Adhesive composition and laminate with adhesive layer

Abstract

To provide an adhesive composition from which a cured product having low relative dielectric constant and excellent thermal conductivity and adhesion can be obtained, and a laminate with an adhesive layer using the same.SOLUTION: An adhesive composition contains a modified polyolefinic resin (A) having a reactive functional group reactive with an epoxy group, a thermal conductive filler (B) having thermal conductivity of 5 W / m K or more, a low dielectric filler (C) having relative dielectric constant of 3.2 or less, and an epoxy resin (D). The adhesive composition has the total content of the thermal conductive filler (B) and the low dielectric filler (C) in the total solid content of the adhesive composition of 50 mass% or less, and a ratio of the thermal conductive filler (B) to the low dielectric filler (C) which is a mass ratio of the thermal conductive filler (B) to the low dielectric filler (C) is 0.1 or more and 10 or less. A laminate with an adhesive layer includes an adhesive layer formed of an adhesive composition, and a base material film contacting at least one surface of the adhesive layer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive composition and a laminate with an adhesive layer.

Background Art

[0002] In recent years, with the improvement in performance, miniaturization, and weight reduction of electronic devices, the demand for products related to flexible printed circuit boards (hereinafter also referred to as "FPC") has been increasing. A flexible printed circuit board is a printed circuit board having flexibility, and circuits can be stacked in a three-dimensional manner with high density in a limited space. In addition, a flexible printed circuit board can gain area for wiring electronic circuits inside by multi-layerization, and a large number of semiconductor components can be mounted on the surface with high density.

[0003] When manufacturing a flexible printed circuit board, a laminate with an adhesive layer in which an adhesive layer formed from an adhesive composition is laminated on a base film made of a resin film is used. Further, when multi-layerizing a flexible printed circuit board, an adhesive composition is used for the lamination.

[0004] The requirements for the performance of flexible printed circuit boards have become higher, and with the increase in the speed of transmission signals, the frequency of signals has been increasing. Along with this, there is an increasing demand for flexible printed circuit boards to have low dielectric characteristics in the high-frequency region. In addition, a flexible printed circuit board generates a large amount of heat, and its performance deteriorates due to the heat generation. Therefore, the adhesive composition used for a flexible printed circuit board is required to have low transmission loss and high heat dissipation.

[0005] Although Patent Document 1 that precedes does not relate to an adhesive composition, a composition for a low dielectric heat dissipation film in which the relative dielectric constant of the cured product at a frequency of 10 GHz is 3.5 or less is disclosed in this Patent Document 1.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent No. 7066654 Summary of the Invention Problems to be Solved by the Invention

[0007] However, the composition of Patent Document 1 is for a low-dielectric heat-dissipating film, and it is not assumed that the composition itself is used as an adhesive. That is, the composition of Patent Document 1 has no adhesiveness in the first place and is not an adhesive composition.

[0008] In addition, when the filling amount of the heat-conductive filler in the adhesive composition is increased, the thermal conductivity of the cured product increases and the heat dissipation property of the cured product improves. However, along with this, the relative dielectric constant of the cured product increases, and it becomes impossible to satisfy the requirement of having low dielectric characteristics in the high-frequency region.

[0009] Also, if an adhesive component is blended with the composition of Patent Document 1 to impart adhesiveness, the thermal conductivity of the cured product decreases and the heat dissipation property of the cured product deteriorates. If the filling amount of the heat-conductive filler is increased to compensate for this, the volume of the adhesive component decreases, so the adhesive strength of the cured product decreases.

[0010] The present invention has been made in view of such problems, and aims to provide an adhesive composition in which the cured product has a low relative dielectric constant and excellent thermal conductivity and adhesiveness, and a laminate with an adhesive layer using the same. Means for Solving the Problems

[0011] The adhesive composition and the laminate with an adhesive layer according to the present invention are as follows.

[0012] [1] A modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, A heat-conductive filler (B) having a thermal conductivity of 5 W / m·K or more, A low-dielectric filler (C) having a relative dielectric constant of 3.2 or less, and an epoxy resin (D), and is an adhesive composition containing The total content of the thermal conductive filler (B) and the low-dielectric filler (C) in the total solid content of the adhesive composition is 50% by mass or less, The mass ratio of the thermal conductive filler (B) to the low-dielectric filler (C), that is, the thermal conductive filler (B) / low-dielectric filler (C) ratio is 0.1 or more and 10 or less, Adhesive composition. [2] The content of the thermal conductive filler (B) in the total solid content of the adhesive composition is 3% by mass or more, The adhesive composition according to [1]. [3] The relative dielectric constant of the cured product of the adhesive composition measured at a frequency of 10 GHz is 3.5 or less, The adhesive composition according to [1] or [2]. [4] The thermal conductive filler (B) is at least one selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide, The adhesive composition according to any one of [1] to [3]. [5] The low-dielectric filler (C) is at least one selected from the group consisting of a fluorine-based filler composed of a fluorine-based resin, an LCP filler composed of a liquid crystal polymer, hollow silica, and fused silica, The adhesive composition according to any one of [1] to [4]. [6] An adhesive layer formed from the adhesive composition according to any one of [1] to [5], and a base material film in contact with at least one surface of the adhesive layer. An adhesive layer laminate. [7] The average particle diameter of the thermal conductive filler (B) is 50% or less of the layer thickness of the adhesive layer, The adhesive layer laminate according to [6].

[0013] In the present disclosure, the term "adhesive layer" means a layer in a state before curing, a B-stage state (i.e., a semi-cured state in which part of it has started to cure and the curing of the adhesive composition further proceeds by heating or the like), or a state after the curing reaction has proceeded to sufficiently form a crosslinked structure. Further, the term "cured product" means a product in a state after the adhesive composition has been subjected to a curing reaction to sufficiently form a crosslinked structure.

Advantages of the Invention

[0014] The above adhesive composition has the above configuration. Therefore, in the cured product of the above adhesive composition, the relative permittivity is low, and the thermal conductivity and adhesiveness are excellent.

[0015] The above laminate with an adhesive layer has the above configuration. Therefore, in the case where the adhesive layer is formed from the cured product of the above adhesive composition, the relative permittivity is low, and the thermal conductivity and adhesiveness are excellent.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited thereto.

[0017] 1. Adhesive Composition The adhesive composition of the present embodiment contains a modified polyolefin-based resin (A) having a reactive functional group that reacts with an epoxy group, a thermal conductive filler (B) having a thermal conductivity of 5 W / m·K or more, a low dielectric filler (C) having a relative permittivity of 3.2 or less, and an epoxy resin (D). In the adhesive composition of the present embodiment, the total content of the thermal conductive filler (B) and the low dielectric filler (C) in the total solid content of the adhesive composition is 50% by mass or less, and the mass ratio of the thermal conductive filler (B) to the low dielectric filler (C), which is the mass ratio of the thermal conductive filler (B) / low dielectric filler (C), is 0.1 or more and 10 or less. Hereinafter, the adhesive composition of the present embodiment will be specifically described.

[0018] 1.1 Modified Polyolefin-Based Resin (A) In the adhesive composition of this embodiment, the modified polyolefin-based resin (A) is an important adhesive component as the base of the adhesive composition.

