JPH04324464A - Image forming method - Google Patents

Abstract

PURPOSE:To provide an image forming method in which corona charging is unnecessitated and sufficient image density and excellent image quality are obtained. CONSTITUTION:Developing bias voltage is impressed on a photosensitive body 2 constituted by successively laminating a light transmissive conductive layer, a carrier injection preventing layer, an amorphous silicon-based photoconductive layer, and a photoconductive amorphous silicon carbide surface layer on a light transmissive supporting body 3 through conductive magnetic toner. Then, the photosensitive body is exposed from the light transmissive supporting body side with the light of specified wavelength which is substantially absorbed by the layer thickness equal to or under that of the photoconductive layer, and optical carrier is temporarily trapped in an area corresponding to a bright part just under a surface insulating layer, then the toner is made to adhere to the surface of the photosensitive body with electric field generated with the optical carrier by interposing the surface layer. While the toner is moved to a transfer part, the charge of the toner and the trapped optical carrier are neutralized through the surface layer and the toner is transferred to a recording paper.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an image forming method, and more particularly to an image forming method using an electrophotographic method that eliminates the need for corona charging, allows exposure and development to be performed almost simultaneously, and eliminates the need for cleaning. It is.

0002

2. Description of the Related Art Hitherto, as the most common electrophotographic process, the Carlson image forming method, which utilizes the charging of a photoreceptor by corona discharge, is widely known and has already been put into practical use.

According to the Carlson method, the surface of the photoreceptor is charged by corona discharge, and then the charge in the exposed area is erased by imagewise exposure to form an electrostatic latent image, and the electrostatic latent image is transferred to the charged toner. The photoreceptor is developed, transferred and fixed onto recording paper to form an image on the recording paper, and then the remaining toner is cleaned and the photoreceptor is used repeatedly. However, the Carlson method has problems such as a complicated device configuration and image forming process, a need for a high voltage power source for corona discharge, and ozone generation due to the use of corona discharge.

In response to this, recently, an image forming method using an electrophotographic method that does not require corona discharge has been proposed (
(See Japanese Patent Publication No. 2-4900, Japanese Patent Publication No. 60-59592, etc.)

According to the image forming method proposed in Japanese Patent Publication No. 2-4900, a photoreceptor is prepared in which a transparent conductive layer, a photoconductive layer, and an insulating layer mainly made of an organic material are sequentially provided on a transparent support. By applying a voltage between the toner and the transparent conductive layer while supplying conductive magnetic toner to the insulating layer side of the photoconductor and exposing the photoconductive layer to light, the insulation layer becomes insulated in bright areas. A charge pair of opposite polarity is formed between the photoconductive layer and the toner with the layer in between, and the toner is attracted to the surface of the photoreceptor by electrostatic force, overcoming the toner transport force caused by magnetic force. After exposure, the toner is removed from the surface of the insulating layer by magnetic force, thereby causing the toner to adhere to the brightly exposed areas on the photoreceptor to form an image.

Furthermore, according to an image forming method proposed in Japanese Patent Publication No. 60-59592, a photoreceptor is used in which a light-transmitting conductive layer, a photosemiconductor layer, and an insulating layer are sequentially provided on a light-transmitting support. Then, a toner image is formed on the insulating layer by exposing the optical semiconductor layer from the side of the transparent support while applying a voltage between the toner supply device and the transparent conductive layer. Thereafter, this toner image is brought into contact with paper, and a voltage of opposite polarity from the voltage applied between the toner supply device and the transparent conductive layer is applied to the back side of the paper, to bring the toner image into contact with the paper. At the same time as it is transferred onto paper, the charge image remaining in the photoconductive layer is erased.

[0007] Furthermore, in such an image forming method,
It has been proposed to use an amorphous silicon layer (hereinafter amorphous silicon is abbreviated as a-Si) as the photoconductive layer (JP-A-63-240553, JP-A-2, No.
-106761).

[0008]

[Problems to be Solved by the Invention] However, according to experiments conducted by the present inventors, it has been found that the image forming method proposed above cannot obtain images with sufficient image density and high image quality. Furthermore, when images are formed repeatedly, there is another problem in that the previous history of the process appears as an afterimage in the images. When an organic insulating layer is used, there is also a problem that the life of the photoreceptor is significantly shortened due to poor abrasion resistance. Furthermore, even when using a photoreceptor equipped with an a-Si photoconductive layer, a satisfactory image density cannot be obtained, and even if an attempt is made to increase the image density by increasing the bias voltage, the photoreceptor Since the dielectric strength of the photoreceptor is low, dielectric breakdown occurs easily, and as a result, the desired image density cannot be obtained.Therefore, it is necessary to improve the layer structure of the photoreceptor.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming method that solves the above-mentioned problems, increases the life of a photoreceptor, and provides sufficient image density and good image quality.

A further object of the present invention is to form an image that eliminates the need for corona discharge, a cleaning process for removing toner from the surface of a photoreceptor, and an erase process for erasing charge images remaining in the photoconductive layer. The purpose is to provide a method.

