JPH0194352A - Overcoat type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To maintain high potential acceptance and high image quality for a long period by forming a second photosensitive layer specified in composition and an interlayer having a thickness in a specified range and a chemical composition of silicon oxide. CONSTITUTION:The photosensitive body is formed by successively laminating on a conductive substrate a first Se-As photosensitive layer 2, the second photosensitive layer 3 made of As2Se3-xTex, x being 0.2-0.7, the 10-500nm thick interlayer 4 made of silicon oxide, and carriers generated by light illumination of the layer 3 are smoothly transferred to the side of the conductive substrate 1, thus permitting the obtained photosensitive body to be greatly improved in potential acceptance and to be used as the photosensitive body high in durability using a laser diode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a photoreceptor for electrophotography, and particularly to an overcoat type high-sensitivity photoreceptor having sensitivity sufficient to be compatible with copiers and printers using an LD as a light source.

[Prior Art] Conventionally, a Se or SeTe layer, A
A photoreceptor having 3 szS6 layers and a polyurethane layer (JP-A-54-1309CI8) is known, but this photoreceptor has many dangling bonds when the 3 AszSe layers are deposited at a low temperature, resulting in lower sensitivity and poor dark decay characteristics. Since deterioration may occur, it is necessary to keep the temperature of the support at 200° C. or higher during vapor deposition. In this case, a problem arises in that Se and SeTe crystallize and the properties deteriorate.

Separately, three layers of As2Se, As2Se3-, Te
, a photoreceptor (Japanese Patent Application Laid-open No. 15940/1983) is known which is provided with a single layer of an inorganic material such as a-SiC or a-SiN. This photoreceptor has a-SiC or a-S on the surface.
Although iN has high hardness and high durability, it is difficult to produce one without defects, and as a result, it has the disadvantage of poor moisture resistance. This tendency is the same for a-3i nausea.

[Objective] The present invention improves the above-mentioned drawbacks of the conventional technology, and provides a photoconductor compatible with LD that has high charging ability and can maintain high image quality over a long period of time, a photoconductor compatible with LD that has high mechanical durability, and is environmentally resistant. The purpose of the present invention is to provide a photoconductor compatible with LD with good performance, and a photoconductor compatible with LD that is not easily affected by external contamination.

[Constituent film] The structure of the present invention for achieving the above object is to sequentially form a Se-As photosensitive layer and an A S 2 Se 3 on a conductive support.
-* T e * In an overcoat type photoreceptor having a photosensitive layer, an intermediate layer, and a protective layer, 1) the value of X in the composition of the A s 2S e 3-x T e *photosensitive layer is 0.2 to 0. 7, 2)
The intermediate layer has a thickness of 100 Å to 5000 Å, and is an overcoat type high-sensitivity photoreceptor whose chemical composition is silicon oxide.

To specifically illustrate this with reference to the drawings, as shown in FIG.
2 S e, -x Te, layer 3, intermediate layer 4, protective layer 5
It has the following.

Each of the above parts will be explained below.

1) Conductive support Most conductive materials can be used, but S
Particularly preferred are materials that exhibit properties that prevent charge injection from the support when bonded to the e-As layer.
Materials with a smaller work function than As materials, such as Cr, Co,
Metals such as Ni5Fe or Al that combines with oxygen itself to form a metal oxide that exhibits blocking properties on the metal surface.
wood is used. In the present invention, Al material, particularly JIS 3003 series Al material, is preferred from the viewpoint of electrical properties, workability, light weight, etc.

2) First photosensitive layer (Se-As layer) The main purpose is to maintain charging ability, and the second layer A
It is necessary to smoothly transfer carriers generated by light irradiation to the g3 Se, -, Ten layer to the conductive support side.

The reason why the first layer is a Se-As layer is that the As 2S e 3-x T e w layer formed as the second layer is formed at a support temperature of 200°C or higher, so it needs to withstand high temperatures. That there is. This is also because crystallization resistance and repeated electrical and mechanical durability are required. Durability at temperatures of about 200 to 250°C is determined by the crystallization temperature of the Se-As layer (Figure 2), and the amount of As added is approximately 28vt% relative to Se.
It is sufficient to add more than that. Desirably close to stoichiometric 35~
It is preferable to add 37 vt% from the viewpoints of structure and electrical stability.

