JP2013058647A - White organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white organic EL element consisting of a single luminescent layer which, while retaining the chromatic purity of white color, maintains the average density of dopants to realize life improvement, thereby offering an organic EL element which excels in power efficiency.SOLUTION: In a white organic EL element having a plurality of organic layers including a hole transport layer, a luminescent layer and an electron transport layer between an anode and a cathode, the luminescent layer contains three or more kinds of dopants differing in maximum luminescent wavelength. More specifically, assuming a B dopant of 430 to 480 nm in maximum luminescent peak wavelength, a G dopant of 500 to 540 nm and an R dopant of 520 to 560 nm, the luminescent layer contains at least three dopants selected from each of these three categories. The B dopant in the luminescent layer is a phosphorescent dopant, which is a phosphorescent luminescent material whose phosphorescence life is less than 1.4 μsec and whose phosphorescence quantum yield is 70% or more. An R dopant/B dopant ratio is 5 to 20 wt%, and a ratio of the B dopant to the entire luminescent layer is 10 to 30 wt%.

Description

  The present invention relates to a white organic electroluminescence device, and more particularly, to a white organic electroluminescence device having both white color purity and a long lifetime.

In recent years, organic electroluminescence elements using organic substances (hereinafter, abbreviated as “organic EL elements” where appropriate) are promising for use as solid light-emitting inexpensive large-area full-color display elements and writing light source arrays. Research and development is actively underway.
The organic EL element is composed of an organic functional layer (single layer portion or multilayer portion) having a thickness of only about 0.1 μm containing an organic light emitting material between a pair of anode and cathode formed on a film. It is a thin film type all solid state device. When a relatively low voltage of about 2 to 20 V is applied to such an organic EL element, electrons are injected from the cathode and holes are injected from the anode into the organic compound layer. It is known that emission is obtained by releasing energy as light when the electrons and holes recombine in the light emitting layer and the energy level returns from the conduction band to the valence band. This technology is expected as a flat display and lighting.
In addition, recently discovered organic EL devices that use phosphorescence can realize a luminous efficiency that is approximately four times that of previous methods that use fluorescence. Research and development of organic functional layer layers and electrodes are conducted all over the world. In particular, as one of the measures to prevent global warming, application to lighting fixtures that occupy much of human energy consumption has begun to be studied. There are many attempts to reduce costs.
When manufacturing a white organic EL element, there are mainly a configuration in which the light emitting layer is a single layer that emits white light, or a configuration in which two or more layers having different emission colors are combined. When this light emitting layer is made into a plurality of layers, white color can be obtained by matching the position where holes and electrons recombine with the interface of the layer, but it is not easy to control the recombination position. For this reason, a structure in which the light emitting layer is formed as a single layer, in which the color variation is small even if the recombination position is slightly moved, has been studied.
In the configuration in which the light emitting layer is formed as a single layer, a plurality of dopants having different emission colors exist in the same layer. In general, due to the relationship between the HOMO and LUMO levels, long wavelength dopants can easily move holes and electrons from low wavelength dopants. To make the emission color white, long wavelength dopants, mainly red The amount of R dopant that develops color is required to be very small. The amount of the B dopant that develops blue color as the short wavelength dopant and the R dopant is about 1% or less as the weight ratio of R dopant / B dopant, and the concentration of the B dopant at this time is adjusted to less than 10%. Yes. On the other hand, it is known that such a low amount of dopant deteriorates the lifetime. There is a demand for a configuration that retains white color purity, adapts an appropriate amount of dopant, and does not lose life.

As a method for maintaining the white color purity, Patent Document 1 proposes shortening the excitation lifetime of the short-wavelength dopant, but there is no description about the lifetime, and it is efficient by making the short-wavelength dopant fluorescent. It is thought that it is lost.
Further, as a method for improving the deterioration of the lifetime, in Patent Document 2, the outflow of holes and electrons is suppressed by changing the concentration of the dopant in the thickness direction in the light emitting layer. There is no description about the color purity of white.

JP 2004-014155 A JP 2005-038672 A

  Accordingly, an object of the present invention is to achieve a lifetime improvement by maintaining an average concentration of the dopant while maintaining the white color purity in a white organic EL element having a single light emitting layer, thereby improving the power efficiency. It is to provide an excellent organic EL element.

