JPH02207267A - Electrostatic latent image carrier - Google Patents

Abstract

PURPOSE:To decrease the recombination level at the boundary between a surface layer consisting of an amorphous carbon and a photoconductive layer and to prevent the image flowing by an electric field effect by incorporating an element to control an optical forbidden band width into the surface layer at the concn. distribution decreasing from the photoconductive layer side thereof toward the free surface side. CONSTITUTION:This carrier is formed by laminating and forming a blocking layer 1, the photoconductive layer 2 and the surface layer 3 in this order on a cylindrical base S having a conductive surface. The surface layer 3 consisting of the non-single crystal layer essentially consisting of a C atom contains the element to control the optical forbidden band width and is added with this element at such concn. distribution at which the concn. decreases from the photoconductive layer 2 side toward the free surface side of the surface layer 3. A sharp change in the optical forbidden band width between the photoconductive layer 2 and the surface layer 3 is, therefore, relieved in the state of maintaining the good electrostatic charge characteristics, etc., by the hydrophobic property and the wide optical forbidden band width. The recombination level at the boundary between the photoconductive layer 3 and the surface layer 3 is decreased in this way, by which the image flowing by the electric field effect is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention provides a method for forming a photoconductive layer made of a non-single crystal semiconductor and a surface layer mainly composed of C atoms on one support having a conductive surface. The present invention relates to an electrostatic latent image carrier in which the following are laminated in this order.

(b) Conventional technology An electrostatic latent film constructed by forming a photoconductive layer made of a non-single-crystal semiconductor, specifically amorphous silicon (a-Si), on a support having a conductive surface. The image carrier is a conventional Se
Compared to photoconductive layers containing CdS as a main component, it has advantages such as high heat resistance, high abrasion resistance, and non-polluting properties.

In such an electrostatic latent image carrier made of a-5i,
A surface layer is laminated on the photoconductive layer for the purpose of protecting the surface, improving printing resistance, improving charging characteristics, preventing image fading under high humidity, and preventing image fading due to charging effects. Normal. The material for this surface layer is
Silicon nitride (S iN ) and silicon carbide (SiC)
) etc. have been used numerically.

However, the surface layer made of SiN or SiC has a problem in that highly hygroscopic 5i-0 bonds are likely to occur on its free surface, and image blur FL is likely to occur under high humidity.

Therefore, the use of amorphous carbon (a, -C) as the surface layer has been proposed in Japanese Patent Application Laid-Open No. 6-289354. This surface layer made of a-C has high hardness, excellent chemical resistance, and high resistance value, so it has excellent printing resistance and charging characteristics.Furthermore, it has low hygroscopicity, so it can be used at high humidity. It also has the advantage that image deletion is less likely to occur.

(C. 1 Problem to be Solved by the Invention However, a-
In the surface layer made of C, the optical forbidden band width is 2
, 4 e'v or more, which is extremely large compared to 6 to 1.8 eV of the photoconductive layer made of a-3i. Therefore, there is a problem in that image blurring is likely to occur due to the electric field effect.

Therefore, an object of the present invention is to prevent image blurring due to the electric field effect while maintaining the fineness and characteristics of the surface layer made of a-C.
The purpose is to stop.

(d) Means for Solving the Problems The present invention provides a photoconductive layer made of a non-single crystal semiconductor mainly composed of S1 atoms or Ge atoms, and a photoconductive layer made of a non-single crystal semiconductor mainly composed of S1 atoms or Ge atoms, on a support having a conductive surface. An electrostatic latent image carrier in which a surface layer made of a non-single crystal as a component is laminated at least in this order, wherein the surface layer -J1 contains an element that controls the optical forbidden band width, and this element is 1) A concentration distribution that decreases at the same rate from the leading conductive layer side to the free surface side is added.

(E) ('rJ14 The surface layer made of a-C according to the present invention has an element that controls the optical forbidden band width in a concentration distribution that decreases from the photoconductive layer side to the free surface side. The abrupt change in the optical band gap between the layer and the photoconductive layer is relaxed.

This reduces the recombination level at the interface between the surface layer and the photoconductive layer while maintaining the insulation properties of the free surface side of the surface layer, that is, high charge retention ability and high hardness, resulting in image distortion caused by the electric field effect. You can prevent 1] 2.

