Flexible metal-clad laminate

Abstract

To provide a flexible metal-clad laminate capable of suppressing a dimensional change in a backlight circuit board for a Mini LED display.SOLUTION: There is provided a flexible metal-clad laminate, comprising: an insulating resin layer including a single or multiple polyimide layers; and a first metal layer laminated on one surface of the insulating resin layer. The first metal layer includes, in an in-plane direction perpendicular to a thickness direction, a region having an area of at least 100 mm×100 mm or more as a first circuit processing region for forming a circuit wiring pattern. The flexible metal-clad laminate satisfies following conditions (i): the insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10-3 or less in the region corresponding to the first circuit processing region in the thickness direction; condition (ii): a rigidity of the first metal layer is 5.0×10-9 [Nm2] or more; and condition (iii): a rigidity of the insulating resin layer is 8.0×10-9 [Nm2] or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flexible metal-clad laminate that is used, for example, as a circuit board material. [Background technology]

[0002] An image display device includes a display panel that displays an image, and a backlight device that illuminates the display panel from the back side. Rigid boards have been widely used for circuit boards (backlight circuit boards) used in backlight devices for Mini LED displays that mount tens of thousands of LED elements. However, rigid boards have problems such as difficulty in meeting the demand for thinner internal parts that accompanies thinner products, difficulty in laser drilling, and difficulty in meeting bending demands such as curved displays. For this reason, the use of flexible circuit boards (FPCs) for backlight circuit boards has been considered (for example, Patent Document 1).

[0003] In the manufacturing process of the backlight circuit board, various processes such as joining, cutting, exposure, etching, and laser drilling are performed. The processing accuracy in these processes is important for maintaining the reliability of the image display device equipped with the backlight circuit board. However, since the flexible metal-clad laminate, which is the material of the FPC, has a structure in which a metal layer and a resin layer with different thermal expansion coefficients are laminated, stress is generated between the layers due to the difference in thermal expansion coefficient between the metal layer and the resin layer, and when a part or all of the stress is released when the metal layer is etched and processed for wiring, it causes expansion and contraction, which causes a change in the dimensions of the wiring pattern. Therefore, in order to ensure the dimensional accuracy of the flexible metal-clad laminate, it has been proposed to control the in-plane retardation of the insulating resin layer (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-61738 A (paragraph 0034, etc.) [Patent Document 2] Patent No. 6839594 (Claims, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] Backlight circuit boards for Mini LED displays tend to have a large board area due to the need to mount tens of thousands of LED elements. Therefore, the flexible metal-clad laminates used as the material for backlight circuit boards also need to have a large circuit processing area for forming the circuit wiring pattern, and superior dimensional accuracy is required throughout the entire area.

[0006] Therefore, a first object of the present invention is to provide a flexible metal-clad laminate capable of suppressing dimensional changes in a backlight circuit board for a Mini LED display, and a second object of the present invention is to provide a flexible circuit board with excellent dimensional accuracy obtained by processing the flexible metal-clad laminate. [Means for solving the problem]

[0007] As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved by controlling the in-plane birefringence (Δn) of the insulating resin layer in a flexible metal-clad laminate and the rigidity of the insulating resin layer and the metal layer, and have thus completed the present invention.

[0008] That is, the flexible metal-clad laminate of the present invention is a flexible metal-clad laminate including an insulating resin layer including a single or multiple polyimide layers, and a first metal layer laminated on one surface of the insulating resin layer, The first metal layer includes, in an in-plane direction perpendicular to the thickness direction, a region having an area of ​​at least 100 mm×100 mm or more as a first circuit processing region for forming a circuit wiring pattern. The flexible metal-clad laminate of the present invention satisfies the following conditions (i) to (iii): (i) the insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in a region corresponding to the first metal layer in a thickness direction; -3 That is: (ii) the rigidity of the first metal layer calculated by the following formula (1) is 5.0 × 10 -9 [Nm 2 ] or more, (iii) The rigidity of the insulating resin layer calculated by the following formula (1) is 8.0 × 10 -9 [Nm 2 ] or more, The present invention is characterized in that:

[0009]

number

[0010] The flexible metal-clad laminate of the present invention may further include a second metal layer on the other surface of the insulating resin layer, The second metal layer may include, in an in-plane direction perpendicular to the thickness direction, a region having an area of ​​at least 100 mm×100 mm or more as a second circuit processing region for forming a circuit wiring pattern. The flexible metal-clad laminate of the present invention satisfies the following conditions (iv) to (v): (iv) the insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in a region corresponding to the second metal layer in a thickness direction; -3 That is: (v) the rigidity of the second metal layer calculated by the formula (1) is 5.0×10 -9 [Nm 2 ] or more, The above condition may be satisfied.

[0011] The flexible metal-clad laminate of the present invention further satisfies the following conditions (vi) to (vii): (vi) the thickness of the insulating resin layer is within the range of 23 μm or more and 50 μm or less; (vii) the thickness of the first metal layer and the second metal layer is within the range of 9 μm or more and 25 μm or less; The above condition may be satisfied.

[0012] The flexible metal-clad laminate of the present invention is long and further meets the following condition (viii): (viii) The absolute values ​​of the dimensional change rate in the longitudinal direction (MD) and the dimensional change rate in the transverse direction (TD) before and after circuit processing of the first metal layer and the second metal layer may both be 0.03% or less.

[0013] The flexible metal-clad laminate of the present invention further satisfies the following condition (ix); (ix) After circuit processing, the variation in the dimensional change rate in the longitudinal direction (MD) and the dimensional change rate in the transverse direction (TD) before and after a further heat treatment at 150°C for 60 minutes may both be 0.005% or less. Effect of the Invention

[0014] The flexible metal-clad laminate of the present invention has excellent dimensional stability because the insulating resin layer has low in-plane birefringence (Δn) and the metal layer and insulating resin layer have high rigidity. Therefore, the flexible circuit board and multilayer flexible circuit board obtained by using the flexible metal-clad laminate of the present invention also have high dimensional stability, and are particularly suitable as circuit boards for backlight devices of Mini LED displays, and the reliability and yield of the display device using the same can be improved. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a flexible metal-clad laminate and a test piece used in evaluating the dimensional stability of a flexible metal-clad laminate according to one embodiment of the present invention. [Diagram 2] 1 is a diagram for explaining the mark positions of a test piece in the evaluation of dimensional stability. [Diagram 3] 1 is a diagram illustrating the amount of dimensional change in the distance between through holes in an evaluation of dimensional stability. [Figure 4]FIG. 1 is an explanatory diagram of a pattern mask on one side in evaluation of dimensional stability. [Diagram 5] FIG. 13 is an explanatory diagram of the other single-sided pattern mask in the evaluation of dimensional stability. [Figure 6] In the evaluation of dimensional stability, (a) is a drawing for explaining the rate of dimensional change in the MD direction, and (b) is a drawing for explaining the rate of dimensional change in the TD direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Next, an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0017] [Flexible metal-clad laminates] The flexible metal-clad laminate of the present invention comprises an insulating resin layer containing a single or multiple polyimide layers, and a first metal layer laminated on one side of the insulating resin layer. The flexible metal-clad laminate of the present invention may comprise a second metal layer on the other side of the insulating resin layer. That is, the flexible metal-clad laminate of the present invention may be a single-sided metal-clad laminate or a double-sided metal-clad laminate. The flexible metal-clad laminate of the present invention is preferably used as a material for FPCs such as backlight circuit boards by forming a wiring layer by processing the wiring circuit such as by etching the metal layer.

