JP7318838B2 - Adhesive composition, adhesive sheet, laminate and printed wiring board - Google Patents

Description

The present invention relates to adhesive compositions. More particularly, it relates to an adhesive composition used for bonding a resin base material and a resin base material or a metal base material. 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 substrate in which an electric circuit is formed on a base material that is made by laminating a thin, soft insulating film such as polyimide and a conductive metal such as copper foil with an adhesive. Unlike rigid substrates, it is very thin and flexible, so it can be used in small gaps and flexible moving parts in electronic devices, so it is used in many electronic devices around us, such as personal computers and smartphones. . Furthermore, in recent years, many FPCs have been installed in automobiles, and adhesives are often required to have high heat resistance and reliability.

Copolyesters are widely used as raw materials for resin compositions used in coating agents, inks, adhesives, etc., and are generally composed of polyhydric carboxylic acids and polyhydric alcohols. It is widely used in various applications such as coating agents and adhesives because it is easy to design molecules by selecting and combining polyhydric carboxylic acids and polyhydric alcohols, and the molecular weight can be freely controlled.

Copolyester has excellent adhesiveness (peel strength) to metals containing copper, and has been used as an adhesive for FPCs by blending a curing agent. (For example, Patent Document 1).

Japanese Patent Publication No. 6-104813

However, the adhesive using the 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 such conventional technical problems. That is, the object of the present invention is to exhibit excellent adhesiveness and solder heat resistance, exhibit excellent adhesiveness even after being exposed to a high temperature environment for a long time, and provide flexibility when made into a semi-cured coating film. The object of the present invention is to provide an adhesive composition which satisfies the tackiness and tackiness, and an adhesive sheet, a laminate and a printed wiring board containing the same.

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

[1] An adhesive composition containing a polyester resin (A1), a polyester resin (A2), and an epoxy resin (B).
Polyester resin (A1): A component (a) having a number average molecular weight of less than 10,000, a glass transition temperature of less than 15° C., and having a total of three functional groups, hydroxyl groups and carboxyl groups, per molecule (a) as a structural unit. and having 3 mol % or more of the component (a) when the total polyvalent carboxylic acid component constituting the polyester resin (A1) is taken as 100 mol %.
Polyester resin (A2): A polyester resin having a number average molecular weight of 10,000 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 comprising the adhesive composition according to [1] or [2].

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

[5] A printed wiring board comprising the laminate according to [4] as a component.

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

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

<Polyester resin (A1)>
The polyester resin (A1) used in the present invention has a number average molecular weight of less than 10,000, a glass transition temperature of less than 15°C, and a component having a total of three functional groups of hydroxyl groups and carboxyl groups per molecule ( It is a polyester resin having a) as a structural unit and having 3 mol% or more of the component (a) when the total polycarboxylic acid component constituting the polyester resin (A1) is taken as 100 mol%. Adhesiveness and long-term heat resistance become favorable because the adhesive composition has the polyester resin (A1).

The polyester resin (A1) has a chemical structure obtained by polycondensation of a polyhydric carboxylic acid component and a polyhydric alcohol component. It consists of one or more selected ingredients. Although the polycarboxylic acid component constituting the polyester resin (A1) is not limited, the following polycarboxylic acids or esters thereof, and polycarboxylic acid anhydrides can be used. Specifically, polyvalent carboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, 2,5-furandicarboxylic 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 naphthalene dicarboxylic acid, and esters thereof. Examples of polycarboxylic anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. In particular, aromatic polycarboxylic acid components are preferred, and naphthalene dicarboxylic acid and terephthalic acid are more preferred. The heat resistance of the adhesive composition can be improved by using the aromatic polycarboxylic acid.

