JPH04234062A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide the electrophotographic sensitive body capable of improving the copy quality for a specified light source in the optical rear recording method. CONSTITUTION:An antireflection layer 4 having specified conditions for the picture exposure light is formed on the surface of the light-transmissive substrate 1 of an electrophtographic sensitive body on the recording light incident side, or the thickness of a light-transmissive conductive layer 2 is controlled so that the reflection of the recording light is prevented. Consequently, loss of the recording exposure light due to the reflection on the surface of the substrate 1 or at the interface between the substrate and the layer 2 is eliminated, the incident light quantity on a photosensitive body layer 3 is substantially increased, and the copy density is enhanced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor for use in an electrophotographic apparatus using a backside recording method, which performs image forming processes of exposure and development almost simultaneously without using corona charging.

0002

2. Description of the Related Art As a conventional electrophotographic apparatus, a so-called Carlson type electrophotographic apparatus, which utilizes charging of a photoreceptor by corona discharge, is widely used. FIG. 6 shows an outline of this conventional electrophotographic apparatus. In this device, a corona charger 18, an exposure device 19, a developing device 20, a transfer device 21, a cleaning device 22, a static eliminator 23, etc. are arranged around a drum-shaped or belt-shaped photoreceptor 17, and charging, exposure, An image is formed on recording paper through the processes of development, transfer, and fixing. In such a Carlson type electrophotographic device, the structure and image forming process of the device are complicated, resulting in a larger device.Also, since corona discharge in the atmosphere is used, the ozone gas generated by it is There is a problem in that it adversely affects each part of the device and the environment in which the device is placed.

[0003] In order to solve this problem, Japanese Unexamined Patent Application Publication No. 1988-
No. 44445, JP-A-58-153957, JP-A-6
1-46961, Japanese Patent Application Laid-Open No. 62-280772, and Journal of the Institute of Image Electronics Engineers, Vol. 16, No. 5 (1987), electrophotographic methods that do not utilize corona charging have been proposed. An example is shown in FIG.

In FIG. 5, a bias potential is applied to the developing device 12, and the photoreceptor 11 is transferred through the conductive magnetic toner 13.
At the same time, from the support side of the photoreceptor 11, L
The ED light emitting element 14 applies recording exposure to form an image on the photoreceptor 11, and then the developing device 1 is applied to the conductive transfer roller 15.
By applying a voltage of the same polarity as 2, an image is transferred onto the recording paper 16. This type of electrophotographic method is called a backside optical recording method.

[0005] The photoreceptor used in this electrophotographic method is basically one in which a light-transmitting conductive layer is formed on a light-transmitting support, and a photoconductive layer made of a photoreceptor material is laminated thereon. . The materials for this photoconductive layer include conventionally used a-Se, a-SeAs, CdS, ZnO,
Organic optical semiconductors (OPC) and the like have been introduced, and a-Si has been proposed in JP-A-63-240553 and JP-A-2-106761.

[0006]

[Problems to be Solved by the Invention] In the electrophotographic method of the optical back recording method, image exposure is performed from the support side of the photoreceptor using a single wavelength light source such as an LED head. There is a problem in that a part of the light is reflected on the surface of the transparent support or the interface between the support and the transparent conductive layer, and is not effectively utilized for the generation of photocarriers.

Therefore, in order to speed up the process, it is necessary to increase the amount of light emitted by the light source and the photosensitivity of the photoreceptor, and if the photoreceptor is in the form of a drum, the support There is also a problem in that the light reflected on the surface is diffusely reflected on the surface of the LED head and inside the photoreceptor, which adversely affects the image quality as unevenness and noise in the image. In addition, the present inventors faced the problem that it was difficult to obtain a large amount of exposure light for each exposed dot, especially when combined with a small and low power consumption dynamic drive type LED head, and the inventors of the present invention faced the problem that it was difficult to obtain a large amount of exposure light for each exposed dot. recognized that the photoreceptor side would also need to be devised to eliminate exposure light loss and effectively introduce it into the photoreceptor layer.

[0008]

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic photoreceptor using a backside recording method, in which a part of the exposure light is transmitted to the surface of the light-transmitting support, or between the support and the transparent support during recording exposure. This improves the conventional problem of reflection at the interface with the photoconductive layer and the ineffective use of photocarrier generation, and increases the printing density by increasing the amount of light incident on the photoconductive layer. The purpose is to improve image quality.