[0018] The first metal layer includes a region having an area of ​​at least 100 mm×100 mm or more in an in-plane direction perpendicular to the thickness direction as a first circuit processing region for forming a circuit wiring pattern. The second metal layer includes a region having an area of ​​at least 100 mm×100 mm or more in an in-plane direction perpendicular to the thickness direction as a second circuit processing region for forming a circuit wiring pattern. The areas of the first circuit processing region and the second circuit processing region may be the same or different. The planar shapes of the first circuit processing region and the second circuit processing region may be the same or different. The first circuit processing region and the second circuit processing region mostly overlap each other when projected in the thickness direction, but may include non-overlapping portions.

[0019] [Insulating resin layer] The insulating resin layer has a single or multiple polyimide layers. The insulating resin layer may contain any resin layer other than the polyimide layer, but is preferably composed of only a polyimide layer in order to obtain excellent dimensional stability.

[0020] The insulating resin layer satisfies the following condition (i); (i) The insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in the region corresponding to the first metal layer in the thickness direction. -3 That is: The in-plane birefringence (Δn) is 3.0×10 -3 If the residual stress exceeds 2.0×10, it means that the residual stress is large, and therefore, by satisfying condition (i), the in-plane dimensional stability of the insulating resin layer is ensured. In particular, when used as a backlight circuit board material, it is preferable that condition (i) is satisfied at least in the region corresponding in the thickness direction to the first circuit processing region of the first metal layer. From this viewpoint, the value of the in-plane birefringence (Δn) in condition (i) is 2.0×10 -3 It is preferable that:

[0021] The insulating resin layer satisfies the following condition (iii): (iii) The stiffness calculated by the above formula (1) is 8.0 × 10 -9 [Nm 2 ] or more, From this viewpoint, when the rigidity of the insulating resin layer is equal to or greater than the above value, high dimensional stability and a supporting function as a substrate can be achieved at the same time. -9 [Nm 2 ] or higher is preferred. The "rigidity" is calculated by the above formula (1) based on the product of the tensile modulus and the thickness. From the viewpoint of increasing the rigidity, the tensile modulus of the insulating resin layer is preferably, for example, in the range of 5.0 GPa to 15.0 GPa, and more preferably in the range of 10.0 GPa to 15.0 GPa. If the tensile modulus of the insulating resin layer is less than the lower limit, it becomes difficult to ensure the rigidity of the insulating resin layer, and the dimensional stability and supporting function are reduced. On the other hand, if the tensile modulus of the insulating resin layer exceeds the upper limit, the flexibility of the FPC when it is bent is reduced.

[0022] In the case of a double-sided metal-clad laminate, the insulating resin layer satisfies the following condition (iv): (iv) The insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in a region corresponding to the second metal layer in the thickness direction. -3 That is: It is preferable that the in-plane birefringence (Δn) value is 3.0×10 -3 If the residual stress exceeds 2.0×10, the residual stress is large, and therefore, by satisfying condition (iv), the dimensional stability within the plane of the insulating resin layer is ensured. In particular, when used as a backlight circuit board material, it is preferable that condition (iv) is satisfied at least in the region corresponding in the thickness direction to the second circuit processing region of the second metal layer. From this viewpoint, the value of the in-plane birefringence (Δn) of condition (iv) is 2.0×10 -3 It is preferable that:

[0023] The layer structure of the insulating resin layer is not particularly limited, but it is preferable that the insulating resin layer has a non-thermoplastic polyimide layer made of a non-thermoplastic polyimide and a thermoplastic polyimide layer made of a thermoplastic polyimide laminated on at least one of the non-thermoplastic polyimide layers. That is, it is preferable that the thermoplastic polyimide layer is provided on one or both sides of the non-thermoplastic polyimide layer. In addition, in the flexible metal-clad laminate of the present invention, it is preferable that the thermoplastic polyimide layer is laminated in contact with the metal layer. Here, the term "non-thermoplastic polyimide" refers to a polyimide that does not generally soften or exhibit adhesiveness even when heated. In the present invention, however, the term "non-thermoplastic polyimide" refers to a polyimide having a storage modulus of 1.0×10 at 30° C. as measured using a dynamic mechanical analyzer (DMA). 9 Pa or more, and the storage modulus at 300°C is 1.0×10 8 In addition, the term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed. In the present invention, however, the term "thermoplastic polyimide" refers to a polyimide whose storage modulus at 30° C. measured by DMA is 1.0×10 9 Pa or more, and the storage modulus at 300°C is 1.0×10 8 This refers to polyimides with a modulus of less than Pa.

[0024] In the insulating resin layer, the non-thermoplastic polyimide and the thermoplastic polyimide contain tetracarboxylic acid residues and diamine residues. The tetracarboxylic acid residues and diamine residues contained in the non-thermoplastic polyimide and the thermoplastic polyimide may be tetracarboxylic acid residues derived from tetracarboxylic dianhydrides and diamine residues derived from diamine compounds that are generally used in the synthesis of polyimides, but it is preferable that both of them are aromatic groups. In other words, the non-thermoplastic polyimide and the thermoplastic polyimide are preferably all aromatic polyimides. By the fact that the tetracarboxylic acid residues and diamine residues contained in the non-thermoplastic polyimide and the thermoplastic polyimide are all aromatic groups, it is possible to reduce the amount of change in the in-plane birefringence of the insulating resin layer in a high temperature environment. In the present invention, the term "tetracarboxylic acid residue" refers to a tetravalent group derived from a tetracarboxylic dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound. A diamine compound is a compound having two amino groups, and the hydrogen atom in each amino group may be substituted with any substituent.

[0025] The tetracarboxylic acid residue contained in the non-thermoplastic polyimide and thermoplastic polyimide is not particularly limited, but for example, a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue) and a tetracarboxylic acid residue derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residue) are preferred. These tetracarboxylic acid residues are likely to form an ordered structure, and can reduce the rate of change of in-plane birefringence (Δn) in a high temperature environment. From this viewpoint, the total amount of PMDA residues and / or BPDA residues is preferably 50 molar parts or more, more preferably in the range of 50 to 100 molar parts, and most preferably in the range of 70 to 100 molar parts, relative to 100 molar parts of all tetracarboxylic acid residues contained in the non-thermoplastic polyimide or thermoplastic polyimide.

[0026] The diamine residue contained in the non-thermoplastic polyimide and the thermoplastic polyimide is not particularly limited, but for example, a diamine residue derived from a diamine compound such as p-phenylenediamine (p-PDA), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'-diaminobiphenyl, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) is preferable. These easily form an ordered structure and can reduce the rate of change of in-plane birefringence (Δn) in a high-temperature environment. From this viewpoint, particularly in non-thermoplastic polyimides, the total amount of these diamine residues is preferably 50 parts by mol or more, more preferably within the range of 50 to 100 parts by mol, and most preferably within the range of 70 to 100 parts by mol, relative to 100 parts by mol of all diamine residues contained in the non-thermoplastic polyimide.

