Polyimide film, and materials for reducing the yellowness of polyimide film, materials for reducing the coefficient of linear expansion, and materials for improving adhesion to metals.

Abstract

The object of the present invention is to further reduce the yellowness and coefficient of thermal expansion of a polyimide film. A polyimide film according to one aspect of the present invention contains α-alumina. Preferably, the α-alumina is dispersed in the polyimide film. In this polyimide film, the α-alumina is in the form of plates and preferably has an aspect ratio of 2 or more. Furthermore, it is preferable that the particle size of the α-alumina is in the range of greater than 0.2 μm and less than or equal to 8 μm.

Description

[Technical Field]

[0001] This invention relates to polyimide films. Furthermore, this invention also relates to materials for reducing the yellowness of polyimide films, materials for reducing the coefficient of thermal expansion, and materials for improving adhesion to metals. [Background technology]

[0002] Polyimide films generally possess excellent thermal stability, electrical properties, and mechanical properties, and are applied to a variety of products used in relatively harsh environments. However, many polyimide films are colored yellow or brown due to the harsh thermal history they undergo during film formation. When such yellow or brown polyimide films are applied as film substrates for liquid crystal display devices, they not only darken the field of view but also impair the original function of the liquid crystal display device. Therefore, colorless and transparent polyimide films have been developed to solve this problem. Now, colorless and transparent polyimide films are widely used as films in liquid crystal display devices, fiber optic cable coatings, waveguides and protective coatings for solar cells, flexible substrates, and OSRs (optical solar reflectors) (see, for example, Japanese Patent Publication No. 62-7733, Japanese Patent Publication No. 2000-313804, Japanese Patent Publication No. 2012-040836, Korean Published Patent No. 10-2015-0046463, etc.). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 62-7733 [Patent Document 2] Japanese Patent Publication No. 2000-313804 [Patent Document 3] Japanese Patent Publication No. 2012-040836 [Patent Document 4] Korean Published Patent No. 10-2015-0046463 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in recent years, there has been a demand for polyimide films that have not only lower yellowness but also a lower coefficient of thermal expansion than the colorless, transparent polyimide films proposed in the past.

[0005] The object of the present invention is to further reduce the yellowness and coefficient of thermal expansion of polyimide films. [Means for solving the problem]

[0006] A polyimide film according to one aspect of the present invention contains α-alumina. Preferably, the α-alumina is dispersed in the polyimide film.

[0007] Incidentally, the polyimide film described above preferably has as its main component a polyimide resin comprising at least one acid-derived moiety selected from the group consisting of (A) a biphenyltetracarboxylic acid compound (BPDA)-derived moiety and a 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane-derived moiety (BPADA), and at least one diamine-derived moiety selected from the group consisting of (B) a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety. In such cases, the diamine-derived moiety preferably includes both a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety, and the molar ratio of the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety to the 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety is in the range of 1 to 4.

[0008] Furthermore, the polyimide film described above preferably has as its main component a polyimide resin comprising at least one acid-derived moiety selected from the group consisting of (A) a biphenyltetracarboxylic acid compound (BPDA)-derived moiety and a 4,4'-(hexafluoroisopropylidene)diphthalic acid compound (6FDA)-derived moiety, and at least one diamine-derived moiety selected from the group consisting of (B) a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety. In such cases, the diamine-derived moiety preferably includes both a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety, and the molar ratio of the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety to the 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety is in the range of 1 to 4.

[0009] Furthermore, the polyimide film described above preferably has as its main component a polyimide resin comprising at least one acid-derived moiety selected from the group consisting of (A) a biphenyltetracarboxylic acid-derived moiety (BPDA) and a 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane-derived moiety (BPADA), and at least one diamine-derived moiety selected from the group consisting of (B) a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety. In such cases, the diamine-derived moiety preferably includes both a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety, and the molar ratio of the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety to the 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety is in the range of 1 to 4.

[0010] In the above polyimide film, α-alumina preferably has a plate-like shape and an aspect ratio of 2 or more.

[0011] In the above polyimide film, α-alumina preferably has a particle size in the range exceeding 0.2 μm and not exceeding 8 μm.

[0012] In the above polyimide film, the yellowness is preferably less than 5.

[0013] In the above polyimide film, the haze is preferably less than 15%.

[0014] In the above polyimide film, the linear expansion coefficient is preferably less than 47 ppm / K.

[0015] For the above polyimide film, under the conditions of a peeling angle of 90° and a peeling speed of 50 mm / min at 25°C under normal pressure, the peeling strength when peeled from a nickel-20 mass% chromium alloy is preferably in the range of 300 N / m or more and 500 N / m or less.

[0016] For the above polyimide film, under the conditions of a peeling angle of 90° and a peeling speed of 50 mm / min at 25°C under normal pressure, the peeling strength when peeled from aluminum is preferably in the range of 90 N / m or more and 110 N / m or less.

[0017] For the above polyimide film, under the conditions of a peeling angle of 90° and a peeling speed of 50 mm / min at 25°C under normal pressure, the peeling strength when peeled from silver is preferably in the range of 115 N / m or more and 150 N / m or less.

[0018] The laminate according to another aspect of the present invention includes the above polyimide film and one metal layer of nickel-chromium alloy, aluminum, and silver laminated on the polyimide film.

[0019] Further, it is preferable that the above laminate further includes a copper layer laminated on the above metal layer.

[0020] The yellowing degree reducing material for a polyimide film according to another aspect of the present invention contains α-alumina as an active ingredient. Note that this invention can also be expressed as follows.

[0021] (1) A yellowing degree reducing material for a polyimide film containing α-alumina (note that this yellowing degree reducing material for a polyimide film may contain only α-alumina). (2) A method of reducing the yellowing degree of a polyimide resin obtained by heating a polyamic acid solution in which α-alumina is dispersed. (3) Use of α-alumina for producing a yellowing degree reducing material for a polyimide film (note that only α-alumina may be used here). (4) Use of a polyamic acid solution containing α-alumina for producing a yellowing degree reducing material for a polyimide film. (5) Use of α-alumina for reducing the yellowing degree of a polyimide film. (6) α-alumina used as a yellowing degree reducing material for a polyimide film.

[0022] The coefficient of linear expansion reducing material for a polyimide film according to still another aspect of the present invention contains α-alumina as an active ingredient. Note that this invention can also be expressed as follows.

[0023] (1) A coefficient of linear expansion reducing material for a polyimide film containing α-alumina (note that this coefficient of linear expansion reducing material for a polyimide film may contain only α-alumina). (2) A method of reducing the coefficient of linear expansion of a polyimide resin obtained by heating a polyamic acid solution in which α-alumina is dispersed. (3) Use of α-alumina for producing a coefficient of linear expansion reducing material for a polyimide film (note that only α-alumina may be used here). (4) Use of a polyamic acid solution containing α-alumina for the production of a material for reducing the coefficient of thermal expansion of polyimide films. (5) Use of α-alumina to reduce the coefficient of thermal expansion of polyimide film. (6) α-alumina used as a material to reduce the coefficient of thermal expansion of polyimide films.

[0024] A further aspect of the present invention relates to a material that improves the metal adhesion of polyimide films, which contains α-alumina as an active ingredient. This invention can also be expressed as follows.

[0025] (1) A material that improves the adhesion to metals of polyimide films containing α-alumina (this material may contain only α-alumina). (2) Use of α-alumina for the manufacture of a material that improves the metal adhesion of polyimide films (Note that in this case, only α-alumina may be used). (3) Use of a polyamic acid solution containing α-alumina for the production of a material that improves the metal adhesion of polyimide films. (4) Use of α-alumina to improve adhesion between polyimide film and metal. (5) α-alumina used as an agent to improve the metal adhesion of polyimide films.

