Multilayer films, metal-clad laminates and circuit boards

Abstract

To improve dielectric characteristics while securing dimensional stability, in a multilayer film having an outer layer part made of multiple polyimide layers on both sides of an inner layer part made of an adhesion layer.SOLUTION: A multilayer film includes a plurality of polyimide layers and an adhesion layer, wherein a) a total thickness of thermoplastic polyimide layers 10A, 10B and non-thermoplastic polyimide layers 20A, 20B laminated on one side of the adhesion layer BS is within a range of 2 μm or more and 20 μm or less, b) a ratio of the elastic modulus parameter of the polyimide layer and the elastic modulus parameter of the adhesion layer satisfies a specific relationship, and c) in the multilayer film as a whole, the dielectric loss tangent at 20 GHz measured with an SPDR resonator is less than 0.0029.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer film, a metal-clad laminate, and a circuit board that are useful as materials for electronic components. [Background technology]

[0002] In recent years, with the progress in miniaturization, weight reduction, and space-saving of electronic devices, there has been an increasing demand for flexible printed circuits (FPCs), which are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Because FPCs allow for three-dimensional, high-density packaging even in limited spaces, their applications are expanding to include wiring for electronic devices such as hard disk drives, DVDs, and smartphones, as well as components such as cables and connectors.

[0003] In addition to increasing density, the advancement of device performance has necessitated the need to accommodate increasingly higher transmission signal frequencies. When transmitting high-frequency signals, high transmission loss along the transmission path can result in inconveniences such as electrical signal loss and long signal delay times. To accommodate increasingly higher transmission signal frequencies, a proposal has been made to improve dielectric properties by interposing a thick adhesive layer between the insulating resin layers of a pair of single-sided metal-clad laminates and using a thermoplastic polyimide derived from dimer acid diamine (DDA), in which the two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups, as the adhesive layer (Patent Document 1). Patent Document 1 specifically discloses a layer structure for the resin portion: thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer / adhesive layer / thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer.

[0004] In order to further improve the dielectric properties in a layer structure such as that of Patent Document 1, it is effective to increase the thickness of the inner layer portion consisting of an adhesive layer with excellent dielectric properties and to reduce the thickness of the outer layer portion consisting of a thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer. However, reducing the thickness of the non-thermoplastic polyimide layer in the outer layer portion reduces the coefficient of thermal expansion (CTE) of the outer layer portion, impairing dimensional accuracy, which has been a bottleneck in further improving the dielectric properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-170417 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to further improve the dielectric properties of a multilayer film having outer layers made of multiple polyimide layers on both sides of an inner layer made of an adhesive layer while maintaining dimensional stability. [Means for solving the problem]

[0007] As a result of extensive research, the inventors have focused on the storage moduli of the inner layer portion and the outer layer portion at a predetermined temperature, and discovered that by controlling the elastic modulus parameters derived from these storage moduli to have a specific relationship, it is possible to increase the proportion of the inner layer portion and reduce the dielectric loss tangent while ensuring the dimensional stability of the multilayer film, thereby completing the present invention. That is, the present invention provides a multilayer film including a plurality of polyimide layers and an adhesive layer, and having the following layer structure (1) or (2): (1) Thermoplastic polyimide layer / non-thermoplastic polyimide layer / adhesive layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, Or, (2) thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer / adhesive layer / thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, The multilayer film of the present invention satisfies the following conditions a) to c): a) The total thickness of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer is within the range of 2 μm to 20 μm, b) satisfying the following formula (i): 65 < P P / P AD < 1,550 …(i) {where P P is the elastic modulus parameter of the polyimide layer, P AD is the elastic modulus parameter of the adhesive layer, and is expressed by the following formulas (ii) to (v); P P =P P1 +P P2 …(ii) P P1 =(E' P100 +E' P200 )×t p1 …(iii) P P2 =(E' P100 +E' P200 )×t p2 …(iv) P AD =(E' AD100 +E' AD200 )×tad …(v) E' P100 : Storage modulus of polyimide layer at 100°C [GPa] E' P200 : Storage modulus of polyimide layer at 200°C [GPa] E' AD100 : Storage modulus of adhesive layer at 100°C [GPa] E' AD200 : Storage modulus of adhesive layer at 200°C [GPa] t p1 : Total thickness [μm] of the thermoplastic polyimide layer and non-thermoplastic polyimide layer laminated on one side of the adhesive layer t p2: Total thickness [μm] of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer tad: adhesive layer thickness [μm] Here, the elastic modulus parameter P of the polyimide layer P is the elastic modulus parameter P calculated by formula (iii) by regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer as one polyimide layer. P1 and the elastic modulus parameter P calculated by formula (iv) regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer as one polyimide layer. P2 The value is obtained by adding up the above. c) The dielectric loss tangent of the entire multilayer film at 20 GHz measured using an SPDR resonator is less than 0.0029; It satisfies the following.

[0008] In the multilayer film of the present invention, the polyimide layer, which is a combination of a thermoplastic polyimide layer and a non-thermoplastic polyimide layer laminated on one side of the adhesive layer, may have a storage modulus of 1.0 GPa or more at 100°C, or a storage modulus of 0.1 GPa or more at 200°C. In addition, in the multilayer film of the present invention, the adhesive layer may have a storage modulus at 100°C of less than 130 MPa, and a storage modulus at 200°C of 40 MPa or less.

[0009] The multilayer film of the present invention has a total thickness of the thermoplastic polyimide layers in the entire multilayer film of T A , the total thickness of the non-thermoplastic polyimide layers is T B , the thickness of the adhesive layer is tad, the following formula (vi); 0.60 ≦ tad / (T A +T B +tad) ≦ 0.99 (vi) The above condition may be satisfied. In the multilayer film of the present invention, the polyimide layer, which is a combination of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer, may have a thermal expansion coefficient in the range of 5 to 35 ppm / K.

[0010] In the multilayer film of the present invention, the adhesive layer may contain a thermoplastic polyimide and a polystyrene elastomer resin, and the content of the polystyrene elastomer resin per 100 parts by weight of the thermoplastic polyimide may be in the range of 10 parts by weight or more and 150 parts by weight or less.

[0011] In the multilayer film of the present invention, the thermoplastic polyimide contained in the adhesive layer may contain acid dianhydride residues derived from an acid dianhydride component and diamine residues derived from a diamine component. In this case, the content of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine formed by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups may be 20 mol % or more relative to the total diamine residues, and the content of diamine residues derived from diamine compounds represented by the following general formula (1) may be within a range of 5 to 50 mol % in total:

[0012] [ka]

[0013] In formula (1), R independently represents a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl group or phenoxy group which may be substituted with a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms; Z independently represents a divalent group selected from -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -COO-, -SO2-, -NH-, or -NHCO-; m1 independently represents an integer of 0 to 4; and m2 independently represents an integer of 0 to 2.

[0014] In the multilayer film of the present invention, the thermoplastic polyimide contained in the adhesive layer may be a crosslinked polyimide in which a ketone group contained in the molecular chain and an amino group of an amino compound having at least two primary amino groups as functional groups form a crosslinked structure via a C=N bond.

[0015] In the multilayer film of the present invention, the thermoplastic polyimide constituting the thermoplastic polyimide layer may contain acid dianhydride residues derived from the acid dianhydride component and diamine residues derived from the diamine component. In this case, the proportion of BPDA residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) to the total acid dianhydride residues may be 40 mol % or more, and the proportion of diamine residues derived from the diamine compound represented by the above general formula (1) to the total diamine residues may be 30 mol % or more.

[0016] In the multilayer film of the present invention, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer may contain acid dianhydride residues derived from the acid dianhydride component and diamine residues derived from the diamine component. In this case, the proportion of acid dianhydride residues having a biphenyl skeleton to all acid dianhydride residues may be 40 mol % or more, and the proportion of diamine residues having a biphenyl skeleton to all diamine residues may be 40 mol % or more.

[0017] The metal-clad laminate of the present invention comprises any of the multilayer films described above and a metal layer laminated on one or both sides of the multilayer film.

[0018] When the metal layer of the metal-clad laminate of the present invention is etched away, the dimensional change rate of the multilayer film after etching may be within ±0.10% based on the multilayer film before etching, and the dimensional change rate after heating at 150°C for 30 minutes may be within ±0.10% based on the multilayer film after etching.

[0019] The circuit board of the present invention is obtained by processing the metal layer of any of the above metal-clad laminates into wiring. [Effects of the Invention]

[0020] By satisfying the conditions a) to c), the multilayer film of the present invention ensures dimensional stability while reducing the thickness of the entire outer layer portion, and improves the dielectric properties of the entire multilayer film. In particular, in the case of condition b, the ratio (P P / P AD ) satisfies the formula (i), and the elastic modulus parameter of the outer layer (P P ) is the elastic modulus parameter of the inner layer (P AD ), the dimensional stability of the entire multilayer film is improved by controlling the thickness of the polyimide layer to be larger within a predetermined range than the thickness of the adhesive layer. The effect of the present invention is particularly effective in a layer structure in which the total thickness or thickness ratio of the outer polyimide layer is relatively small and the thickness or thickness ratio of the adhesive layer is relatively large. Therefore, when applied to circuit boards that transmit high-frequency signals in the GHz band, a metal-clad laminate using the multilayer film of the present invention can achieve reduced transmission loss and improved reliability due to its excellent dimensional stability. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view showing the layer structure of a multilayer film according to a preferred embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the layer structure of a multilayer film according to another preferred embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view showing the layer structure of a metal-clad laminate according to a preferred embodiment of the present invention. [Figure 4] FIG. 2 is a schematic cross-sectional view showing the layer structure of a metal-clad laminate according to another preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. [Multi-layer film] The multilayer film of the present invention comprises a plurality of polyimide layers and an adhesive layer, and has the following layer structure (1) or (2): (1) Thermoplastic polyimide layer / non-thermoplastic polyimide layer / adhesive layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, Or, (2) thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer / adhesive layer / thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, It has.

