JPH04279366A - Edge emission type el printer - Google Patents

Abstract

PURPOSE:To enhance the printing quality or reliability of an edge emission type EL printer by well correcting the synchronism of two driving pulses applied to edge emission type EL elements. CONSTITUTION:Common drivers 22 respectively outputting drive pulses to a line head 20 having edge emission type EL elements 19 connected thereto are connected to individual drivers 27 and a synchronism correction means 29 delaying the phase of the drive pulses of at least one of the drivers 22, 27 in a freely variable manner is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge-emitting EL printer, which is one of electrophotographic line printers.

0002

2. Description of the Related Art Currently, various printers are in practical use, one of which is a line printer. For example, an electrophotographic line printer has a structure in which devices such as a charger, line head, and developer are placed close to the circumferential surface of a photosensitive drum, which is a latent image carrier located on the conveyance path of printing paper. In this system, a latent image is formed by selectively emitting light from a light-emitting element connected to a line head to form a latent image on the circumferential surface of a photosensitive drum charged by a voltage applied by a charger. The toner is developed using the supplied toner and electrostatically transferred to the printing paper. The light emitting element of such a line head is generally an LED (Light).
However, this has problems such as differences in characteristics between mass-produced devices, making it difficult to manufacture a line head with uniform emission intensity.

Therefore, edge-emitting EL (Electro Lumines) is currently used as a light emitting element for line heads.
It has been considered to use a 1.cence element. This edge-emitting EL element has flat plate electrodes formed on the upper and lower surfaces of a dielectric layer surrounding a thin active layer made of zinc sulfide or the like containing an active element, and is different from conventional EL devices in which the upper surface emits light. It is possible to emit ultra-flat light with an emission intensity of about 100 times from the end face of the active layer.

[0004] As a conventional example of a line printer using such an edge-emitting type EL element, a device disclosed in Japanese Unexamined Patent Publication No. 2-274570 by the present applicant will be described with reference to FIGS. 3 to 7. First, as illustrated in FIG. 3, in the edge-emitting EL printer 1, which is a line printer, a printer controller 2 that transfers print data input from an external device (not shown) such as a host computer is connected to an interface 3. A timing controller 8 is connected to the interface 3 via a control circuit 7 to which first and second address counters 4 and 5 and a reference clock generator 6 are connected. Further, each of the interfaces 3 has a three-state 9
~12 are connected to the input/output section of two RAMs (Rand
om Access Memory) 13, 14 via a first data processing circuit 15, and the control circuit 7 and the first and second address counters 4, 5 are connected to the RAM 13, 14 via a selector 16. connected via. Further, the RAMs 13 and 14 are connected via the three states 11 and 12 to a second data processing circuit 17 to which the timing controller 8 is connected.

Further, the second data processing circuit 17 and the timing controller 8 are connected to a drive IC (
Integrated Circuit) 181-1
8q is a line head 20 in which m×n edge-emitting type EL elements 19 are arranged in an array, as illustrated in FIG.
A common driver 22, which is a common drive circuit to which the timing controller 8 is connected, is connected to the line head 20 via m common electrodes 231 to 23m. It is connected. Here, the drive ICs 181 to 18q are:
As illustrated in FIG. 7, it has a structure in which a shift register 24, a latch 25, an exclusive OR circuit 26, and a block driver 27 which is an individual drive circuit are sequentially connected in parallel, and the components 24 to 26 are connected to each other in parallel. A controller 8 is connected.

In this edge-emitting EL printer 1, the line head 20, to which various circuits are connected as described above, serves as a latent image carrier together with a charger, a developer (both not shown), etc. The photosensitive drum (not shown) is disposed close to the circumferential surface of the photosensitive drum (not shown), and this photosensitive drum is located on a conveyance path for printing paper (not shown).

With this configuration, in this edge-emitting EL printer 1, print data including a clock signal inputted from the printer controller 2 via the interface 3 is sent to the first data processing circuit for each main scanning line. 15, the data is compressed by processing such as rearrangement. Therefore,
This compressed print data is temporarily stored in one of the RAMs 13 and 14 during the printing time of one main scanning line, and at the same time, the print data temporarily stored in advance is outputted from the other RAM 14 and 13 at high speed.

[0008] Here, a RAM for temporarily storing print data is used.
13 and 14 are selected by a selector 16 that operates according to the timing input from the printer controller 2 to the first address counter 4. Also, RAM
The print data output from 14 and 13 is performed according to the control circuit 7 and the second address counter 5 which operate in synchronization with a reference clock signal for high-speed output generated from the reference clock generating section 6.

