Polyester, film and adhesive composition, as well as adhesive sheet, laminate and printed wiring board

Abstract

To provide a polyester, film and adhesive composition which are excellent in solvent solubility, heat resistance and adhesive strength, and have low relative dielectric constant and dielectric loss tangent, and excellent in dielectric properties, and to provide an adhesive sheet, laminate and printed wiring board using the same. [Solution] Ester group concentration is 5000eq / 10 6 g or less and a glass transition temperature of -30°C or more.

Description

[Technical Field]

[0001] The present invention relates to polyesters, and more particularly to polyesters, films, and adhesive compositions having excellent dielectric properties, as well as adhesive sheets, laminates, and printed wiring boards having layers formed therefrom. [Background technology]

[0002] Polyesters are widely used as raw materials for resin compositions used in coatings, inks, adhesives, etc. and are generally composed of polycarboxylic acids and polyhydric alcohols. Because they offer flexibility and the ability to freely control molecular weight by selecting and combining polycarboxylic acids and polyhydric alcohols, they are widely used in a variety of applications, including coatings and adhesives.

[0003] Among these, polyester has excellent adhesive properties with metals including copper, and has been used as an adhesive for FPCs and the like by blending it with a curing agent such as epoxy resin (see, for example, Patent Document 1).

[0004] FPCs have excellent flexibility, allowing them to accommodate the increasing functionality and miniaturization of personal computers (PCs) and smartphones. Therefore, they are widely used to incorporate electronic circuit boards into narrow and complex interior spaces. In recent years, electronic devices have become smaller, lighter, more dense, and more powerful. These trends have led to increasingly demanding performance from wiring boards (electronic circuit boards). In particular, the speed of FPC transmission signals has increased, leading to increasingly higher signal frequencies. Accordingly, there is a growing demand for FPCs with low dielectric properties (low dielectric constant, low dielectric dissipation factor) in the high-frequency range. Furthermore, in addition to conventional polyimide (PI) and polyethylene terephthalate (PET) substrates for FPCs, substrate films with low dielectric properties, such as liquid crystal polymer (LCP) and syndiotactic polystyrene (SPS), have been proposed. To achieve these low dielectric properties, measures have been taken to reduce the dielectric loss of FPC substrates and adhesives. Development of adhesives, such as a combination of polyolefin and epoxy (Patent Document 2), is currently underway. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Tokuhei 6-104813 [Patent Document 2] WO2016 / 047289 publication DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] However, the polyester resin described in Patent Document 1 has a high relative dielectric constant and dielectric loss tangent, does not have the low dielectric properties described above, and is unsuitable for FPCs in the high frequency range. Also, the adhesive described in Patent Document 2 cannot be said to have excellent heat resistance when used in reinforcing plates or between layers.

[0007] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide polyesters, films, and adhesive compositions having excellent solvent solubility, heat resistance, adhesive strength, and dielectric properties such as low dielectric constant and dielectric loss tangent, as well as adhesive sheets, laminates, and printed wiring boards having layers formed therefrom. [Means for solving the problem]

[0008] As a result of extensive investigations, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention comprises the following configurations.

[0009] Ester group concentration is 5000eq / 10 6 g or less and a glass transition temperature of -30°C or more.

[0010] The polyester contains 25 mol % or more of the following monomer (A) when the total amount of all constituent components constituting the polyester is taken as 100 mol %: Monomer (A): a polycarboxylic acid component and / or a polyhydric alcohol component having a polycyclic structure

[0011] The polyester contains 10 mol % or more of the following monomer (B) when the total amount of all constituent components of the polyester is taken as 100 mol %: Monomer (B): a polycarboxylic acid component and / or a polyhydric alcohol component having a continuous carbon chain of 10 or more carbon atoms

[0012] The polyester preferably has a relative dielectric constant (εc) of 3.0 or less and a dielectric loss tangent (tan δ) of 0.008 or less at 10 GHz.

[0013] A film containing the polyester.

[0014] An adhesive composition containing the polyester.

[0015] An adhesive sheet having a layer formed from the adhesive composition.

[0016] A laminate having a layer formed from the adhesive composition.

[0017] A printed wiring board comprising the laminate as a component. [Effects of the Invention]

[0018] The polyester of the present invention has excellent solvent solubility, heat resistance, adhesive strength, and dielectric properties, making it suitable for use in base films for FPCs in the high frequency range, FPC adhesives, adhesive sheets, laminates, and printed wiring boards. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described in detail below, however, the present invention is not limited to this embodiment and can be practiced in various modified forms within the scope of the above description.

[0020] <Polyester> The polyester of the present invention has a chemical structure that can be obtained by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component, and the polycarboxylic acid component and the polyhydric alcohol component each consist of one or more selected components.

[0021] The polyester of the present invention has an ester group concentration of 5000 eq / 10 6 The low ester group concentration reduces the polarity of the polymer, resulting in low dielectric properties. The ester group concentration is preferably 4500 eq / 10 6 g or less, more preferably 4000 eq / 10 6 g or less, particularly preferably 3500 eq / 10 6 g or less.

[0022] The dielectric loss tangent of the polyester of the present invention at 10 GHz is preferably 0.008 or less, more preferably 0.005 or less. By using a polyester with a low dielectric loss tangent, an adhesive composition with good low dielectric properties can be formed.

[0023] The relative dielectric constant of the polyester of the present invention at 10 GHz is preferably 3.0 or less, more preferably 2.6 or less. By using a polyester with a low relative dielectric constant, an adhesive composition with good low dielectric properties can be formed.

