JPWO2006093176A1 - ORGANIC ELECTROLUMINESCENCE ELEMENT, IMAGE DISPLAY DEVICE AND LIGHTING DEVICE - Google Patents

Abstract

The present invention provides an organic electroluminescent element that can obtain high luminous efficiency at a low driving voltage and has good productivity, and an image display device and an illuminating apparatus having the organic electroluminescent element. This organic electroluminescent element is an organic electroluminescent element having at least an anode, a cathode, and an organic layer including a light emitting unit between the anode and the cathode on a support substrate. The light emitting unit includes two light emitting layers having different light emission peaks. The light emitting layer contains a light emitting dopant and a light emitting host, and the total film thickness of the organic layer between the anode and the light emitting unit is d1, the film thickness of the light emitting unit is d2, and the light emitting unit When the total film thickness of the organic layer between the cathodes is d3, 5 nm ≦ d2 <30 nm and 5 ≦ (d1 + d3) / d2.

Description

  The present invention relates to an organic electroluminescence element, an image display device having the organic electroluminescence element, and an illumination device.

  Since the organic EL element is self-luminous, it has excellent visibility and can be driven at a low voltage of several volts to several tens of volts, so that the weight including the driving circuit can be reduced. Therefore, the organic EL element is expected to be used as a thin film display, illumination, and backlight.

  The organic EL element is also characterized by abundant color variations. Another feature is that various colors can be emitted by mixing colors combining a plurality of colors.

  Among the luminescent colors, the need for white light emission is particularly high, and it can also be used as a backlight for displays. Furthermore, it is possible to divide into blue, green and red pixels using a color filter.

  There are the following two methods for performing such white light emission.

  1. One light emitting layer is doped with a plurality of light emitting compounds.

  2. A plurality of emission colors are combined from a plurality of emission layers.

  For example, when white is achieved by three colors of blue (B), green (G), and red (R), in the case of 1, when vacuum deposition is used as an element manufacturing method, BGR and the light emitting host compound It becomes quaternary vapor deposition and control becomes very difficult. In addition, there is a method in which BGR and a luminescent host compound are applied by dissolving or dispersing them in a solution, but at present, there is a problem that the coating type organic EL is inferior in durability to the vapor deposition type.

  On the other hand, a method of combining two light emitting layers has been proposed. In the case of using a vapor deposition type, it becomes easier compared to 1.

  As such an organic EL element that emits white light, by laminating two layers of a blue light emitting layer that emits short wavelength light and a yellow light emitting layer that emits long wavelength light, white light is emitted as a color mixture of both light emitting layers. What has been obtained has been proposed (see, for example, Patent Document 1).

  However, in the case of stacking two light emitting layers with different colors (different peak wavelengths), the film quality changes in the two light emitting layers as the driving time of the element, that is, the light emitting time and the applied voltage change. However, there is a problem that the emission center moves due to the change in the degree of hole and electron transport, and as a result, the chromaticity is likely to change.

  In particular, when white is obtained as a mixed color of two light-emitting layers, the problem becomes obvious because white is more sensitive to chromaticity changes than other colors.

  In addition, a high-efficiency organic electroluminescence element is obtained by using an ortho metal complex as a light-emitting material, and a method of obtaining white light by stacking three colors of BGR is disclosed (for example, as a method for obtaining white light) (for example, , See Patent Document 2).

  In addition, in organic EL devices that perform mixed color light emission from a plurality of light-emitting layers having different peak wavelengths, light emission with different peak wavelengths can be used as a method for minimizing chromaticity changes accompanying drive time and voltage changes. A light emitting layer in which three or more light emitting layers are alternately stacked is disclosed (for example, see Patent Document 3).

  By the way, a white light emitting element that achieves white color by combining a plurality of light emitting layers has a structure in which a number of light emitting layers are stacked, so that the thickness of the light emitting layer is increased, and the number of interfaces of the layers is increased, thereby increasing the number of carriers. There is a problem that the injection is hindered and the drive voltage becomes high. In particular, when a phosphorescent light emitting material is used, there is a problem that the driving voltage becomes higher than that of the fluorescent light emitting material.

Although the drive voltage can be lowered by making the light emitting layer thinner, the thin film thickness of the entire device makes it easier to be affected by minute dust on the substrate, resulting in unstable device performance and poor productivity. There was a problem of becoming.
JP 2003-347051 A JP 2001-319780 A JP 2004-63349 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an organic electroluminescence element having high luminous efficiency at a low driving voltage and good productivity, and an image display having the organic electroluminescence element It is in providing an apparatus and an illuminating device.

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

1. In an organic electroluminescent element having at least an anode, a cathode, and an organic layer including a light emitting unit between the anode and the cathode on a support substrate, the light emitting unit has two or more light emitting layers having different emission peaks, and the light emission All layers contain a luminescent dopant and a luminescent host,
When the total film thickness of the organic layer between the anode and the light emitting unit is d1, the film thickness of the light emitting unit is d2, and the total film thickness of the organic layer between the light emitting unit and the cathode is d3, each film An organic electroluminescence device characterized in that the relationship between the thicknesses d1, d2, and d3 satisfies both the following formulas (1) and (2).

Formula (1)
5 nm ≦ d2 <30 nm
Formula (2)
5 ≦ (d1 + d3) / d2
2. 2. The organic electroluminescent element according to 1 above, wherein the relationship between the film thicknesses d1, d2, and d3 satisfies the following formula (3).

Formula (3)
d1 + d2 + d3> 150 nm
3. 3. The light emitting unit according to 1 or 2, wherein the light emitting unit is composed of at least two light emitting layers having different light emission peaks, and at least two adjacent light emitting layers of the light emitting unit contain the same light emitting host compound. Organic electroluminescence element.

