JP2005339949A - Organic el element, its manufacturing method and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of stabilizing, in particular, an interfacial surface between a hole injection/transportation layer and a luminescent layer and thereby improving a characteristic; and to provide its manufacturing method and electronic equipment. <P>SOLUTION: This organic EL element 10 is provided, between a first electrode 3 and a second electrode 4, with a functional layer 5 having the hole injection/transportation layer 8 comprising at least organic compound and the luminescent layer 9. The hole injection/transportation layer 8 is formed by a gas phase method, and the luminescent layer 9 is formed by a liquid phase method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention particularly relates to an organic EL element in which a hole injection / transport layer is formed by a vapor phase method and a light emitting layer is formed by a liquid phase method, a manufacturing method thereof, and an electronic device.

  In recent years, as a self-luminous display, development of an organic electroluminescence element (hereinafter referred to as an organic EL element) using an organic substance in a light emitting layer has been advanced. Specifically, a polymer-type light-emitting material capable of forming a film in a liquid phase has been developed (see, for example, Non-Patent Document 1). Further, with respect to hole injection / transport materials, the discovery of polythiophene derivatives has led to the development of Film formation is possible (for example, refer nonpatent literature 2).

  As a technique using such a coating type hole injection / transport layer forming material capable of forming a film in the liquid phase and a light emitting layer forming material, a method of manufacturing a full color display by an inkjet method is disclosed. (For example, refer to Patent Document 1). Patterning by the ink jet method does not require a mask because pixels can be directly drawn, and thus a high-definition display can be manufactured. Further, since it is a liquid phase process, a vacuum is not required, and therefore it is advantageous in terms of energy cost and material cost, and is particularly effective for patterning of a large area.

  By the way, the organic EL element is desired to have higher performance. Against this background, by introducing a buffer layer at the electrode interface, a reduction in driving voltage and an improvement in luminous efficiency have been attempted. As an attempt to improve durability, an element in which a porphyrin compound such as a phthalocyanine complex is inserted as a hole injecting layer at the interface between the anode (ITO) and the hole injecting and transporting zone (hole injecting and transporting layer) is disclosed. (For example, refer to Patent Document 2).

Furthermore, in order to improve device characteristics, attempts have been made to use light emitted from triplet excitons for EL light emission (see, for example, Patent Document 3). In this technology, PVK (polyvinylcarbazole) is used as a host material, and Ir (ppy) ₃ (tris-2-phenylpyridine-iridium), which is a triplet light emitting material, is doped to realize a highly efficient organic EL device. ing.
Nature, 347 (1990) 539 Nature, 357 (1992) 477 JP-A-10-153967 JP-A 63-295695 Japanese Patent Laid-Open No. 2001-257076

  However, in the method of manufacturing the full color display by applying the hole injection / transport material and the light emitting material, respectively, by the inkjet method, both the hole injection / transport layer and the light emitting layer are formed by the liquid phase method. The hole injection / transport layer is not sufficiently flattened, and its surface is difficult to be a uniform flat surface, so that the interface between the hole injection / transport layer and the light emitting layer becomes unstable, and hole transport is performed. There was a problem that the layer properties were not stable. In addition, since both the hole injection / transport layer forming material and the light emitting layer forming material are applied by a liquid phase method, these materials are applied dissolved or dispersed in a solvent or a dispersion medium. However, the solvent or dispersion medium used for the light emitting layer forming material needs to be selected so as not to redissolve the hole injection / transport layer, and there is a problem that the degree of freedom of selection of the solvent or dispersion medium is low. .

  Further, in a device in which a porphyrin compound is inserted at the interface between the anode (ITO) and the hole injection transport zone (hole injection transport layer), the porphyrin compound functions as a hole injecting layer, so that Although the hole injection property can be improved, this device is basically formed by forming each layer by a vapor phase method and cannot have the advantages of the liquid phase method described above, particularly the ink jet method.

