JPH0740582A - Electrostatic recording device - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize an electrostatic recording device capable of forming a recorded image having arbitrary density gradation characteristics. A magnetic sensor for detecting the positions of the magnetic poles N and S of the magnet roll 15a is provided, and the application start timing of the pulse voltage applied from the LSI 19 to the recording electrode EL is changed between the magnetic pole positions of the magnet roll 15a and output.
When the application start time of this pulse voltage is, for example, the magnetic pole point (the time when the magnetic pole N or the magnetic pole S reaches the φ position), there are gradations of density from the bright portion to the beginning of the halftone portion, and from the end of the halftone portion to the dark portion. Up to θ / 4 from the magnetic pole point, a bright part is uniformly bright and a dark part is uniformly dark, and an image with gradation in the halftone part is obtained. When shifted from the magnetic pole point by θ / 2 early, an image with no gradation from the bright part to the halftone part and from the halftone part to the dark part is obtained, and from the magnetic pole point θ ・ 3/4 If shifted early, an image can be obtained in which the bright and dark parts have gradation and the halftone part has no gradation.

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 forming a pictorial image by transferring a developer conveyed along a predetermined path to a recording medium by an electric field formed according to recording information. Is.

[0002]

2. Description of the Related Art Conventionally, a toner image is formed on an intermediate recording medium on a drum as an electrostatic recording system in which plain paper can be used and a minute gap between the image medium and the recording electrode tip can be accurately secured. A method of transferring the toner image onto a sheet is used. In the case of this method, since the intermediate recording medium is used, the device tends to be large.

Therefore, a method is adopted in which a process for simultaneously recording and developing is adopted to avoid an increase in size of the apparatus. In this method, the recording electrodes are arranged in parallel at equal intervals in the width direction (main scanning direction) at positions facing the counter electrodes that also serve as intermediate recording media in the developer transport path. Then, an electric field is formed in accordance with the recording information to be recorded on the counter electrode, and the conveyed developer is selectively electrostatically adsorbed from the recording electrode to the counter electrode side to form a recorded image of toner. is there.

As a method of transporting the developer to the electrode facing portion, a method of using a magnet roll in which N and S poles are alternately magnetized on the peripheral surface is widely used. In the case of this method, a magnetic field corresponding to the movement of the magnetic pole is formed on the developer carrying path along with the rotation of the magnet roll, and the developer is carried while forming the ears along the magnetic field. Electrostatic recording in which voltage is applied to the recording electrode for an appropriate period of time while the conveyed developer is present on the recording electrode so that linear gradation characteristics of print density are always obtained. A device has been considered (Japanese Patent Application No. 4-313503).

[0005]

However, the linear gradation control of the print density is appropriate when the gradation reproduction faithful to the input is required such as the output of CG (computer graphic) or measurement data. However, when it is required to enhance the contrast in the highlight part (bright part) and shadow part (shadow part) like portraits and landscape images, the floor should be adjusted according to such requirements. It is necessary to change the tonal characteristics.

In view of the above conventional circumstances, the present invention is to realize an electrostatic recording apparatus capable of changing the gradation characteristic of the print density depending on the part of the gradation.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a cylindrical developer carrying member made of a non-magnetic material, a magnetic roll rotatably incorporated in the developer carrying member, and a peripheral surface of the developer carrying member. It has a plurality of recording electrodes arranged side by side with an interval therebetween, and a counter electrode facing the recording electrodes, and a step is formed on the downstream side with respect to the developer transport direction of the recording electrodes, and each recording electrode is formed. A pulse voltage having a pulse width corresponding to the density recording information is applied to the electrodes, and the developer conveyed while forming the spikes in the recording portion where the recording electrode and the counter electrode face each other is rotated to the counter electrode side as the magnetic roll rotates. The present invention is applied to an electrostatic recording device that selectively transfers and forms a recorded image having density gradation.

In the electrostatic recording apparatus of the present invention, the magnetic pole detecting means for detecting the magnetic pole position on the circumferential surface of the magnetic roll, and the timing control for controlling the application start timing of the pulse voltage based on the detection signal from the magnetic pole detecting means. Means for changing the gradation characteristics by changing the application start timing of the pulse voltage between the magnetic poles of the magnetic roll by the timing control means.

