JPH0527610A - Image forming method - Google Patents

Abstract

PURPOSE:To miniaturize and lighten a transfer unit by performing an electrostatic transfer with a comparatively small transfer bias. CONSTITUTION:In a photosensitive body 11 on which an image is repeatedly formed, a stripe-like control electrode 23 which is divided in arbitrary length in a subscanning direction where the photosensitive body 11 is driven, and can be independently controlled, is provided. While electrification, an image exposure, and development are executed on the photosensitive body 11, the control electrode 23 and a transparent conductive layer 15 have the same potential, and the image is developed with toner 23. At the time of transferring, a voltage having the same polarity as that of the bias voltage of a transfer roll 69 is applied on the control electrode, and the transfer is performed while the electrification of the photosensitive body 11 is erased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using an electrophotographic method, which is used in printers, digital copying machines, facsimiles, copying machines and the like.

[0002]

2. Description of the Related Art An electrophotographic method represented by the Carlson method is widely used at present, in which uniform charging of a photosensitive member → formation of a latent image by selective exposure → formation of a toner image by a developer →
The basic process is transfer → fixing. For example,
Book "Basics and Applications of Electrophotographic Technology", edited by The Institute of Electrophotography,
It is described in detail in June 15, 1988, published by Corona Publishing Co., Ltd.

On the other hand, various reports have recently been made on a non-Carlson image forming method which employs the backside exposure recording method, and it is said that the apparatus can be downsized and the process can be simplified. Journal, 16, (5),
306, (1987), JP-A-61-149968, JP-A-63-10071, and JP-A-63-214781.
Issue).

The backside exposure recording system is a method in which toner is supplied to the surface side of a photoconductor to form a toner pool, and the toner pool is used for uniform charging of the photoconductor-rear image exposure-simultaneous development. (Signal) exposure and development can be performed simultaneously.

The conventional photoconductors used for image formation have a basic structure in which, for example, a conductive layer is formed on a substrate, and a photoconductive layer is further provided on the conductive layer. The latent image is formed by utilizing the difference in surface potential. Since the conductive layer which is the back electrode is uniformly formed on the substrate, the potential of the conductive layer is always constant.

By the way, the photosensitive member is sequentially transferred to the charging-image exposure-developing-transfer-erase areas and is processed by each peripheral device in each of these areas. The electrical characteristics are not always uniform. For example, in the above-described image forming system by back exposure, in the charging / exposure / developing area, charges are injected into the photoconductor through the developer to uniformly charge the surface of the photoconductor, and an electrostatic latent image is formed. It is required to have a charging characteristic in which the toner is formed and selectively retained, and the electric attraction force conveys the toner image to the transfer area without destroying the toner image. On the other hand, in the transfer area, the electrostatic charge on the surface of the photoconductor has disappeared due to the need to transfer the toner to the paper by overcoming the electric attraction force and the Van der Waals force acting between the photoconductor surface and the toner. Also, it is necessary to erase the surface of the photoreceptor after the transfer for the next image forming operation. Therefore, if it is possible to control the charging characteristics by controlling the potential of the conductive layer according to the processing region where a specific photoconductor surface exists, it becomes possible to perform more strict control of each processing step, and also to control peripheral devices. The characteristics required for the device are reduced to that extent, and the device can be downsized.

However, in the conventional photoconductor as described above, since the conductive layer as the back electrode is uniformly formed, it is a principle to control the potential of the conductive layer according to each processing region in this way. Is impossible.

Therefore, conventionally, the characteristics of each step in image formation have been improved by improving the performance of peripheral devices.

However, there is a limit to the improvement of this characteristic. For example, there is an electrostatic transfer system using a bias roller or the like. The bias roller transfer guides the transfer paper between the photoconductor having the toner image and the bias roller, and applies a voltage having a polarity opposite to the charging of the toner from the back surface of the transfer paper,
This is a method of electrostatically attracting toner to paper. Therefore, it is desirable that the adsorption force between the toner and the photoconductor is weak,
This is determined exclusively by the electrostatic latent image forming process and the developing process, and there is no method to improve the transfer efficiency other than increasing the bias voltage of the bias roller. Further, this is also limited depending on the type of transfer paper due to its insulating property.

