JPH0129319B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention provides an EL
(Electro Luminescence) Thin film EL that emits light
The present invention relates to a sealing structure for a fluid for protecting thin film EL elements, which is an effective technique for EL display panels using such elements.

<Prior art> Conventionally, for AC-operated thin-film EL elements, a high electric field (about 10 ⁶ V/cm) was regularly applied to the light-emitting layer to improve dielectric strength, luminous efficiency, stability of operation, etc. 0.1-2.0wt% Mn (or Cu,
A three-layer structure ZnS:Mn (or ZnSe:Mn) in which a semiconductor light-emitting layer such as ZuS or ZnSe doped with Al, Br, etc. is sandwiched with a dielectric thin film such as Y ₂ O ₂ or TiO ₂
EL devices have been developed, and improvements in various light-emitting characteristics have been confirmed. This thin film EL element emits high-intensity light when an alternating current electric field of several KHz is applied, and has a long lifespan.

As an example of a thin film EL device, the basic structure of a Zn:Mn thin film EL device is shown in FIG.

Based on FIG. 1, the structure of the thin film EL element will be explained in detail. In ₂ O ₃ and SnO ₂ are placed on a glass substrate 1.
A transparent electrode 2 such as Y ₂ O ₃ is further layered on top of the transparent electrode 2 .
A first dielectric layer 3 made of TiO ₂ , Al ₂ O ₃ , Si ₃ N ₄ , SiO ₂ or the like is formed in an overlapping manner by sputtering or electron beam evaporation. A ZnS light emitting layer 4 is formed on the first dielectric layer 3 by electron beam evaporation of Zn:Mn sintered pellets. At this time, the Zn:Mn sintered pellets used for vapor deposition are pellets in which the concentration of Mn, which is an active substance, is set to suit the purpose. A second dielectric layer 5 made of the same material as the first dielectric layer 3 is laminated on the ZnS light emitting layer 4, and a back electrode 6 made of Al or the like is further deposited thereon. The transparent electrode 2 and the back electrode 6 are connected to an AC power source 7, and the thin film
The EL element is driven.

When an AC voltage is applied between the electrodes 2 and 6, the above AC voltage is induced between the dielectric layers 3 and 5 on both sides of the ZnS light emitting layer 4.
Electrons that are excited and accelerated in a conductor by the electric field generated within the conductor and gain sufficient energy directly
The Mn luminescent center is excited, and when the excited Mn luminescent center returns to the ground state, it emits yellow light. In other words, the Mn
When an atom's electrons are excited and fall to the ground state, approximately
It emits strong light in a wide wavelength range with a peak of 5850 Å.

The thin film EL element having the structure described above can be used as a flat thin display device that takes advantage of the space factor, and can be used to display characters, symbols, still images, etc. It can be used as a means of displaying moving images, etc., and is very effective.

However, the dielectric layer of the thin-film EL element contains many pinholes and microcracks generated during the manufacturing process, and moisture, etc. enters the ZnS light emitting layer 4 through these defects, resulting in heat generation due to EL emission loss, This may lead to delamination, deterioration of device characteristics, etc.

In order to solve the above problem, as shown in Fig. 2, we have developed a method to solve the problem of imperfections peculiar to thin-film EL elements, that is, microscopic thermal damage areas caused by breakdown caused by pinholes etc. during energization. A sealing method has been proposed as an improved technology that prevents and immobilizes the expansion, protects against moisture in atmospheric environments, has a heat dissipation effect, and is also effective against vibration and deflection.

This thin film EL panel adopts a matrix electrode structure in which the transparent electrode 2 and the back electrode 6 shown in FIG. Visually, the position where they intersect corresponds to one pixel on the panel.

To explain based on FIG. 2, transparent electrodes 2 arranged in parallel on a glass substrate 1 at a constant pitch,
A first dielectric layer 3 and a ZnS light emitting layer 4 are sequentially laminated, and on the ZnS light emitting layer 4 there is a second layer consisting of _four Si ₃ N layers and an Al ₂ O ₃ film superimposed on the Si ₃ N ₄ film. A dielectric layer 5 is laminated in a two-layer structure, and back electrodes 6 are arranged in parallel at a constant pitch in a direction perpendicular to the transparent electrode 2, and are provided on the second dielectric layer 5.
A thin film EL element is constructed. In order to seal this thin film EL element, a back glass plate 11 is placed facing the glass substrate 1 with a spacer 10 interposed therebetween, and each joint of the glass substrate 1, spacer 10, and back glass plate 11 is fixed and sealed with an adhesive 12. and constitutes an envelope for the thin film EL element. A thin film EL element is built into the envelope, and an injection fluid 13 for protecting the thin film EL element, such as silicone oil or vacuum grease, is filled and sealed. Injection fluid 13
The conditions required for this are (1) penetration into pinholes, (2) high dielectric strength, (3) excellent heat resistance and moisture resistance, and (4) no reaction with the films that make up the thin film EL element. , (5) It is desirable that the material be a fluid substance with a low vapor pressure and a low coefficient of thermal expansion, but it is particularly required that it has permeability into pinholes, has a somewhat high dielectric strength voltage, and does not react with the films constituting the thin film EL element. The spacer 10 has one micro injection hole 14 for injecting silicone oil, etc.
One to several pieces are provided. Further, the lead terminal portions 15 of the transparent electrode 2 and the back electrode 6 are connected to the glass substrate 1.
One end thereof extends onto the glass substrate 1 outside the envelope via the joint between the rear glass plate 11 and the rear glass plate 11, and is electrically connected to a drive control circuit (not shown).