[0027] In addition, examples of diamine residues contained in non-thermoplastic polyimides and thermoplastic polyimides include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), bis(4-aminophenoxy)-2,5-di-tert-butylbenzene (DTBAB), 4,4-bis(4-aminophenoxy)benzophenone (BAPK), 1,3-bis[2-(4-aminophenyl)-2-propanediol], ... Also preferred are diamine residues derived from diamine compounds such as bis[4-(4-aminophenoxy)phenyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis[4-(4-aminophenoxy)phenyl]ether (BAPE), and bis[4-(4-aminophenoxy)phenyl]sulfone. These have a flexible site, so that they can reduce the elastic modulus of the insulating resin layer and impart flexibility. From this viewpoint, particularly in thermoplastic polyimides, the total amount of these diamine residues is preferably 30 molar parts or more, more preferably in the range of 30 to 100 molar parts, and most preferably in the range of 50 to 100 molar parts, relative to 100 molar parts of the total diamine residues contained in the thermoplastic polyimide.

[0028] In non-thermoplastic polyimides and thermoplastic polyimides, the in-plane birefringence, thermal expansion coefficient, storage modulus, tensile modulus, etc. of the insulating resin layer can be controlled by selecting the types of tetracarboxylic acid residues and diamine residues, and the molar ratios of each when two or more types of tetracarboxylic acid residues or diamine residues are used. In non-thermoplastic polyimides and thermoplastic polyimides, when a plurality of polyimide structural units are present, they may be present as blocks or randomly, but from the viewpoint of suppressing the variation in in-plane birefringence, they are preferably present randomly.

[0029] Generally, polyimide can be produced by reacting tetracarboxylic dianhydride with a diamine compound in a solvent, generating polyamic acid, and then heating to close the ring. For example, tetracarboxylic dianhydride and diamine compound are dissolved in an organic solvent in approximately equal moles, and the mixture is stirred at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to polymerize, thereby obtaining polyamic acid, which is a precursor of polyimide. In the reaction, the reaction components are dissolved so that the generated precursor is in the range of 5 to 30% by weight, preferably in the range of 10 to 20% by weight, in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol, and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such organic solvent is not particularly limited, but it is preferable to adjust the amount of use so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent as necessary. The viscosity of the polyamic acid solution is preferably within the range of 500 cps to 100,000 cps. If it is out of this range, defects such as uneven thickness and streaks are likely to occur in the film during coating work using a coater or the like. The method of imidizing the polyamic acid is not particularly limited, and a heat treatment such as heating at a temperature condition within the range of 80 to 400°C for 1 to 24 hours is preferably used.

[0030] In order to prevent warpage and deterioration of dimensional stability as an insulating resin layer of a circuit board, the insulating resin layer preferably has a coefficient of thermal expansion (CTE) in the range of 10 ppm / K to 30 ppm / K, more preferably in the range of 15 ppm / K to 25 ppm / K. If the CTE is less than 10 ppm / K or more than 30 ppm / K, warpage occurs and dimensional stability decreases. In addition, in a flexible metal-clad laminate, the CTE of the insulating resin layer is more preferably in the range of ±10 ppm / K or less with respect to the CTE of the metal layer, and most preferably in the range of ±5 ppm / K or less.

[0031] The thickness of the insulating resin layer is preferably, for example, in the range of 23 μm to 50 μm, more preferably in the range of 23 μm to 40 μm, as condition (vi). By having the thickness of the insulating resin layer in the above range, it is possible to increase the rigidity of the insulating resin layer alone, which contributes to dimensional stability. If the thickness of the insulating resin layer is less than the lower limit of the above range, problems such as the inability to ensure electrical insulation and difficulty in handling during the manufacturing process due to reduced handleability may occur. On the other hand, if the thickness of the insulating resin layer exceeds the upper limit of the above range, it becomes difficult to control the in-plane birefringence, resulting in problems such as reduced productivity.

[0032] In the insulating resin layer, the non-thermoplastic polyimide layer is a polyimide layer with low thermal expansion, and the thermoplastic polyimide layer is a polyimide layer with high thermal expansion. Here, the low thermal expansion polyimide layer refers to a polyimide layer having a coefficient of thermal expansion (CTE) preferably in the range of 1 ppm / K to 25 ppm / K, more preferably in the range of 3 ppm / K to 25 ppm / K. The high thermal expansion polyimide layer refers to a polyimide layer having a CTE preferably in the range of 35 ppm / K or more, more preferably in the range of 35 ppm / K to 80 ppm / K, and even more preferably in the range of 35 ppm / K to 70 ppm / K. The polyimide layer can be made to have a desired CTE by appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions.

[0033] In addition, in the insulating resin layer, the thickness ratio of the non-thermoplastic polyimide layer to the thermoplastic polyimide layer (non-thermoplastic polyimide layer / thermoplastic polyimide layer) is preferably within the range of 2.0 to 8.0. If this ratio value is less than 2.0, the non-thermoplastic polyimide layer becomes thin relative to the entire insulating resin layer, which tends to increase the variation in in-plane birefringence, and if it exceeds 8.0, the thermoplastic polyimide layer becomes thin, which tends to decrease the adhesive reliability between the insulating resin layer and the metal layer.

[0034] In the insulating resin layer, the thermoplastic polyimide constituting the thermoplastic polyimide layer preferably has a glass transition temperature in the range of 200° C. to 350° C., more preferably in the range of 200° C. to 320° C. Having a glass transition temperature in the above range can improve adhesion to the metal layer.

[0035] [First metal layer and second metal layer] The first metal layer includes a region having an area of ​​at least 100 mm x 100 mm or more, preferably 150 mm x 200 mm or more, as a first circuit processing region for forming a circuit wiring pattern in an in-plane direction perpendicular to the thickness direction. For example, in a backlight circuit board for a Mini LED display, the board area is large because it is necessary to mount tens of thousands of LED elements. The first circuit processing region is a continuous region having an area equivalent to the area of ​​one surface of the backlight circuit board. In the flexible metal-clad laminate of the present invention, the area of ​​the first circuit processing region for forming a circuit wiring pattern is secured as described above, so that it is particularly suitable as a material for a backlight circuit board. There is no particular restriction on the upper limit of the area of ​​the first circuit processing region, but for example, 500 mm x 500 mm is preferable.

[0036] The first metal layer satisfies the following condition (ii); (ii) The rigidity of the first metal layer calculated by the above formula (1) is 5.0 × 10 -9 [Nm 2 ] or more, The satisfaction of condition (ii) indicates that the rigidity of the first metal layer is high enough to suppress dimensional changes in the insulating resin layer. Therefore, by satisfying condition (ii), the dimensional stability of the insulating resin layer can be improved by the first metal layer having high rigidity.

[0037] The second metal layer includes, in the in-plane direction perpendicular to the thickness direction, a region having an area of ​​at least 100 mm x 100 mm or more, preferably 150 mm x 200 mm or more, as a first circuit processing region for forming a circuit wiring pattern. The second circuit processing region is a continuous region having an area equivalent to the area of ​​one surface of the backlight circuit board. The flexible metal-clad laminate of the present invention is particularly suitable as a material for a backlight circuit board by ensuring the area of ​​the second circuit processing region for forming a circuit wiring pattern as described above. There is no particular restriction on the upper limit of the area of ​​the second circuit processing region, but for example, 500 mm x 500 mm is preferable.

[0038] The second metal layer is formed under the following condition (v): (v) The rigidity of the second metal layer calculated by the above formula (1) is 5.0 × 10 -9 [Nm 2 ] or more, Satisfying condition (v) indicates that the rigidity of the second metal layer is high enough to suppress dimensional changes in the insulating resin layer. Therefore, by satisfying condition (v), the rigid second metal layer can improve the dimensional stability of the insulating resin layer.

