Film, laminate, precursor composition, and composition for reducing coefficient of thermal expansion of polyimide resin

Abstract

The present invention addresses the problem of reducing the coefficient of thermal expansion of a polyimide film having a high coefficient of thermal expansion. This film contains a polyimide and an oxide containing a boron element. In addition, the boron-containing oxide is preferably obtained from boric acid and an alumina sol. Further, the film preferably has a coefficient of thermal expansion of 50 ppm / DEG C or less. Further, the film preferably exhibits a light transmittance of 74% or more at a wavelength of 420 nm. Further, the film preferably shows a yellowness (YI) of 6.0 or less. Further, it is preferable that the film exhibit a thermal conductivity in the range of 0.231 W / mK or more and 0.275 W / mK or less.

Description

Technical Field

[0001] The present invention relates to a film having a low coefficient of thermal expansion. Furthermore, the present invention relates to a laminate of the film and a glass substrate. Furthermore, the present invention relates to a precursor composition required for producing the film. Furthermore, the present invention relates to a composition for reducing the coefficient of thermal expansion of a polyimide resin. Background Art

[0002] Polyimide resins have attracted attention as materials that are highly heat-resistant, lightweight, and flexible. Polyimide resins have become an indispensable chemical material for electronic devices such as personal computers, smartphones, automobiles, and televisions. In addition, films made of polyimide resins (hereinafter referred to as "polyimide films") have both heat resistance and insulation properties. Therefore, they are used as base films for flexible printed wiring boards that require high thermal dimensional stability, interlayer insulating films for semiconductors, and the like.

[0003] Furthermore, it is generally believed that the coefficient of thermal expansion of polyimide films is generally around 20ppm / °C, but this is only the thermal expansion coefficient of polyimide films with a specific chemical structure. Among polyimide films, there are characteristic polyimide films such as colorless and transparent ones and those with excellent adhesion. Most of these polyimide films have a thermal expansion coefficient greater than 50ppm / °C. In recent years, such characteristic polyimide films have attracted attention in the manufacture of flexible printed wiring boards, semiconductors, etc., but their use is restricted due to their high thermal expansion coefficient. In addition, this is because, in the manufacture of flexible printed wiring boards, semiconductors, etc., when polyimide films with a thermal expansion coefficient greater than 50ppm / °C are used, the flexible printed wiring boards, semiconductors, etc. are prone to warping, interface peeling, etc.

[0004] In this situation, liquid crystal polymer films, etc., are being used as an alternative to the aforementioned characteristic polyimide films. These films have lower thermal expansion coefficients than the characteristic polyimide films and exhibit less dimensional change. However, liquid crystal polymer films have disadvantages compared to polyimide films, such as poor heat resistance and processability. Prior art literature Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-343610 Summary of the Invention Technical problem to be solved by the invention

[0006] The technical problem of the present invention is to reduce the thermal expansion coefficient of a polyimide film having a relatively high thermal expansion coefficient. Technical means to solve technical problems

[0007] The film of one aspect of the present invention contains a polyimide resin and an oxide containing a boron element. Alternatively, the film may be composed of a polyimide resin and an oxide containing a boron element. Furthermore, the oxide containing a boron element is preferably obtained from boric acid and an alumina sol. Furthermore, the alumina sol contains aluminum oxide (alminium, acidified aluminum oxide), which is primarily composed of aluminum and oxygen. Furthermore, the oxide containing a boron element is preferably an oxide containing boron and aluminum. Furthermore, the oxide containing a boron element is preferably dispersed in a matrix of the polyimide resin. Furthermore, the polyimide resin is preferably the main component of the film.

[0008] Furthermore, the thermal expansion coefficient of the film is preferably 50 ppm / ° C. or less when the film has a thickness of 25 μm.

[0009] Furthermore, the light transmittance of the film at a wavelength of 420 nm is preferably 74% or more when the thickness is 25 μm.

[0010] Furthermore, the yellowness index (YI) of the above-mentioned film is preferably 6.0 or less when the thickness is 25 μm.

[0011] Furthermore, the thermal conductivity of the above-mentioned film is preferably within a range of 0.231 W / mK to 0.275 W / mK.

[0012] The polyimide resin is preferably obtained by imidizing a polyamic acid composed of a dianhydride and a diamine. In this case, boric acid is preferably added in an amount ranging from 2.0% to 20.0% by mass relative to the solid content of the polyamic acid solution. In this case, alumina sol is further added to the solution, and the mass ratio of the solid content of the alumina sol to the boric acid is preferably within a range of 0.5 to 1.5.

