JP2020152765A - Polyimide film and method for producing the same - Google Patents

Abstract

To provide a novel polyimide film and a method of producing the same.SOLUTION: A polyimide film of 50 μm or more in thickness, in which thermal expansion coefficient αMD in film transport direction (MD direction) and thermal expansion coefficient αTD in width direction (TD direction) are 10 ppm/°C or lower.SELECTED DRAWING: None

Description

The present invention relates to a polyimide film and a method for producing the same.

The polyimide film is used for flexible device applications such as flexible printed wiring boards because of its heat resistance and insulating properties (for example, Patent Document 1).

JP-A-2007-162005

An object of the present invention is to provide a novel (particularly thick film) polyimide film.

Another object of the present invention is to provide a polyimide film having a low coefficient of thermal expansion.

Another object of the present invention is to provide a polyimide film having excellent heat resistance.

Another object of the present invention is to provide a polyimide film having a high Young's modulus.

Yet another object of the present invention is to provide a method for producing such a polyimide film.

According to the present inventors, as a polyimide film having a relatively thick thickness (for example, 50 μm or more), a film having sufficient heat resistance and dimensional stability (for example, little dimensional change due to heat) is realistic. It turned out that it does not exist in.

Therefore, the present inventors have made studies by adjusting the types and blending ratios of the monomers constituting the polyimide in order to obtain a polyimide film having high heat resistance and a thick film (for example, a thickness of 50 μm or more). However, probably because the polyimide that can exhibit high heat resistance has a rigid structure, when trying to produce a thick-film polyimide film (especially in a long length), gel is used when the gel film of the polyamic acid solution is heat-treated. In many cases, the film was easily broken and it was difficult to form the film.
Under these circumstances, the present inventors have formed a polyimide film with a polymerization component containing a specific monomer in a specific blending ratio, whereby breakage of the gel film is suppressed, heat resistance is high, and a thick film polyimide film is formed. We found that it could be manufactured.

On the other hand, the present inventors attempted to stretch such a thick (high heat resistant) polyimide film in the heat treatment step of the gel film in order to lower the coefficient of thermal expansion, but the gel film broke. It was easy and difficult to stretch. In particular, the higher the heat resistance of the polyimide film, the more difficult it was to set the stretching conditions in the heat treatment step of the gel film.

As a result of diligent studies to solve the above problems, the present inventors have conducted heat treatment conditions at both ends of the gel film in the width direction (particularly, the amount of air supplied to both ends in the width direction of the gel film) and the draw ratio. By adjusting the above, a thick-film polyimide film can be stably formed (especially in a long length), and by using a specific polymer composition, a thick-film polyimide film having a low thermal expansion coefficient can be formed. We have found that it is possible to produce a film, and have completed the present invention.

The present inventors have obtained various new findings other than the above, and have completed the present invention through further diligent studies.

That is, the present invention relates to the following inventions and the like.
[1]
Polyimide film thermal expansion coefficient alpha _TD thermal expansion coefficient alpha _MD and the width direction (TD direction) is not more than 10 ppm / ° C., the thickness is more than 50μm in the film transport direction (MD direction).
[2]
A polyimide film having a glass transition temperature of 360 ° C. or higher and a thickness of 50 μm or higher.
[3]
Film conveying direction thermal expansion coefficient alpha _TD thermal expansion coefficient alpha _MD and the width direction of the (MD direction) (TD direction) of not more than 10 ppm / ° C., a glass transition temperature of 360 ° C. or higher, the thickness is more than 50μm polyimide the film.
[4]
The polyimide film according to any one of [1] to [3], wherein the Young's modulus in the MD direction and the TD direction is 5.5 GPa or more.
[5]
Any of [1] to [4] in which the proportion of 3,3', 4,4'-diphenyltetracarboxylic dianhydride in the total acid anhydride component among the polymerization components constituting the polyimide is 30 mol% or less. The polyimide film described in.
[6]
The polyimide film according to any one of [1] to [5], wherein the ratio of 4,4'-diaminodiphenyl ether to the total aromatic diamine component among the polymerization components constituting the polyimide is 70 mol% or less.
[7]
The polyimide film according to any one of [1] to [6], which has a length of 1000 m or more.
[8]
The polyimide film according to any one of [1] to [7], which has a width of 1000 mm or more.
[9]
A flexible device provided with the polyimide film according to any one of [1] to [8].
[10]
In gel film of the polyamic acid, both ends of 1% to 5% of the width to the entire film ^width, comprising the step of injecting the air ^{215m 3 / m 2 ~390m 3 /} m 2, a maximum stretching in the MD direction The method for producing a polyimide film according to any one of [1] to [8], wherein the product of the magnification and the maximum draw ratio in the TD direction is 1.60 or less.

According to the present invention, a novel thick polyimide film can be provided. Further, the present invention can provide a polyimide film having a low coefficient of thermal expansion. Since such a film can easily suppress dimensional change (expansion) due to heat, it can be suitably used for flexible device applications and the like.

According to another aspect of the present invention, a polyimide film having excellent heat resistance can be provided. Such a film can be suitably used for flexible device applications and the like.

According to another aspect of the present invention, a polyimide film having a high Young's modulus can be provided. Such a film is excellent in handleability and productivity.

Then, the present invention can provide a method for efficiently producing the above-mentioned polyimide film.