[0039] In the flexible metal-clad laminate of the present invention, the metal constituting the first metal layer and the second metal layer may be, for example, a metal selected from copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth, indium, or an alloy thereof. The metal layer can be formed by a method such as sputtering, vapor deposition, or plating, but it is preferable to use a metal foil from the viewpoint of adhesion. Copper foil is particularly preferable from the viewpoint of conductivity. The copper foil may be either electrolytic copper foil or rolled copper foil. When the flexible metal-clad laminate of the present invention is continuously produced, a long metal foil having a predetermined thickness wound into a roll is used as the metal foil.

[0040] The thickness of the first metal layer and the second metal layer is preferably in the range of 9 μm to 25 μm, more preferably in the range of 10 μm to 20 μm, as the condition (vii). If the thickness of the first metal layer and the second metal layer exceeds 25 μm, the bending stress applied to the metal layer (or wiring layer) when the flexible metal-clad laminate (or FPC) is folded increases, and the folding resistance decreases. In addition, the lower limit of the thickness of the first metal layer and the second metal layer is preferably 9 μm to ensure the rigidity of the condition (ii) or the condition (v). The thickness of the first metal layer and the second metal layer may be the same or different.

[0041] The tensile modulus of the first metal layer and the second metal layer may be, for example, 30 GPa or more, preferably 100 GPa or less, more preferably 50 GPa or more and 100 GPa or less. If the tensile modulus of the first metal layer and the second metal layer is less than the lower limit, it is difficult to ensure the rigidity of condition (ii) or condition (v), and the dimensional stability is reduced. On the other hand, if the tensile modulus of the first metal layer and the second metal layer is more than the upper limit, a large bending stress is applied to the wiring layer when the FPC is bent, and the bending resistance is reduced.

[0042] The flexible metal-clad laminate of the present invention may be prepared, for example, by preparing a resin film including an insulating resin layer, sputtering a metal onto the resin film to form a seed layer, and then forming a metal layer by plating, for example. In this case, a solution of polyamic acid is applied to a supporting substrate, dried, and then the gel film of polyamic acid is peeled off from the supporting substrate and imidized to form a resin film that becomes the insulating resin layer.

[0043] The flexible metal-clad laminate of the present invention may also be prepared by preparing a resin film containing an insulating resin layer, and laminating a metal foil thereon by a method such as thermocompression bonding.

[0044] Furthermore, the flexible metal-clad laminate of the present invention may be prepared by casting a coating liquid containing a polyamic acid, which is a precursor of polyimide, onto a metal foil, drying it to form a coating film, and then heat-treating it to imidize it and form an insulating resin layer (casting method).

[0045] Preferred embodiments of the method for producing a flexible metal-clad laminate of the present invention include, for example, [1] a method in which a solution of polyamic acid is applied to a metal foil, dried, and then imidized to produce an insulating resin layer; [2] a method in which a solution of polyamic acid is applied to a metal foil, dried, and then imidized multiple times; and [3] a method in which polyamic acid is simultaneously applied to a metal foil in a multi-layer laminated state by multi-layer extrusion, dried, and then imidized (hereinafter referred to as multi-layer extrusion method).

[0046] The method [1] above may, for example, include the following steps 1a to 1c; (1a) applying a solution of polyamic acid to a metal foil and drying; (1b) forming a polyimide layer on a metal foil by heat-treating a polyamic acid to imidize it; (1c) obtaining an insulating resin layer by separating the metal foil and the polyimide layer; may include.

[0047] The above method [2] can be carried out in the same manner as the above method [1], except that in the above method [1], step 1a is repeated multiple times to form a laminated structure of polyamic acid on the metal foil.

[0048] The above method [3] can be carried out in the same manner as the above method [1], except that in step 1a of the above method [1], a laminated structure of polyamic acid is simultaneously applied by multi-layer extrusion and dried.

[0049] It is preferable to complete the imidization of the polyamic acid on the metal foil to form the insulating resin layer. Since the polyamic acid resin layer is imidized while being fixed to the metal foil, it is possible to suppress the expansion and contraction change of the polyimide layer during the imidization process and maintain the thickness and dimensional accuracy of the insulating resin layer.

[0050] The flexible metal-clad laminate of the present invention produced as described above is preferably long, for example, 20 m or longer. The flexible metal-clad laminate of the present invention also includes a laminate that is continuously produced and then slit into a certain size in the long longitudinal direction (hereinafter also referred to as MD direction) and width direction (hereinafter also referred to as TD direction).

[0051] The flexible metal-clad laminate of the present invention also satisfies the following condition (viii): (viii) the absolute values ​​of the dimensional change rate in the longitudinal direction (MD) and the dimensional change rate in the transverse direction (TD) before and after circuit processing of the first metal layer and the second metal layer are both 0.03% or less; It is preferable that the condition (viii) is satisfied. Satisfying the condition (viii) means that the residual stress in the insulating resin layer is small and the dimensional stability is high. Therefore, by satisfying the condition (viii), the dimensional change when applied to a backlight circuit board can be suppressed, and the reliability of the display device can be improved. It is sufficient that the condition (viii) is satisfied at least in the areas corresponding to the first circuit area and the second circuit area. Whether or not the condition (viii) is satisfied can be determined by the method described in the Examples below.

[0052] Furthermore, the flexible metal-clad laminate of the present invention satisfies the following condition (ix): (ix) After circuit processing, the variation in the dimensional change rate in the longitudinal direction (MD) and the dimensional change rate in the transverse direction (TD) before and after a heat treatment at 150°C for 60 minutes is 0.005% or less. It is preferable that the condition (ix) is satisfied. By satisfying the condition (ix), high dimensional stability can be obtained even when heated after circuit processing. Therefore, by satisfying the condition (ix), dimensional change when applied to a backlight circuit board can be suppressed, and the reliability of the display device can be improved. Whether or not the condition (ix) is satisfied can be determined by the method described in the Examples below.

[0053] [Effect] When the flexible metal-clad laminate of the present invention is used as a material for a backlight circuit board, the circuit processing area (first circuit processing area, second circuit processing area) in the metal layer is relatively large in area, so that it is necessary to control the in-plane birefringence of the insulating resin layer with higher precision than in conventional FPC materials. Factors that affect the in-plane birefringence of the insulating resin layer include, for example, the type of raw material monomer, the molecular weight of the polyimide precursor and the viscosity of the polyimide precursor solution, the layer structure and thickness of the polyimide layer, and physical and chemical conditions in the manufacturing process. Therefore, in the present invention, the desired in-plane birefringence is controlled by appropriately adjusting the following (A) to (C). (A) Selection of raw material monomer: By selecting raw material monomers and compositions that facilitate the formation of an ordered structure in the polyimides constituting the non-thermoplastic polyimide layer and the thermoplastic polyimide layer of the insulating resin layer, the in-plane birefringence of the insulating resin layer can be reduced. (B) Polyimide layer composition and thickness: The greater the thickness of the thermoplastic polyimide layer having high thermal expansion or softening properties, the greater the fluctuation in the in-plane birefringence of the insulating resin layer. Therefore, by increasing the thickness ratio of the non-thermoplastic polyimide layer and decreasing the thickness ratio of the thermoplastic polyimide layer, the in-plane birefringence and its fluctuation can be reduced in the insulating resin layer. (C) Control of physical conditions: When a load is applied to a gel film of polyamic acid by uniaxial stretching, biaxial stretching, or the like, the in-plane birefringence of the insulating resin layer tends to increase. Conversely, by selecting conditions that do not apply a load, the in-plane birefringence of the insulating resin layer can be suppressed to a small value. Examples of the latter include coating a polyamic acid solution on a metal foil by a casting method, and leaving the coating film to dry. By using any one of the above methods or a combination of two or more of them, the in-plane birefringence can be controlled within an appropriate range even when the circuit processing area is large. In addition, by adjusting the drying temperature of the coating film by the casting method, the heating rate in thermal imidization, the temperature at which imidization is completed, etc., it is possible to prevent softening of the metal layer due to high-temperature, long-term heat treatment, and to suppress a decrease in the rigidity of the first metal layer and the second metal layer.

