JPH0488351A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a high photosensitivity over the entire region of visible light and to stably obtain good images by successively laminating an amorphous silicon layer, a specific 2nd amorphous silicon carbide layer and an optical org. semiconductor layer on a specific 1st amorphous silicon carbide a-SiC layer. CONSTITUTION:The 1st a-SiC layer 2 having the atom compsn. ratios within a 0.2<x<0.5 range in (x) value of Si1-xCx, the a-SiC layer 3, the 2nd a-SiC layer 4 having the atom compsn. ratios within a 0.2<y<0.5 range in (y) value of Si1-yCy, and the optical org. semiconductor layer 5 are successively laminated on a substrate 1. The high photosensitivity over the entire region of visible light is obtd. in this way and the unequal densities of images are decreased, by which the good images are stably obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor comprising an amorphous silicon carbide layer or a laminated layer of an amorphous silicon layer and an organic optical semiconductor layer.

[Prior art and its problems]

The electrophotographic photoreceptor proposed in JP-A-56-14241 has a structure in which amorphous silicon carbide (hereinafter amorphous silicon carbide is abbreviated as a-3iC) and an organic optical semiconductor layer are laminated on a substrate. −
The 3iC layer is used as a carrier excitation layer.

However, according to the electrophotographic photoreceptor having the above structure, the sensitivity on the short wavelength side is good due to the large optical bandgap of the a-3iC layer, but on the other hand, the sensitivity on the long wavelength side is insufficient. As a result, when a PPC (plain paper copying machine) is used, sensitivity is insufficient in the wavelength range of 600 nm or more, ranging from yellow to red, and as a result, for color originals, etc., sensitivity in the visible range is insufficient. The problem is that it cannot be done.

Furthermore, in the electrophotographic photoreceptor proposed in JP-A No. 56-25743, an amorphous silicon photosensitive layer (hereinafter amorphous silicon is abbreviated as a-3i), an a-3iC transition layer, and an organic photosemiconductor layer are formed on a substrate. If the a-3i layer and the aSiC layer are stacked in this way, the sensitivity characteristics will be improved, but on the other hand, the dark decay characteristic of the surface potential will deteriorate, and the dark decay will be faster. As a result, a small unevenness in the surface potential that occurs in the charging section becomes a large unevenness in the surface potential in the developing section after dark decay, and as a result, the density unevenness of the image becomes noticeable, and a good image cannot be obtained. There is a point.

Further, when the a-3i layer is laminated directly on the substrate, there is also a problem that the adhesion between the layer and the substrate is insufficient and peeling occurs.

Therefore, an object of the present invention is to provide a highly reliable electrophotographic photoreceptor that can obtain high photosensitivity over the entire visible light range and that can also stably produce good images by improving the dark decay characteristics of the surface potential. It is about providing.

[Means for solving problems]

The electrophotographic photoreceptor of the present invention has an atomic composition ratio of S l on a substrate.
+ -x The first a-3iC layer whose CxOX value is in the range of 0.2<x<0.5, the a-3i layer, and the atomic composition ratio of the 5in-yC ay value of o<y< It is characterized in that a second a-3iC layer in the range of o and s and an organic optical semiconductor layer are sequentially laminated.

The electrophotographic photoreceptor of the present invention is also characterized in that the first a-3iC layer contains 0601 to 30 atomic percent of oxygen and/or nitrogen.

The present invention will be explained in detail below.

1 and 2 show the layer structure of the electrophotographic photoreceptor of the present invention. Both have a first a-3iC layer 2, a-3 on the substrate 1.
The i-layer 3 and the second a-3iC layer 4 are sequentially laminated,
Furthermore, an organic optical semiconductor layer 5 is laminated. FIG. 2 shows another example, in which an inorganic protective layer 6 is laminated on the organic optical semiconductor layer 5.

In the above layer structure, the first a-3iC layer 2 has the function of blocking carrier injection from the substrate 1 when the photoreceptor is charged, and also improves the adhesion between the photosensitive layer and the substrate 1, so that the film can be peeled off. It has a function to prevent

The a-3i layer 3 and the second a-3iC layer 4 have a function of generating charges, and the organic optical semiconductor layer 4 has a function of transporting charges.

