WO2014030554A1 - Compound having triphenylsilyl pyridyl group and carbazole ring structure and organic electroluminescence device - Google Patents

Abstract

The invention pertains to a compound having a triphenylsilyl pyridyl group and carbazole ring structure represented by general formula (1) and to an organic electroluminescence device having a pair of electrodes and at least one organic layer interposed therebetween, wherein this compound is used as a structural material of at least one organic layer.

Description

Compound having triphenylsilylpyridyl group and carbazole ring structure and organic electroluminescence device

The present invention relates to a compound suitable for an organic electroluminescence element which is a self-luminous element suitable for various display devices and the element, and more specifically, a compound having a triphenylsilylpyridyl group and a carbazole ring structure, and the compound The present invention relates to an organic electroluminescence device using the above.

Since the organic electroluminescence element is a self-luminous element, it has been actively researched because it is brighter and more visible than a liquid crystal element and has a clear display.

In recent years, as an attempt to increase the luminous efficiency of an element, an element that generates phosphorescence using a phosphorescent material, that is, uses light emission from a triplet excited state has been developed. According to the theory of the excited state, when phosphorescent light emission is used, a remarkable improvement in light emission efficiency is expected in that light emission efficiency about four times that of conventional fluorescent light emission becomes possible.
In 1993, M.M. A. Baldo et al. Achieved an external quantum efficiency of 8% with a phosphorescent device using an iridium complex.

Since the phosphorescent material causes concentration quenching, it is supported by doping a charge transporting compound generally called a host compound. The supported phosphorescent emitter is called a guest compound. As this host compound, 4,4′-di (N-carbazolyl) biphenyl (hereinafter abbreviated as CBP) represented by the following formula has been generally used (for example, see Non-patent Document 1).

However, it has been pointed out that CBP has a low glass transition point (Tg) as low as 62 ° C. and strong crystallinity, so that it has poor stability in a thin film state. Therefore, satisfactory device characteristics have not been obtained in scenes where heat resistance is required, such as high luminance light emission.

As research on phosphorescent devices progresses, the elucidation of the energy transfer process between phosphorescent emitters and host compounds advances, and in order to increase luminous efficiency, the excited triplet level of the host compound is higher than the excited triplet level of the phosphorescent emitter. It has become clear that it must be high.

When FIrpic, which is a blue phosphorescent light emitting material represented by the following formula, is doped into the CBP to form a host compound of the light emitting layer, the external quantum efficiency of the phosphorescent light emitting element remains at about 6%. This is because the excited triplet level of FIrpic is 2.67 eV, whereas the excited triplet level of CBP is as low as 2.57 eV, so that confinement of triplet excitons by FIrpic is insufficient with CBP. It was considered. This is demonstrated by the fact that the photoluminescence intensity of a thin film doped with FIrpic in CBP shows temperature dependence. (For example, see Non-Patent Document 2)

As a host compound having a higher triplet level of excitation than CBP, 1,3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP) shown below is known. Since the point (Tg) is as low as 55 ° C. and the crystallinity is strong, the stability in the thin film state is poor. Therefore, satisfactory device characteristics have not been obtained in scenes where heat resistance is required, such as high luminance light emission. (For example, see Non-Patent Document 2)

In addition, it has been found that, when a host compound having a higher excited triplet level is studied, when an iridium complex is doped into an electron transporting or bipolar transporting host compound, high luminous efficiency can be obtained. (For example, see Non-Patent Document 3)

Thus, in order to increase the luminous efficiency of a phosphorescent light emitting device in a practical situation, a host compound of a light emitting layer having a high excited triplet level and high thin film stability has been required.

Japanese Unexamined Patent Publication No. 2007-022986

The object of the present invention is to have a high excited triplet level as a material for a highly efficient organic electroluminescence device, to sufficiently confine triplet excitons of a phosphorescent emitter, and to have high thin film stability. That is, it is to provide a host compound of a light emitting layer having a high glass transition point (Tg), and to provide a high-efficiency, high-brightness organic electroluminescence device using this compound. The physical properties that the organic compound to be provided by the present invention should have include (1) high excitation triplet level, (2) bipolar transportability, and (3) stable thin film state. I can give you. In addition, the physical characteristics that the organic electroluminescence device to be provided by the present invention should have include (1) high luminous efficiency, (2) high emission luminance, and (3) low practical driving voltage. I can give you something.

Therefore, in order to achieve the above object, the present inventors have confirmed that the triphenylsilyl group and the pyridine ring structure have an electron transporting ability, and that the carbazole ring structure has a good heat resistance and a hole transporting ability. A new compound with characteristics suitable for phosphorescent light emitting devices by designing and chemically synthesizing compounds using the excited triplet level as an indicator, and actually measuring the excited triplet level. A compound having a triphenylsilylpyridyl group and a carbazole ring structure was found. Then, various organic electroluminescence devices were prototyped using the compound, and the characteristics of the devices were intensively evaluated. As a result, the present invention was completed.

