Maleimide resin, resin composition, cured product, sheet, laminate, and printed wiring board

Abstract

A maleimide resin according to the present disclosure is obtained by reacting a tetracarboxylic dianhydride (a1), an amine (a2), and maleic anhydride (a3), wherein the tetracarboxylic dianhydride (a1) includes a tetracarboxylic dianhydride having a fluorene skeleton and the amine (a2) includes a dimer diamine and an amine having a biphenyl skeleton.

Description

Maleimide resin, resin composition, cured product, sheet, laminate, and printed wiring board

[0001] The present disclosure relates to a maleimide resin, a resin composition, a cured product, a sheet, a laminate, and a printed wiring board.

[0002] Printed wiring boards and multilayer wiring boards using them are used in products such as mobile communication devices such as mobile phones and smartphones, their base station equipment, network-related electronic devices such as servers and routers, and large computers.

[0003] In recent years, these products have used high-frequency electrical signals to transmit and process large amounts of information at high speed. However, high-frequency signals are highly susceptible to attenuation, and therefore, in order to reduce transmission loss, insulating materials with excellent dielectric properties are required as insulating materials used in the above-mentioned printed wiring boards, multilayer wiring boards, and the like.

[0004] Epoxy resin compositions disclosed in Patent Documents 1 to 3 are known as the insulating material. Patent Document 1 discloses that an epoxy resin composition containing an epoxy resin, an active ester compound, and a triazine-containing cresol novolac resin is effective in reducing dielectric loss tangent. Patent Documents 2 and 3 disclose that a resin composition containing an epoxy resin and an active ester compound as essential components can form a cured product with a low dielectric loss tangent and is useful as an insulating material. However, it has been found that these epoxy resin compositions are unsatisfactory for high-frequency band applications.

[0005] On the other hand, Patent Document 4 reports that a resin film made of a resin composition containing a bismaleimide resin having a long-chain alkyl group as a non-epoxy material and a curing agent has excellent dielectric properties (low relative dielectric constant and low dielectric loss tangent). However, bismaleimide resins made only of long-chain alkyldiamines have problems such as low Tg and low elastic modulus.

[0006] JP 2011-132507 A JP 2015-101626 A JP 2017-210527 A WO 2016 / 114287

[0007] An object of the present disclosure is to provide a novel maleimide resin that can form a cured product having a high elastic modulus and a high Tg while sufficiently maintaining a low dielectric constant and a low dielectric loss tangent, and excellent toughness. Another object of the present disclosure is to provide a resin composition, a cured product, a sheet, a laminate, and a printed wiring board using the maleimide resin.

[0008] The present disclosure provides the following maleimide resins, resin compositions, cured products, sheets, laminates, and printed wiring boards: [1] A maleimide resin obtained by reacting a tetracarboxylic dianhydride (a1), an amine (a2), and maleic anhydride (a3), wherein the tetracarboxylic dianhydride (a1) comprises a tetracarboxylic dianhydride having a fluorene skeleton, and the amine (a2) comprises a dimer diamine and an amine having a biphenyl skeleton. [2] The maleimide resin according to [1] above, wherein the tetracarboxylic dianhydride having a fluorene skeleton comprises at least one of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride. [3] The maleimide resin according to [1] or [2] above, wherein the amine having a biphenyl skeleton comprises at least one of 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-2,2'-diethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-diethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetraethylbiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, and 4,4'-diamino-3,3'-dimethoxybiphenyl. [4] The maleimide resin according to any one of [1] to [3] above, wherein the dimer diamine contains at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2): [In formulas (1) and (2), m, n, p, and q each represent an integer of 1 or greater selected so that m+n=6 to 17 and p+q=8 to 19, and the bond indicated by a dashed line represents a carbon-carbon single bond or a carbon-carbon double bond. However, when the bond indicated by a dashed line is a carbon-carbon double bond, formulas (1) and (2) have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is subtracted by one from the number indicated in formulas (1) and (2)].] [5] The maleimide resin according to any one of [1] to [4] above, having a weight-average molecular weight of 3,000 to 40,000. [6] A resin composition comprising the maleimide resin according to any one of [1] to [5] above. [7] The resin composition according to [6] above, further comprising a polymerization initiator. [8] A cured product of the resin composition according to [6] or [7] above. [9] A sheet comprising the resin composition according to [6] or [7] above and a substrate.

[10] The sheet according to [9] above, wherein the substrate is an organic substrate.

[11] The sheet according to [9] above, wherein the substrate is an inorganic substrate.

[12] A laminate obtained by thermocompression bonding a substrate to the adhesive surface of the sheet according to any one of [9] to

[11] above.

[13] A printed wiring board obtained by using the sheet according to any one of [9] to

[11] above.

[14] A printed wiring board obtained by using the laminate according to

[12] above.

[0009] According to the present disclosure, it is possible to provide a maleimide resin that can form a cured product having a high elastic modulus and a high Tg while sufficiently maintaining a low dielectric constant and a low dielectric loss tangent, and that has excellent toughness. The present disclosure also provides a resin composition, a cured product, a sheet, a laminate, and a printed wiring board using the maleimide resin.

