JP2002216967A - Electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a life-time of an EL element, and reduce electric power consumption. SOLUTION: In the electroluminescence element constituted of a light-emitting layer pinched between a pair of electrodes wherein the light-emitting layer contains a fluorescent material, eluting amount of chlorine ion from the fluorescent material is made to be 10 ppm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device (hereinafter, referred to as an EL device).

[0002]

2. Description of the Related Art Electroluminescence refers to electroluminescence that emits light when a voltage is applied. An EL element formed by forming a light-emitting layer using a phosphor material exhibiting such electroluminescence behavior and sandwiching the light-emitting layer between a pair of electrodes is currently widely used as a backlight of a liquid crystal display or the like. It's being used.

[0003] The EL element used for such an application is required to have a long life and low power consumption. However, in the conventional EL element, these requirements are not necessarily satisfied. Was not satisfied.

In order to satisfy such demands, the content of alkali metal contained in the light emitting layer and the insulating layer of the EL device must be reduced to 20%.
Longer life of EL element by reducing to below ppm,
Achieving low power consumption has been proposed (Japanese Patent Laid-Open No. Hei 3-8295). However, according to the study of the present inventors, satisfactory results were not always obtained even if the alkali metal contents in the light emitting layer and the insulating layer of the EL element were reduced.

On the other hand, sulfides of Group IIa elements such as ZnS and ZnCdS have been conventionally used as phosphor materials for EL devices, but together with Cu as one of the auxiliary components to be doped into these phosphor materials. Cl is often used. Further, there is a case where the particles of the phosphor material are coated with glass or the like for the purpose of moisture proof or the like (for example, see Japanese Patent Application Laid-Open
In this case, chlorine ions derived from silicon tetrachloride used in forming the coating film may be contained in this case.

When an EL element is manufactured using such a phosphor material containing a large amount of chloride ions, when water enters the light-emitting layer, chloride ions are eluted into the water to generate an acid. Corrodes the layer. As a result, the resistance of the electrode layer increases, leading to a decrease in luminance of the EL element over time, and the life is shortened.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an EL device having a long life and low power consumption.

[0008]

According to the present invention, there is provided an electroluminescent device comprising a light emitting layer sandwiched between a pair of electrodes, the light emitting layer including a phosphor material. In the device, the amount of chloride ions eluted from the phosphor material is set to 10 ppm or less.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the EL device of the present invention has a light emitting layer sandwiched between a pair of electrodes.
At least one electrode of the element is a transparent electrode. When only one is a transparent electrode, the other electrode is a back electrode. Here, one embodiment of the present invention is shown in FIG. In the EL device 1 of the present invention shown in FIG. 1, a light emitting layer 4 is disposed between a back electrode layer 2 and a transparent electrode layer 5 to prevent dielectric breakdown of the entire EL device 1 and is necessary for EL light emission. The insulating layer 3 is disposed between the back electrode layer 2 and the light emitting layer 4 so that a high electric field can be stably applied to the light emitting layer 4. Although not shown, a back insulating layer may be provided on the surface of the back electrode layer 2, and a transparent substrate may be provided on the surface of the transparent electrode layer 5.

In the EL device of the present invention having such a structure, the back electrode layer 2, the insulating layer 3, and the transparent electrode layer 5 may have a structure usually used in a conventional EL device. The transparent electrode layer 5 can be preferably formed of ITO (indium tin oxide) or the like.
The TO electrode can be formed by sputtering. The thickness of this transparent electrode layer is usually 0.01 to 1,000 μm, and its surface resistance is usually 500 Ω / □ or less, preferably 1 to 300 Ω / □. The light transmittance of the transparent electrode layer is usually 70% or more, preferably 80% or more. Back electrode layer 2 sandwiching light emitting layer 4 in combination with transparent electrode layer 5
Can be formed from, for example, a carbon-containing resin, a silver paste, or the like. The thickness of this back electrode layer is 5 nm to 1 m.
m is preferable.

[0011] These electrodes need to be provided with electrical connections in order to apply a required voltage to the light emitting layer sandwiched between these electrodes. Specifically, for example, it is preferable to attach a pin terminal to a predetermined portion and further connect a lead wire or the like for connecting to the pin terminal.

The insulating layer 3 is formed, for example, by applying a solution of a mixture of a fluororesin and barium titanate and drying it, or by attaching a foil, sheet, film or the like formed from a mixture of a fluororesin and barium titanate. Can be formed. Suitable fluororesins include:
Polyvinylidene fluoride and the like can be mentioned. The thickness of this insulating layer is preferably 2 to 1,000 μm.

