Adhesive composition and adhesive sheet, laminate and printed wiring board containing the same

Abstract

The present application provides an adhesive composition which is excellent in workability, heat resistance, adhesive strength, relative dielectric constant, dielectric loss tangent, and dielectric properties, and a laminated body and a printed wiring board each containing the adhesive composition. The adhesive composition contains a polycarbodiimide (A) and an amorphous polyol (B), and satisfies (i) and (ii) below, (i) the composition does not contain a compound having an isocyanate group, and (ii) the composition does not contain a compound having an acid value of more than 10 eq / 10 g. 6 g.

Description

Technical Field

[0001] This invention relates to an adhesive composition. More specifically, it relates to an adhesive composition for bonding resin substrates to resin substrates or metal substrates. Particularly, this invention relates to adhesive compositions for flexible printed circuit boards (hereinafter referred to as FPCs), as well as adhesive sheets, laminates, and printed circuit boards containing the same. Background Technology

[0002] Polyols are widely used as adhesives and additives in coating and adhesive applications. Polyester polyols, in particular, have excellent adhesion to copper-containing metals and can be used as adhesives for FPCs, etc., after being mixed with curing agents such as epoxy resins (e.g., Patent Document 1).

[0003] FPCs (Flexible Printed Circuits) possess excellent flexibility, enabling them to meet the demands of multifunctionality and miniaturization in personal computers (PCs), smartphones, and other devices. They are widely used to assemble electronic circuit boards within narrow and complex interiors. In recent years, with the miniaturization, weight reduction, high density, and high power of electronic devices, the performance requirements for circuit boards (electronic circuit boards) have become increasingly stringent. In particular, the high-speed transmission in FPCs necessitates the use of high-frequency signals. Consequently, the demand for low dielectric properties (low dielectric constant, low dielectric loss tangent) in the high-frequency region of FPCs has gradually increased. To achieve such low dielectric properties, strategies have been proposed to reduce the dielectric loss of FPC substrates and adhesives. For FPC substrates, in addition to existing polyimide (PI) and polyethylene terephthalate (PET), substrate films with low dielectric properties such as liquid crystal polymers (LCP) and syndiotactic polystyrene (SPS) have also been proposed. As adhesives, combinations of polyolefins and epoxy resins are being developed (Patent Document 2, etc.). Patent document 3 proposes a thermosetting adhesive for printed circuit boards containing a modified ester resin with a carboxyl group, an epoxy or isocyanate curing agent, and a thermosetting agent.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 6-104813

[0007] Patent Document 2: International Publication No. WO2016 / 047289

[0008] Patent Document 3: Japanese Patent Application Publication No. 2012-131967 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] However, the adhesive composition described in Patent Document 1 contains a high-acid-value polyester. Due to the reaction with epoxy resin to generate hydroxyl groups, it has a relatively high dielectric constant and dielectric loss tangent, lacking the aforementioned low dielectric properties and thus unsuitable for FPCs in high-frequency regions. Furthermore, it is difficult to conclude that the adhesive described in Patent Document 2 possesses excellent heat resistance as an FPC adhesive, and its pot life is also insufficient. The adhesive composition in Patent Document 3 also fails to meet the low dielectric properties and pot life requirements due to the reaction of the high-acid-value polyester with the curing agent and thermosetting aid.

[0011] This invention relates to adhesive compositions addressing related problems in the prior art. Specifically, the object of this invention is to provide an adhesive composition exhibiting excellent pot life, heat resistance, adhesive strength, relative permittivity, low dielectric loss tangent, and superior dielectric properties, as well as adhesive sheets, laminates, and printed circuit boards containing this composition.

[0012] Technical means to solve the problem

[0013] After in-depth research, the inventors discovered that the above-mentioned problems can be solved by the means described below, thereby realizing the present invention.

[0014] That is, the present invention has the following structure.

[0015] [1] An adhesive composition comprising polycarbodiimide (A) and an amorphous polyol (B), and satisfying (i) and (ii) below,

[0016] (i) The composition does not contain compounds having isocyanate groups.

[0017] (ii) The composition does not contain any acid with an acid value exceeding 10 eq / 10. 6 g is a compound.

[0018] [2] According to the adhesive composition of [1], the dielectric loss tangent (tanδ) of the amorphous polyol (B) at 10 GHz is 0.006 or less.

[0019] [3] The adhesive composition according to [1] or [2], wherein the amorphous polyol (B) contains a polyester polyol.

[0020] [4] The adhesive composition according to [1] to [3] contains 0.1 to 10 parts by weight of epoxy resin (C) relative to 100 parts by weight of amorphous polyol (B).

[0021] [5] An adhesive sheet comprising an adhesive layer composed of the adhesive compositions described in [1] to [4].

[0022] [6] A laminate containing an adhesive layer comprising the adhesive compositions described in [1] to [4].

[0023] [7] A printed circuit board containing the laminate described in [6] as a constituent element.

