JP4513060B2 - Organic EL device - Google Patents

Description

  The present invention is a multicolor organic EL that can be used for an organic electroluminescence (hereinafter referred to as organic EL) display having a high definition and excellent visibility and having a wide range of applicability such as display of a portable terminal or an industrial measuring instrument. It relates to the structure of the element.

  As an example of a light-emitting element applied to a display device, an organic EL element having a thin film laminated structure of an organic compound is known. Organic EL elements are thin-film self-luminous elements and have excellent characteristics such as low drive voltage, high resolution, and high viewing angle. Therefore, various studies have been made for their practical application.

The organic EL element has a structure including at least an organic light emitting layer between an anode and a cathode. The organic light emitting layer is a portion that emits light by recombination of holes and electrons generated by applying a voltage to the anode and the cathode. The organic EL element has a structure in which a hole injection layer, a hole transport layer, an electron transport layer and / or an electron injection layer are interposed as required. More specifically, for example, the following structures are exemplified.
(1) Organic light emitting layer (2) Hole injection layer / organic light emitting layer (3) Organic light emitting layer / electron transport layer (4) Hole injection layer / organic light emitting layer / electron transport layer (5) Hole injection layer / Hole transport layer / organic light emitting layer / electron transport layer (6) Hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer

  In the organic EL device having the above-described structures (1) to (6), an anode is connected to the organic light emitting layer or the hole injection layer, and a cathode is connected to the organic light emitting layer, the electron transport layer or the electron injection layer. The An example of the structure of a conventional organic EL element is shown in FIG.

  In an organic EL element, it is known that the emission color can be blue, green, or red depending on the type of dye added to the organic light emitting layer. As one means for realizing a full color display using an organic EL element, it has been studied to arrange three primary color EL elements as sub-pixels (sub-pixels) as pixels (pixels). However, since the light emitting characteristics of the EL elements of the respective colors are different from each other, the formation of the subpixels and the driving method thereof are complicated, which causes a cost increase. Therefore, an attempt has been made to cause the organic EL element to emit white light and to obtain three primary colors from the white light using a color filter. Therefore, it is desired to realize an organic EL element that emits multicolor light that can be used in such a color filter system.

  In the present specification, the “multicolor light-emitting organic EL element” means an organic EL element that simultaneously emits light of two or more different wavelength ranges. In the multicolor light emitting organic EL element, it is possible to realize a white light emitting organic EL element that emits white light by emitting three primary colors or emitting two colors having complementary colors. For this reason, intensive research is being conducted on the type and concentration of the light emitting layer material and the dye added to the light emitting layer. On the other hand, a technique for stacking two or three organic EL units that emit light of different colors has been studied. For example, a charge injection layer / light emitting layer combination is laminated in multiple stages on an insulating transparent substrate via electrodes, and electrodes having the same polarity are electrically connected to each other on the insulating transparent substrate. An organic EL element is proposed (see Patent Document 1). Further, a method of controlling individual organic EL units by stacking a plurality of organic EL units emitting different colors in the vertical direction and disposing internal electrodes between the organic EL units is proposed. (See Patent Document 2). Both of these methods have the problem that the wiring method to the electrodes interposed between the respective organic EL units becomes complicated and the manufacturing process becomes complicated.

  Further, the above method is for individually controlling a plurality of organic EL units stacked in the vertical direction to emit light of a plurality of different colors. However, white light is emitted without individually controlling the plurality of units. Organic EL elements that perform the above have also been studied. For example, a tandem structure in which a plurality of organic EL units that emit different colors is stacked via a conductive layer has been proposed (see Patent Document 3).

