JP4906048B2 - LIGHT EMITTING ELEMENT, LIGHT EMITTING DEVICE, AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to a light-emitting element having a structure in which a plurality of layers are sandwiched between a pair of electrodes, and more particularly to a structure of a layer that can be used as at least one of the plurality of layers.

  A light-emitting device using light emitted from an electroluminescence element (light-emitting element) has attracted attention as a display or illumination device.

  As a light-emitting element used in a light-emitting device, one having a structure in which a layer containing a light-emitting compound is sandwiched between a pair of electrodes is well known.

  In such a light-emitting element, one electrode functions as an anode and the other electrode functions as a cathode, and holes injected from the anode side and electrons injected from the cathode side are recombined to be in an excited state. It forms a molecule and emits light when it returns to the ground state.

  By the way, display devices to be incorporated into various information processing devices that have been rapidly developed in recent years have a particularly high demand for low power consumption. In order to achieve this, attempts have been made to reduce the driving voltage of light-emitting elements. Yes. In view of commercialization, it is important not only to lower the driving voltage but also to extend the life of the light emitting element, and the development of light emitting elements to achieve this is underway.

  For example, Patent Document 1 discloses a technique for reducing a driving voltage of a light emitting element by using a metal oxide having a high work function such as molybdenum oxide for an anode. In addition, the technique disclosed in Patent Document 1 can also provide an effect for extending the life.

However, since molybdenum oxide is easily crystallized, malfunction of the light-emitting element due to crystallization cannot be sufficiently reduced. In other words, since the molybdenum oxide is crystallized to form the convex portion, the flatness is lost, so that there is a problem that short circuit is easily caused and the light emitting element is likely to malfunction.
JP-A-9-63771

An object of the present invention is to provide a light-emitting element that can reduce malfunction due to oxidation and crystallization of a compound.
It is another object of the present invention to provide a light-emitting element that has a low driving voltage and can have a longer lifetime than conventional light-emitting elements.

  The light-emitting element of the present invention has a plurality of layers including a layer containing a light-emitting substance between the first electrode and the second electrode, and at least one of the plurality of layers has the following general formula (1 And a compound (carbazole derivative) having a carbazole skeleton represented by formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the following general formula (1).

Wherein R ¹ is hydrogen, halogen, cyano group, alkyl group having 1 to 20 carbon atoms, haloalkyl group having 1 to 20 carbon atoms, alkoxyl group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group, A substituted or unsubstituted heterocyclic residue, R ^{2 to} R ^{5, which} may be the same or different, each represents hydrogen, halogen, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxyl group having 1 to 20 carbon atoms, C1-C20 acyl group, C1-C20 haloalkyl group, C1-C20 dialkylamino group, C1-C20 diarylamino group, substituted or unsubstituted heterocyclic residue, carbazolyl group Is shown.)

  The structure as described above, that is, a carbazole derivative represented by the general formula (1) and a substance that exhibits electron accepting property with respect to the carbazole derivative represented by the general formula (1) coexist in one layer. Thus, even before the voltage is applied to the light-emitting element, the carbazole derivative represented by the general formula (1) is charged with a substance that exhibits an electron accepting property with respect to the carbazole derivative represented by the general formula (1). Stolen. That is, the carbazole derivative represented by the general formula (1) is oxidized and holes are generated.

  Therefore, the “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” has a function of generating holes. Have.

Therefore, the light-emitting element of the present invention is
Having a plurality of layers between the first electrode and the second electrode;
The plurality of layers include a layer containing a luminescent material and a layer having a function of generating at least one hole,
The layer having a function of generating holes has a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1). Features.

  Then, by providing “a layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)”, the “general formula ( In the layer having a carbazole derivative represented by 1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1), holes can be generated. As a material constituting the second electrode, a conductive film having a high work function or a conductive film having a low work function can be used.

  That is, in the conventional light emitting element, a conductive film having a high work function is used as the anode in order to inject holes from the anode into the layer containing the light emitting substance. However, in the present invention, since a layer having a function of generating holes exists, it is not necessary to use a conductive film having a high work function as the anode.

The “layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” has a function of generating holes. Therefore, the carrier density is increased. As a result, the conductivity is improved,
Change in driving voltage depending on the thickness of “a layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” Less is. Therefore, by changing the thickness of the “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” It is easy to adjust the distance between the layer containing a light-emitting substance and the first electrode or the second electrode.

  In other words, the length of the optical path (optical path length) through which the emitted light passes is set so that the length of the emitted light can be efficiently extracted to the outside or the color purity of the emitted light extracted to the outside is improved. Easy to adjust. Further, by increasing the thickness of the “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)”, The unevenness of the surface of the first electrode can be relaxed, and a short circuit between the electrodes can be easily prevented.

  In addition, since the “layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” has good conductivity, It also has an excellent function of transporting holes.

Therefore, the light-emitting element of the present invention is
Having a plurality of layers between the first electrode and the second electrode;
The plurality of layers include a layer containing a light emitting substance, and a layer having a function of transporting at least one hole,
The layer having a function of transporting holes has a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1). Features.

Further, in the above-described plurality of configurations of the light emitting device of the present invention,
The layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1) includes the layer containing the light-emitting substance and the first Provided between the electrodes,
The device has a structure in which light is emitted when a voltage is applied so that a potential at the first electrode is higher than a potential at the second electrode.

Further, in the above-described plurality of configurations of the light emitting device of the present invention,
The layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1) includes the layer containing the light-emitting substance and the second layer. Provided between the electrodes,
The device has a structure in which light is emitted when a voltage is applied so that a potential at the first electrode is higher than a potential at the second electrode.

Further, in the above-described plurality of configurations of the light emitting device of the present invention,
The layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1) includes the layer containing the light-emitting substance and the first Between the electrode and between the layer containing the luminescent material and the second electrode,
The device has a structure in which light is emitted when a voltage is applied so that a potential at the first electrode is higher than a potential at the second electrode.

  A metal oxide is mentioned as a substance which shows electron-accepting property with respect to the carbazole derivative represented by General formula (1).

  And as a substance which shows an electron-accepting property with respect to the carbazole derivative represented by the above general formula (1), among the metal oxides, oxides of transition metals in any of Groups 4 to 12 of the periodic table are used. It is preferable to use it.

The carbazole derivative represented by the general formula (1) has two triphenylamine skeletons.
And molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), rhenium oxide (ReOx), titanium oxide (TiOx), chromium oxide (CrOx) , Zirconium oxide (ZrOx), hafnium oxide (HfOx), tantalum oxide (TaOx), etc. Have been shown to be particularly electron-accepting.

  Accordingly, examples of the substance that exhibits electron acceptability with respect to the carbazole derivative represented by the general formula (1) include molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), and tungsten oxide. Periodic table such as oxide (WOx), rhenium oxide (ReOx), titanium oxide (TiOx), chromium oxide (CrOx), zirconium oxide (ZrOx), hafnium oxide (HfOx), tantalum oxide (TaOx) It is preferable to use an oxide of any one of Group 4 to Group 8 transition metals.

Moreover, as a substance which shows an electron accepting property with respect to the carbazole derivative represented by the general formula (1), in addition to the metal oxide, for example, as an organic compound, 7,7,8,8-tetracyano-2,3 , 5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, etc., inorganic compounds include FeCl ₃ (iron chloride (III)), AlCl ₃ (aluminum chloride) and the like.

  In addition, in the “layer having a carbazole derivative represented by the general formula (1) and a substance that exhibits an electron accepting property with respect to the carbazole derivative represented by the general formula (1)”, The optimum mixing molar ratio with the carbazole derivative is a substance exhibiting electron accepting property / carbazole derivative = 0.1 to 10, preferably 0.5 to 2.

  Note that the plurality of layers are configured by combining a layer having a substance having a high carrier injection property, a layer having a substance having a high carrier transport property, or the like. Regarding the structure of the plurality of layers, a structure in which a light emitting region is formed in a layer containing a light emitting substance, that is, a structure in which recombination of carriers (carriers) is performed in a layer containing a light emitting substance. The structure of the plurality of layers can be appropriately selected depending on the purpose.

  Further, the layer containing a light-emitting substance may be a single layer or a multilayer. In the case of multiple layers, it is sufficient that at least one layer contains a light-emitting substance.

  Note that the light-emitting element of the present invention may have a structure in which light generated by recombination of carriers in a layer containing a light-emitting substance is emitted from only one of the first and second electrodes to the outside. It is good also as a structure inject | emitted outside from both of two electrodes.

  When light is emitted from the first electrode side, the first electrode is formed of a light-transmitting material, and when light is emitted from the second electrode side, the second electrode is light-transmissive. When light is emitted from both sides of the first and second electrodes, both the first and second electrodes may be formed of a light-transmitting material.

  The light emitting device of the present invention is preferably supported on a substrate, and the substrate is not particularly limited, and those used in conventional light emitting devices, for example, those made of glass, quartz, transparent plastic, etc. Can be used.

  The light-emitting device of the present invention uses any of the light-emitting elements described above as a pixel or a light source.

  The electronic device of the present invention uses a light emitting device using any of the light emitting elements described above as a pixel for a display portion.

  The electronic apparatus of the present invention uses a light-emitting device that uses any of the light-emitting elements described above as a light source for an illumination unit.

  In the light-emitting element of the present invention, at least one layer among the plurality of layers between the first electrode and the second electrode is represented by the carbazole derivative represented by the general formula (1) and the general formula (1). By solving the problem of malfunction of the light-emitting element due to crystallization that occurs when an anode is formed from a metal oxide, by using a layer having a substance that exhibits electron acceptability with respect to the carbazole derivative, In addition, the driving voltage can be reduced.

  In addition, the light-emitting element of the present invention has a voltage in a “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)”. Since electrons are transferred even before application, “a layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” Becomes a highly conductive film. Accordingly, it is possible to provide an electroluminescent element with low driving voltage and low power consumption.

  Furthermore, driving is performed in proportion to the increase in film thickness of the “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)”. There is little increase in voltage.

  Therefore, a “layer having a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” is formed without increasing the voltage. Therefore, it is possible to prevent a short circuit and to optimize an optical design, and it is possible to provide an electroluminescent element with high reliability and high light emission efficiency.

  Furthermore, since the “layer having the carbazole derivative represented by the general formula (1) and the substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1)” is difficult to crystallize, Thus, an electroluminescent element with less malfunction due to the fabrication can be obtained.

