JP5051125B2 - ORGANIC ELECTROLUMINESCENT ELEMENT, METHOD FOR STABILIZING ELECTROMAGNETIC ELECTROLUMINESCENT ELEMENT, LIGHTING DEVICE AND ELECTRONIC DISPLAY DEVICE - Google Patents

Description

  The present invention relates to an organic electroluminescence element, a method for stabilizing luminescence chromaticity of an organic electroluminescence element, an illumination device, and an electronic display device.

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

  On the other hand, an organic EL element has a configuration in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and injects electrons and holes into the light emitting layer to recombine excitons. This is an element that emits light by utilizing the emission of light (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several volts to several tens of volts. Therefore, it has a wide viewing angle, high visibility, and since it is a thin-film type completely solid element, it has attracted attention from the viewpoints of space saving and portability.

  As the development of organic EL elements for practical use in the future, there is a demand for organic EL elements that emit light efficiently and with high luminance with lower power consumption. For example, in Japanese Patent No. 3093796, JP-A 63-264692 discloses a technique for doping a stilbene derivative, distyrylarylene derivative or tristyrylarylene derivative with a small amount of phosphor to improve emission luminance and extend the lifetime of the device. And 8-hydroxyquinoline aluminum complex as a host compound, and a device having an organic light emitting layer doped with a small amount of phosphor is disclosed. Japanese Unexamined Patent Publication No. 3-255190 discloses an 8-hydroxyquinoline aluminum complex. As a host compound, an element having an organic light emitting layer doped with a quinacridone dye is known.

  In the technique disclosed in the above-mentioned patent document, when the emission from the excited singlet is used, the generation ratio of the singlet exciton and the triplet exciton is 1: 3, so the generation probability of the luminescent excited species is 25%. Since the light extraction efficiency is about 20%, the limit of the external extraction quantum efficiency (ηext) is set to 5%.

  However, M.M. A. Baldo et al. , Nature, 395, 151-154 (1998), since Princeton University reported on an organic EL device using phosphorescence emission from an excited triplet. A. Baldo et al. , Nature, 403, 17, 750-753 (2000), and US Pat. No. 6,097,147, research on materials that exhibit phosphorescence at room temperature has become active.

  In addition, recently discovered organic EL devices that use phosphorescence can realize a luminous efficiency that is approximately four times that of previous devices that use fluorescence. Research and development of light-emitting element layer configurations and electrodes are performed all over the world. For example, S.M. Lamansky et al. , J .; Am. Chem. Soc. , 123, 4304 (2001), a number of compounds are being studied for synthesis centering on heavy metal complexes such as iridium complexes.

  In addition, the organic EL element is an all-solid element composed of an organic material film having a thickness of only about 0.1 μm between the electrodes, and the light emission can be achieved with a relatively low voltage of about 2V to 20V. Therefore, it is a technology that is expected as a next-generation flat display and illumination.

  However, since the organic EL element is based on a light emission phenomenon utilizing deactivation from an excited state of an organic material to a ground state, an organic EL element has a short wavelength region such as blue or blue-green. In order to emit light, it is necessary to increase the band gap, and thus a high voltage is required to excite the large gap.

  Further, since the excited state itself is located at a high level, the damage upon returning to the ground state is large, and the lifetime tends to be shorter than that of green or red light emission. In particular, phosphorous that uses light emission from the triplet excited state is used. The tendency becomes remarkable in light emission.

  There are various techniques as means for solving the above-mentioned problems. For example, there is a technique of increasing the molecular weight after forming a constituent layer of an organic electroluminescence element. A bifunctional triphenylamine derivative having two is described. After the compound is formed into a film, a three-dimensionally crosslinked polymer is formed by ultraviolet irradiation (see, for example, Patent Document 1). A technique of adding a material having a vinyl group to a plurality of layers is disclosed, and a polymerization reaction is performed by irradiation with ultraviolet rays or heat at the time of forming an organic layer before the cathode is laminated (for example, see Patent Document 2). Film formation by adding AIBN (azoisobutyronitrile), which is a radical generator, to a mixture of comonomer having vinyl group in the same manner as the material having vinyl group at the end of phosphorescent dopant And a production method in which a polymerization reaction is allowed to proceed (for example, see Patent Document 3), a production method in which a Diels-Alder reaction is caused between two molecules in the same layer (for example, see Patent Document 4), and the like. .

All of the above techniques are methods for completing the polymerization reaction at the time of film formation or immediately after film formation (before attaching the cathode), but are still insufficient from the practical viewpoint of improving the durability of the organic EL device. Therefore, there is a demand for further technology for improving the durability of elements.
Japanese Patent Laid-Open No. 5-271166 JP 2001-297882 A Japanese Patent Laid-Open No. 2003-73666 JP 2003-86371 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic electroluminescence element that has less variation in light emission chromaticity and whose robustness is improved by the use of the element, and a display using the element An apparatus and a lighting device are provided.

  The above object of the present invention has been achieved by the following constitution.

