JP2002270379A - Electroluminescence - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a quantity of emitting light of electroluminescence 1.5 to 2 times over the conventional one. SOLUTION: An ITO transparent electrode having a shape of unevenness, which inorganic transparent fine powder such as alumina, silica, or the like, is distributed and fixed, is formed with the mixture of the inorganic transparent fine powder and ITO, which is made as paint.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroluminescence.

[0002]

2. Description of the Related Art Electroluminescence (hereinafter, referred to as EL) is widely used as a lighting device for a liquid crystal display device mounted on a portable timepiece, a cellular phone, or the like. In recent years, colorization of emission color has been developed as a variety of display devices.

Hereinafter, a conventional EL will be described with reference to the drawings. FIG. 4 is a cross-sectional view showing the structure of a conventional EL, and FIG. 5 is an enlarged cross-sectional view of a main part showing the structure of the conventional EL.

In FIG. 4, EL 10 is a transparent substrate 17.
A transparent electrode 16, a luminescent layer 15 containing luminescent powder 14, a dielectric layer 13, and a back electrode 12 are sequentially formed on the lower surface of the substrate, and then sealed with an insulating film 11 having moisture-proof and insulating properties. .

In the EL 10 having such a structure, an AC voltage is applied between the transparent electrode 16 and the back electrode 12 so that the light emitting layer 15 in the light emitting layer 15 sandwiched between the electrodes 16, 12 is formed. The EL molecules of the phosphor fine powder 14 are excited, and a light emission phenomenon appears. In particular, the transparent electrode 16 is made of indium tin oxide (hereinafter referred to as ITO).
The light emitted from the light emitting layer 15 is transmitted through the transparent electrode 16 and radiated to the outside.
The entire L10 emits light brightly.

The transparent substrate 17 is formed of a transparent resin (polyethylene terephthalate) film, a glass plate, an acrylic plate, or the like, and has a light transmitting property.

The transparent electrode 16 is formed by vacuum-depositing ITO powder obtained by doping indium oxide with tin oxide,
It is formed to a thickness of approximately 0.05 to 0.2 μm. The film surface of the electrode is formed substantially flat. The obtained film has high conductivity and very low electric resistance.

The luminous layer 15 is formed on the upper surface of the transparent electrode 16.
Formed by screen printing. The material is made by dispersing a fine powder of luminescent material doped with a small amount of activator such as copper or manganese or activator such as chlorine with zinc sulfide or the like as a luminescent base material in a high dielectric resin binder, for example, a cyanoresin compound, and forming a paint. It was done.

The thickness of the light emitting layer formed by the above method is 3
The luminescent fine particles 14 having a size of 0 to 60 μm and a size of 10 to 50 μm are randomly dispersed therein.

The dielectric layer 13 is provided for the purpose of protecting the light emitting layer 15 from electrical breakdown, and is made of a material having a high withstand voltage. As such a material, there is barium titanate, which is formed by screen printing with a paint in which barium titanate is dispersed.

Since barium titanate has a high light reflectance, it also serves as a reflector for reflecting light emitted from the light emitting layer 15 to the transparent electrode 16 side.

The back electrode 12 is formed by bonding an aluminum foil or by printing and forming a silver powder or a graphite powder into a paste. The insulating film 11 is made of a resin film such as polyethylene terephthalate, which also has moisture-proof properties, or an insulating resin, and seals the entire EL 10. Although not shown in the figure, an electrode terminal is provided on the rear electrode 12 of the transparent electrode 16 and is connected to an external electrode.

Next, FIG. 5 will be described. When an AC voltage is applied between the transparent electrode 16 and the back electrode 12, the EL molecules of the phosphor fine powder 14 are in an excited state, and exhibit a light emission phenomenon. Then, the emitted light 14A passes through the transparent electrode 16 and the transparent substrate 17, and is emitted to the outside.

[0014]

As described above, the EL having such a structure is provided under a liquid crystal cell in a portable watch and a liquid crystal cell in a telephone or the like to illuminate a display. The area where the EL emits light is designed within a limited display area due to the display area of the device and the like. There is a limit to the amount of emitted light that can be extracted, and it is necessary to improve technical factors including applied voltage and frequency in order to further improve luminance.

[0015] An object of the present invention is to solve the above-mentioned problems, and to improve the luminous efficiency and improve the luminance by 1.5 to 2 times with respect to the conventional EL by forming the transparent electrode. It is to provide an EL that can be used.