The back insulating layer provided on the surface of the back electrode layer as required may be formed, for example, by applying an insulating ink or an insulating resin and drying the applied ink or insulating resin.
It can be formed by attaching a sheet, a film, or the like. In addition, the transparent substrate that can be provided on the surface of the surface electrode layer can be formed from various transparent resins such as a polyester resin, an acrylic resin, a polycarbonate resin, and a vinyl chloride resin.

The light emitting layer 4 can be formed using various phosphor materials conventionally used in EL devices. Suitable phosphor materials include, for example, ZnS, CdZ
It is made of a zinc sulfide-based compound such as nS, ZnSSe, CdZnSe, or a zinc selenide-based compound. The phosphor material Cu in the compound, I, Cl, Al, Mn , NdF 3,
A desired emission color may be obtained by adding an auxiliary component such as Ag or B. Alternatively, particles that encapsulate such a phosphor material may be used.

As shown in FIG. 2, for example, as shown in FIG. 2, a binder resin 6 is formed on the surface of the insulating layer 3 or the transparent electrode layer 5.
Or 8 is applied, the particles 7 of the phosphor material are dispersed on the binder resin, and then the binder resin 8 or 6 is applied so as to cover the phosphor particles 7.
As the binder resin, various transparent resins such as polyester resin, acrylic resin, polycarbonate resin, and vinyl chloride resin similar to the above-mentioned transparent base material can be used. The light-emitting layer is composed of a phosphor material mixed with a binder resin.
It can also be formed by applying the dispersed resin solution to the surface of the transparent electrode layer by screen printing or the like, or by applying it by roll coating or the like. The thickness of the light emitting layer is preferably from 5 to 500 μm.

As described above, when an EL device is manufactured using a phosphor material containing a large amount of chloride ions, the chlorine ions elute into water inside the device to generate an acid. This causes the resistance of the electrode layer to increase, thereby shortening the life of the EL element. The reason that the corrosion of the electrode layer by the chlorine ions contained in the phosphor material is the cause of the shortening of the life of the EL element is that when pure water is added to the phosphor material containing a large amount of chloride ions, the water shows strong acidity. That the EL material is manufactured using this phosphor material,
When the resistance of the electrode layer after driving was measured, it became clear from the fact that the resistance was greatly increased.

Therefore, in the present invention, a phosphor material having a chlorine ion elution amount of 10 ppm or less is used as a phosphor material used for the light emitting layer. If the amount of chlorine ions eluted from the phosphor material contained in the light emitting layer is 10 ppm or less, the above-mentioned problem of electrode corrosion does not occur, and the cause of shortening the life can be eliminated.

In the present invention, the chloride ion elution amount of the phosphor material means a value measured by the following method. That is, for 0.5 g of phosphor material, 10.0 g of ultrapure water
In addition, the mixture is vibrated and stirred with a vibrator 100 times per minute for 1 minute, and the sample after standing for 12 hours is used as a measurement sample. The chloride ion content in this sample water is then measured using anions (chlorine ions).
It is measured by ion chromatography using IonPacAS4A manufactured by Dionex as a column for use. This chlorine ion content is converted as the amount per unit mass of the phosphor, and this is defined as the chloride ion elution amount. As the ultrapure water, one having a resistivity of 18.2 Ωcm is used, and neither the cation nor the anion is detected by the above-mentioned ion chromatography.

As described above, the present inventor has found that the cause of shortening the life of the EL element is chlorine ions eluted from the phosphor material. Therefore, before mixing the phosphor material into the light emitting layer, the chlorine ions eluted are removed by any means such as a method of washing the phosphor material with pure water. Alternatively, the phosphor material may be coated with a material containing no chloride ion. That is, the phosphor material itself may contain chloride ions, and the chlorine ions need not be eluted in the EL element.

[0020]

EXAMPLES Example 1 A high dielectric constant polymer (tetrafluoroethylene-hexafluoroethylene-vinylidene fluoride copolymer manufactured by Sumitomo 3M Ltd., product number THV200G), ethyl acetate, and methyl isobutyl ketone were mixed in a mass ratio of 15: 42.5: 42.5. And uniformly dissolved to prepare a binder resin. As a transparent electrode layer, a polyethylene terephthalate film with ITO (indium-tin-oxide) (manufactured by Oike Kogyo, part number KPC3)
00-75 (A)), the above binder resin was applied to the ITO surface of this film with a bar set of 75 μm using a notch bar. About 2 minutes after the application, before the binder resin was dried, ZnS-based phosphor particles whose chloride ion elution amount measured by the above method was 7.2 ppm were sprayed, and then dried at about 100 ° C. for 4 minutes.

Next, the same binder resin as that described above was applied to the phosphor particles using a notch bar at a bar set of 100 μm using a notch bar, and dried at 100 ° C. for 4 minutes to form a light emitting layer.

