Laminated film, laminate for substrate, circuit board, and electronic device

Abstract

To provide a material which is excellent in low hygroscopicity, adhesion to a copper foil, dimensional stability, toughness and dielectric characteristics, and is useful for high speed communication.SOLUTION: A laminated film has at least A layer and B layer, wherein each of the A layer and the B layer are composed of a resin having a melting point of 250°C or higher and a dielectric loss tangent at a frequency of 10 GHz of 0.006 or less, and the A layer contains an inorganic filler.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate film, a substrate laminate using the laminate film, a circuit board using the substrate laminate, and an electronic device including the circuit board. [Background technology]

[0002] In recent years, mobile information and communication devices such as multi-function mobile phones and tablet terminals are required to send and receive large amounts of data at high speeds, and efforts are being made to increase the frequency of electrical signals. In particular, in the field of mobile information and communication, studies are underway on the fifth-generation mobile communication system (5G). In contrast, conventional circuit boards are designed primarily for communications using low-frequency bands, and therefore have high values ​​for dielectric constant and dielectric loss tangent. The higher the dielectric constant, the greater the propagation delay of electrical signals. Therefore, a lower dielectric constant is preferable to increase the propagation speed of electrical signals and enable high-speed calculations. Furthermore, the dielectric loss tangent (tan δ) indicates the amount of electrical signal propagating through a dielectric that is converted into heat and lost. Therefore, the lower the value, the less signal loss there is and the better the electrical signal transmission rate.

[0003] As described above, circuit boards used in high-frequency bands are preferably manufactured from materials with lower relative dielectric constants and dielectric loss tangents than conventional materials to enable large-capacity, high-speed communication. In light of this, thermosetting polyimide resins and liquid crystal polymers are attracting attention as materials with low relative dielectric constants and dielectric loss tangents. Also, polyarylene ether ketone resins have been proposed, which are said to exhibit excellent low dielectric properties in the frequency range of 800 MHz to 100 GHz, and also to have excellent dimensional stability when inorganic fillers are added (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 213527 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, examples of materials for 5G mobile information communications include polyimide resins and liquid crystal polymers, but thermosetting polyimide resins have the problem of being highly hygroscopic, and liquid crystal polymers have poor adhesion to copper foil when forming circuit boards and problems with supply stability. Furthermore, the polyarylene ether ketone resin described in Patent Document 1 has excellent low dielectric properties and heat resistance, and the addition of an inorganic filler improves dimensional stability, but the addition of an inorganic filler reduces toughness. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a material that has low moisture absorption, dimensional stability, toughness, and excellent dielectric properties, and is particularly useful for high-speed communications. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the inventors discovered that the above-mentioned problems could be solved by using a specific resin containing an inorganic filler as the intermediate layer and specific resins as the front and back layers, and thus completed the present invention.

[0007] That is, the gist of the present invention has the following aspects. [1] A laminated film having at least Layer A and Layer B, wherein each of Layer A and Layer B contains a resin having a melting point of 250°C or higher and a dielectric loss tangent of 0.006 or less at a frequency of 10 GHz, and Layer A contains an inorganic filler. [2] The laminated film according to [1] above, wherein the resin is one or more selected from the group consisting of polyarylene ether ketone resin, thermoplastic polyimide resin, polyetherimide resin and liquid crystal polymer. [3] The laminated film according to [1] or [2] above, wherein the inorganic filler is one or a mixture of two or more selected from the group consisting of silica, mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, titanium dioxide, potassium titanate, lithium titanate, boehmite, and alumina. [4] The laminated film according to any one of the above [1] to [3], wherein the inorganic filler is contained in the resin composition constituting the layer A in an amount of 5% by mass or more. [5] The laminated film according to any one of the above [1] to [4], which is a laminated film of three or more layers, wherein the A layer is an intermediate layer and the B layer is an outermost layer. [6] The laminated film according to any one of the above [1] to [5], wherein the thickness ratio of the layer A to the layer B is 90:10 to 10:90. [7] The laminated film according to any one of the above [1] to [6], which has a relative dielectric constant of 4.0 or less and a dielectric loss tangent of 0.006 or less at a frequency of 12 GHz. [8] The laminated film according to any one of the above [1] to [7], which has a thermal dimensional change rate of -3.0% or more and 3.0% or less when heated to 200°C. [9] The laminated film according to any one of the above [1] to [8], which has a water absorption rate of 1.0% or less.

[10] The laminated film according to any one of the above [1] to [9], which has a relative crystallinity of 50% or more.

[11] The laminated film according to any one of the above [1] to

[10] , wherein the inorganic filler comprises a plate-like inorganic filler.

[12] The laminated film according to any one of the above [1] to

[11] , wherein the inorganic filler has an average aspect ratio of 10 or more.

[13] The laminated film according to any one of the above [1] to

[12] , wherein the inorganic filler has an average maximum diameter of 30 μm or more.

[14] The laminated film according to any one of the above [1] to

[13] , wherein the inorganic filler has an average thickness of 1 μm or less.

[15] The laminate film according to any one of the above [1] to

[14] , which is a cover film or a base film for a substrate.

[16] A laminated film for substrates having at least Layer A and Layer B, wherein Layer A and Layer B each contain a resin having a melting point of 250°C or higher and a dielectric loss tangent of 0.006 or less at a frequency of 10 GHz, and Layer A contains an inorganic filler.

[17] A laminate for a substrate, comprising the laminate film according to any one of the above [1] to

[15] and a copper foil.

[18] A circuit board comprising a conductive circuit formed on the substrate laminate according to

[17] above.

[19] An electronic device comprising the circuit board described in

[18] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a material that is useful for high-speed communications, having low moisture absorption, excellent adhesion to copper foil, dimensional stability, toughness, and dielectric properties. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below, but is not limited to the embodiments described below. Unless otherwise specified, the notation "A to B" for numerical values ​​A and B means "A or more and B or less." In such notation, when a unit is added only to numerical value B, the unit also applies to numerical value A.

