JPH05283168A - Thin-film el display element - Google Patents

Abstract

PURPOSE:To provide a thin-film EL display element having high intensity and high reliability. CONSTITUTION:A mounted thin-film EL display element 300 is constituted of a thin-film EL display element 100 having yellow orange luminescence and a thin-film EL display element 200 having green luminescence. A silicon oil 50 dissolved and dispersed with a red oil-soluble dye concurrently serving for moisture-proofing is filled in the middle portion of them, and they are stuck and sealed. The yellow orange luminescence of the thin-film EL display element 100 is made red luminescence by the filter effect of the silicon oil 50 on the light extraction side in the arrow direction, and the green luminescence of the thin-film EL display element 200 is kept as the original green luminescence without being affected by the silicon oil 50. This thin-film EL display element 300 can provide green luminescence and high-intensity red luminescence, it has a stable luminescence characteristic, and its reliability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film EL (Electrical Electrification) used for, for example, a surface emitting source for a backlight of instruments.
roluminescence) Display element.

[0002]

2. Description of the Related Art Conventionally, a thin film EL display element has been noted as a self-luminous flat display by utilizing a phenomenon of emitting light when an electric field is applied to a phosphor such as zinc sulfide (ZnS). There is. FIG. 4 is a schematic diagram showing a typical cross-sectional structure of the conventional thin film EL display element 10. The thin film EL display element 10 is an optically transparent IT on a glass substrate 1 which is an insulating substrate.
A first electrode 2 made of an O film, a first insulating layer 3 made of tantalum pentoxide (Ta ₂ O ₅ ) and the like, a light emitting layer 4, a second insulating layer 5 and a second electrode 6 made of an ITO film are sequentially laminated. Has been formed. The ITO (Indium Tin Oxide) film is a transparent conductive film in which indium oxide (In ₂ O ₃ ) is doped with tin (Sn),
Due to its low resistivity, it has been widely used for transparent electrodes. As the light emitting layer 4, for example, a material in which zinc sulfide is used as a base material and manganese (Mn) or terbium trifluoride (TbF ₃ ) is added as an emission center is used.
The emission color of the thin film EL display device is determined by the type of additive in zinc sulfide. For example, when manganese (Mn) is added as the emission center, it is yellow-orange, and when terbium trifluoride (TbF ₃ ) is added. Gives a green emission.

[0003]

In the thin film EL display element 10 having the above structure, samarium trifluoride (SmF) is used as a constituent material of the light emitting layer 4 for obtaining red light emission.
Zinc sulfide with addition of ₃ ) is being studied. The thin-film EL display device 10 having the light emitting layer 4 made of this constituent material has a low emission brightness of 1000 cd / m ² (5 KHz drive) at the maximum, and has a poor color purity because the emission spectrum includes components on the shorter wavelength side than red. At present, it is not practical as a display device such as an EL panel. Here, the one disclosed in Japanese Patent Application Laid-Open No. 1-315987 "Multi-color display type thin film electroluminescent element" is known. For this, a method has been proposed in which a red light emission is obtained by using a thin-film EL display element composed of a ZnS: Mn light emitting layer which emits yellow-orange light emission and using a filter for cutting light of 570 nm or less. This thin-film EL display device has a high luminance of yellow-orange light originally emitted from the light-emitting layer, so that it is possible to secure sufficient luminance of red light emission even through a filter. However, the heat resistance temperature of the filter formed by printing the paint containing the pigment and the binder is as low as about 200 ° C. Therefore, it is impossible to insert the filter in the middle of the manufacturing process in which each layer is deposited while heating the glass substrate by vapor deposition, sputtering or the like to form a thin film EL display element. Therefore, the filter is formed only after depositing each layer of the thin film EL display element, and the insertion position is limited. Further, there is a problem that the characteristics of the coating material change due to heat generation during light emission of the thin film EL display element, the emission color changes with time, and the element characteristics deteriorate. Further, in order to form the filter, a paint printing step, a drying step, a patterning step for exposing the electrode lead-out portion, etc. are added. As a result, there has been a problem that the manufacturing process of the thin film EL display element becomes complicated, resulting in a decrease in yield and an increase in cost.

