JPH05182765A - Binder for dispersion type el element and dispersion type el element - Google Patents

Abstract

PURPOSE:To obtain a binder for dispersion type EL element which has an excellent characteristic to satisfy a high brightness, a long service life, and a high luminous efficiency simultaneously. CONSTITUTION:In a binder for dispersion type El element which consists of a cyanoethyl compound, the impurities of the alkaline metallic ion and the harloid ion in the binder are adsorbed and removed by an ion exchange resin of a catin type, anion type, or both ion type, to make the total sum of the impurities less than 30ppm, favorably less than 20ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for a dispersion type EL device, which is composed of a cyanoethyl compound, and a dispersion type EL device.

[0002]

2. Description of the Related Art Generally, a dispersion type EL element is a surface emitting element which emits light when an AC voltage is applied. Since it is low in cost, low in power consumption and easy in large area, it can be used as a backlight of a liquid crystal display device or various display devices. Is used for. This dispersion type EL element is composed of a light emitting layer in which a phosphor powder such as zinc sulfide is dispersed in an organic binder made of a high dielectric constant dielectric such as cyanoethyl cellulose, and an organic binder made of a high dielectric constant dielectric such as cyanoethyl cellulose. , A reflective insulating layer in which a white high-dielectric-constant dielectric powder such as barium titanate is dispersed, a transparent electrode such as ITO, a back electrode such as aluminum, and a water catching layer made of a transparent resin film such as nylon, It is composed of a water trapping layer, a transparent electrode, a light emitting layer, a reflective insulating layer, and a moisture-proof film that hermetically surrounds the back electrode. At present, various cyanoethyl compounds are used as a binder or a mixture as a binder used in the dispersion type EL device. A cyanoethyl compound such as cyanoethylated sorbitol or cyanoethylated saccharose having a large dielectric constant is used as at least one component of the binder for the purpose of improving the brightness of the dispersion type EL device. However, dispersion type E using these binders
Each of the L elements can achieve the purpose of high brightness, but has a fatal problem that it cannot satisfy the requirements of long life and high efficiency. As a method for solving the above-mentioned problems, ethylene cyanohydrin and B, B'-oxydipropionitrile which are reaction by-products produced during the synthesis of a cyanoethyl compound which is a binder for dispersion type EL devices, and acrylonitrile which is an unreacted product. A method of washing and removing impurities in the binder with ion-exchanged water has been proposed. (JP-A-2-252791, JP-A-2
-252792). Further, as an impurity in the binder, a method of washing and removing alkali metal with ion-exchanged water has been proposed. (JP-A-3-8295)

[0003]

However, in the binder for dispersion type EL devices comprising a cyanoethyl compound, the influence of low molecular impurities described in JP-A-2-252791 cannot be ignored, but rather the alkali metal ion in the binder is rather negligible. Since the impurities of the halogen ion and the halogen ion are ion conductive impurities, the influence that causes the ion conductivity is more important when both are used in the dispersion type EL element. In particular, when a high dielectric constant binder is used, even if the content of ion conductive impurities is the same, the effect is large, which is a major cause of difficulty in obtaining a dispersion type EL device having high brightness, long life, and high luminous efficiency. That is, in refining the binder for dispersion type EL devices, purifying and removing only the alkali metal has a tentative effect, but is insufficient to simultaneously satisfy the above-mentioned three characteristics of high brightness, long life, and high luminous efficiency. There was a problem.

[0004]

DISCLOSURE OF THE INVENTION As a result of studies to solve the above-mentioned problems, as a result, a dispersion type E having excellent characteristics which simultaneously satisfy the three characteristics of high brightness, long life and high luminous efficiency.
It has been found that an L element can be obtained. That is, the present invention was achieved by using the following binders for dispersion type EL devices. 1. A binder for a dispersion-type EL device, comprising a cyanoethyl compound having a total amount of impurities of alkali metal ions and halogen ions of 30 ppm or less. 2. A dispersion-type EL device using a binder for a dispersion-type EL device, which comprises a cyanoethyl compound having a total amount of impurities of alkali metal ions and halogen ions of 30 ppm or less. 3. When removing alkali metal ions and halogen ion impurities in a binder composed of a cyanoethyl compound, acetone, N, N'which are good solvents for the binder
-A mixed solvent comprising an organic solvent such as dimethylformamide, N, N'-dimethylacetamide, etc. and ion-exchanged water which is a poor solvent is used, and the mixed component ratio of the mixed solvent maintains an emulsified state without precipitation of the binder. A method for purifying a binder for a dispersion-type EL device, which comprises using a mixed solvent.

