Carbonate resin, its manufacturing method, resin varnish, and manufacturing method of laminated board

Abstract

To provide a resin which enables formation of an epoxy cured product that exhibits a low dielectric constant and a low dielectric loss tangent, and its related techniques.SOLUTION: A carbonate resin is represented by formula (1). In the formula (1), n is an integer of 1 or more, Ar are each independently a residue derived from a bisphenol compound or a residue derived from a biphenol compound, n pieces of R are each independently a residue derived from a bisphenol compound, a residue derived from a biphenol compound or a residue derived from an alicyclic dimethanol compound, at least one R out of the n pieces of R is the residue from the alicyclic dimethanol compound, and both of two X are arylcarbonyl groups, or one X is arylcarbonyl group and the other X is a hydrogen atom.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a carbonate resin, a method for producing the same, a resin varnish, and a method for producing a laminate. [Background technology]

[0002] Carbonate resins having terminal hydroxyl groups and an alicyclic structure, a benzene skeleton, an allyl group, or the like in their structure are known as curable resins having excellent dielectric properties (see, for example, Patent Documents 1 and 2).

[0003] Furthermore, a curable epoxy resin composition containing an epoxy resin and an epoxy resin curing agent containing a low molecular weight paraphenylene ether (PPE) is known as a composition having excellent dielectric properties (see, for example, Patent Document 3).

[0004] Furthermore, an epoxy resin composition containing a polyfunctional aromatic polyester and an epoxy resin is known as a curable resin having excellent dielectric properties (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-089965 [Patent Document 2] Japanese Patent Application Publication No. 2019-089967 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-224860 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-169021 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is a demand for even lower dielectric constants and dielectric loss tangents for curable resins, and there is room for improvement in the conventional techniques aimed at achieving this.

[0007] For example, the curable resins described in Patent Documents 1, 2, and 4 have higher dielectric constants and dielectric loss tangents than the market demands. The composition described in Patent Document 3 has a problem in that it has a lower dielectric constant but a higher dielectric loss tangent than the market demands.

[0008] An object of one aspect of the present invention is to provide a carbonate resin capable of forming an epoxy cured product or a maleimide cured product exhibiting a low dielectric constant and a low dielectric loss tangent, and related art. [Means for solving the problem]

[0009] In order to solve the above problems, a carbonate resin according to one aspect of the present invention is a carbonate resin represented by formula (1), [ka] In the formula (1), n ​​is an integer of 1 or more; each Ar is independently a residue derived from a bisphenol compound or a residue derived from a biphenol compound; n Rs are independently a residue derived from a bisphenol compound, a residue derived from a biphenol compound, or a residue derived from an alicyclic dimethanol compound; at least one R among the n Rs is the residue derived from the alicyclic dimethanol compound; and two Xs shown in the formula (1) are either both arylcarbonyl groups or one is an arylcarbonyl group and the other is a hydrogen atom.

[0010] Further, a method for producing a carbonate resin according to one aspect of the present invention includes: a carbonate resin derived from an aromatic diol compound and having at least two terminal phenolic hydroxyl groups; The method includes an esterification step of reacting the phenolic hydroxyl group with at least one carboxylic acid compound selected from the group consisting of carboxylic acids and carboxylic acid halides to esterify the phenolic hydroxyl group. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to provide a polycarbonate resin capable of forming an epoxy cured product exhibiting a low dielectric constant and a low dielectric loss tangent, and related techniques thereof. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Terminology> As used herein, unless otherwise specified, the term "%" simply means "% by mass." Furthermore, as used herein, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0013] In this specification, the term "dielectric properties" is sometimes used as a general term for the terms "dielectric constant" and "dielectric loss tangent." Furthermore, in this specification, a low dielectric constant and a low dielectric loss tangent may be described as a good dielectric constant and a good dielectric loss tangent, respectively. Furthermore, in this specification, a high dielectric constant and a high dielectric loss tangent may be described as a poor dielectric constant and a poor dielectric loss tangent, respectively. Furthermore, when used in this specification, unless otherwise specified, the term "ester" simply means "carboxylic acid ester."

[0014] Curable resins that make up insulating laminates used in electronic products are required to have excellent dielectric properties, such as low dielectric constant and low dielectric loss tangent. For example, with the advancement of communication standards such as 5G, there is a growing need for insulating materials that can minimize transmission loss even when high-frequency currents flow.

[0015] Such insulating materials include epoxy resins that use polyester resins as curing agents, and the following two reasons are thought to be the causes of the deterioration of the dielectric properties of such epoxy resins: (1) the dielectric properties of the cured product obtained by the curing reaction between polyester resin and epoxy compound gradually deteriorate due to hydrolysis of the ester, and (2) the curing reaction between a resin having a hydroxyl group at its terminal and an epoxy compound generates a hydroxyl group that exhibits high polarity.