1. In an organic electroluminescence device having at least an anode and a cathode on a support substrate, and an organic compound layer including at least one light emitting layer between the anode and the cathode,
At least one layer of the organic compound layer contains a light emitting material A whose emission spectrum shifts to a short wavelength side when energized.

  2. 2. The organic electroluminescence device according to 1, wherein the light-emitting material A contains at least one light-emitting material B having a light emission spectrum having a wavelength shorter than the light emission wavelength of the light-emitting material A at the initial light emission.

  3. 3. The organic electroluminescent element according to 1 or 2 above, wherein the light emitting material A and the material C capable of reacting in the organic compound layer are contained in the same layer as the light emitting material A.

  4). 4. The organic electroluminescence device according to any one of 1 to 3, wherein the light emitting material A is a compound containing any one of the following partial structures in the molecule.

  5). 5. The organic electroluminescence as described in 3 or 4 above, wherein the material C capable of reacting in the organic compound layer is a compound containing any one of the following partial structures in the molecule: element.

  6). 6. The organic electro of any one of 1 to 5 above, wherein the wavelength of the maximum peak existing on the shortest wavelength side of the maximum peak of the emission spectrum after the energization of the luminescent material A is 480 nm or less. Luminescence element.

  7). 7. The organic electroluminescent element according to any one of 1 to 6, wherein the light emitting material A is a phosphorescent dopant.

8). When the organic electroluminescence device according to any one of 1 to 7 is caused to emit light, light emission at a luminance of 10 cd / m ^{2 to} 10,000 cd / m ² is used to suppress a change in chromaticity over time of light emission. A method for stabilizing light emission chromaticity of an organic electroluminescence device, comprising:

  9. 8. An illuminating device comprising the organic electroluminescence element according to any one of 1 to 7 above.

  10. 8. An electronic display device comprising the organic electroluminescence element according to any one of 1 to 7 above.

  According to the present invention, there is provided an organic electroluminescence element in which variation in emission chromaticity is small and fastness is improved by use of the element, a method for stabilizing emission chromaticity of the organic electroluminescence element, a display device and an illumination device using the element I was able to provide.

It is a schematic diagram which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the organic EL element of this invention. It is the schematic of an illuminating device. It is sectional drawing of an illuminating device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Organic EL element 102 Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate with a transparent electrode 108 Nitrogen gas 109 Water catching agent

  In the organic electroluminescence element (also referred to as an organic EL element) of the present invention, variation in emission chromaticity is caused by having the configuration according to any one of claims 1 to 7. There were few organic electroluminescent elements (organic EL elements) whose robustness was improved by use of the elements.

  In addition, the present inventors have succeeded in establishing a light emission chromaticity stabilization method capable of suppressing a change in chromaticity over light emission at a practically sufficient level by causing the organic EL element to emit light under a specific luminance condition. Furthermore, by using the element, a high-luminance display device and lighting device have been successfully obtained.

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

  An organic EL element utilizes a light emission phenomenon when a light emitting material excited by an electric field returns to a ground state, and a high voltage is required in order to emit short-wave light in principle.

  Further, in order to obtain shorter wavelength light emission, a higher excited state is required. Therefore, in principle, it has been found that the shorter the emission wavelength, the shorter the emission lifetime.

  The reason why the present inventors arrived at the present invention is that various problems of the above-mentioned conventionally known organic EL elements are being studied. In the meantime, it was discovered that an element having an emission spectrum that gradually becomes shorter can be realized. Specifically, an organic EL element is actually used (emits light emission at a necessary luminance). Among them, a light-emitting material whose emission wavelength is gradually shortened is found, and the light emission over time is increased by using a combination material that promotes the shortening of the emission spectrum based on the light-emitting material and enhances the robustness of the element. This is a technology that effectively compensates for the decaying emission color.

  When this phenomenon is utilized, for example, in the case of a light emitting device having light emission in the blue and green regions, the blue component usually has a large deterioration with time, and the emission chromaticity gradually becomes green side (xIE in the CIE chromaticity diagram) during use. Value and y value increase direction). For example, a light emitting material whose emission color changes from green to blue during use is included, and an element including a blue light emitting material is relatively Therefore, it is possible to effectively compensate for blue light emission whose luminance decreases quickly (also referred to as light emission color compensation), and to realize an element with little change in light emission color (also referred to as light emission chromaticity change is small).

  Further, when the emission color change is accompanied by a polymerization reaction, the light emitting material on the shorter wavelength side newly generated by energization may be a chain polymer having a high thermal stability or a higher-order network polymer. Since it can be changed, the conventional known organic EL element has a big problem of chromaticity change of light emission over time by continuing energization from the initial use state. In this organic EL element, we have succeeded in realizing an innovative organic EL element based on a completely new concept that has been further enhanced in robustness by continuing to emit light by energization.

<< Luminescent Material A >>
The luminescent material A that is contained in at least one of the constituent layers (organic compound layers) of the organic EL element of the present invention and whose emission spectrum is shifted (moved) to the short wavelength side when the element is energized will be described.