(Object of the Invention) An object of the present invention is to provide an improved technique regarding a fluid sealing structure in a thin film EL panel filled with the above fluid for protecting thin film EL elements. More specifically, the purpose is to reduce stress concentration at the corners of the back plate caused by heat, prevent peeling of the corners, and increase the reliability of the sealing structure of thin-film EL panels.

(Structure of the Invention) The present invention is provided in an envelope formed by sealing with an adhesive the joint portion between a light-transmitting front substrate and a back plate having a different coefficient of thermal expansion from the front substrate and having a concave molded inner surface. , in a thin-film EL panel containing a thin-film EL element configured on the front substrate and an insulating protective fluid for the thin-film EL element, a straight line at a joint between the front substrate and the back plate is provided at a corner of the back plate; The outer side of the back plate or the inner surface facing the recess molding area is chamfered so as to guarantee the resin bonding width X of the portion.

(Example) Hereinafter, one example of the present invention will be described in detail while comparing it with a conventional example.

FIGS. 3 and 4 are a cross-sectional view and a plan view of a conventional thin film EL panel. Transparent electrodes 2 are arranged parallel to each other in the form of strips on a glass substrate 1 at constant pitch intervals, thereby forming a thin film EL element 16. A dish-shaped rear glass plate 17 is superimposed on the glass substrate 1 so as to accommodate the thin film EL element 16, and the thin film EL element is housed in the internal gap thereof. The joint between the glass substrate 1 and the rear glass plate 17 is made of photocurable resin,
It is sealed with an adhesive such as epoxy resin. Soda glass, borosilicate glass, or the like is used as the back glass plate 17, and the housing portion of the EL element structure is recessed to a depth of about 1 mm by sand etching or the like. An injection hole 18 for injecting a fluid is formed at one corner of the concave molding area, into which a hollow injection pipe 19 is inserted. The injection pipe 19 is made of metal and is fixed to the injection hole 18 with adhesive. A thin film is formed in the surrounding air from this injection pipe 19.
The injection fluid for protecting the EL element is sealed and sealed with a glass cap 22.

By the way, when bonding the two glass plates 1 and 17, by making the coefficients of thermal expansion exactly the same,
Stress dependent problems are alleviated. However, when it is necessary to bond different types of glass (having different coefficients of thermal expansion) in terms of cost and physical properties, stress problems are an unavoidable fact. FIG. 5A conceptually shows the conventional configuration shown in FIGS. 3 and 4.
In this case, the adhesive width of the corner part 31 is
Letting the adhesive width of 2 be X, it will be √2X, and the adhesive width will be the longest. Further, due to the structure, it is expected that stress will be concentrated on the corner portion 31, and that an unreasonable force will be applied particularly to the tip portion of the corner. This is clearly demonstrated by the occurrence of peeling from the tip of the corner during the thermal cycle test, which is one of the reliability tests.

On the other hand, FIGS. 5B, C, and D show the structure of the present invention, in which the corner part 31 of the rear glass 17 is chamfered on the outside or on the outside and inside while ensuring the adhesive width X of the straight part of the resin adhesive part 20. This is the only difference from the conventional example shown in FIGS. 3 and 4. Figure 5B shows the longest part of the corner part 31 being equal to the X width of the straight part 32, and Figure 5C
In the fifth example, the grooved corner of the concave molded part of the rear glass plate 17 is chamfered, and the outside of the corner is chamfered while ensuring the same width as the straight part 32.
Figure D is curved and chamfered like Figure 5C.

In this way, the four corners 3 of the back plate 17
1. By chamfering the straight portion 32 to ensure the resin bonding width X, stress concentration at the corner portion due to heat is reduced, and the reliability of thin film EL element sealing is increased. .

(Effect of the invention) As is clear from the above explanation, the thin film of this invention
The sealing structure of the EL panel is such that the corner portion of the back plate is formed with the concave molding on the outside of the back plate or the outer side of the back plate and the recessed molding so as to guarantee the resin bonding width The simple configuration of chamfering the inner side facing the area can reduce the concentrated stress at the corners due to heat and increase the reliability of thin-film EL panels, which has extremely high practical value. It is what it is.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the specific structure of a thin film EL element, Fig. 2 is a block diagram of main parts showing an example of a conventional thin film EL panel, and Fig. 3 is a thin film EL element used to explain an embodiment of the present invention. Figure 4 is a plan view of the thin film EL panel in Figure 3, Figure 5A is a diagram of the main parts of the panel,
FIG. B, FIG. 5C, and FIG. 5D are plan views illustrating embodiments of the present invention, respectively. 1... Glass substrate, 16... Thin film EL element, 1
7... Rear glass plate, 18... Injection hole, 19...
Injection pipe, 20...resin bonded part, 23...recessed part, 22...glass cap, 31...corner part, 32...straight line part.

Claims (1)

[Scope of Claims] 1. The above-mentioned material is placed in an envelope formed by sealing with an adhesive the joint portion between a light-transmitting front substrate and a back plate having a different thermal expansion coefficient from that of the front substrate and having a concave molded inner surface. A thin film EL element constructed on a front substrate and a thin film EL containing an insulating protective fluid for the thin film EL element.
In the panel, a corner portion of the back plate is provided with an outer side of the back plate, or an inner side facing the outside and the concave molded area, so as to ensure a resin bonding width X of the straight part at the joint between the front board and the back plate. A sealing structure for a thin-film EL panel characterized by a chamfered surface.