JPH03233575A - Electrostatic color recorder - Google Patents

Abstract

PURPOSE:To allow the low-voltage driving of a corona ion current head, the enhancement in fineness and miniaturization by providing the corona ion current head which forms electrostatic latent images on a recording medium by the corona ion current controlled by the voltage lower than the electrostatic charge potential of the recording medium. CONSTITUTION:A potential of -600V is applied on the recording medium on a recording drum 1 by using a solid-state corona ion generator 2 for precharging and the corona ion current corresponding to a color image signal is generated by the solid-state corona ion current head 3 for low-voltage driving to erase the charge on the recording drum 1 and to form the electrostatic latent images of reversed electrostatic contrasts. The potential on the recording drum 1 is again uniformly electrostatically charged by using the solid-state corona ion generator 2 in the same manner; thereafter, the corona ion current of the corona ion current head 3 for low-voltage driving is controlled according to the signals by using the color image signal different from the color image signal of the 1st time, by which the reversed electrostatic latent images are formed on the color toner images of the 1st color. The lower current driving, the higher fine ness and smaller size are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrostatic color recording device that performs color recording by forming an electrostatic latent image using a flow of corona ions.

(Prior art) As a color image forming method, an electrostatic latent image is created on an insulating recording medium by a corona ion flow controlled according to an image signal, and then developed using color toner to form a color image. The h″ method for creating
6-62878 discloses that an electrostatic latent image is further formed on the toner image created on the recording medium using this method,
A color recording device is described that obtains a color image by overlapping toner images of different colors. This device uses a corona ion flow head consisting of an electrophotographic corona charger that generates a corona ion flow and a control electrode that controls the generated corona ion flow according to a color image signal. The flow is controlled to form an electrostatic latent image.

Color image formation using this corona ion flow head is
Do it as follows. First, an electrostatic latent image is formed on a recording medium according to a color image signal using a corona ion flow head, and after development with a -component toner, the obtained toner image is temporarily fixed on the recording medium by heat. Thereafter, the recording drum is rotated, and electrostatic latent images are formed using different color image signals on the previously formed toner image, and developed with different color toners. This process is repeated one after another to form a color image on the recording medium, and then the image is thermally transferred onto the recording paper. After the residual toner on the recording medium after transfer is removed by a cleaning device, the recording medium is reused.

FIG. 18(a) is a block diagram of this color recording apparatus. A corona ion flow head 402 is provided around a recording drum 401 using an insulating recording medium, and applies electrostatic charge to the recording drum 401 according to a color image signal. The electrostatic latent image formed in this manner is developed by selecting a color developing device according to the color signal from among the rotary developing device 403 having four developing devices, and the color toner image is transferred to the recording drum 401. formed on top. This color toner image is temporarily fixed on the recording drum 401 by a flash fixing device 404, and an electrostatic latent image is again formed thereon by a corona ion flow head for development. By sequentially repeating this process, a color image is created on the recording drum 401.

The color image created in this way is printed on the recording paper 405.
The images are transferred onto the image at once using a thermal transfer roller 406. The residual toner on the recording drum 401 after the transfer is cleaned by a cleaning device 407 made of a metal blade, and the recording drum 401 is used again.

FIG. 18('D) is a schematic cross-sectional view of the corona ion flow head 402. 6 kV applied to the corona ion generation wire 408 in the corona charger with a diameter of about 80 μm
Generates a corona ion flow at a relatively high voltage. The generated corona ion flow is focused by the ion flow focusing electrode 409 and the focusing mold 1fA 440, and after being on/off controlled by the image information signal 413 applied between the ion flow control electrodes 411 and 412, it is accelerated. It is accelerated by a voltage 414 and reaches the recording medium 401 to form an electrostatic latent image.

Although the color recording apparatus shown in FIG. 18 is capable of multilevel recording, it has the following problems.

■The corona charger requires a high voltage of several kV, and the ion flow control electrodes 411 and 412 require a high bias voltage that determines the electrostatic contrast, and a high signal voltage of 100 to 150 V or more superimposed on that bias voltage. Therefore, it is necessary that the driving IC for driving the corona ion flow head 402 has a high withstand voltage.

■The recording speed is the amount of corona ions from the corona charger (
Corona ion flow density), and the limit is 2 to 3 pages per minute for A4 size recording paper.

■Since the corona charger is a constant current source, the recording drum 40
The potential of the electrostatic latent image on 1 is determined by the current value of the constant current source, and the electrostatic latent image potential changes as the current value changes due to local variations in the amount of corona ions generated.

(2) A fixing device 404 using a flash lamp is used to temporarily adhere the toner image, and a thermal transfer roller 406 is used to transfer the color toner image formed on the recording drum 401 onto the recording paper. Recording drum 40
1 causes characteristic deterioration due to heat.

■Since it is necessary to mechanically remove the residual toner melted on the recording drum 401, a metal blade is required in the cleaning device 407. It is necessary to use an inorganic insulating drum.

■After a color toner image is formed on the recording drum 401, toner images are formed one on top of the other without discharging the electrostatic latent image, so that the previous electrostatic latent image is simultaneously developed in the toner image to be formed next. It ends up.

On the other hand, an electrostatic color recording device is also known that uses a solidified corona ion flow head to control the corona ion flow at high speed and forms a color image with one rotation of the recording drum (Japanese Patent Application Laid-Open No. 60237466). In this color recording device, an electrostatic latent image is formed using a solid corona ion flow head, and after development with a developing device containing color toner, the electric potential on the recording drum containing the color toner image is erased using a static eliminating corona charger. .

Then, image forming stages each consisting of a solid corona ion flow head, a developing device, and a charge eliminating corona charger are provided around the recording drum for each color, and color toner images are successively superimposed on each other.

FIG. 19(a) is a schematic cross-sectional view of this electrostatic color recording device. Around the recording drum 401 made of an insulating recording medium, there are corona ion flow heads 420, 421, 422 that control the corona ion flow according to color signals, and developing devices 423, 424, 425 containing color developers. Electrostatic discharge corona chargers 426 and 427 that eliminate static electricity from the developed electrostatic latent image on the recording drum 401, and the recording drum 401.
A corona charger 4 for making the toner charges of the color toner image formed in a superimposed manner the same polarity as -.
28 is the provision. The color toner image formed on the recording drum 401 is electrostatically transferred onto the recording paper 405 by a transfer corona charger 429. The color toner image on the recording paper 405 is melted and fixed onto the recording paper 405 by a heat fixing device 430 .

On the other hand, the recording drum 401 is reused after the residual toner on the recording drum 401 is cleaned by a cleaning device 407 and the residual charge on the recording drum 401 is eliminated by a static eliminating corona charger 431.

The structure of the solid corona ion flow head (Japanese Unexamined Patent Publication No. 184562/1983) used in FIG. 19(a) will be explained using FIG. 19(b). This solid state corona ion flow head has a corona ion flow discharge hole 435 corresponding to a recording image point in front of a corona ion generator provided with an induction electrode 433 and a corona ion generation electrode 434 via an insulating layer 432. It is configured with an accelerating electrode 436 and controls the corona ion flow on and off by applying a signal voltage 437 higher than the contrast potential of the electrostatic latent image to the corona ion generating electrode 434. The resulting corona ion flow,
Acceleration voltage 438 comparable to the contrast potential of the electrostatic latent image
The insulating recording medium 40 is
1, and forms an electrostatic latent image on the recording medium 401. This solid-state corona ion flow head can generate high-density corona ions and can record at higher speeds than laser printers.

The operation of this corona ion flow head will be explained in more detail. When 43 AC voltages of 40 kHz and 2 kVp-p are applied between the induction electrode 433 and the corona ion generation electrode 434, a high alternating electric field is generated in the slit or hole 440 for electric field concentration, and high density positive and negative corona ions are generated. do. The positive and negative corona ions generated in this way generate a high signal voltage of about -700 to -800V, which is higher than the electrostatic latent image.
37 to the corona ion generating electrode 434, only negative corona ions are selected, and the recording medium 40
Move in direction 1. Corona ions moving in the direction of the recording medium 401 determine the electrostatic contrast 400~
Accelerating electrode 4 to which an accelerating voltage 438 of about 500 μ is applied
36, it is accelerated in the direction of the recording medium 401. In this way, the corona ion flow that reaches the insulating recording medium 401 forms an electrostatic latent image. Such solid corona ion flow heads are arranged as many times as the number of recording pixels (pixels).

The electrostatic color recording device shown in FIG. 19 has the following problems.

(2) The solid corona ion flow head shown in FIG. 19(b) used in this device can only perform binary recording by turning on and off the corona ion flow, and cannot perform multivalue recording.

■An AC corona charger is used as the static eliminating corona charger 431 that neutralizes the color toner image formed on the recording medium 401, but the static neutralizing effect changes when the capacitance determined by the thickness of the toner layer overlapped on the recording medium 401 changes. Since the values are different, it becomes impossible to perform negative charge removal.

(2) The amount of generated corona ions varies depending on the location of the corona charger, and depending on the thickness of the toner layer, the potential of the electrostatic latent image formed next becomes non-uniform.