[0010] [Laminated film] The laminated film of the present invention is a laminated film having at least Layer A and Layer B, each of which is made of a resin having a melting point of 250°C or higher and a dielectric dissipation factor of 0.006 or less at a frequency of 10 GHz, and which is characterized in that Layer A contains an inorganic filler. If the melting point of the resin is less than 250°C, circuit formation cannot be easily performed during the production of a high-frequency circuit board, and problems such as deformation of the resin film and the occurrence of wrinkles occur. From the above viewpoints, the melting point (crystalline melting temperature) of the resin is preferably 280°C or higher, more preferably 300°C or higher, and particularly preferably 320°C or higher. There is no particular upper limit to the melting point, and it is usually 450°C or lower.

[0011] Furthermore, the dielectric loss tangent of the resin at a frequency of 10 GHz is 0.006 or less. If the dielectric loss tangent exceeds 0.006, the loss of electrical signals propagating within the dielectric increases, reducing the signal transmission rate and making large-capacity communication difficult. From the above perspectives, the dielectric loss tangent at a frequency of 10 GHz is preferably 0.005 or less, and more preferably 0.003 or less. There are no particular restrictions on the lower limit, but in practice it is 0.00001 or more.

[0012] The dielectric constant of the resin constituting the laminated film of the present invention at a frequency of 10 GHz is preferably 4.0 or less. When the dielectric constant is 4.0 or less, a sufficient propagation speed of an electric signal can be obtained. From the above viewpoint, the dielectric constant is more preferably 3.5 or less, and even more preferably 3.2 or less. The lower limit is not particularly limited, but is usually 0.1 or more.

[0013] Furthermore, the relative crystallinity of the laminated film of the present invention is preferably 50% or more. When the relative crystallinity is 50% or more, the film has excellent solder heat resistance. From the above viewpoint, the relative crystallinity is more preferably 60% or more.

[0014] In the laminated film of the present invention, it is preferable that Layer B be the outermost layer. The laminated film is preferably a laminated film of three or more layers, with Layer A being the middle layer and Layer B being the outermost layers on both sides of Layer A. The resin constituting the laminated film of the present invention may be the same or different resins for the intermediate layer (layer A) and the outermost layer (layer B) as long as they have the above-mentioned physical properties.Furthermore, the front and back layers constituting the outermost layer may be the same or different resins as long as they have the above-mentioned physical properties.

[0015] The laminated film of the present invention contains an inorganic filler in Layer A (intermediate layer). By containing an inorganic filler in Layer A (intermediate layer), dimensional stability is improved. On the other hand, by containing an inorganic filler, toughness and tenacity are reduced. In contrast, it is preferable that the laminated film of the present invention contains an inorganic filler only in Layer A (intermediate layer) and does not contain an inorganic filler in Layer B (outermost layer; if present on both the front and back surfaces, both outermost layers). By adopting such a configuration, it is possible to maintain good dimensional stability, improve toughness and toughness, and obtain good dielectric properties. However, Layer B (outermost layer) may contain an inorganic filler to the extent that it does not impair the effects of the present invention. Specifically, for example, the inorganic filler may be contained in an amount of 10% by mass or less, preferably 8% by mass or less, and more preferably 5% by mass or less. The inorganic filler is one or a mixture of two or more selected from the group consisting of silica, mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, titanium dioxide, potassium titanate, lithium titanate, boehmite, and alumina.

[0016] The content of the inorganic filler in the intermediate layer (Layer A) is preferably 5% by mass or more in the resin composition constituting the intermediate layer. When the content is 5% by mass or more, good toughness and toughness can be obtained. From the above viewpoints, the content of the inorganic filler is more preferably 8% by mass or more, and even more preferably 10% by mass or more. There is no particular upper limit to the content of the inorganic filler as long as it is within a range in which the effects of the present invention are achieved, but it is usually 50% by mass or less, preferably 45% by mass or less, and more preferably 40% by mass or less, and in particular, by setting it to 35% by mass or less, the number of folding cycles that can be endured is dramatically improved.

[0017] The ratio of the thickness of the intermediate layer (A layer) to the thickness of the outermost layer (B layer) is preferably in the range of 90:10 to 10:90. Within this range, a good balance between dimensional stability, toughness, and toughness is achieved, and good dielectric properties are also obtained. From the above perspectives, the ratio of the thickness of the intermediate layer to the outermost layer is more preferably in the range of 85:15 to 30:70. The thickness of the outermost layer referred to here is the total thickness of the outermost layers when layers B are provided on both the front and back surfaces.

[0018] The laminated film of the present invention preferably has a relative dielectric constant of 4.0 or less at a frequency of 12 GHz. When the relative dielectric constant is 4.0 or less, a sufficient propagation speed of an electric signal can be obtained. From the above viewpoints, the relative dielectric constant is more preferably 3.5 or less, and even more preferably 3.2 or less. The lower limit is not particularly limited, but is usually 3.0 or more. Furthermore, the laminated film of the present invention preferably has a dielectric loss tangent of 0.006 or less at a frequency of 12 GHz. When the dielectric loss tangent is 0.006 or less, the loss of electrical signals propagating within the dielectric is small, a high signal transmission rate can be maintained, and high-capacity communication becomes possible. From the above viewpoints, the dielectric loss tangent at a frequency of 12 GHz is preferably 0.005 or less, and more preferably 0.003 or less. The lower limit is not particularly limited, but in practice it is 0.0001 or more.

[0019] The laminated film of the present invention preferably has a thermal dimensional change rate of -3.0% or more and 3.0% or less when heated to 200°C. If the thermal dimensional change rate is within this range, the film will have excellent operational stability when used as an electronic device. From the above viewpoints, the thermal dimensional change rate is more preferably -2.5% or more and 2.5% or less.

[0020] (Water absorption rate) The water absorption rate of the laminate film according to the present invention is preferably 1.0% or less. When the water absorption rate of the laminate film is 1.0% or less, peeling of the copper foil from the laminate film is easily prevented. Furthermore, migration resistance is improved, making it easier to prevent the occurrence of short circuits. From the above viewpoints, the water absorption rate of the laminate film is preferably 0.9% or less, more preferably 0.87% or less, even more preferably 0.85% or less, and particularly preferably 0.82% or less. As shown in the examples, the water absorption rate can be measured by cutting a test piece from the laminate film, immersing it in water at 23°C for 24 hours, and then measuring the change in mass between before and after immersion.

