JPS61278858A - Selenium photosensitive body for electrophotography - Google Patents

Abstract

PURPOSE:To improve electrophotographic characteristics and resistances to abrasion and crystallization, and to prevent wrinkling by dividing a surface protective layer into 2 layers, and rendering the arsenic content of the first layer in contact with a carrier generating layer lower than that of the second outermost layer. CONSTITUTION:The electrophotographic sensitive body is prepared by successively laminating on a conductive substrate a carrier transfer layer made of amorphous Se or an amorphous Se-Te alloy, the carrier generating layer made of an amorphous Se-Te alloy contg. 20-50 wt.% Te, and the surface protective layers made of an amorphous Se-As alloy divided into the first surface protective layer lower in the As content and the second outermost surface protective layer higher in that, thus permitting the obtained photosensitive body to have electrophotographic characteristics superior in the longer wavelength region of 660-800 nm, and good resistances to abrasion and crystallization, and to be prevented from wrinkling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an electrophotographic photoreceptor having a photosensitive layer made of a selenium-based material and used in electrophotographic plain paper copying machines and optical printers.

[Prior art and its problems]

2. Description of the Related Art In recent years, office automation has rapidly developed and become popular, and in conjunction with this, various printers have been actively developed as output devices. Above all, its high-speed printing performance and high image quality.

Electrophotographic optical printers are attracting attention because of their high reliability and low noise.

Recently, small optical printers with medium to low speeds (printing speeds of around 1,000 lines/minute) have been developed one after another. These small optical printers are mainly used by connecting to office computers, and are also used for Japanese word processors, optical discs, etc.
It is also used as a file system output device, and there is a movement to use it for high-speed facsimile. Furthermore, recently there has been a strong demand for digital plain paper copying machines that can be equipped with various intelligent functions, and this is also used as an output unit.

As a light source for an optical printer, a laser beam, a light emitting diode, or the like is used, and laser beams are often used because of their high printing speed and high image quality. As a laser beam, He −
No. laser beams have been mainly used, but semiconductor laser beams have recently come into use due to the demand for smaller equipment.

Optical printers turn scanning laser beams or light emitting diode arrays on and off depending on the image to be printed.
It consists of a part that performs f control, and an electrophotographic part that receives the control light to form a latent latent image corresponding to a printed image on a charged photoreceptor, and prints the latent image as a toner image. The electrophotographic part has the same configuration as a conventional electrophotographic copier, but the performance of the photoreceptor used here is an important factor that affects the printer's printing speed, image quality, and stability of the printed image. .

As described above, the optical printer uses semiconductor laser light and light emitting diode arrays, and the wavelength of semiconductor laser light is around 790 nm, and the wavelength of light from light emitting diodes is around 660 to 680 nm. For such long-wavelength light, photoreceptors that are conventionally applied mainly to electrophotographic copying machines cannot be used. In conventional photoreceptors, photoconductive materials are selected to have high photosensitivity in the visible wavelength region, and the structure of the photosensitive layer is also devised. This is because the light sensitivity is very low.

Various studies are underway regarding photoconductive materials and photosensitive layer configurations that can be used in photoreceptors suitable for such long wavelength light, but electrophotographic properties (charging potential, photosensitivity, residual potential, etc.) ), there are still many problems in terms of fatigue properties, environmental resistance, printing durability, etc.

For selenium photoreceptors, spraying is also progressing, and a carrier transport layer made of amorphous selenium or an amorphous selenium-tellurium alloy is applied on a conductive substrate to coat 20 to 50 layers of tellurium!
A functionally separated photoreceptor with a multilayer structure, in which a carrier generation layer made of an amorphous selenium-tellurium alloy containing Ikg6 and a surface protection layer made of amorphous selenium or an amorphous alloy of tellurium or arsenic and selenium are sequentially laminated. Proposed. However, although the photoreceptor having such a structure has excellent electrophotographic properties with respect to long wavelength light, there is a problem in its durability.

In other words, in the case of a photoreceptor whose surface protective layer is made of amorphous selenium or an amorphous selenium-tellurium alloy, it exhibits practically sufficient initial electrophotographic characteristics and abrasion resistance during continuous printing. However, it has the disadvantage that the amorphous surface protective layer tends to crystallize if left in a high temperature environment after printing. On the other hand, in the case of a photoreceptor whose surface protective layer is made of an amorphous selenium-arsenic alloy, the glass transition point of the selenium-arsenic alloy is higher than that of selenium-arsenic or selenium-tellurium alloys, and therefore the transition from amorphous to crystalline. The transition to, that is, crystallization, is difficult to occur, and the above-mentioned drawback that the surface protective layer is easily crystallized can be eliminated. Furthermore, as shown in Figure 2, as the amount of arsenic added increases, the glass transition point of the selenium-arsenic alloy increases, so in order to suppress crystallization of the surface protective layer, the more amount of arsenic added, the better. It turns out. However, the carrier transport layer is the base layer.