[0026] Furthermore, the metal in the above-mentioned metal adhesion improving material is preferably a nickel-chromium alloy, aluminum, or silver. [Effects of the Invention]

[0027] The polyimide film according to the present invention contains α-alumina and exhibits not only a lower degree of yellowness than a polyimide film composed solely of polyimide resin, but also a lower coefficient of thermal expansion. Specifically, when the thickness of the polyimide film is 25 μm, the polyimide film exhibits a degree of yellowness of less than 3 and a coefficient of thermal expansion of less than 47 ppm / K. Furthermore, the polyimide film according to the present invention contains α-alumina and has higher adhesion to metals compared to a polyimide film composed solely of polyimide resin. [Brief explanation of the drawing]

[0028] [Figure 1] This graph shows the effect of the aspect ratio of α-alumina on the yellowness (YI) of the α-alumina-containing polyimide films according to Examples 1-5. [Figure 2] This graph shows the effect of the aspect ratio of α-alumina on the coefficient of linear thermal expansion of the α-alumina-containing polyimide films according to Examples 1-5. [Figure 3] This graph shows the effect of α-alumina content (volume %) on the yellowness (YI) of the α-alumina-containing polyimide films according to Examples 1 and 6-10, and the polyimide film according to Comparative Example 1. [Figure 4] This graph shows the effect of α-alumina content (volume %) on the coefficient of linear thermal expansion of the α-alumina-containing polyimide films in Examples 1 and 6-10, and the polyimide film in Comparative Example 1. [Figure 5] This graph shows the effect of the molar ratio of TFMB on the yellowness (YI) of the α-alumina-containing polyimide films according to Examples 11-14 and the polyimide films according to Comparative Examples 4-7. [Figure 6] This graph shows the effect of the molar ratio of TFMB on the coefficient of linear thermal expansion of the α-alumina-containing polyimide films according to Examples 11-14 and the polyimide films according to Comparative Examples 4-7. [Figure 7]This figure shows the test methods for the peel test in Examples 20-23 and Comparative Examples 9-12. [Modes for carrying out the invention]

[0029] The film according to the embodiment of the present invention mainly consists of polyimide resin and α-alumina (α-Al2O3). α-alumina is a trigonal aluminum oxide. This α-alumina is obtained by calcining aluminum hydroxide at 1000°C or higher. During this calcination process, aluminum hydroxide is converted to α-alumina via beymite and γ-alumina. It is obtained by heating beymite. Furthermore, in the production of the film according to the embodiment of the present invention, it is preferable to use powdered α-alumina. Here, the polyimide resin is preferably the main component of the film. Furthermore, it is preferable that the α-alumina is dispersed in the matrix of the polyimide resin. The polyimide resin is obtained by heating and imidizing a polyamic acid solution consisting of an acidic dianhydride and a diamine. That is, the film according to the embodiment of the present invention contains aluminum. The aluminum element can be detected by methods such as X-ray diffraction, X-ray photoelectron spectroscopy, X-ray fluorescence analysis, ICP emission spectroscopy, atomic absorption spectroscopy, and infrared spectroscopy.

[0030] As the α-alumina added to the film according to the embodiment of the present invention, spherical or plate-shaped forms can be used, but plate-shaped forms are preferred due to their greater effect. The aspect ratio of the plate-shaped α-alumina is preferably 2 or more, more preferably 5 or more, even more preferably 10 or more, even more preferably 20 or more, even more preferably 30 or more, even more preferably 40 or more, even more preferably 50 or more, even more preferably 60 or more, and particularly preferably 70 or more. The larger the aspect ratio, the better, and there is no particular upper limit, but if an upper limit were to be set, it would be 100.

[0031] Furthermore, the particle size of the α-alumina added to the film according to the embodiment of the present invention is preferably in the range of greater than 0.2 μm and 8 μm or less, more preferably in the range of greater than 0.2 μm and 6 μm or less, and even more preferably in the range of greater than 0.2 μm and 5 μm or less.

[0032] Furthermore, in the film according to the embodiment of the present invention, the volume ratio of α-alumina to the total volume of the film is preferably in the range of 0.1% to 5% by volume, more preferably in the range of 0.1% to 3% by volume, and 0.1% by volume. volume % or more 2.5 volume It is even more preferable that it be within the range of % or less, and 0.1 volume % or more 2 volume It is even more preferable that it be within the range of % or less, and 0.1 volume % or more 1.5 volume It is even more preferable that it be within the range of % or less, and 0.1 volume % or more 1 volume It is even more preferable that it be within the range of % or less, and 0.1 volume % or more 0.5 volume It is particularly preferable that the percentage be within the range of % or less.

[0033] Furthermore, α-alumina also functions as an antiblocking agent. When α-alumina functions as an antiblocking agent, it is preferable that the volume ratio of α-alumina to the total volume of the film be 0.3% by volume or more, and more preferably 0.4% by volume or more.

[0034] Furthermore, the film according to the embodiment of the present invention may contain components other than polyimide resin and α-alumina, to the extent that it does not impair the spirit of the present invention. Examples of such components include known additives such as mold release agents, dispersants, solid lubricants, anti-settling agents, leveling agents, surface modifiers, water absorbers, gelation inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, plasticizers, anti-skinning agents, surfactants, antistatic agents, defoaming agents, antibacterial agents, antifungal agents, preservatives, and thickeners.

[0035] Incidentally, methods for mixing α-alumina into a polyamic acid solution include, for example, (a) directly mixing α-alumina into the polyamic acid solution, and (b) preparing an α-alumina dispersion by adding α-alumina to an organic solvent, and then adding the dispersion to the polyamic acid solution. In addition, the polyamic acid solution may contain the known additives mentioned above, as well as stoichiometric or greater amounts of dehydrating agents and imidation catalysts.

[0036] Incidentally, the film according to the embodiment of the present invention can be produced by heat molding a polyamic acid solution to which α-alumina has been added (hereinafter sometimes referred to as the additive-containing polyamic acid solution) using a known method. For example, the additive-containing polyamic acid solution can be applied to a support, the coating film can be dried, and the dried coating film can be heated to produce the film according to the embodiment of the present invention.

[0037] Examples of dianhydrides that can be used to prepare polyamic acid solutions according to embodiments of the present invention include pyromellitic dianhydride (PMDA), 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 2,3,3'4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), and 2,2',3,3'-benzophenyl Nontetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 2,2-bis[3,4-(dicarboxyphenoxy)phenyl] Propane dianhydride (BPADA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride, thiodiphthalic anhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 1,2,7,8-phenanthrenetetracarboxylic acid dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride Aromatic tetracarboxylic dianhydrides such as anhydrides and 9,9-bis[4-(3,4'-dicarboxyphenoxy)phenyl]fluorene dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexyl succinic acid dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid dianhydride, 4,Examples include 5'-oxybis(isobenzofuran-1,3-dione), 5,5-[1,4-phenylenebis(oxy)]bis(isobenzofuran-1,3-dione), 4,4'-[2,1-phenylenebis(oxy)]bis(isobenzofuran-1,3-dione), 3,3'-(p-phenylenedioxy)diphthalic anhydride, 5,5'-[1,2-phenylenebis(oxy)bis(isobenzofuran-1,3-dione), 5,5'-[1,3-phenylenebis(oxy)bis(isobenzofuran-1,3-dione), 4,4'-[m-phenylenebis(oxy)bis(isobenzofuran-1,3-dione), 4,5'-[1,4-phenylenebis(oxy)bis(isobenzofuran-1,3-dione), and 1,4-bis(dicarboxyphenoxy)benzene dianhydride. Furthermore, these acidic dianhydrides can also be used in mixtures of two or more types.

