JP5946348B2 - Transparent conductive film and polyimide film for production thereof - Google Patents

Description

  The present invention relates to a transparent conductive film used for various displays and a polyimide film for production thereof.

  A transparent conductive film in which a transparent conductive thin film is formed on one side of a transparent base film with a metal oxide film on various displays, including large displays such as televisions and small displays such as mobile phones, personal computers and smartphones. Is used. Here, as a base film used when producing a transparent conductive film, a polyethylene terephthalate (PET) film is conventionally used for general purposes, but the PET film has a low glass transition temperature of 81 ° C. Therefore, the heat resistance is low, and there are problems such as deformation due to high-temperature heating, and high-temperature treatment has been difficult. Further, since the PET film has a high water absorption rate, it has been desired to improve the moisture absorption resistance.

  Then, examination of the transparent conductive film provided with the transparent conductive thin film in the colorless and transparent polyimide film has been performed (patent documents 1 and 2). However, even if such a colorless and transparent polyimide is transparent, it is higher than the PET film, but lacks a balance of physical properties with other properties such as low heat resistance. For example, the colorless and transparent polyimide film shown in the example of Patent Document 1 has a light transmittance of 80% or more, but has a glass transition temperature of only about 180 to 210 ° C. Here, if the heat resistance of the polyimide film can be increased, it is possible to reduce the resistance value of the transparent electrode by increasing the film formation temperature of the transparent electrode and reduce the power consumption of the display device. Since the polyimide film disclosed in Document 1 has insufficient heat resistance, when a transparent conductive thin film is formed on the surface thereof, the polyimide film cannot withstand the processing temperature necessary to develop sufficient transparency.

Moreover, although the polyimide film shown by the Example of patent document 2 has both the total light transmittance and glass transition temperature superior to PET film, about linear expansion coefficient (CTE), it is 15 ppm / degrees C of PET film. Is much worse than. In addition, although several polyimide films are shown in patent document 3 as what has a fluorine atom in the skeleton of polyimide, although the film shown there also has transmissivity more than fixed, Its linear expansion coefficient is 22 ppm / ° C. or higher. When the linear expansion coefficient of the polyimide film is large, the linear expansion coefficient with a metal oxide such as ITO (CTE: 0 to 10 ppm / K) increases, and when the transparent conductive film is formed, the film warps or the ITO There are concerns about cracks in the film and peeling of the film from the ITO.
Thus, the polyimide film of the transparent conductive film examined so far has not satisfied the balance of transparency, heat resistance, and linear expansion coefficient (dimensional stability).

JP 2002-216542 A Japanese Patent No. 4247448 Special table 2012-503299 gazette

  The present invention provides a transparent conductive film having not only high transparency but also excellent heat resistance and low linear expansion coefficient (dimensional stability) in a transparent conductive film based on polyimide. The purpose is to provide.

  As a result of extensive research, the present inventors have surprisingly been satisfied with all these characteristics by using a polyimide film containing a predetermined repetitive structure and manufactured under specific manufacturing conditions as a base film. The present inventors have found that a transparent conductive film having performance that can be obtained is provided, and have completed the present invention. Moreover, the present inventors have found that a transparent conductive film having such a polyimide film as a base film has an excellent humidity expansion coefficient, and completed the present invention.

また、前記ポリイミドフィルムは、４４０ｎｍから７８０ｎｍの波長領域での透過率が８０％以上であり、熱膨張係数が１０ｐｐｍ／Ｋ以下であり、かつ、ガラス転移温度が３００℃以上であることを特徴とする透明導電性フィルムである。 That is, the present invention is a transparent conductive film in which a transparent conductive thin film is laminated on at least one of the front and back surfaces of a polyimide film,
The polyimide film, it becomes a polyimide layer of a single layer or multiple layers, represented by the main following formula in the polyimide constituting the polyimide layer (1) with structural units a and the following general formula represented (2) Structure The abundance ratio (mol%) with the unit b is in the range of a: b = 85: 15 to 95: 5,

Further, the polyimide film is the transmittance at 780nm wavelength range from 440nm is 80% or more, the thermal expansion coefficient of not more than 10 ppm / K, and, and wherein the glass transition temperature of 300 ° C. or higher It is a transparent conductive film.

