JP2019034904A - Compound having aromatic hydrocarbon group and two phthalimide groups and organic electroluminescent element - Google Patents

Abstract

To provide an organic compound having characteristics excellent in electron injection/transport performance as a material for an organic electroluminescent element having low power consumption and to provide an organic electroluminescent element having low power consumption by using the compound.SOLUTION: The compound has a substituted or unsubstituted aromatic hydrocarbon group and two substituted or unsubstituted phthalimide groups as represented by the following general formula (1).SELECTED DRAWING: None

Description

  The present invention relates to a compound suitable for an organic electroluminescence element (hereinafter sometimes abbreviated as an organic EL element) which is a self-luminous element suitable for various display devices, and an organic EL element using the compound. Specifically, a compound having a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, or a substituted or unsubstituted quarterphenylyl group and two substituted or unsubstituted phthalimide groups, and an organic compound using the compound The present invention relates to an EL element.

  Since organic electroluminescent elements are self-luminous elements, they have been actively researched because they are brighter and have better visibility than liquid crystal elements and can be clearly displayed.

In 1987, Eastman Kodak's C.I. W. Tang et al. Have made a practical organic EL device using an organic material by developing a laminated structure device in which various roles are assigned to each material. They laminate a phosphor capable of transporting electrons and an organic substance capable of transporting holes, and inject both charges into the phosphor layer to emit light. High luminance of 1000 cd / m ² or more can be obtained (for example, see Patent Document 1 and Patent Document 2).

  To date, many improvements have been made for the practical application of organic electroluminescence devices, and various roles have been further subdivided, and sequentially on the substrate, anode, hole injection layer, hole transport layer, light emitting layer, electron High efficiency and durability have been achieved by an electroluminescent device provided with a transport layer, an electron injection layer, and a cathode (see, for example, Non-Patent Document 1).

  Further, the use of triplet excitons has been attempted for the purpose of further improving the luminous efficiency, and the use of phosphorescent emitters has been studied (for example, see Non-Patent Document 2).

  An element utilizing light emission by thermally activated delayed fluorescence (TADF) has also been developed. In 2011, Adachi et al. Of Kyushu University realized an external quantum efficiency of 5.3% by an element using a thermally activated delayed fluorescent material (see, for example, Non-Patent Document 3), and in 2012, 19% The external quantum efficiency exceeding 1 was realized (for example, refer nonpatent literature 4).

  The light-emitting layer can also be produced by doping a charge transporting compound generally called a host material with a phosphor or a phosphorescent material. The selection of an organic material in an organic electroluminescence element has a great influence on various characteristics such as efficiency and durability of the element.

  In an organic electroluminescence device, an electron transport material having good electron injection / transport properties is required in order to realize efficient charge recombination in a light emitting layer. In recent years, performance improvement is particularly expected. In order to improve the luminous efficiency of the blue element, there is a demand for an electron transport material having a wider band gap (smaller electron affinity and larger work function).

  When the electron affinity is small, the electron injection barrier to the light emitting layer used in the blue element is particularly small, and the electron injection efficiency into the light emitting layer is improved, so that the light emission efficiency of the element can be expected to be improved.

  When the work function is large, it is possible to prevent some holes from passing through the light emitting layer, and as a result, the probability of charge recombination within the light emitting layer is improved, and the light emission efficiency of the device is expected to be improved. it can.

Tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq ₃ ), which is a typical luminescent material, is generally used as an electron transport material, but has a work function as small as 5.7 eV and a hole blocking performance. I can't say there is.

  As a method for preventing a part of holes from passing through the light emitting layer and improving the probability of charge recombination in the light emitting layer, there is a method of inserting a hole blocking layer. To date, triazole (TAZ) derivatives (see, for example, Patent Document 3) and bathocuproine (hereinafter abbreviated as BCP) have been proposed as hole blocking materials.

  TAZ has a large work function of 6.3 eV and a high hole blocking capability, but has a high electron affinity of 2.7 eV, so it has a large electron injection barrier to the light emitting layer and is sufficient for improving the efficiency of the device. Absent.