[0019] The modified polyolefin-based resin (A) has a reactive functional group that reacts with an epoxy group. That is, the modified polyolefin-based resin (A) can be said to be a resin in which a reactive functional group that reacts with an epoxy group is introduced into an unmodified polyolefin-based resin, and can also be said to be a resin modified with a modifier having a reactive functional group that reacts with an epoxy group in an unmodified polyolefin-based resin. Furthermore, it can also be said to be a resin in which an unmodified polyolefin-based resin is modified to have reactivity with an epoxy resin (B).

[0020] Examples of the reactive functional group that reacts with an epoxy group include a group having active hydrogen, an active ester group, etc. Examples of the group having active hydrogen include a carboxy group, an amino group, a hydroxyl group, an acid anhydride group, a thiol group, etc. These can be used alone or in combination of two or more. From the viewpoint of reactivity and the like, the reactive functional group that reacts with an epoxy group is preferably a carboxy group or an amino group, and more preferably a carboxy group.

[0021] The modified polyolefin-based resin (A) is preferably an acid-modified polyolefin-based resin. Specifically, it can be a resin having a portion derived from an unmodified polyolefin-based resin and a graft portion derived from a modifier. Preferably, it is a resin obtained by graft-modifying an unmodified polyolefin-based resin with a modifier containing an α,β-unsaturated carboxylic acid or a derivative thereof.

[0022] The production of the modified polyolefin resin (A) by graft modification (graft polymerization) can be carried out by a known method, and a radical initiator may be used during the production. As the production method of the above-mentioned modified polyolefin resin (A), for example, a solution method in which an unmodified polyolefin resin is heated and dissolved in a solvent such as toluene, and the above-mentioned modifier and radical initiator are added, or a melt method in which an unmodified polyolefin resin, a modifier, and a radical initiator are melt-kneaded using a Banbury mixer, a kneader, an extruder, etc. can be mentioned. The usage methods of the unmodified polyolefin resin, the modifier, and the radical initiator are not particularly limited, and these may be added to the reaction system all at once or sequentially. Further, when producing the above-mentioned modified polyolefin resin (A), a modification aid for improving the graft efficiency by a modifier such as α,β-unsaturated carboxylic acid, a stabilizer for adjusting the resin stability, etc. can be further used.

[0023] The unmodified polyolefin resin used in the production of the modified polyolefin resin (A) is not particularly limited as long as it has a structural unit derived from an olefin, but homopolymers or copolymers having 2 to 20 carbon atoms such as ethylene, propylene, butene, pentene, hexene, heptene, octene, 4-methyl-1-pentene, etc. are preferably used. The above-mentioned unmodified polyolefin resin is more preferably a homopolymer or copolymer of an olefin having 2 to 6 carbon atoms. Specific examples of the above-mentioned unmodified polyolefin resin include ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers, etc. These can be used alone or in combination of two or more.

[0024] As the unmodified polyolefin resin used in the production of the modified polyolefin resin (A), specifically, an unmodified polypropylene resin is preferable. In this case, the modified polyolefin resin (A) can specifically be a resin having a portion derived from an unmodified polypropylene resin and a graft portion derived from a modifier, and preferably, it is a resin obtained by graft-modifying an unmodified polypropylene resin with a modifier containing an α,β-unsaturated carboxylic acid or its derivative. The unmodified polypropylene resin has a structural unit derived from propylene and is not particularly limited as long as it has not been modified with a modifier such as an α,β-unsaturated carboxylic acid or its derivative, but a copolymer of propylene and an olefin having 2 to 20 carbon atoms such as ethylene, butene, pentene, hexene, heptene, octene, 4-methyl-1-pentene is preferably used. The above unmodified polypropylene resin is more preferably a copolymer of propylene and an olefin having 2 to 6 carbon atoms.

[0025] The content ratio of the structural units in the above unmodified polyolefin resin and the above unmodified polypropylene resin can be arbitrarily selected. From the viewpoint of being advantageous for adhesion to a difficult-to-adhere adherend, etc., the modified polyolefin resin (A) is preferably a modified resin of an unmodified polypropylene resin selected from the group consisting of an ethylene-propylene copolymer, a propylene-butene copolymer, and an ethylene-propylene-butene copolymer. From the viewpoint of obtaining excellent adhesiveness, etc., it is preferable to use an unmodified polypropylene resin in which the content ratio of propylene units is 50 mol% or more and 98 mol% or less. When the content ratio of propylene units is within the above-mentioned range, flexibility can be imparted to the adhesive portion after adhering two members. The molecular weights of the above unmodified polyolefin resin and the above unmodified polypropylene resin are not particularly limited.

[0026] The modifier can include α,β-unsaturated carboxylic acids and their derivatives. Examples of α,β-unsaturated carboxylic acids include maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, norbornenedicarboxylic acid, and the like. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides, acid halides, amides, imides, esters, and the like. As the above-mentioned modifier, itaconic anhydride, maleic anhydride, aconitic anhydride, and citraconic anhydride are preferred, and itaconic anhydride and maleic anhydride are particularly preferred in terms of adhesiveness. When using the modifier, it may be one or more selected from α,β-unsaturated carboxylic acids and their derivatives, and may be a combination of one or more α,β-unsaturated carboxylic acids and one or more of their derivatives, a combination of two or more α,β-unsaturated carboxylic acids, or a combination of two or more derivatives of α,β-unsaturated carboxylic acids, etc.

[0027] Depending on the purpose, the modifier can include other compounds (other modifiers) in addition to α,β-unsaturated carboxylic acids, etc. Examples of other compounds (other modifiers) include, for example, (meth)acrylate esters represented by the following formula (1), (meth)acrylic acid, other (meth)acrylic acid derivatives, aromatic vinyl compounds, cyclohexyl vinyl ether, and the like. These other compounds may be used alone or in combination of two or more. CH2=CR1COOR2 (1) (In formula (1), R1 is a hydrogen atom or a methyl group, and R2 is a hydrocarbon group.)

[0028] In the formula (1) representing the above (meth)acrylic acid ester, R1 is a hydrogen atom or a methyl group, preferably a methyl group. R2 is a hydrocarbon group, preferably an alkyl group having 8 to 18 carbon atoms. Examples of the compound represented by the above formula (1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, etc. These compounds may be used alone or in combination of two or more. In the present embodiment, since the heat resistance is improved, it is preferable to use a modifier further containing a (meth)acrylic acid ester having an alkyl group with 8 or more and 18 or less carbon atoms. In particular, it is preferable to contain octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, or stearyl (meth)acrylate.

[0029] Examples of (meth)acrylic acid derivatives other than (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, isocyanate-containing (meth)acrylic acid, etc. Examples of aromatic vinyl compounds include styrene, o-methylstyrene, p-methylstyrene, α-methylstyrene, etc. By using an α,β-unsaturated carboxylic acid or its derivative in combination with other modifiers as the above modifier, the graft ratio by the modifier can be improved, the solubility in a solvent can be improved, and the adhesiveness can be further improved. When using other modifiers excluding the (meth)acrylic acid ester represented by the above formula (1), it is desirable that the usage amount does not exceed the total usage amount of the α,β-unsaturated carboxylic acid and its derivative and the (meth)acrylic acid ester.