The present invention has been made to solve the above problems, and its purpose is to obtain high brightness,
A red-emitting thin-film EL display device having high reliability is provided.

[0005]

The constitution of the invention for solving the above-mentioned problems is such that at least a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are provided on an insulating substrate. A thin film EL display device formed by sequentially stacking optically transparent materials on the extraction side, characterized by having a silicone oil in which an oil-soluble dye is dissolved and dispersed so as to cover the extraction side. ..

[0006]

FUNCTION AND EFFECT Silicon oil is arranged so as to cover the light extraction side of the thin film EL display element, and the oil-soluble dye is dissolved and dispersed therein. As the oil-soluble dye, for example, a light emitting layer of a thin film EL display element is
It is composed of zinc sulfide: manganese (ZnS: Mn), and if yellow-orange emission is red emission, it is a red dye intermediate such as an azo type or anthraquinone type. That is, the silicon oil in the thin-film EL display device having the above-mentioned structure has the effect of preventing moisture from being added in addition to the conventional moisture-proof effect.
It has a filter effect of changing the yellow-orange emission of the emission layer made of S: Mn) to red emission. The injection of the silicon oil in which the oil-soluble dye is dissolved and dispersed is performed after the manufacturing process of the thin film EL display element formed by heating the insulating substrate to deposit the insulating layer and the light emitting layer. Therefore, the heating temperature of the substrate is not restricted in the manufacturing process of the thin film EL display element, and the process itself is not complicated. or,
Silicon oil has a larger volume and a smaller area in direct contact with the element than a thin film EL display element that generates heat during light emission. Therefore, the characteristics of the silicone oil in which the oil-soluble dye is dissolved and dispersed are not changed by the heat generation, and the emission color is not changed with time. That is, the thin film EL of the present invention
The display device has high brightness even when the emission color is changed, its emission characteristics are stable, and its reliability is improved.

[0007]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a schematic view showing a vertical section of a thin film EL display device 300 according to the present invention. In the thin film EL display element 300 of FIG. 1, light is extracted in the arrow direction. The thin film EL display element 300 is configured by bonding the thin film EL display element 100 that emits yellow-orange light and the thin film EL display element 200 that emits green light in a mounting process.

One thin film EL display device 100
Is formed by sequentially laminating the following thin films on a glass substrate 11 which is an insulating substrate. In addition, the film thickness of each layer is described below based on the central portion thereof. A first transparent electrode (first electrode) 12 made of optically transparent zinc oxide (ZnO) is formed on a glass substrate 11, and an optically transparent tantalum pentoxide (Ta ₂ O) is formed on the upper surface thereof. ₅ ) The first insulating layer 13 consisting of, zinc sulfide added with manganese (Mn)
(ZnS) emitting layer 14, optically transparent tantalum pentoxide (Ta ₂ O ₅ ) second insulating layer 15, optically transparent zinc oxide (ZnO) second transparent electrode (second The electrode) 16 is formed.

The other thin film EL display device 200
Are basically of the same layer structure as the thin film EL display element 100. That is, the thin film EL display element 20
0 is the first transparent electrode (first electrode) 22, the first insulating layer 23, the light emitting layer 24, and the second insulating layer 2 on the glass substrate 21 in order.
5, a thin film of the second transparent electrode (second electrode) 26 is laminated and configured. Among these, only the composition and the amount of the luminescent center added to the light emitting layer 24 are different. Specifically, in the thin film EL display element 200, the light emitting layer 14 made of zinc sulfide (ZnS) added with manganese (Mn) in the thin film EL display element 100 is replaced with terbium (Tn).
A light emitting layer 24 made of zinc sulfide (ZnS) added with b) is formed. The thin film EL display elements 100 and 200 are sealed by injecting silicon oil 50, in which an oil-soluble dye is dissolved and dispersed, into an intermediate portion between them and bonding them.

