JP2789100B2 - 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 photoreceptor includes Se, Se-Te, A
_There are inorganic materials such as _S2Se3 , ZnO, CdS, and amorphous silicon, and various organic materials. Among them, Se was first commercialized, and then ZnO, CdS, and amorphous silicon were commercialized. As an organic material, PVK-TNF was first put to practical use, and thereafter, a function-separated type photoreceptor in which the functions of charge generation and charge transport were shared by different materials was proposed. The development of is dramatically developing.

Also, an electrophotographic photoreceptor having an organic photoconductive layer laminated on an inorganic photoconductive layer has 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, there is a disadvantage that Se itself is harmful and the sensitivity on the long wavelength side is inferior.

Therefore, Japanese Patent Application Laid-Open No. 56-14241 proposes a laminated photoreceptor comprising an amorphous silicon carbide photoconductive layer and an organic photo-semiconductor layer. Properties and high photosensitivity were obtained.

According to the electrophotographic photoreceptor of the above publication, the chemical formula Si _1-x C _x H
It has a structure in which an amorphous silicon carbide layer represented by _y (where 0 <x <1, 0.05 ≦ y ≦ 0.2) and an organic optical semiconductor layer are sequentially laminated. However, when the present inventors manufactured such an electrophotographic photoreceptor and measured the surface potential and the residual potential, it was found that none of the characteristics were still satisfactory and further improvement was required. did.

Accordingly, the present invention has been completed in view of the above, and an object of the present invention is to provide an electrophotographic photoreceptor capable of obtaining a high surface potential and reducing the residual 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 optical semiconductor layer are sequentially laminated on a conductive substrate, the a-SiC light The conductive layer has a layer structure in which a first layer region and a second layer region are sequentially formed, and the first layer region includes a Group Va element of the periodic table in an amount of 5,000 pp.
m, or the layer region is not substantially contained, and the second layer region contains one group IIIa element of the periodic table.
An electrophotographic photoreceptor characterized in that it is contained within the range of 1,0001,000 ppm.

 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 photo-semiconductor layer (3) has a function of transferring charges.

According to the present invention, a first layer region (2a) and a second layer region (2b) are sequentially formed inside an a-SiC photoconductive layer (2), and the first layer region (2a) has a periodic structure. Contains a group Va element of the table (hereinafter abbreviated as group Va element) within a predetermined range,
Alternatively, the second layer region (2b) is substantially not contained, and is not contained.
Contains a Group IIIa element of the periodic table (hereinafter abbreviated as Group IIIa element) within a predetermined range, thereby improving the surface potential and residual potential.

Another characteristic is that the formation of such a layer region results in an electrophotographic photosensitive member for negative charging.

First, the a-SiC photoconductive layer (2) is made of amorphous S
It is composed of the element i and the element C and the hydrogen (H) element or the halogen element introduced into the dangling bond terminal portion of these elements, and the composition formula thereof may be set as follows.

[Si _1-x C _x ] _1-y A _y (where A is an H element or a halogen element) 0.01 <x <0.5 preferably 0.05 <x <0.5 most preferably 0.1 <x <0.4 0.1 <y <0.5 suitable 0.2 <y <0.5 Optimally 0.25 <y <0.45 Photoconductivity is obtained if the x value is in the range of 0.01 <x <0.5, and the value is set in the range of 0.05 <x <0.5 In this case, the photosensitivity on the short wavelength side is increased, and the photoconductivity is significantly increased, so that the photocarrier excitation function is increased.

Further, when the y value is 0.1 or less, the film quality is deteriorated, whereby the photoconductivity is significantly reduced. When the y value is set in the range of 0.2 <y <0.5, the dark conductivity is reduced and the photoconductivity is reduced. Thus, excellent photoconductivity is obtained, and excellent adhesion to a substrate is also obtained.

The a-SiC photoconductive layer (2) contains hydrogen (H), an element, and a halogen element for terminating dangling bonds. Of these elements, the H element is easily taken into the terminating portion. This is desirable in that the local level density in the band gap is reduced.

The thickness of the a-SiC photoconductive layer (2) is 0.05 to 5 μm.
m, preferably in the range of 0.1 to 3 μm,
Within this range, high photosensitivity is obtained and the residual potential is reduced.