[0010] The maleimide resin of the present disclosure and a resin composition (adhesive composition) using the same can reduce both the dielectric constant and the dielectric loss tangent (hereinafter, both may be collectively referred to as "dielectric properties"), and are excellent in low dielectric properties, particularly in the high frequency band. Furthermore, the cured product (adhesive layer) obtained from the resin composition not only has a high elastic modulus and Tg, but also excellent toughness. Therefore, the resin composition is useful not only as an adhesive used in the production of printed circuit boards (build-up boards, flexible printed wiring boards, etc.) and copper-clad boards for printed wiring boards, but also as an insulating film such as a rewiring layer, a semiconductor interlayer material, a coating agent, a resist ink, a conductive paste, etc.

[0011] Preferred embodiments of the present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiments and can be implemented in various modifications within the scope of the present disclosure.

[0012] In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, "solid content" refers to the non-volatile content of the resin composition excluding volatile substances (water, solvent, etc.), and also includes components that are liquid, syrup-like, or waxy at room temperature (around 25°C).

[0013] [Maleimide Resin and Resin Composition] The maleimide resin of this embodiment is a maleimide resin obtained by reacting a tetracarboxylic dianhydride (a1) (hereinafter also referred to as "component (a1)"), an amine (a2) (hereinafter also referred to as "component (a2)"), and maleic anhydride (a3) ​​(hereinafter also referred to as "component (a3)"). Here, the component (a1) includes a tetracarboxylic dianhydride having a fluorene skeleton, and the component (a2) includes a dimer diamine and an amine having a biphenyl skeleton. The phenyl skeleton may have a lower alkyl (e.g., methyl, ethyl, propyl, etc.) as a substituent.

[0014] The resin composition of this embodiment contains the maleimide resin (A) (hereinafter also referred to as "component (A)"). The resin composition of this embodiment may further contain a polymerization initiator (B) (hereinafter also referred to as "component (B)"). The resin composition of this embodiment may further contain an organic solvent (C) (hereinafter also referred to as "component (C)").

[0015] (Component (A): Maleimide Resin) Component (A) can be obtained by reacting components (a1), (a2), and (a3). Component (A) may have multiple maleimide groups in the molecule. Component (A) may be a bismaleimide resin.

[0016] The tetracarboxylic dianhydride of the component (a1) includes a tetracarboxylic dianhydride having a fluorene skeleton. From the viewpoints of low dielectric properties, a high Tg, or a low coefficient of linear expansion (CTE), the component (a1) preferably contains, as the tetracarboxylic dianhydride having a fluorene skeleton, at least one of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride.

[0017] The component (a1) may further contain a tetracarboxylic acid dianhydride that does not have a fluorene skeleton. The tetracarboxylic acid dianhydride that does not have a fluorene skeleton may have a biphenyl skeleton or an aromatic ring other than biphenyl.

[0018] Examples of tetracarboxylic dianhydrides that do not have a fluorene skeleton include pyromellitic anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 1,3,3a,4,5,9b-hexahydro-5(tetrahydro-2,5-dioxo-3-furanyl)naphtho[1,2-C]furan-1,3-dione, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4 ,4'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2 , 3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)1,4-phenylene, 4,4'-(ethyn-1,2-diyl)diphthalic anhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-di Examples of suitable dianhydrides include carboxylic acid anhydrides, dicyclohexyl-3,4,3',4'-tetracarboxylic acid dianhydride, 3,4'-oxydiphthalic anhydride, 3,4'-biphthalic anhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid dianhydride, and 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid-5,5',6,6'-dianhydride. These may be used alone or in combination of two or more.

[0019] The component (a2) contains a dimer diamine (first amine) and an amine having a biphenyl skeleton (second amine).

[0020] Dimer diamine is a compound derived from dimer acid, which is a dimer of unsaturated fatty acids such as oleic acid, as described in, for example, JP-A-9-12712. By using dimer diamine as component (a2), the dielectric properties of the cured product can be reduced. In this embodiment, any known dimer diamine can be used without particular limitations. The dimer diamine preferably includes, for example, at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2):

[0021]

[0022] In formulas (1) and (2), m, n, p, and q each represent an integer of 1 or greater selected so that m+n=6 to 17 and p+q=8 to 19, and the bond shown by a dashed line represents a carbon-carbon single bond or a carbon-carbon double bond. However, when the bond shown by a dashed line is a carbon-carbon double bond, formulas (1) and (2) have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is reduced by one from the number shown in formulas (1) and (2).

[0023] The dimer diamine may be one represented by the above general formula (2), particularly a compound represented by the following formula (3), from the viewpoints of solubility in organic solvents, heat resistance, heat-resistant adhesion, low viscosity, etc.

[0024] Commercially available dimer diamines include, for example, PRIAMINE 1075 and PRIAMINE 1074 (both manufactured by Croda Japan), etc. These may be used alone or in combination of two or more.

[0025] Examples of amines having a biphenyl skeleton include 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-2,2'-diethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-diethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetraethylbiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, and 4,4'-diamino-3,3'-dimethoxybiphenyl. The amine having a biphenyl skeleton may be a diamine having a biphenyl skeleton.

[0026] The component (a2) may further include a third amine other than the dimer diamine and the amine having a biphenyl skeleton. The third amine may be a diamine or triamine, or may be a diamine. By using an alicyclic diamine as the third amine, the dielectric constant can be further reduced. By using an aromatic diamine as the third amine, the elastic modulus, Tg, and CTE of the cured product can be improved.

