JP2013030674A - Charge transporting organic thin film and organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge transporting organic thin film having excellent charge transporting property, and to provide an organic electroluminescent element including the charge transporting organic thin film.SOLUTION: A charge transporting organic thin film of the present invention is a charge transporting amorphous thin film that is formed on a base and comprises a charge transporting π-conjugated compound including a plurality of π-electron conjugated structural surfaces not parallel with each other. If the π-conjugated compound has electron transporting property then a π-electron conjugated structural surface thereof on which a lowest unoccupied molecular orbital (LUMO) is mainly distributed, is determined as a first π-electron conjugated structural surface, or if the π-conjugated compound has hole transporting property then a π-electron conjugated structural surface thereof on which a highest occupied molecular orbital (HOMO) is mainly distributed, is determined as the first π-electron conjugated structural surface. In such a situation, the first π-electron conjugated structural surface is oriented substantially in parallel with a surface of the base.

Description

  The present invention relates to a charge transporting organic thin film and an organic electroluminescence device.

  In recent years, the need for flat panel displays has increased with the advancement of information technology. As a flat panel display, a non-self-luminous liquid crystal display (LCD), a self-luminous plasma display (PDP), an inorganic electroluminescence (inorganic EL) display, an organic electroluminescence (organic EL) display, etc. are known. However, among these flat panel displays, the organic EL display is particularly attracting attention in terms of self-light emission.

  As an organic electroluminescence element (hereinafter sometimes abbreviated as “organic EL element”), a carrier injection type EL element in an organic solid such as an anthracene single crystal has been studied in detail in the 1960s. Although these elements were of a single layer type, Tang et al. Proposed a stacked organic EL element having a light emitting layer and a hole transport layer between a pair of electrodes. The emission mechanism of these injection-type EL devices is [1] electron injection from the cathode and hole injection from the anode, [2] movement of electrons and holes in the solid, and [3] recombination of electrons and holes. [4] Emission from the generated singlet excitons is common.

As a typical example of the stacked organic EL element, an ITO (Indium Tin Oxide) film is formed on a glass substrate as an anode, and TPD (N, N′-diphenyl-N, N′-di (3-methylphenyl) is formed thereon. ) -1,1′-biphenyl-4,4′-diamine) with a thickness of about 50 nm, and Alq ₃ (tris (8-quinolalite) aluminum) with a thickness of about 50 nm on top of it, Furthermore, the example which comprises an element by vapor-depositing Al and Li alloy as a cathode is mentioned.
By setting the work function of ITO used for the anode to 4.4 to 5.0 eV, holes can be easily injected into the TPD, and a stable metal with a work function as small as possible is selected for the cathode. For example, an alloy of Al and Li or an alloy of Mg and Ag. According to this configuration, green light emission can be obtained by applying a DC voltage of 5 V to 10 V, for example.

An example using conductive liquid crystal as a carrier transport layer is also known. For example, Non-Patent Document 1 discloses that the mobility of a liquid crystal phase (Dh phase) of a discotic liquid crystal that is a long-chain triphenylene compound is 10 ⁻³ to 10 ⁻² cm ² / Vsec, and a mesophase (intermediate phase). , Not a liquid crystal phase) is disclosed to be 10-1 cm ² / Vsec. Further, Non-Patent Document 2 discloses that a mobility in a phenyl naphthalene-based smectic B phase is 10 ⁻³ cm ² / Vsec or more even in a rod-like liquid crystal.
In the conventional organic EL element as described above, the thickness of the organic compound layer is about 50 to 500 nm in total of two or three layers.

JP-A-6-330018 Japanese Patent Laid-Open No. 2001-167887 JP 2001-167888 A

Nature, Vol. 371, p. 141 Junichi Hanna, Applied Physics, Vol. 68, No. 1, p. 26, Organic Electronics, 10, 2009, 127-137 Applied Physics Letters, 93, 2008, 173302.

The conventional organic EL element has a problem that a short-circuit between electrodes tends to occur because a high voltage of about 100 MV / cm is applied to a thin layer having a thickness of about 100 nm. This problem is somewhat alleviated by increasing the thickness of each organic layer or by making the organic layer multi-layered, but there are problems that productivity is lowered and drive voltage is increased. The reason for applying an electric field of about 100 MV / cm is that the carrier mobility of the organic layer is small, and the applied electric field can be reduced if an organic layer with a high mobility can be formed. At present, the mobility of a carrier transport layer generally used in an organic EL element is 10 ⁻⁵ to 10 ⁻³ cm ² / Vsec, and it is said that the limit is about 10 ⁻³ cm ² / Vsec even for an amorphous material.
Therefore, new carrier transport layers and light emitting layers using conductive liquid crystal compounds having high mobility are expected. For example, the conductive liquid crystal having a high carrier transport property includes a discotic liquid crystal and a smectic liquid crystal having a high degree of order.

  In order to solve such problems, it has been proposed to produce an organic amorphous thin film with controlled molecular orientation by spin coating a low molecular weight organic material under strong electric field conditions (Patent Document). 1). However, Patent Document 1 does not disclose information on the molecular orientation state of the obtained organic thin film, and only the second-order nonlinear optical effect has been clarified as the characteristics given by the obtained thin film. . In addition, in an organic EL element, an attempt has been made to use an alignment-controlled thin film by using a conductive liquid crystal compound for the carrier transport layer (see Patent Documents 2 and 3). It was not disclosed, and the characteristics as an organic EL element were not sufficient. Recently, when vapor deposition of a styryl-based compound as a π-conjugated material was performed, it was reported that the orientation in the horizontal direction has priority over the substrate, but the change in charge transport characteristics due to the priority in the horizontal orientation, There is no specific organic semiconductor element utilizing the priority of horizontal alignment (see Non-Patent Documents 3 and 4).

  The present invention has been made in view of such conventional circumstances, and provides a charge transporting organic thin film having excellent charge transporting properties, and an organic electroluminescence device including the charge transporting organic thin film. It is.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies focusing on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the π-conjugated compound constituting the charge transporting organic thin film. It was. As a result, in the π-conjugated compound of the organic layer, it was found that the charge transportability of the organic layer can be improved by controlling the orientation of the π-electron conjugated surface in which HOMO or LUMO is mainly distributed. It came to be completed. That is, the present invention employs the following configuration.

  The charge transporting organic thin film of the present invention is a charge transporting amorphous thin film formed on a substrate and comprising a charge transporting π conjugated compound having a plurality of π electron conjugated structure surfaces that are not parallel to each other. When the π-conjugated compound is electron-transporting, the π-electron conjugated structure surface in which the lowest unoccupied molecular orbital (LUMO) is mainly distributed is shown. When the π-conjugated compound is hole-transporting, the highest When the π-electron conjugated structure surface in which occupied molecular orbitals (HOMO) are mainly distributed is the first π-electron conjugated structure surface, the first π-electron conjugated structure surface is in relation to the surface of the substrate. And are substantially parallel.

In the charge transporting organic thin film of the present invention, it is preferable that the HOMO and the LUMO are derived by an ab initio molecular orbital calculation method using Gaussian09W.
In the charge transporting organic thin film of the present invention, the secondary orientation parameter S with respect to the direction of the transition dipole moment parallel to the first π-electron conjugated structure surface is in the range of −0.1 to −0.5. be able to.
In the charge transporting organic thin film of the present invention, the first π-electron conjugated structure surface has a major axis and a minor axis, and the secondary orientation parameter S with respect to the major axis direction of the first π-electron conjugated structure surface is , -0.1 to -0.5.
In the charge transporting organic thin film of the present invention, the first π-conjugated structure surface may be a π-electron conjugated structure surface having the widest area in the π-conjugated compound.

  The organic electroluminescence device of the present invention is an organic electroluminescence device in which at least one organic layer containing a light emitting material is disposed between two opposing electrodes, and the organic layer is the charge transport device of the present invention. It is characterized by comprising a conductive organic thin film.

  ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element provided with the charge transportable organic thin film which has the outstanding charge transportability, and this charge transportable organic thin film can be provided.

It is a schematic diagram which shows an example of the element to which the charge transportable organic thin film of this embodiment is applied. 2A shows the stable structure of MADN, FIG. 2C shows the molecular orbital of HOMO of MADN, and FIG. 2C shows the molecular orbital of LUMO of MADN. It is a schematic diagram which shows one Embodiment of the organic EL element which concerns on this invention. 4A shows the stable structure of α-NPD, and FIG. 4B shows the HOMO molecular orbital of α-NPD. 5A shows a stable structure of TcTa, and FIG. 5B shows a HOMO molecular orbital of TcTa. 6A shows the stable structure of BCP, and FIG. 6B shows the molecular orbital of LUMO of BCP. FIG. 7A shows a stable structure of mCP, and FIG. 7B shows a molecular orbital of HOMO of mCP. FIG. 8A is a graph showing the analysis result of the element 1 of Comparative Example 1, and FIG. 8B is a graph showing the analysis result of the element 2 of Example 1. It is a graph which shows the current-voltage (IV) characteristic measurement result of the element 1 of the comparative example 1, and the element 2 of Example 1. FIG. 6 is a graph showing a measurement result of current-voltage (IV) characteristics of Study Example 1. It is a graph which shows the orientation parameter S of the examination example 2, and the current density at the time of 2V application. 10 is a graph showing an orientation parameter S of Study Example 3.

  Hereinafter, an embodiment of a charge transporting organic thin film according to the present invention and an organic electroluminescence device using the same will be described. The following embodiments are specifically described for better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

  The charge transporting organic thin film of this embodiment is a charge transporting amorphous thin film comprising a charge transporting π conjugated compound having a plurality of π electron conjugated structure surfaces that are not parallel to each other in the molecular structure. Here, “charge transportability” means electron transportability or hole transportability.

