JPH06227024A - Electrostatic recording apparatus - Google Patents

Abstract

PURPOSE:To record stably a recording image with a high density without decreasing resolution. CONSTITUTION:An electrode EL' is provided on the whole face of a development sleeve 15 in the main scanning direction by keeping a specified interval from the development sleeve 15 and a cylindrical electrode 6 on the upstream side in the development agent carrying direction of a recording electrode EL. In addition, an electric voltage is applied on each recording electrode EL in accordance with the recording information on a part of one writing period in the sub-scanning direction of the development sleeve 15 and the development agent is selectively transferred to a cylindrical electrode 6 and a recording image is formed on the development agent transferred on the whole face of the main scanning direction by means of the electrode EL' and a recovery voltage is applied on each recording electrode EL during the remaining period of one writing period in the sub-scanning direction and the development agent transferred on the whole face of the cylindrical electrode 6 and a part of the selectively transferred development agent are recovered on the recording electrode EL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic recording apparatus for transferring a developer conveyed along a predetermined path to a recording medium in accordance with recording information to form a recorded image.

[0002]

2. Description of the Related Art Conventionally, as one of electrostatic recording devices,
A multi-stylus that arranges a large number of needle-shaped electrodes (stylus) at minute intervals, selectively applies a voltage to each needle-shaped electrode according to an image signal, and discharges directly on paper to form an electrostatic latent image. Printers are known.

In such a multi-stylus printer,
If the distance between the tip of the needle electrode and the surface of the paper is wide, the discharge electric field spreads and the dots formed become large, making it difficult to obtain a high-resolution recorded image. Therefore, a special paper having a gap layer on the surface of the paper is used, and the gap layer and the needle-shaped electrode are brought into sliding contact with each other to secure a minute gap.
However, this multi-stylus printer has a drawback in that the needle electrode is worn because the paper is always in sliding contact with the tip of the needle electrode.

Therefore, an electrostatic recording device which can use plain paper has been devised. This electrostatic recording apparatus is a system in which a cylindrical counter electrode is used as an intermediate recording medium, and a toner image is formed on the counter electrode and transferred onto a sheet. In the case of this method, the size of the apparatus tends to increase due to the use of the intermediate recording medium. Therefore, in general, a process of simultaneously performing recording and development is adopted to avoid the size increase of the apparatus. That is, the recording electrodes are arranged in parallel in the width direction (main scanning direction) of the developer transport path, and the developer is selectively transferred from the recording electrodes onto the surface of the counter electrode according to recording information to form a toner image. At this time, in order to improve the resolution of the toner image formed on the surface of the counter electrode, the distance between the recording electrode and the counter electrode must be made as narrow as possible.

[0005]

However, in the above-mentioned conventional electrostatic recording apparatus, the amount of the developer passing through is small because the gap between the recording electrode and the counter electrode is small,
There is a problem that a high density image cannot be obtained.

The electrostatic recording apparatus of the present invention has been made in view of such a problem, and provides an electrostatic recording apparatus capable of stably recording a high-density recorded image without lowering the resolution. To do.

[0007]

In order to achieve the above object, an electrostatic recording apparatus of the present invention has a developer carrying member laid along a predetermined path and a surface of the developer carrying member. Of the developer carrying member, a plurality of recording electrodes arranged in parallel on the surface of the developer carrying member at intervals, a counter electrode arranged to face the recording electrode, and a recording electrode of the recording electrode. On the upstream side in the developer carrying direction, an electrode provided on the entire surface of the developer carrying member in the main scanning direction at a predetermined distance from the developer carrying member and the counter electrode, and carried along the surface of the developer carrying member. A first power source for applying a voltage to the electrode to transfer the developer to the entire surface of the counter electrode in the main scanning direction, and a part of one writing cycle of the developer carrying member in the sub scanning direction. A voltage is applied to the recording electrode according to recorded information. While applying a voltage, the developer carried along the surface of the developer carrying member is selectively transferred to the counter electrode side to form a recorded image on the developer transferred to the entire surface in the main scanning direction, A recovery voltage is applied to each of the recording electrodes during the rest of one writing cycle in the sub-scanning direction, and the developer transferred to the entire surface of the counter electrode and a part of the selectively transferred developer are partially transferred. And a second power source for recovering to the recording electrode.