Next, the above-mentioned thin film EL display element 1
The manufacturing method of 00 is described below. First, the glass substrate 11
A first transparent electrode 12 was formed on top. As a vapor deposition material,
Gallium oxide (Ga ₂ O ₃ ) was added to zinc oxide (ZnO) powder and mixed, and the mixture was molded into pellets. An ion plating device was used as a film forming device. Specifically, while maintaining the temperature of the glass substrate 11 at 150 ° C., the inside of the ion plating apparatus was evacuated to 5 × 10 ⁻³ Pa. After that, introduce argon (Ar) gas to 6.5 × 10 ^-1
The beam power and the high frequency power were adjusted so that the deposition rate was in the range of 1.0 to 3.0 Å / sec while maintaining the pressure Pa.

Next, a first insulating layer 13 made of tantalum pentoxide (Ta ₂ O ₅ ) was formed on the first transparent electrode 12 by sputtering. Specifically, the temperature of the glass substrate 11 is set to 200 ° C.
And maintain the inside of the sputtering system at 1.0 Pa, and introduce a mixed gas of argon (Ar) and oxygen (O ₂ ) into the sputtering system (200c
c / min) and the deposition rate was 2Å / sec with a high frequency power of 1 kW.

Zinc sulfide (ZnS) is formed on the first insulating layer 13.
Was used as a base material, and a zinc sulfide: manganese (ZnS: Mn) light emitting layer 14 to which manganese (Mn) was added as an emission center was formed by vapor deposition. Specifically, the temperature of the glass substrate 11
The temperature was maintained at 120 ° C., the inside of the sputtering apparatus was maintained at 5 × 10 ⁻⁴ Pa or less, and electron beam evaporation was performed under the conditions of a deposition rate of 1.0 to 3.0 Å / sec.

Next, a second insulating layer 15 made of tantalum pentoxide (Ta ₂ O ₅ ) is formed on the light emitting layer 14 and a first insulating layer 13 is formed thereon.
It was formed by the same method as. The above layers are formed on the glass substrate 11
After the above formation, heat treatment was performed at 400 to 600 ° C. for 2 hours in a vacuum of 5 × 10 ⁻⁴ Pa. By this heat treatment, the crystallinity of the light emitting layer 14 was improved and the emission luminance was increased. After the heat treatment, the second transparent electrode 16 made of a zinc oxide (ZnO) film was formed on the second insulating layer 15 by the same method as the above-mentioned first transparent electrode 12. The film thickness of each layer is such that the first and second transparent electrodes 12,
16 is 3000 Å, the first and second insulating layers 13 and 15 are 4000 Å,
The light emitting layer 14 is 6000Å.

As described above, the thin-film EL display element 200 has the same layer structure as the thin-film EL display element 100 except for the light-emitting layer 24, so that the light-emitting layer 24 is the same.
Only the manufacturing method will be described. The light-emitting layer 24 was formed by high frequency sputtering using zinc sulfide (ZnS) as a base material and zinc sulfide: terbium (ZnS: Tb) to which terbium (Tb) was added as the emission center as a target. Specifically, the temperature of the glass substrate 21 was maintained at 200 ° C., and the inside of the sputtering apparatus was maintained at 0.5 to 10 Pa for sputtering.

Next, the thin film EL display element 100 and the thin film EL display element 200 were mounted. Specifically, the adhesive was screen-printed on the periphery of the glass substrates 11 and 21 except for the oil injection port. Then, the glass substrate 11 and the glass substrate 21 were bonded together, and then heated at 150 ° C. for 1 hour to cure the adhesive. Next, 0.01 to 1 wt% of an azo or anthraquinone red oil-soluble dye was dissolved in silicone oil. Then, the red oil-soluble dye was dissolved and dispersed, and the silicon oil 50 turned red was vacuum-injected from the oil injection port, and finally the oil injection port was sealed with a sealant. The silicone oil 50 has a role of a red transmission filter in addition to the conventional moistureproof effect.