[0011]

[Means for Solving the Problems] The image forming method of the present invention includes a transparent conductive layer, a carrier injection blocking layer, an a-Si photoconductive layer, and a photoconductive amorphous silicon carbide layer formed on a transparent support. A developing bias voltage is applied to a photoreceptor formed by sequentially laminating a surface layer and a surface layer through a conductive magnetic toner, and light of a predetermined wavelength that is substantially absorbed at a thickness equal to or less than the layer thickness of the photoconductive layer is applied. The photocarriers are collected in the area corresponding to the bright area directly under the surface layer, and the toner is attached to the surface of the photoreceptor by the electric field generated by the photocarriers across the surface layer. This method is characterized by neutralizing the toner and the electric charge of the toner, and then transferring the toner to recording paper.

The image forming method of the present invention is also characterized in that there is no erase step or cleaning step after transfer.

Furthermore, in the image forming method of the present invention, a control electrode is disposed on the side facing the photoreceptor of the developing device for applying a developing bias voltage, so that the voltage can be controlled independently of the bias voltage. It is characterized by the following.

Furthermore, the image forming method of the present invention includes the above a-
The layer thickness of the Si-based photoconductive layer is 0.1 to 10% greater than the thickness of the light absorption layer determined for the exposure wavelength of the absorption coefficient of the layer.
．． It is also characterized by the addition of a layer region with a thickness of 0 μm.

Furthermore, in the image forming method of the present invention, the layer thickness of the amorphous silicon carbide surface layer (hereinafter amorphous silicon carbide is abbreviated as a-SiC) is
It is also characterized by being 0.05 to 5 μm.

[0016]

[Examples] The present invention will be explained below with reference to Examples.

FIG. 1 is a schematic diagram showing an image forming apparatus 1 according to the image forming method of the present invention. -S
A drum-shaped photoreceptor in which each layer 4 of an i-based photoconductive layer and an a-SiC surface layer is laminated, 5 is an LED head as an exposure means, 5a is a SELFOC lens array provided on the head, and 6 is a developing device. , 7 is a transfer roller. The LED head 5 and the developing device 6 are arranged almost symmetrically with a certain part of the photoreceptor 2 interposed therebetween. 8 is LE as a light source for erasing
It is a D array and may be arranged outside the photoreceptor 2. Note that this erasing light source is not necessarily required in the present invention. The developing device 6 consists of a cylindrical magnetic pole roller 9 with, for example, eight poles and a conductive sleeve 10 disposed around its outer periphery. Magnetic toner is delivered to the outer circumference of sleeve 10 to form magnetic brush 12 . Further, a bias power supply 13 is provided between the sleeve 10 and the transparent conductive layer, and between the transparent conductive layer and the bias power supply 13, a voltage of + or - 5 to 5 is provided depending on the potential characteristics of the photoreceptor 2. Apply a voltage of 300V. 14 is photoreceptor 2
15 is a recording paper, and 16 is residual toner. In addition to this, means for rotating the developer and means for rotating the photoreceptor 2 are provided.

Next, an image forming method using the image forming apparatus 1 having the above configuration will be explained with reference to FIGS. 2 to 7.

The photoreceptor 2 shown in these figures has a transparent conductive layer 4a and a carrier injection blocking layer 4 on a transparent support 3.
b, an a-Si type photoconductive layer 4c, and an a-SiC surface layer 4d are sequentially laminated.

First, in FIGS. 2 and 3, the a-Si photoconductive layer 4c is removed from the transparent support 3 side of the rotating photoreceptor 2.
Image exposure light is irradiated from the LED head 5 through the SELFOC lens array 5a to form the a-Si photoconductive layer 4c.
When a hole-electron pair is generated as a photocarrier inside,
If a + bias voltage is applied to the developing device 6 side, the bias voltage causes the electrons in the photocarrier pair to become a-S.
Moves to the surface side of the i-based photoconductive layer 4c, and since the a-SiC surface layer 4d has a higher resistance than the a-Si-based photoconductive layer 4c, a region of the a-SiC surface layer 4d corresponding to the bright exposed area Electrons gather directly under the layer and are temporarily trapped, while holes gather on the carrier injection blocking layer side. Such a photoreceptor 2
In response to the flow of charges inside, positive charges are injected into the conductive toner, a large electric field is generated across the surface layer 4d, the toner is attracted to the surface of the surface layer 4d, and the toner is drawn to the exposed bright area. Correspondingly, it adheres to the photoreceptor 2.

Next, as shown in FIG. 4, in the non-exposed area where the light for image exposure is not irradiated, the electric charge in the photoreceptor 2 does not move as described above, so the electric field that attracts the toner to the photoreceptor 2 is also reduced. Since no toner is generated, toner does not adhere, and residual toner from the previous process is collected into the developing device 6 by magnetic force.
This makes it possible to eliminate the need for a cleaning process.

Furthermore, as shown in FIG. 5, the charge of the toner image 14 formed on the photoreceptor 2 in response to image exposure is insulated to the extent that the resistance of the surface layer 4d of the photoreceptor 2 has photoconductivity. Since the surface layer is lower than the surface layer, when the photoreceptor 2 passes through the developing section and reaches the transfer section, the charges temporarily trapped just below the surface layer are combined with and neutralized through the surface layer 4d. At the same time, both the charge on the toner and the charge on the photoreceptor 2 disappear.

