JP2000036386A - White light emitting electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate white light emission using a simple structure without using a complicated and special material and a high degree of a manufacturing technique as before. SOLUTION: A layer 13 to make injection and conveyance of a hole is formed on a positive electrode 11, and light emitting islands 14 and 15 consisting of two of the red, green, and blue emitting organic substances are formed on the hole injection and conveying layer 13 in such a way as dispersed is desired positions. A light emission layer 18 to emit white light by these light emitting islands 14 and 15 and an upper ground layer 16 is provided where the upper ground layer 16 to serve also as a layer to male implantation and conveyance of an electron is formed from the residual color emitting substance on the light emitting islands 14 and 15 and hole conveying layer 13. On this layer 16, a negative electrode 17 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence device utilizing electroluminescence of an organic material, and has a simple structure and a white display light source having a simple structure without requiring complicated materials and film forming techniques. It relates to a luminescence element.

[0002]

2. Description of the Related Art White light emitting organic electroluminescent devices are extremely useful industrially as light sources and display devices. Above all, there is a strong need for application to a backlight for a liquid crystal display device because it can be made lighter and thinner than a conventional combination of a cold cathode tube and a light guide plate. Conventionally, a method of mixing R (red), G (green), and B (blue) light-emitting materials to obtain white light to form a thin film, or R (red), G (green), B
(Blue) A method of laminating a light emitting layer on each of them is known. For example, the white light-emitting organic electroluminescence device shown in FIG. 3 is formed by mixing a dopant having a different emission wavelength into a light-emitting base material and forming a thin film to form a light-emitting layer 31;
A white spectrum can be obtained by combining these emission spectra. In the figure, 32 is a substrate, 33 is a substrate 3
2 and an anode formed on the light emitting layer 31;
Reference numeral denotes a cathode formed on the light emitting layer 31, and reference numeral 35 denotes a power supply connected to the anode 33 and the cathode. In the example of FIG.
PBD (2- (4-biphenylyl) -5 having electron transporting property using K (polyvinyl carbazole) as a host material
-(4-tert-butylphenyl) 1,3,4-
Oxadiazole), blue-emitting TPB (1, 1,
4,4-tetraphenyl-1,3-butadiene), DCM ((4-dicyanomethylene) -2-methyl-6-paradimethylaminostyryl-4etch-pyran) emitting red light,

[0003]

[Chemical formula 1]

A coumarin 6, which emits green light, represented by

[0005]

[Chemical formula 2]

[0006] White light emission is obtained by a structure in which five kinds of light emitting materials of Nile Red emitting red light and a charge transporting material are dispersed as dopants. It is known that the emission spectrum varies depending on the mixing amount. To obtain white light emission, 3 mol% of TPB, 30 wt% of PBD, 0.04 mol% of coumarin 6 and 0.04 mol% of DCM are obtained.
It is considered that 02 mol% and Nile Red are 0.015 mol%. These materials not only have appropriate emission wavelengths and charge injecting / transporting properties, but also disperse uniformly without agglomeration with PVK, and dissolve well in PVK solvent, such as dichloroethane. 2
It is selected to meet the conditions.

[0007]

As described in the above-mentioned prior art example, conventionally, in order to obtain white light emission, complicated and special materials and advanced manufacturing techniques were required. For example, in the prior art example shown in FIG. 3, an appropriate amount of various light emitting materials and charge transporting materials are dispersed in a host polymer to form a light emitting layer. In order to obtain a white spectrum, light emitting materials having a plurality of different emission wavelengths are required, and in order to obtain high luminous efficiency, it is necessary to appropriately combine a charge transporting material as a guest material. In such a complex combination of materials, it is important that the respective materials are not uniformly dispersed and agglomerated with respect to the host material, and that there is no chemical interaction with each other. If aggregation occurs,
This causes a significant decrease in luminous efficiency called concentration quenching. Further, if chemical interaction occurs, exciplexes are formed between the materials to lower the luminous efficiency, and the luminous wavelength shifts to the longer wavelength side, so that a desired white spectrum cannot be obtained. That is, in the mixing method which is an example of the prior art shown in FIG.

[0008] In addition, in terms of the manufacturing method, it is needless to say that quantitative accuracy is required for uniform dispersion. However, when a wet film forming method typified by spin coating is used, all the methods are required. The materials need to be soluble in the same solvent. It is clear that mixing is not possible if it is insoluble, and this point is also a significant material limitation. It is also conceivable to use a dry method of thinning such materials by vapor deposition.However, in this method, various types of materials are simultaneously vapor-deposited while controlling the amount of evaporation, so that the control is difficult and wide. It was extremely difficult to form a uniform film over the area. As described above, the white light-emitting organic electroluminescent element is conventionally formed of a plurality of organic materials in which a white surface light source is extremely complicatedly combined, and is not suitable for easily providing a high-performance white light-emitting device. Was. The present invention solves such a problem, and provides a white light-emitting electroluminescent element that does not use a complicated organic material or a complicated manufacturing method.

