JP2005126431A - Pyrene derivative, light-emitting element, light-emitting device, and electric appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pyrene derivative capable of forming a film with stable quality, to provide a light-emitting element capable of stably emitting light, to provide a light-emitting device given by using the light-emitting element, and to provide an electric appliance. <P>SOLUTION: This pyrene derivative comprises a compound expressed by general formula (1). The light-emitting element has the pyrene derivative expressed by general formula (1) and positioned between a pair of electrodes. Further, the light-emitting element has a light-emitting layer which contains the pyrene derivative expressed by general formula (1) and positioned between the pair of the electrodes. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pyrene derivative that emits light efficiently, has excellent heat resistance, forms a homogeneous film, and has a stable film quality. In addition, the present invention relates to a light-emitting element, a light-emitting device, and an appliance including an anode, a cathode, and a layer containing an organic compound that can emit light by applying an electric field (hereinafter referred to as a “layer containing a light-emitting substance”). .

  Organic compounds have a wider variety of materials than inorganic compounds, and materials having various functions may be synthesized by suitable molecular design. In addition, there is a feature that a formed product such as a film is rich in flexibility and is excellent in workability by being polymerized. Because of these advantages, photonics and electronics using functional organic materials have recently attracted attention.

  For example, a solar cell or a light-emitting element (also referred to as an organic electroluminescent element) can be given as an example of a photoelectronic device using an organic semiconductor material as a functional organic material. These are devices that take advantage of the electrical properties (carrier transport properties) and optical properties (light absorption or light emission) of organic semiconductor materials. In particular, light-emitting elements are making remarkable progress.

  A light-emitting element includes a layer containing a light-emitting substance between a pair of electrodes (an anode and a cathode), and the light-emitting mechanism includes holes injected from the anode when a voltage is applied between the electrodes. Electrons injected from the cathode are said to recombine at the emission center in the layer containing the luminescent material to form molecular excitons that emit energy and emit light when the molecular excitons return to the ground state. Yes. Note that singlet excitation and triplet excitation are known as excited states, and light emission is considered to be possible through either excited state.

  In order to produce a full color display using a light emitting element, it is necessary to arrange pixels emitting light of three primary colors of blue, green, and red on a panel. Various methods can be used as the method, and blue light emission is indispensable in any method, and it is desired to provide a blue light-emitting element with high luminance, efficiency, and color purity.

By the way, as a blue light emitting element, a light emitting element using 1,3,6,8-tetraphenylpyrene and a derivative thereof as a light emitting material has been known (for example, see Patent Document 1 and Non-Patent Document 1). . However, since the thin film of the light emitting material is easily crystallized, it is difficult to maintain a uniform film quality, and it is difficult to obtain stable light emission for a long time. Also, the luminous efficiency was insufficient.
JP 2001-118682 A

Wataru Sotoyama, 7 others, 2003 SID International Symposium Digest of Technical Papers, Vol. 34, 1294-1297 (2003)

  Therefore, an object of the present invention is to provide a pyrene derivative that forms a homogeneous film, is less likely to cause crystallization, and has a stable film quality. It is another object of the present invention to provide a light-emitting element that can stably emit light for a long time, a light-emitting device using the light-emitting element, and an electric appliance.

  As a result of extensive studies, the present inventor has found that the pyrene derivative represented by the following general formula (1) emits light efficiently and is difficult to crystallize. Therefore, the present invention is characterized by a pyrene derivative represented by the following general formula (1).

（式中、Ｒ¹〜Ｒ⁴はそれぞれ同一でも異なっていてもよく、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシル基、アリール基、ジアリールアミノ基、アルキル基あるいはアリール基を置換基として一つ以上有するシリル基、からなる群より選ばれるいずれかの置換基を表す。）

(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an aryl group, a diarylamino group, an alkyl group or an aryl group. It represents any substituent selected from the group consisting of one or more silyl groups as substituents.)

  In addition, by using the above-described pyrene derivative, a light-emitting element that can stably emit light with high efficiency for a long time can be manufactured. Therefore, the light-emitting element of the present invention includes the above-described pyrene derivative. In particular, since the pyrene derivative of the present invention exhibits highly efficient light emission, it is preferable to include the above-described pyrene derivative in the light emitting layer.

