JP2007059118A - Organic electroluminescent element, liquid crystal display, and lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element with high brightness and low drive voltage with the use of both a fluorescent material and a phosphorescent material. <P>SOLUTION: The organic electroluminescent element is provided with an anode and a cathode on a support substrate as well as an organic compound layer between the anode and the cathode containing at least three luminescent layers with different light-emitting wavelengths having a light-emitting maximum at each region of emission spectrum of 440 nm to 480 nm (hereinafter called a blue region), 500 nm to 540 nm (hereinafter called a green region), and 600 nm to 640 nm (hereinafter called a red region), of which, a main emitter contained in at least one layer is phosphorescent, a main emitter contained in at least one luminescent layer in the blue region is fluorescent, and a main emitter contained in a luminescent layer of the largest film thickness is phosphorescent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element, a liquid crystal display device, and a lighting device.

  As a light-emitting electronic display device, there is an electroluminescence display (ELD). Examples of the constituent elements of ELD include inorganic electroluminescent elements (inorganic EL elements) and organic electroluminescent elements (hereinafter also referred to as organic EL elements). Inorganic EL elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.

  An organic EL device has a structure in which a light-emitting layer containing a light-emitting compound is sandwiched between a cathode and an anode, and excitons (excitons) are generated by injecting electrons and holes into the light-emitting layer and recombining them. The device emits light by using the emission of light (fluorescence / phosphorescence) when the exciton is deactivated, and can emit light at a voltage of several V to several tens V, and is self-luminous. Therefore, it has a wide viewing angle, high visibility, and since it is a thin-film type complete solid-state device, it has attracted attention from the viewpoints of space saving and portability.

  Another major feature of the organic EL element is that it is a surface light source, unlike main light sources that have been conventionally used in practice, such as light-emitting diodes and cold-cathode tubes. Applications that can make effective use of this characteristic include illumination light sources and backlights for various displays. In particular, it can be suitably used as a backlight of a liquid crystal full-color display whose demand has been increasing in recent years.

  When used as a backlight of such a full color display, it is used as a white light source. In order to obtain white light with an organic EL element, a method of obtaining a white color by adjusting a light emitting material in one element, a multicolored light emitting pixel, for example, blue, green, and red are separately applied to emit light simultaneously. There are a method of obtaining a white color by mixing colors, a method of obtaining a white color using a color conversion dye (for example, a combination of a blue light emitting material and a color conversion fluorescent dye), and the like.

  However, in view of various demands required for a backlight, such as low cost, high productivity, and a simple driving method, a method of obtaining a white color by mixing light emitting materials in one element is effective for this application. it is conceivable that.

  In this method, in order to obtain white light, in more detail, a method of obtaining white by mixing two light emitting materials having complementary colors in the element, for example, a blue light emitting material and a yellow light emitting material, -There is a method to obtain white color by mixing green and red light emitting materials, but blue, green and red light emission from the viewpoint of color reproducibility and less light loss in the color filter. A method of mixing colors using materials is preferred.

  For example, it has been reported that white organic EL elements can be obtained by doping high-efficiency phosphors of blue, green, and red as light emitting materials (see, for example, Patent Documents 1 and 2).

  In addition, since a brighter organic EL element can be obtained, development of phosphorescent materials has been promoted in recent years (see, for example, Non-Patent Documents 1 and 2 and Patent Document 3). This is because the emission from the conventional phosphor is emission from the excited singlet, and the generation ratio of the singlet exciton and triplet exciton is 1: 3, so the generation probability of the luminescent excited species is 25%. On the other hand, in the case of a phosphorescent material using light emission from an excited triplet, the upper limit of internal quantum efficiency is 100% due to the exciton generation ratio and internal conversion from singlet excitons to triplet excitons. Therefore, in principle, the luminous efficiency is up to four times that of a fluorescent material.

  However, in a high-quality white element using light emitting materials of blue, green, and red, it is necessary that the performance of each color is excellent without missing one color. It is not easy to align the material characteristics of the two. This is particularly difficult for phosphorescent materials.

  Therefore, for example, a method of obtaining a white organic EL element using a part of a phosphorescent material and another part using a fluorescent material is conceivable. However, the details of the light emission process differ between phosphorescent materials and fluorescent materials. For example, the lifetimes of singlet excitons that emit fluorescence and triplet excitons that emit phosphorescence differ greatly, and triplet excitons are generally longer. As a result, a difference appears in the exciton diffusion distance. For this reason, it is expected that the optimum organic layer configuration differs between the element using the fluorescent material and the phosphorescent element.

  Therefore, when a white organic EL element is configured by combining a fluorescent light emitting material and a phosphorescent light emitting material, a configuration of an organic layer considering a combination of characteristics different from the case where each is used alone is desired.

