JP2012111853A - Phosphorescent substance, luminescent layer, and organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphorescent substance capable of mixed vapor deposition with a host material.SOLUTION: The phosphorescent substance is a compound represented by formula (1), wherein Rto Reach independently represent H, halogen, 1-30C alkyl which may have a substituent, 1-30C alkoxy which may have a substituent or 1-30C dialkylamine which may have a substituent; n represents an integer of 0-4; and Rrepresents benzyl which may have a substituent, diphenylmethyl which may have a substituent or triphenylmethyl which may have a substituent.

Description

  The present invention relates to a novel phosphorescent material, and a light emitting layer and an organic electroluminescence device using the same.

The organic electroluminescence element has an anode, a cathode, and a light emitting layer provided between the anode and the cathode and containing a light emitting substance. In the organic electroluminescence element, the light-emitting substance generates excitons by recombination of electrons and holes injected from the electrode into the light-emitting layer. When the exciton is deactivated, the luminescent material emits light.
An organic electroluminescence element can be driven at a low voltage, has excellent viewing angle characteristics, and is thin, so that it can be used for a display device, a lighting device, and the like.

  As the light-emitting substance, a light-emitting substance that generates fluorescence (hereinafter referred to as a fluorescent substance) and a light-emitting substance that generates phosphorescence (hereinafter referred to as a phosphorescent substance) are known. The fluorescent substance emits light when the electron and hole are recombined to be in a singlet excited state and return to the ground state from the state. The phosphorescent substance emits light when it recombines with electrons and holes to be in a triplet excited state and return to the ground state from that state. The luminous efficiency of the phosphorescent material is 3 to 4 times better than the luminous efficiency of the fluorescent material. For this reason, an organic electroluminescence element using a phosphorescent material has attracted attention.

  A light emitting layer of an organic electroluminescence element is generally formed by co-evaporation of a light emitting substance and a host material (Patent Document 1, Patent Document 2, and Patent Document 3). Note that the host material is also called a charge transport material. Charge means electrons and holes (hereinafter the same). The reason for including the host material in the light emitting material in the light emitting layer is to supply electrons and holes to the light emitting material in the light emitting layer through the host material.

And when forming a light emitting layer by a co-evaporation method, the vapor deposition rate of a luminescent substance and the vapor deposition rate of a host material must be controlled.
However, it is difficult to control both of them precisely. Therefore, there is a problem that it is difficult to obtain a light emitting layer having a ratio of both as designed. A light emitting layer in which the ratio between the light emitting substance and the host material is not as designed cannot exhibit the expected light emission characteristics. Therefore, when mass-producing a large number of light emitting layers, variations in the light emission characteristics of the respective light emitting layers are likely to occur.

In this regard, [0022] of Patent Document 3 discloses that a light emitting layer is formed by mixing vapor deposition of a light emitting substance and a host material.
Since the mixed vapor deposition method vaporizes and vaporizes a plurality of substances from one vapor deposition source, the control is simpler than the co-vapor deposition method in which the vaporized substances are vaporized from the vapor deposition sources.
However, a phosphorescent material that can be vapor-deposited by a mixed vapor deposition method with a host material and has excellent luminous efficiency is not well known. Therefore, in order to expand the room for material selection, a novel phosphorescent substance is demanded.

JP 2004-28138 A JP 2009-283329 A JP 2002-25770 A

A first object of the present invention is to provide a phosphorescent material that can be mixed and deposited with a host material.
A second object of the present invention is to provide a light emitting layer that can be easily formed and has excellent light emission efficiency, and an organic electroluminescence device using the light emitting layer.

The phosphorescent substance of the present invention is represented by the following general formula (1).

In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom, a halogen atom, a substituent An optionally substituted alkyl group having 1 to 30 carbon atoms, an optionally substituted alkoxy group having 1 to 30 carbon atoms, or an optionally substituted group having 1 to 30 carbon atoms. Represents a dialkylamine group, n represents an integer of 0 to 4, and R ¹¹ has a benzyl group which may have a substituent, a diphenylmethyl group which may have a substituent or a substituent. Represents an optionally triphenylmethyl group.

In the preferred phosphorescent substance of the present invention, R ^{11 in the} general formula (1) is either a benzyl group which may have a substituent or a diphenylmethyl group which may have a substituent. is there.
In the preferred phosphorescent substance of the present invention, n in the general formula (1) is 0 or 1.

According to another aspect of the present invention, a light emitting layer is provided.
The light emitting layer includes any one of the phosphorescent substances and a host material having a sublimation start temperature of 135 ° C. to 185 ° C. at a vacuum degree of 5 × 10 ⁻⁴ Pa to 1 × 10 ⁻³ Pa. .
In a preferred light-emitting layer of the present invention, the absolute value of the difference between the sublimation start temperatures of the phosphorescent substance and the host material is 10 ° C. or less.
In a preferred light emitting layer of the present invention, the host material is composed of 1,3-bis (N-carbazolyl) benzene, 4,4′-di (N-carbazolyl) biphenyl and 2,6-bis (N-carbazolyl) pyridine. At least one selected.

According to another aspect of the present invention, an organic electroluminescence device is provided.
The organic electroluminescence element includes a first electrode, a second electrode, and one or a plurality of light emitting layers provided between the first electrode and the second electrode, and at least one of the light emitting layers. One of the above light emitting layers.

The phosphorescent substance represented by the general formula (1) of the present invention can be mixed and deposited together with the host material.
Therefore, when the phosphorescent material of the present invention is used, a light emitting layer in which the ratio of the phosphorescent material and the host material is almost as designed can be easily formed.
Moreover, since the light emitting layer of this invention contains the phosphorescence-emitting substance represented by General formula (1), it can be easily formed by the mixed vapor deposition method, and is excellent in luminous efficiency. According to the present invention, it is possible to mass-produce a light emitting layer with little variation in light emission characteristics. Therefore, by using this light emitting layer, it is possible to mass-produce organic electroluminescence elements with little variation in display characteristics.