    The pyrene derivative of the present invention forms a homogeneous film, hardly causes crystallization, and has a stable film quality. Therefore, stable light emission can be obtained for a long time by using the pyrene derivative of the present invention for a light-emitting element. In addition, by using the light-emitting element of the present invention, a light-emitting device that emits light stably for a long time can be obtained.

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

(Embodiment 1)
The pyrene derivative in the present invention has a structure represented by the general formula (1) described above. R ^{1 to} R ⁴ are specifically alkyl groups such as methyl, ethyl, isopropyl and cyclohexyl, alkoxy groups such as methoxy, isopropoxy and hexyloxy, aryl groups such as phenyl, naphthyl and anthryl, or diphenyl Examples thereof include diarylamino groups such as amino groups and carbazolyl groups, and further silyl groups having one or more alkyl groups or aryl groups as substituents.

Further, by appropriately changing the structure of R ^{1 to} R ⁴ in the general formula (1), for example, pyrene derivatives represented by the following structural formulas (2) to (12) can be formed. However, the present invention is not limited to these.

  The pyrene derivative of the present invention has a large molecular weight and forms a three-dimensional structure when the phenyl group is bonded to the ortho position of the phenyl group bonded to the 1, 3, 6, 8 positions of pyrene. Therefore, it has not only excellent heat resistance but also a characteristic of forming a homogeneous film and a characteristic that it is difficult to crystallize, that is, the film quality is stable.

  Further, the pyrene derivative of the present invention has a feature that it emits light efficiently.

  As a method for synthesizing the pyrene derivative of the present invention, various reactions can be applied. For example, as a synthesis scheme of the pyrene derivative represented by the structural formula (2), there is a method shown below. However, the synthesis method of the pyrene derivative of the present invention is not limited to this.

(Embodiment 2)
In this embodiment, a light-emitting element using the pyrene derivative described in Embodiment 1 will be described.

  Note that the element structure of the light-emitting element in the present invention is not particularly limited and can be appropriately selected depending on the purpose. Basically, the light-emitting substance is included between a pair of electrodes (anode and cathode). For example, a structure in which a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer (hole blocking layer), an electron transport layer, an electron injection layer, etc. are appropriately combined) is sandwiched, for example, Anode / hole injection layer / light emitting layer / electron transport layer / cathode, anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, anode / hole injection layer / hole transport layer / light emission Layer / electron transport layer / electron injection layer / cathode, anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode, anode / hole injection layer / hole transport layer / Examples include a light emitting device having a configuration of a light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode. The light-emitting element of the present invention contains the pyrene derivative of the present invention, and includes the pyrene derivative of the present invention in any of the light-emitting layer, the hole transport layer, the hole injection layer, the electron transport layer, and the electron injection layer. May be. In addition, you may laminate | stack from any of an anode and a cathode.

  The light emitting device of the present invention is preferably supported on a substrate. There is no restriction | limiting in particular about a board | substrate, What was used for the conventional light emitting element, for example, what consists of glass, quartz, a transparent plastic, etc. can be used.

  In addition, as the anode material of the light-emitting element of the present invention, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a high work function (work function of 4.0 eV or more). Specific examples of the anode material include indium tin oxide (hereinafter referred to as ITO), indium oxide containing 2 to 20% zinc oxide, gold (Au), platinum (Pt), nickel (Ni). Tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a nitride of metal (TiN) may be used. it can.

On the other hand, as the cathode material, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (work function of 3.8 eV or less). Specific examples of the cathode material include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, aluminum-lithium alloys, or the like These mixed metals, magnesium-silver alloys, or mixed metals thereof can be used. Moreover, you may use a metal oxide or a metal halide as an electron injection layer between a cathode and an organic layer. Specific examples of the electron injection layer include lithium oxide (Li ₂ O), magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ) as a metal oxide, and lithium fluoride (LiF) as a metal halide. Magnesium fluoride (MgF ₂ ), strontium fluoride (SrF ₂ ), or the like can be used.