The polyhydric alcohol component constituting the polyester resin (A1) is not particularly limited, but is 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-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, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, polytetra Polyalkylene ether glycols such as methylene glycol and polypropylene glycol, pentaerythritol, α-methylglucose, mannitol, sorbitol, and polyhydric alcohol components such as dimer diol can be used, and one or more of these can be used. can. In particular, a polyhydric alcohol component having a long-chain alkylene group is preferred, and 1,6-hexanediol and dimer diol are more preferred. 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 sum of hydroxyl groups and carboxyl groups per molecule is trifunctional. The carboxy group may be an acid anhydride group, and the acid anhydride group is counted as bifunctional. The trifunctional groups may be all carboxy groups, all hydroxyl groups, or may have both carboxy 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, trimethylolpropane, Methylolethane can be mentioned. Preferred are trimellitic acid, 4-hydroxyphthalic acid and their anhydrides, and diphenolic acid, and by copolymerizing these, excellent solder heat resistance and long-term heat resistance can be exhibited. The reason for this is not clear, but by introducing branches into a relatively low-molecular-weight polyester resin with a trifunctional component, it becomes a cured coating film that can build a high crosslink density, and long-term heat resistance and solder heat resistance are improved. guessed. Component (a) must be present in an amount of 3 mol % or more, preferably 4 mol % or more, based on 100 mol % of all polycarboxylic acid components constituting the polyester resin (A1). From the viewpoint of preventing gelation during polymerization, the content is preferably 10 mol % or less, more preferably 6 mol % or less.

The polyester resin (A1) used in the present invention can also be copolymerized with a tetravalent or higher polycarboxylic acid component and/or a tetravalent or higher polyhydric alcohol component. Polyvalent carboxylic acid components having a valence of 4 or more include, for example, pyromellitic acid, benzophenonetetracarboxylic acid, aromatic carboxylic acids such as pyromellitic anhydride (PMDA), 1,2,3,4-butanetetracarboxylic acid, and the like. and the like, and these can be used singly or in combination of two or more. Examples of tetrahydric or higher polyhydric alcohol components include pentaerythritol, α-methylglucose, mannitol, and sorbitol, and it is possible to use one or more of these.

The polyester resin (A1) used in the present invention can also be copolymerized with lactones or lactams. For example, ε-caprolactone and ε-caprolactam can be used.

As a method of polymerization condensation reaction for producing the polyester resin (A1) used in the present invention, for example, 1) polyhydric carboxylic acid and polyhydric alcohol are heated in the presence of a known catalyst, and dehydrated and esterified, 2) A polyhydric alcohol-removing polycondensation reaction is performed by heating an alcohol ester of a polyhydric carboxylic acid and a polyhydric alcohol in the presence of a known catalyst, transesterifying the polyhydric alcohol-removing polycondensation reaction. and 3) a method of depolymerizing. 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 oxyacetylcetonate, 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 singly or in combination of two or more.

The polyester resin (A1) used in the present invention has a number average molecular weight of less than 10,000, more preferably 9,000 or less. Also, it is preferably 1,000 or more, more preferably 3,000 or more, and still more preferably 4,000 or more. Within the above range, the adhesive composition can be easily handled when dissolved in a solvent and has excellent adhesiveness.

The glass transition temperature of the polyester resin (A1) used in the present invention is less than 15°C, preferably 10°C or less. Moreover, it is preferably -25° C. or higher. When it is within the above range, the adhesive composition can be easily handled when it is formed into a semi-cured coating film and has excellent adhesiveness.

<Polyester resin (A2)>
The polyester resin (A2) used in the present invention is a polyester resin having a number average molecular weight of 10000 or higher and a glass transition temperature of 15°C or higher. Adhesiveness becomes favorable because an adhesive composition has a polyester resin (A2).

The polyester resin (A2) used in the present invention has a number average molecular weight of 10,000 or more, preferably 11,000 or more, and more preferably 12,000 or more. Also, it is preferably less than 100,000, more preferably less than 70,000, and even more preferably less than 50,000. Within the above range, it is possible to satisfy 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.

The glass transition temperature of the polyester resin (A2) used in the present invention is 15°C or higher. Moreover, it is preferably 100° C. or lower, more preferably 50° C. or lower. Within the above range, it is possible to obtain an adhesive composition that is easy to handle when formed into a semi-cured coating film and that is excellent in adhesiveness.

The polyester resin (A2) has a chemical structure obtained by polycondensation of a polyhydric carboxylic acid component and a polyhydric alcohol component. It consists of one or more selected ingredients. The constituent components constituting the polyester resin (A2) are not particularly limited, and the same components as those for 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. Specifically, although not particularly limited, biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, selected from the group consisting of tetraglycidyldiaminodiphenylmethane, triglycidyl para-aminophenol, tetraglycidylbisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylylenediamine, dimer acid-modified epoxy, and epoxy-modified polybutadiene can be used. N,N,N',N'-tetraglycidyl-m-xylylenediamine, biphenyl-type epoxy resin, novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, or epoxy-modified polybutadiene are preferred. Better adhesiveness can be exhibited.

