KR20230040304A - Resin film and manufacturing method of resin film - Google Patents

Abstract

Provided is a resin film having excellent heat resistance, maintaining a low linear expansion coefficient up to a high temperature region, having a high tensile modulus, having a small ratio of linear expansion coefficient and tensile modulus in the MD and TD directions of the resin film, and having good physical property isotropy. A resin film satisfying the following (1) to (2).
(1) The temperature (A) at which the temperature dependent curve of tanδ, which is the value obtained by dividing the loss modulus by the storage elastic modulus, has a peak is within the range of 250 to 500°C, and the temperature (A) at which the temperature dependent curve of tanδ has a peak and linear expansion The coefficient inflection point temperature (B) is in the relationship of the following formula
(40+0.8×A)≤B<A;
(2) The weight average molecular weight of the resin as a raw material of the resin film is in the range of 50,000 to 500,000, and the molecular weight distribution, which is the value obtained by dividing the weight average molecular weight by the number average molecular weight of the resin, is in the range of 1.0 to 5.0.

Description

Resin film and manufacturing method of resin film

The present invention relates to a resin film and a method for manufacturing the resin film. More specifically, it has excellent heat resistance, maintains a low linear expansion coefficient up to a high temperature region, has a high tensile modulus, has a small ratio of the linear expansion coefficient and tensile modulus in the TD direction to the MD direction of the resin film, and has isotropic physical properties of the resin film. It relates to a resin film excellent in this good transparency and a method for producing the resin film.

In recent years, with the advancement of miniaturization, weight reduction, and convenience of highly functional mobile phones, digital cameras, display devices, and other various electronic devices, instead of the conventionally used hard and impact-resistant glass substrate, heat resistance, low coefficient of linear expansion, and high tensile strength A resin film substrate material having excellent elastic modulus, flexibility, impact resistance and transparency is expected.

The resin film is industrially produced by forming an organic polymer resin material into a film, and as a film forming method, a melt film forming method in which an organic polymer resin is melted and then extruded from a slit-type die, and an organic polymer resin solution is uniformly applied to a support There is a solution film forming method in which coating is applied and the solvent is dried and volatilized. Among organic polymeric resin materials, since polyimide resins and polyamideimide resins, which are particularly excellent in heat resistance, do not melt or melt at very high temperatures, it is common to obtain a resin film by solution film formation.

In such a solution film forming method in which the solvent is dried and volatilized by coating, thickness unevenness or orientation unevenness may occur depending on the coating conditions and drying conditions. For example, in Patent Document 1, by reviewing the coating conditions such as support rotation speed, There is a proposal that reduces cross section unevenness.

In addition, in order to suppress the difference in sagging of the film, it was found that there is a correlation between the sagging, the anisotropic index, the principal axis orientation coefficient, the thermal contraction rate, and the drying temperature, and suppressing the drying temperature unevenness in the width direction, the linear expansion coefficient, that is, the dimension A method for suppressing the difference in change is described (Patent Document 2).

In Patent Literature 3, when manufacturing a polyimide film that causes a significant drop in elastic modulus above the glass transition temperature, both ends of the film are fixed in accordance with the width of the film that changes due to contraction and expansion in the heating process and transported without sagging. Thereby, a manufacturing method for reducing the anisotropy of the linear expansion coefficient in the MD direction (advancing direction) and the TD direction (width direction) of the film is described.

Patent Document 1: Japanese Unexamined Patent Publication No. 2013-203838 Patent Document 2: Japanese Unexamined Patent Publication No. 2018-70842 Patent Document 3: Japanese Unexamined Patent Publication No. 2000-290401

In order to form functional elements such as electrodes and display elements directly on the surface, resin films used as substitutes for glass substrates are required to have high tensile modulus, low CTE, and heat resistance and chemical resistance. Polyimide as a resin suitable for such a resin film, polyamideimide, and polyamic acid as a precursor of polyimide contain many rigid molecular chains with low mobility and have high molecular weight, thereby exhibiting heat resistance, and As a result of high molecular weight, it has a wide distribution in molecular weight.

When applying and drying such a resin solution, if it contains a lot of rigid molecular chains with high molecular weight, wide molecular weight distribution, and low mobility, as the solvent is removed, the orientation direction, degree of orientation, or entanglement of the molecules formed first is reflected. Each domain is formed by a difference between a dense higher order structure and a coarser higher order structure reflecting the orientation direction, degree of orientation, and entanglement of molecules formed later.

When a film is industrially continuously manufactured by application and drying from a resin solution, in order to be conveyed to a heating furnace by roll-to-roll, the continuously manufactured film has the same process and shape as the MD direction (running direction) and TD direction (width direction) has a negative anisotropy. This eutectic and morphological anisotropy affects the formation of domains having different higher-order structures described above, and the orientation direction, degree of orientation, and entanglement of molecules in either the width direction or the forward direction become non-uniform, resulting in differences in dimensional change and physical properties. anisotropy of

In the method of Patent Literature 1, the transverse unevenness in the longitudinal direction is reduced, and the anisotropy of physical properties due to the difference in thickness is suppressed, but the orientation direction of the molecules inside the film, the degree of orientation, and the anisotropy of physical properties due to non-uniformity in entanglement are suppressed It didn't work. Further, in Patent Literature 2, drying is performed under the condition that the drying temperature unevenness in the width direction is 20° C. or less, so that the heat shrinkage rate in the longitudinal direction and the width direction of the film is set to 0.05% or less. The ratio of the maximum value of shrinkage in the width direction to the length direction was 0.33 at most, and the anisotropy of the MD direction (lengthwise direction) and TD direction (width direction) of the heat shrinkage rate was not suppressed.

In the method for producing a polyimide film of Patent Document 3, the film is intentionally shrunk in the width direction in the first half of the step in accordance with the step of gradually passing through a high-temperature furnace sequentially, and in the step of causing sagging of the film in the second half of the step. Although the anisotropy in the width direction and the traveling direction of the film is reduced by widening it in the width direction and manufacturing it without sagging, in the examples, the ratio of the linear expansion coefficient in the MD (flow direction) direction and the TD (width direction) direction of the polyimide film is 0.96, and further reducing the anisotropy becomes a subject.

As described above, polyimide has excellent heat resistance, a low linear expansion coefficient and a high tensile modulus, while having a high molecular weight, wide molecular weight distribution, and a rigid molecular chain with low mobility. Since domains with different high-order structures reflecting degree or entanglement are formed, a resin film that maintains a low linear expansion coefficient up to a high temperature region, has a small ratio of linear expansion coefficient and tensile modulus in the MD and TD directions of the resin film, and has good isotropy in physical properties. Getting it was a challenge.

The inventors of the present invention, as a result of intensive studies to solve the above problems, found that these problems could be solved and reached the present invention. That is, this invention has the following structures.

A resin film satisfying the following (1) to (2).

(1) The temperature (A) at which the temperature dependent curve of tanδ, which is the value obtained by dividing the loss modulus by the storage elastic modulus, has a peak is within the range of 250 to 500°C, and the temperature (A) at which the temperature dependent curve of tanδ has a peak and linear expansion The coefficient inflection point temperature (B) is in the relationship of the following formula

(40+0.8×A)≤B<A

(2) The weight average molecular weight of the resin, which is the raw material of the resin film, is within the range of 50,000 to 500,000, and the molecular weight distribution, which is the value obtained by dividing the weight average molecular weight by the number average molecular weight of the resin, is within the range of 1.0 to 5.0.