  Conventionally, in a charge transporting organic thin film, a technique for orienting a π-conjugated compound constituting the organic thin film in parallel to the plane of a substrate such as an electrode has been disclosed. However, depending on the molecular structure of the π-conjugated compound, all π-electron conjugated structure surfaces in the molecular structure may not be on the same plane.

  As a result of intensive studies on the charge-transporting amorphous thin film containing a π-conjugated compound having a plurality of π-electron conjugated structure surfaces that are not parallel to each other, the present inventors have found the highest π-electron orbital of the π-conjugated compound. It was found that controlling the orientation of the π-conjugated compound in the thin film in consideration of the distribution of occupied molecular orbitals (HOMO) or lowest unoccupied molecular orbitals (LUMO) is important for improving the charge transport property. For the ease of charge (electron, hole) movement, the overlap of π orbitals involved in charge movement in the conductive direction in the thin film is important. Therefore, as in the prior art, it was found that the charge transportability may not necessarily be improved by simply aligning any π-electron conjugated structure surface in the molecule parallel to the surface of the substrate such as an electrode. .

FIG. 1 schematically shows an example of a device to which the charge transporting organic thin film of the present embodiment is applied. The element 10 shown in FIG. 1 is configured by sandwiching a charge transporting organic thin film 5 of the present embodiment (hereinafter sometimes abbreviated as “organic thin film 5”) between a pair of electrodes 1 and 2. Yes. The film thickness of the organic thin film 5 is not specifically limited, For example, it is set as the range of 10-100 nm.
In the organic thin film 5 of this embodiment, the π conjugated compound constituting the organic thin film 5 is a π electron conjugated structure surface in which HOMO or LUMO is mainly distributed among a plurality of π electron conjugated structure surfaces in the molecular structure. The (first π electron conjugated structure surface) is oriented substantially parallel to the surface of the electrode 1 (or electrode 2) which is the base material.

Here, in the present embodiment, the substrate on which the organic thin film 5 is formed may be a crystalline or amorphous plate-like substrate (substrate) having a flat surface. For example, as a crystalline substrate, an inorganic conductive oxide such as ITO (Indium Tin Oxide) is formed on a single crystal substrate made of silicon, sapphire or the like, a substrate on which an organic or inorganic thin film is formed, or a glass substrate. Examples thereof include a substrate on which an electrode is formed or an electrode.
The π-conjugated structure surface of the π-conjugated compound constituting the organic thin film 5 of the present embodiment includes a benzene ring, naphthalene ring, anthracene ring, phenanthroline ring, benzofuran ring, benzodifuran ring, triazine ring, imidazole ring, and benzimidazole ring. , Triazole ring, pyridine ring, oxadiazole ring, carbazole ring and the like.
In this embodiment, the π-electron conjugated structure surface (first π-electron conjugated structure surface) is oriented substantially parallel to the surface of the substrate. Needless to say, the case where they are completely parallel indicates a state in which the π-electron conjugated structure surface and the substrate surface are oriented so that an angle is less than 45 °.

In the organic thin film 5 of the present embodiment, when the π conjugated compound constituting the organic thin film 5 is electron transporting, the π electron conjugated structure surface in which LUMO, which is an orbital involved in electron transfer, is mainly distributed is the base material. Are oriented so as to be substantially parallel to the surface of the electrode 1. Thereby, the overlap of the π electron orbit corresponding to the LUMO of the π conjugated compound adjacent to the film thickness direction (conducting direction) of the organic thin film 5 is increased, and the film thickness direction of the organic thin film 5 sandwiched between the electrodes 1 and 2 is increased. Electron transportability is improved.
Further, in the organic thin film 5 of the present embodiment, when the π conjugated compound constituting the organic thin film 5 is hole transporting, a π electron conjugated structure in which HOMO which is an orbital involved in hole movement is mainly distributed. The surface is oriented so as to be substantially parallel to the surface of the electrode 1 as a substrate. Thereby, the overlap of π electron orbits corresponding to HOMO of the π conjugated compound adjacent to the film thickness direction (conducting direction) of the organic thin film 5 is increased, and the film thickness direction of the organic thin film 5 sandwiched between the electrodes 1 and 2 is increased. Hole transportability is improved.

  If an organic electroluminescence element (hereinafter sometimes abbreviated as “organic EL element”), which will be described later, is configured using the organic thin film 5 of the present embodiment having such a high charge transporting property, an organic material is formed from the electrode. Since the charge injection efficiency into the layer (organic thin film) is improved, the driving voltage of the organic EL element can be lowered.

The distribution of HOMO and LUMO of the π-conjugated compound constituting the organic thin film 5 can be calculated by an ab initio molecular orbital method. HOMO and LUMO calculations using the ab initio molecular orbital method can be performed using general-purpose quantum chemistry calculation software. For example, Gaussian series by Gaussian in the United States, MarcoModel by Schrodinger, Spartan by Wavefunction For example, ABINIT-MP / BioStation manufactured by Advanced Software, Inc., Gaussian09 (Gaussian09W, Gaussian09M) is preferable.
When calculating the HOMO or LUMO distribution of a π-conjugated compound using Gaussian09W, first input the input file by specifying the checkpoint file, initial coordinates of the molecular model, calculation method and basis function, charge and spin multiplicity. Create and perform calculation to optimize structuring and calculate the stable structure of π-conjugated compounds. Subsequently, the HOMO or LUMO distribution of the π-conjugated compound can be visualized by displaying molecular orbitals with respect to the obtained stable structure. As the calculation method for creating and executing the input file, the Hartree-Fock method, the density functional method (DFT), the MP (Moller Plesset perturbation theory) method, and the CC (Coupled Cluster theory) method can be selected. The calculation by Gaussian 09W described later in this specification was performed using the DFT method. In Gaussian 09W, HOMO and LUMO are calculated simultaneously with the calculation of the stable structure, and the distribution of HOMO and LUMO can be visualized by GaussianView.

  For example, the molecular structure of 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN), which is attracting attention as an organic material exhibiting ambipolar charge transportability, is shown below.

MADN has a structure in which naphthalene is bonded to both sides (9th and 10th positions) of anthracene.
FIG. 2 (a) shows the stable structure of MADN calculated for MADN using level B3LYP / 6-31G (d) of the inexperienced molecular orbital calculation method using Gaussian09W. FIG. 2 (b) shows the HOMO molecular orbital of MADN and FIG. 2 (c) shows the LUMO molecular orbital visualized for this stable structure.
As shown in FIG. 2, the HOMO and LUMO molecular orbitals of MADN are in the anthracene ring and hardly exist in the naphthalene ring.
Although MADN is ambipolar charge transporting, in order to apply MADN as one layer of an organic layer disposed between electrodes of an organic EL element as described later, the MADN film is used as a charge transporting or hole transporting layer. In any case of functioning, the orientation of MADN in the film is controlled so that the anthracene ring in which HOMO and LUMO are mainly distributed is oriented in a substantially horizontal direction with respect to the electrode surface as a substrate. As a result, the charge transporting property of the MADN film can be improved, and the driving voltage of the organic EL element can be lowered.

As a method for controlling the orientation of the π-conjugated compound in the organic thin film 5 as described above, the heat treatment is performed after the organic thin film 5 is formed, the heating is performed during the formation of the organic thin film 5, the magnetic field or the electric field is applied, etc. The method of producing sex is mentioned.
As an example, in the case of a MADN film, as shown in the examples described later, the formed MADN film is heat-treated at 140 ° C., or the substrate (film formation surface of the substrate or electrode) at the time of forming the MADN film is used. By setting the temperature to 60 ° C. or higher, a MADN film in which the anthracene ring of MADN is oriented substantially in the horizontal direction with respect to the substrate surface can be formed.

  As described above, in this embodiment, the organic thin film 5 has a molecular orbital involved in charge transfer among a plurality of π-electron conjugated structure surfaces of a π-conjugated compound (HOMO, electron transportability when the π-conjugated compound has hole transportability). In this case, the π-electron conjugated structure surface in which LUMO) is mainly distributed is configured to be oriented substantially horizontally with respect to the substrate surface. Here, “a π-electron conjugated structure surface in which HOMO or LUMO is mainly distributed” means a π-electron conjugate having the largest distribution ratio of HOMO or LUMO among a plurality of π-electron conjugated structure planes of a π-conjugated compound. The structural surface is shown. In addition, among π-conjugated compounds that can form the organic thin film 5 of the present embodiment, HOMO or LUMO may be evenly distributed over a plurality of π-electron conjugated structure surfaces, as will be described later. In that case, it is preferable to align the π-electron conjugated structure surface having the largest area substantially horizontally with respect to the substrate surface, whereby the charge transport property of the organic thin film 5 can be improved.

  In the organic thin film 5 of the present embodiment, a transition parallel to a π-electron conjugated structure surface (first π-electron conjugated structure surface) in which HOMO or LUMO is mainly distributed among a plurality of π-electron conjugated structure surfaces of the π-conjugated compound. The secondary orientation parameter S with respect to the direction of the dipole moment is preferably in the range of −0.1 to −0.5. When the orientation parameter S of the organic thin film S is in the above range, the first π-electron conjugated structure surface is close to the horizontal direction with respect to the substrate surface, and the charge transporting property of the organic thin film 5 is preferable. As shown in the examples described later, the first π-electron conjugated structure surface is oriented in the horizontal direction with respect to the substrate surface rather than the other π-electron conjugated structure surfaces, whereby the first π-electron conjugated structure surface It is confirmed that the secondary orientation parameter S with respect to the direction of the transition dipole moment parallel to is −0.1 or less, and the charge transport property is improved.