[0038] Furthermore, diamines that can be used in the preparation of the polyamic acid solution according to the embodiments of the present invention include, for example, paraphenylenediamine (PPD), metaphenylenediamine (MPDA), 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 2,2-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 3,3'-di Aminodiphenylmethane, 4,4'-diaminodiphenylmethane (MDA), 2,2-bis-(4-aminophenyl)propane, 3,3'-diaminodiphenylsulfone (3,3'-DDS), 4,4'-diaminodiphenylsulfone (4,4'-DDS), diaminobenzotrifluorolide, bis(trifluoromethyl)phenylenediamine, diaminotetra(trifluoromethyl)benzene, diamino(pentafluoroethyl)benzene, 2,2'-bis(trifluoromethyl )benzidine (TFMB), 3,3'-bis(trifluoromethyl)benzidine, 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, bis(aminophenoxy)di(trifluoromethyl) Benzene, bis(aminophenoxy)tetrakis(trifluoromethyl)benzene, bis[(trifluoromethyl)aminophenoxy]benzene, bis[(trifluoromethyl))aminophenoxy]biphenyl, bis{[(trifluoromethyl))aminophenoxy]phenyl}hexafluoropropane, 2,2-bis{4-(p-aminophenoxy)phenyl}hexafluoropropane, 2,2-bis{4-(m-aminophenoxy)phenyl}hexafluoropropane, 2,2-Bis{4-(o-aminophenoxy)phenyl}hexafluoropropane, 2-{4-(p-aminophenoxy)phenyl}-2-{4-(m-aminophenoxy)phenyl}hexafluoropropane, 2-{4-(m-aminophenoxy)phenyl}-2-{4-(o-aminophenoxy)phenyl}hexafluoropropane, 2-{4-(o-aminophenoxy)phenyl}-2-{4-(p-aminophenoxy)phenyl}hexafluoropropane, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether (34ODA), 4,4'-diaminodiphenyl ether (ODA), 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4 Examples include aromatic diamines such as '-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone (BAPSM), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2-bis(3-aminophenyl)1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)1,1,1,3,3,3-hexafluoropropane, and 9,9-bis(4-aminophenyl)fluorene. Furthermore, these diamines can also be used in mixtures of two or more types.

[0039] For the film according to the embodiment of the present invention, from the viewpoint of providing transparency for use as a display component, for example, it is preferable to use 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) as the acid dianhydride, and 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 3,3'-diaminodiphenylsulfone (3,3'-DDS) as the diamine. In addition, other acid dianhydrides and other diamines may be added to the above-mentioned acid dianhydride and diamine without impairing the spirit of the present invention.

[0040] The yellowness (YI) of the film according to the embodiment of the present invention is preferably less than 5, more preferably less than 3, even more preferably less than 2.5, and particularly preferably less than 2. A lower yellowness is preferable, and there is no lower limit, but if a lower limit were to be set, it would be 1. When the thickness of the film according to the embodiment of the present invention is 25 μm, the yellowness (YI) of the film is preferably less than 3, more preferably less than 2.5, and even more preferably less than 2. In this case, even if the film thickness is other than 25 μm, it is sufficient if the yellowness when the film thickness is converted to 25 μm falls within the above range. Furthermore, when the thickness of the film according to the embodiment of the present invention is 50 μm, the yellowness (YI) of the film is preferably less than 5, more preferably less than 3, even more preferably less than 2.5, and particularly preferably less than 2. In this case, even if the film thickness is other than 50 μm, it is sufficient if the yellowness when the film thickness is converted to 25 μm falls within the above range.

[0041] Furthermore, the coefficient of linear expansion of the film according to the embodiment of the present invention is preferably less than 47 ppm / °C, more preferably less than 40 ppm / °C, even more preferably 35 ppm / °C or less, and particularly preferably less than 30 ppm / °C. The smaller the coefficient of linear expansion, the better; there is no particular lower limit, but if a lower limit were to be set, it would be 25 ppm / °C. When the thickness of the film according to the embodiment of the present invention is 25 μm, the coefficient of linear expansion of the film is preferably less than 47 ppm / °C, more preferably less than 40 ppm / °C, even more preferably 35 ppm / °C or less, and particularly preferably less than 30 ppm / °C. In such cases, even if the thickness of the film is other than 25 μm, it is sufficient that the coefficient of linear expansion when the film thickness is converted to 25 μm falls within the above range. Furthermore, when the thickness of the film according to the embodiment of the present invention is 50 μm, the coefficient of linear expansion of the film is preferably less than 47 ppm / °C, more preferably less than 40 ppm / °C, even more preferably 35 ppm / °C or less, and particularly preferably less than 30 ppm / °C. In such cases, even if the thickness of the film is other than 50 μm, it is sufficient if the coefficient of linear expansion when the film thickness is converted to 50 μm falls within the above range of coefficients of linear expansion.

[0042] Furthermore, the total light transmittance of the film according to the embodiment of the present invention is preferably 74% or more, more preferably 75% or more, even more preferably 76% or more, even more preferably 77% or more, even more preferably 78% or more, and particularly preferably 79% or more. The upper limit is 100%. When the thickness of the film according to the embodiment of the present invention is 25 μm, the total light transmittance of the film is preferably 74% or more, more preferably 75% or more, even more preferably 76% or more, even more preferably 77% or more, even more preferably 78% or more, and particularly preferably 79% or more. In such cases, even if the thickness of the film is other than 25 μm, it is sufficient if the total light transmittance when the film thickness is converted to 25 μm falls within the above range of total light transmittance. Furthermore, when the thickness of the film according to the embodiment of the present invention is 50 μm, the total light transmittance of the film is preferably 74% or more, more preferably 75% or more, even more preferably 76% or more, even more preferably 77% or more, even more preferably 78% or more, and particularly preferably 79% or more. In such cases, even if the thickness of the film is other than 50 μm, it is sufficient if the total light transmittance when the film thickness is converted to 50 μm falls within the above range of total light transmittance.

[0043] Furthermore, the tensile strength of the film according to the embodiment of the present invention is preferably in the range of 50 MPa to 250 MPa, and more preferably in the range of 100 MPa to 200 MPa.

[0044] Furthermore, the tensile modulus of the film according to the embodiment of the present invention is preferably in the range of 3.0 GPa to 5.0 GPa, and more preferably in the range of 3.5 GPa to 4.5 GPa.

[0045] Furthermore, the tensile elongation of the film according to the embodiment of the present invention is preferably in the range of 10% to 40%, and more preferably in the range of 13% to 35%.

[0046] The polyimide film according to the present invention can be used as a laminate in which one of the following metal layers—nickel-chromium alloy, aluminum, and silver—is laminated. In other words, in this laminate, one of the following metal layers—nickel-chromium alloy, aluminum, and silver—is laminated onto the polyimide film described above. This laminate can be used as a base material in various electronic devices and lighting equipment, such as flexible printed circuit boards (FPCs), reflectors, or optical substrate reflectors (OSRs). Furthermore, by laminating a copper layer onto the above metal layer in this laminate, the conductivity and durability of the entire laminate can be improved.

