JP4610956B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescence device that emits light by converting electric energy into light.

  Research and development related to various display elements are active today, and organic electroluminescent elements (hereinafter, referred to as “organic EL elements” as appropriate) can be promising because they can emit light with high luminance at a low voltage. Has attracted attention as a display element.

However, the organic EL element has a very low luminous efficiency compared to the inorganic LED element and the fluorescent tube, and has become a big problem.
Most of the organic EL devices currently proposed utilize fluorescence emitted from singlet excitons of organic compound light emitting materials. In the mechanism of simple quantum chemistry, in the exciton state, the ratio of singlet excitons that give fluorescence emission and triplet excitons that give phosphorescence emission is 1: 3, as long as fluorescence emission is used. Only 25% of the excitons can be effectively used, resulting in low emission efficiency. On the other hand, if phosphorescence obtained from triplet excitons can be used, the luminous efficiency can be improved. Based on such an idea, various phosphorescent light emitting devices using iridium phenylpyridine complexes have recently been reported (for example, see Non-Patent Document 1). According to these reports, it is disclosed that a phosphorescent light emitting device using a phenylpyridine complex of iridium has a luminous efficiency 2 to 3 times that of a conventional organic light emitting device using fluorescence. However, considering the points of energy saving and driving durability improvement, this is still low, and there is a strong demand for further improvement in luminous efficiency and luminance.

In addition, studies are being made to improve the luminance and drive durability of organic compounds other than the light-emitting material used in the organic EL element, such as an electron transport material and a hole transport material. Among such organic compounds, it is disclosed that a silacyclopentadiene compound can be used for a light emitting material, an electron transport material, a hole blocking material, and the like (for example, Patent Documents 1 to 3 and Non-Patent Documents 1 to 4). reference.). Silacyclopentadiene compounds are known to have a particularly high electron transporting ability, and organic EL devices using these compounds are expected in terms of improving luminous efficiency. However, on the other hand, driving durability is still unsatisfactory. It is sufficient and improvement is desired.
Japanese Patent No. 2918150 JP 2000-186094 A JP 2001-172284 A “Applied Physics Letters”, 1999, 75, p. 4 “Chemical Physics Letters”, 2001, 339, pp. 161-166 “Chemical Materials” 2001, 13, pp. 2680-2683 “Applied Physics Letters”, 2002, 80, pp. 189-191

  An object of the present invention is to provide an organic electroluminescent device having both high luminous efficiency and high luminance and high driving durability.

The above object of the present invention has been achieved by the following organic electroluminescence device.
<1> An organic electroluminescence device having an organic compound layer including at least one light emitting layer between a pair of electrodes, wherein at least one of the organic compound layers is represented by the following general formula (II) And an organic electroluminescent device comprising at least one triphenylamine derivative in a layer containing the compound represented by formula (II) .

In general formula (II), R ¹ And R ² Is a methyl group, R ³ And R ⁴ Are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁵ ~ R ⁸ Represents a hydrogen atom.

<2> The organic electroluminescent element according to <1>, which has an organic compound layer containing the compound represented by the general formula (II) and at least one triphenylamine derivative between the light emitting layer and the cathode.
<3> The organic electroluminescent element according to <1> or <2>, wherein the light emitting material contained in the light emitting layer is a phosphorescent material.
<4> The organic electroluminescent element according to <3>, wherein the phosphorescent material is a transition metal complex.

  According to the present invention, it is possible to provide an organic electroluminescent element having both high luminous efficiency and high luminance and high driving durability.

Hereinafter, the organic electroluminescence (EL) device of the present invention will be described in detail.
The organic EL device of the present invention is an organic electroluminescent device having an organic compound layer including at least one light emitting layer between a pair of electrodes, and at least one of the organic compound layers is represented by the following general formula (I). And a layer containing the compound represented by the general formula (I) contains at least one hole transporting compound.

  In the organic EL device of the present invention, the organic compound layer containing the compound represented by the general formula (I) and at least one hole transporting compound is an organic compound layer provided between the light emitting layer and the cathode. Preferably, it is an electron transport layer or an electron injection layer, more preferably an electron transport layer.

  Although the mechanism of action in the organic EL device of the present invention is not yet clear, it is presumed as follows. That is, in the organic EL device of the present invention, the compound represented by the general formula (I), which has excellent electron transport performance but low durability against holes, and the hole transport compound are formed of the same organic compound layer ( In particular, by including in the electron transport layer), the hole transporting compound can function as a hole trapping agent to complement the low durability against the holes of the compound represented by the general formula (I). Thus, it is considered that the electron transport performance of the compound represented by the general formula (I) is sufficiently exhibited, and the light emission efficiency and driving durability which are the effects of the present invention are remarkably improved.

  In the following, first, a compound represented by the general formula (I) (and a compound represented by the general formula (II) which is a preferred embodiment thereof), which is a characteristic component in the present invention, and hole transport The functional compound will be described.

<Compound represented by formula (I)>
The compound represented by formula (I) will be described in detail.

In general formula (I), R < ¹ > -R < ⁴ > represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or heteroaryl group each independently. If a substituent can be introduced into R ^{1 to} R ⁴ , it may further have a substituent.
X ¹ and X ² each independently represents an alkyl group, an aryl group, or a heteroaryl group. If a substituent can be introduced into X ¹ and X ² , it may further have a substituent.

Examples of the halogen atom represented by R ^{1 to} R ⁴ include a chlorine atom, a bromine atom, and an iodine atom.
The alkyl group represented by R ^{1 to} R ⁴ is preferably an alkyl group having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms. Preferred examples of the alkyl group represented by R ^{1 to} R ⁴ include a methyl group, an ethyl group, a propyl group, an iso-propyl group, an n-butyl group, and a t-butyl group.

The aryl group represented by R ^{1 to} R ⁴ is a condensed ring aryl group in which a single ring or two or more rings are condensed, preferably 6 to 30 carbon atoms, more preferably 6 to 6 carbon atoms. 20, particularly preferably an aryl group having 6 to 12 carbon atoms. Examples of the aryl group represented by R ^{1 to} R ⁴ include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, a triphenylenyl group, a biphenyl group, and a terphenyl group. Among these, preferably A phenyl group, a triphenylenyl group, a biphenyl group, and a terphenyl group, more preferably a phenyl group, a biphenyl group, and a terphenyl group, and still more preferably a phenyl group.