[0009]

[Means for Solving the Problems] According to the present invention, a light-transmitting conductive layer and a photoreceptor layer including a photoconductive layer are laminated on a light-transmitting support, and the surface of the photoreceptor layer is In a photoreceptor used in electrophotography using a backside recording method, an image is formed on the photoreceptor by applying a developing bias voltage to the developer that is in contact with it and using light incident from the side of the transparent support.
There is provided an electrophotographic photoreceptor characterized in that an antireflection layer against image exposure light is formed on the surface of a transparent support opposite to the surface on which the transparent conductive layer is formed.

Further, according to the present invention, in the photoreceptor used for electrophotography using the optical backside recording method, the thickness of the transparent conductive layer is formed to have an antireflection effect against the incident light. An electrophotographic photoreceptor is provided.

[0011]

[Operation] The present invention will be explained in detail below. The main point of the present invention is to provide a new anti-reflection layer for image exposure light, or
Alternatively, the image exposure light is effectively made to enter the photoconductive layer by making the light-transmitting conductive layer thick enough to have an antireflection effect.

FIG. 1 is a diagram showing the layer structure of a photoreceptor according to the first aspect of the present invention. In FIG. 1, 1 is a transparent support, 2 is a transparent conductive layer, 3 is a photoreceptor layer, and 4 is an antireflection layer.

FIG. 2 is a diagram showing the layer structure of a photoreceptor according to the second aspect of the present invention. In FIG. 2, reference numerals corresponding to those in FIG. 1 indicate the same parts as in FIG.

FIG. 3 is a principle diagram for explaining that when light is incident on a photoreceptor, reflected light is generated at the boundaries between the layers. In FIG. 3, 5 is a medium with a refractive index n 0 , and 6
is a medium with a refractive index n1, 7 is a medium with a refractive index n2, 8 is incident light, 9 is transmitted light, and 10 is reflected light.

The reason why the antireflection effect can be obtained by the antireflection layer 4 in the photoreceptor shown in FIG. 1 will be explained below with reference to FIG. 3. According to FIG. 3, a medium 6 with a refractive index n 1 is inserted between a medium 7 with a refractive index n 2 and a medium 5 with a refractive index n 0 , and light with a wavelength λ is perpendicularly directed from the medium 7 to the medium 5. The reflectance R upon incidence is as follows.

R = (n 0 2 + n 1 2 ) (
n 1 2 + n 2 2 ) -4n0 n 1 2
n 2 + (n 0 2 - n 1 2 ) (n
1 2-n 2 2 ) cos δ/ (n 0 2 +
n 1 2 ) (n 1 2 + n 2 2 ) +4
n 0n 1 2 n 2 + (n 0 2 −n
1 2 ) * * (n 1 2 - n 2 2 )
cos δ... (Equation 1) Here, δ is the phase delay when passing through the medium 6 with the thickness d, and in the case of normal incidence, it is given by the following equation. δ= 4 πn 1 d λ−1 ・
...(Formula 2)

When the medium 5 is air, n 0 =
1. 0, medium 7 is glass and n 2 = 1.5,
The change in R when δ and n 1 are changed is as shown in FIG. 4 (in the figure, in the case of normal incidence, φ0 = 0). In the graph of FIG. 4, the vertical axis shows R and the horizontal axis shows δ. As is clear from FIG. 4, cos δ=-1,
That is, when δ=(2m+1)π (m is an integer), R shows a maximum or minimum, and R = (n1 2 - n0 n 2 ) 2
/(n1 2 +n0 n2) 2...(
It is given by Equation 3). If we set this R as R=0, then n
1 2 = n 0 n 2
...(Formula 4) n 1 d = λ/4+mλ/2
...(Formula 5) is obtained. That is, when medium 6 with n 1 and d that satisfies this condition is inserted between medium 7 and medium 5, R=0 for light with wavelength λ, and no reflection occurs at the interface between medium 5 and medium 6. It disappears.