[0047] In the polyimide film according to an embodiment of the present invention, under normal pressure at 25°C, with a peel angle of 90° and a peel speed of 50 mm / min, the peel strength when peeled from a nickel-20 mass% chromium alloy is preferably 200 N / m or more, more preferably 300 N / m or more, even more preferably 350 N / m or more, even more preferably 400 N / m or more, and particularly preferably 450 N / m or more.

[0048] In the polyimide film according to an embodiment of the present invention, under normal pressure at 25°C, with a peel angle of 90° and a peel speed of 50 mm / min, the peel strength when peeled from aluminum is preferably 90 N / m or more, more preferably 95 N / m or more, even more preferably 100 N / m or more, even more preferably 105 N / m or more, and particularly preferably 110 N / m or more.

[0049] In the polyimide film according to an embodiment of the present invention, under normal pressure at 25°C, with a peel angle of 90° and a peel speed of 50 mm / min, the peel strength when peeled from silver is preferably 115 N / m or more, more preferably 125 N / m or more, even more preferably 135 N / m or more, even more preferably 145 N / m or more, even more preferably 150 N / m or more, and particularly preferably 155 N / m or more.

[0050] <Examples and Comparative Examples> The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. [Examples]

[0051] 1. Preparation of polyamic acid solution containing additives A polyamic acid solution with a solid content of 25% by mass was prepared by reacting 11.01 g of biphenyltetracarboxylic dianhydride (BPDA), 2.17 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 6.66 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 5.16 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) in 75 g of N,N-dimethylacetamide (DMAc). The molar ratio of each monomer in this polyamic acid was BPDA / BPADA / TFMB / 3,3'-DDS, which was 90 / 10 / 50 / 50.

[0052] Next, an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA00610, shape: plate-like, average particle size: 0.6 μm, aspect ratio: 10) in 3.69 g of N,N-dimethylacetamide (DMAc). Then, this α-alumina dispersion was added to the polyamic acid solution described above to prepare an additive-containing polyamic acid solution.

[0053] 2. Film Forming The above-mentioned additive-containing polyamic acid solution was applied to a glass substrate to form a coating film. The coating film was then placed in an 80°C oven and dried for 15 minutes to obtain a precursor film. Next, the precursor film was peeled off the glass substrate, and with its edges fixed in a frame, it was placed in an oven at 180°C and maintained at that temperature for 10 minutes. After that, the oven temperature was raised to 280°C. During this process, the oven temperature was raised from 180°C to 280°C in 22 minutes, and then maintained at 280°C for 5 minutes. As a result, an α-alumina-containing polyimide film was formed on the glass substrate. After this, the jig that had been fixing the edges of the α-alumina-containing polyimide film was removed to obtain an α-alumina-containing polyimide film with a thickness of 25 μm.

[0054] Furthermore, α-alumina does not volatilize even at 280°C. Based on this fact, the amount of α-alumina added and the density (3.97 g / cm³) are as described above. 3 ) as well as the solid content concentration of polyamic acid and the density of polyimide (1.35 g / cm³) 3 The volume percentage of α-alumina relative to the total volume of the α-alumina-containing polyimide film finally obtained was calculated to be 2.6% by volume.

[0055] 3. Measurement of physical properties of α-alumina-containing polyimide film The coefficient of linear expansion, total light transmittance, yellowness (YI), and haze of the obtained 25 μm thick α-alumina-containing polyimide film were determined as follows.

[0056] (1) Linear thermal expansion coefficient of α-alumina-containing polyimide film A 3.5 mm x 13.0 mm piece of film was fixed to a Shimadzu Corporation thermal analyzer (TMA-60), and the temperature was increased to 300°C at a heating rate of 5.0°C / min. The dimensional change of the film piece with respect to temperature, i.e., the TMA curve, was recorded. From the obtained TMA curve, the average linear expansion coefficient from 100°C to 200°C was determined, and the linear expansion coefficient of the film piece was found to be 42.7 ppm / K.

[0057] (2) Total light transmittance of α-alumina-containing polyimide film After fixing a 25.0 mm x 50.0 mm piece of film to a V-750 spectrophotometer manufactured by JASCO Corporation, the film piece was irradiated with light of wavelengths from 380 to 780 nm from a deuterium lamp and a halogen lamp. The result showed a total light transmittance of 86.0% for the film piece.

[0058] (3) Yellowness (YI) of α-alumina-containing polyimide film After fixing a 25.0 mm x 50.0 mm piece of film to a V-750 spectrophotometer manufactured by JASCO Corporation, the yellowness index (YI) of the film piece was measured, and the result was 2.3.

[0059] (4) Hayes After fixing a 25.0 mm x 50.0 mm piece of film to a V-750 spectrophotometer manufactured by JASCO Corporation, the haze of the film piece was measured, and the haze of the film piece was found to be 25.04%. [Examples]

[0060] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 3.69 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 2.6% by volume.

[0061] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 33.7 ppm / K, the total light transmittance was 86.6%, the yellowness (YI) was 2.1, and the haze was 12.15%. [Examples]

[0062] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA05070, shape: plate-like, particle size: 5 μm, aspect ratio: 70) in 3.69 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 2.6% by volume.

[0063] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 32.9 ppm / K, the total light transmittance was 86.9%, the yellowness (YI) was 2.1, and the haze was 13.78%. [Examples]

[0064] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: DIC Corporation, product name: Ceranex, product number: AP10, shape: plate-like, particle size: 8 μm, aspect ratio: 15) in 3.69 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 2.6 volume%.

[0065] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 38.2 ppm / K, the total light transmittance was 86.7%, the yellowness (YI) was 2.4, and the haze was 24.11%. [Examples]

[0066] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: Admatec Co., Ltd., product name: Adfine, product number: AO-502, shape: spherical, particle size: 0.2 μm, aspect ratio: 2) in 3.69 g of N,N-dimethylacetamide (DMAc). The volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 2.6% by volume.

[0067] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 41.1 ppm / K, the total light transmittance was 87.1%, the yellowness (YI) was 2.4, and the haze was 13.15%. [Examples]

[0068] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 0.14 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 0.07 g of N,N-dimethylacetamide (DMAc). The content ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 0.1 volume%.

[0069] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 41.6 ppm / K, the total light transmittance was 87.7%, the yellowness (YI) was 2.9, and the haze was 0.58%. In addition, the antiblocking performance of this α-alumina-containing polyimide film was checked, but sufficient antiblocking performance was not observed. [Examples]

[0070] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 0.14 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 0.28 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 0.2 volume%.

[0071] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 40.8 ppm / K, the total light transmittance was 88.1%, the yellowness (YI) was 2.9, and the haze was 1.19%. [Examples]

[0072] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 0.35 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 0.69 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 0.5 volume%.

[0073] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 39.7 ppm / K, the total light transmittance was 87.6%, the yellowness (YI) was 2.8, and the haze was 3.19%. [Examples]

[0074] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 0.91 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 1.82 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 1.3 volume%.

[0075] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 37.2 ppm / K, the total light transmittance was 87.1%, the yellowness (YI) was 2.5, and the haze was 6.12%. [Examples]

[0076] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that an α-alumina dispersion was prepared by dispersing 3.64 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 7.27 g of N,N-dimethylacetamide (DMAc). The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 5% by volume.

[0077] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 29.1 ppm / K, the total light transmittance was 85.5%, the yellowness (YI) was 1.4, and the haze was 23.85%. [Examples]

[0078] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 6, except that 12.72 g of biphenyltetracarboxylic dianhydride (BPDA), 6.92 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 5.37 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / / TFMB / 3,3'-DDS, was 100 / / 50 / 50. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 0.1% by volume.