  4). 3. The organic electroluminescence according to 1 or 2, wherein the light emitting unit is composed of at least two light emitting layers having different emission peaks, and all the light emitting layers of the light emitting unit contain the same light emitting host compound. Luminescence element.

  5. 5. The organic electroluminescent element according to 3 or 4 above, wherein the junction part of two adjacent light emitting layers of the light emitting unit has a mixed region of two kinds of light emitting dopants.

  6). Any one of 3 to 5 above, wherein all the light emitting layers of the light emitting unit each contain two or more kinds of light emitting dopants, and the concentration of the light emitting dopant continuously changes in the light emitting unit. 2. The organic electroluminescence device according to item 1.

  7. 3. The organic electroluminescence device according to 1 or 2 above, wherein an intermediate layer not containing a light emitting dopant is provided between light emitting layers having different light emission peaks of the light emitting unit.

  8). 8. The organic electroluminescence device according to 7, wherein the intermediate layer contains a light emitting host compound, and at least two adjacent layers of the light emitting unit contain the same light emitting host compound.

  9. 8. The organic electroluminescence device as described in 7 above, wherein the intermediate layer contains a light emitting host compound, and all the layers of the light emitting unit contain the same light emitting host compound.

  10. 10. The organic electroluminescence according to any one of 1 to 9, wherein the d1 is a range defined by the following formula (4) and the d3 is a range defined by the following formula (5). element.

Formula (4)
120 nm ≦ d1 ≦ 180 nm
Formula (5)
30 nm ≦ d3 ≦ 80 nm
11. Among the light emitting layers having different light emission peaks, when the film thickness of the light emitting layer having the light emission peak at the shortest wavelength is d4, the d2 and the d4 satisfy the following formula (6): 11. The organic electroluminescence device according to any one of 1 to 10.

Formula (6)
d2 / d4 <2
12 12. The organic electroluminescent element according to any one of 1 to 11, wherein light emitted from the organic electroluminescent element is white.

  13. 13. The organic electroluminescent element according to any one of 1 to 12, wherein a light emitting dopant contained in at least one light emitting layer among the light emitting layers having different emission peaks is a phosphorescent compound.

  14 13. The organic electroluminescence device according to any one of 1 to 12, wherein a light emitting dopant contained in at least two light emitting layers among the light emitting layers having different emission peaks is a phosphorescent compound.

  15. 13. The organic electroluminescence device according to any one of 1 to 12, wherein the light emitting dopant contained in all the light emitting layers having different light emission peaks is a phosphorescent compound.

  16. 16. An image display device using the organic electroluminescence element according to any one of 1 to 15 above.

  17. 16. An illuminating device using the organic electroluminescence element according to any one of 1 to 15 above.

  According to the configuration of the present invention, it is possible to provide an organic electroluminescence element having high light emission efficiency at a low driving voltage and good productivity, and an image display device and an illumination device including the organic electroluminescence element.

It is the figure which showed an example of the basic layer structure of this invention. It is the schematic diagram which showed an example of the vapor deposition apparatus which has a plurality of light emission host compounds and the vapor deposition boat for several light emission dopants. In Example 3, it is a figure which shows the light emission unit which has a mixed region of 2 types of light emission dopants in the junction part of 2 types of adjacent light emission layers, respectively. It is a figure which shows the light emission unit in which all the layers of the light emission unit in Example 4 contain 2 or more types of light emission dopants, respectively, and a content ratio changes continuously. It is the schematic diagram which showed an example of the display apparatus comprised from an organic EL element. It is a schematic diagram of a display part. It is a schematic diagram of a pixel. It is the schematic diagram which showed an example of the passive matrix system full color display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor 21 Shutter 22 Deposition boat 23 Support substrate A Display part B Control part

  The organic electroluminescence element of the present invention (hereinafter also referred to as organic EL element) has at least an anode, a cathode, and an organic layer including a light emitting unit between the anode and the cathode on a support substrate, and the light emitting unit emits light. The light emitting layer has two or more light emitting layers with different peaks, all of the light emitting layers contain a light emitting dopant and a light emitting host, the total film thickness of the organic layer between the anode and the light emitting unit is d1, and the film thickness of the light emitting unit is d2, when the total film thickness of the organic layer between the light emitting unit and the cathode is d3, the film thickness (d2) of the light emitting unit is 5 nm or more and less than 30 nm, preferably 7 to 27 nm, Most preferably, it is the range of 10-25 nm.

  In addition, one of the characteristics is that the film thickness (d1 + d3) of the organic layer excluding the light emitting unit is five times or more the film thickness (d2) of the light emitting unit.

  With this configuration, an organic electroluminescence element having a low driving voltage and high productivity can be realized while being a white light emitting element in which a plurality of light emitting layers are combined. Further, by using a phosphorescent material as the light emitting dopant, higher efficiency can be achieved.

  The layer structure of the organic electroluminescence element (organic EL element) of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The element configuration shown in FIG. 1 includes a light emitting unit between a cathode and an anode, and the light emitting unit is sandwiched between an electron blocking layer and a hole blocking layer.

  In the present invention, the light emitting unit means from the light emitting layer located closest to the cathode side of the organic electroluminescent element to the light emitting layer located closest to the anode side (for example, in FIG. 1, the light emitting layer 1 and the light emitting layer). 2, the light emitting layer 3 becomes a light emitting unit).

  These electron blocking layers or hole blocking layers are not necessarily required, but with such a configuration, excitation generated by confining electron / hole carriers in the light emitting unit and further by recombination of electrons and holes is performed. These layers are preferably provided because the child can be confined in the light emitting unit.

  As materials for forming the electron blocking layer and the hole blocking layer, known materials can be used.

