JP4801429B2 - LIGHT EMITTING ELEMENT AND LIGHT EMITTING DEVICE HAVING THE LIGHT EMITTING ELEMENT - Google Patents

Description

The present invention relates to a structure of a light-emitting element including an organic compound and an inorganic compound. Further, the present invention relates to a light emitting device having the light emitting element.

Many light-emitting elements used in displays and the like have a structure in which a layer containing a light-emitting substance is sandwiched between a pair of electrodes. Electrons injected from one electrode and injected from the other electrode Light is emitted when excitons formed by recombination with the positive holes return to the ground state.

With respect to such a light-emitting element, research has been conducted for high luminous efficiency, high stability, and prevention of an increase in driving voltage.

For example, Patent Document 1 discloses an organic thin-film light-emitting element with excellent durability that can reduce driving voltage and maintain light-emitting performance. According to Patent Document 1, it is disclosed that a low driving voltage of a light emitting element is achieved by using a metal oxide having a high work function such as molybdenum oxide for an anode.

One cause of deterioration of the light emitting element is crystallization of a substance constituting the light emitting element. Therefore, a material that is difficult to crystallize is desired. For example, Patent Document 2 discloses an organic material having a high glass transition temperature and good heat resistance.
JP-A-9-63771 International Publication No. 00/27946 Pamphlet

This development is still being carried out because it is possible to reduce the power consumption of the light emitting device by achieving a low driving voltage. In particular, when a light-emitting element is incorporated in a portable light-emitting device, it is important to achieve low power consumption.

For this reason, it cannot be said that the means disclosed in Patent Document 1 alone is sufficient, and technical development for achieving further lower drive voltage is required.

Furthermore, for mass production of light emitting devices, it is desired to establish a light emitting element structure with a high yield and a production process thereof.

Accordingly, it is an object of the present invention to provide a light emitting element that achieves a low driving voltage and to provide a light emitting element that can be produced with a high yield. It is another object of the present invention to provide a light-emitting element having a material having good heat resistance, in particular, a material that is difficult to crystallize and easily maintain an amorphous state.

It is another object of the present invention to provide a light emitting device having such a light emitting element.

In view of the above problems, the present invention is characterized by a light-emitting element having a layer containing an organic compound having an glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and an inorganic compound. The organic compound of the present invention has a melting point of 180 ° C. or higher and 400 ° C. or lower.

In addition, the invention is characterized by a light emitting element including an organic compound and an inorganic compound. In addition, the present invention is characterized in that a compound having a spiro ring and a triphenylamine skeleton is used as the organic compound. The present inventors have found that it is preferable to use a benzidine derivative represented by the above general formula (1) as a compound having a spiro ring and a triphenylamine skeleton. Specifically, it has been found that it is preferable to use a benzidine derivative represented by the structural formula (2) as a compound having a spiro ring and a triphenylamine skeleton.

The specific configuration of the present invention is shown below. As the inorganic compound, a case where a metal oxide is used is exemplified.

In the light-emitting element of the present invention, any one of the pair of electrodes and the plurality of layers provided between the pair of electrodes has an organic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and It has a metal oxide.

The organic compound of the present invention comprises N, N′-diphenylbenzidine and 2-bromo-spiro-9,9′-bifluorene or 2-bromo-2 ′, 7′-dialkyl-spiro-9,9′-bifluorene. Is obtained by the coupling reaction of

The organic compound of the present invention can be obtained by a coupling reaction of N, N'-diphenylbenzidine and 2-bromo-spiro-9,9'-bifluorene.

Further, the invention is characterized in that a layer containing an organic compound and an inorganic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower is used as a layer for generating holes. Furthermore, the light-emitting element of the present invention can have an organic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower as a hole transporting substance.

In the present invention, the organic compound has a melting point of 180 ° C. or higher and 400 ° C. or lower.

In the present invention, the organic compound is a compound having a spiro ring and a triphenylamine skeleton, and the light-emitting element of the present invention includes a pair of electrodes and a spiro ring and a triphenyl provided between the pair of electrodes. It has a compound having an amine skeleton and a metal oxide. Such an organic compound has a melting point of 180 ° C. or higher and 400 ° C. or lower, and a glass transition temperature of 90 ° C. or higher, preferably 150 ° C. or higher, more preferably 160 ° C. or higher and 300 ° C. or lower.

（式中、Ｒ^１は、水素または炭素数１〜４のアルキル基のいずれかを表す。） In the present invention, the organic compound is a benzidine derivative represented by the general formula (1). The light-emitting element of the present invention includes a pair of electrodes, a benzidine derivative represented by the general formula (1), and a metal oxide provided between the pair of electrodes.

(In the formula, R ¹ represents either hydrogen or an alkyl group having 1 to 4 carbon atoms.)

In the present invention, the organic compound is a benzidine derivative represented by the structural formula (2). The light-emitting element of the present invention includes a pair of electrodes, a benzidine derivative represented by the structural formula (2), and a metal oxide provided between the pair of electrodes. The benzidine derivative of the present invention has a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower. Such a benzidine derivative is used as a hole transporting substance.

In the present invention, the material used for the inorganic compound may be a metal nitride or a metal nitride oxide in addition to the metal oxide.

For example, in the case where the above-described inorganic compound is used for a layer functioning as an electron-accepting substance, a specific material may be an oxide of any transition metal in Groups 4 to 12 of the periodic table. Among them, oxides of transition metals of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, particularly vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide. Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are preferable.

When the inorganic compound is used for a layer that functions as a substance exhibiting electron donating properties, the metal used for the inorganic compound is a substance selected from alkali metals and alkaline earth metals, specifically lithium (Li ), Calcium (Ca), sodium (Na), potassium (K), magnesium (Mg) and the like. Specific examples of the inorganic compound include the above alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, and the like, specifically lithium oxide (Li ₂ O). , Calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), lithium fluoride (LiF), cesium fluoride (CsF) , Calcium fluoride (CaF ₂ ) and the like.

In the present invention, including an organic compound and an inorganic compound includes a state in which these are mixed or a layer in which these are stacked.

The present invention is characterized by a light-emitting device having the light-emitting element. A specific light-emitting device of the present invention includes a semiconductor film having an impurity region, a first electrode connected to the impurity region, a second electrode provided to face the first electrode, and a first electrode A first layer, a second layer, and a third layer that are sequentially provided between the electrode and the second electrode, and any one of the first layer to the third layer has a glass transition temperature; Is characterized by having an organic compound and a metal oxide at 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower. The light-emitting device of the present invention includes a semiconductor film having an impurity region, a first electrode connected to the impurity region, a second electrode provided to face the first electrode, a first electrode, The first layer, the second layer, and the third layer are sequentially provided between the second electrodes, and any one of the first to third layers includes a spiro ring and a tri-layer. It has a compound having a phenylamine skeleton and a metal oxide.

According to the present invention, a light-emitting element that is difficult to crystallize can be obtained, and a light-emitting element that achieves a low driving voltage can be obtained. In the light emitting device of the present invention, the driving voltage does not increase even when the film thickness is increased. As a result, the light-emitting element can be formed thick, so that it can be produced with high yield. Further, depending on the layer to be thickened, the electrode and the light emitting layer can be separated, so that quenching of light emission can be prevented.

Furthermore, the light-emitting element of the present invention is preferable because of high thermal stability and high heat resistance. In other words, the light emitting element of the present invention has reduced deterioration over time.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode. Note that in all the drawings for describing the embodiments, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

(Embodiment 1)
In this embodiment mode, a light-emitting element in which a benzidine derivative is used as an organic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and a layer having the benzidine derivative and an inorganic compound is used. Is illustrated with reference to FIG. The benzidine derivative of the present invention is a compound having a spiro ring and a triphenylamine skeleton.

As shown in FIG. 1, the light-emitting element of the present invention includes a first electrode 101 and a second electrode 102 facing each other, and in order from the first electrode 101, a first layer 111, a second layer 112, A third layer 113 is stacked. In such a light-emitting element, when a voltage is applied so that the potential of the first electrode 101 is higher than the potential of the second electrode 102, holes are injected from the first layer 111 to the second layer 112. Electrons are injected from the third layer 113 to the second layer 112. Holes and electrons recombine in the second layer 112, bringing the light-emitting substance into an excited state. The excited luminescent material emits light when returning to the ground state.

Next, the first layer 111 to the third layer 113, the first electrode 101, and the second electrode 102 will be described.

The first layer 111 is a layer that generates holes. In order to exhibit such a function, it can be achieved, for example, by a layer containing a hole transporting substance and a substance showing an electron accepting property for the substance. In addition, the substance that exhibits electron acceptability with respect to the hole transporting substance has a molar ratio of 0.5 to 2 (= the substance that exhibits electron acceptability with respect to the hole transporting substance). / Hole transporting substance) is preferably included.

The hole-transporting substance is a substance that has a higher hole-transporting property than electrons. For example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: α- NPD), 4,4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) tri Phenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4′-bis [N Aromatic amine compounds such as-{4- (N, N-di-m-tolylamino) phenyl} -N-phenylamino] biphenyl (abbreviation: DNTPD), phthalocyanine (abbreviation: H ₂ Pc), copper phthalocyanine (abbreviation) : CuPc), Bana An organic compound such as a phthalocyanine compound such as zirphthalocyanine (abbreviation: VOPc) can be used. Note that the hole transporting substance is not limited to these.

In addition, as the substance that exhibits an electron accepting property with respect to the hole transporting substance, any transition metal oxide of Groups 4 to 12 of the periodic table can be used. Among them, transition metal oxides of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, and in particular vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are suitable. Even if it is not an oxide, you may use the said metal nitride and oxynitride. Note that a substance that exhibits an electron accepting property with respect to a hole transporting substance is not limited thereto.

When the first layer 111 is formed of a layer in which a hole transporting material made of an organic compound and a material having an electron accepting property with respect to the hole transporting material made of the inorganic compound are mixed, the first layer 111 has high conductivity. It is preferable. When the conductivity is high, the first layer 111 can be made thicker and the production yield can be improved. Further, by increasing the thickness of the first layer 111, the first electrode 101 and the second layer 112 can be separated. As a result, it is possible to prevent the light emission from being quenched due to the metal.

By using a layer in which such an organic compound and an inorganic compound are mixed, crystallization of the organic compound used for the first layer 111 can be suppressed, and the first layer 111 is not accompanied by an increase in resistance. Can be formed thick. Therefore, even when there is unevenness due to dust or dirt on the substrate, the first layer 111 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

As shown in the following examples, a layer in which a benzidine derivative having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and a molybdenum oxide that is an inorganic compound is mixed in the first layer 111. It was found that when used, it is difficult to deteriorate over time. That is, this structure can provide a light-emitting element with excellent stability.

Note that the first layer 111 may contain another organic compound. Other organic compounds include rubrene and the like. Reliability can be improved by adding rubrene.

In addition, the first layer 111 may be a layer made of a metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, cobalt oxide, or copper oxide.

