JPH0745369A - El element - Google Patents

Abstract

PURPOSE:To improve initial electro-optical properties and reliability by forming a back plate out of conductive paste material where silver particles and carbon particles are mixed together. CONSTITUTION:A transparent electrode layer 4, an electric field light emitting layer 6, a reflective insulating layer 8, and a back plate electrode layer 10 are stacked in order on a transparent glass board 2. This layer 10 is made of conductive paste material in which silver particles and carbon particles are dispersed in binder resin and which has approximately the same resistivity as silver paste. And, the diameter of silver particles is made 10nm to 1mum, and the diameter of carbon particles is 0.05nm to 5nm, and such silver particles and carbon particles are mixed at the rate of 30 to 70 through 90 to 5 by weight. Hereby, initial electro-optical properties and reliability approximately on the same level as the layer 10 of an aluminum foil can be accomplished, and also with this conductive paste, the screen printing propriety is favorable, so the conventional migration of silver particles is suppressed, and the corrosion resistance to an external lead improves, and also the manufacture method can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EL element (electroluminescence element) having a transparent glass substrate,
In particular, the present invention relates to a highly reliable EL element having an excellent light emission life.

[0002]

2. Description of the Related Art In recent years, an EL element has been attracting attention as a backlight of a liquid crystal display device because a light-weight, thin and uniform surface light source can be obtained. The structure of this EL element is, for example,
Using a transparent glass substrate on the light emitting surface side, on this transparent glass substrate, a transparent electrode layer, an electroluminescent layer, and a back electrode layer are laminated, and further, a moisture-proof back plate is laminated from the back electrode side,
The peripheral edges of the transparent glass substrate and the back plate are hermetically sealed with an adhesive.

As a method of forming the back electrode layer of such an EL element, there are a method of laminating a metal foil such as aluminum and copper, a method of depositing aluminum, gold and the like, a method of printing a conductive paste material and the like. However, since the transparent glass substrate may be damaged when pressure is applied and the alignment between the transparent glass substrate and the metal foil is difficult, the method of laminating the metal foil is not used, and the vapor deposition method is also used. Then
A large-scale vacuum system device is required, and in an EL element using a transparent glass substrate, a method of printing a conductive paste material is suitable for forming a back electrode layer.

As a known example of printing a conductive paste material on the back electrode layer, for example, as disclosed in Japanese Patent Laid-Open No. 62-195895, a binder resin prepared by dissolving the conductive paste material in a nonpolar solvent is used. It is disclosed that conductive particles such as silver and carbon are dispersed therein.

However, JP-A-62-195895
In the publication, only one of silver and carbon is dispersed as the conductive particles, and mixing of silver and carbon is not disclosed. Usually, when a conductive paste material made of silver is used, it is excellent in initial electro-optical characteristics such as brightness, luminous efficiency, and color tone, but it is more reliable in terms of brightness life, etc., as compared with one using an aluminum foil for the back electrode layer. There is a problem of being inferior. In addition, when used at high temperature and high humidity, there is a problem that the blackening of the light emitting surface is likely to proceed, and a spot pattern is likely to occur. On the other hand, when a conductive paste material made of carbon is used, it is almost the same in terms of reliability such as brightness life as compared with the one using aluminum foil for the back electrode layer, but the specific resistance is about 5 digits. Since it is high, there is a problem that initial electro-optical characteristics such as brightness, luminous efficiency, and color tone are significantly deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to use a transparent glass substrate in which a conductive paste material is used for the back electrode layer. An object of the present invention is to provide an EL element formed by using the same and having excellent initial electro-optical characteristics and reliability.

[0007]

The inventors of the present invention have excellent initial electro-optical characteristics and reliability by forming the back electrode layer with a conductive paste material in which silver particles and carbon particles are mixed. As a result of earnest research, the following invention was completed under the idea that an EL element could be provided.

That is, the above object is to provide a transparent glass substrate,
A transparent electrode layer, an electroluminescent layer, a reflective insulating layer, and a back electrode layer, which are sequentially formed on this transparent glass substrate, are superposed on this back electrode layer, and are hermetically sealed in the transparent glass substrate at their peripheral portions. In an EL element including a back plate, a back electrode layer is formed by dispersing silver particles and carbon particles in a binder resin, and is formed of a conductive paste material having a specific resistance almost equal to that of the silver paste. This is solved by an EL element characterized by the following.

Preferably, the silver particles have a particle size of 10 nm to 1
μm, while carbon particles are 0.05 nm to 5
nm, and the mixing ratio of silver particles to carbon particles is 30:70 to 90: 5 by weight.

[0010]

Since the conductive paste material of the back electrode layer is made by dispersing silver particles and carbon particles in the binder resin and has a specific resistance which is almost the same as that of the silver paste, the conductive paste material composed of only silver particles is used. Almost the same as a conventional EL element with a back electrode layer formed of a paste material,
Initial electro-optical characteristics such as brightness, luminous efficiency, and color tone can be obtained.
In addition, the reliability such as the brightness life can be obtained, which is almost the same as that of the conventional EL element having the back electrode layer formed of the conductive paste material including only carbon particles.