  In addition, the anode material and cathode material which were mentioned above form an anode and a cathode, respectively, by forming a thin film by a vapor deposition method, sputtering method, etc. The film thickness is preferably 10 to 500 nm.

  In the light-emitting element of the present invention, light generated by recombination of carriers in the layer containing a light-emitting substance is emitted from one or both of the anode and the cathode. That is, when light is emitted from the anode, the anode is formed of a light transmissive material, and when light is emitted from the cathode side, the cathode is formed of a light transmissive material.

  In addition, a known material can be used for the layer containing a light-emitting substance, and either a low molecular material or a high molecular material can be used. Further, the layer containing a light emitting substance contains the pyrene derivative of the present invention. Note that the material for forming a layer containing a light-emitting substance includes not only an organic compound material but also a structure including an inorganic compound in part.

  In addition, the layer containing a light emitting substance includes a hole injection layer made of a hole injecting material, a hole transport layer made of a hole transporting material, a light emitting layer made of a light emitting material, and a hole made of a hole blocking material. A blocking layer (hole blocking layer), an electron transporting layer made of an electron transporting material, an electron injection layer made of an electron injecting material, etc. are appropriately combined, but may be composed of a single layer or a plurality of layers It is good also as a structure which laminated | stacked.

  In the present invention, when a pyrene derivative is used for the light-emitting layer, a layer containing a light-emitting substance can be formed by appropriately combining layers other than the light-emitting layer. That is, the layer containing a light-emitting substance has a structure in which a hole injection layer, a hole transport layer, a hole blocking layer, an electron transport layer, an electron injection layer, or the like is combined as necessary in addition to the light emitting layer. can do. Specific materials used in this case are shown below.

As the hole injecting material, a porphyrin-based compound is effective as long as it is an organic compound, and phthalocyanine (hereinafter referred to as H ₂ -Pc), copper phthalocyanine (hereinafter referred to as Cu-Pc), or the like is used. it can. In addition, there is a material in which a conductive polymer compound is chemically doped, and polyethylenedioxythiophene (hereinafter referred to as PEDOT) doped with polystyrene sulfonic acid (hereinafter referred to as PSS) can also be used.

  As the hole transporting material, an aromatic amine-based compound (that is, a compound having a benzene ring-nitrogen bond) is suitable. Examples of widely used materials include N, N′-bis (3-methylphenyl) -N, N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (hereinafter referred to as TPD). 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (hereinafter referred to as α-NPD) or 4,4′-4 ′, 4 ′ '-Tris (N-carbazolyl) -triphenylamine (hereinafter referred to as TCTA), 4,4', 4 ''-tris (N, N-diphenyl-amino) -triphenylamine (hereinafter referred to as TDATA) , 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (hereinafter referred to as MTDATA) and the like. .

Examples of the electron transporting material include tris (8-quinolinolato) aluminum (hereinafter referred to as Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (hereinafter referred to as Almq ₃ ), bis (10-hydroxybenzo [ h] -quinolinato) beryllium (hereinafter referred to as BeBq ₂ ) and other metal complexes having a quinoline skeleton or benzoquinoline skeleton, and mixed ligand complexes of bis (2-methyl-8-quinolinolato)-(4-hydroxy -Biphenylyl) -aluminum (hereinafter referred to as BAlq) is preferred. Further, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (hereinafter referred to as Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (hereinafter referred to as Zn ( BTZ) ₂ ), tris- (2- (2′hydroxyphenyl) -1-phenyl-1H-benzimidazolate) aluminum (hereinafter referred to as Al (PBI) ₃ ), oxazole, thiazole, benz Some metal complexes have an imidazole ligand.

