JP2668241B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member comprising an amorphous silicon carbide photoconductive layer and an organic optical semiconductor layer.

[Prior art and its problems]

The photoconductive material of the electrophotographic photosensitive member, Se, Se-Te, As 2 S
There are inorganic materials such as e ₃ , ZnO, CdS, and amorphous silicon, and various organic materials. Among them, Se was first commercialized, and ZnO, CdS, and amorphous silicon were also commercialized. On the other hand, as an organic material, PVK-TNF was first put to practical use, and thereafter, a function-separated type photoreceptor in which the functions of generating and transporting charge were shared by different organic materials was proposed. As a result, the development of organic materials has dramatically advanced.

On the other hand, an electrophotographic photosensitive member in which an organic photoconductive layer is laminated on the inorganic photoconductive layer has also been proposed.

For example, there is a laminated photoconductor of a Se layer and an organic optical semiconductor layer,
Although this photoreceptor has already been put to practical use, this photoreceptor has the disadvantage that Se itself is harmful and that the sensitivity on the long wavelength side is poor.

Therefore, Japanese Unexamined Patent Publication No. Sho 56-14241 proposes a laminated photoreceptor comprising an amorphous silicon carbide photoconductive layer and an organic photo-semiconductor layer. Pollution and high light sensitivity were obtained.

However, when the inventors of the present invention produced such an electrophotographic photoreceptor and measured the photosensitivity, residual potential and surface potential of the electrophotographic photoreceptor, none of them had satisfactory characteristics, and further improvement was obtained. It turned out to require.

Accordingly, the present invention has been completed in view of the above,
It is an object of the present invention to provide an electrophotographic photosensitive member which has improved characteristics such as photosensitivity, residual potential and surface potential.

[Means for solving the problem]

According to the present invention, in an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer (hereinafter, amorphous silicon carbide is abbreviated as a-SiC) and an organic photo semiconductor layer are sequentially laminated on a conductive substrate, the a-SiC light is used. The conductive layer has a layer structure in which a first layer region, a second layer region, and a third layer region are sequentially formed, and the first layer region and the third layer region are made of carbon as compared with the second layer region. And the element ratio is expressed as the x value of the composition ratio Si _1-x C _x , 0.2
<X <0.5, the thickness of the first layer region is 0.01 to 1 μm, and the thickness of the second layer region is 0.05 to 5 μm.
m, wherein the thickness of the third layer region is set in the range of 10 to 2000 °.

 Hereinafter, the present invention will be described in detail.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention. According to FIG. 1, an a-SiC photoconductive layer (2) and an organic optical semiconductor layer (3) are provided on a conductive substrate (1). Are sequentially laminated. The a-SiC photoconductive layer (2) has a function of generating charges, and the other organic optical semiconductor layer (3) has a function of transferring charges.

The present invention sequentially forms the first layer region (2a), the second layer region (2b) and the third layer region (2c) inside the a-SiC photoconductive layer (2) as described above. , Which makes the light sensitivity,
The feature is that the residual potential and the surface potential are improved.

Third layer region containing a relatively large amount of carbon (2c)
, The dark conductivity difference between the a-SiC photoconductive layer (2) and the organic photo-semiconductor layer (3) is significantly reduced, and at the interface between both layers (2) and (3). Carriers are no longer trapped.

That is, the dark conductivity of the a-SiC photoconductive layer (2) is about 10 ^-11 to
10 ⁻¹³ (Ω · cm) ⁻¹ , and the dark conductivity of the other organic optical semiconductor layer (3) is about 10 ⁻¹⁴ to 10 ⁻¹⁵ (Ω · cm) ^−1. Carriers generated in the photoconductive layer (2) are caused by a large difference in dark conductivity, and the organic photoconductive layer (3)
It does not flow smoothly. Accordingly, the present inventors formed a third layer region (2c) containing a high content of C element,
The dark conductivity of the layer area (2c) becomes small, and both layers (2)
It was found that the difference in dark conductivity can be reduced at the interface of (3).

Such a third layer region (2c) is represented by the C element content ratio and the thickness as described below.