  Hereinafter, one embodiment of the present invention will be described. 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 the embodiment.

(Embodiment 1)
One mode of a light-emitting element of the present invention will be described with reference to FIG.

  In FIG. 1, a first layer 111, a second layer 112, a third layer 113, a fourth layer 114, and a fifth layer 115 are provided between the first electrode 101 and the second electrode 102. A light-emitting element is shown.

This first layer is a layer formed by mixing a carbazole derivative represented by the general formula (1) and a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1). . Since the first layer has a function of generating holes, it will be referred to as a hole generating layer in the following.
The second layer 112 is a hole transport layer, the third layer 113 is a light emitting layer, and the fourth layer 114 is an electron transport layer. The fifth layer 115 is a layer having a function of generating electrons. Hereinafter, the fifth layer is referred to as an electron generation layer.

  When voltage is applied to the first electrode 101 and the second electrode 102 so that the potential of the first electrode 101 is higher than the potential of the second electrode 102, the light-emitting layer 113 has the first electrode Holes are injected from the 101 side, and electrons are injected from the second electrode 102 side. Then, the holes and electrons injected into the light emitting layer 113 are recombined. The light-emitting layer 113 contains a light-emitting substance, and the light-emitting substance is excited by excitation energy generated by recombination. The luminescent material in the excited state emits light when returning to the ground state.

  In addition, the substance showing electron acceptability with respect to the carbazole derivative represented by the general formula (1) has a molar ratio of 0.1 to 10 with respect to the carbazole derivative represented by the general formula (1). More preferably, it is contained so as to be 0.5 to 2 (= substance showing electron acceptability / carbazole derivative).

  A metal oxide is mentioned as a substance which shows electron-accepting property with respect to the carbazole derivative represented by General formula (1). Among metal oxides, it is preferable to use oxides of transition metals of Groups 4 to 12 of the periodic table, such as molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx). ), Tungsten oxide (WOx), rhenium oxide (ReOx), titanium oxide (TiOx), chromium oxide (CrOx), zirconium oxide (ZrOx), hafnium oxide (HfOx), tantalum oxide (TaOx) It is more preferable to use an oxide of a transition metal of any of Groups 4 to 8 of the periodic table.

Moreover, as a substance which shows an electron accepting property with respect to the carbazole derivative represented by the general formula (1), in addition to the metal oxide, for example, as an organic compound, 7,7,8,8-tetracyano-2,3 , 5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, etc., inorganic compounds include FeCl ₃ (iron chloride (III)), AlCl ₃ (aluminum chloride) and the like.

  Moreover, the substance which shows an electron accepting property with respect to the carbazole derivative represented by General formula (1) may use one type, or may use multiple types.

  Inhibition of crystallization of the hole-generating layer 111 by combining a substance having electron acceptability with the carbazole derivative represented by the general formula (1) and the carbazole derivative represented by the general formula (1) Thus, device malfunction due to crystallization can be reduced.

  In the hole generating layer 111 having such a structure, the carbazole derivative represented by the general formula (1) is deprived of electrons by a substance exhibiting electron accepting properties. That is, the carbazole derivative represented by the general formula (1) is oxidized and holes are generated.

  The light emitting layer 113 includes a light emitting substance. Here, the light-emitting substance is a substance that has good emission efficiency and can emit light of a desired wavelength. The light-emitting layer 113 may be a layer formed only of a light-emitting substance, but when concentration quenching occurs, the light-emitting substance is contained in a layer formed of a substance having an energy gap larger than that of the light-emitting substance. A layer mixed so as to be dispersed is preferable. By including a light-emitting substance in the light-emitting layer 113 in a dispersed manner, light emission can be prevented from being quenched due to concentration. Here, the energy gap refers to an energy gap between the LUMO level and the HOMO level.

  There is no particular limitation on the light-emitting substance, and a substance that has favorable emission efficiency and can emit light with a desired emission wavelength may be used.

  For example, to obtain red light emission, 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] -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), periflanthene, 2,5 -Dicyano-1,4-bis [2- (10-methoxy-1,1,7,7-tetramethyljulolidin-9-yl) ethenyl] benzene, etc., emission spectrum from 600 nm to 680 nm Substance which exhibits emission with a peak can be used as a light-emitting substance.

When green light emission is desired, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), etc., emits light from 500 nm to 550 nm. A substance that emits light having a spectral peak can be used as the light-emitting substance.

  When blue light emission is desired, 9,10-di (2-naphthyl) -2-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 A substance exhibiting light emission having a peak of an emission spectrum from 420 nm to 500 nm, such as -methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), can be used as the light-emitting substance.

As described above, in addition to a substance that emits fluorescence, bis [2- (3 ′, 5′-bis (trifluoromethyl) phenyl) pyridinato-N, C2 ′] iridium (III) picolinate (abbreviation: Ir (CF ₃ ppy) ₂ (pic)), bis [2- (4 ′, 6′-difluorophenyl) pyridinato-N, C ² ′] iridium (III) acetylacetonate (abbreviation: FIr (acac)), bis [2 - (4 ', 6'-difluorophenyl) pyridinato -N, ^{C 2']} iridium (III) picolinate (abbreviation: FIr (pic)), tris (2-phenylpyridinato--N, ^{C 2} ') iridium ( A substance that emits phosphorescence, such as abbreviation: Ir (ppy) ₃ ), can also be used as the light-emitting substance.

  There is no particular limitation on a substance that is included in the light-emitting layer 113 together with the light-emitting substance and is used for dispersing the light-emitting substance, and may be appropriately selected in consideration of an energy gap of the substance used as the light-emitting substance.

For example, anthracene derivatives such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA), or 4,4′-bis (N-carbazolyl) biphenyl (abbreviation: CBP) Carbazole derivatives of 2,3-bis (4-diphenylaminophenyl) quinoxaline (abbreviation: TPAQn), 2,3-bis {4- [N- (1-naphthyl) -N-phenylamino] phenyl} -dibenzo [ In addition to quinoxaline derivatives such as f, h] quinoxaline (abbreviation: NPDiBzQn), bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2-hydroxyphenyl) benzoxazola G] A metal complex such as zinc (abbreviation: ZnBOX) or the like can be used together with a light-emitting substance.

The hole transport layer 112 has a function of transporting holes. In the light-emitting element of this embodiment mode, the hole transport layer 112 has a function of transporting holes from the hole generation layer 111 to the light-emitting layer 113.
By providing the hole transport layer 112, the distance between the hole generation layer 111 and the light emitting layer 113 can be increased, and as a result, the light emission is quenched due to the metal contained in the hole generation layer 111. Can be prevented.

The hole transport layer is preferably formed using a substance having a high hole transport property, and particularly preferably formed using a substance having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher.
Note that a substance having a high hole-transport property has a higher hole mobility than an electron, and the ratio of the hole mobility to the electron mobility (= hole mobility / electron mobility) is 100. Larger than the substance.

Specific examples of a substance that can be used to form the hole-transport layer 112 include 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), 4, 4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) triphenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4′-bis {N- [4- ( N, N-di-m-tolylamino) phenyl] -N-phenylamino} biphenyl (abbreviation: DNTPD), 1,3,5-tris [N, N-di (m-tolyl) amino] benzene (abbreviation: m -MTDAB), 4,4 ', 4''- Squirrel (N- carbazolyl) triphenylamine (abbreviation: TCTA), phthalocyanine _{(abbreviation:} H 2 Pc), copper phthalocyanine (abbreviation: CuPc), or vanadyl phthalocyanine (abbreviation: VOPc), and the like.

  The electron transport layer 114 is a layer having a function of transporting electrons. In the light-emitting element of this embodiment mode, the electron transport layer 114 has a function of transporting electrons from the electron generation layer 115 to the light-emitting layer 113. By providing the electron transport layer 114, the distance between the second electrode 102 and the light-emitting layer 113 can be increased, and as a result, light emission is quenched due to the metal contained in the second electrode 102. Can be prevented.

The electron transport layer is preferably formed using a substance having a high electron transport property, and particularly preferably formed using a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. In addition,
A substance having a high electron-transport property has higher electron mobility than holes, and the ratio of the electron mobility to the hole mobility (= electron mobility / hole mobility) is greater than 100. A substance.

Specific examples of a substance that can be used for forming the electron-transport layer 114 include tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq _3). ), Bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), bis [2- In addition to metal complexes such as (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ) 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (approximately) Name: 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-methylbenzoxa) And sol-2-yl) stilbene (abbreviation: BzOs).

  Note that the hole transport layer 112 and the electron transport layer 114 may be formed using a bipolar substance in addition to the above substances. A bipolar substance is the ratio of the mobility of one carrier to the mobility of the other carrier when the mobility of one of the electrons or holes is compared with the mobility of the other carrier. A substance whose value is 100 or less, preferably 10 or less.

As a bipolar substance, for example, 2,3-bis (4-diphenylaminophenyl) quinoxaline (abbreviation: TPAQn), 2,3-bis {4- [N- (1-naphthyl) -N-phenylamino] phenyl } -Dibenzo [f, h] quinoxaline (abbreviation: NPDiBzQn) and the like. Among bipolar substances, it is particularly preferable to use a substance having a hole and electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more. Alternatively, the hole transport layer 112 and the electron transport layer 114 may be formed using the same bipolar substance.

The electron generating layer 115 is a layer that generates electrons, and is formed by mixing at least one substance selected from a substance having a high electron transporting property and a bipolar substance and a substance that exhibits an electron donating property with respect to these substances. Can be formed. Here, among substances having a high electron transporting property and bipolar substances, a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is particularly preferable.

As the substance having a high electron transporting property and the bipolar substance, those described above can be used, respectively. Moreover, as the substance exhibiting electron donating property, a substance selected from alkali metals and alkaline earth metals, specifically, lithium (Li), calcium (Ca), sodium (Na), potassium (K), Magnesium (Mg) or the like can be used. Alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, alkali metal fluorides, alkaline earth metal fluorides, etc., 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 At least one substance selected from (CsF), calcium fluoride (CaF ₂ ) and the like can also be used as the substance exhibiting electron donating properties.

  The first electrode 101 includes indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 atomic% of zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a material having a high work function such as tantalum nitride. Alternatively, it may be formed using a material having a low work function such as aluminum or magnesium.