Regarding the provision of stripe-shaped electrodes on the photoconductive layer, Japanese Patent Publication Nos. 2-7055 and 2-19791 disclose the first method through the photoconductive layer.
And a second striped electrode are provided so as to intersect with each other without contact,
Further, it is described that an isolated conductor is provided above the intersection and an image is formed by image exposure or by applying a voltage corresponding to the image between the first and second electrodes.

However, this image forming method does not describe at all that the photoconductor can be independently controlled according to its sub-scanning direction, and is completely different in technical concept from the present invention. is there.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the transfer efficiency of toner in a transfer process, and to make the transfer member compact and lightweight.

[0013]

In the image forming method of the present invention, a photoconductor having an image forming photoconductive layer on a conductive substrate is used, and an electrostatic latent image formed on the surface of the photoconductor is developed with toner. In the image forming method in which toner is adhered to the surface of the photoconductor by electrostatically attracting the adhered toner by a transfer member to which a voltage is applied and is transferred onto the transfer material, the subscanning direction in which the photoconductor is driven is changed. It is characterized in that a photosensitive member having a control electrode that can be independently controlled by dividing it into arbitrary lengths is used, and a voltage having the same polarity as that of the transfer member is applied to the control electrode during transfer.

[0014]

EXAMPLE FIG. 1 is a perspective view showing an example of a photosensitive member used in the present invention, in which a control electrode 23 is formed in a non-image forming area.
Illustration of the extraction electrode 25 formed in FIG. The photoconductor 11 is used by being rotated in the direction of arrow R, and processing operations such as image signal exposure and development are sequentially performed in the main scanning direction. In the present invention, the direction intersecting (orthogonal to) the main scanning direction, that is, the driving direction of the photoconductor is called the sub-scanning direction.

FIG. 2 is a cross-sectional view in the main scanning direction showing the layer structure of the photoreceptor of FIG. 1, in which (A) shows a portion where no control electrode is formed and (B) is formed. Shows the part where FIG. 3 is a sectional view in the sub-scanning direction in the image forming area of the same photoconductor.

The photoconductor 11 of this embodiment mainly directs the backside exposure recording system, and uses a cylindrical transparent substrate 13 such as glass. A transparent conductive layer 1 made of In ₂ O ₃ , ITO or the like is formed on the substrate 13.
5 are provided uniformly. A carrier injection blocking layer 21 is provided on the transparent conductive layer 15. A control electrode 23 is embedded in the carrier injection blocking layer 21, the carrier injection blocking layer 21 is interposed between the control electrode 23 and the transparent conductive layer 15, and the two do not directly contact each other.

The control electrode 23 is a striped electrode extending in the main scanning direction of the photoconductor 11 from the image forming area to the non-image forming area.
It is made of the same transparent conductive material as the transparent conductive layer 15. It should be noted that the illustration is for the sake of convenience, and the control electrode 23 has better control characteristics as the stripe width is narrower and the interval is narrower. The control electrode 23 is exposed from the carrier injection blocking layer 21 in the non-image forming area, and the extraction electrode 25 made of a conductor is formed in this portion and is extracted to the outside. An electric signal is supplied to the control electrode 23 by the extraction electrode 25 coming into contact with an external terminal (not shown).

The photoconductive layer 1 is formed on the carrier injection blocking layer 21.
7 and the surface protection layer 19 are formed. The photoconductor 11 from which the control electrode 23 is removed is exactly the same as the conventional photoconductor.

Next, an example of manufacturing the photoconductor shown in FIGS. (1) Cylindrical glass substrate 13 (30 mmφ, 1.6
In ₂ O ₃ is deposited on the (mmt) by a sputtering method to form a transparent conductive layer 15 having a thickness of 1 μm.

(2) As the carrier injection blocking layer 21,
1 μm of a-Si: H: B: O: N by sputtering
m to form a film.

