JP2007250193A - Organic light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white light emitting element for simplifying a layer structure of a color conversion layer of an organic light emitting element with no color change caused by a current flowing the organic light emitting element and deterioration of the organic light emitting element by a relatively simple method with high efficiency. <P>SOLUTION: The organic light emitting element is provided with a substrate, a light emitting part, and the color conversion layer for absorbing light emitted from the light emitting part and emitting light of a longer wavelength than a wavelength of the light emitted from the light emitting part. The light emitting part includes a first electrode, an organic luminous body, and a second electrode from a substrate side, and the color conversion layer is formed of fluorescent dye and inorganic nitride. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic light emitting device that enables multicolor display.

  This organic light emitting element is suitable for display of an image sensor, a personal computer, a word processor, audio, video, car navigation, a telephone, a portable terminal, and an industrial measuring instrument.

  The full-color display manufacturing method using electroluminescent elements includes the “three-color light emitting method” in which elements that emit light in red, blue, and green by applying an electric field, and white light emission is cut with a color filter. "Color filter method" that expresses red, blue, and green, and also absorbs near-ultraviolet light, blue light, blue-green light, or white light, and performs wavelength distribution conversion to emit light in the visible light range. A “color conversion method” using a conversion dye as a filter has been proposed.

  Among these, the color filter system is said to be an advantageous system for producing a large screen display because the electroluminescent element needs only a single color and has fewer process steps than the color conversion system.

As described above, the color filter system uses white light emitted from the electroluminescent element to transmit only light of the required wavelength using the color filter and reproduces colors such as red, blue, and green. , Blue and green light of three wavelengths must be included in a well-balanced manner.
However, it is very difficult to industrially realize the ideal white light emission including all the three wavelength ranges of red, blue, and green necessary for this method with an electroluminescent element.

  As technologies for realizing white light emission, (1) a method using a white light emitting material (see Non-Patent Document 1), (2) a method of mixing red, blue, green, or a light emitting material having a complementary color relationship with these colors (See Non-Patent Document 2.), (3) Red, blue, green, or a method of laminating light emitting materials that are complementary to these colors (see Non-Patent Document 3) has been proposed.

  On the other hand, (4) a method of obtaining white by converting light (blue green) from the light emitting element into red partly by a color conversion filter has been proposed (see Patent Document 1). A color filter in which at least three kinds of filters are arranged independently, each of which transmits light of different wavelength ranges, and a part of light emitted from the light emitting element is transmitted between the color filter and the light emitting element. A complementary color layer that emits light having a wavelength different from the wavelength of the absorbed light is disposed. The complementary color layer can be provided by a simple known wet process by dispersing at least one organic fluorescent dye in the resin. However, since the complementary color layer is formed by a wet process, The remaining moisture diffuses into the light emitting element portion, causing defects such as dark areas (DA) and dark spots (DS) in the pixel portion, and there is a problem that the lifetime of the image is reduced.

On the other hand, since the organic fluorescent dye used for the complementary color layer can also be formed by vapor deposition, it has been proposed to form the organic fluorescent dye layer by vapor deposition (see Patent Document 2). In a dry process including vapor deposition, it is possible to prevent the occurrence of defects such as dark areas and dark spots in the pixel portion. Further, the film thickness of the fluorescent dye can be reduced to 1 μm or less as compared to 10 μm or more in the wet process.
The ability to reduce the thickness of the color conversion layer itself has the effect of reducing the difficulty of the process. Further, a flattening layer having a thickness of several μm as in the prior art is not required, and the entire thickness can be further reduced. In addition, there is an effect that the process can be made all dry.

In addition, a technique for forming a color conversion layer by co-evaporation with a perylene red pigment using a metal oxide as a matrix is disclosed (see Patent Document 3). Examples of the metal oxide include SiO ₂ and TiO ₂ .

