JP4923651B2 - Organic electroluminescence element, display device and lighting device - Google Patents

Description

  The present invention relates to an organic electroluminescence element, a liquid crystal display device, and a lighting device.

  As a light-emitting electronic display device, there is an electroluminescence display (ELD). Examples of the constituent elements of ELD include inorganic electroluminescent elements (inorganic EL elements) and organic electroluminescent elements (hereinafter also referred to as “organic EL elements”). Inorganic electroluminescent elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.

  An organic electroluminescence element has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and injects electrons and holes into the light emitting layer to recombine excitons. This is an element that emits light by utilizing the emission of light (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several volts to several tens of volts. Therefore, it has a wide viewing angle, high visibility, and since it is a thin-film type completely solid element, it has attracted attention from the viewpoints of space saving and portability.

  Another major feature of the organic electroluminescence element is that it is a surface light source, unlike main light sources that have been conventionally used in practice, such as light-emitting diodes and cold-cathode tubes. Applications that can effectively utilize this characteristic include illumination light sources and backlights for various displays. In particular, it can be suitably used as a backlight of a liquid crystal full-color display whose demand has been increasing in recent years.

  When used as a backlight of such a full color display, it is used as a white light source. In order to obtain white light with an organic electroluminescence element, a method of adjusting the light emitting material in one element and obtaining white color by mixing, multicolored light emitting pixels, for example, blue, green, and red, are applied simultaneously to emit light. And a method of obtaining a white color by color mixing and a method of obtaining a white color using a color conversion dye (for example, a combination of a blue light-emitting material and a color conversion fluorescent dye).

  However, in view of various demands required for backlights such as low cost, high productivity, and simple driving method, a method of adjusting the light emitting material in one element and obtaining white color by mixing is effective for this application. In recent years, research and development has been actively promoted.

  In this method, in order to obtain white light, more specifically, a method of obtaining a white color by mixing two colors of light emitting materials having complementary colors in the element, for example, a blue light emitting material and a yellow light emitting material, and blue There is a method of obtaining a white color by mixing light emitting materials of three colors of green and red.

  For example, it has been reported that white organic electroluminescence elements can be obtained by doping high-efficiency phosphors of blue, green, and red as light emitting materials (see Patent Documents 1 and 2).

  In addition, since a brighter organic electroluminescent element can be obtained, development of phosphorescent materials has been promoted in recent years (for example, see Non-Patent Documents 1 and 2 and Patent Document 3). This is because the emission from the conventional phosphor is emission from the excited singlet, and the generation ratio of the singlet exciton and triplet exciton is 1: 3, so the generation probability of the luminescent excited species is 25%. On the other hand, in the case of a phosphorescent material using light emission from an excited triplet, the upper limit of internal quantum efficiency is 100% due to the exciton generation ratio and internal conversion from singlet excitons to triplet excitons. Therefore, in principle, the luminous efficiency is up to four times that of a fluorescent material.

  In an organic electroluminescence device that emits white light, the layers having different emission colors are not separated from each other, but two or more colors of light emitting materials coexist in one layer, and the efficiency is relatively high from a light emitting dopant with high emission energy. There is a method of emitting two colors by energy transfer to a low dopant. This method is one of the effective methods for obtaining a white light emitting element because the number of organic layers can be reduced and the amount of light emitting material used can be reduced.

  However, when this method is used, a change in color balance with respect to the drive current is large, which causes a problem in practical use.

  The present invention relates to a technique for improving the stability of color balance in an organic electroluminescence device having such a light emitting layer configuration, and the low energy light emitting side in the coexisting layer is disposed on the anode side of the two color coexisting light emitting layer. It is related with the technique which improves the stability of color balance, without impairing efficiency by providing the thin film layer containing the luminescent dopant of this.

  Patent Document 4 states that “at least one light emitting layer contains at least two kinds of light emitting materials, at least one kind is a phosphorescent light emitting material, and the light emitting material emitting the shortest wavelength has the shortest excitation lifetime. In the present invention, there is no description regarding the color balance versus driving current stability, which is a problem in the present invention, and there is no description regarding the auxiliary light-emitting layer which is an essential component of the present invention. This is different from the present invention and does not predict the effects of the present invention.