The heteroaryl group represented by R ^{1 to} R ⁴ is a monocyclic ring or a condensed heteroaryl group in which two or more rings are condensed, preferably having 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms. Preferably it is 2-10 heteroaryl groups. Specific examples of the heteroaryl group represented by R ^{1 to} R ⁴ include, for example, a pyridyl group, a quinolyl group, an isoquinolyl group, an acridinyl group, a phenanthridinyl group, a pteridinyl group, a pyrazinyl group, a quinoxalinyl group, a pyrimidinyl group, Quinazolyl, pyridazinyl, cinnolinyl, phthalazinyl, triazinyl, oxazolyl, benzoxazolyl, thiazolyl, benzothiazolyl, imidazolyl, benzoimidazolyl, pyrazolyl, indazolyl, isoxazolyl, benzoisoxazolyl Group, isothiazolyl group, benzoisothiazolyl group, oxadiazolyl group, thiadiazolyl group, triazolyl group, tetrazolyl group, furyl group, benzofuryl group, thienyl group, benzothienyl group, pyrrolyl group, indolyl group, imine group Zopyridinyl group, carbazolyl group and the like, preferably pyridyl group, pyrazinyl group, pyrimidinyl group, triazinyl group, oxazolyl group, thiazolyl group, imidazolyl group, pyrazolyl group, oxadiazolyl group, thiadiazolyl group, triazolyl group, furyl group, thienyl group , A pyrrolyl group, an indolyl group, an imidazopyridinyl group, and a carbazolyl group, more preferably a pyridyl group, a triazinyl group, an imidazopyridinyl group, and a carbazolyl group, and still more preferably a pyridyl group.

The alkyl group, aryl group, or heteroaryl group represented by R ^{1 to} R ⁴ may have a substituent, and the substituent can be selected from the following substituent group A.

(Substituent group A)
An alkyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n -Decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms). , For example, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms). Yes, such as propargyl, 3-pentynyl, etc.), aryl group (preferably having 6 to 30 carbon atoms, more preferred) Has 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, anthranyl, and the like, and an amino group (preferably having 0 to 30 carbon atoms, more preferably Has 0 to 20 carbon atoms, particularly preferably 0 to 10 carbon atoms, and examples thereof include amino, methylamino, dimethylamino, diethylamino, dibenzylamino, diphenylamino, and ditolylamino), alkoxy groups (preferably C1-C30, More preferably, it is C1-C20, Most preferably, it is C1-C10, for example, a methoxy, an ethoxy, butoxy, 2-ethylhexyloxy etc. are mentioned), an aryloxy group ( Preferably it has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms. For example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, etc.), heteroaryloxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably carbon number). 1 to 12, for example, pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc.), acyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to carbon atoms). 12 and examples thereof include acetyl, benzoyl, formyl, pivaloyl, and the like.

  An alkoxycarbonyl group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, etc.), an aryloxycarbonyl group (Preferably 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonyl), acyloxy group (preferably 2 to 2 carbon atoms). 30, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetoxy and benzoyloxy), acylamino groups (preferably 2 to 30 carbon atoms, more preferably carbon atoms) 2 to 20, particularly preferably 2 to 10 carbon atoms, for example, acetylamino, benzoyl Mino and the like), an alkoxycarbonylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino and the like. ), An aryloxycarbonylamino group (preferably having 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino). A sulfonylamino group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include methanesulfonylamino and benzenesulfonylamino), sulfamoyl group (Preferably 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, particularly preferably The number of carbon atoms is 0 to 12, and examples thereof include sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, and the like. -20, particularly preferably 1 to 12 carbon atoms, and examples thereof include carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl and the like.

  An alkylthio group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), an arylthio group (preferably having 6 carbon atoms). To 30, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, etc.), heteroarylthio groups (preferably 1 to 30 carbon atoms, more preferably carbon atoms). The number is 1 to 20, particularly preferably 1 to 12, and examples thereof include pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio, and the like, and a sulfonyl group ( Preferably it has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl, And sulfinyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl and benzenesulfinyl). ), A ureido group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include ureido, methylureido, phenylureido and the like), phosphorus. An acid amide group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as diethyl phosphoric acid amide and phenyl phosphoric acid amide), hydroxy Group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, Pho group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably having 1 to 12 carbon atoms, For example, nitrogen atom, oxygen atom, sulfur atom, specifically, for example, imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl group, azepinyl group, etc. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyl and triphenylsilyl).

The substituent that the alkyl group, aryl group, or heteroaryl group represented by R ^{1 to} R ⁴ may have is an alkyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms). Particularly preferably an aryl group or a heteroaryl group, more preferably an aryl group or a heteroaryl group, further preferably a phenyl group, a biphenyl group, a terphenyl group, or a pyridyl group, and a pyridyl group. Groups are most preferred.

The alkyl group represented by X ¹ and X ² is preferably an alkyl group having 1 to 12 carbon atoms, and specific examples include a methyl group, an ethyl group, a propyl group, an iso-propyl group, an n-butyl group, Examples include t-butyl group.
The aryl group represented by X ¹ and X ² is a condensed ring aryl group obtained by condensing a single ring or two or more rings, preferably an aryl group having 6 to 30 carbon atoms. The aryl group represented by X ¹ and X ^2, for example, a phenyl group, a naphthyl group, an anthryl group, phenanthryl group, pyrenyl group, triphenylenyl group, a biphenyl group, a terphenyl group and the like wherein X ¹ and X ² Is a condensed heteroaryl group in which a single ring or two or more rings are condensed, and is preferably a C1-C20 heteroaryl group. Specific examples of the heteroaryl group represented by X ¹ and X ² include, for example, pyridyl group, quinolyl group, isoquinolyl group, acridinyl group, phenanthridinyl group, pteridinyl group, pyrazinyl group, quinoxalinyl group, pyrimidinyl group, Quinazolyl, pyridazinyl, cinnolinyl, phthalazinyl, triazinyl, oxazolyl, benzoxazolyl, thiazolyl, benzothiazolyl, imidazolyl, benzoimidazolyl, pyrazolyl, indazolyl, isoxazolyl, benzoisoxazolyl Group, isothiazolyl group, benzoisothiazolyl group, oxadiazolyl group, thiadiazolyl group, triazolyl group, tetrazolyl group, furyl group, benzofuryl group, thienyl group, benzothienyl group, pyrrolyl group, indolyl group, imine group Examples thereof include a dazopyridinyl group and a carbazolyl group.

The alkyl group, aryl group and heteroaryl group represented by X ¹ and X ² may further have a substituent, and the substituent can be selected from the substituent group A described above.

<Compound represented by formula (II)>
The compound represented by the general formula (I) in the present invention is preferably a compound represented by the following general formula (II).

In general formula (II), R < ¹ > -R < ⁸ > represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or heteroaryl group each independently. When a substituent can be introduced into R ^{1 to} R ^8, it may further have a substituent.

The halogen atom represented by R ^{1 to} R ⁸ has the same meaning as the halogen atom represented by R ^{1 to} R ⁴ in the general formula (I), and the preferred range is also the same.
The alkyl group represented by R ^{1 to} R ⁸ has the same meaning as the alkyl group represented by R ^{1 to} R ⁴ in the general formula (I), and the preferred range is also the same.
The aryl group represented by R ^{1 to} R ⁸ has the same meaning as the aryl group represented by R ^{1 to} R ⁴ in the general formula (I), and the preferred range is also the same.
The heteroaryl group represented by R ^{1 to} R ⁸ has the same meaning as the heteroaryl group represented by R ^{1 to} R ⁴ in the general formula (I), and the preferred range is also the same.

