KR20240039087A - Adhesive compositions, adhesive sheets, laminates and printed wiring boards - Google Patents

Abstract

An adhesive composition that has excellent adhesion and solder heat resistance, and further exhibits excellent adhesion even after exposure to a high temperature environment for a long period of time, and also satisfies flexibility and tackiness in a semi-cured coating film, and adhesive sheets, laminates, and printed wiring boards containing the same An adhesive composition containing polyester resin (A1), polyester resin (A2) and epoxy resin (B). Polyester resin (A1): has a number average molecular weight of less than 10,000, a glass transition temperature of less than 15°C, and has component (a) as a structural unit having 3 functional groups in total of hydroxyl groups and carboxyl groups per molecule, and is a polyester resin ( A polyester resin containing 3 mol% or more of the component (a) when the total polyhydric carboxylic acid components constituting A1) are 100 mol%. Polyester resin (A2): A polyester resin with a number average molecular weight of 10000 or more and a glass transition temperature of 15°C or more.

Description

Adhesive compositions, adhesive sheets, laminates and printed wiring boards

The present invention relates to adhesive compositions. More specifically, it relates to an adhesive composition used for adhering a resin substrate to a resin substrate or a metal substrate. In particular, it relates to an adhesive composition for flexible printed wiring boards (hereinafter abbreviated as FPC), and adhesive sheets, laminates, and printed wiring boards containing the same.

A flexible printed wiring board (FPC) refers to a board in which an electric circuit is formed on a substrate made by bonding a thin, soft insulating film such as polyimide and a conductive metal such as copper foil with an adhesive. Unlike rigid boards, it is very thin and flexible, so it can be used in small gaps or curved moving parts of electronic devices, so it is used in many nearby electronic devices, such as personal computers and smartphones. Additionally, in recent years, many FPCs have been installed in automobiles, and adhesives are often required to have high heat resistance and reliability.

Copolymerized polyester is widely used as a raw material for resin compositions used in coatings, inks, adhesives, etc., and is generally composed of polyhydric carboxylic acid and polyhydric alcohol. Because it is easy to design molecules by selecting and combining polyhydric carboxylic acids and polyhydric alcohols, and because the molecular weight can be freely controlled, it is widely used in a variety of applications, including coatings and adhesives.

Copolyester has excellent adhesion (peel strength) to metals containing copper, and has been used in FPC adhesives by mixing a curing agent (for example, Patent Document 1).

Patent Document 1: Japanese Patent Publication No. 6-104813

However, the adhesive using copolyester described in Patent Document 1 is inferior in solder heat resistance and does not have the long-term heat resistance required for automotive applications.

The present invention has been made against the background of these problems of the prior art. That is, the object of the present invention is to provide an adhesive composition that has excellent adhesion and solder heat resistance, further exhibits excellent adhesion even after exposure to a high temperature environment for a long period of time, and satisfies flexibility and tackiness when used as a semi-cured coating film, And to provide adhesive sheets, laminates, and printed wiring boards containing the same.

As a result of intensive studies, the present inventors have found that the above problem can be solved by the means shown below, and have arrived at the present invention. That is, the present invention includes the following configurations.

[1] An adhesive composition containing a polyester resin (A1), a polyester resin (A2), and an epoxy resin (B).

Polyester resin (A1): has a number average molecular weight of less than 10,000, a glass transition temperature of less than 15°C, and has component (a) as a structural unit having 3 functional groups in total of hydroxyl groups and carboxyl groups per molecule, and is a polyester resin ( A polyester resin containing 3 mol% or more of the component (a) when the total polyhydric carboxylic acid components constituting A1) are 100 mol%.

Polyester resin (A2): A polyester resin with a number average molecular weight of 10000 or more and a glass transition temperature of 15°C or more.

[2] The adhesive composition according to [1] above, which is an adhesive for printed wiring boards.

[3] An adhesive sheet having an adhesive layer containing the adhesive composition according to [1] or [2] above.

[4] A laminate having an adhesive layer containing the adhesive composition according to [1] or [2] above.

[5] A printed wiring board comprising the laminate described in [4] above as a component.

The adhesive composition of the present invention is excellent in peel strength, solder heat resistance, and long-term heat resistance, and also satisfies flexibility and tackiness in a semi-cured coating film. For this reason, it is suitable for FPC adhesives, adhesive sheets, laminates, and printed wiring boards for automobile applications.

Hereinafter, an embodiment of the present invention will be described in detail below. However, the present invention is not limited to this, and can be implemented with various modifications within the scope described.

