JP3829848B2 - EL device using polythiophene - Google Patents

Description

  The present invention relates to an EL (electroluminescence) device using polythiophene, and more particularly to a device that emits light by applying an electric field to a laminated thin film made of an organic compound.

  An organic EL element has a configuration in which a thin film containing a fluorescent organic compound is sandwiched between a cathode and an anode, and excitons (excitons) are generated by injecting electrons and holes into the thin film and recombining them. It is an element that emits light by utilizing light emission (fluorescence, phosphorescence) when this exciton is deactivated.

The characteristics of the organic EL element are that it can emit surface light with a high luminance of about 100 to 10,000 cd / m ² at a low voltage of about 10 V, and can emit light from blue to red by selecting the type of fluorescent material. That is.

  On the other hand, the problems of organic EL devices are that the light emission life is short, the storage durability and the reliability are low, and this is due to 1) physical changes of organic compounds (due to the growth of crystal domains, etc.) Non-uniform interface causes deterioration of charge injection capability of the device, short circuit and dielectric breakdown, especially when low molecular weight compounds with a molecular weight of 500 or less are used, the appearance and growth of crystal grains occur and the film properties are significantly reduced. In addition, even if the interface of ITO or the like is rough, the appearance and growth of remarkable crystal grains occur, resulting in a decrease in light emission efficiency, current leakage, and no light emission. Spot))),

  2) Cathodic oxidation and delamination (Na, Mg, Al, etc. have been used as metals with a low work function to facilitate electron injection, but these metals react with moisture and oxygen in the atmosphere. In other words, when the organic compound layer is peeled off from the cathode and charge injection cannot be performed, especially when a polymer compound is used and the film is formed by spin coating or the like, the residual solvent or decomposition product during the film formation causes oxidation reaction of the electrode. ), Peeling of the electrode occurs and a partial non-light emitting part is generated).

  3) Low luminous efficiency and large calorific value (current flows through the organic compound, so the organic compound must be placed under a high electric field strength, and it cannot escape from the heat generation. Degradation or destruction of the device occurs due to melting, crystallization, thermal decomposition, etc.),

  4) Photochemical and electrochemical changes of the organic compound layer occur.

  In particular, in order to solve the above problem 1), low molecular weight amorphous compounds and high molecular compounds have been studied. However, although low molecular weight compounds can be deposited, sufficient thin film stability cannot be obtained. In addition, although polymer compounds have thin film stability, they cannot be deposited, so a laminated structure cannot be adopted, and residual solvents and impurities are mixed in to form a film by spin coating, etc., and the deterioration of electrodes and organic substances is significant. There is a big problem. On the other hand, although a polymer that can be deposited recently has been reported (for example, see Non-Patent Document 1), light emission with practical luminance has not been obtained yet.

  Moreover, since the transparent electrode needs to have a low surface resistance (10 to 30Ω / □ or less), ITO glass or the like is used. However, according to the observation with scanning tunneling microscope (STM) and atomic force microscope (AFM), there are unevenness of 200 angstroms on the sputter deposition substrate and 400 angstroms on the EB evaporation substrate, and surface roughness due to damage during ITO patterning There is an environment where crystallization of the organic thin film is easily promoted.

  In order to improve this, measures such as providing a phthalocyanine film on the ITO surface (see, for example, Patent Document 1) or spin-coating polyarylene vinylene have been taken. However, phthalocyanine is microcrystalline and not always effective, and polyarylene vinylene is damaged by the acid at the time of conversion, oxidation of the electrode is accelerated by residual solvent, etc. Since the film was non-uniform, the reliability of the device was not improved.

  Therefore, application of an organic compound that can improve these problems is desired.

  On the other hand, various EL devices having a mixed layer in which two or more compounds having different functions are mixed have recently been proposed for the purpose of improving device performance. For example, in Patent Document 2, for the purpose of improving luminance and durability, a thin film or a mixed thin film of an organic compound having a hole transporting ability and a light emitting function and an organic compound having an electron transporting ability is used as a light emitting layer. In addition, Patent Document 3 proposes that a thin film of a mixture of an organic compound having a hole transporting function and a fluorescent organic compound having an electron transporting function be used for the light emitting layer. Further, Patent Document 4 proposes to provide a mixed layer in which a charge injection material and an organic phosphor are mixed between the charge injection layer and the light emitting layer for the purpose of improving the light emission efficiency and the light emission luminance. . Patent Document 5 discloses that a hole transport layer and / or an electron transport layer and an organic light emitting layer face each other for the purpose of facilitating injection of holes and electrons into the light emitting layer. It has been proposed to provide a mixed layer containing the constituent materials of both layers. Further, in Patent Document 6, when a plurality of organic compound layers are formed, a layer in which compounds having different functions coexist, for example, a layer containing a hole transporting light emitting material, a hole transporting light emitting material, and an electron transporting property. It has been proposed to provide a layer in which the material coexists to increase the luminance of light emission and to exhibit various emission hues and to improve durability. Patent Document 7 proposes that a mixed layer made of a light emitting substance and a charge injection substance is formed between the light emitting layer and the charge injection layer to reduce the driving voltage. Further, in Patent Document 8, the light-emitting layer is made of a thin film in which a hole-conducting organic compound and a rare earth metal organic complex are mixed, and the emission spectrum width is narrow and excellent in monochromaticity, and the conversion efficiency is improved. It has been proposed that Patent Document 9 and Patent Document 10 provide a thin film layer in which the components of the organic light-emitting material thin film layer are a mixture of an organic charge material and an organic light-emitting material, prevent concentration quenching, and widen the selection range of the light-emitting material. It has been proposed to provide a high-luminance full-color element. Further, Patent Document 11 proposes to form a gradient structure layer having a concentration gradient with each component forming each layer between layers, thereby reducing drive voltage and improving durability.

  Furthermore, what uses rubrene for the organic compound layer is proposed. As an organic compound layer doped with rubrene, in an organic EL device having a hole transport layer made of a mixed film of hydrazine derivatives and a light emitting layer of tris (8-quinolinolato) aluminum as the organic compound layer, a hole transport layer In addition, rubrene is doped with rubrene, or the organic interface side half of the hole transport layer and the entire light emitting layer are doped with rubrene. When the hole transport layer is doped, light emission occurs from both tris (8-quinolinolato) aluminum and rubrene. When the hole transport layer and the light emitting layer are doped, the luminous efficiency is improved. In addition, it has been reported that an increase in dark spots during storage can be suppressed (see, for example, Non-Patent Document 2 and Non-Patent Document 3). Further, a triphenyldiamine derivative (TPD) hole transport layer doped with rubrene has been proposed, and it has been reported that the luminance half-life is improved (for example, see Non-Patent Document 4).

Patent Document 12 proposes an organic compound thin film layer composed of a p-type inorganic semiconductor thin film layer and a layer mainly composed of rubrene, so that sufficient emission luminance and stability of emission luminance can be obtained. It is described that
JP 63-295695 A JP-A-2-250292 JP-A-2-291696 JP-A-3-114197 Japanese Patent Laid-Open No. 3-190088 JP-A-4-334894 JP-A-5-182762 JP-A-3-289090 JP-A-4-178487 Japanese Patent Laid-Open No. 5-78655 JP-A-4-357694 JP-A-2-207488 Takashi Fukuda et al., Proceedings of the 41st Annual Meeting of the Polymer Society of Japan (1992) IL-29 Kanai, Yajima, Sato, Proceedings of the 39th Joint Conference on Applied Physics, 28p-Q-8 (1992) Sato, Kanai, Organic Electronics Materials Society (JOEM) Workshop 92 Proceedings, 31 (1992) Fujii, Sano, Fujita, Hamada, Shibata, Proceedings of the 54th Applied Physics Academic Conference, 29p-ZC-7 (1993)

  However, none of these EL elements is satisfactory in terms of improving the light emission lifetime.

  The object of the present invention is to use a photoelectron functional material having a small physical change, photochemical change, and electrochemical change as a hole injecting and transporting material and a light emitting material, and having various emission colors with high reliability and light emission efficiency. This is to realize an EL element using polythiophene. In particular, a high-reliability, high-intensity light-emitting device that uses an organic thin film formed by vapor deposition of a compound with a high molecular weight and suppresses voltage rise and current leakage when driving the device, and the appearance and growth of partial non-light emitting parts. Is to realize.

  It is another object of the present invention to provide an EL element using polythiophene that improves the light emission lifetime and particularly suppresses the initial decrease in luminance.

Such an object is achieved by the present invention of the following (1) to ( 11 ).
(1) It has a first hole injecting and transporting layer and a light emitting layer, and this first hole injecting and transporting layer contains at least one of the polymers represented by the following chemical formula 1, and Has at least one different hole injection transport layer,
The first hole injection transport layer is formed on the anode surface, the second hole injecting and transporting layer laminated on the first hole injection transport layer of the different hole injection transport layer and this is an aromatic three Containing a secondary amine and doped with rubrene, wherein the layer containing at least one of the polymers is formed by vacuum deposition , and has a layer doped with a fluorescent substance, An EL device using polythiophene.

