity without doping a Va group element are further added. The film quality is controlled 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: H photoconductive layer formed on the substrate. It has been found that excellent negative chargeability can be obtained.

Accordingly, the present invention has been accomplished based on the above findings, and an object of the present invention is to provide a negatively charged electrophotographic photosensitive member having excellent image characteristics.

[0010] Another object of the present invention is to provide an electrophotographic photoreceptor in which the production cost can be reduced by not using a phosphine gas or the like.

It is still another object of the present invention to provide an electrophotographic photoreceptor which can increase the light sensitivity to short wavelength visible light and thereby can be used in various models.

[0012]

According to the present invention, an electrophotographic photoreceptor for negative charging according to the present invention comprises a conductive substrate and an a-Si: H charge injection blocking layer and an a-Si: H photoconductive layer sequentially laminated on the conductive substrate. The wave number 2,000 in the infrared absorption spectrum of the photoconductive layer
and intensity Ia in cm ^-1, the intensity at wave number 2100 cm ^-1 I
b is set to satisfy a relational expression of 0.22 ≦ Ib / (Ia + Ib) ≦ 0.35.

[0013]

Diagram 1 of the embodiment of the invention photoreceptor is a layer structure of the photosensitive member 1 according to the embodiment of the invention,
A-Si on the conductive substrate 2 by a glow discharge decomposition method:
A charge injection blocking layer 3 made of H and a photoconductive layer 4 made of a-Si: H are sequentially stacked, and a surface protective layer 5 is stacked on the photoconductive layer 4.

Copper, brass, SUS, A
Metallic conductors such as 1 and Ni, or insulators such as glass and ceramic, each of which has a surface coated with a conductive thin film. The conductive substrate 2 may be a sheet-shaped, belt-shaped or web-shaped flexible conductive sheet, such as a metal sheet such as SUS, Al, or Ni, or a polymer resin film such as polyester, nylon, or polyimide. A metal such as Al or Ni, or a transparent conductive material such as indium tin oxide (ITO) or an organic conductive material is coated thereon by vapor deposition or the like, and is subjected to a conductive treatment.

The surface protective layer 5 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.

The charge injection blocking layer 3 is made of aS
i: H 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, the wave number 2000 cm ^-1 in the infrared absorption spectrum of the photoconductive layer 4. And the intensity Ib at a wave number of 2100 cm ^-1 are 0.2
By setting so as to satisfy the relational expression of 2 ≦ Ib / (Ia + Ib) ≦ 0.35, excellent negative charging ability was obtained.

That is, in the present invention, non-doped a-Si: H shows 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 can be obtained by defining the film quality of the photoconductive layer 4 without doping P by using P.

Specifically, when the photoconductive layer 4 is formed, the film forming speed is set, for example, at 2.5 to 7.0 μm / hour, preferably at 4.0 to 6.0 μm / hour. Si
The quantitative ratio of the [SiH bond] to the [(SiH ₂ ) _n bond], which is the bonding state between atoms and H atoms, is defined.
and intensity Ia in cm ^-1, the intensity at wave number 2100 cm ^-1 I
The IR ratio indicating the relationship with b is expressed as Ib / (Ia + Ib), where 0.22 ≦ IR ratio ≦ 0.35, preferably 0.25 ≦
When the relational expression satisfying the relationship of IR ratio ≦ 0.34 was satisfied, excellent negative charging ability was obtained, and the light sensitivity to short-wavelength visible light was also improved.

In addition, oxygen and nitrogen are contained in the charge injection blocking layer 3 to increase the forbidden band width, thereby making it possible to increase the barrier in terms of the function of blocking charge injection. In addition, the inclusion of oxygen enhances 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. Actually, nitrogen monoxide (NO) gas or the like is used.

Further, in a copying machine, a halogen lamp is used as a light source.
There is a wavelength peak of 600 nm, and 500 to 750 nm
, While the printer uses laser light, LED, or the like near 680 nm as a light source. In the present invention, since the light sensitivity to short-wavelength visible light is increased, both models can be supported.

