JPH0769622B2 - Optical backside recording photoreceptor and image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical backside recording photoreceptor,
In addition, the present invention relates to an image forming apparatus that forms an image by arranging a magnetic brush developing device having a recording electrode and an image exposing means so as to face each other with a photoconductor having a photoconductive layer therebetween.

2. Description of the Related Art Current copying machines or high-speed printers with high printing quality generally use an electrophotographic recording system. This method is a so-called Carlson process in which recording is performed in the steps of uniform charging, image exposure, development, transfer, fixing, charge removal, and cleaning. In this Carlson process, a corona discharger is used for uniform charging, transfer and charge removal. Since the corona discharge has a configuration in which a high voltage of several kV is applied to the corona wire, it requires a high voltage power source and is easily affected by humidity, dust, etc., and thus has a drawback of low reliability. Further, odorous ozone is generated from the corona discharger, and the harmfulness of this ozone to the human body has become a problem in recent years. Further, the Carlson process requires the above-mentioned seven steps, and thus has a drawback that the apparatus becomes complicated and large. Recently, as a solution to these problems, an image forming method has been proposed which can reduce the size of the apparatus by eliminating corona discharge.

[0003]

2. Description of the Related Art FIG. 9 shows an outline of the structure of a conventional image forming apparatus of this type (described in Japanese Patent Application No. 62-30703). In the figure, 1 is a belt-shaped photoreceptor. The photoconductor 1 is configured by laminating a transparent conductive layer 1b and an organic photoconductive layer 1c on a transparent substrate 1a such as polyethylene terephthalate, and the transparent conductive layer 1b is grounded.

The magnetic brush developing device 2 provided on the photoconductive layer 1c side of the photoconductor 1 comprises a magnet roller 2a and a sleeve 2b, and the magnet roller 2a is rotatable. On the surface of the sleeve 2b, there are provided strip-shaped recording electrodes 4 which are insulated from the sleeve 2b by an insulating film 3 and extend in the direction perpendicular to the plane of the drawing.

A voltage having a reverse polarity to the carrier polarity (positive polarity in the figure) of the photoconductive layer 1c is applied to the recording electrode 4 by the first voltage applying means 6, and the sleeve 2b has a reverse polarity to the recording electrode 4. The voltage is applied by the second voltage applying means 7.

The developing device 2 contains a one-component or two-component developer 5, and the developer 5 is conveyed in a clockwise direction indicated by an arrow when the developing device is operated. An image exposure unit 8 is arranged on the transparent substrate 1a side of the photoconductor 1. As the image exposure means 8, an optical system using an LED array,
Examples include an optical system using a liquid crystal shutter, an optical system using electroluminescence, an optical system using a laser, and the like. In this image exposure means 8, the optical axis of the exposure light is the recording electrode 4.
It is arranged so as to intersect with.

The operation of the image forming apparatus having such a configuration is as follows. When the photoconductive layer 1c is imagewise exposed by the image exposure means 8 in the section A of the apparatus having the above structure, photocarriers are generated in the photoconductive layer 1c. Among the photocarriers, carriers having a polarity opposite to the voltage applied to the recording electrode 4 move to the vicinity of the surface of the photoconductive layer 1c and become latent image charges 9. In this way, in the exposed portion, the electrostatic capacity of the photoconductive layer 1c apparently increases, so that the amount of adhered toner increases, and a toner image with a certain degree of contrast is formed between the exposed portion and the non-exposed portion.

Next, at the portion B, the sleeve 2b is provided with a second
By applying a reverse voltage by the voltage applying means 7 and forming a pool of developer, excess toner in the non-exposed portion is collected in the developing device 2 by electrostatic force and magnetic force. At this time, the toner in the exposed portion is also slightly recovered, but most of the toner remains on the photoconductor 1 due to the electrostatic restraining force of the latent image charge 9 and the toner charge, and the toner image 10 is formed.

[0009]

As described above, the conventional photoreceptor is an organic photoreceptor having an organic photoconductive layer.
This organic photoreceptor has the following problems. (1) Since the dark decay is fast, the print density is low and the back fogging easily occurs. (2) Since the surface hardness is low, the printing durability is poor and the life is short at about tens of thousands of sheets. (3) While a low developing bias is applied, the residual potential of the photoconductor is high and the contrast of print density is lowered.

It is an object of the present invention to provide a photoconductor for optical back surface recording and an image forming apparatus capable of extending the dark decay time, reducing the residual potential and improving the life. .

