JPH0279047A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent a picture image from causing flow in high humidity and to obtain superior electrophotographic characteristic under a usual humidity by forming a surface protective layer consisting of an amorphous hydrogenated silicon nitride film contg. C and N atoms in a specified proportion as primary constituting elements. CONSTITUTION:A surface protective layer 4 consisting of amorphous hydrogenated silicon nitride film is formed on the surface of a photoconductive layer 3 consisting of amorphous Si, etc., wherein the ratio of the number of the C atoms to the number of N atoms is regulated to be in a range from 19:1 to 11:9. Thus, a surface protective layer 4 having high water resistance is obtd. since a localized level density near a band edge of an optical band cap in the film is decreased by being compensated by the N atoms, the electrophotographic characteristics are improved, moreover many hydrophobic groups such as C-H bond, C-C bond are contained in the film. Thus, the picture image characteristics are not deteriorated in usual humidity, and generation of flow in the picture image under high humidity is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an electrophotographic photoreceptor used in plain paper copying machines, LED printers, laser printers, and the like.

(B) Conventional technology The A-5I photoreceptor for electrophotography, which uses an amorphous semiconductor such as amorphous silicon (hereinafter referred to as A-5I) as a base material, has excellent characteristics of high sensitivity and long life. However, it has the disadvantage of causing image blurring under high humidity conditions. As a countermeasure against this image blurring, as shown in the Proceedings of the 59th Research Conference of the Society of Electrophotography in 1988, "Improving the Moisture Resistance of an Amorphous Carbon Photoreceptor by Using an Amorphous Carbon Surface Layer," Hydrogenated amorphous carbon (a-C:H
) thin film is used as a surface protective layer of the a-3i photoreceptor. According to this purchase, conventional hydrogenated amorphous silicon carbide (a-5iC: ■) and hydrogenated amorphous silicon nitride (a-5iC:■)
The moisture resistance is greatly improved compared to the a-5i photosensitive material using 8iN:H) as the surface protective layer.

(c) Problems to be solved by the invention However, a-C:H formed by glow discharge method etc.
The film has a large localized level density near the band edge of the optical band gap. Therefore, as a surface protective layer, a-C
In a-5i exposure using a :H film, the image characteristics are poor under normal humidity (approximately 70.chi.).

Therefore, an object of the present invention is to improve moisture resistance without deteriorating image characteristics under normal humidity.

(d) Means for Solving the Problems The present invention provides an electrophotographic photosensitive material comprising a photoconductive layer having an amorphous semiconductor as a base material and a surface protective layer formed on the surface of the photoconductive layer. The surface protective layer is characterized in that it is made of a hydrogenated amorphous carbon nitride film whose main constituent elements are carbon and nitrogen with an atomic ratio in the range of 19:1 to 11:9.

(E) Effect a-C:N:t (In the film, nitrogen atoms in the film bond with carbon atoms in the film so as to reduce the localized level density in the optical band gap, so a- The localized level density in the film is reduced compared to the C:H film.

By controlling the nitrogen concentration in the a-C:N:If model film within an appropriate range, moisture resistance equivalent to that of the a-C:tl film can be obtained.

(f) Embodiment FIG. 1 is a schematic sectional view showing an embodiment of the present invention.
Conductive support such as aluminum or aluminum alloy (1
), an injection blocking layer (2) with a thickness of 0.1-5 μm that prevents injection of electrons or holes from the support (1);
A mixed gas of a silicon hydride gas such as silane (Sill), disilane (Sill14), or trisilane (SiJa) and an impurity-added gas such as diborane (B*Ha) is applied to the surface of the injection blocking layer (2). Film IV formed by decomposition by discharge method, 5-40 μm amorphous silicon (a-5
i) or a photoconductive layer (3) made of an amorphous silicon alloy
Then, on the surface of the photoconductive layer (3), hydrocarbon gas such as methane (CH4), ethane (C=H*), acetylene (C2), etc. and nitrogen (\,), ammonia (NH,), etc. A film with a thickness of 0.1 to 57 mm was formed by decomposing a gas mixture with a gas containing nitrogen atoms using a glow discharge method. It consists of a surface protective layer (4) consisting of a hydrogenated amorphous carbon nitride film (a-C:N:t()) of z+u.

By the way, in the surface protective layer (4) of the present invention, the atomic ratio of carbon to nitrogen is in the range of 19:1 to 11:9.

FIG. 2 shows the relationship between the nitrogen concentration in the surface protective layer (4) and the reciprocal of the B value. Here, BVL is generally determined by the following equation.

(αhν)l/1;B(hcE,,,)a: Absorption coefficient, hν: Incident light energy E0. : Optical bandgap There is a correlation between the increase in B value and the localized level density in the film, and the larger B(fi), the lower the localized level density. Therefore, from Figure 2, Then, the nitrogen concentration is 5% or more,
That is, the atomic ratio of carbon to nitrogen needs to be 19:1 or more.

Furthermore, as the nitrogen concentration in the film increases, hydrophilic nitrogen-hydrogen bonds increase in the film, causing image blurring in high humidity conditions. Table 1 shows the relationship between the atomic ratio of carbon and nitrogen and the state of an electrophotographic image in a high humidity state (relative humidity 90Z).

From Table 1, the atomic ratio of carbon to nitrogen is required to be 1129 or less.

From the above, the surface protective layer (4) is a hydrogenated amorphous carbon nitride film in which the atomic ratio of carbon to nitrogen is in the range of 19:1 to 11:9.

In the surface protective layer (4) thus formed, the localized level density near the band edge of the optical band gap in the film is compensated and reduced by the nitrogen atoms, and the electrophotographic properties are improved. In addition, carbon-hydrogen bonds and carbon-hydrogen bonds are present in the film.
Since it contains many hydrophobic groups such as carbon bonds, it has excellent water resistance.

@Table 2 shows the electrophotographic photoreceptor of the present invention, an electrophotographic photoreceptor having a-C:)l film as a surface protective layer (Comparative Example 1)
and a-5iC film as a surface protective layer (Comparative Example 2). Residual potential at and 400n
It represents the spectral sensitivity at m.

Table 2 As is clear from Table 2, the photoreceptor of the present invention can prevent electrophotographic images from running when used in high humidity conditions, and also has excellent electrophotographic properties even under normal humidity. can be obtained.

In addition, the surface protective layer (4) contains 8% Al, Ga, etc.
The Ia group element may be doped in a range of 500 ppm to 5000 ppm. In case 2, since the surface protective layer (4) contains holes as majority carriers in the film, it increases the 1F ability to inhibit injection of positive surface charges into the surface protective layer (4) when the photoreceptor is positively charged. It is possible to improve the charging ability of the photoreceptor.

(g) Effects of the invention According to the invention, the surface protective layer has an atomic ratio of 19:1.
Since we used a hydrogenated amorphous carbon nitride film whose main constituent elements are carbon and nitrogen in the range of Excellent electrophotographic properties can be obtained under humid conditions and normal humidity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between the nitrogen concentration in the surface protective layer and the reciprocal of B (ti). Leading layer 1, (4) surface protective layer.

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor comprising a photoconductive layer having an amorphous semiconductor as a base material and a surface protective layer formed on the surface of the photoconductive layer, the surface protective layer has an atomic ratio of is 19
An electrophotographic photoreceptor comprising a hydrogenated amorphous carbon nitride film containing carbon and nitrogen as main constituent elements in a ratio of 1 to 11:9.