1) That is, the present invention provides a compound having a triphenylsilylpyridyl group represented by the following general formula (1) and a carbazole ring structure.

(In the formula, R ₁ to R ₁₀ may be the same or different, and may be a hydrogen atom, a deuterium atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms, or the number of carbon atoms. 1 to 6 linear or branched alkoxy groups, trifluoromethyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups, or substituted or unsubstituted condensed polycyclic aromatics Ar represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, and L represents a substituted or unsubstituted aromatic group. An aromatic hydrocarbon, a substituted or unsubstituted aromatic heterocyclic ring or a substituted or unsubstituted condensed polycyclic aromatic divalent group or trivalent group is represented, and n represents 1 or 2.)

2) The compound having a triphenylsilylpyridyl group and a carbazole ring structure described in 1) above is preferably a compound represented by the following general formula (1-1).

3) In the general formula (1) or the general formula (1-1), L is preferably a divalent group or a trivalent group formed by removing two or three hydrogen atoms from benzene.

4) The present invention also provides a compound having a triphenylsilylpyridyl group and a carbazole ring structure as described in 1) or 2) above, in an organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched therebetween. Provides an organic electroluminescence element used as a constituent material of the organic layer.

5) The organic layer in 4) above is preferably a light emitting layer.

6) The light emitting layer in the above 5) preferably contains a phosphorescent light emitting material.

7) It is preferable that the organic electroluminescent element according to 4) further includes a light emitting layer sandwiched between the pair of electrodes.

8) The light emitting layer in the above 7) preferably contains a phosphorescent light emitting material.

9) In the organic electroluminescence device described in 7) or 8) above, the compound having the triphenylsilylpyridyl group and carbazole ring structure described in 1) or 2) above is at least one component in the light emitting layer. It is preferably used as a material.

10) In the organic electroluminescence device according to any one of 6), 8) and 9) above, the phosphorescent light-emitting material is preferably a metal complex containing iridium or platinum.

“A linear or branched alkyl group having 1 to 6 carbon atoms” or “1 to 6 carbon atoms” represented by R ₁ to R ₁₀ in the general formula (1) and the general formula (1-1). As the “6 linear or branched alkoxy group”, specifically, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-pentyl group, i-pentyl group, t-pentyl group, n-hexyl group, i-hexyl group, t-hexyl group, methyloxy group, ethyloxy group, n-propyloxy group, i-propyloxy group, n -Butyloxy group, i-butyloxy group, t-butyloxy group, n-pentyloxy group, i-pentyloxy group, t-pentyloxy group, n-hexyloxy group, i-hexyloxy group, t-hexyloxy group It is possible to increase the UNA group. These groups may have a substituent, and these groups may be bonded to each other to form a ring. Examples of the substituent that these groups may have include the same groups as those defined as R ₁ to R ₁₀ .

"Substituted or unsubstituted aromatic hydrocarbon group" or "substituted or unsubstituted aromatic heterocyclic group" represented by R ₁ to R ₁₀ in formula (1) and formula (1-1) Or “aromatic hydrocarbon group”, “aromatic heterocyclic group” or “fused polycyclic aromatic group” of “substituted or unsubstituted condensed polycyclic aromatic group” specifically includes phenyl group, biphenylyl group , Terphenylyl group, tetrakisphenyl group, styryl group, naphthyl group, anthryl group, acenaphthenyl group, phenanthryl group, fluorenyl group, indenyl group, pyrenyl group, pyridyl group, triazinyl group, pyrimidinyl group, furyl group, pyrrolyl group, thienyl group, Quinolyl, isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, carbolyl, benzoxazolyl Benzothiazolyl group include a quinoxalyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, dibenzothienyl group, a naphthyridinyl group, a phenanthrolinyl group, groups such as acridinyl group.

“Substituted aromatic hydrocarbon group”, “substituted aromatic heterocyclic group” or “substituted condensed polycyclic aromatic represented by R ₁ to R ₁₀ in formula (1) and formula (1-1) Specific examples of the “substituent” in the “group” include a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms, and the number of carbon atoms 1 to 6 linear or branched alkoxy groups, trifluoromethyl group, phenyl group, biphenylyl group, terphenylyl group, naphthyl group, phenanthryl group, aralkyl group, fluorenyl group, indenyl group, pyridyl group, pyrimidinyl group, furyl Group, pyrrolyl group, thienyl group, quinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, carbolyl group, benzoxazolyl group, Examples include a group such as a noxalyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, and a dibenzothienyl group, and these substituents may be further substituted by the substituents exemplified above. They may be bonded to each other to form a ring.