[0008]

That is, in the electrostatic recording apparatus of the present invention,
In addition to the recording electrode, an electrode is provided on the entire surface of the developer carrying member in the main scanning direction at a predetermined distance from the developer carrying member and the counter electrode upstream of the recording electrode in the developer carrying direction. Then, a voltage is applied to each recording electrode in accordance with recording information in a part of one writing cycle of the developer carrying member in the sub-scanning direction,
The developer carried along the surface of the developer carrying member is selectively transferred to the counter electrode side, and a recorded image is formed on the developer transferred to the entire surface in the main scanning direction by the electrode. , A recovery voltage is applied to each of the recording electrodes during the remaining period of one writing cycle in the sub-scanning direction to remove the developer transferred to the entire surface of the counter electrode and a part of the selectively transferred developer. The recording electrodes are recovered.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic sectional view showing the overall construction of an electrostatic recording apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 is a paper feed cassette in which plain papers P are stacked and stored,
It is attached to the side of the machine so that it can be inserted and removed freely. A paper feed roller 2 is disposed above the leading end of the attached paper feed cassette 1 so as to be rotatable in the arrow direction. A standby roll pair 3 is arranged in front of the paper feed roller 2, and after temporarily stopping the progress of the paper P fed by the paper feed roller 2 to adjust the conveyance posture, the image transfer unit on the downstream side is provided. The sheet is re-fed so as to be synchronized with the arrival timing of a recording image described later to T.

A transfer roll 5 is arranged in front of the sheet conveying path 4 extending obliquely downward from the pair of standby rolls 3. A cylindrical electrode 6 as a counter electrode is arranged to face the transfer roll 5. The portions of the cylindrical electrode 6 and the transfer roll 5 that face each other on the peripheral surface serve as the image transfer portion T. As will be described later, the toner recording image is formed on the circumferential surface of the cylindrical electrode 6 and then conveyed to the image transfer portion T along with its rotation. In synchronization with this, the sheet is conveyed from the standby roll pair 3 to the image transfer portion T, so that the toner image is transferred to the transfer roll 5 and the cylindrical electrode 6.
It will be transferred onto the paper sandwiched between them.

In this embodiment, the cylindrical electrode 6 is driven and rotated in the clockwise direction indicated by arrow a. A bias power supply 6a for applying a bias voltage having the same polarity as the toner charging polarity is connected to the cylindrical electrode 6. In this embodiment, a two-component developer including a toner having a negative (-) triboelectric charging characteristic and a magnetic carrier having a positive (+) triboelectric charging characteristic is used as the developer. Therefore, a negative voltage is applied by the bias power source 6a and the voltage value is set to -50V. The cylindrical electrode 6 of this embodiment is arranged in a recording image forming unit U which is detachably attached to the machine body. The configuration of the recording image forming unit U will be described in detail later.

On the downstream side of the image transfer section T, an air suction type conveyor belt 7 is horizontally stretched. A fixing device 8 is disposed in front of the downstream side of the conveyor belt 7.
The fixing device 8 of this embodiment includes a heating roll 8a and a pressure contact roll 8b.
The toner image is heat-fixed when the paper is nipped and conveyed between the rolls 8a and 8b. The sheet of paper which has been fixed is discharged and stacked on the discharge tray 10 in a face-down state with the image side facing down from the discharge port 9. Here, the detailed configuration of the recording image forming unit U will be described with reference to FIG.

