TWI771500B - Polyimide film, metal-clad laminate and circuit substrate - Google Patents

Abstract

The present invention provides a polyimide film with suppressed warpage and no anisotropy of thermal expansion coefficients in the longitudinal direction and the width direction, and a coating using the polyimide film that realizes high dimensional stability and accuracy Metal laminates and circuit boards. A polyimide film, comprising a single-layer or multi-layer polyimide layer, and satisfying: (a) the thickness is in the range of 3 μm or more and 50 μm or less; (b) the thermal expansion coefficient is 10 ppm/K or less; (c) After the 50 mm square polyimide film was dehumidified at 23°C and 50% humidity for 20 hours, it was allowed to stand so that the convex surface of the central part of the polyimide film was in contact with the flat surface, and the average of the floating amount of the four corners was averaged. When the value is the average warpage amount, the average warpage amount is 10 mm or less; (d) The difference between the thermal expansion coefficient (CTE-MD) in the length (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction ±3 ppm/K or less.

Description

Polyimide film, metal-clad laminate and circuit substrate

The present invention relates to a polyimide film, a metal-clad laminate and a circuit substrate.

Polyimide films have excellent properties in heat resistance, chemical resistance, electrical insulation, mechanical strength, and the like, and are therefore widely used in various fields. In particular, it is used as a base film for flexible printed circuit boards (FPC: Flexible Printed Circuits), etc. by virtue of its excellent heat resistance and high rigidity.

In recent years, with the development of miniaturization, weight reduction, and space saving of electronic devices, there is an increasing demand for FPCs that are thin and lightweight, have flexibility, and have excellent durability even if they are repeatedly bent. FPC can achieve three-dimensional and high-density mounting even in a limited space, so its use is expanding to, for example, Hard Disk Drive (HDD), Digital Versatile Disc (DVD), smartphone Wiring of movable parts of electronic equipment, or parts such as cables and connectors.

FPC is produced by laminating a metal foil (usually copper foil) on a polyimide film, or forming a metal layer by sputtering or vapor deposition, and performing wiring processing on the obtained laminate.

For example, in a photolithography step performed on a copper clad laminate or in a process of mounting an FPC, bonding, cutting, and exposure are performed based on an alignment mark provided in the copper clad laminate. , etching and other processing. The machining accuracy in these steps becomes important in maintaining the reliability of the electronic device mounted with the FPC. However, since the copper clad laminate has a structure in which copper layers and resin layers having different thermal expansion coefficients are stacked, stress is generated between the layers due to the difference in thermal expansion coefficients between the copper layers and the resin layers. Part or all of the stress is relieved when the copper layer is etched for wiring processing, thereby causing expansion and contraction, and it becomes a factor for changing the size of the wiring pattern. Therefore, a dimensional change finally occurs in the FPC stage, which causes poor connection between wirings or wirings and terminals, thereby reducing the reliability and yield of the circuit board. Therefore, dimensional stability is a very important characteristic in polyimide films and copper-clad laminates which are circuit board materials.

Patent Document 1 proposes a polyimide film in which the surface orientation of the front and back surfaces of the polyimide film is controlled. However, the dimensional accuracy of the polyimide film in Patent Document 1 is insufficient, and there is a problem that dimensional changes due to thermal expansion tend to occur during high-temperature processing in the production of metal-clad laminates or circuit boards.

Patent Document 2 proposes a polyimide film in which film curl after high temperature treatment is reduced by using polyimide having diaminodiphenyl ethers and phenylenediamines in the main chain, but Dimensional accuracy is not sufficient.

The present applicant obtained the knowledge that a polyimide film having excellent dimensional stability can be obtained by controlling the in-plane retardation of the polyimide film, and filed a patent application in advance (Japanese Patent Application No. 2016-089514). [Prior Art Literature]

[Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2014-201632 [Patent Document 2] International Publication WO2016/11490 Pamphlet

[Problems to be Solved by the Invention] An object of the present invention is to provide a polyimide film with suppressed warpage and small anisotropy of thermal expansion coefficients in the longitudinal direction and the width direction, and a polyimide film using the same The realization of high dimensional stability and accuracy of metal-clad laminates and circuit substrates. [Technical means to solve the problem]

The inventors of the present invention have made diligent studies and found that the above problems can be solved by controlling the thickness, thermal expansion coefficient, and in-plane birefringence (Δn) of the polyimide film, thereby completing the present invention.

That is, the polyimide film of the present invention includes a single or multiple polyimide layer, and the polyimide film is characterized by satisfying the following conditions (a) to (d): (a) Thickness In the range of 3 μm or more and 50 μm or less; (b) The thermal expansion coefficient is 10 ppm/K or less; (c) 50 mm square polyimide film after 20 hours at 23 ° C and 50% humidity When standing still so that the convex surface of the central part is in contact with a flat surface, and taking the average value of the floating amount of the four corners as the average warpage amount, the average warpage amount is 10 mm or less; (d) Length (longitudinal (Machine) Direction, MD)) direction of thermal expansion coefficient (Coefficient of Thermal Expansion-Machine Direction (Coefficient of Thermal Expansion-Machine Direction, CTE-MD)) and width (Transverse Direction (TD)) direction of thermal expansion coefficient (Coefficient of Thermal Expansion-Lateral (Coefficient of Thermal Expansion-Machine Direction, TD)) direction of Thermal Expansion-Transverse Direction, CTE-TD)) is ±3 ppm/K or less.

In addition to the conditions (a) to (d) described above, the polyimide film of the present invention may further satisfy: (e) In-plane birefringence (Δn) is 2×10 ⁻³ or less.

In the polyimide film of the present invention, the polyimide layer may be a multilayer, and may include a single-layer first polyimide layer with the lowest thermal expansion coefficient and a first polyimide layer laminated on the first polyimide layer. A single-layer or multi-layer second polyimide layer on one side. In this case, the coefficient of thermal expansion (CTE1) of the first polyimide layer and the coefficient of thermal expansion (CTE2) of the second polyimide layer may satisfy the following formula (1): 1 ppm/K <(CTE2-CTE1)≤10 ppm/K (1) Here, the CTE1 is the average value of the thermal expansion coefficients in the MD and TD directions of the first polyimide layer, and the CTE2 is the The average value of the thermal expansion coefficients in the MD direction and the TD direction of the second polyimide layer.

In the polyimide film of the present invention, the second polyimide layer may be a single layer.

