JPH04224971A - electrostatic recording device - Google Patents

Abstract

PURPOSE:To make lasting and stable acquisition of dot recording images in high resolution having excellent dot reproducibility possible for an electrostatic recording device that is made up in a compact structure employing non-contact type image formation method in which development and recording are executed simultaneously by a method wherein overlapping development in formation of black dots is restrained and the black dots in correct sizes are formed constantly with developing agent made adherent uniformly. CONSTITUTION:Recording voltage (Vs) that varies between a voltage (-200V) for making it 'on' for formation of black dots by transferring toners and a voltage (0V) for making it 'off' for recording of the transferred toners is applied to recording electrodes in accordance with dot recording information, and thereby a dot recording image is formed. At this time, the voltage for making it 'off' is applied regularly over a time TR around the end of a recording cycle Tw for one dot, regardless of the dot recording information.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact electrostatic recording device that forms an electrostatically recorded image without bringing a recording head into contact with a recording medium.

0002

BACKGROUND OF THE INVENTION Conventionally, a multi-stylus printer is well known as one of electrostatic recording devices. This multi-stylus printer constructs a recording head by arranging a large number of needle-like electrodes (stylus) at minutely even intervals in the main scanning direction, and selectively applies voltage to each needle-like electrode according to the recording signal to print on the paper. An electrostatic latent image is formed by directly discharging the electrostatic latent image. In this case, special paper coated with a high electrical resistance agent is used so that charges can be easily and stably retained on the paper. However, such special paper is not preferred as paper for office use because it is difficult to write on with a pencil or pen, and its quality deteriorates depending on environmental conditions such as humidity, so there are problems with storage stability.

Furthermore, if the distance between the tip of the acicular electrode and the paper surface is large, the discharge electric field will spread and the formed dots will become large, making it difficult to obtain a high-resolution recorded image. For that reason,
A minute gap is secured by providing a gap material on the surface of the paper and bringing the tip of the needle electrode into sliding contact with the gap material. However, when using this method, there is a problem that the tip of the needle electrode is worn out.

[0004] Therefore, as an electrostatic recording method that can use plain paper and accurately ensure a minute distance between the image medium and the tip of the recording electrode, a toner image is formed on a drum-shaped intermediate recording medium. A method is used in which the toner image is transferred onto paper. In this method, the use of an intermediate recording medium tends to increase the size of the apparatus, so a process in which recording and development are performed simultaneously is usually adopted to avoid increasing the size of the apparatus. In this case, a large number of recording electrodes extending in the conveyance direction (sub-scanning direction) of the developer conveyance path are installed in parallel in the width direction (main-scanning direction), and the developer is selectively applied to the recording electrodes according to the dot recording information. The toner is transferred from above to the surface of a counter electrode that also serves as an intermediate recording medium, and a toner recorded image consisting of dots is developed and formed.

However, in the above method, the length of the recording electrode extending in the sub-scanning direction is about 5 to 10 times the pitch of one dot in the sub-scanning direction. That is, the development area is 5 to 10 times the dot pitch. Therefore, when two or more dots are continuously recorded, the amount of toner adhesion tends to increase as the dots come later. For example, in the case of two-dot continuous recording, the second dot is formed by repeated development twice (superimposed development), so the amount of toner attached is approximately twice that of the first dot. In this way, since the amount of toner adhesion increases as the dots come in later order, the dots are enlarged so that the toner pile collapses at the trailing end of the continuously recorded image, and the reproducibility decreases. That is, the outline of the trailing edge of the image is enlarged, and a so-called sharp, low-resolution recorded image is formed.

