JP7077064B2 - Polyimide film - Google Patents

Description

The present invention relates to a polyimide film or the like.

Demand for flexible printed wiring boards (FPCs) is increasing as electronic products become lighter, smaller, and have higher densities. The FPC has a structure in which a circuit made of a metal foil is formed on an insulating film, but a polyimide film has been preferably used as the insulating film because of heat resistance and dimensional stability.

The dimensional stability requirements for such FPCs are becoming more and more stringent with the development of mobile devices and the like in recent years.

In addition, in the mounting of electronic components, thinning, high functionality, and high definition of electronic devices such as liquid crystal televisions, notebook computers, and smartphones have made it possible to implement particularly fine and high-density wiring in the mounting of ICs that drive displays. In order to meet the demand, a COF (Chip On Film) method in which an IC is directly mounted on a flexible wiring board has been developed and put into practical use.

COF requires higher dimensional accuracy than FPC. Therefore, for the copper-clad laminate used for COF, a two-layer type in which a copper layer is directly formed on a polyimide film and no adhesive is used is adopted, which can cope with miniaturization of wiring.

In Patent Document 1, an aromatic diamine component in which 50 to 100 mol% is p-phenylenediamine and an aromatic acid anhydride component in which 50 to 100 mol% is pyromellitic acid dianhydride are used. The thermal expansion coefficient αMD in the machine transport direction (MD) of the film measured in 10 ° C increments under the conditions of measurement temperature: 50 to 400 ° C and temperature rise rate: 10 ° C / min is -15 to 10 ppm / min. The thermal expansion coefficient αTD in the width direction (TD) measured in 10 ° C increments under the above conditions is in the range of -15 to 10 ppm / ° C, and the temperature of the film is raised from 100 ° C to 2 ° C. The reduction rate of the storage elasticity of the MD and TD of the film measured under the condition of heating to 400 ° C. at / min from the value at 100 ° C. is 75% or less, and the MD and TD of the film measured under the above conditions. There is disclosed a polyimide film characterized in that the reduction rate of the loss elastic rate starting from the value at 100 ° C. is 75% or less.
Further, this document describes that the tensile elastic modulus of MD of the film is 5.5 GPa or more, and the tensile elastic modulus of TD of the film is 5.5 GPa or more.

Japanese Unexamined Patent Publication No. 2014-12827 (claims, etc.)

An object of the present invention is to provide a novel polyimide film or the like.

As described above, COF requires high dimensional accuracy, but in recent years, flexible printed boards in which wiring and electronic components are provided in different directions are becoming widespread.
In addition, as the number of electronic component mounting points increases, a large number of electronic components are mounted in the limited space of the printed wiring board, so even in boards suitable for three-dimensional mounting such as rigid flex and flexible printed wiring boards. There has been a need for multi-layered boards such as 3-layer boards and 4-layer boards.

According to the studies by the present inventors, in the case of such a type of substrate provided in different directions or in the case of multi-layering, a complicated design in which the direction in which dimensional accuracy is required is not constant is required. It has become clear that this requirement cannot be fully tolerated. This means that, for example, it is necessary to separately design the flexible printed circuit board according to the part where the IC that drives the display is mounted and the part where a plurality of electronic devices are mounted and a complicated circuit design is required. It can be a major design constraint.

Further, according to the study by the present inventors, in such a polyimide film, a high elastic modulus (tensile force) is obtained from the viewpoint of handleability and dimensional stability in the processing process, but from the viewpoint of productivity and handleability. It was found that high elongation (breaking elongation) is required, but these seem to be in a trade-off relationship with each other, achieving both high elastic modulus and high elongation, and even high dimensions. It was extremely difficult to achieve both while achieving stability.

Under these circumstances, as a result of diligent studies, the present inventors have determined that specific physical properties affect the dimensional stability of the film, and that the physical properties are set to predetermined values in different directions. Excellent dimensional stability can be achieved even when used on a substrate with a complicated design that is not restricted to a specific direction, such as forming wiring, mounting multiple components, or having a multi-layer structure. We have found that a polyimide film having a high elasticity and a high elongation can be obtained in addition to such excellent dimensional stability by setting a specific composition, etc., and have completed the present invention.

That is, the present invention relates to the following inventions and the like.
[1]
The coefficient of thermal expansion (α _MD ) in the _MD direction and the coefficient of thermal expansion (α _TD ) in the _TD direction are both -5 to +5 ppm / ° C. The total value of the elastic modulus (EMD) and the tensile elastic modulus in the _TD direction (ETD) is 15.5 GPa or more, and the breaking elongation (RMD) in the _MD direction and the breaking elongation ( _RTD ) in the _TD direction are A polyimide film that is 20% or more in each case.
[2]
The polyimide film according to [1], wherein both α _MD and α _TD are -3 to +3 ppm / ° C, and | α _MD − α _TD | is 2 ppm / ° C or less.
[3]
The polyimide film according to [1] or [2], wherein | E _MD -E _TD | is 1 GPa or less.
[4]
The polyimide film according to any one of [1] to [3], wherein | R _MD -R _TD | is 15% or less.
[5]
The description in any one of [1] to [4], wherein the heat shrinkage rate (SMD) at 200 ° C. in the _MD direction and the heat shrinkage rate (STD) at 200 ° C. in the _TD direction are both 0.03% or less. Polyimide film.
[6]
The polyimide film according to any one of [1] to [5], wherein both the loop stiffness in the MD direction and the loop stiffness in the TD direction are 75 mN / cm or less.
[7]
The polyimide film according to any one of [1] to [6], wherein the glass transition temperature (glass transition temperature of the polyimide constituting the film) is 370 ° C. or higher.
[8]
[1] to [7], which are composed of a polyimide containing para-phenylenediamine (PPD), an aromatic diamine component containing 4,4-oxydianiline (ODA), and an acid anhydride component as a polymerization component. The polyimide film described in any of them.
[9]
The polyimide film according to [8], wherein the aromatic diamine component contains PPD in an amount of 45 mol% or more and 4,4-ODA in an amount of 55 mol% or less with respect to the entire aromatic diamine component.
[10]
The polyimide film according to [8] or [9], wherein the acid anhydride component contains pyromellitic acid dianhydride (PMDA) in a ratio of 45 mol% or more with respect to the entire acid anhydride component.
[11]
The aromatic diamine component contains 45 to 70 mol% of PPD and 30 to 55 mol% of 4,4-ODA with respect to the entire aromatic diamine component, and the acid anhydride component is the entire acid anhydride component. The polyimide film according to any one of [8] to [10], which contains PMDA in a proportion of 50 to 85 mol%.
[12]
A substrate provided with the polyimide film according to any one of [1] to [11] and a metal layer.
[13]
A substrate comprising the polyimide film according to any one of [1] to [11] and wiring formed on the film.
[14]
The substrate according to [13], wherein wiring in different directions is formed.
[15]
A coverlay film made of the polyimide film according to any one of [1] to [11].
[16]
An electronic component mounting board provided with the board and / or coverlay film according to any one of [12] to [15].
[17]
A substrate having a multilayer structure including the substrate according to any one of [12] to [16] and / or a coverlay film.