[0024] The glass transition temperature of the polyester in the present invention is -30°C or higher, and more preferably -20°C or higher. By setting the glass transition temperature in the range of -30°C or higher, good dielectric properties are exhibited, and further, tackiness (adhesiveness) of the resin surface tends to be suppressed, improving the handleability of the resin. Furthermore, the glass transition temperature is preferably 100°C or lower. By setting the glass transition temperature to 100°C or lower, lamination can be performed even at a low temperature of around 80°C. Furthermore, the lower the glass transition temperature, the better the adhesive strength tends to be.

[0025] The polyester of the present invention preferably contains the following monomer (A) and / or monomer (B) as a constituent component. Monomer (A): a polycarboxylic acid component and / or a polyhydric alcohol component having a polycyclic structure Monomer (B): a polycarboxylic acid component and / or a polyhydric alcohol component having a continuous carbon chain of 10 or more carbon atoms

[0026] <Monomer (A)> Monomer (A) is a polycarboxylic acid component and / or a polyhydric alcohol component having a polycyclic structure. A polycyclic structure refers to a structure in which multiple ring structures composed mainly of carbon are bonded together, and examples include structures having an aromatic skeleton such as naphthalene, anthracene, indane, or tetralin, or an alicyclic skeleton such as decalin, norbornane, or tricyclodecane. The presence of a polycyclic structure increases the free volume of the polyester, thereby exhibiting low dielectric properties.

[0027] Examples of the monomer (A), which is a polyvalent carboxylic acid component or a polyhydric alcohol component having a polycyclic structure, include 2,6-naphthalenedicarboxylic acid, tricyclodecane dimethanol, pentacyclodecane dimethanol, bisphenol fluorene, bisphenoxyethanol fluorene, bisphenoxymethanol fluorene, biscresol fluorene, spiroglycol, and hydrogenated naphthalenedicarboxylic acid.

[0028] The polyester of the present invention preferably contains 25 mol % or more of the monomer (A) when the total amount of all constituent components of the polyester is taken as 100 mol %. It is more preferably 40 mol % or more, even more preferably 50 mol % or more, and particularly preferably 60 mol % or more. By containing the monomer (A) in an amount equal to or greater than the above value, the low dielectric properties are improved, and the effect on the dielectric loss tangent is particularly significant.

[0029] <Monomer (B)> Monomer (B) is a polycarboxylic acid component and / or a polyhydric alcohol component having a continuous carbon chain of 10 or more. A carbon chain is a structure having continuous carbon-carbon bonds. Monomer (B) is a polycarboxylic acid component and / or a polyhydric alcohol component. The carboxylic acid groups or alcohol groups are connected by a continuous carbon chain of 10 or more, which reduces the polar group concentration of the polyester and contributes to low dielectric properties. The carbon chain may contain a ring structure, but the carboxylic acid groups or alcohol groups must be separated by at least 10 carbon atoms. Furthermore, from the perspective of low dielectric properties, it is preferable that the carbon chain does not contain heteroatoms such as nitrogen, oxygen, or sulfur other than the carboxylic acid groups or alcohol groups. It is preferable that the carbon chain is entirely hydrocarbon.

[0030] Examples of the monomer (B), which is a polyvalent carboxylic acid component or a polyhydric alcohol component having a chain of 10 or more consecutive carbon atoms, include dimer acid, dimer diol, dimer acid ester (polyester polyol derived from dimer acid), hydroxyl-terminated polybutadiene, hydroxyl-terminated hydrogenated polybutadiene, hydroxyl-terminated polyisoprene, and hydroxyl-terminated polyolefin.

[0031] The dimer acid refers to a polymeric fatty acid having 20 to 48 carbon atoms obtained by dimerizing C10 to C24 unsaturated fatty acids. It also includes saturated dimer acids obtained by hydrogenating the unsaturated groups. Dimer diols can be obtained by reducing the carboxyl groups of the dimer acids. Vegetable oils may be used as raw materials for dimer acids and dimer diols. Furthermore, dimer diols may include trimers, which are trimers of C10 to C24 unsaturated fatty acids, or saturated trimers obtained by hydrogenating trimers.

[0032] The number average molecular weight of the monomer (B) is preferably at least 300, more preferably at least 400, and even more preferably at least 500. The larger the molecular weight, the lower the polar group concentration, and therefore the lower dielectric properties are improved.

[0033] The polyester of the present invention preferably contains 10 mol % or more of the monomer (B) when the total amount of all constituent components of the polyester is taken as 100 mol %. It is more preferably 15 mol % or more, even more preferably 20 mol % or more, and particularly preferably 25 mol % or more. By containing the monomer (B) in an amount equal to or greater than the above value, low dielectric properties are improved. Furthermore, the polyester also has excellent solvent solubility.

[0034] The polyester of the present invention preferably contains 60 mol% or more of monomer (A) and monomer (B) in total, assuming the total amount of all constituent components of the polyester to be 100 mol%. More preferably, it is 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 85 mol% or more, and most preferably 90 mol% or more. 100 mol% is also acceptable. As described above, by containing 25 mol% or more of monomer (A) and 10 mol% or more of monomer (B), and by containing the total amount of monomer (A) and monomer (B) equal to or greater than the above values, a polyester can be obtained that exhibits extremely excellent low dielectric properties and has a good balance of various physical properties, such as solvent solubility and glass transition temperature.

