JPS61272762A - Electrostatic recording device - Google Patents

Abstract

PURPOSE:To obtain a recording image having constantly stable black density by measuring the surface electric potential of a photoconductive recording medium exposed and destaticized by light having the quantity of light corresponding to the black of an image signal and controlling the bias voltage of a developing unit. CONSTITUTION:An electric potential detecting sensor 4 is arranged between an electric charger 2 and the developing unit 3 to measure the potential level of the photoconductive drum 1 exposed and destaticized by an exposing and destaticizing part 5 and to supply a potential signal D having a corresponding voltage value to a voltage adjusting part 6. The signal D is amplified by an amplifier 61 and the amplified signal is compared with a reference voltage E by a comparator 62 to control a bias voltage VB to be supplied to the developing unit 3 in accordance with the difference. The signal D is the surface voltage measuring value of the drum 1 exposed and destaticized by using a laser beam (corresponding)to the black of an image signal P) obtained at the no modulation of the part 5 as a scanning light point. Consequently the absolute density of the black of the recording image can be held at a constant value independently of the change of charging and exposing/destaticizing characteristics of the drum 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic recording device, and particularly to an electrostatic recording device using reversal development electrophotography.

[Conventional technology]

In general, in an electrostatic recording device that uses reversal development electrophotography, the surface of a photoconductive drum having an optical semiconductor layer on a conductive layer is electrostatically charged almost uniformly to correspond to the density of image information. The electrostatic latent image is created on the surface of the photoconductive drum by irradiating light with an amount of light to remove static electricity according to the amount of exposure, and the electrostatic latent image is reversely developed using powder toner. , the recorded image is obtained by transferring it to paper.

In this case, the charging and lightless static elimination characteristics of the photoconductive drum are major factors in determining the quality of recorded images.

That is, if the charging characteristics are poor and the stain level is lower than the steady value, fogging will occur in the white part of the recorded image, and if the potential increases, the density of the recording surface will decrease and the image will tend to jump.

Even if the charging characteristics are good, if the non-light neutralization characteristics are poor and the residual potential in the exposed area is high, the density on the recording surface will decrease and the image will tend to jump.

The charging and lightless static elimination characteristics cannot be maintained at a constant level because they change due to changes in the ambient temperature and humidity of the photoconductive drum and deterioration of the performance of the optical semiconductor layer based on the number of sheets used.

In conventional electrostatic recording devices, the charged potential of the photoconductive drum is measured with a potential detection sensor, and the voltage of the charging means such as a corona discharger is controlled so that the measurement result is a constant voltage on the band. .

[Problem that the invention seeks to solve]

Maintaining the charged potential of the photoconductive drum at a constant level has the great advantage of ensuring black density in a regular development method in which static electricity is removed by exposure with an exposure amount corresponding to the white density of image information.

However, in the case of the reversal development method, although it has the function of obtaining a relative difference in recorded image density by preventing fogging in white areas, it has the disadvantage that it cannot ensure absolute density for black areas.

[Means for solving problems]

The electrostatic recording device of the present invention includes a photoconductive recording medium having a photosemiconductor layer on a conductive layer, a charging means for charging the surface of the photoconductive recording medium with a substantially uniform electrostatic charge, and a charged an exposure charge eliminator that irradiates a photoconductive recording medium with light having an amount of light corresponding to the density of image information and removes surface charges corresponding to the amount of irradiated light; In an electrostatic recording apparatus equipped with a developing means for recording an electrostatic latent image on paper as a visible image and a potential detecting means for measuring the surface potential of a photoconductive recording medium, The image forming apparatus has a voltage adjusting means for performing exposure static elimination with an exposure amount corresponding to the black density of image information, measuring the residual potential after static elimination using a potential detecting means, and controlling the bias voltage of the developing means according to the measurement result. are doing.

With this configuration, the bias voltage of the developing means changes depending on the residual potential on the surface of the photoconductive recording medium that has been exposed and neutralized with light having an amount of light corresponding to the black density of the image information. The amount of developer attached to the surface of the photoconductive recording medium can be increased or decreased from the means, and an electrostatic recording device can be realized in which the black density of the recorded image transferred to the paper is automatically maintained at a constant value.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The drawing is a configuration diagram showing one embodiment of the present invention, and the electrostatic recording device includes a photoconductive drum 1, a charger 2, a developer 3, a potential detection sensor 4, an exposure charge eliminating section 5, and a voltage adjustment unit. 6.

The photoconductive drum 1 is a drum made of a conductive material such as aluminum, on which a photo-semiconductor layer whose resistance value decreases depending on the amount of light exposure is deposited on the surface of the drum. 11 rotates at a predetermined speed in the direction of the arrow.