[0011]

In order to achieve the above object, the optical back surface recording photoreceptor of the present invention comprises:
A transparent conductive layer, an amorphous silicon photosensitive layer, and an amorphous silicon carbide surface protective layer are sequentially laminated.

Further, in the optical back surface recording photoreceptor having this structure, an amorphous silicon carbide substrate block layer is formed between the transparent conductive layer and the amorphous silicon photosensitive layer.

Further, in the image forming apparatus of the present invention, a transparent conductive layer, an amorphous silicon photosensitive layer, and
A photosensitive body in which an amorphous silicon carbide surface protective layer was sequentially laminated, a magnetic brush developing device having a recording electrode arranged on the surface protective layer side of the photosensitive body, and a transparent substrate side of the photosensitive body were arranged. And an image exposure unit.

Further, in the image forming apparatus having this structure,
An amorphous silicon carbide substrate block layer is formed between the transparent conductive layer and the amorphous silicon photosensitive layer.

[0015]

Operation: The photoconductive layer is made of hydrogenated amorphous silicon (a-
When the main component is Si: H), the hardness is 2500 or more in Vickers hardness, which is three digits or more harder than the conventional organic photoreceptor. Therefore, the printing durability is remarkably improved and the life is remarkably extended.

Further, the a-Si photosensitive member has a dark decay time lengthened and a residual potential increased by using a blocking structure with a surface protection layer of amorphous silicon carbide (a-SiC: H) or a substrate block layer. Can be lowered.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus to which the present invention is applied. In the figure, 11 is an endless belt-shaped photoreceptor. It should be noted that the members having the same configurations as the conventional ones are denoted by the same reference numerals as the conventional ones.

The photoreceptor 11 is formed by depositing ITO on a transparent substrate 12 such as polyethylene terephthalate having a thickness of about 100 μm.
A conductive layer 13 made of (indium oxide) and a photoconductive layer 14 made of a-Si are sequentially formed. The details of the photoconductive layer 14 are as shown in the sectional view of FIG. 2, and the substrate block layer 14A formed on the conductive layer 13, the photosensitive layer 14B formed on the substrate block layer 14A, and the surface protection formed on it. Layer 14C. The conductive layer 13 is connected to ground, and the photoconductor 11 itself is driven by a drive system (not shown).
5 and the driven rollers 16, 17, and 18 are stretched around and run in the direction of the arrow.

In the image forming section, as in the conventional case, the photoconductor 1
1 on which a charged toner image 1 held by the electrostatic force of the latent image charge
9 is formed. In this case, the developer reservoir 2C is provided downstream of the recording electrode 4 in the moving direction of the photoconductor 11 to collect excess toner in the non-exposed portion to the developing device 2 by electrostatic force and magnetic force. Next, the toner image 19
Is electrostatically transferred onto the recording paper 22 by using the transfer conductive rubber roller 21 to which the voltage is applied by the voltage applying means 20. The transferred toner image 23 is fixed on the recording paper 22 by the thermal fixing device 24, and a semi-permanent recorded image 25 is obtained.

On the other hand, the residual toner 26 remaining on the photoconductor 11 after the transfer is destaticized by the destaticizing lamp 27, and the toner 28 that has lost the electrostatic restraint force due to the destaticization is recovered by the developing device 2 and reused. To be done.

The photoconductive layer 14 of the photoconductor 11 used in the image forming apparatus having the above structure and function is formed of a-Si system as described above and has sufficient hardness. . For example, when the photoconductive layer 14 is formed of a-Si: H, the hardness is 2500 or more in Vickers hardness, which is three or more digits higher than that of the conventional organic photoreceptor. Therefore, the printing durability is remarkably improved and the life is remarkably improved to several million sheets.
In addition, the a-Si photoconductor has a long dark decay time, a reduced residual potential, and can improve print density, eliminate back, and realize good contrast. This effect is
It becomes more remarkable by using a blocking structure.

In the above description, the photoconductor is in the form of a belt, but the present invention is also applicable to the case where a drum-shaped photoconductor (a transparent conductive layer and a photoconductive layer are formed on the surface of a transparent drum) is used. The photoconductive layer forming procedure will be described below using this drum-shaped photosensitive member as an example.