In the present invention, a novel polyimide film can be obtained. In particular, the present invention can provide a film having excellent dimensional stability not only in one direction but also in different directions (MD direction, TD direction, etc.) or in any direction.
Further, the present invention can provide a polyimide film having a high elastic modulus and high elongation. Such a film is excellent in handleability and productivity.
Further, in the present invention, it is also possible to provide a polyimide film having physical properties such as low heat shrinkage in addition to such characteristics.

Such a polyimide film of the present invention has particularly good dimensional stability as described above, so that wiring in different directions (for example, film width direction and longitudinal direction) (particularly, narrow pitch wiring) can be performed. It can be suitably used for the purpose of forming, mounting a plurality of electronic components, forming a substrate having a multi-layer structure, etc., and can be efficiently obtained without impairing productivity and handleability. can.

[Polyimide film]
The polyimide film of the present invention satisfies a specific range (value) in physical properties such as a coefficient of thermal expansion, a tensile elastic modulus, and an elongation (elongation at break). The polyimide film of the present invention may satisfy at least one of the physical properties in such a specific range, and may be satisfied by combining these. In a preferred embodiment, these are combined to satisfy (especially at least a specific range of coefficients of thermal expansion, modulus of tensile elasticity and elongation).

Further, the polyimide film may have such a physical property value on both sides (one side and the other side) as long as it satisfies at least one side (one side) of the film.

The coefficient of thermal expansion of the polyimide film is the coefficient of thermal expansion (α _MD ) in the MD direction (machine transport direction, longitudinal direction, vertical direction, length direction, flow direction) and / or the TD direction (width direction, lateral direction, MD direction). The coefficient of thermal expansion (α _TD ) (particularly both α _MD and α _TD ) in the direction perpendicular to) may be, for example, −10 to +10 ppm / ° C. (eg, −8 to +8 ppm / ° C.). It is preferably −5 to +5 ppm / ° C. (for example, -4 to + 4 ppm / ° C.), more preferably −3.5 to +3.5 ppm / ° C. (for example, -3 to +3 ppm / ° C.), and −2.5 to −2.5 to ° C. It may be + 2.5 ppm ° C. (for example, -2 to + 2 ppm / ° C., −1.5 to +1.5 ppm / ° C., -1 to + 1 ppm / ° C.).

Further, in the polyimide film, | α _MD − α _TD | is, for example, 6 ppm / ° C. or less (for example, 5 ppm / ° C. or less), preferably 4 ppm / ° C. or less (for example, 3.5 ppm / ° C. or less), and more preferably. It may be 3 ppm / ° C or lower (for example, 2.5 ppm / ° C or lower), particularly 2 ppm / ° C or lower, and may be 1.5 ppm / ° C or lower (for example, 1.2 ppm / ° C or lower, 1 ppm / ° C or lower, 0.8 ppm). (/ ° C or lower, 0.7 ppm / ° C or lower) is still preferable.

By reducing the coefficient of thermal expansion, it is easy to suppress dimensional changes (expansion) due to heat. Therefore, for example, it is possible to suppress the expansion of the substrate at the processing temperature when mounting electronic components and reduce the risk of mounting defects.
Further, by reducing | αT _MD − αT _TD |, such dimensional change or expansion can be suppressed without variation in multiple directions. Therefore, for example, the degree of freedom in circuit design is dramatically increased without limiting the direction of wiring and the mounting direction of electronic components to one direction.

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

The polyimide film has a tensile elastic modulus in the _MD direction (EMD) and _a tensile elastic modulus in the _TD direction ( _ETD ) (particularly both EMD and _ETD ) in total (EMD + _ETD ) of 12 GPa or more (EMD + ETD). For example, it may be about 13 GPa or more, for example, 14 GPa or more (for example, 14.5 GPa or more), preferably 15 GPa or more (for example, 15.2 GPa or more), and more preferably 15.5 GPa or more (for example, 16 GPa or more). ), In particular, it may be 16.5 GPa or more (for example, 17 GPa or more, 17.2 GPa or more, 17.5 GPa or more, 18 GPa or more).
The upper limit of E _MD + _ETD is not particularly limited, but may be, for example, 40 GPa, 35 GPa, 30 GPa, 28 GPa, 25 GPa, 24 GPa, 23 GPa, 22 GPa, or the like.

A film satisfying such E _MD + _ETD has a relatively high tensile strength, and is advantageous in terms of handleability and dimensional stability in the processing process.

The value of | E _MD - _ETD | is, for example, 3 GPa or less (for example, 2.5 GPa or less), preferably 2 GPa or less (for example, 1.8 GPa or less), and more preferably 1.5 GPa or less (for example, 1.2 GPa or less). It may be 1 GPa or less (for example, 0.8 GPa or less, 0.7 GPa or less, 0.6 GPa or less, 0.5 GPa or less).
A film having such a small difference between _{EMD and ETD has} high isotropic properties. Therefore, for example, dimensional stability (for example, dimensional stability of a substrate that requires a complicated design) can be efficiently improved.

The value of E _MD and / or _ETD (particularly both E _MD and _ETD ) is not particularly limited, but may be, for example, about 3 GPa or more (for example, 4 GPa or more), for example, 4 GPa or more (for example, 4 GPa or more). , 4.5 GPa or more), preferably 5 GPa or more (for example, 5.5 GPa or more), more preferably 6 GPa or more (for example, 6.5 GPa or more), especially 7 GPa or more (for example, 7.2 GPa or more, 7.5 GPa or more, It may be 7.7 GPa or more, 8 GPa or more, 8.2 GPa or more, 8.5 GPa or more, etc.).
The upper limit of E _MD and / or _ETD is not particularly limited, but may be, for example, 25 GPa, 20 GPa, 18 GPa, 15 GPa, 14 GPa, 13 GPa, 12 GPa, 11 GPa, 10.5 GPa, or the like.
A film having such an _EMD and / or _ETD is advantageous in terms of dimensional stability and handleability. For example, such films show high dimensional stability even in high tension processes. Therefore, it is also excellent in handleability.