The alkyl group, aryl group, or heteroaryl group represented by R ^{1 to} R ⁸ may have a substituent, and the substituent can be selected from the substituent group A described above.

The compound represented by general formula (I) or general formula (II) may have a bis-type structure via R ¹ or R ² .

<Method for Synthesizing Compounds Represented by General Formula (I) and General Formula (II)>
The compounds represented by general formula (I) and general formula (II) can be synthesized, for example, according to the method described in Japanese Patent No. 2918150 (method described below).
That is, first, an alkali metal complex is reacted with the acetylene derivative represented by the general formula (A).

In general formula (A), X and Y are each independently a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group, an alkenyloxy group, an alkynyloxy group, a substituted or unsubstituted aryl group. Represents a substituted or unsubstituted heterocycle, or X and Y are combined to form a saturated or unsaturated ring, and R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a substituted Or an unsubstituted alkyl group having 1 to 6 carbon atoms, alkoxy group, aryloxy group, perfluoroalkyl group, perfluoroalkoxy group, amino group, alkylcarbonyl group, arylcarbonyl group, alkoxycarbonyl group, aryloxycarbonyl group, Azo group, alkylcarbonyloxy group, arylcarbonyloxy group, alkoxycarbonyloxy group, arylo group Xoxycarbonyloxy group, sulfinyl group, sulfonyl group, sulfanyl group, silyl group, carbamoyl group, aryl group, heterocyclic group, alkenyl group, alkynyl group, nitro group, formyl group, nitroso group, formyloxy group, isocyano group, cyanate A group, an isocyanate group, a thiocyanate group, an isothiocyanate group, or a cyano group, or a substituted or unsubstituted ring may be condensed.
Subsequently, a silane derivative represented by the following general formula (B) is reacted.

  In general formula (B), X, Y and Z each independently represent a tertiary-butyl group or an aryl group.

  Furthermore, by reacting zinc chloride or a zinc chloride complex, a reactive silacyclopentadiene derivative represented by the following general formula (C) is obtained.

In general formula (C), A represents a zinc halide or a zinc halide complex, and X and Y each independently represent a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group, an alkenyloxy group. Group, an alkynyloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocycle, or X and Y are bonded to form a saturated or unsaturated ring, and R ¹ and R ² are Independently, a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, an alkoxy group, an aryloxy group, a perfluoroalkyl group, a perfluoroalkoxy group, an amino group, an alkylcarbonyl group, an aryl A carbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an azo group, an alkylcarbonyloxy group, an arylcarbonyloxy group, Alkoxycarbonyloxy group, aryloxycarbonyloxy group, sulfinyl group, sulfonyl group, sulfanyl group, silyl group, carbamoyl group, aryl group, heterocyclic group, alkenyl group, alkynyl group, nitro group, formyl group, nitroso group, formyl An oxy group, an isocyano group, a cyanate group, an isocyanate group, a thiocyanate group, an isothiocyanate group, or a cyano group, or a substituted or unsubstituted ring may be condensed.

  As the substituent attached to the acetylene derivative used here, one that does not easily inhibit the reaction between the alkali metal complex and acetylene is preferable, and one that is inactive with respect to the alkali metal complex is particularly preferable. Examples of the alkali metal complex used include lithium naphthalenide, sodium naphthalenide, potassium naphthalenide, lithium 4,4′-ditertiarybutyl-2,2′-biphenylide or lithium (N, N-dimethylamino). ) Naphthalenide. The solvent to be used is not particularly limited as long as it is inactive to an alkali metal or an alkali metal complex, and usually an ether solvent such as ether or tetrahydrofuran is used. Subsequent substituents of the silane derivative used are preferably bulky, and specifically include tertiary-butyldiphenylchlorosilane or ditertiary-butylphenylchlorosilane. Further, as the zinc chloride or zinc chloride complex used subsequently, a zinc chloride solid is used directly, an ether solution of zinc chloride is used, or a tetramethylethylenediamine complex of zinc chloride is used. These zinc chlorides are preferably sufficiently dried. If the amount of water is large, it is difficult to obtain the target product. This series of reactions is preferably performed in an inert gas stream, and argon gas is used. A silacyclopentadiene derivative can be obtained by reacting the reactive silacyclopentadiene derivative thus obtained with a halide represented by the general formula (D) in the presence of a catalyst.

  In general formula (D), X represents a chlorine atom, a bromine atom or an iodine atom, and R represents a halogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an alkylcarbonyl group, an arylcarbonyl A group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfinyl group, a sulfonyl group, a sulfanyl group, a silyl group, an aryl group, a heterocyclic group, an alkenyl group, or an alkynyl group;

  Examples of the catalyst used here include palladium catalysts such as tetrakistriphenylphosphine palladium and dichlorobistriphenylphosphine palladium. In each stage of the first-speed reaction, the reaction temperature is not particularly limited. However, when an alkali metal complex, a silane derivative, zinc chloride, or the like is added and stirred, the temperature is preferably room temperature or lower, and is usually 0 ° C or lower. The reaction temperature after adding the halide is preferably room temperature or higher, and is usually carried out under reflux when tetrahydrofuran is used as a solvent. There is no restriction | limiting in particular also in reaction time, When adding and stirring an alkali metal complex, a silane derivative, zinc chloride, etc., between several minutes to several hours is desirable. The reaction after the halide is added may be traced by a general analytical means such as NMR or chromatography to determine the end point of the reaction.

  Specific examples of the compound represented by the general formula (I) and the compound represented by the general formula (II) in the present invention [Exemplary compounds (S-1) to (S-12) are listed below. The invention is not limited to these examples.

In the present invention, the content of the compound represented by the general formula (I) (or the compound represented by the general formula (II)) is preferably 5 to 95% by mass per one organic compound layer. The content is more preferably 10 to 90% by mass, and further preferably 20 to 80% by mass.
Moreover, the compound represented by general formula (I) (or the compound represented by general formula (II)) may be used individually by 1 type, and may use 2 or more together.

  The compound represented by the general formula (I) described above is included in at least one layer (particularly preferably, the electron transport layer) of the organic compound layer constituting the organic EL element together with the hole transport compound described later. An organic EL device having excellent luminous efficiency and driving durability can be obtained.

<Hole transporting compound>
The hole transporting compound will be described in detail.
The hole transporting compound in the present invention may have any one of the function of injecting holes from the anode, the function of transporting holes, and the function of blocking electrons injected from the cathode. Specifically, tribenzazepine derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, polyarylbenzene derivatives, arylamine derivatives, styrylanthracene derivatives, stilbene derivatives, aromatic tertiary amines Compounds, styrylamine compounds, aromatic dimethylidene compounds, metal complexes of 8-quinolinol derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, amino-substituted chalcone derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, and porphyrin compounds. It is done.