<Polyester resin (A1)>

The polyester resin (A1) used in the present invention has component (a) as a structural unit, which has a number average molecular weight of less than 10,000, a glass transition temperature of less than 15°C, and has 3 functional groups in total of hydroxyl groups and carboxyl groups per molecule. It is a polyester resin containing 3 mol% or more of the component (a) when the total polyhydric carboxylic acid components constituting the polyester resin (A1) are 100 mol%. When the adhesive composition contains polyester resin (A1), adhesiveness and long-term heat resistance are improved.

The polyester resin (A1) has a chemical structure obtained by polycondensation of a polyhydric carboxylic acid component and a polyhydric alcohol component, and the polyhydric carboxylic acid component and the polyhydric alcohol component each contain one or two or more selected components. It is done. The polyhydric carboxylic acid component constituting the polyester resin (A1) is not limited, but polyhydric carboxylic acids or their esters and polyhydric carboxylic acid anhydrides shown below can be used. Specifically, polyhydric carboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, 2,5-furanedicarboxylic acid, adipic acid, sebacic acid, and dimer acid. , 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid, maleic acid, 5-sodium sulfodimethylisophthalic acid, hydrogenated naphthalenedicarboxylic acid, and their esters. there is. Examples of the polyhydric carboxylic acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. In particular, an aromatic polyhydric carboxylic acid component is preferable, and among these, naphthalenedicarboxylic acid and terephthalic acid are more preferable. The heat resistance of the adhesive composition can be improved by using an aromatic polyhydric carboxylic acid.

The polyhydric alcohol component constituting the polyester resin (A1) is not particularly limited and includes 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-1,3-hexanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-propyl -1,3-propanediol, 2,2-din-propyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-din-butyl- 1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, polytetramethylene Polyalkylene ether glycols such as glycol and polypropylene glycol, polyhydric alcohol components such as pentaerythritol, α-methyl glucose, mannitol, sorbitol, and dimer diol can be used, and one or two or more types of these can be used. . In particular, a polyhydric alcohol component having a long-chain alkylene group is preferable, and among these, 1,6-hexanediol and dimer diol are more preferable. By using these polyhydric alcohol components, the adhesive strength of the adhesive composition can be improved.

The polyester resin (A1) used in the present invention contains component (a) as a structural unit. Component (a) is a component in which the total of hydroxyl groups and carboxyl groups per molecule is 3 functional groups. Additionally, the carboxyl group may be an acid anhydride group, and the acid anhydride group is counted as 2 functions. 3 The functional group may be all carboxyl groups or all hydroxyl groups, or may have both carboxyl groups and hydroxyl groups. Examples of such component (a) include trimellitic acid, 4-hydroxyphthalic acid and their acid anhydrides, diphenolic acid, dimethylolbutanoic acid, dimethylolpropionic acid, trimesic acid, glycerin, trimethylolpropane, and trimethylolethane. there is. Preferred are trimellitic acid, 4-hydroxyphthalic acid and their anhydrides, and diphenolic acid, and by copolymerizing them, excellent solder heat resistance and long-term heat resistance can be achieved. Although the reason for this is not clear, it is presumed that by introducing branches into a relatively low-molecular polyester resin with three functional components, a cured coating film can be created with a high crosslinking density, and long-term heat resistance and solder heat resistance are improved. Component (a) needs to be 3 mol% or more, and is preferably 4 mol% or more, based on 100 mol% of all polyhydric carboxylic acid components constituting the polyester resin (A1). Additionally, from the viewpoint of preventing gelation during polymerization, the content is preferably 10 mol% or less, and more preferably 6 mol% or less.

The polyester resin (A1) used in the present invention may copolymerize a tetravalent or higher polyhydric carboxylic acid component and/or a tetravalent or higher polyhydric alcohol component. Examples of tetravalent or higher polyvalent carboxylic acid components include aromatic carboxylic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, pyromellitic anhydride (PMDA), and 1,2,3,4-butanetetracarboxylic acid. aliphatic carboxylic acids, etc., and one or two or more types of these can be used. Examples of tetrahydric or higher polyhydric alcohol components include pentaerythritol, α-methyl glucose, mannitol, and sorbitol, and one or two or more of these can be used.

The polyester resin (A1) used in the present invention may copolymerize lactone or lactam. For example, ε-caprolactone or ε-caprolactam can be used.

As a method of the polymerization condensation reaction for producing the polyester resin (A1) used in the present invention, for example, 1) heating a polyhydric carboxylic acid and a polyhydric alcohol in the presence of a known catalyst, going through a dehydration esterification step, and dehydrating Method of carrying out a polyhydric alcohol/polycondensation reaction, 2) Method of heating the alcohol ester form of a polyhydric carboxylic acid and a polyhydric alcohol in the presence of a known catalyst, conducting a transesterification reaction, and performing a depolyhydric alcohol/polycondensation reaction, 3 ) There is a method of performing depolymerization. In the methods 1) and 2) above, part or all of the acid component may be replaced with an acid anhydride.