[0013] In the above film, the proportion of boron element in the total amount is preferably in the range of 0.5 mass % to 1.6 mass %, and the proportion of aluminum element in the total amount is preferably in the range of 1.5 mass % to 4.6 mass %.

[0014] A laminate according to another aspect of the present invention includes a glass substrate and the above-mentioned film.

[0015] A precursor composition according to another aspect of the present invention contains polyamic acid, boric acid, and alumina sol.

[0016] A composition for reducing the thermal expansion coefficient of a polyimide resin according to another aspect of the present invention contains boric acid and alumina sol as active ingredients. Furthermore, the composition for reducing the thermal expansion coefficient may contain polyamic acid.

[0017] In addition, the present invention can also be expressed as follows. A composition for reducing the thermal expansion coefficient of a polyimide resin containing boric acid and alumina sol. The composition for reducing the thermal expansion coefficient may also contain polyamic acid.

[0018] A method comprises: adding boric acid and alumina sol to a polyamic acid solution and then heating the polyamic acid solution to reduce the thermal expansion coefficient of the obtained polyimide resin.

[0019] Boric acid and alumina sol are used to produce a composition for reducing the thermal expansion coefficient of a polyimide resin. The composition for reducing the thermal expansion coefficient may contain polyamic acid.

[0020] A polyamic acid solution containing boric acid and alumina sol is used to produce a composition for reducing the thermal expansion coefficient of a polyimide resin.

[0021] Boric acid and alumina sol are used to reduce the thermal expansion coefficient of polyimide resin.

[0022] A boric acid and alumina sol used as a thermal expansion coefficient reducer for polyimide resin. Beneficial effects

[0023] The film of the present invention comprises a polyimide resin and a boron-containing oxide, and exhibits a lower coefficient of thermal expansion than a polyimide film composed solely of the same polyimide resin. Specifically, when the film thickness is 25 μm, the thermal expansion coefficient of the film can be reduced to 50 ppm / °C or less. Furthermore, when the polyimide resin is a polyimide resin that forms a film having excellent colorless transparency, the film's coefficient of thermal expansion can be reduced while suppressing a decrease in light transmittance and an increase in yellowness (YI). DETAILED DESCRIPTION

[0024] The film of the embodiment of the present invention is mainly composed of polyimide resin and oxide containing boron element. In addition, here, preferably polyimide resin is the main component of the film. In addition, the oxide containing boron element is preferably dispersed in the matrix of the polyimide resin. Polyimide resin is obtained by heating the polyamic acid solution consisting of acid dianhydride and diamine to imidize. In addition, here, the oxide containing boron element is formed in the polyimide resin by mixing boric acid and alumina sol in polyamic acid solution and heating it. That is, the film of the embodiment of the present invention contains boron element and aluminum element. In addition, the boron element can be detected by ICP emission spectrometry, ICP mass spectrometry, methylene blue absorptiometry, azomethine H absorptiometry, energy dispersive fluorescence X-ray analysis, graphite furnace atomic absorption spectrometry, etc. Furthermore, the aluminum element can be detected by, for example, X-ray diffraction, X-ray photoelectron spectroscopy, fluorescent X-ray analysis, ICP emission spectroscopy, atomic absorption spectrometry, infrared spectroscopy, and the like.

[0025] In addition, in the film of the embodiment of the present invention, the proportion of boron element relative to the total amount of the film is preferably in the range of 0.5 mass% to 1.6 mass% and the proportion of aluminum element relative to the total amount is preferably in the range of 1.5 mass% to 4.6 mass%. It is more preferred that the proportion of boron element relative to the total amount of the film is in the range of 0.7 mass% to 1.6 mass% and the proportion of aluminum element relative to the total amount is in the range of 2.0 mass% to 4.3 mass%. It is more preferred that the proportion of boron element relative to the total amount of the film is in the range of 0.8 mass% to 1.5 mass% and the proportion of aluminum element relative to the total amount is in the range of 2.3 mass% to 4.1 mass%.

[0026] In addition, as a method for mixing boric acid and alumina sol into a polyamic acid solution, for example, there can be cited (a) a method of directly mixing boric acid and alumina sol into a polyamic acid solution; and (b) a method of adding boric acid and alumina sol to an organic solvent to prepare a solution, and then adding the solution to the polyamic acid solution.

