JP2003092002A - Flat light emitting body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat light emitting body with the wave length of the emitted light can be easily adjusted, capable of realizing a white light with good light emitting efficiency and an excellent chromaticity balance. SOLUTION: The flat light emitting body has a transparent base board 1, on the back surface of which, can electroluminescent element 5 composed of a positive electrode 2, an organic light emitting layer 3, and a negative electrode, is formed, an LED element 6 irradiating light toward the inside of the transparent base board 1 is arranged at an end surface of the transparent base board 1, and a front surface side 8 of the transparent base board 1 is illuminated. A white light with well balanced chromaticity is realized by making the electroluminescent element 5 emit a light with complementary color of blue and yellow, and by making the wave length of the emitted light from the LED element 6 600-700 nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat light emitter which can be used for a liquid crystal backlight, a lighting fixture, and the like.

[0002]

2. Description of the Related Art As a flat light emitter used in a liquid crystal backlight or a lighting fixture, one using an electroluminescence element has been proposed. An electroluminescent element emits light when a voltage is applied to a fluorescent substance, and can be classified into an organic electroluminescent element and an inorganic electroluminescent element depending on the fluorescent substance used. In particular, the organic electroluminescence element is capable of planar light emission, capable of high-luminance light emission of about 100 to 100,000 cd / m ² at a low voltage of about 10 V such as a battery, and a combination of materials constituting a fluorescent substance. Since it can emit many colors, it is attracting attention as a planar light emitter.

[0003]

A method for obtaining white light emission by using an organic electroluminescence device is known as RGB method.
There are two methods, one is to synthesize light emission having three wavelengths (red, green and blue) respectively, and the other is to obtain wavelengths using complementary colors such as two wavelengths of blue and yellow and two wavelengths of blue green and orange. . R
In the case of three wavelengths of GB (red, green, blue), the organic electroluminescence element has a lower red emission efficiency and a shorter life than blue or yellow. Therefore, RG
B (red, green, blue) is likely to cause color shift due to deterioration behavior of three different wavelengths, and it is difficult to easily obtain white.
In the case of two wavelengths using complementary colors, although it is possible to increase the luminous efficiency, it is possible to obtain a white color with a small red component and an excellent chromaticity balance for use in backlights for liquid crystals that require full color. Have difficulty.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a planar light-emitting body whose emission wavelength can be easily adjusted.

Still another object of the present invention is to provide a flat light emitting body which has a good luminous efficiency and can realize a white color having an excellent chromaticity balance.

[0006]

Means for Solving the Problems The present inventor has conducted extensive studies in order to achieve the above object, and as a result, has adopted a small wavelength as a point light source in the emission wavelength of light emitted from an organic light emitting layer. The present invention has been completed by finding that a flat light emitting body whose emission wavelength can be easily adjusted can be obtained by reinforcing the light emitted from the existing LED element. In particular, in order to realize a white color that can be suitably used for a liquid crystal backlight, etc., by using an organic electroluminescent element that emits blue, yellow, or the like having good luminous efficiency, and by reinforcing the red component with an LED element, The luminous efficiency is good,
It is possible to obtain a white color excellent in chromaticity balance.

The flat light-emitting body according to claim 1 is provided with an electroluminescence element having an anode, an organic light-emitting layer, and a cathode formed on the back surface of a transparent substrate, and emits light on the front surface side of the transparent substrate. It is characterized in that an LED element for irradiating light into the transparent substrate is provided on an end face of the transparent substrate. According to the above, the light emitted from the LED element enters the transparent substrate, is guided while being totally reflected in the transparent substrate, and a part of the light is emitted from the front surface side of the transparent substrate. It is possible to easily adjust the emission wavelength emitted from the planar light-emitting body by using the light emitted in (1).

According to a second aspect of the present invention, there is provided the planar light emitter according to the first aspect, wherein at least a part of the light incident from the LED element into the transparent substrate is emitted to the front surface side of the transparent substrate. The light-scattering portion is formed on at least a part of the transparent substrate. By the above, LED
A part of the light emitted from the element causes a scattering phenomenon in the light scattering portion, and is more reliably emitted as scattered light on the surface side of the transparent substrate.Therefore, both this scattered light and the light emitted by the organic light emitting layer When the light is mixed, the emission spectrum emitted from the planar light emitter is broadened. As a result, the emission spectrum can be adjusted arbitrarily.

According to a third aspect of the present invention, there is provided a flat light emitting device according to the first or second aspect, wherein the light emitting wavelength generated by the LED element is combined with the light emitting wavelength generated by the electroluminescent element. RGB (red,
It is characterized in that it becomes white in the three-wavelength system (green, blue). With the above, white color with excellent chromaticity balance can be realized.

