JPH044400Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a thin film EL matrix type display panel that displays information such as characters and figures in a dot matrix.

Prior Art For example, an example of the structure of a thin film 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 FIG. 2, 1 is a glass substrate that is a transparent substrate;
is a matrix type thin film EL element formed on the glass substrate 1. 3 in this thin film EL element 2
4 is a transparent electrode in which ITO or the like is formed on the glass substrate ₁ in the form of a large number of stripes at regular pitches in the X direction by _{vapor deposition ;} 5 is a transparent first insulating layer formed by vapor deposition or sputtering, and 5 is a light emitting layer formed by forming ZnS:Mn or the like on this first insulating layer 4 by vapor deposition, etc.;
6 is a transparent second insulating layer formed of Al ₂ O ₃ , Y ₂ O ₃ , etc. by vapor deposition or sputtering on the light emitting layer 5;
Reference numeral 7 denotes a back electrode made of an Al vapor-deposited film formed on the second insulating layer 6 in the form of a large number of stripes at regular pitches in the Y direction.

A thin film EL 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, and the glass substrate 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 [JP-A-57-7086].

In this thin-film EL matrix type display panel, the transparent electrode 3 and the back electrode 7 intersect in a matrix shape as shown in FIG. 3, forming a large number of matrix-shaped pixels m, m, . . . . This transparent electrode 3
One end of each of the back electrodes 7 and 7 is extended to the opposite periphery of the glass substrate 1, and when a driving voltage is selectively applied between the extended ends of the two electrodes 3 and 7, , pixel portions of the light-emitting layer 5 selectively emit light to display desired information in a dot matrix.

Problems to be solved by the invention By the way, when forming the thin film EL element 2, the first
It is difficult to laminate the insulating layer 4, the light emitting layer 5, and the second insulating layer 6 so that the film thickness is uniform, and pinholes occur in places where the film thickness of each layer 4, 5, and 6 is thin. It was easy. As a result, when a driving voltage is applied between the transparent electrode 3 and the back electrode 7, the transparent electrode 3 and A discharge phenomenon occurs between the back electrode 7 and both electrodes 3 and 7 are dielectrically broken down. Here, the back electrode 7 is made of Al, which has good conductivity and adhesion to the second insulating layer 6, and has a relatively high melting point (660° C.). When dielectric breakdown occurs between the electrode 7 and the back electrode 7, Al has a poor evaporation and scattering function.
This is not limited to self-healing dielectric breakdown in which the breakdown area 1a is spot-like (see Figure 4), but also propagation type dielectric breakdown in which the breakdown area b rapidly spreads over the entire surface of the back electrode 7 as shown in Figure 5. leading to. When a propagation-type dielectric breakdown occurs and a breakdown area b is formed over the entire surface of the back electrode 7, the disconnection of the pixel m of the back electrode 7 causes the pixel m to move from the pixel m in the opposite direction to the feeding point. There was a problem in that all the pixels m, m, .

Therefore, in order to solve the problem of the back electrode Al being melted due to dielectric breakdown, leading to wire breakage, the inventor conducted various experiments and considered ITO, which has a much higher melting point than Al (melting point 660℃). transparent conductive thin film and a high melting point metal thin film with a melting point of 1500℃ or higher (e.g. Ti (melting point
1675℃), Ta (melting point 1996℃), etc. as a back electrode (Utility Application No. 61-4743).
issue). Although this technology was able to significantly improve fusion cutting compared to conventional Al, it was still not perfect.

In order to solve the above-mentioned problem, the present inventor conducted further experimental studies and found that a low melting point material is extremely effective, and the back electrode 7 is made of Sn,
One or two metal materials with a lower melting point than Al selected from the group of Zn, Pb, Cd, In, Tl, Bi, and Sb.
A technique for forming an alloy of at least one of the above metal materials was disclosed (Japanese Patent Application Laid-open No. 52319/1983). Since this uses a metal material that has a lower melting point than Al and has an evaporation scattering function, when dielectric breakdown occurs between the transparent electrode 3 and the back electrode 7, the area around the breakdown point on the back electrode 7 is relatively At a low energy level or low current level, it evaporates and scatters instantly, and the part acting as a discharge point (electrode) instantly disappears, so the discharge stops instantly and the electrode breaks down. For this reason, the broken hole in the electrode is limited to a small area at the discharge point and its surrounding area, and remains approximately in the shape of a spot as shown in FIG. In this way, a self-healing dielectric breakdown in which the breakdown region is spot-like is actively formed to avoid propagation type dielectric breakdown and to prevent disconnection at the back electrode.