  In addition, in the case where light emission from triplet excitons is used for EL light emission, PEDOT: PSS (polyethylenedioxythiophene-polystyrenesulfonate) formed by a liquid phase method is used as the hole transport layer. As described above, the interface with the light emitting layer formed thereon becomes unstable, and there is a problem that the hole transport layer property is not stable.

  The present invention has been made in view of the above circumstances, and its object is to stabilize the interface between the hole injecting / transporting layer and the light emitting layer, thereby improving the characteristics thereby. And a manufacturing method thereof, and an electronic device.

In order to achieve the above object, the method of manufacturing an organic EL device according to the present invention has a function having a hole injection / transport layer made of at least an organic compound and a light emitting layer between the first electrode and the second electrode. In the method of manufacturing an organic EL device comprising a layer, a gas phase step of forming the hole injection / transport layer on the first electrode by a gas phase method, and the light emission on the hole injection / transport layer And a liquid phase step of forming a layer by a liquid phase method.
According to this method for producing an organic EL element, the hole injection / transport layer is formed by a vapor phase method, so that the surface becomes a uniform flat surface as compared with the case where it is formed by a liquid phase method. The interface with the light emitting layer is stabilized, and the hole transport layer property from the hole injection / transport layer to the light emitting layer is improved. In addition, since the hole injection / transport layer is formed by a vapor phase method, a material that is relatively difficult to dissolve in a solvent can be used as a material for forming the hole injection / transport layer. The degree of freedom of selection of the solvent or dispersion medium used for the layer forming material is increased.

In the method of manufacturing the organic EL device, it is preferable that the light emitting layer is formed by a droplet discharge method such as an ink jet method in the liquid phase process.
In this way, since a pixel can be drawn directly, a mask is not required, and thus a high-definition display can be manufactured. Further, since it is a liquid phase process, a vacuum is not required, and therefore it is advantageous in terms of energy cost and material cost, and is particularly effective for patterning of a large area.

The organic EL device of the present invention is an organic EL device comprising a functional layer having at least a hole injection / transport layer made of an organic compound and a light emitting layer between a first electrode and a second electrode. The hole injection / transport layer is formed by a vapor phase method, and the light emitting layer is formed by a liquid phase method.
According to this organic EL device, since the hole injection / transport layer is formed by a vapor phase method, the interface with the light emitting layer is stabilized as described above, and the hole injection / transport layer is changed to the light emitting layer. As a result, the hole transport layer property is improved and driving stability is improved. In addition, the degree of freedom in selecting the solvent or dispersion medium used for the material for forming the light emitting layer is increased.

In the organic EL device, the hole injection / transport layer is preferably made of a porphyrin compound. The porphyrin compound is preferably a phthalocyanine complex, and in that case, the phthalocyanine complex is preferably vanadyl phthalocyanine.
In this way, the driving stability is further improved and the color purity of the light emission obtained is increased.

In the organic EL element, the hole injection / transport layer may be made of an aromatic amine compound.
Even if it does in this way, drive stability becomes favorable and the color purity of the light emission obtained increases.

Moreover, in the said organic EL element, it is preferable that the said light emitting layer contains the luminescent material which can light-emit from a triplet exciton.
If it does in this way, luminous efficiency will improve and it will become an organic EL element excellent in a display characteristic.

In the organic EL element, the light emitting layer preferably contains a light emitting material having a carbazole group.
If it does in this way, luminous efficiency will improve and it will become an organic EL element excellent in a display characteristic.

An electronic apparatus according to the present invention includes the organic EL element described above.
According to this electronic device, as described above, the hole transport layer property is improved, the driving stability is increased, and the organic EL device has a greater degree of freedom in selecting a solvent or a dispersion medium used for the material for forming the light emitting layer. Since the device is provided, this electronic device itself has improved display characteristics and productivity.