[0030] As described above, the modified polyolefin resin (A) can have at least a graft portion derived from a modifier. Hereinafter, the content ratio of the graft portion contained in the modified polyolefin resin (hereinafter also referred to as "graft mass") will be described.

[0031] The modified polyolefin resin (A) can have a graft portion derived from an α,β-unsaturated carboxylic acid or a derivative thereof. In the modified polyolefin resin (A), the graft mass of the graft portion derived from an α,β-unsaturated carboxylic acid or a derivative thereof is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 18% by mass or less, based on 100% by mass of the modified polyolefin resin (A) from the viewpoint of adhesiveness. When the graft mass is 0.1% by mass or more, the solubility in a solvent is excellent, and the adhesiveness to an adherend made of a metal or the like is particularly excellent. Further, when the graft mass is 20% by mass or less, sufficient adhesiveness to an adherend made of a resin or the like can be obtained.

[0032] The graft mass of the graft portion derived from an α,β-unsaturated carboxylic acid or a derivative thereof in the modified polyolefin resin (A) can be determined by an alkali titration method. However, when the derivative of the α,β-unsaturated carboxylic acid is an imide or the like having no acid group, the graft mass can be determined by Fourier transform infrared spectroscopy.

[0033] When the modified polyolefin resin (A) contains a graft portion derived from the (meth)acrylate represented by the above formula (1), the graft mass is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.3% by mass or more and 25% by mass or less, based on 100% by mass of the modified polyolefin resin (A). When the graft mass is 0.1% by mass or more and 30% by mass or less, the solubility in a solvent is excellent, and the adhesiveness to an adherend can be further improved.

[0034] When the modifier contains a (meth)acrylate represented by the above formula (1), the graft mass in the obtained modified polyolefin resin (A) can be determined by Fourier transform infrared spectroscopy.

[0035] The radical initiator used in the production of the modified polyolefin resin (A) can be appropriately selected from known ones. For example, it is preferable to use organic peroxides such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and cumene hydroperoxide.

[0036] Examples of the modifying aid that can be used in the production of the modified polyolefin resin (A) include divinylbenzene, hexadiene, and dicyclopentadiene. Examples of the stabilizer include hydroquinone, benzoquinone, and nitrosophenylhydroxy compounds.

[0037] The weight average molecular weight Mw of the modified polyolefin resin (A) is preferably 30,000 or more and 250,000 or less, more preferably 50,000 or more and 200,000 or less. When the weight average molecular weight Mw of the modified polyolefin resin (A) is within the above range, an adhesive composition excellent in solubility in a solvent, initial adhesiveness to an adherend, and solvent resistance at the adhered portion after adhesion can be obtained.

[0038] The acid value of the modified polyolefin resin (A) is preferably 0.1 mgKOH / g or more and 50 mgKOH / g or less, more preferably 0.5 mgKOH / g or more and 40 mgKOH / g or less, and further preferably 1.0 mgKOH / g or more and 30 mgKOH / g or less. When the acid value of the modified polyolefin resin (A) is within the above range, the adhesive composition is sufficiently cured, and good adhesiveness, heat resistance, and low dielectric properties can be obtained.

[0039] The content of the modified polyolefin resin (A) is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more with respect to 100 parts by mass of the solid content of the adhesive composition. When the content of the modified polyolefin resin (A) is 50 parts by mass or more, it is easier to exhibit good adhesiveness. In addition, the content of the modified polyolefin resin (A) is preferably 99 parts by mass or less with respect to 100 parts by mass of the solid content of the adhesive composition.

[0040] 1.2 Thermal Conductive Filler (B) In the adhesive composition of the present embodiment, the thermal conductive filler (B) is important as a component for improving the thermal conductivity of the cured product of the adhesive composition.

[0041] The thermal conductive filler (B) has a thermal conductivity of 5 W / m·K or more. The thermal conductivity of the thermal conductive filler (B) can basically be determined by identifying the substance constituting the thermal conductive filler (B) and specifying the thermal conductivity from known literature (such as Chemical Handbook, known databases, etc.) for the identified substance, or by measuring the thermal conductivity of a sample of the identified substance. The material of the substance can be identified by methods such as the laser flash method. Also, the thermal conductivity of the substance sample can be determined by measuring the thermal conductivity of the substance sample in accordance with JIS R 1611.

[0042] From the viewpoint of improving the thermal conductivity of the cured product of the adhesive composition, the lower limit value of the thermal conductivity of the thermal conductive filler (B) is preferably 7 W / m·K or more, more preferably 10 W / m·K, and even more preferably 15 W / m·K or more. Also, the upper limit value of the thermal conductivity of the thermal conductive filler (B) is not particularly limited from the viewpoint of improving the thermal conductivity of the cured product of the adhesive composition, but from the viewpoints of insulation and the like, it is preferably 1000 W / m·K or less, more preferably 750 W / m·K or less, and even more preferably 500 W / m·K or less. In addition, the upper limit value and the lower limit value of the thermal conductivity of the above thermal conductive filler (B) can be arbitrarily combined.

[0043] Specific examples of the heat conduction filler (B) include boron nitride, aluminum nitride, aluminum oxide, magnesium oxide, etc. These can be used alone or in combination of two or more. Among these heat conduction fillers (B), boron nitride and aluminum nitride are preferable from the viewpoints of heat conductivity, dispersibility, etc., and boron nitride is more preferable.

[0044] The shape of the heat conduction filler (B) is not particularly limited. From the viewpoint of improving the dispersibility of the heat conduction filler (B), etc., the shape is preferably spherical, and more preferably a true sphere.

[0045] The lower limit of the content of the heat conduction filler (B) in the total solid content of the adhesive composition is preferably 3% by mass or more, more preferably 4% by mass or more, and further preferably 5% by mass or more from the viewpoint of improving the heat conductivity of the cured product of the adhesive composition. The upper limit of the content of the heat conduction filler (B) in the total solid content of the adhesive composition is not particularly limited from the viewpoint of improving the heat conductivity of the cured product of the adhesive composition, but is preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less from the viewpoints of adhesive strength, relative permittivity, etc. Note that the upper limit and the lower limit of the content of the heat conduction filler (B) can be arbitrarily combined.

[0046] 1.3 Low dielectric filler (C) In the adhesive composition of the present embodiment, the low dielectric filler (C) is important as a component for enhancing the low dielectric property of the cured product of the adhesive composition.

[0047] The low-dielectric filler (C) has a relative permittivity of 3.2 or less. The relative permittivity of the low-dielectric filler (C) can basically be determined by identifying the substance constituting the low-dielectric filler (C) and specifying the relative permittivity from known literature (such as Chemical Handbook, known databases, etc.) for the identified substance, or by measuring the relative permittivity for a sample of the identified substance. The material of the substance can be identified by methods such as the cavity resonator method. Also, the relative permittivity of the substance sample can be determined by measuring the relative permittivity of the substance sample in accordance with JIS C 2138.

