JPS5855634B2 - Thin film EL panel - Google Patents

Description

[Detailed description of the invention] The present invention uses EL (Electr) by applying an alternating electric field.

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.

Conventionally, for AC-operated thin-film EL elements, a high electric field (about 106 V/crIL) is regularly applied to the light-emitting layer to improve dielectric strength, luminous efficiency, operational stability, etc.
0.1 to 2.0 wt% Mn (or Cu s A
ZnS 5ZnSe doped with l*Br, etc.)
Three-layer structure ZnS:Mn (or Zn5
e:Mn) EL devices have been developed, and improvements in light emitting properties have been confirmed.

This thin film EL element emits light with high brightness when an alternating current electric field of several KHz is applied, and is characterized by long life.

It was also discovered that the light emission of 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 voltage from the high voltage side. In the process of increasing the applied voltage to a thin film EL element having hysteresis characteristics, when light, electric field, heat, etc. are applied, the thin film EL element
The element is excited to a state of luminescence brightness corresponding to its intensity,
The so-called memory phenomenon, in which the luminance remains high even when light, electric field, heat, etc. are removed and the original state is restored, has opened up a new field of application for display technology.

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 Al2O3, Si3N4, 5i02, 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, which is obtained by performing ZnS:Mnn sintered pellet lamination beam evaporation.

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 laminated on the ZnS light emitting layer 4, and an AI layer is further layered thereon.
A back electrode 6 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 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 in the ZnS light emitting layer 4 excites the electrons into the conductor, accelerates them, and obtains sufficient energy. , directly excites the Mn luminescent center, and emits yellow light when the excited Mn luminescent center returns to the ground state.

In other words, when the electrons accelerated by a high electric field excite the electrons of the Mn atoms that have entered the Zn site, which is the luminescence center in the ZnS luminescent layer 4, and fall to the ground state, a strong emission occurs in a wide wavelength range with a peak of approximately 5850A. Exhibits 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, moving images, etc. in computer output display terminal equipment and various other display devices that contain characters and figures. It can be used as a means of displaying images, etc.

Thin-film EL panels as flat flat 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 (FDPs), which are also flat display devices. It has a wider operating temperature range than liquid crystal display (LCD).
It has many advantages such as fast 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 and ε are very effective as 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 moisture, etc. enters the ZnS light emitting layer 4 through these defects, causing heat generation due to EL emission loss and device characteristics. lead to deterioration.

In order to solve the above problem, as shown in FIG. 2, a structure is constructed in which the back surface of the thin film EL element (the side opposite to the glass substrate 10) is coated with an insulating film 8 such as a Si3N4 film or an Al2O3 film to protect it. A structure is implemented in which the insulating film 8 is further coated with a resin 9 for protection.

Furthermore, a vacuum-sealed structure has been proposed.

In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted.

However, the formation of a protective film by coating the insulating film 8 on each of the thin films 3 and 4° 5 constituting the thin film EL element is prone to pinholes and the like due to the adhesion of microscopic dust and foreign matter. As the area increases, there are drawbacks such as 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 electricity is applied, 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, leaks from the damaged area.
Penetrates into the luminescent layer.

In order to realize the protection method by thin film coating,
Both thin-film EL elements and protective films are required to be completely uniform, but it is extremely difficult to produce sufficiently dense EL light-emitting layers and dielectric layers that do not contain various structural defects using thin-film production technology at the current stage. It is difficult and not a realistic 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 drawbacks such as inability to dissipate heat generated due to EL emission loss.

Regarding the coagulable resin coating, if the adhesion between the resin and the thin-film EL element is strong, vibrations generated during energization, stress-strain during handling, thermal stress-strain, etc. will have an adverse effect such as delamination of the thin-film EL element.

On the other hand, if the adhesion is weak, a gap is created due to vibration, deflection, and heat generation, 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. A sealing method in which oil or other fluid is injected has been proposed as a sealing method that is effective in improving the effectiveness, vibration, and deflection.

FIG. 3 shows an example of a thin film EL panel using this fluid injection side stop 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 based on FIG. 3, transparent electrodes 2, a first dielectric layer 3, and a ZnS light emitting layer 4 are arranged in parallel on a glass substrate 1.
are sequentially laminated, and on the ZnS light emitting layer 4, a second dielectric layer 5 consisting of a Si3N film and an Al2O3 film superimposed on the Si3N4 film is laminated in a two-layer structure, and further perpendicular to the transparent electrode 2. The back electrodes 6 arranged in parallel in the direction of
A thin film EL element is formed by providing the dielectric layer on the dielectric layer.

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, the spacer 10, and the back glass plate 11 is bonded with an adhesive 12. It is fixedly sealed and constitutes an envelope for the thin film EL element.

Note that the spacer 10 can also be eliminated by forming the back glass plate 11 in a dish shape.

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) permeability into pinholes, (2) high dielectric strength, (3) excellent heat resistance and moisture resistance, and (4) thin film EL element constituent film. (5) It is desirable that it is a fluid substance that is vaporous and has a small coefficient of thermal expansion, but it should be particularly permeable to pinholes and have a somewhat high dielectric strength voltage, and it should not react with the films that constitute the thin film EL element. It takes.

