JP2754919B2 - Multi-color display EL display - Google Patents

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 (hereinafter, referred to as EL) element having two or more different emission colors, which is arranged in a plane to obtain a multicolor display.
The present invention relates to an L display, and more particularly to a multi-color display EL display that has a small difference in luminance between EL light-emitting elements of different emission colors and that can display an appropriate intermediate color.

[0002]

2. Description of the Related Art Hitherto, a multi-color display EL display in which light-emitting elements having different emission colors are arranged on a plane has been known, for example, as shown in FIG. In this example, two types of EL light-emitting elements having different emission colors are used. FIG. 5A is a schematic plan view, and FIG. 5B is a schematic cross-sectional view taken along line AA in FIG. It is. A plurality of strip-shaped transparent electrodes 22 are arranged in parallel on a transparent substrate 21, on which a first insulating layer 23 (not shown in FIG. 5A),
Light emitting layers 24 and 25 are stacked. The light-emitting layers are formed such that two types of light-emitting layers form a band and are alternately arranged in a plane, and their center lines are on the center lines of the band-shaped transparent electrodes 22. On the upper surfaces of the light emitting layers 24 and 25, the second
The insulating layer 26 (not shown in FIG. 5A) is uniformly laminated, and a plurality of strip-shaped back electrodes 29 are laminated on the second insulating layer 26. This strip-shaped back electrode 29
Are arranged in a direction perpendicular to the direction of the transparent electrode 22,
It has a matrix structure.

In such a multicolor EL display, when a voltage is selectively applied from the transparent electrode 22 and the back electrode 29, the light emitting layer at the intersection of the electrode matrix to which the voltage is applied emits light.

In the above example, two types of EL light emitting elements having different emission colors are used. A red light emitting element (for example, a light emitting layer is formed by adding CaS as a base material to E
u, F), a blue light-emitting device (for example, a light-emitting layer of SrS: Ce, F), a green light-emitting device (for example, a light-emitting layer of ZnS: Tb, F).
Are arranged in a plane to form a full-color E
An L display is also known.

[0005]

However, in the conventional multi-color display EL display, even when the same voltage is applied to the EL elements having different emission colors, the emission luminance differs depending on the material of the emission layer. For example, an EL light-emitting element emitting orange light in which a light emitting layer is obtained by adding Mn which is a light emitting center substance to ZnS which is a base material (ZnS: Mn), and a green light emitting EL light emitting layer in which a light emitting layer is ZnS: Tb, F. In the light emitting element, the luminance of an orange light emitting element using ZnS: Mn as a light emitting layer is high. FIG. 6 shows a comparison between the applied voltage and the luminance of an EL light emitting element using ZnS: Mn for the light emitting layer and an EL light emitting element using ZnS: Tb, F, and the applied voltage is increased. And ZnS: Mn using Z
Light emission starts in a state where a voltage lower than that using nS: Tb, F is applied. Even when the applied voltage is further increased, light is always emitted at a higher luminance than that using ZnS: Tb, F which emits green light. .

When the two kinds of light emitting layers are arranged in a plane and a voltage is applied equally from the transparent electrode and the back electrode arranged in a matrix to display an intermediate color, the luminance of the orange light emitting element is increased. Therefore, even if both light sources emit light uniformly, the color becomes almost orange, and a color corresponding to a substantially intermediate point between orange and green cannot be displayed. For this reason, there is a problem that an image displayed in different colors is not clear.

Further, even when a full-color EL display is formed by using three kinds of light-emitting layers of red, blue and green, a blue light-emitting element having a high luminance has not been developed and the color tone is deteriorated. There is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in consideration of the above-described problems.
It is intended to provide an L display.

[0009]

In order to achieve the above-mentioned object, the present invention provides a transparent electrode, a first insulating layer,
A multi-color display E in which two or more EL light-emitting elements having different emission colors are arranged in a plane, wherein the light-emitting layer, the second insulating layer, and the back electrode are laminated in this order.
In the L display, it is assumed that the two or more types of EL light emitting elements having different emission colors are stacked with insulating layers having different dielectric constants due to different emission colors.

