JPH03181987A - Driving method of thin film EL display device - 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] [Industrial application field] The present invention relates to a method for driving a thin film EL display device.

[Conventional technology]

In general, thin film EL elements can achieve higher brightness and longer life by applying an alternating current voltage with a symmetrical waveform to the pixels.

Conventionally, the driving method for a thin film EL display device is a bidirectional push method in which a driving voltage is applied to the thin film EL element from the scanning side and the signal side, and bipolar elements are used on the scanning side and the signal side.
-Pull symmetrical driving method (Japanese Patent Application Laid-Open No. 61-282895
(see Japanese Patent Laid-Open No. 143096/1983), and a method in which driving voltage is applied to the thin film EL element from the scanning side and the signal side, and a discharge process is provided in order to reduce power consumption during driving (see Japanese Patent Laid-Open No. 143096/1986). can give.

[Problem to be solved by the invention]

In the method for driving the thin film EL display device described above, drive voltage is applied to the thin film EL element from the scanning side and the signal side.
A voltage is also applied to non-selected pixels of the element. Therefore, in order to avoid light emission leakage from non-selected pixels in the thin film EL element, it is necessary to adjust the driving voltage according to the brightness/voltage characteristics of the light emitting layer of the thin film EL element. Further, power supplies are required on both the scanning side and the signal side. In order to reduce costs, it is necessary to reduce the number of processes and parts used, but this point is not taken into consideration.

The present invention is a thin film that improves the above drawbacks, eliminates the need for a driving power source on the signal side, and does not apply voltage to non-selected pixels of the thin film EL element, thereby preventing leakage of light from the thin film EL element and providing good display quality. An object of the present invention is to provide a method for driving an EL display device.

[Means to solve the problem]

In order to achieve the above object, the present invention drives a thin film EL element in which two sets of strip-shaped electrode groups perpendicular to each other on both sides of an EL light emitting layer are provided as a scanning side electrode group and a signal side electrode group by a line sequential driving method. In a method for driving a thin film EL display device that performs a dot matrix display, two types of voltages are used as drive voltages, which have the same absolute value but different polarities, and whose absolute values are equal to or higher than the light emission starting voltage of the thin film EL element. one of the two types of voltages is applied only to one scanning electrode in the scanning electrode group during scanning, the other scanning electrode is in a floating state, and the thin film EL element in the signal electrode group is The driving voltage of each pixel in the thin film EL element is controlled by connecting the signal side electrode connected to the selected pixel to a ground potential point and setting the signal side electrode connected to the non-selected pixel of the thin film EL element in a floating state. Turn on/off.

〔Example〕

FIG. 1 shows an example of a drive circuit for a thin film EL display device used in implementing the present invention.

In this example, a driving voltage is applied to the thin film EL element only from the scanning side, and no driving voltage is applied from the signal side. In Fig. 1, 1 is E which performs dot matrix display.
This is a thin film EL device consisting of an L display panel, and two sets of striped electrode groups orthogonal to each other are provided on both sides of an EL light emitting layer as a scanning side electrode group and a signal side electrode group. 2
, 3 have the same absolute value but different polarities, and the absolute value is E
This is a power supply that generates a voltage (+HV, -HV) that is higher than the light emission start voltage of the pixel in the L display panel. 4,5
CP1 . is a plurality of switching elements CP1 . CP2
．． --・-CPN, CN1. CN2. ---This is a switching element group consisting of CNN. 6, 7 are these switching element groups CP□, cp2 . ...CPN, CN
□.

CN2. ...Logic circuits such as shift registers and latches that control CNN. Reference numeral 8 denotes a plurality of switching elements RP□, RP2 . . . . A switching element group consisting of RPN; 9 is a plurality of switching elements RN for turning on and off -HV to each scanning side electrode of the EL display panel 1;
, ,RN2. . . . A switching element group consisting of RN□. 10.11 is a logic circuit such as a shift register. Switching element RP□, RP,...RPN
have one end connected to each scanning side electrode of the EL display panel 1 and the other end connected to a common line, and the switching elements RN, , RN2 . ...The RNN also has one end connected to each scanning side electrode of the EL display panel 1, and the other end connected to a common line. 12 is a switching element RP□
, RP2. . . . A switch that switches and connects the common line of RPN to the power supply 2 and the ground potential point, 13 is a switching element R
N1. This is a switch that connects the common line of RN, , . . . , RNN to the power supply 3 and the ground potential point.

Next, the operation of this drive circuit will be explained.

This drive circuit basically uses two types of voltages +HV whose absolute values are equal to or higher than the light emission start voltage of the pixels of the EL display panel 1, and whose absolute values are equal and have different polarities as the drive voltages for the scanning side electrodes of the EL display panel 1. , -HV to select each pixel of the EL display panel 1 by switching the signal side electrode of the EL display panel 1 between a grounded state and a floating state.

This controls non-selection. When applying a positive polarity voltage to the scanning side electrode of the EL display panel 1, mode
The case where a voltage of negative polarity is applied to the scanning side electrode of the display panel 1 is referred to as mode (2).

