JP7357880B2 - New cyclic compounds and their uses - Google Patents

Description

The present invention relates to a novel cyclic boron compound, a light emitting material and an organic thin film containing the compound, and an organic electronic device containing the organic thin film.

In recent years, there has been increasing interest in organic electronic devices, which are characterized by their flexible structure and ability to be made into large areas, and their ability to be manufactured using inexpensive and high-speed printing methods.
Typical organic electronic devices include organic EL elements, organic solar cell elements, organic photoelectric conversion elements, and organic transistor elements. Organic EL elements are expected to be the main target for next-generation display applications as flat panel displays, and are being applied to everything from mobile phone displays to TVs, and development continues with the aim of making them even more sophisticated. Organic solar cell elements are being studied as flexible and inexpensive energy sources, and organic transistor elements are being researched to be applied to flexible displays and inexpensive ICs.

In the field of organic electronic devices, there is a need for better materials to construct devices. For this reason, a large number of materials have been studied in various fields, but none with sufficient performance has yet been found, and efforts are still being made to develop materials useful for various devices.

In recent years, several groups have reported on organic photoelectric conversion elements, which are expected to be used in next-generation solar cells and optical sensors. For example, Patent Document 1 shows an example in which a quinacridone derivative or a quinazoline derivative is used in a photoelectric conversion element, and Patent Document 2 shows an example in which a diketopyrrolopyrrole derivative is used.
In an image sensor, a hole blocking layer or an electron blocking layer is inserted between the photoelectric conversion part and the electrode part for the purpose of reducing leakage current from the photoelectric conversion part in the dark in order to obtain an S/N ratio. methods are commonly used.

Hole blocking layers and electron blocking layers, which are generally widely used in the field of organic electronic devices, are placed at the interface between electrodes or conductive films and other films in the device's constituent films, and are used to block holes, respectively. It also plays a role in controlling the reverse movement of electrons and adjusting the leakage of unnecessary holes or electrons, and should be selected and used in consideration of heat resistance, transmission wavelength, film formation method, etc., depending on the device application. It is something that can be done.
Patent Document 3 has an example using fullerene as a hole blocking layer, and Patent Document 4 has an example using 1,4,5,8-naphthalene-tetracarboxylic anhydride (NTCDA) as a hole blocking layer. It is shown. However, the performance requirements for materials used in photoelectric conversion elements are particularly high, and conventional hole blocking layers and electron blocking layers are insufficient in terms of leakage current prevention properties, heat resistance to process temperatures, and visible light transparency. It cannot be said that it has sufficient performance, and it has not yet been used commercially.

Patent No. 4972288 Patent No. 5022573 Special Publication No. 2013-544440 Special table 2014-506736 publication

New J.Chem. , 1998, 869-874.

An object of the present invention is to provide an organic electronic device and an organic photoelectric conversion element that have excellent leakage current prevention properties, heat resistance against process temperatures, visible light transparency, and the like.

As a result of research to solve the above-mentioned problems, the present inventors discovered that the above-mentioned problems could be solved by using a new cyclic boron compound with a specific structure in the block layer of an organic photoelectric conversion element, and completed the present invention. I ended up doing it.
That is, the present invention is as follows.
[1] The following formula (1)

(In formula (1), R ₁ to R ₃ each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group, and multiple R _1s may be the same or different. Often, a plurality of R ₂ may be the same or different, and a plurality of R ₃ may be the same or different. In addition, adjacent R ₁ to R ₃ may be bonded to form an aromatic ring or a heterocyclic ring. ).
[2] The compound according to the above item [1], wherein all of R ₁ to R ₃ are hydrogen atoms.
[3] The compound according to the above item [1], wherein at least one of R ₁ and R ₃ is an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group.
[4] A luminescent material containing the compound described in any one of the preceding sections [1] to [3].
[5] An organic thin film containing the compound described in any one of [1] to [3] above.
[6] An organic electronics device comprising the organic thin film according to item [5].
[7] The organic electronics device according to the preceding paragraph [6], which is a photoelectric conversion element.

The novel compound of the present invention, which has a main absorption band in the ultraviolet region, can be used in various organic electronic devices, and by using the compound, a near-infrared photoelectric conversion element with an excellent contrast ratio can be obtained.

FIG. 1 shows a cross-sectional view illustrating an embodiment of a photoelectric conversion element of the present invention. FIG. 2 shows a schematic cross-sectional view showing an example of the layer structure of an organic electroluminescent device. FIG. 3 shows the emission spectrum of Example 2.

Hereinafter, the content of the present invention will be explained in detail. The explanation of the constituent elements described herein is based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

The compound of the present invention is represented by the following formula (1).

In formula (1), R ₁ to R ₃ each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group, and multiple R _1s may be the same or different from each other. , a plurality of R ₂ may be the same or different, and a plurality of R ₃ may be the same or different. Further, adjacent R ₁ to R ₃ may be combined to form an aromatic ring or a heterocycle.

The aliphatic hydrocarbon group represented by R ₁ to R ₃ in formula (1) can be a saturated or unsaturated linear, branched, or cyclic aliphatic hydrocarbon, and the number of carbon atoms thereof is 1 or less. The number is preferably from 1 to 20, more preferably from 1 to 8, and even more preferably from 1 to 4. Here, specific examples of saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon groups include methyl group, ethyl group, propyl group, iso-propyl group, n-butyl group, iso- Butyl group, allyl group, t-butyl group, n-pentyl group, n-hexyl group, n-octyl group, n-decyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-cetyl group , n-heptadecyl group, n-butenyl group, 2-ethylhexyl group, 3-ethylheptyl group, 4-ethyloctyl group, 2-butyloctyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, etc. Can be mentioned.
The aliphatic hydrocarbon group represented by R ₁ to R ₃ in formula (1) is preferably a linear or branched aliphatic hydrocarbon group, and preferably a linear or branched alkyl group. More preferably, it is a methyl group, ethyl group, propyl group, n-butyl group, iso-butyl group, t-butyl group, n-hexyl group, n-octyl group or 2-ethylhexyl group. preferable.