<Polyimide film>
The polyimide film of the present invention satisfies a specific range (value) in physical properties such as a coefficient of thermal expansion and a glass transition temperature.

The coefficient of thermal expansion of the polyimide film is the coefficient of thermal expansion (α _MD ) in the film transport direction (MD direction, longitudinal direction, longitudinal direction, length direction, flow direction) and / or width direction (TD direction, lateral direction, MD direction). In the coefficient of thermal expansion (α _TD ) (particularly both α _MD and α _TD ) in the direction perpendicular to, for example, 10 ppm / ° C. or less (for example, 9.5 ppm / ° C. or less, 9 ppm / ° C. or less, 8.5 ppm). / ° C or lower), preferably 8 ppm / ° C or lower (for example, 7.5 ppm / ° C or lower, 7 ppm / ° C or lower, 6.5 ppm / ° C or lower), more preferably 6 ppm / ° C or lower (for example, 5.5 ppm or lower). It may be 5 ppm or less).

The lower limit of the coefficient of thermal expansion of the polyimide film is not particularly limited, but in α _MD and / or α _TD (particularly both α _MD and α _TD ), for example, 1 ppm / ° C. or higher, 1.5 ppm / ° C. or higher, 2 ppm. It may be / ° C. or higher, 2.5 ppm / ° C. or higher, 3 ppm / ° C. or higher, 3.5 ppm / ° C. or higher, or the like.

An appropriate range (for example, 1 to 9 ppm / ° C., 2 to 7 ppm / ° C., etc.) may be set by appropriately combining these upper limit values and lower limit values (others are the same).

α _MD and α _TD may be values measured at both ends of the polyimide film (for example, both ends having a width of 1% to 5% with respect to the entire film width).

The method for measuring the coefficient of thermal expansion is not particularly limited, but for example, it may be measured under the conditions of a temperature range of 50 to 200 ° C. and a heating rate of 10 ° C./min.

The glass transition temperature (Tg) of the polyimide film may be, for example, 350 ° C. or higher (for example, 355 ° C. or higher, 360 ° C. or higher, 365 ° C. or higher, 370 ° C. or higher, 375 ° C. or higher), preferably 380 ° C. or higher. (For example, 385 ° C. or higher, 390 ° C. or higher, 395 ° C. or higher), more preferably 400 ° C. or higher.

The upper limit of the glass transition temperature of the polyimide film is not particularly limited, but may be, for example, 450 ° C. or lower, 440 ° C. or lower, 430 ° C. or lower, 420 ° C. or lower, or the like.

An appropriate range (for example, 350 to 430 ° C., 380 to 430 ° C., etc.) may be set by appropriately combining these upper limit values and lower limit values (the same applies to the others).

The method for measuring the glass transition temperature is not particularly limited, but for example, the method described in Examples described later may be used.

The Young's modulus of the polyimide film is such that the Young's modulus in the MD direction and / or the Young's modulus in the TD direction (particularly, both the Young's modulus in the MD direction and the Young's modulus in the TD direction) is 5.2 GPa or more (for example, 5. 3 GPa or more (5.4 GPa or more), preferably 5.5 GPa or more (for example, 5.8 GPa or more), more preferably 6.0 GPa or more (for example, 6.3 GPa or more, 6.5 GPa or more) Good.

The method for measuring Young's modulus is not particularly limited, but for example, the method described in Examples described later may be used.

The above-mentioned physical properties (coefficient of thermal expansion, glass transition temperature, Young's modulus) may be an average value of two or more measurement points (for example, 2 to 10 points). The measurement points are not particularly limited, but may be, for example, points taken on a straight line of the polyimide film (for example, on a straight line in the TD direction) or points taken at equal intervals.

The thickness of the polyimide film can be appropriately selected depending on the intended use, and is, for example, 40 μm or more (for example, 45 μm or more), preferably 50 μm or more (for example, 55 μm or more), and more preferably 60 μm or more (for example, 61 μm or more). ) May be.

The upper limit of the thickness of the polyimide film is not particularly limited, but may be, for example, 200 μm or less, 180 μm or less, 150 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, and the like.

An appropriate range (for example, 50 to 200 μm, 50 to 100 μm, etc.) may be set by appropriately combining these upper limit values and lower limit values (others are the same).
In the present invention, even such a relatively thick film can achieve both a high glass transition temperature and a low coefficient of thermal expansion.

The polyimide film may contain inorganic particles (or fillers). The inorganic particles are not particularly limited, and are, for example, oxides (for example, titanium oxide, silica, etc.), inorganic acid salts [for example, carbonates (for example, calcium carbonate), phosphates (for example, calcium phosphate, hydrogen phosphate, etc.). Calcium), etc.]. These may be used alone or in admixture of two or more.

The average particle size of the inorganic particles may be, for example, 0.01 to 5 μm, preferably 0.02 to 2 μm (for example, 0.03 to 1 μm), and more preferably about 0.05 to 0.5 μm.
The average particle size of the inorganic particles was measured by, for example, a laser diffraction / confusion type particle size distribution measuring device LA-920 manufactured by Horiba Seisakusho in a slurry state dispersed in DMAc (N, N-dimethylacetamide). In the particle size distribution, the median diameter is defined as the average particle size.

The content of the inorganic particles is not particularly limited as long as it does not interfere with the effect of the present invention, but is, for example, 0.05% by mass or more, preferably 0.1 to 1.5% by mass, and further, with respect to the polyimide film. It may be preferably 0.2 to 1.0% by mass.