[0027] When the third amine is a diamine, examples of the diamine include 1,3-diaminopropane, norbornanediamine, 4,4-methylenedianiline, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis[3-fluoro-4-aminophenyl]fluorene, 9,9-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, )phenyl]fluorene, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane, 4,4'-(hexafluoroisopropylidene)dianiline, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.02,6]decane, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, isophoronediamine, 4,4'-methylenebis(cyclohexylamine), 4,4'-methyl ethylenebis(2-methylcyclohexylamine), 1,1-bis(4-aminophenyl)cyclohexane, 2,7-diaminofluorene, 4,4'-ethylenedianiline, 4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(2-ethyl-6-methylaniline), 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]ether Examples thereof include bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, (4,4'-diamino)diphenyl ether, (3,3'-diamino)diphenyl ether, paraphenylenediamine, orthophenylenediamine, metaphenylenediamine, bis[4-(3-aminophenoxy)phenyl]sulfone, and bis[4-(4-aminophenoxy)phenyl]sulfone. These may be used alone or in combination of two or more.

[0028] When the third amine is a triamine, examples of the triamine include tris(2-aminomethyl)amine, tris(2-aminoethyl)amine, tris(2-aminopropyl)amine, 2-(aminomethyl)-2-methyl-1,3-propanediamine, trimer triamine, 3,4,4'-triaminodiphenyl ether, 1,2,4-triaminobenzene, 1,3,5-triaminobenzene, 1,2,3-triaminobenzene, 1,3,5-triazine-2,4,6-triamine, 2,4,6-triaminopyrimidine, 1,3,5-tris(4-aminophenyl)benzene, and 1,3,5-tris(4-aminophenoxy)benzene. These may be used alone or in combination of two or more. Of these, aliphatic triamines are preferred from the viewpoint of the solubility of the synthesized component (A) in organic solvents, and tris(2-aminomethyl)amine and tris(2-aminoethyl)amine, which have a small number of carbon atoms, are more preferred from the viewpoint of achieving a high Tg.

[0029] The third amine may include one or both of the above-mentioned diamines and triamines, or may include an amine other than the diamines and triamines.

[0030] In component (a2), the molar ratio of the second amine to the total amount of amines (moles of second amine / (moles of dimer diamine+moles of second amine)) may be 70 mol% or less, or may be 50 mol% or less. When this ratio is 70 mol% or less, the dielectric properties of the cured product can be further reduced.

[0031] By using dimer diamine as the diamine, the dielectric properties of the cured product can be reduced. On the other hand, when dimer diamine is used alone as the amine, the elastic modulus and Tg of the cured product decrease, and the CTE increases. In contrast, by using an amine having a biphenyl skeleton in combination with dimer diamine, the elastic modulus, Tg, CTE, and toughness of the cured product can be improved while maintaining the dielectric properties.

[0032] Component (A) can be produced by various known methods. For example, components (a1) and (a2) are first subjected to a polyaddition reaction at a temperature of about 60 to 120°C, preferably 70 to 90°C, for typically about 0.1 to 2 hours, preferably 0.1 to 1.0 hour. The resulting polyaddition product is then subjected to an imidization reaction, i.e., a dehydration ring-closing reaction, at a temperature of about 80 to 250°C, preferably 100 to 200°C, for about 0.5 to 30 hours, preferably 0.5 to 10 hours. The product of the dehydration ring-closing reaction is then subjected to a maleimidization reaction, i.e., a dehydration ring-closing reaction, with component (a3) ​​at a temperature of about 60 to 250°C, preferably 80 to 200°C, for about 0.5 to 30 hours, preferably 0.5 to 10 hours, to obtain the desired component (A).

[0033] In the imidization reaction or maleimidization reaction, various known reaction catalysts, dehydrating agents, and organic solvents described below can be used. Examples of reaction catalysts include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline, and organic acids such as methanesulfonic acid and paratoluenesulfonic acid monohydrate. These can be used alone or in combination of two or more. Examples of dehydrating agents include aliphatic acid anhydrides such as acetic anhydride, and aromatic acid anhydrides such as benzoic anhydride. These can be used alone or in combination of two or more.

[0034] Component (A) can be purified by various known methods to increase its purity. For example, first, component (A) dissolved in an organic solvent and pure water are placed in a separatory funnel. The separatory funnel is then shaken and allowed to stand. Subsequently, the aqueous layer and the organic layer are separated, and only the organic layer is recovered, thereby purifying component (A).

[0035] An example of a possible structure of the component (A) produced by the above method is shown in the following general formula (4): General formula (4) is intended for the case where the component (a2) is a diamine.

[0036] In general formula (4), X's each independently represent a tetravalent organic group, Y's each independently represent a divalent organic group, and a represents an integer of 1 or more. However, at least one of the multiple Y's represents a divalent organic group derived from dimer diamine, and at least one of the multiple Y's represents a divalent organic group derived from the above-mentioned amine having a biphenyl skeleton. Furthermore, at least one of the multiple X's represents a tetravalent organic group having a fluorene skeleton.