However, in a thin film EL matrix type display panel having a back electrode 7 made of the above-mentioned material, the adhesion of the back electrode 7 to the second insulating layer 6 is weak, so that both side edges of the back electrode 7 are floating. Become. In particular, in a pixel m where the transparent electrode 3 and the back electrode 7 intersect, as shown in FIG. Its both side edges n,
A new problem has arisen in that it becomes difficult to apply an electric field to n, and it no longer emits light.

Therefore, the purpose of the present invention is to provide a thin film EL panel that has a self-healing function that suppresses the spread of the breakdown area at the back electrode when dielectric breakdown occurs, and that has a strong adhesion force to the second insulating layer of the back electrode. It is about providing.

Means for Solving the Problems The present invention has been proposed in view of the above-mentioned problems.The technical means for achieving the above-mentioned object is to form striped transparent electrodes on a transparent substrate, In a thin film EL panel having a thin film EL element formed by sequentially laminating an insulating layer, a light emitting layer, a second insulating layer, and a striped back electrode, a metal material having an evaporation and scattering function with a lower melting point than Al, or A thin metal film with strong adhesion to the second insulating layer is interposed as a base for the back electrode made of an alloy.

Function According to the thin film EL panel according to the present invention, the above-mentioned second layer is used as the base of the back electrode made of a metal material or alloy having a melting point lower than that of Al and having an evaporation scattering function.
Because a metal thin film with strong adhesion is interposed to the insulating layer, if dielectric breakdown occurs between the transparent electrode and the back electrode and a discharge phenomenon occurs, the area around the breakdown point on both the back electrode and the metal thin film Both evaporate and scatter instantaneously at a relatively low energy level or low current level, and the portion that acts as a discharge point (electrode) disappears instantaneously, so that the discharge stops instantaneously, and at the same time, the destruction of the electrode stops. Therefore, the broken hole in the electrode is limited to a small area around the discharge point and its surrounding area, and remains approximately in the shape of a spot. In this way, a self-healing dielectric breakdown in which the breakdown area in the back electrode and metal thin film becomes a spot is actively formed, and disconnection of the back electrode due to propagation type dielectric breakdown is avoided, and
The metal thin film interposed between the second insulating layer and the back electrode maintains the adhesion of the back electrode to the second insulating layer.

Example A first example of a thin film EL panel according to the present invention is shown below.
This will be explained with reference to the figures. 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 FIG. 1, 9 is a glass substrate which is a light-transmitting substrate, and 10 is a thin film EL element according to the present invention formed on the glass substrate 9. In FIG. 11 in this thin film EL element 10 is ITO on the glass substrate 9.
12 is a transparent electrode in which Al ₂ O ₃ , Y ₂ O _3, etc. is formed on the transparent electrode 11 and the glass substrate 9 by vapor deposition or sputtering. a transparent first insulating layer,
13 is a light emitting layer formed of ZnS:Mn or the like by vapor deposition on this first insulating layer 12; 14 is the light emitting layer 1;
3, a transparent second insulating layer formed of Al ₂ O ₃ , Y ₂ O ₃ , etc. by vapor deposition or sputtering; 15 is this second insulating layer;
A metal thin film formed in a large number of stripes at a constant pitch in the Y direction by vapor deposition or the like on the second insulating layer 14, such as Al, Ni, Ti, Cr, etc., is attached to the second insulating layer 14. Select a metal material with high adhesive strength. The thickness of this metal thin film 15 is, for example, 10~
It is set as small as possible, about 500 Å, and the optimal condition is about 30 to 100 Å. This is because, similar to the back electrode described below, when a dielectric breakdown occurs, the metal thin film 15 made of a metal material with a high melting point, such as the above-mentioned material, instantly applies a relatively low energy level or low current level to the area around the breakdown point. This is to cause it to evaporate and scatter. Note that even if the thickness of the metal thin film 15 is set as small as possible as described above, the adhesion force to the second insulating layer 14 will not decrease. 16
is a back electrode formed by laminating the metal thin film 15 in the same pattern by vapor deposition or the like on the metal thin film 15 as a base for the second insulating layer 14, and this back electrode 16 is made of a metal material having a lower melting point than Al; For example, as mentioned earlier, Sn, Zn, Pb, Cd, In, Tl, Bi
and Sb, or an alloy of two or more of the above metal materials.
Note that since the metal thin film 15 and the back electrode 16 are made of metal, there is no problem in their adhesion. 17 is a concave plate-shaped cover glass which is adhesively fixed on the glass substrate 9, and an insulating protective fluid such as silicone oil is sealed inside this cover glass, as in the conventional case.