The present invention also provides the transparent conductive film, a transparent conductive film humidity expansion coefficient of the polyimide film is characterized by the following der Rukoto RH 15 ppm /%.

  The method for producing the polyimide film in the present invention is not particularly limited. For example, i) Polyamic acid resin solution, which is a raw material of the polyimide film, is cast on an arbitrary substrate and molded into a film shape. A gel film having a self-supporting property by heating and drying on a substrate, and then peeling off from the substrate and further heat-treating at a high temperature to imidize to form a polyimide film, or ii) a polyamic acid resin The solution is cast-applied on an arbitrary substrate such as copper foil using an applicator, pre-dried, then heat-treated for solvent removal and imidization, and the substrate used during imidation is peeled off or etched The method of removing by etc. is mentioned. When the resin solution is cast-applied to a substrate or a substrate, the viscosity of the resin solution is preferably in the range of 500 to 70000 cps. In addition, coating may be performed after appropriately performing a surface treatment on the surface of the substrate or base material to be the application surface of the resin solution. In the above, it is appropriate that the drying conditions are 150 ° C. or lower for 2 to 30 minutes, and the heat treatment for imidization is performed at a temperature of about 130 to 360 ° C. for about 2 to 30 minutes.

  The polyimide used as the base film in the present invention can be produced by polymerizing raw material diamine and acid anhydride in the presence of a solvent to form polyamic acid as a polyimide precursor resin, and then imidizing by heat treatment. It can be made into a film form by forming it into a film form. Here, the molecular weight of the polyimide can be mainly controlled by changing the molar ratio of the raw material diamine and acid anhydride, but the molar ratio is usually 1: 1.

  As an example of a method for producing a polyamic acid, first, a diamine is dissolved in an organic solvent, and then an acid dianhydride is added to the solution, followed by stirring to produce a polyamic acid that is a polyimide precursor. Examples of the organic solvent to be used include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and these can be used alone or in combination of two or more. The step of imidizing the polyamic acid can be performed by using thermal imidization by heat dehydration or chemical imidization using a condensing agent such as acetic anhydride.

Polyimide constituting the polyimide film of the present invention, in the general formula (1) ratio and the structural unit b represented by the structural units a in the general formula (2) represented the mole percent a: b = 85 : 15 to 95: is made of a range of 5.

  Here, the structural unit of the general formula (1) mainly improves properties such as low thermal expansion and high heat resistance, and the structural unit of the general formula (2) is effective for improving high transparency. is there. Such a preferred embodiment of the polyimide film does not exclude the inclusion of structural units other than the structural units a and b represented by the general formulas (1) and (2). However, structural units other than the structural units a and b are preferably included in a molar ratio of less than 10%, and most preferably a polyimide film composed of only the structural units a and b.

  The raw material diamine and acid anhydride constituting the structural units other than the structural units a and b represented by the general formulas (1) and (2) are not particularly limited, and are known diamines and acid anhydrides. One kind or two or more kinds can be appropriately selected and used.

  In addition, the polyimide film in the present invention may be made of a single layer of polyimide or may be made of a plurality of layers of polyimide, and a preferable thickness range thereof is 5 to 100 μm, and more preferably 10 to 10 μm. 50 μm. If the thickness of the polyimide film is less than 5 μm, wrinkling is likely to occur when forming a conductive thin film, and handling properties are likely to be problematic, and if it exceeds 100 μm, it takes time to dry and imidize during film production. However, if this is applied to a product, it will be contrary to the demand for thin and light weight. When the polyimide film is a single layer, it is preferable that the polyimide layer itself has the structural units a and b described above. On the other hand, in the case of a plurality of layers, it is preferable that the main polyimide layer has the structural units a and b described above. Here, the main polyimide layer refers to a polyimide layer occupying the largest proportion of the thickness among the plurality of polyimide layers constituting the polyimide film.