[0048] From the viewpoint of improving the low-dielectric property of the cured product of the adhesive composition, the upper limit value of the relative permittivity of the low-dielectric filler (C) is preferably 3.1 or less, more preferably 3.0 or less, and even more preferably 2.8 or less. Note that the lower limit value of the relative permittivity of the low-dielectric filler (C) is not particularly limited.

[0049] Specific examples of the low-dielectric filler (C) include fluorine-based fillers composed of fluorine-based resins, LCP fillers composed of liquid crystal polymers, hollow silica, fused silica, etc. These can be used alone or in combination of two or more. Note that hollow silica is silica having a hollow structure inside. Also, fused silica is obtained by melting crushed silica powder and then cooling it. Among these low-dielectric fillers (C), from the viewpoints of low-dielectric property, dispersibility, etc., fluorine-based fillers and LCP fillers are preferred, and fluorine-based fillers are more preferred.

[0050] The fluororesin constituting the fluorine-based filler is a polymer containing fluorine atoms. Specific examples of the fluororesin constituting the fluorine-based filler include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and the like. Among these fluororesins, from the viewpoints such as having a low relative permittivity and dielectric tangent, polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymer are preferred, and polytetrafluoroethylene is more preferred.

[0051] The shape of the low-dielectric filler (C) is not particularly limited. From the viewpoint of improving the dispersibility of the low-dielectric filler (C), etc., the shape of the low-dielectric filler (C) is preferably spherical, and more preferably truly spherical.

[0052] The lower limit of the content of the low-dielectric filler (C) in the total solid content of the adhesive composition is preferably 1% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass or more from the viewpoint of improving the low-dielectric property of the cured product of the adhesive composition. The upper limit of the content of the low-dielectric filler (C) in the total solid content of the adhesive composition is not particularly limited from the viewpoint of improving the thermal conductivity of the cured product of the adhesive composition, but from the viewpoints of adhesiveness, etc., it is preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less. The upper limit and the lower limit of the content of the above low-dielectric filler (C) can be arbitrarily combined.

[0053] 1.4 Total content of the thermal conductive filler (B) and the low-dielectric filler (C) The adhesive composition of this embodiment contains a thermal conductive filler (B) and a low dielectric filler (C). That is, the adhesive composition of this embodiment uses the thermal conductive filler (B) and the low dielectric filler (C) in combination. Therefore, the adhesive composition of this embodiment can adjust the thermal conductivity and relative permittivity of the cured product to a desired range, and can achieve both high thermal conductivity and low dielectric properties of the cured product. However, in the adhesive composition of this embodiment, the total content of the thermal conductive filler (B) and the low dielectric filler (C) is 50% by mass or less. When the total content of the thermal conductive filler (B) and the low dielectric filler (C) exceeds 50% by mass, even if the balance between the thermal conductivity and the low dielectric properties in the cured product is achieved, the filler component in the adhesive composition increases, and accordingly, the proportion of the adhesive component decreases. As a result, it becomes difficult to ensure the adhesiveness of the cured product.

[0054] From the viewpoints of the adhesiveness of the cured product, the uniformity of the composition, etc., the upper limit value of the total content of the thermal conductive filler (B) and the low dielectric filler (C) is preferably 49% by mass or less, more preferably 48% by mass or less, and further preferably 45% by mass or less. On the other hand, from the viewpoint of the thermal conductivity of the cured product, etc., the lower limit value of the total content of the thermal conductive filler (B) and the low dielectric filler (C) is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. The upper limit value and the lower limit value of the total content of the thermal conductive filler (B) and the low dielectric filler (C) can be arbitrarily combined.

[0055] 1.5 Thermal Conductive Filler (B) / Low Dielectric Filler (C) Ratio In the adhesive composition of this embodiment, the thermal conductive filler (B) / low dielectric filler (C) ratio is 0.1 or more and 10 or less. The thermal conductive filler (B) / low dielectric filler (C) ratio is the mass ratio of the thermal conductive filler (B) to the low dielectric filler (C). The thermal conductive filler (B) / low dielectric filler (C) ratio is an important ratio for improving the thermal conductivity of the cured product and at the same time reducing the relative permittivity.

[0056] When the ratio of the thermal conductivity filler (B) / low dielectric filler (C) is less than 0.1, it becomes difficult to adjust the thermal conductivity of the cured product to a high level. From the viewpoint of improving the thermal conductivity of the cured product and the like, the lower limit value of the ratio of the thermal conductivity filler (B) / low dielectric filler (C) is preferably 0.12 or more, more preferably 0.125 or more, and still more preferably 0.15 or more. On the other hand, from the viewpoint of improving the dielectric properties and the like, the upper limit value of the ratio of the thermal conductivity filler (B) / low dielectric filler (C) is preferably 9.5 or less, more preferably 8.5 or less, and still more preferably 7 or less. The upper limit value and the lower limit value of the ratio of the thermal conductivity filler (B) / low dielectric filler (C) can be arbitrarily combined.

[0057] 1.6 Epoxy resin (D) In the adhesive composition of the present embodiment, the epoxy resin (D) reacts with reactive functional groups such as carboxy groups included in the modified polyolefin-based resin (A), and is an important component for expressing the adhesiveness to the adherend and the heat resistance of the cured adhesive.

[0058] Examples of the epoxy resin (D) include bisphenol A type epoxy resins, bisphenol F type epoxy resins, or hydrogenated products thereof; glycidyl ester type epoxy resins such as diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, glycidyl p-hydroxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl succinate, diglycidyl adipate, diglycidyl sebacate, triglycidyl trimellitate; glycidyl ether type epoxy resins such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, polyglycidyl ether of sorbitol, polyglycidyl ether of polyglycerol; glycidyl amine type epoxy resins such as triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane; linear aliphatic epoxy resins such as epoxidized polybutadiene, epoxidized soybean oil, etc., but are not limited thereto. Also, novolak type epoxy resins such as phenol novolak epoxy resin, o-cresol novolak epoxy resin, bisphenol A novolak epoxy resin can also be used.

[0059] Furthermore, examples of the epoxy resin (D) include brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, dicyclopentadiene skeleton-containing epoxy resin, naphthalene skeleton-containing epoxy resin, anthracene type epoxy resin, tertiary butyl catechol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, bisphenol S type epoxy resin, and the like. These epoxy resins (D) may be used alone or in combination of two or more. Among these epoxy resins (D), an epoxy resin having no glycidylamino group is preferable because the storage stability of the laminate with an adhesive layer is improved. Also, as the epoxy resin (D), a polyfunctional epoxy resin having an alicyclic skeleton is preferable and an epoxy resin having a dicyclopentadiene skeleton is more preferable because an adhesive composition excellent in dielectric properties can be obtained.

[0060] The epoxy resin (D) preferably has two or more epoxy groups in one molecule. This is because a crosslinked structure can be formed by the reaction with the modified polyolefin resin (A) to exhibit high heat resistance. Also, when an epoxy resin having two or more epoxy groups is used, the degree of crosslinking with the modified polyolefin resin (A) is sufficient and sufficient heat resistance can be obtained.

