JP2010198921A - Organic el element using transparent conductive film laminate, and manufacturing method of these - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element having an electrode in which light transmission characteristics are improved. <P>SOLUTION: The organic EL element has a transparent conductive film lamination layer that includes a substrate, an underlying layer installed on the substrate and consisting of metal other than silver, and a silver thin film layer consisting of silver or a silver alloy installed on the underlying layer, in which a film thickness of the underlying layer is thinner than that of the silver thin film layer. Furthermore, a manufacturing method of these organic EL elements is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL device using a transparent conductive film laminate, and a method for producing the same. In particular, the present invention relates to an organic EL element using a transparent conductive film laminate including a silver thin film that can be used as a transparent conductive film of an organic EL element, and a method for producing the same.

  In recent years, organic electroluminescence (hereinafter also referred to as organic EL) elements have been actively studied for practical use. Since the organic EL element can realize a high current density at a low voltage, it is expected to realize high light emission luminance and light emission efficiency. This organic EL element is provided with a first electrode and a second electrode that sandwich an organic EL layer, and an electrode from which light is extracted, for example, an upper electrode of a top emission type organic EL element has a high transmittance. In addition, low resistance is required. In addition, it has been proposed to use, for example, an oxide transparent electrode as a transparent electrode on the light extraction side, and this material includes an oxide transparent conductive film (TCO) material (indium-tin oxide (ITO), indium- Zinc oxide (IZO) or the like is used. Lowering the resistance of the transparent conductive film is also desirable from the viewpoint of reducing the power consumption of the element.

  In order to solve the above problems, when an electrode is formed only with an oxide transparent conductive film such as ITO or IZO, oxygen is introduced into the atmosphere during the film formation in order to improve optical characteristics, electrical characteristics, etc. There is a need to. In the top emission type organic EL element, it is necessary to form an organic EL layer before forming the oxide transparent conductive film, and this organic EL layer may be attacked by oxygen.

  In order to prevent this drawback, it has been proposed to provide a transparent buffer layer. However, since the specific resistance of the transparent conductive film alone is about two orders of magnitude higher than that of the metal film, it is necessary to increase the film thickness. Yes, productivity becomes a problem. Furthermore, since transparent conductive films such as ITO and IZO have a considerable absorption in a wavelength region of less than 500 nm, there is a problem that the transmittance decreases when the film thickness is increased. Therefore, it is difficult for the transparent conductive film to achieve both low resistance and high transmittance.

  From the viewpoint of mitigating damage to the organic EL layer when forming the oxide transparent conductive film by sputtering, ion plating, or the like, it has been proposed to use a metal thin film for the buffer layer (Patent Document 1, Non-Patent Document). 1). An MgAg thin film or the like is disclosed as an example of the buffer layer. When a metal buffer layer is used, the metal buffer layer can have an effect of reducing resistance. However, even in this method, there is a trade-off that if the metal thin film is formed thick in order to reduce the resistance of the metal buffer layer and the organic EL layer, the transmittance is deteriorated.

  Therefore, gold, silver, copper, and the like are considered as metals having high electrical conductivity and high visible light transmittance, that is, metals having a small trade-off, and a transparent electrode combining these metals with an oxide transparent conductive film has been proposed. (Patent Documents 2 to 4). For example, Patent Document 2 discloses a TCO / protective layer (Au, Ni, Al), Patent Document 3 describes TCO / AuX (X is Mg, etc.), and Patent Document 4 describes a TCO / Ag / electron injection layer. A structure is disclosed.

  In addition, a transparent electrode using only a metal having a high visible light transmittance has been proposed as a material having no damage during the formation of the oxide transparent conductive film (Patent Documents 5 and 6, Non-Patent Document 2). In addition, Patent Document 7 discloses a light-emitting device in which a semi-reflective electrode and a conductive semi-reflective layer are formed on a light-emitting layer.

JP-A-8-185984 JP 2003-77651 A Japanese Patent Laid-Open No. 2005-276739 JP 2005-32563 A JP 2004-200141 A JP 2003-045673 A JP 2007-335347 A

Nature vol. 380, March 7, 1996, pp. 29 Journal Display Technology Vol. 1 No. 1, (September 2005), p. 105

  Among metals having high electrical conductivity and high visible light transmittance, silver has a relatively flat transmittance expected from a complex refractive index in the visible light region, a low specific resistance, and is highly expected as a transparent electrode material. However, the silver thin film has a problem that the actual transmittance is worse than the transmittance expected from the complex refractive index. As this reason, formation of silver oxide can be considered. In other words, silver easily reacts with oxygen and easily forms silver oxide on the surface, but this silver oxide has a high refractive index and a relatively high absorption in a wavelength region of 500 nm or less, so that the transmittance is considered to decrease. It is done. In general, a silver thin film having a thickness of 10 nm or less is not a continuous and uniform film but a discontinuous island-shaped film, which not only has a high resistance, but also absorbs and transmits in the visible light region by local surface plasmon resonance. Deteriorating properties.

Therefore, the light transmission characteristics of the transparent electrode using a silver thin film proposed so far have not been practically sufficient.
The present invention has been made to solve such problems, and an object of the present invention is to use an organic structure that can be used as an electrode with improved light transmission characteristics in a transparent electrode using a silver thin film. An object is to provide an EL element. Furthermore, an object of this invention is to provide the manufacturing method of the said organic EL element.

In the present invention, when a silver thin film is formed, a thin film made of a metal different from silver is formed below the silver thin film, and when a laminated structure including the silver thin film is formed, a silver laminated body is obtained rather than a thin film of silver having the same film thickness. This is based on the finding that is superior in transmission characteristics and flatness.
The organic EL device of the present invention is characterized in that an electrode including this silver laminate is used. Then, a silver laminated body is demonstrated. This laminate includes a substrate, an underlayer made of a metal other than silver provided on the substrate, and a silver thin film layer made of silver or a silver alloy provided on the underlayer, and the thickness of the underlayer Is a transparent conductive film laminate characterized by being thinner than the film thickness of the silver thin film layer. In the present invention, the substrate may include a support substrate and a dielectric or semiconductor thin film provided on the support substrate, and the base layer may be provided on the dielectric or semiconductor thin film. The thickness of the underlayer is preferably from 0.1 nm to 4 nm, and the thickness of the silver thin film layer is preferably from 5 nm to 30 nm.

In the present invention, the metal other than silver in the underlayer is preferably selected from the group consisting of gold, aluminum, copper, indium, tin and zinc.
The first aspect of the present invention is an organic EL device using the silver laminated film as an electrode film laminated body. The organic EL element includes at least a substrate, a first electrode provided on the substrate, an organic EL layer provided on the first electrode, and a second electrode provided on the organic EL layer. An organic EL element including the first electrode or the second electrode, or both of which are a laminated transparent conductive film composed of a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, The underlayer of the laminated transparent conductive film is provided on the side close to the substrate, and the thickness of the underlayer is smaller than the thickness of the silver thin film layer. Here, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode is a microresonator that enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is the optical distance that constitutes. In the organic EL device of the present invention, an oxide transparent conductive film can be further provided on the silver thin film layer.