■As a control voltage for the corona ion flow, the recording drum 401
A high voltage (400V to 500V or more) similar to the electrostatic contrast potential of the electrostatic latent image above is required, a high-voltage driving IC with a large mounting area is required, and high-definition devices require high-density mounting. Not suitable for heads.

In order to completely eliminate static electricity, we also proposed a method in which a photoreceptor is installed as a recording medium on a transparent drum with a conductive layer, and after forming toner images of each color on the photoreceptor drum, the static electricity is removed by irradiating light from inside the drum. has been done. However, in this method, the charge on the recording drum that electrostatically attracts the toner image is erased, and there is no charge to hold the toner, so that the toner tends to scatter.

In addition, in corona charger charging, which makes the color toner on the recording drum have the same polarity before transfer, since the corona charger is a constant current source, the potential changes due to differences in toner layer thickness and local variations in the amount of corona ions generated. There is a drawback that electrostatic transfer is not performed uniformly.

On the other hand, in order to reduce the control voltage of the corona ion flow head, there is a method of moving the corona ion flow generated by a corona charger with a high-speed air flow and applying a control voltage perpendicular to the moving direction of the corona ion flow. (Unexamined Japanese Patent Publication No. 61
-255870). According to this method, low voltage drive of about 30V is possible. However, when using this corona ion flow head, it is necessary to apply a high accelerating voltage of about 2 kV to the recording drum, so the developing device and the like around the recording drum must be insulated from the high voltage. Furthermore, since the control electrode structure of the corona ion flow head becomes complicated, high-density packaging becomes difficult.

Furthermore, Japanese Patent Laid-Open No. 61-62050 discloses a color recording apparatus using this head.

This color recording apparatus has corona ion flow heads for recording and developing devices for the required number of colors around the recording drum, and does not take measures such as static elimination.

Therefore, there is a drawback that memory of the previous image is generated in the next image.

(Problems to be Solved by the Invention) As described above, multi-value recording is possible with a corona ion flow control head that uses a corona charcite as a corona ion generator and has an accelerating electrode and a control electrode. to
Since a signal voltage on the ova is required, and a bias voltage higher than the electrostatic latent image potential is added to the signal voltage, the driving IC is required to have a high breakdown voltage.

In addition, the transfer efficiency changes due to differences in the embedding of color toner layers formed overlappingly on the recording drum and local variations in the amount of corona ions generated, resulting in different colors of the color image transferred to the recording paper. Furthermore, the transfer efficiency varies depending on the environmental humidity, and the color changes depending on the environmental humidity. Further, in color recording, the amount of waste toner is several times that of black and white images, which has the disadvantage of deteriorating user maintenance.

In a recording device using a solid-state corona ion flow head, the signal voltage applied to the corona ion generating electrode is a quality voltage (400 to 5
00V or more), and the electrostatic contrast is determined by the withstand voltage of the driving IC. Therefore, in order to obtain sufficient electrostatic contrast, the driving voltage for corona ion control becomes high, and the mounting area of the driving IC becomes large, making it unsuitable for manufacturing high-definition heads that require high-density mounting. . Further, since the static elimination effect of the previous toner image formed on the recording drum is not uniform, the electrostatic latent image formed next becomes non-uniform.

The corona ion flow head, which uses high-speed airflow to lower the driving voltage and enables multilevel recording, is not suitable for high-definition heads because of its complicated structure.

Furthermore, with the method of temporarily fixing a single color toner image onto the recording drum using heat, the recording drum is resistant to heat, and it is necessary to clean the recording drum with a metal blade to remove the toner fused with heat. Therefore, the surface hardness must be high, and recording drums that satisfy such conditions are limited to expensive ones.

This invention was made in view of the above-mentioned problems, and enables low-voltage driving, high definition, and miniaturization of a corona ion flow head, and enables high-speed electrostatic latent images with high electrostatic contrast and uniformity. An object of the present invention is to provide an electrostatic color recording device which can transfer a color toner image on a recording drum with a -degree electrostatic transfer and can obtain a high-quality color image.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the color recording device according to the present invention, according to one aspect, records a recording material around a recording drum having a recording medium on its circumference. A charging means that uniformly charges the medium to a predetermined potential, and a low-voltage drive that forms an electrostatic latent image on the recording medium by a corona ion flow controlled at a voltage lower than the charging potential of the recording medium by one stage of charging. a plurality of developing means for developing an electrostatic latent image formed by the corona ion flow head with toner of a predetermined color to form a color toner image; a charging means; a corona ion flow head; A corona ion generating means for irradiating corona ions onto a plurality of color toner images formed one on top of the other on a recording medium by a plurality of developing means to make the potential of the plurality of color toner images uniform, and the corona ions. An electrostatic transfer means that electrostatically transfers a plurality of color toner images whose potentials are made uniform by a generation means onto a recording paper in one transfer, and a cleaning means that removes residual toner on the recording medium are arranged. It is composed of

A configuration in which the cleaning means is removed is also possible by using a contact developing device having a cleaning function as at least one of the plurality of developing means (for example, the first color developing means).

According to another aspect, charging means for uniformly charging the recording medium, a corona ion flow head for low voltage driving for forming an electrostatic latent image, and an electrostatic latent image are arranged around the recording drum in a predetermined manner. A plurality of image forming stages each having a developing means for developing with toner of a color to form a color toner image are arranged, and further, the potentials of the plurality of color toner images formed in an overlapping manner by the image forming stages are made uniform. An electrostatic transfer means for electrostatically transferring a plurality of color toner images onto a recording paper in one transfer, and a cleaning means for removing residual toner are arranged.

The cleaning means may be eliminated and a contact developer may be used instead as the developing means in at least one imaging stage.

The charging means for precharging and the corona ion generation means for making the potentials of a plurality of color toner images uniform are each constructed by providing an induction electrode and a corona ion generation electrode with an insulator interposed therebetween. Preferably, it is constituted by a solid state corona ion generator.

A corona ion flow head for low-voltage drive is a solid-state head that is constructed by installing an induction electrode and a corona ion generation electrode with an insulator in between, and a shielding electrode that shields the leakage magnetic field from the induction electrode. A corona ion generator and a control electrode for controlling corona ions from the solid state corona ion generator at a voltage lower than the charging potential of the recording medium by the precharging charging means for each recording pixel. The space charge due to a large amount of corona ions generated from the corona ion generating electrode is controlled by a low voltage of about 30 V, and corona ion flow control that allows gradation recording is performed in accordance with the image signal.

The D electric transfer means is preferably constructed by sequentially laminating a conductive layer and a resistance layer on the circumferential surface of a foamed elastic support column supported by a metal shaft, and has mechanical properties and electrical properties designed independently. The color toner image is electrostatically transferred onto the recording paper by pressing this roller against the circumferential surface of the recording drum through the recording paper.

(Function) In the electrostatic color recording device according to the present invention, by using a corona ion flow head that can be driven at low voltage to form an electrostatic latent image, the chip area of the driving JtjlC is reduced, and the size of the corona ion flow head is reduced. In addition, a uniform electrostatic latent image with high electrostatic contrast can be obtained.

This low-voltage drive corona ion flow head controls the space charge of the corona ion flow generated on a large plate with a low voltage signal voltage according to the image (No. 7), and a part of the controlled corona ion flow Corona ions are accelerated by the surface potential on the recording drum, reach the recording drum, erase the charge on the recording drum, and form an inverted electrostatic latent image. It does not affect the image.

In addition, when forming an electrostatic latent image using this low-voltage driving corona ion flow head, the recording medium on the recording drum is precharged to a -like potential, so that the electrostatic latent image is formed on the color toner image on the recording drum. Even if the charge is not removed before forming the electrostatic latent image, the new electrostatic latent image will not become non-uniform. In this case, if a solid corona ion generator is used as the charging means for precharging, the surface potential on the recording drum is determined by the bias voltage applied to the solid corona ion generator, so that a constant potential is always maintained on the recording drum. This will be applied to the color toner image.

On the other hand, by electrostatically transferring the color toner image formed on the recording drum to the recording paper, residual toner is prevented from fusing onto the recording drum, and residual toner can be cleaned using ordinary resin blade cleaning. Therefore, the recording medium can be a general low-cost T8H machine.

When the above-mentioned functionally separated soft roller is used as the electrostatic transfer means, high transfer efficiency that is stable even under environmental changes can be obtained. This reduces the amount of toner remaining on the recording drum after transfer, and it becomes possible to remove the cleaning device by utilizing the cleaning action of the contact developing device. By using a developing device which also serves as a cleaning device and which applies black toner, the influence on the image (color variation) due to the contamination of the wiped-off residual color toner is reduced. As a result, an electrostatic color recording device that does not generate waste toner and is easy to maintain for the user is realized.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. FIGS. 1 and 2 are schematic cross-sectional views showing an embodiment of an electrostatic color recording apparatus that forms a color image by rotating a recording drum a plurality of times.