Mounted thin film EL display device 30
At 0, the thin film EL display device 100 was caused to emit light and the emission spectrum was measured from the direction of the arrow. The peak thereof was shifted to the long wavelength side of 610 nm, and red emission with good color purity was obtained. Thus, in the thin film EL display element 300, the thin film EL display element 100
The yellow-orange emission of is observed from the glass substrate 21 side,
Red light is emitted by passing through the silicone oil 50 in which the red oil-soluble dye is dissolved and dispersed. On the other hand, the green light emission of the thin film EL display device 200 is not affected by the fact that it does not pass through the silicone oil 50. That is, the mounted thin film EL display element 30
0, the thin film EL display elements 100, 200
When a voltage is applied independently to, red light emission and green light emission are obtained, respectively. In the mounted thin film EL display element 300, the thin film EL display element 100,
By simultaneously applying voltages to 200 and adjusting those voltages, a mixed color of red and green can be displayed, and multicoloring can be realized.

As described above, the thin film EL display element 300 includes the thin film EL display element 100 and the thin film E.
The L display element 200 is formed by sealing the glass substrate 11, 21 with the second transparent electrodes 16, 26 facing each other and injecting a silicone oil 50 in which a red oil-soluble dye is dissolved and dispersed into the middle portion thereof. Has been done. here,
Only the glass substrate 21 is placed on the second transparent electrode 16 of the thin film EL display device 100, and the space portion thereof is filled with the silicone oil 50 in which the red oil-soluble dye is dissolved and dispersed to be mounted. Obviously, a display element can be formed.

FIG. 2 is a characteristic diagram showing a visible light transmission curve of a silicon oil used in the above-mentioned thin film EL display device 300 by a spectrophotometer. The red oil-soluble dye was not added (0 wt%), the transmittance of 90% or more was maintained up to the wavelength of 300 nm, and the 0.1% was added, the transmittance of wavelength shorter than 610 nm was 3% or less. Became. The brightness of yellow-orange emission of a thin film EL display device having a zinc sulfide: manganese (ZnS: Mn) light emitting layer 14 is about 2800 cd / m ² (1 KHz drive) when silicon oil containing no red oil-soluble dye is used. When the silicone oil added with the red oil-soluble dye was used, the luminance of the transmitted red light emission was about 700 cd / m ² (1 KHz drive).

FIG. 3 is a schematic view showing a vertical section of a second embodiment of the thin film EL display device according to the present invention.
The thin film EL display element 500 according to the present embodiment is a red light emitting thin film EL display element 10 of the first embodiment.
On the structure of the thin film EL display element 200 of 0 and green emission, a thin film EL display element 400 having a light emitting layer 34 is further combined to form a triple stacked thin film EL display element. The layers of the thin film EL display elements 100 and 200 of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. On the glass substrate 31 (lower side in the drawing) of the thin film EL display element 400,
A first transparent electrode 32 made of zinc oxide (ZnO) and a first insulating layer 33 made of tantalum pentoxide (Ta ₂ O ₅ ) were formed by the same method as in the previous embodiment. Then, the light emitting layer 34 is formed thereon.
Was formed by the sputtering method. The light emitting layer 34 is made of zinc sulfide (ZnS) as a base material, and thulium trifluoride (TmF ₃ ) is added as a light emitting center, and emits blue light. A second insulating layer 35 made of tantalum pentoxide (Ta ₂ O ₅ ) and a second transparent electrode 36 were formed on the light emitting layer 34 by the same method as in the above-mentioned embodiment. First and second transparent electrodes 32, 3
The film thickness of 6 was 3000Å, the film thickness of the first and second insulating layers 33 and 35 was 4000Å, and the film thickness of the light emitting layer 34 was 6000Å. And
These three thin film EL display elements 100, 20
When mounting 0,400, the silicon oil 50 in which the red oil-soluble dye is dissolved and dispersed between the glass substrate 11 and the glass substrate 21 described above, or between the glass substrate 21 and the glass substrate 31. Injected only ordinary silicone oil 51.