  Furthermore, low electron transportability is a major problem in TAZ, and it has been necessary to produce an organic electroluminescent element in combination with an electron transport material with higher electron transportability (see, for example, Non-Patent Document 5). ).

  BCP, like TAZ, has a large work function of 6.7 eV and a high hole blocking capability, but has a large electron affinity of 2.8 eV, which increases the barrier for electron injection into the light-emitting layer and improves the efficiency of the device. Is not enough.

  Further, since BCP has a low glass transition point (Tg) of 83 ° C., the stability of the thin film is poor and it cannot be said that BCP functions sufficiently as a hole blocking layer.

  TPBi has been proposed as an electron transport material having high thin film stability, high electron injection / transport properties and high hole blocking ability (Patent Document 4).

  Although TPBi has a large work function of 6.2 eV and a high hole blocking capability, TPBi has a large electron affinity of 2.7 eV, so it has a large electron injection barrier to the light emitting layer, which is sufficient for improving the efficiency of the device. Absent.

  Although any material has a high hole blocking ability, it has a narrow band gap, so that it has a large electron injection barrier to the light emitting layer, which is not sufficient for improving the efficiency of a blue element. In order to improve the device characteristics of an organic electroluminescence device, an organic compound having excellent electron injection / transport performance and hole blocking capability and a wider band gap is required.

JP-A-8-48656 Japanese Patent No. 3194657 Japanese Patent No. 2734341 Japanese Patent No. 399794

Proceedings of the 9th meeting of the Japan Society of Applied Physics 55-61 pages (2001) Proceedings of the 9th Workshop of the Japan Society of Applied Physics 23-31 pages (2001) Appl. Phys. Let. 98,083302 (2011) Nature, 492, 234 (2012) Journal of the Japan Society of Applied Physics, Journal of Organic Molecules and Bioelectronics, Vol.11, No.1, pages 13-19 (2000)

  An object of the present invention is to provide an organic compound having excellent electron injection / transport performance as a material for a low power consumption organic electroluminescence device, and further using this compound, a low power consumption organic electroluminescence device is provided. The object is to provide a luminescence element. The physical properties of the organic compound suitable for the present invention include (1) good electron injection / transport properties, (2) high hole blocking properties, and (3) wide band gap. Can do. In addition, as a physical characteristic of an element suitable for the present invention, high luminous efficiency can be mentioned.

  Therefore, in order to achieve the above object, the present inventors have various phthalimide groups having a large electron-withdrawing property and various substituted or unsubstituted aromatics that can be expected to have good electron transport properties due to the abundance of π electrons. As a result of designing a compound in which a divalent group of a hydrocarbon group is combined, making various organic electroluminescent devices using the compound, and intensively evaluating the characteristics of the device, the present invention has been completed.

  1) That is, the present invention relates to a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, or a substituted or unsubstituted quarter, as represented by the following general formula (1), (2) or (3). It is a compound having a phenyl group and two substituted or unsubstituted phthalimide groups.

（１）

(1)

(In the formula, R _{1 to} R ₁₆ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent. A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.)

（２）

(2)

(In the formula, R _{1 to} R ₂₀ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent. A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.)

（３）

(3)

(Wherein R _{1 to} R ₂₄ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.)

（１−２） 2) Moreover, this invention is a compound of said 1) which has an unsubstituted biphenylyl group and two unsubstituted phthalimide groups, as represented by the following general formula (1-2).

(1-2)

  3) Further, the present invention provides an organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched between them, wherein the compound described in either 1) or 2) above is at least one organic layer. The organic EL element is characterized in that it is used as a constituent material.

  4) Moreover, this invention is an organic EL element of the said 3) description whose said organic layer is an electron carrying layer.

  5) Moreover, this invention is an organic EL element of the said 3) description whose said organic layer is a hole-blocking layer.

  6) Moreover, this invention is an organic EL element of the said 3) description whose said organic layer is an electron injection layer.

  7) Moreover, this invention is an organic EL element of the said 3) description whose said organic layer is a positive hole injection layer.