[0009]

The electrostatic recording apparatus of the present invention performs density gradation recording by changing the application start timing of the pulse voltage between the magnetic poles of the magnetic roll.

Thus, when it is required to emphasize the brightness of the bright portion or the imprint portion, it is possible to easily change the linear gradation characteristic to the pictorial (pictorial) gradation characteristic. You can

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing the overall configuration of the electrostatic recording device according to the embodiment. In FIG. 1, a paper feed cassette 1 is loaded with plain paper P and stored therein, and is removably inserted into a side portion of a main body device. A paper feed roller 1a is arranged above the front end of the inserted paper feed cassette 1 so as to be rotatable in the clockwise direction indicated by the arrow. Paper feed roller 1a
In front of (in the paper feeding direction), conveyance guide plates 2a and 2b made of an insulating member are arranged.
The standby roll pair 3 is disposed between them. Standby roll pair 3
Causes the paper P fed by the paper feed roller 1a to temporarily stop its progress, adjusts the conveyance posture thereof, and re-feeds the paper P downstream in synchronization with the transfer timing of the recorded image. The image transfer portion D is provided in front of the downstream transport guide plate 2b.
Is located. In the image transfer portion D, a transfer charger 4 and a counter electrode 5 which also serves as an image carrier are arranged so as to face each other, and the counter electrode 5 is configured to be rotatable in the counterclockwise direction indicated by arrow a. The image transfer section D transfers the toner image formed on the counter electrode 5 onto the lower surface of the sheet P passing between the transfer charger 4 and the counter electrode 5. The toner image formed on the counter electrode 5 is created by the image forming unit 12 described later.

On the downstream side of the image transfer section D, an air-sucking type conveying belt 7 is stretched in a substantially horizontal direction, and conveys a sheet P while sucking it up. A fixing device 8 is disposed in front of the downstream side of the conveyor belt 7. The fixing device 8 includes a heating roll 8a and a pressure contact roll 8b.
The toner image transferred to the lower surface of the paper is thermally fixed while the paper P is sandwiched and conveyed between a and 8b. The paper P on which the toner image is heat-fixed is discharged from the discharge port 9 onto the paper discharge tray 10 in a face-down state with the image side facing down.

FIG. 3 is an enlarged perspective view of the image forming section 12 described above. As shown in the figure, the image forming section 12 is composed of a toner storage layer 12a and a development recording layer 12b. Toner is stored in the toner storage layer 12a, and a stirring member 13 for preventing the toner from aggregating is rotatably arranged (see FIG. 2). This toner storage layer 12a
The toner inside is replenished from the toner replenishing port 14 to the development recording layer 12b.

In the development recording layer 12b, the developing roll 1
Five and two auger rolls 16a and 16b extend in parallel with each other. The auger rolls 16a and 16b are
Each is equipped with a plurality of stirring blades, the auger roll 16a rotates in the direction of arrow B, and on the contrary, the auger roll 16b
Rotates in the direction of arrow C to circulate the developer d (toner and carrier) in the development recording layer 12b while stirring. As a result, the developer d causes a predetermined triboelectric charge.

The developing roll 15 is located above the auger roll 16b. The developing roll 15 includes a magnet roll 15a as a developer conveying means, a fixed sleeve 15b as a developer carrying member containing the magnet roll 15a, and a recording electrode sheet as an electrode driving means laid on the surface of the fixed sleeve 15b. It is composed of 15c.

The magnet roll 15a contained in the fixed sleeve 15b has N and S magnetic poles alternately magnetized on its peripheral surface, and at the time of image recording, the arrow of the same figure is accompanied by the rotation of a rotary shaft which will be described later. It rotates by being driven counterclockwise as indicated by D. By this rotation, a rotating magnetic field that causes the magnetic carrier particles in the developer d to rotate is formed on the outer peripheral surface of the fixed sleeve 15b. By this magnetic field, the development recording tank 12
The developer d, which circulates and flows horizontally in b, is attracted to the peripheral surface of the bottom portion of the fixed sleeve 15b, and on the conveying path formed on the cover film 20 (described later) on the peripheral surface of the fixed sleeve 15b, the developer d of the magnet roll 15a. It is conveyed upward in the clockwise direction opposite to the direction of rotation indicated by arrow d.

