JPH04171696A - Distributed el element - Google Patents

Abstract

PURPOSE:To perform coating treatment easily and safely, suppress the deterioration of phosphors, and increase a moisture-proof effect by applying the coating treatment of organosilazane having the alkyl group with the carbon number 2-30 at the ordinary temperature on the grain surface of phosphors. CONSTITUTION:A light emitting paint mixed and dispersed with phosphors, high-dielectric constant binder resin and an organic solvent is coated on a transparent electrode 2 on a glass plate 1 and dried, and phosphors 4 coated with organosilazane 3 having the alkyl group with the carbon number 2-30 on the grain surface are mixed and dispersed to form a light emitting layer 5. An insulating paint mixed and dispersed with high-dielectric constant binder resin and an organic solvent is coated on the light emitting layer 5 and dried to form a reflecting insulating layer 6. The infiltration of moisture into the phosphors can be effectively prevented, and a distributed EL element having little aging deterioration of luminance, excellent stability and a long life is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distributed EL element, and more particularly to a long-life distributed EL element that exhibits little luminance deterioration over time, is excellent in stability, and has a long life.

[Conventional technology]

Generally, the light-emitting layer in a dispersion type EL element is prepared by preparing a light-emitting paint by dissolving a high dielectric constant binder resin in an organic solvent and uniformly mixing and dispersing a phosphor therein, and then applying this light-emitting paint to a transparent electrode, etc. It is formed by applying it on top and drying it.

In such a distributed EL element, when a high electric field is applied to the phosphor, for example, ZnS, which is the luminescent matrix, and Cu, CE, etc., which form the luminescent center, move, causing defects and non-radiative Center formation occurs and the brightness decreases. In particular, when water is present, ZnS+2Hz○→S 02 + Z n, + 2
As the reaction shown by H2 progresses and ZnS decomposes, the generation of defects and the formation of non-radiative centers tend to occur, resulting in a significant decrease in brightness.

Therefore, in order to prevent moisture from entering from outside the phosphor, a moisture-proof film is formed on the surface of the phosphor particles. For example, a moisture-proof film made of silane camping agent or silicon oxide is used. Coating phosphors has been done. (Unexamined Japanese Patent Publication No. 62-19'5894) [Problems to be Solved by the Invention] However, the phosphor on which this type of moisture-proof film is formed does not use a silane coupling agent or a moisture-proof film such as silicon oxide to fluoresce. When coating the particle surface of a body, it is heated at a high temperature of 250 to 500°C, which causes the phosphor itself to change color and deteriorate, resulting in a corresponding reduction in brightness.
In the case of silicon oxide, it is performed by a gas phase reaction and uses silicon tetrachloride, so it lacks safety.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation.
Coating with organosilazane having 0 alkyl groups makes the coating process easy and safe, suppresses deterioration of the phosphor, provides sufficient moisture-proofing effect, reduces luminance deterioration over time, and improves stability. This makes it possible to obtain a dispersion type EL element with excellent long life.

In this invention, the organosilazane having an alkyl group having 2 to 30 carbon atoms, which is coated on the particle surface of the phosphor mixed and dispersed in the light-emitting layer, chemically adsorbs well to the phosphor at room temperature and has high moisture resistance. It has water repellency. 1st
The figure shows the adsorption mechanism of organodisilazane, which is a type of organosilazane, with a phosphor using a reaction formula. It chemically adsorbs at room temperature and forms a strong moisture-proof film with high moisture-repellency and water repellency.

This effectively prevents moisture from entering the phosphor, and the phosphor whose particle surface is coated with organosilazane can be mixed and dispersed in a high dielectric constant binder resin to form a light-emitting layer. Then, the deterioration of brightness over time is small,
A long-life dispersion type EL element with excellent stability can be obtained.

In order to fully exhibit the moisture-proofing effect, such organosilazane preferably has an alkyl group having 2 to 30 carbon atoms;
It is not possible to effectively prevent moisture intrusion. Examples of organosilazane having an alkyl group having 2 to 30 carbon atoms include (CH3)25i (N
H)2/□, CI8H37S i (NH)3/□, C
3HzS 1 (NH)3/□, C+. Hz+SI
Examples include CH3(NH)2/□.