  As described above, in the light-emitting element of this embodiment mode, the first electrode 101 can be formed without depending on the work function of the substance. This is because the hole generating layer 111 is provided between the first electrode 101 and the light emitting layer 113.

  In addition, for the second electrode 102, in addition to indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 atomic% of zinc oxide, gold (Au), platinum (Pt), nickel ( Using a material having a high work function such as Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and tantalum nitride. It may be formed using a substance having a low work function such as aluminum or magnesium.

  As described above, in the light-emitting element of this embodiment mode, the second electrode 102 can be formed regardless of the work function of the substance. This is because the electron generating layer 115 is provided between the second electrode 102 and the light emitting layer 113.

  Note that in this embodiment mode, a light-emitting element including the hole-transporting layer 112 and the electron-transporting layer 114 in addition to the hole-generating layer 111 and the light-emitting layer 113 has been described; however, the mode of the light-emitting element is not necessarily limited thereto. It is not a thing.

  For example, a light emitting element in which an electron injection layer 116 is provided instead of the electron generation layer 115 as shown in FIG. The electron injection layer 116 is a layer having a function of assisting injection of electrons from the second electrode 102 to the electron transport layer 114.

  By providing the electron injection layer 116, the difference in electron affinity between the second electrode 102 and the electron transport layer 114 is reduced, and electrons are easily injected. The electron injection layer 116 is a substance having a higher electron affinity than the substance forming the electron transport layer 114 and a lower electron affinity than the substance forming the second electrode 102, or the electron transport layer 114 and the second transport layer 114. It is preferable to use a substance whose energy band is bent when it is provided as a 1 to 2 nm thin film between the electrode 102 and the electrode 102.

  Specific examples of materials that can be used to form the electron injection layer 116 include alkali metal or alkaline earth metal, alkali metal fluoride, alkaline earth metal fluoride, alkali metal oxide, and alkaline earth. Examples thereof include inorganic substances such as metal oxides. These materials are preferable because the energy band bends when provided as a thin film.

  In addition to inorganic substances, substances that can be used to form the electron transport layer 114 such as BPhen, BCP, p-EtTAZ, and TAZ are also more preferable than those used to form the electron transport layer 114. In addition, by selecting a substance having a high electron affinity, it can be used as a substance for forming the electron injection layer 116.

  That is, it is preferable to form the electron injection layer 116 so that the electron affinity in the electron injection layer 116 is relatively larger than the electron affinity in the electron transport layer 114. Note that in the case where the electron-injecting layer 116 is provided, the second electrode 102 is preferably formed using a substance having a low work function such as aluminum.

  Further, a hole blocking layer 117 may be provided between the light emitting layer 113 and the electron transporting layer 114 as shown in FIG. By providing the hole blocking layer 117, holes can be prevented from penetrating through the light emitting layer 113 and flowing toward the second electrode 102, and the carrier recombination efficiency can be increased. In addition, the excitation energy generated in the light emitting layer 113 can be prevented from moving to another layer such as the electron transport layer 114.

  The hole blocking layer 117 is formed of a material that can be used to form the electron transport layer 114 such as BAlq, OXD-7, TAZ, or BPhen, and more particularly than a material that is used to form the light emitting layer 113. It can be formed by selecting a substance having a large ionization potential and excitation energy.

  That is, the hole blocking layer 117 may be formed so that the ionization potential in the hole blocking layer 117 is relatively larger than the ionization potential in the electron transport layer 114.

  Similarly, a layer may be provided between the light emitting layer 113 and the hole transporting layer 112 to prevent electrons from passing through the light emitting layer 113 and flowing toward the first electrode 101. .

  Note that whether or not to provide the hole transport layer 112, the electron transport layer 114, and the like may be appropriately selected by the practitioner of the invention. For example, the metal may be formed without the hole transport layer 112 and the electron transport layer 114. These layers are not necessarily provided when there is no problem such as quenching caused by extinction.

  In the light-emitting element of this embodiment described above, a change in driving voltage depending on the thickness of the hole generation layer 111 is small. Therefore, the distance between the light emitting layer 113 and the first electrode 101 can be easily adjusted by changing the thickness of the hole generating layer 111.

  In other words, the length of the optical path (optical path length) through which the emitted light passes is set so that the length of the emitted light can be efficiently extracted to the outside or the color purity of the emitted light extracted to the outside is improved. Easy to adjust. In addition, by increasing the thickness of the hole generation layer 111, unevenness on the surface of the first electrode 101 can be relaxed, and a short circuit between the electrodes can be easily prevented.

  In the light-emitting element of this embodiment, the change in driving voltage depending on the thickness of the electron generation layer 115 is small. Therefore, it is easy to adjust the length of the optical path (optical path length) through which the emitted light passes by changing the thickness of the electron generating layer 115. In addition, by increasing the thickness of the electron generation layer 115, unevenness on the surface of the second electrode 102 can be relaxed, and a short circuit between the electrodes can be easily prevented.

(Embodiment 2)
One mode of the light-emitting element of the present invention will be described with reference to FIG.

  FIG. 2 shows a light-emitting element having a first layer 213, a second layer 212, and a third layer 211 between the first electrode 201 and the second electrode 202. . The first layer 213 is formed by sequentially stacking an electron transport layer 221, a light emitting layer 222, a hole transport layer 223, and a hole generation layer 224. The second layer 212 generates electrons, and the third layer 211 generates holes.

  Here, the hole generation layer 224 is provided on the first electrode 201 side with respect to the light emitting layer 222, and the electron transport layer 221 is provided on the second electrode 202 side with respect to the light emitting layer 222. When a voltage is applied to the first electrode 201 and the second electrode 202 so that the potential of the first electrode 201 is higher than the potential of the second electrode 202, the third electrode 211 to the second electrode 202 are applied. Holes are injected into. Further, electrons are injected from the second layer 212 and holes are injected from the first electrode 201 into the first layer 213. The electrons and holes injected into the first layer 213 are recombined in the light emitting layer 222. The light-emitting layer 222 contains a light-emitting substance, and the light-emitting substance is excited by excitation energy generated by recombination. The luminescent material in the excited state emits light when returning to the ground state.

  The third layer 211 and the hole generation layer 224 each include a carbazole derivative represented by the general formula (1) and a substance that exhibits an electron accepting property with respect to the carbazole derivative represented by the general formula (1). It is a layer formed by mixing. In the third layer 211 and the hole-generating layer 224, the carbazole derivative represented by the general formula (1) deprives electrons with a substance having an electron accepting property with respect to the carbazole derivative represented by the general formula (1). Is called. That is, the carbazole derivative represented by the general formula (1) is oxidized and holes are generated.

Note that, in each of the third layer 211 and the hole generation layer 224, carbazole having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more among the carbazole derivatives represented by the general formula (1). It is preferable to use a derivative. In addition, the substance showing electron acceptability with respect to the carbazole derivative represented by the general formula (1) has a molar ratio of 0.1 to 10 with respect to the carbazole derivative represented by the general formula (1). More preferably, it is contained in each layer so as to be 0.5 to 2 (= substance showing electron acceptability / carbazole derivative). There is no particular limitation on the substance exhibiting electron accepting properties, but it is preferable to use a metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, or rhenium oxide. By combining with these metal oxides, crystallization of the third layer 211 or the hole generation layer 224 can be suppressed, and malfunction of the element due to crystallization can be reduced.

  The second layer 212 is a layer that generates electrons, and is a mixture of at least one substance selected from a substance having a high electron transporting property and a bipolar substance, and a substance that exhibits an electron donating property to these substances. Can be formed.

Here, among substances having a high electron transporting property and bipolar substances, a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is particularly preferable. As the substance having a high electron transporting property and the bipolar substance, those described above can be used, respectively.

Moreover, as the substance exhibiting electron donating property, a substance selected from alkali metals and alkaline earth metals, specifically, lithium (Li), calcium (Ca), sodium (Na), potassium (K), Magnesium (Mg) or the like can be used. Alkali metal oxides or alkaline earth metal oxides, alkali metal nitrides, alkaline earth metal nitrides, alkali metal fluorides, alkaline earth metal fluorides, etc., 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 ), or the like can also be used as a substance exhibiting electron donating properties.

The electron transport layer 221 is a layer having a function of transporting electrons. In the light-emitting element of this embodiment mode, the electron transport layer 221 has a function of transporting electrons from the second layer 212 to the light-emitting layer 222. By providing the electron transport layer 221, the distance between the second layer 212 and the light emitting layer 222 can be increased, and as a result, light emission is quenched due to the metal contained in the second layer 212. Can be prevented. The electron transport layer is preferably formed using a substance having a high electron transport property, and particularly preferably formed using a substance having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher.
For specific examples of the substance that can be used for forming the electron-transport layer 221, the description of the specific examples of the substance that can be used for forming the electron-transport layer 114 in Embodiment 1 is applied mutatis mutandis.

  The light emitting layer 222 contains a light emitting substance. The light-emitting layer 222 may be a layer formed only of a light-emitting substance, but when concentration quenching occurs, the light-emitting substance is contained in a layer made of a substance having an energy gap larger than that of the light-emitting substance. A layer mixed so as to be dispersed is preferable. By including a light-emitting substance in the light-emitting layer 222 in a dispersed manner, light emission can be prevented from being quenched due to concentration. Note that the description of the light-emitting substance in Embodiment 1 is applied to the light-emitting substance. Here, a substance that is included in the light-emitting layer 222 together with the light-emitting substance and is used for dispersing the light-emitting substance is included in the light-emitting layer 113 together with the light-emitting substance described in Embodiment 1 and the light-emitting substance is dispersed. The description of substances used for this purpose shall apply mutatis mutandis.

The hole transport layer 223 is a layer having a function of transporting holes. In the light-emitting element of this embodiment mode, the hole transport layer 223 has a function of transporting holes from the hole generation layer 224 to the light-emitting layer 222. By providing the hole-transporting layer 223, the distance between the hole-generating layer 224 and the light-emitting layer 222 can be increased. As a result, light emission is quenched due to the metal contained in the hole-generating layer 224. Can be prevented. The hole-transport layer 223 is preferably formed using a substance having a high hole-transport property, and particularly preferably formed using a substance having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. . For specific examples of the substance that can be used for forming the hole-transport layer 223, the description of the specific examples of the substance that can be used for forming the hole-transport layer 112 in Embodiment 1 is applied mutatis mutandis. .