  In Patent Document 4, there is a description of a white organic EL element in which a fluorescent light-emitting material and a phosphorescent light-emitting material are used together, but there is no description of a description of a layer configuration in consideration of characteristics due to the combined use.

In addition, when trying to obtain light emission at a certain wavelength, a device using a phosphorescent device generally tends to have a higher driving voltage due to its electronic characteristics, and although it has a higher light emission efficiency, it can be driven at a lower voltage. There is also a problem that phosphorescent light-emitting elements are difficult to use for required applications.
JP-A-6-207170 JP 2004-235168 A US Pat. No. 6,097,147 International Publication No. 20/50101013 Pamphlet M.M. A. Baldo et al. , Nature, 395, 151-154 (1998) M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000)

  An object of the present invention is to provide an organic electroluminescence element having a high luminance and a low driving voltage, and a liquid crystal display device and an illuminating device using the same, in which a fluorescent material and a phosphorescent material are used in combination.

  The above problem could be solved by the following configuration.

  (1) A light emission spectrum of 440 nm to 480 nm (hereinafter referred to as blue region), 500 nm to 540 nm (hereinafter referred to as green region), 600 nm to 640 nm (between the anode and the cathode on the support substrate and between the anode and the cathode) (Hereinafter referred to as the red region) each having an organic compound layer including at least three light emitting layers having different emission wavelengths, each having a light emission maximum, and the main light emitter included in at least one layer is a phosphorescent light emitter, The main electroluminescent material contained in at least one of the light emitting layers in the blue region is a fluorescent light emitting material, and the main light emitting material contained in the thickest light emitting layer is a phosphorescent light emitting device. Luminescence element.

  (2) The organic electroluminescence device as described in (1) above, wherein the main light emitter contained in the thinnest light emitting layer is a fluorescent light emitter.

  (3) The organic electroluminescent element as described in (1) or (2) above, wherein the total thickness of the light emitting layers is 30 nm or less.

(4) The chromaticity in the CIE1931 color system with a 2-degree viewing angle front luminance of 1000 cd / m ² is X = 0.33 ± 0.07 and Y = 0.33 ± 0.07. The organic electroluminescence device according to any one of (1) to (3).

  (5) A liquid crystal display device comprising the organic electroluminescence element according to any one of (1) to (4) as a backlight.

  (6) An illumination device using the organic electroluminescence element according to any one of (1) to (4) as a light source.

  According to the present invention, it is possible to provide an organic electroluminescence element having a high luminance and a low driving voltage, and a liquid crystal display device and a lighting device using the same, in which a fluorescent material and a phosphorescent material are used in combination.

  In the present invention, a high-brightness organic EL element, particularly a white light-emitting organic EL element, and a liquid crystal display device using the organic EL element, with the configuration defined in any one of claims 1 to 6, A lighting device could be provided.

  Hereinafter, details of each component according to the present invention will be sequentially described.

<< Organic EL element >>
The organic EL element of the present invention will be described.

<< Light emission and front luminance of organic EL elements >>
The emission color of the organic EL device of the present invention and the compound related to the organic EL device is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a luminance meter CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

The organic EL device of the present invention has a chromaticity in the CIE 1931 color system of X = 0.33 ± 0 at a 2 ° viewing angle front luminance of 1000 cd / m ² without a light collecting member such as a light collecting sheet attached. 0.07, Y = 0.33 ± 0.07.

  The emission spectrum of the organic EL device of the present invention has a maximum emission wavelength of 440 to 480 nm (hereinafter referred to as a blue region), 500 to 540 nm (hereinafter referred to as a green region), and 600 to 640 nm (hereinafter referred to as a red region). And at least three light emitting layers having different emission wavelengths.

  In the present invention, it is preferable that these light emitting layers are used and the light emission maximum wavelength is in each region of 440 to 480 nm, 500 to 540 nm, and 600 to 640 nm as the emission spectrum of the entire device. Furthermore, the minimum light emission intensity between each maximum wavelength is 60% or less of the light emission maximum intensity in the adjacent wavelength region, and any of the blue region, between the green regions or between the green region and the red region is 45% or less. Preferably, the minimum emission wavelength between the blue region and the green region is 470 to 510 nm, the minimum emission wavelength between the green region and the red region is 570 to 600 nm, or a light emitting panel by combining color filters, When forming a liquid crystal display device, it is more preferable that the spectral transmission characteristics of the color filter and the minimum emission wavelength are adjusted so as to satisfy the following relationship.