According to the invention of claim 1, in the white organic electroluminescent element sandwiched between the anode and the cathode, and having a plurality of organic layers including a hole transport layer, a light emitting layer, and an electron transport layer,
The light emitting layer includes three or more kinds of dopants having different maximum emission wavelengths, and a B emission dopant having a maximum emission peak wavelength of 430 to 480 nm, a G dopant of 500 to 540 nm, and an R dopant of 520 to 560 nm. A light emitting layer comprising at least three dopants each selected from a classification;
The B dopant in the light emitting layer is a phosphorescent dopant, a phosphorescent material having a phosphorescence lifetime of less than 1.4 μsec and a phosphorescence quantum yield of 70% or more,
The ratio of R dopant / B dopant is 5 to 20 wt%,
A white organic electroluminescence device is provided in which the ratio of the B dopant to the entire light emitting layer is 10 to 30 wt%.

（環Ａ及び環Ｂは５員または６員の芳香族炭化水素環または芳香族複素環を表し、Ａｒは芳香族炭化水素環、芳香族複素環、非芳香族炭化水素環または非芳香族複素環を表す。
Ｒ_１及びＲ_２はそれぞれ独立に、水素原子、ハロゲン原子、シアノ基、アルキル基、アルケニル基、アルキニル基、アルコキシ基、アミノ基、シリル基、アリールアルキル基、アリール基、ヘテロアリール基、非芳香族炭化水素環基または非芳香族複素環基を表し、さらに置換基を有していてもよい。
Ｒａ、Ｒｂ及びＲｃはそれぞれ独立に、水素原子、ハロゲン原子、シアノ基、アルキル基、アルケニル基、アルキニル基、アルコキシ基、アミノ基、シリル基、アリールアルキル基、アリール基、ヘテロアリール基、非芳香族炭化水素環基または非芳香族複素環基を表し、さらに置換基を有していてもよい。
ｎａ及びｎｃは１または２を表し、ｎｂは１〜４の整数を表す。
Ｌ’はMに配位したモノアニオン性の二座配位子のうちの１つまたは複数であり、Mは原子番号４０以上且つ元素周期表における８〜１０族の遷移金属原子を表し、ｍ’は０〜２の整数を表し、ｎ’は少なくとも１であり、ｍ’＋ｎ’は２または３である。） According to invention of Claim 2, the said B dopant consists of a structure of General formula (1), The white organic electroluminescent element of Claim 1 characterized by the above-mentioned is provided.

(Ring A and Ring B represent a 5- or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring, and Ar represents an aromatic hydrocarbon ring, aromatic heterocyclic ring, non-aromatic hydrocarbon ring or non-aromatic heterocyclic ring. Represents a ring.
R ₁ and R ₂ are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
Ra, Rb and Rc are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
na and nc represent 1 or 2, and nb represents an integer of 1 to 4.
L ′ is one or more of monoanionic bidentate ligands coordinated to M, M represents a transition metal atom having an atomic number of 40 or more and a group 8 to 10 in the periodic table, m 'Represents an integer of 0 to 2, n' is at least 1, and m '+ n' is 2 or 3. )

  According to the invention of claim 3, the R dopant in the light emitting layer has a high concentration in the vicinity of the hole transport layer and a low concentration in the vicinity of the electron transport layer. A white organic electroluminescence device is provided.

  According to the invention of claim 4, the ratio of the R dopant / B dopant is 10 to 50 wt% in the high concentration portion of the R dopant and 0 to 5 wt% in the low concentration portion. The white organic electroluminescent element of 3 is provided.

  According to invention of Claim 5, the said light emitting layer is produced with a wet process, The white organic electroluminescent element as described in any one of Claims 1-4 characterized by the above-mentioned is provided.

  According to invention of Claim 6, the said light emitting layer is produced by coating twice, The white organic electroluminescent element as described in any one of Claims 1-5 characterized by the above-mentioned is provided.

