JP4432299B2 - Planar light emitter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat light emitter that can be used in a backlight for liquid crystal, a lighting fixture, and the like.
[0002]
[Prior art]
As a planar light-emitting body employed in a liquid crystal backlight or a lighting fixture, a device using an electroluminescence element has been proposed. An electroluminescent element emits light when a voltage is applied to a fluorescent material, and can be classified into an organic electroluminescent element and an inorganic electroluminescent element depending on the fluorescent material used. In particular, the organic electroluminescence element is capable of planar light emission, can emit light with a high luminance of about 100 to 100000 cd / m ² at a low voltage of about 10 V such as a battery, and the combination of materials constituting the fluorescent substance. Since it can emit a large number of colors, it attracts attention as a flat light emitter.
[0003]
[Problems to be solved by the invention]
A method of obtaining white light emission using an organic electroluminescence element includes a method of obtaining light emission having three wavelengths of RGB (red, green, blue), and two wavelengths of blue and yellow or blue green and orange. There is a method of obtaining by using a wavelength having a complementary color relationship such as a wavelength. In the case of three wavelengths of RGB (red, green, and blue), the organic electroluminescence element has a red light emitting efficiency and a lifetime that are lower than those of blue and yellow. For this reason, color deviation is likely to occur due to different deterioration behaviors of RGB (red, green, blue) three wavelengths, and it is difficult to easily obtain white. In the case of two wavelengths using complementary colors, the luminous efficiency can be increased, but for use in liquid crystal backlights and the like that require a full color, it is possible to obtain a white color with little red component and excellent chromaticity balance. Have difficulty.
[0004]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flat light emitter in which the emission wavelength can be easily adjusted.
[0005]
Furthermore, another object of the present invention is to provide a flat light emitter capable of realizing white having good luminous efficiency and excellent chromaticity balance.
[0006]
[Means for Solving the Problems]
As a result of intensive research to achieve the above object, the present inventor has reinforced the light emitted from the LED element employed as a point light source with a smaller wavelength of the light emitted from the organic light emitting layer. As a result, it has been found that a flat light emitter with easy adjustment of the emission wavelength can be obtained, and the present invention has been completed. In particular, in order to realize white that can be suitably used for a backlight for liquid crystal, etc., by using an organic electroluminescent element that emits blue or yellow with good luminous efficiency, the red component is reinforced with an LED element, The light emission efficiency is good, and a white color excellent in chromaticity balance can be obtained.
[0007]
The planar light emitter according to claim 1 is provided with an electroluminescent element having an anode, an organic light emitting layer, and a cathode formed on the back surface of the transparent substrate, and emits light on the surface side of the transparent substrate. An LED element that irradiates light into the transparent substrate is provided on the end face, and a part of the light generated by the LED element is part of the light generated by the electroluminescence element while being guided through the transparent substrate. And a light scattering portion is formed on at least a part of the transparent substrate so that a part of the synthesized light is emitted to the surface side of the transparent substrate . By the above, it is possible to easily adjust the emission wavelength emitted from the planar light emitter by using the light emitted from the LED element and guided while totally reflecting inside the transparent substrate and the light emitted from the organic light emitting layer. Is.
[0009]
Flat light emitting body according to claim 2, wherein, in the flat light emitting body according to claim 1 wherein, the emission wavelength generated by the LED element, when combining the emission wavelength generated by the electroluminescent device, RGB (red, green, blue ) It is characterized by being white in a three-wavelength system. As described above, white having excellent chromaticity balance can be realized.
[0010]
The flat light emitter according to claim 3 is the flat light emitter according to claim 1 or claim 2 , wherein the light emission color of the electroluminescence element is a complementary color of blue and yellow, and the light emission wavelength of the LED element is 600. It is characterized by being -700 nm.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0012]
As shown in FIG. 1, the planar light emitter according to the present invention includes an electroluminescent element 5 in which an anode 2 made of a transparent conductive film, an organic light emitting layer 3, and a cathode 4 are sequentially formed on the back surface of a transparent substrate 1. . The transparent substrate 1 may be a transparent glass plate such as soda lime glass or non-alkali glass, or a transparent plastic plate. The transparent substrate 1 only needs to be light-transmitting, and in addition to being colorless and transparent, the transparent substrate 1 may be slightly colored or ground glass.
[0013]
As the anode 2, the cathode 4, and the organic light emitting layer 3, those conventionally used for the electroluminescence element 5 can be used as they are. The organic light emitting layer 3 is formed in a multilayer structure in which a hole transport layer is laminated on the anode 2 side and an electron injection layer is laminated on the cathode 4 side. A positive voltage is applied to the anode 2 and a negative voltage is applied to the cathode 4. 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. Thus, the light 11 emitted from the organic light emitting layer 3 passes through the anode 2 made of the transparent conductive film and the transparent substrate 1 and is extracted from the surface side of the transparent substrate 1. The dotted line arrows in FIG. 2 schematically show the traveling direction of the light 11 emitted from the organic light emitting layer 3. The electroluminescence element 5 can emit light with a high luminance of about 100 to 100,000 cd / m ² at a low voltage of about 10 V, such as a battery.