Embodiment 1 FIG. 1 is a schematic cross-sectional view showing the first embodiment of the present invention. On a cylindrical support S having a conductive surface, a blocking layer 1, a photoconductive layer 2 and a surface layer 3 are laminated in this order.The blocking layer 1 is made of a material containing a-3i as a main component and has a thickness of 02 to 10 μm, preferably 1 to 5 II m, and To prevent the injection of electrons from the S side, an element belonging to III ffl of the periodic table is doped, and to prevent the injection of holes, an element belonging to group II of the periodic table is doped.

The photoconductive layer 2 is made of a material having the same <a-3i as its main component, and is formed to have a thickness of 1 to 40 μm, preferably 20 to 30 μm, and is optionally coated with oxygen to increase the resistance value. Nitrogen, carbon, etc. are doped.

The surface layer 3, which is a feature of the present invention, is composed of a first layer 3a on the side in contact with the photoconductive layer 2 and a second layer 3b laminated thereon. 2 layers 3b
The thickness of the surface layer 3 is 173 or less of the total thickness of the surface layer 3. Each layer is made of a material containing a-C as a main component and an element that controls the optical forbidden band width, and the concentration of the element contained in the first layer 3a is higher than that of the second layer 3b.
It is higher than that of . The element that controls the optically forbidden width is preferably B or AI, but is limited to Ga, In, which belongs to Group III of the periodic table, and N, P, which belongs to Group V of the periodic table. AS, St), C
Also use r etc.

FIG. 7 is a characteristic diagram showing the relationship between the doping concentration of the above elements (13 and AI) in a-C and the optical forbidden band width, and from the figure, a-C is an element of B or AI. As the concentration of addition increases, the optical forbidden band width tends to decrease.

Therefore, according to this structure, as is clear from FIG. 2 showing the band profile of the electrostatic latent image carrier of the first embodiment, the optical forbidden band width of the first layer 3a of the surface layer 3 is 2
It is smaller than that of layer 3b, and the sudden change in the optical forbidden band width between the photoconductive layer 2 and the surface layer 3 is alleviated, and the recombination level at the interface is reduced, resulting in a reduction in the level due to the electric field effect. Image drift is suppressed.

FIG. 3 is a schematic cross-sectional view showing a second embodiment of the present invention. In this embodiment, the surface layer 3 is formed from the photoconductive layer 2 side by forming a first layer 3C, a second layer 3d, and a third layer 3e. It is composed of three layers laminated in order, and the concentration of the element added to each of these layers to control the optical forbidden band width is determined by the third layer 3e.
It is configured so that it becomes smaller gradually toward the sides.

The thickness of the third layer 3e is 1 of the total thickness of the surface +43.
It is set not to exceed 73.

With this structure, t'L is determined by the third layer 3e, the second layer 3d, and the third layer 3d of the surface layer 3, as is clear from FIG. 1 layer 3C
The optical forbidden band widths of the photoconductive layer 2 and the surface layer 3 decrease in this order as -). Therefore, the rapid change in the optical forbidden band width between the photoconductive layer 2 and the surface layer 3 is alleviated, and reconsolidation at the interface is suppressed. The a-level is reduced and image blur due to electric field effect is suppressed. Furthermore, the change in the optical forbidden band width at the interface between each layer 3C13d of the surface layer 3 and the layer C is also relaxed compared to the first embodiment, and the recombination level is reduced, so that the image flow due to the electric field effect is reduced. It is possible to suppress it more effectively.

Furthermore, FIG. 5 is a schematic cross-sectional view showing a third embodiment of the invention, and the surface layer 3 contains an element that controls the optical forbidden band width, as shown in FIG. The element is added at a concentration that gradually decreases from the layer 2 side toward the free surface side, and an element that controls the optical forbidden band width is added at a constant concentration on the free surface side, or The region to which no element is added is formed with a thickness of 173 times or less of the total thickness of the first surface layer 3.

In this Wt structure, as is clear from FIG. 6, which shows the band profile of the static latent image carrier of the first embodiment, the optical forbidden band width of the surface layer 3 is on the side of the photoconductive layer 2. It gradually increases from the point toward the free surface, and therefore,
A sudden change in the optical forbidden band width between the photoconductive layer 2 and the surface layer 3 is relaxed, the recombination level at the interface is reduced, and image blur due to the electric field effect is suppressed. Furthermore, the surface layer 3 is
Since it does not have a recombination level inside, it is possible to more effectively suppress image blur due to electric field effect.

Next, based on the manufacturing apparatus shown in FIG. 9, electrostatic latent image carriers having the structures shown in the second and third embodiments will be described as a specific example 1 and a specific example 2.