The polyimide film may have a relatively large size. The length of such a polyimide film is, for example, 1 m or more (for example, 5 m or more), 10 m or more (for example, 20 m or more), preferably 30 m or more (for example, 40 m or more), and more preferably 50 m or more (for example). , 100 m or more), 200 m or more, 300 m or more, 500 m or more, 1000 m or more, 2000 m or more, 3000 m or more, 5000 m or more, and the like.

The upper limit of the length of the polyimide film is not particularly limited, and may be, for example, 30,000 m, 20,000 m, 10,000 m, or the like.

The width of the polyimide film is not particularly limited, but is, for example, 30 mm or more (for example, 45 mm or more, 75 mm or more, 100 mm or more), preferably 150 mm or more (for example, 155 mm or more), and more preferably 200 mm or more (for example, 250 mm or more). It may be 500 mm or more, 1000 mm or more, 1500 mm or more, 2000 mm or more, and the like.

The upper limit of the width of the polyimide film is not particularly limited, but may be, for example, 10000 mm, 8000 mm, 5000 mm, 4000 mm, 3000 mm or the like.

The polyimide film may be in a wound state, that is, in a roll shape (roll).

<Polyimide (polyamic acid)>
The polyimide film (or the polyimide or polyamic acid constituting the polyimide film) usually contains an aromatic diamine component and an acid anhydride component (tetracarboxylic acid component) as a polymerization component. The polymerization component may contain other polymerization components as long as the aromatic diamine component and the acid anhydride component are the main components.
The polyimide film is not particularly limited, but first, a polyamic acid (polyamic acid) solution is obtained by polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent.

The polyimide film of the present invention preferably contains oxydianiline (ODA) (or diaminodiphenyl ether, for example, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, etc.) as an aromatic diamine component. You may. By using the aromatic diamine component containing oxydianiline in this way, it is easy to efficiently obtain a polyimide film having the above-mentioned physical properties.

The aromatic diamine component may contain other than oxydianiline.
Specific examples of such aromatic diamine components other than oxydianiline include para-phenylenediamine (PPD), meta-phenylenediamine, benzidine, para-xylylenediamine, 4,4'-diaminodiphenylmethane, and 4,4'-diamino. Diphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis (3-methyl-5-aminophenyl) benzene and Examples thereof include these amide-forming derivatives, and PPD and the like are preferable. These may be used alone or in admixture of two or more.

When the aromatic diamine component contains ODA (particularly 4,4'-ODA), the proportion of ODA in the total aromatic diamine component is, for example, 80 mol% or less (for example, 75 mol% or less), preferably 70. It may be mol% or less (for example, 68 mol% or less, 65 mol% or less, 63 mol% or less), more preferably 60 mol% or less.
The lower limit of the ratio of ODA (particularly 4,4'-ODA) in the entire aromatic diamine component is not particularly limited, and is, for example, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, and the like. It may be 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol% and the like.

An appropriate range (for example, 20 to 80 mol%, 25 to 75 mol%, etc.) may be set by appropriately combining these upper limit values and lower limit values (the same applies to the others).
Typically, the proportion of ODA (particularly 4,4'-ODA) in the total aromatic diamine component is 40-80 mol% (eg 45-75 mol%), 50-75 mol% (eg 50-75 mol%). It may be 70 mol%) or the like, or it may be 55 to 65 mol%.

When the aromatic diamine component contains PPD, the proportion of PPD in the entire aromatic diamine component is, for example, 20 mol% or more (for example, 25 mol% or more), preferably 30 mol% or more (for example, 32). It may be mol% or more), more preferably 35 mol% or more (for example, 37 mol% or more, 40 mol% or more).
The upper limit of the proportion of PPD in the entire aromatic diamine component is not particularly limited, and is, for example, 99 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65. It may be mol%, 60 mol%, 55 mol%, 50 mol% and the like.

An appropriate range (for example, 20 to 80 mol%, 25 to 75 mol%, etc.) may be set by appropriately combining these upper limit values and lower limit values (the same applies to the others).
Typically, the proportion of PPD in the total aromatic diamine component is 20-60 mol% (eg 25-55 mol%), 25-50 mol% (eg 30-50 mol%), 35-45 mol. It may be% or the like.

When the aromatic diamine component contains ODA (particularly 4,4'-ODA) and PPD, the ODA (particularly 4,4'-ODA): PPD (molar ratio) is, for example, 40:60 to 80:20 (eg, 40:60 to 80:20). , 50:50 to 80:20, 55:45 to 80:20, 55:45 to 75:25), preferably 50:50 to 70:30 (eg, 55:45 to 70:30) Good. With such a blending ratio, it is easy to efficiently obtain a polyimide film having the above-mentioned physical properties.

The polyimide film of the present invention may preferably contain 3,3', 4,4'-diphenyltetracarboxylic dianhydride as an acid anhydride component. By using the acid anhydride component containing 3,3', 4,4'-diphenyltetracarboxylic dianhydride (BPDA) as described above, it is easy to efficiently obtain a polyimide film having the above-mentioned physical properties.