The electrostatic color recording device shown in FIG. 1 includes a solid corona ion generator 2 for precharging and a solid corona ion flow head 3 for low voltage driving around a recording drum 1 having an insulating recording medium on its circumferential surface. , a non-contact developer 4.5.6 each having color toners of different colors, a solid corona ion generator 7 that makes the potentials of the color toner images that have been developed superimposed the same, and a color toner image on the recording drum 1. It is constructed by disposing a functionally separated soft roller 9 for transfer, which electrostatically transfers the toner onto the recording paper 8, and a cleaning device [¥10] which removes the residual toner after the transfer. The thermal fixing device 11 is for fixing the color toner image transferred to the recording paper 8 to the recording paper 8.

Next, the process of forming a color toner image on the recording paper 8 will be described. First of all, using the solid corona ion generator 2 for precharging, the recording medium on the recording drum 1 is
Apply a potential of 0v.

Next, the solid corona ion flow head 3 for low voltage drive generates a corona ion flow according to the color image signal to erase the charge on the recording drum 1 and achieve an electrostatic contrast of 450.
forms an inverted electrostatic latent image. This electrostatic latent image is
Reversal development is performed using toner of negative polarity using the first developing device 4 to which a bias voltage of v is applied. During this first color toner image formation, the solid corona ion generator 7 for making the polarity of the toner images on the recording drum 1 the same is not operated. Further, the functionally separated soft roller 9 is kept separate from the recording drum 1. Further, the cleaning blade 12 is also separated from the recording drum 1 to prevent disturbances in the developed toner image.

Next, the recording drum 1 is rotated to form a second toner image on the formed toner image. That is, similarly to the first time, the solid corona ion generator 2 for precharging is used to uniformly charge the recording drum 1 to a potential of 600 V again. Thereafter, the corona ion flow of the low-voltage driving corona ion flow head 3 is controlled according to the signal using a color image signal different from the color image signal of the second time, and the inverted electrostatic latent image is transferred to the first time. color toner image. This inverted electrostatic latent image is developed by a non-contact developing device 5 using color toner of a color corresponding to the color image signal, starting from the first color toner image.

Repeat the above color image creation process as many times as necessary, and then
Two color toner images are formed one on top of the other on a recording drum 1. Since each toner layer has a different potential, the potential of the color toner images formed in layers on the recording drum 1 in this way is changed to a -like potential using a solid corona ion generator 7 for static elimination. do. Thereafter, the recording paper 8 is conveyed, and the function-separated soft roller 9 is brought into contact with the recording paper 8 from the back side, and the color toner image is electrostatically transferred onto the recording paper 8.

The color toner image transferred onto the recording paper 8 is fixed onto the recording paper 8 by a heat fixing device 11, and then transferred onto the recording drum 1.
The color toner remaining thereon is mechanically cleaned off by a cleaning blade 12, and then it is reused. In this apparatus, liquid development may be used as the development method. It goes without saying that the polarities of the potentials may all be reversed.

FIG. 2 is a schematic cross-sectional view of the electrostatic color recording apparatus with the cleaning device removed, and the recording drum 1 is precharged by a solid corona ion generator 2 to a potential of 600V. Next, using the low-voltage driving solid state corona ion flow head 3, the charge on the recording drum 1 is erased with a positive corona ion flow controlled according to the black and white image signal, and an electrostatic contrast of about 450 Create an inverted electrostatic latent image. This electrostatic latent image is reversely developed using a black contact developer 13 to which a bias voltage of 400 cm is applied. After this first toner image formation, the recording drum 1 is rotated and precharged in the same manner as during the second image formation, and the potential on the recording drum 1 is again uniformly charged to about 600V. Thereafter, the low-voltage driving corona ion flow head 3 is controlled in accordance with the color image signal, and an inverted electrostatic latent image for a color image is formed on the previously formed black and white toner image. This reversed color electrostatic latent image is reversely developed on the monochrome toner image using a non-contact developing device 5 with color toner of a color corresponding to the color image signal.

The above color image forming process is repeated as many times as necessary to form the same black and white toner image.

During this time, stop conveying the black and white contact developer.1. B. Prevent the developing device from coming into contact with the toner image on the recording drum.

Further, the functionally separated soft roller 9 and the cleaning blade 12 are mechanically separated from the recording drum 1 to prevent the developed toner image on the recording drum 1 from being disturbed.

The color toner image created on this recording drum 1 is
Since each battery has its own potential during precharging, the solid corona ion generator 7 for weight removal is operated to give a negative potential. After that, the recording paper 8 is conveyed, and the functionally separated soft roller 9 is brought into mechanical contact with the back side of the recording paper 8.
A negative voltage is applied to electrostatically transfer the color toner image onto the recording paper 8. The color toner image transferred onto the recording paper 8 is fixed onto the recording paper by a thermal fixing device 11. on the other hand,
The recording drum 1, which whitens the color toner remaining after the transfer, is used as it is in the next color image forming process. This recording drum 1 is uniformly charged to 600 V by a solid corona ion generator 2 for precharging residual color toner, and a negative corona ion flow is applied by a solid corona ion flow head 3 according to a black and white image signal. An inverted electrostatic latent image is created.

This electrostatic latent image is developed with a contact developer 13 containing black toner. During this development, the potential of 600V was 17. The resulting residual toner in the non-image area is cleaned by a developing device with a bias voltage of 400V. On the other hand, the residual toner in the image area remains as it is, and a new black toner image is formed on the residual toner, and then a color image is formed. The remaining color toner on the recording drum 1 at this time cannot be identified due to light absorption of the black toner. In this way, color toner images can be created repeatedly.

When creating a monochromatic image using the electrostatic color recording apparatus shown in FIG. 1, which is equipped with a cleaning device, the necessary color developing devices are operated and the image is formed by rotating the recording drum - times.

On the other hand, in the case of the electrostatic color recording device shown in FIG. 2 in which the cleaning device has been removed, the recording drum 1 is rotated one more time after development with the necessary color developing device, and the remaining toner is cleaned with the contact developing device 13 containing black toner. do.

Note that when a color image is formed using the two heads as in the two embodiments described above, a good color image without any color shift can be formed, but the recording speed will be low. Next, an embodiment of an electrostatic color recording apparatus that forms a color image by rotating a recording drum will be described with reference to FIGS. 3 and 4.

First, the case of FIG. 3, which includes a cleaning device, will be explained. Around the recording drum 1, there are three sets consisting of a solid corona ion generator for precharging, a solid corona ion flow head for low voltage drive, and a contact or non-contact developing device 4,5.6 for whitening colored toner. Image forming stage 14
, 15° 16 are provided, and color toner images are successively formed on the recording drum 1 in an overlapping manner. This color toner image is made to have the same polarity as - by a solid corona ion generator 7 which makes the toner potential on the recording drum 1 the same, and is electrostatically transferred to the recording paper 8. As in the previous embodiment, the transfer is performed using a functionally separated soft roller 9 which has high transfer efficiency and good environmental stability. The color toner image transferred onto the recording paper 8 is fixed onto the recording paper 8 by a thermal fixing device 11 . On the other hand, the residual toner on the recording drum 1 after the transfer is cleaned by the cleaning device 10, and the recording drum 1 is used again. In this color recording apparatus, a liquid developer may be used for the developing device.

FIG. 4 shows an electrostatic color recording device in which the cleaning device is removed and color recording is performed by rotating the recording drum.A contact developing device 13 for black toner, which also serves as a cleaning device, is installed around the recording drum 1. A color image forming stage 1 including a forming stage 17 and a non-contact color developing device 6
Provide 4°15.16. The contact developing device 13 may be a two-component developing device or a -component developing device.

First, the black and white image forming stage 17 is used, and the recording drum 1 is heated by the solid corona ion generator for precharging.
After uniformly charging the recording drum 1 to
Above is an electrostatic charge with an inverted electrostatic contrast of about 500V.
Form P't R. This inverted electrostatic latent image is
Reversal development is carried out using a contact developing device 13 for black color having a cleaning function to which a bias voltage (2) is applied. Then,
A color recording stage 14 is used to precharge the black and white toner image, and an electrostatic latent image is formed by a solid corona ion flow head for low voltage drive, and a color toner image is superimposed using the non-contact developing device 4. do. Similar color image creation steps are performed at image forming stages 15 and 16 to form a color image on the black and white toner image. The color toner image on the recording drum 1 is made uniform in potential by a solid corona ion generator 7 for static elimination, and the color toner image is electrostatically transferred onto the recording paper 8 conveyed by a function-separated soft roller 9. transcribed into. The color toner image transferred onto the recording paper 8 is fixed onto the recording paper 8 by a thermal fixing device 11 .

On the other hand, a recording drum 1 having residual color toner after transfer
enters the next color image forming process. During image formation, the remaining color toner is uniformly charged again by a solid corona ion generator for precharging. Then, as before, a black and white image (ei
A negative corona ion flow is applied from above the residual toner to obtain an inverted electrostatic latent image. This electrostatic latent image is developed by a contact developing device 13 that applies black toner.