Patent Document 5 states that “the organic light-emitting layer adjacent to one specific organic light-emitting layer is doped with an auxiliary light-emitting material that emits light of a color similar to the light emission color of the basic light-emitting material in the specific light-emitting layer. An organic electroluminescence device characterized by the above is disclosed. However, in the present invention, the main light emitting layer is a light emitting layer containing the two kinds of light emitting materials, and an auxiliary light emitting layer is additionally provided. Therefore, the configuration of the present invention is completely different from the patent. The patent is for a substantially fluorescent light-emitting material, which is different from the present invention.
JP-A-6-207170 JP 2004-235168 A US Pat. No. 6,097,147 JP 2004-14155 A JP 2004-6165 A M.M. A. Baldo et al. , Nature, 395, 151-154 (1998) M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000)

  The present invention has been made in view of the above-described problems, and has an object of improving chromaticity versus driving current stability in an organic electroluminescence element that has a plurality of light emitting materials having different emission wavelengths, and emits white light in particular. An excellent element, and a display device and an illumination device using the element are provided.

  The above object of the present invention is achieved by the following means.

1. In an organic electroluminescent device having at least one main light emitting layer containing a host compound and a phosphorescent material between an anode and a cathode, and an auxiliary light emitting layer containing a host compound and a phosphorescent material , the main light emitting layer emits light maximum energy contain different two or more phosphorescent materials or 0.2 eV, and in phosphorescent light emitting material, which contains a large phosphorescent material of the most luminous energy at the maximum molar concentration, and the auxiliary light-emitting layer present between the main light-emitting layer and the anode, and the auxiliary light-emitting layer, among the phosphorescent material main emitting layer contains the lowest than large phosphorescent material emitting energy emission energy of the phosphorescent material As a main light emitting material, and the main light emitting layer and the auxiliary light emitting layer contain at least one common host compound, and a film of the main light emitting layer The organic electroluminescent device but characterized in that it is a 2 to 20 nm.

2. Wherein in all of the phosphorescent materials contained in the main light-emitting layer containing two or more phosphorescent materials, according to the 1-emitting quantum efficiency of most emission maximum short phosphorescent material wavelength is equal to or highest Organic electroluminescence element.

3. 3. The organic electroluminescence device according to 1 or 2 , wherein the auxiliary light emitting layer is thinner than the main light emitting layer and has a thickness of 1 nm to 5 nm.

4). Display device characterized by using an organic electroluminescent device according to any one of the 1-3.

5. Lighting device characterized by use of an organic electroluminescent device according to any one of the 1-3.

  With the above configuration of the present invention, an organic electroluminescence element having a plurality of light emitting materials having different emission wavelengths, and particularly excellent in chromaticity versus driving current stability, a display device and an illumination using the same An apparatus can be provided.

  The organic electroluminescent device of the present invention is an organic electroluminescent device having at least one main light emitting layer and an auxiliary light emitting layer between an anode and a cathode, wherein the main light emitting layer has two or more kinds different in emission maximum energy by 0.2 eV or more. And the phosphorescent material having the largest emission energy is contained in the maximum molar concentration, and the auxiliary light emitting layer is disposed between the main light emitting layer and the anode, or the phosphorescent light emitting material. It is characterized in that it is present between the main light emitting layer and the cathode and contains a light emitting material on the low energy side in the main light emitting layer as the main light emitting material. The main light emitting layer and the auxiliary light emitting layer may be directly adjacent to each other or indirectly adjacent to each other through a non-light emitting intermediate layer.

  Here, the “maximum light emission energy” means light energy corresponding to the maximum wavelength among the wavelengths of light emitted by the phosphorescent material.

  Hereinafter, the detailed description of the present invention and each component according to the present invention will be sequentially described.

《Organic electroluminescence device》
The organic electroluminescence element of the present invention will be described.

<Light emission and front brightness>
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). It is determined by the color when the result measured with CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

Preferred chromaticity as a white light emitting element is X = 0.33 ± 0.07 and Y = 0.33 ± 0.07 in the CIE1931 color system, and more preferably, the element is a condensing member such as a condensing sheet. The chromaticity in the CIE 1931 color system at 1000 cd / m ² without X is in the region of X = 0.33 ± 0.07 and Y = 0.33 ± 0.07.