Since the carrier generation layer is made of amorphous selenium or an amorphous selenium-tellurium alloy, if the photoreceptor is exposed to high temperatures above the glass transition point (approximately 45°C) of the underlayer for a long time, the underlayer and surface protective layer will be damaged. The difference in thermal expansion coefficient between the two causes wrinkles in the surface protective layer, resulting in the disadvantage of wrinkles. In order to prevent the occurrence of wrinkles, either reduce the thickness of the surface protective layer or
The amount of arsenic added must be reduced. However, from the viewpoint of crystallization resistance, it is not preferable to reduce the amount of arsenic added, and from the viewpoint of abrasion resistance during continuous printing, there is a problem that the film thickness cannot be made thinner than a certain level.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems and to
It is an object of the present invention to provide a selenium photoreceptor for electrophotography, which has excellent electrophotographic properties in a long wavelength region of 800 nm to 800 nm, has good abrasion resistance and crystallization resistance, and is free from wrinkles.

[Key points of the invention]

The object of the present invention is to form a carrier transport layer made of amorphous selenium or an amorphous selenium-tellurium alloy on a transparent substrate, and an amorphous selenium-tellurium alloy containing 20 to 50% by weight of tellurium.
A carrier generation layer made of tellurium alloy and amorphous selenium
In an electrophotographic photoreceptor formed by sequentially laminating a surface protection layer made of an arsenic alloy, the surface protection layer is divided into two layers, and the arsenic content of the first surface protection layer in contact with the carrier generation layer is removed. This is achieved by making the arsenic content smaller than that of the second surface protective layer that forms the surface.

[Embodiments of the invention]

One of the properties that the surface protective layer (hereinafter also referred to as OCL) should have is crystallization resistance, which depends on the arsenic content of the selenium-arsenic alloy that is the constituent material of OCL. The following experiment was conducted to determine the practically effective arsenic content. Outer diameter 120
The aluminum cylinder (2) was maintained at a temperature of 60° C., and selenium was vacuum-deposited on its outer surface to a thickness of 50 cm to form a carrier transport layer (hereinafter also referred to as OTL). On this layer, a selenium-tellurium alloy containing U weight % of tellurium is applied to a thickness of 0.3 μm.
Franche vapor deposition was carried out on m to form a carrier generation layer (hereinafter also referred to as CGL). On this layer, a layer with the composition and film thickness shown in Table 1 was flash-deposited as OCL, and photoreceptor sample N
a1 to Kan4 were produced. These samples were attached to a commercially available semiconductor laser printer with a -component developer development method at a printing speed of 20 sheets/min, and 1500 sheets were printed on the B44 layer.
In both cases, extremely clear images were stably obtained. Next, these samples were left in a constant temperature atmosphere at 50°C, and the change in chargeability (the electric charge fi flowing into the photoconductor necessary to give a predetermined charging potential to the photoconductor surface by corona discharge) was carefully examined. . As a result, it was observed that the chargeability of the samples decreased as the surface crystallization progressed, but as shown in Table 1, the iiO when left until such crystallization started significantly decreased depending on the sample. This difference in crystallization start time is due to the fact that as the amount of arsenic added to OCL increases, the thermal stability of OOL improves, and if the amount of arsenic added is 3 atoms or more, it is sufficiently stable for practical use. It is.

Another property that OCL should have is wear resistance.

Form up to OGL according to sample 1, and add 3 arsenic on top of it.
Film thickness 2.2 made of selenium-arsenic alloy containing JJKl
Continuous printing tests were conducted on the photoreceptor sample N115, in which an OOL of .mu.m was formed, using a semiconductor laser printer using a two-component developer, 9 reversal development, and 7 plus cleaning methods. After printing on 140,000 sheets of paper with a width of 18 inches and a length of 1/2, the thickness of the OOL was examined using an optical interference thickness gauge, and 0.05 μm of wear was observed. Practically speaking, printing durability of at least 10,000 sheets or more is required, so the OCL film thickness must be 0.1 μm or more with some margin in consideration of variations.

According to the above results, in order to maintain good heat resistance and abrasion resistance of the photoreceptor, the OOL should be a layer of 0.1 μm or more in thickness made of a selenium-arsenic alloy containing 3 or more atoms of arsenic. Must. However, when a photoreceptor having this unusual OOL is exposed to a high temperature atmosphere, wrinkles occur on the OCL surface. The present invention further eliminates this wrinkling by dividing the OCL into two layers with different concentrations of arsenic.