  The orientation parameter S is represented by the following formula (A) when the angle between the orientation axis of the molecule and the direction perpendicular to the substrate is θ (°) (see Non-Patent Document 4).

(In the formula (A), k _xy represents an extinction coefficient in the horizontal direction with respect to the substrate, and k _z represents an extinction coefficient in the vertical direction with respect to the substrate.)
Here, the x and y, and isotropic two directions perpendicular to and optically to one another, when the extinction coefficient of these directions to k _x and k _y, is _{k xy =} k x ₌ k _y .
In the formula (A), k _xy and k _z can be obtained by optical evaluation such as spectral ellipsometry of the organic thin film 5. For example, when the organic thin film is not optically anisotropic, S = 0, when the molecular orientation direction in the organic thin film is completely perpendicular to the substrate, S = 1, When the molecular orientation direction is completely horizontal to the substrate, S = −0.5. Therefore, in the present embodiment, the lower limit value of the preferable range of the orientation parameter S described above is set to −0.5.

  In the organic thin film 5 of the present embodiment, the orientation axis of the molecule serving as the setting reference for θ in the formula (A) is on the π-electron conjugated structure surface (first π-electron conjugated structure surface) in which HOMO or LUMO is mainly distributed. The direction of the parallel transition dipole moment. Here, the transition dipole moment of each direction including the direction parallel to the π-electron conjugated structure surface of the π-conjugated compound constituting the organic thin film 5 is an electron using Gaussian 09W time-dependent density functional theory (TD-DFT). It can be obtained from the calculation result of the excited state. Since the direction, magnitude, and wavelength of the transition dipole moment are described in the obtained calculation result, it is possible to determine which absorption by comparing these with the peak wavelength of the extinction coefficient curve of the organic thin film 5 actually measured. It can be determined in which direction the peak is derived from the transition dipole moment.

  In the organic thin film 5 of the present embodiment, the orientation axis of the molecule serving as the setting reference for θ in the formula (A) is the transition dipole moment parallel to the first π-electron conjugated structure surface in which HOMO or LUMO is mainly distributed. However, when the first π-electron conjugated structure surface has a major axis and a minor axis such as anthracene as in the above-mentioned MADN, the major axis direction of the first π-electron conjugated structure surface is The orientation parameter S is preferably set as the molecular orientation axis. In this case, the orientation parameter S is preferably in the range of −0.1 to −0.5 as described above.

  In the organic thin film 5 of the present embodiment, when the first π electron conjugated structure surface is linear, the linear direction (long direction) of the first π electron conjugated structure surface is the molecular alignment axis, It is preferable to set the orientation parameter S. In this case, the orientation parameter S is preferably in the range of −0.1 to −0.5 as described above.

  Further, in the organic thin film 5 of the present embodiment, when the first π electron conjugated structure surface is circular or square, it is in the plane of the first π electron conjugated structure surface (parallel to the conjugated structure surface). It is preferable to set the orientation parameter S with the direction of the transition dipole moment as the orientation axis of the molecule. In this case, the orientation parameter S is preferably in the range of −0.1 to −0.5 as described above.

As described above, the organic thin film 5 of the present embodiment has a molecular orbital involved in charge transfer among the plurality of π-electron conjugated structure surfaces of the π-conjugated compound (in the case where the π-conjugated compound has hole transportability, HOMO, In the case of electron transporting property, the π-electron conjugated structure surface in which LUMO) is mainly distributed is configured to be oriented substantially horizontally with respect to the substrate surface. Therefore, the overlap of the π orbitals involved in charge transfer is increased, whereby the organic thin film 5 having good charge transportability is obtained.
The charge transporting organic thin film 5 of the present embodiment is applicable to various organic electronic devices such as an organic electroluminescence element and an organic thin film transistor. Since the organic thin film 5 of the present embodiment has high charge transportability, the organic thin film 5 is applied as at least one layer of the organic layer constituting the organic electroluminescence element (organic EL element). Charge injection efficiency into the organic layer (organic thin film 5) is improved, and the driving voltage of the organic EL element can be lowered.

Hereinafter, an embodiment of an organic electroluminescence element (organic EL element) using the organic thin film 5 of the present embodiment will be described.
FIG. 3 is a schematic diagram showing one embodiment of the organic EL element according to the present invention.
The organic EL element 20 according to the present embodiment shown in FIG. 3 includes a first electrode (anode) 12 formed on a substrate 11 such as a glass plate, and a second electrode (cathode) disposed to face the first electrode 12. 19 and an organic EL layer (organic layer) 7 sandwiched between the pair of electrodes 12 and 19.

The organic EL layer 7 can use a known organic EL material. For example, the organic EL layer 7 includes an organic layer including an organic layer having at least an organic light emitting layer 7 made of an organic light emitting material between the first electrode 12 and the second electrode 19. Although composed of the EL layer 7, it is not limited to these.
The organic EL layer 7 in the organic EL element 20 of the present embodiment is composed of an organic light emitting layer 15 and a hole transporting or electron transporting charge transporting layer as shown in FIG. A multilayer structure may be used, and specific examples include the following configurations, but the present invention is not limited thereto.

(1) Organic light emitting layer 15
(2) Hole transport layer 14 / organic light emitting layer 15
(3) Organic light emitting layer 15 / electron transport layer 17
(4) Hole transport layer 14 / organic light emitting layer 15 / electron transport layer 17
(5) Hole injection layer 13 / hole transport layer 14 / organic light emitting layer 15 / electron transport layer 17
(6) Hole injection layer 13 / hole transport layer 14 / organic light emitting layer 15 / electron transport layer 17 / electron injection layer 18
(7) Hole injection layer 13 / hole transport layer 14 / organic light emitting layer 15 / hole prevention layer 16 / electron transport layer 17
(8) Hole injection layer 13 / hole transport layer 14 / organic light emitting layer 15 / hole prevention layer 16 / electron transport layer 17 / electron injection layer 18
(9) Hole injection layer 13 / hole transport layer 14 / electron blocking layer / organic light emitting layer 15 / hole blocking layer 16 / electron transport layer 17 / electron injection layer 18
Here, each of the organic light emitting layer 15, the hole injection layer 13, the hole transport layer 14, the hole prevention layer 16, the electron prevention layer, the electron transport layer 17 and the electron injection layer 18 may have a single layer structure or a multilayer structure. Good.

Since the organic thin film 5 of the present embodiment has a good charge transporting property, the hole injection layer 13, the hole transport layer 14, the electron blocking layer, the organic light emitting layer 15, and the holes of the organic EL element 20 of the present embodiment. It is preferable that the organic thin film 5 of the above embodiment is applied to at least one of the prevention layer 16, the electron transport layer 17, and the electron injection layer 18.
Here, at least one layer constituting the organic EL element 7 of the organic EL element 20 is composed of a charge transporting π-conjugated compound, and the π-conjugated compound has a plurality of non-parallel π-electron conjugated structure surfaces in its molecular structure. In this case, the organic thin film 5 of the present embodiment can be applied. In addition, the layer and compound which can apply the orientation of the organic thin film 5 are mentioned later.

Hereinafter, each component of the organic EL element 20 will be described.
It is preferable that the 1st electrode 12 and the 2nd electrode 19 function as an anode or a cathode. Examples of the material constituting the cathode include alkali metals and alkaline earth metals. When considering stability, the cathode is a calcium film, aluminum film, aluminum lithium alloy, aluminum copper alloy, aluminum copper silicon alloy, laminated film of calcium and aluminum, lithium, sodium potassium alloy, magnesium alloy film, barium film, A barium compound film, a cesium film, a cesium compound film, a fluorine compound film, or the like is preferable. Examples of the material constituting the anode include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), indium oxide, tin oxide, Cd ₂ SnO ₄ , zinc oxide, copper iodide, gold, platinum, and the like. It is done. FIG. 3 shows the case where the first electrode 12 is an anode and the second electrode 19 is a cathode. However, the present invention is not limited to this, and the first electrode 12 is a cathode and the second electrode 19 is an anode. It may be. In that case, the layered structure of the organic EL layer 7 may be reversed upside down from that in FIG. 3, the hole transporting layer is disposed on the anode side, and the electron transporting layer is disposed on the cathode side.

The first electrode 12 and the second electrode 19 can be formed on the substrate using the above materials by a known method such as an EB (electron beam) vapor deposition method, a sputtering method, an ion plating method, or a resistance heating vapor deposition method. However, the present invention is not limited to these forming methods. If necessary, the formed electrode can be patterned by a photolithographic fee method or a laser peeling method, or a patterned electrode can be directly formed by combining with a shadow mask.
The film thickness of the first electrode 12 and the second electrode 16 is preferably 50 nm or more. When the film thicknesses of the first electrode 12 and the second electrode 19 are less than 50 nm, the wiring resistance increases, so that the drive voltage may increase.

  The organic light emitting layer 15 may be composed of only an organic light emitting material, or may be composed of a combination of a light emitting dopant and a host material, and optionally a hole transport material, an electron transport material, and an additive (donor). , An acceptor, etc.), etc., and these materials may be dispersed in a polymer material (binding resin) or an inorganic material. From the viewpoint of luminous efficiency and lifetime, those in which a luminescent dopant is dispersed in a host material are preferable.

As the organic light emitting material, a known light emitting material for organic EL can be used. Such light-emitting materials are classified into low-molecular light-emitting materials, polymer light-emitting materials, and the like. Specific examples of these compounds are given below, but the present invention is not limited to these materials. The light-emitting material may be classified into a fluorescent material, a phosphorescent material, and the like, and it is preferable to use a phosphorescent material with high light emission efficiency from the viewpoint of reducing power consumption.
Here, specific compounds are exemplified below, but the present invention is not limited to these materials.