  When the polyimide film is composed of a plurality of layers, the elastic modulus of the polyimide layer in contact with the transparent conductive thin film is preferably lower than that of other polyimide layers adjacent to the polyimide layer. That is, it is preferable that a polyimide layer having a low elastic modulus in contact with the transparent conductive thin film is provided outside the main polyimide layer. Since the polyimide having the structural units a and b described above has a relatively hard property with an elastic modulus of about 5 to 10 GPa, the polyimide layer having a lower elastic modulus is arranged so as to be in contact with the transparent conductive thin film. To do. Specifically, the elastic modulus of the polyimide layer in contact with the transparent conductive thin film should be less than 5 GPa, preferably 0.1 GPa or more and less than 5 GPa, and more preferably 2 GPa or more and less than 5 GPa. By providing a polyimide layer having a low elastic modulus on the side in contact with the transparent conductive thin film, the low elastic modulus polyimide layer relieves stress and is generated in the transparent conductive film while maintaining the heat resistance as the base film. Problems such as the occurrence of warpage and cracks that are a concern during the subsequent display manufacturing process can be suppressed.

  The polyimide layer having the above elastic modulus and in contact with the transparent conductive thin film is formed of a widely known material such as a polyimide containing one or more structural units of each component exemplified below. In general, the transmittance of these polyimides in the visible light region is lower than that of the polyimide having the structural units a and b described above, and the linear expansion coefficient (CTE) is relatively high. Therefore, the thickness of the polyimide layer in contact with the transparent conductive thin film is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. Accordingly, the thickness ratio of the main polyimide layer and the low elastic modulus polyimide layer (main polyimide thickness / low elastic polyimide thickness) is preferably 3 to 50, and more preferably 5 to 20.

  In the present invention, the polyimide layer in contact with the transparent conductive thin film only needs to have a lower elastic modulus than the other polyimide layers located on the side opposite to the side in contact with the transparent conductive thin film, and the polyimide film is composed of a plurality of layers. Those that do not reduce the transmittance are desirable. As a polyimide which gives such a polyimide layer, desired characteristics can be expressed with known diamines and acid anhydrides in addition to those containing the structural units a and b represented by the general formulas (1) and (2). Thus, it may be obtained by appropriately combining one type or two or more types.