Japanese Patent No. 3189438 US Pat. No. 5,703,436 US Pat. No. 6,337,492 Japanese Patent No. 2949230

In the above tandem structure, the conductive layer disposed between the plurality of organic EL units has a function of a charge generation layer, and has a single-layer structure and a two-layer structure that forms a pn junction. It is disclosed. As the material of the first layer in this two-layer structure, a transparent conductive oxide and metal such as ITO are disclosed, and as the material of the second layer, ITO, metal, diamond-like carbon (DLC), copper phthalocyanine, aluminum Chelate compounds (such as Alq ₃ ) are disclosed. However, disposing a transparent conductive oxide such as ITO and a metal between the organic EL units has a problem of damage to the layers constituting the organic EL unit. Also, Alq ₃ cannot function as a p-type material. Therefore, although copper phthalocyanine is promising, copper phthalocyanine has a problem that it absorbs visible light and becomes optically disadvantageous.

  Therefore, a two-layer structure forming a pn junction that can be disposed without damaging the layers constituting the organic EL unit using a material that does not absorb visible light or has little visible light absorption. There is a need for a charge generation layer.

  The organic EL device of the present invention includes at least two organic EL units including at least a hole transport layer, an organic light emitting layer and an electron transport layer between an anode and a cathode, an n-type charge generation layer including a phthalocyanine compound, and a phthalocyanine. An organic EL element including a charge generation composite layer which is a laminate of a p-type charge generation layer containing a compound, wherein the charge generation composite layer is disposed between the organic EL units. . The n-type charge generation layer preferably contains an antimony phthalocyanine compound, and the p-type charge generation layer preferably contains titanyl phthalocyanine. Here, the at least two organic EL units described above may emit light in different wavelength ranges. In this case, it is desirable that the organic EL unit closest to the light extraction side among at least two organic EL units emits red light. The organic EL device of the present invention can emit white light.

  By adopting the configuration as described above, a charge generation composite layer that is a laminate of an n-type charge generation layer containing an antimony phthalocyanine compound and a p-type charge generation layer containing titanyl phthalocyanine is disposed between a plurality of organic EL units. Thus, light emission from the organic EL units arranged in multiple stages can be efficiently obtained. This configuration is particularly effective for realizing a white light-emitting organic EL element that emits three primary colors, or a white light-emitting organic EL element that emits two colors having a complementary color relationship. A white light-emitting organic EL element that emits three primary colors is particularly useful as a light source unit for manufacturing a full-color display using a color filter method.

  The organic EL device of the present invention includes an anode, at least two organic EL units, one or more charge generation composite layers, and a cathode, and the plurality of organic EL units includes a hole transport layer, an organic light emitting layer, and an electron. It includes at least a transport layer, and each of the one or more charge generation composite layers is disposed between the organic EL units.

  A schematic cross-sectional view of the organic EL device of the first embodiment of the present invention is shown in FIG. In the configuration of FIG. 1, the first electrode 20 is an anode, the second electrode 40 is a cathode, and a charge generation composite layer 50 is laminated between the first organic EL unit 30a and the second organic EL unit 30b. ing.

  As the substrate 10, an insulating substrate made of glass, plastic, or the like, or a substrate in which an insulating thin film is formed on a semiconductive or conductive substrate can be used. Alternatively, a flexible film formed from polyolefin, acrylic resin, polyester resin, polyimide resin, or the like may be used as the substrate 10. In the case of adopting a bottom emission method in which light emission is extracted from the substrate 10 side, the substrate 10 is preferably excellent in visible light transmittance. For this purpose, it is desirable to use a glass substrate, a substrate made of various plastics, or a flexible film. In addition, when active matrix driving as described later is performed, a switching element such as a TFT may be provided on the substrate 10.

The first electrode 20 may be either an anode or a cathode. In the configuration shown in FIG. 1, the first electrode 20 is an anode. In the case of adopting the bottom emission method, the first electrode 20 is required to have visible light transparency, so that transparent conductive metal oxides such as SnO ₂ , In ₂ O ₃ , ITO, IZO, and ZnO: Al are used. Is used. In the present invention, “having visible light transparency” means having a transmittance of 50% or more with respect to light having a wavelength of 400 to 800 nm. More preferably, it has a transmittance of 85% or more for light having a wavelength of 400 to 800 nm. When the first electrode 20 is used as a cathode, it is preferable to provide an electron injection layer (to be described later) in the organic EL unit so as to contact the first electrode 20 in order to improve electron injection efficiency.