When producing the polyester resin (A1) used in the present invention, conventionally known polymerization catalysts, such as titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, and titanium oxyacetylacetonate, antimony trioxide, Antimony compounds such as tributoxyantimony, germanium compounds such as germanium oxide and tetra-n-butoxygermanium, and acetates such as magnesium, iron, zinc, manganese, cobalt, and aluminum can be used. These catalysts can be used one type or two or more types together.

The number average molecular weight of the polyester resin (A1) used in the present invention is less than 10000, and more preferably 9000 or less. Additionally, it is preferably 1000 or more, more preferably 3000 or more, and still more preferably 4000 or more. If it is within the above range, an adhesive composition that is easy to handle when dissolved in a solvent and has excellent adhesive properties can be obtained.

The glass transition temperature of the polyester resin (A1) used in the present invention is less than 15°C, and is preferably 10°C or less. Additionally, it is preferable that it is -25°C or higher. If it is within the above range, an adhesive composition that is easy to handle when used as a semi-cured coating film and has excellent adhesive properties can be obtained.

<Polyester resin (A2)>

The polyester resin (A2) used in the present invention is a polyester resin with a number average molecular weight of 10000 or more and a glass transition temperature of 15°C or more. When the adhesive composition contains polyester resin (A2), adhesiveness becomes good.

The number average molecular weight of the polyester resin (A2) used in the present invention is 10,000 or more, preferably 11,000 or more, and more preferably 12,000 or more. Additionally, it is preferably less than 100,000, more preferably less than 70,000, and even more preferably less than 50,000. If it is within the above range, the solution viscosity that is easy to handle, the flexibility of the semi-cured coating film, and the tackiness of the semi-cured coating film can be satisfied.

The glass transition temperature of the polyester resin (A2) used in the present invention is 15°C or higher. Moreover, it is preferable that it is 100 degrees C or less, and it is more preferable that it is 50 degrees C or less. If it is within the above range, it can be used as an adhesive composition that is easy to handle and has excellent adhesive properties when used as a semi-cured coating film.

The polyester resin (A2) has a chemical structure obtained by polycondensation of a polyhydric carboxylic acid component and a polyhydric alcohol component, and the polyhydric carboxylic acid component and the polyhydric alcohol component each contain one or two or more selected components. It is done. The components constituting the polyester resin (A2) are not particularly limited, and the same components as the polyester resin (A1) can be used.

<Epoxy Resin (B)>

The adhesive composition of the present invention contains an epoxy resin (B). The epoxy resin (B) 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. Although not specifically limited, biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, Tetraglycidyldiaminodiphenylmethane, triglycidylparaminophenol, tetraglycidylbisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylylenediamine, At least one selected from the group consisting of dimer acid-modified epoxy and epoxy-modified polybutadiene can be used. Preferably, it is N,N,N',N'-tetraglycidyl-m-xylylenediamine, biphenyl-type epoxy resin, novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, or epoxy-modified polybutadiene. , by using these, better adhesion can be achieved.

In the adhesive composition of the present invention, the content of the epoxy resin (B) is preferably 0.1 part by mass or more, more preferably 1 part by mass, based on a total of 100 parts by mass of the polyester resin (A1) and the polyester resin (A2). It is more than the mass part. If the amount is above the lower limit, a sufficient curing effect can be obtained and excellent adhesion and solder heat resistance can be achieved. Moreover, it is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. If it is below the above upper limit, long-term heat resistance becomes good. That is, by keeping it within the above range, an adhesive composition having better adhesiveness, solder heat resistance, and long-term heat resistance can be obtained.

<Adhesive composition>

The adhesive composition of the present invention contains polyester resin (A1), polyester (A2), and epoxy resin (B). By using two types of polyester resins with specific characteristics in combination, the adhesive strength after curing, solder heat resistance, and long-term heat resistance can be improved.

The mass ratio of the polyester resin (A1) and the polyester resin (A2) in the adhesive composition of the present invention is the polyester resin when the total of the polyester resin (A1) and the polyester resin (A2) is 100 parts by mass. It is preferable that (A1) is 10 parts by mass or more and 90 parts by mass or less. More preferably, it is 20 parts by mass or more, and even more preferably, it is 25 parts by mass or more. Moreover, 80 parts by mass or less is more preferable, and even more preferably, it is 75 parts by mass or less. When the mass ratio of the two is within the above range, appropriate tackiness of a semi-cured coating film, excellent adhesion, and solder heat resistance can be achieved simultaneously.