  In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (hereinafter referred to as PBD), 1,3-bis [ Oxadiazole derivatives such as 5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (hereinafter referred to as OXD-7), 3- (4-tert-butyl Phenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole (hereinafter referred to as TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl)- Triazole derivatives such as 5- (4-biphenylyl) -1,2,4-triazole (hereinafter referred to as p-EtTAZ), bathophenanthroline (hereinafter referred to as BPhen), bathocuproin (hereinafter referred to as “p-EtTAZ”) Phenanthroline derivatives such as BCP), 2,2 ′, 2 ″-(1,3,5-benzenetriyl) -tris (1-phenyl-1H-benzimidazole (hereinafter referred to as TPBI), 1, 3,5-tris (4,4 ′, 4 ″ (1-phenyl-1H-benzimidazolyl) -benzolyl) -benzene (hereinafter referred to as TPBIBB), N-phenyl-2,4,5,7-tetrakis A benzimidazole derivative such as (1-phenyl-1H-benzimidazole (hereinafter referred to as PBIC) can be used.

  As the hole blocking material, BAlq, OXD-7, TAZ, p-EtTAZ, BPhen, BCP and the like described above can be used.

  Note that the pyrene derivative of the present invention can be used as a host material or a guest material of the light emitting layer.

Guest materials in the case where a pyrene derivative is used as the host material of the light emitting layer include quinacridone, diethylquinacridone (DEQ), rubrene, perylene, DPT, Co-6, PMDFB, BTX, ABTX, DCM, DCJT, and tris (2 -Phenylpyridine) iridium (hereinafter referred to as Ir (ppy) ₃ ), 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin-platinum (hereinafter referred to as PtOEP), etc. A triplet light-emitting material (phosphorescent material) can be used.

  Further, as a host material when a pyrene derivative is used as a guest material of the light emitting layer, TPD, α-NPD, 4,4′-bis (carbazolyl) -biphenyl (hereinafter referred to as CBP), TCTA, PBD, OXD- 7, BCP, etc. can be used.

  As described above, a light-emitting element is formed using the pyrene derivative of the present invention, which has material characteristics that emit light efficiently, has excellent heat resistance, forms a homogeneous film, and does not easily crystallize and has stable film quality. Thus, a light-emitting element that can emit light efficiently and stably for a long time can be manufactured.

(Embodiment 3)
In this embodiment mode, a light-emitting device of the present invention will be described.

  In this embodiment mode, a light-emitting element using the pyrene derivative of the present invention described in Embodiment Mode 2 is manufactured over a substrate formed of glass, quartz, transparent plastic, or the like. A passive light-emitting device can be manufactured by manufacturing a plurality of such light-emitting elements over one substrate.

  In addition to a substrate made of glass, quartz, transparent plastic, or the like, a light emitting element in contact with a thin film transistor (TFT) array may be manufactured, for example, as shown in FIG. Thus, an active matrix light-emitting device in which driving of the light-emitting element is controlled by the TFT can be manufactured. In FIG. 5, TFT 11 and TFT 12 are formed on a substrate 10, and a light emitting element 13 is connected. Specifically, when a current is passed from the TFT 11 to the first electrode 14 via the wiring 17, an electric field is applied between the first electrode 14 and the second electrode 16, and the layer 15 containing a light emitting substance is formed. Emits light. Although FIG. 5 shows a gate of a staggered TFT, the structure of the TFT is not particularly limited. For example, a staggered type or an inverted staggered type may be used. Further, the crystallinity of the semiconductor layer constituting the TFT is not particularly limited, and may be crystalline or amorphous.

  In Example 1, a synthesis example of the pyrene derivative of the present invention represented by the structural formula (2) is specifically illustrated.

  First, according to the above reaction scheme (A-1), 10.4 g (44.8 mmol) of 2-bromobiphenyl distilled under a nitrogen atmosphere was added to a dry tetrahydrofuran (hereinafter referred to as THF) solution, and then 1.56 N -A hexane solution of butyllithium (31 ml, 48 mmol) was added dropwise at -78 ° C. After completion of dropping, the mixture was stirred at -78 ° C for 1 hour. After completion of the stirring, the above suspension is added to the dried zinc chloride under a nitrogen atmosphere and stirred at room temperature for 1 hour. After completion of the stirring, 4.64 g (9.0 mmol) of 1,3,6,8-tetrabromopyrene is added, and 517 mg (0.45 mmol) of tetrakistriphenylphosphine palladium is further added. Then reflux for 24 hours. After completion of the reflux, the reaction solution is concentrated, and the precipitated solid is washed with 3% hydrochloric acid, water and ethanol, and further washed with hexane. Finally, it was washed with a small amount of THF to obtain a light blue powder, 1,3,6,8-tetra-2- (phenyl) phenyl-pyrene (the above structural formula (2); hereinafter referred to as TBiPy). . The yield at this time was 48%.

