JP2008109163A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element having high luminous efficiency and excelling in color purity. <P>SOLUTION: The light-emitting element emits light by electric energy with a light-emitting matter that exists between a positive electrode and a negative electrode, wherein the light-emitting element contains organic materials having sublimiation properties, and triplet-emitting substances, as well as, a molecular weight of 600 or larger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is an element that can convert electrical energy into light, and can be used in the fields of display elements, flat panel displays, backlights, lighting, interiors, signs, signboards, electrophotographic machines, optical signal generators, and the like. It relates to an element.

  In recent years, research on an organic laminated thin film light emitting device in which light is emitted when electrons injected from a cathode and holes injected from an anode are recombined in an organic phosphor sandwiched between both electrodes has been actively conducted. This element is attracting attention because it is thin, has high luminance emission under a low driving voltage, and multicolor emission by selecting a fluorescent material.

This study was conducted by C.D. W. Since Tang et al. Have shown that organic thin-film light-emitting elements emit light with high brightness, many research institutions have studied (see Non-Patent Document 1). A typical structure of an organic laminated thin film light emitting device presented by a research group of Kodak Company is a diamine compound having a hole transport property on an indium tin oxide (ITO) glass substrate and tris (8-quinolinolato) aluminum which is a light emitting layer. Further, Mg: Ag was sequentially provided as a cathode, and green light emission of 1000 cd / m ² was possible with a driving voltage of about 10V. Some organic multilayer thin film light emitting elements have different configurations such as those provided with an electron transport layer in addition to the above-described element constituent elements, but basically follow the configuration of Kodak Company.

  As the light emitting material constituting the light emitting layer, only the host material or a material obtained by doping the host material with a dopant material is used. Luminescent materials are required to have the three primary colors red, green, and blue for full color displays.

As a light emitting material, a fluorescent (singlet light emitting) material has been generally used. However, due to the difference in spin multiplicity when electrons and holes are recombined to excite molecules, singlet is used. Since 25% of excitons and 75% of triplet excitons are generated, it has been attempted to use a phosphorescent (triplet emission) material to improve luminous efficiency. Princeton University This group shows that the luminous efficiency is significantly higher than that of conventional fluorescent materials (see Non-Patent Document 2).
Applied Physics Letters, (USA), 1987, 51, 12, 913-915 Applied Physics Letters, (USA), 1999, Vol. 75, No. 1, pp. 4-6

  However, the light-emitting element manufactured by the above-described conventional technique has insufficient durability, and improvement of the phosphorescent material itself, improvement of a hole transport material, a host material, an electron transport material, and the like is desired.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such problems of the prior art, and to provide a light emitting element having high luminous efficiency and color purity and excellent durability.

  That is, the present invention is an element in which a luminescent substance is present between an anode and a cathode and emits light by electric energy, and includes an organic material having a sublimation property and a molecular weight of 600 or more and a triplet luminescent material. A light-emitting element is characterized.

  The light emitting device of the present invention has high luminous efficiency, high brightness, excellent color purity, and improved durability.

  In the present invention, if the anode is transparent for extracting light, the conductive metal oxide such as tin oxide, indium oxide and ITO, or the metal such as gold, silver and chromium, the inorganic conductive material such as copper iodide and copper sulfide. The conductive polymer such as conductive material, polythiophene, polypyrrole, polyaniline and the like are not particularly limited, but it is particularly preferable to use ITO glass or Nesa glass. The resistance of the electrode is not limited as long as a current sufficient for light emission of the light emitting element can be supplied, but it is preferably low resistance from the viewpoint of power consumption of the light emitting element. For example, ITO glass of 300Ω / □ or less functions as an element electrode, but at present, it is possible to supply a substrate of about 10Ω / □, and it is particularly preferable to use a low resistance product.

The thickness of the ITO film in the case of using ITO glass can be arbitrarily selected according to the resistance value, but is usually preferably between 100 and 300 nm. Moreover, the thickness of a glass substrate should just have sufficient thickness to maintain mechanical strength, and, specifically, 0.5 mm or more is preferable. As for the material of the glass substrate, alkali-free glass is preferable because it is better that there are fewer ions eluted from the glass, but commercially available soda lime glass with a barrier coat such as SiO ₂ can also be used. A plastic substrate may also be used.