[0021] <Resin> The resin constituting the laminated film of the present invention is not particularly limited as long as it has a melting point of 250°C or higher and a dielectric loss tangent of 0.006 or less at a frequency of 10 GHz. Specific examples include polyarylene ether ketone resin, polyetherimide resin, thermoplastic polyimide resin, and liquid crystal polymer. These resins may be used singly or in combination of two or more.

[0022] <Polyarylene ether ketone resin> Polyarylene ether ketone resins are crystalline resins consisting of arylene groups, ether groups, and carbonyl groups. Specific examples include polyether ether ketone (PEEK) resins represented by chemical formula (1), polyether ketone (PEK) resins represented by chemical formula (2), polyether ketone ketone (PEKK) resins represented by chemical formula (3), polyether ether ketone ketone (PEEKK) resins represented by chemical formula (4), and polyether ketone ether ketone ketone (PEKEKK) resins represented by chemical formula (5).

[0023] [ka]

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] Among the above polyarylene ether ketone resins, polyether ether ketone (PEEK) resin and polyether ketone (PEK) resin are preferred from the viewpoints of availability, production cost, and moldability, and polyether ether ketone (PEEK) resin is particularly preferred. The polyarylene ether ketone resin may be used alone or in combination of two or more thereof. The polyarylene ether ketone resin may also be a copolymer having two or more of the chemical structures represented by the above (1) to (5).

[0029] <Thermoplastic polyimide resin> The thermoplastic polyimide resin used in the present invention is obtained by polymerizing a tetracarboxylic acid component and a diamine component. The thermoplastic polyimide resin preferably has a repeating unit derived from the tetracarboxylic acid component (a-1) and a repeating unit derived from the aliphatic diamine component (a-2).

[0030] Examples of the tetracarboxylic acid component (a-1) constituting the thermoplastic polyimide resin include alicyclic tetracarboxylic acids such as cyclobutane-1,2,3,4-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, and cyclohexane-1,2,4,5-tetracarboxylic acid, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid, naphthalene-1,4,5,8-tetracarboxylic acid, and pyromellitic acid. In addition, alkyl esters of these compounds can be used in the polymerization of the thermoplastic polyimide resin.

[0031] In particular, it is preferable that more than 50 mol% of the tetracarboxylic acid component (a-1) is pyromellitic acid. When the tetracarboxylic acid component (a-1) is mainly composed of pyromellitic acid, the resin composition for substrates of the present invention has excellent heat resistance, secondary processability, and low water absorption. From this viewpoint, it is more preferable that pyromellitic acid accounts for 60 mol% or more of the tetracarboxylic acid component (a-1), further preferably 80 mol% or more, and particularly preferably 90 mol% or more, and it is particularly preferable that all (100 mol%) of the tetracarboxylic acid component (a-1) is pyromellitic acid.

[0032] The diamine components constituting the thermoplastic polyimide resin preferably contain aliphatic diamine (a-2) as the main component. That is, it is preferable that more than 50 mol% of the diamine components are aliphatic diamine (a-2), more preferably 60 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more, and it is particularly preferable that all (100 mol%) of the diamine components are aliphatic diamine (a-2). This allows the resin composition for substrates of the present invention to have good heat resistance, low water absorbency, moldability, secondary processability, etc. Note that the aliphatic diamine in the present invention also includes alicyclic diamines.

[0033] The aliphatic diamine (a-2) is not particularly limited as long as it is a diamine component having amino groups at both ends of a hydrocarbon group, and examples thereof include alicyclic diamines, linear aliphatic diamines, and branched aliphatic diamines. When heat resistance, heat aging resistance, and the like are important, the aliphatic diamine (a-2) preferably contains an alicyclic diamine. The alicyclic diamine may have amino groups bonded to both ends of the cyclic hydrocarbon (i.e., carbon atoms that constitute the ring but are not adjacent to each other), or may have amino groups bonded to a carbon atom of the cyclic hydrocarbon and to the end of the hydrocarbon bonded to the cyclic hydrocarbon, or may have amino groups bonded to the ends of each of the two hydrocarbons bonded to the cyclic hydrocarbon. Specific examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4'-methylenebis(2-methylcyclohexylamine), isophoronediamine, norbornanediamine, bis(aminomethyl)tricyclodecane, etc. Among these, 1,3-bis(aminomethyl)cyclohexane is preferably used from the viewpoints of heat resistance, heat aging resistance, moldability, secondary processability, etc.

[0034] On the other hand, when toughness, moldability, and secondary processability are important, it is preferable that the aliphatic diamine (a-2) contains at least one of a linear aliphatic diamine and a branched aliphatic diamine. The linear aliphatic diamine and the branched aliphatic diamine preferably have amino groups at both ends of the linear hydrocarbon chain and at both ends of the branched hydrocarbon chain. The linear aliphatic diamine is not particularly limited as long as it is a diamine component having amine groups at both ends of an alkyl group, and specific examples include ethylenediamine (carbon number 2), propylenediamine (carbon number 3), butanediamine (carbon number 4), pentanediamine (carbon number 5), hexanediamine (carbon number 6), heptanediamine (carbon number 7), octanediamine (carbon number 8), nonanediamine (carbon number 9), decanediamine (carbon number 10), undecanediamine (carbon number 11), dodecanediamine (carbon number 12), tridecanediamine (carbon number 13), tetradecanediamine (carbon number 14), pentadecanediamine (carbon number 15), hexadecanediamine (carbon number 16), and the like. Examples of such diamines include linear aliphatic diamines having about 2 to 50 carbon atoms, such as tetracontanediamine (carbon number 16), heptadecanediamine (carbon number 17), octadecanediamine (carbon number 18), nonadecanediamine (carbon number 19), eicosanediamine (carbon number 20), triacontanediamine (carbon number 30), tetracontanediamine (carbon number 40), and pentacontanediamine (carbon number 50). Among these, from the viewpoints of excellent moldability, secondary processability, and low moisture absorption, linear aliphatic diamines having 4 to 20 carbon atoms are preferred, linear aliphatic diamines having 5 to 16 carbon atoms are more preferred, and linear aliphatic diamines having 6 to 12 carbon atoms are even more preferred. Examples of branched aliphatic diamines include those in which a branched structure having preferably 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, is bonded to these linear aliphatic diamines. From the viewpoint of crystallinity, it is particularly preferable that the aliphatic diamine (a-2) contains a linear aliphatic diamine.