<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 dissolves polyester resin and epoxy resin. Specifically, for example, 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, trichlorethylene, Halogenated hydrocarbons such as dichlorethylene, chlorobenzene, and chloroform; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, Ketone solvents such as pentanone, hexanone, cyclohexanone, isophorone, and acetophenone, cellosolves such as methyl cellosolve and ethyl cellosolve, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate. Ester-based solvents such as ethylene glycol monon-butyl ether, ethylene glycol monoiso-butyl ether, ethylene glycol monotert-butyl ether, diethylene glycol monon-butyl ether, diethylene glycol monoiso-butyl ether, triethylene Glycol ether-based solvents such as glycol monon-butyl ether and tetraethylene glycol monon-butyl ether can be used, and one or two or more of these can be used in combination. In particular, from the viewpoint of work environment and dryness, toluene and cyclohexanone are preferable.

The organic solvent is preferably in the range of 100 to 1000 parts by mass based on a total of 100 parts by mass of the polyester resin (A1) and polyester resin (A2). By exceeding the above lower limit, liquid phase and pot life become good. Additionally, setting it below the above upper limit is advantageous in terms of manufacturing costs and transportation costs.

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

<Flame retardant>

A flame retardant may be added to the adhesive composition of the present invention as needed. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Among them, phosphorus-based flame retardants are preferable, and known phosphorus-based flame retardants such as phosphoric acid esters such as trimethyl phosphate, triphenyl phosphate, tricresyl phosphate, etc., phosphates such as aluminum phosphinate, and phosphazene can be used. These may be used individually, or two or more types may be used in arbitrary combination. When containing a flame retardant, it is preferable to contain the flame retardant in the range of 1 to 200 parts by mass, based on a total of 100 parts by mass of the polyester resin (A1), polyester resin (A2) and epoxy resin (B), and 5 to 150 parts by mass. The range of parts by mass is more preferable, and the range of 10 to 100 parts by mass is most preferable. By keeping it within the above range, flame retardancy can be achieved while maintaining adhesiveness and solder heat resistance.

<Tackifier>

A tackifier may be added to the adhesive composition of the present invention as needed. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic-based petroleum resins, alicyclic-based petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used for the purpose of improving adhesive strength. These may be used individually, or two or more types may be used in arbitrary combination. When containing a tackifier, it is preferably contained in the range of 1 to 200 parts by mass, based on a total of 100 parts by mass of the polyester resin (A1), polyester resin (A2) and epoxy resin (B), and 5 to 150 parts by mass. The range of parts by mass is more preferable, and the range of 10 to 100 parts by mass is most preferable. By keeping it within the above range, the effect of the tackifier can be exhibited while maintaining adhesiveness and solder heat resistance.

<Filler>

Fillers may be added to the adhesive composition of the present invention as needed. Examples of the organic filler include powders of heat-resistant resins such as polyimide, polyamidoimide, fluororesin, and liquid crystal polyester. Additionally, inorganic fillers include, for example, 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, hydroxide. Examples include aluminum and magnesium hydroxide, and among these, silica is preferred because of its ease of dispersion and the effect of improving heat resistance. Hydrophobic silica and hydrophilic silica are generally known as silica, but here, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. is preferred to provide hygroscopic resistance. When blending silica, the blending amount is preferably 0.05 to 30 parts by mass based on a total of 100 parts by mass of the polyester resin (A1), polyester resin (A2), and epoxy resin (B). By exceeding the above lower limit, heat resistance can be further achieved. In addition, by setting it below the above upper limit, poor dispersion of silica and excessively high solution viscosity are suppressed, and workability is improved.

<Silane coupling agent>

A silane coupling agent may be added to the adhesive composition of the present invention as needed. Mixing a silane coupling agent is very desirable because adhesion to metal and heat resistance characteristics are improved. The silane coupling agent is not particularly limited, but includes those having an unsaturated group, those having an epoxy group, and those having an amino group. Among these, from the viewpoint of heat resistance, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltriethoxysilane. A silane coupling agent having an epoxy group such as is more preferable. When blending a silane coupling agent, the blending amount is preferably 0.5 to 20 parts by mass based on a total of 100 parts by mass of the polyester resin (A1), polyester resin (A2), and epoxy resin (B). By keeping it within the above range, solder heat resistance and adhesiveness can be improved.

<Laminate>

The laminate of the present invention is one in which an adhesive composition is laminated on a base material (two-layer laminate of base material/adhesive layer) or a base material is further bonded together (3-layer laminate of base material/adhesive layer/substrate). Here, the adhesive layer refers to a layer of the adhesive composition after applying the adhesive composition of the present invention to a substrate and drying it. The laminate of the present invention can be obtained by applying the adhesive composition of the present invention to various substrates, drying them, and further laminating other substrates according to a conventional method.

<Description>

In the present invention, the substrate is not particularly limited as long as it can form an adhesive layer by applying and drying the adhesive composition of the present invention, but may include resin substrates such as film-type resins, metal substrates such as metal plates and metal foil, and paper. I can hear it.