  The ITO film forming method is not particularly limited, such as an electron beam method, a sputtering method, or a chemical reaction method.

  In the present invention, the cathode is not particularly limited as long as it is made of a material capable of efficiently injecting electrons into the light emitting material. Specifically, platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium Lithium, cesium, sodium, potassium, calcium, magnesium and the like. In particular, lithium, cesium, sodium, potassium, calcium, magnesium, or alloys containing these low work function metals are effective for increasing the electron injection efficiency and improving device characteristics.

  However, since these low work function metals are generally unstable in the atmosphere, for example, the organic layer is doped with a small amount of lithium, cesium, or magnesium (1 nm or less in the film thickness display of vacuum deposition). Although it is preferable to use an electrode having high stability, an inorganic salt such as lithium fluoride can also be used, and is not particularly limited thereto. Furthermore, for electrode protection, metals such as platinum, gold, silver, copper, iron, tin, aluminum, indium, or alloys using these metals, and inorganic substances such as silica, titania, silicon nitride, polyvinyl alcohol, vinyl chloride, Preferred examples include laminating hydrocarbon polymers.

  The method for producing the cathode is not particularly limited as long as conduction can be achieved, such as a resistance heating method, an electron beam method, a sputtering method, an ion plating method, and a coating method.

  In the present invention, the light-emitting substance corresponds to both a substance that emits light by itself and a substance that assists the light emission, and refers to a compound that participates in light emission. Specifically, a light emitting material, a hole transport material, an electron transport material, a hole blocking material, and the like are applicable.

  The light emitting device of the present invention can have various configurations other than the anode and the cathode, for example, 1) hole transport layer / light emitting layer, 2) hole transport layer / light emitting layer / electron transport layer, 3) light emitting layer / Electron transport 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) Light emitting layer / hole blocking layer / electron transport Layer and 7) in the case of a light emitting layer.

  In the present invention, the light-emitting substance needs to include an organic material having a molecular weight of 600 or more and a triplet light-emitting material, and the triplet light-emitting material often plays a role of light emission itself, so that the light emission constituting the light-emitting layer is particularly important. It is preferable that it is contained in a material, and it is preferable to be used as a dopant material mentioned later especially.

  Triplet light-emitting materials have higher luminous efficiency than conventional singlet light-emitting materials, and light-emitting elements using triplet light-emitting materials are desired to have a broader application range and higher durability.

  In order to obtain light emission efficiently, it is necessary to recombine electrons and holes in the light-emitting layer. However, the recombination energy that is not used for light emission becomes heat, so the light-emitting layer is most damaged. It is easy to receive. Therefore, an organic material having a molecular weight of 600 or more is preferably used in the light emitting layer because it has excellent heat resistance. The molecular weight is more preferably 803 or more, and still more preferably 900 or more.

  The molecular weight of the triplet light-emitting material is only slightly contained in the film, and therefore has little influence on its durability.

  The light emitting element is preferably manufactured by laminating each material, but since the ITO substrate which is an anode is generally used for the substrate, the hole transport layer is most easily influenced by the base. Therefore, an organic material having a molecular weight of 600 or more is preferably used in the hole transport layer because it has excellent thin film stability.

  The metal layer that is the cathode is generally formed last, but vapor deposition is used for film formation, and the organic layer that has already been laminated tends to be adversely affected by the radiant heat at that time. Therefore, an organic material having a molecular weight of 600 or more is preferably used in the electron transport layer because of excellent heat resistance.

  Since the triplet light emitting material emits light by a mechanism different from that of the conventional fluorescent material (singlet light emission), the material group used together with the conventional fluorescent material is not always applicable to the combination with the triplet light emitting material as it is. . In particular, it is often not applicable when used in the same layer. Therefore, when considering a combination with a triplet material, compounds represented by the following general formulas (1) to (5) can be given as preferred examples of organic materials having a molecular weight of 600 or more.

