JP2006156417A - Polymeric el element and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost organic EL element having improved productivity by solving a problem of defect generation and short life of a conventional organic EL element. <P>SOLUTION: The polymeric EL element is formed by successively laminating a transparent or translucent conductive layer 2, a polymeric light emission layer 3, and a cathode layer 5 on a base material 1. The cathode layer is formed by a gold foil with a thickness of not less than 1μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic thin film EL element utilizing the electroluminescence (hereinafter simply referred to as EL) phenomenon of an organic thin film, and more particularly to a polymer EL element having an organic light emitting layer made of a polymeric fluorescent substance.

  In general, an organic thin film EL element is formed by laminating an anode, an organic light emitting layer, and a cathode. The organic light emitting layer may have a multilayer structure in which a hole injection layer, a hole transport layer, a phosphor layer, an electron injection layer, and the like are stacked. When an electric current is passed between the anode and the cathode, light emission occurs in the organic phosphor layer, and light can be extracted outside by making one of the electrodes transparent.

  Typical examples of the organic light emitting layer include copper phthalocyanine for the hole injection layer and N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl- for the hole transport layer. Examples include 4,4′-diamine and tris (8-quinolinol) aluminum used for the phosphor layer. These organic layers are all low molecular weight compounds, and each layer is laminated by a vacuum deposition method such as a resistance heating method with a thickness of about 0.01 to 0.1 μm. For this reason, in order to manufacture an organic thin-film EL device using a low molecular material, a vacuum vapor deposition apparatus in which a plurality of vapor deposition kettles are connected is required, and the emission characteristics are deteriorated or produced due to material deterioration due to heating during vapor deposition. There are problems such as low performance and high manufacturing cost.

  In addition, the organic layer is a low-molecular deposit, so the strength of the film is weak. Therefore, metal materials such as aluminum, magnesium, and silver, which are used as cathodes, require vacuum deposition equipment such as vacuum deposition or sputtering, and are produced from the equipment surface. It was an obstacle to practical use in terms of performance and cost. Further, in vacuum film formation, defects such as pinholes are likely to occur in the cathode layer, and moisture, oxygen, etc. invade from the pinholes and cause deterioration of the device, which contributes to a reduction in device life.

  In contrast, in recent years, polymer EL elements using polymers as organic layers have been proposed. A polymer is used as the organic layer, in which a low-molecular fluorescent dye is dissolved in a polymer such as polystyrene, polymethyl methacrylate, or polyvinyl carbazole, a polythiophene derivative, a polyparaphenylene derivative, or a polyphenylene vinylene derivative (PPV). Polymer fluorescent substances such as polyalkylfluorene derivatives (PAF) are used. These polymer light emitters can be formed into a film by a wet method such as spin coating or flexographic printing by making them soluble in a solution. However, the metal used as the cathode is vacuum-deposited by a method such as vacuum deposition or sputtering, and problems such as pinholes in the cathode layer, productivity, and cost are the same as in the case of the low-molecular organic EL element described above. Was causing problems.

  Further, as described above, when the cathode is formed by vacuum film formation, the vapor deposition layer has a thickness of about 1 μm at most, so that entry of water vapor, oxygen, etc. into the element cannot be prevented. It is necessary to perform sealing, etc., and there is a problem that the whole element becomes thick and heavy. Especially when a plastic film is used as a base material, these methods cannot be substantially employed. .

  As described above, an object of the present invention is to solve the problems of defects and short lifetime of conventional organic EL elements, improve the productivity of the elements, and provide an inexpensive organic EL element.

  The present invention has been made in view of the above problems, and claim 1 is a polymer EL in which a transparent or translucent conductive layer, a polymer light emitting layer, and a cathode layer are sequentially laminated on a substrate. A polymer EL device, wherein the cathode layer is made of a metal foil having a thickness of 1 μm or more, and the polymer light emitting layer comprises at least a hole transport layer and a polymer phosphor layer. The polymer EL device according to claim 1, wherein the substrate is made of a plastic film. 3. The polymer EL device according to claim 1, wherein the base material is a plastic film. 4. The metal foil according to claim 1, wherein the metal foil is a metal foil in which an alkali metal or an alkaline earth metal or an alloy containing them is deposited on an aluminum foil. It is a molecular EL device. According to a fifth aspect of the polymer EL device, the polymer light emitting layer is coated on the conductive layer side of the plastic film on which the transparent or semi-transparent conductive layer is laminated, and then bonded to the metal foil. In the manufacturing method, a first laminated film in which a hole transport layer is coated on the conductive layer side of a plastic film in which a transparent or translucent conductive layer is laminated is prepared, A method for producing a polymer EL device, comprising: preparing a second laminated film coated with a polymer light emitting layer on the surface; and bonding the coating surfaces of the first laminated film and the second laminated film to each other. is there.