[0024] The effects of the invention

[0025] Since the adhesive composition of the present invention can be thermosetting without carboxyl groups, it can maintain its pot life at room temperature and suppress the generation of functional groups that deteriorate low dielectric properties. Therefore, the adhesive composition has excellent dielectric properties, bond strength, solder heat resistance and pot life, and is suitable for use as an adhesive for FPCs in high-frequency regions, for bonding sheets, laminates and printed circuit boards. Detailed Implementation

[0026] Hereinafter, one embodiment of the present invention will be described in detail. However, the present invention is not limited thereto, and various modifications may be made within the scope described.

[0027] <Adhesive Composition>

[0028] The adhesive composition of the present invention contains polycarbodiimide (A) and an amorphous polyol (B), and satisfies the following (i) and (ii),

[0029] (i) The composition does not contain compounds having isocyanate groups.

[0030] (ii) The composition does not contain any acid with an acid value exceeding 10 eq / 10. 6 g is a compound.

[0031] <Requirement (i)>

[0032] The adhesive composition of the present invention does not contain compounds having isocyanate groups. Compounds having isocyanate groups refer to, in addition to isocyanate compounds such as common isocyanate curing agents, also including polycarbodiimides and polyols having isocyanate groups. Since the adhesive composition of the present invention can be thermosetting even without containing compounds having isocyanate groups, the pot life is improved by eliminating the reaction between the hydroxyl groups and isocyanate groups of the amorphous polyol, which does not react at low temperatures, or the reaction between the isocyanate groups and moisture.

[0033] <Requirement (ii)>

[0034] The adhesive composition of the present invention does not contain any substance with an acid value exceeding 10 eq / 10. 6The compound contains g. By keeping the acid value within the above range, the reaction between the carboxyl group and the carbodiimide bond, which reacts at low temperatures, can be prevented, thereby improving pot life. Here, the adhesive composition does not contain any compound with an acid value exceeding 10 eq / 10. 6 The compound g refers to polycarbodiimide (A) and amorphous polyol (B) whose acid values ​​do not exceed 10 eq / 10. 6 g.

[0035] <Polycarbodiimide (A)>

[0036] The polycarbodiimide (A) used in this invention must have at least two carbodiimide bonds in its molecule, lack isocyanate groups, and have an acid value not exceeding 10 eq / 10. 6 There are no specific limitations on g. By using polycarbodiimide (A) to thermocure the hydroxyl groups of the amorphous polyol (B) with the carbodiimide bond, heat resistance and adhesion can be improved.

[0037] In the adhesive composition of the present invention, the content of polycarbodiimide (A) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of amorphous polyol (B). By exceeding the lower limit value, the crosslinking density can be increased, resulting in good solder heat resistance. Furthermore, this content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. By exceeding the upper limit value, excellent solder heat resistance and low dielectric properties can be achieved. That is, within the above range, an adhesive composition with excellent solder heat resistance and low dielectric properties can be obtained. Commercially available polycarbodiimide (A) products include, for example, those manufactured by Nisshin Textile Chemicals Co., Ltd. under the trade names CARBODILITE (registered trademark) V-02B, ElastostabH01, V-03, V-09, and V-09GB, which can be used alone or in combination.

[0038] <Amorphous Polyols (B)>

[0039] The amorphous polyol (B) used in this invention is selected only if it has two or more hydroxyl groups in its molecule, does not have isocyanate groups, and has an acid value of 10 eq / 10. 6 For amounts below g, there are no particular limitations. From a service life perspective, the amorphous polyol (B) needs to be amorphous. As the amorphous polyol (B), at least one selected from the group consisting of polyester polyols, polyurethane polyols, polyether polyols, polycarbonate polyols, and polyolefin polyols can be used. Polyester polyols are preferred. By using polyester polyols with excellent flexibility, both adhesion and solder heat resistance can be achieved.

[0040] The amorphous polyol (B) used in this invention preferably has a dielectric loss tangent (tanδ) of 0.006 or less. More preferably, it has a dielectric loss tangent of 0.005 or less, and even more preferably, it has a dielectric loss tangent of 0.004 or less. Although the lower limit is not particularly limited, it can also be 0.0001 or more in practical use. In order to adjust the amorphous polyol (B) to have a low dielectric loss tangent, for example, as a structural unit constituting the amorphous polyol (B), it can be achieved by including structural units with long-chain hydrocarbon groups having 10 or more carbon atoms, such as polyolefins and dimer acid derivatives (dimer acids, dimer diamines, dimer diols, etc.); and structural units with condensation rings, such as naphthalene dicarboxylic acid, hydrogenated naphthalene dicarboxylic acid, and tricyclodecanediethanol, as main components, either alone or in appropriate combinations.

[0041] <Polyester Polyols>

[0042] The polyester polyol in this invention is composed of a chemical structure obtained by condensation polymerization of a polycarboxylic acid component and a polyol component, and is composed of one or more components selected from the polycarboxylic acid component and the polyol component.

[0043] The polycarboxylic acid component contained in the polyester polyol of the present invention is preferably an aromatic polycarboxylic acid or an alicyclic polycarboxylic acid, more preferably an aromatic dicarboxylic acid or an alicyclic dicarboxylic acid. Excellent dielectric properties can be achieved by using only aromatic or alicyclic polycarboxylic acid components as constituents.