In the polyimide film of the present invention, the first polyimide layer may include a polyimide containing a tetracarboxylic acid residue and a diamine residue, and the polyimide contained in the first polyimide layer may be All the diamine residues contained in 20 mol% or more of diamine residues derived from a diamine compound represented by the following general formula (A1).

[hua 1]

In the general formula (A1), the linking group X ₀ represents a single bond, and Y independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, which may be substituted by a halogen atom or a phenyl group. , or an alkenyl group, n ₁ represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4.

In the polyimide film of the present invention, at least one layer of the second polyimide layer may include polyimide containing a tetracarboxylic acid residue and a diamine residue. In this case, the diamine compound derived from the diamine compound represented by the general formula (A1) may be contained in an amount of 20 mol% or more with respect to all the diamine residues contained in the polyimide. amine residue.

The metal-clad laminate of the present invention includes: an insulating layer; and a metal layer on at least one side of the insulating layer, and the insulating layer includes any one of the polyimide films described above.

The circuit board of the present invention is obtained by subjecting the metal layer in the metal-clad laminate to circuit processing. [Effect of invention]

The polyimide film of the present invention is a film that suppresses warpage and has a small anisotropy using low thermal expansion polyimide, and therefore is used in metal-clad laminates and circuit boards using the polyimide film. , can achieve high dimensional stability accuracy. Moreover, since the polyimide film of this invention is excellent in handleability and can reduce the dimensional change at the time of processing, it can also be used suitably for formation of the metal-clad laminated board and circuit board using the said polyimide film.

Next, embodiments of the present invention will be described.

[Polyimide Film] The polyimide film of one embodiment of the present invention is a polyimide film including a single or multiple polyimide layer, and satisfies the following conditions (a) to (d) ).

(a) The thickness is in the range of 3 μm to 50 μm. In order to control the thermal expansion coefficient, the thickness of the polyimide film of the present embodiment is in the range of 3 μm to 50 μm, preferably in the range of 3 μm to 30 μm, more preferably in the range of 10 μm to 28 μm , In particular, it is suitable to be in the range of 15 μm to 25 μm. When the thickness of the polyimide film of the present embodiment is less than 3 μm, the handling of the manufacturing step may become difficult due to the decrease in electrical insulation or workability, and when the thickness exceeds 50 μm, in-plane double-layered The control of the refractive index (Δn) becomes difficult, and the thermal expansion coefficient tends to increase.

(b) The thermal expansion coefficient is 10 ppm/K or less. In order to reduce the dimensional change, the thermal expansion coefficient of the polyimide film of the present embodiment is preferably in the range of 10 ppm/K or less, preferably 7 ppm/K or less. If the coefficient of thermal expansion exceeds 10 ppm/K, when a metal-clad laminate or a circuit board using the polyimide film of the present invention as a base material is produced, the dimensional change is not reduced, and problems such as positional displacement of electronic components may occur. .

(c) The convex surface of the central portion of the 50 mm square polyimide film after the humidity was lowered at 23° C. and the humidity of 50% for 20 hours (here, the “convex surface” refers to the polyimide that is gently curved as a whole. The curved outer peripheral side surface of the amine film segment) was allowed to stand still in contact with a flat surface, and when the average value of the floating amount of the four corners was taken as the average warpage amount, the average warpage amount was 10 mm or less. In order to improve workability when manufacturing metal-clad laminates and circuit boards using the polyimide film of this embodiment as a base material, and to prevent positional displacement of electronic components due to floating during processing, this embodiment The average warpage amount of the polyimide film is preferably in the range of 10 mm or less, preferably in the range of 5 mm or less.

(d) The difference between the thermal expansion coefficient (CTE-MD) in the length (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ±3 ppm/K or less. The CTE-MD and CTE-TD of the polyimide film of the present embodiment are designed to reduce the dimensional change during processing when manufacturing metal-clad laminates and circuit boards using the polyimide film of the present embodiment as a base material. The difference is preferably within a range of ±3 ppm/K or less, preferably within a range of ±1 ppm/K or less.

Moreover, it is preferable that the polyimide film which concerns on one Embodiment of this invention satisfy|fills the following condition (e) in addition to the conditions (a)-(d) mentioned above.

(e) The in-plane birefringence (Δn) is 2×10 ⁻³ or less. The in-plane birefringence (Δn) of the polyimide film of the present embodiment is preferably 2×10 ⁻³ or less, preferably 0.8×10 ⁻³ or less, and more preferably 0.6×10 ⁻³ or less.

In addition, the polyimide film of one embodiment of the present invention is preferably a polyimide film including a plurality of polyimide layers.

When the polyimide film of one embodiment of the present invention includes a plurality of polyimide layers, the polyimide layer includes a single-layer first polyimide layer having the lowest thermal expansion coefficient and a first polyimide layer laminated on the second polyimide layer. A single-layer or multi-layer second polyimide layer on one side of a polyimide layer, and the coefficient of thermal expansion (CTE1) of the first polyimide layer and the coefficient of thermal expansion of the second polyimide layer (CTE2) is preferably within the following formula (1): 1 ppm/K<(CTE2-CTE1)≤10 ppm/K...(1). By changing the thermal expansion coefficient in the thickness direction of the polyimide film, the reduction in retardation (ROL) in the thickness direction can be prevented, and the average warpage amount can be reduced. The difference between CTE1 and CTE2 (CTE2-CTE1) is preferably within a range of 2 ppm/K or more and 10 ppm/K or less, and more preferably within a range of 2 ppm/K or more and 7 ppm/K or less. Here, CTE1 is the average value of the thermal expansion coefficients in the MD direction and the TD direction of the first polyimide layer, and CTE2 is the average value of the thermal expansion coefficients in the MD direction and the TD direction of the second polyimide layer.

<Form of Polyimide Film> As described above, if the polyimide film of the present embodiment satisfies the conditions (a) to (d), the form of the polyimide film is not particularly limited, and may be a film containing an insulating resin ( sheet), and may be in a state of being laminated on a base material such as a copper foil, a glass plate, a polyimide-based film, a polyamide-based film, and a resin sheet such as a polyester-based film.

<Filler> The polyimide film of this embodiment may contain an inorganic filler as needed. Specific examples of the inorganic filler include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and the like. These can be used alone or in combination of two or more.

<Polyimide> The polyimide film of the present embodiment has a polyimide layer in which the resin component contains polyimide, and includes a single layer or a plurality of layers. Here, when the polyimide layer includes a plurality of layers, it may include a first polyimide layer having a single layer with the lowest thermal expansion coefficient, and a single layer including a single layer laminated on one side of the first polyimide layer. or multiple second polyimide layers. In addition, in this specification, when a "1st polyimide layer" and a "2nd polyimide layer" are not distinguished, it describes only as "polyimide layer".