The recording image forming unit U generally comprises the above-mentioned cylindrical electrode 6, a toner storage tank 11 for storing the replenishment toner t0, and a development recording tank 12 having a recording means and a developer conveying means. Inside the toner storage tank 11, the stirring blade 1
1a is rotatably arranged. The stirring blade 11a stirs the stored replenishment toner t0 to prevent aggregation. A toner supply port Os is formed at the boundary between the toner storage tank 11 and the development recording tank 12, and a toner supply roll 13 is installed at this toner supply port Os. The toner replenishing roll 13 is rotated according to the toner concentration of the developer d flowing in the developing and recording tank 12, and replenishes the replenishment toner t0 into the developing and recording tank 12 by an appropriate amount. As a result, the toner concentration of the developer d in the development recording tank 12 is controlled within the proper range. The developer is not limited to a two-component developer, and a one-component developer such as a magnetic toner composed of an insulating resin, magnetic fine powder and colorant particles can also be used. In this case, the toner density control as described above becomes unnecessary.

At the bottom of the developing and recording tank 12, two auger rolls 14a and 14b are installed so as to extend parallel to each other in the direction perpendicular to the paper surface. These auger rolls 14a, 14b
Are rotated in the opposite directions B and C, respectively, and circulate and flow the developer d in the horizontal direction while stirring. In the present embodiment, the size of the stirring blades of both auger rolls 14a and 14b is made different, and a large stirring blade auger roll 14a is disposed below the toner replenishing roll 13.

A developing sleeve 15 as a developer carrying member for forming a vertical conveying path for the developer is installed horizontally extending diagonally above the auger roll 14b of the small stirring blade. Inside the developing sleeve 15, a magnet roll 16 as a developer carrying means is rotatably mounted inside. Different magnetic poles are alternately magnetized on the circumferential surface of the magnet roll 16, and by rotating the magnet roll 16 in the clockwise direction indicated by the arrow D,
The developer d is conveyed in the direction indicated by the arrow E along the peripheral surface of the developing sleeve 15.

Thus, the developing sleeve 15 is arranged in parallel and opposite to the cylindrical electrode 6 described above. In this case, the both are arranged from the vertical normal line r of the developing sleeve 15 to the toner conveying direction E. The arrangement is such that the center of the cylindrical electrode 6 is located on the normal line r'rotated upstream by the central angle of the developing sleeve 15 by the angle θ. Therefore, the peripheral surface of the cylindrical electrode 6 is closest to the developer carrying path formed along the peripheral surface of the developing sleeve 15 on the normal line r '. The position where the peripheral surface of the cylindrical electrode 6 is closest to the developer transport path is the recording portion W for forming a toner recording image as described later.

As described above, by setting the recording portion W at the position inclined by the angle θ to the upstream side, the amount of the developer retained on the upstream side of the recording portion without providing the developer conveyance restricting member is as follows. Then, it can be automatically controlled to a substantially constant proper amount.

The amount of the developer d conveyed on the developer conveying path along the developer conveying direction E is regulated in the vicinity of the upstream side of the recording portion W where the developer conveying path is narrowed. As a result, among the developer d whose progress is regulated, those in the area near the surface of the developing sleeve 15 where the magnetic force of the magnet roll 16 is sufficiently circulate as shown by the arrow in that area,
When the magnet roll 16 has moved to a region where the magnetic force hardly reaches, the auger roll 14 is moved by pressure as shown by the arrow G.
fall on b. In this case, when the amount of the developer regulated to be conveyed increases, the amount of the developer that flows and returns as shown by the arrow G naturally increases, and the amount of staying developer is automatically controlled to a substantially constant appropriate amount. It As a result, it is possible to easily and surely prevent the generation of the immobile developer without performing a troublesome operation such as adjusting the posture of the regulating member. Further, the amount of the developer carried into the recording portion W can be properly regulated without providing a unique developer transport regulation member. Therefore, the cost for installing the developer transport restricting member such as the doctor blade is reduced and simplification of the structure is promoted.

On the peripheral surface of the developing sleeve 15 on the downstream side of the recording portion W, a scraping plate 17 is erected vertically with its tip abutting against the peripheral surface of the developing sleeve 15. Due to the scraping plate 17, the residual developer d'not used in the recording section W is circulated horizontally at the bottom of the developing and recording tank 12.
It is scraped up.