[0021] Configuration FIG. 2 of the image forming apparatus is an image forming apparatus 7 equipped with a printer constituting the photosensitive member of the present invention, 8 denotes a photosensitive member, a corona charger 9 to the peripheral surface of the photoconductor 8, Exposure device 10 (LED head) that irradiates light after the charging, developing device 12 provided with toner 11 for forming a toner image on the surface of photoconductor 8, and transfer for transferring the toner image to transfer material 13 And a cleaning unit 15 for removing the residual toner on the surface of the photoreceptor after the transfer, and a charge removing unit 16 for removing the residual electrostatic latent image after the transfer. 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 are repeated. The peripheral surface of the photoconductor 8 is charged by the corona charger 9. By exposing the image with the exposure device 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 black 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.

The image forming apparatus 7 has a printer configuration. However, if an optical system such as a lens or a mirror that transmits reflected light from a document is used in place of the exposure unit 10, the image forming apparatus 7 has the same configuration as an image forming apparatus having a copier. Become.

The image forming apparatus 7 employs ordinary dry development, but is also applicable to liquid developers used for wet development.

[0025]

EXAMPLE On a cylindrical substrate made of Al having a purity of 99.9%, charges were formed by a glow discharge decomposition method under the film forming conditions shown in Table 1 (the conditions are values in one chamber). The injection blocking layer 3, the photoconductive layer 4, and the surface protective layer 5 were laminated.

[0026]

[Table 1]

In forming the charge injection blocking layer 3, the PH ₃ gas and the flow rate ratio of the SiH ₄ gas were used as shown in Table 2 below.
As shown in the figure, it was introduced in various ways. Then, negative chargeability, positive chargeability, sensitivity on the short wavelength side, and sensitivity on the long wavelength side were measured and evaluated, respectively.

[0028]

[Table 2]

The negative chargeability is indicated by a circle when a charge of 400 V or more is obtained with a charge amount of 0.3 μC / cm ² ,
If the charge was less than 0 V, the mark was x. The positive chargeability is a charge amount of 0.3 μC / cm ^2, a mark of less than 50 V is marked with a circle, and a charge of 50 V or more is marked with a cross.
Marked.

Regarding the sensitivity on the short wavelength side, when the energy required for lowering the surface potential from 500 V to 50 V by exposure at 550 nm is less than 1.0 μJ / cm ² , the mark is “○”, and 1.0 to 2.0 μJ. / Cm ² , the mark was Δ, and when it exceeded 2.0 μJ / cm ² , the mark was X.

Regarding the sensitivity on the long wavelength side, when the energy required for lowering the surface potential from 500 V to 50 V by exposure at 700 nm is less than 1.0 μJ / cm ² , a mark “○” indicates that the energy is 1.0 to 2.0 μJ. / Cm ² , the mark was Δ, and when it exceeded 2.0 μJ / cm ² , the mark was X.

As is evident from Table 2, when the PH ₃ gas is not doped at all, the sensitivity on the short wavelength side and the negative charging ability are excellent.

Next, based on the film forming conditions of the photoreceptor as shown in Table 3, the charge injection blocking layer was manufactured without doping the P element.

[0034]

[Table 3]

Then, when the photoconductive layer is formed, SiH
₄ Various photoreceptors were prepared by changing the gas flow rate (deposition rate) in various ways, and the negative chargeability, positive chargeability, short wavelength sensitivity, long wavelength sensitivity, and appearance were measured as shown in Table 4. And Table 4 also shows the results.

[0036]

[Table 4]

The negative chargeability is a charge amount of 0.3 μC / cm ² , and the case where the charge is 400 V or more is indicated by a circle.
If the charging is 0 V or more and less than 400 V, the mark is 100 V
If less than the above, it was marked as x.

The positive chargeability is indicated by a circle when the charge amount is 0.3 μC / cm ^{2 and} the charge amount is less than 30 V.
If the charge was 50 V, the mark was Δ, and if the charge was 50 V or more, the mark was X.