[0023] FIG. 1 shows a cross-sectional structure of a multilayer film 100 according to one embodiment of the present invention. The multilayer film 100 has a layer structure in which a thermoplastic polyimide layer 10A, a non-thermoplastic polyimide layer 20A, an adhesive layer BS, a non-thermoplastic polyimide layer 20B, and a thermoplastic polyimide layer 10B are laminated in this order. Here, the thermoplastic polyimide layer 10A and the non-thermoplastic polyimide layer 20A, which are the outer layer portions on one side, constitute a first insulating resin layer 40A, and the thermoplastic polyimide layer 10B and the non-thermoplastic polyimide layer 20B, which are the outer layer portions on the other side, constitute a second insulating resin layer 40B. Thus, the multilayer film 100 has a structure in which the first insulating resin layer 40A, which is the outer layer portion, the adhesive layer BS, which is the inner layer portion, and the second insulating resin layer 40B, which is also the outer layer portion, are laminated in this order.

[0024] Unlike the layer configuration of the prior art, the multilayer film 100 has a layer configuration in which only one thermoplastic polyimide layer is laminated in each of the outer layer portions, the first insulating resin layer 40A and the second insulating resin layer 40B. In this way, by making the outer layer portion on one side of the adhesive layer BS a two-layer configuration and concentrating the thermoplastic polyimide layer (thermoplastic polyimide layer 10A or thermoplastic polyimide layer 10B) on each side to one layer, it is possible to reduce the thickness of the outer layer portion while ensuring adhesion to the metal layer when it is laminated on the outside.

[0025] 2 shows a cross-sectional structure of a multilayer film 101 according to another preferred embodiment of the present invention. The multilayer film 101 has a layer structure in which a thermoplastic polyimide layer 10A, a non-thermoplastic polyimide layer 20A, a thermoplastic polyimide layer 30A, an adhesive layer BS, a thermoplastic polyimide layer 30B, a non-thermoplastic polyimide layer 20B, and a thermoplastic polyimide layer 10B are laminated in this order. Here, the thermoplastic polyimide layer 10A, the non-thermoplastic polyimide layer 20A, and the thermoplastic polyimide layer 30A constitute a first insulating resin layer 40A, and the thermoplastic polyimide layer 10B, the non-thermoplastic polyimide layer 20B, and the thermoplastic polyimide layer 30B constitute a second insulating resin layer 40B. Therefore, the multilayer film 101 has a structure in which the first insulating resin layer 40A, the adhesive layer BS, and the second insulating resin layer 40B are laminated in this order.

[0026] 1 and 2, the thermoplastic polyimide layers 10A, 10B, 30A, and 30B may be made of the same or different types of thermoplastic polyimides. The non-thermoplastic polyimide layer 20A and the non-thermoplastic polyimide layer 20B may also be made of the same or different types of non-thermoplastic polyimides. Details of the preferred polyimides used for the first insulating resin layer 40A and the second insulating resin layer 40B will be described later. The first insulating resin layer 40A and the second insulating resin layer 40B may contain, as appropriate, plasticizers, curable resin components such as epoxy resins, curing agents, curing accelerators, organic or inorganic fillers, coupling agents, flame retardants, etc.

[0027] The multilayer films 100 and 101 satisfy the following conditions a) to c). a) The total thickness of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer is within the range of 2 μm to 20 μm. Condition a specifies that, in the configuration example shown in FIG. 1, the total thickness of the thermoplastic polyimide layer 10A and the non-thermoplastic polyimide layer 20A, and the total thickness of the thermoplastic polyimide layer 10B and the non-thermoplastic polyimide layer 20B, which are laminated on one side of the adhesive layer BS, are both within the range of 2 μm to 20 μm. Condition a also specifies that, in the configuration example shown in FIG. 2, the total thickness of the thermoplastic polyimide layer 10A, the non-thermoplastic polyimide layer 20A, and the thermoplastic polyimide layer 30A, and the total thickness of the thermoplastic polyimide layer 10B, the non-thermoplastic polyimide layer 20B, and the thermoplastic polyimide layer 30B, which are laminated on one side of the adhesive layer BS, are both within the range of 2 μm to 20 μm. That is, in FIGS. 1 and 2, the thickness of the first insulating resin layer 40A and the thickness of the second insulating resin layer 40B are both within the range of 2 μm to 20 μm. By setting the thickness of the outer layers, the first insulating resin layer 40A and the second insulating resin layer 40B, within a predetermined range, it is possible to maximize the thickness and thickness ratio of the adhesive layer BS, which has relatively excellent dielectric properties, thereby improving the dielectric properties of the entire multilayer film 100, 101. If the thickness of the first insulating resin layer 40A or the second insulating resin layer 40B is less than 2 μm, adhesion to the metal layer when a metal layer is laminated on the outside may be impaired. If the thickness exceeds 20 μm, it will be difficult to increase the thickness and thickness ratio of the adhesive layer BS, making it difficult to achieve a low dielectric tangent for the entire multilayer film 100, 101. From this perspective, the thickness of the first insulating resin layer 40A and the second insulating resin layer 40B is preferably within the range of 2 μm to 12 μm, more preferably within the range of 2 μm to 8 μm, and most preferably within the range of 2 μm to 5 μm.

[0028] In Figures 1 and 2, the thickness of thermoplastic polyimide layers 10A and 10B is preferably in the range of 0.5 µm or more and 3 µm or less, and more preferably in the range of 1 µm or more and 2 µm or less, from the viewpoint of ensuring sufficient adhesion with a metal layer when the metal layer is laminated on the outside. Furthermore, the thickness of the non-thermoplastic polyimide layers 20A, 20B is preferably in the range of 1 μm or more and 10 μm or less, more preferably 1.5 μm or more and 5 μm or less, from the viewpoint of preventing excessive reduction in the coefficient of thermal expansion (CTE) while ensuring the self-supporting properties of the entire multilayer film 100, 101. In addition, in FIG. 2, the thickness of the thermoplastic polyimide layers 30A and 30B is preferably in the range of 0.5 μm or more and 3 μm or less, more preferably 1 μm or more and 2 μm or less, from the viewpoint of adhesion to the adhesive layer BS and dielectric properties. The thermoplastic polyimide layers 10A, 10B, 30A, and 30B may have the same or different thicknesses, and the non-thermoplastic polyimide layers 20A and 20B may have the same or different thicknesses. Furthermore, the first insulating resin layer 40A and the second insulating resin layer 40B may have the same or different thicknesses.

[0029] b) The following formula (i) is satisfied: 65 < P P / P AD < 1,550 …(i) {where P P is the elastic modulus parameter of the polyimide layer, P AD is the elastic modulus parameter of the adhesive layer, and is expressed by the following formulas (ii) to (v); P P =P P1 +P P2 …(ii) P P1 =(E' P100 +E' P200 )×t p1 …(iii) P P2 =(E' P100 +E' P200 )×t p2 …(iv) P AD =(E' AD100 +E' AD200 )×tad …(v) E' P100 : Storage modulus of polyimide layer at 100°C [GPa] E' P200 : Storage modulus of polyimide layer at 200°C [GPa] E' AD100 : Storage modulus of adhesive layer at 100°C [GPa] E' AD200 : Storage modulus of adhesive layer at 200°C [GPa] t p1 : Total thickness [μm] of the thermoplastic polyimide layer and non-thermoplastic polyimide layer laminated on one side of the adhesive layer t p2 : Total thickness [μm] of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer tad: adhesive layer thickness [μm] Here, the elastic modulus parameter P of the polyimide layer P is the elastic modulus parameter P calculated by formula (iii) by regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer as one polyimide layer. P1 and the elastic modulus parameter P calculated by formula (iv) regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer as one polyimide layer. P2 The value is obtained by adding up the above.

[0030] Condition b is the elastic modulus parameter (P AD ) to the elastic modulus parameter (P P ) ratio (P P / P AD The elastic modulus parameter (P P ) is the product (P P1 ) and the product of the sum of the storage elastic moduli and the thickness of the second insulating resin layer 40B at the same temperature (P P2 ) and the elastic modulus parameter (P AD ) is the product of the thickness and the sum of the storage moduli of the adhesive layer BS at 100°C and 200°C in the process temperature range during thermocompression bonding, for example.

[0031] Here, the ratio of the elastic modulus parameters of the outer layer and the inner layer (P P / P AD The significance of using the index of thermal expansion or contraction is explained below. The residual stress in each layer after thermocompression bonding, which causes dimensional changes before and after etching due to the heat treatment during thermocompression bonding and the etching treatment of the metal layer, is thought to be affected by differences in the storage modulus and thickness of each layer. That is, with regard to the storage modulus of each layer, the storage modulus in the process temperature range is important, and since the storage modulus changes significantly with temperature, the higher the storage modulus, the greater the stress during thermal expansion or thermal contraction. Furthermore, with regard to thickness, it is thought that layers with a large thickness ratio are more likely to affect dimensional changes. Because the adhesive layer BS in the inner layer has superior dielectric properties compared to the polyimide layer, the thickness ratio of the adhesive layer BS is increased to improve the dielectric properties of the entire multilayer film 100, 101. However, in order to achieve a high level of both dimensional stability and dielectric properties, we investigated how to control the optimal balance between the storage modulus and thickness of each layer for both the outer and inner layers. As a result, we calculated a parameter consisting of the sum of the storage modulus at 100°C and 200°C and the product of the thickness as a representative value of the storage modulus in the process temperature range of each layer, and found that the desired dimensional stability can be achieved by controlling the ratio of this parameter within a specified range. Based on this knowledge, we calculated the elastic modulus parameter (P AD ) versus the elastic modulus parameter (P P ) ratio (P P / P AD ) is an index that simply expresses the ratio of the magnitude of residual stress in the outer layer to the magnitude of residual stress in the inner layer using the storage modulus. In order to suppress dimensional changes due to residual stress after thermocompression bonding, the ratio (P P / P AD ) satisfies the formula (i), and the elastic modulus parameter of the outer layer (P P ) is the elastic modulus parameter of the inner layer (P AD ) within a predetermined range, the dimensional stability of the entire multilayer film 100, 101 is improved.

[0032] Assuming that the thickness of the outer layer of condition a is satisfied, the ratio (P P / P AD If the ratio (P) is 65 or less, the dimensional change due to residual stress after thermocompression bonding may become large, which may impair dimensional stability. If it is 1,550 or more, dimensional stability may be maintained, but a low dielectric loss tangent cannot be achieved, making it difficult to satisfy the next condition c. From this perspective, it is necessary to P / P AD The lower limit of the ratio (P) is preferably 70 or more, more preferably 80 or more, and most preferably 90 or more. P / P AD ) is preferably 1200 or less, more preferably 900 or less, and most preferably 500 or less.

