JP2013084554A - Organic el element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element which allows film formation while suppressing damage to an organic light-emitting layer when a transparent electrode is formed in a cathode by a sputtering method, and to provide a method for manufacturing the same.SOLUTION: The method for manufacturing the organic EL element forms a first electrode (anode) 3, a light-emitting medium layer 5, and a second electrode (cathode) 6 in this order on a substrate 2. In forming the second electrode (cathode) 6, a first transparent electrode 10 made of a conductive metal oxide is formed on the light-emitting medium layer 5 by a vapor deposition method, and then a second transparent electrode 11 made of a conductive metal oxide is formed on the first transparent electrode 10 by a sputtering method.

Description

The present invention relates to an organic EL element utilizing an EL (electroluminescence) phenomenon of an organic thin film and a method for manufacturing the same.

An organic EL element has a structure in which an organic light emitting layer exhibiting at least an EL phenomenon is sandwiched between an electrode as an anode and an electrode as a cathode, and when a voltage is applied between the electrodes (anode and cathode), Holes and electrons are injected into the organic light emitting layer, and the holes and electrons are recombined in the organic light emitting layer, whereby the organic light emitting layer emits light.
In such an organic EL element, for the purpose of increasing luminous efficiency, a functional layer is provided between at least one of the anode and the organic light emitting layer and between the organic light emitting layer and the cathode. Between the anode and the organic light emitting layer, at least one of a hole injection layer and a hole transport layer is provided as the functional layer, and between the organic light emitting layer and the cathode, an electron transport is provided as the functional layer. At least one of the layer and the electron injection layer is provided, and these are appropriately selected and provided.

Each layer provided as a functional layer between the anode and the organic light emitting layer or between the organic light emitting layer and the cathode is formed of an organic material or an inorganic material. Here, the organic material includes a low molecular material and a high molecular material.
Examples of using low molecular weight materials include, for example, copper phthalocyanine (CuPc) for the hole injection layer and N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1 for the hole transport layer. , 1'-biphenyl-4,4'diamine (TPD), tris (8-quinolinol) aluminum (Alq3) for the organic light emitting layer, 2- (4-biphenylyl) -5- (4-tert-butyl for the electron transport layer -Phenyl) -1,3,4, -oxadizole (PBD), and those using LiF for the electron injection layer.
Each layer made of these low molecular materials generally has a thickness in the range of 0.1 nm to 200 nm, and is mainly a vacuum deposition method such as a resistance heating method or a dry method (dry process) in a vacuum such as a sputtering method. ).
In addition, since there are a wide variety of low molecular weight materials, the combination is expected to improve luminous efficiency, luminous luminance, lifetime, and the like.

On the other hand, examples of the polymer material include a material obtained by dissolving a low-molecular light-emitting dye in a polymer such as polystyrene, polymethyl methacrylate, and polyvinyl carbazole in an organic light-emitting layer, or a polyphenylene vinylene derivative (hereinafter also referred to as PPV). ), Polymer phosphors such as polyalkylfluorene derivatives (hereinafter also referred to as PAF), and polymer phosphors such as rare earth metals.

These polymer materials are generally dissolved or dispersed in a solvent and formed into a film having a thickness in the range of 1 nm to 100 nm by using a wet method such as coating or printing.
When using the wet method as described above, it is possible to form a film in the atmosphere, the equipment is inexpensive, and the size can be easily increased compared to the case where a dry method in vacuum such as a vacuum deposition method is used. There is an advantage that the film can be formed efficiently in a short time.

In addition, the organic thin film formed using a polymer material is less likely to crystallize and agglomerate, and further covers pinholes and foreign materials in other layers, thus preventing defects such as short circuits and dark spots. There are also advantages.
When an organic light emitting medium layer including an organic light emitting layer is formed by a wet coating method using a coating material of a polymer material, the organic light emitting layer is red (R), green (G), blue ( It is necessary to coat the organic light-emitting materials having the respective emission colors of B) separately using an organic light-emitting ink obtained by dissolving or stably dispersing in an organic solvent.

For the anode and the cathode, a reflective electrode such as Al or Ag or a transparent electrode made of a conductive metal oxide such as ITO (indium tin composite oxide) or IZO (indium zinc composite oxide) is used. As a general organic EL element, there is a bottom emission method in which a transparent electrode is used for the anode, a reflective electrode is used for the cathode, and light is extracted from the substrate side.
On the other hand, in recent years, due to improvements in luminous efficiency and applications, a reflective electrode is used for the anode, a transparent electrode is used for the cathode, light is extracted from the opposite side of the substrate, and a transparent electrode is used for both the anode and cathode. Transparent EL elements that extract light from the light have been developed.

And when forming a transparent electrode using this conductive metal oxide, it can be formed with a stable film quality without substantially changing the composition of the film forming material, and a film of a refractory metal or a compound can be formed. Furthermore, the mainstream is to use a sputtering method in which a reactive gas such as oxygen is introduced to form an oxide film.
However, when a transparent electrode is formed on the cathode as in the top emission method or the transparent EL element, the sputtering method is used to cause a problem that Ar plasma or γ electrons collide with the organic light emitting layer and cause damage. Introducing oxygen gas into the chamber to form a film causes the organic light emitting layer to react with oxygen and deteriorate.