[0079] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 37.5 ppm / K, the total light transmittance was 87.3%, the yellowness (YI) was 4.0, and the haze was 0.6%. [Examples]

[0080] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 6, except that 12.56 g of biphenyltetracarboxylic dianhydride (BPDA), 8.20 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 4.24 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / / TFMB / 3,3'-DDS, was 100 / / 60 / 40. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 0.1% by volume.

[0081] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 35.7 ppm / K, the total light transmittance was 86.9%, the yellowness (YI) was 4.2, and the haze was 0.8%. [Examples]

[0082] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 6, except that 12.41 g of biphenyltetracarboxylic dianhydride (BPDA), 9.45 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 3.14 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / / TFMB / 3,3'-DDS, was 100 / / 70 / 30. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 0.1% by volume.

[0083] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 32.4 ppm / K, the total light transmittance was 86.3%, the yellowness (YI) was 4.4, and the haze was 1.0%. [Examples]

[0084] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 6, except that 12.26 g of biphenyltetracarboxylic dianhydride (BPDA), 10.67 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 2.07 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / / TFMB / 3,3'-DDS, was 100 / / 80 / 20. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 0.1% by volume.

[0085] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 30.2 ppm / K, the total light transmittance was 86.0%, the yellowness (YI) was 4.7, and the haze was 1.0%. [Examples]

[0086] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 9, except that 10.63 g of biphenyltetracarboxylic dianhydride (BPDA), 2.09 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 10.29 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 1.99 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / BPADA / TFMB / 3,3'-DDS, was 90 / 10 / 80 / 20. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 1.3% by volume.

[0087] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 35.7 ppm / K, the total light transmittance was 87.1%, the yellowness (YI) was 2.7, and the haze was 8.8%. [Examples]

[0088] The desired α-alumina-containing polyimide film was obtained by the same method as shown in Example 15, except that an α-alumina dispersion was prepared by dispersing 1.85 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 3.69 g of N,N-dimethylacetamide (DMAc). The volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 2.6% by volume.

[0089] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 29.3 ppm / K, the total light transmittance was 86.0%, the yellowness (YI) was 2.3, and the haze was 16.3%. [Examples]

[0090] The desired α-alumina-containing polyimide film was obtained by the same method as shown in Example 6, except that 2000 ppm of an internal release agent and 0.5% by mass of an antifoaming agent were added to the solid content of the polyamic acid solution. The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 0.1% by volume.

[0091] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 43.2 ppm / K, the total light transmittance was 87.8%, the yellowness (YI) was 3.1, and the haze was 0.64%. In addition, the antiblocking performance of this α-alumina-containing polyimide film was checked, but sufficient antiblocking performance was not observed. [Examples]

[0092] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that (a) an α-alumina dispersion was prepared by dispersing 0.32 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) in 0.64 g of N,N-dimethylacetamide (DMAc), and (b) 2000 ppm of an internal release agent and 0.5 mass% of an antifoaming agent were added relative to the solid content of the polyamic acid solution. The volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was found to be 0.46 volume%.

[0093] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 39.2 ppm / K, the total light transmittance was 87.6%, the yellowness (YI) was 2.9, and the haze was 1.89%. In addition, when the antiblocking performance of this α-alumina-containing polyimide film was confirmed, sufficient antiblocking performance was observed. [Examples]

[0094] The desired α-alumina-containing polyimide film was obtained using the same method as shown in Example 9, except that the film was formed to a thickness of 50 μm.

[0095] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 38.3 ppm / K, the total light transmittance was 86.2%, the yellowness (YI) was 4.2, and the haze was 10.0%. [Examples]

[0096] 1. Preparation of polyamic acid solution containing additives A polyamic acid solution containing additives was prepared in the same manner as shown in Example 1, except that (a) 0.32 g of α-alumina (manufacturer: Kinsei Matec Co., Ltd., product name: Seraph, product number: YFA02050, shape: plate-like, particle size: 2 μm, aspect ratio: 50) was dispersed in 0.64 g of N,N-dimethylacetamide (DMAc) to prepare an α-alumina dispersion, and (b) 2000 ppm of an internal release agent and 0.5% by mass of an antifoaming agent were added relative to the solid content of the polyamic acid solution.

[0097] 2. Film Forming The above-mentioned additive-containing polyamic acid solution was applied to a glass substrate to form a coating film. The coating film was then placed in an 80°C oven and dried for 15 minutes to obtain a precursor film. Next, the precursor film was peeled off the glass substrate, and with its edges fixed in a frame, it was placed in an oven at 175°C and maintained for 5 minutes. After that, the oven temperature was raised to 300°C. During this process, the oven temperature was raised from 175°C to 300°C in 25 minutes, and then maintained at 300°C for 5 minutes. As a result, an α-alumina-containing polyimide film was formed on the glass substrate. After this, the jig that had been fixing the edges of the α-alumina-containing polyimide film was removed to obtain an α-alumina-containing polyimide film with a thickness of 50 μm.

[0098] Furthermore, α-alumina does not volatilize even at 300°C. Based on this fact, the amount of α-alumina added and the density (3.97 g / cm³) are as described above. 3 ) as well as the solid content concentration of polyamic acid and the density of polyimide (1.35 g / cm³)3 The volume percentage of α-alumina relative to the total volume of the α-alumina-containing polyimide film finally obtained from the above was calculated to be 0.46% by volume.

[0099] 3. Measurement of physical properties of α-alumina-containing polyimide film The physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1. The coefficient of thermal expansion was 42.7 ppm / K, the total light transmittance was 87.3%, the yellowness (YI) was 4.5, and the haze was 3.43%.

[0100] 4. Formation of a metal layer on an α-alumina-containing polyimide film The α-alumina-containing polyimide film obtained above was cut to 65 mm x 30 mm to prepare a measurement film. This measurement film was then placed in a magnetron sputtering apparatus (Canon Anelva Corporation E-200S). Subsequently, one side of this measurement film was subjected to plasma treatment for 90 seconds based on the following (processing condition 1). Note that "achievable vacuum" in (processing condition 1) to (processing condition 3) below refers to the achievable vacuum in the vacuum chamber of the magnetron sputtering apparatus (Canon Anelva Corporation E-200S).

[0101] (Processing condition 1) ·Achieved vacuum level: 1.5×10 -3 Pa • Gas used for plasma generation: Argon gas • Gas flow rate: 12 sccm • Type of applied power: RF (Radio Frequency) • Output power: 10W

[0102] The surface of the polyimide film subjected to the above plasma treatment was sputtered using a magnetron sputtering apparatus (E-200S, manufactured by Canon Anelva Corporation) according to the following (treatment condition 2) to form a 20 nm thick underlayer (metal layer) made of nickel-20 mass% chromium alloy on the surface, thereby obtaining a polyimide film with an underlayer.

[0103] (Processing condition 2) ·Achieved vacuum level: 1.5×10 -3 Pa • Spatter gas: Argon gas • Gas flow rate: 12 sccm • Type of applied power: DC (series) Output power: 50W • Target shape: 2-inch diameter disc • Target material: Nickel-chromium alloy (Manufacturer: Toyoshima Seisakusho Co., Ltd., Nickel-20% by mass chromium, purity 99.9% by mass)

[0104] Next, the base layer formed above was subjected to sputtering using a magnetron sputtering apparatus (Canon Anelva Corporation E-200S) based on the following (processing condition 3) to form a copper layer with a thickness of 0.5 μm, thereby obtaining a polyimide film for forming a plating base layer. In other words, in this polyimide film for forming a plating base layer, a base layer (metal layer) made of nickel-20 mass% chromium alloy is formed on the surface of the polyimide film subjected to the plasma treatment described above, and a copper layer is laminated on this base layer to form the plating base layer.