  Next, although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer unit / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer unit / hole blocking Layer / electron transport layer / cathode (iv) anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emission Layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode Here, when the light emitting layer unit has a plurality of light emitting layers, a non-light emitting intermediate layer is provided between the light emitting layers. Preferably it is.

<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 configuration of the light emitting layer according to the present invention is not particularly limited as long as it satisfies the requirements of the present invention described in the above claims. Also, when the number of light emitting layers is more than three, the same There may be a plurality of layers having an emission spectrum or an emission maximum wavelength.

  The total thickness of the light emitting layer is not particularly limited, but from the viewpoint of improving the uniformity of the film, preventing unnecessary application of a high voltage during light emission, and improving the stability of the emission color with respect to the drive current. It is preferable to adjust to the range of 2 nm-5 micrometers, More preferably, it adjusts to the range of 2 nm-200 nm.

  The film thickness of each light emitting layer is preferably adjusted to a range of 2 nm to 100 nm, and more preferably adjusted to a range of 2 nm to 20 nm.

  For the production of the light-emitting layer, a light-emitting dopant or a host compound, which will be described later, is formed and formed by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, or an ink-jet method. it can.

  In the present invention, at least one light emitting layer has two or more kinds of phosphorescent light emitting materials having different light emission maximum energy of 0.2 eV or more, and phosphorescence having the largest light emitting energy among the phosphorescent light emitting materials contained in the layers. The light emitting material has a maximum molar concentration, and the light emitting material on the low energy side of the light emitting layer is mainly emitted through a region adjacent to the light emitting layer or a non-light emitting intermediate layer between the light emitting layer and the cathode. An auxiliary light emitting layer contained as a material is provided.

  The auxiliary light emitting layer in the present invention includes a phosphorescent light emitting material having the longest emission maximum wavelength in the light emitting layer having the two or more types of phosphorescent light emitting materials, and the content of the light emitting material is the two or more types of phosphorescent light emitting materials. Is a light emitting layer that is 1/5 or less of the content of the phosphorescent material having the longest light emission maximum wavelength in the main light emitting layer (also referred to as “main photosensitive layer”).

  The auxiliary light emitting layer is provided on the cathode side or the anode side adjacent to the light emitting layer having the two or more types of phosphorescent light emitting materials or through a non-light emitting intermediate layer. The cathode side or the anode side can be appropriately selected depending on the light emitting position in the light emitting layer having the two or more kinds of phosphorescent light emitting materials as the main light emitting layer.

  The thickness of the auxiliary light emitting layer is smaller than that of the main light emitting layer, and is preferably 1 nm or more and 5 nm or less. If it is thicker than 5 nm, or thicker than the main light emitting layer, an increase in driving voltage cannot be ignored, which is not preferable. In addition, the effect of stabilizing the color balance is reduced.

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

(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. More preferably, the phosphorescence quantum yield is less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

  As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary luminescent colors can be obtained.

  As a host compound concerning this invention, the compound represented by following General formula (1) is mentioned as an example of the compound used preferably. Moreover, the said compound is preferably used also for the adjacent layer (for example, hole-blocking layer etc.) of a light emitting layer.

  An organic EL device comprising a compound represented by the following general formula (1) in a light emitting layer or an adjacent layer of the light emitting layer and using the phosphorescent emitter according to the present invention for the light emitting layer has high luminous efficiency, A high-luminance element can be obtained.

  << Compound Represented by Formula (1) >>

In the formula, Z ₁ represents an aromatic heterocyclic ring which may have a substituent, Z ₂ represents an aromatic heterocyclic ring or an aromatic hydrocarbon ring which may each have a substituent, and Z ₃ represents a divalent linking group or a simple bond. R ₁₀₁ represents a hydrogen atom or a substituent.

In the general formula (1), examples of the aromatic heterocycle represented by Z ₁ and Z ₂ include a furan ring, a thiophene ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, a benzimidazole ring, Diazole 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, carboline ring And a ring in which the carbon atom of the hydrocarbon ring is further substituted with a nitrogen atom. Furthermore, the aromatic heterocyclic ring may have a substituent represented by R ₁₀₁ described later.

In the general formula (1), examples of the aromatic hydrocarbon ring represented by Z ₂ include 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, pyranthrene ring, anthraanthrene ring and the like. Furthermore, the aromatic hydrocarbon ring may have a substituent represented by R ₁₀₁ described later.

