JPH04308772A - Edge 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]

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] Therefore, as a first conventional example of an edge-emitting EL printer, which is a line printer using such an edge-emitting EL element, the present applicant has published Japanese Patent Application Laid-Open No. 2-2745.
The device disclosed in Japanese Patent No. 70 will be explained based on FIGS. 4 to 7. First, as illustrated in FIG. 4, this edge-emitting EL printer 1 has a printer controller 2 connected to an interface 3 that transfers print data input from an external device (not shown) such as a host computer.
A timing controller 8 is connected to this 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. The interface 3 also includes two RAMs (Random Access Memory
) 13 and 14 via a first data processing circuit 15, and the control circuit 7 and the first and second address counters 4 and 5 are connected to the RAM 13 and 14 via a selector 16. has been done. Furthermore, the R.A.
M13 and M14 are connected to the second data processing circuit 17 to which the timing controller 8 is connected via the three states 11 and 12.

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 EL elements 19 are arranged in an array, as illustrated in FIG.
The common driver 22 to which the timing controller 8 is connected is connected to the line head 20 via m common electrodes 231 to 23m. Here, the drive ICs 181 to 18q have a structure in which a shift register 24, a latch 25, an exclusive OR circuit 26, and a block driver 27 are sequentially connected in parallel, and the timing controller 8 is connected to the components 24 to 26.
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 27n and the common driver 22 of 181 to 188 are synchronously controlled by the timing controller 8, so that low voltage and high voltage drive pulses are sent from the block electrodes 211 to 21n and the common electrodes 231 to 23m to the line head. 20 is repeatedly output. At this time,
By performing synchronous control of these drive pulses, the voltage of the combined drive pulse is set to be higher than or equal to the threshold voltage of the edge-emitting type EL element 2 and less than or equal to the threshold voltage of the edge-emitting type EL element 2, so that light emission and non-emission are controlled.

Therefore, in this edge-emitting type EL printer 1, as illustrated in FIG. 6, the above-mentioned operation is performed four times during the printing time T0 of one main scanning line, and
In this case, line emission is repeated 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, as illustrated in FIG. 7, the main scanning line printed as described above is beautiful with minute jagged steps at the edge, and moreover, the pixel light emission is repeated multiple times. Since one pixel is formed by one pixel, white spots are also prevented from occurring.

[0011] Here, actually the above-mentioned edge-emitting type E
When implementing the L printer 1, for example, an edge-emitting type EL
If the light emitting operation of the element 19 is excited at a drive voltage of about 240 (V) and stabilized at about 250 (V), then the output voltage of the common driver 22 is set to 250 (V) and the output voltage of the block driver 27 is set to 20 (V). ) and synchronously control these to generate drive pulses of 230 (V) and 270 (V).

[0012] A specific example of the common driver 22 that generates the above-mentioned high-voltage driving pulses is the device disclosed in US Pat. No. 4,899,184. Therefore, the edge-emitting type EL disclosed in the above specification
The structure of the common driver of the printer will be explained based on FIG. 8. This common driver 28 has positive and negative high potential electrodes 2
Two MOSs (
Metal-Oxide-Semiconductor
) type FET (Field-Effect Tran
pulse generation circuit 36 consisting of 32 to 35
, 37 are formed, and these pulse generation circuits 36
, 37 are connected to common electrodes 401 to 404 via distribution circuits 381 to 384 and 391 to 394, respectively, each consisting of switching elements such as FETs. Note that the common driver 28, which is a combination of various transistors, FETs, etc. as described above, is formed as, for example, one IC.

In this configuration, in this common driver 28, the positive and negative high voltage currents inputted from the high potential electrodes 29 and 30 are converted into positive and negative high voltage pulses by the pulse generation circuits 36 and 37, and then sent to the distribution circuit 381. ~384,391
~394 switching for each common electrode 401~404
to be distributed. By doing so, this common driver 28, as illustrated in FIG. ~404 are output at predetermined timings.

[0014]

[Problem to be solved by the invention] The above-mentioned edge-emitting type E
In the common driver 28 of the L printer, the high potential electrode 29
, 30 is converted into positive and negative continuous high voltage pulses by the pulse generation circuits 36 and 37, and distributed by the distribution circuits 381 to 384 and 391 to 394, so that each common electrode High voltage pulses 431 to 434 having a predetermined shape can be output to 401 to 404.