  The second aspect of the present invention is a method for producing the above organic EL element. 1st Embodiment of this manufacturing method is related with the manufacturing method of a bottom emission type organic EL element. This method includes (a) a step of forming a transparent first electrode on a transparent substrate, (b) a step of forming an organic EL layer on the first electrode, and (c) a second step on the organic EL layer. At least a step of forming an electrode, wherein the first electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film Is formed on the side close to the substrate, and the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the first electrode is in a vacuum state by resistance heating vapor deposition or electron beam vapor deposition. The film is formed continuously while maintaining the above. Here, in the organic EL element, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is manufactured to have an optical distance that constitutes a microresonator.

  In the present invention, the second electrode may be a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy. In this case, the base layer of the laminated transparent conductive film Is formed on the side close to the substrate, and the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the second electrode is in a vacuum state by resistance heating vapor deposition or electron beam vapor deposition. The film is continuously formed while maintaining the above.

  The second embodiment of the manufacturing method of the present invention relates to a method for manufacturing a top emission type organic EL element. The method includes (i) a step of forming a first electrode on a substrate, (ii) a step of forming an organic EL layer on the first electrode, and (iii) a transparent second electrode on the organic EL layer. Including at least a step of forming, wherein the second electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, The step of forming the second electrode is formed on the side close to the substrate and the underlayer is thinner than the silver thin film layer, and the step of forming the second electrode maintains a vacuum state by resistance heating evaporation or electron beam evaporation. The film is formed continuously as it is. Here, in the organic EL element, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is manufactured to have an optical distance that constitutes a microresonator.

  In the present invention, the first electrode is a laminated transparent conductive film comprising an underlayer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the underlayer of the laminated transparent conductive film is on the side close to the substrate And the step of forming the first electrode is continued while maintaining the vacuum state by resistance heating vapor deposition or electron beam vapor deposition. To form a film. The second embodiment may include (iv) a step of further forming an oxide transparent conductive film on the silver thin film layer.

  ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element which improved the light transmission characteristic with the transparent conductive film laminated body containing a silver thin film can be provided.

(A)-(d) is the schematic which shows the transparent conductive film laminated body of this invention. (A)-(c) is the schematic which shows the manufacturing process of the transparent conductive film laminated body of this invention. (A)-(d) is the schematic which shows the organic EL element of this invention (in the figure, a white arrow shows the radiation | emission direction of light). (A)-(d) is the schematic which shows the manufacturing process of the organic EL element of this invention. (A)-(d) is the schematic which shows the manufacturing process of the organic EL element of this invention. It is the graph which compared the transmittance | permeability of the transparent conductive film laminated body of this invention with the conventional one. It is the graph which compared the transmittance | permeability of the transparent conductive film laminated body of this invention with the conventional one. It is the graph which compared the transmittance | permeability of the transparent conductive film laminated body of this invention with the conventional one. It is a figure which shows the emission spectrum in the experimental example 4 (sample 1 and sample 2) and the comparative experiment example 4 (sample 3) in the electric current density of 10 mA / cm < ² >. It is a figure which shows the emission spectrum in Example 1 and the comparative example 1 in the current density of 10 mA / cm < ² >.

The present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view showing a silver laminate according to the present invention. The first embodiment of the laminate includes a substrate, a base layer made of a metal other than silver provided on the substrate, and a silver thin film layer made of silver or a silver alloy provided on the base layer. FIG. 1A is a schematic view showing this laminate.
As shown in FIG. 1A, the transparent conductive film laminate 100 includes a substrate 102, a base layer 104 on the substrate, and a silver thin film layer 106 on the base layer. As a second embodiment, as shown in FIG. 1B, the substrate 102 may include a support substrate 110 and a dielectric or semiconductor thin film 112 provided thereon. When the dielectric is provided on the support substrate, the support substrate may be a conductor. The semiconductor thin film can be a switching element such as a TFT or MIM. Furthermore, as a third embodiment, an oxide transparent conductive film 108 (for example, ITO, IZO, etc.) is further provided on the silver thin film layer 106 as shown in FIGS. May be.

In this specification, the silver thin film layer means a thin film layer made of silver or a silver alloy. Examples of the silver alloy include an alloy (trade name: APC, manufactured by Furuya Metal Co., Ltd.) in which a small amount of Pd and Cu are added (a few at%) to silver.
In this invention, it is preferable that the film thickness of a base layer is thinner than the film thickness of a silver thin film layer. Further, the underlayer may be island-shaped. In addition, it is preferable that the silver thin film layer forms the continuous uniform film instead of island shape. In the present invention, the thickness of the underlayer is preferably 0.1 nm to 4 nm, and the thickness of the silver thin film layer is preferably 5 nm to 30 nm. By setting the thickness of the underlayer to 4 nm or less, the underlayer is formed in an island shape, and the subsequent silver thin film layer is formed as a continuous uniform flat film even if the thickness is about 10 nm. It is formed. In addition, by setting the thickness of the underlayer to 4 nm or less, the influence on the transmittance can be reduced even if the underlayer is formed of a material having relatively high absorption.

  The underlayer can be made of a metal other than silver, but is preferably selected from gold (Au), aluminum (Al), copper (Cu), indium (In), tin (Sn), or zinc (Zn). It is preferable. In particular, gold and aluminum are preferable. These metals have the advantage that they are easier to handle than, for example, alkali metals and alkaline earth metals, and that the damage to the organic EL layer is small because they can be formed by vapor deposition as in the case of silver.

The substrate can be a dielectric such as glass or plastic. When a conductor such as a metal substrate is used as the support substrate, a dielectric is provided between the support substrate and the electrode. Further, the substrate may be composed of a support substrate and a switching element (for example, TFT, MIM, etc.) provided thereon.
The transparent electrode using the silver thin film of the present invention can improve visible light transmission characteristics. Although this mechanism is not clear, the formation of silver oxide that can be formed at the initial stage of silver film formation is suppressed by providing a base layer containing a metal different from silver, particularly gold, aluminum, etc. under the silver thin film. It is thought that there is. Further, it is considered that a silver thin film is uniformly formed by such an underlayer, and local surface plasmon formation due to island formation of the silver thin film is suppressed.

Next, with reference to FIG. 2, the manufacturing method of a silver laminated body is demonstrated.
This manufacturing method includes (1) forming a base layer made of a metal other than silver on a substrate and forming a silver thin film layer made of silver or a silver alloy on the base layer.
In this film forming process, first, the base layer 104 is formed on the substrate 102 (FIG. 2A). For the base layer 104, a conventional method such as a sputtering method, an evaporation method, or an ion plating method can be used. In the present invention, in consideration of forming a transparent conductive film on a material that is weak against high energy particles, it is preferable to use a low energy film formation method in which the energy of the film formation particles is about 1 eV or less. For example, it is preferable to use resistance heating vapor deposition or electron beam vapor deposition. Next, a silver thin film layer 106 is formed (FIG. 2B). The silver thin film layer can be formed by various methods as in the case of the underlayer. For example, it is preferable to use a low energy film forming method in which the energy of the film forming particles is about 1 eV or less. For example, resistance heating vapor deposition or electron beam vapor deposition can be used. When the underlayer is formed using resistance heating vapor deposition or electron beam vapor deposition, the silver thin film layer is preferably formed continuously while maintaining a vacuum state.

