JPH03193368A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To eliminate an image density fluctuation and a color difference fluctuation by a method wherein a signal voltage subjected to a pulse width modulation by an image signal is applied to a corona ion generation source as a corona ion flow control voltage, and a corona ion accelerating bias voltage changeable in voltage value is applied between a corona ion flow recording head and a recording medium. CONSTITUTION:A signal voltage 8 is subjected to a pulse width modulation by an image signal which is transmitted from an image signal source 71 to be recorded, whereby a halftone recording can be conducted. A corona ion accelerating bias voltage 11 having a maximum voltage of +500V for obtaining an electrostatic latent image contrast is applied between a conductive substrate 10a of an insulating recording medium 10 provided with an insulating layer 10b on the corona ion flow recording head. Gradation characteristics can be obtained with arbitrary image density and gamma value by changing either or both of the voltage value of the corona ion accelerating bias voltage 11 and the variable waveform of the signal voltage 8 in a cycle without changing the pulse-width modulated signal voltage 8.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Field of Application) (7) The invention is an electrostatic method for recording images by forming an electrostatic latent image on a recording medium using a corona ion flow recording head. The present invention relates to a recording device, and particularly to an electrostatic recording device that enables halftone recording in which tone characteristics can be arbitrarily changed.

(Prior Art) Conventionally, electrophotographic recording devices used in optical printers such as laser printers have a high volume resistance (~1014 Ωcm) as a recording medium in the dark, and a volume resistance of 4 to 5 digits when irradiated with light. A decreasing photoreceptor is used. To form a visible image on recording paper using such a photoreceptor, first apply a surface potential on the photoreceptor using corona ion charges generated by a corona charger, and then modulate it according to the signal to be recorded. The surface potential is selectively erased by irradiating the surface with light such as a laser beam through a rotating mirror optical system to form an inverted electrostatic latent image. This electrostatic latent image is developed with a developer containing colored fine particles (toner) having a charge of the same polarity as the surface potential to form a toner image on the photoreceptor. Next, the toner image is transferred to the recording paper using an electrostatic force having a polarity opposite to that of the toner, thereby obtaining a visible image on the recording paper.

The gradation characteristics of the toner image obtained in this way are determined by the μ
((For the amount of light expressed as the product of the emitted light intensity and the light irradiation time,
It is determined by the γ value of the γ characteristic indicating the surface potential attenuation characteristic of the photoreceptor and the development characteristics of the toner developer with respect to the electrostatic latent image contrast. When the sensitivity of the photoreceptor is increased in order to increase the recording speed, the γ value of the photoreceptor increases, and the surface potential on the photoreceptor is attenuated by a small amount of light. Therefore, since the surface potential of the photoreceptor varies greatly due to minute changes in irradiated light or leaked light, optical printers perform binary recording, and when gradation recording is required, the dither method is used. In the dither method, one stroke is formed by a collection of several recorded dots, and pseudo gradation is expressed by changing the number of dots. Therefore, in order to perform multi-gradation recording, it is necessary to increase the number of recording dots that can be assigned to one dot, and therefore, an optical printer with higher resolution is required. Further, in order to facilitate multi-gradation recording, if the sensitivity of the photoreceptor is decreased to reduce the γ value, the recording speed will decrease. In this way, the gradation characteristics in electrophotographic recording are
There is a difficulty in that the gradation characteristics cannot be arbitrarily controlled because they depend on the γ value of the photoreceptor material and the development characteristics of the developer and toner material.

On the other hand, there is a recording method in which a corona ion stream is irradiated onto an insulating recording medium to form an electrostatic latent image, and the image is developed to form an image. The solid-state corona ion flow recording head mainly includes a plurality of corona ion generators divided for each recording pixel and a common accelerating electrode having a corona ion flow discharge hole corresponding to the recording pixel. A bias voltage as high as the electrostatic latent image contrast is applied to the corona ion generator in accordance with the recording signal, and the corona ion flow is controlled on and off to generate electrostatic 4! Ifg! form. A corona ion generator consists of a corona induction electrode and a corona ion generation electrode divided into recording pixels arranged close to each other on an insulating substrate, and can generate high-density corona ions, making it more efficient than optical printers. high-speed recording is possible (Therout
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In the solid corona ion flow recording head disclosed in Japanese Patent Laid-Open No. 61-184562, only binary recording is considered. Therefore, a method of performing gradation recording using a corona ion flow has been proposed (Japanese Patent Laid-Open No. 59-62878).

This method uses a corona ion flow recording 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 an image signal. Controls the ion flow rate to form an electrostatic latent image.

The gradation characteristics of the electrostatic latent image are adjusted by controlling the corona ion flow irradiation time by pulse width modulation of the image signal. Therefore, when the development characteristics change due to developer toner replacement, it is possible to obtain gradation characteristics that match the development characteristics, but in order to do so, it is necessary to change the pulse width for each signal according to the gradation characteristics. There is a need. In addition, in the case of color recording, in order to reduce color difference fluctuations when replacing a large number of color toners, it is necessary to adjust the pulse width modulation to match the development characteristics of the color toners. Part 5! The disadvantage is that the I adjustment is complicated.

Another method that allows gradation recording using a corona ion flow recording head is as described in Japanese Patent Laid-Open No. 61-255870, in which a corona ion flow generated by a corona charger is conveyed by a high-speed air flow, and the corona ion flow is There is a method in which the flow rate of corona ions is controlled by applying a control voltage perpendicular to the moving direction of the ion flow. According to this method, gradation recording is possible by changing the driving voltage that controls the corona ion flow. However, because the control electrodes for the corona ion flow are complicated, there is a limit to the high definition of the head. Further, when the gradation characteristics change due to replacement of the developer, etc., it is necessary to adjust the magnitude of the driving voltage for each recording pixel, and in the case of color recording, even more complicated adjustment is required.

By the way, when performing gradation recording with an electrostatic recording device, the pixel width or electrostatic contrast of the electrostatic latent image changes due to random feeding unevenness of the recording drum caused by mechanical vibration of the device, etc. This may cause image quality deterioration. Particularly in the halftone density region, image density fluctuations are noticeable. In the case of color recording, the image density varies for each color due to uneven feeding of the recording drum that occurs for each color, and the color difference of the color image changes, resulting in a significant deterioration of image quality. In a laser printer, since the laser scanning rotating mirror rotates at a constant speed at high speed, the recording timing of the main scan cannot be changed in accordance with the timing of uneven feeding of the recording drum.

Therefore, a large flywheel is installed on the recording drum,
There is also a color laser recording device that eliminates uneven feeding. However, with this method, it was difficult to make the device smaller and lighter.

On the other hand, there is a recording method such as an LED or LCD printer that uses an LED or LCD head for electrophotographic recording and performs line scanning with simultaneous drives.

With this method, the main scanning timing of the head can be changed, so by detecting uneven feeding of the recording drum and adjusting the timing of the main scanning of the head to match the uneven feeding, electrostatic latent images such as - can be created on the recording drum. can be formed. In order to prevent density fluctuations in halftone recording with a resolution of 400 dpi, it is necessary to keep fluctuations in feeding unevenness on the recording drum to 2 to 3 microns or less. The conventional method for detecting feeding unevenness is to provide slits at intervals equal to or coarser than the recording dot width around the recording drum or on a timing disk that rotates together with the recording drum, and detect the slit intervals using an optical system and a photodetector. There is a known method for creating the main scanning timing. In this method, the detection resolution of feed unevenness is determined by the slit spacing, and the feed unevenness fluctuation is determined by the slit spacing.
In order to meet the requirement of 3 microns or less,
It was difficult to form slits at intervals of 3 microns or less. Furthermore, even if such high-definition slits can be formed, floating toner inside the device fills up the slit intervals, causing a new problem of timing errors.