JP 2004-319471 A JP 2003-133062 A International Publication No. 01/62868 pamphlet J. Appl. Phys., 65, 3610 (1989) Appl.Phys.Let., 67,2281 (1995) 55th Annual Meeting of the Japan Society of Applied Physics (Preliminary Proceedings), 19p-H-6 (1994)

However, the vapor-deposited fluorescent dye layer described in Patent Document 2 is disposed between the substrate and the anode, and the refractive index composed of SiO _x , SiO _x N _y or the like is continuously formed on the substrate side or the anode side of the fluorescent dye layer. Since the changed protective layer is provided, there is a problem that the protective layer disposing process is complicated.
On the other hand, the metal oxides used in Patent Document 3 are SiO ₂ and TiO ₂ , and the refractive indexes of SiO ₂ and TiO ₂ are 1.5 and 2.3 to 2.55, respectively. In order to introduce luminescence from the color conversion layer, SiO ₂ has a refractive index that is too low, and TiO ₂ has a refractive index that is too high, resulting in poor optical matching and low light extraction efficiency. . That is, in order to eliminate the poor optical matching, it has been desired to apply a material having a more appropriate refractive index.

As a result of intensive studies in view of such circumstances, the present inventor has found that the above problem can be solved when the color conversion layer of the organic light-emitting element is composed of a fluorescent dye and an inorganic nitride, and has reached the present invention.
That is, the organic light emitting device of the present invention includes a substrate, a light emitting unit, and a color conversion layer that absorbs light emitted from the light emitting unit and emits light having a wavelength longer than that of light emitted from the light emitting unit. The light emitting unit includes a first electrode, an organic light emitter, and a second electrode from the substrate side, and the color conversion layer is made of a fluorescent dye and an inorganic nitride.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to simplify the layer structure of the color conversion layer of an organic light emitting element, a highly efficient white light emitting element can be provided by a comparatively simple method, and the electric current and organic light emitting element which flow through an organic light emitting element It is possible to provide a white light emitting element that does not change in color due to deterioration of the color.

The present invention will be described below with reference to the drawings.
The organic light emitting device of the present invention has a substrate 1, a light emitting portion, and a color conversion layer 7. The light emitting portion has a first electrode, an organic light emitter, and a second electrode from the substrate side. The light emitting unit may further include a hole injection layer and an electron transport layer as necessary.
The color conversion layer 7 is provided between the substrate 1 and the first electrode 8. Color filter layers 3, 4, 5 may be provided between the color conversion layer 7 and the substrate 1. The color conversion layer 7 may be provided with a planarization layer 6 thereon (substrate 1 side).

Color filter:
The color filter provided between the color conversion layer 7 and the substrate 1 may be a color filter used for a flat panel display such as a liquid crystal display. In recent years, a pigment dispersion type color filter in which a pigment is dispersed in a photoresist is used. Used.

  The color filters for flat panel displays are a blue color filter that transmits light with a wavelength of 400 to 550 nm, a green color filter that transmits light with a wavelength of 500 to 600 nm, and a red color filter that transmits light with a wavelength of 600 nm or more. These are generally arranged, and a black matrix that does not transmit light in the visible range is generally disposed between the color filter pixels, mainly for the purpose of improving contrast. Yes.

Color conversion layer:
The color conversion layer also has a role of protecting the color filter, and it is necessary to select a material and a process that are rich in light transmittance and can be disposed without deteriorating the color filter. Further, it is preferable that the refractive index be such that light from the organic light emitting layer emitted from the first electrode can be efficiently incident on the color conversion layer and can be efficiently emitted to the substrate side.
In addition, a transparent electrode film is usually provided on a color conversion layer provided on a color filter, and this transparent electrode film is often formed by a sputtering method. Is also required.
In order to meet such demands, the color conversion layer of the present invention comprises a nitrogen compound and an organic fluorescent dye. Examples of the nitrogen compound include metal nitrides and metal oxynitrides. Specifically, SiNx (x = 0.5 to 1.5), AlNx (x = 1.0 to 1.1), SiOxNy (x = 0-0.5, y = 1.34-1.0), a-SiN: H, and the like.

