JP2010080117A - Light emitting element, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element having improved external quantum efficiency for actualizing display superior in color reproductivity, and to provide a display device. <P>SOLUTION: The light emitting element includes pixels each consisting a plurality of sub pixels having R, G, B emission colors, the sub pixels each having a laminated structure including a reflecting electrode, a dielectric layer provided on a light reflecting layer, a light emission layer provided on the dielectric layer, a transparent electrode provided on the light emission layer, an insulating layer provided on the transparent electrode, and a transparent layer provided on the insulating layer, the sub pixels being arranged adjacent to each other on two dimensions. The sub pixels are set so that the laminated structures are equal in thickness. On the other hand, some of the sub pixels have emission color spectral properties shifted from one of subtractive three elementary colors and color conversion layers are provided thereon for correcting color shift. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting element, and more particularly to an organic EL light emitting element used for a flat display or the like.

As a configuration for full-color display devices using organic EL light emitting elements, a configuration in which light emitting elements that emit blue, green, and red light are arranged has been proposed. In this configuration, a configuration is proposed in which a configuration of a light-emitting element in which a transparent electrode, an organic EL layer, and a reflective electrode are sequentially arranged directly on a transparent substrate is employed, and a color conversion layer is provided on the light emitting side. (For example, refer to Patent Document 1).
In addition, a configuration is proposed in which a configuration of a light-emitting element in which a reflective electrode, an organic EL layer, and a transparent electrode arranged directly on a transparent substrate are sequentially stacked and a color conversion layer is provided on the transparent electrode is proposed. (For example, refer to Patent Document 2).

In addition, a configuration of a light emitting device in which a reflective electrode, a transparent conductive layer, an organic EL layer, and a transparent electrode arranged directly on a transparent substrate are sequentially laminated, and a color conversion layer is provided on the transparent electrode is provided. It has been proposed (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 6-132081 JP 2000-195670 A JP-A-2005-116516

At present, in an organic EL light emitting device having a resonator structure with two electrodes, by providing a color conversion layer, components in an unnecessary wavelength region of the emitted color are reduced and the color purity of extracted light is improved. There is a way.
However, the provision of the color conversion layer absorbs components in an unnecessary wavelength region, so that there is a problem that the light extraction efficiency is lowered and the load is large for power consumption and element life.

  An object of the present invention is to provide an organic EL light emitting element capable of improving the light extraction efficiency and capable of displaying with excellent color reproducibility, and an organic EL display device using the organic EL light emitting element.

The light-emitting element according to the present invention includes a plurality of sub-pixels each having R, G, and B as emission colors, and each sub-pixel includes a first electrode, a light-emitting layer, a second electrode, a resin layer, and a transparent layer. Are laminated in this order, and the thickness of the laminated structure from the first electrode to the second electrode is set to be equal for each subpixel,
On the other hand, among the sub-pixels, the spectral characteristics of the emission color are deviated from the emission spectrum of one of the three required primary colors. A color conversion layer to be corrected is provided.

Here, the light emitting layer may have a laminated structure.
More preferably, the light emitting layer may include an organic EL layer including an organic EL light emitter.
The light emitting layer may further include an electron transport layer and a hole transport layer provided on both sides of the organic EL layer.
It is desirable to have a dielectric layer between the light emitting layer and the first electrode.
The dielectric layer is preferably transparent with respect to light reflected by the first electrode, and the second electrode is a transparent electrode.

The insulating layer is a sealing resin that seals the light emitting layer including the transparent electrode, and the transparent layer is a resin that seals the resin-sealed subpixels in an envelope such as a glass substrate. Is desirable.
The color conversion layer is bonded to the transparent layer. On the other hand, in the remaining sub-pixels, the transparent layer is preferably adjusted to a thickness equal to the total thickness of the color conversion layer and the transparent layer. .

  Further, the sub-pixel provided with the color conversion layer may be a sub-pixel that emits blue light, and the remaining sub-pixels may be sub-pixels that emit red and green light.