(Problems to be Solved by the Invention) As described above, in conventional electrophotographic recording devices, the gradation characteristics are determined by the γ value of the photoreceptor material and the characteristics of the developer, and it is not possible to arbitrarily control the gradation characteristics. It was difficult. In addition, when applying the dither method that can realize pseudo gradations in binary recording to electrophotographic recording, an extremely high-resolution optical scanning device is required, and in order to facilitate multi-gradation recording, the sensitivity of the photoreceptor must be increased. If the γ value is decreased by decreasing the γ value, there is a problem in that the recording speed decreases.

An electrostatic recording device that uses a corona ion flow recording head to form an electrostatic latent image on an insulating recording medium can perform gradation recording by pulse width modulating the signal voltage, but the development characteristics due to toner exchange of the developer In order to adjust the gradation characteristics with respect to changes in , it is necessary to adjust the pulse width in pulse width modulation for each signal, and this adjustment is complicated. Particularly when recording in color, changing the development characteristics causes color differences and significantly deteriorates image quality, so the signal pulse width must be adjusted for each color each time the toner is replaced, making the adjustment even more complicated. .

On the other hand, in an electrostatic recording device, if there is uneven feeding of the recording drum, image density fluctuations and color difference variations occur depending on the uneven feeding of the recording drum when recording halftone images or color images.
Significantly degrades image quality. In order to correct this uneven feeding, it is necessary to detect uneven feeding, but conventional uneven feeding detection devices have a problem in that the detection resolution is insufficient.

The first object of the present invention is to provide an electrostatic recording device using a corona ion flow recording head that can control gradation characteristics arbitrarily by electrical control without changing the pulse width of a pulse-width-modulated signal voltage. It is about providing.

The second object of this invention is to detect minute unevenness in the feeding of the recording drum, give the recording head main scanning timing suitable for the uneven feeding, and thereby reduce image density fluctuations and color difference fluctuations in color recording caused by uneven feeding. An object of the present invention is to provide an electrostatic recording device that can be removed.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the first object, the present invention uses a corona ion flow recording head having a plurality of corona ion generation sources,
Electrostatic recording in which an electrostatic latent image is formed on a recording medium by generating a corona ion current according to the image signal to be recorded from this corona ion flow recording head, and this electrostatic latent image is developed to record an image. In the apparatus, means for applying a signal voltage whose pulse width is modulated by an image signal as a corona ion flow control voltage to a corona ion generation source, and a corona ion acceleration bias whose voltage value is variable between the corona ion flow recording head and the recording medium. and a means for applying a voltage.

According to another aspect, there is provided means for applying a bias voltage for accelerating corona ions whose voltage value changes over time within the period of the signal voltage and whose changing waveform is variable between the corona ion flow recording head and the recording medium. .

In addition, in an electrostatic recording device that records a color image by performing the above electrostatic latent image formation and development process for each color, a pulse width modulated signal voltage is applied to the corona ion generation source as a corona ion flow control voltage. and a bias for accelerating corona ions in which at least one of the voltage value and the temporal change waveform of the voltage value within the period of the signal voltage is independently variable for each color, between the corona ion flow recording head and the recording medium. It has means for applying voltage.

On the other hand, in order to achieve the second objective, a recording drum, a member that rotates together with the recording drum and in which slits are formed at a coarser pitch than the recording resolution on the recording drum, and an optical system that magnifies the image of the slits. and an optical sensor having a higher resolution than the recording resolution of the recording drum, which detects the image of the slit magnified by this optical system, and a feeding unevenness detection device that detects feeding unevenness of the recording drum.

(Function) In this invention, gradation characteristics are obtained by pulse width modulating the signal voltage applied to the corona ion flow recording head, and at the same time, the bias voltage for corona ion acceleration applied between the accelerating electrode and the recording medium is controlled. With this, arbitrary gradation characteristics can be obtained. According to this method, arbitrary gradation characteristics can be obtained for the same pulse-width modulated image signal, and it is possible to selectively set high-contrast or soft-contrast images. In other words, if only the voltage of the bias voltage for accelerating corona ions is changed, the density in the gradation characteristics will change, and if the changing waveform of the bias voltage for accelerating corona ions is changed within the period of the signal voltage, the gradation characteristics will change. The γ value at changes.

When recording a color image, by changing the voltage value and change waveform of the bias voltage for corona ion acceleration for each color to set the gradation characteristics, it is possible to easily adjust the gradation characteristics even when the developer or recording medium is changed. A toned image is obtained.

When halftone recording or color halftone recording is sufficiently achieved in this manner, uneven feeding of the recording drum becomes more noticeable on the image. In this invention, it is possible to minutely detect uneven feeding of the recording drum, and by setting the main scanning timing of the recording head based on this, it is possible to obtain high-quality images without density unevenness or color difference fluctuations.

(Example) The present invention will be explained in detail below.

First, the electrostatic latent image forming process of the electrostatic recording device capable of controlling gradation according to the present invention using a corona ion flow recording head will be described. FIG. 1 shows a corona ion flow recording head having a solid state corona ion generator that generates corona ions using alternating current, and a drive circuit for controlling gradation.

The solid corona ion flow recording head shown in FIG. 1 consists of a corona ion generating electrode 2 having an independent corona ion generating hole 1 according to the recording image point, and a corona ion generating electrode 4 formed with an insulating layer 3 interposed therebetween. It consists of a generator 5 and a common accelerating electrode 6 with individual corona ion generation holes. An AC voltage 7 of 3 kVp-p and 40 kHz for generating corona ions is applied between the corona ion generating electrode 2 and the corona induction electrode 4. In addition, between the corona ion generating electrode 2 and the accelerating electrode 6, there is a signal voltage 8 (for example, +400V) that controls on/off the corona ion flow, and a signal voltage 8 (for example, +400V) that controls the corona ion flow when there is no image signal (when the signal voltage 8 is 0). A cutoff voltage 9 (for example -200V) for blocking the flow is applied in a superimposed manner. The signal voltage 8 is pulse width modulated by the image signal to be recorded from the image signal source 71, thereby making halftone recording possible. In order to generate such a signal voltage 8, it is possible to first pulse-width-modulate an analog image signal having gradation, and then perform pulse-width modulation by turning on and off the DC voltage using the pulse-width-modulated image signal. Alternatively, the DC voltage may be pulse width modulated directly by the analog image signal.

Then, corona ions of maximum +500V are applied to provide an electrostatic latent image contrast between the conductive substrate 10a of the insulating recording medium 10 in which the insulating layer 10b is provided on the conductive substrate 10a and the accelerating electrode 6 of the corona ion flow recording head. An acceleration bias voltage 11 is applied. This bias voltage 11 for accelerating corona ions is a variable voltage, and the voltage value is kept constant during recording, or is pulse width modulated in synchronization with the main scanning of the image signal by a synchronization signal from a synchronization signal source 72. This is a voltage whose voltage value changes within the period of the signal voltage 8. By changing the voltage value of the corona ion acceleration bias voltage 11 and/or the change waveform within the period of the signal voltage 8 without changing the pulse width modulated signal voltage 8, arbitrary image density and γ value can be set. It is possible to obtain the same gradation characteristics.