Examples of the low molecular light emitting material used for the organic light emitting layer 15 include aromatic dimethylidene compounds such as 4,4′-bis (2,2′-diphenylvinyl) -biphenyl (DPVBi), 5-methyl-2- [ Oxadiazole compounds such as 2- [4- (5-methyl-2-benzoxazolyl) phenyl] vinyl] benzoxazole, 3- (4-biphenylyl) -4-phenyl-5-t-butylphenyl- Triazole derivatives such as 1,2,4-triazole (TAZ), styrylbenzene compounds such as 1,4-bis (2-methylstyryl) benzene, thiopyrazine dioxide derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, diphenoquinone derivatives Fluorescent organic materials such as fluorenone derivatives, and azomethine zinc complexes (8- Rokishikinorinato) aluminum complex (Alq ₃₎ fluorescence emitting organic metal complex such as, BeBq (bis (benzoquinolinolato) beryllium complex), DTVBi (4,4'- bis - (2,2-di -p- tolyl - vinyl ) -Biphenyl), Eu (DBM) ₃ (Phen) (tris (1,3-diphenyl-1,3-propanediono) (monophenanthroline) Eu (III)), further diphenylethylene derivatives, triphenylamine derivatives , Diaminocarbazole derivatives, bisstyryl derivatives, aromatic diamine derivatives, quinacridone compounds, perylene compounds, coumarin compounds, distyrylarylene derivatives (DPVBi), oligothiophene derivatives (BMA-3T), and the like.

  Examples of the polymer light emitting material used for the organic light emitting layer 15 include poly (2-decyloxy-1,4-phenylene) (DO-PPP), poly [2,5-bis- [2- (N, N, N-triethylammonium) ethoxy] -1,4-phenyl-alt-1,4-phenyllene] dibromide (PPP-NEt3 +), poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4 -Phenylene vinylene] (MEH-PPV), poly [5-methoxy- (2-propanoxysulfonide) -1,4-phenylene vinylene] (MPS-PPV), poly [2,5-bis- (hexyloxy) ) -1,4-phenylene- (1-cyanovinylene)] (CN-PPV), poly (9,9-dioctylfluorene) (PDAF) Such polyspiro derivatives and the like.

  When the organic light emitting layer 15 is composed of a light emitting dopant and a host material, as the host material of the organic light emitting layer 15, 4,4′-bis (carbazole) biphenyl, 9,9-di (4-dicarbazole- Benzyl) fluorene (CPF), 1,3-bis (carbazol-9-yl) benzene (mCP), poly (N-octyl-2,7-carbazole-O-9,9-dioctyl-2,7-fluorene) (PCF), 4,4′-bis (carbazol-9-yl) biphenyl (CBP), 9,9 ′-(5- (triphenylsilyl) -1,3-phenylene) bis (9H-carbazole) (SimCP ), Bis (3,5-di (9H-carbazol-9-yl) phenyl) diphenylsilane (SimCP2), 9- (4-tert-butylphenyl) -3,6- (Triphenylsilyl) -9H-carbazole (CzSi), 2,2′-bis (4-carbazol-9-yl) phenyl) -biphenyl (BCBP), 9,9 ′-((2,6-diphenylbenzo [1,2-b: 4,5-b ′] difuran-3,7-diyl) bis (4,1-phenylene)) bis (9H-carbazole) (CZBDF), carbazole derivatives such as 4- (diphenyl) Phosphoyl) -N, N-diphenylaniline (HM-A1) and other aniline derivatives, 1,3-bis (9-phenyl-9H-fluoren-9-yl) benzene (mDPFB), 1,4-bis (9 -Phenyl-9H-fluoren-9-yl) benzene (pDPFB), 9,9-spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1) Fluorene derivatives of bis (2-methylphenyl) diphenylsilane (UGH1), 1,4-bistriphenylsilylbenzene (UGH2), propane-2,2′-diylbis (4,1-phenylene) dibenzoate (MMA1), 4,4′-bis (diphenylphosphine oxide) biphenyl (PO1), 2,8-bis (diphenylphosphoryl) dibenzo [b, d] thiophene (PPT), 4- (diphenylphosphoryl) -N, N-diphenylaniline (HM-A1), 2,4-bis (phenoxy) -6- (3-methyldiphenylamino) -1,3,5-triazine (BPMT), 2-methyl-9,10-di ( Naphthalen-2-yl) anthracene (MADN) and the like.

When the organic light emitting layer 15 is comprised from a luminescent dopant and host material, as a luminescent dopant contained in the organic light emitting layer 15, the well-known dopant material for organic EL can be used. Examples of such dopant materials include p-quarterphenyl, 3,5,3,5 tetra-t-butylsecphenyl, 3,5,3,5-tetra-t-butyl-p-quinkphenyl, Fluorescent materials such as styryl derivatives, bis [(4,6-difluorophenyl) -pyridinato-N, C2 ′] picolinate iridium (III) (FIrpic), bis (4 ′, 6′-difluorophenylpolydinato) tetrakis ( 1-pyrazoyl) borate iridium (III) (FIr6), tris (2-phenylpyridyl) iridium (III) (Ir (ppy) ₃ ), tris (1-phenylisoquinoline) iridium (III) (Ir (piq) ₃ ) And phosphorescent organic metal complexes.

The charge injection transport layer is a charge injection layer (hole injection layer 13) for the purpose of more efficiently injecting charges (holes, electrons) from the electrodes 12, 19 and transporting (injection) to the organic light emitting layer 15. , Electron injection layer 18) and charge transport layer (hole transport layer 14, electron transport layer 17), and may be composed of only the charge injection transport material exemplified below, and optionally an additive (donor, Etc.) may be included.
As the charge injecting and transporting material, known charge transporting materials for organic EL and organic photoconductors can be used. Such charge injecting and transporting materials are classified into hole injecting and transporting materials and electron injecting and transporting materials. Specific examples of these compounds are given below, but the present invention is not limited to these materials.

Examples of the hole injecting and transporting material constituting the hole injecting layer 13 and / or the hole transporting layer 14 include oxides such as vanadium oxide (V ₂ O ₅ ) and molybdenum oxide (MoO ₂ ), and inorganic p-type semiconductors. Materials, porphyrin compounds, N, N′-bis (3-methylphenyl) -N, N′-bis (phenyl) -benzidine (TPD), N, N′-di (naphthalen-1-yl) -N, N '-Diphenyl-benzidine (α-NPD), tris (4- (9H-carbazol-9-yl) phenyl) amine (TcTa), 4,4'-(cyclohexane-1,1-diyl) bis (N, N -Di-p-tolylaniline) (TAPC), 2,2'-bis (N, N-diphenylamine) -9,9'-spirobifluorene (DPAS), N1, N1 '-(biphenyl-4,4' -Diyl) screw ( 1-phenyl-N4, N4-di-m-tolylbenzene-1,4-diamine) (DNTPD), 1,3-bis (carbazol-9-yl) benzene (mCP), N3, N3, N3 ″ ′, N3 ″ ′-tetra-p-tolyl- [1,1 ′: 2 ′, 1 ″: 2 ″, 1 ″ ′-quarterphenyl] -3,3 ″ ′-diamine (BTPD), 4,4 ′-( Aromatic tertiary such as diphenylsilanediyl) bis (N, N-di-p-tolylaniline) (DTASi), 2,2-bis (4-carbazol-9-ylphenyl) adamantine (Ad-Cz) Low molecular weight materials such as amine compounds, hydrazone compounds, quinacridone compounds, styrylamine compounds, 2-methyl-9,10-di (naphthalen-2-yl) anthracene (MADN), polyaniline (PANI), polyaniline- Brain sulfonic acid (PANI-CSA), 3,4-polyethylenedioxythiophene / polystyrene sulfonate (PEDOT / PSS), poly (triphenylamine) derivative (Poly-TPD), polyvinylcarbazole (PVCz), poly (p Examples thereof include polymer materials such as -phenylene vinylene (PPV) and poly (p-naphthalene vinylene) (PNV).

  The material used as the hole injection layer 13 is the highest occupied molecular orbital (HOMO) as compared with the hole injection and transport material used for the hole transport layer 14 in that the injection and transport of holes from the anode is performed more efficiently. It is preferable to use a material having a low energy level, and the hole transport layer 14 is preferably a material having a higher hole mobility than the hole injection transport material used for the hole injection layer 13.

  In order to improve the hole injection / transport property, it is preferable to dope the hole injection / transport material with an acceptor. As the acceptor, a known acceptor material for organic EL can be used. Although these specific compounds are illustrated below, this invention is not limited to these materials.

Examples of acceptor materials that can be doped into the hole injection transport material constituting the hole injection layer 13 and / or the hole transport layer 14 include Au, Pt, W, Ir, POCl ₃ , AsF ₆ , Cl, Br, I, Inorganic materials such as vanadium oxide (V ₂ O ₅ ) and molybdenum oxide (MoO ₂ ), TCNQ (7,7,8,8, -tetracyanoquinodimethane), TCNQF ₄ (tetrafluorotetracyanoquinodimethane), Compounds having a cyano group such as TCNE (tetracyanoethylene), HCNB (hexacyanobutadiene), DDQ (dicyclodicyanobenzoquinone), compounds having a nitro group such as TNF (trinitrofluorenone), DNF (dinitrofluorenone), fluoranil, Organic materials such as chloranil and bromanyl are listed. Among these, compounds having a cyano group such as TCNQ, TCNQF ₄ , TCNE, HCNB, DDQ and the like are more preferable because they can increase the carrier concentration more effectively.