  The first electrode 201 includes indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 atomic% of zinc oxide, gold (Au), platinum (Pt), nickel (Ni), and tungsten. (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a material having a high work function such as tantalum nitride. Alternatively, it may be formed using a material having a low work function such as aluminum or magnesium. As described above, in the light-emitting element of this embodiment mode, the first electrode 201 can be formed without depending on the work function of the substance. This is because the hole generating layer 224 is provided between the first electrode 201 and the light emitting layer 222.

  In addition, for the second electrode 202, in addition to indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20 atomic% of zinc oxide, gold (Au), platinum (Pt), nickel ( Using a material having a high work function such as Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and tantalum nitride. You may form using a substance with low work functions, such as aluminum and magnesium. As described above, in the light-emitting element of this embodiment mode, the second electrode 202 can be formed without depending on the work function of the substance. This is because the third layer 211 and the second layer 212 are provided between the second electrode 202 and the light-emitting layer 222.

  Note that in this embodiment mode, a light-emitting element in which the first layer 213 that includes a light-emitting substance is a multilayer including the electron-transport layer 221, the light-emitting layer 222, the hole-transport layer 223, and the hole-generation layer 224 is described. The mode of the light emitting element is not necessarily limited to this.

For example, a light emitting element in which a hole injection layer 225 is provided instead of the hole generation layer 224 as shown in FIG. The hole injection layer 225 is a layer having a function of assisting injection of holes from the first electrode 201 to the hole transport layer 223. By providing the hole injection layer 225, the difference in ionization potential between the first electrode 201 and the hole transport layer 223 is alleviated, and holes are easily injected. The hole injection layer 225 has a lower ionization potential than the material forming the hole transport layer 223 and has a higher ionization potential than the material forming the first electrode 201, or the hole transport layer 223. It is preferable to use a substance whose energy band is bent when it is provided as a 1 to 2 nm thin film between the first electrode 202 and the second electrode 202. Specific examples of a substance that can be used for forming the hole-injection layer 225 include phthalocyanine-based compounds such as phthalocyanine (abbreviation: H ₂ Pc) and copper phthalocyanine (CuPc), or poly (ethylenedioxythiophene) / Examples thereof include a polymer such as a poly (styrenesulfonic acid) aqueous solution (PEDOT / PSS). It is preferable to form the hole injection layer 225 so that the ionization potential in the hole injection layer 225 is relatively larger than the ionization potential in the hole transport layer 223. Note that in the case where the hole injection layer 225 is provided, the first electrode 201 is preferably formed using a substance having a high work function such as indium tin oxide.

  Further, a hole blocking layer 226 may be provided between the light emitting layer 222 and the electron transporting layer 221 as shown in FIG. By providing the hole blocking layer 226, holes can be prevented from penetrating the light emitting layer 222 and flowing toward the second electrode 202, and the carrier recombination efficiency can be increased. In addition, the excitation energy generated in the light-emitting layer 222 can be prevented from moving to another layer such as the electron transport layer 221.

  The hole blocking layer 226 is formed of a material that can be used to form the electron transport layer 221 such as BAlq, OXD-7, TAZ, or BPhen, and more particularly than a material that is used to form the light emitting layer 222. It can be formed by selecting a substance having a large ionization potential and excitation energy. That is, the hole blocking layer 117 may be formed so that the ionization potential in the hole blocking layer 226 is relatively larger than the ionization potential in the electron transport layer 221. Similarly, a layer for preventing electrons from penetrating through the light emitting layer 222 and flowing toward the first electrode 201 may be provided between the light emitting layer 222 and the hole transport layer 223. .

  Note that whether or not to provide the hole transport layer 223 and the electron transport layer 221 may be selected as appropriate by the practitioner of the invention. For example, even if the hole transport layer 223 and the electron transport layer 221 are not provided, If there is no problem such as quenching, it is not always necessary to provide these layers.

  In the light-emitting element as described above, the electron affinity of the substance having a high electron-transport property included in the second layer 212 and the layer in contact with the second layer 212 among the layers included in the first layer 213 The difference from the electron affinity of the contained substance is preferably 2 eV or less, more preferably 1.5 eV or less. More specifically, when the second layer 212 and the electron transport layer 221 are in contact with each other as in the light-emitting element illustrated in FIG. 2, the electron transporting substance contained in the second layer 212 and the electron The difference in electron affinity from the substance having an electron transporting property contained in the transport layer 221 is preferably 2 eV or less, and more preferably 1.5 eV or less. In this manner, by bonding the second layer 212 and the first layer 213, electrons can be efficiently injected from the second layer 212 to the first layer 213.

  The light-emitting element of the present invention described above is an element in which a change in driving voltage depending on the thicknesses of the third layer 211 and the hole generation layer 224 is small. Therefore, the distance between the light emitting layer 222 and the first electrode 201 or the second electrode 202 can be easily adjusted by changing the thickness of the third layer 211 or the hole generation layer 224. In other words, the length of the optical path (optical path length) through which the emitted light passes is set so that the length of the emitted light can be efficiently extracted to the outside or the color purity of the emitted light extracted to the outside is improved. Easy to adjust. In addition, by increasing the thickness of the third layer 211 or the hole generation layer 224, unevenness on the surface of the first electrode 201 or the second electrode 202 can be reduced, and a short circuit between the electrodes can be easily prevented. it can.

(Embodiment 3)
The light emitting device of the present invention can reduce malfunction caused by oxidation and crystallization of a compound. Moreover, the short circuit between electrodes can be prevented by increasing the thickness of the hole generating layer. Further, by changing the thickness of the hole generating layer, the optical path length can be adjusted, the efficiency of taking out emitted light can be increased, and light emission with good color purity can be obtained. Therefore, when the light-emitting element of the present invention is used as a light-emitting element included in each pixel provided in the light-emitting device, a favorable light-emitting device with few display defects due to malfunction of the light-emitting element can be obtained. In addition, by using the light-emitting element of the present invention as a light-emitting element included in each pixel provided in the light-emitting device, a light-emitting device that can provide an image with a favorable display color can be obtained. In addition, by using the light-emitting element of the present invention for a light source, a light-emitting device that can be favorably illuminated with few defects due to malfunction of the light-emitting element can be obtained.

  In this embodiment, a circuit configuration and a driving method of a light-emitting device having a display function will be described with reference to FIGS.

  FIG. 7 is a schematic view of a light emitting device to which the present invention is applied as viewed from above. In FIG. 7, a pixel portion 6511, a source signal line driver circuit 6512, a writing gate signal line driver circuit 6513, and an erasing gate signal line driver circuit 6514 are provided over a substrate 6500. The source signal line drive circuit 6512, the write gate signal line drive circuit 6513, and the erase gate signal line drive circuit 6514 are each an FPC (flexible printed circuit) 6503 which is an external input terminal via a wiring group. Connected. The source signal line driver circuit 6512, the writing gate signal line driver circuit 6513, and the erasing gate signal line driver circuit 6514 receive a video signal, a clock signal, a start signal, a reset signal, and the like from the FPC 6503, respectively. . A printed wiring board (PWB) 6504 is attached to the FPC 6503. Note that the driver circuit portion is not necessarily provided over the same substrate as the pixel portion 6511 as described above. For example, an IC chip mounted on an FPC on which a wiring pattern is formed (TCP) or the like is used. It may be used and provided outside the substrate.

  In the pixel portion 6511, a plurality of source signal lines extending in the column direction are arranged side by side in the row direction. In addition, current supply lines are arranged side by side in the row direction. In the pixel portion 6511, a plurality of gate signal lines extending in the row direction are arranged side by side in the column direction. In the pixel portion 6511, a plurality of sets of circuits including light-emitting elements are arranged.

  FIG. 8 is a diagram illustrating a circuit for operating one pixel. The circuit illustrated in FIG. 8 includes a first transistor 901, a second transistor 902, and a light-emitting element 903.

  Each of the first transistor 901 and the second transistor 902 is a three-terminal element including a gate electrode, a drain region, and a source region, and has a channel region between the drain region and the source region. Here, since the source region and the drain region vary depending on the structure and operating conditions of the transistor, it is difficult to limit which is the source region or the drain region. Therefore, in this embodiment, regions functioning as a source or a drain are referred to as a first electrode and a second electrode, respectively.

  The gate signal line 911 and the writing gate signal line driving circuit 913 are provided so as to be electrically connected or disconnected by a switch 918. The gate signal line 911 and the erasing gate signal line driver circuit 914 are provided so as to be electrically connected or disconnected by a switch 919. The source signal line 912 is provided so as to be electrically connected to either the source signal line driver circuit 915 or the power source 916 by the switch 920. The gate of the first transistor 901 is electrically connected to the gate signal line 911. The first electrode of the first transistor is electrically connected to the source signal line 912, and the second electrode is electrically connected to the gate electrode of the second transistor 902. The first electrode of the second transistor 902 is electrically connected to the current supply line 917, and the second electrode is electrically connected to one electrode included in the light-emitting element 903. Note that the switch 918 may be included in the write gate signal line driver circuit 913. The switch 919 may also be included in the erase gate signal line driver circuit 914. Further, the switch 920 may also be included in the source signal line driver circuit 915.

  There is no particular limitation on the arrangement of transistors, light-emitting elements, and the like in the pixel portion. For example, they can be arranged as shown in the top view of FIG. In FIG. 9, the first electrode of the first transistor 1001 is connected to the source signal line 1004, and the second electrode is connected to the gate electrode of the second transistor 1002. The first electrode of the second transistor 1002 is connected to the current supply line 1005, and the second electrode is connected to the electrode 1006 of the light emitting element. Part of the gate signal line 1003 functions as a gate electrode of the first transistor 1001.

  Next, a driving method will be described. FIG. 10 is a diagram for explaining the operation of a frame over time. In FIG. 10, the horizontal direction represents the passage of time, and the vertical direction represents the number of scanning stages of the gate signal line.

  When image display is performed using the light emitting device of the present invention, the screen rewriting operation and the display operation are repeatedly performed during the display period. The number of rewrites is not particularly limited, but is preferably at least about 60 times per second so that a person viewing the image does not feel flicker. Here, a period during which one screen (one frame) is rewritten and displayed is referred to as one frame period.