It is preferable that the resin film further satisfies (3) to (4).

(3) The linear expansion coefficient measured in the range of 35 to 200 ° C. in both MD and TD directions is in the range of -5 ppm / ° C to +55 ppm / ° C, and the linear expansion coefficient is in the TD direction with respect to the MD direction The ratio of is in the range of 0.97 to 1.03

(4) The tensile modulus of elasticity in both MD and TD directions is in the range of 2 to 20 GPa, and the ratio of the tensile modulus in the TD direction to the MD direction is in the range of 0.97 to 1.03.

The resin film preferably has a yellow index of 10 or less, a light transmittance of 70% or more at a wavelength of 400 nm, and a total light transmittance of 85% or more.

Step A of applying a resin solution onto a support and drying it to produce a resin film laminate containing a solvent;

Step B of peeling the support from the laminate to obtain a solvent-containing resin film;

Step C of removing the solvent from the resin film containing the solvent or performing a dehydration ring closure reaction while removing the solvent,

The manufacturing method of the said resin film characterized by performing at least a part of said process C by microwave heating.

The resin solution preferably contains at least one resin selected from the group consisting of polyamic acid, polyimide and polyamideimide, and a solvent having a dipole moment in the range of 3.0 to 6.0 D and dissolving the resin. do.

According to the present invention, even when a resin solution composed of polyimide, polyamideimide, and polyamic acid, which is a precursor of polyimide, containing many rigid molecular chains having a high molecular weight and a wide molecular weight distribution and low mobility, is coated and dried, A resin film having excellent heat resistance, maintaining a low coefficient of linear expansion up to a high temperature range, having a high tensile modulus, having a small ratio of linear expansion coefficient and tensile modulus in the MD and TD directions of the resin film, and excellent isotropy in physical properties and excellent transparency can be obtained. can

Hereinafter, the resin film of the embodiment of the present invention and the manufacturing method of the resin film will be described. The resin film of the present invention is a film that satisfies the following (1) to (2).

(1) The temperature (A) at which the temperature dependent curve of tanδ, which is the value obtained by dividing the loss modulus by the storage elastic modulus, has a peak is within the range of 250 to 500 ° C, the temperature at which the temperature dependent curve of tanδ has a peak and the temperature of the inflection point of the linear expansion coefficient (B) exists in the relationship of the following formula.

(40+0.8×A)≤B<A

The tanδ temperature dependence curve with respect to temperature is an index for changing the viscoelasticity of the resin due to temperature change, and when the tanδ temperature dependence curve exceeds the temperature at which it peaks, the viscosity of the resin increases markedly and the strength decreases. Therefore, in terms of heat resistance required for replacement of glass substrates used in mobile phones, digital cameras, display devices, and other various electronic devices, the temperature at which the tan δ temperature dependence curve peaks is within the range of 250 to 500 ° C. It is necessary, preferably within the range of 260 to 480 ° C, more preferably within the range of 270 to 460 ° C. The method of measuring the temperature at which the temperature dependence curve of tan δ of the resin film becomes a peak follows the method described in Examples.

The resin film expands or contracts due to temperature change, and the linear expansion coefficient is an index of the change. The linear expansion coefficient of the resin film is not always constant with respect to the measured temperature range, and the linear expansion coefficient increases at a specific temperature according to the resin film. This specific temperature is called the temperature of the inflection point of the coefficient of linear expansion.

It is preferable that the resin film of this invention is obtained by apply|coating and drying a resin solution. When a resin film is obtained by applying and drying a resin solution, as the solvent is removed, a more dense higher-order structure reflecting the orientation direction, degree of orientation, and entanglement of molecules formed first, and the orientation direction, degree of orientation, and entanglement of molecules formed later A coarser higher-order structure reflecting , and each domain is formed. At this time, when the resin contains more rigid molecular chains with a higher molecular weight and a wider molecular weight distribution and low mobility, the coarseness of the higher order structure of each domain is more greatly different.

The temperature at which the tanδ temperature dependence curve peaks and the temperature at the inflection point of the linear expansion coefficient are both the physical property inflection point temperatures, but the temperature at which the tanδ temperature dependence curve peaks is the average change in physical properties of higher-order structures of different roughness formed at the stage of production of the resin film. Since the coefficient of linear expansion reflects the change in physical properties of the coarse higher order structure formed at the stage of preparation of the resin film, the temperature of the inflection point of the coefficient of linear expansion (B) is always higher than the temperature (A) at which the temperature dependence curve of tanδ becomes a peak. lower (B<A). In addition, the value obtained by subtracting the inflection point temperature of the linear expansion coefficient from the temperature at which the tan δ temperature dependence curve peaks tends to increase as the temperature at which the tan δ temperature dependence curve peaks is higher. In order to maintain a low linear expansion coefficient required for replacement of glass substrates and a low linear expansion coefficient even at high temperatures in the substrate processing process, the linear expansion coefficient inflection point temperature (B) is preferably higher, and specifically, the temperature dependence of tanδ For the temperature (A) at which the curve becomes a peak, it is preferable to satisfy the expression (40+0.8xA)≤B. The method of measuring the temperature of the inflection point of the linear expansion coefficient of the resin film is in accordance with the method described in Examples.

(2) The weight average molecular weight of the resin, which is a raw material of the resin film, is within the range of 50,000 to 500,000, and the molecular weight distribution, which is the value obtained by dividing the weight average molecular weight by the number average molecular weight of the resin, is within the range of 1.0 to 5.0.

The weight average molecular weight of the resin as a raw material of the resin film of the present invention is within the range of 50,000 to 500,000, more preferably 80,000 to 400,000, still more preferably 100,000 to 300,000, and particularly preferably 120,000 to 200,000. If the weight average molecular weight is greater than or equal to the above lower limit, high tensile modulus, flexibility, and impact resistance required for replacement of glass substrates can be satisfied. Moreover, it becomes easy to satisfy the said formula as a weight average molecular weight is below the said upper limit. Moreover, it is preferable that the weight average molecular weight of resin in a resin solution is within the said range.

The molecular weight distribution, which is a value obtained by dividing the weight average molecular weight of the resin as a raw material of the resin film of the present invention by the number average molecular weight, is within the range of 1.0 to 5.0, more preferably 1.5 to 4.5, still more preferably 2.0 to 4.0. When the molecular weight distribution is equal to or greater than the lower limit, the cost of resin purification can be reduced, and when the molecular weight distribution is equal to or less than the upper limit, it becomes easy to satisfy the above expression. The method for measuring the weight average molecular weight and molecular weight distribution of the resin, which is a raw material of the resin film, follows the method described in Examples.

The resin film of the present invention preferably further satisfies the following (3) to (4).

(3) The linear expansion coefficient measured in the range of 35 to 200 ° C. in both MD and TD directions is in the range of -5 ppm / ° C to +55 ppm / ° C, and the linear expansion coefficient is in the TD direction with respect to the MD direction The ratio of is in the range of 0.97 to 1.03.

It is preferable that the average linear expansion coefficient measured in the range of 35-200 degreeC of both MD direction and TD direction of the resin film in this invention is -5 ppm/degreeC - +55 ppm/degreeC. More preferably -4 ppm/°C to +45 ppm/°C, still more preferably -3 ppm/°C to +35 ppm/°C. If the linear expansion coefficient is within the above range, the difference in linear expansion coefficient with the functional element can be kept small, and separation of the resin film and the functional element can be avoided even when subjected to a heat application process, resulting in excellent workability.