The alkoxy group represented by R ₁ to R ₃ in formula (1) is a substituent in which an oxygen atom and an alkyl group are bonded. Examples of the alkyl group in the alkoxy group include R 1 to R ₃ in formula (1). The alkyl groups described as specific examples in the section of the aliphatic hydrocarbon group represented by R ₃ can be mentioned.
The alkoxy group represented by R ₁ to R ₃ in formula (1) may have a substituent such as an alkoxy group.

The aromatic group represented by R ₁ to R ₃ in formula (1) is not particularly limited as long as it is a residue obtained by removing one hydrogen atom from the aromatic ring of an aromatic compound, and includes, for example, a phenyl group, a biphenyl group, Examples include an indenyl group, a naphthyl group, an anthryl group, a fluorenyl group, a pyrenyl group, a phenanthyl group, and a mestyl group, with a phenyl group or a naphthyl group being preferred, and a phenyl group being more preferred. Incidentally, the aromatic compound that can become an aromatic group may have a substituent, and the substituent that may have this is not particularly limited, but may include an alkyl group having 1 to 4 carbon atoms, a halogen atom, or a phenyl group. A group is preferable, and a methyl group, a fluorine atom, or a phenyl group is more preferable.

The heterocyclic group represented by R ₁ to R ₃ in formula (1) is not particularly limited as long as it is a residue obtained by removing one hydrogen atom from the heterocycle of a heterocyclic compound, and includes, for example, a furanyl group, a thienyl group, Thienothienyl group, pyrrolyl group, imidazolyl group, N-methylimidazolyl group, thiazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolyl group, indolyl group, benzopyrazyl group, benzopyrimidyl group, benzothienyl group, benzothiazolyl group, pyri Dinothiazolyl group, benzimidazolyl group, pyridinoimidazolyl group, N-methylbenzimidazolyl group, pyridino-N-methylimidazolyl group, benzoxazolyl group, pyridinooxazolyl group, benzothiadiazolyl group, pyridinothia Examples include diazolyl group, benzoxadiazolyl group, pyridinooxadiazolyl group, carbazolyl group, phenoxazinyl group and phenothiazinyl group, and thienyl group, thienothienyl group, thiazolyl group, pyridyl group, benzothiazolyl group, benzothiadiazolyl group. or a pyridinothiadiazolyl group, and a thienyl group, a thiazolyl group, a benzothiazolyl group, or a benzothiadiazolyl group is more preferable. In addition, the heterocyclic compound which can become a heterocyclic group may have a substituent, and the substituent which may have this is not specifically limited.

Adjacent R ₁ to R ₃ in formula (1) are bonded together (i.e., R ₁ and R ₂ are bonded to each other, and/or R ₂ and R ₃ are bonded to each other) to form an aromatic ring or a hetero It may form a ring. Examples of the ring structure that R ₁ to R ₃ may combine to form include a benzene ring, a naphthalene ring, a furan ring, a pyrrole ring, an imidazole ring, a thiophene ring, a pyrazole ring, an oxazole ring, a thiazole ring, a pyridine ring, and Examples include five-membered or six-membered aromatic rings such as a pyrazine ring.
The ring structure formed by bonding adjacent R ₁ to R ₃ may have a substituent, and preferred examples of the substituent that may have such a substituent include R 1 to R ₃ in formula (1). Examples include those similar to the aliphatic hydrocarbon group, alkoxy group, aromatic group, and heterocyclic group represented by R ₃ , an alkylthio group, and a halogen atom. In addition, the alkylthio group here is a substituent in which an alkyl group and a sulfur atom are bonded, and examples of the alkyl group possessed by the alkylthio group include aliphatic hydrocarbons represented by R ₁ to R ₃ in formula (1). Examples include the alkyl groups listed as specific examples in the group section.

It is preferable that all of R ₁ to R ₃ in formula (1) are hydrogen atoms.
Further, as R ₁ to R ₃ in formula (1), it is also preferable that at least one of R ₁ and R ₃ is _an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group; It is more preferable that at least one of _{R 3} is an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group, R ₂ is a hydrogen atom, and one of R ₁ and R ₃ is an aliphatic hydrocarbon group, and R 2 is a hydrogen atom. More preferably, it is a hydrogen group, an alkoxy group, an aromatic group, or a heterocyclic group, and the others are hydrogen atoms.

The compound represented by the formula (1) can be synthesized using a compound represented by the following formula (A) synthesized by a known method disclosed in Non-Patent Document 1 as a starting material, for example, as shown in the scheme below. It can be synthesized by a method.

The method for purifying the compound represented by formula (1) is not particularly limited, and known methods such as recrystallization, column chromatography, and vacuum sublimation purification can be employed. Moreover, these methods can be combined as necessary.

Specific examples of the compound represented by formula (1) are shown below, but the compound of the present invention is not limited to these specific examples.

Since the compound represented by formula (1) of the present invention is a compound having blue light-emitting characteristics, it can be used as a light-emitting material. Specific applications of the luminescent material include organic EL devices and the like.

The thin film of the present invention contains a compound represented by formula (1) of the present invention.
The thin film of the present invention can be produced by a general dry film forming method or wet film forming method. Specifically, vacuum processes such as resistance heating evaporation, electron beam evaporation, sputtering, and molecular layering methods, solution processes such as casting, spin coating, dip coating, blade coating, wire bar coating, spray coating, and other coating methods, and inkjet printing. , printing methods such as screen printing, offset printing, and letterpress printing, and soft lithography methods such as microcontact printing.