(Here, R ^{1 to} R ¹⁰ may be the same or different, and are selected from hydrogen, an alkyl group, an aryl group, an alkoxy group, and a condensed aromatic hydrocarbon ring structure formed between adjacent substituents. X ¹ is selected from a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl chain, a heterocyclic chain, a silyl chain, an ether chain, and a thioether chain, and n is 2 or more. Represents the natural number of

(Here, R ¹¹ is selected from hydrogen, alkyl, and aryl groups. N represents a natural number of 4 or more.)

(Here, R ^{12 to} R ²¹ may be the same or different and are selected from hydrogen, an alkyl group, an aryl group, an alkoxy group, and a condensed aromatic hydrocarbon ring structure formed between adjacent substituents. R ^{16 and} R ¹⁷ may be linked together, and X ² is a single bond, alkyl chain, cycloalkyl chain, alkylene chain, aryl chain, heterocyclic chain, silyl chain, ether chain, thioether chain. It is selected from any one or a combination thereof, and n represents a natural number of 2 or more.)

(Here, R ^{22 to} R ²⁹ may be the same or different, and are selected from hydrogen, an alkyl group, an aryl group, and an alkoxy group, provided that one of R ^{22 to} R ²⁹ is a bond to X ^3. X ³ is selected from a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl chain, a heterocyclic chain, a silyl chain, an ether chain, and a thioether chain, either alone or in combination. Represents a natural number of 2 or more.)

(Wherein R ³⁰ represents a substituent modified at any position, and is selected from hydrogen, an alkyl group, an aryl group, and an alkoxy group. X ⁴ is a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl group. A chain, a heterocyclic chain, a silyl chain, an ether chain, or a thioether chain is selected from one or a combination thereof, Y is selected from oxygen or nitrogen, and in the case of nitrogen, any of hydrogen, alkyl group, and aryl group N represents a natural number of 2 or more.) Among these substituents, the alkyl group means a saturated aliphatic hydrocarbon group such as a methyl group or an ethyl group, and these are unsubstituted. But it may be replaced. The aryl group represents an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group, which may be unsubstituted or substituted. The alkoxy group represents an aliphatic hydrocarbon group via an ether bond such as a methoxy group, and these may be unsubstituted or substituted. In view of the effects of the present invention, these substituents are a list of hydrogen on each compound and substituents having equivalent properties.

X ^{1 to} X ⁵ are linking chains for linking, and by being linked by a linking chain, they can impart heat resistance and thin film forming ability that could not be obtained with conventional single compounds, Further, durability as an element can be imparted, and a useful light-emitting element can be obtained. The bond chain may be a single bond, an alkyl chain, an alkylene chain, a cycloalkyl chain, an aryl chain, a heterocyclic chain, a silyl chain, an ether chain, or a thioether chain, but it has thermal stability and electron and / or hole transport. Preferred bond chains for enhancing the performance include a single bond, an alkylene chain, an aryl chain, and a heterocyclic chain. Furthermore, a rigid and bulky structure is desirable for further heat resistance and thin film formation, and specifically, a bonded chain composed of a plurality of aryl chains is more preferable.

  Specific examples of the organic material compounds represented by the general formulas (1) to (5) having a molecular weight of 600 or more are shown below, but are not limited thereto.

  The luminescent substance may be composed of only organic materials represented by the general formulas (1) to (5) having a molecular weight of 600 or more and triplet materials, or may be combined with other conventionally used materials. I do not care.

  The organic material having a molecular weight of 600 or more of the present invention has sublimability. As used herein, sublimation is not a strict meaning that a solid is vaporized without passing through a liquid, but is used in a broad sense that a thin film can be formed by volatilization without being decomposed when heated in a vacuum. ing. The light-emitting element in the present invention preferably has a laminated structure, but if it is an organic compound having sublimation properties, it is easy to form the laminated structure by a dry process such as a vacuum evaporation method. In addition, when a doping layer is formed in the light emitting layer, a doping layer having excellent controllability can be formed by using a co-evaporation method with a host material or a method of pre-mixing with a host material and simultaneously evaporating. Furthermore, it is necessary to obtain a desired patterned light emission when configuring a display that displays in a matrix or a segment system, but an organic compound having a sublimation property can be easily patterned by patterning in a dry process. .