During this development, residual toner in the non-image area is cleaned by a developing device to which a bias voltage of 400V is applied. The residual color toner in the image area remains as it is, a new black toner image is formed on the residual color toner, and a color image is formed again. At this time, the color image formed by the residual toner on the recording drum 1 is not identified by the light absorption of the black toner. In this way, color toner images can be formed repeatedly.

To create an RLT color image, the necessary color image forming stages are operated in the electrostatic color recording station 2 in which the cleaning device 12 of FIG. 3 is located.

On the other hand, in the case of the electrostatic color recording device shown in Fig. 4, which does not have a cleaning device, after forming an image on the necessary color stage, the recording drum is rotated once and the remaining toner is cleaned using a contact developing device that heats black toner. There is a need to.

In the electrostatic color device of each embodiment described above, the solid corona ion generator for precharging and the solid corona ion flow head for low voltage driving may be used in an integrated manner.

Next, the electrostatic latent image forming process using the low-voltage driven corona ion flow head will be described in detail.

FIG. 5 is a diagram showing the configuration of a precharge corona ion generator and a low voltage driving corona ion head. In this device, a recording medium 21 configured by providing an insulating layer 2 on a conductive substrate 22 is heated to a surface potential of, for example, +600 V by a precharging corona ion generator 24 before forming an electrostatic latent image. After uniformly charging so that An electrostatic latent image is formed on the surface. The precharging corona ion generator 24 is provided with a corona ion generating electrode 27 having a steeply cut slit 26 for concentrating an electric field for generating corona ions on one side of an insulating substrate 25, and a corona ion generating electrode 27 having a sharply cut slit 26 for concentrating an electric field for generating corona ions on one side of an insulating substrate 25. The slit 26 is provided with an induction electrode 28 for forming an electric field. Between these picture electrodes 27 and 28, a peak voltage of 900 cm and a frequency of 20
An alternating current voltage 29 for generating corona ions of kllz is applied, so that positive and negative corona ions are generated. In addition, the corona ion generating electrode 27 includes
A positive bias voltage 30 (+ (iooV)) approximately equal to the surface potential (charged potential) applied to the recording medium 21 is applied, and only positive corona ions move toward the recording medium 21, creating a corona charge on the recording medium 21. 6I52 is accumulated.As a result, the surface potential VS of the recording medium 21 becomes +600V.

Using this solid corona ion generator 24, the recording medium 21
When precharging is performed, a large amount of corona ions are generated, and a surface potential equal to the potential defined by the bias voltage 30 is created on the recording medium 21. Therefore, even if a color toner image already exists on the recording medium 21, a stable surface potential can be applied to the color toner image regardless of the thickness of the color toner layer.

The recording medium 21 thus charged to a -like surface potential Vs is then conveyed in the direction of the arrow to a low-voltage driving corona ion flow head consisting of a plurality of elements provided corresponding to the recording pixels. It reaches below 31. This low voltage driven corona ion flow head 31 has a corona ion generator 37.
and a control electrode 38 for controlling the flow of corona ions through the through-hole for corona ions.

The corona ion generator 37 is provided with an induction electrode 33 and a corona ion generation electrode 35 common to each recording image point on both sides of an insulating substrate 32 made of ceramic or the like.

The corona ion generating electrode 35 is provided with a common corona ion generating slit 34 for electric field concentration having a steep cut surface corresponding to each recording dot. A shielding electrode 36 is provided in the corona ion generation slit 34 for shielding a wasteful electric field generated by the alternating current voltage for corona ion generation. It is set to the potential. A +30V bias voltage 41 is applied to the corona ion generating electrode 35 and the shielding electrode 36 to shield the corona ion flow, and a peak-to-peak voltage of 2 kV, 40 kHz is applied between the induction electrodes 33 to generate corona ions in synchronization with the signal voltage. By applying the AC voltage 39, a large amount of positive and negative corona ions are generated. Among these positive and negative corona ions, negative polarity corona ions 53 are used for electrostatic latent image formation.
A bias voltage 40 for generating corona ions is applied to the corona ion generating electrode 35 so that more ions are generated.

On the other hand, a signal voltage 42 of about +30V, for example, is applied to the control electrode 38 having a through hole for corona ion flow.

Note that the corona ion generating electrode 35 and the shielding electrode 36 are set to earth potential, and the voltage No. 1d of the control electrode 38 is set to -13.
It may be biased to 0V.

Of the positive and negative corona ions generated from the corona ion generating electrode 35, only the negative corona ions 53 are selected by the control electrode 38 to which a signal voltage 39 is applied, and are accelerated at a surface potential of +00 (IV) on the recording medium 21. The inverted electrostatic latent image 54 reaches the recording medium 21 and lowers its surface potential to +200 V or less.Thereby, an inverted electrostatic latent image 54 of 400 V or more and a high electrostatic contrast is obtained on the recording medium 21.

A plurality of such corona ion flow heads 31 are arranged in a line with the corona ion generator 37 common to eight recording pixels. In that case, the control electrode 38 is provided individually corresponding to each recording pixel, and is connected to a driving IC (not shown). Image signals corresponding to each recording pixel point are manually input to this driving IC in parallel from an image signal source, and the driving signal (signal voltage 42) from the driving IC is controlled according to λ・1 for each recording pixel point. is supplied to the electrode 38.

h゛, The corona ion generating electrode 35 and the shielding electrode 36 of the corona ion generator 37 are biased to a corona ion shielding voltage by a bias voltage 41, and are connected to an AC power source (not shown) that generates an AC voltage 39 for generating corona ions. be done. This AC power supply and the image signal source described above operate in synchronization with a synchronization signal from a synchronization signal source (not shown).

When forming an electrostatic latent image using the low-voltage driven corona ion flow head 31 in this way, a portion of the large amount of generated corona ion flow is controlled and used. Not affected by Furthermore, since the corona ion flow is accelerated by the surface potential of the recording medium 21 given by the precharge corona ion generator 24, even when color toner images are formed in a superimposed manner as in the present invention, the surface potential on the recording medium 21 is A stable electrostatic latent image can be created on a color toner image.

Next, the operation of this low voltage driven corona ion flow head 31 will be explained in detail. First, the function of the shielding electrode 36 provided within the corona ion generating slit 20 of the corona ion generating electrode 35 will be explained using FIG.

In the case of the corona ion generator without the shielding electrode 36 shown in Fig. mb (a), the recording medium 21 is set to a surface potential of +eoov, the control electrode 38 is set to +30■, and the corona ion generator 37 generates corona ions. When the electrodes 35 are each biased to +30V and an AC voltage with a peak-to-peak voltage of 1.800V for corona ion generation is applied to the induction electrode 33, negative corona ions are generated from the corona ion generation electrode 35 and the recording medium 21 reach. The potential distribution at this time is as shown in FIG. 6(b).

On the other hand, if a shielding electrode 36 is provided to have the same potential as the corona ion generating electrode as shown in FIG. 7(a),
The potential distribution becomes as shown in FIG. 7(b).

That is, when the shield electrode 36 is present, the potential difference between the corona ion generator 37 and the control electrode 38 is several tens of volts.
The following results, and by simply setting the control electrode 38 to 0■, it becomes possible to apply a reverse electric field to negative corona ions, and the negative corona ions can be controlled. Furthermore, the corona ion generating electric field of the corona ion generating electrode field is hardly affected, and stable corona ions are generated. On the other hand, positive corona ions of opposite polarity generated by the AC voltage applied to the corona ion generating electrode 35 and the induction electrode 33 do not reach the recording medium 21 due to the reverse electric field between the recording medium 21 and the control electrode 38. It is absorbed by the control electrode 38.

Note that even if such a shielding electrode 36 is provided, the amount of corona ions generated does not decrease. The reason for this is that the region where corona ions are generated is a strong electric field region several microns near the corona ion generating electrode 35, and the electric field fluctuation in this region is 1
50 μm in the 00 μm corona ion generation slit 34
This is because there is almost no change even if the shielding electrode 36 having a width of m is provided.

Next, the above-mentioned operating principle will be further explained theoretically. The basic operation is almost the same as that of a diode vacuum tube, but the difference is that a vacuum tube deals with electrons, whereas the present invention deals with corona ions. Therefore, the relational expression between carrier velocity and voltage is different, resulting in a difference in the two basic equations for corona ion current. Here, explanation will be given using the basic equation and the equation of corona ion current derived from it.

The basic equation showing the behavior of corona ions is shown by the following equation.

■, −ρ ・ υ (3
) Here, ■ is the potential at a point a distance y from the corona ion generator 37, εa is the relative dielectric constant of air, ε0 is the dielectric constant in vacuum, and ρ is the corona ion flow existing as a space charge at the distance y. The amount of charge due to, ■ is the velocity at distance y, μ is the mobility of the corona ion, 1. is the corona ion current at distance y.