Subsequently, an insulating resin is applied on the light emitting layer with a bar set of 100 μm using a notch bar,
After drying at about 100 ° C. for 4 minutes, an insulating layer was formed. This insulator forming resin is 100 g of the same resin as the binder resin described above.
Insulator particles (barium titanate manufactured by Fuji Titanium Co., Ltd., product number HPBT-1, Na content 7.4 ppm) were mixed at a ratio of 36 g and uniformly dispersed.

Subsequently, a vacuum degree of 0.67 Pa
(5 mTorr), an Al film was formed by a sputtering method using an Al target under a film forming condition of a discharge current of 1.0 A to form a back electrode layer, thereby obtaining an EL element.

A power supply device (manufactured by Kikusui Electronics Co., Ltd., product number PCR500L) between the transparent electrode layer and the back electrode layer of this EL element
Were connected and a sine wave voltage of 400 Hz was applied at an execution voltage of 100 V. As a result, uniform light emission was obtained over the entire light emitting surface defined by the back electrode layer. Power consumption (unit: WT-110E, manufactured by Yokokawa Electric Co., Ltd.)
W) was measured, and the power consumption per unit volume of the EL element was calculated. The luminance was measured over time using a luminance meter (manufactured by Topcon Corporation, product number BM-8), and the life was indicated by the time until the luminance decreased to half the initial luminance. The results are shown in Table 1 below.

Example 2 An EL device was manufactured in the same manner as in Example 1, except that 0.2 g of an alkali metal-containing solution (20% sodium ethoxide / ethanol solution manufactured by Wako Pure Chemical Industries, Ltd.) was added to 120 g of the binder resin. did. The sodium ion concentration of this EL element was 770 ppm in the binder resin of the light emitting layer and 222 ppm in the insulating layer.
pm. The power consumption, lifetime, and alkali metal ion concentration of this EL element were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 An EL device was prepared in the same manner as in Example 1 except that the same phosphor as used in Example 1 was washed before use.
The device was manufactured. Washing of the phosphor was performed using methanol, and after washing, the phosphor was sufficiently dried at about 100 ° C. As a result, the chlorine ion elution amount of the phosphor measured after washing was 1.
It was 2 ppm. The power consumption, lifetime, and alkali metal ion concentration of this EL element were measured in the same manner as in Example 1.
Table 1 shows the results.

Comparative Example 1 An EL element was manufactured and consumed in the same manner as in Example 1 except that ZnS-based phosphor particles having a chloride ion elution value of 620 ppm measured by the above method were used as the phosphor material. Measure power, life, alkali metal ion concentration,
Table 1 shows the results.

Comparative Example 2 In the same manner as in Example 2, 0.2 g of an alkali metal-containing solution (20% sodium ethoxide / ethanol solution manufactured by Wako Pure Chemical Industries, Ltd.) was added to 120 g of the binder resin.
EL in the same manner as in Example 1 except that ZnS-based phosphor particles having the same chloride ion elution amount of 620 ppm as in Example 1 were used.
An element was manufactured, and its power consumption, life, and alkali metal ion concentration were measured. The results are shown in Table 1.

Comparative Example 3 An EL element was manufactured in the same manner as in Example 1 except that ZnS-based phosphor particles having a chloride ion elution amount of 1000 ppm were used as the phosphor material. And the alkali metal ion concentration were measured, and the results are shown in Table 1.

[0030]

[Table 1]

As is clear from the results shown in Table 1, in the present invention, by using a material having a chlorine ion elution amount of 10 ppm or less as the phosphor material, the life of the EL element is prolonged and the power consumption is reduced. . Furthermore, as is clear from Example 2 and Comparative Example 2, merely reducing the alkali metal concentration in the phosphor material is not enough to improve the life of the device and reduce the power consumption, as in the present invention. In addition, the amount of chloride ion eluted must be 10 ppm or less.

[0032]

As described above, according to the present invention, the life of the EL element is improved by reducing the chlorine ion outflow of the phosphor material contained in the light emitting layer of the EL element to 10 ppm or less. In addition, power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an EL device of the present invention.

FIG. 2 is a schematic sectional view showing a specific structure of a light emitting layer in the EL device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... EL element 2 ... Back electrode layer 3 ... Insulating layer 4 ... Emitting layer 5 ... Transparent electrode layer 6, 8 ... Binder resin 7 ... Phosphor particles

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB00 AB05 CA05 CA06 CB01 DA04 DA05 DB02 DC01 DC02 DC03 DC05 EB05 EC01 FA01

Claims (2)

[Claims] 1. A light-emitting layer sandwiched between a pair of electrodes, wherein the light-emitting layer contains a phosphor material, and a chlorine ion elution amount from the phosphor material is 10 ppm or less. Electroluminescent element. 2. The electroluminescent device according to claim 1, wherein the light emitting layer includes phosphor material particles dispersed in a binder resin.