[0035] The polyester of the present invention may contain a polycarboxylic acid component and a polyhydric alcohol component other than the monomers (A) and (B). The polycarboxylic acid component other than the monomers (A) and (B) is not particularly limited, but the polycarboxylic acid component is preferably an aromatic polycarboxylic acid component or an alicyclic polycarboxylic acid component, and more preferably an aromatic dicarboxylic acid component or an alicyclic dicarboxylic acid component. The use of an aromatic polycarboxylic acid component or an alicyclic polycarboxylic acid component as a copolymerization component can exhibit excellent dielectric properties.

[0036] The aromatic dicarboxylic acid component is not particularly limited, but examples thereof include terephthalic acid, isophthalic acid, orthophthalic acid, 4,4'-dicarboxybiphenyl, and 5-sodium sulfoisophthalic acid.

[0037] The alicyclic dicarboxylic acid component is not particularly limited, but examples thereof include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0038] The polyhydric alcohol component other than the monomer (A) and the monomer (B) is not particularly limited, but examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n aliphatic polyhydric alcohols such as 2-n-propyl-1,3-propanediol, 2,2-di-n-propyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2-ethyl-1,3-hexanediol; alicyclic polyhydric alcohols such as 1,4-cyclohexanedimethanol; and polyalkylene ether glycols such as polytetramethylene glycol and polypropylene glycol. Among these, one or more kinds can be used.

[0039] The polyester of the present invention may also be copolymerized with a trivalent or higher polycarboxylic acid component and / or a trivalent or higher polyhydric alcohol component. Examples of trivalent or higher polycarboxylic acid components include aromatic carboxylic acids such as trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, trimesic acid, trimellitic anhydride (TMA), and pyromellitic anhydride (PMDA), and aliphatic carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid. These may be used singly or in combination of two or more. Examples of trivalent or higher polyhydric alcohol components include glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, and sorbitol. These may be used singly or in combination of two or more. However, copolymerization of a large amount of trivalent or higher polycarboxylic acid component and / or trivalent or higher polyhydric alcohol component is undesirable because it may deteriorate the dielectric properties of the polyester. When a trivalent or higher polycarboxylic acid component and / or a trivalent or higher polyalcohol component is copolymerized, it is preferably 3 mol % or less, more preferably 2 mol % or less, based on 100 mol % of the total of all constituent components.

[0040] Examples of methods for the polymerization / condensation reaction to produce the polyester of the present invention include 1) a method in which a polycarboxylic acid and a polyhydric alcohol are heated in the presence of a known catalyst, followed by a dehydration esterification step and then a polyhydric alcohol removal / polycondensation reaction, 2) a method in which an alcohol ester of a polycarboxylic acid and a polyhydric alcohol are heated in the presence of a known catalyst, followed by a transesterification step and then a polyhydric alcohol removal / polycondensation reaction, and 3) a method in which depolymerization is performed. In the methods 1) and 2), part or all of the acid component may be replaced with an acid anhydride.

[0041] When producing the polyester of the present invention, a conventionally known polymerization catalyst can be used, for example, titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, and titanium oxyacetylcetonate, antimony compounds such as antimony trioxide and tributoxyantimony, germanium compounds such as germanium oxide and tetra-n-butoxygermanium, and acetates of magnesium, iron, zinc, manganese, cobalt, aluminum, etc. These catalysts can be used alone or in combination of two or more.

[0042] The number average molecular weight of the polyester in the present invention is preferably 5,000 or more, more preferably 10,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. A molecular weight within the above range is preferable because it is easy to handle when dissolved in a solvent, has good adhesive strength, and is excellent in dielectric properties.

[0043] The acid value of the polyester in the present invention is not particularly limited, but can be appropriately designed depending on the curing agent used in combination. 6 g or less, and 100eq / 10 6 g or less is more preferable, and 50eq / 10 6 g or less, and more preferably 40eq / 10 6 g or less is particularly preferable, and 30eq / 10 6 g or less is most preferable. In the case of epoxy curing, 20eq / 10 6 g or more is preferable, 50eq / 10 6 g or more is more preferable, and 100 eq / 10 6 By setting the resin acid value within the above range, it is possible to expect effects such as a good pot life, improved substrate adhesion, and improved crosslinkability. From the viewpoint of low dielectric properties, isocyanate curing systems are preferred.

[0044] Methods for increasing the acid value of the polyester of the present invention include, for example, (1) adding a trivalent or higher polycarboxylic acid and / or a trivalent or higher polycarboxylic anhydride after the polycondensation reaction and allowing it to react (acid addition), or (2) intentionally modifying the resin during the polycondensation reaction by applying heat, oxygen, water, or the like. The polycarboxylic anhydride used in the acid addition method is not particularly limited, but examples include trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3,3,4,4-benzophenonetetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, and ethylene glycol bisanhydrotrimellitate, and these can be used alone or in combination of two or more. Trimellitic anhydride is preferred.

[0045] The polyester of the present invention can be used as a film. When the polyester of the present invention is used as a film, the polyester may be processed into a film as it is and used, or various fillers such as glass fiber or silica may be dispersed in the polyester and processed into a film and used. The thickness and shape of the film of the present invention are not particularly limited, and this also includes forms often called sheets. The film of the present invention has excellent dielectric properties and is therefore suitable as a CCL base film for rigid substrates and FPCs for high-speed transmission.

[0046] The polyester of the present invention can be used as an adhesive, and is particularly suitable as an adhesive for FPCs in the high frequency range because of its excellent dielectric properties. When the polyester of the present invention is used as an adhesive, it can further contain a curing agent to form an adhesive composition.