When forming multiple layers of thin films, a method combining multiple of the above methods may be employed. The thickness of each layer is not particularly limited, but is usually in the range of 0.5 to 5,000 nm, preferably in the range of 1 to 1,000 nm, and more preferably in the range of 5 to 500 nm.

The molecular weight of the compound represented by formula (1) is, for example, 1,500 or less when it is intended to be used by forming an organic layer containing the compound represented by formula (1) by a vapor deposition method. It is preferably at most 1,200, more preferably at most 1,000, even more preferably at most 1,000. The lower limit of molecular weight is the lowest possible molecular weight of the compound represented by formula (1).
Note that the compound represented by formula (1) may be formed into a film by a coating method regardless of its molecular weight. If a coating method is used, it is possible to form a film even with a compound having a relatively large molecular weight.
In addition, the molecular weight in this specification means the value calculated by the EI-GCMS method.

[Organic electronic devices]
The organic electronic device of the present invention includes the thin film of the present invention (hereinafter, the thin film may be referred to as an organic thin film). Examples of organic electronic devices include organic thin film transistors, organic photoelectric conversion elements, organic solar cell elements, organic electroluminescent elements (hereinafter referred to as "organic EL elements" or "organic light emitting elements"), organic light emitting transistor elements, and organic light emitting transistor elements. Examples include semiconductor laser elements. The present invention focuses on organic photoelectric conversion elements and organic EL elements, which are expected to be used particularly in near-infrared applications. Here, an organic photoelectric conversion element and an organic EL element, which are one of the embodiments of the present invention, will be described.

[Organic photoelectric conversion element]
The compound represented by formula (1) has little absorption in the visible region and can be used for the blocking layer in the organic photoelectric conversion element (hereinafter sometimes simply referred to as "photoelectric conversion element") of the present invention. In addition, the maximum absorption of an absorption band in this specification means the value of the wavelength at which the absorbance is maximum in the absorbance spectrum measured by absorption spectrum measurement, and the maximum absorption wavelength (λmax) is the maximum absorption wavelength among the maximum absorptions. It means maximum absorption on the long wavelength side.

An organic photoelectric conversion element is an element in which a photoelectric conversion part including a photoelectric conversion film is arranged between two opposing electrode films, an upper electrode and a lower electrode, and light enters the photoelectric conversion part from above one electrode. It is the one that is incident. The photoelectric conversion section generates electrons and holes according to the amount of incident light, and a signal corresponding to the charge is read out by the semiconductor, and the element indicates the amount of incident light according to the absorption wavelength of the photoelectric conversion film section. It is. A readout transistor may be connected to the lower electrode film. When a large number of photoelectric conversion elements are arranged on an array, the photoelectric conversion elements serve as imaging elements because they indicate incident position information in addition to the amount of incident light. In addition, regarding the incidence of light, if the absorption wavelength of the photoelectric conversion element including the electrode present at the rear part is not blocked by the photoelectric conversion element present at the front part, a plurality of photoelectric conversion elements may be stacked. . Furthermore, when the plurality of photoelectric conversion elements described above each absorb different visible light, the image sensor becomes a multicolor image sensor, forming a full-color photodiode.

Although typical device structures of the photoelectric conversion device of the present invention are explained in detail in FIG. 1, the present invention is not limited to these structures. In each embodiment of FIG. 1, 1 is an insulating part, 2 is an upper electrode, 3 is an electron block layer, 4 is a photoelectric conversion part, 5 is a hole block layer, 6 is a lower electrode, and 7 is an insulating base material or a photoelectric conversion part. Each represents a conversion element. Although the readout transistor is not shown in the figure, it is sufficient if it is connected to the lower electrode, and furthermore, if the semiconductor is transparent, it may be formed as a film under the lower electrode. The incident light may be incident from either the top or the bottom as long as the absorption wavelength of the photoelectric conversion section is not extremely blocked by anything other than the photoelectric conversion section.

Here, the photoelectric conversion section is often composed of multiple layers such as a photoelectric conversion layer, an electron transport layer, a hole transport layer, an electron block layer, a hole block layer, a crystallization prevention layer, and an interlayer contact improvement layer. It is not limited to these. By using one or more thin film layers selected from the group consisting of an electron transport layer, a hole transport layer, an electron block layer, and a hole block layer (hereinafter also referred to as a "carrier block layer"), efficiency can be achieved even with weak light energy. This is preferable because an element that converts well into an electric signal can be obtained.

In addition, in organic imaging devices, it is generally thought that the aim is to improve performance by reducing dark current for the purpose of high contrast and power saving, so it is preferable to insert a carrier block layer into the layer structure. . These carrier block layers are generally used in the field of organic electronic devices, and each has a function of controlling the reverse movement of holes or electrons in the constituent films of the device.

An organic semiconductor film is generally used for the photoelectric conversion layer, but the organic semiconductor film may be one layer or multiple layers, and in the case of one layer, a P-type organic semiconductor film, an N-type organic semiconductor film, Or a mixed film thereof (bulk heterostructure) is used. On the other hand, in the case of multiple layers, it is about 2 to 10 layers, and it is a structure in which either a P-type organic semiconductor film, an N-type organic semiconductor film, or a mixed film thereof (bulk heterostructure) is laminated. A buffer layer may be inserted.

The organic semiconductor film contains triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, and metal phthalocyanine compounds, depending on the wavelength band to be absorbed. Compounds, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, carbazole derivatives, naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, phenylbutadiene derivatives, styryl derivatives, quinoline derivatives, tetracene Derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives, quinacridone derivatives, coumarin derivatives, fullerene derivatives, porphyrin derivatives, metal complexes (Ir complexes, Pt complexes, Eu complexes, etc.), etc. can be used.