[0061] The content of the epoxy resin (D) is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less, based on 100 parts by mass of the modified polyolefin resin (A). When the content of the epoxy resin (D) is 1 part by mass or more, sufficient adhesiveness can be obtained. When the content of the epoxy resin (D) is 20 parts by mass or less, the peel adhesion strength and dielectric properties become good.

[0062] 1.7 Other Components In addition to the modified polyolefin resin (A), thermal conductive filler (B), low dielectric filler (C), and epoxy resin (D) described above, the adhesive composition of this embodiment may contain other thermoplastic resins, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, inorganic fillers, leveling agents, defoamers, pigments, ultraviolet absorbers, lubricants, solvents, etc., to an extent that does not affect the functions of the adhesive composition.

[0063] (Thermoplastic resin) Examples of the other thermoplastic resins include polyolefin resins, styrene elastomers, phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, and polyvinyl resins. These thermoplastic resins may be used alone or in combination of two or more.

[0064] Specific examples of the polyolefin resin include ethylene-α-olefin copolymers such as ethylene-propylene terpolymer (EPDM, EPT), ethylene-propylene copolymer (EPM), ethylene-butene copolymer, ethylene-propylene-butene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer, and the unmodified polyolefin resins described in the column of the above-mentioned modified polyolefin resin (A). These may be used alone or in combination of two or more.

[0065] Specific examples of the styrene elastomer include styrene-ethylene·butylene-styrene block copolymer (SEBS), styrene-ethylene·propylene-styrene block copolymer (SEPS), styrene-ethylene·butene·styrene-styrene block copolymer (SEBSS), styrene-isobutylene-styrene block copolymer (SIBS), and styrene-isoprene-styrene block copolymer (SIS). These may be used alone or in combination of two or more.

[0066] (Tackifier) Examples of the above-mentioned tackifier include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, p-t-butylphenol-acetylene resin, phenol-formaldehyde resin, xylene-formaldehyde resin, petroleum hydrocarbon resin, hydrogenated hydrocarbon resin, and terpin resin. These tackifiers may be used alone or in combination of two or more kinds.

[0067] (Flame retardant) The above-mentioned flame retardant may be either an organic flame retardant or an inorganic flame retardant. Examples of the organic flame retardant include phosphorus-based flame retardants such as melamine phosphate, polymelamine phosphate, guanidine phosphate, polyguanidine phosphate, ammonium phosphate, polyammonium phosphate, ammonium amide phosphate, polyammonium amide phosphate, carbamate phosphate, polycarbamate phosphate, aluminum tris(diethylphosphate), aluminum tris(methylethylphosphate), aluminum tris(diphenylphosphate), zinc bis(diethylphosphate), zinc bis(methylethylphosphate), zinc bis(diphenylphosphate), titanyl bis(diethylphosphate), titanium tetrakis(diethylphosphate), titanyl bis(methylethylphosphate), titanium tetrakis(methylethylphosphate), titanyl bis(diphenylphosphate), and titanium tetrakis(diphenylphosphate); nitrogen-based flame retardants such as triazine compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Examples of the inorganic flame retardant include metal hydroxides such as aluminum hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide; metal oxides such as tin oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide; and zinc carbonate, barium carbonate, zinc borate, and hydrated glass. These flame retardants may be used alone or in combination of two or more kinds.

[0068] (Hardener) Examples of the above-mentioned curing agent include, but are not limited to, amine-based curing agents and acid anhydride-based curing agents. Examples of the amine-based curing agent include melamine resins such as methylated melamine resin, butylated melamine resin, and benzoguanamine resin, dicyandiamide, 4,4'-diphenyldiaminosulfone, and the like. Examples of the acid anhydride include aromatic acid anhydrides and aliphatic acid anhydrides. These curing agents may be used alone or in combination of two or more.

[0069] The content of the curing agent is preferably 1 to 100 parts by mass, more preferably 5 to 70 parts by mass, based on 100 parts by mass of the epoxy resin (D).

[0070] (Curing accelerator) The above-mentioned curing accelerator can be used for the purpose of promoting the reaction between the modified polyolefin-based resin (A) and the epoxy resin (D), and a tertiary amine-based curing accelerator, a tertiary amine salt-based curing accelerator, an imidazole-based curing accelerator, etc. can be used.

[0071] Examples of the tertiary amine-based curing accelerator include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene, and the like.

[0072] Examples of the tertiary amine salt-based curing accelerator include formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, or phenol novolak resin salt of 1,8-diazabicyclo[5.4.0]undecene, and formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, or phenol novolak resin salt of 1,5-diazabicyclo[4.3.0]nonene, and the like.

[0073] Examples of imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and the like. These curing accelerators may be used alone or in combination of two or more.

[0074] When the adhesive composition of the present embodiment contains a curing accelerator, the content of the curing accelerator is preferably 1 part by mass or more and 15 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less, and still more preferably 2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the epoxy resin (D). If the content of the curing accelerator is within the above range, it is possible to easily exhibit excellent adhesiveness and heat resistance.

[0075] (Coupling agent) Examples of the coupling agent include silane coupling agents such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, imidazole silane; titanate coupling agents; aluminate coupling agents; zirconium coupling agents and the like. These may be used alone or in combination of two or more.

[0076] (Heat aging inhibitor) Examples of the heat aging inhibitor include, for example, antioxidants. Specific examples thereof include phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol, n-octadecyl 3-(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate]; sulfur antioxidants such as dilauryl 3,3’-thiodipropionate, dimyristyl 3,3’-dithiopropionate; phosphorus antioxidants such as tris(nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite and the like. These may be used alone or in combination of two or more.

[0077] (Inorganic filler) Examples of the inorganic filler include powders composed of titanium oxide, zinc oxide, carbon black, talc, copper, silver and the like. These may be used alone or in combination of two or more.

[0078] (Lubricant) Examples of the above lubricant include oleic acid amide, stearic acid amide, erucic acid amide, etc. These may be used alone or in combination of two or more kinds.

[0079] (Solvent) The adhesive composition of this embodiment can be produced by mixing a modified polyolefin-based resin (A), a thermal conductive filler (B), a low dielectric filler (C), an epoxy resin (D), and other components as necessary. The mixing method is not particularly limited as long as the adhesive composition becomes uniform. Since the adhesive composition is preferably used in the state of a solution or a dispersion, usually a solvent such as an organic solvent is also used.

[0080] Examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane, etc. These solvents may be used alone or in combination of two or more kinds. When the adhesive composition contains a solvent and is a solution or a dispersion (resin varnish) in which each component is dissolved or dispersed in the solvent, coating on the base film and formation of the adhesive layer can be carried out smoothly, and an adhesive layer with a desired thickness can be easily obtained.

[0081] When the adhesive composition of the present embodiment contains a solvent such as an organic solvent, from the viewpoint of workability including the formation of the adhesive layer, the solid content concentration is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less. When the solid content concentration is 80% by mass or less, the viscosity of the solution is appropriate and it is easy to coat uniformly. In the present disclosure, "solid content" means the components excluding the solvent.