[0044] There are no particular limitations on the aromatic dicarboxylic acid component; terephthalic acid, isophthalic acid, phthalic acid, 4,4'-dicarboxybiphenyl, sodium isophthalate-5-sulfonate, naphthalic acid, or their esters can be used. Naphthalic acid is preferred because it provides excellent dielectric properties.

[0045] As an alicyclic dicarboxylic acid, there are no particular limitations, and 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hydrogenated naphthalic acid, etc. can be used.

[0046] The polyol contained in the polyester polyol in this invention is not particularly limited, and may include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n- 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, aliphatic polyols such as dimer diols, aliphatic polyols such as 1,4-cyclohexanediethanol, tricyclodecanediethanol, polytetramethylene glycol, polypropylene glycol, etc., may be used, one or more of them. Dimer diols and tricyclodecanediethanol are preferred, as they can achieve excellent dielectric properties.

[0047] Methods for the polycondensation reaction of the polyester polyol of the present invention include, for example: 1) heating a polycarboxylic acid and a polyol in the presence of a known catalyst, followed by a dehydration esterification step to carry out a polyol-condensation reaction; 2) heating an alcohol ester of a polycarboxylic acid and a polyol in the presence of a known catalyst, followed by a transesterification reaction to carry out a polyol-condensation reaction; 3) depolymerization methods, etc. In methods 1) and 2), some or all of the acid component may be replaced with an anhydride.

[0048] When manufacturing the polyester polyol of the present invention, known polymerization catalysts may include, for example, titanium compounds such as tetrabutyl titanate, tetraisopropyl titanate, and titanium acetylacetone oxide; antimony compounds such as antimony trioxide and antimony tributoxy; germanium compounds such as germanium oxide and germanium tetrabutoxy; and acetates of magnesium, iron, zinc, manganese, cobalt, aluminum, etc. One or more of these catalysts may be used.

[0049] The number average molecular weight of the polyester polyol in this invention is preferably 5,000 or more, more preferably 10,000 or more. Furthermore, it is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. When within these ranges, dissolution in a solvent is easy, and the dielectric properties are excellent, therefore it is preferred.

[0050] <Epoxy Resin (C)>

[0051] The adhesive composition of the present invention may contain an epoxy resin (C). The epoxy resin (C) used in the present invention is not particularly limited as long as it has epoxy groups in its molecule; preferably, it is an epoxy resin having two or more epoxy groups in its molecule. Specifically, there are no particular limitations, but at least one type selected from the group consisting of biphenyl-type epoxy resins, naphthalene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, phenolic varnish-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, tetraglycidyl diaminodiphenylmethane, triglycidyl p-aminophenol, tetraglycidyl diaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-phenylenediamine, dimer acid-modified epoxy resins, and epoxy-modified polybutadiene can be used. From the viewpoint of exhibiting excellent adhesion, N,N,N',N'-tetraglycidyl-m-phenylenediamine, biphenyl-type epoxy resin, phenolic varnish-type epoxy resin, dicyclopentadiene-type epoxy resin, dimer acid-modified epoxy resin, or epoxy-modified polybutadiene are preferred. N,N,N',N'-tetraglycidyl-m-phenylenediamine is more preferred.

[0052] In the adhesive composition of the present invention, the content of epoxy resin (C) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of amorphous polyol (B). Sufficient curing effect can be obtained at or above the lower limit value, achieving excellent adhesion and solder heat resistance. Furthermore, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Pot life and low dielectric properties become good at or below the upper limit value. That is, within the above range, an adhesive composition exhibiting excellent low dielectric properties in addition to adhesion, solder heat resistance, and pot life can be obtained.

[0053] 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 is capable of dissolving the amorphous polyol (B) and polycarbodiimide (A). Specifically, for example, the following can be used: aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcohol solvents such as methanol, ethanol, isopropanol, butanol, pentanol, hexanol, propylene glycol, and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanol, hexanone, cyclohexanone, and isophorone. Ketone solvents such as acetophenone, cellosolvers such as methyl and ethyl methyl solvents, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate, and glycol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-isobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-isobutyl ether, triethylene glycol mono-n-butyl ether, and tetraethylene glycol mono-n-butyl ether can be used, either individually or in combination with two or more. Methylcyclohexane and toluene are preferred, especially considering their suitability for the working environment and drying properties.

[0054] The organic solvent is preferably in the range of 100 to 1000 parts by mass relative to 100 parts by mass of amorphous polyol (B). Above the lower limit, the liquid properties and shelf life are improved. Furthermore, below the upper limit, it is advantageous in terms of manufacturing and transportation costs.

[0055] Furthermore, the adhesive composition of the present invention may also contain other components as needed. Specific examples of such components include: flame retardants, tackifiers, fillers, and silane coupling agents.