Here, the hole transport layer has the function of transporting generated holes from the photoelectric conversion layer to the electrode, facilitating the movement of holes from the photoelectric conversion layer to the electrode, and the function of blocking electron movement from the electrode. has. In addition, the electron transport layer has the function of transporting generated electrons from the photoelectric conversion layer to the electrode, facilitating the movement of electrons from the photoelectric conversion layer to the electrode, and the function of blocking the movement of holes from the electrode. . Further, the hole blocking layer has the function of preventing the movement of holes from the electrode to the photoelectric conversion layer, preventing recombination within the photoelectric conversion layer, and reducing dark current. The electron blocking layer has the function of preventing electrons from moving from the electrode to the photoelectric conversion layer, preventing recombination within the photoelectric conversion layer, and reducing dark current. Further, the hole blocking layer and the electron blocking layer preferably have high transmittance at the absorption wavelength of the photoelectric conversion layer, or are preferably used in the form of a thin film, so as not to interfere with light absorption of the photoelectric conversion layer. Furthermore, in the photoelectric conversion layer, upon receiving incident light, electrons and holes are generated, respectively, and are transported to electrodes, thereby sending them as electrical signals to a readout circuit.

The electrode film that can be used in an organic photoelectric conversion element is a hole-transporting photoelectric conversion film included in the photoelectric conversion layer, or a hole-transporting film that extracts and collects holes from the hole-transporting film, or a photoelectric conversion film that is included in the photoelectric conversion layer. In order to extract electrons from an electron-transporting photoelectric conversion film or an electron-transporting film and discharge them, a hole-transporting photoelectric conversion film, an adjacent film such as a hole-transporting film, or an electron-transporting photoelectric conversion film, an electron transporting film, etc. The material is selected in consideration of adhesion with adjacent membranes such as transport membranes, electron affinity, ionization potential, stability, etc., and is not particularly limited, but specific examples include tin oxide (NESA), Conductive metal oxides such as indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel, and tungsten; copper iodide, sulfide Examples include inorganic conductive substances such as copper; conductive polymers such as polythiophene, polypyrrole, and polyaniline, and carbon. Further, if necessary, a plurality of materials may be used or the structure may be composed of two or more layers. The resistance of the electrode is also not limited, as long as it does not unnecessarily impede light reception by the element, but from the viewpoint of signal strength and power consumption of the element, low resistance is preferable. For example, an ITO substrate with a sheet resistance value of 300 Ω/□ or less can function as an element electrode, but it is also possible to supply a substrate with a sheet resistance of several Ω/□, so it is desirable to use a low-resistance product. The thickness of ITO can be arbitrarily selected according to the resistance value, but is usually used between 5 and 500 nm, preferably between 10 and 300 nm. Examples of methods for forming a film such as ITO include a vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, and a coating method. UV-ozone treatment, plasma treatment, etc. can be performed as necessary.

Materials for the transparent electrode film include ITO, IZO, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO ₂ , FTO (fluorine-doped tin oxide). ) etc. are particularly preferred. At the absorption peak wavelength of the photoelectric conversion film included in the photoelectric conversion section including the transparent electrode film, the light transmittance of the transparent electrode film is preferably 60% or more, more preferably 80% or more, and particularly preferably 95% or more.

In addition, when multiple photoelectric conversion layers are laminated, the electrodes inside the laminated film need to transmit light of wavelengths other than the light detected by each photoelectric conversion film, and preferably 90% or more of the absorbed light, and It is preferable to use a material that transmits 95% or more of light.

It is preferable that the electrode film be produced without plasma. By creating an electrode film without plasma, the influence of plasma on the substrate can be reduced, and photoelectric conversion characteristics can be improved. Here, plasma-free means that plasma is not generated during the formation of the electrode film, or that the distance from the plasma generation source to the substrate is 2 cm or more, preferably 10 cm or more, and more preferably 20 cm or more, and that plasma does not reach the substrate. This means a state in which the amount of plasma generated decreases.

Examples of devices that do not generate plasma during electrode film formation include electron beam evaporation devices (EB evaporation devices) and pulsed laser evaporation devices. Hereinafter, a method for forming a transparent electrode film using an EB evaporation apparatus will be referred to as an EB evaporation method, and a method for forming a transparent electrode film using a pulsed laser evaporation apparatus will be referred to as a pulsed laser evaporation method.

As for an apparatus that can realize a state in which plasma can be reduced during film formation (hereinafter referred to as a plasma-free film forming apparatus), for example, a facing target sputtering apparatus, an arc plasma evaporation method, etc. can be considered.

When a transparent conductive film is used as an electrode film, a DC short or an increase in leakage current may occur. One of the reasons for this is thought to be that fine cracks introduced into the photoelectric conversion film are covered with a dense film such as TCO, increasing electrical conduction with the electrode film on the opposite side. Therefore, in the case of an electrode having a relatively inferior film quality such as Al, an increase in leakage current is unlikely to occur. By controlling the thickness of the electrode film relative to the thickness of the photoelectric conversion film (depth of cracks), increase in leakage current can be greatly suppressed.

Normally, making a conductive film thinner than a certain range causes a sudden increase in resistance value, but in the solid-state image sensor of this embodiment, the sheet resistance is preferably 100 to 10,000 Ω/□, and the film can be made thinner. There is a large degree of freedom in the range of film thickness. Furthermore, the thinner the transparent conductive thin film is, the less light it absorbs, and the light transmittance generally increases. An increase in light transmittance is very preferable because it increases light absorption in the photoelectric conversion film and increases photoelectric conversion ability.

The hole blocking layer is formed by using a hole blocking substance alone or by laminating and mixing two or more types of substances. Examples of hole-blocking substances used include phenanthroline derivatives such as bathophenanthroline and bathocuproine, silole derivatives, quinolinol derivative metal complexes, oxadiazole derivatives, and oxazole derivatives. The compound is not particularly limited as long as it can prevent the compound from flowing out of the device. The compound represented by the above formula (1) can be particularly suitably used as a material for the hole blocking layer. The method for forming the hole blocking layer thin film of the organic photoelectric conversion element may be as described below. For the purpose of preventing leakage current, the thinner the film is, the better; however, since a sufficient amount of current is required to read out signals when light is incident, it is better to make the film as thin as possible. Generally, the thickness of the power generation layer is preferably about 5 to 500 nm.