  According to the present invention, in a white organic EL device having a single light emitting layer, the lifetime is improved by maintaining the average concentration of the dopant while maintaining the white color purity, and the power efficiency is excellent. An organic EL element can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.
As a result of intensive studies to achieve the above object, the present inventors have found that a phosphorescent dopant exhibiting the shortest emission wavelength among the light emitting layer is dispersed in the light emitting host material of the light emitting layer. By using a phosphorescent material that has a phosphorescence lifetime at room temperature of less than 1.4 μsec and a phosphorescence quantum yield of 70% or more in the state of the film, the ratio of R dopant / B dopant that can extend the lifetime is It has been found that at 5 to 20 wt%, a long life is achieved while maintaining the white color purity.
Furthermore, it has been found that the lifetime is improved by combining the phosphorescent material of the general formula (1). This is because the triplet exciton lifetime is shortened and the probability of returning to the ground state as it is before transferring energy from the excited B dopant to the G dopant or R dopant is increased. It is difficult to transfer energy by maintaining a reasonable distance from other dopants in the film by introducing a specific substituent on the outer periphery of the molecule, for example, rather than the effects of The details are unknown.

《Phosphorescent dopant》
The phosphorescent dopant compound according to the present invention is a compound in which light emission from an excited triplet is observed, specifically, 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 dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.
There are two types of light emission of the phosphorescent dopant in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the luminescent host compound, and this energy is used as the phosphorescent dopant. The energy transfer type in which light emission from the phosphorescent dopant is obtained by moving to the other, and the other is that the phosphorescent dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant compound occurs. In any case, the excited state energy of the phosphorescent dopant is required to be lower than the excited state energy of the host compound.
The phosphorescent dopant of the present invention has a phosphorescence lifetime at room temperature (25 ° C.) of less than 1.4 μsec and a phosphorescence quantum yield of 70% or more in the state of a film dispersed in the light emitting host material of the light emitting layer.
Phosphorescence quantum yield is not good after co-evaporating on quartz glass at a thickness of 40 nm with a ratio of luminescent host: phosphorescent dopant = 9: 1 to form a film in which the phosphorescent dopant is dispersed in the luminescent host material. It can be measured using a film sealed in an active gas atmosphere.
The phosphorescence lifetime is obtained by irradiating a nitrogen laser beam having an excitation wavelength of 337 nm at room temperature with a luminescence lifetime measurement apparatus manufactured by Hamamatsu Photonics, using the above film in which a phosphorescent dopant is dispersed in a light emitting host material. It was measured by the decay time of the emission intensity after the excitation pulse ended.
When the initial emission intensity is I0, the emission intensity I after t seconds is defined by the following equation using the emission lifetime τ.
I = I0 exp (-t / τ)
The phosphorescence dopant used in the present invention had a phosphorescence lifetime of less than 1.4 μsec, which was a short lifetime among phosphorescent materials.

環Ａ及び環Ｂは５員または６員の芳香族炭化水素環または芳香族複素環を表し、Ａｒは芳香族炭化水素環、芳香族複素環、非芳香族炭化水素環または非芳香族複素環を表す。好ましくは、Ａｒは芳香族炭化水素環または芳香族複素環であり、より好ましくは芳香族炭化水素環であり、さらに好ましくはベンゼン環である。
Ｒ_１及びＲ_２はそれぞれ独立に、水素原子、ハロゲン原子、シアノ基、アルキル基、アルケニル基、アルキニル基、アルコキシ基、アミノ基、シリル基、アリールアルキル基、アリール基、ヘテロアリール基、非芳香族炭化水素環基または非芳香族複素環基を表し、さらに置換基を有していてもよい。
Ｒａ、Ｒｂ及びＲｃはそれぞれ独立に、水素原子、ハロゲン原子、シアノ基、アルキル基、アルケニル基、アルキニル基、アルコキシ基、アミノ基、シリル基、アリールアルキル基、アリール基、ヘテロアリール基、非芳香族炭化水素環基または非芳香族複素環基を表し、さらに置換基を有していてもよい。
ｎａ及びｎｃは１または２を表し、ｎｂは１〜４の整数を表す。
Ｌ’はＭに配位したモノアニオン性の二座配位子のうちの１つまたは複数であり、Ｍは原子番号４０以上且つ元素周期表における８〜１０族の遷移金属原子を表し、ｍ’は０〜２の整数を表し、ｎ’は少なくとも１であり、ｍ’＋ｎ’は２または３である。 (About B dopant)
The B dopant used in the present invention will be described. B dopant is represented by the following general formula (1).