  Since the electron blocking layer confines electrons so that electrons do not leak from the light emitting unit, the material forming the electron blocking layer is preferably smaller in electron affinity than the material forming the light emitting unit.

  In addition, since the hole blocking layer confines holes so that holes do not leak from the light emitting unit, the material forming the hole blocking layer preferably has a higher ionization potential than the material forming the light emitting unit.

  Further, in order to confine triplet excitons generated by recombination of electrons and holes, the material forming the hole blocking layer and the electron blocking layer is more than the excited triplet energy of the phosphorescent compound of the light emitting unit. Larger is preferred.

  Furthermore, it is preferable to provide a hole transport layer and an electron transport layer so as to sandwich them. A known material can be used for the hole transport layer and the electron transport layer, and it is preferable to use a material having high conductivity from the viewpoint of lowering the driving voltage.

  In the present invention, the light emitting unit is composed of at least two light emitting layers having different light emission peaks, and preferably has two or three layers.

  All the light emitting layers of the light emitting unit contain a light emitting host and a light emitting dopant.

  In the present invention, it is preferable that two adjacent light emitting layers of the light emitting unit are composed of the same light emitting host compound, and it is more preferable that all the light emitting layers are composed of the same light emitting host compound. By using the same light emitting host compound in the light emitting layer, the adhesion between the layers is improved, the carrier injection barrier between different layers is relaxed, and the driving voltage can be lowered. The same effect can be obtained when a mixed region is provided between the two light emitting layers, or when the concentration of the light emitting dopant is continuously changed in the light emitting unit.

  In the present invention, a light emitting layer having a different emission peak means that the emission maximum wavelength differs by at least 10 nm or more when the emission peak is measured by PL.

  In PL measurement, a vapor deposition film is formed on a quartz substrate with a composition using a light-emitting dopant and a light-emitting host compound in a light-emitting layer, or a thin film formed by spin coating or dipping is prepared by a wet process such as a polymer. The maximum wavelength of light emission can be determined by measuring the luminescence of the deposited film or thin film produced and measured with a fluorometer.

  In the present invention, the light emitting unit has two or more light emitting layers having different light emission peaks. Between the light emitting layer and the light emitting layer, a non-light emitting intermediate layer (containing a light emitting dopant) is provided. It is also preferable that an intermediate layer is also provided. By providing the intermediate layer, it becomes easier to control the injection of carriers into the light emitting layer, and color shift can be prevented.

  As the material of the intermediate layer, known materials can be used, but the interlayer has the same luminescent host compound as the luminescent host compound contained in the adjacent luminescent layer, thereby improving the adhesion between the layers, and between the different layers. The carrier injection barrier is relaxed. More preferably, all the layers of the light emitting unit (light emitting layer and intermediate layer) contain the same host compound, thereby further improving the adhesion between layers and further reducing the carrier injection barrier between different layers. .

  The color when the organic EL of the present invention is turned on is not particularly limited, but is preferably white.

  For example, when two light emitting layers having different light emission peaks are used, it is preferable to obtain a white color by a combination of light emitting layers that emit blue and yellow, blue and orange, or blue green and red.

  For example, when there are three types of light emitting layers having different light emission peaks and the light emitting layer is composed of three layers, it is preferable to obtain white by combining blue, green, and red light.

  With such a configuration, it can be used for various light sources such as illumination and backlight.

  The emission color is not limited to white.

  By making a single color (for example, blue, green, red) emit light with a plurality of light emitting layers having different emission peaks, it is possible to adjust the color more delicately.

  In the present invention, it is preferable that the layer thickness d1 of the organic layer between the anode and the light emitting layer and the layer thickness d3 of the organic layer between the light emitting layer and the cathode satisfy the following ranges.

  120 nm ≦ d1 ≦ 180 nm and 30 nm ≦ d3 ≦ 80 nm, more preferably 130 nm ≦ d1 ≦ 170 nm and 40 nm ≦ d3 ≦ 70 nm.

  By setting the conditions as defined above, it is possible to optically enhance blue light emission, which has lower light emission efficiency than other colors, and to increase the light emission efficiency of the white element.

  Further, in the present invention, for the same reason as above, when the film thickness of the light emitting layer having the light emission peak at the shortest wavelength among the light emitting layers having different light emission peaks is d4, d2 and d4 satisfy the following formula. It is preferable.

  d2 / d4 <2, more preferably d2 / d4 <1.5.

(Luminescent host compound and luminescent dopant)
The mixing ratio of the light-emitting dopant to the light-emitting host compound, which is the main component in the light-emitting layer, is preferably in the range of 0.1% by mass to less than 30% by mass.

  However, in the present invention, it is preferable to use a phosphorescent compound (phosphorescent dopant) as the light emitting dopant of at least one light emitting layer, and it is more preferable to use a phosphorescent compound as the light emitting dopant of two or more light emitting layers, It is best to use a phosphorescent compound as the light-emitting dopant for all light-emitting layers. The light emitting dopant may be a mixture of a plurality of types of compounds, and may be a phosphorescent dopant having a metal complex or other structure.

  The light-emitting dopant is roughly classified into two types: a fluorescent dopant that emits fluorescence and a phosphorescent dopant that emits phosphorescence.

  Representative examples of fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes. Stilbene dyes, polythiophene dyes, rare earth complex phosphors, and the like.

  A typical example of the phosphorescent dopant is preferably a complex compound containing a metal of Group 8, Group 9, or Group 10 in the periodic table of elements, more preferably an iridium compound or an osmium compound, and most preferably. Is an iridium compound.

  Specific examples of the phosphorescent dopant are compounds described in the following patent publications.