A recording electrode sheet 18 having a large number of recording electrodes formed in parallel at one end is laid on the peripheral surface of the developing sleeve 15 on the upstream side from the recording portion W. As shown in FIG. 3, the recording electrode sheet 18 has a large number of recording electrode wires 18a having recording electrodes EL at the tips thereof extending parallel to each other in the sheet longitudinal direction along the circumferential direction of the peripheral surface of the developing sleeve 15. At the same time, they are arranged in parallel in the sheet width direction (main scanning direction) at a predetermined fine pitch. In this case, the number of recording electrode lines 18a, that is, the number of recording electrodes EL corresponds to the maximum number of data for one main scanning line. The recording electrode sheet 18 of this embodiment is a flexible printed circuit board (FPC).
The recording electrode lines 18a (recording electrodes EL) made of a large number of non-magnetic conductive materials are arranged on the base film 18b made of a flexible insulating material with a spacing of 40 μm.
It is laid at a density of 4.6 μm pitch (300 DPI). An insulating protective coat (not shown) is applied to the surface of the recording electrode sheet 18 except for the tip end region. The tip portion of the recording electrode wire 18a which is not covered with the insulating protective coat serves as the recording electrode EL.

A plurality of LSIs 19 as electrode driving circuit elements (second power source) are mounted on the end portion of the recording electrode sheet 18 opposite to the recording electrode forming side. A plurality of recording electrode wires 18a are separately connected to the plurality of LSIs 19 and connected to each other. Each LSI 19 is connected to a recording control unit (not shown) that controls the entire recording operation of the electrostatic recording apparatus of this embodiment. The recording control unit sends a recording signal corresponding to the recording information to the LSI 19, and also selectively sends an instruction signal for carrying out cleaning of untransferred toner, which will be described later, during non-recording in which no recording signal is sent.

As shown in FIG. 4, flat portions 15a, 15b and 15c are formed on the peripheral surface of the developing sleeve 15 at three locations on the recording portion W and upstream and downstream sides thereof. The end of the recording electrode sheet 18 on which the recording electrode EL is formed is projected in a curved shape above the area of the substantially half upstream side of the plane portion 15a of the recording portion W.
In this embodiment, an electrode EL ′ is provided on the entire surface of the developing sleeve 15 in the main scanning direction at a predetermined distance from the developing sleeve 15 and the cylindrical electrode 6, on the upstream side of the recording electrode EL in the developer conveying direction. .

The protruding end portion of the recording electrode sheet 18 is laid on a spring plate member (not shown) curved to have substantially the same curvature as the peripheral surface of the developing sleeve 15. As a result, the recording electrode E
Since L is elastically supported in the hollow, the developer d can be flexibly held in the minute gap of the recording portion W formed by the peripheral surface of the cylindrical electrode 6. In the recording portion W, the tip of the recording electrode EL is lightly pressed against the cylindrical electrode 6, but it may be set to a minute gap that allows the toner to pass through.

On the flat surface portion 15b on the upstream side of the recording portion W, the end portion of the recording electrode sheet 18 on which the LSI 19 is mounted is laid. In this way, L on the peripheral surface of the developing sleeve 15
By forming the flat portion 15b for SI installation, the LS
Installation of I19 becomes easy. Then, on the recording electrode sheet 18 and the LSI 19 laid on the flat portion 15b,
A cover film 20 made of a non-magnetic material is covered with a curved surface having substantially the same curvature as the peripheral surface of the developing sleeve 15. As a result, the surface of the cover film 20 serves as a developer transport path, and it is possible to prevent the LSI 19 from being damaged by friction with the developer or the like. Further, since the cover film 20 is bent and installed in an arc shape, the developer can be smoothly moved along the surface thereof. Instead of covering the cover film 20, the surface of the recording electrode sheet 18 may be coated with a non-magnetic material. The recording electrode line portion that connects the recording electrode EL and the LSI 19 of the electrode driving circuit element serves as a connecting member that constitutes an electrode driving means with the electrode driving circuit element.