  As the partial structure of the compound used for the light-emitting material A according to the present invention (this partial structure may include a functional site that emits light when the element is energized), the structure of the organic EL element of the present invention to be described later Various known patents that describe compounds used in hole transport layers, hole injection layers, electron injection layers, light emitting layers, hole blocking layers, electron transport layers, electron blocking layers, etc. Partial structures contained in the compounds described in literatures, references, etc. can be used.

  Among them, the light emitting material A according to the present invention is preferably contained in the light emitting layer of the organic EL device of the present invention. In the light emitting layer, a host compound described later or a dopant (also referred to as a light emitting dopant) is used. Or a light emitting material that does not require doping, but is preferably a dopant (a light emitting dopant, where the light emitting dopant includes a phosphorescent dopant and a fluorescent dopant), and particularly preferably phosphorescent. It is a dopant.

  Here, the phosphorescent dopant and the fluorescent dopant will be described in detail in the constituent layers of the organic EL element described later.

  Here, in order to show the function as the light emitting material A related to the organic EL element of the present invention, that is, to have the function of performing the above-described light emission color compensation, the organic EL element of the present invention is made to emit light. It is important to utilize active species (such as active radicals) generated within the device, light (photons generated by light emission), or Joule heat, and the action of the active species, the action of light, or The emission wavelength of the luminescent material A due to chemical change due to Joule heat (the emission wavelength when the luminescent material A is not changed in molecular structure due to the active species, light, Joule heat, etc. immediately after the start of energization) Is preferably shifted to the short wavelength side. For this purpose, it is preferable that a substituent that shortens the emission wavelength of the light emitting material is provided in the molecule of the light emitting material by a reaction or action that occurs in the device.

<< Substituent >>
The range of the reaction here also includes conversion to a reaction that occurs inside the organic EL device (in some cases, a chemical reaction or simply an isomer (structural isomer, rotational isomer, etc.)) by energizing the organic EL device of the present invention. As a substituent that shortens the emission wavelength of the light emitting material by introducing the substituent, a substituent that lengthens the emission wavelength of the light emitting material by introducing the substituent is introduced into the light emitting material, which is generated inside the device. Therefore, it is necessary to design such that the emission wavelength is changed by the action of the active species, etc.

  In order to increase the emission wavelength of the luminescent material A, the conjugate system is expanded to lower the LUMO (lowest orbital orbital) energy level, to increase the HOMO (highest occupied orbital) energy level, or to an electronic effect. It is common to use either lowering the LUMO (lowest orbital) energy level or increasing the HOMO (highest occupied orbit) energy level, or both.

  Furthermore, in order to shorten the emission wavelength compared to the original state, such substituents cause chemical changes due to active species (active radicals, etc.) generated inside the device, light, or Joule heat. It is preferable that the luminescent material has the substituent shown.

  In the organic EL light-emitting layer, all the materials constituting the layer may be a light-emitting material, or a light-emitting dopant and a light-emitting host may coexist. Moreover, multiple types of light emission dopants may exist, and the multicolor light emitting element by which the light emitting layer was laminated | stacked may be sufficient.

  In the case of an element in which the light emitting layer is composed of a light emitting dopant and a light emitting host, the chemical change of the light emitting material may utilize a reaction with the light emitting host. A reaction may occur.

  Therefore, when utilizing a chemical reaction with a luminescent host, it is preferable to introduce into the luminescent host a substituent capable of reacting with the reactive group substituted on the luminescent material (ie, luminescent dopant).

  For example, when a hydroxyl group (—OH) is substituted in the light emitting material, a material having an isocyanate group (—NCO) or an isothiocyanate group (—NCS) introduced is selected as the light emitting host, or When the vinyl group (-=) is substituted, it is necessary to take a method such as selecting a light emitting host into which a radically polymerizable vinyl group (-=) is introduced.

  Usually, in a so-called “phosphorescent device” that utilizes phosphorescent light emission, it is considered effective to mix a phosphorescent dopant with a light emitting host in a mass ratio of about 1% to 20% in terms of light emission efficiency. When phosphorescent light emission is used in the present invention, it is preferable to use a light emitting host together, and the light emitting host material is a substitution capable of chemically reacting with a reactive phosphorescent light emitting material (phosphorescent dopant). It preferably has a group.

  The most preferred form of the present invention is that an anion generated in the light-emitting layer is obtained by allowing at least one material substituted with a vinyl group to both the light-emitting dopant and the light-emitting host to coexist in the same layer and energizing the light-emitting element. A radical or cation radical is used as a polymerization initiator to form a chain or network polymer.

  As a result, the light-emitting element is more robust than the initial state, and an ideal light-emitting element that gradually increases in durability as it is used can be realized.

  Hereinafter, although the specific example of the luminescent material A which concerns on this invention is shown, this invention is not limited to these.

  Among the above compounds, P-1 to P-48 are compounds used as phosphorescent dopants, and F-1 and F-2 are compounds used as fluorescent dopants.

<< Luminescent Material B >>
The luminescent material B according to the present invention will be described.