[In Chemical Formula 1, R ₃ and R ₄ each represent a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and these may be the same or different. R ₃ and R ₄ may be bonded to each other to form a ring. X ₁ and X ₂ each represent a hydrogen atom or a halogen atom, and these may be the same or different. n is 4-100. ]
( 2 ) An EL device using the polythiophene according to (1) above, wherein tris (8-quinolinolato) aluminum is further laminated on the second hole injecting and transporting layer.
( 3 ) An EL device using the polythiophene of (1) or (2 ) further having an electron injecting and transporting layer.
( 4 ) In the EL device using the polythiophene according to any one of the above (1) to ( 3 ), each has at least one layer containing a hole injection / transport compound and a layer containing an electron injection / transport compound. , EL using a polythiophene in which the difference in ionization potential Ip or the electron affinity Ea between the hole injecting and transporting compound and the electron injecting and transporting compound in the layer is 0.2 eV or more element.
( 5 ) The electron-injecting / transporting compound, wherein the layer containing the hole-injecting / transporting compound is laminated on the first hole-injecting / transporting layer and includes the second hole-injecting / transporting layer. An EL device using the polythiophene according to ( 4 ) above, wherein a layer containing is further laminated on the layer containing the hole injecting and transporting compound.
( 6 ) In the EL device using the polythiophene according to any one of (1) to ( 5 ), a polythiophene having at least one layer containing a mixture of a hole injecting / transporting compound and an electron injecting / transporting compound is used. EL element.
( 7 ) An EL device using the polythiophene according to ( 6 ), wherein the layer containing the mixture is a light emitting layer.
( 8 ) The above ( 6 ) or ( 7 ), wherein the difference in ionization potential Ip or electron affinity Ea between the hole injecting and transporting compound and the electron injecting and transporting compound, or the difference between them is 0.2 eV or more. EL element using the polythiophene.
( 9 ) An EL device using the polythiophene according to any one of ( 4 ) to ( 8 ), wherein the absolute value of the ionization potential Ip of the hole injection / transport compound is 5.4 eV or less.
( 10 ) An EL device using the polythiophene according to any one of ( 4 ) to ( 9 ), wherein the electron injecting / transporting compound is tris (8-quinolinolato) aluminum.
( 11 ) An EL device using the polythiophene according to any one of (1) to ( 10 ), wherein the fluorescent substance is rubrene.

(14) A layer containing at least one of a polymer having a structural unit represented by the following chemical formula 2 and a copolymer having a structural unit represented by the following chemical formula 2 and a structural unit represented by the following chemical formula 3 EL element using polythiophene having at least one layer.

[In Chemical Formula 2, R ₁ and R ₂ each represent a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and these may be the same or different. In Chemical Formula 3, R ₃ and R ₄ each represent a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, which may be the same or different. R ₃ and R ₄ may be bonded to each other to form a ring. However, in any polymer or copolymer, the terminal group is a hydrogen atom or a halogen atom. ]
(15) An EL device using the polythiophene according to (14), wherein a layer containing at least one of the polymer and the copolymer is formed by a vacuum deposition method.
(16) An EL device using the polythiophene according to (14) or (15), wherein the light-emitting layer contains at least one of the polymer and the copolymer.
(17) An EL device using the polythiophene according to (16), wherein the light emitting layer also serves as a hole injecting and transporting layer.
(18) The method according to (14) or (15) above, comprising a hole injecting and transporting layer and a light emitting layer, wherein the hole injecting and transporting layer contains at least one of the polymer and the copolymer. An EL device using polythiophene.
(19) In addition to the hole injecting and transporting layer containing at least one of the polymer and the copolymer, and further comprising at least one hole injecting and transporting layer different from the above (18) EL device using polythiophene.
(20) An EL device using the polythiophene according to (18) or (19) further having an electron injecting and transporting layer.

  In the present invention, a polymer having a structural unit represented by Chemical Formula 2 (hereinafter, also referred to as “polymer I”) and a copolymer having a structural unit represented by Chemical Formula 2 and a structural unit represented by Chemical Formula 3 ( Hereinafter, one or more of “copolymer II”) is used as a light emitting material or hole injecting and transporting material, and a polymer represented by chemical formula 1 (hereinafter also referred to as “polymer III”). As a hole injecting and transporting material, it is used for a light emitting layer and a hole injecting and transporting layer.

  Since all of the above polymers have a five-membered ring with an excess of π electrons, the ionization potential is small and the ability to inject holes is very high, so that the driving voltage can be lowered when used as a hole material. . Further, since the molecule itself is relatively linear and the distance between molecules in the film state is short, the hole mobility is high and the hole transport ability is excellent. Therefore, by controlling the thickness of the combined light-emitting layer, electron-injecting and transporting layer, or hole-injecting and transporting layer, the degree of freedom in the design of the recombination region is improved, which depends on the design of the emission spectrum and the interference effect of both electrodes. The light emission luminance and the spatial distribution of the light emitting region of the element can be controlled.

Therefore, the polymer can be used as appropriate in the light emitting layer and the hole injecting and transporting layer, and when used in the hole injecting and transporting layer, high brightness of about 100 to 1000 cdm ^-2 or more is stable. can get. In addition, it has high heat resistance and durability, and can be driven stably even at an element current density of about 1000 mAcm ⁻² .

  In addition, the polymer thin film is almost amorphous and has good film quality, so that there is no unevenness and uniform light emission is possible.

  Further, the EL element of the present invention emits light efficiently at a low voltage.

  The emission maximum wavelength of the EL element of the present invention is about 350 to 700 nm. In particular, the emission maximum wavelength when one or more of the above-mentioned polymer I and copolymer II is used in the light emitting layer as a light emitting material is 400 to 400 by selecting the degree of polymerization, the bonding position and the substituent. It can be anything up to 700 nm. Therefore, blue light emission can be obtained stably.

  In addition, “Takashi Fukuda et al., 41st (1992) Annual Meeting of Polymer Science Society Proceedings 1L-29” discloses the same vacuum deposition of poly (thiophene-2,5-diyl) as the polymer III of the present invention. An EL element having a film as a light emitting layer has been reported. This material uses poly (thiophene-2,5-diyl) as a light emitting material. As in the present invention, other fluorescent substances are used for the light emitting layer. There is no suggestion of a configuration in which an injection transport layer is separately provided and poly (thiophene-2,5-diyl) is used for the hole injection transport layer. Therefore, the use of poly (thiophene-2,5-diyl) as the hole injecting and transporting layer material has been revealed for the first time by the invention of this application.

  According to the present invention, an EL element using polythiophene that can stably obtain high luminance is realized. In addition, heat resistance and durability are high, and stable driving is possible. Furthermore, there is no unevenness and uniform light emission is possible, and light is emitted efficiently at a low voltage.

  In the case where the mixed layer is a light emitting layer, the initial luminance is not lowered and the light emission life is extended. In addition, when rubrene is doped, the initial luminance is improved and the light emission lifetime is extended.

  Hereinafter, a specific configuration of the present invention will be described in detail.

  An EL device using the polythiophene of the present invention (hereinafter also referred to as “EL device”) uses a polymer I, a copolymer II, and a polymer III, which are polythiophenes having a specific structure. In this case, the polymer I and the copolymer II are used for the light emitting layer and the hole injection transport layer, and the polymer III is used for the hole injection transport layer.

  First, the polymer I will be described. The polymer I has a structural unit of Chemical Formula 2, and is represented by Chemical Formula 4, for example.

When chemical formula ₂ and chemical formula 4 are described, R ₁ and R ₂ each represent a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, which may be the same or different.

The aromatic hydrocarbon group represented by R ₁ and R ₂ may be unsubstituted or substituted, and preferably has 6 to 15 carbon atoms. Examples of the substituent when having a substituent include an alkyl group, an alkoxy group, an amino group, and a cyano group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a methoxyphenyl group, a biphenyl group, and a naphthyl group.

Examples of the aliphatic hydrocarbon group represented by R ₁ and R ₂ include an alkyl group and a cycloalkyl group, and these may be unsubstituted or may have a substituent. Especially, a C1-C6 thing is preferable and a methyl group, an ethyl group, i-propyl group, t-butyl group etc. are mentioned specifically ,.

R ₁ and R ₂ are preferably a hydrogen atom or an aromatic hydrocarbon group, particularly preferably a hydrogen atom.

The average degree of polymerization of the polymer I in the layer (m in Chemical Formula 4) is 4 to 100, preferably 5 to 40, and more preferably 5 to 20. In this case, even if the repeating unit represented by Chemical Formula 2 is the same polymer (homopolymer), it is a copolymer (copolymer) composed of structural units having different combinations of R ₁ and R ₂ in Chemical Formula _2. There may be. The copolymer may be any of a random copolymer, an alternating copolymer, a block copolymer and the like.

  Moreover, the weight average molecular weight of the polymer I in a layer is about 300-10000.

The terminal group (X ₁ and X _{2 in} Chemical Formula 4) of the polymer I is a hydrogen atom, a halogen atom such as chlorine, bromine or iodine. This end group is generally introduced depending on the starting material in the synthesis of the polymer I. Furthermore, other substituents can be introduced at the final stage of the polymerization reaction.