[0033] c) The dielectric loss tangent of the entire multilayer film at 20 GHz measured using an SPDR resonator is less than 0.0029. Condition c stipulates that the dielectric loss tangent of the entire multilayer film 100, 101 must be significantly lower than that of the prior art. If the dielectric loss tangent of the entire multilayer film 100, 101 at 20 GHz is less than 0.0029, it is possible to effectively reduce electrical signal loss in the transmission path of high-frequency signals in the GHz band, for example, from 1 GHz to 60 GHz, making it possible to apply the film to circuit boards used in high-speed communications such as 5G communications and beyond. From this perspective, the dielectric loss tangent of the entire multilayer film 100, 101 at 20 GHz is preferably 0.0025 or less, and more preferably 0.0020 or less. From the same viewpoint, the relative dielectric constant of the entire multilayer films 100, 101 at 20 GHz measured using an SPDR resonator is preferably 3.0 or less, and more preferably within the range of 2.9 to 1.5.

[0034] It is preferable that the multilayer films 100 and 101 satisfy at least one of the following conditions d) to g) in addition to the conditions a) to c).

[0035] d) The polyimide layer, which is a combination of a thermoplastic polyimide layer and a non-thermoplastic polyimide layer laminated on one side of the adhesive layer, has a storage modulus of 1.0 GPa or more at 100°C and a storage modulus of 0.1 GPa or more at 200°C. Condition d specifies that the first insulating resin layer 40A and the second insulating resin layer 40B each have a storage modulus of 1.0 GPa or greater at 100°C and a storage modulus of 0.1 GPa or greater at 200°C. Satisfying condition d means that the storage modulus of the outer layer portion is higher than that of the adhesive layer BS, which is the inner layer portion, in the thermocompression bonding temperature range (100°C to 200°C). It is believed that increasing the elastic modulus parameter of the outer layer portion by a certain amount relative to that of the inner layer portion is effective in suppressing dimensional changes due to residual stress after thermocompression bonding. Therefore, by taking into account condition e, which will be described below, the storage modulus of the outer layer portion can be controlled to be higher than that of the inner layer portion, thereby improving the dimensional stability of the entire multilayer film 100, 101. From this perspective, the storage modulus of the first insulating resin layer 40A and the second insulating resin layer 40B at 100°C is preferably in the range of 2 GPa to 10 GPa, more preferably in the range of 3 GPa to 8 GPa. The storage modulus at 200° C. is preferably in the range of 0.5 GPa or more and 8 GPa or less, and more preferably in the range of 1 GPa or more and 5 GPa or less. The storage modulus of the first insulating resin layer 40A and the second insulating resin layer 40B may be the same or different, but is preferably the same from the viewpoint of suppressing warpage.

[0036] e) The adhesive layer has a storage modulus of less than 130 MPa at 100°C and a storage modulus of 40 MPa or less at 200°C. Condition e specifies the storage modulus of the thermoplastic polyimide (hereinafter sometimes referred to as "adhesive polyimide") constituting the adhesive layer BS in the thermocompression temperature range (100°C to 200°C). Satisfying condition e means that the storage modulus is below 130 MPa and not excessively high within the temperature range of 100°C to 200°C. The residual stress after thermocompression, which causes dimensional changes due to etching or heating of the metal layer after laminating an outer metal layer, increases with the storage modulus of the adhesive layer BS at the thermocompression temperature and is also thought to increase with the thickness and thickness ratio of the adhesive layer BS. Therefore, by using a resin whose storage modulus does not increase excessively within the thermocompression temperature range, the residual stress after thermocompression bonding can be reduced and dimensional stability can be ensured even if the thickness and thickness ratio of the adhesive layer BS is increased to a certain extent. From this perspective, the storage modulus of the adhesive layer BS at 100°C is preferably in the range of 0.01 MPa to 100 MPa, and more preferably in the range of 0.1 MPa to 50 MPa. The storage modulus at 200° C. is preferably in the range of 0.01 MPa or more and 30 MPa or less, and more preferably in the range of 0.1 MPa or more and 20 MPa or less.

[0037] f) The total thickness of the thermoplastic polyimide layers in the entire multilayer film is T A , the total thickness of the non-thermoplastic polyimide layers is T B , the thickness of the adhesive layer is tad, and the following formula (vi) is satisfied: 0.60 ≦ tad / (T A +T B +tad) ≦ 0.99 (vi) Condition f is the total thickness of the multilayer film 100, 101 (T A +T B + tad) to the thickness tad of the adhesive layer BS, tad / (T A +T B + tad) is set within a predetermined range. A is the total thickness of the thermoplastic polyimide layers 10A and 10B in FIG. 1 or the total thickness of the thermoplastic polyimide layers 10A, 10B, 30A, and 30B in FIG. 2, and the thickness TB is the total thickness of the non-thermoplastic polyimide layer 20A and the non-thermoplastic polyimide layer 20B. Thickness ratio tad / (T A +T B By making the thickness ratio tad / (T + tad) satisfy the formula (vi), it is possible to achieve a balance between a low dielectric tangent of the entire multilayer film 100, 101 and dimensional stability. A +T B If the thickness ratio tad / (T +tad) is less than 0.60, the thickness ratio of the adhesive layer BS becomes relatively small, making it difficult to achieve a low dielectric tangent for the entire multilayer film 100, 101, and increasing the transmission loss during high-frequency signal transmission. A +T B The lower limit of +tad) is preferably 0.65 or more, more preferably 0.70 or more, and most preferably 0.80 or more. On the other hand, the thickness ratio tad / (T A +T B If the thickness ratio tad / (T + tad) exceeds 0.99, the thickness ratio of the adhesive layer BS becomes too large relatively, making it difficult to ensure adhesion with the metal layer and also making it difficult to maintain the dimensional stability of the entire multilayer film 100, 101. A +T B The upper limit of +tad) is preferably 0.96 or less, more preferably 0.94 or less.

[0038] The total thickness of the multilayer films 100 and 101 (T A +T B +tad) is, for example, preferably in the range of 70 to 500 μm, more preferably in the range of 100 to 300 μm. A +T B If +tad) is less than 70 μm, the effect of suppressing transmission loss of high frequency signals when used in a circuit board will be insufficient, and if it exceeds 500 μm, there is a risk of a decrease in productivity.

[0039] Furthermore, the thickness tad of the adhesive layer BS is preferably greater than 50 μm. The effect of the present invention, namely, achieving both excellent dielectric properties and dimensional stability, is particularly effective in a laminate structure in which the thickness tad of the adhesive layer BS is greater than 50 μm. From this perspective, the thickness tad of the adhesive layer BS is preferably, for example, in the range of more than 50 μm to 450 μm, and more preferably in the range of 60 to 250 μm. If the thickness tad of the adhesive layer BS is less than the above-mentioned lower limit, problems such as an insufficient low dielectric tangent and insufficient dielectric properties may occur. On the other hand, if the thickness tad of the adhesive layer BS exceeds the above-mentioned upper limit, problems such as a decrease in dimensional stability may occur.

[0040] g) The total thickness of the thermoplastic polyimide layers in the entire multilayer film is T A , the total thickness of the non-thermoplastic polyimide layers is T B When 0.1 ≦ (T A ) / (T A +T B ) ≦ 0.6 (vii) Condition g is the sum (T A +T B ) for the total thickness T A The ratio of (T A +T B ) is the total thickness of the entire outer layer portion provided on both sides of the adhesive layer BS (i.e., the total thickness of the first insulating resin layer 40A and the second insulating resin layer 40B). Thus, the total thickness ratio (T A ) / (T A +T B ) satisfies formula (vii), so that even if the thicknesses of the first insulating resin layer 40A and the second insulating resin layer 40B, which are the outer layer portions, are made thinner in accordance with condition a than in the prior art, it is possible to prevent the CTE of the outer layer portions from becoming excessively low, and it is possible to sufficiently ensure adhesion to a metal layer when a metal layer is laminated on the outside.

[0041] The coefficient of thermal expansion (CTE) of the non-thermoplastic polyimide layers 20A, 20B included in the outer layer portion tends to decrease as the thickness decreases. This tendency is particularly noticeable when the non-thermoplastic polyimide layers 20A, 20B are formed by a casting method. The reason for this is thought to be that the thinner the thickness of the coating film is during the heat treatment, the more the solvent volatilizes, and the more the molecules are oriented. Therefore, the thickness ratio (T A ) / (T A +T B If the thickness ratio (T A ) / (T A +T B The lower limit of ) is preferably selected from, for example, 0.17, 0.20, 0.25, 0.30, or 0.40. On the other hand, the thickness ratio (T A ) / (T A +T B If the thickness ratio (T) exceeds 0.6, it may be difficult to maintain the dimensional stability of the entire multilayer film 100, 101, for example, when a metal layer is laminated on the outside and then the metal layer is etched or heat-treated. A ) / (T A +T B The upper limit of ) is preferably 0.55 or less, more preferably 0.50 or less.

[0042] When the multilayer films 100, 101 are used as insulating resin layers of circuit boards, for example, the coefficient of thermal expansion (CTE) of the entire film is preferably in the range of 10 to 30 ppm / K, more preferably in the range of 10 to 25 ppm / K, and most preferably in the range of 10 to 20 ppm / K, in order to prevent warpage and a decrease in dimensional stability. If the CTE is less than 10 ppm / K or more than 30 ppm / K, warpage may occur or dimensional stability may decrease.

[0043] Furthermore, when applied as an insulating resin layer of a circuit board, for example, in order to prevent warping and a decrease in dimensional stability, the coefficient of thermal expansion (CTE) of the first insulating resin layer 40A or the second insulating resin layer 40B laminated on one side of the adhesive layer BS is preferably in the range of 5 to 35 ppm / K, more preferably in the range of 8 to 30 ppm / K, and most preferably in the range of 10 to 25 ppm / K. The coefficient of thermal expansion (CTE) of the first insulating resin layer 40A and the second insulating resin layer 40B may be the same or different, but is preferably the same from the viewpoint of suppressing warpage.