  WO 00/70655 pamphlet, JP 2002-280178, JP 2001-181616, JP 2002-280179, JP 2001-181617, JP 2002-280180, JP 2001-247859, JP 2002-299060, JP 2001-313178, JP 2002-302671, JP 2001-345183, JP 2002-324679, International Publication No. 02/15645 pamphlet, JP 2002-332291 A, JP 2002-50484 A, JP 2002-332292 A, JP 2002-83684 A, JP 2002-540572 A, JP 2002-2002 A. No. 117978, JP 20 JP-A-2-338588, JP-A-2002-170684, JP-A-2002-352960, WO01 / 93642, JP-A-2002-50483, JP-A-2002-1000047, JP-A-2002. No. -173744, JP-A No. 2002-359082, JP-A No. 2002-17584, JP-A No. 2002-363552, JP-A No. 2002-184582, JP-A No. 2003-7469, JP-T-2002-525808. Gazette, JP2003-7471, JP2002-525833, JP2003-31366, JP2002-226495, JP2002-234894, JP2002-2335076 JP 2002-241751 A JP 2001-319779, JP 2001-319780, JP 2002-62824, JP 2002-1000047, JP 2002-203679, JP 2002-343572, JP 2002-203678 gazette etc.

  Some examples are shown below. The present invention is not limited to these.

(Luminescent host compound)
The luminescent host compound used in the present invention is a compound having a phosphorescence quantum yield of phosphorescence of less than 0.01 at room temperature (25 ° C.).

  The light-emitting host compound used in the present invention is not particularly limited in terms of structure, but is typically a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, or a furan derivative. A compound having a basic skeleton such as an oligoarylene compound, or a carboline derivative or a diazacarbazole derivative (herein, a diazacarbazole derivative is at least one carbon atom of a hydrocarbon ring constituting a carboline ring of a carboline derivative) Represents the one substituted with a nitrogen atom).

  Of these, carboline derivatives, diazacarbazole derivatives and the like are preferably used.

  Specific examples of carboline derivatives, diazacarbazole derivatives, carbazole derivatives and the like are given below, but the present invention is not limited thereto.

  The light emitting host compound used in the present invention may be a 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 compound). But you can.

  As the light-emitting host compound, a compound having a hole transporting ability and an electron transporting ability and preventing a long wavelength of light emission and having a high Tg (glass transition temperature) is preferable.

  As specific examples of the luminescent host compound, compounds described in the following documents are suitable. 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, other constituent layers that can be used in the organic EL element of the present invention will be described.

《Hole blocking layer》
The hole blocking layer has the function of an electron transport layer in a broad sense, and is made of a material that has a function of transporting electrons but has a very small ability to transport holes, and blocks holes while transporting electrons. Thus, the probability of recombination of electrons and holes can be improved.

  Examples of the hole blocking layer include, for example, JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and the forefront of industrialization thereof (issued by NTT Corporation on November 30, 1998)” Can be applied as the hole blocking layer according to the present invention. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

《Electron blocking 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 film thickness of the hole blocking layer and the electron blocking 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 includes a 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 is not particularly limited, and is conventionally used as a hole charge injection / transport material in an optical transmission material or a well-known material used for a hole injection layer or a hole transport layer of an EL element. Any one can be selected and used.

  The hole transport material has 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, stilbenes Derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers, and the like can be given.

  As the hole transport material, those described above can be used, and 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-4-3086 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. The hole transport material preferably has a high Tg.

  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, an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, it is about 5 nm-5000 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

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

《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 with a single layer or multiple layers.

  Conventionally, in the case of a single-layer electron transport layer and a plurality of layers, the following materials are used as the electron transport material (also serving as a hole blocking material) used for the electron transport layer adjacent to the cathode side with respect to the light emitting layer. Are known.

  Further, the electron transport layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and as the material thereof, any one of conventionally known compounds can be selected and used. .

  Examples of materials used for this electron transport layer (hereinafter referred to as electron transport materials) include heterocyclic tetracarboxylic acid anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, carbodiimides, Examples include fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. 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 ₃ ), 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 metal of these metal complexes is 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 transport 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. 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, 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, it is about 5-5000 nm. This electron transport layer may have a single layer structure composed of one or more of the above materials.

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

<< 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, between the anode and the light emitting layer or the hole transport layer, and You may exist between a cathode, a light emitting layer, or an electron carrying layer.

  An injection layer is a layer provided between an electrode and an organic layer in order to lower drive voltage or improve light emission luminance. “Organic EL element and its forefront of industrialization (issued on November 30, 1998 by NTS Corporation) 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 or aluminum Metal buffer layer represented by lithium fluoride, alkali metal compound buffer layer represented by lithium fluoride, alkaline earth metal compound buffer layer represented by magnesium fluoride, oxide buffer layer represented by aluminum oxide, etc. It is done.

  The buffer layer (injection layer) is preferably a very thin film, and although it depends on the material, the film thickness is preferably in the range of 0.1 nm to 100 nm.

  This injection layer can be formed by thinning the above material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of an injection | pouring layer, Usually, it is about 5-5000 nm. This injection layer may have a single-layer structure made of one or more of the above materials.

"anode"
As the anode according to the organic EL device of the present invention, an electrode having a work function (4 eV or more) metal, alloy, electrically conductive compound and a mixture thereof as an electrode material 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, a thin film may be formed by depositing these electrode materials 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 (100 μm or more) Degree), a pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. When light emission is extracted from the anode, it is desirable that the transmittance is 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 according to the present invention, a cathode having a work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof 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, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, such as a magnesium / silver mixture, magnesium, from the viewpoint of electron injectability and durability against oxidation, etc. / 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 the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 1000 nm, preferably 50 nm to 200 nm. In order to transmit 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.