In addition, as a phosphor whose particle surface is coated with organosilazane having an alkyl group having 2 to 30 carbon atoms, Cu, Cl, M
Any of the phosphors generally used in dispersion type EL elements, such as phosphors activated with one or more elements such as n, AI, Ag, etc. as a luminescent center, is suitably used.

Further, as the high dielectric constant binder resin used in the light emitting layer, any high dielectric constant binder resin that is generally used in the light emitting layer of a dispersion type EL element can be suitably used.
Cyanoethylated cellulose, cyanoethylated pullulan,
Cyanoethylated polyvinyl alcohol, cyanoethylated hydroxycellulose, cyanoethylated sucrose,
A cyanoethylated phenoxy resin or the like is preferably used.

In addition, examples of organic solvents include dimethylformamide, normal methyl 2-pyrrolidone, dimethyl sulfoxide, isophorone, acetone, methyl ethyl ketone, etc.
Any material used in the light emitting layer of a distributed EL device can be used.

In this way, a dispersion type EL element having a light-emitting layer in which a phosphor whose particle surface is coated with an organosilazane having an alkyl group having 2 to 30 carbon atoms is mixed and dispersed is produced, for example, as shown in FIGS. 2 and 3. A luminescent paint prepared by mixing and dispersing the above-mentioned phosphor, high dielectric constant binder resin, organic solvent, etc. is applied onto a transparent electrode 2 made of indium-tin oxide or the like on a glass plate 1, and then dried. A light-emitting layer 5 is formed by mixing and dispersing a phosphor 4 coated with an organosilazane 3 having an alkyl group having 2 to 30 carbon atoms on the particle surface, and then barium titanate or the like is applied on the light-emitting layer 5. After applying an insulating paint prepared by mixing and dispersing a high dielectric constant binder resin and an organic solvent, etc., and drying it to form a reflective insulating layer 6, a back electrode 6 and a single pole 7 made of aluminum or the like are further formed. , these are sealed with a moisture-proof film 8. Note that 9 is an AC power source, and the distributed EL element 10 is driven by connecting the transparent electrode 2 and the back electrode 7 to the AC power source 9.

Here, the transparent electrode 2 is formed in the same manner as the transparent electrode of a conventional dispersion type EL element. For example, the transparent electrode 2 made of indium-tin oxide, In2O3, SnO2, gold, etc. It is formed by a sputtering method.

Further, the reflective insulating layer 6 formed on the light emitting layer 5 is made of a high dielectric constant inorganic compound such as barium titanate, lead ditanate, titanium dioxide, etc., and a high dielectric constant binder resin and an organic solvent used in the light emitting layer 5. The insulating paint is prepared by mixing and dispersing the insulating paint, and this insulating paint is applied onto the light emitting layer 5 and dried.

Furthermore, the back electrode 7 formed on the reflective insulating layer 6 is formed in the same manner as the back electrode of a conventional distributed EL element,
For example, metal electrodes such as aluminum, gold, molybdenum, and chromium, as well as metal oxide electrodes such as SnO2 and InzO:+, are formed by vacuum evaporation or resistance heating, and methods such as heat-pressure bonding of AI foil, etc. But it is formed.

As the moisture-proof film 8, a 37-fluorochloroethylene film or the like is used.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Phosphor ZnS: Cu, 30 parts by weight of Cl, 30 parts by weight of toluene
Parts by weight and organosilazane (CHz) 2S t (
NH) 2/□2 parts by weight into a screw bottle equipped in an ultrasonic cleaner, and the temperature of the cleaning solution was adjusted to 25°C.
The mixture was mixed for 1 hour. After mixing, the mixture was stored overnight and filtered with suction. After filtration, dry in vacuum at 80°C for 24 hours,
A phosphor whose particle surface was coated with organosilazane was obtained.

Next, this moisture-proof treated phosphor ZnS:Cu,Cl
70 parts by weight of 40 parts by weight of cyanoethylated pullulan were dissolved in 20 parts by weight of dimethylformamide.
A luminescent paint was prepared by mixing and dispersing while heating to °C.

Next, apply this luminescent paint to a thickness of 1.1 mm as shown in Figure 2.
It was applied by screen printing onto a 0.2 μm thick transparent electrode 2 made of indium-tin oxide formed on a glass plate 1, and dried at 70"C for 24 hours to form a 4" thick transparent electrode 2.
A light emitting layer 5 having a thickness of 0 μm was formed.

