JPH1092580A - Thin film electroluminescent element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film electroluminescent element provided with an insulating layer, with which an ordinary wet process can be applied at the patterning of an electrode layer formed on the insulating layer provided on a light emitting layer, and to provide the manufacture thereof. SOLUTION: In an electroluminescent element formed by laminating a first electrode layer 21, a first insulating layer 31, a light emitting layer 4 made of alkaline earth group sulfide, to which at least rare earth group element is added, a second insulating layer 32 and a second electrode layer 22 in order on an insulating board 11, density of the second insulating layer 32 is set at a value more than 87% of the density of single crystal of the material, which forms the second insulating layer. As the material of the second insulating layer 32, any one of aluminum oxide, tantalum oxide and aluminium nitride is used. An electroluminescent device using this EL element is provided with a sealing board 12 and color filters 5r, 5g, 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film electroluminescent device used for a multicolor light emitting display and a method for manufacturing the same.

[0002]

2. Description of the Related Art A thin-film electroluminescence (hereinafter, referred to as EL) element, which is one of the elements for a flat display, is sharp, has high contrast, and has a small viewing angle dependency. Research and development are progressing as display elements for mounting.

FIG. 2 shows a conventional monochromatic thin film EL device.
(A) is a plan view, (b) is an XX sectional view in (a). A first electrode layer 21 on a glass substrate 11;
The first insulating layer 31, the light emitting layer 4, the second insulating layer 32, the second
The sealing substrate 12 is covered via the sealing member 7 on the thin-film EL element in which the electrode layers 22 are sequentially laminated, and after the silicone oil 6 is injected into the inside, the hermetically sealed. A drive power source E is connected to both electrode layers, and a pulse voltage of both polarities is applied to
L is emitted.

[0004] A thin film EL device is manufactured according to the following manufacturing process. (1) The first electrode layer 2 is formed on a glass substrate as the insulating substrate 11, and a predetermined pattern (for example, a strip shape) is formed by a photo process. The first electrode layer 21 is a metal layer such as molybdenum (Mo) or tungsten (W), or a transparent conductive layer such as indium tin oxide (hereinafter referred to as ITO).

(2) The first insulating layer 31 is formed. First
The insulating layer 31 is a laminated film of a silicon oxide (hereinafter, referred to as SiO ₂ ) film and a silicon nitride (hereinafter, referred to as Si ₃ N ₄ ) film. (3) A phosphor layer made of ZnS: Mn that emits yellow-orange light is formed as the light-emitting layer 4 and heat-treated. (4) The second insulating layer 6 is formed. It is a stacked film in the reverse order of the first insulating layer.

(5) The second electrode 7 is formed into a film, and a predetermined pattern (for example, a rectangular shape orthogonal to the first electrode) is formed by a photo process. The second electrode layer 22 is a transparent conductive layer such as ITO or a metal electrode such as aluminum (Al). Monochromatic light emitting thin film EL using ZnS: Mn described above
Although displays have already been put to practical use, colorization has become indispensable as display contents have diversified.

Phosphors used in the light emitting layer of the color thin film EL device include CaS: Eu, ZnS: Sm, and Sr for red.
S: Eu, etc., for green, ZnS: Tb, CaS: Ce, etc., for blue
Alkaline earth sulfides such as SrS: Ce and a laminated film of SrS: Ce and ZnS: Mn for white color are used. When color emission is performed using a white light-emitting material, a white thin-film EL element is superimposed on a sealing substrate, on which a color filter is usually prepared in advance, and light separated into three primary colors is emitted from the sealing substrate side (see FIG. 1).

As the second insulating layer covering the light emitting layer using such an alkaline earth sulfide, an insulating film formed by sputtering is usually used. However, the following problems arise. Yes, a color EL display has not been realized.

[0009]

When patterning the second electrode layer on the light emitting layer using the alkaline earth sulfide, the wet process using an ordinary aqueous solution passes through the second insulating layer. Patterning of the second electrode was not possible because moisture penetrated into the light emitting layer and the alkaline earth sulfide was hydrolyzed. For this reason, patterning of the second electrode requires a complicated and expensive process such as a dry process or a non-aqueous process.