  The light-emitting material B according to the present invention is a material (compound) that exhibits an emission spectrum having a wavelength shorter than the light emission wavelength of the light-emitting material A in the initial stage of light emission. Specifically, the light-emitting material B is included in an organic EL element. A preferable example is one obtained by removing the reactive substituent from A.

  In addition, the light emitting material A according to the present invention may be simply a compound (also referred to as a material) having a light emission wavelength shorter than the light emission wavelength of the light emitting material A at the initial light emission.

  That is, it is preferable that the light emission wavelength region of the light emitting material B is close to the light emission wavelength region that is newly developed when the light emitting material A is chemically structurally modified by energization.

  The layer in which B is present may be the same layer as A or a different layer.

  B need not be one type, and any number of types B may coexist.

  In addition to A and B, there may be a light emitting material, and the light emitting material may be substituted with a reactive substituent such as A.

  Here, the chemical structural modification means that when the luminescent material A undergoes a chemical reaction when the element is energized (for example, the luminescent material A having the above-described substituent generates an active radical species by energization). Then, by starting self-polymerization or copolymerization reaction, a polymer is formed, and the compound A having a substituent capable of condensing with the reactive group of compound A and the compound A are condensed by the generated Joule heat. A new compound is produced, and the case where the film physical properties starting from isomerization to a structural isomer or the like changes) is also an example.

  Furthermore, in this invention, conventionally well-known phosphorescence dopant, a fluorescent dopant, etc. which are used for a light emitting layer in the structure layer of an organic EL element mentioned later can also be used as the light emitting material B which concerns on this invention.

<< Material C capable of reacting in organic compound layer >>
The light emitting material A and the material C capable of reacting in the organic compound layer will be described.

  The material capable of reacting in the organic compound layer according to the present invention preferably has the above substituent as described in claim 5 of the present application. It is a material that can be copolymerized or polycondensed with the active species of the luminescent material A to be generated by energization.

  Hereinafter, although the specific example of the material C which concerns on this invention is given, this invention is not limited to these.

  Note that specific examples of the material C are all compounds having a function as a light-emitting host compound. Of course, C is preferably present in the same layer as the light-emitting material A, but may be present in any layer other than the light-emitting layer, such as an electron transport layer, a hole transport layer, and an intermediate layer.

<Method for stabilizing emission chromaticity>
The organic EL device of the present invention contains a light emitting material whose emission wavelength is gradually shortened during use (light emission at a necessary luminance), and the emission spectrum based on the light emitting material is shortened. This completes a technique for effectively compensating for the emission color that decays over time.

  As an energization method for changing the light emission of the organic EL element of the present invention to a shorter wave emission spectrum (also referred to as light emission having a shorter emission wavelength or emission peak shorter) by continuing energization, A so-called DC drive in which a current is continuously passed, a so-called pulse drive in which a current is intermittently passed, or an alternating current drive may be used, and the current density at that time is not particularly limited.

However, the emission spectrum gradually changes during use (at least one emission spectrum shape of the light emitting material in the light emitting element changes), and from the viewpoint of substantially compensating the emission color, near the actual luminance to be used. It is preferable to emit light at a suitable level and generate appropriate active species, photons, or heat inside the device. Specifically, the current density is 0.01 mA / cm ^{2 to} 1000 mA / cm ^2. Is preferred.

<< Constituent layers of organic EL elements >>
The constituent layers of the organic EL element of the present invention will be described. In this invention, although the preferable specific example of the layer structure of an organic EL element is shown below, this invention is not limited to these.

(I) Anode / light emitting layer / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) Anode / anode buffer layer / hole transport layer / light emitting layer / hole Blocking layer / electron transport layer / cathode buffer layer / cathode In the organic EL device of the present invention, the blue light emitting layer preferably has a light emission maximum wavelength of 430 nm to 480 nm, and the green light emitting layer has a light emission maximum wavelength of 510 nm to 550 nm, The red light emitting layer is preferably a monochromatic light emitting layer having a light emission maximum wavelength in the range of 600 nm to 640 nm, and is preferably a display device using these. Alternatively, a white light emitting layer may be formed by laminating at least three light emitting layers. Further, a non-light emitting intermediate layer may be provided between the light emitting layers. The organic EL element of the present invention is preferably a white light emitting layer, and is preferably a lighting device using these.

  Each layer which comprises the organic EL element of this invention is demonstrated.

<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 total film thickness of the light emitting layer is not particularly limited, but from the viewpoint of improving the uniformity of the film, preventing unnecessary application of high voltage during light emission, and improving the stability of the emission color with respect to the drive current. It is preferable to adjust in the range of 2 nm to 5 μm, more preferably in the range of 2 nm to 200 nm, and particularly preferably in the range of 10 nm to 100 nm.

  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.

  The light emitting layer of the organic EL device of the present invention preferably contains a light emitting host compound and at least one kind of light emitting dopant (such as a phosphorescent dopant (also referred to as a phosphorescent dopant) or a fluorescent dopant).

(Host compound (also called luminescent host))
The host compound used in the present invention will be described.

