JPH06191087A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent occurrence of a malfunction by applying an effectively controller high voltage to a light emitting element such as an end light emission type EL element, etc. CONSTITUTION:The image forming apparatus comprises a drive controller 32 for controlling a common driver 34 and a line head 35 according to control signals Cm and Li, and a delay circuit 32a which outputs a control signal Hv by delaying an output timing by a time T2 from the signals Cm and Li. The apparatus further comprises an output controller 33a which applies OFF positive and negative high voltages Vp and Vn and ON positive and negative high voltages Vr and Vm generated from a high-voltage power source 33 at an output timing of the signal Hv from the circuit 32a to a line head 35 via the driver 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for exposing and recording image data on a photosensitive member by using a line head composed of a plurality of light emitting elements, for example, edge emitting EL (electro-luminescence) elements. .

[0002]

2. Description of the Related Art Generally, as shown in FIG. 4, an edge emitting EL element 1 used in a line head for forming an exposure image on a photoconductor such as an electroluminescent printer is made of zinc sulfide containing an active element. The thin film active layer 2 is surrounded by dielectric layers 3 and 4, and plate electrodes 5 are formed on the upper and lower surfaces of these dielectrics 3 and 4, respectively.
It has a multilayer structure in which 6 is provided.

As shown in FIG. 5, the line head 7 is formed by arranging the edge emitting EL elements 1 on a substrate 8 in a line. A rod lens array (not shown) is provided so as to face the tip of each edge emitting EL element 1 of the line head 7.

In the edge emitting EL device 1, as shown in FIG. 6 (a), the flat electrodes 5 and 6 have a voltage (O) which does not exceed the predetermined positive and negative threshold voltages + Vth and -Vth.
Even if the positive and negative voltages Vp and Vn for FF are applied, no light is emitted, but as shown in FIG. 6B, a voltage exceeding the range of the positive and negative threshold voltages + Vth and -Vth (the positive and negative voltages for ON). When the voltages Vr and Vm) are applied, a flat light beam is emitted.

A conventional image forming apparatus using a line head 7 composed of such an edge emitting EL element 1 is shown in FIG.
The circuit configuration is as shown in. That is, the power source 1
The control power of + 5V is supplied from 1 to the drive controller 12, and the drive power of + 24V is supplied to the high-voltage power supply 13. With this high-voltage power supply 13, +24
Positive and negative high voltage Vp and Vn for turning off from the V power source and O
Positive and negative high voltage Vr and Vm for N are generated and output to the common driver 14.

The common driver 14 is provided with output terminals COM1, ..., 6 for the line head 7, and has a waveform as shown in FIG. 6 (a) or FIG. 6 (b). Positive and negative high voltage voltages Vp and Vn for OFF input from the high voltage power source 13 or positive and negative high voltage voltages Vn for ON
r and Vm are alternately applied to the line head 7.

The common driver 14 is controlled by a control signal Cm output from the drive controller 12, and the line head 7 is controlled by a control signal Li output from the drive controller 12.

FIG. 8 shows timings of the control signals Cm and Li from the drive controller 12 and the positive and negative high voltage for OFF Vp and Vn output from the high voltage power supply 13.

The drive controller 12 creates control signals Cm and Li based on image data from an image data creating unit (not shown), and outputs positive and negative high voltage Vp and Vn for ON and positive and negative voltages for OFF. High voltage Vr and V
It is designed to output at the same timing as m.

[0010]

In the conventional image forming apparatus, the common driver 14 alternately applies the positive and negative high voltage outputted from the high voltage power source 13 to the line head 7. A predetermined rise time T1 (for example, about several tens of ms) is required until the control of the common driver 14 becomes stable. During this time T1, the line head 7 is in a no-load state, and the control signal Cm (control signal Li) from the controller 12 and the positive and negative high voltage Vp and Vn (for OFF output from the high voltage power supply 13). When the positive and negative high voltage Vr and Vm for ON are output at the same timing, the high voltage is applied to the unloaded line head 7 until the time T1 elapses.

Therefore, for example, as shown in FIG.
The positive high voltage Vp for F further rises and may exceed the positive threshold voltage + Vth. If the positive high voltage for OFF Vp temporarily exceeds the positive threshold voltage + Vth as described above, the edge emitting EL element 1 of the applied line head 7 emits light, and this light emission occurs. As a result, the photoreceptor is exposed and recorded.