  8) Moreover, this invention is an organic EL element of the said 3) description whose said organic layer is a light emitting layer.

“An optionally substituted linear or branched alkyl group having 1 to 8 carbon atoms” represented by R _{1 to} R ₂₄ in the general formulas (1) to (3), “substitution” In the “cycloalkyl group having 5 to 10 carbon atoms which may have a group” or “the linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent”. A linear or branched alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or a linear or branched alkenyl group having 2 to 6 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, Cyclopen Group, cyclohexyl group, 1-adamantyl group, 2-adamantyl group, vinyl group, allyl group, isopropenyl group, 2-butenyl group, etc., and these groups are single bonds, substituted or unsubstituted. A ring may be formed by bonding to each other via a methylene group, an oxygen atom or a sulfur atom.

“A linear or branched alkyl group having 1 to 8 carbon atoms having a substituent” represented by R _{1 to} R ₂₄ in the general formulas (1) to (3), “a carbon atom having a substituent” Specific examples of the “substituent” in the “cycloalkyl group of 5 to 10” or “straight-chain or branched alkenyl group of 2 to 6 carbon atoms having a substituent” include deuterium atom, cyano Group, nitro group; halogen atom such as fluorine atom, chlorine atom, bromine atom and iodine atom; linear or branched alkyloxy group having 1 to 6 carbon atoms such as methyloxy group, ethyloxy group and propyloxy group An alkenyl group such as a vinyl group or an allyl group; an aryloxy group such as a phenyloxy group or a tolyloxy group; an arylalkyloxy group such as a benzyloxy group or a phenethyloxy group; Group: aromatic hydrocarbon group such as phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, fluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group or condensed polycyclic ring Aromatic group; pyridyl group, pyrimidinyl group, triazinyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, Examples thereof include aromatic heterocyclic groups such as quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbolinyl group, and these substituents are further exemplified by the substituents exemplified above. Replace It can have. These substituents may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring.

“A linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent” represented by R _{1 to} R ₂₄ in the general formulas (1) to (3) or “ “C1-C6 linear or branched alkyloxy group” or “C5-C10 cycloalkyloxy group optionally having substituent (s)” or “C5-C10 cycloalkyloxy group” As the “cycloalkyloxy group”, specifically, methyloxy group, ethyloxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group , Cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, cyclooctyloxy group, 1-adamantyloxy group, 2-adamanti Such group may be mentioned, these groups to each other is a single bond, a substituted or unsubstituted methylene group, via an oxygen atom or a sulfur atom may bond to each other to form a ring.

“A linear or branched alkyloxy group having 1 to 6 carbon atoms having a substituent” or “carbon having a substituent” represented by R _{1 to} R ₂₄ in the general formulas (1) to (3) The “substituent” in the “cycloalkyloxy group having 5 to 10 atoms” includes the above-mentioned “straight or branched alkyl group having 1 to 8 carbon atoms having a substituent”, “substituent” The same as those described for the “substituent” in the “cycloalkyl group having 5 to 10 carbon atoms” or “the linear or branched alkenyl group having 2 to 6 carbon atoms having a substituent”. Examples of possible modes are the same.

  The compound represented by the general formula (1), (2) or (3) of the present invention is a novel compound and has a wider band gap and lower electron affinity than conventional electron transport materials. The electron injection barrier to the layer is small. Furthermore, since the work function is large, the hole blocking property is high. Therefore, an element using the compound of the present invention has an effect of improving luminous efficiency.

  The compound represented by the general formula (1), (2) or (3) of the present invention can be used as a constituent material of an electron injection layer and / or an electron transport layer of an organic EL device. By using a material with a wider band gap and lower electron affinity than conventional materials, the efficiency of electron injection and transport from the electron transport layer to the light-emitting layer is improved, realizing an organic EL device with improved light-emitting efficiency. Has the effect of being able to.