[0014]
The anode 2 is an electrode for injecting holes into the device, 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 large work function, and the work function is 4 eV or more. It is better to use one. Examples of the material of the anode 2 include conductive transparent materials such as metals such as gold, CuI, ITO (indium-tin oxide: indium tin oxide), SnO ₂ , and ZnO. The anode 2 can be produced, for example, by forming these electrode materials on the surface of the transparent substrate 1 into a thin film by a method such as vacuum vapor deposition or sputtering. In order to transmit 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. Furthermore, the sheet resistance of the anode 2 is preferably several hundred Ω / □ or less, particularly preferably 100 Ω / □ or less. Here, the film thickness of the anode 2 varies depending on the material in order to control the light transmittance, sheet resistance, and other characteristics of the anode 2 as described above, but is set to a range of 500 nm or less, preferably 10 to 200 nm. It is good.
[0015]
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 and a mixture thereof having a small 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 can be produced, for example, by forming these electrode materials into a thin film by a method such as vacuum deposition or sputtering. Moreover, in order to irradiate the light emission in the organic light emitting layer 3 to the anode 2 side, it is preferable to make the light transmittance of the cathode 4 10% or less. The film thickness of the cathode 4 varies depending on the material in order to control characteristics such as light transmittance of the cathode 4, but is usually 500 nm or less, preferably 100 to 200 nm.
[0016]
The light emitting material or doping material used for 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-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, distilbene Derivatives, distilarylene derivatives, and various fluorescent dyes, but are not limited thereto. It is also preferable to include 90 to 99.5 parts by weight of a light emitting material selected from these compounds and 0.5 to 10 parts by weight of a doping material. The organic light emitting layer 3 has a thickness of 0.5 to 500 nm, more preferably 0.5 to 200 nm.
[0017]
The organic light emitting layer 3 has a hole transport layer laminated on the anode 2 side, and the material constituting the hole transport layer has the ability to transport holes, and the hole injection effect from the anode 2 And a compound that has an excellent hole injection effect for the organic light emitting layer 3, prevents movement of electrons to the hole transport layer, and has an excellent thin film forming ability. Specifically, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD) and 4,4 Aromatic diamine compounds such as' -bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, Polyarylalkanes, butadiene, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), and polyvinylcarbazole, polysilane, polyethylene dioxide thiophene (PEDOT) ) And other polymer materials such as conductive polymers Charge.
[0018]
The organic light emitting layer 3 has an electron injection layer laminated on the cathode 4 side, and the material constituting the electron injection layer has the ability to transport electrons, and the electron injection effect from the cathode 4 And a compound having an excellent electron injection effect with respect to the organic light emitting layer 3, further preventing movement of holes to the electron injection layer, and having an excellent thin film forming ability. Specifically, fluorene, bathophenanthroline, bathocuproine, anthraquinodimethane, diphenoquinone, oxazole, oxadiazole, triazole, imidazole, anthraquinodimethane, etc. and their compounds, metal complex compounds or nitrogen-containing five-membered ring derivatives is there. Furthermore, the polymer material used for a polymer organic electroluminescent element can also be used. For example, polyparaphenylene and derivatives thereof, fluorene and derivatives thereof, and the like. The electron injection layer can be formed, for example, by co-evaporating bathophenanthroline and Cs (cesium) at a molar ratio of 1: 1.
[0019]
The flat light emitter is characterized in that an LED element 6 for irradiating light into the transparent substrate 1 is provided on the end surface of the transparent substrate 1. The light 12 emitted from the LED element 6 enters the transparent substrate 1 from the end face of the transparent substrate 1, and is guided while being totally reflected in the transparent substrate 1. Further, the planar light emitter has a light scattering portion 7 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 as scattered light 13 to the surface side 8 by the light scattering portion 7 due to a scattering phenomenon. The flat light emitter emits light from the flat light emitter by mixing the scattered light 13 generated by a scattering phenomenon with 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.
[0020]
The light scattering portion 7 is formed by subjecting the surface side 8 of the transparent substrate 1 to sand blasting to form minute irregularities or disposing a diffusion bead layer. Further, the light scattering portion 7 is formed on the surface side 8 of the transparent substrate 1 as long as the light 12 emitted from the LED element 6 is emitted to the surface side 8 of the transparent substrate 1 by a scattering phenomenon. However, the inside of the transparent substrate 1 is not limited.
[0021]
In order to adjust the emission spectrum emitted from the planar light emitter, the light 12 emitted from the LED element 6 reinforces a smaller wavelength than the emission wavelength of the light 11 emitted from the organic light emitting layer 3. For this purpose, the LED element 6 is appropriately selected to have a specific emission wavelength.
[0022]
For example, the electroluminescence element 5 that emits red light has a low light emission efficiency of about 3 Lm / W or less, while the red LED element 6 has a high light emission efficiency of 10 to 20 Lm / W. Moreover, the electroluminescence element 5 that emits blue and yellow light using complementary colors has a high light emission efficiency of 5 to 15 Lm / W.