(3) By the lift-off method, the interval is 10 μm.
A control electrode 23 pattern of In ₂ O ₃ having a width of 10 μm and a thickness of 0.1 μm is formed.

(4) The gap of the control electrode 23 is filled with a-Si: H: B: O: N by the lift-off method.

(5) a-S by sputtering method
A carrier injection blocking layer 21 is completed by forming a film of i: H: B: O: N with a thickness of 0.5 μm.

(6) a-S by sputtering method
A film of i: H is formed to form a photoconductive layer 17 having a thickness of 10 μm.

(7) A-Si: C is deposited by a sputtering method to form a surface protective layer 19 having a thickness of 0.5 μm.

(8) The extraction electrode 25 made of gold is formed on the control electrode 23 in the non-image forming area by the lift-off method.
To form.

In the above description, the control electrode 23 has a stripe shape, and the stripe control electrode 23 is clearly partitioned by another material (carrier injection blocking layer) in the sub-scanning direction. This is not necessary. That is, a (transparent) conductive layer is formed over the entire surface direction to form a layered control electrode, and the specific resistance of this electrode layer may have anisotropic conductivity in the sub-scanning direction higher than in the main scanning direction. . As a result, the sub-scanning direction can be selected with an arbitrary width (length), and an electric signal can be supplied to the entire image forming area in the main scanning direction in units of this width.

FIG. 4 is a partial perspective view showing another embodiment of the photoconductor used in the present invention, showing a non-image forming area. For convenience of illustration, the photoconductor 11 is developed in a plane. Further, FIG. 5 is a sectional view in the main scanning direction corresponding to FIG. 2 described above.

This embodiment is the same as the photosensitive member shown in FIGS. 1 to 3 except for the vicinity of the extraction electrode 25 in the non-image forming area. An auxiliary extraction electrode 27 made of a conductor is provided on the control electrode 23 in the non-image forming area, and an extraction electrode 25 is provided in a non-contact state with the auxiliary extraction electrode 27. The auxiliary extraction electrode 27 and the extraction electrode 25 are connected by a control photoconductive layer 29. Whether or not each control electrode 23 is electrically connected to the outside through the extraction electrode 25 is determined by irradiating the control photoconductive layer 29 with light and converting the control photoconductive layer 29 into a conductor. You can choose. It is also possible to omit the auxiliary extraction electrode 27 and directly couple the control electrode 23 and the extraction electrode 25 with the control photoconductive layer 29.

FIG. 6 is a perspective view corresponding to FIG. 4 showing another embodiment of the photosensitive member used in the present invention. 4, except that the extraction electrode 25 is continuous in the sub-scanning direction.
This is the same as the photoconductor shown in FIG. Individual control electrode 25
Can be controlled by the control photoconductive layer 29. According to this configuration, the structure of the extraction electrode 25 is simplified,
There is no need for a fine processing technique to form it, and further, for example, only a ring-shaped metal member may be fitted to the photoconductor 11, and it is easy to contact an external terminal and there is no problem in strength.

FIG. 7 is a perspective view corresponding to FIGS. 4 and 6 showing another photosensitive member used in the present invention. The auxiliary extraction electrode 29 is omitted, and the control photoconductive layer 29 is also extracted as the extraction electrode 25.
The structure is the same as that of FIG. 6 except that it is continuous in the sub-scanning direction in the same manner as. Since only the control photoconductive layer 29 in the portion irradiated with light is made conductive, the control electrodes 25 can be individually selected and controlled.

FIG. 8 is a general explanatory view of an image forming method by the backside exposure recording method. A transparent conductive layer 15 and a photoconductive layer 17 are formed on a hollow cylindrical substrate 13 such as glass to form a drum-shaped photoreceptor 11.

Inside the cylindrical substrate 13, that is, the photoreceptor 1.
An LED array 51 serving as an image signal exposure device is arranged on the back side of 1, and back exposure is performed via a condensing element 53 (selfoc lens).

