JPH02239593A - Thin film el panel - Google Patents

Abstract

PURPOSE:To provide a thin film EL panel which has a self-restoration function to suppress the expansion of the breakage when a dielectric breakdown is generated, and prevents the burning-out of an electrode, by placing a thin film with a positive resistant temperature coefficient between a transparent electrode and a back electrode. CONSTITUTION:As the material for a thin film 15 which has a positive resistant temperature coefficient, a material with the coefficient as large as possible is preferable, and a sintered ceramics made by mixing a minute amount of additive such as La2O3, Ce2O3, and Ta2O to BaT:O3, or the like is suitable. Such a material has resistivity of 10<3>-10<5>OMEGAcm at the room temperature, and generates a very large resistance increase as the temperature rises. By making such a material into a thin film by a spattering and forming it on the second insulating layer 14, the resistance is increased rapidly responding to the temperature rise following the current increase at a dielectric breakdown. As a result, the current increase is suppressed to avoid a propagation type dielectric breakdown, the breakdown is made into a self-restoration type breakdown to restrict the breakage into relatively a small spot form, and a burning-out of the above electrode is prevented.

Description

[Detailed description of the invention] Sho 1” Jl Shi 1 Branch 1 The present invention relates to thin film EL panels.

For example, light 1! An example of the structure of an EL matrix type display panel will be explained with reference to FIG.

The left half of FIG. 2 is a sectional view in the X direction, and the right half is a sectional view in the Y direction orthogonal to the X direction. In Figure 2, 1
2 is a glass substrate which is a light-transmitting substrate, and 2 is a matrix type thin film EL element formed on the glass substrate 1. 3 in this thin film EL element 2 is an I.D. T
．． A transparent electrode 4 is made of a large number of stripes of M208, Y208, etc. formed by vapor deposition or sputtering on the transparent electrode 3 and the glass substrate 1. 1 is an insulating layer, 5 is a light-emitting layer formed by depositing ZnS:llln or the like on the first insulating layer 4, and 6 is a light-emitting layer formed by depositing M20s, Y203, etc. on the light-emitting layer 5 by vapor deposition or sputtering. the formed transparent second insulating layer, 7
is a back electrode made of a vapor-deposited M film formed on the second insulating layer 6 in the form of a large number of stripes at a constant pitch in the Y direction.

A thin 111EL matrix type display panel is constructed by fixing a concave plate-shaped cover glass 8 onto the glass substrate 1 via an adhesive so as to surround the thin film EL element 2. In order to improve the moisture resistance of the thin film EL element 2, an insulating protective fluid such as silicone oil is sealed in the envelope consisting of the thin film EL element 1 and the cover glass 8.

(Japanese Unexamined Patent Publication No. 57-708G) This thin IIEL matrix type display. In the panel, the transparent electrode 3 and the back electrode 7 intersect in a matrix as shown in FIG.
... to form. One end of each of the transparent electrodes 3 and the back electrode 7 is extended to the opposite peripheral part of the glass substrate 1 every other time, and a driving voltage is selected between the extended ends of the two electrodes 3 and 7. When the voltage is applied selectively, the pixel portions of the light emitting layer 5 selectively emit light, thereby displaying desired information in a dot matrix.

By the way, when forming the thin film EL element 2, it is difficult to laminate the first insulating layer 4, the light emitting layer 5, and the second insulating layer 6 so that their thicknesses are uniform; Pinholes were likely to occur at locations where the film thickness of .8 was thin. As a result, when a driving voltage is applied between the transparent electrode 3 and the back electrode 7,
A discharge phenomenon occurs between the transparent electrode 3 and the back electrode 1 through the pinholes generated in the first insulating layer 4, the light emitting layer 5, and the second insulating layer 6, causing dielectric breakdown of both electrodes 3 and 7. be done. Here, the −F back electrode 7 is made of MM, which has good conductivity and good adhesion to the second insulating layer 6 and has a relatively high melting point (860° C.), so it is transparent as described above. When dielectric breakdown occurs between the electrode 3 and the back electrode 7, since the evaporation and scattering function of M is poor, the breakdown area 1a becomes a spot rod, resulting in not only a self-healing dielectric breakdown [see Figure 4], but also a self-healing type dielectric breakdown as shown in Figure 5. As shown in FIG. 3, the breakdown region b rapidly spreads over the entire surface of the back electrode 7, leading to propagation type dielectric breakdown. When propagation type dielectric breakdown occurs in this way and a breakdown area b is formed on the entire surface of the back electrode 7, the disconnection of the pixel m of the back electrode 7 causes
All pixels msIn in the opposite direction from the pixel m to the feeding point...
・There was a problem in that the display function was significantly degraded because all of the lights could no longer emit light.

Therefore, as a means to solve the above problems, ! ) Increase the thickness of the insulating film.

2) Create a slit in the transparent electrode or back electrode to divide one pixel into multiple pixels.

3) Use a metal such as Sn, which has a lower melting point than M, for the back electrode.

methods have been developed. However, in method I), the operating voltage is high, so the driver IC for driving
A problem has arisen in that it is difficult and expensive to obtain. In addition, although method 2) reduces the rate of wire breakage, it does not provide a fundamental solution, and if dielectric breakdown occurs, even if the wire breakage is avoided, the normal light emitting area in one pixel will be reduced. The problem has arisen that the display function is significantly impaired. Method 3} is an extremely effective method for preventing wire breakage, but it has problems such as Sn having low mechanical strength and being easily damaged during the manufacturing process of thin MEL panels.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thin IIEL panel that has a self-healing function that suppresses the spread of dielectric breakdown when it occurs, and prevents electrode disconnection.