Therefore, as a solution for reducing damage to the organic light emitting layer, for example, there is a technique described in Patent Document 1. In this technique, a protective electrode layer is formed on an organic light emitting layer by resistance heating vapor deposition, and a transparent electrode is formed on the protective electrode by dielectric bonding sputtering. Here, a method has been proposed in which the protective electrode layer is formed of an alkali metal or alkaline earth metal alloy or mixture.

JP 11-162652 A

However, in the technique described in Patent Document 1, since the protective electrode layer also functions as an electron injection layer, the protective electrode layer has a thickness of 5 nm to 5 nm in consideration of the carrier balance with holes. It can be selected only within the range of 20 nm. Therefore, there is a possibility that it does not function as a protective film for sufficiently reducing sputter damage.
Accordingly, the present invention has an object to provide an organic EL element capable of forming a film while suppressing damage to the organic light emitting layer when a transparent electrode is formed on the cathode by sputtering, and a method for manufacturing the same. Yes.

In order to solve the above problems, a method of manufacturing an organic EL element according to claim 1 includes a step of forming a first electrode on a substrate and a light emitting medium layer including an organic light emitting layer on the first electrode. And a step of forming a second electrode on the luminescent medium layer, wherein the step of forming the second electrode is conducted on the luminescent medium layer by vapor deposition. Forming a first transparent electrode made of a conductive metal oxide, and forming a second transparent electrode made of a conductive metal oxide on the first transparent electrode by sputtering or ion plating. It is characterized by providing.

According to a second aspect of the present invention, there is provided a method for manufacturing an organic EL element according to the first aspect of the present invention, wherein the vapor deposition method is any one of a resistance heating method and an electron beam vapor deposition method, and the sputtering method is a magnetron. Either the sputtering method or the opposed target sputtering method is used, and the ion plating method includes any one of a resistance heating method and an electron beam method, a direct current excitation type, and a high frequency excitation type sputtering. It is characterized by using a combination of laws.
Furthermore, the manufacturing method of the organic EL element according to claim 3 is the invention according to claim 1 or 2, wherein the transmittance of the first transparent electrode and the second transparent electrode is 70% or more, and the second transparent electrode The transmittance of the electrode is higher than that of the first transparent electrode.

According to a fourth aspect of the present invention, in the method for manufacturing an organic EL element, in the invention according to any one of the first to third aspects, the step of forming the light emitting medium layer forms a hole injection layer on the first electrode. And a step of forming the organic light emitting layer on the hole injection layer, and a step of forming an electron injection layer on the organic light emitting layer.
Furthermore, the method for manufacturing an organic EL element according to claim 5 further includes a step of forming a reflective electrode between the substrate and the first electrode in the invention according to any one of claims 1 to 4. It is characterized by.

Moreover, the manufacturing method of the organic EL element which concerns on Claim 6 forms the at least 1 layer among the layers which the said luminescent medium layer contains in the invention which concerns on any one of Claims 1-5 by a wet process method. It is characterized by.
Furthermore, an organic EL element according to a seventh aspect is characterized by being manufactured using the method for manufacturing an organic EL element according to any one of the first to sixth aspects.

According to the present invention, when forming the second electrode, which is a transparent electrode made of a conductive metal oxide, on the light emitting medium layer including the organic light emitting layer, the first vapor deposition method does not damage the organic light emitting layer. After forming the transparent electrode, a second transparent electrode is formed thereon by sputtering. In this manner, by forming the first transparent electrode between the light emitting medium layer and the second transparent electrode, Ar plasma or γ electron damage to the organic light emitting layer by the sputtering method, or deterioration due to reaction with oxygen can be prevented. Can be suppressed.

As a result, it is possible to provide an organic EL element having improved light extraction efficiency from the opposite side to the substrate in the top emission method and from both sides in the transparent EL element.

It is sectional drawing which shows schematic structure of the organic EL element in this embodiment. It is sectional drawing which shows the detailed structure of a board | substrate. It is a figure which shows schematic structure of the relief printing apparatus used for a relief printing method.

(First embodiment)
Hereinafter, a configuration of an organic EL element according to the present embodiment and a method for manufacturing the organic EL element according to the first embodiment of the present invention (hereinafter referred to as “this embodiment”) will be described with reference to the drawings. .
(Constitution)
FIG. 1 is a cross-sectional view showing a schematic configuration of an organic EL element in the present embodiment.
In the figure, reference numeral 1 denotes an organic EL element. The organic EL element 1 includes a substrate 2, a first electrode 3 formed on the substrate 2, a partition wall 4 formed on the substrate 2 so as to surround the first electrode 3, and a first electrode 3 And the second electrode 6 formed on the light emitting medium layer 5.
In this embodiment, the first electrode 3 is an anode, the second electrode 6 is a cathode, the organic EL element 1 is a transparent EL element in which both the anode 3 and the cathode 6 are formed of transparent electrodes, and the organic EL element 1 is The case where an active matrix driving type organic EL element is used will be described. In this case, the anode 3 is formed as a pixel electrode partitioned by the partition 4 for each pixel, and the cathode 6 is formed as a counter electrode formed on the entire surface of the element.

Note that the configuration of the organic EL element 1 is not limited to the active matrix drive type. For example, the passive matrix drive type organic EL element in which each electrode (the anode 3 and the cathode 6) is formed in a perpendicular stripe shape. It is good.
Moreover, the organic EL element 1 can also be a top emission system in which only the cathode 6 is formed of a transparent electrode. Furthermore, a reverse structure in which the first electrode 3 is a cathode and the second electrode 6 is an anode may be employed.