The acid anhydride component may contain other than 3,3', 4,4'-diphenyltetracarboxylic dianhydride.
Specific examples of acid anhydride components other than such 3,3', 4,4'-diphenyltetracarboxylic dianhydride include pyromellitic acid, 2,3', 3,4'-diphenyltetracarboxylic acid. , 3,3', 4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3 , 5,6-tetracarboxylic acids and aromatic tetracarboxylic dianhydride components such as amide-forming derivatives thereof are mentioned, and pyromellitic dianhydride (PMDA) and the like are preferable. These may be used alone or in admixture of two or more.

When the acid anhydride component contains BPDA, the proportion of BPDA in the total acid anhydride component is, for example, 35 mol% or less (for example, less than 35 mol%, 33 mol% or less), preferably 30 mol% or less (for example, 30 mol% or less). 28 mol% or less), more preferably 25 mol% or less (for example, 23 mol% or less, 20 mol% or less, 18 mol% or less, 15 mol% or less).
The lower limit of the proportion of BPDA in the entire acid anhydride component is not particularly limited, and may be, for example, 1 mol%, 3 mol%, 5 mol%, 8 mol%, 10 mol% or the like.

An appropriate range (for example, 1 to 30 mol%, 5 to 25 mol%, etc.) may be set by appropriately combining these upper limit values and lower limit values (the same applies to the others).
Typically, the proportion of BPDA in the total acid anhydride component is 3 to 30 mol% (for example, 5 to 25 mol%) and 5 to 20 mol% (for example, 8 to 8 to 8 to the total amount of the acid anhydride component). 18 mol%) and the like, and may be 5 to 15 mol%.

When the acid anhydride component contains PMDA, the proportion of PMDA in the total acid anhydride component is, for example, 65 mol% or more (for example, more than 65 mol%, 67 mol% or more), preferably 70 mol% or more (for example, 70 mol% or more). For example, it may be 72 mol% or more), more preferably 75 mol% or more (for example, 77 mol% or more, 80 mol% or more, 82 mol% or more, 85 mol% or more).
The upper limit of the proportion of PMDA in the total acid anhydride component is not particularly limited, and may be, for example, 100 mol%, 99 mol, 97 mol%, 95 mol%, 92 mol%, 90 mol% or the like.

An appropriate range (for example, 67 to 99 mol%, 70 to 95 mol%, etc.) may be set by appropriately combining these upper limit values and lower limit values (the same applies to the others).
Typically, the proportion of PMDA in the total acid anhydride component is 67-99 mol% (eg 70-97 mol%), 70-95 mol% (eg 72-92 mol%), 75-95 mol. % (Eg, 77-90 mol%).

When the acid anhydride component contains PMDA and BPDA, the PMDA: BPDA (molar ratio) may be, for example, 95: 5 to 70:30, preferably 90: 10 to 80:20. With such a blending ratio, it is easy to efficiently obtain a polyimide film having the above-mentioned physical properties.

Further, in the present invention, specific examples of the organic solvent used for forming the polyamic acid solution include, for example, sulfoxide-based solvents such as dimethylsulfoxide and diethylsulfoxide, N, N-dimethylformamide, N, N-diethylformamide and the like. Formamide-based solvent, acetamide-based solvent such as N, N-dimethylacetamide, N, N-diethylacetamide, pyroridone-based solvent such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, phenol, o-, Examples thereof include phenolic solvents such as m- or p-cresol, xylenol, halogenated phenol and catechol, and aprotonic polar solvents such as hexamethylphosphoramide and γ-butyrolactone, which may be used alone or in combination of two or more. It is desirable to use as a mixture using, but it is also possible to use aromatic hydrocarbons such as xylene and toluene.

The polymerization method may be any known method. For example, (1) first put the entire amount of the aromatic diamine component in the solvent, and then add the acid anhydride component to the total amount of the aromatic diamine component (equal molar). A method of polymerizing in addition to.
(2) A method in which the entire amount of the acid anhydride component is first put into a solvent, and then the aromatic diamine component is added so as to be equivalent to the acid anhydride component for polymerization.
(3) After putting one aromatic diamine component (a1) in a solvent, mix for the time required for the reaction at a ratio of one acid anhydride component (b1) to 95 to 105 mol% with respect to the reaction component. After that, the other aromatic diamine component (a2) is added, and then the other acid anhydride component (b2) is adjusted so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent. A method of adding and polymerizing.
(4) After putting one acid anhydride component (b1) in a solvent, mix for the time required for the reaction at a ratio of one aromatic diamine component (a1) to 95 to 105 mol% with respect to the reaction component. After that, the other acid anhydride component (b2) is added, and then the other aromatic diamine component (a2) is added so that the total aromatic diamine component and the total acid anhydride component are substantially equivalent. And polymerize.
(5) One aromatic diamine component and an acid anhydride component are reacted in a solvent so that either one becomes excessive to prepare a polyamic acid solution (A), and the other aromatic diamine component is prepared in another solvent. And the acid anhydride component are reacted so that either one becomes excessive to prepare a polyamic acid solution (B). A method of mixing each of the polyamic acid solutions (A) and (B) thus obtained to complete the polymerization. At this time, if the aromatic diamine component is excessive when preparing the polyamic acid solution (A), the acid anhydride component is excessive in the polyamic acid solution (B) and the acid anhydride component is excessive in the polyamic acid solution (A). In the case of, the aromatic diamine component is excessive in the polyamic acid solution (B), the polyamic acid solutions (A) and (B) are mixed, and the total aromatic diamine component and the total acid anhydride component used in these reactions are mixed. Adjust so that they are almost equivalent.