A developing unit 55, a transfer roller 69 (transfer member), a cleaning blade 75, and fixing rollers 71 and 73 are provided around the photosensitive drum 11.

The developing unit 55 includes a mag roller 57 having several magnetic poles (N and S poles) enclosed by a conductive sleeve 59, and a doctor blade 61 for regulating the toner layer thickness. The toner 63 is conveyed to the surface of the photoconductor 11 by rotating the mag roller 57 or the sleeve 59 or both, and the toner 63 forms a toner pool 65 between the photoconductor 11 and the sleeve 59. Photoconductive layer 1 through conductive toner
The charge injection into 7, the back exposure and the simultaneous development are performed.

When forming an image, the conductive sleeve 5 is used.
A developing bias voltage is applied to 9. When the photoconductive layer 17 contacts the toner 63 in the toner pool 65, the toner 6
Charges are injected into the photoconductive layer 17 via the third layer 3. The photoconductive layer 17 has a signal exposure position by the LED array 51,
The toner pool 65 needs to be charged to a voltage required for development.

When the image signal is selectively exposed by the LED array 51, the potential of the photoconductive layer 17 in the exposed portion is lowered to generate a potential difference, and the toner 63 is selectively attached onto the photoconductive layer 17. Then, the photoconductive layer 17 and the toner pool 65
When the toner layer is separated, the developed toner 63 remains selectively on the photoconductive layer 17 without being disturbed, and a toner image is formed on the surface of the photoconductor 11.

Next, the toner image (toner 63) is
By the transfer roller 69 to which the bias voltage is applied, the paper 8
1 (transferred material), and the fixing roller 7 heated
1 is heat-fixed to form an image. Reference numeral 73 represents a pressure roller.

On the other hand, the photoconductor 11 on which the toner 63 has been transferred and removed further rotates, the residual toner is removed by the cleaning blade 75, and the erase exposure (not shown) is performed.
Thus, the surface charge is removed and the state returns to the initial state and the image formation is performed again.

In such an image forming method, the photosensitive member 11 is subjected to various treatments, but the transparent conductive layer 15 which should be called the back electrode of the photosensitive member 11 is continuous. Therefore, the photosensitive member is subjected to each treatment process. The conventional image forming method cannot be controlled from the 11 side. The control of each processing process depends exclusively on the peripheral devices arranged around the photoconductor 11, that is, the exposure device, the charging device, the developing device, and the transfer device.

On the other hand, in the image forming method of the present invention,
As the auxiliary control means, a photoconductor having a control electrode 23 that can be independently controlled by dividing the sub-scanning direction into arbitrary lengths is used. By controlling the photoconductor 11 in each processing process, transfer characteristics or Further, the erase characteristic and the developing characteristic can be improved, and further, other processes such as formation of the electrostatic latent image (exposure process) are not adversely affected.

FIG. 9 is a perspective view of the periphery of the photoconductor for explaining the image forming method of the present invention. However, in reality, as shown in FIG. 8, the sleeve 59 (developing roller) and the photoconductor 11 face each other with a gap, and the toner reservoir 6 is provided between them.
5 is formed. Further, the transfer paper 81 is guided between the photoconductor 11 and the transfer roller 69. In addition, the extraction electrode 25
Are not shown.

FIG. 10A is an explanatory view showing an embodiment of the present invention, in which the photoconductor 11 is developed on a plane and the main scanning direction is seen from the non-image forming area side. FIG. 10B is a side view thereof. Further, FIG. 11 is an explanatory diagram similar to FIG. 10A, but for the purpose of showing the charged state, only the control electrode 23 is shown from the sub-scanning direction.
As the photoconductor 11, the photoconductor shown in FIGS. The basic process operation other than the use of the auxiliary control electrode 23 is the same as that described with reference to FIG. Further, FIG. 12 shows changes in the potential of the control electrode 23 with respect to the transparent conductive layer 15 in each processing zone for image formation.