The C element content ratio may be set in the range of 0.2 <x <0.5, preferably 0.3 <x <0.5, as the x value of Si _1-x C _x ,
If it is 0.2 or less, the difference in dark conductivity between the two layers (2) and (3) cannot be reduced as required, and thus the respective characteristics of photosensitivity and residual potential cannot be improved, and the x value But
When it is 0.5 or more, carriers are easily trapped in the a-SiC photoconductive layer, and the photosensitivity characteristic is deteriorated.

In addition, the thickness should be set in the range of 10 to 2000Å, preferably 500 to 1000Å.If it is less than 10Å, the characteristics of photosensitivity and residual potential cannot be improved, and if it exceeds 2000Å, it remains. The electric potential tends to increase.

The first layer region (2a) also contains a relatively large amount of carbon, which reduces the dark conductivity, so that carriers of the substrate (1) flow into the a-SiC photoconductive layer (2). , Thereby increasing the surface potential.

Such a first layer region (2a) is represented by a C element content ratio and a thickness as follows.

The C element content ratio may be set in the range of 0.2 <x <0.5, preferably 0.3 <x <0.5, as the x value of Si _1-x C _x ,
When the value is 0.2 or less, it is impossible to increase the charging ability by preventing injection of carriers from the substrate. On the other hand, when the value x is 0.5 or more, the residual potential becomes large.

The thickness is 0.01 to 1 μm, preferably 0.05 to 0.5 μm
When the thickness is less than 0.01 μm, the charging ability cannot be increased, and when the thickness exceeds 1 μm, the residual potential increases.

The second layer region (2b) is a main photocarrier generation layer of the a-SiC photoconductive layer (2), and its element ratio may be set within the following range.

The second layer region (2b) is composed of amorphous Si element and C
Element, and further, a hydrogen (H) element for terminating the dangling bond of both elements and a halogen element (this terminating element is hereinafter abbreviated as A element), and the composition formula of these elements Is expressed as [Si _1-x C _x ] _1-y A _y , the x value is 0.05 <x <0.5, preferably 0.1 <x <
Within the range of 0.4, y value is 0.1 <y <0.5, preferably 0.2 <y
<0.5, and optimally, 0.25 <y <0.45. When the x value or the y value is set within the above range, excellent photoconductive properties and high photosensitivity properties can be obtained.

The thickness of the second layer region (2b) is 0.05 to 5 μm, preferably
It may be set within the range of 0.1 to 3 μm, and within this range, high photosensitivity is selected and the residual potential becomes low.

Such first layer area (2a), second layer area (2b)
Also, the C element content of each of the third layer regions (2c) may be changed in the layer thickness direction. For example, FIGS.
There is an example shown in FIG. 10, in which the horizontal axis is the layer thickness direction, a is the interface between the first layer region (2a) and the substrate (1), and b is the first layer region (2a). And the second layer region (2b), c is the interface between the second layer region (2b) and the third layer region (2c), d is the third layer region (2c) and the organic optical semiconductor layer ( 3) represents the interface, and the vertical axis represents the C element content.

When the C element content is changed in the layer thickness direction inside the first layer region (2a), the second layer region (2b) or the third layer region (2c), the C element content The ratio (x value) corresponds to the average content ratio of C element per the entire layer regions (2a) (2b) (2c).

The substrate (1) includes a metal conductor such as copper, brass, SUS, or Al, or an insulator such as glass or ceramics coated with a conductor thin film. -It is advantageous in terms of adhesion to the SiC layer.

Further, the electrophotographic photoreceptor of the present invention can be set to a negative charge type or a positive charge type by selecting the material of the organic photo semiconductor layer (3). That is, in the case of a negatively charged electrophotographic photoreceptor, an electron donating compound is selected for the organic photoconductor layer (3), while in the case of a positively charged electrophotographic photoreceptor, an electron is supplied to the organic photoconductor layer (3). An inhalable compound is selected.

The electron donating compound may be a high molecular weight compound such as poly-
There are N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymer, and the like, and low molecular weight compounds such as oxadiazole, oxazole, pyrazoline, triphenylmethane,
There are hydrazone, triarylamine, N-phenylcarbazole, stilbene, etc., and these low molecular substances are polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate, polyvinyl acetate,
It is used by being dispersed in a binder such as urea resin.

Electron-withdrawing compounds include 2.4.7-trinitrofluorene.