1 is a schematic cross-sectional view of an organic electroluminescence element according to one embodiment of the present invention. The schematic sectional drawing of the organic electroluminescent element which concerns on other embodiment of this invention. The schematic sectional drawing of the organic electroluminescent element produced in the Example.

[Phosphorescent substance]
The phosphorescent substance of the present invention is an organic platinum complex represented by the following general formula (1).

In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom, a halogen atom, C1-C30 alkyl group which may have a substituent, C1-C30 alkoxy group which may have a substituent, or C1-C30 which may have a substituent. N represents an integer of 0 to 4, and R ¹¹ represents a benzyl group which may have a substituent, a diphenylmethyl group which may have a substituent or a substituent. The triphenylmethyl group which may have is represented.
In the present specification, “may have a substituent” means “having a substituent or not having a substituent”. The notation “A to B” means “A or more and B or less”.

When the alkyl group, alkoxy group or dialkylamine group has a substituent, the substituent is not particularly limited. For example, an —OH group, —SO ₃ H group, —COOH group, a halogeno group such as fluorine or chlorine, An amino group, a nitro group, etc. are mentioned. Each of the alkyl group, alkoxy group or dialkylamine group may have one or more substituents. Further, the alkyl group, alkoxy group or dialkylamine group may not have a substituent.
In addition, each carbon moiety of the alkyl group, alkoxy group or dialkylamine group may be linear or branched.

In the phosphorescent substance represented by the general formula (1), R ^{1 to} R ¹⁰ each independently have a hydrogen atom, a halogen atom, or a substituent having 1 to 30 carbon atoms. Even in any case of an alkyl group, an optionally substituted alkoxy group having 1 to 30 carbon atoms, or an optionally substituted dialkylamine group having 1 to 30 carbon atoms, light emitting characteristics And can be vapor-deposited with the host material.

In the general formula (1), R ² is preferably other than a hydrogen atom, more preferably a halogen atom or a halogenated alkyl group having 1 to 30 carbon atoms (particularly, a halogenated alkyl group having 1 to 6 carbon atoms). Group) or a halogenated alkoxy group having 1 to 30 carbon atoms (particularly, a halogenated alkoxy group having 1 to 6 carbon atoms).
In the general formula (1), each of R ² and R ⁴ is preferably other than a hydrogen atom, more preferably a halogen atom or a halogenated alkyl having 1 to 30 carbon atoms. A group (particularly a halogenated alkyl group having 1 to 6 carbon atoms) or a halogenated alkoxy group having 1 to 30 carbon atoms (particularly a halogenated alkoxy group having 1 to 6 carbon atoms).

In the general formula (1), R ⁹ and R ¹⁰ preferably each independently have a hydrogen atom, a C 1-30 alkyl group which may have a substituent, or a substituent. And an alkoxy group having 1 to 30 carbon atoms. More preferably, R ⁹ and R ¹⁰ are each independently an optionally substituted alkyl group having 1 to 12 carbon atoms or an optionally substituted group having 1 to 12 carbon atoms. It is an alkoxy group, More preferably, it is a C1-C6 alkyl group which may have a substituent, Most preferably, it is a C1-C4 alkyl group.

By selecting the above preferred atoms or groups as at least R ² , R ⁴ , R ⁹ and R ¹⁰ , a phosphorescent material that can be satisfactorily mixed and deposited with the preferred host material described later can be obtained.

Although n in the general formula (1) is not particularly limited as long as it is an integer of 0 to 4, it is preferably an integer of 0 to 2, and more preferably 0 or 1. When n in the general formula (1) is 0, an organic platinum complex having a structure in which R ¹¹ is directly bonded to the main skeleton is obtained.
The organic platinum complex in which n in the general formula (1) is 0 or 1 can be synthesized relatively easily.
In addition, the organoplatinum complex in which n in the general formula (1) is 0 or 1 has an appropriate sublimation start temperature approximate to the sublimation start temperature of the host material. Although the reason why the organic platinum complex in which n in the general formula (1) is 0 or 1 has an appropriate sublimation start temperature is not clear, it is presumed that R ¹¹ is close to the platinum complex.

R ^{11 in the} general formula (1) is any of a benzyl group which may have a substituent, a diphenylmethyl group which may have a substituent, or a triphenylmethyl group which may have a substituent. It is.
Such a phosphorescent substance having R ¹¹ emits light in a predetermined color (for example, orange) and has excellent light emission characteristics, and can be mixed and deposited with a host material.
When the benzyl group, diphenylmethyl group or triphenylmethyl group has a substituent, the substituent is not particularly limited. For example, —OH group, —SO ₃ H group, —COOH group, halogeno such as fluorine and chlorine, etc. Groups, amino groups, nitro groups, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and the like.
Further, when the benzyl group, diphenylmethyl group or triphenylmethyl group has a substituent, the substituent is preferably a substituent other than a heterocyclic group, and more preferably a substituent other than a carbazole group. More preferred. When the substituent is a heterocyclic group such as a carbazole group, the phosphorescent substance may have an excessively high sublimation start temperature.
The carbazole group has a charge transport function. Even when the phosphorescent substance does not have a carbazole group, the phosphorescent substance of the present invention is deposited together with the host material, and thus can emit light well.

When the benzyl group, diphenylmethyl group or triphenylmethyl group of R ¹¹ has a substituent, the substituent may be bonded to carbon in the benzene ring such as a benzyl group, or the benzene ring It may be bonded to other carbon.
A preferable example of R ¹¹ is any one of the following formulas (2) to (4).