The polymerization method is not limited to these, and other known methods may be used.

The polyamic acid solution thus obtained usually contains 5 to 40% by weight of solids, preferably 10 to 30% by weight of solids. The viscosity is usually 10 to 2000 Pa · s as measured by a Brookfield viscometer, and is preferably 100 to 1000 Pa · s for stable liquid feeding. Further, the polyamic acid in the organic solvent solution may be partially imidized.

Moreover, the polyamic acid solution may contain the above-exemplified inorganic particles. The method of mixing the polyamic acid solution and the inorganic particles is not particularly limited, and the inorganic particles may be added to the polyamic acid solution obtained as described above, and the polyamic acid is polymerized in the presence of the inorganic particles. You may.

<Manufacturing method of polyimide film>
The polyamic acid solution (polyimide precursor) obtained as described above is supplied to the support and formed into a film on the support.

Specifically, a gel film (a film having self-supporting property) can be obtained by cyclizing a polyamic acid on a support.
A gel film can usually be obtained by casting (coating) a polyamic acid solution onto a support and partially drying and curing (imidizing) it.

The method of supplying to the support is not particularly limited, but for example, a method of discharging from a mouthpiece provided with a slit may be used.

The support is not particularly limited, and examples thereof include a metal rotating drum and an endless belt.

The temperature of the support is not particularly limited, and may be, for example, 30 to 200 ° C., preferably 40 to 150 ° C., and more preferably 50 to 120 ° C.

The temperature of the support can be controlled by (i) a liquid or gas heat medium, (ii) radiant heat from an electric heater or the like.

In the film forming step, the method of cyclizing a polyamic acid is roughly classified by a cyclization (imidization) method (thermal ring closure method, chemical ring closure method).

Specifically, in the (i) thermal ring closure method, a polyamic acid solution may be cast into a film, heated, and thermally dehydrated and cyclized to obtain a gel film. On the other hand, in the (ii) chemical ring closure method, a gel film may be obtained by chemically decyclizing the polyamic acid solution with a catalyst (cyclization catalyst) and a dehydrating agent (converter).
In the present invention, the chemical ring closure method may be particularly preferably used.

Examples of the cyclization catalyst include amines such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), heterocyclic tertiary amines (eg, isoquinoline, pyridine, etc.). (Β-picoline, etc.) and the like. These may be used alone or in admixture of two or more. Of these, heterocyclic tertiary amines such as β-picoline are preferred.

Examples of the dehydrating agent include acid anhydrides, for example, aliphatic carboxylic acid anhydrides (for example, acetic anhydride, propionic anhydride, butyric anhydride, etc.), aromatic carboxylic acid anhydrides (for example, benzoic anhydride, etc.) and the like. .. These may be used alone or in admixture of two or more. Among these, acetic anhydride and / or benzoic anhydride are preferable, and acetic anhydride is particularly preferable.

The amounts of the cyclization catalyst and the dehydrating agent used are not particularly limited, but are, for example, about 1 mol or more (for example, 1.5 to 10 mol) with respect to 1 mol of the amide group (or carboxyl group) of the polyamic acid. It may be.

The timing of adding (mixing) the cyclization catalyst or dehydrating agent to the polyamic acid solution is not particularly limited as long as the gel film can be formed, but when the polyamic acid solution contains inorganic particles, the polyamic acid solution and the inorganic are added. It is often added after mixing with the particles.

The cyclization catalyst and the dehydrating agent may be dissolved or dispersed in an appropriate solvent and mixed. Examples of the solvent include the above-exemplified solvents.

The drying method is not particularly limited, and may be partially imidized and dried. For example, while molding a polyamic acid solution into a film on a support, the volatile components such as an organic solvent released while ring-closing are dried by receiving heat from the support, hot air, or a heat source such as an electric heater. May be used as a gel film.

A polyimide film can be obtained by imidizing (further imidizing) the film (gel film) obtained in the film forming step.

The polyimide film can be obtained, for example, through a step of heat-treating the obtained gel film (imidization step). The heat treatment promotes drying (and desolvation) and imidization.

The imidization step may be performed on the support or the gel film peeled from the support.

The gel film may be dried (and desolvated) before the imidization step.

The heat treatment and the drying treatment may be performed by passing the gel film through a heating furnace (such as a tenter heating furnace) while grasping both ends in the width direction.

When the drying treatment is performed, the drying temperature is not particularly limited, but may be, for example, 50 ° C. or higher, preferably 55 ° C. or higher, and more preferably 60 ° C. or higher.

When the drying treatment is performed, the drying time is not particularly limited, but may be, for example, about 15 seconds to 30 minutes.

The heat treatment and the drying treatment may be performed while the stretching treatment is performed from the viewpoint of obtaining a polyimide film having a low coefficient of thermal expansion.
The stretching treatment may be performed in either the MD direction or the TD direction, or may be performed in both the MD direction and the TD direction. When stretching is performed in both the MD direction and the TD direction, the order of the stretching directions is not particularly limited, but it is preferable to perform the stretching in the MD direction and then the stretching in the TD direction.
Further, the stretching in the MD direction and the TD direction may be performed in multiple stages. In particular, in the present invention, the polyimide film of the present invention having the above physical properties (particularly, the coefficient of thermal expansion) can be easily obtained efficiently by stretching in the MD direction and then stretching in the TD direction in two steps.

