JP2012221767A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which has high luminous efficiency, lasts long, and is small in chromaticity variation against brightness changes.SOLUTION: An organic electroluminescent element includes on a substrate an organic functional layer containing an anode, a cathode and a light-emitting layer. The element is such that, of the layers comprising the light-emitting layer, (i) the one positioned closest to the anode side is, in its layer thickness, 15% or less of the thickness of the entire light-emitting layer and, in its blue phosphorescent dopant compound concentration, 40 vol.% or more, (ii) the one positioned closest to the cathode side is, in its layer thickness, 50% or more of the thickness of the entire light-emitting layer and, in its blue phosphorescent dopant compound concentration, 10 vol.% or more and 30 vol.% or less, and (iii) the one positioned between the layer positioned closest to the anode side and the layer positioned closest to the cathode side is, in its blue phosphorescent dopant compound concentration, lower than that of the layer positioned closest to the anode side and higher than that of the layer positioned closest to the cathode side.

Description

  The present invention relates to a multicolor phosphorescent organic electroluminescent element having a plurality of phosphorescent dopant compounds having different emission wavelengths, and particularly emitting white light, and an illumination device using the same.

  As a light-emitting electronic display device, there is an electroluminescence display (hereinafter abbreviated as ELD). As a constituent element of ELD, an inorganic electroluminescence element (hereinafter also referred to as an inorganic EL element) and an organic electroluminescence element (hereinafter also referred to as an organic EL element) can be given.

Inorganic EL elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.
On the other hand, an organic electroluminescence device has a configuration in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode. By injecting electrons and holes into the light emitting layer and recombining them, excitons ( Is an element that emits light by using light emission (fluorescence / phosphorescence) when the exciton is deactivated, and can emit light at a voltage of several volts to several tens of volts. Since it is a light-emitting type, it has a wide viewing angle, high visibility, and since it is a thin-film type complete solid-state device, it has attracted attention from the viewpoints of space saving and portability.
The organic electroluminescence element is also a major feature that it is a surface light source, unlike main light sources that have been put to practical use in the past, such as light emitting diodes and cold cathode tubes. Applications that can effectively utilize this characteristic include illumination light sources and various display backlights. In particular, it is also suitable to be used as a backlight of a liquid crystal full color display whose demand has been increasing in recent years.

When the organic electroluminescence element is used as such an illumination light source or a display backlight, it is used as a light source that exhibits white or a so-called light bulb color (hereinafter collectively referred to as white).
In order to obtain white light emission with an organic electroluminescence element, (1) a method of adjusting a plurality of light emitting dopants having different emission wavelengths in one element and obtaining white color by mixing, or (2) a multicolor light emitting pixel, for example, , Blue, green, and red colors are simultaneously emitted and mixed to obtain white by mixing colors, (3) a method for obtaining white using a color conversion dye (for example, a combination of a blue light emitting material and a color conversion fluorescent dye) )and so on.
Judging from various requirements for light sources for illumination and backlights, such as low cost, high productivity, and simple driving method, (1) Adjusting multiple light emitting dopants with different light emission wavelengths in one element and mixing colors Thus, the method of obtaining a white color is effective for these applications, and research and development has been actively promoted in recent years.

The method for obtaining white light by the method (1) described above will be described in more detail. (I) Color mixing using two light emitting dopants having complementary colors in the element, for example, a blue light emitting dopant and a yellow light emitting dopant. And (ii) a method of obtaining white by mixing colors using light emitting dopants of three colors of blue, green, and red.
For example, a method of (ii), that is, a method of obtaining a white organic electroluminescent device by doping high-efficiency blue, green, and red phosphors as light emitting materials is disclosed (for example, patents). References 1 and 2).

In addition, in an organic electroluminescence device that emits white light, (iii) a layer having different emission colors is not formed as a separate layer, but two or more colors of light-emitting dopants are allowed to coexist in one layer to emit light with high emission energy. There is a method of emitting multiple colors by energy transfer from a dopant to a light emitting dopant with relatively low efficiency.
Since this method can reduce the number of organic layers and reduce the amount of light-emitting dopant, it is one of the effective methods for obtaining a white light-emitting organic EL device. For example, Patent Document 3 discloses an organic electroluminescent device in which a red light emitting layer and a blue light emitting layer are sequentially provided from an anode, and the red light emitting layer contains at least one green light emitting dopant. ing.

By the way, in recent years, a phosphorescent dopant capable of obtaining a higher-luminance organic electroluminescence device has been actively developed for fluorescent materials (see, for example, Patent Document 4 and Non-Patent Documents 1 and 2).
In the case of light emission from a conventional fluorescent material, it is light emission from an excited singlet, and the generation ratio of singlet excitons to triplet excitons is 1: 3. In contrast, in the case of a phosphorescent dopant using light emission from an excited triplet, the upper limit of the internal quantum efficiency is determined by the exciton generation ratio and the internal conversion from a singlet exciton to a triplet exciton. Therefore, in principle, the luminous efficiency is up to four times that of the fluorescent dopant.