[Organic EL element]
Organic EL devices have attracted attention because they can be used for self-luminous large-area color displays, lighting, and other applications, and many developments have been made. Its structure has two layers, a light emitting layer and a charge transport layer, between opposing electrodes consisting of a cathode and an anode; an electron transport layer, a light emitting layer and a hole transport layer are stacked between the opposing electrodes. Those having a structure having three layers; and those having three or more layers are known, and those having a single light-emitting layer are also known.

Although FIG. 2 shows a typical element structure of an organic photoelectric conversion element that is one embodiment of the organic electronics device of the present invention, the present invention is not limited to this structure. In the embodiment of FIG. 2, 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.

Here, the hole transport layer has a function of injecting holes from the anode, transporting the holes to the light emitting layer, facilitating the injection of holes into the light emitting layer, and a function of blocking electrons. Further, the electron transport layer has a function of injecting electrons from the cathode, transporting the electrons to the light emitting layer, facilitating the injection of electrons to the light emitting layer, and a function of blocking holes. Furthermore, in the light-emitting layer, excitons are generated by recombination of the injected electrons and holes, and the energy emitted during the process of radiation deactivation of the excitons is detected as luminescence.

An anode that can be used in an organic EL device is an electrode that has the function of injecting holes into a hole injection layer, a hole transport layer, and a light emitting layer. Generally, metal oxides, metals, alloys, conductive materials, etc. having a work function of 4.5 eV or more are suitable. Materials suitable for the anode of organic EL elements are not particularly limited, but include conductive metal oxides such as tin oxide (NESA), indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO), and gold. , metals such as silver, platinum, chromium, aluminum, iron, cobalt, nickel and tungsten, inorganic conductive substances such as copper iodide and copper sulfide, conductive polymers such as polythiophene, polypyrrole and polyaniline, and carbon. Among these, it is preferable to use ITO or NESA.

The anode may be made of a plurality of materials, if necessary, or may be composed of two or more layers made of different materials. The resistance of the anode is not limited as long as it can supply sufficient current for light emission of the device, but from the viewpoint of power consumption of the device, it is preferable to have a low resistance. For example, an ITO substrate with a sheet resistance value of 300 Ω/□ or less can function as an element electrode, but it is also possible to supply a substrate with a sheet resistance of several Ω/□, so it is desirable to use a low-resistance product. The thickness of ITO can be arbitrarily selected according to the resistance value, but it is usually used between 5 and 500 nm, preferably between 10 and 300 nm. Examples of methods for forming a film such as ITO include a vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, and a coating method.

A cathode that can be used in an organic EL device is an electrode that has the function of injecting electrons into an electron injection layer, an electron transport layer, and a light emitting layer. Generally, metals and alloys with a small work function (approximately 4 eV or less) are suitable. Specific examples include platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, calcium, and magnesium, but they can improve device characteristics by increasing electron injection efficiency. For this purpose, lithium, sodium, potassium, calcium or magnesium is preferable. As the alloy, an alloy containing these low work function metals with metals such as aluminum or silver, or an electrode having a structure in which these are laminated can be used. It is also possible to use an inorganic salt such as lithium fluoride in the laminated electrode. Furthermore, when emitted light is extracted to the cathode side instead of the anode side, the cathode may be a transparent electrode that can be formed into a film at a low temperature. Examples of the cathode film forming method include a vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, and a coating method, but the method is not particularly limited. The resistance of the cathode is not limited as long as it can supply sufficient current for light emission of the device, but from the viewpoint of power consumption of the device, it is preferably a low resistance, and is preferably on the order of several hundred to several Ω/□. The thickness of the cathode is usually 5 to 500 nm, preferably 10 to 300 nm.

The cathode is protected with oxides or nitrides such as titanium oxide, silicon nitride, silicon oxide, silicon nitride oxide, germanium oxide, or mixtures thereof, polyvinyl alcohol, vinyl chloride, hydrocarbon polymers, fluorine polymers, etc. However, it can be sealed with dehydrating agents such as barium oxide, phosphorus pentoxide, and calcium oxide.

Furthermore, in order to extract light emission, it is generally preferable to fabricate electrodes on a substrate that has sufficient transparency in the light emission wavelength region of the device. Examples of the transparent substrate include a glass substrate and a polymer substrate. Soda lime glass, alkali-free glass, quartz, etc. are used for the glass substrate. The thickness of the glass substrate only needs to be sufficient to maintain mechanical and thermal strength, and is preferably 0.5 mm or more. As for the material of the glass, it is preferable that there are few ions eluted from the glass, and examples thereof include non-alkali glass, but commercially available soda lime glass coated with a barrier coating such as SiO ₂ may also be used. Examples of substrates made of polymers other than glass include polycarbonate, polypropylene, polyether sulfone, polyethylene terephthalate, and acrylic substrates.

The organic thin film of an organic EL element is formed in one or more layers between an anode and a cathode. By incorporating the compound represented by formula (1) into the organic thin film, an element that emits light using electrical energy can be obtained.

The "layers" formed by organic thin films include a hole transport layer, an electron transport layer, a hole transport light emitting layer, an electron transport light emitting layer, a hole blocking layer, an electron blocking layer, a hole injection layer, and an electron injection layer. It means a layer, a light-emitting layer, or a single layer that has the functions of these layers as shown in Structure Example 9 below. The structure of the layer forming the organic thin film in the present invention may be any of the structures listed in the following structural examples 1) to 9).