[0016] The present inventors have studied these problems and have made the following discoveries. Regarding (1) above, they discovered that by using a carbonate main chain structure in a resin, it is possible to reduce hydrolysis of ester bonds, as in polyester resins that have ester bonds within the main chain structure rather than at the terminals, thereby reducing the deterioration of dielectric properties over time. Furthermore, regarding (2) above, they discovered that by esterifying the phenolic hydroxyl groups at the terminals of the resin to form active ester groups, it is possible to prevent the generation of hydroxyl groups during the curing reaction while maintaining reactivity with epoxy compounds. Combining these discoveries, the present inventors discovered that by introducing an active ester group having a specific structure at the terminal of a carbonate main chain structure, it is possible to obtain a significant improvement in dielectric properties despite a small ester group equivalent, and thus completed the present invention.

[0017] One aspect of the present invention will be described in detail below.

[0018] <Carbonate resin> One aspect of the present invention relates to a carbonate resin. Hereinafter, "a carbonate resin according to one aspect of the present invention" may be abbreviated as "the present carbonate resin." The present carbonate resin is represented by formula (1).

[0019] [ka] In formula (1), n ​​is an integer of 1 or more. n is preferably an integer of 100 or less, more preferably an integer of 75 or less, and even more preferably an integer of 50 or less. This reduces the weight-average molecular weight of the present carbonate resin, and improves the fluidity of the present carbonate resin.

[0020] In formula (1), Ar, i.e., aryl, is independently a residue derived from a bisphenol compound or a residue derived from a biphenol compound. Also, in formula (1), n ​​R's are independently a residue derived from a bisphenol compound, a residue derived from a biphenol compound, or a residue derived from an alicyclic dimethanol compound.

[0021] As used herein, the term "residue derived from a bisphenol compound" refers to a group having a structure obtained by removing two phenolic hydroxyl groups from a bisphenol compound. The bisphenol compound may have one or more substituents on at least one of the two phenylene groups bonded via a linking group. Examples of such substituents include an allyl group and an alkyl group.

[0022] Examples of the bisphenol compounds include bisphenol A, bisphenol F, bisphenol B, bisphenol AP, bisphenol C, bisphenol E, bisphenol S, and bisphenol Z; and allyl group-containing bisphenol compounds in which one or more allyl groups are bonded to at least one of the hydroxyphenyl groups of these bisphenol compounds.

[0023] As used herein, the term "residue derived from a biphenol compound" refers to a group having a structure obtained by removing two phenolic hydroxyl groups from a biphenol compound. The biphenol compound may have one or more substituents on at least one of the two directly bonded phenylene groups. Examples of such substituents include an allyl group, an alkyl group, and a halogen group.

[0024] Examples of such biphenol compounds include biphenol, halogenated biphenol, and alkylbiphenol; and allyl group-containing biphenol compounds in which one or more allyl groups are bonded to at least one of the hydroxyphenyl groups of these biphenol compounds.

[0025] As used herein, the term "residue derived from an alicyclic dimethanol compound" refers to a group having a structure in which two hydroxyl groups have been removed from an alicyclic dimethanol compound. The alicyclic dimethanol compound may have one or more substituents on the alicyclic group. Examples of such substituents include an allyl group, an alkyl group, and a halogen group.

[0026] The alicyclic group contained in the alicyclic dimethanol compound may have a monocyclic structure or a polycyclic structure. The number of carbon atoms in the alicyclic group is preferably 6 to 20, and more preferably 8 to 15. Examples of the alicyclic group include a cyclohexylene group, a tricyclodecanediyl group, a perhydro-1,4;5,8-naphthylene-2,3-diyl group, and a bicyclo[2.2.1]heptane-2,3-diyl group.

[0027] The residue derived from an alicyclic dimethanol compound is preferably a residue derived from a compound selected from the group consisting of cyclohexanedimethanol, tricyclodecanedimethanol, trans-2,3-di(hydroxymethyl)-perhydro-1,4,5,8-dimethanonaphthalene, and trans-2,3-di(hydroxymethyl)bicyclo[2.2.1]heptane; and isomers and mixtures of isomers of these alicyclic dimethanol compounds. When Ar in formula (1) is a residue derived from one of these compounds having a bulky alicyclic group, the present carbonate resin can be provided, which can form a cured product exhibiting a lower dielectric loss tangent.