In the general formula (1), examples of the substituent represented by R ₁₀₁ include an alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group). 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.) Etc.), aryl groups (eg phenyl group, naphthyl group etc.), aromatic heterocyclic groups (eg furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group) , Thiazolyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (eg Pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cyclo An alkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), an aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), an 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.), alkoxycarbonyl group (eg methyl Xycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, 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, cyclohexane) A silcarbonyl group, an octylcarbonyl group, a 2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a phenylcarbonyl group, a naphthylcarbonyl group, a pyridylcarbonyl group, etc.), an acyloxy group (for example, an acetyloxy group, an ethylcarbonyloxy group, a butylcarbonyloxy group) Octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonyl) Amino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylca Carbonylamino 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, methylsulfinyl group, ethylsulfide group, etc.) Sulfonyl 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, ethyl group) Amino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridyla Group), halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon groups (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), And cyano group, nitro group, hydroxy 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 addition, a plurality of these substituents may be bonded to each other to form a ring.
Preferred substituents are an alkyl group, a cycloalkyl group, a fluorinated hydrocarbon group, an aryl group, and an aromatic heterocyclic group.

  As the divalent linking group, in addition to hydrocarbon groups such as alkylene, alkenylene, alkynylene, and arylene, those containing a hetero atom may be used, and a thiophene-2,5-diyl group, pyrazine-2, It may be a divalent linking group derived from a compound having an aromatic heterocyclic ring (also called a heteroaromatic compound) such as a 3-diyl group, or may be a chalcogen atom such as oxygen or sulfur. . Further, it may be a group such as an alkylimino group, a dialkylsilanediyl group, or a diarylgermandiyl group that connects and connects heteroatoms.

  A mere bond is a bond that directly bonds the connecting substituents together.

In the present invention, Z _{1 in the} general formula (1) is preferably a 6-membered ring. Thereby, luminous efficiency can be made higher. Furthermore, the lifetime can be further increased.
In the present invention, it is preferable that the Z ₂ in the general formula (1) is a 6-membered ring. Thereby, luminous efficiency can be made higher. Furthermore, the lifetime can be further increased.

Furthermore, it is preferable that Z ₁ and Z _{2 in} the general formula (1) are both 6-membered rings because the luminous efficiency can be further increased. Furthermore, it is preferable because the lifetime can be further increased.

  Hereinafter, although the specific example of a compound represented by General formula (1) based on this invention is shown, this invention is not limited to these.

  The light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (deposition polymerization property). (Light emitting host).

  As the known host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable.

Specific examples of known host compounds include compounds described in the following documents. For example, Japanese Patent Application Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette, 2002-338579 gazette. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. 2002-302516, 2002-305083, 2002-305084, 2002-308837, and the like.
In the present invention, a compound having a glass transition point of 90 ° C. or higher is preferable, and a compound of 100 ° C. or higher is more preferable.

(Glass transition point (Tg))
Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

(Luminescent dopant)
As the light-emitting dopant according to the present invention, a fluorescent compound or a phosphorescent emitter (also referred to as a phosphorescent compound or a phosphorescent compound) can be used. From the viewpoint of obtaining an organic EL element with higher luminous efficiency. The light-emitting dopant used in the light-emitting layer or light-emitting unit of the organic EL device of the present invention (sometimes simply referred to as a light-emitting material) contains the above-mentioned host compound and at the same time contains a phosphorescent emitter. preferable.

(Phosphorescent emitter)
The phosphorescent material according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.) and has a phosphorescence quantum yield of 25. Although it is defined as a compound of 0.01 or more at ° C., a preferable 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 Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence emitter according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

  There are two types of light emission of phosphorescent emitters in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent emitter. Energy transfer type to obtain light emission from the phosphorescent emitter, and another is a carrier in which the phosphorescent emitter becomes a carrier trap and recombination of carriers occurs on the phosphorescent emitter to obtain light emission from the phosphorescent emitter. Although it is a trap type, in any case, it is a condition that the excited state energy of the phosphorescent emitter is lower than the excited state energy of the host compound.

  The phosphorescent luminescent material can be appropriately selected from known materials used for the light emitting layer of the organic EL device.