The above equation indicates a steady state in which space charges due to corona ions exist, and the period of the alternating current voltage 39 for corona ion generation applied between the induction electrode 33 and the corona ion generation electrode 35 is recorded by the corona ions. The period of the signal voltage 42 applied to the control electrode 38 needs to be sufficiently longer than the time required to reach the medium 21 (approximately 2 μsec), and the period of the signal voltage 42 applied to the control electrode 38 must also be sufficiently longer than this time. By proactively creating and controlling space charges in this way, low-voltage drive is made possible.In contrast to the conventional method, corona ion on/off control is achieved by removing space charges. However, multi-level recording is not possible with the conventional method, and they are fundamentally different.

Furthermore, it is preferable to apply an alternating current voltage (preferably a rectangular wave) so that the signal voltage 42 and the generation of negative corona ions are synchronized, so that an approximation to a steady state is established.

The negative corona ions generated in this way are transferred to the control electrode 3
When a voltage Vg is applied between the corona ion generating electrode 35 and the corona ion generation electrode 35, corona ions 7i5 flow in the direction of the recording medium 21 having the surface potential VS as a stream of corona ions 7i5 expressed by the following equation.

(4) Here, a is the distance between the recording medium 21 and the control electrode 38, and b is the distance between the control electrode 38 and the corona ion generator 37. k is a voltage amplification factor that takes into account the peripheral effect of the control electrode 38 corresponding to the grid, as in the case of a diode vacuum tube. In other words, if the corona ion through holes on the control electrode 38 are approximated as existing periodically like the grid of a vacuum tube, the voltage amplification factor changes as a function of the distance from the electrode center due to the effect of the control electrode 38. Its value is minimum at the center of the electrode.

When the amount of corona ion generation is small, the corona ion current according to equation (4) flows until it reaches a saturation current, but the current becomes constant above that saturation current value. Therefore, when using the amount of corona ions generated or less, the electrode structure, control electrode 38
It changes depending on the voltage applied to the recording medium 21 and the surface potential of the recording medium 21.

From the above, by setting the alternating current flow pressure 39 for corona ion generation of each element of the corona ion flow head 31 to a voltage higher than the voltage that obtains the amount of corona ion generation necessary for recording, it is possible to reduce the variation in the corona ion generation electrode 35. It is possible to suppress fluctuations in the amount of corona ions generated. In addition, the control voltage that shields the corona ion flow is expressed by the following equation,
The voltage at which the amplification factor is minimum at the center of the electrode is the maximum shielding voltage value. By applying this voltage to the control electrode 38, it becomes possible to shield the corona ion current.

Vg--Vs/k
(5) Furthermore, the signal voltage applied to the control electrode 38 preferably has a smaller value than the bias voltage applied to the corona ion generating electrode 35. This value is the corona ion generating electrode 35
If the voltage is higher than the voltage of The potential with respect to the electrode 38 fluctuates, further deteriorating the usage efficiency of corona ions. Therefore, it is preferable to set the control electrode voltage according to the signal to Ov that maximizes the corona ion current.

Next, the response speed of the corona ion recording device will be explained. Since the initial surface potential VSO on the recording medium 21 decreases with time t due to the negative corona ion flow reaching the surface, the corona ion current also gradually decreases. As a result, the surface potential Vs that changes over time is expressed by the following equation, taking this point into consideration. Here, the potential of the control electrode 38 is set to 0, which maximizes the corona ion current 1 during signal input.
It was set as v.

(6).

Note that Cp is the capacitance of the recording medium 21.

FIG. 8 shows a specific configuration example of an electrostatic color recording device (printer) constructed based on the above theoretical consideration. In FIG. 8, 100 is a main body, and a recording drum 101 having a recording medium formed on the circumferential surface is provided in the main body 101. As in Figure 1, a solid corona ion generator 102 for precharging, a solid corona ion flow head 103 for low voltage driving, non-contact developing devices 104, 105, and 106 each having a different color toner are used for development. A roller transfer device 300 that uses a solid corona ion generator 107 that makes the potential of color toner images the same, and a functionally separated soft roller for transfer that electrostatically transfers the color toner image on the recording drum 101 to 10 g of recording paper.
, and a cleaning device 110 for removing residual toner after transfer are sequentially provided. The color toner image transferred to the recording paper 108 is fixed to the recording paper 108 by a thermal fixing device 111.

The recording drum 101 is constructed by forming a cylindrical recording medium in which a 50 μm thick resin-based insulating layer is provided on a conductive layer. 500 μm on this recording drum 101
A solid corona ion generator 102 for precharging is provided at a location. This corona ion generator 102 has an induction electrode with a width of 1-m and a length equal to the width of a 2-μm-thick recording medium on an insulating substrate such as a ceramic, and an 8-μm-thick induction electrode on the insulating substrate.
A thick resin-based insulating layer is uniformly applied, and a 2 μm thick corona ion generating electrode having a 100 μm wide slit is provided on the layer with a length equal to the length of the recording drum 101 in the main scanning direction. There is. Further, the slit is set to be located above the induction electrode. An amplitude voltage of 1800V is applied between the induction electrode and the corona ion generation electrode.

Positive and negative corona ions are generated by applying an alternating voltage with a frequency of 5kllz. + eoo for the corona ion generating electrode
A bias voltage of V is applied, and only positive corona ions are deposited on the recording drum 101, which is charged to +600 V.

10 near the corona ion generating electrode of the corona ion generator
In the μm range, a strong alternating current electric field generates positive and negative corona ion currents along the corona ion generating electrode as large as 2.8×1O−4 A/1. For this reason, 50μ
The m-thick recording drum 101 is charged to +600V, which is equal to the bias voltage, in a short time of about 100 μsec.

Next, this charged recording drum 101 is conveyed to the position of the corona ion flow head 103, where negative corona ions are generated according to the image signal, the +coov surface charge is erased, and the electrostatic potential is reversed. An image is formed. The corona ion generator in the corona ion flow head 103 has almost the same structure as the precharge corona ion generator 102, but a 50 μm wide shielding electrode is provided in the 100 μm wide slit of the corona ion generating electrode. They differ in some respects. In addition, a 10μm hole with a 100μm through hole corresponding to each recording dot was placed 60μm from the corona ion generator.
A control electrode with a thickness of m is provided, and further 2
Recording drum 1 with a surface potential of +600μm at 000μm
01 is transported. The resolution of this head is 10 wood 1 va
- corresponds to

Next, the operation of the electrostatic color recording apparatus shown in FIG. 8 will be explained with reference to FIGS. 5, 9, and 10. Corona ion generation electrode of the corona ion flow head 103 (35 in FIG.
) and the shielding electrode (36 in Fig. 5) are connected to the same ground potential, and between the induction electrodes 33 is a sine wave or rectangular wave with an amplitude voltage of 2 kV and a frequency of 40 kllz synchronized with the pulse width modulated signal voltage. An alternating current voltage is applied, which produces positive and negative corona ion currents of approximately 2.8 x 10-'A/cll. Among these corona ion currents, only negative corona ion currents are connected to the control electrode (38 in Figure 5).
) and reaches the third recording drum 101.

The amplification factor of the corona ion flow head 103 at this time differs depending on the distance from the center of the electrode, as shown in FIG. 9, based on calculations similar to those for the triode vacuum tube. The amplification factor has a minimum value of "16" at the center of the electrode, and a larger value of "30" at the periphery. Therefore, from equation (5), the cutoff voltage of the negative corona ion current accelerated by the surface potential (+600 V) of the recording drum 101 is maximum at the center.

At this time, by applying a reverse bias of +30 V to the corona ion generating electrode, the corona ion current can be interrupted. In this way, the bias voltage (
By applying +30V as 41) in FIG. 5 and applying +30V and Ov signal voltages to the control electrode 38,
The on/off of the corona ion current is the function of the mouth. The maximum value of the corona ion current flowing at this time is given by equation (5): 1
．． 3X 10'A/c- and the corona ion current produced from the corona ion generator (2,8X 10'
A/c+n). Therefore, even if there are variations in the corona ion generators that make up the corona ion recording head, a sufficient amount of corona ions can be supplied, and the corona ion flow determined by the control voltage can be secured for each recording dot. There is no difference in the amount of corona ions generated.

Furthermore, the signal voltage (42 in Figure 5) applied to the control electrode of this corona ion flow head 103 is synchronized with the 5 kHz corona ion generation AC voltage (39 in Figure 5) applied to the corona ion generator. This is given every 100 seconds of negative corona ion generation time.

Next, FIG. 10 shows the surface potential attenuation characteristics of the recording drum 101 with respect to elapsed time when a corona ion current corresponding to an image signal is applied.

After 100 μsec, +60 on the recording drum 101
The surface potential of 0V decreases to +150V at the center of the pixel, and 45
An electrostatic latent image with high electrostatic contrast at 0V is obtained. Although the corona ion current value slightly decreases around the image point, an electrostatic contrast of about 350 V can be obtained. Since the potentials at the center and the periphery of the pixel are different in this way, the corona ion generators may be arranged in a staggered manner so that adjacent pixels overlap to obtain a uniform potential. This 100μ5
The printing speed of ee (1 cycle: 200.cz 5ee) is 1
At a resolution of 0 lines/ml, the continuous flow is approximately 90 sheets/minute (equivalent to A4).