[0006]

OBJECT OF THE INVENTION The present invention has been made in view of the problems of the prior art described above, and is a static image forming apparatus that has excellent dot reproducibility and is capable of stably forming high-resolution, high-quality recorded images over a long period of time. To provide an electrical recording device at low cost with a compact structure convenient for downsizing.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention includes a developer conveying means for conveying the developer along a predetermined developer conveying path, and a developer conveying means for conveying the developer along a predetermined developer conveying path; It has a plurality of recording electrodes arranged in an extending manner, and a counter electrode arranged with a required gap from the recording electrodes and movable in the sub-scanning direction. An electrostatic recording device that forms a dot recorded image corresponding to the dot recorded information by applying a recording voltage and forming a developer transfer electric field between the opposite electrode and the developer that transfers the developer to the opposite electrode side. In the method, a developer recovery electric field for recovering a part of the transferred developer is applied between the recording electrode and the opposing electrode within a one-dot recording period for forming one dot in the sub-scanning direction. This is the main point.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically explained below based on the embodiments shown in FIGS. 1 to 10. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a recording apparatus as an embodiment of the present invention. In the figure, reference numeral 1 denotes a paper feed cassette loaded with plain paper P, which is detachably mounted on the side of the machine. A paper feed roller 1a is disposed above the tip of the inserted paper feed cassette 1 so as to be rotatable in the direction of the arrow. In front of the paper feed roller 1a, upper and lower conveyance guide plates 2a and 2b made of insulating members are laid to form a paper transport path. A pair of standby rolls 3 is disposed in this paper feed path, and after temporarily stopping the advance of the paper P fed out by the paper feed roller 1a and adjusting the conveyance posture, the paper P is transferred to the image transfer section T on the downstream side. The image is re-fed in synchronization with the arrival timing of the recorded image, which will be described later.

At the image transfer section Ot on the downstream side of the standby roll pair 3, a transfer charger 4 is arranged opposite to a cylindrical electrode 5 which also serves as an image carrier. In this example, the cylindrical electrode 5 is driven and rotated in the counterclockwise direction indicated by arrow A. On the opposite circumferential surface of the cylindrical electrode 5, a recording image forming unit U, which will be described later, is arranged to face the cylindrical electrode 5. A toner recorded image is formed on the surface of the cylindrical electrode 5 by this recorded image forming unit U, and as the cylindrical electrode 5 rotates, the toner recorded image is conveyed to the image transfer section Ot and transferred onto the paper that is being fed again. The configuration of the recorded image forming unit U will be explained in detail later.

[0010] A separation claw 6 is disposed downstream of the image transfer section Ot with its tip pressed against the circumferential surface of the cylindrical electrode. An air suction conveyor belt 7 is stretched horizontally downstream of the separation claw 6, and the back side of the paper is separated from the circumferential surface of the cylindrical electrode 5 by the separation claw 6 after the recorded image has been transferred. is conveyed toward the fixing device 8 provided in front of it while being sucked. The fixing device 8 consists of a heating roll 8a and a pressure roll 8b, and thermally fixes the toner image when the paper is held between the two rolls and conveyed. After the fixing, the sheets are discharged from the discharge port 9 and stacked on the paper discharge tray 10 in a face-down state with the image side facing down.

As described above, in the recording apparatus of this example,
Since the entire paper transport path from paper feeding to paper ejection is formed in a substantially straight shape, the paper passing operation is generally smooth, and paper passing defects such as image defects and paper jams are less likely to occur. It also has the advantage that the above-mentioned straight sheet passing path can achieve a face-down sheet discharge state that does not require page alignment, which is preferable for the recording apparatus.

The detailed structure of the recording image forming unit U will now be explained. As shown in FIG. 2, the recorded image forming unit U generally includes a development recording tank 12 that includes a recording means and a developer conveying means, and a developer storage tank 11 that stores developer for replenishment. In the developer storage tank 11, a stirring blade 11a is rotatably disposed. In this example, an insulating magnetic toner is used as the developer, which is a one-component developer containing at least an insulating resin, a magnetic fine powder, and colorant particles, and has a negative (-) friction charge polarity. Note that the developer is not limited to a one-component developer, but may also be a two-component developer, for example, a mixture of a magnetic carrier and an insulating toner in a predetermined ratio.