[0056] Flame retardants

[0057] Flame retardants may also be mixed into the adhesive composition of the present invention as needed. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxides. Among these, phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (e.g., trimethyl phosphate, triphenyl phosphate, tricresyl phosphate, etc.), phosphates (e.g., aluminum phosphonate, etc.), and phosphazenes can be used. These can be used alone or in combination of two or more. When containing a flame retardant, it is preferable to contain 1 to 200 parts by weight of the flame retardant relative to 100 parts by weight of the total amorphous polyol (B) and polycarbodiimide (A) components; more preferably, 5 to 150 parts by weight; and most preferably, 10 to 100 parts by weight. Within the above ranges, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0058] <Tackifier>

[0059] The adhesive composition of the present invention may also incorporate a tackifier as needed. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, copolymer petroleum resins, styrene resins, and hydrogenated petroleum resins, which can be used to improve adhesive strength. These can be used alone or in combination of two or more. When containing a tackifier, the amount is preferably in the range of 1 to 200 parts by weight relative to a total of 100 parts by weight of the amorphous polyol (B) and polycarbodiimide (A), more preferably in the range of 5 to 150 parts by weight, and most preferably in the range of 10 to 100 parts by weight. Within the above ranges, the tackifier effect can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0060] <packing>

[0061] Fillers may also be mixed into the adhesive composition of the present invention as needed. Examples of organic fillers include powders of heat-resistant resins such as polyimide, polyamide-imide, fluororesin, and liquid crystal polyester. Examples of inorganic fillers include, for instance, silica (SiO2), alumina (Al2O3), titanium dioxide (TiO2), tantalum oxide (Ta2O5), zirconium oxide (ZrO2), silicon nitride (Si3N4), boron nitride (BN), calcium carbonate (CaCO3), calcium sulfate (CaSO4), zinc oxide (ZnO), magnesium titanate (MgO·TiO2), barium sulfate (BaSO4), organobentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Silica is preferred from the perspective of ease of dispersion and improved heat resistance.

[0062] As silica, conventional hydrophobic silica and hydrophilic silica are known. Here, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc., is preferred to impart moisture resistance. When incorporating silica, the amount is preferably 0.05 to 30 parts by mass relative to 100 parts by mass of the total amorphous polyol (B) and polycarbodiimide (A). Above the lower limit, heat resistance can be further improved. Furthermore, below the upper limit, poor dispersion of silica and excessively high solution viscosity can be suppressed, resulting in good workability.

[0063] <Silane Coupling Agent>

[0064] The adhesive composition of the present invention may also be mixed with a silane coupling agent as needed. Mixing with a silane coupling agent improves the adhesion to metals and heat resistance, making it highly preferred. There are no particular limitations on the silane coupling agent; examples include silane coupling agents with unsaturated groups, silane coupling agents with epoxy groups, and silane coupling agents with amino groups. From the viewpoint of heat resistance, silane coupling agents with epoxy groups, such as γ-epoxypropoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are further preferred. When a silane coupling agent is incorporated, its amount is preferably 0.5 to 20 parts by mass relative to the total of 100 parts by mass of the amorphous polyol (B) and polycarbodiimide (A). Within this range, the heat resistance and adhesion of the solder can be improved.

[0065] <Layered Body>

[0066] The laminate of the present invention is a laminate obtained by laminating an adhesive composition onto a substrate (a two-layer laminate of substrate / adhesive layer), or a laminate obtained by further bonding substrates (a three-layer laminate of substrate / adhesive layer / substrate). 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 using conventional methods and drying them, and by further laminating other substrates.

[0067] <Substrate>

[0068] As for the substrate in this invention, there is no particular limitation as long as the adhesive composition of this invention can be coated and dried to form an adhesive layer. Examples include resin substrates such as film resins, metal substrates such as metal plates or metal foils, and paper.

[0069] Examples of resin substrates include polyester resins, polyamide resins, polyimide resins, polyamide-imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorinated resins. Film-like resins (hereinafter also referred to as substrate films) are preferred.

[0070] As the metal substrate, any existing known conductive material suitable for use in circuit boards can be used. Examples of raw materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their respective alloys, electroplated products, and metals treated with zinc or chromium compounds. Metal foil is preferred, and copper foil is more preferred. The thickness of the metal foil is not particularly limited, but it is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more. Furthermore, 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; on the other hand, if the thickness is too thick, the processing efficiency during circuit fabrication may decrease. The metal foil is usually provided in roll form. The form of the metal foil used in manufacturing the printed circuit board of the present invention is not particularly limited. When using a strip-shaped metal foil, its length is not particularly limited. Furthermore, its width is not particularly limited, but is preferably around 250 to 500 cm. There is no particular limitation on the surface roughness of the substrate, but it is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less. In addition, practically, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more.

[0071] Examples of paper products include woodfree paper, kraft paper, roll paper, and glassine paper. Additionally, examples of composite raw materials include glass epoxy resin.

[0072] From the perspective of adhesion and durability to the adhesive composition, polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, fluorinated resin, SUS steel plate, copper foil, aluminum foil or glass epoxy resin are preferred as the substrate.