According to this layer structure, the second a-3iC layer 4 absorbs mainly the light on the short wavelength side of the light incident from the surface side of the organic optical semiconductor layer 5, and then the remaining light mainly on the long wavelength side is absorbed. is a-
3i layer 3, and as a result, the photosensitivity is increased in the entire visible region.

First, for the first a-3iC layer 2, the range of element ratios is set as follows.

Si1-x Cx 0.2<x<0.5 Preferably 0.3<x<0.5 If the y value is less than 0.2, carrier injection from the substrate l cannot be sufficiently prevented, and , the dark decay characteristics cannot be improved, and the adhesion to the substrate 1 cannot be sufficiently ensured. y
If the value is 0.5 or more, the a-3i layer 3 and the second a-
Photocarriers generated in the 3iC layer 4 do not flow smoothly to the substrate I, resulting in decreased photosensitivity and increased residual potential.

Moreover, the thickness of the first a-3iC layer 2 is 0.01 to 1.0
μm, preferably within the range of 0.05 to 0.5 μm,
Within this range, good dark decay characteristics can be obtained and the adhesion of the film will also be good.

Furthermore, the optical energy gap of the first a-3iC layer 2 is preferably increased to provide a difference of 0.1 eV or more, preferably 0.2 eV or more, compared to the a-Si layer 3. Injection of carriers from the inside can be effectively prevented.

In the a-5i layer 3, carriers are well excited by long wavelength light, and its photosensitivity can be increased.

For this purpose, it is desirable to set the thickness of the layer within the range of 0.05 to 5.0 μm, preferably 0.1 to 3.0 μm.

Moreover, the optical energy gap of this a-3i layer 3 (
When Eg apt (hereinafter abbreviated as Eg apt) is set within the range of 1.6 to 1.9 eV, good photoconductivity and high photosensitivity can be obtained.

Regarding the second a-SiC layer 4, its element ratio is set as follows.

St+-yCy 0<y<0.5 Preferably 0.05<y<0.4 Optimally 0.1<y<0.3 If the y value is 0.5 or more, the photoconductivity will be significant. As a result, the excitation function of photocarriers decreases, photosensitivity decreases, and the residual potential also increases.

Further, the thickness of the second a-3iC layer 4 is set to 0.05 to 3.0.
If it is set within the range of .mu.m, preferably from 0.1 to 2.5 .mu.m, carrier excitation by short wavelength light can be performed satisfactorily, and the photosensitivity on the short wavelength side can be sufficiently increased.

Furthermore, E opt of the second a-3iC layer 4 is a-3
0. compared to i-layer 3. leV or more, preferably 0.2eV
It is only necessary to set the wavelength to be larger than that, and as a result, the light on the long wavelength side reaches the a-5i layer 3 without being absorbed much.

Each of the above three types of layers 2. 3. 4 are amorphous layers, and their dangling bonds are terminated with hydrogen (H) elements or halogen elements. The content of the element A (H or halogen) in the a-3i layer 3 and the second a-3iC layer 4 is preferably set within the following ranges.

a-Si, -□A! When expressed as a Z value by a-(SIC)+-t A, 0.05 < z < 0.5, preferably 0°l < z < 0.45 In addition, in the photoreceptor having the above layer structure, the a-3i layer 3 and the second a-3iC layer 4 contain 1 to IO00 ppm of elements from group I of the periodic table, preferably 30 to 300 ppm.
When rn is contained, it becomes suitable for a negatively charging photoreceptor, and on the other hand,
500p of Group Va elements of the periodic table in each layer 3 and 4
Prn or less, preferably 1100 pp or less, is suitable for a positive charging photoreceptor, and the photosensitivity of both photoreceptors can be further increased.

The above-mentioned group-II [a group elements include B, A1. Ga, I
Group Va elements include N, P, As, and S.
B and Bi are preferable because each of the B and P elements has excellent covalent bonding properties and can sensitively change semiconductor properties, and also provides excellent charging ability and photosensitivity.

