JPS592157B2 - Thin film EL panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes EL (Electro
The present invention relates to a structure for injecting and sealing a fluid for protecting thin film EL elements, which is an effective technology for EL display panels using thin film EL elements that emit luminescence.

Conventionally, for AC-operated thin film EL elements, a high electric field (about 106 V/(V7!)) is regularly applied to the light-emitting layer in order to improve the maximum breakdown voltage, luminous efficiency, and stability of operation.
0.1 to 2.0 wt% Mn (or Cu, Al, B
A three-layer structure ZnS Mn (or ZnSe:Mn) EL device has been developed, in which a semiconductor light emitting layer made of ZnS, ZnSe, etc. doped with ZnS, ZnSe, etc., is sandwiched between dielectric thin films such as Y203, TiO2, etc., and improvements in various light emitting characteristics have been developed. It has been confirmed.

This thin film EL element emits light with high brightness when an alternating current electric field of several KH2 is applied, and is characterized by long life. FIG. 1 shows the basic structure of a ZnS:Mn thin film EL device as an example of a thin film EL device.

The structure of the thin film EL element will be explained in detail based on FIG.
A first dielectric layer 3 made of l2O3, Si3N4, SiO2, etc. is formed in an overlapping manner by sputtering, electron beam evaporation, or the like.

A ZnS light emitting layer 4 is formed on the first dielectric layer 3 by electron beam evaporation of ZnS:Mn sintered pellets. At this time, the ZnS:Mn sintered pellets used for vapor deposition are pellets in which Mn, which is an active substance, is set at a concentration depending on the purpose. A second dielectric layer 5 made of the same material as the first dielectric layer 3 is provided on the ZnS light emitting layer 4.
are laminated, and a back electrode 6 made of Al or the like is further formed by vapor deposition thereon. The transparent electrode 2 and the back electrode 6 are connected to an AC power source 7, and the thin film EL element is driven. electrode 2,
When an AC voltage is applied between the dielectric layers 3 and 5 on both sides of the ZnS light emitting layer 4, the above AC voltage is induced between the dielectric layers 3 and 5 on both sides of the ZnS light emitting layer 4. Therefore, the electric field generated within the ZnS light emitting layer 4 Electrons that are excited and accelerated by the conductor and have obtained sufficient energy directly excite the Mn emission center, and the excited Mn
When the n-emission center returns to the ground state, it emits yellow light.

That is, when the electrons accelerated by a high electric field excite the electrons of the precipitated Mn atoms that enter the Zn site, which is the luminescence center in the ZnS luminescent layer 4, and fall to the ground state, the electrons emit light in a wide wavelength range with a peak of approximately 5850A. Exhibits strong luminescence. 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 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 a thin-film EL device 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 and interlayer damage. This may lead to peeling, deterioration of device characteristics, etc.

In order to solve the above problem, as shown in Fig. 2, the micro thermal damage area that occurs due to breakdown caused by imperfections peculiar to thin film EL elements, such as pinholes, during energization is expanded. A sealing method has been proposed as an improved technology that prevents and immobilizes the structure, protects moisture in atmospheric environments, has heat dissipation effects, 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. The crossing position corresponds to one picture element on the panel when viewed from a plan view.

To explain based on FIG. 2, transparent electrodes 2 and a first dielectric layer 3 are arranged in parallel at a constant pitch on a glass substrate 1.
, a ZnS light emitting layer 4 is sequentially laminated, and on the ZnS light emitting layer 4 there is a Si3N4 film and an Al2O layer superimposed on the Si3N4 film.
A second dielectric layer 5 consisting of three films is laminated in a two-layer structure, and back electrodes 6 are arranged in parallel with a constant pitch in a direction perpendicular to the transparent electrode 2. 5
A thin film EL element is formed on the top of the thin film EL element.

In order to seal this thin film EL element, a back glass plate 11 is arranged to face the glass substrate 1 with a spacer 10 in between, and each joint of the glass substrate 1, spacer 10, and back glass plate 11 is fixed with an adhesive 12. It is sealed and forms an envelope for the thin film EL device. A thin film EL element is built in 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. The conditions required for the injection fluid 13 are (1) penetration into pinholes, (2) high dielectric strength, and (
3) It is desirable to be a fluid substance that has excellent heat resistance and moisture resistance, (4) does not react with the constituent films of the thin film EL element, and (g) has low vapor pressure and coefficient of thermal expansion, but is particularly permeable to pinholes. It is necessary that the dielectric strength is high to some extent and that it does not react with the films that constitute the thin film EL element. The spacer 10 is provided with one to several micro injection holes 14 for injecting silicone oil or the like. Further, one end of the lead terminal portion 15 of the transparent electrode 2 and the back electrode 6 is extended onto the glass substrate 1 outside the envelope via the joint between the glass substrate 1 and the back glass plate 11, and the drive control circuit ( (not shown). 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.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a cross-sectional view of a thin film EL panel for explaining one embodiment of the present invention.

Transparent electrodes 2 are arranged parallel to each other in a strip shape on a glass substrate 1 with a constant pitch interval? A thin film EL element 16 is constructed.