As shown in FIG. 10, one frame is time-divided into four subframes 501, 502, 503, and 504 including a writing period 501a, 502a, 503a, and 504a and a holding period 501b, 502b, 503b, and 504b. . A light emitting element to which a signal for emitting light is given is in a light emitting state in the holding period. The ratio of the length of the holding period in each subframe is as follows: first subframe 501: second subframe 502: third subframe 503: fourth subframe 504 = 2 ³ : 2 ² : 2 ¹ : 2 ⁰ = 8: 4: 2: 1. As a result, 4-bit gradation can be expressed. However, the number of bits and the number of gradations are not limited to those described here. For example, eight subframes may be provided so that 8-bit gradation can be performed.

  An operation in one frame will be described. First, in the subframe 501, the write operation is performed in order from the first row to the last row. Therefore, the start time of the writing period differs depending on the row. From the row in which the writing period 501a ends, the storage period 501b is started in order. In the holding period, the light-emitting element to which a signal for emitting light is given is in a light-emitting state. Further, the processing proceeds to the next subframe 502 in order from the row in which the holding period 501b ends, and the writing operation is performed in order from the first row to the last row as in the case of the subframe 501. The operation as described above is repeated until the holding period 504b of the subframe 504 ends. When the operation in the subframe 504 is completed, the process proceeds to the next frame. Thus, the accumulated time of the light emission in each subframe is the light emission time of each light emitting element in one frame. Various display colors having different brightness and chromaticity can be formed by changing the light emission time for each light emitting element and combining them in various ways within one pixel.

  When it is desired to forcibly end the holding period in the row that has already finished writing and has shifted to the holding period before the writing up to the last row is completed as in the subframe 504, after the holding period 504b. It is preferable to provide an erasing period 504c and control to forcibly enter a non-light emitting state. Then, the row that is forcibly set to the non-light-emitting state is kept in the non-light-emitting state for a certain period (this period is referred to as a non-light-emitting period 504d). Then, as soon as the writing period of the last row ends, the next (or frame) writing period starts in order from the first row. Accordingly, it is possible to prevent the writing period of the subframe 504 and the writing period of the next subframe from overlapping.

  In this embodiment, the subframes 501 to 504 are arranged in order from the longest holding period. However, the subframes 501 to 504 are not necessarily arranged as in the present embodiment. For example, the subframes 501 to 504 may be arranged from the shortest holding period. Alternatively, a long holding period and a short holding period may be arranged at random. In addition, the subframe may be further divided into a plurality of frames. That is, the gate signal line may be scanned a plurality of times during the period when the same video signal is applied.

  Here, the operation of the circuit shown in FIG. 8 in the writing period and the erasing period will be described.

  First, the operation in the writing period will be described. In the writing period, the gate signal line 911 in the n-th row (n is a natural number) is electrically connected to the writing gate signal line driving circuit 913 via the switch 918 and is connected to the erasing gate signal line driving circuit 914. Is disconnected. The source signal line 912 is electrically connected to the source signal line driver circuit through the switch 920. Here, a signal is input to the gate of the first transistor 901 connected to the gate signal line 911 in the n-th row (n is a natural number), and the first transistor 901 is turned on. At this time, video signals are simultaneously input to the source signal lines from the first column to the last column. Note that the video signals input from the source signal lines 912 in each column are independent from each other. A video signal input from the source signal line 912 is input to the gate electrode of the second transistor 902 through the first transistor 901 connected to each source signal line. At this time, a current value supplied from the current supply line 917 to the light-emitting element 903 is determined by a signal input to the second transistor 902. Then, depending on the current value, the light emitting element 903 determines light emission or non-light emission. For example, in the case where the second transistor 902 is a p-channel transistor, the light-emitting element 903 emits light by inputting a low level signal to the gate electrode of the second transistor 902. On the other hand, in the case where the second transistor 902 is an n-channel transistor, the light-emitting element 903 emits light when a high level signal is input to the gate electrode of the second transistor 902.

  Next, the operation in the erasing period will be described. In the erasing period, the gate signal line 911 in the n-th row (n is a natural number) is electrically connected to the erasing gate signal line driving circuit 914 via the switch 919, and is connected to the writing gate signal line driving circuit 913. Not connected. The source signal line 912 is electrically connected to the power source 916 through the switch 920. Here, a signal is input to the gate of the first transistor 901 connected to the gate signal line 911 in the n-th row, and the first transistor 901 is turned on. At this time, the erase signal is simultaneously input to the source signal lines from the first column to the last column. The erase signal input from the source signal line 912 is input to the gate electrode of the second transistor 902 through the first transistor 901 connected to each source signal line. At this time, current supplied from the current supply line 917 to the light-emitting element 903 is blocked by a signal input to the second transistor 902. Then, the light emitting element 903 is forced to emit no light. For example, in the case where the second transistor 902 is a p-channel transistor, the light-emitting element 903 does not emit light when a high level signal is input to the gate electrode of the second transistor 902. On the other hand, in the case where the second transistor 902 is an n-channel transistor, the light emitting element 903 does not emit light by inputting a low level signal to the gate electrode of the second transistor 902.

  In the erasing period, for the nth row (n is a natural number), a signal for erasing is input by the operation as described above. However, as described above, the nth row may be an erasing period and the other row (mth row (m is a natural number)) may be a writing period. In such a case, it is necessary to input a signal for erasure to the n-th row and a signal for writing to the m-th row using the source signal line in the same column. It is preferable to operate as described above.

  Immediately after the light emitting element 903 in the n-th row does not emit light by the operation in the erasing period described above, the gate signal line and the erasing gate signal line driving circuit 914 are immediately disconnected, and the switch The source signal line and the source signal line driver circuit 915 are connected by switching 920. Then, the source signal line and the source signal line driver circuit 915 are connected, and the gate signal line and the writing gate signal line driver circuit 913 are connected. Then, a signal is selectively input from the writing gate signal line driving circuit 913 to the m-th signal line, the first transistor is turned on, and the source signal line driving circuit 915 receives the final signal from the first column. A signal for writing is input to the source signal lines up to the column. By this signal, the m-th row light emitting element emits light or does not emit light.

  Immediately after the writing period for the m-th row is completed as described above, the erasing period for the (n + 1) -th row is started. For this purpose, the gate signal line and the writing gate signal line driving circuit 913 are disconnected, and the switch 920 is switched to connect the source signal line to the power source 916. Further, the gate signal line and the writing gate signal line driving circuit 913 are disconnected, and the gate signal line is connected to the erasing gate signal line driving circuit 914. Then, a signal is selectively input from the erasing gate signal line driving circuit 914 to the gate signal line of the (n + 1) th row to turn on the signal to the first transistor, and an erasing signal is input from the power supply 916. In this way, when the erasing period of the (n + 1) th row is finished, the writing period immediately proceeds to the mth row. Thereafter, similarly, the erasing period and the writing period may be repeated until the erasing period of the last row is operated.

  In this embodiment, the mode in which the m-th writing period is provided between the n-th erasing period and the (n + 1) -th erasing period has been described. An m-th writing period may be provided between the period and the n-th erasing period.

  Further, in this embodiment, when the non-light emission period 504d is provided as in the subframe 504, the erasing gate signal line driver circuit 914 and a certain gate signal line are brought into a non-connected state, and writing is performed. The operation of connecting the gate signal line driving circuit 913 and the other gate signal lines is repeated. Such an operation may be performed particularly in a frame in which a non-light emitting period is not provided.

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

  In FIG. 11, what is surrounded by a dotted line is a transistor 11 provided to drive the light emitting element 12 of the present invention. The light emitting element 12 is a light emitting element of the present invention having a layer 15 in which a hole generating layer, an electron generating layer, and a layer containing a light emitting substance are stacked between a first electrode 13 and a second electrode 14. . The drain of the transistor 11 and the first electrode 13 are electrically connected by a wiring 17 penetrating the first interlayer insulating film 16 (16a, 16b, 16c). The light emitting element 12 is separated from another light emitting element provided adjacent thereto by a partition wall layer 18. The light-emitting device of the present invention having such a structure is provided over the substrate 10 in this embodiment.

  Note that the transistor 11 illustrated in FIG. 11 is a top-gate transistor in which a gate electrode is provided on the side opposite to a substrate with a semiconductor layer as a center. However, the structure of the transistor 11 is not particularly limited, and may be, for example, a bottom gate type. In the case of a bottom gate, the semiconductor layer forming a channel may be formed with a protective film (channel protection type), or the semiconductor layer forming the channel may be partially concave ( Channel etch type). Note that 21 is a gate electrode, 22 is a gate insulating film, 23 is a semiconductor layer, 24 is an n-type semiconductor layer, 25 is an electrode, and 26 is a protective film.

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

The semi-amorphous semiconductor is as follows. A semiconductor having an intermediate structure between amorphous and crystalline (including single crystal and polycrystal) and having a third state that is stable in terms of free energy, has a short-range order, and has a lattice distortion. It contains a crystalline region. Further, at least a part of the region in the film contains crystal grains of 0.5 to 20 nm. The Raman spectrum is shifted to the lower wavenumber side than 520 cm ⁻¹ . In X-ray diffraction, diffraction peaks of (111) and (220) that are derived from the Si crystal lattice are observed. In order to terminate dangling bonds (dangling bonds), hydrogen or halogen is contained at least 1 atomic% or more. It is also called a so-called microcrystalline semiconductor (microcrystal semiconductor). It is formed by glow discharge decomposition (plasma CVD) of a compound gas containing silicon. As the gas of the compound containing silicon, SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _4, or the like can be used. The silicon-containing compound gas may be diluted with H ₂ , or H ₂ and one or more kinds of rare gas elements selected from He, Ar, Kr, and Ne. The dilution rate is in the range of 2 to 1000 times. The pressure is generally in the range of 0.1 Pa to 133 Pa, and the power supply frequency is 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature may be 300 ° C. or less, preferably 100 to 250 ° C. As an impurity element in the film, impurities of atmospheric components such as oxygen, nitrogen, and carbon are desirably 1 × 10 ²⁰ / cm ³ or less, and in particular, the oxygen concentration is 5 × 10 ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁹ / cm ³ or less. Note that the mobility of a TFT (thin film transistor) using a semi-amorphous semiconductor is approximately 1 to 10 m ² / Vsec.