Examples of the electron injecting and transporting material constituting the electron injecting layer 18 and / or the electron transporting layer 17 include an inorganic material that is an n-type semiconductor, 1,3-bis (2- (2,2′-pyridin-6-yl). ) -1,3,4-oxadiazo-5-yl) benzene (Bpy-OXD), 1,3-bis (5- (4- (tert-butyl) phenyl) -1,3,4-oxadiazole Oxadiazole derivatives such as 2-yl) benzene (OXD7), triazole derivatives such as 3- (4-biphenyl) -4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), thio Pyrazine dioxide derivative, benzoquinone derivative, naphthoquinone derivative, anthraquinone derivative, diphenoquinone derivative, fluorenone derivative, benzodifuran derivative, 2-methyl-9 , 10-di (naphthalen-2-yl) anthracene (MADN), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), tris (2,4,6-trimethyl-3- ( Pyridin-3-yl) phenyl) borane (3TPYMB), 2,2 ′, 2 ″-(1,3,5-benztolyl) -tris (1-phenyl-1H-benzimidazole) (TPBI), 4,7 -Diphenyl-1,10-phenanthroline (BPhen), diphenylbis (4- (pyridin-3-yl) phenyl) silane (DPPS), 1,3,5-tri ((3-pyridyl) -phen-3-yl ) Low molecular weight materials such as benzene (TmPyPB), 1,3,5-tri (p-pyrid-3-yl-phenyl) benzene (TpPyPB); poly (oxadiazole) ( Polymer materials such as Poly-OXZ) and polystyrene derivatives (PSS), etc. In particular, examples of the electron injection material include fluorides such as lithium fluoride (LiF) and barium fluoride (BaF ₂ ), lithium oxide ( And oxides such as Li ₂ O).

  The material used for the electron injection layer 18 has a lowest unoccupied molecular orbital (LUMO) energy level as compared with the electron injection / transport material used for the electron transport layer 17 in that the electron injection / transport from the cathode is performed more efficiently. It is preferable to use a high material, and as the material used for the electron transport layer 17, it is preferable to use a material having a higher electron mobility than the electron injection transport material used for the electron injection layer 18.

  In order to further improve the electron injection / transport property, it is preferable to dope the electron injection / transport material with a donor. As the donor, a known donor material for organic EL can be used. Although these specific compounds are illustrated below, this invention is not limited to these materials.

  As a donor material that can be doped into the electron injection transport material constituting the electron injection layer 18 and / or the electron transport layer 17, an inorganic material such as an alkali metal, an alkaline earth metal, a rare earth element, Al, Ag, Cu, or In, Anilines, phenylenediamines, benzidines (N, N, N ′, N′-tetraphenylbenzidine, N, N′-bis- (3-methylphenyl) -N, N′-bis- (phenyl) -benzidine N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine, etc.), triphenylamines (triphenylamine, 4,4′4 ″ -tris (N, N-diphenyl-) Amino) -triphenylamine, 4,4′4 ″ -tris (N-3-methylphenyl-N-phenyl-amino) -triphenylamine, 4,4′4 ″ -tris (N- ( -Naphthyl) -N-phenyl-amino) -triphenylamine, etc.), triphenyldiamines (N, N'-di- (4-methyl-phenyl) -N, N'-diphenyl-1,4-phenylenediamine) ) Compounds having an aromatic tertiary amine as a skeleton, condensed polycyclic compounds such as phenanthrene, pyrene, perylene, anthracene, tetracene and pentacene (however, the condensed polycyclic compound may have a substituent), TTF There are organic materials such as (tetrathiafulvalene), dibenzofuran, phenothiazine, carbazole, etc. Among them, compounds having aromatic tertiary amine skeleton, condensed polycyclic compounds, and alkali metals increase the carrier concentration more effectively. It is more preferable because

As the electron blocking layer, the same materials as those described above as the hole transport layer 14 and the hole injection layer 13 can be used.
As the hole blocking layer 16, the same materials as those described above can be used as the electron transport layer 17 and the electron injection layer 18.

  The organic EL layer 7 such as the organic light emitting layer 15, the hole transport layer 14, the electron transport layer 17, the hole injection layer 13, the electron injection layer 18, the hole prevention layer 16, and the electron prevention layer is formed using the above materials as a solvent. Using dissolved and dispersed organic EL layer forming coating solution, spin coating method, dipping method, doctor blade method, discharge coating method, spray coating method and other coating methods, ink jet method, letterpress printing method, intaglio printing method, Known wet processes such as screen printing method, microgravure coating method, etc., resistance heating vapor deposition method, electron beam (EB) vapor deposition method, molecular beam epitaxy (MBE) method, sputtering method, organic vapor phase It can be formed by a known dry process such as vapor deposition (OVPD) or a laser transfer method. When the organic EL layer 7 is formed by a wet process, the coating liquid for forming the organic EL layer 7 may contain additives for adjusting the physical properties of the coating liquid such as a leveling agent and a viscosity modifier. Good.

  The film thickness of each layer constituting the organic EL layer 7 is usually about 1-1000 nm, and more preferably 10-200 nm. If the film thickness of each layer constituting the organic EL layer 7 is less than 10 nm, the properties that are originally required (charge (electron, hole) injection characteristics, transport characteristics, confinement characteristics) may not be obtained, There is a risk of pixel defects due to foreign matter such as dust. Moreover, when the film thickness of each layer constituting the organic EL layer 7 exceeds 200 nm, the drive voltage increases, which may lead to an increase in power consumption.

  When the charge transporting organic thin film 5 according to the present invention described above is applied to any one of the layers constituting the organic EL layer 7, the organic thin film is heated after the organic thin film is formed as described above. The orientation may be controlled by heating the thin film at the time of film formation, or by generating orientation by applying a magnetic field or an electric field. Thereby, among the plurality of π-electron conjugated structure surfaces of the π-conjugated compound constituting the layer, the π-electron conjugated structure surface in which HOMO or LUMO mainly involved in charge transfer is mainly distributed is the surface of the substrate 11 (and the electrode 12). The charge transport property of the layer can be improved by orienting it substantially parallel to the layer. Thereby, since the charge transport property of the organic EL layer 7 of the organic EL element 20 is improved, the charge injection efficiency from the electrodes 12 and 19 to the organic EL layer 7 can be improved, and the driving voltage of the organic EL element 20 is reduced to a low voltage. Can be

  Hereinafter, in the organic EL layer 7 of the organic EL element 20, examples of a π-conjugated compound to which the above-described orientation of the organic thin film 5 according to the present invention can be applied and a layer composed of the compound are shown.

  N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine (α-NPD), which is a representative hole transport material constituting the hole injection layer 13 and the hole transport layer 14 The molecular structure of is shown below.

In addition, the stable structure of α-NPD calculated by level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W is shown in FIG. 4 (a), and the HOMO of α-NPD calculated by the same calculation method is shown in FIG. The molecular orbitals are shown in FIG.
In the hole-transporting α-NPD, the molecular orbitals of HOMO involved in hole transport are mainly distributed in the central biphenyl portion, and the molecular orbitals of HOMO in the naphthalene portion are few. Therefore, when α-NPD is used as the hole injection layer 13 or the hole transport layer 14, the charge transport property is considered to be low even if the naphthalene ring is oriented in the horizontal direction with respect to the substrate 11 (electrode 12). It is considered that the charge transport property can be improved by orienting the biphenyl portion so as to be substantially parallel to the substrate 11 (electrode 12).

  The molecular structure of 4,4 ′, 4 ″ -tris (carbazol-9-yl) triphenylamine (TcTa), which is a hole transport material constituting the hole injection layer 13 and the hole transport layer 14, is shown below.

Further, FIG. 5A shows the stable structure of TcTa calculated by the level B3LYP / 6-31G of the inexperienced molecular orbital calculation method using Gaussian09W, and the molecular orbital of the HOMO of TcTa calculated by the same calculation method is shown. Shown in 5 (b).
In the hole-transporting TcTa, HOMO molecular orbitals involved in hole transport are distributed throughout the molecule, but the carbazole part has the widest π-electron conjugated structure surface. It is considered that the charge transporting property is improved by arranging the substrate horizontally with respect to the substrate.

  The molecular structure of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), which is an electron transport material constituting the electron injection layer 18 and the electron transport layer 17, is shown below.

Further, FIG. 6A shows the stable structure of BCP calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian 09W, and the LUMO molecular orbital of BCP calculated by the same calculation method is shown in FIG. It is shown in 6 (b).
In the electron transporting BCP, the molecular orbitals of LUMO involved in electron transport are mainly distributed in the phenanthroline portion, and the phenanthroline is oriented so as to be substantially horizontal with respect to the substrate 11 (electrode 12). Therefore, it is considered that the charge transport property can be improved.

  Molecular structure of 1,3-bis (carbazol-9-yl) benzene (mCP) used as a host material of the organic light emitting layer 15 or a hole transport material constituting the hole injection layer 13 and the hole transport layer 14 Is shown below.

In addition, FIG. 7A shows the stable structure of mCP calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, and the molecular orbital of HOMO of mCP calculated by the same calculation method is shown in FIG. 7 (b).
The hole-transporting mCP has a large HOMO molecular orbital spread involved in hole transport in the carbazole portion, and the carbazole ring is oriented substantially in the horizontal direction with respect to the substrate 11 (electrode 12). It is considered that the charge transport property is enhanced.

  4,4 ′-(cyclohexane-1,1-diyl) bis (N, N-di-p-tolylaniline) (TAPC), which is a hole injection material constituting the hole injection layer 13 or the hole transport layer 14 The molecular structure of is shown below.