[0027] The purity of the boric acid used to make the film of the embodiment of the present invention is preferably 99.5% or more. In addition, as the alumina sol, an alumina sol having a solid content of 10% by mass or more is preferred. In addition, the purity of the boric acid and the solid content of the alumina sol can be appropriately selected according to the thermal expansion coefficient, light transmittance, and yellowness (YI) of the target film. In addition, the amount of boric acid added relative to the solid content of the polyamic acid solution is preferably in the range of 1.0% by mass or more and 30.0% by mass or less, more preferably in the range of 2.0% by mass or more and 20.0% by mass or less, and further preferably in the range of 3.0% by mass or more and 10.0% by mass or less.

[0028] In the film production according to the embodiment of the present invention, the mass ratio of the solid content of the alumina sol to the boric acid is preferably in the range of 0.5 to 1.5, and more preferably in the range of 0.6 to 0.9.

[0029] Furthermore, regarding the film of the embodiment of the present invention, the polyamic acid solution to which boric acid and alumina sol are added (hereinafter referred to as the polyamic acid solution containing additives) can be heat-formed by a known method. For example, the polyamic acid solution containing additives can be applied to a support, the coating can be dried, and the dried coating can be heated to produce the film of the embodiment of the present invention.

[0030] Examples of the acid dianhydride that can be used to prepare the polyamic acid solution according to the embodiment of the present invention include pyromellitic dianhydride (PMDA), 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), bis(3,4- 1,1-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, oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride, thiodiphthalic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride Aromatic tetracarboxylic dianhydrides such as carboxylic acid dianhydrides, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 9,9-bis[4-(3,4'-dicarboxyphenoxy)phenyl]fluorene dianhydride; cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexylsuccinic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride, 4,5'-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), 1,4-bis(dicarboxyphenoxy)phthalic anhydride, etc. Furthermore, two or more of these acid dianhydrides may be mixed and used.

[0031] In addition, examples of diamines that can be used to prepare the polyamic acid solution of the embodiment of the present invention include p-phenylenediamine (PPD), m-phenylenediamine (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, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane (MDA), 2,2-bis-(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfone (33DDS), 4,4'-diaminodiphenyl sulfone (44DDS), diaminodiphenyl sulfone (DDS), ...(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfone (33DDS), 4,4'-diaminodiphenyl sulfone (44DDS), 2,2-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane (MDA), 2,2 trifluorotoluene (Diaminobenzotrifluoroethyl), bis(trifluoromethyl)phenylenediamine, diaminotetrakis(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)bis(trifluoromethyl)benzene, bis(aminophenoxy)tetrakis(trifluoromethyl)benzene, bis[(trifluoromethyl)benzene] methyl)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'-diaminophenoxy 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,Aromatic diamines such as 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. Two or more of these diamines may be used in combination.

[0032] Furthermore, for the film according to an embodiment of the present invention, from the perspective of imparting mechanical properties such as durability (e.g., bending durability), it is preferred to use 3,3',4,4'-biphenyltetracarboxylic dianhydride as the dianhydride and p-phenylenediamine as the diamine, or to use 3,3',4,4'-biphenyltetracarboxylic dianhydride as the dianhydride and 4,4'-diaminodiphenyl ether as the diamine. Furthermore, for the film according to an embodiment of the present invention, from the perspective of imparting transparency as a display component, for example, it is preferred to use 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) as the dianhydrides, and use 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 3,3'-diaminodiphenyl sulfone (33DDS) as the diamine. Furthermore, other acid dianhydrides and other diamines may be added to the above-mentioned acid dianhydrides and diamines within a range not impairing the gist of the present invention.

[0033] When the thickness of the film of the embodiment of the present invention is 25 μm, the thermal expansion coefficient of the film is preferably 50.0 ppm / °C or less. In addition, the thermal expansion coefficient is more preferably 45 ppm / °C or less, further preferably 44 ppm / °C or less, further preferably 43 ppm / °C or less, further preferably 42 ppm / °C or less, further preferably 41 ppm / °C or less, and particularly preferably 40 ppm / °C or less. In addition, the lower limit is 17 ppm / °C. In addition, the lower limit may be 20 ppm / °C, 25 ppm / °C, 30 ppm / °C, 35 ppm / °C, or 39 ppm / °C. In addition, the thermal expansion coefficient can be adapted to the application and substrate (target material) by adjusting the amount of boric acid and alumina sol added.