Next, for the first layer region (2a), the Va group element is set to 0.
5,000 5,000 ppm (note that 0 ppm is substantially not contained), preferably 0 to 3,000 ppm, whereby n
A photo-carrier generated in the a-SiC photoconductive layer (2), particularly negative charges, can flow smoothly to the substrate side, and the carrier on the substrate side is an a-SiC photoconductive layer (2). Can be prevented. That is, it can be said that the first layer region (2a) has non-ohmic contact with the substrate (1) in that it has a rectifying property.

Therefore, the surface potential increases due to the non-ohmic contact, and the residual potential decreases.

If the content of such a Va group element exceeds 5,000 ppm, internal defects in this layer region increase, the film quality deteriorates, and the surface potential and the residual potential increase.

The first layer region (2a) is desirably set more specifically by its thickness together with the content of the Va group element.

That is, the thickness of the first layer region (2a) may be set in the range of 0.05 to 5 μm, preferably 0.1 to 3 μm, and within this range, the residual potential can be reduced and the withstand voltage of the photoconductor is increased. This is advantageous in that it can be used.

Moreover, it is desirable to set the SiC composition ratio of the first layer region (2a) together with the content and thickness of the Va group element as follows.

That is, when represented by the composition formula Si _1-x C _x , it is preferable to set within the range of 0.1 <x <0.5, and within this range, the surface potential can be increased and the adhesion to the substrate can be enhanced. .

Further, when setting the C element ratio as described above, the ratio is preferably set to be larger than that of the second layer region (2b), which can increase the surface potential and increase the adhesion to the substrate. Is advantageous.

The Va element includes N, P, As, Sb, and Bi, but the P element has excellent covalent bonding properties and can change semiconductor characteristics sensitively. It is desirable in that it can be done.

For the second layer region (2b), group IIIa elements
1,000 ppm, preferably 30 to 300 ppn, thereby
A P-type semiconductor layer is formed on the side of the organic photoconductive layer (3) inside the a-SiC photoconductive layer (2), and photocarriers generated in this layer (2), particularly positive charges, are transferred to the organic photoconductive layer (3). The surface potential is increased, and the residual potential is reduced.

When the amount of the group IIIa element is less than 1 ppm, the charging ability cannot be improved, and when it exceeds 1,000 ppm, the ability to generate photoexcited carriers is inferior and the photosensitivity decreases.

The second layer region (2b) is desirably set more specifically by its thickness together with the content of the group IIIa element.

That is, the thickness of the second layer region (2b) may be set in the range of 0.05 to 5 μm, and preferably in the range of 0.1 to 3 μm. Within this range, high photosensitivity is obtained and the residual potential is reduced. .

The IIIa group elements include B, Al, Ga, In, etc., but since the B element has excellent covalent bonding and can change semiconductor characteristics sensitively, excellent charging ability and photosensitivity are obtained. It is desirable in that it can be done.

As described above, according to the electrophotographic photoreceptor of the present invention, a-
A pn junction is formed in the SiC photoconductive layer (2), so that among the carriers generated in this layer (2), holes go to the organic photo-semiconductor layer (3) and electrons go to the substrate (1). Heading. Therefore, a negatively charged electrophotographic photosensitive member is obtained.

In such a negatively charged electrophotographic photoreceptor, an electron-donating compound is selected for the organic photo-semiconductor layer (3), and the compound is, for example, poly-N-vinylcarbazole, polyvinylpyrene, or the like having a high molecular weight. Polyvinyl anthracene, pyrene-formaldehyde polycondensate, etc., and low molecular weight oxadiazole, oxazole, pyrazoline, triphenylmethane, hydrazone, triarylamine, N-phenylcarbazole, stilbene, etc. The molecular substance is used by being dispersed in a binder such as polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate, and urea resin.

In addition, the substrate (1) includes a metal derivative such as copper, brass, SUS, or Al, or a substrate obtained by coating an insulator such as glass or ceramic with a conductive thin film. This is advantageous in terms of adhesion to the a-SiC layer.

Further, when the substrate (1) is a flexible conductive sheet, a metal sheet such as Ni or stainless steel is used, or a metal such as Al or Ni is coated on a polymer resin such as polyester film, nylon or polyimide. SnO ₂ , ITO
A material obtained by conducting a conductive treatment such as vapor deposition on a transparent conductive material such as, or an organic conductive material is used.