  The compound represented by the general formula (1), (2) or (3) of the present invention can also be used as a constituent material of the light emitting layer of the organic EL device. Compared with conventional materials, the material of the present invention, which has excellent electron transport properties and a wide band gap, is used as a host material for a light emitting layer, and a phosphor or phosphorescent light emitter called a dopant is supported to form a light emitting layer. By using it, the drive voltage is lowered, and an organic EL element with improved luminous efficiency can be realized.

  Since the compound represented by the general formula (1), (2) or (3) of the present invention has a wide band gap and a small electron affinity, the electron injection barrier to the light emitting layer of the blue device is particularly small. Further, since it has a large work function and a high hole blocking property, it is useful as a constituent material for an electron injection layer, an electron transport layer, or a light emitting layer of an organic EL element. An organic EL device produced using the compound of the present invention can improve luminous efficiency.

1 is a 1H-NMR chart of the compound of Example 1 of the present invention (Compound 1). It is the figure which showed Example 5 and the EL element structure of Comparative Examples 1-3.

  The compound represented by the general formula (1), (2) or (3) of the present invention is a novel compound, and these compounds can be synthesized, for example, as follows. Corresponding substituted or unsubstituted biphenylyl group, substituted or unsubstituted terphenylyl group or substituted or unsubstituted quarterphenylyl group diamine and various substituted or unsubstituted phthalic anhydrides with N, N -It can be synthesized by conducting a dehydration reaction in a polar solvent such as dimethylformamide.

  Specific examples of preferred compounds among the compounds represented by the general formula (1), (2) or (3) are shown below, but the present invention is not limited to these compounds.

（化合物１）

(Compound 1)

（化合物２）

(Compound 2)

（化合物３）

(Compound 3)

（化合物４）

(Compound 4)

（化合物５）

(Compound 5)

（化合物６）

(Compound 6)

（化合物７）

(Compound 7)

（化合物８）

(Compound 8)

（化合物９）

(Compound 9)

（化合物１０）

(Compound 10)

（化合物１１）

(Compound 11)

（化合物１２）

(Compound 12)

（化合物１３）

(Compound 13)

（化合物１４）

(Compound 14)

（化合物１５）

(Compound 15)

（化合物１６）

(Compound 16)

（化合物１７）

(Compound 17)

（化合物１８）

(Compound 18)

（化合物１９）

(Compound 19)

（化合物２０）

(Compound 20)

（化合物２１）

(Compound 21)

（化合物２２）

(Compound 22)

（化合物２３）

(Compound 23)

（化合物２４）

(Compound 24)

（化合物２５）

(Compound 25)

（化合物２６）

(Compound 26)

（化合物２７）

(Compound 27)

（化合物２８）

(Compound 28)

（化合物２９）

(Compound 29)

（化合物３０）

(Compound 30)

（化合物３１）

(Compound 31)

（化合物３２）

(Compound 32)

（化合物３３）

(Compound 33)

（化合物３４）

(Compound 34)

（化合物３５）

(Compound 35)

（化合物３６）

(Compound 36)

（化合物３７）

(Compound 37)

（化合物３８）

(Compound 38)

（化合物３９）

(Compound 39)

（化合物４０）

(Compound 40)

（化合物４１）

(Compound 41)

（化合物４２）

(Compound 42)

（化合物４３）

(Compound 43)

（化合物４４）

(Compound 44)

（化合物４５）

(Compound 45)

（化合物４６）

(Compound 46)

（化合物４７）

(Compound 47)

（化合物４８）

(Compound 48)

（化合物４９）

(Compound 49)

（化合物５０）

(Compound 50)

（化合物５１）

(Compound 51)

（化合物５２）

(Compound 52)

（化合物５３）

(Compound 53)

（化合物５４）

(Compound 54)

（化合物５５）

(Compound 55)

（化合物５６）

(Compound 56)

（化合物５７）

(Compound 57)

（化合物５８）

(Compound 58)

（化合物５９）

(Compound 59)

（化合物６０）

(Compound 60)

（化合物６１）

(Compound 61)

（化合物６２）

(Compound 62)

（化合物６３）

(Compound 63)

（化合物６４）

(Compound 64)

（化合物６５）

(Compound 65)