  When calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in TAPC, each benzene ring is a π electron conjugated structure surface, and each π electron conjugated structure surface is hexagonal or HOMO, which is a circle and involved in hole transport, is relatively unevenly distributed in the benzene ring bonded to cyclohexane. Therefore, it is considered that the charge transport property can be improved by orienting the benzene ring bonded to cyclohexane so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 2,2′-bis (N, N-diphenylamine) -9,9′-spirobifluorene (DPAS), which is a hole injection material constituting the hole injection layer 13 or the hole transport layer 14, is shown below. Shown in

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in DPAS, each benzene ring has a π-electron conjugated structure surface, and HOMO is involved in hole transport. Is mainly distributed in the diphenylamine part. Therefore, it is considered that the charge transport property can be improved by orienting the diphenylamine portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  N1, N1 ′-(biphenyl-4,4′-diyl) bis (N1-phenyl-N4, N4-di-m-tolyl) which is a hole injection material constituting the hole injection layer 13 or the hole transport layer 14 The molecular structure of benzene-1,4-diamine (DNTPD) is shown below.

  When calculated by a non-empirical molecular orbital calculation method level B3LYP / 6-31G using Gaussian09W, in DNTPD, individual benzene rings are not on the same plane, and each has a π-electron conjugated structure surface. HOMO that participates in hole transport spreads at the part of four benzene rings sandwiched between N atoms. Therefore, it is considered that the charge transport characteristics can be improved by aligning these benzene rings so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  N3, N3, N3 ″ ′, N3 ″ ′-tetra-p-tolyl- [1,1 ′: 2 ′, 1 ″: hole transport materials constituting the hole transport layer 14 or the hole injection layer 13: The molecular structure of 2 ″, 1 ″ ′-quarterphenyl] -3,3 ″ ′-diamine (BTPD) is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in BTPD, each benzene ring is not on the same plane, and each has a π-electron conjugated structure surface. HOMO involved in hole transport is distributed mainly in benzene rings bonded to N atoms. Therefore, it is considered that the charge transport characteristics can be improved by aligning this portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 4,4 ′-(diphenylsilanediyl) bis (N, N-di-p-tolylaniline) (DTASi), which is a hole transport material constituting the hole transport layer 14 or the hole injection layer 13, It is shown below.

  When calculated with the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in DTASi, each benzene ring is a π-electron conjugate plane, and HOMO involved in hole transport is Mainly distributed in benzene rings bonded to N atoms. Therefore, it is considered that the charge transport property can be improved by orienting the benzene ring bonded to the N atom so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 2,2-bis (4-carbazol-9-ylphenyl) adamantine (Ad-Cz), which is a hole transport material constituting the hole transport layer 14 or the hole injection layer 13, is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in Ad-Cz, each carbazole ring and benzene ring form separate non-parallel π-electron conjugated structure surfaces. ing. HOMO involved in hole transport is mainly distributed in the carbazole part. Therefore, it is considered that the charge transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 4,4'-bis (carbazol-9-yl) biphenyl (CBP), which is the host material of the organic light emitting layer 15, is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in CBP, each carbazole ring and benzene ring form separate π electron conjugated structure planes, and all π The electron conjugate structure surfaces are not parallel to each other. In CBP, HOMO involved in hole transport is mainly distributed in the carbazole part. Therefore, it is considered that the hole transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in the biphenyl portion sandwiched between N atoms. Therefore, it is considered that the electron transport property can be improved by orienting the biphenyl portion sandwiched between N atoms so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of bis (2-methylphenyl) diphenylsilane (UGH1) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in UGH1, each benzene ring separately forms a π-electron conjugated structure surface that is not parallel to each other. In UGH1, HOMO involved in hole transport is distributed mainly in benzene rings to which methyl groups are bonded. Therefore, it is considered that the hole transport property can be improved by orienting the benzene ring to which the methyl group is bonded so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in benzene rings to which no methyl group is bonded. Therefore, it is considered that the electron transport property can be improved by orienting the benzene ring to which no methyl group is bonded so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 1,4-bistriphenylsilylbenzene (UGH2) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in UGH2, each benzene ring separately forms a π-electron conjugate structure surface that is not parallel to each other. In UGH2, HOMO and LUMO are distributed mainly in a benzene ring sandwiched between Si atoms. Therefore, it is considered that the charge transport property can be improved by orienting the benzene ring sandwiched between Si atoms so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 9,9 '-(5- (triphenylsilyl) -1,3-phenylene) bis (9H-carbazole) (SimCP), which is the host material of the organic light emitting layer 15, is shown below.

  When calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, each carbazole ring and benzene ring separately form a π-electron conjugated structure surface in SimCP. In SimCP, HOMO involved in hole transport is mainly distributed in the carbazole part. Therefore, it is considered that the hole transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in the central benzene ring. Therefore, it is considered that the electron transport property can be improved by aligning the central benzene ring so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of bis (3,5-di (9H-carbazol-9-yl) phenyl) diphenylsilane (SimCP2) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in SimCP2, each carbazole ring and benzene ring separately form a π-electron conjugated structure surface. In SimCP2, HOMO involved in hole transport is mainly distributed in the carbazole part. Therefore, it is considered that the hole transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in benzene rings in which Si atoms and N atoms are bonded. Therefore, it is considered that the electron transport property can be improved by orienting the benzene ring in which Si atoms and N atoms are bonded so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 9,9-spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, each benzene ring forms a π-electron conjugated structure surface that is not parallel to each other in SPPO1. In SPPO1, HOMO involved in hole transport is mainly distributed in the fluorene portion not bonded to the P atom. Therefore, it is considered that the hole transport property can be improved by orienting the fluorene portion not bonded to the P atom so as to be substantially in the horizontal direction with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in the fluorene portion bonded to the P atom. Therefore, it is considered that the electron transport property can be improved by orienting the fluorene portion bonded to the P atom so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of propane-2,2'-diylbis (4,1-phenylene) dibenzoate (MMA1), which is the host material of the organic light emitting layer 15, is shown below.

  As calculated by level B3LYP / 6-31G of ab initio molecular orbital calculation using Gaussian09W, in MMA1, each benzene ring forms a π-electron conjugated structure surface that is not parallel to each other. In MMA1, HOMO involved in hole transport is distributed mainly in the benzene ring to which O atoms are bonded. Therefore, it is considered that the hole transport property can be improved by orienting the benzene ring to which O atoms are bonded so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in the terminal benzene ring. Therefore, it is considered that the electron transport property can be improved by orienting the terminal benzene ring so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 9- (4-tert-butylphenyl) -3,6-bis (triphenylsilyl) -9H-carbazole (CzSi), which is the host material of the organic light emitting layer 15, is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in CzSi, the central carbazole ring and other benzene rings are separately formed with a π-electron conjugated structure surface. Yes. In CzSi, HOMO and LUMO are mainly distributed in the carbazole part. Therefore, it is considered that the charge transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 4,4'-bis (diphenylphosphine oxide) biphenyl (PO1), which is the host material of the organic light emitting layer 15, is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, the two benzene rings (biphenyl part) in the middle are on the same plane in PO1, and one π electron conjugated structure surface Are not parallel to the π-electron conjugated structure surface of the other benzene ring (diphenyl moiety). In PO1, HOMO and LUMO are mainly distributed in the diphenyl moiety. Therefore, it is considered that the charge transport characteristics can be improved by orienting the diphenyl portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 2,2'-bis (4-carbazol-9-yl) phenyl) -biphenyl (BCBP), which is the host material of the organic light emitting layer 15, is shown below.

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in BCBP, the carbazole rings on both sides and the four central benzene rings are not on the same plane and are not parallel to each other. A structural surface is formed. In BCBP, HOMO involved in hole transport is mainly distributed in the carbazole part. Therefore, it is considered that the hole transport property can be improved by aligning the carbazole portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in phenyl and biphenyl moieties bonded to carbazole. Therefore, it is considered that the electron transport characteristics can be improved by aligning the phenyl and biphenyl moieties bonded to carbazole so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 2,8-bis (diphenylphosphoryl) dibenzo [b, d] thiophene (PPT) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in the PPT, the central dibenzothiophene and the benzene ring are π-electron conjugated structure surfaces that are not parallel to each other. In PPT, HOMO and LUMO are mainly distributed in the dibenzothiophene part. Therefore, it is considered that the charge transport characteristics can be improved by aligning the dibenzothiophene portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 4- (diphenylphosphoryl) -N, N-diphenylaniline (HM-A1) which is the host material of the organic light emitting layer 15 is shown below.

  When calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in HM-A1, each benzene ring separately forms a π-electron conjugated structure surface that is not parallel to each other. In HM-A1, HOMO involved in hole transport is mainly distributed in the diphenylaniline part. Therefore, it is considered that the hole transport property can be improved by aligning the diphenylaniline portion so as to be substantially in the horizontal direction with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is distributed mainly in a benzene ring sandwiched between N and P atoms. Therefore, it is considered that the electron transport property can be improved by orienting the benzene ring sandwiched between the N atom and the P atom so as to be substantially in the horizontal direction with respect to the substrate 11 (electrode 12).

  9,9 ′-((2,6-diphenylbenzo [1,2-b: 4,5-b ′] difuran-3,7-diyl) bis (4,1-diyl) which is a host material of the organic light emitting layer 15 The molecular structure of (phenylene)) bis (9H-carbazole) (CZBDF) is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in CZBDF, the central benzodifuran, the carbazole at both ends, and other benzene rings form a π-electron conjugated structure surface. ing. In CZBDF, HOMO and LUMO are mainly distributed in the dibenzofuran part. Therefore, it is considered that the charge transport property can be improved by orienting the dibenzofuran portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 2,4-bis (phenoxy) -6- (3-methyldiphenylamino) -1,3,5-triazine (BPMT), which is the host material of the organic light emitting layer 15, is shown below.