[0073] <Adhesive Sheets>

[0074] In this invention, the adhesive sheet refers to a sheet formed by laminating the aforementioned laminate and the release substrate using an adhesive composition. Specific configurations include laminate / adhesive layer / release substrate, or release substrate / adhesive layer / laminate / adhesive layer / release substrate. By laminating the release substrate, it functions as a protective layer for the substrate. Furthermore, by using the release substrate, it can be demolded from the adhesive sheet, and the adhesive layer can be further transferred to other substrates.

[0075] The adhesive sheet of the present invention can be obtained by applying and drying the adhesive composition of the present invention onto various laminates using conventional methods. Furthermore, after drying, if a release substrate is adhered to the adhesive layer, it can be wound without adhesion to the substrate, resulting in excellent operability. Simultaneously, the adhesive layer is protected, leading to excellent preservation and ease of use. Moreover, if other release substrates are adhered as needed after coating and drying on the release substrate, the adhesive layer itself can be transferred to other substrates.

[0076] <Mold Release Material>

[0077] There are no particular limitations on the release substrate. For example, a release substrate can be made by applying a pore-filling agent coating such as clay, polyethylene, or polypropylene to both sides of paper such as wood pulp paper, kraft paper, roll paper, or glassine paper, and then applying an organosilicon-based, fluorine-based, or alkyd-based release agent on each coating. Additionally, various individual olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as release substrates made by coating the aforementioned release agents onto films such as polyethylene terephthalate. Based on reasons such as the release force between the release substrate and the adhesive layer, and the negative impact of organosilicon on electrical properties, it is preferable to use a release substrate that has undergone pore-filling treatment with polypropylene on both sides of the wood pulp paper before applying an alkyd-based release agent, or to use an alkyd-based release agent on polyethylene terephthalate.

[0078] Furthermore, the method for applying the adhesive composition to the substrate in this invention is not particularly limited, and examples include comma coating machines and reverse roller coating machines. Alternatively, depending on the requirements, the adhesive layer can be applied directly or by transfer onto the rolled copper foil or polyimide film, which is a component material of the printed circuit board. The thickness of the dried adhesive layer can be appropriately varied as needed, and is preferably in the range of 5 to 200 μm. By making the adhesive film thickness 5 μm or more, sufficient adhesive strength can be obtained. In addition, by being 200 μm or less, it is easy to control the amount of residual solvent in the drying process, and bubbling is less likely to occur during the pressing of the printed circuit board. There are no particular limitations on the drying conditions, but the residual solvent rate after drying is preferably 1% by mass or less. By being 1% by mass or less, foaming of residual solvent during the pressing of the printed circuit board can be suppressed, and bubbling is less likely to occur.

[0079] Printed Circuit Boards

[0080] The printed circuit board of this invention comprises a laminate formed of metal foil for forming conductive circuits and a resin substrate as a constituent element, such as a flexible substrate, a rigid substrate, or an encapsulation substrate. The printed circuit board can be manufactured, for example, using a metal-clad laminate via a subtractive process or other existing known methods. Depending on the requirements, so-called flexible printed circuit boards (FPCs), flat cables, tape-and-reel (TAB) circuit boards, etc., which partially or completely cover the conductive circuits formed by metal foil using a cover film, screen printing ink, etc., are collectively referred to as printed circuit boards.

[0081] The printed circuit board of the present invention can adopt any layered structure as a printed circuit board. For example, it can be a printed circuit board composed of four layers: a substrate film layer, a metal foil layer, an adhesive layer, and a cover film layer. Alternatively, it can be a printed circuit board composed of five layers: a substrate film layer, an adhesive layer, a metal foil layer, an adhesive layer, and a cover film layer.

[0082] Furthermore, depending on the requirements, it can be a structure formed by stacking two or three or more of the above-mentioned printed circuit boards.

[0083] The adhesive composition of the present invention is suitable for use in various adhesive layers of printed circuit boards. In particular, when used as an adhesive, the adhesive composition of the present invention exhibits high adhesion not only to existing polyimide, polyester film, and copper foil constituting printed circuit boards, but also to low-polarity resin substrates such as LCP, providing reflow solderability and excellent low dielectric properties of the adhesive layer itself. Therefore, it is suitable as an adhesive composition for use in cover films, laminates, resin-coated copper foils, and adhesive sheets.

[0084] In the printed circuit board of the present invention, any resin film that has been conventionally used as a substrate for printed circuit boards can be used as the substrate film. Examples of resins used as the substrate film include polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorinated resin. In particular, it also exhibits excellent adhesion to low-polarity substrates such as liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resin.

[0085] <Covering film>

[0086] As the cover film, any existing known insulating film can be used as the insulating film for printed circuit boards. For example, films made from various polymers such as polyimide, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid fiber, polycarbonate, polyarylate, polyamide-imide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resins can be used. Polyimide films or liquid crystal polymer films are more preferred.

[0087] In addition to using the materials of the aforementioned layers, the printed circuit board of the present invention can be manufactured using any of the existing known processes.