Examples of the resin base material include polyester resin, polyamide resin, polyimide resin, polyamidoimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine resin. Preferably, it is a film-type resin (hereinafter also referred to as a base film layer).

For the metal substrate, any conventionally known conductive material that can be used for circuit boards can be used. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as respective alloys, plated products, and metals treated with other metals such as zinc and chromium compounds. Metal foil is preferable, and copper foil is more preferable. There is no particular limitation regarding the thickness of the metal foil, but it is preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 10 μm or more. Also, it is 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, and on the other hand, if the thickness is too thick, processing efficiency during circuit manufacturing may decrease. Metal foil is usually provided in roll form. The form of the metal foil used when manufacturing the printed wiring board of the present invention is not particularly limited. When using a ribbon-shaped metal foil, its length is not particularly limited. Additionally, the width is 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 still more preferably 1.5 μm or less. In addition, for practical purposes, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and still more preferably 0.7 μm or more.

Examples of paper include fine paper, kraft paper, roll paper, and glassine paper. Also, examples of composite materials include glass epoxy and the like.

In terms of adhesion and durability with the adhesive composition, the base materials include polyester resin, polyamide resin, polyimide resin, polyamidoimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, fluorine resin, SUS steel sheet, copper foil, aluminum foil, or glass epoxy are preferred.

<Adhesive sheet>

In the present invention, the adhesive sheet is a product in which the above-described laminate and a release base material are laminated using an adhesive composition. Specific structural aspects include a laminate/adhesive layer/mold release base material or a release base material/adhesive layer/laminated body/adhesive layer/mold release base material. By laminating the release substrate, it functions as a protective layer for the substrate. Additionally, by using the release base material, the release base material can be released from the adhesive sheet and the adhesive layer can be transferred to another base material.

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 a conventional method. In addition, when the release substrate is attached to the adhesive layer after drying, it can be rolled up without bleeding to the back of the substrate, which improves operability. Additionally, since the adhesive layer is protected, preservability is excellent and it is easy to use. Additionally, after applying and drying the adhesive to a release substrate, it is possible to transfer the adhesive layer itself to another substrate by adhering to another release substrate as needed.

<Modified base material>

The release substrate is not particularly limited, but for example, an application layer of a filler such as clay, polyethylene, or polypropylene is formed on both sides of paper such as fine paper, kraft paper, roll paper, or glassine paper, and each application layer is formed. Examples include those on which a silicone-based, fluorine-based, or alkyd-based mold release agent is applied. In addition, examples include the application of the release agent on various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as on films such as polyethylene terephthalate. For reasons such as the release force of the release base material and the adhesive layer and the adverse effects of silicone on the electrical properties, both sides of the fine paper were filled with polypropylene and an alkyd-based release agent was used on top, or an alkyd-based release agent was used on the polyethylene terephthalate. It is preferable to use a mold release agent.

In addition, the method for coating the adhesive composition on the substrate in the present invention is not particularly limited, and includes a comma coater, reverse roll coater, etc. Alternatively, if necessary, the adhesive layer can be formed directly or by transfer on rolled copper foil or polyimide film, which are constituent materials of the printed wiring board. The thickness of the adhesive layer after drying is appropriately changed as needed, but is preferably in the range of 5 to 200 μm. Sufficient adhesive strength can be obtained by setting the adhesive film thickness to 5 μm or more. In addition, setting it to 200 μm or less makes it easier to control the amount of residual solvent in the drying process and makes it difficult for expansion to occur during pressing in the manufacture of printed wiring boards. Drying conditions are not particularly limited, but the residual solvent ratio after drying is preferably 1% by mass or less. By setting it to 1% by mass or less, foaming of the residual solvent during printing of the printed wiring board is suppressed, making it difficult for swelling to occur.

<Printed wiring board>

The printed wiring board in the present invention includes a laminate formed of metal foil and a resin substrate forming a conductor circuit as constituent elements. Printed wiring boards are manufactured by conventionally known methods such as subtractive methods, for example, using metal-clad laminates. It is a general term for so-called flexible circuit boards (FPC), flat cables, and tape automated bonding (TAB) circuit boards, etc., in which a conductor circuit formed of metal foil is partially or completely covered with a cover film or screen printing ink, as needed. there is.

The printed wiring board of the present invention can have any laminated configuration that can be employed as a printed wiring board. For example, it can be a printed wiring board composed of four layers: a base film layer, a metal foil layer, an adhesive layer, and a cover film layer. Additionally, for example, it can be used as a printed wiring board composed of five layers: a base film layer, an adhesive layer, a metal foil layer, an adhesive layer, and a cover film layer.

Additionally, if necessary, the above-described printed wiring board may be stacked in two or three or more units.

