JPH08222372A - Electroluminescent element - Google Patents

Abstract

PURPOSE: To provide an electroluminescent element which has a phosphor pigment of good emission efficiency and emits light at high brightness. CONSTITUTION: In an electroluminescent element having an emitter layer 3 sandwiched between a back electrode 1 and a transparent electrode 4 and made to emit light by application of a predetermined voltage to the electrodes 1, 4, a phosphor layer 5, in which a phosphor pigment for obtaining a predetermined luminescent color is dispersed in an organic binder solution, is provided on the emitting surface of the emitter layer 3. In the phosphor layer 5, the phosphor pigment is dispersed in the organic binder so that the emission spectrum of the phosphor which the emitter layer 3 has approximately coincides with the excitation spectrum of the phosphor pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device for obtaining a predetermined luminescent color by means of a fluorescent substance and a fluorescent pigment, and in particular, an electroluminescent device (hereinafter referred to as E
L element).

[0002]

2. Description of the Related Art Conventionally, when a desired color of light emission is desired for an EL element, JP-A-60-220597 and JP-A-1-24 are used.
As disclosed in Japanese Patent No. 3392, etc., a wavelength conversion phosphor layer containing a fluorescent pigment on the light emitting surface side of an electroluminescent phosphor layer (including light components of all colors from blue to red) ) (Former), or by obtaining the light-emitting layer by dispersing the phosphor particles and pigment particles for obtaining a predetermined light-emitting color in the binder (latter), to obtain a predetermined light-emitting color. Are known.

[0003]

Recently, EL elements have come to be used as various backup illuminations for liquid crystal displays and the like. Even in EL elements utilizing the excited light emission of the fluorescent pigment having the above-mentioned structure, It cannot be said that the light emission characteristics are fully utilized, and there is a demand for an EL element for obtaining higher brightness light emission.

[0004]

In order to solve the above-mentioned problems, the present invention comprises sandwiching a light-emitting layer in which a fluorescent substance is dispersed in an organic binder solution with a pair of electrodes, at least one of which is translucent. In an electroluminescent device in which the light emitting layer emits light by applying a predetermined voltage to an electrode, a fluorescent layer having a fluorescent pigment for obtaining a predetermined emission color is provided on the light emitting surface side of the light emitting layer, and the fluorescent layer is provided. In the organic binder solution, the light-emitting layer contains the fluorescent pigment so that the peak wavelength of the excitation spectrum of the fluorescent pigment of the fluorescent layer is substantially the same as the peak wavelength of the emission spectrum of the fluorescent material of the light-emitting layer. It is characterized by being dispersed in.

Further, a light emitting layer in which a fluorescent substance and a fluorescent pigment are dispersed in an organic binder solution is sandwiched by a pair of electrodes, at least one of which is transparent, and a predetermined voltage is applied to each electrode. In the electroluminescent device in which the light-emitting layer emits light, the light-emitting layer has a peak wavelength of an emission spectrum of the phosphor, and the fluorescent pigment is used so that a peak wavelength of an excitation spectrum of the fluorescent pigment substantially matches. It is characterized by being dispersed in the organic binder solution.

[0006]

By configuring the light emitting portion so that the peak wavelength of the emission spectrum of the fluorescent substance and the peak wavelength of the excitation spectrum of the fluorescent pigment are substantially the same, an EL element with high luminous efficiency and high luminance emission is obtained. .

[0007]

EXAMPLES Hereinafter, the EL device of the present invention will be explained based on the examples shown in the attached drawings, and the EL device having a peak wavelength (yellow emission) near 515 (nm) in the fluorescence spectrum will be explained. .

FIG. 1 is a cross-sectional view of an essential part showing the structure of an EL element,
FIG. 2 is a diagram showing an emission spectrum of the EL element.

As shown in FIG. 1, the EL device of this embodiment has a back electrode 1, an insulating layer 2 and a light emitting layer 3, a transparent electrode 4, and a fluorescent layer 5 which are sequentially laminated, and the whole of them is sealed. It is composed of moisture-proof films 6 and 7 which are surrounded by.

The back electrode 1 is made of a reflective material such as aluminum (Al).

The insulator layer 2 is made of barium titanate (BaTi
O ₃ ) etc. are uniformly dispersed in an organic binder solution composed of cyanoethyl cellulose etc., a coating film is formed on the back electrode 1 by screen printing or the like, and then dried to obtain an insulator layer 2.

