JPH0399863A - End light-emitting type el printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an edge-emitting EL printer using a line head comprising an array of edge-emitting EL elements.

2. Description of the Related Art In recent years, a line precipitator is one of the printers developed using electrophotography.

This line printer has devices such as a charger, line head, developer, and transfer device placed close to each other on the circumference of a photosensitive drum. A latent image is formed by scanning light by selectively emitting light from a light emitting element connected to the head, and this latent image on the circumferential surface of the photosensitive drum is developed with toner supplied from a developing device to form this toner image. It is designed to be transferred onto printing paper using a transfer device. LEDs and the like are used as light emitting elements in such line heads, but these have problems such as difficulty in achieving both light emission intensity and responsiveness.

Currently, it is being considered to use an edge emitting type EL element as a light emitting element for a line head. Therefore, a line head using this edge-emitting type EL element will be explained based on FIGS. 7 and 8. As illustrated in FIG. 8, the edge-emitting EL element 2 of the line head 1 has a thin active layer 3 made of zinc sulfide or the like containing an active element.
is surrounded by dielectric layers 4 and 5 from above and below, plate electrodes 6 and 7 are formed on the upper and lower surfaces of these dielectric layers 4.5, and extremely flat light is emitted from the end surface of the active layer 3. It is possible to obtain zero emission intensity about 100 times that of conventional EL, which emits light. Then, as illustrated in FIG. 7, the edge-emitting EL elements 2 having the above structure are arranged in an array using film technology or the like, and a rod lens array (not shown) or the like is attached to the line head 1. is formed.

Therefore, by connecting a drive circuit to the line head 1 having the above structure and placing it close to the circumferential surface of the photosensitive drum, which is a photosensitive member, together with a charging device, a developing device, a transfer device, etc., each edge-emitting type E
By selectively causing the L elements 2 to emit light, images can be formed using dot matrix, and an electrophotographic line printer (not shown) can be manufactured.

Problems to be Solved by the Invention The edge-emitting type EL element 2 as described above emits light when an alternating current driving pulse is applied thereto. Therefore, as a method of driving a line head l made up of such edge-emitting type EL elements 2, both electrodes 6 and 7 are attached to each edge-emitting type EL element 2.
A conceivable method is to constantly apply driving pulses from 1 to 3, and control the synchronization of these driving pulses so that the potential of the combined pulse is set to be higher than or equal to the threshold voltage of the edge-emitting type EL element 2 and to control light emission.

With this control method, each edge-emitting type EL
A DC bias will be applied to element 2. However,
Due to its characteristics, the edge-emitting type EL element 2 deteriorates in the thin film and its optical output decreases even if it does not emit light if a pulse with an asymmetrical potential is applied. Therefore, in the method of constantly applying a DC bias to the edge-emitting type EL element 2 regardless of the presence or absence of printing as described above, the edge-emitting type EL element 2
The line head 1 consisting of the element 2 undergoes significant aging, and the durability of the edge-emitting EL printer 1 is low.

Means for Solving the Problems A line head is provided in which edge-emitting type EL elements having opposite electrodes formed on the outer surface of a dielectric layer surrounding an active layer are arranged in series, and each edge-emitting type EL element of this line head is A drive circuit is provided that performs synchronous control by applying positive and negative asymmetric drive pulses from both electrodes, and one of the drive pulses applied from this drive circuit to the edge-emitting EL element during non-printing while the power is turned on is set to the reference potential of the other. A means for preventing element deterioration is provided to generate pulses of positive and negative symmetrical voltages.

A line head is provided in which edge-emitting type EL elements each having electrodes formed opposite to each other are arranged on the outer surface of a dielectric layer surrounding the active layer. A drive circuit is provided which performs synchronous control by applying drive pulses, and one of the drive pulses applied from this drive circuit to the edge-emitting EL element during non-printing while the power is turned on is set to a positive and negative symmetrical voltage with respect to the other reference potential. By providing a means to prevent device deterioration with a pulse of Deterioration of the edge-emitting type EL element can be reduced compared to the case where the voltage is applied.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 6. First, the structure of the drive circuit of this edge-emitting EL printer 8 will be explained based on the block diagram exemplified in FIG. First, a timing controller 14 is connected to the interface 9 via a control circuit 13 to which two address counters 10 and 11 and a reference clock 12 are connected.
is connected.

The interface 9 also has two RAs and an M19, each of which has three states 15 to 18 connected to its input/output section.
．． 20 via a first data processing circuit 21, and these RAMs 19 and 20 are connected to the control circuit 13 and the address counter 10 and 11 via a selector 22. Furthermore, the RAM1
9 and 20, the three-state 1 is connected to the second data processing circuit 23 to which the timing controller 14 is connected.
7.18.

Also, each latch 24. ~24. and exclusive OR circuit 2
5. ~25. and driver 26□~26. and eight shift registers 29 . connected to the block electrodes 28 of the line head 27 via. ~29. , the data processing circuit 2
3 are connected in parallel. Note that this edge-emitting EL printer 8 includes the eight sets of members 24 to 26.
29 are each one IC30, ~30. formed within.

The timing controller 14 also includes a common electrode 31 .of the line head 27 . .about.31m and the common driver 32 connected to the latches 24, .about.24. and shift register 29. ~29. and exclusive OR circuit 25.
~25. It is connected to the.

The structure of the optical system and the like of the line head 27 is similar to that of the line head 1 described above.