[0028] In formula (1), at least one R among n Rs is a residue derived from an alicyclic dimethanol compound. That is, the carbonate resin has a carbonate structure and an alicyclic structure in the main chain. This allows the carbonate resin to have a low dielectric tangent and high solubility in solvents.

[0029] In formula (1), assuming that all n R's are 100 mol%, the proportion of R's that are residues derived from alicyclic dimethanol compounds is preferably 20 mol% or more, more preferably 50 mol% or more. This makes it possible to provide a carbonate resin that can produce a cured product that exhibits a lower dielectric loss tangent while maintaining flame retardancy. Furthermore, in formula (1), assuming that all n R's are 100 mol%, the proportion of R's that are residues derived from alicyclic dimethanol compounds is preferably 90 mol% or less, more preferably 80 mol% or less. This makes it possible to achieve a lower dielectric loss tangent.

[0030] In formula (1), each Ar is preferably independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), or formula (R6). In formula (1), each of the n Rs is preferably independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), formula (R6), or formula (R7).

[0031] [ka]

[0032] The groups represented by formula (R1), formula (R2), and formula (R3) are residues derived from bisphenol A, bisphenol F, and biphenol, respectively. These bisphenol compounds and biphenol compounds are inexpensive and easily available. Therefore, when Ar in formula (1) is a group represented by formula (R1), formula (R2), or formula (R3), the production cost of the carbonate resin can be reduced.

[0033] In formulas (R4), (R5), and (R6), p is 1 or 2, preferably 1. In formulas (R4), (R5), and (R6), q is an integer of 0 to 2, preferably 1. That is, the groups represented by formulas (R4), (R5), and (R6) are residues derived from allyl group-containing bisphenol A, allyl group-containing bisphenol F, and allyl group-containing biphenol, respectively. These bisphenol compounds and biphenol compounds are inexpensive and easily available. Furthermore, the groups represented by formulas (R4), (R5), and (R6) have (p+q) allyl groups that can undergo a favorable curing reaction with a maleimide compound. Therefore, when Ar in formula (1) is a group represented by formula (R4), formula (R5), or formula (R6), the production cost of the present carbonate resin can be reduced and the present carbonate resin can be provided which can undergo a favorable curing reaction with a maleimide compound.

[0034] In formula (R7), R 8 is an alicyclic group. That is, the group represented by formula (R7) is a residue derived from an alicyclic dimethanol compound.

[0035] In formula (1), at least one of n R's is preferably a group represented by formula (R7).

[0036] In formula (1), both of the two X's are arylcarbonyl groups, or one is an arylcarbonyl group and the remaining X is a hydrogen atom. That is, in the carbonate resin represented by formula (1), the terminal of the carbonate resin represented by -ArOX has, as an active ester group, a carboxylic acid ester group formed by bonding the oxygen atom in -ArO- to the carbonyl group constituting the arylcarbonyl group represented by X. That is, at least one of the terminals of the carbonate resin represented by formula (1) has an active ester group due to esterification.

[0037] That is, as shown in formula (1), unlike conventional polyester resins, the present carbonate resin has an active ester group at the terminal, and the main chain structure has a carbonate bond (also called a carbonic acid ester bond) rather than a carboxylic acid ester bond. Here, the carbonate bond has the advantage of being less susceptible to hydrolysis than a carboxylic acid ester bond. Therefore, the present carbonate resin can avoid the hydrolysis of ester bonds that occurs in polyester resins and suppress the increase in the relative dielectric constant and dielectric loss tangent over time that results from this hydrolysis. Therefore, the present carbonate resin can preferably maintain an extremely low relative dielectric constant and dielectric loss tangent compared to conventional polyester resins. Therefore, the present carbonate resin can preferably maintain a high level of low dielectric constant and low dielectric loss tangent, which are required for materials used in communication devices such as 5G. Furthermore, as described below, the present carbonate resin has a small number of active ester groups, i.e., a high ester group equivalent, which significantly improves dielectric properties.

[0038] Examples of aryl groups constituting an arylcarbonyl group include phenyl, benzyl, naphthyl, and polyvalent aromatic groups. The aryl group may have one or more substituents. Examples of the substituents include allyl, alkyl, alkoxy, nitro, and halogen groups.

[0039] In formula (1), it is preferable that each X is independently a group represented by formula (X1), formula (X2), or formula (X3).

[0040] [ka]

[0041] The groups represented by formula (X1), formula (X2), and formula (X3) are derived from benzene, naphthalene, and a polyvalent aromatic compound, respectively. These compounds have a strong effect of activating esters, thereby enhancing the reactivity of the carbonate resin with an epoxy compound. Furthermore, since X in formula (1) is a group derived from one of these compounds, the polarity of the resulting hydroxyl group is reduced when the ester group remaining after the curing reaction between the carbonate resin and the epoxy compound is hydrolyzed, thereby reducing the gradual deterioration of dielectric properties.