<< Substrate (also referred to as substrate, substrate, support, etc.) >>
The substrate of the organic EL device of the present invention is not particularly limited in the type of glass, plastic and the like, and is not particularly limited as long as it is transparent. Examples of the substrate preferably used include glass and quartz. And a light transmissive resin film. A particularly preferable substrate is a resin film that can give flexibility to the organic EL element.

  Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose triacetate. Examples thereof include films made of (TAC), cellulose acetate propionate (CAP) and the like.

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and the film should be a high barrier film having a water vapor transmission rate of 0.01 g / m ² · day · atm or less. preferable.

  The external extraction efficiency at room temperature for light emission of the organic electroluminescence device of the present invention is preferably 1% or more, more preferably 2% 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.

  When used in lighting applications, a film (such as an antiglare film) that has been roughened to reduce unevenness in light emission can be used in combination.

<< Method for producing organic EL element >>
As an example of the method for producing the organic EL device of the present invention, an organic material comprising an anode / hole injection layer / hole transport layer / light emitting layer (two or more layers) / hole blocking layer / electron transport layer / cathode buffer layer / cathode is used. A method for manufacturing an EL element will be described.

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

  As a method for forming a thin film containing this organic compound, there are a spin coat method, a cast method, an ink jet method, a vapor deposition method, a printing method, etc., but a uniform film is easily obtained and pinholes are not easily generated. From the point of view, a vacuum deposition method or a spin coating method is particularly preferable. Further, a different film forming method may be applied for each layer.

When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 ° C. to 450 ° C., a vacuum degree of 10 ⁻⁶ Pa to 10 ⁻² Pa, and a vapor deposition rate of 0 It is desirable to select appropriately within a range of 0.01 nm to 50 nm / second, a substrate temperature of −50 to 300 ° C., and a film thickness of 0.1 nm to 5 μm.

  A vapor deposition apparatus that can be used in the method for forming an organic EL element of the present invention is shown in FIG.

  FIG. 2 is a schematic view of a vapor deposition apparatus having a plurality of vapor deposition boats for a plurality of light emitting host compounds and a plurality of light emission dopants. By controlling the heating temperature of each boat and the opening / closing of the shutter associated with each boat, a light emitting unit having light emitting layers having different light emission peaks can be formed.

  In the vapor deposition apparatus, an intermediate layer boat is provided, and an intermediate layer that does not contain a light emitting dopant is provided between two adjacent light emitting layers of the light emitting unit, thereby preventing color misregistration due to voltage fluctuation, etc. Is preferable.

  In addition, by using the above evaporation apparatus, all of the light emitting layers having different light emission peaks contain a light emitting dopant and a light emitting host compound, and two adjacent light emitting layers can be composed of the same light emitting host compound. All of the light-emitting layers having different peaks can be composed of the same light-emitting host compound, and each of the light-emitting units has a mixed region of two kinds of light-emitting dopants at the junction of two light-emitting layers adjacent to each other. In addition, the entire layer of the light emitting unit can have a configuration for various purposes, such as having an inclined mixed region that contains two or more kinds of light emitting dopants and the content ratio gradually changes. The effect of lowering the drive voltage can be obtained.

  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 nm 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.

<Display device>
The display device of the present invention will be described.

  The image display apparatus using the organic EL element of the present invention may be monochromatic or multicolor. In the case of a multicolor display device, a shadow mask is provided for each color light emitting unit, and three or more light emitting layers are formed for each color by vapor deposition, casting, spin coating, ink jet, printing, or the like.

  When patterning is performed on the light emitting unit, the method is not limited, but a vapor deposition method, an inkjet method, and a printing method are preferable. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.

  In the case of a single color, for example, white, two or more light-emitting layers are formed on one surface without patterning by a vapor deposition method, a cast method, a spin coating method, an ink jet method, a printing method, or the like.

  In addition, it is possible to reverse the production order and produce the cathode, the electron transport layer, the hole blocking layer, the light emitting layer (two or more layers), the hole transport layer, and the anode in this order.

  When a DC voltage is applied to the image 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. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

  In the case of a white display device, it can be used as a display device, a display, or various light sources. In display devices and displays, full-color display is possible by using a white organic EL element as a backlight.

  Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images.

  Light emitting 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, light sources for optical sensors, etc. However, it is not limited to this.

《Lighting device》
The lighting device of the present invention will be described.

  The organic EL element of the present invention may be used as an organic EL element having a resonator structure. The use of the organic EL element having such a resonator structure is as a light source for an optical storage medium, an electrophotographic copying machine, and the like. Light sources, optical communication processor light sources, optical sensor light sources, and the like.

  Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a type for directly viewing a still image or a moving image. It may be used as a display device (display). When used as a display device for reproducing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more organic EL elements of the present invention having different emission colors.

  When the organic EL device of the present invention is used as a white light emitting device, full color display can be performed by combination with a BGR color filter.

  The organic EL element of the present invention can also be applied to an organic EL element that emits substantially white light as a lighting device.

  Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.

  FIG. 5 is a schematic diagram illustrating an example of a display device including organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.

  The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like.

  The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.

  FIG. 6 is a schematic diagram of the display unit A.

  The display unit A includes a wiring unit including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.

  FIG. 6 shows a case where the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

  The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions (details are shown in FIG. Not shown).

  When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.

  When the organic EL device of the present invention is used as a white light emitting device, full color display can be performed by combination with a BGR color filter.

  Next, the light emission process of the pixel will be described.

  FIG. 7 is a schematic diagram of a pixel.

  The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full-color display can be performed by using a white light-emitting organic EL element as the organic EL element 10 divided into a plurality of pixels and combining it with a BGR color filter.

  In FIG. 7, an image data signal is applied from the control unit B to the drain of the switching transistor 11 through the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is supplied to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

  By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.