  The hole transport layer is a layer that administers holes from the anode and further transports holes, and the material used for the hole transport layer (hereinafter referred to as hole transport material) is single or different hole transport. It may be used by being laminated or mixed with the material.

  The light emitting layer is a layer that actually controls light emission by accumulating electric energy injected from the anode and the cathode as energy for light emission. A material used for the light emitting layer (hereinafter referred to as a light emitting material) is preferably a compound having fluorescence or phosphorescence.

  In addition, when light emission is obtained using a light emitting material, energy storage and actual light emission are performed with a single light emitting material, and energy transition is used to separate functions and use a combination of a plurality of light emitting materials. There is. The latter case is classified into a light-emitting material (hereinafter referred to as a host material) responsible for storing electric energy and a light-emitting material (hereinafter referred to as a dopant material) that receives the stored energy and actually controls light emission. Such a function separation method is called a doping method, and a light-emitting element with high efficiency, high color purity, and high durability can be obtained by this method.

  These light emitting materials can be used alone or in combination of a plurality of kinds, and the light emitting layer can be used in multiple layers.

  In the doping method, the dopant material may be contained in the host material as a whole, or may be partially contained, and a layer made of the dopant material is laminated on a layer made of the host material. It may be. You may use a host material individually or in mixture of multiple.

  The dopant material of the light-emitting material may be a single triplet light-emitting material or a mixture of a plurality of triplet light-emitting materials. Further, one or more known singlet dopant materials and a triplet light-emitting material may be used. You may mix and use.

  The electron transport layer is a layer that administers electrons from the cathode and further transports electrons. The material used for the electron transport layer (hereinafter referred to as an electron transport material) is laminated or mixed with a single electron transport material or a different electron transport material. You may use it.

  The hole blocking layer is a layer that efficiently blocks holes from the anode from flowing to the cathode without recombination, and a material used for the hole blocking layer (hereinafter referred to as a hole blocking material) is used alone or It may be used by laminating or mixing with different hole blocking materials.

  The hole transporting material is a material that efficiently transports holes from the anode between electrodes to which an electric field is applied, has a high hole injection efficiency, and efficiently transports injected holes. Is preferred. For this purpose, it is required to be made of a material having a low ionization potential, a high hole mobility, excellent stability, and a trapping impurity that is unlikely to be generated during manufacture and use. An organic material having a molecular weight of 600 or more according to the present invention may be mentioned as satisfying such a condition. Among them, the organic materials represented by the general formulas (1) to (3) are particularly preferable. In addition, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine, N, N′-dinaphthyl-N, N′— Triphenylamines such as diphenyl-4,4′-diphenyl-1,1′-diamine, carbazole derivatives such as bis (N-allylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivatives, stilbene compounds, Hydrazone compounds, oxadiazole derivatives, phthalocyanine derivatives, heterocyclic compounds typified by porphyrin derivatives, in the polymer system, polycarbonate and styrene derivatives having the above monomers in the side chain, polyvinylcarbazole, polysilane, etc. are preferably mentioned, A thin film necessary for light-emitting element fabrication is formed, and holes can be injected from the anode. It is not particularly limited as long as it is a compound capable of transporting holes.

  Examples of the host material include organic materials having a molecular weight of 600 or more according to the present invention. Among them, organic materials represented by general formulas (1) to (5) are particularly preferable examples. Although not particularly limited, fused ring derivatives such as anthracene, phenanthrene, pyrene, perylene, chrysene, etc., which have been known as light emitters, quinolinol derivatives such as tris (8-quinolinolato) aluminum have been known. Metal complexes, benzoxazole derivatives, stilbene derivatives, benzthiazole derivatives, thiadiazole derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, oxadiazole derivatives, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, bis ( N-carbazolyl) Biphenyl and other carbazole derivatives, triazole derivatives, phenanthroline derivatives, triphenylamine derivatives, quinolinol derivatives and different ligands Combined metal complex, oxadiazole derivative metal complex, benzazole derivative metal complex, coumarin derivative, pyrrolopyridine derivative, perinone derivative, thiadiazolopyridine derivative, in polymer system, polyphenylene vinylene derivative, polyparaphenylene derivative, and polythiophene Derivatives can be used.