Further, the electrophotographic photoreceptor of the present invention can be made to be of a negatively charged type or a positively charged type by selecting the material for the organic optical semiconductor layer 5. That is, in the case of a negatively charged electrophotographic photoreceptor, an electron pressurizing compound is selected for the organic semiconductor layer 5, while in the case of a positively charged electrophotographic photoreceptor, an electron-withdrawing compound is selected for the organic photoconductor layer 5. It will be done.

The electron-withdrawing compound may have a high molecular weight, such as poly-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymer, etc., and low molecular weight ones include oxadiazole, ogisazole, pyrazoline, triphenylmethane,
These include hydrazone, triarylamine, N-phenylcarbazole, and stilbene.These low-molecular substances include polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate,
It is used after being dispersed in a binder such as urea resin.

Examples of the electron-withdrawing compound include 2,4,7-dolinitrofluorenone.

The substrate 1 may be a metal conductor such as copper, brass, SO3, AI, or Ni, or an insulator such as glass or ceramics whose surface is coated with a conductive thin film.

The substrate 1 may be a flexible conductive sheet in the form of a sheet, belt or web. Aj7S for such a seat
AI on metal sheets such as Ni and stainless steel, or polymer resins such as polyester films, nylon, and polyimide! , Ni metal or 5n02, composite oxide of indium and tin + ITO (Indium T
A transparent conductive material such as (in oxide) or an organic conductive material subjected to conductive treatment such as vapor deposition is used.

Furthermore, a protective layer 6 may be provided as shown in FIG. This layer 6 is an a-8i layer or an a-3iC layer (the element ratio is St, the a value of -aCa is 0≦a<0.95, preferably within the range of 0.5<a<0.95). ), or the aSi layer or the a-3iC layer may contain elements such as nitrogen or oxygen. By providing such a layer as the protective layer 6, wear resistance is improved compared to when the organic optical semiconductor layer is exposed on the surface. Moreover, since the surface of the protective layer 6 is chemically stable and does not undergo deterioration, image fading does not occur during long-term use.

Furthermore, when the first a-3iC layer 2 contains the element B of oxygen and/or nitrogen in the total amount as shown below, the adhesion to the substrate 1 and the resistance from the substrate I are improved compared to the case where the element B is not contained. The stopping power of carrier injection is enhanced.

(Sl+-!Cx)+-bBb 0.0001<b<0.3 Preferably 0.001<b<0.1 Next, a method for manufacturing the electrophotographic photoreceptor of the present invention will be described.

First a-3iC layer 2, a-3i layer 3 and second a-3
To form the iC layer and the protective layer 6 made of a-Si, a-3iC, amorphous 5i-C-N elements, 5i-C-0-N elements, etc., glow discharge decomposition method,
There are thin film forming methods such as ion blasting, reactive sputtering, vacuum evaporation, and CVD.

When forming a SiC layer using glow discharge decomposition method, S
A gas containing an i element and a gas containing a C element are combined, and this mixed gas is subjected to plasma decomposition to form a film.

The second Si element-containing gas is 5IH4,512H1,5I
There are JaSiF4.5iC14, 5iHC1*, etc.
In addition, C element-containing gases include CH4, C, H,, C2H2
, C, H, etc. Among them, C2H2 is preferable because it can provide high-speed film formation.

The organic photosemiconductor layer is formed by a dip coating method or a coating method. According to the latter coating method, a photosensitive material dispersed in a solvent is applied using a coater, and then hot air drying is performed.

Thus, according to the electrophotographic photoreceptor of the present invention, since the carrier excitation layer has a tandem structure in which the a-3iC layer and the a-3i layer are laminated, light incident from the organic photosemiconductor layer 5 side is transmitted to the second layer. The a-3iC layer 4 mainly absorbs light on the short wavelength side, and then the a-3i layer 3 absorbs mainly the light on the long wavelength side that has passed through the layer 4.
Compared to a single excitation layer, the photosensitivity is increased over the entire visible region, and the residual potential is reduced.

In addition, as shown in Figure 3, an a-Si layer and an a-
A known electrophotographic photoreceptor R having a structure in which 3iC layers are laminated
If so, the a-3i layer does not effectively block carrier injection from the substrate, and the injected carriers accelerate the dark decay of the surface potential. The decrease in surface potential up to the point becomes large.