Further, although not shown, the negative high voltage for OFF Vn further drops, resulting in a negative threshold voltage -V.
It may exceed th. As described above, when the negative high voltage for OFF Vn temporarily exceeds (lowers) the negative threshold voltage -Vth, the edge emitting EL element 1 of the applied line head 7 emits light. The light emission causes the photosensitive member to be exposed and recorded.

As described above, when the photoconductor corresponding to the non-printed portion which is not originally printed is exposed, when the exposed image is transferred onto the paper with toner or the like, the non-printed portion is usually stained as "toner fog". However, there is a problem in that printing is performed.

Therefore, according to the present invention, it is possible to apply a controlled high voltage surely to a light emitting element such as an edge emitting electroluminescence element, and prevent the occurrence of troubles such as toner fogging. The purpose is to provide a device.

[0015]

SUMMARY OF THE INVENTION According to the present invention, a plurality of light emitting elements such as edge emitting electroluminescent elements are arranged in an array to form a line head, and image data is formed on a charged photoreceptor by the line head. In an image forming apparatus for exposure recording, a high voltage output means for outputting a high voltage to a line head, and a high voltage output by the high voltage output means for each light emitting element of the line head are controlled based on image data. And a line head control means for applying the voltage to the light emitting elements of the line head by the line head control means before the output timing of the high voltage to the line head by the high voltage output means.

[0016]

In the present invention having such a structure, first, before the high voltage is output from the high voltage output means by the line head control means, each light emitting element of the line head is output based on the image data. Thus, the high voltage output from the high voltage output means is controlled.

Next, the high voltage output means outputs the high voltage, and the line head control means reliably outputs the high voltage output from the high voltage output means to each light emitting element of the line head based on the image data. It is controlled and applied.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to the edge emitting EL.
The present invention is applied to an image forming apparatus for a photoconductor that uses a line head having (electro-luminescence) elements formed in an array.

FIG. 1 is a block diagram showing a circuit configuration of a main part of the image forming apparatus. A power supply 31 supplies a control power supply of +5 V to a drive controller 32 as a line head control means, and a drive power supply of +24 V. Is supplied to the high voltage power supply 33 as high voltage output means. The high-voltage power supply 33 generates positive and negative high-voltage voltages Vp and Vn for turning off and positive and negative high-voltage voltages Vr and Vm for turning on from a + 24V power supply, and the output control unit 33a provided in the high-voltage power supply 33 causes At the timing of the output control signal Hv output from the delay circuit 32a provided in the drive controller 32, the generated positive and negative high voltage voltages Vp and Vn for OFF and the positive and negative high voltage voltages Vr and Vm for ON are generated.
And are output to the common driver 34.

The common driver 34 is provided with output terminals COM1, ..., 6 for the line head 35, and the positive and negative high voltage voltages Vp and Vn for OFF input or the positive and negative voltage for ON input from the high voltage power source 33. One of the high voltage Vr and Vm is selected, and positive and negative high voltage are alternately applied to the edge emitting EL element of the line head 35.

The line head 35 is composed of a plurality of edge emitting EL elements arranged in a line in parallel with the axis of a cylindrical photosensitive member (not shown). By the light emission, image information is exposed and recorded on the photosensitive material on the surface of the photoconductor.

The common driver 34 is controlled by a control signal Cm output from the drive controller 32, and the line head 35 is controlled by a control signal Li output from the drive controller 32.

The delay circuit 32a has a control signal C
The control signal Hv is set to a preset time T2 (the common driver 34 and the line head 35) for m and Li.
In consideration of the rise time, the output is delayed by about several tens [ms]). FIG. 2 shows each control signal Cm, which is output from the drive controller 32.
The timings of Li, Hv and the positive and negative high voltage Vp and Vn for OFF output from the high voltage power supply 33 are shown.

In the present embodiment having such a configuration, image data is input to the drive controller 32 from an image data creating section (not shown), and the common driver 34 and the common driver 34 are supplied based on the image data. The control signals Cm and Li for the line head 35 are created and output.

At this moment, the common driver 34 and the line head 35 are controlled based on the control signals Cm and Li from the drive controller 32, but the high voltage power source 33
Power is not being supplied from the line head 3
The edge-emitting EL element that constitutes element 5 does not emit light. The control signal Cm for the common driver 34 and the line head 35
The operation by Li and Li is unstable at the time of rising.

After the lapse of T2, the operations of the common driver 34 and the line head 35 become substantially stable, and the control signal Hv is input from the drive control controller 32 to the output control section 33a of the high voltage power supply 33. Then, the output control unit 33 a outputs the positive and negative high voltage voltages Vp and Vn for OFF and the positive and negative high voltage voltages Vr and Vm for ON to the common driver 34.