By disposing the electrode driving circuit element of the recording electrode EL on the peripheral surface of the developing sleeve 15 as described above,
The connecting member can be made as short as possible. That is, the recording electrode line connecting the recording electrode EL and the LSI 19 can be short. From these, not only is the recording electrode sheet 18 small and inexpensive, but the so-called antenna effect due to the recording electrode wire is also reduced, making it less susceptible to noise. As a result, it is possible to stably form a recorded image that accurately corresponds to the recorded information. Further, by disposing the electrode driving circuit element on the upstream side of the recording electrode EL, the recording electrode EL is configured to project in the forward direction (trailing direction) with respect to the rotation direction of the cylindrical electrode 6, so that the recording electrode EL is formed.
Will not be damaged.

The flat portion 15c on the downstream side of the recording portion W is formed in order to quickly convey the residual developer d'which is carried out without being transferred to the cylindrical electrode 6 in the recording portion W to the downstream side.
By cutting off the peripheral surface portion of the developing sleeve 15 to form the flat surface portion 15c, the developer conveying path (the surface of the flat surface portion 15c) becomes closer to the magnet roll 16 as compared with the case where it is not formed, and the magnet roll 16 has a corresponding portion. The magnetic force increases and the carrying force increases. Therefore, the residual developer d ′ can be quickly carried out from the recording portion W, and the toner recording image formed on the circumferential surface of the cylindrical electrode 6 is not disturbed by the residual developer d ′. Hereinafter, a conventional recording image forming operation including only the recording electrodes EL will be described.

In FIG. 2, when the magnet roll 16 is driven to rotate in the direction of arrow E, a rotating magnetic field for rotating the magnetic carrier particles in the developer d is formed on the outer peripheral surface of the developing sleeve 15. The rotating magnetic field attracts the developer d circulating and flowing in the horizontal direction at the bottom of the developing recording tank 12 to the peripheral surface side of the developing sleeve 15, and the cover film 20.
It is conveyed in the counterclockwise direction e opposite to the rotating direction of the magnet roll 16 while forming the top.

In FIG. 4, the amount of the developer d conveyed upward along the surface of the cover film 20 is regulated on the upstream side of the recording portion W where the peripheral surface of the cylindrical electrode 6 is close and the conveying path is narrowed. To form a developer pool Rt. And
The developer particles that have moved far from the developer transport path (the surface of the recording electrode sheet 18) within the regulated developer are separated from the magnetic field of the magnet roll 16 and naturally fall to the bottom of the development recording tank 12 as indicated by an arrow G. . As a result, the developer pool Rt
The amount of the developer forming the toner is automatically controlled to an appropriate amount, and the generation of the immobile developer is reliably prevented. Further, the amount of the developer carried into the recording portion W is properly controlled, and a proper amount of the developer particles is smoothly carried into the minute gap between the elastically supported recording electrode EL and the circumferential surface of the cylindrical electrode 6 and is flexibly held. It As a result, the developer is excessively compacted in the recording portion W and the recording electrode EL
It is possible to prevent the problem of fusing on the surface of the cylindrical electrode 6 and stably form a high-resolution recorded image having a sufficient image density on the circumferential surface of the cylindrical electrode 6 in the following manner.

That is, in the recording portion W, the peripheral surface of the cylindrical electrode 6 is rotationally moved with respect to the recording electrode EL while maintaining a minute gap, and the developer d is carried into the minute gap in an appropriate amount as described above. . In this recording unit W, each recording electrode EL
On the other hand, the LSI 19 of the electrode drive circuit element, that is, the second power source selectively applies the recording voltage according to the recording data. In this case, the 1-bit recording data is, for example, "H".
At this time, the corresponding recording electrode EL is -20 in this embodiment.
A voltage of 0 V (ON voltage) is applied. A bias voltage of -50 V is applied to the cylindrical electrode 6 facing the recording electrode EL by the bias power supply 6a in this embodiment. Therefore, from the circumferential surface of the cylindrical electrode 6 toward the recording electrode EL, 15
An electric field is formed based on the potential difference of 0V. The ears of the developer d pass through the recording portion W in which such an electric field is formed while contacting the peripheral surface of the cylindrical electrode 6. At this time, since the negatively charged toner particles move to a higher potential,
Only the toner particles on the recording electrode EL to which the ON voltage of −200 V is applied are selectively transferred onto the circumferential surface of the cylindrical electrode 6 to form one black dot.

