TWI741030B - Polyimide film - Google Patents

Abstract

The present invention provides a polyimide film with characteristics such as small difference in dimensional changes. In the polyimide film, set both the linear expansion coefficient αMD in the transport direction (MD) of the film and the linear expansion coefficient αTD in the width direction (TD) to be 7 ppm/℃ or less, and the ultrasonic pulse will be measured. The value of the anisotropy index AI expressed by the following formula at the propagation velocity V is set to 15 or less over the entire width. AI = (VMAX^2－VMIN^2)/(VMAX^2＋VMIN^2) (where VMAX^2 represents the square of the maximum pulse propagation velocity, and VMIN^2 represents the square of the minimum pulse propagation velocity)

Description

Polyimide film

The invention relates to a polyimide film and a manufacturing method thereof. Furthermore, this invention relates to the flexible metal laminated board provided with this polyimide film and metal foil.

Flexible printed circuits (FPC: Flexible printed circuits) are generally manufactured by the following method: a flexible insulating film formed of various insulating materials is used as a substrate, and the surface of the substrate is heated, The metal foil is bonded by crimping. As the insulating film, a polyimide film excellent in heat resistance and electrical insulation can be preferably used.

In recent years, in order to achieve the miniaturization and weight reduction of electronic equipment, the miniaturization of wiring installed on the substrate is being promoted, and the components to be installed are also equipped with miniaturization and high density. Therefore, if the size change after the formation of fine wiring becomes large, the mounting position of the part deviates from the design stage, and the problem that the part and the substrate cannot be connected well.

Attempts are being made to reduce the dimensional change of such polyimide films. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2015-10107) describes that the step change can be reduced by the following polyimide film, the film width of the polyimide film is 1m or more, and the film The machine conveying direction (MD) is the benchmark, and the orientation coefficient AI (45, 135) value of the film at 45° and 135° is below 12 in the entire width. The diagonal The dimensional change rate of the flexible metal laminate in the direction of (45°, 135°) before and after etching is -0.05~0.05%, and at least one side has a thermoplastic polyimide layer with a thickness of 0.5~20μm.

In this way, further improvement of polyimide film is being sought.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-10107

The object of the present invention is to provide a polyimide film with less difference in dimensional changes in the film forming width direction and a flexible metal laminated board provided with the polyimide film.

Another object of the present invention is to provide a polyimide film with less one-sided elongation after heat treatment and a flexible metal laminated board provided with the polyimide film.

Yet another object of the present invention is to provide a method for producing a polyimide film having the above-mentioned characteristics with excellent film forming properties.

According to the research conducted by the inventors of the present invention, it is known that although the film of Patent Document 1 can improve the dimensional change to a certain extent, there is a difference in the dimensional change of the whole film, or a unilateral elongation phenomenon caused by heat treatment occurs. In addition, in order to simultaneously reduce the difference in dimensional change and the reduction of unilateral elongation, it is studied to adjust the imidization of the support, but it is difficult to achieve film breakage such as rupture of the holding part at the same time.

Under this circumstance, the inventors of the present invention have repeatedly carried out further intensive research, and found that in the polyimide film, the alignment properties of all angles are specified by a specific AI value instead of just as in Patent Document 1. Specifying the orientation of a specific angle and combining the specific AI value with a specific linear expansion coefficient can not only simply reduce the dimensional change, but also suppress the difference, and also reduce the unilateral elongation after heat treatment, and then It was found that in order to ensure excellent film formation and adjust such AI value or linear expansion coefficient, it is necessary to adjust the condensation of the polyimide film precursor film. The imidization rate of the film, etc. Based on this knowledge, further research was advanced, and the present invention was completed.

That is, the present invention relates to the following inventions.

[1] A polyimide film in which both the linear expansion coefficient αMD in the transport direction (MD) of the film and the linear expansion coefficient αTD in the width direction (TD) are less than 7ppm/℃, and when measuring the ultrasonic pulse At the propagation velocity V, the anisotropy index AI value represented by the following formula is 15 or less over the entire width.

AI=(VMAX^2-VMIN^2)/(VMAX^2+VMIN^2)

(In the formula, VMAX^2 represents the square of the maximum value of pulse propagation velocity, and VMIN^2 represents the square of the minimum value of pulse propagation velocity)

[2] The polyimide film described in [1] has a film width of 1000 mm or more, and the difference in the coefficient of linear expansion in the film width direction of αMD (the difference between the maximum value and the minimum value) is 2 ppm/°C or less.

[3] The polyimide film as described in [1] or [2], the film width of which is 1000mm or more, and the difference of the linear expansion coefficient in the film width direction of αTD (the difference between the maximum value and the minimum value) is 2 ppm /℃ below.

[4] The polyimide film according to any one of [1] to [3], wherein the polyimide film comprises the following polyimine, and the polyimide is an aromatic containing p-phenylenediamine The diamine component and one or more acid anhydride components selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride are used as polymerization components.

[5] The method for producing a polyimide film as described in any one of [1] to [4], which is to prepare a gel film (especially It is a self-supporting gel film that is partially dried and hardened), and the gel film is heat-treated (especially by holding both ends of the gel film in the width direction while passing it through a heating furnace for heat treatment (drying) And heat treatment)].

[6] The manufacturing method as described in [5], wherein the imidization rate of the gel film (gel film peeled from the support) is 55 to 75%.

[7] A flexible metal laminated board provided with the polyimide film and metal foil as described in any one of [1] to [4].

The polyimide film of the present invention has less difference in dimensional changes in the width direction of the film (film). In addition, the polyimide film of the present invention has less unilateral elongation after heat treatment.

In addition, in the flexible metal laminated board obtained by using the polyimide film of the present invention, the dimensional change before and after the metal foil is removed is smaller in the width direction of the polyimide film.

