JPH021301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrophotographic photoreceptor, more specifically, a photoreceptor having a multilayer structure in which an intermediate layer and a photoconductive layer are sequentially laminated on a conductive substrate, and the photoconductive layer The present invention relates to an amorphous silicon photoreceptor for electrophotography, which is mainly composed of amorphous silicon.

Prior Art Photoconductors using inorganic photoconductive materials such as selenium (Se), cadmium sulfide (CdS), and zinc oxide (ZnO) are conventionally used as electrophotographic photoconductors used in copiers or laser printers. Photoreceptors using organic photoconductive materials such as PVK, poly-N-vinylcarbazole (PVK), and trinitrofluorenone (TNF) are commonly used. Selenium-based photoreceptors have the advantage of high sensitivity and long life, and that sensitization or durability can be easily improved by alloying. However, problems remain in terms of mechanical strength and heat resistance. Photoreceptors using zinc oxide generally have the disadvantages of low sensitivity and short life. A photoreceptor using cadmium sulfide usually has a relatively thick transparent insulating layer on its top surface, and when used, it undergoes primary charging → reverse polarity secondary charging → image exposure or primary charging → reverse polarity secondary charging. Simultaneous charge image exposure → uniform exposure
It requires a complicated latent image formation process called the NP method. Furthermore, photoreceptors using organic photoconductive materials generally have a short lifespan and have the drawbacks that the sensitivity of the organic semiconductor itself is relatively low. As mentioned above, each of the electrophotographic photoreceptors used conventionally has problems that need to be solved, and there are still photoreceptors that have sufficient characteristics such as high durability, high heat resistance, and high light sensitivity. The reality is that this has not been achieved.

From this point of view, recently, photoreceptors that do not have the above-mentioned drawbacks, that is, have excellent mechanical strength such as surface hardness and abrasion resistance, have high heat resistance, long life, and high light sensitivity, and have a wide range of colors. As a new photoreceptor with excellent properties, amorphous silicon (also known as amorphous silicon) is used as a photoconductive material.
Amorphous silicon photoreceptors using amorphous silicon as the main material are attracting attention. The amorphous silicon film used in this photoreceptor is formed, for example, by glow discharge decomposition of silane (SiH ₄ ) gas using a plasma CVD method (Plasma-Chemical Vaper Deposition method). In this case, in the amorphous silicon film,
Hydrogen atoms generated by the decomposition of the raw material silane gas are automatically incorporated, and the hydrogen-containing amorphous silicon film obtained in this way has a higher dark resistance than one that does not contain hydrogen, and at the same time Has high photoconductivity. In addition, the spectral sensitivity range is wide, from about 380 nm to
It has panchromaticity up to 700 nm, has high photosensitivity, and can provide good photosensitivity even in the infrared region with longer wavelengths.

In addition, it has excellent mechanical strength such as surface hardness and abrasion resistance, so if a surface layer is to be provided on the surface during use, it can be relatively thin, and therefore a Carlson method such as charging → exposure is used. be able to.

For the above reasons, it can be said that amorphous silicon photoreceptors are ideal electrophotographic photoreceptors with excellent mechanical strength, durability, photosensitivity, panchromaticity, long wavelength sensitivity, etc. .

However, the amorphous silicon photoreceptor described above has the following practical drawbacks. In other words, although a photoconductive layer mainly composed of amorphous silicon has a high dark resistance, it is not sufficient to maintain an electrostatic latent image. In the case of a photoconductor having a photoconductive layer as a main component, dark decay is fast even if a considerable amount of charge is applied to the surface of the photoconductor to form an electrostatic latent image. This charge may not be sufficiently retained until the developing process.

In addition, the charging characteristics have a large dependence on the atmosphere of the external environment, that is, humidity and temperature dependence, and changes in the external environment can cause the charging characteristics to fluctuate greatly, and in particular, the charging characteristics deteriorate significantly in a high temperature and humid atmosphere. . Furthermore, since the charging characteristics are difficult to stabilize, stable high-quality images cannot be obtained at all times. Alternatively, when the photoreceptor is used repeatedly, as the number of repetitions increases, the charging potential tends to decrease and the image quality tends to deteriorate.