When patterning is required for the underlayer and the silver thin film layer, for example, the above evaporation method may be applied through a mask capable of forming a desired pattern.
Optionally, an oxide transparent conductive film such as IZO or ITO can be formed on the silver thin film layer. The oxide transparent conductive film can be formed by a conventional method such as sputtering.

In the case where patterning is required for the oxide transparent conductive film, for example, the film may be formed through a mask capable of forming a desired pattern.
In the method for producing a transparent conductive film laminate of the present invention, the base layer of the transparent conductive film laminate is formed on the side close to the substrate. That is, it is necessary to form an underlayer prior to the silver thin film layer. By doing in this way, a silver thin film layer is formed uniformly and the transmittance | permeability of an electrode can be improved. Moreover, the conditions for forming the laminated transparent conductive film by applying resistance heating vapor deposition or electron beam vapor deposition are not particularly limited as long as the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer. For example, in resistance heating vapor deposition, the heating power is adjusted according to the target film thickness, the crucible temperature is heated above the melting point of the metal material for film formation, the vapor deposition rate is controlled, and the metal film with the target film thickness is formed. . In the case of electron beam evaporation, the evaporation rate is controlled by adjusting the current value of the electron gun. For a target film thickness of 0.1 nm to 4 nm, the deposition rate is preferably 0.05 to 1 cm / s, for example, from the balance of film thickness controllability and productivity. The degree of vacuum in the vapor deposition chamber before vapor deposition is preferably evacuated to 2 × 10 ⁻⁵ Pa or less, and the degree of vacuum during vapor deposition is desirably on the order of 10 ⁻⁵ Pa.
(First aspect)
Next, a first aspect of the present invention will be described with reference to FIG.

  The first aspect of the present invention is an organic EL element in which the above-described silver laminate is applied to the first electrode and / or the second electrode. The organic EL element includes at least a substrate, a first electrode provided on the substrate, an organic EL layer provided on the first electrode, and a second electrode provided on the organic EL layer. An organic EL element including the first electrode or the second electrode, or both of which are a laminated transparent conductive film composed of a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, The underlayer of the laminated transparent conductive film is provided on the side close to the substrate, and the thickness of the underlayer is smaller than the thickness of the silver thin film layer. Here, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode is a microresonator that enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is the optical distance that constitutes.

The organic EL element of the present invention may be a top emission method or a bottom emission method.
In the top emission type organic EL element (first embodiment), as shown in FIG. 3A, a substrate 302, a first electrode 308 provided on the substrate, and a first electrode provided on the substrate 302 are provided. The organic EL layer 310, the base layer 304 on the organic EL layer 310, and the silver thin film layer 306 on the base layer. The second electrode 312 of the organic EL element is a laminated transparent conductive film composed of a base layer and a silver thin film layer. As for the underlayer 304 and the silver thin film layer 306 constituting the second electrode, the underlayer is provided on the side close to the substrate, and the silver thin film layer is provided on the organic EL layer side.

  FIG. 3A shows an example of a passive matrix organic EL element including a plurality of first electrodes and a plurality of second electrodes provided in a direction orthogonal to the first electrodes. An EL element can also be used. For example, a substrate made of a support substrate and a switching element provided thereon may be used as the substrate 302. The switching element may be any structure known in the art such as TFT, MIM, and the like.

  In the case of the top emission method, the first electrode is not necessarily a laminated transparent conductive film composed of the underlayer and the silver thin film layer of the present invention, but as shown in FIG. 3B, together with the second electrode 312 The first electrode 308 can be a laminated transparent conductive film. In this case, the laminated transparent conductive film of the first electrode and the laminated transparent conductive film of the second electrode may be the same type or different types.

  In the present invention, an oxide transparent conductive film such as IZO or ITO can be formed on the laminated transparent conductive film of the second electrode by a top emission method. That is, an oxide transparent conductive film such as IZO or ITO can be optionally formed on the silver thin film layer of the laminated transparent conductive film as the second electrode. The oxide transparent conductive film can be formed by a conventional method such as sputtering.

  In the bottom emission type organic EL element (second embodiment), as shown in FIG. 3C, a transparent substrate 314 and an underlying layer 304 and a silver thin film layer 306 provided on the substrate 314 are used. A first transparent electrode 308 that is a laminated transparent conductive film, an organic EL layer 310 provided on the first electrode, and a second electrode 312 on the organic EL layer 310. The base layer 304 and the silver thin film layer 306 constituting the first electrode are provided with a base layer on the substrate side and a silver thin film layer on the organic EL layer side.

  In the case of the bottom emission method, the second electrode is not necessarily a laminated transparent conductive film composed of the underlayer and the silver thin film layer of the present invention. However, as shown in FIG. The second electrode 312 can be a laminated transparent conductive film. In this case, the laminated transparent conductive film of the first electrode and the laminated transparent conductive film of the second electrode may be the same type or different types.

Various conditions such as the material and film thickness of the underlayer and the silver thin film layer used in the organic EL device of the present invention are as described in the first embodiment.
In the top emission method, when the first electrode is not a silver laminated film according to the present invention but a normal electrode, or in the bottom emission method, the second electrode is not a silver laminated film according to the present invention but a normal electrode In this case, for example, the following materials can be used as the material of each electrode.

In the case of adopting a top emission method in which light emitted from the organic EL layer 310 is extracted from the second electrode 312 side, the first electrode 308 preferably has reflectivity. The reflective first electrode 308 can be formed by stacking a metal film made of a highly reflective metal, an amorphous alloy or a microcrystalline alloy, and a conductive metal oxide over the metal film. The conductive metal oxide includes SnO ₂ , In ₂ O ₃ , ITO, IZO, ZnO: Al, and the like, and is a layer that is desirably provided in order to improve hole injection efficiency. High reflectivity metals include Al, Ag, Mo, W, Ni, Cr, and the like. High reflectivity amorphous alloys include NiP, NiB, CrP, CrB, and the like. The highly reflective microcrystalline alloy includes NiAl and the like. The highly reflective metal, amorphous alloy or microcrystalline alloy can be formed by any method known in the art such as vapor deposition or sputtering. The first electrode 308 can be used as the cathode also when the top emission method is employed. Also in this case, the first electrode 308 is formed by laminating a metal film made of the above-described highly reflective metal, amorphous alloy or microcrystalline alloy, or a conductive metal oxide on the metal film. Can do. Alternatively, the first electrode 308 may be formed using an alloy (for example, Mg / Ag alloy) of a metal having a high reflectance and a metal having a low work function.

  When the bottom emission method is employed, the second electrode 308 is preferably a reflective electrode. In this case, the second electrode 312 is formed of the above-described highly reflective metal, amorphous alloy, or microcrystalline alloy. Alternatively, when the second electrode 312 is a cathode, the second electrode 312 may be formed using an alloy (for example, Mg / Ag alloy) of a metal having a high reflectance and a metal having a low work function. In addition, when the bottom emission method is employed, the second electrode 312 can be used as an anode. In this case, a laminated structure of the above-described conductive metal oxide and a reflective metal is desirable. The conductive metal oxide is disposed on the organic EL layer side and used to improve the hole injection efficiency.