Therefore, it can be suitably used for flexible metal laminated boards (FPC) etc. where fine wiring is formed.

Furthermore, according to the manufacturing method of the present invention, by adjusting the imidization rate of the gel film, etc., it is possible to manufacture a polyimide film with excellent film-forming properties as described above.

1: Short strip film

2: membrane end

a: unilateral elongation value

Fig. 1 is a graph showing the unilateral elongation values measured in the examples.

[Polyimide film]

The polyimide film of the present invention has a specific linear expansion coefficient and anisotropy index (AI value). By combining such a specific coefficient of linear expansion with a specific AI value, it is possible to efficiently produce a film with less difference in dimensional changes and less unilateral elongation after heat treatment.

Furthermore, the coefficient of linear expansion or AI value can be determined by, for example, the composition of the polyimide constituting the film, the production conditions of the film (the gel film’s imidization rate, elongation conditions, the temperature of the support, the imid The speed of chemical conversion, drying conditions, etc.) are selected and adjusted.

First, in the polyimide film of the present invention, both the linear expansion coefficient αMD in the transport direction (MD) of the film and the linear expansion coefficient αTD in the width direction (TD) are less than 7ppm/°C, preferably 6ppm/ °C or less, more preferably 5 ppm/°C or less, especially 4.5 ppm/°C or less.

In the polyimide film of the present invention, the difference in the linear expansion coefficient in the film width direction of αMD may be, for example, 3 ppm/°C or less, preferably 2 ppm or less, and more preferably 1.5 ppm or less.

In the polyimide film of the present invention, the difference in the linear expansion coefficient in the film width direction of αTD may be, for example, 3 ppm/°C or less, preferably 2 ppm/°C or less, and more preferably 1.5 ppm or less.

In addition, the linear expansion coefficient can be measured, for example, using TMA-50 (manufactured by Shimadzu Corporation) under the conditions of a measurement temperature range of 50 to 200°C and a temperature increase rate of 10°C/min.

For example, the linear expansion coefficient can be selected at 2 points in the film width direction where both ends of the self-made film width enter the inner side of 200mm, and within the range of the straight line connecting the 2 points, select 1 within ±200mm of the center of the straight line that includes the 2 points. Point and any two points, at least use these five points to measure the linear expansion coefficient, and obtain the average value of the obtained measured values.

In addition, the difference (difference) of the linear expansion coefficient in the width direction of the film can be selected, for example, at 2 points in the width direction of the film where both ends of the self-made film width enter the inside of 200mm, and the two points can be selected within the range of the straight line connecting the two points. Measure the linear expansion coefficient of at least one point within ±200mm of the central part of the straight line and any two points, and obtain the difference between the maximum value and the minimum value among the obtained measured values.

In addition, when measuring the propagation velocity V of the ultrasonic pulse of the polyimide film of the present invention, the anisotropy index AI value represented by the following formula is 15 or less over the entire width [e.g., 0-15 (e.g., 0.5 ~14.8), preferably 14.5 or less (e.g., 1 to 14.2), more preferably 14 or less (e.g., 2 to 13.8), especially 13.5 or less (e.g., 3 to 13.2)].

AI=(VMAX^2-VMIN^2)/(VMAX^2+VMIN^2)

(In the formula, VMAX^2 represents the square of the maximum value of pulse propagation velocity, and VMIN^2 represents the square of the minimum value of pulse propagation velocity)

In addition, the AI value can be measured as follows, for example.

Choose 2 points in the film width direction where both ends of the self-made film width enter the inner side of 200mm, and select 1 point within ±200mm of the central part of the straight line connecting the 2 points and any 2 points within the range of the straight line connecting the 2 points Point, use at least these 5 points to measure AI. AI can be measured using SST-2500 manufactured by Nomura Corporation. If SST-2500 is used, the ultrasonic velocities in 16 directions can be automatically measured in units of 11.25° with respect to the surface direction of the film from 0° to 180° (0° parallel to MD). Furthermore, the angle (alignment angle) refers to the direction of the alignment axis, with the mechanical transport direction (MD) of the film as the reference line of 0°, and it is expressed as the angle on the side rotating in the clockwise direction. Set the maximum pulse propagation velocity among the obtained velocities in each direction as VMAX, and set the minimum pulse propagation velocity among the obtained velocities in each direction as VMIN, and calculate AI based on these values.

The width (film width) of the polyimide film of the present invention is not particularly limited, and in particular, it can be 1000mm or more (for example, 1200~2500mm), preferably 1500mm or more (for example, 1700~2500mm), and more preferably It is 2000mm or more (for example, 2000~2500mm).

Even in such a relatively wide film, the present invention can satisfy the specific linear expansion coefficient and anisotropy index (AI value) as described above, and reduce the difference in dimensional change (heat shrinkage) or the heat treatment. Side stretch.

The thickness (average thickness) of the polyimide film of the present invention is not particularly limited, and can be appropriately selected according to the application. For example, it can be 1 μm or more (for example, 1 to 300 μm), preferably 2 to 200 μm, and more preferably About 3~150μm (for example, 5~100μm).

As described above, the polyimide film of the present invention has less dimensional change (heat shrinkage) in the width direction of the film or less unilateral elongation after heat treatment. Also, it is obtained by using the polyimide film of the present invention The difference in the dimensional change rate of the flexible metal laminate in the width direction of the film is small.

For example, in the polyimide film of the present invention, before and after removing the metal foil of the flexible metal laminate, the difference in the dimensional change rate in the width direction of the film can be 0.05% or less, preferably 0.04% or less.