[0034] Furthermore, when the film according to an embodiment of the present invention has a thickness of 25 μm, the film preferably has a light transmittance of 74% or greater at a wavelength of 420 nm. Furthermore, this light transmittance is more preferably 75% or greater, further preferably 76% or greater, further preferably 77% or greater, further preferably 78% or greater, and particularly preferably 79% or greater. The upper limit is 100%. Films having such light transmittance exhibit a low coefficient of thermal expansion and are suitable for display applications, etc.

[0035] Furthermore, when the thickness of the film of the embodiment of the present invention is 25 μm, the yellowness (YI) of the film is preferably 6.0 or less. In addition, the yellowness is more preferably 5.0 or less, more preferably 4.5 or less, more preferably 4.0 or less, and particularly preferably 3.5 or less. In addition, its lower limit is 2.0. In addition, its lower limit can be 2.5 or 3.0. A film with such yellowness shows a low thermal expansion coefficient and can be suitable for display applications, etc.

[0036] In addition, the tensile strength of the film of the embodiment of the present invention is preferably in the range of more than 50MPa and less than 250MPa. In addition, this tensile strength is more preferably in the range of more than 100MPa and less than 200MPa. By containing the oxide containing boron element, the film of the embodiment of the present invention can show a low thermal expansion coefficient, and can show a tensile strength of the same degree as the tensile strength originally had with the polyimide film.

[0037] Further, the tensile modulus of the film of the embodiment of the present invention is preferably in the scope of more than 3.0GPa and below 5.0GPa. In addition, this tensile modulus is more preferably in the scope of more than 3.5GPa and below 4.5GPa. By containing the oxide containing boron element, the film of the embodiment of the present invention can illustrate low thermal expansion coefficient, and can illustrate the tensile modulus of equal degree or more than the tensile modulus that polyimide film originally had.

[0038] 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%.

[0039] Furthermore, the thermal conductivity of the film according to the embodiment of the present invention is preferably in the range of 0.231 W / mK to 0.275 W / mK. Furthermore, the thermal conductivity is more preferably in the range of 0.231 W / mK to 0.243 W / mK. Furthermore, the thermal conductivity may be in the range of 0.240 W / mK to 0.275 W / mK, more preferably in the range of 0.245 W / mK to 0.275 W / mK, further preferably in the range of 0.250 W / mK to 0.275 W / mK, further preferably in the range of 0.255 W / mK to 0.275 W / mK, and particularly preferably in the range of 0.260 W / mK to 0.275 W / mK.

[0040] <Examples and Comparative Examples> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1

[0041] 1. Preparation of polyamic acid solution containing additives 12.07 g of biphenyltetracarboxylic dianhydride (BPDA), 5.34 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 8.22 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 6.37 g of 3,3'-diaminodiphenyl sulfone (33DDS) were reacted in 74.5 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution having a solid content of 30% by mass.

[0042] Next, 2.56 g of 99.5% pure boric acid (manufactured by NACALAITESQUE, INC.) and 11.18 g of alumina sol (solid content 20.0 wt%, manufactured by Nissan Chemical Co., Ltd.) were added to 26.5 g of N,N-dimethylacetamide (DMAc) to prepare a mixed solution of boric acid and alumina sol (hereinafter referred to as the "mixed solution"), and the mixed solution was added to the above-mentioned polyamic acid solution to prepare a polyamic acid solution containing additives.

[0043] 2. Film formation After the above-mentioned polyamic acid solution containing additives is coated on a glass substrate to form a coating film, the coating film is placed in an oven at 80°C and dried for 15 minutes to obtain a precursor film. Next, after the precursor film is peeled off from the glass substrate, the precursor film is placed in an oven at a temperature of 180°C and maintained for 10 minutes while the end of the precursor film is fixed with a frame. Afterwards, the temperature of the oven is raised to 280°C. In addition, at this time, the temperature of the oven is raised from 180°C to 280°C in 22 minutes, and maintained for 5 minutes after the temperature of the oven reaches 280°C. As a result, a film is formed on the glass substrate. Afterwards, the fixture fixing the end of the film is removed to obtain a film with a thickness of 25 μm.

[0044] Furthermore, the boron element in the boric acid, the aluminum element in the alumina sol, and the boron-containing compounds, aluminum-containing compounds, and compounds containing both elements do not volatilize even at 280°C. Based on this fact, the content ratios of boron and aluminum relative to the total amount of the final film were calculated based on the amounts of boric acid and alumina sol added and the solid content concentration of the polyamic acid. The results were: 1.3% by mass for the former and 3.5% by mass for the latter.