A horizontal developer circulation path 13 shown in FIG. 3 is formed at the bottom of the development recording tank 12. As shown in FIG. In FIG. 3, in a pair of parallel longitudinal paths 13a, 13b in this horizontal circulation path 13, a pair of auger rolls 14a, 1
4b is rotatably installed. Each auger roll 14a
, 14b have a plurality of spiral blades 14a2, 14b2 erected on the circumferential surface of each shaft 14a1, 14b1, and reverse feed blades 14a3, 14b3 with opposite helical directions are erected at one end of each (Fig. 4). Then, each auger roll 14a, 14b is moved along the longitudinal path 13a so that the respective reverse feed blades 14a3, 14b3 are located on opposite sides of each other.
, 13b, respectively. These pair of auger rolls 14a and 14b are driven to rotate in opposite directions to each other and in a direction that conveys the developer toward the reverse feed blades 14a3 and 14b3, as shown by arrows B and C. As a result, at each corner portion where the reverse feed blades 14a3 and 14b3 are provided, conveyance forces in opposite directions collide with each other, and the magnetic toner is ejected in the right angle direction and flows toward the other longitudinal path. In this manner, in this example, the magnetic toner is stirred and circulated in the direction shown by the broken arrow D, and at this time, the magnetic toner can be sufficiently triboelectrically charged. In addition, Augarol 14a
, 14b, it is possible to triboelectrically charge the developer to a sufficient amount by changing the material and shape of the developer.

The center of the horizontal circulation path 13 constructed as described above is surrounded by a wall S to prevent the circulating developer from entering.
A space S surrounded by w is formed. As shown in FIG. 2, the auger roll 14 closer to the developer storage tank 11
A replenishment port 11b for replenishing magnetic toner d0 is provided above the auger roll 14a along the axial direction of the auger roll 14a.

Above the other auger roll 14b, a developing sleeve 15 for conveying the developer in the vertical direction is installed in the horizontal direction. The developing sleeve 15 has a magnet roll 16 rotatably built therein, and has the above-mentioned cylindrical electrode 5.
are placed facing each other. Different magnetic poles are alternately magnetized on the circumferential surface of the magnet roll 16, and by driving and rotating the magnet roll 16 in the counterclockwise direction shown by arrow H, the magnetic toner d is spread along the circumferential surface of the developing sleeve 15. and transport it in the clockwise direction shown by the dashed arrow.

Near the circumferential surface of the developing sleeve 15, which serves as a developer conveyance path, and on the upstream side in the developer conveyance direction, there is a doctor blade 1 for regulating the layer thickness of the magnetic toner d to an appropriate thickness.
2a is installed. Further, a toner scattering prevention plate 12b is provided above the doctor blade 12a. The toner scattering prevention plate 12b is provided to prevent the developer transported downstream under the layer thickness regulation by the doctor blade 12a from scattering outside the recording image forming unit U and staining the image. In this example, the upper end of the tank wall of the developing and recording tank 12 is bifurcated, and one side is formed as a doctor blade 12a and the other side is formed as a toner scattering prevention plate 12b.

A recording section W for forming a toner recorded image on the circumferential surface of the cylindrical electrode 5 is configured as follows on the downstream side of the above-mentioned toner layer thickness regulating section in the toner transport direction.

A recording electrode sheet 17 having a large number of recording electrodes is provided in an area on the upstream side of the circumferential surface of the developing sleeve 15 from the position closest to the circumferential surface of the cylindrical electrode 5 (in this example, the left half circumferential surface in the figure). It has been covered. As shown in FIG. 4, the recording electrode sheet 17 has a large number of recording electrode wires 17a extending parallel to each other in the longitudinal direction of the sheet along the circumferential direction of the circumferential surface of the developing sleeve 15, and arranged at a predetermined fine pitch. They are arranged in parallel in the width direction (toner conveyance path width direction: main scanning direction). The number of recording electrode lines 17a is made to correspond to the maximum number of data for one main scanning line. The recording electrode sheet 17 of this example is made of a flexible printed circuit board (FPC), and has recording electrode wires 17a made of a large number of non-magnetic conductive materials.
40 on the base film 17b made of a flexible insulating material.
84.6μm pitch (300DPI) with μm gap maintained.
) is patterned with a density of The surface of the recording electrode sheet 17 is coated with an insulating coat 17c except for the small area Z at the tip. This insulation coat 17c is
The coating is applied to ensure insulation between each recording electrode wire 17a and to prevent wear of the recording electrode wire 17a due to friction with magnetic toner.