In addition, in the polyimide film of the present invention, the thermal shrinkage rate difference at 200°C in the width direction may be 0.05% or less, preferably 0.04% or less, and more preferably 0.02% or less.

Furthermore, the difference in the dimensional change rate in the width direction of the film or the difference in the thermal shrinkage rate can be, for example, two points in the film width direction where the two ends of the self-made film width enter the inner side of 200mm, and the range of the straight line connecting the two points can be selected to include At least one point and any two points within ±200mm of the central part of the two-point straight line shall be used to measure the dimensional change rate or thermal shrinkage rate at least at these five points to determine the maximum value and the minimum value among the measured values obtained Poorly obtained.

Furthermore, the polyimide film of the present invention has a width of 508mm and a length of 6.5m, when treated at 200°C for 30 minutes, the unilateral elongation (the length of a in Fig. 1 described later) can be less than 5mm, preferably 4mm Hereinafter, it is more preferably 3.5 mm or less.

The film of the present invention is composed (or formed) of polyimide. Hereinafter, the manufacturing method of polyimide and film is demonstrated.

[Polyimine and manufacturing method of polyimide film]

Polyimide (or polyamide acid) has an aromatic diamine component and an acid anhydride component as a polymerization component.

Specifically, in the production of polyimide (or polyimide film), first, by polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent, a polyimide acid (polyimide film) is obtained. Amine precursor) solution.

The aromatic diamine component usually contains at least p-phenylenediamine (PPD). The aromatic diamine component may contain other than p-phenylenediamine as a specific example of the above-mentioned aromatic diamine components other than p-phenylenediamine Examples include: m-phenylenediamine, benzidine, p-xylylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diamine Diphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-Dimethoxybenzidine, 1,4-bis(3-methyl-5-aminophenyl)benzene and their amide-forming derivatives.

These can be used individually by 1 type, and 2 or more types can also be mixed and used for it.

The aromatic diamine component is preferably a combination of p-phenylenediamine (PPD) and 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether (DPE), especially It is preferably a combination of p-phenylenediamine (PPD) and 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether (DPE), especially p-phenylenediamine (PPD) ) And 4,4'-diaminodiphenyl ether (DPE) combination.

When the aromatic diamine component contains p-phenylenediamine, the ratio of p-phenylenediamine relative to the aromatic diamine component may be, for example, 20 mol% or more (for example, 25-100 mol%), preferably 30 mol% or more (for example, 31~80 mol%), more preferably 35 mol% or more (for example, 37~70 mol%), usually 30-50 mol% (for example, 35~ 45 mol%).

When combining p-phenylenediamine (PPD) with 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether (DPE), the ratio can be PPD /DPE (Mole Ratio)=80/20~30/70, preferably 75/25~35/65 (for example, 70/30~35/65), usually 60/40~30/70( For example, 50/50~35/65, preferably 45/55~37/63).

Examples of acid anhydride components (or acid amide-forming derivatives) include pyromellitic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3',3,4'- Biphenyltetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 2,2-bis(3,4-dicarboxybenzene) (Base) ether, pyridine-2,3,5,6-tetracarboxylic acid and other aromatic tetracarboxylic acid anhydrides. These can be used individually by 1 type, and 2 or more types can also be mixed and used for it. Among them, pyromellitic dianhydride (PMPA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) are preferred, and a combination of these is particularly preferred.

When the acid anhydride component contains BPDA, the ratio of BPDA to the acid anhydride component may be, for example, 15 mol% or more (for example, 15-100 mol%), preferably 20 mol% or more (for example, 22-90 mol%). Ear%), preferably 25 mol% or more (for example, 28~80 mol%), more preferably 30 mol% or more (for example, 32~60 mol%), usually 25~45 mol% Ear% (for example, 30-40 mole%).

In the case of combining pyromellitic dianhydride (PMPA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), the ratio can be PMPA/BPDA (mole ratio )=90/10~20/80, preferably 85/15~30/70, more preferably about 80/20~35/65 (for example, 75/25~40/60), usually 70/ 30~50/50 (for example, 70/30~55/45, preferably 69/31~60/40).

As the organic solvent used in the formation of the polyamide acid solution, for example, sulfinic solvents such as dimethyl sulfite and diethyl sulfite, N,N-dimethylformamide, N,N- Formamide solvents such as diethylformamide, acetamide solvents such as N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidine Pyrrolidone solvents such as ketones and N-vinyl-2-pyrrolidone, phenolic solvents such as phenol, ortho, meta, or p-cresol, xylenol, halogenated phenol, catechol, or hexamethyl Aprotic polar solvents such as phosphamide and γ-butyrolactone are preferably used alone or as a mixture of two or more, and aromatic hydrocarbons such as xylene and toluene can also be used.

The polymerization method can be performed by any known method, for example, the following method:

(1) First, the total amount of aromatic diamine components is added to the solvent, and then the acid anhydride components are added so that the total amount of aromatic diamine components becomes equivalent (equal to moles) to perform polymerization.

(2) First, the total amount of the acid anhydride component is added to the solvent, and then the aromatic diamine component is added so as to be equivalent to the acid anhydride component to perform polymerization.

(3) An aromatic diamine component (a1) is added to the solvent, and then the ratio of the mono anhydride component (b1) relative to the reaction component to 95~105 mol% is mixed for the time required for the reaction, and Then, another aromatic diamine component (a2) is added, and then another acid anhydride component (b2) is added so that the total aromatic diamine component and the total acid anhydride component become approximately equivalent, and polymerization is performed.

(4) An acid anhydride component (b1) is added to the solvent, and then an aromatic diamine component (a1) is mixed with the reaction component at a ratio of 95 to 105 mol% for the time required for the reaction. Then, another acid anhydride component (b2) is added, and then another aromatic diamine component (a2) is added so that the total aromatic diamine component and the total acid anhydride component become approximately equivalent, and polymerization is performed.