The ratio of the linear expansion coefficient of the resin film in the TD direction to the MD direction in the present invention is preferably in the range of 0.97 to 1.03. It is more preferably 0.975 to 1.025, still more preferably 0.98 to 1.02. If the ratio of the TD direction to the MD direction of this linear expansion coefficient is within the above range, the resin film can be used in the processing process with the functional element without distinguishing between the MD and TD directions, and the workability and yield can be improved. . The method for measuring the coefficient of linear expansion of the resin film follows the method described in Examples.

(4) The tensile modulus of elasticity in both MD and TD directions is in the range of 2 to 20 GPa, and the ratio of the tensile modulus in the TD direction to the MD direction is in the range of 0.97 to 1.03.

The tensile modulus of elasticity of the resin film of the present invention is preferably in the range of 2 to 20 GPa in both MD and TD directions. More preferably, it is 2.5-15 GPa, More preferably, it is 3-10 GPa. When the tensile modulus of elasticity is equal to or greater than the above lower limit, peeling between the resin film and the functional element can be avoided, and handleability is excellent. Moreover, a resin film can be used as a flexible film as tensile elasticity modulus is below the said upper limit.

It is preferable that the ratio of the TD direction to the MD direction of the tensile modulus of elasticity of the resin film in the present invention is in the range of 0.97 to 1.03. It is more preferably 0.975 to 1.025, still more preferably 0.98 to 1.02. When the ratio of the tensile modulus in the TD direction to the MD direction is within the above range, the resin film can be applied to the functional element processing process regardless of the MD and TD directions, and workability and yield can be improved. The method for measuring the tensile modulus of elasticity of the resin film is in accordance with the method described in Examples.

Since the resin film of the present invention is mainly used for front plates and around electrodes of image display devices such as touch panels and displays, the yellowness index (yellow index) is preferably 10 or less, more preferably 7 or less, and further Preferably it is 5 or less, More preferably, it is 3 or less. The lower limit of the yellowness of the resin film is not particularly limited, but is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.3 or more for use as a flexible electronic device. The method for measuring the yellowness index (yellow index) of the resin film is in accordance with the method described in Examples.

Since the resin film of the present invention is mainly used for the front plate and electrode periphery of image display devices such as touch panels and displays, the light transmittance at a wavelength of 400 nm is preferably 70% or more, more preferably 72% or more, , More preferably, it is 75% or more, and even more preferably, it is 80% or more. The upper limit of the light transmittance of the resin film at a wavelength of 400 nm is not particularly limited, but for use as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, still more preferably 97% or less. The method for measuring the light transmittance of the resin film at a wavelength of 400 nm was the method described in Examples.

Since the resin film of the present invention is mainly used for front plates and around electrodes of image display devices such as touch panels and displays, the total light transmittance is preferably 85% or more, more preferably 86% or more, still more preferably It is 87% or more, and more preferably 88% or more. The upper limit of the total light transmittance of the resin film is not particularly limited, but for use as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, still more preferably 97% or less. The method for measuring the total light transmittance of the resin film is in accordance with the method described in Examples.

The resin film of the present invention is preferably obtained by coating and drying a resin solution so as to reach a temperature at which a desired tan δ temperature dependence curve becomes a peak. As the resin solution, it is preferable to use a resin solution containing at least one resin selected from the group consisting of polyamic acid, polyimide and polyamideimide. A resin solution can be obtained by any of the following manufacturing methods.

The polyamic acid solution can be obtained by stirring and/or mixing diamines and tetracarboxylic acids in a solvent, and increasing the molecular weight while forming an amide bond through a condensation reaction.

As a first method, the polyimide solution can be obtained by increasing the molecular weight while heating and stirring and/or mixing diamines and tetracarboxylic acids in a solvent while generating an imide bond in one step by a dehydration ring-closing reaction. In addition, as a second method, after obtaining the above-described polyamic acid solution, an imidation accelerator and an imidation agent are added, and while stirring and / or mixing, high molecular weight is generated while generating an imide bond in two stages by a dehydration ring closure reaction. You can get it.

The polyamideimide solution can be obtained by high molecular weight while generating an amide bond and an imide bond in one step by a decarboxylation reaction while stirring and/or mixing diisocyanates and tricarboxylic acids in a solvent.

When increasing the molecular weight of the above polyamic acid, polyimide and polyamideimide, dicarboxylic acids can be used as copolymerization components within a range that does not impair the properties of the resin solution and resin film.

The resin solution used in the present invention is a resin solid obtained by pouring the resin solution obtained above into a poor solvent to precipitate a resin component, washing, filtering, and drying, or a resin solid obtained by casting and drying the resin solution into a soluble solvent. It can also be obtained by melting.

As the tetracarboxylic acids, tricarboxylic acids, and dicarboxylic acids, aromatic tetracarboxylic acids (including acid anhydrides thereof) commonly used in polyimide synthesis and polyamideimide synthesis, aliphatic tetracarboxylic acids (the acid (including anhydrides), alicyclic tetracarboxylic acids (including their acid anhydrides), aromatic tricarboxylic acids (including their acid anhydrides), aliphatic tricarboxylic acids (including their acid anhydrides), alicyclic tricarboxylic acids Acids (including their acid anhydrides), aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and the like can be used. Among them, aromatic tetracarboxylic acid anhydrides and alicyclic tetracarboxylic acid anhydrides are preferable, aromatic tetracarboxylic acid anhydrides are more preferable from the viewpoint of heat resistance, and alicyclic tetracarboxylic acids from the viewpoint of light transmittance. is more preferable. When the tetracarboxylic acid is an acid anhydride, one or two anhydride structures may be used in the molecule, but preferably one having two anhydride structures (dianhydride) is good. Tetracarboxylic acids, tricarboxylic acids, and dicarboxylic acids may be used alone or in combination of two or more.

As aromatic tetracarboxylic acids for obtaining a colorless and highly transparent polyimide in the present invention, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, 3 ,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid) 1,4-phenylene, bis(1,3-dioxo -1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro -2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetra Carboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1 ,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-di yloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl) Bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3- dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'- (3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4 ,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(toluene-2,5-di yloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1, 4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1 -dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4' -(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid; 3,3',4,4'-diphenylsulfone Tetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 2,2',3,3'-bi Phenyltetracarboxylic acid, 2,2'-diphenoxy-4,4',5,5'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9 '-fluorene) -2,6-diylbis (oxycarbonyl)] diphthalic acid, 4,4'-[spiro (xanthene-9,9'-fluorene) -3,6-diylbis (oxycarbonyl) bornyl)] tetracarboxylic acids such as diphthalic acid and acid anhydrides thereof. Among these, dianhydrides having two acid anhydride structures are suitable, particularly 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride and 4,4'-oxydiphthalic dianhydride. this is preferable Moreover, aromatic tetracarboxylic acids may be used independently and may use 2 or more types together. Aromatic tetracarboxylic acids are preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and even more preferably 50% by mass or more of all tetracarboxylic acids, when importance is placed on heat resistance. Preferably it is 80 mass % or more.

