JPH0317674B2 - - Google Patents

Abstract

PURPOSE:To enable a multiplicity of Le elements to be controlled by driving a small number of electrodes, by dividing a back electrode and a transparent electrode into respective groups, and driving the EL elements by multiple combinations of the electrode groups. CONSTITUTION:In an EL panel are disposed 2048 EL elements, which are energized by combinations of a transparent electrode group 26 divided into 32 groups as first electrode groups, namely, D1-D64, with a back electrode group 22 divided into 32 groups as second electrode groups orthogonal to the first electrode groups, namely, S1-S32. Of the transparent electrodes divided into the 32 groups, the same-numbered electrodes, e.g., the first electrodes in each of the groups are connected to each other in common by a bus BD1. With this construction, when the electrode D1 and the electrode S1 are energized, the first EL element is driven, and when the electrode D1 and the electrode S2 are energized, the 65th EL element is driven. With this electrode construction, the 2048 EL element can be driven by driving the 64+32=96 electrodes.

Description

[Detailed Description of the Invention] [Summary] A plurality of electroluminescent (hereinafter referred to as EL) light emitting parts are used as a light source for exposing a photosensitive medium by multiplexing driving a plurality of groups of orthogonal electrodes, respectively. EL to energize
In a printing apparatus using a device, when controlling the EL element, sufficient light energy is applied to expose the photosensitive medium within a certain time determined by the moving time of the photosensitive medium, or in other words, the printing speed. A driving pulse is applied to the EL element in this manner, and then the orthogonal electrode group is controlled so as to sufficiently attenuate the output light of the EL element so as not to affect the non-exposure of the photosensitive medium in the next row.

[Industrial application field]

The present invention relates to an electronic printing device,
Electronic printing device using more specific EL elements
Regarding an EL element drive control circuit.

[Conventional technology]

As recent electronic printing devices, those using a laser, a light emitting diode (LED), or a liquid crystal LCD as a light source are known. Laser printing devices have only one light source, so there is no problem with the uniformity of the light source, but the problem is that the optical system that scans the laser beam perpendicular to the direction of movement of the photosensitive medium is complicated, making it unsuitable for miniaturization. There is. LED printing devices use as a light source a plurality of LED elements arranged in a line perpendicular to the direction of movement of the photosensitive medium, corresponding to the number of dots, and because the LED elements are solid-state, they are suitable for miniaturization. However, depending on the number of dots, e.g.
Since it uses 1,980 to 2,048 LED elements arranged in a row, there are variations in individual brightness and changes over time, and to compensate for this, it is necessary to install a resistor etc. for each LED element. There's a problem. Furthermore, LCD printing devices, for example, control the light irradiated onto the photosensitive medium by transmitting or cutting off the light from a fluorescent lamp, but the heat generated by the fluorescent lamp causes changes in the characteristics of the LCD. However, there is a problem in that a cooling system must be provided to prevent this.

It is assumed that an EL element using an electroluminescent phenomenon is used as the light source or other light control device of the electronic printing device. For example, as shown in FIG. 6, the light emitted from the EL panel 12 is focused through a self-focusing lens system 13 on a photosensitive drum 14 on which a photosensitive medium is mounted and rotating as shown by arrow A. The photosensitive medium on the photosensitive drum 14 is exposed. The EL panel 12 has a glass substrate 1
21, transparent electrode 122, insulating layer 123, ZnS
Mn-doped light emitting layer 124, back electrode 125
A moisture-proof protective cover 126 is formed as shown in cross section in FIG. A plurality of transparent electrodes 122 are provided in the direction perpendicular to the drawing, corresponding to one dot on the photosensitive medium, and the transparent electrodes and the back electrode 125 correspond to the number of dots in one row in the light emitting layer 124. A light emitting section is defined. That is, the light emitting section within the EL panel 12 corresponds to the aforementioned LED element array.

As mentioned above, the printing device using the EL panel 12 can be easily miniaturized, and since the light-emitting layer 124 and other layers are uniformly formed in the semiconductor process, a plurality of light-emitting parts can be uniformly formed, and the above-mentioned
Unlike LED element arrays, this has the advantage that individual variations do not occur and a complicated adjustment system is not required.