In the adhesive composition of the present invention, the content of the epoxy resin (B) is preferably 0.1 parts by mass or more with respect to a total of 100 parts by mass of the polyester resin (A1) and the polyester resin (A2). , more preferably 1 part by mass or more. When it is at least the above lower limit, a sufficient curing effect can be obtained, and excellent adhesiveness and soldering heat resistance can be exhibited. Also, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. When the content is equal to or less than the above upper limit value, the long-term heat resistance becomes good. That is, within the above range, it is possible to obtain an adhesive composition having more excellent adhesiveness, soldering heat resistance and long-term heat resistance.

<Adhesive composition>
The adhesive composition of the present invention comprises polyester resin (A1) as well as polyester (A2) and epoxy resin (B). By using two kinds of polyester resins having specific characteristics together, it is possible to improve adhesive strength after curing, soldering heat resistance, and long-term heat resistance.

The mass ratio of the polyester resin (A1) and the polyester resin (A2) in the adhesive composition of the present invention is, when the total of the polyester resin (A1) and the polyester resin (A2) is 100 parts by mass, the polyester resin (A1) is preferably 10 parts by mass or more and 90 parts by mass or less. More preferably 20 parts by mass or more, still more preferably 25 parts by mass or more. Moreover, it is more preferably 80 parts by mass or less, and still more preferably 75 parts by mass or less. When the mass ratio of both is within the above range, appropriate tackiness of the semi-cured coating film, excellent adhesiveness and soldering heat resistance can be achieved at the same time.

<Organic solvent>
The adhesive composition of the invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it dissolves the polyester resin and the epoxy resin. Specifically, for example, aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, octane and decane; and alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane and ethylcyclohexane. Halogenated hydrocarbons such as hydrogen, trichlorethylene, dichlorethylene, chlorobenzene, and chloroform, alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol, acetone, methyl isobutyl ketone, ketone solvents such as methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone and acetophenone; cellosolves such as methyl cellosolve and ethyl cellosolve; ester 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, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol mono-n-butyl ether, etc. A glycol ether solvent or the like can be used, and one or more of these can be used in combination. In particular, toluene and cyclohexanone are preferred in terms of working environment and drying properties.

The organic solvent is preferably in the range of 100 to 1000 parts by mass with respect to 100 parts by mass in total of the polyester resin (A1) and the polyester resin (A2). By making it more than the said lower limit, liquid state and pot-life property become favorable. Moreover, setting the content to the above upper limit or less is advantageous in terms of manufacturing costs and transportation costs.

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

<Flame retardant>
The adhesive composition of the present invention may optionally contain a flame retardant. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Among them, phosphorus-based flame retardants are preferable, and known phosphorus-based flame retardants such as phosphate esters such as trimethyl phosphate, triphenyl phosphate, tricresyl phosphate, etc., phosphates such as aluminum phosphinate, and phosphazenes can be used. . These may be used alone, or may be used in any combination of two or more. When a flame retardant is contained, it is preferable to contain the flame retardant in the range of 1 to 200 parts by mass with respect to a total of 100 parts by mass of the polyester resin (A1), the polyester resin (A2) and the epoxy resin (B). A range of up to 150 parts by weight is more preferred, and a range of 10 to 100 parts by weight is most preferred. By setting the content within the above range, flame retardancy can be exhibited while adhesiveness and solder heat resistance are maintained.

<Tackifier>
A tackifier may be added to the adhesive composition of the present invention, if necessary. Examples of tackifiers include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymer petroleum resins, styrene resins and hydrogenated petroleum resins. used in These may be used alone, or may be used in any combination of two or more. When a tackifier is contained, it is preferably contained in the range of 1 to 200 parts by weight, preferably 5 to 150 parts by weight, with respect to a total of 100 parts by weight of the polyester resin (A1), the polyester resin (A2) and the epoxy resin (B). A range of parts by weight is more preferred, and a range of 10 to 100 parts by weight is most preferred. By setting it within the above range, the effect of the tackifier can be exhibited while maintaining adhesiveness and soldering heat resistance.