As alicyclic tetracarboxylic acids, 1,2,3,4-cyclobutane tetracarboxylic acid, 1,2,3,4-cyclopentane tetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid Boxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3 ,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octo-7-en-2 ,3,5,6-tetracarboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene- 2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3, 6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclo Pentanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid (aka "norbonane-2-spiro-2'-cyclopentanone-5' -spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid'), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2' '-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbonane- 5,5'',6,6''-tetracarboxylic acid (aka "norbonane-2-spiro-2'-cyclohexanone-6'-spiro-2''-norbonane-5,5'' ,6,6'-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6 ,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro -α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclooctanone-α '-spiro-2''-norbonan-5,5'',6,6 ''-tetracarboxylic acid, norbonane-2-spiro-α-cyclononanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, Norbonane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α -Cycloundecanone-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclododecanone-α'- Spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclotridecanone-α'-spiro-2''-novo I-5,5'',6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbonane-5,5'' ,6,6''-tetracarboxylic acid, norbonane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbonane-5,5'',6,6''- Tetracarboxylic acid, norbonane-2-spiro(methylcyclopentanone)-α'-spiro-2''-norbonane-5,5'',6,6''-tetracarboxylic acid, norbonane- Tetracarboxylic acids such as 2-spiro(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid and their acid anhydrides can be heard Among these, dianhydrides having two acid anhydride structures are suitable, particularly 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,3,4-cyclohexanetetracarboxylic dianhydride. Water and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetra Carboxylic acid dianhydride is more preferable, and 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride is still more preferable. Moreover, these may be used independently and may use 2 or more types together. Alicyclic tetracarboxylic acids are preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, of all tetracarboxylic acids, for example, when importance is placed on transparency. More preferably, it is 80 mass % or more.

As tricarboxylic acids, trimellitic acid, 1,2,5-naphthalene tricarboxylic acid, diphenyl ether-3,3',4'-tricarboxylic acid, diphenylsulfone-3,3',4' - Aromatic tricarboxylic acids such as tricarboxylic acids, or hydrogenated products of the aromatic tricarboxylic acids such as hexahydrotrimellitic acid, ethylene glycol bistrimellitate, propylene glycol bistrimellitate, and 1,4-butanediol and alkylene glycol bistrimellitates such as bistrimellitate and polyethylene glycol bistrimellitate, and monohydrides and esters thereof. Among these, a monohydride having one acid anhydride structure is suitable, and trimellitic anhydride and hexahydrotrimellitic anhydride are particularly preferable. In addition, these may be used individually or may be used combining plurality.

Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid, or 1,6-cyclohexanedicarboxylic acid. Hydrogenates of the above aromatic dicarboxylic acids, such as oxalic acid, succinic acid, glutalic acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 2-methyl succinic acid, and acid chlorides or ester compounds thereof; and the like. Among these, aromatic dicarboxylic acids and hydrogenated products thereof are suitable, and terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid are particularly preferred. In addition, dicarboxylic acids may be used independently or may be used in combination of plurality.

Diamines or diisocyanates for obtaining colorless and highly transparent polyimide in the present invention are not particularly limited, and aromatic diamines, aliphatic diamines, and alicyclic diamines commonly used in polyimide synthesis and polyamideimide synthesis. , aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and the like can be used. From the viewpoint of heat resistance, aromatic diamines are preferred, and from the viewpoint of transparency, alicyclic diamines are preferred. Moreover, when aromatic diamines which have a benzoxazole structure are used, it becomes possible to express a high elastic modulus, low thermal contraction property, and a low linear expansion coefficient with high heat resistance. Diamines and diisocyanates may be used independently or may use 2 or more types together.

As aromatic diamines, for example, 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis (4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy) cy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sul Feed, bis[4-(3-aminophenoxy)phenyl] sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy) ) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine , 4-amino-N- (4-aminophenyl) benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2 ,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-dia Minodiphenylsulfide, 3,3'-diaminodiphenylsulfoxide, 3,4'-diaminodiphenylsulfoxide, 4,4'-diaminodiphenylsulfoxide, 3,3'-diaminodi Phenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'- Diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl ]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-( 4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2, 2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy) ) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl ]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)- 3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4 -Aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4 -aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy) ) Benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [ 4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl] sulfone, bis[4-( 3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[ 4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenylsulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl ] Sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4, 4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]di Phenylsulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl] sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene , 1,3-bis[4-(4 -aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1 ,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α ,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4' -Diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'- Diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5' -phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-dia Mino-4,5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'- Diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4- Bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5- Biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzo Nitrile, 4,4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'- Fluorene) -2,6-diylbis (oxycarbonyl)] bisaniline, 4,4'-[spiro (xanthene-9,9'-fluorene) -2,6-diylbis (oxycarbonyl) ]bisaniline, 4,4'-[spiro(xanthen-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, 9,10-bis(4-aminophenyl) Adenine, 2,4-bis(4-aminophenyl)cycle Some or all of the hydrogen atoms on dimethyl lobutane-1,3-dicarboxylic acid and the aromatic ring of the aromatic diamine are halogen atoms, alkyl groups or alkoxyl groups having 1 to 3 carbon atoms, cyano groups, or alkyl or alkoxyl groups aromatic diamines in which some or all of the hydrogen atoms of are substituted with halogen atoms, a halogenated alkyl group having 1 to 3 carbon atoms, or an alkoxyl group. In addition, the aromatic diamines having the benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole and 6-amino-2-(p-aminophenyl)benzo. Oxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzo oxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzooxazolo)-4-(6-aminobenzooxazolo)benzene, 2,6- (4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2 -d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2, 6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1 ,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, etc. can be heard Among these, in particular, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4-amino-N-(4-aminophenyl)benzamide, 4,4'-diaminodiphenyl Sulfone and 3,3'-diaminobenzophenone are preferred. Moreover, aromatic diamines may be used individually or may be used combining plurality.

As alicyclic diamines, for example, 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino- 2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane , 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine), etc. can be heard Among these, 1,4-diaminocyclohexane and 1,4-diamino-2-methylcyclohexane are particularly preferred, and 1,4-diaminocyclohexane is more preferred. Moreover, alicyclic diamines may be used independently or may be used combining plurality.

Examples of diisocyanates include diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5 ,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3 '- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3' - or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate , diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4,4'-diisocyanate, benzo Phenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p -xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-(2,2-bis(4-phenoxyphenyl)propane) diisocyanate, 3,3'- or 2,2'-dimethyl Biphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'- Aromatic diisocyanates such as diisocyanate and 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and diisocyanates obtained by hydrogenating any of these diisocyanates (e.g., isophorone diisocyanate, 1,4-diisocyanate) Cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate) and the like. Among these, diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 3, tolylene-2,4-diisocyanate, 3, 3'-dimethylbiphenyl-4,4'-diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 1,4-cyclohexane diisocyanate are preferable. In addition, diisocyanates may be used independently or may be used in combination of plurality.

The solvent used in the resin solution of the present invention has a dipole moment in the range of 3.0 to 6.0 D and is a solvent that dissolves at least one resin selected from the group consisting of polyamic acid, polyimide and polyamideimide. desirable. When the dipole moment is within the above range, the uniform heating effect of microwave heating used in the solvent removal step of the resin film described later is excellent, and it becomes easy to improve the isotropy of physical properties of the obtained resin film.