Next, the effects when the signal voltage 8 is pulse width modulated and when the bias voltage 11 for accelerating corona ions is varied will be explained in detail with reference to FIGS. 2 and 3. FIG. 2 is a diagram for explaining the gradation characteristics when the bias voltage 11 for accelerating corona ions is kept constant and the signal voltage 8 is pulse width modulated.
(b) is a constant bias voltage 11 for accelerating corona ions,
(c) shows the recording medium 1 corresponding to the pulse width W of the signal voltage 8.
The surface potential (electrostatic latent image potential) above 0 is shown. When a pulse width modulated signal voltage 8 whose pulse width W changes according to the image signal is applied to the corona ion generating electrode 2, the surface potential of the recording medium 10 increases exponentially and eventually becomes saturated. Here, when the voltage value of the bias voltage 11 for accelerating corona ions is changed as shown by the dashed-dotted line, the surface potential of the recording medium 10 changes as shown by the dashed-dotted line even if the pulse width of the signal voltage 8 is the same. As a result, the image density among the gradation characteristics changes.

Next, the gradation characteristics of the electrostatic latent image when the voltage of the corona ion accelerating bias voltage 11 is changed over time within the period T of the pulse width modulated signal voltage 8 will be explained with reference to FIG. The bias voltage 11 for accelerating corona ions is set to the pulse width modulated signal voltage 8 in FIG. 3(a).
When increasing logarithmically as shown in b), the recording medium 10
As shown in FIG. 3(c), the surface potential increases approximately linearly. Here, when the changing waveform of the bias voltage 11 for accelerating corona ions is changed as shown by the dashed-dotted line, even if the pulse width of the signal voltage 8 is the same, the surface potential of the recording medium 10 changes as shown by the dashed-dotted line. The γ value in the key characteristic will change.

The above points will be explained and explained in detail using mathematical formulas. The corona ion current i flowing between the accelerating electrode 6 and the recording medium 10 when the signal voltage 8 is applied is expressed by the following equation.

i−ρ・υ (1) v−μ・E−
, cz (Vb-Vs) /d (2) where ρ is the corona ion density generated in the corona ion generator 5, υ is the corona ion flow velocity, E is the accelerating electric field between the accelerating electrode 6 and the recording medium 10, vb is the bias voltage for accelerating corona ions, and d is the ff [,
μ is the mobility of corona ions, and Vs is the surface potential of the recording medium 10.

The surface potential Vs of the recording medium 10 is expressed by the following equation, where CO is the capacitance of the recording medium 10.

The surface potential Vs of the recording medium 10 changes almost linearly with time as shown in equation (6).

If the bias voltage 11 for accelerating corona ions is vb, then
When vb is constant, the surface potential Vs of the recording medium 10 is expressed by the following equation.

As described above, when the bias voltage vb for accelerating corona ions is constant, the surface potential Vs of the recording medium 10 changes exponentially with time t.

On the other hand, the bias voltage vb for accelerating corona ions is expressed by formula (5)
By changing the voltage value and waveform of the bias voltage 11 for accelerating corona ions exponentially in synchronization with the signal voltage 8 and within its period T as shown in FIG. The gradation characteristics of the image, that is, the density and γ value of the image can be changed arbitrarily. Here, the unit pulse width (minimum pulse width) of the pulse width modulated signal voltage 8 is preferably an integral multiple of the period of the high frequency alternating current voltage 7 for corona ion generation applied to the corona ion generator 5. . In this way, corona ions can be generated many times within the pulse width of the pulse width modulated signal voltage 8, making it possible to express stable gradations.

Instead of the solid-state corona ion generator 5 that generates corona ions using a high-frequency AC voltage 7, a solid-state corona ion generator that can generate corona ions using a direct current, which was previously proposed by the present inventors, may be used. good. An outline of the solid state corona ion generator that generates corona ions using direct current will be explained using FIG. 4.

Generally, when gas is discharged between opposing electrodes under high atmospheric pressure such as in the atmosphere, if the distance between the electrodes becomes less than 100m, stable corona discharge like the corona charger used in electrophotography will no longer occur. A streamer discharge is generated in the form of an impulse from the large-current corona ion flow before the spark discharge. Therefore, an air gap region 14 is provided between the corona induction electrode 12 and the corona ion generation electrode 13,
In the solid state corona ion generator 15 that directly discharges the image electrodes 12 and 13 by placing the distance between them close to several tens of microns, the discharge energy is limited and the corona ion current and discharge time are controlled in order to operate stably. It is necessary to prevent electrode damage due to corona discharge. Here, a capacitor 1 is connected between the corona induction electrode 12 and the corona ion generation electrode 13.
6 is connected to charge the capacitor 16 through the resistor 17, and the accumulated charge in the capacitor 16 is used for corona discharge. In this way, it is possible to generate corona ions intermittently by repeatedly charging and discharging the capacitor 16, and by controlling the corona ion current and discharge time, it is possible to stably generate unipolar corona ions using the DC voltage 18. be.

Next, we will show an example of another corona ion flow recording head in which the gradation characteristics can be arbitrarily controlled by changing the bias voltage for accelerating corona ions in this manner.

FIG. 5 shows an example in which the present invention is applied to a corona ion flow recording head disclosed in Japanese Unexamined Patent Publication No. 59-62878. A corona ion current is generated by applying a direct current high voltage to the corona ion generating corona wire 20 of the corona charger 19, and the corona ion current is focused by applying a focusing voltage 22 to the focusing electrode 21. A focused corona ion stream is applied between the control electrodes 23.24.
The irradiation time onto the recording medium 10 is controlled by a pulse width modulated signal voltage 8 of 150V. Control electrode 24
By changing the voltage value of the bias voltage 11 for accelerating corona ions applied to the recording medium 10 or by temporally changing the voltage value within one period of the signal voltage 8, the recording medium can be The surface potential of 10 can be changed to any gradation characteristic.

Next, an example using a corona ion flow recording head that enables low voltage driving will be described. First, the operation of the low voltage driven corona ion flow recording head will be explained using FIG.

Using the solid corona ion generator 5 for precharging, the recording medium 10 is uniformly charged to -600 cm.

The charge due to this −-like charging is indicated by 25. The solid corona ion generator 5 includes a corona ion generating electrode 2 and an insulating layer 3.
and a corona induction electrode 4. 40kHz between the corona induction electrode 4 and the corona ion generation electrode 2,
By applying an AC voltage 7 of about 2 kVp-p,
Generates positive and negative corona ions. Further, by applying a negative bias voltage 26 to the corona ion generating electrode 2, a negative corona ion flow is applied to the recording medium 10, and the recording medium 10 is negatively charged. In this precharging, since the solid corona ion generator 5 generates a large amount of corona ions, a surface potential equal to the bias voltage 26 is applied to the recording medium 10, and a stable surface potential can always be obtained.

On the other hand, a solid corona ion flow recording head 27 for low voltage driving
is constructed as follows. A corona ion generating electrode 30 having a common corona induction electrode 28 and a common corona ion generating hole 29 is provided to each element corresponding to the recording dots via an insulating layer 3 made of polyimide or the like. A shielding electrode 31 is provided at the center of the corona ion generation hole 29 so that the corona ion flow moving toward the recording medium 10 is not affected by the electric field from the corona induction electrode 28 .

On the corona ion generator configured in this manner, a corona ion control electrode 33 is arranged which is separated for each element via an insulating layer 32 made of polyimide or the like.