(Specific example) Original i.) Using a plasma CVD device in which a hollow cylindrical discharge electrode 1 is placed in a sealed container 10 in which gas is contained, an outer circumference is placed inside the discharge electrode 11 of this CVD device. A conductive support S whose surface has been cleaned is rotatably inserted concentrically. After loading the support S into the sealed container 10 in this way, the rotary pump 12 and the mechanical bomber bomb 13 are operated to pump l x 1 t inside the sealed container.
Evacuate to about 1-' Torr. And support I
2 (i
(1 to 30 (1"
H, gas, and H2 gas as a dilution gas are introduced to maintain the gas pressure at about 0.1 to 1 OTorr. The mixing ratio of this ll+ B, H, gas to S+H++H is set to approximately several 1.000 ppm to several 1100 ppm, and the dilution rate of Ht gas (S iH, /'(S if (, 10 H+)) is set to 0.1 or more. It is controlled by the mass flow controller 14. In this state, high frequency power with a frequency of 1356\111z is applied from the high frequency power source 15 with the discharge electrode] 1 set to the high frequency potential and the support body S set to the ground potential at [1.05 W/cm' or more]. A blocking layer 1 with a thickness of 1 to 54 m is formed on the surface of the support S by generating plasma between the support S and the discharge electrode 11 and decomposing the source gas such as SiH and gas for a certain period of time. Form.

After the formation of the blocking layer 1, the residual gas in the sealed container 10 is reduced to about IX 10-'' Torr.The raw material gases are S+Ht gas, H, gas, and H.

Introduce B, H, based on . In this reaction, the gas pressure is maintained at about 0.1 to 10 Torr, and the hydrogen dilution ratio (S i H, , / (S i H, +I-12)
) is 0.1 or more, and the gas flow rate ratio (B 2He/ (S + Ll 40B , H[)) is 0.('l]-], 000 ppm, preferably 0.0
Mass flow controller 1 so that it becomes 01-1O0pp
Controlled by 4. In this state, the frequency is 13.56M
Applying high frequency power of 0.5 W/Cm' or more from the Hz high lXd wave power source 15 to raise the blaster upright for a certain period of time,
A photoconductive layer 2 having a film thickness of ~50 mm is formed on the blocking layer 1--.

Furthermore, following the formation of the photoconductive layer 2, a surface layer 3, which is a feature of the present invention, is formed. First, in order to exhaust the residual gas in the sealed volume r:r10, the pressure is reduced to about IX 10-'Torr. And C, H2 gas as raw material gas,
■-1, Gas and H, B and H based on gas.

Introduce the gas and maintain the gas pressure at about 01 to If) Torr, and reduce the hydrogen dilution rate (C, H, /' (C, H, + H,)
) to 01 or higher.

In this state, first, the flow rate ratio of B, H, and gas (B, H.

, '(C, II , + B , I(,)) 1.000
-100. OOOppm, preferably 5. CHiO~
50, control the mass 70 controller I/roller]1 so as to obtain OOOppm (0,5Z to 5Z). In this state, from the 3.56M11z high frequency power source 15 for frequency power, 0,0
A high frequency power of 5 II'/cm' or more is applied to generate plasma for a certain period of time, and a film thickness of 1 is formed on the photoconductive layer 2.
0 to 3 μm, preferably 1 (l OA to 17t m
A first layer 3C is formed.

Next, the flow rate ratio of B and H gases (B IIT 8//(
C11-11+ B , Hs)) at 100-10. O
The mass flow controller 14 is controlled so that the amount is OOppm, preferably 500 to 5,000ppm. In this state, the high frequency power supply 15 whose frequency is ]356\If-1z
A high frequency power of 011X''/cm' or more is applied to generate plasma for a certain period of time, and the first layer 3cJ: has a film thickness of 0.
．． 001-3pm, preferably 0.001-1p second
Form layer 3d.

Finally, stop B, H, gas, C2H, gas and H,
Gas is introduced into the sealed container 10. In this state, a high frequency power of 0.05 W/cm or more is applied from the high frequency power source 15 to generate plasma for a certain period of time, and the second layer 3d-1
- film thickness 0. O(+1-2pm, preferably 0.01
A third layer 3e of −14 m is formed.