The adhesive composition of the present invention can be suitably used for each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it has high adhesion to resin substrates such as conventional polyimide, polyester film, copper foil, and aluminum foil that constitute printed wiring boards, and solder reflow resistance can be obtained. Therefore, it is suitable as an adhesive composition used for coverlay films, laminated boards, resin-coated copper foil, bonding sheets, and reinforcing materials.

In the printed wiring board of the present invention, any resin film conventionally used as a base material for printed wiring boards can be used as the base film. Examples of the resin of the base film include polyester resin, polyamide resin, polyimide resin, polyamidoimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine resin.

<Cover Film>

For the cover film, any conventionally known insulating film as an insulating film for printed wiring boards can be used. For example, various polymers such as polyimide, polyester, polyphenylene sulfide, polyether sulfone, polyether ether ketone, aramid, polycarbonate, polyarylate, polyamideimide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin. Any manufactured film can be used. More preferably, it is a polyimide film.

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

In a preferred embodiment, a semi-finished product in which an adhesive layer is laminated on a cover film layer (hereinafter referred to as “semi-finished product on the cover film side”) is manufactured. On the other hand, a semi-finished product in which a desired circuit pattern is formed by laminating a metal foil layer on a base film layer (hereinafter referred to as a “two-layer semi-finished product on the base film side”) or an adhesive layer is laminated on the base film layer and a metal foil layer is placed on top of the semi-finished product. A semi-finished product (hereinafter referred to as “three-layer semi-finished product on the base film side”) that is laminated to form a desired circuit pattern is manufactured (hereinafter referred to as “base film side”, combining the two-layer semi-finished product on the base film side and the three-layer semi-finished product on the base film side). (referred to as “semi-finished products”). By bonding the semi-finished product on the cover film side and the semi-finished product on the base film side obtained in this way, a four- or five-layer printed wiring board can be obtained.

The semi-finished product on the base film side may be prepared, for example, by (A) applying a resin solution forming the base film to the metal foil and initially drying the coating film; (B) heat treating the laminate of the metal foil and the initially dried coating film obtained in (A); It is obtained by a manufacturing method including a drying process (hereinafter referred to as “heat treatment/solvent removal process”).

For forming the circuit in the metal foil layer, conventionally known methods can be used. The additive method may be used, or the subtractive method may be used. Preferably it is a subtractive method.

The obtained semi-finished product on the base film side may be used as is for pasting with the semi-finished product on the cover film side, or may be used for pasting with the semi-finished product on the cover film side after pasting and storing the release film.

The semi-finished product on the cover film side is manufactured, for example, by applying an adhesive to the cover film. If necessary, a crosslinking reaction in the applied adhesive can be performed. In a preferred embodiment the adhesive layer is semi-cured.

The obtained semi-finished product on the cover film side may be used as is for pasting with the semi-finished product on the base film side, or may be used for pasting with the semi-finished product on the base film side after pasting and storing the release film.

The semi-finished product on the base film side and the semi-finished product on the cover film side are each stored in, for example, a roll form and then bonded together to produce a printed wiring board. Any method can be used for joining, for example, using a press or roll. Additionally, the two can also be bonded together while being heated by a method such as using a heating press or a heating roll device.

The semi-finished product on the reinforcing material side is suitably manufactured by applying an adhesive to the reinforcing material, for example, in the case of a soft and rollable reinforcing material such as polyimide film. Additionally, in the case of reinforcing plates that are hard and cannot be wound, such as metal plates such as SUS or aluminum, or plates made of glass fibers cured with epoxy resin, it is suitable to be manufactured by transfer coating an adhesive previously applied to a release substrate. Additionally, if necessary, a crosslinking reaction in the applied adhesive can be performed. In a preferred embodiment the adhesive layer is semi-cured.

The obtained semi-finished product on the reinforcing material side may be used as is for bonding with the back side of the printed wiring board, or may be used for bonding with the semi-finished product on the base film side after bonding and storing a release film.

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

Example

Hereinafter, the present invention will be described in detail through examples. Meanwhile, in the present Examples and Comparative Examples, simply referring to parts refers to parts by mass.

(Physical property evaluation method)

(Measurement of polyester resin composition)

Using a 400 MHz ¹ H-nuclear magnetic resonance spectrum device (hereinafter sometimes abbreviated as NMR), the molar ratio of the polyhydric carboxylic acid component and polyhydric alcohol component that constitute the polyester resin was quantified. Deuterated chloroform was used as the solvent. In addition, in Table 1, when the acid value of the polyester resin is raised by post-acid addition, the total of polyhydric carboxylic acid components other than the acid component used in post-acid addition is set to 100 mol%, and each component The mole ratio is indicated.