The method for measuring the tensile elastic modulus is not particularly limited, but may be measured under the condition of a tensile speed of 100 mm / min, for example.

The polyimide film has a breaking elongation (RMD) in the _MD direction and / or a breaking elongation (RTD) in the _TD direction (particularly both _RMD and _RTD ) of 10% or more (for example, 12% or more). It may be about 15% or more (for example, 17% or more), preferably 20% or more (for example, 22% or more), more preferably 25% or more (for example, 27% or more), and particularly 30%. It may be more than 32% (for example, 32% or more, 33% or more, 35% or more, etc.).
The upper limit of R _MD or R _TD is not particularly limited, but may be, for example, 90%, 80%, 75%, 70%, 65%, 60%, 55%, 50% or the like.

A film satisfying such R _MD and / or R _TD is advantageous in terms of productivity and handleability.

The value of | R _MD -R _TD | is, for example, 30% or less (for example, 25% or less), preferably 20% or less (for example, 18% or less), and more preferably 15% or less (for example, 12% or less). It may be 10% or less (for example, 8% or less, 7% or less, 6% or less, 5% or less).
A film having such a small difference between R _MD and R _TD has high isotropic properties. Therefore, for example, dimensional stability (for example, dimensional stability of a substrate that requires a complicated design) can be efficiently improved.

The method for measuring the elongation at break is not particularly limited, but may be measured under the condition of a tensile speed of 100 mm / min, for example.

The heat shrinkage rate (SMD) in the _MD direction at 200 ° C. and / or the heat shrinkage rate (STD) in the _TD direction at 200 ° C. (particularly both _SMD and _STD ) of the polyimide film is 1% or less (for example). , 0.8% or less), for example, 0.5% or less (for example, 0.3% or less), preferably 0.2% or less (for example, 0.15% or less), more preferably. May be 0.1% or less (for example, 0.07% or less), particularly 0.05% or less (for example, 0.04% or less), and 0.03% or less (for example, 0.025% or less). ) May be.
The heat shrinkage rate can be expressed by the following formula when the size of the film before heating at 200 ° C. is L1 and the size of the film after heating at 200 ° C. is L2.
Heat shrinkage rate (%) =-| (L2-L1) / L1 | × 100
The lower limit of S _MD and / or _STD is not particularly limited, and may be, for example, 0% (or detection limit), 0.005%, 0.01%, or the like.
A film having such an S _MD and / or _STD is advantageous in terms of dimensional stability and the like. For example, it is possible to efficiently reduce dimensional changes when passing through a high-temperature process such as mounting an IC chip.

The value of | S _MD - _STD | can be selected from the range of, for example, about 0.5% or less (for example, 0.4% or less), and for example, 0.3% or less (for example, 0.2% or less). , Preferably 0.1% or less (for example, 0.08% or less), more preferably 0.05% or less (for example, 0.04% or less), particularly 0.03% or less (for example, 0.02% or less). ), And may be 0.015% or less (for example, 0.01% or less).
Such a film having a small difference between _SMD and _STD is advantageous in terms of dimensional stability and the like. For example, the dimensional stability of a substrate having a wiring design arranged in different directions can be efficiently improved.

The method for measuring S _MD and / or _STD is not particularly limited, and for example, the method described in Examples described later may be used for measurement.

The loop stiffness (LMD) in the _{MD direction and / or the loop stiffness (LTD) in the TD direction (particularly both L MD and LTD} ) of the polyimide film is, _for example, 150 mN / cm or less (for example, 100 mN / cm or less). It may be preferably 75 mN / cm or less, more preferably 60 mN / cm, particularly 50 mN / cm or less, or 40 mN / cm or less (30 mN / cm or less, 25 mN / cm or less, etc.).

A polyimide film having such loop stiffness can reduce the springback, particularly the springback in a wiring board or the like, and can easily reduce the stress on the connection points of electronic components when incorporated into an electronic device.

The value of | L _MD -L _TD | may be, for example, 30 mN / cm or less (for example, 20 mN / cm or less), preferably 10 mN / cm or less, more preferably 5 mN / cm, and particularly 3 mN / cm or less. It may be 2 mN / cm or less (1.5 mN / cm or less, 1 mN / cm or less, etc.).
It can be said that such a film having a small difference between L _MD and _LTD is relatively isotropic, and it is easy to realize the above-mentioned effect regardless of the direction of the film.

The method for measuring the loop stiffness is not particularly limited, but for example, it may be measured by the method described later.

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.].

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, more preferably more preferably, with respect to the polyimide film. It may be 0.2 to 1.0% by mass.

The thickness of the polyimide film is not particularly limited and can be appropriately selected depending on the intended use and the like. For example, the thickness of the polyimide film may be 1 to 200 μm (for example, 2 to 150 μm), preferably 3 to 100 μm (for example, 4 to 90 μm), and more preferably 5 to 80 μm (for example, 6 to 60 μm). , 7 to 50 μm, 10 to 40 μm, and the like.

The glass transition temperature (Tg) of the polyimide film (or the polyimide constituting the polyimide film) is not particularly limited, but is, for example, 200 ° C. or higher (for example, 230 to 500 ° C.), preferably 250 ° C. or higher (for example, 280 to 450 ° C.). ° C.), more preferably 300 ° C. or higher (for example, 330 to 420 ° C.), and particularly 350 ° C. or higher (for example, 360 ° C. or higher, 365 ° C. or higher, 370 ° C. or higher, etc.).
As described above, the polyimide film of the present invention may have a relatively high Tg. Such a polyimide film having a high Tg has high heat resistance. Therefore, for example, the dimensional change rate can be kept small without deformation in a high temperature process such as chip mounting.
The glass transition temperature is not particularly limited, but may be, for example, a measured value by the method described later (Tanδ method).

The polyimide film may have a relatively large size. The length of such a polyimide film is 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). It may be 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 may be, for example, 30 mm or more (for example, 45 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, 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, 2000 mm, 1500 mm and the like.