On the other hand, when the 1-bit recording data is "L", the voltage applied to the recording electrode EL by the LSI 19 is switched to the ground potential (off voltage) side. As a result, the potential difference seen from the cylindrical electrode 6 to the recording electrode EL at the ground potential is −50 V, and the toner particles of negative polarity are recorded on the recording electrode E.
It is retained on the L side and does not transfer. In this way
Soil is surely prevented from occurring.

As described above, the potential of each recording electrode EL is selectively controlled to -200 V and the ground potential according to the input recording data, and the toner recording image is formed on the surface of the cylindrical electrode 6 in the recording portion W. In order to adjust the density of the toner recording image, the bias voltage of the bias power source 6a may be changed. In that case, an appropriate adjustment range is about 0 to -50V, and the closer to 0V, the higher the image density.

In the recording portion W, the developer not transferred to the cylindrical electrode 6 side and remaining on the recording electrode EL side drops onto the downstream surface of the flat portion 15a immediately after the toner recording image is formed. The residual developer d'is transported to the downstream flat surface portion 15c by the rotating magnetic field described above. Since the surface of the downstream flat surface portion 15c is formed close to the magnet roll 16, a strong rotating magnetic field is formed on the surface thereof compared to the developer transport path on the upstream side of the recording portion such as the surface of the cover film 20. The residual developer d'has been carried out is promptly carried out to the downstream side. Therefore, the residual developer d'is left in the immediately downstream portion of the recording portion W, so that the toner recording image on the circumferential surface of the cylindrical electrode 6 is not disturbed.

In FIG. 1, the toner recording image formed on the surface of the cylindrical electrode 6 is conveyed to the image transfer portion T along with the rotation of the cylindrical electrode 6 in the counterclockwise direction (a), and the timing is measured by the standby roll pair 3 here. And is transferred onto the paper that is re-fed. The untransferred toner that has not been transferred and remains on the circumferential surface of the cylindrical electrode 6 is returned to the recording portion W again as the cylindrical electrode 6 rotates. The untransferred toner remaining on the circumferential surface of the cylindrical electrode 6 is removed from the circumferential surface of the cylindrical electrode 6 by the scraping effect of the developer circulating and flowing in the developer pool Rt.

As described above, since the untransferred toner is removed and the cleaning is surely performed on the circumferential surface of the cylindrical electrode 6 and the recording operation is performed again after the untransferred toner is removed, there is no image defect such as an afterimage due to defective cleaning. A high quality recorded image is stably formed. Further, since the entire recording means including the recording electrode EL, the LSI 19 as the electrode driving means for the electrode, and the recording electrode wire 18a that is a connecting member for the recording electrode EL is provided on the upstream side of the recording portion W, the formed recorded image is recorded from the time of recording. It is not disturbed by the cleaning electric field when shifting to the non-recording time.

The residual developer d ′ discharged and conveyed downstream from the recording section W is developed by the scraping plate 17 into the developing sleeve 15.
It is scraped off from the peripheral surface and dropped back to the bottom of the development recording tank 12. The residual developer d ′ returned is the auger roll 1
The developer d, which circulates and flows in the horizontal direction as the 4a and 14b rotate, is agitated and mixed. The above is the conventional image forming operation, but the image forming operation in consideration of the features of the present embodiment will be described below in comparison with the conventional one.

5A and 5B, the recording portion W is cut along the sub-scanning direction in order to explain the image forming operation when only the recording electrodes EL are taken into consideration as in the prior art. It is a schematic explanatory view shown. In this case, in order to improve the cutting of the trailing edge of the toner image transferred to the cylindrical electrode 6, a part of the transferred toner is collected on the recording electrode EL side. However, in order to improve the resolution, the recording electrode EL and the cylindrical electrode 6 are in contact with each other with a light pressure or are arranged to face each other at an extremely narrow interval. Therefore, only a small amount of developer is conveyed between the recording electrode EL and the cylindrical electrode 6, and it is difficult to obtain a sufficient image density by transferring the developer by the operation of only the recording electrode EL.