(Measurement of glass transition temperature)

It was measured using a differential scanning calorimeter (SII, DSC-200). 5 mg of sample (polyester resin) was placed in an aluminum push lid container, sealed, and cooled to -50°C using liquid nitrogen. Next, the temperature is raised to 150°C at a temperature increase rate of 20°C/min, and in the endothermic curve obtained during the temperature increase, there is an extension of the baseline before the endothermic peak appears (below the glass transition temperature) and a tangent line toward the endothermic peak (of the peak). The temperature of the intersection of the tangent line representing the maximum slope from the vertical rise portion to the apex of the peak was taken as the glass transition temperature (unit: ℃).

(Measurement of number average molecular weight)

A sample of polyester resin was dissolved and/or diluted in tetrahydrofuran so that the resin concentration was about 0.5% by weight, and filtered through a polytetrafluoroethylene membrane filter with a pore diameter of 0.5 μm, which was used as a sample for measurement. The molecular weight was measured by gel permeation chromatography (GPC) using tetrahydrofuran as a mobile phase and a differential refractometer as a detector. The flow rate was 1 mL/min and the column temperature was 30°C. For the columns, KF-802, 804L, and 806L manufactured by Showa Denko were used. Monodisperse polystyrene was used as the molecular weight standard.

Hereinafter, examples of synthesis of the polyester resin used in the present invention are shown.

(Manufacture example of polyester resin (a1))

In a reaction vessel equipped with a stirrer, condenser, and thermometer, 159 parts of terephthalic acid, 20 parts of trimellitic anhydride, 412 parts of isophthalic acid, 171 parts of 2-butyl-2-ethyl-1,3-propanediol, and 1,6-hexanediol. 503 parts of tetrabutyl orthotitanate as a catalyst was added at 0.03 mol% based on the total polyhydric carboxylic acid components, and an esterification reaction was performed while heating and dehydrating from 160°C to 220°C over 4 hours. Next, in the polycondensation reaction step, the pressure inside the system was reduced to 5 mmHg over 20 minutes, and the temperature was further raised to 250°C. Next, the pressure was reduced to 0.3 mmHg or less, and a polycondensation reaction was performed for 60 minutes, then cooled to 220°C, 7 parts of trimellitic anhydride and 16 parts of pyromellitic anhydride were added, and the mixture was allowed to react for 30 minutes and taken out. As a result of composition analysis by NMR, the obtained polyester resin (a1) was found to have a molar ratio of terephthalic acid/trimellitic anhydride/isophthalic acid/2-butyl-2-ethyl-1,3-propanediol/1,6-hexanediol/ It was a copolyester of trimellitic anhydride/pyromellitic anhydride = 27/3/70/20/80/1/2. Additionally, the glass transition temperature was 7°C and the number average molecular weight was 8300.

(Manufacture example of polyester resin (a2) to (a6))

According to the production example of polyester resin (a1), the types of raw materials and mixing ratios were changed, and polyester resins (a2) to (a6) having the compositions shown in Table 1 were synthesized. The results are listed in Table 1.

Hereinafter, manufacturing examples of adhesive compositions serving as examples of the present invention and adhesive compositions serving as comparative examples are shown.

Additionally, the following was used as the epoxy resin (B).

Epoxy resin (b1): Cresol novolac type epoxy (YDCN-700-10 (manufactured by Nittetsu Chemical & Material Co., Ltd.))

Epoxy resin (b2): Glycidylamine type epoxy (TetradX (manufactured by Mitsubishi Chemical Corporation))

<Example 1>

30 parts by mass of polyester resin (a1) and 70 parts by mass of polyester resin (a2) obtained in the above synthesis example were dissolved in cyclohexanone to prepare a cyclohexanone varnish with a solid content concentration of 50% by mass. In this varnish, epoxy resin (b1) and epoxy resin (b2) were mixed in an amount of 7 parts by mass and 1 part by mass, respectively, based on a total of 100 parts by mass of polyester resin (a1) and (a2), to form an adhesive composition (S1). ) was obtained.

The obtained adhesive composition (S1) was evaluated for peel strength, solder heat resistance, semi-cured coating film flexibility, semi-cured coating film tackiness, and long-term heat resistance. The results are listed in Table 2.

<Examples 2 to 5, Comparative Examples 1 to 9>

Adhesive compositions (S2) to (S14) were prepared in the same manner as in Example 1 except that the types and mixing amounts of polyester resin and epoxy resin were changed as shown in Table 2, and each evaluation was performed. The results are listed in Table 2.

<Evaluation of adhesive composition>

(Peel strength (adhesiveness))

The adhesive composition was applied to a 12.5 µm thick polyimide film (Apical (registered trademark), manufactured by Shakaneka Co., Ltd.) so that the thickness after drying was 25 µm, and dried at 130°C for 3 minutes. The adhesive film (B stage sample) thus obtained was bonded to rolled copper foil (Nittetsu Chemical & Material Co., Ltd., Espanex series) with a thickness of 18 μm. For bonding, the glossy surface of the rolled copper foil was brought into contact with the adhesive layer and pressed for 280 seconds at 170°C under a pressure of 2 MPa to achieve bonding. Next, it was cured by heat treatment at 170°C for 3 hours to obtain a sample for evaluating peel strength. Peel strength was measured under the conditions of 25°C, film pulling, tensile speed of 50 mm/min, and 90° peeling. This test indicates adhesive strength at room temperature.