In the electrostatic color recording device according to the present invention described above, it is possible to lower the signal voltage for corona ion flow control from the conventional several hundred volts to 30 to 40 volts or less.

In addition, the high bias voltage of several hundred volts for accelerating corona ions, which was conventionally applied between the recording drum and the control electrode, is no longer necessary, and as a result, the high bias voltage of several hundred volts, which is applied between the control electrode and the ion generation electrode, is no longer necessary. The bias voltage can be reduced to several tens of volts.

In this way, a low voltage drive IC with a small mounting area can be used as the drive IC of the corona ion flow head section, and it is possible to manufacture a small corona ion recording head in which the drive ICs are all mounted on the head substrate. Also, unlike conventional methods, by controlling the space charge generated by corona ions,
Corona ion current can be determined only by applied voltage, and variations in corona ion flow caused by manufacturing variations in corona ion generating electrodes are eliminated, making it possible to provide a stable corona ion recording head. In addition, in conventional heads for corona ion recording, the recording potential on the recording drum was determined by the withstand voltage of the driving IC, so the recording potential was limited to about 150V at most. As described above, the only toner capable of developing a low surface potential was a conductive magnetic toner. Because of this conductivity, electrostatic transfer to recording paper has not been possible, and thermal or pressure transfer has been used. Therefore, wiping off of the residual toner caused by toner fusion on the recording medium is done by scraping off the residual toner with a metal blade, and the recording medium is limited to an alumite coating with a high surface height. Furthermore, because magnetic toner was used, colorization was not possible.

On the other hand, according to this embodiment, since a high recording voltage can be controlled by a low-voltage driving IC, an insulating toner for developing the high recording potential used in electrophotography can be used, and it is possible to transfer the toner to the recording paper. The electrostatic transfer becomes nI-effective, toner melting to the recording drum is eliminated, and residual toner can be wiped off with a wiping blade made of commonly used resin, so the recording medium is also made of inexpensive resin-based insulation. body becomes available for use.

Corona ion generator 1 for precharging as described above.
The recording drum 101 is coated with positive corona ions in step 02, and on which an electrostatic latent image is formed by selectively supplying negative corona ions according to the image signal with the corona ion flow head 103. Next, the recording drum 101 is developed. The container 104 is reached. Developer 1
The developing process in 04 will be explained using FIG.

On the recording drum 101, which is provided on a conductive substrate and is composed of an insulating layer, residual toner of negative polarity 21 in the image area 210 remaining after the transfer of the previous image formation and residual fog in the non-image area 212 are deposited. Toner is present. This residual fog toner is positively charged fog toner 213 of opposite polarity.
Or it is part of a negative polarity fog toner (not shown) (FIG. 11(a)). Next, the cathode process (Fig. 11(b)
)), the negative polarity D is set by the recharger 104 at
When static electricity is removed using C voltage (or AC voltage may also be used), the potential on the recording medium 9 is uniformly removed due to the characteristics of corona discharge, and becomes a potential of -50V (or OV). At this time, regardless of the amount of residual toner, the potential of the recording drum 101 becomes uniform due to leakage current such as creeping discharge of toner particles. The polarity of the residual toner on the recording drum 101 is completely converted to negative polarity 215 by this static elimination process. By the recording process (FIG. 11(C)) using the head unit 114 on the recording drum 101, which has a low negative potential (or zero potential), a positive electrostatic potential is created according to the recording signal. form an image.

As a result, a higher potential 21B is applied to the new image area due to the corona ion flow, and the non-image area is not given any charge and becomes the same potential as the static elimination process. At this time, the toner in the newly formed image area becomes positive polarity 217 due to the ion flow according to the signal. In the next development process that also serves as wiping (FIG. 11(d)), the bias voltage 21
At the same time as the residual toner 217 is wiped off by the developing roller 112 biased to a positive voltage at 8, development is performed. The negative polarity toner 220 existing in the non-image area formed at this time moves in the direction of the arrow to the developing roller 112 biased to a positive potential in the direction of the arrow. On the other hand, the residual toner 217 at a highly positive potential in the image area moves to the developing roller 112 whose potential is lower than the potential in the image area. At the same time, the developing negative toner 221 of the developing roller 112 moves onto the recording drum 101 in the image area where the potential is high. In this way, the wiping process and the developing process are completed at the same time (FIG. 11(e)), and the image area on the positively charged recording drum 101 is filled with negative developing toner 22.
3 is attached and a visible image is formed. On the other hand, low negative potential 2
A small amount of positive polarity toner 225 or negative polarity fog toner (not shown) may adhere to the non-image area 24 in some cases.

The entire image forming process is thus completed.

FIG. 12 shows the recording drum 101 in the image forming process.
The above shows the potential change. Figure 12 (a) (b) (c
) (d) (c) shows potentials corresponding to each image forming process, where the solid line represents the potential of the image area and the dotted line represents the potential of the non-image area. The potential on the recording drum 101 after the image formation after the previous development and transfer processes (FIG. 12(a)) is +450V in the image-formed area.
The voltage is -30V in the non-image area. In the static elimination process (FIG. 12(b)), the electric potential is made uniform to 50 V regardless of whether the image is formed or the non-image area by the bricharger 104. The following recording process (
In FIG. 12(C)), the new image area is charged to +500V, and the non-image area is kept at -50V. Development process (
In FIG. 12(d)), +50 of the residual toner of the previous image
Depolar residual toner 236 in new image area at 0v
The negative polarity residual toner 238 in the non-development area is applied to the low potential side developing roller biased to +200V.
It moves to the developing roller in the direction of the arrow on the high potential side where the image is developed. On the other hand, the negative polarity developing toner 23 on the developing roller
9 moves to the high potential side of 500V in the image area and development is performed. The recording drum 101 that has completed development in this way
The upper potential (FIG. 12(e)) rises to +450V in the new image area due to development, and rises from -50V to -30V in the non-image area due to contact with the developing roller. Finishing the color toner image forming process.

Next, the recording drum 101 is rotated, and a second toner image and a second toner image are sequentially formed on the first toner image. Of course, during the second and third toner image formation, developing devices 105 and 106 are used, respectively.

After three color toner images are formed on the recording drum 101 in this way, they are brought to a uniform potential by the solid corona ion generator 107 for weight removal, and then transferred to a roller transfer device 300 using a functionally separated soft roller. The color toner images are electrostatically transferred onto the recording paper 108 all at once. A cassette 119 is installed inside the main body 101, from which recording sheets 108 are sequentially taken out one by one via a take-out roller 116. The recording paper 108 taken out by the take-out roller 116 is conveyed to the circumferential surface of the recording drum 101 and onto the roller transfer device 300, where the color toner image is transferred, and further onto the recording paper 108.
transcribed into. After the transferred color toner image is fixed on the recording paper 108 by a thermal fixing device 111, the recording paper 108 is carried out from an exit 120. Recording paper 108
On the upstream side of the conveyance path, there is a pair of aligning rollers 117a.

117b is provided. Recording drum 101 after transfer
The color toner remaining thereon is mechanically cleaned by a cleaning blade 112 and then reused.

Next, potential fluctuations on the recording drum during color image formation will be explained with reference to FIG. This figure 13 shows the second
The figure shows potential fluctuations on the recording drum when a color image is formed by an electrostatic color recording apparatus that rotates the recording drum three times without the cleaning device shown in the figure. Figure 13 (1) (n) (
In) is the potential fluctuation on the recording drum when a black and white image is formed using the black and white image signal of the first color when there is residual color toner from the previous image formation on the recording drum 1;
IV) (V) (Vl) is the potential fluctuation when a yellow and magenta image is formed on the first color toner image using the second and third color yellow and magenta signals, (
Similarly, (■) (■) and (■) respectively show the potential fluctuations on the recording drum 1 when forming the fourth color cyan image.

FIG. 13(I) shows that after a surface potential of 600 V is applied to the recording drum 1 by precharging by the solid corona ion generator 2, negative corona ions are applied to the image area by the solid corona ion flow head 3. An electrostatic latent image is formed and 50
This shows a state where the voltage has decreased to about V.

FIG. 13(U) shows residual toner 50 on this recording drum 1.
The state is shown when wiping is performed using the contact developing unit 4 which also serves as a cleaning bias biased to 0■, and at the same time reverse development is performed using positive polarity black toner. Residual color toner in non-image areas on the positive voltage side of the developing bias is wiped off by a contact developing device. - On the other hand, in the image area, black toner is developed over the residual color toner. Due to this developed black toner, the remaining color toner on the recording drum 1 cannot be identified.

FIG. 13 (III) shows the solid corona ion generator 2 from above the black toner image developed for the next toner image formation.
to uniformly charge the recording drum 1 again and raise the surface potential of the recording drum 1 to 600V.
Shows the state when it is set to .

The surface potential at this time is determined by the bias voltage applied to the solid corona ion generator 2, and is also determined by the difference in capacitance due to the difference in toner layer thickness between the image area where black toner exists and the non-image area where black toner does not exist. Regardless, the aoov is constant.

