JPS61114493A - Aging for thin film electroluminescence panel - 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 Industrial Application) The present invention relates to a method for aging a thin film electroluminescent panel that exhibits electroluminescence by applying an alternating current voltage.

(Prior art and its problems) In the conventional thin-film electroluminescent elements (hereinafter referred to as thin-film EL elements) constituting AC-operated thin-film electroluminescent panels, the brightness and luminous efficiency have been improved.
In order to obtain long-term operation stability, α5~3rro1% Mn4 or 'rb Fs is used as the luminescent center.
, SmFa, PrFa, etc. added to Zn8. Z
Y2O3; J) or Al120
a, PbTi0a, BaTiOs, 5izNa
A thin film EL element with a so-called double insulation structure, which is sandwiched from both sides by insulation layers such as EL elements, has been used.

An example of the basic structure of a conventional double insulating pan thin film EL device is shown in the fifth example.
As shown in the figure.

In FIG. 5, 12 is a glass substrate, 13 is InzOs
, 8nOz, substrate side transparent electrode made of ITO or metal thin film, etc., 14 is an electron beam or A11 on it.
zOs, PbTiOs, BaTiOs, 8i3N
Insulating layer 4 etc., 15 Mn, T deposited on it
bFs, 8mFm.

This is a light-emitting layer made of Zn8 containing a light-emitting center such as PrFs. This light emitting layer 15 is also manufactured using an electron beam evaporation method, a sputter evaporation method, or the like. Reference numeral 16 denotes an insulating layer deposited on the light emitting layer 15, and the deposition method and material are the same as those for the insulating layer 14. Reference numeral 17 is six electrodes made of Ag or ITO deposited thereon, and reference numeral 18 is an AC power supply for roughly moving the EL element, which is connected to the electrodes 13 and 17.

Next, the light emission principle of the ELX element will be briefly explained with respect to the element having the structure shown in FIG. Before the start of light emission, the space between the electrodes 13 and 17 is considered to constitute a simple capacitor with the light emitting layer 15 as a dielectric. Therefore, between electrodes 13 and 17 there is an electric current @
When an AC voltage of 18 is applied, the light emitting layer 15 and the insulating layer 1
A voltage corresponding to each capacitance is applied to 4.16. When the electric field applied to the light emitting layer 15 becomes sufficiently high (approximately I
QV/cm or more) electrons are excited in the conduction band of the light emitting layer 15. These electrons are accelerated by the electric field and collide with the luminescent center with sufficient energy to excite the luminescent center.

When the electrons in the luminescent center return to the ground state after being brought to an appropriately excited state, light with an energy value unique to the luminescent center is emitted. In reality, the emission spectrum is broadened to some extent due to interaction with the crystal lattice. Mn, TbFs, and Sm, which are the luminescent centers mentioned earlier,
Since the luminescence energy of Fa, PrF3, etc. is in the visible region, strong luminescence is observed.

When a panel using such a thin film EL element is put into practical use, in order to eliminate changes in the luminescent properties during the initial luminescence, it is necessary to stabilize the luminescent properties by allowing the panels to emit light for several to hundreds of hours. There is. This process is called aging.

Conventionally, this process involved applying an alternating current voltage to the panel to cause it to emit light. However, although this conventional aging method is effective in stabilizing the light emitting characteristics of thin-film EL panels, it generates many dielectric breakdown points mainly at panel defects such as pinholes during aging, especially in the early stages of aging. Particularly large failure points are broken display lines and missing display pixels.

This has the drawback of lowering the yield in the aging process.

(Object of the Invention) The present invention eliminates such conventional drawbacks and provides a thin film E.
The purpose is to reduce the size of the dielectric breakdown point in the early stage of aging of the L panel, thereby reducing the display line breakage and display pixel chipping of the panel, suppressing the occurrence of defective panels, and improving the yield in the aging process. shall be.

(Structure of the Invention) The method for aging a thin film electroluminescent panel of the present invention involves applying a DC voltage to a thin film electroluminescent panel driven by AC to micro-destruct the defective parts existing in the panel. This method is characterized by having a first aging step in which the thin film electroluminescent panel is removed, and a second aging step in which an AC voltage is applied to the thin film electroluminescent panel to cause it to emit light.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention, in which 1 is a DC power source that can vary the voltage, 2 is a resistor, 3 is a thin film EL panel, 4 is a pixel such as an EL element, 5 is the column electrode,
6 is a row electrode. By selecting an appropriate value for resistor 2, f
It is possible to suppress the current flowing through the iEL element at the time of dielectric breakdown of the element, and to minimize the size of the breakdown point. However, if the resistance is too large, the current flowing through the element at the time of dielectric breakdown will be extremely small, and breakdown will virtually never occur. Therefore, the value of this resistor 2 has a suitable range, preferably between 100Ω and IOMΩ, preferably about IMΩ. The first aging process is completed by gradually increasing the voltage of the DC power supply 1 using the circuit configuration shown in FIG. 1 until the voltage applied to each pixel JiC exceeds the light emission start voltage of each pixel. The subsequent second aging step is similar to the conventional step.

When the size of the thin film EL panel is small and the total area of the pixels that are simultaneously aged is about Q, l cm" or less, the purpose of the invention can be fully achieved by the method described in the first embodiment. However, the method described in the first embodiment can fully achieve the object of the invention. When the total area of pixels that undergo simultaneous aging becomes approximately Q, l Cm'' or more, the electric charge charged in each pixel flows to the dielectric breakdown point, so the current flowing from the DC power supply 1 to the EL panel 3 in Figure 1 is It is not sufficient to limit the number to 2. That is, it is necessary to limit the current flowing into the dielectric breakdown point by some method. In such cases, use the following method.