Thus, according to the electrophotographic photosensitive member of the present invention, the photosensitivity and the surface potential can be increased and the residual potential can be reduced by forming the C element high content layer region.

Further, in the electrophotographic photoreceptor of the present invention, a-SiC
A group IIIa element of the periodic table (hereinafter referred to as IIIa)
Group element) is contained in an amount of 1 to 500 ppm, preferably 2 to 200 ppm.

The IIIa group element content is represented by an average value of the entire a-SiC layer, and the average content is 1 ppm.
In the following cases, the dark conductivity tends to increase, and a decrease in photosensitivity is observed.On the other hand, when the concentration is 500 ppm or more, the dark conductivity increases significantly, and the photoconductivity with respect to the dark conductivity further increases. The ratio becomes small, and it becomes difficult to obtain the desired photosensitivity.

When the group IIIa element is contained in the a-SiC photoconductive layer (2), its doping distribution may be uniform or non-uniform in the thickness direction of the layer. When the layer (2) is non-uniformly doped, a layer region containing no group IIIa element may be present in a part of the layer (2). In that case, a group-IIIa element-containing a-SiC layer region and group IIIa element may be included. The average content of the Group IIIa element in the entire a-SiC layer including both a-SiC layer regions containing no element must be 1 to 500 ppm.

This IIIa group element includes B, Al, Ga, In, etc., but B has excellent covalent properties and can change semiconductor characteristics sensitively, and furthermore, excellent charging ability and photosensitivity are obtained. This is desirable.

 Next, a method for producing the electrophotographic photoreceptor of the present invention will be described.

For forming the a-SiC layer, there are a thin film forming method such as a glow discharge decomposition method, an ion plating method, a reactive sputtering method, a vacuum evaporation method, and a CVD method.

When glow discharge decomposition is used, the gas containing Si element and C
Element-containing gases are combined, and this mixed gas is plasma-decomposed to form a film. The Si element-containing gas includes SiH ₄ , Si ₂ H ₆ , S
i ₃ H ₈ , SiF ₄ , SiCl ₄ , SiHCl _3, etc., and C element-containing gas includes CH ₄ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H _8, etc., among them C ₂ H ₂ is desirable in that high-speed film forming properties can be obtained.

The glow discharge decomposition apparatus used in this embodiment will be described with reference to FIG.

In the figure, the first tank (4), the second tank (5), the third tank (6), and the fourth tank (7) are respectively SiH ₄ , C ₂ H ₂ ,
B ₂ H ₆ , (B ₂ H ₆ is diluted with hydrogen at a concentration of 40 ppm) and H ₂
Are sealed, and these gases respectively correspond to the first control valve (8), the second control valve (9), the third control valve (10) and the fourth control valve (10).
Released when the regulating valve (11) is opened. The flow rates of the released gas are respectively mass flow controllers (12) (13) (1
4) Controlled by (15), each gas is mixed and sent to the main pipe (16). Incidentally, (17) and (18) are stop valves.

The gas flowing through the main tube (16) flows into the reaction tube (19), the capacitive coupling type discharge electrode (20) is installed inside the reaction tube (19), and the tubular film formation substrate is provided. (twenty one)
Is placed on the substrate support (22), and the substrate support (22)
Is rotationally driven by a motor (23), and the substrate (21) is rotated accordingly. The electrode (20) has a power of 50W ~ 3k
W, high frequency power of frequency 1-50MHz is applied, and
The substrate (21) is heated to a temperature of about 200 to 400 ° C, preferably about 200 to 350 ° C by a suitable heating means. Further, the reaction tube (19) is connected to the rotary pump (24) and the diffusion pump (25) so that the vacuum state (gas pressure during discharge 0.1 to 2.0 Torr) required during film formation by glow discharge can be maintained. Can be set.

When the a-SiC layer is formed on the substrate (21) using the glow discharge decomposition apparatus having such a configuration, the first control valve (8), the second control valve (9), and the third control valve (10) are used. ) And fourth
Open the control valve (11) to release each gas of SiH ₄ , C ₂ H ₂ , B ₂ H ₆ , H ₂ , and determine the release amount by mass flow controller (12)
(13) Controlled by (14) and (15), each gas is mixed and flows into the reaction tube (19) via the main pipe (16). When the vacuum state inside the reaction tube, the substrate temperature, and the high-frequency power for electrode application are set to predetermined conditions, glow discharge occurs, and the a-SiC film containing B element is rapidly deposited on the substrate as the gas is decomposed. To form.