In order to solve this problem, in the first embodiment of the present invention, as shown in FIG. 4, in addition to the recording electrode EL, the developing sleeve 15 and the cylinder are provided on the upstream side of the recording electrode EL in the developer carrying direction. An electrode EL 'is provided on the entire surface of the developing sleeve 15 in the main scanning direction at a predetermined distance from the electrode 6. That is, since the gap f is provided between the recording electrode sheet 18 and the electrode EL ′, the developer d can pass not only on the electrode EL ′ but also through the gap f. Therefore, on the recording electrode EL, not only the remaining developer whose density has been lowered by the entire transfer of the toner by the electrode EL ′, but also the new developer that has been conveyed through the gap f is conveyed.

A voltage as shown in FIG. 7 is applied to the recording electrode EL and the electrode EL ', that is, the first voltage is applied to the electrode EL'.
V ₁ is constantly applied by the power source E ₁ of the recording electrode EL
Applied in accordance with the V ₂ is recorded information by LSI19 as a second power source to. In this embodiment, as described above, since the toner of negative polarity is used, the recording electrode E
By applying a negative voltage to L, for example, V ₂ = −200V, the toner is transferred to the cylindrical electrode 6 side. And
When not applied (GND), the bias voltage (−50 V) of the bias power supply 6a collects the toner transferred to the cylindrical electrode 6 on the recording electrode EL side.

First, as shown in FIG. 7, a negative voltage V ₁ is continuously applied to the electrode EL ′ to transfer the toner of the developer supplied to the entire surface of the cylindrical electrode 6 in the main scanning direction (see FIG. 6 (a)). Next, at the time of image formation, a negative voltage V ₂ (ON voltage of −200 V) as shown in FIG. 7 is selectively applied to the recording electrodes EL in accordance with recording data in a part (t _on ) of one writing cycle T _w . Is applied. As a result, the toner is selectively transferred to the cylindrical electrode 6 side. In this case, the recording electrode E
Not only the remaining developer whose density has been lowered by the entire transfer of toner but also the new developer is conveyed to L through the gap f, so that a recorded image having a higher toner density than in the conventional case is obtained by the cylindrical electrode 6 Is formed on the toner transferred to the entire surface (FIG. 6B). Then, in the remaining period (t _off ) of one writing cycle T _w , a part of the developer and the selectively transferred toner are transferred to the entire surface of the recording electrode EL side by the off voltage having V ₂ as GND. It collects and improves the disconnection of the image in the sub-scanning direction (FIG. 6C).

That is, in this embodiment, solid printing is first performed with the electrode EL '(FIG. 6A). Next, a high density image is formed by the recording electrode EL. When the image formation at that time is viewed dot by dot, the dots to which the pulse voltage is applied to the recording electrodes EL are further printed on the dots printed by the electrodes EL ′ (FIG. 6B). or,
In the dot where the pulse voltage is not applied to the recording electrode EL, that is, in the non-recording dot portion, by setting V ₂ to GND, a part of the toner transferred by the electrode EL ′ and the recording electrode EL ′ is collected on the recording electrode EL side. Yes (off in Figure 7
Part). According to the above embodiment, as shown in FIG. 8, it is possible to form an image with higher density without lowering the resolution as compared with the conventional image.

FIG. 9 is a diagram showing a second embodiment of the present invention. In this embodiment, as in the first embodiment of FIG. 4, a gap f is provided between the recording electrode sheet 18 and the electrode EL ′, and the shape of the electrode EL ′ is an inverted V shape with a raised central portion. In order to uniformly secure the minute gap g, both ends are curved along the counter electrode 6 toward the downstream side in the developer transport direction.
Here, the gap g is large enough to pass the toner (10 μm) but not the carrier (20 μm).