The support temperature when depositing the Se-As layer was 2 as described above.
00°C or higher is desirable. The reason for this is that when the film is formed at a low temperature, structural defects such as dangling bonds increase in the layer, and unevenness occurs in the layer structure, resulting in large repeated surface potential fluctuations, resulting in a decrease in the sensitivity of residual potential accumulation, and dark decay. This is because not only the characteristics deteriorate but also the image becomes uneven.

On the other hand, the film thickness is 30 mm from the viewpoint of ensuring charging ability and repeatability.
~100 μm, preferably 50 to 70 μl.

3) Second photosensitive layer (As2Sei-x Ten layer) This layer must have photosensitivity even in the near-infrared region because it is also used in copiers and printers that use a 760-820 nm laser diode (LD) as a light source. be. As2Se3 material has good electrical, mechanical, and thermal properties, and is also highly sensitive, so it is often used in medium- and high-speed copying machines, but its long-wavelength sensitivity almost disappears at about 780 rv, so it is not used for the above-mentioned LDs. . In order to make this material suitable for LD use, a sensitizer is required. T e SS is generally used as a sensitizer.
There are elements such as b-, GesBi, etc., but among these elements, Te is relatively easy to handle and provides a sensitizing effect.

When alloying As5Se and Te, it is desirable to stabilize the structure as much as possible, so generally As
Preferably, alloying is performed in the form of 2S e3-x Ten.

The above value of X is determined by the required sensitivity.

For example, when using a 780nrA LD, the optical bandwidth (Egopt) required for the photoreceptor is 1.59eV. The relationship between the band width and the above-mentioned X value of the second photosensitive layer is shown in FIG. From this graph, the value of X for 1.59 eV is approximately 0.3.

Also, in 820nn+ LD, E gopt is 1.51e
Since it is V, the value of X is 0.5. Therefore, L.D.
If the X value of As2Se3□Te, a photoreceptor that can be used in the area, is 0.2≦X≦0.7, it can be used as a photoreceptor for LD.

In addition, the As2Se3-x Ten layer is thick enough to generate enough carriers to obtain sensitivity, and
The film thickness must be such that it does not affect the layer, repeatedly lower the potential, or accumulate more residual potential than necessary.

From the above, A s 2 S e 3-I T e 1
The thickness of the layer is preferably about 1 to 20 μm, preferably about 3 to 10 μm.

Furthermore, since the layer must be structurally and electrically homogeneous, it is desirable that the support temperature during vapor deposition be as high as possible.
It is preferable to set the temperature to about 450°C. Just the first layer S
e-As layer and second layer A s 2 S e 3-x
Since it is unfavorable to create a barrier at the interface with T e x in terms of electrical properties, the interface between these two layers is between the Se-As layer and As2.
Se, -, Te, if the layer is in a mixed crystal state, or if the second layer side is between 1 μm and 1.5 μm thick, T is closer to the surface layer.
eSet the deposition conditions so that there is a concentration gradient where the concentration increases.
It is advantageous to do so.

4) Intermediate layer The intermediate layer is a layer that plays an important role in imparting high charging ability to this photoreceptor.

In order to have high charging ability, the photosensitive layer must have a function to prevent charge from being injected into the photosensitive layer during charging.

As a means for forming a blocking function, +014~ on the photosensitive layer is used.
Form an insulating thin film of about 1018 Ω/cat, or perform surface treatment on a Se-As photoreceptor alloyed with high concentrations of As or Te or a Se-Te photoreceptor using corona discharge, etc., to remove arsenic oxide or There is a method of forming a blocking layer of tellurium oxide that has been put to practical use.

In the latter case, although it is a relatively simple means for improving charging ability, the blocking property lacks uniformity. Easily affected by the environment. If not used, charging characteristics will deteriorate. The blocking layer has many disadvantages, such as being easily removed by friction, and insufficient charging ability when the blocking layer has a low volume resistivity (for example, a high Te concentration).

Therefore, it is important to form a permanently stable blocking layer in order to obtain a photoreceptor that exhibits high-quality image forming properties, is highly durable, and has a high charging ability that is stable against environmental changes.

In consideration of this, we have found that when silicon monoxide (S i O) yS- is used as an intermediate layer for the second photosensitive layer, the charging ability and/or
The dark decay characteristics are improved, and an improvement of 20 to 30% is observed compared to the case where the chargeability is improved by corona discharge or the like, and there is no loss in Photo Ga1n (sensitivity).

Furthermore, it was found that there was almost no deterioration in image characteristics even in a high humidity environment, making it an excellent material.