The “substituted or unsubstituted aromatic hydrocarbon group”, “substituted or unsubstituted aromatic heterocyclic group” or “substituted or substituted” represented by Ar in the general formula (1) and the general formula (1-1) As the “aromatic hydrocarbon group”, “aromatic heterocyclic group” or “fused polycyclic aromatic group” of the “unsubstituted fused polycyclic aromatic group”, specifically, phenyl group, biphenylyl group, terphenylyl group, Tetrakisphenyl, styryl, naphthyl, anthryl, acenaphthenyl, phenanthryl, fluorenyl, indenyl, pyrenyl, pyridyl, triazinyl, pyrimidinyl, furyl, pyrrolyl, thienyl, quinolyl, isoquinolyl Group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, carbolyl group, benzoxazolyl group, benzo Azolyl group include a quinoxalyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, a phenanthrolinyl group, a group such as an acridinyl group.

In the “substituted aromatic hydrocarbon group”, “substituted aromatic heterocyclic group” or “substituted condensed polycyclic aromatic group” represented by Ar in the general formula (1) and the general formula (1-1), Specific examples of the substituent include deuterium atom, fluorine atom, chlorine atom, cyano group, nitro group, linear or branched alkyl group having 1 to 6 carbon atoms, and 1 to 6 carbon atoms. Linear or branched alkoxy group, trifluoromethyl group, phenyl group, biphenylyl group, terphenylyl group, naphthyl group, phenanthryl group, aralkyl group, fluorenyl group, indenyl group, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group , Thienyl group, quinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, carbolyl group, benzoxazolyl group, quinoxa Group, benzoimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, etc., and these substituents may be further substituted by the substituents exemplified above. They may be bonded to each other to form a ring.

“Substituted or unsubstituted aromatic hydrocarbon”, “substituted or unsubstituted aromatic heterocycle” or “substituted or unsubstituted” represented by L in formula (1) and formula (1-1) Specific examples of the “aromatic hydrocarbon”, “aromatic heterocycle” or “fused polycyclic aromatic” of “condensed polycyclic aromatic” include the following groups. Benzene, biphenyl, terphenyl, tetrakisphenyl, styrene, naphthalene, anthracene, acenaphthalene, fluorene, phenanthrene, indane, pyrene, pyridine, pyrimidine, triazine, furan, pyrrole, thiophene, quinoline, isoquinoline, benzofuran, benzothiophene, indoline, Examples thereof include carbazole, carboline, benzoxazole, benzothiazole, quinoxaline, benzimidazole, pyrazole, dibenzofuran, dibenzothiophene, naphthyridine, phenanthroline, and acridinine.
Further, the “divalent or trivalent group of substituted or unsubstituted aromatic hydrocarbon” represented by L in the general formula (1) and the general formula (1-1), “substituted or unsubstituted aromatic” The “divalent or trivalent group of heterocyclic ring” or the “substituted or unsubstituted condensed polycyclic aromatic divalent group or trivalent group” is the above “aromatic hydrocarbon”, “aromatic heterocycle” or “ A divalent group formed by removing two hydrogen atoms from a “fused polycyclic aromatic” or a trivalent group formed by removing three hydrogen atoms.
L in the general formula (1) and the general formula (1-1) is preferably a “divalent or trivalent group of a substituted or unsubstituted aromatic hydrocarbon”, particularly a divalent group derived from benzene. Alternatively, a trivalent group is more preferable, and a divalent group derived from benzene is particularly preferable.

The compound having a triphenylsilylpyridyl group and a carbazole ring structure represented by the general formula (1) and the general formula (1-1) of the present invention is a novel compound and has a higher excited triplet level than conventional materials. It has an excellent ability to confine triplet excitons and is stable in a thin film state.

In the general formulas (1) and (1-1) of the present invention, n represents 1 or 2, and n is more preferably 1.
In the general formulas (1) and (1-1) of the present invention, when L is a divalent group derived from benzene, the bonding position of the triphenylsilylpyridyl group and the carbazole ring structure is 1, 3 The -position (meta bond) or 1,2-position (ortho bond) is preferred, and the 1,2-position (ortho bond) is more preferred.
In the general formulas (1) and (1-1) of the present invention, the triphenylsilylpyridyl group is preferably any one of the following groups a) to e).