Further, small charging unevenness in the charging section becomes large unevenness in surface potential in the developing section, and therefore, unevenness in image density becomes large, so there is a problem in that it is difficult to obtain good image characteristics. Furthermore, if the dark decay is fast, fluctuations in the surface potential at the developing area tend to increase, making it difficult to stably obtain images of good quality during continuous use. On the other hand, if the electrophotographic photoreceptor T of the present invention is used, the first a-3i layer has a higher dark resistance than the a-3i layer and a larger IJ opt.
Since the C layer 2 is provided and can effectively block carrier injection from the substrate 1 and slow dark decay, the above-mentioned problems can be improved.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) Using a capacitively coupled glow discharge decomposition apparatus for producing electrophotographic photoreceptors, the first a was deposited on an AI substrate under the film forming conditions shown in Table 1.
-3iC layer 2, a-3i layer 3, and second a-3iC layer 4 were laminated in this order.

Next, an organic optical semiconductor layer 5 was formed to a thickness of 15 μm.

In its formation, 2.4.7-dolinitrofluorenone is dissolved in a solvent of 1.4-dioxane, a polyester resin (Refsan-LS2-11) is added,
Ultrasonic dispersion was performed for 40 minutes. The resulting solution was applied using a bar coater and then dried with hot air at 80°C.

[Margin 1 below] (In the positively charged electrophotographic photoreceptor obtained by
Carbon content ratio (X value and y value), H content ratio (binary value), and Eg opt of each layer were measured by X-ray microanalysis and infrared absorption method, and (αhν) of the transmitted light spectrum measured by visible light spectrometer. When determined by plotting 1'' versus hv, the results shown in Table 1 were obtained.

Further, in producing the electrophotographic photoreceptor of this example, the first a-SiC layer and the a-Si layer were not formed, and the second a-SiC layer and the a-SiC layer were not formed.
Comparative Example A was obtained by forming only the iC layer and forming the rest in the same manner as in this example.

Furthermore, in producing the electrophotographic photoreceptor of this example, the first a-3iC layer was not formed, and the a-3i layer and the second a-3iC layer were formed.
Comparative Example B was prepared by forming only the 3iC layer and forming the rest in the same manner as in this example.

When the spectral sensitivities of the electrophotographic photoreceptor of the present invention and Comparative Example A were measured, the results shown in FIG. 4 were obtained. In the figure, the horizontal axis is the wavelength, and the vertical axis is the photosensitivity, and the change in surface potential in response to exposure with a light intensity of 0.3 μW/co+' at each wavelength is measured using a surface electrometer with a light transmission probe. It was determined by the reciprocal of the exposure amount required to halve the surface potential.

As is clear from the results shown in FIG.
It can be seen that the photosensitivity is higher on the long wavelength side of 600 nm or more compared to the above.

In addition, the photosensitivity of Comparative Example B was similar to that of this example, but on the other hand, when we followed the progress of the surface potential in the dark after charging, we found that the photosensitivity of this example was as shown in Figure 5. It can be seen that the dark decay of the surface potential is faster than that of the body, the charge is low, and the potential unevenness is large.

Furthermore, when the photoreceptor of this example and Comparative Example B were left in an environment of 35°C and 95% RH for 24 hours, no change was observed in the photoreceptor of this example, whereas in Comparative Example B, the substrate It was also confirmed that the film peeled off from the a-3i layer, and there was a problem in the adhesion of the film.

(Example 2) In producing an electrophotographic photoreceptor similar to (Example 1),
By changing the film forming conditions and changing the composition and thickness of each of the first a-SiC layer, a-3i layer, and second a-3iC layer, 10 types of photosensitive materials A-J shown in Table 2 were prepared. The dark decay, photosensitivity, and residual potential of each photoreceptor were evaluated. When the binary values of each layer in the table were measured by the IR method, all values were within the range of 0.05<z<0.5.

In addition, regarding dark decay, photosensitivity, and residual potential in the table, ◎ marks are cases where the best results were obtained, O marks are cases where somewhat better results were obtained, and △ marks are cases where slightly better results were obtained. This is a case where an inferior result is obtained.