Thus, according to the present invention, the surface potential and the residual potential are improved by forming the layer region containing the Va group element and the IIIa group element within a predetermined range in the a-SiC photoconductive layer, and By setting the SiC element ratio within a predetermined range, the light sensitivity is improved.

In the electrophotographic photoreceptor of the present invention, the content of the Va group element and the content of the IIIa element of each of the first layer region (2a) and the second layer region (2b) are determined along the layer thickness direction. It may be changed. Examples are shown in FIG. 6 to FIG.

In these figures, the horizontal axis is the layer thickness direction, S is the interface between the substrate (1) and the first layer region (2a), and t is the first layer region (2a) and the second layer region (2b). ), U represents an interface between the second layer region (2b) and the organic optical semiconductor layer (3).
The vertical axis represents the content of the Va group element or the IIIa group element.

Thus, the first layer region (2a) or the second layer region (2a)
When the content of the Group Va element or the Group IIIa element is changed in the layer thickness direction in b), the element content is the average content of the entire layer region (2a) (2b). Corresponding to

When the content of the Va group element or the IIIa group element is changed as described above, an intrinsic semiconductor layer is formed between the first layer region (2a) and the second layer region (2b). There are cases.

 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
There are i ₃ H ₈ , SiF ₄ , SiCl ₄ , SiHCl ₃ and the like, and the C element-containing gas includes CH ₄ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H ₈ , and especially 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), the fourth tank (7), and the fifth tank (8) are provided with SiH ₄ , C ₂ H ₂ , and PH _{3 respectively.} , B ₂ H ₆ (both PH ₃ gas and B ₂ H ₆ gas are diluted with hydrogen gas) and H ₂ are sealed, and these gases are respectively corresponding to the first preparation valve (9), Preparation valve (10), third preparation valve (11), fourth preparation valve (12)
And is released by opening the fifth preparation valve (13). The flow rate of the released gas is controlled by mass flow controllers (14) (15) (16) (17) (18), respectively.
Each gas is mixed and sent to the main pipe (19). still,
(20) and (21) are stop valves.

The gas flowing through the main tube (19) flows into the reaction tube (22). Inside the reaction tube (22), a capacitively coupled discharge electrode (23) is installed. Substrate (2
4) is placed on the substrate support (25) and the substrate support (2
5) is rotationally driven by the motor (26), and the substrate (24) is rotated accordingly. Then, power (50) is applied to the electrode (23).
High frequency power of w ~ 3Kw, frequency 1 ~ 50MHz is applied, and the substrate (24) is about 200 ~ 400
C., preferably about 200-350.degree. Also,
The reaction tube (22) is connected to a rotary pump (27) and a diffusion pump (28), so that a required reduced pressure state (gas pressure during discharge: 0.01 to 2.0 Torr) is maintained during film formation.

When the a-SiC layer is formed on the substrate (24) using the glow discharge decomposition apparatus having such a configuration, the first preparation valve (9), the second preparation valve (10), and the third preparation valve (11). ) And the fifth
Open the preparation valve (13) to release each gas of SiH ₄ , C ₂ H ₂ , PH ₃ , and H ₂ , and determine the release amount by mass flow controller (14)
(15) Controlled by (16) and (18), each gas is mixed and flows into the reaction tube (22) via the main pipe (19). 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 the P element is rapidly deposited on the substrate as the gas is decomposed. Form.

After the a-SiC layer is formed by the thin film forming method as described above, an organic optical semiconductor layer is formed next.

The organic optical semiconductor layer is formed by a dip coating method or a coating method, the former being immersed in a coating liquid in which a photosensitive material is dispersed in a solvent, and then pulled up at a constant speed, and
This is a method of performing natural drying and heat aging (about 150 ° C., about 1 hour). According to the latter coating method, it is applied to a photosensitive material dispersed in a solvent using a coater (coating machine). 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 is the carbon content ratio, that is, the X value of Si _1-x C _x , The vertical axis represents the conductivity, and the circle represents the emission wavelength of 55.
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.