<Evaluation criteria>

◎: 1.0 N/mm or more

○: 0.5 N/mm or more but less than 1.0 N/mm

×: less than 0.5 N/mm

(Solder heat resistance)

Samples for evaluation were produced in the same manner as for measuring peel strength. A sample piece measuring 2.0 cm x 2.0 cm was immersed in a solder bath melted at 288°C, and changes in appearance (presence or absence of swelling) were confirmed.

<Evaluation criteria>

○: No expansion for more than 60 seconds

×: Expansion occurs in less than 60 seconds

(Semi-cured film flexibility)

The adhesive composition was applied to a 100 µm thick Teflon (registered trademark) sheet so that the dried thickness was 25 µm, and dried at 130°C for 3 minutes. Next, the state of the coating film when bent more than 180 degrees was checked.

<Evaluation criteria>

○: No cracks

×: With cracks

(Semi-cured coating tackiness)

The adhesive composition was applied to a 100 µm thick Teflon (registered trademark) sheet so that the dried thickness was 25 µm, and dried at 130°C for 3 minutes. Next, a polyimide film with a thickness of 12.5 μm (Apical (registered trademark) manufactured by Shakaneka Co., Ltd.) was overlaid on the coated surface, and the adhesive strength was confirmed after applying a load of 2 MPa for 10 seconds at 25°C. The measurement of strength was performed under the same conditions as the measurement of peel strength.

<Evaluation criteria>

○: 0.2 N/mm or less

×: exceeds 0.2 N/mm

(Long-term heat resistance)

The adhesive composition was applied to a 12.5 µm thick polyimide film (Apical (registered trademark), manufactured by Shakaneka Co., Ltd.) so that the thickness after drying was 25 µm, and dried at 130°C for 3 minutes. The adhesive film (B stage sample) thus obtained was bonded to rolled copper foil (Nittetsu Chemical & Material Co., Ltd., Espanex series) with a thickness of 18 μm. For bonding, the glossy surface of the rolled copper foil was brought into contact with the adhesive layer and pressed for 280 seconds at 170°C under a pressure of 2 MPa to achieve bonding. Next, it was cured by heat treatment at 170°C for 3 hours to obtain a sample for evaluating peel strength. This sample was left standing in an oven at 150°C in an air atmosphere for 1000 hours, and the peeling strength after 1000 hours was measured. Peel strength was measured under the conditions of 25°C, film pulling, tensile speed of 50 mm/min, and 90° peeling. This test demonstrates the long-term reliability of adhesive strength.

<Evaluation criteria>

○: 0.5 N/mm or more

×: less than 0.5 N/mm

As is clear from Table 2, since Examples 1 to 5 contain all of the polyester resin (A1), polyester resin (A2), and epoxy resin (B), the peel strength, solder heat resistance, semi-cured coating film flexibility, Both semi-cured film tackiness and long-term heat resistance were excellent. On the other hand, since the adhesive compositions of Comparative Examples 1 to 9 do not contain any of the polyester resin (A1), polyester resin (A2), and epoxy resin (B), adhesiveness, solder heat resistance, semi-cured coating film flexibility, All characteristics of semi-cured coating film tackiness and long-term heat resistance could not be satisfied simultaneously.

The adhesive composition of the present invention has excellent adhesiveness and solder heat resistance, and further exhibits excellent adhesive properties even after exposure to a high temperature environment for a long period of time, so it is useful as an adhesive for FPC in automobile applications.

Claims (5)

An adhesive composition containing a polyester resin (A1), a polyester resin (A2), and an epoxy resin (B).
Polyester resin (A1): has a number average molecular weight of less than 10000, a glass transition temperature of less than 15°C, and has component (a) as a structural unit having 3 functional groups in total of hydroxyl groups and carboxyl groups per molecule, and is a polyester resin ( A polyester resin containing 3 mol% or more of the component (a) when the total polyhydric carboxylic acid components constituting A1) are 100 mol%.
Polyester resin (A2): A polyester resin with a number average molecular weight of 10000 or more and a glass transition temperature of 15°C or more. The adhesive composition according to claim 1, which is an adhesive for printed wiring boards. An adhesive sheet having an adhesive layer containing the adhesive composition according to claim 1 or 2. A laminate having an adhesive layer containing the adhesive composition according to claim 1 or 2. A printed wiring board comprising the laminate according to claim 4 as a component.