The present invention will be described in detail below.
FIG. 1 is a side cross-sectional view showing a main part of an embodiment of an organic EL device provided with the organic EL element of the present invention, and reference numeral 1 in FIG. 1 denotes the organic EL device. The organic EL device 1 has a transparent electrode (first electrode) 3 and a cathode (second electrode) 4 that function as an anode on a substrate 2, and functions between the transparent electrode 3 and the cathode 4. The layer 5 is of a type called so-called bottom emission in which light emitted from the functional layer 5 is emitted from the substrate 2 side. The transparent electrode 3, the cathode 4, and the functional layer 5 constitute the organic EL element 10 of the present invention.

The base 2 is configured by forming a driving element (not shown) made of a TFT element, various wirings, etc. on a transparent substrate (not shown) such as a glass substrate. A transparent electrode 3 is formed thereon via an insulating film or a planarizing film.
The transparent electrode 3 is formed by patterning for each single dot region formed on the substrate 2, and is connected to the driving element made of a TFT element, the various wirings, and the like. (Indium Tin Oxide).

Around the transparent electrode 3 are formed a single dot area, that is, an inorganic bank 6 and an organic bank 7 that define a dot area for displaying one of the colors red, green, and blue. The functional layer 5 is provided in the recess surrounded by the inorganic bank 6 and the organic bank 7.
The functional layer 5 includes a hole injection / transport layer 8 and a light emitting layer 9 in this embodiment. If necessary, in addition to the hole injection / transport layer 8 and the light emitting layer 9, an electron transport / injection layer (not shown) may be provided on the light emitting layer 9.

As a material for forming the hole injection / transport layer 8, a material formed by a vapor phase method such as a vapor deposition method, for example, a porphyrin compound or an aromatic amine compound is preferably used.
The porphyrin compound may be any natural or synthetic compound derived from or containing a porphyrin structure, including the porphyrin itself. Preferred porphyrin compounds include those shown in the following structural formula (1).

In the structural formula (1), Q is —N═ or —C (R) ═, and M is a metal, a metal oxide, or a metal halide. R is hydrogen, an alkyl group, or an aryl group, and T ¹ and T ² represent hydrogen, or together, complete an unsaturated six-membered ring, which has a substituent such as alkyl or halogen. Including. Preferred six-membered rings are those formed with carbon, sulfur, and nitrogen ring carbons. Preferred alkyl moieties contain about 1 to 6 carbon atoms, while phenyl constitutes a preferred aryl moiety.

  Moreover, a phthalocyanine complex can be mentioned as an especially preferable thing in such a porphyrin compound. Porphyrin compounds generally and phthalocyanines specifically have a structure containing a metal having a positive valence of 2 or greater. Specific examples of such a metal include magnesium, zinc, palladium, nickel, copper, lead, and platinum. In particular, vanadyl phthalocyanine (vanadium oxide phthalocyanine) containing vanadium oxide (VO) is preferable among the phthalocyanine complexes.

  On the other hand, the aromatic amine compound has steric properties and is suitable for formation of an amorphous state. Specifically, TPD shown in the following structural formula (2), α-NPD shown in the structural formula (3), etc. Is preferred.

  As a material for forming the light emitting layer 9, a known light emitting material capable of emitting fluorescence or phosphorescence is used. In particular, in the present embodiment, in order to perform full-color display, those whose emission wavelength bands correspond to the three primary colors of light as described above are used. That is, one pixel is constituted by three light emitting layers (dots) of a light emitting layer corresponding to red, a light emitting layer corresponding to green, and a light emitting layer corresponding to blue, and these pixels emit light in gradation. As a result, the organic EL device 1 performs full color display as a whole.

Specific examples of the material for forming the light emitting layer 9 include (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinylcarbazole ( PVK), polythiophene derivatives, and polysilane-based polymer materials such as polymethylphenylsilane (PMPS) are preferably used.
These polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, A low molecular material such as quinacridone can also be used by doping, and light emission of a desired color can be obtained by appropriately selecting these doping materials. For example, yellow (red) light emission can be obtained by doping rubrene, and blue light emission can be obtained by doping perylene.