  Among these, the hole transporting compound is preferably an arylamine derivative. Examples of arylamine derivatives include, for example, “CMC Publishing,“ Chemical Function Data Collection for Organic Electronic Device Researchers ”by Chinamiya Adachi, Takato Koyamada, Yoshiyuki Nakajima, pages 36 to 42,“ CMC Triphenylamine derivatives described in pages 136 to 137 of the publication “Organic EL materials and displays”, supervised by Junji Kido, can be preferably used.

In the present invention, the content of the hole transporting compound contained in the organic compound layer together with the compound represented by the general formula (I) is 5 to 95% by mass per organic compound layer. Preferably, it is 10-90 mass%, More preferably, it is 20-80 mass%. A positive hole transport compound may be used individually by 1 type, and may use 2 or more together.
The content ratio of the hole transporting compound and the compound represented by the general formula (I) per layer of the organic compound layer is preferably 1:20 to 20: 1 by mass ratio, and 1:10. -10: 1 is more preferable, and 1: 5 to 5: 1 is more preferable.

-Configuration of organic EL element-
Next, the configuration of the organic EL element of the present invention will be described.
The organic EL device of the present invention is configured to have an organic compound layer including at least one light emitting layer between a pair of electrodes of an anode and a cathode provided on a substrate. Examples of the organic compound layer other than the light emitting layer include a hole transport layer, a hole injection layer, an electron injection layer, an electron transport layer, and a protective layer.
In addition, each of these layers may have other functions, and the same layer may be laminated. Various materials can be used for forming each layer.

<Anode>
The anode supplies holes to a hole injection layer, a hole transport layer, a light emitting layer, and the like, and a metal, an alloy, a metal oxide, an electrically conductive compound, or a mixture thereof can be used. A material having a work function of 4 eV or more is preferable.
Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide and indium tin oxide (ITO), metals such as gold, silver, chromium and nickel, and these metals and conductive metal oxides. Mixtures or laminates thereof, inorganic conductive substances such as copper iodide and copper sulfide, organic conductive materials such as polyaniline, polythiophene and polypyrrole, and laminates of these with ITO, preferably conductive It is a metal oxide, and ITO is particularly preferable in terms of productivity, high conductivity, transparency, and the like.
The thickness of the anode can be appropriately selected depending on the material, but is usually preferably in the range of 10 nm to 5 μm, more preferably 50 nm to 1 μm, still more preferably 100 nm to 500 nm.

Usually, the anode is formed by layering on the above-mentioned soda-lime glass, non-alkali glass, transparent resin substrate or the like. When glass is used, it is preferable to use non-alkali glass as the material in order to reduce ions eluted from the glass. Moreover, when using soda-lime glass, it is preferable to use what gave barrier coatings, such as a silica. Transparent resin substrates include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polycarbonate, polyethersulfone, polyarylate, allyl diglycol carbonate, polyimide, polycycloolefin, norbornene resin, poly (chlorotrine). Fluoroethylene), Teflon (registered trademark), and polytetrafluoroethylene-polyethylene copolymer.
The thickness of the substrate is not particularly limited as long as it is sufficient to maintain the mechanical strength, but when glass is used, a thickness of 0.2 mm or more, preferably 0.7 mm or more is usually used.
Various methods are used for producing the anode depending on the material. For example, in the case of ITO, an electron beam method, a sputtering method, a resistance heating vapor deposition method, a chemical reaction method (such as a sol-gel method), a dispersion of indium tin oxide is used. A film is formed by a method such as coating.
The anode can be driven to lower the drive voltage of the element or increase the light emission efficiency by washing or other processing. For example, in the case of ITO, UV-ozone treatment, plasma treatment, etc. are effective.

<Cathode>
The cathode supplies electrons to the electron injection layer, the electron transport layer, the light emitting layer, and the like. The adhesion, ionization potential, and stability between the negative electrode and the adjacent layer, such as the electron injection layer, the electron transport layer, and the light emitting layer. It is selected in consideration of etc.
As a material for the cathode, a metal, an alloy, a metal halide, a metal oxide, an electrically conductive compound, or a mixture thereof can be used. Specific examples include alkali metals (for example, Li, Na, K, etc.) and The fluoride or oxide, alkaline earth metal (eg, Mg, Ca, etc.) and the fluoride or oxide thereof, gold, silver, lead, aluminum, sodium-potassium alloy or mixed metal thereof, lithium-aluminum alloy or Examples thereof include mixed metals, magnesium-silver alloys or mixed metals thereof, rare earth metals such as indium and ytterbium, preferably materials having a work function of 4 eV or less, more preferably aluminum, lithium-aluminum alloys or the like. A mixed metal, a magnesium-silver alloy, or a mixed metal thereof.
The cathode can take not only a single layer structure of the above-mentioned compounds and a mixture thereof but also a laminated structure containing the above-mentioned compounds and a mixture thereof. For example, a laminated structure of aluminum / lithium fluoride and aluminum / lithium oxide is preferable.
The thickness of the cathode can be appropriately selected depending on the material, but is usually preferably in the range of 10 nm to 5 μm, more preferably 50 nm to 1 μm, still more preferably 100 nm to 1 μm.
For production of the cathode, methods such as an electron beam method, a sputtering method, a resistance heating vapor deposition method, a coating method, and a transfer method are used, and a metal can be vapor-deposited alone or two or more components can be vapor-deposited simultaneously. Furthermore, a plurality of metals can be vapor deposited at the same time to form an alloy electrode, or a previously prepared alloy may be vapor deposited.
The sheet resistance of the anode and the cathode is preferably low, and is preferably several hundred Ω / □ or less.

<Organic compound layer>
The organic compound layer in the present invention will be described.
The organic EL device of the present invention has a plurality of organic compound layers including a light emitting layer, and other organic compound layers other than the light emitting layer include a hole transport layer, an electron transport layer, a charge blocking layer, and a hole. Examples thereof include an injection layer and an electron injection layer.
Each layer constituting the organic compound layer is formed by a dry film forming method such as vapor deposition or sputtering, dipping, spin coating, dip coating, casting, die coating, roll coating, bar coating, gravure coating, etc. The film can be suitably formed by any of a wet film forming method, a transfer method, a printing method, and the like.

(Light emitting layer)
The light-emitting layer receives holes from the anode, the hole injection layer, or the hole transport layer when an electric field is applied, receives electrons from the cathode, the electron injection layer, or the electron transport layer, and recombines holes and electrons. It is a layer which has the function to provide and to emit light.
As the light emitting layer in the present invention, a charge transport function and a light emitting function are separated to obtain better performance, or a phenomenon in which agglomeration occurs in a high concentration light emitting material and the excited state is non-radiatively deactivated (concentration quenching). In order to prevent this, it is preferable that the charge transport material (host material) is doped with the light emitting material as a dopant.