  Here, the host compound in the present invention is a phosphorescent quantum yield of phosphorescence emission at a room temperature (25 ° C.) having a mass ratio of 20% or more in the compound contained in the light emitting layer. Is defined as a compound of less than 0.1. The phosphorescence quantum yield is preferably 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 (deposition polymerization property). A light emitting host), or one or more compounds such as the material C may be used.

  As a known host compound that may be used in combination, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable.

  Specific examples of known host compounds include compounds described in the following documents.

  JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

(Luminescent dopant)
The light emitting dopant according to the present invention will be described.

  As the light-emitting dopant according to the present invention, a fluorescent dopant (also referred to as a fluorescent compound) or a phosphorescent dopant (also referred to as a phosphorescent emitter, a phosphorescent compound, a phosphorescent compound, or the like) can be used. From the viewpoint of obtaining an organic EL device with high luminous efficiency, the light emitting dopant used in the light emitting layer or the light emitting unit of the organic EL device of the present invention (sometimes simply referred to as a light emitting material) contains the above host compound. At the same time, it is preferable to contain a phosphorescent dopant.

(Phosphorescent dopant)
The phosphorescent dopant according to the present invention will be described.

  The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent dopant is a compound that emits phosphorescence at room temperature (25 ° C.) and has a phosphorescence quantum yield of 25. Although it is defined as a compound of 0.01 or more at ° C., a preferable phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

  There are two types of light emission of phosphorescent dopants 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 dopant. The energy transfer type that obtains light emission from the phosphorescent dopant, and the other is that the phosphorescent dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. Although it is a trap type, in any case, the excited state energy of the phosphorescent dopant is required to be lower than the excited state energy of the host compound.

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

  The phosphorescent dopant 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.

  Although the specific example of the compound used as a phosphorescence dopant below is shown, this invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like. In addition, the preferable aspect of said luminescent material A is a case where it is used as a phosphorescence dopant.

(Fluorescent dopant (also called fluorescent compound))
Fluorescent dopants (fluorescent compounds) include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes Examples thereof include dyes, stilbene dyes, polythiophene dyes, and rare earth complex phosphors.

  Next, an injection layer, a blocking layer, an electron transport layer and the like used as the constituent layers of the organic EL element of the present invention will be described.

<< 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>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. 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.

  The hole blocking layer preferably contains the azacarbazole derivative mentioned as the host compound.

  In the present invention, when a plurality of light emitting layers having different light emission colors are provided, the light emitting layer having the shortest wavelength of light emission is preferably closest to the anode among all the light emitting layers. In this case, it is preferable to additionally provide a hole blocking layer between the shortest wave layer and the light emitting layer next to the anode next to the anode. Furthermore, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer provided at the position has an ionization potential of 0.3 eV or more larger than the host compound of the shortest wave emitting layer.

  The ionization potential is defined by the energy required to emit an electron at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be obtained by the following method, for example.

  (1) Using Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA The ionization potential can be obtained as a value obtained by rounding off the second decimal place of the value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. This calculation value is effective because the correlation between the calculation value obtained by this method and the experimental value is high.

  (2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a method known as ultraviolet photoelectron spectroscopy can be suitably used by using a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd.

  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 film thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 nm to 100 nm, and more preferably 5 nm 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 also two of those described in US Pat. No. 5,061,569. Having a condensed aromatic ring in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-3086 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 8 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 as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used 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 nm-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. Pat. 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.

  Also, 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), etc., and the central metals of these metal complexes are In, Mg, Cu , Ca, Sn, Ga, or Pb can also be used as an 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 an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting 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 nm-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.

"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 substances 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 pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. 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 nm to 1000 nm, preferably 10 nm 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, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. 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 a 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 nm 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 light emission luminance is improved, which is convenient.

  Moreover, after producing the said metal by the film thickness of 1 nm-20 nm to a cathode, the 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.

《Support substrate》
As a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. May be opaque. 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.

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± 2)% RH) is preferably 0.01 g / (m ² · 24 h) or less, and further, oxygen measured by a method according to JIS K 7126-1987. A high barrier film having a permeability of 10 ⁻³ ml / (m ² · 24 h · MPa) or less and a water vapor permeability of 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

  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.

  The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight 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 such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.

  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.

  In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

<Sealing>
As a sealing means used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example.

  As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient. Further, transparency and electrical insulation are not particularly limited.

  Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. 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 has a oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ ml / (m ² · 24 h · MPa) or less, and a method according to JIS K 7129-1992. It is preferable that the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured in (1) is 1 × 10 ⁻³ g / (m ² · 24 h) 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 like screen printing.

  In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . 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 can be injected in the gas phase and liquid phase. preferable. A vacuum is also possible. 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) and 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 perchloric acid) Barium, magnesium perchlorate, and the like), and 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 on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film. In particular, when the 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, and the like used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. 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 extracted outside the device, This is because the 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 element side surface.

  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 (US Pat. No. 4,774,435), A method of improving efficiency by providing a light collecting property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an element (Japanese Patent Laid-Open No. 1-220394), and light emission from a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the bodies (Japanese Patent Laid-Open No. 62-172691), a flat having a lower refractive index between the substrate and the light emitter than the substrate A method of introducing a layer (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer and a light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951) Gazette).