When adopting a top emission method in which light emission is extracted from the opposite side of the substrate 10, the first electrode is made of a highly reflective metal (such as Al, Ag, Mo, W, or an alloy thereof, NiP, NiB, CrP, CrB). It is desirable to reflect the light emitted by each of the organic EL units 30 by using an amorphous metal or alloy such as NiAl or a microcrystalline alloy such as NiAl. When the top emission method is employed and the first electrode 20 is used as an anode, SnO ₂ , In ₂ having a high work function is formed on a highly reflective metal in order to improve hole injection efficiency. It is desirable to have a multilayer structure in which transparent conductive metal oxides such as O ₃ , ITO, IZO, and ZnO: Al are stacked. In this case, the metal having high reflectivity also functions as an auxiliary electrode because the resistivity is lower than that of the transparent conductive metal oxide. When the first electrode 20 is used as a cathode, it is preferable to provide an electron injection layer (to be described later) in the organic EL unit so as to contact the first electrode 20 in order to improve electron injection efficiency. Alternatively, the first electrode 20 used as a cathode is formed using an alkali metal such as Li, Na, K, or Cs, an alkaline earth metal such as Ba, Ca, or Sr or an alloy containing them, or a rare earth metal. Also good.

  The second electrode 40 may be either an anode or a cathode. In the configuration shown in FIG. 1, the second electrode 40 is a cathode. When employing the bottom emission method, it is desirable to form the second electrode 40 using a metal having a high reflectivity and reflect light emitted from each of the organic EL units 30 in the direction of the substrate 10. When the second electrode 40 is used as a cathode, it is preferable to provide an electron injection layer (to be described later) in the organic EL unit so as to contact the second electrode 40 in order to improve the electron injection efficiency. Alternatively, the second electrode 40 used as a cathode is formed using an alkali metal such as Li, Na, K, or Cs, an alkaline earth metal such as Ba, Ca, or Sr or an alloy containing them, or a rare earth metal. Also good.

  When the second electrode 40 is used as an anode, the second electrode 40 has a multilayer structure of the above-described transparent conductive metal oxide and a highly reflective metal, and the transparent conductive metal oxide is formed with the organic EL unit 30. It is desirable to improve the hole injection efficiency by making contact.

  On the other hand, when the top emission method is adopted, it is desirable to form the second electrode 40 from a transparent conductive metal oxide having visible light permeability. When the top emission method is employed and the second electrode 40 is used as a cathode, an electron injection layer (to be described later) is provided on the organic EL unit to be in contact with the second electrode 40 in order to improve electron injection efficiency. Is preferred.

  The first electrode 20 and the second electrode 40 can be formed by any method known in the art such as vapor deposition and sputtering.

  In the present invention, each of the first electrode 20 and the second electrode 40 may be formed from a plurality of stripe-shaped partial electrodes to perform passive matrix driving. In this case, the direction in which the stripe-shaped partial electrode of the first electrode 20 extends intersects the direction in which the stripe-shaped partial electrode of the second electrode 40 extends, and is preferably orthogonal. Alternatively, as described above, a plurality of switching elements (TFTs, etc.) are provided on the surface of the substrate 10, and the first electrode 20 is configured from a plurality of partial electrodes corresponding to the plurality of switching elements on a one-to-one basis, thereby driving the active matrix. May be performed. In this case, the second electrode 40 is formed as an integrated electrode.