However, even if the phosphorescent material described above is used, it is still insufficient to meet the demand for improving the efficiency and lifetime of the organic electroluminescence device, and various attempts have been made.
For example, it is disclosed that the lifetime is improved by continuously changing the dopant material in the light emitting layer from the anode side to the cathode side. (For example, refer to Patent Documents 5 and 6). According to this technique, the means for continuously changing the concentration of the luminescent dopant is the control of the vapor deposition rate in the vacuum vapor deposition method, so that the reproducibility is poor and there is a problem as production suitability.
Furthermore, it is also disclosed that efficiency and lifetime are improved by gradually reducing the dopant material in the light emitting layer from the anode side to the cathode side (see, for example, Patent Documents 7 and 8). According to the technology, these are disclosures of configurations only for blue light emission or green light emission monochromatic system. For example, the above-mentioned white light-emitting dopants of two or more colors coexist in one layer, and the dopant concentration is gradually increased. When changed, it was found that the stability of chromaticity against luminance change was insufficient depending on conditions.
In particular, in the illumination light source application, there is a strict demand for the stability of the luminescent color, and in order to put the organic electroluminescence element to practical use in the illumination light source, how to ensure the stability of chromaticity in addition to efficiency and lifetime. Is an important issue.

JP-A-6-207170 JP 2004-235168 A International Publication No. 2004/077786 US Pat. No. 6,097,147 JP 2003-229272 A Japanese Patent Laid-Open No. 2004-6102 JP 2007-227117 A International Publication No. 2008/035595

M.M. A. Baldo et al. , Nature, 395, 151-154 (1998) M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000)

  Accordingly, a main object of the present invention is an organic electroluminescence device that emits white light using a plurality of phosphorescent dopant compounds having different emission wavelengths, and has high luminous efficiency and long life and chromaticity variation with respect to luminance change. It is to provide a small organic electroluminescence device.

In order to solve the above problems, according to the present invention,
In an organic electroluminescent device having an organic functional layer including an anode, a cathode, and a light emitting layer on a substrate,
The light emitting layer is composed of at least three layers;
Each layer constituting the light emitting layer includes a host compound, a blue phosphorescent dopant compound having an emission maximum wavelength of less than 480 nm, and a phosphorescent dopant compound of a color other than blue,
Of the layers constituting the light emitting layer,
(I) The layer located on the most anode side has a layer thickness of 15% or less of the total thickness of the light emitting layer and a blue phosphorescent dopant compound concentration of 40% by volume or more,
(Ii) the layer located on the most cathode side has a layer thickness of 50% or more of the total thickness of the light emitting layer and a blue phosphorescent dopant compound concentration of 10% by volume to 30% by volume;
(Iii) The layer located between the layer located closest to the anode side and the layer located closest to the cathode side has a blue phosphorescent dopant compound concentration lower than the blue phosphorescent dopant compound concentration of the layer located closest to the anode side, There is provided an organic electroluminescence device characterized in that the concentration is higher than the blue phosphorescent dopant compound concentration of the layer located closest to the cathode side.

  ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element with high luminous efficiency and long lifetime, and a small chromaticity fluctuation | variation with respect to a brightness | luminance change can be provided.

It is the schematic which shows an example of the illuminating device incorporating the organic EL element of this invention. It is sectional drawing which shows an example of the illuminating device incorporating the organic EL element of this invention.

  Hereinafter, although the detail of each component of the white phosphorescence emission organic electroluminescent element (henceforth "organic EL element") concerning preferable embodiment of this invention is demonstrated one by one, this invention is not limited to these. .

<< White chromaticity of organic electroluminescence element >>
The emission color of the organic EL element of the present invention and the compound related to the element is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). The result of measurement with CS-1000 (manufactured by Konica Minolta Sensing) is determined by the color when applied to the CIE chromaticity coordinates.
The preferred chromaticity as a white element in the present invention is that the correlated color temperature is 2500 K to 7000 K, and in the CIE 1931 color system, the y value deviation from the black body radiation at each color temperature is 0.1 or less.

<< Layer structure of organic EL element >>
Next, although the preferable specific example of the layer structure of an organic EL element is shown below, this invention is not limited to these.
(I) Anode / light emitting layer / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emitting layer / hole Blocking layer / electron transport layer / cathode buffer layer / cathode

<Light emitting layer>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.
The light emitting layer according to the present invention is composed of at least three layers, each layer constituting the light emitting layer includes a host compound, a blue phosphorescent dopant compound having an emission maximum wavelength of less than 480 nm, and a phosphorescent dopant compound of a color other than blue, Contains.
Among the layers constituting the light emitting layer,
(I) The layer located on the most anode side has a layer thickness of 15% or less of the total thickness of the light emitting layer and a concentration of the blue phosphorescent dopant compound of 40% by volume or more,
(Ii) The layer located closest to the cathode side has a layer thickness of 50% or more of the total thickness of the light emitting layer and a concentration of the blue phosphorescent dopant compound of 10% by volume to 30% by volume;
(Iii) In the layer located between the layer located closest to the anode and the layer located closest to the cathode, the concentration of the blue phosphorescent dopant compound is higher than the concentration of the blue phosphorescent dopant compound in the layer located closest to the anode. It is low and is higher than the concentration of the blue phosphorescent dopant compound in the layer located closest to the cathode side.
Furthermore, the layer located on the most anode side preferably has a layer thickness of 10% or less of the entire light emitting layer, and preferably has a blue phosphorescent dopant compound concentration of 60% by volume or more.
The layer located closest to the cathode side preferably has a layer thickness of 70% or more of the total thickness of the light emitting layer, and preferably has a blue phosphorescent dopant compound concentration of 15% by volume to 25% by volume. .