[0088] In a preferred embodiment, a semi-finished product with an adhesive layer laminated on a cover film layer is manufactured (hereinafter referred to as "cover film-side semi-finished product"). On the other hand, the following semi-finished products are manufactured: a semi-finished product in which a metal foil layer is laminated on a substrate film layer and a desired circuit pattern is formed (hereinafter referred to as "substrate film-side 2-layer semi-finished product"), or a semi-finished product in which an adhesive layer is laminated on a substrate film layer, and then a metal foil layer is laminated on top of it and a desired circuit pattern is formed (hereinafter referred to as "substrate film-side 3-layer semi-finished product") (hereinafter, the substrate film-side 2-layer semi-finished product and the substrate film-side 3-layer semi-finished product are collectively referred to as "substrate film-side semi-finished product"). By bonding the cover film-side semi-finished product and the substrate film-side semi-finished product obtained therefrom, a 4-layer or 5-layer printed circuit board can be obtained.

[0089] For the substrate film side semi-finished product, for example, it can be obtained by a manufacturing method including the following steps: (A) coating the above-mentioned metal foil with a resin solution constituting the substrate film and performing initial drying of the coating film; (B) performing heat treatment and drying on the laminate of the metal foil and the initial dried coating film obtained in (A) (hereinafter referred to as "heat treatment and desolventizing process").

[0090] The circuitry in the metal foil layer can be formed using existing, known methods. Both additive and subtractive methods can be employed. Subtractive methods are preferred.

[0091] The resulting substrate film-side semi-finished product can be directly used for bonding with the cover film-side semi-finished product. Alternatively, it can be used for bonding with the cover film-side semi-finished product after bonding and storing the release film.

[0092] For the cover film-side semi-finished product, it can be manufactured, for example, by applying an adhesive to the cover film. If necessary, a cross-linking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is allowed to partially cure.

[0093] The resulting cover film-side semi-finished product can be directly used for bonding with the substrate film-side semi-finished product, or it can be used for bonding with the substrate film-side semi-finished product after being bonded and stored with the release film.

[0094] Printed circuit boards are manufactured by laminating the substrate film-side semi-finished product and the cover film-side semi-finished product, respectively, in roll form, for example. Any lamination method can be used, such as a press or rollers. Alternatively, the two parts can be laminated while being heated, using a heated press or heated roller device.

[0095] For semi-finished products on the reinforcing material side, for example, when the reinforcing material is a flexible, rollable material such as a polyimide film, it is suitable to manufacture it by coating the reinforcing material with an adhesive. Furthermore, when the reinforcing material is a rigid, non-rollable reinforcing plate such as a metal sheet like SUS or aluminum, or a plate made by curing glass fiber with epoxy resin, it is suitable to manufacture it by transferring an adhesive pre-coated to a release substrate. Additionally, if necessary, the coated adhesive can undergo a cross-linking reaction. In a preferred embodiment, the adhesive layer is semi-cured.

[0096] The resulting reinforcing material side semi-finished product can be directly used for bonding to the back of the printed circuit board, or it can be used for bonding to the substrate film side semi-finished product after being bonded and stored with the release film.

[0097] The substrate film-side semi-finished product, the cover film-side semi-finished product, and the reinforcing material-side semi-finished product are all laminates for printed circuit boards in this invention.

[0098] Example

[0099] The present invention will be specifically described below with reference to specific embodiments. It should be noted that in the present embodiments and comparative examples, the term "parts" refers to parts by mass.

[0100] <Methods for evaluating physical properties>

[0101] (Composition determination of amorphous polyols)

[0102] Using 400MHz 1 1H nuclear magnetic resonance (NMR) spectroscopy is used to quantify the molar ratios of the structural units that make up amorphous polyols. Deuterated chloroform is used as the solvent.

[0103] (Determination of glass transition temperature)

[0104] The determination was performed using a differential scanning calorimeter (SII, DSC-200). 5 mg of the sample (amorphous polyol) was placed in an aluminum-capped container and sealed, then cooled to -50°C using liquid nitrogen. The temperature was then increased to 150°C at a rate of 20°C / min. The temperature at which the extended baseline before the endothermic peak (below the glass transition temperature) intersects the tangent to the endothermic peak (the tangent with the steepest slope between the rising portion of the peak and the apex) was taken as the glass transition temperature (Tg, in °C).

[0105] (Determination of amorphousness)

[0106] In the endothermic curves obtained under the same conditions as the glass transition temperature determination described above, the endothermic peaks that do not appear after the glass transition temperature is observed are used to determine amorphous properties.

[0107] (Determination of acid value)

[0108] Dissolve 0.2 g of the amorphous polyol sample in 40 ml of chloroform, and titrate with 0.01 N potassium hydroxide ethanol solution to determine the concentration per 10 ml of chloroform. 6 g of carboxyl resin equivalent (eq / 10) 6 g). Phenolphthalein is used as an indicator.

[0109] Relative permittivity (ε) c and dielectric loss tangent (tanδ)

[0110] An amorphous polyol dissolved in a solvent was coated onto a 100 μm thick Teflon sheet until the dried thickness reached 25 μm. The sheet was then dried at 130°C for 3 minutes. The Teflon sheet was then peeled off to obtain the test adhesive resin sheet. The obtained test adhesive resin sheet was then cut into strips of 8 cm × 3 mm to obtain the test samples. The relative permittivity (ε...) c The dielectric loss tangent (tanδ) was measured using Network Analyzers (manufactured by Anritsu) with the resonant cavity perturbation method at a temperature of 23°C and a frequency of 10 GHz.