  As calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation method using Gaussian09W, in BPMT, a π-electron conjugated structure surface in which triazine ring and benzene ring are not parallel to each other is formed. In BPMT, HOMO involved in hole transport is mainly distributed in diphenylamino groups. Therefore, it is considered that the hole transport property can be improved by aligning the diphenylamino group so as to be substantially horizontal with respect to the substrate 11 (electrode 12). In addition, LUMO involved in electron transport is mainly distributed in the triazine ring and the benzene ring bonded to the triazine ring via an O atom. Therefore, the electron transport characteristics can be improved by orienting the triazine ring and the benzene ring bonded to the triazine ring via an O atom so as to be substantially horizontal with respect to the substrate 11 (electrode 12). Conceivable.

  2,2 ′, 2 ″-(1,3,5-benztolyl) -tris (1-phenyl-1H-benzimidazole) (TPBI), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18 The molecular structure of is shown below.

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in TPBI3, each benzimidazole and benzene ring form a π-electron conjugated structure surface that is not parallel to each other. LUMO involved in electron transport is distributed mainly in the central benzene ring. Therefore, it is considered that the charge transport property can be improved by aligning the central benzene ring so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 3- (4-biphenyl) -4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18, It is shown below.

  As calculated by the level B3LYP / 6-31G of ab initio molecular orbital calculation using Gaussian09W, in TAZ, the triazole ring and each benzene ring form a π-electron conjugated structure surface that is not parallel to each other. LUMO involved in electron transport is distributed mainly in the benzene ring on the triazole side of biphenyl. Therefore, it is considered that the charge transport property can be improved by orienting the benzene ring on the triazole side of biphenyl so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 4,7-diphenyl-1,10-phenanthroline (BPhen), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18, is shown below.

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in BPhen, the phenanthroline ring and each benzene ring form a π-electron conjugated structure surface that is not parallel to each other. LUMO involved in electron transport is mainly distributed in the phenanthroline part. Therefore, it is considered that the charge transport property can be improved by aligning the phenanthroline portion so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of diphenylbis (4- (pyridin-3-yl) phenyl) silane (DPPS), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18, is shown below.

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in DPPS, each pyridine ring and each benzene ring form non-parallel π-electron conjugated structure surfaces. LUMO involved in electron transport is mainly distributed in the pyridine ring and the benzene ring bonded to the pyridine ring. Therefore, it is considered that the charge transport property can be improved by orienting the pyridine ring and the benzene ring bonded to the pyridine ring so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 1,3,5-tri ((3-pyridyl) -phen-3-yl) benzene (TmPyPB), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18, is shown below.

  As calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in TmPyPB, each pyridine ring and each benzene ring form a π-electron conjugated structure surface that is not parallel to each other. LUMO involved in electron transport is distributed mainly in four benzene rings (1,3,5-triphenylbenzene portion). Therefore, it is considered that the charge transport characteristics can be improved by aligning the four benzene rings so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The molecular structure of 1,3,5-tri (p-pyrid-3-yl-phenyl) benzene (TpPyPB), which is an electron transport material constituting the electron transport layer 17 or the electron injection layer 18, is shown below.

  When calculated by the level B3LYP / 6-31G of the ab initio molecular orbital calculation method using Gaussian09W, in TpPyPB, each pyridine ring and each benzene ring form a π-electron conjugated structure surface that is not parallel to each other. LUMO involved in electron transport is distributed mainly in four benzene rings (1,3,5-triphenylbenzene portion). Therefore, it is considered that the charge transport characteristics can be improved by aligning the four benzene rings so as to be substantially horizontal with respect to the substrate 11 (electrode 12).

  The π-conjugated compound constituting the organic EL layer 7 exemplified above and the layer composed of the compound are examples. However, as described above, at least one of the layers constituting the organic EL layer 7 is described above. The charge transporting organic thin film 5 according to the present invention can be applied. Thereby, among the plurality of π-electron conjugated structure surfaces of the π-conjugated compound constituting the layer, the π-electron conjugated structure surface in which HOMO or LUMO mainly involved in charge transfer is mainly distributed is the surface of the substrate 11 (and the electrode 12). The charge transport property of the layer can be improved by orienting it substantially parallel to the layer. Therefore, since the charge transport property of the organic EL layer 7 of the organic EL element 20 is improved, the charge injection efficiency from the electrodes 12 and 19 to the organic EL layer 7 can be improved, and the drive voltage of the organic EL element 20 is lowered. it can.

  In addition, the organic EL element according to the present invention may be composed of a bottom emission type device that emits emitted light to the substrate side, or a top emission type that emits light to the opposite side of the substrate instead. It may consist of devices. In addition, the driving method of the organic light emitting element of the present invention is not particularly limited and may be an active driving method or a passive driving method, but it is preferable to drive the organic light emitting element by the active driving method. Employing the active drive method is preferable because the light emission time of the organic light-emitting element can be extended compared to the passive drive method, the drive voltage for obtaining a desired luminance can be reduced, and the power consumption can be reduced.

  EXAMPLES Hereinafter, although this invention is further explained in full detail based on an Example, this invention is not restrict | limited to a following example.

(Comparative Example 1)
As the substrate, a glass having a thickness of 0.7 mm on which an IZO (registered trademark, indium zinc oxide) film having a thickness of 150 nm patterned as an electrode and a wiring was formed was used. This substrate was washed with water, then subjected to pure water ultrasonic cleaning for 10 minutes, acetone ultrasonic cleaning for 10 minutes, and isopropyl alcohol vapor cleaning for 5 minutes, and dried at 100 ° C. for 1 hour.
Next, the substrate after cleaning was irradiated with UV light in a nitrogen atmosphere containing a small amount of oxygen to perform surface cleaning treatment, and then introduced into a vacuum deposition apparatus. Thereafter, 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN) having a film thickness of 100 nm was formed on the substrate by vacuum evaporation. Next, using a shadow mask having an electrode and a wiring pattern, Al is vapor-deposited to form an aluminum (Al) electrode having a thickness of 100 nm on the MADN film, and then sealed in a glove box. 1 element 1 was produced.

Example 1
After depositing MADN having a film thickness of 100 nm on IZO (registered trademark) in the same procedure as the element 1 of Comparative Example 1, heat treatment was performed at 140 ° C. for 30 minutes in a glove box in a nitrogen atmosphere in which oxygen and moisture concentrations were controlled. .
Next, the heat-treated MADN-equipped substrate is returned to the vacuum deposition chamber, and an electrode is formed by depositing Al with a thickness of 100 nm on the MADN film using a shadow mask having electrodes and wiring patterns. Then, the device 2 of Example 1 was produced.

In order to investigate the molecular orientation of the MADN films of element 1 (comparative example 1) and element 2 (example 1), the substrates of element 1 and element 2 were taken out immediately before the Al deposition, and a spectroscopic ellipsometer (manufactured by JA Woollam) M-2000U).
The measurement data of the spectroscopic ellipsometer was analyzed, and the optical constants (refractive index n and extinction coefficient k) of the MADN films on the substrates of the elements 1 and 2 were derived. FIG. 8A shows the analysis result of the element 1 (Comparative Example 1), and FIG. 8B shows the analysis result of the element 2 (Example 1). The analysis of the measurement data was performed with a model in which the MADN film had uniaxial symmetry in the direction perpendicular to the substrate. In the graph shown in FIG. 8, “kx, ky” is an extinction coefficient in the horizontal direction with respect to the substrate, “kz” is an extinction coefficient in the direction perpendicular to the substrate, and “nx, ny” is with respect to the substrate. The refractive index in the horizontal direction, “nz”, indicates the refractive index in the vertical direction with respect to the substrate.

As shown in FIGS. 8A and 8B, two peaks are observed in the extinction coefficients “kx, ky” and “kz”, and the level B3LYP of the ab initio molecular orbital calculation method using Gaussian09W is used. From the calculation result of the transition dipole moment of MADN molecule by / 6-31G (d), the peak near the wavelength of 250 nm is derived from the transition dipole moment in the long axis direction (y direction) of anthracene shown in FIG. The peak near the wavelength of 400 nm was derived from the transition dipole moment in the minor axis direction (x direction) of anthracene shown in FIG.
The orientation parameter S for the transition dipole moment in the major axis direction (y direction) of the anthracene of the MADN film at the peak near the wavelength of 250 nm, and the minor axis direction of the anthracene in the peak near the wavelength of 400 nm (x direction; π conjugate plane of the naphthalene ring) The orientation parameter S for the transition dipole moment in the horizontal direction was determined from the above formula (A). The results are shown in FIG. 8 (a) and FIG. 8 (b).

  From the result of FIG. 8A, in the element 1 of Comparative Example 1 that was not subjected to heat treatment, the anthracene constituting MADN had a strong anisotropy in the minor axis direction (x direction in FIG. 2A), and the naphthalene ring It can be seen that tends to be more horizontal than perpendicular to the substrate. On the other hand, in the element 2 of Example 1 subjected to the heat treatment shown in FIG. 8B, the anisotropy in the major axis direction of the anthracene constituting the MADN (y direction in FIG. 2A) becomes strong, The anthracene ring changed to a tendency to be oriented in a horizontal direction rather than perpendicular to the substrate, and the anthracene ring was oriented substantially horizontally with respect to the substrate.