  The phosphorescent emitter according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex compound). ), Rare earth complexes, and most preferred are iridium compounds.

  Specific examples of the compound used as the phosphorescent emitter are shown below, but the present invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

(Fluorescent light emitter)
Representative examples of fluorescent emitters (also referred to as “fluorescent dopants”) include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamines. And dyes based on dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, and rare earth complex phosphors.

  In addition, conventionally known dopants can also be used in the present invention. For example, WO 00/70655 pamphlet, JP 2002-280178 A, JP 2001-181616 A, JP 2002-280179 A, JP 2001-181617 A, JP 2002-280180 A, JP 2001-247859 A, JP 2002-299060 A, JP 2001-313178 A, JP 2002-302671 A, JP JP 2001-345183 A, JP 2002-324679 A, WO 02/15645 Pamphlet, JP 2002-332291 A, JP 2002-50484 A, JP 2002-332292 A, JP 2002-2002 A. -83684 publication, special table 2002 JP 40572, JP 2002-117978, JP 2002-338588, JP 2002-170684, JP 2002-352960, WO 01/93642, JP 2002-50483. JP, JP-A No. 2002-1000047, JP-A No. 2002-173684, JP-A No. 2002-359082, JP-A No. 2002-175854, JP-A No. 2002-363552, JP-A No. 2002-184582 JP, 2003-7469, JP 2002-525808, JP 2003-7471, JP 2002-525833, JP 2003-31366, JP 2002-226495, JP JP 2002-234894, JP No. 002-235076, JP 2002-241751, JP 2001-319779, JP 2001-319780, JP 2002-62824, JP 2002-1000047, JP 2002 No. 203679, JP-A No. 2002-343572, JP-A No. 2002-203678, and the like.

<Non-light emitting intermediate layer>
A non-light emitting intermediate layer (also referred to as an undoped region or the like) used in the present invention will be described. The non-light emitting intermediate layer is a layer provided between the light emitting layers in the case of having a plurality of light emitting layers.

  The film thickness of the non-light emitting intermediate layer is preferably in the range of 1 nm to 50 nm, and more preferably in the range of 3 nm to 10 nm to suppress interaction such as energy transfer between adjacent light emitting layers, and This is preferable because a large load is not applied to the current-voltage characteristics.

  The material used for the non-light emitting intermediate layer may be the same as or different from the host compound of the light emitting layer, but may be the same as the host material of at least one of the adjacent light emitting layers. preferable.

  The non-light emitting intermediate layer may contain a compound (for example, a host compound) common to the non-light emitting layers, and each of the common host materials (here, the common host material is used) means phosphorescence. In the case where the physicochemical characteristics such as luminescence energy and glass transition point are the same or the molecular structure of the host compound is the same, etc.), the injection barrier between the light emitting layer and the non-light emitting layer is contained. Thus, even if the voltage (current) is changed, the hole and electron injection balance can be easily maintained. Furthermore, the host compound contained in each light emitting layer in the undoped light emitting layer is a major problem in the conventional organic EL device production by using a host material having the same physical characteristics or the same molecular structure. The complexity of device fabrication can also be eliminated.

  Further, in an organic EL device having a blue light-emitting layer, the host material having the excited triplet energy of the blue phosphorescent emitter is the highest, but is larger than that of the blue phosphorescent emitter. The light emitting layer and the non-light emitting intermediate layer may contain a common host material.

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.
On the other hand, in order to optimally adjust the injection balance of holes and electrons, it is also preferable that the non-light emitting intermediate layer functions as a blocking layer described later, that is, a hole blocking layer and an electron blocking layer. It is given as.

<< 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>
As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. 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 ionization potential is defined by the energy required to emit an electron at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be obtained by the following method, for example.

  (1) Keywords using Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), which is molecular orbital calculation software manufactured by Gaussian, USA. The ionization potential can be obtained as a value obtained by rounding off the second decimal place of the 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 by using a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd.
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 that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The film thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 nm to 100 nm, and more preferably 5 nm 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. For example, 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, Examples thereof include 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 two more described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 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 described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, it is preferable to use these materials because a light-emitting element with higher efficiency can be obtained.
The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5 nm-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 similarly to the hole injection layer and the hole transport layer, inorganic such as n-type-Si and n-type-SiC can be used. A semiconductor can also be used as an electron transport material.