  Specific examples of triplet light-emitting materials include tris (2-phenylpyridyl) iridium complex, tris {2- (2-thiophenyl) pyridyl} iridium complex, and tris {2- (2-benzothiophenyl) pyridyl} iridium complex. , Tris (2-phenylbenzothiazole) iridium complex, tris (2-phenylbenzoxazole) iridium complex, trisbenzoquinoline iridium complex, bis (2-phenylpyridyl) (acetylacetonato) iridium complex, bis {2- (2 -Thiophenyl) pyridyl} iridium complex, bis {2- (2-benzothiophenyl) pyridyl} (acetylacetonato) iridium complex, bis (2-phenylbenzothiazole) (acetylacetonato) iridium complex, bis (2-phenyl) Benzoxazo ) (Acetylacetonato) iridium complex, bisbenzoquinoline (acetylacetonato) iridium complex, bis {2- (2,4-difluorophenyl) pyridyl} (acetylacetonato) iridium complex, tetraethylporphyrin platinum complex, {Tris (Cenoyltrifluoroacetone) mono (1,10-phenanthroline)} europium complex, {tris (cenoyltrifluoroacetone) mono (4,7-diphenyl-1,10-phenanthroline)} europium complex, {Tris (1,3 -Diphenyl-1,3-propanedione) mono (1,10-phenanthroline)} europium complex, trisacetylacetone terbium complex, and the like, but are not limited thereto. Among phosphorescent (triplet luminescent) materials, an iridium complex or a platinum complex is preferably used because of good emission characteristics.

  Although it does not specifically limit as a known singlet dopant material, Specifically, conventionally known condensation of phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopylene, dibenzopyrene, rubrene, etc. Ring derivatives, benzoxazole derivatives, benzthiazole derivatives, benzimidazole derivatives, benztriazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, imidazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazoline derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, Cyclopentadiene derivatives, bisstyryl derivatives such as bisstyryl anthracene derivatives and distyrylbenzene derivatives, pyromethene derivatives and metal complexes thereof, Orchid derivatives, benzofuran derivatives, phenylisobenzofuran, dimesitylisobenzofuran, di (2-methylphenyl) isobenzofuran, di (2-trifluoromethylphenyl) isobenzofuran, isobenzofuran derivatives such as phenylisobenzofuran, dibenzofuran derivatives, 7-dialkylaminocoumarin derivatives, 7-piperidinocoumarin derivatives, 7-hydroxycoumarin derivatives, 7-methoxycoumarin derivatives, 7-acetoxycoumarin derivatives, 3-benzthiazolylcoumarin derivatives, 3-benzimidazolylcoumarin derivatives, 3 -Coumarin derivatives such as benzoxazolyl coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives, polymethine derivatives, cyanine derivatives, oxobenzanthrase Derivatives, xanthene derivatives, rhodamine derivatives, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives, pyrrolopyridine derivatives, furopyridine derivatives, 1,2,5-thiadiazolopyrene Derivatives, perinone derivatives, pyrrolopyrrole derivatives, squarylium derivatives, violanthrone derivatives, phenazine derivatives, acridone derivatives, diazaflavin derivatives, and the like can be used.

  The electron transport material needs to efficiently transport electrons from the cathode between electrodes to which an electric field is applied, and has high electron injection efficiency, and it is preferable to transport the injected electrons efficiently. For that purpose, it is required that the material has a high electron affinity, a high electron mobility, excellent stability, and a material that does not easily generate trapping impurities during manufacture and use. Examples of the electron transporting material satisfying such conditions include organic materials having a molecular weight of 600 or more according to the present invention. Among them, organic materials represented by the general formulas (4) and (5) are particularly preferable. In addition, quinolinol derivative metal complexes represented by tris (8-quinolinolato) aluminum, tropolone metal complexes, flavonol metal complexes, perylene derivatives, perinone derivatives, naphthalene, coumarin derivatives, oxadiazole derivatives, aldazine derivatives, bisstyryl derivatives, A pyrazine derivative, a phenanthroline derivative, and the like may be mentioned, but are not particularly limited.