On the other hand, EL elements generally emit smaller output light than LED elements, emit light only when a driving voltage is applied to the electrodes, and then the output light _attenuates . It is necessary to drive the EL element such that a pulse drive electrode is applied between the electrodes and output light energy S ₁ sufficient for exposing the photosensitive medium is obtained. On the other hand, a certain amount of time depending on the relaxation time is required for the output light to decay, and the extinction period T _OFF is shown in Figure 7.
A pause period is required during which the pulse drive voltage to the electrodes is prohibited.

If sufficient output light energy is not obtained, the exposure of the photosensitive medium will be insufficient, and on the other hand, if a dot that should be blank in the next row is scanned before the sufficient output light energy _S2 has not decayed, afterglow will occur. This results in exposure. Therefore, the light emitting part of the EL element corresponding to the dot to be printed must be controlled so that sufficient output light energy is obtained, and the output light energy is sufficiently low in order to prepare for the next row of non-printing. . Moreover, since the sum of the light emission period T _ON and extinction period T _OFF shown in FIG. 7 defines the printing speed per line (one dot) on the photosensitive medium, from the aspect that the printing speed must be increased, The above-mentioned light emission period T _ON and extinction period T _OFF need to be optimal according to the printing speed.

That is, when an EL element is used as a light source of an electronic printing device, it is necessary to control the EL element to satisfy the contradictory requirements as described above.

In response to such a demand, a control circuit as shown in FIG. 8, for example, has been proposed.

The control circuit shown in FIG. 8 includes a timing controller 101, an X-side clock generator 102, an interval control circuit 103, and a Y-side clock generator 1.
04, AND gate 105, AND gate 106 with inverted input, shift register 107, latch circuit 1
08, AND gate row 109, X side drive circuit 11
0, and a Y-side drive circuit 111 are connected as shown. The X-side drive circuit 110 and the Y-side drive circuit 111 drive the plurality of transparent electrodes 122 and the back electrode 125 of the EL light source panel 12 described above with reference to FIG. Therefore, in this example, the X-side clock generator 102, AND
The gate 105, shift register 107, latch circuit 108, AND gate array 109, and X-side drive circuit 110 are for driving a plurality of transparent electrodes. On the other hand, the Y side clock generator 10
4. The AND gate 106 with inverting input and the Y-side drive circuit 111 are for driving one back electrode.

The EL light source panel 12 has a plurality of light emitting parts in one row in the moving direction of the photosensitive medium and in a direction perpendicular to the moving direction, 2048 in this example, and has one back electrode and a transparent electrode. It has 2048 pieces arranged in parallel and at equal intervals. Therefore, the 2048-bit shift register 107 receives serial data SDATA of 2048 bits per line, that is, 1 dot in the moving direction of the photosensitive medium, and the 2048 flip-flops that hold the serial data SDATA correspond to the number of bits in the shift register 107. 1, an AND gate array 109 including 2048 AND gates, and an X-side drive circuit 110 for driving 2048 transparent electrodes.

The operation of the control circuit shown in FIG. 8 is shown in FIGS. 9a to 9d.
This will be explained with reference to the signal waveform diagram.

FIG. 9 shows the i-th X side, that is, the transparent electrode 1
This is an example of the case where one is driven, and the other one is
A case will be exemplified in which ~i-1, i+1~2048 transparent electrodes also operate simultaneously in parallel. However, since the operating principles of these other electrodes are the same, their description will be omitted below.