At this time, since the operations of the common driver 34 and the line head 35 have already been almost stable, as shown in FIG. 3, for example, the positive high voltage Vp for OFF has a positive voltage threshold value. It stabilizes at a preset voltage value lower than the voltage + Vth. Although not shown, the negative high voltage Vn for OFF also stabilizes at a preset voltage value higher (not lower than) the negative threshold voltage −Vth.

Here, the common driver 34 alternately applies positive and negative high voltage voltages Vp and Vn for OFF and positive and negative high voltage voltages Vr and Vm for ON to the line head 35 based on the control signal Cm. 6 is converted into the waveform shown in FIG. 6, and the OFF and ON high voltages having the converted waveform are supplied to the line head 35.

In the line head 35, based on the control signal Li, each end surface emitting EL element forming the line head 35 is turned off by the common driver 34.
Either the high voltage for ON or the high voltage for ON is selected and applied.

Therefore, the edge emitting EL element to which the high voltage for ON is applied emits light, and the photoconductor irradiated with the emitted light is exposed. Further, since the high voltage for OFF has a waveform in the range lower than the positive threshold voltage + Vth and higher than the negative threshold voltage −Vth, the applied edge emitting EL element does not emit light reliably, The portion of the photoreceptor corresponding to this edge emitting EL element is not exposed.

As described above, according to this embodiment, the common driver 34 and the line head 35 are controlled by the control signal Cm.
And a drive control controller 32 controlled by Li,
A delay circuit 32a that outputs the control signal Hv with the output timing delayed by a time T2 from the control signals Cm and Li.
And the positive and negative high voltage voltages Vp and Vn for OFF and the positive and negative high voltage voltages Vr and Vm for ON generated by the high voltage power supply 33 at the output timing of the control signal Hv from the delay circuit 32a via the common driver 34. Line head 35
By providing the output control section 33a for applying the voltage to the common driver 34 and the line head 35 by the drive control controller 32, the control timing of the common driver 34 and the line head 35 can precede the output timing of the high voltage by the high voltage power supply 33.

Therefore, a controlled high voltage can be applied to each of the edge emitting EL elements of the line head 35, and as a result, the positive high voltage for OFF has a positive threshold voltage. Since the high voltage for OFF is not exceeded and the high negative voltage for OFF does not fall below the negative threshold voltage, the edge emitting type E to which the high voltage for OFF is applied.
L element does not emit light. That is, it is possible to prevent problems such as toner fogging.

[0033]

As described above in detail, according to the present invention,
An image forming apparatus capable of reliably applying a controlled high voltage to a light emitting element such as an edge emitting electroluminescence element, and thus preventing occurrence of a defect such as toner fogging due to an increase in applied voltage. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of essential parts of an embodiment of the present invention.

FIG. 2 is a diagram showing the timing of output of each control signal and output of positive and negative high voltage for OFF in the same embodiment.

FIG. 3 is a diagram showing a waveform at the time of outputting a positive high voltage for OFF of the embodiment.

FIG. 4 is a perspective view showing an edge emitting electroluminescent element.

FIG. 5 is a diagram showing a part of a line head formed of an edge emitting electroluminescence element formed on a substrate.

FIG. 6 is a diagram showing a waveform of positive and negative high voltage for OFF and a waveform of positive and negative high voltage for ON.

FIG. 7 is a block diagram showing a circuit configuration of a main part of a conventional example.

FIG. 8 is a diagram showing a timing of outputting each control signal and outputting a positive and negative high voltage for OFF in the conventional example.

FIG. 9 is a diagram showing a waveform at the time of outputting a positive high voltage for OFF in the conventional example.

[Explanation of symbols]

32 ... Drive controller, 32a ... Delay circuit, 33
... high-voltage power supply, 33a ... output control section, 34 ... common driver, 35 ... line head.

Claims (1)

[Claims] 1. An image forming apparatus in which a plurality of light emitting elements such as edge emitting electroluminescent elements are arranged in an array to form a line head, and image data is exposed and recorded on a charged photoconductor by the line head. A high voltage output means for outputting a high voltage to the line head, and a high voltage output by the high voltage output means is controlled and applied to each light emitting element of the line head based on the image data. Line head control means is provided, and the control timing of each light emitting element of the line head by the line head control means precedes the output timing of the high voltage to the line head by the high voltage output means. Image forming apparatus.