The organic EL layer 310 includes at least an organic light emitting layer and 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. Specifically, an organic EL element substrate having the following layer structure including a cathode and an anode is employed.
(1) Anode / organic light emitting layer / cathode (2) Anode / hole injection layer / organic light emitting layer / cathode (3) Anode / organic light emitting layer / electron injection layer / cathode (4) Anode / hole injection layer / organic Light emitting layer / electron injection layer / cathode (5) Anode / hole transport layer / organic light emitting layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron injection layer / Cathode (7) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer / cathode In the above layer configuration, the anode and the cathode are the first electrode 308 or the second electrode 312. Either.

  The material of the organic light emitting layer can be selected according to the desired color tone. For example, in order to obtain light emission from blue to blue-green, fluorescent whitening such as benzothiazole, benzimidazole, and benzoxazole Agents, styrylbenzene compounds, aromatic dimethylidene compounds, and the like can be used. Alternatively, the organic light emitting layer may be formed by using the above-mentioned material as a host material and adding a dopant thereto. As a material that can be used as a dopant, for example, perylene (blue), which is known to be used as a laser dye, can be used.

Materials for the electron transport layer include oxadiazole derivatives such as PBD and TPOB; triazole derivatives such as TAZ; triazine derivatives; phenylquinoxalines; thiophene derivatives such as BMB-2T and BMB-3T; aluminum tris (8 An aluminum complex such as (quinolinolato) (Alq ₃ ) can be used.
As a material for the electron injection layer, an aluminum complex such as Alq ₃ , an aluminum complex doped with an alkali metal or an alkaline earth metal, or bathophenanthroline added with an alkali metal or an alkaline earth metal can be used. In the present invention, it is preferable to provide an electron injection layer in the organic EL layer.

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 hole transport layer, 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.) can be used.

Each layer constituting the organic EL layer 310 can be formed by using any means known in the art such as resistance heating vapor deposition. The organic EL layer thus formed emits light having a certain width in its emission spectrum, and has a light emission peak at a wavelength of 450 nm to 480 nm, for example, if it emits blue light.
The first electrode, the organic EL layer, and the second electrode formed as described above may be protected by a planarization layer and / or a passivation layer (not shown). Known materials are used for the planarizing layer and the passivation layer. For example, when a polymer material is used as the planarizing layer, a material in which an imide-modified silicone resin or an inorganic metal compound (TiO, Al ₂ O ₃ , SiO _2, etc.) is dispersed in acrylic, polyimide, silicone resin or the like. , Photo-curing resins and / or thermosetting resins such as acrylate monomers / oligomers / polymers having reactive vinyl groups, resist resins, fluororesins, or epoxy resins having a mesogenic structure with high thermal conductivity Can be mentioned. The passivation layer can be made of an inorganic oxide such as SiO _x , SiN _x , SiN _x O _y , AlO _x , TiO _x , TaO _x , ZnO _x, or an inorganic nitride. As the passivation layer, various polymer materials described in the above planarization layer can also be used. The formation method of the planarization layer and the passivation layer is not particularly limited, and can be formed by a conventional method such as a sputtering method, a CVD method, a vacuum evaporation method, a dip method, or a sol-gel method. Conditions such as the film thickness of the planarization layer and the passivation layer are the same as in the past.

Further, in the organic EL element of the present invention, the reflecting surfaces formed by the first electrode and the second electrode form a microresonator structure, and the resonator length is the light of the light emitted from the organic EL layer. The condition is that the specific wavelength (for example, 450 nm to 480 nm for blue) is enhanced.
The condition that the wavelength λ _EL of light emitted from the organic EL layer is enhanced is a condition that is enhanced when light having the wavelength λ _EL emerges perpendicularly to the element surface, and constitutes the organic EL layer. , The electron injection layer, the electron transport layer, the organic light emitting layer, the hole transport layer, and the hole injection layer, where d _{i is} the film thickness, n _i is the refractive index, and the light in the first electrode and the second electrode When the phase change at the time of reflection is δ ₁ and δ ₂ , it is approximately expressed by equation (1).

.Sigma.n _i d _i is the sum of the optical distance of each layer disposed between the reflective surfaces. In this formula, the electron injection / transport layer, light-emitting layer, and hole injection / transport layer, which are organic layers, generally have almost the same refractive index, and therefore, reflection at the interface between the layers caused by the difference in the refractive index of these layers is ignored. However, it is an approximate expression under the assumption that light reflection occurs only at the first electrode or the second electrode, which is purely a reflective electrode or a transflective electrode.

The reflective surface formed by the first electrode and the second electrode is an interface between the metal film constituting each electrode and the organic layer or oxide transparent conductive layer that is disposed between and in contact with the metal film. It can be approximated as Therefore, here, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode is Σd _i .
If the resonance condition for λ _{EL is obtained} by theoretical calculation, strictly considering that the light emitted from the organic EL layer undergoes multiple reflection at the interface of each layer, the complex refractive index of each layer is used. Since the reflectance of the laminated film can be obtained by sequentially calculating, the film thicknesses of the electron injecting and transporting layer, the light emitting layer, and the hole injecting and transporting layer may be determined in this way.

Further, by using the formula (1), the film thickness d _i of each layer is determined, and an element having a film thickness changed by 10 nm, for example, in the vicinity of the total film thickness (Σd _i ) at that time is produced. A film thickness condition that enhances _EL may be found.
Thus, the organic EL element of the present invention comprises a microresonator using a laminated transparent conductive film composed of a base layer and a silver thin film layer on the first electrode or the second electrode, or both of them, as described above. Light of a specific wavelength with enhanced light intensity can be extracted outside with high efficiency.
(Second aspect)
Next, the manufacturing method of the organic EL element which is the 2nd aspect of this invention is demonstrated. The manufacturing method of 1st Embodiment is a manufacturing method of the organic EL element of a bottom emission system (refer FIG. 4). The manufacturing method includes (a) a step of forming a transparent first electrode on a transparent substrate, (b) a step of forming an organic EL layer on the first electrode, and (c) a first step on the organic EL layer. Including at least a step of forming two electrodes, wherein the first electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, The base layer is formed on the side close to the substrate, and the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the first electrode is performed by resistance heating vapor deposition or electron beam vapor deposition. In this method, the film is continuously formed while maintaining the state. Here, in the organic EL element, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is manufactured to have an optical distance that constitutes a microresonator.

The manufacturing method of the first embodiment will be described with reference to FIG. FIG. 4 shows an example of manufacturing a bottom emission type passive organic EL element.
In step (a), as shown in FIG. 4A, a base layer 304 is formed on a transparent substrate 314. In the present invention, the underlayer 304 can be formed by a conventional method such as sputtering, vapor deposition, or ion plating. Next, a silver thin film layer 306 is formed (FIG. 4B). The silver thin film layer can be formed by various methods like the underlayer. In the present invention, the underlayer and the silver thin film layer can be formed using, for example, a vapor deposition method such as resistance heating vapor deposition or an electron beam vapor deposition method, or a sputtering method such as a DC magnetron sputtering method. When the underlayer is formed using resistance heating vapor deposition or electron beam vapor deposition, the silver thin film layer is preferably formed continuously while maintaining a vacuum state.