The recording electrode sheet 15c is provided with a base film made of a flexible insulating material, and line electrodes 17 made of a non-magnetic conductive material are juxtaposed on the base film at a predetermined fine pitch in the width direction of the base film. ing. The number of line electrodes 17 is equal to the maximum number of data for one main scanning line of the image.

The above-mentioned recording electrode sheet 15c is laid on the fixed sleeve 15b so that the recording surface of the recording portion W, which will be described later in detail, makes about 1/4 of the peripheral surface of the fixed sleeve 15b, and is provided in the scraping wall 18. It extends to the central space 18 '. Then, one end portion forms the recording portion W by the tip of the line electrode 17, and the other end portion is provided with a plurality of LSIs 19 which are large-scale integrated circuits. Except for the tip portion forming the recording portion W, a plurality of LSIs 19 are arranged. It is covered with a cover film 20. This protects the developer d carried on the fixed sleeve 15b and the recording electrode sheet 15c from contacting the LSI 19 and damaging the LSI 19.

The LSI 19 is connected to the line electrodes 17 divided into a suitable number of lines, and outputs a voltage (recording signal) according to the image data to the line electrodes 17. This wire electrode 1
The output time (application time) of the recording signal to 7 is determined by the control signal from the recording control unit described later.

FIG. 1 is an enlarged view of the recording portion W where the above-mentioned counter electrode 5 and the developing roller 15 face each other. As shown in the figure, the counter electrode 5 is disposed above the developing roll 15, and the exposed tip of the line electrode 17 on the developing roll 15 forms a recording electrode EL to face the counter electrode 5. To do. In this structure, the facing portion of the recording electrode EL and the counter electrode 5 forms the recording portion W. The counter electrode 5 is made of an aluminum pipe or the like, and a predetermined voltage is applied from the bias power source 5a.
Further, the counter electrode 5 is configured to be rotatable in the arrow A direction by the rotation of a rotation shaft (not shown). Further, a step G is formed in the recording portion W in order to make a recorded image clear.
Further, a magnetic sensor 22 as a magnetic pole position detecting means is arranged in the counter electrode 5. The position of the magnetic sensor 22 is located upstream of the distance R from the line connecting the counter electrode 5 and the center of the developing roll 15 (referred to as the vertical line O1 -O2). The magnetic sensor 22 detects the strength of the magnetic field created by the magnetic poles N and S in the rotating magnet roll 15a and outputs it to the recording controller 21.
The recording control unit 21 as the timing control unit is configured to recognize the magnetic pole position based on the detection signal output from the magnetic sensor 22 and output the control signal to the LSI 19 based on this recognition.

Next, by the electrostatic recording device having the above-mentioned structure,
A process of recording (developing) toner on the counter electrode 5 will be described. First, as shown in FIG. 4, the developer d (toner T and carrier C) adheres to the peripheral surface of the fixed sleeve 15b due to the magnetic force of the magnet roll 15a, and the fixed sleeve 1 rotates as the magnet roll 15a rotates in the direction of arrow d.
5b and the recording electrode sheet 15c are moved in the arrow E direction to reach the recording portion W. A bias power source 5a is provided on the counter electrode 5.
A bias voltage is applied to the line electrode 17 and the recording signal (voltage) applied to the line electrode 17 (recording electrode EL).
Due to the potential difference between the toner T and the carrier C, the toner T erected at the tip of the carrier C is electrostatically attracted to the counter electrode 5.