Ring A and Ring B represent a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocycle, and Ar represents an aromatic hydrocarbon ring, aromatic heterocycle, non-aromatic hydrocarbon ring or non-aromatic heterocycle Represents. Preferably, Ar is an aromatic hydrocarbon ring or an aromatic heterocyclic ring, more preferably an aromatic hydrocarbon ring, and still more preferably a benzene ring.
R ₁ and R ₂ are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
Ra, Rb and Rc are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
na and nc represent 1 or 2, and nb represents an integer of 1 to 4.
L ′ is one or more of monoanionic bidentate ligands coordinated to M, M represents a transition metal atom of atomic number 40 or more and group 8 to 10 in the periodic table, m 'Represents an integer of 0 to 2, n' is at least 1, and m '+ n' is 2 or 3.

式中、Ｒｄ’、Ｒｄ”及びＲｄ’”は水素原子または置換基を表し、Ｒｄ’、Ｒｄ”及びＲｄ’”で表される置換基としては、他の基との連結部位、水素原子または置換基を表し、ＣＲ”が複数ある場合、各々のＣＲ”は同じでも異なっていても良く、また複数のＲ”が互いに結合して環を形成してもよい。 In the general formula (1), specific examples of the monoanionic bidentate ligand coordinated to M represented by L ′ include a ligand of the following formula.

In the formula, Rd ′, Rd ″ and Rd ′ ″ represent a hydrogen atom or a substituent, and examples of the substituent represented by Rd ′, Rd ″ and Rd ′ ″ include a linking site with another group, a hydrogen atom or In the case where a plurality of CR ″ are present, each CR ″ may be the same or different, and a plurality of R ″ may be bonded to each other to form a ring.

  Examples of the substituent represented by the substituent represented by Rd ′, Rd ″ and Rd ′ ″ 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, Hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), non-aromatic carbonization Hydrogen ring group (for example, cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.), cycloalkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.) ), Tetrahydronaphthalene ring, 9,10-dihydroanthracene ring A monovalent group derived from a biphenylene ring, etc.), a non-aromatic heterocyclic group (for example, epoxy ring, aziridine ring, thiirane ring, oxetane ring, azetidine ring, thietane ring, tetrahydrofuran ring, dioxolane ring, pyrrolidine ring, pyrazolidine) Ring, imidazolidine ring, oxazolidine ring, tetrahydrothiophene ring, sulfolane ring, thiazolidine ring, ε-caprolactone ring, ε-caprolactam ring, piperidine ring, hexahydropyridazine ring, hexahydropyrimidine ring, piperazine ring, morpholine ring, tetrahydropyran Ring, 1,3-dioxane ring, 1,4-dioxane ring, trioxane ring, tetrahydrothiopyran ring, thiomorpholine ring, thiomorpholine-1,1-dioxide ring, pyranose ring, diazabicyclo [2,2,2]- Octane ring Monovalent group derived from noxazine ring, phenothiazine ring, oxanthrene ring, thioxanthene ring, phenoxathiin ring, etc.), aromatic hydrocarbon group (for example, 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, monovalent group derived from anthraanthrene ring, etc.), aromatic heterocyclic group (for example, silole ring, furan ring, thiophene ring) , Oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine Ring, pyrazine ring, triazine ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, benzimidazole ring, benzthiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, phthalazine ring, thieno Thiophene ring, carbazole ring, azacarbazole ring (representing any one or more of the carbon atoms constituting the carbazole ring replaced by a nitrogen atom), dibenzosilole ring, dibenzofuran ring, dibenzothiophene ring, benzothiophene ring, dibenzofuran Rings in which any one or more of the carbon atoms constituting the ring are replaced by nitrogen atoms, benzodifuran rings, benzodithiophene rings, acridine rings, benzoquinoline rings, phenazine rings, phenanthridine rings, phenanthroline rings, cyclers Ring, kindlin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, naphthofuran ring, naphthothiophene ring, naphthodifuran ring, naphthodithiophene ring, anthra Monovalent group derived from furan ring, anthradifuran ring, anthrathiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, dibenzocarbazole ring, indolocarbazole ring, dithienobenzene ring), alkoxy Groups (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), aryloxy groups (for example, phenoxy group, naphthyloxy group, etc.), alkylthio groups ( For example Methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl, etc.) 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, dodecylamino Nosulfonyl 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, dodecylcarbonyl group) Oxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propyl group) Bonylamino 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, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylamino Carbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, Tilureido 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) 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 or heteroarylsulfonyl group (for example, phenylsulfo group) Nyl 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 (for example, fluorine atom, chlorine atom, bromine atom, fluorocarbon group (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, penta) Fluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono group and the like.