In particular, in the present invention, it is preferable to use a material obtained by adding (doping) a light-emitting material (phosphorescent material) capable of emitting light from triplet excitons to the polymer material. Specifically, a light-emitting material capable of emitting light from triplet excitons such as Ir (ppy) ₃ [tris-2-phenylpyridine-iridium] in a light-emitting material having a carbazole group such as polyvinyl carbazole (PVK) What added (dope) is used suitably. Note that when polyvinyl carbazole (PVK) is doped with Ir (ppy) ₃ , green light emission can be obtained.

The cathode 4 is formed so as to cover all pixel regions, and is formed from a co-deposited film of bathocuproine (BCP) and cesium (Cs) and an aluminum layer laminated on the co-deposited film. It has been done.
A sealing layer 11 is formed on the cathode 4. The sealing layer 11 has a known configuration formed by a protective layer and an adhesive layer made of an epoxy resin or the like, and a sealing substrate made of a glass substrate or the like.

In order to manufacture the organic EL device 1 having such a configuration, first, a TFT element, various wirings, and the like are formed on a transparent substrate in the same manner as in the prior art, and further, an interlayer insulating film and a planarizing film are formed to form a substrate 2. Get.
Next, an ITO film is formed on the substrate 2 by vapor deposition or the like, and further patterned to form the transparent electrode 3.

Subsequently, an inorganic bank 6 made of SiO ₂ is formed on the substrate 2 so as to surround the transparent electrode 3, and an organic bank 7 made of resin is further formed on the inorganic bank 6, whereby FIG. ), Recesses 12 are formed on the transparent electrode 3. Examples of the material used for the organic bank 7 include polyimide and acrylic resin. These materials having a structure containing a fluorine element in advance may be used.
After forming the concave portion 12 has an inorganic bank 6 and the organic bank 7, by performing the continuous process in an oxygen plasma -CF ₄ plasma substrate 2 as necessary to control the wettability on the substrate It may be.

  Next, as the vapor phase step, the material for forming the hole injection / transport layer 8 is selectively arranged in the concave portion 12 by using, for example, a mask (not shown) by a vapor deposition method that is a vapor phase method, As shown in FIG. 2B, a hole injection / transport layer 8 is formed. When the hole injection / transport layer 8 is formed by the vapor phase method as described above, the hole injection / transport layer is obtained by being closely adhered to the flat transparent electrode 3 also formed by the vapor phase method (vapor deposition method). The layer 8 also has a sufficiently uniform flat surface as compared with the case where the surface is formed by a liquid phase method, for example.

  Next, as shown in FIG. 2C, a light emitting layer 9 is formed on the hole injection / transport layer 8 in the recess 12 as a liquid phase process. In forming the light emitting layer 9, a droplet discharge method (inkjet method) is particularly preferably employed as the liquid phase method. That is, in forming the light emitting layer 9, it is necessary to make a red light emitting layer, a green light emitting layer, and a blue light emitting layer, respectively. This is because it is possible to easily form each light emitting layer only by placing it at a desired position. In forming the light emitting layer 9, a solvent that does not re-dissolve the hole injection / transport layer 8 is used as a solvent for dissolving the light emitting layer forming material. It is preferable because it can be kept in a good state.

  In the present invention, since the hole injection / transport layer 8 is formed by a vapor phase method, a material that is relatively hardly dissolved in a solvent can be used as a material for forming the hole injection / transport layer 8. Accordingly, the solvent or dispersion medium used as the material for forming the light emitting layer 9 formed thereon has a greater degree of freedom in selection than when the hole injection / transport layer 8 is formed by the liquid phase method. That is, when the hole injecting / transporting layer 8 is formed by a liquid phase method, it is necessary to use a material that is easily dissolved in a solvent as the forming material. Therefore, the solvent or dispersion used for the forming material of the light emitting layer 9 accordingly. This is because the degree of freedom in selecting the medium is reduced.