The draw ratio (MDX) in the MD direction can be adjusted by adjusting the thickness of the polyimide film and the like, but from the viewpoint of easily obtaining the polyimide film having the coefficient of thermal expansion, for example, it is 1.01 to 1.3 times. It may be preferably 1.05 to 1.3 times, more preferably 1.05 to 1.25 times.

The heat treatment conditions for stretching in the MD direction are not particularly limited, but may be, for example, a heat treatment temperature of 50 to 70 ° C. and a heat treatment time of about 1 to 5 minutes.

At the time of heat treatment or drying treatment, air (for example, hot air) may be blown to both ends in the width direction of the gel film.
The method of injecting air is not particularly limited. For example, the gel film may be fixed to the pin plate on the chain while being pressed by a brush roller, and air may be injected onto the pin plate.

In the present invention, a step of injecting air onto both ends of the gel film in the TD direction [particularly, both ends having a width of 1% to 5% with respect to the entire film width] (hereinafter, may be simply referred to as an "air injection step"). ), It is easy to obtain a polyimide film efficiently by suppressing the breakage of the gel film.

The air injection step may be any stage in the heat treatment or the drying treatment, but it is preferably after stretching in the MD direction.

In the air injection step, the temperature of the air is not particularly limited, but may be, for example, 240 to 250 ° C.

Further, in the air injection step, by adjusting the injection amount of air, it is easy to suppress the breakage of the gel film and efficiently obtain the polyimide film.
Injection quantity of air may be suitably adjusted depending on the thickness of the polyimide film, when the thickness is to produce a polyimide film of less than 50μm~60μm, for ^example, and the like ^{215m 3 / m 2 ~285m 3 /} m 2 Good.
When producing a polyimide film having a thickness of 60 μm or more, the amount of air injected is, for example, 285 m ³ / m ^{2 to} 390 m ³ / m ² (preferably 320 m ³ / m ^{2 to} 390 m ³ / m ² ). It may be.

In the air injection step, stretching may be performed in the TD direction.

The draw ratio (TDX) in the TD direction in the air injection step is, for example, 1.01 to 1.33 times (for example, 1.01 to 1.30 times), preferably 1 from the viewpoint of suppressing breakage of the gel film. .05 to 1.30 times (for example, 1.1 to 1.30 times), more preferably 1.15 to 1.30 times (for example, 1.20 to 1.30 times), particularly preferably 1.25 times. It may be ~ 1.30 times.

Further, in the air injection step, the heat treatment conditions are not particularly limited, but may be, for example, a heat treatment temperature of 50 to 70 ° C. and a heat treatment time of about 1 to 5 minutes.

Further heat treatment may be performed after the air injection step.
The heat treatment conditions in this heat treatment step are not particularly limited, but may be, for example, a heat treatment temperature of 230 to 250 ° C. and a heat treatment time of about 2 to 30 minutes.
Further, in this heat treatment step, stretching may be performed in the TD direction.
The draw ratio (TDX) in the TD direction in this heat treatment step is, for example, 1.01 to 1.3 times, preferably 1.01 to 1.25 times, more preferably 1 from the viewpoint of suppressing the breakage of the gel film. It may be ~ 1.2 times, particularly preferably 1-1.15 times (for example, 1 to 1.05 times).

Further, in stretching, the product of the maximum stretching ratio in the MD direction and the maximum stretching ratio in the TD direction is, for example, 1 from the viewpoint of efficiently obtaining a polyimide film having the physical properties of the present invention (particularly, the coefficient of thermal expansion). It may be .63 or less, preferably 1.60 or less (for example, 1.58 or less).
Further, the lower limit of the product of the maximum draw ratio in the MD direction and the maximum draw ratio in the TD direction is set to, for example, 1 from the viewpoint that the polyimide film having the physical properties (particularly the coefficient of thermal expansion) of the present invention can be easily obtained. It may be .10 or more, preferably 1.20 or more (for example, 1.30 or more), and more preferably 1.40 or more (for example, 1.45 or more, 1.50 or more).

In this way, a polyimide film is obtained. The obtained polyimide film may be further subjected to an annealing treatment or an easy-adhesion treatment (for example, an electric treatment such as a corona treatment or a plasma treatment or a blast treatment).

The thickness of the polyimide film may be adjusted such as the solid content concentration, the viscosity, and the amount of polymer cast on the support so as to have a predetermined thickness.

[Flexible device]
The polyimide film of the present invention is used for various flexible devices [for example, display devices (for example, liquid crystal displays, organic EL displays, electronic paper), metal laminated substrates (for example, circuit boards such as flexible printed wiring boards), solar cell substrates]. It can be used for, and is particularly suitable for metal laminated substrate applications.

That is, the present invention also includes a flexible device provided with the polyimide film of the present invention.

The method for manufacturing the flexible device is not particularly limited, and a conventionally known method can be used. The display device and the solar cell substrate can be manufactured, for example, by the methods described in JP-A-2016-204569 and JP-A-2012-35583.

The metal laminated substrate is not particularly limited as long as it includes the polyimide film and the metal layer, but preferred embodiments will be exemplified below.

The type of metal constituting the metal layer (metal foil) is not particularly limited, but for example, copper (copper alone, copper alloy, etc.), stainless steel and its alloy, nickel (nickel alone, nickel alloy, etc.), aluminum (aluminum). , Aluminum alloy, etc.).

The metal is preferably copper. By laminating such a metal layer and a polyimide film, a metal laminated substrate can be obtained.