The transparent conductive layer 15, which is the back electrode of the photoconductive layer 17, is evenly provided over the entire surface of the photoconductive layer 17, so that the transparent conductive layer 15 can be located in any processing zone. The potential of 17 is constant and is grounded in this embodiment. On the other hand, since the control electrode 23 is divided in the sub-scanning direction, it can be controlled depending on where it is located in the processing zone. 9 and 10
As shown in FIG. 4, when the photoconductor 11 rotates in the direction of arrow R and comes to be positioned in the charging zone and the exposure / development zone, those control electrodes 23 are fixed to the first fixed zone.
It makes electrical contact with the external terminal 31. When the photoconductor 11 further rotates to reach the transfer zone, the control electrode 23 makes electrical contact with the fixed second external terminal 33. Since these external terminals 31 and 33 are electrically insulated from each other, different external signals can be applied to the control electrode 23 depending on the position where the photoconductor 11 (control electrode 23) is present. As shown, the potential on the transparent conductive layer 15 can be changed. This state will be specifically described with reference to FIG.

When the photoconductor 11 is in the charging zone and the exposure / development zone, the first external terminal 31 is grounded and the control electrode 21 has the same potential as the transparent conductive layer 15. Therefore,
The control electrode 23 does not adversely affect the charging characteristic, the electrostatic latent image forming characteristic, and the developing characteristic, and the toner image is formed as described with reference to FIG. In addition, as shown by the one-dot chain line in FIG.
A voltage having the same polarity as the developing bias voltage applied from the developing unit (voltage having the same polarity as the charging polarity of the toner) is applied to the control electrode 23 for a short time immediately before the development is completed, and the unexposed portion (latent image) It is also possible to separate the toner 63 of the non-forming portion). At this time, the third external terminal is provided. As a result, the toner separation characteristic of the non-image portion is improved, and the quality can be improved.

When the photoconductor 11 is further rotated, the control electrode 23 starts to contact the second external terminal 33 immediately before the transfer zone. A voltage having the same polarity as that of the transfer roller 69 is applied between the control electrode 23 and the transparent conductive layer 15 from the second external terminal 33 to form a charge pair. As a result, the electric charge between the toner 63 attached to the image portion and the photoconductive layer 17 begins to be neutralized, and the play race is performed.

Further, in the transfer zone, the transfer sheet passes between the toner image formed on the photoconductor 11 and the transfer roller 69 at the same speed as the peripheral speed of the photoconductor 11, and the toner 63 is attached. The toner 63 is transferred by overcoming the Coulomb force of the photoconductor 11 (photoelectric layer 17) that is weakening over time. Thus, in the transfer,
By transferring to the transfer paper 81 while playing race,
The transfer efficiency can be improved with a relatively small transfer bias voltage.

For a while after the transfer, the control electrode 23 is set to the second
When the electric field given by the transfer roller 69 and the control electrode 23 does not reach the external terminal 33 continuously, and the transfer ends and the toner is deprived of the toner, the electric charge under the surface layer of the photoreceptor 11 is
The electric charge of the control electrode 23 suddenly becomes equal to that of the control electrode 23, and as a result, the erase ends (post erase). In this way, by performing the transfer that also serves as the erase, the erase time can be shortened, and the diameter of the photosensitive drum can be reduced.
There is no need to provide a separate erase means.

The external terminals may be provided over substantially the entire circumference of the photoconductor 11 by extending the first external terminals 31 and covering the portions other than the areas where the second external terminals 33 are provided.

Although the examples have been described above, the image forming method and the photoconductor to be used in the present invention are not limited thereto, and various modifications can be made. One example is as shown below. (1) It can be applied to ordinary Carlson processes other than the back exposure method. In this case, since the transparency of the photoreceptor is not required, the conductive layer on the substrate and the control electrode may be opaque.

(2) Corona discharge is adopted instead of bias roller transfer. (3) The material of the photoconductive layer and the shape of the photoconductor are not particularly limited, and may be a Se-based photoconductive layer or an organic-based photoconductive layer.
A belt-shaped photoreceptor may be used.