In the formulas (2) to (4), X ¹ , X ² and X ³ each independently represent a substituent, and a, b and c attached thereto represent the number of substitutions.
Specific examples of the substituent represented by X ¹ , X ² and X ³ are as exemplified above, and are particularly preferably substituents other than the heterocyclic group, and further substituents other than the carbazole group. It is more preferable that
The subscripts a, b and c in the formulas (2) to (4) are each independently an integer of 0 to 5, preferably an integer of 0 to 2, more preferably 0 or 1. is there. Wherein when a to c is 0, the formula (2) to the compound of formula (4) has no substituent ^X 1, ^{X 2} and ^{X 3.}

The phosphorescent substance has a sublimation start temperature close to that of a general-purpose host material. Moreover, since the phosphorescent substance is excellent in heat resistance, it can be sublimated before it decomposes. For this reason, a light emitting layer can be formed by mixing and vapor-depositing this phosphorescent substance and a general purpose host material. ADVANTAGE OF THE INVENTION According to this invention, the novel phosphorescent substance which can be vapor-deposited with a host material can be provided, and the room for material selection expands.
Note that the phosphorescent substance of the present invention is not used only for the purpose of mixed vapor deposition with a host material. The phosphorescent substance of the present invention can also form a light emitting layer by co-evaporation with a host material, for example.
The decomposition temperature of the phosphorescent material of the present invention is a temperature exceeding the sublimation start temperature, and is 220 ° C. to 260 ° C., preferably 230 ° C. to 250 ° C. The sublimation start temperature of the phosphorescent material is 135 ° C. to 185 ° C., preferably 140 ° C. to 180 ° C., more preferably 145 ° C. to 180 ° C. The sublimation start temperature is a measured value at a degree of vacuum of 5 × 10 ⁻⁴ Pa to 1 × 10 ⁻³ Pa (hereinafter the same).

[Organic electroluminescence device]
FIG. 1 is a reference diagram showing one configuration example of the organic electroluminescence element of the present invention.
In FIG. 1, the organic electroluminescence element 10 includes a first electrode 11, a second electrode 12, and one light emitting layer 19 provided between the first electrode 11 and the second electrode 12.
An electron transport layer 13 is provided between the first electrode 11 and the light emitting layer 19, and a hole transport layer 14 is provided between the second electrode 12 and the light emitting layer 19. An electron injection layer 15 is provided between the first electrode 11 and the electron transport layer 13, and a hole injection layer 16 is provided between the second electrode 12 and the hole transport layer 14.
Usually, a 1st electrode or / and a 2nd electrode are provided on a board | substrate. In FIG. 1, the second electrode 12 is provided on the substrate 17.

FIG. 2 is a reference diagram showing another configuration example of the organic electroluminescence element of the present invention.
In FIG. 2, the organic electroluminescence element 20 includes a first electrode 21, a second electrode 22, and a light emitting layer 29 provided between the first electrode 21 and the second electrode 22. In this configuration example, the light emitting layer 29 has a multilayer structure. That is, the light emitting layer 29 includes a first light emitting layer 291 and a second light emitting layer 292. A separation layer 28 is provided between the first light emitting layer 291 and the second light emitting layer 292 as necessary. The light emitting layer 29 is not limited to a two-layer structure, and may be three or more layers.
An electron transport layer 23 is provided between the first electrode 21 and the light emitting layer 29, and a hole transport layer 24 is provided between the second electrode 22 and the light emitting layer 29. An electron injection layer 25 is provided between the first electrode 21 and the electron transport layer 23, and a hole injection layer 26 is provided between the second electrode 22 and the hole transport layer 24. In FIG. 2, the second electrode 22 is provided on the substrate 27.

However, FIG.1 and FIG.2 has each shown the structural example of the organic electroluminescent element in case a 1st electrode is a cathode and a 2nd electrode is an anode.
When the first electrode is an anode and the second electrode is a cathode, a hole transport layer is provided between the first electrode and the light-emitting layer, and a hole injection layer is provided between the first electrode and the hole transport layer. On the other hand, an electron transport layer is provided between the second electrode and the light emitting layer, and an electron injection layer is provided between the second electrode and the electron transport layer.

(electrode)
Each of the first electrode and the second electrode is made of a conductive film.
The material for forming the first electrode and the second electrode is not particularly limited. When the second electrode or the first electrode is used as an anode, the electrode forming material includes indium tin oxide (ITO); indium tin oxide containing silicon oxide (ITSO); gold; platinum; nickel; tungsten; copper; Etc.
On the other hand, when the first electrode or the second electrode is used as a cathode, the electrode forming material is aluminum; an alkali metal such as lithium or cesium; an alkaline earth metal such as magnesium or calcium; a rare earth metal such as ytterbium. And alloys such as aluminum-lithium alloys and magnesium-silver alloys.

In order to emit light from the light emitting layer to the outside, one or both of the first electrode and the second electrode needs to have translucency. Therefore, at least one of the first electrode and the second electrode is, for example, a conductive film made of a light-transmitting electrode forming material; a very thin conductive film (for example, having a thickness of several nm to Etc.). Examples of the electrode forming material having translucency include metal oxides such as ITO and zinc oxide.
The formation method of the first electrode and the second electrode is not particularly limited, and examples thereof include a sputtering method, a vapor deposition method, and an ink jet method.

(Light emitting layer)
The light emitting layer includes the phosphorescent substance and the host material described in the section of [Phosphorescent substance]. The light emitting layer may contain one or more selected from the above phosphorescent materials.
Further, when the organic electroluminescence device has a plurality of light emitting layers (when the light emitting layer has a multilayer structure), all the light emitting layers may contain the phosphorescent substance and the host material, or One of the light emitting layers may contain the phosphorescent substance and the host material.