[0037] The molecular weight of the (A) component can be controlled by the number of moles of the (a1) component and the (a2) component, and the smaller the number of moles of the (a1) component is relative to the number of moles of the (a2) component, the smaller the molecular weight can be. For the purpose of easily achieving the effects of the present disclosure, the number of moles of the (a1) component per mole of the (a2) component, i.e., [number of moles of the (a1) component] / [number of moles of the (a2) component], is usually about 0.30 to 0.98, preferably 0.40 to 0.96, more preferably 0.50 to 0.94, and even more preferably 0.60 to 0.90.

[0038] From the viewpoint of solubility in solvents and heat resistance, the molecular weight of component (A) is preferably a weight average molecular weight (Mw) of 3,000 to 40,000, and may be 4,000 to 30,000, 5,000 to 28,000, 7,000 to 27,000, or 8,000 to 26,500. A weight average molecular weight of 40,000 or less results in good solubility in organic solvents, while a weight average molecular weight of 3,000 or more tends to provide a sufficient effect of improving heat resistance. Mw can be measured by gel permeation chromatography (GPC) and converted using a calibration curve of standard polystyrene.

[0039] The component (A) can be used alone or in combination of two or more.

[0040] (Component (B): Polymerization Initiator) As the component (B), various known polymerization initiators that can be used in resin compositions can be used without any particular limitation. Specific examples of the component (B) include organic peroxides, imidazole compounds, phosphine compounds, and phosphonium salt compounds. These can be used alone or in combination of two or more. Among these, organic peroxides and imidazole compounds are particularly preferred because they have excellent functionality as polymerization initiators and are also excellent in terms of low dielectric properties.

[0041] Examples of organic peroxides include methyl ethyl ketone peroxide, methylcyclohexanone peroxide, methylacetoacetate peroxide, acetylacetone peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(4,4-di-t-butylperoxy)cyclohexane, t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)cyclododecane, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, t-butyl hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-hexyl hydroperoxide, dicumyl peroxide, 2,5-dimethyl -2,5-bis(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy)diisopropylbenzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, cinnamic acid peroxide, m-toluoyl peroxide, benzoyl peroxide, diisopropyl Peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumyl peroxyneodecanoate, 1,1,3,3,-Tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy Examples of suitable peroxybenzoates include tert-butylperoxymethylperoxymethyl esters, tert-butyl ... Among these organic peroxides, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy)diisopropylbenzene, etc. are preferred.

[0042] Examples of the imidazole compound include 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-vinyl-2-methylimidazole, 1-propyl-2-methylimidazole, 2-isopropylimidazole, 1-cyanomethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-phenylimidazole. Among these, 1-cyanoethyl-2-phenylimidazole and 2-ethyl-4-methylimidazole are preferred because they have high solubility in the resin composition of this embodiment. These can be used alone or in combination of two or more.

[0043] Examples of phosphine compounds include primary phosphines, secondary phosphines, and tertiary phosphines. Primary phosphines include alkyl phosphines such as ethylphosphine and propylphosphine, and phenylphosphine. Secondary phosphines include dialkyl phosphines such as dimethylphosphine and diethylphosphine, and secondary phosphines such as diphenylphosphine, methylphenylphosphine, and ethylphenylphosphine. Tertiary phosphines include trialkyl phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, and trioctylphosphine, tricyclohexylphosphine, triphenylphosphine, alkyldiphenylphosphines, dialkylphenylphosphines, tribenzylphosphine, tritolylphosphine, tri-p-styrylphosphine, tris(2,6-dimethoxyphenyl)phosphine, tri-4-methylphenylphosphine, tri-4-methoxyphenylphosphine, and tri-2-cyanoethylphosphine. Among these, tertiary phosphines are preferably used. These may be used alone or in combination of two or more.

[0044] Examples of the phosphonium salt compound include tetraphenylphosphonium salts, alkyltriphenylphosphonium salts, compounds having tetraalkylphosphonium, etc., and specific examples include tetraphenylphosphonium thiocyanate, tetraphenylphosphonium tetra-p-methylphenylborate, butyltriphenylphosphonium thiocyanate, tetraphenylphosphonium phthalic acid, tetrabutylphosphonium 1,2-cyclohexyldicarboxylic acid, tetrabutylphosphonium 1,2-cyclohexyldicarboxylic acid, tetrabutylphosphonium lauric acid, etc. These may be used alone or in combination of two or more.

[0045] The content of the (B) component is not particularly limited, but may be 0.1 to 10.0 parts by mass, 0.2 to 5.0 parts by mass, 0.3 to 3.0 parts by mass, 0.3 to 2.0 parts by mass, or 0.3 to 1.0 parts by mass per 100 parts by mass of the (A) component.

[0046] (Component (C): Organic Solvent) The component (C) is not particularly limited as long as it dissolves the component (A). Examples of the component (C) include aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, pseudocumene, and anisole; alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclopentanone, cyclohexanone, isophorone, and acetophenone; cellosolves such as methyl cellosolve and ethyl cellosolve; methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate, γ-butyl ether, and the like. Examples of suitable solvents include ester solvents such as tyrolactone; glycol ether solvents such as 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, and tetraethylene glycol mono-n-butyl ether; and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. These solvents can be used alone or in combination of two or more. Among these, aromatic hydrocarbons such as toluene and mesitylene, which have high solubility for component (A), are preferably used.