(Configuration of substrate 2)
Next, a detailed configuration of the substrate 2 will be described.
FIG. 2 is a cross-sectional view showing a detailed configuration of the substrate 2. Here, the substrate 2 is described as a TFT substrate provided with a thin film transistor (TFT) 20.
As shown in FIG. 2, the TFT 20 and the anode 3 (pixel electrode) are provided on the upper surface of the substrate (support) 2, and the thin film transistor 20 and the anode 3 are electrically connected.
As the substrate 2, any material can be used as long as it has mechanical strength and insulation and is excellent in dimensional stability. For example, plastic films and sheets such as glass, quartz, polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, and polyethylene naphthalate can be used.

The material of the substrate 2 is, for example, a metal oxide such as silicon oxide or aluminum oxide, a metal fluoride such as aluminum fluoride or magnesium fluoride, silicon nitride, aluminum nitride, etc. Translucent substrate made of metal nitride, metal oxynitride such as silicon oxynitride, polymer resin film such as acrylic resin, epoxy resin, silicon resin, polyester resin, aluminum, stainless steel, etc. Metal foils, sheets, plates and the like can also be used.

Further, as the material of the substrate 2, for example, a non-translucent base material obtained by laminating a metal film such as aluminum, copper, nickel, stainless steel on the plastic film or sheet may be used. Here, the translucency of the substrate 2 may be selected according to which surface the light is extracted from.
The substrate 2 made of these materials is subjected to moisture-proofing treatment or hydrophobic treatment by forming an inorganic film or applying a fluororesin in order to avoid intrusion of moisture into the organic EL element 1. It is preferable. In particular, in order to avoid the intrusion of moisture into the light emitting medium layer 8, it is preferable to reduce the moisture content and gas permeability coefficient in the substrate 2.

As the thin film transistor 20, a known thin film transistor can be used. Specifically, a thin film transistor composed mainly of an active layer 21 in which source / drain regions and a channel region are formed, a gate insulating film 22 and a gate electrode 23 can be mentioned.
Here, the structure of the thin film transistor 20 is not limited to the above, and for example, a staggered type, an inverted staggered type, a top gate type, a coplanar type, or the like can be applied.
The configuration of the active layer 21 is not particularly limited, and for example, an inorganic semiconductor material such as amorphous silicon, polycrystalline silicon, microcrystalline silicon, cadmium selenide, thiophene oligomer, poly (p-ferri), or the like. It can be formed of an organic semiconductor material such as (lenvinylene).

The active layer 21 is formed using, for example, any of the following methods (a) to (c).
(A) A method of laminating amorphous silicon by plasma CVD and ion doping. Specifically, using SiH ₄ gas, amorphous silicon is formed by LPCVD, amorphous silicon is crystallized by solid phase growth to obtain polysilicon, and then ion doping is performed by ion implantation.
(B) Amorphous silicon is formed by LPCVD using Si ₂ H ₆ gas or PECVD using SiH ₄ gas, annealed with a laser such as an excimer laser, and amorphous silicon is crystallized to obtain polysilicon. After that, ion doping by an ion doping method (low temperature process).
(C) Polysilicon is laminated by low pressure CVD or LPCVD, thermally oxidized at 1000 [° C.] or higher to form a gate insulating film 22, and an n ⁺ polysilicon gate electrode 23 is formed thereon, and then Ion doping method (high temperature process).

As the gate insulating film 22, a film normally used as a gate insulating film can be used. That is, as the gate insulating film 22, for example, SiO ₂ formed by PECVD, LPCVD, or the like, or SiO ₂ obtained by thermally oxidizing a polysilicon film can be used.
As the gate electrode 23, those usually used as a gate electrode can be used. That is, examples of the material of the gate electrode 23 include metals such as aluminum and copper (refractory metals such as titanium, tantalum, and tungsten), polysilicon, silicides of refractory metals, polycides, and the like.

Note that the thin film transistor 20 may have a single gate structure, a double gate structure, or a multi-gate structure having three or more gate electrodes. Moreover, you may have a LDD structure and an offset structure. Further, two or more thin film transistors may be arranged in one pixel.
Moreover, the organic EL element 1 of this embodiment needs to be connected so that the thin film transistor 20 functions as a switching element of the organic EL element 1. Therefore, as shown in FIG. 2, the drain electrode 24 of the thin film transistor 20 and the anode 3 are electrically connected.
Here, reference numeral 25 is attached to the source electrode of the thin film transistor 20, reference numeral 26 is attached to the scanning line, and reference numeral 27 is attached to the transistor insulating film interposed between the thin film transistor 20, the anode 3 and the partition 4. doing.

(Configuration of anode 3)
Next, a detailed configuration of the anode 3 will be described.
The anode 3 is formed by patterning on the substrate 2 and is partitioned by the partition walls 4 to form pixel electrodes corresponding to the respective pixels. When the organic EL element 1 is a transparent EL element, the anode 3 is required to be transparent in order to extract light from the anode side. Therefore, the material of the anode 3 is ITO (indium tin composite oxide) or IZO ( Conductive metal oxides such as indium zinc composite oxide) and AZO (zinc aluminum composite oxide) are used. It is also preferable to select a material having a high work function such as ITO.