  Examples of organic fluorescent dyes include rhodamine dyes such as rhodamine B, rhodamine 6G, basic violet 11 and basic red 2; cyanine dyes; 4,4-difluoro-1,3,5,7-tetraphenyl-4- Bora-3a, 4a-diaza-sindacene, propanedinitrile, Nile red, 1-ethyl-2- [4- (p-dimethylaminophenyl) -13-butadienyl] -pyridinium-perchlorate (pyridine 1), etc. Pyridine dyes; Oxazine dyes; N ′, N′-bis (2,6-xylyl) perylene-3,4: 9,10-bis-dicarboximide (DPP-PTCDI), N ′, N′-dimethyl Select from perylene dyes such as perylene-3,4: 9,10-bis-dicarboximide (DMe-PTCDI) Door can be.

  This color conversion layer is preferably formed by co-evaporation of a nitrogen compound and an organic fluorescent dye. In the color conversion layer formed by co-evaporation, the organic fluorescent dye is dispersedly arranged with a nitrogen compound as a matrix, and thus stably exists without causing concentration quenching, so that the lifetime of the element is increased.

  The color conversion layer preferably has a refractive index of 1.8 to 2.2. Since the refractive index of the first electrode is 2.0 to 2.2 and the refractive index of the organic light emitter is 1.8 to 2.0, when the refractive index of the color conversion layer is within the above range, Light emitted from the light emitting portion can be efficiently incident on the color conversion layer and emitted to the substrate side.

The refractive index of the nitrogen compound shown in the specific example is 2.0 for SiNx (x = 0.5 to 1.5), 2.1 for AlNx (x = 1.0 to 1.1), and SiOxNy (x = 0 to 0.5, y = 1.34 to 1.0) is 1.8 to 2.0, and a-SiN: H is 1.95. Any of these is preferably used from the viewpoint of the refractive index. be able to.
On the other hand, SiOx (x = 1.8 to 2.2), which is often used as a protective layer, has a low refractive index of 1.40 to 1.55, and the light extraction efficiency is 10 to 15% disadvantageous. .

Flattening layer The flattening layer is generally formed by a coating method. In this case, as a material that can be applied, a photocurable or photothermal combination type curable resin is treated with light or light and heat to generate radical species or ionic species to be polymerized or crosslinked to be insoluble and infusible. Is common.

Specific examples of the photocurable or photothermal combination type curable resin include acrylic polyfunctional monomers and oligomers having a plurality of acryloyl groups and methacryloyl groups, polycarbonate, polyethylene terephthalate, polyethersulfone, polyvinyl butyral, polyphenylene ether, polyamide, Thermoplastic resins such as polyetherimide, norbornene resin, methacrylic resin, isobutylene maleic anhydride copolymer resin, cyclic olefin resin; epoxy resin, phenol resin, urethane resin, curable acrylic resin, vinyl ester resin, imide resin Thermosetting resin such as resin, urethane resin, urea resin, melamine resin; silicone polymer; or trifunctional or tetrafunctional with polystyrene, polyacrylonitrile, polycarbonate, etc. Alkoxysilane may be mentioned a resin-modified silicone polymers comprising.
When a flattening layer is formed, it can be cured at a high temperature of 50 ° C. or higher, and the influence of moisture can be suggested, rather than forming a flattening layer on the color conversion layer. Excellent.

Organic light emitting unit The organic light emitting unit sandwiches an organic light emitter between a pair of electrodes, and the organic light emitter includes at least an organic light emitting layer, and if necessary, a hole injection layer, a hole transport layer, and / or It has a structure with an electron injection layer interposed. More specifically, for example, the following structures are exemplified.
(1) Anode / organic light emitting layer / cathode (2) Anode / hole injection layer / organic light emitting layer / cathode (3) Anode / organic light emitting layer / electron injection layer / cathode (4) Anode / hole injection layer / organic Light emitting layer / electron injecting layer / cathode (5) Anode / hole injecting layer / hole transporting layer / organic light emitting layer / electron injecting layer / cathode In the structure of (1) to (5) above, at least of the anode and the cathode One is desirably transparent in the wavelength range of the light emitted by the organic light emitter, and emits light through the transparent electrode so that the light is incident on the color conversion film. In this technique, it is known that it is easy to make the anode transparent, and in the present invention, it is preferable to make the anode transparent.