[0045] 3. Determination of membrane properties The thermal expansion coefficient, light transmittance, yellowness (YI), tensile strength, tensile modulus, tensile elongation, and thermal conductivity of the obtained film having a thickness of 25 μm were determined as shown below.

[0046] (1) Thermal expansion coefficient of the film A film cut into 3.5 mm x 13.0 mm pieces was mounted in a thermal analyzer (TMA-60) manufactured by Shimadzu Corporation. The temperature was raised to 300°C at a rate of 5.0°C / min, and the dimensional changes of the film with temperature were recorded, forming a TMA curve. The average thermal expansion coefficient from 100°C to 200°C was calculated from the resulting TMA curve. The result was a thermal expansion coefficient of 40.5 ppm / °C (see Table 1).

[0047] (2) Film light transmittance A film cut into 50.0 mm x 50.0 mm was fixed to a spectrophotometer UV-2550 (Shimadzu Corporation) and irradiated with 420 nm wavelength light from a deuterium lamp. The results showed that the light transmittance through the film was 76% (see Table 1).

[0048] (3) Yellowness of the film (YI) A film piece cut into 50.0 mm x 50.0 mm was fixed to a spectrophotometer UV-2550 (Shimadzu Corporation), and the yellowness index (YI) of the film was measured. The result was that the yellowness index (YI) of the film was 4.4 (see Table 1).

[0049] (4) Tensile properties of the film The distance between the upper and lower chucks of the Shimadzu Autograph AGS-10KNG was set to 30 mm. A film punched with a JIS No. 3 dumbbell (JIS K6301) was secured to the chucks. The film was stretched at a rate of 50 mm / minute while a load cell measured the load corresponding to the displacement of the upper chuck. A stress-strain curve was recorded. The tensile strength, tensile modulus, and tensile elongation of the film were determined from the resulting stress-strain curve. The results were: a tensile strength of 133 MPa, a tensile modulus of 4.3 GPa, and a tensile elongation of 28.6% (see Table 2).

[0050] (5) Thermal conductivity of the film Referring to JIS R2616, a 2 cm × 2 cm piece of film was cut from the above film. Next, a transistor was set on one surface of the film via thermal grease. In addition, an aluminum heat sink was set on the opposite surface via thermal grease. Next, a current was applied to the transistor to increase the temperature of the transistor until the temperature of the transistor reached 60°C and maintained at 60°C for 3 minutes. During this period, a thermocouple was used to measure the temperature A of the transistor surface and the temperature B of the surface on the heat sink side of the film. In addition, the power consumption at this time was measured. Next, the temperature A, temperature B and power consumption of each surface were substituted into the following formula to calculate the thermal resistance. Thermal resistance = (transistor surface temperature A - diaphragm heat sink placement side temperature B) / power consumption Finally, the target thermal conductivity is calculated by substituting the thermal resistance, the thickness of the diaphragm, and the cross-sectional area of ​​the transistor obtained above into the following formula. Thermal conductivity = diaphragm thickness / (transistor cross-sectional area × thermal resistance) As a result, the thermal conductivity of the film was 0.259 W / mK (see Table 1).

[0051] In addition, after the above-mentioned polyamic acid solution containing additives was applied to a glass substrate to form a coating film, the coating film was placed in an 80°C oven, and the oven was heated to 150°C after 15 minutes. In addition, at this time, it took 20 minutes for the oven temperature to reach 150°C from 70°C. After the oven temperature reached 150°C, the temperature was maintained for 10 minutes, and then the oven was heated to 300°C. In addition, at this time, it took 25 minutes for the oven temperature to reach 300°C from 150°C. After the oven temperature reached 300°C, the temperature was maintained for 5 minutes. As a result, a film with a thickness of 25 μm was formed on the glass substrate.

[0052] When the adhesiveness of the film to the glass plate was confirmed, it was confirmed that the film was well adhered to the glass plate. Example 2

[0053] The target film was obtained by the same method as in Example 1, except that the amount of alumina sol added was changed from 11.18 g to 12.78 g. Furthermore, based on the results described in Example 1, the content ratios of boron and aluminum relative to the total film volume were determined to be 1.3% by mass for the former and 4.0% by mass for the latter.

[0054] In addition, the physical properties of the obtained film were measured using the same method as shown in Example 1, and the results were: thermal expansion coefficient of 39.1 ppm / °C, light transmittance at a wavelength of 420 nm was 74%, yellowness (YI) was 4.8, tensile strength was 129 MPa, tensile elastic modulus was 4.2 GPa, tensile elongation was 27.3%, and thermal conductivity was 0.271 W / mK (see Tables 1 and 2).