  Each of the organic EL units 30 (the first organic EL unit 30a and the second organic EL unit 30b in FIG. 1) includes at least a hole transport layer 31, an organic light emitting layer 32, and an electron transport layer 33, as necessary. Further, a hole injection layer and / or an electron injection layer may be further included. FIG. 1 illustrates a configuration in which the first electrode 20 is an anode and the second electrode 40 is a cathode, and both the first organic EL unit 30a and the second organic EL unit 30b have hole transport layers (31a, 31b). ) / Organic light emitting layer (32a, 32b) / electron transport layer (33a, 33b). Those skilled in the art will readily understand that when the configuration in which the first electrode 20 is a cathode and the second electrode 40 is an anode is adopted, the stacking order of the constituent layers of the organic EL unit 30 is reversed. Let's go. Arbitrary methods known in the art can be used for forming each constituent layer of the organic EL unit, but a vacuum deposition method is usually used.

  The hole transport layer 32 can be formed using a material having a triarylamine partial structure, a carbazole partial structure, or an oxadiazole partial structure (for example, TPD, α-NPD, PBD, m-MTDATA, etc.).

  The material of the organic light emitting layer 32 can be selected according to a desired color tone. For example, in order to obtain light emission from blue to blue-green, fluorescence enhancement such as benzothiazole, benzimidazole, and benzoxazole is possible. It is possible to use whitening agents, styrylbenzene compounds, aromatic dimethylidyne compounds, and the like. Alternatively, the organic light emitting layer 32 may be formed by using the above-mentioned material as a host material and adding a dopant thereto. Examples of materials that can be used as the dopant include coumarin derivatives (eg, coumarin 6) that are known to be used as laser dyes, perylene, rubrene, quinacridones, DCM, metal porphyrin complexes (eg, PtOEP), and the like. Can be used.

The electron transport layer 33 includes an oxadiazole derivative such as PBD and TPOB; a triazole derivative such as TAZ; a triazine derivative; a phenylquinoxaline; a thiophene derivative such as BMB-2T and BMB-3T; ) (Alq ₃ ) or an aluminum complex. The film thickness of the electron transport layer 33 can be appropriately selected in consideration of the driving voltage, transparency, and the like, but in a normal case, it is preferably 40 nm or less.

  As a material for the hole injection layer, phthalocyanine (Pc) (including copper phthalocyanine (CuPc)) or indanthrene compounds can be used.

  As a material for the electron injection layer, an alkali metal such as Li, Na, K, or Cs, an alkaline earth metal such as Ba, Ca, or Sr or an alloy containing them, a rare earth metal, or a fluoride of these metals is used. Can be, but is not limited to. Alternatively, an aluminum quinolinol complex doped with an alkali metal or an alkaline earth metal may be used. In the configuration of the present invention, it is preferable to provide an electron injection layer from the viewpoint of improving the electron injection efficiency. The film thickness of the electron injection layer can be appropriately selected in consideration of the driving voltage, transparency, and the like, but in a normal case, it is preferably 10 nm or less.

  Each layer constituting the organic EL unit 30 can be formed by using any means known in the art such as vapor deposition (resistance heating or electron beam heating).

  The charge generation composite layer 50 includes an n-type charge generation layer 51 that functions as an electron generation layer and a p-type charge generation layer 52 that functions as a hole generation layer. The charge generation composite layer 50 is disposed between the organic EL units 30. The n-type charge generation layer 51 is disposed in contact with the electron transport layer of one organic EL unit or the electron injection layer when present. The p-type charge generation layer is arranged in contact with the hole transport layer of the other organic EL unit or, if present, the hole injection layer. In the configuration of FIG. 1, the charge generation composite layer 50 is disposed between the first organic EL unit 30a and the second organic EL unit 30b, and the n-type charge generation layer 51 is the electron transport layer of the first organic EL unit 30a. The p-type charge generation layer 52 is in contact with the hole injection layer 31b of the second organic EL unit 30b.

  The n-type charge generation layer 51 is formed from an antimony phthalocyanine compound having n-type semiconductivity. The antimony phthalocyanine compound used in the present invention is a dihalogen (phthalocyaninato) antimony (V) radical anion having the structure of the formula (I) (see Patent Document 4).