The phosphorescent substance of the present invention forms a light emitting layer together with a host material and can emit light.
The light emitting layer may contain components other than the phosphorescent substance and the host material as long as the effects of the present invention are not impaired.

The host material is not particularly limited, and one or more types selected from conventionally known materials can be used.
Examples of the host material include a compound having a carbazole skeleton, a compound having a fluorene skeleton, a compound having a diarylamine skeleton, a compound having a pyridine skeleton, a compound having a pyrazine skeleton, a compound having a triazine skeleton, and a compound having an arylsilane skeleton Etc. Since the charge transport function is excellent, it is preferable to use a host material having a carbazole skeleton in the molecule.

In particular, it is preferable to use a host material whose absolute value of the difference between the sublimation start temperature of the phosphorescent substance and the sublimation start temperature of the host material is 10 ° C. or less. It is more preferable to use what is 5 degrees C or less.
0 ° C. ≦ | sublimation start temperature of phosphorescent substance−sublimation start temperature of host material | ≦ 5 ° C. to 10 ° C.

The use of a host material and a phosphorescent material having a difference in sublimation start temperature within the above range enables formation of a light emitting layer by a mixed vapor deposition method without requiring particularly precise control.
Further, it is preferable to use a host material whose host material has a sublimation start temperature lower than that of the phosphorescent substance. This is because the host material has a higher doping ratio than the guest material (phosphorescent substance) during mixed vapor deposition, and therefore it is desirable that the phosphorescent substance is more difficult to sublimate.
Specifically, the sublimation start temperature of the host material used is 135 ° C. to 185 ° C., preferably 140 ° C. to 180 ° C. Moreover, the decomposition temperature of the host material used is a temperature exceeding the sublimation start temperature, and is 220 ° C. to 370 ° C.

Examples of such host materials include 1,3-bis (N-carbazolyl) benzene, 4,4′-di (N-carbazolyl) biphenyl and 2,6-bis (N-carbazolyl) as shown in the following formula group. ) Pyridine.
Hereinafter, in this specification, 1,3-bis (N-carbazolyl) benzene is “mCP”, 4,4′-di (N-carbazolyl) biphenyl is “CBP”, and 2,6-bis (N-carbazolyl). ) Pyridine is sometimes abbreviated as “26mCPy”.
As the host material, one or more selected from mCP, CBP and 26 mCPy are preferably used.

The light emitting layer of the present invention can be obtained by forming a phosphorescent material and a host material by an appropriate method.
Although the film forming method is not particularly limited, it is preferable to form the light emitting layer by vapor deposition because a thin light emitting layer can be formed.
Furthermore, since a light emitting layer containing a phosphorescent substance and a host material can be easily formed at a ratio almost as designed, it is more preferable to form a light emitting layer by a mixed vapor deposition method.
Here, the mixed vapor deposition method is a vapor deposition method in which a plurality of different substances are vaporized simultaneously from one evaporation source, and the plurality of vaporized substances are simultaneously deposited on an object to be processed. On the other hand, in the co-evaporation method, a plurality of different substances are vaporized from a plurality of vapor deposition sources provided in one processing chamber, and the plurality of vaporized substances are mixed in a gas phase state and adhered onto the object to be processed. It is a vapor deposition method.
The mixed vapor deposition method is easier to control the vapor deposition process than the co-vapor deposition method. For this reason, according to the mixed vapor deposition method, a light emitting layer with little variation in light emission characteristics can be mass-produced.

Formation of the light emitting layer by mixed vapor deposition can be performed according to a conventionally known vacuum vapor deposition method.
The formation process will be briefly described. One or more of the phosphorescent substances and one or two of the host material are put in one crucible at a predetermined ratio, and the crucible is vacuumed. Heat.
The mixing ratio of the phosphorescent substance and the host material is not particularly limited. Generally, when the total amount of the phosphorescent substance and the host material is 100 parts by mass, the phosphorescent substance is preferably 5% by mass to 50% by mass, more preferably 5% by mass to It is 35 mass%, More preferably, it is 5 mass%-25 mass%. If the mixing ratio of the phosphorescent substance is too small, sufficient light emission cannot be expected. On the other hand, if the phosphorescent substance is too much, the luminous efficiency may be lowered.
The heating temperature is preferably not less than the sublimation start temperature of the phosphorescent substance and the host material and less than the decomposition temperature, and specifically 150 ° C. to 220 ° C.

(Electron transport layer and electron injection layer)
The electron transport layer is a layer having a function of transporting electrons injected from the electrode functioning as a cathode to the light emitting layer. The electron injection layer is a layer having a function of assisting injection of electrons from the electrode to the electron transport layer. The electron transport layer and the electron injection layer are not always necessary. However, the organic electroluminescence element is preferably provided with at least an electron transport layer, and more preferably provided with both an electron transport layer and an electron injection layer.
By providing the electron transport layer, electrons can be easily injected into the light emitting layer, and further, light from the light emitting layer can be prevented from being quenched by the metal of the electrode.

  The material for forming the electron transport layer is not particularly limited as long as the material has an electron transport function. Examples of the material for forming the electron transport layer include tris (8-quinolinolato) aluminum (abbreviation: Alq3) and bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (abbreviation: BAlq). 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD) and 1,3-bis [5- (p-tert- Heteroaromatic compounds such as butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7); poly (2,5-pyridin-diyl) (abbreviation: PPy) And the like. The material for forming the electron transport layer may be used alone or in combination of two or more. The electron transport layer may have a multilayer structure of two or more layers.