The operation of this solid corona ion flow recording head is as follows. Corona induction electrode 28 and corona ion generation electrode 30
Or between the shield electrodes 31, 40kllz, 3kVp
-p is applied to generate a large amount of positive and negative corona ions in the corona ion hole 29. A surface potential of -600 V is applied to the recording medium 10 by precharging, and only positive polarity corona ions 35 are used to form an electrostatic latent image. Due to the large amount of positive corona ions generated in this way, a space charge is generated between the shielding electrode 31 and the control electrode 33.
By applying a signal voltage 36 of approximately 0V, corona ion flow control becomes possible. Pulse width modulated signal voltage 36
is O, the control electrode 33 is +3 with respect to the shield electrode 31.
The positive polarity corona ion flow is cut off by setting the voltage to 0V. When the signal voltage 36 is applied, the control electrode 33 is set to 0■ with respect to the shield electrode 31, and the corona ion flow is turned on. In this on state, one 60 of the recording medium 10
A positive corona ion flow is accelerated at a surface potential of 0V, erasing the negative charge on the recording medium 10 and forming an electrostatic latent image 37. Note that the above-mentioned DC corona ion generator proposed by the present inventor may be used instead of the AC corona ion generator of the solid-state corona ion flow recording head for precharging and low voltage driving.

At this time, a bias voltage 38 for accelerating the corona ion flow is applied between the corona ion generating electrode 30 and the recording medium 10.

The corona ion flow acceleration bias voltage 38 is temporally variable with an arbitrary voltage waveform in synchronization with the pulse width modulated signal voltage 36. By doing so, the gradation characteristics of the electrostatic latent image on the recording medium 10 can be arbitrarily controlled.

This point will be explained using FIGS. 7 and 8. As shown in FIG. 7, the recording medium when the pulse width modulated signal voltage 36 (a) is applied to the control electrode 33 and the bias voltage 38 (Va) for accelerating corona ions is constant as shown in (b). The change in the surface potential Vs on No. 10 is shown in (C). In this case, a corona ion current II flows as expressed by the following equation.

Low-voltage driving is possible by controlling the space charge. When a signal voltage 36 of Vg is applied between the shield electrode 31 and the control electrode 33, this positive corona ion current 1
i is accelerated by the difference between the surface potential Vs of the recording medium 10 and the bias voltage Va, and has the following value.

If −ρ・υ (9
) Here, Vi is the potential at a distance y from the shielding electrode 31 in the corona ion flow recording head in the direction of the recording medium 10, ε0 is the dielectric constant in vacuum, εa is the relative dielectric constant of air,
ρ is the space charge density of the corona ion flow at the distance y,
υ is the corona ion flow velocity at the position of distance y, μ is the corona ion mobility, and Ii is the corona ion current at the position of distance y. At this time, it is assumed that sufficient corona ions are supplied from the corona ion generating electrode 30 in the on state where the corona ion flow 39 is flowing. Thus, positive (10) where a is the distance between the recording medium 10 and the control electrode 33, and b is the distance between the control voltage 33 and the corona ion generating electrode 30. As in the case of the triode vacuum tube, k is a voltage amplification factor that takes into account the peripheral effect of the control electrode 33 corresponding to the grid. That is, if the corona ion through-holes 33a on the control electrode 33 are approximated as existing periodically like the grid of a vacuum tube, the voltage amplification factor is
varies as a function of distance from the electrode center due to the effect of
Its value is minimum at the center of the electrode.

When such a corona ion current flows, the recording medium 10
The surface potential Vs attenuates with time as shown by the following equation.

(11) Note that Cp is the capacitance of the recording medium 10. The signal voltage 36 pulse width modulated in this way is applied to the control electrode 3.
3, the surface potential of the recording medium 10 has a value determined by the pulse width of the signal voltage 36.

On the other hand, as shown in FIG. 8, in synchronization with the pulse width modulated signal voltage 36 of (a), the -600 of
When applying the bias voltage 38 for accelerating corona ions with a waveform varying from (2) to Ov, the surface potential Vs changes almost linearly as shown in (e).

Furthermore, by setting the AC voltage for generating corona ions of each element of the corona ion flow recording head to a value higher than the amount of corona ions generated necessary for recording, fluctuations in the amount of corona ions generated due to variations in the corona ion generating electrode 30 can be suppressed. It is possible to suppress it.

Further, the control voltage Vg for shielding the corona ion flow is expressed by the following equation, and the voltage at which the amplification factor is minimum at the center of the electrode is the maximum shielding voltage value. This voltage is applied to the corona ion control electrode 3.
3 as a control voltage, it becomes possible to interrupt the corona ion current.

Vg --Vs/k (12) FIG. 9 shows a specific example of the configuration of an electrostatic recording device constructed based on the above theoretical considerations. In FIG. 9, 101 is a main body, and inside this main body 101, a recording drum 103 as a recording medium (carrier) 10 is provided. Te Buri Charger 104. Head section 114 for corona ion flow recording. Developing device 111° Roller transfer device 118
are arranged in sequence.

The recording drum 103 is constructed by forming a cylindrical resin insulating layer with a thickness of 50 μm on a conductive layer. 50 mm above this recording drum 103, +eo
A precharger 104 is provided, which is a corona charger for uniform charging that provides an initial potential of ov. As this recharger 104, 5 on the recording drum 103 is used.
A solid state corona ion generator may be provided at 00 μm.

This corona ion generator is installed on an insulating substrate such as ceramic with a length equal to the width of a 2 μm thick recording medium (1 m+ width).
* An induction electrode is provided, on which a resin insulating layer with a thickness of 8 μm is uniformly applied, and a corona ion generating electrode with a thickness of 2 μm having a slit of 100 μm width is placed on top of the induction electrode for main scanning of the recording drum 103. The length is equal to the length in the direction. Further, the slit is set to be located on the dielectric electrode.

An alternating current voltage with an amplitude voltage of 1800 V and a frequency of 50 kHz is applied between the induction electrode and the corona ion generating electrode to generate positive and negative corona ions. A bias voltage of +600V is applied to the corona ion generating electrode, and only positive corona ions are deposited on the recording drum 103, which is charged to +600V.

Near lO of the corona ion generating electrode of the corona ion generator
In the .mu.m range, a strong alternating electric field generates large positive and negative corona ion currents along the corona ion generating electrode, on the order of 2.8X to'A/mark. For this reason, 50 μm
The thick recording drum 103 is charged to +600V, which is equal to the bias voltage, in a short time of about 100 μsec.

Next, this charged recording drum 103 is conveyed to the head unit 114 for corona ion recording, where negative corona ions are generated according to the recording signal, the surface charge of +1 lioV is erased, and the reversed electrostatic charge is generated. A latent image is formed.

The corona ion generation source in the head section 114 is the bricharger 1 that uniformly charges the recording drum 103 described above.
It has almost the same structure as No. 04, but differs in that a 50 μm wide shielding electrode is provided in the 100 μm wide rib of the corona ion generating electrode. Further, a 10 μm thick control electrode with a 100 μm through hole (corresponding to 33a in FIG. 6) corresponding to each recording dot is provided at a distance of 60 μm from the corona ion generation source, and further 200 μm from the control electrode.
A recording drum 103 with a surface potential of +600V is conveyed to a location m. The resolution of this head is equivalent to 10 lines/frame.

Next, the operation of the electrostatic recording apparatus shown in FIG. 9 will be explained with reference to FIG. 6. The corona ion generating electrode (30 in FIG. 6) and the shielding electrode (31 in FIG. 6) of the head section 114 are connected to the same ground potential, and the electrode between the induction electrodes 28 is synchronized with a pulse width modulated signal voltage. A sine wave or rectangular AC voltage with an amplitude voltage of 1800V and a frequency of 5kl12 is applied, and as a result, the positive and negative voltages are approximately 2.8X 10-'A/
A corona ion current of cm is produced. Among these corona ion currents, only negative corona ion currents are selected by the corona ion control electrode (33 in FIG. 6) and reach the recording drum 103. The amplification factor of the head section 104 at this time varies depending on the distance from the center of the electrode, as shown in FIG. 10, 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, the formula (1
From 2), the cutoff voltage of the negative corona ion current accelerated by the surface potential (+600 V) of the recording drum 103 is maximum at the center. At this time, +38V is applied to the corona ion generating electrode.
By applying a reverse bias of , the corona ion current can be blocked.