The polyimide constituting the polyimide layer is obtained by imidizing the polyimide obtained by reacting tetracarboxylic dianhydride and diamine. Therefore, in the polyimide film of the present embodiment, the polyimide constituting the polyimide layer includes a tetracarboxylic acid residue derived from tetracarboxylic dianhydride and a diamine residue derived from diamine . Further, in the present invention, the term "tetracarboxylic acid residue" refers to a tetravalent group derived from tetracarboxylic dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound.

Hereinafter, specific examples of the polyimide used in the present embodiment will be understood by describing the acid anhydride and the diamine.

The tetracarboxylic acid residue contained in the polyimide can be preferably mentioned, for example: Tetracarboxylic acid residues derived from tetracarboxylic dianhydride, BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, etc. Among them, tetracarboxylic acid residues (hereinafter also referred to as BPDA residues) derived from BPDA are easy to form ordered structures and can reduce the amount of change in in-plane birefringence (Δn) under high temperature environments. , so it is especially preferred. In addition, the BPDA residue can impart self-supporting properties to the gel film of polyimide, which is a precursor of polyimide, but on the other hand, tends to increase the CTE after imidization. From this viewpoint, the BPDA residue is preferably in the range of 20 mol % to 70 mol %, more preferably 20 mol % with respect to all the tetracarboxylic acid residues contained in the polyimide. % to 60 mol% is suitable.

The tetracarboxylic acid residues other than the BPDA residue contained in the polyimide can preferably be exemplified: tetracarboxylic acid residues derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA) known as PMDA residues). The PMDA residue is preferably in the range of 0 mol% to 60 mol%, more preferably 0 mol% to 50 mol%, relative to all the tetracarboxylic acid residues contained in the polyimide. within the appropriate range. The PMDA residue is arbitrary, but is a residue that functions to control the thermal expansion coefficient and control the glass transition temperature.

Examples of other tetracarboxylic acid residues include tetracarboxylic acid residues derived from the following aromatic tetracarboxylic dianhydrides: 3,3',4,4'-diphenyltetracarboxylic dianhydride, 4,4' 4'-Oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2 ,3,3',4'-benzophenone tetracarboxylic dianhydride or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-di Phenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3'',4,4''-p-terphenyltetracarboxylic dianhydride, 2,3,3 '',4''-p-terphenyltetracarboxylic dianhydride or 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxybenzene yl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxylate Phenyl)methane dianhydride, bis(2,3-dicarboxyphenyl) bis(2,3-dicarboxyphenyl) bis(3,4-dicarboxyphenyl) bis(3,4-dicarboxyphenyl) bis(3,4-dicarboxyphenyl) bis(3,4-dicarboxyphenyl) dianhydride, 1,1-bis(2,3-dicarboxybenzene base) ethanedianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethanedianhydride, 1,2,7,8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7 -Phenanthrene-tetracarboxylic dianhydride or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4- Dicarboxyphenyl) tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetra Carboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5, 6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid Anhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic Acid dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride Anhydride or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid Dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxybenzene oxy) diphenylmethane dianhydride and the like.

Among the tetracarboxylic acid residues contained in polyimide, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic acid Tetracarboxylic acid residues derived from tetracarboxylic dianhydrides of carboxylic dianhydride, 4,4'-oxydiphthalic anhydride and 2,3',3,4'-diphenyltetracarboxylic dianhydride With respect to all the tetracarboxylic acid residues contained in the polyimide, the content is preferably 20 mol % or less, and more preferably 15 mol % or less. When these tetracarboxylic acid residues exceed 20 mol % with respect to all tetracarboxylic acid residues contained in polyimide, the molecular orientation decreases, and it becomes difficult to control the in-plane birefringence (Δn).

In the polyimide film of the present embodiment, the diamine residue contained in the polyimide preferably includes, for example, a diamine residue derived from a diamine compound represented by the following general formula (A1). (hereinafter sometimes referred to as "A1 residue").

[hua 1]

In the formula (A1), the linking group X ₀ represents a single bond or -COO-, and Y independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms or an alkane having 1 to 3 carbon atoms which may be substituted by a halogen atom or a phenyl group An oxy group, a perfluoroalkyl group having 1 to 3 carbon atoms, or an alkenyl group, n ₁ represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. Here, "independently" means that in the formula (A1), a plurality of substituents Y, integer p, and integer q may be the same or different.

The A1 residue easily forms an ordered structure and promotes the alignment of the molecular chain in the in-plane direction, thus suppressing the in-plane birefringence (Δn). From this viewpoint, the A1 residue is preferably 20 mol % or more, more preferably 50 mol % or more, and still more preferably 70 mol % of all the diamine residues contained in the polyimide. It is suitable to be in the range of mol% to 99 mol%.

In addition, the A1 residue preferably includes, for example, a diamine residue represented by the following general formula (1).

[hua 2]

In the general formula (1), R ₁ and R ₂ independently represent an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, or an alkyl group having 2 carbon atoms, which may be substituted by a halogen atom or a phenyl group. ~3 alkenyl.

The diamine residue represented by the general formula (1) tends to form an ordered structure, and in particular, it is possible to advantageously suppress the amount of change in the in-plane birefringence (Δn) in a high temperature environment. From such a viewpoint, the diamine residue represented by the general formula (1) is preferably 20 mol % or more, more preferably 50 mol % of all the diamine residues contained in the polyimide. It is suitable to be in the range of 60 mol% or more to 90 mol% more preferably.

Preferred specific examples of the diamine residue represented by the general formula (1) include diamine residues derived from the following diamine compounds: 2,2'-dimethyl-4,4'-diamino Biphenyl (2,2'-dimethyl-4,4'-diaminobiphenyl, m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (2,2'-diethyl-4, 4'-diaminobiphenyl, m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (2,2'-diethoxy-4,4'-diaminobiphenyl, m-EOB), 2 ,2'-dipropoxy-4,4'-diaminobiphenyl (2,2'-dipropoxy-4,4'-diaminobiphenyl, m-POB), 2,2'-n-propyl-4,4 '-Diaminobiphenyl (2,2'-n-propyl-4,4'-diaminobiphenyl, m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (2,2 '-divinyl-4,4'-diaminobiphenyl, VAB), 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (4,4 '-diamino-2,2'-bis(trifluoromethyl)biphenyl, TFMB) etc. Among these diamine compounds, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is easy to form an ordered structure, which can reduce the in-plane birefringence (Δn) in a high temperature environment ), so it is particularly preferable to be .