FIG. 5 is a schematic cross-sectional view showing the recording section W on an enlarged scale. As shown in the figure, if the tip of the recording electrode wire 17a is exposed without being covered with the insulating coat 17c, a necessary recording electric field can be efficiently formed between it and the circumferential surface of the opposing cylindrical electrode 5. The exposed tip of the recording electrode wire 17c is
This becomes a recording electrode EL that substantially performs a recording operation. If the length L of the recording electrode EL along the toner transport direction (sub-scanning direction) is too short, the strength of the recording electric field will become small and the image density will decrease. .6 μm). On the other hand, if the length L of the recording electrode EL is ensured excessively,
The electric field strength spreads and the sharpness of the image decreases.

In FIG. 2, on the downstream side of the recording unit W in the toner transport direction, there is a wall Sw1 on the side of the developer storage tank 11 that surrounds the central space S of the horizontal circulation path 13 described above.
is extended, and its tip is brought into contact with the circumferential surface of the developing sleeve 15. As a result, the magnetic toner d', which is not transferred in the recording section W but remains on the circumferential surface of the developing sleeve 15 and is conveyed with the rotation of the magnet roll 16, is transferred to the horizontal circulation path 1.
The magnetic toner d is scraped onto the replenishment tank side path 13a of No.3.
This prevents the inconvenience of intruding into the central space S or being directly returned to the upstream side along the circumferential surface of the developing sleeve 15 without passing through the horizontal circulation path 13. Note that a dedicated flat plate member for scraping off the residual magnetic toner d' adhering to the developing sleeve 15 may be provided separately from the peripheral wall of the central space S. In this case, the scraping member may be supported in the vertical direction, its tip abutted on the circumferential surface of the developing sleeve 15, and its other end extended to the bottom of the central space S. Furthermore, if the scraping member is made of a magnetic material, the magnetic force of the magnet roll 16 can be blocked, and a smoother scraping and return effect can be obtained.

The recording electrode sheet 17, which has been laid out over about half of the circumferential surface of the developing sleeve 15 as described above, is pulled out horizontally and then lowered vertically, extending into the central space S of the horizontal circulation path described above. It has been set up. A plurality of drive circuit elements 18 are provided in the vertically extending portion of the recording electrode sheet 17 to apply a recording voltage to each recording electrode EL according to recording data.
It is equipped with. As shown in FIG. 4, each drive circuit element 18 is provided with the recording electrode line 1 of the recording electrode sheet 17 described above
7a are divided into N pieces and connected to each other. Like this,
By storing and installing the other end of the recording electrode sheet 17 on which the drive circuit element 18 is mounted in the central space S, the drive circuit element 18 can be protected from dust such as developer, and the structure of the development recording tank 12 can be made conspicuous. It can be made more compact.

In FIG. 2, each drive circuit element 18 is connected to the recording control section C by a signal line (indicated by a broken line) so as to be able to transmit electrical signals. This drive circuit element 18 outputs a recording voltage Vs as shown in FIG. 6 to each recording electrode in response to bit-form dot recording information and a recording voltage control signal sent from the recording control section C. The recording voltage Vs is -200V (
It is a binary signal voltage that changes between 0V (on voltage) and 0V (off voltage). For example, when the 1-bit recording information input from the recording control unit C is “H”, the drive circuit element 18
An on-voltage of -200V is applied to the corresponding recording electrode EL. As a result, since the bias power supply 5a is connected to the cylindrical electrode facing the recording electrode and a bias voltage of -30V is applied, a bias voltage of -30V is applied from the cylindrical electrode 5 to the recording electrode EL.
A toner transfer electric field is created based on a potential difference of 70V. Since the negatively charged magnetic toner d moves toward the higher potential, the recording electrode E to which a voltage of -200V is applied
Only the magnetic toner d on L is selectively transferred to the surface of the cylindrical electrode 5, forming one black dot. On the other hand, when the 1-bit input recording information is "L", the off-voltage of 0 is applied to the recording electrode EL.
Apply V. As a result, the potential difference seen from the cylindrical electrode 5 to its corresponding recording electrode EL becomes -30V, and a toner collection electric field opposite in direction to the above-mentioned toner transfer electric field is formed in the recording portion W.

In the present invention, as can be seen from the explanatory diagram of FIG. 6 showing the relationship between recording voltage, image, and dot shape, when forming one black dot, the entire recording period Tw of one dot is The structure is such that an on-voltage is not applied over a period of time, and an off-voltage is forcibly applied only for a predetermined time TR at the end of the one-dot recording period Tw, and the forced off-voltage acts as a developer recovery electric field. This forced-off voltage application time TR is secured periodically for each one-dot recording period Tw, as shown, not only in the case of recording one black dot alone, but also in the case of continuous recording of two or more black dots. In this case, the length of the forced off voltage application time TR needs to be set to be longer than the time (effective time) required for the toner particles to actually reverse transfer from the cylindrical electrode 5 to the surface of the recording electrode EL, that is, to be collected. It has been experimentally confirmed that the effective time for this toner transfer is about 10 μsec, and therefore, it is necessary to ensure the forced off voltage application time TR to be 10 μsec or more. Also, when the 1-dot recording period Tw exceeds 1 msec,
In order to ensure the effectiveness of the toner recovery effect, it is necessary to set the ratio of the forced off voltage application time TR to the one-dot recording period Tw to 1% or more.

Incidentally, the 1-dot recording period Tw in this example is:
The recording image forming speed (process speed) was set to 42.3 m.
m/sec], the dot density is 30 as mentioned above.
Since the dot diameter of 0DPI is 0.0846mm, T
w=0.0846/42.3=2.0 [msec]. Therefore, the forced off voltage application time TR in this example is 2.
It is preferable to set it to 0.02 msec or more, which is 1% of 0 msec. Note that the process speed is the advancing speed of the paper being conveyed to the transfer position Ot in FIG.
This is made to match the moving speed of the circumferential surface of the cylindrical electrode 5.

In order to secure the above-mentioned forced off voltage application time TR, a recording voltage control signal is output from the recording control section C to the drive circuit element 18. In this example, an AND circuit is provided in the drive circuit element 18 corresponding to each recording electrode, and this A
A method is adopted in which the above-mentioned recording voltage control signal and dot recording information are input to the ND circuit, and the recording voltage is switched to an on voltage and an off voltage based on the AND signal output from the AND circuit and output to each recording electrode EL. There is. In this case, AND
Even if the dot recording information input to the circuit is "H", when the recording voltage control signal switches from "H" to "L", the logical product also becomes "
As a result, the recording voltage control signal changes from "H" to "L" in the 1-dot recording period Tw.
”, the recording voltage switches from the on voltage to the forced off voltage.On the other hand, when the dot recording information is “L”
In this case, even if the recording voltage control signal switches from "H" to "L", the output signal of the AND circuit remains "L" throughout the 1-dot recording period Tw and does not change. remains at the off-voltage.

As described above, by ensuring the required length of forced off voltage application time TR at the end of each black dot recording period Tw, black dots of accurate size to which toner is evenly adhered can be formed. Therefore, dot recorded images with excellent dot reproducibility can be stably obtained. The recorded image forming operation will be explained below.