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

In FIG. 4, the horizontal axis represents the X value of Si _1-x C _x , the vertical axis represents the hydrogen content, that is, the y value of [Si _1-x C _x ] _{1-y Hy} , 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
Is within the range of 0.2 <x <0.5, the ratio between the photoconductivity and the dark conductivity becomes remarkably large, and it can be seen that excellent photosensitivity is obtained.

(Example 2) Next, in this example, SiH ₄ gas was supplied at a flow rate of 200 sccm and 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, various a-SiC films were formed in which the carbon content ratio x was set to 0.3 and the hydrogen content y was changed, and the photoconductivity and dark conductivity of each film were measured. The result as shown in the figure was obtained.

In FIG. 5, the horizontal axis is the hydrogen content, that is, [Si _1-x C _x ] _1-y H _y
The vertical axis represents the conductivity, and the mark ○ represents the emission wavelength 55.
It is a plot of the photoconductivity with respect to light of 0 nm (light quantity 50 μW / cm ² ), the mark ● represents the plot of dark conductivity, and e, f
Are the respective characteristic curves.

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

(Example 3) A flat aluminum plate (25 mm x 50 mm) whose surface was polished was placed inside a reaction tube of a glow discharge decomposition apparatus, and a first layer region (2a) was sequentially formed on the flat plate under the film forming conditions shown in Table 1. )
And a second layer region (2b).

Next, a disk-shaped (3 mmφ) aluminum electrode was formed by a vacuum evaporation method, and a photoconductive member as shown in FIG. 16 was produced. In the figure, (29) and (30) are a flat plate and an aluminum electrode, respectively.

The first layer region (2a) and the second
For each layer area (2b)
The P element content and the B element content were measured by the secondary ion mass spectrometry, and the results shown in Table 2 were obtained.

A voltage was applied to the thus obtained a-SiC photoconductive member on the aluminum electrode (30) side as shown in FIG. 16 and the flat plate (29) was conductive to the ground side, and the voltage-current characteristics were measured. And the results as shown in FIG. 17 were obtained.

In this example, no PH ₃ gas was introduced when forming the first layer region, and no B ₂ H ₆ gas was introduced when forming the second layer region. Exactly the same film formation conditions were set, whereby the P element and B
An a-SiC photoconductive member containing no element was manufactured, and this was used as a comparative example, and its voltage-current characteristics were also measured.

In FIG. 17, the horizontal axis is the voltage applied to the aluminum electrode (30), the vertical axis is the current value, ○ is a measurement plot of the a-SiC photoconductive member according to the present invention, and ● is a comparative example. A
-It is a measurement plot of a SiC photoconductive member, and g and h are respective characteristic curves.

As is clear from FIG. 17, according to the a-SiC photoconductive member of the present invention, almost no current flows even when a negative voltage is applied to the aluminum electrode (30).
When a positive voltage is applied to the device, an extremely large current flows.

Example 4 The same a-SiC photoconductive layer as in Example 3 was formed on an aluminum substrate, and then an organic optical semiconductor layer (having a thickness of about 15 μm) in which a hydrazone compound was dispersed in polycarbonate was formed. A photoreceptor was used.

The properties of the thus obtained electrophotographic photosensitive member were measured by an electrophotographic property measuring apparatus. As a result, excellent photosensitivity and surface potential were obtained, and a low residual potential was obtained.

(Example 5) In producing the electrophotographic photoreceptor of the above (Example 4), an electrophotographic photoreceptor obtained by using the comparative example of the (Example 3) as an a-SiC photoconductive layer and further forming the same organic optical semiconductor layer When the photosensitivity of this electrophotographic photoreceptor was measured, it was about 10% lower than that of the electrophotographic photoreceptor of (Example 4), and the residual potential was increased by about 7%.

(Example 6) In this example, an a-SiC photoconductive layer containing no P element was formed in the first layer region under the film forming conditions shown in Table 3, and the other film forming conditions were changed to (Example 3) and An electrophotographic photosensitive member was set in the same manner as in (Example 4).

When the carbon content and the B element content of the a-SiC photoconductive layer obtained as described above were measured, the results shown in Table 4 were obtained.

The electrophotographic photoreceptor thus obtained also had excellent photosensitivity and surface potential, and low residual potential.