The underlayer and the silver thin film layer are patterned in a stripe shape as necessary. For this patterning, for example, the above evaporation method may be applied through a mask capable of forming a desired pattern.
The underlayer of the laminated transparent conductive film of the organic EL device of the present invention is formed on the side close to the substrate. That is, it is necessary to form an underlayer prior to the silver thin film layer. By doing in this way, a silver thin film layer is formed uniformly and the transmittance | permeability of an electrode can be improved. Moreover, the conditions for forming the laminated transparent conductive film by applying resistance heating vapor deposition or electron beam vapor deposition are not particularly limited as long as the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer. For example, in resistance heating thermal evaporation, the heating power is adjusted according to the target film thickness, the crucible temperature is heated above the melting point of the metal material to be formed, and the evaporation rate is controlled to form the metal film with the target film thickness. To do. In the case of electron beam evaporation, the evaporation rate is controlled by adjusting the current value of the electron gun. For a target film thickness of 0.1 nm to 4 nm, the deposition rate is preferably 0.05 to 1 cm / s, for example, from the balance of film thickness controllability and productivity. The degree of vacuum in the vapor deposition chamber before vapor deposition is preferably evacuated to 2 × 10 ⁻⁵ Pa or less, and the degree of vacuum during vapor deposition is desirably on the order of 10 ⁻⁵ Pa. In the case of sputtering, for example, an inline DC magnetron sputtering apparatus is used to adjust the discharge pressure, the discharge power, and the substrate transport speed by using Ar as the underlying layer metal target and Ar as the discharge gas. A base layer having a thickness can be formed.

Next, the formation of the organic EL layer 310 in the step (b) shown in FIG. 4C and the formation of the second electrode 312 in the step (c) shown in FIG.
Step (b) is a step of forming the organic EL layer 310 on the first electrode. The organic EL layer 310 has the above-described configuration, and each of the constituent layers can be formed using any means known in the art such as resistance heating vapor deposition.

  Step (c) is a step of forming the second electrode 312 on the organic EL layer 310. The second electrode can be formed by any method known in the art such as a vapor deposition method and a sputtering method using the above-described materials. However, in order to reduce damage to the organic EL layer, the second electrode can be formed. It is preferable to use a low energy film formation method in which the energy of the film particles is about 1 eV or less. When the second electrode is formed as a plurality of stripe patterns, the second electrode can be formed by the above method through a mask or the like in a direction orthogonal to the first electrode.

  In addition, when using the laminated transparent conductive film of the present invention as the second electrode, the second electrode may be formed in the same manner as the first electrode forming method described above (FIG. 4E). In order to mitigate damage to the formed organic EL layer, a low energy film formation method having energy of about 1 eV or less is preferable. For example, it is preferable to apply resistance heating vapor deposition or electron beam vapor deposition. In the case of forming a plurality of second electrodes, resistance heating vapor deposition or electron beam vapor deposition may be applied through a mask to form a pattern in a direction perpendicular to the first electrodes.

In the first embodiment, the conventional conditions can be used as they are as the conditions for forming the organic EL layer and the second electrode (when formed with a material other than the silver thin film layer).
Next, a method for manufacturing a top emission type organic EL element according to the second embodiment will be described. The manufacturing method includes (i) a step of forming a first electrode on a substrate, (ii) a step of forming an organic EL layer on the first electrode, and (iii) a second electrode transparent on the organic EL layer. The second electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film comprises The step of forming the second electrode formed on the side close to the substrate and having a thickness of the underlayer thinner than the thickness of the silver thin film layer is performed by resistance heating vapor deposition or electron beam vapor deposition. The method is characterized in that the film is continuously formed while being maintained. Here, in the organic EL element, the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer. It is manufactured to have an optical distance that constitutes a microresonator.

The manufacturing method of the second embodiment will be described with reference to FIG. FIG. 5 shows an example of manufacturing a top emission type passive organic EL element.
First, as shown in FIG. 5A, the first electrode 308 is formed on the substrate 302 in the step (i), and the organic EL layer 310 is formed in the step (ii).
In step (i), a first electrode 308 is formed on the substrate 302. The first electrode can be formed by any method known in the art such as a vapor deposition method and a sputtering method using the above-described materials. When the first electrode is formed as a plurality of stripe patterns, the first electrode may be formed by the above method through a mask or the like, or an electrode material is formed on the entire surface of the substrate and photolithography is performed. A desired pattern may be formed by a method.

Next, the organic EL layer 310 is formed in step (ii). In this step, the organic EL layer 310 is formed on the first electrode 308. The organic EL layer 310 has the above-described configuration, and each of the constituent layers can be formed using any means known in the art such as resistance heating vapor deposition.
Next, as shown in FIGS. 5B and 5C, the second electrode 312 is formed on the organic EL layer 310 in the step (iii). The second electrode includes a base layer 304 and a silver thin film layer 306. First, the base layer 304 is formed (FIG. 5B). The underlayer 304 can be formed by any method known in the art such as a vapor deposition method or a sputtering method. For example, in order to reduce damage to the already formed organic EL layer, a film is formed. It is preferable to use a low energy film formation method in which the energy of the particles is about 1 eV or less. For example, resistance heating vapor deposition or electron beam vapor deposition can be used. Next, a silver thin film layer 306 is formed (FIG. 5C). As the film formation method, the film can be formed by various methods as in the case of the base layer. However, in order to reduce damage to the already formed organic EL layer, for example, the energy of the film formation particles is as low as about 1 eV or less. It is preferable to use an energy film formation method. For example, resistance heating vapor deposition or electron beam vapor deposition can be used. In the case of using resistance heating vapor deposition or electron beam vapor deposition, the silver thin film layer is preferably formed continuously while maintaining the vacuum state when the underlayer is formed.

The underlayer and the silver thin film layer are patterned in a stripe shape as necessary. For this patterning, for example, through a mask that can form a desired pattern (for example, when formed as a plurality of stripe patterns, the second electrode is patterned in a direction perpendicular to the first electrode). The above evaporation method may be applied.
When the laminated transparent conductive film of the present invention is used as the first electrode 308, the first electrode may be formed in the same manner as the organic EL element forming method of the first embodiment described above (FIG. 5). (D)). In the case of forming a plurality of first electrodes, resistance heating vapor deposition or electron beam vapor deposition may be applied through a mask to form a pattern in a direction orthogonal to the second electrode.