As one example of the purification method, an organic solvent which dissolves the cyanoethyl compound well, such as acetone, N,
Impurities of alkali metal ions and halogen ions by dissolving or emulsifying in a mixed solvent of N'-dimethylformamide, N, N'-dimethylacetamide and the like and a poor solvent of ion-exchanged water and adding an ion-exchange resin to the mixed liquid Are removed by adsorption. After removing the ion-exchange resin from this mixed solution, a poor solvent for the cyanoethyl compound, for example, a large amount of ion-exchanged water is added to precipitate and wash the cyanoethyl compound. The organic solvent used in the present invention may be any organic solvent that dissolves the cyanoethyl compound well without phase separation with ion-exchanged water, and the mixing component ratio of the organic solvent and ion-exchanged water is the ion-exchange resin ion-exchange resin. In order to improve the performance, the more ion-exchanged water, the better. However, it is practically preferable that the cyanoethyl compound is in an emulsified state without being completely precipitated. A purified cyanoethyl compound is obtained by appropriately combining the above-mentioned purification operations by adsorption with an ion exchange resin and reprecipitation, followed by dehydration and drying, preferably drying under reduced pressure. Incidentally, as the ion exchange resin, cation and anion ion exchange resins may be used separately or amphoteric ion exchange resins may be used, and may be appropriately selected depending on the species and amount of the ion conductive impurities contained. good.
The method is not limited to the batch type, semi-batch type or continuous type ion exchange process. The cyanoethyl compound thus obtained has an extremely small amount of cationic anionic impurities, and is therefore excellent as a binder for dispersion type EL devices. That is, the dispersion-type EL device using the binder obtained in the present invention has features which have not been obtained in the past such as extremely high brightness, long life and high luminous efficiency.

[0006]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 250 parts by weight of cyanoethylated pullulan (manufactured by Shin-Etsu Chemical Co., Ltd.) is emulsified and dispersed in a mixed solvent of 1000 parts by weight of a good solvent, acetone, and 350 parts by weight of a poor solvent, ion-exchanged water, and amphoteric ions. Exchange resin (Mitsubishi Kasei Co., Ltd. Diaion SKIB, SAIOA)
Add 2.5 parts by weight to remove by adsorption. After removing the ion exchange resin, precipitation washing is performed with ion exchange water. Finally, vacuum drying was performed to remove ion-exchanged water and acetone. As for the ion conductive impurities in the cyanoethylated pullulan thus obtained, the total amount of impurities of alkali metal ions and halogen ions was 20 ppm or less, respectively. (Sample A).

Example 2 The same as Example 1 except that the adsorption purification with the amphoteric ion exchange resin was repeated 4 times. The ionic conductive impurities in the cyanoethylated pullulan thus obtained had a total amount of impurities of alkali metal ions and halogen ions of 5 pp, respectively.
It was m or less. (Sample B).

Example 3 250 parts by weight of cyanoethylated sorbitol (manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in a mixed solvent of 250 parts by weight of good solvent acetone and 225 parts by weight of poor solvent ion-exchanged water to prepare an amphoteric ion-exchange resin. After the addition of 2.5 parts by weight (similar to Example 1) for adsorption purification,
The ion exchange resin was removed. After repeating this operation four times, vacuum distillation was performed to remove the mixed solvent, and finally vacuum drying was performed to completely remove ion-exchanged water and acetone. As for the ion conductive impurities in the cyanoethylated sorbitol thus obtained, the total amount of impurities of alkali metal ions and halogen ions was 3 ppm or less, respectively. (Sample C).