According to a fourth aspect of the present invention, there is provided the flat light emitting device according to any one of the first to third aspects, wherein the electroluminescent elements emit light of complementary colors of blue and yellow and the LED element. Emission wavelength of 600 ~
It is characterized by being 700 nm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the flat light emitting device according to the present invention comprises an electroluminescent device 5 having an anode 2, a light emitting layer 3 and a cathode 4 formed of a transparent conductive film on a back surface of a transparent substrate 1 in this order. I have it. The transparent substrate 1 is
A transparent glass plate such as soda lime glass or non-alkali glass, or a transparent plastic plate can be used. The transparent substrate 1 need only be light-transmissive, and in addition to being colorless and transparent, it may be slightly colored or frosted glass-like.

As the anode 2, the cathode 4, and the organic light emitting layer 3, those conventionally used in the electroluminescence element 5 can be used as they are. The organic light emitting layer 3 is formed in a multi-layer structure in which a hole transport layer is stacked on the anode 2 side and an electron injection layer is stacked on the cathode 4 side. A positive voltage is applied to the anode 2 and a negative voltage is applied to the cathode 4. When the voltage is applied, the electrons injected through the electron injection layer and the holes injected through the hole transport layer are combined in the organic light emitting layer 3 to emit light. The light 11 emitted from the organic light emitting layer 3 in this manner is used for the anode 2 and the transparent substrate 1 which are made of a transparent conductive film.
And is taken out from the surface side of the transparent substrate 1. The dotted arrow in FIG. 2 indicates the light 1 emitted from the organic light emitting layer 3.
1 schematically shows the traveling direction of 1. The electroluminescence element 5 is capable of emitting light with high brightness of about 100 to 100,000 cd / m ² at a low voltage of about 10 V such as a battery.

The anode 2 is an electrode for injecting holes into the device, and it is preferable to use an electrode material composed of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function. Is preferably 4 eV or more. Examples of the material of the anode 2 include a metal such as gold, CuI, ITO (indium-tin oxide: indium tin oxide), SnO.
₂ and conductive transparent materials such as ZnO. Anode 2
Can be produced, for example, by forming these electrode materials into a thin film on the surface of the transparent substrate 1 by a method such as a vacuum deposition method or a sputtering method. Also,
In order to transmit the light emitted from the organic light emitting layer 3 through the anode 2 and irradiate the light to the outside, the light transmittance of the anode 2 is preferably 70% or more. Further, the sheet resistance of the anode 2 is preferably several hundred Ω / □ or less, and particularly preferably 10
It is set to 0 Ω / □ or less. Here, the film thickness of the anode 2 varies depending on the material in order to control the characteristics such as the light transmittance and the sheet resistance of the anode 2 as described above, but is 500 nm.
Below, it is preferable to set in the range of 10 to 200 nm.

Further, the cathode 4 is an electrode for injecting electrons into the organic light emitting layer 3, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound or a mixture thereof having a small work function. The work function is preferably 5 eV or less. Examples of the electrode material of the cathode 4 include sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al ₂ O ₃ mixture, Al. / LiF mixture and the like. The cathode 4 is
For example, these electrode materials can be formed by forming a thin film by a method such as a vacuum vapor deposition method or a sputtering method. Further, in order to irradiate the light emission in the organic light emitting layer 3 to the anode 2 side, the light transmittance of the cathode 4 is set to 1
It is preferably 0% or less. The film thickness of the cathode 4 is
In order to control the light transmittance and other characteristics of the cathode 4, it varies depending on the material, but is usually 500 nm or less, preferably 100 to
The range is preferably 200 nm.

The light emitting material or doping material used in the organic light emitting layer 3 is anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline. , Bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-)
Quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-
Terphenyl-4-yl) amine, 1-aryl-2,
Examples thereof include, but are not limited to, 5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, distilbenzene derivative, distilarylene derivative, and various fluorescent dyes. Further, 90 to 99.5 parts by weight of a light emitting material selected from these compounds,
It is also preferable to include 0.5 to 10 parts by weight of the doping material. The thickness of the organic light emitting layer 3 is 0.5 to 500 n.
m, and more preferably 0.5 to 200 nm.