The case where (Equation 4) and (Equation 5) are satisfied at the same time is particularly called the no-reflection condition, but if there is no such suitable medium, select medium 6 where n 1 < n 2 . Even if (Equation 5) is satisfied, the reflectance decreases,
It has an anti-reflection effect.

In the present invention, the medium 5 corresponds to the air layer, the medium 6 corresponds to the antireflection layer 4, and the medium 7 corresponds to the transparent support 1. In the present invention, appropriate materials are selected in consideration of the stability of the material itself used for the antireflection layer, the adhesion between the antireflection layer and the transparent support, and the ease of coating formation. do.

[0020] The material of this antireflection layer is TiO 2
, In2O3, SnO2, ITO(In2
O3:SnO2), SiO2, SiO2,
Al2O3, WO3, CdO, CeO2
, Sb2O5, ZrO2, ZnS, CdS
, Cd2SnO4, MgF2, CaF2
, LiF 2 , AlF 3 , NaF, CeF 3
oxides such as Ag, Au, Cr, Al, Ni, etc., metal thin films such as Ag, Au, Cr, Al, Ni, etc., and combinations thereof can be used, and the material, thickness, and combination can be selected as appropriate depending on the material of the support and the wavelength of exposure. selected. Methods for forming this antireflection layer include vapor deposition, sputtering, CVD, coating, dipping, and spraying.

The transparent support 1 may be made of glass (Pyrex glass, soda glass, borosilicate glass, etc.), quartz,
They include transparent inorganic materials such as sapphire, and transparent organic resins such as fluororesin, polyester, polycarbonate, polyethylene, polyethylene terephthalate, vinylon, epoxy, and mylar, and are provided in shapes such as drums and belts.

The transparent conductive layer 2 contains ITO (indium tin oxide), tin oxide, lead oxide, indium oxide,
Using transparent conductive materials such as copper iodide, Al, Ni,
A metal such as Au may be formed thin enough to be semitransparent.

The transparent conductive layer 2 can be formed by vacuum deposition, active reaction deposition, RF sputtering, DC sputtering, RF magnetron sputtering, DC magnetron sputtering,
It is formed by a thermal CVD method, a plasma CVD method, a spray method, a coating method, a dipping method, or the like. The thickness of the transparent conductive layer 2 is usually several tens to tens of thousands of angstroms, preferably several hundred to several thousand angstroms.

The photoconductive material laminated as the photoreceptor layer 3 includes a-Si type materials such as a-Si and a-SiC;
-Se, a-AsSe, a-SeTe, etc., C
Various materials such as dS, ZnO, and organic optical semiconductors (OPC) can be used, but in particular, a-Si photoreceptor materials offer high photosensitivity, excellent durability, non-pollution, etc. Excellent properties can be obtained. Further, more desirable characteristics can be obtained by laminating a charge injection blocking layer or a surface layer, but these layers are formed by a glow discharge decomposition method, a sputtering method, an ECR method, a vapor deposition method, etc. At this time, an element for dangling bond termination, such as hydrogen (H) or halogen, is contained. In addition, each of these layers contains C 2 , O 2 ,
It is preferable to appropriately contain N 2 , Ge, IIIa group elements, Va 2 group elements, and the like.

[0025] The thickness of the charge injection device layer is 0.01 to 5 μm.
m, preferably within the range of 0.3 to 3 μm,
The thickness of the surface layer is 0.05 to 5 μm, preferably 0.05 μm.
It is preferably within the range of 1 to 3 μm. The thickness of the entire photoreceptor layer is preferably in the range of 1 to 15 .mu.m, preferably 2 to 10 .mu.m, in order to ensure the necessary charging and dielectric strength, and to suppress the absorption of exposed light and residual potential.

Next, according to the second aspect of the present invention, the key point is to make the transparent conductive layer 2 thick enough to have an antireflection effect. Thereby, an antireflection effect can be obtained for light that passes through the transparent support 1 and enters the photoreceptor layer 3.

In the present invention, the fact that an antireflection effect can be obtained can be considered by following the same procedure as described above with reference to FIG. Here, the medium 5 corresponds to the transparent support 1, the medium 6 corresponds to the transparent conductive layer 2, and the medium 7 corresponds to the photoreceptor layer 3. That is, in the above (Formula 4) and (Formula 5),
If the transparent conductive layer 2 is formed so as to simultaneously satisfy both equations, a non-reflection condition is achieved. If there is no such suitable medium, the same effect as described above can be obtained even if the transparent conductive layer 2 is formed with a layer thickness that satisfies (Formula 5) using a transparent conductive material that satisfies n0 < n 1 < n 2. has an anti-reflective effect.