[0009]

According to the present invention, there is provided a white light-emitting electroluminescent device according to the present invention, wherein a layer for injecting and transporting holes is formed on an anode, and red, green, and
Of the organic materials that emit blue light, light-emitting islands made of two-color light-emitting materials are formed by dispersing them in desired arrangements, and the remaining one color of light-emitting islands and the hole transport layer are placed on these light-emitting islands and the hole transport layer. A light emitting layer that emits white light is provided by a light emitting island and an upper layer formed by forming an upper layer also serving as a layer for injecting and transporting electrons with a light emitting material, and a cathode is formed on the upper layer. With this configuration, white light can be easily emitted by the upper layer and the light emitting islands of the other two colors.

As the above-mentioned upper layer, aluminum quinolylate, which is an aluminum complex, is desirable from the viewpoint of having an electron transporting property and a green light emitting property.

When the upper layer is made of the above-mentioned material, in order to emit white light, the light emitting islands of the two colors are composed of a distyrylbiphenyl derivative having blue light emission and a dicyanomethylene derivative having red light emission. It is desirable.

[0012]

FIG. 1 shows an embodiment of the present invention. The film-coated glass substrate 12 on which the transparent conductive film ITO forming the anode 11 is formed is subjected to ultrasonic cleaning in a mixed solvent of acetone and isopropyl alcohol, and then to ozone cleaning while irradiating UV, so that the hole injection transport layer 13 is TPD.
(N, N'-diphenyl-N, N'-3-methylphenyl) -1,1'-biphenyl-4,4'-diamine) was vacuum deposited to a thickness of 400 °. Further, DPVBi (1,4-bis (2,2-diphenylvinyl) biphenyl), which is a distyrylbiphenyl derivative having a light emission peak wavelength at 440 nm, is used as a blue light-emitting material at 300 °.
Which is a dicyanomethylene derivative having an emission peak wavelength at 650 nm as a red light-emitting material.
M was vapor-deposited at predetermined positions to a thickness of 400 ° to form blue light emitting islands 14 from a blue light emitting material and red light emitting islands 15 from a red light emitting material. Further, Alq3 (tris (8-hydroxyquinolinato) aluminum (III)), which is an aluminum complex which is an electron injecting / transporting material and a green light emitting material, is vapor-deposited on the entire surface of the light emitting islands 14 and 15 and the hole injection layer 13 by 500 °. Then, upper layer 1
6 was formed. The cathode 17 on which the upper layer 16 was formed was made of Mg
And Ag were co-deposited so that the atomic ratio was 10: 1 to a thickness of 700 Å, and then Ag alone was deposited thereon to a thickness of 1000 Å to form a protective film. All vacuum depositions have a degree of vacuum of 5 × 10 ^-4
The test was performed at Pa or lower.

A blue light emitting island 14 and a red light emitting island 15;
Light-emitting layer 1 that emits white light in cooperation with green upper layer 16
8 are configured. Therefore, the number of dispersed arrangements of the blue light emitting islands 14 and the red light emitting islands 15, the size of each island, and the position of dispersion are determined by the relationship with the green upper ground layer 16. FIG. 2 is a plan view of the white light-emitting organic electroluminescence device shown in FIG. 1 and 2, the size of each of the blue light emitting islands 14 and the red light emitting islands 15 is 0.05 to 0.2 mm in diameter. The average number of dispersed blue light emitting islands 14 and red light emitting islands 15 is 300 to 1000 / cm ² , respectively. The light emitting islands 14, 15
Is formed in a circular shape in the illustrated example, but may be a square shape as long as it can emit light, and is not caught by that shape.

As shown in FIG. 2, the light-emitting islands 14 and 15 are arranged such that the blue light-emitting islands 14 and the red light-emitting islands 15 are alternately arranged in the horizontal direction, and also in the vertical direction.
And the red light emitting islands 15 are arranged alternately. When a DC voltage of 10 V was applied between the cathode 17 and the anode 11 to the organic thin film electroluminescence device having such a structure, light was emitted at a luminance of 150 cd / m ² .
The emission color was white.

[0015]

As described above, according to the present invention, the organic EL device is simpler than the conventional white light-emitting organic EL device without deteriorating the characteristics of the organic electroluminescent device such as low-voltage driving and high-luminance light emission. And a high-performance white light-emitting organic electroluminescent element having a simple structure.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a white light emitting electroluminescent device according to the present invention.

FIG. 2 is a plan view of the white light-emitting organic electroluminescence device shown in FIG.

FIG. 3 is a cross-sectional view showing a conventional white light-emitting organic electroluminescent element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Anode 12 Transparent substrate 13 Hole injection / transport layer 14 Blue light emitting island 15 Red light emitting island 16 Electron injection / transport layer / green light emitting portion 17 Cathode 18 Light emitting layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/14 H05B 33/14 B

Claims (2)

[Claims] 1. A light emitting island comprising a light emitting material of two colors among organic materials which emit red, green and blue, respectively, on a layer for injecting and transporting holes on an anode. Are formed in a desired arrangement, and an upper ground layer, which also serves as a layer for injecting and transporting electrons, is formed on the light emitting islands and the hole transport layer by the remaining one color light emitting material. A white light-emitting electroluminescent element, comprising: a light-emitting layer that emits white light by the light-emitting islands and the upper layer; and a cathode formed on the upper layer. 2. The method according to claim 1, wherein the upper layer is made of aluminum quinolylate, one of the light emitting islands of the two colors is made of a distyrylbiphenyl derivative, and the other light emitting island is made of a dicyanomethylene derivative. White light emitting electroluminescent element.