The compound having a triphenylsilylpyridyl group and a carbazole ring structure represented by the general formula (1) and the general formula (1-1) of the present invention is an organic electroluminescence device (hereinafter abbreviated as an organic EL device). It can be used as a constituent material of an organic layer, particularly a light emitting layer, more preferably a light emitting layer containing a phosphorescent light emitting material. By using the compound of the present invention, which is superior in bipolar transportability as compared with conventional materials, it has an effect that luminous efficiency is improved and practical driving voltage is lowered.

The compound having a triphenylsilylpyridyl group and a carbazole ring structure according to the present invention is useful as a host compound for a light emitting layer of an organic EL device. By producing an organic EL device using the compound, high efficiency and high brightness can be obtained. An organic EL element with a low driving voltage can be obtained.

FIG. 1 is a ¹ H-NMR chart of the compound of Example 1 of the present invention (Compound 10). FIG. 2 is a ¹ H-NMR chart of the compound of Example 2 of the present invention (Compound 3). FIG. 3 is a diagram showing the EL element configurations of Example 6 and Comparative Example 1.

The compound having a triphenylsilylpyridyl group and a carbazole ring structure according to the present invention is a novel compound, and these compounds can be synthesized, for example, as follows. First, a corresponding carbazolylphenyl intermediate is synthesized by performing a cross-coupling reaction such as Suzuki coupling between the corresponding carbazole derivative and the corresponding halogenated benzene derivative (for example, see Non-Patent Document 4). Can do. The corresponding carbazolylphenyl intermediate is converted into a corresponding borate ester, and then subjected to a cross-coupling reaction such as Suzuki coupling with the corresponding dihalogenated pyridyl derivative, and then the corresponding borate ester The compound having a triphenylsilylpyridyl group and a carbazole ring structure of the present invention can be synthesized by reacting with lithiated compound or lithiated compound and further with triphenylsilyl chloride.

Specific examples of preferable compounds among the compounds having a triphenylsilylpyridyl group represented by the general formula (1) and a carbazole ring structure are shown below, but the present invention is not limited to these compounds. .

These compounds were purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization using a solvent, crystallization method, and the like. The compound was identified by NMR analysis. As a physical property value, a glass transition point (Tg) and a work function were measured. The glass transition point (Tg) is an index of the stability of the thin film state, and the work function is an index of the energy level as the light emitting host material.

The glass transition point (Tg) was measured with a high sensitivity differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.) using powder.

The work function was measured using an atmospheric photoelectron spectrometer (AC-3 type, manufactured by Riken Keiki Co., Ltd.) by forming a 100 nm thin film on the ITO substrate.

The excited triplet level of the compound of the present invention can be calculated from the measured phosphorescence spectrum. The phosphorescence spectrum can be measured using a commercially available spectrophotometer. As a general phosphorescence spectrum measurement method, a sample is dissolved in a solvent and irradiated with excitation light at a low temperature (for example, see Non-Patent Document 5), or the sample is deposited on a silicon substrate. There is a method of measuring a phosphorescence spectrum by irradiating excitation light at a low temperature by using a thin film (for example, see Patent Document 1). The excited triplet level can be calculated by reading the wavelength of the first peak on the short wavelength side of the phosphorescence spectrum or the wavelength of the rising position on the short wavelength side and converting it to the light energy value according to the following equation. The excited triplet level is an indicator of the confinement of triplet excitons in the phosphorescent emitter.

Where E is the value of light energy, h is Planck's constant (6.63 × 10 ⁻³⁴ Js), c is the speed of light (3.00 × 10 ⁸ m / s), and λ is the short wavelength of the phosphorescence spectrum. It represents the wavelength (nm) where the side rises. And 1 eV becomes 1.60 × 10 ⁻¹⁹ J.

As the structure of the organic EL device of the present invention, on the substrate sequentially, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transport layer, a cathode, Further, there may be mentioned those having an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, several organic layers can be omitted. For example, an anode, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode can be sequentially formed on the substrate. , Anode, hole transport layer, light emitting layer, electron transport layer, and cathode.

The light emitting layer, the hole transport layer, and the electron transport layer may each have a structure in which two or more layers are stacked.

As the anode of the organic EL element of the present invention, an electrode material having a large work function such as ITO or gold is used. As a hole injection layer of the organic EL device of the present invention, in addition to a porphyrin compound typified by copper phthalocyanine, a naphthalenediamine derivative, a starburst type triphenylamine derivative, a molecule having three or more triphenylamine structures, Triphenylamine trimers and tetramers such as arylamine compounds having a structure linked by a divalent group containing no bond or hetero atom, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and coating-type polymers Materials can be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As a hole transport layer of the organic EL device of the present invention, in addition to a compound containing an m-carbazolylphenyl group, N, N′-diphenyl-N, N′-di (m-tolyl) -benzidine (hereinafter referred to as “a”) N, N′-diphenyl-N, N′-di (α-naphthyl) -benzidine (hereinafter abbreviated as NPD), N, N, N ′, N′-tetrabiphenylylbenzidine, etc. Benzidine derivatives, 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (hereinafter abbreviated as TAPC), various triphenylamine trimers and tetramers, and carbazole derivatives can be used. . These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. In addition, as a hole injection / transport layer, a coating type such as poly (3,4-ethylenedioxythiophene) (hereinafter abbreviated as PEDOT) / poly (styrene sulfonate) (hereinafter abbreviated as PSS) is used. These polymer materials can be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

Further, in the hole injection layer or the hole transport layer, a material in which trisbromophenylamine hexachloroantimony is further P-doped to a material usually used in the layer, or a polymer having a TPD structure in its partial structure A compound or the like can be used.

As an electron blocking layer of the organic EL device of the present invention, 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (hereinafter abbreviated as TCTA), 9,9-bis [4- (carbazole- 9-yl) phenyl] fluorene, 1,3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP), 2,2-bis (4-carbazol-9-ylphenyl) adamantane (hereinafter Ad) Carbazole derivatives such as 9- [4- (carbazol-9-yl) phenyl] -9- [4- (triphenylsilyl) phenyl] -9H-fluorene And a compound having an electron blocking action such as a compound having a triarylamine structure can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As the light emitting layer of the organic EL device of the present invention, various metal complexes such as metal complexes of quinolinol derivatives including tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq ₃ ), anthracene derivatives, bisstyrylbenzene derivatives , Pyrene derivatives, oxazole derivatives, polyparaphenylene vinylene derivatives, and the like can be used. The light-emitting layer may be composed of a host material and a dopant material. In this case, a compound having a triphenylsilylpyridyl group and a carbazole ring structure represented by the general formula (1) of the present invention as the host material, mCP , Thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, and the like can be used. As the dopant material, quinacridone, coumarin, rubrene, anthracene, perylene and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used.

Further, a phosphorescent light emitting material can be used as the light emitting material. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. Green phosphorescent emitters such as Ir (ppy) ₃ , blue phosphorescent emitters such as FIrpic and FIr6, and red phosphorescent emitters such as Btp ₂ Ir (acac) and Ir (piq) ₃ are used. As a host material, a compound having a triphenylsilylpyridyl group and a carbazole ring structure represented by the general formula (1) of the present invention, a hole injection / transport host material such as CBP, TCTA, and mCP can be used. A carbazole derivative or the like can be used. As an electron transporting host material, p-bis (triphenylsilyl) benzene (hereinafter abbreviated as UGH2) or 2,2 ′, 2 ″-(1,3,5-phenylene) -tris (1-phenyl) -1H-benzimidazole) (hereinafter abbreviated as TPBI) and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used.

In order to avoid concentration quenching, it is preferable to dope the phosphorescent light-emitting material into the host material by co-evaporation in the range of 1 to 30 weight percent with respect to the entire light-emitting layer.

These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

In addition, an element having a structure in which a light-emitting layer manufactured using a compound having a different work function as a host material is stacked adjacent to a light-emitting layer manufactured using the compound of the present invention can be manufactured (for example, non-patented). Reference 6).

As the hole blocking layer of the organic EL device of the present invention, phenanthroline derivatives such as bathocuproine (hereinafter abbreviated as BCP), aluminum (III) bis (2-methyl-8-quinolinato) -4-phenylphenolate (hereinafter referred to as “BCP”). In addition to metal complexes of quinolinol derivatives such as BAlq), various rare earth complexes, oxazole derivatives, triazole derivatives, triazine derivatives, and the like can be used. These materials may also serve as the material for the electron transport layer. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As an electron transport layer of the organic EL device of the present invention, various metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, thiadiazole derivatives, carbodiimide derivatives, quinoxaline, in addition to metal complexes of quinolinol derivatives including Alq ₃ and BAlq. Derivatives, phenanthroline derivatives, silole derivatives, benzimidazole derivatives such as TPBI, and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As the electron injection layer of the organic EL device of the present invention, an alkali metal salt such as lithium fluoride and cesium fluoride, an alkaline earth metal salt such as magnesium fluoride, and a metal oxide such as aluminum oxide can be used. In the preferred selection of the electron transport layer and the cathode, this can be omitted.

Furthermore, in the electron injecting layer or the electron transporting layer, a material usually used for the layer and further doped with a metal such as cesium can be used.

As the cathode of the organic EL device of the present invention, an electrode material having a low work function such as aluminum or an alloy having a lower work function such as a magnesium silver alloy, a magnesium indium alloy, or an aluminum magnesium alloy is used as the electrode material.

Hereinafter, embodiments of the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

<Synthesis of 3- [2- {5- (triphenylsilyl) pyridin-2-yl} phenyl] -9-phenyl-9H-carbazole (Compound 10)>
In a reaction vessel purged with nitrogen, 30 g of 9-phenyl-3- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl) -9H-carbazole, 2-bromo-iodobenzene 68.9 g, 1M aqueous potassium carbonate solution 75 ml, 2-ethoxyethanol 30 ml, dioxane 45 ml were added and nitrogen was bubbled. Tetrakistriphenylphosphinepalladium (2.34 g) was added, and the mixture was heated with stirring and refluxed for 24 hours. The reaction solution was cooled to room temperature, the organic layer was collected by a liquid separation operation, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane / toluene), and 28 g of white powder of 3- (2-bromophenyl) -9-phenyl-9H-carbazole (88% yield) Got.

The obtained 3- (2-bromophenyl) -9-phenyl-9H-carbazole (13 g) and anhydrous THF (130 ml) were added to a reaction vessel purged with nitrogen and cooled to -60 ° C. Subsequently, 40 ml of a hexane solution (1.65 mol / L) of n-butyllithium was added dropwise and stirred for 2 hours, and then 6.8 g of trimethyl borate was added dropwise and stirred for 3 hours. After raising the temperature to room temperature, 30 ml of 10% aqueous ammonium chloride solution was added and stirred for 1 hour. The reaction solution was extracted with toluene, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene / methanol) to give 7.8 g of 2- (9-phenyl-9H-carbazol-3-yl) phenylboronic acid white powder (yield). 88%).

The resulting 2- (9-phenyl-9H-carbazol-3-yl) phenylboronic acid (3.0 g), 2,5-dibromopyridine (2.0 g), 2M aqueous potassium carbonate solution (12 ml), toluene (24 ml), and ethanol (6 ml) were purged with nitrogen. In addition to the reaction vessel, nitrogen was bubbled for 1 hour while irradiating ultrasonic waves. Subsequently, 0.3 g of tetrakis (triphenylphosphine) palladium (0) was added, heated with stirring, and refluxed for 20 hours. The reaction solution was cooled to room temperature, the organic layer was collected by a liquid separation operation, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene) and white powder of 3- [2- (5-bromopyridin-2-yl) phenyl] -9-phenyl-9H-carbazole 1.7 g (yield: 43%) was obtained.

The obtained 3- [2- (5-bromopyridin-2-yl) phenyl] -9-phenyl-9H-carbazole (7.5 g) and dehydrated cyclopentylmethyl ether (120 ml) were added to a nitrogen-substituted reaction vessel, and the temperature was reduced to -5 ° C. Cooled down. Subsequently, 18 ml of a hexane solution (1.65 mol / L) of n-butyllithium was added dropwise, then 9.0 g of triphenylsilyl chloride was added, stirred for 1 hour, then warmed to room temperature, and further stirred for 7 hours. .
The organic layer was collected by a liquid separation operation, dehydrated using anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: NH silica gel, eluent: ethyl acetate / cyclohexane) and further crystallized to give 3- [2- {5- (triphenylsilyl) pyridin-2-yl } Phenyl] -9-phenyl-9H-carbazole (1.8 g, yield: 17%) was obtained.

The structure of the obtained white powder was identified using NMR. ^The results of ¹ H-NMR measurement are shown in FIG.

^The following 34 hydrogen signals were detected by ¹ H-NMR (THF-d8). δ (ppm) = 8.69 (1H), 8.05 (1H), 8.01 (1H), 7.76 (1H), 7.65 (2H), 7.60 (2H), 7.56 (1H), 7.51-7.34 (15H), 7.30-7.20 (8H), 7.14 (1H), 6.91 (1H).

<Synthesis of 3- [3- {5- (triphenylsilyl) pyridin-2-yl} phenyl] -9-phenyl-9H-carbazole (Compound 3)>
In a reaction vessel purged with nitrogen, 46.0 g of (9-phenyl-9H-carbazol-3-yl) boronic acid, 49.9 g of 3-bromo-iodobenzene, 81 ml of 2M aqueous potassium carbonate solution, 368 ml of toluene, 92 ml of ethanol, tetrakistri 2.8 g of phenylphosphine palladium was added, heated with stirring, and refluxed for 9 hours. The reaction solution was cooled to room temperature, the organic layer was collected by a liquid separation operation, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane / toluene), and 23.4 g of 3- (3-bromophenyl) -9-phenyl-9H-carbazole white powder (yield 65 %).

The obtained 3- (3-bromophenyl) -9-phenyl-9H-carbazole 31.3 g, bis (pinacolato) diborane 23.8 g, potassium acetate 23.0 g, toluene 626 ml, [1,1′-bis (diphenyl) Phosphino) ferrocene] palladium (II) dichloride (1.9 g) was added to a nitrogen-substituted reaction vessel, heated with stirring, and refluxed for 6.5 hours. The reaction solution was cooled to room temperature and filtered to obtain a crude product by concentrating the filtrate obtained under reduced pressure. The crude product was purified by column chromatography (carrier: diol silica gel, eluent: hexane / toluene), and 3- {3- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolane- There was obtained 37.3 g (yield 107%) of 2-yl) phenyl} -9-phenyl-9H-carbazole as a colorless oil.

The obtained 3- {3- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl) phenyl} -9-phenyl-9H-carbazole 35.3 g, 2,5 -18.8 g of dibromopyridine, 150 ml of 2M aqueous potassium carbonate solution, 600 ml of toluene, 150 ml of ethanol, and 4.6 g of tetrakis (triphenylphosphine) palladium were added to a reaction vessel purged with nitrogen, heated with stirring, and refluxed for 5 hours. . The reaction solution was cooled to room temperature, the organic layer was collected by a liquid separation operation, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: NH silica gel, eluent: hexane / toluene) to give 3- {3- (5-bromopyridin-2-yl) phenyl} -9-phenyl-9H-carbazole. 25.1 g (yield: 67%) of white powder was obtained.

The obtained 3- {3- (5-bromopyridin-2-yl) phenyl} -9-phenyl-9H-carbazole (19.7 g) and dehydrated cyclopentyl methyl ether (450 ml) were added to a nitrogen-substituted reaction vessel, and the temperature was reduced to -60 ° C. Cooled down. After dropwise addition of 51 ml of a hexane solution (1.6 mol / L) of n-butyllithium, 24.4 g of triphenylsilyl chloride was added, and the mixture was warmed to room temperature and stirred for 7 hours.
The organic layer was collected by a liquid separation operation, dehydrated with anhydrous magnesium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: NH silica gel, eluent: hexane / toluene) to give 3- [3- {5- (triphenylsilyl) pyridin-2-yl} phenyl] -9-phenyl- 3.5 g (yield: 10%) of 9H-carbazole white powder was obtained.

The structure of the obtained white powder was identified using NMR. ^The results of ¹ H-NMR measurement are shown in FIG.

^The following 34 hydrogen signals were detected by ¹ H-NMR (THF-d8). δ (ppm) = 8.80 (1H), 8.59 (1H), 8.54 (1H), 8.25 (1H), 8.08 (1H), 8.00 (1H), 7.96 (1H), 7.81 (1H), 7.78 (1H), 7.68-7.58 (10H), 7.55 (1H), 7.51-7.38 (13H), 7.25 (1H).

About the compound of this invention, the glass transition point was calculated | required with the highly sensitive differential scanning calorimeter (The Seiko Instruments make, DSC6200).

Glass transition point
Inventive Example 1 Compound 102 ° C.

The compound of the present invention has a glass transition point of 100 ° C. or higher. This indicates that the thin film state is stable in the compound of the present invention.

Using the compound of the present invention, a deposited film having a thickness of 100 nm was prepared on an ITO substrate, and the work function was measured with an atmospheric photoelectron spectrometer (AC-3 type, manufactured by Riken Keiki Co., Ltd.).

Work Function Compound of the Invention Example 1 5.70 eV
Inventive Example 2 compound 5.71 eV
CBP 6.00eV

Thus, the compound of the present invention shows a suitable energy level as compared with CBP generally used as a luminescent host.

About the compound of this invention, after forming a 100 nm thin film and cooling to 77K, the phosphorescence spectrum was measured by irradiating excitation light using a fluorescence phosphorescence spectrophotometer (Horiba, FluoroMax-4 type). . The wavelength at the rising position on the short wavelength side of the phosphorescence spectrum was read, and the excited triplet level was calculated by converting the wavelength value into light energy.

Excited triplet level Compound of Example 1 of the present invention 2.64 eV
Inventive Example 2 compound 2.70 eV
CBP 2.57eV

Thus, the compound of the present invention has a value larger than the triplet energy of commonly used CBP and has the ability to sufficiently confine the triplet energy excited in the light emitting layer.

As shown in FIG. 3, the organic EL element has a hole transport layer 3, a light emitting layer 4, an electron transport layer 5, and an electron injection layer 6 on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. The cathode (aluminum electrode) 7 was deposited in this order.