In addition, when the organic EL element 1 is a top emission type in which light is extracted from above, a highly reflective metal material (Cr, A1, Ag, Mo, W, etc.), a metal oxide, or a metal on the substrate 2 is used. After forming a single layer or a laminate of fine particle dispersion films in which fine particles of material are dispersed in an epoxy resin, an acrylic resin, or the like, the anode 3 is formed using a conductive metal oxide such as ITO or IZO. In this case, since the resistivity of the reflective electrode is lower than that of the conductive metal oxide, the reflective electrode functions as an auxiliary electrode, and reflects light emitted from the organic light-emitting layer 8 described later to the cathode 6 side to produce light. Can be used effectively.

(Configuration of partition wall 4)
Next, the detailed structure of the partition 4 is demonstrated.
The partition 4 is formed on the substrate 2 and is formed so as to partition the light emitting region corresponding to the pixel by surrounding the periphery of the anode 3.
In general, the active matrix driving type organic EL element 1 has an anode 3 formed for each pixel (sub-pixel), and each pixel tries to occupy as wide an area as possible. Therefore, the most preferable shape of the partition 4 formed so as to cover the end portion (side surface) of the anode 3 is basically a lattice shape that divides the anode 3 by the shortest distance.

Moreover, the material of the partition 4 is made to contain an ethylenically unsaturated compound, a photoinitiator, and an alkali-soluble binder at least. Furthermore, the material of the partition walls 4 preferably contains a surfactant and the like, and also contains a solvent.
The preferable height of the partition wall 4 is in the range of 0.1 μm to 10 μm, and more preferably in the range of 0.5 μm to 2 μm. The reason is that if the height of the partition 4 is too high, the formation and sealing of the cathode 6 (counter electrode) is prevented, and if the height of the partition 4 is too low, the end of the anode 3 cannot be covered, This is because, when the medium layer 5 is formed, colors are mixed with adjacent pixels.

(Configuration of the light emitting medium layer 5)
Next, a detailed configuration of the light emitting medium layer 5 will be described.
As shown in FIG. 1, the luminescent medium layer 5 is formed on the anode 3 in the partition wall 4 and is sandwiched between the anode 3 and the cathode 6. The light emitting medium layer 5 includes a hole injection layer 7 formed on the anode 3, an organic light emitting layer 8 formed on the hole injection layer 7, and an electron injection layer 9 formed on the organic light emitting layer 8. It is comprised including.
The thickness of the hole injection layer 7 is preferably in the range of 20 nm to 100 nm. This is because short-circuit defects are likely to occur when the thickness of the hole injection layer 7 is thinner than 20 nm, and when the thickness of the hole injection layer 7 exceeds 100 nm, the current is reduced due to the increase in resistance. Because.

Examples of the material for the hole injection layer 7 include polyaniline derivatives, polythiophene derivatives, polyvinylcarbazole (PVK) derivatives, poly (3,4-ethylenedioxythiophene) (PEDOT), and the like. These materials are dissolved or dispersed in a solvent, and the hole injection layer 7 is formed by using various coating methods using a spin coater or the like and a relief printing method.
Moreover, when using an inorganic material as a material of the hole injection layer 7, for example, Cu ₂ O, Cr ₂ O ₃ , Mn ₂ O ₃ , FeOx (x to 0.1), NiO, CoO, Pr ₂ O ₃ , Ag ₂ O, MoO ₂ , Bi ₂ O ₃ , ZnO, TiO ₂ , SnO ₂ , ThO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO _2, or the like is used. Then, the hole injection layer 7 is formed using a vapor deposition method or a sputtering method. However, the material is not limited to these.

The organic light emitting layer 8 is a layer that emits light by recombining holes and electrons, and is formed so as to cover the hole injection layer 7 when the display light emitted from the organic light emitting layer 8 is monochromatic. However, in order to obtain multicolor display light, it can be suitably used by performing patterning as necessary.
Examples of the organic light emitting material for forming the organic light emitting layer 8 include, for example, coumarin-based, perylene-based, pyran-based, anthrone-based, porphyrin-based, quinacridone-based, N, N′-dialkyl-substituted quinacridone-based, naphthalimide-based, N, N '-Diaryl-substituted pyrrolopyrrole, iridium complex and other luminescent dyes dispersed in polymers such as polystyrene, polymethyl methacrylate, polyvinylcarbazole, polyarylene, polyarylene vinylene and polyfluorene Examples include polymer materials. However, the material is not limited to these.

Moreover, said organic luminescent material is set as organic luminescent ink by melt | dissolving in a solvent or disperse | distributing stably.
Here, examples of the solvent for dissolving or dispersing the organic light-emitting material include toluene, xylene, acetone, anisole, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and the like, or a mixed solvent thereof. In particular, aromatic organic solvents such as toluene, xylene, and anisole are preferable from the viewpoint of the solubility of the organic light emitting material. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to the organic luminescent ink as needed.

As the electron injection layer 9, a material having high transparency, high electron injection efficiency into the organic light emitting layer 8 and a small work function is used. Specific examples of the material include alkali metal and alkaline earth metal compounds such as Ca, Cs, LiF, and BaF ₂ . The material of the electron injection layer 9, for example, as an organic material, Alq _3, and the like.
In general, the thickness of the electron injection layer 9 is preferably selected within the range of 0.1 nm or more and 50 nm or less in order to determine the optimum thickness in consideration of carrier balance.