The polyimide film may be in a rolled state, that is, in a roll shape.

(Manufacturing method of polyimide and polyimide film)
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 may preferably contain para-phenylenediamine (PPD) as an aromatic diamine component. By using the aromatic diamine component containing para-phenylenediamine in this way, it is easy to efficiently obtain a polyimide film having the above-mentioned characteristics and physical properties.
The aromatic diamine component may contain other than para-phenylenediamine. Specific examples of the aromatic diamine component other than such paraphenylenediamine include metaphenylenediamine, benzidine, paraxylylene diamine, oxydianiline (ODA) (or diaminodiphenyl ether, for example, 4,4'-diaminodiphenyl ether. , 3,4'-diaminodiphenyl ether, etc.), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, Examples thereof include 3,3'-dimethoxybenzidine, 1,4-bis (3-methyl-5-aminophenyl) benzene and amide-forming derivatives thereof. These may be used individually by 1 type, or may be used by mixing 2 or more types.

As the aromatic diamine component, a combination of PPD and ODA (for example, ODA containing 4,4'-ODA and / or 3,4'-ODA, particularly at least 4,4'-ODA) is preferable. Above all, by adjusting the amount of PPD and 4,4'-ODA, the polyimide film of the present invention can be easily obtained efficiently.

When the aromatic diamine component contains PPD, the ratio of PPD in the aromatic diamine component may be selected from the range of, for example, 30 mol% or more (for example, 35 mol% or more) with respect to the total amount of the aromatic diamine component. It is often preferably 40 mol% or more (for example, 42 mol% or more), more preferably 45 mol% or more (for example, 47 mol% or more), and may be 50 mol% or more. The upper limit of the proportion of PPD in the aromatic diamine component is not particularly limited, and is, for example, 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 68 mol. %, 65 mol% and the like.

Typically, the proportion of PPD in the aromatic diamine component is 40 to 80 mol% (for example, 42 to 75 mol%) and 45 to 70 mol% (for example, 47 to 68) with respect to the total amount of the aromatic diamine component. Mol%), 50-65 mol%, etc., and usually 50-70 mol%.

When the aromatic diamine component contains ODA (particularly 4,4'-ODA), the ratio of ODA in the aromatic diamine component is, for example, 70 mol% or less (for example, 65) with respect to the total amount of the aromatic diamine component. It may be selected from the range of (mol% or less), preferably 60 mol% or less (for example, 58 mol% or less), more preferably 55 mol% or less (for example, 53 mol% or less), and 50 mol% or less. May be. The lower limit of the ratio of ODA (particularly 4,4'-ODA) in the aromatic diamine component is not particularly limited, and is, for example, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25. It may be mol%, 30 mol%, 32 mol%, 35 mol% and the like.

Typically, the proportion of ODA (particularly 4,4'-ODA) in the aromatic diamine component is 20 to 60 mol% (for example, 25 to 58 mol%) or 30 to 30 to the total amount of the aromatic diamine component. It may be 55 mol% (for example, 32 to 53 mol%), and usually 30 to 50 mol%.

Specific examples of the acid anhydride component include pyromellitic acid, 3,3', 4,4'-diphenyltetracarboxylic acid, 2,3', 3,4'-diphenyltetracarboxylic acid, 3,3',. 4,4'-Benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6-tetra Aromatic tetracarboxylic acid anhydride components such as carboxylic acids and their amide-forming derivatives include pyromellitic acid dianhydride (PMDA), 3,3', 4,4'-diphenyltetracarboxylic acid dianhydride. (BPDA) is preferable, and it is particularly preferable that the acid anhydride component contains at least pyromellitic acid dianhydride. These may be used individually by 1 type, or may be used by mixing 2 or more types.

When the acid anhydride component contains PMDA, the proportion of PMDA is, for example, 30 mol% or more (for example, 40 mol% or more), preferably 45 mol% or more (for example, 50 mol%) with respect to the total acid anhydride component. % Or more), more preferably 55 mol% or more (for example, 58 mol% or more), 60 mol% or more (for example, 62 mol% or more, 65 mol% or more, 68 mol% or more, 70 mol). % Or more, 72 mol% or more, 75 mol% or more, etc.).
The upper limit of the proportion of PMDA in the acid anhydride component is not particularly limited and may be, for example, 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol% or the like.

Typically, the proportion of PMDA in the acid anhydride component is 45 to 95 mol% (for example, 48 to 92 mol%) and 50 to 90 mol% (for example, 55 to 88) with respect to the total amount of the acid anhydride component. May be 60-85 mol% (eg 63-82 mol%), 65-80 mol%, etc., and usually 50-85 mol% (eg 50-80 mol%). good.

When the acid anhydride component contains BPDA, the ratio of BPDA in the acid anhydride component is, for example, 70 mol% or less (for example, 60 mol% or less), preferably 55 mol, based on the total amount of the acid anhydride component. % Or less (for example, 50 mol% or less), more preferably 45 mol% or less (for example, 42 mol% or less), 40 mol% or less (for example, 38 mol% or less, 35 mol% or less, It may be 32 mol% or less, 30 mol% or less, 28 mol% or less, 25 mol% or less, etc.).
The lower limit of the ratio of BPDA in the acid anhydride component is not particularly limited, and may be, for example, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol% and the like.

By using a polyamic acid composed of such an aromatic diamine component and an acid anhydride component as a raw material (precursor) for a polyimide film, it is easy to adjust the physical properties of the polyimide film within the above range, which is preferable. ..

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 dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide and the like. Formamide solvent, acetamide solvent such as N, N-dimethylacetamide, N, N-diethylacetamide, pyrrolidone 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, or 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 it 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 adding and polymerizing so as to become.
(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, the acid anhydride component (b1) is mixed at a ratio of 95 to 105 mol% with respect to the reaction component for the time required for the reaction. After that, the other aromatic diamine component (a2) is added, and then the other acid anhydride component (b2) is made so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent. Method of adding and polymerizing.
(4) After putting one acid anhydride component (b1) in a solvent, the mixture is mixed for a time required for the reaction at a ratio of 95 to 105 mol% of one aromatic diamine component (a1) 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 approximately equivalent. And polymerize.
(5) One aromatic diamine component and an acid anhydride component are reacted in an excess in a solvent to prepare a polyamic acid solution (A), and the other aromatic diamine component is prepared in another solvent. The polyamic acid solution (B) is prepared by reacting with the acid anhydride component so that either of them becomes excessive. 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 polyamic acid solution (B), the aromatic diamine component is excessive, and the polyamic acid solutions (A) and (B) are mixed to form the total aromatic diamine component and the total acid anhydride component used in these reactions. Adjust so that the amount is almost the same. 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.