One type or several types of phosphorescent dopant compounds of colors other than blue contained in the light emitting layer of the present invention may be used.
The phosphorescent dopant compound of a color other than blue preferably includes at least one red phosphorescent dopant compound having at least one emission maximum wavelength of 580 nm or more and 650 nm or less in order to obtain the above-described white light emission, and more preferably at least one emission maximum wavelength. It is more preferable to include a red phosphorescent dopant compound having a wavelength of 580 nm to 650 nm and a green phosphorescent dopant compound having an emission maximum wavelength of 500 nm to less than 580 nm.
Moreover, it is preferable that the host compound, the blue phosphorescent dopant compound, and the phosphorescent dopant compounds of other colors other than blue used in at least three light emitting layers are the same compound.
In order to further reduce chromaticity variation with respect to luminance change, it is preferable that phosphorescent dopant compounds of colors other than blue in at least three light emitting layers are contained in the same volume%.
The content of phosphorescent dopant compounds other than blue is not particularly limited, but is preferably adjusted as appropriate so that the above-described white light emission can be obtained.
In addition, in order to reduce the chromaticity variation with respect to the luminance change with higher luminous efficiency and longer lifetime, the total thickness (total) of the light emitting layer is preferably 60 nm or more and 120 nm or less.

With the light emitting layer having the configuration of the present invention, a white phosphorescent organic electroluminescence device having high luminous efficiency and long life and small chromaticity variation with respect to luminance change can be obtained.
The mechanism of action that brings about the effect of the present invention is not necessarily elucidated and is not speculated. However, phosphorescent layers, particularly phosphorescent layers that emit blue light, have a large energy gap, and electrons or holes. It is expected that there will be a large barrier to the injection of such charges into the light emitting layer. Although the structure of the present invention is expected to improve the injection of this charge into the light emitting layer, the effect of the present invention is not obtained in any combination with any material, and particularly the blue color of the present invention. It has been found that a remarkable effect can be obtained in combination with a phosphorescent dopant and further with a host compound.

  Hereinafter, a light-emitting dopant compound (also simply referred to as a light-emitting dopant) and a light-emitting host compound (also simply referred to as a light-emitting host) included in the light-emitting layer will be described.

(1) Luminescent dopant A phosphorescent dopant is used as the luminescent dopant according to the present invention.
The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent dopant is a compound that emits phosphorescence at room temperature (25 ° C.), and the phosphorescence quantum yield is 25 ° C. Although defined as 0.01 or more compounds, the preferred phosphorescence quantum yield is 0.1 or more.
The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention can be obtained if the above phosphorescence quantum yield (0.01 or more) is achieved in any solvent. Good.
There are two types of phosphorescent dopants in principle. One is that the recombination of carriers occurs on the light-emitting host on which carriers are transported to generate an excited state of the light-emitting host, and this energy is transferred to the phosphorescent dopant. In the energy transfer type in which light emission from the phosphorescent dopant is obtained, and in the other, the carrier trap type in which light emission from the phosphorescent dopant is obtained by recombination of carriers on the phosphorescent dopant, where the phosphorescent dopant becomes a carrier trap. In any case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the light emitting host.

The phosphorescent dopant can be appropriately selected from known ones used in the light emitting layer of the organic EL element, and in the present invention, at least one blue phosphorescent dopant compound having an emission maximum wavelength of less than 480 nm, A phosphorescent dopant compound of a color other than blue.
In the present invention, the phosphorescent dopant compound other than blue color refers to a compound having an emission maximum wavelength of 500 nm or more. As described above, at least one is a red phosphorescent dopant compound having a maximum wavelength of 580 nm or more and 650 nm or less. Preferably there is.

  In the present invention, the blue phosphorescent dopant having an emission maximum wavelength of less than 480 nm preferably has at least one partial structure selected from general formulas (A) to (C).

In the general formula (A), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, “Rb” and “Rc” each represents a hydrogen atom or a substituent, and “A1” represents an aromatic Represents a residue necessary to form an aromatic ring or an aromatic heterocyclic ring, and “M” represents Ir or Pt.
In the general formula (B), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, and “Rb”, “Rc”, “Rb ₁ ” and “Rc ₁ ” are each a hydrogen atom or Represents a substituent, “A1” represents a residue necessary to form an aromatic ring or an aromatic heterocycle, and “M” represents Ir or Pt.
In the general formula (C), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, “Rb” and “Rc” each represents a hydrogen atom or a substituent, and “A1” represents an aromatic Represents a residue necessary to form an aromatic ring or an aromatic heterocyclic ring, and “M” represents Ir or Pt.

  In the general formulas (A) to (C), Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, and the aliphatic group represented by Ra includes an alkyl group (for example, a methyl group, an ethyl group, Group, propyl group, butyl group, pentyl group, isopentyl group, 2-ethyl-hexyl group, octyl group, undecyl group, dodecyl group, tetradecyl group), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group), and the like. As the aromatic group, for example, phenyl group, tolyl group, azulenyl group, anthranyl group, phenanthryl group, pyrenyl group, chrysenyl group, naphthacenyl group, o-terphenyl group, m-terphenyl group, p-terphenyl group, Examples include acenaphthenyl group, coronenyl group, fluorenyl group, perylenyl group, etc. It may have. As the heterocyclic group, for example, pyrrolyl group, indolyl group, furyl group, thienyl group, imidazolyl group, pyrazolyl group, indolizinyl group, quinolinyl group, carbazolyl group, indolinyl group, thiazolyl group, pyridyl group, pyridazinyl group, thiadiazinyl group, An oxadiazolyl group, a benzoquinolinyl group, a thiadiazolyl group, a pyrrolothiazolyl group, a pyrrolopyridazinyl group, a tetrazolyl group, an oxazolyl group, a chromanyl group, and the like can be mentioned, and these groups each may have a substituent.