After the a-SiC layer is formed by the thin film forming method as described above, the organic photosemiconductor layer is then formed.

The organic photosemiconductor layer is formed by a dip coating method or a coating method. The former is immersed in a coating solution in which the photosensitive material is dispersed in a solvent, then pulled up at a constant speed, and then naturally dried and heat-aged (about 150 ° C, about 1 hour).
According to the latter coating method, a photosensitive material dispersed in a solvent is applied using a coater (coating machine), and then hot-air drying is performed.

〔Example〕

 Next, examples of the present invention will be described.

(Example 1) using a glow discharge decomposition apparatus of FIG. 2, a SiH ₄ gas 20
At a flow rate of 0 sccm, H ₂ gas was flowed at a flow rate of 270 sccm and C ₂
The flow rate of the H ₂ gas was changed, the gas pressure was set to 0.6 Torr, the high frequency power was set to 150 W, the substrate temperature was set to 250 ° C., and an a-SiC film (thickness: about 1 μm) was formed by glow discharge.

Thus, the carbon content ratio of the a-SiC film was changed, and the amount of carbon in the film was measured by the XMA method.
When the photoconductivity and the dark conductivity were measured, the results as shown in FIG. 3 were obtained.

In FIG. 3, the horizontal axis represents the carbon content ratio, that is, the x value of Si _1-x C _x , the vertical axis represents the conductivity, and the circles represent the emission wavelength of 50.
It is a plot of the photoconductivity with respect to light of 0 nm (light quantity 50 μW / cm ² ).
Are the respective characteristic curves.

Further, the hydrogen content of each of the a-SiC films was determined by infrared absorption measurement, and the results shown in FIG. 4 were obtained.

In Figure 4, the horizontal axis is the x value of the Si _1-x C _x, vertical axis hydrogen content, is namely [Si _1-x C _x] y value of _1-y H _y, ○ mark Si
It is a plot of the amount of hydrogen bonded to the atom, the mark ● is a plot of the amount of hydrogen bonded to the C atom, and c and d are the respective characteristic curves.

As is clear from FIG. 4, it can be seen that the a-SiC films of this example all have y values in the range of 0.3 to 0.4.

As is clear from FIG. 3, the carbon content ratio x
It can be seen that when the ratio is within the range of 0.05 <x <0.5, the ratio of photoconductivity and dark conductivity is remarkably increased, and excellent photosensitivity is obtained.

(Example 2) Next, in this example, SiH ₄ gas was used at a flow rate of 200 sccm to remove C
₂ H ₂ gas is introduced at a flow rate of 20 sccm, H ₂ gas is introduced at a flow rate of 0 to 1000 sccm, and high frequency power is 50 to 300 W and gas pressure is increased.
The pressure was set to 0.3 to 1.2 Torr, and an a-SiC film (thickness: about 1 μm) was formed by glow discharge.

Thus, the carbon content ratio x was set to 0.3, various a-SiC films were formed in which the hydrogen content y was changed, and the photoconductivity and dark conductivity of each film were measured.
The result as shown in FIG. 5 was obtained.

In FIG. 5, the horizontal axis is the hydrogen content, measured [Si _1-x C _x ] _1-y H _y
, The vertical axis represents the conductivity, and the mark 印 represents the emission wavelength.
It is a plot of the photoconductivity for light of 550 nm (light quantity 50 μW / cm ² ), the mark ● is a plot of dark conductivity, and e,
f is each characteristic curve.

As is clear from FIG. 5, when the y value exceeds 0.2,
It can be seen that a high photoconductivity as well as a low dark conductivity is obtained.

(Example 3) Next, the present inventors conducted a-Si under the film forming conditions shown in Table 1.
C photoconductive layer (2) was formed.

An organic photo-semiconductor layer (thickness: about 15 μm) in which a hydrazone compound was dispersed in polycarbonate was formed on the thus-formed a-SiC photoconductive layer to obtain an electrophotographic photoreceptor.