[0054] The flexible metal-clad laminate of the present invention has high dimensional stability and is therefore particularly suitable as a material for a backlight circuit board for a backlight device that irradiates light from a large number of LED elements mounted in a first circuit processing area or a second circuit processing area toward a display panel. In addition, it can meet the demand for thinning and has sufficient flexibility, so it can also meet the bending demands of curved displays, etc.

[0055] [Flexible circuit board] The metal layer of the flexible metal-clad laminate of the present invention is processed into a pattern by a conventional method to form a wiring layer, thereby manufacturing a flexible circuit board (FPC) according to one embodiment of the present invention. The flexible circuit board of the present invention may be a multi-layer flexible circuit board. The flexible circuit board of the present invention comprises an insulating resin layer including a single or multiple polyimide layers, and a first wiring layer laminated on at least one surface of the insulating resin layer. The flexible circuit board may comprise a second wiring layer on the other surface of the insulating resin layer. The flexible circuit board of the present invention satisfies the above-mentioned conditions (i) to (iii) of the flexible metal-clad laminate of the present invention, and preferably further satisfies conditions (iv) to (ix).

[0056] The flexible circuit board of the present invention can be preferably used not only as a backlight circuit board, but also as a circuit board material in electronic devices such as in-vehicle liquid crystal displays, display devices such as electronic paper, organic EL lighting, solar cells, touch panels, camera modules, inverters, converters and their components, and electronic devices such as HDDs, DVDs, mobile phones, smartphones, tablet terminals, automotive electronic control units (ECUs), and power control units (PCUs). EXAMPLES

[0057] The features of the present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to the examples. In the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[0058] [Viscosity measurement] The viscosity was measured at 25° C. using an E-type viscometer (manufactured by Brookfield, product name: DV-II+Pro). The rotation speed was set so that the torque was 10% to 90%, and the value was read when the viscosity stabilized 2 minutes after the start of the measurement.

[0059] [Measurement of glass transition temperature (Tg) and storage modulus] A polyimide film measuring 5 mm × 20 mm was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by TA Instruments Japan, product name: RSA-G2) at a heating rate of 10 °C / min from 25 °C to 300 °C and a frequency of 1 Hz. The temperature at which the change in elastic modulus (tan δ) was maximum was defined as the glass transition temperature. The storage modulus at 30 °C measured using DMA was 1.0 × 10 9 Pa or more, and the storage modulus at 300°C is 1.0×10 8 Those with a storage modulus of less than 1.0 x 10 Pa at 30°C are considered "thermoplastic" and 9 Pa or more, and the storage modulus at 300°C is 1.0×10 8Those showing a strength of 100 Pa or more were categorized as "non-thermoplastic."

[0060] [Measurement of coefficient of thermal expansion (CTE)] A polyimide film measuring 3 mm x 20 mm was heated from 30°C to 265°C at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, product name: 4000SA), and then held at that temperature for 10 minutes. The film was then cooled at a rate of 5°C / min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

[0061] [Measurement of in-plane retardation (RO)] The retardation in the in-plane direction of a given sample was measured using a birefringence meter (Photonic Lattice, product name: Wide Range Birefringence Evaluation System WPA-100, measurement area: MD: 140 mm × TD: 100 mm). The incident angle was 0°, and the measurement wavelength was 543 nm.

[0062] [Preparation of samples for evaluation of in-plane retardation (RO)] A polyimide film obtained by etching the metal layer of a long flexible metal-clad laminate was cut into A4 size (MD: 297 mm × TD: 210 mm) at each of the two left and right ends (left and right) in the TD direction and the center (center) in the area corresponding to the area where the metal layer was formed, to prepare sample L (left), sample R (right), and sample C (center).

[0063] [Evaluation of in-plane birefringence (Δn)] The in-plane retardation (RO) was measured for each of Sample L, Sample R, and Sample C. The maximum measured value of each sample was divided by the thickness of the evaluation sample to obtain the "in-plane birefringence (Δn)", the difference between the maximum and minimum values ​​of the in-plane retardation (RO) measurements was obtained as the "variation (ΔRO) of in-plane retardation in the width direction (TD)", and the value obtained by dividing this ΔRO by the thickness of the evaluation sample was obtained as the "variation [Δ(Δn)] of in-plane birefringence in the width direction (TD)".

[0064] [Measurement of tensile modulus of polyimide film] A polyimide film measuring 12.7 mm x 177.8 mm was set in a Tensilon tester (manufactured by Toyo Seiki Seisakusho, product name: Strograph VG-1F) with a gauge length of 101.6 mm in an environment of 23°C temperature and 50% relative humidity, and a tensile test was performed in a 180° direction at a speed of 50 mm / min until breakage. A stress-strain curve (X-axis: strain, Y-axis: stress) was created, and the slope of the stress-strain curve in the strain range of 3 to 20% was calculated to obtain the tensile modulus of elasticity.

[0065] [Measurement of tensile modulus of single-sided metal-clad laminate] A single-sided metal-clad laminate measuring 12.7 mm x 177.8 mm (however, in the case of a double-sided metal-clad laminate, one of the metal layers on the press surface was etched away) was set with a gauge length of 101.6 mm on a Tensilon tester (manufactured by Toyo Seiki Seisakusho, product name: Strograph VG-1F) in an environment of 23°C temperature and 50% relative humidity, and a tensile test was performed in a 180 degree direction at a speed of 50 mm / min until breakage occurred, and a stress-strain curve (X-axis: strain, Y-axis: stress) was created. The slope of the stress-strain curve in the strain range of 0.05 to 0.2% was calculated to obtain the tensile modulus of elasticity. The stress is calculated as tensile stress using the following formula (2) based on the initial cross-sectional area of ​​the test piece (before stress is applied).

[0066]

number

[0067] The strain is calculated as tensile strain based on the gauge length using the following formula (3) or formula (4).

[0068]

number

[0069] In addition, the nominal tensile strain value is calculated based on the initial grip distance using the following formula (5) or formula (6).

[0070]

number

[0071] [Calculation method for the tensile modulus of the metal layer in single-sided metal-clad laminates] Calculate using the following formula. (tensile modulus of elasticity of single-sided metal-clad laminate × thickness of single-sided metal-clad laminate) – (tensile modulus of elasticity of polyimide film × thickness of polyimide film) / thickness of metal layer

[0072] [Calculation method for the rigidity of metal layer or insulating resin layer] It is calculated by the following formula (1). The stiffness was calculated with the sample width being 1 mm unit width. Here, the i-th layer (i is an integer) counting from the reference surface among the layers constituting the metal-clad laminate is defined as the i-th layer. The "reference surface" means, for example, the surface of the polyimide layer on which no metal layer is laminated, when assuming a single-sided metal-clad laminate in which one metal layer is laminated on one side of one polyimide layer.

