JPS6041436B2 - Thin film EL panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes EL (Electro
This invention relates to the structure of a thin film EL panel, which is an effective technology for EL display panels using thin film EL elements that emit light (luminescence).

Conventionally, for AC-operated thin-film EL devices, a high electric field (approximately 1 volt/skin) is regularly applied to the light-emitting layer to increase the dielectric strength,
0.1 to increase the luminous efficiency and stability of operation.
2. A semiconductor light-emitting layer made of ZnS, ZnSe, etc. doped with t% of Mn (or Cu, Kawa, Br, etc.) is made of Y203,
Three-layer structure Z sandwiched with dielectric thin films such as Ti02
An nS:Mn (or ZnSe:Mn) EL device has been developed, and improvements in various light-emitting characteristics have been confirmed.

This thin-film L element emits high-intensity light upon application of an alternating current electric field of several K ratio, and is characterized by long life. It has also been discovered that this thin film EL element has a hysteresis characteristic in which the luminance of the light emitted by the same applied voltage differs in the process of increasing the applied voltage and in the process of decreasing the applied voltage from the high voltage side. In the process of increasing the voltage applied to the thin film EL element having this hysteresis characteristic, the thin film EL element to which light, electric field, heat, etc. are applied is excited to a state of light emission brightness corresponding to the intensity of the light, electric field, heat, etc.
The so-called memory phenomenon, in which the luminance remains high even after the electric field, heat, etc. are removed and the original state is restored, has opened up a new field of use for display technology. Thin film EL
FIG. 1 shows the basic structure of a ZnS:Mn thin film EL device as an example of the device.

To specifically explain the structure of a thin film EL element using FIG. 1, transparent electrodes 2 such as ln203, Sn02, etc. are placed on a glass substrate 1, and Y203, Tj02, A
A first dielectric layer 3 made of I203, Si3N4, Si02, etc. is formed in an overlapping manner by sputtering, electron beam deposition, or the like.

A ZnS light emitting layer 4 is formed on the first dielectric layer 3 by electron beam evaporation of a ZnS:Mn sintered pellet. At this time, the ZnS:Mn sintered pellet used for vapor deposition is a pellet in which the concentration of Mn, which is an active substance, is set to suit the purpose. A second dielectric layer 5 is laminated on the ZnS light emitting layer 4 by a vapor deposition method or the like, and A
A back electrode 6 made of I or the like is formed by vapor deposition.

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. When an AC voltage is applied between the electrodes 2 and 6, the above AC voltage will be induced between the dielectric layers 3 and 5 on both sides of the ZnS light emitting layer 4, and therefore the electric field generated within the ZnS light emitting layer 4 will cause conduction. Electrons that are excited and accelerated by the band and have obtained sufficient energy directly excite the Mn luminescent center, and when the excited Mn luminescent center returns to the ground state, it emits yellow light.

That is, electrons accelerated by a high electric field excites Mn atoms that have entered the Zn side, which is the luminescent center in the ZnS luminescent layer 4, and
When it falls to the ground state, it emits strong light in a wide wavelength range with a peak of approximately 5850A. The thin film EL element having the structure described above can be used for flat thin display devices that take advantage of the space factor, and for use in computer output display terminals and other various display devices that contain characters, symbols, and still images. It can be used as a means of displaying work images, etc. Thin-film EL panels used as flat panel display devices have a lower operating voltage than conventional cathode ray tubes (CRTs), and are superior in terms of weight and strength compared to plasma display panels (PDPs), which are also flat display devices. It has many advantages over liquid crystals (LCDs), such as a wider operating temperature range and faster response speed. Furthermore, since it can be used as a pure solid matrix type panel, it has a long operating life, and its address accuracy makes it very effective as an input/output display means for computers and the like. However, the dielectric layer of a thin-film EL device contains many pinholes and microcracks that occur during the manufacturing process, and Zn does not pass through these defects.
Moisture or the like enters the S light emitting layer 4, causing heat generation due to EL emission loss and deterioration of device characteristics.

In order to solve the above problems, we have developed a structure in which the back surface of the thin film EL element is coated with an insulating film such as a Si3N4 film or an AI203 film, a structure in which a resin is further coated on the insulating film, or a structure in which it is protected by vacuum sealing. A structure has been developed to

However, forming a protective film by coating each of the thin films 3, 4, and 5 constituting a thin film EL element with an insulating film has the disadvantage that pinholes are easily formed due to the adhesion of microscopic dust and foreign matter, and that the surface area is large. There are problems such as the difficulty in producing a uniform protective film free of defects.