Here, by observing the conveyance state of the developer d in the recording portion W, it is confirmed that a state in which the toner T (developer d) hardly exists on the recording electrode EL periodically occurs. The cause of this phenomenon will be briefly described below.
That is, as shown in FIG. 4, the developer d is conveyed on the peripheral surface of the fixed sleeve 15b while forming the ears along the magnetic force lines H of the magnet roll 15a. Therefore, the magnetic pole N,
Alternatively, the ear of the toner T located directly above S is the fixed sleeve 1.
The ears of the toner T standing vertically from the surface of the circumference of 5b and located in the middle of the magnetic pole are in a posture substantially parallel to the surface of the fixed sleeve 15b. Then, due to the rotating magnetic field generated by the rotation of the magnet roll 15a in the arrow D direction, the ears of the toner T rotate and move in the arrow E direction opposite to that while rotating. And
In this example, as described above, in order to improve the sharpness at the front and rear ends of the dot in the sub-scanning direction, the position of the step G (the tip of the recording electrode EL) is shifted from the vertical line O1-O2 by the distance R to the upstream side in the developer conveying direction. There is. As shown in the figure, in the magnet roll 15a, any magnetic pole thereof, for example, the magnetic pole N1 is a vertical line O1.
When the magnetic pole is arranged at a position rotated by an angle φ from the position on −O2, the spikes of the toner T on the recording electrode EL are moved to the counter electrode 5
Assuming that the position of the magnetic pole N1 that stands upright with respect to the peripheral surface is φ, if the magnet roll 15a rotates by an angle half the central angle θ between the magnetic poles from the above-described phase, as shown in FIG. The ears of the toner T on the EL are laid substantially parallel to the peripheral surface of the counter electrode 5 (in a tangential direction. The ears of the toner T in this lying state are strongly attracted to the magnetic pole S2 adjacent to the rear side, and Since the step G is formed immediately downstream of the recording electrode EL, most of the ears of the sleeping toner T drop from above the recording electrode EL to the lower surface of the step G. As a result, the toner T is left on the recording electrode EL. The state in which the toner T is almost absent does not recover until the magnet roll 15a further rotates by the half magnetic pole angle (θ / 2) and the magnetic pole S2 reaches the position of φ.

The dropping phenomenon of the toner T described above is a periodic phenomenon that occurs each time each magnetic pole of the magnet roll 15a passes through the position of the magnetic pole S2 in FIG. 5, and the cycle is that the magnet roll 15a rotates by the magnetic pole angle θ. It's time to do it.

In the present embodiment, the voltage application start time (1 dot recording timing) for forming 1 dot is varied with respect to the rotation time between the magnetic pole angles θ of the magnet roll 15a to obtain the image density level. The tonality characteristic is set.

A detailed description will be given below. FIG. 6 is an explanatory diagram of a so-called previous stage for explaining the present embodiment. (A) shows a pulse width setting method with even intervals for obtaining N-level density gradation, and (b) shows the change over time of the magnetic flux density in the recording section W at this time. c) shows the relationship between the number of gradations and the image density in that case.

The figure shows the magnetic pole N of the magnet roll 15a.
Is at the position of φ, the line electrode 17 (recording electrode EL)
It is set as the start time of the application of the pulse voltage applied to the. That is, it is a time when the magnetic toner T on the recording electrode EL is in a state of standing vertically (in the state of FIG. 4) on the peripheral surface of the counter electrode at the start of application. From this, the magnet roll 15a rotates by θ / 2, and the magnetic flux density of the recording portion W changes as shown in FIG. 6 (b). In response to this, the ears of the toner T rotate 90 degrees from the standing state. Move to sleep. As described above, during the period in which the ears of the toner T change from the state of standing vertically to the state of lying, the toner T remains
(Developer) is sufficiently present. This period is referred to as period A.
Then, while the magnet roll 15a further rotates .theta. / 2, the magnetic flux density of the recording portion W further changes as shown in FIG. 6B, and accordingly, the ears of the toner T in the lying state have a magnetic force. Falls to the lower surface of the step G (see FIG. 5). During this period, the recording portion W is in a state of almost no developer. This period is referred to as period B.