[0035] The thermoplastic polyimide resin may contain structural units derived from diamine components other than the aliphatic diamine (a-2). Specific examples of the other diamine components include 1,4-phenylenediamine, 1,3-phenylenediamine, 2,4-toluenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, α,α'-bis(4-aminophenyl)-1,4'-diisopropylbenzene, α,α'-bis(3-aminophenyl)-1,4-diisopropylbenzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, α,α'-bis(4-aminophenyl)-1,4 ... Examples of the diamine component include aromatic diamine components such as aminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,6-diaminonaphthalene, 1,5-diaminonaphthalene, p-xylylenediamine, and m-xylylenediamine; ether diamine components such as polyethylene glycol bis(3-aminopropyl) ether and polypropylene glycol bis(3-aminopropyl) ether; and siloxane diamines.

[0036] The aliphatic diamine (a-2) may contain at least one of a linear aliphatic diamine and a branched aliphatic diamine, or an alicyclic diamine, or both. However, from the viewpoint of achieving a good balance of various performances, it preferably contains at least one of a linear aliphatic diamine and a branched aliphatic diamine, and an alicyclic diamine, and more preferably contains both a linear aliphatic diamine and an alicyclic diamine. When both a linear aliphatic diamine and a branched aliphatic diamine and an alicyclic diamine are contained, the content ratio, on a molar basis, of the linear aliphatic diamine and / or the branched aliphatic diamine to the alicyclic diamine is preferably in the range of 1:99 to 90:10, more preferably 1:99 to 80:20, even more preferably 1:99 to 70:30, particularly preferably 10:90 to 70:30, particularly preferably 20:80 to 70:30, and most preferably 25:75 to 60:40. When the ratio of the linear aliphatic diamine and / or the branched aliphatic diamine to the alicyclic diamine contained in the aliphatic diamine (a-2) is in this range, the balance of heat resistance, heat aging resistance, toughness, moldability, etc. is likely to be excellent.

[0037] The thermoplastic polyimide resin may be crystalline. A crystalline thermoplastic polyimide resin exhibits a crystalline melting peak in differential scanning calorimetry (DSC) measurements. The specific crystalline melting temperature of the thermoplastic polyimide resin is preferably 260°C or higher and 350°C or lower, more preferably 270°C or higher and 345°C or lower, and even more preferably 280°C or higher and 340°C or lower. If the crystalline melting temperature of the thermoplastic polyimide resin is equal to or higher than the lower limit, the laminated film is likely to have sufficient heat resistance. On the other hand, if the crystalline melting temperature is equal to or lower than the upper limit, molding or secondary processing can be easily performed at a relatively low temperature, which is preferable.

[0038] The glass transition temperature of the thermoplastic polyimide resin is preferably 150°C or higher and 300°C or lower, more preferably 160°C or higher and 280°C or lower, even more preferably 170°C or higher and 260°C or lower, particularly preferably 175°C or higher and 250°C or lower, and particularly preferably 180°C or higher and 240°C or lower. If the glass transition temperature of the thermoplastic polyimide resin is above the above lower limit, the heat resistance of the laminated film tends to be sufficient. On the other hand, if the glass transition temperature is below the above upper limit, molding at a relatively low temperature is easy, which is preferable.

[0039] <Polyetherimide resin> The polyetherimide resin is not particularly limited, and its production method and properties are described in, for example, US Pat. Nos. 3,905,942 and 3,803,085.

[0040] Specifically, the polyetherimide resin used in the present invention preferably has a repeating unit represented by the following general formula (6): When the polyetherimide resin has the following repeating unit structure, it is preferable in that various performances can be easily improved.

[0041] [ka]

[0042] In the general formula (6), Y 1 ~Y 6 each independently represents a hydrogen atom, an alkyl group, or an alkoxy group; Ar 7 ~Ar 9 each independently represents an arylene group having 6 to 24 carbon atoms which may have a substituent; X 1 represents a direct bond, or any of -O-, -SO2-, -S-, -C(=O)-, or a divalent aliphatic hydrocarbon group. The polyetherimide resin preferably has a structure in which the repeating unit represented by the general formula (6) is repeated, for example, 10 to 1,000 times, and the number of repeating units is more preferably 20 to 700, and even more preferably 30 to 500. If the number of repeating units is within this range, the viscosity when melted is not too high, resulting in excellent moldability, and various properties such as heat resistance and heat aging resistance tend to be well-balanced.

[0043] Y 1 ~Y 6 The alkyl group in the formula (I) is, for example, an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 2 carbon atoms. Specific preferred examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, an n-hexyl group, and an isohexyl group. 1 ~Y 6 The alkoxy group in Y is, for example, an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 2 carbon atoms, and specifically preferred are a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentyloxy group, an n-hexyloxy group, etc. 1 ~Y 6 may be the same or different. 1 ~Y 6 is preferably a hydrogen atom. Ar 7 ~Ar 9In the formula, examples of the arylene group include a phenylene group, a naphthylene group, and an anthracenylene group. Examples of the substituent of the arylene group include an alkyl group, a halogen, an alkoxy group, and a halogen-substituted alkyl group. The alkyl group and alkoxy group as the substituent have, for example, 1 to 6 carbon atoms, preferably 1 to 2 carbon atoms, and specific examples thereof are as described above. The halogen-substituted alkyl group is a group in which one or more hydrogen atoms of the alkyl group are substituted with halogen. The alkyl group in the halogen-substituted alkyl group is the same as described above. Examples of the halogen include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom. Ar 7 ~Ar 9 may be the same or different. 7 ~Ar 9 When the arylene group has a substituent, the number of carbon atoms in the arylene group is preferably 6 to 24. Ar 7 ~Ar 9 is preferably a phenylene group which may have a substituent, and among these, a phenylene group is preferred. X 1 The divalent aliphatic hydrocarbon group in is preferably a divalent aliphatic hydrocarbon group having 1 to 6 carbon atoms, and more preferably a divalent saturated aliphatic hydrocarbon group. A divalent saturated aliphatic hydrocarbon group is -C y H 2y It is represented by - (y is an integer of 1 to 6), and specific examples thereof include a methylene group, a dimethylene group, a trimethylene group, a propylene group, an ethylidene group (-CH(CH3)-), and a dimethylmethylene group (-C(CH3)2-). X 1 is preferably a divalent saturated aliphatic hydrocarbon group, and more preferably a dimethylmethylene group (-C(CH3)2-).