In this way, the surface layer 3 consisting of the first layer 3C, the second layer 3d and the third layer 3e is coated with a thickness of 100 to 5 μm, preferably 50 μm.
Formed at 0 to 5.0 OOA. At this time, the thickness of the third layer 3e is formed to be 173 times or less of the total thickness of the surface layer 3.

As a result of the above, the optical forbidden band width is 1 on the photoconductive layer 2.
．． 7-2. OeV, 2.0-2.3eV and 2.3-2
．． The first layer 3c, the second layer 3d and the third layer have a value of 6eV.
The surface layer 3 consisting of the layer 3e can be formed in a laminated manner.

(Specific Example 2) A blocking layer 1 and a photoconductive layer 2 are formed on a support S in the same manner as in Specific Example 1 described in .

Thereafter, first, the pressure is reduced to about IXIO-'Torr in order to exhaust the residual gas in the sealed container 10. And C2Hr gas, H, gas and H as humiliating gas.

Gas-based AI (CH,), by introducing gas,
While maintaining the gas pressure at about 0.1 to 1.0 Torr, the hydrogen dilution rate (C + FI + / (C, H, + I-1
, )) is set to 01 or more -L.

In this state, high frequency power of 0.05 W/cm' or more is applied from the high frequency power source 15 to generate plasma for a certain period of time. At this time, the flow rate ratio of Al(CH3)5 gas (AI(C
II, /(C, H, +AI(CHI)3)) is 1,000 to 100.0O0 at the start of the formation of the surface layer 3.
ppm, preferably 1,000 to 50.0O0ppm, and then as the surface layer 3 is formed, the gas flow rate is gradually decreased to 4 (l<cIr,), and finally controls the flow rate ratio of AI(CH,) and gas to Oo-1O0pp. Under such control, a film thickness of 1 (H'1.L to 5
Form a surface layer 3 of pm, preferably 500-5.000 pm.

As a result of the above steps, it is possible to form a surface layer 3 on the photoconductive layer 2 in which the optical forbidden band width gradually increases from the photoconductive layer 2 side toward the free surface side.

Note that although specific examples 1 and 2 use a glow discharge method, the method is not limited to this in any way; for example, a photo CV method is used.
D method, molecular beam epitaxy method, or high frequency ion blating method may be used. When using the molecular beam epitaxy method, a monomolecular beam of dinocon or carbon is used, and when using the high frequency ion blating method,
Silicon and carbon are used as evaporation sources in a hydrogen atmosphere.

(G) Effects of the Invention According to the present invention, the surface layer consisting of a non-phosphorous crystal layer containing C atoms as a main component contains an element that controls the optical forbidden band width,
This element has a concentration distribution of 1.1 that decreases from the photoconductive layer side to the free surface side of the surface layer; ・Ω addition! Therefore, while maintaining the excellent properties of the surface layer consisting of a-C, that is, hydrophobicity and good charging properties due to a wide optical bandgap,
The rapid change in the optical forbidden width between the photoconductive layer and the surface layer can be alleviated, and therefore, the recombination at the interface between the photoconductive layer and the surface layer is reduced, and the electric field is reduced. Image blur due to effects can be suppressed.

[Brief explanation of the drawing]

1, 3, and 5 are schematic cross-sectional views showing the first, second, and third embodiments of the electrostatic latent image carrier of the present invention, and FIGS. The figure is an energy band diagram showing the band profile of the electrostatic latent image bearing members of the first, second and third embodiments, and FIG. 7 shows the doping concentration of elements (B and AI) in a-C and the optical A characteristic diagram showing the relationship between the forbidden band width and -. Fig. 8 is a characteristic diagram showing the concentration distribution of the element added to the surface layer in the third embodiment to control the optical forbidden band width. Fig. 9 is a characteristic diagram showing the relationship between the electrostatic FIG. 2 is a schematic diagram showing an example of a manufacturing apparatus for a latent image carrier. Support, 1 surface layer. outgoing person

Claims (2)

[Claims] (1) A photoconductive layer made of a non-single crystal semiconductor mainly composed of Si atoms or Ge atoms and a surface layer made of a non-single crystal semiconductor mainly composed of C atoms are formed on a support having a conductive surface. , an electrostatic latent image carrier laminated in at least this order, wherein the surface layer contains an element that controls the optical forbidden band width, and the element decreases from the photoconductive layer side toward the free surface side. An electrostatic latent image carrier characterized by being doped with a specific concentration distribution. (2) The electrostatic latent image carrier according to item 1, wherein the element is an element belonging to Group III or Group V of the periodic table.