The metal layer may be formed on at least one side of the polyimide film, and may be formed on both sides of the polyimide film.

In the metal laminated substrate, the thickness of the metal layer is not particularly limited, but may be, for example, about 1 to 150 μm (for example, 1.5 to 100 μm, 2 to 80 μm, 3 to 50 μm, etc.), and may be about 2 to 12 μm. It may be.

As long as the metal laminated plate includes the polyimide film and the metal layer, the form of the lamination is not particularly limited and depends on the purpose of use of the polyimide film, for example, the polyimide film and the metal layer are directly laminated. The polyimide film and the metal foil may be laminated (bonded) via an adhesive layer (adhesive layer).

The adhesive component constituting the adhesive layer is not particularly limited, and may be, for example, a thermosetting resin or a thermoplastic resin.

The method for producing such a metal laminate is not particularly limited, and it can be produced according to a conventionally known production method depending on the form of the metal laminate and the like. For example, a method of laminating a layer containing copper as a main component by an electroplating method on one or both sides of a polyimide film on a metal layer containing nickel chromium as a main component formed by a sputtering method is common. A typical metal laminated substrate (copper-clad laminate, copper-clad laminate) of the present invention is provided with nickel-chromium alloy layers on both sides of a polyimide film, and has a predetermined thickness (for example, a thickness of 2 to 12 μm). It is obtained by forming the copper of the above by an electroplating method.

In the metal laminated substrate, a desired wiring (metal wiring, wiring pattern) can be formed by etching the metal layer.

Therefore, the present invention also includes a base plate (metal wiring board, metal wiring board) including the polyimide film and wiring (metal wiring) formed on the polyimide film. Such a metal wiring board may usually be a flexible printed circuit board.

The wiring (wiring circuit, metal wiring) may be formed on at least one side of the polyimide film, or may be formed on both sides of the polyimide film.

The method for manufacturing the metal wiring board (flexible printed circuit board) is not particularly limited, and a known method can be used.

The present invention includes various combinations of the above configurations within the technical scope of the present invention as long as the effects of the present invention are exhibited.

Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to such Examples.

(Synthesis Example 1)
Pyromellitic dianhydride (PMDA) (molecular weight 218.12) / 3,3', 4,4'-diphenyltetracarboxylic dianhydride (BPDA) (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (4,4'-ODA) (molecular weight 200.24) / paraphenylenediamine (PPD) (molecular weight 108.14) was prepared in a molar ratio of 87/13/60/40, and DMAC (N, N) was prepared. -Dimethylacetamide) was made into a 20% by weight solution and polymerized to obtain a polyamic acid solution having 3800 poisons at 25 ° C. In this polyamic acid solution, dried N, N-dimethylacetamide was 1.8 mol per polyamic acid unit, acetic anhydride was 3.0 mol per polyamic acid unit, and betapicolin was 2.9 mol per polyamic acid unit. Mixing was made to prepare a mixture of polyamic acid solutions.

(Synthesis Example 2)
Pyromellitic dianhydride (molecular weight 218.12) / 3,3', 4,4'-diphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4'-diaminodiphenyl ether (molecular weight 200.24) / Paraphenylenediamine (molecular weight 108.14) was prepared in a molar ratio of 65/35/82/18, polymerized in a 20% by weight solution in DMAC (N, N-dimethylacetamide), and polymerized at 25 ° C. A polyamic acid solution having a molecular weight of 3200 was obtained. In this polyamic acid solution, dried N, N-dimethylacetamide was 1.9 mol with respect to the polyamic acid unit, acetic anhydride was 2.8 mol with respect to the polyamic acid unit, and betapicolin was 2.6 mol with respect to the polyamic acid unit. Mixing was made to prepare a mixture of polyamic acid solutions.

[Example 1]
The mixture of the polyamic acid solution obtained in Synthesis Example 1 is extruded into a rotating stainless steel drum at 71.5 ° C. from a T-shaped slit die having a base slit width of 1.3 mm, and the ratio of support speed / base discharge speed is adjusted. As 10.6, a self-supporting gel film was obtained by casting on a rotating metal support at 72 ° C.

(Stretching step in MD direction)
This gel film was transported in a heating furnace at a temperature of 64 ° C. in the furnace at a transport speed of 60 seconds while stretching 1.22 times in the MD direction.

The gel film obtained in the stretching step in the MD direction is conveyed in a heating furnace at a temperature of 64 ° C. at a transfer rate of 25 seconds while stretching 1.26 times in the TD direction. It was. This heat treatment was performed while supplying 320 m ³ / m ² of hot air at 245 ° C. to both ends having a width of 2% of the entire film width of the gel film. This step is shown as heat treatment (1) in Table 1.

The gel film obtained in the previous paragraph was transported in a heating furnace at a temperature of 238 ° C. in the furnace at a transport speed of 85 seconds while stretching 1.03 times in the TD direction. Then, both ends 78 mm in the TD direction of the film were cut and then wound to obtain a polyimide film having a width of 2050 mm, a length of 1500 m, and a thickness of 61.5 μm. This step is shown as heat treatment (2) in Table 1.

[Example 2]
A polyimide film having a width of 2050 mm, a length of 3000 m, and a thickness of 61.5 μm was obtained in the same manner as in Example 1 except that no stretching was performed during the heat treatment at a temperature of 238 ° C. in the furnace.
In Table 1, when the stretching ratio is 1, it means that stretching is not performed (no stretching).