(5) The polyamide acid solution (A) is adjusted by reacting an aromatic diamine component and an acid anhydride component in a solvent in an excessive manner so that the other aromatic diamine component and the acid anhydride component are either If it becomes excessive, it is reacted in another solvent to adjust the polyamide acid solution (B). The polyamide acid solutions (A) and (B) obtained in this way are mixed to complete the polymerization. At this time, when the aromatic diamine component is excessive when adjusting the polyamide acid solution (A), the acid anhydride component is excessive in the polyamide acid solution (B), and again, the polyamide acid solution (A) When the acid anhydride component is excessive, the aromatic diamine component is excessive in the polyamide acid solution (B), and the polyamide acid solution (A) and (B) are mixed to obtain the total aromatic content used in the reaction. The group diamine component and the total acid anhydride component are adjusted so that they are approximately equivalent. In addition, the polymerization method is not limited to these, and other well-known methods may be used.

Furthermore, the polyamide acid solution may optionally contain chemically inert organic fillers such as titanium oxide, fine silicon dioxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, polyimide fillers, etc., in order to obtain the smoothness of the film. Inorganic fillers, etc.

The polyamide acid solution usually contains about 5-40% by weight of solid content, and preferably contains about 10-30% by weight of solid content. Moreover, its viscosity is obtained by the Brookfield viscometer The measured value meter can usually be about 10~2000Pa‧s, for stable liquid delivery, it is preferably about 100~1000Pa‧s. In addition, the polyamide in the organic solvent solution can be partially imidized.

Next, the manufacturing method of a polyimide film is demonstrated. Film-making (manufacturing) polyimide film can undergo, for example, the step (1) of obtaining a gel film by subjecting a polyamide acid solution to a cyclization reaction, and heating (and desolventizing) the obtained gel film The step (2) is obtained. Furthermore, drying and imidization are performed by heat treatment.

In step (1), the method of subjecting the polyamide acid solution to the cyclization reaction is not particularly limited. Specifically, (i) casting the polyamide acid solution into a film and thermally dehydrating it can be mentioned. The method of obtaining a gel film (thermal closed loop method), or (ii) mixing a cyclization catalyst and a conversion agent (dehydrating agent) in a polyamic acid solution to chemically decyclize it to make a gel film and use it The method of obtaining a gel film by heating (chemical closed loop method), etc., is particularly preferred as the latter method. The above-mentioned polyamide acid solution may contain a gelation retarder and the like. The gelation retarder is not particularly limited, and acetone or the like can be used.

Examples of cyclization catalysts include amines, such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), heterocyclic tertiary amines (for example, iso Quinoline, pyridine, β-picoline, etc.) and so on. These can be used individually by 1 type, and 2 or more types can also be mixed and used for it. Among these, heterocyclic tertiary amines such as β-picoline are preferred.

Examples of the dehydrating agent include acid anhydrides, such as aliphatic carboxylic anhydrides (for example, acetic anhydride, propionic anhydride, butyric anhydride, etc.), aromatic carboxylic anhydrides (for example, benzoic anhydride, etc.), and the like. These can be used individually by 1 type, and 2 or more types can also be mixed and used for it. Among them, acetic anhydride and/or benzoic anhydride are preferred, and acetic anhydride is particularly preferred.

The usage amount of the cyclization catalyst and the dehydrating agent is not particularly limited, and it can be 1 mol or more (for example, 1.5~10Mo Ears), preferably 2 mols or more (for example, 2.2 to 8 mols), more preferably 2.5 mols or more (for example, 2.7 to 5 mols), usually 2 to 4 mols (for example, 2.5~3.3 mol).

Gel film (gel film with self-supporting properties) can usually be cast (coated) on a support by casting a polyamide solution (especially a polyamide solution mixed with a cyclization catalyst and a conversion agent) on a support The body is partially dried and hardened (imidized).

More specifically, the gel film can be obtained by casting a polyamide acid solution from a nozzle with a slit on a support to form a film shape, by heating from the support, hot air or Heating from a heat source such as an electric heater causes it to perform a closed-loop reaction to dry free organic solvents and other volatile components, thereby forming a self-supporting gel film, and then peeling off from the support.

It does not specifically limit as a support body, A metal (for example, stainless steel) drum, an endless belt, etc. are mentioned as an example. The temperature of the support is not particularly limited. For example, it can be 30~200°C, preferably 40~150°C, more preferably 50~120°C, especially 70~100°C (for example, 75~95°C) about.

Furthermore, the temperature of the support can be controlled by (i) liquid or gas heat medium, (ii) radiant heat of electric heater, etc.

The imidization rate of the gel film (gel film for heat treatment, gel film peeled from the support) can be, for example, 50~80%, preferably 52~78%, and more preferably 55~ About 75% (for example, 57~73%).

Furthermore, the rate of line (PEI) using FT-IR (fourier transform infrared radiation , Fourier transform infrared spectroscopy), represented by the formula below using the ratio 1375cm ^-1 1500cm ^-1 to the peak height of the obtained.

The imidization rate (%)=A/B×100

[Wherein, A represents (peak height measurement 1375cm ^-1 of the membrane of the target) / (peak height measured 1500cm ^-1 of the membrane of the target), B represents (Be polyimide film of 1375cm ^-1 of the reference ^{Peak height)/(1500cm -1} peak height of the film used as the reference))

By setting the imidization rate of the gel film within the above-mentioned range, the polyimide film of the present invention can be easily and efficiently obtained.

In step (2), the gel film is heated [and dried (desolventizing)]. Generally, step (2) may include a step of holding both ends of the gel film in the width direction while passing it through a heating furnace (tenter heating path, etc.) for heat treatment (and drying).