As the solvent used in the resin solution of the present invention, for example, N,N-dimethylformamide (dipole moment: 3.86 D), N,N-dimethylacetamide (DMAc) (dipole moment: 3.72 D), N-methyl- 2-pyrrolidone (NMP) (dipole moment: 4.09 D), N-methyl-ε-caprolactam (dipole moment: 4.23 D), dimethylsulfoxide (dipole moment: 3.96 D), dimethylsulfone (dipole moment: 4.47 D), sulfolane (dipole moment: 4.68 D), 1,3-dimethyl-2-imidazolidinone (dipole moment: 4.07 D), 1,3-dimethyl-2-pyrimidinone (dipole moment: 4.17 D) ), 3-methyl-2-oxazolidone (dipole moment: 4.10 D), hexamethylphosphoramide (dipole moment: 5.54 D), γ-butyrolactone (GBL) (dipole moment: 4.27 D), etc. , These may be used independently or may use 2 or more types together. In addition to these solvents, poor solvents such as toluene (dipole moment: 0.36 D) and xylene (dipole moment: 0.00 to 0.64 D) may be used to the extent that resin solids do not precipitate and the uniform heating effect of microwave heating is not impaired. good night. In addition, the value of the dipole moment in the case of mixing two or more types of solvent is made into the weighted average value of each value.

Fine particles may be added to the resin solution of the present invention within a range not impairing the properties of the resin film. The fine particles may be inorganic fine particles or organic fine particles. Examples of the inorganic fine particles include silicon nitride, silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, tin oxide, calcium carbonate, barium sulfate, talc, kaolin, calcium sulfate, and the like. can Further, examples of the organic fine particles include polyamide-based resins, polyimide-based resins, benzoguanamine-based resins, and melamine-based resins, and these fine particles may be used in combination.

The resin solid content concentration of the resin solution of the present invention is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, still more preferably 10 to 30% by mass. A resin solid content concentration of at least the lower limit is preferable from the viewpoint of obtaining a film thickness necessary for the resin film, and a concentration of the resin solid content of the upper limit is preferably from the viewpoint of obtaining solution fluidity that does not impair the physical property isotropy of the resin film.

It is preferable that the resin film in this invention is a resin film obtained by the manufacturing method of the resin film mentioned later. Specifically, it is a polymer film having an imide bond in the main chain, preferably a polyimide film or a polyamideimide film, more preferably a polyimide film.

The lower limit of the thickness of the resin film in the present invention is preferably 3 μm or more, more preferably 5 μm or more, still more preferably 7 μm or more, from the viewpoint of strength and handleability required for the resin film. The upper limit of the thickness of the resin film is preferably 250 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less, from the viewpoint of uniformly removing the solvent.

A preferred method for producing the resin film of the present invention is

Step A of applying and drying the resin solution on a support to produce a resin film laminate containing a solvent;

Step B of peeling the support from the resin film layered product containing the solvent to obtain a resin film containing the solvent;

Step C of removing the solvent from the resin film containing the solvent or performing a dehydration ring closure reaction while removing the solvent,

It is characterized in that at least part of the step C is performed by microwave heating.

Process A is explained. Process A is a process of applying and drying a resin solution on a support to produce a resin film laminate (hereinafter simply referred to as a laminate) containing a solvent. In the laminate, a dried product of the resin solution is laminated on the support.

Examples of the support used in the present invention include resin film substrates, stainless steel belt substrates, and glass substrates. As the resin film substrate, it is preferable to use a resin film substrate that does not swell or elute in the solvent contained in the resin solution, such as a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polyolefin-based (PP) film, A cycloolefin type (COP) film etc. are mentioned. Further, in order to peel the solvent-containing resin film from the support, it is preferable to use a support having easy peelability.

Examples of the method for applying the resin solution on the support include a die coating method, a comma coating method, a blade coating method, a roll coating method, a knife coating method, and a bar coating method. may be combined A comma coat method, a die coat method, or a combination thereof is preferred from the viewpoint of productivity.

Examples of the method of drying the resin solution on the support include blow drying, hot air drying, infrared heat drying, and electrothermal heating and drying from the support, among which two methods may be combined. As solvent content of the resin film containing the solvent after drying, it is preferable that it is 3-50 mass %, More preferably, it is 5-40 mass %, More preferably, it is 7-30 mass %. When the solvent content is at least the above lower limit, the difference between the solvent content and higher molecular structure of the resin film side in contact with the support and the opposite side is small, the physical property anisotropy in the thickness direction of the resin film is reduced, and curling of the resin film is suppressed. If it is below the upper limit, deformation of the resin film after peeling from the support is suppressed, and handling becomes easy.

Process B is explained. Step B is a step of peeling the support from the layered product to obtain a resin film containing a solvent.

The method of peeling the solvent-containing resin film from the support is not particularly limited, but is a method of lifting from the edge with tweezers or the like, a cut is made in the laminate, an adhesive tape is adhered to one side of the cut, and then that A method of rolling up from a tape portion, a method of vacuum adsorbing one side of a sheathed portion of a resin film, and then a method of rolling up from that portion, and the like.

Process C is explained. Step C is a step of removing the solvent from the resin film containing the solvent or carrying out a dehydration ring closure reaction while removing the solvent, and at least a part of step C is subjected to microwave heating.

Microwave heating used in the solvent removal step of a solvent-containing resin film after peeling from a support is based on vibrating dipoles of molecules contained in a heated object by microwaves as its heating principle. Therefore, the absorption efficiency of microwaves depends on the magnitude of the dipole moment and the ease with which molecules move by following the period of the microwaves. Therefore, in order to efficiently and uniformly heat and remove the solvent from the resin film containing the solvent using microwaves, a solvent having the above-mentioned dipole moment value is specified.

As the frequency of the microwave heating device used in the present invention, it is preferable to select a frequency at which molecules of the solvent having the above-mentioned dipole moment value are easy to move. However, in general, a heating device with a frequency of 2,450 MHz is common due to restrictions by the radio wave law and restrictions of microwave electron tubes. However, 915 MHz can be used as long as it is not interfered with by other communications. In the present invention, it is more preferable to select the frequencies 2,450 MHz and 915 MHz in this circumstance. In addition, the intensity of the microwave is appropriately selected in view of conditions such as foaming, orange peel, and waviness on the surface of the resin film.

By using a resin solution containing a solvent having a specified dipole moment value and using microwave heating, the resin film is uniformly heated and dried in the solvent removal step, and the difference in roughness of the formed higher order structure is reduced, and the formula ( It becomes easy to achieve 40+0.8×A)≤B<A. In addition, the isotropy of physical properties of the resulting resin film can be improved, and the ratio of the linear expansion coefficient in the TD direction to the MD direction and the ratio of the tensile modulus in the TD direction to the MD direction of the resin film can be easily adjusted within a preferred range.

In the present invention, air drying, hot air drying, infrared heating drying, and the like can be used in combination with microwave heating, and two of these methods may be combined.

In the temperature rise profile in the solvent removal step using the heating method, the initial temperature is preferably in the range of 50 to 200 ° C., and if it is at least the lower limit of the specified range, it is easy to suppress the temperature fluctuation in the drying furnace, and the initial temperature is If it is less than the upper limit of the specified range, it is easy to suppress foaming of the resin film and orange peel on the surface due to rapid heating of the solvent, and the difference in solvent content between the surface of the resin film and the inside of the resin film or in the higher order structure of the polymer becomes smaller, and it becomes easy to achieve the expression (40+0.8×A)≤B<A.