[0047] <Curing agent> As the curing agent, epoxy resin, polyisocyanate, polycarbodiimide, etc. can be used. Crosslinking with these curing agents can increase the cohesive force of the resin and improve heat resistance. Among them, polyisocyanate is preferred because it has little effect on heat resistance and dielectric properties.

[0048] <Epoxy resin> The epoxy resin used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but preferably has two or more epoxy groups in the molecule. Specifically, it is not particularly limited, but at least one selected from the group consisting of biphenyl-type epoxy resin, naphthalene-type epoxy resin, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, novolac-type epoxy resin, alicyclic epoxy resin, dicyclopentadiene-type epoxy resin, tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidyl bisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylenediamine, and epoxy-modified polybutadiene can be used. Biphenyl-type epoxy resin, novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, or epoxy-modified polybutadiene is preferred. Dicyclopentadiene-type epoxy resin or novolac-type epoxy resin is more preferred.

[0049] In the adhesive composition of the present invention, the content of the epoxy resin is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of polyester. By setting the content at or above the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Furthermore, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. By setting the content at or below the upper limit, good pot life and low dielectric properties can be achieved. In other words, by setting the content within the above range, an adhesive composition can be obtained that has excellent adhesion, solder heat resistance, pot life, and low dielectric properties.

[0050] <Polycarbodiimide> The polycarbodiimide used in the present invention is not particularly limited as long as it has a carbodiimide group in the molecule. A polycarbodiimide having two or more carbodiimide groups in the molecule is preferred. By using a polycarbodiimide, the carboxyl group of the polyester reacts with the carbodiimide group, enhancing the interaction between the adhesive composition and the substrate, thereby improving adhesion.

[0051] In the adhesive composition of the present invention, the content of polycarbodiimide is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of polyester. By adjusting the content to be equal to or greater than the lower limit, interaction with the substrate is exhibited, resulting in good adhesive properties. Furthermore, the content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. By adjusting the content to be equal to or less than the upper limit, excellent pot life and low dielectric properties can be exhibited. In other words, by adjusting the content within the above range, an adhesive composition having excellent low dielectric properties in addition to adhesion, solder heat resistance, and pot life can be obtained.

[0052] <Polyisocyanate> The polyisocyanate used in the present invention is not particularly limited as long as it is an isocyanate compound that reacts with polyester and hardens.

[0053] Examples of polyisocyanates include aromatic or aliphatic diisocyanate compounds and trivalent or higher polyisocyanate compounds. These isocyanate compounds may be either low-molecular-weight compounds or high-molecular-weight compounds. Examples include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate; aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and isophorone diisocyanate; and trimers of these isocyanate compounds. Also included are compounds containing terminal isocyanate groups obtained by reacting an excess amount of the isocyanate compound with a low-molecular-weight active hydrogen compound such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, or triethanolamine. Further examples include compounds containing terminal isocyanate groups obtained by reacting an excess amount of the isocyanate compound with various polyester polyols, polyether polyols, polyamides, or other polymeric active hydrogen compounds. These isocyanate compounds can be used alone or in combination of two or more. Among these, a trimer of a hexamethylene diisocyanate compound is particularly preferred.

[0054] In the adhesive composition of the present invention, the polyisocyanate content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of polyester. By adjusting the content to be equal to or greater than the lower limit, interaction with the substrate is exhibited, resulting in good adhesion. Furthermore, the content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. By adjusting the content to be equal to or less than the upper limit, excellent pot life and low dielectric properties can be exhibited. In other words, by adjusting the content within the above range, an adhesive composition having particularly excellent low dielectric properties can be obtained, in addition to adhesion, solder heat resistance, and pot life.

[0055] <Organic solvents> The adhesive composition of the present invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it can dissolve the polyester and the curing agent. Specific examples of such solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone-based solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; cellosolves such as methyl cellosolve and ethyl cellosolve; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate; ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, and diethylene glycol mono-n-butyl ether. Glycol ether solvents such as diethylene glycol monoisobutyl ether, triethylene glycol mono-n-butyl ether, and tetraethylene glycol mono-n-butyl ether can be used, and these can be used alone or in combination of two or more. Methylcyclohexane and toluene are particularly preferred from the viewpoint of working environment and drying properties.

[0056] The organic solvent is preferably in the range of 100 to 1000 parts by mass relative to 100 parts by mass of polyester. By setting the amount to above the lower limit, the liquid state and pot life are improved. On the other hand, by setting the amount to below the upper limit, it is advantageous in terms of production costs and transportation costs.

[0057] The adhesive composition of the present invention may further contain other components as needed, such as a flame retardant, a tackifier, a filler, and a silane coupling agent.

[0058] <Flame retardant> The adhesive composition of the present invention may optionally contain a flame retardant. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (e.g., trimethyl phosphate, triphenyl phosphate, tricresyl phosphate), phosphate salts (e.g., aluminum phosphinate), and phosphazenes can be used. These flame retardants may be used alone or in any combination of two or more. When a flame retardant is included, it is preferably included in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyester and curing agent components combined. By using the flame retardant in this range, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0059] <Tackifier> The adhesive composition of the present invention may optionally contain a tackifier. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins. These tackifiers are used to improve adhesive strength. They may be used alone or in any combination of two or more. When a tackifier is added, it is preferably contained in an amount ranging from 1 to 200 parts by mass, more preferably from 5 to 150 parts by mass, and most preferably from 10 to 100 parts by mass, per 100 parts by mass of the polyester and curing agent components combined. By using the tackifier within this range, the effects of the tackifier can be exhibited while maintaining adhesion, solder heat resistance, and electrical properties.