λ _BG −20 nm ≦ λ ₁ ≦ λ _BG +10 nm
λ _GR −20 nm ≦ λ ₂ ≦ λ _GR +10 nm
Here, λ ₁ is the minimum emission wavelength between the blue region and the green region, λ ₂ is the minimum emission wavelength between the green region and the red region, and λ _BG is the transmittance of the color filter blue pixel in the wavelength range of 450 to 550 nm. Λ _GR is a wavelength at which the product of the transmittance of the green color filter and the transmittance of the red pixel is maximized in the wavelength range of 550 to 630 nm.

  The light-emitting layer according to the organic EL element of the present invention will be described in detail in the layer configuration of the organic EL element described later.

  Next, although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer unit / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer unit / hole blocking Layer / electron transport layer / cathode (iv) anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emission Layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode Here, the light emitting layer unit has at least three light emitting layers having different light emission wavelengths, and non-light emitting layers between the light emitting layers. It is preferable to have an intermediate layer.

<Light emitting layer>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.

  The configuration of the light emitting layer according to the present invention is not particularly limited as long as the light emission maximum wavelength satisfies the above requirements, but the light emission maximum wavelength is a blue light emitting layer in the blue region, and a green light emission in the green region. A light emitting layer having at least three layers of a red light emitting layer in the red region.

  In addition, when the number of light emitting layers is more than four, there may be a plurality of layers having the same emission spectrum or emission maximum wavelength.

  Hereinafter, in the present invention, a layer having an emission maximum wavelength of 440 to 480 nm is referred to as a blue light emitting layer, a layer in the range of 500 to 540 nm is referred to as a green light emitting layer, and a layer in the range of 600 to 640 nm is referred to as a red light emitting layer.

  It is preferable to have a non-light emitting intermediate layer between each light emitting layer.

  In the present invention, the main light emitter contained in at least one layer is a phosphorescent light emitter, and the main light emitter contained in at least one of the light emitting layers in the blue region is a fluorescent light emitter.

  The main light emitter included in the light emitting layer refers to a light emitter that bears the largest part in the light emission intensity generated from the light emitting layer, and the light emitted by the main light emitter is preferably 50% or more of the light emission of the light emitting layer. .

  In the present invention, the total thickness of the light emitting layers is preferably 30 nm or less, and more preferably 25 nm or less because a lower driving voltage can be obtained. In the present invention, the total sum of the thicknesses of the light emitting layers is a thickness including the intermediate layers when a non-light emitting intermediate layer exists between the light emitting layers.

  The film thickness of each light emitting layer is preferably adjusted to a range of 2 to 25 nm, more preferably adjusted to a range of 2 to 20 nm.

  In the present invention, the main light emitter contained in the thickest layer among the light emitting layers is a phosphorescent light emitter.

  Moreover, it is preferable that the main light emitter contained in the thinnest layer is a fluorescent light emitter.

  In general, when the thickness of the light emitting layer is reduced, the current-voltage characteristics shift to the low voltage side. That is, a large current can be passed through the element at a lower voltage. Therefore, if the emission quantum efficiency is constant, it is preferable that the power efficiency is improved by reducing the thickness of the light emitting layer, that is, the driving voltage necessary to achieve a certain luminance can be lowered. However, it is generally known that when the thickness of the light emitting layer is made thinner than about 30 nm, the light emission quantum efficiency is lowered, and as a result, the power efficiency is lowered. This is because, for example, in a phosphorescent light emitting layer, when the film thickness is reduced, diffusion of triplet excitons occurs beyond the light emitting layer, and the deactivation probability in other layers increases, resulting in a decrease in light emission efficiency. Presumed to be due to the cause.

  In the present invention, in an organic electroluminescence device having a phosphorescent light emitter and a fluorescent light emitter, a structure in which the thickness of the phosphorescent light emitting layer is maximized, more preferably, the thickness of the fluorescent light emitting layer is minimized is a low driving voltage. Found to be effective in obtaining

  For the production of the light-emitting layer, a light-emitting dopant or a host compound, which will be described later, is formed and formed by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, or an ink-jet method. it can.

  In the present invention, a plurality of luminescent compounds may be mixed in each light emitting layer within a range that maintains the above spectral shape requirements, and phosphorescent light emitters and fluorescent light emitters are mixed and used in the same light emitting layer. May be.

  In the present invention, it is preferable that the light emitting layer contains a host compound and a light emitting dopant (also referred to as a light emitting dopant compound) and emits light from the dopant.

  As the host compound contained in the light emitting layer of the organic EL device of the present invention, a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) of less than 0.1 is preferable. More preferably, the phosphorescence quantum yield is less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

  As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary luminescent colors can be obtained.

  The light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (evaporation polymerizable light emitting host). )But it is good.

  As the known host compound, a compound having a hole transporting ability and an electron transporting ability, preventing an increase in the wavelength of light emission, and having a high Tg (glass transition temperature) is preferable. Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

  Specific examples of known host compounds include compounds described in the following documents. For example, Japanese Patent Application Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette, 2002-338579 gazette. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. 2002-302516, 2002-305083, 2002-305084, 2002-308837, and the like.