Furthermore, even if a complete protective film is formed, imperfections in a minute area of the thin film EL element will cause breakdown on the light emitting surface when energized, and as a result, the protective film will also be damaged due to thermal damage in the minute area. Moisture in the atmosphere, which is thought to be the main cause of destruction and deterioration of thin-film EL elements, enters the light-emitting layer from the damaged area. In order to realize a protection method using a thin film coating, both the thin film EL element and the protective film must be completely uniform, but the current state of the art in producing thin films is sufficient to ensure that the thin film EL element and the protective film are sufficiently dense and free from various structural defects. EL
Producing the emissive and dielectric layers is extremely difficult and not a practical method.

On the other hand, vacuum sealing has the disadvantages of deterioration of the degree of vacuum due to outgas when thermal breakdown occurs due to breakdown due to imperfections in the thin film EL element mentioned above, and the complexity of the vacuum sealing process. be. In addition, both thin film coating and vacuum sealing have disadvantages such as not being effective in dissipating heat generated due to EL emission loss.As for coagulable resin coating, if the adhesiveness between the resin and thin film EL element is strong, vibrations that occur when electricity is applied, Stress distortion during handling, thermal stress distortion, etc. have an adverse effect such as peeling between the eyebrows of the thin film EL element. On the other hand, if the adhesion is weak, vibration, deflection, and heat generation may cause gaps, making it impossible to prevent moisture from entering the atmosphere. In view of the above drawbacks, we have developed a new technology that prevents and fixes the expansion of minute heat damage areas caused by breakdown caused by pinholes and other imperfections unique to thin film EL elements, and improves moisture protection and heat dissipation in atmospheric environments. effect, more vibration,
A sealing method and a sealing method in which fluid such as oil is injected have been proposed as improved techniques that are effective against deflection.

FIG. 2 shows an example of a thin film EL panel using this fluid injection sealing method.

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 with reference to FIG. 2, a transparent electrode 2, a first exhibiting layer 3, and a ZnS light-emitting layer 4 arranged in parallel on a glass substrate 1 are sequentially laminated, and on the ZnS light-emitting layer 4, a layer of Si3N4 and a layer of Si3N4 are layered. A second dielectric layer 5 consisting of an AI203 film superimposed on a Si3N4 film is laminated in a two-layer structure, and a back electrode 6 is arranged in parallel in a direction orthogonal to the transparent electrode 2. provided on the body layer,
A thin film EL element is constructed.

In order to seal this thin film EL element, a back glass plate 11 is arranged to face the glass substrate 1 with a smoother 10 interposed therebetween, and each joint of the glass substrate 1, the smoother 10, and the 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 L 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. The conditions required for the injection fluid 13 are '1) permeability into pinholes, {2} high dielectric strength, and '
3) It has excellent heat resistance and moisture resistance, does not react with the constituent films of the thin film EL element, and is desirable to be a fluid substance with vapor properties and a small coefficient of thermal expansion, but it is particularly difficult to penetrate into pinholes. It is necessary that the dielectric strength voltage is high to some extent and that it does not react with the films that constitute the thin film EL element. As the substrate 10, an insulating plastic sheet of Teflon or polyimide resin having a thickness of 0.5 mm is used, but silicone rubber, glass, etc. may also be used. One to several micro injection holes 14 for injection of silicone oil, etc. are provided around the baser 0. The injection hole 14 may be formed in the back glass plate 11. Epoxy resin or the like is used as the adhesive 12, and the adhesive 12 is attached to the joints of the outer case except for the recessed holes 14. 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). When an alternating current voltage is applied through the transparent electrode 2 and the back electrode 6, a light emitting display is performed on a pixel-by-pixel basis from the front surface of the glass substrate 1. The thin film EL panel with the above structure has the effect of preventing atmospheric moisture from entering the element.
It has an excellent effect of dramatically improving the reliability and lifespan of devices.

However, even with the above structure, the effect of preventing moisture intrusion is not perfect, and there is a problem that the injected fluid itself, such as sealing oil, contains moisture, and this moisture enters the thin film EL element and causes deterioration of the element characteristics. remains. It is technically difficult to completely remove moisture contained in the injection fluid before injection, and even after performing a gas venting operation, some moisture remains in the injection fluid. In view of the above-mentioned problems, the present invention allows moisture contained in the injection fluid for protecting thin-film EL elements to be adsorbed to an absorber, thereby completely protecting the thin-film EL element from moisture, establishing further reliability, and absorbing water. The purpose of the present invention is to provide a new and useful thin film EL panel that can prevent body sedimentation and suppress moisture intrusion even during long-term use. Hereinafter, the present invention will be explained in detail according to embodiments with reference to the drawings.

FIG. 3 is a cross-sectional configuration diagram of essential parts of a thin film EL panel showing one embodiment of the present invention.

The same reference numerals as in FIG. 2 indicate the same contents, and the explanation will be omitted. As in FIG. 2, a thin film EL element is housed in an envelope, and filled with injection fluid 13 such as silicone oil or vacuum grease.