[0047] The amount of component (C) used is not particularly limited, but it is usually sufficient to use it in a range such that the nonvolatile content of the resin composition of this embodiment is about 20 to 65 mass %.

[0048] The resin composition of this embodiment is prepared according to a commonly employed method. Examples of the preparation method include melt mixing, powder mixing, and solution mixing. In addition, in this case, other components than the essential components of this embodiment, such as a mold release agent, a flame retardant, an ion trapping agent, an antioxidant, an adhesion promoter, a stress reducing agent, a colorant, a coupling agent, and an inorganic filler, may be blended within a range that does not impair the effects of the present disclosure. The resin composition of this embodiment may also contain a resin other than the component (A), such as an epoxy resin, a (meth)acrylate compound, a vinyl compound, a benzoxazine compound, or a maleimide compound other than the component (A).

[0049] (Mold Release Agent) A mold release agent is added to improve releasability from a mold. As the mold release agent, any of known agents can be used, such as carnauba wax, rice wax, candelilla wax, polyethylene, polyethylene oxide, polypropylene, montanic acid, montan wax which is an ester compound of montanic acid with saturated alcohol, 2-(2-hydroxyethylamino)ethanol, ethylene glycol, glycerin, etc., stearic acid, stearic acid ester, stearic acid amide, etc. These can be used alone or in combination of two or more.

[0050] (Flame retardant) The flame retardant is added to impart flame retardancy, and any known flame retardant can be used, and is not particularly limited. Examples of the flame retardant include phosphazene compounds, silicon compounds, zinc molybdate-supported talc, zinc molybdate-supported zinc oxide, aluminum hydroxide, magnesium hydroxide, and molybdenum oxide. These can be used alone or in combination of two or more.

[0051] (Ion trapping agent) The ion trapping agent is added to capture ionic impurities contained in the liquid resin composition and prevent thermal degradation and moisture absorption degradation. Any known ion trapping agent can be used, and there are no particular limitations. Examples of the ion trapping agent include hydrotalcites, bismuth hydroxide compounds, and rare earth oxides. These can be used alone or in combination of two or more.

[0052] (Inorganic Filler) The inorganic filler can be any known inorganic filler that can be used in a resin composition, without any particular limitation. Examples of inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, boron nitride, silica, graphite powder, and boehmite. Among these, silica is particularly preferred because of its low dielectric loss tangent. The inorganic fillers can be used alone or in combination of two or more.

[0053] The average particle size of the inorganic filler may be 50 nm or more, 100 nm or more, or 200 nm or more, and may be 10 μm or less, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less. The average particle size of the inorganic filler is preferably 100 nm to 10 μm or 50 nm to 5.0 μm, more preferably 100 nm to 3.0 μm, and even more preferably 200 nm to 1.0 μm. When the average particle size of the inorganic filler is within the above range, the surface roughness of the sheet can be reduced and adhesion to substrates such as polyimide films and copper foils can be improved.

[0054] The average particle size of the inorganic filler is determined by the median diameter (d50) at 50% of the cumulative particle size in the volume cumulative particle size distribution. The average particle size can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0055] The inorganic filler is preferably surface-treated, preferably with a coupling agent, more preferably with a silane coupling agent. By surface-treating the inorganic filler, not only can the dispersibility of the inorganic filler in an organic solvent be improved, but also the surface roughness of the sheet surface can be further reduced, and the adhesion to substrates such as polyimide films and copper foils can be improved.

[0056] Examples of the coupling agent include silane coupling agents, titanium coupling agents, and aluminum coupling agents. Examples of the silane coupling agent include methacrylsilane, acrylic silane, aminosilane, phenylaminosilane, imidazole silane, phenylsilane, vinylsilane, and epoxysilane. These can be used alone or in combination of two or more.

[0057] When the resin composition contains an inorganic filler, the content thereof may be 5 to 75 mass%, 5 to 50 mass%, 5 to 35 mass%, or 10 to 30 mass%, based on the total amount of solids (non-volatile content) of the resin composition (100 mass%). When the content of the inorganic filler is 75 mass% or less, a decrease in adhesiveness tends to be suppressed, and when it is 5 mass% or more, the effect of reducing the dielectric loss tangent and the effect of improving heat resistance tend to be sufficiently obtained.

[0058] [Cured Product] The cured product of this embodiment is obtained by curing the resin composition of this embodiment. Specifically, it can be obtained by heat treating the composition at about 150 to 250°C for about 10 minutes to 3 hours.

[0059] The shape of the cured product of the present embodiment is not particularly limited, but when used for bonding substrates, it can be in the form of a sheet having a thickness of usually about 1 to 200 μm, preferably about 3 to 100 μm, and the thickness can be adjusted appropriately depending on the application.