[Example 3]
The amount of the polyamic acid solution supplied to the stainless steel drum was adjusted so that the thickness of the obtained polyimide film was 50 μm, and the amount of hot air supplied to both ends of the gel film was 215 m ³ / m ^2, and the stretching shown in Table 1 was performed. A polyimide film having a width of 2000 mm, a length of 3000 m, and a thickness of 50 μm was obtained in the same manner as in Example 1 except that the magnification was set.

[Example 4]
A polyimide film having a width of 2050 mm, a length of 3000 m, and a thickness of 61.5 μm was obtained in the same manner as in Example 1 except that the draw ratios shown in Table 1 were used.

[Example 5]
Same as Example 2 except that the polyamic acid solution obtained in Synthesis Example 2 was used, the temperature of the rotating stainless steel drum was set to 76 ° C, and the amount of hot air supplied to both ends of the gel film was set to 215 m ³ / m ^2. A polyimide film having a width of 2050 mm, a length of 3000 m, and a thickness of 61.5 μm was obtained.

[Reference example 1]
Stretching and heat treatment were carried out in the same manner as in Example 1 except that the stretching ratios shown in Table 1 were set, but the gel film broke and film formation could not be performed.

[Reference example 2]
The amount of hot air supplied to both ends of the gel film was 215 m ³ / m ^2, and stretching and heat treatment were performed in the same manner as in Example 1 except that the stretching ratios shown in Table 1 were set, but the gel film broke and the gel film broke. The film could not be formed.

[Reference example 3]
Stretching and heat treatment were performed in the same manner as in Example 2 except that the amount of hot air supplied to both ends of the gel film was 430 m ³ / m ² , but the gel film broke and film formation could not be performed. ..

The obtained polyimide film was evaluated by the following method. The results are shown in Table 1.

[Measurement of coefficient of thermal expansion (CTE)]
Using TMA-60 (manufactured by Shimadzu Corporation), the measurement was performed under the conditions of a distance between chucks: 10 mm, a measurement temperature range: 50 to 200 ° C., and a heating rate: 10 ° C./min.
The coefficient of thermal expansion was calculated as an average value measured at four points other than both ends of the polyimide film (width of 1% to 5% with respect to the entire film width).

[Measurement of glass transition temperature (Tg)]
Using a dynamic viscoelasticity measuring device (DMS6000, manufactured by Hitachi High-Tech Science), the measurement was performed in a measurement temperature range of 25 to 400 ° C., a heating rate of 2 ° C./min, a frequency of 5 Hz, and a nitrogen atmosphere. The temperature of the peak top of the obtained Tan δ was defined as the glass transition temperature (Tg).

[Measurement of Young's modulus (tensile modulus)]
It was measured using RTM-250 (manufactured by A & D Co., Ltd.) under the condition of tensile speed: 100 mm / min.

[Evaluation of film forming property]
The film-forming property of the polyimide film was evaluated in the heat treatment (2) according to the following evaluation criteria.
⊚: The gel film could be formed without breaking for 3000 m or more.
◯: The gel film could be formed without breaking for 1000 m or more.
Δ: The gel film could be formed without breaking for 500 m or more.
X: The gel film broke during film formation, and film formation could not be performed at all.

As shown in Table 1, in Examples 1 to 4, polyimide films having excellent film-forming properties and α _MD and α _TD of 10 ppm / ° C. or less were obtained. In addition, the polyimide film obtained in the examples had a high Tg.

The present invention can provide a polyimide film useful for flexible printing devices and the like.

Claims (10)

Polyimide film thermal expansion coefficient alpha _TD thermal expansion coefficient alpha _MD and the width direction (TD direction) is not more than 10 ppm / ° C., the thickness is more than 50μm in the film transport direction (MD direction). A polyimide film having a glass transition temperature of 360 ° C. or higher and a thickness of 50 μm or higher. Film conveying direction thermal expansion coefficient alpha _TD thermal expansion coefficient alpha _MD and the width direction of the (MD direction) (TD direction) of not more than 10 ppm / ° C., a glass transition temperature of 360 ° C. or higher, the thickness is more than 50μm polyimide the film. The polyimide film according to any one of claims 1 to 3, wherein the Young's modulus in the MD direction and the TD direction is 5.5 GPa or more. The invention according to any one of claims 1 to 4, wherein the proportion of 3,3', 4,4'-diphenyltetracarboxylic dianhydride in the total acid anhydride component among the polymerization components constituting the polyimide is 30 mol% or less. Polyimide film. The polyimide film according to any one of claims 1 to 5, wherein the ratio of 4,4'-diaminodiphenyl ether to the total aromatic diamine component among the polymerization components constituting the polyimide is 70 mol% or less. The polyimide film according to any one of claims 1 to 6, which has a length of 1000 m or more. The polyimide film according to any one of claims 1 to 7, which has a width of 1000 mm or more. A flexible device comprising the polyimide film according to any one of claims 1 to 8. In gel film of the polyamic acid, both ends of 1% to 5% of the width to the entire film ^width, comprising the step of injecting the air ^{215m 3 / m 2 ~390m 3 /} m 2, a maximum stretching in the MD direction The method for producing a polyimide film according to any one of claims 1 to 8, wherein the product of the magnification and the maximum draw ratio in the TD direction is 1.60 or less.