[0073]

number

[0074] In formula (1), "neutral plane" means a neutral plane in a metal-clad laminate, and the neutral plane position [NP], which is the distance from the reference plane to the neutral plane, is calculated by the following formula (7). In formula (7), hi is the distance between the center plane of the i-th layer and the reference plane, and ti is the thickness of the i-th layer. Here, the "center plane of the i-th layer" is a virtual plane located in the center of the thickness direction of the i-th layer. The calculation of the neutral plane position is described, for example, in Japanese Patent No. 6320031 and Japanese Patent Laid-Open No. 2022-155041.

[0075]

number

[0076] [Measurement of dimensional change rate] 1) The process of preparing the test specimen As illustrated in Fig. 1, a test piece 10 is prepared by cutting a long flexible metal-clad laminate 100 to a predetermined length. In the following description, the longitudinal direction of the long flexible metal-clad laminate 100 is defined as the MD direction, and the width direction is defined as the TD direction (the same applies to the test piece 10). The test piece 10 is assumed to be a backlight circuit board for a display, and has MD 350 mm x TD 250 mm. Although not shown, the flexible metal-clad laminate 100 has an insulating resin layer and a metal layer laminated on one side or both sides of the insulating resin layer.

[0077] 2) A process for forming multiple marks on a test piece In this step, a virtual rectangle 20 (hereinafter, referred to as the rectangle 20) having sides parallel to the MD and TD directions is assumed in the test piece 10. The length of the short side of this virtual rectangle 20 is set to a length corresponding to the width (length in the TD direction) of the flexible metal-clad laminate 100, and the area of ​​the virtual rectangle 20 is set to an area that can cover the range to be processed into a backlight circuit board of a display. Specifically, the length of the short side of the rectangle 20 is set to 80% of the length in the TD direction of the test piece 10 (width of the flexible metal-clad laminate 100), and when the width (length in the TD direction) of the flexible metal-clad laminate 100 is 250 mm, the length of the short side of the virtual rectangle 20 is set to 200 mm. The length of the rectangle 20 in the MD direction is set to 300 mm.

[0078] 2, multiple marks were formed at equal intervals on each straight line on each side including the four corners of an imaginary rectangle 20. The marks were circular through-holes 30 (hereinafter referred to as holes 30) formed at equal intervals (5 cm) in the MD and TD directions.

[0079] 3) First measurement process In this step, a measuring machine (manufactured by Mitutoyo Corporation, product name: Quick Vision QV-APEX QV-X404P1L-C) is used to measure the positions of the multiple holes 30. Then, the distance L0 between adjacent holes 30 is calculated from the measurement results of the positions of the holes 30. For example, if the number of holes 30 is seven in the MD direction, the distance L0 is calculated for six intervals between adjacent holes 30. Here, the distance L0 between adjacent holes 30 means the distance from the center 30a of a certain hole 30 to the center 30a of the adjacent hole 30, as shown in FIG. 3. At this time, the interval between the two holes 30 that are farthest apart in the MD direction is L2, and the interval between the holes 30 that are farthest apart in the TD direction is L4. The measurement of the positions of the holes 30 was performed by a method of detecting the positions of the holes 30 based on an image of the test piece 10, and before the measurement, the test piece 10 was left to stand for 24 hours in an environment of 23°C and 50 RH%.

[0080] 4) Etching process In this step, a part of the metal layer of the test piece 10 is etched. The etching step is divided into the following steps. (1) Dry film resist compression (2) Exposure and development (3) Etching (4) Dry film resist stripping Additionally, steps (1) and (2) were carried out in a clean room that was not affected by ultraviolet light.

[0081] (1) Dry film resist compression A roll of dry film resist (hereinafter referred to as DFR, manufactured by Asahi Kasei Corporation, product name: AQ-2075) was attached to a flexible metal-clad laminate by thermocompression bonding at 110°C, 0.4 MPa, and a line speed of 1 m / min using a dry film laminator (manufactured by MCK Corporation, product name: ML-400W).

[0082] (2) Exposure and development Next, the test piece 10 with the dry film resist thermocompression bonded and the wiring pattern mask were placed on an exposure machine (manufactured by Hitec Co., Ltd., product name: HTE-102ED), and exposure was performed with an exposure dose of 70 mJ. In this process, a pattern mask (black: metal foil part, white: polyimide layer part, size: MD350mm x TD250mm, proportion of wiring layer: 45%) shown in FIG. 4 was placed on one side of the flexible metal-clad laminate, and a pattern mask (black: metal foil part, white: polyimide layer part, size: MD350mm x TD250mm, proportion of wiring layer: 36%) shown in FIG. 5 was placed on the other side. Next, a developing device (manufactured by Camellia Co., Ltd.) was used to prepare a 1% sodium carbonate aqueous solution, and the film resist was developed under spray pressure conditions of 30°C and 0.2 MPa.

[0083] (3) Etching The copper foil portion was etched using an etching device (manufactured by Camellia) with an etching solution (manufactured by Toagosei Co., Ltd., product name: ferric chloride solution) under conditions of 30° C. and 0.2 MPa.

[0084] (4) Dry film resist stripping Using a dry film resist stripping device (manufactured by Camellia), a 3% aqueous solution of sodium hydroxide was prepared, and the dry film resist of the hardened portion was stripped under conditions of 35° C. and 0.1 to 0.15 MPa.

[0085] 5)Heating process In this step, the etched test piece 10 was placed in an oven (manufactured by Espec Corp., product name: CONVECTION OVEN) and heated at 150° C. for 1 hour.

[0086] 6) Second measurement process In this step, the positions of the holes 30 were measured again after the above etching in the same manner as in the first measurement step, and the distance L1 between adjacent holes 30 was calculated from the measurement results of the positions of the holes 30. In addition, the interval L3 between the two holes 30 that were furthest apart in the MD direction and the interval L5 between the holes 30 that were furthest apart in the TD direction were calculated.

[0087] 7) Calculation of dimensional change rate Before and after etching and heating, the dimensional change rate in the MD direction for the distance between the two holes 30 that are furthest apart in the MD and TD directions in the sheet was calculated by calculating the difference L3-L2 between the distance L2 obtained in the first measurement process and the distance L3 obtained in the second measurement process, and the dimensional change rate was calculated using the following formula. Dimensional change rate in MD direction (%) = (L3-L2) / L2×100 Based on the above formula, the dimensional change rate in the MD direction within the sheet was calculated for five points A to E in FIG. 6(a), and the average value was taken as the dimensional change rate. In addition, the dimensional change rate in the TD direction was calculated by calculating the difference L5-L4 between the distance L4 obtained in the first measurement step and the distance L5 obtained in the second measurement step, and the dimensional change rate was calculated using the following formula. Dimensional change rate in TD direction (%) = (L5-L4) / L4×100 Based on the above formula, the dimensional change rate in the MD direction within the sheet was calculated for seven points A to G in FIG. 6(b), and the average value was taken as the dimensional change rate.

[0088] 8) Calculating the variation in dimensional change rate Before and after etching and heating, the difference L1-L0 between the distance L0 obtained in the first measurement process and the distance L1 obtained in the second measurement process is calculated for the distance between the same two holes 30. Then, for all the distances between the holes 30 arranged in the same straight line, the dimensional change rate is calculated using the following formula. Dimensional change rate (%) = (L1-L0) / L0 x 100 From the calculated dimensional change rate, the standard deviation in each of the MD and TD was calculated using the following formula (8).