（化合物６６）

(Compound 66)

（化合物６７）

(Compound 67)

（化合物６８）

(Compound 68)

（化合物６９）

(Compound 69)

（化合物７０）

(Compound 70)

（化合物７１）

(Compound 71)

（化合物７２）

(Compound 72)

（化合物７３）

(Compound 73)

（化合物７４）

(Compound 74)

（化合物７５）

(Compound 75)

（化合物７６）

(Compound 76)

（化合物７７）

(Compound 77)

（化合物７８）

(Compound 78)

  These compounds were purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, and the like. The compound was identified by NMR analysis. As physical property values, melting point, glass transition point (Tg), band gap and work function were measured. The melting point is an index of vapor deposition, the glass transition point (Tg) is an index of stability in a thin film state, the work function is an index of hole blocking ability, and the band gap is This is a parameter for calculating the electron affinity.

  Melting | fusing point and glass transition point were measured using the high sensitivity differential scanning calorimeter DSC6200 by Seiko Instruments Inc. using powder.

  The work function was measured using a atmospheric photoelectron spectrometer AC-3 manufactured by Riken Keiki Co., Ltd. after a 100 nm thin film was formed on the ITO substrate.

  The band gap can be calculated from an ultraviolet-visible absorption spectrum measured with a commercially available spectrophotometer. It can be calculated by reading the wavelength of the absorption edge on the long wavelength side and converting it to the energy value of light according to the following formula.

Here, Eg is the band gap value converted to light energy, h is the Planck constant (6.63 × 10 ⁻³⁴ Js), c is the speed of light (3.00 × 10 ⁸ m / s), and λ is It represents the wavelength (nm) of the absorption edge on the long wavelength side of the UV-visible absorption spectrum. 1 eV is 1.60 × 10 ⁻¹⁹ J.

In general, the electron affinity (Ea) can be calculated from the work function (Ip) and the band gap (Eg) according to the following formula.

  As the structure of the organic EL device of the present invention, an anode, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and a cathode are sequentially formed on the substrate, and the anode and the hole transport layer Examples include those having a hole injection layer between them, those having an electron injection layer between the electron transport layer and the cathode, and those having an electron blocking layer between the light emitting layer and the hole transport layer. In these multilayer structures, several organic layers can be omitted. For example, a structure having an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode sequentially on a substrate can be used. .

  Each of the light emitting layer, the hole transport layer, and the electron transport layer may have a structure in which two or more layers are stacked.

  As the anode of the organic EL element of the present invention, an electrode material having a large work function such as ITO or gold is used. As the hole injection layer of the organic EL device of the present invention, in addition to a porphyrin compound typified by copper phthalocyanine, a starburst type triphenylamine derivative, three or more triphenylamine structures in the molecule, single bond or heterocycle Triphenylamine trimers and tetramers such as arylamine compounds having a structure linked by a divalent group containing no atoms, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and coating-type polymer materials are used. be able to. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

  As the hole transport layer of the organic EL device of the present invention, N, N′-diphenyl-N, N′-di (m-tolyl) -benzidine (hereinafter abbreviated as TPD) or N, N′-diphenyl- Benzidine derivatives such as N, N′-di (α-naphthyl) -benzidine (hereinafter abbreviated as NPD), N, N, N ′, N′-tetrabiphenylylbenzidine, 1,1-bis [(di- 4-Tolylamino) phenyl] cyclohexane (hereinafter abbreviated as TAPC), various triphenylamine trimers and tetramers can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. Further, as a hole injection / transport layer, a coating type such as poly (3,4-ethylenedioxythiophene) (hereinafter abbreviated as PEDOT) / poly (styrene sulfonate) (hereinafter abbreviated as PSS) is used. These polymer materials can be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

  In addition, in the hole injection layer or the hole transport layer, a material that is usually used for the layer is further P-doped with trisbromophenylamine hexachloroantimony or the like, or a TPD structure having a partial structure. Molecular compounds and the like can be used.