[Margin below]

As is clear from the results shown in Table 2, it can be seen that photoreceptors D to G are excellent in all of dark decay, photosensitivity, and residual potential.

(Example 3) Using a capacitively coupled glow discharge decomposition apparatus for producing an electrophotographic photoreceptor, the first a
-3iC layer 2, a-3i layer 3 and second aSiCSiC
Laminated layer by layer.

Next, the organic optical semiconductor layer 5 was formed to a thickness of 15 μm in the same manner as in (Example 1).
It was formed with.

[Margin below]

In the positively charged electrophotographic photoreceptor thus obtained,
Carbon content ratio (X value and y value), H content ratio (binary value), and Eg apt of each layer are measured by X-ray microanalysis and infrared absorption method, and (αhν) of the transmitted light spectrum measured by visible light spectrometer. When determined by plotting 1'' versus hv, the results shown in Table 3 were obtained.

Further, in producing the electrophotographic photoreceptor of this example, the first a-SiC layer and the a-3i layer were not formed, and the second a-SiC layer and the a-3i layer were not formed.
Comparative Example C was obtained by forming only the C layer and forming the rest in the same manner as in this example.

Furthermore, in producing the electrophotographic photoreceptor of this example, NO gas was not introduced during the formation of the first a-3iC layer;
The Si layer and the second a-3iC layer were formed in the same manner, and the others were formed in the same manner as a comparative example.

When the spectral sensitivities of the electrophotographic photoreceptor of the present invention and Comparative Example C were measured, the same results as shown in FIG. 4 were obtained.

In addition, the photosensitivity of the comparative example was similar to that of this example, but on the other hand, when we followed the progress of the surface potential in the dark after charging, the surface potential was higher than that of the photoreceptor of this example. It can be seen that the dark decay is about 20% faster, the charging is low, and the potential unevenness is large.

(Example 4) In producing an electrophotographic photoreceptor similar to (Example 3),
By changing the NO gas and changing the total content of 0 and N elements in the first a-3iC layer, eight types of -R photoreceptors were prepared as shown in Table 4, and the dark of each photoreceptor was Attenuation, photosensitivity and residual potential were evaluated. When the y value of each layer in the table was measured using the IR method, all of them were 0.05<z<0
．． It was within the range of 5.

Table 4 [Margin below] *marks are outside the scope of the present invention.

As is clear from the results shown in Table 4, it can be seen that photoreceptors L to Q are excellent in all of dark decay, photosensitivity, and residual potential.

〔Effect of the invention〕

As described above, according to the present invention, high photosensitivity can be obtained over the entire visible light range, the residual potential is small, and there is little density unevenness in the image, which makes it possible to stably produce good images. A high-performance and highly reliable electrophotographic photoreceptor could be provided.

Furthermore, in the electrophotographic photoreceptor of the present invention, the film has excellent adhesion to the substrate, and reliability is also improved in this respect.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the layer structure of the electrophotographic photoreceptor of the present invention, FIG. 3 is a diagram illustrating attenuation of surface potential, and FIG. 4 is a diagram illustrating photosensitivity with respect to wavelength. FIG. 5 is a diagram showing the attenuation of the surface potential in the example. 2: First amorphous silicon carbide layer 3: Amorphous silicon layer 4: First amorphous silicon carbide layer 5: Organic optical semiconductor layer 6: Protective layer

Claims (2)

[Claims] (1) On the substrate, the atomic composition ratio is Si_1_-_xC_x(
7) Form a first amorphous silicon carbide layer having an x value in the range of 0.2<x<0.5, and on the first amorphous silicon carbide layer, an amorphous silicon layer with an atomic composition ratio of Si_1_- An electrophotographic photoreceptor characterized in that a second amorphous silicon carbide layer and an organic optical semiconductor layer are sequentially laminated with a y value of _yC_y in the range of 0<y<0.5. (2) The electrophotographic photoreceptor according to claim 1, wherein the first amorphous silicon carbide layer contains 0.01 to 30 at % of oxygen and/or nitrogen.