Incidentally, FIG. 6B shows the magnet roll 15
Although the case where the time point when the magnetic pole N of a reaches the position of φ is the application start time point of the pulse voltage is shown, even when the time point when the magnetic pole S reaches the position of φ is the application start time point of the pulse voltage, the above-mentioned recording unit The state of change of the toner amount in W is the same. However, in this case, the magnetic flux density curve in Fig. 6 (b) is inverted vertically (or horizontally).

In the same figure (a), these two periods A and B are set to 1
The maximum application time of the applied pulse voltage to be processed once is set, this period A + B is equally divided into (N-1) pieces, and this divided time should be applied to the recording electrode EL corresponding to the recording information of one dot. The unit pulse width of the applied pulse voltage is set, and this unit pulse width is multiplied by 0 to (N-1) according to the density gradations 1 to N, and this is multiplied by 0, Tw2, Tw3,
Tw4 ... Twi ... Twn are set. The recording density of the image changes according to the change of the pulse width of the applied pulse voltage and the change of the magnetic flux density of the recording portion W (corresponding to the above-mentioned change of the toner amount state).

First, considering the change in concentration corresponding to the change in pulse width of the applied pulse voltage, the pulse width of the applied pulse voltage is changed during the period in which the applied pulse voltage changes from time 0 to Tw4 shown in FIG. This corresponds to a recording period of a relatively small amount, that is, a small amount of toner to be transferred to the counter electrode 5, that is, a recording period from a bright portion (highlight portion) of an image to an initial halftone portion. On the other hand, the period during which the applied pulse voltage changes from time Twi to Twn is when the pulse width of the applied pulse voltage is relatively large, that is, when the amount of toner to be transferred to the counter electrode 5 must be large, that is, the halftone of the image. It corresponds to the recording period from the end part to the dark part (shadow part).

Next, considering the density change corresponding to the change of the magnetic flux density of the recording portion W, the magnet roll 15a is located at the magnetic pole point (the position of the magnetic pole N or S is φ) with respect to the recording portion W shown in FIG. In the period A of θ / 2 rotation from the rotation position), the toner T (developer d) is sufficiently present in the recording portion W as described above. Therefore, the amount of toner transferred from the recording electrode EL to the counter electrode 5 is large in proportion to the magnitude of the pulse width of the applied pulse voltage, that is, in proportion to the length of the application time of the applied pulse voltage. The density of one dot becomes higher. Therefore, the density gradation clearly changes.
Therefore, as shown in FIG. 7C, in the period A, the curve of the concentration characteristic is almost a straight line. Meanwhile, the same figure (b)
In the period B shown in (1), almost no developer is present in the recording portion W. Therefore, even if the pulse width of the applied pulse voltage is increased, that is, the application time of the applied pulse voltage is increased,
There is almost no toner transferred from the recording electrode EL to the counter electrode 5, and the image density does not increase. Therefore, the density gradation hardly changes. Therefore, as shown in FIG. 7C, the concentration characteristic curve in the period B is almost flat.

From the above, assuming that the start of the pulse voltage (the start point of application of the pulse voltage) is the magnetic pole point, as shown in FIG. 6C, the concentration characteristic curve shows from the highlight portion to the beginning of the halftone. In the portion (the pulse width of the applied pulse voltage is from time 0 to Tw4), the density characteristic is good, that is, there is gradation. Further, it is shown that the density characteristic is not good, that is, there is no gradation in the shadow portion (the pulse width of the applied pulse voltage is from Twi to Twn) from the end of the halftone.

In this embodiment, the printing process is performed by shifting the start of the pulse voltage from the magnetic pole point for a predetermined time according to the required gradation characteristics. FIG. 7 shows the relationship between the applied pulse voltage and the image density when the start of the pulse voltage is shifted by θ / 4 earlier than the magnetic pole point. In this case, the correspondence between the periods A and B in which the magnetic flux density changes with respect to the change in the pulse width of the applied pulse voltage shown in FIG. 6 (a) (reprinted in FIG. 7 (a)) is shown in FIG. 7 (b). It changes as shown. That is, the timing at which the period A appears in the longest application time of the applied pulse voltage is shifted to the center,
The state of the period B '(the same state as the latter half of the period B) appears before the period A, and the first half of the period B appears after the period A.