The thermal decomposition temperature of the obtained TBiPy was found to be 414 ° C. from TG-DTA measurement. The results of DSC measurement are shown in FIG. 2 that the glass transition point T _g is 148 ° C., the crystallization temperature T _c is 260 ° C., and the melting point T _m is 304 ° C. As described above, it was found that the pyrene derivative of the present invention has a high glass transition point, a melting point, and a decomposition temperature, and is excellent in heat resistance. Further, in FIG. 2, the peak indicating the crystallization temperature is unclear, suggesting that the material is difficult to crystallize. Actually, when a film was formed by using a vacuum deposition method, a homogeneous film could be formed.

When the fluorescence spectrum of the TBiPy thin film was measured, a fluorescence spectrum having a maximum peak at 457 nm with respect to the excitation wavelength (355 nm) was obtained (FIG. 3).
Further, when the ultraviolet / visible region absorption spectrum of the TBiPy thin film was measured, the maximum absorption wavelength was obtained at 389 nm (FIG. 4).

  Furthermore, the value of the HOMO level measured using the photoelectron spectrometer AC-2 (manufactured by Riken Keiki Co., Ltd.) was −5.77 eV. 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. 4) as the energy gap was −2.79 eV.

  In this embodiment, a light-emitting element is manufactured using the pyrene derivative of the present invention as part of a layer containing a light-emitting substance. Specifically, the case of using the pyrene derivative of the present invention as a light-emitting layer is described. The element structure will be described with reference to FIG.

  First, the first electrode 101 of the light emitting element is formed over the substrate 100. Note that in this embodiment, the first electrode 101 functions as an anode. The material is ITO, which is a transparent conductive film, and is formed with a film thickness of 110 nm by a sputtering method.

  Next, a layer 102 containing a light-emitting substance is formed over the first electrode (anode) 101. Note that the layer 102 containing a light-emitting substance in this embodiment includes a hole injection layer 111, a hole transport layer 112, a light emission layer 113, a hole blocking layer (hole blocking layer) 114, an electron transport layer 115, and an electron injection layer 116. It has the laminated structure which consists of.

  The substrate on which the first electrode 101 is formed is fixed to a substrate holder of a commercially available vacuum deposition apparatus with the surface on which the first electrode 101 is formed facing downward, and copper is attached to the evaporation source provided in the vacuum deposition apparatus. Phthalocyanine (hereinafter referred to as Cu-Pc) is added, and the hole injection layer 111 is formed with a thickness of 20 nm by a vapor deposition method using a resistance heating method. Note that a known hole injecting material can be used as a material for forming the hole injecting layer 111.

  Next, the hole transport layer 112 is formed using a material having excellent hole transportability. As a material for forming the hole transport layer 112, a known hole transport material can be used. In this embodiment, α-NPD is used to form a film with a thickness of 40 nm.

  Next, the light emitting layer 113 is formed. Note that holes and electrons recombine in the light-emitting layer 113 to emit light. In this embodiment, TBiPy is used as a material for forming the light-emitting layer 113 as a pyrene derivative of the present invention, and is formed by a vapor deposition method with a thickness of 30 nm.

  Next, the hole blocking layer 114 is formed. As a material for forming the hole blocking layer 114, a known electron transporting material can be used. In this embodiment, BAlq is used and a film thickness of 10 nm is formed by an evaporation method.

Next, the electron transport layer 115 is formed. As a material for forming the electron transport layer 115, a known electron transport material can be used. In this embodiment, Alq ₃ is used and a film thickness of 20 nm is formed by a vapor deposition method.