  Examples of diamines and acid anhydrides used as raw materials here include bis [4- (aminophenoxy) phenyl] sulfone 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p- Phenylenediamine, 2,4-diaminomesitylene, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,5,3 ', 5'-tetramethyl-4,4'-diaminodiphenylmethane, 2,4- Toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4 , 4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4 '-Diaminodiphenyl sulfide, 3,3'- Aminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diamino Biphenyl, 3,3'-dimethoxybenzidine, 4,4 "-diamino-p-terphenyl, 3,3" -diamino-p-terphenyl, bis (p-aminocyclohexyl) methane, bis (p-β-amino -t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5- Aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4 -Bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine Amine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 4- (1H, 1H, 11H-eicosafluoroundecanoxy) -1,3-diaminobenzene, 4- (1H, 1H-perfluoro-1-butanoxy) -1,3-diaminobenzene, 4- (1H, 1H-perfluoro-1-heptanoxy) -1,3-diamino Benzene, 4- (1H, 1H-perfluoro-1-octanoxy) -1,3-diaminobenzene, 4-pentafluorophenoxy-1,3-diaminobenzene, 4- (2,3,5,6-tetrafluoro Phenoxy) -1,3-diaminobenzene, 4- (4-fluorophenoxy) -1,3-diaminobenzene, 4- (1H, 1H, 2H, 2H-perfluoro-1-hexanoxy) -1 , 3-Diaminobenzene, 4- (1H, 1H, 2H, 2H-perfluoro-1-dodecanoxy) -1,3-diaminobenzene, (2,5) -diaminobenzotrifluoride, diaminotetra (trifluoromethyl) Benzene, diamino (pentafluoroethyl) benzene, 2,5-diamino (perfluorohexyl) benzene, 2,5-diamino (perfluorobutyl) benzene, 2,2'-bis (trifluoromethyl) -4,4 ' -Diaminobiphenyl, 3,3'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, octafluorobenzidine, 4,4'-diaminodiphenyl ether, 2,2-bis (4-aminophenyl) hexafluoropropane 1,3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetrade Fluoroheptane, 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 3,3'-bis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 3,3 ', 5, 5′-tetrakis (trifluoromethyl) -4,4′-diaminodiphenyl ether, 3,3′-bis (trifluoromethyl) -4,4′-diaminobenzophenone, 4,4′-diamino-p-terphenyl, 1,4-bis (p-aminophenyl) benzene, p- (4-amino-2-trifluoromethylphenoxy) benzene, bis (aminophenoxy) bis (trifluoromethyl) benzene, bis (aminophenoxy) tetrakis (tri Fluoromethyl) benzene, 2,2-bis {4- (4-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (3-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (2-Aminophe Xyl) phenyl} hexafluoropropane, 2,2-bis {4- (4-aminophenoxy) -3,5-dimethylphenyl} hexafluoropropane, 2,2-bis {4- (4-aminophenoxy) -3.5 -Ditrifluoromethylphenyl} hexafluoropropane, 4,4′-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4′-bis (4-amino-3-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) diphenylsulfone, 4,4'-bis (3-amino-5-trifluoromethylphenoxy) diphenylsulfone, 2,2-bis {4- (4-amino-3-trifluoromethylphenoxy) phenyl} hexafluoropropane, bis {(trifluoromethyl) aminophenoxy} biphenyl, bis [{(trifluoromethyl) aminophenoxy} phenyl] Hexafluoropropane, bis {2-[(aminophenoxy) phenyl] hexafluoroisopropyl} benzene, 4,4′-bis (4-aminophenoxy) octafluorobiphenyl, 4,4′-diaminodiphenylsulfone, trans-1 , 4-diaminocyclohexane, 4,4'-diaminocyclohexylmethane, 2,2'-bis (4-aminocyclohexyl) -hexafluoropropane, 2,2'-bis (trifluoromethyl) -4,4'-diamino Bicyclohexane etc. are mentioned.

The acid anhydrides include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3 , 3'-benzophenonetetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenonetetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1 , 2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4, 8-Dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6 , 7-Hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene -1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetra Rubonic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, 3,3``, 4,4''-p-terphenyltetracarboxylic dianhydride, 2,2``, 3, 3 ''-p-terphenyltetracarboxylic dianhydride, 2,3,3``, 4 ''-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyl Phenyl) -propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-di Carboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride 1,1-bis (2,3-dicarboxyphenyl) ethane Dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10- Tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8 -Tetracarboxylic dianhydride, phenanthrene-1, 2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3 , 4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3, 4,5-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, (trifluoromethyl) pyromellitic dianhydride, di (trifluoromethyl) pyromellitic acid Two Water, di (heptafluoropropyl) pyromellitic dianhydride, pentafluoroethyl pyromellitic dianhydride, bis {3,5-di (trifluoromethyl) phenoxy} pyromellitic dianhydride, 2,2 -Bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 5,5'-bis (trifluoromethyl) -3,3 ', 4,4'-tetracarboxybiphenyl dianhydride, 2,2 ', 5,5'-Tetrakis (trifluoromethyl) -3,3', 4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis (trifluoromethyl) -3,3 ', 4, 4'-tetracarboxydiphenyl ether dianhydride, 5,5'-bis (trifluoromethyl) -3,3 ', 4,4'-tetracarboxybenzophenone dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} Benzene dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} trifluoromethylbenzene Water, bis (dicarboxyphenoxy) trifluoromethylbenzene dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) benzene dianhydride, bis (dicarboxyphenoxy) tetrakis (trifluoromethyl) benzene dianhydride , 2,2-bis {(4- (3,4-dicarboxyphenoxy) phenyl) hexafluoropropane dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} biphenyl dianhydride, bis {(trifluoromethyl ) Dicarboxyphenoxy} bis (trifluoromethyl) biphenyl dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} diphenyl ether dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) biphenyl dianhydride, 3 , 3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,4-cyclohexanedicarboxylic acid , 1,2,3,4-cyclobutane tetracarboxylic dianhydride, and the like.

