JPH01107268A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve durability of characteristics against the change of environment and photosensitive characteristics of an electrophotographic sensitive body by reducing the concn. of Si atoms on an uppermost surface of an upper barrier layer which is susceptible to the influence of water, and at the depth near the uppermost surface to zero concn. or to an allowably low concn. CONSTITUTION:Concentrations of Si atoms and H atoms forming an upper barrier layer 4 are held at an almost same concentration as the concn. of a charge maintaining layer 3 at an interface between the charge maintaining layer 3, and the concn. of C atoms is held at <=0.1%. Also, the Si atoms are distributed to decrease toward the uppermost surface, and H atoms and C atoms are distributed to increase toward the same direction, wherein the atomic concn. of Si atoms is adjusted to <=0.1% at the uppermost surface. Thus, the decrease of charged potential due to discontinuity of concn. at the interface between the charge maintaining layer 3 and the upper barrier layer 4, and the increase of residual potential are kept at small values. By this constitution, the characteristics of an electrophotographic sensitive body against the change of environment, wherein the electrophotographic sensitive body is to be used, and the photosensitive characteristic thereof are improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an electrophotographic photoreceptor mainly made of amorphous silicon;
In particular, it relates to improvements in its use environment characteristics.

(Prior Art) Conventional electrophotographic photoreceptors mainly made of amorphous silicon, such as positively charged photoreceptors, are formed by sequentially laminating a conductive substrate (1) and a conductive substrate (1) on this as shown in FIG. lower barrier layer (
2), a potential holding layer (3), and an upper barrier layer (4), and each layer except for the conductive substrate (1) is generally formed as follows. That is, the lower barrier layer (2)
As shown in the figure, amorphous Si and H have uniform atomic concentration distribution in the thickness direction.

It is made of B, O, and N to have a strong P-type conductivity with a thickness of approximately 50 to 10 μm, and electrons injected from the conductive substrate (1) are transferred to the potential holding layer (3) and further to its potential holding layer (3). Preventing it from reaching the upper barrier layer (4). The potential holding layer (3) has a dark resistance ρ mainly composed of amorphous St and HlB with uniform atomic concentration distribution in the thickness direction, as shown in FIG. is 1011 to 1016Ω・Ω (1 when irradiated with light)
It has a photoconductivity of 04 to 1010 Ω·cm) and is made to be able to maintain a potential of about 500 to 1500 V in the dark. In addition, the upper barrier layer (4) has a thickness of 500 to 5μ
m thickness, and is formed mainly of amorphous St, C, and H, each having a uniform atomic concentration distribution in the thickness direction as shown in FIG.
) is made to have a high energy barrier to the genuine bill to prevent it from being injected.

(Prior Art and Its Problems) However, in the conventional photoreceptor as described above, the higher the temperature in the environment in which it is used, the worse the reproducibility of the original image becomes and the sharpness becomes less clear. For example, according to the results of a copy cycle test on a product having photosensitive characteristics as shown in Table 1 below, normal images can be obtained even after a 500,000 copy cycle test at a room temperature of 25° C. and a relative humidity of 50%. However, at a room temperature of 25° C. and a relative humidity of 95%, the reproducibility of the original image disappears at all after the 500,000 copy cycle test, resulting in a so-called test failure.

Moreover, in the conventional photoreceptor, the concentrations of Si and H forming the upper barrier layer (4) and the potential holding layer (3) are discontinuous at the interface between the two, and in particular, the concentration of C atoms in the potential holding layer (3) is discontinuous.
In (3), the concentration is less than 5% (not shown in the figure because it is a small amount), but on the upper barrier layer side, the concentration rapidly increases to 30 to 95% within a layer thickness of about 0 to 100 layers from the interface. changes. This indicates that there is a large difference in the optical energy gap between the upper barrier layer (4) and the potential holding layer (3), resulting in an interface structure with a large lattice mismatch in the microscopic crystal structure. This indicates that the charging potential decreases due to the increase in the interface state based on this, and the residual potential increases, deteriorating the photosensitive characteristics, indicating that there is room for improvement in the photosensitive characteristics.

Table 1 (Object of the Invention) The present invention provides an electrophotographic product mainly made of amorphous silicon that has improved photosensitive properties such as an increase in charging potential and a decrease in residual potential, as well as improved usage environment characteristics. This was done for the purpose of providing photoreceptors. The present invention will be described in detail below using the drawings.

(Means of the Invention for Solving the Problems) The inventors of the present invention have conducted various studies on the development of the above-mentioned flow test, and have found that the cause thereof lies in the following points.

That is, in the conventional photoreceptor, as described above with reference to FIG. 2, the concentration distribution of Si atoms in the upper barrier layer (4) is uniform in the thickness direction, and Si atoms are exposed at the outermost surface.