  Next, the light emitting dopant according to the present invention will be described.

  As the light-emitting dopant according to the present invention, a fluorescent compound or a phosphorescent material (also referred to as a phosphorescent compound or a phosphorescent compound) is used.

  The phosphorescent material according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.) and has a phosphorescence quantum yield of 25 ° C. In this case, the phosphorescence quantum yield is preferably 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence emitter according to the present invention can achieve the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

  There are two types of light emission of phosphorescent emitters in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent emitter. Energy transfer type to obtain light emission from the phosphorescent emitter, and another is a carrier in which the phosphorescent emitter becomes a carrier trap and recombination of carriers occurs on the phosphorescent emitter to obtain light emission from the phosphorescent emitter. Although it is a trap type, in any case, it is a condition that the excited state energy of the phosphorescent emitter is lower than the excited state energy of the host compound.

  The phosphorescent luminescent material can be appropriately selected from known materials used for the light emitting layer of the organic EL device.

  The phosphorescent emitter according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex compound). Rare earth complexes, most preferably iridium compounds.

  Specific examples of the compound used as the phosphorescent emitter are shown below, but the present invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

  Representative examples of fluorescent emitters (fluorescent dopants) include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes. Examples thereof include dyes, perylene dyes, stilbene dyes, polythiophene dyes, and rare earth complex phosphors.

  Conventionally known dopants can also be used in the present invention. For example, International Publication No. 00/70655 pamphlet, JP-A Nos. 2002-280178, 2001-181616, 2002-280179, 2001 181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178, 2002-302671, 2001-345183, 2002. No. 324679, International Publication No. 02/15645, JP 2002-332291 A, 2002-50484, 2002-332292, 2002-83684, JP 2002-540572, JP 2 No. 02-117978, No. 2002-338588, No. 2002-170684, No. 2002-352960, Pamphlet of International Publication No. 01/93642, JP 2002-50483, No. 2002-1000047. No. 2002-173684, No. 2002-359082, No. 2002-17584, No. 2002-363552, No. 2002-184582, No. 2003-7469, No. 2002-525808. JP-A 2003-7471, JP-T 2002-525833, JP-A 2003-31366, JP-A 2002-226495, JP-A 2002-234894, JP-A 2002-2335076, JP-A 2002-24175 Gazette, 2001-319779, 2001-319780, 2002-62824, 2002-1000047, 2002-203679, 2002-343572, 2002-203678. A gazette etc. are mentioned.

  A non-light emitting intermediate layer (also referred to as an undoped region or the like) used in the present invention will be described.

  The non-light emitting intermediate layer is a layer provided between the light emitting layers in the case of having a plurality of light emitting layers.

  The film thickness of the non-light emitting intermediate layer is preferably in the range of 1 to 20 nm, and more preferably in the range of 3 to 10 nm, which suppresses interaction such as energy transfer between adjacent light emitting layers, and the element. This is preferable because a large load is not applied to the current-voltage characteristics.

  The material used for the non-light emitting intermediate layer may be the same as or different from the host compound of the light emitting layer, but may be the same as the host material of at least one of the adjacent light emitting layers. preferable.

  The non-light-emitting intermediate layer may contain a non-light-emitting layer, a compound common to each light-emitting layer (for example, a host compound), and each common host material (where a common host material is used) , Phosphorescent emission energy, glass transition point and other physicochemical properties, and the case where the host compound has the same molecular structure, etc.). The injection barrier is reduced, and it is possible to obtain an effect that the injection balance of holes and electrons can be easily maintained even when the voltage (current) is changed. Furthermore, by using a host material having the same physical characteristics or the same molecular structure as that of the host compound contained in each light emitting layer in the undoped light emitting layer, device fabrication, which is a major problem in conventional organic EL device fabrication, is achieved. Complexity can also be eliminated.

  In the organic EL device of the present invention, since the host material is responsible for carrier transport, a material having carrier transport capability is preferable. Carrier mobility is used as a physical property representing carrier transport ability, but the carrier mobility of an organic material generally depends on the electric field strength. Since a material having a high electric field strength dependency easily breaks the balance between injection and transport of holes and electrons, it is preferable to use a material having a low electric field strength dependency of mobility for the intermediate layer material and the host material.

  On the other hand, in order to optimally adjust the injection balance of holes and electrons, it is also preferable that the non-light emitting intermediate layer functions as a blocking layer described later, that is, a hole blocking layer and an electron blocking layer. As mentioned.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be.

  An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

  The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

  The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.

  The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

  The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.

  On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

  The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

  The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.

  Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and two more described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-30 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 688 are linked in a starburst type ( MTDATA) and the like.

  Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material.

  JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, it is preferable to use these materials because a light-emitting element with higher efficiency can be obtained.

  The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  Alternatively, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Conventionally, in the case of a single electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. As long as it has a function of transferring electrons to the light-emitting layer, any material can be selected and used from among conventionally known compounds. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives Thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum. Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and similarly to the hole injection layer and the hole transport layer, inorganic such as n-type-Si and n-type-SiC can be used. A semiconductor can also be used as an electron transport material.

  The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

  Further, an electron transport layer having a high n property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use an electron transport layer having such a high n property because an element with lower power consumption can be manufactured.

《Support substrate》
There are no particular limitations on the type of glass, plastic, etc., as the support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) according to the organic EL device of the present invention. It may be. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned. An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability measured by a method in accordance with JIS K 7129-1992 is 0.01 g / m ^2. It is preferably a barrier film of day · atm or less, and further, the oxygen permeability measured by a method according to JIS K 7126-1992 is 10 ⁻³ g / m ² / day or less, water vapor permeability Is preferably a high barrier film of 10 ⁻³ g / m ² / day or less, and the water vapor permeability and oxygen permeability are both 10 ⁻⁵ g / m ² / day or less, Further preferred.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

<Method for forming barrier film>
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma weighting. A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

  Examples of the opaque support substrate include metal plates / films such as aluminum and stainless steel, opaque resin substrates, ceramic substrates, and the like.

  The external extraction efficiency at room temperature of light emission of the organic EL device of the present invention is preferably 1% or more, more preferably 5% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.

  Here, an example of a layer structure of a transparent barrier film used for the support substrate according to the present invention will be described with reference to FIG. 3, and an example of an atmospheric pressure plasma discharge treatment apparatus preferably used for forming the barrier layer will be described with reference to FIG. Will be described.

  FIG. 3 is a schematic diagram illustrating an example of a layer configuration of a barrier film (also referred to as a gas barrier film) and a density profile thereof.

  The barrier film 201 (which may be transparent or opaque) has a configuration in which layers having different densities are stacked on the base material 202. In the present invention, a medium density layer 204 is provided between the low density layer 203 and the high density layer 205, and the medium density layer 204 is also provided on the high density layer 205, and these low density layer and medium density layer are provided. FIG. 3 shows an example in which a unit composed of a high-density layer and a medium-density layer is one unit, and two units are stacked. At this time, the density distribution in each density layer is uniform, and the density change between adjacent layers is stepped. In FIG. 3, the medium density layer 204 is shown as one layer, but a configuration of two or more layers may be adopted as necessary.

  FIG. 4 is a schematic view showing an example of an atmospheric pressure plasma discharge treatment apparatus for treating a substrate.

  The atmospheric pressure plasma discharge processing apparatus is an apparatus having at least a plasma discharge processing apparatus 230, an electric field applying means 240 having two power supplies, a gas supply means 250, and an electrode temperature adjusting means 260.

  FIG. 4 shows an interval (discharge space) 232 between the counter electrode between the roll rotating electrode (first electrode) 235 and the rectangular tube fixed electrode group (second electrode) 236 (each electrode is also a rectangular tube fixed electrode 236). Thus, the substrate F is subjected to plasma discharge treatment to form a thin film. In FIG. 4, a pair of rectangular tube type fixed electrode group (second electrode) 236 and roll rotating electrode (first electrode) 235 form one electric field. Is formed. FIG. 4 shows a configuration example in which a total of five units having such a configuration are provided. In each unit, the type of raw material to be supplied, the output voltage, and the like are controlled arbitrarily and independently. A mold barrier film (also referred to as a transparent gas barrier layer) can be formed continuously.

In the discharge space (between the counter electrodes) 232 between the roll rotating electrode (first electrode) 235 and the square tube type fixed electrode group (second electrode) 236, the roll rotating electrode (first electrode) 235 has a first power source. The first high-frequency electric field having the frequency ω ₁ , the electric field intensity V ₁ , and the current I ₁ from the frequency 241, and the frequency ω ₂ from each second power source 242 corresponding to the square tube fixed electrode group (second electrode) 236, respectively. A second high frequency electric field of electric field strength V ₂ and current I ₂ is applied.

  A first filter 243 is installed between the roll rotation electrode (first electrode) 235 and the first power source 241. The first filter 243 easily passes a current from the first power source 241 to the first electrode. In addition, the current from the second power source 242 is grounded so that the current from the second power source 242 to the first power source is difficult to pass.

  In addition, a second filter 244 is installed between the square tube type fixed electrode group (second electrode) 236 and the second power source 242, and the second filter 244 is connected to the second electrode from the second power source 242. It is designed so that the current from the first power source 241 is grounded and the current from the first power source 241 to the second power source is difficult to pass.

