JP7780353B2 - Polyester, film and adhesive composition, as well as adhesive sheet, laminate and printed wiring board - Google Patents

Description

The present invention relates to polyesters. More specifically, it relates to polyesters, films, and adhesive compositions having excellent dielectric properties, as well as adhesive sheets, laminates, and printed wiring boards having layers formed therefrom.

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 flexibility and molecular weight can be freely controlled by selecting and combining polycarboxylic acids and polyhydric alcohols, they are widely used in a variety of applications, including coatings and adhesives.

Among these, polyester has excellent adhesive properties with metals, including copper, and has been used as an adhesive for FPCs and other devices when blended with a curing agent such as epoxy resin (see, for example, Patent Document 1).

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, complex interior spaces. In recent years, electronic devices have become smaller, lighter, denser, and more powerful. These trends have led to increasingly demanding performance from wiring boards (electronic circuit boards). In particular, as FPCs transmit signals at higher speeds, their frequencies are becoming increasingly higher. This has led to increased 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 are being taken to reduce the dielectric loss of FPC substrates and adhesives. Development of adhesives, such as combinations of polyolefin and epoxy (Patent Document 2), is currently underway.

Tokuho 6-104813 WO2016/047289 publication

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

The present invention was made in response to these problems in the prior art. Specifically, the object of the present invention is to provide polyesters, films, and adhesive compositions that have excellent solvent solubility, heat resistance, and adhesive strength, as well as low dielectric constants and dielectric dissipation factors, and have excellent dielectric properties, as well as adhesive sheets, laminates, and printed wiring boards having layers formed therefrom.

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.

A polyester having an ester group concentration of 5000 eq/10 ⁶ g or less and a glass transition temperature of −30° C. or higher.

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 polyvalent carboxylic acid component and/or a polyhydric alcohol component having a polycyclic structure

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

It is preferable that the polyester has a relative dielectric constant (εc) of 3.0 or less and a dielectric loss tangent (tanδ) of 0.008 or less at 10 GHz.

A film containing the polyester.

An adhesive composition containing the polyester.

An adhesive sheet having a layer formed from the adhesive composition.

A laminate having a layer formed from the adhesive composition.

A printed wiring board containing the laminate as a component.

The polyester of the present invention has excellent solvent solubility, heat resistance, adhesive strength, and dielectric properties. Therefore, it is suitable for use in base films and adhesives for FPCs in the high-frequency range, as well as adhesive sheets, laminates, and printed wiring boards.

One embodiment of the present invention is described in detail below. However, the present invention is not limited to this embodiment, and can be implemented in various modified forms within the scope described above.

<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.

The polyester of the present invention has an ester group concentration of 5000 eq/ ¹⁰ g or less. A low ester group concentration reduces the polarity of the polymer, thereby exhibiting low dielectric properties. The ester group concentration is preferably 4500 eq/ ¹⁰ g or less, more preferably 4000 eq/ ¹⁰ g or less, and particularly preferably 3500 eq/ ¹⁰ g or less.

The dielectric dissipation factor of the polyester of the present invention at 10 GHz is preferably 0.008 or less, and more preferably 0.005 or less. A polyester with a low dielectric dissipation factor can be used to form an adhesive composition with excellent low dielectric properties.

The relative dielectric constant of the polyester of the present invention at 10 GHz is preferably 3.0 or less, and more preferably 2.6 or less. A polyester with a low relative dielectric constant can form an adhesive composition with excellent low dielectric properties.

The glass transition temperature of the polyester in the present invention is -30°C or higher. More preferably, it is -20°C or higher. By setting the glass transition temperature in the range of -30°C or higher, good dielectric properties are exhibited and the 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 temperatures as low as 80°C. Furthermore, the lower the glass transition temperature, the better the adhesive strength tends to be.

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 chain of 10 or more consecutive carbon atoms

<Monomer (A)>
Monomer (A) is a polycarboxylic acid component and/or a polyhydric alcohol component having a polycyclic structure. The polycyclic structure refers to a structure in which multiple ring structures composed mainly of carbon are bonded, and examples thereof include structures having an aromatic skeleton such as naphthalene, anthracene, indane, or tetralin, and 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.

Examples of monomer (A), which is a polyvalent carboxylic acid component or 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.

The polyester of the present invention preferably contains 25 mol% or more of 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 monomer (A) at this level or more, low dielectric properties are improved, with a particularly large effect on the dielectric loss tangent.