Furthermore, 40 parts by weight of cyanethylated pullulan was dissolved in 20 parts by weight of dimethylformamide, and 40 parts by weight of barium titanate was mixed and dispersed therein to prepare an insulating paint, and this insulating paint was applied onto the luminescent layer 5 by screen printing. The reflective insulating layer 6 with a thickness of 60 μm was formed by coating the film on the substrate and drying it at 70° C. for 24 hours.

Next, aluminum is vapor-deposited on this reflective insulating layer 6 by a resistance heating vapor deposition method to form a back electrode 7 made of aluminum, and these are covered with a moisture-proof film 8.
A dispersion type EL element 10 as shown in the figure was manufactured.

Example 2 In the moisture-proofing treatment of the phosphor in Example 1, organosilazane (CH:+)231 (NH)zy. Instead of organosilazane CI 8 H3□5i(NH)3
The moisture-proofing treatment of the phosphor was carried out in the same manner as in Example 1 except that the same amount of phosphor /2 was used.

Next, after leaving this moisture-proof treated phosphor in a 90% RH atmosphere for about 48 hours, the same amount of the phosphor used in Example 1 was used in place of the phosphor used in Example 1, and a dispersed EL was produced in the same manner as in Example 1.
Element 10 was produced.

Comparative Example 1 In Example 1, the moisture-proofing treatment of the phosphor was omitted, and the phosphor Z
A dispersion type EL device was produced in the same manner as in Example 1, except that the same amount of nS:Cu and CI was used in place of the moisture-proofed phosphor of Example 1.

Comparative Example 2 In Example 2, the moisture-proofing treatment of the phosphor was omitted, and the phosphor Z
nS: Cu, CI in a 90% RH atmosphere as it is about 4
After leaving it for 8 hours, a dispersion type EL element was produced in the same manner as in Example 2, except that the same amount of the moisture-proofed phosphor of Example 2 was used.

The dispersion type EL elements obtained in each example and comparative example were
200V/400Hz at 0°C, 190%RH atmosphere
It was operated with AC drive, and the change in brightness over time was observed over eight cycles.

FIGS. 4 and 5 show the results as relationship diagrams between luminance and driving time. As is clear from FIGS. 4 and 5, the distributed EL element obtained in Example 1 Compared to the dispersion type EL element obtained in Comparative Example 1, the initial brightness decreases due to the moisture-proofing treatment, but the luminance half-life time is almost twice that of the dispersion type EL element obtained in Example 2. Compared to the dispersion type EL element obtained in Comparative Example 2, the initial brightness is lowered by the moisture proofing treatment, but the brightness half-life time is approximately twice as long.

〔Effect of the invention〕

As is clear from FIGS. 4 and 5, the dispersion EL devices obtained in this invention (Examples 1 and 2) are both compared to the dispersion EL devices obtained in Comparative Examples 1 and 2. ,
The luminance half-life time is long, almost 2.

Therefore, the distributed EL obtained by this invention is
It can be seen that a dispersion type EL element with little luminance deterioration over time, excellent stability, and long life can be obtained.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the adsorption mechanism by which organodisilazane is adsorbed onto the surface of phosphor particles using a reaction formula, and Figure 2 is a cross-sectional diagram showing an example of a dispersion type EL element obtained by this invention. , FIG. 3 is a partially enlarged sectional view of the light emitting layer of the dispersion type BL element shown in FIG. It is. DESCRIPTION OF SYMBOLS 1... Glass plate, 2... Transparent electrode, 3... Organosilazane, 4... Fluorescent substance, 5... Light emitting layer, 6...
・Reflective insulation layer, 7... Back electrode, 8... Moisture-proof film, 10... - Dispersed EL element patent applicant Hitachi Maxell Co., Ltd. Patent applicant Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. In a dispersed EL device having a light-emitting layer in which a phosphor is dispersed in a high dielectric constant binder resin, the phosphor is coated in the light-emitting layer with an organosilazane whose particle surface has an alkyl group having 2 to 30 carbon atoms. A dispersion type EL element characterized by mixing and dispersing