Therefore, in the case of an amorphous silicon photoreceptor, it is preferable to use an intermediate layer in order to improve the above-mentioned drawbacks. However, the conventional intermediate layer made of a polymer material cannot take full advantage of the advantages of a photoconductive layer mainly made of amorphous silicon, and therefore has high adhesion and mechanical strength with the amorphous silicon photoconductive layer. Moreover, it is desired to provide an intermediate layer having a large charge retention ability.

OBJECTS OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that reliably eliminates the above-mentioned drawbacks of amorphous silicon photoreceptors by providing an intermediate layer compatible with a photoconductive layer mainly composed of amorphous silicon. It is about providing.

An object of the present invention is to provide an electrophotographic photoreceptor that has excellent charge retention during the charging process.

Another object of the present invention is to provide an all-environment electrophotographic photoreceptor whose charging characteristics are not affected by changes in the external atmosphere.

Another object of the present invention is to provide an electrophotographic photoreceptor with excellent repeatability.

Still another object of the present invention is to provide an electrophotographic photoreceptor having excellent electrophotographic properties such as mechanical strength, durability, lifespan, heat resistance, and photosensitivity.

Structure of the Invention The electrophotographic photoreceptor of the present invention has a multilayer structure in which an intermediate layer and a photoconductive layer are sequentially laminated on a conductive substrate, and the photoconductive layer is mainly made of amorphous silicon. In the photoreceptor, the intermediate layer is made of a material obtained by drying and curing a solution containing at least one type of zirconium complex.

The structure of the electrophotographic photoreceptor of the present invention is as shown in the figure, in which 1 is a photoconductive layer mainly composed of amorphous silicon, and 2 is an intermediate layer consisting of a dried and cured product of a solution containing a zirconium complex. , 3 is a conductive substrate.

The intermediate layer 2 functions as a charge blocking layer that prevents charge from being injected from the conductive substrate side into the photoconductive layer during charging treatment, and also functions as an adhesive layer between the conductive substrate and the photoconductive layer. can have. Furthermore, the intermediate layer can function as a layer for absorbing and relaxing internal stress caused by heat generated due to the difference in thermal expansion coefficient (or thermal contraction coefficient) between the conductive substrate and the photoconductive layer. This can prevent the photoconductive layer from peeling off from the substrate or cracking in the photoconductive layer due to internal stress caused by heat.

The intermediate layer 2 contains at least one zirconium complex.
It is formed by drying and curing a solution containing various types.
Zirconium complexes suitable for the intermediate layer include zirconium tetrakisacetylacetonate, zirconium dibutoxybisacetylacetonate,
Zirconium tributoxy acetylacetonate, zirconium tetrakis ethyl acetoacetate, zirconium butoxy tris ethyl acetoacetate, zirconium dibutoxy bis ethyl acetoacetate, zirconium tributoxy monoethylacetoacetate, zirconium tetrakis ethyl lactate, zirconium dibutoxy bis ethyl lactate, bisacetyl Examples include zirconium acetonate bisethylacetoacetate, zirconium monoacetylacetonate trisethylacetoacetate, zirconium bisacetylacetonate bisethyl lactate, and zirconium trifluoroacetylacetone.

These may be used as a mixed solution of two or more types. Alternatively, a solution containing a mixture of these zirconium complexes and an organosilicon compound may be used. As the organosilicon compound, compounds generally called silane coupling agents are suitable, and examples thereof include the following. Vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β(aminoethyl)
γ-aminopropyltrimethoxysilane, N-β
(aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,
Methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, monophenyltrimethoxysilane.

The thickness of the intermediate layer can be set arbitrarily, but it is preferably 10 μm or less, particularly 1 μm or less. This intermediate layer can be formed by coating by an appropriate method such as spray coating, dip coating, knife coating, roll coating, or the like.

Further, the drying and curing temperature of the intermediate layer can be set at any temperature between room temperature and 400°C.