Such a first layer 111 can be formed by an evaporation method. When forming a layer in which a plurality of compounds are mixed as the first layer 111, a co-evaporation method can be used. The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

Next, the second layer 112 which is a layer including a light emitting layer will be described. The layer including the light emitting layer may be a single layer or a multilayer composed of only the light emitting layer. As a specific multilayer, it includes a plurality of layers selected from any of an electron transport layer and a hole transport layer in addition to a light emitting layer. In FIG. 1, the second layer 112 is a multilayer including a light emitting layer 123, an electron transport layer 124, and a hole transport layer 122.

The hole transport layer 122 has a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, represented by any one of the general formula (1) or structural formulas (2) to (4). A benzidine derivative can be used.

Since the benzidine derivative of the present invention has high heat resistance, by using the benzidine derivative of the present invention as a hole transport material, it is possible to form the hole transport layer 122 with little characteristic change due to heat. Further, since the benzidine derivative of the present invention is difficult to crystallize, the hole transport layer 122 that is difficult to crystallize can be formed by using the benzidine derivative of the present invention as a hole transport material.

Note that the hole transport layer 122 is a layer formed by combining two or more layers made of the benzidine derivative of the present invention represented by the general formula (1) or any one of the structural formulas (2) to (4). May be.

Furthermore, it is preferable to use a layer in which a benzidine derivative and an inorganic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and an inorganic compound are used for the hole transport layer 122. By mixing with an inorganic compound, crystallization of the benzidine derivative can be further suppressed, and the layer can be formed thick without increasing resistance. Therefore, even when the substrate has unevenness due to dust, dirt, or the like, it is hardly affected by the unevenness due to the thick film of the hole transport layer 122 having a benzidine derivative. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

As such an inorganic compound, a metal oxide, a metal nitride, or a metal oxynitride can be used. For example, as the metal oxide, any transition metal oxide of Groups 4 to 12 of the periodic table can be used. Among them, transition metal oxides of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, and in particular vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are suitable.

Next, the light emitting layer 123 will be described. The light-emitting layer 123 is preferably a layer in which a light-emitting substance is dispersed and included in a substance having an energy gap larger than that of the light-emitting substance. However, the light emitting layer is not limited to this. Note that the energy gap is an energy gap between the LUMO level and the HOMO level. As the light-emitting substance, a substance that has favorable emission efficiency and can emit light with a desired emission wavelength may be used.

A substance used for dispersing the light-emitting substance is, for example, an anthracene derivative such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA) or 4,4′-bis. In addition to carbazole derivatives such as (N-carbazolyl) biphenyl (abbreviation: CBP), bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2-hydroxyphenyl) benzoxa Zolato] metal complexes such as zinc (abbreviation: ZnBOX) can be used. However, substances used for bringing the light-emitting substance into a dispersed state are not limited to these materials. When the light-emitting substance is dispersed as described above, it is possible to prevent light emitted from the light-emitting substance from being quenched due to the concentration.

In order to cause white light emission to appear from such a light emitting layer 123, for example, TPD (aromatic diamine) and 3- (4-tert-butylphenyl) -4-phenyl are sequentially formed from the first electrode 101. 5- (4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), tris (8-quinolinolato) aluminum (abbreviation: _Alq 3), _Alq 3 doped with Nile red that is a red light emitting pigment, Alq _The structure which laminated | stacked ₃ by the vapor deposition method etc. can be used.

In addition, in order from the first electrode 101 side, NPB, NPB doped with perylene, bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), BAlq doped with DCM1 A structure in which Alq ₃ is laminated by vapor deposition or the like can be used.

Poly (N-vinylcarbazole) containing 30 wt% 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD) as an electron transporting agent (Abbreviation: PVK) and white light emission can be obtained by dispersing an appropriate amount of four kinds of dyes (TPB, coumarin 6, DCM1, Nile red).

In addition, by forming the light emitting layer 123 as a laminate and forming the first and second light emitting materials with materials that emit light having complementary colors such as red and blue-green, white light emission can be obtained. .

When light is emitted in such a white system, full color display can be performed using a color filter or a color conversion layer. In addition, when a color filter or a color conversion layer is a single color, monocolor display can be performed.

Note that in addition to the light-emitting element that can obtain white light emission, a material for the light-emitting layer 123 can be selected as appropriate. For example, the light emitting layer 123 may be made of red (R), green (G), and blue (B) light emitting materials.

For example, when red light emission is desired, 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl]-is added to the light-emitting layer 123. 4H-pyran (abbreviation: DCJTI), 4-dicyanomethylene-2-methyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJT), 4-dicyanomethylene-2-tert-butyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJTB) and perifuranthene 2,5-dicyano-1,4-bis [2- (10-methoxy-1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] benzene, bis [2,3-bis (4 -F Orofeniru) Kinokisarinaito] iridium (acetylacetonate) (abbreviation: Ir _[Fdpq] 2 acac), or the like can be used. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 600 nm to 700 nm can be used.

To obtain green light emission, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), or the like is used for the light-emitting layer 123. be able to. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 500 nm to 600 nm can be used.

In order to obtain blue light emission, 9,10-bis (2-naphthyl) -tert-butylanthracene (abbreviation: t-BuDNA), 9,9′-bianthryl, 9,10− Diphenylanthracene (abbreviation: DPA), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-gallium (abbreviation: BGaq), bis (2-Methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq) or the like can be used. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 400 nm to 500 nm can be used.

Thus, even when the light emitting layer 123 is formed so as to have red (R), green (G), and blue (B) light emitting materials, a color filter or a color conversion layer is provided, The peak or the like may be adjusted. The color filter and the color conversion layer may be formed on the side where light emission is extracted to the outside, and can be provided on either the substrate side on which the thin film transistor is formed or the substrate side opposite to the substrate side.

Next, the electron transport layer 124 will be described. The electron transport layer 124 is a layer having a function of transporting electrons injected from the second electrode 102 to the light emitting layer 123. In this manner, by providing the electron transport layer 124 and separating the second electrode 102 and the light-emitting layer 123, it is possible to prevent the light emission from being quenched due to the metal.

Note that there is no particular limitation on the electron-transporting layer 124, and tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (5-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), metal complexes having a quinoline skeleton or a benzoquinoline skeleton, etc. Can be used. In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn (BTZ) ) ₂ ) and the like may be formed by a metal complex having an oxazole-based or thiazole-based ligand. In addition, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert- Butylphenyl) -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), or the like.

The electron transport layer 124 is preferably formed using a substance having a higher electron mobility than a hole mobility. The electron transport layer 124 is more preferably formed using a substance having an electron mobility of 10 ⁻⁶ cm ² / Vs or higher. Further, the electron transport layer 124 may be a layer having a multilayer structure formed by combining two or more layers made of the substances described above.

Furthermore, it is preferable to use a layer in which the organic compound and the inorganic compound are mixed in the electron transport layer 124. By mixing with an inorganic compound, crystallization of the organic compound can be further suppressed, and the layer can be formed thick without increasing resistance. Therefore, even when the substrate has unevenness due to dust, dirt, etc., the electron transport layer 124 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

As such an inorganic compound, a metal oxide, a metal nitride, or a metal oxynitride can be used. Examples of the metal oxide include lithium oxide (Li ₂ O), calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), and magnesium oxide (MgO). Other examples include lithium fluoride (LiF), cesium fluoride (CsF), and calcium fluoride (CaF ₂ ).

Such a second layer 112 can be manufactured by an evaporation method. Note that a co-evaporation method can be used when a mixed layer is formed among the layers included in the second layer 112. The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

Next, the third layer 113 which is a layer for generating electrons will be described. Examples of such a third layer 113 include a layer containing an electron transporting substance and a substance that exhibits an electron donating property with respect to the substance.

Note that an electron-transporting substance is a substance having a higher electron-transporting property than holes. For example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum ( Abbreviations: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), Bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ), etc. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole ( Abbreviation: PBD), 1,3-bis [5- (p-tert-butylphenyl) -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-methyl- Benzoxazol-2-yl) stilbene (abbreviation: BzOS) or the like can be used. The third layer 113 can be formed using an n-type semiconductor. However, the electron transporting substance is not limited to these.

In addition, the substance that exhibits an electron donating property with respect to the electron transporting substance is a substance selected from alkali metals and alkaline earth metals, specifically lithium (Li), calcium (Ca), and sodium (Na). , Potassium (K), magnesium (Mg), or the like can be used. Specific examples of the material include alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, and the like. Specifically, lithium oxide (Li ₂ O ), Calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), lithium fluoride (LiF), cesium fluoride (CsF) ), Calcium fluoride (CaF ₂ ), and the like. However, the substance that exhibits an electron donating property with respect to the electron transporting substance is not limited thereto. A substance that exhibits an electron donating property with respect to an electron transporting substance has a molar ratio of 0.5 to 2 with respect to the electron transporting substance (= a substance that exhibits an electron donating property with respect to an electron transporting substance / It is preferably contained so as to be an electron transporting substance).

The third layer 113 may be a layer made of a substance such as zinc oxide, zinc sulfide, zinc selenide, tin oxide, or titanium oxide.

The third layer 113 is preferably formed from a layer in which the organic compound as described above and an inorganic compound are mixed. As a result, the conductivity of the third layer 113 can be increased. When the conductivity is high, the third layer 113 can be made thicker and the production yield can be improved. Further, by increasing the thickness of the third layer, the light emitting layer 123 and the second electrode 102 can be separated from each other, and quenching of light emission can be prevented.

Further, by using a layer in which an organic compound and an inorganic compound are mixed, crystallization of the organic compound used for the third layer 113 can be suppressed, and the third layer 113 is formed thick without increasing resistance. It becomes possible to do. Therefore, even if there is unevenness due to dust or dirt on the substrate, the third layer 113 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

Such a third layer 113 can be manufactured by an evaporation method. When a mixed layer is formed as the third layer 113, a co-evaporation method can be used. The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

In the light-emitting element as described above, the electron affinity of the electron transporting substance contained in the third layer 113 and the substance contained in the layer in contact with the third layer 113 among the layers contained in the second layer 112. The difference from the electron affinity is preferably 2 eV or less, more preferably 1.5 eV or less. In addition, when the third layer 113 is formed of an n-type semiconductor, the work function of the n-type semiconductor and electrons of a substance included in a layer in contact with the third layer 113 among the layers included in the second layer 112. The difference from the affinity is preferably 2 eV or less, more preferably 1.5 eV or less. In this manner, by bonding the second layer 112 and the third layer 113, injection of electrons from the third layer 113 to the second layer 112 is facilitated.

Note that the present invention is characterized by a light-emitting element having an organic compound (typically a benzidine derivative) having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and an inorganic compound between a pair of electrodes. Thus, the present invention is not limited to the light emitting element configuration shown in FIG. For example, although the structure in which the electron transport layer 124 formed in contact with the third layer 113 is shown, the electron transport layer 124 may not be provided. Then, the light emitting layer 123 is in contact with the third layer 113. In this case, the light-emitting layer 123 may be formed using a substance for dispersing the light-emitting substance. Similarly, the hole transport layer 122 may not be provided.

Further, a substance that can emit light without being dispersed, such as Alq ₃ , can be used for the light-emitting layer 123. Since Alq ₃ or the like is a light-emitting substance with good carrier transportability, a layer made of only Alq ₃ can function as a light-emitting layer without being dispersed. In this case, the light emitting layer 123 corresponds to the light emitting substance itself.