In this way, by applying +38V as a bias voltage (34 in FIG. 6) to the corona ion generating electrode 30 and applying +38V and a signal voltage of 0 to the control electrode 33, the corona ion current can be turned on and off. Can be turned off. The maximum value of the corona ion current flowing at this time is given by equation (8): 1
．． 3X 1O-5A/C-, and the corona ion current generated from the corona ion source (2,8X 10-'A
/c+n). Therefore, even if there are variations in the corona ion generation sources 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.

In addition, the signal voltage (36 in FIG. 6) applied to the control electrode of this head section 114 is the 5 volt applied to the corona ion generation source.
It is applied every 100 seconds of negative corona ion generation time in synchronization with the corona ion generation voltage of kllz (34 in FIG. 6).

Next, FIG. 11 shows the surface potential decay characteristics of the recording drum 103 with respect to elapsed time when a corona ion current corresponding to an image signal is applied.

After 100 μSee, + ao on the recording drum 103
The surface potential of ov drops to +150v at the center of the image, and 45
An electrostatic latent image with a high electrostatic contrast of 0 is obtained. At the periphery of the image point, the corona ion current value decreases slightly, and an electrostatic contrast of about 350 ■ is 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 100μ
The printing speed of 5eC (one cycle: 200μ5ec) is 10 lines/m+* resolution, and the continuous printing speed is about 90 sheets/minute (equivalent to A4).

By using the electrostatic recording device according to the present invention described above, it becomes 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 voltage of several 100 V 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 corona ion flow applied between the control electrode and the ion generating electrode is cut off. The Iasumi pressure required for this can be reduced by several tens of volts.

In this way, a low-voltage drive IC with a small mounting area can be used as the drive IC in the head section for corona ion recording, making it possible to use a small-sized corona ion recording drive IC with only one drive IC mounted on the head board. It becomes possible to manufacture In addition, unlike conventional methods, by controlling the space charge generated by corona ions, the corona ion current can be determined only by the applied voltage, eliminating variations in the corona ion flow that were caused by manufacturing variations in the corona ion generating electrode, and stabilizing it. A corona ion recording head can be provided. 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 that the recording potential was limited to about 150 cm 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 the high recording L1 voltage can be controlled by a low-voltage drive IC, an insulating toner that is not developed at a normal high recording potential used in electrophotography can be used, and the recording paper This enables electrostatic transfer to the recording drum, prevents toner from fusing to the recording drum, and allows the use of commonly used resin wiping blades to wipe off residual toner, making it possible to use inexpensive resin-based insulation for recording media. body becomes available for use.

Furthermore, it is possible to create colors using ordinary resin-based insulating toner.

As mentioned above, by applying an electric charge to the recording drum in advance,
By utilizing the space charge caused by corona ions, it is possible to control the corona ion current with low voltage, and high-speed printing is also possible.

In the above example, a solid corona ion source was used, but it goes without saying that a corona charger commonly used in electrophotography may also be used. Further, in this example, negative polarity corona ions were used, but positive polarity corona ions can also be used by reversing the polarity. Furthermore, although a reversed image was created as an electrostatic latent image, a regular electrostatic latent image was also created by inputting a signal to erase the charge on the imaged area on the recording drum using corona ion recording. be able to.

Further, the corona ion generation AC voltage applied to the corona ion flow generator may have a frequency that is an integral multiple of the signal voltage so that many peak voltages are included in the human input signal.

In this way, positive corona ions are deposited on the recording drum 103 by the recharger 104, and negative corona ions according to the print information signal selectively reach the head section 114, forming an electrostatic latent image. . Then, the next developing step is carried out.

The developing device 111 is configured to perform both wiping off of residual toner and a developing process, and is provided with a developing roller 112. The developing process in the developing device 111 will be explained using FIG. 12.

On the recording drum 103, which is provided on a conductive substrate and is composed of an insulating layer, residual toner 211 of negative polarity in the image 1 image area 210 remaining after the transfer of the previous image formation and the negative polarity residual toner 211 in the non-image area 212 are stored. Residual fog toner is present. This residual fog toner is positively charged fog toner 21 of opposite polarity.
3 or a part of a negative polarity fog toner (not shown) (FIG. 12(a)). Next, the cathode process (Fig. 12 (
In b)), when the charger 1.04 is used to remove static electricity using a negative DC 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 the potential on the recording medium 9 is -50V (or GV). ) becomes the potential. At this time, regardless of the amount of residual toner, the potential of the recording drum 103 also decreases due to leakage current such as creeping discharge of toner particles.
The potential will be different. The polarity of the residual toner on the recording drum 103 is completely converted to negative polarity 215 by this static elimination process. In this way, -like low negative potential (or zero potential)
By a recording process (FIG. 12C) using the head unit 114, a positive electrostatic latent image is formed on the recording drum 103, which has now been formed, in accordance with the recording signal.

As a result, a high positive potential of 21 G 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 in 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. 12(d)), the bias voltage is 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 103 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. 12(e)), and the image area on the positively charged recording drum 103 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 be attached to the non-image area 24 in some cases.

The entire image forming process is thus completed.

FIG. 13 shows the recording drum 103 in the image forming process.
The above shows the potential change. (a) (b) (c) in Figure 11
) (d) (e) shows potentials corresponding to each image forming process, where the solid line represents the potential in the image area, and the dotted line represents the potential in the non-image area. The potential on the recording drum 103 after image formation after the previous development and transfer processes (FIG. 13(a)) is +450cm in the image-formed area.
In the non-image area, the voltage is -30V. In the static elimination process (Fig. 13(b)), the recharger 10
4, the potential is made uniform to 150 V regardless of whether the image is formed or the non-image area. In the next recording process (FIG. 13(C)), the new image area is charged to +500V, and the non-image area is kept at -50V. In the developing process (Fig. 13(d)), the residual toner of the previous image is
Ten-polar residual toner 23 in the new image area of 500V
6, the negative polarity residual toner 238 in the non-development area is applied to the low potential side developing roller biased to +200V.
Move to the developing roller in the direction of the arrow on the high potential side that has been developed to 0V. On the other hand, the negative polarity developing toner 2 on the developing roller
39 is moved to the high potential side of 500V in the image area and development is performed.

The potential (
Figure 13(C)) shows +4 by development in the new image area.
50■, in the non-image area, the voltage rises from -50V to -30V due to contact with the developing roller, and the voltage on the recording drum 10 increases.
3. Finish the image forming process above. No image memory is generated for the newly formed image in this way. When image formation is completed on the recording drum 103 as described above, this image is transferred to the transfer material P (recording paper) on the roller transfer device 118.
will be transcribed into.

A cassette 119 is installed in the lower part of the main body 101, and transfer materials P are sequentially taken out one by one via a take-out roller 116.

The transfer material P taken out by the take-out roller 116 is conveyed onto the circumferential surface of the recording drum 103 and onto the roller transfer device 118, where it is transferred and taken out to the outside. Furthermore, a pair of aligning rollers 117a and 117b are provided on the upstream side of the conveyance path of the transfer material P.

Next, the transfer operation in the roller transfer device 118 is performed in the 14th
This will be explained using figures.

The developed toner 233 formed on the recording drum 103 and the rotation of the recording drum 103 (in the direction of the arrow) are transferred to the toner transfer section (section a-b). At the toner transfer section, the developed toner 233 is pressed against the recording paper, which is the transfer material P.