For the light emitting layer 3, 70 parts by weight of a fluorescent material such as zinc sulfide (ZnS) "trade name 723" manufactured by Sylvania was added to an organic binder solution similar to that of the insulator layer 2 and uniformly dispersed. Then, 30 parts by weight of an organic binder made of cyanoethyl cellulose or the like is added to an organic solvent, and 70 parts by weight of the fluorescent material is added to the organic binder to uniformly disperse the organic binder. A film is formed and then dried to obtain the light emitting layer 3 (the phosphor material is basically greenish blue).

The transparent electrode 4 is formed by depositing, for example, indium oxide, tin oxide, or the like as a conductive fine powder having a visible light transmitting property on one surface of a transparent sheet 8 made of a polyester film by a vapor deposition or sputtering method. 4 is arranged so as to be in contact with the light emitting layer 3.

The fluorescent layer 5 is prepared by adding 515 of fluorescent spectrum in an organic binder solution made of epoxy resin or the like.
A fluorescent pigment material having a peak wavelength (yellow) in the vicinity of (nm), for example, "manufactured by Shin Roihi, trade name FA-00"
5 "in an amount of 60 parts by weight and uniformly dispersed (110 parts by weight of an organic binder made of an epoxy resin or the like in an organic solvent, and 60 parts by weight of a fluorescent pigment material is uniformly dispersed therein) to make a transparent A film is formed by screen printing on the surface of the transparent sheet 9 forming the electrode 4 (on the side of the non-transparent electrode 4), and then dried to obtain the fluorescent layer 5.

The moisture-proof films 6 and 7 are made of a polymer film or the like, and surround the light emitting portion 9 composed of the back electrode 1, the insulating layer 2, the light emitting layer 3, the transparent electrode 4 and the fluorescent layer 5 described above. And laminate processing.

The light emitting layer 3 and the fluorescent layer 5 have the light emitting characteristics (emission spectrum) shown in FIG. The light emission characteristics in FIG. 2 are measured by a spectrofluorometer “Shimadzu Corporation, model name RF-5000”, the horizontal axis indicates the wavelength of light (nm), and the vertical axis indicates the emission intensity (arbitrary unit). Is shown.

The emission spectrum A (indicated by a dotted line) of the light emitting layer 3 made of a fluorescent substance (ZnS) has an emission intensity of 490 (n).
m) has a characteristic such that it becomes maximum at a wavelength of light (the emission spectrum A of the light emitting layer 3 is E
An L element was manufactured by removing the fluorescent layer 5 and
It was obtained by applying a driving voltage of 28 V and using the measuring instrument). On the other hand, the excitation spectrum B of the fluorescent layer 5 (fluorescent pigment) obtained by monitoring the light of 515 nm which is the peak wavelength of the fluorescent spectrum by the measuring instrument (shown by the one-dot chain line) has the emission intensity of the fluorescent light. Like the emission spectrum A of the body, it has a characteristic that it becomes maximum at the wavelength of light near 490 (nm).

In the EL device of this example, the peak wavelength at which the emission intensity of the emission spectrum A of the light emitting layer 3 is maximized,
The fluorescent layer 5 is determined by determining the content of the fluorescent pigment in the fluorescent layer 5 so that the peak wavelengths at which the emission intensity of the excitation spectrum B of the fluorescent layer 5 is maximized substantially coincide with each other and dispersing the fluorescent pigment in the organic binder solution. However, when a predetermined voltage (driving voltage) is applied to a lead pin or the like (not shown) provided on the back electrode 1 and the transparent electrode 4, the emission spectrum C (shown by the solid line) is obtained. The emission intensity of about 1.5 times or more compared to the emission intensity of the light emitting layer 3 was obtained, which means that an EL element emitting high brightness light was obtained.

With such a configuration, the peak wavelength of the emission spectrum A of the light emitting layer 3 and the peak wavelength of the excitation spectrum B of the fluorescent layer 5 are made to substantially coincide with each other, whereby the fluorescent pigment of the fluorescent layer 5 is subjected to electric field excitation. Since the light emitted from the phosphor of the light emitting layer 3 is best absorbed, and the energy of the absorbed light can be converted into the emission color (yellow) very efficiently,
An EL device with high emission brightness can be obtained.