[0023]
Therefore, the planar light emitter uses a light emitting element that emits blue and yellow colors complementary to the electroluminescence element 5, and the red LED element 6 having an emission wavelength of 600 to 700 nm is disposed on the end face of the transparent substrate 1. The luminous efficiency is good, and there is no color shift and the chromaticity balance is excellent. The planar light emitter can realize a white planar light emitter of RGB (red, green, blue) three-wavelength system.
[0024]
【Example】
Example 1
A glass substrate having a thickness of 0.7 mm was used as the transparent substrate. One surface (front side) of this glass substrate was subjected to sandblasting to form a light scattering portion having an average roughness of 2 μm. 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, and then dried and further subjected to UV ozone cleaning. Thereafter, this substrate was set in a vacuum deposition apparatus, and 4,4′-bis [N- (naphthyl) was used as a hole transport layer under a reduced pressure of 1 × 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa). ) -N-phenyl-amino] biphenyl (manufactured by Dojin Chemical Laboratory Co., Ltd.) was deposited to a thickness of 300 mm at a deposition rate of 1 to 2 mm / s. Next, a layer obtained by doping α-NPD with 1% by mass of rubrene (manufactured by ACROS ORGANICSN.V.) As a yellow light emitting layer was laminated to a thickness of 100 mm. Furthermore, as a blue light emitting layer, a layer obtained by doping 12% by mass of a DSA derivative (BCzVBi, manufactured by Idemitsu Kosan Co., Ltd.) having a caribazolyl group at the terminal to a distyryl biphenyl derivative (DPVBi, manufactured by Idemitsu Kosan Co., Ltd.) to a thickness of 500 mm. Laminated. Next, bathophenanthroline (manufactured by Dojindo Laboratories Co., Ltd.) and Cs (cesium) were co-deposited to a thickness of 200 mm at a molar ratio of 1: 1 as an electron injection layer. Subsequently, aluminum was deposited to a thickness of 1500 で at a deposition rate of 10 Å / s to form a cathode. In this way, a transparent substrate having an electroluminescence element that emits blue and yellow light was produced.
[0025]
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 disposed on the end face of the transparent substrate to obtain a flat light emitter.
[0026]
Since this planar light emitter uses an electroluminescent element and a red LED element that emit blue and yellow light, it has good luminous efficiency.
[0027]
(Comparative Example 1)
In Example 1, a transparent substrate having electroluminescent elements emitting blue and yellow light was obtained in the same manner as Example 1 except that a red LED element was disposed.
[0028]
(Measurement of whiteness)
The chromaticity coordinates of the planar light emitter of Example 1 were measured. The measurement was performed under the condition of 100 cd / m ² using a multichannel analyzer (PMA-10 manufactured by Hamamatsu Photonics Co., Ltd.) by connecting the electroluminescence element and the red LED element to a power source (KEYTHLEY 236 model). The chromaticity coordinates indicate better white as the values are closer to X = 0.33 and Y = 0.33. The flat light emitter of Example 1 was white light emission including red component light, and had good white light emission with chromaticity coordinates (X = 0.32, Y = 0.33).
[0029]
The chromaticity coordinates of Comparative Example 1 were measured. The measurement was performed in the same manner as in Example 1 with the electroluminescence element connected to a power source. Since Comparative Example 1 has no red component light, it is white with a slight green color, and the chromaticity coordinates are (X = 0.30, Y = 0.39), and the degree of white light emission compared to the example. Was low.
[0030]
【The invention's effect】
Since the flat light-emitting body which concerns on Claims 1-3 equips the end surface of a transparent substrate with the LED element which irradiates light in this transparent substrate, the light emitted from the organic light emitting layer and a part of the light radiate | emitted from the LED element Both can be used to easily adjust the emission wavelength of light emitted from the flat light emitter.
[0031]
Furthermore, the planar light emitter according to claim 3 has particularly good luminous efficiency by using an organic electroluminescence element that emits blue or yellow light with good luminous efficiency and reinforcing the red component with an LED element. , White having an excellent chromaticity balance can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of the present invention.
FIG. 2 is a schematic view schematically showing the emitted light beam.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode 3 Organic light emitting layer 4 Cathode 5 Electroluminescence element 6 LED element 7 Light scattering part

Claims (3)

An electroluminescent device having an anode, an organic light emitting layer, and a cathode formed on the back surface of the transparent substrate, and in a flat light emitter that emits light on the surface side of the transparent substrate, light is transmitted into the transparent substrate on the end surface of the transparent substrate. A part of the light generated by the LED element is synthesized with a part of the light generated by the electroluminescence element while being guided in the transparent substrate. A flat light emitter , wherein a light scattering portion is formed on at least a part of a transparent substrate so that a part of the light is emitted to the surface side of the transparent substrate . Emission wavelength generated by the LED element, when combining the emission wavelength generated by the electroluminescent device, RGB (red, green, blue) three-wavelength system flat emission according to claim 1, characterized in that the white color body. The planar light-emitting body according to claim 1 or 2, wherein a light emission color of the electroluminescence element is a complementary color of blue and yellow, and a light emission wavelength of the LED element is 600 to 700 nm.

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