[0009] Therefore, this output print signal for one main scanning line is reprocessed by the second data processing circuit 17 into a form suitable for printing, and is input in parallel to drive ICs 181 to 188 and held there. . And these drive ICs
The block drivers 271 to 27q and the common driver 22 of 181 to 188 are synchronously controlled by the timing controller 8, so that the block electrodes 211 to 21n and the common electrodes 231 to 23m are synchronously controlled by the timing controller 8.
Low and high voltage drive pulses VB and VC are repeatedly outputted to the line head 20 from , and these drive pulses V
By performing synchronous control of B and VC, the drive pulse V
When the voltage of the difference signal between B and VC becomes greater than or equal to the threshold voltage VTH of the edge-emitting type EL element 19 and less than or equal to the threshold voltage VTH, light emission and non-light emission are controlled.

Therefore, in this edge-emitting type EL printer 1, for example, the above-mentioned operation is performed for a printing time T of one main scanning line.
The line head 20 repeats line emission four times in the width of one main scanning line. Therefore, such a selective light emitting operation of the line head 20 is performed on the peripheral surface of the photosensitive drum charged by the applied voltage of the charger to form a latent image, and this latent image is formed by toner supplied from the developer. It is developed and electrostatically transferred to printing paper. Here, the main scanning lines printed as described above are shown in FIG.
As illustrated in , the jagged edges on the edges are small and beautiful, and since one pixel is formed by repeating pixel light emission multiple times, white spots are also prevented from occurring.

In the edge-emitting type EL printer 1, for example, 2,560 edge-emitting type EL elements 19 are arranged in series in the line head 20, the number of common electrodes 23 is eight, and the number of drive ICs 18 is 8. If there are 8, then 2560÷8÷8=40, and one drive IC18
This means that 40 block electrodes 211 to 2140 are connected. Here, such a drive IC 18, as illustrated in the time chart of FIG. 8, when a drive pulse is applied to the x-th common electrode 23x, (
40 print data corresponding to the (x+1)th common electrode 23x+1 are stored in the shift register 24 according to the shift clock CLK, and the (x+1)th common electrode 23
Before the driving pulse is applied to 3x+1, it is held in the latch 25 by the latch strobe STB and the exclusive OR circuit 2
6 to the edge-emitting EL element 19 of the line head 20.
is output to. At this time, by changing the frame signal PC input to the other input terminal of the exclusive OR circuit 26 at a predetermined timing as shown in the figure to either "1" or "0", each edge light emission Emission and non-emission of the type EL element 19 are controlled.

0012

By doing as described above, it is possible to obtain an edge-emitting type EL printer 1 that uses the edge-emitting type EL element 19 as a light emitting element. Here, in such an edge-emitting type EL printer 1, the capacitive load of the edge-emitting type EL element 19 may be uneven between lots due to manufacturing errors or the like. In this case, the capacitive load of the edge-emitting type EL element 19 of the line head 20 differs for each edge-emitting type EL printer 1, and the rise and fall times of the drive pulses applied to each common electrode 231 to 23m are different. may change.

When the rise and fall times of the drive pulses applied to the common electrodes 231-23m change with respect to the drive pulses applied to the block electrodes 211-21n in this way, as illustrated in FIG. During non-emission control, spike-like noise that exceeds the threshold voltage VTH of the edge-emitting EL element 19 may occur, or during emission control, the voltage may drop below the threshold voltage VTH of the edge-emitting EL element 19. . In this case, in some edge-emitting type EL printers 1, minute light emission occurs while the edge-emitting type EL element 19 is not emitting light, and in other edge-emitting type EL printers 1, the edge-emitting type EL
As the amount of light emitted from the L element 19 decreases, the printing quality of each edge-emitting EL printer 1 deteriorates, and the reliability of the entire device decreases.

[0014]

[Means for Solving the Problem] An end surface in which a common drive circuit that outputs a high voltage drive pulse and an individual drive circuit that outputs a low voltage drive pulse to an edge emitting type EL element connected to a line head are connected. A light-emitting EL printer is provided with synchronization correction means for variably delaying the phase of a drive pulse of at least one of a common drive circuit and an individual drive circuit.

[0015]

[Operation] The synchronization correction means variably delays the phase of the drive pulses of at least one of the common drive circuit and the individual drive circuits, thereby synchronizing the drive pulses that are not synchronized due to manufacturing errors of edge-emitting type EL elements. Therefore, it is possible to satisfactorily correct deterioration in print quality due to minute light emission during non-emission of the edge-emitting type EL element and shortening of light emission time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An edge-emitting EL printer according to the present invention will be explained with reference to FIGS. 1 and 2. First, in this edge-emitting type EL printer 28, as illustrated in FIG. 1, the drive ICs 181 to 18q that incorporate block drivers 271 to 27q, which are individual drive circuits, are synchronized to variably delay the phase of their drive pulses. A phase adjustment device 29, which is a correction means, is connected. Here, as illustrated in FIG.
It has a structure in which it is connected to the transfer line of the frame signal PC, and is connected to the input line of the shift clock CLK having a predetermined period. Note that the other structure is similar to the edge-emitting type EL printer 1 described above.