Examples 4 to 6 Mixtures of the cyanoethyl compounds obtained in Examples 1 to 3 in the predetermined compounding ratios shown in Table 1 were used as binders for dispersion type EL devices.
After dissolving these binders in N, N'-dimethylacetamide, 4 parts by weight of barium titanate is added to 1 part by weight of cyanoethyl compound, dispersed, and coated on an aluminum plate so that the thickness after drying becomes 10 μm. Then, a reflective insulator layer was formed. Similarly, 5 parts by weight of a phosphor (# 723 manufactured by Sylvania) was added to 1 part by weight of a cyanoethyl compound, dispersed, and coated on the reflective insulator layer so that the thickness after drying was 50 μm. Was formed and dried. On the other hand, I
After the TO film is formed on one side of PET, the transparent surface electrode with the terminal attached thereto and the light emitting layer of the reflective insulating layer light emitting layer formed on the back electrode are heated and laminated on the ITO surface of the surface electrode Attach the back terminal, seal the water catching layer made of a transparent resin film such as nylon, 4cm x 14c
It was cut into a size of m and sealed with a moisture-proof layer made of a resin film such as polyfluoroethylene chloride. Luminance, luminous efficiency and 20 ° C. × 65% RH when an AC electric field of 100 V / 400 Hz is applied between both electrodes of the obtained dispersion type EL device.
Table 1 shows the time until the luminance is reduced to half when the light is kept on under the above environmental conditions.

[0011]

[Table 1]

Comparative Examples 1 and 2 Commercially available cyanoethylated pullulan contains 55 ppm of alkali metal ion impurities and 40 ppm of halogen ion impurities. (Sample D). In addition, commercially available cyanoethylated sorbitol,
5 ppm of impurities of alkali metal ions and 7 ppm of impurities of halogen ions are contained. (Sample E). Using a mixture of these cyanoethyl compounds in the predetermined mixing ratio shown in Table 2 as a binder for dispersion type EL devices, dispersion type EL devices were prepared in the same manner as in Examples 4 to 6 and the same test was conducted. The results are shown in Table 2.

[0013]

[Table 2]

Comparative Example 3 The same as Example 1 except that 1.25 parts by weight of a cation ion exchange resin (Diaion SKIB manufactured by Mitsubishi Kasei Co., Ltd.) was used in place of the amphoteric ion exchange resin in Example 1. is there. The amount of ion conductive impurities in the cyanoethylated pullulan thus obtained was such that the alkali metal ion impurities were 20 ppm or less and the halogen ion impurities were 40 ppm.
(Sample F). Using a mixture of this cyanoethyl compound in the prescribed mixing ratio shown in Table 2 as a binder for dispersion type EL devices, dispersion type EL devices were prepared in the same manner as in Examples 4 to 6, and the same test was conducted. The results are shown in Table 2.

According to Tables 1 and 2, the dispersion type EL device manufactured by using the binder containing less impurities of alkali metal ions and halogen ions contained in the binder for the dispersion type EL device has a longer brightness and a longer luminous efficiency. You can see that

[0016]

The binder of the present invention comprises a cyanoethyl compound containing very few impurities of alkali metal ions and halogen ions. When this binder is used as a binder of a dispersion type EL device, it has high brightness, long life and high luminous efficiency. A dispersion type EL device can be obtained.

Claims (3)

[Claims] 1. A binder for a dispersion-type EL device, comprising a cyanoethyl compound having a total amount of impurities of alkali metal ions and halogen ions of 30 ppm or less. 2. A dispersion-type EL device using a binder for a dispersion-type EL device, which comprises a cyanoethyl compound having a total amount of impurities of alkali metal ions and halogen ions of 30 ppm or less. 3. Acetone, which is a good solvent for the binder when removing alkali metal ions and halogen ion impurities in the binder composed of a cyanoethyl compound,
A mixed solvent comprising an organic solvent such as N, N'-dimethylformamide and N, N'-dimethylacetamide and ion-exchanged water which is a poor solvent is used, and the mixed component ratio of the mixed solvent is such that the binder does not precipitate. A method for purifying a binder for a dispersion-type EL device, which comprises using a mixed solvent which maintains an emulsified state.