When the i-th serial data SDATA is "1" in the first row printing, "1" data is transferred to the i-th AND gate 10 through the i-th shift register 107 and the i-th latch circuit 108.
9 is applied. On the other hand, the X side clock generator 10
2, a clock pulse XCLK with period τ is applied to AND gate 105 under the control of timing controller 1. Similarly, a Y-side clock pulse YCLK having a period τ and a phase shift of 180° from the X-side clock pulse XCLK is applied to the gate 106. These clock pulses XCLK and YCLK are continuous pulses. Under the control of the timing controller 101, the interval control circuit 10
3, the enable signal S _ENA is output at a high level, that is, "1" for the period T _ON , and at a low level, that is, "0" for the period T _OFF .
Therefore, from the gate 105, three consecutive positive X
The side clock pulse SX is applied to the gate array 109 (FIG. 9a), and from the i-th AND gate to which "1" is applied to one input terminal, the clock pulse SX shown in FIG.
A pulse similar to that is applied to the X-side drive circuit 110. In response to the pulse application, the X-side drive circuit 11
0 applies a driving voltage pulse XVDi having an amplitude of 200 V to the i-th transparent electrode (upper part of FIG. 9c). Similarly, three consecutive Y-side clock pulses SY are applied to the Y-side drive circuit 111 from the gate 106, and a drive voltage pulse YVD (not shown, but shown in FIG. A voltage with the same phase as SY of b and an amplitude of 200 V) is applied to the back electrode. Therefore, the respective driving pulses are applied between the transparent electrode and the back electrode.
Combined AC drive pulse VD of XVDi and YVD
(VD=XVDi-YVD) is applied (FIG. 9c).

Due to the AC drive pulse VD, the i-th light emitting section emits light when the pulse is applied, and then the output light attenuates. However, since six consecutive AC drive pulses are applied faster than their decay, the output light gradually rises and finally reaches the maximum value _MX1 .
During the next period T _OFF , the enable signal S _ENA is at a low level, so no AC drive pulse is applied to any electrode. Therefore, the output light of the above-mentioned light-transmitting portion decreases according to its attenuation characteristics. If the integral value S _L of these output light energies is sufficiently larger than the threshold value, the corresponding dot on the photosensitive medium is exposed and becomes a black dot.

The above period T _ON corresponds to the light emission time, and the period T _OFF
corresponds to the extinction time. Sum of these periods T ₁ =
T _ON + T _OFF is the exposure time for printing one dot in the moving direction of the photosensitive medium.

If the i-th data of the next row is "1", the same process is performed for the period T ₂ , where T ₂ =T ₁ .

Furthermore, if the i-th data in the next row is “0”, the period T ₃ , where T ₃ =T ₂ =
No drive pulse is applied to T ₁ , and the output light only attenuates. The integral value S _D of the afterglow energy during the period T ₃ is a value that does not expose the photosensitive medium.

In order to obtain sufficient contrast, the ratio of S _D and S _L is preferably S _D /S _D 0.1. Here S _D =
∫ ^∞TOFF MX ₂ e ^-t/ 〓, T OFF can be approximated by dt, (τ: relaxation time of light emission), and T _OFF is set so that the above S _D /S _L 0.1 is satisfied.

Such relaxation time is
The concentration of Mn in the luminescence center varies greatly on the order of 0.1 to 1 ms.

Furthermore, assuming high-speed printing of 20 sheets/minute on A4 size photosensitive media, T ₁ = T ₂ = T ₃ =
It is 0.88ms. Therefore, if T _OFF = 0.5ms, T _ON
=0.38ms. Since the light emission response of the EL element is short, multiple driving pulses can be applied to the electrodes within the T _ON period to obtain the output light energy necessary for photosensing.

[Problem that the invention seeks to solve]

The above EL elements can be controlled simultaneously and independently by 2048
This has to be done for each EL element, which poses a problem in that the control circuit becomes extremely complex. especially,
Since high voltage is required to drive EL,
There is a problem in that a large number of high-voltage and expensive drive elements are required.

Therefore, there is a need for an EL device for a printing apparatus and its control circuit, which can satisfy the above-mentioned control operation for each EL element and can simplify the circuit.