<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 refers to 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 via a continuous carbon chain of 10 or more, thereby reducing the polar group concentration of the polyester and contributing 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, and the carbon chain is preferably entirely hydrocarbon.

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

The above-mentioned dimer acid refers to a polymeric fatty acid having 20 to 48 carbon atoms obtained by dimerizing C10-24 unsaturated fatty acids. It also includes saturated dimer acids obtained by hydrogenating these unsaturated groups. Dimer diols are obtained by reducing the carboxyl groups of the above-mentioned dimer acids. Vegetable oils may also be used as raw materials for dimer acids and dimer diols. Furthermore, dimer diols may include trimers, which are trimers of C10-24 unsaturated fatty acids, or saturated trimers obtained by hydrogenating trimers.

The number average molecular weight of monomer (B) is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more. The higher the molecular weight, the lower the polar group concentration, thereby improving low dielectric properties.

The polyester of the present invention preferably contains 10 mol% or more of monomer (B), assuming the total amount of all constituent components of the polyester to be 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 monomer (B) in an amount equal to or greater than the above-mentioned value, low dielectric properties are improved. Furthermore, the polyester also has excellent solvent solubility.

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. It may even be 100 mol%. As described above, by containing 25 mol% or more of monomer (A) and 10 mol% or more of monomer (B), and by containing a 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 well-balanced variety of physical properties, such as solvent solubility and glass transition temperature.

The polyester of the present invention can contain a polycarboxylic acid component and a polyhydric alcohol component other than monomer (A) and monomer (B). The polycarboxylic acid component other than monomer (A) and monomer (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. Excellent dielectric properties can be achieved by using an aromatic polycarboxylic acid component or an alicyclic polycarboxylic acid component as a copolymerization component.

Aromatic dicarboxylic acid components are not particularly limited, but examples that can be used include terephthalic acid, isophthalic acid, orthophthalic acid, 4,4'-dicarboxybiphenyl, and 5-sodium sulfoisophthalic acid.

The alicyclic dicarboxylic acid component is not particularly limited, but examples that can be used include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

Polyhydric alcohol components other than monomer (A) and monomer (B) are not particularly limited, but 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-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 can be used, and one or more of these can be used.

The polyester of the present invention can 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 can 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 can 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 polyhydric alcohol component are copolymerized, their amount is preferably 3 mol% or less, and more preferably 2 mol% or less, of the total of 100 mol% of all constituent components.

Examples of polymerization/condensation reaction methods for producing 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 reaction and then a polyhydric alcohol removal/polycondensation reaction; and 3) a method in which depolymerization is performed. In methods 1 and 2 above, some or all of the acid component may be replaced with an acid anhydride.

When producing the polyester of the present invention, conventional polymerization catalysts can be used, such as 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, and aluminum. These catalysts can be used alone or in combination of two or more.

The number-average molecular weight of the polyester in the present invention is preferably 5,000 or more, and more preferably 10,000 or more. It is also 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 exhibits excellent dielectric properties.

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. In the case of isocyanate curing, it is preferably 200 eq/10 ⁶ g or less, more preferably 100 eq/10 ⁶ g or less, even more preferably 50 eq/10 ^{6 g} or less, particularly preferably 40 eq/10 ⁶ g or less, and most preferably 30 eq/10 6 g or less. In the case of epoxy curing, it is preferably 20 eq/10 ⁶ g or more, more preferably 50 eq/10 ⁶ g or more, and most preferably 100 eq/10 ⁶ g or more. By setting the resin acid value within the above range, good pot life, substrate adhesion, and improved crosslinkability can be expected. From the viewpoint of low dielectric properties, isocyanate curing systems are preferred.

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 is complete and allowing the reaction to proceed (acid addition), or (2) intentionally modifying the resin during the polycondensation reaction by applying heat, oxygen, water, or the like. The polycarboxylic acid 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. These can be used alone or in combination of two or more. Trimellitic anhydride is preferred.

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 boards and FPCs for high-speed transmission.

The polyester of the present invention can be used as an adhesive. In particular, since the polyester of the present invention has excellent dielectric properties, it is suitable as an adhesive for FPCs in the high frequency range.
When the polyester of the present invention is used as an adhesive, it can further contain a curing agent to form an adhesive composition.

<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.