(Configuration of cathode 6)
Next, a detailed configuration of the cathode 6 will be described.
As shown in FIG. 1, the cathode 6 includes a first transparent electrode 10 and a second transparent electrode 11. In this embodiment, since the cathode 6 is composed of a transparent electrode, the materials of the first transparent electrode 10 and the second transparent electrode 11 are ITO (indium tin composite oxide), IZO (indium zinc composite oxide), AZO. (Zinc aluminum composite oxide) and other conductive metal oxides such as SnO, IGZO, GZO, ZnO are used.

Here, the first transparent electrode 10 is formed by vapor deposition, and the second transparent electrode 11 is formed by sputtering or ion plating. The first transparent electrode 10 plays a role of protecting the sputter damage and oxygen reaction on the organic light emitting layer 8 during the formation of the second transparent electrode 11, and is a film having a transmittance of 70% or more. The second transparent electrode 11 is a film having a transmittance of 70% or higher and a higher transmittance than that of the first transparent electrode 10. Furthermore, since the second transparent electrode 11 functions as an auxiliary electrode, the specific resistance is preferably 10 ⁻³ [Ω · mm] or less.

The film thicknesses of the first transparent electrode 10 and the second transparent electrode 11 are the effects of transmittance and pinholes, the first transparent electrode 10 has a function of protecting sputter damage and oxygen reaction, and the second transparent electrode 11 has In consideration of the function as the auxiliary electrode, it is preferable that the thickness be in the range of 30 nm to 500 nm.

(About sealed body)
In the case where the organic EL element 1 is manufactured using the above-described transparent EL element, in order to extract display light radiated from the light emitting medium layer 5 through the sealing body on the side opposite to the substrate 2, , Light transparency is required.
In addition, the organic EL element 1 can emit light by sandwiching a light emitting material (light emitting medium layer 5) between electrodes (anode 3 and cathode 6) and passing an electric current. Some organic light emitting materials are easily degraded by moisture and oxygen in the atmosphere. For this reason, normally, the organic EL element 1 is provided with a sealing body (not shown) for shielding from the outside. Such a sealing body can be formed by providing a resin layer on a sealing material, for example.

As a material for the sealing material, it is necessary to use a base material having low moisture and oxygen permeability. Here, examples of the material for the sealing material include ceramics such as alumina, silicon nitride, and boron nitride, glass such as alkali-free glass and alkali glass, quartz, and a moisture-resistant film. Examples of the moisture-resistant film include a film in which SiOx is formed on both surfaces of a plastic substrate by a CVD method, a film having a low permeability and a water absorption property, or a polymer film coated with a water absorbing agent. Here, the water vapor transmission rate of the moisture resistant film is preferably 110 ⁻⁶ [g / m 2 / day] or less.

Examples of the material of the resin layer include a photo-curing adhesive resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and an ethylene ethyl acrylate (EEA) made of an epoxy resin, an acrylic resin, a silicon resin, or the like. ) Acrylic resins such as polymers, vinyl resins such as ethylene vinyl acetate (EVA), thermoplastic resins such as polyamide and synthetic rubber, and thermoplastic adhesive resins such as acid-modified products of polyethylene and polypropylene. .

Examples of the method for forming the resin layer on the sealing material include a solvent solution method, an extrusion lamination method, a melt / hot melt method, a calendar method, a nozzle coating method, a screen printing method, a vacuum laminating method, and a hot roll. The laminating method etc. can be mentioned.
In this case, it is possible to contain a hygroscopic or oxygen-absorbing material as necessary. Here, the thickness of the resin layer formed on the sealing material is arbitrarily determined depending on the size and shape of the organic EL display device to be sealed, but is preferably in the range of 5 μm to 500 μm.

In the above description, the sealing body is formed as a resin layer on the sealing material. However, the sealing body can be directly formed on the organic EL element 1 side.
The organic EL element 1 and the sealing body are bonded together in a sealing chamber.
Here, when the sealing body has a two-layer structure of a sealing material and a resin layer, and a thermoplastic resin is used for the resin layer, it is preferable to perform only pressure bonding with a heated roll. On the other hand, when a thermosetting adhesive resin is used for the resin layer, it is preferable to perform heat curing at a curing temperature after the pressure bonding with a heated roll. Moreover, when using a photocurable adhesive resin for a resin layer, after crimping | bonding with a roll, it can harden | cure by further irradiating light.

In addition, before sealing using the sealing material as described above, or instead, for example, as a passivation film, a dry process such as an EB vapor deposition method or a CVD method is used to form a silicon nitride film, alumina, or oxide. It is also possible to use a sealing body made of an inorganic thin film such as a silicon film. Moreover, it is also possible to use the sealing body which combined these.
In this case, the thickness of the passivation film described above can be in the range of 100 nm to 500 nm. In particular, the thickness of the passivation film is preferably in the range of 150 nm or more and 300 nm or less, although it depends on the moisture permeability of the material, the water vapor light permeability, and the like.
In addition, when the organic EL element 1 has the above-described top emission type structure, it is necessary to consider light transmission in addition to the above characteristics, so that the total average in the visible light wavelength region is 70 [%] or more. Any is suitable.

(Method for producing organic EL element 1)
Next, a method for manufacturing the organic EL element 1 will be described.
When manufacturing the organic EL element 1, first, an anode forming step of forming the anode 3 on the substrate 2 is performed. That is, the method for manufacturing the organic EL element 1 includes an anode forming step. In the anode forming step, the anode 3 is formed by a dry film forming method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method depending on the material of the anode 3. Can be used. In addition to the dry film forming method, the anode 3 may be formed by a gravure printing method, a wet film forming method such as a screen printing method, or the like.