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

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

  Further, the first interlayer insulating film 16 may be a multilayer as shown in FIGS. 11A and 11C, or may be a single layer. Note that 16a is made of an inorganic material such as silicon oxide or silicon nitride, and 16b is an organic group having a skeleton structure composed of a bond of acrylic or siloxane (silicon (Si) and oxygen (O)) and containing at least hydrogen as a substituent. (For example, alkyl groups, aromatic hydrocarbons), or fluoro groups as substituents, or organic groups containing at least hydrogen and fluoro groups as substituents), self-flattened silicon oxide, etc. that can be coated and formed It consists of a substance that has sex. Further, 16c is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. Thus, the 1st interlayer insulation film 16 may be formed using both an inorganic substance or an organic substance, or may be formed by either one of an inorganic film and an organic film.

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

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

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

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

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

As described above, in this embodiment mode, an active light-emitting device that controls driving of a light-emitting element using a transistor has been described. In addition to this, a light-emitting element is driven without particularly providing a driving element such as a transistor. A passive light emitting device may be used. FIG. 12 is a perspective view of an example of a passive light emitting device manufactured by applying the present invention. In FIG. 12, a layer 955 in which a layer containing a light-emitting substance, an electron generation layer, and a hole generation layer are sequentially stacked is provided over a substrate 951 between an electrode 952 and an electrode 956. An end portion of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided over the insulating layer 953. The side wall of the partition wall layer 954 has an inclination such that the distance between one side wall and the other side wall becomes narrower as it approaches the substrate surface. That is, the cross section in the short side direction of the partition wall layer 954 has a trapezoidal shape, and the bottom side (the side facing the insulating layer 953 in the same direction as the surface direction of the insulating layer 953) is the upper side (surface of the insulating layer 953 The direction is the same as the direction and is shorter than the side not in contact with the insulating layer 953. In this manner, by providing the partition layer 954, defects in the light-emitting element due to static electricity or the like can be prevented.
Note that what is illustrated in FIG. 12 is an example of a passive light-emitting device, and is not limited to this structure.
A passive light emitting device can also be driven with low power consumption by including the light emitting element of the present invention that operates at a low driving voltage.

(Embodiment 5)
A light-emitting device using the light-emitting element of the present invention as a pixel performs a good display operation with few display defects due to a malfunction of the light-emitting element. Therefore, by applying such a light-emitting device to a display portion, an electronic device with few misperceptions of a display image due to display defects can be obtained. In addition, a light-emitting device using the light-emitting element of the present invention as a light source can be favorably illuminated with few defects due to malfunction of the light-emitting element. Therefore, by using such a light emitting device as an illuminating unit such as a backlight, by mounting the light emitting device of the present invention in this way, a dark part is locally formed due to a defect of the light emitting element. Such malfunctions can be reduced and a good display can be achieved.

  An example of an electronic device in which the light-emitting device to which the present invention is applied is shown in FIG.

  FIG. 13A illustrates a personal computer manufactured by applying the present invention, which includes a main body 5521, a housing 5522, a display portion 5523, a keyboard 5524, and the like. A personal computer can be completed by incorporating a light-emitting device using the light-emitting element of the present invention as a pixel as shown in FIG. 7 as a display portion. Further, a personal computer can be completed even if a light emitting device using the light emitting element of the present invention as a light source is incorporated as a backlight.

  Specifically, as illustrated in FIG. 14, a lighting device in which a liquid crystal device 5512 and a light-emitting device 5513 are fitted in a housing 5511 and a housing 5514 may be incorporated as a display portion. In FIG. 14, an external input terminal 5515 is attached to the liquid crystal device 5512, and the light-emitting device 5513 includes a light-emitting element array 5516 using the light-emitting element of the present invention and a light guide plate 5517. The light-emitting element array 5516 is formed by forming one or a plurality of light-emitting elements according to the present invention. Light emitted from the light-emitting element array 5516 has a surface facing the liquid crystal device 5512 of the light guide plate by the light guide plate. The liquid crystal device 5512 is emitted from the entire surface.

  Note that the light-emitting device 5513 illustrated in FIG. 14 includes a light-emitting element array and a light guide plate; however, the structure is not limited to this. For example, the light emitting element of the present invention may be formed over a wider area without providing a light guide plate, and light emitted from the light emitting element may be directly emitted to the liquid crystal device 5512 side without passing through the light guide plate. .

  FIG. 13B illustrates a telephone manufactured by applying the present invention. The main body 5552 includes a display portion 5551, an audio output portion 5554, an audio input portion 5555, operation switches 5556 and 5557, an antenna 5553, and the like. ing. A telephone can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  FIG. 13C illustrates a television set manufactured by applying the present invention, which includes a display portion 5531, a housing 5532, a speaker 5533, and the like. A television receiver can be completed by incorporating a light-emitting device having the light-emitting element of the present invention as a display portion.

  As described above, the light-emitting device of the present invention is very suitable for use as a display portion of various electronic devices. Note that the electronic device is not limited to that described in this embodiment, and may be another electronic device such as a navigation device.

  Further, among the above electronic devices, as an example of incorporating a light emitting device using the light emitting element of the present invention as a light source as a backlight, only a personal computer was shown, but this is not limited to a personal computer, As long as the electronic device uses a backlight, the light-emitting element of the present invention can be used as a light source in any electronic device.

The carbazole derivative used for the light-emitting element of the present invention has a structure represented by the general formula (1) described above. Specifically, R ¹ represents hydrogen, a halogen element such as fluorine or chlorine, a cyano group, an alkyl group such as a methyl group, an ethyl group, an isopropyl group, or a cyclohexyl group, or a haloalkyl group such as a trifluoromethyl group. Or an alkoxyl group such as a methoxy group, an ethoxy group, an isopropoxy group, a cyclohexyloxy group, or an aryl group such as a phenyl group, a naphthyl group, an anthryl group, or a heterocyclic residue such as an imidazolyl group, an oxathiolyl group, a thiazolyl group, Etc. R ^{2 to} R ⁵ may be the same as or different from each other. Specifically, hydrogen, a halogen element such as fluorine or chlorine, a cyano group, or an alkyl such as a methyl group, an ethyl group, an isopropyl group, or a cyclohexyl group. Group, or alkoxyl group such as methoxy group, ethoxy group, isopropoxy group, cyclohexyloxy group, or acyl group such as acetyl group, acroyl group, malonyl group, benzoyl group, naphthoyl group, or haloalkyl group such as trifluoromethyl group Or a dialkylamino group such as a dimethylamino group, a diethylamino group or a diisopropylamino group, a diarylamino group such as a diphenylamino group or a carbazolyl group, or a heterocyclic residue such as an imidazolyl group, an oxathiolyl group or a thiazolyl group, etc. Be Although the specific example was given regarding R < ¹ > -R < ⁵ >, R < ¹ > -R < ⁵ > is not limited to these.

Specific examples of the carbazole derivative used in the present invention include, for example, carbazole derivatives represented by the following structural formulas (2) to (76) by appropriately changing the structures of R ^{1 to} R ⁵ in the general formula (1). Can be mentioned. However, the carbazole derivative used in the present invention is not limited to these.

In Example 1, a plurality of specific examples of the carbazole derivative used in the present invention are shown, but various reactions can be applied as a synthesis method of the carbazole derivative used in the present invention.
In this example, a synthesis example of the carbazole derivative represented by the structural formula (56), which is an example of the carbazole derivative used in the present invention, is specifically illustrated. However, the method for synthesizing the carbazole derivative represented by the structural formula (56) used in the present invention is not limited thereto. Note that a synthesis scheme of a synthesis example of the carbazole derivative represented by the structure (56) described in this example is shown below.

  Under an argon atmosphere, 16.59 g (30 mmol) of N-ethyl-3,6-dibromocarbazole and 12.09 g (66 mmol) of N- (3-methylphenyl) -N-phenylamine were dissolved in 100 ml of dehydrated xylene. To this, 5.7 g (30 mmol) of copper iodide and 22.8 g (200 mmol) of transcyclohexanediamine were added and stirred at 160 ° C. for 30 minutes. After the completion of stirring, 27.6 g (130 mmol) of potassium phosphate was added, and the mixture was further stirred for 9 days. After completion of the stirring, the temperature was returned to room temperature, 300 ml of toluene was added, and the precipitated substance was filtered. The obtained filtrate was concentrated, diethyl ether was added thereto, and the precipitated material was filtered. When methanol was added to the obtained filtrate, a tar-like product was deposited on the wall of the beaker. This was left to stand overnight, and the liquid phase was removed by decantation to obtain a tar-like product. The obtained tar-like product was purified by silica gel column chromatography with hexane: chloroform (1: 2), and 3,6-bis [N- (3-methylphenyl) -N-phenylamino], a light blue powder, was obtained. -9-ethylcarbazole (the above structural formula (56); hereinafter referred to as EtCzmP2) was obtained. The obtained EtCzmP2 was subjected to sublimation purification at a high temperature setting of 300 ° C. and a low temperature of 200 ° C. The yield after sublimation purification was about 10%.

  In addition, it turned out that the decomposition temperature of obtained EtCzmP2 is 310 degreeC from the thermogravimetry-differential thermal analysis (TG-DTA) measurement. When a film was formed using a vacuum deposition method, a homogeneous film could be formed.

  In addition, when the fluorescence spectrum was measured for the EtCzmP2 thin film and the solution (solvent is methanol), the maximum peak at 435 nm with respect to the excitation wavelength (312 nm) in the case of the thin film, A fluorescence spectrum having a maximum peak at 400 nm was obtained with respect to the excitation wavelength (290 nm) (FIG. 15). In addition, when an ultraviolet / visible region absorption spectrum was measured for a thin film of EtCzmP2 and a solution (the solvent was methanol), a maximum absorption wavelength was obtained at 312 nm in the case of the thin film and 303 nm in the case of the solution. (FIG. 16).

  Furthermore, the value of the HOMO level measured using the photoelectron spectrometer AC-2 (manufactured by Riken Keiki Co., Ltd.) was −5.18 eV. Also. The value of the LUMO level estimated by adding the value to the value of the HOMO level using the absorption edge of the absorption spectrum (FIG. 16) as the energy gap was -1.71 eV.

  In this example, a synthesis example of the carbazole derivative represented by the structural formula (75) which is an example of the carbazole derivative used in the present invention is specifically illustrated.

  In this example, a raw material N-phenyl-3,6-dibromocarbazole (12.03 g, 30 mmol) was used, and the carbazole derivative represented by the structural formula (75) 3 was produced in the same manner as in Example 1 above. , 6-bis [N- (3-methylphenyl) -N-phenylamino] -9-phenylcarbazole (hereinafter referred to as PhCzmP2) was obtained. The obtained PhCzmP2 was purified by sublimation at a high temperature setting of 290 ° C. and a low temperature of 90 ° C. The yield after sublimation purification was about 10%.