Configuration example 1) Hole transport layer/electron transport light emitting layer.
2) Hole transport layer/emissive layer/electron transport layer.
3) Hole-transporting light-emitting layer/electron-transporting layer.
4) Hole transport layer/light emitting layer/hole blocking layer.
5) Hole transport layer/light emitting layer/hole blocking layer/electron transport layer.
6) Hole transporting light emitting layer/hole blocking layer/electron transporting layer.
7) In each of the combinations 1) to 6) above, a configuration in which a hole injection layer is provided before the hole transport layer or the hole transportable light emitting layer.
8) In each of the above combinations 1) to 7), an electron injection layer is further provided before the electron transport layer or the electron transport light emitting layer.
9) A structure in which the materials used in the combinations 1) to 8) are mixed, and there is only one layer containing the mixed materials.
Note that 9) may be a single layer formed of a material generally referred to as a bipolar luminescent material; or a single layer containing a luminescent material and a hole-transporting material or an electron-transporting material may be provided. Generally, by forming a multilayer structure, charges, that is, holes and/or electrons, can be efficiently transported and these charges can be recombined. Furthermore, by suppressing charge quenching, it is possible to prevent a decrease in the stability of the device and improve the efficiency of light emission.

The hole injection layer and the hole transport layer are formed by laminating a single hole transport material or a mixture of two or more of the materials. As hole transport materials, N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4''-diphenyl-1,1'-diamine, N,N'-dinaphthyl-N , N'-diphenyl-4,4'-diphenyl-1,1'-diamine and other triphenylamines; bis(N-allylcarbazole) or bis(N-alkylcarbazole); pyrazoline derivatives, stilbene compounds, Heterocyclic compounds typified by hydrazone compounds, triazole derivatives, oxadiazole derivatives, and porphyrin derivatives; in polymer systems, polycarbonates, styrene derivatives, polyvinylcarbazole, polysilanes, and the like having the above-mentioned monomers in their side chains can be preferably used. The material is not particularly limited as long as it can form a thin film necessary for device fabrication, inject holes from the electrode, and transport holes. The hole injection layer provided between the hole transport layer and the anode to improve the hole injection property may be a phthalocyanine derivative, m-MTDATA (4,4',4''-tris[phenyl (m-tolyl) Examples of polymers include starburst amines such as ( ) amino] triphenylamine), polythiophenes such as PEDOT (poly(3,4-ethylenedioxythiophene)), and polyvinylcarbazole derivatives.

The electron transport layer is formed by laminating a single electron transport material or a mixture of two or more of the materials. As an electron transport material, it is necessary to efficiently transport electrons from a negative electrode between electrodes to which an electric field is applied. It is preferable that the electron transport material has high electron injection efficiency and efficiently transports the injected electrons. To this end, the electron transport material is required to have a high electron affinity, high electron mobility, excellent stability, and be less likely to generate trapping impurities during production and use. Substances that meet these conditions include quinolinol derivative metal complexes such as tris(8-quinolinolato)aluminum complexes, tropolone metal complexes, perylene derivatives, perinone derivatives, naphthalimide derivatives, naphthalic acid derivatives, oxazole derivatives, and oxadiazoles. Examples include, but are not limited to, derivatives such as thiazole derivatives, thiadiazole derivatives, triazole derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, benzoxazole derivatives, and quinoxaline derivatives. These electron transport materials can be used alone, but they may also be used in a stacked or mixed manner with different electron transport materials. Examples of the electron injection layer provided between the electron transport layer and the cathode to improve electron injection properties include metals such as cesium, lithium, and strontium, and lithium fluoride.

The hole blocking layer is formed by using a hole blocking substance alone or by laminating or mixing two or more types of substances. Preferred hole blocking substances include phenanthroline derivatives such as bathophenanthroline and bathocuproine, silole derivatives, quinolinol derivative metal complexes, oxadiazole derivatives, and oxazole derivatives. The hole-blocking substance is not particularly limited as long as it is a compound that can prevent holes from flowing out from the cathode side to the outside of the device and a decrease in luminous efficiency.

A light-emitting layer means an organic thin film that emits light, and can be said to be, for example, a hole transport layer, an electron transport layer, or a bipolar transport layer that has strong luminescence. The light-emitting layer may be formed of a light-emitting material (a host material, a dopant material, etc.), and may be a mixture of a host material and a dopant material or a host material alone. The host material and dopant material may each be one type, or may be a combination of a plurality of materials.

The dopant material may be contained entirely or partially in the host material. The dopant material may be layered or dispersed. Examples of the light emitting layer include the aforementioned hole transport layer and electron transport layer. Materials used for the light emitting layer include carbazole derivatives, anthracene derivatives, naphthalene derivatives, phenanthrene derivatives, phenylbutadiene derivatives, styryl derivatives, pyrene derivatives, perylene derivatives, quinoline derivatives, tetracene derivatives, perylene derivatives, quinacridone derivatives, coumarin derivatives, Examples include porphyrin derivatives and phosphorescent metal complexes (Ir complexes, Pt complexes, Eu complexes, etc.).

Methods for forming organic thin films for organic EL devices generally include vacuum processes such as resistance heating evaporation, electron beam evaporation, sputtering, and molecular lamination, and solution processes such as casting, spin coating, dip coating, blade coating, and wire bar coating. We employ coating methods such as coating and spray coating, printing methods such as inkjet printing, screen printing, offset printing, and letterpress printing, soft lithography methods such as microcontact printing, and methods that combine multiple of these methods. I can do it. The thickness of each layer is not limited as it depends on the resistance value and charge mobility of each material, but is selected from 0.5 to 5,000 nm. Preferably it is 1 to 1,000 nm, more preferably 5 to 500 nm.

Among the organic thin films constituting the organic EL element, one or more thin films such as a light emitting layer, a hole transport layer, an electron transport layer, etc., present between the anode and cathode electrodes have a compound represented by the above formula (1). By containing the compound, an element that efficiently emits light even with low electrical energy can be obtained.