  When considering the transport balance between holes and electrons, the hole blocking material needs to be able to efficiently block the holes from the anode from flowing to the cathode side without recombination, and the hole injection efficiency is low. It is preferable. For this purpose, it is required that the material has a high ionization potential, a low hole mobility, excellent stability, and a material that does not easily generate trapping impurities during manufacture and use. As the hole blocking material satisfying such a condition, the above electron transporting material can be used, but the electron transporting ability may be low. These hole blocking materials may be used alone or in combination with or mixed with different hole blocking materials.

  In the present invention, each layer constituting the luminescent material is formed by vacuum deposition, and among them, a resistance heating method, an electron beam method, a sputtering method, and a molecular lamination method are preferable. Although the thickness of each layer depends on the resistance value and cannot be limited, it is usually preferably between 1 and 1000 nm.

  In the present invention, electrical energy mainly refers to a direct current, but a pulse current or an alternating current can also be used. The current value and the voltage value are not particularly limited, but the maximum luminance should be obtained with the lowest possible energy in consideration of the power consumption and life of the light emitting element.

  The light-emitting element of the present invention is preferably a display that displays by a matrix and / or segment system.

  Note that a matrix refers to a display in which pixels for display are arranged in a grid, and a character or an image is displayed by a set of pixels. The shape and size of the pixel are determined by the application. For example, a rectangular pixel with a side of 300 μm or less is normally used for displaying images and characters on a personal computer, monitor, television, etc. In a large display such as a display panel, a pixel with a side of mm order is used. . In monochrome display, pixels of the same color may be arranged. However, in color display, red, green, and blue pixels are displayed side by side. In this case, there are typically a delta type and a stripe type. The matrix driving method may be either a line sequential driving method or an active matrix. The line-sequential driving has an advantage that the structure is simple. However, the active matrix may be superior in consideration of the operation characteristics. Therefore, it is necessary to properly use the active matrix depending on the application.

  In the segment method, a pattern is formed so as to display predetermined information, and a predetermined region is caused to emit light. For example, the time and temperature display in a digital clock or a thermometer, the operation status display of an audio device or an electromagnetic cooker, the panel display of an automobile, and the like can be given. The matrix display and the segment display may coexist in the same panel.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated, this invention is not limited by these examples. In the examples, the film thickness is a crystal oscillation type film thickness monitor display value.

Example 1
A glass substrate (manufactured by Asahi Glass Co., Ltd., 15Ω / □, electron beam beam product) on which an ITO transparent conductive film was deposited to 150 nm was cut into 30 × 40 mm and etched. The obtained substrate was ultrasonically washed with “Semicocrine 56” (manufactured by Furuuchi Chemical Co., Ltd.) and ultrapure water for 15 minutes each and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the light-emitting element, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. First, 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl (αNPD: molecular weight 589) was deposited as a hole transporting material by a resistance heating method to a thickness of 60 nm. Next, 2,2′-bis (4- (N, N′-diphenylamino) phenyl) spiro-9,9′-bifluorene (molecular weight: 803) is used as the host material of the light-emitting material, and tris (2- Using a phenylpyridyl) iridium complex (Ir (ppy) ₃ : molecular weight 655), the film was co-evaporated to a thickness of 30 nm so that the dopant was 8 wt%. Next, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BTCPN: molecular weight 360) was vapor-deposited by 10 nm as a hole blocking material. Next, as an electron transporting material, a tris (8-quinolinol) aluminum complex (molecular weight 459) was deposited to a thickness of 50 nm. Next, after doping the organic layer with 0.5 nm of lithium, aluminum was deposited to 200 nm to form a cathode, and a 5 × 5 mm square light emitting device was manufactured. From this light emitting device, an emission spectrum similar to the phosphorescence spectrum of the dopant material was observed, and high luminance green light emission with good color purity was obtained.