Here, as the patterning method of the anode 3, an existing patterning method such as a mask vapor deposition method, a photolithography method, a wet etching method, a dry etching method, or the like can be used depending on the material of the anode 3 and the film forming method. In the case where a TFT substrate (see FIG. 2) on which TFTs are formed is used as the substrate 2, it is formed so as to be conductive corresponding to the lower pixel.
Then, after forming the anode 3 on the substrate 2, a partition formation process is performed in which the partition 4 surrounding the periphery of the anode 3 is formed on the substrate 2. That is, the method for manufacturing the organic EL element 1 includes a partition wall forming step. In the partition formation step, as a method for forming the partition 4 on the substrate 2 on which the anode 3 is formed, for example, an inorganic film is uniformly formed on the substrate 2 on which the anode 3 is formed, masked with a resist, and then dried. Examples thereof include a method of etching, and a method of laminating a photosensitive resin on the substrate 2 on which the anode 3 is formed and forming a predetermined pattern by a photolithography method.

Further, if necessary, a water repellant is added to the material of the partition walls 4 or plasma or UV is irradiated to impart liquid repellency to the ink to the partition walls 4 after the partition walls 4 are formed. You can also.
After the partition wall 4 is formed on the substrate 2 by the partition wall forming step, a light emitting medium layer forming step for forming the light emitting medium layer 5 on the anode 3 is performed. That is, the method for manufacturing the organic EL element 1 includes a light emitting medium layer forming step.

The light emitting medium layer forming step includes a hole injection layer forming step for forming the hole injection layer 7 so as to cover the anode 3 and an organic light emitting layer forming step for forming the organic light emitting layer 8 on the hole injection layer 7. And an electron injection layer forming step of forming the electron injection layer 9 on the organic light emitting layer 8.
In the hole injection layer forming step, the material of the hole injection layer 7 is dissolved or dispersed in a solvent according to the material of the hole injection layer 7, and various coating methods using a spin coater, slit coating method, spray coating, etc. A method of forming by a method, a bar coating method, a dip coating method, a relief printing method, or a method of forming by a resistance heating vapor deposition method is used.

In addition to these methods, for example, dry heating methods such as resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, and sputtering, and wet deposition such as spin coating and sol-gel methods. Existing film forming methods such as a film method can also be used.
In the organic light emitting layer forming step, an existing film forming method such as an ink jet printing method, a nozzle print printing method, a relief printing method, a gravure printing method, a screen printing method or the like is used depending on the material of the organic light emitting layer 8. Use. In particular, when the organic light emitting layer 8 is separately applied to each light emitting color using an organic light emitting ink in which an organic light emitting material is dissolved or stably dispersed in a solvent, the ink is transferred between the partition walls 4 and patterned. It is preferable to use an ink jet method, a nozzle printing method, and a relief printing method.
That is, in the organic light emitting layer forming step, an organic light emitting ink in which an organic light emitting material as a material of the organic light emitting layer 8 is dissolved or dispersed in a solvent on the hole injection layer 7 formed to cover the anode 3 is used. The organic light emitting layer 8 is patterned and formed by coating. In addition, you may form the organic light emitting layer 8 using methods other than the film-forming method mentioned above.

Hereinafter, a procedure for forming the organic light emitting layer 8 by the above-described relief printing method will be described.
FIG. 3 is a diagram showing a schematic configuration of a relief printing apparatus 30 used in the relief printing method. As shown in FIG. 3, the relief printing apparatus 30 is an apparatus used when pattern printing is performed on an organic light emitting ink made of an organic light emitting material on a substrate 2 on which an anode 3 and a hole injection layer 7 are formed. It has an ink tank 31, an ink chamber 32, an anilox roll 33, and a plate cylinder 35 on which a relief plate 34 provided with a convex portion is mounted.

The ink tank 31 contains organic luminescent ink diluted with a solvent, and the organic luminescent ink is fed into the ink chamber 32 from the ink tank 31.
The anilox roll 33 is rotatably supported by the ink chamber 32 in contact with the ink supply unit of the ink chamber 32.

When the pattern printing is performed, the ink layer 36 of the organic light emitting ink supplied to the surface of the anilox roll 33 is formed with a uniform film thickness as the anilox roll 33 rotates. The ink of the ink layer 36 is transferred to the convex portion of the relief plate 34 mounted on the plate cylinder 35 that is driven to rotate in the vicinity of the anilox roll 33.
And the ink in the convex part of the relief printing plate 34 is printed with respect to the to-be-printed board | substrate (board | substrate 2) installed in the stage (flat stand) 37, and passes through a drying process as needed, and an organic light emitting layer on the board | substrate 2 14 will be formed.

After the organic light emitting layer 8 is formed in this way, an electron injection layer forming step for forming the electron injection layer 8 on the organic light emitting layer 8 in the pixel is performed. In this electron injection layer forming step, the electron injection layer 8 is formed using a resistance heating method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or the like depending on the material. In this way, the light emitting medium layer 5 is formed.
After the light emitting medium layer 5 is formed by the light emitting medium layer forming step, a step of forming the cathode 6 composed of the first transparent electrode 10 and the second transparent electrode 11 on the substrate 2 and the light emitting medium layer 5 is performed.