[0010]

In the multi-color display EL display having such a configuration, the insulating layer laminated with the light emitting layer corresponds to the light emitting layer arranged in a plane, and a material having a different dielectric constant due to a difference in the material of the light emitting layer. The element using a material with a high dielectric constant for the insulating layer, even when the same voltage is applied to all the electrodes, is more transient than using a material with a lower dielectric constant. As a result, the voltage applied to both sides of the light emitting layer increases, and the light emission luminance increases. Thereby, the light emission luminance is adjusted. In particular, a high-dielectric-constant material is used as an insulating layer for a light-emitting-layer element having a low light-emitting luminance, and a somewhat low-dielectric-constant material is used for a light-emitting-layer element with a high light-emitting luminance. Adjustments can be made in the same manner, and an appropriate intermediate color display is realized.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a multicolor display E according to an embodiment of the present invention.
1 shows a schematic sectional view of an L display. This EL display has two light emitting elements of orange and green. A plurality of transparent electrodes 2 made of ITO (Indium Tin Oxide) are arranged on a transparent substrate 1 in a strip shape.
A first insulating layer 3 made of SiO ₂ has a thickness of 2500 °
It is deposited with a thickness of. On the upper surface of the first insulating layer 3,
A plurality of band-shaped light emitting layers 5 using ZnS: Mn that emits orange light by applying a voltage, and ZnS: Tb, F that emits green light.
Are arranged alternately in a plane. The light emitting layers have a thickness of 5000 °, and each light emitting layer is located on the transparent electrodes 2 arranged in a strip shape, and the adjacent light emitting layers are not in contact with each other and are spaced apart. On each of the light emitting layers 4 and 5, the second
Insulating layers 6 and 7 are laminated, but a second insulating layer 7 made of SiO ₂ is formed on the light emitting layer 5 made of ZnS: Mn.
But, ZnS: Tb, on the light-emitting layer 4 consisting of F Ta ₂
A second insulating layer 6 made of O ₅ is laminated. These second insulating layers 6, 7 have a thickness of 2500 °. An inter-element insulating layer 8 made of polyimide is formed between the light emitting layers 4 and 5 formed separately. Second
A back electrode 9 made of Al is formed on the upper surfaces of the insulating layers 6 and 7, and the back electrode 9 is divided into strips in a direction perpendicular to the transparent electrode 2 and has a matrix structure as a whole.

In such a multicolor EL display, when a pulse-like voltage is selectively applied from the transparent electrode 2 and the back electrode 9, the light emitting layer at the intersection of the selected matrix electrodes emits light. The light emitting layer at the intersection is Zn
If the light emitting layer 5 is made of S: Mn, it emits orange light,
The light emitting layer 4 made of ZnS: Tb, F emits green light.

FIG. 2 shows the relationship between the light emission luminance and the voltage applied between the electrodes of the orange light emitting element and the green light emitting element in the multicolor EL display of the above embodiment. As shown in this figure, in the multicolor EL display of this embodiment, when the applied voltage is increased, ZnS:
The orange light-emitting element using Mn and the green light-emitting element using ZnS: Tb, F start emitting light at almost the same voltage, and emit light at almost the same luminance even when the applied voltage is further increased. This is because the use of Ta ₂ O _5, which has a higher dielectric constant than SiO _2, as the second insulating layer on the portion above the light emitting layer 4 made of ZnS: Tb, F that emits green light, makes it possible to emit green light. The light emission luminance of the conventional example as shown in FIG. 6 is increased, the difference in the light emission luminance in the conventional example is corrected, and as shown in FIG. 2, the orange light emitting element and the green light emitting element are adjusted to have substantially the same luminance. It is.

Next, a method of manufacturing the multicolor EL display of the above embodiment will be described with reference to FIGS. As shown in FIG. 3A, the transparent substrate 1
A layer of ITO having a thickness of about a predetermined thickness is deposited by an EB evaporation method or a sputtering method, and a plurality of strip-shaped transparent electrodes 2 are formed by a photolithography method. On top of this, SiO
A first insulating layer 3 made of _2-deposit by sputtering or plasma CVD method, or the like. On the first insulating layer 3, as shown in FIG.
S: An Mn layer 15 is deposited by an EB evaporation method or a sputtering method, and then a SiO ₂ layer 17 serving as a _second insulating layer is formed.
Is deposited.

Next, a SiO ₂ layer 17 serving as a _second insulating layer
A resist 10 corresponding to the planar shape and dimensions of the orange light emitting layer is formed on the substrate (FIG. 3C). This resist 10
Is used as a mask to form a SiO ₂ layer 17 serving as a _second insulating layer,
For example, buffered hydrofluoric acid (volume ratio HF: NH ₄ F =
1:10), and then the ZnS: Mn layer 15 as a light emitting layer is etched by, for example, diluted hydrochloric acid (volume ratio conc. HCl: H ₂ O = 1: 1).
An orange light emitting layer as shown in (d) is formed. Further, a ZnS: Tb, F layer 14 serving as a green light emitting layer is formed thereon at a thickness of 5000 ° from the above, followed by a Ta ₂ O ₅ layer serving as a _second insulating layer on the green light emitting layer. 16 is deposited (FIG. 3E).