[0016]

The gist of the present invention to achieve the above object is as follows.

1. In the transparent substrate, a transparent electrode, a luminescent layer, a dielectric layer, and a back electrode are sequentially laminated, and an AC voltage is applied between the transparent electrode and the back electrode to cause the luminescent layer to emit light. The electrodes are
It is characterized by being constituted by an ITO electrode film having irregularities.

2. The transparent electrode has a transparent inorganic fine powder dispersed,
It is characterized by being fixed.

3. The transparent inorganic fine powder is selected from inorganic compounds.

4. The transparent inorganic fine powder has an outer diameter of 1 to 5 μm.
m.

5. One of the inorganic compounds is characterized by being alumina.

6. One of the inorganic compounds is characterized by being silica.

7. In the production of a transparent electrode, the electrode comprises:
It is characterized by being formed by screen printing and firing on a transparent substrate by a mixture of a paint and transparent inorganic fine powder.

8. The paint and the inorganic fine powder are characterized in that the weight ratio is 100 parts by weight to 10 to 30 parts by weight.

9. The screen printing is performed in a thickness of 5 to 15 μm.

10. The paint is characterized by being composed of indium organic acid, tin organic acid and a binder.

11. The organic acid indium is characterized in that indium acetylacetone is selected.

12. The organic acid tin is characterized in that dibutyltin acetate is selected.

13. The binder is characterized in that nitrocellulose is selected.

14. The mixture of organic acid indium and organic acid tin and the binder are 1.5 to 6% by weight to 98.5 to 94% by weight.
It is characterized by being

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIGS. 1, 2 and 3 show an EL showing an embodiment of the present invention. FIG. 1 is a cross-sectional view showing the structure of the EL.
FIG. 2 is an enlarged sectional view of a main part showing the structure of the EL, and FIG.
FIG. 4 is a cross-sectional view showing a method for forming a transparent electrode of EL.

As shown in FIGS. 1 and 2, EL 1 is composed of a transparent electrode 7 in which a transparent inorganic fine powder 8 is dispersed and fixed on the lower surface of a transparent base 9, a luminescent layer 6 containing the luminescent fine powder 5, a dielectric After the layer 4 and the back electrode 3 are sequentially formed, they are sealed with an insulating film 2 having moisture-proof and insulating properties.

The transparent inorganic fine powder 8 is dispersed and fixed in the transparent electrode 7. As transparent inorganic fine powder,
Alumina, silica and the like are selected. This fine powder is
A size of 5 μm is preferable. If the size is smaller than 5 μm, the unevenness is reduced, and the increase in luminance is poor. On the other hand, if it is too large, the thickness of the transparent electrode 7 becomes uneven, and the resistance value varies greatly. Transparent inorganic fine powder 8
Has a thickness of about 0.1 μm, and the transparent electrode 7 is fixed at this thickness. Then, when an AC voltage is applied between the transparent electrode 7 and the back electrode 3, the EL molecules are brought into an excited state, exhibiting a light emission phenomenon, and the light 5a
Is a transparent substrate 9 through a transparent inorganic fine powder 8 and a transparent electrode 7.
Radiated from outside.

Next, a method for forming the transparent electrode 7 in which the transparent inorganic fine powder 8 is dispersed will be described with reference to FIG. As shown in Fig. 3 (a), first, a mixture of inorganic acid indium acetylacetone indium and a small amount of organic acid tin diptyltin diacetate as a dopant is mixed with a nitrocellulose binder to form a paint. Further, the above-mentioned transparent inorganic fine powder such as alumina and silica is dispersed in this paint, and the resulting mixture is screen-printed on a transparent substrate 9 such as a glass plate to form a transparent electrode print layer 7A. The printing thickness is about 10 μm. Here, the thickness of the transparent electrode printing layer 7A is preferably in the range of 5 to 15 μm. If the thickness is smaller than this, the resistance value of the transparent electrode increases and the fixing strength of the transparent inorganic fine powder decreases, which is not preferable. On the other hand, increasing the thickness is not preferable because the number of times of printing increases and the printing cost also increases.

The mixture ratio of the mixture of indium acetylacetonate and dibutyltin diacetate and nitrocellulose is 1.5 to 6% by weight to 98.5 to 94% by weight. If it is less than this, the resistance value will be large, and if it is more than this, cracks will easily occur after firing.