Specifically, the gel film peeled from the support is not particularly limited, and it is usually possible to extend in the conveying direction while restricting the moving speed by a rotating roller. The extension in the conveying direction can be carried out at a temperature below 140°C. The MDX is usually 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times (for example, 1.15 to 1.3 times).

In addition, the gel film (especially the gel film extending in the conveying direction) can be introduced into the tenter device, and both ends in the width direction are held by the tenter clips, while moving together with the tenter clips, while extending in the width direction.

The extension in the width direction can be carried out at a temperature above 200°C. The stretching ratio (TDX) may be 1.1 to 1.5 times that of MDX, preferably 1.2 to 1.45 times. The specific stretching ratio (TDX) can be, for example, 1.1 to 2 times, preferably 1.3 to 1.8 times, and more preferably 1.35 to 1.7 times (for example, 1.4 to 1.6 times).

The polyimide film obtained in this way can be obtained. The obtained polyimide film may be further subjected to annealing treatment or easy subsequent treatment (for example, electrical treatment such as corona treatment, plasma treatment, or sandblasting treatment).

[Flexible metal laminated board]

The polyimide film of the present invention can be used, for example, as an insulating film of a flexible metal laminate (flexible printed wiring board).

Therefore, the present invention includes a flexible metal laminated board provided with the polyimide film of the present invention. Such a flexible metal laminated board usually includes a polyimide film and metal foil.

The type of metal constituting the metal foil is not particularly limited, and examples include copper and copper alloys, stainless steel and its alloys, nickel and nickel alloys (including 42 alloys), aluminum and aluminum alloys, and the like. Copper and copper alloys are preferred. In addition, it is also possible to use those formed with an anti-rust layer or a heat-resistant layer (for example, plating treatment of chromium, zinc, etc.), a silane coupling agent, etc., on the surface of these metals. Preferably copper and/or copper containing at least one of nickel, zinc, iron, chromium, cobalt, molybdenum, tungsten, vanadium, beryllium, titanium, tin, manganese, aluminum, phosphorus, silicon, etc. and copper Alloys, these can be preferably used in circuit processing. A particularly desirable metal foil is a copper foil formed by rolling or electrolytic plating, and its thickness is preferably 3 to 150 μm, more preferably 3 to 35 μm.

The metal foil may not be subjected to any roughening treatment on both sides, or it may be subjected to roughening treatment on one or both sides.

As long as the flexible metal laminate has a polyimide film and a metal foil, the form of the laminate is not particularly limited. For example, the polyimide film and the metal foil can be directly laminated, or the polyimide film Laminated (bonded) with metal foil via an adhesive layer (adhesive layer).

The adhering component constituting the adhesive layer is not particularly limited, and may be any of thermosetting resin and thermoplastic resin, for example. In particular, the subsequent layer may contain thermoplastic polyimide.

Therefore, the present invention also includes an adhesive film (laminated film) having a thermoplastic polyimide layer (an adhesive layer including a thermoplastic polyimide) on at least one side of the above-mentioned polyimide film.

Thermoplastic polyimide can be obtained by imidizing polyimide as a precursor. Regarding the thermoplastic polyimide precursor, there is no particular limitation, and all known ones can be used. Polyamide acid. In addition, for its production, well-known raw materials, reaction conditions, and the like can also be used. In addition, inorganic or organic fillers can be added as needed.

The glass transition temperature of the thermoplastic polyimide may be about 150°C to 350°C, for example.

The subsequent film can be obtained by providing an adhesive layer containing thermoplastic polyimide on at least one side of the above-mentioned polyimide film (non-thermoplastic polyimide film). As a specific manufacturing method, a method of forming an adhesive layer on a polyimide film that becomes a base film, or forming an adhesive layer into a sheet and bonding it to the above polyimide film can be preferably exemplified The method and so on. Among them, in the case of using the former method, if the polyamide which is the precursor of the thermoplastic polyimide contained in the adhesive layer is completely imidized, the solubility in organic solvents may decrease. In this case, it may become difficult to provide the above-mentioned adhesive layer on the polyimide film. Therefore, from the above point of view, it is more preferable to adopt the following procedure: prepare a solution containing polyamide acid as a precursor of thermoplastic polyimide, apply it to the substrate film, and then proceed to change.

The method of casting and coating the polyimide film on the polyimide film is not particularly limited, and existing methods such as die nozzle coating, reverse coating, and knife coating can be used. When the adhesive layer is formed continuously, the effect of the invention becomes obvious. That is, the method is as follows: take up the polyimide film obtained in the above-mentioned manner, and unwind it, and continuously apply a solution containing polyimide as a precursor of the thermoplastic polyimide. In addition, the above-mentioned polyamide acid solution may contain other materials such as fillers according to the application. In addition, the thickness structure of each layer of the heat-resistant adhesive film may be appropriately adjusted so as to have a total thickness suitable for the application.

As a method of imidization, either a heating imidation method or a chemical imidization method can be used. When any of the imidization procedures are used, the imidization is efficiently promoted for heating, and the temperature at this time is preferably set to (the glass transition temperature of the thermoplastic polyimide -100°C)~( Within the range of glass transition temperature +200℃), it is better to set at (thermoplastic poly The glass transition temperature of imine is within the range of -50℃)~(glass transition temperature +150℃). A higher heating temperature is likely to cause imidization, and therefore can increase the imidization rate, which is better in terms of productivity. However, if it is too high, the thermoplastic polyimide may be thermally decomposed. On the other hand, if the heating temperature is too low, it is difficult to carry out the imidization even if it is chemical imidization, and the time required for the imidization step becomes long.