  In addition, it is preferable that the polymer I is comprised only by the structural unit of Chemical formula 2, but if it is 10 mol% or less, it may contain the other monomer component.

A specific example of the polymer I is shown in Chemical formula 5. In the chemical formula 5, the combination of R ₁ and R ₂ of the chemical formulas _{2 to} 4 is shown.

  Next, the copolymer II will be described. Copolymer II has a structural unit of Chemical Formula 2 and a structural unit of Chemical Formula 3, and is represented by Chemical Formula 6, for example.

Chemical formula 2 is the same as that of the polymer I. Therefore, R ₁ and R ₂ in Chemical Formula 6 are the same as those in Chemical Formula ₂ .

Regarding chemical formula ₃ , R ₃ and R ₄ each represent a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, which may be the same or different.

Specific examples of the aromatic hydrocarbon group and the aliphatic hydrocarbon group represented by R ₃ and R ₄ can be the same as those described for R ₁ and R _{2 in} Chemical Formula ₂ . Also preferred for R ₃ and R ₄ are the same as R ₁ and R ₂ . Further, R ₃ and R ₄ may be bonded to each other to form a ring and condensed to a thiophene ring. In this case, examples of the condensed ring include a benzene ring. The same applies to R ₃ and R ₄ in Chemical Formula 6.

  The average degree of polymerization of copolymer II in the layer (v + w in chemical formula 6) is 4 to 100, preferably 5 to 40, more preferably 5 to 20, as with polymer I. Further, the ratio of the structural unit of chemical formula 2 to the structural unit of chemical formula 3 is about 10/1 to 1/10 in molar ratio of the structural unit of chemical formula 2 / the structural unit of chemical formula 3.

  The weight average molecular weight of the copolymer II in the layer is about 300 to 10,000.

Further, the end groups (X ₁ and X ₂ in Chemical Formula 6) of the copolymer II are the same as those of the polymer I, and generally depend on the starting material or the ratio thereof in the synthesis of the copolymer II.

  The copolymer II is preferably composed of a structural unit of Chemical Formula 2 and a structural unit of Chemical Formula 3 as in the case of the polymer I. However, if it is 10 mol% or less, it contains other monomer components. It may be. Further, the copolymer II may be any of a random copolymer, an alternating copolymer, a block copolymer, etc., and the structural formula of Chemical Formula 6 includes such a structure. Furthermore, the structural units of Chemical Formula 2 and Chemical Formula 3 may be the same or different.

A specific example of copolymer II is shown in Chemical formula 7. In the chemical formula 7, the combination of R ₁ and R ₂ of the chemical formula ₂ , the combination of R ₃ and R ₄ of the chemical formula ₃ , that is, the combination of R ₁ , R ₂ , R ₃ and R ₄ of the chemical formula 6 is shown.

Further, the polymer III of Chemical Formula 1 will be described. When chemical formula 1 is described, R ₃ and R ₄ have the same meanings as those of chemical formula 3, and preferred ones are also the same.

X ₁ and X ₂ may be the same as or different from each other, and are a hydrogen atom or a halogen atom such as chlorine, bromine or iodine, as in the terminal group of the polymer I or copolymer II. X ₁ and X ₂ depend on the starting materials in the synthesis of polymer III.

n represents an average degree of polymerization, and is 4 to 100, preferably 5 to 40, and more preferably 5 to 20 in the layer as in the case of the polymer I and the copolymer II. In this case, the combination of R ₃ and R ₄ may be the same polymer (homopolymer), or the combination of R ₃ and R ₄ may be a different copolymer (copolymer). The copolymer may be any of a random copolymer, an alternating copolymer, a block copolymer and the like.

  The weight average molecular weight of the polymer III in the layer is about 300 to 10,000.

  The polymer III preferably has a structure as shown in Chemical Formula 1 but may contain other monomer components as long as it is 10 mol% or less, like the polymers I and II. .

A specific example of the polymer III is shown in Chemical formula 9. In the chemical formula 9, the combination of R ₃ and R _{4 in} the chemical formula 8 is shown. Note that chemical formula 8 is the same as chemical formula 1, but will be described again.

The polymer I, copolymer II and polymer III of the present invention can be obtained by condensation polymerization of a dihalogenated aryl compound. Preferably, (1) a method in which a Grignard reaction is performed and polymerization is performed using a Ni complex such as dichloro (2,2′-bipyridine) nickel [NiCl ₂ (bpy)] [Yamamoto T., et al., Bull. Chem. Soc. Jpn., 56, 1497 (1983)] and (2) a method of polymerization using bis (1,5-cyclooctadiene) nickel [Ni (cod) ₂ ] [T. Yamamoto, et al ., Polym. J., 22, 187 (1990)], etc.

  Such a polymer can be identified by elemental analysis, infrared absorption spectrum (IR), nuclear magnetic resonance spectrum (NMR) or the like.

  The average degree of polymerization (n) and the weight average molecular weight can be determined by a light scattering method, gel permeation chromatography (GPC), liquid chromatography, mass spectrum, or the like.

  The melting point is 300 ° C. or higher, or no melting point, and a high-quality film in an amorphous state or a microcrystalline state can be obtained by vacuum deposition.

  Below, the synthesis example of these polymers is shown. The results of elemental analysis are also shown.

(Synthesis Example 1)
<Synthesis of Poly (thiophene-2,4-diyl) [Polymer I-1: End Group H or Br]>
Bis (1,5-cyclooctadiene) nickel (Ni (cod) ₂ ) 1.58 g (5.71 mmol), 2,2′-bipyridine 0.90 g (5.75 mmol) and 1,5-cyclooctadiene 1.0 ml was mixed with 50 ml of N, N-dimethylformamide in a nitrogen atmosphere, and 1.15 g (4.76 mmol) of 2,4-dibromothiophene was further added, followed by stirring at 60 ° C. for 18 hours. As a result, a reddish brown polymer was obtained as a precipitate. In order to remove nickel compounds and the like from the obtained polymer, the polymer was washed with hydrochloric acid-ethanol solution, ethylenediamine aqueous solution, toluene, hot water, and ethanol. The yield was 91%.

Elemental analysis
CHS Br
Calculated value (%) 58.5 2.45 39.55 0.0 (C ₄ H ₂ S) _n
Measured value (%) 57.07 2.07 35.50 5.56

(Synthesis Example 2)
<Synthesis of Poly (thiophene-2,5-diyl) [Polymer III-1: End Group H or Br]>
Bis (1,5-cyclooctadiene) nickel (Ni (cod) ₂ ) 1.58 g (5.71 mmol), 2,2′-bipyridine 0.90 g (5.75 mmol) and 1,5-cyclooctadiene 1.0 ml was mixed with 50 ml of N, N-dimethylformamide in a nitrogen atmosphere, and 1.15 g (4.76 mmol) of 2,5-dibromothiophene was further added, followed by stirring at 60 ° C. for 18 hours. As a result, a reddish brown polymer was obtained as a precipitate. In order to remove nickel compounds and the like from the obtained polymer, the polymer was washed with hydrochloric acid-ethanol. The yield was 98%.

Elemental analysis
CHS Br
Calculated value (%) 58.5 2.45 39.55 0.0 (C ₄ H ₂ S) _n
Measured value (%) 53.45 2.32 35.84 6.39

(Synthesis Example 3)
<Poly (3-phenyl-thiophene-2,4-diyl) [Polymer I-3: End group H or Br]>
Bis (1,5-cyclooctadiene) nickel (Ni (cod) ₂ ) 1.58 g (5.71 mmol), 2,2′-bipyridine 0.90 g (5.75 mmol) and 1,5-cyclooctadiene 1.0 ml was mixed with 50 ml of N, N-dimethylformamide in a nitrogen atmosphere, and 1.19 g (5.0 mmol) of 2,4-dibromo-3-phenylthiophene was further added, followed by stirring at 60 ° C. for 18 hours. As a result, a light brown polymer was obtained as a precipitate. In order to remove nickel compounds and the like from the obtained polymer, the polymer was washed with hydrochloric acid-ethanol solution, ethylenediamine aqueous solution, toluene, hot water, and ethanol. The yield was 90%.

Elemental analysis
CHS Br
Calculated value (%) 75.8 3.8 20.2 0.0 (C ₁₀ H ₆ S) _n
Measured value (%) 74.5 3.7 18.6 3.0

(Synthesis Example 4)
<Synthesis of Poly (3,4-dimethylthiophene-2,5-diyl) [Polymer III-5: End Group H or Br]>
Bis (1,5-cyclooctadiene) nickel (Ni (cod) ₂ ) 1.58 g (5.71 mmol), 2,2′-bipyridine 0.90 g (5.75 mmol) and 1,5-cyclooctadiene 1.0 ml was mixed with 50 ml of N, N-dimethylformamide in a nitrogen atmosphere, and further 1.40 g (5.2 mmol) of 2,5-dibromo-3,4-dimethylthiophene was added, followed by stirring at 60 ° C. for 18 hours. . As a result, an orange polymer was obtained as a precipitate. In order to remove nickel compounds and the like from the obtained polymer, the polymer was washed with hydrochloric acid-ethanol solution, ethylenediamine aqueous solution, toluene, hot water, and ethanol. The yield was 80%.