In the general formulas (A) to (C), examples of the substituent represented by Rb, Rc, Rb ₁ and Rc ₁ include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group, a pentyl group). Group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group etc.), cycloalkyl group (eg cyclopentyl group, cyclohexyl group etc.), alkenyl group (eg vinyl group, allyl group etc.), alkynyl Group (eg, ethynyl group, propargyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), aromatic heterocyclic group (eg, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group) , Triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, phthala Nyl group, etc.), heterocyclic group (eg pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group etc.), alkoxyl group (eg methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group) Group, dodecyloxy group, etc.), cycloalkoxyl group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, Propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alcohol Sicarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.) ), Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group) Naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, Pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, Butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (eg, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group) Group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenyl Carbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group) Octylureido group, dodecylureido group, phenylureido group naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, Tylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl Group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, Amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, Phthalylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluoro) Phenyl group, etc.), cyano group, nitro group, hydroxyl group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.). These substituents may be further substituted with the above substituents.

  In the general formulas (A) to (C), A1 represents a residue necessary for forming an aromatic ring or an aromatic heterocyclic ring. Examples of the aromatic ring include a benzene ring, a biphenyl ring, a naphthalene ring, and an azulene ring. , Anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, fluorene ring, fluoranthrene ring Naphthacene ring, pentacene ring, perylene ring, pentaphen ring, picene ring, pyrene ring, pyranthrene ring, anthraanthrene ring, etc., and the aromatic heterocycle includes furan ring, thiophene ring, pyridine ring, pyridazine ring , Pyrimidine ring, pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring Imidazole ring, pyrazole ring, thiazole ring, indole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, phthalazine ring, carbazole ring, carboline ring, diazacarbazole ring (carbonization constituting carboline ring) A ring in which one of the carbon atoms of the hydrogen ring is further substituted with a nitrogen atom).

The structures of the general formulas (A) to (C) are partial structures, and a ligand corresponding to the valence of the central metal is necessary for the structure itself to be a light-emitting dopant of a completed structure.
Specifically, halogen (for example, fluorine atom, chlorine atom, bromine atom or iodine atom), aryl group (for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, biphenyl group, naphthyl group) , Anthryl group, phenanthryl group, etc.), alkyl group (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), alkyloxy group, aryloxy group , Alkylthio group, arylthio group, aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, carbazolyl group , Carbolinyl group, phthalazinyl group, etc.), one Formula (A) ~ partial structure such as metal except for the (C) can be mentioned.
In the general formulas (A) to (C), M represents Ir or Pt, and Ir is particularly preferable.
A tris body having a completed structure with three partial structures of the general formulas (A) to (C) is preferable.

  Hereinafter, although the compound which has the partial structure of the said general formula (A)-(C) of the light emission dopant which concerns on this invention is illustrated, it is not limited to these.

  Specific examples of compounds used as multicolor phosphorescent dopants other than blue are shown below, but are not limited thereto. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

(2) Host compound The host compound contained in the light emitting layer of the organic EL device of the present invention is preferably a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C) of less than 0.1. A compound having a phosphorescence quantum yield of less than 0.01 is preferable.
As the host compound, one type of compound may be used alone, or a plurality of types of compounds may be used in combination.
The light-emitting host compound used in the present invention is not particularly limited in terms of structure, but typically, a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, a furan derivative, Those having a basic skeleton such as an oligoarylene compound, or a carboline derivative or a diazacarbazole derivative (here, a diazacarbazole derivative is a compound in which at least one carbon atom of a hydrocarbon ring constituting a carboline ring of a carboline derivative is nitrogen Represents an atom substituted with an atom.) And the like.

  As the luminescent host compound used in the luminescent layer according to the present invention, a compound represented by the following general formula (a) is preferable.

  In the general formula (a), “X” represents NR ′, O, S, CR′R ″ or SiR′R ″, “R ′” and “R ″” each represents a hydrogen atom or a substituent, “Ar” represents an aromatic ring, and “n” represents an integer of 0 to 8.

In the general formula (a), the substituents represented by R ′ and R ″ in X are each an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group). Group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, 1-propenyl group, 2 -Butenyl group, 1,3-butadienyl group, 2-pentenyl group, isopropenyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (aromatic carbocyclic group, aryl group, etc.) For example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, an Ryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc., aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group) Group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom) ), A phthalazinyl group, etc.), a heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), an alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, Hexyloxy group, oct Ruoxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group). Propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (for example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (Eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, etc.) Xycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, Dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group) 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy (For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethyl group) Carbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (For example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, A cyclohexylaminocarbonyl group, an octylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, a dodecylaminocarbonyl group, a phenylaminocarbonyl group, a naphthylaminocarbonyl group, a 2-pyridylaminocarbonyl group, etc.), a ureido group (for example, a methylureido group, Ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl) Group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, Dilsulfinyl group etc.), alkylsulfonyl group (eg methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group etc.), arylsulfonyl group or heteroarylsulfonyl group (eg , Phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group) Anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, Tafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono Groups and the like.
These substituents may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.