During this time, a high-voltage transfer voltage of about 1 kV to 3 kV, which is opposite in polarity to the charge (negative polarity in this figure) of the developed toner supplied by the high-voltage generation circuit, acts on the developed toner 233, and the developed toner 233 is electrostatically transferred. The image 310 is transferred onto the transfer material P, and an image 310 is formed on the transfer material P. In the toner transfer portion (section a-b), the recording drum 103 and the transfer material P come into close contact with each other due to elastic deformation of the elastic layer 303 of the transfer roller 300, forming 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.

The thirteenth diagram schematically shows an example of the transfer roller 300.
It is a diagram. Reference numeral 301 denotes a resistive layer, which is formed to be longer in the axial direction by d than the end of the conductive layer 302 and the end of the conductive elastic layer 313 which is treated to conduct electricity from the end of the elastic layer 303 . This length d is preferably in the range of 0.5 to 5 degrees, as will be described later. In this case, the length d is the resistive layer 30
2 is formed to be sufficiently longer than the conductive layer 303 in the axial direction, and then the conductive layer 303 is cut to a predetermined length, thereby easily controlling the conductive layer 303.

The function of the transfer roller 6 shown in this embodiment will be explained using FIG. 16. 103 is a recording drum (width L in the axial direction), 3
08 is a power source that applies a high voltage of opposite polarity (positive in this case) to the toner to the transfer roller 300, and 314 is a leaf spring that supplies the high voltage to the transfer roller 300. resistive layer 301
is 2 mm from the end face of the conductive layer 302 and the conductive elastic layer 313
(the axial width of the resistive layer LR-D R+ 4 mm). Such a transfer roller 30
0 and the recording drum 103, the width of the transfer material P is naturally shorter than the width of the transfer roller, so the end of the transfer roller 300, which is a single elastic body, deforms as shown in the figure. do. In the transfer roller 300, since the end of the resistive layer is formed to the outside of the end of the conductive layer, the photoreceptor and the conductive part do not come into contact with each other or come close to each other as described above, so short circuits and discharges do not occur. Also, there are no transfer voltage fluctuations or pinholes on the photoreceptor. The amount of protrusion from this end is preferably 0.5 + mm or more, since no discharge occurs even at a transfer voltage of 3 kV. However, if it is too long, it will break due to fatigue due to deformation of this part, so it is preferably 5 mm or less.

Such a transfer roller 300 is provided in FIG. 309 is a cleaner for the transfer roller 300;
-5 is the cleaning blade, 312 is the fixture, 306
307 is a spring for pressing the cleaning blade against the transfer roller 300, and a plate 307 receives the scraped toner. Since the transfer roller 300 and the recording drum 10B are always in contact with each other when there is no transfer material P between them, residual toner from the recording drum 103 adheres to the transfer roller 300.

If the toner 311 attached to the transfer roller 300 is left as it is, it will gradually accumulate thickly, causing stains on the back of the transfer material P, or changing the resistance value between the transfer roller 300 and the transfer material P, thereby changing the transfer conditions. may change. The cleaner 309 is intended to prevent this. The cleaning plate 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 end of the cleaning blade 305 in the roller axial direction is connected to the transfer roller 305.
It is preferable that the length is such that it does not come in contact with the . When the end of the cleaning blade 305 comes into contact with the transfer roller 300, a large deformation occurs at the contact point, the roller surface is squeezed by a large force, and the resistance layer is eventually damaged and torn. Also, the pressing force of this cleaning blade is 100g~4
00g/20am is good, preferably 150g to 300
g/20cm is good. If the pressing force is too weak, cleaning will not be completed, and if it is too strong, rotation of the transfer roller 300 will be hindered and the surface of the transfer roller will be damaged.

By the way, in roller transfer, if the transfer pressure is too high, development occurs in which the toner in the center of the toner image is not transferred to the transfer device. For example, in character records, white blank characters, i.e.
Only character shapes are recorded. FIG. 17 shows the relationship between the transfer pressure and the rate at which voids occur when the roller transfer device shown in FIG. 14 is used. The rate at which hollow areas appear is expressed as the rate shown in the overall image of the white background area in the transferred image obtained by transferring a square independent toner image. If the percentage of hollow spots is 10% or less, a transferred image with no practical problems can be obtained. However, if the transfer pressure is too low, the nip width becomes narrow and the transfer density decreases. A transfer pressure in the range of 20 to 300 g/cj is suitable for the toner transfer device of the present invention, and preferably a transfer pressure of 20 to 200+r/cj is used. When the rubber hardness of the elastic layer of the transfer roller 300 is 30 or less, the relationship shown in FIG. Pressure must be kept low. For example, if the rubber hardness is 45, the transfer pressure can only be in the range of 20 to 50 g/d.

In such a range of leaning pressure and transfer pressure, if the depth of the four parts on the surface of the transfer roller 300 is 150 μm or more, the influence of the recesses cannot be fully covered. That is, during transfer, the nip width becomes narrow in the concave portion, resulting in poor transfer, and during cleaning, the toner cannot be wiped off, resulting in stains on the back of the transfer material (recording paper). Therefore, the depth of the four parts of the transfer roller surface is 150μ
m or less, preferably 120 μm or less.

FIG. 18 shows the relationship between the volume resistance value of the resistive layer of the transfer roller and the toner transfer efficiency using environmental humidity as a parameter. Toner transfer efficiency is the amount of toner transferred to the transfer material (
The ratio of the amount of transferred toner (referred to as the amount of transferred toner) to the sum of the amount of transferred toner and the amount of toner remaining on the toner image bearing member is expressed as a percentage. The resistive resin sheet forming the resistive layer can be designed with emphasis only on electrical properties.

If the volume resistance value of the resistive layer is too low, when a transfer voltage is applied, discharge occurs between the resistive layer and the toner image carrier, or toner of opposite polarity is generated due to charge injection, resulting in a significant reduction in transfer efficiency. Furthermore, if the volume resistance value is too high, the transfer voltage distributed to the toner layer will be low, and the transfer efficiency will be reduced. As shown in FIG. 18, the volume resistance of the resistive layer of the transfer roller 300 of the toner transfer device according to the present invention is 108
The range of ~1015Ω/master is good, especially 109~1012
The range of Ω/life can be used appropriately.

According to this roller transfer device, since no electrical contact or discharge occurs between the conductive layer of the transfer roller 300 and the recording drum, good image quality can be recorded without fluctuations in transfer voltage and transfer unevenness. The photoreceptor will not be destroyed. Further, a cleaning blade 305 is attached to the transfer roller 300.
Since cleaning is performed by attaching the transfer roller to the back of the recording paper, it is possible to prevent so-called back staining, in which toner adhering to the surface of the transfer roller adheres to the back of the recording paper. The transfer material P thus transferred is conveyed to the paper exit 120, and recording of the image is completed.

Next, an embodiment of a color electrostatic recording device that uses the above-described low-voltage driven corona ion flow recording head and can control gradation will be described with reference to FIG. 19. This color electrostatic recording device forms a color image by rotating a recording drum multiple times, and is equipped with a solid corona ion generator 41 for precharging and a low-temperature solid corona ion generator 41 around the recording drum 40 using an insulating recording medium. A voltage-driven solid corona ion flow recording head 42, non-contact developing devices 43, 44, and 45 each having color toner of a different color, and the charge of the color toner images developed on the recording drum 40 are made uniform. It is constructed by arranging a solid corona ion generator 46, a function-separated transfer roller 48 that electrostatically transfers a color toner image onto a recording paper 47, and a cleaning device 49 that cleans residual toner on the recording drum after transfer. be done. The color toner image transferred onto the recording paper 47 is fixed to the recording paper by a thermal fixing device 50. According to the present invention, a variable voltage is applied to the corona ion generating electrode in the low voltage driven corona ion flow recording head 42 as a pressure for accelerating corona ions.