The injection fluid 13 filled in the outer vessel is a mixture of silicone oil, etc., which has been sufficiently degassed in advance, and a moisture absorber made of fine particle silica gel, etc. with a particle size of 3 to 75 mounds, and the amount of silica gel is silicone oil 10cc
The suitable amount range is 0.5 to 52. Since silicone oil and the like are nonionic, silica gel can adsorb ionic water without being hindered by silicone oil and the like. The silica gel mixed in the injection fluid 13 at a high concentration is not dissolved in the injection fluid, and if the use is continued in a stationary state for a long time, the silica gel will become unevenly distributed due to precipitation. Silica gel removes moisture contained in the injection fluid 13, and therefore, if it is unevenly distributed, moisture absorption from the injection fluid 13 will be incomplete. In order to prevent uneven distribution of the silica gel, a stopper plate 16 having a large number of through holes 17 is provided in the gap formed between the back glass plate 11 and the thin film EL element. Figure 4 A, B
2A and 2B are plan views showing various shapes of this stopper plate 16. FIG. The gap size between the glass substrate 1 and the back glass plate 11 is usually 0.5 to 1. By inserting the stopper plate 16, the gap between the back glass plate 11 and the thin film EL element is partially set to the 0 to 0.3 side, and the movement of the silica gel is prevented in this area. The portion of the through hole 17 becomes a pool of silica gel whose movement is prevented. Injecting fluid into the envelope is as follows.

That is, after bonding the outer vessel, both were flooded from 100:00 to 20,000, and after being degassed under a reduced pressure of 10 orr or less, the outer vessel and the fluid storage tank in which the injection fluid was stored were placed in a vacuum chamber. to be installed. An injection pipe serving as a fluid suction passage is attached to the injection hole 14 of the envelope, and the tip of the injection pipe is separated from the injection fluid in the fluid storage tank. In this state, the pressure inside the vacuum chamber is reduced to vent the injected fluid and the thin film EL element. Next, the fluid storage tank is raised while maintaining the vacuum, and the tip of the injection pipe is inserted into the injection fluid. Thereafter, the vacuum chamber is returned to atmospheric pressure, and as a result, the injection fluid in the fluid storage tank 20 is injected into the outer container through the injection pipe.
At this time, the temperature inside the vacuum chamber can be raised as necessary to improve the fluidity of the injected fluid.

When the injection operation of the injection fluid is completed, the injection pipe and the injection pipe near the envelope joint are crimped and temporarily sealed.

Thereafter, the injection pipe in the temporary sealing section is cut, and the cut section is sealed and reinforced with epoxy resin, completing the enclosing operation process.
In the above process, when injecting fluid using the pressure difference between the inside and outside of the panel, the back glass plate 11 may be distorted inward due to the pressure difference, which may cause damage to the thin film EL element. do.

However, by using an elastic material for the stopper plate 16, it can act as a cushion against distortion and prevent damage to the thin film EL element. Suitable materials for this purpose include silicone rubber, synthetic resin such as polyurethane, or silk-like fibers. As explained in detail above, according to the present invention, the moisture in the atmosphere is removed from the thin film EL panel by the thin film EL element protection fluid injected into the thin film EL panel.
This not only prevents moisture from entering the thin-film EL element, but also prevents moisture from entering the thin-film EL element because the moisture contained in the fluid itself is adsorbed by the moisture absorber in the fluid and the moisture absorber does not become unevenly distributed even during long-term use. The intrusion prevention effect becomes even more remarkable, and the display life of the thin-film EL panel is dramatically improved.

Further, since the stopper plate is elastic and is provided between the back plate and the thin-film EL element, there is an advantage that the thin-film L element is prevented from being damaged when the protective fluid is injected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a specific structure of a thin film EL element. FIG. 2 is a cross-sectional configuration diagram of essential parts showing an example of a conventional thin film EL panel. FIG. 3 is a cross-sectional configuration diagram of main parts showing one embodiment of the present invention. FIGS. 4A and 4B are plan views showing the structure of the stopper plate. 1...Glass base, 10...
・Subesa, 11... Rear glass plate, 13...
... Injection fluid, 16 ... Stopper plate. Younger brother's Figure 2 Figure 3 Building the Buddha Figure 4 '8

Claims (1)

[Claims] 1. In a thin-film EL panel in which a thin-film EL element is built in an envelope consisting of a translucent front substrate and a back plate, and display is performed via the translucent front substrate, In addition to injecting a protective fluid containing a moisture absorber, a porous and elastic stopper plate is provided between the back plate and the thin film EL element to prevent uneven distribution of the moisture absorber. Characteristic thin film EL panel.