JPH0524155Y2 - - Google Patents

Description

[Detailed explanation of the invention] (Industrial application field) This invention is an electroluminescent panel,
In particular, it relates to the thickness of the back electrode of an electroluminescent panel having an AC type thin film double insulation structure.

(Prior Art) Research and development have been conducted on electroluminescent panels (hereinafter simply referred to as EL panels) having an AC type thin film double insulation structure suitable for application to large display devices. For example, it is disclosed in the following documents.

Literature: IEICE Technical Report, 82 (68) CPM82-10, P15~
17 (June 25, 1982) IEICE Literature: Japan Society for the Promotion of Science, 125th Committee on Photoelectric Interconversion, 109th Material No. 416, P7 (February 24, 1982)
(Japanese) Literature: Japan Society for the Promotion of Science, 125th Committee on Photoelectric Interconversion, 109th Meeting Material No. 418, P18 (February 1982)
24th) Literature: SID 81 Digest (SID 81
DIGEST), P22-23 Literature: SID 83 Digest (SID 83
DIGEST), P141-142 Literature: Proceedings of the SID, 24/2,
P120-121.

Before explaining the EL panel of this invention, we will explain the conventional EL panel.
I will explain about the EL panel.

FIG. 4 is a cross-sectional view of the main part schematically showing the structure of a typical light emitting element of such a conventional EL panel (hatching etc. indicating the cross section are omitted).
It is. In FIG. 4, 10 is a glass substrate, 1
2 is provided on this glass substrate 10, for example.
A transparent electrode made of ITO. Reference numeral 14 denotes a first insulating film provided on the transparent electrode 12, for example, a SiO ₂ (silicon dioxide) film with a thickness of 1000 Å from the transparent electrode 12 side and a Ta ₂ O ₅ (tantalum pentoxide) film with a thickness of 3000 Å on the upper side. ) has a double membrane structure with a membrane. A light-emitting film 16 is provided on the first insulating film 14, and for example, the light-emitting film 16 is made of ZnS:Mn (zinc manganese sulfide) with a thickness of 6000 Å.
A second insulating film 18 made of the same material and having the same structure as the first insulating film 14 is provided on the first insulating film 14.
It has a structure in which a back electrode 20 made of A (aluminum) is provided on the upper side of the electrode 8 .

The transparent electrode 12 of the EL panel having such a structure,
When an AC voltage is continuously applied between the back electrode 20 and the back electrode 20, the light emitting film 16 starts emitting light. This light emission from the EL panel can be visually observed from the direction indicated by arrow 22 in the figure.

In the EL panel having this structure, at least one of the first insulating film 14, the light-emitting film 16, and the second insulating film 18 may be partially peeled off for some reason, or dust may be attached to it. If such a defect exists, it will break through the first insulating film 14, the light-emitting film 16, and the second insulating film 18 when an AC voltage is applied, and a hole 24 with a diameter _d1 of about 30 to 60 μm will open, and the ITO transparent The aluminum back electrode 20, which has a lower melting point than the electrode 12, also has a hole 26 with a diameter _d2 . The appearance of such fractured holes 24 and 26 is schematically shown in FIG. 5 as a cross-sectional view of the main part (hatching etc. indicating the cross section are omitted).

By the way, the EL structure disclosed in each document
When the thickness ratio (t/T) between the back electrode thickness t and the lamination thickness T was investigated for the panel, the results shown in the following table were obtained.

Table Literature Name t/T Literature 3000Å/14500Å=0.21 Literature 500Å/15000Å=0.03 Literature 200nm/1950nm=0.10 Literature 1000Å/13000Å=0.08 Literature 0.1μm/1.1μm =0.09 Literature 1500Å/14000Å=0. 11 It can be understood from this table As such, the thickness t of the back electrode 20 of the EL panel disclosed in these documents, the lamination thickness T, and the ratio t/T are in the range of t/T=0.03 to 0.21.

For each document related to the thickness shown in this table,
When the sizes of the fracture holes 24 and 26 in the EL panel were investigated, it was found that the fracture holes 26, which had a hole diameter _d2 larger than the hole diameter _d1 , were all generated in the back electrode 20.

The reason for the size relationship of the breakdown films 24 and 26 is that the first insulating film 14, the light-emitting film 16, and the second insulating film 18 are heated and vaporized by instantaneous discharge at the time of breakdown, and at the same time, the back electrode 20 It is presumed that the hole diameter d ₂ is larger than the hole diameter d ₁ due to heat generation and vaporization of the central portion, and the surrounding melted portion expanding due to surface tension.

Figure 6 shows the EL with these fracture holes 24 and 26.
FIG. 3 is a schematic perspective view of main parts for explaining the operation of the panel. As can be understood from this figure, when an AC voltage is applied between the transparent electrode 12 and the back electrode 20, the intersection of these electrodes will emit light if there is no defect, but the broken hole 24 as described above will emit light. If a large fracture hole 26 occurs, the back electrode 20, which is normally formed in a straight line, will be broken in the width direction, and as a result, the EL panel cannot display a matrix.

(Problem to be solved by the invention) As described above, in the EL panel of the conventional structure, the film thickness ratio t/ T is t/T=0.03~
If it is within the range of 0.21, the diameter d ₂ of the hole created in the back electrode is larger than the diameter d ₁ of the hole created in the lamination, resulting in disconnection of the back electrode, which causes the EL panel to fail. There was a problem in that each pixel in the display could not be made to emit light reliably, and therefore a high-definition matrix display could not be performed.

This invention was created in view of the problems of the conventional methods mentioned above, and therefore, the purpose of this invention is to improve the hole diameter.
This is an alternating current that solves the problem of the hole diameter _d2 being larger than _d1 , and has a structure that allows high-definition matrix display without causing disconnection in the back electrode and without causing display brightness unevenness. Our objective is to provide an EL panel with a thin film double insulation structure.

(Means for solving the problem) In order to achieve this purpose, this invention
According to the structure of the EL panel, the back electrode is made of aluminum, the thickness of this back electrode is t, and the laminated thickness of the first insulating film, the light emitting film, and the second insulating film is T.
In this case, the film thickness ratio t/T is set to t/T≧0.5.

(Function) The inventor of this device created an EL panel structure similar to the structure shown in FIG. By setting the laminated thickness T of the insulating film 18 to various values, the film thickness ratio t/T and the breakdown holes 24 and 26 are determined.
An experiment was conducted to investigate the relationship between the diameter ratio d ₂ /d ₁ .

Figure 2 is a diagram to explain the results of this experiment.
The horizontal axis shows the film thickness ratio t/T, and the vertical axis shows the diameter ratio d ₂ /d ₁ .

As can be understood from this experimental result, when the film thickness ratio is smaller than about 0.5, the diameter ratio becomes larger than 1, and when the film thickness ratio is around 0.5, the diameter ratio becomes 1. It can be seen that as the thickness ratio becomes larger than 0.5, the diameter ratio becomes smaller than 1.

Therefore, by setting the film thickness ratio t/T to be t/T≧0.5, the diameter _d2 of a breakdown hole that may occur in the back electrode due to the application of an AC voltage can be made smaller than the diameter _d1 of a breakdown hole that may occur in the stack of the first insulating film, the light-emitting film, and the second insulating film.
For this reason, in the case of a high-definition EL panel having about 10 rear electrodes per mm, even if a destruction hole is formed in the rear electrode made of aluminum, which has a low melting point, there is no risk of a complete disconnection.
Since aluminum is a low resistance material, the difference in resistance between both ends of the rear electrode is extremely small, and therefore there is no risk of a voltage drop at the ends of the rear electrode causing uneven display brightness when a drive voltage is applied to the rear electrode. In addition, since the rear electrode is made of only one material, aluminum, the process of forming the rear electrode is simple.

(Example) Examples of the EL panel of this invention will be described below with reference to the drawings. Note that the drawings are shown schematically to the extent that this invention can be understood, and therefore, the dimensions, shapes, materials, and arrangement relationships of each component are not limited to the explanations of the illustrated examples below. . Further, in these figures, components that are substantially the same as those shown in FIGS. 4 to 6 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 is a cross-sectional view of a main part of the EL panel structure for explaining the state of the fracture holes that occur when an alternating current voltage is applied to the EL panel structure of this invention. Note that hatching and the like indicating the cross section are omitted.

In the EL panel shown in this example, as already explained, when the thickness of the back electrode 20 made of aluminum is t, and the laminated thickness of the first insulating film 14, the light emitting film 16, and the second insulating film 18 is T, The film thickness ratio t/T is set to t/T≧0.5, and the thickness t of the back electrode relative to the lamination thickness T is made larger than the conventional thickness.

An AC voltage is continuously applied between the transparent electrode 12 and the back electrode 20 of the EL panel having such a structure to cause the EL panel to emit light. At this time, if there are various defects as already explained, the transparent electrode 12 and the back electrode 2, which are formed in a straight line,
The fracture hole 24 is located at the intersection that is almost perpendicular to 0.
and 26 occur. In this case, the diameter d ₂ of the fracture hole 26 of the back electrode 20 is smaller than the diameter d ₁ of the fracture hole 24, and the vicinity of the fracture hole 26 of the back electrode 20 is raised. This is because the first insulating film 14, the light-emitting film 16, and the second insulating film 18 are heated and vaporized by an instantaneous discharge at the time of breakdown, and at the same time, the back electrode 20 also generates heat and its center is vaporized. Since the thickness of the back electrode 20 is thick, the amount of vaporization is large, and the surrounding melted portion is small, so the melted portion of the back electrode 20 is pushed up by the gas pressure caused by the vaporization of the first insulating film 14, the light emitting film 16, and the second insulating film 18. Therefore, it is presumed that the area near the fracture hole swells.

However, as shown in the main part perspective view of FIG. 3, although the fracture hole 24 (indicated by a dotted line) is large, the diameter d ₂ of this fracture hole 26 (indicated by a solid line) Since the width of the broken hole 26 is smaller than the maximum width at the intersection, there is no fear that the broken hole 26 will break the straight back electrode 20 in the width direction. Therefore,
For example, even in high-definition EL matrix display panels with about 10 lines per 1 mm or more in some cases,
This panel can be driven with high reliability.

In the above-mentioned embodiments, the size of the fractured hole was explained in terms of the diameter, but if the shape of the fractured hole is not circular, this diameter means the maximum width of the fractured hole.

Furthermore, in the above-mentioned embodiments, the constituent parts of the EL panel were explained as examples made of specific materials, but this invention is not limited to these materials in any way, but may be applied to other materials used in the construction of the EL panel. It can also be applied when formed from general materials.

(Effects of the invention) As is clear from the above explanation, according to the EL panel of this invention, the film thickness ratio t/T is set in a new region such as t/T≧0.5, which is different from the conventional one, so that the back The size of the fracture hole in the electrode is the first insulating film,
The holes are smaller than those formed in the light-emitting film and the second insulating film. Therefore, even in a high-definition EL panel with about 10 lines/1 mm or less, the back electrode made of aluminum, which has a low melting point, will prevent the holes from breaking. There is no risk of disconnection. In addition, since aluminum is a low resistance material, the difference in resistance between both ends of the back electrode is extremely small. Therefore, when a driving voltage is applied to the back electrode, uneven display brightness may occur at the end of the back electrode. There is no risk of significant voltage drop. Therefore, the EL panel of this invention can perform a good matrix display. Furthermore, since the back electrode is made of one type of material, aluminum, the process for forming the back electrode is simple.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the main part in a state where a fracture hole has occurred to explain an embodiment of the EL panel of this invention, and Figure 2 shows the thickness of the back electrode to explain the EL panel of this invention. An explanatory diagram showing the relationship between the film thickness ratio of the first insulating film, the light-emitting film, and the second insulating film and the diameter ratio of the fracture hole, and Figure 3 is a diagram for explaining the operation of the EL panel of this invention. A perspective view of the main part, Figure 4 is an EL panel used to explain this invention and the conventional EL panel.
Figure 5 is a cross-sectional view of the main part of a light emitting element, Figure 5 is a cross-sectional view of the main part of an EL panel to explain the state of the conventional fracture hole, and Figure 6 is a perspective view of the main part to explain the operation of the conventional EL panel. be. 10...Glass substrate, 12...Transparent electrode, 14
...First insulating film, 16... Luminescent film, 18... Second insulating film, 20... Back electrode, 22... Viewing direction,
24, 26... Destruction hole.

Claims (1)

[Claims for Utility Model Registration] A light-emitting film, first and second insulating films provided to sandwich the light-emitting film from both sides, a transparent electrode provided on the outside of the first insulating film, and a second insulating film. In an electroluminescent panel having an AC type thin film double insulation structure including a back electrode provided on the outside of the membrane, the back electrode is made of aluminum,
and an electroluminescent panel characterized in that t/T≧0.5, where t is the thickness of the back electrode and T is the laminated thickness of the first insulating film, the light emitting film, and the second insulating film. .