Elemental analysis
CHS Br
Calculated value (%) 65.4 5.48 29.1 0.0 (C ₆ H ₆ S) _n
Measured value (%) 65.1 5.51 27.0 2.0

(Synthesis Example 5)
<Synthesis of Thiophene-2,4-diyl-thiophene-2,5-diyl (1: 1) Copolymer [Copolymer II-1: Terminal Group H or Br]>
Bis (1,5-cyclooctadiene) nickel (Ni (cod) ₂ ) 1.58 g (5.71 mmol), 2,2′-bipyridine 0.90 g (5.75 mmol) and 1,5-cyclooctadiene 1.0 ml is mixed with 50 ml of N, N-dimethylformamide in a nitrogen atmosphere, and then 0.63 g (2.6 mmol) of 2,5-dibromothiophene and 0.63 g (2.6 mmol) of 2,4-dibromothiophene. ) And stirred at 60 ° C. for 18 hours. As a result, a reddish brown polymer was obtained as a precipitate. In order to remove nickel compounds and the like from the obtained polymer, the polymer was washed with hydrochloric acid-ethanol solution, ethylenediamine aqueous solution, toluene, hot water, and ethanol. The yield was 93%.

Elemental analysis
CHS Br
Calculated value (%) 58.5 2.45 39.55 0.0 (C ₄ H ₂ S) _n
Measured value (%) 57.1 2.10 36.2 4.0

  Other exemplary compounds can be synthesized in the same manner according to the above or according to the above.

  The EL device of the present invention has at least one organic compound layer, and at least one organic compound layer contains the polymer of the present invention. A configuration example of the EL element of the present invention is shown in FIG. The EL element 1 shown in the figure has an anode 3, a hole injection / transport layer 4, a light emitting layer 5, an electron injection / transport layer 6, and a cathode 7 in this order on a substrate 2.

  The light emitting layer has a hole and electron injection function, a transport function thereof, and a function of generating excitons by recombination of holes and electrons. The hole injecting and transporting layer has the function of facilitating the injection of holes from the anode, the function of transporting holes and the function of hindering the transport of electrons, and the electron injecting and transporting layer prevents the injection of electrons from the cathode. It has a function to facilitate, a function to transport electrons, and a function to prevent the transport of holes, and these layers increase and confine holes and electrons injected into the light-emitting layer and optimize the recombination region. To improve luminous efficiency. The electron injecting and transporting layer and the hole injecting and transporting layer are provided as necessary in consideration of the height of each function of electron injection, electron transport, hole injection and hole transport of the compound used for the light emitting layer. For example, when the hole injection / transport function or electron injection / transport function of the compound used in the light-emitting layer is high, the light-emitting layer is not provided with the hole injection / transport layer or the electron injection / transport layer, but the hole injection / transport layer or the electron injection It can be set as the structure which serves as a transport layer. In some cases, neither the hole injection transport layer nor the electron injection transport layer may be provided. Further, each of the hole injecting and transporting layer and the electron injecting and transporting layer may be provided with a layer having an injection function and a layer having a transport function.

  The polymer I and copolymer II of the present invention are preferably used in a light emitting layer or a hole injecting and transporting layer. In this case, it can be used only for the light emitting layer or only for the hole injecting and transporting layer, and it is also preferable to use it for the hole injecting and transporting / light emitting layer that also serves as the hole injecting and transporting layer. In some cases, it may be used for a light emitting layer that also serves as a hole injecting and transporting layer, a light emitting layer and an electron injecting and transporting layer.

  On the other hand, the polymer III of the present invention is preferably used for a hole injecting and transporting layer.

  First, the case where the polymer I and the copolymer II of the present invention are used in a light emitting layer will be described. In this case, another fluorescent substance may be used in combination in the light emitting layer. As such a fluorescent substance, for example, at least one selected from compounds such as compounds disclosed in JP-A 63-264692, for example, compounds such as coumarin, quinacridone, rubrene, and styryl dyes may be used. Can be mentioned. In addition, organic phosphors such as metal complex dyes such as tetraphenylbutadiene, anthracene, perylene, coronene, 12-phthaloperinone derivatives, and tris (8-quinolinolato) aluminum. The content of such a fluorescent substance is preferably 5 mol% or less of the polymer I and copolymer II of the present invention. By appropriately selecting and adding such a compound, emitted light can be shifted to the long wavelength side.

  The light emitting layer may contain a singlet oxygen quencher. Examples of such quenchers include nickel complexes, rubrene, diphenylisobenzofuran, and tertiary amines. The content of such a quencher is preferably 10 mol% or less of the polymer I and copolymer II of the present invention.

  When the polymer I and copolymer II of the present invention are used in the light emitting layer, the hole injecting and transporting layer and the electron injecting and transporting layer include various organic compounds used in ordinary organic EL devices, for example, Various organic compounds described in JP-A 63-295695, JP-A-2-191694, JP-A-3-792 and the like can be used. For example, an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, or the like can be used for the hole injecting and transporting layer. Can be used organometallic complex derivatives such as tris (8-quinolinolato) aluminum, oxadiazole derivatives, pyridine derivatives, pyrimidine derivatives, quinoline derivatives, quinoxaline derivatives, diphenylquinone derivatives, perylene derivatives, fluorene derivatives, and the like.

  In addition, the polymer I, copolymer II, and polymer III of the present invention can also be used for the hole injecting and transporting layer. In addition, it is also preferable that the light emitting layer also serves as the hole injecting and transporting layer without separately providing the hole injecting and transporting layer.

  When the hole injecting and transporting layer is divided into a hole injecting layer and a hole transporting layer, a preferred combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to laminate in order of a compound layer having a small ionization potential from the anode (ITO or the like) side. Further, it is preferable to use a compound having a good thin film property on the anode surface. Such a stacking order is the same when two or more hole injection / transport layers are provided. By adopting such a stacking order, the driving voltage is lowered, and the occurrence of current leakage and the generation / growth of a partial non-light emitting portion (dark spot) can be prevented. In addition, in the case of forming an element, since vapor deposition is used, a thin film of about 1 to 10 nm can be made uniform and pinhole-free, so that the ion injection potential is small in the hole injection layer and the visible portion has absorption. Even if such a compound is used, it is possible to prevent a decrease in efficiency due to a change in color tone of light emission or reabsorption.

  When the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferred combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to laminate in the order of the layer of the compound having a large electron affinity value from the cathode side. Such a stacking order is the same when two or more electron injecting and transporting layers are provided.

  Next, the case where the polymer I, the copolymer II, and the polymer III of the present invention are used for the hole injecting and transporting layer will be described. In this case, the hole injection / transport material as described above can be used in combination for the hole injection / transport layer. Moreover, it can also laminate | stack with the positive hole injection transport layer using such a positive hole injection transport material. Particularly preferably, a first hole injection / transport layer using the polymer of the present invention is formed on the anode surface, and a second hole injection / transport layer using another hole injection / transport material as described above is further formed. It is to laminate. With such a laminated structure, the hole injection / transport function is improved and the performance as an element is improved. Furthermore, the rough surface of the anode surface such as ITO is covered, and the organic compound layer laminated on the upper portion is stabilized.

  In particular, an aromatic tertiary amine such as tetraphenyldiaminobiphenyl derivative (TPD) is preferable as the second hole injecting and transporting material in the laminated structure. This is because such a compound usually has an ionization potential that is equal to or greater than that of the polymer of the present invention, and therefore a preferred combination can be selected by appropriately selecting the polymer of the present invention.

  The polymer of the present invention has an ionization potential Ip having an absolute value of about 4.8 to 5.4 eV and an electron affinity Ea of about 1.8 to 3.0 eV.

  When the polymer of the present invention is used for the hole injecting and transporting layer, the fluorescent substance used for the light emitting layer may be selected from those having longer wavelength fluorescence as described above. What is necessary is just to select suitably from 1 or more types of the fluorescent substance used together with the polymer I of this, and the copolymer II. Such a light-emitting layer may be one using tris (8-quinolinolato) aluminum or the like, and such a light-emitting layer may be an electron injection / transport / light-emitting layer that also serves as an electron injection / transport layer. In addition, when using the polymer of this invention for a positive hole injection transport layer, the polymer I of this invention and the copolymer II can also be used for a light emitting layer. In addition, the above-described electron injection / transport material can be used for the electron injection / transport layer. About another structure, it is the same as that of the case where the polymer of this invention is used for a light emitting layer.

  The thickness of the light-emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited and vary depending on the forming method, but usually about 1 to 1000 nm, particularly 8 to 200 nm, per layer. It is preferable that

  The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times depending on the design of the recombination / light emitting region. When the injection layer and the transport layer for electrons or holes are separated, the injection layer is preferably 1 nm or more, and the transport layer is preferably 20 nm or more. In this case, the upper limit of the thickness of the injection layer and the transport layer is usually about 100 nm for the injection layer and about 1000 nm for the transport layer. Such a film thickness is the same when two injecting and transporting layers are provided to form the first and second injecting and transporting layers.