[0060] <Filler> The adhesive composition of the present invention may contain a filler as needed. Examples of organic fillers include powders of heat-resistant resins such as polyimide and polyamideimide. Examples of inorganic fillers include silica (SiO), alumina (AlO), titania (TiO), tantalum oxide (TaO), zirconia (ZrO), silicon nitride (SiN), boron nitride (BN), calcium carbonate (CaCO), calcium sulfate (CaSO), zinc oxide (ZnO), magnesium titanate (MgO·TiO), barium sulfate (BaSO), organic bentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred due to its ease of dispersion and its ability to improve heat resistance. Generally, hydrophobic silica and hydrophilic silica are known as silica, but in this case, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferred to impart moisture absorption resistance. When silica is added, the amount is preferably 0.05 to 30 parts by mass per 100 parts by mass of the polyester and curing agent components combined. By adjusting the amount to above the lower limit, further heat resistance can be achieved. Furthermore, by adjusting the amount to below the upper limit, poor dispersion of silica and excessively high solution viscosity can be prevented, improving workability.

[0061] <Silane coupling agent> A silane coupling agent may be blended into the adhesive composition of the present invention as needed. The inclusion of a silane coupling agent is highly preferred because it improves adhesion to metals and heat resistance. The silane coupling agent is not particularly limited, but examples include those having an unsaturated group, an epoxy group, and an amino group. Among these, silane coupling agents having an epoxy group, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred from the perspective of heat resistance. When a silane coupling agent is blended, its blend amount is preferably 0.5 to 20 parts by mass per 100 parts by mass of the polyester and curing agent components combined. By adjusting the blend amount within this range, solder heat resistance and adhesion can be improved.

[0062] <Laminate> The laminate of the present invention is a substrate to which an adhesive composition is laminated (a two-layer laminate of substrate / adhesive layer), or a substrate is further attached (a three-layer laminate of substrate / adhesive layer / substrate). Here, the adhesive layer refers to the layer of adhesive composition remaining after the adhesive composition of the present invention is applied to a substrate and dried. The laminate of the present invention can be obtained by applying the adhesive composition of the present invention to various substrates according to a conventional method, drying it, and then laminating another substrate on it.

[0063] <Base material> In the present invention, the substrate is not particularly limited as long as it is possible to apply the adhesive composition of the present invention to the substrate and dry it to form an adhesive layer. Examples of the substrate include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and paper.

[0064] Examples of the resin substrate include polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. A film-like resin (hereinafter also referred to as a substrate film layer) is preferred.

[0065] The metal substrate can be any conventionally known conductive material that can be used for circuit boards. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc or chromium compounds. Metal foil is preferred, and copper foil is more preferred. The thickness of the metal foil is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more. It is also preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit. On the other hand, if the thickness is too thick, processing efficiency during circuit fabrication may decrease. Metal foil is usually provided in a roll form. The form of the metal foil used in producing the printed wiring board of the present invention is not particularly limited. When a ribbon-shaped metal foil is used, its length is not particularly limited. Its width is also not particularly limited, but is preferably about 250 to 500 cm. The surface roughness of the substrate is not particularly limited, but is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less. In practical terms, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more.

[0066] Examples of the paper include fine paper, kraft paper, roll paper, glassine paper, etc. Examples of the composite material include glass epoxy, etc.

[0067] In terms of adhesive strength with the adhesive composition and durability, the substrate is preferably a polyester resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, a polyolefin resin, a fluorine-based resin, a SUS steel plate, a copper foil, an aluminum foil, or a glass epoxy.

[0068] <Adhesive sheet> In the present invention, the adhesive sheet is formed by laminating the laminate and a release substrate via an adhesive composition. Specific configurations include laminate / adhesive layer / release substrate, or release substrate / adhesive layer / laminate / adhesive layer / release substrate. Laminating the release substrate functions as a protective layer for the substrate. Furthermore, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

[0069] The adhesive sheet of the present invention can be obtained by applying the adhesive composition of the present invention to various laminates and drying them according to conventional methods. Furthermore, by attaching a release substrate to the adhesive layer after drying, the adhesive can be wound up without causing offset onto the substrate, resulting in excellent operability, and the adhesive layer is protected, resulting in excellent storage stability and ease of use. Furthermore, after application to a release substrate and drying, the adhesive layer itself can be transferred to another substrate by attaching another release substrate as needed.

[0070] <Release base material> The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, with coating layers of clay, polyethylene, polypropylene, or other filler on both sides, and then a silicone-based, fluorine-based, or alkyd-based release agent coated on each of these coating layers. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate coated with the above-mentioned release agent. Due to factors such as the release force between the release substrate and the adhesive layer and the adverse effect of silicone on electrical properties, it is preferable to use a polypropylene-sealed film on both sides of fine paper and then apply an alkyd-based release agent thereon, or an alkyd-based release agent on polyethylene terephthalate.