In mode ■, switching element RP1. The common line of RP2°...RPN is connected to the power supply 2 by a switch 12 and +H is applied, and the switching elements RN1... R.N.
2. ...RN, the common line is connected to the ground potential point by a switch 13. At this time, the switching element RN,
.

RN2. The common line of RN, . . . is connected to the ground potential point when the switching element group 8 is turned on. This is to prevent bipolar HV from being applied to both ends of RN. In this state, the scanning side switching elements RN1. RN2. ...
RN, are all turned off by the output signal of logic circuit II, and switching elements RP1. RP2. ...IIIPN
In this case, only the switching element connected to the scanning side electrode of the EL display panel l to be scanned is turned on by the signal from the logic circuit 10, and all other switching elements are turned on by the logic circuit 1.
It is turned off by a signal from 0. As a result, in the scanning-side electrode group of the EL display panel 1, voltage +H is applied only to the scanning-side electrodes that are scanned. On the other hand, the signal side switching element cp1. cp2. . . cp are all turned off by the output signal of the logic circuit 6, and the switching elements CN1 . CN2. ...By turning on and off the CNN according to the display signal from the logic circuit 7, each pixel of the EL display panel is selected or non-selected.

Here, in order to simplify the explanation, the first pixel will be explained using FIG. 2. In FIG. 2, 14 is a pixel connected to the first signal side electrode and the first scanning side electrode in the EL display panel 1, and the switching element CP
□, CN□, RP1. Connected to RN engineering. If this pixel 14 is a selection WI element, the switching element C
N is turned on by a signal from the logic circuit 6, and the pixel 14 emits light when +HV is applied between both ends during scanning when +HV is applied from the power supply 2 to the first scanning side electrode. When the pixel 14 is a non-selected pixel, the switching element CN is turned off by a signal from the logic circuit 6, and one end of the pixel 14 is in an open state, so that no voltage is applied and no light is emitted.

In mode ■, switching element RN1. RN2
゜...The common line of RNN is connected to the power supply 3 by the switch 13, and the switching element RP1. RP2. ...RP
The N common line is connected to ground potential by a switch 12. At this time, switching element RP1. RP2.・
. . . RP, is connected to the ground potential point as in the case of mode I8. Similarly, when the switching element group 9 is turned on, the switching elements RP□, RP, . . . RP, This is to prevent bipolar HV from being applied to both ends. In this state, the scanning side switching element RP, RP2. ...
RPN are all turned off by the output signal of logic circuit 10, and switching elements RN, RN2 . ...RNN is E
Only the switching element connected to the scanning electrode of the L display panel 1 to be scanned is turned on by a signal from the logic circuit 11, and all other switching elements are turned off by the signal from the logic circuit 11. As a result, in the scanning side electrode group of the EL display panel 1, the voltage -H is applied only to the scanning side electrodes that are scanned.

On the other hand, the signal side switching element CN1. CN2.・
...CNN are all turned off by the output signal of the logic circuit 7, and the switching elements cp1. cp2. ...cp,
selects or de-selects each pixel of the EL display panel 1 by turning on or off according to a display signal from the logic circuit 6.

Next, similar to the case of mode I, explanation will be made using FIG. 2.

When pixel 14 is a selected pixel, switching element C
P□ is turned on by a signal from the logic circuit 6, and the pixel 14 emits light when -HV is applied between both ends during scanning when -HV is applied from the power supply 3 to the first scanning side electrode. When the pixel 14 is a non-selected pixel, the switching element CP1 is turned off by a signal from the logic circuit 6, and one end of the pixel 14 is in an open state, so that no voltage is applied and no light is emitted.

FIGS. 4 and 5 show the operation of each element as described above in each mode.

By alternately performing Mode I and Mode H for each pixel, +HV and -HV are applied from the scanning side electrode to the selected pixel, and no voltage is applied to the non-selected pixel. In other words,
Leakage of light emission from non-selected pixels can be prevented.

Note that the present invention does not impose any restrictions on the method of switching the mode for compensating the polarity of each pixel. For example, the method of switching the mode for compensating the polarity of each pixel for each scanning line, or It is possible to use a method of switching the mode for compensating the polarity of the pixel every time one screen is displayed. Further, the present invention provides a power supply voltage +
HV.

There are no restrictions on the HV except that the absolute value thereof is equal to or higher than the light emission starting voltage. moreover,
The present invention does not impose any restrictions on thin film EL display devices. For example, the light emitting layer material of a thin film EL device is ZnS.
, Zn5e, CaS, 5rSe, Ca
5e and their mixed crystals, Mn or lanthanum-based rare earths are used as the luminescent center of the light emitting layer, and Y2O3, Sin□, Al□03. Ta2
05 etc., Si, N4. ITO is used as a transparent electrode material for thin film EL devices using nitrides such as BN and AIN, or ferroelectrics such as tungsten bronze series and Perodesky 1~ series.