Thereafter, the toner that has released the charge has a weak bond with the photoreceptor 2 that has also released the charge, so that it is easily transferred to the recording paper, and as shown in FIG.
The image is transferred onto the recording paper 15 by the transfer roller 7 to which a voltage is applied via the transfer roller 5, and then fixed by a fixing means (not shown) to form a recorded image.

Next, as shown in FIG. 7, since there is no charge remaining on the photoreceptor 2 after the toner layer 14 has been transferred, there is no particular need for an erase process such as irradiation of static eliminating light from the erase light source 8. , the photoreceptor 2 returns to its initial state. Furthermore, since the electrical attraction between the photoreceptor 2 and the residual toner 16 on its surface has already disappeared, the residual toner 16 is easily collected by the developing device 6 by the magnetic force of the developing device 6 and used again for image formation. Ru.

Although the case where the erase process is not necessary has been described here, in order to stably return the photoreceptor 2 to its initial state after transfer, it is necessary to irradiate the erase process with light for eliminating static electricity from the erase light source 8, etc. An erase step may also be provided.

As described above, image formation is performed by repeating each process shown in FIGS. 2 to 7.

According to the image forming method of the present invention, in FIGS. 2 and 3 of the above-described process, light of a predetermined wavelength that is substantially absorbed below the layer thickness of the a-Si photoconductive layer 4c is used. This increases the generation efficiency of photocarriers, and also tends to form a layer region with high dark resistance near the interface with the surface layer 4d even during image exposure, and as a result, the surface layer The lateral movement of the charges gathered directly under 4d is suppressed, and an image with good resolution is formed.

According to experiments repeatedly conducted by the present inventors, the thickness of the a-Si photoconductive layer 4c is equal to the thickness of the light absorption layer determined from the absorption coefficient of this layer 4c for light at the exposure wavelength. It is desirable that the thickness is further increased by 0.1 to 10.0 μm. The layer area with such thickness is called surface layer 4.
If it is formed near the interface with d, the above object can be achieved more advantageously.

FIG. 9 shows a typical a-Si:H layer (Ego
pt: 1.76 eV), the change in the thickness of the light absorption layer determined from the absorption coefficient with respect to the wavelength of light is shown. According to the figure, the depth at which 90% of incident light is absorbed in the a-Si:H layer is approximately 0.4 μm for a wavelength of 550 nm.
Approximately 0.6 μm for a general EL emission wavelength of 580 nm, approximately 0.8 μm for 600 nm, and approximately 2 μm for a general LED emission wavelength of 660 nm.
．． It can be seen that it is approximately 3.8 μm for 2 μm and 700 nm.

Such a change in the thickness of the light absorption layer varies depending on the light absorption characteristics of the a-Si photoconductive layer 4c used, but in any case, the thickness of the a-Si photoconductive layer 4c can be changed by image exposure. The thickness of the light absorption layer determined from the absorption coefficient for the wavelength of light used for
By adding a thickness of ~10.0 μm, exposure light can be almost completely absorbed and photocarriers can be effectively generated, and the thickness of this layer does not need to be made thicker than necessary.

Furthermore, by setting the thickness of this layer 4c to the necessary minimum based on the above, the electric field applied to the photoconductive layer 4c and the surface layer 4d due to the bias voltage during image formation can be reduced even at a low bias voltage. Since the height is sufficiently high, good image formation can be performed.

[0032] In the present invention, in order to enhance the effect of static elimination after transfer, an erasing static elimination light may be used. It is preferable to use light whose wavelength is longer than that of the above-mentioned exposure light source as the erasing static-eliminating light. This makes it easier for light to reach directly beneath the surface layer 4d, allowing efficient erasing.

Next, a typical layer structure of the photoreceptor 2 used in the present invention is shown in FIG. 10, and will be specifically described with reference to the same figure.

[0034] The materials constituting the translucent support 3 include:
Examples include Pyrex glass, soda glass, borosilicate glass, etc., inorganic materials such as quartz and sapphire, and heat-resistant organic resin materials such as fluororesin, polyester, polycarbonate, polyethylene terephthalate, and epoxy.

Materials constituting the transparent conductive layer 4a include indium tin oxide (ITO), tin oxide, lead oxide, indium oxide, copper iodide, etc. A thin metal layer made of thinned Al, Ni, Au, etc. may also be used. The layer formation method includes vacuum evaporation method,
Active reactive vapor deposition method, RF sputtering method, DC sputtering method, RF magnetron sputtering method, DC magnetron sputtering method, thermal CVD method, plasma C
Examples include the VD method, spray method, coating method, and dipping method.

When the surface of the photoreceptor 2 comes into contact with the developer while a bias voltage is applied, the carrier injection blocking layer 4b
By preventing the injection of carriers from the transparent conductive layer 4a to the a-Si photoconductive layer 4c, image noise can be removed.
To improve image quality by increasing electrostatic contrast between exposed and unexposed areas, and to reduce background fog during development.