  In the transparent conductive film of the present invention, a transparent conductive thin film is provided on a polyimide film as a base film. A known metal oxide film can be applied as the transparent conductive thin film. For example, metal oxide films such as indium oxide, cadmium oxide and tin oxide to which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc, germanium and the like are added as impurities, and zinc oxide and titanium oxide to which aluminum is added as impurities. Can be mentioned. Among them, an indium oxide (ITO) thin film containing 2 to 15% by weight of tin oxide is excellent in transparency and conductivity, and is preferably used.

  When laminating these transparent conductive thin films on a polyimide film, vapor deposition methods that deposit films from the gas phase such as sputtering, vacuum deposition, ion plating, and plasma CVD are applicable. Is done. In order to reduce the specific resistance of the transparent conductive thin film to 1 mΩ · cm or less, it is necessary to set the base film temperature during film formation to 250 ° C. to 350 ° C., so the glass transition temperature (Tg) of the polyimide film is high. It is desirable that the glass transition temperature should be 300 ° C. or higher, preferably in the range of 320 to 450 ° C. Further, if the glass transition temperature is less than 300 ° C., the processing temperature cannot be increased, and it becomes difficult to improve the transparency of the transparent conductive thin film.

  When the transparent conductive film of the present invention is used as an electrode substrate for an organic EL device or a liquid crystal display device, a gas barrier layer may be provided on at least one surface of the polyimide film in order to prevent moisture and oxygen from entering the device. Good. Here, an inorganic oxide film such as silicon oxide, aluminum oxide, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon nitride, silicon nitride oxide, etc. is suitably exemplified as a gas barrier layer having a barrier property against oxygen, water vapor, and the like. In addition, the film may be composed of only one kind of composition, or a film in which two or more kinds of compositions are confused may be selected.

  The thickness of the gas barrier layer is preferably 10 nm to 1 μm, and more preferably 50 to 200 nm. If the difference in CTE between the inorganic oxide gas barrier layer and the polyimide film as the base film is large, curling may occur during the subsequent TFT manufacturing process, dimensional stability may deteriorate, and the transparent conductive thin film may There is a risk of occurrence of cracks and peeling. In addition, warping is generally a problem when a large area film is manufactured. However, if the polyimide film of the present invention is used, the difference in CTE from the gas barrier layer is small. Is done. Table 1 shows typical inorganic films forming the gas barrier layer and their thermal expansion coefficients. Here, since the coefficient of thermal expansion varies depending on the manufacturing method even if the composition is the same, the values shown in Table 1 are approximate.

  The linear expansion coefficient (CTE) of the metal oxide constituting the transparent conductive thin film is 10 ppm / K or less, and the CTE of the material forming the gas barrier layer shown in Table 1 is included in 0 to 10 ppm / K. If the CTE of the polyimide film adjacent thereto is not a value close to this, the transparent conductive film may be warped or the transparent conductive thin film may be cracked or peeled off. Therefore, the polyimide film of the present invention has a coefficient of thermal expansion (CTE) of 15 ppm / K or less, preferably 0 to 10 ppm / K.

  Moreover, although the thickness of a transparent conductive thin film is set according to surface resistance, 5-10 nm is preferable. The warp is generally a problem when a large-area film is produced. However, if the polyimide film of the present invention has a small difference in CTE from the transparent conductive thin film and the gas barrier layer, problems such as these Is resolved.

  The polyimide film used in the present invention may have a transmittance of 80% or more in a wavelength region of 440 nm to 780 nm with a predetermined thickness, and the thickness range is not limited. Preferably, the film is formed of a polyimide that gives a transmittance of 80% or more in a wavelength region of 440 nm to 780 nm when the film is formed into a film having a thickness of 25 μm. And the structural unit b represented by the general formula (2) can be obtained in the above range. If the transmittance in the above wavelength region is less than 80%, it becomes impossible to extract light emission sufficiently.