Next, a method for manufacturing the polyimide film will be described. As a method for forming a polyimide film, a method of casting a polyamic acid (polyamic acid) solution into a film and thermally decyclizing and desolving the polyimide film to obtain a polyimide film, and a method of adding a cyclization catalyst and a dehydrating agent to the polyamic acid solution. A method of obtaining a polyimide film by mixing and chemically decyclizing to prepare a gel film and heat-desolving the gel film can be mentioned. The latter method has a coefficient of thermal expansion and humidity expansion of the obtained polyimide film. It is preferable because the coefficient can be kept low.

In the method of chemically decyclizing, the polyamic acid solution is first prepared. In the present invention, the polyamic acid solution may usually contain the above-mentioned inorganic particles.

The polyamic acid solution used here may be a pre-polymerized polyamic acid solution, or may be one that is sequentially polymerized when the inorganic particles are contained.

The polyamic acid solution can contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelation retarder and the like.

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 individually by 1 type, or may be used by mixing 2 or more types.

Examples of the dehydrating agent include acid anhydrides, for example, aliphatic carboxylic acid anhydrides (eg, acetic anhydride, propionic anhydride, butyric anhydride, etc.), aromatic carboxylic acid anhydrides (eg, benzoic acid anhydride, etc.) and the like. .. These may be used individually by 1 type, or may be used by mixing 2 or more types.
The gelation retarder is not particularly limited, and acetylacetone or the like can be used.

As a method for producing a polyimide film from a polyamic acid solution, a polyamic acid solution (particularly, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent) is cast on a support, molded into a film, and supported. Examples thereof include a method in which imidization is partially promoted on the body to form a self-supporting gel film, which is then peeled off from the support, heat-dried / imidized, and heat-treated.

Examples of the support include a rotating drum made of metal and an endless belt, but the support is not particularly limited as long as it is made of a uniform material.

The gel film is usually heated to 20 to 200 ° C., preferably 40 to 150 ° C. by heat reception from a support and / or heat from a heat source such as hot air or an electric heater, and undergoes a ring closure reaction to release an organic solvent or the like. By drying the volatile matter, it becomes self-supporting and is peeled off from the support.

The gel film peeled off from the support may be stretched. The apparatus and method of the stretching treatment are not limited as long as it is possible to combine stretching in the transport direction (MD) and stretching in the width direction (TD) at a predetermined magnification. The stretch ratio for producing a film having the effect of the present invention is usually 1.05 to 1.9 times, preferably 1.05 to 1.9 times, at a temperature of 200 ° C. or higher, for example, at a stretch ratio (MDX) in the MD direction. It may be 1.1 to 1.6 times, more preferably 1.1 to 1.3 times. The stretch ratio (TDX) of TD is usually 1.05 to 1.3 times the stretch ratio (MDX) of MD, preferably 1.1 to 1.25 times, and more preferably 1.1 to 1.2 times. It may be doubled.

The film may be heat-treated at a temperature of 250 to 500 ° C. for 15 seconds to 30 minutes with hot air and / or an electric heater or the like.

The solid content concentration, viscosity, and amount of polymer cast on the support are adjusted so that the thickness of the film becomes a predetermined thickness (for example, 7 to 75 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm). Is preferable.

It is preferable that the polyimide film thus obtained is further annealed. By doing so, the heat of the film is relaxed and the heat shrinkage rate can be kept small. The temperature of the annealing treatment is not particularly limited, but is preferably 200 ° C. or higher and 500 ° C. or lower, more preferably 200 ° C. or higher and 370 ° C. or lower, and particularly preferably 210 ° C. or higher and 350 ° C. or lower. By heat relaxation from the annealing treatment, the heat shrinkage rate at 200 ° C. can be suppressed within the above range, which is preferable because the dimensional accuracy is further improved.

Further, in order to give the obtained polyimide film adhesiveness, the film surface may be subjected to an electric treatment such as corona treatment or plasma treatment or a physical treatment such as blast treatment, and these physical treatments may be performed. It can be done according to the conventional method. The pressure of the atmosphere when plasma treatment is performed is not particularly limited, but is usually preferably in the range of 13.3 to 1330 kPa, preferably in the range of 13.3 to 133 kPa (100 to 1000 Torr), and 80.0 to 120 kPa (600 to 900 Torr). Is more preferred.

The atmosphere in which the plasma treatment is performed contains at least 20 mol% of the inert gas, preferably 50 mol% or more of the inert gas, more preferably 80 mol% or more, and 90 mol% or more. Is the most preferable. The inert gas contains He, Ar, Kr, Xe, Ne, Rn, N ₂ and a mixture of two or more thereof. A particularly preferred inert gas is Ar. Further, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane and the like are mixed with the inert gas. You may. Preferred mixed gas combinations used as the atmosphere for plasma treatment of the present invention are argon / oxygen, argon / ammonia, argon / helium / oxygen, argon / carbon dioxide, argon / nitrogen / carbon dioxide, argon / helium / nitrogen, argon. / Helium / nitrogen / carbon dioxide, argon / helium, helium / air, argon / helium / monosilane, argon / helium / disilane and the like.

The processing power density at the time of plasma treatment is not particularly limited, but is preferably 200 W / min / m ² or more, more preferably 500 W / min / m ² or more, and most preferably 1000 W / min / m ² or more. The plasma irradiation time for performing the plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of the plasma treatment can be fully exhibited without deterioration of the film. The gas type, gas pressure, and treatment density of the plasma treatment are not limited to the above conditions and may be performed in the atmosphere.

As described above, the polyimide film of the present invention has specific characteristics and physical properties, and such an embodiment can be adjusted by appropriately selecting the above conditions and the like.

For example, in the polymerization step of polyamic acid, the types and content ratios of the aromatic diamine component and the acid anhydride component are appropriately adjusted within a predetermined range, and further, in the film forming step, the stretch ratios of MD and TD are appropriately adjusted within a predetermined range. By adjusting or the like, it is possible to efficiently adjust to a polyimide film having desired characteristics.

