JPH0451027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for developing an electrostatic image in an electrostatic recording device such as an electrophotographic copying device. The present invention relates to a developing method in which an electrostatic image on an image carrier is developed with toner in the developing area.

[Prior art]

Conventionally, a developing method is known in which an oscillating electric field is generated in the developing area using an alternating voltage, and the developed density is adjusted by changing the amplitude of the alternating voltage or the voltage value of the DC component voltage. A developing method is known from JP-A-55-118048, and a developing method in which the frequency of the alternating voltage is changed to adjust the developed density is also known from JP-A-55-118048.
Known from No. 133058. This method of adjusting the developing density by changing the strength and frequency of the oscillating electric field has the advantage that it is cheaper than the method of changing the aperture of the optical system, and is more adaptable than the method of changing the light source intensity. However, the method of changing the strength of the oscillating electric field has the risk of causing fogging, and the method of changing the frequency has a narrow range of change in developing density, so in any case, the gradation was sufficiently reproduced. It is difficult to adjust the development density to obtain a clear recorded image. In addition, in order to change the strength of the oscillating electric field in response to changes in the electrostatic image potential and background potential, two types of changing voltages are required, which makes the power supply complex, and it is difficult to convert the frequency. Another problem is that the power supply is complicated.

[Object of the Invention] The present invention is capable of adjusting the developing density so that a clear recorded image with sufficiently reproduced gradation can be obtained by applying an oscillating electric field to the developing area, and moreover, the power supply device is The purpose of the present invention is to provide a developing method that is easily configured.

[Structure of the invention]

The present invention provides a developing method in which development is performed by applying an oscillating electric field to a developer consisting of toner particles and an insulating magnetic carrier, and causing the toner particles to fly from a magnetic brush onto the surface of an image carrier. The periodic waveform voltage generated is adjusted by amplification, boosting, and phase control that cuts a certain part of the waveform, and the waveform of the periodic waveform voltage is changed using the superimposed voltage of the periodic waveform voltage and the DC voltage. The present invention is a developing method characterized in that an oscillating electric field is applied to develop an electrostatic image on an image carrier with the toner particles in the developing area, and with this configuration, the above object is achieved.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a developing device for carrying out the method of the present invention.

In FIG. 1, numeral 1 rotates in the direction of the arrow, and an electrostatic latent image is formed on the surface by a known charging and exposure device (not shown) or an electrostatic latent image forming device using a multi-stylus electrode or an ion control electrode. A drum-shaped image carrier having an electrophotographic photoreceptor layer or dielectric layer to be formed, 2 a developing sleeve made of a non-magnetic material such as aluminum, 3 a developing sleeve 2
The developing sleeve 2 and the magnet 3 constitute a developer transport carrier. The developing sleeve 2 and the magnet body 3 can rotate relative to each other, and the figure shows that the developing sleeve 2 rotates to the left and the magnet body 3 rotates to the right. Further, the N and S magnetic poles of the magnet body 3 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the magnetic force forms a layer of developer D consisting of toner particles and carrier particles on the surface of the developing sleeve 2. It is attached to form a so-called magnetic brush. This magnetic brush is moved in the same direction as the rotation of the developing sleeve 2 by the rotation of the developing sleeve 2 and the magnet body 3, and is conveyed to the developing area A. 4 is a layer thickness regulating blade made of magnetic or non-magnetic material that regulates the height and amount of the magnetic brush on the surface of the developing sleeve 2; 5 is a cleaning blade that removes the magnetic brush that has passed through the developing area A from above the developing sleeve 2; , 6 is a developer reservoir, 7 is a stirring screw that stirs the developer D in the developer reservoir 6 to uniformly mix the toner particles and carrier particles, 8 is a toner hopper for replenishing toner particles T, 9 is a developer A toner supply roller having a concave portion on its surface for dropping toner particles T into the agent reservoir 6; 10 a periodic voltage generating circuit that generates a sinusoidal voltage (waveform T) as shown in FIG. 2; 11 an output from 10; It is configured to phase-control the periodic voltage wave, extract only a specific portion γ of each half-wave (T/2), convert it as shown by the solid line in FIG. 3A, or further amplify it. The waveform shaping circuit 12 is a DC power supply circuit that superimposes a DC bias voltage on the AC voltage obtained as described above. The value of γ is determined by the waveform shaping circuit 1.
It can be changed by adjusting the constant of 1, and by changing γ, the output waveform will be as shown in Figure 3 B or C.
It changes like this.