[0044] [Polyimide] Next, the polyimide constituting the first insulating resin layer 40A, the second insulating resin layer 40B, and the adhesive layer BS will be described. In the present invention, the term "polyimide" refers to a resin made of a polymer having an imide group in its molecular structure, such as polyimide, polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc. When a polyimide has a plurality of structural units, they may exist as blocks or randomly, but random existence is preferred. Furthermore, 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 using a dynamic viscoelasticity measuring device (DMA) is 1.0 × 10 9 Pa or more, and the storage modulus at 300°C is 1.0 × 10 8 In addition, "non-thermoplastic polyimide" generally refers to a polyimide that does not soften or exhibit adhesiveness even when heated. In the present invention, however, the "non-thermoplastic polyimide" refers to a polyimide having a storage modulus of 1.0 × 10 Pa at 30°C as measured using a dynamic viscoelasticity measuring device (DMA). 9 Pa or more, and the storage modulus at 300°C is 1.0 × 10 8 This refers to polyimides with a modulus of tensile strength of 100 Pa or more.

[0045] <Thermoplastic polyimide> The thermoplastic polyimide used to form the thermoplastic polyimide layers 10A, 10B, 30A, and 30B in the first insulating resin layer 40A and the second insulating resin layer 40B is obtained by reacting an acid dianhydride component with a diamine component containing an aliphatic diamine and / or an aromatic diamine, and contains an acid dianhydride residue derived from the acid dianhydride component and a diamine residue derived from the diamine component. By selecting the types of acid dianhydride and diamine components, or by selecting the respective molar ratios when two or more types of acid anhydrides or diamines are used, the thermal expansion, adhesiveness, glass transition temperature, and other properties of the thermoplastic polyimide can be controlled. In the present invention, the term "acid dianhydride residue" refers to a tetravalent group derived from an acid dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound.

[0046] The thermoplastic polyimide used to form the thermoplastic polyimide layers 10A, 10B, 30A, and 30B can be made using monomers commonly used in the synthesis of thermoplastic polyimides as the raw acid dianhydride and diamine components, but it is preferable to use aromatic acid dianhydrides and aromatic diamines. Examples of aromatic dianhydrides that can be used preferably include pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, paraphenylenebis(trimellitate anhydride) (TAHQ), and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is the most preferred. In order to reduce the polar group concentration and improve the dielectric properties while ensuring adhesion to the substrate, the thermoplastic polyimide layers 10A, 10B, 30A, and 30B preferably contain BPDA residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) in an amount of 40 mol % or more, and more preferably in the range of 45 to 80 mol %, relative to the total acid dianhydride residues.

[0047] As the aromatic diamine, it is preferable to use a diamine compound represented by the following general formula (1) from the viewpoint of ensuring appropriate flexibility and adhesion to the substrate.

[0048] [ka]

[0049] In general formula (1), R independently represents a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl group or phenoxy group which may be substituted with a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms; Z independently represents a divalent group selected from -O-, -S-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CO-, -COO-, -SO2-, -NH-, or -NHCO-; m1 independently represents an integer of 0 to 4; and m2 independently represents an integer of 0 to 2.

[0050] Examples of the diamine compound represented by general formula (1) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 1,3-bis(3-aminophenoxy)benzene (APB), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene (bisaniline-M), and 4,4'-diaminodiphenyl ether (DAPE).

[0051] In order to ensure adhesion to a metal layer when a metal layer is laminated even when the thickness of the thermoplastic polyimide layers 10A, 10B, 30A, and 30B is thin, the content of diamine residues derived from the diamine compound represented by general formula (1) is preferably 30 mol % or more, more preferably 50 mol % or more, and even more preferably within the range of 70 to 90 mol %, relative to all diamine residues.

[0052] <Non-thermoplastic polyimide> The non-thermoplastic polyimide used to form the non-thermoplastic polyimide layers 20A, 20B in the first insulating resin layer 40A and the second insulating resin layer 40B is obtained by reacting an acid dianhydride component with a diamine component containing an aliphatic diamine and / or an aromatic diamine, and contains an acid dianhydride residue derived from the acid dianhydride component and a diamine residue derived from the diamine component. By selecting the types of the acid dianhydride component and the diamine component, or by selecting the respective molar ratios when two or more types of acid anhydrides or diamines are used, the thermal expansion properties, dielectric properties, and the like of the non-thermoplastic polyimide can be controlled.

[0053] The non-thermoplastic polyimide layers 20A and 20B can be formed using monomers commonly used in the synthesis of non-thermoplastic polyimides as the acid dianhydride and diamine raw materials. However, from the viewpoint of controlling the coefficient of thermal expansion (CTE) of the outer layer portion and ensuring dimensional stability, it is preferable to use an aromatic acid dianhydride having a biphenyl skeleton or an aromatic diamine having a biphenyl skeleton. Examples of aromatic acid dianhydrides having a biphenyl skeleton include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,3',3,4'-biphenyltetracarboxylic dianhydride, with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) being particularly preferable. The non-thermoplastic polyimide layers 20A, 20B control the coefficient of thermal expansion (CTE) of the outer layer portions to ensure the dimensional stability of the entire multilayer film 100, 101, and also increase the storage modulus of the outer layer portions to satisfy condition d. Therefore, the content of dianhydride residues having a biphenyl skeleton relative to the total dianhydride residues is preferably 40 mol % or more, and more preferably within the range of 45 to 70 mol %.

[0054] Furthermore, examples of aromatic diamines having a biphenyl skeleton include 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'-di-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), with 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) being particularly preferred. It can be used.

[0055] The non-thermoplastic polyimide layers 20A, 20B control the coefficient of thermal expansion (CTE) of the outer layer portions to ensure the dimensional stability of the entire multilayer film 100, 101, and also increase the storage modulus of the outer layer portions to satisfy condition d. Therefore, the content of diamine residues having a biphenyl skeleton relative to all diamine residues is preferably 40 mol % or more, and more preferably within the range of 70 to 100 mol %.

[0056] <Adhesive polyimide> The adhesive polyimide, which is a preferred resin constituting the adhesive layer BS, is a thermoplastic polyimide obtained by reacting an acid dianhydride component with a diamine component containing an aliphatic diamine. As the acid dianhydride component serving as the raw material for adhesive polyimide, monomers generally used in the synthesis of thermoplastic polyimides can be used, such as 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylenebis(trimellitic acid monoester anhydride) (TAHQ), and ethylene glycol. Aromatic acid dianhydrides such as bisanhydrotrimellitate (TMEG), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 2,3',3,4'-biphenyltetracarboxylic dianhydride are preferred, with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) being more preferred. The adhesive polyimide preferably contains 40 to 100 mol %, and more preferably 50 to 90 mol %, of acid dianhydride residues derived from one or more of the above aromatic acid dianhydrides relative to the total acid dianhydride residues. More preferably, the total amount of acid dianhydride residues derived from the two aromatic acid dianhydrides is within a range of 40 to 100 mol % relative to the total amount of acid dianhydride residues. Most preferably, the amount of 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) is within a range of 50 to 90 mol %, and the amount of the aromatic acid dianhydrides excluding BTDA is within a range of 10 to 50 mol %.

[0057] As the diamine component serving as the raw material for the adhesive polyimide, a monomer commonly used in the synthesis of thermoplastic polyimides can be used, but it is preferable to use a dimer diamine composition from the viewpoint of controlling the storage modulus of the adhesive layer BS to satisfy condition b and condition e, as well as lowering the dielectric tangent and improving the dielectric properties of the entire multilayer film 100, 101 to satisfy condition c. That is, the adhesive polyimide preferably contains 20 mol% or more, more preferably 50 mol% or more, and most preferably 70 to 100 mol% of diamine residues derived from the dimer diamine composition relative to the total diamine residues. By including the diamine residues derived from the dimer diamine composition in the above amounts, the adhesive layer BS can have a lower glass transition temperature (lower Tg) to improve thermocompression bonding properties, and can also have a lower elastic modulus to alleviate internal stress and improve the dielectric properties of the adhesive layer BS. If the content of diamine residues derived from the dimer diamine composition relative to the total diamine residues is less than 20 mol%, transmission loss during high-frequency transmission may increase, or the adhesive layer BS interposed between the first insulating resin layer 40A and the second insulating resin layer 40B may not have sufficient adhesiveness.

[0058] The dimer diamine composition is a mixture containing the following component (a) as a main component and optionally containing components (b) and (c), and is a purified product in which the amounts of components (b) and (c) are controlled. (a) Dimer diamine (b) Monoamine compounds obtained by substituting the terminal carboxylic acid group of a monobasic acid compound having 10 to 40 carbon atoms with a primary aminomethyl group or an amino group. (c) Amine compounds obtained by substituting the terminal carboxylic acid group of a polybasic acid compound having a hydrocarbon group having 41 to 80 carbon atoms with a primary aminomethyl group or an amino group (excluding the dimer diamine).

[0059] The dimer diamine of component (a) refers to a diamine in which the two terminal carboxylic acid groups (—COOH) of a dimer acid are replaced with primary aminomethyl groups (—CH—NH) or amino groups (—NH). Dimer acids are known dibasic acids obtained by the intermolecular polymerization of unsaturated fatty acids. Their industrial production process is largely standardized in the industry, and they are obtained by dimerizing unsaturated fatty acids with 11 to 22 carbon atoms using a clay catalyst or the like. Industrially obtained dimer acids are primarily composed of a 36-carbon dibasic acid obtained by dimerizing 18-carbon unsaturated fatty acids such as oleic acid, linoleic acid, and linolenic acid. However, depending on the degree of purification, they may contain arbitrary amounts of monomer acid (18 carbon atoms), trimer acid (54 carbon atoms), and other polymerized fatty acids with 20 to 54 carbon atoms. Although double bonds remain after the dimerization reaction, in the present invention, dimer acids that have been further hydrogenated to reduce the degree of unsaturation are also included in the definition of dimer acids. The dimer diamine of component (a) can be defined as a diamine compound obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with a primary aminomethyl group or an amino group.

[0060] Dimer diamine is characterized by its ability to impart properties derived from the dimer acid skeleton. Specifically, because dimer diamine is a macromolecular aliphatic molecule with a molecular weight of approximately 560 to 620, it can increase the molecular molar volume and relatively reduce the polar groups in polyimides. These characteristics of dimer diamine are believed to contribute to improving the dielectric properties of polyimides by reducing their relative dielectric constant and dielectric dissipation factor while suppressing a decrease in their heat resistance. Furthermore, because dimer diamine contains two freely movable hydrophobic chains with 7 to 9 carbon atoms and two linear aliphatic amino groups with a length approaching 18 carbon atoms, it not only imparts flexibility to polyimides but also allows them to have asymmetric or nonplanar chemical structures, thereby potentially lowering the dielectric constant of polyimides.