[0028] When the photoreceptor layer 3 is of a-Si type,
Its refractive index is about 3.0 to 3.5 for a-Si,
Approximately 2.4 ~ for SiC, a-SiN, and a-SiO
3.2, about 3.4 for a-SiGe and a-SiSn
4.0, and on the other hand, most oxide-based transparent conductive materials have a refractive index smaller than these, so various materials such as ITO, tin oxide, and indium oxide can be used for the transparent conductive layer 2. is available.

The manufacturing method of the transparent conductive layer 2, and the specifications, materials, and manufacturing methods of each layer of the transparent support 1 and the photoreceptor layer 3 may be the same as those described in the first invention.

[0030] Furthermore, in this second invention, it goes without saying that the antireflection layer 4 shown in the first invention may be used in combination. In this case, the antireflection effect can be further enhanced.

As described above, either an anti-reflection layer having an appropriate refractive index and thickness as determined by the above formula depending on the exposure wavelength is provided on the surface of the transparent support, or a transparent conductive layer is coated with a reflective layer. By setting the thickness to have a preventive effect, it is possible to eliminate loss due to reflection of exposure light at the surface of the transparent support or the interface between the support and the transparent conductive layer. As a result, the photoreceptor layer can be efficiently exposed to light, and diffuse reflection on the inside of the photoreceptor can be eliminated, and image disturbance and noise can be eliminated.

Therefore, especially in combination with a light source such as a dynamic drive type LED head where it is difficult to obtain a large amount of exposure light, the exposure light from the transparent support can be efficiently introduced into the photoreceptor layer. By reducing the amount of emitted light and the photosensitivity of the photoreceptor to the minimum required amount,
This is advantageous because the increase in equipment costs can also be suppressed.

[0033]

Examples (Example 1) A photoreceptor for electrophotography using an optical back recording method using an LED head with an exposure wavelength of 660 nm was prepared under the following conditions.

When a transparent cylindrical support made of borosilicate glass with a refractive index n 2 =1.5 is used as the support,
From (Formula 4) and (Formula 5), the no-reflection condition is n 1 =1.
2, d = 137.5 (+m*275) nm, but since there is no stable material that satisfies these requirements at the same time, we created this cylinder with a thickness of 360 nm by vapor deposition of magnesium fluoride (MgF2) with a refractive index of 1.38. The inner circumferential surface of the shaped support was coated.

Next, a transparent conductive layer made of ITO was formed on the outer circumferential surface of this support to a thickness of 1000 Å by a reactive vapor deposition method, and further, using a capacitively coupled glow discharge decomposition device,
a-S containing group IIIa elements under the conditions shown in Table 1.
i-charge injection blocking layer, a-Si photoconductive layer, and a-SiC
A photoreceptor layer with a thickness of approximately 6 μm consisting of a surface layer is laminated,
An electrophotographic photoreceptor for backside recording was fabricated.

[0036]

[Table 1]

This photoreceptor is installed in an electrophotographic apparatus using a backside recording method having the configuration shown in FIG. +1 between the translucent electrode layer on the body
While applying a voltage of 0.0 V, image exposure is performed at a wavelength of 660 nm and an exposure amount of 0.7 μJ/cm2 to form a toner image on the photoreceptor, and the toner image is transferred to recording paper and thermally fixed. I did it and got the image. When this image was evaluated, O. D. has an image density of 1.2,
The image was of good resolution, with no background fog or image distortion.

[0038] Furthermore, when the reflectance of the antireflection layer side of the support of this photoreceptor at a wavelength of 660 nm was examined, it was found that
It was about 1%.

(Comparative Example 1) A photoreceptor without the antireflection layer 4 was produced under the same conditions as in Example 1 except that the inner peripheral surface was not coated with the antireflection layer. When this photoreceptor was subjected to image evaluation in the same manner as in Example 1, it was found that O. D. is 1.1
The image density was somewhat low, and no particular background fog was observed, but disturbances were observed at the edges of the image, and the image was inferior in resolution compared to Example 1.