The organic light-emitting layer 3 has a hole-transporting layer laminated on the side of the anode 2, and the material constituting the hole-transporting layer has a capability of transporting holes, A compound having a hole injecting effect, an excellent hole injecting effect on the organic light emitting layer 3 and preventing electrons from moving to the hole transporting layer and having an excellent thin film forming ability can be mentioned. Specifically, a phthalocyanine derivative, a naphthalocyanine derivative, a porphyrin derivative, N, N'-bis (3-methylphenyl)-
(1,1'-biphenyl) -4,4'-diamine (TP
D) and an aromatic diamine compound such as 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, Pyrazoline derivative, tetrahydroimidazole, polyarylalkane, butadiene, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), and polyvinylcarbazole, polysilane, A polymer material such as a conductive polymer such as polyethylene dioxide thiophene (PEDOT) can be used.

In the organic light emitting layer 3, an electron injection layer is laminated on the cathode 4 side, and the material forming the electron injection layer has a capability of transporting electrons, A compound having an electron injection effect, an excellent electron injection effect on the organic light-emitting layer 3, a hole migration to the electron injection layer, and a thin film forming ability can be mentioned. Specifically, fluorene, bathophenanthroline, bathocuproine, anthraquinodimethane, diphenoquinone, oxazole, oxadiazole, triazole, imidazole, anthraquinodimethane, etc., or a compound thereof, a metal complex compound or a nitrogen-containing five-membered ring derivative is used. is there. Furthermore, the polymer material used for a polymer organic electroluminescent element can also be used. For example, polyparaphenylene and its derivative, fluorene and its derivative, and the like. The electron injection layer can be formed by co-evaporating bathophenanthroline and Cs (cesium) at a molar ratio of 1: 1.

The planar light-emitting device is characterized in that the end face of the transparent substrate 1 is provided with an LED element 6 for irradiating the transparent substrate 1 with light. The light 12 emitted from the LED element 6 is transmitted from the end surface of the transparent substrate 1 to the transparent substrate 1
The light enters inside and is guided while being totally reflected inside the transparent substrate 1. Further, in the above-mentioned planar light emitting body, the light scattering portion 7 is formed on the surface side 8 of the transparent substrate 1. A part of the light 12 emitted from the LED element 6 is emitted to the surface side 8 as scattered light 13 due to a scattering phenomenon in the light scattering portion 7. The planar light emitter emits light from the planar light emitter by mixing the scattered light 13 generated by a scattering phenomenon of a part of the light 12 emitted from the LED element 6 and the light 11 emitted from the organic light emitting layer 3. The emission spectrum can be arbitrarily adjusted.

In the formation of the light-scattering portion 7, the surface side 8 of the transparent substrate 1 is subjected to sandblasting to form fine irregularities, or a diffusion bead layer is arranged. The light scattering portion 7 is formed on the surface side 8 of the transparent substrate 1 if the light 12 emitted from the LED element 6 is emitted to the surface side 8 of the transparent substrate 1 due to a scattering phenomenon. However, it may be inside the transparent substrate 1.

In order to adjust the emission spectrum emitted from the planar light-emitting body, the light 12 emitted from the LED element 6 reinforces a small wavelength of the light 11 emitted from the organic light-emitting layer 3. . Therefore, the LED element 6 is to appropriately select one having a specific emission wavelength.

For example, the electroluminescence element 5 that emits red light has a low luminous efficiency of about 3 Lm / W or less, whereas the red LED element 6 has a luminous efficiency of 10 to 10.
It is as high as 20 Lm / W. In addition, an electroluminescence element 5 that emits blue and yellow light using complementary colors
Has a high luminous efficiency of 5 to 15 Lm / W.

Therefore, as the above-mentioned plane light-emitting body, one which emits blue and yellow which are complementary colors to each other is used for the electroluminescence element 5, and the emission wavelength is 60 at the end face of the transparent substrate 1.
By arranging the red LED element 6 of 0 to 700 nm,
The luminous efficiency is good, there is no color shift, and the chromaticity balance is excellent. The planar light emitter is RGB (red, green,
Blue) It is possible to realize a three-wavelength white planar light emitter.

[0024]

Example 1 A transparent substrate having a thickness of 0.7 m
m glass substrate was used. Sandblasting is applied to one surface (front side) of this glass substrate to obtain an average roughness of 2
A μm light scattering part was formed. Next, ITO (indium-tin oxide) was sputtered on the other surface (back side) of the glass substrate to form an anode having a sheet resistance of 7Ω / □. This was subjected to ultrasonic cleaning with acetone, pure water and isopropyl alcohol for 15 minutes, dried, and further UV ozone cleaned. After that, this substrate is set in a vacuum vapor deposition device and
4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (Dojindo Co., Ltd.) was used as a hole transport layer under reduced pressure of × 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa). 30) at a deposition rate of 1-2 Å / s
It was evaporated to a thickness of 0Å. Next, as a yellow light emitting layer, α-NP
Lubren (ACROS ORGANICS N.V.
Of 1% by mass was laminated to a thickness of 100 Å.
Further, as a blue light emitting layer, a layer in which a distyryl biphenyl derivative (DPVBi, manufactured by Idemitsu Kosan Co., Ltd.) is doped with a DSA derivative (BCzVBi, manufactured by Idemitsu Kosan Co., Ltd.) having a carbazolyl group at its end at 12 mass% is 500 Å.
It was laminated thickly. Next, bathophenanthroline (manufactured by Dojindo Laboratories Co., Ltd.) and Cs (cesium) were co-deposited as an electron injection layer at a molar ratio of 1: 1 to a thickness of 200Å. Subsequently, aluminum was deposited at a deposition rate of 10Å / s,
It was vapor-deposited to a thickness of 1500Å and used as a cathode. In this way
A transparent substrate having an electroluminescent element that emits blue and yellow light was produced.