  In the general formula (a), X is preferably NR ′ or O, and R ′ is particularly preferably an aromatic hydrocarbon group or an aromatic heterocyclic group.

In the general formula (a), examples of the aromatic ring represented by Ar include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring may be a single ring or a condensed ring, and may be unsubstituted or may have a substituent as described later.
In the general formula (a), examples of the aromatic hydrocarbon ring represented by Ar include a benzene ring, biphenyl ring, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, fluorene ring, fluoranthrene ring, naphthacene ring, pentacene ring, perylene ring, pentaphen ring, picene ring, pyrene ring, Examples include a pyranthrene ring and anthraanthrene ring. These rings may further have a substituent.
In the general formula (a), examples of the aromatic heterocycle represented by Ar include a furan ring, a dibenzofuran ring, a thiophene ring, an oxazole ring, a pyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, and a triazine ring. , Benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indazole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, cinnoline ring, quinoline Ring, isoquinoline ring, phthalazine ring, naphthyridine ring, carbazole ring, carboline ring, diazacarbazole ring (showing a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom), etc. Can be mentioned. These rings may further have a substituent.
Among the above, in the general formula (a), the aromatic ring represented by Ar is preferably a carbazole ring, carboline ring, dibenzofuran ring, or benzene ring, and particularly preferably used is a carbazole ring or carboline. Ring, benzene ring. Among these, a benzene ring having a substituent is preferable, and a benzene ring having a carbazolyl group is particularly preferable.
Further, in the general formula (a), the aromatic ring represented by Ar is preferably a condensed ring having 3 or more rings, as shown below, and is an aromatic hydrocarbon condensed in which 3 or more rings are condensed. Specific examples of the ring include naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, chrysene ring, benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene Ring, coronene ring, benzocoronene ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen ring, picene ring, pyranthrene ring, coronene ring, Naphthocoronene ring, Ovalene ring, Ansula Ntoren ring and the like. In addition, these rings may further have a substituent.
Specific examples of the aromatic heterocycle condensed with three or more rings include an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, a cyclazine ring, Kindin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (any one of the carbon atoms constituting the carboline ring is a nitrogen atom Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, A Tiger thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan Tren ring (naphthaldehyde thiophene ring), and the like. In addition, these rings may further have a substituent.
Here, in the general formula (a), the substituent that the aromatic ring represented by Ar may have is the same as the substituent represented by R ′ and R ″.

  In the general formula (a), n represents an integer of 0 to 8, preferably 0 to 2, and particularly preferably 1 or 2 when X is O or S.

  Specific examples of the light-emitting host compound represented by the general formula (a) are shown below, but are not limited thereto.

The host compound used in the present invention may be a low molecular compound, a high molecular compound having a repeating unit, or a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (evaporation polymerizable light emitting host). .
As the host compound, a compound having a hole transporting ability and an electron transporting ability, which prevents emission of longer wavelengths and has a high Tg (glass transition temperature) is preferable.
In the present invention, at least three light emitting layers are provided. The host compound may be different for each light emitting layer, but the same compound can provide excellent driving life characteristics and chromaticity stability. To preferred.
In addition, the host compound preferably has a lowest excited triplet energy (T1) larger than 2.7 eV because higher luminous efficiency can be obtained. The lowest excited triplet energy as used in the present invention refers to the peak energy of an emission band corresponding to the transition between the lowest vibrational bands of a phosphorescence emission spectrum observed at a liquid nitrogen temperature after dissolving a host compound in a solvent.
In the present invention, a compound having a glass transition point of 90 ° C. or higher is preferable, and a compound having a glass transition temperature of 130 ° C. or higher is preferable because excellent driving life characteristics can be obtained.
Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).
In the organic EL device of the present invention, since the host material is responsible for carrier transport, a material having carrier transport capability is preferable. Carrier mobility is used as a physical property representing carrier transport ability, but the carrier mobility of an organic material generally depends on the electric field strength. Since a material having a high electric field strength dependency easily breaks the balance of hole and electron injection / transport, it is preferable to use a material having a low electric field strength dependency of mobility for the intermediate layer material and the host material.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be.
An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. .
The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.
The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.
The hole blocking layer preferably contains the carbazole derivative mentioned as the light emitting host.
Further, in the present invention, when a plurality of light emitting layers having different emission colors are provided, it is preferable that the layer whose emission maximum wavelength is the shortest is the closest to the anode in the light emitting layer. It is preferable to additionally provide a hole blocking layer between the shortest wave layer and the light emitting layer next to the anode next to the layer. Further, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer provided at the position has an ionization potential of 0.3 eV or more larger than the light emitting host of the shortest wave emitting layer.
The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be determined by, for example, the following method.
(1) Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA, is used as a keyword. The ionization potential can be obtained as a value obtained by rounding off the second decimal place of a value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. This calculation value is effective because the correlation between the calculation value obtained by this method and the experimental value is high.
(2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a method known as ultraviolet photoelectron spectroscopy can be suitably used using a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki.

  On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material having a function of transporting holes while having a remarkably small ability to transport electrons. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The layer thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer.
The hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic.
Examples of hole transport materials include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives. Fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.
Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and also two of those described in US Pat. No. 5,061,569. Having a condensed aromatic ring in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-3086 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 8 are linked in a starburst type ( MTDATA) and the like.
Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material. JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used because a light-emitting element with higher efficiency can be obtained.