The first layer 111 to the third layer 113 can be formed by the same method. Therefore, it can be formed continuously without being released to the atmosphere. In this way, by continuously forming the first layer 111 to the third layer 113 without releasing to the atmosphere, it is possible to reduce impurity contamination at the interface or the like.

Next, the electrode will be described. The first electrode 101 and the second electrode 102 are formed using a conductive material. In addition, the electrode provided on the side from which light from the light emitting layer is extracted needs to have a light transmitting property in addition to the conductivity. In addition, in order to have translucency, it can also obtain by forming the non-translucent material very thinly.

The material of the first electrode 101 is translucency such as indium tin oxide (ITO), indium tin oxide containing silicon oxide (hereinafter referred to as ITSO), indium oxide containing zinc oxide, in addition to aluminum (Al). In addition to materials, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), or A metal material such as palladium (Pd) can be used. Note that the first electrode 101 can be formed using, for example, a sputtering method, an evaporation method, or the like. However, the material of the first electrode 101 is not limited to these.

In the case where the above material having non-light-transmitting property is used and the first electrode 101 needs to have light-transmitting property, the material may be thinly formed.

For the first electrode 101, a single layer or a stacked layer of the above metal materials can be used. Therefore, when a stacked layer is used for the first electrode 101, a structure in which the above material is formed thin and a light-transmitting material is stacked thereover can be used. Needless to say, the first electrode 101 may be formed using the thin material as a single layer. In order to prevent the resistance from increasing by forming the first electrode 101 thin, an auxiliary wiring can be provided. In addition, the use of lamination can prevent high resistance.

The material of the second electrode 102 is gold (Au) in addition to a light-transmitting material such as indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), and indium oxide containing zinc oxide. Metal materials such as platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), or palladium (Pd) Can be used. However, the material of the second electrode 102 is not limited to these.

In the case where the above-described material having non-light-transmitting property is used and the second electrode 102 needs to have light-transmitting property, the material may be formed thin.

The second electrode 102 can be a single layer or a stacked layer of the above metal materials. Therefore, when a stacked layer is used for the second electrode 102, a structure in which the above material is formed thin and a light-transmitting material is stacked thereover can be used. Needless to say, the second electrode 102 may be formed using the thin material described above in a single layer. In order to prevent the resistance from increasing by forming the second electrode 102 thin, an auxiliary wiring can be provided. In addition, the use of lamination can prevent high resistance.

Note that the first electrode 101 or the second electrode 102 can be an anode or a cathode depending on a voltage applied to the light-emitting element, respectively. In the case of an anode, a material having a high work function (work function of 4.0 eV or more) is used. In the case of a cathode, a material having a small work function (work function of 3.8 eV or less) is used.

The first electrode 101 or the second electrode 102 can be formed by a sputtering method, an evaporation method, or the like. Note that in the case of using the vapor deposition method, the first electrode 101, the first layer 111 to the third layer 113, and the second electrode 102 can be continuously formed without being released to the atmosphere. . Thus, by continuously forming the light emitting elements without releasing to the atmosphere, it is possible to reduce the contamination of impurities at the interface and the like.

As described above, in the present invention, holes are formed using a layer having an organic compound (typically a benzidine derivative) having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and an inorganic compound. By forming the generated layer, it is possible to obtain a light-emitting element with little change in element characteristics due to change in characteristics of the hole transport layer due to heat.

In addition, a layer that generates holes is formed using a layer including an organic compound (typically a benzidine derivative) having an glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and an inorganic compound. Thus, a light-emitting element with little deterioration due to crystallization of the layer can be obtained.

As a result, a light-emitting element that achieves a low driving voltage can be obtained. In addition, even when the light emitting element of the present invention is thickened, the driving voltage is not improved. As a result, the light-emitting element can be formed thick, so that it can be produced with high yield. Further, by increasing the thickness of the layer, the light emitting layer and the first electrode or the light emitting layer and the second electrode can be separated from each other, so that quenching of light emission can be prevented.

As described above, in this embodiment, the organic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower has been described using a benzidine derivative. The light-emitting element is characterized by having a mixed layer and is not limited to this embodiment mode as long as the effect of reducing deterioration with time is obtained.

(Embodiment 2)
A mode of a light-emitting element using a layer having a spiro ring and a benzidine derivative of the present invention which is a compound having a triphenylamine skeleton and an inorganic compound is described with reference to FIGS.

As shown in FIG. 18, the light-emitting element of the present invention has a first electrode 101 and a second electrode 102 facing each other, and in order from the first electrode 101, a first layer 111, a second layer 112, A third layer 113 is stacked. In such a light-emitting element, when a voltage is applied so that the potential of the first electrode 101 is higher than the potential of the second electrode 102, holes are injected from the first layer 111 to the second layer 112. Electrons are injected from the third layer 113 to the second layer 112. Holes and electrons recombine in the second layer 112, bringing the light-emitting substance into an excited state. The excited luminescent material emits light when returning to the ground state.

Next, the first layer 111 to the third layer 113, the first electrode 101, and the second electrode 102 will be described.

The first layer 111 is a layer that generates holes. In order to exhibit such a function, it can be achieved, for example, by a layer containing a hole transporting substance and a substance showing an electron accepting property for the substance. In addition, a substance having an electron accepting property with respect to a hole transporting substance has a molar ratio of 0.5 to 2 with respect to the hole transporting substance (= electron accepting property with respect to the hole transporting substance). (Substance / hole transporting substance).

The hole-transporting substance is a substance that has a higher hole-transporting property than electrons. For example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: α- NPD), 4,4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) tri Phenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4′-bis [N Aromatic amine compounds such as-{4- (N, N-di-m-tolylamino) phenyl} -N-phenylamino] biphenyl (abbreviation: DNTPD), phthalocyanine (abbreviation: H ₂ Pc), copper phthalocyanine (abbreviation) : CuPc), Bana An organic compound such as a phthalocyanine compound such as zirphthalocyanine (abbreviation: VOPc) can be used. Note that the hole transporting substance is not limited to these.

In addition, as the substance that exhibits an electron accepting property with respect to the hole transporting substance, any transition metal oxide of Groups 4 to 12 of the periodic table can be used. Among them, transition metal oxides of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, and in particular vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are suitable. Even if it is not an oxide, you may use the said metal nitride and oxynitride. Note that a substance that exhibits an electron accepting property with respect to a hole transporting substance is not limited thereto.

When the first layer 111 is formed of a layer in which a hole transporting material made of an organic compound and a material having an electron accepting property with respect to the hole transporting material made of the inorganic compound are mixed, the first layer 111 has high conductivity. It is preferable. When the conductivity is high, the first layer 111 can be made thicker and the production yield can be improved. Further, by increasing the thickness of the first layer 111, the first electrode 101 and the second layer 112 can be separated. As a result, it is possible to prevent the light emission from being quenched due to the metal.

By using a layer in which such an organic compound and an inorganic compound are mixed, crystallization of the organic compound used for the first layer 111 can be suppressed, and the first layer 111 is not accompanied by an increase in resistance. Can be formed thick. Therefore, even when there is unevenness due to dust or dirt on the substrate, the first layer 111 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

Further, as shown in the following examples, it was found that when a layer in which a benzidine derivative and a molybdenum oxide that is an inorganic compound are mixed is used for the first layer 111, deterioration with time is difficult. That is, this structure can provide a light-emitting element with excellent stability.

Note that the first layer 111 may contain another organic compound. Other organic compounds include rubrene and the like. Reliability can be improved by adding rubrene.

In addition, the first layer 111 may be a layer made of a metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, cobalt oxide, or copper oxide.

Such a first layer 111 can be formed by an evaporation method. When forming a layer in which a plurality of compounds are mixed as the first layer 111, a co-evaporation method can be used. The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

Next, the second layer 112 which is a layer including a light emitting layer will be described. The layer including the light emitting layer may be a single layer or a multilayer composed of only the light emitting layer. As a specific multilayer, it includes a plurality of layers selected from any of an electron transport layer and a hole transport layer in addition to a light emitting layer.
In FIG. 18, the second layer 112 is a multilayer including the light-emitting layer 123, the electron transport layer 124, and the hole transport layer 122.

For the hole transport layer 122, the benzidine derivative of the present invention represented by the general formula (1) or any one of the structural formulas (2) to (4) can be used.

Since the benzidine derivative of the present invention has high heat resistance, by using the benzidine derivative of the present invention as a hole transport material, it is possible to form the hole transport layer 122 with little characteristic change due to heat. Further, since the benzidine derivative of the present invention is difficult to crystallize, the hole transport layer 122 that is difficult to crystallize can be formed by using the benzidine derivative of the present invention as a hole transport material.

The hole transport layer 122 is a multilayer formed by combining two or more layers made of the benzidine derivative of the present invention represented by the general formula (1) or any one of the structural formulas (2) to (4). May be.

Furthermore, a layer in which the benzidine derivative of the present invention and an inorganic compound are mixed is preferably used for the hole transport layer 122. By mixing with an inorganic compound, crystallization of the benzidine derivative can be further suppressed, and the layer can be formed thick without increasing resistance. Therefore, even when the substrate has unevenness due to dust or dirt, it is hardly affected by the unevenness due to the thick film of the hole transport layer having a benzidine derivative. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

As such an inorganic compound, a metal oxide, a metal nitride, or a metal oxynitride can be used. For example, as the metal oxide, any transition metal oxide of Groups 4 to 12 of the periodic table can be used. Among them, transition metal oxides of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, and in particular vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are suitable.

Next, the light emitting layer 123 will be described. The light-emitting layer 123 is preferably a layer in which a light-emitting substance is dispersed and included in a substance having an energy gap larger than that of the light-emitting substance. However, the light emitting layer is not limited to this. Note that the energy gap is an energy gap between the LUMO level and the HOMO level. As the light-emitting substance, a substance that has favorable emission efficiency and can emit light with a desired emission wavelength may be used.

A substance used for dispersing the light-emitting substance is, for example, an anthracene derivative such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA) or 4,4′-bis. In addition to carbazole derivatives such as (N-carbazolyl) biphenyl (abbreviation: CBP), bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2-hydroxyphenyl) benzoxa Zolato] metal complexes such as zinc (abbreviation: ZnBOX) can be used. However, substances used for bringing the light-emitting substance into a dispersed state are not limited to these materials. When the light-emitting substance is dispersed as described above, it is possible to prevent light emitted from the light-emitting substance from being quenched due to the concentration.

In order to cause white light emission to appear from such a light emitting layer 123, for example, TPD (aromatic diamine) and 3- (4-tert-butylphenyl) -4-phenyl are sequentially formed from the first electrode 101. 5- (4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), tris (8-quinolinolato) aluminum (abbreviation: _Alq 3), _Alq 3 doped with Nile red that is a red light emitting pigment, Alq _The structure which laminated | stacked ₃ by the vapor deposition method etc. can be used.

In addition, in order from the first electrode 101 side, NPB, NPB doped with perylene, bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), BAlq doped with DCM1 A structure in which Alq ₃ is laminated by vapor deposition or the like can be used.

Poly (N-vinylcarbazole) containing 30 wt% 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD) as an electron transporting agent (Abbreviation: PVK) and white light emission can be obtained by dispersing an appropriate amount of four kinds of dyes (TPB, coumarin 6, DCM1, Nile red).