As the LED element, one red LED element (FR1111C, manufactured by Stanley Electric Co., Ltd.) having a peak wavelength of 626 nm was used. A red LED element was arranged on the end face of the transparent substrate to obtain a flat light emitting body.

Since this planar light emitting device uses the electroluminescence element which emits blue and yellow light and the red LED element, it has a high luminous efficiency.

(Comparative Example 1) In Example 1, red LE
A transparent substrate having electroluminescent elements emitting blue and yellow light was obtained in the same manner as in Example 1 except that the D element was arranged.

(Measurement of Whiteness) The chromaticity coordinates of the planar luminescent material of Example 1 were measured. For the measurement, the electroluminescence element and the red LED element are powered (KEYTHLEY23
6 models) and a multi-channel analyzer (PMA-10, manufactured by Hamamatsu Photonics KK) was used under the condition of 100 cd / m ² . As for the chromaticity coordinates, the closer the values are to X = 0.33 and Y = 0.33, the better the white color is. The planar light-emitting body of Example 1 emits white light including red component light and has chromaticity coordinates (X = 0.
32, Y = 0.33), and the white light emission was excellent.

The chromaticity coordinates of Comparative Example 1 were measured. The measurement is
The electroluminescence device was connected to a power source, and the same procedure as in Example 1 was performed. Comparative Example 1 is white with a slight green color because there is no red component light, and the chromaticity coordinate is (X
= 0.30, Y = 0.39), the degree of white light emission was low as compared with the examples.

[0030]

The flat light emitting device according to claims 1 to 4 is provided with an LED element for irradiating light into the transparent substrate at the end face of the transparent substrate. Therefore, a part of the light emitted from the LED element and the organic light emission. It is possible to easily adjust the emission wavelength emitted from the planar light-emitting body by using both of the light emitted from the layers.

Further, the flat light-emitting body according to claim 4 uses an organic electroluminescence element that emits blue, yellow, or the like, which has particularly good luminous efficiency, and uses a red component as LE.
By reinforcing with the D element, it is possible to obtain a white color that has good luminous efficiency and excellent chromaticity balance.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic view schematically showing a light ray emitted in the same as above.

[Explanation of symbols]

1 transparent substrate 2 anode 3 Organic light emitting layer 4 cathode 5 Electroluminescence element 6 LED element 7 Light scattering part

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/14 F21Y 101: 02 // F21Y 101: 02 105: 00 105: 00 113: 02 113: 02 F21S 1/00 FE 5/00 Z (72) Inventor Yasuhisa Kishigami 1048 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works Co., Ltd. F-term within the company (reference) 2H091 FA23Z FA31Z FA41Z FA44Z FA45Z FB02 FD06 LA15 LA16 LA20 LA30 3K007 AB04 CA01 CA05 CB01 DA01 DA02 EB00 EC00 5F041 AA14 CB36 DA83 EE25 FF11

Claims (4)

[Claims] 1. An anode, an organic light emitting layer, and
In a planar light emitting device that includes an electroluminescent element having a cathode formed thereon and emits light on the surface side of a transparent substrate,
A planar light-emitting body, comprising an LED element for irradiating light into the transparent substrate on an end surface of the transparent substrate. 2. A light scattering portion is formed on at least a part of the transparent substrate so that at least a part of light incident from the LED element into the transparent substrate is emitted to the front surface side of the transparent substrate. The planar light emitter according to claim 1. 3. The emission wavelength generated by the LED element is
The planar light-emitting body according to claim 1 or 2, wherein when the emission wavelengths generated by the electroluminescence element are combined, white is obtained by an RGB (red, green, blue) three-wavelength system. 4. The emission color of the electroluminescence element is a complementary color of blue and yellow, and the emission wavelength of the LED element is 600 to 700 nm. Flat light emitter.