The underlayer of the laminated transparent conductive film of the organic EL device of the present invention is formed on the side close to the substrate. That is, it is necessary to form an underlayer prior to the silver thin film layer. By doing in this way, a silver thin film layer is formed uniformly and the transmittance | permeability of an electrode can be improved. Moreover, the conditions for forming the laminated transparent conductive film by applying resistance heating vapor deposition or electron beam vapor deposition are not particularly limited as long as the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer. For example, in resistance heating thermal evaporation, the heating power is adjusted according to the target film thickness, the crucible temperature is heated above the melting point of the metal material to be formed, and the evaporation rate is controlled to form the metal film with the target film thickness. To do. In the case of electron beam evaporation, the evaporation rate is controlled by adjusting the current value of the electron gun. For a target film thickness of 0.1 nm to 4 nm, the deposition rate is preferably 0.05 to 1 cm / s, for example, from the balance of film thickness controllability and productivity. The degree of vacuum in the vapor deposition chamber before vapor deposition is preferably evacuated to 2 × 10 ⁻⁵ Pa or less, and the degree of vacuum during vapor deposition is desirably on the order of 10 ⁻⁵ Pa.

  Although FIG. 5 shows an example of manufacturing a passive organic EL element, the present invention includes an active organic EL element. In this case, a substrate 302 including at least a support substrate and a switching element may be formed as the substrate 302 in the step (i). The switching element may have any structure known in the art, such as TFT and MIM. The switching element can be formed by any known method. Optionally, a planarization insulating film that covers the switching element and planarizes the upper surface thereof may be formed except for a terminal portion that connects the switching element and the first electrode. The planarization insulating film can be formed using any material and method known in the art.

In the second embodiment, the conventional conditions can be used as they are as the conditions for forming the organic EL layer and the first electrode (when formed with a material other than the silver thin film layer).
In both the first embodiment and the second embodiment, the resonator length of the microresonator structure can be determined in the same manner as the method described in the first aspect.

Hereinafter, the present invention will be described in detail with reference to experimental examples and examples.
(Experimental example 1)
This experimental example is an example of a transparent conductive film laminate in which an aluminum (Al) layer is formed as a base layer on a glass substrate and silver (Ag) is formed as a silver thin film layer on the base layer.
Using a glass substrate (length 50 mm × width 50 mm × thickness 0.7 mm; Corning 1737 glass), an underlayer (Al) is formed with a resistance heating vapor deposition apparatus to a thickness of 1 nm at a film formation rate of 0.5 mm / s. Thus, Ag was formed to a thickness of 10 nm at a deposition rate of 1 Å / s. Degree of a vacuum of the deposition chamber at this time was ^{3 × 10 -5 Pa~8 × 10 -5} Pa.
(Comparative Experimental Example 1)
An electrode composed of a silver thin film layer was produced in the same manner as in Experimental Example 1 except that no underlayer was provided on the glass substrate.
(Evaluation methods)
The transmittance of the obtained transparent conductive film laminate was measured by the following procedure.

<Measurement of transmittance>
The transmittance was measured using UV-2100PC (manufactured by Shimadzu Corporation) using only the glass substrate of the same lot as the glass substrate used in Examples and Comparative Examples as a reference.
The measurement results are shown in FIG. As shown in FIG. 6, in the electrode laminate of the present invention, the transmittance increased over the entire visible light region.
(Experimental example 2)
This experimental example is an example of a transparent conductive film laminate in which α-NPD is formed on a glass substrate, and an Al layer as a base layer and an Ag layer as a silver thin film layer are formed on the α-NPD.

Using a glass substrate (length 50 mm × width 50 mm × thickness 0.7 mm; made by Corning Corporation 1737 glass), 4,4′-bis [N- (1-naphthyl) -N-phenyl A layer composed of amino] biphenyl (α-NPD) was formed to a thickness of 200 nm at a film formation rate of 3 Å / s. The degree of vacuum in the vapor deposition chamber at this time was about 10 ⁻⁵ Pa. Next, without breaking the vacuum, the underlayer (Al) was formed with a resistance heating vapor deposition apparatus at a film formation rate of 0.5 nm / s to 1 nm, and subsequently, Ag was formed at a film formation rate of 1 mm / s to 10 nm. Degree of a vacuum of the deposition chamber at this time was ^{3 × 10 -5 Pa~8 × 10 -5} Pa.
(Comparative Experimental Example 2)
An electrode composed of an α-NPD layer and a silver thin film layer was produced in the same manner as in Experimental Example 2 except that no underlayer was provided.

The transmittance of the prepared sample was measured according to the evaluation method described in Experimental Example 1. The measurement results are shown in FIG. As shown in FIG. 7, in the electrode laminate of the present invention, the transmittance increased over the entire visible light region.
(Experimental example 3)
In this experimental example, α-NPD is formed on a glass substrate, an Al layer as an underlayer and an Ag layer as a silver thin film layer are formed on the α-NPD, and an oxide transparent on the silver thin film layer. It is an example of the transparent conductive film laminated body in which the electrically conductive film (IZO) was formed.

Using a glass substrate (length 50 mm × width 50 mm × thickness 0.7 mm; made by Corning Corporation 1737 glass), 4,4′-bis [N- (1-naphthyl) -N-phenyl A layer composed of amino] biphenyl (α-NPD) was formed to a thickness of 200 nm at a film formation rate of 3 Å / s. The degree of vacuum in the vapor deposition chamber at this time was about 10 ⁻⁵ Pa. Next, without breaking the vacuum, an underlying layer (Al) was formed with a resistance heating vapor deposition apparatus to a thickness of 1 nm at a film formation rate of 0.5 Å / s, and then Ag was formed to a thickness of 10 nm at a film formation rate of 1 Å / s. Degree of a vacuum of the deposition chamber at this time was ^{3 × 10 -5 Pa~8 × 10 -5} Pa. Next, an IZO film was formed by DC magnetron sputtering (discharge gas: Ar + 0.5% O ₂ , discharge pressure: 0.3 Pa, discharge power: 1.45 W / cm ² , substrate transport speed 81 mm / min).
(Comparative Experiment 3)
An electrode composed of an α-NPD layer, a silver thin film layer, and an IZO layer was produced in the same manner as in Experimental Example 3 except that no underlayer was provided.

The transmittance of the prepared sample was measured according to the evaluation method described in Experimental Example 1. The measurement results are shown in FIG. As shown in FIG. 8, in the electrode laminate of the present invention, the transmittance increased over the entire visible light region.
(Experimental example 4)
This experimental example is an example of a top emission type organic EL element having the following two types of layer structures on a glass substrate.

(Sample 1)
Ag / Au / hole injection layer / hole transport layer / light emitting layer / electron transfer layer / electron injection layer / lower electrode (cathode) / glass substrate (Sample 2)
IZO / Ag / Au / hole injection layer / hole transport layer / light emitting layer / electron transfer layer / electron injection layer / lower electrode (cathode) / glass substrate (Preparation of sample 1)
Using a glass substrate (50 mm × 50 mm × thickness 0.7 mm; Corning 1737 glass), DC magnetron sputtering method (film formation condition: target Cr ₃ B; discharge gas Ar; discharge pressure 0.3 Pa; discharge power 0. 68 W / cm ² ), the lower electrode material (CrB) as the first electrode was formed to a thickness of 100 nm.