FIG. 5 shows the output (second
Figure 4 is a waveform obtained by boosting the voltage, then controlling the phase, and then superimposing a DC bias voltage, and Figure 4 is a waveform obtained by controlling the phase of the boost waveform in Figure 2, then boosting it, and then superimposing a DC bias voltage. In the phase-controlled voltage waveform, the vertical rising edge and the falling straight line portion do not react immediately during step-up conversion, so the former has a slightly slower waveform, but practically the same effect can be obtained.

The output thus obtained is applied to the developing sleeve 2 via the protective resistor 13, and an oscillating electric field is generated in the developing area A between the developing sleeve 2 and the image carrier 1 whose conductive base is grounded.

FIGS. 6 and 7 are block diagrams of circuits used to obtain the outputs shown in FIGS. 4 and 5, respectively. FIG. 8 is an example of a phase control circuit used for the waveform shaping shown in FIG. 7, and is a relatively simple circuit using a trigger diode and a triac. The output of the periodic voltage amplification circuit is connected to IP in the figure. Adjustment variable resistor R ₁ , dummy R ₂ , and capacitor C ₁ are phase circuits, and the voltage V _e1 across C ₁ is the trigger.
When the breakover voltage of the diode Dtr is reached, the trigger diode is switched and C is discharged, a signal current is given to the gate G to start the triac Tr, and the voltage applied to the primary side of the step-up transformer changes. The voltage with the modified waveform is output from the secondary side OP of the transformer. Changing R ₁ changes the charging rate of C ₁ and at the same time changes the conduction angle of the triac, making it possible to adjust the value of γ.

Test results using a copying machine equipped with the present developing device will be described below.

The copying device used in the test incorporated a developing device with the same configuration as that shown in FIG. 1 (the periodic wave voltage generating circuit used was the one in FIG. 7), and A negatively charged photoreceptor consisting of a charge generation layer and a charge transport layer made of an organic photoconductor was used.
In the experiment, the surface speed of the image carrier in the arrow X direction was 120 mm/
sec, the distance between the image carrier 1 and the developing sleeve 2 (that is, the developing area A) is 750 μm, the rotation speed in the direction of the arrow of the developing sleeve 2 with an outer diameter of 30 mm is 65 r.pm, and the layer thickness regulating blade is made of a non-magnetic material. 4 and the developing sleeve 2 is 350 μm, the rotation speed in the direction of the arrow of the magnet 3 having 8 equally spaced N and S magnetic poles with a magnetic flux density of 900 Gauss is 700 rpm, and the average particle diameter superimposed on the developer D. is 30μm
A two-component developer (EP310 manufactured by Minolta) consisting of an insulating magnetic carrier with a specific resistance of about 1 x 10 ¹⁴ Ωcm and an insulating non-magnetic toner with a superimposed average particle size of 13 μm, containing magnetic powder dispersed in a resin. The experiment was carried out under conditions using a commercially available developer).

Electrostatic images with various potentials are formed on the image carrier using gray scale, and the developing sleeve 2
The period T or 500 μsec has a waveform as shown in Figure 5.
Development was carried out by applying an oscillating voltage of 1, and the relationship between the electrostatic image potential and the recorded image density was determined. The experiment was repeated by changing the γ/T ratio of the applied periodic wave voltage, and the results shown in FIG. 9 were obtained.

Note that development in this case is performed by toner particles flying from the magnetic brush onto the surface of the image carrier 1 without the magnetic brush formed on the developing sleeve 2 rubbing the surface of the image carrier 1. This method is based on a so-called non-contact jumping development method. The recorded image density is the image density of a recording paper obtained by transferring a developed toner image onto a recording paper by a transfer device (not shown) and fixing the transferred toner image by a fixing device. Even if a periodic waveform voltage (FIG. 5) oscillated by a circuit such as that shown in FIG. 6 is applied for development, a recorded image density curve similar to that shown in FIG. 9 can be obtained.