In the general formula (1), M is an atomic number of 40 or more and a group 8-10 transition metal atom in the periodic table of the elements. Among them, Os, Ir, and Pt are preferable, and Ir is more preferable.
In the general formula (1), m ′ represents an integer of 0 to 2, n ′ is at least 1, and m ′ + n ′ represents 2 or 3. Preferably, n ′ is 3 or 2, and m ′ is 0.
The compound represented by the general formula (1) according to the present invention can be synthesized by referring to a known method described in International Publication No. 2006-121811, etc.

  The compound represented by the general formula (1) according to the present invention can be synthesized by referring to a known method described in International Publication No. 2006-121811, etc.

Although the specific example of the dopant compound which can be preferably used in this invention is given to the following, this invention is not limited to these.

(About G dopant and R dopant)
As the G dopant and the R dopant, fluorescent dopants (also referred to as fluorescent compounds) and phosphorescent dopants (also referred to as phosphorescent emitters, phosphorescent compounds, phosphorescent compounds, etc.) can be used.
Fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes , Polythiophene dyes, rare earth complex phosphors, and the like, and compounds having a high fluorescence quantum yield such as laser dyes.
It can select suitably from the well-known things used for the light emitting layer of an organic EL element, and can use it.
The phosphorescent dopant 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, a platinum compound (platinum complex compound), or a rare earth complex. Among them, the most preferable is an iridium compound.

Although the specific example of the compound used as a phosphorescent body is shown below, this invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1
711 or the like.

Hereinafter, the detail of each component of the organic EL element of this invention is demonstrated sequentially.
<< Layer structure of organic EL element >>
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

<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 not particularly limited in its configuration as long as the contained light emitting material satisfies the above requirements.
Moreover, there may be a plurality of layers having the same emission spectrum and emission maximum wavelength.
It is preferable to have a non-light emitting intermediate layer between each light emitting layer.

The total thickness of the light emitting layers in the present invention is preferably in the range of 1 to 100 nm, and more preferably 30 nm or less because a lower driving voltage can be obtained. In addition, the sum total of the film thickness of the light emitting layer as used in the field of this invention is a film thickness also including the said intermediate | middle layer, when a nonluminous intermediate | middle layer exists between light emitting layers.
The thickness of each light emitting layer is preferably adjusted to a range of 1 to 50 nm, more preferably adjusted to a range of 1 to 20 nm. There is no particular limitation on the relationship between the film thicknesses of the blue, green and red light emitting layers.

For the production of the light emitting layer, a light emitting material or a host compound, which will be described later, is formed by forming a film by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, or the like. it can.
In the present invention, a plurality of light emitting materials may be mixed in each light emitting layer, and a phosphorescent light emitting material and a fluorescent light emitting material may be mixed and used in the same light emitting layer.
In the present invention, the structure of the light-emitting layer preferably contains a host compound and a light-emitting material (also referred to as a light-emitting dopant compound) and emits light from the light-emitting material.

As the host compound contained in the light emitting layer of the organic EL device according to the present invention, a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) of less than 0.1 is preferable. More preferably, the phosphorescence quantum yield is less than 0.01. Moreover, it is preferable that the volume ratio in the layer is 50% 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 luminescent material mentioned later, and can thereby obtain arbitrary luminescent colors.

The host compound 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 (evaporation polymerizable light emitting host). )But it is good.
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. Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

  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.

Next, the light emitting material will be described.
The phosphorescent dopant described above is used as the light emitting material according to the present invention.

<< 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 azacarbazole derivative mentioned as the host compound.

In the present invention, when a plurality of light emitting layers having different light emission colors are provided, the light emitting layer having the shortest wavelength of light emission is preferably closest to the anode among all the light emitting layers. In this case, 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 anode. Furthermore, 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 host compound of the shortest wave 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) Using 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 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 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.

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, 2001-102175, J. Pat. 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.

  Also, 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), etc., and the central metals of these metal complexes are In, Mg, Cu , Ca, Sn, Ga, or Pb can also be used as an 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.

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 nm-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 is used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. 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 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, 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 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 light emission luminance is improved, which is convenient.
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.