[0055] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate. Example 3

[0056] The target film was obtained by the same method as in Example 1, except that the amount of alumina sol added was changed from 11.18 g to 7.99 g. Furthermore, based on the results described in Example 1, the content ratios of boron and aluminum relative to the total film volume were determined to be 1.3% by mass for the former and 2.5% by mass for the latter.

[0057] In addition, the physical properties of the obtained film were measured using the same method as shown in Example 1, and the results were: thermal expansion coefficient of 41.3 ppm / °C, transmittance at 420 nm of 78%, yellowness (YI) of 5.9, tensile strength of 123 MPa, tensile elastic modulus of 4.1 GPa, tensile elongation of 30.0%, and thermal conductivity of 0.252 W / mK (see Tables 1 and 2).

[0058] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate. Example 4

[0059] The target film was obtained by the same method as in Example 1, except that the amount of boric acid added was changed from 2.56 g to 1.59 g, and the amount of alumina sol added was changed from 11.18 g to 7.99 g. Furthermore, based on the results described in Example 1, the content ratios of boron and aluminum relative to the total film volume were determined to be 0.9% by mass for the former and 2.6% by mass for the latter.

[0060] In addition, the physical properties of the obtained film were measured using the same method as shown in Example 1, and the results were: thermal expansion coefficient of 43.2 ppm / °C, transmittance at 420 nm of 79%, yellowness (YI) of 3.5, tensile strength of 145 MPa, tensile elastic modulus of 3.9 GPa, tensile elongation of 35.0%, and thermal conductivity of 0.245 W / mK (see Tables 1 and 2).

[0061] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate. Example 5

[0062] 1. Preparation of polyamic acid solution containing additives 11.67 g of biphenyltetracarboxylic dianhydride (BPDA), 5.16 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 12.70 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 2.46 g of 3,3'-diaminodiphenyl sulfone (33DDS) were reacted in 74.5 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution having a solid content of 30% by mass.

[0063] Next, 1.59 g of 99.5% pure boric acid (manufactured by NACALAITESQUE, INC.) and 7.99 g of alumina sol (solid content 20.0 wt%, manufactured by Nissan Chemical Co., Ltd.) were added to 26.5 g of N,N-dimethylacetamide (DMAc) to prepare a mixed solution of boric acid and alumina sol (hereinafter referred to as the "mixed solution"). The mixed solution was added to the above-mentioned polyamic acid solution to prepare a polyamic acid solution containing additives.

[0064] 2. Film formation The target film was obtained in the same manner as in Example 1. The content ratios of boron and aluminum relative to the total film volume were determined based on the results of Example 1. The former was 0.9 mass % and the latter was 2.6 mass %.

[0065] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were as follows: thermal expansion coefficient of 44.5 ppm / °C, transmittance at 420 nm of 78%, yellowness (YI) of 5.9, tensile strength of 123 MPa, tensile elastic modulus of 4.1 GPa, tensile elongation of 30.0%, and thermal conductivity of 0.243 W / mK (see Tables 1 and 2).

[0066] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate. Example 6

[0067] 1. Preparation of polyamic acid solution containing additives 17.85 g of biphenyltetracarboxylic dianhydride (BPDA) and 12.15 g of 4,4′-diaminodiphenyl ether (ODA) were reacted in 70.0 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution having a solid content of 30% by mass.

[0068] Next, 1.50 g of 99.5% pure boric acid (manufactured by NACALAITESQUE, INC.) and 7.50 g of alumina sol (solid content 20.0 wt%, manufactured by Nissan Chemical Co., Ltd.) were added to 23.0 g of N,N-dimethylacetamide (DMAc) to prepare a mixed solution of boric acid and alumina sol (hereinafter referred to as the "mixed solution"). The mixed solution was added to the above-mentioned polyamic acid solution to prepare a polyamic acid solution containing additives.

[0069] 2. Film formation The target film was obtained in the same manner as in Example 1. The content ratios of boron and aluminum relative to the total film volume were determined based on the results of Example 1. The former was 0.9 mass % and the latter was 2.6 mass %.

[0070] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were as follows: thermal expansion coefficient of 42.7 ppm / °C, tensile strength of 158 MPa, tensile elastic modulus of 4.3 GPa, tensile elongation of 20.9%, and thermal conductivity of 0.245 W / mK (see Tables 1 and 2).

