JP2847016B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus using an array head in which a plurality of electroluminescent elements are arranged as exposure means.

[0002]

2. Description of the Related Art In this type of electrophotographic apparatus, as shown in FIG. 7, a photosensitive drum 2 is provided at a substantially central portion of a housing 1, and a charger 3 and a plurality of electrophotographic devices are provided around the photosensitive drum 2. An exposure device 4, a developing device 5, a transfer charger 6, a static elimination charger 7, and the like using an array head in which luminescence elements (hereinafter, referred to as EL elements) are arranged.

At the time of printing, the surface of the photosensitive drum 2 is uniformly charged by the charging charger 3, and the surface of the charged photosensitive drum is irradiated with light emitted from the array head of the exposure device 4 based on image information to form an image. Information is recorded as an electrostatic latent image, and toner is caused to adhere to the electrostatic latent image from the developing roller 8 of the developing device 5.

On the other hand, a sheet feeding roller 10 is
To transfer the transfer paper to the transfer path for transfer.

The toner image formed on the photosensitive drum 2 is transferred to a transfer sheet at the position of the transfer charger 6, and the transfer sheet is thermally fixed by a heat fixing device including a heat roller 11 and a pressure roller 12. Discharge to the outside. The charge remaining on the surface of the photosensitive drum after the transfer is removed by the charge removing charger 7 to prepare for the next charging.

As shown in FIG. 8, each EL element of the array head has a thin-film active layer made of zinc sulfide containing an active element between a pair of dielectric layers 13 and 14 as a light emitting layer 15 in a sandwich shape. Each of the dielectric layers 13 and 14 is formed by laminating flat electrodes 16 and 17 on the outer surface thereof.
By applying a voltage equal to or higher than the threshold value | ± Vth | between the light emitting layers 6 and 17, the light emitting layer 15 emits light with a flat light flux in the end face direction.

As shown in FIG. 9, for example, as shown in FIG. 9, a plurality of sets of EL elements 18 are arranged as a set, and a channel electrode 19 is provided in common for each set of EL elements 18 and a common electrode is provided for each EL element 18 individually. An electrode 20 is provided.
A voltage is applied to each channel electrode by a channel driver 21, and a voltage is applied to each common electrode by a common driver 22. The common electrodes are connected to the common electrodes of the corresponding EL element 18 of each set, and are respectively connected to common (1), common (2), common (3), common (4), and common (5) from the common driver 22. The common (6) voltage signal is applied to the corresponding common electrode.

The channel driver 21 generates a channel applied voltage based on the frame signal and the print data signal from the control unit 23, and the common driver 22 selects the common timing signal from the control unit 23 and the common (1) to (6). A common applied voltage is generated by a signal.

The timing of the voltage signal applied to the commons (1) to (6), the timing of the frame signal and the timing of the print data signal are as shown in FIG.

When printing, the control unit 23 operates as shown in FIG.
Exposure control as shown in FIG. First, the main motor is rotated to start the operation of the photosensitive drum 2 and the transport rollers arranged on the transport path of the transfer paper.

Then, it is determined whether or not the exposure by the array head is exposure in the print range. If the exposure is in the print range, a print data signal based on print information is output to the channel driver 21 as exposure data. The light emission of the array head is controlled.

If the exposure is in the non-printing range, a full emission data signal for causing all the EL elements 18 to emit light is output to the channel driver 21 as exposure data to control the light emission of the array head. That is, pre-exposure and post-exposure are performed for the purpose of, for example, removing charges and making the potential uniform.

When the above processing is performed for the steps of pre-exposure, exposure of one page based on print data, and post-exposure, the operation of the main motor is stopped. Thus, printing of one page is completed. At this time, if there is data of the next page, the main motor is operated again and the same processing is repeated.

In the exposure apparatus using such a conventional EL element array head, the pre-exposure and post-exposure performed before and after the paper, that is, in the non-printing range, as shown in FIG. Each EL element emits light continuously by setting the threshold value | ± Vth | or more every time the polarity of the common signal is inverted.

[0015]

However, when the EL elements of the array head emit light continuously as described above, the average light emission amount PB from the array head becomes too large, and the deterioration of the photosensitive member is accelerated and the life is shortened. There was a problem of letting it.

For example, if it is assumed that normal printing is set to 5%, one page is printed on three rotations of the photosensitive drum, and pre-exposure and post-exposure for one rotation of the photosensitive drum are performed before and after that, the pre-exposure and post-exposure Since continuous emission is performed, each of pre-exposure and post-exposure corresponds to 33.3% of printing when converted to printing.
This corresponds to the exposure amount when printing 6 to 7 sheets of paper when viewed from 5% normal printing. Therefore, in the printing process of one sheet, if the pre-exposure and the post-exposure are included,
This means that 15 sheets have been printed, and the photoreceptor is degraded accordingly.

Accordingly, the present invention provides an electrophotographic apparatus capable of suppressing the average amount of light emitted from an array head during exposure in a non-printing range to a low level by simple control, thereby preventing deterioration of the photosensitive member and preventing a reduction in the life of the photosensitive member. provide.