The polyimide film thus obtained has the above-mentioned characteristics. Therefore, as will be described later, it is suitable for various uses, particularly for forming a substrate on which wiring (pattern) in different directions is formed, a substrate on which a plurality of electronic components are mounted, a substrate having a multilayer structure, and the like.

[Metal laminate, metal wiring board]
The polyimide film of the present invention can be suitably used for laminating with a metal layer (metal foil) to form a substrate [metal laminate (metal laminate, metal laminate)]. In particular, the polyimide film of the present invention is suitable as a film for a circuit board, particularly a flexible printed circuit board (FPC).

Therefore, the present invention includes a substrate provided with (used) the polyimide film. That is, such a substrate (metal laminate) includes the polyimide film and a metal layer.

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 alloys, 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. Further, those having a rust preventive layer, a heat resistant layer (for example, plating treatment of chromium, zinc, etc.), a silane coupling agent, or the like formed on the surface of these metals can also be used. It preferably contains at least one component of copper and / or nickel, zinc, iron, chromium, cobalt, molybdenum, tungsten, vanadium, beryllium, titanium, tin, manganese, aluminum, phosphorus, silicon and the like and copper. Copper alloys, which are preferred for circuit processing. Particularly desirable metal layers include copper formed by rolling or electroplating.

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 substrate 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 manufacturing such a metal laminated substrate is not particularly limited, and can be manufactured according to a conventionally known manufacturing method depending on the form of the metal laminated substrate and the like. For example, a method of laminating a layer containing copper as a main component by an electroplating method on one side 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. In a typical metal laminated substrate (copper-clad laminate, copper-clad laminate) of the present invention, for example, nickel-chromium alloy layers are provided on both sides of a polyimide film, and a predetermined thickness (for example, a thickness of 2 to 12 μm) is provided on the nickel-chromium alloy layers. It is obtained by forming the copper of the above by an electroplating method.

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

Therefore, the present invention also includes a substrate (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.

In such a metal wiring board, wiring (for example, wiring on the same film surface) may be formed at one place or a plurality of places, and when the wiring is formed at a plurality of places, the wiring is formed in the same direction or in a different direction. You may.

In particular, in the present invention, wiring may be formed in different directions (different directions at a plurality of locations). The mode of forming in different directions is not particularly limited, but for example, wiring may be formed in at least two directions along the MD direction and the TD direction of the polyimide film.
That is, at least wiring along the MD direction of the polyimide film (wiring with the wiring crossing direction as the TD direction) and wiring along the TD direction of the polyimide film (wiring with the wiring crossing direction as the MD direction) are formed on the polyimide film. May be good.

The size (pitch) of the wiring is not particularly limited, but it can be efficiently formed even with a narrow pitch. The size of such wiring may be, for example, a line width of about 30 μm or less (for example, 20 μm or less, 15 μm or less, 10 μm or less), and a line spacing (line spacing) of 40 μm or less (for example, 20 μm or less, 15 μm or less). Hereinafter, it may be about 10 μm or less).

In a metal wiring board (polyimide film constituting a metal wiring board), the coefficient of thermal expansion in the cross-wiring direction is often small, reflecting the coefficient of thermal expansion of the polyimide film, for example, 12 ppm / ° C. or less (for example, 10 ppm /). ° C. or lower), preferably 8 ppm / ° C. or lower (for example, 2 to 8 ppm / ° C.), more preferably 7 ppm / ° C. or lower (for example, 3 to 7 ppm / ° C.), and 6 ppm ° C. or lower (for example, for example). 3 to 6 ppm / ° C.) is still preferable.

When the wiring is formed at a plurality of locations or in different directions, it is preferable to satisfy the above-mentioned coefficient of thermal expansion. For example, when wiring is formed along the MD direction and the TD direction, it is preferable that the coefficients of thermal expansion in these wiring transverse directions (that is, the TD direction and the MD direction) both satisfy the above-mentioned coefficient of thermal expansion.

Further, when the wiring is formed at a plurality of locations or in different directions, it is preferable that the coefficient of thermal expansion is small and the variation thereof is small at all locations or in the wiring crossing direction.
For example, when the wiring is formed along the MD direction and the TD direction (that is, when the wiring crossing direction is the TD direction and the MD direction), the | α _MD in the metal wiring board (polyimide film constituting the metal wiring board). -Α _TD | is often small reflecting the value in the polyimide film, for example, 7 ppm / ° C. or less (for example, 6 ppm / ° C. or less), preferably 5 ppm / ° C. or less (for example, 4.5 ppm / ° C. or less). ), More preferably 4 ppm / ° C. or lower (for example, 3.5 ppm / ° C. or lower), particularly 3 ppm / ° C. or lower, 2.5 ppm / ° C. or lower, 2 ppm / ° C. or lower, 1.5 ppm / ° C. or lower, etc. Is still preferable.
The value of | α _MD − α _TD | may be a value (or an average value thereof) in each wiring, or may be calculated using α _MD and α _TD in different wirings.
For example, when wiring A having the MD direction as the wiring crossing direction and wiring B having the TD direction as the wiring crossing direction are formed, | α _MD − α _TD | in the wiring A and | α _MD − α _TD | (in wiring B). Alternatively, the average value of these values may be used as the above value, and | α _MD − α _TD | can be obtained from the values of α _MD in the wiring A (crossing direction) and α _TD in the wiring B (crossing direction).

By reducing the coefficient of thermal expansion, it is easy to suppress dimensional changes (expansion) due to heat. Therefore, for example, it is possible to suppress the expansion of the substrate at the processing temperature when mounting electronic components and reduce the risk of mounting defects.
Further, by reducing | α _MD − α _TD |, such dimensional change or expansion can be suppressed in multiple directions. Therefore, for example, the degree of freedom in circuit design is dramatically increased without limiting the mounting direction of the electronic component to one direction.

The method for manufacturing the metal wiring board (flexible printed circuit board) is not particularly limited, and a known method can be used, but in particular, it may be manufactured by a semi-additive method or a subtractive method.