[0105] (Processing condition 3) ·Achieved vacuum level: 1.5×10 -3 Pa • Spatter gas: Argon gas • Gas flow rate: 12 sccm • Type of applied power: RF (Radio Frequency) Output power: 200W • Target shape: 2-inch diameter disc • Target material: Copper (Manufacturer: Toyoshima Seisakusho Co., Ltd., purity 99.99% by mass)

[0106] The polyimide film forming the plating underlayer obtained above was loaded into an electroplating apparatus, and copper plating was performed according to the following (processing condition 4) to form a copper film on the plating underlayer of the polyimide film forming the plating underlayer, thereby obtaining a copper-plated substrate. This copper plating process was carried out until the thickness of the copper film formed on the plating underlayer reached 45 μm.

[0107] (Processing condition 4) ·DC stabilized power supply: Kikusui Electronics Co., Ltd. PMX18-5A ·Anode: Copper • Cathode: Polyimide film for forming the plating underlayer. Plating solution composition: sulfuric acid:copper sulfate = 2:1 Processing temperature: 25℃ • Current value: 2.0mA / dm 2

[0108] 5. Evaluation of the peel strength of α-alumina-containing polyimide film The copper-plated substrate obtained above was cut to 55 mm x 3 mm to obtain a measurement substrate. An incision was made at the interface between the nickel-20 mass% chromium alloy underlayer (metal layer) and the polyimide film on this measurement substrate, and approximately 1 mm of the edge of the nickel-20 mass% chromium alloy underlayer on which the copper coating was formed was peeled off. Then, the underlayer was further peeled off to a length of 5 mm using tweezers, and cellophane tape was attached to the peeled portion. This cellophane tape was then gripped by the gripping part of a precision universal testing machine (AGS-10kNG, Shimadzu Corporation). Next, double-sided tape was attached to the side of the polyimide film on the measurement substrate where the copper coating was not formed, and the measurement substrate was fixed to the jig part of the precision universal testing machine. Then, a peel test was performed based on the following (measurement condition 1) (see Figure 7). As a result, the peel strength between the polyimide film and the nickel-20 mass% chromium alloy underlayer (metal layer) on which the copper coating was formed was 479.5 N / m.

[0109] (Measurement condition 1) • Peeling angle: 90° • Peeling speed: 50 mm / min • Measurement temperature: 25°C under normal pressure • Load cell used: 10N load cell (Load capacity: 10N) [Examples]

[0110] A target α-alumina-containing polyimide film was obtained using the same method as shown in Example 20. Then, a target copper-plated substrate was obtained using the same method as shown in Example 20, except that the plasma treatment time for one side of the polyimide film was set to 75 seconds. The obtained copper-plated substrate was cut to 55 mm × 3 mm to obtain a measurement substrate, and the peel strength between the polyimide film and the underlying layer (metal layer) made of nickel-20 mass% chromium alloy on which the copper coating was formed was measured using the same method as shown in Example 20, and the peel strength was 302.8 N / m. [Examples]

[0111] The desired α-alumina-containing polyimide film was obtained using the same method as shown in Example 20. Then, a plating underlayer-forming polyimide film was obtained using the same method as shown in Example 20, except that the "target material" in (processing condition 2) was changed from nickel-chromium alloy to aluminum (manufacturer: USTRON Corporation, purity 99.99 mass%), and the "type of applied power" in (processing condition 2) was changed from DC (series) to RF (radio frequency). In other words, in this plating underlayer-forming polyimide film, an underlayer (metal layer) made of aluminum is formed on the surface of the plasma-treated polyimide film, and a copper layer is laminated on this underlayer to form the plating underlayer.

[0112] Next, a copper-plated substrate was obtained from a polyimide film forming a plating underlayer, obtained by the same method as shown in Example 20. The obtained copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate. The peel strength between the polyimide film and the underlayer (metal layer) made of aluminum on which the copper coating was formed was measured by the same method as shown in Example 20, and the peel strength was 107.3 N / m. [Examples]

[0113] The desired α-alumina-containing polyimide film was obtained using the same method as shown in Example 20. Then, a plating underlayer-forming polyimide film was obtained using the same method as shown in Example 20, except that the "target material" in (processing condition 2) was changed from nickel-chromium alloy to silver (manufacturer: USTRON Corporation, purity 99.99 mass%), and the "type of applied power" in (processing condition 2) was changed from DC (series) to RF (radio frequency). In other words, in this plating underlayer-forming polyimide film, an underlayer (metal layer) made of silver is formed on the surface of the plasma-treated polyimide film, and a copper layer is laminated on this underlayer to form the plating underlayer.

[0114] Next, a copper-plated substrate was obtained from a polyimide film forming a plating underlayer, obtained by the same method as shown in Example 20. The obtained copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate. The peel strength between the polyimide film and the silver underlayer (metal layer) on which the copper coating was formed on this measurement substrate was measured by the same method as shown in Example 20, and the peel strength was 143.8 N / m. [Examples]

[0115] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 2, except that 7.98 g of biphenyltetracarboxylic dianhydride (BPDA), 5.17 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 9.93 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 1.92 g of 3,3'-diaminodiphenylsulfone (3,3'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / 6FDA / TFMB / 3,3'-DDS, was 70 / 30 / 80 / 20. Furthermore, the volume percentage of α-alumina relative to the total volume of this α-alumina-containing polyimide film was found to be 2.6% by volume.

[0116] Furthermore, when the physical properties of the obtained α-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 33.3 ppm / K, the total light transmittance was 86.2%, the yellowness (YI) was 2.3, and the haze was 15.37%. [Examples]

[0117] The target α-alumina-containing polyimide film was obtained by the same method as shown in Example 2, except that 10.63 g of biphenyltetracarboxylic dianhydride (BPDA), 2.09 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 10.29 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 1.99 g of 4,4'-diaminodiphenylsulfone (4,4'-DDS) were reacted in 75 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution with a solid content of 25% by mass. The molar ratio of each monomer in this polyamic acid, BPDA / BPADA / TFMB / 4,4'-DDS, was 90 / 10 / 80 / 20. Furthermore, when the volume ratio of α-alumina to the total volume of this α-alumina-containing polyimide film was determined, it was found to be 2.6% by volume.

[0118] Further, when the physical properties of the obtained α-alumina-containing polyimide film were measured in the same manner as in Example 1, the linear expansion coefficient was 30.4 ppm / K, the total light transmittance was 86.0%, the yellowness index (YI) was 1.8, and the haze was 19.62%.

[0119] (Comparative Example 1) The target polyimide film was obtained in the same manner as in Example 1 except that the α-alumina dispersion was not added to the polyamic acid solution (that is, α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0120] Further, when the physical properties of the obtained polyimide film were measured in the same manner as in Example 1, the linear expansion coefficient was 47.7 ppm / K, the total light transmittance was 88.0%, the yellowness index (YI) was 3.0, and the haze was 0.05%. Also, the antiblocking performance of this polyimide film was confirmed, but there was no sufficient antiblocking performance at all.

[0121] (Comparative Example 2) 1.41 g of boehmite (manufacturer: Kawai Lime Industry Co., Ltd., trade name: Celasure, product number: BMF240, shape: flaky, particle diameter: 2 μm, aspect ratio: 40) was dispersed in 2.82 g of N,N-dimethylacetamide (DMAc) to prepare a boehmite dispersion, and the target boehmite-containing polyimide film was obtained in the same manner as in Example 1 except that the boehmite dispersion was added to the polyamic acid solution instead of the α-alumina dispersion.