In addition, by forming the light emitting layer 123 as a laminate and forming the first and second light emitting materials with materials that emit light having complementary colors such as red and blue-green, white light emission can be obtained. .

When light is emitted in such a white system, full color display can be performed using a color filter or a color conversion layer. In addition, when a color filter or a color conversion layer is a single color, monocolor display can be performed.

In addition to the light-emitting element that can emit white light as described above, the material of the light-emitting layer 123 can be selected as appropriate. For example, the light emitting layer 123 may be made of red (R), green (G), and blue (B) light emitting materials.

For example, when red light emission is desired, 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl]-is added to the light-emitting layer 123. 4H-pyran (abbreviation: DCJTI), 4-dicyanomethylene-2-methyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJT), 4-dicyanomethylene-2-tert-butyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -4H-pyran (abbreviation: DCJTB) and perifuranthene 2,5-dicyano-1,4-bis [2- (10-methoxy-1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] benzene, bis [2,3-bis (4 -F Orofeniru) Kinokisarinaito] iridium (acetylacetonate) (abbreviation: Ir _[Fdpq] 2 acac), or the like can be used. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 600 nm to 700 nm can be used.

To obtain green light emission, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), or the like is used for the light-emitting layer 123. be able to. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 500 nm to 600 nm can be used.

In order to obtain blue light emission, 9,10-bis (2-naphthyl) -tert-butylanthracene (abbreviation: t-BuDNA), 9,9′-bianthryl, 9,10− Diphenylanthracene (abbreviation: DPA), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-gallium (abbreviation: BGaq), bis (2-Methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq) or the like can be used. However, the present invention is not limited to these materials, and a substance exhibiting light emission having an emission spectrum peak from 400 nm to 500 nm can be used.

Thus, even when the light emitting layer 123 is formed so as to have red (R), green (G), and blue (B) light emitting materials, a color filter or a color conversion layer is provided, The peak or the like may be adjusted. The color filter and the color conversion layer may be formed on the side where light emission is extracted to the outside, and can be provided on either the substrate side on which the thin film transistor is formed or the substrate side opposite to the substrate side.

Next, the electron transport layer 124 will be described. The electron transport layer 124 is a layer having a function of transporting electrons injected from the second electrode 102 to the light emitting layer 123. In this manner, by providing the electron transport layer 124 and separating the second electrode 102 and the light-emitting layer 123, it is possible to prevent the light emission from being quenched due to the metal.

Note that there is no particular limitation on the electron-transporting layer 124, and tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (5-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), metal complexes having a quinoline skeleton or a benzoquinoline skeleton, etc. Can be used. In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn (BTZ) ) ₂ ) and the like may be formed by a metal complex having an oxazole-based or thiazole-based ligand. In addition, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert- Butylphenyl) -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), or the like.

The electron transport layer 124 is preferably formed using a substance having a higher electron mobility than a hole mobility. The electron transport layer 124 is more preferably formed using a substance having an electron mobility of 10 ⁻⁶ cm ² / Vs or higher. Further, the electron transport layer 124 may be a layer having a multilayer structure formed by combining two or more layers made of the substances described above.

Furthermore, it is preferable to use a layer in which the organic compound and the inorganic compound are mixed in the electron transport layer 124. By mixing with an inorganic compound, crystallization of the organic compound can be further suppressed, and the layer can be formed thick without increasing resistance. Therefore, even when the substrate has unevenness due to dust, dirt, etc., the electron transport layer 124 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

As such an inorganic compound, a metal oxide, a metal nitride, or a metal oxynitride can be used. Examples of the metal oxide include lithium oxide (Li ₂ O), calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), and magnesium oxide (MgO). Other examples include lithium fluoride (LiF), cesium fluoride (CsF), and calcium fluoride (CaF ₂ ).

Such a second layer 112 can be manufactured by an evaporation method. Note that a co-evaporation method can be used when a mixed layer is formed among the layers included in the second layer 112.
The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

Next, the third layer 113 which is a layer for generating electrons will be described. Examples of such a third layer 113 include a layer containing an electron transporting substance and a substance that exhibits an electron donating property with respect to the substance.

Note that an electron-transporting substance is a substance having a higher electron-transporting property than holes. For example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum ( Abbreviations: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), Bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ), etc. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole ( Abbreviation: PBD), 1,3-bis [5- (p-tert-butylphenyl) -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-methyl- Benzoxazol-2-yl) stilbene (abbreviation: BzOS) or the like can be used. The third layer 113 can be formed using an n-type semiconductor. However, the electron transporting substance is not limited to these.

In addition, the substance that exhibits an electron donating property with respect to the electron transporting substance is a substance selected from alkali metals and alkaline earth metals, specifically lithium (Li), calcium (Ca), and sodium (Na). , Potassium (K), magnesium (Mg), or the like can be used. Specific examples of the material include alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, and the like. Specifically, lithium oxide (Li ₂ O ), Calcium oxide (CaO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), lithium fluoride (LiF), cesium fluoride (CsF) ), Calcium fluoride (CaF ₂ ), and the like. However, the substance that exhibits an electron donating property with respect to the electron transporting substance is not limited thereto. A substance that exhibits an electron donating property with respect to an electron transporting substance has a molar ratio of 0.5 to 2 with respect to the electron transporting substance (= a substance that exhibits an electron donating property with respect to an electron transporting substance / It is preferably contained so as to be an electron transporting substance).

The third layer 113 may be a layer made of a substance such as zinc oxide, zinc sulfide, zinc selenide, tin oxide, or titanium oxide.

The third layer 113 is preferably formed from a layer in which the organic compound as described above and an inorganic compound are mixed. As a result, the conductivity of the third layer 113 can be increased. When the conductivity is high, the third layer 113 can be made thicker and the production yield can be improved. Further, by increasing the thickness of the third layer, the light emitting layer 123 and the second electrode 102 can be separated from each other, and quenching of light emission can be prevented.

Further, by using a layer in which an organic compound and an inorganic compound are mixed, crystallization of the organic compound used for the third layer 133 can be suppressed, and the third layer 113 is formed thick without increasing resistance. It becomes possible to do. Therefore, even if there is unevenness due to dust or dirt on the substrate, the third layer 113 is hardly affected by the unevenness due to the thick film. Therefore, defects such as a short circuit between the first electrode 101 and the second electrode 102 due to unevenness can be prevented.

Such a third layer 113 can be manufactured by an evaporation method. When a mixed layer is formed as the third layer 113, a co-evaporation method can be used. The co-evaporation method includes co-evaporation method by resistance heating evaporation, co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, other film formation by resistance heating evaporation and sputtering method, electron beam It can be formed by combining the same type and different types of methods such as vapor deposition and sputtering. Moreover, although the said example has shown the layer containing 2 types of materials, it is as above-mentioned that it can form combining the same kind and different method similarly when it contains 3 or more types of materials.

In the light-emitting element as described above, the electron affinity of the electron transporting substance contained in the third layer 113 and the substance contained in the layer in contact with the third layer 113 among the layers contained in the second layer 112. The difference from the electron affinity is preferably 2 eV or less, more preferably 1.5 eV or less. In addition, when the third layer 113 is formed of an n-type semiconductor, the work function of the n-type semiconductor and electrons of a substance included in a layer in contact with the third layer 113 among the layers included in the second layer 112. The difference from the affinity is preferably 2 eV or less, more preferably 1.5 eV or less. In this manner, by bonding the second layer 112 and the third layer 113, injection of electrons from the third layer 113 to the second layer 112 is facilitated.

Note that the present invention is characterized by a light-emitting element having an organic compound typified by a benzidine derivative and an inorganic compound between a pair of electrodes, and is not limited to the structure of the light-emitting element shown in FIG. For example, although the structure in which the electron transport layer 124 formed in contact with the third layer 113 is shown, the electron transport layer 124 may not be provided. Then, the light emitting layer 123 is in contact with the third layer 113. In this case, the light-emitting layer 123 may be formed using a substance for dispersing the light-emitting substance. Similarly, the hole transport layer 122 may not be provided.

Further, a substance that can emit light without being dispersed, such as Alq ₃ , can be used for the light-emitting layer 123. Since Alq ₃ or the like is a light-emitting substance with good carrier transportability, a layer made of only Alq ₃ can function as a light-emitting layer without being dispersed. In this case, the light emitting layer 123 corresponds to the light emitting substance itself.

The first layer 111 to the third layer 113 can be formed by the same method. Therefore, it can be formed continuously without being released to the atmosphere. In this way, by continuously forming the first layer 111 to the third layer 113 without releasing to the atmosphere, it is possible to reduce impurity contamination at the interface or the like.

Next, the electrode will be described. The first electrode 101 and the second electrode 102 are formed using a conductive material. In addition, the electrode provided on the side from which light from the light emitting layer is extracted needs to have a light transmitting property in addition to the conductivity. In addition, in order to have translucency, it can also obtain by forming the non-translucent material very thinly.

In addition to aluminum (Al), the first electrode 101 is made of a light-transmitting material such as indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), and indium oxide containing zinc oxide. , Gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), or 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. However, the material of the first electrode 101 is not limited to these.

In the case where the above material having non-light-transmitting property is used and the first electrode 101 needs to have light-transmitting property, the material may be thinly formed.

For the first electrode 101, a single layer or a stacked layer of the above metal materials can be used. Therefore, when a stacked layer is used for the first electrode 101, a structure in which the above material is formed thin and a light-transmitting material is stacked thereover can be used. Needless to say, the first electrode 101 may be formed using the thin material as a single layer. In order to prevent the resistance from increasing by forming the first electrode 101 thin, an auxiliary wiring can be provided. In addition, the use of lamination can prevent high resistance.

In addition, the material of the second electrode 102 is light-transmitting material such as indium tin oxide (ITO), indium tin oxide containing silicon oxide (hereinafter also referred to as ITSO), indium oxide containing zinc oxide, Gold (Au), Platinum (Pt), Nickel (Ni), Tungsten (W), Chromium (Cr), Molybdenum (Mo), Iron (Fe), Cobalt (Co), Copper (Cu), or Palladium (Pd) A metal material such as can be used. However, the material of the second electrode 102 is not limited to these.

In the case where the above-described material having non-light-transmitting property is used and the second electrode 102 needs to have light-transmitting property, the material may be formed thin.

The second electrode 102 can be a single layer or a stacked layer of the above metal materials. Therefore, when a stacked layer is used for the second electrode 102, a structure in which the above material is formed thin and a light-transmitting material is stacked thereover can be used. Needless to say, the second electrode 102 may be formed using the thin material described above in a single layer. In order to prevent the resistance from increasing by forming the second electrode 102 thin, an auxiliary wiring can be provided. In addition, the use of lamination can prevent high resistance.

Note that the first electrode 101 or the second electrode 102 can be an anode or a cathode depending on a voltage applied to the light-emitting element, respectively. In the case of an anode, a material having a high work function (work function of 4.0 eV or more) is used. In the case of a cathode, a material having a small work function (work function of 3.8 eV or less) is used.