One of the present inventions has been proposed in view of the above-mentioned problems, and the technical means for achieving the above-mentioned object is to provide a transparent electrode, a first insulating layer, a light-emitting layer, a second In a thin IIEL panel formed by successively laminating an insulating layer and a back electrode, a thin film having a positive temperature coefficient of resistance is interposed between the transparent electrode and the back electrode.

1. According to the thin IIEL panel according to the present invention, since a thin film having a positive temperature coefficient of resistance is interposed between the transparent electrode and the back electrode, pinholes and the like can cause dielectric breakdown, and the thin film between the transparent electrode and the back electrode. Even if the current increases rapidly, the temperature of the bottle hole increases rapidly due to Joule heat, etc., so the resistance of the thin film having the positive temperature coefficient of resistance also increases rapidly.
The sudden increase in i-flow at the pinhole portion is suppressed, and the progress of dielectric breakdown is suppressed. Therefore, propagating breakdown is avoided and
A self-healing dielectric breakdown occurs in which the breakdown is limited to a relatively small spot, thereby preventing the electrode from breaking.

Example 1 An example of a thin film EL panel according to the present invention will be described with reference to FIG. The left half of FIG. 1 is a sectional view in the X direction, and the right half is a sectional view in the Y direction. In Figure 1,
9 is a glass substrate which is a transparent substrate, and IO is a thin EL element f according to the present invention formed on the glass substrate θ. The eyes of this thin IIEL element IO are placed on the glass substrate 9. T. 12 is a transparent electrode in which M203, Y203, etc. is formed by vapor deposition or sputtering on a transparent electrode 1 and a glass substrate 9. A first insulating layer 33 is a light-emitting layer formed by depositing ZnS''Mn or the like on the first insulating layer l2, and 14 is a light-emitting layer formed of Al'20 on the light-emitting layer l3.
A transparent second insulating layer 15 formed of Y203, Y203, or the like by vapor deposition or a sputtering method is a thin film having a positive temperature coefficient of resistance according to the present invention formed on this second insulating layer.

As this thin film material, it is desirable to use a material with a coefficient as large as possible; for example, BaT:Os, La2's +Ce
Additives such as 203 + Ta 205 in trace amounts (e.g. 0
．． 1 to 0.3 mol%) and sintered ceramic is suitable. This material is 103-1050cm at room temperature
It has a certain degree of resistivity, and as the temperature rises, the resistance increases significantly. For example, the temperature rises from room temperature to approximately 300℃. In this case, there is a resistance change of 3 to 5 orders of magnitude. By forming such a material into a thin film using sputtering or the like and forming it on the second insulating layer, the resistance increases rapidly in response to the temperature rise accompanying the increase in current at the time of dielectric breakdown, thereby suppressing the increase in current. to avoid propagating breakdown,
This results in a self-healing dielectric breakdown where the breakdown is limited to a relatively small spot, thus preventing the electrode from breaking.

In the embodiment shown in FIG. 1, the thin film 15 having a positive temperature coefficient of resistance is formed between the back electrode iB and the second insulating layer 14, but it is not limited to this position; It may be formed between the insulating layer l2 and the transparent electrode H, or may be formed on both. Also, a thin film with a positive temperature coefficient of resistance!
The material of No. 5 is not limited to the above-mentioned BaT:Os-based material, and may be other oxide-based materials or alloy-based materials.

According to the thin GEL panel according to the present invention, since a thin film having a positive temperature coefficient of resistance is interposed between the transparent electrode and the back electrode, dielectric breakdown occurs between the electrodes and the current increases rapidly. However, as a result of the sudden increase in resistance as the temperature rises, the increase in current is suppressed and the progress of dielectric breakdown is suppressed. Therefore, propagation-type dielectric breakdown is avoided, and self-recovery type dielectric breakdown occurs in which the breakdown is limited to a relatively small, suboto-like shape, which has the effect of preventing disconnection of the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an embodiment of a thin 1iEL panel according to the present invention, in which the left half is a cross-sectional view in the X direction, and the right half is a cross-sectional view in the Y direction. FIG. 2 is a sectional view showing an example of the structure of a conventional thin IIEL panel, with the left half being a sectional view in the X direction and the right half being a sectional view in the Y direction. FIG. 3 is a partial plan view showing a pixel portion in a thin EL panel. FIG. 4 is a partial plan view showing self-recovery dielectric breakdown at the back electrode, and FIG. 5 is a partial plan view showing propagation type breakdown at the back electrode. 9...Transparent substrate, 0...Thin film EL element,! ...Transparent electrode, 2...First insulating layer, 3...Light emitting layer, 4...Second insulating layer, 5...Thin film having a positive temperature coefficient of resistance, 6... Back electrode. ``<Ichi no Dai Ko Prisoner 15 Js2 Shoichi, fL!j Minister L, No 1 I Taka = 4 pieces;
: Breaking 1 "4 teffi s. fig. fig. fig.

Claims (1)

[Claims] On a transparent substrate, a transparent electrode, a first insulating layer, a light emitting layer,
What is claimed is: 1. A thin film EL panel comprising a second insulating layer and a back electrode layered in sequence, characterized in that a thin film layer having a positive temperature coefficient of resistance is interposed between the electrodes.