Next, the electron injection layer 116 is formed. As a material for forming the electron injection layer 116, a known electron injection material can be used. In this embodiment, calcium fluoride (hereinafter referred to as CaF ₂ ) is used, and a deposition method is performed with a film thickness of 2 nm. To form.

  In this manner, the layer 102 containing a luminescent substance formed by stacking the hole injection layer 111, the hole transport layer 112, the light emitting layer 113, the hole blocking layer 114, the electron transport layer 115, and the electron injection layer 116. Then, the second electrode 103 functioning as a cathode is formed by a sputtering method or an evaporation method. Note that in this embodiment, the second electrode 103 is obtained by forming aluminum (150 nm) over the layer 102 containing a light-emitting substance by an evaporation method.

  Thus, a light-emitting element using the pyrene derivative of the present invention is formed.

When a voltage is applied to the formed light-emitting element, blue light emission is observed at a voltage of 5 V or more at the light-emitting element, and blue light emission with an emission luminance of 2098 cd / m ² at the applied voltage of 10 V (light emission CIE color coordinate: x = 0.169, y = 0.162) were observed. The luminous efficiency at that time was 1.03 cd / A.

  In this example, the case of using the pyrene derivative of the present invention as the guest material of the light-emitting layer will be described with reference to FIGS. In this example, the configurations of the first electrode, the second electrode, the hole injection layer, the hole transport layer, the hole blocking layer, the electron transport layer, and the electron injection layer are the same as in Example 1. Description is omitted.

  As shown in FIG. 6, the light emitting layer 213 formed in contact with the hole transport layer 212 in the layer 202 containing the light emitting substance formed over the first electrode 201 is formed of the host material and the pyrene derivative of the present invention. It forms by using the guest material which is.

  Specifically, CBP is used as a host material, TBiPy is used as a guest material, and a film thickness of 30 nm is formed by a co-evaporation method. The ratio of the guest material was 5 wt%.

  In this manner, the layer 202 containing a light-emitting substance formed by stacking the hole injection layer 211, the hole transport layer 212, the light emitting layer 213, the hole blocking layer 214, the electron transport layer 215, and the electron injection layer 216. By forming the second electrode 203 thereon, a light-emitting element using the pyrene derivative of the present invention is formed over the substrate 200.

When a voltage is applied to the formed light emitting element, blue light emission is observed at a voltage of 7 V or more at the light emitting element, and blue light emission (light emission CIE color coordinate: x = 0) at an emission voltage of 74 cd / m ² is applied. 170, y = 0.159) was observed. The luminous efficiency at this time was 1.43 cd / A.

Since the pyrene derivative of the present invention has an efficient light-emitting property, it can be used as a guest material in a light-emitting layer including a light-emitting substance as shown in this embodiment. In addition, since the pyrene derivative of the present invention has excellent heat resistance and is difficult to crystallize when formed, the lifetime of the light-emitting element can be increased.

(Comparative Example 1)
In this comparative example, 1, 3, 6, 8-tetra (4-biphenylyl) pyrene (hereinafter referred to as t (bp) py) is used as the guest material of the light emitting layer, and the other configuration is the example. An element similar to 3 is described with reference to FIG.

  As shown in FIG. 7, the light-emitting layer 313 formed in contact with the hole-transport layer 312 among the layers 302 containing the light-emitting substance formed over the first electrode 301 is formed using the host material and the t of this comparative example. (Bp) It is formed by using a guest material that is py.

  Specifically, CBP is used as a host material, t (bp) py is used as a guest material, and a film thickness of 30 nm is formed by a co-evaporation method. The ratio of the guest material was 5 wt% as in Example 3.

  In this manner, the layer 302 containing a light-emitting substance formed by stacking the hole injection layer 311, the hole transport layer 312, the light emitting layer 313, the hole blocking layer 314, the electron transport layer 315, and the electron injection layer 316. By forming the second electrode 303 thereon, a light-emitting element using t (bp) py is formed over the substrate 300.