[0122] Note that boehmite does not volatilize even at 280°C and is not converted into other substances. Based on this fact, the above-mentioned addition amount and density of boehmite (3.03 g / cm 3 ) as well as the solid content concentration of the polyamic acid and the density of the polyimide (1.35 g / cm 3The volume percentage of boymite relative to the total volume of the boymite-containing polyimide film finally obtained was calculated to be 2.6% by volume.

[0123] Furthermore, when the physical properties of the obtained beymite-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 38.1 ppm / K, the total light transmittance was 87.3%, the yellowness (YI) was 3.8, and the haze was 9.16%.

[0124] (Comparative Example 3) A γ-alumina dispersion was prepared by dispersing 1.58 g of γ-alumina (manufacturer: Kawai Lime Industry Co., Ltd., product name: Cerasure, product number: BMF240γ, shape: flake-like, particle size: 2 μm, aspect ratio: 40) in 3.16 g of N,N-dimethylacetamide (DMAc). The desired γ-alumina-containing polyimide film was obtained by the same method as shown in Example 1, except that the γ-alumina dispersion was added to the polyamic acid solution instead of the α-alumina dispersion. The volume ratio of γ-alumina to the total volume of this γ-alumina-containing polyimide film was found to be 2.6% by volume.

[0125] Furthermore, when the physical properties of the obtained γ-alumina-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 37.5 ppm / K, the total light transmittance was 86.1%, the yellowness (YI) was 5.1, and the haze was 20.67%.

[0126] (Comparative Example 4) The target polyimide film was obtained using the same method as shown in Example 11, except that the α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0127] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 40.3 ppm / K, the total light transmittance was 87.4%, the yellowness (YI) was 4.2, and the haze was 0.2%.

[0128] (Comparative Example 5) The target polyimide film was obtained using the same method as shown in Example 12, except that the α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0129] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 37.5 ppm / K, the total light transmittance was 87.0%, the yellowness (YI) was 4.5, and the haze was 0.2%.

[0130] (Comparative Example 6) The target polyimide film was obtained using the same method as shown in Example 13, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0131] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 34.1 ppm / K, the total light transmittance was 87.0%, the yellowness (YI) was 5.0, and the haze was 0.1%.

[0132] (Comparative Example 7) The target polyimide film was obtained using the same method as shown in Example 14, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0133] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 31.9 ppm / K, the total light transmittance was 86.0%, the yellowness (YI) was 5.1, and the haze was 0.1%.

[0134] (Comparative Example 8) The target polyimide film was obtained using the same method as shown in Example 15, except that the α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0135] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 40.8 ppm / K, the total light transmittance was 87.5%, the yellowness (YI) was 4.0, and the haze was 0.9%.

[0136] (Comparative Example 9) The target polyimide film was obtained using the same method as shown in Example 19, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0137] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 47.5 ppm / K, the total light transmittance was 87.6%, the yellowness (YI) was 4.9, and the haze was 0.2%.

[0138] Furthermore, the target copper-plated substrate was prepared from the polyimide film obtained above using the same method as shown in Example 20. This copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate, and the peel strength between the polyimide film on this measurement substrate and the underlying layer (metal layer) made of nickel-20 mass% chromium alloy on which the copper coating was formed was measured using the same method as shown in Example 20, and the peel strength was 161.5 N / m.

[0139] (Comparative Example 10) The target polyimide film was obtained using the same method as shown in Example 19, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0140] Furthermore, the target copper-plated substrate was prepared from the polyimide film obtained above using the same method as shown in Example 21. This copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate, and the peel strength between the polyimide film on this measurement substrate and the underlying layer (metal layer) made of nickel-20 mass% chromium alloy on which the copper coating was formed was measured using the same method as shown in Example 20, and the peel strength was 125.7 N / m.

[0141] (Comparative Example 11) The target polyimide film was obtained using the same method as shown in Example 19, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0142] Furthermore, the target copper-plated substrate was prepared from the polyimide film obtained above using the same method as shown in Example 22. This copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate, and the peel strength between the polyimide film and the aluminum underlayer (metal layer) on which the copper coating was formed was measured using the same method as shown in Example 20, and the peel strength was 83.9 N / m.

[0143] (Comparative Example 12) The target polyimide film was obtained using the same method as shown in Example 19, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0144] Furthermore, the target copper-plated substrate was prepared from the polyimide film obtained above using the same method as shown in Example 23. This copper-plated substrate was then cut to 55 mm × 3 mm to obtain a measurement substrate, and the peel strength between the polyimide film and the silver underlayer (metal layer) on which the copper coating was formed on this measurement substrate was measured using the same method as shown in Example 20, and the peel strength was 113.1 N / m.

[0145] Table 1 shows the peel strengths for Examples 20-23 and Comparative Examples 9-12 described above.

[0146] [Table 1]

[0147] (Comparative Example 13) The target polyimide film was obtained using the same method as shown in Example 24, except that α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0148] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 39.9 ppm / K, the total light transmittance was 88.3%, the yellowness (YI) was 3.3, and the haze was 0.12%.

[0149] (Comparative Example 14) The target polyimide film was obtained using the same method as shown in Example 25, except that the α-alumina dispersion was not added to the polyamic acid solution (i.e., α-alumina was not added to the polyamic acid solution prepared in this comparative example).

[0150] Furthermore, when the physical properties of the obtained polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 40.1 ppm / K, the total light transmittance was 89.5%, the yellowness (YI) was 2.6, and the haze was 0.21%.

[0151] (Reference example 1) (a) A silica dispersion was prepared by dispersing 0.019 g of silica (manufacturer: Fuji Silysia Chemical Co., Ltd., product name: Silysia, product number: 310P, shape: spherical, particle size: 2 μm) in 0.038 g of N,N-dimethylacetamide (DMAc), and this silica dispersion was added to the polyamic acid solution instead of the α-alumina dispersion. (b) The target silica-containing polyimide film was obtained by the same method as shown in Example 2, except that 2000 ppm of an internal release agent and 0.5% by mass of an antifoaming agent were added relative to the solid content of the polyamic acid solution.

[0152] Furthermore, silica does not volatilize even at 280°C and is not converted into other substances. Based on this fact, the amount of silica added and the density (2.20 g / cm³) are as described above. 3 ) as well as the solid content concentration of polyamic acid and the density of polyimide (1.35 g / cm³) 3 The volume percentage of silica relative to the total volume of the silica-containing polyimide film finally obtained was calculated to be 0.05% by volume.

[0153] Furthermore, when the physical properties of the obtained silica-containing polyimide film were measured using the same method as shown in Example 1, the coefficient of thermal expansion was 44.5 ppm / K, the total light transmittance was 87.7%, the yellowness (YI) was 3.2, and the haze was 2.00%. In addition, when the antiblocking performance of this silica-containing polyimide film was confirmed, sufficient antiblocking performance was observed.