[0071] In the present invention, the method for coating the adhesive composition onto a substrate is not particularly limited, but examples include a comma coater and a reverse roll coater. Alternatively, if necessary, an adhesive layer can be formed directly or by transfer onto rolled copper foil or polyimide film, which are components of a printed wiring board. The thickness of the adhesive layer after drying can be appropriately adjusted as needed, but is preferably in the range of 5 to 200 μm. By making the adhesive film thickness 5 μm or more, sufficient adhesive strength can be obtained. Furthermore, by making the thickness 200 μm or less, it is easy to control the amount of residual solvent during the drying process, and blisters are less likely to occur during pressing in the production of printed wiring boards. The drying conditions are not particularly limited, but the residual solvent content after drying is preferably 1% by mass or less. By making it 1% by mass or less, foaming of the residual solvent during pressing of the printed wiring board is suppressed, making blisters less likely to occur.

[0072] <Printed wiring board> The printed wiring board of the present invention includes, as a component, a laminate formed from a metal foil forming a conductor circuit and a resin substrate. The printed wiring board is manufactured by a conventionally known method, such as a subtractive method, using a metal-clad laminate. The term "printed wiring board" collectively refers to so-called flexible circuit boards (FPCs), flat cables, circuit boards for tape automated bonding (TAB), etc., in which a conductor circuit formed from metal foil is partially or entirely covered with a cover film, screen printing ink, etc., as necessary.

[0073] The printed wiring board of the present invention can have any laminated structure that can be used as a printed wiring board. For example, it can be a printed wiring board consisting of four layers: a base film layer, a metal foil layer, an adhesive layer, and a cover film layer. Alternatively, it can be a printed wiring board consisting of five layers: a base film layer, an adhesive layer, a metal foil layer, an adhesive layer, and a cover film layer.

[0074] Furthermore, if necessary, two or more of the above printed wiring boards may be stacked.

[0075] The adhesive composition of the present invention can be suitably used in each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it exhibits high adhesion to not only conventional polyimide, polyester film, and copper foil that constitute printed wiring boards, but also low-polarity resin substrates such as LCP, and can achieve solder reflow resistance, and the adhesive layer itself has excellent low dielectric properties. Therefore, it is suitable as an adhesive composition for use in coverlay films, laminates, resin-coated copper foils, and bonding sheets.

[0076] In the printed wiring board of the present invention, any resin film conventionally used as a substrate for printed wiring boards can be used as the substrate film. Examples of resins for the substrate film include polyester resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorine-based resins. In particular, the film has excellent adhesion to low-polarity substrates such as liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resins.

[0077] <Cover film> The cover film can be any insulating film conventionally known as an insulating film for printed wiring boards. For example, films made from various polymers such as polyimide, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid, polycarbonate, polyarylate, polyamideimide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin can be used. Polyimide film or liquid crystal polymer film is more preferred.

[0078] The printed wiring board of the present invention may be made of any conventionally known material other than the materials for each layer described above. It can be produced using a process.

[0079] In a preferred embodiment, a semi-finished product is produced in which an adhesive layer is laminated on a cover film layer (hereinafter referred to as a "cover film-side semi-finished product"). On the other hand, a semi-finished product is produced in which a metal foil layer is laminated on a base film layer to form a desired circuit pattern (hereinafter referred to as a "base film-side two-layer semi-finished product"), or a semi-finished product is produced in which an adhesive layer is laminated on a base film layer and a metal foil layer is laminated on top of it to form a desired circuit pattern (hereinafter referred to as a "base film-side three-layer semi-finished product"). Hereinafter, the base film-side two-layer semi-finished product and the base film-side three-layer semi-finished product are collectively referred to as a "base film-side semi-finished product"). By bonding the cover film-side semi-finished product thus obtained and the base film-side semi-finished product together, a four-layer or five-layer printed wiring board can be obtained.

[0080] The substrate film semi-finished product can be obtained, for example, by a manufacturing method including: (A) a step of applying a solution of a resin that will become the substrate film to the metal foil and initially drying the coating; and (B) a step of heat-treating and drying the laminate of the metal foil and the initially dried coating obtained in (A) (hereinafter referred to as the "heat-treatment and desolvation step").

[0081] The circuit can be formed on the metal foil layer by a conventionally known method. Either an additive method or a subtractive method may be used. The subtractive method is preferred.

[0082] The obtained semi-finished product on the base film side may be used as it is for bonding to the semi-finished product on the cover film side, or may be used for bonding to the semi-finished product on the cover film side after a release film has been attached and stored.

[0083] The cover film semi-finished product is produced, for example, by applying an adhesive to the cover film. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

[0084] The obtained cover film side semi-finished product may be used as it is for bonding to the base film side semi-finished product, or may be used for bonding to the base film side semi-finished product after a release film has been attached and stored.

[0085] The substrate film-side semi-finished product and the cover film-side semi-finished product are stored, for example, in the form of a roll, and then bonded together to produce a printed wiring board. Any bonding method can be used, and for example, they can be bonded together using a press or a roll. They can also be bonded together while heating them using a method such as a hot press or a hot roll device.

[0086] For example, in the case of a reinforcing material that is soft and can be wound up, such as a polyimide film, the reinforcing material semi-finished product is preferably produced by applying an adhesive to the reinforcing material. Furthermore, in the case of a reinforcing plate that is hard and cannot be wound up, such as a metal plate such as SUS or aluminum, or a plate made of glass fiber cured with an epoxy resin, it is preferably produced by transfer coating an adhesive that has been applied in advance to a release substrate. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

[0087] The obtained semi-finished product on the reinforcing material side may be used as it is for bonding to the rear surface of a printed wiring board, or may be used for bonding to a semi-finished product on the base film side after a release film has been attached and stored.