[0082] 1.8 Dielectric properties of the cured product of the adhesive composition 1.8.1 Relative permittivity of the cured product of the adhesive composition For the adhesive composition of the present embodiment, the relative permittivity (Dk, εr) of the cured product of the adhesive composition measured at a frequency of 10 GHz is preferably 3.5 or less. If the relative permittivity is 3.5 or less, it can be suitably used for FPC-related products with strict requirements for dielectric properties, which can cope with further increases in signal speed and further increases in signal frequency in recent years. The relative permittivity is preferably 3.3 or less, more preferably 3.0 or less, and even more preferably 2.8 or less. The relative permittivity can be adjusted by the types and contents of the respective components in the adhesive composition. The details of the measurement method of the relative permittivity will be described in detail in the examples described later.

[0083] 1.8.2 Dielectric tangent of the cured product of the adhesive composition For the adhesive composition of the present embodiment, the dielectric tangent (Df, tanδ) of the cured product of the adhesive composition measured at a frequency of 10 GHz is preferably 0.01 or less. If the dielectric tangent is 0.01 or less, it can be suitably used for FPC-related products with strict requirements for dielectric properties, which can cope with further increases in signal speed and further increases in signal frequency in recent years. The dielectric tangent is preferably 0.008 or less, more preferably 0.007 or less, and even more preferably 0.005 or less. The measurement method of the dielectric tangent can be measured in the same manner as the measurement method of the relative permittivity described in detail in the examples described later.

[0084] 1.9 Thermal conductivity of the cured product of the adhesive composition The adhesive composition of this embodiment preferably has a thermal conductivity of 0.2 W / m·K or more for the cured product of the adhesive composition. If the thermal conductivity is 0.2 W / m·K or more, it becomes easier to suppress the performance degradation due to heat generation of FPC-related products by improving the heat dissipation of the cured product. The lower limit value of the thermal conductivity is preferably 0.25 W / m·K or more, more preferably 0.3 W / m·K or more, and even more preferably 0.35 W / m·K or more. The method for measuring the thermal conductivity will be described in detail in the examples below.

[0085] 2. Laminated body with an adhesive layer The laminated body with an adhesive layer of this embodiment includes an adhesive layer formed from the above-described adhesive composition and a base film in contact with at least one surface of the adhesive layer. The state of the adhesive layer is as defined above. Hereinafter, the laminated body with an adhesive layer of this embodiment will be specifically described.

[0086] As one aspect of the laminated body with an adhesive layer, a coverlay film can be mentioned. A coverlay film is usually a laminated body in which an adhesive layer is formed on at least one surface of a base film and it is difficult to peel the base film from the adhesive layer.

[0087] Examples of the base film included in the laminated body with an adhesive layer include a polyimide film, a polyether ether ketone film, a polyphenylene sulfide film, an aramid film, a polyethylene naphthalate film, a liquid crystal polymer film, etc. Among these, from the viewpoints of adhesiveness and electrical properties, a polyimide film, a polyethylene naphthalate film, and a liquid crystal polymer film are preferable.

[0088] As a method for manufacturing the laminated body with an adhesive layer, for example, after applying a resin varnish containing the above-described adhesive composition and a solvent to the surface of a base film such as a polyimide film to form a resin varnish layer, the solvent is removed from this resin varnish layer, whereby a laminated body with an adhesive layer having a B-stage adhesive layer formed thereon can be manufactured.

[0089] When removing the solvent, the drying temperature is preferably 40 to 250°C, more preferably 70 to 170°C. Drying can be performed by passing the laminate coated with the adhesive composition through a furnace where hot air drying, far-infrared heating, high-frequency induction heating, etc. are carried out.

[0090] In addition, if necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. As the release film, known ones such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, polymethylpentene (TPX) film, fluororesin film, etc. can be used.

[0091] Another aspect of the laminate with an adhesive layer is a bonding sheet. The bonding sheet is also one in which the above adhesive layer is formed on the surface of the base film, but the base film functions as a release film. Also, the bonding sheet may be in a form having an adhesive layer between two release films. The release film is peeled off when using the bonding sheet. The same release films as those described above can be used.

[0092] As a method for manufacturing the bonding sheet, for example, there is a method of applying a resin varnish containing the above adhesive composition and solvent on the surface of the release film and drying it in the same manner as in the case of the coverlay film.

[0093] The thickness of the adhesive layer can be preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, still more preferably 10 μm or more and 50 μm or less in order to fully exhibit the adhesive strength. Also, the thickness of the base film can be preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, still more preferably 5 μm or more and 30 μm or less from the viewpoint of thinning the laminate with an adhesive layer, etc.

[0094] In the adhesive composition used for forming the adhesive layer, the above-described thermal conductive filler (B) preferably has an average particle diameter of 50% or less of the layer thickness of the adhesive layer. According to this configuration, it is difficult for the thermal conductive filler (B) to protrude from the layer surface of the adhesive layer, it is easy to secure the adhesive area, and it is easy to secure excellent adhesiveness. The average particle diameter of the thermal conductive filler (B) described above is the arithmetic mean value of the particle diameter measurement values measured for 10 arbitrary thermal conductive filler (B) particles in the SEM cross section along the thickness direction of the adhesive layer.

[0095] From the viewpoint of the adhesiveness of the adhesive layer, etc., the upper limit value of the average particle diameter of the thermal conductive filler (B) is more preferably 90% or less, and even more preferably 80% or less of the layer thickness of the adhesive layer. The lower limit value of the average particle diameter of the thermal conductive filler (B) is preferably 1% or more, more preferably 2% or more, and even more preferably 4% or more of the layer thickness of the adhesive layer from the viewpoint of thermal conductivity, etc. The upper limit value and the lower limit value of the average particle diameter of the thermal conductive filler (B) can be arbitrarily combined.

[0096] In the adhesive composition used for forming the adhesive layer, the above-described low dielectric filler (C) preferably has an average particle diameter of 50% or less of the layer thickness of the adhesive layer. According to this configuration, it is difficult for the low dielectric filler (C) to protrude from the layer surface of the adhesive layer, it is easy to secure the adhesive area, and it is easy to secure excellent adhesiveness. The average particle diameter of the low dielectric filler (C) described above is the arithmetic mean value of the particle diameter measurement values measured for 10 arbitrary low dielectric filler (C) particles in the SEM cross section along the thickness direction of the adhesive layer.

[0097] From the viewpoint of the adhesiveness of the adhesive layer, etc., the upper limit value of the average particle diameter of the low dielectric filler (C) is more preferably 90% or less, and even more preferably 80% or less of the layer thickness of the adhesive layer. The lower limit value of the average particle diameter of the low dielectric filler (C) is preferably 1% or more, more preferably 2% or more from the viewpoint of dispersibility, etc. of the adhesive layer. The upper limit value and the lower limit value of the average particle diameter of the low dielectric filler (C) can be arbitrarily combined.

[0098] 3. Flexible Copper-Clad Laminate The flexible copper-clad laminate of this embodiment includes a base film on one surface of the adhesive layer in the above-mentioned laminate with an adhesive layer, and a copper foil on the other surface of the adhesive layer. Specifically, the flexible copper-clad laminate can be configured such that the base film and the copper foil are bonded together using the above-mentioned laminate with an adhesive layer. That is, the flexible copper-clad laminate can be formed by laminating a base film, an adhesive layer, and a copper foil in this order. Note that the adhesive layer and the copper foil may be formed on both surfaces of the base film. Since the above-described adhesive composition has excellent adhesiveness to articles containing copper, the flexible copper-clad laminate has excellent stability as an integrated product.