(Example 7) In producing the electrophotographic photoreceptor of (Example 4), the present inventors changed the PH ₃ gas flow rate and the B ₂ H ₆ gas flow rate. P of layer 1
The element content and the B element content in the second layer region were changed
Fifteen kinds of electrophotographic photosensitive members (photosensitive members A to 0) were produced.

When the photosensitivity, surface potential and residual potential of these electrophotographic photosensitive members were measured, the results shown in Table 5 were obtained.

In the same table, the light sensitivity was classified into four stages of ◎, ○, Δ and × by relative evaluation, ◎ indicates the case where the best light sensitivity was obtained, In this case, the light sensitivity was obtained, the mark Δ was when the light sensitivity was slightly inferior to the others, and the mark X was when the light sensitivity was the lowest.

The evaluation of surface potential characteristics was also 4 for ◎, ○, △ and ×.
The mark ◎ indicates that the highest surface potential was obtained, the mark 場合 indicates that a somewhat higher surface potential was obtained, and the mark △ indicates that no higher surface potential was observed. , And the mark x indicates the case where the surface potential decreased most.

In addition, the residual potential was also relatively evaluated in four steps, and ◎ indicates the case where the residual potential was the smallest, and
The mark indicates the case where a decrease in the residual potential was somewhat recognized, the mark Δ indicates the case where the decrease in the residual potential was not recognized as compared with the others, and the mark x indicates the case where the residual potential was highest.

As is clear from Table 1, photoconductors A to C and photoconductors E to
L has excellent photosensitivity and has a high surface potential,
A decrease in the residual potential was observed.

However, the photoreceptors D, M, and N have poor photosensitivity and surface potential,
Further, it can be seen that the photoreceptor 0 has not been improved in any of the characteristics of photosensitivity, surface potential and residual potential.

〔The invention's effect〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-
By forming each layer region containing a Group Va element and a Group IIIa element within a predetermined range inside the SiC photoconductive layer, excellent photosensitivity is obtained, surface potential is increased, and residual potential is reduced. Could be reduced.

Further, according to this electrophotographic photoreceptor, the a-SiC photoconductive layer is in non-ohmic contact with the substrate, whereby the rectifying function is enhanced, and a high surface potential and a low residual potential for negative charging electrophotography are used. A photoreceptor was provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the layer structure of the electrophotographic photoreceptor 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 the carbon content ratio and the conductivity. FIG. 4 is a diagram showing the relationship between the carbon content ratio and the hydrogen content, FIG. 5 is a diagram showing the relationship between the hydrogen content and the conductivity, and FIG. 6, FIG. 8, FIG. 9,
FIG. 10, FIG. 11, FIG. 12, FIG. 13, FIG. 14, and FIG. 15 show the group Va element content and group IIIa element content in the thickness direction of the amorphous silicon carbide photoconductive layer. FIG. FIG. 16 is an explanatory diagram for measuring the voltage-current characteristics of the photoconductive member, and FIG. 17 is a diagram showing the voltage-current characteristics. DESCRIPTION OF SYMBOLS 1 ... Conductive substrate 2 ... Amorphous silicon carbide photoconductive layer 2a ... 1st layer area 2b ... 2nd layer area 3 ... Organic optical semiconductor layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-14241 (JP, A) JP-A-58-21256 (JP, A) JP-A-56-62255 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G03G 5/08 319 G03G 5/08 313

Claims (2)

(57) [Claims] 1. An electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic optical semiconductor layer are sequentially laminated on a conductive substrate, wherein the amorphous silicon carbide photoconductive layer has a first layer region and a second layer. The first layer region contains a Group Va element of the periodic table in a range of 5,000 ppm or less (not including 0), and the second layer region has a periodic structure. Table IIIa group elements from 1 to 1,000
An electrophotographic photoreceptor characterized by being contained in the ppm range. 2. An electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic optical semiconductor layer are sequentially laminated on a conductive substrate, wherein the amorphous silicon carbide photoconductive layer includes a group Va element of the periodic table and Thickness not containing any of Group IIIa elements of the periodic table 0.1 to 3 μm
1-1,000 pp of the first layer region and group IIIa element of the periodic table
2. An electrophotographic photoreceptor, wherein a second layer region contained in the range of m is sequentially laminated.