  In addition, the recombination region and light emission can be controlled by controlling the film thickness while considering the carrier mobility and carrier density (determined by the ionization potential and electron affinity) of the light-emitting layer, electron injection transport layer, and hole injection transport layer to be combined. The region can be designed freely, and it is possible to design the light emission color, control the light emission luminance / light emission spectrum by the interference effect of both electrodes, and control the spatial distribution of light emission.

  In the present invention, when an electron injecting and transporting compound and a hole injecting and transporting compound are used in combination, more specifically, a layer containing an electron injecting and transporting compound and a layer containing a hole injecting and transporting compound are included. In the EL element, the difference in ionization potential Ip or the electron affinity Ea between the electron injecting and transporting compound and the hole injecting and transporting compound contained in these layers, or the difference between them is 0.2 eV or more. It is preferable that

  By setting the Ip difference and Ea difference between these two compounds within the above ranges, a layer containing an electron injecting and transporting compound and a hole injecting compound, such as a combination of an electron injecting and transporting layer and a hole injecting and transporting layer Since the energy state (level) of the layer containing the carrier is optimized, the carrier blocking effect at the interface is enhanced, and the injection of carriers that are polarly inferior or unstable is less likely to occur, so that the organic compound in each layer is damaged. It becomes difficult to generate deactivation points of carriers and excitons in the carrier recombination region and the light emitting region. As a result, stable light emission is obtained, and the lifetime is greatly improved. On the other hand, when these differences are reduced, the carrier blocking effect at the interface cannot be obtained.

  In the above, when one or both of the layer containing the electron injecting and transporting compound and the layer containing the hole injecting and transporting compound are present in two or more layers, at least one of the layers containing the electron injecting and transporting compound The above relationship may be satisfied between the layer and at least one of the layers containing the hole injecting / transporting compound, but it is preferable that the layers closer to each other satisfy the above relationship.

  In particular, a layer containing an electron injecting and transporting compound and a hole injecting and transporting compound such as a hole injecting and transporting layer and an electron injecting and transporting / emitting layer, an electron injecting and transporting layer and a hole injecting and transporting / light emitting layer, etc. In the structure in which the layers to be contained are stacked, it is preferable that the Ip difference and Ea difference between the electron injecting and transporting compound and the hole injecting and transporting compound in each of the above layers are in the above range.

  This is because the carrier blocking effect at the interface is easily exhibited in the layers closer to each other, particularly in the laminated configuration.

  Furthermore, it is preferable to apply the above laminated structure when the hole injecting and transporting layer containing the polymer of the present invention is a first hole injecting and transporting layer. A layer containing the above hole injecting and transporting compound is provided as, for example, a second hole injecting and transporting layer on the injecting and transporting layer, and a layer containing the above electron injecting and transporting compound is further laminated thereon. It is preferable to provide it.

  By adopting such a configuration, in addition to the carrier blocking effect described above, an element stabilizing effect can be further obtained.

  The electron injecting and transporting compound can be selected from the above electron injecting and transporting materials, and the hole injecting and transporting compound can be selected from the above hole injecting and transporting materials. In some cases, the polymer of the present invention may be selected and used. Further, each of the electron injecting and transporting compound and the hole injecting and transporting compound may be used alone or in combination of two or more.

  When each of the above layers contains two or more electron injection / transport compounds or hole injection / transport compounds, the above Ip difference and Ea difference are usually the main component (content of usually 50 wt% or more). ).

  Any of the above differences may be in the above range, but it is particularly preferable that both the differences are in the above range. In particular, when tris (8-quinolinolato) aluminum is used as the electron injecting and transporting material, the difference in Ip is preferably in the above range.

  The upper limit of the difference at this time is not particularly limited, but is usually about 1 eV, and it is preferable that all of the above differences are in the range of 0.2 to 1 eV.

  The hole injecting and transporting material used in the above generally has an ionization potential Ip of an absolute value of 5.4 eV or less, and this value is particularly preferable when used in combination with tris (8-quinolinolato) aluminum. The lower limit of this value is not particularly limited, but is usually about 4.8 eV, and this value is preferably in the range of 4.8 to 5.4 eV.

  The absolute value of the electron affinity Ea of the hole injecting and transporting material is preferably about 1.8 to 3.0 eV.

  On the other hand, the electron injecting and transporting material used together with the hole injecting and transporting material usually has an ionization potential Ip in an absolute value range of 5.4 to 6.5 eV and an electron affinity Ea in an absolute value of 2.5 to 3.5 eV. It is preferable to select from those within the range.

  In particular, tris (8-quinolinolato) aluminum is preferably used as the electron injecting and transporting material in the above configuration. The absolute value of the ionization potential Ip of this complex is usually about 5.6 to 5.7 eV, and the absolute value of the electron affinity Ea is about 2.9 to 3.0 eV.

  In the above, preferred combinations of the hole injecting and transporting material and the electron injecting and transporting material are as follows.

[Electron injection and transport material Hole injection and transport material]
(1) Tris (8-quinolinolato) aluminum N, N'-bis (m-methylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (2) Tris (8- Quinolinolato) aluminum 1,1'-bis (4-di-p-tolylaminophenyl) cyclohexane (3) Tris (8-quinolinolato) aluminum N, N'-bis (pt-butylphenyl) -N, N'-diphenyl -1,1'-biphenyl-4,4'-diamine (4) Tris (8-quinolinolato) aluminum N, N'-bis (pn-butylphenyl) -N, N'-diphenyl-1,1'-biphenyl -4,4'-diamine

  In the present invention, it is preferable to provide a mixed layer containing a mixture of an electron injecting and transporting compound and a hole injecting and transporting compound.

  At this time, since a hopping conduction path of carriers is formed in the mixed layer, each carrier moves in a material that is more dominant in polarity. In other words, holes move in the hole injecting and transporting solid, and electrons move in the electron injecting and transporting solid, so that carrier injection with the opposite polarity is less likely to occur, so each organic compound is less likely to be damaged. In addition, deactivation points of carriers and excitons are hardly generated in the carrier recombination region and the light emitting region. As a result, stable light emission is obtained, and the lifetime is greatly improved.

  The mixed layer is preferably a light emitting layer, and preferably one or both of an electron injecting and transporting compound and a hole injecting and transporting compound have a light emitting function.

  The mixing ratio of the electron injecting / transporting compound and the hole injecting / transporting compound in the above mixed layer depends on the mobility of carriers, but the weight ratio of the electron injecting / transporting compound: hole injecting / transporting compound is 60. Is preferably 40 to 40:60, and particularly preferably about 50:50.

  The electron injecting and transporting compound used for the mixing can be selected from the above electron injecting and transporting materials, and the hole injecting and transporting compound can be selected from the above hole injecting and transporting materials. In some cases, the polymer of the present invention may be selected and used. Furthermore, in the mixed layer, each of the electron injecting and transporting compound and the hole injecting and transporting compound may be used alone or in combination of two or more. The mixed layer may be doped with a fluorescent substance in order to increase the emission intensity. In this case, rubrene is preferred as the fluorescent substance.

  The difference in ionization potential Ip or electron affinity Ea between the hole injecting and transporting material used in the mixed layer and the electron injecting and transporting material, or the difference between them is preferably 0.2 eV or more.

  By making the Ip difference and Ea difference between the materials within the above ranges, in addition to the carrier blocking effect described above, the effect of each carrier moving in a more dominant substance is improved, and the light emission is further stabilized. In addition, the lifetime of the element is further improved. On the other hand, if these differences are too small, it is difficult to obtain the effects of carrier blocking and movement as described above.

  Any of the above differences may be in the above range, but it is particularly preferable that both the differences are in the above range, and tris (8-quinolinolato) aluminum is particularly used as the electron injecting and transporting material. In some cases, it is preferable that the difference of Ip is in the above range, and further, the upper limit value of the difference between Ip and Ea or the absolute value of Ip and Ea, and tris (8-quinolinolato) aluminum as the electron injection / transport material. Preferred examples and preferred combinations of the hole injecting and transporting material and electron injecting and transporting material used in combination are the same as described above.

  In the present invention, when the mixed layer as described above is provided, it is preferable to provide the mixed layer as a light emitting layer so as to be sandwiched between the electron injecting and transporting layer and the hole injecting and transporting layer. And it is preferable that a mixed layer mixes using the electron injection transport compound and hole injection transport compound of both layers which contact | connect. Further, the hole injecting and transporting layer is preferably formed as a second hole injecting and transporting layer on the first hole injecting and transporting layer using the polymer of the present invention as a hole injecting and transporting material.

  In addition, as a method for forming the mixed layer, co-evaporation is preferably performed by evaporating from different deposition sources. However, if the vapor pressure (evaporation temperature) is the same or very close, the mixture is previously mixed in the same deposition boat, It can also be deposited.

  In the mixed layer, it is preferable to mix both compounds uniformly, but in some cases, the compounds may be present in an island shape. Further, the thickness of the mixed layer is preferably less than the thickness of the organic compound layer from the thickness corresponding to one molecular layer, specifically 1 to 85 nm, more preferably 5 to 60 nm, In particular, the thickness is preferably 5 to 50 nm. Note that the mixed layer is preferably a part of the organic compound layer present in the device. If all the organic compound layers are mixed layers, it may be difficult to obtain uniform emission with high luminance.