The transparent conductive layer 1 is provided uniformly.
In principle, it is possible to omit 5 and form an image only with the control electrode 23 of the present invention. But in this case,
The pitch and lines of the control electrodes 23, the control conditions (for example, the voltage of the developing roller), etc. are very difficult and unrealistic.

[0053]

According to the present invention, a control electrode that can be independently controlled by dividing the sub-scanning direction of a photoreceptor on which a repeated image forming method is performed into arbitrary lengths is provided. By applying a voltage having the same polarity as the transfer bias voltage applied by the transfer member, good transfer efficiency can be obtained with a relatively small transfer bias, and the transfer unit can be downsized.

Erase is performed at the same time as the transfer,
The erase unit can be simplified or omitted.
Therefore, it is possible to form an appropriate image with a simple and small device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a photoconductor used in the present invention.

FIG. 2 is a cross-sectional view in the main scanning direction showing an example of the layer structure of a photoconductor used in the present invention.

FIG. 3 is a cross-sectional view in the sub-scanning direction showing an example of the layer structure of the photoconductor used in the present invention.

FIG. 4 is a partial perspective view showing another embodiment of the photoconductor used in the present invention.

5 is a cross-sectional view of the photoconductor of FIG. 4 in the main scanning direction.

FIG. 6 is a partial perspective view showing another embodiment of the photoconductor used in the present invention.

FIG. 7 is a partial perspective view showing another embodiment of the photoconductor used in the present invention.

FIG. 8 is an explanatory diagram showing an example of an image forming process to which the image forming method of the present invention is applied.

FIG. 9 is a perspective view of the periphery of a photoconductor for explaining the image forming method of the present invention.

FIG. 10A is an explanatory diagram showing an example of the image forming method of the present invention. (B) is a side view of (A).

FIG. 11 is an explanatory diagram showing an operation mechanism of the image forming method of the present invention.

FIG. 12 is an explanatory diagram showing changes in the potential of the control electrode with respect to the transparent conductive layer.

[Explanation of symbols]

11 photoconductor 13 Base 15 Transparent conductive layer 17 Photoconductive layer 19 Surface protection layer 21 carrier injection blocking layer 23 Control electrodes 25 Extraction electrode 27 Auxiliary extraction electrode 29 Photoconductive layer for control 31 1st external terminal 33 Second external terminal 51 LED array 53 Condensing element 55 Development Unit 57 mag roller 59 Sleeve 61 doctor blade 63 toner 65 Toner pool 69 Transfer roller 71 fixing roller 73 Pressure roller 75 cleaning blade 81 paper

Claims (6)

[Claims] 1. A photoreceptor having an image forming photoconductive layer on a conductive substrate is used, an electrostatic latent image formed on the photoreceptor surface is developed with toner, and the toner is attached to the photoreceptor surface. In an image forming method in which toner is electrostatically attracted by a transfer member to which a voltage is applied and transferred onto a material to be transferred, the sub-scanning direction in which the photoconductor is driven can be divided into arbitrary lengths and independently controlled. An image forming method characterized in that a voltage having the same polarity as that of a transfer member is applied to a control electrode at the time of transfer using a photoconductor having a control electrode. 2. The image forming method according to claim 1, wherein at the time of forming the electrostatic latent image, the control electrode and the conductive substrate have substantially the same potential. 3. The image forming method according to claim 1, wherein a voltage having the same polarity as the charging of the toner is applied to the control electrode at the end of the development. 4. The anisotropic conductive layer according to claim 1, wherein the control electrode is an anisotropic conductive layer having a smaller specific resistance in the main scanning direction intersecting with the sub scanning direction than the specific resistance in the sub scanning direction. The image forming method described. 5. The control electrode according to claim 1, wherein the control electrode comprises a stripe-shaped electrode group which is provided intermittently in the sub-scanning direction and continuously extends in the main-scanning direction. Image forming method. 6. The image forming according to claim 4, wherein the control electrode is taken out to the outside through a control photoconductor connected to the control electrode in a portion outside the image forming area of the photoconductor. Method.