The temperature increase profile in the solvent removal step using the above heating method preferably has a final temperature in the range of 300 to 500 ° C., and if it is at least the lower limit of the specified range, it is easy to suppress the amount of residual solvent in the resin film, and the final temperature It becomes easy to suppress thermal deterioration of a resin film as it is below the upper limit of a designated range.

The temperature increase profile in the solvent removal step using the above heating method is preferably increased at a temperature increase rate of 5 to 60 ° C./min, a stepwise increase in two or more steps, or a method in which either one or both are combined. . When the temperature increase rate is equal to or greater than the lower limit of the specified range, the working time in the solvent removal process can be shortened, and when the temperature is equal to or less than the upper limit of the specified range, foaming of the resin film and orange peel on the surface due to rapid heating of the solvent are suppressed. It becomes easy to do, and the difference between the solvent content and the higher order structure of the polymer between the surface of the resin film and the inside of the resin film decreases, and it becomes easy to achieve the formula (40+0.8xA)≤B<A.

When the temperature is raised in a stepwise manner, the number of steps is preferably 2 to 10, and the rate of temperature increase between each step is preferably 10 to 100°C/min. If the step number is at least the lower limit of the specified range, it is easy to suppress foaming of the resin film and orange peel on the surface due to rapid heating of the solvent, and also the solvent content and high molecular structure of the resin film surface and inside the resin film The difference in is small, and it becomes easy to achieve the expression (40+0.8xA)≤B<A. In addition, when the number of steps is equal to or less than the upper limit of the specified range, the work efficiency is improved.

It is preferable to determine the initial temperature, the final temperature, the heating rate, and the number of steps so that the total drying time in the solvent removal step is 5 to 100 minutes. When the total drying time is equal to or greater than the lower limit of the specified range, it is easy to suppress foaming of the resin film and orange peel on the surface due to rapid heating of the solvent, while productivity is improved and thermal deterioration of the resin film is prevented when the total drying time is equal to or less than the upper limit. suppression becomes easier.

In the solvent removal step in the present invention, the resin film can be further stretched. The draw ratio in this stretching operation is preferably 1.5 to 4.0 times in the MD (long) direction and 1.4 to 3.0 times in the TD (short) direction, and the ratio of the draw ratio in the MD direction to the draw ratio in the TD direction (MD/ TD) preferably exceeds 1.0. By setting the stretching conditions within the above range, the average coefficient of linear expansion measured in the range of 35 to 200 ° C. in both the MD and TD directions of the resin film and the tensile modulus in both the MD and TD directions are within a preferable range. it becomes easier to do

The solvent content of the resin film after the solvent removal step is preferably in the range of 0.01 to 5.0% by mass, more preferably in the range of 0.02 to 4.0% by mass, still more preferably in the range of 0.03 to 3.0% by mass. By setting the solvent content to the lower limit or more, thermal deterioration of the resin film due to excessive high-temperature treatment is suppressed, and by setting the solvent content to the upper limit or less, it is easy to make the coefficient of linear expansion and the tensile modulus within a preferable range.

Example

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the following examples unless departing from the gist thereof.

On the other hand, each measured value in Examples and Comparative Examples was measured by the following method unless otherwise noted.

<Temperature dependence curve peak temperature of tanδ of resin film>

In each of three samples in the flow direction (MD direction) and width direction (TD direction) of the resin film, storage modulus (E`), loss modulus (E") and loss modulus divided by storage modulus tanδ ( A temperature dependence curve of =E"/E') was obtained, the peak temperature was obtained, and the average value in the flow direction (MD direction) and width direction (TD direction) was calculated.

Device name: DMA Q800 manufactured by TA Instruments

Sample length: 15-20 mm

Sample width: 4 mm

Heating start temperature: 25°C

Heating end temperature: 500℃

Heating rate: 5℃/min

Measurement frequency: 10 Hz

<Inflection point temperature of linear expansion coefficient of resin film>

At each of three samples in the flow direction (MD direction) and width direction (TD direction) of the resin film, the expansion and contraction was measured under the following conditions, and the temperature at the inflection point of the expansion and contraction at the time of the second temperature increase was read, and the flow direction (MD) direction) and the average value of the width direction (TD direction) was calculated.

Device name: TMA-4000SA manufactured by Burker AXS

Sample length: 15 mm

Sample width: 2 mm

Distance between chucks: 10 mm

Load: 5 gf

1st heating start temperature: 25℃

1st heating end temperature: 200℃

1st heating rate: 20℃/min

Temperature drop rate: 5℃/min

2nd heating start temperature: 30°C

2nd heating end temperature: 500℃

2nd heating rate: 10℃/min

Atmosphere: Argon

<Weight average molecular weight, number average molecular weight and molecular weight distribution of resin>

8 mg of the resin sample was weighed, immersed in 8 ml of a solvent, and stirred for 3 hours to obtain a resin solution. The resin solution was analyzed by gel permeation chromatography (GPC) under the following conditions, and the weight average molecular weight, number average molecular weight and molecular weight distribution were calculated in terms of standard polystyrene.

Device name: Tosoh Corporation HLC-8420GPC

Column: TSKgel SuperAWH-H×2

Solvent: DMAc (30 mM of lithium bromide added)

Flow rate: 0.3 ml/min

Concentration: 0.1%

Injection volume: 10 μl

Temperature: 40℃

Detector: RI

<Thickness of resin film>

It was measured using a micrometer (Militron 1245D, manufactured by Fine Lupe Co., Ltd.).

<Coefficient of linear expansion (CTE) of resin film>

In each of three samples in the flow direction (MD direction) and width direction (TD direction) of the resin film, the expansion and contraction was measured under the following conditions, and at intervals of 15 ° C, such as 35 ° C to 50 ° C and 50 ° C to 65 ° C. The expansion/contraction rate/temperature of was measured, this measurement was performed up to 200°C, and the average value of all measured values was calculated as CTE.

Device name: TMA4000S manufactured by MAC Science

Sample length: 20 mm

Sample width: 2 mm

Heating start temperature: 25°C

Heating end temperature: 400℃

Heating rate: 5℃/min

Atmosphere: Argon

<Tensile modulus of elasticity of resin film>

What was cut into strips of 100 mm x 10 mm each in the flow direction (MD direction) and width direction (TD direction) of the resin film was used as a test piece. The test piece was cut out from the central part in the width direction. Under the following conditions, the tensile modulus of elasticity was measured for each of three samples in the MD direction and the TD direction, and the average value of all the measured values was obtained.

Device name: Autograph (R) AG-5000A manufactured by Shimadzu Corporation

Distance between chucks: 40 mm

Temperature: 25℃

Tensile speed: 50 mm/min

<Yellowness Index (Yellow Index, YI) of Resin Film>

Using a color meter (ZE6000, manufactured by Nippon Denshoku Co., Ltd.) and a C2 light source, the tristimulus values XYZ values of the resin film were measured according to ASTM D1925, and the yellowness index (YI) was calculated by the following formula. In addition, the same measurement was performed three times and the arithmetic average value was adopted.

YI=100×(1.28X-1.06Z)/Y

<400 nm light transmittance of resin film>

Using a spectrophotometer ("U-2001" manufactured by Hitachi, Ltd.), the light transmittance of the resin film at a wavelength of 400 nm was measured, and the obtained value was calculated according to Runbelt-Vale's law and converted to a thickness of 20 μm, The obtained value was taken as the 400 nm light transmittance of the resin film. In addition, the same measurement was performed three times and the arithmetic average value was adopted.