  By using the metal foil as the cathode according to the present invention, it becomes possible to produce a polymer EL element more easily, and the cathode metal foil becomes a barrier layer of moisture, oxygen, etc., and the element sealing step Can be omitted or simplified.

  As the base material according to the present invention, a glass substrate or a plastic film or sheet can be used. If a plastic film is used, a polymer EL element can be produced by winding, and the element can be provided at low cost. As the plastic film, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyether sulfone, polymethyl methacrylate, polycarbonate and the like can be used. Also, other gas barrier films such as ceramic vapor-deposited film, polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer saponified product, etc. are laminated on the side where the conductive layer is not formed, or a color filter layer is provided by printing. You may do it.

  As the transparent conductive layer, a composite oxide of indium and tin (hereinafter referred to as ITO) can be used, and can be formed on the substrate by vapor deposition or sputtering. Alternatively, a precursor such as indium octylate or indium acetone can be applied on a substrate and then formed by an application pyrolysis method in which an oxide is formed by thermal decomposition. Alternatively, a material in which a metal such as aluminum, gold, or silver is vapor-deposited in a translucent state can be used.

  The glass or plastic substrate on which the transparent or translucent conductive layer is laminated does not need to be produced specifically for the present invention, and a commercially available substrate is used according to the resistivity and light transmittance of the conductive layer. be able to.

  The transparent or translucent conductive layer may be patterned by etching as necessary, or may be activated by UV treatment, plasma treatment, or the like. Further, instead of etching, nitrocellulose, polyamide, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, acrylic resin, urethane resin, or the like may be printed as an insulating layer.

  The polymer light-emitting layer that can be used in the present invention may be a single layer of a polymer phosphor or a multilayer structure composed of a hole transport layer, a polymer phosphor layer, and the like. When a hole transport layer is provided, copper phthalocyanine or a derivative thereof, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methyl) Phenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine, etc. Although low molecular weight compounds such as aromatic amines can be used, polyaniline, polythiophene, polyvinylcarbazole, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid, etc. can be formed by a wet method. Possible and more preferred.

  As polymeric fluorescent substance layers, 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-based Or a polymer fluorescent material such as polyarylvinylene or polyfluorene can be used, such as those obtained by dissolving a fluorescent dye such as polystyrene, polymethyl methacrylate, or polyvinyl carbazole.

  These polymer phosphor layers are made of a polymer phosphor material in a single or mixed solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, and water. It can be dissolved and formed into a film using a coating or printing method such as spin coating, spray coating, flexo, gravure, micro gravure, or intaglio offset.

  As the cathode material, a metal foil such as aluminum, copper, or nickel can be used. Alternatively, a metal foil such as aluminum obtained by depositing, sputtering, or plating calcium, magnesium, silver, gold, or the like can be used. The thickness of the metal foil is difficult to handle at 1 μm or less, preferably 5 μm or more, and more preferably 15 μm or more in order to prevent pinholes in the foil. By preventing pinholes in the foil, it is possible to prevent moisture and oxygen from entering the element, and it is possible to extend the lifetime of the element with a simple configuration. A film such as polyethylene terephthalate or nylon may be laminated in advance on the back surface of the metal foil in order to facilitate handling during production.

  In the polymer EL device of the present invention, a polymer light emitting layer is coated on a substrate on which a transparent or semitransparent conductive layer is laminated. When the substrate is glass, methods such as spin coating, roll coating, spray coating, slot coating, flexo, offset, and intaglio offset can be used. When a wound film is used as the substrate, various coating methods such as flexo, gravure, gravure offset, micro gravure, flexo, die coating, and roll coating can be used. In particular, a method in which patterning such as flexography, offset, intaglio offset, and gravure can be performed simultaneously with coating is preferable. In addition, when the polymer light-emitting layer is composed of two or more layers, taking into account the solubility of the materials constituting each layer, for example, use a difference in solubility such as selecting a water-soluble and oil-soluble resin. Alternatively, the coating conditions may be selected so that the time from coating to drying is shortened and the lower layer is not substantially affected. The coating thickness is 0.01 to 10 μm, preferably 0.05 to 0.5 μm, depending on the structure of the element.

  Next, the conductive substrate coated with the polymer light emitting layer and the metal foil are pressure-bonded or thermo-compressed between a metal roll or a rubber roll to form an element by lamination. Alternatively, a conductive substrate coated with the polymer light emitting layer and a metal foil may be inserted into an exterior bag, and the exterior bag may be vacuum-packed and pressure bonded. At this time, by using a gas barrier bag as the exterior bag, it is preferable that the element can be sealed at the same time. Further, as a pretreatment for pressure bonding or hot pressing, the surface of the polymer light emitting layer may be subjected to a surface treatment such as ultraviolet ray, electron beam, corona, etc. to improve the adhesion to the metal foil.