The diamine residues other than the diamine residues represented by the general formula (1) can be preferably exemplified by p-phenylenediamine (p-PDA), m-phenylenediamine (m-phenylenediamine, m- A diamine residue derived from PDA), etc., more preferably a diamine residue derived from p-PDA (hereinafter also referred to as a PDA residue). The PDA residue is preferably in the range of 0 mol % to 80 mol %, more preferably in the range of 0 mol % to 50 mol %, relative to all the diamine residues contained in the polyimide Inside is appropriate. The PDA residue is arbitrary, but is a residue that functions to control the thermal expansion coefficient and control the glass transition temperature.

In addition, in the present specification, regarding the "diamine compound", the hydrogen atoms in the two amino groups at the terminal may be substituted, for example, -NR ₃ R ₄ (here, R ₃ and R ₄ independently represent any arbitrary group such as an alkyl group). Substituents).

In addition, in order to improve the elongation, bending resistance, etc. when used as a polyimide film, it is preferable that the polyimide contains a group selected from the following general formulas (2) to (4) represented by the following general formulas. At least one diamine residue in the group consisting of diamine residues.

[hua 3]

In the formula (2), R ₅ and R ₆ each independently represent a halogen atom, or an alkyl group having 1 to 4 carbon atoms that may be substituted by a halogen atom, an alkoxy group, or an alkenyl group, and X independently represents a group selected from the group consisting of: -O-, -S-, _-CH2- , -CH( _CH3 )-, -C( _CH3 ) _2- , -CO-, -COO-, _-SO2- , -NH- or -NHCO- In the divalent group, m and n independently represent an integer of 0 to 4.

[hua 4]

In the above formula (3), R ₅ , R ₆ and R ₇ each independently represent a halogen atom, or an alkyl group having 1 to 4 carbon atoms which may be substituted by a halogen atom, an alkoxy group, or an alkenyl group, and X independently represents selected from -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -COO-, -SO ₂ -, -NH- or In the divalent group in -NHCO-, m, n and o independently represent an integer of 0 to 4.

[hua 5]

In the formula (4), R ₅ , R ₆ , R ₇ and R ₈ each independently represent a halogen atom, or an alkyl group having 1 to 4 carbon atoms which may be substituted by a halogen atom, an alkoxy group, or an alkenyl group, X ₁ and X ₂ each independently represent a single bond, selected from -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -COO A divalent group in -, -SO ₂ -, -NH- or -NHCO-, except when both X ₁ and X ₂ are single bonds, m, n, o and p independently represent 0 to 4 Integer.

In addition, "independently" means that in one of the above-mentioned formulas (2) to (4), or in the formulas (2) to (4), a plurality of linking groups X, linking groups X ₁ , The linking group X ₂ , the plurality of substituent groups R ₅ , the substituent group R ₆ , the substituent group R ₇ , the substituent group R ₈ , and the integer m, the integer n, the integer o, and the integer p may be the same or different.

Since the diamine residues represented by the general formulae (2) to (4) have a flexible portion, flexibility can be imparted to the polyimide film. Here, since the diamine residues represented by the general formula (3) and the general formula (4) have three or four benzene rings, in order to suppress an increase in the coefficient of thermal expansion (CTE), it is preferable to bond with benzene The end group of the loop is set to the para position. In addition, from the viewpoint of imparting flexibility to the polyimide film and suppressing an increase in the coefficient of thermal expansion (CTE), the diamine residues represented by the general formulae (2) to (4) are relative to the polyimide All the diamine residues contained are preferably in the range of 10 mol % to 40 mol %, more preferably in the range of 10 mol % to 30 mol %. When the diamine residue represented by the general formula (2) to the general formula (4) is less than 10 mol %, the elongation in the case of forming a film will decrease, and the bending resistance and the like will decrease. On the other hand, if it exceeds 40 mol %, the orientation of the molecules decreases, and it becomes difficult to reduce the CTE.

In the general formula (2), preferably one or more of m and n is 0. In addition, preferable examples of the group R ₅ and the group R ₆ include: C 1 to 4 which may be substituted by a halogen atom. An alkyl group, or an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group. In addition, in the general formula (2), preferred examples of the linking group X include -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -SO ₂ - or -CO-. Preferred specific examples of the diamine residue represented by the general formula (2) include diamine residues derived from the following diamine compounds: 4,4'-diaminodiphenyl ether (4,4' -diamino diphenyl ether, 4,4'-DAPE), 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3 ,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,4 '-Diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4, 4'-Diaminodiphenylene, 3,3'-diaminodiphenylene, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3' - Diaminobenzophenone, etc.

In the general formula (3), one or more of m, n, and o is preferably 0, and preferable examples of the group R ₅ , the group R ₆ , and the group R ₇ include those having 1 to 4 carbon atoms. An alkyl group which may be substituted by a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group. In addition, in the general formula (3), preferable examples of the linking group X include -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -SO ₂ - or -CO-. Preferred specific examples of the diamine residue represented by the general formula (3) include diamine residues derived from the following diamine compounds: 1,3-bis(4-aminophenoxy)benzene (1 ,3-bis(4-aminophenoxy)benzene, TPE-R), 1,4-bis(4-aminophenoxy)benzene (1,4-bis(4-aminophenoxy)benzene, TPE-Q), bis(4-aminophenoxy)benzene 4-Aminophenoxy)-2,5-di-tert-butylbenzene (bis(4-aminophenoxy)-2,5-di-tert-butyl benzene, DTBAB), 4,4-bis(4-amino) Phenoxy)benzophenone (4,4-bis(4-aminophenoxy)benzophenone, BAPK), 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4 -Bis[2-(4-aminophenyl)-2-propyl]benzene, etc.

In the general formula (4), one or more of m, n, o, and p is preferably 0, and preferable examples of the group R ₅ , the group R ₆ , the group R ₇ , and the group R ₈ include: An alkyl group having 1 to 4 carbon atoms which may be substituted by a halogen atom, or an alkoxy group having 1 to 3 carbon atoms, or an alkenyl group. In addition, in the general formula (4), preferable examples of the linking group X ₁ and the linking group X ₂ include a single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -SO ₂ - or -CO-. However, from the viewpoint of providing a bent portion, the case where both the linking group X ₁ and the linking group X ₂ are single bonds is excluded. Preferred specific examples of the diamine residue represented by the general formula (4) include diamine residues derived from the following diamine compounds: 4,4′-bis(4-aminophenoxy)biphenyl (4,4'-bis(4-aminophenoxy)biphenyl, BAPB), 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis[4 -(4-Aminophenoxy)phenyl]ether (2,2'-bis[4-(4-aminophenoxy)phenyl]ether, BAPE), bis[4-(4-aminophenoxy)phenyl] Mushroom and so on.