<Total light transmittance (TT) of resin film>

The total light transmittance (TT) of the resin film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). As a light source, a D65 lamp was used. In addition, the same measurement was performed 3 times and the arithmetic average value was adopted.

[Synthesis Example 1 (Preparation of Polyamic Acid Solution A)]

After purging the inside of the reaction vessel equipped with a nitrogen inlet pipe, a thermometer, and a stirring bar with nitrogen, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added to the reaction vessel under a nitrogen atmosphere at 1470.8 parts by mass. , 775.6 parts by mass of 4,4'-oxydiphthalic acid (ODPA), 3202.4 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 21795 parts by mass of N,N- Dimethylacetamide (DMAc) was added and dissolved, followed by stirring at room temperature for 24 hours to obtain a polyamic acid solution A having a solid content of 17.2 parts by mass and a reduced viscosity of 4.5 dl/g. Table 1 shows the measurement results of the weight average molecular weight, number average molecular weight, and molecular weight distribution of the resin in the obtained resin solution.

[Synthesis Example 2 (Preparation of Polyimide Solution B)]

After purging the inside of the reaction vessel equipped with a nitrogen inlet tube, thermometer, and stirring rod with nitrogen, 551 parts by mass of N,N-dimethylacetamide (DMAc) and 64.1 parts by mass of 2,2'- were added to the reaction vessel under a nitrogen atmosphere. Ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) was added and stirred to dissolve TFMB in DMAc. Then, 44.4 parts by mass of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6FDA) and 29.4 parts by mass of biphenyltetracar were added under a nitrogen stream while stirring the inside of the reaction vessel. A boxylic acid dianhydride (BPDA) was added over about 10 minutes, and the polymerization reaction was carried out by continuously stirring for 6 hours while adjusting the temperature so as to be in the temperature range of 20 to 40°C as it was, and a viscous polyamic acid solution was obtained.

Next, after diluting by adding 410 parts by mass of DMAc to the obtained polyamic acid solution, 25.83 parts by mass of isoquinoline was added as an imidation accelerator, and the polyamic acid solution was maintained at a temperature range of 30 to 40° C. while stirring, there As an imidation agent, 122.5 parts by mass of acetic anhydride was slowly added dropwise over about 10 minutes, and then the liquid temperature was maintained at 30 to 40° C. and stirred continuously for 12 hours to further carry out a chemical imidation reaction to obtain polyimide. got a solution.

Next, 1000 parts by mass of the obtained imidation agent and the polyimide solution containing the imidation accelerator were transferred to a reaction vessel equipped with a stirring device and a stirring blade, and heated to a temperature of 15 to 25°C while stirring at a speed of 120 rpm. 1500 parts by mass of methanol was added dropwise thereto at a rate of 10 g/min. It was confirmed that the polyimide solution became cloudy at the point where about 800 parts by mass of methanol was injected, and precipitation of powdery polyimide was confirmed. Next, 1500 parts by mass of methanol was introduced to complete the precipitation of polyimide. Subsequently, the contents of the reaction container were separated by filtration with a suction filtration device, and further washed and filtered using 1000 parts by mass of methanol. Thereafter, 50 parts by mass of the polyimide powder separated by filtration was dried at 50° C. for 24 hours using a dryer equipped with a local exhaust system, and further dried at 260° C. for 2 hours to remove the remaining volatile components and obtain polyimide powder got The reduced viscosity of the obtained polyimide powder was 2.1 dl/g. Next, 42 parts by mass of the obtained polyimide powder was dissolved in 168 parts by mass of DMAc to obtain a polyimide solution B having a solid content of 20 parts by mass. Table 1 shows the measurement results of the weight average molecular weight, number average molecular weight, and molecular weight distribution of the resin in the obtained resin solution.

[Synthesis Example 3 (Preparation of Polyimide Solution C)]

124.15 parts by mass of 4,4'-diaminodiphenylsulfone (4,4'-DDS), 124.15 parts by mass of 3,3'-diaminodiphenylsulfone (3,3'-DDS) and 750 parts by mass of gamma butyrolactone (GBL) were added. Subsequently, after adding 248.18 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA), 58.8 parts by mass of biphenyltetracarboxylic dianhydride (BPDA), 335 parts by mass of GBL, and 390 parts by mass of toluene at room temperature, the internal The temperature was raised to 160°C, and imidation was performed by heating under reflux at 160°C for 1 hour. After completion of the imidation, the temperature was raised to 180°C, and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed, the temperature was returned to room temperature, and 1149 parts by mass of GBL was added so that the solid content was 20 parts by mass, thereby obtaining a polyimide solution C having a reduced viscosity of 0.6 dl/g. Table 1 shows the measurement results of the weight average molecular weight, number average molecular weight, and molecular weight distribution of the resin in the obtained resin solution.

[Synthesis Example 4 (Preparation of Polyimide Solution D)]

384.38 parts by mass of norbornane-2-spiro-α-cyclopentanone-α'-spiro-2 while introducing nitrogen gas into a reaction vessel equipped with a nitrogen inlet tube, a Dean Stark apparatus, a reflux tube, a thermometer, and a stirring bar. ''-norbonane-5,5'',6,6''-tetracarboxylic dianhydride (CpODA), 348.45 parts by mass of 9,9-bis(4-aminophenyl)fluorene (BAFL), 36.00 mass After adding part triethylamine, 1465 parts by mass of N-methyl-2-pyrrolidone (NMP), 1465 parts by mass of gamma butyrolactone (GBL), and 360 parts by mass of toluene at room temperature, the internal temperature is raised to 180 ° C., Heating imidation was performed at 180 degreeC for 3 hours, distilling off toluene, and the polyimide solution was obtained.

Next, 2500 parts by mass of the obtained polyimide solution was transferred to a reaction vessel equipped with a stirrer and a stirring blade, and was maintained at a temperature of 15 to 25°C while stirring at a speed of 120 rpm, where 50000 parts by mass of acetone was added at 10 g/ drop rate per minute. At the point where about 2500 parts by mass was injected, it was confirmed that the polyimide solution became cloudy, and precipitation of powdery polyimide was confirmed. Subsequently, the remaining 2500 parts by mass of acetone was charged to complete the polyimide precipitation. Subsequently, the contents of the reaction container were separated by filtration with a suction filtration device, and further washed and filtered using 2000 parts by mass of methanol. Thereafter, 300 parts by mass of the polyimide powder separated by filtration was dried at 50° C. for 24 hours using a dryer equipped with a local exhaust system, and further dried at 260° C. for 2 hours to remove remaining volatile components, and polyimide powder got The reduced viscosity of the obtained polyimide powder was 0.7 dl/g. Next, 42 parts by mass of the obtained polyimide powder was dissolved in 168 parts by mass of NMP to obtain a polyimide solution D having a reduced viscosity of 0.7 dl/g and a solid content of 20 parts by mass. Table 1 shows the measurement results of the weight average molecular weight, number average molecular weight, and molecular weight distribution of the resin in the obtained resin solution.

[Synthesis Example 5 (Preparation of polyamic acid solution E)]

After purging the inside of the reaction vessel equipped with a nitrogen inlet tube, thermometer, and stirring rod with nitrogen, 196.1 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added to the reaction vessel under a nitrogen atmosphere. , 227.3 parts by mass of 4-amino-N- (4-aminophenyl) benzamide (DABAN), and 1694 parts by mass of N, N-dimethylacetamide (DMAc) were added and dissolved, followed by stirring at room temperature for 24 hours, A polyamic acid solution E having a reduced viscosity of 4.5 dl/g and a solid content of 20 parts by mass was obtained. Table 1 shows the measurement results of the weight average molecular weight, number average molecular weight, and molecular weight distribution of the resin in the obtained resin solution.