FIG. 4 shows an example of VI characteristics when SiO is used for the intermediate layer. When SiO is the intermediate layer, as shown in 2 in Figure 4, when (+) is applied to the surface layer side of the photoreceptor, there is almost no positive charge (hole) injected from the surface layer, so ten charges occur. Conversely, when (=) is applied, the so-called intermediate layer side, which is less likely to be charged, is N-type, A s
2S e , -x T e , side has a P-type structure,
It is thought that it operates as an N-P junction.

Sio and A s 2 using analysis methods such as XPS' and FT-IR
When the bonding layer of the S e v-x T e x layer is analyzed, As-0 (e.g. As203, As
205, etc.) and a small amount of Te-0 (e.g. TeO2, etc.), compared to when there is no intermediate layer.
Since the number is significantly increased, it is clear that it was formed by joining the intermediate layer.

Judging from the situation, this As-0 and Te-0 are thought to be formed by combining O in SiC with As and Te in the As2Se, -, Tea layer, and this form is
When the surface of the Se3-x Te layer is treated with corona discharge to improve charging ability, the material formed at the interface improves the charging ability because it is similar to the substance formed on the surface of the photosensitive layer. There is no doubt that they are involved in the improvement.

The thickness of SiO as the intermediate layer should be such that the blocking layer formed on the As2.Sei-xTe@ surface is not damaged during the formation of the protective layer.

Since the Si0 layer is formed by vacuum evaporation, it is easy to obtain uniformity, and unlike resin-based films that are formed by coating or dipping, it is possible to make the film even thinner. Therefore, a film thickness of 100 to 5,000× is within the practical range, and preferably a film thickness of 200 to 2,000 people can sufficiently achieve the intended purpose.

5) Protective layer The protective layer is essential for improving the mechanical durability of the photosensitive layer. The necessary conditions for a protective layer are: ■ It must have high mechanical durability. ■ It must not retain residual charge more than necessary. ■ It must be substantially transparent under near-infrared light. ■ It cannot be degraded by external factors such as electric fields, light, and ozone. ■ Good surface smoothness ■ Moisture resistance and non-hygroscopic ■ No toner filming ■ Possessing solvent resistance.

As a practical protective layer that can withstand 80 to 1 million copies, for example, ester crosslinked styrene-MMA resin with a resistance control agent of 5N having an average particle size of 0.05 to 0.2 μm may be used.
40 to 80vt of conductive fine powder such as Oz, TiOz, etc.
% mix and use spray method or dipping method to make 2 to 1
It is coated on the intermediate layer to a thickness of 0μ layer, or by optical CV.
a-SiC:HSa- using D or plasma CVD equipment
8iN:HSa-8iC:0:H,a-B:N
There is a method of overcoating an inorganic layer of 1012 to 1013 Ω·elf, such as an a-0 layer, with a thickness of 500 Å to 5 μI.

Examples and comparative examples are shown below. Note that the amounts (parts) of each component described in Examples and Comparative Examples are parts by weight.

Example 1 In a vacuum evaporation apparatus equipped with one 5US cylindrical boat (first boat) and one isometric boat (second boat), a photoreceptor support of 80φ x 340mm x 3t (unit IIIll) was used as a support for the photoreceptor. ) was prepared and placed in the first boat.
e-As alloy (As: 35.5vt%) 550
gr, second boat A S 2 S e 2,5 T
e a, 525gr was input. Then, the support temperature was set to 225℃, the first boat to 420℃, and the second boat to 440℃.
℃, and the first boat was first energized at a vacuum level of 1×10' Torr or less to deposit a Se-As layer of about 55 μm.

Next, the second boat is energized to reduce the As-8e-Te layer to about 5μ.
m was deposited. The photoreceptor obtained in this way was set in another vacuum evaporation device, a speed of 1 rotation/sec was applied, approximately 214B of silicon monoxide (S i O) was put into the evaporation boat, and the degree of vacuum was 5X 10". The entire amount was evaporated for about 4 minutes at an evaporation rate of 3 to 8 Torr/sec to produce an intermediate layer of about 960 SiC films.

Further, 2 parts of ester cross-linked styrene-MMA resin, 14 parts of toluene, and 3 parts of 5N02 fine powder (manufactured by Mitsubishi Metals) with an average particle size of 0.1 μm were mixed and dispersed in a ball mill for 120 hours, and the liquid was applied by dipping. It was dried at ℃ for 30 minutes to form a protective layer of about 5 μm. Table 1 shows photoreceptor characteristics.
Shown below.