When forming a film, first, a transparent electrode (ITO) is vapor-deposited on a cylindrical transparent substrate (material: quartz) by a tens of μm sputtering method, and this transparent substrate 101 is vacuumed in a film forming apparatus shown in FIG. Set in the container 102. Then, the inside of the vacuum container 102 is set to 10 ⁻⁷ t by an oil diffusion pump or the like (not shown).
Exhaust to orr.

Next, the transparent substrate 101 is rotated at a constant speed by the motor 103 and heated to 200 to 300 ° C. (preferably 250 ° C.) by the heater 104. Here, the pump is a mechanical booster pump (PM
B) Switch to 105 and rotor pump (RP) 106,
Disilane (Si ₂ H ₆ ) gas (or silane (Si
H ₄ ) gas) and propane (C ₃ H ₈ ) gas in the cylinder 10
7 ₁ , 107 ₂ , 107 ₃ to a flow rate regulator (not shown),
It is introduced into the vacuum container 102 through the valve.

The gas pressure is kept constant (10 ^-2 to several torr).
After step r), high frequency power is applied to the discharge electrode 109 from the RF power source 108 to cause glow discharge. The energy of this plasma excites and decomposes the material gas,
A substrate block layer of a-Si _{1 -X} C _X : H (corresponding to the substrate block layer 14A in FIG. 2) is formed on the substrate 101.

Next, the introduced gas is changed to Si ₂ H ₆ (or SiH
₄ ) only, and a photosensitive layer of a-Si: H (photosensitive layer 1 in FIG. 2)
4B) is deposited. Next, we introduced C ₃ H ₈ again,
A surface protective layer of a-Si _1-X C _X : H (corresponding to the surface protective layer 14C in FIG. 2) is formed. The film forming conditions at this time are as shown in Table 1 below.

[Table 1]

The characteristics of the thus obtained photoreceptor are evaluated by the conventional Carlson process, and the results are shown in FIGS.
Shown in.

As is apparent from FIG. 4, the charging potential is 200V.
On the other hand, the residual potential is 5 V, and the time (dark decay time) required for half of the potential difference to decay is about 50 seconds, which is 1
It is improved to almost 5 times compared to 0 seconds. This value greatly improves the 20 seconds required in the printing process. Further, as is apparent from FIG. 5, this photoreceptor has sufficient photosensitivity and the half-exposure energy at wavelength λ = 750 nm was 0.6 μJ / cm ² .

The substrate block layer and the surface layer are formed of a-Si.
_{When formed of 1-X} C _X : H, these are a-Si.
_The residual potential can be lowered as compared with the case of forming with _1-X N _X : H, because the C element is more compatible with the Si element in that it is a bond than the N element. This is because the number of impurity levels is reduced, and therefore charges are less likely to be trapped, and stable film characteristics are thereby obtained.

In the above description of the film forming procedure, the photosensitive layer is undoped a-Si: H and is an n-type semiconductor (electrons are main carriers).
By mixing ₂ H ₆ ) gas to form a film, it is possible to dope boron (B) and make it i-type to p-type (the main carrier is a hole). In this case, the substrate block layer may be a highly doped layer (P + layer) of B of a-Si: H. Cylinder 107 ₄ of FIG. 3 are those of the B ₂ H ₆ for supplying.

In the above description of the film forming procedure, the substrate block is used.
The a-Si _1-XC_X: By H
Although formed, even if only the surface layer of these is formed
The present invention can be achieved.

By the way, when performing color printing (multicolor printing) by electrophotography, it is necessary to overlap a plurality of colors. In the case of full-color output, all three colors are usually represented by the three primary colors and black. The paper comes into contact with the toner four times, and the fixing is performed after the toner of each color is transferred. However, the accuracy of superimposing each color limits the expression accuracy (dot density) of the color.

FIG. 6 is an explanatory view of a conventional alignment procedure, which shows a first drum 31, a second drum 32, a third drum 33, and a fourth drum.
When each color is represented by the four drums of the drum 34, the paper 200 is fixed on the belt 35, and the rotation of the belt 35 and the rotation of the first to fourth drums 31 to 34 are mechanically synchronized to determine the position. It was producing accuracy. 36, 37, 38, 39
Is a transfer device.

In this method, the accuracy of electrophotography exceeds ±
There was a color shift of about 100 μm. In order to solve this problem, small magnetic powder (10-100μ
m) is attached outside the printing area, and the magnetic field of the magnetic powder 40 is applied to the DC SQUID (Superco) in front of each drum as illustrated for the first drum 31 in FIG.
nducing Quantum Interferer
ence Device: superconducting quantum interferometer) 41 to measure the position and movement of the paper.