[0071] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate. Example 7

[0072] 1. Preparation of polyamic acid solution containing additives 12.07 g of biphenyltetracarboxylic dianhydride (BPDA), 5.34 g of 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 8.22 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 6.37 g of 4,4'-diaminodiphenyl sulfone (44DDS) were reacted in 74.5 g of N,N-dimethylacetamide (DMAc) to prepare a polyamic acid solution having a solid content of 30% by mass.

[0073] Next, 2.56 g of 99.5% pure boric acid (manufactured by NACALAI TESQUE, INC.) and 11.18 g of alumina sol (solid content 20.0 wt%, manufactured by Nissan Chemical Co., Ltd.) were added to 26.5 g of N,N-dimethylacetamide (DMAc) to prepare a mixed solution of boric acid and alumina sol (hereinafter referred to as the "mixed solution"). The mixed solution was added to the above-mentioned polyamic acid solution to prepare a polyamic acid solution containing additives.

[0074] 2. Film formation The target film was obtained in the same manner as in Example 1. The content ratios of boron and aluminum relative to the total film volume were determined based on the results of Example 1. The former was 1.3% by mass and the latter was 3.5% by mass.

[0075] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were as follows: thermal expansion coefficient of 45.3 ppm / °C, transmittance at 420 nm of 74%, yellowness (YI) of 5.5, tensile strength of 124 MPa, tensile elastic modulus of 3.0 GPa, tensile elongation of 18.8%, and thermal conductivity of 0.256 W / mK (see Tables 1 and 2).

[0076] Furthermore, a laminate of the film and the glass plate was formed in the same manner as in Example 1, and adhesion of the film to the glass plate was confirmed. As a result, it was confirmed that the film was well adhered to the glass plate.

[0077] (Comparative Example 1) 1. Preparation of polyamic acid solution containing additives A polyamic acid solution having a solid content of 30% by mass was prepared in the same manner as in Example 1.

[0078] Next, 2.56 g of 99.5% pure boric acid (manufactured by Nacalai Tesque, Inc.) was added to 26.5 g of N,N-dimethylacetamide (DMAc) to prepare a boric acid solution, which was then added to the polyamic acid solution to prepare a boric acid-containing polyamic acid solution.

[0079] 2. Film formation The target film was obtained by the same method as described in Example 1, except that the polyamic acid solution containing the additive was replaced with a polyamic acid solution containing boric acid. Furthermore, based on the results described in Example 1, the content ratios of boron and aluminum relative to the total film volume were determined, and the results were: 1.4% by mass of boron and 0% by mass of aluminum.

[0080] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were as follows: thermal expansion coefficient of 150 ppm / °C, light transmittance at a wavelength of 420 nm of 11%, yellowness (YI) of 62, tensile strength of 113 MPa, tensile elastic modulus of 3.9 GPa, and tensile elongation of 3.2% (see Tables 1 and 2).

[0081] (Comparative Example 2) The target film was obtained by the same method as described in Example 1, except that 2.56 g of 99.5% pure boric acid (manufactured by Nacalai Tesque, Inc.) was replaced with 11.18 g of alumina sol (solid content 20.0 wt %, manufactured by Nissan Chemical Co., Ltd.). Furthermore, based on the results described in Example 1, the content ratios of boron and aluminum relative to the total film volume were determined to be 0% by mass for the former and 3.7% by mass for the latter.

[0082] In addition, the physical properties of the obtained film were measured using the same method as shown in Example 1, and the results were: thermal expansion coefficient of 51.0 ppm / °C, transmittance at 420 nm of 79%, yellowness (YI) of 3.4, tensile strength of 141 MPa, tensile elastic modulus of 3.8 GPa, and tensile elongation of 30.0% (see Tables 1 and 2).

[0083] (Comparative Example 3) 1. Preparation of polyamic acid solution A polyamic acid solution having a solid content of 30% by mass was prepared in the same manner as in Example 1.

[0084] 2. Film formation The target film was obtained by the same method as in Example 1 except that the polyamic acid solution containing additives was replaced with the above-mentioned polyamic acid solution. That is, the content ratio of boron and aluminum elements relative to the total film amount was 0 mass %.

[0085] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were: thermal expansion coefficient of 51.0 ppm / °C, light transmittance at a wavelength of 420 nm of 80%, and yellowness (YI) of 3.2 (see Table 1).

[0086] (Comparative Example 4) 1. Preparation of polyamic acid solution A polyamic acid solution having a solid content of 30% by mass was prepared in the same manner as in Example 6.