This layer 4b is preferably an insulating layer, but a high resistance layer or an a-Si based p-type or n-type semiconductor layer can also be used instead. Here, the insulating layer refers to a layer that has an extremely high volume resistivity and has the property of blocking the movement of both positive and negative charges within the layer. Furthermore, a high-resistance layer refers to a layer whose volume resistivity is smaller than that of an insulating layer but larger than that of a photoconductive layer. In particular, a material having a property of blocking the movement of charges of one polarity but allowing the movement of charges of the other polarity within the layer is preferable for photoreceptors.

This layer 4b has electrical properties that prevent the injection of carriers from the transparent conductive layer 4a, and also has a transparent property so as not to absorb light for image exposure from the side of the transparent support 3. (large optical band gap or high light transmittance), and has good adhesion to the transparent conductive layer 4a and the a-Si photoconductive layer 4c, and has a high adhesion to the a-Si photoconductive layer 4c. It must have the property of not causing major deterioration even when heated during formation.

The insulating layer used for this layer 4b is made of insulating amorphous silicon carbide (a-SiCX).
), amorphous silicon oxide (a-SiOX
), amorphous silicon nitride (a-SiNX
), a-SiC・O, a-SiC・N, a-SiO・
N, a-Si type insulating layer such as a-SiC・O・N, polyethylene terephthalate, parylene, polytetrafluoroethylene, polyimide, polyfluoroethylene propylene, urethane resin, epoxy resin, polyester resin, polycarbonate resin, acetic acid It is preferable to use cellulose resin or other organic insulating layer. In forming an a-Si-based insulating layer, it is also possible to use a material in which the content of C, N, O, etc. is varied in the layer thickness direction.

Further, when a high resistance layer is used as this layer 4b, especially a-SiCX, a-SiOX, a-
A-Si based high resistance layers such as SiNX, a-SiO.N, a-SiC.O.N. (N)
It is formed by reducing the content of or adjusting the film forming conditions as appropriate. In addition, when an a-Si based p-type or n-type semiconductor layer is used as this layer 4b, it is necessary to increase the optical band gap compared to the a-Si based photoconductive layer 4c or to improve the adhesion. In order to increase the resistance, elements such as C, O, and N are contained, and further, an impurity element is contained in order to prevent injection of carriers from the transparent conductive layer 4a. That is, in order to prevent the injection of negative charge carriers, the periodic table IIIa
Group elements (hereinafter, Group IIIa elements of the periodic table are abbreviated as Group IIIa elements) from 1 to 10,000 ppm, preferably 1
00 to 5,000 ppm, and on the other hand, in order to prevent the injection of positive charge carriers, Va
Group elements (hereinafter, Group Va elements of the periodic table are abbreviated as Group Va elements) at 5,000 ppm or less, preferably 300 to 3,
It is preferable to contain 000 ppm. These elements may have a gradient in the layer thickness direction, and in that case, the average content of the entire layer may be within the above range.

When a group IIIa element is contained in this manner, a positive developing bias is used, whereas when a group Va element is contained, a negative developing bias is used.

Here, as group IIIa elements and group Va elements, element B and element P, respectively, have excellent covalent bonding properties and can sensitively change semiconductor properties, and are said to have excellent injection blocking ability. desirable in that respect.

The thickness of such carrier injection blocking layer 4b, high resistance layer, or semiconductor layer is preferably in the range of 0.01 to 5 μm, preferably 0.1 to 3 μm, so that good injection blocking ability can be achieved. It is easy to secure, and unnecessary absorption of exposure light in this layer 4b can be suppressed, photocarriers can be effectively generated in the a-Si photoconductive layer 4c, and increase in residual potential can be suppressed.

The a-Si photoconductive layer 4c is formed by, for example, a glow discharge decomposition method, a sputtering method, an ECR method, a vapor deposition method, etc., and when it is formed, hydrogen (H) or a halogen element is added to terminate the dangling bond. Contain up to 40 atom%. In addition, in order to obtain desired electrical properties such as dark conductivity and photoconductivity, and optical band gap of this layer, group IIIa elements and Va group elements may be contained, C, N, O, etc. It is preferable to contain the following elements. In particular, when a-SiC is used for the photoconductive layer 4c, Si1
-X The X value of CX is 0<X≦0.5, preferably 0.
It is preferable to set it in the range of 05≦X≦0.45, and this range is desirable because it has a higher resistance than the a-Si layer and can ensure good carrier travel. II
Group Ia elements and Group Va elements include B element and P element, respectively.
It is desirable because the element has excellent covalent bonding properties and can sensitively change semiconductor properties, and also because excellent photosensitivity properties can be obtained.

Furthermore, if a layer region with an enhanced photocarrier generation function and a layer region with a carrier transport function are laminated in the a-Si photoconductive layer 4c, the photosensitivity and It is possible to improve both electrostatic contrast and withstand voltage.