-Charge transport material (host material)-
Examples of the host material applied to the light emitting layer include carbazole derivatives (for example, those described in “Applied Physics Letters”, 1999, Vol. 74, No. 3, p. 442), tribenzoazepine. Derivatives (JP-A-10-59943, JP-A-10-219241, JP-A-10-316875, JP-A-10-324680, JP-A-10-330365, JP-A-2001-97953), triazole derivatives (US Pat. No. 3,121,197) Oxazole derivatives (US Pat. No. 3,257,203), imidazole derivatives (Japanese Patent Publication No. 37-16096), polyarylalkane derivatives (US Pat. Nos. 3,615,402, 3,820,899, 3,542,544, Japanese Patent Publication Nos. 45-555, 51). -10 983, JP-A-51-93224, JP-A-55-17105, JP-A-56-4148, JP-A-55-108667, JP-A-55-156953, JP-A-56-36656), polyarylbenzenoid derivatives 10-255985, JP-A No. 2002-260861), arylamine derivatives (US Pat. Nos. 3,567,450, 3,180,703, 3,240,597, 3,658,520, 4,232,103, 4,175,961, and 4,01376) -35702, 39-27577, JP-A-55-144250, JP-A-56-119132, JP-A-56-22437, West German Patent No. 1110518), a styrylanthracene derivative (JP-A-56-46234), Stilbene derivatives (Japanese Patent Laid-Open No. 61-210363, 61-228451, 61-14642, 61-72255, 62-47646, 62-36684, 62-10652, 62-30255, 60-93445, 60- 94462, 60-174749, 60-175052), aromatic tertiary amine compounds and styrylamine compounds (Japanese Patent Laid-Open Nos. 63-295695, 53-27033, 54-58445, and 54-). 149634, 54-64299, 55-79450, 55-144250, 56-119132, 61-295558, 61-98353, JP-A-8-239655, U.S. Pat. No.), aromatic dimethylidene compounds (JP-A-6-330034), pyrazoline derivatives and Zolone derivatives (US Pat. Nos. 3,180,729, 4,278,746, JP-A-55-88064, 55-88065, 49-105537, 55-51086, 56-80051, 56-88141) 57-45545, 54-112437, 55-74546), phenylenediamine derivatives (US Pat. No. 3,615,404, JP-B 51-10105, JP-P 46-3712, JP-P 47-25336, 54-53435, 54-110536, 54-1119925), amino-substituted chalcone derivatives (US Pat. No. 3,526,501), fluorenone derivatives (JP-A 54-110837), hydrazone derivatives (US Pat. 3717462, JP-A-54-59143, 55-52063 55-52064, 55-46760, 55-85495, 57-11350, 57-148799), silazane derivatives (US Pat. No. 4,950,950), porphyrin compounds (JP-A-63) -295695), anthraquinodimethane derivatives and anthrone derivatives (JP 57-149259, 58-55450, 63-104061, JP 61-225151, 61-233750), diphenoquinone Derivatives, thiopyrandioxide derivatives and carbodiimide derivatives ("Polymer Preprints, Japan", 1988, Vol. 37, No. 3, p. 681), fluorenylidenemethane derivatives (JP-A-60-69657, JP-A-61-143764, JP-A-61-148159)), distyrylpyrazine derivatives ("Chemistry Letters", 1990, p.189). , JP-A-2-252793, JP-A-5-178842), heterocyclic tetracarboxylic acid anhydride derivatives ("Japanese Journal of Applied Physics", 1988, 27, L269), porphyrins and the like Phthalocyanine derivatives (Japanese Patent Laid-Open No. 63-295965), metal complexes of 8-quinolinol derivatives (Journal of the Institute of Electronics, Information and Communication Engineers, 1990, C-2, p.661), and benzoxazole as a ligand From the viewpoint of hole and electron transport properties, it is preferable to contain at least one host material selected from the group of metal complexes having a benzothiazole ligand and a metal complex having benzothiazole as a ligand. More preferred.

In order to efficiently transfer energy from the triplet excited state of the host material to the light emitting material, the energy level (T ₁ level) of the lowest triplet excited state of the host material is higher than the T ₁ level of the light emitting material. Is preferably high. Since the T ₁ level of the luminescent material becomes higher as the emission wavelength is shorter, a high T ₁ host material is required in the light emitting layer for a short wave light emitting element, while T ₁ is the highest occupied orbit of the host material ( HOMO) and the lowest unoccupied orbit (LUMO), which are related to the ability to inject and transport charges (generally, the larger the energy difference between HOMO and LUMO, the less the charge is injected and the higher the electrical insulation) Therefore, it is important to select an optimal T ₁ level host material.
In particular, the T ₁ level of the light emitting layer host material for a blue light emitting element having an emission maximum wavelength of 500 nm or less is 62 kcal / mol or more (259 kJ / mol or more), 85 kcal / mol or less (355 kJ / mol or less). Preferably, they are 65 kcal / mol or more (272 kJ / mol or more) and 80 kcal / mol or less (334 kJ / mol or less).

  As a host material satisfying the above physical property values, host materials described in JP-A Nos. 2002-1000047 and 2002-338579 are preferable, and host materials described in JP-A No. 2002-1000047 are more preferable. A preferable range of the host material described in JP-A No. 2002-1000047 is as described in the publication.

The light emitting layer in the present invention is preferably formed by a vapor deposition method.
The vapor deposition method is a vacuum vapor deposition method in which a substance is heated and evaporated under high vacuum (10 ⁻² Pa or less) and a gaseous substance is deposited on a target to form a film from an evaporation source. The heating method for evaporation includes a resistance heating method, a high frequency heating method, an electron beam heating method, a laser heating method, etc., but the resistance heating method is the most common. Further, there are a sputtering method, an ion plating method, a molecular beam epitaxy method, and the like as a method for evaporating the material by a method other than heating, which can be properly used depending on the purpose. As a vapor deposition method in a broader sense, there is a CVD method in which a film is formed by a chemical reaction on the target surface, and the vapor deposition method referred to in this specification includes all these vapor deposition techniques. Details of the vapor deposition method are described in Chapter 8 of "New Format / Vacuum Handbook" (edited by ULVAC, Inc.) published by Ohm.

  In the case of forming a film with a mixture of two or more substances, a mixture of a plurality of substances may be put into one evaporation source to evaporate, but in this method, the composition of the substance in the evaporated gas is kept constant. A difficult method is to fly molecules simultaneously from different evaporation sources. There is also known a method (Japanese Patent No. 3362504) in which a plurality of substances are sequentially stacked on a heated substrate to form a uniform film using diffusion by heat.

The light-emitting layer created by the vapor deposition method does not contain impurities, oxygen, and moisture derived from solvents, binders, etc., compared to the case where it is created by a wet film formation method typified by a spin coating method or an inkjet method. A light emitting layer thin film having a desired film thickness can be easily obtained without being concerned about driving durability and without worrying about dissolving an existing lower layer with a solvent.
Further, by performing masking at the time of vapor deposition, different light emitting materials and host materials can be used for each pixel to have different light emitting characteristics, which is suitable for manufacturing a fine color display with high definition and high image quality.