In FIG. 2, when the magnet roll 16 is driven and rotated in the direction of the arrow E, a rotating magnetic field is formed on the outer peripheral surface of the developing sleeve 15 that causes the particles of the magnetic toner d to rotate, and the magnetic toner d forms ears. While doing so, it is transported in the direction of the arrow opposite to the rotation direction of the magnet roll 16. The conveyed magnetic toner d is conveyed to the recording section W after being cut to a predetermined thickness by the doctor blade 12a. At this time, the magnetic toner d used in this example is triboelectrically charged to a negative polarity due to friction between the toners and the peripheral surface of the developing sleeve 15. In the recording section W, a recording voltage Vs is applied to each recording electrode EL with a forced off voltage application time TR ensured as shown in FIG. 6, and a toner recorded image with excellent dot reproducibility is formed in the following manner. .

FIG. 5 is a schematic cross-sectional view showing the state of the recording section W at point (3) in FIG. At time (3), immediately before continuous recording of two black dots is performed, an off voltage (0V) is applied to the recording electrode EL by the drive circuit element, a bias voltage of -30V is applied to the cylindrical electrode 5 by the bias power supply 5a, and recording is performed. In portion W, a toner collection electric field is formed in the direction indicated by the arrow. The magnetic toner d charged with negative (-) polarity and transported to the recording section W moves in the opposite direction to the direction of the electric field, so it is held on the recording electrode EL side by the toner collection electric field and is transferred to the circumferential surface of the cylindrical electrode 5. Does not metastasize to the side.

In FIG. 6, the recording voltage Vs is equal to the on-voltage (
-200V) to start recording one black dot, and an on-voltage is applied for a time TD to form a toner transfer electric field. The state of the recording section W at time point (3) immediately before switching from the application of the on voltage to the application of the forced off voltage is as shown in FIG. An on-voltage is applied to the recording electrode EL by a drive circuit element, and a -
Since the bias voltage of 30 V remains applied, a toner transfer electric field is formed in the recording portion W in the direction shown by the arrow. Therefore, the magnetic toner d moves to the cylindrical electrode 5 side and adheres to its circumferential surface, and is carried out from the recording section W as the cylindrical electrode 5 rotates in the direction of arrow A, and is transferred to the first black dot dB.
1 is forming.

Next, as shown in FIG. 6, at time (3) when the recording voltage Vs is switched from the on voltage to the forced off voltage, the electric field of the recording section W is switched to the toner collection electric field, as shown in FIG. At time (3), the magnetic toner d transferred to the surface of the cylindrical electrode 5 of the recording portion W is collected toward the recording electrode EL. In this way, since the toner transfer electric field is switched to the toner collection electric field before the end of one dot recording period, superimposed development is suppressed, and the magnetic toner d is uniformly adhered to the entire dot area to form an accurate image of a predetermined size. A first black dot dB1 is formed.

In FIG. 6, time point (2) is the time when one dot recording period Tw has passed since point (2), and the recording voltage was switched from on voltage to forced off voltage in order to accurately form the second dot in continuous dot recording. This is the point in time. At this time point (2), as shown in FIG. dB
Continuing from 1, it is being formed accurately with a uniform amount of toner adhesion.

[0032] Here, the state of the recording section W at the above-mentioned time points (1) and (2) will be compared with the conventional case where no forced off voltage application time is provided. At time point (2) in FIG. 11, which shows the conventional recording voltage Vs', the on-voltage continues to be applied to the recording electrode, so a toner transfer electric field is formed in the recording area W as shown in FIG. There is even. Therefore,
At the first black dot dB1' in the continuous dot recording that is being formed on the circumferential surface of the cylindrical electrode 5, a larger amount of toner adheres toward the rear end. Then, the on-voltage continues to be applied to the recording electrode EL until a time point after one dot recording period Tw shown in FIG. 11 is reached. Therefore, the point in time
In FIG. 13, which shows the state in FIG.
It can be seen that the amount of toner adhesion is large. A large amount of toner adhering to the rear end of the second black dot dB2' tends to crumble and enlarge the dot.