The roll rotating electrode 235 may be the second electrode, and the square tube fixed electrode group 236 may be the first electrode. In any case, the first power source is connected to the first electrode, and the second power source is connected to the second electrode. The first power supply preferably applies a higher frequency electric field strength (V ₁ > V ₂ ) than the second power supply. Further, the frequency has the ability to satisfy ω ₁ <ω ₂ .

The current is preferably I ₁ <I ₂ . The current I ₁ of the first high-frequency electric field is preferably 0.3 to 20 mA / cm ² , more preferably 1.0 to 20 mA / cm ² . The current I ₂ of the second high-frequency electric field is preferably 10 to 100 mA / cm ² , more preferably 20 to 100 mA / cm ² .

  The gas G generated by the gas generator 251 of the gas supply means 250 is introduced into the plasma discharge processing container 231 from the air supply port while controlling the flow rate.

  The base material F is unwound from the original winding (not shown) and is transported, or transported from the previous process, and air or the like accompanying the base material is blocked by the nip roll 265 via the guide roll 264. Then, while being wound while being in contact with the roll rotating electrode 235, it is transferred between the square tube fixed electrode group 236, the roll rotating electrode (first electrode) 235 and the square tube fixed electrode group (second electrode) 236, An electric field is applied from both sides to generate discharge plasma between the counter electrodes (discharge space) 232. The base material F forms a thin film with a gas in a plasma state while being wound while being in contact with the roll rotating electrode 235. The substrate F passes through the nip roll 266 and the guide roll 267, and is taken up by a winder (not shown) or transferred to the next step.

  Discharged treated exhaust gas G ′ is discharged from the exhaust port 253.

  In order to heat or cool the roll rotating electrode (first electrode) 235 and the rectangular tube type fixed electrode group (second electrode) 236 during the thin film formation, a medium whose temperature is adjusted by the electrode temperature adjusting means 260 is used as a liquid feed pump. P is sent to both electrodes via the pipe 261, and the temperature is adjusted from the inside of the electrode. Reference numerals 268 and 269 denote partition plates that partition the plasma discharge processing vessel 231 and the outside.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive.

  The sealing member may be disposed so as to cover the display area of the organic EL element, and may be concave or flat. Moreover, transparency and electrical insulation are not particularly limited.

  Specifically, a glass plate, a polymer plate, a film, a metal plate, a film, etc. are mentioned. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Furthermore, the polymer film preferably has an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻³ g / m ² / day or less. Further, it is more preferable that both the water vapor permeability and the oxygen permeability are 10 ⁻⁵ g / m ² / day or less.

  For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used. Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

  In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print it like screen printing.

  In addition, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. it can. In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can. Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster-ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

  In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil is injected in the gas phase and the liquid phase. Is preferred. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.

  Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate, etc.) ), Metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, barium perchlorate, In particular, anhydrous salts are preferably used in sulfates, metal halides and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided outside the sealing film or the sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when the pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.

  Moreover, after producing the said metal with a film thickness of 1-20 nm on a cathode, a transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material quoted by description of the anode on it, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<< Method for producing organic EL element >>
As an example of the method for producing the organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode will be described.

  First, a desired electrode material, for example, a thin film made of a material for an anode is formed on a suitable support substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode. To do. Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, and an electron transport layer, which are organic EL element materials, is formed thereon.

As a method for thinning the organic compound thin film, there are a vapor deposition method and a wet process (spin coating method, casting method, ink jet method, printing method) as described above, but it is easy to obtain a uniform film and a pinhole. From the point of being difficult to form, a vacuum deposition method, a spin coating method, an ink jet method, and a printing method are particularly preferable. Further, a different film forming method may be applied for each layer. When employing a vapor deposition method for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within the range of 50 nm / second, substrate temperature −50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm. After forming these layers, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained. The organic EL element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.

  In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order. When a DC voltage is applied to the multicolor liquid crystal display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

  The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index of about 1.6 to 2.1), and only about 15 to 20% of light generated in the light emitting layer can be extracted. It is generally said. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the side surface of the device.

  As a method for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (for example, US Pat. No. 4,774,435). ), A method of improving the efficiency by giving the substrate a light condensing property (for example, JP-A-63-314795), a method of forming a reflective surface on the side surface of the element (for example, JP-A-1-220394) Gazette), a method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), and a substrate between the substrate and the light emitter. A method of introducing a flat layer having a lower refractive index than that (for example, Japanese Patent Application Laid-Open No. 2001-202827), a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside). Method of forming There is 1-283751 JP), and the like.

  In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.

  In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

  When a low refractive index medium is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower. .

  Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Furthermore, it is preferable that it is 1.35 or less.

  The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate.