Regarding the imidization time, it takes sufficient time for the imidization and drying to be substantially completed, and it is not particularly limited.

The thickness of the thermoplastic polyimide is preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 20 μm or less.

As a heating and compression bonding method of non-thermoplastic polyimide and metal, there is a solution of polyimide acid and/or polyimide, which is the precursor of thermoplastic polyimide, coated on a non-thermoplastic polyimide film and then applied A method of bonding with metal after drying, or forming a thermoplastic polyimide on the metal in the same way before bonding with a non-thermoplastic polyimide film, the bonding can use heating and pressing and/or continuous lamination. As the heating and pressing method, for example, it can be manufactured by superimposing a metal foil cut into a specific size of a pressing machine with polyimide, and performing thermocompression bonding by heating and pressing.

The continuous lamination method is not particularly limited. For example, there is a method of sandwiching between a roll and a roll for bonding. For this roller, metal rollers, rubber rollers, etc. can be used. There is no restriction on the material, as the metal roll, steel or stainless steel can be used. It is preferable to use a treatment roll whose surface is hard-plated with chromium, tungsten carbide, etc. to increase the surface hardness. As the rubber roller, it is preferable to use heat-resistant silicone rubber or fluorine-based rubber on the surface of the metal roller.

In addition, continuous lamination can be carried out by the following method called conveyor belt lamination, that is, the upper and lower metal rollers form a set, and the two upper and lower rollers are arranged in series between the upper and lower rollers. The sewn stainless steel conveyor belt is arranged in between, and the conveyor belt is pressurized by a metal roller, and then It is heated by metal rollers or other heat sources.

As the lamination temperature, a temperature range of 200 to 400°C is preferable. It is also preferable to perform heating annealing after heating and pressing and/or continuous lamination.

The flexible metal laminated board of the present invention can be used as various flexible wiring boards equipped with miniaturized and high-density components as long as the metal foil is etched to form required pattern wiring. Of course, the use of the present invention is not limited to this, as long as it is a laminate containing metal foil, it can of course be used in various applications.

As long as the present invention exerts the effects of the present invention, it is included in the technical scope of the present invention that various combinations of the above-mentioned configurations are included.

[Example]

Next, the present invention will be further described in detail by citing examples, but the present invention is not limited by these examples at all, and various changes can be made by persons with common sense in the art within the technical idea of the present invention.

The methods for measuring various characteristics in the present invention are described below.

(Imidation rate)

The so-called imidization rate refers to the extent to which the imidin group of the target film exists relative to the polyimide film of the product.

Using FT-IR, the following expression is obtained by using the ratio of the peak heights of ^{1375 cm -1} and 1500 cm ^-1.

The imidization rate (%)=A/B×100

[Wherein, A represents (peak height measurement 1375cm ^-1 of the membrane of the target) / (peak height measured 1500cm ^-1 of the membrane of the target), B represents (Be polyimide film of 1375cm ^-1 of the reference ^{Peak height)/(1500cm -1} peak height of the film used as the reference))

In addition, the polyimide film used as the benchmark is a film that has been dried and heat-treated.

(AI value)

The propagation velocity V of the ultrasonic pulse is measured using the following SST-2500 (Sonic Sheet Tester) manufactured by Nomura Corporation. If SST-2500 is used, the ultrasonic velocity in 16 directions can be automatically measured in units of 11.25° with respect to the surface direction of the film from 0 to 180 degrees (0 degrees parallel to the MD direction). According to the obtained maximum speed (MAX) and minimum speed (MIN) of the speeds in each direction, the anisotropy index (Anisotoropy Index: AI) represented by formula 1 is obtained. Using the films obtained in the following Examples and Comparative Examples, the measurements were performed in the following measurement ranges.

(Equation 1): AI=(VMAX^2-VMIN^2)/(VMAX^2+VMIN^2)

(In the formula, VMAX^2 represents the square of the maximum value of pulse propagation velocity, and VMIN^2 represents the square of the minimum value of pulse propagation velocity)

Select 2 points in the film width direction (TD direction) where both ends of the self-made film width enter the inner side of 200mm, and select 1 point within ±200mm of the center of the line that includes the two points within the range of the straight line connecting the two points And further any 2 points, at least these 5 points are used for measurement.

The AI value is measured at at least 5 points on a straight line in the film width direction, and the maximum AI value (AI value MAX) among the measured points is recorded in the table. That is, if the anisotropy in the width direction of the film is estimated to be the largest, it becomes the AI value MAX (by showing the AI value MAX, it can be understood that the AI value is equal to or less than the AI value MAX in the entire width of the film). If the AI value MAX (or the AI value in the entire width) is large, the unilateral elongation of the film after heat treatment will become worse, and defects such as wrinkles will occur during winding. In addition, the dimensional change rate of the flexible metal laminated board obtained by using the polyimide film before and after removal of the metal foil is not uniform in the film forming width direction.

(The difference between the coefficient of thermal expansion (CTE) and CTE in the width direction of the film)

Using TMA-50 (manufactured by Shimadzu Corporation), in the measurement temperature range of 50 to 200 ℃, heating up At a speed of 10°C/min, the measurement is performed in the following measurement range.

Select 2 points in the film width direction (TD direction) where both ends of the self-made film width enter the inner side of 200mm, and select 1 point within ±200mm of the center of the line that includes the two points within the range of the straight line connecting the two points And further any 2 points, at least these 5 points are used for measurement.

Then, according to the value of each measurement point, the CTE in the MD direction (ppm/°C) and the CTE in the TD direction (ppm/°C) are obtained with average values.

In addition, regarding each of the CTE (ppm/°C) in the MD direction and the CTE (ppm/°C) in the TD direction among the values of the measurement points, the difference between the maximum value and the minimum value is set as the MD-CTE difference in the width direction (ppm/℃) and the TD-CTE difference in the width direction (ppm/℃).

