JPH05326147A - Electroluminescent element capable of taking out light from both surfaces - Google Patents

Abstract

PURPOSE:To provide an EL element capable of taking out light from both surfaces by dispersing and fixing a conductive fine powder which has specified particle size and volume resistivity and is transparent to visual lights onto a current limiting layer with a transparent binder. CONSTITUTION:Onto a transparent elliptic base 1, a transparent electrode 2, a light emitting layer 3, a current limiting layer 4 onto which a conductive fine powder is dispersed and fixed with a transparent binder, and a transparent back plate 5 are successively laminated to provide an EL element. In this constitution, the conductive fine powder has a particle size less than 100nm, and is transparent to visual lights, and its volume resistivity is set less than 10<5>OMEGAcm. When the thickness of the current limiting layer 5 is 500nm, the visual light transmittance of the limiting layer 5 is preferably 50% or more, and indium oxides are used. The ratio of the conductive fine powder to the transparent binder resin preferably ranges from 50/50 to 60/60 by weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence element (EL element), and more particularly, to a hybrid EL element capable of direct current driving capable of extracting light from both sides.

[0002]

2. Description of the Related Art An EL display to which an EL element is applied is one of the promising flat panel displays which has been rapidly prevailing in terminals of portable type computers in recent years. Two types of EL elements are known, a thin film type EL element and a powder type EL element. Recently, a hybrid EL element (also called a hybrid EL element or a composite EL element) in which a thin film type and a powder type are combined. ) Has become the focus of attention as a powerful display element (for example, British Patent Publication 217).
6340A and 2176341A).

[0003]

However, in the above-mentioned conventional hybrid molding EL element, M is used as the conductive powder.
Since black fine powder such as nO ₂ , TiO ₂ , Fe ₃ O ₄ , and carbon black was used, light could only be extracted from one direction of the EL element to the outside.

[0004]

According to the present invention, a transparent electrode, a light emitting layer, a current limiting layer comprising conductive fine powder dispersed and fixed with a transparent binder and a transparent back electrode are sequentially provided on a transparent insulating substrate. A laminated electroluminescent device, wherein the conductive fine powder has a particle size of 100 nm or less, is transparent to visible light, and has a volume resistivity of 10 ⁵ Ωcm or less. It is an electroluminescent element that can extract light from the.

The thickness of the current limiting layer of the present invention is preferably 5 μm to 30 μm. The current limiting layer serves to prevent the resistivity of the light emitting layer from decreasing during light emission, and prevent an excessive current from flowing through the EL device to destroy the device. The larger the resistance of the current limiting layer is, the more stable it will be against breakdown, but if it is too large, the voltage drop in the current limiting layer becomes large, which leads to an increase in the drive voltage of the EL element. 50 to 50 μm per unit area (1 cm ² ) in the film thickness direction in the range of 30 to 30 μm.
It is preferable to have a resistance value of Ω to 200 Ω, that is, a resistivity of 1 × 10 ⁴ Ωcm to 5 × 10 ⁵ Ωcm.

The conductive fine particles constituting the current limiting layer of the present invention have a volume resistivity of 10 ⁵ Ωcm or less, a particle diameter of 100 nm or less, and are transparent to visible light. is necessary. Then, the thickness of the current limiting layer in which the conductive fine particles are dispersed in the organic binder is 500
nm, the visible light transmittance of the current limiting layer is 50%
It is preferable to make it above. Examples of such fine particles include indium tin oxide, indium oxide, tin oxide doped with antimony or fluorine, indium, aluminum, zinc oxide doped with silicon, cadmium indium oxide, cadmium tin oxide, and a mixed oxide thereof. The thing can be illustrated.

The weight ratio of the conductive fine particles to the transparent binder resin is preferably about 20/80 to 90/10, more preferably 50/50 to 60/60. As a method for dispersing the fine particles in the binder, a method in which the fine particles are directly dispersed in a binder resin diluted with a solvent to have an appropriate viscosity, or a sol of fine particles is prepared in advance and dispersed in the binder resin Any method can be used.

Examples of binder resins that can be used in the present invention include vinyl resins, polyester resins, polyamide resins, cellulose resins, polyurethane resins, urea resins, epoxy resins, melamine resins, and silicone resins. Examples of the resin include a hydroxyl group, a carboxyl group, a sulfonyl group, a polar group such as a nitro group, and an epoxy group, an isocyanuric group, a polymer resin having a reactive group such as a silanol group is preferably used. There is.

[0009]

The function of the substrate, the transparent electrode, and the
Since the current limiting layer and the transparent back electrode are both transparent to visible light, the light emitted from the light emitting layer can be extracted in both directions of the EL device.