The color image forming process in this example will be explained with reference to FIG. 20. I, II, m, and IV represent the order of steps. First, a potential of -eoov is applied to the recording medium on the recording drum 40 using the solid corona ion generator 41 for precharging. Next, the control electrode of the solid corona ion flow recording head 42 for low voltage driving is pulse width modulated by the yellow image signal as shown in FIG. 20(a).
Apply the signal voltage shown in to control the corona ion flow. At this time, the corona ion flow recording head 42 is
) is applied as a constant bias voltage for accelerating corona ions of 0* to erase the charge on the recording drum 40 and create an inverted electrostatic latent image. This electrostatic latent image is transferred to a bias voltage of −5
Reversal development is performed using a negative polarity yellow toner using a 00V color developing device 43. The gradation characteristics of this electrostatic latent image have values shown in FIG. 20(C) that match the development characteristics of yellow toner. During this first color image formation, the solid corona ion generator 46 that makes the toner polarity on the recording drum 40 uniform is not operated. Further, the functionally separated transfer roller 48 and the cleaning blade 49 are connected to the recording drum 4.
0 to prevent disturbance of the developed toner image on the recording drum.

Next, the recording drum 40 is rotated to form a second magenta toner image on the yellow toner image formed in the first color image forming step. For that purpose, like the first time, we used a solid corona ion generator 4 for precharging.
1 to uniformly charge the potential on the recording drum 40 to -eoov. Next, the bias voltage of the solid corona ion flow recording head 42 for low-voltage driving is set to the waveform shown in FIG. The corona ion flow is controlled to form an inverted electrostatic latent image on the yellow toner image. This inverted electrostatic latent image gives the gradation characteristics shown in FIG. 20(e) to the pulse width of the signal voltage modulated by the magenta image signal.

The electrostatic latent image on this yellow toner image is reversely developed by a non-contact developing device 44 having magenta toner.

The color image forming process as described above is similarly performed for each cyan and black toner image to form a color image on the recording drum 40. At this time, Fig. 20 (f')
A bias voltage shown in is applied to the low-voltage driving solid corona ion flow recording head 42 to form an electrostatic latent image having gradation characteristics matching the development characteristics of each color toner shown in FIG. 20(g). Since the color toner image thus formed on the recording drum 40 has a different potential for each toner layer, a solid corona ion generator 46 for static elimination is used to -
The electrostatic transfer of color toner images is performed at various potentials. Thereafter, the recording paper 47 is conveyed, and the functionally separated transfer roller 48 is brought into contact with the recording paper 47 from the back side to electrostatically transfer the color toner image onto the recording paper 47. The color toner image transferred onto the recording paper 47 is transferred to the heat fixing device 5.
0 is transferred onto the recording paper 47. The color toner remaining on the recording drum 40 after the transfer is mechanically cleaned by a cleaning blade 49, and the recording drum 40 is used again.

In the color electrostatic recording device as described above, it is also possible to make the change waveform of the bias voltage for accelerating corona ions common to each color, and change only the voltage value to change the tone of the color image. It goes without saying that liquid development may be used as the development method, and furthermore, the polarity of the potentials may be completely reversed. In this way, by using a corona ion flow recording head, we can provide a corona ion acceleration bias voltage waveform that is pulse width modulated and synchronized with the signal voltage, or we can create arbitrary gradation characteristics on the recording medium by changing the voltage value for each color. All methods of providing an electrostatic latent image are included in the present invention.

Next, an embodiment in which a feeding unevenness detection device is added to the recording drum will be described. As shown in FIG. 19, a disk 52 is provided on the rotating shaft of the recording drum 40, in which a slit 51 for timing generation for detecting feeding unevenness is cut.

FIG. 21 is a side view of this feeding unevenness detection device, in which a CCD sensor 53 and a light source 54 are provided facing the periphery of the disk 52 with the disk 52 in between.
A magnifying lens system 55 is provided between the disc 52 and the disc 52 . CC the feeding unevenness within 2 to 3 μm on the recording drum 40
In order to detect one element of the D sensor 53, the magnification (k) of the lens needs to satisfy the following condition.

(2-3)×γ×≧p Here, the reduction ratio of the disk 52 with respect to the recording drum 40 is γ
, the element pitch of the CCD sensor is 9 μm. Also, the distance between the slits 51 provided on the disk 52 is L (mm).
Then, the total number m of elements required for the CCD sensor 53 is expressed as follows: An integral multiple of the number of elements q shown in the following equation is required. This value is the number of elements included in one main scanning pitch calculated from allowable unevenness in feed.

q > (1000/n) ÷ (2~3) (1
4) As a result, assuming that the allowable feed unevenness is 2 μm,
When the resolution is 240 dpl (16 lines/mm), the number of elements of the CCD sensor 53 included in one main scanning pitch is q
becomes 32. At this time, the reduction ratio γ of the disk 52 with respect to the recording drum 40 is set to 1/2, and the total number of elements m of the CCD sensor 53 is 3016 (-23X 63
), the required spacing between the slits 51 on the disk 52 is 2,0 I 6 m+i.

To read the unevenness of feeding on the recording drum 40 at 2 μm,
It is necessary to detect a variation of 1 μm on the disk 52 reduced to 1/2. From this, when the element pitch of the CCD sensor 52 is 14 μm, in order to accommodate a positional variation of 1 μm with one CCD sensor element, the magnification rate of the magnifying lens system 55 is 1 μm.
It may be increased by 4 times.

In this way, by using a combination of the high-definition CCD sensor 53 and the magnifying lens system 55, even if the pitch of the slit 51 is coarser than the resolution on the recording drum 40, uneven feeding of the recording drum 40 can be detected with sufficient precision. I'll come.

Next, the operation of this feeding unevenness detection device will be explained using FIG. 22.

As the recording drum 40 rotates, the slit 5 on the disk 52
The image of the edge 56 of No. 1 is moved on the CCD sensor 53 in the direction of the arrow, and as shown in FIG.
The scanning time T3□ of the 32 elements of the D sensor 53 is made equal to the main scanning time of the corona ion flow recording head. resolution 40
A4 size (length:
When printing 40 sheets per minute (30 Dmra), the main scanning time T3□ of the print head is as follows.

t3□= 80sec x 1000/(16 pieces x
300mu+ x 40 pieces) -0,313<ll1se
c) (15) Therefore, the period Ts of the main scanning clock that drives the CCD sensor element 53 is Ts = 0.313/32- (1,0098(m
sec) (1B), and the frequency of the main scanning clock is 110.009g-102kllz.

In addition, the scanning time T2o, 6 for all 2016 elements is calculated by the formula %
(Formula %) Now, when uneven feeding occurs on the recording drum at the timing of the t6th clock next to the t5th clock of the main scanning clock shown in FIG. 22(b), the output signal of the CCD sensor element 53 is The result will be as shown in Figure 22 (C) or (d). When the feeding speed of the recording drum decreases, the output signal of the CCD sensor element 53 that occurs at the timing of the t6th clock does not increase, and becomes the same as the output signal S of the t99th clock, as shown in FIG. 22 (C). . On the other hand, when the feeding speed of the recording drum increases, the second
As shown in FIG. 2(d), the output signal "6+67" of the t6th clock and furthermore the t77th clock is output. Therefore, C
When the number of output signals from the CD sensor 53 is counted and the output of the corona ion flow recording head is turned on every time 32 output signals are output, the head operates at a position equal to the main scanning interval of the recording head, and the recording drum It is possible to correct uneven feeding.