[0061] The dimer diamine composition used should be one in which the dimer diamine content of component (a) has been increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more, by a purification method such as molecular distillation. By increasing the dimer diamine content of component (a) to 96% by weight or more, the broadening of the molecular weight distribution of the polyimide can be suppressed. If technically possible, it is best for the entire dimer diamine composition (100% by weight) to be composed of component (a) dimer diamine. In addition, the dimer diamine composition preferably has a total area percentage of components (b) and (c) of 4% or less, preferably less than 4%, in a chromatogram obtained by GPC measurement. The area percentage of the chromatogram of component (b) is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less, and the area percentage of the chromatogram of component (c) is preferably 2% or less, more preferably 1.8% or less, and even more preferably 1.5% or less. By achieving these ranges, a rapid increase in the molecular weight of the polyimide can be suppressed, and an increase in the dielectric loss tangent of the resin film over a wide frequency range can be suppressed. Note that components (b) and (c) do not necessarily need to be present in the dimer diamine composition.

[0062] Commercially available dimer diamine compositions are available, such as PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan. When using these commercially available products, they are preferably purified to reduce the amount of components other than dimer diamine, and for example, it is preferable to make the dimer diamine content 96% by weight or more. The purification method is not particularly limited, but known methods such as distillation and precipitation purification are suitable.

[0063] The adhesive polyimide may be made from a diamine compound other than the dimer diamine composition as long as the effect of the invention is not impaired. Preferred examples of diamine compounds that can be used for the adhesive polyimide include the diamine compounds represented by the general formula (1).

[0064] Among the diamine compounds represented by general formula (1), the adhesive polyimide preferably contains, for example, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 1,3-bis(3-aminophenoxy)benzene (APB), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), or the like.

[0065] In order to increase the flexibility of the adhesive layer BS and alleviate residual stress after thermocompression bonding due to the low elastic modulus, the adhesive polyimide preferably contains diamine residues derived from the diamine compound represented by general formula (1) in the range of 5 to 50 mol %, more preferably 10 to 30 mol %, of all diamine residues.

[0066] In adhesive polyimides, the thermal expansion coefficient, glass transition temperature, dielectric properties, etc. can be controlled by selecting the types of acid dianhydride components and diamine components, and when two or more types of acid dianhydrides or diamines are used, by selecting their respective molar ratios.

[0067] The weight-average molecular weight of the adhesive polyimide is preferably in the range of 10,000 to 400,000, more preferably in the range of 20,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the adhesive layer BS tends to decrease and the adhesive layer BS tends to become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and the adhesive layer BS tends to have defects such as uneven thickness and streaks during coating.

[0068] The adhesive polyimide is most preferably a completely imidized structure. However, a portion of the polyimide may be an amic acid. The imidization rate can be determined by measuring the infrared absorption spectrum of the polyimide thin film by the single-reflection ATR method using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) at 1015 cm -1Based on the benzene ring absorber near 1780cm -1 It can be calculated from the absorbance of the C=O stretching derived from the imide group.

[0069] The adhesive polyimide preferably has a glass transition temperature (Tg) of 250°C or less, more preferably in the range of 40°C to 200°C. A Tg of 250°C or less allows thermocompression bonding at low temperatures, thereby alleviating internal stress generated during lamination and suppressing dimensional changes after circuit processing. If the Tg of the adhesive polyimide exceeds 250°C, the temperature required for bonding between the first insulating resin layer 40A and the second insulating resin layer 40B becomes too high, which may impair dimensional stability after circuit processing.

[0070] By using the adhesive polyimide described above, the adhesive layer BS has excellent flexibility and dielectric properties (low dielectric constant and low dielectric loss tangent).

[0071] The adhesive layer BS preferably contains a polystyrene elastomer resin in addition to the adhesive polyimide. The polystyrene elastomer resin is a copolymer of styrene or a derivative thereof with a conjugated diene compound, including its hydrogenated derivative. Examples of styrene or a derivative thereof include, but are not limited to, styrene, methylstyrene, butylstyrene, divinylbenzene, and vinyltoluene. Examples of conjugated diene compounds include, but are not limited to, butadiene, isoprene, and 1,3-pentadiene. The polystyrene elastomer resin is preferably hydrogenated, which further improves its thermal stability and makes it less susceptible to changes such as decomposition and polymerization, and also enhances its aliphatic properties, thereby improving its compatibility with the adhesive polyimide.

[0072] The copolymer structure of the polystyrene elastomer resin may be a block structure or a random structure. Preferred examples of the polystyrene elastomer resin include styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), but are not limited to these.

[0073] The weight-average molecular weight of the polystyrene elastomer resin is, for example, preferably in the range of 50,000 to 300,000, and more preferably in the range of 80,000 to 270,000.If the weight-average molecular weight is lower than the above range, the effect of improving the dielectric properties may be insufficient, while if it is higher, the viscosity of a composition containing an adhesive polyimide and a solvent may become high, making it difficult to produce a resin film. Furthermore, from the viewpoint of significantly lowering the dielectric loss tangent of the resin film, the weight-average molecular weight of the polystyrene elastomer resin is preferably 100,000 or less, more preferably in the range of 50,000 to 100,000, and most preferably in the range of 70,000 to 100,000. By ensuring that the weight-average molecular weight of the polystyrene elastomer resin is 100,000 or less, it is possible to significantly improve the dielectric properties of the resin film.

[0074] The acid value of the polystyrene elastomer resin is preferably 10 mgKOH / g or less, more preferably 1 mgKOH / g or less, and even more preferably 0 mgKOH / g. By incorporating a polystyrene elastomer resin with an acid value of 10 mgKOH / g or less, the dielectric loss tangent of the formed resin film can be reduced and good peel strength can be maintained. On the other hand, if the acid value exceeds 10 mgKOH / g, the increase in polar groups deteriorates the dielectric properties, and compatibility with the adhesive polyimide deteriorates, resulting in poor adhesion when the resin film is formed. Therefore, the lower the acid value, the better, and a polystyrene elastomer that is not acid-modified (i.e., one with an acid value of 0 mgKOH / g) is most suitable. In the present invention, excellent adhesion can be achieved when the adhesive polyimide contains residues derived from aliphatic diamines. Therefore, even when a polystyrene elastomer resin that is not acid-modified (i.e., has strong aliphatic properties) is used, a decrease in adhesive strength can be avoided.

[0075] The polystyrene elastomer resin preferably has a content of styrene units [—CH2CH(C6H5)—] in the range of 10 to 65% by weight, more preferably 20 to 65% by weight, and most preferably 30 to 60% by weight. If the content of styrene units in the polystyrene elastomer resin is less than 10% by weight, the elastic modulus of the resin decreases, making it difficult to handle as a film. If the content exceeds 65% by weight, the resin becomes rigid, making it difficult to use as an adhesive, and the reduced rubber content in the polystyrene elastomer resin leads to poor dielectric properties. Furthermore, by having the styrene unit content within the above range, the proportion of aromatic rings in the resin film is increased, which makes it possible to increase the absorbency in the ultraviolet region when forming via holes (through holes) and blind via holes by laser processing during the process of manufacturing a circuit board using the resin film, thereby further improving laser processability.

[0076] As the polystyrene elastomer resin, commercially available products can be appropriately selected and used. Examples of commercially available polystyrene elastomer resins that can be preferably used include A1535HU (trade name), A1536HU (trade name), G1652MU (trade name), G1726VS (trade name), G1645VS (trade name), FG1901GT (trade name), G1650MU (trade name), G1654HU (trade name), G1730VO (trade name), and MD1653MO (trade name), manufactured by KRATON. Among these, MD1653MO (trade name), G1726VS (trade name), and the like, manufactured by KRATON, are more preferably used, as they have a weight-average molecular weight of 100,000 or less.

[0077] The content of the polystyrene elastomer resin per 100 parts by weight of adhesive polyimide is preferably in the range of 10 to 150 parts by weight, more preferably in the range of 50 to 120 parts by weight. If the content of the polystyrene elastomer resin per 100 parts by weight of adhesive polyimide is less than 10 parts by weight, the effect of reducing the dielectric tangent may not be fully achieved. On the other hand, if the weight ratio of the polystyrene elastomer resin exceeds 150 parts by weight, the adhesiveness of the formed resin film may decrease, and the solids concentration of the composition containing the adhesive polyimide and a solvent may become too high, increasing the viscosity and making it difficult to handle.

[0078] The total content of adhesive polyimide and polystyrene elastomer resin is preferably 60 to 100% by weight, more preferably 80 to 100% by weight, of the total resin components constituting the adhesive layer BS.

[0079] In addition to the polystyrene elastomer resin, the adhesive layer BS may contain, as appropriate, plasticizers, curable resin components such as epoxy resins, curing agents, curing accelerators, organic or inorganic fillers, coupling agents, flame retardants, etc.

[0080] <Synthesis of Polyimide> The thermoplastic polyimides and non-thermoplastic polyimides constituting the first insulating resin layer 40A and the second insulating resin layer 40B, and the adhesive polyimide constituting the adhesive layer BS, can be produced by reacting the above-mentioned acid dianhydride and diamine compound in a solvent to produce polyamic acid, which is then subjected to thermal ring closure. For example, polyamic acid, a polyimide precursor, can be obtained by dissolving approximately equimolar amounts of the acid dianhydride and diamine compound in an organic solvent and stirring at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to cause a polymerization reaction. During the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is in the range of 5 to 50 wt %, preferably 10 to 40 wt %, of 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, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and cresol. 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 solvents is not particularly limited, but it is preferable to adjust the amount so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 50% by weight.

[0081] The synthesized polyamic acid is usually advantageously used as a solution in a reaction solvent, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Polyamic acid is also advantageously used because it generally has excellent solvent solubility. The viscosity of the polyamic acid solution is preferably within the range of 500 mPa·s to 100,000 mPa·s. If the viscosity is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating using a coater or the like.

[0082] The method for imidizing the polyamic acid to form the adhesive polyimide is not particularly limited, and a suitable method is, for example, heat treatment in which the polyamic acid is heated at a temperature in the range of 80 to 400° C. for 0.1 to 24 hours.