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 sealed with an adhesive such as photocurable resin (Photobond). Details of the manufacturing process of the back glass plate 17 are shown in FIG. Soda glass with a thickness of 3 mm is used as the back glass plate 17, and the housing portion of the EL element structure is formed into a recess with a depth of about 1 mm by sand etching. 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. Fluid injection and sealing are performed via the operations shown in FIGS. 5A, B and 6 A, B, C.

An envelope composed of a glass substrate 1 and a rear glass plate 17 and a fluid storage tank 20 are placed in a vacuum chamber 21 as shown in FIG. 5A.

At this time, the tip of the injection pipe 19 of the envelope is connected to the fluid storage tank 20.
It is separated from the injection fluid inside. In this state, the pressure inside the vacuum chamber 21 is reduced, and the injected fluid and the gas from the thin film EL element 16 are vented. Next, the fluid storage tank 20 is raised while maintaining the vacuum, and the tip of the injection pipe 19 is inserted into the injection fluid as shown in FIG. 5B. Thereafter, the vacuum chamber 21 is returned to atmospheric pressure, whereby the injection fluid in the fluid storage tank 20 is injected into the envelope via the injection pipe 19. At this time, the temperature inside the vacuum chamber 21 can be raised as necessary to improve the fluidity of the injected fluid.

When the injection operation of the injection fluid is completed, in the state shown in FIG. 5B, the injection pipe 19 and the injection pipe 19 near the envelope joint are crimped and sealed as shown in FIG. 6A.

Thereafter, the injection pipe 19 at the sealed portion is cut as shown in FIG. 6B, and a resin adhesive 22 made of epoxy resin is applied to completely seal the injection pipe 19 at the cut portion. Next, a glass cap 24 having a concave portion 23 in which the sealing portion of the injection pipe 19 can be placed is placed on the rear glass plate 17 of the sealing portion of the injection pipe 19 with adhesive, and as shown in FIG. 6C. As shown, a double sealing structure for the injection fluid is constructed. As the adhesive for bonding the glass cap 24 to the rear glass plate 17, a light hardening adhesive (Photobond) or the like is used. With the above steps, the enclosing operation process is completed.

The glass cap 24 is made of soda glass measuring 20 mm x 20 mm and having a thickness of 3 mm as shown in the side and bottom views of FIGS. 7A and 7B. A concave portion 23 containing the tip and the resin adhesive 22 and having a slight gap for storing leaked injection fluid is processed by sand etching or the like. The double sealing structure of the present invention will be explained below.

Resin adhesives and glass generally have a large difference in coefficient of thermal expansion, and the coefficient of thermal expansion of the epoxy resin (Thor Seal) used for sealing the injection pipe 19 is 5×10.
-37C, which is an extremely large value compared to the coefficient of thermal expansion of glass (Tempax), which is 3.2X10-67C. Therefore, if the epoxo resin is formed thickly to strongly seal the cut portion of the injection pipe 19, the adhesive surface will peel off when a thermal cycle test is performed. To prevent this, if the epoxy resin is made thinner, the injected fluid, Zolicon oil, expands when the temperature rises and breaks the epoxy resin.
This may lead to leakage of silicone oil. The double sealing structure of the present invention is very effective in solving such problems, and after sealing the injection pipe 19 with the resin adhesive 22,
By covering the outer periphery with a glass cap 24 to form an external sealing structure, the reliability of the sealing portion is improved. The concave portion 23 inside the glass cap 24 reliably stores the injection fluid such as silicone oil leaked from the resin adhesive 22 of the injection pipe 19 and prevents it from leaking outside. Glass cap 24 and back glass plate 17
Photobond is a relatively soft resin that adheres
Deformation strain of the bonded portion due to thermal expansion is absorbed by the resin itself. As described above, in the thin film EL panel sealing structure of the present invention, the fluid inlet is sealed with an adhesive and the glass cap is further covered to form a double seal, so that the oil expands due to thermal changes. Even if leaked oil leaks from the injection port, the leaked oil can be reliably stored in the gap inside the glass cap, which has an expansion coefficient similar to that of the rear glass plate, resulting in high sealing reliability and great practical value. Become.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a specific structure of a thin film EL element. FIG. 2 is a diagram illustrating a main part of an example of a conventional thin film EL panel. FIG. 3 is a diagram showing the main part of a thin film EL panel for explaining an embodiment of the present invention. FIG. 4 is a cross-sectional view of the back glass plate used in the thin film EL panel of FIG. 3.
FIGS. 5A, B and 6A, B, and C are manufacturing process diagrams illustrating embodiments of the present invention. FIGS. 7A and 7B are a front view and a bottom view of the glass disk. DESCRIPTION OF SYMBOLS 1...Glass substrate, 16...Thin film EL element, 17...Back glass plate, 18...Injection hole, 19...
・Injection pipe, 20...Fluid storage tank, 21...
...Vacuum chamber, 22...Adhesive, 23...
...Concave portion, 24...Glass cap.

Claims (1)

[Claims] 1. In a thin film EL panel in which a thin film EL element and an insulating protective fluid for the thin film EL element are housed in an envelope consisting of a translucent front substrate and a back plate, the After sealing the opening of the protective fluid injection tube, a glass cap was placed over the injection tube to form a cavity between the injection tube and the glass cap, thereby forming a reservoir for the protective fluid leaked from the injection tube. A thin film EL panel characterized by: