JP5285851B2 - Oxadiazole derivative and light emitting element using oxadiazole derivative - Google Patents

Description

The present invention relates to oxadiazole derivatives. The present invention also relates to a light-emitting element, a light-emitting device, and an electronic device using the oxadiazole derivative.

  Organic compounds are more diverse than inorganic compounds, and there is a possibility that substances having various functions can be designed and synthesized. Due to these advantages, attention has been focused on electronics using organic compounds in recent years. For example, a solar cell, a light emitting element, a transistor, and the like using an organic compound as a functional material are typical examples.

These are devices that utilize the electrical properties and optical properties of organic compounds, and in particular, research and development of light-emitting elements using organic compounds as light-emitting substances are making remarkable progress.

The structure of this light-emitting element is a simple structure in which a light-emitting layer containing an organic compound, which is a light-emitting substance, is provided between the electrodes. From the characteristics such as thin and light, high-speed response, and direct current low-voltage drive, It attracts attention as a flat panel display element. In addition, a display using this light-emitting element is characterized by excellent contrast and image quality and a wide viewing angle.

The light emitting mechanism of a light emitting element using an organic compound as a light emitting substance is a carrier injection type. In other words, by applying a voltage with the light emitting layer sandwiched between the electrodes, holes and electrons injected from the electrodes are recombined, and the luminescent material becomes excited, and emits light when the excited state returns to the ground state. . The types of excited states include a singlet excited state (S ^* ) and a triplet excited state (T ^* ). Further, the statistical generation ratio of the light emitting element is considered to be S ^* : T ^* = 1: 3.

A compound that converts a singlet excited state into light emission (hereinafter referred to as a fluorescent compound) does not emit light (phosphorescence) from the triplet excited state at room temperature, and only emits light (fluorescence) from the singlet excited state. Observed. Therefore, the theoretical limit of the internal quantum efficiency (ratio of photons generated with respect to injected carriers) in a light emitting device using a fluorescent compound is 25% on the basis that S ^* : T ^* = 1: 3. It is said that.

On the other hand, if a compound that converts a triplet excited state into light emission (hereinafter referred to as a phosphorescent compound) is used, the internal quantum efficiency can be theoretically made 75 to 100%. That is, the light emission efficiency is 3 to 4 times that of the fluorescent compound. For these reasons, in order to realize a highly efficient light-emitting element, a light-emitting element using a phosphorescent compound has been actively developed in recent years (see, for example, Non-Patent Document 1).

In the case where a light-emitting layer of a light-emitting element is formed using the above-described phosphorescent compound, in order to suppress concentration quenching of the phosphorescent compound and quenching due to triplet-triplet annihilation, the phosphorescence is included in a matrix formed of another substance. Often formed such that the compound is dispersed. At this time, a substance that becomes a matrix is called a host material, and a substance dispersed in the matrix such as a phosphorescent compound is called a guest material.

When a phosphorescent compound is used as a guest material, the property required for the host material is to have triplet excitation energy (energy difference between the ground state and the triplet excited state) larger than that of the phosphorescent compound. CBP used as a host material in Non-Patent Document 1 is known to have a triplet excitation energy larger than that of a phosphorescent compound that emits green to red light, and is a host material for the phosphorescent compound. As widely used.

However, CBP has a problem in that the driving voltage becomes high because of its poor ability to receive holes and electrons in exchange for its large triplet excitation energy. Therefore, a substance having a large triplet excitation energy, easily accepting and transporting both holes and electrons (that is, a substance having a bipolar property) is required as a host material for a phosphorescent compound.

In addition, since the singlet excitation energy (energy difference between the ground state and the singlet excited state) is larger than the triplet excitation energy, a substance having a large triplet excitation energy also has a large singlet excitation energy. Therefore, a substance having a large triplet excitation energy and having a bipolar property as described above is also useful in a light-emitting element using a fluorescent compound as a light-emitting substance.

M.M. A. Bardo, 4 others, Applied Physics Letters, Vol. 75, no. 1, 4-6 (1999)

In view of the above, an object of the present invention is to provide a substance having a large excitation energy, particularly a substance having a large triplet excitation energy. Another object of the present invention is to provide a bipolar substance.

Another object is to provide a light-emitting element with high emission efficiency by applying such a substance to the light-emitting element. Another object is to provide a light-emitting element with low driving voltage.

Furthermore, it is an object to provide a light-emitting device with low power consumption by manufacturing a light-emitting device using the above-described light-emitting element. Another object is to provide an electronic device with low power consumption by applying such a light-emitting device to the electronic device.

As a result of intensive studies, the present inventors have found that an oxadiazole derivative represented by the following general formula (G1) can solve the problem. Therefore, the structure of the present invention is an oxadiazole derivative represented by the following general formula (G1).

（式中、Ａ_ｍは、一般式（Ａｍ１）、または（Ａｍ２）、または（Ａｍ３）のいずれかで表される置換基である。また、α、β^１、β^２は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(Wherein, _{A m} of the general formula (Am1), or (Am2), or (Am3) is a substituent represented by any one of. Furthermore, alpha, beta ^1, beta ² is 6 carbon atoms represents an arylene group 25. the _a ^r 1 _~A ^{r 6} represents an aryl group having 6 to 25 carbon atoms. the ^R 1 to R ³ is hydrogen or an alkyl group having 1 to 4 carbon atoms, or carbon, It represents any of an aryl group having 6 to 25. R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms.

The general formula (G1), when applied general formula (Am1) as a substituent A _m, oxadiazole derivatives of the present invention is represented by the following general formula (G2). Therefore, the structure of the present invention is an oxadiazole derivative represented by the following general formula (G2).

（式中、α、β^１は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１〜Ａ_ｒ ^２は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^２は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(In the formula, α and β ¹ represent an arylene group having 6 to 25 carbon atoms. A _r ^{1 to} A _r ² represent an aryl group having 6 to 25 carbon atoms. R ^{1 to} R ² are It represents either hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms.)

Here, β ¹ in the general formula (G2) is preferably a phenylene group in order to obtain larger triplet excitation energy and chemical stability at the same time. Therefore, a preferable structure of the present invention is an oxadiazole derivative represented by the following general formula (G3).

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１〜Ａ_ｒ ^２は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^２は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The _A ^r 1 _~A ^{r 2} represents an aryl group having 6 to 25 carbon atoms. The ^R 1 to R ² is hydrogen or, It represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms.)

In addition, since a larger triplet excitation energy can be obtained and synthesis is easy, A _r ¹ is preferably a substituted or unsubstituted phenyl group. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G4). Note that it is preferable that α is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group because it can be synthesized at a low cost and with a high yield.

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^２は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^２は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。）

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The _A ^{r 2} represents an aryl group having 6 to 25 carbon atoms. The ^R 1 to R ² are hydrogen or carbon atoms 1, 4 represents an alkyl group having 4 or an aryl group having 6 to 25 carbon atoms, and R ^{5 to} R ⁹ are hydrogen, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, Or represents a phenyl group.)

  In particular, when α is a 1,4-phenylene group, it is preferable because chemical stability and high carrier transportability can be obtained. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G5).

（式中、Ａ_ｒ ^２は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^２は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。）

_{(Wherein, A} ^{r 2} represents an aryl group. The ^R 1 to R ² of 6 to 25 carbon atoms, hydrogen, or an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms, R ^{5 to} R ⁹ each represent hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group.

Further, A _r ^2, in order to obtain a larger triplet excitation energy, is preferably a substituted or unsubstituted phenyl group. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G6).

（式中、Ｒ^１〜Ｒ^２は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。またＲ^１０〜Ｒ^１４は、水素、または炭素数１〜４のアルキル基、またはフェニル基のいずれかを表す。）

(In the formula, R ^{1 to} R ² represent either hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. R ^{5 to} R ⁹ represent hydrogen or carbon. It represents any of an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group, and R ^{10 to} R ¹⁴ are hydrogen, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Represents one of these.)

Then, the above general formula in (G1), when applied general formula (Am2) as a substituent A _m, oxadiazole derivatives of the present invention is represented by the following general formula (G7). Therefore, the structure of the present invention is an oxadiazole derivative represented by the following general formula (G7).

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１およびＡ_ｒ ^３は、炭素数６〜２５のアリール基を表す。またＲ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(In the formula, α represents an arylene group having 6 to 25 carbon atoms, A _r ¹ and A _r ³ represent an aryl group having 6 to 25 carbon atoms, and R ³ represents hydrogen or 1 carbon atom. Represents an alkyl group having ˜4 or an aryl group having 6 to 25 carbon atoms, and R ⁴ represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. )

Here, since larger triplet excitation energy can be obtained and synthesis is easy, A _r ¹ is preferably a substituted or unsubstituted phenyl group. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G8). Note that it is preferable that α is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group because it can be synthesized at a low cost and with a high yield.

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^３は、炭素数６〜２５のアリール基を表す。またＲ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。）

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The _A ^{r 3} represents an aryl group having 6 to 25 carbon atoms. The ^{R 3} is hydrogen or alkyl of 1 to 4 carbon atoms, group, or an aryl group having 6 to 25 carbon atoms. the ^{R 4} represents either an alkyl group or an aryl group having 6 to 25 carbon atoms, 1 to 4 carbon atoms. the ^R 5 ~ R ⁹ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group.)

In particular, when α is a 1,4-phenylene group, it is preferable because chemical stability and high carrier transportability can be obtained. Further, when R ³ is hydrogen, synthesis is easy and it is preferable. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G9).

（式中、Ａ_ｒ ^３は、炭素数６〜２５のアリール基を表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。）

_{(Wherein, A} ^{r 3} represents an aryl group having 6 to 25 carbon atoms. The ^{R 4} represents either an alkyl group or an aryl group having 6 to 25 carbon atoms, 1 to 4 carbon atoms. The R ^{5 to} R ^{9 each} represent hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group.

Further, A _r ^3, in order to obtain a larger triplet excitation energy, is preferably a substituted or unsubstituted phenyl group. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G10).

（式中、Ｒ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。またＲ^１０〜Ｒ^１４は、水素、または炭素数１〜４のアルキル基、またはフェニル基のいずれかを表す。）

(In the formula, R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. R ^{5 to} R ⁹ are hydrogen or alkyl having 1 to 4 carbon atoms. A group, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group, and R ^{10 to} R ¹⁴ each represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. )

Then, the above general formula in (G1), when applied general formula (Am3) as a substituent A _m, oxadiazole derivatives of the present invention is represented by the following general formula (G11). Therefore, the structure of the present invention is an oxadiazole derivative represented by the following general formula (G11).

（式中、α、β^２は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１およびＡ_ｒ ^４〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。）

(In the formula, α and β ² represent an arylene group having 6 to 25 carbon atoms. A _r ¹ and A _r ^{4 to} A _r ⁶ represent an aryl group having 6 to 25 carbon atoms.)

Here, in order to obtain larger triplet excitation energy and at the same time obtain chemical stability, β ² in the general formula (G11) is preferably a phenylene group. Therefore, a preferable structure of the present invention is an oxadiazole derivative represented by the following general formula (G12).

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１およびＡ_ｒ ^４〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。）

(In the formula, α represents an arylene group having 6 to 25 carbon atoms. A _r ¹ and A _r ^{4 to} A _r ⁶ represent an aryl group having 6 to 25 carbon atoms.)

In addition, A _r ⁵ and A _r ⁶ are preferably a substituted or unsubstituted phenyl group in order to obtain larger triplet excitation energy. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G13).

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１およびＡ_ｒ ^４は、炭素数６〜２５のアリール基を表す。またＲ^１５〜Ｒ^２４は、水素、または炭素数１〜４のアルキル基、またはフェニル基のいずれかを表す。）

(In the formula, α represents an arylene group having 6 to 25 carbon atoms, A _r ¹ and A _r ⁴ represent an aryl group having 6 to 25 carbon atoms, and R ^{15 to} R ²⁴ represent hydrogen, or It represents either an alkyl group having 1 to 4 carbon atoms or a phenyl group.)

In addition, since a larger triplet excitation energy can be obtained and synthesis is easy, A _r ¹ is preferably a substituted or unsubstituted phenyl group. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G14). Note that it is preferable that α is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group because it can be synthesized at a low cost and with a high yield.

（式中、αは、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^４は、炭素数６〜２５のアリール基を表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。またＲ^１５〜Ｒ^２４は、水素、または炭素数１〜４のアルキル基、またはフェニル基のいずれかを表す。）

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The _A ^{r 4} represents an aryl group having 6 to 25 carbon atoms. The ^R 5 to R ⁹ is hydrogen or a carbon number 1, 4 represents an alkyl group having 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group, and R ^{15 to} R ²⁴ are either hydrogen, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Represents.)

In particular, when α is a 1,4-phenylene group, it is preferable because chemical stability and high carrier transportability can be obtained. ^Further, when R 15 ^{to R 24} are hydrogen, synthesis is easy preferable. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G15).

（式中、Ａ_ｒ ^４は、炭素数６〜２５のアリール基を表す。またＲ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。）

_{(Wherein, A} ^{r 4} represents an aryl group having 6 to 25 carbon atoms. The ^R 5 to R ⁹ is hydrogen or an alkyl group having 1 to 4 carbon atoms or alkoxy group having 1 to 4 carbon atoms,, Or represents a phenyl group.)

Furthermore, A _r ⁴ is preferably a substituted or unsubstituted phenyl group in order to obtain a larger triplet excitation energy. Therefore, another structure of the present invention is an oxadiazole derivative represented by the following general formula (G16).

（式中、Ｒ^５〜Ｒ^９は、水素、または炭素数１〜４のアルキル基、または炭素数１〜４のアルコキシ基、またはフェニル基のいずれかを表す。またＲ^１０〜Ｒ^１４は、水素、または炭素数１〜４のアルキル基、またはフェニル基のいずれかを表す。）

^(Wherein, R 5 to R ⁹ is hydrogen or an alkyl group having 1 to 4 carbon atoms or alkoxy group having 1 to 4 carbon atoms or a phenyl group. The ^R 10 ^{to R 14,,} it is It represents either hydrogen, an alkyl group having 1 to 4 carbon atoms, or a phenyl group.)

In the oxadiazole derivatives of the present invention represented by the general formulas (G1) to (G16) described above, examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an isopropyl group, an isobutyl group, and a tert group. -A butyl group etc. are mentioned. Moreover, as a C1-C4 alkoxy group, a methoxy group, an ethoxy group, an isopropoxy group, an isobutoxy group, a tert-butoxy group etc. are mentioned. Examples of the aryl group having 6 to 25 carbon atoms include phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 4-tert-butylphenyl group, 1-naphthyl group, 2-naphthyl group, 2 -Biphenyl group, 3-biphenyl group, 4-biphenyl group, 99-dimethylfluoren-2-yl group, spiro-9,9'-bifluoren-2-yl group and the like can be mentioned. Examples of the arylene group having 6 to 25 carbon atoms include 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 2,5-dimethyl-1,4-phenylene group, 1,4 -Naphthylene group, 1,5-naphthylene group, 4,4'-biphenylene group, 9-dimethylfluorene-2,7-diyl group, spiro-9,9'-bifluorene-2,7-diyl group, etc. .

Since the oxadiazole derivative of the present invention represented by the general formulas (G1) to (G16) described above has a light-emitting property, it can be applied to a light-emitting element. Therefore, the structure of the present invention is a light-emitting element including the above-described oxadiazole derivative.

Moreover, the oxadiazole derivative of the present invention has a large excitation energy. In addition, since both holes and electrons can be transported, it is optimal as a host material for the light emitting layer in the light emitting element. Accordingly, another structure of the present invention is a light-emitting element having a light-emitting layer containing the above-described oxadiazole derivative and a light-emitting substance.

In particular, since the oxadiazole derivative of the present invention is characterized by having large triplet excitation energy, a phosphorescent compound is suitable as the light-emitting substance. With such a structure, a light-emitting element with excellent light emission efficiency and driving voltage can be obtained.

Further, a light-emitting element in which a layer containing the oxadiazole derivative of the present invention is provided in contact with the light-emitting layer is also an embodiment of the present invention. Since the oxadiazole derivative of the present invention has large excitation energy, such a configuration can prevent excitons generated in the light-emitting layer from diffusing to other layers. As a result, a light-emitting element with high emission efficiency can be obtained.

  In addition, since the light-emitting element of the present invention obtained in this way has the characteristics of high light emission efficiency and low driving voltage, a light-emitting device (image display device or light-emitting device) using the light-emitting element is Low power consumption can be realized. Therefore, the present invention includes a light-emitting device using the light-emitting element of the present invention. In addition, electronic devices using the light-emitting device are also included.

Note that the light-emitting device in this specification includes an image display device or a light-emitting device using a light-emitting element. In addition, a module in which a connector such as an anisotropic conductive film or TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package) is attached to a light emitting element, a module in which a printed wiring board is provided on the end of a TAB tape or TCP, Alternatively, a module in which an IC (integrated circuit) is directly mounted on a light emitting element by a COG (Chip On Glass) method is included in the light emitting device. Furthermore, a light emitting device used for a lighting fixture or the like is also included.

By implementing the present invention, a substance having a large excitation energy, particularly a substance having a large triplet excitation energy can be obtained. In addition, a bipolar substance can be obtained.

In addition, by applying such a substance to a light-emitting element, a light-emitting element with high emission efficiency can be provided. In addition, a light-emitting element with low driving voltage can be provided.

Further, by manufacturing a light-emitting device using the above-described light-emitting element, a light-emitting device with low power consumption can be provided. In addition, by applying such a light-emitting device to an electronic device, an electronic device with low power consumption can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.

(Embodiment 1)
In Embodiment 1, the oxadiazole derivative of the present invention will be described. The oxadiazole derivative of the present invention is represented by the following general formula (G1).

（式中、Ａ_ｍは、一般式（Ａｍ１）、または（Ａｍ２）、または（Ａｍ３）のいずれかで表される置換基である。また、α、β^１、β^２は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(Wherein, _{A m} of the general formula (Am1), or (Am2), or (Am3) is a substituent represented by any one of. Furthermore, alpha, beta ^1, beta ² is 6 carbon atoms represents an arylene group 25. the _a ^r 1 _~A ^{r 6} represents an aryl group having 6 to 25 carbon atoms. the ^R 1 to R ³ is hydrogen or an alkyl group having 1 to 4 carbon atoms, or carbon, It represents any of an aryl group having 6 to 25. R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms.

  The oxadiazole derivative represented by the general formula (G1) includes a halogenated oxadiazole derivative represented by the following general formula (OXD1), and the following general formula (Am1 ′) or (Am2 ′) or (Am3 ′). ) Is coupled with a metal catalyst or the like. Therefore, in the following, first, the following synthesis method (OXD1) will be disclosed.

（式中、αは炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１は、炭素数６〜２５のアリール基を表す。またＸ^１は、ハロゲン基を表し、好ましくはブロモ基またはヨード基である。）

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The _A ^{r 1} represents an aryl group having 6 to 25 carbon atoms. The ^{X 1} represents a halogen group, preferably a bromo group or an iodo Group.)

（式中、β^１、β^２は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^２〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(Wherein, beta ^1, beta ² represents an arylene group having 6 to 25 carbon atoms. The _A ^r 2 _~A ^{r 6} represents an aryl group having 6 to 25 carbon atoms. The ^R 1 to R ³ is , Hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms, and R ⁴ represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. Represents any of the groups.)

≪a. Synthesis Method of Halogenated Oxadiazole Derivative (OXD1) >>
The halogenated oxadiazole derivative represented by the general formula (OXD1) can be synthesized as shown in the following synthesis scheme (a). That is, a halogenated aryl hydrazide (B) is synthesized by first reacting an ester (A) of a halogenated aryl carboxylic acid with hydrazine. Next, a halogenated aryl hydrazide (B) and an arylcarboxylic acid halide (C) are reacted to obtain a diacyl hydrazine derivative (D). Furthermore, the halogenated oxadiazole derivative (OXD1) can be obtained by dehydrating and ring-closing the diacylhydrazine derivative (D) with a dehydrating agent to form a 1,3,4-oxadiazole ring. In the following scheme (a), R represents an alkyl group. Α represents an arylene group having 6 to 25 carbon atoms. A _r ¹ represents an aryl group having 6 to 25 carbon atoms. X ¹ and X ² each represent a halogen group, preferably a bromo group or an iodo group.

As the dehydrating agent, phosphoryl chloride, thionyl chloride or the like can be used.

Further, the method for synthesizing the halogenated oxadiazole derivative (OXD1) is not limited to the above scheme (a), and other known methods can be used.

≪b. Synthesis Method of Secondary Amines (Am1 ′), (Am2 ′) and (Am3 ′) >>
Next, a method for synthesizing each secondary amine represented by the general formulas (Am1 ′), (Am2 ′), and (Am3 ′) will be described.

<B1. Synthesis Method of Secondary Amine (Am1 ′)>
The secondary amine represented by the above general formula (Am1 ′) can be synthesized as shown in the following synthesis scheme (b1). That is, first, a halogenated arylcarbazole derivative (G) is synthesized by coupling a dihalogenated arene (E) and a carbazole derivative (F) using a metal catalyst in the presence of a base. Next, a secondary amine (Am1 ′) can be obtained by coupling the halogenated arylcarbazole derivative (G) and the arylamine (H) using a metal catalyst in the presence of a base. In the following scheme (b1), β ¹ represents an arylene group having 6 to 25 carbon atoms. The _A ^{r 2} represents an aryl group having 6 to 25 carbon atoms. R ^{1 to} R ^{2 each} represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. X ³ and X ⁴ each represent a halogen group, preferably a bromo group or an iodo group.

As the base, an inorganic base such as potassium carbonate or sodium carbonate, or an organic base typified by metal alkoxide such as sodium tert-butoxide can be used. Examples of the metal catalyst include a palladium catalyst and monovalent copper. Specific examples include palladium acetate, palladium chloride, bis (dibenzylideneacetone) palladium (0), and copper (I) iodide.

Further, the method for synthesizing the secondary amine (Am1 ′) is not limited to the above scheme (b1), and other known methods can be used.

<B2. Synthesis Method of Secondary Amine (Am2 ′)>
The secondary amine represented by the above general formula (Am2 ′) can be synthesized as shown in the following synthesis scheme (b2). That is, first, the halogenated carbazole derivative (J) is synthesized by halogenating the 3-position of the carbazole derivative (I) with a halogenating agent. Next, the secondary amine (Am2 ′) can be obtained by coupling the halogenated carbazole derivative (J) and the arylamine (K) using a metal catalyst in the presence of a base. Note that in the following scheme _{(b2), A} ^{r 3} represents an aryl group having 6 to 25 carbon atoms. R ³ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. X ⁵ represents a halogen group, preferably a bromo group or an iodo group.

As the halogenating agent, N-bromosuccinimide (NBS), N-iodosuccinimide (NIS), or the like can be used. As the base and metal catalyst, the above <b1. Those enumerated in <Method for synthesizing secondary amine (Am1 ')> can be used.

In addition, the method for synthesizing the secondary amine (Am2 ′) is not limited to the above scheme (b2), and other known methods can be used.

<B3. Synthesis Method of Secondary Amine (Am3 ′)>
The secondary amine represented by the above general formula (Am3 ′) can be synthesized as shown in the following synthesis scheme (b3). That is, first, a triarylamine (L) is halogenated with a halogenating agent to synthesize a monohalogenated triarylamine (M). Next, a secondary amine (Am3 ′) can be obtained by coupling a monohalogenated triarylamine (M) and an arylamine (N) using a metal catalyst in the presence of a base. Note that in the following scheme (b3), β ² represents an arylene group having 6 to 25 carbon atoms. A _r ^{4 to} A _r ⁶ represent an aryl group having 6 to 25 carbon atoms. X ⁶ represents a halogen group, preferably a bromo group or an iodo group.

As the halogenating agent, N-bromosuccinimide (NBS), N-iodosuccinimide (NIS), or the like can be used. As the base and metal catalyst, the above <b1. Those enumerated in <Method for synthesizing secondary amine (Am1 ')> can be used.

The method for synthesizing the secondary amine (Am3 ′) is not limited to the above scheme (b3), and other known methods can be used.

≪c. Synthesis Method of Oxadiazole Derivative Represented by General Formula (G1) >>
The halogenated oxadiazole derivative (OXD1) obtained in the above scheme (a) and the secondary amine (Am1 ′) or (Am2 ′) or (Am3) obtained in the above schemes (b1) to (b3). The oxadiazole derivative of the present invention represented by the general formula (G1) is obtained by coupling any of ') with a metal catalyst in the presence of a base. The scheme is shown in the following scheme (c). Note that in the following scheme (c), _{A m} of the general formula (Am1), or (Am2), or (Am3) is a substituent represented by any one of the. Moreover, (alpha), (beta) ¹ , (beta) ² represents a C6-C25 arylene group. A _r ^{1 to} A _r ⁶ represent an aryl group having 6 to 25 carbon atoms. R ^{1 to} R ^{3 each} represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms. R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms. X ¹ represents a halogen group, preferably a bromo group or an iodo group.

As the base and metal catalyst, the above <b1. Those enumerated in <Method for synthesizing secondary amine (Am1 ')> can be used.

A combination of (OXD1) and (Am1 ′) corresponds to the oxadiazole derivative of the above general formula (G2), and a combination of (OXD1) and (Am2 ′) is the above general formula. This corresponds to the oxadiazole derivative of (G7), and a combination of (OXD1) and (Am3 ′) corresponds to the oxadiazole derivative of the above general formula (G11).

<< Specific Structural Formula of Oxadiazole Derivative Represented by General Formula (G1) >>
Next, a specific structure of the oxadiazole derivative of the present invention will be described using the following general formula (G1).

（式中、Ａ_ｍは、一般式（Ａｍ１）、または（Ａｍ２）、または（Ａｍ３）のいずれかで表される置換基である。また、α、β^１、β^２は、炭素数６〜２５のアリーレン基を表す。またＡ_ｒ ^１〜Ａ_ｒ ^６は、炭素数６〜２５のアリール基を表す。またＲ^１〜Ｒ^３は、水素、または炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。またＲ^４は、炭素数１〜４のアルキル基、または炭素数６〜２５のアリール基のいずれかを表す。）

(Wherein, _{A m} of the general formula (Am1), or (Am2), or (Am3) is a substituent represented by any one of. Furthermore, alpha, beta ^1, beta ² is 6 carbon atoms represents an arylene group 25. the _a ^r 1 _~A ^{r 6} represents an aryl group having 6 to 25 carbon atoms. the ^R 1 to R ³ is hydrogen or an alkyl group having 1 to 4 carbon atoms, or carbon, It represents any of an aryl group having 6 to 25. R ⁴ represents either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms.

First, as the structure of the arylene group α in the general formula (G1), more specifically, any structure shown in the following structural formula group (α) can be applied. However, the present invention is not limited to these.

As the structure of the aryl group A _r ¹ in the general formula (G1), more specifically, any structure shown in the following structural formula group (A _r ) can be applied. However, the present invention is not limited to these.

Next, a description will be given substituent _{A m} in the general formula (G1). Substituent _{A m,} as shown in the above general formula (G1) (Am1), or (Am2), or is represented by any one of (Am3), more specifically, the following structural formula group Any structure of (Am1-1) to (Am1-10), structural formula group (Am2-1) to (Am2-5), or structural formula group (Am3-1) to (Am3-9) is applied can do. However, the present invention is not limited to these.

Structural formula group (α), structural formula group (A _r ), structural formula groups (Am1-1) to (Am1-10), structural formula groups (Am2-1) to (Am2-5) as described above The oxadiazole derivatives of the present invention are constituted by appropriately combining the structural formula groups (Am3-1) to (Am3-9). Hereinafter, specific structural formulas of the oxadiazole derivatives of the present invention will be described. Are listed (the following structural formulas (1) to (140)). However, the present invention is not limited to these.

(Embodiment 2)
In Embodiment Mode 2, a mode of a light-emitting element using the oxadiazole derivative of the present invention described in Embodiment Mode 1 as a host material of a light-emitting layer will be described with reference to FIGS.

FIG. 1 is a diagram illustrating a light-emitting element having a light-emitting layer 113 between a first electrode 101 and a second electrode 102. The light emitting layer 113 is a layer containing the oxadiazole derivative of the present invention and a light emitting substance. In Embodiment 2, the oxadiazole derivative of the present invention is a host material in the light-emitting layer 113, and the light-emitting substance is a guest material.

By applying a voltage to such a light-emitting element, holes injected from the first electrode 101 side and electrons injected from the second electrode 102 side recombine in the light-emitting layer 113, and The luminescent material is excited. Then, light is emitted when the luminescent substance in the excited state returns to the ground state. Since the oxadiazole derivative of the present invention has bipolar properties, it can efficiently receive both holes and electrons and transport them to the light-emitting substance. Therefore, the light-emitting element of the present invention can generate an excited state of the light-emitting substance with a low driving voltage. In addition, since the oxadiazole derivative of the present invention has high excitation energy, the light-emitting substance in an excited state can efficiently emit light without being quenched. Note that in the light-emitting element of Embodiment 2, the first electrode 101 functions as an anode, and the second electrode 102 functions as a cathode.

There is no particular limitation on the light-emitting substance (that is, the guest material); however, since the oxadiazole derivative of the present invention has large triplet excitation energy, the guest material is preferably a phosphorescent compound. Specifically, bis [2- (4 ′, 6′-difluorophenyl) pyridinato-N, C ^{2 ′} ] iridium (III) picolinate (abbreviation: FIrpic), tris (2-phenylpyridinato-N, C ^{2 ′} ) iridium (III) (abbreviation: Ir (ppy) ₃ ), bis (2-phenylpyridinato-N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir (ppy) ₂ (acac)) ), Bis (2-phenylbenzothiazolate-N, C ^{2 ′} ) iridium (III) acetylacetonate (abbreviation: Ir (bt) ₂ (acac)), tris (2-phenylquinolinato-N, C2 ′) ) iridium (III) (abbreviation: Ir _(pq) 3), bis (2-phenylquinolinato--N, C2 ') iridium (III) acetylacetonate (abbreviation: Ir (pq ₂ (acac)), bis [2- (2'-benzo [4, 5-alpha] thienyl) pyridinato -N, C ^{3 ']} iridium (III) acetylacetonate (abbreviation: _Ir (btp) 2 (acac) ), Bis (1-phenylisoquinolinato-N, C2 ′) iridium (III) acetylacetonate (abbreviation: Ir (piq) ₂ (acac)), (acetylacetonato) bis [2,3-bis (4 -Fluorophenyl) quinoxalinato] iridium (III) (abbreviation: Ir (Fdpq) ₂ (acac)), 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin platinum (II) (Abbreviation: PtOEP).

As the light-emitting substance, a fluorescent compound can be used. Specifically, perylene, 2,5,8,11-tetra (tert-butyl) perylene (abbreviation: TBP), 4,4′-bis [ 2- (N-ethylcarbazol-3-yl) vinyl] biphenyl (abbreviation: BCzVBi), 5,12-diphenyltetracene, N, N′-dimethylquinacridone (abbreviation: DMQd), N, N′-diphenylquinacridone (abbreviation) : DMQd), 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJTI), rubrene, Coumarin 6, Coumarin 30, etc. are mentioned.

  Although there is no particular limitation on the first electrode 101, it is preferable that the first electrode 101 is formed of a material having a high work function when functioning as an anode as in the second embodiment. Specifically, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), indium oxide containing 2 to 20 wt% zinc oxide (IZO), gold (Au), platinum ( Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or the like can be used. Note that the first electrode 101 can be formed using, for example, a sputtering method, an evaporation method, or the like.

  Although there is no particular limitation on the second electrode 102, it is preferable that the second electrode 102 be formed of a material having a low work function when functioning as a cathode as in the second embodiment. Specifically, in addition to aluminum (Al) and indium (In), alkali metals such as lithium (Li) and cesium (Cs), alkaline earth metals such as magnesium (Mg) and calcium (Ca), erbium (Er Or rare earth metals such as ytterbium (Yb). An alloy such as an aluminum lithium alloy (AlLi) or a magnesium silver alloy (MgAg) can also be used. Note that the second electrode 102 can be formed by, for example, a sputtering method, an evaporation method, or the like.

  Note that in order to extract emitted light to the outside, one or both of the first electrode 101 and the second electrode 102 is an electrode made of a conductive film that transmits visible light such as ITO, or transmits visible light. It is preferable that the electrode is formed with a thickness of several to several tens of nm so as to be able to.

  Further, a hole transport layer 112 may be provided between the first electrode 101 and the light emitting layer 113 as shown in FIG. Here, the hole transport layer is a layer having a function of transporting holes injected from the first electrode 101 to the light-emitting layer 113. In this manner, by providing the hole-transport layer 112 and separating the first electrode 101 and the light-emitting layer 113, it is possible to prevent the light emission from being quenched due to the metal. However, the hole transport layer 112 is not always necessary.

  There is no particular limitation on a substance included in the hole-transport layer 112; typically, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), 4, 4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4′-bis [N- (9,9-dimethylfluoren-2-yl) -N— Phenylamino] biphenyl (abbreviation: DFLDPBi), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) triphenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N— An aromatic amine compound such as (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: m-MTDATA) can be used. Alternatively, a high molecular compound such as poly (4-vinyltriphenylamine) (abbreviation: PVTPA) can be used.

  Note that the hole transport layer 112 may have a multilayer structure formed by stacking two or more layers. Further, two or more kinds of substances may be mixed and formed.

  Further, an electron transport layer 114 may be provided between the second electrode 102 and the light emitting layer 113 as shown in FIG. Here, the electron transporting layer is a layer having a function of transporting electrons injected from the second electrode 102 to the light emitting layer 113. In this manner, by providing the electron-transport layer 114 and separating the second electrode 102 and the light-emitting layer 113, it is possible to prevent the light emission from being quenched due to the metal. However, the electron transport layer 114 is not always necessary.

Although there is no particular limitation on a substance included in the electron-transport layer 114, typically, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq _3). ), Bis (10-hydroxybenzo [h] quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (abbreviation: BAlq), bis [2- ( Metal complexes such as 2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ) and bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ). . 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert-butyl) Phenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl) -1 , 2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), 4,4′-bis (5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs), etc. Aromatic aromatic compounds can also be used. Alternatively, a high molecular compound such as poly (2,5-pyridine-diyl) (abbreviation: PPy) can be used.

  Note that the electron transport layer 114 may have a multilayer structure formed by stacking two or more layers. Further, two or more kinds of substances may be mixed and formed.

  Further, a hole injection layer 111 may be provided between the first electrode 101 and the hole transport layer 112 as shown in FIG. Here, the hole injection layer is a layer having a function of assisting injection of holes from the electrode functioning as an anode into the hole transport layer 112. However, the hole injection layer 111 is not always necessary.

Although there is no particular limitation on the substance constituting the hole injection layer 111, vanadium oxide (VOx), niobium oxide (NbOx), tantalum oxide (TaOx), chromium oxide (CrOx), molybdenum oxide (MoOx) Metal oxides such as tungsten oxide (WOx), manganese oxide (MnOx), rhenium oxide (ReOx), and ruthenium oxide (RuOx) can be used. Alternatively, a phthalocyanine compound such as phthalocyanine (abbreviation: H ₂ Pc) or copper phthalocyanine (CuPC) can be used. In addition, a substance constituting the hole transport layer 112 described above can be used. Alternatively, a high molecular compound such as a mixture of poly (ethylenedioxythiophene) and poly (styrenesulfonic acid) (abbreviation: PEDOT / PSS) can be used.

  Alternatively, a composite material obtained by mixing an organic compound and an electron acceptor may be used for the hole injection layer 111. Such a composite material is excellent in hole injecting property and hole transporting property because holes are generated in the organic compound by the electron acceptor. In this case, the organic compound is preferably a material excellent in transporting the generated holes, and specifically, for example, a substance (such as an aromatic amine compound) constituting the hole transport layer 112 described above is used. be able to. The electron acceptor may be any substance that exhibits an electron accepting property with respect to an organic compound. Specifically, it is preferably a transition metal oxide, for example, vanadium oxide (VOx), niobium oxide (NbOx), tantalum oxide (TaOx), chromium oxide (CrOx), molybdenum oxide (MoOx). ), Tungsten oxide (WOx), manganese oxide (MnOx), rhenium oxide (ReOx), ruthenium oxide (RuOx), and the like. A Lewis acid such as iron (III) chloride or aluminum (III) chloride can also be used. Alternatively, an organic compound such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ) can be used.

  Note that the hole injection layer 111 may have a multilayer structure in which two or more layers are stacked. Further, two or more kinds of substances may be mixed and formed.

  Further, an electron injection layer 115 may be provided between the second electrode 102 and the electron transport layer 114 as shown in FIG. Here, the electron injection layer is a layer having a function of assisting injection of electrons from the electrode functioning as a cathode to the electron transport layer 114. However, the electron injection layer 115 is not always necessary.

Although there is no particular limitation on the substance constituting the electron injection layer 115, an alkali metal compound such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), lithium oxide (LiOx), or Alkaline earth metal compounds can be used. Alternatively, a rare earth metal compound such as erbium fluoride (ErF ₃ ) can be used. In addition, a substance constituting the electron transport layer 114 described above can be used.

Alternatively, a composite material obtained by mixing an organic compound and an electron donor may be used for the electron injection layer 115. Such a composite material is excellent in electron injecting property and electron transporting property because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, for example, a substance (metal complex, heteroaromatic compound, or the like) constituting the electron transport layer 114 described above is used. Can be used. The electron donor may be any substance that exhibits an electron donating property to the organic compound. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be given. Moreover, an alkali gold compound and an alkaline earth metal compound are preferable, and lithium oxide (LiOx), calcium oxide (CaOx), barium oxide (BaOx), cesium carbonate (Cs ₂ CO ₃ ), and the like can be given. A Lewis base such as magnesium oxide can also be used. Alternatively, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.

  In the light-emitting element of the present invention described above, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 113, the electron transport layer 114, and the electron injection layer 115 are formed by an evaporation method, an inkjet method, or a coating method, respectively. Or any other method. The first electrode 101 or the second electrode 102 may be formed by any method such as a sputtering method, an evaporation method, an inkjet method, or a coating method.

(Embodiment 3)
In Embodiment 3, an embodiment of a light-emitting element using the oxadiazole derivative of the present invention as an exciton block layer will be described with reference to FIGS. The exciton block layer is a kind of a hole transport layer or an electron transport layer provided in contact with the light emitting layer. In particular, the excitation energy is larger than the excitation energy of the light emitting layer, and excitons in the light emitting layer have other excitons. It is a layer having a function of blocking so as not to move to the layer.

In the light-emitting element shown in FIG. 2, a light-emitting layer 213 is provided between a first electrode 201 functioning as an anode and a second electrode 202 functioning as a cathode. An exciton block layer 220a made of the oxadiazole derivative of the present invention is provided in contact with the anode side of the light emitting layer 213. Therefore, in the case of FIG. 2, the exciton block layer 220a is a kind of hole transport layer.

In the light-emitting element illustrated in FIG. 3, a light-emitting layer 213 is provided between the first electrode 201 that functions as an anode and the second electrode 202 that functions as a cathode. An exciton block layer 220b made of the oxadiazole derivative of the present invention is provided in contact with the cathode side of the light emitting layer 213. Therefore, in the case of FIG. 3, the exciton block layer 220b is a kind of electron transport layer.

With the configuration as shown in FIGS. 2 and 3, excitons generated in the light-emitting layer 213 can be efficiently confined in the light-emitting layer 213, and the light emission efficiency can be increased. In addition, since the oxadiazole derivative of the present invention has bipolar properties, it can be used as an exciton block layer on either the anode side or the cathode side of the light emitting layer as shown in FIGS. There is. Therefore, although not shown in FIGS. 2 and 3, an exciton block layer made of the oxadiazole derivative of the present invention can be provided on both sides of the light emitting layer 213.

Here, various structures can be applied to the light-emitting layer 213. For example, as an example, the light-emitting layer 213 including a host material and a guest material may be formed. Specific examples of the host material in that case include NPB, DFLDPBi, Alq ₃ , BAlq, and the like, 4,4′-di (9-carbazolyl) biphenyl (abbreviation: CBP), 2-tert-butyl-9,10 -Di (2-naphthyl) anthracene (abbreviation: t-BuDNA), 9- [4- (9-carbazolyl) phenyl] -10-phenylanthracene (abbreviation: CzPA), and the like can be given. Specific examples of the guest material include 9- (4- {N- [4- (carbazol-9-yl) phenyl] -N in addition to the phosphorescent compound and the fluorescent compound described in Embodiment 2 above. -Phenylamino} phenyl) -10-phenylanthracene (abbreviation: YGAPA) or the like can be used.

  Note that the first electrode 201 may have a structure similar to that of the first electrode 101 described in Embodiment 2 above. The second electrode 202 may have a structure similar to that of the second electrode 102 described in Embodiment 2 above.

In the third embodiment, as shown in FIGS. 2 and 3, the hole injection layer 211, the hole transport layer 212, the electron transport layer 214, and the electron injection layer 215 are provided. With regard to the above, the structure of each layer described in Embodiment 2 may be applied. However, these layers are not necessarily required, and may be provided as appropriate depending on the characteristics of the element.

(Embodiment 4)
In Embodiment 4, one mode of a light-emitting device including the light-emitting element of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the light emitting device.

  In FIG. 4, a transistor 11 provided for driving the light emitting element 12 of the present invention is surrounded by a square dotted line. The light-emitting element 12 is a light-emitting element of the present invention having a layer 15 including a light-emitting layer between a first electrode 13 and a second electrode 14, and includes the oxadiazole derivative of the present invention. Specifically, the light emitting element 12 has a configuration as shown in the second and third embodiments. The drain region of the transistor 11 and the first electrode 13 are electrically connected by a wiring 17 penetrating the first interlayer insulating film 16 (16a, 16b, 16c). The light emitting element 12 is separated from another light emitting element provided adjacent thereto by a partition wall layer 18. The light emitting device of the present invention having such a configuration is provided on the substrate 10 in the fourth embodiment.

  Note that the transistor 11 illustrated in FIGS. 4A and 4B is a top-gate transistor in which a gate electrode is provided on the side opposite to a substrate with a semiconductor layer as a center. However, the structure of the transistor 11 is not particularly limited, and may be, for example, a bottom gate type. In the case of a bottom gate, the semiconductor layer forming a channel may be formed with a protective film (channel protection type), or the semiconductor layer forming the channel may be partially concave ( Channel etch type).

  Further, the semiconductor layer included in the transistor 11 may be either crystalline or non-crystalline. Moreover, a semi-amorphous etc. may be sufficient.

The semi-amorphous semiconductor is as follows. A semiconductor having an intermediate structure between amorphous and crystalline (including single crystal and polycrystal) and having a third state that is stable in terms of free energy, has a short-range order, and has a lattice distortion. It contains a crystalline region. Further, at least a part of the region in the film contains crystal grains of 0.5 to 20 nm. The Raman spectrum derived from the L—O phonon is shifted to the lower wavenumber side than 520 cm ⁻¹ . In X-ray diffraction, diffraction peaks of (111) and (220) that are derived from the Si crystal lattice are observed. In order to terminate dangling bonds (dangling bonds), it contains at least 1 atomic% of hydrogen or halogen. It is also called a so-called microcrystalline semiconductor. A gas containing silicide is formed by glow discharge decomposition (plasma CVD). As the gas containing silicide, SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4, and the} like can be used. The gas containing the silicide may be diluted with H ₂ , or H ₂ and one or more kinds of rare gas elements selected from He, Ar, Kr, and Ne. The dilution rate is in the range of 2 to 1000 times, the pressure is in the range of approximately 0.1 Pa to 133 Pa, and the power supply frequency is 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature may be 300 ° C. or less, preferably 100 to 250 ° C. As an impurity element in the film, an impurity of atmospheric components such as oxygen, nitrogen, and carbon is desirably 1 × 10 ²⁰ atoms / cm ³ or less, and in particular, the oxygen concentration is preferably 5 × 10 ¹⁹ atoms / cm ³ or less. Is 1 × 10 ¹⁹ atoms / cm ³ or less. Note that the mobility of a TFT (thin film transistor) using a semi-amorphous semiconductor is approximately 1 to 10 cm ² / Vsec.

  Further, specific examples of the crystalline semiconductor layer include those made of single crystal or polycrystalline silicon, silicon germanium, or the like. These may be formed by laser crystallization, or may be formed by crystallization by a solid phase growth method using nickel or the like, for example.

  Note that in the case where the semiconductor layer is formed of an amorphous material, for example, amorphous silicon, the transistor 11 and other transistors (transistors constituting a circuit for driving a light emitting element) are all configured by N-channel transistors. It is preferable that the light-emitting device have a structured circuit. Other than that, a light-emitting device having a circuit including any one of an N-channel transistor and a P-channel transistor, or a light-emitting device including a circuit including both transistors may be used.

  Furthermore, the first interlayer insulating film 16 (16a to 16c) may be a multilayer as shown in FIGS. 4A and 4C, or may be a single layer. Note that 16a is made of an inorganic material such as silicon oxide or silicon nitride, and 16b is an organic group having a skeleton structure composed of a bond of acrylic or siloxane (silicon (Si) and oxygen (O)) and containing at least hydrogen as a substituent. ), And a self-flattening material such as silicon oxide that can be coated and formed. Further, 16c is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. Thus, the 1st interlayer insulation film 16 (16a-16c) may be formed using both an inorganic film or an organic film, or was formed by either one of an inorganic film and an organic film But you can.

  The partition layer 18 preferably has a shape in which the radius of curvature continuously changes at the edge portion. The partition layer 18 is formed using acrylic, siloxane, resist, silicon oxide, or the like. The partition wall layer 18 may be formed of any one of an inorganic film and an organic film, or may be formed using both.

  4A and 4C, only the first interlayer insulating film 16 (16a to 16c) is provided between the transistor 11 and the light emitting element 12, but as shown in FIG. 4B. In addition to the first interlayer insulating film 16 (16a, 16b), the second interlayer insulating film 19 (19a, 19b) may be provided. In the light emitting device shown in FIG. 4B, the first electrode 13 penetrates through the second interlayer insulating film 19 and is connected to the wiring 17.

  Similar to the first interlayer insulating film 16, the second interlayer insulating film 19 may be a multilayer or a single layer. 19a has self-flatness such as acrylic or siloxane (an organic group in which a skeleton structure is composed of a bond of silicon (Si) and oxygen (O) and includes at least hydrogen as a substituent) and silicon oxide that can be coated and formed. Consists of material. Further, 19b is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. Thus, the second interlayer insulating film 19 may be formed using both an inorganic film or an organic film, or may be formed of any one of an inorganic film and an organic film.

  In the light-emitting element 12, when each of the first electrode and the second electrode is formed using a light-transmitting substance, the first electrode and the second electrode are represented by the white arrows in FIG. Light emission can be extracted from both the electrode 13 side and the second electrode 14 side. In addition, in the case where only the second electrode 14 is formed using a light-transmitting substance, light emission is extracted only from the second electrode 14 side as represented by a white arrow in FIG. be able to. In this case, it is preferable that the first electrode 13 is made of a material having a high reflectivity, or a film (reflective film) made of a material having a high reflectivity is provided below the first electrode 13. In addition, in the case where only the first electrode 13 is formed using a light-transmitting substance, light emission is extracted only from the first electrode 13 side as represented by a white arrow in FIG. be able to. In this case, it is preferable that the second electrode 14 is made of a highly reflective material, or a reflective film is provided above the second electrode 14.

  In addition, the light emitting element 12 may be one in which the layer 15 is stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is higher than the potential of the first electrode 13. Alternatively, the layer 15 may be stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is lower than the potential of the first electrode 13. In the former case, the transistor 11 is an N-channel transistor, and in the latter case, the transistor 11 is a P-channel transistor.

  As described above, in Embodiment 4, an active light-emitting device that controls driving of a light-emitting element by a transistor has been described. In addition, a light-emitting element is driven without providing a driving element such as a transistor. A passive light emitting device may be used.

  Since the light-emitting device described in Embodiment 4 uses the light-emitting element of the present invention, the light-emitting efficiency is high and the driving voltage is low. Therefore, the power consumption is low.

(Embodiment 5)
Since a light-emitting device using the light-emitting element of the present invention can display a good image, an electronic device that can provide excellent images can be obtained by applying the light-emitting device of the present invention to a display portion of the electronic device. Can do. In addition, a light-emitting device including the light-emitting element of the present invention has high light emission efficiency and low driving voltage, and thus can be driven with low power consumption. Therefore, by applying the light-emitting device of the present invention to a display portion of an electronic device, an electronic device with low power consumption can be obtained, for example, a telephone having a long standby time can be obtained. An embodiment of an electronic device in which a light emitting device to which the light emitting element of the present invention is applied is mounted is shown below.

  FIG. 5A illustrates a computer manufactured by applying the present invention, which includes a main body 511, a housing 512, a display portion 513, a keyboard 514, and the like. A computer can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  FIG. 5B illustrates a telephone manufactured by applying the present invention. The main body 522 includes a display portion 521, an audio output portion 524, an audio input portion 525, operation switches 526 and 527, an antenna 523, and the like. ing. A telephone can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  FIG. 5C illustrates a television receiver manufactured by applying the present invention, which includes a display portion 531, a housing 532, a speaker 533, and the like. A television receiver can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  As described above, the light-emitting device of the present invention is very suitable for use as a display portion of various electronic devices.

  In the fifth embodiment, a computer or the like is described, but in addition to this, a light emitting device having the light emitting element of the present invention may be mounted in a navigation device or a lighting device.

<< Synthesis Example 1 >>
In this synthesis example 1, the oxadiazole derivative of the present invention represented by the structural formula (1) of Embodiment 1, 2- (4- {N- [4- (carbazol-9-yl) phenyl] -N- A specific example of synthesis of (phenylamino} phenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: YGAO11) is specifically illustrated.

<Step 1; Synthesis of 2- (4-bromophenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: O11Br)>
In Step 1, O11Br was synthesized according to the following procedures (i) to (iii).

(I) Synthesis of 4-bromobenzohydrazide First, 3.0 g (13.9 mmol) of methyl-4-bromobenzoate was placed in a 100 mL three-necked flask, 10 mL of ethanol was added and stirred, and then 4.0 mL of hydrazine monohydrate. And heated and stirred at 78 ° C. for 5 hours. The obtained solid was washed with water and collected by suction filtration to obtain 2.0 g of a white solid of 4-bromobenzohydrazide as a target product (yield 67%).

(Ii) Synthesis of 1-benzoyl-2- (4-bromobenzoyl) hydrazine Next, 2.0 g (13.9 mmol) of 4-bromobenzohydrazide obtained in (i) above was placed in a 300 mL three-necked flask, and N- After adding 7 mL of methyl-2-pyrrolidone (abbreviation: NMP) and stirring, a mixture of 2.5 mL of N-methyl-2-pyrrolidone and 2.5 mL (21.5 mmol) of benzoyl chloride was added dropwise with a 50 mL dropping funnel, Stir at 0 ° C. for 3 hours. The obtained solid was washed with water and an aqueous sodium carbonate solution in this order, and collected by suction filtration. When recrystallization was performed with acetone, 3.6 g of a white solid of 1-benzoyl-2- (4-bromobenzoyl) hydrazine as a target product was obtained (yield 80%).

(Iii) Synthesis of O11Br Further, 15 g (47 mmol) of 1-benzoyl-2- (4-bromobenzoyl) hydrazine obtained by the method shown in (ii) above was placed in a 200 mL three-necked flask, and 100 mL of phosphoryl chloride was added, The mixture was heated and stirred at 100 ° C. for 5 hours. After the reaction, phosphoryl chloride was completely distilled off, and the resulting solid was washed with water and an aqueous sodium carbonate solution in this order, and collected by suction filtration. When recrystallization was performed with methanol, 13 g of a white solid of O11Br, which was the target product of Step 1, was obtained (yield 89%). The synthesis scheme of Step 1 described above is shown in the following scheme (a-1).

<Step 2; Synthesis of 4- (carbazol-9-yl) diphenylamine (abbreviation: YGA)>
In Step 2, YGA was synthesized according to the following procedures (i) to (ii).

(I) Synthesis of 9- (4-bromophenyl) carbazole First, 56 g (240 mmol) of p-dibromobenzene, 31 g (180 mmol) of carbazole, 4.6 g (24 mmol) of copper iodide, 66 g (480 mmol) of potassium carbonate, 18- 2.1 g (8 mmol) of crown-6-ether was placed in a 300 mL three-necked flask, purged with nitrogen, 8 mL of N, N′-dimethylpropylene urea (abbreviation: DMPU) was added, and the mixture was stirred at 180 ° C. for 6 hours. The reaction mixture was cooled to room temperature, and the precipitate was removed by suction filtration. The filtrate was washed with diluted hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution and saturated brine in that order, and then dried over magnesium sulfate. After drying, the solution is naturally filtered and concentrated. The resulting oily substance is purified by silica gel column chromatography (hexane: ethyl acetate = 9: 1) and recrystallized from chloroform and hexane to obtain the desired product. 21 g of a light brown plate crystal of 9- (4-bromophenyl) carbazole was obtained (yield 35%).

(Ii) Synthesis of YGA Next, 5.4 g (17 mmol) of 9- (4-bromophenyl) carbazole obtained in (i) above, 1.8 mL (20 mmol) of aniline, bis (dibenzylideneacetone) palladium (0) 0.1 g (0.2 mmol) and 3.9 g (40 mmol) of sodium tert-butoxide were placed in a 200 mL three-necked flask and replaced with nitrogen, and 0.1 mL of 10% hexane solution of tri (tert-butyl) phosphine and 50 mL of toluene were added. , And stirred at 80 ° C. for 6 hours. The reaction mixture was filtered through Florisil, Celite, and alumina, and the filtrate was washed with water and saturated brine, and then dried over magnesium sulfate. After drying, the solution was naturally filtered and then concentrated, and the resulting oil was purified by silica gel column chromatography (hexane: ethyl acetate = 9: 1). 1 g was obtained (yield 73%). The synthesis scheme of Step 2 described above is shown in the following scheme (b-1).

<Step 3; 2- (4- {N- [4- (carbazol-9-yl) phenyl] -N-phenylamino} phenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: YGAO11) Synthesis)
O11Br (3.0 g, 10.0 mmol) obtained in Step 1, YGA (3.4 g, 10.0 mmol) obtained in Step 2, and sodium tert-butoxide (1.9 g, 19.9 mmol) were placed in a 100 mL three-necked flask and purged with nitrogen. , 45 mL of toluene, 0.3 mL of 10% hexane solution of tri (tert-butyl) phosphine, and 0.3 g (0.6 mmol) of bis (dibenzylideneacetone) palladium (0) were added, and the mixture was heated and stirred at 120 ° C. for 5 hours. After the reaction, the mixture was filtered through celite, and the filtrate was washed with water and dried over magnesium sulfate. After drying, the solution was filtered and the filtrate was concentrated. The obtained solid was dissolved in toluene and purified by silica column chromatography. Column purification was performed by first using toluene as a developing solvent and then using a mixed solvent of toluene: ethyl acetate = 1: 1 as a developing solvent. When recrystallization was performed with chloroform and hexane, 4.7 g of a light yellow solid of YGAO11, which was the target product of Synthesis Example 1, was obtained (yield 85%). The synthesis scheme of Step 3 described above is shown in the following scheme (c-1).

In addition, the analysis result by the nuclear magnetic resonance spectroscopy (< ¹ > H-NMR) of obtained YGAO11 is shown below. A ¹ H-NMR chart is shown in FIG. 6A, and an enlarged view thereof is shown in FIG. From this, it was found that in Synthesis Example 1, the oxadiazole derivative YGAO11 of the present invention represented by the above structural formula (1) was obtained.

¹ H-NMR (CDCl ₃ , 300 MHz): δ = 7.14-7.53 (m, 19H), δ = 8.03 (d, J = 8.7, 2H), δ = 8.11-8 .15 (m, 4H)

Further, sublimation purification of the obtained YGAO11 was performed by a train sublimation method. The sublimation purification was performed at 265 ° C. for 12 hours under a reduced pressure of 7 Pa with an argon flow rate of 3 mL / min. When sublimation purification was performed on 4.5 g of YGAO11, the yield was 3.4 g and the yield was 76%.

Next, the absorption spectrum and emission spectrum of YGAO11 were measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (model V550 manufactured by JASCO Corporation), and the emission spectrum was measured using a fluorometer (FS920 manufactured by Hamamatsu Photonics). The measurement was performed at room temperature for the toluene solution and the deposited film. FIG. 7A shows the measurement result of the toluene solution, and FIG. 7B shows the measurement result of the deposited film. The horizontal axis represents wavelength, and the vertical axis represents the intensity of absorption and emission.

As shown in FIG. 7A, the oxadiazole derivative YGAO11 of the present invention has an absorption peak at 362 nm in a toluene solution. The emission spectrum has a peak at 431 nm. The emission spectrum was measured by excitation at a wavelength of 362 nm.

Moreover, as shown in FIG.7 (b), the vapor deposition film of the oxadiazole derivative YGAO11 of this invention has an absorption peak at 369 nm. The emission spectrum has a peak at 456 nm. The emission spectrum was measured by excitation at a wavelength of 369 nm.

In addition, using the data of the absorption spectrum of FIG.7 (b), when the absorption edge was calculated | required by tauc plot and the energy gap of YGAO11 was calculated | required by making the energy of the absorption edge into an energy gap, it was 3.06eV. This shows that the oxadiazole derivative YGAO11 of the present invention has a large excitation energy.

  The ionization potential of YGAO11 in a thin film state was 5.49 eV as a result of measurement by atmospheric photoelectron spectroscopy (manufactured by Riken Keiki Co., Ltd., AC-2). As a result, it was found that the HOMO level was −5.49 eV. Further, when the LUMO level was determined from the energy gap value and the HOMO level determined above, it was -2.43 eV.

  Moreover, the optimal molecular structure in the ground state of YGA011 was calculated by B3LYP / 6-311 (d, p) of density functional theory (DFT). DFT is used in this calculation because it has better calculation accuracy than the Hartree-Fock (HF) method, which does not take into account electronic correlation, and the calculation cost is lower than the perturbation method (MP) method, which is the same level of calculation accuracy. did. The calculation was performed using a high performance computer (HPC) (manufactured by SGI, Altix 3700 DX). By applying the time-dependent density functional theory (TDDFT) B3LYP / 6-311 (d, p) in the molecular structure optimized by DFT, the singlet excitation energy (energy gap) of YGA011 was calculated. Singlet excitation energy was calculated to be 3.18 eV. The triplet excitation energy of YGAO11 was calculated to be 2.53 eV. From the above results, it can be seen that the oxadiazole derivative of the present invention is a substance having a large excitation energy. In particular, it can be seen that the substance has a large triplet excitation energy.

  Moreover, the glass transition point was measured using the differential scanning calorimeter (DSC, the Perkin Elmer company make, Pyris1). First, the sample was heated to 330 ° C. at 40 ° C./min, and then cooled to room temperature at 40 ° C./min. Thereafter, the temperature was raised to 330 ° C. at 10 ° C./min, and cooled to room temperature at 40 ° C./min, and then measured. As a result, it was found that the glass transition point (Tg) of YGAO11 was 99 ° C.

Next, the oxidation characteristics and reduction characteristics of YGAO11 were examined by cyclic voltammetry (CV) measurement. As the measuring apparatus, an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A) was used. The solution in CV measurement uses dehydrated dimethylformamide (DMF) as a solvent, and dissolves the supporting electrolyte tetra-n-butylammonium perchlorate (n-Bu ₄ NClO ₄ ) to a concentration of 100 mM. YGAO11 which is a measurement object was prepared by dissolving to a concentration of 1 mM. In addition, as a working electrode, a platinum electrode (manufactured by BAS Co., Ltd., PTE platinum electrode), and as an auxiliary electrode, a platinum electrode (manufactured by BAS Inc., Pt counter electrode for VC-3 ( 5 cm)), and an Ag / Ag ⁺ electrode (manufactured by BAS Co., Ltd., RE5 nonaqueous solvent system reference electrode) was used as a reference electrode.

  The oxidation characteristics were measured by first scanning the working electrode potential with respect to the reference electrode from −0.11 V to 0.90 V, and then scanning from 0.90 V to −0.11 V. The reduction characteristics were measured by first scanning the potential of the working electrode with respect to the reference electrode from −0.07 to −2.60 V, and then scanning from −2.60 V to −0.07 V. The scan speed for CV measurement was set to 0.1 V / s.

FIG. 8A shows a CV curve examined for the oxidation characteristics of YGAO11, and FIG. 8B shows a CV curve examined for the reduction characteristics. In FIG. 8, the horizontal axis represents the potential of the working electrode with respect to the reference electrode, and the vertical axis represents the value of current flowing between the working electrode and the auxiliary electrode. As shown in FIG. 8, in YGAO11, both an oxidation peak and a reduction peak were clearly observed. Specifically, a current indicating oxidation around 0.87V (vs.Ag/Ag ⁺ electrode) was observed, a current indicating reduction near -2.40V (vs.Ag/Ag ⁺ electrode) was observed . From this, it was found that YGAO11 is a substance that easily contains holes and electrons.

<< Synthesis Example 2 >>
In Synthesis Example 2, the oxadiazole derivative of the present invention represented by the structural formula (51) of Embodiment 1, 2-phenyl-5- {4- [N-phenyl-N- (9-phenylcarbazole-3) -Yl) amino] phenyl} -1,3,4-oxadiazole (abbreviation: PCAO11) will be specifically exemplified.

<Step 1; Synthesis of 2- (4-bromophenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: O11Br)>
Since it was described in Step 1 of Synthesis Example 1, it is omitted here.

<Step 2; Synthesis of N-phenyl- (9-phenylcarbazol-3-yl) amine (abbreviation: PCA)>
In Step 2, PCA was synthesized according to the following procedures (i) to (ii).

(I) Synthesis of 3-bromo-9-phenylcarbazole First, 24.3 g (100 mmol) of N-phenylcarbazole was dissolved in 600 mL of glacial acetic acid, and 17.8 g (100 mmol) of N-bromosuccinimide was slowly added. Stir for hours. This reaction solution was added dropwise to 1 L of ice water with stirring, and the precipitated white solid was washed three times with water. The obtained solid was dissolved in 150 mL of diethyl ether and washed with a saturated aqueous sodium hydrogen carbonate solution and water. After washing, the organic layer was dried with magnesium sulfate. After filtering this and concentrating the filtrate, about 50 mL of methanol was added to the obtained solid, and it was uniformly dissolved by irradiation with ultrasonic waves. A white precipitate was obtained by allowing this solution to stand. This was recovered by filtration and dried to obtain 28.4 g of a white powder of 3-bromo-9-phenylcarbazole as a target product (yield 88%).

(Ii) Synthesis of PCA Next, under nitrogen, 19 g (60 mmol) of 3-bromo-9-phenylcarbazole obtained in (i), 340 mg (0.6 mmol) of bis (dibenzylideneacetone) palladium (0), 1 , 1-bis (diphenylphosphino) ferrocene (abbreviation: DPPF) 1.6 g (3.0 mmol) and sodium tert-butoxide 13 g (180 mmol) were added to 110 mL of dehydrated xylene and 7.0 g (75 mmol) of aniline. . This was stirred with heating at 90 ° C. for 7.5 hours in a nitrogen atmosphere. After completion of the reaction, about 500 mL of toluene warmed to 50 ° C. was added to the obtained suspension, followed by filtration through Florisil, alumina, and celite. The obtained filtrate was concentrated, hexane and ethyl acetate were added to the precipitated solid, and ultrasonic waves were irradiated. The obtained suspension was filtered, and the filtrate was dried to obtain 15 g of PCA cream powder, which is the target product of Step 2, (yield 75%). The synthesis scheme of Step 2 described above is shown in the following scheme (b-2).

<Step 3; of 2-phenyl-5- {4- [N-phenyl-N- (9-phenylcarbazol-3-yl) amino] phenyl} -1,3,4-oxadiazole (abbreviation: PCAO11) Synthesis>
O11Br (1.0 g, 3.3 mmol) obtained in Step 1, PCA (1.1 g, 3.3 mmol) and sodium tert-butoxide (0.6 g, 6.7 mmol) obtained in Step 2 were placed in a 100 mL three-necked flask and purged with nitrogen. Thereafter, 15 mL of toluene and 0.1 mL of a 10% hexane solution of tritert-butylphosphine were added to further purge with nitrogen. Thereto was added 0.1 g (0.2 mmol) of bis (dibenzylideneacetone) palladium (0), and the mixture was stirred at 80 ° C. for 5 hours. After completion of the reaction, the obtained solid was dissolved in chloroform, washed with water, filtered through celite, and the filtrate was further washed with water. The obtained organic layer was dried over magnesium sulfate, filtered, and the filtrate was concentrated. The obtained solid was dissolved in toluene and purified by silica column chromatography. Column purification was performed by first using toluene as a developing solvent and then using a mixed solvent of toluene: ethyl acetate = 1: 1 as a developing solvent. When recrystallized with chloroform and hexane, 0.99 g of a yellow solid of PCAO11 which is the target product of Synthesis Example 2 was obtained (yield 54%). The synthesis scheme of Step 3 described above is shown in the following scheme (c-2).

In addition, the analysis result by the nuclear magnetic resonance spectroscopy (< ¹ > H-NMR) of PCAO11 obtained at the said step 3 is shown below. A ¹ H-NMR chart is shown in FIG. 9A, and an enlarged view thereof is shown in FIG. 9B. This indicates that in Synthesis Example 2, the oxadiazole derivative PCAO11 of the present invention represented by the above structural formula (51) was obtained.

¹ H-NMR (CDCl ₃ , 300 MHz): δ = 7.11-7.65 (m, 20H), δ = 7.93 (d, J = 9.0, 2H), δ = 8.03-7 .98 (m, 2H), δ = 8.12 (m, 2H)

Further, sublimation purification of the obtained PCAO11 was performed by a train sublimation method. The sublimation purification was performed at 270 ° C. for 12 hours under a reduced pressure of 7 Pa with an argon flow rate of 3 mL / min. When sublimation purification was performed on 0.99 g of PCAO11, the yield was 0.71 g and the yield was 72%.

Next, the absorption spectrum and emission spectrum of PCAO11 were measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (model V550 manufactured by JASCO Corporation), and the emission spectrum was measured using a fluorometer (FS920 manufactured by Hamamatsu Photonics). The measurement was performed at room temperature for the toluene solution and the deposited film. The measurement result of the toluene solution is shown in FIG. 10 (a), and the measurement result of the deposited film is shown in FIG. 10 (b). The horizontal axis represents wavelength, and the vertical axis represents the intensity of absorption and emission.

As shown in FIG. 10A, the oxadiazole derivative PCAO11 of the present invention has an absorption peak at 366 nm in a toluene solution. The emission spectrum has a peak at 456 nm. The emission spectrum was measured by excitation at a wavelength of 366 nm.

Further, as shown in FIG. 10B, the deposited film of the oxadiazole derivative PCAO11 of the present invention has an absorption peak at 377 nm. The emission spectrum has a peak at 483 nm. The emission spectrum was measured by excitation with a wavelength of 356 nm.

In addition, it was 2.97 eV when the absorption gap was calculated | required using the data of the absorption spectrum of FIG.10 (b), the absorption edge was calculated | required by tauc plot, and the energy of the absorption edge was made into the energy gap. This shows that the oxadiazole derivative PCAO11 of the present invention has a large excitation energy.

  The ionization potential of PCAO11 in a thin film state was 5.30 eV as a result of measurement by atmospheric photoelectron spectroscopy (AC-2, manufactured by Riken Keiki Co., Ltd.). As a result, it was found that the HOMO level was −5.30 eV. Further, when the LUMO level was determined from the energy gap value and the HOMO level determined above, it was -2.33 eV.

  Moreover, the optimal molecular structure in the ground state of PCA011 was calculated by B3LYP / 6-311 (d, p) of density functional theory (DFT). DFT is used in this calculation because it has better calculation accuracy than the Hartree-Fock (HF) method, which does not take into account electronic correlation, and the calculation cost is lower than the perturbation method (MP) method, which is the same level of calculation accuracy. did. The calculation was performed using a high performance computer (HPC) (manufactured by SGI, Altix 3700 DX). By applying the time-dependent density functional theory (TDDFT) B3LYP / 6-311 (d, p) in the molecular structure optimized by DFT, the singlet excitation energy (energy gap) of PCA011 was calculated. Singlet excitation energy was calculated to be 3.11 eV. The triplet excitation energy of PCAO11 was calculated to be 2.50 eV. From the above results, it can be seen that the oxadiazole derivative of the present invention is a substance having a large excitation energy. In particular, it can be seen that the substance has a large triplet excitation energy.

  Moreover, the glass transition point was measured using the differential scanning calorimeter (DSC, the Perkin Elmer company make, Pyris1). First, the sample was heated to 280 ° C. at 40 ° C./min, and then cooled to room temperature at 40 ° C./min. Thereafter, the temperature was increased to 280 ° C. at 10 ° C./min and cooled to room temperature at 40 ° C./min. As a result, it was found that the glass transition point (Tg) of PCAO11 was 103 ° C.

Next, the oxidation characteristic and reduction characteristic of PCAO11 were examined by cyclic voltammetry (CV) measurement. The measurement apparatus and the solution concentration for CV measurement were the same as those in Synthesis Example 1 above.

  The oxidation characteristic was measured by first scanning the potential of the working electrode with respect to the reference electrode from −0.22 V to 0.80 V, and then scanning from 0.80 V to −0.22 V. The reduction characteristics were measured by first scanning the potential of the working electrode with respect to the reference electrode from −0.60 V to −2.70 V, and then scanning from −2.70 V to −0.60 V. The scan speed for CV measurement was set to 0.1 V / s.

FIG. 11 (a) shows the CV curve examined for the oxidation characteristics of PCAO11, and FIG. 11 (b) shows the CV curve examined for the reduction characteristics. In FIG. 11, the horizontal axis represents the potential of the working electrode with respect to the reference electrode, and the vertical axis represents the current value flowing between the working electrode and the auxiliary electrode. As shown in FIG. 11, both an oxidation peak and a reduction peak were clearly observed in PCAO11. From this, it was found that PCAO11 is a substance that easily contains holes and electrons.

<< Synthesis Example 3 >>
In Synthesis Example 3, the oxadiazole derivative of the present invention represented by the structural formula (91) of Embodiment 1, 2- {4- [N- (4-diphenylaminophenyl) -N-phenylamino] phenyl} A synthesis example of -5-phenyl-1,3,4-oxadiazole (abbreviation: DPAO11) is specifically exemplified.

<Step 1; Synthesis of 2- (4-bromophenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: O11Br)>
Since it was described in Step 1 of Synthesis Example 1, it is omitted here.

<Step 2: Synthesis of N, N, N′-triphenyl-1,4-phenylenediamine (abbreviation: DPA)>
In Step 2, DPA was synthesized according to the following procedures (i) to (ii).

(I) Synthesis of 4-bromotriphenylamine First, 25 g (100 mmol) of triphenylamine, 18 g (100 mmol) of N-bromosuccinimide and 400 mL of ethyl acetate were placed in a 1000 mL Erlenmeyer flask and stirred at room temperature in air for 18 hours. After completion of the reaction, the organic layer and aqueous layer were obtained by washing twice with a saturated aqueous sodium carbonate solution. The aqueous layer was extracted twice with ethyl acetate, and the extract was combined with the organic layer and washed with saturated brine. After drying with magnesium sulfate, the solution was naturally filtered and the filtrate was concentrated. The obtained colorless solid was recrystallized with ethyl acetate-hexane to obtain 22 g of a colorless powdery solid of 4-bromotriphenylamine as the target product. (Yield 66%).

(Ii) Synthesis of N, N, N′-triphenyl-1,4-phenylenediamine (abbreviation: DPA) 0.56 g (6 mmol) of 4-bromotriphenylamine obtained in (i) above, bis (dibenzylidene) Acetone) palladium (0) 0.35 g (0.6 mmol), sodium tert-butoxide 0.58 g (6 mmol) was placed in a 100 mL three-necked flask, and 5 mL of toluene was added and the atmosphere was replaced with nitrogen. Then, aniline 0.56 g (6 mmol), 0.37 mL (1.8 mmol) of a 10% hexane solution of tritert-butylphosphine was added, and the mixture was heated and stirred at 80 ° C. for 5 hours. After the reaction, saturated brine was added to terminate the reaction, and the aqueous layer was extracted with about 100 mL of ethyl acetate. The extract was dried over magnesium sulfate and filtered. The filtrate was concentrated and purified on a silica gel column of ethyl acetate: hexane = 1: 20 to obtain 0.24 g of a light yellow powdery solid of DPA which is the target product of Step 2 (yield). 42%). The synthesis scheme of Step 2 described above is shown in the following scheme (b-3).

<Step 3; Synthesis of 2- {4- [N- (4-diphenylaminophenyl) -N-phenylamino] phenyl} -5-phenyl-1,3,4-oxadiazole (abbreviation: DPAO11)>
0.61 g (2.0 mmol) of O11Br obtained in Step 1, 0.67 g (2.0 mmol) of DPA obtained by the method shown in Step 2, 1.0 g (10.4 mmol) of sodium tert-butoxide, bis (dibenzylidene) Acetone) palladium (0) 0.014 g (0.02 mmol) was placed in a 50 mL three-necked flask and purged with nitrogen. Toluene 7 mL, tritert-butylphosphine 10% hexane solution 0.1 mL was added and heated at 80 ° C. for 8 hours. Stir. After completion of the reaction, the obtained solid was dissolved in chloroform, washed in order with water and saturated brine, and then filtered through celite. The filtrate was concentrated, and the resulting solid was dissolved in toluene and purified by silica column chromatography. Column purification was performed by first using toluene as a developing solvent and then using a mixed solvent of toluene: ethyl acetate = 1: 1 as a developing solvent. Recrystallization from chloroform and hexane gave 0.65 g of a yellow solid of DPAO11, which was the target product of Synthesis Example 3, (yield 58%). The synthesis scheme of Step 3 described above is shown in (c-3) below.

In addition, the analysis result by the nuclear magnetic resonance spectroscopy (< ¹ > H-NMR) of DPAO11 obtained at the said step 3 is shown below. A ¹ H-NMR chart is shown in FIG. 12A, and an enlarged view thereof is shown in FIG. From this, it was found that in Synthesis Example 3, the oxadiazole derivative DPAO11 of the present invention represented by the above structural formula (91) was obtained.

¹ H-NMR (CDCl ₃ , 300 MHz): δ = 7.00-7.37 (m, 21H), δ = 7.52 (m, 3H), δ = 7.95 (d, J = 9.0) , 2H), δ = 8.10-8.13 (m, 2H)

Next, the absorption spectrum and emission spectrum of DPAO11 were measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (model V550 manufactured by JASCO Corporation), and the emission spectrum was measured using a fluorometer (FS920 manufactured by Hamamatsu Photonics). The measurement was performed at room temperature for the toluene solution and the deposited film. FIG. 13A shows the measurement result of the toluene solution, and FIG. 13B shows the measurement result of the deposited film. The horizontal axis represents wavelength, and the vertical axis represents the intensity of absorption and emission.

As shown in FIG. 13 (a), the oxadiazole derivative DPAO11 of the present invention has an absorption peak at 369 nm in a toluene solution. The emission spectrum has a peak at 498 nm. The emission spectrum was measured by excitation at a wavelength of 369 nm.

Moreover, as shown in FIG.13 (b), the vapor deposition film | membrane of the oxadiazole derivative DPAO11 of this invention has an absorption peak at 373 nm. The emission spectrum has a peak at 504 nm. The emission spectrum was measured by excitation at a wavelength of 373 nm.

In addition, using the data of the absorption spectrum of FIG. 13B, the absorption edge was obtained by tauc plot, and the energy gap of DPAO11 was obtained by using the energy at the absorption edge as the energy gap, which was 2.99 eV. This shows that the oxadiazole derivative DPAO11 of the present invention has a large excitation energy.

  Further, the ionization potential of DPAO11 in a thin film state was measured by photoelectron spectroscopy in the atmosphere (manufactured by Riken Keiki Co., Ltd., AC-2), and found to be 5.41 eV. As a result, it was found that the HOMO level was −5.41 eV. Furthermore, when the LUMO level was determined from the energy gap value determined above and the HOMO level, it was -2.42 eV.

  Moreover, the glass transition point was measured using the differential scanning calorimeter (DSC, the Perkin Elmer company make, Pyris1). First, the sample was heated to 280 ° C. at 40 ° C./min, and then cooled to room temperature at 40 ° C./min. Thereafter, the temperature was increased to 280 ° C. at 10 ° C./min and cooled to room temperature at 40 ° C./min. As a result, it was found that the glass transition point (Tg) of DPAO11 was 72 ° C.

Next, the oxidation characteristics and reduction characteristics of DPAO11 were examined by cyclic voltammetry (CV) measurement. The measurement apparatus and the solution concentration for CV measurement were the same as those in Synthesis Example 1 above.

  The oxidation characteristic was measured by first scanning the potential of the working electrode with respect to the reference electrode from −0.35 V to 0.60 V, and then scanning from 0.60 V to −0.35 V. The reduction characteristic was measured by first scanning the potential of the working electrode with respect to the reference electrode from −0.32 V to −2.60 V, and then scanning from −2.60 V to −0.32 V. The scan speed for CV measurement was set to 0.1 V / s.

FIG. 14A shows a CV curve examined for the oxidation characteristics of DPAO11, and FIG. 14B shows a CV curve examined for the reduction characteristics. In FIG. 14, the horizontal axis represents the potential of the working electrode with respect to the reference electrode, and the vertical axis represents the current value flowing between the working electrode and the auxiliary electrode. As shown in FIG. 14, both oxidation peak and reduction peak were clearly observed in DPAO11. From this, it was found that DPAO11 is a substance in which holes and electrons can easily enter.

In Example 2, an example of a light-emitting element using the oxadiazole derivative YGAO11 of the present invention synthesized in Synthesis Example 1 of Example 1 as a host material of a light-emitting layer and a green-emitting phosphorescent compound as a guest material Is specifically exemplified. The element structure is shown in FIG.

<< Production of Light-Emitting Element of Example 2 >>
First, a glass substrate on which indium tin oxide containing silicon oxide (ITSO) is formed to a thickness of 110 nm is prepared. The ITSO surface was covered with an insulating film so that the surface was exposed with a size of 2 mm square. Note that ITSO is the first electrode 101 that functions as an anode of the light-emitting element. As a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with a porous resin brush, baked at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

Next, the substrate was fixed to a holder provided in the vacuum deposition apparatus so that the surface on which ITSO was formed faced down.

After reducing the pressure in the vacuum apparatus to 10 ⁻⁴ Pa, NPB represented by the following structural formula (i) and molybdenum oxide (VI) are NPB: molybdenum oxide (VI) = 4: 1 (mass ratio). Thus, the hole injection layer 111 was formed by co-evaporation. The film thickness was 50 nm. Note that co-evaporation is an evaporation method in which a plurality of different substances are simultaneously evaporated from different evaporation sources. Next, the hole transport layer 112 was formed by evaporating NPB to a thickness of 10 nm. Furthermore, on the hole transport layer 112, the oxadiazole derivative YGAO11 of the present invention and Ir (ppy) ₂ (acac) represented by the following structural formula (ii) are converted into YGAO11: Ir (ppy) ₂ (acac) = The light emitting layer 113 was formed by co-evaporation so that it might become 1: 0.08 (mass ratio). The film thickness was 30 nm. Next, BCP represented by the following structural formula (iii) was deposited by 10 nm to form the electron transport layer 114. Further, Alq ₃ represented by the following structural formula (iv) and lithium (Li) are co-deposited on the electron transport layer 114 so that Alq ₃ : Li = 1: 0.01 (mass ratio). Thus, the electron injection layer 115 was formed. The film thickness was 30 nm. Finally, a 200-nm-thick aluminum film was formed as the second electrode 102 functioning as a cathode, whereby the light-emitting element of the present invention was obtained. Note that, in the above-described vapor deposition process, the vapor deposition was all performed by a resistance heating method.

<< Production of Light-Emitting Element of Comparative Example 1 >>
For comparison, a light emitting device of Comparative Example 1 was fabricated in the same manner as in Example 2 except that CBP represented by the following structural formula (v) was used instead of the oxadiazole derivative YGAO11 of the present invention. . That is, the light-emitting layer 113 of the light-emitting element of Comparative Example 1 was formed by co-evaporation so that CBP: Ir (ppy) ₂ (acac) = 1: 0.08 (mass ratio). CBP is a known compound that is widely used as a host material of a phosphorescent compound.

<< Operation Characteristics of Light-Emitting Elements of Example 2 and Comparative Example 1 >>
After performing the operation | work which seals the light emitting element of Example 2 and the comparative example 1 which were obtained by the above in the glove box of nitrogen atmosphere so that a light emitting element might not be exposed to air | atmosphere, the operating characteristic of these light emitting elements Was measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

FIG. 15A shows the current density-luminance characteristics and FIG. 15B shows the voltage-luminance characteristics of the light-emitting elements of Example 2 and Comparative Example 1, respectively. FIG. 15 shows that the current density-luminance characteristics are the same, but the voltage-luminance characteristics are better in Example 2. For example, when compared with a voltage of 4.0 V, the light-emitting element of Example 2 flows with a current density of 4.76 mA / cm ² and emits light with a luminance of 2080 cd / m ^2. In the light-emitting element No. 1, current flowed only at a current density of 1.16 mA / cm ² , and the light emission luminance was 568 cd / m ² . Therefore, it was found that the driving voltage of the light emitting element of Example 2 was lower than that of the light emitting element of Comparative Example 1. FIG. 16 shows voltage-current density characteristics of the light-emitting elements of Example 2 and Comparative Example 1. From this graph, it can be seen that the oxadiazole derivative of the present invention is more likely to pass current than CBP. This is thought to have led to a reduction in drive voltage. 28 shows emission spectra when a current of 1 mA is passed through the light-emitting elements of Example 2 and Comparative Example 1. FIG. When a voltage of 4.0 V was applied, the CIE chromaticity coordinates of the light emitting device of Example 2 were (x, y) = (0.32, 0.65), and the CIE chromaticity of the light emitting device of Comparative Example 1 The coordinates were (x, y) = (0.33, 0.64), and in all cases, green light emission from Ir (ppy) ₂ (acac) which is a guest material was obtained.

In addition, FIG. 17A shows luminance-current efficiency characteristics of these light-emitting elements. FIG. 17B is a graph in which the vertical axis of FIG. 17A is converted to external quantum efficiency. FIG. 17 indicates that the light-emitting element of Example 2 exhibits high current efficiency exceeding 40 cd / A at 1000 cd / m ² . In addition, the external quantum yield of the light-emitting element of Example 2 at 1000 cd / m ² was 12%. Further, when the power efficiency of the light-emitting element of Example 2 at 1000 cd / m ² was obtained, it was 39 lm / W, which showed high power efficiency.

As described above, by using the oxadiazole derivative of the present invention as a host material for a light-emitting layer and using a phosphorescent compound as a guest material to produce a light-emitting element, high luminous efficiency can be obtained and a driving voltage can be set. It was found that it can be reduced. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

In this Example 3, an example of a light-emitting element using the oxadiazole derivative YGAO11 of the present invention synthesized in Synthesis Example 1 of Example 1 as a host material of a light-emitting layer and using a phosphorescent compound emitting red light as a guest material. Is specifically exemplified. The element structure is shown in FIG.

First, a glass substrate on which indium tin oxide containing silicon oxide (ITSO) is formed to a thickness of 110 nm is prepared. The ITSO surface was covered with an insulating film so that the surface was exposed with a size of 2 mm square. Note that ITSO is the first electrode 101 that functions as an anode of the light-emitting element. As a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with a porous resin brush, baked at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

Next, the substrate was fixed to a holder provided in the vacuum deposition apparatus so that the surface on which ITSO was formed faced down.

After depressurizing the inside of the vacuum apparatus to 10 ⁻⁴ Pa, NPB and molybdenum oxide (VI) are co-evaporated so that NPB: molybdenum oxide (VI) = 4: 1 (mass ratio), thereby forming holes. An injection layer 111 was formed. The film thickness was 50 nm. Next, the hole transport layer 112 was formed by evaporating NPB to a thickness of 10 nm. Furthermore, on the hole transport layer 112, the oxadiazole derivative YGAO11 of the present invention and Ir (Fdpq) ₂ (acac) represented by the following structural formula (vi) are converted into YGAO11: Ir (Fdpq) ₂ (acac) = The light emitting layer 113 was formed by co-evaporation so that it might be set to 1: 0.05 (mass ratio). The film thickness was 30 nm. Next, BAlq represented by the following structural formula (vii) was deposited by 10 nm to form the electron transport layer 114. Further, Alq ₃ and lithium (Li) were co-evaporated on the electron transport layer 114 so that Alq ₃ : Li = 1: 0.01 (mass ratio), whereby the electron injection layer 115 was formed. The film thickness was 50 nm. Finally, a 200-nm-thick aluminum film was formed as the second electrode 102 functioning as a cathode, whereby the light-emitting element of the present invention was obtained. Note that, in the above-described vapor deposition process, the vapor deposition was all performed by a resistance heating method.

The light-emitting element was sealed in a glove box in a nitrogen atmosphere so that the light-emitting element was not exposed to the atmosphere, and then the operating characteristics of the light-emitting element were measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

FIG. 18A shows the current density-luminance characteristics and FIG. 18B shows the voltage-luminance characteristics of this light-emitting element. In the light-emitting element of Example 3, when a voltage of 5.8 V was applied, a current flowed at a current density of 18.0 mA / cm ² , and light was emitted with a luminance of 1020 cd / m ² . From this, it was found that the light-emitting element of the present invention operates at a low voltage. Note that when a voltage of 5.8 V was applied, the CIE chromaticity coordinates of the light emitting element of Example 3 were (x, y) = (0.71, 0.29), and Ir (Fdpq) which is a guest material ₂ ) Deep red light emission from ₂ (acac) was obtained.

In addition, FIG. 19A shows luminance-current efficiency characteristics of the light-emitting element. FIG. 19B is a graph in which the vertical axis of FIG. 19A is converted to external quantum efficiency. As can be seen from FIG. 19, the light-emitting element of Example 3 has a maximum luminous efficiency of 6.63 cd / A despite the fact that it emits deep red light with low visibility, and exhibits a very high luminous efficiency. It was. The external quantum efficiency at that time was 13.9%.

As described above, a light-emitting element with high emission efficiency and low driving voltage can be manufactured by using the oxadiazole derivative of the present invention as a host material for a light-emitting layer and using a phosphorescent compound as a guest material. Was found to be obtained. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

In Example 4, a light emitting device was manufactured in the same manner as Example 3 except that Alq was used instead of BAlq of the electron transport layer 114.

The light-emitting element was sealed in a glove box in a nitrogen atmosphere so that the light-emitting element was not exposed to the atmosphere, and then the operating characteristics of the light-emitting element were measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

The current density-luminance characteristics of this light-emitting element are shown in FIG. 20A, and the voltage-luminance characteristics are shown in FIG. In the light-emitting element of Example 4, when a voltage of 5.4 V was applied, a current flowed at a current density of 25.7 mA / cm ² , and light was emitted with a luminance of 824 cd / m ² . From this, it was found that the light-emitting element of the present invention operates at a low voltage. Note that when a voltage of 5.4 V was applied, the CIE chromaticity coordinates of the light-emitting element of Example 4 were (x, y) = (0.70, 0.30), and Ir (Fdpq) which is a guest material ₂ ) Deep red light emission from ₂ (acac) was obtained.

In addition, FIG. 21A shows luminance-current efficiency characteristics of these light-emitting elements. FIG. 21B is a graph in which the vertical axis of FIG. 21A is converted to external quantum efficiency. As can be seen from FIG. 21, the light emitting device of Example 4 has a very high luminous efficiency with a maximum luminous efficiency of 4.87 cd / A, despite the deep red light having low visibility. It was. Further, the external quantum efficiency at that time was 11.3%.

As described above, a light-emitting element with high emission efficiency and low driving voltage can be manufactured by using the oxadiazole derivative of the present invention as a host material for a light-emitting layer and using a phosphorescent compound as a guest material. Was found to be obtained. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

In Example 5, an example of a light-emitting element using the oxadiazole derivative DPAO11 of the present invention synthesized in Synthesis Example 3 of Example 1 as a host material of a light-emitting layer and a phosphorescent compound emitting red light as a guest material Is specifically exemplified. The element structure is shown in FIG.

First, a glass substrate on which indium tin oxide containing silicon oxide (ITSO) is formed to a thickness of 110 nm is prepared. The ITSO surface was covered with an insulating film so that the surface was exposed with a size of 2 mm square. Note that ITSO is the first electrode 101 that functions as an anode of the light-emitting element. As a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with a porous resin brush, baked at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

Next, the substrate was fixed to a holder provided in the vacuum deposition apparatus so that the surface on which ITSO was formed faced down.

After depressurizing the inside of the vacuum apparatus to 10 ⁻⁴ Pa, NPB and molybdenum oxide (VI) are co-evaporated so that NPB: molybdenum oxide (VI) = 4: 1 (mass ratio), thereby forming holes. An injection layer 111 was formed. The film thickness was 50 nm. Next, the hole transport layer 112 was formed by evaporating NPB to a thickness of 10 nm. Furthermore, on the hole transport layer 112, the oxadiazole derivative DPAO11 of the present invention and Ir (Fdpq) ₂ (acac) are combined with DPAO11: Ir (Fdpq) ₂ (acac) = 1: 0.10 (mass ratio). The light emitting layer 113 was formed by co-evaporation. The film thickness was 30 nm. Next, the electron transport layer 114 was formed by evaporating BCP to a thickness of 10 nm. Further, Alq ₃ and lithium (Li) were co-evaporated on the electron transport layer 114 so that Alq ₃ : Li = 1: 0.01 (mass ratio), whereby the electron injection layer 115 was formed. The film thickness was 50 nm. Finally, a 200-nm-thick aluminum film was formed as the second electrode 102 functioning as a cathode, whereby the light-emitting element of the present invention was obtained. Note that, in the above-described vapor deposition process, the vapor deposition was all performed by a resistance heating method.

The light-emitting element was sealed in a glove box in a nitrogen atmosphere so that the light-emitting element was not exposed to the atmosphere, and then the operating characteristics of the light-emitting element were measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

The current density-luminance characteristics of this light emitting element are shown in FIG. 22A, and the voltage-luminance characteristics are shown in FIG. In the light-emitting element of Example 5, when a voltage of 7.0 V was applied, a current flowed at a current density of 42.1 mA / cm ² , and light was emitted with a luminance of 965 cd / m ² . From this, it was found that the light-emitting element of the present invention operates at a low voltage. When a voltage of 7.0 V was applied, the CIE chromaticity coordinates of the light-emitting element of Example 5 were (x, y) = (0.70, 0.29), and Ir (Fdpq) which is a guest material ₂ ) Deep red light emission from ₂ (acac) was obtained.

In addition, FIG. 23A shows luminance-current efficiency characteristics of these light-emitting elements. FIG. 23B is a graph in which the vertical axis of FIG. 23A is converted to external quantum efficiency. As can be seen from FIG. 23, the light-emitting element of Example 5 exhibited a high luminous efficiency with a maximum luminous efficiency of 2.99 cd / A, despite the deep red emission with low visibility. Moreover, the external quantum efficiency at that time was 7.10%.

As described above, a light-emitting element with high emission efficiency and low driving voltage can be manufactured by using the oxadiazole derivative of the present invention as a host material for a light-emitting layer and using a phosphorescent compound as a guest material. Was found to be obtained. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

In Example 6, an example of a blue light emitting element using the oxadiazole derivative YGAO11 of the present invention synthesized in Synthesis Example 1 of Example 1 as an exciton block layer will be specifically exemplified. The element structure is shown in FIG.

<< Production of Light-Emitting Element of Example 6 >>
First, a glass substrate on which indium tin oxide containing silicon oxide (ITSO) is formed to a thickness of 110 nm is prepared. The ITSO surface was covered with an insulating film so that the surface was exposed with a size of 2 mm square. Note that ITSO is the first electrode 201 that functions as an anode of the light-emitting element. As a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with a porous resin brush, baked at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

Next, the substrate was fixed to a holder provided in the vacuum deposition apparatus so that the surface on which ITSO was formed faced down.

After depressurizing the inside of the vacuum apparatus to 10 ⁻⁴ Pa, NPB and molybdenum oxide (VI) are co-evaporated so that NPB: molybdenum oxide (VI) = 4: 1 (mass ratio), thereby forming holes. An injection layer 211 was formed. The film thickness was 50 nm. Next, the hole transport layer 212 was formed by evaporating NPB to a thickness of 10 nm. Further, an exciton block layer 220a was formed on the hole transport layer 212 by depositing 2 nm of the oxadiazole derivative YGAO11 of the present invention. Furthermore, by co-evaporating CzPA represented by the following structural formula (viii) and YGAPA represented by the following structural formula (ix) so that CzPA: YGAPA = 1: 0.04 (mass ratio). The light emitting layer 213 was formed. The film thickness was 30 nm. Next, the electron transport layer 214 was formed by vapor-depositing Alq ₃ by 10 nm. Further, on the electron transport layer 214, Alq ₃ and lithium (Li) were co-evaporated so that Alq ₃ : Li = 1: 0.01 (mass ratio), whereby the electron injection layer 215 was formed. The film thickness was 20 nm. Finally, a 200-nm-thick aluminum film was formed as the second electrode 202 functioning as a cathode, whereby the light-emitting element of the present invention was obtained. Note that, in the above-described vapor deposition process, the vapor deposition was all performed by a resistance heating method.

<< Production of Light-Emitting Element of Comparative Example 2 >>
For comparison, the light emitting device of Comparative Example 2 was fabricated in the same manner as Example 6 except that the exciton block layer 220a in the light emitting device of Example 6 was not provided.

<< Operation Characteristics of Light-Emitting Elements of Example 6 and Comparative Example 2 >>
After performing the operation | work which seals the light emitting element of Example 6 and Comparative Example 2 which were obtained by the above in the glove box of nitrogen atmosphere so that a light emitting element might not be exposed to air | atmosphere, the operating characteristic of these light emitting elements Was measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

FIG. 24A shows the current density-luminance characteristics and FIG. 24B shows the voltage-luminance characteristics of the light-emitting elements of Example 6 and Comparative Example 2, respectively. FIG. 24 shows that the voltage-luminance characteristics are the same, but the current density-luminance characteristics are better in Example 6. That is, as shown in the luminance-current efficiency characteristics of FIG. 25, Example 6 shows that the current efficiency is higher. When a voltage of 5.2 V was applied (the luminance of the light emitting element of Example 6 was 546 cd / m ² and the luminance of the light emitting element of Comparative Example 2 was 421 cd / m ² ), the CIE chromaticity of the light emitting element of Example 6 was used. The coordinates are (x, y) = (0.15, 0.13), and the CIE chromaticity coordinates of the light emitting element of Comparative Example 2 are (x, y) = (0.15, 0.14). In either case, blue light emission from YGAPA as a guest material was obtained.

From the above, it was found that a light-emitting element having high light emission efficiency can be obtained by using the oxadiazole derivative of the present invention as an exciton block layer. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

  In this example, 9- (4- {N- [4- (9-carbazolyl) phenyl] -N-phenylamino} represented by the structural formula (201) used in the light-emitting element manufactured in another example was used. A method for synthesizing (phenyl) -10-phenylanthracene (abbreviation: YGAPA) will be described.

[Step 1]
A method for synthesizing 9-phenyl-10- (4-bromophenyl) anthracene (abbreviation: PA) will be described.
(I) Synthesis of 9-phenylanthracene A synthesis scheme (f-1) of 9-phenylanthracene is shown below.

5.4 g (21.1 mmol) of 9-bromoanthracene, 2.6 g (21.1 mmol) of phenylboronic acid, 60 mg (0.21 mmol) of palladium acetate (Pd (OAc) ₂ ), potassium carbonate (K ₂ CO ₃ ) 10 mL (20 mmol) of aqueous solution (2 mol / L), 263 mg (0.84 mmol) of tri (o-tolyl) phosphine (P (o-tolyl) ₃ ), 1,2-dimethoxyethane (abbreviation: DME) 20 mL was mixed and stirred at 80 ° C. for 9 hours. After the reaction, the precipitated solid was collected by suction filtration, dissolved in toluene, and filtered through Florisil, Celite, and alumina. The filtrate was washed with water and saturated brine, and dried over magnesium sulfate. After natural filtration, the filtrate was concentrated to obtain 21.5 g of a light brown solid of 9-phenylanthracene, which was the target product, in a yield of 85%.

(Ii) Synthesis of 10-bromo-9-phenylanthracene A synthesis scheme (f-2) of 10-bromo-9-phenylanthracene is shown below.

6.0 g (23.7 mmol) of 9-phenylanthracene was dissolved in 80 mL of carbon tetrachloride, and a solution of 3.80 g (21.1 mmol) of bromine in 10 mL of carbon tetrachloride was added dropwise to the reaction solution using a dropping funnel. . After completion of dropping, the mixture was stirred at room temperature for 1 hour. After the reaction, an aqueous sodium thiosulfate solution was added to stop the reaction. The organic layer was washed with aqueous sodium hydroxide (NaOH) solution and saturated brine, and dried over magnesium sulfate. After natural filtration, the solution was concentrated, dissolved in toluene, and filtered through Florisil, Celite, and alumina. The filtrate was concentrated and recrystallized with dichloromethane and hexane to obtain 7.0 g (yield 89%) of 10-bromo-9-phenylanthracene as a target product.

(Iii) Synthesis of 9-iodo-10-phenylanthracene A synthesis scheme (f-3) of 9-iodo-10-phenylanthracene is shown below.

After dissolving 3.33 g (10 mmol) of 9-bromo-10-phenylanthracene in 80 mL of tetrahydrofuran (abbreviation: THF) and setting to −78 ° C., n-BuLi (1.6 mol / L) was added to the reaction solution from the dropping funnel. 7.5 mL (12.0 mmol) was added dropwise and stirred for 1 hour. A solution prepared by dissolving 5 g (20.0 mmol) of iodine in 20 mL of THF was added dropwise, and the mixture was further stirred at −78 ° C. for 2 hours. After the reaction, an aqueous sodium thiosulfate solution was added to stop the reaction. The organic layer was washed with aqueous sodium thiosulfate solution and saturated brine, and dried over magnesium sulfate. The solution after natural filtration was concentrated and recrystallized with ethanol to obtain 3.1 g of a target substance, 9-iodo-10-phenylanthracene, which was a pale yellow solid in a yield of 83%.

(Iv) Synthesis of 9-phenyl-10- (4-bromophenyl) anthracene (abbreviation: PA) Synthesis scheme (f-4) of 9-phenyl-10- (4-bromophenyl) anthracene (abbreviation: PA) It is shown below.

9-iodo-10-phenylanthracene 1.0 g (2.63 mmol), p-bromophenylboronic acid 542 mg (2.70 mmol), tetrakis (triphenylphosphine) palladium (0) (Pd (PPh ₃ ) ₄ ) 46 mg ( 0.03 mmol), 3 mL (6 mmol) of a 2 mol / L calcium carbonate (K ₂ CO ₃ ) aqueous solution and 10 mL of toluene were stirred at 80 ° C. for 9 hours. After the reaction, toluene was added, followed by filtration through Florisil, Celite, and alumina. The filtrate was washed with water and saturated brine, and dried over magnesium sulfate. After natural filtration, the filtrate was concentrated and recrystallized with chloroform and hexane to obtain 562 mg of a light brown solid of 9-phenyl-10- (4-bromophenyl) anthracene, which was the target product, in a yield of 45%.

[Step 2]
A method for synthesizing 9- (4- {N- [4- (9-carbazolyl) phenyl] -N-phenylamino} phenyl) -10-phenylanthracene (abbreviation: YGAPA) will be described. A synthesis scheme (f-5) of 9- (4- {N- [4- (9-carbazolyl) phenyl] -N-phenylamino} phenyl) -10-phenylanthracene (abbreviation: YGAPA) is shown below.

409 mg (1.0 mmol) of 9-phenyl-10- (4-bromophenyl) anthracene, 339 mg (1.0 mmol) of YGA synthesized in Step 2 of Synthesis Example 1, bis (dibenzylideneacetone) palladium (0) (abbreviation: Pd (dba) ₂ ) 6 mg (0.01 mmol), sodium-tert-butoxide (tert-BuONa) 500 mg (5.2 mol), tri (tert-butyl) phosphine (P (tert-Bu) ₃ ) 0.1 mL, The mixture was stirred at 10 mL of toluene at 80 ° C. for 4 hours. After the reaction, the solution was washed with water, the aqueous layer was extracted with toluene, combined with the organic layer, washed with saturated brine, and dried over magnesium sulfate. The oily product obtained by natural filtration and concentration was purified by silica gel column chromatography (hexane: toluene = 7: 3), and recrystallized from dichloromethane and hexane. As a result, 534 mg yield of YGAPA, a yellow powdered solid, was obtained. Obtained at 81%. When this compound was measured by a nuclear magnetic resonance method (NMR), 9- (4- {N- [4- (9-carbazolyl) phenyl] -N-phenylamino} phenyl) -10-phenylanthracene (abbreviation: YGAPA) ). ¹ H-NMR of YGAPA is shown in FIGS.

  In this example, synthesis of 9- [4- (N-carbazolyl)] phenyl-10-phenylanthracene (abbreviation: CzPA) represented by the structural formula (202) used in the light-emitting element manufactured in another example was used. A method will be described.

(I) Synthesis of 9- [4- (N-carbazolyl)] phenyl-10-phenylanthracene (abbreviation: CzPA) 9- [4- (N-carbazolyl)] phenyl-10-phenylanthracene (abbreviation: CzPA) A synthesis scheme (h-1) is shown below.

9-phenyl-10- (4-bromophenyl) anthracene 1.3 g (3.2 mmol), carbazole 578 mg (3.5 mmol), bis (dibenzylideneacetone) palladium (0) 50 mg (0.017 mmol), t-butoxy A mixture of 1.0 mg (0.010 mmol) of sodium, 0.1 mL of tri (t-butylphosphine) and 30 mL of toluene was heated to reflux at 110 ° C. for 10 hours. After the reaction, the solution was washed with water, the aqueous layer was extracted with toluene, combined with the organic layer, washed with saturated brine, and dried over magnesium sulfate. The oily product obtained by natural filtration and concentration was purified by silica gel column chromatography (hexane: toluene = 7: 3) and recrystallized from dichloromethane and hexane to obtain the desired product 9- [4- (N-carbazolyl)]. 1.5 g of phenyl-10-phenylanthracene (abbreviation: CzPA) was obtained in a yield of 93%. Sublimation purification was performed on 5.50 g of the obtained CzPA under conditions of 270 ° C. under an argon stream (flow rate: 3.0 mL / min) and a pressure of 6.7 Pa. As a result, 3.98 g was recovered and the recovery rate was 72%. Met.

The NMR data of the obtained CzPA are shown below. ¹ H NMR (300 MHz, CDCl ₃ ): δ = 8.22 (d, J = 7.8 Hz, 2H), δ = 7.86-7.82 (m, 3H), δ = 7.61-7. 36 (m, 20H). FIG. 27 shows a ¹ H NMR chart.

<< Synthesis Example 4 >>
In Synthesis Example 4, the oxadiazole derivative of the present invention represented by the structural formula (68) of Embodiment 1, 2- (3- {N- [4- (carbazol-9-yl) phenyl] -N- A specific example of synthesis of (phenylamino} phenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: mYGAO11) is specifically illustrated.

<Step 1; Synthesis of 2- (3-bromophenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: mO11Br)>
In Step 1, mO11Br was synthesized according to the following procedures (i) to (iii).

(I) Synthesis of 3-bromobenzoylhydrazine 10 g (44 mmol) of ethyl-3-bromobenzoate was placed in a 200 mL three-necked flask, 50 mL of ethanol was added and stirred, 12 mL of hydrazine monohydrate was added, and the mixture was heated to 78 ° C. And reacted for 5 hours. After the reaction, when water was added to the reaction solution, a solid was precipitated. The precipitated solid was collected by suction filtration. The collected solid was washed in about 500 mL of water, and collected again by suction filtration. As a result, the target white solid was obtained in a yield of 8.1 g and a yield of 86%.

(Ii) Synthesis of 1-benzoyl-2- (3-bromobenzoyl) hydrazine Next, 5.0 g (23 mmol) of 3-bromobenzoylhydrazine obtained in (i) above was placed in a 300 mL three-necked flask, and N-methyl- 10 mL of 2-pyrrolidone was added and stirred. To this mixture, a mixed solution of 10 mL of N-methyl-2-pyrrolidone and 3.2 mL (28 mmol) of benzoyl chloride was dropped with a 50 mL dropping funnel. After completion of the dropwise addition, the mixture was heated and stirred at 80 ° C. for 3 hours to be reacted. After the reaction, water was added to the reaction solution to deposit a solid. The precipitated solid was obtained by suction filtration. The obtained solid was washed with about 1 L of water and collected by suction filtration. The collected solid was washed with methanol, and then collected by suction filtration to obtain 7.1 g of a target white solid in a yield of 96%.

(Iii) Synthesis of mO11Br Further, 7.1 g (22 mmol) of 1-benzoyl-2- (3-bromobenzoyl) hydrazine obtained by the method shown in (ii) above was placed in a 300 mL three-necked flask, and 100 mL of phosphoryl chloride was added. In addition, this mixture was heated and stirred at 100 ° C. for 5 hours to be reacted. After the reaction, when phosphoryl chloride in the flask was completely distilled off, a solid was obtained. The obtained solid was washed with water and an aqueous sodium carbonate solution in this order, and the obtained solid was collected by suction filtration. When the collected solid was recrystallized with methanol, the target white solid was obtained in a yield of 4.9 g and a yield of 73%. The synthesis scheme of Step 1 described above is shown in the following scheme (a-4).

<Step 2; 2- (3- {N- [4- (carbazol-9-yl) phenyl] -N-phenylamino} phenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: mYGAO11) Synthesis)
2.0 g (6.6 mmol) of 2- (3-bromophenyl) -5-phenyl-1,3,4-oxadiazole (abbreviation: mO11Br) obtained in Step 1 was obtained in Step 2 of Synthesis Example 1. 4- (carbazol-9-yl) diphenylamine (abbreviation: YGA) 2.2 g (6.6 mmol), sodium tert-butoxide 1.3 g (13 mmol), bis (dibenzylideneacetone) palladium (0) 0.1 g (0 0.2 mmol) was placed in a 100 mL three-necked flask, and the inside of the flask was purged with nitrogen. To this mixture, 40 mL of toluene and 0.1 mL of a 10% hexane solution of tri (tert-butyl) phosphine were added. This mixture was heated and stirred at 80 ° C. for 5 hours to be reacted. After the reaction, toluene was added to the reaction mixture, and the suspension was suction filtered through celite. The obtained filtrate was washed with water, a saturated aqueous sodium hydrogen carbonate solution and saturated brine in this order, and then the organic layer and the aqueous layer were separated. Magnesium sulfate was added to the organic layer and dried. This mixture was subjected to suction filtration to remove magnesium sulfate, and the obtained filtrate was concentrated to obtain a solid. The obtained solid was dissolved in toluene and purified by silica gel column chromatography. In column chromatography, first, toluene was used as a developing solvent, and then a mixed solvent of toluene: ethyl acetate = 1: 4 was used as a developing solvent. The obtained fraction was concentrated to obtain a solid. When the obtained solid was recrystallized with a mixed solvent of chloroform and hexane, 2.6 g of a target white solid was obtained in a yield of 71%. The synthesis scheme of Step 3 described above is shown in the following scheme (c-4).

In addition, the analysis result by nuclear magnetic resonance spectroscopy (< ¹ > H-NMR) of obtained mYGAO11 is shown below. A ¹ H-NMR chart is shown in FIG. 29 (a), and an enlarged view thereof is shown in FIG. 29 (b). From this, it was found that in Synthesis Example 4, the oxadiazole derivative mYGAO11 of the present invention represented by the structural formula (68) was obtained.

¹ H NMR (CDCl ₃ , 300 MHz): δ = 7.11-7.19 (m, 1H), 7.20-7.55 (m, 19H), 7.80 (d, J = 7.3 Hz, 1H), 7.98 (s, 1H), 8.07-8.19 (m, 4H)

  Sublimation purification of the obtained white solid was performed by a train sublimation method. The sublimation purification was performed for 3 hours by heating the material to 272 ° C. under a reduced pressure of 7.0 Pa while flowing argon at a flow rate of 3.0 mL / min. When 1.6 g of mYGAO11 was purified by sublimation, the yield was 1.0 g and the recovery rate was 63%.

Next, the absorption spectrum and emission spectrum of mYGAO11 were measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (model V550 manufactured by JASCO Corporation), and the emission spectrum was measured using a fluorometer (FS920 manufactured by Hamamatsu Photonics). The measurement was performed at room temperature for the toluene solution. The measurement result of the toluene solution is shown in FIG. The horizontal axis represents wavelength, and the vertical axis represents the intensity of absorption and emission.

As shown in FIG. 30, the oxadiazole derivative mYGAO11 of the present invention has an absorption peak at 293 nm in a toluene solution. The emission spectrum has a peak at 448 nm. The emission spectrum was measured by excitation at a wavelength of 314 nm.

In Example 10, an example of a light-emitting element using the oxadiazole derivative mYGAO11 of the present invention synthesized in Synthesis Example 4 of Example 9 as a host material of a light-emitting layer and using a phosphorescent compound emitting red light as a guest material Is specifically exemplified. The element structure is shown in FIG.

First, a glass substrate on which indium tin oxide containing silicon oxide (ITSO) is formed to a thickness of 110 nm is prepared. The ITSO surface was covered with an insulating film so that the surface was exposed with a size of 2 mm square. Note that ITSO is the first electrode 101 that functions as an anode of the light-emitting element. As a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with a porous resin brush, baked at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

Next, the substrate was fixed to a holder provided in the vacuum deposition apparatus so that the surface on which ITSO was formed faced down.

After depressurizing the inside of the vacuum apparatus to 10 ⁻⁴ Pa, NPB and molybdenum oxide (VI) are co-evaporated so that NPB: molybdenum oxide (VI) = 4: 1 (mass ratio), thereby forming holes. An injection layer 111 was formed. The film thickness was 50 nm. Next, the hole transport layer 112 was formed by evaporating NPB to a thickness of 10 nm. Further, on the hole transport layer 112, the oxadiazole derivative mYGAO11 of the present invention and Ir (Fdpq) ₂ (acac) represented by the structural formula (vi) are expressed as mYGAO11: Ir (Fdpq) ₂ (acac) = The light emitting layer 113 was formed by co-evaporation so that it might become 1: 0.06 (mass ratio). The film thickness was 30 nm. Next, the electron transport layer 114 was formed by vapor-depositing BAlq represented by the structural formula (vii) with a thickness of 10 nm. Further, Alq ₃ and lithium (Li) were co-evaporated on the electron transport layer 114 so that Alq ₃ : Li = 1: 0.01 (mass ratio), whereby the electron injection layer 115 was formed. The film thickness was 50 nm. Finally, a 200-nm-thick aluminum film was formed as the second electrode 102 functioning as a cathode, whereby the light-emitting element of the present invention was obtained. Note that, in the above-described vapor deposition process, the vapor deposition was all performed by a resistance heating method.

The light-emitting element was sealed in a glove box in a nitrogen atmosphere so that the light-emitting element was not exposed to the atmosphere, and then the operating characteristics of the light-emitting element were measured. The measurement was performed at room temperature (atmosphere kept at 25 ° C.).

The current density-luminance characteristics of this light emitting element are shown in FIG. 31A, and the voltage-luminance characteristics are shown in FIG. In the light-emitting element of Example 10, when a voltage of 5.2 V was applied, a current flowed at a current density of 37.5 mA / cm ² , and light was emitted with a luminance of 1110 cd / m ² . From this, it was found that the light-emitting element of the present invention operates at a low voltage. When a voltage of 5.2 V was applied, the CIE chromaticity coordinates of the light-emitting element of Example 10 were (x, y) = (0.70, 0.30), and Ir (Fdpq) which is a guest material ₂ ) Deep red light emission from ₂ (acac) was obtained.

In addition, FIG. 32 shows luminance-current efficiency characteristics of the light-emitting element. As can be seen from FIG. 32, the light emitting element of Example 10 emitted light efficiently with a maximum value of the luminous efficiency of 4.42 cd / A, despite the deep red light emission with low visibility. In addition, the external quantum efficiency at that time was 8.1%.

In addition, FIG. 33 shows voltage-current characteristics of the light-emitting element. From this figure, it can be seen that the oxadiazole derivative of the present invention is easy to pass current. This is thought to have led to a reduction in drive voltage.

As described above, by using the oxadiazole derivative of the present invention as a host material for a light-emitting layer and using a phosphorescent compound as a guest material to produce a light-emitting element, a light-emitting element that emits light efficiently and has a low driving voltage Was found to be obtained. Therefore, it was found that by implementing the present invention, a light-emitting element with low power consumption can be obtained.

3A and 3B each illustrate an element structure of a light-emitting element including an oxadiazole derivative of the present invention. 3A and 3B each illustrate an element structure of a light-emitting element including an oxadiazole derivative of the present invention. 3A and 3B each illustrate an element structure of a light-emitting element including an oxadiazole derivative of the present invention. 4A and 4B illustrate a light-emitting device using a light-emitting element of the present invention. 4A and 4B each illustrate an electronic device using a light-emitting device of the present invention. It shows a ¹ H-NMR chart of the oxadiazole derivatives YGAO11 of the present invention. The figure which shows the ultraviolet-visible absorption spectrum and emission spectrum of the oxadiazole derivative YGAO11 of this invention. The figure which shows the CV curve of the oxadiazole derivative YGAO11 of this invention. It shows a ¹ H-NMR chart of the oxadiazole derivatives PCAO11 of the present invention. The figure which shows the ultraviolet-visible absorption spectrum and emission spectrum of the oxadiazole derivative PCAO11 of this invention. The figure which shows the CV curve of the oxadiazole derivative PCAO11 of this invention. It shows a ¹ H-NMR chart of the oxadiazole derivatives DPAO11 of the present invention. The figure which shows the ultraviolet-visible absorption spectrum and emission spectrum of the oxadiazole derivative DPAO11 of this invention. The figure which shows the CV curve of the oxadiazole derivative DPAO11 of this invention. FIG. 9 shows operating characteristics of light-emitting elements of Example 2 and Comparative Example 1. FIG. 9 shows operating characteristics of light-emitting elements of Example 2 and Comparative Example 1. FIG. 9 shows operating characteristics of light-emitting elements of Example 2 and Comparative Example 1. FIG. 10 shows operating characteristics of the light-emitting element of Example 3. FIG. 10 shows operating characteristics of the light-emitting element of Example 3. FIG. 10 shows operating characteristics of the light-emitting element of Example 4; FIG. 10 shows operating characteristics of the light-emitting element of Example 4; FIG. 10 shows operating characteristics of the light-emitting element of Example 5. FIG. 10 shows operating characteristics of the light-emitting element of Example 5. FIG. 6 shows operating characteristics of light-emitting elements of Example 6 and Comparative Example 2. FIG. 6 shows operating characteristics of light-emitting elements of Example 6 and Comparative Example 2. 9 shows a ¹ H-NMR chart of (4- {N- [4- (9- carbazolyl) phenyl] -N- phenylamino} phenyl) -10-phenylanthracene. 9- [4- (N- carbazolyl)] shows a ¹ H-NMR chart of the phenyl-10-phenyl anthracene. FIG. 6 shows emission spectra of light-emitting elements of Example 2 and Comparative Example 1. It shows a ¹ H-NMR chart of the oxadiazole derivatives mYGAO11 of the present invention. The figure which shows the ultraviolet-visible absorption spectrum and emission spectrum of the oxadiazole derivative mYGAO11 of this invention. FIG. 18 shows operating characteristics of the light-emitting element of Example 10; FIG. 18 shows operating characteristics of the light-emitting element of Example 10; FIG. 18 shows operating characteristics of the light-emitting element of Example 10;

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 11 Transistor 12 Light emitting element 13 First electrode 14 Second electrode 15 Layer 16 including light emitting layer Interlayer insulating film 17 Wiring 18 Partition layer 19 Interlayer insulating film 101 First electrode 102 Second electrode 111 Hole injection Layer 112 hole transport layer 113 light emitting layer 114 electron transport layer 115 electron injection layer 201 first electrode 202 second electrode 211 hole injection layer 212 hole transport layer 213 light emission layer 214 electron transport layer 215 electron injection layer 220a exciton Block layer 220b Exciton block layer 511 Main body 512 Case 513 Display unit 514 Keyboard 521 Display unit 522 Main unit 523 Antenna 524 Audio output unit 525 Audio input unit 526 Operation switch 531 Display unit 532 Case 533 Speaker

Claims (8)

An oxadiazole derivative represented by General Formula (G1).

(Wherein, Am has the general formula (Am1), it was or is a substituent represented by any of (Am3). Furthermore, alpha, beta ^1, beta ² is an arylene group having 6 to 25 carbon atoms the expressed. the ^{Ar 1, Ar 2, Ar 4} ~Ar 6 represents an aryl group having 6 to 25 carbon atoms. the R ¹ ~ R ² is hydrogen, an alkyl group having a carbon number of 1-4 or a carbon atoms, Represents any of 6 to 25 aryl groups .) An oxadiazole derivative represented by General Formula (G2).

(In the formula, α and β ¹ represent an arylene group having 6 to 25 carbon atoms, Ar ^{1 to} Ar ² represent an aryl group having 6 to 25 carbon atoms, and R ^{1 to} R ² represent hydrogen , alkyl group having a carbon number of 1-4, or an aryl group having 6 to 25 carbon atoms.) An oxadiazole derivative represented by General Formula (G3).

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The Ar ¹ to Ar ² represents an aryl group having 6 to 25 carbon atoms. The R ¹ to R ² are hydrogen, carbon number 1 Represents an alkyl group of ˜4 or an aryl group of 6 to 25 carbon atoms.) An oxadiazole derivative represented by General Formula (G4).

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The Ar ² represents an aryl group having 6 to 25 carbon atoms. The R ¹ to R ² are hydrogen, the carbon number 1-4 alkyl group, or an aryl group having 6 to 25 carbon atoms. the R ⁵ to R ⁹ is hydrogen, an alkyl group having a carbon number of 1-4, an alkoxy group having a carbon number of 1-4 or a phenyl group, Represents either one.) An oxadiazole derivative represented by General Formula (G11).

(In the formula, α and β ² represent an arylene group having 6 to 25 carbon atoms. Ar ¹ and Ar ^{4 to} Ar ⁶ represent an aryl group having 6 to 25 carbon atoms.) An oxadiazole derivative represented by General Formula (G12).

(In the formula, α represents an arylene group having 6 to 25 carbon atoms. Ar ¹ and Ar ^{4 to} Ar ⁶ represent an aryl group having 6 to 25 carbon atoms.) An oxadiazole derivative represented by General Formula (G13).

(Wherein, alpha represents an arylene group having 6 to 25 carbon atoms. The Ar ¹ and Ar ⁴ represents an aryl group having 6 to 25 carbon atoms. The R ¹⁵ to R ²⁴ are hydrogen, carbon number 1 -4 represents an alkyl group or a phenyl group.) The light emitting element containing the oxadiazole derivative as described in any one of Claims 1 thru | or 7.

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