An object of the present invention is to provide a thin-film EL device having an insulating layer which can be applied to an electrode layer formed on an insulating layer on a light-emitting layer by a conventional wet process using an aqueous solution for patterning. It is to provide a manufacturing method thereof.

[0011]

In order to achieve the above-mentioned object, a first electrode layer, a first insulating layer, and a light emitting device comprising an alkaline earth sulfide to which at least a rare earth element is added are provided on an insulating substrate. Layer, a second insulating layer, and a second electrode are sequentially laminated.
It is assumed that the density (mass / volume) of the insulating layer exceeds 87% of the density of the single crystal of the material forming the second insulating layer.

The constituent material of the second insulating layer is preferably any one of aluminum oxide, tantalum oxide and aluminum nitride. In the method for manufacturing a thin-film electroluminescence element, the second insulating layer may be formed by thermal CVD using a surface reaction. The aluminum oxide is preferably formed using a mixed gas of a trimethylaluminum gas and water vapor.

The tantalum oxide is preferably formed by using a mixed gas of tantalum pentachloride gas and water vapor. The aluminum nitride is preferably formed using a mixed gas of aluminum trichloride gas and ammonia.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have found that the cause of intrusion of moisture into the light emitting layer is as follows: (1) cracks in the light emitting layer caused by heat treatment for increasing luminance or (2) protrusions generated during the formation of the light emitting layer. Due to the surface shape of the light emitting layer such as abnormal crystal grains
(3) The ratio of the density of the material constituting the second insulating layer to the density of the single crystal of the same material (relative density)
It has also been found that the decrease in the value has a great effect. Since the second insulating layer having a high relative density according to the present invention has no fine pinholes and has a smooth coating regardless of the surface shape of the light-emitting layer, moisture is removed during wet etching of the second electrode layer. The light-emitting layer is not hydrolyzed.

The water resistance of the second insulating layer was confirmed as follows. The substrate on which the second insulating layer was stacked was immersed in water, and the area in which moisture penetrated into the light emitting layer and the light emitting layer (SrS: Ce) was hydrolyzed and discolored was examined. The area ratio to the total area of the light emitting layer was calculated. From Table 1, it was found that under the condition that the pinhole was reduced and the relative film density was set to 87% or more, moisture did not enter the light emitting layer, and the second electrode could be wet-patterned with an aqueous solution. did.

FIG. 1 shows a multicolor thin film EL according to an embodiment of the present invention.
It is sectional drawing of an apparatus. Conventional single-color thin-film EL device (Fig. 2)
Only the differences from the above will be described. By applying a pulse voltage from a power source E to the second electrode layer 22 facing the first electrode layer 21, a laminated film of a layer made of SrS: Ce and a layer made of ZnS: Mn is formed as a light emitting layer 4a that emits white light. The white light to be emitted is then separated by the color filters 5r, 5g, and 5b formed on the sealing substrate 12 to obtain three primary colors of red, green, and blue (abbreviated as R, G, and B). Hereinafter, the manufacturing process will be described.

(1) A tungsten film (W) is formed as a first electrode layer on a non-alkali glass substrate 11 by DC sputtering to a thickness of 200 nm, and then the W film is patterned by dry etching with CF ₄ gas. First electrode 2
And (2) A laminated film of silicon oxide and silicon nitride was sequentially formed as a first insulating layer 31 on the entire surface of the substrate 11 by high-frequency reactive sputtering. Each film thickness is 5 for silicon oxide.
0 nm and 200 nm for silicon nitride. (3) As the light emitting layer 4a, a ZnS: Mn film was formed by 400 nm electron beam evaporation. Thereafter, a 1000 nm SrS: Ce film was continuously formed by electron beam evaporation without breaking vacuum. Then, for the purpose of improving the crystallinity of SrS: Ce and increasing the brightness,
Heat treatment was performed at 600 ° C. for 30 minutes in a hydrogen sulfide atmosphere. (4) As the second insulating layer 32, a film having a high relative density was formed by the constituent materials and the film forming method described in the example. (5) As the second electrode 6, an ITO film was formed to a thickness of 200 nm by DC sputtering, and the ITO film was patterned by a wet process. (6) Finally, the sealing substrate 12 on which the color filter 5 is formed is opposed and fixed using the sealing member 7 to form the thin film EL.
The device. Here, a silicone oil 6 is provided between the EL element substrate 11 and the sealing substrate 12 with a color filter.
And a spacer (not shown) having a diameter of 10 μm was inserted to keep the distance between the EL element and the color filter constant. Example 1 In the above manufacturing process (4), two film forming methods were tried for an aluminum oxide film as the second insulating layer.