Example 2 Using the same equipment as in Example 1, 550 gr of Se-As alloy (As: 35.5vt%) was placed in the first boat.

A S 2 S e 2.3 T e O on the second boat
, 715gr.

Then, the support temperature was 225°C, the first boat was 420°C,
Set the second boat at 445°C and set the IX 10' To
First, the first boat is energized at a vacuum level below rr, and the Se-A
An s-layer was deposited to a thickness of about 55 μm.

Next, the second boat is energized to reduce the As-8e-Te layer to about 3μ.
m was vapor-deposited to form a photosensitive layer.

The photoreceptor obtained in this manner was set in another vacuum evaporation device, a rotation speed of 1 rotation/second was applied, approximately 110 mg of silicon monoxide (S i O) was put into the evaporation boat, and the degree of vacuum was 5.
The entire amount was evaporated for about 4 minutes at a deposition rate of X 10' Torr and 8 to 8 A/see to form an intermediate layer of about 525 StO films.

The protective layer was formed by the same method as in Example 1, with an intermediate layer having a thickness of about 5 μm. The photoreceptor characteristics are shown in Table 1.

Comparative Example 1 In a vacuum evaporation apparatus equipped with one 5US cylindrical boat (first boat) and one isometric boat (second boat), an 80φ x 340 ix 3t was used as a support for the photoreceptor.
Prepare an A1 drum of (unit ■) and put Se-
As alloy (35.5wt% As) 550gr
, to the second boat A s 2 S e 2,5 T e
o, 525gr was added.

Then, the support temperature was 225°C, the first boat was 420°C,
Set the second boat at 445°C and
First, energize the first boat at a vacuum level below orr and Se-A
An s-layer was deposited to a thickness of about 55 μm.

Next, the second boat is energized to reduce the As-Se-Te layer to about 5μ.
A photoreceptor was formed by vapor deposition. The photoreceptor characteristics are shown in Table 1.

Comparative Example 2 A photoconductor prepared under the same conditions as Comparative Example 1 was coated with a polycarbonate resin (trade name: Panlite, manufactured by Tijin Kasei) having a volume resistivity of 7 x 10" ohm・elm after drying and curing. , dissolved in a mixed solvent of 8 parts of dichloromethane, and formed into a film at 10°C using a dipping method.
It was dried at 30°C for 1 hour to produce a 2000X intermediate layer.

The photoreceptor characteristics are shown in Table 1.

Table 1 Characteristics of each sample - List of symbols in Table 1 Vs: Potential after 20 seconds of application of +6 kV Do: Dark decay ratio after 20 seconds from Vs v Crocodile: Residual potential after 20 seconds of light decay 8780 i 711 On 1 wavelength Light sensitivity (ltoo
-100 Volt) △VD: Amount of repeat variation in dark area potential △vL: Repeat variation in bright area potential fl (780 ns light incident with a spectrophotometer) [Effect] As shown in Table 1, the charging property is unstable; As with low durability
As a result of using an intermediate layer material that forms a blocking layer on the -3e-Te photoreceptor, which can significantly improve chargeability, we have achieved the following results: 1) A highly durable L material with significantly improved chargeability.
D photoreceptor is now possible.

2) Furthermore, it has become possible to create a photoreceptor with good moisture resistance and almost no decrease in resolution even under high humidity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of the photoreceptor of the present invention, and FIG. 2 is an explanatory diagram showing the structure of the photoreceptor of the present invention.
A graph showing the relationship between the concentration and the crystallization temperature of this layer. Figure 3 shows the relationship between the value of X and the optical bandwidth (E gopt) in the second photosensitive layer (As2Se3-*.Te, layer). FIG. 4 is a graph showing the difference in rectification properties (VI characteristics) depending on the presence or absence of an intermediate layer on the second photosensitive layer. r... Conductive support, 2... First photosensitive layer, 3...
Second photosensitive layer, 4... intermediate layer, 5... protective layer.

Claims (1)

[Scope of Claims] An overcoat type photoreceptor having a Se-As photosensitive layer, an As_2Se_3_-_xTe_x photosensitive layer, an intermediate layer, and a protective layer on a conductive support, comprising: 1) the composition of the As_2Se_3_-_xTe_x photosensitive layer; 2) The intermediate layer has a thickness of 100 Å to 5000 Å, and has a chemical composition of silicon oxide. body.