  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 medium having a low refractive index 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. Further, it is preferably 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 or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency. This method uses 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. Light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating in any layer or medium (in a transparent substrate or transparent electrode), and the light is removed. I want to take it 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. Therefore, 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 in 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.

<Condenser sheet>
The organic EL device of the present invention is processed on the light extraction side of the substrate so as to provide, for example, a microlens array structure, or combined with a so-called condensing sheet, for example, with respect to a specific direction, for example, the device light emitting surface. By condensing in the front direction, the luminance in a specific direction can be increased.

  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 μm 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, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex 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.

<< 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 / electron transport layer / electron injection layer / cathode will be described.

  First, a desired electrode material, for example, a thin film made of an anode material is formed on a suitable substrate so as to have a film thickness of 1 μm or less, preferably 10 nm to 200 nm, to form an anode.

  Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are organic EL element materials, is formed thereon.

  As a method for forming each of these layers, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, printing method) and the like as described above, but it is easy to obtain a homogeneous film and it is difficult to generate pinholes. In view of the above, film formation by a coating method such as a spin coating method, an ink jet method, or a printing method is preferable in the present invention.

  Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used. Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

  After these layers are formed, a thin film made of a cathode material is formed thereon by 1 μm or less, preferably by a method such as vapor deposition or sputtering so that the film thickness is in the range of 50 nm to 200 nm. By providing, a desired organic EL element can be obtained.

  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 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.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.

  In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

  The light emission color of the organic EL device of the present invention and the compound according to the present invention 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 the total CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

Further, when the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 Cd / m ² is X when the 2-degree viewing angle front luminance is measured by the above method. = 0.33 ± 0.07 and Y = 0.33 ± 0.1.

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

  The structures of the compounds used in the following examples are shown below.

Example 1
<< Preparation of organic EL element OLED-1 >>
Transparent support provided with this ITO transparent electrode after patterning on a substrate (NH45 manufactured by NH Techno Glass) made of ITO (indium tin oxide) with a thickness of 150 nm on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 200 mg of α-NPD is put in a molybdenum resistance heating boat, and 300 mg of F-1 as a fluorescent dopant is put in another molybdenum resistance heating boat. 200 mg of Alq ₃ was placed in a molybdenum resistance heating boat and attached to a vacuum deposition apparatus.

Next, after the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, the heating boat containing α-NPD was energized and heated, and deposited on the transparent support substrate at a deposition rate of 0.1 nm / sec. The hole transport layer was provided. Furthermore, the heating boat containing F-1 was energized and heated, and deposited on the hole transport layer at a deposition rate of 0.2 nm / second to provide a light emitting layer having a thickness of 30 nm. In addition, the substrate temperature at the time of vapor deposition was room temperature.

Further, the heating boat containing Alq ₃ was energized and heated, and deposited on the light emitting layer at a deposition rate of 0.1 nm / second to further provide an electron transport layer having a thickness of 30 nm. In addition, the substrate temperature at the time of vapor deposition was room temperature. Then, 0.5 nm of lithium fluoride and 100 nm of aluminum were vapor-deposited, the cathode was formed, and the organic EL element OLED-1 which has a structure layer of FIG. 1 was produced.

  A lighting device as shown in FIGS. 7 and 8 was formed and evaluated.

  FIG. 7 shows a schematic diagram of the lighting device, and the organic EL element 101 is covered with a stainless steel sealing can 102 (in addition, the sealing operation with the stainless steel sealing can is performed by placing the organic EL element 101 in the atmosphere. (This was carried out in a glove box under a nitrogen atmosphere without contact with (in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more) and bonded using a stainless steel sealing can 102 and an ultraviolet curable adhesive.) . FIG. 8 is a cross-sectional view of the lighting device. In FIG. 6, reference numeral 105 denotes a cathode, 106 denotes an organic EL layer, and 107 denotes a glass substrate with a transparent electrode. The stainless steel sealing can 102 is filled with nitrogen gas 108 and provided with a water catching agent 109 (using barium oxide as a dehydrating agent).

The organic EL element OLED-1 thus produced was evaluated for light emission characteristics according to a conventional method. When a direct current was applied to OLED-1, light emission started from about 4 V and the emission color was blue-green. Next, the voltage was adjusted to 2000 cd / m ^2, and the device was driven at a constant current while maintaining the current density at that time, and after about 250 hours, the emission color changed to blue. This is because the vinyl group of the light emitting material F-1 is radically polymerized by energization to form the F-1 network polymer, and the conjugation of the vinyl group is lost and the emission color is changed from blue-green to blue. Conceivable.

Example 2
<< Preparation of organic EL element OLED-2 >>
In the production of the organic EL element OLED-1 of Example 1, an organic EL element OLED-2 was produced in the same manner except that vapor deposition was performed by a conventional method so as to obtain the element configuration shown in FIG.