Examples of other diamine residues include diamine residues derived from the following aromatic diamine compounds: 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4- (3-Aminophenoxy)phenyl]diphenyl, bis[4-(3-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-( 3-Aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9 -Bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4 -(3-Aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4 ,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3, 3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylene bis(1- Methylethylene)] bisaniline, 4,4'-[1,3-phenylene bis(1-methylethylene)] bisaniline, bis(p-aminocyclohexyl)methane, bis(p-beta) -Amino-tert-butylphenyl) ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1) -Dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4- Diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5- Diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, oxazine, etc.

In the polyimide, by selecting the kinds of the tetracarboxylic acid residues and the diamine residues, or the molar ratio of each when two or more tetracarboxylic acid residues or diamine residues are used, it can be obtained. Control thermal expansion coefficient, storage elastic coefficient, tensile elastic coefficient, etc. In addition, in the case of having a plurality of structural units of polyimide, it may exist in the form of a block or may exist randomly, but from the viewpoint of suppressing the variation in the in-plane birefringence (Δn), it is relatively The best is to exist randomly.

<The manufacturing method of the polyimide film> The form of the manufacturing method of the polyimide film of the present embodiment is, for example: [1] After coating a solution of polyimide on a support substrate, drying it, and adding a polyimide A method for producing a polyimide film by amination; [2] After coating a solution of polyimide on a support substrate and drying, peeling off the gel film of polyimide from the support base, adding polyimide A method for producing a polyimide film by amination. In addition, when the polyimide film of the present embodiment is a polyimide film including a multi-layered polyimide layer, the form of the manufacturing method thereof includes, for example: [3] Repeating multiple steps on a support substrate A method of imidization (casting method) after coating and drying of a solution of urethane; , the method of imidization (multilayer extrusion method), etc.

The method of [1] may include, for example, the following steps 1a to 1c: (1a) The step of coating a solution of polyamic acid on a support substrate and drying it; A step of forming a polyimide layer by heat-treating the amino acid to imidize, thereby forming a polyimide layer; and (1c) a step of separating the support substrate from the polyimide layer, thereby obtaining a polyimide film.

The method of [2] may include, for example, the following steps 2a to 2c: (2a) The step of coating the polyamide acid solution on the support substrate and drying it; (2b) The support substrate and polyamide The step of separating the gel film of acid; and (2c) the step of obtaining a polyimide film by subjecting the gel film of polyimide to heat treatment to imidize.

In the method [3], in the method [1] or the method [2], step 1a or step 2a is repeated a plurality of times to form a laminated structure of polyamic acid on the support substrate. It is carried out in the same manner as the above-mentioned [1] method or [2] method.

In the method of [4], in the step 1a of the method [1] or the step 2a of the method [2], the laminated structure of polyamic acid is simultaneously coated and dried by multilayer extrusion, and other than that, It can be carried out in the same manner as the above-mentioned [1] method or [2] method.

In the polyimide film produced in the present invention, it is preferable to complete the imidization of the polyimide on the support substrate. Since the imidization is carried out in a state where the resin layer of the polyimide is fixed on the support substrate, the change in expansion and contraction of the polyimide layer during the imidization process can be suppressed, and the polyimide can be maintained. The thickness or dimensional accuracy of the film.

In addition, the in-plane birefringence (Δn) can also be controlled by separating the polyamide gel film on the support substrate and uniaxially or biaxially stretching the polyamide gel film , simultaneous or sequential imidization. In this case, in order to control Δn more precisely, it is preferable to appropriately adjust conditions such as the stretching operation and the temperature increase rate during imidization, the completion temperature of imidization, and the load.

<Synthesis of polyimide> Generally, polyimide can be produced by reacting tetracarboxylic dianhydride and a diamine compound in a solvent to generate polyimide and then heating and ring-closing. For example, by dissolving tetracarboxylic dianhydride and diamine compound in an organic solvent at approximately equimolar levels, and stirring at a temperature in the range of 0° C. to 100° C. for 30 minutes to 24 hours to carry out a polymerization reaction, a product as Polyimide is a precursor of polyimide. During the reaction, the reaction components are dissolved in the organic solvent so that the produced precursor may be in the range of 5 to 30% by weight, preferably in the range of 10 to 20% by weight. Examples of the organic solvent used in the polymerization reaction include N,N-dimethylformamide (N,N-dimethylformamide, DMF), N,N-dimethylacetamide (N,N-dimethylacetamide) , DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO) ), hexamethylphosphamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether Ether (triglyme), cresol, etc. These solvents can be used in combination of two or more, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. In addition, the usage-amount of such an organic solvent is not specifically limited, It is preferable to adjust and use so that the density|concentration of the polyamic acid solution obtained by a polymerization reaction may become about 5 weight% - 30weight%.

The synthesized polyamic acid is usually advantageously used in the form of a reaction solvent solution, and can be concentrated, diluted or replaced with other organic solvents as necessary. In addition, since polyamic acid is generally excellent in solvent solubility, it can be used advantageously. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If it deviates from the said range, when coating operation with a coater etc. is performed, it is easy to generate|occur|produce defects, such as thickness unevenness and a streak, in a film. The method of imidizing the polyamic acid is not particularly limited, and for example, a heat treatment such as heating in the solvent at a temperature in the range of 80° C. to 400° C. for 1 hour to 24 hours is suitably employed.

<Metal-clad laminate> The material of the metal layer in the metal-clad laminate of the present embodiment is not particularly limited, and examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, and tin. , zirconium, tantalum, titanium, lead, magnesium, manganese, and their alloys. Among them, copper or a copper alloy is particularly preferred.

The thickness of the metal layer is not particularly limited. For example, when copper foil is used as the metal layer, it is preferably 35 μm or less, and more preferably within a range of 5 μm to 25 μm. From the viewpoint of production stability and workability, the lower limit value of the thickness of the copper foil is preferably 5 μm.

Regarding the metal-clad laminate of the present embodiment, in order to improve the adhesion between the polyimide film and the metal layer, the surface of the polyimide film may be subjected to modification treatment such as plasma treatment, for example. In addition, the layer in contact with the metal layer in the polyimide film may be, for example, laminated with a thermoplastic polyimide layer. The metal-clad laminate in this embodiment may be a single-sided metal-clad laminate or a double-sided metal-clad laminate.