The first electrode 101 or the second electrode 102 can be formed by a sputtering method, an evaporation method, or the like. Note that in the case of using the vapor deposition method, the first electrode 101, the first layer 111 to the third layer 113, and the second electrode 102 can be continuously formed without being released to the atmosphere. . Thus, by continuously forming the light emitting elements without releasing to the atmosphere, it is possible to reduce the contamination of impurities at the interface and the like.

As described above, the present invention changes the characteristics of the hole transport layer due to heat by forming a layer that generates holes using a layer having an organic compound typified by a benzidine derivative and an inorganic compound. Thus, a light-emitting element with little change in element characteristics due to the above can be obtained.
In addition, by forming a layer that generates holes using a layer including an organic compound typified by the benzidine derivative of the present invention and an inorganic compound, a light-emitting element that is less deteriorated due to crystallization of the layer is obtained. Obtainable.

As a result, a light-emitting element that achieves a low driving voltage can be obtained. In addition, even when the light emitting element of the present invention is thickened, the driving voltage is not improved. As a result, the light-emitting element can be formed thick, so that it can be produced with high yield. Further, by increasing the thickness of the layer, the light emitting layer and the first electrode or the light emitting layer and the second electrode can be separated from each other, so that quenching of light emission can be prevented.

(Embodiment 3)
In this embodiment, a structure of a light-emitting element which is different from that in the above embodiment will be described.

As illustrated in FIG. 2, the light-emitting element described in this embodiment includes a first electrode 101 and a second electrode 102 that are opposed to each other, and the first layer 111 and the second electrode 102 are sequentially formed from the first electrode 101. The layer 112, the third layer 113, and the fourth layer 128 are stacked, and the fourth layer 128 is provided. The fourth layer 128 can be formed using a material similar to that of the first layer 111, and the other structures are the same as those in the above embodiment; thus, description thereof is omitted.

When the fourth layer 128 is provided in this manner, damage when forming the second electrode 102 can be further reduced.

The fourth layer 128 is preferably a layer in which an organic compound and an inorganic compound are mixed. As such an inorganic compound, a metal oxide, a metal nitride, or a metal oxynitride can be used. For example, as the metal oxide, any transition metal oxide of Groups 4 to 12 of the periodic table can be used. Among them, transition metal oxides of any of Groups 4 to 8 of the periodic table are often highly electron-accepting, and in particular vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, Ruthenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide are suitable.

Thus, when an organic compound and an inorganic compound are mixed, a low driving voltage can be maintained even when the fourth layer 128 is thickened.

(Embodiment 4)
In this embodiment mode, a typical example is an organic compound having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower. A general formula is used for a benzidine derivative having a spiro ring and a triphenylamine skeleton. explain.

One aspect of the present invention is a benzidine derivative represented by the general formula (1).

一般式（１）において、Ｒ^１は、水素または炭素数１〜４のアルキル基のいずれか一を表す。

In General Formula (1), R ¹ represents any one of hydrogen or an alkyl group having 1 to 4 carbon atoms.

The benzidine derivative of the present invention includes N, N′-diphenylbenzidine and 2-bromo-spiro-9,9′-bifluorene or 2-bromo-2 ′, 7′-dialkyl-spiro-9,9′-bifluorene. It is a compound obtained by coupling reaction.

The benzidine derivative of the present invention is a light-emitting element having a layer containing an organic compound obtained by a coupling reaction of N, N′-diphenylbenzidine and 2-bromo-spiro-9,9′-bifluorene. .

The benzidine derivative of the present invention has a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower. Further, the melting point satisfies 180 ° C. or more and 400 ° C. or less.

Since the benzidine derivative of the present invention has good heat resistance, the use of the benzidine derivative of the present invention makes it possible to obtain a light-emitting element with little characteristic change due to heat. Further, since the benzidine derivative of the present invention is easily maintained in an amorphous state, a light-emitting element with little deterioration due to crystallization can be obtained by using the benzidine derivative of the present invention.

(Embodiment 5)
In this embodiment, an organic compound typified by a benzidine derivative having a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower and having a spiro ring and a triphenylamine skeleton is represented by Structural Formulas (2) to A description will be given using (5).

The benzidine derivatives represented by structural formulas (2) to (5) have a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and have good heat resistance. Moreover, the benzidine derivatives represented by structural formulas (2) to (5) are difficult to crystallize. Furthermore, the melting points of the benzidine derivatives represented by the structural formulas (2) to (5) are as high as 180 ° C. or higher and 400 ° C. or lower.

The method for synthesizing the benzidine derivative of the present invention is not particularly limited. As shown in the synthesis scheme (a-1), N, N′-diphenylbenzidine and 2-bromo-spiro-9,9 ′ are used. It can be synthesized by a coupling reaction with bifluorene or 2-bromo-2 ′, 7′-dialkyl-spiro-9,9′-bifluorene.

In Synthesis Scheme (a-1), R ¹⁰ represents hydrogen or an alkyl group having 1 to 4 carbon atoms. Here, the alkyl group having 3 or 4 carbon atoms is preferably branched.

The benzidine derivative of the present invention described above can be used as a material for forming a hole transport layer, that is, a hole transport material.

The benzidine derivative of the present invention has a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower. Further, the melting point satisfies 180 ° C. or more and 400 ° C. or less.

Since the benzidine derivative of the present invention has good heat resistance, the use of the benzidine derivative of the present invention makes it possible to obtain a light-emitting element with little characteristic change due to heat. Further, since the benzidine derivative of the present invention is easily maintained in an amorphous state, a light-emitting element with little deterioration due to crystallization can be obtained by using the benzidine derivative of the present invention.

(Embodiment 6)
The light-emitting element of the present invention can be applied to a pixel portion of a light-emitting device having a display function or an illumination portion of a light-emitting device having an illumination function. Since the light-emitting element of the present invention has little deterioration due to characteristic change or crystallization due to heat, light emission with less defects of images and illumination light due to deterioration of the light-emitting element is achieved by using the light-emitting element of the present invention. A device can be obtained. Thus, in this embodiment, a cross-sectional structure of a pixel portion having a light-emitting element is described.

FIG. 3 is a cross-sectional view using a p-type thin film transistor (TFT) as a semiconductor element that controls supply of current to the light-emitting element. The first electrode of the light-emitting element functions as an anode, and the second electrode An example of a case in which functions as a cathode is illustrated.

FIG. 3A is a cross-sectional view of a pixel in the case where the TFT 601 is p-type and light emitted from the light-emitting element 603 is extracted from the first electrode 101 side (in the direction of the dotted arrow). In FIG. 3A, a TFT 601 provided over a substrate 600 is connected to a semiconductor film, a gate electrode provided through a gate insulating film over the semiconductor film, and an impurity region formed in the semiconductor film. Wiring. A wiring included in the TFT 601 is electrically connected to the first electrode 101 of the light-emitting element 603.

The TFT 601 is covered with an interlayer insulating film 608, and a partition wall 609 having an opening is formed over the interlayer insulating film 608. A part of the first electrode 101 is exposed in the opening of the partition wall 609. In the opening, the first electrode 101, the electroluminescent layer 605, and the second electrode 102 are sequentially stacked. Note that the electroluminescent layer 605 in this embodiment refers to the first layer 111 to the third layer 113 in addition to the fourth layer 128 in the above embodiment. That is, the electroluminescent layer 605 refers to a layer between the first electrode 101 and the second electrode 102.

The interlayer insulating film 608 is formed using an organic resin film, an inorganic insulating film, or an insulating film including a Si—O—Si bond formed using a siloxane-based material as a starting material (hereinafter referred to as a siloxane-based insulating film). Can do. Note that siloxane has a skeleton structure of a bond of silicon (Si) and oxygen (O). As a substituent, an organic group containing at least hydrogen (for example, an alkyl group or an aromatic hydrocarbon) is used. A fluoro group may be used as a substituent. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used as a substituent. A material called a low dielectric constant material (low-k material) may be used for the interlayer insulating film 608. The interlayer insulating film 608 may be a single layer or a stacked layer.

The partition wall 609 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. For example, acrylic, polyimide, polyamide, or the like can be used for the organic resin film, and silicon oxide, silicon nitride oxide, or the like can be used for the inorganic insulating film. When a photosensitive organic resin film is used for the partition wall 609, the side wall of the opening formed in the organic resin film can be formed to have an inclined surface formed with a continuous curvature. As a result, disconnection of the first electrode 101, the electroluminescent layer 605, and the second electrode 102 can be prevented. The partition wall 609 may be a single layer or a stacked layer. Note that when the light-emitting element of the present invention is used, the thickness of the electroluminescent layer 605 can be increased, so that a short circuit between the first electrode 101 and the second electrode 102 can be prevented.

In FIG. 3A, in order to extract light emitted from the first electrode 101 (in the direction of the dotted arrow), the first electrode 101 is formed using a material that transmits light or a thickness that transmits light. In addition to the light-transmitting material, for example, titanium nitride and aluminum are mainly used in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, and the like. The first electrode 101 can be a stack of a component film, a three-layer structure including a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film. Note that in the case where a material other than a light-transmitting material is used, the first electrode 101 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Further, since the TFT 601 is a p-type thin film transistor, the first electrode 101 is formed using a material suitable for use as an anode.

The second electrode 102 is formed to have a thickness that reflects or shields light or shields light. Further, the second electrode 102 is formed using a material suitable for use as a cathode. That is, it can be formed of a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds of these metals In addition to (calcium fluoride, calcium nitride), rare earth metals such as Yb and Er can be used.

The electroluminescent layer 605 is composed of one or a plurality of layers. In the above embodiment, the boundary between each layer is shown (see FIGS. 1, 2, and 18), but it is not necessarily clear. In some cases, the materials composing each other's layers are partially mixed to make the interface unclear.

In the case of the pixel shown in FIG. 3A, light emitted from the light-emitting element 603 can be extracted from the first electrode 101 side as indicated by a dotted arrow.

Next, FIG. 3B is a cross-sectional view of a pixel in the case where the TFT 601 is p-type and light emitted from the light-emitting element 603 is extracted from the second electrode 102 side (in the direction of the dotted arrow). In FIG. 3B, the structures of the TFT 601, the electroluminescent layer 605, the interlayer insulating film 608, the partition 609, and the like provided over the substrate 600 are the same as those in FIG.

In FIG. 3B, in order to extract light emitted from the second electrode 102 (in the direction of the dotted arrow), the first electrode 101 is formed with a material that reflects or blocks light or a film thickness that blocks light. Further, since the TFT 601 is a p-type thin film transistor, the first electrode 101 is formed using a material suitable for use as an anode. For example, in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., a laminate of titanium nitride and a film containing aluminum as a main component, a titanium nitride film A structure including three layers of a film containing aluminum and aluminum as a main component and a titanium nitride film can be used for the first electrode 101.

The first electrode 101 and the wiring connected to the TFT 601 can be formed from the same material. Therefore, the number of steps for the first electrode 101 can be reduced.

The second electrode 102 is formed using a material that transmits light or a thickness that transmits light. Further, the second electrode 102 is formed using a material suitable for use as a cathode. That is, it can be formed of a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds of these metals In addition to (calcium fluoride, calcium nitride), rare earth metals such as Yb and Er can be used. In the case where such a material that does not transmit light is used for the second electrode 102, the second electrode 102 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Note that other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide to which gallium is added (GZO) can also be used. Alternatively, indium tin oxide containing ITO and silicon oxide (ITSO), or indium oxide containing silicon oxide and zinc oxide (ZnO) may be used.