When a voltage is applied to the formed light-emitting element, blue light emission is observed at a voltage of 6 V or more in the light-emitting element, and blue light emission (light emission CIE color coordinate: x = 0) at an emission voltage of 296 cd / m ² is applied. .154, y = 0.140). The luminous efficiency at this time was 1.03 cd / A, which was slightly inferior to that of Example 3 having the same element configuration. Furthermore, the film quality of this light emitting device was deteriorated as compared with the cases of Examples 2-3.

In this embodiment, a light-emitting device having the light-emitting element of the present invention in a pixel portion will be described with reference to FIG. 8A is a top view illustrating the light-emitting device, and FIG. 8B is a cross-sectional view taken along line A-A ′ in FIG. 8A. Reference numeral 601 indicated by a dotted line denotes a driving circuit portion (source side driving circuit), 602 denotes a pixel portion, and 603 denotes a driving circuit portion (gate side driving circuit). Reference numeral 604 denotes a sealing substrate, reference numeral 605 denotes a sealing material, and the inside surrounded by the sealing material 605 is a space 607.

  Note that the routing wiring 608 is a wiring for transmitting a signal input to the source side driving circuit 601 and the gate side driving circuit 603, and a video signal, a clock signal, an FPC (flexible printed circuit) 609 serving as an external input terminal, Receives start signal, reset signal, etc. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes not only a light-emitting device body but also a state in which an FPC or a PWB is attached thereto.

  Next, a cross-sectional structure is described with reference to FIG. A driver circuit portion and a pixel portion are formed over the element substrate 610. Here, a source side driver circuit 601 that is a driver circuit portion and a pixel portion 602 are shown.

  Note that the source side driver circuit 601 is a CMOS circuit in which an n-channel TFT 623 and a p-channel TFT 624 are combined. The TFT forming the driving circuit may be formed by a known CMOS circuit, PMOS circuit or NMOS circuit. Further, in this embodiment, a driver integrated type in which a drive circuit is formed on a substrate is shown, but this is not always necessary, and it can be formed outside the substrate.

  The pixel portion 602 is formed by a plurality of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain thereof. Note that an insulator 614 is formed so as to cover an end portion of the first electrode 613. Here, a positive photosensitive acrylic resin film is used.

  In order to improve the film forming property, a curved surface having a curvature is formed at the upper end portion or the lower end portion of the insulator 614. For example, when positive photosensitive acrylic is used as a material for the insulator 614, it is preferable that only the upper end portion of the insulator 614 has a curved surface with a curvature radius (0.2 μm to 3 μm). As the insulator 614, either a negative type that becomes insoluble in an etchant by photosensitive light or a positive type that becomes soluble in an etchant by light can be used.

  Over the first electrode 613, a layer 616 containing a light-emitting substance and a second electrode 617 are formed. Here, as a material used for the first electrode 613 functioning as an anode, a material having a high work function is preferably used. For example, in addition to a single layer film such as an ITO film, an indium oxide film containing 2 to 20% zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a titanium nitride film and aluminum are the main components. For example, a three-layer structure including a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film can be used. Note that with a stacked structure, resistance as a wiring is low, good ohmic contact can be obtained, and a function as an anode can be obtained.

  The layer 616 containing a light-emitting substance is formed by an evaporation method using an evaporation mask or an inkjet method. The layer 616 containing a light-emitting substance contains the pyrene derivative of the present invention. The material used in combination with these pyrene derivatives may be a low molecular material, a medium molecular material (including oligomers and dendrimers), or a high molecular material. In addition, as a material used for a layer including a light-emitting substance, an organic compound is usually used in a single layer or a stacked layer. However, in the present invention, a structure in which an inorganic compound is used for part of a film formed of an organic compound is also included. I will do it.

Furthermore, as a material used for the second electrode (cathode) 617 formed over the layer 616 containing a light-emitting substance, a material having a low work function (Al, Ag, Li, Ca, or alloys thereof MgAg, MgIn, AlLi , CaF ₂ , or CaN) may be used. Note that in the case where light generated in the layer 616 containing a light-emitting substance passes through the second electrode 617, a thin metal film and a transparent conductive film (ITO, A stack with indium oxide containing 2 to 20% zinc oxide, zinc oxide (ZnO), or the like is preferably used.