When the characteristics of the electrophotographic photosensitive member thus obtained were evaluated by an electrophotographic characteristics measuring device, excellent photosensitivity was obtained, the surface potential was increased, and a low residual potential was obtained.

(Example 4) In forming the first layer region and the third layer region of the electrophotographic photosensitive member of (Example 3), the inventors of the present invention used SiH ₄ gas, C ₂ H ₂ gas and H ₂ gas. Change each flow rate,
Moreover, the film forming time is changed, whereby the x value and thickness of Si _1-x C _{x in} each layer region are changed, and the second layer region is the same as the electrophotographic photoreceptor of (Example 3). , And thus 13 types of electrophotographic photoconductors (photoconductor A to
M) was produced.

When the photosensitivity, residual potential and surface potential of these photoconductors were measured, the results shown in Table 2 were obtained.

In the table, the light sensitivity is classified into three stages of ◎, ○ and Δ by relative evaluation, ◎ indicates the case where the best light sensitivity was obtained, and ○ indicates that the light sensitivity was somewhat superior. Is obtained, and the mark Δ is a case where the photosensitivity is slightly inferior to the others.

The residual potential is also evaluated in three levels relative to each other. The ◎ mark is when the residual potential becomes small, the ○ mark is when the decrease in residual potential is recognized to some extent, and the Δ mark is compared with other cases. This is the case where no reduction in the residual potential was observed.

In addition, the surface potential is also relatively evaluated in three stages, and ◎ indicates that the surface potential is the largest, and
The mark indicates that the surface potential was somewhat higher, and the mark indicates that the surface voltage was inferior to the others.

As is clear from Table 2, photoconductors D to G and photoconductor
I, J, and M were found to have excellent photosensitivity, and high surface potential and reduction of residual potential were observed.

However, the photoconductors A and H have the x value of the first layer region, the photoconductor L has the x value of the third layer region, and the photoconductor C has the x value of the third layer region.
The thicknesses of the layer regions of the photoconductors B and K deviate from the thicknesses of the first layer region of the photoconductors B and K, respectively. Therefore, no improvement in photosensitivity, residual potential or surface potential was observed.

〔The invention's effect〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-
By forming a layer region containing a high content of C element inside the SiC photoconductive layer, excellent photosensitivity was obtained, and further, the surface potential could be increased and the residual potential could be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the layer structure of the electrophotographic photosensitive member of the present invention, FIG. 2 is a schematic view of a glow discharge decomposition apparatus used in Examples, and FIG. 3 is a line showing the relationship between carbon content and conductivity. FIG. 4 is a diagram showing the relationship between carbon content and hydrogen content, FIG. 5 is a diagram showing the relationship between hydrogen content and conductivity, and FIG. 6, FIG. 7, FIG. 8, FIG. 9 and FIG.
FIG. 10 is a diagram showing the carbon content in the thickness direction of the amorphous silicon carbide photoconductive layer. 1 ... Conductive substrate 2 ... Amorphous silicon carbide photoconductive layer 2a ... First layer region 2b ... Second layer region 2c ... Third layer region 3 ... Organic photo-semiconductor layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Ito 1166, Haseno, Hachimizo-cho, Yokaichi, Shiga Prefecture Inside the Shiga Yokaichi Plant, Kyocera Corporation (72) Inventor, Nishi Takemura 1166, Hanaeno, Hachimizo-cho, Yokaichi, Shiga Prefecture 6 Kyocera Corporation Shiga Yokaichi Plant

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor comprising an amorphous silicon carbide photoconductive layer and an organic photosemiconductor layer sequentially laminated on a conductive substrate, wherein the amorphous silicon carbide photoconductive layer has a first layer region and a second layer region. And a third layer region are sequentially formed, and the first layer region and the third layer region are formed.
The layer region contains more carbon than the second layer region, and when the element ratio is expressed as the x value of the composition ratio Si _1-x C _x , it is set within the range of 0.2 <x <0.5, Further, the thickness of the first layer region is 0.01 to 1 μm, and the thickness of the second layer region is 0.1 μm.
An electrophotographic photoreceptor wherein the thickness of the third layer region is set in the range of 10 to 2000 mm.