  When the scanning signal is moved to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, even if the driving of the switching transistor 11 is turned off, the capacitor 13 maintains the potential of the charged image data signal, so that the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.

  That is, the organic EL element 10 emits light by the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 10 of each of the plurality of pixels 3. It is carried out. Such a light emitting method is called an active matrix method.

  Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.

  The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

  In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

  FIG. 8 is a schematic view of a passive matrix display device. A plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a grid pattern so as to face each other with the pixel 3 interposed therebetween.

  When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal. In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.

  In the white organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as necessary during film formation. When patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire element layer may be patterned.

  As described above, the white light-emitting organic EL element of the present invention is used as a kind of lamp such as home lighting, interior lighting, and exposure light source as various light emitting light sources and lighting devices in addition to the display device and display. It is also useful for display devices such as backlights for liquid crystal display devices.

  Others such as backlights for watches, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. There are a wide range of uses such as household appliances.

Example 1
<< Production of organic EL element >>
<Preparation of Organic EL Element 1-1>
A transparent substrate in which this ITO transparent electrode was provided after patterning was performed on a substrate (NH45 manufactured by NH Techno Glass Co., Ltd.) formed by depositing 110 nm of ITO (indium tin oxide) on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode. The supporting substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus. Meanwhile, 200 mg of copper phthalocyanine (CuPc) is put into a molybdenum resistance heating boat, 200 mg of α-NPD is put into another molybdenum resistance heating boat, and 200 mg of m-TDATA is put into another molybdenum resistance heating boat. Put 200 mg of H-14 in a resistance heating boat, put 200 mg of H-15 in another resistance heating boat made of molybdenum, put 100 mg of Ir-12 in another resistance heating boat made of molybdenum, and put it in another resistance heating boat made of molybdenum 100 mg of Ir-15 was placed, 200 mg of H-16 was placed in another molybdenum resistance heating boat, and 200 mg of Alq ₃ was placed in another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus.

Next, after reducing the vacuum chamber to 4 × 10 ⁻⁴ Pa, the heating boat containing CuPc was heated by energization, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / sec to form a 20 nm hole injection layer. Was provided.

  Further, the heating boat containing α-NPD was energized and heated, and deposited on the hole injection layer at a deposition rate of 0.1 nm / sec to provide a 100 nm hole transport layer.

  Furthermore, the heating boat containing m-TDATA was energized and heated, and was deposited on the hole transport layer at a deposition rate of 0.1 nm / sec to provide a 15 nm electron blocking layer.

  Further, the heating boat containing H-14 and Ir-12 is energized and heated, and is co-evaporated on the hole transport layer at a mass ratio and film thickness as shown in Table 1 to produce a yellow light emitting layer 1. Was provided.

  Further, the heating boat containing H-15 and Ir-15 was energized and heated, and co-evaporated on the light emitting layer 1 with the mass ratio and film thickness as shown in Table 1 to form a blue light emitting layer 2. Provided.

  Further, the heating boat containing H-16 was energized and heated, and deposited on the light emitting layer at a deposition rate of 0.1 nm / sec to provide a 10 nm thick hole blocking layer.

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 / sec to provide an electron transport layer having a thickness of 40 nm.

  In addition, the substrate temperature at the time of vapor deposition was room temperature.

  Then, 0.5 nm of lithium fluoride was vapor-deposited as a cathode buffer layer, and also aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-1 was produced.

<Preparation of organic EL element 1-2>
A transparent substrate in which this ITO transparent electrode was provided after patterning was performed on a substrate (NH45 manufactured by NH Techno Glass Co., Ltd.) formed by depositing 110 nm of ITO (indium tin oxide) on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode. The support substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaned for 5 minutes. After poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) dispersion was formed on this transparent support substrate by spin coating at 3000 rpm for 30 seconds. And dried at 200 ° C. for 1 hour to provide an 80 nm hole injection layer. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus. On the other hand, 200 mg of α-NPD is put in a molybdenum resistance heating boat, 200 mg of m-TDATA is put in another resistance heating boat made of molybdenum, 200 mg of H-14 is put in another resistance heating boat made of molybdenum, another resistance made of molybdenum Put 200 mg of H-15 in a heating boat, put 100 mg of Ir-12 in another molybdenum resistance heating boat, put 100 mg of Ir-15 in another molybdenum resistance heating boat, and put H- in another resistance heating boat made of molybdenum. 200 mg of 16 was added, and 200 mg of Alq ₃ was added to another molybdenum resistance heating boat, which was attached to a vacuum deposition apparatus.

Next, the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, and the heating boat containing α-NPD was energized and heated, and deposited on the hole injection layer at a deposition rate of 0.1 nm / sec. The hole transport layer was provided.

  Furthermore, the heating boat containing m-TDATA was energized and heated, and was deposited on the hole transport layer at a deposition rate of 0.1 nm / sec to provide a 15 nm electron blocking layer.

  Further, the heating boat containing H-14 and Ir-12 is energized and heated, and is co-evaporated on the hole transport layer at a mass ratio and film thickness as shown in Table 1 to produce a yellow light emitting layer 1. Was provided.

  Further, the heating boat containing H-15 and Ir-15 was energized and heated, and co-evaporated on the light emitting layer 1 with the mass ratio and film thickness as shown in Table 1 to form a blue light emitting layer 2. Provided.

  Further, the heating boat containing H-16 was energized and heated, and deposited on the light emitting layer 2 at a deposition rate of 0.1 nm / sec to provide a 10 nm thick hole blocking layer.

Furthermore, the heating boat containing Alq ₃ was energized and heated, and deposited on the hole blocking layer at a deposition rate of 0.1 nm / sec to provide an electron transport layer having a thickness of 40 nm.