[0044] In the above general formula (6), Ar 9may be a 1,4- or 1,3-arylene group having 6 to 24 carbon atoms which may have a substituent, but is preferably a 1,4-arylene group having 6 to 24 carbon atoms which may have a substituent. When the bonding positions with the imide group are the 1 and 4 positions, the structure is stable and heat aging resistance is improved, and excellent low water absorption, heat resistance, and impact resistance also tend to be easily achieved. Therefore, the polyetherimide resin is preferably represented by the following general formula (7).

[0045] [ka]

[0046] In the general formula (7), Y 1 ~Y 6 each independently represents a hydrogen atom, an alkyl group, or an alkoxy group; Ar 7 ~Ar 9 each independently represents an arylene group having 6 to 24 carbon atoms which may have a substituent; X 1 represents a direct bond, or any of -O-, -SO2-, -S-, -C(=O)-, and a divalent aliphatic hydrocarbon group. 9 The imide group is Ar 9 It is bonded to the 1st and 4th positions of the group.

[0047] Y in general formula (7) 1 ~Y 6 , X 1 is as explained above. Ar 9 Examples of the arylene group in Ar include a 1,4-phenylene group, a 1,4-naphthylene group, and a 1,4-anthracenylene group. These arylene groups may have a substituent as described above, and the substituent is as described above. 9 is preferably a 1,4-phenylene group which may have a substituent, and more preferably a 1,4-phenylene group. In addition, in the general formula (7), Ar 7 , Ar 8 is as explained above, but Ar7 and Ar 8 is preferably a 1,4-arylene group having 6 to 24 carbon atoms which may have a substituent, and examples of the 1,4-arylene group include a 1,4-phenylene group, a 1,4-naphthylene group, and a 1,4-anthracenylene group. These arylene groups may have a substituent as described above, and the substituent is as described above. Ar 7 and Ar 8 is more preferably a 1,4-phenylene group which may have a substituent, and even more preferably a 1,4-phenylene group.

[0048] Specifically, the polyetherimide resin used in the present invention preferably has a structure represented by the following formula (8). When the polyetherimide resin has the following structure, the laminate film of the present invention tends to have excellent heat aging resistance, and also tends to easily achieve excellent low water absorption, heat resistance, and impact resistance. Furthermore, moldability and secondary processability tend to be good.

[0049] [ka] In the general formula (8), n (the number of repetitions) is usually an integer ranging from 10 to 1,000, preferably from 20 to 700, and more preferably from 30 to 500. When n is within this range, the viscosity when melted is not too high, resulting in excellent moldability, and a good balance of various properties such as heat resistance and heat aging resistance tends to be achieved.

[0050] Specific examples of polyetherimide resins having the above structure are commercially available from Sabic Innovative Plastics under the trade name "Ultem" series.

[0051] The glass transition temperature of the polyetherimide resin is preferably 160°C or higher and 300°C or lower, more preferably 170°C or higher and 290°C or lower, even more preferably 180°C or higher and 280°C or lower, particularly preferably 190°C or higher and 270°C or lower, and especially preferably 200°C or higher and 260°C or lower. When the glass transition temperature of the polyetherimide resin is equal to or higher than the lower limit, the heat resistance of the laminated film tends to be sufficient. On the other hand, when the glass transition temperature of the polyetherimide resin is equal to or lower than the upper limit, molding or secondary processing can be performed at a relatively low temperature, and therefore, when blended with other resins, decomposition or deterioration of the other resins is unlikely to occur.

[0052] <Liquid Crystal Polymer> The liquid crystal polymer may be any polymer having liquid crystallinity (particularly, a polymer that exhibits orientation when it has fluidity), and preferably, a wholly aromatic polyester is used. Examples of monomers for obtaining wholly aromatic polyesters include aromatic fused ring-containing monomers, aromatic single ring-containing monomers, etc. These monomers have a plurality (particularly two) of hydroxyl groups and / or carboxyl groups capable of forming an ester bond.

[0053] Preferred examples of the aromatic fused ring-containing monomer include naphthalene-based monomers such as 2,6-dihydroxynaphthalene, 2,6-naphthalenedicarboxylic acid, and 6-hydroxy-2-naphthoic acid. Examples of aromatic monocyclic monomers include benzene-based monomers such as 4-hydroxybenzoic acid, hydroquinone, terephthalic acid, and isophthalic acid, and biphenol-based monomers such as 4,4'-biphenol.

[0054] Particularly preferred wholly aromatic polyesters include 4-hydroxybenzoic acid-based polyesters obtained by polymerization of monomer components containing 4-hydroxybenzoic acid. Examples of 4-hydroxybenzoic acid-based wholly aromatic polyesters include 4-hydroxybenzoic acid homopolymers obtained by polymerization of a monomer component consisting solely of 4-hydroxybenzoic acid; linear aromatic polyester polymers obtained by polymerization of a monomer component containing a linear aromatic monomer such as 4,4'-biphenol, hydroquinone, or terephthalic acid and 4-hydroxybenzoic acid; bent-neck aromatic polyester polymers obtained by polymerization of a bent-neck aromatic monomer such as isophthalic acid and 4-hydroxybenzoic acid; and crankshaft aromatic polymers obtained by polymerization of a crankshaft aromatic monomer such as 2,6-dihydroxynaphthalene, 2,6-naphthalenedicarboxylic acid, or 6-hydroxy-2-naphthoic acid and 4-hydroxybenzoic acid.

[0055] The wholly aromatic polyester is preferably a wholly aromatic polyester obtained by polymerization of a monomer component containing an aromatic fused ring-containing monomer, more preferably a wholly aromatic polyester obtained by polymerization of a monomer component containing an aromatic fused ring-containing monomer and 4-hydroxybenzoic acid, and most preferably a crankshaft aromatic polymer obtained by polymerization of a monomer component containing a crankshaft aromatic monomer and 4-hydroxybenzoic acid. By including such a wholly aromatic polyester in the laminate film, the heat resistance, processability, etc. are further improved. Furthermore, when the liquid crystal polymer is a 4-hydroxybenzoic acid-based wholly aromatic polyester (excluding homopolymers), the molar ratio of 4-hydroxybenzoic acid to other aromatic monomers (e.g., aromatic fused ring-containing monomers) (4-hydroxybenzoic acid / other aromatic monomers) is, for example, 10 / 90 to 90 / 10, preferably 60 / 40 to 90 / 10.