[0083] <Crosslinking of adhesive polyimide> When an adhesive polyimide has a ketone group, the ketone group can be reacted with the amino group of an amino compound having at least two primary amino groups as functional groups to form a C=N bond, thereby forming a crosslinked structure. The formation of a crosslinked structure can improve the heat resistance of the adhesive polyimide. Examples of tetracarboxylic acid anhydrides suitable for forming adhesive polyimides having ketone groups include 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), and examples of diamine compounds include aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

[0084] Examples of amino compounds that can be used to crosslink adhesive polyimides include dihydrazide compounds, aromatic diamines, and aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds tend to form crosslinked structures even at room temperature, raising concerns about the storage stability of the varnish. On the other hand, aromatic diamines require high temperatures to form crosslinked structures. When a dihydrazide compound is used, it is possible to achieve both the storage stability of the varnish and a shortened curing time. Examples of dihydrazide compounds include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and diglycerides. Preferred dihydrazide compounds include cholic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridine dioic acid dihydrazide, itaconic acid dihydrazide, etc. The above dihydrazide compounds may be used alone or in combination of two or more.

[0085] When crosslinking an adhesive polyimide, the amino compound is added to a resin solution containing an adhesive polyimide having a ketone group, and a condensation reaction is caused between the ketone group in the adhesive polyimide and the primary amino group of the amino compound. This condensation reaction hardens the resin solution to form a cured product. In this case, the amino compound can be added in such an amount that the total number of primary amino groups per mole of ketone group is 0.004 to 1.5 moles, preferably 0.005 to 1.2 moles, more preferably 0.03 to 0.9 moles, and most preferably 0.04 to 0.5 moles. If the amount of amino compound added is such that the total number of primary amino groups per mole of ketone group is less than 0.004 moles, the crosslinking of the adhesive polyimide by the amino compound will be insufficient, and the adhesive layer BS will tend not to exhibit heat resistance after curing. If the amount of amino compound added is such that the total number of primary amino groups per mole of ketone group is more than 1.5 moles, the unreacted amino compound will act as a thermoplasticizer, tending to reduce the heat resistance of the adhesive layer BS.

[0086] The conditions for the condensation reaction for crosslinking are not particularly limited, as long as they are conditions under which the ketone group in the adhesive polyimide reacts with the primary amino group of the amino compound to form an imine bond (C=N bond). The temperature for the thermal condensation is preferably within the range of, for example, 120 to 220°C, more preferably within the range of 140 to 200°C, for reasons such as discharging water produced by the condensation outside the system or simplifying the condensation step when the thermal condensation reaction is carried out subsequently to the synthesis of the adhesive polyimide. The reaction time is preferably about 30 minutes to 24 hours, and the end point of the reaction can be determined by measuring the infrared absorption spectrum using, for example, a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) at 1670 cm -1 The decrease or disappearance of the absorption peak due to the ketone group in the polyimide resin near 1635 cm -1 This can be confirmed by the appearance of an absorption peak derived from a nearby imine group.

[0087] The thermal condensation of the ketone group of the adhesive polyimide with the primary amino group of the amino compound can be carried out, for example, by (a) adding an amino compound and heating the mixture following the synthesis (imidization) of the adhesive polyimide, (b) charging an excess amount of an amino compound as a diamine component in advance, and then heating the adhesive polyimide together with the remaining amino compound that is not involved in the imidization or amidation following the synthesis (imidization) of the adhesive polyimide, or (c) processing the adhesive polyimide composition to which the amino compound has been added into a predetermined shape (for example, after applying it to any substrate or forming it into a film) and then heating it.

[0088] The formation of imine bonds has been described as a method for forming a crosslinked structure to impart heat resistance to adhesive polyimides, but the present invention is not limited to this. For example, an adhesive polyimide can be cured by blending an epoxy resin, an epoxy resin curing agent, or the like.

[0089] [Metal-clad laminate] The metal-clad laminate of this embodiment includes multilayer films 100, 101 and metal layers laminated on one or both sides of the multilayer films 100, 101.

[0090] 3 shows a cross-sectional configuration of a metal-clad laminate 200 according to a preferred embodiment of the present invention. The metal-clad laminate 200 has a structure in which a metal layer 110A and a metal layer 110B are laminated on both sides of a multilayer film 100. Therefore, the metal-clad laminate 200 has a structure in which the metal layer 110A, the first insulating resin layer 40A, the adhesive layer BS, the second insulating resin layer 40B, and the metal layer 110B are laminated in this order. The metal layer 110A and the metal layer 110B are located on the outermost sides, respectively, with the first insulating resin layer 40A and the second insulating resin layer 40B disposed inside them, and the adhesive layer BS is further disposed between the first insulating resin layer 40A and the second insulating resin layer 40B. A metal-clad laminate 200 having such a layer structure can also be considered to have a structure in which a first single-sided metal-clad laminate (C1) having a metal layer 110A, a thermoplastic polyimide layer 10A, and a non-thermoplastic polyimide layer 20A laminated in that order is bonded to a second single-sided metal-clad laminate (C2) having a metal layer 110B, a thermoplastic polyimide layer 10B, and a non-thermoplastic polyimide layer 20B laminated in that order is bonded together with an adhesive layer BS so that the insulating layer sides face each other.

[0091] FIG. 4 shows a cross-sectional configuration of a metal-clad laminate 201 according to another preferred embodiment of the present invention. The metal-clad laminate 201 has a structure in which a metal layer 110A and a metal layer 110B are laminated on both sides of a multilayer film 101. Therefore, the metal-clad laminate 201 has a structure in which the metal layer 110A, the first insulating resin layer 40A, the adhesive layer BS, the second insulating resin layer 40B, and the metal layer 110B are laminated in this order. The metal layer 110A and the metal layer 110B are located on the outermost sides, respectively, with the first insulating resin layer 40A and the second insulating resin layer 40B disposed inside them, and the adhesive layer BS is further disposed between the first insulating resin layer 40A and the second insulating resin layer 40B. A metal-clad laminate 201 having such a layer structure can also be considered to have a structure in which a first single-sided metal-clad laminate (C1) having a metal layer 110A, a thermoplastic polyimide layer 10A, a non-thermoplastic polyimide layer 20A, and a thermoplastic polyimide layer 30A laminated in that order, and a second single-sided metal-clad laminate (C2) having a metal layer 110B, a thermoplastic polyimide layer 10B, a non-thermoplastic polyimide layer 20B, and a thermoplastic polyimide layer 30B laminated in that order, are bonded together with an adhesive layer BS so that the insulating layer sides face each other.

[0092] The material of the metal layer 110A and the metal layer 110B is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or a copper alloy is particularly preferable. The material of the wiring layer in the circuit board of this embodiment, which will be described later, is also the same as that of the metal layer 110A and the metal layer 110B.

[0093] The thickness of the metal layer 110A and the metal layer 110B is not particularly limited, but when a metal foil such as copper foil is used, it is preferably 35 μm or less, and more preferably in the range of 5 to 25 μm. From the viewpoint of production stability and handling, the lower limit of the thickness of the metal foil is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Furthermore, commercially available copper foil may be used as the copper foil.

[0094] The metal foil may be subjected to a surface treatment using, for example, siding, aluminum alcoholate, aluminum chelate, or a silane coupling agent for the purpose of, for example, rust prevention or improving adhesive strength.

[0095] When metal layers 110A, 110B are removed by etching, it is preferable that the dimensional change rate of multilayer films 100, 101 after etching is within ±0.10% based on multilayer films 100, 101 before etching, and it is also preferable that the dimensional change rate after heating at 150°C for 30 minutes is within ±0.10% based on multilayer films 100, 101 after etching. A dimensional change rate of within ±0.10% after etching and heating means that dimensional change during circuit processing is small, which can improve the reliability of circuit boards such as FPCs. Here, the dimensional change rate can be measured by the following procedure. First, a 150 mm square test piece made from metal-clad laminates 200 and 201 is exposed to and developed at 100 mm intervals to form a position measurement target. After measuring the pre-etching (normal) dimensions in an atmosphere at 23±2°C and 50±5% relative humidity, the copper on the test piece other than the target is removed by etching (liquid temperature 40°C or less, time 10 minutes or less). After leaving the test piece in an atmosphere at 23±2°C and 50±5% relative humidity for 24±4 hours, the post-etching dimensions are measured. The dimensional change rate relative to the normal state at three locations in the MD (longitudinal direction) and TD (transverse direction) is calculated, and the average of these values ​​is used as the post-etching dimensional change rate. The post-etching dimensional change rate can be calculated using the following formula: Dimensional change rate after etching (%) = (BA) / A x 100 A: Target distance before etching B: Target distance after etching Next, the test piece is heated in an oven at 150°C for 30 minutes, and the distance between the target positions is measured after that. The dimensional change rate after etching is calculated at three locations in each of the MD (longitudinal direction) and TD (transverse direction), and the average value of these values ​​is used as the dimensional change rate after heat treatment. The dimensional change rate due to heat can be calculated using the following formula. Heat dimensional change rate (%) = (C-B) / B x 100 B: Target distance after etching C: Target distance after heating

[0096] [Manufacturing of metal-clad laminates] The metal-clad laminates 200, 201 can be manufactured, for example, by the following method 1 or method 2. The adhesive polyimide that forms the adhesive layer BS may be crosslinked as described above. [Method 1] First, a first single-sided metal-clad laminate (C1) and a second single-sided metal-clad laminate (C2) having the layer structure described above are prepared. Next, the adhesive polyimide or its precursor, which will become the adhesive layer BS, is formed into a sheet to form an adhesive sheet. This adhesive sheet is placed between the first insulating resin layer 40A of the first single-sided metal-clad laminate (C1) and the second insulating resin layer 40B of the second single-sided metal-clad laminate (C2), and they are bonded together by thermocompression. [Method 2] First, a first single-sided metal-clad laminate (C1) and a second single-sided metal-clad laminate (C2) are prepared. Next, a solution of the adhesive polyimide or its precursor, which will form the adhesive layer BS, is applied to a predetermined thickness on either the first insulating resin layer 40A of the first single-sided metal-clad laminate (C1) or the second insulating resin layer 40B of the second single-sided metal-clad laminate (C2), or both, and dried to form a coating film. Then, the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) are bonded together by thermocompression on the side of the coating film.