The transparent electrode of the anode is formed by laminating conductive metal oxides such as SnO ₂ , In ₂ O ₃ , ITO, IZO, ZnO: Al by sputtering. The transmittance of the transparent electrode is preferably 50% or more, and more preferably 85% or more with respect to light having a wavelength of 400 to 800 nm. It is desirable that the anode has a thickness of usually 50 nm or more, preferably 50 nm to 1 μm, more preferably 100 to 300 nm.

  The cathode reflective electrode is preferably formed using a highly reflective metal, amorphous alloy, microcrystalline alloy, or the like. Examples of the highly reflective metal include Al, Ag, Mo, W, Ni, and Cr. Examples of the high reflectivity amorphous alloy include NiP, NiB, CrP, and CrB. Examples of the highly reflective microcrystalline alloy include NiAl. Alternatively, other alloys (for example, Mg / Ag alloy) containing the above-described highly reflective metal can be used.

  The patterns of the anode and the cathode may be formed in parallel stripes so as to cross each other. In that case, the organic light emitting device of the present invention can perform matrix driving. That is, when a voltage is applied to a specific stripe of the anode and a specific stripe of the cathode, a portion where the stripes intersect in the organic light emitting layer emits light. Therefore, by applying a voltage to selected stripes of the anode and the cathode, it is possible to emit light only in a portion where the specific color conversion film and / or color filter layer is located.

  Alternatively, the anode may be a uniform planar electrode having no stripe pattern, and the cathode may be patterned so as to correspond to each pixel. In that case, a so-called active matrix drive can be performed by providing a switching element corresponding to each pixel.

  In order to obtain blue to blue-green light emission as the organic light emitting layer, for example, fluorescent whitening agents such as benzothiazole, benzimidazole, and benzoxazole, metal chelated oxonium compounds, styrylbenzene compounds, aromatic dimethylidins Compounds and the like are preferably used.

  As a material for the hole injection layer, phthalocyanines (Pc) containing copper phthalocyanine (CuPc) or indanthrene compounds can be used.

  The hole transport layer can be formed using a material having a triarylamine partial structure, a carbazole partial structure, or an oxadiazole partial structure (eg, TPD, α-NPD, PBD, m-MTDATA, etc.).

  As the material for the electron injection layer, alkali metals such as Li, Na, K, or Cs, alkaline earth metals such as Ba and Sr, alloys containing them, rare earth metals, or fluorides of these metals may be used. Yes, but not limited to them. In the configuration of the present invention, it is preferable to provide an electron injection layer from the viewpoint of improving the electron injection efficiency. The film thickness of the electron injection layer can be appropriately selected in consideration of the driving voltage, transparency, and the like, but in a normal case, it is preferably 10 nm or less. Alternatively, an aluminum quinolinol complex doped with an alkali metal or an alkaline earth metal may be used.

The present invention will be further described below with reference to the drawings.
In the examples and comparative examples, the organic EL display was formed with a pixel number of 60 × 80 × RGB and a pixel pitch of 0.33 mm.
FIG. 1 shows an example of a cross-sectional view of an organic light emitting device of the present invention.

<Example 1>
Production of color filter:
On a transparent glass substrate (Corning 1737 glass) 1, a black matrix material (CK-7001: manufactured by Fujifilm Electronic Material), a red color filter material (CR-7001: manufactured by Fujifilm Electronic Material), a green color filter material (CG-) 7001: Fujifilm Electronic Material) and blue color filter material (CB-7001: Fujifilm Electronic Material) are used, and black matrix 2 and color filters 3, 4, 5 (red, green and blue) by photolithography ) Was formed. The thickness of each layer was 1 μm.