When the light emitting layer is formed by vapor deposition, it is preferable to contain only a material having a molecular weight of 3000 or less as a material constituting the light emitting layer. In particular, polymer materials such as polymers and oligomers are not preferable because they are low in volatility and difficult to deposit, and the materials themselves have a molecular weight distribution, making it difficult to obtain light emission with good reproducibility.
High molecular weight compounds having a molecular weight of 3000 or more are difficult to evaporate by heating even under high vacuum conditions, and thin film formation by vacuum deposition tends to be difficult.
In particular, when a substance outside the range of 200 or more and 2000 or less is selected, a low molecular weight compound having a molecular weight of 200 or less is too volatile and difficult to form a thin layer upon vacuum deposition. This is because it tends to be difficult to evaporate by heating underneath.
Moreover, from the easiness of vapor deposition, it is preferable that the material which comprises a light emitting layer is not an ionic compound but a neutral molecular compound.
The light-emitting layer thin film formed by vapor deposition is preferably a uniform non-crystalline thin film (amorphous film) free from defects such as thinness and pinholes, and changes in the performance of the light-emitting element when recrystallization occurs due to aging or heat Therefore, the melting point and the glass transition temperature (Tg) are preferably high. The melting point of the material constituting the light emitting layer is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, further preferably 250 ° C. or higher, and Tg is preferably 70 ° C. or higher, more preferably 100 ° C. or higher, and still more preferably 120 ° C. ℃ or more.
As a host material satisfying the above required performance, a carbazole derivative that has a high T ₁ level, is unlikely to cause crystallization, has a long excited state lifetime, and can be expected to have high emission efficiency is most preferable.

  Although the specific example of the host material used suitably for this invention below is given, this invention is not limited to these.

-Luminescent material-
The luminescent material may be either a fluorescent compound that emits light from singlet excitons or a phosphorescent compound that emits light from triplet excitons.
Examples of light-emitting materials that can be used in the present invention include benzoxazole derivatives, benzimidazole derivatives, benzothiazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed fragrances. Group compounds, perinone derivatives, oxadiazole derivatives, oxazine derivatives, aldazine derivatives, pyralidine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, cyclopentadiene derivatives, styrylamine derivatives, Diketopyrrolopyrrole derivatives, aromatic dimethylidin compounds, metal complexes of 8-quinolinol derivatives and metal complexes of pyromethene derivatives, rare S complex, various metal complexes typified by transition metal complexes such as iridium trisphenylpyridine complexes and platinum porphyrin complexes, polythiophene, polyphenylene, polyphenylene vinylene polymer compounds include compounds such as organic silane derivatives.

Although the film thickness of a light emitting layer is not specifically limited, Usually, the thing of the range of 1 nm-5 micrometers is preferable, More preferably, it is 5 nm-1 micrometer, More preferably, it is 10 nm-500 nm.
There may be one or a plurality of light emitting layers, and each light emitting layer emits light in a different light emission color, for example, may emit white light as a whole, or may emit white light from a single light emitting layer. May be. When there are a plurality of light emitting layers, each light emitting layer may be formed of a single material or may be formed of a plurality of compounds. For example, in the case of a mixed system including a host material and a light emitting material, the host material may be a single material or a mixture of a plurality of types. The light emitting material may be a single material or a mixture of a plurality of materials. The mixing ratio when the light emitting layer in the present invention is a mixed system of a charge transport material and a light emitting material is preferably 10,000: 1 to 100: 5, and more preferably 10,000: 5 to 100: 2.

(Hole injection layer, hole transport layer)
The material contained in the hole injection layer and the hole transport layer has one of the function of injecting holes from the anode, the function of transporting holes, or the function of blocking electrons injected from the cathode. If it is.
The materials constituting the hole injection layer and the hole transport layer include tribenzazepine derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, polyarylbenzene derivatives, arylamine derivatives, styryl. Anthracene derivatives, stilbene derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, metal complexes of 8-quinolinol derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, amino-substituted chalcone derivatives, fluorenone derivatives, hydrazones One or more selected from the group of derivatives, silazane derivatives and porphyrin compounds are preferred. Preferable examples of these compounds are the same as those of the corresponding compounds described in the section of the host material.

Further, when the hole transport layer is a layer adjacent to the light emitting layer containing the phosphorescent compound, the triplet excitons generated in the light emitting layer are prevented from moving to the hole transport layer. The energy level (T ₁ level) in the lowest triplet excited state is preferably higher than the T ₁ level of the light emitting material or the host material contained in the light emitting layer. In particular, the T ₁ level of a hole transport material for a blue light emitting device having an emission maximum wavelength of 500 nm or less is preferably 62 kcal / mol or more (259 kJ / mol or more), 85 kcal / mol or less (355 kJ / mol or less), and 65 kcal. / Mol or more (272 kJ / mol or more) and 80 kcal / mol or less (334 kJ / mol or less).
As a hole transport material satisfying the above physical property values, a hole transport material described in JP-A No. 2002-1000047 is preferable, and a preferable range of the hole transport material described in JP-A No. 2002-100466 is the same as that of the same specification. As described in the book.
Among the above compound groups, tribenzazepine derivatives can be expected to have high luminous efficiency at high T ₁ , and arylamine derivatives can be expected to improve durability due to high stability. More preferred.
In addition, carbazole, polysilane compounds, poly (N-vinylcarbazole), aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, and derivatives thereof as necessary Can be added.

The thickness of the hole injection layer is not particularly limited, but is usually preferably in the range of 0.2 nm to 1 μm, more preferably 1 nm to 0.2 μm, and further preferably 2 nm to 100 nm. .
The thickness of the hole transport layer is not particularly limited, but is usually preferably in the range of 1 nm to 5 μm, more preferably 5 nm to 1 μm, and even more preferably 10 nm to 500 nm.
The hole injection layer and the hole transport layer may have a single layer structure composed of one or more of the materials described above, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

As a method for forming the hole injection layer and the hole transport layer, a vacuum deposition method, an LB method, a method in which the hole injection transport material is dissolved or dispersed in a solvent, a coating method, an ink jet method, a printing method, or a transfer method is used. It is done.
In the case of the coating method, it can be dissolved or dispersed together with the resin component. Examples of the resin component include polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, and poly (N -Vinyl carbazole), hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicone resin, and the like.

Among the above-described layer forming methods, the hole transport layer is preferably installed by vapor deposition. By installing by the vapor deposition method, a thin film having a uniform and constant film thickness can be formed, and the durability tends to be improved.
When the hole transport layer is installed by vapor deposition, the material of the hole transport layer may be composed of a low molecular organic compound having a molecular weight of 3000 or less and / or a low molecular organic metal compound having a molecular weight of 3000 or less, like the light emitting layer material. preferable.