Regarding the metal-clad laminate of the present embodiment, for example, a resin film including the polyimide film of the present embodiment may be prepared, and metal may be sputtered to form a seed layer, for example, by copper plating. A copper layer is formed.

In addition, the metal-clad laminate of this embodiment may be prepared by preparing a resin film including the polyimide film of this embodiment, and laminating metal foil thereon by a method such as thermocompression bonding.

<Circuit board> The metal-clad laminate of the present embodiment is mainly useful as a material for circuit boards such as FPC. That is, by patterning the metal layer of the copper-clad laminate of this embodiment by a common method to form a wiring layer, a circuit board such as an FPC which is an embodiment of the present invention can be produced.

[Examples] Hereinafter, the characteristics of the present invention will be described in more detail by showing examples. However, the scope of the present invention is not limited to the Examples. In addition, in the following examples, unless otherwise specified, various measurements and evaluations were performed by the following methods.

[Measurement of Coefficient of Thermal Expansion (CTE)] Using a thermomechanical analyzer (trade name: 4000SA, manufactured by Bruker), a load of 5.0 g was applied to one side of a polyimide film with a size of 3 mm × 20 mm. The temperature was increased from 30°C to 250°C at a constant temperature increase rate, and then kept at the temperature for 10 minutes, then cooled at a rate of 5°C/min, and the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C was obtained. . In addition, the CTE-MD is the thermal expansion coefficient in the length (MD) direction, and the CTE-TD is the thermal expansion coefficient in the width (TD) direction.

[Measurement of in-plane retardation (RO)] Using a birefringence meter (trade name: wide range birefringence evaluation system WPA-100, manufactured by Photonic-Lattice, Inc., measurement area: MD: 200 mm×TD: 150 mm), and obtained the retardation in the in-plane direction of a predetermined sample. In addition, the incident angle was 0°, and the measurement wavelength was 543 nm.

[Preparation of samples for evaluation of in-plane retardation (RO)] In the polyimide film, the left and right ends (Left and Right) and the center in the TD direction of the polyimide film are respectively represented by A4 size (TD: 210 mm x MD: 297 mm) was cut to prepare sample L (left), sample R (right), and sample C (center).

[Evaluation of In-Plane Birefringence (Δn)] For each of the sample L, the sample R, and the sample C, the in-plane retardation (RO) was measured. The value obtained by dividing the maximum value of the measured values of each sample by the thickness of the sample for evaluation was defined as "in-plane birefringence (Δn)".

[Measurement of Retardation (ROL) and Birefringence (Δnz) in Thickness Direction] For a sample (thickness: 0.5 μm) prepared by thin film cutting of a polyimide film (thickness: 0.5 μm), a microscope type birefringence was used. The retardation in the thickness direction (ROL) was measured with a refractometer (trade name: Microscope Mounted Birefringence Distribution Observation Camera PI-micro, manufactured by Photonic-Lattice Co., Ltd.). In addition, the incident angle was 0°, and the measurement wavelength was 520 nm. In addition, the value obtained by dividing the value of ROL by the thickness (0.5 μm) of the thin film cut sample is referred to as “birefringence (Δnz)”.

[Measurement of Warpage] Regarding the warpage of the polyimide film, a polyimide film having a size of 50 mm × 50 mm was dehumidified at 23° C. and a humidity of 50% for 20 hours. It stood still so that it might be in contact with a flat surface, and the distance that the four corners of the sample floated from the standstill surface was measured, and the average value was made into the average warpage amount.

The abbreviations used in Examples and Comparative Examples represent the following compounds. m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl DAPE: 4,4'-diaminodiphenyl ether PMDA: pyromellitic dianhydride BPDA: 3,3', 4,4'-Biphenyltetracarboxylic dianhydride DMAc: N,N-Dimethylacetamide

(Synthesis Example 1) In a 300 ml separable flask, 2.550 g of DAPE (0.0127 mol) and 15.333 g of m-TB (0.0721 mol) were put into a 300 ml separable flask under a nitrogen stream so that the solid content concentration would be 15% by weight. and 212.5 g of DMAc, which were dissolved by stirring at room temperature. Next, after adding 6.0847 g of BPDA (0.0207 mol) and 13.532 g of PMDA (0.0620 mol), stirring was continued at room temperature for 3 hours to perform a polymerization reaction to prepare a polyamic acid solution a.

Next, the polyamic acid solution a was uniformly coated on the stainless steel support substrate so that the thickness after curing was about 25 μm, and then heated and dried at 130°C. Furthermore, stepwise heat treatment was performed from 130° C. to 360° C., imidization was completed, and resin film 1 (CTE: 7.6 ppm/k) was prepared.

(Synthesis Example 2) In a 300 ml separable flask, 1.188 g of DAPE (0.0059 mol) and 16.740 g of m-TB (0.0787 mol) were put into a 300 ml separable flask under nitrogen flow so that the solid content concentration would be 15% by weight. and 212.5 g of DMAc, which were dissolved by stirring at room temperature. Next, after adding 6.071 g of BPDA (0.0206 mol) and 13.502 g of PMDA (0.0618 mol), stirring was continued at room temperature for 3 hours to perform a polymerization reaction to prepare a polyamic acid solution b.

Next, the polyamic acid solution b was uniformly applied on a stainless steel support substrate so that the thickness after curing was about 25 μm, and then heated and dried at 130°C. Furthermore, a stepwise heat treatment was performed from 130° C. to 360° C. to complete imidization, thereby preparing resin film 2 (CTE: 3.9 ppm/k).

(Synthesis Example 3) In a 300 ml separable flask, 0.862 g of DAPE (0.0043 mol) and 17.381 g of m-TB (0.0817 mol) were put into a 300 ml separable flask under a nitrogen stream so that the solid content concentration would be 15% by weight. and 212.5 g of DMAc, which were dissolved by stirring at room temperature. Next, after adding 3.703 g of BPDA (0.0126 mol) and 15.554 g of PMDA (0.0712 mol), stirring was continued at room temperature for 3 hours to perform a polymerization reaction to prepare a polyamic acid solution c.

Next, the polyamic acid solution c was uniformly coated on a stainless steel support substrate so that the thickness after curing was about 25 μm, and then heated and dried at 130°C. Furthermore, a stepwise heat treatment was performed from 130° C. to 360° C. to complete imidization, thereby preparing resin film 3 (CTE: 1.3 ppm/k).