Next, as for the mixing ratio of the transparent inorganic fine powder, 10 to 30 parts by weight of the paint formed by the above mixing is mixed with 100 parts by weight. If the weight is less than this, the uneven portion becomes sparse, the increase in brightness is small, and uneven brightness occurs partially. On the other hand, if the weight is larger than this, the printing workability deteriorates.

After forming the transparent electrode printing layer 7A, FIG.
As shown in (b), by baking at a temperature of about 500 ° C., nitrocellulose as a binder evaporates, and the coating of the transparent electrode 7 made of indium oxide and tin oxide becomes a transparent substrate 9 such as glass. It is formed so as to cover the transparent inorganic fine powder 8.

Nitrocellulose as a binder is selected as a suitable binder because it easily forms an oxide film on indium or tin.

The coating of the transparent electrode 7 formed in this way has a strong bonding force, and firmly fixes the transparent inorganic fine powder 8. Further, a material having high transparency can be obtained.

Next, FIG. 3C shows the transparent electrode 7 shown in FIG.
The light emitting layer 6 is formed on the light emitting layer 6 by the same method as the conventional method. The luminous body layer 6, the dielectric layer 4, the back electrode 3, and the insulating film 2 are the same as those in the related art, and thus the description is omitted.

[0041]

As described above, according to the present invention, by adopting the above-described structure in the transparent electrode 7, the unevenness of the transparent electrode is increased, and the transparent electrode 7 penetrates into the luminous body layer 6.
The light 5 emitted inside the luminous body layer 6 by being formed
a can be taken out from the portion of the transparent inorganic fine powder 8 that has penetrated, and a large amount of light can be emitted to the front side. Also, by forming a transparent electrode having irregularities, the surface area in contact with the luminescent layer becomes very large,
A large amount of emitted light can be taken out, and the luminance can be greatly improved 1.5 to 2 times as compared with the related art, and the EL of the present invention is extremely effective.

[Brief description of the drawings]

FIG. 1 is a sectional view of an EL structure showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of an EL structure showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a method of forming an EL transparent electrode according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the structure of a conventional EL.

FIG. 5 is an enlarged sectional view of a main part showing a structure of a conventional EL.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 EL 2 insulating film 3 back electrode 4 dielectric layer 5 luminescent fine powder 6 luminescent layer 7 transparent electrode 8 transparent inorganic fine powder 9 transparent base 5a light

Claims (14)

[Claims] 1. An electroluminescent device in which a transparent electrode, a luminescent layer, a dielectric layer, and a back electrode are sequentially laminated on a transparent substrate, and an AC voltage is applied between the transparent electrode and the back electrode to cause the luminescent layer to emit light. In luminescence, the transparent electrode has an uneven shape, and is formed of indium tin oxide (Indi-tin oxide).
um Tin Oxide) Electroluminescence characterized by comprising an electrode film. 2. The electroluminescence according to claim 1, wherein the transparent electrode has a transparent inorganic fine powder dispersed and fixed therein. 3. The electroluminescence according to claim 2, wherein the transparent inorganic fine powder is selected from inorganic compounds. 4. The transparent inorganic fine powder has an outer diameter of 1 to 5 μm.
The electroluminescence according to claim 2 or 3, wherein 5. The electroluminescence according to claim 3, wherein one of the inorganic compounds is alumina. 6. The electroluminescence according to claim 3, wherein one of the inorganic compounds is silica. 7. The method according to claim 1, wherein in the production of the transparent electrode, the electrode is formed by screen-printing a mixture of a paint and a transparent inorganic fine powder on a transparent substrate, followed by firing. luminescence. 8. The paint and the transparent inorganic fine powder are 100 parts by weight.
8. The composition of claim 7, wherein the amount is from 10 to 30 parts by weight.
Electroluminescence as described. 9. The electroluminescence according to claim 7, wherein the screen printing is performed with a thickness of 5 to 15 μm. 10. The electroluminescence according to claim 7, wherein the paint is composed of an organic indium, an organic tin, and a binder. 11. The organic acid indium is selected from indium acetylacetone.
Electroluminescence as described. 12. The electroluminescence according to claim 10, wherein the organic acid tin is selected from dibutyltin acetate. 13. The electroluminescence according to claim 10, wherein nitrocellulose is selected as the binder. 14. The electroluminescence according to claim 10, wherein the weight ratio of the mixture of the organic indium and the organic tin and the binder is 1.5 to 6% to 98.5 to 94%.