In the same manner as the method for forming the orange light emitting layer, the resist 11 is formed at a position corresponding to the portion where the green light emitting layer is formed.
(FIG. 4A), and using the resist 11 as a mask, a layer 16 of Ta ₂ O ₅ and ZnS: T to be a green light emitting layer.
The layers 14 of b and F are removed by etching (FIG. 4B).
After etching the Ta ₂ O ₅ layer 16, ZnS: Tb, F
Hydrochloric acid (conc. HCl: H ₂ O = 1: 1) or the like is used as an etchant for etching the layer 14 of FIG.
Since the O ₂ layer 7 is deposited and is resistant to the above-mentioned etchant, the light emitting layer formed earlier by over-etching is not etched. When the etching is completed, the resist 11 is removed, polyimide is applied to fill the concave portions 8 formed between the light emitting layers, and the polyimide is removed from each light emitting layer portion by etching. At this time, the etchant (tetramethylammonium hydroxide) of polyimide is SiO ₂ , Ta ₂ O ₅
Is hardly etched. After the polyimide is removed by etching, an Al layer having a thickness of 4000 ° is deposited by EB evaporation or sputtering, and patterned to form a back electrode 9 (FIG. 4C).

According to the above method, the multi-color display E of this embodiment is
L display can be manufactured, and in such a method, a light emitting layer and an insulating layer laminated thereon are successively deposited, a resist is provided on the insulating layer, and etching is performed. The light emitting layer is not polluted, and uneven brightness is not generated, and the reliability of the device is not reduced.

The embodiment described above has two colors, orange and green.
Although an EL display having EL light-emitting elements of different colors has been described, an EL display having another light-emitting color may be used. In this case, the second insulating layer may have a different dielectric constant depending on the material of the light-emitting layer. Different suitable materials can be used. Also, the insulating substrate, the electrodes, the first insulating layer, and the like can be made of other suitable materials. Further, the multi-color display EL display of the present invention is not limited to the one having two-color EL light-emitting elements, but is a full-color EL having three-color EL light-emitting elements.
In this case, the second insulating layer can be made of a different material for each of the three color light emitting elements, and the same material can be used for the two color light emitting elements for the other one color light emitting element. Different materials can be used.

[0019]

As described above, in the multicolor EL display of the present invention, the insulating layer laminated with the light emitting layer is
Since the materials correspond to the light emitting layers arranged in a plane and have different dielectric constants depending on the material of the light emitting layer, all of the E
Even when the voltage applied between the transparent electrode and the back electrode of the L light emitting element is equal, the voltage applied to both surfaces of the light emitting layer is different due to the difference in the dielectric constant of the insulating layer, and the light emission luminance of the light emitting layer is adjusted. As a result, it is possible to correct a difference in light emission luminance depending on the type of the light emitting layer, and to obtain a multicolor EL display capable of displaying an appropriate intermediate color.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of a multicolor EL display according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a voltage applied to an electrode of a light emitting element of the multicolor display EL display of the embodiment and light emission luminance.

FIG. 3 is an explanatory diagram showing a method of manufacturing a multicolor display EL display according to the embodiment.

FIG. 4 is an explanatory diagram showing a method of manufacturing the multicolor display EL display according to the embodiment.

FIG. 5 is a schematic diagram showing a conventional multicolor display EL display.

FIG. 6 is a diagram illustrating a relationship between a voltage applied to an electrode of a light emitting element of a conventional multicolor EL display and light emission luminance.

[Description of sign]

REFERENCE SIGNS LIST 1 transparent substrate 2 transparent electrode 3 first insulating layer 4 green light emitting layer 5 orange light emitting layer 6 second insulating layer made of Ta ₂ O ₅ 7 _second insulating layer made of SiO ₂ 8 inter-element insulating layer made of polyimide 9 Back electrode 10, 11 Resist

Claims (1)

(57) [Claims] 1. A dual-insulation-structure thin-film EL light-emitting device comprising a transparent substrate, a transparent electrode, a first insulating layer, a light-emitting layer, a second insulating layer, and a back electrode, which are sequentially laminated. -Color display EL in which EL light-emitting elements having different emission colors are arranged in a plane
2. A multi-color display according to claim 1, wherein said at least two EL light-emitting elements having different emission colors are stacked with insulating layers having different dielectric constants due to different emission colors.