The material for forming the electron injection layer is not particularly limited. For example, an alkali metal compound such as lithium fluoride (LiF) or cesium fluoride (CsF); an alkaline earth metal compound such as calcium fluoride (CaF ₂ ) A material for forming the electron transport layer; and the like. The material for forming the electron injection layer may be used alone or in combination of two or more. The electron injection layer may have a multilayer structure of two or more layers.
The formation method of an electron carrying layer and an electron injection layer is not specifically limited, For example, a sputtering method, a vapor deposition method, the inkjet method, the coating method etc. are mentioned.

(Hole transport layer and hole injection layer)
The hole transport layer is a layer having a function of transporting holes injected from the electrode functioning as an anode to the light emitting layer. The hole injection layer is a layer having a function of assisting injection of holes from the electrode to the hole transport layer. The hole transport layer and the hole injection layer are not necessarily required. However, the organic electroluminescent element is preferably provided with at least a hole transport layer, and more preferably provided with both a hole transport layer and a hole injection layer.
By providing the hole transport layer, holes can be easily injected into the light emitting layer, and further, the light from the light emitting layer can be prevented from being quenched by the metal of the electrode.

  The material for forming the hole transport layer is not particularly limited as long as the material has a hole transport function. As a material for forming the hole transport layer, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) or 4,4′-bis [N- (3 -Methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD); such as 4,4′-di (N-carbazolyl) biphenyl and 1,3-bis (N-carbazolyl) benzene Carbazole derivatives; polymer compounds; and the like. The material for forming the hole transport layer may be used alone or in combination of two or more. The hole transport layer may have a multilayer structure of two or more layers.

The material for forming the hole injection layer is not particularly limited, and examples thereof include metal oxides such as vanadium oxide, niobium oxide and tantalum oxide; phthalocyanine compounds such as phthalocyanine; 3,4-ethylenedioxythiophene and And a polymer compound such as a mixture of polystyrene sulfonic acids (abbreviation: PEDOT / PSS); a material for forming the hole transport layer; The material for forming the hole injection layer may be used alone or in combination of two or more. The hole injection layer may have a multilayer structure of two or more layers.
The formation method of a positive hole transport layer and a positive hole injection layer is not specifically limited, For example, a sputtering method, a vapor deposition method, the inkjet method, the coating method etc. are mentioned.

(substrate)
The said board | substrate is not specifically limited, For example, a glass plate, a ceramic board, a synthetic resin film etc. are mentioned. In the case where light from the light emitting layer is emitted to the outside through the substrate, a light-transmitting substrate is used. Examples of the light-transmitting substrate include a glass plate and a transparent synthetic resin film.
Note that various wirings for driving the organic electroluminescence element, a drive circuit, and / or a switching element may be provided on the surface of the substrate.

  When a voltage is applied to the electrode of the organic electroluminescence element, electrons injected from the first electrode side and holes injected from the second electrode side are recombined in the light emitting layer. Thereby, the phosphorescent substance of the present invention is in a triplet excited state. Thereafter, the phosphorescent material in the excited state emits light when returning to the ground state. Thus, the emission color of the light emitting layer containing the phosphorescent material of the present invention is usually orange.

The organic electroluminescent element of this invention can be used for a display apparatus and an illuminating device.
As the light extraction structure of the organic electroluminescence element, a top emission type, a bottom emission type, a multiphoton type, or the like can be adopted.

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

[Synthesis Example A]
Synthesis Example A is a production example of an organic platinum complex (hereinafter referred to as platinum complex (A)) represented by the following formula (A).

(Synthesis of Compound 1)
Compound 1 was synthesized according to the method described in the literature (Synthesis of Characterization of Phosphorescent Cyclometalated Platinum Complexes, Brooks, J., et. Al., Inorg. Chem., 2002, 41, 12, 3055-3066). A synthesis scheme of Compound 1 is shown below.

(Synthesis of Compound 2)
Under a nitrogen atmosphere, benzyl bromide (0.9 g, 5.2 mmol), sodium acetylacetonate n hydrate (3.2 g, 26 mmol), sodium iodide (0.4 g, 2.6 mmol) in DMF (32 mL) The solution dissolved in was heated to 70 ° C. and reacted for 7 hours. After evaporating the solvent from the solution under reduced pressure, the target product was isolated using column chromatography (silica gel, hexane: ethyl acetate / 5: 1) to obtain Compound 2 as a colorless oil (0 .8 g, 81%). A synthesis scheme of Compound 2 is shown below.

(Synthesis of platinum complex (A))
A solution in which the above compound 1 (0.27 g, 0.3 mmol), the above compound 2 (0.24 g, 0.89 mmol) and sodium carbonate (0.5 g) are dissolved in 2-ethoxyethanol (10 mL) under a nitrogen atmosphere. Was heated to 100 ° C. and stirred for 12 hours. After the solvent was distilled off from this solution under reduced pressure, distilled water and toluene were added. The separated organic layer was washed three times with distilled water, and then water was removed using anhydrous magnesium sulfate. Furthermore, after the solvent was distilled off under reduced pressure, the target compound was isolated using column chromatography (silica gel, hexane: dichloromethane / 1: 1) to obtain a platinum complex (A) as a yellow powder. (163 mg, 45%). A synthesis scheme of the platinum complex (A) is shown below.

[Synthesis Example B]
Synthesis Example B is a production example of an organic platinum complex (hereinafter referred to as platinum complex (B)) represented by the following formula (B).

(Synthesis of Compound 3)
Compound 3 was synthesized according to the method described in the literature (Synthesis of Characterization of Phosphorescent Cyclometalated Platinum Complexes, Brooks, J., et. Al., Inorg. Chem., 2002, 41, 12, 3055-3066). A synthesis scheme of Compound 3 is shown below.