《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. A particularly preferable support substrate 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 polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.
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 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.
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. 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, measured oxygen permeability 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 transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH is preferably intended ^{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, 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 can be injected in the gas phase and liquid phase. preferable. A vacuum is also possible. 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, and the like used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

《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 direction of the element side surface.
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 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, 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 a method for thinning the organic compound thin film, a vapor deposition method or a wet process (spin coating method, casting method, ink jet method, spray coating method, blade coating method, air knife coating method, wire bar coating method, gravure coating method, Flexographic coating method, reverse coating method, reverse roll coating method, extrusion coating method, etc.). Different film forming methods may be applied for each layer.
When employing a vapor deposition method for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within the range of 50 nm / second, substrate temperature −50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm. In the case of the vapor deposition method, it is preferable to consistently produce from the hole injection layer to the cathode by one evacuation, but it 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.
Moreover, when using a wet process, it is preferable to apply | coat in an inert gas atmosphere and a clean environment. Specifically, the cleanliness measured in accordance with JIS B9920 is a class 100 or less, the dew point temperature is −70 ° C. or less, the oxygen concentration is 1 ppm or less, and the environment is under an atmospheric pressure condition of 10 ° C. to 45 ° C. Is preferred.
In addition, the light emitting layer is particularly preferably prepared by coating twice. Specifically, a coating film having a smaller ratio of R dopant / B dopant is applied to the first coating liquid before the coating liquid having a predetermined concentration is once applied and dried by heating. Thus, it is possible to form a gradient of the ratio such that the ratio of R dopant / B dopant has a gradient. Furthermore, in order to make the interfacial mixing more uniform, it is preferable to leave it in a state containing a large amount of solvent after coating the coating solution for the second time.

After forming these organic 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 thickness of 1 μm or less, preferably in the range of 50 to 200 nm. By providing, a desired organic EL element can be obtained.
Moreover, when applying an electrode, you may melt | dissolve and apply | coat a metal, an alloy, an electroconductive compound, and these mixtures with a low melting | fusing point, a metal dispersion | distribution, etc.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.
The light emission color of the organic EL device of the present invention and the compound according to the present invention 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 the total CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.
When the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE 1931 color system at 1000 Cd / m 2 is X = It is in the region of 0.33 ± 0.07, Y = 0.33 ± 0.1.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
The compounds used in the examples described below are shown.

<< Production of organic EL element >>
A transparent support provided with this ITO transparent electrode after patterning a substrate (NA45 manufactured by NH Techno Glass Co., Ltd.) formed by depositing 100 nm of ITO (indium tin oxide) on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 200 mg of HT-30 is put in a molybdenum resistance heating boat, and 200 mg of HT-2 is put in another molybdenum resistance heating boat, and another molybdenum resistance is put. Put 200 mg of cDP-3 in a heating boat, put 200 mg of Ir-1 in another molybdenum resistance heating boat, put 200 mg of De Ir-6 in another molybdenum resistance heating boat, and put it in another resistance heating boat made of molybdenum. 200 mg of HS-24 was put, 200 mg of ET-8 was put into another molybdenum resistance heating boat, and 200 mg of ET-7 was put into another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus.
Next, the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing HT-30, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / second to inject 10 nm holes. A layer was provided.
Further, the heating boat containing HT-2 was energized and heated, and was deposited on the hole injection layer at a deposition rate of 0.1 nm / second to provide a 30 nm hole transport layer.
Further, the heating boat containing cDP-3, Ir-1, Ir-6, HS-24 was energized and heated, and the deposition rate was 0.02 nm / second, 0.0002 nm / second, 0.0002 nm / second, and the deposition rate was 0.1. At 40 nm, a 40 nm light emitting layer was provided by co-evaporation on the hole transport layer.
Further, the heating boat containing ET-8 was energized and heated, and was deposited on the light emitting layer at a deposition rate of 0.1 nm / second to provide a 10 nm hole blocking layer.
Further, the heating boat containing ET-7 was energized and heated, and was deposited on the hole blocking layer at a deposition rate of 0.1 nm / second to provide an electron transport layer of 30 nm.
Then, 0.5 nm of lithium fluoride was vapor-deposited as a cathode buffer layer, and also aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1 was produced.