Next, a vapor-deposited film of bathocuproine (BCP) and cesium is formed so as to cover the light emitting layer 9 and the organic bank 7 by vapor deposition as in the conventional method, and further, Al (aluminum) is formed thereon. Thus, the cathode 4 having a laminated structure of co-deposited film / Al is formed.
Thereafter, a protective layer and an adhesive layer are formed on the cathode 4, and a sealing substrate is attached to form the sealing layer 11, thereby obtaining the organic EL device 1 shown in FIG. 1.

  In the organic EL device 1 thus obtained, since the hole injection / transport layer 8 is formed by the vapor phase method, the interface with the light emitting layer 9 is stabilized as described above. The hole transport layer property from the hole injection / transport layer 8 to the light emitting layer 9 is improved, and the driving stability is high. Further, the degree of freedom in selecting a solvent or a dispersion medium used for the material for forming the light emitting layer is increased, and the productivity is improved.

(Example 1)
As shown in FIG. 3, an organic EL device (organic EL element) 1a having substantially the same configuration as that shown in FIG. 1 was produced as follows.
That is, in Example 1, the transparent electrode 3 made of ITO was formed on the glass substrate (base 2) by the sputtering method, and then the surface of the formed transparent electrode 3 was washed and further subjected to oxygen plasma treatment.

Next, VOPc (vanadyl phthalocyanine) was formed into a thickness of about 50 nm on the transparent substrate 3 by vapor deposition to form a hole injection / transport layer 8.
Next, PVK (polyvinylcarbazole), PBD (2- (4-biphenyl) -5- (4-butylphenyl) -1,3,4-oxadiazole) and Ir (ppy) ₃ were prepared at 70:30: The mixture is mixed at a mixing ratio (weight ratio) of 3, and further liquefied using an organic solvent such as dichloroethane, chloroform, toluene, cyclohexane, etc. to form a light emitting layer forming material for green, and this is spin coated as a liquid phase method The light emitting layer 9 having a thickness of about 75 nm was formed by coating by the method and further drying.
Next, a co-deposited film of bathocuproine (BCP) and cesium is formed in a state of covering the light emitting layer 9, and further, Al (aluminum) is formed thereon, thereby forming a co-deposited film / Al laminated structure. A cathode 4 was formed.
Thereafter, an epoxy resin is applied on the cathode 4 to form a protective layer (adhesive layer), and a glass substrate (sealing substrate) is further pasted to form the sealing layer 11, thereby forming an organic EL device (organic). EL element) 1a was obtained.

The luminance half-life of the organic EL device 1a thus obtained was 200 hours when measured by emitting light at a constant current drive with an initial luminance of 200 cd / m ² at room temperature. Further, when the color purity of the obtained emitted light was examined, the CIE chromaticity coordinates were (0.27, 0.64).

(Example 2)
An organic EL device (organic EL element) having substantially the same configuration as that shown in FIG. 3 was produced as follows.
That is, in Example 2, PEDOT: PSS (polyethylenedioxythiophene-polystyrene sulfonate) was applied on the transparent electrode 3 shown in FIG. 3 by a liquid phase method (spin coating method), and dried to inject holes. A layer (not shown) was formed.
Next, similarly to Example 1 shown in FIG. 3, VOPc (vanadyl phthalocyanine) is formed to a thickness of about 50 nm on the hole injection layer made of PEDOT: PSS to form the hole injection / transport layer 8. Further, a light emitting layer 9 was formed by a liquid phase method using a mixture of PVK, PBD, and Ir (ppy) ₃ . Then, the sealing layer 11 was formed like Example 1 shown in FIG. 3, and the organic EL apparatus (organic EL element) was obtained.

The luminance half life of the organic EL device 1a thus obtained was 150 hours when measured by emitting light with constant current drive at an initial luminance of 200 cd / m ² at room temperature. Further, when the color purity of the obtained emitted light was examined, the CIE chromaticity coordinates were (0.30, 0.61).