On the outer periphery of the photoconductive drum 1, there are provided a charger 2 which carries out a corona discharge parallel to the axis 11, and a developer 3 which rotates in the direction of the arrow B in synchronization with the rotation of the photoconductive drum 1. a transfer corotron, which is not part of the paper transport path and which transfers the developed image formed on the surface of the photoconductive drum 1 onto the paper;
A cleaning section for cleaning developer such as powder toner remaining on the surface of the photoconductive drum 10 is sequentially arranged.

The charger 2 has one to three thin electrodes stretched in the axial direction along the outer periphery of the photoconductive drum 1 as discharge electrodes. Charge a predetermined electrostatic charge.

For example, if the electrostatic recording device is of a type that does not emit light with a scanning light point, such as a facsimile, the non-light static eliminator 5 includes a laser 51 such as helium/neon, and an acousto-optic modulator 52.
, a modulator driver 53, a beam diameter conversion lens 54, a slit 55, a rotating polygon mirror 56, and a Pθ lens 57.

The non-light static eliminator 5 main scans the surface of the charged photoconductive drum 1 along the axial direction with a scanning light spot of a laser beam optically modulated according to the image signal P, and eliminates the charged charges. Photostatic charge removal is performed to form an electrostatic latent image. In this case, the light modulation is set so that the light intensity of the scanning light spot is maximized for black of the image signal P and minimized for white.

Another example is the photoconductive drum 1 in a copying machine, etc.
There is a linear exposure along the axial direction. A negative film is used for the original to be copied, and the surface of the photoconductive drum 1 is irradiated with light transmitted through the original from a rod-shaped light source through a slit parallel to the axial direction of the photoconductive drum 1.
The light source and slit are moved in synchronization with the rotation of the In this case, a lens is placed between the slit and the optical path of the photoconductive drum 1 so that the image of the slit is formed on the surface of the photoconductive drum 10. By irradiating the photoconductive drum 1 with the photoconductive drum 1, black and white reversal copying can be performed.

In the following description, a case will be described in which the non-light neutralization section 5 is a scanning light spot.

The developing device 3 performs reversal development of the electrostatic latent image described above using powder toner having the same polarity as the charge polarity charged on the photoconductive drum 1. A bias voltage VB of the same polarity as the powder toner is applied from the voltage adjustment section 6 to the developing device 3 at the time of initial setting, and the amount of adhesion of the powder toner to the electrostatic latent image on the photoconductive drum 1 is controlled. It's in control. The developed image on the photoconductive drum 1 is transferred to paper and then fixed to obtain a recorded image.

The potential detection sensor 4 is disposed between the charging device 2 and the developing device 3, and measures the potential level of the photoconductive drum 1 after exposure static elimination by the exposure static eliminating section 5, and detects the potential level of the voltage value corresponding to the level. The signal is supplied to the voltage adjustment section 6.

The voltage adjustment section 6 includes an amplifier 61 and a comparator 62, and after amplifying the potential signal, compares it with a reference voltage E set in advance in the comparator 62, and supplies it to the developing device 3 according to the difference value between the two. Controls bias voltage Vn.

Here, the potential signal RI is a measured value of the surface voltage of the photoconductive drum 1 that has been subjected to non-photoconductive charge removal using the non-modulated laser beam (corresponding to black of the image signal P) of the exposure charge removal unit 5 as a scanning light spot. .

At the time of initial setting prior to scanning of the image signal P, the photoconductive drum 1 is rotated in the direction A of the arrow, and the photoconductive drum 1 is charged with a predetermined charge by the charger 2.

Next, ultrasonic power is supplied from the modulator driver 53 of the exposure static elimination section 5 to the acousto-optic modulator 52, and the acousto-optic modulator 5
Drive 2. Note that the image signal P is not supplied to the modulator driver 53 at the initial setting (this state corresponds to continuous points in the image signal P), and the ultrasound signal frequency applied to the power amplifier of the modulator driver 53 is initially set. It is set value.

The acousto-optic modulator 52 controls the amount of output modulated light (+1st order light) in proportion to the magnitude of the supplied ultrasonic power, and controls the deflection angle of the output modulated light in proportion to the ultrasonic frequency. . Note that there is no output modulated light with a deflection angle corresponding to the initial setting value of the ultrasonic frequency.

The light intensity of the scanning light spot during modulation is considered.

The laser beam from the laser 51 is incident on the acousto-optic modulator 52, and output modulated light is emitted with a beam light amount corresponding to the above-mentioned ultrasonic power and a deflection angle corresponding to the ultrasonic frequency.

The emitted laser beam is converted into a predetermined beam diameter by a beam diameter conversion lens 54, passes through a slit 55 whose size is approximately equal to the beam diameter, is deflected by a rotating polygon mirror 56, and is reflected by an Fθ lens 57. A scanning light spot having a size corresponding to the slit 55 is imaged on the main scanning line of the photoconductive drum 1.

In the case of the output modulated light having the deflection angle corresponding to the initial setting value of the ultrasonic frequency, the entire slit 55t passes through.