[0089]

number

[0090] The abbreviations used in the examples and comparative examples represent the following compounds. PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene DAPE: 4,4'-diaminodiphenyl ether BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane p-PDA: p-phenylenediamine DMAc: N,N-dimethylacetamide

[0091] (Synthesis Example 1) Under a nitrogen stream, 17.3 parts by weight of m-TB (0.081 mol parts), 10.2 parts by weight of TPE-R (0.035 mol parts), and DMAc in an amount such that the solid content concentration after polymerization was 15% by weight were charged into the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 25.1 parts by weight of PMDA (0.115 mol parts) were added, and the mixture was stirred at room temperature for 3 hours to carry out the polymerization reaction, thereby obtaining a polyamic acid solution a. The solution viscosity of the polyamic acid solution a was 38,200 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution a was 427°C, non-thermoplastic, and had a thermal expansion coefficient of 22 (ppm / K).

[0092] (Synthesis Example 2) Under a nitrogen stream, 23.0 parts by weight of m-TB (0.108 mol parts), 3.5 parts by weight of TPE-R (0.012 mol parts), and DMAc in an amount such that the solid content concentration after polymerization was 15% by weight were charged into the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 26.0 parts by weight of PMDA (0.119 mol parts) were added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution b. The solution viscosity of the polyamic acid solution b was 41,100 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution b was 421°C, non-thermoplastic, and had a thermal expansion coefficient of 10 (ppm / K).

[0093] (Synthesis Example 3) Under a nitrogen stream, 12.3 parts by weight of m-TB (0.058 mol parts), 10.1 parts by weight of TPE-R (0.035 mol parts), 2.5 parts by weight of p-PDA (0.023 mol parts), and an amount of DMAc such that the solid content concentration after polymerization is 15% by weight were charged into the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 17.5 parts by weight of PMDA (0.080 mol parts) and 10.1 parts by weight of BPDA (0.034 mol parts) were added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution c. The solution viscosity of the polyamic acid solution c was 42,700 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution c was 360°C, non-thermoplastic, and had a thermal expansion coefficient of 18 (ppm / K).

[0094] (Synthesis Example 4) Under a nitrogen stream, 30.2 parts by weight of BAPP (0.074 parts by mole) and an amount of DMAc such that the solid content concentration after polymerization would be 15% by weight were added to the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 22.3 parts by weight of BPDA (0.076 parts by mole) was added, and the mixture was stirred at room temperature for 3 hours to carry out the polymerization reaction, thereby obtaining polyamic acid solution d. The solution viscosity of polyamic acid solution d was 9,800 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution d was 252°C, and the thermoplasticity and thermal expansion coefficient were 46 (ppm / K).

[0095] (Synthesis Example 5) Under a nitrogen stream, 11.7 parts by weight of DAPE (0.058 mol parts), 11.4 parts by weight of TPE-R (0.039 mol parts), and DMAc in an amount such that the solid content concentration after polymerization was 15% by weight were charged into the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 29.5 parts by weight of BPDA (0.100 mol parts) were added, and the mixture was stirred at room temperature for 3 hours to carry out the polymerization reaction, thereby obtaining a polyamic acid solution e. The solution viscosity of the polyamic acid solution e was 11,200 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution e was 265°C, and the thermoplasticity and thermal expansion coefficient were 58 (ppm / K).

[0096] (Synthesis Example 6) Under a nitrogen stream, 17.6 parts by weight of TPE-R (0.060 mol parts), 1.6 parts by weight of p-PDA (0.015 mol parts), and an amount of DMAc such that the solid content concentration after polymerization was 15% by weight were charged into the reaction vessel, and the mixture was stirred at room temperature to dissolve. Next, 22.8 parts by weight of BPDA (0.077 mol parts) were added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby obtaining a polyamic acid solution f. The solution viscosity of the polyamic acid solution f was 7,800 cps. The glass transition temperature of the polyimide obtained from this polyamic acid solution f was 239°C, and the thermoplasticity and thermal expansion coefficient were 65 (ppm / K).

[0097] [Example 1] Polyamic acid solution d was uniformly cast on a long copper foil 1 (electrolytic copper foil, thickness: 12 μm, width: 1080 mm) so that the thickness after curing was 2.5 μm, and then heated and dried. On top of that, resin solution a' in which 3,4,5-trifluorophenylboronic acid was blended with polyamic acid solution a (blended so that the amount was 0.1 mol per 1 mol of the structural unit of polyamic acid) was uniformly cast on top of that so that the thickness after curing was 20 μm, and then heated and dried. Furthermore, polyamic acid solution d was uniformly cast on top of that so that the thickness after curing was 2.5 μm, and then heated and dried. After that, imidization was completed by stepwise heat treatment, and a single-sided metal-clad laminate 1a was prepared. The maximum temperature of the heat treatment at this time was 280 ° C.

[0098] The polyimide layer side of the single-sided metal-clad laminate 1a was placed in contact with a separately prepared long copper foil 1, and the two were thermocompression-bonded to prepare a double-sided metal-clad laminate 1.

[0099] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 0.68×10 -3 Variation in in-plane birefringence in the transverse direction (TD) of the polyimide layer [△(△n)]: 0.12×10 -3 Tensile modulus of polyimide layer: 8.4GPa Stiffness of polyimide layer: 1.1×10-8 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 1a: 27.1 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 1a: 61.3 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 1a: 8.8×10 -9 Nm 2 Dimensional change rate in MD direction: -0.006% Dimensional change rate in TD direction: +0.004% Variation in dimensional change rate in MD direction: 0.002% Variation in dimensional change rate in TD direction: 0.003%

[0100] [Example 2] A single-sided metal-clad laminate 2a and a double-sided metal-clad laminate 2 were prepared in the same manner as in Example 1, except that a long copper foil 2 (rolled copper foil, thickness: 12 μm, width: 540 mm) was used instead of the copper foil 1, polyamic acid solution e was used instead of the polyamic acid solution d, and polyamic acid solution b was used instead of the polyamic acid solution a.

[0101] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 1.6×10 -3 Variation in in-plane birefringence across the width of the polyimide layer [△(△n)]: 0.2×10 -3 Tensile modulus of polyimide layer: 8.8GPa Stiffness of polyimide layer: 1.1×10 -8 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 2a: 18.4 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 2a: 36.2 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 2a: 5.2×10 -9 Nm 2 Dimensional change rate in MD direction: -0.008% Dimensional change rate in TD direction: +0.005% Variation in dimensional change rate in MD direction: 0.004% Variation in dimensional change rate in TD direction: 0.003%

[0102] [Example 3] A single-sided metal-clad laminate 3a and a double-sided metal-clad laminate 3 were prepared in the same manner as in Example 1, except that a long copper foil 3 (electrolytic copper foil, thickness: 12 μm, width: 1080 mm) was used instead of the copper foil 1, polyamic acid solution f was used instead of the polyamic acid solution d, and polyamic acid solution c was used instead of the polyamic acid solution a.

[0103] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 2.4×10 -3 Variation in in-plane birefringence across the width of the polyimide layer [△(△n)]: 0.24×10 -3 Tensile modulus of polyimide layer: 6.8GPa Stiffness of polyimide layer: 8.9×10 -9 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 3a: 23.4 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 3a: 55.5 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 3a: 8.0×10 -9 Nm 2 Dimensional change rate in MD direction: +0.009% Dimensional change rate in TD direction: +0.009% Variation in dimensional change rate in MD direction: 0.005% Variation in dimensional change rate in TD direction: 0.005%

[0104] [Example 4] A single-sided metal-clad laminate 4a and a double-sided metal-clad laminate 4 were prepared in the same manner as in Example 1, except that a copper foil 1 having a different thickness (electrolytic copper foil, thickness: 18 μm, width: 1080 mm) was used.