It should be noted that, due to the above-mentioned structure, E having high emission brightness is obtained.
Although the L element could be obtained, as another method, for example, 70 parts by weight of the fluorescent material and 20 parts by weight of the fluorescent pigment material are uniformly dispersed in the same organic binder solution as that of the light emitting layer 3 described above. By dispersing and forming a coating on the surface of the insulator layer 2 by a means such as screen printing with a fluorescent pigment, a light emitting layer is formed, whereby the peak wavelength of the emission spectrum of the fluorescent substance and the excitation spectrum of the fluorescent pigment are An EL element having a peak wavelength substantially equal to that of the EL element can be obtained, and high-luminance light emission can be obtained similarly to the EL element having the above-described configuration.

Further, in this embodiment, the fluorescent layer 5 is formed on the transparent sheet 8. However, the location of the fluorescent layer 5 of the present invention is not limited to this. For example, the light emitting layer 3 and the transparent layer are transparent. It may be between the electrode 6 or between the transparent electrode 6 and the transparent sheet 9, that is, it may be arranged so as to be positioned on the light emitting surface side of the light emitting layer 3.

In this embodiment, an EL element which emits yellow light has been described as an example. However, in EL elements which obtain other emission colors, the peak wavelength of the emission spectrum of the phosphor and the fluorescence are the same as in the present invention. By making the peak wavelength of the excitation spectrum of the pigment (for example, dye for dye laser) substantially coincide with each other, it is possible to provide an EL element capable of high-luminance emission of other emission colors.

The peak wavelength of the emission spectrum of the fluorescent substance and the peak wavelength of the excitation spectrum of the fluorescent pigment may be slightly different from each other as long as high-luminance emission can be obtained.

[0024]

According to the present invention, a light emitting layer in which a fluorescent substance is dispersed in an organic binder solution is sandwiched by a pair of electrodes, at least one of which is translucent, and a predetermined voltage is applied to each of the electrodes. In the electroluminescent device in which the light emitting layer emits light, a fluorescent layer having a fluorescent pigment for obtaining a predetermined emission color is provided on the light emitting surface side of the light emitting layer, and the fluorescent layer is the fluorescent light included in the light emitting layer. For the peak wavelength of the emission spectrum of the body,
The fluorescent pigment is dispersed in an organic binder solution so that the peak wavelengths of the excitation spectra of the fluorescent pigments in the fluorescent layer are substantially the same, and the fluorescent substance and the fluorescent pigment are organic binders. At least one of the light-emitting layers dispersed in a solution is sandwiched by a pair of translucent electrodes, and the light-emitting layer emits light by applying a predetermined voltage to each of the electrodes. With respect to the peak wavelength of the emission spectrum of the fluorescent substance, the fluorescent pigment is dispersed in the organic binder solution so that the peak wavelength of the excitation spectrum of the fluorescent pigment is substantially the same. Thus, it is possible to obtain an EL element having a high luminous efficiency and capable of emitting light with high brightness.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an EL device showing an embodiment of the present invention.

FIG. 2 is a diagram showing an emission spectrum of a sympathetic example.

[Explanation of symbols]

 1 Back Electrode 3 Light-Emitting Layer 4 Transparent Electrode 5 Fluorescent Layer A Emission Spectrum of Light-Emitting Layer B Excitation Spectrum of Fluorescent Layer C Emission Spectrum of EL Element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Zhang Yi, 1-1 190, Fujihashi, Nagaoka City, Niigata Prefecture, Japan Nippon Seiki Co., Ltd. R & D Center

Claims (2)

[Claims] 1. A light emitting layer in which a phosphor is dispersed in an organic binder solution is sandwiched by a pair of electrodes, at least one of which is translucent, and a predetermined voltage is applied to each of the electrodes to cause the light emitting layer to emit light. In the electroluminescent element of, a fluorescent layer having a fluorescent pigment for obtaining a predetermined emission color is provided on the light emitting surface side of the light emitting layer, and the fluorescent layer has an emission spectrum of a fluorescent substance included in the light emitting layer. The electroluminescent device, wherein the fluorescent pigment is dispersed in an organic binder solution so that the peak wavelength of the excitation spectrum of the fluorescent pigment of the fluorescent layer substantially coincides with the peak wavelength of. 2. A light-emitting layer in which a fluorescent substance and a fluorescent pigment are dispersed in an organic binder solution is sandwiched by a pair of electrodes, at least one of which is translucent, and a predetermined voltage is applied to each of the electrodes. In the electroluminescent device in which the light-emitting layer emits light, the light-emitting layer has a peak wavelength of an emission spectrum of the phosphor, and the fluorescent pigment is used so that a peak wavelength of an excitation spectrum of the fluorescent pigment substantially matches. An electroluminescent device characterized by being dispersed in the organic binder solution.