[Means for solving problems]

In view of the above-mentioned problems and demands, the present invention provides a first electrode group in which each group has a plurality of electrodes and corresponding electrodes of each group are commonly connected, and each group of the first electrode group. and an EL device having a plurality of electroluminescent EL light emitting parts defined by the electrodes of the first and second electrode groups as a light source. The printing device exposes a photosensitive medium to light, and in order to expose one unit in the moving direction of the photosensitive medium, the electrodes of each group of the first electrode group are sequentially selected in response to printing data. An electroluminescent device characterized by having a control circuit that simultaneously repeats the operation of selecting each electrode of the second electrode group multiple times and further deselects the first and second electrode groups for a certain period of time. A printing apparatus using a cent device is provided.

〔Example〕

FIG. 1 shows a printing device according to an embodiment of the present invention.
The diagram shows the drive control circuit diagram of the EL panel.

In FIG. 1, 1 is a data generation circuit, 2 is a timing controller, 3 is a 2048-bit shift register, 4 is a 2048 latch circuit, 5 is a push-pull drive circuit, 6 is a pull-only drive circuit,
7 is a 2048-bit shift register, 8 and 9 are switching elements, and 10 is a 2048 diode string. 20 indicates an EL panel.

A cross-sectional view of the EL panel 20 is shown in FIG. The EL
The panel 20 includes a glass substrate 21, a transparent electrode 22,
An insulating layer 23, a light emitting layer 25, a back electrode 26, a bus bar electrode 27, a crossover 28, and a moisture-proof protective cover 29 fixed to the glass substrate 21 via adhesives 24a and 24b are formed as shown.

Figure 3 is a perspective view of the electrode structure of the EL panel.
Figure 4 shows a schematic diagram of the electrode structure of the EL panel.
There are 2048 EL elements formed in a row in the EL panel, and these EL elements are divided into transparent electrode groups divided into 32 groups as the first electrode group, as shown in Figure 4. 26, that is, D ₁ to _{D 64} , and a second electrode group orthogonal thereto, which is a combination of the back electrode group 22, which is divided into 32 groups, that is, S ₁ to S ₃₂ . However, in Figure 3, among these, D ₁ ~
Only D ₅ and S ₁ to _{S 4} are described, and 30 indicates a through hole of the bus bar electrode 27.

Referring to FIG. 3, each group includes 64 transparent electrodes and the divided electrodes S ₁ to S ₃₂ of the back electrode are formed orthogonally. However, split electrode S ₁
~S ₃₂ are each electrically isolated. on the other hand,
The transparent electrodes divided into 32 groups are those with the same number in each group, for example, the first EL element is driven by the bus BD ₁ and the electrode S ₁ , and the electrode D ₁ and the 65th EL by energizing electrode S ₂
The element is driven. The same applies below.

From the above electrode structure, the push-pull drive circuit 5 is
The pull-only drive circuit 6 drives 64 electrodes.
Drives 32 electrodes.

The operation of the circuit of FIG. 1 will be explained with reference to FIGS. 5a to 5k. In Figure 1, DATA is serial data, CLK is a clock signal, STRB ₁ , STRB ₂
respectively indicate strobe signals.

As mentioned above, assuming that A4 size photosensitive media is printed at a rate of 2 pages/minute, the column synchronization signal
SYNC _ROW period T = 8.8ms (Figure 5a), divided synchronization signal for scanning one frame into 32 divisions
SYNC _DIV period τ = 340us, output time to repeat this divided output 24 times T _OUT = 8.16ms, output off time
T _OFF =640 μs (Figure 5b). Here, repeating the 32-division scan 24 times is necessary for exposure when the light-emitting layer 25 of the EL panel is made of ZnS doped with 0.5 wt% Mn and the photoreceptor is made of As ₂ Se ₃ . This is to obtain approximately 1 μJ/cm ² of energy.

Pulse voltages VD ₁ to VD ₆₄ corresponding to the serial input data DATA are applied to the transparent electrodes D ₁ to D ₆₄ via the push-pull drive circuit 5 (see Fig. 5 c to
e). On the other hand, a low level V _L , a floating level V _F , and a high level are sequentially applied to the back electrodes S ₁ to S ₃₂ .
Voltages VS ₁ to VS ₃₂ of V _H are applied (Fig. 5 f to
h). Low level V _L is generated when switching elements 8 and 9 are off in FIG.
is on, high level V _H is pull-only driver 6
is off, switching element 8 is on, switching element 9 is off, and the floating level is set to pull-only driver 6 and switching elements 8 and 9.
are both turned off. Low level V _L period t ₁ = 10 μs, high level V _H period s ₂
= 20μs, the period during which is the floating level _VF . The high level V _H is equal to the voltage applied to the switching element + V _R .