  In addition, the substrate temperature at the time of vapor deposition was room temperature.

  Then, 0.5 nm of lithium fluoride was vapor-deposited as a cathode buffer layer, and also aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-2 was produced.

<Preparation of organic EL elements 1-3, 1-4, 1-6 to 1-8>
In the production of the organic EL element 1-2, the organic EL elements 1-3, 1-4, and 1-6 to 1-8 were produced in the same manner except that the light emitting layer was changed to the configuration shown in Table 1. .

<Organic EL element 1-5>
In the production of the organic EL element 1-1, an organic EL element 1-5 was produced in the same manner except that the light emitting layer was changed to the configuration shown in Table 1.

<Preparation of Organic EL Elements 1-9 to 1-11: Comparative Example>
In the production of the organic EL element 1-1, the organic EL elements 1-9 to 1-11 were similarly performed except that the hole injection layer, the hole transport layer, and the light emitting layer were changed to the configurations shown in Table 1. Was made.

  In addition, the mass% display in the light emitting layer 1 and the light emitting layer 2 of Table 1 is demonstrated.

  For example, in the organic EL element 1-1 of Table 1, the material of the light emitting layer 1 is described as H-14: Ir-12 (3 mass%, 20 nm), but this is the total mass of the light emitting layer 1. Among them, H-14 represents 97 mass%, Ir-12 represents 3 mass%, and the film thickness of the light emitting layer 1 is 20 nm.

  This display is the same for the other white light-emitting organic electroluminescence elements 1-1 to 1-12.

<Evaluation>
Each obtained element was evaluated by the following method.

(Measurement of external extraction quantum efficiency, power efficiency, dark spot generation rate)
About the produced organic EL element, the external extraction quantum efficiency (%) when a ^2.5 mA / cm ² constant current was applied in a dry nitrogen gas atmosphere at 23 ° C. was measured. For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used. Further, power efficiency (lm (lumen) / W) was measured as an index of lowering drive voltage and power consumption. In addition, the dark spot generation rate (how many dark spots are generated in 10 elements) was also measured as an index of the stability of productivity and element performance, and Table 2 shows the obtained results.

  The measurement results of the external extraction quantum efficiency and power efficiency shown in Table 2 are expressed as relative values when the measured value of the organic EL element 1-12 is 100.

  In addition, the compound used for formation of each layer is shown below.

  It can be seen that the sample of the present invention has high luminous efficiency, no dark spots, stable element performance, and high production efficiency.

Example 2
In the production of the organic EL elements 1-1 to 1-8 described in Example 1, the organic EL element 2 was similarly prepared except that H-16 was provided as an intermediate layer between the respective light emitting layers by a 2 nm deposition method. -1 to 2-8 were produced, and together with the organic EL devices 1-1 to 1-8 produced in Example 1, the following chromaticity deviation was evaluated, and the obtained results are shown in Table 3.

<Evaluation of chromaticity shift>
Deviation of chromaticity in the CIE chromaticity diagram, represents the deviation of the chromaticity coordinates at the time of chromaticity coordinates and 5000 cd / ^{m 2} brightness at 100 cd / ^{m 2} brightness. In addition, it measured using CS-1000 (made by Konica Minolta Sensing) in 23 degreeC and dry nitrogen gas atmosphere.

  As can be seen from the results shown in Table 3, the organic EL elements 2-1 to 2-8 are less susceptible to chromaticity shifts at high voltages than the organic EL elements 1-1 to 1-8. I understand that.

Example 3
In the production of the organic EL element 1-8 described in Example 1, a mixed region of H-16, Ir-13, and Ir-1 between the light emitting layer 1 and the light emitting layer 2 in the light emitting unit as shown in FIG. 1. An organic EL device 3-8 was produced in the same manner except that a mixed region 2 of H-16, Ir-1, and Ir-9 was provided in a thickness of 2 nm between the light emitting layer 2 and the light emitting layer 3, respectively. However, in the mixed region 1, the Ir-13 deposition rate is decreased from the deposition start time and decreased to 0 when reaching the film thickness of 2 nm, so that the Ir-1 deposition rate is increased from the deposition start time to a film thickness of 2 nm. When reaching the value, the mass ratio with H-16 was adjusted to be the same as that of the light emitting layer 2. Similarly, in the mixed region 2, the deposition rate of Ir-9 is decreased from the deposition start time and decreased to 0 when the film thickness reaches 2 nm, so that the Ir-9 deposition rate is increased from the deposition start time to a film thickness of 2 nm. When reaching the value, the mass ratio with H-16 was adjusted to be the same as that of the light emitting layer 3.

<Measurement of power efficiency>
About the produced organic EL element, the power efficiency (lm (lumen) / W) when a ^2.5 mA / cm < ² > constant current was applied in 23 degreeC and dry nitrogen gas atmosphere was measured, and the result obtained was shown in Table 4 Shown in For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used in the same manner.

  In addition, the measurement result of the power efficiency of Table 4 was represented by the relative value when the measured value of the organic EL element 1-8 is set to 100.

  As is clear from the results shown in Table 4, it was confirmed that the drive voltage of the organic EL element 3-8 was lower than that of the organic EL element 1-8.

Example 4
In the production of the organic EL element 1-8 described in Example 1, in the same manner except that the concentration of the luminescent dopant was continuously changed in the light emitting unit in all layers of the light emitting unit as shown in FIG. Organic EL element 4-8 was produced.

  However, the light emitting unit of FIG. 4 was produced as follows.