Next, Figure 13 (mV
). The non-image area remains at a constant surface potential of 600V regardless of the presence or absence of black toner, but the image area irradiated with negative polarity corona ions with the yellow signal drops to 50V. At this time, positive corona ions in the image area generated from the solid corona ion flow head 3 are accelerated by a potential of 600 cm on the recording drum 1, erase this charge, and lower the potential on the recording medium 1. Therefore, the black toner in the yellow image area is not charged to the opposite polarity due to the difference in capacitance due to the thickness of the toner layer, unlike in conventional electrostatic color recording devices, and the electrostatic contrast is stable. A latent image can be formed.

The electrostatic latent image formed on this black toner image is the 13th
As shown in Figure (V), yellow toner is developed with a non-contact developing device 5 that heats it. This non-contact development T15 is 600
An AC voltage of 1.2 kV r p biased with a DC voltage of v is applied. In the image area, a high developing voltage of +200V, which is a superimposed AC voltage of 1.2 kVp-p biased with a DC voltage of aoov, is applied between the recording drum 1 and the yellow toner of positive polarity flies onto the recording drum 1. Then, development is performed. On the other hand, the toner in the non-image area remains on the recording drum 1 without being electrostatically attracted to the non-contact developing device 5. In this way, black and yellow images are formed.

Hereinafter, a positive pre-charging process (■) similar to that shown in FIGS. ) and developing step (■) are repeated for each color of magenta and cyan to form a color toner image on the recording drum 1. After that, Figure 13 (IX
), the solid corona ion generator 7 for charge removal converts the color toner on the recording drum 1 into the same polarity i? After that, the image is electrostatically transferred onto the recording paper 8 by a roller transfer device using a functionally separated soft roller 9 (300 in FIG. 8).

Next, the transfer operation in the roller transfer device will be explained using FIG. 14. FIG. 14 shows in detail the configuration of the vicinity of the roller transfer device using the function-separated soft roller 300 shown in FIG. As described above, the recording drum 1
The developed toner 233 of the toner image formed on 01 is transferred to the toner transfer section (section a-b) as the recording drum 101 rotates (in the direction of the arrow). The developed toner 233 is brought into pressure contact with the recording paper 108 at the toner transfer section. During this time, a high voltage transfer voltage of 1 kV to 3 kV of opposite polarity to the developing toner voltage 6S (negative polarity in this figure) supplied by the high voltage generation circuit acts on the developing toner 233.
is electrostatically transferred to the recording paper 108 to form a toner image 310 on the recording paper 108. In the toner transfer section (section a-b), the elastic layer 30 of the functionally separated soft roller 300
Due to the elastic deformation of 3, the recording drum 101 and the recording paper 1
08 is in close contact and forms a wide nip width. In this region, the flexible structure of the elastic layer 303 allows the transfer pressure to be kept almost constant. Further, since the volume resistivity of the resistive layer 301 has almost no pressure dependence, it is possible to obtain uniform transfer over the entire nip width region. 1st
In Figure 4, 309 is a cleaner for the roller 300;
5 is a cleaning blade, 312 is a stopper, 306 is a spring for pressing the cleaning blade against the roller 300, and 307 is a plate for receiving the scraped toner. Since the roller 300 and the recording drum 101 are always in contact when there is no recording paper between them, the residual toner on the recording drum 101 will adhere to the roller 300. If the toner 311 attached to the roller 300 is left as it is, it will gradually accumulate thickly, causing stains on the back of the recording paper 108, or changing the resistance value between the roller 300 and the recording paper 108 to change the transfer conditions. Sometimes it happens. The cleaner 309 is for preventing this.

The cleaning blade 305 is preferably made of various rubbers such as polyurethane, nitrile, and nethylene propylene, and plastics such as polyethylene and polycarbonate, with polyurethane rubber being particularly preferred. The length of the cleaning blade 305 is preferably such that the end portion in the roller axial direction does not come into contact with the roller 300. When the end of the cleaning blade 305 comes into contact with the roller 300, a large deformation occurs at the contact point, the roller surface is squeezed with a large force, and the resistance layer is eventually damaged and torn. Also, the pressing force of the cleaning blade is 100g to 400g.
/ 20cm is good, preferably 150g to 300g
/ 20cm is good.

If the pressing force is too weak, cleaning will not be completed, and if the pressing force is too strong, rotation of the roller 300 will be hindered and the surface of the transfer roller will be damaged.

FIG. 15 shows a specific configuration of a function-separated soft roller 300, which the present inventors have already proposed (Japanese Patent Application No. 18 (No. 1), published in Japanese Patent Application No. 1983-104. It has a structure in which mechanical and electrical properties can be designed independently, and has the advantage of being stable against environmental changes and being able to transfer each layer of color toner images at once with high transfer efficiency.This functionally separated type The soft roller 300 has a foamed elastic support column 303 made of a sponge roller on a metal shaft 304, and a thin conductive layer 30 on top of the foamed elastic support column 303.
2 and a resistive layer 301 for providing stable transfer efficiency against environmental humidity fluctuations. In addition,
At both ends of the foamed elastic support column 303, there are conductive elastic layers 313 for establishing electrical continuity between the conductive layer 302 and the metal shaft 304. Furthermore, at both ends of this roller 300,
A guide ring 314 is provided to bring the roller 300 into contact with the recording drum under a certain pressure.

The foam support column 303 is used to prevent the "hollowing" phenomenon in which the center of the image dot is not transferred. roller 300
When the contact pressure between the toner and the recording drum exceeds 18 [1 g/c-], the toner on the recording drum physically coagulates, resulting in a phenomenon in which the center of the image dot of the toner image is not transferred. Therefore, a soft elastic body is used so that the transfer roller and the recording drum come into contact under this pressure or less. On the other hand, the resistive layer 301 always provides a stable high transfer efficiency (85% or more) against environmental humidity fluctuations, and also provides a constant high transfer efficiency (85% or more) even for each toner layer thickness on the recording drum. 8
5% or more). Its electrical resistance value is 10'Ω・C in the volume direction.
- to 10'Ω·C- is optimal.

The function of this functionally separated soft roller 300 will be explained with reference to FIG. 16. In conventional charger transfer, the 16th
As shown in Figure (a), the transfer efficiency changes greatly with changes in the environmental humidity (R11>. For example, the transfer voltage is 5.4k.
When the environmental humidity changes from 4096 to 8096, the transfer efficiency decreases from 90% to about 15%. Furthermore, as the toner layers on the recording drum overlap as shown in FIG. 16(b), the transfer efficiency changes greatly depending on the thickness of the toner layer. For example, when the transfer voltage is 5.4 kV and the number of toner layers increases by one layer, two layers, and three layers, the transfer efficiency greatly fluctuates from 8096.100% to 50%. In this way, when a color toner image formed on a recording drum is transferred to recording paper by a single electrostatic transfer, if conventional charger transfer is used, the color toner image on the recording medium drum cannot be faithfully transferred. . However, when this function-separated soft roller is used, as shown in FIGS. 16(c) and 16(d), stable transfer with consistently high transfer efficiency is achieved despite environmental humidity and changes in the toner layer on the recording drum. n■ Becomes Noh. FIG. 16(C) shows the stability of transfer efficiency against environmental humidity fluctuations. Even when the environmental humidity changes from a dry state of 30% to a high humidity state of 8,500 at a transfer voltage of 1 kV, a transfer efficiency of 85-6 or higher can be maintained. Furthermore, even when the toner layers are overlapped on the recording drum as shown in FIG. 16(d), each layer is
A transfer efficiency of 526 or more can be ensured.

In this way, when a functionally separated soft roller that provides stable and high transfer efficiency is used, the amount of residual toner on the recording drum is reduced. As a result, if a function-separated soft roller is used in an electrostatic color recording device without a cleaning device as shown in Figures 1 and 3, the amount of residual toner on the recording drum will be reduced and the residual toner will be completely removed. It can also be removed satisfactorily using a contact developer.

In this way, it is possible to stably operate the electrostatic color recording device, which has a simple structure and is easy to maintain for the user, without worrying about the occurrence of afterimages due to poor cleaning.

In the above example, positive polarity corona ions were used from the precharge corona ion generator, but negative polarity corona ions can also be used by reversing the polarity.

FIG. 17 shows the precharging corona ion generator 24 and the electrostatic latent image forming corona ion flow head 31 in that case.
This figure shows the relationship between the polarities of various voltages supplied to the ion and the polarity of corona ions.

In addition, in the example, a reversed image was created as an electrostatic latent image, but by manually applying a signal to erase the charge on the imaged area on the recording drum using a corona ion flow head, a regular electrostatic latent image can also be created. can be created.

[Effects of the Invention] As is clear from the above description, according to the present invention, the following effects can be obtained.

(1) By using a corona ion flow head that can be driven at low voltage to form an electrostatic latent image, the chip area of the driving IC can be reduced, making it possible to downsize and increase the precision of the corona ion flow head. Furthermore, an electrostatic latent image with a uniform potential and high electrostatic contrast can be obtained, and the electrostatic latent image is not affected by local variations in the amount of corona ions generated.