<< Production of organic EL elements 2-15 >>
In the production of the organic EL device 1, the B dopant was changed to the compounds shown in Table 1, and the R / B ratio (R dopant / wt% wt ratio of B dopant) and the B / EML material ratio (B dopant / material of the entire light emitting layer). The organic EL elements 2 to 15 were produced in the same manner except that the deposition rates of the B dopant and the R dopant were adjusted so that the (wt% ratio) was the ratio shown in Table 1.

<< Production of organic EL elements 16-20 >>
In the production of the organic EL element 1, when the light emitting layer is divided into 1/3 (40/3 nm) regions in the film thickness direction, the vicinity of the HTL (hole transport layer), the center, and the vicinity of the ETL (electron transport layer) Organic EL elements 16 to 20 were produced in the same manner except that the deposition rate of the R dopant was adjusted so that the average R / B ratio in the region was the ratio described in Table 1.

<< Production of organic EL element 21 >>
A solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% by mass with pure water on the same transparent support substrate as described above. After forming a thin film by spin coating under conditions of 3000 rpm and 30 seconds, the film was dried at 200 ° C. for 1 hour to provide a first hole transport layer having a thickness of 20 nm.
The substrate was transferred to a nitrogen atmosphere, and the conditions of 1500 rpm and 30 seconds were used on the first hole transport layer using a solution of 47 mg of HT-44 and 3 mg of HT-45 dissolved in 10 ml of toluene. Below, a thin film was formed by spin coating. Ultraviolet light was irradiated at 120 ° C. for 90 seconds to carry out photopolymerization / crosslinking, followed by vacuum drying at 60 ° C. for 1 hour to form a second hole transport layer having a thickness of about 20 nm.
On this second hole transport layer, a solution of 100 mg HS-1 and 20 mg DP-5, 3 mg cGD-2, 3 mg cRD-2 dissolved in 10 ml butyl acetate was used at 800 rpm for 30 seconds. Under the conditions, a thin film was formed by spin coating. Thereafter, it was immediately vacuum-dried at 60 ° C. for 1 hour to obtain a light emitting layer having a film thickness of about 40 nm.
Next, a thin film was formed on the light emitting layer by spin coating under a condition of 1500 rpm and 30 seconds using a solution of 50 mg of ET-13 dissolved in 10 ml of hexafluoroisopropanol (HFIP). Furthermore, it vacuum-dried at 60 degreeC for 1 hour, and was set as the electron carrying layer with a film thickness of about 20 nm.
Subsequently, this substrate is fixed to a substrate holder of a vacuum deposition apparatus, and after the vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, 0.4 nm of potassium fluoride is deposited as a cathode buffer layer, and further, 110 nm of aluminum is deposited. Thus, a cathode was formed, and an organic EL element 21 was produced.

<< Production of Organic EL Element 22 >>
In the production of the organic EL element 21, the light-emitting layer was formed at 100 rpm for 30 seconds using a solution in which 100 mg HS-1 and 20 mg DP-5, 6 mg cGD-2, 3 mg cRD-2 were dissolved in 10 ml butyl acetate. After forming a thin film by the spin coating method under the conditions described above, a solution of 100 mg HS-1 and 20 mg DP-5, 1 mg cGD-2, 3 mg cRD-2 dissolved in 10 ml butyl acetate was used. A thin film was formed by spin coating under the condition of 1000 rpm for 30 seconds. Thereafter, it was immediately vacuum-dried at 60 ° C. for 1 hour to obtain a light emitting layer having a film thickness of about 40 nm.
When the light emitting layer was divided into regions of 1/3 (about 13 nm) in the film thickness direction, the average R / B ratio of that region was the ratio shown in Table 1. It is considered that such a gradient of R / B ratio is formed by mixing the light emitting layer interface by coating twice.

<< Production of organic EL element 23 >>
In the production of the organic EL element 22, the time from application of the light emitting layer to drying was allowed to stand for 1 hour, followed by vacuum drying at 60 ° C. for 1 hour to obtain a light emitting layer having a film thickness of about 40 nm.
When the light emitting layer was divided into regions of 1/3 (about 13 nm) in the film thickness direction, the average R / B ratio of that region was the ratio shown in Table 1. It is estimated that the interfacial mixing is performed uniformly by changing the drying process.