As is clear from Fig. 9, without changing the amplitude, bias, or frequency of the periodic wave voltage,
By simply changing the γ/T ratio, it is possible to adjust the recorded image density, that is, the developed density, to remain constant even if the electrostatic image potential changes by about 300 V. With this adjustment method, the amplitude and bias can be changed. Since there is no risk of fogging occurring, therefore,
Clear recorded images with excellent gradation reproducibility can be easily obtained.

Note that the method of the present invention is not limited to the above-mentioned example, and the waveform of the periodic waveform voltage may be a rectangular wave, a sine wave, or another waveform to which phase control is applied.

In addition, in the above example, a trigger diode was used to configure the phase control circuit to perform waveform shaping, but the circuit configuration is not limited to that, and includes a unidirectional transistor (UJT), a silicon symmetrical switch (SSS), a silicon unilateral A combination of a trigger element such as a switch (SUS) or a neon tube and a thyristor may be used. moreover,
By providing a wire or grid-shaped control electrode between the carrier 1 and the developing sleeve 2 so as not to prevent the toner from flying from the magnetic brush to the electrostatic image, and applying an oscillating voltage to the control electrode. The present invention may be applied to a device that generates an oscillating electric field in the developing area, or a device in which a magnetic brush rubs the surface of the image carrier 1. Furthermore, as in the embodiment, a carrier (preferably one having a high resistivity of 10 ¹³ Ωm or more and a weight average particle size of 50 μm or less, and the above-mentioned resistivity is
After placing the particles in a container with a cross-sectional area of 0.50 cm ² and tapping them, a load of 1 Kg/cm ² is applied to the packed particles, and a voltage is applied to generate an electric field of 1000 V/cm between the load and the bottom electrode. By using a non-contact jumping development method using a two-component developer consisting of a toner and a current value obtained by reading the current value when it is applied, sufficient adjustment with excellent gradation reproducibility can be performed.

In the present invention, changes to change the γ/T ratio (change the conduction angle) can of course be made manually, but also by using a computer or the like based on detection of electrostatic image potential, toner image density, etc. This can easily be done automatically. Of course, it can also be used in combination with the previously known conventional image density adjustment method.

〔Effect of the invention〕

According to the present invention, as described above, by changing the selection time of the time selection conversion, it is possible to greatly adjust the developing density without causing fog, and it is possible to achieve sharpness with excellent gradation reproducibility. The excellent effects that a recorded image can be obtained and the power supply device can be constructed relatively easily can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a developing device that implements the method of the present invention, FIGS. 2 to 5 are waveform graphs showing examples of periodic waveform voltage, and FIGS. 6 and 7 are waveform graphs showing examples of periodic waveform voltage. FIG. 8 is a block diagram of a periodic wave voltage generator, FIG. 8 is an example of a phase control circuit, and FIG. 9 is a graph showing the relationship between electrostatic image potential and recorded image density when γ/T is varied. 1... Image carrier, 2... Developing sleeve, 3...
Magnet body, 4... Layer thickness regulation blade, 5... Cleaning blade, 6... Developer reservoir, 7... Stirring screw, 8... Toner hopper, 9... Toner supply roller, 10... Periodic voltage generation circuit, 11
... Waveform shaping circuit, 12 ... DC power supply, 13 ...
protection resistance.

Claims (1)

[Claims] 1. A developing method in which an oscillating electric field is applied to a developer made of toner particles and an insulating magnetic carrier, and the toner particles are caused to fly from a magnetic brush to the surface of an image carrier, thereby developing the image.
The periodic waveform voltage generated in the development area is adjusted by amplifying, boosting, and phase control that cuts a certain part of the waveform, and changing the waveform of the periodic waveform voltage using the superimposed voltage of the periodic waveform voltage and the DC voltage. 1. A developing method, comprising: applying a vibrating electric field of a certain magnitude to develop an electrostatic image on an image carrier with the toner particles in the developing area.