  In the formula, X represents Cl, Br, or I, preferably Cl. Moreover, the phthalocyanine which is a ligand may have a substituent such as a hydrocarbon group or an alkoxy group, provided that the synthesis of the compound of the formula (I) is not hindered. The compound of the formula (I) can be prepared by electrolytic one-electron reduction or chemical one-electron reduction (for example, using metallic silver) of the corresponding dihalogen (phthalocyaninato) antimony (V) cation (Patent Document) 4). The compound of the formula (I) has a light transmittance superior to copper phthalocyanine in the visible region (particularly 400 to 600 nm). In the present invention, it is most preferable to use a dichloro (phthalocyaninato) antimony (V) radical anion. The n-type charge generation layer 51 preferably has a thickness of 5 to 30 nm in order to achieve both sufficient electron generation capability and high visible light transmittance.

  The p-type charge generation layer 52 is formed from a phthalocyanine compound having p-type semiconductivity. In addition, it is desirable to have excellent light transmittance in the visible region (particularly 400 to 600 nm). The phthalocyanine compound used in the p-type charge generation layer 52 of the present invention is preferably titanyl phthalocyanine having the structure of the formula (II). The phthalocyanine that is a ligand may have a substituent such as a hydrocarbon group or an alkoxy group.

  The compound of the formula (II) has a light transmittance superior to copper phthalocyanine in the visible region (particularly 400 to 600 nm). The p-type charge generation layer 52 desirably has a thickness of 5 to 20 nm in order to achieve both sufficient hole generation capability and high visible light transmittance.

  The n-type charge generation layer 51 and the p-type charge generation layer 52 that form the charge generation composite layer 50 can be formed by any method known in the art, such as vapor deposition and sputtering. Further, FIG. 1 illustrates a configuration in which the first electrode 20 is an anode and the second electrode 40 is a cathode. When employing a configuration in which the first electrode 20 is a cathode and the second electrode 40 is an anode, it is easy for those skilled in the art to reverse the stacking order of the n-type charge generation layer 51 and the p-type charge generation layer 52. Will understand.

  In this embodiment, the organic light emitting layer 32a of the first organic EL unit 30a and the organic light emitting layer 32b of the second organic EL unit 30b emit light of different wavelengths, more preferably light of two wavelengths having a complementary color relationship. It is preferable to form so as to release. For example, if one emits blue light and the other emits red light, white light is emitted as the entire element. More preferably, the organic EL unit close to the light extraction side emits red light, and the other organic EL unit emits blue light. For example, in the configuration of FIG. 1, when the first electrode 20 is transparent and the second electrode is reflective, the first organic EL unit 30a emits red light and the second organic EL unit 30b emits blue light. Emits light. By adopting such a configuration, the red light emitted from the first organic EL unit 30a is extracted outside without passing through the charge generation composite layer 50, so that the red light extraction efficiency can be improved. .

  In the configuration of FIG. 1, when the first electrode 20 is used as a cathode and the second electrode 40 is used as an anode, it is only necessary to reverse the order of the stacked structure in each organic EL unit and the charge generation composite layer. It will be apparent to those skilled in the art.

  Further, the organic EL element of the present invention may have three or more organic EL units and two or more charge generation composite layers, wherein each of the charge generation composite layers is between two organic EL units. Be placed. A schematic cross-sectional view of the organic EL device of the second embodiment of the present invention having three organic EL units and two charge generation composite layers is shown in FIG. In the configuration of FIG. 2, the first electrode 20 is an anode, the second electrode 40 is a cathode, and a first charge generation composite layer 50a is provided between the first organic EL unit 30a and the second organic EL unit 30b. The second charge generation composite layer 50b is laminated between the second organic EL unit 30b and the third organic EL unit 30c.

  The first electrode 20, the second electrode 40, the respective organic EL units 30 (a, b, c), and the respective charge generation composite layers 50 (a, b) are the same as those described in the first embodiment. is there.