By scanning the surface of the photoconductive drum 1 with this scanning light spot, the charged charges are removed in accordance with the amount of exposure, and the potential is lowered.

On the other hand, the potential detection sensor 4 measures the surface potential with respect to a predetermined area of the photoconductive drum 1 and outputs a potential signal. When the potential is measured, a synchronization timing signal T is sent from the recording control section (not shown) to the comparator 6 of the voltage adjustment section 6.
2.

The potential signal is amplified by an amplifier 61 and then supplied to a comparator 62. The comparator 62 compares a preset reference voltage E and the amplified potential signal D', and increases or decreases the output bias voltage VB according to the difference between the two.

That is, when the potential signal D' is low, the photoconductive drum 1
Since the residual potential is low, the bias voltage VB is lowered to reduce the adhesion amount of powder toner, thereby controlling the black density of the recorded image to decrease and preventing blurring of the recorded image.

When the potential signal D' is high, the residual potential of the photoconductive drum 1 is high, so by increasing the bias voltage VB and increasing the amount of powder toner adhering, the black density of the recorded image is controlled in the direction of increasing. This prevents recorded images from skipping.

In either case, control is performed so that the absolute black density of the recorded image is maintained at a constant value, regardless of changes in the charging and exposure static elimination characteristics of the photoconductive drum 1.

When the bias voltage VB is out of the adjustment range, the ultrasonic power from the modulator driver 53 of the exposure static elimination unit 5 is adjusted to control the amount of modulated light output from the acousto-optic modulator 52. Thereby, the life of the photoconductive drum 1 can be extended.

Adjustment of the bias voltage VB is performed only during the supply period of the synchronous timing signal T, and when the synchronous timing signal T disappears, the value of the bias voltage VB is identified at that time. This fixation persists until the next initial setting is performed. Therefore, the bias voltage VB can be set to an appropriate value corresponding to the change in the exposure static elimination characteristic.

Following the scanning at the time of initial setting, the image signal P is supplied to the modulator driver 53, the ultrasonic signal of the modulator driver 53 is modulated according to the image signal P, and the output modulated light from the acousto-optic modulator 52 is The intensity changes.

Therefore, the amount of light of the scanning light spot that illuminates the surface of the photoconductive drum 1 changes, and an electrostatic latent image that corresponds to the image signal P and is inverted in black and white is formed on the surface of the photoconductive drum 10.

As described above, the electrostatic latent image is developed by the developing device 3, and is transferred and fixed onto paper, thereby obtaining a recorded image with stable black density.

The above-mentioned initial setting of the voltage value of the bias voltage VB may be performed every time one screen is recorded, once at the start of communication for one day, or once at the beginning of one communication.

Note that, prior to measuring the potential of the exposed portion that has been neutralized, the charged potential of the photoconductive drum 1 is measured using the potential detection sensor 4, and as in the case of bias voltage adjustment described above, the high voltage indicated by the dotted line in the figure is By using the conventional method of controlling the high voltage supplied to the charger 2 by the control unit 7 and the high voltage generation unit 8 and setting the amount of charge to a predetermined value, recording with even better white areas can be achieved. Images can be obtained and recording stability is improved.

As explained above, in this example, laser light such as helium or neon was used as the exposure light source, and the light was modulated by an acousto-optic modulator. It's okay.

〔Effect of the invention〕

As described above, the electrostatic recording device of the present invention adds a voltage adjustment means to measure the surface potential of a photoconductive recording medium that has been subjected to lightless static elimination with light having an amount of light corresponding to the black color of the image signal. ,
By controlling the bias voltage of the developing device according to the measurement results, it is possible to obtain a recorded image that always has a stable black density regardless of the surface potential of the photoconductive recording medium after path light static elimination. This has the effect of improving quality and maintaining good recorded image quality over a long period of time.

[Brief explanation of drawings]

The figure is a configuration diagram showing an embodiment of the present invention. In the figure, 1... photoconductive drum, 2...
...Charger, 3...Developer, 4...
Potential detection sensor, 5... Exposure static eliminator, 6...
...Voltage adjustment section.

Claims (1)

[Claims] a photoconductive recording medium having an optical semiconductor layer on a conductive layer;
A charging means for charging the photoconductive recording medium with a substantially uniform electric charge; and a charging means for irradiating the charged photoconductive recording medium with light of an amount corresponding to the density of image information to remove static electricity in accordance with the amount of exposure. a developing means for recording an electrostatic latent image generated on the photoconductive recording medium as a visible image on paper as a visible image on paper; and a developing means for measuring the potential on the photoconductive recording medium. In an electrostatic recording device having a potential detection means, the potential detection means detects a potential on the photoconductive recording medium that has been subjected to exposure charge removal with an exposure amount corresponding to the black density of the image information prior to exposure charge removal of the image information. An electrostatic recording apparatus characterized by comprising a voltage adjusting means for measuring and controlling a bias voltage of the developing means according to the measurement result.