[0105] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 0.75×10 -3 Variation in in-plane birefringence across the width of the polyimide layer [△(△n)]: 0.14×10 -3 Tensile modulus of polyimide layer: 8.8GPa Stiffness of polyimide layer: 1.1×10 -8 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 4a: 30.9 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 4a: 62.3 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 4a: 3.0×10 -8 Nm 2 Dimensional change rate in MD direction: -0.008% Dimensional change rate in TD direction: +0.006% Variation in dimensional change rate in MD direction: 0.003% Variation in dimensional change rate in TD direction: 0.003%

[0106] [Example 5] A single-sided metal-clad laminate 5a and a double-sided metal-clad laminate 5 were prepared in the same manner as in Example 2, except that a copper foil 2 having a different thickness (rolled copper foil, thickness: 18 μm, width: 540 mm) was used.

[0107] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 1.4×10 -3 Variation in in-plane birefringence across the width of the polyimide layer [△(△n)]: 0.18×10 -3 Tensile modulus of polyimide layer: 8.4GPa Stiffness of polyimide layer: 1.1×10 -8 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 5a: 22.1 GPa Tensile modulus of elasticity of the metal layer in the single-sided metal-clad laminate 5a: 41.3 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 5a: 2.0×10 -8 Nm 2 Dimensional change rate in MD direction: -0.009% Dimensional change rate in TD direction: +0.004% Variation in dimensional change rate in MD direction: 0.005% Variation in dimensional change rate in TD direction: 0.005%

[0108] [Example 6] A single-sided metal-clad laminate 6a and a double-sided metal-clad laminate 6 were prepared in the same manner as in Example 2, except that a long copper foil 4 (electrolytic copper foil, thickness: 18 μm, width: 1080 mm) was used instead of the copper foil 2, and a resin solution b' in which 3,4,5-trifluorophenylboronic acid was mixed with polyamic acid solution b (mixed so that the amount was 0.1 mol per 1 mol of the structural unit of polyamic acid) was cast so that the thickness after curing would be 33 μm, thereby making the polyimide layer 38 μm thick.

[0109] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 1.3×10 -3 Variation in in-plane birefringence across the width of the polyimide layer [△(△n)]: 0.19×10 -3 Tensile modulus of polyimide layer: 8.9GPa Stiffness of polyimide layer: 4.1×10 -8 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 6a: 21.8 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 6a: 51.9 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 6a: 2.5×10 -8 Nm 2 Dimensional change rate in MD direction: -0.003% Dimensional change rate in TD direction: +0.005% Variation in dimensional change rate in MD direction: 0.004% Variation in dimensional change rate in TD direction: 0.005%

[0110] [Comparative Example 1] Copper foil 5 (copper foil 1 slitted) was laminated on both sides of a commercially available long polyimide film 1 (thickness: 25 μm, width: 250 mm) and thermally pressed to prepare a double-sided metal-clad laminate 7. One of the metal layers of the double-sided metal-clad laminate 7 was removed by etching to prepare a single-sided metal-clad laminate 7b.

[0111] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 3.6×10 -3 Tensile modulus of polyimide layer: 5.5GPa Stiffness of polyimide layer: 7.2×10 -9 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 7b: 24.1 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 7b: 61.0 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 7b: 8.8×10 -9 Nm 2 Dimensional change rate in MD direction: -0.027% Dimensional change rate in TD direction: +0.016% Variation in dimensional change rate in MD direction: 0.005% Variation in dimensional change rate in TD direction: 0.006%

[0112] [Comparative Example 2] A long copper foil 6 (rolled copper foil, thickness: 12 μm, width: 250 mm) was laminated on both sides of a commercially available long polyimide film 2 (thickness: 25 μm, width: 250 mm) and thermally compressed to prepare a double-sided metal-clad laminate 8. In addition, one of the metal layers of the double-sided metal-clad laminate 8 was etched away to prepare a single-sided metal-clad laminate 8b.

[0113] The evaluation results are as follows: Polyimide layer CTE: 17ppm / K In-plane birefringence of polyimide layer (△n): 9.6×10 -3 Tensile modulus of polyimide layer: 5.7GPa Stiffness of polyimide layer: 7.4×10 -9 Nm 2 Tensile modulus of elasticity of single-sided metal-clad laminate 8b: 17.9 GPa Tensile modulus of elasticity of the metal layer in single-sided metal-clad laminate 8b: 44.0 GPa Stiffness of the metal layer in the single-sided metal-clad laminate 8b: 6.3×10 -9 Nm 2 Dimensional change rate in MD direction: -0.017% Dimensional change rate in TD direction: +0.014% Variation in dimensional change rate in MD direction: 0.008% Variation in dimensional change rate in TD direction: 0.008%

[0114] Although the embodiment of the present invention has been described in detail above for the purpose of illustration, the present invention is not limited to the above embodiment, and various modifications are possible. [Explanation of symbols]

[0115] 10... test piece, 20... virtual rectangle, 30... through hole, 30a... center, 100... flexible metal-clad laminate

Claims

1. A flexible metal-clad laminate comprising an insulating resin layer including a single or multiple polyimide layers, and a first metal layer laminated on one surface of the insulating resin layer, The first metal layer includes, in an in-plane direction perpendicular to the thickness direction, a region having an area of ​​at least 100 mm x 100 mm or more as a first circuit processing region for forming a circuit wiring pattern, and satisfies the following conditions (i) to (iii): (i) the insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in a region corresponding to the first metal layer in a thickness direction; －３ That is: (ii) the rigidity of the first metal layer calculated by the following formula (1) is 5.0 × 10 －９ [Nm ２ ] or more, (iii) The rigidity of the insulating resin layer calculated by the following formula (1) is 8.0 × 10 －９ [Nm ２ ] or more, A flexible metal-clad laminate comprising: [0010]

2. a second metal layer on the other surface of the insulating resin layer; The second metal layer includes, in an in-plane direction perpendicular to the thickness direction, a region having an area of ​​at least 100 mm × 100 mm or more as a second circuit processing region for forming a circuit wiring pattern, and the following conditions (iv) to (v) are satisfied: (iv) the insulating resin layer has an in-plane birefringence (Δn) value of 3.0×10 in a region corresponding to the second metal layer in a thickness direction; －３ That is: (v) The rigidity of the second metal layer calculated by the formula (1) is 5.0 × 10 －９ [Nm ２ ] or more, The flexible metal-clad laminate according to claim 1 , which satisfies the above.

3. Furthermore, the following conditions (vi) to (vii) are satisfied: (vi) the thickness of the insulating resin layer is within the range of 23 μm or more and 50 μm or less; (vii) the thickness of the first metal layer and the second metal layer is within the range of 9 μm or more and 25 μm or less; The flexible metal-clad laminate according to claim 2, which satisfies the above.

4. It is long and further meets the following condition (viii): (viii) A flexible metal-clad laminate as described in claim 2, wherein the absolute values ​​of the dimensional change rate in the longitudinal direction (MD direction) and the dimensional change rate in the width direction (TD direction) before and after circuit processing of the first metal layer and the second metal layer are both 0.03% or less.

5. Furthermore, the following condition (ix): (ix) A flexible metal-clad laminate as described in claim 4, in which the variation in the dimensional change rate in the longitudinal direction (MD) and the dimensional change rate in the transverse direction (TD) before and after further heat treatment at 150°C for 60 minutes after circuit processing is 0.005% or less.

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