<Filler>
The adhesive composition of the present invention may optionally contain a filler. Examples of organic fillers include powders of heat-resistant resins such as polyimide, polyamideimide, fluororesin, and liquid crystal polyester. 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 ( _CaCO3 ), calcium sulfate (CaSO4), zinc oxide ( _ZnO ), magnesium titanate (MgO- _TiO2 ), barium sulfate ( _BaSO4 ), organic bentonite, clay , mica, aluminum hydroxide, magnesium hydroxide, etc. Among these, silica is preferable from the viewpoint of ease of dispersion and 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 used to impart moisture absorption resistance. is good. When silica is blended, the blending amount is 0.05 to 30 parts by mass with respect to a total of 100 parts by mass of the polyester resin (A1), the polyester resin (A2) and the epoxy resin (B). preferable. Further heat resistance can be expressed by making it more than the said lower limit. In addition, when the content is equal to or less than the above upper limit, poor dispersion of silica and excessive increase in 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, if necessary. Addition of a silane coupling agent is very preferable because it improves adhesion to metals and heat resistance. Although the silane coupling agent is not particularly limited, examples thereof include those having an unsaturated group, those having an epoxy group, and those having an amino group. Among these, epoxy such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane is used from the viewpoint of heat resistance. A silane coupling agent having a group is more preferred. When blending a silane coupling agent, the blending amount is 0.5 to 20 parts by mass with respect to a total of 100 parts by mass of the polyester resin (A1), the polyester resin (A2) and the epoxy resin (B). is preferred. Soldering heat resistance and adhesiveness can be improved by setting it in the said range.

<Laminate>
The laminate of the present invention is obtained by laminating an adhesive composition on a base material (two-layer laminate of base material/adhesive layer), or further laminating a base material (base material/adhesive layer/ A three-layer laminate of substrates). Here, the adhesive layer refers to a layer of the adhesive composition after the adhesive composition of the present invention has been 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, drying it, and further laminating another substrate according to a conventional method.

<Base material>
In the present invention, the substrate is not particularly limited as long as the adhesive composition of the present invention can be applied and dried to form an adhesive layer. Examples include metal substrates such as plates and metal foils, papers, and the like.

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

Any conventionally known conductive material that can be used for circuit boards can be used as the metal substrate. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, and their alloys, plated products, and metals treated with other metals such as zinc and chromium compounds. Metal foil is preferred, and copper foil is more preferred. Although the thickness of the metal foil is not particularly limited, 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 still more preferably 20 μm or less. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit. Metal foils are usually 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 using a ribbon-shaped metal foil, the length is not particularly limited. Also, the width is not particularly limited, but it 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. Moreover, it is practically preferably 0.3 μm or more, more preferably 0.5 μm or more, and still more preferably 0.7 μm or more.

Examples of papers include woodfree paper, kraft paper, roll paper, glassine paper, and the like. Moreover, glass epoxy etc. can be illustrated as a composite material.

Based on adhesive strength and durability with the adhesive composition, polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, fluororesin, A SUS steel plate, copper foil, aluminum foil, or glass epoxy is preferred.

<Adhesive sheet>
In the present invention, the adhesive sheet is obtained by laminating the laminate and the release substrate via an adhesive composition. Specific configuration modes include laminate/adhesive layer/release substrate, or release substrate/adhesive layer/laminate/adhesive layer/release substrate. By laminating the release base material, it functions as a protective layer for the base material. Moreover, by using a 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 in a conventional manner. In addition, when a release base material is applied to the adhesive layer after drying, it is possible to wind up the product without set-off to the base material, resulting in excellent workability and preservability due to the protection of the adhesive layer. excellent and easy to use. Further, if the adhesive layer itself is applied to a release base material and dried, and if necessary, another release base material is applied, the adhesive layer itself can be transferred to another base material.

<Release substrate>
The release substrate is not particularly limited, but for example, a coated layer of filler such as clay, polyethylene, polypropylene, etc. is applied to both sides of paper such as woodfree paper, kraft paper, roll paper, and glassine paper. and a silicone type, fluorine type or alkyd type release agent is applied on each coating layer. 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 release agent. For reasons such as the release force between the release base material and the adhesive layer, and the fact that silicone has an adverse effect on electrical properties, both sides of high-quality paper are filled with polypropylene and an alkyd-based release agent is used on top of it. Alternatively, it is preferable to use an alkyd release agent on polyethylene terephthalate.