The following evaluation was performed about the produced organic EL elements 1 to 23. The results are shown in Table 2 below.
(Power efficiency)
Using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing Co., Ltd.), the front luminance and luminance angle dependency of each organic EL element were measured, and the power efficiency at a front luminance of 1000 cd / m ² was obtained.
The power efficiency is expressed as a relative value that sets the power efficiency of the organic EL element 1 to 100.

(Luminescent life)
The organic EL device continuously emitted light at room temperature under a constant current condition of ^2.5 mA / cm ² , and the time (τ1 / 2) required to obtain half the initial luminance was measured. In addition, the light emission lifetime was represented by the relative value which sets the organic EL element 1 to 100.

(Color balance)
The result measured with a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing Co., Ltd.) at the time of continuous light emission under a constant current condition of ^2.5 mA / cm ² is applied to the CIE chromaticity coordinates, and the front angle is 2 degrees. When the luminance is measured, the chromaticity in the CIE 1931 color system at 1000 Cd / m ² is X = 0.33 and Y = 0.33 is set as the center of white. The color balance was calculated from the following calculation with the chromaticity of the organic EL element 1 and the distance between the white centers set to 100.
Assuming that the chromaticity X1, Y1 of the organic EL element 1 and the chromaticity Xa, Ya of the organic EL element to be measured,
Color balance = √ ((Xa-0.33) ^ 2 + (Ya-0.33) ^ 2) / √ ((X1-0.33) ^ 2 + (Y1-0.33) ^ 2)

As shown in Table 2, the organic EL elements 6 to 8, 11, 12, and 14 to 23, which are examples of the present invention, have the results in each evaluation, and the organic EL elements 1 to 5, 9, 10, and 13 of the comparative examples. It was favorable compared with (especially the organic EL element 1 of a comparative example).

Claims (6)

In a white organic electroluminescence device sandwiched between an anode and a cathode and having a plurality of organic layers including a hole transport layer, a light emitting layer, and an electron transport layer,
The light emitting layer includes three or more kinds of dopants having different maximum emission wavelengths, and a B emission dopant having a maximum emission peak wavelength of 430 to 480 nm, a G dopant of 500 to 540 nm, and an R dopant of 520 to 560 nm. A light emitting layer comprising at least three dopants each selected from a classification;
The B dopant in the light emitting layer is a phosphorescent dopant, a phosphorescent material having a phosphorescence lifetime of less than 1.4 μsec and a phosphorescence quantum yield of 70% or more,
The ratio of R dopant / B dopant is 5 to 20 wt%,
The white organic electroluminescence device according to claim 1, wherein a ratio of the B dopant to the entire light emitting layer is 10 to 30 wt%. The white organic electroluminescence device according to claim 1, wherein the B dopant has a structure of the general formula (1).

(Ring A and Ring B represent a 5- or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring, and Ar represents an aromatic hydrocarbon ring, aromatic heterocyclic ring, non-aromatic hydrocarbon ring or non-aromatic heterocyclic ring. Represents a ring.
R ₁ and R ₂ are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
Ra, Rb and Rc are each independently a hydrogen atom, halogen atom, cyano group, alkyl group, alkenyl group, alkynyl group, alkoxy group, amino group, silyl group, arylalkyl group, aryl group, heteroaryl group, non-aromatic Represents a hydrocarbon ring group or a non-aromatic heterocyclic group, and may further have a substituent.
na and nc represent 1 or 2, and nb represents an integer of 1 to 4.
L ′ is one or more of monoanionic bidentate ligands coordinated to M, M represents a transition metal atom having an atomic number of 40 or more and a group 8 to 10 in the periodic table, m 'Represents an integer of 0 to 2, n' is at least 1, and m '+ n' is 2 or 3. )   3. The white organic electroluminescence device according to claim 1, wherein the R dopant in the light emitting layer has a high concentration in the vicinity of the hole transport layer and a low concentration in the vicinity of the electron transport layer.   4. The white organic electroluminescence device according to claim 3, wherein the ratio of the R dopant / B dopant is 10 to 50 wt% in a high concentration portion of the R dopant and 0 to 5 wt% in a low concentration portion. .   The white organic electroluminescence device according to claim 1, wherein the light emitting layer is produced by a wet process.   The white organic electroluminescence device according to any one of claims 1 to 5, wherein the light emitting layer is produced by coating twice.