  The ionization potential Ip in the present invention is obtained by using a low energy electron spectrometer “Model AC-1” (manufactured by Riken Keiki Co., Ltd.) according to the description of Shirahashi, Isobe, Uda, Electronic Materials, 123 (1985). It is the value measured using the sample which formed the vapor deposition film of the layer on the board | substrate which has an ITO transparent electrode, or a slide glass.

  The low-energy electron spectroscopy apparatus has the configuration shown in FIG.

  As shown in FIG. 2, the spectroscopic device 10 includes an ultraviolet lamp 11, a monochromator 12, a detector 13, a low energy electronic counter 14, a control device 15, a calculation display device 16, and an XY stage 17. -The sample S is mounted on the Y stage to perform measurement.

  A deuterium lamp is used as the ultraviolet lamp 11, and the light emitted from this lamp is dispersed into an arbitrary wavelength of 200 to 360 nm by the monochromator 12 and irradiated on the surface of the sample S. When light of 200 to 360 nm is converted into energy using an equation of E = hν = h (c / λ) (E: energy, h: Planck's constant, ν: frequency, λ: wavelength), each is 6.2. ~ 3.4 eV. When this light is swept from the lower excitation energy toward the higher one, electron emission due to the photoelectric effect starts at a certain energy. This energy is a value generally called a photoelectric work function. The photoelectrons thus emitted are counted using the detector 13 and the low-energy electron counting device 14, and after performing calculations such as background correction and correction of counting down during the dead time, as shown in FIG. Excitation energy and emitted electron quantity characteristics (basic characteristics) are displayed on the display of the arithmetic display device 16.

As shown in the basic characteristics, the light emission rate (C ount P er S econd: CPS) relationship of the excitation energy (eV) is the vertical axis n-th power of the light emission rate and (CPS) ^n, excites the transverse axis If it is energy, it can be expressed by a linear relationship. Here, the value of n usually adopts 1/2.

  The control device 15 performs wavelength driving of the monochromator 12, control of the sample position by the XY stage 17, and count control of the low energy electronic coefficient device 14.

  Therefore, in the present invention, the photoelectric work function obtained from FIG. 3 is defined as the ionization potential Ip.

  On the other hand, the electron affinity Ea in the present invention is measured by a spectroscopic method, and is obtained by calculating an energy gap from an absorption edge of an ultraviolet (UV) absorption spectrum.

  In the present invention, it is preferable to dope rubrene into the organic compound layer.

  Doping may be performed on the entire organic compound layer, and preferably on the entire hole injecting and transporting layer. As will be described later, it is considered that rubrene is preferably present at the contact interface between the carrier recombination region, the light emitting region and the vicinity thereof, for example, the organic compound layer of the hole injection transport layer. There is no need to do this, and the hole-injecting and transporting layer on the side of the light-emitting layer (including the case where the electron-injecting and transporting layer also serves as the electron-injecting and transporting layer), Although it may be a half region, it is generally the whole hole injection transport layer. In some cases, the entire region of the hole injecting and transporting layer or the hole injecting and transporting layer, a half region on the side of the light emitting layer or the electron injecting and transporting layer, and the hole injecting and transporting layer of the light emitting layer or the electron injecting and transporting layer It can also be a side half area. In particular, in the hole injecting and transporting layer, the combined use of the hole injecting and transporting material and rubrene is preferable, and the second hole injecting and transporting doped with rubrene on the first hole injecting and transporting layer using the polymer of the present invention. It is preferable to provide a layer.

  The doping concentration of rubrene is not preferred because rubrene causes concentration quenching, and it is preferably 0.1 to 50 wt%, more preferably 0.1 to 30 wt%, particularly about the entire doping layer. It is preferable to set it as 0.1-20 wt%.

  As described above, in the present invention, the ionization potential Ip between the layer containing a hole injection / transport compound such as a hole injection / transport layer and the layer containing an electron injection / transport compound such as an electron injection / transport layer is preferably The difference or difference in electron affinity Ea, or the difference between the two is optimized to increase the carrier blocking effect at the interface, and the inferior or unstable carrier injection is less likely to occur. It becomes difficult to receive deactivation points of carriers and excitons in the carrier recombination region and the light emitting region. In addition, particularly when rubrene is doped, rubrene has a bipolar transport property, and rubrene also causes carrier recombination, so that the organic compound is further damaged less. In addition, since rubrene is present in the vicinity of the carrier recombination region, energy transfer from excitons to rubrene occurs, resulting in less non-radiative deactivation, resulting in stable emission and a significant improvement in lifetime. To do.

  In the present invention, rubrene is preferably used as the fluorescent substance, but other fluorescent substances may be doped in addition to rubrene.

  In the present invention, it is preferable to use a material having a low work function, for example, Li, Na, Mg, Al, Ag, In, or an alloy containing one or more of these materials for the cathode. Further, the cathode preferably has fine crystal grains, and particularly preferably in an amorphous state. The thickness of the cathode is preferably about 10 to 1000 nm.

In order to cause the EL element to emit light, at least one of the electrodes needs to be transparent or translucent, and as described above, the cathode material is limited, so that the transmittance of emitted light is preferably 80% or more. It is preferable to determine the material and thickness of the anode so that Specifically, for example, ITO, SnO ₂ , Ni, Au, Pt, Pd, polypyrrole doped with a dopant, or the like is preferably used for the anode. The thickness of the anode is preferably about 10 to 500 nm. Moreover, in order to improve the reliability of an element, it is necessary for a drive voltage to be low, However As a preferable thing, 10-30 ohms / square ITO is mentioned.

  The substrate material is not particularly limited, but in the illustrated example, a transparent or translucent material such as glass or resin is used to extract emitted light from the substrate side. Further, the emission color may be controlled by using a color filter film or a dielectric reflection film on the substrate.

  Note that when an opaque material is used for the substrate, the stacking order shown in FIG. 1 may be reversed.

  Next, a method for producing an EL element using the polythiophene of the present invention will be described.

  The cathode and the anode are preferably formed by vapor deposition such as vapor deposition or sputtering.

  For the formation of the hole injecting and transporting layer, the light emitting layer, and the electron injecting and transporting layer, it is preferable to use a vacuum deposition method because a homogeneous thin film can be formed. As a result, even a thin film of about 1 to 10 nm can be made uniform and pinhole-free, so that it is possible to prevent a decrease in efficiency due to a change in color tone of light emission and reabsorption. When the vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less can be obtained. If the crystal grain size exceeds 0.1 μm, non-uniform light emission occurs, the drive voltage of the device must be increased, and the charge injection efficiency is also significantly reduced. The lower limit of the crystal grain size is not particularly limited, but is usually about 0.001 μm.

The conditions for vacuum deposition are not particularly limited, but it is preferable that the degree of vacuum is 10 ⁻⁵ Torr (10 ⁻³ Pa) or less and the deposition rate is about 0.1 to 1 nm / sec. Moreover, it is preferable to form each layer continuously in a vacuum. If formed continuously in a vacuum, impurities can be prevented from adsorbing to the interface of each layer, so that high characteristics can be obtained. In addition, the driving voltage of the element can be lowered.

  In the case of using a vacuum deposition method for forming each of these layers, when a plurality of compounds are contained in one layer, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

  When depositing the polymer of the present invention, it is preferably deposited in the form of 5 to 40, more preferably 5 to 20, monomer units. It can be confirmed by infrared absorption spectrum (IR), liquid chromatography, GPC, mass spectrum, fluorescence spectrum, absorption spectrum, and the like that the deposited compound is the above compound. More specifically, the vapor-deposited material may be dissolved in an organic solvent such as toluene and measured by the above method.

  The EL element of the present invention is usually used as a direct current drive type EL element, but can be alternating current driven or pulse driven. The applied voltage is usually about 2 to 20V.

  Hereinafter, specific examples of the present invention will be shown together with comparative examples, and the present invention will be described in more detail.

< Reference Example 1>
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Subsequently, the polymer III-1 [poly (thiophene-2,5-diyl)] of Chemical formula 9 was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 30 nm to form a hole injection transport layer.

  Next, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited to a thickness of 50 nm at a vapor deposition rate of 0.2 nm / sec to obtain a light-emitting layer that also served as an electron injecting and transporting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to the EL element and a current was passed, it was confirmed that 500 cd / m ² of yellow green light emission (maximum light emission wavelength λmax = 501 nm) was observed at 7 V, 100 mA / cm ² , and this light emission was in a dry nitrogen atmosphere. And was stable for 3000 hours or more, and there was no appearance or growth of a partial non-light-emitting portion.

< Reference Example 2>
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Next, the polymer I-1 [poly (thiophene-2,4-diyl)] of Chemical formula 5 was deposited at a deposition rate of 0.2 nm / sec to a thickness of 30 nm to form a hole injecting and transporting layer.