FIG. 2 is a circuit configuration diagram showing a second embodiment of the present invention. In this case, the total area of the pixels 4 connected to each resistor 2a, 2b, . . . is approximately αl cm"
The following shall apply. Further, the value of each resistor is the same as in the first embodiment. The voltage of the DC power supply 1 used for aging is also the same as in the first embodiment. Further, if the total area of pixels connected to one column electrode exceeds 0.1 cm, a circuit similar to that on the column electrode side of the second embodiment is provided on the row electrode side.

Using the second embodiment allows aging of large area panels, but has the disadvantage that increasing the number of row and column electrodes requires connecting a large number of resistors to each electrode. be. In this case, the following method is used.

FIG. 3 is a circuit configuration diagram showing a third embodiment of the present invention, in which 7 is a current detection circuit that detects the current flowing through the EL panel 3 and converts it into a voltage, 8 is a reference voltage source, and 9 is the EL panel. 3 is a comparator circuit that outputs a specific signal when the current flowing through it increases and as a result the output voltage of the current detection circuit exceeds a reference voltage; 10 is a comparator circuit that outputs a specific signal when the current flowing from the comparator circuit 9 to the EL panel 3 is a constant value; A circuit 11 is a voltage control circuit which controls the output signal of the placement circuit 10 and controls the voltage applied to the EL panel. When dielectric breakdown occurs in the EL panel 3 and current begins to flow, and a signal is output from the comparator circuit 9 indicating that the current exceeds the current value set by the reference voltage source 8, the circuit 10 The fact that the current exceeds the reference current is memorized, and the voltage control circuit 1
1 to short-circuit between the row electrode 6 and column electrode 5 of the EL panel 3 at the time [, in FIG. This cuts off the current flowing from the DC power supply 1 to the EL panel 3, and at the same time
The charges stored in each pixel of the L panel 3 are immediately discharged through the control circuit 11. Therefore, EL panel 3
The current flowing into the dielectric breakdown point of the dielectric is limited, and the size of the breakdown point remains extremely small. When the current flowing through the dielectric breakdown point disappears, the voltage of the DC power source 1 is lowered appropriately and the circuit 10 is reset at time t2 in FIG. 4, and the voltage is applied to the EL panel 3 again. This process is repeated, and the first aging ends at time t3 when the DC voltage applied to the EL panel 3 exceeds the light emission start voltage. Note that the vertical axis in FIG. 4 indicates the voltage applied to the pixel 4 of the EL panel 3.

The reference current value for detecting dielectric breakdown current is based on the experimental result that the product of the reference current value and the total area of the pixels 4 of the EL panel 3 is 0.1 to l Q mA @cm''< 1 mA e (m
About 2 was desirable.

Further, the second aging step after this is similar to the conventional method.

Note that the actual circuit of the third embodiment can be easily realized using ICs, transistors, and the like.

By using the aging method shown in the third embodiment, it is possible to efficiently age large-area panels at the same time.

If the area of the panel is very large, the column electrodes are divided into several groups as in the second embodiment, and the first aging step is performed for each group using the method shown in the third embodiment. do.

When we compared the aging of EL panels created under the same conditions using the example described above and the conventional method, we found that aging using the conventional method caused large dielectric breakdown during aging, resulting in many display pixel defects. However, when the aging method of this embodiment is used, although dielectric breakdown occurs in the first aging process, it is very small, less than 50 microns, and new dielectric breakdown occurs in the second aging process. However, the effectiveness of the example was demonstrated, which is a problem in practice.

The polarity of the DC power supply during aging that minimizes the size of the insulation fracture depends on the thicknesses of the insulating layer material 1 light emitting layer material and 6 films constituting the EL panel. For this reason, which polarity should be used for aging, or whether aging should be carried out by alternating the polarity as appropriate, is determined using a test sample depending on each case.

(Effects of the Invention) The method of the present invention minimizes the size of dielectric breakdown points that occur during the aging process of thin-film EL panels, thereby making it possible to age thin-film EL panels with a high yield. It is effective in reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing the first step in the first embodiment of the present invention. FIG. 2 is a circuit configuration diagram showing the first step in the second embodiment of the present invention. FIG. 3 is a circuit configuration diagram showing the first step in the third embodiment of the present invention. FIG. 4 is a schematic diagram showing the voltages applied to the pixels of the EL panel when the third embodiment is used, from the start to the end of the first aging process. Fifth
The figure is a cross-sectional view of a general AC-driven thin film EL element. 1...DC power supply, 2...Resistor, 3...
... Thin film EL panel, 4 ... Pixel of thin film EL panel, 5 ... Column electrode, 6 ... Row electrode, 7 ... Current detection Circuit, 8... Reference voltage source, 9... Comparison circuit, 1o... Memory circuit, 11... Voltage control circuit. io＼ to C)≧ sake

Claims (3)

[Claims] (1) A first aging step in which a DC voltage is applied to a thin-film electroluminescent panel driven by AC drive to micro-destruct the defective portions existing in the panel, and the defective portions are removed; A method for aging a thin film electroluminescent panel, comprising a second aging step of applying an alternating current voltage to cause light emission. (2) A method for aging a thin film electroluminescent panel according to claim (1), characterized in that the DC voltage is gradually increased. (3) In the method for aging a thin film electroluminescent panel according to claim (1), the first aging step gradually increases the DC voltage to reduce the dielectric breakdown current generated in the defective part of the panel. When the DC voltage reaches a certain value or more, the application of the DC voltage is stopped instantaneously, the charge on the panel is discharged, and then the DC voltage is increased again from the voltage at the time of stopping. Characteristic aging method.