[0097] The first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) used in methods 1 and 2 can be produced, for example, by repeatedly applying and drying a solution of a polyamic acid, which is a precursor of a thermoplastic polyimide or a non-thermoplastic polyimide, onto a metal foil that will become the metal layers 110A and 110B, and then heat-treating it to imidize it. The adhesive sheet used in Method 1 can be produced, for example, by (1) applying a solution of polyamic acid to a supporting substrate, drying the solution, heat-treating it to form an imidization product, and then peeling it off from the supporting substrate to form an adhesive sheet; (2) applying a solution of polyamic acid to a supporting substrate, drying the solution, peeling the polyamic acid gel film from the supporting substrate, and heat-treating it to form an imidization product to form an adhesive sheet; or (3) applying a solution of the adhesive polyimide to a supporting substrate, drying the solution, and then peeling it off from the supporting substrate to form an adhesive sheet. In the above, the method for applying the polyimide solution (or polyamic acid solution) onto the metal foil, supporting substrate, or insulating resin layer is not particularly limited, and it can be applied using, for example, a coater such as a comma, die, knife, or lip coater.

[0098] The metal-clad laminates 200, 201 of this embodiment obtained as described above can be used to manufacture circuit boards such as single-sided FPCs or double-sided FPCs by processing the metal layers 110A and / or 110B into wiring circuits, for example by etching them.

[0099] [Circuit board] Metal-clad laminates 200 and 201 of the present embodiment are useful primarily as circuit board materials for FPCs, rigid-flex circuit boards, etc. That is, by processing one or both of two metal layers 110A and 110B of metal-clad laminates 200 and 201 of the present embodiment into a pattern by a conventional method to form a wiring layer, a circuit board such as an FPC according to one embodiment of the present invention can be manufactured. [Example]

[0100] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, various measurements and evaluations were carried out according to the following methods unless otherwise specified.

[0101] [Measurement of thermal expansion coefficient] A 3mm x 20mm polyimide film was heated at a constant rate of 20°C / min from 30°C to 210°C while applying a 5.0g load using a TMA (trade name: TMA / SS6000, manufactured by Hitachi High-Technologies Corporation). After holding the film at that temperature for 10 minutes, the film was cooled at a rate of 5°C / min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 200°C to 100°C.

[0102] [Storage modulus measurement] The storage modulus was measured on a sample film measuring 5 mm x 20 mm 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 modulus (tan δ) was maximum was taken as the glass transition temperature. Note that the storage modulus at 30°C measured using DMA was 1.0 x 10 9 Pa or more, and the storage modulus at 300°C is 1.0 × 10 8 Those showing a storage modulus of less than 1.0 x 10 Pa are considered "thermoplastic" and have a storage modulus of 1.0 x 10 Pa at 30°C. 9 Pa or more, and the storage modulus at 300°C is 1.0 × 10 8 Those showing a thermal expansion coefficient of 100 Pa or more were categorized as "non-thermoplastic."

[0103] [Measurement of relative permittivity and dielectric loss tangent] The dielectric constant Dk and dielectric loss tangent Df of the resin sheet at 20 GHz were measured using a vector network analyzer (Agilent, product name E8363C) and an SPDR resonator. The material used for the measurement was left for 24 hours under the conditions of temperature: 24 to 26°C and humidity: 45°C to 55%RH.

[0104] [Viscosity measurement] The viscosity was measured at 25°C using an E-type viscometer (Brookfield, product name: DV-II+Pro). The rotation speed was set so that the torque was 10% to 90%, and the viscosity was read when the viscosity stabilized 2 minutes after the start of measurement.

[0105] [Measurement of weight average molecular weight (Mw)] The weight-average molecular weight was measured by gel permeation chromatography (HLC-8220GPC manufactured by Tosoh Corporation). Polystyrene was used as a standard substance, and tetrahydrofuran (THF) was used as a developing solvent.

[0106] [Measurement of dimensional change rate after etching] First, a 150mm square test piece made from a metal-clad laminate is exposed to and developed at 100mm intervals to form a position measurement target. The pre-etching (normal) dimensions are measured in an atmosphere of 23±2°C and 50±5% relative humidity, after which the copper on the test piece other than the target is removed by etching (liquid temperature 40°C or less, time 10 minutes or less). After leaving the test piece in an atmosphere of 23±2°C and 50±5% relative humidity for 24±4 hours, the post-etching dimensions are measured. The dimensional change rate relative to the normal state at three locations in the MD (longitudinal) direction is calculated, and the average of these values ​​is used as the post-etching dimensional change rate. The post-etching dimensional change rate can be calculated using the following formula: Dimensional change rate after etching (%) = (BA) / A x 100 A: Target distance before etching B: Target distance after etching

[0107] [Measurement of dimensional change rate after heating] Next, the test piece whose dimensional change rate after etching was measured was heat-treated in an oven at 150°C for 30 minutes, and the distance between the target positions was then measured. The dimensional change rate after etching was calculated at three locations in the MD (longitudinal) direction, and the average value of these values ​​was used as the dimensional change rate after heat treatment. The dimensional change rate after heating can be calculated using the following formula. Heat dimensional change rate (%) = (C-B) / B x 100 B: Target distance after etching C: Target distance after heating

[0108] The abbreviations used in the examples represent the following compounds. BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene Bisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene NMP: N-methyl-2-pyrrolidone DMAc: N,N-dimethylacetamide BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride DDA: aliphatic diamine having 36 carbon atoms (manufactured by Croda Japan Co., Ltd., trade name: PRIAMINE 1074, amine value: 205 mg KOH / g, mixture of dimer diamines with cyclic and chain structures, dimer content: 95% by weight or more) BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane N-12: Dodecanedioic acid dihydrazide OP935: organic phosphinic acid aluminum salt (manufactured by Clariant Japan, trade name: Exolit OP935) Polystyrene elastomer resin: Kraton, product name: MD1653MO (hydrogenated polystyrene elastomer, styrene unit content: 30% by weight, Mw: 80,499, acid value: none)

[0109] (Synthesis Example 1) <Preparation of polyamic acid solution for insulating resin layer> Under a nitrogen atmosphere, 69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), and DMAc (to a solids concentration of 12 wt%) were added to a reactor and stirred at room temperature. Next, 194.39 g of PMDA (0.891 mol) and 393.31 g of BPDA (1.337 mol) were added and the polymerization reaction was continued with stirring at room temperature for 3 hours to prepare polyamic acid solution 1 (viscosity: 2,700 mPa s). The storage modulus of the polyimide film prepared using polyamic acid solution 1 was 4.3 × 10 at 30 °C. 9 Pa, 9.4 × 10 at 300 °C 7 Pa and was thermoplastic.

[0110] (Synthesis Example 2) <Preparation of polyamic acid solution for insulating resin layer> Under a nitrogen atmosphere, 64.20 g of m-TB (0.302 mol), 5.48 g of bisaniline-M (0.016 mol), and DMAc (to a solids concentration of 15 wt%) were added to a reactor and stirred at room temperature. Next, 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol) were added and the polymerization reaction was continued with stirring at room temperature for 3 hours to prepare polyamic acid solution 2 (viscosity: 28,000 mPa s). The storage modulus of the polyamic acid solution 2 was 7.0 × 10 at 30 °C. 9 Pa, 5.4 × 10 at 300 °C 8 Pa and was non-thermoplastic.

[0111] (Synthesis Example 3) <Preparation of resin solution for adhesive layer> A 500 ml separable flask was charged with 21.34 g of BTDA (0.06622 mol), 12.99 g of BPDA (0.04414 mol), 46.7042 g of DDA (0.08741 mol), 8.97104 g of BAPP (0.02185 mol), 126 g of NMP, and 84 g of xylene, and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. This polyamic acid solution was heated to 190 °C and stirred for 5 hours. 65 g of xylene was added to complete the imidization, preparing Polyimide Solution 1 (solids content: 31 wt%, weight average molecular weight: 35,886, viscosity: 2,580 mPa s).

[0112] (Production Example 1) <Preparation of Resin Sheet for Adhesive Layer> Polyimide varnish 1 was prepared by blending 0.46 g of N-12, 2.54 g of OP935, and 7.62 g of polystyrene elastomer resin with 40.97 g of polyimide solution 1 (12.7 g as solid content), and diluting with 45.23 g of xylene.

[0113] Polyimide varnish 1 was applied to the silicone-treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying would be 50 μm, and then the coating was dried by heating at 80°C for 15 minutes and peeled off from the release substrate to prepare resin sheet 1. The storage modulus properties of resin sheet 1 are as follows: Storage modulus (25°C): 901 MPa Storage modulus (100°C): 5.0 MPa Storage modulus (200°C): 2.0 MPa

[0114] (Production Example 2) <Preparation of single-sided metal-clad laminate> Polyamic acid solution 1 was uniformly applied to copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) to a thickness of approximately 1.6 μm after curing, and then heated and dried at 120°C to remove the solvent. Next, polyamic acid solution 2 was uniformly applied thereon to a thickness of approximately 2.4 μm after curing, and then heated and dried at 120°C to remove the solvent. Further, stepwise heat treatment from 120°C to 360°C was performed to complete the imidization, and a single-sided metal-clad laminate 1 was prepared.

[0115] (Examples 3-4) Single-sided metal-clad laminates 2 and 3 were prepared in the same manner as in Preparation Example 2, except that the thicknesses of polyamic acid solution 1 and polyamic acid solution 2 after curing were changed as shown in Table 1.

[0116] [Table 1]

[0117] (Production Example 5) Polyamic acid solution 1 was uniformly applied to copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) to a thickness of approximately 2 μm after curing, and then heated and dried at 120 ° C to remove the solvent. Next, polyamic acid solution 2 was uniformly applied thereon to a thickness of approximately 21 μm after curing, and then heated and dried at 120 ° C to remove the solvent. Further, polyamic acid solution 1 was uniformly applied thereon to a thickness of approximately 2 μm after curing, and then heated and dried at 120 ° C to remove the solvent. Further, stepwise heat treatment from 120 ° C to 360 ° C was performed to complete the imidization, and a single-sided metal-clad laminate 4 was prepared.

[0118] <Preparation of Polyimide Film> The copper foil layers of single-sided metal-clad laminates 1 to 4 were etched away using an aqueous ferric chloride solution to prepare polyimide films 1 to 4. The thermal expansion coefficient and storage modulus of the polyimide layers were measured using the prepared polyimide films 1 to 4. The results are shown in Table 2 or Table 3.

[0119] [Example 1] Polyimide varnish 1 was applied to the insulating resin layer side of single-sided metal-clad laminate 1 so that the thickness after drying was 46 μm, and then dried by stepwise heat treatment from 80°C to 200°C to prepare single-sided metal-clad laminate 1 with an adhesive layer. Two single-sided metal-clad laminates 1 with adhesive layers were prepared, laminated with the adhesive layer sides facing each other, and pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare metal-clad laminate 1. The copper foil layer of metal-clad laminate 1 was also etched away to obtain multilayer film 1. Dimensional change rate was measured using metal-clad laminate 1, and dielectric properties and thermal expansion coefficient were measured using multilayer film 1.