[0088] The base film side semi-finished product, the cover film side semi-finished product, and the reinforcing material side semi-finished product are all laminates for printed wiring boards of the present invention. [Example]

[0089] The present invention will be described in more detail below with reference to examples. In these examples and comparative examples, "parts" simply refers to parts by mass.

[0090] (Physical property evaluation method) Determination of polyester composition 400MHz 1 Using a H-nuclear magnetic resonance spectrometer (hereinafter sometimes abbreviated as NMR), the molar ratios of the polycarboxylic acid components and polyhydric alcohol components that make up the polyester were quantified. Deuterated chloroform was used as the solvent. When the acid value of the polyester was increased by acid post-addition, the molar ratio of each component was calculated by setting the total of the acid components other than the acid component used in the acid post-addition as 100 mol %.

[0091] Calculation method for ester group concentration 2 x 10 of the reciprocal of the average molecular weight of the units formed from each acid component and each glycol component 6 For example, in the case of a polyester consisting of naphthalenedicarboxylic acid (molecular weight 244) and dimer diol (molecular weight 570), the average molecular weight of the product unit is 750 g / mol, so the ester group concentration is 2667 eq / 10 6 It is calculated as g.

[0092] Glass transition temperature measurement Measurement was performed using a differential scanning calorimeter (DSC-200, manufactured by SII Corporation). 5 mg of the sample (polyester) was placed in an aluminum container with a lid, sealed, and cooled to -50°C using liquid nitrogen. The sample was then heated to 150°C at a heating rate of 20°C / min. The glass transition temperature (Tg, unit: °C) was determined by the temperature at the intersection of the extension of the baseline before the endothermic peak (below the glass transition temperature) and the tangent to the endothermic peak (the tangent showing the maximum slope from the rising part of the peak to the peak peak) in the endothermic curve obtained during the heating process.

[0093] Measurement of number average molecular weight The polyester sample was dissolved and / or diluted with tetrahydrofuran to a resin concentration of approximately 0.5 wt% and filtered through a 0.5 μm pore size polytetrafluoroethylene membrane filter to prepare the measurement sample. The molecular weight was measured by gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was 1 mL / min and the column temperature was 30°C. The columns used were Showa Denko KF-802, 804L, and 806L. Monodisperse polystyrene was used as the molecular weight standard.

[0094] Acid number measurement 0.2 g of polyester sample was dissolved in 40 ml of chloroform and titrated with 0.01 N potassium hydroxide ethanol solution to obtain 10% polyester. 6 Equivalents per g (eq / 10 6 g) was determined. Phenolphthalein was used as an indicator.

[0095] Relative permittivity (ε c ) and dielectric tangent (tanδ) Polyester dissolved in toluene to a solids concentration of 30% was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying would be 25 μm, and the sheet was dried at 130°C for 3 minutes. The Teflon (registered trademark) sheet was then peeled off to obtain a resin sheet for testing. The obtained resin sheet for testing was then cut into strips of 8 cm x 3 mm to obtain test samples. The relative dielectric constant (ε c The dielectric loss tangent (tan δ) and the dielectric loss tangent (tan δ) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method under conditions of a temperature of 23° C. and a frequency of 10 GHz. <Evaluation criteria for relative permittivity> ◎: 2.3 or less ○: Over 2.3 and 3.0 or less ×: Over 3.0 <Evaluation criteria for dielectric loss tangent> ◎: 0.005 or less ○: Over 0.005 and 0.008 or less ×: More than 0.008

[0096] Tackiness Polyester varnish dissolved in toluene to a solids concentration of 30% was applied to a polyester film (Toyobo E5101, 50 μm thick, corona-treated surface) to a dry thickness of 25 μm and dried at 130°C for 3 minutes. At room temperature (23°C), the dried adhesive sheet was cut into a width of 25 mm and a length of 200 mm. The adhesive layer surface was attached to a rolled copper foil substrate (JX Metals BHY series). A 2 kg rubber roller was then rolled back and forth from above at a speed of 20 mm / sec, pressing the adhesive sheet against the substrate. The adhesive sheet was then peeled at a 180° angle at a peel speed of 300 mm / min, and the condition of the peeled substrate was confirmed. Interface peeling without adhesive residue on the substrate was evaluated as ◯, while transfer of the adhesive layer to the substrate was evaluated as ×. <Evaluation criteria for tackiness> ○: No adhesive residue and no interfacial peeling ×: There is adhesive residue or the adhesive layer is transferred to the substrate side

[0097] Solvent solubility The polyester was dissolved in toluene at 80° C. for 6 hours with stirring so that the solid content concentration became 60% by mass or 50% by mass, and the solubility was evaluated according to the following criteria. <Evaluation criteria for solvent solubility> ◎: Completely dissolved with no residue at a solids concentration of 60% by mass ○: Completely dissolved with no residue at a solid concentration of 50% by mass ×: Resin remains undissolved at a solid content of 50% by mass