[0056] Commercially available liquid crystal polymers can also be used, such as the "Sumika Super LCP" series manufactured by Sumitomo Chemical Co., Ltd., the "XYDER" series manufactured by Solvay, the "VECTRA" series manufactured by Celanese, and the "UENO LCP" series manufactured by Ueno Pharmaceutical Co., Ltd. The liquid crystal polymer may be used alone or in combination of two or more.

[0057] The resin used in the laminated film of the present invention is preferably any one of polyarylene ether ketone resin, polyetherimide resin, and thermoplastic polyimide resin from the viewpoint of adhesion to copper foil. In particular, from the viewpoints of heat resistance, mechanical strength, and water absorption resistance, it is more preferable that the resins constituting both the A layer and the B layer are polyarylene ether ketone, and when the B layer is provided on both the front and back surfaces, it is even more preferable that the resins constituting the intermediate layer and both outermost layers are polyarylene ether ketone.

[0058] <Inorganic filler> The intermediate layer (layer A) in the laminate film of the present invention contains an inorganic filler, the main component of which is one or a mixture of two or more selected from the group consisting of silica, mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, titanium dioxide, potassium titanate, lithium titanate, boehmite, and alumina. Among these, mica, which is a plate-like inorganic filler as described below, is preferred, and synthetic mica containing few impurities is preferred. Note that the plate-like shape referred to here also includes flaky and thin-plate shapes.

[0059] The inorganic filler is preferably plate-shaped and has an average maximum diameter of 30 μm or more. By making the average maximum diameter 30 μm or more, the dimensional stability of the laminated film is improved. From the above viewpoints, the average maximum diameter is more preferably 40 μm or more, and even more preferably 50 μm or more. Furthermore, the average thickness of the plate-like inorganic filler is preferably 1 μm or less. By setting the average thickness of the plate-like inorganic filler to 1 μm or less, the dimensional stability of the laminated film is improved. From the above viewpoint, the average thickness is more preferably 0.5 μm or less. Furthermore, the average aspect ratio (average maximum diameter / average thickness) of the plate-like inorganic filler is preferably 10 or more. By setting the average aspect ratio to 10 or more, the dimensional stability of the laminated film is improved. From the above viewpoints, the average aspect ratio is more preferably 20 or more, and even more preferably 40 or more. The average maximum diameter, average thickness, and average aspect ratio can be measured and calculated by observation using a scanning electron microscope. By incorporating the inorganic filler as described above, the molding shrinkage rate and linear expansion coefficient are small, and good dimensional stability is obtained. Furthermore, the heat resistance and mechanical strength are excellent, and the molding processability is also excellent.

[0060] A method for blending an inorganic filler into the intermediate layer (A layer) is to prepare a resin composition for forming the intermediate layer (A layer) by incorporating an inorganic filler into the above-mentioned resin. A known manufacturing method can be used to obtain a resin composition by incorporating an inorganic filler into the above-mentioned resin. Specifically, a method can be used in which the inorganic filler is added from a side hopper while the resin is melt-kneaded using a twin-screw kneader or the like, and then kneaded. For the kneading, a single screw extruder, a co-kneader, a multi-screw extruder, or the like can also be used. In addition to the inorganic filler, various stabilizers, lubricants, antistatic agents, etc. may also be added to the film as appropriate.

[0061] The method for producing the laminated film is not particularly limited, and examples thereof include a coextrusion method in which the resin compositions of the respective layers are coextruded and laminated, an extrusion lamination method in which the respective layers are formed into films and then laminated, and a thermocompression bonding method in which the respective layers are formed into films and then thermocompression bonded, etc. Among these, from the viewpoints of thinning and productivity, the coextrusion method is preferred.

[0062] [Laminate for substrates] <Substrate> The laminated film of the present invention is preferably used for various substrates and may constitute at least a part of the substrate. The substrate is typically a circuit board having a circuit. Examples of the circuit board include flexible printed circuits (FPC) and flexible cupper clad laminate (FCCL). The laminated film of the present invention has a good balance of various properties such as dimensional stability, toughness, and dielectric properties, and also has low water absorption. Therefore, it satisfies the required properties of substrates and is suitable for use in substrates. In particular, the laminated film of the present invention has excellent solder heat resistance, and is less likely to crack when bent, even after being heated to high temperatures in a soldering process or the like. Therefore, it is particularly suitable for the above-mentioned FPCs and FCCLs.

[0063] The present invention provides a laminate for a substrate. The laminate for a substrate is a laminate comprising the laminate film of the present invention and copper foil. The laminate for a substrate may be used to form a circuit to form a circuit board. In the circuit board, the copper foil may be patterned into a predetermined shape by etching or the like to form wiring or the like. The thickness of the copper foil is, for example, 1 to 80 μm, preferably 3 to 50 μm, and more preferably 5 to 30 μm.

[0064] The laminated film of the present invention preferably constitutes either a base film or a cover film. The base film serves as the substrate of a circuit board, and copper foil is preferably provided on the base film. The copper foil is generally bonded to the base film via an adhesive layer. The adhesive layer is not particularly limited, but examples thereof include epoxy resin adhesives, acrylic resin adhesives, and phenol resin adhesives, with epoxy resin adhesives being preferred among these. Alternatively, the copper foil may be surface-treated with a surface treatment agent such as a silane coupling agent, and then bonded to the base film via the surface treatment agent, or the copper foil may be directly bonded to the base film without the use of a surface treatment agent or an adhesive layer.

[0065] A cover film, sometimes called a coverlay film, is a film that covers and protects copper foil and other materials provided on a base film. Cover films are used by being attached to the copper foil surface of a base film or rigid substrate, which serves as the base material for a circuit board. The cover film is generally bonded to a substrate such as a base film or a rigid substrate via an adhesive layer. The adhesive used for the adhesive layer is as described above. The adhesive layer may be omitted as appropriate. In this case, the cover film may be bonded to a copper foil that has been surface-treated with a surface treatment agent such as a silane coupling agent, or may be bonded directly to the copper foil without an adhesive layer or a surface treatment agent. In addition, copper foil is generally patterned and provided partially on the substrate, but in the areas of the substrate where copper foil is not provided, the cover film may be directly adhered to the substrate or may be attached to the substrate via an adhesive layer.