(Electron injection layer, electron transport layer)
As a material included in the electron injection layer and the electron transport layer, any material having one of a function of injecting electrons from the cathode, a function of transporting electrons, and a function of blocking holes injected from the anode Good.
The organic EL device of the present invention preferably has a layer containing a compound having an ionization potential of 5.9 eV or more (more preferably 6.0 eV or more) between the cathode and the light emitting layer, and has an ionization potential of 5.9 eV or more. It is more preferable to have an electron transport layer.
The compound represented by the general formula (I) and the hole transporting compound are included in the electron transporting layer or the electron injecting layer from the viewpoint of improving the light emission characteristics and driving durability which are the effects of the present invention. And is most preferably contained in the electron transport layer.

When the compound represented by the general formula (I) is contained in the electron transport layer, the electron transport layer may be composed of only the compound represented by the general formula (I) and the hole transporting compound, You may use together the material (other electron transport material) illustrated below.
The content ratio when the compound represented by the general formula (I) and another electron transporting material are used in combination can be arbitrarily selected, but is preferably 1:10 to 10: 1, and 1: 5 ~ 5: 1 is more preferred.

  Specific examples of materials that can be used for the electron injection layer and the electron transport layer include triazole, oxazole, oxadiazole, imidazole, fluorenone, anthraquinodimethane, anthrone, diphenylquinone, thiopyran dioxide, carbodiimide, and fluorenylidenemethane. , Distyrylpyrazine, naphthalene, perylene, and other aromatic ring tetracarboxylic anhydrides, metal complexes of phthalocyanine, 8-quinolinol, metal phthalocyanines, metal complexes having benzoxazole and benzothiazole as ligands , Organosilanes, and derivatives thereof. Preferable examples of these compounds are the same as the corresponding compounds described in the description of the host material.

  In the organic EL device of the present invention, it is preferable to use a layer containing a compound having an ionization potential of 5.9 eV or more (more preferably 6.0 eV or more) between the cathode and the light emitting layer. It is more preferable to use an electron transport layer having an ionization potential of 5.9 eV or more. By providing a layer (block layer) containing such a compound, it is possible to prevent a decrease in luminous efficiency and deterioration in durability due to holes passing through the light emitting layer and flowing into the electron transport layer.

Further, when the electron transport layer is a layer adjacent to the light emitting layer containing the phosphorescent compound, the lowest triplet of the electron transport material is prevented so that triplet excitons generated in the light emitting layer do not move to the electron transport layer. The energy level (T ₁ level) in the excited state is preferably higher than the T ₁ level of the light emitting material or the light emitting layer host material. In particular, the T ₁ level of a hole transport material for a blue light emitting device having an emission maximum wavelength of 500 nm or less is preferably 62 kcal / mol or more (259 kJ / mol or more), 85 kcal / mol or less (355 kJ / mol or less), and 65 kcal. / Mol or more (272 kJ / mol or more) and 80 kcal / mol or less (334 kJ / mol or less).
Examples of other electron transport materials that satisfy the above physical property values include the electron transport materials described in JP-A No. 2002-1000047. A preferable range of the electron transport material described in JP-A No. 2002-1000047 is as described in the same specification.

  In addition, carbazole, polysilane compounds, poly (N-vinylcarbazole), aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, and derivatives thereof as necessary Can be added.

The thickness of the electron injection layer is not particularly limited, but is usually preferably in the range of 0.2 nm to 1 μm, more preferably 1 nm to 0.2 μm, and further preferably 2 nm to 100 nm.
Although the film thickness of an electron carrying layer is not specifically limited, Usually, the thing of the range of 1 nm-5 micrometers is preferable, More preferably, it is 5 nm-1 micrometer, More preferably, it is 10 nm-500 nm.
The electron injection layer and the electron transport layer may have a single layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.
As a method for forming the electron injection layer and the electron transport layer, a vacuum deposition method, an LB method, a method in which the electron injection / transport material is dissolved or dispersed in a solvent, a coating method, an ink jet method, a printing method, a transfer method, and the like are used.
In the case of the coating method, it can be dissolved or dispersed together with the resin component. As the resin component, for example, those exemplified in the case of the hole injection transport layer can be applied.
Among the layer forming methods described above, the electron transport layer is preferably installed by vapor deposition. By installing by the vapor deposition method, a thin film having a uniform and constant film thickness can be formed, and the durability tends to be improved.
Moreover, when installing an electron carrying layer by a vapor deposition method, it is preferable that the material of an electron carrying layer also consists of a low molecular organic compound with a molecular weight of 3000 or less and / or a low molecular organometallic compound with a molecular weight of 3000 or less like the light emitting layer material. .

(Protective layer)
The organic EL light-emitting device of the present invention may have a protective layer in order to prevent moisture and oxygen from entering. As a material contained in the protective layer, any material may be used as long as it has a function of preventing materials that promote device deterioration such as moisture and oxygen from entering the device.
Specific examples thereof include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni, MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, and Fe ₂ O. ₃ , metal oxides such as Y ₂ O ₃ and TiO ₂ , metal fluorides such as MgF ₂ , LiF, AlF ₃ , and CaF ₂ , SiN _x , SiO _x N _y Such as nitride, polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, tetrafluoroethylene And a copolymer obtained by copolymerizing a monomer mixture containing at least one comonomer, a fluorine-containing copolymer having a cyclic structure in the copolymer main chain, a water-absorbing substance having a water absorption of 1% or more, a water absorption of 0 .1% or less of moisture-proof substances and the like.
There is also no particular limitation on the method for forming the protective layer. For example, vacuum deposition, sputtering, reactive sputtering, MBE (molecular beam epitaxy), cluster ion beam, ion plating, plasma polymerization (high frequency excitation) (Ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, printing method, transfer method can be applied.

-Manufacturing method of organic EL element-
As a method for producing the organic EL element of the present invention, a production method suitably used will be described below, but the present invention is not limited thereto.

First, a substrate having an ITO thin film as a transparent electrode is washed with a solvent and then subjected to UV-ozone treatment. Furthermore, a hole injection layer and a hole transport layer are formed in this order on the transparent electrode by a vapor deposition method. A light emitting layer is formed thereon by co-evaporating a metal complex and a host material in a vacuum. The metal complex and the host material are as defined above, and the preferred ranges are also the same. The host material and the metal complex used for the light emitting layer preferably have a molecular weight of 3000 or less, and the material constituting the light emitting layer preferably has a molecular weight of 3000 or less. Vapor deposition is facilitated by setting the molecular weight range to the above range.
As the deposition, a known deposition method can be used. Further thereon, an electron transport layer and an electron injection layer are provided in this order, a patterned mask is placed thereon, and a back electrode (cathode) is formed by vapor deposition. A block layer containing an electron transport material can be provided between the electron transport layer and the light emitting layer. A lead wire is connected to each of the anode and the cathode to form a light emitting laminate. The light emitting laminate obtained here is sealed to produce an organic EL element.