In this way, the position on the recording drum can always be detected with high precision and the corona ion flow recording head can be controlled. As a result, even if there is uneven feeding of the recording drum, the electrostatic latent image is always formed at an accurate position on the recording drum, and fluctuations in image density due to uneven feeding will not occur.

This method of correcting uneven feeding is not limited to the case where this corona ion flow recording head is used, but can also be applied to electrostatic recording devices such as LED printers and LCD printers that use electrophotography. Furthermore, it can be applied to all recording methods using simultaneous drive recording heads.

[Effects of the Invention] As explained above, by changing the accelerating voltage applied between the corona ion flow recording head and the recording medium, the signal can be generated by electrical control, without depending on the recording material unlike electrophotographic recording. The γ characteristics of the electrostatic latent image can be changed independently of the voltage. As a result, there is no need to adjust the pulse width modulation of individual signals for each image, and arbitrary gradation characteristics can be obtained by simply changing the voltage waveform for accelerating corona ions, allowing you to set soft or high contrast images. can.

Furthermore, by adjusting the bias voltage for accelerating corona ions in accordance with the development characteristics of the developer, the γ characteristics of the electrostatic latent image can be determined. Thereby, the gradation characteristics of the toner image can be controlled to always be constant when replacing the developer. Also,
If applied to color image formation using color developers with different development characteristics for each color, it is possible to adjust the gradation characteristics of the container without changing the pulse width modulated signal voltage for each color.

Furthermore, by detecting uneven feeding of the recording drum and adjusting the timing of the main scan of the recording head to match the uneven feeding of the recording drum, image density fluctuations that occur in halftone areas of images and intermediate color areas of color images can be reduced. Fluctuations in color difference in color images can be prevented and good images can be formed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a corona ion flow recording head and its drive circuit in an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining the gradation characteristic control operation in the embodiment of FIG. 1. , FIG. 4 and FIG. 5 are diagrams showing a corona ion flow recording head and its driving circuit in another embodiment of the present invention, and FIG. 6 is a diagram showing a corona ion flow recording head and its driving circuit in another embodiment of the present invention. Diagrams showing the circuit, Figures 7 and 8
The figure is a diagram for explaining the gradation characteristic control operation in the embodiment of FIG. 6, FIG. 9 is a diagram showing the configuration of an electrostatic recording apparatus to which the embodiment of FIG. 6 is applied, and FIG. A diagram showing the relationship between the amplification factor of the head section and the distance from the center of the electrode in the diagram,
FIG. 11 is a diagram showing the surface potential attenuation characteristics of the recording drum in FIG. 9, FIG. 12 is a diagram showing the developing process of the developing device in FIG. 9, and FIG. 13 is a diagram showing the recording in the image forming process in FIG. 9. Diagram showing potential changes on the drum, No. 14
The figure is a diagram for explaining the configuration and transfer operation of the roller transfer device in Figure 9, Figure 15 is a diagram schematically showing an example of the configuration of the transfer roller in Figure 14, and Figure 16 is the function of this transfer roller. Figure 17 is a diagram for explaining the 14th
Figure 18 is a diagram showing the relationship between the transfer pressure and the rate of occurrence of hollow toner images when using the roller transfer device shown in the figure. Figure 18 is the volume of the resistive layer of the transfer roller in Figure 14 with environmental humidity as a parameter. A diagram showing the relationship between resistance value and toner transfer efficiency, FIG. 19 is a diagram showing the configuration of a color electrostatic recording device to which the present invention is applied, and FIG. 20 is a diagram showing the color image formation of the color electrostatic recording device of FIG. 19. A diagram for explaining the gradation characteristic control operation in the process, FIG. 21 is a side view showing the configuration of the recording drum feeding unevenness detection device in FIG. 19, and FIG. 22 is a diagram for explaining the operation of FIG. 21. It is a signal waveform diagram. 1... Corona ion generation hole, 2.13° 30... Corona ion generation electrode, 3, 32... Insulating layer, 4, 12
．． 28...Corona induction electrode, 5゜15...Solid corona ion generator, 6...Acceleration electrode, 7.34...AC voltage for generating corona ions, 8゜36...Pulse width modulated signal voltage, 9... cutoff voltage, 10... recording medium, 11.38... bias voltage for corona ion acceleration, 16... capacitor, 17... resistor, 18...
... DC voltage for generating corona ions, 19... Corona charger, 20... Corona wire for generating corona ions, 21... Focusing electrode, 22... Voltage for focusing, 23.
24.33... Control electrode, 25... Charged charge, 26
... DC voltage for generating corona ions, 27 ... Solid corona ion flow recording head for low voltage drive, 29 ... Corona ion generation holes, 31 ... Shielding electrode, 35 ... Corona ions, 37. ...Electrostatic latent image, 39...Corona ion flow, 40...Recording drum, 41...Corochi ion generator for precharging, 42...Corona ion flow head, 43-45...Color development 46...Corona ion generator for static elimination, 47...Recording paper, 48...Functionally separated transfer roller, 49...Cleaning blade, 50...Heat fixing device, 51...Slit , 52・
... Disc, 53... CCD sensor. Distance from the center of the electrode (0" m) Normally 0 Figure 1 Figure 14 Transfer pressure (9/CrTl") Figure 7 Figure 4o11! Body resistance (Ω cm) Figure 8 Figure 19 Government 20 figure

Claims (5)

[Claims] (1) A corona ion flow recording head having multiple corona ion generation sources is used to generate a corona ion flow according to the image signal to be recorded from this corona ion flow recording head to form an electrostatic latent image on the recording medium. In an electrostatic recording apparatus that records an image by forming an electrostatic latent image and developing the electrostatic latent image, means for applying a signal voltage whose pulse width is modulated by an image signal to the corona ion generation source as a corona ion flow control voltage; An electrostatic recording apparatus comprising means for applying a bias voltage for accelerating corona ions having a variable voltage value between the corona ion flow recording head and the recording medium. (2) A corona ion flow recording head having multiple corona ion generation sources is used to generate a corona ion flow according to the image signal to be recorded from this corona ion flow recording head to form an electrostatic latent image on the recording medium. In an electrostatic recording apparatus that records an image by forming an electrostatic latent image and developing the electrostatic latent image, means for applying a signal voltage whose pulse width is modulated by an image signal to the corona ion generation source as a corona ion flow control voltage; and means for applying a bias voltage for accelerating corona ions whose voltage value changes over time within the period of the signal voltage and whose changing waveform is variable between the corona ion flow recording head and the recording medium. An electrostatic recording device characterized by: (3) A corona ion flow recording head having multiple corona ion generation sources is used to generate a corona ion flow according to the image signal to be recorded from this corona ion flow recording head to form an electrostatic latent image on the recording medium. In an electrostatic recording device that records a color image by forming and developing this electrostatic latent image for each color, a signal pulse width modulated by an image signal is applied to the corona ion generation source as a corona ion flow control voltage. means for applying a voltage; and a corona in which at least one of a voltage value and a temporal change waveform of the voltage value within a period of the signal voltage is independently variable for each color between the corona ion flow recording head and the recording medium. An electrostatic recording device comprising means for applying a bias voltage for accelerating ions. (4) The apparatus further comprises charging means for uniformly charging the recording medium to a predetermined potential before the corona ion flow recording head generates the corona ion flow according to the image signal. , 2 or 3. (5) a recording drum, a member in which slits are formed at a pitch coarser than the recording resolution on the recording drum that rotates together with the recording drum; an optical system that magnifies the image of the slit; and an optical system that magnifies the image of the slit; 1. An electrostatic recording apparatus comprising: an optical sensor having a resolution higher than the recording resolution for detecting an image of a slit, and a feeding unevenness detection device for detecting feeding unevenness of the recording drum.