JPS58115443A - Photosensitive body - Google Patents

Abstract

PURPOSE:To stably hold high surface charge, by providing a carrier transport layer consisting of a dielectric semiconductor, on a function separating type electrophotographic sensitive body. CONSTITUTION:In a function separating type electrophotographic sensitive body which has been provided with a carrier transport layer 2, a generating layer 3 for generating a carrier, and a surface protecting layer as necessary, on a conductive substrate 1, a dielectric semiconductor consisting of a perovskite type oxide such as SrTiO3, KTaO3, etc. is used for the carrier transport layer. In this way, a high dielectric constant is obtained, large electrostatic charge can be held even in case of low surface potential, the photosensitive body can be thinned in order to obtain the same performance, also sensitivity of the photosensitive body is raised since mobility of the carrier is large, furthermore, the carrier of a long life is obtained since the oxide semiconductor is an indirect transition type semiconductor, and the photosensitive body whose sensitivity is scarcely dropped is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a functionally separated photoreceptor in which carrier generation by light and a layer for holding the generated carriers are formed of different materials.

Various information processing devices have been developed in recent years, and among them, devices such as electrophotography, electronic copying machines, and laser printers have been widely put into practical use as devices that streamline the creation of documents, drawings, and the like.

These types of devices have in common that the image is held electrostatically, and the electrostatic charge is held by a photoreceptor provided with a photoconductive layer.

The photoreceptor used in the above-mentioned device is generally required to have high photosensitivity and high resistance necessary to maintain surface electrostatic charge. The resistance value required for the actual image forming process exceeds 1018Ω, but there are only a limited number of materials that have such high resistance and high photoconductivity. There wasn't.

That is, as a conventionally used photoconductive material, one in which amorphous selenium or CdS is mixed with a resin binder is known. However, the above-mentioned amorphous selenium is expensive and crystallically unstable, and changes from an amorphous state to a polycrystalline state due to heat applied during the copying process, geothermal shock, or mechanical shock, resulting in resistance value. The disadvantage is that the photoreceptor loses its properties due to a decrease in the photoreceptor. Another problem is that selenium itself is a toxic substance and must be handled with great care during production.

On the other hand, a photoconductive layer made of a mixture of CdS and a resin binder cannot be said to be an ideal photoreceptor because the resin binder is soft and has low durability, and CdS is said to be toxic.

Amorphous silicon y (aSi) photoreceptors have recently been in the spotlight as photoreceptors that compensate for the above-mentioned drawbacks. However, photoreceptors using this type of material have a
The CVD growth rate of the 51 layer is slow, with growth progressing only at a rate of several angstroms per second. Amorphous silicon has a very large light absorption coefficient, and a thickness of about 1 μm is sufficient for generating light carriers. However, in order to function as a photoreceptor, it is necessary to retain electrostatic charge on the generated carriers, and it is necessary to provide the carrier with a thickness of 20 to 30 μm. In order to obtain such a thick photoreceptor, C
When fabricated using the VD method, it takes a day and a night, which has the disadvantage of not being suitable for mass production.As the photoreceptor, a material that has both high photoconductivity and high resistance as mentioned above is required. However, as in the case of aSi, attempting to obtain both properties from one material poses problems in practical use, such as the production time required.

To address the above-mentioned problems, recently, photoreceptors have been devised in which high photoconductivity and high resistance are separately focused, and these functions are assigned to different materials.

For example, amorphous selenium is used as a photoconductor layer, this layer is used as a photocarrier generation layer during exposure, and under the amorphous selenium layer that becomes the photocarrier generation layer, an organic semiconductor layer such as TNF is used as a carrier transport layer. Although the manufacturing process is complicated because it has a multilayer structure, it has good functionality, and its application to high-end electronic copying machines is being considered. The functionally separated photoreceptor with the organic semiconductor layer interposed therein can obtain high photoconductivity and high resistance, but the mobility (μ) in the organic semiconductor layer is small and therefore requires time for response. Furthermore, there is still a drawback that it is difficult to provide sufficient surface charge.

The present invention eliminates the drawbacks of the conventional devices described above and provides a photoreceptor that can stably maintain a high surface charge.

The figure is a cross-sectional view of a photoreceptor according to the present invention. In the figure 1
1 is a substrate made of a conductor such as aluminum, and a photoreceptor is manufactured using the substrate 1 as a support. The photoreceptor has a carrier transport layer 2 on the substrate 1. A photocarrier generation layer 3 and a surface protection film 4 are sequentially laminated.

The optical carrier generation layer 8 plays the role of generating optical carriers using reflected light from the document surface or writing light from a laser beam, etc., and uses a highly sensitive photoconductor such as amorphous silicon or amorphous chalcogenide.
The film thickness is approximately 1 μm. Although the photoreceptor can be constructed by directly exposing the photocarrier generation layer 8, a pad basecon made of 5iBN4 or the like is applied to suppress carrier injection during charge retention characteristics and to protect the surface. Preferably, a membrane 4 is provided.