  As an electron blocking layer of the organic EL device of the present invention, 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (hereinafter abbreviated as TCTA), 9,9-bis [4- (carbazole- 9-yl) phenyl] fluorene, 1,3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP), 2,2-bis (4-carbazol-9-ylphenyl) adamantane (hereinafter Ad) A triphenylsilyl group represented by 9- [4- (carbazol-9-yl) phenyl] -9- [4- (triphenylsilyl) phenyl] -9H-fluorene, and the like. And a compound having an electron blocking action such as a compound having a triarylamine structure can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As the light emitting layer of the organic EL device of the present invention, in addition to the compounds represented by the general formulas (1) to (3) of the present invention, metal complexes of quinolinol derivatives such as Alq ₃ , various metal complexes, anthracene Derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, polyparaphenylene vinylene derivatives, and the like can be used. In addition, the light emitting layer may be composed of a host material and a dopant material, and in addition to the light emitting material, a thiazole derivative, a benzimidazole derivative, a polydialkylfluorene derivative, or the like can be used as the host material. As the dopant material, quinacridone, coumarin, rubrene, perylene, and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used.

Further, a phosphorescent light emitting material can be used as the light emitting material. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. Green phosphorescent emitters such as Ir (ppy) ₃ , blue phosphorescent emitters such as FIrpic and FIr6, red phosphorescent emitters such as Btp ₂ Ir (acac), and the like are used as host materials. As the hole-injecting / transporting host material, 4,4′-di (N-carbazolyl) biphenyl (hereinafter abbreviated as CBP), carbazole derivatives such as TCTA, mCP, and the like can be used. As an electron transporting host material, p-bis (triphenylsilyl) benzene (hereinafter abbreviated as UGH2) and 2,2 ′, 2 ″-(1,3,5-phenylene) -tris (1-phenyl) -1H-benzimidazole) (hereinafter abbreviated as TPBi) and the like can be used.

  In order to avoid concentration quenching, the host material of the phosphorescent light emitting material is preferably doped by co-evaporation in the range of 1 to 30 weight percent with respect to the entire light emitting layer.

  In addition, a material that emits delayed fluorescence, such as PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN, can be used as the light-emitting material (see, for example, Non-Patent Documents 3 and 4).

  These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

  As the hole blocking layer of the organic EL device of the present invention, in addition to the compounds represented by the general formulas (1) to (3) of the present invention, phenanthroline derivatives such as bathocuproine (hereinafter abbreviated as BCP), BAlq In addition to metal complexes of quinolinol derivatives such as these, various rare earth complexes, oxazole derivatives, triazole derivatives, triazine derivatives, and other compounds having a hole blocking action can be used. These materials may also serve as the material for the electron transport layer. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to the vapor deposition method.

As an electron transport layer of the organic EL device of the present invention, in addition to the compounds represented by the general formulas (1) to (3) of the present invention, various metal complexes of quinolinol derivatives including Alq ₃ and BAlq, Metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, thiadiazole derivatives, carbodiimide derivatives, quinoxaline derivatives, phenanthroline derivatives, silole derivatives, and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

  As an electron injection layer of the organic EL device of the present invention, in addition to the compounds represented by the general formulas (1) to (3) of the present invention, alkali metal salts such as lithium fluoride and cesium fluoride, magnesium fluoride, and the like Alkaline earth metal salts and metal oxides such as aluminum oxide can be used, but this can be omitted in the preferred selection of the electron transport layer and the cathode.

  Furthermore, in the electron injecting layer or the electron transporting layer, a material usually used for the layer may be further doped with a metal such as cesium or a metal complex such as lithium quinoline.

  As the cathode of the organic EL device of the present invention, an electrode material having a low work function such as aluminum, or an alloy having a lower work function such as a magnesium silver alloy, a magnesium indium alloy, or an aluminum magnesium alloy is used as the electrode material.