  Next, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited to a thickness of 50 nm at a deposition rate of 0.2 nm / sec, that is, a light emitting layer that also served as an electron injection transport layer, that is, electron injection transport / light emission. Layered.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to this EL element and current was passed, light emission of 800 cd / m ² at 8 V, 100 mA / cm ² (maximum light emission wavelength λmax = 500 nm) was confirmed, and this light emission was in a dry nitrogen atmosphere. And was stable for 3000 hours or more, and there was no appearance or growth of a partial non-light-emitting portion.

<Example 1 >
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Subsequently, the polymer III-1 [poly (thiophene-2,5-diyl)] of Chemical formula 9 was deposited to a thickness of 10 nm to form a first hole injection transport layer.

  Next, N, N′-bis (m-methylphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD-1) was vapor-deposited to a thickness of 50 nm. A two-hole injection transport layer was obtained.

  Next, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited to a thickness of 50 nm at a vapor deposition rate of 0.2 nm / sec to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to this EL element and a current was applied, emission of 3000 cd / m ² of yellow green color (maximum emission wavelength λmax = 500 nm) was confirmed at 7 V, 100 mA / cm ² , and this emission was in a dry nitrogen atmosphere. Up to 1000 hours, there was no appearance and growth of a partial non-light emitting portion, and stable light emission was exhibited. Further, when 10 elements similar to this element were caused to emit light, no current leakage occurred in any of the elements.

< Reference Example 3 >
In Reference Example 1, in addition to the light-emitting layer of tris (8-quinolinolato) aluminum, m-bis [2- (4-tert-butylphenyl) -1,3,4-oxadiazole] benzene as an electron injecting and transporting material Was used to prepare an EL device in which an electron injecting and transporting layer was separately provided. In this case, the thickness of the light emitting layer was 50 nm, the thickness of the electron injecting and transporting layer was 10 nm, and the electron injecting and transporting layer was formed by vapor deposition in the same manner as the light emitting layer.

Even in such an element, the same good results as in Reference Example 1 were obtained.

<Comparative Example 1>
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Next, N, N′-bis (m-methylphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD-1) was deposited to a thickness of 50 nm and positive A hole injection transport layer was obtained.

  Next, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited to a thickness of 50 nm at a vapor deposition rate of 0.2 nm / sec to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to the EL element and a current was passed, emission of 2500 cd / m ² of yellow green (light emission maximum wavelength λmax = 505 nm) was confirmed at 18 V, 100 mA / cm ² , and this light emission was in a dry nitrogen atmosphere. In 100 hours, the appearance and growth of partially non-light-emitting parts were observed. In addition, when 10 elements similar to this element were caused to emit light, all 10 elements leaked current by 300 hours, resulting in a significant reduction in luminance.

<Example 2 >
A glass substrate having an ITO transparent electrode (anode) having a thickness of 100 nm was ultrasonically cleaned using a neutral detergent, acetone, and ethanol. The substrate was lifted from boiling ethanol, dried, fixed to a substrate holder of a vacuum deposition apparatus, and the vacuum chamber was depressurized to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  First, the polymer III-1 [poly (thiophene-2,5-diyl)] of Chemical formula 9 was vapor-deposited to a thickness of about 10 nm at a vapor deposition rate of about 0.1 nm / sec to form a first hole injection transport layer. .

  Next, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane was deposited at a deposition rate of 0.1 to 0.2 nm / sec to a thickness of about 50 nm to form a second hole injecting and transporting layer. .

  Further, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited at a vapor deposition rate of 0.1 to 0.2 nm / sec to a thickness of about 50 nm to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of about 200 nm to form a cathode to obtain an EL element.

A DC voltage was applied to the EL element, and it was continuously driven at a constant current density of 10 mA / cm ² in a dry atmosphere. In the initial stage, 7.0 V, 300 cd / m ² of yellow-green light (maximum emission wavelength λmax = 500 nm) was confirmed. The luminance half-life was 24 hours, during which the drive voltage rose 2.1V.

<Comparative example 2>
A glass substrate having an ITO transparent electrode (anode) having a thickness of 100 nm was ultrasonically cleaned using a neutral detergent, acetone, and ethanol. The substrate was lifted from boiling ethanol, dried, fixed to the substrate holder of the vapor deposition apparatus, and the pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  First, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane was deposited at a deposition rate of 0.2 nm / sec to a thickness of 50 nm to form a hole injecting and transporting layer.

  Next, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited to a thickness of 50 nm at a vapor deposition rate of 0.2 nm / sec to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an organic EL device.

A DC voltage was applied to the EL element, and it was continuously driven at a constant current density of 10 mA / cm ² in a dry atmosphere. Initially, emission of 8.5V, 360 cd / m ² of yellow-green color (maximum emission wavelength λmax = 500 nm) was confirmed. The driving voltage increased to 11.5 V after 3 hours, and dielectric breakdown occurred after 19 hours.

<Example 3 >
A glass substrate having an ITO transparent electrode (anode) having a thickness of 200 nm was subjected to ultrasonic cleaning using a neutral detergent, acetone, and ethanol. The substrate was lifted from boiling ethanol, dried, washed with UV / O ₃ , fixed to a substrate holder of a vacuum deposition apparatus, and the vacuum chamber was depressurized to 1 × 10 ⁻⁴ Pa or less.

  First, the polymer III-1 [poly (thiophene-2,5-diyl)] of Chemical formula 9 was deposited at a deposition rate of about 0.1 nm / sec to a thickness of about 20 nm to form a first hole injection transport layer. .

Then, the vacuum chamber was returned to the atmosphere, and the vacuum chamber was again depressurized to 1 × 10 ⁻⁴ Pa or less, and then N, N′-bis (m-methylphenyl) -N, N′-diphenyl-1,1 ′. -Biphenyl-4,4'-diamine (TPD-1) was deposited at a deposition rate of 0.1 to 0.2 nm / sec to a thickness of about 55 nm to form a second hole injecting and transporting layer.

  Further, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited at a vapor deposition rate of 0.1 to 0.2 nm / sec to a thickness of about 50 nm to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of about 200 nm to form a cathode to obtain an EL element.

A DC voltage was applied to the EL element, and it was continuously driven at a constant current density of 10 mA / cm ² in a dry atmosphere. Initially, light emission of 5.6 V, 210 cd / m ² of yellow-green color (maximum emission wavelength λmax = 500 nm) was confirmed. The luminance half-life was 130 hours, during which the drive voltage rose 1.8V. Moreover, there was no appearance and growth of a partial non-light emitting part. After that, no current leak occurred and stable light emission was exhibited.

<Example 4 >
In Example 3 , after forming the second hole injecting and transporting layer to a thickness of about 35 nm, tris (8-quinolinolato) aluminum as the second hole injecting and transporting material and the electron injecting and transporting material while maintaining the reduced pressure state. Were co-deposited at approximately the same deposition rate (0.1 to 0.2 nm / sec) to form a mixed layer with a thickness of about 40 nm. This mixed layer is a light emitting layer.

Thereafter, in the same manner as in Example 3 , an electron injecting and transporting layer having a thickness of about 30 nm was formed using tris (8-quinolinolato) aluminum, a cathode was formed, and an EL device was obtained.

Similarly to Example 3, it was continuously driven at a constant current density of 10 mA / cm ^{2 in} a dry atmosphere. Initially, emission of 6.9 V, 280 cd / m ² of yellow-green color (maximum emission wavelength λmax = 505 nm) was confirmed. The luminance half-life was 1050 hours, during which the drive voltage rose 3.2V. Moreover, there was no appearance and growth of a partial non-light emitting part. After that, no current leak occurred and stable light emission was exhibited.

  Absolute value of ionization potential Ip of N, N′-bis (m-methylphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD-1) used in the mixed layer Was 5.40 eV, and the absolute value of the electron affinity Ea was 2.40 eV. On the other hand, the absolute value of the ionization potential Ip of tris (8-quinolinolato) aluminum was 5.64 eV, and the absolute value of the electron affinity Ea was 2.95 eV.

  The ionization potential Ip is measured with a low energy electron spectrometer AC-1 (manufactured by Riken Keiki Co., Ltd.) for a sample film in which a measurement compound deposition film (deposition rate 0.2 nm / sec) is formed on a glass substrate to a thickness of about 10 nm. It was obtained. The electron affinity Ea is obtained from the ultraviolet absorption spectrum.

  Further, the absolute value of the ionization potential Ip of the polymer III-1 was 5.0 eV.

<Example 5 >
In Example 4 , a device was obtained in the same manner except that the thickness of the mixed layer was 20 nm, and the characteristics were examined in the same manner.

As a result, light emission of 6.1 V, 280 cd / m ² of yellow green color (maximum emission wavelength λmax = 500 nm) was confirmed in the initial stage. The luminance half-life was 1000 hours, during which the drive voltage rose 3.1V. In addition, there was no appearance and growth of a partial non-light emitting portion, and no current leakage occurred thereafter, and stable light emission was exhibited.

<Example 6 >
In Example 4 , a device was obtained in the same manner except that the thickness of the mixed layer was 10 nm, and the characteristics were examined in the same manner.