The amount of this magnetic powder is changed for each paper when there are a plurality of papers in the apparatus. Based on this measurement information, the exposure timing is determined for each drum to eliminate color misregistration. In this case, not only the latent image formation timing but also the paper feeding speed may be adjusted. The DC SQUID is configured by connecting two Josephson couplings in parallel with a superconductor and can measure a magnetic flux of 10 ⁻¹⁵ T or more.

In FIG. 7, 42 is a pre-charger, 43 is an exposure device, 44 is a developing device, 45 is a transfer device, 46 is a static eliminator, and 47.
Is a cleaner.

The alignment method using the magnetic powder can be applied to the case where color printing is performed by the apparatus shown in FIG. In FIG. 8, reference numeral 48 is a drum, 49 is a developing unit, and other members similar to those in FIG. 7 are denoted by the same reference numerals as those in FIG. 7. The developing section 49 includes developing devices 50 ₁ , 50 ₂ , 50 for each color.
₃ , 50 ₄ can be selectively positioned at the developing position, and one drum can print four colors. In this case, the paper 200 supplied to the transfer position as indicated by the arrow is circulated four times along the path indicated by the arrow in the figure to perform four times of transfer, and the exposure start timing for each color is DC. It is adjusted by measuring the magnetic field of the magnetic powder 40 with the SQUID 41.

DC SQUA as shown in each of these examples
By adopting the timing adjustment method by ID,
The color misregistration that occurred at a size of 100 μm can be made smaller than the dot diameter ( ~ 60 μm) of the latent image of electrophotography by one digit or more, and high-precision multicolor printing is possible. It is also applicable to an image forming apparatus to which the invention is applied.

[0039]

As described above, according to the present invention, since the photoconductive layer of the photoconductor is composed mainly of a-Si, the dark decay time can be lengthened and printing can be performed. It is possible to improve the density and eliminate the bag. Further, the surface hardness of the photoconductor is improved, and the life can be greatly improved. Furthermore, by using a blocking structure with a surface protective layer of a-SiC: H or a substrate block layer, the residual potential becomes low due to its stable film characteristics, which allows good contrast even when a low developing bias is applied. Is obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a photoconductor according to an exemplary embodiment of the present invention.

FIG. 3 is an explanatory diagram of a procedure for forming a photoconductive layer of a photoconductor according to an example of the present invention.

FIG. 4 is a graph showing dark decay characteristics of the photoconductor of the example of the present invention.

FIG. 5 is a graph showing the photosensitivity characteristics of the photoconductor of the example of the present invention.

FIG. 6 is a side view showing a color superimposing procedure by a conventional Carlson process.

7 is a DC S for solving the problem of the method of FIG.
It is a side view which shows the timing adjustment system by QUID.

FIG. 8 is a side view showing another example of the timing adjustment method by DC SQUID.

FIG. 9 is a schematic configuration diagram of a main part of a conventional image forming apparatus.

[Explanation of symbols]

 2 Magnetic Brush Developing Device 4 Recording Electrode 8 Image Exposure Means 11 Photoreceptor 12 Transparent Substrate 13 Conductive Layer 14 Photoconductive Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Kamaji 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Masatoshi Kimura 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (56) References JP-A 63-240553 (JP, A) JP-A 54-143645 (JP, A) JP-A 57-115551 (JP, A) JP-A 57-52180 (JP, A)

Claims (4)

[Claims] 1. A photoconductor for optical back surface recording, comprising a transparent substrate, a transparent conductive layer, an amorphous silicon photosensitive layer, and an amorphous silicon carbide surface protective layer, which are sequentially laminated on the transparent substrate. 2. An optical backside recording photoreceptor according to claim 1, wherein an amorphous silicon carbide substrate block layer is formed between the transparent conductive layer and the amorphous silicon photosensitive layer. 3. A photosensitive member comprising a transparent substrate, a transparent conductive layer, an amorphous silicon photosensitive layer, and an amorphous silicon carbide surface protective layer, which are sequentially laminated on the transparent substrate, and a recording disposed on the surface protective layer side of the photosensitive member. An image forming apparatus comprising: a magnetic brush developing device having an electrode; and an image exposing means arranged on the transparent substrate side of the photoconductor. 4. The image forming apparatus according to claim 3, wherein an amorphous silicon carbide substrate block layer is formed between the transparent conductive layer and the amorphous silicon photosensitive layer.