In this configuration, in this edge-emitting type EL printer 28, the first switch 321 of the phase adjustment device 29 is normally conductive, and image formation is performed in the same manner as in the conventional edge-emitting type EL printer 1. Do this. In this edge-emitting EL printer 28, as illustrated in FIG. 10, due to manufacturing errors, the common electrodes 231 to 23
3m and the drive pulses applied to the block electrodes 211 to 21n are not synchronized, the phases of the drive pulses of the block drivers 271 to 27q are delayed by a predetermined time under the control of the phase adjustment device 29, as illustrated in FIG. The drive pulses are synchronized in this way. In other words, this edge-emitting type EL printer 28 has a synchronization shift time of Tx
= 1.0 (μs) and the shift clock period is CLK = 0
．． In the case of 5 (μs), the first switch 321 of the phase adjustment device 29 is turned off, and the third switch 323 is turned off.
is turned on and the frame signal PC transfer time is set to 1.0 (μ
s).

By doing this, this edge-emitting type E
Due to manufacturing errors, the L printer 28 uses an edge-emitting type EL.
If the drive pulses are not synchronized because the capacitive load of the element 19 is different from the designed value, the phase adjustment device 29 can synchronize the drive pulses and correct the printing quality favorably.

In this embodiment, the edge-emitting EL printer 28 is illustrated in which the phase adjustment device 29 is connected to the block drivers 271-27q to delay the driving pulses applied to the block electrodes 211-21n, but the present invention is not limited to the above format, but may also be an edge-emitting type EL printer (
(not shown) or an edge-emitting EL printer (not shown) in which two phase adjustment devices 29 are connected to the block drivers 271 to 27q and the common driver 22, respectively.

Furthermore, in the edge-emitting EL printer 28 of this embodiment, the phase adjustment device 29 connected to the block drivers 271-27q delays the driving pulses applied to the block electrodes 211-21n.
The drive pulse applied to 1 to 21n is the common electrode 231.
If there is a delay with respect to the drive pulse applied at ~23m, correction is not possible. Therefore, the common electrode 231
The drive pulse applied to ~23m is the block electrode 211
By designing the edge-emitting EL printer 28 so that there is a delay with respect to the drive pulse applied to 21n, and correcting this at the time of shipment, it is possible to always maintain good print quality even with only one phase adjustment device 29. Can be adjusted.

[0021]

Effects of the Invention As described above, the present invention comprises a common drive circuit that outputs high voltage drive pulses to the edge emitting type EL elements connected to the line head, and an individual drive circuit that outputs low voltage drive pulses. In an edge-emitting EL printer in which a latent image carrier in which at least a charger, a line head, and a developer are arranged in close proximity is located on a conveyance path of printing paper, at least a common drive circuit and an individual drive circuit are connected. By providing a synchronization correction means that variably delays the phase of one of the drive pulses, the phase of the drive pulse of one of the drive circuits is delayed by a predetermined time under the control of this synchronization correction means. Since it is possible to synchronize drive pulses that are not synchronized due to manufacturing errors in the device, it is possible to effectively correct deterioration in print quality due to minute light emission during non-emission of edge-emitting type EL devices and shortening of light emission time. ,
This has the advantage that an edge-emitting EL printer with good printing quality and high reliability can be realized with a simple structure.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of main parts.

FIG. 3 is a block diagram showing a conventional example filed by the applicant in the past.

FIG. 4 is a block diagram of main parts.

FIG. 5 is a time chart showing drive pulses output by a common drive circuit.

FIG. 6 is a time chart showing synchronization of drive pulses.

FIG. 7 is a front view of a printed image.

FIG. 8 is a block diagram showing the internal structure of the drive IC.

FIG. 9 is a time chart showing operation timing within the drive IC.

FIG. 10 is a time chart showing a defective state of drive pulse synchronization.

[Explanation of symbols]

19 Edge-emitting EL element 20
line head 21
Individual electrode 22 Common drive circuit 23
individual electrodes

Claims (1)

[Claims] 1. An edge-emitting EL printer that connects a common drive circuit that outputs high-voltage drive pulses to edge-emitting EL elements connected to a line head and an individual drive circuit that outputs low-voltage drive pulses. An edge-emitting type EL printer characterized in that a synchronization correction means is provided for variably delaying the phase of a drive pulse of at least one of the common drive circuit and the individual drive circuit.