  The polyimide film used in the present invention has a humidity expansion coefficient of 15 ppm /% RH or less, and preferably 0 to 10 ppm /% RH. If the humidity expansion coefficient exceeds 15 ppm /% RH, misalignment due to dimensional changes during the manufacturing process and problems in the reliability test occur.

  The polyimide film used in the present invention preferably has an in-plane retardation of 10 nm or less. If the retardation exceeds 10 nm, a uniform contrast viewing angle characteristic may not be obtained.

Furthermore, the polyimide film used in the present invention preferably has a surface roughness Ra on the side where the transparent conductive thin film of the polyimide film is laminated is 5 nm or less. If the surface roughness Ra exceeds 5 nm, the thickness of the transparent conductive film cannot be ignored and the resistance value may increase.
In addition, about the characteristic value of these polyimide films, when a polyimide film is formed from a some polyimide layer, it shows with the whole film containing all the polyimide layers.

  The transparent conductive film of the present invention not only has low thermal expansibility and excellent dimensional stability, but also has high transmittance in the visible region, excellent transparency, and excellent heat resistance. Therefore, a transparent conductive film mainly using a PET film as a base film has been used so far, but it can be suitably used as a substitute for this problem.

  Hereinafter, the contents of the present invention will be described more specifically based on examples and the like, but the present invention is not limited to the scope of these examples.

  First, the abbreviations for monomers and solvents used in the synthesis of polyimide, and various physical property measurement methods and conditions in the examples are shown below.

TFMB: 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl PMDA: pyromellitic dianhydride DMAc: N, N-dimethylacetamide 6FDA: 2,2′-bis (3,4- Dicarboxyphenyl) hexafluoropropane dianhydride BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride

[Coefficient of thermal expansion (CTE)]
Tensile test of polyimide film with a size of 3mm x 15mm in a temperature range from 30 ° C to 260 ° C at a constant heating rate (20 ° C / min) while applying a 5.0g load with a thermomechanical analysis (TMA) device The coefficient of thermal expansion (ppm / K) was measured from the amount of elongation of the polyimide film with respect to temperature.

[Transmissivity (%)]
The average value of the light transmittance from 440 nm to 780 nm was determined for a polyimide film (50 mm × 50 mm) with a U4000 spectrophotometer.

[Glass transition temperature (Tg)]
The glass transition temperature was measured at a rate of 10 ° C./min from room temperature to 400 ° C. while applying a 1 Hz vibration using a 10 mm wide sample using a viscoelasticity analyzer (RSA-II manufactured by Rheometric Science Effy Co., Ltd.). It was determined from the maximum loss tangent (Tan δ) when the temperature was raised at.

[Retardation]
Retardation in the in-plane direction of the polyimide film was determined using a spectroscopic polarimeter “Poxi-spectra” manufactured by Tokyo Instruments.

[Surface roughness (Ra)]
The surface roughness Ra of the air surface of the polyimide film (the surface not touching the metal foil at the time of film creation) was observed in the tapping mode using an atomic force microscope (AFM) “Multi Mode 8” manufactured by Bruker. . Observation of a 10 μm square field of view was performed four times, and the average value thereof was obtained. The surface roughness (Ra) represents the arithmetic average roughness (JIS B0601-1991).

[Humidity expansion coefficient (CHE)]
Cut into a size of 25 cm × 25 cm in the state of a laminated body of copper foil and polyimide film, an etching resist layer is provided on the copper foil side, and this has 16 square points of 16 mm on four sides of a square of 30 cm on one side. It was formed in a pattern to be placed in place. The exposed portion of the etching resist opening was etched to obtain a CHE measurement polyimide film having 16 copper foil remaining points. After drying this film at 120 ° C. for 2 hours, each film was allowed to stand for 24 hours at 23 ° C./30% RH / 50% RH / 70% RH constant temperature and humidity at 24 ° C. and measured with a two-dimensional measuring machine. The humidity expansion coefficient (ppm /% RH) was determined from the dimensional change between the copper foil points at humidity.