Fabrication of planarization layer:
On this color filter, a UV curable resin (epoxy-modified acrylate) was applied as a planarizing layer 6 by a spin coating method, and a planarizing layer having a thickness of 2 μm was formed by irradiation with high-pressure ultraviolet rays. Even when the planarizing layer was formed, the color filter pattern was not deformed, and the upper surface of the planarizing layer was flat.

Production of color conversion layer:
As the color conversion layer 7, a matrix material SiN and a red fluorescent dye DPP-PTCDI are co-deposited on the planarizing layer 6 so that the red fluorescent dye is 2% by volume with respect to the matrix material, and the film thickness is 500 nm. The color conversion layer 7 was obtained. The internal pressure of the vacuum chamber during film formation of the color conversion layer was 1 × 10 ⁻⁴ Pa.

Production of organic light emitting part:
As shown in FIG. 1, on the color conversion layer formed as described above, an organic light emitting portion composed of anode 8 / organic light emitter 9 / cathode 10 was formed. The organic light-emitting body 9 has a stacked structure of hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer.

  First, after applying a resist material on the upper surface of the color conversion layer 7, patterning was performed on a pattern in which the anode 8 was desired to be produced by photolithography. Thereafter, a transparent electrode (IDIXO) is formed on the entire surface by sputtering, and then unnecessary portions of the transparent electrode are removed by a resist stripping solution, and the light emitting portions (red, green, and blue) of the respective colors are positioned. An anode 8 having a stripe pattern with a width of 0.094 mm, a gap of 0.016 mm, and a film thickness of 100 nm was obtained.

Next, the substrate 1 on which the anode is formed is mounted in a resistance heating vapor deposition apparatus, and the vacuum is broken on the organic light emitter 9 composed of the hole injection layer, the hole transport layer, the organic light emitting layer, the electron transport layer and the electron injection layer. The film was formed in sequence without. During film formation, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. As the hole injection layer, copper phthalocyanine (CuPc) having a thickness of 100 nm was stacked. As the hole transport layer, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD) having a thickness of 20 nm was stacked. As the organic light emitting layer, 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVBi) having a thickness of 30 nm was laminated. As the electron transport layer, aluminum chelate (Alq) having a thickness of 20 nm was laminated. As the electron injection layer, 1 nm of LiF was laminated.

  Further, it is made of Al having a film thickness of 200 nm using a mask capable of obtaining a stripe pattern having a width of 0.30 mm and a gap of 0.03 mm perpendicular to the stripe-shaped partial electrode line of the anode (IDIXO) 7 without breaking the vacuum. A cathode 10 was formed. The organic light emitting device thus obtained was moved into a glove box in a dry nitrogen atmosphere (both oxygen concentration and moisture concentration of 10 ppm or less), and sealed using sealing glass (not shown) and a UV curable adhesive. .

A driving test was performed using the three organic light-emitting elements obtained, and the initial characteristics immediately after the panel fabrication and the luminance retention after 1000 hours of continuous driving were examined. Note that the luminance retention rate is represented with an initial characteristic of 1. The initial characteristic was set to 1 in Example 1.
(Driving condition)
Line sequential scanning: drive frequency 60 Hz, duty 1/60
100 μA current per pixel
The results are shown in Table 1.

<Example 2>
The same procedure as in Example 1 was carried out except that AlN was used as the matrix for forming the color conversion layer 7 and co-evaporated so that the volume percentage of the red fluorescent dye DPP-PTCDI was 1% and the film thickness of the color conversion layer was 350 nm. An organic light emitting device was produced. Using the obtained three organic light emitting devices, a driving test was conducted in the same manner as in Example 1 to examine the initial characteristics and the luminance retention rate. The results are shown in Table 1 together with the results of Example 1.

<Example 3>
Implemented except that SiO _0.5 N was used for the matrix for forming the color conversion layer 7 and co-evaporation was performed so that the volume percentage of the red fluorescent dye DMe-PTCDI was 0.5% and the film thickness of the color conversion layer was 400 nm. An organic light emitting device was produced in the same manner as in Example 1. Using the obtained three organic light emitting devices, a driving test was conducted in the same manner as in Example 1 to examine the initial characteristics and the luminance retention rate. The results are shown in Table 1 together with the results of Example 1.