At this time, in order to increase the generation of photocarriers in the photoexcitation layer region, the conditions during film formation are (1) formed at a low film formation rate, and (2) increased dilution rate with H2 or He. , (3) It is preferable to contain a larger amount of the element to be doped than the transport layer.

Further, the carrier transport layer region mainly has the role of increasing the withstand voltage of the photoreceptor 2 and allowing carriers injected from the excitation layer region to travel smoothly to the surface of the photoreceptor 2, but in this layer region, Also, carriers are generated by the light transmitted through the photoexcitation layer region, contributing to the photosensitivity of the photoreceptor 2.

Furthermore, when the a-Si photoconductive layer 4c is formed by laminating a photoexcitation layer region and a transport layer region, the thickness of the photoexcitation layer region is set to be approximately equal to the above absorption depth. That's good.

The a-SiC surface layer 4d is formed by the same thin film forming means as the a-Si photoconductive layer 4b. When forming the bond, hydrogen (H) or a halogen element is added to terminate the dangling bond. In addition, in order to obtain desired electrical properties such as dark conductivity and photoconductivity, and optical band gap of this layer 4d, I
It is preferable to contain a group IIa element or a group Va element, or to contain elements such as N and O.

A-S having photoconductivity as the surface layer 4d
By using iC, adhesion to the a-Si photoconductive layer 4c is good, and properties such as abrasion resistance and environmental resistance are also improved, allowing stable image formation over a long period of time.

When a-SiCX is used for both the surface layer 4d and the a-Si photoconductive layer 4c, the surface layer 4d contains a larger amount of C than the amount of C contained in the photoconductive layer 4c. The amount of C in this surface layer 4d is 0.05≦X<0.6, preferably 0.1≦X, as the X value of Si1-X CX
A range of ≦0.5 is preferable. Further, a gradient may be formed in the amount of C within this layer 4d, or in addition to C, N, O, G
The adhesion, environmental resistance, and photoconductivity can be further improved by incorporating e.g.

The thickness of the surface layer 4d may be 0.05 to 5 μm, preferably 0.1 to 3 μm. If the thickness is less than 0.05 μm, this layer 4d can sufficiently improve the dielectric strength and
It is not possible to effectively trap photocarriers to contribute to the formation of toner images and improve image density, and when used repeatedly, the lifespan is shortened due to wear. If it exceeds 5 μm, the electric field (lines of electric force) in this layer 4d will spread in the direction of the film surface when forming a fine charge pattern, resulting in a decrease in resolution and making it impossible to obtain sufficient resolution. do not have. Further, since a large amount of charge remains in the layer 4d, problems such as a decrease in image density, background fog, and changes in image density during repeated use occur.

[0053] The overall thickness of the photoreceptor layer thus obtained depends on the above settings, but when an LED or EL is used as the exposure light source, it is approximately 1 to 15 μm, preferably 1 to 5 μm.
Within this range, exposure light is sufficiently absorbed to exhibit good photosensitivity, and the withstand voltage as a photoreceptor can be ensured, and good images can be obtained with a low bias voltage.

As described above, according to the present invention, the exposure and absorption region of the a-Si photoconductive layer 4c is limited, thereby forming a layer region with a large dark resistance value, and thereby forming an image in which a good image can be obtained. I was able to suggest a method.

In addition to the above configuration, the present invention may be modified as follows.

For example, in the above explanation of the operation, we have described the case where a positive voltage is used as the developing bias voltage, but even when a negative voltage is used, the polarity of the charge will simply be opposite to the above explanation, and there will be no problem at all. Image formation is performed using a similar principle.

Further, although the LED head 5 is used as the exposure means, an EL head, a fluorescent print head, a plasma image bar, a laser, a liquid crystal shutter, a ferroelectric shutter, etc. may also be used. Furthermore, the erase light source 8 also has an LE
In addition to the D array, light sources such as halogen lamps, fluorescent lamps, and EL arrays can be used.

Next, the present inventors have found a desirable developing means for the above operation, and will explain this with reference to FIG.

This figure is an explanatory diagram showing a developer reservoir 17 formed by a part of the photoreceptor 2 and the developing device 6.

The developing device 6 that holds the developer consists of a conductive sleeve 10 and a magnetic pole roller 9 disposed inside the sleeve 10. The developer is transported by fixing the magnetic pole roller 9 and rotating the sleeve 10. Alternatively, the sleeve 10 may be fixed and the internal magnetic pole roller 9 may be rotated.

When the developer is rotated in the opposite direction to the photoreceptor 2, a developer pool 17 is generated on the downstream side (the side where the developer leaves) of the closest portion between the developer 6 and the photoreceptor 2. The developer reservoir 17 is a portion separated by a broken line in the figure. That is, the part of the developer that protrudes from the original height is the developer reservoir 17, and the conveyance speed of the developer, the height of the developer, the gap between the sleeve 10 and the surface of the photoreceptor 2, etc.
It is set appropriately depending on the rotational speed of the developer reservoir 17 and the required size of the developer reservoir 17.