  When a direct current voltage was applied to the obtained organic EL element OLED-2, light emission started at about 4 V, and the emission color at that time was yellow.

When the voltage was adjusted to 2000 cd / m ² and the device was driven at a constant current while maintaining the current density, the emission color gradually changed to yellow-green in about 100 hours, and further about 200 hours. Later, the emission color changed to green. There was almost no color change after that.

In addition, in the element (OLED-2-2) in which the light emission host is changed from H-1 to m-CP, the light emission color at the start of light emission was similarly yellow, but the light was emitted for 300 hours at an initial luminance of 2000 cd / m ^2. After that, the emission color was yellowish green and then gradually approached green, but did not become completely green like the element using H-1 (OLED-2).

  This suggests that, even in a light-emitting device containing a phosphorescent dopant, the polymerization reaction proceeds during energization, but it is suggested that the reaction proceeds slowly when the density of reactive groups is low, and at the same time, the light-emitting dopant P-5. It is also suggested that copolymerization occurred between the luminescent host H-1 and the luminescent host H-1.

Example 3
<< Preparation of organic EL element OLED-3 >>
In the production of the organic EL element OLED-1 of Example 1, the organic EL element OLED-3 was produced in the same manner except that the element configuration was formed by vapor deposition so as to have the element configuration shown in FIG. did.

  When a direct current voltage was applied to the obtained organic EL element OLED-3, light emission started at about 4 V, and the light emission color at that time was orange.

When the voltage of the device was adjusted to 2000 cd / m ² and the device was driven at a constant current while maintaining the current density at that time, the emission color changed to yellow in about 100 hours. Further, after about 100 hours, the emission color became green. Further, after 100 hours, the color turned blue-green, and gradually became closer to blue.

  This suggests that the three vinyl groups of P-3, which is a trifunctional dopant, were polymerized with energization, the vinyl group concentration was gradually decreased, and finally polymerized almost. Therefore, it was found that a network polymer was formed by including a polyfunctional compound.

Example 4
<< Preparation of organic EL element OLED-4 >>
In the production of the organic EL element OLED-1 of Example 1, the organic EL element OLED-4 was produced in the same manner except that the element structure was vapor-deposited by a conventional method so as to have the element structure shown in FIG. did.

  In the constituent layers, the second layer is a red / green light emitting layer, the third layer is an intermediate layer, the fourth layer is an emission color compensation layer for changing the emission color from green to blue by energization, the fifth layer is an intermediate layer, The sixth layer is a blue light emitting layer.

When a DC voltage was applied to the obtained organic EL element OLED-4, light emission started at about 5 V, and the emission color at that time was white. Further, when the voltage was adjusted to 5000 cd / m ² and driving at constant current while maintaining the current density at that time, the emission color hardly changed even after about 300 hours (CIE chromaticity coordinates). Then, immediately after light emission (x = 0.38, y = 0.41), after 300 hours (x = 0.39, y = 0.43), there was no significant change).

In the organic EL element OLED-4-2 having no emission color compensation layer (fourth layer) and an intermediate layer (fifth layer) formed as a comparative element, the initial luminance is the same as that of the organic EL element OLED-4. When driven at a constant current of 5000 cd / m ² , the emission color already changed to yellowish after about 100 hours.

  The CIE chromaticity coordinates immediately after light emission were (x = 0.37, y = 0.38), but after 100 hours of light emission, it changed greatly (x = 0.44, y = 0.51). .

  From the above results, it was found that the organic EL element OLED-4 provided with the emission color compensation layer was a good element with very little change in emission color over time with emission.

  Further, as a comparison, an organic EL element OLED-4-3 in which the reactive light-emitting host H-1 of the organic EL element OLED-4 is replaced with m-Cp is produced, and the light emission lifetime is reduced to the organic EL element OLED-. 4-2, compared with organic EL element OLED-4.

An initial luminance 5000 cd / m ² 300 hours, the light emission luminance after being constant current drive, the organic EL element OLED-4 is 3180cd / m ^2, the organic EL element OLED-4-2 is 1720cd / m ^2, OLED-4 -3 was 2110 cd / m ² .

  From this, the polymer that emits blue light, which is considered to be generated during the energization in the emission color compensation layer of the organic EL element OLED-4, is more robust and has a longer lifetime than the low molecular dopant that originally existed. Was suggested.

  In addition, in the organic EL element OLED-4-3 using m-Cp having the same dopant structure and having no reactive group in the light emitting host, the remarkable light emission lifetime improving effect as in OLED-4 is not recognized. From these results, it was suggested that it is effective to form a copolymer by coexisting a luminescent host capable of reacting with a reactive dopant in order to improve the luminescence lifetime.

Example 5
<< Preparation of organic EL element OLED-5 >>
In the production of the organic EL element OLED-1 of Example 1, an organic EL element OLED-5 was produced in the same manner except that vapor deposition was performed by a conventional method so as to obtain the element configuration shown in FIG.

  In the constituent layers, the second layer is a red light emitting layer, the third layer is an intermediate layer, the fourth layer is a light emitting color compensation layer for changing the light emitting color from orange to green to blue by energization, the fifth layer is an intermediate layer, The sixth layer is a blue light emitting layer.