  Also in this embodiment, the organic light emitting layer of each organic EL unit 30 may emit light having different wavelengths. More preferably, each of the organic EL units 30 emits light in one of the red region, the green region, and the blue region, and the organic EL element as a whole includes components in three wavelength regions of red, green, and blue in a balanced manner. It emits white light. Such a configuration is particularly useful as a light source unit of a full color display using a color filter method. For example, the first organic EL unit 30a may emit red light, the second organic EL unit 30b may emit green light, and the third organic EL unit 30c may emit blue light. There is no particular limitation as to which unit emits light in which wavelength range, but it is preferable that the organic EL unit closest to the light extraction side emits red light. With such a configuration, the red light can be extracted outside without passing through the charge generation composite layer 50, so that the red light extraction efficiency can be improved.

[Example 1]
An organic EL light emitting device according to the present invention having the structure of FIG. 1 was produced by the following procedure. First, an In—Zn oxide film having a thickness of 200 nm was deposited on a glass substrate 10 at room temperature by a DC sputtering method to obtain a first electrode 20 used as an anode. An In—Zn oxide firing target was used as the sputtering target, and a mixed gas of Ar and oxygen was used as the sputtering gas.

Subsequently, the substrate 10 on which the first electrode 20 is formed is mounted in a resistance heating vapor deposition apparatus, and the hole transport layer 31a, the organic light emitting layer 32a, and the electron transport layer 33a are sequentially formed without breaking the vacuum. One organic EL unit 30a was formed. During film formation, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. As the hole transport layer 31a, 4,4′-bis [N- (2-naphthyl) -N-phenylamino] biphenyl (α-NPD) having a thickness of 20 nm was stacked. As the organic light emitting layer 32a, 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi) having a thickness of 20 nm was stacked. During the lamination of the organic light emitting layer 32a, 5% perylene by volume was co-deposited as a dopant. As the electron transport layer 33a, 20 nm-thick Alq ₃ was laminated.

  Next, without breaking the vacuum, dichloro (phthalocyanite) antimony (V) radical anion (compound of formula (I) (X = Cl)) is laminated by vapor deposition to form an n-type charge generation layer 51 having a thickness of 10 nm. Subsequently, titanyl phthalocyanine was laminated by vapor deposition to form a p-type charge generation layer 52 having a thickness of 10 nm.

  Furthermore, the same procedure as the first organic EL unit 30a was repeated to form the second organic EL unit 30b having the hole transport layer 31b, the organic light emitting layer 32b, and the electron transport layer 33b.

  Next, without breaking the vacuum, a 200 nm-thick Mg / Ag (10: 1 weight ratio) layer was deposited by vapor deposition to form a second electrode 40 used as a cathode. The structure thus obtained was sealed with a sealing glass and a UV curable adhesive under a dry nitrogen atmosphere in the glove box (both oxygen and moisture concentrations were 10 ppm or less) to obtain an organic EL device. The organic EL element of this example is a bottom emission type, and both the first and second organic EL units emit blue light.

The obtained organic EL element emitted blue light. As a result of measuring voltage-instantaneous luminance characteristics of this device, luminance of 642 cd / m ² was obtained at a current density of 0.6 × 10 ⁻² A / cm ² . The continuous energization lifetime half-life in which the luminance is reduced by half in continuous energization of current giving an initial luminance of 1000 cd / m ² was 3000 hours.

[Comparative Example 1]
The procedure of Example 1 was repeated to obtain an organic EL element, except that the second organic unit 30b was not formed. The obtained organic EL element is a conventional organic EL element having one organic EL unit.

The obtained organic EL element emitted blue light and had a luminance of 695 cd / m ² at a current density of 1.0 × 10 ⁻² A / cm ² . The continuous energization life half-life was 1500 hours.

[Example 2]
According to the procedure of Example 1, the structure below the second organic EL unit 30b was formed. Next, the charge generation composite layer 50 forming procedure described in the first embodiment is repeated to form the charge generation composite layer 50b, and then the organic EL unit 30 forming procedure described in the first embodiment is repeated to form the third organic EL. Unit 30c was formed. Finally, according to the procedure of Example 1, the second electrode 40 was formed to obtain an organic EL element having the structure shown in FIG. The organic EL element of the present embodiment has three organic EL units, and all of the first to third organic EL units 30a to 30c emit blue light.