  According to the light emitting device of the present invention, since the thickness of the laminated structure is set to be equal for each subpixel, for example, when manufacturing a display in which a large number of subpixels are arranged two-dimensionally, This eliminates the need for troublesome operations such as determining the film formation conditions and adjusting the film thickness for each sub-pixel. Yes. On the other hand, the thickness of the laminated structure depends on the wavelength of each color of R, G, and B from the resonant structure. Therefore, when the thickness of the laminated structure is aligned for each subpixel as described above, May exhibit an emission spectrum that deviates from the required emission spectrum. However, in the present invention, since a color conversion layer is provided for the subpixel in which such color misregistration occurs, the light extracted to the outside becomes light having the required emission spectrum characteristics and used as a display. If it does, a thing with high color reproducibility will be obtained. On the other hand, since it is not necessary to provide a color conversion layer in a subpixel in which no color misregistration occurs, the light extraction efficiency from the subpixel can be maintained high.

  In summary, according to the present invention, it is possible to provide a light-emitting element that can be manufactured at low cost, yet has high color reproducibility and high light extraction efficiency.

Hereinafter, light-emitting elements according to embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a top emission type light emitting element 10 as a light emitting element according to Embodiment 1 of the present invention. The light emitting element 10 includes a plurality of subpixels each having a light emission color of R, G, and B, and is arranged in parallel on the substrate 11 via a bank 19. First, the reflective electrode 12 is formed on the substrate 11 as a first electrode. A dielectric layer 13 is formed on the reflective electrode 12, and a light emitting layer 14 having a multilayer structure including an organic EL layer is formed on the dielectric layer 13. The light emitting layer 14 is configured by sequentially laminating an electron transport layer, an organic EL layer, and a hole transport layer (not shown) in order from the dielectric layer 13 side. A transparent electrode 15 is provided on the light emitting layer 14. The thickness of the laminated portion from the reflective electrode 12 to the transparent electrode 15 is set to be equal for each subpixel.

Each subpixel is sealed with an insulating layer 18 from above the transparent electrode 15. Since the light emitting layer deteriorates when exposed to moisture or oxygen, the insulating layer 18 prevents the entry of these components. The insulating layer 18 is transparent and is made of a material such as SiN.
On the insulating layer 18, a resin layer 16 is formed as a transparent layer and is sealed between the glass plate 20. The light emitted from each subpixel is emitted to the outside from this glass plate. In the case of the top emission type, a glass plate is used on the outermost side, but in the case of the bottom emission type, an outer wall having no translucency is used. In this embodiment, the outermost glass plate and outer wall are collectively referred to as an envelope.

  Among the sub-pixels, the color deviation is corrected on the resin layer 16 of the sub-pixel when one of the three primary colors (R, G, B) requiring the spectral characteristics of the emission color is shifted. A color conversion layer 17 is provided. In this embodiment, the color conversion layer 17 is provided on the blue subpixel. A color conversion layer is not provided on the remaining subpixels. The main configuration of the color conversion layer 17 is determined by which color shift is corrected. When a filter is used as the color conversion layer, the value of light extraction efficiency varies depending on the film thickness. In that case, it is convenient to match the light extraction efficiency of the remaining sub-pixels not provided with the color conversion layer, and the thickness of the color conversion layer 17 should be determined in this respect. FIG. 2 is a graph showing the relationship between the thickness of the color conversion layer and the external quantum efficiency (light extraction efficiency).

  The resin layer 16 differs from the color conversion layer 17 in that the light extraction efficiency does not change as much as the left depending on the film thickness (see FIG. 3). Therefore, there is no problem with respect to light extraction efficiency even if the resin layer provided on the subpixel without the color conversion layer is thick. In this embodiment, as shown in FIG. 1, the thickness of the resin layer on the red and green subpixels is made equal to the total thickness of the resin layer 16 and the color conversion layer 17 on the blue subpixel. .

Below, each component which comprises this light emitting element 10 is demonstrated still in detail.
<Board>
For the substrate 11, glass plates such as soda glass, non-fluorescent glass, phosphoric acid glass, boric acid glass, quartz, acrylic resin, styrene resin, polycarbonate resin, epoxy resin, polyethylene, polyester, silicone resin, etc. A plastic plate and a plastic film, a metal plate such as alumina, and a metal foil can be used.

In the case of so-called bottom emission in which light is extracted from the substrate 11 side as shown in the second embodiment, the substrate 11 is required to be a transparent substrate such as a glass substrate.
<Reflective electrode>
The reflective electrode 12 is made of magnesium, silver, or an alloy thereof. The reflective electrode 12 preferably has a thickness of 5 to 50 nm.