  Further, when the light emitting element was driven at 1 mA pulse in a vacuum cell (duty ratio 1/60, current value at the time of pulse 60 mA), an emission spectrum similar to the phosphorescence spectrum of the dopant material was observed, and the color purity was good. High luminance green light emission was confirmed.

  Furthermore, when durability was evaluated by direct current drive of 20 mA / square centimeter, high-luminance green light emission with good color purity was obtained even after 100 hours.

Comparative Example 1
A light emitting device was fabricated in exactly the same manner as in Example 1 except that 4,4′-bis (N-carbazolyl) biphenyl (CBP: molecular weight 484) was used as the host material of the light emitting material. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-brightness green light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Later, a significant decrease in brightness was observed.

Example 2
2,2′-bis {5- (4-t-butylphenyl) 1,3,4-oxadiazol-2-yl} spiro-9,9′-bifluorene (molecular weight: 717) as a host material for the light-emitting material A light emitting device was produced in the same manner as in Example 1 except that was used.

  From this light emitting device, an emission spectrum similar to the phosphorescence spectrum of the dopant material was observed, and high luminance green light emission with good color purity was obtained. Furthermore, when durability was evaluated by direct current drive of 20 mA / square centimeter, high-luminance green light emission with good color purity was obtained even after 100 hours.

Example 3
4,4′-bis (N-carbazolyl) biphenyl (CBP: molecular weight 484) is used as the host material of the light emitting material, and N, N′-bis (4-diphenylamino-4-biphenyl)-is used as the hole transport material. A light emitting device was produced in the same manner as in Example 1 except that N, N′-diphenylbenzidine (molecular weight 975) was used. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-brightness green light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Even after that, high luminance green light emission with good color purity was obtained.

Example 4
A light-emitting device was produced in the same manner as in Example 3 except that ethylcarbazole tetramer linked at the 3,6-position was used as the hole transport material. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-brightness green light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Even after that, high luminance green light emission with good color purity was obtained.

Example 5
4,4′-bis (N-carbazolyl) biphenyl (CBP: molecular weight 484) is used as the host material of the light emitting material, and 2,2 ′, 7,7′-tetrakis (2-phenanthroyl) spiro is used as the hole blocking material. A light emitting device was produced in exactly the same manner as in Example 1 except that -9,9'-bifluorene (molecular weight 1029) was used. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-brightness green light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Even after that, high luminance green light emission with good color purity was obtained.

Example 6
4,4′-bis (N-carbazolyl) biphenyl (CBP: molecular weight 484) is used as the host material of the luminescent material, and 2,2 ′, 7,7′-tetrakis (2,2-diphenylvinyl) is used as the electron transport material. ) A light emitting device was produced in the same manner as in Example 1 except that spiro-9,9'-bifluorene (molecular weight 1029) was used. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-brightness green light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Even after that, high luminance green light emission with good color purity was obtained.

Example 7
A light emitting device was manufactured in the same manner as in Example 4 except that 2,2′-bis (2,2-diphenylethen-1-yl) spiro-9,9′-bifluorene (molecular weight: 673) was used as the electron transporting material. did. From this light emitting device, an emission spectrum similar to the phosphorescence spectrum of the dopant material was observed, and high luminance green light emission with good color purity was obtained.

Example 8
A light-emitting element was fabricated in exactly the same manner as in Example 1 except that bis {2- (2-benzothiophenyl) pyridyl} (acetylacetonato) iridium complex was used as a dopant material for the light-emitting material. An emission spectrum similar to the phosphorescence spectrum of the dopant material was observed from this light-emitting element, and high-intensity red light emission with good color purity was obtained. When durability was evaluated by DC driving at 20 mA / square centimeter, 100 hours was obtained. Even after this, high-luminance red light emission with good color purity was obtained.