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

<Synthesis of N, N'-3,3'-biphenylene-diphthalimide (Compound 1)>
In a reaction vessel purged with nitrogen, 5.71 g of 3-bromoaniline, 5.00 g of 3-aminophenylboronic acid, 40 ml of toluene, 10 ml of ethanol, 24.9 ml of 2M aqueous potassium carbonate solution, tetrakis (triphenylphosphine) palladium (0) 0 .77 g was added and heated to reflux with stirring for 5 hours. After cooling to room temperature, 100 ml of toluene and 100 ml of city water were added for liquid separation, dehydrated with anhydrous magnesium sulfate, and concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: ethyl acetate: n-hexane = 1: 1), and 4.9 g (81% yield) of yellow oil of biphenyl-3,3′-diamine was obtained. Obtained.

  The obtained biphenyl-3,3'-diamine (4.83 g), phthalic anhydride (8.15 g) and N, N-dimethylformamide (50 ml) were added to a nitrogen-substituted reaction vessel, and the mixture was heated at 120 ° C for 5 hours with stirring. The mixture was cooled to room temperature and the precipitate was collected. The precipitate was recrystallized from 1,2-dichlorobenzene to obtain 7.1 g (yield 61%) of white powder of N, N′-3,3′-biphenylene-diphthalimide (Compound 1).

  The structure of the resulting white powder was identified using NMR. The result of 1H-NMR measurement is shown in FIG.

The following 16 hydrogen signals were detected by 1H-NMR (DMSO-d6).
δ (ppm) = 7.98-8.00 (4H), 7.92-7.93 (4H), 7.82 (2H), 7.79-7.80 (2H), 7.65-7 .68 (2H), 7.49-7.50 (2H).

About the compound of this invention, melting | fusing point and glass transition point were calculated | required with the highly sensitive differential scanning calorimeter (The Seiko Instruments make, DSC6200).
Melting point Glass transition point Compound of Example 1 of the present invention 329 ° C. O.

Using the compound of the present invention, a deposited film having a thickness of 100 nm was formed on an ITO substrate, and the work function was measured with an atmospheric photoelectron spectrometer (AC-3 type, manufactured by Riken Keiki Co., Ltd.).
Work Function Compound of Invention Example 1 6.19 eV

  Thus, the compound of the present invention shows an equivalent energy level as compared with the work function of a general hole blocking layer such as TAZ or BCP, and has a good hole blocking ability. I understand that.

Using the compound of the present invention, a deposited film having a film thickness of 50 nm is prepared on a quartz substrate, an ultraviolet-visible absorption spectrum is measured with a commercially available spectrophotometer, and the band gap is calculated from the wavelength of the absorption edge on the long wavelength side. Calculated. In addition, the electron affinity was calculated from the work function and the band gap value.
Band gap Electron affinity Compound of the present invention Example 1. 3.84 eV 2.35 eV
Alq ₃ 2.70 eV 3.00 eV
TPBi 3.30 eV 2.80 eV

As described above, the compound of the present invention shows a wide value compared to the band gap of general electron transport materials such as Alq ₃ and TPBi, and has a small electron affinity, and particularly good electrons for the blue light emitting layer. It turns out that it has injectability.

  As shown in FIG. 2, the organic EL element has a hole transport layer 3, a light emitting layer 4, a hole blocking layer 5, and an electron transport layer 6 on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. The electron injection layer 7 and the cathode (aluminum electrode) 8 were deposited in this order.

  Specifically, the glass substrate 1 on which ITO having a film thickness of 150 nm was formed was washed with an organic solvent, and then the surface was washed by UV ozone treatment. Then, this glass substrate with an ITO electrode was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, TAPC was formed as a hole transport layer 3 so as to cover the transparent anode 2 so as to have a film thickness of 40 nm at a deposition rate of 1.0 Å / s. On this hole transport layer 3, mCP and blue phosphorescent emitter FIrpic as the light emitting layer 4 are subjected to binary vapor deposition at a vapor deposition rate where the vapor deposition rate ratio is mCP: FIrpic = 94: 6, resulting in a film thickness of 30 nm. Formed as follows. On this light emitting layer 4, the compound of Example 1 of the present invention (Compound 1) was formed as a hole blocking layer 5 and electron transporting layer 6 so as to have a film thickness of 45 nm at a deposition rate of 1.0 Å / s. On the hole blocking layer 5 and electron transport layer 6, lithium fluoride was formed as the electron injection layer 7 so as to have a film thickness of 0.5 nm at a deposition rate of 0.1 Å / s. Finally, aluminum was deposited to a thickness of 150 nm to form the cathode 8. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere.