〔curl〕
A transparent conductive thin film (conductive layer) was formed by laminating 100 nm of indium tin oxide (ITO, In: Sn = 9: 1) on the obtained film to obtain a transparent conductive film. The floating four corners of a 10 cm square transparent conductive film placed on a flat surface with the convex surface down were visually observed. The result was ◎ for flat and 、 for slight curling.

[Resistivity]
In accordance with JIS K7194, the surface resistivity was measured by a four-terminal method, and the specific resistance was calculated.

[Example 1]
(Polyimide A)
Under a nitrogen stream, 25.2 g of TFMB was dissolved in the solvent DMAc while stirring in a 200 ml separable flask. Next, 14.5 g of PMDA and 5.2 g of 6FDA were added to this solution. Thereafter, the solution was stirred at room temperature for 5 hours to conduct a polymerization reaction, and kept for a whole day and night. A viscous polyamic acid solution was obtained, and it was confirmed that polyamic acid A having a high polymerization degree was produced.

  The polyamic acid solution obtained above was applied on an 18 μm thick copper foil (electrolytic copper foil “DFF” manufactured by Mitsui Mining & Smelting Co., Ltd.) using an applicator so that the film thickness after heat treatment was about 25 μm. The temperature was raised from 90 ° C. to 360 ° C. at a rate of 22 ° C. per minute to obtain a laminate of copper foil and polyimide. Next, this laminate was immersed in a ferric chloride etching solution, and the copper foil was removed to obtain a film-like polyimide A. Table 2 shows the results of various evaluations of the obtained film-like polyimide A.

[Example 2]
(Polyimide B)
While stirring in a 200 ml separable flask under a nitrogen stream, 25.7 g of TFMB as diamine and 15.7 g of PMDA and 3.6 g of 6FDA were charged as diamines, respectively, and then the solution was continuously stirred at room temperature for 5 hours. The polymerization reaction was performed and kept for a whole day and night. A viscous polyamic acid solution was obtained, and it was confirmed that polyamic acid B having a high polymerization degree was produced.

  Using the polyamic acid solution obtained above, a copper foil and polyimide laminate was obtained in the same manner as in Example 1, and this laminate was immersed in a ferric chloride etchant to remove the copper foil, A film-like polyimide B was obtained.

Example 3
(Polyimide C)
Under a nitrogen stream, 26.3 g of TFMB was dissolved in the solvent DMAc while stirring in a 200 ml separable flask. Next, 16.9 g of PMDA and 1.8 g of 6FDA were added to this solution. Thereafter, the solution was stirred at room temperature for 5 hours to conduct a polymerization reaction, and kept for a whole day and night. A viscous polyamic acid solution was obtained, and it was confirmed that polyamic acid C having a high polymerization degree was produced.

  Using the polyamic acid solution obtained above, a copper foil and polyimide laminate was obtained in the same manner as in Example 1, and this laminate was immersed in a ferric chloride etchant to remove the copper foil, A film-like polyimide C was obtained.

[ Reference Example 5 ]
(Polyimide D)
Film-like polyimide D was obtained in the same manner as polyimide A, except that 23.4 g of TFMB was used as the diamine, and 10.3 g of PMDA and 11.3 g of 6FDA were used as the acid anhydride.

[ Reference Example 6 ]
(Polyimide E)
Film-like polyimide E was obtained in the same manner as in polyimide A, except that 23.0 g of TFMB was used as the diamine and 9.3 g and 6FDA of 12.7 g were used as the acid anhydride.

[ Reference Example 7 ]
(Polyimide F)
A film-like polyimide F was obtained in the same manner as polyimide A except that 23.5 g of TFMB was used as the diamine and 21.5 g of BPDA was used as the acid anhydride.