  Alternatively, the polymer light emitting layer may be coated on both sides of a transparent or translucent conductive substrate and a metal foil, and laminated by a method such as pressure bonding, thermocompression bonding, or vacuum packaging. In particular, when a polymer EL device is composed of a hole transport layer and a polymer light-emitting layer, a transparent or semi-transparent conductive substrate and a metal foil are coated and laminated, respectively. Even if the solubility with the molecular light-emitting material is the same, the layers can be stacked without causing any problems.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1
This will be described below with reference to FIG. As a polymer light-emitting layer 3 on a glass substrate 1 with ITO, poly [2-methoxy-5- (2′-ethyl-hexyloxy) -1,4-phenylene vinylene (Poly [2-methoxyl] represented by the following chemical formula 1 is used. −5- (2′-ethyl-hexyloxy) -1,4-phenylene vinylene] (hereinafter referred to as “MEH-PPV”) was applied by spin coating to a thickness of 0.1 μm. Further, 0.01 μm of calcium was formed on the aluminum foil 5 having a thickness of 25 μm by vacuum deposition. Subsequently, the polymer light emitting layer on the glass substrate and the calcium deposited layer 4 of aluminum foil were pressure-bonded under reduced pressure. Further, the aluminum foil and the glass substrate were fixed with an ultraviolet curable resin 6 to produce a polymer EL device according to the present invention as shown in FIG. When a voltage of 5 V was applied to this polymer EL element, uniform light emission of 50 cd / m ² could be obtained.

(Example 2)
This will be described below with reference to FIG. Polyvinylidene chloride coated polyester film 7 (12 μm) coated with polyvinylidene chloride coating layer 8 and ITO-coated polyester film 10 (75 μm) polyester surface were dry laminated with urethane adhesive 9. Next, pattern printing is performed on the ITO surface of the laminated film with urethane resin as an insulating layer 11 with a direct gravure with a thickness of 2 μm, and further MEH-PPV with a polymer light emitting layer 3 with a direct gravure with a thickness of 0.1 μm. The first laminated film 13 was produced. Further, the polyester film 12 (12 μm) and the aluminum foil 5 (20 μm) were dry-laminated with the urethane adhesive 9 to produce a second laminated film 14. A urethane-based adhesive 9 is printed in a pattern on the aluminum foil surface of the second laminated film, dry-laminated with the polymer light-emitting layer surface of the first laminated film, and is made of the present invention as shown in FIG. A molecular EL device was produced. When a voltage of 5 V was applied to this polymer EL element, uniform light emission of 30 cd / m ² could be obtained.

(Example 3)
This will be described below with reference to FIG. In the first laminated film of Example 2, MEH-PPV was used as the hole transport layer 15 in place of a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid (Baytron P TPAI4083 manufactured by Bayer). 1 laminated film was produced. Next, polydihexylfluorene represented by the following chemical formula 2 is printed in a pattern on the second laminated film 14 of Example 2 as the polymer light-emitting layer 3, and then the first laminated film is coated with urethane adhesive 9. The polymer EL device according to the present invention as shown in FIG. 3 was produced by dry lamination. When a voltage of 5 V was applied to this polymer EL element, uniform light emission of 30 cd / m ² could be obtained.

It is explanatory drawing which shows one Example of the polymer EL element of this invention. It is explanatory drawing which shows the other Example of the polymer EL element of this invention. It is explanatory drawing which shows the other Example of the polymer EL element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Transparent electrically conductive film 3 ... Polymer light emitting layer 4 ... Calcium vapor deposition layer

Claims (6)

  A polymer EL device in which a transparent or translucent conductive layer, a polymer light emitting layer, and a cathode layer are sequentially laminated on a substrate, wherein the cathode layer is made of a metal foil having a thickness of 1 μm or more. Polymer EL element.   The polymer EL device according to claim 1, wherein the polymer light emitting layer comprises at least a hole transport layer and a polymer phosphor layer.   The polymer EL device according to claim 1, wherein the substrate is made of a plastic film.   4. The polymer EL device according to claim 1, wherein the metal foil is a metal foil in which an alkali metal, an alkaline earth metal, or an alloy containing them is plated or deposited on an aluminum foil.   A method for producing a polymer EL element, comprising: coating a polymer light emitting layer on the conductive layer side of a plastic film on which a transparent or translucent conductive layer is laminated, and then press-bonding to a metal foil.   A first laminated film in which a hole transport layer is coated on the conductive layer side of a plastic film on which a transparent or semi-transparent conductive layer is laminated is produced, and a second layer in which a polymer light emitting layer is coated on a metal foil. A method for producing a polymer EL device, comprising: producing a laminated film, and pressing the coating surfaces of the first laminated film and the second laminated film, respectively.

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