[0010]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a diagram showing the layer structure of the hybrid EL device of the present invention. FIG. 2 is a diagram showing the current density dependence of the luminance of the light emission observed on the glass substrate side and the current limiting layer side of the EL device of the present invention.

A transparent electrode film such as indium tin oxide (ITO) is formed as a transparent electrode 2 on the glass substrate 1 by sputtering, vacuum deposition or the like, and then formed into a predetermined shape by a method such as photolithography. Pattern. The light emitting layer 3 is formed thereon by vacuum deposition method, sputtering method, M
It is formed using a method such as the OCVD method. Examples of the material of the light emitting layer include ZnS, ZnSe, CdS, and other 2-6 group compounds, transition metals such as Mn and Cu, and Tb, Sm, and Dy.
A rare earth element such as the above or a fluoride or chloride thereof doped with an emission center is often used. On top of that, the current limiting layer 4 is transparent to visible light and
A conductive fine powder having a particle size of 00 nm or less is hardened with a transparent organic binder to form a fine powder layer of about ten and several μm by a method such as a spray method. Finally, the transparent back electrode 5 is formed by vacuum evaporation or sputtering to complete the hybrid EL device of the present invention.

In the case of manufacturing a dot matrix type display panel, thereafter, the transparent back electrode and the current limiting layer are simultaneously scratched by using a diamond needle or the like to perform electrode patterning in a predetermined shape. The EL element is driven by applying a DC voltage between the transparent electrode 2 and the transparent back electrode 5 to cause light emission. Example ITO was deposited as a transparent electrode on a transparent glass substrate to a thickness of about 500 nm by a reactive sputtering method. Subsequently, Zn doped with 0.3% by weight of Mn as a light emitting layer
S was formed into a film by using an electron beam evaporation method of about 1 μm. Next, a paint in which antimony tin oxide containing 10 wt% of antimony is dispersed in a mixed liquid of a binder resin and a thinner is applied by an applicator coating method and dried to have a resistivity of 6.
A current limiting layer having a thickness of 2 × 10 ⁴ Ωcm and a thickness of 8.5 μm was formed. Next, as a transparent back electrode, ITO was formed into a film with a thickness of about 500 nm by the reactive sputtering method. When the EL device thus produced was connected to a DC drive circuit to emit light, light emission was obtained from both sides. FIG. 2 shows the current density dependence of the luminance of light emission observed on the substrate side and the current limiting layer side. About 65% of light on the glass side was obtained from the current limiting layer side. Conventional Example MnO ₂ powder produced by the electrolysis method was crushed with a ball mill to an average particle size of 0.3 μm, and this was mixed with a binder resin so that the volume ratio of MnO ₂ powder to the binder resin was 3: 7. A mixed liquid with a thinner was added and dispersed to prepare a paint. This paint was applied by a spray method onto the light emitting layer of the glass substrate on which the light emitting layer and the transparent electrode were formed in the same manner as in the example, and dried to have a resistivity of 1.3 × 1.
A current limiting layer having a thickness of 0 ⁵ Ωcm and a thickness of 13 μm was formed. Next, as a back electrode, aluminum was formed into a film with a thickness of about 600 nm by using a vapor deposition method. The device thus manufactured was able to obtain light only from one direction of the glass substrate.

[0013]

According to the EL element of the present invention, by sequentially stacking panels having monochrome light emitting layers of three primary colors,
It is possible to manufacture a multi-color panel. Further, the color filter can be easily formed by printing the color filter on the transparent back electrode. Further, since there is no high temperature firing operation after the step of forming the transparent back electrode, an organic filter can be used, and a display body capable of displaying pictures and characters on a glass substrate can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a layer structure of a hybrid EL device of the present invention.

FIG. 2 is a diagram showing the current density dependence of the luminance of the light emission observed on the substrate side and the current limiting layer side of the hybrid EL device of the present invention.

[Explanation of symbols]

1 ... Glass substrate, 2 ... Transparent electrode, 3 ... Light emitting layer, 4 ... Current limiting layer, 5 ... Transparent back electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunji Wada 3-5-11 Doshumachi, Chuo-ku, Osaka-shi, Osaka Within Nippon Sheet Glass Co., Ltd. (72) Inventor Katsuhisa Enjoji 3-chome, Dosho-machi, Chuo-ku, Osaka 5th-11th Nippon Sheet Glass Co., Ltd.

Claims (1)

[Claims] 1. An electroluminescent device comprising a transparent insulating substrate, a transparent electrode, a light emitting layer, a current limiting layer in which conductive fine powder is dispersed and fixed by a transparent binder, and a transparent back electrode, which are sequentially laminated. The electroconductive fine powder has a particle size of 100 nm or less, is transparent to visible light, and has a volume resistivity of 10 ⁵ Ωcm or less, and an electroluminescent element capable of extracting light from both sides.