[0040] Also, 66 on the inner circumferential surface of the support of this photoreceptor
When we investigated the reflectance for a wavelength of 0 nm, it was approximately 5%.
Met.

(Example 2) The support has a refractive index n 2 =1.5.
Using a transparent cylindrical support made of borosilicate glass,
Next, a transparent conductive layer made of ITO with a refractive index of 2.0 was formed on the outer peripheral surface of this support to a thickness of 165 nm using a reactive vapor deposition method.
A-Si injection blocking layer, a-Si injection blocking layer, a
A -Si photoconductive layer and an a-SiC surface layer were sequentially laminated to produce a photoreceptor.

When this photoreceptor was subjected to image evaluation in the same manner as in (Example 1), it was found that O. D. An image with an image density of 1.2 and good resolution without background fog or image disturbance was obtained.

[0043] In addition, 66 in the transparent conductive layer of this photoreceptor
When we investigated the reflectance for a wavelength of 0 nm, it was found to be approximately 0.
It was 6%.

(Comparative Example 2) A photoreceptor was manufactured under the same conditions as in Example 2 except that the ITO layer thickness was 70 nm.

When this photoreceptor was subjected to image evaluation in the same manner as in (Example 2), it was found that O. D. The image density was rather low at 1.1, and no background fog was observed, but Comparative Example 2
Similarly to the image, there were disturbances at the edges and the resolution was poor.

[0046] Also, in the transparent photoconductive layer of this photoreceptor,
The reflectance for a wavelength of 60 nm was approximately 5.5%.

[0047]

Effects of the Invention As described above, an antireflection layer having an appropriate refractive index and thickness as determined by the above formula depending on the exposure wavelength is provided on the surface of a transparent support, or By making the conductive layer thick enough to have an antireflection effect, it is possible to eliminate the reflection of exposure light on the surface of the transparent support or at the interface between the support and the transparent conductive layer, thereby preventing the photoreceptor from being reflected. The layers could be exposed to light efficiently, increasing print density, eliminating diffuse reflection inside the photoreceptor, and eliminating image disturbances and noise.

Particularly in combination with a dynamic drive type LED head, it is no longer necessary to increase the amount of light emitted by the head itself or the photosensitivity of the photoreceptor more than necessary, and this is advantageous in speeding up the process.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the layer structure of a photoreceptor according to a first aspect of the present invention.

FIG. 2 is a cross-sectional view showing the layer structure of a photoreceptor according to a second aspect of the present invention.

FIG. 3 is a principle diagram for explaining that reflected light occurs at the boundaries of each layer when light is incident on a photoreceptor.

FIG. 4 is a diagram showing the relationship between the amount of phase change of light incident on the thin film and the reflectance.

FIG. 5 is a schematic diagram showing an electrophotographic process using a backside recording method.

FIG. 6 is a schematic diagram showing a conventional Carlson type electrophotographic process.

[Explanation of symbols]

1 Translucent support 2 Translucent conductive layer 3 Photoreceptor layer 4. Anti-reflection layer

Claims (2)

[Claims] 1. A light-transmitting conductive layer and a photoreceptor layer consisting of a photoconductive layer are sequentially laminated on a light-transparent support, and a developing bias is applied to a developer brought into contact with the surface of the photoreceptor layer. By applying a voltage and by light incident from the transparent support side,
In the electrophotographic photoreceptor used for electrophotography using a backside recording method, in which an image is formed on the photoreceptor layer, the surface of the transparent support is opposite to the surface on which the transparent conductive layer is formed. An electrophotographic photoreceptor characterized in that an antireflection layer against the incident light is formed on a side surface. 2. A light-transmitting conductive layer and a photoreceptor layer consisting of a photoconductive layer are sequentially laminated on a light-transparent support, and a developer brought into contact with the surface of the photoreceptor layer is applied with a developing bias. By applying a voltage and by light incident from the transparent support side,
The electrophotographic photoreceptor used for electrophotography using a backside recording method, in which an image is formed on the photoreceptor layer, is characterized in that the light-transmitting conductive layer has a thickness that has an antireflection function against the incident light. An electrophotographic photoreceptor.