  Thus, the electrical characteristics of MADN films having different orientations were evaluated by measuring the current-voltage (IV) characteristics of device 1 and device 2. The measurement result of the IV characteristic is shown in FIG. As a result, the element 2 of the example 1 is more likely to flow current with respect to the applied voltage than the element 1 of the comparative example 1, and the naphthalene ring constituting the MADN is oriented horizontally with respect to the substrate. Also, it is shown that the charge transportability is higher when the anthracene ring is oriented substantially in the horizontal direction with respect to the substrate. That is, as shown in FIG. 2 (a), an anthracene ring in which the molecular orbitals of HOMO are mainly distributed rather than the naphthalene ring in which the molecular orbitals of HOMO are hardly distributed is oriented horizontally with respect to the substrate. It is apparent that the charge transport property is higher when the is oriented horizontally with respect to the substrate. From the above results, in order to improve the charge transportability by controlling the orientation of the thin film, the distribution of molecular orbitals of HOMO (or LUMO) is taken into consideration, and π electrons in which HOMO (or LUMO) is mainly distributed It was confirmed that it is important to orient the conjugated structure surface substantially parallel to the substrate.

(Example 2)
An IZO (registered trademark) substrate was prepared in the same manner as in Example 1, washed, and introduced into a vacuum deposition apparatus.
Next, the substrate temperature is raised to 80 ° C. in the vapor deposition chamber, and in that state, 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN) is formed to a thickness of 100 nm on IZO (registered trademark). Vapor deposited. After the deposition, the substrate temperature was lowered to 40 ° C. or lower, and Al was deposited to a thickness of 100 nm using a shadow mask having an electrode and a wiring pattern to form an aluminum (Al) electrode on the MADN film. Thereafter, the deposited substrate was sealed in a glove box to produce the element 3 of Example 2.

As a result of evaluating the orientation of the MADN film deposited under the same conditions as the device 3 of Example 2 by spectroscopic ellipsometry in the same manner as in Example 1 and Comparative Example 1, it was the same as the MADN film of the device 2 of Example 1. I found out.
Moreover, when the current-voltage (IV) characteristic of the element 3 was measured, the IV characteristic of the element 3 of Example 2 was also substantially the same as that of the element 2 of Example 1, and from the element 1 of Comparative Example 1 However, the current flowed more easily with respect to the applied voltage.
From the result of the element 3 of Example 2, as in Example 1 above, the anthracene ring is oriented horizontally with respect to the substrate rather than the naphthalene ring constituting the MADN oriented horizontally with respect to the substrate. It was shown that the charge transporting property is increased.

(Comparative Example 2)
As in Comparative Example 1, as a substrate, 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN) having a film thickness of 100 nm was formed on an IZO (registered trademark) substrate at room temperature by vacuum deposition. .
Next, an Alq ₃ (tris (8-quinolato) aluminum) film having a thickness of 50 nm was formed on the MADN film by vacuum deposition.
Next, using a shadow mask having an electrode and a wiring pattern, Al was vapor-deposited to form an aluminum (Al) electrode having a thickness of 100 nm on the Alq ₃ film, and then sealed in a glove box. Element 4 of Example 2 was produced.

(Example 3)
After depositing MADN having a film thickness of 100 nm on IZO (registered trademark) in the same procedure as the element 4 of Comparative Example 2, heat treatment was performed at 140 ° C. for 30 minutes in a glove box in a nitrogen atmosphere in which oxygen and moisture concentrations were controlled. .
Next, the substrate with MADN after the heat treatment was returned to the vacuum deposition chamber, and an Alq ₃ (tris (8-quinolalite) aluminum) film having a thickness of 50 nm was formed on the MADN film by vacuum deposition.
Next, using a shadow mask having an electrode and a wiring pattern, an Al film having a thickness of 100 nm was deposited on the MADN film to form an electrode, which was then sealed in a glove box to produce the device 5 of Example 3. did.

  When the IV characteristics of the element 4 of the comparative example 2 and the element 5 of the example 3 were measured, the IV characteristic of the element 5 was more likely to flow current with respect to the applied voltage than the element 4. It was also shown that the structure has higher charge transportability when the anthracene ring is oriented horizontally with respect to the substrate than when the naphthalene ring constituting MADN is oriented horizontally with respect to the substrate.

(Examination example 1)
After forming the MADN film in the same manner as in Example 1 and Comparative Example 1, (1) heat treatment is not performed, (2) heat treatment is performed at 100 ° C. for 30 minutes, and (3) heat treatment is performed at 140 ° C. for 30 minutes. After performing the treatment under any of the conditions, Al electrodes were formed and sealed in the same manner as in Example 1 and Comparative Example 1.
About each obtained element, the current-voltage (IV) characteristic measurement was performed. The results are shown in FIG.
From the results shown in FIG. 10, the MADN film changes its orientation by heat treatment at 140 ° C. after the film formation, and the anthracene ring is oriented substantially horizontally to the substrate rather than the naphthalene ring, thereby improving the charge transport property. I understood.

(Examination example 2)
About each element which produced the element similarly to the examination example 1 except having changed the heat processing temperature after film-forming of a MADN film into 20 degreeC, 80 degreeC, 100 degreeC, 120 degreeC, and 140 degreeC. The orientation parameter S and the current density when 2 V was applied were measured. The result is shown in FIG. In FIG. 11, “S-anthracene y” indicates an orientation parameter S with respect to the transition dipole moment in the long axis direction (y direction) of anthracene at the peak near the wavelength of 250 nm of the extinction coefficient as shown in FIG. . Further, “S-anthracene x” is a transition dipole moment in the short axis direction of the anthracene (x direction; horizontal direction to the π conjugate plane of the naphthalene ring) at the peak of the extinction coefficient near 400 nm as shown in FIG. Shows the orientation parameter S for.
From the results shown in FIG. 10, the MADN film has its orientation changed by heat treatment at 140 ° C. after the film formation, and the orientation parameter “S-anthracene y” is −0.15 or less, which is more anthracene than the naphthalene ring. The ring was oriented substantially horizontally with respect to the substrate, and the charge transportability was improved.

(Examination example 3)
A device was fabricated in the same manner as in Comparative Example 1 except that the IZO (registered trademark) substrate temperature during the formation of the MADN film was changed from room temperature to 120 ° C. The obtained element was evaluated by spectroscopic ellipso in the same manner as in Example 1 and Comparative Example 1, and the orientation parameter S at the extinction coefficient peak near the wavelength of 250 nm and the orientation at the extinction coefficient peak near the wavelength of 400 nm were measured. Parameter S was measured. The result is shown in FIG.
As shown in FIG. 12, by forming a MADN film at a substrate temperature of 60 ° C. or higher, an alignment parameter S derived from a peak near a wavelength of 250 nm and an alignment parameter S derived from a peak near a wavelength of 400 nm The magnitude relationship is reversed, and it can be seen that the anthracene ring has changed its orientation to be horizontal with respect to the substrate rather than the naphthalene ring in MADN. From this result, it is understood that when the orientation parameter S is −0.1 or less, the anthracene ring in which HOMO is mainly distributed is oriented substantially horizontally with respect to the substrate, and the charge transport property is improved.

  The present invention can be used for, for example, an organic electroluminescence element (organic EL element), a color conversion light emitting element, a light conversion light emitting element, a photoelectric conversion element, an organic thin film transistor, an organic laser diode element, and the like. It can also be used for display devices, lighting devices, electronic devices and the like using the above.

  DESCRIPTION OF SYMBOLS 1, 2 ... Electrode, 5 ... Charge transportable organic thin film, 7 ... Organic EL layer (organic layer), 10 ... Element, 11 ... Substrate, 12, 19 ... Electrode, 13 ... Hole injection layer, 14 ... Hole transport Layer, 15 ... organic light emitting layer, 16 ... hole blocking layer, 17 ... electron transport layer, 18 ... electron injection layer, 20 ... organic electroluminescence element (organic EL element).

Claims (6)

A charge-transporting amorphous thin film comprising a charge-transporting π-conjugated compound formed on a substrate and having a plurality of non-parallel π-electron conjugated structure surfaces,
When the π-conjugated compound is electron transporting, a π-electron conjugated structure surface in which the lowest unoccupied molecular orbital (LUMO) is mainly distributed,
When the π-conjugated compound is hole transporting, when the π-electron conjugated structure surface in which the highest occupied molecular orbital (HOMO) is mainly distributed is the first π-electron conjugated structure surface,
The charge transporting organic thin film characterized in that the first π-electron conjugated structure surface is oriented substantially parallel to the surface of the substrate.   2. The charge transporting organic thin film according to claim 1, wherein the HOMO and the LUMO are derived by an ab initio molecular orbital calculation method using Gaussian09W.   The second-order orientation parameter S with respect to the direction of the transition dipole moment parallel to the first π-electron conjugated structure surface is in the range of −0.1 to −0.5. The charge transporting organic thin film described in 1.   The first π-electron conjugated structure surface has a major axis and a minor axis, and a secondary orientation parameter S with respect to the major axis direction of the first π-electron conjugated structure surface is −0.1 to −0.5. The charge-transporting organic thin film according to any one of claims 1 to 3, wherein the charge-transporting organic thin film is in the range.   The charge transporting organic thin film according to any one of claims 1 to 4, wherein the first π-conjugated structure surface is a π-electron conjugated structure surface having the widest area in the π-conjugated compound. An organic electroluminescence device in which at least one organic layer containing a luminescent material is disposed between two opposing electrodes,
The said organic layer comprises the electric charge transportable organic thin film as described in any one of Claims 1-5, The organic electroluminescent element characterized by the above-mentioned.