Further, by selecting silver particles and carbon particles having a specific particle diameter, and making the silver particles and the carbon particles have a specific mixing ratio, initial electro-optical characteristics such as brightness, luminous efficiency and color tone, It is possible to obtain an EL element that is excellent in both reliability such as brightness life.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the EL device of this embodiment in cross section. This EL element has a transparent glass substrate 2, and a transparent electrode layer 4 made of an ITO (indium oxide / tin oxide alloy) thin film is laminated on the transparent glass substrate 2. On the transparent electrode layer 4, an electroluminescent layer 6 formed by dispersing and coating electroluminescent phosphor particles in a suitable binder, an organic binder having a high dielectric constant, and a powder of barium titanate or the like having a high dielectric constant. A reflective insulating layer 8 dispersed and applied, and a back electrode layer 10 made of a conductive paste material in which silver particles and carbon particles are mixed are sequentially laminated. A back plate 12 made of a multilayer film containing aluminum foil is laminated on the back electrode layer 10, and a peripheral edge portion of the back plate 12 is provided with a sealing resin layer 14 made of an adhesive such as hot melt or the like. The electrode portion 102 of the back electrode layer 10, which will be described later, the current collecting band 16 and the transparent glass substrate 2 are hermetically sealed. Preferably, a current collecting band layer is formed on the transparent electrode layer 4 with a material such as a silver paste or an aluminum vapor deposition film along one edge portion or a peripheral edge portion of the electroluminescent layer 6.

Here, the transparent glass substrate 2 may be ordinary soda glass, and has a plate thickness of about 0.1 to 5.0 mm, and in consideration of weight, a substrate of about 0.4 to 1.1 mm. preferable. Further, in order to prevent alkali elution from glass, a thin film of silica, alumina or the like may be coated. The transparent electrode layer 2 can be formed of a material such as tin oxide or indium oxide in addition to ITO by a method such as vacuum deposition, sputtering, or a sol-gel method, and is usually several Ω /
It is possible to use a □ to several thousands Ω / □, but it is preferable to use a Ω / □ to 300 Ω / □.

The electroluminescent layer 6 can be formed by applying a paste in which zinc sulfide-based electroluminescent phosphor particles are dispersed in a suitable organic binder to a film thickness of 20 to 60 μm by screen printing or the like. Similarly, the reflective insulating layer 8 is also formed by screen printing to have a thickness of 10 to 30 μm.

Of particular note is the back electrode layer 10.
Are formed of a conductive paste material in which silver particles and carbon particles are dispersed in a binder resin. As the binder resin, acrylic resin, epoxy resin, urethane resin,
Saturated polyester resin, silicone resin and the like can be exemplified, and as the silver particles, ordinary commercially available ones can be used, but the particle size thereof is 0.05 to 5 μm, preferably in order to obtain a low resistance value as the conductive paste material. It is 0.5 to 3 μm. Examples of the carbon particles include channel black, oil furnace black, acetylene black, thermal black, graphite and the like, and the particle size thereof is 10 nm to 1 μm in order to obtain a low resistance value as a conductive paste material.

Such silver particles and carbon particles are mixed in a weight ratio of 30:70 to 95: 5.
In order to reduce the resistance value of the conductive paste material, it is desirable that the particle size of the carbon particles be small and that the carbon particles be uniformly dispersed.

Since the printability of such a conductive paste material is good, the back electrode layer 10 usually has a thickness of 3 μm to 3 μm.
It is formed with a thickness of 0 μm. It should be noted that the specific resistance of such a conductive paste is 5 × 10 ⁻⁵ ,
This specific resistance is almost the same as that of the silver paste alone.
Further, in the case of the silver paste, the migration property is poor, whereas when the back electrode layer 10 is formed using such a conductive paste material, the migration resistance is excellent and the corrosion resistance to the external lead portion is improved. The overcoating with the carbon paste, which has been carried out in the case of the silver paste, can be omitted.

Hereinafter, the EL device having such a structure will be described.
The luminous efficiency and the efficiency half-life in the case of manufacturing with the external dimensions of cm × 100 cm will be described. For comparison, a conventional EL device was prepared in which the back electrode layer 10 was the same except that it was formed of aluminum foil, silver paste, and carbon paste.

The luminous efficiency is measured at 1 kHz, 100 V,
It is a relative value when driving with a sine wave and setting the case of aluminum foil as 100. Silver paste: 100%. Carbon paste: 80%. Example: 98%.

The efficiency half-life is measured at 60 ° C. and 80% RH.
Under the environmental conditions of 1 kHz, driving was performed with a sine wave at 1 kHz and 100 V, and the luminance half-life time was measured. Aluminum foil ・ ・ ・ 1000 hours. Silver paste: 600 hours. Carbon paste: 1100 hours. Example: 1050 hours.

[0022]

As described above, according to the present invention, by forming the back electrode layer with a specific conductive paste material that mixes silver particles and carbon particles, it is almost the same as the back electrode layer of aluminum foil. It is possible to provide an EL element having excellent initial electro-optical characteristics and reliability. Since this conductive paste has good screen printing suitability, it suppresses the migration of conventional silver particles, improves the corrosion resistance to the external lead-out part, and is simple in the manufacturing method, so it has high industrial utility value. It is a thing.

[Brief description of drawings]

FIG. 1 is a sectional view of an EL device according to an embodiment of the present invention.

[Explanation of reference numerals] 2 transparent glass substrate 4 transparent electrode layer 6 electroluminescent layer 8 reflective insulating layer 10 back electrode layer 12 back plate 14 sealing resin layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Shimizu 100 491, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd.

Claims (2)

[Claims] 1. A transparent glass substrate, a transparent electrode layer, an electroluminescent layer, a reflective insulating layer, and a back electrode layer, which are sequentially formed on the transparent glass substrate, and are overlapped with the back electrode layer and a peripheral portion thereof. In an EL device comprising a back plate hermetically sealed in the transparent glass substrate, the back electrode layer is formed by dispersing silver particles and carbon particles in a binder resin, and is almost the same as the silver paste. An EL element formed of a conductive paste material having a specific resistance. 2. The silver particles have a particle size of 10 nm to 1 μm.
On the other hand, the carbon particles have a thickness of 0.05 nm to 5
2. The EL device according to claim 1, wherein the EL device has a thickness of 30 nm and a mixing ratio of silver particles and carbon particles of 30:70 to 90: 5 by weight.