(Comparative example)
With respect to the organic EL device (organic EL element) 1a having the configuration shown in FIG. 3, only the hole injection / transport layer 8 is formed as follows, and the rest is similar to the organic EL device (organic EL element) 1a. Thus, an organic EL device (organic EL element) of a comparative example was produced.
That is, in place of the hole injection / transport layer 8 made of VOPc (vanadyl phthalocyanine) by a vapor phase method, PEDOT: PSS (polyethylenedioxythiophene-polystyrenesulfonate) is applied by a liquid phase method (spin coating method) and dried. As a result, the hole injection / transport layer 8 was formed.

The luminance half life of the organic EL device thus obtained was 30 hours when measured by emitting light with constant current drive at an initial luminance of 200 cd / m ² at room temperature. Further, when the color purity of the obtained emitted light was examined, the CIE chromaticity coordinates were (0.32, 0.60).
From the results of Example 1, Example 2, and Comparative Example, Examples 1 and 2 of the present invention have a luminance half-life significantly increased from 30 hours to 200 hours and 150 hours as compared with Comparative Examples by the conventional method. It was confirmed that the driving stability was improved. Further, regarding the color purity, it was confirmed that the color purity as green was increased by decreasing the X value in the CIE chromaticity coordinates and increasing the Y value as compared with the comparative example.

  In the above embodiment, the case where the present invention is applied to a bottom emission type organic EL device (organic EL element) has been described. However, the present invention is not limited to this, and the emitted light is emitted from the side opposite to the substrate. Can be applied to a so-called top emission type.

Such an organic EL device (organic EL element) of the present invention is preferably used as a display unit in various electronic devices such as portable information processing devices such as word processors and personal computers, mobile phones and wristwatch-type electronic devices. Can do.
FIG. 4 is a perspective view showing a mobile phone as an example of such an electronic apparatus. In FIG. 4, reference numeral 1000 denotes a mobile phone body, and reference numeral 1001 denotes a display unit using the organic EL device 1.
Since the electronic apparatus (mobile phone) shown in FIG. 4 includes the display unit 1001 made of the organic EL device, display characteristics and productivity of the display unit 1001 are particularly improved.

It is principal part sectional drawing of the organic electroluminescent apparatus (element) of this invention. (A)-(c) is process explanatory drawing of the manufacturing method of an organic electroluminescent apparatus. It is principal part side sectional drawing of the organic electroluminescent apparatus (element) of an Example. It is a perspective view which shows an example of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Organic EL apparatus, 2 ... Base | substrate, 3 ... Transparent electrode (1st electrode),
4 ... cathode (second electrode), 5 ... functional layer, 8 ... hole injection / transport layer, 9 ... light emitting layer,
10 ... Organic EL element

Claims (10)

In the method for producing an organic EL device comprising a functional layer having at least a hole injection / transport layer made of an organic compound and a light emitting layer between the first electrode and the second electrode,
A vapor phase step of forming the hole injection / transport layer on the first electrode by a vapor phase method;
And a liquid phase step of forming the light emitting layer on the hole injection / transport layer by a liquid phase method.   2. The method of manufacturing an organic EL element according to claim 1, wherein in the liquid phase step, the light emitting layer is formed by a droplet discharge method. In an organic EL element comprising a functional layer having at least a hole injection / transport layer made of an organic compound and a light emitting layer between a first electrode and a second electrode,
The hole injection / transport layer is formed by a vapor phase method,
An organic EL element, wherein the light emitting layer is formed by a liquid phase method.   4. The organic EL device according to claim 3, wherein the hole injection / transport layer is made of a porphyrin compound.   The organic EL device according to claim 4, wherein the porphyrin compound is a phthalocyanine complex.   6. The organic EL device according to claim 5, wherein the phthalocyanine complex is vanadyl phthalocyanine.   4. The organic EL device according to claim 3, wherein the hole injection / transport layer is made of an aromatic amine compound.   The organic light-emitting device according to claim 3, wherein the light-emitting layer contains a light-emitting material capable of emitting light from triplet excitons.   The organic light-emitting device according to any one of claims 3 to 8, wherein the light-emitting layer contains a light-emitting material having a carbazole group. An electronic apparatus comprising the organic EL element according to claim 3.

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