Although there is no restriction | limiting in particular about the layer thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm.
The hole transport layer may have a single layer structure composed of one or more of the above materials.
Alternatively, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.
In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Conventionally, in the case of a single electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. As long as it has a function of transferring electrons to the light-emitting layer, any material can be selected and used from among conventionally known compounds. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives Thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.
In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.

Although there is no restriction | limiting in particular about the layer thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm.
The electron transport layer may have a single layer structure composed of one or more of the above materials.
Further, an electron transport layer having high n property doped with impurities may be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.
In the present invention, it is preferable to use an electron transport layer having such a high n property because an element with lower power consumption can be manufactured.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used.
Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used.
For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used.
When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.
Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used.
Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like.
Among these, a mixture of an electron injecting metal and a second metal, which is a stable metal having a larger work function value than this, from the point of durability against electron injection and oxidation, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.
The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.
After producing the above metal with a film thickness of 1 to 20 nm on the cathode, a transparent or semi-transparent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode thereon. By application, an element in which both the anode and the cathode are transmissive can be manufactured.

《Support substrate》
As a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. May be opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film.
Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Polyetherimide, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, and cycloolefin resins such as ARTON (manufactured by JSR) or APEL (manufactured by Mitsui Chemicals).

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and a barrier film having a water vapor permeability of 0.01 g / m ² / day · atm or less is preferable. Furthermore, a high barrier film having an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻⁵ g / m ² / day or less is preferable.
As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

  Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.

The external extraction quantum efficiency at room temperature of light emission of the organic EL device of the present invention is preferably 1% or more, more preferably 5% or more. Here, external extraction quantum efficiency (%) = (number of photons emitted to the outside of the organic EL element) / (number of electrons sent to the organic EL element) × 100.
In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

<Sealing>
As a sealing means used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example.
As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient. Further, transparency and electrical insulation are not particularly limited.
Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned.
Furthermore, the polymer film oxygen permeability measured by the method based on JIS K 7126-1987 is ^{1 × 10 -3 ml / m 2} / 24h or less, as measured by the method based on JIS K 7129-1992, water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)%) is preferably that of ^{1 × 10 -3 g / (m} 2 / 24h) or less.
For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.
In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print like screen printing.

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.
Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.
Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film.
In particular, when the sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used. It is preferable to use a film.

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said.
This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the side surface direction of the element.

As a method for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (US Pat. No. 4,774,435), A method of improving efficiency by providing a light collecting property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an element (Japanese Patent Laid-Open No. 1-220394), and light emission from a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the bodies (Japanese Patent Laid-Open No. 62-172691), a flat having a lower refractive index between the substrate and the light emitter than the substrate A method of introducing a layer (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer and a light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951) Gazette).
In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.
In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower.
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less.
The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium.
This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate.

The method of introducing a diffraction grating into an interface or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency.
This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction. Light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating in any layer or medium (in a transparent substrate or transparent electrode), and the light is removed. I want to take it out.
The introduced diffraction grating desirably has a two-dimensional periodic refractive index.
This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. Therefore, the light extraction efficiency does not increase so much. However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.
As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or in the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated.
At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium.
The arrangement of the diffraction grating is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

<Condenser sheet>
The organic EL device of the present invention is processed on the light extraction side of the substrate so as to provide, for example, a microlens array structure, or combined with a so-called condensing sheet, for example, with respect to a specific direction, for example, the device light emitting surface. By condensing in the front direction, the luminance in a specific direction can be increased.
As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, Sumitomo 3M brightness enhancement film (BEF) can be used. As the shape of the prism sheet, for example, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.
Moreover, in order to control the light emission angle from a light emitting element, you may use together a light diffusing plate and a film with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<< Method for producing organic EL element >>
As an example of the method for producing the organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode will be described.

  First, a desired electrode material, for example, a thin film made of an anode material is formed on a suitable supporting substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 nm to 200 nm. Make it.

Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, and an electron transport layer, which are organic EL element materials, is formed thereon.
As a method of thinning the organic compound thin film, a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, printing method, LB method (Langmuir-Blodget method), spray method, printing method, slot type coater. However, the vacuum deposition method, spin coating method, ink jet method, printing method, and slot type coater method are particularly preferred from the standpoint that a homogeneous film can be easily obtained and pinholes are hardly formed. Further, different film forming methods may be applied for each layer. However, since the light emitting layer of the present invention has at least three layers, it is difficult to form a film by a wet process. Is preferred.
When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 ° C. to 450 ° C., a vacuum degree of 10 ⁻⁶ Pa to 10 ⁻² Pa, and a vapor deposition rate of 0. It is desirable to select appropriately within the range of 01 nm / second to 50 nm / second, substrate temperature −50 ° C. to 300 ° C., film thickness (layer thickness) 0.1 nm to 5 μm, preferably 5 nm to 200 nm.

  After forming these layers, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 nm to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

The organic EL device is preferably manufactured from the hole injection layer to the cathode consistently by one vacuum drawing, but may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.
In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order.
When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 V to 40 V with the anode as + and the cathode as-. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

(1) Preparation of sample (1.1) Preparation of organic EL element 101 Patterning was performed on a support substrate in which ITO (indium tin oxide) was formed to a thickness of 110 nm on a glass substrate having a thickness of 0.7 mm as an anode. After this, the transparent support substrate with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. Fixed to the substrate holder.