High level voltage applied to the above transparent electrode side
When VD ₁ to _{VD 64} match the low-level voltage V _L applied to the back electrode side, high-level drive voltages VDRV ₁ to VDRV ₃₂ of, for example, 200 V DC are applied to the corresponding EL elements. At the end of one division period, the low level voltage is applied to the transparent electrode, and the high level voltage V _H is applied to the back electrode at the same time, and the -DC200V drive voltage VDRV ₁ to VDRV ₃₂ is fully applied.
is applied to the EL element (FIG. 5 i-k). After the above driving voltage application is repeated 24 times for the same data, both the transparent electrode and the back electrode are set to a low level during the period T _OFF , and no driving voltage is applied to the EL element.

That is, for the period T _OUT , the driving voltage is repeatedly applied to the EL element 24 times for the same data to obtain sufficient output light energy for exposure, and the period T OUT is repeated 24 times.
T _OFF attenuates the output light energy in preparation for the next row. In this way, by dividing the back electrode and the transparent electrode into groups and driving them multiplexed, it is possible to obtain the output light characteristics required of the printing apparatus. In this case, it is possible to drive 2048 EL elements by driving 64+32=96 electrodes. Although the reduction in the number of driven electrodes makes the control circuit a little more complicated, it contributes to a significant reduction in the cost of expensive circuit elements for driving high voltages of several hundred volts.

The above embodiment describes the case where an AC drive method is adopted for a thin film EL panel, but a DC drive method is used for each of a powder EL panel and a thin film EL panel.
The same applies to both AC drives.

〔Effect of the invention〕

As described above, according to the present invention, a large number of
The EL elements can be controlled by driving a small number of electrodes, and a control circuit for an EL printing device with a low cost and simple circuit configuration can be provided.

[Brief explanation of the drawing]

FIG. 1 shows a printer for a printing device as an embodiment of the present invention.
EL device drive control circuit diagram, Figure 2 is a cross-sectional view of the EL device in Figure 1, Figure 3 is a perspective view showing the electrode structure of the EL device in Figure 1, and Figure 4 is a diagram of the EL device in Figure 1. Schematic diagram of the electrode structure; Figures 5a to 5k are signal waveform diagrams in the control circuit in Figure 1; Figure 6 is a schematic diagram of the configuration of the EL printing device;
Figure 7 is a drive waveform diagram of the EL element, and Figure 8 is a diagram of the conventional drive waveform.
A control circuit diagram of the EL printing apparatus, FIGS. 9a to 9d are signal waveform diagrams in the control circuit of FIG. (Explanation of symbols), 1...Data generation circuit, 2...
...Timing controller, 3...Shift register, 4...Latch circuit, 5...Push-pull drive circuit, 6...Pull-only drive circuit, 7...Shift register, 8, 9...Switching element, 10
...Diode string.

Claims (1)

[Claims] 1. A first electrode group in which each group has a plurality of electrodes and the corresponding electrodes of each group are commonly connected, and each group of the first electrode group is provided in a cross shape. Printing in which a photosensitive medium is exposed to light using a second electrode group having a plurality of electrodes and an EL device having a plurality of electroluminescent EL light emitting parts defined by the electrodes of the first and second electrode groups as a light source. In order to expose one unit of light in the moving direction of the photosensitive medium, the apparatus sequentially selects the electrodes of each group of the first electrode group in response to printing data, and simultaneously selects the electrodes of the second electrode group. Printing using an electroluminescent device characterized by having a control circuit that repeats the operation of selecting each electrode multiple times and further deselects the first and second electrode groups for a certain period of time. Device.