[0111] The following are examples of the synthesis of amorphous polyols used in this invention.

[0112] Synthesis example of amorphous polyol (b1)

[0113] 275 parts of dimethyl naphthalenecarboxylate, 5 parts of trimellitic anhydride, 264 parts of dimer diol, 125 parts of tricyclodecanediethanol, 76 parts of ethylene glycol, and tetrabutyl titanate as a catalyst (0.03 mol% relative to the total acid content) were added to a reaction vessel equipped with a stirrer, condenser, and thermometer. The mixture was heated from 160°C to 220°C over 4 hours, undergoing a dehydration process while simultaneously carrying out an esterification reaction. Next, for the polycondensation reaction, the pressure within the system was reduced to 5 mmHg over 20 minutes, and then the temperature was further increased to 250°C. Then, the pressure was reduced to below 0.3 mmHg, and a polycondensation reaction was carried out for 60 minutes before the mixture was removed. The obtained amorphous polyol (a1), according to NMR compositional analysis, is a polyester polyol with a molar ratio of naphthalenedicarboxylic acid / triphenyl phthalic anhydride / dimer diol / tricyclodecanediethanol / ethylene glycol = 97 / 3 / 40 / 55 / 5. Furthermore, it has a glass transition temperature of 17°C and an acid value of 3 eq / 10. 6 g. The dielectric loss tangent is 0.0035 (10 GHz), and no crystallization melting peak was observed, indicating amorphous properties.

[0114] Synthesis example of amorphous polyol (b2)

[0115] Following the polycondensation polymerization of amorphous polyol (b1), 2 parts of trimellitic anhydride were added to synthesize amorphous polyol (b2) with carboxyl groups introduced at the end of the polyester polyol. Its glass transition temperature was 25℃ and its acid value was 40 eq / 10. 6 g. The dielectric loss tangent is 0.0030 (10 GHz), and no crystallization melting peak was observed, indicating amorphous properties.

[0116] Hereinafter, examples of adhesive compositions as embodiments of the present invention and examples of manufacturing adhesive compositions as comparative examples will be presented.

[0117] The following products were used as amorphous polyols (b3).

[0118] Amorphous polyol (b3): ​​SA-90 (a polyether polyol manufactured by SABIC) has a dielectric loss tangent of 0.0066 (10 GHz) and an acid value of 0 eq / 10. 6 g is amorphous.

[0119] The following products were used as polycarbodiimide (A).

[0120] (a1): V-03 (polycarbodiimide manufactured by Nisshin Textile Chemicals Co., Ltd., with 0% by weight content of isocyanate groups)

[0121] (a2): V-05 (polycarbodiimide manufactured by Nisshin Textile Chemicals Co., Ltd., with an isocyanate group content of 8.2% by weight)

[0122] The following products were used as epoxy resin (C).

[0123] (c1): B-Tough C2x (dimer acid modified epoxy resin manufactured by Croda)

[0124] (c2): tetrad X (glycidylamine type epoxy resin manufactured by Mitsubishi Gas Chemical Co., Ltd.)

[0125] (Example 1)

[0126] The amorphous polyol (b1) obtained in the above synthesis example was dissolved in toluene to prepare a toluene varnish with a solid content concentration of 40% by mass. Polycarbodiimide (a1) was mixed into this toluene varnish in a ratio of 3 parts per 100 parts of the amorphous polyol (b1) to obtain an adhesive composition (S1).

[0127] For the obtained adhesive composition (S1), various evaluations were performed on relative permittivity, dielectric loss tangent, peel strength, solder heat resistance, and pot life. The results are recorded in Table 1.

[0128] (Examples 2-14, Comparative Examples 1-8)

[0129] Except for changing the type of amorphous polyol (B) and the types and mixing amounts of polycarbodiimide (A) and epoxy resin (C) as shown in Table 1, adhesive compositions (S2) to (S22) were prepared in the same manner as in Example 1, and various evaluations were performed. The results are recorded in Table 1.

[0130] <Evaluation of Adhesive Compositions>

[0131] (relative permittivity (ε) c and dielectric loss tangent (tanδ)

[0132] The adhesive composition was applied to a 100 μm thick Teflon sheet until it dried to a thickness of 25 μm, and then dried at 130°C for 3 minutes. After curing at 180°C for 5 hours, the Teflon sheet was peeled off to obtain the test adhesive resin sheet. The obtained test adhesive resin sheet was then cut into strips of 8 cm × 3 mm to obtain the test samples. The relative permittivity (ε...) c The dielectric loss tangent (tanδ) was measured using Network Analyzers (manufactured by Anritsu) with the resonant cavity perturbation method at a temperature of 23°C and a frequency of 10 GHz.