In the present invention, the method of coating the substrate with the adhesive composition is not particularly limited, but examples thereof include a comma coater and a reverse roll coater. Alternatively, if necessary, an adhesive layer can be provided directly or by a transfer method on the rolled copper foil or polyimide film, which are the constituent materials of the printed wiring board. The thickness of the adhesive layer after drying may be changed as required, but is preferably in the range of 5 to 200 μm. Sufficient adhesive strength can be obtained by setting the thickness of the adhesive film to 5 μm or more. Further, by setting the thickness to 200 μm or less, it becomes easier to control the amount of residual solvent in the drying process, and blisters are less likely to occur during pressing in the manufacture of printed wiring boards. The drying conditions are not particularly limited, but the residual solvent rate after drying is preferably 1% by mass or less. When the amount is 1% by mass or less, foaming of the residual solvent is suppressed during pressing of the printed wiring board, and blisters are less likely to occur.

<Printed wiring board>
The printed wiring board in the present invention includes, as constituent elements, a laminate formed from a metal foil forming a conductor circuit and a resin base material. A printed wiring board is manufactured, for example, by a conventionally known method such as a subtractive method using a metal-clad laminate. If necessary, so-called flexible circuit boards (FPC), flat cables, tape automated bonding ( It is a general term for circuit boards for TAB).

The printed wiring board of the present invention can be of any laminate construction 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. Further, for example, a printed wiring board can be made up 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, a configuration in which two or three or more of the above printed wiring boards are laminated can be employed.

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 adhesiveness with conventional resin substrates such as polyimide, polyester film, copper foil, and aluminum foil that constitute printed wiring boards, and has solder reflow resistance. can be obtained. Therefore, it is suitable as an adhesive composition used for coverlay films, laminates, resin-coated copper foils, 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 resins for the base film include polyester resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfides, syndiotactic polystyrene, polyolefin resins, fluorine resins, and the like.

<Cover film>
As the cover film, any insulating film conventionally known as an insulating film for printed wiring boards can be used. 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 are used. It is possible. More preferably, it is a polyimide film.

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

In a preferred embodiment, a semi-finished product is produced by laminating an adhesive layer on a cover film layer (hereinafter referred to as a "cover film-side semi-finished product"). 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 a semi-finished product in which an adhesive layer is laminated on a base film layer. , a semi-finished product in which a desired circuit pattern is formed by laminating a metal foil layer thereon (hereinafter referred to as "base film side 3-layer semi-finished product") (hereinafter referred to as "base film side 2-layer semi-finished product"). Together with the base film side three-layer semi-finished product, it is referred to as the “base film side semi-finished product”). By laminating the semi-finished product on the cover film side and the semi-finished product on the base film side thus obtained, a printed wiring board having four or five layers can be obtained.

The semi-finished product on the substrate film side includes, for example, (A) a step of applying a solution of a resin that will be the substrate film to the metal foil and initially drying the coating film, and (B) the metal foil obtained in (A) and It is obtained by a production method including a process of heat-treating and drying the laminate with the initially dried coating film (hereinafter referred to as "heat-treatment/solvent removal process").

A conventionally known method can be used to form a circuit in the metal foil layer. An additive method may be used, or a subtractive method may be used. A subtractive method is preferred.

The semi-finished product on the base film side thus obtained may be used as it is for lamination with the semi-finished product on the cover film side. may be used.

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

The semi-finished product on the cover film side thus obtained may be used as it is for bonding to the semi-finished product on the base film side. may be used for

The base film-side semi-finished product and the cover film-side semi-finished product are each stored in the form of rolls, for example, and then laminated together to manufacture a printed wiring board. Any method can be used as the bonding method, and for example, the bonding can be performed using a press or a roll. Also, both can be bonded together while being heated by a method such as using a hot press or a hot roll device.

For example, in the case of a soft and windable reinforcing material such as a polyimide film, the reinforcing material-side semi-finished product is preferably manufactured by applying an adhesive to the reinforcing material. In addition, in the case of reinforcing plates such as metal plates such as SUS and aluminum, and glass fiber hardened plates with epoxy resin that cannot be rolled up, the adhesive applied in advance to the release base material can be transferred and applied. It is preferably manufactured. Moreover, a cross-linking reaction in the applied adhesive can be carried out as necessary. In a preferred embodiment, the adhesive layer is semi-cured.