FIG. 14 shows the state of the recording section W from time point (2) shown in FIG. 11 to time point (2) when continuous recording of two dots is completely completed by applying an off voltage for one dot recording period Tw. . From now on, 2 dot continuous recording time (2
Even if the recording voltage Vs is immediately switched to the OFF voltage after passing through ×Tw) and toner collection is started, a large amount of toner adhering to the trailing edge of the dot collapses and the dot is enlarged, causing the dot to spread onto the surface of the 5th circumference of the cylindrical electrode. It can be seen that an inaccurate two-dot continuous recording toner image is formed.

On the other hand, at time point (2) in FIG. 6, which shows the recording voltage Vs of this example, as shown in FIG. , dB2, a continuous dot recording image with excellent dot reproducibility and a sharp trailing edge is clearly formed on the circumferential surface of the cylindrical electrode 5.

As described above, a dot recording image corresponding to input recording information is formed on the circumferential surface of the cylindrical electrode 5 with excellent dot reproducibility. This dot recorded image is carried out from the recording section W toward the image transfer section as the cylindrical electrode 5 rotates. At this time, since a step G equal to the thickness of the recording electrode sheet 17 is formed immediately downstream of the recording section W as shown in FIG. Immediately after the toner d' passes through the recording section W, it moves away from the surface of the cylindrical electrode 5. Therefore, the inconvenience that the toner recorded image formed on the circumferential surface of the cylindrical electrode 5 in the recording portion W is disturbed due to mutual interference with the residual magnetic toner d' can be reliably avoided.

In FIG. 1, the toner recorded image formed on the surface of the cylindrical electrode 5 is conveyed to the image transfer section Ot as the cylindrical electrode 5 rotates in the counterclockwise direction A, and here the timing is measured by the standby roll pair 3. The image is then transferred onto the paper that is re-fed. Incidentally, in order to adjust the density of the above-mentioned toner recorded image, it is sufficient to change the bias voltage of the bias power supply 5a. In that case, the appropriate adjustment range is 0~-50V
The closer it is to 0V, the higher the image density becomes.

In FIG. 2, the magnetic toner d' remaining in the recording section W without being transferred to the cylindrical electrode 5 side moves downstream with the rotation of the magnet roll 16, and is removed from the surface of the developing sleeve 15 by the scraping wall Sw1. The toner is scraped off, falls onto the auger roll 14a, and is stirred and mixed with the magnetic toner d0 that is replenished from the replenishment port 11b.

As the auger roll 14a rotates, the fallen and returned residual magnetic toner d' and the replenishing magnetic toner d0 are mixed and stirred and circulated and conveyed. In FIG. 3, the magnetic toner that is circulated in the direction of the dashed arrow N is conveyed in the vertical direction again by the rotating magnetic field of the magnet roll 16 extending above it when being conveyed along the longitudinal path 13b on the anti-replenishment side. Ru.

As described above, in the recording section W, the cylindrical electrode 5
The residual magnetic toner d′ that was not transferred to the side but was transported downstream
is scraped onto the horizontal circulation path 13, and smoothly returned to the upstream side while being stirred through this horizontal circulation path 13,
The toner is used again to form a recorded image. In this case, the magnetic toner d before being conveyed in the vertical direction is
Since the developing sleeve 1 is being conveyed while being stirred along the axial direction (width direction of the toner conveying path: main scanning direction),
5. It is uniformly supplied over the entire width direction of the circumferential surface. Therefore, the magnetic toner d is always uniformly supported on the circumferential surface of the developing sleeve 15 over the entire width direction and is conveyed to the recording section W, thereby stably producing a high-quality recorded image with uniform image density as described above. It becomes possible to obtain Further, when the magnetic toner d is circulated and conveyed while being stirred in the horizontal circulation path 13, the magnetic toner particles rub against each other, and the magnetic toner is sufficiently triboelectrically charged.

It should be noted that the present invention is not limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, Figure 2
In the embodiment shown in FIG. 1, a negatively (-) chargeable toner was used as the toner, but it is also possible to use a positively (+) chargeable toner. In that case, the bias voltage applied to the recording electrode and the counter electrode may be of positive (+) polarity.