When aging is performed by applying a driving voltage between the transparent electrode 10 and the back electrode 16, the transparent electrode 1
Even if dielectric breakdown occurs between the electrode 0 and the back electrode 16 and a discharge phenomenon occurs, the back electrode 16 is made of one type of metal material or an alloy of two or more types of metal material with a lower melting point than Al, which has an evaporation and scattering function. In addition, although the metal thin film 15 is made of a metal material with a high melting point, the thickness of the metal thin film 15 is set as small as possible to substantially maintain the evaporation and scattering function. In both cases, the area around the breakdown point instantaneously evaporates and scatters at a relatively low energy level or low current level, and at the same time, the breakdown of the electrode stops. Therefore, the fracture hole in the electrode is limited to the discharge point and its surrounding area. As a result, the breakdown region in the back electrode 16 and the metal thin film 15 does not reach a propagation type dielectric breakdown, but remains a self-recovery type dielectric breakdown in the form of a spot. As a result, disconnection of the back electrode is prevented. Further, the metal thin film 1 as a base of the back electrode 16 is
5, the second insulating layer 14 of the back electrode 16
Adhesion to is maintained.

In the above embodiment, the back electrode 16 is made of Sn,
Although the invention is made of one kind of metal material selected from the group of Zn, Pb, Cd, In, Tl, Bi, and Sb, or an alloy of two or more of the above metal materials, the present invention is not limited to this. , an alloy of at least one metal material from the above group and another metal material other than this group, e.g.
Sn−Ag, Sn−Cu, Pb−Mg, Pb−Te, In−
The back electrode is formed of Mg, In-Te, Bi-Mg, Bi-Te, Sb-Te alloy, or an alloy of Al or Ga with at least one metal material of Sn, In, Mg, Zn, Te, and Ag. You may. At this time, if the composition ratio of the metal material in the above alloy is selected to a predetermined value, the melting point will be lower than that of Al, for example, 600℃ or less, and more preferably 400℃ or less.
It is possible to set the temperature between ℃ and 200℃.

In addition, thin films of low melting point materials generally have low hardness and weak adhesion in the plane direction, so they easily evaporate and scatter (evaporate and scatter) even at low energy due to the pressure and heat of the evaporated substances during discharge. It is possible to prevent the continuation of electrical discharge and to keep the fracture pores small. Therefore, if the melting point is lower than that of Al, a self-healing dielectric breakdown mode is likely to occur, and propagation type dielectric breakdown can be avoided, so that disconnection of the electrode can be prevented. However, if the melting point is too low, it tends to be extremely difficult to form and stably maintain the back electrode.

Effects of the invention According to the thin-film EL panel according to the invention, a metal thin film with strong adhesion to the second insulating layer is interposed as a base for the back electrode made of a metal material or alloy having a lower melting point than Al. Because of this, even if dielectric breakdown occurs between the transparent electrode and the back electrode during panel operation, the breakdown region will not become a propagation type dielectric breakdown, and it will be easy to keep it to a self-recovery type dielectric breakdown. It is possible to prevent wire breakage. Further, the adhesion of the back electrode to the second insulating layer is maintained, and the generation of undesired non-light-emitting portions can be prevented, thereby providing a highly reliable thin film EL panel.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a thin film EL panel according to the present invention, with the left half being a sectional view in the X direction and the right half being a sectional view in the Y direction. Figure 2 is a cross-sectional view showing an example of the structure of a conventional thin-film EL panel. The left half is a cross-sectional view in the X direction, the right half is a cross-sectional view in the Y direction, and the third
The figure is a partial plan view showing the pixel part in a thin-film EL panel, Figure 4 is a partial plan view showing self-healing dielectric breakdown at the back electrode, and Figure 5 is a partial plan view showing propagation type dielectric breakdown at the back electrode. 6 are partial plan views for explaining the adhesion state in the pixel portion of the thin film EL panel. 9...Transparent substrate, 10...Thin film EL element, 1
DESCRIPTION OF SYMBOLS 1... Transparent electrode, 12... First insulating layer, 13...
...Light emitting layer, 14...Second insulating layer, 15...Metal thin film, 16...Back electrode.

Claims (1)

[Claims for Utility Model Registration] A thin film EL in which a striped transparent electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a striped back electrode are sequentially laminated on a transparent substrate.
In the thin film EL panel having the element, a metal thin film with strong adhesion to the second insulating layer is interposed as a base for the back electrode made of a metal material or alloy with a lower melting point than Al. Thin film EL panel.