<Comparative Example 1>
An organic light emitting device was produced in the same manner as in Example 1 except that the following color conversion film was formed instead of the planarization layer 6 and a gas barrier layer was formed instead of the color conversion layer 7.

Color conversion film:
0.05 g of coumarin 6 and 0.04 g of rhodamine B were added to 25 g of photoresist “VPA100” (trade name, Nippon Steel Chemical Co., Ltd.) to obtain a coating solution for a color conversion film. This coating liquid was applied onto a color filter, and a color conversion film having a thickness of 2 μm was formed by a photolithographic method.

Gas barrier layer:
Next, a SiO ₂ film having a thickness of 0.5 μm was deposited on the color conversion film by a sputtering method to form a gas barrier layer. An RF-planar magnetron type apparatus was used as the sputtering apparatus, and SiO ₂ was used as the target. Ar was used as the sputtering gas, and the substrate temperature during formation was set to 80 ° C.

  Using the obtained three organic light emitting devices, a driving test was conducted in the same manner as in Example 1 to examine the initial characteristics and the luminance retention rate. The results are shown in Table 1 together with the results of Example 1.

<Comparative example 2>
Similar to Example 1, except that SiO ₂ was used as a matrix for forming the color conversion layer 7 and co-evaporation was performed so that the volume percentage of the red fluorescent dye DPP-PTCDI was 1% and the film thickness of the color conversion layer was 500 nm. Thus, an organic light emitting device was produced. Using the obtained three organic light emitting devices, a driving test was conducted in the same manner as in Example 1 to examine the initial characteristics and the luminance retention rate. The initial characteristics of the organic light emitting device of Comparative Example 2 were 15 to 20% lower than the initial characteristics of Example 1. There was no difference in luminance retention.

  As is clear from these results, it can be seen that the organic light-emitting device of the present invention is superior in both initial characteristics and luminance retention compared to conventional organic light-emitting devices.

  ADVANTAGE OF THE INVENTION According to this invention, the white light emitting element which does not change the color by the electric current sent through an organic light emitting element and the deterioration of an organic light emitting element can be provided, and it contributes greatly to the performance improvement of various display elements.

It is a typical structure figure showing one embodiment of an organic light emitting element of the present invention.

Explanation of symbols

1 substrate, 2 black matrix, 3 red color filter,
4 Green color filter 5 Blue color filter 6 Flattening layer 7 Color conversion layer 8 First electrode 9 Organic light emitter 10 Second electrode

Claims (6)

  An organic light emitting device comprising: a substrate; a light emitting portion; and a color conversion layer that absorbs light emitted from the light emitting portion and emits light having a wavelength longer than that of light emitted from the light emitting portion. The unit includes a first electrode, an organic light emitter, and a second electrode from the substrate side, and the color conversion layer is made of a fluorescent dye and an inorganic nitride.   The organic light-emitting device according to claim 1, wherein the color conversion layer has a refractive index of 1.8 to 2.2.   3. The organic light emitting device according to claim 1, wherein the color conversion layer is formed by co-evaporation of a fluorescent dye and an inorganic nitride.   The said fluorescent pigment | dye is 1 or more types chosen from a rhodamine pigment | dye, a cyanine pigment | dye, a pyridine pigment | dye, an oxazine pigment | dye, and a perylene pigment | dye, The any one of Claims 1-3 characterized by the above-mentioned. Organic light emitting device.   The inorganic nitride is SiNx (x = 0.5 to 1.5), AlNx (x = 1.0 to 1.1), SiOxNy (x = 0 to 0.5, y = 1.34 to 1.0). ), A-SiN: H, which is at least one selected from the group consisting of H and H, and the organic light emitting device according to claim 1. 6. The color conversion layer according to claim 1, wherein the color conversion layer is between the substrate and the first electrode, and light emitted from the color conversion layer emitted through the substrate is white. The organic light emitting element as described.

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