[0060] [Sheet] The sheet of this embodiment comprises the resin composition of this embodiment and a substrate. The sheet of this embodiment can be obtained, for example, by applying the resin composition of this embodiment to a substrate (sheet substrate) and drying it. Examples of the substrate include organic substrates such as polyimide, polyimide-silica hybrid, polyamide, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate resin (PMMA), polystyrene resin (PSt), polycarbonate resin (PC), acrylonitrile-butadiene-styrene resin (ABS), ethylene terephthalate, phenol, phthalic acid, aromatic polyester resin obtained from hydroxynaphthoic acid or the like and parahydroxybenzoic acid (so-called liquid crystal polymer: "Vextar" manufactured by Kuraray Co., Ltd., etc.). Among these, polyimide film, particularly polyimide-silica hybrid film, is preferred in terms of heat resistance and dimensional stability. The substrate may be made of glass, iron, aluminum, 42 alloy, copper, or other metals, or inorganic materials such as ITO, silicon, silicon carbide, etc. The thickness of the substrate can be appropriately set depending on the application.

[0061] [Laminate] The laminate of this embodiment can be obtained by thermocompression bonding a substrate to the adhesive surface of the sheet. Examples of the substrate include organic substrates such as polyimide, polyimide-silica hybrid, polyamide, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate resin (PMMA), polystyrene resin (PSt), polycarbonate resin (PC), acrylonitrile-butadiene-styrene resin (ABS), ethylene terephthalate, phenol, phthalic acid, aromatic polyester resin (liquid crystal polymer) obtained from hydroxynaphthoic acid or the like and parahydroxybenzoic acid. The substrate may also be glass, iron, aluminum, 42 alloy, copper, or other metals, or inorganic substrates such as ITO, silicon, or silicon carbide. The thickness of the substrate can be appropriately set depending on the application. The laminate may also be further heat-treated.

[0062] [Printed Circuit Board and Printed Wiring Board] The printed circuit board of this embodiment uses the above-mentioned sheet or the above-mentioned laminate. The printed circuit board of this embodiment can be obtained, for example, by further laminating the adhesive surface of the above-mentioned sheet to the inorganic substrate surface of the above-mentioned laminate. The printed circuit board preferably uses a polyimide film as the organic substrate and a metal foil (particularly copper foil) as the inorganic substrate. Then, the metal surface of such a printed circuit board is soft-etched to form a circuit, and the above-mentioned sheet is further laminated thereon and hot-pressed to obtain a printed wiring board.

[0063] The present disclosure will be specifically described below with reference to examples and comparative examples, but the present disclosure is not limited thereto. In each example, parts and percentages are by mass unless otherwise specified.

[0064] [Synthesis of Maleimide Resin] To synthesize a maleimide resin, the following components (a1) to (a3), an acid catalyst, and a solvent were prepared. (Component (a1)) BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (manufactured by JFE Chemical Corporation, trade name "BPAF") PMDA: pyromellitic anhydride (manufactured by Daicel Corporation) BISDA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (manufactured by SABIC, trade name "BISDA-1000") s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by JFE Chemical Corporation, trade name "BPDA") a-BPDA: 2,3',3,4'-biphenyltetracarboxylic dianhydride (manufactured by JFE Chemical Corporation, trade name "a-BPDA") ODPA: 4,4'-oxydiphthalic anhydride (manufactured by Manac Corporation, trade name "ODPA") (Component (a2)) DDA: dimer diamine (manufactured by Croda Japan Co., Ltd., trade name "PRIAMINE 1075") mTBHG: 4,4'-diamino-2,2'-dimethylbiphenyl (manufactured by Wakayama Seika Kogyo Co., Ltd., trade name "m-TB-HG") NBDA: norbornanediamine (manufactured by Mitsui Fine Chemicals, Inc.) TAEA: tris(2-aminoethyl)amine (manufactured by Tokyo Chemical Industry Co., Ltd.) (Component (a3)) Maleic anhydride (manufactured by Fuso Chemical Co., Ltd.) (Acid catalyst) Methanesulfonic acid aqueous solution (manufactured by BASF, trade name "Lutropur MSA") (Solvent) Pseudocumene (manufactured by Toyo Gosei Co., Ltd., aromatic high-boiling point solvent) Solmix A-11 (manufactured by Japan Alcohol Sales Co., Ltd., alcohol-based solvent) Toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) γ-butyrolactone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0065] Synthesis Example 1 34.38 parts by mass of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 135.84 parts by mass of pseudocumene, 1.922 parts by mass of Solmix A-11, and 31.00 parts by mass of γ-butyrolactone were added to a 0.3 L flask equipped with a condenser, a nitrogen inlet tube, a thermocouple, and a stirrer. After addition, the temperature was raised to 80°C and maintained at that temperature for 0.5 hours. 26.85 parts by mass of dimer diamine (DDA) was added dropwise, and then 10.62 parts by mass of 4,4'-diamino-2,2'-dimethylbiphenyl (mTBHG) was added. After addition, 1.92 parts by mass of an aqueous methanesulfonic acid solution was added, and the temperature was raised to 160°C. After the temperature was raised, 40.00 parts by mass of toluene was added, and a dehydration ring-closing reaction was carried out at 160°C for 1 hour. Water and alcohol were removed from the reaction solution, and an intermediate polyimide resin was obtained. Subsequently, the polyimide resin was cooled to 130°C, and 7.36 parts by mass of maleic anhydride was added, and the temperature was raised to 160°C. A dehydration ring-closing reaction was carried out at 160°C for 4 hours. Water was removed from the reaction solution, and a maleimide resin was obtained.