Each of the deposition crucibles in the vacuum deposition apparatus was filled with the constituent material of each layer in an optimum amount for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.
Next, after reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing compound HT-1 was heated by energization, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / second. A hole injection layer (HIL) was provided. Next, Compound HT-2 was deposited at a deposition rate of 0.1 nm / sec to provide a 20 nm hole transport layer (HTL).
Then, the host compound 1-1, the blue phosphorescent dopant compound D-66, the green phosphorescent dopant compound Ir-1d, and the red phosphorescent dopant compound Ir-14d were deposited at a deposition rate of 0.4 nm / second, 0.1 nm / second,. A light-emitting layer (EML) was formed by co-evaporation to a thickness of 80 nm at 001 nm / second and 0.001 nm / second.
Thereafter, Compound ET-1 was deposited to a thickness (layer thickness) of 30 nm to form an electron transport layer, and KF was further formed to a thickness of 2 nm. Furthermore, aluminum 110nm was vapor-deposited and the cathode was formed.

Next, the non-light-emitting surface of the element was covered with a glass case, and an “organic EL element 101” having the configuration shown in FIGS. 1 and 2 was produced.
FIG. 1 shows a schematic diagram of an organic EL element.
The organic EL element 101 is covered with a glass cover 102. The sealing operation with the glass cover 102 was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without bringing the organic EL element 101 into contact with the atmosphere.
FIG. 2 shows a cross-sectional view of the organic EL element.
As shown in FIG. 2, a cathode 105 and an organic EL layer 106 are formed on a glass substrate 107 with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

(1.2) Preparation of organic EL element 102 In preparation of the organic EL element 101, after forming a hole transport layer, host compound 1-1, blue phosphorescent dopant compound D-66, green phosphorescent dopant compound Ir-1d and red The phosphorescent dopant compound Ir-14d was co-deposited to a thickness of 20 nm at a deposition rate of 0.15 nm / second, 0.35 nm / second, 0.001 nm / second, and 0.001 nm / second, respectively, and the anode side light emitting layer ( A first layer), and then a host compound 1-1, a blue phosphorescent dopant compound D-66, a green phosphorescent dopant compound Ir-1d, and a red phosphorescent dopant compound Ir-14d are deposited at a deposition rate of 0.4 nm / second, 0 Co-evaporated to a thickness of 60 nm at 1 nm / second, 0.001 nm / second, and 0.001 nm / second to form a cathode side light emitting layer (third layer). .
Otherwise, the “organic EL element 102” was prepared in the same manner as the organic EL element 101.

(1.3) Preparation of organic EL element 103 In preparation of the organic EL element 101, after forming a hole transport layer, host compound 1-1, blue phosphorescent dopant compound D-66, green phosphorescent dopant compound Ir-1d and red The phosphorescent dopant compound Ir-14d was co-deposited to a thickness of 20 nm at a deposition rate of 0.30 nm / second, 0.20 nm / second, 0.001 nm / second, and 0.001 nm / second, respectively. A first layer), and then a host compound 1-1, a blue phosphorescent dopant compound D-66, a green phosphorescent dopant compound Ir-1d, and a red phosphorescent dopant compound Ir-14d are deposited at a deposition rate of 0.4 nm / second, 0 Co-evaporated to a thickness of 60 nm at 1 nm / second, 0.001 nm / second, and 0.001 nm / second to form a cathode side light emitting layer (third layer). .
Otherwise, the “organic EL element 103” was prepared in the same manner as the organic EL element 101.

(1.4) Preparation of organic EL element 104 In preparation of the organic EL element 101, after forming a hole transport layer, host compound 1-1, blue phosphorescent dopant compound D-66, green phosphorescent dopant compound Ir-1d and red The phosphorescent dopant compound Ir-14d was co-deposited at a deposition rate of 0.15 nm / second, 0.35 nm / second, 0.001 nm / second, and 0.001 nm / second to a thickness of 5 nm, and the anode side light emitting layer ( A first layer), and then a host compound 1-1, a blue phosphorescent dopant compound D-66, a green phosphorescent dopant compound Ir-1d, and a red phosphorescent dopant compound Ir-14d are deposited at a deposition rate of 0.3 nm / second, 0 Co-evaporated to a thickness of 15 nm at 2 nm / second, 0.001 nm / second, and 0.001 nm / second to form an intermediate light emitting layer (second layer). Host compound 1-1, blue phosphorescent dopant compound D-66, green phosphorescent dopant compound Ir-1d, and red phosphorescent dopant compound Ir-14d, respectively, with a deposition rate of 0.4 nm / second, 0.1 nm / second, and 0.001 nm, respectively. The cathode-side light-emitting layer (third layer) was formed by co-evaporation to a thickness of 60 nm at a rate of 0.001 nm / second / second.
Otherwise, the “organic EL element 104” was produced in the same manner as in the production of the organic EL element 101.

(1.5) Production of organic EL elements 105 to 118 In the production of the organic EL element 104, the first light emitting layer, the second light emitting layer, the host compound of the third light emitting layer, the blue phosphorescent dopant compound, the green phosphorescent dopant compound, and the red color. The volume ratio and film thickness (layer thickness) of the phosphorescent dopant compound were controlled so as to have the values shown in Table 1 to form a film by vapor deposition.
Other than that, “organic EL elements 105 to 118” were manufactured in the same manner as the organic EL element 101.

(2) Sample Evaluation The organic EL elements 101 to 118 obtained as described above were evaluated for external extraction quantum efficiency, light emission lifetime, and chromaticity stability with different luminances as follows.