Therefore, uniform, high-quality color toner images can be formed on the recording drum.

(2) In order to precharge the recording medium on the recording drum to a uniform potential before forming an electrostatic latent image with a low-voltage driving corona ion flow head, a static elimination process is performed before forming the electrostatic latent image. If you do not do this, the new electrostatic latent image will not become non-uniform.In particular, if a solid corona ion generator is used as the charging means for precharging, the color toner images formed overlappingly on the recording drum will be The color toner layer can be stably transferred to the recording paper by applying a charge to the recording paper.

(3) By electrostatically transferring the color toner image formed on the recording drum to the recording paper, residual toner will not be fused onto the recording drum, and a normal resin blade can be used to clean the residual toner. Since cleaning can be used, the recording medium can be a general low-cost organic insulator, and the device can be realized at low cost.

(4) When a function-separated soft roller is used as the electrostatic transfer means, stable and high transfer efficiency can be obtained even when the environmental humidity fluctuates, and high-quality color image recording can always be performed. Furthermore, since the amount of toner remaining on the recording drum after transfer is reduced, the amount of waste toner is reduced, and user maintenance can be reduced.

(5) Therefore, if a functionally separated soft roller is used in a color recording device in which the cleaning device has been removed, residual toner will be reduced and cleaning by the contact developing device will be sufficient, which will eliminate the problem that occurs when cleaning is insufficient. It is possible to prevent the occurrence of memory of the previous image. In addition, if a developing device with black toner is used in the developing device that also serves as a cleaning device, there will be less variation in color due to the contamination of residual color toner that has been wiped off, which is also advantageous for achieving high image quality. .

[Brief explanation of drawings]

Figure 1 shows an embodiment of an electrostatic color recording device with a cleaning device that forms a color image with three rotations of the recording drum, and Figure 2 shows an example of an electrostatic color recording device that forms a color image with three rotations of the recording drum and uses a contact developer. A diagram showing an embodiment of an electrostatic color recording device that performs cleaning. FIG. 3 shows an electrostatic color recording device with a cleaning device that forms a color image by rotating the recording drum. FIG. 4 shows one revolution of the recording drum. Figure 5 shows an embodiment of an electrostatic color recording device in which a color image is formed using a contact developer and cleaning is performed using a contact developing device. A diagram showing the configuration of a corona ion flow head for low voltage drive and the operation of forming an electrostatic latent image. Figures 6 and 7 are diagrams for explaining the effect of the shielding electrode in Figure 5. Figure 8 is a diagram showing the operation of forming an electrostatic latent image. FIG. 9 is a diagram showing a specific example of the configuration of the electrostatic color printer according to the invention; FIG. 9 is a diagram showing the relationship between the amplification factor of the corona ion flow head in FIG.
Figure 0 is a diagram showing the surface potential attenuation characteristics of the recording drum in Figure 8, Figure 11 is a diagram showing the developing process of the developing device in Figure 8, and Figure 12 is a diagram showing the recording drum in the image forming process in Figure 8. The above diagram shows potential changes, FIG. 13 shows surface potential changes on the recording medium when color toner images are formed on the recording medium in the present invention, and FIG. 14 shows the roller transfer in FIG. 8. Figure 15 is a diagram for explaining the configuration of the device and transfer operation, Figure 15 is a diagram showing the structure of the functionally separated soft roller in Figure 14, and Figure 16 is a diagram comparing the characteristics of the corona charger and the functionally separated soft roller. Figure 17 shows other configurations of the precharging corona ion generator and the low-voltage drive corona ion flow head for forming electrostatic latent images used in the present invention, and the operation of the electrostatic latent image. 18 and 19 are diagrams showing examples of conventional electrostatic color recording devices. DESCRIPTION OF SYMBOLS 1... Recording drum, 2... Solid corona ion generator for precharging, 3... Solid corona ion flow head for low voltage drive, 4, 5.6... Non-contact developing device, 7...・
Solid corona ion generator for toner potential control, 8...Recording paper, 9...Functionally separated soft roller, 10...Cleaning device, 11..., Heat fixing device, 12...
Cleaning blade, 13...Contact developing device that also serves as cleaning, 14, 15.16... Image forming stage having a non-contact developing device, 17... Image forming stage having a contact developing device, 24... Precharge Solid corona ion generator for use, 31... Solid corona ion flow head for low voltage drive, 32... Insulating cover plate, 33... Induction electrode, 34... Slit for corona ion generation, 35...
・Corona ion generating electrode, 36...shielding electrode, 37・
... Corona ion source, 38... Control electrode.

Claims (7)

[Claims] (1) Charging means for uniformly charging the recording medium to a predetermined potential, and a corona controlled at a voltage lower than the charging potential of the recording medium by the charging means, arranged around a recording drum having a recording medium on its circumferential surface. A corona ion flow head that forms an electrostatic latent image on the recording medium using an ion flow, and a color toner image is formed by developing the electrostatic latent image formed by the corona ion flow head with toner of a predetermined color. A plurality of color toner images are produced by irradiating corona ions onto a plurality of color toner images formed overlappingly on the recording medium by a plurality of developing means, the charging means, a corona ion flow head, and a plurality of developing means. a corona ion generating means for making the potential uniform; and an electrostatic transfer means for electrostatically transferring a plurality of color toner images whose potentials are made uniform by the corona ion generating means onto a recording paper in one transfer. and a cleaning means for removing residual toner on the recording medium. (2) Charging means for uniformly charging the recording medium to a predetermined potential, and a corona controlled at a voltage lower than the charging potential of the recording medium by the charging means, arranged around a recording drum having a recording medium on its circumferential surface. A corona ion flow head that forms an electrostatic latent image on the recording medium using an ion flow, and a color toner image is formed by developing the electrostatic latent image formed by the corona ion flow head with toner of a predetermined color. , a plurality of developing means, at least one of which is a contact developing device, the charging means, a corona ion flow head, and a plurality of developing means to apply corona ions onto a plurality of color toner images formed overlappingly on the recording medium. corona ion generating means for uniformizing the potentials of the plurality of color toner images by irradiation; and a single electrostatic transfer of the plurality of color toner images whose potentials have been made uniform by the corona ion generating means. An electrostatic color recording device characterized in that an electrostatic color recording device is provided with an electrostatic transfer means for transferring the image onto a recording paper. (3) Charging means for uniformly charging the recording medium to a predetermined potential around a recording drum having a recording medium on its circumferential surface, and corona ions controlled at a voltage lower than the charging potential of the recording medium by this charging means. A corona ion flow head that forms an electrostatic latent image on the recording medium by a current, and a developer that forms a color toner image by developing the electrostatic latent image formed by the corona ion flow head with toner of a predetermined color. a plurality of image forming stages each having a means for irradiating corona ions onto a plurality of color toner images formed overlappingly on the recording medium by these image forming stages, and uniformizing the potential of the plurality of color toner images; an electrostatic transfer means for electrostatically transferring a plurality of color toner images whose potentials are made uniform by the corona ion generation means onto a recording paper in one transfer; 1. An electrostatic color recording device comprising a cleaning means for removing residual toner on a medium. (4) Charging means for uniformly charging the recording medium to a predetermined potential around a recording drum having a recording medium on its circumference, and corona ions controlled at a voltage lower than the charging potential of the recording medium by this charging means. A corona ion flow head that forms an electrostatic latent image on the recording medium by a flow, and a color toner image is formed by developing the electrostatic latent image formed by the corona ion flow head with toner of a predetermined color. a plurality of image forming stages each having a developing means, at least one of which is a contact developing device, and irradiating corona ions onto a plurality of color toner images formed overlappingly on the recording medium by these image forming stages; A corona ion generating means for uniformizing the electric potential of these plurality of color toner images, and a plurality of color toner images whose electric potentials have been made uniform by this corona ion generating means are electrostatically transferred onto a recording paper in one transfer. An electrostatic color recording device characterized by disposing an electrostatic transfer means for transferring. (5) The charging means and the corona ion generating means are each a solid corona ion generator configured by providing an induction electrode and a corona ion generating electrode with an insulator interposed therebetween. 5. The color electrostatic recording device according to 2, 3, or 4. (6) The corona ion flow head includes a corona ion generator configured by providing an induction electrode and a corona ion generating electrode with an insulator interposed therebetween, and further providing a shielding electrode for shielding magnetic field leakage from the induction electrode. , a solid corona ion flow head having a control electrode for controlling the corona ions from the corona ion generator for each recording image point with a voltage lower than the charging potential of the recording medium by the charging means. The color electrostatic recording device according to claim 1, 2, 3, or 4. (7) The electrostatic transfer means has a roller configured by sequentially laminating a conductive layer and a resistive layer on the circumferential surface of a foamed elastic support column supported by a metal shaft, and this roller is used for the recording. 5. The color electrostatic device according to claim 1, wherein the color toner image is electrostatically transferred onto the recording paper by pressing it against the peripheral surface of the recording drum through paper. Recording device.