In the thermal CVD as the first film forming method, the substrate on which the light emitting layer is formed is placed in a mixed gas of a gas obtained by heating and vaporizing trimethyl aluminum and water vapor, and the substrate is maintained at 300 ° C. An aluminum oxide film was formed. In the sputtering as the second film formation method, an aluminum oxide (Al ₂ O ₃ ) target and a gas pressure of 133 mPa Ar were used and a power of ² W / cm ² was applied to form a 200 nm-thick aluminum oxide film. .

In the case of the sputtered insulating layer, since the light emitting layer was obviously deteriorated after the electrode patterning in the above-mentioned manufacturing process (5), the above-mentioned manufacturing process (6) was performed only in the case of the thermal CVD insulating layer, and the EL device was assembled. Was. An EL device formed up to the above-described manufacturing process (6) without patterning the second electrode layer by forming a second insulating layer having the same configuration as the first insulating layer in the reverse order, and emitting luminance and its reliability (long-term energizing light emission) test)
The EL device using the thermal CVD aluminum oxide insulating layer had the same characteristics.

It was feared that the light-emitting layer would absorb moisture due to water vapor during thermal CVD and the light-emitting characteristics would be degraded. However, the light-emitting characteristics did not change as described above. At the time of thermal CVD, only one molecular layer of water is adsorbed on the surface of the light emitting layer, and the deposition of the aluminum oxide film starts immediately. Therefore, it is estimated that the water in the light emitting layer is small and no hydrolysis occurs. When the density of the second insulating layer formed at the same time was calculated from Rutherford backscattering measurement, the film density of the thermal CVD insulating layer was 92% of that of single crystal aluminum oxide, and 87% of the sputtered insulating layer.

Further, the substrate on which the film was formed up to the second insulating layer was immersed in water, the area of the discolored portion of the luminescent layer due to hydrolysis was measured, and the area ratio to the total area of the luminescent layer was determined. It was a measure of gender. The water resistance of the thermal CVD insulation layer and the water resistance of the sputter insulation layer were 0% and 30%, respectively. Table 1 shows film materials, film forming methods, film forming conditions, relative densities, and water resistance. Table 1 also shows the data of Example 2 and thereafter.

[0022]

[Table 1] Example 2 In the same manner as in Example 1, two film forming methods were attempted for a tantalum oxide film as the second insulating layer. In thermal CVD as the first film forming method, a substrate on which a light emitting layer is formed is placed in a mixed gas of a gas obtained by heating and evaporating tantalum pentachloride and water vapor, and is maintained at 350 ° C. A film was formed.

In the second sputtering method, a target of tantalum (Ta) and a gas pressure of 403 mPa and 30% O _{2 are used.}
Is used, and an electric power of 4 W / cm ² is applied and the film thickness is 200 nm.
Was formed. In the case of the sputtered insulating layer, since the light emitting layer was obviously changed after the electrode patterning in the manufacturing process (5), the manufacturing process (6) was performed only in the case of the thermal CVD insulating layer, and the EL device was assembled. When the emission luminance and its reliability were examined in the same manner as in Example 1, it was the same as Example 1. Further, as a result of examining the relative density and the water resistance in the same manner as in Example 1, the thermal CVD tantalum oxide and the sputtered tantalum oxide were each 93%,
85% and 0%, 25%. Example 3 In the same manner as in Example 1, two film forming methods were attempted for an aluminum nitride film as the second insulating layer.

In the thermal CVD as the first film forming method, the substrate on which the light-emitting layer is formed is placed in a mixed gas of a gas in which aluminum trichloride is heated and vaporized and ammonia, and is maintained at 450 ° C. Was formed. In the second sputtering method, an aluminum (Al) target and Ar containing 50% N ₂ at a gas pressure of 670 mPa were used, and a power of 1 W / cm ² was applied to form a 200 nm-thick aluminum nitride film. Filmed.