  The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film 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 a high n property doped with impurities can also 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.

《Support base》
The support substrate (hereinafter also referred to as a substrate, a substrate, a substrate, a support, etc.) according to the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent or opaque. It may be. In the case where light is extracted from the support base side, the support base is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support base is a resin film capable of giving flexibility to the organic EL element.

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, Cycloolefin resins such as polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned. On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability measured by a method in accordance with JIS K 7129-1992 (25 ± 0.5 ° C., It is preferable that the relative humidity (90 ± 2)% RH) is a barrier film of 1 × 10 ⁻³ g / (m ² · 24 h) or less, and further measured by a method based on JIS K 7126-1987. The oxygen permeability is 1 × 10 ⁻³ ml / m ² · 24 h · atm or less, and the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is 1 × 10 ^−3. It is preferable that it is a high barrier film of g / (m ² · 24h) or less.

  As a material for forming the barrier film, any material may be used as long as it 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 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 layers made of organic materials. 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.

<Method for forming barrier film>
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma weighting. 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 base include metal plates / films such as aluminum and stainless steel, opaque resin substrates, ceramic substrates, and the like.

  The external extraction 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, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support base with an adhesive.

  The sealing member may be disposed so as to cover the display area of the organic EL element, and may be concave or flat. Moreover, 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 has a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method in accordance with JIS K 7129-1992, 1 × 10 ⁻³ g / (M ² · 24h) It is preferable that the film has a barrier property of not more than 1, and furthermore, the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ⁻³ ml / m ² · 24h ·. It is preferable that the film has a high barrier property with a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 1 × 10 ⁻³ g / (m ² · 24 h) 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 a reactive vinyl group of acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylate. be able to. Moreover, the 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 it like screen printing.

  In addition, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. it can. 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 the element such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like is used. it can. Furthermore, 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, sputtering, reactive sputtering, molecular beam epitaxy, 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 is injected in the gas phase and the liquid phase. Is preferred. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.

  Examples of the hygroscopic compound include metal oxides (eg, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (eg, 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, barium perchlorate, In particular, 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 outside the sealing film or the sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when 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. Is preferably used.

"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) that can form 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. ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. 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 nm to 1000 nm, preferably 10 nm 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, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. 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 a 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 nm 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 emission luminance is advantageously improved.

  Moreover, after producing the said metal by the film thickness of 1 nm-20 nm to a cathode, the transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material quoted by description of the anode on it, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<< 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 / hole blocking layer / electron transport layer / cathode will be described.
First, a desired electrode material, for example, a thin film made of a material for an anode is formed on a suitable support base 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. To do. 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 for thinning the organic compound thin film, there are a vapor deposition method and a wet process (spin coating method, casting method, ink jet method, printing method) as described above, but it is easy to obtain a uniform film and a pinhole. From the point of being difficult to form, a vacuum deposition method, a spin coating method, an ink jet method, and a printing method are particularly preferable. Further, different film forming methods may be applied for each layer. 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, a vapor deposition rate of 0. It is desirable to select appropriately within a range of 01 nm / second to 50 nm / second, a substrate temperature of 50 ° C. to 300 ° C., and a film thickness of 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 element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, 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.

  An organic electroluminescence element emits light inside a layer having a higher refractive index than air (refractive index of about 1.6 to 2.1), and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said that there is no. 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 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 direction of the side surface of the device.

  As a technique 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 (for example, US Pat. No. 4,774,435). A method for improving efficiency by providing a substrate with a light condensing property (for example, JP-A-63-314795). A method of forming a reflective surface on the side surface of the element (for example, Japanese Patent Laid-Open No. 1-220394). A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between a substrate and a light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691). A method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter (for example, JP-A-2001-202827). There is a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951).

In the present invention, these methods can be used in combination with the organic electroluminescence device of the present invention, but 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, A method of forming a diffraction grating between any layers of the transparent 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 low refractive index medium 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. Furthermore, it is preferable that it is 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 that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. 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 or second-order diffraction. The light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light 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. 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 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 gratings is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

<Condenser sheet>
The organic electroluminescence device of the present invention is processed to provide a structure on the microlens array, for example, on the light extraction side of the support base (substrate), or in combination with a so-called condensing sheet, for example, Condensing light in the front direction with respect to the element light emitting surface can increase the luminance in a specific direction.
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 μm 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, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a substrate may be formed with a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or the apex angle is rounded and the pitch is changed randomly. Other shapes may also 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.