In a more specific embodiment, a wiring (wiring circuit) is patterned on a copper-clad laminate (for example, a copper-clad laminate having a copper thickness of about 1 to 3 μm) by a photolith method, and a resist layer at a location where wiring is desired is formed. After peeling, a method of forming a wiring (for example, a wiring having a copper thickness of 7 to 10 μm) on an exposed thin copper layer by electrolytic copper plating, and then removing a resist layer, a thin copper layer, and a base metal layer (semi-additive method). ), Or a copper-clad laminate (for example, a copper-clad laminate with a copper thickness of 7 to 10 μm) is patterned with a wiring circuit using the photolith method, and copper at a location where no wiring is formed by etching. It may be manufactured by a method (subtractive method) in which the resist layer is peeled off after removing the layer and the underlying metal layer.

If necessary, tin or gold may be formed in the wiring (copper wiring or the like) in an amount of 0.1 to 0.5 μm by an electroless plating method.

Further, for circuit protection, a solder resist may be laminated on a necessary portion, or a coverlay film may be laminated. Alternatively, a solder resist and a coverlay film can be combined to protect the required parts.

[Coverlay film]
The polyimide film of the present invention can also form a cover film. Therefore, the present invention also includes a coverlay film made of the polyimide film.

Such a coverlay film is particularly a substrate on which wiring in different directions is formed (such as the metal wiring board, a metal wiring board in which the polyimide film is not the polyimide film in the metal wiring board), and a substrate on which a plurality of components are mounted. It may be a coverlay film for at least one kind of substrate selected from (such as a mounting substrate described later) and a substrate having a multilayer structure (such as a substrate described later).

Since the coverlay film covers wiring and components (electronic components), the dimensional stability of the coverlay film may affect the formed wiring and mounted components. Therefore, it is important that the coverlay film also exhibits excellent dimensional stability and the like.

The coverlay film may be composed of only a polyimide film, or may be composed of a polyimide film and an adhesive layer (adhesive layer).

The thickness of the coverlay film (or the polyimide film constituting the coverlay film) is not particularly limited, but may be, for example, 1 to 100 μm, preferably 3 to 50 μm, and more preferably about 5 to 25 μm.
Further, in the coverlay film, the thickness of the adhesive layer is not particularly limited, but may be, for example, 1 to 300 μm (for example, 2 to 200 μm), preferably 3 to 150 μm (for example, 5 to 100 μm). It may be -80 μm (eg, 3-60 μm, preferably 5-50 μm, more preferably 10-30 μm).

The coverlay film is used, for example, to cover a metal layer (wiring of a metal wiring board) of a metal wiring board. Such a metal wiring board (metal wiring board) is composed of a base film (base film) and a metal layer (wiring). The base film may be the polyimide film or a polyimide film other than the polyimide film, but in particular, both the coverlay film and the base film may be the polyimide film.
By combining the polyimide film in both the coverlay film and the base film of the metal wiring board in this way, excellent dimensional stability and the like can be efficiently exhibited.

[Mounting board]
The present invention also includes the metal wiring board (metal wiring board) and / or the mounting board provided with the coverlay film (electronic component mounting board). Such a mounting substrate may be, for example, a chip-on-film (COF) substrate.

In such a mounting board, the number of components (electronic components) to be mounted may be one, a plurality, and particularly a plurality. In the present invention, even when a plurality of parts are mounted, excellent dimensional stability and the like can be efficiently exhibited. Therefore, even if a plurality of parts are used, high-precision mounting is possible.

In a typical aspect, the component may be mounted on the wiring of the board in which the wiring is formed in different directions. A more specific mounting board includes a board (metal wiring board) in which wiring (metal wiring) is formed in at least two directions along the MD direction and the TD direction of the polyimide film, and electronic components are mounted on the wiring. It may have been done.

The component (electronic component) can be selected according to the application and is not particularly limited, and examples thereof include an IC chip, a capacitor, a transistor, a memory, and an inductor. These parts may be used alone or in combination of two or more.

[Substrate with multi-layer structure]
The polyimide film of the present invention is also suitable as a film constituting a substrate having a multilayer structure.

The substrate having such a multi-layer structure may be typically a substrate having a multi-layer structure including the metal wiring board and / or the coverlay film at least. According to a substrate having such a multi-layer structure, excellent dimensional stability and the like can be exhibited in spite of the multi-layer structure, and a substrate having a multi-layer structure can be formed with high accuracy. In particular, a multilayer structure substrate requires interlayer connection, but according to the polyimide film of the present invention, interlayer connection by via holes can be enabled with high position accuracy.

For example, a substrate having a multilayer structure (for example, a multilayer flexible printed circuit board) usually covers a plurality of laminated metal wiring boards and a metal wiring board (or wiring of the metal wiring board) of the outermost layer thereof. However, at least one of the plurality of metal wiring boards (base films) and / or coverlay films may be the polyimide film.

In particular, in the substrate having a multilayer structure, all of the base film constituting the metal wiring substrate and the film constituting the coverlay film (or all the polyimide films constituting the substrate having the multilayer structure) are the polyimide films. Is preferable.

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 with reference to examples, but the present invention is not limited to these examples.

In the examples, PPD stands for para-phenylenediamine, 4,4'-ODA stands for 4,4'-oxydianiline (4,4'-diaminodiphenyl ether), PMDA stands for pyromellitic acid dianhydride, and BPDA stands for BPDA. Represents 3,3', 4,4'-diphenyltetracarboxylic acid dianhydride, and DMAc represents N, N-dimethylacetamide, respectively.

[Example 1]
(Creation of polyimide film)
Prepare PPD (molecular weight 108.14), 4,4'-ODA (molecular weight 200.24), PMDA (molecular weight 218.12), BPDA (molecular weight 294.22) at a molar ratio of 60/40/80/20. Then, the solution was made into a 20% by weight solution in DMAc and polymerized to obtain a polyamic acid solution of 3500 poise. To this, a DMAc slurry of silica having an average particle diameter of 0.3 μm was added in an amount of 0.3% by weight based on the weight of the resin, and the mixture was sufficiently stirred and dispersed.
Acetic anhydride (molecular weight 102.09) and β-picoline were mixed and stirred at a ratio of 17% by weight to this solution. The obtained mixture was cast on a stainless steel drum rotating at 75 ° C. from a T-shaped slit die and peeled off to obtain a self-supporting gel film having 55% by weight of residual volatile components and a thickness of about 0.05 mm.
This gel film is stretched 1.25 times in the transport direction at 65 ° C., and then stretched 1.45 times in the direction perpendicular to the transport direction in a heating furnace at 250 ° C. for 50 seconds at 400 ° C. The heat treatment was continuously performed for 75 seconds. By adjusting the transport speed, a polyimide film having a thickness of 25 μm was obtained.