<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, although not particularly limited, at least one selected from the group consisting of biphenyl-type epoxy resins, naphthalene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidyl bisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylenediamine, and epoxy-modified polybutadiene can be used. Biphenyl-type epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, and epoxy-modified polybutadiene are preferred. Dicyclopentadiene-type epoxy resins and novolac-type epoxy resins are more preferred.

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, per 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 achieved. 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. Setting the content at or below the upper limit results in good pot life and low dielectric properties. In other words, by setting the content within the above range, an adhesive composition can be obtained that has excellent low dielectric properties in addition to adhesion, solder heat resistance, and pot life.

<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 groups of the polyester react with the carbodiimide groups, enhancing the interaction between the adhesive composition and the substrate, thereby improving adhesion.

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 setting the content at or above 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. Setting the content at or below the upper limit can achieve excellent pot life and low dielectric properties. In other words, by setting the content within the above range, an adhesive composition can be obtained that has excellent low dielectric properties in addition to adhesion, solder heat resistance, and pot life.

<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.

Examples of polyisocyanates include aromatic or aliphatic diisocyanate compounds and trivalent or higher polyisocyanate compounds. These isocyanate compounds may be either low-molecular-weight 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 terminal isocyanate group-containing compounds obtained by reacting an excess amount of the above isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, and 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 with two or more types. Of these, trimers of hexamethylene diisocyanate compounds are particularly preferred.

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 setting the content at or above 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. Setting the content at or below the upper limit can achieve excellent pot life and low dielectric properties. 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 particularly excellent low dielectric properties.

<Organic solvent>
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.

The organic solvent is preferably in the range of 100 to 1,000 parts by mass per 100 parts by mass of polyester. Setting it at or above the lower limit results in a good liquid state and pot life. Setting it at or below the upper limit is advantageous in terms of manufacturing costs and transportation costs.

The adhesive composition of the present invention may further contain other components as needed. Specific examples of such components include flame retardants, tackifiers, fillers, and silane coupling agents.

<Flame retardants>
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 weight, more preferably 5 to 150 parts by weight, and most preferably 10 to 100 parts by weight, per 100 parts by weight 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.

<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. These 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 weight, more preferably from 5 to 150 parts by weight, and most preferably from 10 to 100 parts by weight, per 100 parts by weight of the polyester and curing agent components combined. By using the tackifier within this range, the effects of the tackifier can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

<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 ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), boron nitride (BN), calcium carbonate (CaCO ₃ ), calcium sulfate (CaSO ₄ ), zinc oxide (ZnO), magnesium titanate (MgO.TiO ₂ ), barium sulfate (BaSO ₄ ), organic bentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred due to its ease of dispersion and its heat resistance.
While hydrophobic and hydrophilic silica are commonly known as silica, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferred here for its 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 adding silica at or above the lower limit, further heat resistance can be achieved. By adding silica at or below the upper limit, poor dispersion of the silica and excessively high solution viscosity can be prevented, improving workability.

<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. Silane coupling agents are not particularly limited, but examples include those containing unsaturated groups, epoxy groups, and amino groups. Among these, silane coupling agents containing epoxy groups, 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 maintaining the blend amount within this range, solder heat resistance and adhesion can be improved.

<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 laminated (a three-layer laminate of substrate/adhesive layer/substrate). Here, the adhesive layer refers to the layer of the adhesive composition of the present invention 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 and drying them according to a conventional method, and then laminating another substrate on top of it.

<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.

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

Any conventionally known conductive material suitable for circuit boards can be used as the metal substrate. Examples of materials include various metals such as stainless steel, 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. There are no particular limitations on the thickness of the metal foil, but it 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 achieve 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 typically provided in roll form. The form of the metal foil used in manufacturing the printed wiring board of the present invention is not particularly limited. When ribbon-shaped metal foil is used, its length is not particularly limited. Its width is also not particularly limited, but is preferably approximately 250 to 500 cm. There are no particular restrictions on the surface roughness of the substrate, but it is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less. For practical purposes, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more.

Examples of paper include fine paper, kraft paper, roll paper, and glassine paper. Examples of composite materials include glass epoxy.

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

<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.

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 standard 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. Furthermore, 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.

<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 a polyethylene terephthalate film on which an alkyd-based release agent is applied.