As a result, 6.4 V, 290 cd / m ² of yellow-green light (maximum light emission wavelength λmax = 500 nm) was confirmed in the initial stage. The half-life time of the luminance was 800 hours, during which the drive voltage rose 3.0V. In addition, there was no appearance and growth of a partial non-light emitting portion, and no current leakage occurred thereafter, and stable light emission was exhibited.

<Example 7 >
In Example 4 , a device was obtained in the same manner except that the thickness of the mixed layer was 5 nm, and the characteristics were examined in the same manner.

As a result, light emission of 6.0 V, 250 cd / m ² of yellow green color (maximum emission wavelength λmax = 500 nm) was confirmed in the initial stage. The half-life time of the luminance was 500 hours, and the drive voltage increase during that time was 2.6V. In addition, there was no appearance and growth of a partial non-light emitting portion, and no current leakage occurred thereafter, and stable light emission was exhibited.

From the results of Examples 3 to 7 , it can be seen that the provision of the mixed layer improves the initial luminance and increases the half-life.

In Examples 3 and 4 , an EL device was fabricated using a combination of the compounds (2) to (4) other than the above (1) exemplified in [Best Mode for Carrying Out the Invention]. When the characteristics were examined, the same tendency as described above was observed between the laminated structure and the mixed layer.

<Example 8 >
A glass substrate having an ITO transparent electrode (anode) having a thickness of 200 nm was subjected to ultrasonic cleaning using a neutral detergent, acetone, and ethanol. The substrate was lifted from boiling ethanol, dried, washed with UV / O ₃ , fixed to a substrate holder of a vacuum deposition apparatus, and the vacuum chamber was depressurized to 1 × 10 ⁻⁴ Pa or less.

  First, poly (thiophene-2,5-diyl) was deposited at a deposition rate of about 0.1 nm / sec to a thickness of about 20 nm to form a first hole injecting and transporting layer.

The vacuum chamber was then returned to the atmosphere, and the vacuum chamber was again depressurized to 1 × 10 ⁻⁴ Pa or less, and then N, N′-bis (m-methylphenyl) -N, N′-diphenyl-1,1′- Biphenyl-4,4′-diamine (TPD-1) and rubrene were co-deposited at a deposition rate of 0.1 to 0.2 nm / sec and 0.01 to 0.02 nm / sec to a total thickness of about 55 nm, A second hole injection transport layer was obtained.

  Further, while maintaining the reduced pressure state, tris (8-quinolinolato) aluminum was vapor-deposited at a vapor deposition rate of 0.1 to 0.2 nm / sec to a thickness of about 50 nm to form an electron injection transport / light-emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of about 200 nm to form a cathode to obtain an EL element.

A DC voltage was applied to the EL element, and it was continuously driven at a constant current density of 10 mA / cm ² in a dry atmosphere. Initially, yellow light emission of 5.3 V, 290 cd / m ² (maximum light emission wavelength λmax = 550 nm) was confirmed. The luminance half-life was 260 hours, during which the drive voltage increased 1.6 V.

From the results of Example 8 , it can be seen that doping with rubrene improves the initial luminance and increases the half-life.

In Reference Examples 1 to 3 and Examples 1 to 8 , one or more of the polymers or copolymers shown in Chemical Formulas 4 to 9 are used in the hole injecting and transporting layer instead of the polymer. When an EL device was produced using the same, good results equivalent to Reference Examples 1 to 3 and Examples 1 to 8 were obtained.

  The absolute value of the ionization potential Ip of these polymers or copolymers is in the range of 4.8 to 5.4 eV, and N, N′-bis (m-methylphenyl) -N, N′-diphenyl. -1,1′-biphenyl-4,4′-diamine or 1,1-bis (4-p-tolylaminophenyl) cyclohexane (Ip absolute value = 5.40 eV) or the like for the second hole injecting and transporting layer A compound suitable for use in the first hole injecting and transporting layer could be selected in combination with the compound.

< Reference Example 4 >
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Next, the polymer I-1 [poly (thiophene-2,4-diyl)] of Chemical formula 5 was vapor-deposited to a thickness of 300 nm at a vapor deposition rate of 0.2 nm / sec to obtain a light emitting layer.

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to the EL element and a current was applied, 10 cd / m ² of blue light emission (maximum light emission wavelength λmax = 480 nm) was confirmed at 11 V, 100 mA / cm ² , and this light emission was observed in a dry nitrogen atmosphere. It was stable for over 1000 hours.

< Reference Example 5 >
A glass substrate having an ITO transparent electrode (anode) with a thickness of 100 nm is ultrasonically cleaned with a neutral detergent, acetone, and ethanol, dried by boiling out from boiling ethanol, and fixed to a substrate holder of a vapor deposition apparatus. The pressure was reduced to 1 × 10 ⁻⁶ Torr (1.3 × 10 ⁻⁴ Pa).

  Subsequently, the copolymer II-1 [thiophene-2,4-diyl-thiophene-2,5-diyl copolymer] of Chemical formula 7 was vapor-deposited to a thickness of 30 nm at a vapor deposition rate of 0.2 nm / sec to obtain a light emitting layer. .

  Further, while maintaining the reduced pressure state, MgAg (weight ratio 10: 1) was vapor-deposited at a vapor deposition rate of 0.2 nm / sec to a thickness of 200 nm to obtain a cathode to obtain an EL element.

When a voltage was applied to the EL element and a current was applied, 10 cd / m ² of yellow-green light emission (maximum emission wavelength λmax = 530 nm) was confirmed at 10 V, 100 mA / cm ² , and this emission was in a dry nitrogen atmosphere. And was stable for 1000 hours or more, and there was no appearance or growth of a partial non-light-emitting portion.

In Reference Examples 4 and 5 , when an EL element was produced in the light emitting layer using one or more of the polymers or copolymers of Chemical Formulas 4 to 7 instead of the polymer or copolymer, Good results equivalent to Reference Examples 4 and 5 were obtained.

  From the above, it is clear that the EL device using the polythiophene of the present invention is a highly reliable device that does not leak current and does not generate and grow a non-light emitting portion (dark spot).

It is a side view which shows the structural example of the organic EL element of this invention. It is a block diagram which shows the structure of a low energy electron spectrometer. It is a graph which shows the relationship between excitation energy and an electron yield.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... EL element, 2 ... Substrate, 3 ... Anode, 4 ... Hole injection transport layer, 5 ... Light emitting layer, 6 ... Electron injection transport layer, 7 ... Cathode, 10 ... Low energy electron spectrometer, 11 ... Ultraviolet lamp, DESCRIPTION OF SYMBOLS 12 ... Monochromator, 13 ... Detector, 14 ... Low energy electronic counter, 15 ... Control apparatus, 16 ... Calculation display apparatus, 17 ... XY stage.

Claims (11)

A first hole injecting and transporting layer and a light emitting layer, wherein the first hole injecting and transporting layer contains at least one of the polymers represented by the following chemical formula 1; Having at least one hole injection transport layer;
The first hole injection transport layer is formed on the anode surface,
The second hole injecting and transporting layer laminated on the first hole injecting and transporting layer is different from the above hole injecting and transporting layer, contains an aromatic tertiary amine, and is doped with rubrene,
A layer containing at least one of the polymers is formed by a vacuum deposition method;
An EL element using polythiophene having a layer doped with a fluorescent substance.

The EL device using polythiophene according to claim 1, wherein tris (8-quinolinato) aluminum is further laminated on the second hole injecting and transporting layer. Furthermore, the EL element using the polythiophene of Claim 1 or 2 which has an electron injection transport layer. In the EL device using the polythiophene according to any one of claims 1 to 3 , each of the layer containing a hole injecting and transporting compound and the layer containing an electron injecting and transporting compound has at least one layer, An EL device using polythiophene having a difference in ionization potential Ip or electron affinity Ea between the hole injecting and transporting compound and the electron injecting and transporting compound in the layer, or a difference between them of 0.2 eV or more. The layer containing the hole injecting and transporting compound is laminated on the first hole injecting and transporting layer, includes the second hole injecting and transporting layer, and contains the electron injecting and transporting compound. The EL device using polythiophene according to claim 4 , wherein a layer is further laminated on the layer containing the hole injecting and transporting compound. An EL device using the polythiophene according to any one of claims 1 to 5 , wherein the EL uses a polythiophene having at least one layer containing a mixture of a hole injection / transport compound and an electron injection / transport compound. element. The EL device using polythiophene according to claim 6 , wherein the layer containing the mixture is a light emitting layer. The polythiophene according to claim 6 or 7 , wherein the difference in ionization potential Ip or the difference in electron affinity Ea between the hole injecting and transporting compound and the electron injecting and transporting compound, or the difference between them is 0.2 eV or more. EL element. The EL element using the polythiophene according to any one of claims 4 to 8 , wherein an absolute value of an ionization potential Ip of the hole injection transport compound is 5.4 eV or less. The EL device using the polythiophene according to any one of claims 4 to 9 , wherein the electron injecting and transporting compound is tris (8-quinolinolato) aluminum. The EL element using the polythiophene according to any one of claims 1 to 10 , wherein the fluorescent substance is rubrene.

Images