(Synthesis of platinum complex (B))
Under a nitrogen atmosphere, compound 3 (0.25 g, 0.3 mmol), compound 2 (0.17 g, 0.89 mmol) shown in Synthesis Example (A) and sodium carbonate (0.5 g) were mixed with 2-ethoxyethanol (0.5 g). The solution dissolved in 10 mL) was heated to 100 ° C. and stirred for 12 hours. After the solvent of this solution was distilled off under reduced pressure, distilled water and toluene were added. The separated organic layer was washed three times with distilled water, and then water was removed using anhydrous magnesium sulfate. Furthermore, after the solvent was distilled off under reduced pressure, the target compound was isolated using column chromatography (silica gel, hexane: dichloromethane / 1: 1) to obtain a platinum complex (B) as a yellow powder. (113 mg, 33%). A synthesis scheme of the platinum complex (B) is shown below.

[Synthesis Example C]
Synthesis Example C is a production example of an organic platinum complex represented by the following formula (C) (hereinafter referred to as platinum complex (C)).

(Synthesis of Compound 4)
A solution of diphenylmethanol (1.1 g, 6.0 mmol), acetylacetone (0.6 g, 6.0 mmol), p-toluenesulfonic acid (57 mg, 0.3 mmol) dissolved in nitromethane (6 mL) under a nitrogen atmosphere. Refluxed and allowed to react for 1.5 hours. After evaporating the solvent from the solution under reduced pressure, the target product was isolated using column chromatography (silica gel, hexane: ethyl acetate / 5: 1) to obtain Compound 4 as a colorless solid (1 .58 g, 99%). A synthesis scheme of Compound 4 is shown below.

(Synthesis of platinum complex (C))
Under a nitrogen atmosphere, Compound 1 (0.27 g, 0.3 mmol), Compound 4 (0.24 g, 0.89 mmol) and sodium carbonate (0.5 g) shown in Synthesis Example A were mixed with 2-ethoxyethanol (10 mL). The solution dissolved in) was heated to 100 ° C. and stirred for 12 hours. After the solvent of this solution was distilled off under reduced pressure, distilled water and toluene were added. The separated organic layer was washed three times with distilled water, and then water was removed using anhydrous magnesium sulfate. Furthermore, after the solvent was distilled off under reduced pressure, the target compound was isolated using column chromatography (silica gel, hexane: dichloromethane / 1: 1) to obtain a platinum complex (C) as a yellow powder. (93 mg, 23%). A synthesis scheme of the platinum complex (C) is shown below.

[Synthesis Example D]
Synthesis Example D is a production example of an organic platinum complex (hereinafter referred to as platinum complex (D)) represented by the following formula (D).

  Under a nitrogen atmosphere, Compound 3 (0.25 g, 0.3 mmol) shown in Synthesis Example B, Compound 4 (0.24 g, 0.89 mmol) shown in Synthesis Example C and sodium carbonate (0.5 g) were added. A solution dissolved in 2-ethoxyethanol (10 mL) was heated to 100 ° C. and stirred for 12 hours. After the solvent of this solution was distilled off under reduced pressure, distilled water and toluene were added. The separated organic layer was washed three times with distilled water, and then water was removed using anhydrous magnesium sulfate. Furthermore, after the solvent was distilled off under reduced pressure, the target compound was isolated using column chromatography (silica gel, hexane: dichloromethane / 1: 1) to obtain a platinum complex (D) as a yellow powder. (45 mg, 12%). A synthesis scheme of the platinum complex (D) is shown below.

[Synthesis Example E]
Synthesis Example E is a production example of an organic platinum complex (hereinafter referred to as platinum complex (E)) represented by the following formula (E).

  Under nitrogen atmosphere, compound 3 (0.87 g, 1.0 mmol), acetylacetone (0.3 g, 3.1 mmol) and sodium carbonate (1.0 g) shown in Synthesis Example B above were added to 2-ethoxyethanol (20 mL). The dissolved solution was heated to 100 ° C. and stirred for 16 hours. The solvent was distilled off under reduced pressure, and the target product was isolated from the resulting black solid using column chromatography (silica gel, dichloromethane) to obtain a platinum complex (E) as a yellow powder (0.49 g, 49 %).

[Measurement of thermophysical properties of platinum complexes (A) to (E)]
About each of the said platinum complexes (A) thru | or (E), using a vacuum thermobalance (product made from ULVAC, Inc., product name "VAP9000"), the degree of vacuum is 5 x ^10-4 Pa to 1 x ^10-3 Pa. The sublimation start temperature (T _sub ) (° C.) was measured.
Moreover, about each of the said platinum complexes (A) _{thru |} or (E), decomposition temperature ( _Td0.5% ) was used using the thermogravimetry apparatus (The Seiko Instruments Co., Ltd. product name "TG / _DTA6200 "). ) (° C) was measured. In addition, 0.5% weight reduction _| decrease temperature ( _Td0.5% ) was made into decomposition temperature.
The results are shown in Table 1. However, since the sublimation start temperature is estimated to have a large measurement error, the first digit of the measured value is rounded off (hereinafter the same).

[Measurement of thermophysical properties of host material]
The sublimation start temperature (T _sub ) and decomposition temperature (T _d0.5% ) were measured for each of the host materials mCP, CBP, and 26 mCPy. However, for 26mCPy, the decomposition temperature was not measured. Their measuring methods are the same as those of the platinum complex. The results are also shown in Table 1.

  As shown in Table 1, all of the platinum complexes (A) to (E) sublimate below the decomposition temperature. Accordingly, the platinum complexes (A) to (E) are compounds that can be formed by vacuum deposition.