Therefore, when the pulse width of the applied pulse voltage is small, there is no gradation characteristic in the period B ', when there is a large pulse width of the applied pulse voltage, there is no gradation characteristic in the period B, and the applied pulse voltage When the pulse width of A is medium, the density characteristics with the gradation of the period A are obtained. Therefore, in the image recorded at the start timing of this pulse voltage, the bright portion is uniformly bright, the dark portion is uniformly dark, and good density gradation is obtained only in the halftone portion. To emphasize the halftone part of the image,
The start timing of this pulse voltage is used.

Next, FIG. 8 shows the relationship between the applied pulse voltage and the image density when the start of the pulse voltage is shifted by θ / 2 earlier than the magnetic pole point. in this case,
Periods A and B in which the magnetic flux density changes in response to changes in the pulse width of the applied pulse voltage shown in FIG. 6 (a) (reprinted in FIG. 8 (a))
The correspondence of changes as shown in FIG. 8 (b). That is, the timing at which the period A appears within the longest application time of the applied pulse voltage is shifted to the latter half, and the period B appears in the first half.

Therefore, from the time when the pulse width of the applied pulse voltage is the minimum to the time when it is the intermediate value, there is no gradation characteristic in the period B, and when the pulse width of the applied pulse voltage is the intermediate value, it is the maximum. Until then, the density characteristics having the gradation of the period A can be obtained. Therefore, the image recorded at the start timing of this pulse voltage is almost uniformly bright from the bright portion to the halftone portion, and on the other hand, good density gradation can be obtained from the halftone portion to the dark portion. When it is desired to emphasize the dark part from the halftone part of the image, the start timing of this pulse voltage is used.

Next, FIG. 9 shows the relationship between the applied pulse voltage and the image density when the start of the pulse voltage is deviated from the magnetic pole point by .theta..3 / 4. In this case, the timing at which the period A appears within the longest application time of the applied pulse voltage is further shifted, and the period B appears at the center. And
The state of the period A ′ (the same state as the latter half of the period A) appears before the period B. The first half of the period A follows the period B.

Therefore, when the pulse width of the applied pulse voltage is small, the density characteristic has the gradation of the period A ', even when the pulse width of the applied pulse voltage is large, the density characteristic has the gradation of the period A, and the applied pulse voltage. When the pulse width is of an intermediate value, density characteristics without gradation in period B are obtained. Therefore, in the image recorded at the start timing of the pulse voltage, good density gradation can be obtained in the bright portion and the dark portion, and the gradation in the middle portion is not good. The start timing of this pulse voltage is used when it is desired to emphasize the high-latt portion and the shadow portion of the image.

The density gradation characteristics respectively shown in FIGS. 6 to 9C described above are summarized in FIG. The density gradation characteristics I shown in the figure are as follows: curve a is the density gradation characteristics shown in FIG. 6 (c), curve b is the density gradation characteristics shown in FIG. 7 (c),
The curve c is the density gradation characteristic shown in FIG. 8 (c), and the curve d
Is the density gradation characteristic shown in FIG. 9 (c). These characteristic curves a, b, c, d divide the magnetic pole interval θ into four equal parts as described above, and the application of the pulse voltage is started at the magnetic pole point and θ /
It is the case where the time points are shifted from the arbitrary magnetic pole point in the order of 4 points, θ / 2 time point, and θ3 / 4 time point in order of increasing speed, every 1/4. By setting the start of application of the pulse voltage in several stages between these four states, the gradation curve shown in the figure can be changed almost continuously.

As described above, since any gradation characteristic can be selected depending on the application timing, various gradation characteristics can be selected from linear gradation characteristics to gradation characteristics for emphasizing the contrast between highlight and shadow areas. The electrostatic recording used can be performed.

As a result, even if the charge characteristics of the carrier to be used differ depending on the color of the toner and the print density characteristics differ, a recording signal having a pulse width matching the characteristic of the corresponding toner color is output to the corresponding recording electrode. By doing so, it is possible to realize a full-color printer with natural print density and faithful gradation characteristics.