[0154] <Considerations regarding the examples, comparative examples, and reference examples> It was revealed that all α-alumina-containing polyimide films obtained in Examples 1-5 exhibited reduced yellowness (YI) and thermal expansion coefficient compared to the polyimide film obtained in Comparative Example 1, the beymite-containing polyimide film obtained in Comparative Example 2, and the γ-alumina-containing polyimide film obtained in Comparative Example 3. Furthermore, it was revealed that the α-alumina-containing polyimide film obtained in Example 24 exhibited reduced yellowness (YI) and thermal expansion coefficient compared to the polyimide film obtained in Comparative Example 13, and the α-alumina-containing polyimide film obtained in Example 25 exhibited reduced yellowness (YI) and thermal expansion coefficient compared to the polyimide film obtained in Comparative Example 14. In other words, it was revealed that α-alumina can reduce the yellowness (YI) and thermal expansion coefficient of polyimide films, regardless of the manufacturer, product name, or product number. Furthermore, Figure 1 shows a graph illustrating the effect of the aspect ratio of α-alumina on the yellowness (YI) of the α-alumina-containing polyimide films according to Examples 1-5, and Figure 2 shows a graph illustrating the effect of the aspect ratio of α-alumina on the coefficient of linear expansion of the α-alumina-containing polyimide films according to Examples 1-5. As shown in Figures 1 and 2, it became clear that as the aspect ratio of α-alumina increases, the yellowness (YI) and coefficient of linear expansion of the α-alumina-containing polyimide films decrease.

[0155] Furthermore, based on the results of Examples 1 and 6-10, Figure 3 shows a graph illustrating the effect of α-alumina content on the yellowness (YI) of the α-alumina-containing polyimide film, and Figure 4 shows a graph illustrating the effect of α-alumina content on the coefficient of linear expansion of the α-alumina-containing polyimide film. As shown in Figures 3 and 4, it became clear that as the α-alumina content increased, the yellowness (YI) and coefficient of linear expansion of the α-alumina-containing polyimide film decreased. In other words, it was suggested that the yellowness (YI) and coefficient of linear expansion of the α-alumina-containing polyimide film can be controlled by controlling the α-alumina content.

[0156] Furthermore, based on the results of Examples 11-14 and Comparative Examples 4-7, Figure 5 shows a graph illustrating the effect of the molar ratio of TFMB on the yellowness (YI) of α-alumina-containing polyimide films and polyimide films, and Figure 6 shows a graph illustrating the effect of the molar ratio of TFMB on the linear expansion coefficient of α-alumina-containing polyimide films and polyimide films. As shown in Figures 5 and 6, it became clear that even films made of polyimides with different compositions can obtain the effect of adding α-alumina, i.e., the effect of reducing yellowness (YI) and linear expansion coefficient.

[0157] Furthermore, the results from Examples 17 and 18 revealed that even when internal release agents and defoaming agents are mixed into the α-alumina-containing polyimide film, the effects of reducing the yellowness (YI) and coefficient of thermal expansion of α-alumina can be fully enjoyed.

[0158] Furthermore, the results from Examples 6 and 18 revealed that when the α-alumina content in an α-alumina-containing polyimide film exceeds a certain value, α-alumina functions as an antiblocking agent.

[0159] Finally, the results from Examples 20-23 and Comparative Examples 9-12 revealed that the peel strength between the α-alumina-containing polyimide film and the underlying layer (metal layer) made of nickel-chromium alloy, aluminum, or silver in the α-alumina-containing polyimide film according to the present invention is higher than that of the α-alumina-free polyimide film. From this, it was revealed that the α-alumina-containing polyimide film has higher adhesion to the metal layer compared to the α-alumina-free polyimide film. [Industrial applicability]

[0160] The film according to the present invention exhibits a lower yellowness (YI) and coefficient of linear expansion than a polyimide film made solely of the same polyimide resin. Furthermore, the film according to the present invention has high adhesion to metals. For this reason, the film according to the present invention can be used, for example, as a component or material for electrical and electronic equipment, a component or material that is not for electrical or electronic equipment, a heat-resistant tape, a substrate, coverlay, etc., for solar cells (e.g., silicon solar cells and perovskite solar cells). Examples of substrates for solar cells (e.g., silicon solar cells and perovskite solar cells) include terrestrial solar panels and space solar panels. Examples of substrates include circuit boards for mounting light-emitting elements and substrates for printing barcodes. Examples of electrical and electronic equipment include computers (e.g., personal computers, smartphones, foldable smartphones, automotive control systems, car navigation systems, etc.), television receivers, wearable devices (e.g., AR / VR glasses, smartwatches, etc.), lighting equipment, display devices (e.g., computer displays, large display devices, large vision devices, LED display devices, LED vision devices, various monitors such as digital signage), MRI machines, and automobile headlights. Examples of components and materials for electrical and electronic equipment include flexible printed circuit boards (FPCs), antennas, OSRs (optical solar reflectors), LiDAR, home and office lighting, design lighting, transparent antennas, electromagnetic shielding, and back panel reflectors for direct-lit LEDs. Examples of components and materials that are not electrical or electronic equipment include conference room partitions, office windows, car headlight windows, glass surfaces of buildings and automobiles, aircraft and automobile windows, and packaging materials.

Claims

1. At least one acid-derived moiety selected from the group consisting of a biphenyltetracarboxylic acid (BPDA)-derived moiety and a 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane-derived moiety (BPADA), A diamine-derived moiety selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety, and It mainly consists of polyimide resin, It contains α-alumina in a volume percentage range of 0.1% to less than 1%. Transparent polyimide film.

2. At least one acid-derived moiety selected from the group consisting of a biphenyltetracarboxylic acid-derived moiety (BPDA) and a 4,4'-(hexafluoroisopropylidene)diphthalic acid-derived moiety (6FDA), A diamine-derived moiety selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety, and It mainly consists of polyimide resin, It contains α-alumina in a volume percentage range of 0.1% to less than 1%. Transparent polyimide film.

3. The diamine-derived moiety includes both the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and the 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety. The molar ratio of the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety to the 3,3'-diaminodiphenylsulfone (3,3'-DDS)-derived moiety is within the range of 1 to 4. A transparent polyimide film according to claim 1 or 2.

4. At least one acid-derived moiety selected from the group consisting of a biphenyltetracarboxylic acid (BPDA)-derived moiety and a 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane-derived moiety (BPADA), A diamine-derived moiety selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and a 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety. It mainly consists of polyimide resin, It contains α-alumina in a volume percentage range of 0.1% to less than 1%. Transparent polyimide film.

5. The diamine-derived moiety includes both the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety and the 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety. The molar ratio of the 2,2'-bis(trifluoromethyl)benzidine (TFMB)-derived moiety to the 4,4'-diaminodiphenylsulfone (4,4'-DDS)-derived moiety is within the range of 1 to 4. The transparent polyimide film according to claim 4.

6. The α-alumina is plate-like and has an aspect ratio of 2 or more. The transparent polyimide film according to claim 1.

7. The α-alumina has a particle size in the range of greater than 0.2 μm and less than or equal to 8 μm. The transparent polyimide film according to claim 1.

8. The degree of yellowness is less than 5. The transparent polyimide film according to claim 1.

9. The haze is less than 15%. The transparent polyimide film according to claim 8.

10. The coefficient of linear expansion is less than 47 ppm / K. The transparent polyimide film according to claim 1.

11. A transparent polyimide film according to claim 1, A metal layer laminated on the transparent polyimide film is one of nickel-chromium alloy, aluminum, and silver. A laminate comprising the above.

12. The metal layer further comprises a layer of copper laminated on the aforementioned metal layer. The laminate according to claim 11.

13. A yellowing reduction agent for polyimide films, with α-alumina as the active ingredient.

14. A material for reducing the coefficient of linear expansion of polyimide films, with α-alumina as the active ingredient.

15. An agent that improves the adhesion of polyimide films to metals, with α-alumina as the active ingredient.

16. The aforementioned metal is a nickel-chromium alloy, aluminum, or silver. The material for improving adhesion to metals according to claim 15.

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