The semi-finished product on the reinforcing material side thus obtained may be used as it is for bonding to the back surface of the printed wiring board, or it may be used for bonding to the semi-finished product on the base film side after being stored after being bonded with a release film. You may

The base film-side semi-finished product, the cover film-side semi-finished product, and the reinforcing material-side semi-finished product are all the printed wiring board laminate of the present invention.

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, in the present examples and comparative examples, parts simply indicate parts by mass.

(Physical property evaluation method)
(Measurement of composition of polyester resin)
A 400 MHz ¹ H-nuclear magnetic resonance spectrometer (hereinafter sometimes abbreviated as NMR) was used to determine the molar ratios of the polyhydric carboxylic acid component and the polyhydric alcohol component constituting the polyester resin. Deuterated chloroform was used as the solvent. In Table 1, when the acid value of the polyester resin is increased by post-acid addition, the total of polyvalent carboxylic acid components other than the acid component used for post-acid addition is 100 mol%, and the molar ratio of each component was written.

(Measurement of glass transition temperature)
It was measured using a differential scanning calorimeter (DSC-200, SII). 5 mg of a sample (polyester resin) was placed in an aluminum lid-shaped container, sealed, and cooled to -50°C using liquid nitrogen. Then, the temperature is raised to 150 ° C. at a rate of 20 ° C./min, and in the endothermic curve obtained in the heating process, the baseline extension line before the endothermic peak (below the glass transition temperature) and the endothermic peak The glass transition temperature (unit: °C) was defined as the temperature at the intersection with the tangent line (the tangent line indicating the maximum slope from the rising portion of the peak to the apex of the peak).

(Measurement of number average molecular weight)
A polyester resin sample was dissolved and/or diluted with tetrahydrofuran so that the resin concentration was about 0.5% by weight, filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm, and used as a measurement sample. bottom. 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. Showa Denko KF-802, 804L, and 806L columns were used. Monodisperse polystyrene was used as a molecular weight standard.

Synthesis examples of the polyester resin used in the present invention are shown below.

(Production example of polyester resin (a1))
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, 1,6 were placed in a reaction vessel equipped with a stirrer, condenser and thermometer. -503 parts of hexanediol, 0.03 mol% of tetrabutyl orthotitanate as a catalyst with respect to the total polyvalent carboxylic acid component were charged, and the temperature was raised from 160 ° C. to 220 ° C. over 4 hours, and the esterification reaction was carried out through the dehydration step. did Next, in the polycondensation reaction step, the pressure in 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 after conducting a polycondensation reaction for 60 minutes, the mixture was 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. , took this out. As a result of composition analysis by NMR, the resulting 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- It was a copolymerized polyester of hexanediol/trimellitic anhydride/pyromellitic anhydride=27/3/70/20/80/1/2. Further, the glass transition temperature was 7° C. and the number average molecular weight was 8,300.

(Production example of polyester resins (a2) to (a6))
Polyester resins (a2) to (a6) having the compositions shown in Table 1 were synthesized by changing the types and blending ratios of the raw materials according to the production example of the polyester resin (a1). The results are listed in Table 1.

Production examples of adhesive compositions serving as examples of the present invention and adhesive compositions serving as comparative examples are shown below.
In addition, the following was used as an epoxy resin (B).
Epoxy resin (b1): cresol novolac type epoxy (YDCN-700-10 (manufactured by Nippon Steel Chemical & Materials Co., Ltd.))
Epoxy resin (b2): glycidylamine type epoxy (Tetrad X (manufactured by Mitsubishi Gas Chemical Company, Inc.))

