JPS60185394A - Electric field light emitting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an electroluminescent device that emits light by applying an electric field to a phosphor layer.

(Prior Art and its Problems) The phenomenon of light emission caused by applying an electric field to a manganese-diffused fluorescent material such as ZnS has been known as electroluminescence (hereinafter referred to as EL). A conventional electroluminescent device using EL is explained with reference to FIG. 1.
is a transparent insulating plate (made of a glass substrate, a plastic film substrate, etc.); 2 is a transparent electrode formed inside the transparent insulating substrate 1;
It is a layer with a sheet resistance of 0.07 or more, which is made of a thin film of metal oxide of 0.2 $, a thin film of gold, palladium, etc., or a thin film of metal such as aluminum, copper, etc. in which small mesh holes are formed. 3 is a counter electrode provided facing the transparent electrode 2, and is made of, for example, metal powder such as silver dispersed in an organic polymer or inorganic binder, or a thin film of metal such as aluminum or copper. Become. Reference numeral 4 denotes a phosphor layer provided between the transparent electrode 2 and the counter electrode 3, in which phosphor powder made by doping ZnS with an activator such as copper or manganese and an activator (=1) such as chlorine is coated with an organic polymer. It is made by dispersing it in a binder. Phosphor powders also include those using elements of the genus group, -valent metals, transition metals, etc. Similarly, 5 is the (
It is an insulating layer provided in 1f1, and is made of TiO2 or BaTi.
A high dielectric constant powder such as f'+3 is dispersed in a) mechanical polymer binder. These layers are entirely covered with a moisture-proof protective film 6 made of 1fitrifluoroethylene, epoxy resin, or the like. When an AC voltage is applied between the transparent electrode 2 and the counter electrode 3, an electric field corresponding to the voltage and frequency is applied to the phosphor layer 4, causing it to emit light. Note that there is also a DC electroluminescent device that can omit the insulating layer 5 and can be driven by DC voltage.

However, in the electroluminescent device as described in "-", there is a problem in that moisture enters inside and the phosphor of the phosphor layer 4 decomposes in a very short time, resulting in severe deterioration of luminance.

In this case, although the entire structure is covered with the moisture-proof protective film 6, a small amount of moisture enters from the surface of the moisture-proof protective film 8, the adhesive part, and the lead wire extraction part.
The moisture-proofing effect was not sufficient.

Therefore, as shown in FIG. 1, on the display surface side of the transparent insulating substrate 1 and/or on the side opposite to the light emitting surface of the counter electrode 3, a transparent material made of nylon 6, nylon 6.6, etc. is coated with a transparent and hygroscopic material. A light emitting device on the market is known which is provided with a relatively large hygroscopic film 7. By providing the hygroscopic film 7 in this manner, the hygroscopic film 7 absorbs the moisture that has entered, thereby dramatically extending the life of the electroluminescent device.

However, since such a hygroscopic film 7 has a low dehydration start temperature and easily releases moisture when the ambient temperature rises, the internal humidity increases, causing great damage to the electroluminescent device and shortening its lifespan. There was a problem.

Similar to the hygroscopic film 7, examples are also known in which an inorganic desiccant such as zeolite, silica gel, or calcium oxide is used to absorb internal moisture. Since such an inorganic desiccant has a high dehydration start temperature, the above-mentioned problem does not occur. Examples of using an inorganic desiccant include applying an adhesive to the opposite side of the counter electrode 3 from the light emitting part and applying inorganic desiccant powder to the opposite side, and applying the inorganic desiccant powder to the opposite electrode 3 of the moisture-proof protective film 6. An adhesive is applied to the contacting side and a desiccant powder is attached to it, or an inorganic desiccant powder is attached to the hygroscopic film 7 described in 1- above via an adhesive, and this is applied to the opposite electrode 3 to emit light. There are some that are installed on the opposite side.

However, in this example of using the inorganic desiccant powder, there is a problem that the inorganic desiccant powder is scattered during the manufacturing process of the electroluminescent device. Generally, in the manufacturing of electroluminescent devices, in order to ensure product reliability and quality stability, and to avoid contamination of foreign substances such as dust, it is usually done in a clean room, and inorganic desiccant powder is used. will introduce a source of dust.