[0018]

SUMMARY OF THE INVENTION The present invention comprises a channel electrode and a common electrode, applies a voltage of which polarity is inverted to the common electrode, and obtains positive and negative signals obtained by exclusive OR of a frame signal and a print data signal. A negative voltage is applied to the channel electrode, and an array head in which a plurality of electroluminescent elements arranged to emit light when a voltage equal to or higher than a threshold is applied between both the channel electrode and the common electrode is used as exposure means. In an electrophotographic apparatus that exposes a photoreceptor based on print information, attaches toner to the exposed photoreceptor, develops the toner image, and transfers the toner image obtained by the development onto transfer paper for printing, the photoreceptor is exposed to the photoreceptor. Means for judging whether or not the exposure in the printing area is exposure, and a frame signal when the judgment means judges the exposure in the printing area. Positive and negative voltages obtained by exclusive OR with the data signal are applied to the channel electrodes of the respective electroluminescent elements, and when the determining means determines exposure in the non-printing range, the print data signal is replaced with a frame signal. Control means for applying a positive or negative fixed voltage obtained by exclusive OR of two frame signals to the channel electrode of each electroluminescence element.

[0019]

In the present invention having such a configuration, when the exposure to the photosensitive member is performed in the printing range, the positive and negative voltages obtained by the exclusive OR of the frame signal and the print data signal are applied to each of the electro-optical elements. The voltage is applied to the channel electrode of the luminescence element. Accordingly, each of the electroluminescent elements emits light and emits light based on the print data signal, and exposes the photoconductor.

When the exposure of the photosensitive member is performed in the non-printing range, a frame signal is used instead of the print data signal, whereby a positive or negative fixed value obtained by an exclusive OR of two frame signals is used. A voltage is applied to the channel electrode of each electroluminescent device. As a result, the potential difference between the channel electrode and the common electrode of each electroluminescent element becomes equal to or greater than the threshold value at every other inversion cycle of the common signal, causing each electroluminescent element to emit light. That is, each electroluminescence element alternately repeats light emission and non-light emission, and the average light emission amount is reduced.

[0021]

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

The configuration of the electrophotographic apparatus in this embodiment is the same as that of FIG. 7, and the configuration of the array head and the configuration of the light emission control circuit thereof are the same as those of FIG.

The exposure control according to the present embodiment is performed based on FIG. First, the main motor is rotated to start the operation of the photosensitive drum 2 and the transport rollers arranged on the transport path of the transfer paper.

The photosensitive drum 2 by the array head
It is determined whether or not the exposure is an exposure in the print range. If the exposure is in the print range, a print data signal based on the print information is output to the channel driver 21 as exposure data to control the light emission of the array head. Do.

In the case of exposure in a non-printing range, a frame signal is used as exposure data. That is, a frame signal is output to the channel driver 21 instead of the print data signal, and light emission control of the array head is performed.

Exposure in the non-printing range is performed as pre-exposure and post-exposure before and after a sheet on which print data is printed, as shown in FIG.

The channel driver 21 is provided with an exclusive OR circuit 211 shown in FIG. The exclusive OR circuit 211 is connected to the + Va terminal and the -Vb terminal to take an exclusive OR of the input frame signal and the print data signal. When both signals are at the high level or the low level, the voltage signal of -Vb is output. And when one signal is high level and the other signal is low level or vice versa, + Va
Is output. At the time of exposure in the non-printing range, the print data signal is replaced with the frame signal, so that two identical frame signals are input to the exclusive OR circuit 211, so that the output is fixed at a voltage signal of -Vb. .

The above processing is performed for printing one sheet of paper. When the post-exposure is completed, the operation of the main motor is stopped. Thus, printing of one page is completed. At this time, if there is data of the next page, the main motor is operated again and the same processing is repeated.

In the embodiment having such a configuration, when the main motor rotates to perform printing, first, pre-exposure is performed. In this pre-exposure, the controller 23 outputs a frame signal to the channel driver 21 instead of the original frame signal and print data signal. That is, the same print data signal as the frame signal shown in FIG. 4B and the frame signal shown in FIG. 4C is input to the exclusive OR circuit 211.

As a result, the voltage applied to the channel electrode output from the exclusive OR circuit 211 is fixed at -Vb as shown in FIG.

On the other hand, the voltage of the common signal applied from the common driver 22 to the common electrode 20 of each EL element 18 is a voltage alternately inverted between + VP and -VN as shown in FIG. I have.

As a result, the potential difference between the channel electrode 19 and the common electrode 20 of each EL element 18 becomes + VP-(-Vb) when the common signal is + VP, and its absolute value becomes larger than the common signal voltage. When the common signal is -VN, it becomes -VN-(-Vb), and its absolute value becomes smaller than the common signal voltage.

Accordingly, if Vb is set so that the threshold value + Vth required for each EL element 18 to emit light is (+ VP + Vb)> + Vth> + VP, and (-VN + Vb)>-Vth, each EL element can be obtained. As shown in FIG. 6, the reference numeral 18 emits light at every other inversion cycle of the common signal. That is, the light emission is intermittent.