<Example 1>
30 parts by mass of the polyester resin (a1) and 70 parts by mass of the polyester resin (a2) obtained in the Synthesis Example were dissolved in cyclohexanone to prepare a cyclohexanone varnish having a solid concentration of 50% by mass. Epoxy resin (b1) and epoxy resin (b2) were blended into this varnish so as to be 7 parts by mass and 1 part by mass, respectively, with respect to a total of 100 parts by mass of polyester resins (a1) and (a2). A product (S1) was obtained.
The obtained adhesive composition (S1) was evaluated for peel strength, soldering heat resistance, semi-cured film flexibility, semi-cured 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 blending amounts of the 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 (manufactured by Kaneka Corporation, Apical (registered trademark)) so that the thickness after drying was 25 μm, and dried at 130° C. for 3 minutes. The adhesive film (B stage product) thus obtained was laminated to a 18 μm thick rolled copper foil (manufactured by Nippon Steel Chemical & Materials Co., Ltd., Espanex series). The bonding was performed by pressing the rolled copper foil so that the glossy surface of the rolled copper foil was in contact with the adhesive layer and pressing for 280 seconds under a pressure of 2 MPa at 170°C. Then, it was cured by heat treatment at 170° C. for 3 hours to obtain a sample for peel strength evaluation. The peel strength was measured under the conditions of 25° C., film pulling, tensile speed of 50 mm/min, and 90° peeling. This test shows the bond strength at room temperature. <Evaluation Criteria>
◎: 1.0 N / mm or more ○: 0.5 N / mm or more and less than 1.0 N / mm ×: less than 0.5 N / mm

(solder heat resistance)
An evaluation sample was prepared in the same manner as the peel strength measurement. A sample piece of 2.0 cm×2.0 cm was immersed in a solder bath melted at 288° C., and a change in appearance (presence or absence of swelling) was checked. <Evaluation Criteria>
○: no swelling for 60 seconds or more ×: swelling for less than 60 seconds

(Flexibility of semi-cured coating film)
The adhesive composition was applied to a Teflon (registered trademark) sheet having a thickness of 100 μm so that the thickness after drying was 25 μm, and dried at 130° C. for 3 minutes. Next, the state of the coating film when bent at 180° C. or more was confirmed.
<Evaluation Criteria>
○: No cracks ×: Cracks present

(Semi-cured coating film tackiness)
The adhesive composition was applied to a Teflon (registered trademark) sheet having a thickness of 100 μm so that the thickness after drying was 25 μm, and dried at 130° C. for 3 minutes. Next, a 12.5 μm-thick polyimide film (manufactured by Kaneka Co., Ltd., Apical (registered trademark)) was placed on the coated surface, and a load of 2 MPa was applied at 25° C. for 10 seconds, and then the adhesive strength was confirmed. The strength measurement was performed under the same conditions as the peel strength measurement.
<Evaluation Criteria>
○: 0.2 N / mm or less ×: more than 0.2 N / mm

(Long-term heat resistance)
The adhesive composition was applied to a 12.5 μm-thick polyimide film (manufactured by Kaneka Corporation, Apical (registered trademark)) so that the thickness after drying was 25 μm, and dried at 130° C. for 3 minutes. The adhesive film (B stage product) thus obtained was laminated to a 18 μm thick rolled copper foil (manufactured by Nippon Steel Chemical & Materials Co., Ltd., Espanex series). The bonding was performed by pressing the rolled copper foil so that the glossy surface of the rolled copper foil was in contact with the adhesive layer and pressing for 280 seconds under a pressure of 2 MPa at 170°C. Then, it was cured by heat treatment at 170° C. for 3 hours to obtain a sample for peel strength evaluation. This sample was allowed to stand in an oven at 150° C. for 1000 hours in an air atmosphere, and the peel strength was measured after 1000 hours. The 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 bond strength.
<Evaluation Criteria>
○: 0.5 N / mm or more ×: less than 0.5 N / mm

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

The adhesive composition of the present invention is excellent in adhesiveness and solder heat resistance, and exhibits excellent adhesiveness even after being exposed to a high-temperature environment for a long time. Therefore, it is useful as an adhesive for automotive FPCs. is.

Claims (5)

An adhesive composition containing a polyester resin (A1), a polyester resin (A2), and an epoxy resin (B).
Polyester resin (A1): A component (a) having a number average molecular weight of less than 10,000, a glass transition temperature of less than 15° C., and having a total of three functional groups, hydroxyl groups and carboxyl groups, per molecule (a) as a structural unit. and having 3 mol % or more of the component (a) when the total polyvalent carboxylic acid component constituting the polyester resin (A1) is taken as 100 mol %.
Polyester resin (A2): A polyester resin having a number average molecular weight of 10,000 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 comprising the adhesive composition according to claim 1 or 2. A laminate having an adhesive layer comprising the adhesive composition according to claim 1 or 2. A printed wiring board comprising the laminate according to claim 4 as a component.