(Production Example 1) The polyamic acid solution a prepared in Synthesis Example 1 was uniformly coated with a thickness of 180 μm on a copper foil having a thickness of 18 μm, and then heated and dried at 130° C. to remove the solvent. Next, heat treatment was performed at a temperature increase rate of about 15°C/min from 160°C to 360°C and imidization was performed to prepare a support substrate 1 having a polyimide layer having a thickness of 25 μm formed on copper foil.

[Example 1] The polyimide solution b prepared in Synthesis Example 2 was uniformly applied on the surface of the support substrate 1 on the polyimide layer side so that the thickness after curing was about 25 μm, and then Heat and dry at 130°C. Then, stepwise heat treatment is performed from 130° C. to 360° C. to complete imidization, and after cooling to normal temperature, the polyimide film 1 is prepared by peeling from the support substrate 1 .

The evaluation results of the polyimide film 1 are as follows. Moreover, in the polyimide film before peeling from a support base material, let the surface contacting a support base material be A surface, and let the other surface be a B surface. CTE: 3.9 ppm/K CTE-MD: 3.8 ppm/K CTE-TD: 4.0 ppm/K In-plane retardation (RO): 18 nm In-plane birefringence (Δn): 0.72×10 ^-3 Average warpage: 1.0 mm Retardation (ROL) at a point 4 μm away from the A surface in the depth direction: 70 nm Retardation (ROL) at a location 20 μm away from the B surface in the depth direction: 69 nm 4 μm away from the A surface in the depth direction Birefringence of the spot (Δnz): 140×10 ^-3 Birefringence of the spot 20 μm away from the B-plane in the depth direction (Δnz): 138×10 ^-3

[Example 2] The polyimide solution c prepared in Synthesis Example 3 was uniformly applied to the surface of the support substrate 1 on the polyimide layer side so that the thickness after curing was about 12.5 μm, and then Heat and dry at 130°C. The polyamic acid solution a prepared in Synthesis Example 1 was uniformly applied thereon so that the thickness after curing was about 12.5 μm, and after heating and drying at 130° C., a stepwise heat treatment was performed from 130° C. to 360° C. , and the imidization was completed, and after cooling to normal temperature, it was peeled off from the support substrate 1 , thereby preparing the polyimide film 2 .

The evaluation results of the polyimide film 2 are as follows. CTE of each layer: 1.5 ppm/K (A side) and 8.2 ppm/K (B side) CTE-MD: 6.6 ppm/K CTE-TD: 6.1 ppm/K In-plane retardation (RO): 11 nm in-plane Birefringence (Δn): 0.44×10 ^-3 Average amount of warpage: 1.2 mm CTE difference between the first polyimide layer (A side) and the second polyimide layer (B side) (CTE2- CTE1): 6.7 ppm/K

[Example 3] On the surface of the support substrate 1 on the polyimide layer side, the polyimide solution c prepared in Synthesis Example 3 was uniformly applied so that the thickness after curing was about 16 μm, and then Heat and dry at 130°C. The polyamic acid solution b prepared in Synthesis Example 2 was uniformly applied thereon so that the thickness after curing was about 9 μm, and after heating and drying at 130°C, a stepwise heat treatment was performed from 130°C to 360°C , and the imidization was completed, and after cooling to normal temperature, it was peeled off from the support substrate 1 , thereby preparing the polyimide film 3 .

The evaluation results of the polyimide film 3 are as follows. CTE of each layer: 2.5 ppm/K (A side) and 5.1 ppm/K (B side) CTE-MD: 4.0 ppm/K CTE-TD: 4.3 ppm/K In-plane retardation (RO): 3.0 nm in-plane Birefringence (Δn): 0.12×10 ^-3 Average amount of warpage: 0.7 mm CTE difference between the first polyimide layer (A side) and the second polyimide layer (B side) (CTE2- CTE1): 2.6 ppm/K A nickel-20 wt% chromium alloy target and a copper target for forming a base metal layer into a film were installed in the sputtering cathodes of a roll-to-roll sputtering apparatus, respectively. . After evacuating the inside of the apparatus in which the polyimide film 3 was installed, argon gas was introduced, and the pressure in the apparatus was kept at 1.3 Pa to prepare the polyimide film 1 with a copper thin film layer. The film thickness of the base metal layer (nickel-20% by weight chromium alloy) was 20 nm, and the film thickness of the copper thin film layer was 200 nm.

Using the polyimide film 1 with a copper thin film layer, a conductor circuit layer was formed by a semi-additive method to prepare a circuit board.

[Example 4] A multi-manifold type three-layer coextrusion three-layer die with a lip width of 200 mm was used to prepare in Synthesis Example 3 from the side close to the support substrate 1 The polyamic acid solution c and the polyamic acid solution b prepared in Synthesis Example 2 were extruded and cast coated on the polyimide resin layer side of the support substrate 1 in the manner of a sequential two-layer structure. . Then, stepwise heat treatment is performed at a temperature of 130° C. to 360° C. to complete imidization, and after cooling to normal temperature, the polyimide film 4 is prepared by peeling from the support substrate 1 .

The evaluation results of the polyimide film 4 are as follows. CTE of each layer: 2.3 ppm/K (A side) and 5.3 ppm/K (B side) CTE-MD: 4.2 ppm/K CTE-TD: 4.5 ppm/K In-plane retardation (RO): 5 nm in-plane Birefringence (Δn): 0.20×10 ^-3 Average amount of warpage: 1.3 mm 1st polyimide layer (A side, thickness: 16 μm) and 2nd polyimide layer (B side, thickness: 16 μm) : 9 μm) CTE difference (CTE2-CTE1): 3.0 ppm/K

(Reference Example 1) The polyamide prepared in Synthesis Example 2 was uniformly coated on the surface of the support substrate 2 (made of stainless steel, thickness: 16 μm) that had undergone mold release treatment so that the thickness after curing would be about 35 μm. After the amine acid solution b, it was dried by heating at 130°C. Then, stepwise heat treatment is performed from 130° C. to 380° C. to complete imidization, and after cooling to normal temperature, the polyimide film 5 is prepared by peeling from the support substrate 2 .

The evaluation results of the polyimide film 5 are as follows. CTE-MD: 3.9 ppm/K CTE-TD: 3.8 ppm/K In-plane retardation (RO): 18 nm In-plane birefringence (Δn): 0.51×10 ^-3 Average warpage: 11.3 mm

(Reference Example 2) The polyamic acid solution a obtained in Synthesis Example 1 was uniformly applied on the support substrate 2 so that the thickness after curing was about 16 μm, and then heated and dried at 130°C. The polyamic acid solution b obtained in Synthesis Example 2 was uniformly applied thereon so that the thickness after curing was about 9 μm, and after heating and drying at 130°C, a stepwise process was performed from 130°C to 360°C. After heat treatment to complete imidization, and after cooling to normal temperature, the polyimide film 6 is prepared by peeling off from the support base 2 .