[0066] The maleimide resin was placed in a separatory funnel, and 500 parts by mass of pure water was added. The separatory funnel was shaken and allowed to stand. After standing, the aqueous layer and organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass vessel equipped with a cooler, a nitrogen inlet tube, a thermocouple, a stirrer, and a vacuum pump, heated to 88 to 93°C, and the water was removed. The vessel was then heated to 100°C and the solvent was partially removed for 0.5 hours under a reduced pressure of 0.1 MPa from atmospheric pressure, yielding a solution of maleimide resin (A-1) of component (A).

[0067] (Synthesis Example 2) The formulation of each component was changed as shown in Table 1 to obtain a maleimide resin before purification. 500 g of isopropanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1 L glass container equipped with a stirrer. Next, while stirring at 300 rpm, the obtained maleimide resin was placed in the container and further stirred for 30 minutes to cause reprecipitation. The reprecipitated maleimide resin was recovered. The recovered maleimide resin and 500 g of isopropanol were placed in a 1 L glass container and stirred at 300 rpm for 30 minutes. After stirring, the maleimide resin was recovered and dried at 70°C for 12 hours to obtain maleimide resin (A-2) of component (A).

[0068] Synthesis Examples 3 to 9 Solutions of maleimide resins (A-3) to (A-9) were obtained in the same manner as in Synthesis Example 1, except that the amounts of each component were changed as shown in Table 1.

[0069] (Synthesis Examples 10, 12 to 14) Solutions of maleimide resins (A-10), (A-12) to (A-14) were obtained in the same manner as in Synthesis Example 1, except that the blending amounts of each component were changed as shown in Table 2.

[0070] Synthesis Example 11 A maleimide resin (A-11) was obtained in the same manner as in Synthesis Example 2, except that the amounts of each component were changed as shown in Table 2.

[0071] Synthesis Examples 15 to 19 Solutions of maleimide resins (A-15) to (A-19) were obtained in the same manner as in Synthesis Example 1, except that the amounts of each component were changed as shown in Table 3.

[0072] (Nonvolatile Content) 0.75 g ± 0.25 g of each of the solutions of maleimide resins (A-1), (A-3) to (A-10), (A-12) to (A-14), and (A-15) to (A-19) and the powders of maleimide resins (A-2) and (A-11) were weighed out using a precision balance and placed in a metal Petri dish. After drying at 150 ° C. for 0.5 hours in a hot air dryer, the nonvolatile content (NV) was calculated using the following formula: NV (mass%) = {(W3 - W1) / W2} × 100 W1: Mass (g) of the empty metal Petri dish W2: Mass (g) of the maleimide resin solution or powder before drying W3: Mass (g) of the metal Petri dish + maleimide resin after drying

[0073] (Weight Average Molecular Weight) The weight average molecular weight (Mw) of the maleimide resin was measured by gel permeation chromatography (GPC). A sample prepared by dissolving maleimide resin in tetrahydrofuran (THF) to a concentration of 3% by mass was injected in an amount of 50 μL into a column (GL-R420 (Hitachi High-Tech Fielding Corporation) x 1, GL-R430 (Hitachi High-Tech Fielding Corporation) x 1, GL-R440 (Hitachi High-Tech Fielding Corporation) x 1) heated to 30 ° C., and measurement was performed using THF as the developing solvent at a flow rate of 1.6 mL / min. The detector used was an L-3350 RI detector (Hitachi, Ltd.), and Mw was calculated from the elution time using a molecular weight / elution time curve prepared using standard polystyrene (Tosoh Corporation). The maleimide resin (A-11) of Synthesis Example 11 was insoluble in THF, and therefore the Mw could not be measured.

[0074]

[0075]

[0076]

[0077] [Examples 1 to 14 and Comparative Examples 1 to 5] (Preparation of Resin Compositions) The maleimide resin compositions of Examples 1 to 9 were prepared by blending the components shown below in the compositions shown in Table 4. The maleimide resin compositions of Examples 10 to 14 were prepared by blending the components shown below in the compositions shown in Table 5. The maleimide resin compositions of Comparative Examples were prepared by blending the components shown below in the compositions shown in Table 6. The blending amount of component (A) shown in Tables 4 to 6 indicates the blending amount (parts by mass) including the solvent. The maleimide resin composition of Comparative Example 2, which used maleimide resin (A-11), could not be evaluated because it was insoluble in solvent.

[0078] Component (A): Maleimide resin Maleimide resins (A-1) to (A-19) prepared in Synthesis Examples 1 to 19 Component (B): Polymerization initiator (B-1) DCP (manufactured by NOF Corporation, trade name "Percumyl D", dicumyl peroxide) Component (C): Organic solvent (C-1) Toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) (C-2) DMF (N,N-dimethylformamide)

[0079] (Preparation of cured sheet) Using an applicator, the maleimide resin composition was applied onto Cu foil (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "3EC-M2S-VLP") so that the thickness after drying would be 100 μm, and the composition was dried in a dryer at 130°C for 30 minutes. Subsequently, the composition was cured in a nitrogen dryer at 200°C for 1 hour. After curing, the composition was cooled to room temperature, and then the copper foil was removed by etching with an aqueous ammonium persulfate solution, and the composition was dried at 110°C for 30 minutes to prepare a cured sheet.