(Objective of the invention) L1 object of the present invention is 1-, in view of the problems of the prior art described above,
To provide a light-emitting device on the market that can maintain a low internal humidity even when the external temperature is high to further extend the life of the device, and prevents the generation of dust during the manufacturing process.

(Structure of the Invention) In the electroluminescent device according to the present invention, a desiccant layer made of a hygroscopic polymer in which an inorganic desiccant powder is embedded is provided on the surface of the counter electrode opposite to the light emitting surface.

In the present invention, as the inorganic desiccant powder 17, for example, zeolite, silica gel, molecular sieve, calcium oxide, etc. can be used. Further, as the hygroscopic polymer, polyvinyl alcohol, various celluloses such as ethyl cellulose, various nylons such as nylon 6 and nylon 6.6, etc. can be used.

When forming the desiccant layer, for example, an inorganic desiccant powder is dispersed and mixed in a hygroscopic polymer, the resulting paste is formed into a sheet by printing, a roll coater, a doctor knife, etc., and this sheet is can be formed by arranging it on the side opposite to the light emitting surface of the counter electrode of the electroluminescent device. Alternatively, the desiccant layer may be formed by directly applying the above-mentioned base to the side of the counter electrode opposite to the light emitting part or the side of the moisture-proof protective film that is in contact with the counter electrode.

In this way, the inorganic desiccant powder can be brought into the manufacturing process of the electroluminescent device in a state completely adhering to the hygroscopic polymer, eliminating the source of dust and producing reliable and stable quality. Electroluminescent devices can be manufactured. Further, since the water absorbed in the hygroscopic polymer is stably retained in the inorganic desiccant powder, release of the absorbed water is suppressed, and the life of the electroluminescent device can be extended.

(Embodiments of the Invention) As shown in FIG. 2, in an electroluminescent device embodying the present invention, a desiccant layer 11 is formed on the opposite side of the counter electrode 3 to the light emitting surface. As shown in FIG. 3, the desiccant layer 11 is made of an inorganic desiccant powder 12 such as Ceolly, silica gel, molecular sieve, calcium oxide, etc., polyvinyl alcohol, various celluloses such as ethyl cellulose, →-Iron 6, Nylon 6, etc. The paste is dispersed in a hygroscopic polymer 13 such as various types of nylon, such as No.
It is formed into a sea I-shape with a thickness of ~0.3mmmm. Note that in FIG. 2, the same parts as in FIG. 1 are given the same reference numerals.

When manufacturing this electroluminescent device, a transparent electrode 2 is formed on one side of a transparent insulating substrate 1 by means such as vapor deposition or coating, and a moisture-proof protective film 6 is formed on the opposite side of the transparent insulating substrate 1.
Paste Paste. Further, a coating liquid containing a binder having a high dielectric constant and a phosphor powder is applied to the inner surface of the transparent electrode 2 and dried to form a phosphor layer 4. On the other hand, a coating liquid containing a high dielectric constant binder and a high dielectric constant inorganic powder is applied to one side of a counter electrode 3 made of a metal plate or the like and dried to form an insulating layer 5.

Further, a sheet-like desiccant layer 11 as shown in 1- is pasted on the opposite surface of the counter electrode 3. Then, the phosphor layer 4 of the transparent electrode 2 and the insulating layer 5 of the counter electrode 3 are placed facing each other and bonded under heat and pressure. Thereafter, it is cut into a predetermined size, voltage application terminals are provided, and a moisture-proof protective film 6 is heat-sealed to form an electroluminescent device.

Example 1 Inorganic desiccant powder such as sufficiently dehydrated silica gel, molecular sieve, 'GM calcium, etc. is kneaded into dried polyvinyl alcohol, and the mixture is rolled to a thickness of 0.1 to 0.3 m.
The desiccant layer 11 is formed as a desiccant layer 11. These steps are performed in a dry atmosphere. This desiccant layer 11 is
As shown in the figure, an electroluminescent device is manufactured by providing a counter electrode 3 on the side opposite to the light emitting surface and securing it with a moisture-proof protective film 8 made of trifluorochloroethylene or the like.