[0087] 2. Film formation The target film was obtained by the same method as in Example 1 except that the polyamic acid solution containing additives was replaced with the above-mentioned polyamic acid solution. That is, the content ratio of boron and aluminum elements relative to the total film amount was 0 mass %.

[0088] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results showed that the thermal expansion coefficient was 51.0 ppm / °C (see Table 1).

[0089] (Comparative Example 5) 1. Preparation of polyamic acid solution A polyamic acid solution having a solid content of 30% by mass was prepared in the same manner as in Example 7.

[0090] 2. Film formation The target film was obtained by the same method as in Example 1 except that the polyamic acid solution containing additives was replaced with the above-mentioned polyamic acid solution. That is, the content ratio of boron and aluminum elements relative to the total film amount was 0 mass %.

[0091] 3. Determination of membrane properties The physical properties of the obtained film were measured in the same manner as in Example 1. The results were: thermal expansion coefficient of 55.7 ppm / °C, light transmittance at a wavelength of 420 nm of 78%, and yellowness (YI) of 4.6 (see Table 1).

[0092] [Table 1]

[0093] [Table 2]

[0094] Based on the results shown in the Examples and Comparative Examples above, it is clear that the thermal expansion coefficient of the films obtained in this Example is suppressed compared to polyimide films without boric acid, without alumina sol, or without either addition. Furthermore, it is clear that the films obtained in this Example exhibit comparable tensile properties to polyimide films without boric acid, without alumina sol, or without either addition. Furthermore, it is clear that the films obtained in Examples 1 to 5 exhibit comparable colorless transparency to polyimide films without either boric acid or alumina sol. Industrial Applicability

[0095] Compared with the polyimide film consisting only of the same polyimide resin, the film of the present invention shows a low thermal expansion coefficient, for example, it can be used as components and parts of electrical and electronic equipment, heat-resistant belts, substrates, cover layers (kabalei) etc. constituting solar cells (such as silicon solar cells, perovskite solar cells, etc.). In addition, as substrates, for example, circuit substrates for mounting light-emitting elements, substrates for barcode printing, etc. can be given. In addition, as electrical equipment and electronic equipment, for example, computers (such as personal computers, smart phones, car control devices, car navigation devices, etc.), television receivers, wearable devices (such as AR / VR glasses, smart watches, etc.), lighting equipment, display devices (such as computer displays, large display devices, large visual devices, LED display devices, LED visual devices) can be given. In addition, as components and parts of electrical and electronic equipment, for example, flexible printed circuit boards (FPCs), antennas, reflectors, etc. can be given.

Claims

1. A membrane, wherein The membrane contains: Polyimide resin, and Oxides containing the element boron.

2. The film according to claim 1, wherein The oxide containing boron is an oxide containing boron and aluminum.

3. The film according to claim 1 or 2, wherein The oxide containing the boron element is obtained from boric acid and aluminum oxide sol.

4. The film according to claim 1 or 2, wherein The thermal expansion coefficient is 50ppm / °C or less.

5. The film according to claim 4, wherein The light transmittance at a wavelength of 420 nm is 74% or more.

6. The film according to claim 5, wherein The yellowness index, i.e., YI, is 6.0 or less.

7. The film according to claim 4, wherein The thermal conductivity is within a range of 0.231 W / mK to 0.275 W / mK.

8. The film according to claim 4, wherein The polyimide is obtained by imidizing a polyamic acid composed of an acid dianhydride and a diamine. Boric acid is added to the polyamic acid solution in an amount within a range of 2.0% by mass or more and 20.0% by mass or less relative to the solid content of the polyamic acid solution.

9. The film according to claim 8, wherein Alumina sol is further added to the solution, The mass ratio of the solid content of the alumina sol to the boric acid is within a range of 0.5 to 1.

5.

10. The film according to claim 1 or 2, wherein The blending ratio of the boron element to the total amount is within a range of 0.5 mass % to 1.6 mass %. The blending ratio of the aluminum element to the total amount is within a range of 1.5 mass % to 4.6 mass %.

11. A laminate, wherein: The laminate comprises: Glass substrate, and The film according to claim 1 or 2.

12. A precursor composition, wherein The precursor composition comprises: Polyamic acid, Boric acid, and Alumina sol.

13. A composition for reducing the thermal expansion coefficient of a polyimide resin, wherein: The composition takes boric acid and alumina sol as effective ingredients.

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