Example 4
Under a nitrogen stream, 18.9 g of TFMB was dissolved in the solvent DMAc while stirring in a 200 ml separable flask. Then 26.1 g of 6FDA was added to this solution. Thereafter, the solution was stirred at room temperature for 5 hours to conduct a polymerization reaction, and kept for a whole day and night. A viscous polyamic acid solution G was obtained, and it was confirmed that a polyamic acid having a high degree of polymerization was produced.

  Next, the polyamic acid solution C obtained in Example 3 was applied onto a rolled copper foil having a thickness of 18 μm using an applicator so that the film thickness after the heat treatment was about 25 μm, and 1 at a temperature of 90 ° C. to 130 ° C. Heated for 5 to 5 minutes. Thereafter, a polyamic acid solution G is further applied on the obtained polyamic acid and copper foil laminate to a thickness of 5 μm, and the temperature is raised from 90 ° C. to 360 ° C. at a rate of 22 ° C. per minute. A laminate comprising a copper foil and two layers of polyimide was obtained.

  Next, this laminate was immersed in a ferric chloride etchant to obtain a polyimide laminate film. It was 4.5 GPa when the single layer film of the polyimide G was created with the same method, and the elasticity modulus was measured.

[Comparative Example 1]
Indium tin oxide was laminated on a commercially available 100 μm PET film in the same manner as the polyimide film to obtain a transparent conductive film.

Table 2 shows the characteristic values of the obtained polyimide films A to F and C and G multilayer polyimide films (C / G films). As shown in Table 2, as is clear from the results obtained from Examples 1 to 4, Reference Examples 5 to 7 and Comparative Example 1, the polyimide satisfying the conditions of the present invention is excellent in transparency. There was no warpage, and the surface roughness and retardation of the polyimide resin layer were low. Moreover, curl when the transparent conductive thin film was formed was hardly confirmed, and the evaluation regarding the generation of cracks was also good. On the other hand, a film made of a film that does not satisfy the conditions of the present invention cannot increase the substrate temperature when forming the conductive layer, and has a high specific resistance. For this reason, at the same conductive layer thickness, the resistivity is higher than that of polyimide that satisfies the conditions of the present invention. If the thickness of the conductive layer is increased in order to reduce the resistivity, it becomes difficult to develop sufficient transparency.

Claims (6)

A transparent conductive film in which a transparent conductive thin film is laminated on at least one of the front and back surfaces of a polyimide film,
The polyimide film, it becomes a polyimide layer of a single layer or multiple layers, represented by the main following formula in the polyimide constituting the polyimide layer (1) with structural units a and the following general formula represented (2) Structure The abundance ratio (mol%) with the unit b is in the range of a: b = 85: 15 to 95: 5,

Further, the polyimide film is the transmittance at 780nm wavelength range from 440nm is 80% or more, the thermal expansion coefficient of not more than 10 ppm / K, and, and wherein the glass transition temperature of 300 ° C. or higher Transparent conductive film. The polyimide film, a transparent conductive film according to claim 1, the humidity expansion coefficient is characterized by the following der Rukoto RH 15 ppm /%. The transparent conductive film according to claim 1 , wherein the polyimide film has an in- plane retardation of 10 nm or less. The polyimide film, a transparent conductive film according to any one of claims 1 to 3 surface roughness Ra of the side where the transparent conductive thin film are laminated is 5nm or less. A polyimide film used as a base film in the production of a transparent conductive film,
The polyimide film, it becomes a polyimide layer of a single layer or multiple layers, represented by the main following formula in the polyimide constituting the polyimide layer (1) with structural units a and the following general formula represented (2) Structure The abundance ratio (mol%) with the unit b is in the range of a: b = 85: 15 to 95: 5,

Further, the polyimide film is the transmittance at 780nm wavelength range from 440nm is 80% or more, the thermal expansion coefficient of not more than 10 ppm / K, and, and wherein the glass transition temperature of 300 ° C. or higher A polyimide film for producing a transparent conductive film. The polyimide film for producing a transparent conductive film according to claim 5, wherein the polyimide film has a humidity expansion coefficient of 15 ppm /% RH or less.