[0133] <Evaluation Criteria for Relative Permittivity>

[0134] ○: 3.0 or less

[0135] ×: Exceeds 3.0

[0136] Evaluation Criteria for Dielectric Loss Tangent

[0137] ○: Below 0.004

[0138] △: 0.004 or higher, 0.006 or lower

[0139] ×: Exceeds 0.006

[0140] (Peel strength (adhesion))

[0141] The adhesive composition was coated onto a 12.5 μm thick polyimide film (manufactured by Kaneka Corporation, Apical (registered trademark)) until its dried thickness reached 25 μm, and then dried at 130°C for 3 minutes. The resulting adhesive film (Grade B) was then laminated onto an 18 μm thick rolled copper foil (manufactured by Nippon Steel Chemical & Materials Co., Ltd., Espanex). The bonding was achieved by applying pressure at 170°C and 2 MPa for 280 seconds with the glossy surface of the rolled copper foil in contact with the adhesive layer. The film was then heat-treated at 180°C for 5 hours and cured to obtain a sample for peel strength evaluation. For peel strength, a 90° peel test was performed at 25°C with a tensile speed of 50 mm / min, and the peel strength was measured under these conditions. This test result represents the adhesive strength at room temperature.

[0142] <Evaluation Criteria>

[0143] ◎: 1.0 N / mm or higher

[0144] ○: 0.7 N / mm or higher and less than 1.0 N / mm

[0145] △: Above 0.5 N / mm and less than 0.7 N / mm

[0146] ×: Less than 0.5 N / mm

[0147] (Solder heat resistance)

[0148] Prepare samples using the same method described above. Immerse a 2.0cm × 2.0cm sample piece in a molten solder bath at 288°C and check for any changes in appearance, such as expansion.

[0149] <Evaluation Criteria>

[0150] ◎: No expansion after 60 seconds

[0151] ○: Expansion occurs after 30 seconds to less than 60 seconds.

[0152] △: Expansion occurs after 10 seconds to less than 30 seconds.

[0153] ×: Expansion occurs within 10 seconds.

[0154] (Applicability Period)

[0155] The adhesive composition in solution was left to stand at 25°C, and the number of days from solution to gelation was determined.

[0156] <Evaluation Criteria>

[0157] ○: If the mixture has not gelled after 7 days or more.

[0158] △: Gelation occurs after 1 to 7 days following mixing.

[0159] ×: Gelation occurs less than 1 day after mixing.

[0160]

[0161] As can be clearly seen from Table 1, Examples 1-14 exhibit excellent dielectric properties, peel strength, solder heat resistance, and pot life. On the other hand, in Comparative Example 1, the carboxyl groups of the amorphous polyol (b2) reacted rapidly with the carbodiimide bonds of the polycarbodiimide (a1) after mixing, resulting in gelation. In Comparative Examples 2 and 3, the carboxyl groups reacted with the epoxy groups, resulting in insufficient pot life. Although Comparative Examples 4 and 5 contained an acid value of 10 eq / 10... 6 Amorphous polyols (b1) or amorphous polyols (b3) with an acid value below g, but containing acid values ​​exceeding 10 eq / 10 6 The amorphous polyol (b2) in g causes the carboxyl groups to react rapidly with the carbodiimide bonds of polycarbodiimide (a1) upon mixing, resulting in gelation. Comparative Examples 6 and 7 contain isocyanate groups in polycarbodiimide (a2), leading to insufficient pot life and inadequate solder heat resistance. In the comparative examples, the absence of polycarbodiimide results in insufficient curing, leading to poor peel strength and solder heat resistance.

[0162] Industrial availability

[0163] The adhesive composition of the present invention has excellent pot life, peel strength and solder heat resistance, and further has a low relative dielectric constant and dielectric loss tangent, making it suitable as an adhesive for circuit boards (flexible substrates, rigid substrates, and encapsulation substrates) applicable to high-frequency regions.

Claims

1. An adhesive composition comprising polycarbodiimide A and amorphous polyol B, and satisfying (i), (ii), (iii) and (iv) below. (i) The composition does not contain compounds having isocyanate groups. (ii) The composition does not contain any acid with an acid value exceeding 10 eq / 10. 6 g of compounds, (iii) The content of polycarbodiimide A is 1 to 20 parts by weight relative to 100 parts by weight of amorphous polyol B. (iv) Amorphous polyol B is at least one selected from the group consisting of polyester polyols and polyether polyols.

2. The adhesive composition according to claim 1, wherein, The dielectric loss tangent, tanδ, of amorphous polyol B at 10 GHz is below 0.

006.

3. The adhesive composition according to claim 1 or 2, wherein, Amorphous polyol B contains polyester polyol.

4. The adhesive composition according to any one of claims 1 or 2, wherein, It contains 0.1 to 10 parts by weight of epoxy resin C relative to 100 parts by weight of amorphous polyol B.

5. An adhesive sheet comprising an adhesive layer formed of the adhesive composition according to any one of claims 1 to 4.

6. A laminate comprising an adhesive layer formed of the adhesive composition according to any one of claims 1 to 4.

7. A printed circuit board comprising the laminate of claim 6 as a constituent element.

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