Therefore, the outermost surface of St, which is exposed to the positive corona discharge for charging performed each time copying, has high hygroscopicity, and is also susceptible to toner contact, paper contact, and other mechanical and chemical influences.

It is transformed into a SiOx surface which is inferior to physical stimulation. Therefore, as mentioned above, under high humidity conditions such as relative humidity of 95%, the moisture adsorbed on the outermost surface and ionic components such as NOx in the atmosphere will normally cause the
The lateral resistance is reduced to below 10''Ω·cm.

For this reason, it is clear that the electrostatic charge latent image of the original image after being positively charged by positive corona discharge will be spread laterally through the low resistance region on the outermost surface, resulting in counterflow and loss of reproducibility of the original image. was made into

Based on the above study results, the present invention aims to reduce the concentration of Si atoms at the outermost surface of the upper barrier layer, which is easily affected by moisture, and at the depth in the vicinity thereof to zero or to a level that does not cause any problem, in order to improve the usage environment characteristics. The present invention was conceived based on the idea that it would be better to do so, and the present invention has a structure as shown in the cross-sectional structural diagram shown in FIG. 3 (the same reference numerals as in FIGS. It is characterized by:

That is, first, the concentration of Si atoms in the upper barrier layer (4) is gradually decreased from the interface with the potential holding layer (3) toward the surface, to a low concentration of 0.1% or less at the outermost surface, for example. At the same time, the concentration of C atoms is, for example, 5% or less at the interface with the potential holding layer (3), and 95 to 3% at the outermost surface.
The distribution is such that the concentration increases toward the surface so that it becomes 0%. Moreover, in addition to this, the unbonded unpaired electrons of the 5i-C and C-C bonds (
In order to prevent an increase in the number of trap centers due to dangling bonds (DANGLING BOND), the concentration of H atoms is, for example, 500 to 1 from the outermost surface of the upper barrier layer (4).
Electricity is generated by bonding H atoms to dangling bonds by setting the concentration of H at the outermost surface to, for example, 15 to 50%, so that the concentration is uniform at the highest concentration within a thickness of 0 μm, or the distribution continues to increase toward the outermost surface. inactivate it.

Then, by increasing the C/Si ratio while inactivating the dangling bonds with H atoms, the optical energy gap is increased, and thereby the Si atom concentration becomes 0.1% or less as described above. The outermost surface of the upper barrier N(4) is essentially an amorphous carbon film, that is, the optical energy gear Bg is Eg≧2, OeV, and the dark resistance ρ. is ρ. ≧10′3Ω·l. Then, due to corona discharge, S becomes SiOx, which easily absorbs moisture.
Even in a copy cycle test under high humidity conditions such as 95% relative humidity with no i present on the surface, the surface lateral resistance ρD was ρn≧1011Ω・c
Degraded to below m (conventional structure deteriorated to below 1Ω in 10 days)
This is to prevent the occurrence of a galvanic flow. In addition, by making the outermost surface an amorphous carbon film that is more resistant to mechanical, chemical, and physical stimuli than St, it is possible to form an outermost surface that is resistant to stimuli such as toner contact 9 paper contact. It is.

Secondly, the decreasing distribution of the Si atom concentration in the upper barrier layer (4) and the increasing distribution of the H atom concentration in the potential holding layer (3)
The point is that the concentration is gradually and continuously started from the same concentration as the concentration at the interface. As a result, the interface state density is lowered to reduce the occurrence of distortion in the film, and the potential holding layer (3) and upper barrier layer (4) are reduced as in the conventional photoreceptor described above with reference to FIG. The reduction in charging potential due to discontinuity of concentration at the interface and the increase in residual potential are suppressed to a minimum, thereby improving the use environment characteristics and the photosensitivity characteristics.

Of course, it is also possible to make the entire upper barrier M (4) an amorphous carbon film, but in this case, the potential holding layer (3) at the interface
), which causes a large discontinuity with the Si atom concentration.
This is not preferable because it causes deterioration of photosensitive characteristics such as a decrease in charging potential. Furthermore, even when a portion including the outermost surface is formed into an amorphous carbon film, if amorphous carbonization is performed at a deep position from the outermost surface as shown by the dotted line in Fig. 3, the Si atomic concentration will decrease. Since the change becomes rapid and results in a drop in the charging potential, for example, the thickness of the upper barrier layer (4) should be set to 500 to 5 μm.
m, the formation of an amorphous carbon film is from 100 to 50 m from the outermost surface.
It is recommended that the number be within the range of 00 people.

Next, examples of the present invention will be described.

(Example) Table 2 shows the characteristics of a photoreceptor produced using the reaction apparatus according to the high frequency glow discharge CVD method shown in FIG. Approximately 1O is placed in the reaction chamber (5) by the motor (6).
A substrate holder (8) rotated at r, p, m and capable of heating the substrate (1) to 300"C ± 2°C by means of an internal heating device (7) has an outer diameter of 100 vm and a length of 300".
A cylindrical conductive substrate (1) made of aluminum and having a diameter of 1 mm is attached.