  H-16, Ir-13, Ir-1 and Ir-9 were simultaneously energized and heated to adjust the deposition rate and start vacuum deposition. Deposition was started so that the mass ratio was H-16: Ir-13: Ir-1: Ir-9 = 96.8: 3: 0.1: 0.1 when the light emitting unit film thickness was 0 nm. When the deposition rate of H-16 was kept constant, the mass ratio reached 94.9: 2: 3: 0.1 when the film thickness reached 18 nm, and the mass ratio reached 91 when the film thickness reached 22 nm. .9: 0.1: 3: 5, Ir-13, Ir-1, Ir- so that the mass ratio becomes 90.8: 0.1: 0.1: 9 when the film thickness reaches 25 nm. The deposition rate of 9 was adjusted.

<Measurement of power efficiency>
About the produced organic EL element, the power efficiency (lm (lumen) / W) when a ^2.5 mA / cm < ² > constant current was applied in 23 degreeC and dry nitrogen gas atmosphere was measured, and the result obtained was shown in Table 5 Shown in For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used in the same manner.

  The power efficiency measurement results shown in Table 5 are expressed as relative values when the measured value of the organic EL element 1-8 is 100.

  As is clear from the results shown in Table 5, it was confirmed that the driving voltage of the organic EL element 4-8 was lower than that of the organic EL element 1-8.

Example 5
In the production of the organic EL elements 1-1 to 1-8 described in Example 1, the hole injection layer and the hole transport layer were changed to m-MTDATA: F4-TCNQ (mass ratio 99: 1) co-deposition film. Organic EL elements 5-1 to 5-8 were prepared in the same manner except that Alq ₃ was changed to a BPhen: Cs (mass ratio 75:25) co-deposited film and LiF was not deposited.

  It was confirmed that the organic EL elements 5-1 to 5-8 all had a driving voltage of 3 to 6 V lower than the organic EL elements 1-1 to 1-8.

Example 6
<Image display device using white organic EL element>
In the production of the organic EL element 1-7 described in Example 1, when the non-light-emitting surface was covered with a glass case and a color filter was attached to the light-emitting surface and used as an image display device, good color display performance was exhibited. It could be used as an excellent image display device.

Example 7
<Production of lighting device using white organic EL element>
In the production of the organic EL element 1-2 described in Example 1, the non-light emitting surface was covered with a glass case to obtain a lighting device. The illumination device could be used as a thin illumination device that emits white light with high luminous efficiency.

Claims (17)

In an organic electroluminescent element having at least an anode, a cathode, and an organic layer including a light emitting unit between the anode and the cathode on a support substrate, the light emitting unit has two or more light emitting layers having different emission peaks, and the light emission All layers contain a luminescent dopant and a luminescent host,
When the total film thickness of the organic layer between the anode and the light emitting unit is d1, the film thickness of the light emitting unit is d2, and the total film thickness of the organic layer between the light emitting unit and the cathode is d3, each film An organic electroluminescence device characterized in that the relationship between the thicknesses d1, d2, and d3 satisfies both the following formulas (1) and (2).
Formula (1)
5 nm ≦ d2 <30 nm
Formula (2)
5 ≦ (d1 + d3) / d2 2. The organic electroluminescent element according to claim 1, wherein the relationship between the film thicknesses d1, d2, and d3 satisfies the following formula (3).
Formula (3)
d1 + d2 + d3> 150 nm   The light emitting unit is composed of at least two light emitting layers having different light emission peaks, and at least two adjacent light emitting layers of the light emitting unit contain the same light emitting host compound. Or the organic electroluminescent element of 2nd term | claim.   The light emitting unit is composed of at least two light emitting layers having different light emission peaks, and all the light emitting layers of the light emitting unit contain the same light emitting host compound. The organic electroluminescent element of the item.   5. The organic electroluminescence device according to claim 3, wherein a junction portion of two adjacent light emitting layers of the light emitting unit has a mixed region of two kinds of light emitting dopants.   All of the light emitting layers of the light emitting unit each contain two or more kinds of light emitting dopants, and the concentration of the light emitting dopant continuously changes in the light emitting unit. 6. The organic electroluminescence device according to any one of items 5.   The organic electroluminescence device according to claim 1 or 2, wherein an intermediate layer not containing a light emitting dopant is provided between light emitting layers having different light emission peaks of the light emitting unit.   The organic electroluminescence device according to claim 7, wherein the intermediate layer contains a light emitting host compound, and at least two adjacent layers of the light emitting unit contain the same light emitting host compound.   The organic electroluminescence device according to claim 7, wherein the intermediate layer contains a light emitting host compound, and all the layers of the light emitting unit contain the same light emitting host compound. The range of any one of claims 1 to 9, wherein the d1 is a range defined by the following formula (4) and the d3 is a range defined by the following formula (5). The organic electroluminescent element of description.
Formula (4)
120 nm ≦ d1 ≦ 180 nm
Formula (5)
30 nm ≦ d3 ≦ 80 nm The light-emitting layer having a light emission peak at the shortest wavelength among the light-emitting layers having different light emission peaks, where d4 and d4 satisfy the following formula (6): The organic electroluminescent element according to any one of the ranges 1 to 10.
Formula (6)
d2 / d4 <2   The organic electroluminescence element according to any one of claims 1 to 11, wherein light emitted from the organic electroluminescence element is white.   The light-emitting dopant contained in at least one light-emitting layer among the light-emitting layers having different emission peaks is a phosphorescent compound. 13. Organic electroluminescence device.   The light-emitting dopant contained in at least two light-emitting layers among the light-emitting layers having different emission peaks is a phosphorescent compound. 13. Organic electroluminescence device.   The organic electroluminescent element according to any one of claims 1 to 12, wherein a light emitting dopant contained in all light emitting layers having different light emission peaks is a phosphorescent compound.   An image display device using the organic electroluminescence element according to any one of claims 1 to 15.   An illuminating device using the organic electroluminescent element according to any one of claims 1 to 15.