Note that when the photoreceptor 2 and the developer are rotated in opposite directions, a developer pool 17 is generated downstream of the closest portion between the developing device 6 and the photoreceptor 2, and the developer is transferred to the photoreceptor. The developer is more stable and has higher reproducibility than the case where the developer is rotated in the same direction as the photoreceptor 2 and the circumferential speed of the developer is made larger than the circumferential speed of the photoreceptor 2. Therefore, in order to stably obtain the developer reservoir 17 with good reproducibility, it is preferable to rotate the photoreceptor 2 and the developer in opposite directions.

Reference numeral 18 denotes a control electrode, which is provided on the sleeve 10 at a location closest to the photoreceptor 2, and is insulated from the sleeve 10 with an insulator 19. Control electrode 1
8, so that a uniform electric field is applied to the photoreceptor 2 and the developer.
The sleeve 10 is shaped like a band along its length.

It is preferable to provide a voltage applying means 20 for setting the potential of the control electrode 18 independently of the potential of the developing device 6.

For example, a conductive magnetic toner is used as the developer, which forms the magnetic brush 12 and the developer reservoir 17, and may be a one-component developer as long as it has the necessary conductivity. A two-component developer may be used in which a carrier and an insulating toner are mixed at a predetermined mixing ratio to obtain the required conductivity.

The image exposure position is not the closest position A between the surface of the photoreceptor 2 and the developing sleeve 10, but the position B of the developer reservoir 17 formed on the downstream side by rotating the photoreceptor 2 in the opposite direction. Preferably, it is located in the latter half of the developer reservoir 17 on the downstream side. By performing exposure at the position of the developer reservoir 17, the application of the developing bias voltage to the photoconductor 2 is sufficiently stabilized before exposure, the influence of the history of the photoconductor 2 is suppressed, and the The residual toner 16 on the surface and the toner in the background of the image are sufficiently collected. Furthermore, since exposure is performed to generate photocarriers after the application of the developing bias voltage to the photoreceptor 2 is sufficiently stable, the surface layer 4
Since the charge is efficiently transferred to d and the electric field formed across the surface layer 4d becomes sufficiently large, the electric attraction between the toner and the photoreceptor 2 is strong, resulting in a good toner image 14.
is formed. After the toner image 14 is formed, the photoreceptor 2 quickly leaves the developer reservoir 17, so the photoreceptor 2
The toner image 14 on the surface of the toner image 14 is not disturbed by mechanical forces such as developer collisions or friction, and a toner image 14 with good resolution can be obtained.

Furthermore, at the position of the developer reservoir 17, the distance between the surface of the photoreceptor 2 and the magnetic pole roller 9 is greater than at position A, where the surface of the photoreceptor 2 and the developing sleeve 10 are closest. Therefore, the magnetic force that attracts the developer toward the magnetic pole roller 9 becomes weaker, and a portion of the residual toner 16 formed on the surface of the photoreceptor 2 is collected toward the developing device 6 by the magnetic force, resulting in a decrease in image density. It is possible to prevent the resolution from being degraded due to the disturbance caused by the magnetic force.

Furthermore, a strip-shaped control electrode 18 is provided, and its potential is adjusted to a predetermined potential by a voltage applying means 20. For example, the control electrode 18 is grounded to have a common potential with the transparent conductive layer 4a. Alternatively, the potential is set lower or higher than the potential of the sleeve 10.

By providing the control electrode 18 that can apply a potential independently of the sleeve 10 in this manner, the surface charge remaining on the photoreceptor 2 is neutralized through the developer, or the surface charge of the photoreceptor 2 is It is possible to equalize the potentials and cancel the influence of the history of the photoreceptor 2 due to the previous image forming process. As a result, during repeated use, for example, when the photoreceptor 2 is rotated several times to obtain one image, A stable developing state and recorded image can be obtained.

Here, when the potential of the control electrode 18 is adjusted,
Optimum image forming conditions for image density, background fog, etc. can be adjusted. Furthermore, although the mechanism is not clear at present, in the image evaluation experiments conducted by the present inventors, by increasing the potential of the control electrode 18 and lowering the potential of the sleeve 10, toner adheres to the non-exposed area. However, so-called reversal development, in which toner does not adhere to the exposed areas, has also become possible.

Next, each example will be described in detail.

(Example 1) An ITO layer with a thickness of 1000 Å was formed as a transparent conductive layer 4a on the outer peripheral surface of a transparent cylindrical glass substrate by active reaction vapor deposition, and then capacitively coupled glow discharge decomposition was performed on the ITO layer. Using an apparatus, the a-SiC insulating injection blocking layer 4b, the a-Si photoconductive layer 4c, and the photoconductive a-SiC surface layer 4d were sequentially laminated under the film-forming conditions shown in Table 1.
Photoreceptor A was produced. At this time, the thickness of the a-Si photoconductive layer 4c is 660 nm, which is the wavelength of the LED used for the exposure light source 15.
0 from approximately 2.2 μm, which is the thickness that absorbs 90% of the light of m
．． It was set to 2.4 μm thick by 2 μm.