The photoconductive layer mainly composed of amorphous silicon (No. 1) can be formed on a substrate by a method such as a glow discharge method, a sputtering method, an ion plating method, or a vacuum evaporation method. Among them, according to a method (glow discharge method) in which silane (SiH ₄ ) gas is decomposed by glow discharge using plasma CVD method, electrophotographic photoreceptors with high dark resistance and high light sensitivity, etc. that automatically contain an appropriate amount of hydrogen in the film can be produced. A photoconductive layer with optimum properties can be obtained using the following methods. In this case, in order to more efficiently contain hydrogen, plasma CVD
Hydrogen (H ₂ ) gas may be introduced into the apparatus simultaneously with the silane gas. In addition, for the purpose of controlling the dark resistance or charging polarity of the amorphous silicon photoconductive layer film, dopants such as diborane (B ₂ H ₆ ) gas and phosphine (PH ₃ ) gas are added to the above gas.
Boron (B) is mixed into the photoconductive layer by mixing gas.
Alternatively, it is also possible to add (dope) an impurity element such as phosphorus (P). Furthermore, halogen atoms, carbon atoms, oxygen atoms, Atom, nitrogen atom, etc. may be contained. Furthermore, it is also possible to add elements such as germanium (Ge) to the photoconductive layer film for the purpose of increasing the sensitivity in the long wavelength range.
In order to add and contain elements other than the above-mentioned hydrogen into the amorphous silicon photoconductive layer, in the plasma CVD apparatus,
Glow discharge decomposition may be performed by introducing gasified products of these elements together with silane gas, which is the main raw material.

Silane (SiH ₄ ) is produced by the above plasma CVD method.
In the method of forming an amorphous silicon photoconductive layer in which gas is decomposed by glow discharge, effective discharge conditions, that is, effective conditions for forming an amorphous silicon film are as follows, taking the case of AC discharge as an example. Frequency is usually
0.1~30MHz, preferably 5~20MHz, degree of vacuum during discharge 0.1~5Torr, substrate heating temperature 100~400℃
It is.

The thickness of the photoconductive layer mainly composed of amorphous silicon can be set arbitrarily, but it is 1 μm to 200 μm, especially 10 μm to
100 μm is suitable.

The conductive substrate 3 in the attached drawings includes Al, Ni,
A substrate made of a metal such as Cr, Fe, stainless steel, or brass, or a substrate made of an intermetallic compound such as In ₂ , SnO ₂ , Cul, or CrO ₂ can be used. Further, the shape of the substrate can be any shape such as a cylinder, a flat plate, or an endless belt.

Examples Next, the electrophotographic photoreceptor of the present invention will be explained with reference to comparative examples and examples.

(i) Comparative example Hydrogen was deposited on a cylindrical Al substrate by glow discharge decomposition of silane (SiH ₄ ) gas using a capacitively coupled plasma CVD device capable of forming an amorphous silicon film on a cylindrical substrate. An amorphous silicon film containing . The conditions for forming the amorphous silicon film at this time were as follows.

A cylindrical Al substrate is installed at a predetermined position in the reaction chamber of a plasma CVD device, the substrate temperature is maintained at a predetermined temperature of 250°C, and 100% silane (SiH ₄ ) gas is supplied into the reaction chamber at a rate of 120 c.c./min. , 100 ppm diborane (B ₂ H ₆ ) gas diluted with hydrogen was introduced at 20 c.c. per minute, and 100% hydrogen (H ₂ ) gas was introduced at a rate of 90 c.c. per minute, and the inside of the reaction vessel was heated to 0.5 Torr. After maintaining the inner thickness of 13.56MHz
An alternating frequency power source was turned on to generate a glow discharge, and the output of the alternating frequency power source was maintained at 85W. In this way, a photoreceptor was obtained having a photoconductive layer mainly made of amorphous silicon with a thickness of 25 μm on a cylindrical Al substrate. The photoreceptor thus obtained had a hard surface, excellent wear resistance and heat resistance, high dark resistance and high light sensitivity, and had excellent electrophotographic photoreceptor characteristics. Furthermore, it was possible to charge either positively or negatively, and had bipolar charging properties.

This photoreceptor was positively charged to an initial potential of 550V. This operation of exposing to light with a wavelength of 650 nm was repeated at a rate of 40 times per minute. The residual potential at this time is
Although it was stable at 0V, the charging potential tended to decrease as the number of repetitions increased, and after 1000 repetitions, the charging potential decreased to 75% of the initial charging potential.
It had decreased to a value of %.