The carrier transport layer 2 interposed between the optical carrier generation layer 8 and the substrate 1 is made to be a thicker film than the optical carrier generation layer 8. The carrier transport layer 2 is required to have a resistance value necessary to maintain the surface electrostatic potential, that is, a high resistance of about IOΩ, and the carriers generated in the photocarrier generation layer 3 can easily move. A high degree of mobility (μ
) is desirable. Such characteristics cannot be obtained simply by using a resistor with a high resistance value. In other words, in the case of a resistor, it takes several tens of seconds to several minutes for the carrier to pass through the resistive layer, and when used as a photoreceptor in a copying machine, it takes a long time as described above after irradiation with light. In short, if carriers were transported, the response would be extremely poor and would be impractical. Therefore, in the present invention, a dielectric semiconductor made of a perovskite oxide such as S r TiOB or KT a OB is used as the carrier transport layer 2 .

It is known that the perovskite oxide exhibits paraelectricity over a wide temperature range from low temperatures to temperatures higher than room temperature, and has a conduction band and becomes a semiconductor. Peropskite oxides have a dielectric constant of several hundreds near room temperature, and a mobility (μ) of several tens of cyl/see, V
It has a large mobility exceeding .

Furthermore, they generally have a large band gap.

By using an oxide semiconductor having the above characteristics as a carrier transport layer, the following advantages can be obtained as a photoreceptor.

First, by having a large dielectric constant, a large surface electrostatic charge can be held in proportion to the dielectric constant. That is,
In electrophotography, a latent image is turned into a visible image by electrostatically attracting toner to the electrostatic charge held on the photoreceptor.
When the electrostatic permittivity ε of the photoreceptor is large, a large electrostatic charge can be held at a lower surface potential. As a result, a thin photoreceptor can function as a photoreceptor.

In addition, a large carrier mobility (μ) increases the sensitivity of the photoreceptor and directly increases the response speed.
The performance of the photoreceptor was significantly improved.

Furthermore, the above-mentioned oxide semiconductor is said to be an indirect transition type semiconductor, and long-life carriers can be obtained, so that optical carriers are less likely to be lost in the carrier transport layer, and there is little decrease in photosensitivity.

An oxide semiconductor having many advantages as described above can be formed on the substrate I by a conventionally known vapor deposition method, sputtering method, reactive sputtering method, or the like.

Alternatively, the oxide semiconductor produced by the above method may be once formed into powder 7, mixed with a binder, and applied onto the substrate l to be laminated.

For example, SrTi0g naturally contains a small amount of oxygen defects during manufacturing, and these defects are caused by the action of toner.
It has a resistance of 010 to 1070, but this resistance value can be increased by heat treatment in oxygen or lowered by heat treatment in vacuum, and it is also possible to change the resistance value by using other dobigs. It is.

Next, specific examples of the present invention will be described.
iOB powder (with a diameter of several microns or less) is mixed with an acrylic resin binder at a volume ratio of 10:8, a solvent is added, and the mixture is kneaded, and then the mixture is placed on an aluminum drum, which is conventionally used in PPC copying machines. to form a carrier transport layer having a thickness of 25 μm.

Subsequently, amorphous silicon was deposited on the aluminum drum on which the carrier transport layer was formed by about 3 μm using the glow discharge CVD method.
The layer is formed to have a thickness of m and is used as a photocarrier generating layer. In forming the amorphous silicon layer, stabilization was performed using hydrogen, and a trace amount of boron was added to increase the resistance value. After the carrier transport layer and the photocarrier generation layer are laminated, passivation made of several hundred angstroms of silicon nitride is applied on the surface to produce a functionally separated photoreceptor. Using the photoreceptor having the above structure, processes such as uniformly charged nine-image exposure, development, transfer and fixing were carried out to produce a copy image, and a good quality image was obtained.

As described above, according to the present invention, since a photoreceptor is manufactured by interposing a dielectric semiconductor layer, carriers generated by light can be efficiently retained, and a large electrostatic charge can be obtained with a low surface potential. Compared to conventional devices, the device can function with a thinner photoreceptor, making the device manufacturing more economical. Also, since the surface potential is low,
The device design becomes easier, and the load on the electric circuit, corona discharge member, etc. can be reduced, and the durability of the device can be increased.

[Brief explanation of drawings]

The figure is a sectional view showing an embodiment according to the present invention. Substrate 2: Carrier transport layer 3: Photocarrier generation layer
4: Basoshibasicon Membrane Agent Patent Attorney Aihiko Fukushi

Claims (1)

[Claims] 1. In a photoreceptor supported on a substrate conductor for forming an electrostatic potential, a carrier generation layer that generates carriers by light, and a dielectric provided on the substrate conductor side with respect to the photocarrier generation layer. A photoreceptor comprising a carrier transport layer made of a semiconductor.