[Production Example 1 of Polyimide Film (Examples 1 to 5)]

Polyamic acid solution A was applied using a die coater onto a mirror-finished stainless steel endless continuous belt (coating width: 1240 mm) as a film production support, and dried at 90 to 115° C. for 10 minutes. After drying, the self-supporting polyamic acid film (containing 9% by mass of residual solvent) was peeled off from the support and both ends were cut to obtain a green film.

The obtained green film is held at both ends of the film by a pin tenter so that the final pin sheet interval is 1140 mm, and inserted into a continuous heating furnace equipped with a microwave heating zone and a hot air circulator, heating at 170 ° C. for 1 minute in the first step, and then The temperature was raised to 230 ° C. at a heating rate of 60 ° C./min, followed by heating at 230 ° C. for 1 minute in the second step, followed by heating to 350 ° C. at a heating rate of 60 ° C./min, and heat treatment at 350 ° C. for 5 minutes in the third step. At this time, 50 kW of 2,450 MHz microwave was induced into the microwave heating zone. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter, and rolled up to obtain a resin film 1A shown in Table 2. In the same manner, polyamic acid solution A was replaced with other resin solutions B, C, D, and E, and the coating thickness to the support was also changed to obtain resin films 1B, 1C, 1D, and 1E. Table 2 shows the evaluation results of the properties of the obtained resin film.

[Production Example 2 of Polyimide Film (Examples 6 to 10)]

Polyamic acid solution A was coated on the surface with a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak point density (Spd) of 20/square μm or less, and It was applied to a non-layered polyester film using a comma coater (coating width: 1240 mm), and dried at 90 to 115° C. for 10 minutes. After drying, the self-supporting polyamic acid film (containing 10% by mass of residual solvent) was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was held at both ends of the film by a pin tenter so that the final pin sheet distance was 1140 mm, and inserted into a continuous heating furnace equipped with a microwave heating zone and a hot air circulator, and the temperature was raised from 170 ° C to 350 ° C at a rate of 15 ° C. /min, and the temperature was raised. At this time, 40 kW of 2,450 MHz microwave was induced into the microwave heating zone. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a resin film 2A shown in Table 2. In the same manner, polyamic acid solution A was replaced with other resin solutions B, C, D, and E, and the coating thickness to the support was also changed to obtain resin films 2B, 2C, 2D, and 2E. Table 2 shows the evaluation results of the properties of the obtained resin film.

[Production Example 3 of Polyimide Film (Comparative Examples 1 to 5)]

Polyamic acid solution A was applied using a die coater onto a mirror-finished stainless steel endless continuous belt (coating width: 1240 mm) as a film production support, and dried at 90 to 115° C. for 10 minutes. After drying, the self-supporting polyamic acid film (containing 9% by mass of residual solvent) was peeled off from the support and both ends were cut to obtain a green film.

The obtained green film was held by a pin tenter at both ends of the film so that the final pin sheet interval was 1140 mm, and inserted into a continuous heating furnace equipped with a hot air circulator, and heated from 170 ° C to 350 ° C at a heating rate of 15 ° C / min The temperature was raised. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll to obtain a resin film 3A shown in Table 3. In the same manner, polyamic acid solution A was replaced with other resin solutions B, C, D, and E, and the coating thickness to the support was changed to obtain resin films 3B, 3C, 3D, and 3E. Table 3 shows the evaluation results of the properties of the obtained resin film.

[Production Example 4 of Polyimide Film (Comparative Examples 6 to 10)]

Polyamic acid solution A was coated on the surface with a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak point density (Spd) of 20/square μm or less, and It was applied to a non-layered polyester film using a comma coater (coating width: 1240 mm), and dried at 90 to 115° C. for 10 minutes. After drying, the self-supporting polyamic acid film (containing 10% by mass of residual solvent) was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was held at both ends of the film by a pin tenter so that the final pin sheet interval was 1140 mm, and inserted into a continuous heating furnace equipped with a microwave heating zone and a hot air circulator, and the temperature was raised from 170 ° C to 350 ° C at a rate of 70 ° C. The temperature was raised by heating at /min, and heat treatment was performed at 350°C for 4 minutes. At this time, 50 kW of 2,450 MHz microwave was induced into the microwave heating zone. Thereafter, it was cooled to room temperature for 2 minutes, and portions with poor flatness at both ends of the film were cut out with a slitter and wound into a roll shape to obtain a resin film 4A shown in Table 3. In the same manner, polyamic acid solution A was replaced with other resin solutions B, C, D, and E, and the coating thickness to the support was changed to obtain resin films 4B, 4C, 4D, and 4E. Table 3 shows the evaluation results of the properties of the obtained resin film.

[Table 1]

[Table 2]

[Table 3]

As described above, the resin film of the present invention has excellent heat resistance and transparency, maintains a low linear expansion coefficient up to a high temperature region, has a high tensile modulus, and has a ratio of linear expansion coefficient and tensile modulus in the MD and TD directions of the resin film. Since it is small and has good isotropy in physical properties, it is very useful for the front plate of image display devices such as touch panels and displays, and around electrodes.

Claims (5)

A resin film satisfying the following (1) to (2).
(1) The temperature (A) at which the temperature dependent curve of tanδ, which is the value obtained by dividing the loss modulus by the storage elastic modulus, has a peak is within the range of 250 to 500°C, and the temperature (A) at which the temperature dependent curve of tanδ has a peak and linear expansion The coefficient inflection point temperature (B) is in the relationship of the following formula
(40+0.8×A)≤B<A
(2) The weight average molecular weight of the resin, which is the raw material of the resin film, is within the range of 50,000 to 500,000, and the molecular weight distribution, which is the value obtained by dividing the weight average molecular weight by the number average molecular weight of the resin, is within the range of 1.0 to 5.0. The resin film according to claim 1, which further satisfies (3) to (4).
(3) The linear expansion coefficient measured in the range of 35 to 200 ° C. in both MD and TD directions is in the range of -5 ppm / ° C to +55 ppm / ° C, and the linear expansion coefficient is in the TD direction with respect to the MD direction The ratio of is in the range of 0.97 to 1.03
(4) The tensile modulus of elasticity in both MD and TD directions is in the range of 2 to 20 GPa, and the ratio of the tensile modulus in the TD direction to the MD direction is in the range of 0.97 to 1.03. The resin film according to claim 1 or 2, which has a yellow index of 10 or less, a light transmittance of 70% or more at a wavelength of 400 nm, and a total light transmittance of 85% or more. Step A of applying a resin solution onto a support and drying it to produce a resin film laminate containing a solvent;
Step B of peeling the support from the laminate to obtain a solvent-containing resin film;
Step C of removing the solvent from the resin film containing the solvent or performing a dehydration ring closure reaction while removing the solvent,
The manufacturing method of the resin film in any one of Claims 1-3 characterized by performing at least one part of said process C by microwave heating. The method according to claim 4, wherein the resin solution is at least one resin selected from the group consisting of polyamic acid, polyimide and polyamideimide, and the dipole moment is in the range of 3.0 to 6.0 D and dissolves the resin. A method for producing a resin film containing a solvent.