  Next, a photoresist (product name: TFR-1150, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is spin-coated on the CrB film, pre-baked in a clean oven maintained at 80 ° C. for 30 minutes, and then a photomask having a 2 mm wide electrode pattern shape. Was developed with a high pressure mercury lamp and developed with a developer (NMD-3, manufactured by Tokyo Ohka Kogyo Co., Ltd.). Thereafter, post-baking was performed for 30 minutes in a clean oven maintained at 90 ° C. to form a photoresist pattern having an electrode pattern shape. The sample was rocked in an etching solution for Cr at room temperature (product name: HY solution, manufactured by Wako Pure Chemical Industries, Ltd.) for 5 minutes to etch unnecessary CrB film, and stripping solution (product name: 104, Tokyo Ohka Kogyo Co., Ltd.). The resist was peeled off, and rinsed with pure water and dried with a rinser drier to form a CrB lower electrode having a width of 2 mm.

Next, an organic EL layer was formed as follows. The organic EL layer was formed through a metal shadow mask and formed in a 24 mm × 24 mm region at the center of the glass substrate.
First, a vapor deposition crucible containing an aluminum quinolinol complex (Alq ₃ ) and a Li alkali dispenser (manufactured by SAES Getters) are placed in a resistance heating vapor deposition vacuum chamber, and heated at the same time to obtain a mole of Alq ₃ : Li = 1: 1. An electron injection layer having an Alq ₃ : Li co-deposited film with a ratio of 10 nm was formed. Subsequently, only 10 nm of Alq ₃ was deposited as an electron transport layer. A light-emitting layer made of 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi) was formed to a thickness of 30 nm on the electron transport layer. On this light emitting layer, a hole transport layer composed of 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD) was formed to 20 nm, and 4,4 ′ ′ was formed on the hole transport layer. , 4 ″ -tris (3-methylphenylphenylamino) -triphenylamine (m-MTDATA) was formed by vacuum deposition in the same manner as Alq ₃ in order of 70 nm. The vapor deposition rates of the organic layer deposition from the electron injection layer to the hole injection layer were all 1 Å / s, and the degree of vacuum in the vapor deposition chamber at this time was on the order of 10 ⁻⁵ Pa.

Next, using a metal shadow mask for a second electrode having an electrode pattern shape opening with a width of 2 mm perpendicular to the first electrode (lower electrode), resistance heating vapor deposition is performed on the hole injection layer (during vapor deposition). The degree of vacuum is 5 × 10 ^{−5 to} 7 × 10 ⁻⁵ Pa, the deposition rate is 0.1 Å / s, and the underlayer (Au) is formed to 0.5 nm, and then silver (Ag) is heated by resistance to 20 nm on the underlayer. A second electrode (upper electrode) was formed by vapor deposition (vacuum degree during vapor deposition: 5 × 10 ^{−5 to} 6 × 10 ⁻⁵ Pa, vapor deposition rate: 1.0 kg / s).

  Subsequently, the sample was transferred to a nitrogen-substituted dry box, and sealed therein using a sealing glass plate (length 41 mm × width 41 mm × thickness 1.1 mm, OA-10 manufactured by Nippon Electric Glass). Sealing was performed by applying an epoxy adhesive to the vicinity of the four sides of the sealing glass plate, and attaching the sample to the sample so as to cover the organic EL layer, thereby obtaining Sample 1. During the film forming process after the organic EL layer and when transporting to the dry box after forming the second electrode, each process was performed so that the sample was not exposed to the atmosphere.

(Preparation of sample 2)
The silver thin film layer is formed in the same manner as the sample 1 is obtained, and then a DC magnetron sputtering method (discharge gas: Ar + 0.5% O ₂ , discharge is performed thereon via a metal shadow mask for the second electrode. IZO was deposited at a pressure of 0.3 Pa, discharge power of 1.45 W / cm ² , and a substrate transfer speed of 81 mm / min. The obtained sample was sealed so as to cover the organic EL layer in the same manner as the procedure described in the preparation of Sample 1 to obtain Sample 2.
(Comparative Experimental Example 4)
Each layer up to the hole injection layer was formed in the same manner as the sample 1 was obtained. Next, using a metal shadow mask for the second electrode on the hole injection layer, a silver (Ag) film was formed by 20 nm resistance heating vapor deposition without providing a base layer to form a second electrode (upper electrode). did. Thereafter, sealing was performed so as to cover the organic EL layer in the same manner as Sample 1, and Sample 3 was obtained.

(Evaluation)
Since the organic EL elements of Samples 1 to 3 prepared in Experimental Example 4 and Comparative Experimental Example 4 have the opaque first metal electrode (100 nm CrB), the transmittance cannot be compared. Therefore, the current efficiency value and the emission spectrum of these samples were measured and used as evaluation results.

The emission spectra of Sample 1, Sample 2 and Sample 3 at a current density of 10 mA / cm ² are shown in FIG. Samples 1 and 2 having the second electrode with high transparency obtained blue-green light emission, but sample 3 had a strong effect of multiple interference because the transparency of the second electrode was low, and a completely different spectrum was obtained. It has been.
The current efficiencies at this time were 6.8 cd / A, 7.4 cd / A, and 5.4 cd / A for Sample 1, Sample 2, and Sample 3, respectively. High luminous efficiency was obtained with sample 2).
Example 1
The present embodiment is an example of a top emission type organic EL element in which a microresonator structure is formed by first and second electrodes.

The layer structure of the sample is
Ag / Al / hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer / first electrode (cathode) / glass substrate.
(Sample adjustment)
Using a glass substrate (50 mm × 50 mm × thickness 0.7 mm; Corning 1737 glass), DC magnetron sputtering method (film formation conditions: target product name APC-TR, Furuya Metals Co., Ltd. Ag alloy; discharge gas Ar Discharge pressure 0.5 Pa; discharge power 0.58 W / cm ² ) to form a first electrode lower electrode material (Ag alloy) of 100 nm.

  Next, a photoresist (product name: TFR-1150, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is spin-coated on the silver alloy film, prebaked in a clean oven maintained at 80 ° C. for 30 minutes, and then an electrode pattern having a width of 2 mm. Using a mask, exposure with a high pressure mercury lamp and development with a developer (NMD-3, manufactured by Tokyo Ohka Kogyo Co., Ltd.) were performed. Thereafter, post-baking was performed for 30 minutes in a clean oven maintained at 90 ° C. to form a photoresist pattern having an electrode pattern shape. The sample was shaken for 20 seconds in an etching solution (product name: SEA2, manufactured by Kanto Chemical Co., Ltd.) maintained at 22 ° C., and an unnecessary silver alloy film was etched to remove the stripping solution (product name: stripping solution 104, Tokyo). The resist was peeled off by Oka Kogyo Co., Ltd., rinsed with pure water, and dried with a rinser dryer to form a silver alloy first electrode (lower electrode) having a width of 2 mm.