The compound represented by the above formula (1) can be suitably used as a hole transport layer, a light emitting layer, or an electron transport layer. For example, it can be used in combination with or mixed with the above-mentioned electron transport material, hole transport material, luminescent material, etc.

When the compound represented by the above formula (1) is used as a host material in combination with a dopant material, specific examples of the dopant material include perylene derivatives such as bis(diisopropylphenyl)perylenetetracarboxylic acid imide, perinone derivatives, 4- (dicyanomethylene)-2methyl-6-(p-dimethylaminostyryl)-4H pyran (DCM) and its analogs, metal phthalocyanine derivatives such as magnesium phthalocyanine and aluminum chlorophthalocyanine, rhodamine compounds, deazaflavin derivatives, coumarin derivatives, oxazine compounds, squarylium compounds, violanthrone compounds, Nile Red, pyrromethene derivatives such as 5-cyanopyromethene-BF ₄ complex, and phosphorescent materials such as Eu complexes with acetylacetone, benzoylacetone and phenanthroline as ligands, Ir complexes, Ru complexes, Porphyrins such as Pt complexes and Os complexes, orthometal metal complexes, and the like can be used, but are not particularly limited to these. Furthermore, when two types of dopant materials are mixed, it is also possible to use an assist dopant such as rubrene to efficiently transfer energy from the host dye to obtain light emission with improved color purity. In any case, in order to obtain high luminance characteristics, it is preferable to dope with a substance having a high fluorescence quantum yield.

The amount of the dopant material to be used is usually 30% by mass or less based on the host material since concentration quenching occurs if it is too large. Preferably it is 20% by mass or less, more preferably 10% by mass or less. As a method of doping the host material with the dopant material in the light emitting layer, it can be formed by a co-evaporation method with the host material, but it may also be mixed with the host material in advance and then vapor-deposited at the same time. It is also possible to use it by sandwiching it between host materials. In this case, one or more dopant layers may be laminated with the host material.

These dopant layers may be used alone or in combination. In addition, the dopant material can be used as a polymeric binder such as polyvinyl chloride, polycarbonate, polystyrene, polystyrene sulfonic acid, poly(N-vinylcarbazole), poly(methyl)(meth)acrylate, polybutyl methacrylate, polyester, polysulfone, Solvent-soluble resins such as polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polysulfone, polyamide, ethyl cellulose, vinyl acetate, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), polyurethane resin, phenol resin, It can also be used by dissolving or dispersing it in curable resins such as xylene resins, petroleum resins, urea resins, melamine resins, unsaturated polyester resins, alkyd resins, epoxy resins, and silicone resins.

Organic EL elements can be suitably used as flat panel displays. It can also be used as a flat backlight, and in this case, either one that emits colored light or one that emits white light can be used. Backlights are mainly used for the purpose of improving the visibility of display devices that do not emit light by themselves, and are used in liquid crystal display devices, watches, audio equipment, automobile panels, display boards, signs, etc. In particular, conventional backlights for personal computers, where liquid crystal display devices, especially thinner ones, are difficult to make thinner because they consist of fluorescent lamps and light guide plates. The backlight using the element is characterized by being thin and lightweight, so the above-mentioned problems can be solved. Similarly, it can be usefully used for lighting.

By using the compound represented by the above formula (1) of the present invention, an organic EL display device with high luminous efficiency and long life can be obtained. Furthermore, by combining thin film transistor elements, it becomes possible to provide at low cost an organic EL display device in which the on/off phenomenon of applied voltage is electrically controlled with high precision.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. The structures of the compounds described in the synthesis examples were determined by mass spectrometry spectroscopy (EI-MS, HR-MS) and nuclear magnetic resonance spectroscopy (NMR) as necessary. In the examples, ¹ H-NMR spectra were measured using Avance 500 (Bruker), EI-MS spectra were measured using GCMS-QP2010 (Shimadzu Corporation), and HR-MS measurements were performed using JMS-T100CV (JEOL). went. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer UV-1700 (Shimadzu Corporation). The emission spectrum was measured using an absolute PL quantum yield measuring device C11347 (Hamamatsu Photonics).

[Example 1] Synthesis of the compound represented by formula (1-1) in the above specific example 2,2'-dimethylbenzo[1,3]dioxole-4- synthesized according to Non-Patent Document 1 in a flask. Boronic acid (4.02 g, 16.7 mmol) and methylene chloride (80 ml) were charged and stirred to dissolve. The mixture was cooled to 0° C., and trifluoroacetic acid (40 ml; 59.6 g, 0.52 mmol) was slowly added thereto, followed by reaction at room temperature for 3 hours. The precipitated solid was filtered and the obtained solid was purified to obtain 0.86 g (1.8 mmol, yield 43%) of the compound represented by formula (1-1). The measurement results of the EI-MS spectrum and NMR spectrum of the compound represented by formula (1-1) were as follows.
EI-MS (m/z): 472 [M] ^+
1 H NMR (400 MHz, CDCl3): δ 7.88 (dd, 4 H), 7.59 (dd, 4 H), 7.32 (t, 4 H)

[Example 2] Preparation of organic thin film of the present invention and evaluation thereof A 50 nm film of the compound represented by formula (1-1) obtained in Example 1 was formed on a quartz substrate by resistance heating vacuum evaporation. An organic thin film of the invention was produced. As a result of measuring the absorption spectrum of the organic thin film on the quartz substrate obtained above, the maximum absorption wavelength and absorption edge were 311 nm and 327 nm, respectively, showing absorption in the near ultraviolet region and no absorption in the visible region.
Furthermore, when the compound represented by formula (1-1) was irradiated with ultraviolet rays, blue light emission with maximum emission at 422 nm was observed (see emission spectrum in FIG. 3), and solid-state light emission was observed.