Table 1 shows the measurement results of the light emission characteristics when a current of 10 mA / cm ² was passed through the organic EL device produced using the compound of Example 1 (Compound 1) of the present invention.

[Comparative Example 1]
For comparison, instead of the hole blocking layer 5 and the material of the electron transport layer 6 in Example 5 to Alq _3, An organic EL device was produced in the same manner as in Example 5. Table 1 shows the measurement results of the light emission characteristics when a current density of 10 mA / cm ² was passed through the produced organic EL element.

[Comparative Example 2]
For comparison, an organic EL device was produced in the same manner as in Example 5 by replacing the material of the hole blocking layer 5 and electron transporting layer 6 in Example 5 with TPBi. Table 1 shows the measurement results of the light emission characteristics when a current density of 10 mA / cm ² was passed through the produced organic EL element.

[Comparative Example 3]
For comparison, the material of the hole blocking layer 5 in Example 5 BCP, replacing the material of the electron transport layer 6 in Alq _3, An organic EL device was produced in the same manner as in Example 5. Table 1 shows the measurement results of the light emission characteristics when a current density of 10 mA / cm ² was passed through the produced organic EL element.

As shown in Table 1, the luminous efficiency when a current density of 10 mA / cm ² was passed was 7.63% for Alq ₃ , 14.6% for TPBi, and 7.59% for BCP / Alq _3. Thus, the compound of Example 5 (Compound 1) of the present invention was highly efficient at 25.8%. Moreover, high values were also shown for luminance and power efficiency when a current density of 10 mA / cm ² was passed.

As is clear from these results, the organic EL device using the compound of the present invention has a light emission efficiency and a power efficiency as compared with a device using Alq ₃ or TPBi used as a general electron transport material. It was found that the improvement of can be achieved.

  Since the compound having a substituted or unsubstituted aromatic hydrocarbon group and two substituted or unsubstituted phthalimide groups of the present invention has good electron injection / transport performance and a wide band gap, it is suitable as a compound for organic EL devices. Are better. By producing an organic EL device using the compound, high efficiency can be obtained and durability can be improved. For example, it has become possible to develop home appliances and lighting.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent anode 3 Hole transport layer 4 Light emitting layer 5 Hole blocking layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims (8)

A substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, or a substituted or unsubstituted quarterphenylyl group represented by any one of the following general formulas (1), (2), or (3) And a compound having two substituted or unsubstituted phthalimide groups.

(1)
(In the formula, R _{1 to} R ₁₆ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent. A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.)

(2)
(In the formula, R _{1 to} R ₂₀ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent. A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.)

(3)
(Wherein R _{1 to} R ₂₄ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) A linear or branched alkyl group having 1 to 8 carbon atoms, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, and an optionally substituted carbon atom having 2 to 6 carbon atoms A linear or branched alkenyl group, an optionally substituted linear or branched alkyloxy group having 1 to 6 carbon atoms, and an optionally substituted carbon atom of 5 To 10 cycloalkyloxy groups.) The compound of Claim 1 which has an unsubstituted biphenylyl group and two unsubstituted phthalimide groups represented by the following general formula (1-2).

(1-2)   In the organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched therebetween, the compound according to claim 1 or 2 is used as a constituent material of at least one organic layer. A characteristic organic EL element.   The organic EL device according to claim 3, wherein the organic layer is an electron transport layer.   The organic EL device according to claim 3, wherein the organic layer is a hole blocking layer.   The organic EL device according to claim 3, wherein the organic layer is an electron injection layer.   The organic EL device according to claim 3, wherein the organic layer is a hole injection layer.   The organic EL device according to claim 3, wherein the organic layer is a light emitting layer.

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