  The method of introducing a diffraction grating into an interface that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. This method was generated from the light emitting layer by utilizing the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction. Of the light, light that cannot be emitted due to total reflection between layers, etc. is diffracted by introducing a diffraction grating into any layer or medium (inside a transparent substrate or transparent electrode). Is going to be taken out.

  The introduced diffraction grating desirably has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. The light extraction efficiency does not increase so much.

  However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.

  As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated.

  At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium. The arrangement of the diffraction grating is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

  The organic EL device of the present invention can be processed on the light extraction side of the support substrate, for example, by providing a structure on a microlens array, or by combining with a so-called condensing sheet, in a specific direction, for example, the device light emitting surface. On the other hand, the brightness | luminance in a specific direction can be raised by condensing in a front direction.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a substrate may be formed with a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or the apex angle is rounded and the pitch is changed randomly. Other shapes may be used.

  Moreover, in order to control the light emission angle from a light emitting element, you may use together a light diffusing plate and a film with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. Examples of light sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, and light sources for optical sensors. Although it is not limited to this, it can be effectively used particularly as a backlight of a liquid crystal liquid crystal display device combined with a color filter and a light source for illumination.

  When used as a backlight of a display in combination with a color filter, it is preferably used in combination with the light collecting sheet in order to further increase the luminance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

<< Production of Organic EL Element 1 >>
After patterning a support substrate in which 120 nm of ITO (indium tin oxide) is formed on a glass substrate having a thickness of 30 mm × 30 mm and a thickness of 0.7 mm as an anode, the transparent support substrate with the ITO transparent electrode is made of isopropyl alcohol. Ultrasonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.

  Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

Next, after reducing the pressure to 4 × 10 ⁻⁴ Pa, the current crucible for deposition containing m-MTDATA was heated and heated, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / second to form a 20 nm hole. An injection layer was provided.

  Next, α-NPD was deposited in the same manner to provide a 20 nm hole transport layer.

  Subsequently, each light emitting layer and its intermediate | middle layer were provided in the following procedures.

  The compound (A-1) and the compound (A-2) were co-deposited at a deposition rate of 0.1 nm / second so as to have a film thickness ratio of 97: 3 to form a 13-nm blue fluorescent light-emitting layer. Subsequently, the compound (A-3) was deposited by 2 nm at a deposition rate of 0.1 nm / second.

  Next, Compound (A-3) and Illustrative Compound Ir-1 were co-deposited at a deposition rate of 0.1 nm / second so that the film thickness ratio was 95: 5 to form a 3 nm green phosphorescent light-emitting layer. Subsequently, the compound (A-3) was deposited by 2 nm at a deposition rate of 0.1 nm / second.

  Next, the compound (A-3) and the exemplified compound Ir-14 were co-deposited at a deposition rate of 0.1 nm / second so as to have a film thickness ratio of 92: 8 to form a 10-nm red phosphorescent light-emitting layer. The total thickness of the light emitting layers including the non-light emitting intermediate layer between the light emitting layers was 30 nm.

  Subsequently, the deposition crucible containing BAlq is energized and heated, and 10 nm is deposited on the layer at a deposition rate of 0.1 nm / second to form a hole blocking layer, and then BCP and CsF are mixed at a film thickness ratio of 4 1: Co-deposited with 40 nm at a deposition rate of 0.1 nm / second to provide an electron transport layer.

  Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1 was produced.

<< Production of Organic EL Element 2 >>
After reducing the pressure to 4 × 10 ⁻⁴ Pa on the substrate subjected to the same cleaning treatment as that used in the organic EL element 1, the deposition crucible containing m-MTDATA is energized and heated, It vapor-deposited on the transparent support substrate with the vapor deposition rate of 0.1 nm / sec, and provided the 20 nm hole injection layer.

  Next, α-NPD was deposited in the same manner to provide a 25 nm hole transport layer.

  Next, in the same manner as in the organic EL element 1, a blue fluorescent light emitting layer 10 nm, an intermediate layer 2 nm, a green phosphorescent light emitting layer 2 nm, an intermediate layer 2 nm, and a red phosphorescent light emitting layer 8 nm were formed.

  Next, a hole blocking layer, an electron transport layer, and a cathode were formed in the same manner as in the organic EL element 1, and an organic EL element 2 was produced.

<< Production of Organic EL Element 3 >>
The film thickness of the blue fluorescent light emitting layer is 7 nm, the compound (A-1) and the compound (A-2) are in a film thickness ratio of 95: 5, the intermediate layer is 2 nm, the green phosphorescent light emitting layer is 3 nm, the compound (A-3) and the compound. Ir-1 is organic except that the film thickness ratio is 96: 4, the intermediate layer is 2 nm, the red phosphorescent light emitting layer is 10 nm, and the compound (A-3) and the compound Ir-14 are changed to a film thickness ratio of 94: 6. An organic EL element 3 was produced in the same manner as the EL element 2.