[Example 3] Production of a photoelectric conversion element of the present invention and its evaluation A 100 nm film of tin phthalocyanine was vacuum-formed as a photoelectric conversion layer on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm), and a 100 nm film of tin phthalocyanine was formed on it as a photoelectric conversion layer. As a block layer, the compound represented by formula (1-1) obtained in Example 1 was deposited to a thickness of 50 nm by resistance heating vacuum evaporation. Further, a 100 nm thick aluminum film was vacuum-formed as an electrode thereon to produce a photoelectric conversion element of the present invention.
For the photoelectric conversion element obtained above, the brightness ratio was calculated from the measurement results of the current value in the dark and the current value when irradiated with light when a voltage of 3V was applied using ITO and aluminum as electrodes, and the results are displayed. Shown in 1.

[Example 4] Synthesis of the compound represented by formula (1-2) in the above specific example 2,2',7-trimethylbenzo[1,3]dioxole synthesized according to Non-Patent Document 1 was placed in a flask. 4-boronic acid (80 mg, 0.38 mmol) and methylene chloride (5 ml) were charged and dissolved with stirring. The mixture was cooled to 0°C, trifluoroacetic acid (5 ml) was added thereto, and the mixture was stirred at room temperature for 4.5 hours. The precipitated solid was filtered and the obtained solid was purified to obtain 18 mg (0.034 mmol, yield 35.9%) of the compound represented by formula (1-2) as a white solid. The measurement results of the EI-MS spectrum, HR-MS spectrum, and NMR spectrum of the compound represented by formula (1-2) were as follows.
EI-MS (m/z): 528 [M+H] ⁺
HRMS (FD-TOF-MS) Calcd for C ₂₈ H ₂₀ B ₄ O ₈ [M] ⁺ : 528.1530. Found: 528.1530.
¹ H NMR (500 MHz, CDCl ₃ ) δ 7.79 (d, 4H, J=7.5Hz) δ 7.11 (d, 4H, J=9.0Hz), and δ 2.58 (s, 12H).

[Example 5] Synthesis of the compound represented by formula (1-6) in the above specific example. 6-Butyl-2,2'-dimethylbenzo[1,3] synthesized according to Non-Patent Document 1 in a flask. Dioxole-4-boronic acid (660 mg, 2.64 mmol) and methylene chloride (10 ml) were charged and dissolved with stirring. The mixture was cooled to 0°C, trifluoroacetic acid (10 ml) was added thereto, and the mixture was stirred at room temperature for 5 hours. The precipitated solid was filtered and the obtained solid was purified to obtain 142 mg (0.20 mmol, yield 31.0%) of the compound represented by formula (1-6) as a white solid. The measurement results of the EI-MS spectrum, HR-MS spectrum, and NMR spectrum of the compound represented by formula (1-6) were as follows.
EI-MS (m/z): 696 [M+H] ⁺
HRMS (FD-TOF-MS) Calcd for C ₄₀ H ₄₄ B ₄ O ₈ [M] ⁺ : 696.3408. Found: 696.3411.
¹ H NMR (500 MHz, CDCl ₃ ) δ 7.85 (d, 4H, J=2.0Hz) δ 7.63 (d, 4H, J=2.0Hz), and δ 1.45 (s,9H).

[Comparative Example 1] Production of a photoelectric conversion element for comparison and its evaluation 1,4,5,8-naphthalene-tetracarboxylic anhydride (NTCDA) was used instead of the compound represented by formula (1-1). A comparative photoelectric conversion element was produced in the same manner as in Example 3, except for the following, and the contrast ratio was calculated. The results are shown in Table 1.

[Comparative Example 2] Production of a photoelectric conversion element for comparison and its evaluation 3,4,9,10-perylene-tetracarboxylic anhydride (PTCDA) was used instead of the compound represented by formula (1-1). A comparative photoelectric conversion element was produced in the same manner as in Example 3, except for the following, and the contrast ratio was calculated. The results are shown in Table 1.

[Comparative Example 3] Production of a comparative photoelectric conversion element and its evaluation A comparative photoelectric conversion element was produced according to Example 3, except that fullerene (C60) was used instead of the compound represented by formula (1-1). A conversion element was manufactured and the contrast ratio was calculated. The results are shown in Table 1.

From the results in Table 1, it can be seen that the photoelectric conversion device of the present invention using the compound represented by formula (1) in the hole blocking layer is superior to the comparative photoelectric conversion device using a known compound in the electron blocking layer. It shows a brightness ratio that is more than one order of magnitude higher, and it is clear that it is suitable as a material for organic photoelectric conversion elements.

The compound of the present invention not only has excellent visible transparency and solid-state luminescence, but also has stable sublimation and excellent organic photoelectric conversion properties, and is extremely useful as an organic electronic device material.

(Figure 1)
1 Insulating part 2 Upper electrode film 3 Electron blocking layer 4 Photoelectric conversion layer 5 Hole blocking layer 6 Lower electrode film 7 Insulating base material or other photoelectric conversion element

(Figure 2)
1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Cathode

Claims (7)

The following formula (1)

(In formula (1), R ₁ to R ₃ each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group, and multiple R _1s may be the same or different. Often, a plurality of R ₂ may be the same or different, and a plurality of R ₃ may be the same or different. In addition, adjacent R ₁ to R ₃ may be bonded to form an aromatic ring or a heterocyclic ring. ). The compound according to claim 1, wherein all of R ₁ and R ₃ are hydrogen atoms . The compound according to claim 1, wherein at least one of all R ₁ and all R ₃ is an aliphatic hydrocarbon group, an alkoxy group, an aromatic group, or a heterocyclic group. A luminescent material comprising the compound according to any one of claims 1 to 3. An organic thin film comprising the compound according to any one of claims 1 to 3. An organic electronic device comprising the organic thin film according to claim 5. The organic electronics device according to claim 6, which is a photoelectric conversion element.

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