[0041]

As described in detail above, according to the present invention, the magnetic sensor for detecting the magnetic pole position of the magnet roll is provided, and the application start timing of the pulse voltage applied to the recording electrode is set between the magnetic pole positions of the magnet roll. Since it is possible to change and output with, it is possible to realize electrostatic recording with various gradation characteristics from linear gradation characteristics to gradation characteristics that emphasize the contrast of the highlight portion and the shadow portion.

Further, it is possible to provide an inexpensive full-color electrostatic recording device, which is suitable for a full-color electrostatic recording device in which gradation expression is important.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view near a recording section W section.

FIG. 2 is an overall configuration diagram of an electrostatic recording device according to an embodiment.

FIG. 3 is an enlarged perspective view of an image forming unit of the electrostatic recording device.

FIG. 4 is a schematic cross-sectional view near a recording section W section.

FIG. 5 is a schematic cross-sectional view in the vicinity of a recording section W section.

FIG. 6 (a) is a diagram showing a change in uniform voltage application time,
(b) is a diagram showing a change in the magnetic flux density corresponding to the voltage application time when the voltage application start is the magnetic pole point, and (c) is an image density change characteristic diagram in that case.

FIG. 7 (a) is a diagram showing a change in uniform voltage application time,
(b) is a diagram showing a change in the magnetic flux density corresponding to the voltage application time when the voltage application start is deviated from the magnetic pole point by 1/4 between the magnetic poles, and (c) is a change characteristic diagram of the image density in that case. .

FIG. 8 (a) is a diagram showing a change in uniform voltage application time,
(b) is a diagram showing a change in the magnetic flux density corresponding to the voltage application time when the voltage application start is shifted from the magnetic pole point by 1/2 between the magnetic poles, and (c) is an image density change characteristic diagram in that case. .

FIG. 9 (a) is a diagram showing a change in uniform voltage application time,
(b) is a diagram showing a change in the magnetic flux density corresponding to the voltage application time when the voltage application start is deviated from the magnetic pole point by 3/4 between the magnetic poles, and (c) is a change characteristic diagram of the image density in that case. .

FIG. 10 is a diagram illustrating that an arbitrary change characteristic of image density can be obtained.

[Explanation of symbols]

 1 Paper Feed Cassette 1a Paper Feed Roller 2a, 2b Conveyance Guide Plate 3 Standby Roll Pair 4 Transfer Charger 5 Counter Electrode 7 Conveyor Belt 8 Fixing Device 8a Heating Roll 8b Pressure Contact Roll 9 Ejection Port 10 Ejection Tray 12 Image Forming Part 12a Toner Storage layer 12b Development recording layer 13 Stirring member 14 Toner supply port 15 Development roll 15a Magnet roll 15b Fixed sleeve 15c Recording electrode sheet 16a, 16b Auger roll 17 Wire electrode 19 LSI 20 Cover film 21 Recording control unit 22 Magnetic sensor C Carrier d Development Agent D Image transfer part EL Recording electrode H Magnetic field line G Step difference T Toner W Recording part

Claims (1)

[Claims] 1. A cylindrical developer carrying member made of a non-magnetic material, a magnetic roll rotatably contained in the developer carrying member, and a magnetic roller arranged in parallel on the peripheral surface of the developer carrying member. A plurality of recording electrodes provided and a counter electrode arranged to face the recording electrodes are provided, and a step is formed on the downstream side with respect to the developer carrying direction of the recording electrodes. A pulse voltage having a corresponding pulse width is applied, and the developer conveyed while forming the spikes in the recording portion where the recording electrode and the counter electrode face each other as the magnetic roll rotates is selectively transferred to the counter electrode side. In an electrostatic recording device for forming a recorded image having a density gradation by transferring, magnetic pole detection means for detecting a magnetic pole position on the circumferential surface of the magnetic roll, and the pulse voltage based on a detection signal from the magnetic pole detection means. Application start timing And a control timing controlling means is provided, electrostatic recording apparatus characterized by changing the gradation characteristics by varying the application start time of the pulse voltage between the magnetic poles of the magnetic roll by the timing control means.