In the thin film EL display device 500 having the above structure, red, green and blue light emission colors are obtained by applying a voltage to the light emitting layer 14, the light emitting layer 24 or the light emitting layer 34, respectively. Furthermore, three light emitting layers 1
Color mixing is obtained by simultaneously emitting two or three of 4, 24 and 34, and by combining these, multi-color and full-color can be realized.

In both the first and second embodiments, a red oil-soluble dye is dissolved in place of the conventional moisture-proof silicon oil itself in the process of producing a yellow-orange light-emitting thin film EL display device. Only use dispersed silicone oil. That is, the thin-film EL display device mounted with the present invention can obtain red light emission with high brightness and high reliability by the conventional process as it is.
The luminance of red light emission of the thin film EL display device according to the present invention was about 700 cd / m ² (1 KHz drive) as described above, which was sufficiently practical. Further, in the thin-film EL display device according to the present invention, even in the continuous light emission test for 10,000 hours, the change in the filter characteristics of the silicon oil in which the red oil-soluble dye was dissolved and dispersed and the change in the light emission characteristics with time were not observed.

The present invention is not limited to the above-described embodiment, but various modifications such as the following are possible. (1) Zinc sulfide: manganese that emits yellow-orange light in the light-emitting layer
Instead of (ZnS: Mn), for example, strontium sulfide: cerium (SrS: Ce) that emits blue-green light is used. Then, as the oil-soluble dye that covers the light extraction side of the thin film EL display element, for example, silicon oil in which a blue dye intermediate such as an azo type or anthraquinone type is dissolved and dispersed is used. The thin film EL display element having such a configuration can be blue with high color purity. (2) First and second insulating layers 13, 15, 23, 25, 33,
35 was composed of tantalum pentoxide (Ta ₂ O ₅ ), but Al ₂ O
₃ , PbTiO ₃ , Y ₂ O ₃ , SiON, Si ₃ N ₄ may be used. (3) Thin-film EL display element 2 in the second embodiment
The formation positions of 00 and 400 are not limited to this configuration. For example, in FIG. 3, the thin film EL display element 200 may be below the glass substrate 21, and the thin film EL display element 400 may be above the glass substrate 21. good. That is,
The position where the silicon oil in which the red oil-soluble dye is dissolved and dispersed is injected is on the light extraction side from the yellow-orange light emitting thin film EL display element and on the opposite side to the light extraction from the green or blue light emitting thin film EL display element. good. (4) Regarding the positional relationship between the green light emitting thin film EL display element 200 and the blue light emitting thin film EL display element 400, the two may be interchanged in consideration of the chromaticity and luminance required as a device of each light emitting element.

[Brief description of drawings]

FIG. 1 is a schematic view showing a vertical section of a thin film EL display device according to a specific example of the present invention.

FIG. 2 is a characteristic diagram showing a visible light transmission curve by a spectrophotometer of silicon oil used in the thin film EL display element of the device of the example.

FIG. 3 is a schematic view showing a vertical cross section of another embodiment of the thin film EL display element according to the present invention.

FIG. 4 is a schematic view showing a vertical section of a conventional thin film EL display device.

[Explanation of symbols]

11,21-Glass substrate (insulating substrate) 12,22-First transparent electrode (first electrode) 13,23-First insulating layer 14,24-Light emitting layer 15,25-Second insulating layer 16,26- Second transparent electrode (second electrode) 50-Silicon oil in which red oil-soluble dye is dissolved and dispersed 100,200-Thin film EL display element 300- (Mounted) thin film EL display element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Gen Moto Ishihara, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Nobue Ito, 1-1, Showa-cho, Kariya city, Aichi prefecture Sozo Co., Ltd.

Claims (1)

[Claims] 1. A first electrode, a first insulating layer, and
A thin-film EL display device in which a light emitting layer, a second insulating layer, and a second electrode are sequentially laminated by at least an optically transparent material for the light extraction side, and is oil-soluble so as to cover the light extraction side. A thin film EL display device comprising a silicon oil in which a dye is dissolved and dispersed.