<Application>
The organic electroluminescence element of the present invention can be used as a display device, a display, or various light sources. Examples of light sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, and light sources for optical sensors. Although it is not limited to this, it can be effectively used especially as a backlight of a liquid crystal display device combined with a color filter and a light source for illumination.

  When used as a backlight of a display in combination with a color filter, it is preferably used in combination with the light collecting sheet in order to further increase the luminance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

<< Production of Organic EL Element 1-1 >>
After patterning a support substrate in which 120 nm of ITO (indium tin oxide) was formed on a glass substrate having a thickness of 30 mm × 30 mm and a thickness of 0.7 mm as an anode, the transparent support substrate to which this ITO transparent electrode was attached was isopropyl alcohol. Was subjected to ultrasonic cleaning, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.

  Each of the vapor deposition crucibles in the vacuum vapor 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.

Then, after reducing the vacuum to 4 × 10 ⁻⁴ Pa, the vapor deposition crucible containing m-MTDATA was energized and heated, and deposited on the transparent support substrate at a deposition rate of 0.1 nm / second. A hole injection layer was provided. Next, α-NPD was deposited in the same manner to provide a 30 nm hole transport layer. Subsequently, each light emitting layer and its intermediate | middle layer were provided in the following procedures.

  CBP and compounds (A-1) and (A-2) were co-deposited at a deposition rate of 0.1 nm / second so that (A-1) was 8% by mass and (A-2) was 1% by mass. A 10 nm phosphorescent emitting layer was formed.

  The molar concentration ratio of the compounds (A-1) and (A-2) in the layer was 7: 1. Further, the maximum energy of light emission is larger in the compound (A-1) than in (A-2).

  Next, 5 nm of BAlq was deposited at a deposition rate of 0.1 nm / second, a hole blocking layer adjacent to the cathode side was formed on the light emitting layer, and then the deposition rate of BCP and CsF was 80:20 in a film thickness ratio. An electron transport layer was provided by depositing 40 nm at 0.1 nm / second.

  Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-1 was produced.

<< Production of Organic Electroluminescence Element 1-2 >>
In the same manner as in the organic electroluminescence device 1-1, after providing the hole transport layer, the deposition rate of CBP and the compound (A-2) was adjusted so that the concentration of (A-2) was 0.3% by mass. Co-evaporation was performed at 0.1 nm / second, and a 3 nm co-evaporation layer was provided. Next, CBP and compounds (A-1) and (A-2) were combined at a deposition rate of 0.1 nm / second so that (A-1) was 8% by mass and (A-2) was 1% by mass. Evaporation was performed to form a 10 nm phosphorescent light emitting layer.

  The molar concentration ratio of the compounds (A-1) and (A-2) in the 10 nm light emitting layer was 7: 1. The content of the compound (A-2) contained in the 3 nm light emitting layer was about 10% of the compound (A-2) contained in the 10 nm light emitting layer.

  Next, 5 nm of BAlq was deposited at a deposition rate of 0.1 nm / second, a hole blocking layer adjacent to the cathode side was formed on the light emitting layer, and then the deposition rate of BCP and CsF was 80:20 in a film thickness ratio. An electron transport layer was provided by depositing 40 nm at 0.1 nm / second.

  Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-2 was produced.

<< Preparation of Organic Electroluminescence Element 1-3 >>
In the same manner as in the organic electroluminescence device 1-2, after providing the hole transport layer, the deposition rate of CBP and the compound (A-2) was adjusted so that the concentration of (A-2) was 0.2% by mass. Co-evaporation was performed at 0.1 nm / second to provide a 7 nm co-evaporation layer. Next, CBP and compounds (A-1) and (A-2) were combined at a deposition rate of 0.1 nm / second so that (A-1) was 8% by mass and (A-2) was 1% by mass. Evaporation was performed to form a 10 nm phosphorescent light emitting layer.

  The molar concentration ratio of the compounds (A-1) and (A-2) in the 10 nm light emitting layer was 7: 1. The content of the compound (A-2) contained in the 7 nm light emitting layer was about 15% of the compound (A-2) contained in the 10 nm light emitting layer.