(The difference in thermal shrinkage in the width direction of the film)

Cut 200mm in the film mechanical transport direction (MD direction) and 200mm in the film width direction (TD direction). Measure the film size (L1) after leaving it in a room adjusted to 25℃ and 60%RH for 2 days, and then measure it as After heating at 200°C for 60 minutes, the film size (L2) after being placed in a room adjusted to 25°C and 60RH% for 2 days again, and the heat shrinkage rate is calculated by the following formula.

Thermal shrinkage (%)=-{(L2-L1)/L1}×100

Furthermore, the difference in the heat shrinkage rate in the width direction of the film is determined by selecting 2 points in the width direction of the film (TD direction) where both ends of the self-made film width enter the inner side of 200mm, and choose to include the 2 points within the range of the straight line connecting the two points. 1 point and any 2 points within ±200mm of the central part on the straight line of the point, measure the film cut out at least including each of these 5 points (as the center), and obtain the measured value (heat shrinkage) Rate) is the difference between the maximum value and the minimum value.

(Difference in the dimensional change rate in the width direction of the film)

Based on JIS C6481 5.16, 4 holes are formed on the center and diagonal of the adhesive film of the sample, and the distance between each hole and the center is measured. Then, attach the copper foil and implement the etching step The metal foil was removed from the flexible metal laminated plate in a step, and after that, the distance of each of the four holes was measured again in the same manner as before the etching step. Set the measured value of the distance of each hole before metal foil removal as D1, and the measured value of the distance of each hole after metal foil removal as D2, and calculate the dimensional change rate before and after etching (4 holes The average value).

Size change rate (%)={(D2-D1)/D1}×100

This kind of dimensional change rate is to select 2 points in the film width direction (TD direction) where both ends of the self-made film width enter the inner side of 200mm, and select the center of the line that includes the two points within the range of the line connecting the two points At least one point within ±200 mm and further two arbitrary points are measured for at least these five points, and the difference between the maximum value and the minimum value is taken as the difference in the dimensional change rate in the width direction of the film.

Furthermore, the metal laminated board is produced by a single-area-layer adhesive layer (thermoplastic polyimide layer) of a polyimide film, and then laminating and calendering a copper foil on the side of the adhesive layer. Specifically, the film is coated with a polyamide acid solution of thermoplastic polyimide in such a way that the thickness after drying becomes 2μm [add 1,3-bis(4-aminophenoxy)benzene to the solvent dimethyl Stir in the base acetamide until it dissolves; then, add 4,4'-dihydroxydiphthalic anhydride and stir to obtain the polyamide acid solution], and heat the amide at 150°C It is heated for 10 minutes, and thermally imidized at 350°C for 1 minute (following the production of the film). Thereafter, copper foil was bonded to the thermoplastic polyimide side at 350°C/30 minutes to produce a flexible metal laminate.

(One-sided elongation value)

The unilateral elongation value (mm) shown in Figure 1 (a) was measured according to the following procedure.

The polyimide film was cut into short strips with a length of 6.5m with a width of 508mm.

The short strip film was heated in a hot air oven at 200°C for 30 minutes without applying external force, and then taken out from the oven.

For the largest bending arc and string when spreading the sample on a flat floor and making it tightly connected The distance (one-sided elongation value) is measured.

(Examples 1~5)

Prepare pyromellitic dianhydride (PMPA, molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, molecular weight 294.22) at a molar ratio of 65/35/60/40 /4,4'-Diaminodiphenyl ether (DPE, molecular weight 200.24)/p-phenylenediamine (PPD, molecular weight 108.14), made into 20% by weight in DMAC (N,N-dimethylacetamide) The polymerization was carried out to obtain a polyamide acid solution of 3500 poise at 25°C.

Β-picoline and acetic anhydride were added to the polyamide solution so that the molar ratio relative to the polyamide acid became 3.0, and thereafter, it was cast from a nozzle onto a stainless steel support at 90°C, and Obtain a self-supporting polyimide gel film.

The gel film is peeled off from the support, conveyed via nip rollers, and stretched in the longitudinal direction. After stretching in the longitudinal direction, the two ends of the film are fixed and stretched horizontally on one side and dried in the tenter on the other side. After drying, heat treatment is performed using an electric heater to obtain a polyimide film.

The thickness of the polyimide film is changed by controlling the ratio of nozzle ejection speed/support rotation speed to obtain a polyimide film with an average thickness of 7.5 to 38 μm.

(Reference example 1)

Prepare pyromellitic dianhydride (PMPA, molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, molecular weight 294.22) at a molar ratio of 75/25/60/40 /4,4'-Diaminodiphenyl ether (DPE, molecular weight 200.24)/p-phenylenediamine (PPD, molecular weight 108.14), made into 20% by weight in DMAC (N,N-dimethylacetamide) The polymerization was carried out to obtain a polyamide acid solution of 3500 poise at 25°C.

Β-picoline and acetic anhydride were added to the polyamide solution so that the molar ratio relative to the polyamide acid became 3.3, and then cast on a stainless steel support at 75°C to obtain Self-supporting polyimide gel film.

The gel film is peeled off from the support, conveyed via nip rollers, and stretched in the longitudinal direction. After stretching in the longitudinal direction, the two ends of the film are fixed and stretched horizontally on one side and dried in the tenter on the other side. After drying, heat treatment is performed using an electric heater to obtain a polyimide film.