<< Production of Organic EL Element 4 >>
The film thickness of the blue fluorescent light-emitting layer is 5 nm, the intermediate layer is 2 nm, the green phosphorescent light-emitting layer is 7 nm, the compound (A-3) and the compound Ir-1 are 98.5: 1.5 in the film thickness ratio, the intermediate layer is 2 nm, red An organic EL element 4 was produced in the same manner as the organic EL element 3 except that the phosphorescent light emitting layer was changed to 8 nm.

  In addition, in the organic EL elements 2 to 4, the film thickness ratio of each compound was changed in order to adjust the chromaticity approximately equal to that of the organic EL element 1.

<< Evaluation of sealing process and power efficiency of organic EL element, drive voltage >>
The non-light emitting surface of each of the organic EL elements 1 to 4 is covered with a glass case (in addition, the sealing operation with the glass cover is a glove box (purity 99.999 in a nitrogen atmosphere without bringing the organic EL element into contact with the atmosphere). %) In a high-purity nitrogen gas atmosphere)), after making the illumination device as shown in FIGS. 1 and 2, using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) The power efficiency and current-voltage characteristics of each organic EL element were evaluated.

The evaluation results are shown in Table 1. In Table 1, the power efficiency is a relative value with the power efficiency of the organic EL element 1 as 100, and the voltage is used to pass a current equivalent to the drive current necessary for obtaining a luminance of 500 cd / m ² in the organic EL element 1. A necessary voltage is indicated by a change width with respect to the organic EL element 1. The negative change width indicates that an equivalent current value can be obtained at a lower voltage.

  The emission peaks of the emission spectra of the organic EL elements 1 to 4 were in the blue region 450 nm, the green region 510 nm, and the red region 620 nm.

  When comparing the organic EL elements 1 and 2, it can be seen that even if the thickness of the light emitting layer is reduced, the power efficiency is remarkably lowered.

  On the other hand, among the three light emitting layers, the organic EL element 3 having the thickest phosphorescent light emitting layer has a lower voltage than the organic EL element 1 without losing power efficiency.

  Furthermore, among the three light emitting layers, the fluorescent light emitting layer has the smallest film thickness, in other words, the organic EL element 4 having the largest film thickness ratio of the phosphorescent light emitting layer is different from the organic EL elements 1 and 3 in terms of power efficiency. You can see that it has improved.

It is the schematic of an illuminating device. It is sectional drawing of an illuminating device. It is a schematic diagram which shows an example of the laminated constitution of a barrier film, and its density profile. It is the schematic which shows an example of the atmospheric pressure plasma discharge processing apparatus which processes a base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 107 Glass substrate with a transparent electrode 106 Organic EL layer 105 Cathode 102 Glass cover 108 Nitrogen gas 109 Water trapping agent 201 Barrier film 202 Base material 203 Low density layer 204 Medium density layer 205 High density layer 230 Plasma discharge treatment apparatus 231 Plasma discharge treatment vessel 235 Roll rotation electrode 236 Square tube type fixed electrode group 240 Electric field application means 250 Gas supply means 251 Gas generator 253 Exhaust port 260 Electrode temperature adjustment means F Base material P Liquid feed pump 261 Piping 266 Nip roll 267 Guide roll 268, 269 Partition plate

Claims (6)

An emission spectrum of 440 nm to 480 nm (hereinafter referred to as a blue region), 500 nm to 540 nm (hereinafter referred to as a green region), 600 nm to 640 nm (hereinafter referred to as a red region) between an anode and a cathode on the support substrate and between the anode and the cathode. Each region) has an organic compound layer including at least three light-emitting layers having different emission wavelengths, the main light-emitting body included in at least one layer being a phosphorescent light-emitting body, and at least blue An organic electroluminescent element, wherein a main light emitter contained in one of the light emitting layers in the region is a fluorescent light emitter, and a main light emitter contained in the lightest light emitting layer is a phosphorescent light emitter. 2. The organic electroluminescence device according to claim 1, wherein a main light emitter contained in the light emitting layer having the thinnest film thickness is a fluorescent light emitter. 3. The organic electroluminescence device according to claim 1, wherein the total thickness of the light emitting layers is 30 nm or less. The chromaticity in the CIE 1931 color system at a 2 ° viewing angle front luminance of 1000 cd / m ² is X = 0.33 ± 0.07 and Y = 0.33 ± 0.07. The organic electroluminescent element of any one of -3. It has the organic electroluminescent element of any one of Claims 1-4 as a backlight, The liquid crystal display device characterized by the above-mentioned. An illuminating device using the organic electroluminescence element according to any one of claims 1 to 4 as a light source.

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