[0080] [Measurement of Elastic Modulus and Tg] Test pieces with a sample size of 20 mm × 10 mm were prepared using the cured sheets, and the elastic modulus at 20°C and Tg (tan δ peak) were measured using a dynamic viscoelasticity measuring device (manufactured by SII NanoTechnology Inc., product name "DMS6100") under the conditions of a frequency of 1 Hz, a measurement temperature of -40°C to 220°C, and a heating rate of 10°C / min.

[0081] [Linear expansion coefficient] A test piece measuring 30 mm x 4 mm was prepared from the cured sheet. The linear expansion coefficient (CTE) of this test piece was measured using a thermomechanical analyzer (trade name "TMA / SS7100", manufactured by Hitachi High-Tech Science Corporation). The measurement mode was tensile mode, the measurement load was 50 mN, the measurement atmosphere was air, and the heating rate was 5°C / min. The measurement result from the second run at -20 to 40°C was taken as the CTE.

[0082] [5% Weight Loss Temperature] 6.0 to 10.0 mg of the cured sheet was weighed and placed in an open-type sample container (manufactured by Seiko Denshi Co., Ltd., product name "P / N SSC000E030"), and measurement was performed under conditions of a nitrogen flow rate of 300 mL / min and a temperature rise rate of 10°C / min. The 5% weight loss temperature (T ｄ５ The measurement device used was a TG / DTA7200 (manufactured by Hitachi High-Tech Science Corporation).

[0083] [Evaluation of Dielectric Properties] A test piece measuring 50 mm x 100 mm was prepared using the cured sheet. Using this test piece, the relative permittivity (Dk) and dielectric loss tangent (Df) at 10 GHz were measured using a network analyzer (manufactured by KEYSIGHT Technologies, product name "P5003A") and a split cylinder resonator (manufactured by KEYSIGHT Technologies). From the measurement results, evaluation was performed based on the following criteria. When the evaluation result was A or B, it can be said that the dielectric properties were sufficiently low. <Dk Evaluation Criteria> A: Less than 2.5 B: 2.5 or more but less than 2.8 C: 2.8 or more <Df Evaluation Criteria> A: Less than 0.0030 B: 0.0030 or more but less than 0.0050 C: 0.0050 or more

[0084] [Evaluation of Toughness] Using an applicator, the maleimide resin composition was applied to a surface of Film Vina (registered trademark) (PET film, manufactured by Fujimori Kogyo Co., Ltd., product name "NS14", thickness 75 μm) so that the thickness after drying would be 50 μm, and the coating was dried in a dryer at 130°C for 30 minutes to obtain an adhesive sheet. A test piece with a sample size of 10 mm x 50 mm was prepared using the adhesive sheet, and the minimum diameter at which the adhesive sheet broke was measured using a mandrel tester. The measurement results were evaluated based on the following criteria. <Toughness Criteria> A: 10.0 mm or less B: 10.1 mm or more, 15.0 mm or less C: 15.1 mm or more

[0085]

[0086]

[0087]

[0088] As is clear from the results shown in Tables 4 and 5, it was confirmed that the resin compositions using the maleimide resins of the Examples had excellent cured product properties, including low dielectric properties (low Dk and low Df), high elastic modulus, high Tg, low CTE, and high toughness. Therefore, use of the maleimide resins of the present disclosure is expected to dramatically improve the properties of laminates such as printed circuit boards and encapsulants for electronic components such as semiconductors.

Claims

1. A maleimide resin obtained by reacting a tetracarboxylic dianhydride (a1), an amine (a2) and maleic anhydride (a3), wherein the tetracarboxylic dianhydride (a1) includes a tetracarboxylic dianhydride having a fluorene skeleton, and the amine (a2) includes a dimer diamine and an amine having a biphenyl skeleton.

2. The maleimide resin according to claim 1, wherein the tetracarboxylic dianhydride having a fluorene skeleton contains at least one of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride.

3. The maleimide resin according to claim 1, wherein the amine having a biphenyl skeleton contains at least one of 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-2,2'-diethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-diethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl, 4,4'-diamino-3,3',5,5'-tetraethylbiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, and 4,4'-diamino-3,3'-dimethoxybiphenyl.

4. The maleimide resin according to claim 1, wherein the dimer diamine contains at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2): [In formulas (1) and (2), m, n, p, and q each represent an integer of 1 or more selected such that m+n=6 to 17 and p+q=8 to 19, and the bond shown by the dashed line represents a carbon-carbon single bond or a carbon-carbon double bond. However, when the bond shown by the dashed line is a carbon-carbon double bond, formulas (1) and (2) have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is reduced by one from the number shown in formulas (1) and (2)] 5. The maleimide resin according to claim 1, having a weight average molecular weight of 3,000 to 40,000.

6. A resin composition comprising the maleimide resin according to any one of claims 1 to 5.

7. The resin composition according to claim 6, further comprising a polymerization initiator.

8. A cured product of the resin composition according to claim 6.

9. A sheet comprising the resin composition according to claim 6 and a substrate.

10. The sheet of claim 9, wherein the substrate is an organic substrate.

11. The sheet of claim 9, wherein the substrate is an inorganic substrate.

12. A laminate comprising the sheet according to claim 9 and a substrate further heat-pressed to the adhesive surface of the sheet.

13. A printed wiring board using the sheet according to claim 9.

14. A printed wiring board comprising the laminate according to claim 12.