[0120] [Examples 2 to 3] Metal-clad laminates 2 to 3 and multilayer films 2 to 3 were prepared in the same manner as in Example 1, except that the dried thickness of polyimide varnish 1 was changed to 37.5 μm and single-sided metal-clad laminate 1 was changed to single-sided metal-clad laminates 2 and 3.

[0121] The layer structures and evaluation results of the produced metal-clad laminates 1 to 3 and multilayer films 1 to 3 are shown in Table 2. In Table 2, the total thickness of the thermoplastic polyimide layers is T A , the total thickness of the non-thermoplastic polyimide layers is T B、 The thickness of the adhesive layer is designated as tad.

[0122] [Table 2]

[0123] (Comparative Example 1) Fluororesin sheets (manufactured by Asahi Glass Co., Ltd., product name: Adhesive Perfluororesin EA-2000) with thicknesses of 50 μm and 25 μm and two single-sided metal-clad laminates 2 were prepared, and the two fluororesin sheets were laminated so as to be sandwiched between the insulating resin layer sides of the two single-sided metal-clad laminates 2, and pressed together at 320°C for 5 minutes under a pressure of 3.5 MPa to prepare metal-clad laminate 4. The evaluation results of metal-clad laminate 4 and multilayer film 4 after copper foil removal are shown in Table 3.

[0124] (Comparative Example 2) Two single-sided metal-clad laminates 4 were prepared, and the insulating resin layer side of each was overlapped on both sides of resin sheet 1, and the laminates were pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare metal-clad laminate 5. Table 3 shows the evaluation results of metal-clad laminate 5 and multilayer film 5 after copper foil removal.

[0125] (Comparative Example 3) Metal-clad laminate 6 was prepared in the same manner as in Comparative Example 2, except that a fluororesin sheet (manufactured by Asahi Glass Co., Ltd., product name: Adhesive Perfluoro Resin EA-2000, thickness: 50 μm) was used instead of resin sheet 1 and pressure-bonded at 320°C for 5 minutes under a pressure of 3.5 MPa. The evaluation results of metal-clad laminate 6 and multilayer film 6 after copper foil removal are shown in Table 3.

[0126] [Table 3]

[0127] A comparison of Comparative Examples 1 and 3 shows that when the inner layer has a high storage modulus at high temperatures, the thinner the outer polyimide layer, the more significantly the dimensional stability deteriorates. Furthermore, a comparison of Comparative Example 1 and Example 2 shows that the application of an adhesive layer with low elasticity at room temperature results in a greater deterioration in dimensional stability, demonstrating that the storage modulus at the process temperature range, rather than at room temperature, is important for ensuring dimensional stability. From the above results, in a configuration in which a dimension control layer is provided as an outer layer and a low dielectric layer is provided as an inner layer, in order to make the outer layer thin and achieve a low dielectric constant as a laminated film, it is important to control the thickness balance of each layer and the storage modulus of the inner layer in the processing temperature range within a predetermined range.

[0128] Specifically, the index (P P / P AD In Comparative Example 1, P P / P AD Since the thickness is too small, the influence of the adhesive layer is strong, resulting in a deterioration in the dimensions. In order to ensure sufficient dimensional stability, a thickness (P) exceeding that of Comparative Example 3 and at least equal to that of Example 1 is required. P / P AD ) is required. Also, as in Comparative Example 2, (P P / P AD If the dimensional stability is ensured, the dielectric properties will be deteriorated due to the excessive thickness of the polyimide layer.

[0129] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible. [Explanation of symbols]

[0130] 10A, 10B, 30A, 30B...thermoplastic polyimide layers, 20A, 20B...non-thermoplastic polyimide layers, 100, 101...multilayer films, 110A, 110B...metal layers, 200, 201...metal-clad laminates, BS...adhesive layers

Claims

1. A multilayer film comprising a plurality of polyimide layers and an adhesive layer, The following layer structure (1) or (2): (1) thermoplastic polyimide layer / non-thermoplastic polyimide layer / adhesive layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, Or, (2) thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer / adhesive layer / thermoplastic polyimide layer / non-thermoplastic polyimide layer / thermoplastic polyimide layer, and The following conditions a) to c) are met: a) the total thickness of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer is in the range of 2 μm to 20 μm; b) satisfying the following formula (i): 65 < P Ｐ / P ＡＤ < 1,550 …(i) {where P Ｐ is the elastic modulus parameter of the polyimide layer, P ＡＤ is the elastic modulus parameter of the adhesive layer, and is expressed by the following equations (ii) to (v): P Ｐ =P Ｐ１ +P Ｐ２ …(ii) P Ｐ１ =(E' Ｐ１００ +E' Ｐ２００ )×t ｐ１ …(iii) P Ｐ２ =(E' Ｐ１００ +E' Ｐ２００ )×t ｐ２ …(iv) P ＡＤ =(E' ＡＤ１００ +E' ＡＤ２００ )×tad …(v) E' Ｐ１００ : Storage modulus of polyimide layer at 100 ° C [GPa] E' Ｐ２００ : Storage modulus of polyimide layer at 200 ° C [GPa] E' ＡＤ１００ : Storage modulus of adhesive layer at 100 ° C [GPa] E' ＡＤ２００ : Storage modulus of adhesive layer at 200 ° C [GPa] t ｐ１ : Total thickness [μm] of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer t ｐ２ : Total thickness [μm] of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer tad: adhesive layer thickness [μm] Here, the elastic modulus parameter P of the polyimide layer is expressed as Ｐ is the elastic modulus parameter P calculated by formula (iii) by regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer as one polyimide layer. Ｐ１ and the elastic modulus parameter P calculated by formula (iv) regarding the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on the other side of the adhesive layer as one polyimide layer. Ｐ２ It is the value obtained by adding up the above. c) the multilayer film as a whole has a dielectric loss tangent at 20 GHz measured using an SPDR resonator of less than 0.0029; A multilayer film characterized by satisfying the above.

2. 2. The multilayer film according to claim 1, wherein the polyimide layer, which is a combination of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer, has a storage modulus of 1.0 GPa or more at 100°C and a storage modulus of 0.1 GPa or more at 200°C.

3. 3. The multilayer film according to claim 1, wherein the adhesive layer has a storage modulus of less than 130 MPa at 100°C and a storage modulus of 40 MPa or less at 200°C.

4. The total thickness of the thermoplastic polyimide layers in the entire multilayer film is T Ａ , the total thickness of the non-thermoplastic polyimide layer is T Ｂ , the thickness of the adhesive layer is represented by the following formula (vi): 0.60 ≦ tad / (T Ａ +T Ｂ +tad) ≦ 0.99 ・・・(we) The multilayer film according to any one of claims 1 to 3, which satisfies the above.

5. 5. The multilayer film according to claim 1, wherein the polyimide layer, which is a combination of the thermoplastic polyimide layer and the non-thermoplastic polyimide layer laminated on one side of the adhesive layer, has a thermal expansion coefficient in the range of 5 to 35 ppm / K.

6. 6. The multilayer film according to claim 1, wherein the adhesive layer contains a thermoplastic polyimide and a polystyrene elastomer resin, and the content of the polystyrene elastomer resin per 100 parts by weight of the thermoplastic polyimide is in the range of 10 parts by weight or more and 150 parts by weight or less.

7. 7. The multilayer film according to claim 6, wherein the thermoplastic polyimide contained in the adhesive layer contains acid dianhydride residues derived from an acid dianhydride component and diamine residues derived from a diamine component, and the content of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine obtained by substituting two terminal carboxylic acid groups of a dimer acid with primary aminomethyl groups or amino groups is 20 mol % or more relative to the total diamine residues, and the content of diamine residues derived from diamine compounds represented by the following general formula (1) is within the range of 5 to 50 mol % in total: 【Chemistry 1】 [In formula (1), R independently represents a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl group or phenoxy group which may be substituted with a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms; Z independently represents -O-, -S-, -CH ２ -, -CH(CH ３ )-, -C(CH ３ ) ２ -, -CO-, -COO-, -SO ２ represents a divalent group selected from -, -NH-, or -NHCO-, m １ are independently integers from 0 to 4, m ２ represents an integer of 0 to 2.]

8. 8. The multilayer film according to claim 6 or 7, wherein the thermoplastic polyimide contained in the adhesive layer is a crosslinked polyimide in which a ketone group contained in the molecular chain and an amino group of an amino compound having at least two primary amino groups as functional groups form a crosslinked structure via a C=N bond.

9. 9. The multilayer film according to claim 1, wherein the thermoplastic polyimide constituting the thermoplastic polyimide layer contains acid dianhydride residues derived from an acid dianhydride component and diamine residues derived from a diamine component, and the proportion of BPDA residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to all acid dianhydride residues is 40 mol % or more, and the proportion of diamine residues derived from a diamine compound represented by the following general formula (1) relative to all diamine residues is 30 mol % or more: 【Chemistry 2】 [In formula (1), R independently represents a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl group or phenoxy group which may be substituted with a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms; Z independently represents -O-, -S-, -CH ２ -, -CH(CH ３ )-, -C(CH ３ ) ２ -, -CO-, -COO-, -SO ２ represents a divalent group selected from -, -NH-, or -NHCO-, m １ are independently integers from 0 to 4, m ２ represents an integer of 0 to 2.]

10. 10. The multilayer film according to claim 1, wherein the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains acid dianhydride residues derived from the acid dianhydride component and diamine residues derived from the diamine component, and the proportion of acid dianhydride residues having a biphenyl skeleton relative to all acid dianhydride residues is 40 mol % or more, and the proportion of diamine residues having a biphenyl skeleton relative to all diamine residues is 40 mol % or more.

11. A metal-clad laminate comprising the multilayer film according to any one of claims 1 to 10 and a metal layer laminated on one or both sides of the multilayer film.

12. A metal-clad laminate as described in claim 11, wherein when the metal layer is etched and removed, the dimensional change rate of the multilayer film after etching is within ±0.10% based on the multilayer film before etching, and the dimensional change rate after heating at 150°C for 30 minutes is within ±0.10% based on the multilayer film after etching.

13. A circuit board obtained by processing the metal layer of the metal-clad laminate according to claim 11 or 12 into wiring.

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