[0066] [Circuit board] The circuit board of the present invention is obtained by forming a conductive circuit on the above-mentioned substrate laminate. The wiring pattern of the conductive circuit can be formed by etching, plating, printing, or the like.

[0067] [Electronic equipment] Electronic devices manufactured using the circuit board of the present invention have excellent dielectric properties and are therefore effective as mobile information and communication devices such as multi-function mobile phones and tablet terminals. More specifically, they are expected to be used as 5G terminals that can meet requirements such as ultra-high speed, large capacity, low latency, and multiple simultaneous connections, as well as for applications such as automobile collision prevention millimeter-wave radar devices, advanced driver assistance systems, and artificial intelligence. [Example]

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The evaluation methods and sample treatment methods in the examples and comparative examples are as follows.

[0069] (Evaluation method) The films produced in the above Examples and Comparative Examples were evaluated and measured for various items as follows: Here, the "vertical" direction of the film refers to the direction in which the film-shaped molded product is extruded from the T-die, and the direction perpendicular to this in the plane of the film is called the "horizontal" direction. (1) Phase crystallinity Each film was heated from room temperature to 380°C at a rate of 10°C / min, and the heat of crystallization ΔHc and the heat of crystalline fusion ΔHm were obtained from the area of ​​the exothermic peak during resin crystallization and the area of ​​the endothermic peak during resin crystalline melting. Using these, the relative crystallinity was calculated using the following formula. Relative crystallinity (%) = {(|ΔHm| - |ΔHc|) / ΔHm} × 100 (2) Glass transition temperature and crystalline melting temperature In accordance with JIS K7121:2012, a differential scanning calorimeter Pyris1 DSC (manufactured by PerkinElmer) was used to measure the glass transition temperature (Tg) and crystalline melting temperature (Tm) of each resin from the DSC curves obtained by heating the resins from 23 to 400°C at a rate of 10°C / min, then cooling them to 23°C at a rate of 10°C / min, and then heating them again to 400°C at a rate of 10°C / min. The crystalline melting temperature (Tm) was taken as the peak top temperature of the detected endothermic peak, and was taken as the melting point of each resin. (3) Relative permittivity The laminated films obtained in each of the Examples and Comparative Examples were measured in accordance with JIS C2565:1992 under conditions of a temperature of 23°C, a humidity of 30%, and a frequency of 12 GHz. (4) Dielectric tangent The laminated films obtained in each of the Examples and Comparative Examples were measured in accordance with JIS C2565:1992 under conditions of a temperature of 23°C, a humidity of 30%, and a frequency of 12 GHz. (5) Dielectric tangent and relative permittivity of resin The dielectric loss tangent and relative permittivity of each resin were measured in the same manner as above, except that each resin pellet was hot-pressed at 380°C to form a film with a thickness of 200 μm, and the frequency was changed from 12 GHz to 10 GHz. (6) Linear expansion coefficient The laminated films obtained in each example and comparative example were measured in the extrusion direction (MD) and width direction (TD, perpendicular to the extrusion direction). Measurements of the linear expansion coefficient of the laminated films were performed in accordance with JIS K7197:2012, with a measurement chuck distance of 10 mm and a width direction of 6 mm. The linear expansion coefficient was measured using a thermal analyzer (Mettler-Toledo "TMA / SDTA841") in tensile mode, with a heating rate of 5°C / min and a reheating rate of 5°C / min from 25°C to 250°C. The linear expansion coefficient was calculated from the slope of the change in dimension from 25°C to 125°C. (7) Dimensional change rate due to heating A 120 mm x 120 mm piece was cut out from the laminated film obtained in each Example and Comparative Example, and heated at 200°C for 30 minutes with a gauge length of 100 mm in accordance with JIS K7133. The thermal dimensional change rate of the film was calculated using the following formula. Dimensional change rate after heating (%) = (dimension after heating - dimension before heating) / dimension before heating x 100 (8) Number of folding times For the laminated films obtained in each of the Examples and Comparative Examples, the number of times they could be folded in the MD and TD directions was measured in accordance with JIS P8115 using an MIT folding endurance tester ("BE-202" manufactured by Tester Sangyo Co., Ltd.) under conditions of a folding angle of 135 degrees, a folding speed of 175 times / min, and a load of 9.8 N. (9) Water absorption rate A test piece having a diameter of 10 cm (thickness of 50 μm) was cut out from the laminated film obtained in each of the Examples and Comparative Examples, and used as a measurement sample. In accordance with JIS K7209:2000, the obtained measurement sample was immersed in water at 23°C for 24 hours, and the water absorption rate was measured from the change in mass before and after immersion. Water absorption rate (%) = ((mass after immersion - mass before immersion) / mass before immersion) x 100

[0070] (Materials used) <Front and back layers: Polyether ether ketone> (B)-1: Polyether ether ketone (repeating unit of chemical formula (1), crystalline melting temperature = 343°C, glass transition temperature = 143°C, relative dielectric constant = 3.0, dielectric dissipation factor = 0.0029) <Middle layer: Mica reinforced polyetheretherketone> (A)-1: A masterbatch containing 70% by mass of the polyether ether ketone used in (B-1) above and 30% by mass of the following mica: (A)-2: A masterbatch containing 76% by mass of the polyether ether ketone used in (B-1) above and 24% by mass of the following mica: <Mica> Mica: Plate-like, average maximum diameter 4.0 μm, average thickness 0.13 μm, average aspect ratio 33

[0071] Example 1 (B)-1 was used as the raw material for the front and back layers (hereafter referred to as "Layer B"), and (A)-1 was used as the raw material for the middle layer (hereafter referred to as "Layer A"). These were melted separately using two 40mm diameter extruders. Layer B was divided into two halves in the feed block and laminated in the feed block in the order Layer B / Layer A / Layer B. This was extruded from a T-die as a two-type, three-layer laminate film. To crystallize the outermost layers, the film was pressed against a 210°C cast roll, resulting in a lamination ratio of 1 / 5 / 1 (Layer B's thickness ratio to the entire film = 28%). The extruder temperatures for Layer B, Layer A, the feed block, and the die were all 380°C. The 50 μm two-type three-layer laminate film produced as described above was evaluated for dielectric constant, dielectric loss tangent, thermal dimensional change rate, folding endurance, and water absorption. The evaluation results are shown in Table 1. The relative crystallinity of the obtained laminate film was 100%.