The obtained organic EL element emitted blue light and had a luminance of 948 cd / m ² at a current density of 0.6 × 10 ⁻² A / cm ² .

[Example 3]
When forming the organic light emitting layer 32a of the first organic EL unit 30a, 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM) is used as a dopant instead of perylene. Except that it was used, the procedure of Example 1 was repeated to obtain an organic EL device. The organic EL element of the present embodiment is a bottom emission type, in which the first organic EL unit 30a emits red light and the second organic EL unit 30b emits blue light.

  The light emission of the obtained organic EL element was white light having chromaticity (x, y) = (0.36, 0.40) in the CIE XYZ color system. In this embodiment, since the red light emitted from the first organic EL unit 30a is emitted to the outside without passing through the charge generation composite layer, the charge generation composite layer does not absorb longer wavelengths of 600 nm or more. The desired chromaticity could be obtained.

[Example 4]
When forming the organic light emitting layer 32a of the first organic EL unit 30a, 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM) is used as a dopant instead of perylene. The organic EL device was obtained by repeating the procedure of Example 2 except that coumarin 6 was used instead of perylene as a dopant when forming the organic light emitting layer 32b of the second organic EL unit 30b. The organic EL element of the present embodiment is a bottom emission method, the first organic EL unit 30a emits red light, the second organic EL unit 30b emits green light, and the third organic EL unit 30c emits blue light. Is emitted.

  The light emission of the obtained organic EL device was white light having chromaticity (x, y) = (0.30, 0.32) in the CIE XYZ color system. In the present example, the green light emitted from the second organic EL unit 30b was hardly absorbed by the charge generation composite layer 50a, and a desired chromaticity could be obtained.

  As is clear from the results of Examples 1 and 2 and Comparative Example 1, the organic EL element having a multistage structure according to the present invention has a luminance equal to or higher than that of the conventional organic EL element with a smaller current density. It can be seen that the luminous efficiency is high. Further, from comparison between Example 1 and Comparative Example 1, it can be seen that the multi-stage organic EL element of the present invention has a longer life than the conventional organic EL element. This is thought to be due to the fact that the current density could be reduced as the luminous efficiency improved.

  Further, as shown in Examples 3 and 4, by adding different dopants to each organic EL unit, light of different colors can be obtained from each organic EL unit, and the entire device is a multicolor light emitting organic type. An EL element could be obtained.

It is typical sectional drawing which shows the structure of the organic EL element of the 1st embodiment of this invention which has two organic EL units. It is typical sectional drawing which shows the structure of the organic EL element of the 2nd embodiment of this invention which has three organic EL units. It is typical sectional drawing which shows the structure of the organic EL element of a prior art.

Explanation of symbols

10 substrate 20 first electrode 30 (a, b, c) organic EL unit 31 (a, b, c) hole transport layer 32 (a, b, c) organic light emitting layer 33 (a, b, c) electron transport Layer 40 Second electrode 50 (a, b) Charge generation composite layer 51 (a, b) n-type charge generation layer 52 (a, b) p-type charge generation layer

Claims (4)

At least two organic EL units including at least a hole transport layer, an organic light emitting layer and an electron transport layer between the anode and the cathode, an n-type charge generation layer including a phthalocyanine compound, and a p-type charge generation layer including a phthalocyanine compound An organic EL element including a charge generation composite layer, wherein the charge generation composite layer is disposed between the organic EL units, and the n-type charge generation layer is composed only of an antimony phthalocyanine compound. An organic EL device , wherein the p-type charge generation layer is formed of only titanyl phthalocyanine . The organic EL element according to claim 1 , wherein the at least two organic EL units emit light in different wavelength ranges. The organic EL element according to claim 2 , wherein the organic EL unit closest to the light extraction side among the at least two organic EL units emits red light. The organic EL element according to claim 2, wherein the organic EL element emits white light.

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