Specifically, the glass substrate 1 on which ITO having a thickness of 150 nm was formed was washed with an organic solvent, and then the surface was washed by oxygen plasma treatment. Then, this glass substrate with an ITO electrode was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.001 Pa or less.
Subsequently, TAPC was formed as a hole transport layer 3 so as to cover the transparent anode 2 so as to have a film thickness of 30 nm at a deposition rate of 1.0 kg / sec. On this hole transport layer 3, the compound (compound 10) of Example 1 of the present invention and the green phosphorescent emitter Ir (ppy) ₃ are used as the light-emitting layer 4. 10): Dual deposition was performed at a deposition rate of Ir (ppy) ₃ = 93: 7 to form a film thickness of 40 nm. On the light emitting layer 4, the TPBI was formed as the electron transport layer 5 so as to have a film thickness of 45 nm at a deposition rate of 1.0 Å / sec. On the electron transport layer 5, lithium fluoride was formed as the electron injection layer 6 so as to have a film thickness of 0.5 nm at a deposition rate of 0.1 Å / sec. Finally, aluminum was deposited to a thickness of 150 nm to form the cathode 7. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere.

The measurement results of the light emission characteristics when a DC voltage was applied to the organic EL device produced using the compound of Example 1 of the present invention (Compound 10) are shown in Table 1.

[Comparative Example 1]
For comparison, the material of the light emitting layer 4 in Example 6 was changed from the compound of Example 1 (Compound 10) to CBP, and an organic EL device was produced under the same conditions. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere. Table 1 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the produced organic EL element.

As shown in Table 1, the driving voltage when a current density of 10 mA / cm ² was passed was the compound of Example 1 of the present invention (Compound 10) with respect to 7.7 V of the organic EL device using CBP. In the organic EL element used, the voltage was lowered to 5.9V. In addition, the luminance when a current density of 10 mA / cm ² was passed was greatly improved. In addition, luminous efficiency and external quantum efficiency were improved.

As described above, the compound of the present invention has a high excited triplet level, transfers energy well to the phosphorescent emitter, sufficiently confines the triplet excitons of the phosphorescent emitter, and also has a thin film stability. Since it is good, it can be said that it is excellent as a host compound of the light emitting layer.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2012-181997 filed on August 21, 2012, the contents of which are incorporated herein by reference.

The compound having a triphenylsilylpyridyl group and a carbazole ring structure of the present invention has a high excited triplet level, can sufficiently confine the triplet exciton of the phosphor, and has good thin film stability. It is excellent as a host compound for the light emitting layer. In addition, by producing an organic EL element using the compound, the luminance and light emission efficiency of the conventional organic EL element can be remarkably improved, and thus the performance of the mobile electronic product can be improved.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent anode 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Electron injection layer 7 Cathode

Claims (10)

1. A compound represented by the following general formula (1) having a triphenylsilylpyridyl group and a carbazole ring structure.
   

   

   
   (In the formula, R ₁ to R ₁₀ may be the same or different, and may be a hydrogen atom, a deuterium atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms, or the number of carbon atoms. 1 to 6 linear or branched alkoxy groups, trifluoromethyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups, or substituted or unsubstituted condensed polycyclic aromatics Ar represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, and L represents a substituted or unsubstituted aromatic group. An aromatic hydrocarbon, a substituted or unsubstituted aromatic heterocyclic ring or a substituted or unsubstituted condensed polycyclic aromatic divalent group or trivalent group is represented, and n represents 1 or 2.)
2. The compound having a triphenylsilylpyridyl group and a carbazole ring structure according to claim 1, represented by the following general formula (1-1).
   

   
3. 3. The general formula (1) or the general formula (1-1), wherein L is a divalent group or a trivalent group formed by removing two or three hydrogen atoms from benzene. A compound having a triphenylsilylpyridyl group and a carbazole ring structure.
4. 3. An organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched therebetween, wherein the compound having a triphenylsilylpyridyl group and a carbazole ring structure according to claim 1 or 2 is the organic layer. An organic electroluminescence device used as a constituent material of
5. The organic electroluminescence device according to claim 4, wherein the organic layer is a light emitting layer.
6. The organic electroluminescent element according to claim 5, wherein the light emitting layer contains a phosphorescent light emitting material.
7. The organic electroluminescence device according to claim 4, further comprising a light emitting layer sandwiched between the pair of electrodes.
8. The organic electroluminescence device according to claim 7, wherein the light emitting layer contains a phosphorescent light emitting material.
9. The compound having a triphenylsilylpyridyl group and a carbazole ring structure according to claim 1 or 2 is used as at least one constituent material in the light emitting layer. The organic electroluminescent element of description.
10. The organic electroluminescent element according to any one of claims 6, 8, and 9, wherein the phosphorescent light emitting material is a metal complex containing iridium or platinum.

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