In this configuration, in this edge-emitting EL printer 8, the print signal input via the interface 9 is compressed by processing such as rearranging in the first data processing circuit 21 for each main scanning line; Two RAMI 9
．． It is stored in one side of the RAM 20. That is, within the scanning time of the - line, the print signal is temporarily stored in one of the RAMs 19 and 20 selected according to the timing control of the address counter 10. At this time, in the edge-emitting EL printer 8, the control circuit 13 and the address counter 11, which operate in synchronization with the reference clock for high-speed output generated from the reference clock 12, send the print signal stored at high speed from the other RAM. It is designed to output . Therefore, this output print signal is reprocessed by the second data processing circuit 23 into a form suitable for printing, and the I
C30, ~30. are output and held in parallel.

And this IC30, ~30. and common driver 32
are controlled by the timing controller 14, and the block electrodes 281 to 28n and the common electrodes 31. -31m, low voltage and high voltage drive pulses are output to the line head 27, respectively.

That is, as illustrated in FIG. 4, in the edge-emitting EL printer 8 of this embodiment, a low-voltage driving pulse v1 having a positive potential with respect to the reference potential Ov is applied to the block electrodes 28. ~2
A high-voltage driving pulse V, which is applied to the common electrode 3 and which is asymmetric between positive and negative and whose reference potential is positive, is applied to the common electrode 3.
1, and the difference v, -v between these pulses is applied to the edge emitting type EL element 2. Therefore, by controlling the synchronization of the two drive pulses V, , V, the voltage applied to the edge-emitting type EL element 2 becomes equal to or higher than the threshold value, and the emission/non-emission of the edge-emitting type EL element 2 is controlled.

Therefore, in this edge-emitting type EL printer 8, the above-mentioned operation is performed in one step as shown in the timing chart illustrated in FIG.
During the line printing time T, the line head 27 repeats line emission four times in the width of one main scanning line. Therefore, as illustrated in Fig. 3, the lines printed in the above manner are beautiful with minimal jagged deviations at the edges, and one pixel is formed by four light emitting operations. Therefore, no white spots occur in the sub-scanning direction.

In this edge-emitting EL printer 8, the presence or absence of printing is detected by a detection circuit (not shown), which is a means for preventing element deterioration, by monitoring input signals to the interface 9 and the power-on value of the device. ing. Therefore, when this detection circuit detects that the device is not printing even though the power is turned on, one of the drive pulses being applied to the line head 27 from each electrode 28, 31 is set to the other reference. Converts to a pulse that has a positive and negative symmetrical voltage with respect to the potential.

Therefore, as illustrated in FIGS. 5 and 6, this edge-emitting type EL printer 8 has block electrodes 28. The drive pulse ■ applied to ~28n is set to the reference potential 1/2 of the drive pulse v applied to the common electrode 31.
Control is performed so that the voltage pulse is symmetrical in positive and negative with respect to V. This is in response to the fact that it is difficult to output drive pulses with positive and negative symmetry in the current IC30, etc., and by doing this, the edge-emitting type EL element 2 has potentials of v, -v, A constant voltage pulse of =1/2V, which is symmetrical in positive and negative directions, is applied. Therefore, due to its characteristics, the edge-emitting type EL element 2 to which a pulse with a symmetrical potential is applied suffers less deterioration than a case in which a pulse with an asymmetrical potential is applied.

Note that in the illustrated edge-emitting EL printer 8, the high-voltage driving pulse (V) applied to the common electrode 31 is set to half the positive potential of the low-voltage driving pulse (V) applied to the block electrode 28. , Edge-emitting EL element 2 when not printing
The pulses applied to the device are of extremely low voltage, so it can be expected that there will be less deterioration and the power consumption of the device will be lower.

Further, in the edge-emitting EL printer 8 of this embodiment, the line head 27 is wired in a matrix with n block electrodes 28 and m common electrodes 31, but the present invention is not limited to the above structure. For example, the present invention is also applicable to an edge emitting type EL printer (not shown) in which line head wiring is formed of an individual electrode provided for each edge emitting type EL element and one common electrode.

Effects of the Invention As described above, the present invention provides a line head in which edge-emitting type EL elements having opposite electrodes formed on the outer surface of a dielectric layer surrounding an active layer are arranged in series, and each edge-emitting type of the line head A drive circuit is provided for synchronous control by applying positive and negative asymmetric drive pulses to the EL element from both electrodes, and one of the drive pulses applied to the edge-emitting EL element during non-printing while the power is turned on is transmitted from this drive circuit. By providing a device deterioration prevention means that generates pulses with positive and negative symmetric voltages with respect to the other reference potential, edge-emitting type E
Because of its characteristics, the deterioration of edge-emitting type EL elements can be reduced compared to the case where a DC bias or a pulse with positive/negative asymmetric potential is applied. This has the advantage that it is possible to prevent a decrease in the optical output of the EL element, to reduce aging of the line head, and to obtain a highly durable edge-emitting type EL printer.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a timing chart, Fig. 3 is an explanatory diagram of a printed image, Figs. 4 to 6 are timing charts, and Fig. 7 shows a conventional example. A perspective view of the line head, and FIG. 8 is a perspective view of an edge-emitting type EL element. 2... Edge-emitting EL element, 6, 7... Electrode, 8...
...Edge-emitting EL printer, 27...Line head, ■...Drive pulse

Claims (1)

[Claims] A line head is provided in which edge-emitting type EL elements each having electrodes formed opposite to each other are arranged on the outer surface of a dielectric layer surrounding the active layer. A drive circuit that applies drive pulses for synchronous control is provided, and one of the drive pulses applied from this drive circuit to the edge-emitting type EL element during non-printing while power is on is set to a voltage symmetrical in positive and negative with respect to the other reference potential. An edge-emitting EL printer, characterized in that it is provided with means for preventing element deterioration by generating a pulse of .