For the film formation of the first transparent electrode 10, a resistance heating method or an electron beam evaporation method that does not damage the organic light emitting layer 8 is used. However, when a conductive metal film is formed by this vapor deposition method, the film may segregate due to lattice defects such as oxygen vacancies, resulting in a decrease in transmittance and a high resistance film.
Therefore, the first transparent electrode 10 has a transmittance of 70% or more, and a film thickness that can prevent sputter damage and oxygen reaction to the organic light emitting layer 8 when the second transparent electrode 11 described later is formed. To form.

The second transparent electrode 11 is formed by magnetron type or counter target type sputtering, resistance overheating, or ion beam ion plating.
The magnetron sputtering method is characterized in that a magnet is placed on the back surface of a target and a γ electron is confined in the vicinity of the target by applying a magnetic field. Since γ electrons take a trajectory entangled with magnetic field lines, plasma concentrates in the vicinity of the target, and damage to the substrate can be reduced. At the same time, the γ-electron moving distance becomes long, so that high-speed sputtering can be performed at a low gas pressure. However, since the lines of magnetic force disappear in the center of the target, it is not possible to completely prevent incidence to high energy particles caused by γ electrons or negative ions emitted from the target.

In opposed target sputtering, a target with magnets on the back is placed face-to-face so that a perpendicular DC magnetic field can be applied between the targets, and high-energy electrons are constrained by magnetic lines of force to separate the substrate and plasma. It is a feature that can be done. In the case of the magnetron sputtering method, negative ions generated from sputtering gas and the like are accelerated in the direction of the substrate by the Coulomb force and may be damaged. In the case of the opposed target sputtering method, both the magnetic field and the electric field are targets. Therefore, it is possible to reduce the collision of negative ions with the substrate. For this reason, it is preferable to select an opposed target sputtering method with little damage.

Further, O ₂ gas can be introduced by the sputtering method, and a film having better transmittance of the second transparent electrode 11 than the first transparent electrode 10 formed by the vapor deposition method can be formed.

The ion plating method is a technique in which, in principle, gas vapor is used to activate and deposit some of the evaporated particles as ions or excited particles. The vapor deposition particles sublimated by the resistance superheating method or the electron beam method are further ionized by the plasma of the reaction gas and then formed on the substrate. At this time, when a transparent conductive film such as ITO or IZO is used as a deposition material, it is annealed by sublimation and becomes a film having high crystallinity, and O ₂ gas can be introduced in the same manner as the sputtering method. A film having lower resistance and better transmittance than the sputtering method can be formed.
After forming the cathode 6 in this manner, the above-described sealing body is formed, and the manufacture of the organic EL element 1 is completed.

(Effect of this embodiment)
As described above, in this embodiment, when forming a cathode (second electrode) made of a conductive metal oxide on a light emitting medium layer including an organic light emitting layer, a vapor deposition method that does not damage the organic light emitting layer. After forming the first transparent electrode using, the second transparent electrode is formed by sputtering or ion plating. In this way, by forming the first transparent electrode between the light emitting medium layer and the second transparent electrode, Ar plasma and γ electron damage to the organic light emitting layer by sputtering and ion plating methods, and oxygen Deterioration due to reaction can be suppressed.

Moreover, since the resistance heating method or the electron beam vapor deposition method is used as the vapor deposition method, the first transparent electrode can be appropriately formed without damaging the organic light emitting layer. And an ion plating method comprising a combination of the magnetron sputtering method or the facing target sputtering method, or any one of a resistance heating method and an electron beam method, and a sputtering method of either direct current excitation type or high frequency excitation type. A second transparent electrode having better transmittance than the first transparent electrode can be formed.
Furthermore, since the transmittance of the first transparent electrode and the second transparent electrode is 70% or more, it is possible to effectively extract light from the cathode side.

Further, when forming the light emitting medium layer, first, a hole injection layer is formed on the anode (first electrode), then an organic light emitting layer is formed on the hole injection layer, and then on the organic light emitting layer. An electron injection layer is formed on the substrate. Thus, while providing a hole injection layer between an anode and an organic light emitting layer and providing an electron injection layer between an organic light emitting layer and a cathode, the luminous efficiency of an organic EL element can be increased. At that time, it is possible to efficiently form a film by forming at least one of the layers included in the light emitting medium layer by a wet process method.
Therefore, the organic EL element produced by the above manufacturing method can be an organic EL element with improved light extraction efficiency.

(Example)
Hereinafter, with reference to FIG. 1 to FIG. 3, as a result of manufacturing the organic EL element 1 of the example and the organic EL element of the comparative example as examples of the above-described first embodiment, the physical properties of both were evaluated. Will be described.

The organic EL element 1 of the embodiment is a transparent EL element that extracts light from both sides of the substrate. When the organic EL element 1 is manufactured, the thin film transistor that functions as the switching element provided on the substrate 2 as the substrate 2. 20 and an active matrix substrate provided with an anode 3 (pixel electrode) formed thereabove.
The size of the active matrix substrate (substrate 2) is 200 [mm] × 200 [mm]. Further, the above active matrix substrate has a diagonal of 5 inches and a display having 320 × 240 pixels arranged in the center.
Then, an ITO film having a thickness of 150 nm was formed on the above active matrix substrate by sputtering, and this was used as the anode 3.