[0073]

[Table 1]

This photoreceptor A is mounted on an image forming apparatus as shown in FIG.
A developing bias voltage Vs = +30 V is applied between the photoreceptor a, image exposure is performed under conditions of a wavelength of 660 nm and an exposure amount of 0.5 μJ/cm2, a toner image is formed on the photoreceptor, and the toner image is recorded. The image was transferred to paper and heat-fixed to obtain an image.

When this image was evaluated, it was found that the image had an optical density (hereinafter referred to as O.D.) of 1.3 and had good resolution without background fog.

[0076] Even if image formation is repeated,
No influence of previous history such as afterimages or changes in image density was observed, and good image evaluation results were obtained.

(Example 2) In producing photoreceptor A, a
-The thickness of the Si photoconductive layer 4c is set to 666 nm, the wavelength of the LED of the light source.
Photoreceptor B was prepared with a thickness of 1.5 μm, which is smaller than about 2.2 μm, which absorbs 90% of 0 nm light.

This photoreceptor B was installed in the image forming apparatus having the configuration shown in FIG. 1 in the same manner as in (Example 1), and the bias voltage was set to +20V so that the electric field of the photoreceptor layer was the same, and the other conditions were the same. When image evaluation was performed, it was found that photocarriers were not sufficiently generated and the image density was O. D. It was 0.8, which was insufficient.

(Example 3) In producing photoreceptor A, a
-The thickness of the Si photoconductive layer 4c is set to 666 nm, the wavelength of the LED of the light source.
15 from the thickness of approximately 2.2 μm, which absorbs 90% of 0 nm light.
A photoreceptor C was fabricated with a diameter larger than 17 μm.

This photoreceptor C was installed in the image forming apparatus having the configuration shown in FIG. 1 in the same manner as in (Example 1), and the bias voltage was set to +200 V so that the electric field of the photoreceptor layer was the same, and the other conditions were the same. When the image was evaluated, the image density was O. D.
At 1.2, images with generally good background fog and resolution were obtained.

However, when image evaluation was performed under the same conditions with a bias voltage of +100V, a sufficient electric field was not obtained in the surface layer 4d to form a toner image, and the image density was O. D. The image quality was as low as 0.9.

(Example 4) In producing photoreceptor A, a
A photoreceptor D was produced in the same manner except that the -SiC insulating injection blocking layer 4b was not formed.

When this photoreceptor D was installed in the image forming apparatus having the configuration shown in FIG. 1 in the same manner as in (Example 1) and the image was evaluated under the same conditions as in (Example 1), it was found that the background of the image was slightly fogged. The results were slightly inferior to those of photoreceptor A.

(Example 5) In producing photoreceptor A, a
In place of the -SiC insulating injection blocking layer 4b, an insulating layer made of polyimide and having a thickness of 0.2 μm was formed by a coating and drying method. Furthermore, using a capacitively coupled glow discharge decomposition device, an a-Si photoconductive layer 4c and a photoconductive a-SiC surface layer 4d similar to (Example 1) are sequentially laminated thereon to form a photoreceptor E. was created.

When this photoreceptor E was installed in an image forming apparatus having the configuration shown in FIG. 1 and image evaluation was performed under the same conditions as in Example 1, O. D. The image had an image density of 1.3, had no background fog, and had good resolution.

(Example 6) In producing photoreceptor A, photoconductive a-SiC surface layer 4d was not laminated and the other conditions were the same as those for photoreceptor A.
Photoreceptor F without d was produced.

When this photoreceptor F was installed in an image forming apparatus having the configuration shown in FIG. 1 and image evaluation was performed under the same conditions as in Example 1, it was found that the potential contrast was insufficient and the image density was low.
The image had noticeable background fog, and the results were inferior to those of photoreceptor A. Furthermore, the durability against repeated use was poor, and image defects due to surface abrasion and insufficient withstand voltage were observed after several hundred images were formed.

(Example 7) In producing photoreceptor A, a photoconductive a-SiC surface layer 4d was formed as shown in Table 2, and the other conditions were the same as those for photoreceptor A. was created.

[0089]

[Table 2]

This photoreceptor G was mounted on an image forming apparatus as shown in FIG. 1, and the image was evaluated under the same conditions as in Example 1. D. The image density was 1.3, and the image had good resolution and no background fog.

[0091] Even if image formation is repeated,
Similar to photoreceptor A, no influence of previous history such as afterimage or change in image density was observed, and good image evaluation results were obtained.

In the image forming methods shown in (Example 1) and (Example 7), the control electrode 18 is removed and the control electrode voltage V
When an image forming method was carried out under the same conditions except that E was not applied, some fogging occurred on the back, although it was within a practically usable range.

Furthermore, in the same image forming methods shown in (Example 1) and (Example 7), when the image was formed while irradiating the erase light using the erase light source 8, the photoreceptor before image formation was The condition was stable, and images of good image quality were stably obtained.

[0094]

Effects of the Invention According to the image forming method of the present invention, a-S
By laminating a photoconductive SiC surface layer on the i-based photoconductive layer, photocarriers are temporarily trapped directly under the surface layer region corresponding to the brightly exposed area, and the photocarriers cause the surface insulating layer to Since the toner can be attached to the surface of the photoreceptor by the electric field generated between the toner and the toner, the image density can be increased, good toner image formation can be performed, and an erase step can be made unnecessary.