In the case of the sputtered insulating layer, since the light emitting layer was obviously changed after the electrode patterning in the above-mentioned manufacturing process (5), the above-mentioned manufacturing process (6) was performed only in the case of the thermal CVD insulating layer, and the EL device was assembled. When the light emission luminance and its reliability were examined in the same manner as in Example 1, the result was the same as in Example 1. The relative density and the water resistance were examined in the same manner as in Example 1. As a result, the thermal CVD aluminum nitride and the sputtered aluminum nitride were 94%, 83%, 0%, and 45%, respectively. Comparative Example A case of a silicon nitride film in which high luminance was not obtained due to hydrolysis during the production process (4) will be described.

In the RF plasma used as the first film forming method,
Silane gas (SiH): Ammonia (NH): Hydrogen gas (H)
= 1: 4: 16, gas pressure 133 Pa, 0.5 W / cm ²
Is applied, and the substrate on which the film is formed up to the light-emitting layer is placed, and 30
While maintaining the temperature at 0 ° C., a 200 nm-thick tantalum oxide film was formed. In the reactive sputtering as the second film forming method, a 200 nm-thick silicon nitride film was formed by using a Si target and N ₂ at a gas pressure of 400 mPa and applying power of ² W / cm ² .

The relative density and water resistance of the RF plasma silicon nitride film and the reactive sputtered silicon nitride film were 85%, 85%, 35%, and 40%, respectively. From the above examples, it can be seen that if the relative density of the second insulating layer exceeds 87%, the second insulating layer can withstand the manufacturing process (5) and can be patterned by a normal wet process.

[0028]

According to the present invention, a first electrode layer, a first insulating layer, a light emitting layer made of an alkaline earth sulfide to which at least a rare earth element is added, and a second insulating layer are provided on an insulating substrate. In the thin-film electroluminescence device in which the second electrode layer is sequentially laminated, the density of the second insulating layer is set to exceed 87% of the density of the single crystal of the material forming the second insulating layer. Since the insulating layer does not transmit moisture, a wet process can be applied to the patterning of the second electrode layer on the second insulating layer.
Therefore, the light emitting layer is not affected by the wet process,
A multicolor thin film EL element having high luminance and high reliability can be obtained, and a multicolor thin film EL can be manufactured using this.

As described above, the patterning of the second electrode layer can be easily performed, the yield is high, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multicolor thin film EL device according to an embodiment of the present invention.

FIGS. 2A and 2B show a conventional monochromatic thin-film EL device, wherein FIG. 2A is a plan view and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Glass substrate 21 1st electrode 31 1st insulating layer 4 Light emitting layer 4a White light emitting layer 32 2nd insulating layer 22 2nd electrode 5 Color filter 5r Red filter 5g Green filter 5b Blue filter 12 Sealing glass substrate 6 Silicone oil 7 Sealing member E Power supply

Claims (6)

[Claims] 1. A first electrode layer, a first insulating layer, a light emitting layer made of an alkaline earth sulfide to which at least a rare earth element is added, a second insulating layer, and a second electrode on an insulating substrate. Wherein the density of the second insulating layer exceeds 87% of the density of a single crystal of the material constituting the second insulating layer. 2. The thin-film electroluminescence device according to claim 1, wherein the constituent material of the second insulating layer is any one of aluminum oxide, tantalum oxide and aluminum nitride. 3. The thin film electroluminescent device according to claim 1, wherein the second insulating layer is formed by thermal CVD using a surface reaction. A method for manufacturing an electroluminescence element. 4. The method according to claim 3, wherein the aluminum oxide according to claim 2 is formed using a mixed gas of trimethylaluminum gas and water vapor. 5. The method according to claim 3, wherein the tantalum oxide according to claim 2 is formed using a mixed gas of tantalum pentachloride gas and water vapor. 6. The method for manufacturing a thin film electroluminescent device according to claim 3, wherein the aluminum nitride according to claim 2 is formed using a mixed gas of aluminum trichloride gas and ammonia.