(Reference example 2)

Prepare pyromellitic dianhydride (PMPA, molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, molecular weight 294.22) at a molar ratio of 75/25/60/40 /4,4'-Diaminodiphenyl ether (DPE, molecular weight 200.24)/p-phenylenediamine (PPD, molecular weight 108.14), made into 20% by weight in DMAC (N,N-dimethylacetamide) The polymerization was carried out to obtain a polyamide acid solution of 3500 poise at 25°C.

Β-picoline and acetic anhydride were added to the polyamide solution so that the molar ratio of the polyamide acid became 2.8, and then cast on a stainless steel support at 75°C to obtain Self-supporting polyimide gel film.

The gel film is peeled off from the support, conveyed via nip rollers, and stretched in the longitudinal direction. After stretching in the longitudinal direction, the two ends of the film are fixed and stretched horizontally on one side and dried in the tenter on the other side. After drying, heat treatment is performed using an electric heater to obtain a polyimide film.

(Reference example 3)

Prepare pyromellitic dianhydride (PMPA, molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, molecular weight 294.22) at a molar ratio of 75/25/60/40 /4,4'-Diaminodiphenyl ether (DPE, molecular weight 200.24)/p-phenylenediamine (PPD, molecular weight 108.14), made into 20% by weight in DMAC (N,N-dimethylacetamide) The polymerization was carried out to obtain a polyamide acid solution of 3500 poise at 25°C.

The polyamide solution was added to the polyamide solution in such a way that the molar ratio relative to the polyamide acid became 2.5. Add β-picoline and acetic anhydride, and then cast on a stainless steel support at 75°C to obtain a self-supporting polyimide gel film.

The gel film is peeled off from the support, conveyed via nip rollers, and stretched in the longitudinal direction. After stretching in the longitudinal direction, the two ends of the film are fixed and stretched horizontally on one side and dried in the tenter on the other side. After drying, heat treatment is performed using an electric heater to obtain a polyimide film.

(Reference example 4)

Prepare pyromellitic dianhydride (PMPA, molecular weight 218.12)/3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, molecular weight 294.22) at a molar ratio of 65/35/82/18 /4,4'-Diaminodiphenyl ether (DPE, molecular weight 200.24)/p-phenylenediamine (PPD, molecular weight 108.14), made into 20% by weight in DMAC (N,N-dimethylacetamide) The polymerization was carried out to obtain a polyamide acid solution of 3500 poise at 25°C.

Β-picoline and acetic anhydride were added to the polyamide solution so that the molar ratio relative to the polyamide acid became 2.8, and then cast on a stainless steel support at 95°C to obtain Self-supporting polyimide gel film.

The gel film is peeled off from the support, conveyed via nip rollers, and stretched in the longitudinal direction. After stretching in the longitudinal direction, the two ends of the film are fixed and stretched horizontally on one side and dried in the tenter on the other side. After drying, heat treatment is performed using an electric heater to obtain a polyimide film.

The composition of the polyimide, the production conditions of the polyimide film, and the various physical properties of the polyimide film are summarized in Table 1 below.

According to the above results, it can be confirmed that the polyimide film of the present invention has a small difference in dimensional changes in the film width direction, and one-sided elongation is also small.

[Industrial availability]

The polyimide film of the present invention can be used for flexible printed wiring boards and the like.

Claims (7)

A polyimide film in which both the linear expansion coefficient αMD in the transport direction (MD) of the film and the linear expansion coefficient αTD in the width direction (TD) are below 7ppm/℃, and the propagation velocity V of the ultrasonic pulse is measured When, the anisotropy index AI value expressed by the following formula is less than 15 within the entire width; AI=(VMAX^2-VMIN^2)/(VMAX^2+VMIN^2) (where VMAX^2 It represents the square of the maximum value of pulse propagation velocity, VMIN^2 represents the square of the minimum value of pulse propagation velocity), VMAX and VMIN are measured in 16 directions with a unit of 11.25° from 0 to 180 degrees to the surface of the film. The maximum speed and minimum speed in the ultrasonic speed. If the polyimide film of claim 1 has a film width of 1000mm or more, and the difference in the coefficient of linear expansion in the width direction of the αMD is 2ppm/℃ or less, the difference in the coefficient of linear expansion in the width direction of the film is as follows Obtained: Choose 2 points from the points where both ends of the self-made film width enter the inner side of 200mm in the film width direction, select 1 point within ±200mm of the center of the straight line that includes the 2 points within the range of the straight line connecting the 2 points, and Furthermore, at any two points, the difference between the maximum value and the minimum value among the measured values obtained by measuring the linear expansion coefficient using these five points. If the polyimide film of claim 1 or 2 has a film width of 1000 mm or more, and the difference in the linear expansion coefficient in the film width direction of αTD is 2 ppm/℃ or less, the difference in the linear expansion coefficient in the film width direction is Obtained as follows: in the film width direction Choose 2 points from the points where both ends of the self-made film width enter the inner side of 200mm, and select 1 point within ±200mm of the center of the straight line that includes the 2 points within the range of the straight line connecting the 2 points, and then any 2 points, use this The difference between the maximum value and the minimum value among the measured values obtained by measuring the linear expansion coefficient at 5 points. The polyimide film of claim 1 or 2, wherein the polyimide film comprises polyimine, and the polyimine is an aromatic diamine component containing p-phenylenediamine, and is selected from pyromellitic acid One or more acid anhydride components in the group consisting of dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride are used as polymerization components. For example, the manufacturing method of the polyimide film of claim 1 or 2, which is a self-supporting coagulation that is partially dried and hardened by casting a polyimide precursor solution on a support. The gel film is dried and heat-treated by passing through a heating furnace while holding both ends of the gel film in the width direction. Such as the manufacturing method of claim 5, wherein the imidization rate of the gel film is 55 to 75%. A flexible metal laminated board comprising the polyimide film and metal foil according to any one of claims 1 to 4.

Images