FIG. 10 is a perspective view of FIG. 9, and FIG. 11 is a view of FIG. 10 seen from the upstream side in the developer transport direction on the recording electrode EL. As shown in the figure, the electrode EL 'has a tapered surface which is an inclined surface extending leftward and rightward with the protrusion P as the apex.

The image forming operation is the same as that of the first embodiment, but in this embodiment, the size of the gap g is such that the carrier cannot pass therethrough, so that it is conveyed onto the recording electrode EL through the gap f. Only new developer coming is supplied. More specifically, when the developer is transported to the vicinity of the electrode EL ′, only the toner passes through the gap g and is used for the entire transfer by the electrode EL ′. Depending on the shape of the carrying direction E, the gap g, and the electrode EL ', the carrying is carried out in the direction of A in FIG.
That is, in FIG. 11, the carrier is conveyed in two left and right directions along the tapered surface provided separately from the protrusion P in the left and right directions, and is returned to the scraping plate 17 through the groove 21.

In this embodiment, as in the first embodiment, the developer whose concentration has been lowered by the entire surface transfer by the electrode EL 'is not conveyed onto the recording electrode EL but is supplied through the gap f to a new development. Since the recorded image is formed only by the agent, it is possible to form a recorded image having a higher density than that of the first embodiment.

[0046]

As described above in detail, according to the electrostatic recording apparatus of the present invention, the main scanning of the developer carrying member is maintained at a predetermined distance from the developer carrying member and the counter electrode in addition to the recording electrode. Since an electrode is provided on the entire surface in the direction, and the entire surface of the developer is transferred by this electrode, the recording image is formed by the recording electrode. Therefore, it is possible to stably record a high-density recorded image without lowering the resolution.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the overall configuration of an electrostatic recording device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of a recording image forming unit U and its peripheral portion of the electrostatic recording device shown in FIG.

FIG. 3 is a perspective view showing a configuration of a recording electrode sheet and its peripheral portion.

FIG. 4 is a schematic cross-sectional view of the periphery of the recording unit according to the first embodiment.

FIG. 5 is a diagram for explaining a conventional image forming operation.

FIG. 6 is a diagram for explaining an image forming operation of the present invention.

FIG. 7 is a diagram showing waveforms of voltages applied to an electrode EL ′ and a recording electrode EL.

FIG. 8 is a diagram showing a comparison between the conventional method and the present embodiment regarding the image density.

FIG. 9 is a schematic cross-sectional view of the periphery of a recording unit according to a second example.

FIG. 10 is a perspective view of FIG. 9.

11 is a diagram of FIG. 10 viewed from the upstream side in the developer transport direction on the recording electrode.

[Explanation of symbols]

6 ... Cylindrical electrode, 15 ... Developing sleeve, 16 ... Magnet roll, 19 ... Electrode drive circuit element (second power supply), EL
... recording electrode, EL '... electrode, E ₁ ... first power supply.

Claims (1)

[Claims] 1. A developer carrying member laid along a predetermined path, a developer carrying means for carrying a developer along the surface of the developer carrying member, and a gap on the surface of the developer carrying member. A plurality of recording electrodes arranged in parallel with each other, a counter electrode arranged to face the recording electrode, and a predetermined distance from the developer carrying member and the counter electrode on the upstream side of the recording electrode in the developer transport direction. An electrode provided while being provided on the entire surface of the developer carrying member in the main scanning direction, and a voltage for transferring the developer carried along the surface of the developer carrying member to the entire surface of the counter electrode in the main scanning direction. A first power source to be applied to the electrodes, and a voltage is applied to each of the recording electrodes according to recording information in a part of one writing cycle of the developer carrying member in the sub-scanning direction,
The developer conveyed along the surface of the developer carrying member is selectively transferred to the counter electrode side to form a recorded image on the developer transferred to the entire surface in the main scanning direction, and the sub scanning is performed. A recovery voltage is applied to each of the recording electrodes for the rest of one writing cycle in the direction, and the developer transferred to the entire surface of the counter electrode and a part of the selectively transferred developer are transferred to the recording electrodes. An electrostatic recording device, comprising: a second power supply for collecting.