Next, an organic EL layer was formed as follows. The organic EL layer was formed through a metal shadow mask and formed in a 24 mm × 24 mm region at the center of the glass substrate.
First, a vapor deposition crucible containing an aluminum quinolinol complex (Alq ₃ ) and a Li alkali dispenser (manufactured by SAES Getters) are placed in a resistance heating vapor deposition vacuum chamber, and heated at the same time to obtain a mole of Alq ₃ : Li = 1: 1. An electron injection layer having an Alq ₃ : Li co-deposited film with a ratio of 10 nm was formed. Subsequently, only 10 nm of Alq ₃ was deposited as an electron transport layer. On the electron transport layer, a light-emitting layer host composed of 9,10-di (2-naphthyl) anthracene (ADN), and 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi) as a light-emitting dopant A light emitting layer added with 3 vol% was 30 nm, and a hole transport layer made of 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD) was formed on the light emitting layer at a thickness of 20 nm. 4,4 ', 4 "-Tris {2-naphthyl (phenyl) amino} triphenylamine (2-TNATA) and 2,3,5,6-tetrafluoro-7,7,8,8- on the hole transport layer A co-deposited film of tetracyanoquinodimethane (F ₄ -TCNQ) was formed by vacuum deposition in the same manner as Alq ₃ in order of 120 nm so that the film thickness ratio was 2-TNATA: F ₄ -TCNQ = 100: 2. Membrane . Evaporation rate of the organic layer deposition other than the dopant from the electron injection layer to the hole injection layer was performed in all 1 Å / s, the degree of vacuum in the deposition chamber at this time was 10 -5 ^Pa stand.

Next, using a metal shadow mask for a second electrode having an electrode pattern shape opening with a width of 2 mm perpendicular to the first electrode (lower electrode), resistance heating vapor deposition is performed on the hole injection layer (during vapor deposition). The degree of vacuum is 5 × 10 ^{−5 to} 7 × 10 ⁻⁵ Pa, the deposition rate is 0.1 Å / s, and the underlayer (Al) is formed to have a thickness of 0.5 nm. A second electrode (upper electrode) was formed by vapor deposition (vacuum degree during vapor deposition: 5 × 10 ^{−5 to} 6 × 10 ⁻⁵ Pa, vapor deposition rate: 1.0 kg / s).

Subsequently, the sample was transferred to a nitrogen-substituted dry box, and sealed therein using a sealing glass plate (length 41 mm × width 41 mm × thickness 1.1 mm, OA-10 manufactured by Nippon Electric Glass). Sealing is performed by applying an epoxy adhesive in which spacer beads having a diameter of 10 μm are dispersed to the vicinity of the four sides of the sealing glass plate, and affixing the sample to the sample so as to cover the organic EL layer. Obtained. During the film forming process after the organic EL layer and when transporting to the dry box after forming the second electrode, each process was performed so that the sample was not exposed to the atmosphere.
(Comparative Example 1)
Each layer up to the hole injection layer was formed in the same manner as the procedure for obtaining Example 1. Next, using a metal shadow mask for the second electrode on the hole injection layer, a silver (Ag) film is formed by resistance heating vapor deposition without providing an underlayer, and a second electrode (upper electrode) is formed. did. Thereafter, sealing was performed so as to cover the organic EL layer in the same manner as in Example 1 to obtain an organic EL element.

(Evaluation)
Since the organic EL elements produced in Example 1 and Comparative Example 1 have an opaque metal first electrode (100 nm silver alloy), the transmittance cannot be compared. Therefore, the current efficiency value and the emission spectrum of these samples were measured and used as evaluation results.
The emission spectra of Example 1 and Comparative Example 1 at a current density of 10 mA / cm ² are shown in FIG. In both Example 1 and Comparative Example 1, the half-value width of the emission spectrum is narrow due to the microresonator effect, but Example 1 having the second electrode with high transparency has higher peak intensity than Comparative Example 1. Yes. This is because the second electrode of Comparative Example 1 absorbs more visible light than the second electrode of Example 1.

The current efficiency at this time is 4.9 cd / A and 3.9 cd / A in Example 1 and Comparative Example 1, respectively, and a high luminous efficiency is obtained with the organic EL device (Example 1) according to the present invention. It was.
Thereby, the effect by using the electrode by the laminated silver thin film by this invention was shown also in the case of the organic EL element which has the microresonator structure which used the electrode which consists of a silver thin film as a transflective electrode.

100 Transparent conductive film laminate 102, 302 Substrate 104, 304 Underlayer 106, 306 Silver thin film layer 108 Oxide transparent conductive film 110 Support substrate 112 Semiconductor thin film 300 Organic EL element 308 First electrode 310 Organic EL layer 312 Second electrode 314 Transparent substrate

Claims (10)

  An organic EL element comprising at least a substrate, a first electrode provided on the substrate, an organic EL layer provided on the first electrode, and a second electrode provided on the organic EL layer. The first electrode or the second electrode, or both of them, is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, An underlayer is provided on the side close to the substrate, and the thickness of the underlayer is smaller than the thickness of the silver thin film layer, and the reflective surface formed by the first electrode and the reflective surface formed by the second electrode An organic EL element characterized in that the distance between them is an optical distance that constitutes a microresonator that enhances the light intensity of a specific wavelength among the light emitted from the organic EL layer.   The organic EL element according to claim 1, further comprising an oxide transparent conductive film provided on the silver thin film layer.   The organic EL element according to claim 1 or 2, wherein the thickness of the underlayer is 0.1 nm to 4 nm.   4. The organic EL device according to claim 1, wherein the silver thin film layer has a thickness of 5 nm to 30 nm.   5. The organic EL element according to claim 1, wherein a metal other than silver of the underlayer is selected from the group consisting of gold, aluminum, copper, indium, tin, and zinc. (A) forming a transparent first electrode on a transparent substrate;
(B) forming an organic EL layer on the first electrode;
(C) including at least a step of forming a second electrode on the organic EL layer;
The first electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film is formed on a side close to the substrate. And the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the first electrode is continuously formed by resistance heating vapor deposition or electron beam vapor deposition while maintaining a vacuum state. And the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode further increases the light intensity of a specific wavelength among the light emitted from the organic EL layer. A method of manufacturing an organic EL element, wherein the optical distance is such that   The second electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film is formed on the side close to the substrate And the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the second electrode is continuously formed while maintaining the vacuum state by resistance heating vapor deposition or electron beam vapor deposition. The method for producing an organic EL element according to claim 6, wherein: (I) forming a first electrode on the substrate;
(Ii) forming an organic EL layer on the first electrode;
(Iii) including at least a step of forming a transparent second electrode on the organic EL layer;
The second electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film is formed on the side close to the substrate And the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the second electrode is continuously formed while maintaining the vacuum state by resistance heating vapor deposition or electron beam vapor deposition. And the distance between the reflective surface formed by the first electrode and the reflective surface formed by the second electrode further increases the light intensity of a specific wavelength among the light emitted from the organic EL layer. A method of manufacturing an organic EL element, wherein the optical distance is such that   The first electrode is a laminated transparent conductive film comprising a base layer made of a metal other than silver and a silver thin film layer made of silver or a silver alloy, and the base layer of the laminated transparent conductive film is formed on a side close to the substrate. And the film thickness of the underlayer is formed thinner than the film thickness of the silver thin film layer, and the step of forming the first electrode is continuously formed by resistance heating vapor deposition or electron beam vapor deposition while maintaining a vacuum state. The method for producing an organic EL element according to claim 8, wherein:   (Iv) The method for producing an organic EL element according to claim 8, further comprising the step of further forming an oxide transparent conductive film on the silver thin film layer.

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