Further, when this photoreceptor was negatively charged and the same operation was performed, the same phenomenon as in the case of positively charging was observed. However, 1.5 times more current was required than in the case of positive charging.

(ii) Example 1 2 parts by weight of zirconium tetrakis acetylacetonate and γ were placed on an Al pipe having the same shape as the comparative example.
- Spray coating a solution consisting of 1 part by weight of methacryloxypropyltrimethoxysilane and 50 parts by weight of n-butanol, drying at 250°C for 2 hours,
An intermediate layer with a thickness of 0.6 μm was provided. Next, on this intermediate layer, a photoconductive layer mainly composed of amorphous silicon having the same content as that of the comparative example was provided with approximately the same thickness as that of the comparative example, by the same method as that of the comparative example. The thus obtained photoreceptor had a hard surface, excellent wear resistance and heat resistance, and high photosensitivity, and had excellent electrophotographic photoreceptor properties. Furthermore, it was possible to charge either positively or negatively, and had bipolar charging properties.

Therefore, the above-mentioned characteristics of the present photoreceptor were excellent and were no different from those of the photoreceptor obtained in the comparative example. Further, almost no increase in residual potential due to the introduction of the intermediate layer was observed, and there was no problem at all in practical use.

When this photoconductor was positively charged and the initial potential was set to 550V, the same as in the comparative example, and the exposure operation was repeated under the same conditions as the comparative example, the residual potential at this time was stable at 2V, a value that does not pose a practical problem, and it was repeatedly No decrease in charging potential was observed as the number increased, and the charging potential was always stable.

Further, when this photoreceptor was negatively charged and the same operation was performed, it showed good stability of the charging potential as in the case of positively charging. Furthermore, the current required to obtain a charging potential (absolute value) of 550V was equal for both positive and negative charging.

(iii) Example 2 1 part by weight of zirconium tetrakis acetylacetonate was placed on an Al pipe having the same shape as the comparative example.
A solution consisting of 30 parts by weight of methyl alcohol was applied by dipping, dried and cured at 250°C for 1 hour,
An intermediate layer with a thickness of 0.3 μm was provided.

Next, on this intermediate layer, a photoconductive layer mainly composed of amorphous silicon having the same content as that of the comparative example was provided by the same method as that of the comparative example and having almost the same thickness as that of the comparative example.

When the photoreceptor thus obtained was subjected to the process of positively charging, exposing, negatively charging, and exposing 1000 times each, no decrease in the charging potential was observed in either case of positive or negative charging, indicating that it was stable. The residual potential was almost 0V.

Furthermore, the corona current required for a charging potential of ±550V was the same for positive and negative charging.

As described above, in an amorphous silicon photoreceptor without an intermediate layer, the charging potential decreases significantly as the number of repetitions increases, whereas in an amorphous silicon photoreceptor provided with an intermediate layer according to the present invention, the charging potential decreases significantly as the number of repetitions increases. remained almost constant even under the condition of increasing the number of repetitions.

Effects of the Invention According to the electrophotographic photoreceptor of the present invention, the intermediate layer has high adhesion with the photoconductive layer mainly composed of amorphous silicon and has high mechanical strength, so it is possible to use a relatively thin intermediate layer. Therefore, the residual potential does not become so large. Therefore, a simple copying process such as the Carlson method can be used to form the latent image. Furthermore, since the electrophotographic photoreceptor of the present invention has a high charge retention ability, its charging characteristics are not affected by the external environment or the number of times it is used, and it has excellent mechanical strength, as well as durability, longevity, and heat resistance. It has excellent electrophotographic properties such as light sensitivity and photosensitivity.

[Brief explanation of drawings]

The drawing is a sectional view showing the structure of the electrophotographic photoreceptor of the present invention. 1... Photoconductive layer, 2... Intermediate layer, 3... Conductive substrate.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor having a multilayer structure in which an intermediate layer and a photoconductive layer are sequentially laminated on a conductive substrate, and the photoconductive layer is mainly made of amorphous silicon,
An electrophotographic photoreceptor, wherein the intermediate layer is made of a material obtained by drying and curing a solution containing at least one type of zirconium complex.