In the case of the pixel shown in FIG. 3B, light emitted from the light-emitting element 603 can be extracted from the second electrode 102 side as indicated by a dotted arrow.

Next, FIG. 3C is a cross-sectional view of a pixel in the case where the TFT 601 is p-type and light emitted from the light-emitting element 603 is extracted from the first electrode 101 side and the second electrode 102 side (in the direction of the dotted arrow). Indicates.
3C, the structure of the TFT 601, the electroluminescent layer 605, the interlayer insulating film 608, the partition wall 609, and the like provided over the substrate 600 is similar to that in FIG.

In FIG. 3B, light emission is extracted to the first electrode 101 side and the second electrode 102 side (in the direction of the dotted arrow), so that the first electrode 101 and the second electrode 102 reflect or shield light. It is formed with a material or a film thickness to be shielded. That is, the first electrode 101 can be formed in a manner similar to that of the first electrode 101 in FIG. The second electrode 102 can be formed in a manner similar to that of the second electrode 102 in FIG.

In the case of the pixel shown in FIG. 3C, light emitted from the light-emitting element 603 can be extracted from the first electrode 101 side and the second electrode 102 side as indicated by dotted arrows.

Note that the pixel configuration of the present invention is not limited to this. For example, an n-type TFT can be used for a semiconductor element that controls current supplied to the light-emitting element 603. In this case, it is preferable that the first electrode 101 function as a cathode and the second electrode 102 function as an anode.

Further, the connection structure between the first electrode 101 and the wiring included in the TFT 601 is not limited to that shown in FIG. For example, unlike the connection structure illustrated in FIGS. 3A and 3C, the wiring included in the TFT 601 may be formed after the first electrode 101 is formed.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 7)
In this embodiment mode, a pixel circuit used in the light-emitting device is described. An example in which digital gradation display is performed will be described.

FIG. 4A illustrates an example of an equivalent circuit diagram of the pixel 350. The signal line 614, the power supply line 615, the scanning line 616, a light emitting element 603 and a transistor 610 functioning as a TFT at the intersection thereof. 601 and the capacitor 612. The structure described in any of the above embodiments is used for the light-emitting element 603. A video signal is input to the signal line 614 by a signal line driver circuit. The transistor 610 can control supply of the video signal to the gate of the transistor 601 in accordance with a selection signal input to the scan line 616. The transistor 601 is a driving transistor that can control supply of current to the light-emitting element 603 in accordance with the potential of the video signal. The capacitor 612 can hold a voltage between the gate and the source of the transistor 601. Note that although the capacitor 612 is illustrated in FIG. 4A, the capacitor 612 is not necessarily provided when it can be covered by the gate capacitance of the transistor 601 or other parasitic capacitance.

FIG. 4B is an equivalent circuit diagram of a pixel 351 in which a transistor 618 and a scan line 619 are newly provided in the pixel 350 illustrated in FIG. The transistor 618 can make a state in which the gate and the source of the transistor 601 have the same potential and the current does not flow through the light-emitting element 603, so that a subframe can be generated as compared with a period in which a video signal is input to all pixels. The length of the period can be shortened. Further, depending on the driving method, even in the pixel illustrated in FIG. 4A, a state in which no current flows through the light-emitting element 603 can be forcibly formed.

FIG. 4C is an equivalent circuit diagram of a pixel 352 in which a transistor 625 and a wiring 626 are newly provided in the pixel 351 illustrated in FIG. The potential of the gate of the transistor 625 is fixed by the wiring 626. The transistor 601 and the transistor 625 are connected in series between the power supply line 615 and the light emitting element 603. Therefore, in FIG. 4C, the value of the current supplied to the light-emitting element 603 is controlled by the transistor 625, and whether or not the current is supplied to the light-emitting element 603 can be controlled by the transistor 601.

Note that the pixel circuit of the present invention is not limited to the structure shown in this embodiment mode, and analog gradation display can be used in addition to digital gradation display. This embodiment can be freely combined with the above embodiment.

(Embodiment 8)
In this embodiment mode, a structure of a light-emitting device including the light-emitting element is described.

FIG. 5 shows a panel in a state where driving circuits such as the signal line driving circuit 302 and the scanning line driving circuit 303 are provided around the pixel portion 300. Note that a panel refers to a state in which the pixel portion 300, the signal line driver circuit 302, and the scanning line driver circuit 303 are provided over the same substrate, and includes a state in which an FPC (flexible printed circuit) is connected thereto. It is.

The pixel portion 300 includes a plurality of pixels 355, and each pixel is provided with the light-emitting element described above. A semiconductor element (corresponding to the TFT 601 in FIG. 4) for controlling the supply of current to the light emitting element is connected to the light emitting element. A cross section of a pixel including a light emitting element is as described in the above embodiment mode. Further, the pixel 355 may have any of the equivalent circuits described in the above embodiments. Note that the pixel portion of the present invention is not limited to this, and may have a passive structure.

Two scanning line driving circuits are provided via the pixel portion 300. These are referred to as a first scanning line driving circuit 303a and a second scanning line driving circuit 303b. Note that one or three or more scanning line driver circuits may be provided. The first scan line driver circuit 303a and the second scan line driver circuit 303b include circuits that function as shift registers 311a and 311b, level shifters 312a and 312b, and buffers 313a and 313b, respectively. The shift registers 311a and 311b have first and second gate start pulses (G1SP and G2SP), first and second gate clock signals (G1CK and G2CK), and inverted signals (G1CKB and G2CKB) of the clock signals, respectively. ) Etc. are input.

Scan lines (G1... Gn) are connected to the first and second scan line driver circuits 303a and 303b, and supply signals to the respective pixels 355 provided in the pixel portion 300. A semiconductor element (corresponding to the transistor 610 in FIG. 4) for selecting each pixel is connected to the scanning line, and the semiconductor element is selected when a video signal is written to the pixel.

The signal line driver circuit 302 includes circuits that function as a shift register 321, a first latch 322, a second latch 323, a level shifter 324, and a buffer 325. A signal such as a start pulse (SSP) is input to the shift register 321, data (DATA) such as a video signal is input to the first latch 322, and a latch (LAT) signal is input to the second latch 323. The Signal lines (S 1... Sm) are connected to the signal line driver circuit 302, and a video signal is input to each pixel 355 provided in the pixel portion 300.

Such a signal line driver circuit 302, the scan line driver circuit 303, and the pixel portion 300 can be formed using semiconductor elements provided over the same substrate. For example, it can be formed using a thin film transistor provided over a glass substrate.

Next, the cross-sectional structure of the panel shown in FIG. 5 will be described with reference to FIG.

FIG. 6A is an enlarged view of a cross section of the first scan line driver circuit 303 a, the second scan line driver circuit 303 b, and the pixel portion 300 which are provided over the substrate 600. The pixel portion 300 is provided with a TFT 601 and a capacitor 612 that control supply of current to the light emitting element 603. Note that the capacitor 612 can function as a structure in which an insulator is provided between a pair of conductors. In this embodiment, a conductor formed of the same layer as a gate electrode and an interlayer insulating film 608 are provided. A capacitor element 612 is constituted by the insulator and gate insulating film made of the above and the conductor made of the same layer as the wiring of the TFT 601. However, it is not limited to this configuration.

Note that the structures of the light-emitting element 603 and the TFT 601 can be freely combined with the structure described in Embodiment Mode 5.

The first and second scanning line driving circuits 303a and 303b have CMOS circuits 630a and 630b each formed of a thin film transistor. Since the buffers 313a and 313b of each scanning line driver circuit are simpler circuits than other circuits, the CMOS circuits 630a and 630b can be applied. Of course, the CMOS circuits 630a and 630b may be applied to other circuits.

Although not illustrated in FIG. 6A, the CMOS circuits 630a and 630b can be applied to a circuit included in the signal line driver circuit 302.

Then, the counter substrate 650 is attached using the sealant 651. For the sealing material 651, a known material such as an epoxy resin can be used. In FIG. 6A, a sealant 651 is provided so as to cover part of the scan line driver circuit. As a result, the panel can be narrowed.

As a result of bonding, a space is formed between the substrate 600 and the counter substrate 650. Since the light-emitting element 603 is deteriorated by air or moisture, the space is preferably filled with an inert gas such as nitrogen. A resin or the like may be filled. Furthermore, a spacer may be arranged to hold the gap. The spacer may have a function as a desiccant.

A connection terminal 652 for inputting a signal to the first and second scanning line driving circuits 303a and 303b is provided outside the sealing material 651. The connection terminal 652 is connected to the FPC through an anisotropic conductive film.

In FIG. 6A, bonding is performed using the sealant 651, but bonding can also be performed using a resin filled in the space.

FIG. 6B is a cross-sectional view in the case where the counter substrate 650 is provided with the black matrix 655 and the color filter 656. The color filter 656 is provided so as to be disposed at least above the light emitting element 603.

The black matrix 655 is provided so as to be arranged above the wiring such as the scanning lines (G1... Gn), the signal lines (S1... Sm), or the power supply lines (V1... Vm). The black matrix 655 may be provided over the first and second scan line driver circuits 303a and 303b. The other structures are the same as those in FIG.

Although FIG. 6B illustrates the case where the color filter 656 is used, a color conversion layer may be further combined.

In FIG. 6B, the color filter 656 is provided on the counter substrate 650 side; however, a color filter may be provided on the substrate 600 side. For example, it can be disposed on the back surface of the substrate 600 or formed over the second electrode 102.

Similarly, the black matrix 655 is not limited to the structure provided on the counter substrate 650 side, and may be provided on the substrate 600 side. In addition, a black pigment can be mixed in the interlayer insulating film 608 to function as a black matrix.

6A and 6B, the thin film transistor exemplifies a so-called GOLD (Gate Overlapped LDD) structure in which a low concentration impurity region overlaps a gate electrode. In addition, a so-called LDD (Lightly Doped Drain) structure that does not overlap with the gate electrode may be used.

In this embodiment mode, a panel in which a scan line driver circuit and a signal line driver circuit are provided over the same substrate as the pixel portion 300 is illustrated; however, the present invention is not limited to this. For example, each drive circuit may be formed from an IC chip. In this case, the IC chip can be mounted on the substrate by a COG method or a TAB method.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 9)
As an electronic device including the light emitting device of the present invention, a television device (also simply referred to as a television or a television receiver), a digital camera, a digital video camera, a mobile phone device (also simply referred to as a mobile phone or a mobile phone), a PDA Such as portable information terminals, portable game machines, computer monitors, computers, sound reproduction apparatuses such as car audio, and image reproduction apparatuses equipped with recording media such as home game machines. A specific example will be described with reference to FIG.

A portable information terminal device illustrated in FIG. 7A includes a main body 9201, a display portion 9202, and the like. The light emitting device of the present invention can be applied to the display portion 9202. As a result, it is possible to provide a portable information terminal in which low power consumption is achieved without increasing the driving voltage even when the thickness of the light emitting element is increased. Furthermore, since the light-emitting element of the present invention can be thickened, the yield of portable information terminals is improved.