A 13.5 MHz high frequency power source (9) ((9a
) is an oscillator and (9b) is a matching adjuster) is connected to a high pressure cylinder (11a011b) (llb
) (llc) (lid), and the mass flow controller Q21 Niyosu flow rate is precisely adjusted 5
Necessary gases such as iHa, Ih+ BzHb/l (z + CJz) are supplied using the pressure adjustment valve (13a), mechanical booster pump (13b), and rotary pump (13
c) into a reaction chamber (5) which is evacuated and whose gas pressure is constantly regulated. Then, under the conditions such as flow rate, pressure, high frequency output, deposition time, etc. shown in Table 3 and in the same manner as before, Si, H, B, 0°N with a thickness of 3 pm was deposited on the conductive substrate (1) as shown in Fig. 3. A lower barrier layer consisting of (
After forming 2), 20 μm thick Si,
A potential holding layer (3) made of H and B is formed. Finally, Si, H, and C atoms are deposited on top of it in a manner that matches the atomic composition ratio of the potential holding layer (3), and then the Si atoms decrease in the thickness direction.

An upper barrier layer (4) having a thickness of 3,000 layers is formed by distributing the concentration of H and C atoms in an increasing direction.

Table 3: As is clear from a comparison of Tables 1 and 2, which show the photosensitive characteristics of the conventional photoreceptor and those of the present invention, the photoreceptor according to the present invention has a charging potential of approximately 40% higher than that of the conventional photoreceptor. rise,
The residual voltage was also reduced by about 50%, indicating that excellent photosensitivity characteristics could be obtained. Moreover, the room temperature is 25°
According to the results of a 500,000-sheet copy cycle test at 95% relative humidity, the present invention reproduces the original image well and obtains clear images with high resolution, whereas the conventional method results in galvanometric flow. was confirmed.

(Effects of the Invention) As is clear from the above, according to the present invention, the upper barrier layer, which plays a very important role in electrophotographic photoreceptors, has the required characteristics, namely: (1) Formation at the interface with the potential holding layer; The interface states caused by the difference in lattice constants should be as small as possible, and the interface trap density should be low.

■ The upper barrier layer should be a high-resistance material with low surface charge conductivity (ρゎ≧IQIIΩ·cm).

■ As a window material for the photoreceptor, it must have a large optical energy gap that does not absorb long wavelength light of 800 nm.

■ High lateral resistance to surface charges (ρ).

≧10I3Ω・cm), it is possible to maintain high lateral resistance even under the operating environment conditions.

■ It should have a long life with little deterioration in photosensitivity against mechanical, chemical, and physical stimuli such as corona discharge, toner contact, and paper contact.9 Strong light irradiation.

It is possible to provide an electrophotographic photoreceptor having an upper barrier layer that can substantially satisfy the above requirements, and therefore an electrophotographic photoreceptor mainly made of amorphous silicon that has excellent usage environment characteristics and photosensitive characteristics.

Although the above description has been made using a positively charged photoreceptor as an example, the present invention can also be applied to a negatively charged photoreceptor to obtain similar effects. Further, in the embodiment, a high frequency glow discharge CVD method was used, but various conventionally known manufacturing methods such as a sputtering method, a microwave CVD method, a direct current discharge CVO method, etc. can be used.

[Brief explanation of the drawing]

1 and 2 are structural cross-sectional views of a conventional photoreceptor, FIG. 3 is a structural cross-sectional view of the photoreceptor of the present invention, and FIG. 4 is an example of a reaction apparatus used for manufacturing the photoreceptor. (1)... Conductive substrate, (2)... Lower barrier layer, (
3)... Potential holding layer, (4)... Upper barrier layer, (5
)...Reaction chamber, (6)...Motor, (7)...
... Heating device, (8) ... Substrate holder, (9) ...
High frequency power supply, (9a)... Oscillator, (9b)... Matching adjuster, Q(1)... Counter electrode, (lla
) (llb) (llc) (lid)...High pressure gas cylinder, 02)...Mass flow controller, (1
3a)...Pressure adjustment valve, (13b)...Mechanical booster pump, (13c)...Rotary pump. Patent applicant: 1 person other than Shindengen Kogyo Co., Ltd.

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor mainly made of amorphous silicon, in which a lower barrier layer, a potential holding layer, and an upper barrier layer are sequentially laminated on a conductive substrate, Si and H atoms forming the upper barrier layer At the interface with the potential holding layer, the concentration of C atoms is set to be approximately the same concentration as that of the potential holding layer, and the concentration of C atoms is set to 0.1% or less, and the distribution of Si atoms decreases toward the outermost surface, and the distribution of H and C atoms increases. , and Si atoms are 0.1% on the outermost surface.
A photoreceptor for electrophotography, characterized in that the atomic concentration is as follows.