As a result, the average light emission PA of the array head
Will be lower. That is, PA <PB (conventional average light emission amount)
Becomes Therefore, it is possible to prevent the photosensitive drum 2 from deteriorating due to the pre-exposure. This effect is the same in the post-exposure performed after the exposure in the printing range is completed.

As described above, since the average light emission amount of the array head in the exposure in the non-printing range can be suppressed to a low level, the deterioration of the photoconductor can be prevented, and the life of the photoconductor drum can be prevented from being shortened.

Further, the control is simple because only the existing frame signal is used instead of the print data signal.

By the way, the EL element 18 does not immediately stop emitting light even when the application of the voltage equal to or higher than the threshold value is stopped, and emits light for a while because of the emission characteristics. Therefore, if the amount of light necessary for exposing the photosensitive member is set so that the light emission is continued even when the light emission is continued, the pre-exposure is performed even if the EL element 18 is controlled to emit light at every other polarity inversion cycle of the common signal. Also, no trouble occurs in post-exposure.

When printing on paper,
As shown in FIG. 5C, a print data signal that changes to a high level and a low level based on the print information is input to the exclusive OR circuit 211.

Therefore, at this time, the voltage applied to the channel electrode 19 of each EL element 18 changes to + Va or -Vb depending on the level relationship between the frame signal and the print data signal as shown in FIG.

As described above, the potential difference between the channel electrode 19 and the common electrode 20 of each EL element 18 is determined only when the print data signal is at a low level instructing printing (+ VP + V
b) or (-VN -Va). That is, the absolute value of the potential difference becomes equal to or greater than the absolute value | ± Vth | of the threshold value, and light is emitted.

In the above embodiment, during exposure in the non-printing range (pre-exposure or post-exposure), a negative fixed voltage is generated by exclusive OR of two frame signals and applied to the channel electrode of each electroluminescence element. However, the present invention is not necessarily limited to this.
Alternatively, a positive fixed voltage may be generated by exclusive OR of two frame signals and applied to the channel electrode of each electroluminescence element.

[0042]

As described above in detail, according to the present invention, when an exposure is performed using an array head in which a plurality of electroluminescence elements are arranged, the exposure from the array head when exposing a non-print area is performed. An object of the present invention is to provide an electrophotographic apparatus capable of suppressing the average light emission amount to be low by simple control, thereby preventing the deterioration of the photosensitive member and preventing the life of the photosensitive member from shortening.

[Brief description of the drawings]

FIG. 1 is a flowchart of exposure control showing an embodiment of the present invention.

FIG. 2 is a view showing the operation of the main motor of the embodiment and timings of data.

FIG. 3 is a diagram showing an exclusive OR circuit of the embodiment.

FIG. 4 is a waveform chart showing signals and voltages of respective units at the time of pre-exposure in the embodiment.

FIG. 5 is a waveform chart showing signals and voltages of respective units during printing according to the embodiment.

FIG. 6 is a waveform chart showing a relationship between a potential difference between a common channel electrode and light emission amount at the time of pre-exposure in the embodiment.

FIG. 7 is a diagram illustrating a schematic configuration of an electrophotographic apparatus.

FIG. 8 is a perspective view showing a configuration of an electroluminescence element.

FIG. 9 is a diagram showing a control circuit configuration of an array head in which electroluminescent elements are arranged.

FIG. 10 is a diagram showing timings of a common signal, a frame signal, and data for driving an array head.

FIG. 11 is a flowchart showing conventional exposure control.

FIG. 12 is a waveform diagram showing a relationship between a potential difference between a common channel electrode and a light emission amount in a conventional pre-exposure.

[Explanation of symbols]

 18 electroluminescent element 19 channel electrode 20 common electrode 21 channel driver 22 common driver

Claims (1)

(57) [Claims] 1. A channel electrode and a common electrode, wherein a voltage of which polarity is inverted is applied to the common electrode, and positive and negative voltages obtained by an exclusive OR of a frame signal and a print data signal are applied to the channel electrode. Then, an array head in which a plurality of electroluminescent elements that emit light when a voltage equal to or higher than a threshold value is applied between both the channel electrode and the common electrode is used as an exposure unit. In an electrophotographic apparatus that performs exposure, develops toner by attaching toner to the exposed photoconductor, and transfers the toner image obtained by the development onto transfer paper to perform printing, the exposure to the photoconductor is performed in a printing range. Judging means for judging whether or not the exposure is performed, and when the judging means judges the exposure in the printing range, exclusive use of the frame signal and the print data signal is performed. The positive and negative voltages obtained by the logical sum are applied to the channel electrodes of the respective electroluminescent elements, and when the determination means determines the exposure in the non-printing range, the print data signal is replaced with the frame signal instead of the frame signal. An electrophotographic apparatus, further comprising control means for applying a positive or negative fixed voltage obtained by exclusive OR of signals to a channel electrode of each of the electroluminescent elements.