[0098] Peel strength (adhesion) The polyester of the present invention was blended with a curing agent to prepare an adhesive composition, and the adhesive properties were evaluated. (b1): Polyisocyanate (Sumidur N3300 (manufactured by Sumika Covestro Urethane Co., Ltd.)) (b2): Epoxy resin (Epicron HP-7200H (DIC Corporation)) A toluene varnish with a solid content concentration of 30% by mass was prepared by dissolving polyester in toluene, and a curing agent was added to the varnish in the proportion (parts by mass) shown in Table 1 relative to 100 parts of polyester to prepare an adhesive composition. The adhesive composition was applied to a 12.5 μm thick polyimide film (Apical®, manufactured by Kaneka Corporation) to a dry thickness of 25 μm, and then dried at 130°C for 3 minutes. The adhesive film (B-stage product) obtained in this manner was bonded to an 18 μm thick rolled copper foil (BHY series, manufactured by JX Metals Corporation). The bonding was performed by pressing the shiny side of the rolled copper foil against the adhesive layer at 160°C under a pressure of 2 MPa for 30 seconds to bond the foil. The film was then heat-treated at 170°C for 3 hours to cure the film, yielding a sample for peel strength evaluation. Peel strength was measured at 25°C by a 90° peel test at a pulling speed of 50 mm / min. This test indicates adhesive strength at room temperature. <Evaluation criteria> ◎:1.0N / mm or more ○: 0.8N / mm or more and less than 1.0N / mm △: 0.5N / mm or more and less than 0.8N / mm ×: Less than 0.5N / mm

[0099] heat resistance Measurements were performed using a differential thermal and thermogravimetric simultaneous analyzer (Shimadzu Corporation, DTG-60). 50 mg of polyester was placed in a platinum cell and heated to 1000°C at a rate of 5°C / min in a nitrogen atmosphere with a flow rate of 20 ml / min. Decomposition progresses at high temperatures, and the temperature at which the weight is 95% of the initial weight is defined as the 5% weight loss temperature, which is used as an index of heat resistance. <Evaluation criteria for heat resistance> ○: 5% weight loss temperature is 300℃ or higher ×: 5% weight loss temperature is less than 300℃

[0100] The following describes examples of the production of the polyester of the present invention and comparative polyesters.

[0101] Example 1 Production example of polyester (a1) A reaction vessel equipped with a stirrer, condenser, and thermometer was charged with 326 parts of dimethyl 2,6-naphthalenedicarboxylate, 1520 parts of dimer diol (Croda, Pripol 2033), and 0.03 mol% tetrabutyl orthotitanate as a catalyst relative to the total acid components. The temperature was raised from 160°C to 220°C over 4 hours, and an esterification reaction was carried out through a dehydration process. Next, the polycondensation reaction process was carried out by reducing the pressure in the system to 5 mmHg over 20 minutes and then raising the temperature to 250°C. The pressure was then reduced to 0.3 mmHg or less, and the polycondensation reaction was carried out for 60 minutes, after which the product was removed. The composition of the resulting polyester (a1) was analyzed by NMR, revealing a molar ratio of 2,6-naphthalenedicarboxylic acid / dimer diol of 100 / 100. The glass transition temperature was -17°C. The obtained polyester (a1) was evaluated for solvent solubility, tackiness, heat resistance, relative dielectric constant, dielectric loss tangent, and adhesiveness. The evaluation results are shown in Table 1.

[0102] (Examples 2 to 9, Comparative Examples 1 to 6) Production examples of polyesters (a2) to (a15) Polyesters (a2) to (a15) were synthesized in accordance with the production example for polyester (a1), but by changing the types and blending ratios of raw materials. For polyester (a9), 8 parts by mass of trimellitic anhydride was added after the polymerization reaction was completed, and the mixture was reacted at 230°C for 30 minutes to carry out acid post-addition. The physical properties and evaluation results are shown in Table 1. PTMG1000 is polytetramethylene ether glycol (average molecular weight 1000).

[0103] The monomers (B) used in the examples are as follows: Dimer acid: Pripol 1013 (number average molecular weight 565), manufactured by Croda Dimer diol: Pripol 2033 (number average molecular weight approximately 560), manufactured by Croda Dimer acid ester: Priplast 3197 (number average molecular weight approximately 2000, polyester polyol derived from dimer acid), manufactured by Croda

[0104] [Table 1] [Industrial Applicability]

[0105] The polyester of the present invention has excellent solvent solubility, heat resistance, adhesive strength, and particularly low dielectric properties, and is therefore useful as an adhesive or base film for FPCs in the high frequency range.

Claims

1. A polyester having a chemical structure that can be obtained by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component, Ester group concentration is 5000 eq / 10 6 g or less, glass transition temperature is -30°C or higher, acid value is 3 eq / 10 6 g or more and 50 eq / 10 6 g or less, and when the total amount of all constituent units is taken as 100 mol %, contains 50 mol % or more of groups derived from the following monomer (B), and has a relative dielectric constant (εc) of 3.0 or less and a dielectric dissipation factor (tanδ) of 0.008 or less at 10 GHz (excluding polyesters for powder coatings). Monomer (B): At least one component selected from dimer acid, dimer diol, dimer acid ester, and hydroxyl-terminated polyisoprene

2. 2. The polyester according to claim 1, wherein the total amount of the groups derived from the following monomer (A) and the groups derived from the monomer (B) is 60 mol % or more when the total amount of all constituent components constituting the polyester is 100 mol %: Monomer (A): a polyvalent carboxylic acid component and / or a polyhydric alcohol component having a polycyclic structure

3. 3. The polyester according to claim 2, wherein the polyester contains groups derived from the monomer (A) in an amount of 25 mol % or more when the total amount of all structural units constituting the polyester is taken as 100 mol %.

4. A film comprising the polyester according to any one of claims 1 to 3.

5. An adhesive composition comprising the polyester according to any one of claims 1 to 3.

6. An adhesive sheet having a layer formed from the adhesive composition according to claim 5.

7. A laminate having a layer formed from the adhesive composition according to claim 5.

8. A printed wiring board comprising the laminate according to claim 7 as a component.

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