As the spacer 10, an insulating plastic sheet such as Teflon or polyimide resin having a thickness of 0.511 nm is used, but other materials such as silicone rubber and glass may also be used.

The spacer 10 is provided with one to several micro injection holes 14 for injection of silicone oil, etc., around the spacer 10 .

The injection hole 14 may be formed in the back glass plate 11.

Epoxy resin or the like is used as the adhesive 12,
Adhesive 12 is applied to the joints of the envelope except for injection 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.

Since the thin film EL panel is translucent, it is necessary to provide a background color for the light emission when displaying light emission.

Conventionally, in order to obtain this background color, a structure in which black vinyl or the like is stretched over the back glass plate 11 or a structure in which a colored paint is applied to the back glass plate 11 has been used.

The present invention includes a dye in the protective injection fluid 13 of a thin film EL panel, and forms a background color by coloring the protective injection fluid 13 or by inserting a colored plate into the envelope together with the injection fluid. The object of the present invention is to provide a new and useful thin film EL panel with improved contrast.

The present invention will now be described in detail according to embodiments and with reference to the drawings.

FIG. 4 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. 3 indicate the same contents, and the explanation will be omitted.

As in FIG. 3, a thin film EL element is housed in an envelope, and injection fluid 13' is made of silicone oil containing a coloring dye.
is filled and enclosed.

On the inner surface of the rear glass plate 11 constituting the envelope, a sheet-like moisture absorber made of aluminum foil coated with silica gel is attached in order to adsorb moisture contained in the injected fluid itself.

Silica gel has a non-ionic injection fluid 13', so
Ionic moisture can be adsorbed without being hindered by the injection fluid.

The moisture absorber 16 is made of epoxy resin or the like and is attached to the back glass plate 11.
is glued to.

Injecting fluid into the envelope, heat both to 100℃~2 after bonding the envelope.
After raising the temperature to 00° C. and degassing under reduced pressure below IF'' Torr, the injection hole 14 is inserted into a bath of silicone oil or the like.

After the fluid is injected, the injection hole 14 is sealed with epoxy resin or the like.

Although the moisture absorber 16 is made of aluminum foil coated with silica gel, it may be coated on glass or plastic, or a sheet of only silica gel may be directly attached to the back glass 11.

It is desirable that the coloring dye contained in the silicone oil satisfies the following conditions.

(1) Silicone oil at room temperature or 60-70℃
Dissolves easily.

(2) When colored silicone oil is injected into an envelope with a thickness of approximately 1 μ, the silicone oil has almost no optical transparency.

(3) When dissolved in silicone oil, it does not reduce the electrical insulation properties of silicone oil.

(4) Moisture absorber 1 when dissolved in silicone oil
Does not reduce the adsorption performance of No. 6.

(5) The characteristics of the thin film EL element are not deteriorated.

Coloring dyes that meet this condition include Zudan Blue, a blue dye, and Zudan Black, a dark purple dye.
Contains about 0.01 to 1.0% by weight.

With the above configuration, a blue or black background color for the light emitted by the thin film EL element is uniformly formed in the injected fluid 13', and the moisture absorber 16 and the rear glass plate 11 are provided for the light emitted from the injected fluid 13'. Due to its opacity, it cannot be seen from the display side.

FIGS. 5 and 6 are sectional views of main parts of a thin film EL panel showing other embodiments of the present invention, respectively.

The same reference numerals as in FIG. 3 indicate the same contents, and the explanation will be omitted.

The structure shown in Figure 5 is a moisture absorber 1 made by pasting silica gel.
6' is colored to form the background color.

In the configuration shown in FIG. 6, a background plate 17 made of colored synthetic fibers is inserted between the moisture absorber 16 and the thin film EL element.

The background plate 17 must be sufficiently permeable to the injection fluid 13.

As explained in detail above, according to the present invention, the fluid for protecting thin film EL elements injected into the thin film EL panel not only prevents moisture in the atmosphere from entering the thin film EL elements, but also prevents moisture from entering the thin film EL elements. Since the background color for the display is formed within the envelope, the display life and display quality of the thin film EL panel are dramatically improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a specific structure of a thin film EL element. FIG. 2 is a block diagram of a conventional thin film EL device. FIG. 3 is a diagram illustrating a main part of an example of a conventional thin film EL panel. FIG. 4 is a cross-sectional configuration diagram of essential parts of a thin film EL panel for explaining one embodiment of the present invention. FIGS. 5 and 6 are sectional views showing the main parts of a thin film EL panel showing other embodiments of the present invention. 1...Glass substrate, 10...Spacer, 11...
Back glass plate, 13... Injection fluid, 16... Moisture absorber, IT... Background plate.

Claims (1)

[Claims] 1. In a thin-film EL panel in which a thin-film EL element is built into an envelope consisting of a translucent front substrate and a back plate, and display is performed via the translucent front substrate, A thin film EL panel characterized in that a protective fluid for preventing moisture from entering the thin film EL element is injected and a background color for a display is formed in the protective fluid to improve contrast.