(2.1) External extraction quantum efficiency The external extraction quantum efficiency (%) when a ^2.5 mA / cm ² constant current was applied to the prepared organic EL device was measured. A spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used for the measurement. The external extraction quantum efficiency was expressed as a relative value with the measured value of the organic EL element 101 as 100. The measurement results are shown in Table 2.

(2.2) Luminescence Life The produced organic EL element is continuously driven by applying a current with a front luminance of 4000 cd / m ² until the front luminance reaches the initial half value (2000 cd / m ² ). The time required was obtained and this was defined as the light emission lifetime. The light emission lifetime was expressed as a relative value with the measured value of the organic EL element 101 as 100. The measurement results are shown in Table 2.

(2.3) Measurement chromaticity variation range of chromaticity variation range is determined front luminance 300cd ^{/ m 2} ~4000cd ^/ m 2 in the CIE 1931, x, the maximum distance ΔE fluctuation of y-value in the formula, A to results Classified as D.
ΔE = (Δx ² + Δy ² ) ^1/2
A: ΔE is less than 0.01 B: ΔE is 0.01 or more and less than 0.015 C: ΔE is 0.015 or more and less than 0.02 D: ΔE is 0.02 or more Among A to D, “A” is The chromaticity variation with respect to the luminance change is the smallest and stable. The classification results are shown in Table 2.

As is clear from the results in Table 2, the samples 104 to 106, 108, 111, 112, 114, 115, 117, and 118 are compared with other samples in terms of external extraction quantum efficiency, emission lifetime, and chromaticity stability. It was excellent in all aspects.
Accordingly, the light emitting layer is composed of at least three layers, and each layer is an organic EL element including a host compound, a blue phosphorescent dopant compound, and a phosphorescent dopant compound of a color other than blue, and the layers constituting the light emitting layer Among them, (i) the anode-side light emitting layer has a layer thickness of 15% or less of the entire light-emitting layer and the blue phosphorescent dopant compound concentration is 40% by volume or more, and (ii) the cathode-side light-emitting layer has a light-emitting layer thickness. (Iii) the blue phosphorescent dopant compound concentration of the first layer is set to a blue phosphorescent dopant compound concentration of the intermediate light emitting layer, and the blue phosphorescent dopant compound concentration is set to 10 vol% or more and 30 vol% or less. Setting it to be lower than the concentration and higher than the concentration of the blue phosphorescent dopant compound in the third layer has high luminous efficiency, long life, and little chromaticity variation with respect to luminance change. It proves useful to provide an EL element.

DESCRIPTION OF SYMBOLS 101 Organic EL element 102 Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate with a transparent electrode 108 Nitrogen gas 109 Water catching agent

Claims (4)

In an organic electroluminescent device having an organic functional layer including an anode, a cathode, and a light emitting layer on a substrate,
The light emitting layer is composed of at least three layers;
Each layer constituting the light emitting layer includes a host compound, a blue phosphorescent dopant compound having an emission maximum wavelength of less than 480 nm, and a phosphorescent dopant compound of a color other than blue,
Of the layers constituting the light emitting layer,
(I) The layer located on the most anode side has a layer thickness of 15% or less of the total thickness of the light emitting layer and a blue phosphorescent dopant compound concentration of 40% by volume or more,
(Ii) the layer located on the most cathode side has a layer thickness of 50% or more of the total thickness of the light emitting layer and a blue phosphorescent dopant compound concentration of 10% by volume to 30% by volume;
(Iii) The layer located between the layer located closest to the anode side and the layer located closest to the cathode side has a blue phosphorescent dopant compound concentration lower than the blue phosphorescent dopant compound concentration of the layer located closest to the anode side, An organic electroluminescence device characterized in that the concentration is higher than the blue phosphorescent dopant compound concentration of the layer located closest to the cathode side. The organic electroluminescent device according to claim 1,
The organic phosphor element, wherein the blue phosphorescent dopant compound has at least one partial structure selected from general formulas (A) to (C).

[In the formula (A), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, “Rb” and “Rc” each represents a hydrogen atom or a substituent, and “A1” represents an aromatic Represents a residue necessary to form an aromatic ring or an aromatic heterocyclic ring, and “M” represents Ir or Pt. ]

[In the formula (B), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, and “Rb”, “Rc”, “Rb ₁ ” and “Rc ₁ ” are each a hydrogen atom or Represents a substituent, “A1” represents a residue necessary to form an aromatic ring or an aromatic heterocycle, and “M” represents Ir or Pt. ]

[In the formula (C), “Ra” represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, “Rb” and “Rc” each represents a hydrogen atom or a substituent, and “A1” represents an aromatic Represents a residue necessary to form an aromatic ring or an aromatic heterocyclic ring, and “M” represents Ir or Pt. ] The organic electroluminescent element according to claim 1 or 2,
The organic electroluminescent device, wherein the host compound is represented by the general formula (a).

[In the formula (a), “X” represents NR ′, O, S, CR′R ″ or SiR′R ″, “R ′” and “R ″” each represents a hydrogen atom or a substituent, “Ar” represents an aromatic ring, and “n” represents an integer of 0 to 8. ] In the organic electroluminescent element as described in any one of Claims 1-3,
An organic electroluminescence device, wherein the thickness of the entire light emitting layer is 60 nm or more and 120 nm or less.

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