Next, 5 nm of BAlq was deposited at a deposition rate of 0.1 nm / second, a hole blocking layer adjacent to the cathode side was formed on the light emitting layer, and then the deposition rate of BCP and CsF was 80:20 in a film thickness ratio. An electron transport layer was provided by depositing 40 nm at 0.1 nm / second.
Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-3 was produced.

<< Preparation of Organic Electroluminescence Element 1-4 >>
In the same manner as in the organic electroluminescence device 1-2, after providing the hole injection layer, the compound (A-3) was deposited at a deposition rate of 0.1 nm / second to form a 30 nm hole transport layer. Next, CBP and compounds (A-1) and (A-2) were combined at a deposition rate of 0.1 nm / second so that (A-1) was 8% by mass and (A-2) was 1% by mass. Evaporation was performed to form a 10 nm phosphorescent light emitting layer.

  The molar concentration ratio of the compounds (A-1) and (A-2) in the 10 nm light emitting layer was 7: 1. The content of the compound (A-2) contained in the 3 nm light emitting layer was about 12% of the compound (A-2) contained in the 10 nm light emitting layer.

  Next, CBP and the compound (A-2) were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of (A-2) was 0.4% by mass to provide a 3 nm co-evaporated layer.

Next, 5 nm of BAlq was deposited at a deposition rate of 0.1 nm / second, a hole blocking layer adjacent to the cathode side was formed on the light emitting layer, and then the deposition rate of BCP and CsF was 80:20 in a film thickness ratio. An electron transport layer was provided by depositing 40 nm at 0.1 nm / second.
Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-4 was produced.

<Evaluation of element sealing treatment, front luminance, and chromaticity>
Cover each non-light-emitting surface of the organic electroluminescent elements 1-1 to 1-4 obtained in the above-described embodiments with a glass case (in the sealing operation with the glass cover, the organic electroluminescent element is brought into contact with the atmosphere. A glove box under nitrogen atmosphere (performed in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or more) After the illumination device as shown in FIGS. The front luminance and chromaticity of each element were evaluated using (Konica Minolta Sensing Corp.).

Stability of color balance in the present invention, the chromaticity coordinate values in the CIE1931 color system in the front luminance 300 cd / m ² and _{^{5000cd / m 2 (x 1,}} y 1), measured (x _2, y ₂₎ , Defined by the following formula.

ΔE = √ ((x ₁ −x ₂ ) ² + (y ₁ −y ₂ ) ² )

  Table 1 shows the results. From Table 1, it is clear that the organic electroluminescence device having the auxiliary light emitting layer of the present invention has excellent performance in terms of chromaticity stability. It is also shown that the auxiliary light emitting layer preferably has a thickness of 5 nm or less.

Schematic of lighting device Cross section of the lighting device

Explanation of symbols

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 (5)

In an organic electroluminescent device having at least one main light emitting layer containing a host compound and a phosphorescent material between an anode and a cathode, and an auxiliary light emitting layer containing a host compound and a phosphorescent material , the main light emitting layer emits light maximum energy contain different two or more phosphorescent materials or 0.2 eV, and in phosphorescent light emitting material, which contains a large phosphorescent material of the most luminous energy at the maximum molar concentration, and the auxiliary light-emitting layer present between the main light-emitting layer and the anode, and the auxiliary light-emitting layer, among the phosphorescent material main emitting layer contains the lowest than large phosphorescent material emitting energy emission energy of the phosphorescent material As a main light emitting material, and the main light emitting layer and the auxiliary light emitting layer contain at least one common host compound, and a film of the main light emitting layer The organic electroluminescent device but characterized in that it is a 2 to 20 nm. Wherein in all phosphorescent material contained in the main light-emitting layer containing two or more phosphorescent materials, to claim 1 where the light emitting quantum efficiency of most emission maximum short phosphorescent material wavelength and wherein the highest The organic electroluminescent element of description. The organic electroluminescent device according to claim 1 or 2, wherein the thickness of the auxiliary light emitting layer is thinner than the main light emitting layer, and is 1nm or more 5nm below. Display device characterized by using an organic electroluminescent device according to any one of claims 1-3. Lighting device characterized by use of an organic electroluminescent device according to any one of claims 1-3.

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