However, as mentioned above, the pulse generation circuits 36 and 37 formed by the FETs 32 to 35 generate excessive heat in order to generate continuous high voltage pulses, and it is necessary to install a large heat sink (not shown). This impedes improvements in productivity and reduction in size and weight of the common driver 28.

[0016] At present, the edge-emitting type EL element 1
No. 9 has been found to have better durability when the application intervals of positive and negative drive pulses are made equal. In other words,
As described above, the driving method in which a predetermined number of continuous driving pulses are applied to each of the common electrodes 401 to 404 and then paused until the application of the next pulse reduces the durability of the edge-emitting type EL element 19. As illustrated in , the common electrode 4
A driving method has been considered in which only one positive and negative driving pulse is applied alternately when each pulse is applied to 01 to 404, and is disclosed, for example, in Japanese Patent Application No. 3-43053 by the present applicant.

Such drive pulses can also be generated by the common driver 28 in which the pulse generation circuits 36 and 37 are formed by the FETs 32 to 35 as described above, but in this case, the pulses are generated in synchronization with the output time of the drive pulses. Generation circuit 36
, 37 and the distribution circuits 381 to 384 and 391 to 394, control is complicated and power consumption tends to increase.

[0018]

[Means for solving the problem] The invention according to claim 1 includes:
m×n edge-emitting type EL elements connected to a line head are wired in a matrix with m common electrodes and n block electrodes, and a common terminal that outputs high voltage pulses to these common electrodes and block electrodes. An edge-emitting type EL in which a driver and a block driver that outputs low voltage pulses are connected to each other, and a latent image carrier in which at least a charger, a line head, and a developer are arranged close to each other is located on a printing paper conveyance path.
In a printer, a pulse generation circuit is formed in which a switching circuit consisting of a bipolar transistor is provided between the positive and negative high potential electrodes and a center potential electrode, and a pulse generation circuit is formed in which a common driver is individually connected to the common electrode. .

According to the second aspect of the invention, switching circuits each comprising a bipolar transistor are provided between the positive and negative output terminals of the pulse generating circuit and the common electrode.

[0020]

[Operation] The invention as claimed in claim 1 forms a pulse generating circuit in which a switching circuit consisting of a bipolar transistor is provided between the positive and negative high potential electrodes and the center potential electrode, and the common driver is connected to the common electrode individually. Since each high-voltage pulse is generated by an independent pulse generation circuit, the amount of heat generated is reduced, contributing to the productivity and miniaturization and weight reduction of edge-emitting EL printers. In addition, high voltage pulses with equal intervals between positive and negative drive pulses and which drive an edge-emitting type EL element with good durability can be generated by utilizing voltage holding, which is a characteristic of bipolar transistors.

[0021] According to the invention as claimed in claim 2, switching circuits each comprising a bipolar transistor are provided between the positive and negative output terminals of the pulse generating circuit and the common electrode, so that these switching circuits can connect the common electrode and the positive and negative output terminals. By turning on and off the connection with the output terminals, the other high voltage pulse is applied to the bipolar transistors that are provided between these output terminals and the positive and negative high potential electrodes and output positive and negative high voltage pulses, respectively. can be prevented.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An edge-emitting type EL printer according to the invention as claimed in claim 1 will be explained based on FIGS. 1 and 2. First, the structure of the edge-emitting EL printer (not shown) of this embodiment except for the common driver 44 is the same as that of the edge-emitting EL printer 1 described above.
It is almost the same. Therefore, the structure of the common driver 44 of this edge-emitting type EL printer will be explained below. As illustrated in FIG. 1, this common driver 44 includes m pulse generation circuits each including switching circuits 46 and 47 provided with bipolar transistors 45 between positive and negative high potential electrodes 29 and 30 and a center potential electrode 31. 481-48
m is connected to common electrodes 231 to 23m, respectively. Note that the switching circuits 46 and 47 of the common driver 44 of this embodiment include positive and negative high potential electrodes 29,
Constant current circuits 50 to 53 are provided by combining a bipolar transistor 45 directly connected to 30 and center potential electrode 31 and a resistor 49, and two control signal input terminals 54 to 57 and one high voltage Pulse output terminals 58, 5
9 are formed respectively.

[0023] Also, the center potential electrode 31 referred to here is
It is an electrode whose potential is the same as the reference potential of the high voltage pulses generated by the switching circuits 46 and 47.