A digital video camera shown in FIG. 7B includes a display portion 9701, a display portion 9702, and the like. The light-emitting device of the present invention can be applied to the display portion 9701. As a result, it is possible to provide a digital video camera that achieves low power consumption without increasing the driving voltage even when the thickness of the light emitting element is increased. Furthermore, since the light-emitting element of the present invention can be thickened, the yield of digital video cameras is improved.

A cellular phone shown in FIG. 7C includes a main body 9101, a display portion 9102, and the like. The light emitting device of the present invention can be applied to the display portion 9102. As a result, it is possible to provide a mobile phone that achieves low power consumption without increasing the driving voltage even when the thickness of the light emitting element is increased. Furthermore, since the light-emitting element of the present invention can be thickened, the yield of mobile phones is improved.

A portable television device illustrated in FIG. 7D includes a main body 9301, a display portion 9302, and the like. The light emitting device of the present invention can be applied to the display portion 9302. As a result, it is possible to provide a portable television device that achieves low power consumption without increasing the driving voltage even when the thickness of the light emitting element is increased. Further, since the light-emitting element of the present invention can be thickened, yield of a portable television device is improved.
In addition, as a portable television device, a wide range from a small one mounted on a portable terminal such as a cellular phone to a medium-sized one that can be carried and a large one (for example, 40 inches or more). The light emitting device of the present invention can be applied.

A portable computer illustrated in FIG. 7E includes a main body 9401, a display portion 9402, and the like. The light emitting device of the present invention can be applied to the display portion 9402. As a result, a portable computer with low power consumption can be provided without increasing the driving voltage even when the thickness of the light emitting element is increased. Further, since the light-emitting element of the present invention can be thickened, the yield of a portable computer is improved.

A television device illustrated in FIG. 7F includes a main body 9501, a display portion 9502, and the like. The light emitting device of the present invention can be applied to the display portion 9502. As a result, it is possible to provide a television device that achieves low power consumption without increasing the driving voltage even when the thickness of the light-emitting element is increased. Further, since the light-emitting element of the present invention can be thickened, the yield of television devices is improved.

Thus, according to the present invention, it is possible to provide an electronic device in which low power consumption is achieved without increasing the driving voltage even when the thickness of the light emitting element is increased.

Example 1
In this example, a light-emitting element manufactured using a layer in which an organic compound and an inorganic compound are mixed in a layer that generates holes will be described with reference to FIGS.

A first electrode 701 was formed by depositing indium tin oxide containing silicon over the glass substrate 700 by a sputtering method. The film thickness was set to 110 nm.

Next, DNTPD, molybdenum oxide, and rubrene are formed over the first electrode 701 by a co-evaporation method in a vacuum to form a layer 711 including DNTPD, molybdenum oxide, and rubrene. did. The mass ratio of DNTPD, molybdenum oxide, and rubrene was 1: 0.5: 0.02, and the film thickness was 120 nm.

Next, NPB was deposited on the layer 711 made of DNTPD, molybdenum oxide, and rubrene by an evaporation method in a vacuum to form a layer 722 made of NPB. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were deposited on the layer 722 made of NPB by a co-evaporation method in a vacuum to form a layer 723 containing Alq ₃ and coumarin 6. Incidentally, coumarin 6 was to include 0.01 wt% with respect to Alq _3.
Thus, coumarin 6 is in a state of being dispersed in Alq _3. The film thickness was 37.5 nm.

Then, over the layer 723 containing Alq ₃ and coumarin 6, a Alq _3, it was deposited by evaporation in vacuum to form a layer 724 made of Alq _3. The film thickness was 37.5 nm.

Next, lithium fluoride was deposited on the layer 724 made of Alq ₃ by an evaporation method in a vacuum to form a layer 713 made of lithium fluoride. The film thickness was 1 nm.

Next, a second electrode 702 was formed by depositing aluminum over the layer 713 made of lithium fluoride by a vacuum evaporation method. The film thickness was set to 200 nm.

In the light emitting element manufactured as described above, when a voltage is applied to the first electrode 701 and the second electrode 702 to pass a current, the coumarin 6 emits light.

At this time, the first electrode 701 functions as an anode and the second electrode 702 functions as a cathode. A layer 711 made of DNTPD, molybdenum oxide, and rubrene is a layer that generates holes, a layer 722 made of NPB is a hole transport layer, and a layer 723 containing Alq ₃ and coumarin 6 is a light emitting layer. The layer 724 made of Alq ₃ functions as an electron transport layer, and the layer 713 made of lithium fluoride functions as a layer for generating electrons.

FIG. 9 shows current density-luminance characteristics when the light-emitting element of this example is held at 105 ° C., FIG. 10 shows voltage-luminance characteristics, and FIG. 11 shows luminance-current efficiency characteristics.
9, the horizontal axis represents current density, the vertical axis represents luminance, the horizontal axis in FIG. 10 represents current density, the vertical axis represents luminance, the horizontal axis in FIG. 11 represents voltage, and the vertical axis represents luminance.
Each element is in an initial state (Sample 1), after 30 hours (Sample 2), after 154 hours (Sample 3), and after 462 hours (Sample 4).

Based on these results, the luminance deterioration (standardization evaluation) with respect to the elapsed time when applying 7 (V) is shown (see FIG. 12).
FIG. 12 also shows the results of using a layer made of DNTPD and rubrene as the layer 711 that generates holes as the sample of the present invention (Sample A) and the comparative sample (Sample B).

As can be seen from FIG. 12, Sample A is less deteriorated with time than Sample B. That is, a stable light-emitting element can be obtained by using a layer in which molybdenum oxide is mixed in a layer that generates holes.

Thus, even if DNTPD is used as the organic compound, it is possible to achieve an effect that deterioration with time is reduced. In addition, since the glass transition temperature of DNTPD is 94 degreeC, when this is considered, the glass transition temperature of this invention will be 80 degreeC or more, Preferably it will be 90 degreeC or more and 300 degrees C or less.

(Example 2)
(Synthesis Example) A method for synthesizing the benzidine derivative represented by the structural formula (2) will be described.

[Step 1]
A method for synthesizing 2-bromo-spiro-9,9′-bifluorene will be described.

Into a 100 mL three-necked flask, 1.26 g (0.052 mol) of magnesium was put, the inside of the system was put under vacuum, and the mixture was heated and stirred for 30 minutes to activate. After cooling to room temperature, the system is placed under a nitrogen stream, 5 mL of diethyl ether and a few drops of dibromoethane are added, and 11.65 g (0.050 mol) of 2-bromobiphenyl dissolved in 15 mL of diethyl ether is slowly added dropwise to complete the addition. Thereafter, the mixture was refluxed for 3 hours to obtain a Grignard reagent. In a 200 mL three-necked flask, 11.7 g (0.045 mol) of 2-bromofluorenone and 40 mL of diethyl ether were placed. The synthesized Grignard reagent was slowly added dropwise to the reaction solution. After completion of the addition, the mixture was refluxed for 2 hours and further stirred overnight (15 hours) at room temperature. After completion of the reaction, the reaction solution was washed twice with a saturated aqueous ammonium chloride solution, the aqueous layer was extracted twice with ethyl acetate, and the organic layer was washed with saturated brine. After drying with magnesium sulfate, suction filtration and concentration were performed to obtain 18.76 g of solid 9- (2-biphenylyl) -2-bromo-9-fluorenol in a yield of 90%.

Next, the synthesized 9- (2-biphenylyl) -2-bromo-9-fluorenol (18.76 g, 0.045 mol) and 100 mL of glacial acetic acid were placed in a 200 mL three-necked flask, and a few drops of concentrated hydrochloric acid were added, followed by refluxing for 2 hours. did. After completion of the reaction, the precipitate was collected by suction filtration, and washed by filtration with a saturated aqueous sodium hydrogen carbonate solution and water. The obtained brown solid was recrystallized with ethanol to obtain 10.24 g of a light brown powdery solid in a yield of 57%. This light brown powdery solid was confirmed to be 2-bromo-spiro-9,9′-bifluorene by nuclear magnetic resonance (NMR). ¹ H-NMR of this compound was as follows.

¹ H-NMR of this compound is shown below.
¹ H-NMR (300 MHz, CDCl ₃ ) δ ppm: 7.86-7.79 (m, 3H), 7.70 (d, 1H, J = 8.4 Hz), 7.47-7.50 (m , 1H), 7.41-7.34 (m, 3H), 7.12 (t, 3H, J = 7.7 Hz), 6.85 (d, 1H, J = 2.1 Hz), 6.74. -6.70 (m, 3H)

Moreover, the synthesis scheme (b-1) of the synthesis method described above is shown below.

[Step 2]
A method for synthesizing N, N′-bis (spiro-9,9′-bifluoren-2-yl) -N, N′-diphenylbenzidine (abbreviation: BSPB) will be described.

In a 100 mL three-necked flask, 1.00 g (0.0030 mol) of N, N′-diphenylbenzidine, 2.49 g (0.0062 mol) of 2-bromo-spiro-9,9′-bifluorene synthesized by the synthesis method of Step 1 , Bis (dibenzylideneacetone) palladium (0) 170 mg (0.30 mmol), tert-butoxy sodium 1.08 g (0.011 mol) were added, and the system was placed under a nitrogen stream. 0.6 mL of 10 wt% hexane solution of tert-butyl) phosphine was added and stirred at 80 ° C. for 6 hours. After completion of the reaction, the reaction solution was cooled to room temperature, water was added, and the precipitated solid was collected by suction filtration and washed with dichloromethane. The obtained white solid was purified by alumina column chromatography (chloroform) and recrystallized with dichloromethane. As a result, 2.66 g of white powdery solid was obtained in a yield of 93%.

When the obtained white powdery solid was analyzed by nuclear magnetic resonance (NMR), the following results were obtained, confirming that it was a benzidine derivative represented by the structural formula (2). In addition, FIG. 19 shows a ¹ H-NMR chart. ¹ H-NMR (300 MHz, DMSO-d ₆ ) δ ppm: 7.93-7.89 (m, 8H), 7.39-7.33 (m, 10H), 7.19-7.14 (m, 8H), 7.09-6.96 (m, 6H), 6.89-6.84 (m, 8H), 6.69 (d, 4H, J = 7.5 Hz), 6.54 (d, 2H, J = 7.8 Hz), 6.25 (d, 2H, J = 2.4 Hz)

A synthesis scheme (b-2) of the synthesis method described above is shown below. Thus, the compound of the present invention can be synthesized by a coupling reaction of N, N'-diphenylbenzidine and 2-bromo-spiro-9,9'-bifluorene.