[0099] As a method for manufacturing a flexible copper-clad laminate, for example, the adhesive layer of the above-mentioned laminate with an adhesive layer and the copper foil are brought into surface contact, and thermal lamination is performed at a temperature of, for example, 80°C or higher and 150°C or lower, and then the adhesive layer is cured by post-curing. The conditions for post-curing can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

[0100] 4. Flexible Flat Cable The flexible flat cable of this embodiment includes a base film on one surface of the adhesive layer in the above-mentioned laminate with an adhesive layer, and a copper wiring on the other surface of the adhesive layer. Specifically, the flexible flat cable can be configured such that the base film and the copper wiring are bonded together using the above-mentioned laminate with an adhesive layer. That is, the flexible flat cable can be formed by laminating a base film, an adhesive layer, and a copper wiring in this order. Note that the adhesive layer and the copper wiring may be formed on both surfaces of the base film. Since the above-described adhesive composition has excellent adhesiveness to articles containing copper, the flexible flat cable has excellent stability as an integrated product.

[0101] As a method for manufacturing a flexible flat cable, for example, there is a method in which the adhesive layer of the above-described laminate with an adhesive layer is brought into contact with a copper wiring, and thermal lamination is performed at a temperature of, for example, 80°C or higher and 150°C or lower, and the adhesive layer is further cured by post-cure. The conditions for post-cure can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited and can be appropriately selected as desired.

Examples

[0102] The present invention will be described more specifically based on examples, but the present invention is not limited thereto. In the following, parts and % are based on mass unless otherwise specified.

[0103] 1. Evaluation method (1) Weight-average molecular weight Mw Under the following conditions, GPC measurement was performed to determine the weight-average molecular weight Mw of the modified polyolefin-based resin (A). The weight-average molecular weight Mw was converted based on the retention time measured by GPC with reference to the retention time of standard polystyrene. Apparatus: Alliance 2695 (manufactured by Waters) Columns: 2 TSKgel SuperMultipore HZ-H, 2 TSKgel Super HZ2500 (manufactured by Tosoh Corporation) Column temperature: 40°C Eluent: Tetrahydrofuran 0.35 ml / min Detector: RI (differential refractive index detector)

[0104] (2) Acid value 1 g of the modified polyolefin-based resin (A) was dissolved in 30 ml of toluene, and a burette of the same company's "APB-510-20B" was connected to the automatic titrator "AT-510" manufactured by Kyoto Electronics Industry Co., Ltd. Potentiometric titration was performed using a 0.01 mol / L benzyl alcohol KOH solution as the titration reagent, and the number of mg of KOH per 1 g of the resin was calculated.

[0105] (3) Dielectric properties (relative permittivity) of the cured product of the adhesive composition A release PET film with a thickness of 38 μm was prepared, and the predetermined liquid adhesive composition described in Tables 1 and 2 was applied to the release-treated surface thereof. Next, the film with the coating film was left standing in an oven and dried at 90 °C for 3 minutes to form a film (adhesive layer) with a thickness of 50 μm, thereby obtaining an adhesive layer. Next, the adhesive layer was left standing in an oven and cured at 180 °C for 60 minutes. Thereafter, the release film was peeled off to obtain a test piece (100 mm × 80 mm) composed of the cured product of the adhesive composition. The relative permittivity (Dk, εr) was measured under the conditions of a temperature of 23 °C and a frequency of 10 GHz by the split post dielectric resonator method (SPDR method) using a network analyzer 85071E-300 (manufactured by Agilent Technologies). When the relative permittivity was 3.5 or less, it was described as "A" indicating that the cured product had a low relative permittivity. When the relative permittivity was more than 3.5, it was described as "C" indicating that the cured product had a high relative permittivity.

[0106] (4) Thermal conductivity of the cured product of the adhesive composition A release PET film with a thickness of 38 μm was prepared, and the predetermined liquid adhesive composition described in Tables 1 and 2 was applied to the release-treated surface thereof. Next, the film with the coating film was left standing in an oven and dried at 90 °C for 3 minutes to form a B-stage adhesive layer (thickness: 25 μm), thereby obtaining a laminate with an adhesive. Next, the laminate with the adhesive was left standing in an oven and cured at 180 °C for 60 minutes to obtain a cured product of the C-stage adhesive composition. Thereafter, the release PET film was peeled off and used as a test piece (cured product of the adhesive composition). Next, for this test piece, the thermal conductivity (W / m·K) in the thickness direction was measured using a thermal conductivity measuring device (manufactured by Resca, "TCM1001"). When the thermal conductivity was 0.2 W / m·K or more, it was described as "A" indicating that the cured product had excellent thermal conductivity. When the thermal conductivity was less than 0.2 W / m·K, it was described as "C" indicating that the cured product had poor thermal conductivity.

[0107] (5) Peel adhesion strength of the cured product of the adhesive composition A release PET film with a thickness of 38 μm was prepared, and the predetermined liquid adhesive composition described in Table 1 and Table 2 was roll-coated on its release-treated surface. Next, this film with the coating was left standing in an oven and dried at 90°C for 3 minutes to form an adhesive layer in the B-stage state (thickness: 25 μm). Next, it was superposed on the polyimide film surface of a copper-clad laminate (a laminate of a 25-μm-thick polyimide film and an 18-μm-thick copper foil) so that the adhesive layer was in surface contact, and lamination was performed under the conditions of a temperature of 120°C, a pressure of 0.4 MPa, and a speed of 0.5 m / min. Next, the release PET film was peeled off. Next, a 35-μm-thick rolled copper foil was superposed on the adhesive layer surface of the laminate composed of the copper-clad laminate / adhesive layer so as to be in surface contact with the surface of the adhesive layer, and lamination was performed under the conditions of a temperature of 120°C, a pressure of 0.3 MPa, and a speed of 0.5 m / min. The laminate in this state was designated as Substrate A. Next, this Substrate A (copper-clad laminate / adhesive layer / rolled copper foil) was heated and pressed at a temperature of 180°C and a pressure of 3 MPa for 30 minutes to obtain a flexible copper-clad laminate. Then, an adhesive test piece cut into a size of 10 mm × 100 mm was obtained from this flexible copper-clad laminate. Next, in order to evaluate the adhesiveness, in accordance with JIS C 6481 "Test Methods for Copper-Clad Laminates for Printed Wiring Boards", the 180° peel adhesion strength (N / cm) when peeling the copper-clad laminate of the above adhesive test piece from the copper foil was measured under the conditions of a temperature of 23°C and a tensile speed of 50 mm / min. The width of the adhesive test piece during measurement was 10 mm.

[0108] When the 180° peel adhesion strength of the above adhesive test piece was 3 N / cm or more, it was described as "A", assuming that the cured product had excellent adhesiveness. When the 180° peel adhesion strength of the above adhesive test piece was less than 3 N / cm, it was described as "C", assuming that the cured product had poor adhesiveness.