[0072] Example 2 A sample was prepared in the same manner as in Example 1, except that the casting roll speed was adjusted to change the film thickness to 100 μm. The evaluation results are shown in Table 1. The relative crystallinity of the obtained laminated film was 100%.

[0073] Example 3 The extruder rotation speed and cast roll speed of Layer A and Layer B were adjusted to change the lamination ratio to 1 / 9 / 1 (thickness ratio of Layer B to the entire film = 18%). Aside from changing Layer A to the dry-blended (A)-2 raw material, a sample was produced in the same manner as in Example 2. The evaluation results are shown in Table 1. The relative crystallinity of the resulting laminated film was 100%.

[0074] Example 4 A sample was produced in the same manner as in Example 2, except that the extruder rotation speed and cast roll speed of Layer A and Layer B were adjusted to change the lamination ratio to 1 / 5 / 1 (thickness ratio of Layer B to the entire film = 28%). The evaluation results are shown in Table 1. The relative crystallinity of the obtained laminated film was 100%.

[0075] Example 5 A sample was produced in the same manner as in Example 2, except that the extruder rotation speed and cast roll speed of Layer A and Layer B were adjusted to change the lamination ratio to 1 / 3 / 1 (thickness ratio of Layer B to the entire film = 40%). The evaluation results are shown in Table 1. The relative crystallinity of the obtained laminated film was 100%.

[0076] Comparative Example 1 A polyether ether ketone monolayer film was obtained under the same conditions as in Example 2, except that only one extruder was used and (B)-1 was used as the raw material. This film was evaluated in the same manner as in Example 1. The results are shown in Table 1. The relative crystallinity of the obtained film was 100%.

[0077] Comparative Example 2 A mica-reinforced polyether ether ketone monolayer film was obtained under the same conditions as in Example 1, except that only one extruder was used and (A)-1 was used as the raw material. This film was evaluated in the same manner as in Example 1. The results are shown in Table 1. The relative crystallinity of the obtained film was 100%.

[0078] Comparative Example 3 A mica-reinforced polyether ether ketone monolayer film was obtained under the same conditions as in Example 2, except that only one extruder was used and dry-blended (A)-2 was used as the raw material. This film was evaluated in the same manner as in Example 1. The results are shown in Table 1. The relative crystallinity of the obtained film was 100%.

[0079] [Table 1]

[0080] The laminated films obtained in Examples 2 to 5 all had a dielectric loss tangent of 0.004 or less, and therefore had excellent dielectric properties. These dielectric properties were due to the use of polyether ether ketone in the front and back layers, and the films also had excellent thermal dimensional change and water absorption. Furthermore, all of the laminate films obtained in Examples 1 to 5 had good folding strength, but the laminate films obtained in Examples 3 to 5 were particularly excellent in folding strength and toughness. This is thought to be because the strength was imparted to the laminate films by reducing the filler amount compared to Example 1. From the above results, it is clear that the laminated film of the present invention is excellent in dielectric properties, dimensional stability under heat, folding strength, and water absorption.

[0081] On the other hand, Comparative Example 1 has excellent folding strength and dielectric properties, but does not have sufficient dimensional stability under heat. In Comparative Examples 2 and 3, although the dimensional stability under heating is excellent, the dielectric properties are insufficient. [Industrial Applicability]

[0082] The present invention provides a material that is useful as a material for high-speed communications, having low moisture absorption, excellent adhesion to copper foil, dimensional stability, toughness, and dielectric properties, and is therefore useful for devices such as fifth-generation mobile communications systems (5G), as well as in a wide range of industries, including the automotive, semiconductor, medical, energy, and aerospace fields.

Claims

1. A laminated film having at least Layer A and Layer B, each of Layer A and Layer B containing a resin having a melting point of 250°C or higher and a dielectric dissipation factor of 0.006 or less at a frequency of 10 GHz, the resin composition constituting Layer A containing 10% by mass or more of an inorganic filler, and Layer B containing 5% by mass or less of an inorganic filler, the laminated film having three or more layers in which Layer A is an intermediate layer and Layer B is an outermost layer, and the laminated film has a relative dielectric constant of 4.0 or less at a frequency of 12 GHz and a dielectric dissipation factor of 0.006 or less.

2. 2. The laminate film according to claim 1, wherein the resin is one or more selected from the group consisting of polyarylene ether ketone resins, thermoplastic polyimide resins, polyetherimide resins, and liquid crystal polymers.

3. 3. The laminated film according to claim 1, wherein the inorganic filler is one or a mixture of two or more selected from the group consisting of silica, mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, titanium dioxide, potassium titanate, lithium titanate, boehmite, and alumina.

4. The laminated film according to any one of claims 1 to 3, wherein the layer B does not contain an inorganic filler.

5. 5. The laminated film according to claim 1, wherein the thickness ratio of the A layer to the B layer is 90:10 to 10:

90.

6. The laminated film according to any one of claims 1 to 5, wherein the thermal dimensional change rate when heated to 200°C is -3.0% or more and 3.0% or less.

7. The laminated film according to any one of claims 1 to 6, which has a water absorption rate of 1.0% or less.

8. The laminated film according to any one of claims 1 to 7, which has a relative crystallinity of 50% or more.

9. The laminated film according to any one of claims 1 to 8, wherein the inorganic filler comprises a plate-like inorganic filler.

10. The laminated film according to claim 9 , wherein the plate-like inorganic filler has an average aspect ratio of 10 or more.

11. The laminated film according to claim 9 or 10, wherein the average maximum diameter of the plate-like inorganic filler is 30 μm or more.

12. The laminated film according to any one of claims 9 to 11, wherein the average thickness of the plate-like inorganic filler is 1 µm or less.

13. The laminate film according to any one of claims 1 to 12, which is a cover film or a base film for a substrate.

14. A laminate for a substrate, comprising the laminate film according to any one of claims 1 to 13 and a copper foil.

15. A circuit board comprising a conductive circuit formed on the substrate laminate according to claim 14.

16. An electronic device comprising the circuit board according to claim 15.

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