<Dielectric layer>
The dielectric layer 13 is made of a conductive material having sufficient translucency for the light generated in the light emitting layer 15. As a material constituting the dielectric layer 13, indium tin oxide (ITO), indium zinc oxide (IZO), or the like is preferable. This is because good conductivity can be obtained even if the film is formed at room temperature.

<Light emitting layer>
The light emitting layer 14 is not limited to a single layer and may have a multilayer structure. The light emitting layer may include an organic EL layer containing an organic light emitter. Furthermore, an electron transport layer and a hole transport layer may be further included with the organic EL layer interposed therebetween. Furthermore, an electron injection layer and / or a hole injection layer may be provided. The electron injection layer and the hole injection layer can be formed by vapor deposition, spin coating, casting, or the like.

<Electron transport layer>
Specific examples of the electron transporting layer having electron transporting ability include nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, diphequinone derivatives, perylenetetracarboxyl derivatives, anthraquinodimethane derivatives, fluorenylidene of JP-A-5-163488. Compounds such as methane derivatives, anthrone derivatives, oxadiazole derivatives, perinone derivatives, quinoline complex derivatives, and the like can be used.

<Organic EL layer>
Specific examples of the organic EL layer include oxinoid compounds, perylene compounds, coumarin compounds, azacoumarin compounds, oxazole compounds, oxadiazole compounds, perinone compounds, pyrrolopyrrole compounds, naphthalene compounds, anthracenes described in JP-A-5-163488. Compound, fluorene compound, fluoranthene compound, tetracene compound, pyrene compound, coronene compound, quinolone compound and azaquinolone compound, pyrazoline derivative and pyrazolone derivative, rhodamine compound, chrysene compound, phenanthrene compound, cyclopentadiene compound, stilbene compound, diphenylquinone compound, styryl Compounds, butadiene compounds, dicyanomethylenepyran compounds, dicyanomethylenethiopyran compounds, fluorescein compounds, Metal compounds of lithium compounds, thiapyrylium compounds, serenapyrylium compounds, telluropyrylium compounds, aromatic aldadiene compounds, oligophenylene compounds, thioxanthene compounds, anthracene compounds, cyanine compounds, acridine compounds, 8-hydroxyquinoline compounds, 2, 2 ′ -Fluorescent materials such as metal chains of bipyridine compounds, chains of Schiff salts and Group III metals, oxine metal chains, and rare earth chains can be used. The organic EL layer can be formed by vapor deposition, spin coating, casting, or the like.

<Hole transport layer>
Specific examples of the hole transport layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives described in Japanese Patent Application No. 3-333517. Amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, porphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds, butadiene compounds, polystyrene derivatives, hydrazone derivatives, triphenylmethane derivatives, Tetraphenylbenzine derivatives and the like can be used, but particularly preferred are polyphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds. .

<Transparent electrode>
The transparent electrode 15 is preferably made of a conductive material that transmits only light of a specific wavelength with respect to the light generated in the light emitting layer 14. The material constituting the transparent electrode 15 is preferably indium tin oxide (ITO), indium zinc oxide (IZO), or the like. This is because good conductivity can be obtained even if the film is formed at room temperature.

<Color conversion layer>
The color conversion layer 17 has a function of transmitting part of the light emitted from the light emitting layer 14, absorbing part of the light, and emitting light having a wavelength different from the absorbed wavelength. As the color conversion layer 14, a colored transparent filter, a dichroic mirror, a band pass filter, or the like can be used. Examples of the constituent material of the color conversion layer 14 include organic pigments, particle-added organic pigments, metal oxides, resins containing the metal oxides, inorganic or organic fluorescent dyes, and the like.

<Transparent layer>
The transparent layer 16 has a function of transmitting light emitted from the light emitting layer 14 with almost no attenuation. Therefore, any of silicon oxynitride, silicon nitride, or resin can be used as the transparent layer.
As shown in FIG. 3, the thickness of the transparent layer has little influence on the light extraction efficiency. Therefore, the thickness of the transparent layer does not have to be uniform between the sub-pixels. However, since the transparent layer 16 also has the role of sealing the subpixels in the envelope, a minimum film thickness of about 500 nm is required.

<Insulating layer>
As the insulating layer 18, a thin film of SiN or SiON is used. The insulating layer 18 is required to have a sealing function for preventing moisture and oxygen from entering the light emitting layer, and is also required to have a high transmittance because it is on the emission path of light emitted from the light emitting layer 14. For this purpose, it is necessary that the refractive index approximates that of the light emitting layer 14 and the transparent layer 15 and that no reflective interface is formed.
Example 1
About the organic EL element 10 which concerns on Example 1 of this invention, the optical simulation was performed on condition of the following.