FIG. 17 shows the ¹ H NMR spectrum of the obtained PhCzmP2, and FIG. 18 shows an enlarged view of the region surrounded by the two-dot chain line (A) in FIG. 17 and 18, the vertical axis indicates the relative intensity of the signal, and the horizontal axis indicates a dimensionless value δ obtained by dividing the difference in resonance frequency between the sample and the reference sample by the frequency of the apparatus oscillator.

The ¹ H NMR data of the obtained PhCzmP2 is as follows.
¹ H NMR (300 MHz, DMSO-d); δ = 3.31 (s, 6H), 6.74 (s, 2H), 6.75 (d, j = 6.0, 4H), 6.85- 6.91 (m, 6H), 7.08 (t, j = 7.8, 2H), 7.15-7.20 (m, 6H), 7.33 (d, j = 8.7, 2H) ), 7.51 (t, j = 7.2, 1H), 7.58-7.68 (m, 4H), 7.91 (s, 2H)

  In addition, it turned out that the decomposition temperature of obtained PhCzmP2 is 230 degreeC. When a film was formed using a vacuum deposition method, a homogeneous film could be formed.

  In addition, when the fluorescence spectrum was measured for the thin film of PhCzmP2 and the solution (solvent is methanol), in the case of the thin film, the maximum peak at 430 nm with respect to the excitation wavelength (308 nm), and in the case of the solution, A fluorescence spectrum having a maximum peak at 439 nm was obtained with respect to the excitation wavelength (320 nm) (FIG. 19). Moreover, when the ultraviolet-visible region absorption spectrum was measured for the thin film of PhCzmP2, the maximum absorption wavelength was obtained at 308 nm (FIG. 20).

  Further, the value of the HOMO level measured by the same method as in Example 2 was −5.40 eV, and the value of the LUMO level was −2.39 eV.

  In this example, a synthesis example of the carbazole derivative represented by the structural formula (76) which is an example of the carbazole derivative used in the present invention is specifically illustrated.

In this example, using the raw materials N-phenyl-3,6-dibromocarbazole 12.03 g (30 mmol) and 12.18 g (72 mmol) of diphenylamine, the structural formula (76) was obtained in the same manner as in Example 2 above. 3,6-bis (N, N-diphenylamino) -9-phenylcarbazole (hereinafter referred to as PhCzP2) was obtained. The obtained PhCzP2 was subjected to sublimation purification at a high temperature setting of 270 ° C. and a low temperature of 175 ° C. The yield after sublimation purification was about 50%.
FIG. 21 shows a ¹ H NMR spectrum of the obtained PhCzP2, FIG. 22 shows a ¹³ C NMR spectrum, and FIG. 23 shows an enlarged view of a region surrounded by a broken line (A) in FIG. 21 to 23, the vertical axis represents the relative intensity of the signal, and the horizontal axis represents a dimensionless value δ obtained by dividing the difference in resonance frequency between the sample and the reference sample by the frequency of the apparatus oscillator.
The data of ¹ H NMR and ¹³ C NMR of the obtained PhCzP2 are as follows.
¹ H NMR (300 MHz, DMSO-d); δ = 6.88-6.95 (m, 12H), 7.17-7.23 (m, 10H), 7.35 (d, j = 4.5 , 6H), 7.56-7.69 (m, 5H), 7.97 (s, 2H)
¹³ C NMR (75 MHz, DMSO-d); δ = 111.1, 119.4, 121.6, 122.0, 123.6, 126.4, 126.8, 127.8, 129.3, 130 .2, 136.7, 138.2, 139.9, 148.0

  The decomposition temperature of the obtained PhCzP2 was found to be 365 ° C. by TG-DTA measurement. When a film was formed using a vacuum deposition method, a homogeneous film could be formed.

  In addition, when the fluorescence spectrum was measured for the thin film of PhCzP2 and the solution (the solvent was dichloromethane), in the case of the thin film, the maximum peak at 429 nm with respect to the excitation wavelength (313 nm), and in the case of the solution, A fluorescence spectrum having a maximum peak at 435 nm was obtained with respect to the excitation wavelength (315 nm) (FIG. 24). Further, when the ultraviolet / visible region absorption spectrum of the thin film of PhCzP2 and the dichloromethane solution was measured, the maximum absorption wavelength was obtained at 313 nm for the thin film and 305 nm for the solution (FIG. 25).

  Furthermore, the value of the HOMO level measured by the same method as in Example 2 was −5.31 eV, and the value of the LUMO level was −2.57 eV.

In this example, 3,6-bis [N- (3-methylphenyl) -N-phenylamino] -9-phenylcarbazole (PhCzmP2) represented by the structural formula (75) synthesized in Example 3 was used. On the other hand, a film formation example of a layer including molybdenum oxide which is a substance exhibiting electron accepting property is illustrated.

First, a glass substrate is fixed to a substrate holder in a vacuum deposition apparatus. Then, PhCzmP2 and molybdenum oxide (VI) were put in separate resistance heating evaporation sources, and a layer containing PhCzmP2 and molybdenum oxide was formed by a co-evaporation method in a vacuum state. At this time, co-evaporation was performed so that the ratio of PhCzmP2 and molybdenum oxide was 4: 1 by mass. Therefore, the molar ratio is PhCzmP2: molybdenum oxide = 1.0: 1.1. That is, the molar ratio of molybdenum oxide to PhCzmP2 which is a carbazole derivative is 1.1. The film thickness was 100 nm.

The result of measuring the absorption spectrum of the mixed film of PhCzmP2 and molybdenum oxide formed in this manner is shown in A in FIG. For comparison, the absorption spectrum of only the film of PhCzmP2 (thickness 90 nm) is shown as B in FIG. In FIG. 26, the vertical axis represents absorbance and the horizontal axis represents wavelength.

As can be seen from FIG. 26, in the mixed film of A, new absorption that was not observed in the film of PhCzmP2 alone was observed (the part surrounded by a broken line in the figure). This is because electrons are exchanged between PhCzmP2 and molybdenum oxide, and it is considered that molybdenum oxide receives electrons from PhCzmP2 and holes are generated in PhCzmP2.

  Therefore, in the mixed film of PhCzmP2 and molybdenum oxide formed in this example, carriers are generated internally, so that the structure of the light-emitting element has a mixed film of PhCzmP2 and molybdenum oxide. The driving voltage of the light emitting element can be reduced.

In this example, 3,6-bis (N, N-diphenylamino) -9-phenylcarbazole (PhCzP2) represented by the structural formula (76) synthesized in Example 4 and its electron accepting property are shown. A film formation example of a layer including molybdenum oxide as a substance is illustrated.

First, a glass substrate is fixed to a substrate holder in a vacuum deposition apparatus. Then, in a state where PhCzP2 and molybdenum oxide (VI) are put in separate resistance heating evaporation sources and evacuated, a layer containing PhCzP2 and molybdenum oxide (mixture of PhCzP2 and molybdenum oxide) is formed by a co-evaporation method. Film). At this time, co-evaporation was performed so that the ratio of PhCzP2 and molybdenum oxide was 4: 1 by mass. Therefore, the molar ratio is PhCzP2: molybdenum oxide = 1.0: 1.0. That is, the molar ratio of molybdenum oxide to PhCzP2 which is a carbazole derivative is 1.0. The film thickness was 80 nm.

The result of measuring the absorption spectrum of the mixed film of PhCzP2 and molybdenum oxide formed in this manner is shown in A of FIG. For comparison, an absorption spectrum of a film of only PhCzP2 (film thickness 90 nm) is shown as B in FIG. In FIG. 27, the vertical axis represents absorbance and the horizontal axis represents wavelength.

As can be seen from FIG. 27, in the mixed film of A, new absorption that was not seen in the film of PhCzP2 alone was observed (the part surrounded by a broken line in the figure). This is because electrons are exchanged between PhCzP2 and molybdenum oxide, and it is considered that molybdenum oxide receives electrons from PhCzP2 and holes are generated in PhCzP2.

  Therefore, in the mixed film of PhCzP2 and molybdenum oxide formed in this example, carriers are generated internally, so that the structure of the light-emitting element has a mixed film of PhCzP2 and molybdenum oxide. The driving voltage of the light emitting element can be reduced.

In this example, 3,6-bis [N- (3-methylphenyl) -N-phenylamino] -9-phenylcarbazole (PhCzmP2) represented by the structural formula (75) synthesized in Example 3 was used. An example of manufacturing a light-emitting element in which a layer including molybdenum oxide which is a substance showing an electron accepting property is used as the first layer (hole generation layer) 111 in FIG.

First, indium tin oxide containing silicon oxide (ITSO) with a thickness of 110 nm was formed as a first electrode 101 over a glass substrate. ITSO was formed by sputtering. Note that the size of the first electrode 101 was 2 mm × 2 mm. Next, as a pretreatment for forming a light-emitting element over the first electrode 101, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, etc.) at 200 ° C. Heat treatment was performed for 1 hour, and UV ozone treatment was performed for 370 seconds.

  Next, a layer containing PhCzmP2 and molybdenum oxide (a mixed film of PhCzmP2 and molybdenum oxide) with a thickness of 40 nm was formed as the hole-generating layer 111. At this time, a layer containing PhCzmP2 and molybdenum oxide was formed by co-evaporation so that the ratio of PhCzmP2 and molybdenum oxide was 4: 2. Therefore, the molar ratio is PhCzmP2: molybdenum oxide = 1.0: 2.1. That is, the value of the molar ratio of molybdenum oxide to PhCzmP2 which is a carbazole derivative is 2.1.

Subsequently, NPB was formed to a thickness of 10 nm as the hole transport layer 112. On these laminated films, a co-deposited film of Alq ₃ and coumarin 6 was formed as a light emitting layer 113 with a film thickness of 40 nm. At this time, a co-evaporation film of Alq ₃ and coumarin 6 was formed by co-evaporation so that the ratio of Alq ₃ and coumarin 6 was 1: 0.01 by mass ratio.