  When a direct current voltage was applied to the obtained organic EL element OLED-5, light emission started at about 5 V, and the emission color at that time was white. In addition, P-3 which confirmed that the luminescent color changed from orange to blue by electricity supply in the organic EL element OLED-3 of Example 3 was used for the organic EL element OLED-5 in the luminescent color compensation layer. Further, bifunctional H-2 was used as the light emitting host.

Further, when the voltage was adjusted to 5000 cd / m ² and driving at constant current while maintaining the current density at that time, the emission color hardly changed even after about 300 hours (CIE chromaticity coordinates). Then, immediately after light emission (x = 0.37, y = 0.39) and after 300 hours (x = 0.38, y = 0.42), there was no significant change).

The light emission life was further better than that of the organic EL element OLED-4 of Example 4, and the light emission luminance after being driven at a constant initial brightness of 5000 cd / m ² for 300 hours was 3450 cd / m ² .

Example 6
<< Preparation of organic EL element OLED-6 >>
A glass substrate ITO was coated with PEDOT / PSS to a thickness of 40 nm with a spin coater, dried at 200 ° C. for 1 hour in the atmosphere, and then adjusted to have the component ratio of the second layer in FIG. -2 (occupying 84.7% by mass of the second layer) as a main component and containing three kinds of dopants (P-9, P-10, P-11), the total solid content concentration is 0.2 mass. % Dichloroethane solution was coated with a spin coater to a thickness of 50 nm. The obtained second layer has a function of light emitting layer / light emitting color compensation.

  This was put in a vacuum vapor deposition machine, and after drying the substrate at about 80 ° C. for 1 hour under vacuum, the third layer BAlq (30 nm), the fourth layer LiF (0.5 nm), and finally Al (100 nm) were added. Vapor deposition was performed, and sealing treatment similar to that of the organic EL element OLED-1 of Example 1 was performed to prepare an organic EL element OLED-6.

The organic EL element OLED-6 thus obtained was yellowish white and emitted light for 300 hours under constant current drive with an initial luminance of 2000 cd / m ² , but the emission color did not change.

(In CIE chromaticity coordinates, there was no significant change immediately after light emission (x = 0.37, y = 0.45) and after 300 hours (x = 0.38, y = 0.46)).
The organic EL element OLED-4 obtained in Example 4 and the organic EL element OLED-5 obtained in Example 5 in which the emission chromaticity compensation layer is formed by the vapor deposition method even if the light emission chromaticity compensation layer is formed. Similarly, it was confirmed that the reaction proceeded with energization, and that an emission color compensation effect was obtained.

  In addition, the light emitting host of the light emitting layer and light emitting color compensation layer of the organic EL element OLED-6 was changed from H-2 to H-6, and the light emitting dopant (dopant whose emission color changes) was changed from P-9 to P-7. A similar light emission color compensation effect was confirmed for the element (OLED-6-2).

  Furthermore, the effect (emission color compensation effect) was confirmed both in the combination of the luminescent host: H-7 and the luminescent dopant: P-6 and in the combination of the luminescent host: H-4 and the luminescent dopant: P-3.

Claims (10)

In an organic electroluminescence device having at least an anode and a cathode on a support substrate, and an organic compound layer including at least one light emitting layer between the anode and the cathode,
At least one layer of the organic compound layer contains a light emitting material A whose emission spectrum shifts to a short wavelength side when energized. 2. The organic material according to claim 1, comprising at least one kind of the light emitting material A and a light emitting material B exhibiting an emission spectrum having a wavelength shorter than the light emission wavelength of the light emitting material A at an early stage of light emission. Electroluminescence element. The light-emitting material A and the material C capable of reacting in the organic compound layer are contained in the same layer as the light-emitting material A, or claim 2 or claim 2 The organic electroluminescent element of description. The luminescent material A is a compound containing any one of the following partial structures in the molecule, wherein the luminescent material A is any one of claims 1 to 3. The organic electroluminescent element of description.
The material C capable of reacting in the organic compound layer is a compound containing any one of the following partial structures represented in the molecule: Claim 3 or Claims 5. The organic electroluminescence device according to item 4.
The wavelength of the maximum peak existing on the shortest wavelength side of the maximum peak of the emission spectrum after the energization of the luminescent material A is 480 nm or less, wherein the wavelength range is 480 nm or less. The organic electroluminescent element of any one of Claims. The organic light-emitting device according to any one of claims 1 to 6, wherein the luminescent material A is a phosphorescent dopant. When the organic electroluminescent device according to any one of claims 1 to 7 is caused to emit light, light is emitted at a luminance of 10 cd / m ^{2 to} 10,000 cd / m ^2. A method for stabilizing light emission chromaticity of an organic electroluminescence element, characterized by suppressing a change in chromaticity over time. An illuminating device comprising the organic electroluminescent element according to any one of claims 1 to 7. An electronic display device comprising the organic electroluminescence element according to any one of claims 1 to 7.