  As each constituent member constituting this organic EL element, an AgPdCu alloy (abbreviation: APC) was used as a light reflecting layer (corresponding to the reflecting electrode 12). ITO (equivalent to dielectric layer 13) 70 nm, hole injection layer 30 nm, intermediate layer (equivalent to electron transport layer) 20 nm, organic EL layer 70 nm, hole injection layer thickness 20 nm, ITO (transparent electrode) 15) in a thickness of 100 nm. Further, the resin layer 16 on the red and green subpixels has a thickness of 3500 nm, the resin layer 16 on the blue subpixel has a thickness of 500 nm, and the color conversion layer 17 has a thickness of 3000 nm.

  2 and 3 show optical simulation results regarding light emission from the light emitting layer. FIG. 2 is a graph showing the relationship between the thickness of the color filter (CF) as the color conversion layer and the external quantum efficiency. FIG. 3 is a graph showing the relationship between the thickness of the transparent layer and the external quantum efficiency. As can be seen from FIG. 2, the external quantum efficiency does not depend on the film thickness of the transparent layer. Further, according to FIG. 3, it can be seen that the external quantum efficiency depends on the film thickness of the color conversion layer, and the external quantum efficiency decreases as the film thickness increases.

  The present invention can be used for an organic EL display device used for a flat light source, a flat display, and the like.

It is sectional drawing which shows the structure of the light emitting element 10 which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the thickness of the color conversion layer in the light emitting element which concerns on Example 1 of this invention, and external quantum efficiency. It is a figure which shows the relationship between the thickness of the transparent layer and external quantum efficiency in the light emitting element which concerns on Example 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light emitting element 11 Substrate 12 Reflective electrode 13 Dielectric layer 14 Light emitting layer 15 Transparent electrode 16 Transparent layer 17 Color conversion layer 18 Insulating layer

Claims (15)

Each pixel is composed of a plurality of sub-pixels having R, G, and B emission colors, and each sub-pixel has a configuration in which a first electrode, a light-emitting layer, a second electrode, an insulating layer, and a transparent layer are stacked in this order. In addition, the thickness of the laminated structure from the first electrode to the second electrode is set to be equal for each subpixel, and among the subpixels, the spectral characteristics of the emission color are among the three primary colors originally required. A light-emitting element having a color conversion layer that corrects a color shift is provided above the stacked structure of the subpixel.   The light emitting device according to claim 1, wherein the light emitting layer has a laminated structure.   The light emitting device according to claim 1, wherein the light emitting layer includes an organic EL layer including an organic EL light emitter.   The light emitting device according to claim 3, wherein the light emitting layer further includes an electron transport layer and a hole transport layer provided on both sides of the organic EL layer.   The light emitting device according to claim 1, further comprising a dielectric layer between the light emitting layer and the first electrode.   The light emitting device according to claim 5, wherein the dielectric layer is transparent with respect to light reflected by the first electrode, and the second electrode is a transparent electrode. The light emitting device according to claim 6, wherein the dielectric layer and the second electrode are made of an oxide.   The light emitting device according to claim 7, wherein the oxide is ITO or IZO. The insulating layer is a sealing resin for sealing the light emitting layer including the second electrode, and the transparent layer is a resin for sealing the resin-sealed subpixel to an envelope such as a glass substrate. The light emitting device according to claim 1.   The color conversion layer is bonded to the transparent layer, and in the remaining subpixels, the transparent layer is adjusted to a thickness equal to the total thickness of the color conversion layer and the transparent layer. The light emitting device according to claim 1. The light emitting device according to claim 10, wherein a color conversion layer is not provided on a subpixel that does not deviate from an originally required emission spectrum characteristic or is within an allowable range.   The light emitting device according to claim 11, wherein the subpixel provided with the color conversion layer is a subpixel emitting blue light, and the remaining subpixels are subpixels emitting red and green light.   The light emitting device according to claim 12, wherein the color conversion layer is selected from the group consisting of a coloring filter, a dichroic filter, and a bandpass filter.   The light emitting device according to claim 12, wherein the color conversion layer contains a fluorescent dye.   A display device comprising the light-emitting element according to claim 1.

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