In this configuration, in the common driver 44 of this edge-emitting type EL printer, switching circuits 46 and 47 formed by bipolar transistors 45 are input to each input terminal 54 to 57, as illustrated in FIG. TTL (Transistor)
or Logic) level control signals 60 to 63 to generate positive high voltage pulses and negative high voltage pulses, and each pulse generation circuit 481 to 48m outputs the output terminals 58 and 59. High voltage pulse 6 of ±300 (V) is applied to each common electrode 231 to 23m from
It is designed to output 41 to 64 m.

At this time, in this common driver 44, each of the high voltage pulses 641 to 64m is generated by an independent pulse generation circuit 481 to 48m, and furthermore, since the output timing of the high voltage pulse 64 is not continuous, it is bipolar. Switching circuit 46, 4 provided with transistor 45
7 is discontinuous. Therefore, the common driver 44 has a reduced amount of heat generated, and the heat sink can be made smaller or omitted, contributing to the productivity and reduction in size and weight of the edge-emitting EL printer.

Moreover, in this common driver 44, in order to improve the durability of the edge-emitting type EL element 19 as described above, only one positive and negative driving pulse is outputted alternately when each pulse is applied. The pulse is formed using the voltage retention of the bipolar transistor 45. In other words, this bipolar transistor 45 characteristically maintains the applied voltage, and furthermore, the edge-emitting type EL element 2 which is the load
is equivalently a capacitive load, so as illustrated in FIG. Since there is no need to maintain the input of the control signal between the rise and fall of the bipolar transistor 45
It is possible to shorten the operating time and save power.

Further, in this common driver 44, constant current circuits 50 to 53 are provided by combining a resistor 49 with a bipolar transistor 45 directly connected to the positive and negative high potential electrodes 29 and 30 and the center potential electrode 31. Therefore, the amount of current is regulated at the rise and fall of the high voltage pulses 641 to 64m, reducing power consumption. In other words, this common driver 44 has a voltage of ±300 (V), for example.
At the rise and fall of the high voltage pulses 641 to 64m, approximately 0.7 (V
) is generated, so the current value is determined by the constant of this resistor 49. More specifically, when the positive high voltage pulse 64 rises and the edge emitting type EL element 19 is charged with a positive high voltage, the constant current circuit 50 connected to the positive high potential electrode 29 is energized. When the positive high voltage pulse 64 falls and the positive high voltage of the edge emitting type EL element 19 is discharged, the constant current circuit 5 connected to the center potential electrode 31
1 regulates the amount of current applied, and the constant current circuits 52 and 53 similarly regulate the amount of current applied to the negative high voltage pulse 64.

Therefore, this common driver 44 generates each of the high voltage pulses 641 to 64m by independent pulse generation circuits 481 to 48m, and its power consumption is also reduced by constant current circuits 50 to 53. The amount of heat generated is reduced, which contributes to the productivity and miniaturization and weight reduction of the edge-emitting type EL printer.Moreover, the interval between positive and negative drive pulses is equal, and the edge-emitting type EL element 19 is driven with good durability. The high voltage pulse 64 is generated by utilizing the voltage holding characteristic of the bipolar transistor 45, and there is no need to maintain the input of the control signal at the rise and fall of the high voltage pulse 64, making it easy to control. Edge-emitting type E
This can contribute to improving the productivity of L printers.

Here, in the common driver 44 of this edge-emitting type EL printer, the bipolar transistors 45a provided between the positive and negative high potential electrodes 29, 30 and the output terminals 58, 59 are connected to each other. The other high voltage pulse may be applied to the other bipolar transistor 45, and the voltage to the bipolar transistor 45 is twice that of the other bipolar transistor 45. For this reason, in the common driver 44 described above, there is a concern that productivity may be reduced because only a predetermined bipolar transistor 45a needs to be manufactured with a large capacity.

[0030] Therefore, a device that solves this problem will be described as an embodiment of the invention as claimed in claim 2 with reference to FIG. First, the structure of the edge-emitting type EL printer (not shown) of this embodiment, except for the common driver 65, is substantially the same as the edge-emitting type EL printer 1 described above. This common driver 65 connects the output terminals 58 and 59 of positive and negative high voltage pulses of the pulse generation circuits 481 to 48m and the common electrode 2.
3, switching circuits 66 and 67 each comprising a bipolar transistor 45 are provided.