Regarding the sensitivity on the short wavelength side, when the energy required for lowering the surface potential from 500 V to 50 V by exposure at 550 nm is less than 1.0 μJ / cm ² , the mark is “○”, and 1.0 to 2.0 μJ. / Cm ² , the mark was Δ, and when it exceeded 2.0 μJ / cm ² , the mark was X.

Regarding the sensitivity at the long wavelength side, when the energy required for lowering the surface potential from 500 V to 50 V by exposure at 700 nm is less than 1.0 μJ / cm ² , a mark “、” indicates that the energy is 1.0 to 2.0 μJ. / Cm ² , the mark was Δ, and when it exceeded 2.0 μJ / cm ² , the mark was X.

Regarding the external appearance, a mark ○ indicates that no protruding defect was formed during film formation, and a mark X indicates that a defect occurred.

The thus-obtained photoreceptor of the present invention (IR ratio = 0.25 to 0.34) was mounted on the image forming apparatus 7 (dry development: toner average particle diameter 8 μm), and an image was formed by the Carlson method. A 300,000 sheet running test was performed to measure the image characteristics and the degree of toner adhesion. As a result, no image defects such as white spots, black spots, and image deletion were found.

On the other hand, when the film formation rate was 1.0 μm / hour or 2.0 μm / hour, the discharge was not stable, and the film was peeled off during the film formation, resulting in axial unevenness. The axis unevenness indicates unevenness of the charging characteristics in the axial direction of the cylindrical substrate, and affects the unevenness of the film thickness. In addition, when the film is formed with low power, the discharge is not stable, and the film is easily peeled. Even if it does not peel, the discharge tends to concentrate downward, resulting in uneven film thickness.

On the other hand, when the IR ratio is 0.36,
When the R ratio is 0.41, a-Si:
(SiH ₂ ) _n bonds increase in H, and the negative level decreases due to localized levels trapping carriers caused by dangling bonds.

[0045]

As described above, according to the electrophotographic photoreceptor of the present invention, even if the a-Si: H charge injection blocking layer not doped with valence electron controlling impurities is formed by the glow discharge decomposition method, Wave number 2000 cm ^-1 in infrared absorption spectrum for a-Si: H photoconductive layer provided thereon
Is defined so as to satisfy the relational expression of 0.22 ≦ Ib / (Ia + Ib) ≦ 0.35 with respect to the intensity Ia at the wave number of 2100 cm ⁻¹ and the intensity Ib at the wave number of 2100 cm ^−1, which is excellent without using a phosphine gas or the like. It was able to be used for negative charging of image characteristics.

Further, in the present invention, since phosphine gas which is highly toxic and has a bad effect on the human body even at a low concentration is not used, no safety management measures are required, and the production cost can be reduced accordingly. In addition, since such a doping gas is not used, highly accurate doping control is not required, thereby reducing variations in electrophotographic characteristics and reducing the production cost.

Further, according to the present invention, the photosensitivity to short-wavelength visible light can be increased, so that both photoreceptors for copiers and printers, and electrophotographic photosensitive members for various models The body could provide.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a layer configuration of a photoreceptor according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 8 Photoreceptor 2 Substrate 3 Photosensitive layer 5 Photoconductive layer 6 Surface protective layer 7 Image forming apparatus 9 Corona charger 10 Exposure device 11 Toner 12 Developing machine 13 Transfer material 14 Transfer device 15 Cleaning means 16 Static elimination means

Claims (1)

[Claims] A charge injection blocking layer made of hydrogenated amorphous silicon and a photoconductive layer made of hydrogenated amorphous silicon are sequentially laminated on a conductive substrate, and a wave number of 2000 c in an infrared absorption spectrum of the photoconductive layer is obtained.
The intensity Ia at m ^-1 and the intensity Ib at a wavenumber of 2100 cm ^-1
Characterized by satisfying the relational expression 0.22 ≦ Ib / (Ia + Ib) ≦ 0.35.