[Example 2]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 60/40/75/25.

[Example 3]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 65/35/75/25.

[Example 4]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 60/40/65/35.

[Example 5]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 50/50/80/20.

[Example 6]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 50/50/75/25.

[Example 7]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 50/50/65/35.

[Reference Example 1]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 40/60/75/25.

[Reference Example 2]
A polyimide film having a thickness of 25 μm was obtained by the same procedure as in Example 1 except that PPD, 4,4'-ODA, PMDA, and BPDA had a molar ratio of 40/60/75/25.

The following characteristics of each of these films were evaluated.

(1) Tensile elastic modulus RTM-250 (manufactured by A & D Co., Ltd.) was used, and the measurement was performed under the condition of tensile speed: 100 mm / min.

(2) Breaking elongation was measured using RTM-250 (manufactured by A & D Co., Ltd.) under the condition of tensile speed: 100 mm / min.

(3) Coefficient of thermal expansion (CTE)
Measurement was performed using TMA-60 (manufactured by Shimadzu Corporation) under the conditions of a measurement temperature range of 50 to 200 ° C. and a heating rate of 10 ° C./min.

(4) The film size (L1) was measured after being left in a room adjusted to a heating shrinkage rate of 25 ° C. and 60% RH for 2 days, and then heated to 200 ° C. for 60 minutes and then returned to 25 ° C. and 60% RH. After being left in the adjusted room for 2 days, the film size (L2) was measured and evaluated by the following formula calculation.
Heat shrinkage rate (%) =-| (L2-L1) / L1 | × 100

(5) Loop Stiffness Measurement was performed using Loop Stiffness Testa DA (manufactured by Toyo Seiki Seisakusho) under the conditions of a sample width of 10 mm, a loop length of 50 mm, and a compression distance of 10 mm.

(6) Glass transition temperature Using a dynamic viscoelasticity measuring device (DMS6000, manufactured by Hitachi High-Tech Science), the measurement was performed under 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).

The results are shown in the table below together with the composition. In the table below, "MD" indicates each physical property value in the MD direction, and "TD" indicates each physical property value in the TD direction.

The polyimide film of the present invention is excellent in dimensional stability, handleability, productivity and the like.
In particular, since the polyimide film of the present invention is excellent in dimensional stability not only in one direction but also in different directions, and thus in any direction, wiring in different directions (for example, MD direction and TD direction) is narrowly pitched. It can be suitably used as a polyimide film used for the purpose of providing the film, mounting a plurality of electronic components, or forming a multilayer structure.

Claims (19)

The coefficient of thermal expansion (α _MD ) in the MD direction and the coefficient of thermal expansion (α _TD ) in the TD direction are both −3 to +3 ppm / ° C., and | α _MD −α _TD | is 3 ppm / ° C. or less, and is in the MD direction. The total value of the tensile elastic modulus (EMD) and the tensile elastic modulus (ETD) in the _TD direction is 15.5 GPa or more, and the breaking elongation in the _MD direction ( _RMD ) and the breaking elongation in the _TD direction (RTD). ) Is 20% or more, a polyimide film. The coefficient of thermal expansion (α _MD ) in the MD direction and the coefficient of thermal expansion (α TD) in the TD direction _are both _{-5 to} +5 ppm / ° C. The total value of the elastic modulus (EMD ) and the tensile elastic modulus (ETD) in the TD direction is _15.5 GPa or more, and the breaking elongation (RMD) in the _MD direction and the breaking elongation ( _RTD ) in the _TD direction are A polyimide film having a glass transition temperature of 20% or more and a glass transition temperature (glass transition temperature of the polyimide constituting the film) of 370 ° C. or higher . The polyimide film according to claim 1 or 2 , wherein both α _MD and α _TD are -3 to +3 ppm / ° C., and | α _MD − α _TD | is 2 ppm / ° C. or less. The polyimide film according to any one of claims 1 to 3, wherein | E _MD -E _TD | is 1 GPa or less. E _MD + E _TD The polyimide film according to any one of claims 1 to 4, wherein the amount is 16 GPa or more. The polyimide film according to any one of claims 1 to 5 , wherein | R _MD -R _TD | is 15% or less. The polyimide film according to any one of claims 1 to 6 , wherein both the heat shrinkage rate (SMD) at 200 ° C. in the _MD direction and the heat shrinkage rate (STD) at 200 ° C. in the _TD direction are 0.03% or less. .. The polyimide film according to any one of claims 1 to 7 , wherein both the loop stiffness in the MD direction and the loop stiffness in the TD direction are 75 mN / cm or less. The polyimide film according to any one of claims 1 , 3 to 8 , wherein the glass transition temperature (glass transition temperature of the polyimide constituting the film) is 370 ° C. or higher. Any of claims 1 to 9 , which is composed of a polyimide containing para-phenylenediamine (PPD), an aromatic diamine component containing 4,4-oxydianiline (ODA), and an acid anhydride component as a polymerization component. The polyimide film described in. The polyimide film according to claim 10 , wherein the aromatic diamine component contains PPD in an amount of 45 mol% or more and 4,4-ODA in an amount of 55 mol% or less with respect to the entire aromatic diamine component. The polyimide film according to claim 10 or 11 , wherein the acid anhydride component contains pyromellitic acid dianhydride (PMDA) in a ratio of 45 mol% or more with respect to the entire acid anhydride component. The aromatic diamine component contains 45 to 70 mol% of PPD and 30 to 55 mol% of 4,4-ODA with respect to the entire aromatic diamine component, and the acid anhydride component is the entire acid anhydride component. The polyimide film according to any one of claims 10 to 12 , which contains PMDA in a proportion of 50 to 85 mol%. A substrate provided with the polyimide film according to any one of claims 1 to 13 and a metal layer. A substrate comprising the polyimide film according to any one of claims 1 to 13 and wiring formed on the film. The substrate according to claim 15 , wherein wiring in different directions is formed. A coverlay film made of the polyimide film according to any one of claims 1 to 13 . An electronic component mounting substrate comprising the substrate according to any one of claims 14 to 17 and / or a coverlay film. A substrate having a multilayer structure comprising the substrate according to any one of claims 14 to 18 and / or a coverlay film.