In this configuration, the common driver 65 of this edge-emitting type EL printer connects the common electrodes 231 to 23m in substantially the same manner as the common driver 44 described above.
outputs high voltage pulses 641 to 64m. At this time, in this common driver 65, the switching circuits 66, 6
By turning on and off the connection with the common electrode 23 at step 7, the bipolar transistor 45a, which is provided between the positive and negative high potential electrodes 29 and 30 and the output terminals 58 and 59 and outputs positive and negative high voltage pulses respectively, is connected to the other bipolar transistor 45a. Since no high voltage pulse is applied, the voltage to the transistor may be the same as that of the other bipolar transistors 45. Therefore, in this common driver 65, it is not necessary to manufacture only a predetermined bipolar transistor 45a with a large capacity, so productivity is extremely high.

[0032]

Effects of the Invention According to the invention described in claim 1, m×n edge-emitting type EL elements connected to a line head are wired in a matrix with m common electrodes and n block electrodes, and these common A common driver that outputs high-voltage pulses and a block driver that outputs low-voltage pulses are connected to electrodes and block electrodes, respectively, and a latent image carrier in which at least a charger, a line head, and a developer are arranged in close proximity is printed. In an edge-emitting EL printer located on the paper conveyance path, a pulse generation circuit is formed in which a switching circuit consisting of a bipolar transistor is provided between the positive and negative high potential electrodes and the center potential electrode, and the common driver is connected to the common driver. Since each high-voltage pulse is generated by a pulse generation circuit individually connected to the electrode, the amount of heat generated is reduced, making the edge-emitting EL printer more productive and smaller and lighter. In addition, the interval between positive and negative drive pulses is even, making it an edge-emitting type EL.
High voltage pulses that drive devices with good durability can be generated by utilizing voltage holding, which is a characteristic of bipolar transistors, and control signal input can be sustained from the rise to the fall of the high voltage pulse. Since this is not necessary, it is possible to reduce power consumption, and it has effects such as realizing power saving of an edge-emitting type EL printer that is easy to reduce in size and weight and improve productivity.

The invention as claimed in claim 2 provides switching circuits made of bipolar transistors between the positive and negative output terminals of the pulse generating circuit and the common electrode, so that these switching circuits can connect the common electrode and the positive and negative output terminals. By turning on and off the connection with the output terminals, the other high voltage pulse is applied to the bipolar transistors that are provided between these output terminals and the positive and negative high potential electrodes and output positive and negative high voltage pulses, respectively. Since it is not necessary to manufacture these bipolar transistors with twice the voltage to other bipolar transistors, it is possible to contribute to improving the productivity of edge-emitting EL printers. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention according to claim 1.

FIG. 2 is a time chart.

FIG. 3 is a circuit diagram showing an embodiment of the invention according to claim 2.

FIG. 4 is a block diagram showing a first conventional example filed by the present applicant in the past.

FIG. 5 is a block diagram of main parts.

FIG. 6 is a time chart.

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

FIG. 8 is a block diagram showing a second conventional example.

FIG. 9 is a time chart.

FIG. 10 is a time chart showing the prior art.

[Explanation of symbols]

19 Edge-emitting EL element 21
Block electrode 23
Common electrode 29 Positive high potential electrode 30
Negative high potential electrode 31
Center potential electrodes 44, 65 Common driver 45 Bipolar transistor 46
, 47 switching circuit 48 pulse generation circuit 58, 59
Output terminal 64 High voltage pulse 66, 67
switching circuit

Claims (2)

[Claims] Claim 1: m×n edge-emitting EL elements connected to a line head are wired in a matrix with m common electrodes and n block electrodes, and a high voltage is applied to these common electrodes and block electrodes. A common driver that outputs pulses and a block driver that outputs low-voltage pulses are connected to each other, and a latent image carrier in which at least a charger, the line head, and a developer are arranged close to each other is positioned on a conveyance path of printing paper. In an edge-emitting EL printer, a pulse generation circuit is formed in which switching circuits each consisting of a bipolar transistor are provided between positive and negative high potential electrodes and a center potential electrode, and the common driver is individually connected to the common electrode. An edge-emitting EL printer characterized in that it is formed using the pulse generation circuit described above. [Claim 2] Claim 1, characterized in that switching circuits each comprising a bipolar transistor are provided between the positive and negative output terminals of the pulse generation circuit and the common electrode.
The edge-emitting EL printer described.