ZnO type etc. can be used. The structure of the film EL element may be a so-called insulating structure in which the above-mentioned insulating layer is provided on one or both sides of the light emitting layer, or a structure in which no insulating layer is provided.

In the example of the present invention, SrS:Ce was used for the light emitting layer.
A thin film EL display device with a display capacity of ×32 dots was created and used, and NchMO3IC and PchM were used as driving elements.
The above drive circuit was created using O5IC.

The EL display panel 111 in the thin film EL display device was fabricated using SrS:Ce as a light emitting layer and having a structure as shown in FIG. 3. That is, the EL display panel 1 is
A structure was created in which two sets of stripe-shaped electrode groups 21 and 24, which are orthogonal to each other, are provided on both sides of the L light-emitting layer 23 with an insulating layer 22 in between. The striped electrode group 21 is formed by forming a film of 2000 λ using RF magnetron sputtering as a target using ZnO doped with 2 wt% Al2O3 at a substrate temperature of 300°C, and then etching to form a film with a thickness of 3 mm (electrode wires @ 200° C.).
A transparent electrode with a diameter of micrometer (μm) was created. l@Green M22 is produced by EB evaporation method using Y2O as the evaporation source, and the substrate temperature is 70°C.
00-5000 A bottom membrane was used. The light emitting layer 23 was formed by using SrS doped with 0.1 mo1% of l::ec13 as a vapor deposition source and forming a 1 μm thick film 6 at a substrate temperature of 450° C. The striped electrode group 24 was formed by depositing Al using a resistance wire heating evaporation method, and then by etching to form a back electrode with 3 mans (electrode line width: 200 μm).

The above drive circuit has a 32-bit output as a drive element, and each has a built-in shift register and latch.
It was created using hMO5IC and PchMO5IC.

A TTL control circuit was used to control the drive element.

12- In the above drive circuit, NchMO5 is used as a switching element.
Although IC and PchMO5IC are used, the type of switching element is not limited, and for example, CMO5, bipolar transistor, etc. can be used.

The driving voltage HV is such that the brightness of the EL display panel 1 is 1 cd/
The voltage (190V) was obtained by adding 60V to the voltage of cm2. Also, the method of switching between the two modes is to alternate between each scanning line! , mode (2) was performed, and a method was used in which this was switched every frame.

As an evaluation of the thin film EL display device, data was input from a microcomputer into the thin film EL display device to reproduce still images and moving images. Good display quality with no leakage of light emission from non-selected pixels was obtained for both still images and moving images without adjusting the voltage.

〔Effect of the invention〕

As described above, according to the present invention, a thin film EL element in which two sets of striped electrode groups orthogonal to each other are provided on both sides of an EL light emitting layer as a scanning side electrode group and a signal side electrode group is driven by a line sequential driving method. In a method for driving a thin film EL display device that performs a dot matrix display, the driving voltages have the same absolute value but different polarities, and the absolute value is the same as that of the thin film E.
Using two types of voltages that are higher than the light emission starting voltage of the L element,
One of the two types of voltages is applied only to one scan-side electrode during scanning in the scan-side electrode group, and the other scan-side electrode is brought into a floating state, and the selected pixel of the thin film EL element in the signal-side electrode group is The drive voltage of each pixel in the thin film EL element is turned on/off by connecting the signal side electrode connected to the ground potential point and setting the signal side electrode connected to the non-selected pixel of the thin film EL element in a floating state.
Since the drive voltage is applied to the thin-film EL element only from the scanning side electrode, only two power supplies that output positive and negative polarity voltages are used as power supplies, eliminating the need for a signal-side drive power supply. Become. Furthermore, since no voltage is applied to non-selected pixels of the thin film EL element, leakage of light from the thin film EL element does not occur, and good display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the drive circuit of the thin film EL display device used in the implementation of the present invention, FIG. 2 is a circuit diagram showing the configuration of one pixel in the dynamic drive circuit, and FIG. A perspective view showing the EL display device, and FIGS. 4 and 5 are diagrams showing the operation of each element in the drive circuit. 1... Thin film EL element, 2, 3... Power supply, 4,5°8
．． 9... Switching element group, 12.13... Switch. 5-

Claims (1)

[Claims] A thin film EL display in which a thin film EL element is provided with two sets of striped electrode groups orthogonal to each other on both sides of an EL light emitting layer as a scanning side electrode group and a signal side electrode group, and is driven by a line sequential driving method to perform a dot matrix display. In the driving method of the device, two types of voltages having the same absolute value but different polarities and having an absolute value equal to or higher than the light emission starting voltage of the thin film EL element are used as driving voltages, Applying one of the two types of voltages only to one scanning side electrode and setting the other scanning side electrodes in a floating state,
Connecting the signal side electrode connected to the selected pixel of the thin film EL element in the signal side electrode group to a ground potential point, and bringing the signal side electrode connected to the unselected pixel of the thin film EL element into a floating state. A method for driving a thin film EL display device, comprising: turning on/off a driving voltage for each pixel in the thin film EL element.