Example 9
A glass substrate (manufactured by Asahi Glass Co., Ltd., 15Ω / □, electron beam beam product) on which an ITO transparent conductive film is deposited to 150 nm is cut into 30 × 40 mm, and 300 μm pitch (remaining width 270 μm) × 32 pieces by photolithography. Patterned into stripes. One side of the ITO stripe in the long side direction is expanded to a pitch of 1.27 mm (opening width 800 μm) in order to facilitate electrical connection with the outside. The obtained substrate was subjected to ultrasonic cleaning with “Semicocrine 56” and ultrapure water for 15 minutes, respectively, and then dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the light-emitting element, placed in a vacuum vapor deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁴ Pa or less. First, 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl (αNPD) was deposited as a hole transporting material by a resistance heating method to a thickness of 60 nm. Next, 2,2′-bis (4- (N, N′-diphenylamino) phenyl) spiro-9,9′-bifluorene is used as the host material of the light-emitting material, and tris (2-phenylpyridyl) iridium complex is used as the dopant material. Using (Ir (ppy) ₃ ), it was co-evaporated to a thickness of 30 nm so that the dopant was 8 wt%. Next, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BTCPN) was deposited as a hole blocking layer by 10 nm. Next, a tris (8-quinolinol) aluminum complex was deposited to a thickness of 50 nm as an electron transporting material. Next, the mask in which 16 250 μm openings (corresponding to the remaining width of 50 μm and 300 μm pitch) were formed by wet etching on a 50 μm thick Kovar plate was replaced in a vacuum so as to be orthogonal to the ITO stripe. And it fixed with the magnet from the back so that an ITO board | substrate might contact | adhere. And after doping lithium with a 0.5 nm organic layer, aluminum was vapor-deposited 200 nm, and the 32 * 16 dot matrix element was produced. When this element was driven in matrix, characters could be displayed without crosstalk.

Claims (5)

A light-emitting element in which a light-emitting substance exists between an anode and a cathode and emits light by electric energy, and includes a sublimation and an organic material having a molecular weight of 600 or more and a triplet light-emitting material. element. The organic material is at least one selected from the group consisting of compounds represented by the following general formulas (1) to (5).

(Here, R ^{1 to} R ¹⁰ may be the same or different, and are selected from hydrogen, an alkyl group, an aryl group, an alkoxy group, and a condensed aromatic hydrocarbon ring structure formed between adjacent substituents. X ¹ is selected from a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl chain, a heterocyclic chain, a silyl chain, an ether chain, and a thioether chain, and n is 2 or more. Represents the natural number of

(Here, R ¹¹ is selected from hydrogen, alkyl, and aryl groups. N represents a natural number of 4 or more.)

(Here, R ^{12 to} R ²¹ may be the same or different and are selected from hydrogen, an alkyl group, an aryl group, an alkoxy group, and a condensed aromatic hydrocarbon ring structure formed between adjacent substituents. R ^{16 and} R ¹⁷ may be linked together, and X ² is a single bond, alkyl chain, cycloalkyl chain, alkylene chain, aryl chain, heterocyclic chain, silyl chain, ether chain, thioether chain. It is selected from any one or a combination thereof, and n represents a natural number of 2 or more.)

(Here, R ^{22 to} R ²⁹ may be the same or different, and are selected from hydrogen, an alkyl group, an aryl group, and an alkoxy group, provided that one of R ^{22 to} R ²⁹ is a bond to X ^3. X ³ is selected from a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl chain, a heterocyclic chain, a silyl chain, an ether chain, and a thioether chain, either alone or in combination. Represents a natural number of 2 or more.)

(Wherein R ³⁰ represents a substituent modified at any position, and is selected from hydrogen, an alkyl group, an aryl group, and an alkoxy group. X ⁴ is a single bond, an alkyl chain, a cycloalkyl chain, an alkylene chain, an aryl group. A chain, a heterocyclic chain, a silyl chain, an ether chain, or a thioether chain is selected from one or a combination thereof, Y is selected from oxygen or nitrogen, and in the case of nitrogen, any of hydrogen, alkyl group, and aryl group (N represents a natural number of 2 or more.) The light-emitting element according to claim 1, wherein the triplet light-emitting material is an iridium complex or a platinum complex. 2. The light-emitting element according to claim 1, wherein the organic material and the triplet light-emitting material are contained in the same layer. The light emitting device according to claim 1, wherein the light emitting device is a display that displays in a matrix and / or segment system.