The evaluation results of the polyimide film 6 are as follows. CTE-MD: 13.5 ppm/K CTE-TD: 14.6 ppm/K In-plane retardation (RO): 19.4 nm In-plane birefringence (Δn): 0.78×10 ^-3 Average warpage: 13.0 mm

[Example 5] The polyamic acid solution b prepared in Synthesis Example 2 was uniformly coated on the support substrate 2 so that the thickness after curing was about 18 μm, and dried by heating. The polyamic acid solution c prepared in Synthesis Example 3 was uniformly applied thereon so that the thickness after curing was about 20 μm. After heating and drying, heat treatment was performed to complete imidization. After cooling to room temperature, the support was removed from the support. The base material 2 was peeled off, whereby a polyimide film 7 was prepared.

The evaluation results of the polyimide film 7 are as follows. CTE of each layer: 2.6 ppm/K (A side) and 7.8 ppm/K (B side) CTE-MD: 5.3 ppm/K CTE-TD: 5.5 ppm/K In-plane birefringence (Δn): 1.4× 10 ^-3 Average amount of warpage: 8.0 mm CTE difference (CTE2 -CTE1): 5.2 ppm/K

It was confirmed that Examples 1 to 5 and Reference Example 1 to Reference Example 2 are polyimide films in which a polyimide solution was applied to a support substrate and dried and imidized on the support substrate. , and in any of the polyimide films, the CTE isotropy is good, and the in-plane birefringence is also low, so the dimensional stability is excellent.

Comparing Example 1 and Reference Example 1 in which the polyimide layer is a single layer, since the thickness of the polyimide film and the birefringence (Δnz) in the thickness direction are controlled with high precision in Example 1, the The average warpage amount was suppressed to 10 mm or less. In Reference Example 1 in which the polyimide layer was a single layer and the thickness of the polyimide film was 35 μm or less, the average warpage amount exceeded 10 mm. When the amine layer is two layers, the average warpage amount can be suppressed to 10 mm or less.

In addition, when comparing Examples 2 to 5 and Reference Example 2 in which the polyimide layers are multilayered, in Examples 2 to 4, the layers directly laminated on the support base material have low thermal expansion. The characteristic first polyimide layer is designed to have a coefficient of thermal expansion (CTE) smaller than the CTE of the second polyimide layer within the range that satisfies the formula (1), thereby suppressing warpage toward the A surface side. warpage, and the average warpage of the polyimide film was suppressed to 10 mm or less. On the other hand, in Reference Example 2, the polyimide layer having a large CTE among the two polyimide layers was disposed on the A surface side, and as a result, the average warpage amount exceeded 10 mm. In the case of forming a plurality of polyimide layers on a support substrate so far, the control of the CTE between the layers in consideration of the birefringence (Δnz) in the thickness direction has not been performed, so the layers are directly laminated on the support substrate. The Δnz of the A surface side of the polyimide layer was lower, the CTE tended to increase as compared with the B surface side, and like Reference Example 2, warpage toward the A surface side was likely to occur. On the other hand, as shown in Examples 2 to 5, in consideration of the birefringence (Δnz) in the thickness direction, it was confirmed that the layer directly laminated on the support substrate was the first polyimide A multilayer polyimide film in which warpage is suppressed can be produced by designing the CTE to be smaller than the CTE of the other polyimide layers (the second polyimide layer) to be laminated.

As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not limited by the said embodiment.

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Claims (7)

A polyimide film, characterized in that it comprises a single-layer or multi-layer polyimide layer, and satisfies the following conditions a to e: condition a: the thickness is within the range of 3 μm or more and 50 μm or less; condition b: The coefficient of thermal expansion is 10 ppm/K or less; Condition c: The polyimide film of 50 mm square after being dehumidified for 20 hours at 23° C. and humidity of 50% is allowed to stand still so that the convex surface of the central part is in contact with the flat surface, and When the average value of the floating amount of the four corners is taken as the average warpage amount, the average warpage amount is 10 mm or less; Condition d: The difference between the thermal expansion coefficient in the longitudinal direction and the thermal expansion coefficient in the width direction is ±3ppm/K or less; Condition e: The in-plane birefringence is 2×10 ^-3 or less. The polyimide film according to claim 1, wherein the polyimide layer is a multilayer, and includes a single-layer first polyimide layer with the lowest thermal expansion coefficient and a first polyimide layer laminated on the first polyimide layer. 1 single-layer or multi-layer second polyimide layer on one side of the polyimide layer, the thermal expansion coefficient CTE1 of the first polyimide layer and the thermal expansion coefficient CTE2 of the second polyimide layer satisfy the following The formula (1):

Here, CTE1 is the average value of thermal expansion coefficients in the longitudinal direction and transverse direction of the first polyimide layer, and CTE2 is the average value of thermal expansion coefficients in the longitudinal direction and transverse direction of the second polyimide layer. The polyimide film according to claim 2, wherein the second polyimide layer is a single layer. The polyimide film according to claim 2 or item 3, wherein the first polyimide layer comprises a polyimide comprising tetracarboxylic acid residues and diamine residues, and Contains 20 mol% or more of diamine residues derived from a diamine compound represented by the following general formula (A1) with respect to all the diamine residues contained in the polyimide,

In formula (A1), the linking group X ₀ represents a single bond, and Y independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, or an alkene, which may be substituted by a halogen atom or a phenyl group. base, n ₁ represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. The polyimide film according to item 2 or item 3 of the claimed scope, wherein at least one layer of the second polyimide layer comprises polyimide containing tetracarboxylic acid residues and diamine residues amine, and contains 20 mol% or more of diamine residues derived from a diamine compound represented by the following general formula (A1) with respect to all the diamine residues contained in the polyimide:

In formula (A1), the linking group X ₀ represents a single bond, and Y independently represents a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, or an alkene, which may be substituted by a halogen atom or a phenyl group. base, n ₁ represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. A metal-clad laminate, comprising: an insulating layer; and a metal layer on at least one side of the insulating layer, wherein the insulating layer comprises the one described in any one of items 1 to 5 of the scope of the patent application of polyimide film. A circuit board obtained by performing circuit processing on a metal layer in the metal-clad laminate described in claim 6 of the patent application scope.