The present invention will be explained below by way of examples with reference to drawings and comparative examples. FIG. 1 shows a conceptual cross-sectional view of the photoreceptor of the present invention, in which 1o is a conductive substrate, 20 is a carrier transport layer (C
TL), 30 is a carrier generation layer (car,, )
, the button has the first surface protective layer (ocLx) 41 and the second
Surface protective layer (0CL2) This is a surface protective layer similar to 42.

Example 1.2 An aluminum cylinder with an outer diameter of 1201 m as a tetraelectric substrate IO was maintained at a temperature of 60'C, and selenium (S) was coated on its outer surface.
e) was vacuum-deposited to a thickness of 50 μm to form CTL 20.

Thereon, a selenium-tellurium alloy containing 4.17 ft % of tellurium (Tθ) was deposited in 7 lashes to a film thickness of 0.3 μm to obtain CGL30. On top of this layer OCL l and OC
Photoreceptors of Examples 1 and 2 were fabricated by sequentially forming layers I and 2 having the compositions and thicknesses shown in Table 2 by flash vapor deposition.

Comparative Examples 1, 2, 3.4 OTL 20 and CjGL 30 were formed on the Toden substrate 10 according to Example 1, and then a layer with the composition and film thickness shown in Table 2 as 0CLI was flash-deposited. (X:L) Photoreceptors of Comparative Examples 1, 2.3, and 4, which are single-layer OCL, were prepared.

The above six types of photoreceptors were left in a constant temperature bath at a temperature of 65° C. for 60 minutes, and then taken out into a room temperature atmosphere, and the occurrence of wrinkles on the surface of the photoreceptors was examined. The results are OOL 1 and OOL 2
The composition and film thickness are shown in Table 2.

In Table 2, the O mark indicates that no wrinkles were observed.
The Δ mark indicates that some wrinkles were observed, and the X mark indicates that many wrinkles were generated.

As mentioned above, OCL or at least 001. The outer surface of the O
When CL is a single layer, wrinkles are already observed in Comparative Example 1 with a film thickness of 0.1 μm, and wrinkles tend to increase as the film thickness increases in Comparative Examples 2, 3, and 4. On the other hand, when OCL is divided into two layers according to the present invention and the content of OCLI in the inner layer in contact with CGL is reduced, the film thickness of OOL 2, which is the outer surface, is reduced to 1. No wrinkles were observed even when the thickness was as thick as .2, and the effect was extremely significant.

Examples 3 and 4.5 Up to 0 GL30, it was formed according to Example 1, and then
(, Ll and OCL 2, layers having the compositions and film thicknesses shown in Table 3 were sequentially formed by 7 lash evaporation, and Example 3
．． Photoreceptors Nos. 4 and 5 were produced.

Comparative Example 5.6 A photoreceptor of Comparative Example 5.6 was prepared in the same manner as in Example 3 except that the composition and film thickness of 0(1!L1) were as shown in Table A-3.

The above five types of photoreceptors were subjected to the same heating test as in the case where the results shown in Table 2 were obtained, and the occurrence of wrinkles was investigated. The results are also summarized in Table 3.

Table 3 According to Table 3, the content of 90CLI must be 0.5 atoms or more. In addition, when the hydrogen content of 0-CLI exceeds 2 atoms, it becomes too close to the hydrogen content of 0CL2, and O
Since the effect of dividing CL into two layers is reduced, 0CL1
The content of carbon atoms is preferably 2 atoms or less.

Example 6.7 QC! The film thickness of L1 is 0.4 μm + 2.0, respectively.
Photoreceptors of Examples 6 and 7 were produced in the same manner as in Example 5 except that the thickness was set to μm.

Comparative Example 7 A photoconductor of Comparative Example 7, which was the same as Example 6 except that the film thickness of 0CLI was 2.3 μm, was produced.

The occurrence of wrinkles was similarly investigated for the photoreceptors of the above 3FFL class, but no wrinkles were observed in Examples 6 and 7, and wrinkles due to drying were observed in Comparative Example 7. . The film thickness of OCL l is preferably 2.0 μm or less. On the other hand, the film thickness of 0CL40 needs to be 0.5 μm or more in terms of the charging ability of the photoreceptor, and considering the case where the film thickness of 00L2 is 0.1 μm, the film thickness of 0CLI is 0.5 μm or more.
A thickness of 4 μm or more is required.

Examples 8, 9, 10 OCL up to 30 was formed according to Example 1, and Ic
0CLI and QC! Layers having the composition and film thickness shown in Table 4 were successively formed as L2 by 7-lash vapor deposition to produce photoreceptors of Examples 8, 9 and 10.

Comparative Example 8 A photoreceptor of Comparative Example 8, which was the same as Example O except that the film thickness of OCT 2 was 0.8 μm, was tabulated.