In addition, compared to the case where the surface layer is an insulating layer, the volume resistance is small enough to have photoconductivity, so carriers trapped across the surface layer during the time from image formation to transfer. Because the toners combine and neutralize each other through the surface layer, toner transfer to the recording paper becomes easier, and
This made it possible to eliminate the need for an erase process.

Further, according to the image forming method of the present invention, a
- The thickness of the Si-based photoconductive layer is set to 0.1 in the light absorption layer region that absorbs 90% of the light determined from the absorption coefficient for the wavelength of light.
By adding a thickness of ~10.0 μm, it was possible to almost completely absorb exposure light and effectively generate photocarriers. By setting the thickness of the a-Si photoconductive layer to the necessary minimum value set above, the voltage applied to the photoconductive layer by the bias voltage during image formation becomes sufficiently high even at a low bias voltage. Good image formation can be performed.

In the conventional photoreceptor equipped with an a-Si type photoconductive layer, in addition to the low film formation rate,
μm layer thickness is required, which requires a manufacturing time of 8 to 10 hours, which significantly increases manufacturing costs.In contrast, according to the image forming method of the present invention, a-Si photoconductive The thickness of the layer only needs to be 2 to 3 μm, and by forming such a very thin layer, the manufacturing time can be shortened and the manufacturing cost can be reduced.

Furthermore, in the conventional image forming method using the Carlson method, corona charging is performed, which generates ozone, and moreover, Se-based photoconductive layers are often used, which has an adverse effect on the human body. However, according to the present invention, ozone is not generated and harmless a-Si is used.
Since a layer is used, there is no problem in terms of environmental pollution.

Furthermore, in the image forming method of the present invention,
Since the light source can be installed inside the drum-shaped photoreceptor, and the erasing and cleaning processes can be omitted, there is no need for associated installation materials, and as a result, it is possible to use multiple devices such as fax machines, printers, digital copiers, etc. It has become possible to realize an ultra-compact device with advanced functions.

Furthermore, according to the image forming method of the present invention, a carrier injection blocking layer is formed between the light-transmitting conductive layer and the a-Si photoconductive layer, so that light-transmitting is prevented during image formation. Since injection of carriers from the photoconductive layer to the a-Si photoconductive layer can be prevented, the electrostatic contrast between the exposed and non-exposed areas can be increased to improve image density, and the background during development can be prevented. It was possible to reduce fog.

Furthermore, according to the image forming method of the present invention, residual toner can be efficiently reused, fog on the background of an image can be reduced, and a good image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an image forming apparatus using an electrophotographic method according to the present invention.

FIG. 2 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 3 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 4 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 5 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 6 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 7 is a schematic diagram showing the operating principle of the electrophotographic method according to the present invention.

FIG. 8 is a configuration diagram of main parts of the image forming method of the present invention.

FIG. 9 is a diagram showing the depth of light absorption versus wavelength.

FIG. 10 is a cross-sectional view showing the layer structure of a photoreceptor according to the present invention.

[Explanation of symbols]

2 Photoreceptor 5 LED head 6 Developing device 7 Transfer roller 8 Light source for erasing 4a Translucent conductive layer 4b Carrier injection blocking layer 4c Photoconductive layer 4d Surface layer

Claims (6)

[Claims] 1. A photoreceptor comprising a light-transmitting conductive layer, a carrier injection blocking layer, an amorphous silicon-based photoconductive layer, and a photoconductive amorphous silicon carbide surface layer sequentially laminated on a light-transmitting support; While applying a developing bias voltage through the magnetic toner, the light-transmitting support is exposed to light of a predetermined wavelength that is substantially absorbed below the layer thickness of the photoconductive layer to form a layer immediately below the surface layer. The photocarriers are collected in a region corresponding to the bright part of the photoreceptor, and then the toner is attached to the surface of the photoreceptor by an electric field generated by the photocarriers across the surface layer, and then the charges of the photocarrier and the toner are neutralized. An image forming method characterized in that the toner is transferred to recording paper. 2. The image forming method according to claim 1, wherein the next image formation is performed without a cleaning step after the transfer. 3. The image forming method according to claim 1, wherein the next image formation is performed without passing through the step of irradiating the photoconductive layer with light to erase photocarriers remaining directly under the surface layer after the transfer. 4. A developing device for applying a developing bias voltage is provided to face the surface layer of the photoreceptor, and a potential independent of the developing bias voltage is provided between the developing device and the surface layer. The image forming method according to claim 1, further comprising a control electrode. 5. The amorphous silicon-based photoconductive layer comprises:
2. The image forming method according to claim 1, wherein the layer thickness is the sum of the thickness of the light-absorbing layer region whose absorption coefficient of the layer is determined with respect to the wavelength of the exposure, plus a layer region having a thickness of 0.1 to 10.0 μm. Method. 6. The image forming method according to claim 1, wherein the amorphous silicon carbide surface layer has a layer thickness of 0.05 to 5 μm.