[Example 1-1]
FIG. 3 is a structural diagram of the organic electroluminescence element produced in Example 1.
This organic electroluminescence element was produced as follows.
A glass plate with an electrode (manufactured by Nippon Sheet Glass Co., Ltd.) obtained by laminating ITO (indium-tin oxide) having a sheet resistance of 10Ω / □ functioning as an anode transparent electrode on a glass substrate was obtained. The thickness of this anode transparent electrode was 150 nm.
PEDOT / PSS (a mixture of 3,4-ethylenedioxythiophene and polystyrene sulfonic acid) was applied onto the ITO layer of the electrode-attached glass plate by a spin coating method (6000 rpm, 60 seconds). Thereafter, the coating film was dried at 180 ° C. for 20 minutes. In this way, a PEDOT / PSS layer having a thickness of 200 nm was laminated as a hole injection layer on the glass plate with an electrode.
On this PEDOT / PSS layer, NPB (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) functioning as a hole transport layer was vacuum deposited. The vapor deposition rates were 0.5 to 1.0 kg / sec, respectively. In this way, an NPB layer having a thickness of 40 nm was laminated on the PEDOT / PSS layer.

  Next, the substrate on which the NPB layer was laminated was fixed to a holder of a vapor deposition apparatus. A mixture of platinum complex (A) and mCP was put in a quartz crucible of the vapor deposition apparatus at a mixing ratio of platinum complex (A): mCP (mass ratio) = 10: 90. Next, the inside of the vapor deposition apparatus was evacuated, and the crucible was heated using an electric block heater so that the temperature in the crucible became 200 ° C., and mixed vapor deposition was performed. The deposition rate was 0.1 nm / sec. In this way, a 25 nm thick light emitting layer made of a mixture of the platinum complex (A) and mCP was laminated on the NPB layer.

On this light emitting layer, OXD-7 (1,3-bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene) functioning as an electron transport layer Was deposited by vacuum evaporation to laminate an OXD-7 layer having a thickness of 40 nm. The deposition rate was 0.5 to 1.0 kg / sec.
Further, LiF / Al functioning as a cathode electrode was sequentially deposited on the OXD-7 layer. The deposition rate of LiF was 0.1 Å / sec, and the deposition rate of Al was 5.0 Å / sec. The thickness of the LiF / Al layer was 150 nm.

About the obtained organic electroluminescent element, DC voltage was applied between ITO which is the anode electrode, and Al which is a cathode electrode. When voltage was applied, orange light emission was confirmed from the element. The luminance of the emitted light was measured using a light distribution measuring device (product name “Organic EL luminous efficiency measuring device EL1003” manufactured by Precise Gauge Co., Ltd.) to evaluate the luminous efficiency. The measured values and luminous efficiency obtained from the measuring machine are shown in Table 2.
However, each measured value of Table 2 is a value when making an organic electroluminescent element shine at 1000 cd / m < ² >.
In Table 2, “Bias” is the drive voltage, “J” is the current density, “QE” is the external quantum yield, “PE” is the power efficiency, “LE” is the luminous efficiency, and “CRI” is The color rendering values and “CIE” represent chromaticity coordinates, respectively.

[Example 1-2 to Example 1-4]
An organic electroluminescence device was produced in the same manner as in Example 1-1 except that the mixing ratio of the platinum complex (A) and mCP was changed as shown in Table 2. About each organic electroluminescent element, when the voltage was applied like Example 1-1, all the elements light-emitted orange. The luminance of the emitted light was measured in the same manner as in Example 1-1. The results are shown in Table 2.

[Example 2]
Except that the platinum complex (B) was used in place of the platinum complex (A) and that the mixing ratio of the platinum complex (B) and mCP was 15:85, the same as in Example 1-1 above. Thus, an organic electroluminescence element was produced. When a voltage was applied to the organic electroluminescence element in the same manner as in Example 1-1, all the elements emitted orange light. The luminance of the emitted light was measured in the same manner as in Example 1-1. The results are shown in Table 3.

[Example 3]
The platinum complex (C) was used instead of the platinum complex (A), the CBP was used instead of the mCP, the mixing ratio of the platinum complex (C) and CBP was 15:85, and the crucible An organic electroluminescent element was produced in the same manner as in Example 1-1 except that the inner temperature was 230 ° C. When a voltage was applied to the organic electroluminescence element in the same manner as in Example 1-1, all the elements emitted orange light. The luminance of the emitted light was measured in the same manner as in Example 1-1. The results are shown in Table 3.

[Example 4]
The use of platinum complex (D) instead of platinum complex (A), the use of 26 mCPy instead of mCP, the mixing ratio of this platinum complex (D) and 26 mCPy of 15:85, and the crucible An organic electroluminescence element was produced in the same manner as in Example 1-1 except that the inner temperature was 210 ° C. When a voltage was applied to the organic electroluminescence element in the same manner as in Example 1-1, all the elements emitted orange light. The luminance of the emitted light was measured in the same manner as in Example 1-1. The results are shown in Table 3.

[Comparative Example 1-1]
An organic electroluminescence device was produced in the same manner as in Example 1-1 except that the platinum complex (E) was used instead of the platinum complex (A). When a voltage was applied to the organic electroluminescence element in the same manner as in Example 1-1, no light emission was observed.

[Comparative Examples 1-2 to 1-4]
An organic electroluminescence device was produced in the same manner as in Examples 1-2 to 1-4 except that platinum complex (E) was used instead of platinum complex (A). In any of these organic electroluminescence elements, no light emission was observed.