Example 2 Dry ethyl cellulose is dissolved in an organic solvent such as dehydrated calpitol, and inorganic desiccant powder such as sufficiently dehydrated silica gel, molecular sieve, calcium carbonate, etc. is dispersed in this, and the resulting solution is used for printing, roll coater, doctor knife, etc. The desiccant layer 11 is formed into a sheet by the method described in the following. These steps are performed in a dry atmosphere. This desiccant layer 11 is provided on the side opposite to the light emitting surface of the counter electrode 3 as shown in FIG.
An electroluminescent device is manufactured by Jd Il=.

Comparative Example 1 As shown in FIG. 1, an electroluminescent device is manufactured by providing a hygroscopic film 7 made of a nylon sheet on the side opposite to the light emitting surface of the counter electrode 3.

Comparative Example 2 Instead of the desiccant layer 11 shown in FIG. 2, a desiccant layer made by adhering inorganic desiccant powder to the surface of a nylon sheet via an adhesive was placed on the side opposite to the light emitting surface of the counter electrode 3. to manufacture an electroluminescent device.

Figure 4 shows how the luminance deterioration changes over time when the electroluminescent devices of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are continuously lit in an atmosphere of 40° C. and 90% humidity. . In the figure, A is Example 1.8 is Example 2, and C is Comparative Example 1.
．． 0 represents Comparative Example 2.

The results show that all three examples, Example 1, Example 2, and Comparative Example 2, exhibit better life characteristics than Comparative Example 1, which provided only a hygroscopic film. In addition, there was almost no difference in the results between the champions of Example 1, Example 2, and Comparative Example 2, but in the case of Comparative Example 2, the process of adhering the inorganic desiccant powder to the nylon sheet I. There was a risk that the desiccant powder from the NA machine would scatter.

(Effects of the Invention) As described below, according to the present invention, a desiccant layer in which an inorganic desiccant powder is embedded in a hygroscopic polymer is provided on the surface of the counter electrode opposite to the light emitting surface. Therefore, the inorganic desiccant powder can be introduced into the manufacturing process of the electroluminescent device in a completely fixed state in the hygroscopic polymer. This eliminates the source of dust and makes it possible to manufacture a reliable and stable quality electroluminescent device. Further, since the water absorbed in the hygroscopic polymer is stably retained in the inorganic desiccant powder, release of the absorbed water is suppressed, and the life of the electroluminescent device can be extended.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing a conventional electroluminescent device, Fig. 2 is a side sectional view showing an embodiment of an electroluminescent device according to the present invention, and Fig. 3 is a desiccant layer used in the electroluminescent device. FIG. 4 is a graph showing the humidity life characteristics of the electroluminescent devices P and I according to the present invention and the conventional electroluminescent device. In the figure, 1 is a transparent insulating substrate, 2 is a transparent electrode, 3 is a counter electrode, 4 is a phosphor layer, 5 is an insulating layer, 6 is a moisture-proof protective film,
11 is a desiccant layer, 12 is an inorganic desiccant powder, and +3 is a hygroscopic polymer. 2 Figure 1 Figure 2 Figure 3 Figure 1 Figure 4 Figure 0 1000 2000 Takema (hr)

Claims (1)

[Scope of Claims] (1) In an electroluminescent device in which at least a phosphor layer is provided between a transparent electrode and a counter electrode, the desiccant layer made of a hygroscopic polymer in which an inorganic desiccant powder is embedded is An electroluminescent device characterized by being provided on a surface of a counter electrode opposite to a light emitting surface. (2. In claim 1, the inorganic desiccant powder includes zeolite, silica gel, molecular sieve,
An electroluminescent device made of a material selected from calcium liquefaction. (3) The electroluminescent device according to claim 1 or 2, wherein the hygroscopic polymer is selected from polyvinyl alcohol, various celluloses, and various nylons.