[0109] 2. Raw Materials of the Adhesive Composition As the raw materials of the adhesive composition, the following were prepared. (1) Modified Polyolefin-Based Resin (A) As the modified polyolefin-based resin (A), an acid-modified polypropylene-based resin (a1) was produced by the method shown below.

[0110] 100 parts by mass of a propylene / 1-butene copolymer (molar ratio: propylene / 1-butene = 70 / 30) was heated and melted in a four-necked flask under a nitrogen atmosphere. After that, while maintaining the temperature inside the system at 170 °C and stirring, 1.5 parts by mass of maleic anhydride as an unsaturated carboxylic acid and 1.2 parts by mass of dicumyl peroxide as a radical generator were each added over 1 hour, and then reacted for 1 hour. After the reaction was completed, the obtained reaction product was poured into a large amount of acetone to solidify the resin. This resin was cut finely and processed into pellets. Next, this pelletized resin was mixed with acetone three times the mass of the resin and stirred at 50 °C for 1 hour to wash the resin. Next, after recovering the resin, the resin was washed in the same manner again to remove free maleic anhydride. Next, the washed resin was dried under reduced pressure in a vacuum dryer to obtain a modified polyolefin resin (a1). The acid-modified polyolefin resin (a1) as the obtained modified polyolefin resin (A) had a weight average molecular weight Mw of 150,000 and an acid value of 10 mgKOH / g.

[0111] (2) Thermal Conductive Filler (B) · Boron nitride (b1) (manufactured by Saint-Gobain, "PCTP2") · Boron nitride (b2) (manufactured by Saint-Gobain, "PCTF5") Note that the thermal conductivity of boron nitride is about 40 W / m·K, satisfying the requirement of the thermal conductive filler (B) that the thermal conductivity is 5 W / m·K or more.

[0112] (3) Low Dielectric Filler (C) · PTFE filler (c1) (manufactured by AGC, "EA-2000") (relative permittivity: 2.2 or less) · LCP filler (c2) (manufactured by ENEOS, "LF-31P") (relative permittivity: 2.5 or less)

[0113] (4) Epoxy Resin (D) · Dicyclopentadiene skeleton-containing epoxy resin (d1) (hereinafter, also referred to as DCPD-type epoxy resin (d1)) (manufactured by DIC, "EPICLON HP-7200")

[0114] (5) Others · Curing accelerator (imidazole-based curing accelerator) (manufactured by Shikoku Kasei Co., Ltd., "Curezol C11Z") · Solvent (mixed solvent consisting of toluene and methylcyclohexane (mass ratio = 20:80) The amount of the solvent was appropriately adjusted so that the solid content concentration of the adhesive composition was 15 to 30% by mass.

[0115] 3. Manufacture and evaluation of the adhesive composition Into a 1000 ml flask equipped with a stirrer, the above raw materials were added at the predetermined ratios shown in Tables 1 and 2, and the solvent was added and stirred at room temperature (25 °C) for 6 hours to dissolve, thereby preparing each adhesive composition and conducting an evaluation. The results are shown in Tables 1 and 2.

[0116] 4. Manufacture and evaluation of the laminate with an adhesive layer Using the above adhesive composition, a laminate with an adhesive layer was manufactured and evaluated as described in the explanations regarding the above evaluation methods. The results are shown in Tables 1 and 2.

[0117]

Table 1

[0118]

Table 2

[0119] According to Tables 1 and 2, the following can be understood. That is, Sample 1C does not use the thermal conductive filler (B) and the low dielectric filler (C) in combination, and uses only the thermal conductive filler (B). Therefore, Sample 1C cannot adjust the relative dielectric constant of the cured product to be low.

[0120] Sample 2C does not use the thermal conductive filler (B) and the low dielectric filler (C) in combination, and uses only the low dielectric filler (C). Therefore, Sample 2C has almost the thermal conductivity of the resin used in the adhesive composition, and cannot improve the thermal conductivity of the cured product.

[0121] Although Sample 3C uses both the thermal conductivity filler (B) and the low dielectric filler (C), the total content of both is more than the value defined in the present disclosure. Therefore, even if Sample 3C can balance the thermal conductivity and low dielectric property of the cured product, it cannot ensure the adhesiveness of the cured product.

[0122] Although Sample 4C uses both the thermal conductivity filler (B) and the low dielectric filler (C), the ratio of the thermal conductivity filler (B) / low dielectric filler (C) is larger than the value defined in the present disclosure. Therefore, Sample 4C cannot adjust the relative dielectric constant of the cured product to be low.

[0123] Although Sample 5C uses both the thermal conductivity filler (B) and the low dielectric filler (C), the ratio of the thermal conductivity filler (B) / low dielectric filler (C) is smaller than the value defined in the present disclosure. Therefore, Sample 4C cannot adjust the thermal conductivity of the cured product to be high.

[0124] In contrast, Samples 1 to 11 satisfy the requirements defined in the present disclosure for the adhesive composition. Therefore, it was confirmed that for Samples 1 to 11, the cured product has a low relative dielectric constant and is excellent in thermal conductivity and adhesiveness.

[0125] According to the above results, it can be said that the present disclosure can provide an adhesive composition in which the cured product has a low relative dielectric constant and is excellent in thermal conductivity and adhesiveness, and a laminate with an adhesive layer using the same.

[0126] The present invention is not limited to the above-described embodiments and examples, and various modifications are possible without departing from the gist thereof. In addition, each configuration shown in the above-described embodiments and examples can be arbitrarily combined.

Claims

1. A modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, a thermal conductive filler (B) having a thermal conductivity of 5 W / m·K or more, a low dielectric filler (C) having a relative permittivity of 3.2 or less, and an epoxy resin (D), wherein the adhesive composition contains, the total content of the thermal conductive filler (B) and the low dielectric filler (C) in the entire solid content of the adhesive composition is 50% by mass or less, and the mass ratio of the thermal conductive filler (B) to the low dielectric filler (C), i.e., the thermal conductive filler (B) / low dielectric filler (C) ratio, is 0.1 or more and 10 or less. An adhesive composition.

2. The content of the thermal conductive filler (B) in the entire solid content of the adhesive composition is 3% by mass or more. The adhesive composition according to Claim 1.

3. The relative permittivity of the cured product of the adhesive composition measured at a frequency of 10 GHz is 3.5 or less. The adhesive composition according to Claim 1.

4. The thermal conductive filler (B) is at least one selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, and magnesium oxide. The adhesive composition according to Claim 1.

5. The low dielectric filler (C) is at least one selected from the group consisting of a fluorine-based filler composed of a fluorine-based resin, an LCP filler composed of a liquid crystal polymer, hollow silica, and fused silica. The adhesive composition according to Claim 1.

6. An adhesive layer laminate comprising an adhesive layer formed from the adhesive composition according to any one of Claims 1 to 5, and a base film in contact with at least one surface of the adhesive layer.

7. The average particle diameter of the thermal conductive filler (B) is 50% or less of the layer thickness of the adhesive layer. The adhesive layer laminate according to Claim 6.

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