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 applied directly or by transfer to rolled copper foil or polyimide film, which are components of printed wiring boards. The thickness of the adhesive layer after drying can be adjusted as needed, but is preferably in the range of 5 to 200 μm. An adhesive film thickness of 5 μm or more provides sufficient adhesive strength. Furthermore, a thickness of 200 μm or less makes it easier to control the amount of residual solvent during the drying process, reducing the risk of blisters during pressing in the production of printed wiring boards. The drying conditions are not particularly limited, but a residual solvent ratio of 1% by mass or less after drying is preferred. A thickness of 1% by mass or less prevents residual solvent from foaming during printing wiring board pressing, reducing the risk of blisters.

<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.

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. It can also 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.

Furthermore, if necessary, two or more of the above printed wiring boards can be stacked.

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 not only to the conventional polyimide, polyester film, and copper foil that make up printed wiring boards, but also to 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 foil, and bonding sheets.

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 resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. In particular, the film has excellent adhesion even to low-polarity substrates such as liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resin.

<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.

The printed wiring board of the present invention can be manufactured by any conventionally known process, except for using the materials for each layer described above.

In a preferred embodiment, a semi-finished product is produced in which an adhesive layer is laminated onto a cover film layer (hereinafter referred to as a "cover film-side semi-finished product"). Alternatively, a semi-finished product is produced in which a metal foil layer is laminated onto 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 onto a base film layer and a metal foil layer is laminated thereon 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 "base film-side semi-finished product"). By bonding the cover film-side semi-finished product and the base film-side semi-finished product thus obtained together, a four-layer or five-layer printed wiring board can be obtained.

The substrate film semi-finished product can be obtained, for example, by a manufacturing method including: (A) a step of applying a solution of the 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/solvent-removal step").

The circuitry on the metal foil layer can be formed using conventional methods. This can be an additive method or a subtractive method. The subtractive method is preferred.

The resulting substrate film semi-finished product may be used as is to be bonded to the cover film semi-finished product, or it may be used to bond to the cover film semi-finished product after a release film has been attached and stored.

The cover film side 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.

The resulting cover film semi-finished product may be used as is to be bonded to the base film semi-finished product, or it may be used to bond to the base film semi-finished product after a release film has been attached and stored.

The base film semi-finished product and the cover film semi-finished product are stored, for example, in roll form, and then laminated together to produce a printed wiring board. Any lamination method can be used, and they can be laminated together using a press or roll, for example. They can also be laminated together while heating, using a heated press or heated roll device, for example.

For example, in the case of a reinforcing material that is soft and can be wound up, such as 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 (e.g., SUS or aluminum) or a plate made of glass fiber cured with epoxy resin, it is preferable to produce the reinforcing material semi-finished product 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.

The resulting reinforcing material semi-finished product may be used as is to be bonded to the backside of a printed wiring board, or it may be stored with a release film attached and then used to be bonded to a base film semi-finished product.

The base film side semi-finished product, cover film side semi-finished product, and reinforcing material side semi-finished product are all laminates for printed wiring boards according to the present invention.

The present invention will be explained in more detail below using examples. Note that in these examples and comparative examples, "parts" simply refers to parts by mass.

(Physical property evaluation method)
Measurement of polyester composition: Using a 400 MHz ^1H -nuclear magnetic resonance spectrometer (hereinafter sometimes abbreviated as NMR), the molar ratios of the polycarboxylic acid components and polyhydric alcohol components constituting 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 %.

Calculation method for ester group concentration: The ester group concentration was calculated as 2 × 10 ⁶ times the reciprocal of the average molecular weight of the units formed from each acid component and each glycol component. For example, in the case of a polyester composed of naphthalenedicarboxylic acid (molecular weight 244) and dimer diol (molecular weight 570), the average molecular weight of the formed units is 750 g/mol, so the ester group concentration is calculated to be 2667 eq/10 ⁶ g.

Measurement of Glass Transition Temperature: Measurement was performed using a differential scanning calorimeter (SII, DSC-200). 5 mg of a 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 endothermic curve obtained during the heating process was analyzed to determine the glass transition temperature (Tg, unit: °C) as the temperature at the intersection of an extension of the baseline before the endothermic peak appears (below the glass transition temperature) and a tangent to the endothermic peak (a tangent showing the maximum slope from the rising part of the peak to the peak top).

Measurement of Number Average Molecular Weight A polyester sample was dissolved and/or diluted with tetrahydrofuran to a resin concentration of approximately 0.5 wt %, and filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm to prepare a 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. Showa Denko KF-802, 804L, and 806L columns were used. Monodisperse polystyrene was used as the molecular weight standard.