Further, Alq ₃ was formed to a thickness of 10 nm as the electron transport layer 114. A co-deposited film of Alq ₃ and Li was formed as the electron generating layer 115 with a thickness of 30 nm. At this time, a co-evaporation film of Alq ₃ and Li was formed by co-evaporation so that the ratio of Alq ₃ and Li was 1: 0.01 by mass ratio. Finally, Al was formed to a thickness of 200 nm as the second electrode 102 to complete the element. Note that each of the hole generation layer 111, the hole transport layer 112, the light emitting layer 113, the electron transport layer 114, the electron generation layer 115, and the second electrode 102 was formed by a vacuum evaporation method using resistance heating.

When a voltage of 7.6 V is applied between the first electrode 101 and the second electrode 102 of the light-emitting element manufactured as described above, a current flows at a current density of 10.5 mA / cm ² , and 1100 cd / m. A high brightness of ² was obtained. The emission color was green emission derived from Coumarin 6. 28 shows current density-luminance characteristics, voltage-luminance characteristics in FIG. 29, and luminance-current efficiency characteristics in FIG. 30, respectively. 28, the vertical axis represents luminance L, the horizontal axis represents current density J, and in FIG. 29, the vertical axis represents luminance L, the horizontal axis represents voltage V, and in FIG. 30, the vertical axis represents current efficiency η, The horizontal axis indicates the luminance L. From these results, it can be seen that the light-emitting element of this example exhibits good characteristics.

In this example, 3,6-bis [N- (3-methylphenyl) -N-phenylamino] -9-phenylcarbazole (PhCzmP2) represented by the structural formula (75) synthesized in Example 3 was used. An example of manufacturing a light-emitting element in which a layer containing molybdenum oxide which is a substance exhibiting electron accepting property is used as the third layer 211 and the hole-generating layer 224 in FIG.

First, ITSO with a thickness of 110 nm was formed as a first electrode 201 over a glass substrate. ITSO was formed by sputtering. Note that the size of the first electrode 201 was 2 mm × 2 mm. Next, as pretreatment for forming a light-emitting element over the first electrode 201, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, or the like) at 200 ° C. Heat treatment was performed for 1 hour, and UV ozone treatment was performed for 370 seconds.

  Next, a layer containing PhCzmP2 and molybdenum oxide (a mixed film of PhCzmP2 and molybdenum oxide) with a thickness of 40 nm was formed as the hole-generating layer 224. At this time, a layer containing PhCzmP2 and molybdenum oxide was formed by co-evaporation so that the ratio of PhCzmP2 and molybdenum oxide was 4: 2. Therefore, the molar ratio is PhCzmP2: molybdenum oxide = 1.0: 2.1. That is, the value of the molar ratio of molybdenum oxide to PhCzmP2 which is a carbazole derivative is 2.1.

Subsequently, NPB was formed to a thickness of 10 nm as the hole transport layer 223. On these laminated films, a co-deposited film of Alq ₃ and coumarin 6 was formed as a light emitting layer 222 with a thickness of 40 nm. At this time, a co-evaporation film of Alq ₃ and coumarin 6 was formed by co-evaporation so that the ratio of Alq ₃ and coumarin 6 was 1: 0.01 by mass ratio.

Further, Alq ₃ was formed to a thickness of 10 nm as the electron transport layer 221. In this manner, the first layer 213 including the hole generation layer 224, the hole transport layer 223, the light emitting layer 222, and the electron transport layer 221 was formed over the first electrode 201.

Then, a co-deposited film of Alq ₃ and Li was formed to a thickness of 30 nm as the second layer 212 that generates electrons on the electron transport layer 221. At this time, a co-evaporation film of Alq ₃ and Li was formed by co-evaporation so that the ratio of Alq ₃ and Li was 1: 0.01 by mass ratio. Subsequently, a layer containing PhCzmP2 and molybdenum oxide (a mixed film of PhCzmP2 and molybdenum oxide) with a thickness of 20 nm was formed as the third layer 211 that generates holes. At this time, a layer containing PhCzmP2 and molybdenum oxide was formed by co-evaporation so that the ratio of PhCzP2 and molybdenum oxide was 4: 2. Therefore, the molar ratio is PhCzmP2: molybdenum oxide = 1.0: 2.1. That is, the value of the molar ratio of molybdenum oxide to PhCzmP2 which is a carbazole derivative is 2.1.

  Finally, Al was formed to a thickness of 200 nm as the second electrode 202 to complete the element. Note that each of the hole generation layer 224, the hole transport layer 223, the light emitting layer 222, the electron transport layer 221, the second layer 212, the third layer 211, and the second electrode 102 is formed by a vacuum evaporation method using resistance heating. Was deposited.

  When voltage is applied between the first electrode 201 and the second electrode 202 of the light-emitting element manufactured as described above, green light emission derived from coumarin 6 is obtained, and it is confirmed that the light-emitting element functions well. It was done.

4A and 4B illustrate one embodiment of a light-emitting element of the present invention. 4A and 4B illustrate one embodiment of a light-emitting element of the present invention. 4A and 4B illustrate one embodiment of a light-emitting element of the present invention. 4A and 4B illustrate one embodiment of a light-emitting element of the present invention. 4A and 4B illustrate one embodiment of a light-emitting element of the present invention. 4A and 4B illustrate one embodiment of a light-emitting element of the present invention. FIG. 6 is a top view illustrating one embodiment of a light-emitting device of the present invention. 4A and 4B each illustrate one embodiment of a circuit for driving pixels provided in a light-emitting device of the present invention. 4A and 4B illustrate one embodiment of a pixel portion included in a light-emitting device of the present invention. 4 is a frame diagram illustrating a driving method for driving pixels included in the light-emitting device of the present invention. FIG. 3A and 3B each illustrate one embodiment of a cross section of a light-emitting device of the present invention. 4A and 4B illustrate one embodiment of a light-emitting device of the present invention. 6A and 6B illustrate one embodiment of an electronic device to which the present invention is applied. The figure explaining the illuminating device to which this invention is applied. The figure which shows the fluorescence spectrum of the carbazole derivative used for this invention. The figure which shows the ultraviolet-visible region absorption spectrum of the carbazole derivative used for this invention. It shows a ¹ H NMR spectrum of the carbazole derivative used in the present invention. Enlarged view of the ¹ H NMR spectrum of the carbazole derivative used in the present invention. The figure which shows the fluorescence spectrum of the carbazole derivative used for this invention. The figure which shows the ultraviolet-visible region absorption spectrum of the carbazole derivative used for this invention. It shows a ¹ H NMR spectrum of the carbazole derivative used in the present invention. The figure which shows the ¹³ C NMR spectrum of the carbazole derivative used for this invention. The enlarged view of the ¹³ C NMR spectrum of the carbazole derivative used for this invention. The figure which shows the fluorescence spectrum of the carbazole derivative used for this invention. The figure which shows the ultraviolet-visible region absorption spectrum of the carbazole derivative used for this invention. The figure which shows the comparison with the absorption spectrum of the mixed film of PhCzmP2 and molybdenum oxide, and the absorption spectrum of a PhCzmP2 single film. The figure which shows the comparison with the absorption spectrum of the mixed film of PhCzP2 and molybdenum oxide, and the absorption spectrum of a PhCzP2 independent film | membrane. FIG. 10 shows current density-luminance characteristics of the element shown in Example 7. FIG. 16 shows voltage-luminance characteristics of the element shown in Example 7. FIG. 11 shows luminance-current efficiency characteristics of the element shown in Example 7.

Explanation of symbols

101 1st electrode 102 2nd electrode 111 Hole generation layer 112 Hole transport layer 113 Light emitting layer 114 Electron transport layer 115 Electron generation layer 116 Electron injection layer 117 Hole blocking layer 201 1st electrode 202 2nd electrode 211 3rd layer 212 2nd layer 213 1st layer 221 Electron transport layer 222 Light emitting layer 223 Hole transport layer 224 Hole generation layer 225 Hole injection layer 226 Hole blocking layer 6500 Substrate 6503 FPC
6504 Printed wiring board 6511 Pixel portion 6512 Source signal line drive circuit 6513 Write gate signal line drive circuit 6514 Erase gate signal line drive circuit 901 Transistor 902 Transistor 903 Light emitting element 911 Gate signal line 912 Source signal line 913 Write gate Signal line drive circuit 914 Erasing gate signal line drive circuit 915 Source signal line drive circuit 916 Power supply 917 Current supply line 918 Switch 919 Switch 920 Switch 1001 Transistor 1002 Transistor 1003 Gate signal line 1004 Source signal line 1005 Current supply line 1006 Electrode 501 Sub Frame 502 Subframe 503 Subframe 504 Subframe 501a Writing period 501b Holding period 502a Writing period 502b Holding period 503a Writing Only period 503b holding period 504a writing period 504b holding period 504c erasing period 504d non-light emitting period 10 substrate 11 transistor 12 light emitting element 13 first electrode 14 second electrode 15 layer 16 interlayer insulating film 17 wiring 18 partition layer 19 interlayer insulating film 951 Substrate 952 Electrode 956 Electrode 955 Layer 953 Insulating layer 954 Partition layer 953 Insulating layer 5521 Main body 5522 Housing 5523 Display portion 5524 Keyboard 5511 Housing 5512 Liquid crystal device 5513 Light emitting device 5514 Housing 5515 External input terminal 5516 Light emitting element array 5551 Display portion 5552 Main body 5553 Antenna 5554 Audio output unit 5555 Audio input unit 5556 Operation switch 5531 Display unit 5532 Housing 5533 Speaker

Claims (7)

A plurality of layers including a layer containing a light-emitting substance between the first electrode and the second electrode;
Among the plurality of layers, a carbazole derivative represented by the following structural formula (75) and a carbazole represented by the structural formula (75) are provided between the first electrode and the layer containing the light-emitting substance. A light-emitting element including a metal oxide that exhibits an electron-accepting property with respect to a derivative.
In claim 1,
The light-emitting element, wherein the metal oxide is one selected from oxides of transition metals of Groups 4 to 12 of the periodic table. In claim 1,
The light-emitting element, wherein the metal oxide is one selected from oxides of transition metals of Groups 4 to 8 of the periodic table. In claim 1,
The metal oxide is selected from molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, rhenium oxide, titanium oxide, chromium oxide, zirconium oxide, hafnium oxide, and tantalum oxide. A light emitting element characterized by the above. A light-emitting device using the light-emitting element according to claim 1 as a light source. A light-emitting device provided with a pixel having the light-emitting element according to claim 1 . An electronic apparatus using the light emitting device according to claim 5 .