  The obtained organic EL element is allowed to emit light by applying a direct current voltage, and a driving durability test is performed with the initial luminance, and the durability can be evaluated by setting the time when the luminance is halved as a half time.

  Examples of the organic EL device of the present invention will be described below, but the present invention is not limited to these examples.

[Example 1]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 150 nm (manufactured by Geomat Corp .; electron beam film-formed product; sheet resistance 15 Ω) is 2 mm wide using ordinary photolithography and hydrochloric acid etching. The anode was formed by patterning into stripes. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally with ultraviolet ozone cleaning. installed. After the apparatus was roughly evacuated with an oil rotary pump, the apparatus was evacuated with a cryopump until the degree of vacuum in the apparatus was 2 × 10 ⁻⁶ Torr (about 2.7 × 10 ⁻⁴ Pa) or less.

Next, the copper phthalocyanine (CuPc, crystal form is β type) shown below placed in a molybdenum boat arranged in the apparatus was heated and heated to a vacuum degree of 1.4 × 10 ⁻⁶ Torr (about 1.9 ×). 10 ⁻⁴ Pa), vapor deposition was performed at a deposition rate of 0.1 nm / second to form a 10 nm thick hole injection layer.

Next, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD) shown below, placed in a ceramic crucible arranged in the above apparatus, was added to the crucible. Evaporation was performed by heating with a surrounding tantalum wire heater to form a hole transport layer. The degree of vacuum during deposition was 9.0 × 10 ⁻⁷ Torr (about 1.2 × 10 ⁻⁴ Pa), the deposition rate was 0.2 nm / second, and the thickness of the hole transport layer was 60 nm.

Subsequently, 4,4′-N, N′-dicarbazole-biphenyl (CBP) shown below as a main component (host material) of the light emitting layer is shown below as a phosphorescent organometallic complex as a subcomponent (dopant). An iridium complex (Ir (ppy) ₃ ) was placed in a ceramic crucible, and a film was formed by a binary simultaneous vapor deposition method. The deposition rate of CBP is controlled to 0.1 nm / second, and the deposition rate is controlled so that the iridium complex (Ir (ppy) ₃ ) is contained in an amount of 5% by mass with respect to the host. Laminated on the hole transport layer. The degree of vacuum at the time of vapor deposition was 1.3 × 10 ⁻⁶ Torr (about 1.7 × 10 ⁻⁴ Pa).

Further, as the electron transporting layer, the exemplified compound (S-2) which is a compound represented by the general formula (I) and α-NPD which is a hole transporting compound are vapor deposition rates by a binary simultaneous vapor deposition method. Lamination was performed at a thickness of 10 nm at 0.1 nm / second. The degree of vacuum during the deposition was 7.0 × 10 ⁻⁷ Torr (about 0.9 × 10 ⁻⁴ Pa).

  In addition, the substrate temperature at the time of vacuum-depositing said positive hole transport layer, a light emitting layer, and an electron carrying layer was hold | maintained at room temperature.

Here, the element on which the electron transport layer has been deposited is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide stripe-shaped shadow mask is orthogonal to the ITO stripe of the anode as a mask for cathode deposition. In the same manner as in the formation of the organic compound layer after being in close contact with the device and installed in another vacuum vapor deposition apparatus, the degree of vacuum in the apparatus is 2 × 10 ⁻⁶ Torr (about 2.7 × 10 ⁻⁴ Pa). ) Exhaust until below.

Thereafter, a three-layer cathode was formed as follows.
First, magnesium fluoride (MgF ₂ ) is deposited on a molybdenum boat at a deposition rate of 0.1 nm / second, a degree of vacuum of 7.0 × 10 ⁻⁶ Torr (about 9.3 × 10 ⁻⁴ Pa), and 1.5 nm. Was formed on the electron transport layer. Next, aluminum is similarly heated by a molybdenum boat to form an aluminum layer having a film thickness of 40 nm at a deposition rate of 0.5 nm / second and a degree of vacuum of 1 × 10 ⁻⁵ Torr (about 1.3 × 10 ⁻³ Pa). did. Further, in order to increase the conductivity of the cathode, silver is heated by a molybdenum boat in the same manner as described above, and the deposition rate is 0.3 nm / second, the degree of vacuum is 1 × 10 ⁻⁵ Torr (about 1.3 × A silver layer having a thickness of 40 nm was formed at 10 ⁻³ Pa) to complete the cathode.
The substrate temperature during the deposition of the above three-layer cathode was kept at room temperature.

  As described above, an organic EL element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. Evaluation was made by the following method using the obtained organic EL element.

-Evaluation-
Using a source measure unit type 2400 manufactured by Toyo Technica, direct voltage was applied to the organic EL element to emit light, and the initial light emitting performance was measured.
The luminous efficiency (%) is the luminous efficiency at ₁₀₀ Cd / m ² as the external quantum efficiency (η ₁₀₀ ) (%), and the luminance / current (Cd / A) is the slope of the luminance-current density characteristic. Table 1 shows the values at 100 cd / m ² .
In addition, a driving durability test was performed at an initial luminance of 1000 Cd / m ² , and the test results are shown in Table 1 with the time when the luminance was halved as half time (T _1/2 ) (Hr).
This device emitted green light (the maximum wavelength of the emission spectrum was 515 nm), and the light emission was identified to be derived from an iridium complex (Ir (ppy) ₃ ).

[Examples 2 to 5, Comparative Examples 1 to 3]
In the production of the organic EL device of Example 1, the electron transporting compound (compound represented by the general formula (I)) and the hole transporting compound in the electron transporting layer were changed as shown in Table 1 below. Except having done, it carried out similarly to Example 1, and produced the organic EL element of Examples 2-5 and Comparative Examples 1-3.
About each obtained organic EL element, evaluation similar to Example 1 was performed. The results are shown in Table 1.
The maximum wavelength of the emission spectrum of these devices was 515 nm, and the emission was identified to be derived from an iridium complex (Ir (ppy) ₃ ).

  The structures of the comparative compounds, TPD, and PPD listed in Table 1 are shown below.

  The organic EL device of the present invention can be suitably used in the fields of display devices, displays, backlights, electrophotography, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, optical communications, and the like.

Claims (4)

An organic electroluminescent element having an organic compound layer including at least one light emitting layer between a pair of electrodes, wherein at least one of the organic compound layers contains a compound represented by the following general formula (II) , And the organic electroluminescent element which contains at least 1 sort (s) of a triphenylamine derivative in the layer containing the compound represented by this general formula (II) .

(In general formula (II), R ¹ and R ² each independently represent a methyl group, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ^{5 to} R ⁸ each represent a hydrogen atom.) The organic electroluminescent element of Claim 1 which has an organic compound layer containing the compound represented by general formula (II) and at least 1 type of triphenylamine derivative between a light emitting layer and a cathode. The organic electroluminescent element according to claim 1, wherein the light emitting material contained in the light emitting layer is a phosphorescent material. The organic electroluminescent element according to claim 3, wherein the phosphorescent material is a transition metal complex.