Measurement of Acid Value 0.2 g of a polyester sample was dissolved in 40 ml of chloroform and titrated with a 0.01 N potassium hydroxide ethanol solution to determine the acid value equivalent per 10 ⁶ g of polyester (eq/10 ⁶ g). Phenolphthalein was used as an indicator.

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

Tack: A polyester varnish dissolved in toluene to a solids concentration of 30% was applied to a polyester film (Toyobo E5101, thickness 50 μm, 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, and the adhesive layer surface was attached to a rolled copper foil substrate (JX Metals Corporation, BHY series). A 2 kg rubber roller was then rolled from above at a speed of 20 mm / sec, moving back and forth twice to press the adhesive sheet. The adhesive sheet was then peeled at a 180 ° 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 ◯, and adhesive layer transfer to the substrate side was evaluated as ×.
<Evaluation criteria for tackiness>
○: No adhesive residue and interface peeling ×: Adhesive residue or adhesive layer transferred to the substrate side

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 solid content concentration of 60% by mass. ○: Completely dissolved with no residue at a solid content concentration of 50% by mass. ×: Resin remains undissolved at a solid content concentration of 50% by mass.

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 (Epiclon HP-7200H (manufactured by DIC Corporation))
A toluene varnish having a solids 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) thus obtained was then laminated to an 18 μm thick rolled copper foil (BHY series, manufactured by JX Metals Corporation). The laminate was bonded 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. The laminate was then cured by heat treatment at 170°C for 3 hours to obtain a sample for peel strength evaluation. Peel strength was measured by a 90° peel test at 25°C, with the film pulled at a tensile speed of 50 mm/min. This test indicates adhesive strength at room temperature.
<Evaluation criteria>
◎: 1.0 N/mm or more ○: 0.8 N/mm or more and less than 1.0 N/mm △: 0.5 N/mm or more and less than 0.8 N/mm ×: Less than 0.5 N/mm

Heat resistance was measured 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 heating rate of 5°C/min in a nitrogen atmosphere at 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°C or higher ×: 5% weight loss temperature is less than 300°C

Below are examples of the production of polyesters of the present invention and comparative polyesters.

Example 1
Production Example of Polyester (a1) 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 were charged into a reaction vessel equipped with a stirrer, condenser, and thermometer. 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, in the polycondensation reaction process, the pressure inside the system was reduced to 5 mmHg over 20 minutes, and the temperature was further increased to 250°C. Next, the pressure was reduced to 0.3 mmHg or less, and the polycondensation reaction was carried out for 60 minutes, after which the product was removed. Composition analysis of the obtained polyester (a1) by NMR revealed that the molar ratio of 2,6-naphthalenedicarboxylic acid/dimer diol was 100/100 [molar ratio]. 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.

(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 of Polyester (a1), except that the types and blending ratios of raw materials were changed. For Polyester (a9), 8 parts by mass of trimellitic anhydride was further 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).

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

The polyester of the present invention has excellent solvent solubility, heat resistance, and adhesive strength, and is particularly excellent in low dielectric properties, making it useful as an adhesive for FPCs in the high-frequency range, as well as a base film.

Claims (8)

A polyester having a chemical structure that can be obtained by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component,
A polyester (excluding those for use in powder coatings) having an ester group concentration of 5,000 eq/ ¹⁰ g or less, a glass transition temperature of -30°C or higher, an acid value of 3 eq/10 ^g or more and 50 eq/ ¹⁰ g or less, and containing 50 mol % or more of groups derived from the following monomer (B) when the total amount of all constituent units is taken as 100 mol %, and having a relative dielectric constant (εc) of 3.0 or less and a dielectric dissipation factor (tanδ) of 0.008 or less at 10 GHz:
Monomer (B): At least one component selected from dimer acid, dimer diol, dimer acid ester, and hydroxyl-terminated polyisoprene 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 The polyester according to claim 2, wherein the polyester contains 25 mol % or more of groups derived from the monomer (A), when the total amount of all structural units constituting the polyester is 100 mol %. A film containing the polyester described in any one of claims 1 to 3. An adhesive composition containing the polyester described in any one of claims 1 to 3. An adhesive sheet having a layer formed from the adhesive composition described in claim 5. A laminate having a layer formed from the adhesive composition described in claim 5. A printed wiring board comprising the laminate of claim 7 as a component.