  Further, the sealing substrate 604 is bonded to the element substrate 610 with the sealant 605, whereby the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. Yes. Note that the space 607 includes a structure filled with a sealant 605 in addition to a case where the space 607 is filled with an inert gas (nitrogen, argon, or the like).

  Note that an epoxy-based resin is preferably used for the sealant 605. Moreover, it is desirable that these materials are materials that do not transmit moisture and oxygen as much as possible. In addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), Mylar, polyester, acrylic, or the like can be used as a material for the sealing substrate 604.

  As described above, a light-emitting device having the light-emitting element of the present invention can be obtained. In such a light-emitting device using the present invention, since crystallization in the light-emitting element is suppressed, stable light emission can be obtained for a long time.

  Note that the light-emitting device described in this embodiment can be implemented by freely combining the structures of the light-emitting elements described in Embodiments 1 to 3.

  In this embodiment, various electric appliances completed using a light-emitting device having a light-emitting element according to the present invention will be described.

  As an electric appliance in which a light emitting device formed using the present invention is mounted, a video camera, a digital camera, a goggle type display, a navigation system, a sound reproduction device (car audio, audio component, etc.), a personal computer, a game machine, portable information A terminal (mobile computer, mobile phone, portable game machine, electronic book, etc.), an image playback device equipped with a recording medium (specifically, a recording medium such as a digital video disc (DVD)) is played back, and the image is displayed. And a display device). FIG. 9 illustrates and describes some of these electronic devices.

  FIG. 9A illustrates a display device, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. It is manufactured by using a light emitting device formed using the present invention for the display portion 2003. The display device includes all information display devices such as a computer, a TV broadcast receiver, and an advertisement display.

  Here, FIG. 9B shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The display device 2703 is manufactured using the light-emitting device having the light-emitting element of the present invention.

  As described above, the applicable range of the light-emitting device having the light-emitting element of the present invention is extremely wide, and the light-emitting element used for the light-emitting device is formed using the pyrene derivative of the present invention, and thus has a low driving voltage and a long lifetime. It has the feature of being. Therefore, by applying this light-emitting device to electric appliances in various fields, low power consumption and long life (that is, a good display image can be obtained for a long time) can be realized.

3A and 3B each illustrate an element structure of a light-emitting element of the present invention. The figure which shows the DSC chart of a pyrene derivative. The figure which shows the fluorescence spectrum of a pyrene derivative. The figure which shows the ultraviolet and visible region absorption spectrum of a pyrene derivative. FIG. 6 illustrates a light-emitting device. 3A and 3B each illustrate an element structure of a light-emitting element of the present invention. 3A and 3B each illustrate an element structure of a light-emitting element of the present invention. FIG. 6 illustrates a light-emitting device. The figure explaining an electric appliance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Substrate 101 First electrode 102 Layer 103 containing luminescent substance Second electrode 111 Hole injection layer 112 Hole transport layer 113 Light emission layer 114 Hole blocking layer 115 Electron transport layer 116 Electron injection layer

Claims (5)

A pyrene derivative represented by the following general formula (1).

(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an aryl group, a diarylamino group, an alkyl group or an aryl group. It represents any substituent selected from the group consisting of one or more silyl groups as substituents.) A light-emitting element including a pyrene derivative represented by the following general formula (1) between a pair of electrodes.

(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an aryl group, a diarylamino group, an alkyl group or an aryl group. It represents any substituent selected from the group consisting of one or more silyl groups as substituents.) A light-emitting element including a light-emitting layer including a pyrene derivative represented by the following general formula (1) between a pair of electrodes.

(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an aryl group, a diarylamino group, an alkyl group or an aryl group. It represents any substituent selected from the group consisting of one or more silyl groups as substituents.) A light-emitting device using the light-emitting element according to claim 2. An electric appliance having the light emitting device according to any one of claims 1 to 4, wherein the video camera, a digital camera, a goggle type display, a navigation system, a sound reproducing device, a personal computer, a game machine, and portable information An electric appliance selected from an image reproducing device provided with a terminal and a recording medium.

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