In addition, in FIG. 6, the forced off voltage application time TR
is set once at the end of the 1-dot recording period TW, but it can also be set in the first half or center of the 1-dot recording period TW, or it can be set multiple times within the 1-dot recording period TW. Good too.

[0042]

As described above in detail, according to the present invention, by controlling the recording voltage so that a toner collection electric field can be formed periodically over a predetermined period every time one black dot is formed. , it is possible to suppress overlapping development and stably form one black dot of an accurate size with a uniform amount of toner adhesion. As a result, even in a continuous dot recorded image, the toner can be applied substantially uniformly and sharply to the rear end, and a high resolution dot recorded image with excellent dot reproducibility can be obtained. Furthermore, since the electrostatic recording device of the present invention uses a non-contact recording method, there is no risk of the recording electrodes being worn out. Therefore, the durability of the recording head is improved, and the above-mentioned electrostatic recording device that stably forms high-resolution and accurate recorded images over a long period of time can be made smaller and cheaper by using a method that performs development and recording at the same time. can be provided to

[Brief explanation of the drawing]

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

FIG. 2 is a schematic cross-sectional view showing a recorded image forming unit and its peripheral configuration in the electrostatic recording apparatus.

FIG. 3 is a plan cross-sectional view showing a horizontal circulation path of the recording image forming unit.

FIG. 4 is a perspective view showing the entire recording image forming unit.

FIG. 5 is a schematic cross-sectional view showing a recording section of the recorded image forming unit.

FIG. 6 is an explanatory diagram showing the relationship between the recording voltage applied to the recording section and the formed image and dot shape.

FIG. 7 is a schematic cross-sectional view showing a state of the recording section at a time different from that shown in FIG. 5;

FIG. 8 is a schematic cross-sectional view showing the state of the recording section at a different point in time.

FIG. 9 is a schematic cross-sectional view showing the state of the recording section at a different point in time.

FIG. 10 is a schematic cross-sectional view showing the state of the recording section at yet another different point in time.

FIG. 11 is a timing chart showing recording voltages in a conventional electrostatic recording device.

FIG. 12 is a schematic cross-sectional view showing the state of a recording section in a conventional electrostatic recording device.

FIG. 13 is a schematic cross-sectional view showing the state of a conventional recording section at different times.

FIG. 14 is a schematic cross-sectional view showing the state of the conventional recording section at a different point in time.

[Explanation of symbols]

4...Transfer charger 5...Cylindrical electrode 5a...Bias power supply (cylindrical electrode side) 11...Developer storage tank 12...Development recording tank 13...Horizontal circulation route 14a, 14b... Augerol 15...Developing sleeve 16...Magnet roll 17...Recording electrode sheet 17a...Recording electrode line 17c...Insulation coat 18...Drive circuit element C... Recording control section EL...Recording electrode G...step S...Central space U...recording image forming unit W...recording section

Claims (2)

[Claims] 1. A developer transport means for transporting developer along a predetermined developer transport path, a plurality of recording electrodes extending along the developer transport direction along the developer transport path, and a plurality of recording electrodes extending along the developer transport direction; a counter electrode arranged with a required gap between the electrodes and movable in the sub-scanning direction; a recording voltage is applied to each of the recording electrodes according to dot recording information; In an electrostatic recording device that forms a dot recorded image corresponding to the dot recording information by forming a developer transfer electric field that transfers the developer to the counter electrode side, the electrostatic recording device forms one dot in the sub-scanning direction. An electrostatic recording device characterized in that a developer recovery electric field for recovering a part of the transferred developer is applied between the recording electrode and the counter electrode within a dot recording period. 2. The forced formation time of the developer recovery electric field is 1% or more of the one-dot recording period, and 10 μsec.
The electrostatic recording device according to claim 1, wherein the electrostatic recording device is set to be equal to or higher than c.