Further, the glass transition temperature, crystallization temperature, and melting point of the obtained compound were examined using a differential scanning calorimeter (DSC: Differential Scanning Calorimetry, manufactured by PerkinElmer, model number: Pyris1 DSC). Here, the measurement by DSC was performed according to the following procedure. First, after heating the sample (the obtained compound) to 450 ° C. at a temperature increase rate of 40 ° C./min, the sample was cooled to a glass state by cooling at a cooling rate of 40 ° C./min. And the sample which became a glass state was heated with the temperature increase rate of 10 degree-C / min, and the measurement result as shown in FIG. 17 was obtained. In FIG. 17, the horizontal axis represents temperature (° C.), and the vertical axis represents heat flow (upward is endothermic) (mW). From the measurement results, it was found that the obtained compound had a glass transition temperature of 172 ° C. and a crystallization temperature of 268 ° C. Moreover, it turned out that melting | fusing point is 323 degreeC or more and 324 degrees C or less from the intersection of the tangent in 312 degreeC and the tangent in 327 degreeC or more and 328 degrees C or less. That is, it can be seen that BSPB synthesized as in this example has a glass transition temperature of 150 ° C. or higher, preferably 160 ° C. or higher and 300 ° C. or lower, and a melting point of 180 ° C. or higher and 400 ° C. or lower.

  In addition, when 4.74 g of the obtained compound was purified by sublimation under conditions of 14 Pa and 350 ° C. for 24 hours, 3.49 g could be recovered, and the recovery rate was 74%.

Thus, the obtained compound exhibits a high glass transition temperature of 172 ° C. and has good heat resistance. Moreover, in FIG. 17, the peak showing crystallization of the obtained compound was broad, and it was found that the obtained compound was a substance difficult to crystallize.

(Example 3)
A light-emitting element manufactured using a compound (hereinafter, simply referred to as BSPB) having a glass transition temperature of 172 ° C. obtained by the synthesis described in the above Example and Step 2 will be described with reference to FIGS.

A first electrode 701 was formed by depositing indium tin oxide containing silicon over the glass substrate 700 by a sputtering method. The film thickness was set to 110 nm.

Next, BSPB, molybdenum oxide, and rubrene are formed over the first electrode 701 by a co-evaporation method in a vacuum, and a layer 711 including BSPB, molybdenum oxide, and rubrene is formed. Formed. The mass ratio of BSPB, molybdenum oxide, and rubrene was 2: 0.75: 0.04, and the film thickness was 120 nm.

Next, NPB was deposited on the layer 711 made of BSPB, molybdenum oxide, and rubrene by a vacuum evaporation method to form a layer 722 made of NPB. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were deposited on the layer 722 made of NPB by a co-evaporation method in a vacuum to form a layer 723 containing Alq ₃ and coumarin 6. Incidentally, coumarin 6 was to include 0.01 wt% with respect to Alq _3. Thus, coumarin 6 is in a state of being dispersed in Alq _3. The film thickness was 37.5 nm.

Then, over the layer 723 containing Alq ₃ and coumarin 6, a Alq _3, it was deposited by evaporation in vacuum to form a layer 724 made of Alq _3. The film thickness was 37.5 nm.

Next, lithium fluoride was deposited on the layer 724 made of Alq ₃ by an evaporation method in a vacuum to form a layer 713 made of lithium fluoride. The film thickness was 1 nm.

Next, a second electrode 702 was formed by depositing aluminum over the layer 713 made of lithium fluoride by a vacuum evaporation method. The film thickness was set to 200 nm.

In the light emitting element manufactured as described above, when a voltage is applied to the first electrode 701 and the second electrode 702 to pass a current, the coumarin 6 emits light.

At this time, the first electrode 701 functions as an anode and the second electrode 702 functions as a cathode. A layer 711 made of BSPB, molybdenum oxide, and rubrene is a layer that generates holes, a layer 722 made of NPB is a hole transport layer, and a layer 723 containing Alq ₃ and coumarin 6 is a light emitting layer. The layer 724 made of Alq ₃ functions as an electron transport layer, and the layer 713 made of lithium fluoride functions as a layer for generating electrons.

FIG. 13 shows current density-luminance characteristics of the light-emitting element of this example held at 105 ° C., FIG. 14 shows voltage-luminance characteristics, and FIG. 15 shows luminance-current efficiency characteristics. 13, the horizontal axis represents current density, the vertical axis represents luminance, the horizontal axis represents voltage, the vertical axis represents luminance, the horizontal axis represents luminance, and the vertical axis represents current density in FIG. Each element is in an initial state (Sample 5) and after 30 hours (Sample 6).

Based on these results, the luminance deterioration (standardization evaluation) with respect to the elapsed time when 7 (V) is applied is shown (see FIG. 16). FIG. 16 also shows the results of using a layer made of BSPB and rubrene as the layer 711 that generates holes as the sample of the present invention (SampleC) and the comparative sample (SampleD).

It can be seen from FIG. 16 that SampleC is less deteriorated with time than SampleD. That is, a stable light-emitting element can be obtained by using a layer in which molybdenum oxide is mixed in a layer that generates holes.

Furthermore, it can be seen that SampleC is less deteriorated with time than SampleA. Thus, by using a layer in which BSPB having a higher glass transition temperature or higher melting point and molybdenum oxide are mixed, a light-emitting element that is thermally stable and has high heat resistance can be obtained. Furthermore, a light-emitting element in which the driving voltage does not increase even when such a layer is thickened can be obtained.

Example 4
In this example, measurement results of voltage-luminance characteristics of a light-emitting element having a layer in which an organic compound and an inorganic compound are mixed, and results of a current driving test are shown.

First, as a light-emitting element that does not have a layer in which an organic compound and an inorganic compound are mixed, BSPB (film thickness 50 nm), NPB (film thickness 10 nm), a mixed layer of Alq ₃ and coumarin 6 (film thickness 37.5 nm, Alq ₃ and coumarin mixing ratio (molar ratio) = 1: 0.01), Alq ₃ (thickness 37.5 nm), LiF (thickness 1 nm), and Al (thickness 200 nm) were sequentially laminated (Sample 8). ).

As a light-emitting element having a layer in which an organic compound and an inorganic compound are mixed, a mixed layer of BSPB, molybdenum oxide, and rubrene (a film thickness of 120 nm, a mixture ratio of BSPB, molybdenum oxide, and rubrene ( (Molar ratio) = 2: 0.75: 0.04), NPB (film thickness 10 nm), mixed layer of Alq ₃ and coumarin 6 (film thickness 37.5 nm, mixed ratio of Alq ₃ and coumarin (molar ratio)) = 1: 0.01), Alq ₃ (film thickness 37.5 nm), LiF (film thickness 1 nm), and Al 2 (film thickness 200 nm) were sequentially stacked (Sample 9).

FIG. 20 shows the voltage-luminance (cd / m ² ) characteristics of Sample 8 and Sample 9. It can be seen that Sample 9 having molybdenum oxide has a lower voltage for obtaining the same luminance, that is, a driving voltage.

Next, FIG. 21 shows the results of a constant current driving test when the initial luminance is 3000 cd / m ² for Sample 8 and Sample 9. It can be seen that Sample 9 having molybdenum oxide is a more reliable device with a slower deterioration rate.

It is the figure which showed the light emitting element of this invention. It is the figure which showed the light emitting element of this invention. It is sectional drawing which showed the light emitting element of this invention. It is the figure which showed the pixel circuit of this invention It is the figure which showed the panel of this invention It is sectional drawing which showed the panel of this invention It is the figure which showed the electronic device of this invention It is the figure which showed the light emitting element of this invention. It is the figure which showed the current density-luminance characteristic of the light emitting element of this invention. It is the figure which showed the voltage-luminance characteristic of the light emitting element of this invention. It is the figure which showed the luminance-current efficiency characteristic of the light emitting element of this invention. It is the figure which showed the deterioration characteristic of the light emitting element of this invention It is the figure which showed the current density-luminance characteristic of the light emitting element of this invention. It is the figure which showed the voltage-luminance characteristic of the light emitting element of this invention. It is the figure which showed the luminance-current efficiency characteristic of the light emitting element of this invention. It is the figure which showed the deterioration characteristic of the light emitting element of this invention It is the measurement result which carried out differential scanning calorimetry analysis of the benzidine derivative of the present invention. It is the figure which showed the light emitting element of this invention. It is a figure which shows the result analyzed by the nuclear magnetic resonance method about the white powdery solid synthesize | combined in step 2 of Example 2. FIG. It is a figure which shows the voltage-luminance characteristic of the light emitting element of this invention. It is a figure which shows the result of the constant current drive test of the light emitting element of this invention.

Claims (14)

And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: emitting element having a glass transition temperature and having an organic compound and metal oxide is less than 0.99 ° C. or more on 3 00 ° C.. And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: glass transition temperature has an organic compound and metal oxide is less than 0.99 ° C. or more on 3 00 ° C., the organic compound, N, and N'- diphenyl benzidine, 2-bromo - spiro-9,9' A light-emitting element obtained by a coupling reaction with bifluorene or 2-bromo-2 ′, 7′-dialkyl-spiro-9,9′-bifluorene. A first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is positive a layer that generates holes, wherein the light emitting element is a hole layer for generating characterized by having an organic compound and a metal oxide having a glass transition temperature of 3 00 ° C. or less over 0.99 ° C. or more. A first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is positive is a layer for generating holes, the layer for generating holes, the glass transition temperature has an organic compound and metal oxide is 3 00 ° C. or less over 0.99 ° C. or more, the organic compound, N, N It is obtained by coupling reaction of '-diphenylbenzidine with 2-bromo-spiro-9,9'-bifluorene or 2-bromo-2', 7'-dialkyl-spiro-9,9'-bifluorene. A light emitting element.   5. The light-emitting element according to claim 1, wherein the organic compound is a compound having a spiro ring and a triphenylamine skeleton. 6. The light-emitting element according to claim 1, wherein the organic compound is a benzidine derivative represented by the general formula (1).

(In the formula, R ¹ represents either hydrogen or an alkyl group having 1 to 4 carbon atoms.) 6. The light-emitting element according to claim 1, wherein the organic compound is a benzidine derivative represented by a structural formula (2).

  And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: A light-emitting element comprising a compound having a spiro ring and a triphenylamine skeleton and a metal oxide. And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: A light-emitting element having a benzidine derivative represented by the general formula (1) and a metal oxide.

(In the formula, R ¹ represents either hydrogen or an alkyl group having 1 to 4 carbon atoms.) And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: A light-emitting element having a benzidine derivative represented by the structural formula (2) and a metal oxide.

And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: a layer general formula (1) benzidine derivative and a metal oxide represented by a are mixed, said benzidine derivative as the hole-transporting substance, before Symbol mixed Mashimashi layer is a layer that generates holes A light emitting device characterized by the above.

(In the formula, R ¹ represents either hydrogen or an alkyl group having 1 to 4 carbon atoms.) And a first layer, a second layer, and a third layer provided between the pair of electrodes, and any one of the first layer to the third layer is: a layer with structural formula (2) benzidine derivative and a metal oxide represented by are mixed, the benzidine derivative as the hole-transporting substance, it is pre-Symbol mixed Mashimashi layer is a layer for generating holes A light emitting device characterized by the above.

  The metal oxide according to any one of claims 1 to 12, wherein the metal oxide is vanadium oxide, molybdenum oxide, niobium oxide, rhenium oxide, tungsten oxide, ruthenium oxide, titanium oxide, chromium oxide, zirconium. A light-emitting element which is any one of an oxide, a hafnium oxide, and a tantalum oxide. A light emitting device comprising the light emitting element according to claim 1 and a transistor electrically connected to the light emitting element.

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