Further, the partition wall 4 was formed in a shape that surrounds the periphery of the anode 3 to partition the pixels. Here, when the partition 4 is formed, first, an acrylic photoresist material is formed on the entire surface of the active matrix substrate with a thickness of 2 μm, and then the above-described photoresist material is subjected to photolithography. A partition wall 4 having a width of 30 μm was formed on the anode 3. The width of each pixel was 80 μm × 150 μm.

Next, on the anode 3 formed as described above, molybdenum oxide (MoOx) having a thickness of 20 nm was formed by sputtering film formation to form the hole injection layer 7. Next, a polyphenylene vinylene derivative which is an organic light emitting material and has a high electron transporting property is dissolved in toluene so that its concentration becomes 1% to obtain an organic light emitting ink. The organic light emitting layer 8 was printed by the relief printing method according to the line pattern on the anode 3 sandwiched between the partition walls 4 and set in the printing device 30, followed by a drying process. At this time, 150 [line / inch] anilox roll 33 and a water developing type photosensitive resin plate were used. The organic light emitting layer 8 was printed with a target film thickness of 60 nm.

Next, as the electron injection layer 9, a LiF film was formed by a resistance heating vapor deposition method using a metal mask so as to have a thickness of 2 nm.
Next, as the formation of the cathode 6, first transparent electrode 10 was formed by using ITO as a vapor deposition material by resistance heating vapor deposition using a metal mask. Furthermore, the second transparent electrode 11 was formed on the first transparent electrode 10 by using an opposed target sputtering method using ITO as a target material. The sputtering conditions were such that the volume ratio of the mixed gas of Ar gas and O 2 gas was Ar: O 2 = 100: 2, the introduction pressure was 1.0 [Pa], and the power was 500 W. The film thickness of each electrode was 100 nm for the first transparent electrode 10 and 200 nm for the second transparent electrode 11. The transmittance was 72% for the first transparent electrode 10 and 85% for the second transparent electrode 10. .

Then, a glass plate as a sealing material is placed on the active matrix substrate on which the cathode 6 is formed as described above so as to cover the entire light emitting region, and then bonded at about 90 [° C.] for about one hour. The agent was thermally cured and sealed.

(Comparative example)
In the organic EL element of the comparative example, the first transparent electrode 10 was not formed, and only the second transparent electrode 11 was formed on the light emitting medium layer 5.
Other materials, thicknesses of the respective layers, and processes were the same as those in the above-described example.
(Evaluation of physical properties with respect to Examples and Comparative Examples) As a result of comparing the luminance of light extracted from the opposite side of the substrate 2 between the organic EL element of the example and the organic EL element of the comparative example, the comparative example was 90 [cd / m. ² ], while the example obtained a result of improved characteristics of 200 [cd / m ² ].

From the comparison between the example and the comparative example, it was confirmed that the example can reduce the sputter damage and oxygen reaction to the organic light emitting layer 8 as compared with the comparative example.

DESCRIPTION OF SYMBOLS 1 ... Organic EL element, 2 ... Substrate (TFT substrate), 3 ... Anode, 4 ... Partition, 5 ... Light emitting medium layer, 6 ... Cathode, 7 ... Hole injection layer, 8 ... Organic light emitting layer, 9 ... Electron injection layer DESCRIPTION OF SYMBOLS 10 ... 1st transparent electrode, 11 ... 2nd transparent electrode, 20 ... Thin-film transistor (TFT), 21 ... Active layer, 22 ... Gate insulating film, 23 ... Gate electrode, 24 ... Drain electrode, 25 ... Source electrode, 26 ... Scanning line, 27 ... transistor insulating film, 30 ... letter printing apparatus, 31 ... ink tank, 32 ... ink chamber, 33 ... anilox roll, 34 ... ink layer, 35 ... letplate, 36 ... plate cylinder, 37 ... stage

Claims (7)

  An organic EL comprising: a step of forming a first electrode on a substrate; a step of forming a light emitting medium layer including an organic light emitting layer on the first electrode; and a step of forming a second electrode on the light emitting medium layer. In the method of manufacturing an element, the step of forming the second electrode includes a step of forming a first transparent electrode made of a conductive metal oxide on the light emitting medium layer by a vapor deposition method, and the first transparent electrode. And a step of forming a second transparent electrode made of a conductive metal oxide by a sputtering method or an ion plating method.   As the vapor deposition method, any one of a resistance heating method and an electron beam vapor deposition method is used. As the sputtering method, any one of a magnetron sputtering method and an opposed target sputtering method is used. As the ion plating method, 2. The method of manufacturing an organic EL element according to claim 1, wherein a combination of any one of a resistance heating method and an electron beam method and a sputtering method of any one of a direct current excitation type and a high frequency excitation type is used.   The transmittance of the first transparent electrode and the second transparent electrode is 70% or more, and the transmittance of the second transparent electrode is higher than the transmittance of the first transparent electrode. Or the manufacturing method of the organic EL element of 2.   The step of forming the light emitting medium layer includes a step of forming a hole injection layer on the first electrode, a step of forming the organic light emitting layer on the hole injection layer, and an electron on the organic light emitting layer. The method for producing an organic EL element according to claim 1, further comprising a step of forming an injection layer.   The method for producing an organic EL element according to claim 1, further comprising a step of forming a reflective electrode between the substrate and the first electrode.   The method for manufacturing an organic EL element according to claim 1, wherein at least one of the layers included in the light emitting medium layer is formed by a wet process method.   An organic EL device produced by using the method for producing an organic EL device according to claim 1.

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