All of the organic electroluminescence elements of Examples 1-1 to 1-4 and Examples 2 to 4 using the platinum complexes (A) to (D) emitted light. On the other hand, none of the organic electroluminescence elements of Comparative Examples 1-1 to 1-4 using the platinum complex (E) emitted light.
In the platinum complexes (A) and (B), a benzyl group is bonded to a specific position of the main skeleton (platinum complex part), and in the platinum complexes (C) and (D), a diphenylmethyl group is bonded to a specific position of the main skeleton. is doing. In contrast, the platinum complex (E) does not have an aromatic ring such as a benzyl group in the main skeleton. Further, the sublimation start temperatures of the platinum complexes (A) to (D) are substantially the same as the sublimation start temperatures of the respective host materials mCP, CBP, and 26 mCPy. On the other hand, the sublimation start temperature of the platinum complex (E) is 20 ° C. lower than that of mCP. From these, it is an important element for the platinum complex to emit light that an aromatic ring such as a benzyl group is bonded to R ¹¹ of the general formula (1), and the platinum complex (E) of Comparative Example 1 It can be seen that a good light emitting layer cannot be formed by the mixed vapor deposition method.

  The triphenylmethyl group has the same structure as the benzyl group and diphenylmethyl group. Therefore, from the results of the above examples, even when the platinum complex of the general formula (1) having a triphenylmethyl group is used, it can be mixed and deposited with a host material and emits light, similarly to the platinum complex having a benzyl group. It is estimated that a light-emitting layer having excellent efficiency can be formed.

[Reference Example 1-1]
An organic electroluminescence device was produced in the same manner as in Example 1-1 except that the light emitting layer was formed by a co-evaporation method instead of the mixed evaporation method.
Specifically, a predetermined amount of platinum complex (A) and mCP are put in separate crucibles, the temperature in the crucible containing platinum complex (A) is 190 ° C., and the temperature in the crucible containing mCP is 200. Each was heated to a temperature of ° C. At this time, in order to control the vapor deposition rate ratio so that the mass ratio of platinum complex (A) and mCP of the target light emitting layer is 10:90, both vapor deposition rates are stabilized over 30 minutes. It was. Thus, the light emitting layer whose mass ratio of platinum complex (A) and mCP is 10:90 was formed. However, when the ratio of the platinum complex (A) and mCP in the obtained light emitting layer was confirmed, there was a difference of about 5% from the target ratio.
About the organic electroluminescent element of the reference example 1-1, it was made to light-emit like Example 1-1, and the brightness | luminance of the orange light emission was measured. The results are shown in Table 4.

  Moreover, the light emitting layer by the co-evaporation method of Reference Example 1-1 was separately produced in the same manner as the above procedure. When the ratio of the platinum complex (A) and mCP in the light emitting layer was confirmed for each of the plurality of light emitting layers, there was a difference of about ± 5% from the target ratio. Thus, the production of the light emitting layer by co-evaporation varied depending on the production time.

[Reference Example 1-2]
A light emitting layer was prepared in the same manner as in Reference Example 1-1 except that the mass ratio of platinum complex (A) and mCP in the target light emitting layer was controlled to 20:80. A luminescence element was produced. When the ratio of the platinum complex (A) and mCP in the light emitting layer of Reference Example 1-2 obtained was confirmed, there was a difference of about 5% from the target ratio.
The organic electroluminescence element of Reference Example 1-2 was caused to emit light in the same manner as in Example 1-1, and the brightness of the orange light emission was measured. The results are shown in Table 4.

  Moreover, the light emitting layer by the co-evaporation method of Reference Example 1-2 was produced a plurality of times in the same manner as described above. When the ratio of the platinum complex (A) and mCP in the light emitting layer was confirmed for each of the plurality of light emitting layers, there was a difference of about ± 5% from the target ratio.

The phosphorescent substance of the present invention can be used as a material for forming a light emitting layer of an organic electroluminescence element.
The light emitting layer and the organic electroluminescent element of the present invention can be used as a display device, a lighting device and the like.

  DESCRIPTION OF SYMBOLS 10,20 ... Organic electroluminescent element, 11, 21 ... 1st electrode, 12, 22 ... 2nd electrode, 13, 23 ... Electron transport layer, 14, 24 ... Hole transport layer, 15, 25 ... Electron injection layer, 16, 26 ... hole injection layer, 17, 27 ... substrate, 19, 29 ... light emitting layer

Claims (7)

A phosphorescent substance represented by the following general formula (1).

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ may each independently have a hydrogen atom, a halogen atom or a substituent. Represents an alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, or a dialkylamine group having 1 to 30 carbon atoms which may have a substituent, and n Represents an integer of 0 to 4, and R ¹¹ represents a benzyl group which may have a substituent, a diphenylmethyl group which may have a substituent, or a triphenyl which may have a substituent. Represents a methyl group. The phosphorescence-emitting property according to claim 1, wherein R ^{11 in the} general formula (1) is either a benzyl group which may have a substituent or a diphenylmethyl group which may have a substituent. material.   The phosphorescent substance according to claim 1 or 2, wherein n in the general formula (1) is 0 or 1. The phosphorescent substance according to any one of claims 1 to ³ , and a host material having a sublimation start temperature of 135 ° C to 185 ° C at a degree of vacuum of 5 x ^10-4 Pa to 1 x ^10-3. A light emitting layer containing.   The light emitting layer according to claim 4, wherein an absolute value of a difference between sublimation start temperatures of the phosphorescent substance and the host material is 10 ° C. or less.   The host material is at least one selected from 1,3-bis (N-carbazolyl) benzene, 4,4′-di (N-carbazolyl) biphenyl, and 2,6-bis (N-carbazolyl) pyridine. Item 6. The light emitting layer according to Item 4 or 5.   It has a 1st electrode, a 2nd electrode, and the 1 or several light emitting layer provided between the said 1st electrode and a 2nd electrode, At least 1 of the said light emitting layer is Claims 4-6 An organic electroluminescence device, which is the light emitting layer according to any one of the above.

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