Comparative Example 9 A photoconductor of Comparative Example 9 was produced which was the same as Example 10 except that the film thickness of 0CL2 was 0.7 μm.

The occurrence of wrinkles was similarly investigated for the above five types of photoreceptors. The results are summarized in Table 4.

From the viewpoint of abrasion resistance, it is preferable that the fourth coating 00L2 be as thick as possible without causing wrinkles. In Comparative Example 9, wrinkles were observed, but in Example 8, no wrinkles were observed, and QC! L
If the arsenic content of No. 2 is appropriately selected, the film thickness can be applied up to 0.7 μm. Furthermore, the arsenic contained in OCL 2 is preferably 3 atoms or more, but on the other hand, arsenic in selenium acts as an electron trap, and if the number of arsenic exceeds 5 atoms, this electron This is not preferable because the trap effect cannot be ignored and the charging ability of the photoreceptor decreases.

In addition to the above results, regarding the film thickness, wear resistance and OC
In order to avoid problems caused by local scratches on L, it is preferable that it be as thick as possible without causing wrinkles.
Regarding the composition, considering that the electrophotographic properties of the photoreceptor will be more stable if there is less arsenic within the allowable range of heat resistance.
QC! As for L l, Hisha's content is t 0.5~2 y! ,
The film thickness is 0.4 to 2.0 μm, and the OCL 2 contains t3 to 5 atoms, and the film thickness is 0.1 to 0.7 μm.
It is preferable to blow by mouth, and more preferably QCLI is 0.8 to 1.5 atoms containing arsenic and #thickness 1 to 2 μm.
, as OCL2, arsenic-containing 1[3 to 4 width, film fE
j, 0.5 □ ~ 0.7 μm.

In the above example, selenium was used as OTL, but selenium
A similar effect can be obtained by using a tellurium alloy.

〔Effect of the invention〕

According to the present invention, a carrier transport layer made of amorphous selenium or an amorphous selenium-tellurium alloy is provided on a conductive substrate,
In an electrophotographic photoreceptor in which a carrier generation layer made of an amorphous selenium-tellurium alloy containing 20 to 50 weight i of tellurium and a surface protection layer made of an amorphous selenium-arsenic alloy are sequentially laminated. , the surface protective layer is divided into two parts, the O-1 surface preservation layer in contact with the carrier generation layer is a layer with a low arsenic concentration, and the first surface protective layer on the side that will become the outer surface is a layer with a high arsenic concentration. . With this configuration, 660
It is possible to obtain a photoreceptor that has excellent electrophotographic properties in the long wavelength region of 800 nm to 800 nm, has good abrasion resistance and crystallization resistance, and is free from wrinkles. By interposing the first surface protective layer between the carrier generation layer 1- and the second surface protective layer, the difference in thermal strain between the two layers is alleviated, and wrinkles on the surface of the photoreceptor are prevented. Even if the carrier generation layer contains a large enough amount of tellurium to have sufficient photosensitivity to long wavelength light, the surface of the carrier generation layer can be covered with selenium, which has a high arsenic content and good crystallization resistance.・This is because it has become possible to protect the film with an arsenic metal layer that is thick enough to provide sufficient printing durability.

The effect of the present invention is extremely large, as it provides an excellent electrophotographic photoreceptor for optical printers or intelligent digital plain paper copying machines, which are expected to rapidly develop and become popular in the future.

[Brief explanation of drawings]

FIG. 1 is a conceptual cross-sectional view showing one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the carbon content and the glass transition point of a selenium-arsenic alloy. 10... Conductive substrate, 20... Carrier transport layer, 3
0...Carrier generation layer, 40...Surface protection layer, 41
...first surface protective layer, 42...second surface protective layer. ' Figure 1 V-1# content (atomic %)

Claims (1)

[Claims] 1) A carrier transport layer made of amorphous selenium or an amorphous selenium-tellurium alloy on a conductive substrate, and an amorphous selenium-tellurium alloy containing 20 to 50% by weight of tellurium. A selenium photoreceptor for electrophotography comprising a carrier generation layer made of a carrier-generating layer and a surface protection layer made of an amorphous selenium-arsenic alloy, wherein the surface protection layer is in contact with the carrier generation layer. and a second surface protection layer formed on the first surface protection layer and serving as the outer surface of the surface protection layer, and the arsenic content of the first surface protection layer is greater than the arsenic content of the second surface protection layer. A selenium photoreceptor for electrophotography, characterized in that the content is less than that of selenium. 2) In the photoreceptor according to claim 1, the first
The surface protective layer is a layer with a thickness of 0.4 to 2.0 μm containing 0.5 to 2.0 at% arsenic, and the second surface protective layer is
A selenium photoreceptor for electrophotography, characterized in that it is a layer having a thickness of 0.1 to 0.7 μm and containing up to 5 atom % of arsenic.