[0042] In formula (X1), formula (X2), and formula (X3), A, B, D, E, and G each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, or a halogen group. Furthermore, a and g each independently represent an integer from 0 to 5, b represents an integer from 0 to 3, and d and e each independently represent an integer from 0 to 4. That is, the groups represented by formula (X1), formula (X2), and formula (X3) may have a substituent selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, and a halogen group. These substituents can further activate the active ester group represented by -ArOCOX, thereby enhancing the reactivity with epoxy compounds.

[0043] In formula (X3), Z is a single bond between carbon atoms, -O-, -CO-, -CH2-, -C(CH3)2-, or -SO2-.

[0044] As used herein, the term "major component" refers to the component that is contained in the largest amount among the components that make up a resin. Typically, the term "major component" refers to the component that accounts for the largest mass % of the total amount of the resin among the components that make up a resin. The content of the major component may be 50 mass % or more, preferably 80 mass % or more, more preferably 90 mass % or more, and may even be 100 mass % based on the total amount of the resin. The content of the compound represented by formula (1) in the present carbonate resin can be measured by a conventionally known method such as gel permeation chromatography (GPC).

[0045] The present carbonate resin may contain multiple types of compounds represented by formula (1) that are different in at least one of n, Ar, R, and X. In this case, the total content of the multiple types of compounds represented by formula (1) among the components constituting the present carbonate resin should satisfy the definition of the main component.

[0046] The softening point of the present carbonate resin is preferably 70°C or higher, more preferably 90°C or higher. This can improve the blocking resistance of the present carbonate resin. The softening point of the present carbonate resin is preferably 130°C or lower, more preferably 120°C or lower. This can improve the flowability of the present carbonate resin.

[0047] The softening point of the present carbonate resin can be measured according to JIS K 6910:2007 or a method based thereon.

[0048] The melt viscosity of the carbonate resin at 200°C is preferably 0.1 Pa·s (Pascal seconds) or more, more preferably 0.5 Pa·s or more. This improves the blocking resistance of the carbonate resin. The melt viscosity of the carbonate resin at 200°C is preferably 10 Pa·s or less, more preferably 5 Pa·s or less. This improves the flowability of the carbonate resin.

[0049] The melt viscosity of the present carbonate resin at 200°C can be measured using a conventionally known melt viscometer.

[0050] The weight-average molecular weight of the present carbonate resin is preferably 2,000 or more, more preferably 4,000 or more. This can improve the blocking resistance of the present carbonate resin. The weight-average molecular weight of the present carbonate resin is preferably 20,000 or less, more preferably 15,000 or less. This can improve the flowability of the present carbonate resin.

[0051] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the present carbonate resin can be measured by a conventionally known method such as gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0052] The equivalent weight of the -ArOX terminal group of this carbonate resin, i.e., the sum of the ester group equivalent weight of the active ester group and the hydroxyl group equivalent weight, is preferably 100 g / eq or more, more preferably 800 g / eq or more. This allows the carbonate resin to produce a cured product that achieves extremely low relative dielectric constant and dielectric dissipation factor when reacted with, for example, an epoxy compound. Therefore, the low dielectric constant and low dielectric dissipation factor required for materials used in communication devices such as 5G (fifth generation communication standard) can be achieved. Furthermore, the sum of the ester group equivalent weight of the active ester group and the hydroxyl group equivalent weight is not limited, but is preferably 10,000 g / eq or less, more preferably 2,000 g / eq or less. This allows the carbonate resin to have sufficient curability. Here, from the viewpoint of achieving an even lower dielectric constant and a lower dielectric loss tangent, the ratio of the ester group equivalent to the total of the ester group equivalent and the hydroxyl group equivalent of the active ester group is preferably 50% or more, more preferably 75% or more, and most preferably 100%.

[0053] The ester group equivalent of the present carbonate resin means the number average molecular weight of the present carbonate resin per 1 mole of ester groups contained in the present carbonate resin. The ester group equivalent of the present carbonate resin can be calculated by a conventionally known method.

[0054] [Application] Because this carbonate resin has an active ester group at its terminal, it has excellent reactivity with epoxy compounds and can be used as a curing agent for curing epoxy resins, i.e., an epoxy resin curing agent. Epoxy resins using this carbonate resin as a curing agent can be cured by heating.

[0055] Furthermore, the cured product of epoxy resin cured with this carbonate resin has a lower dielectric constant and a lower dielectric dissipation factor than the cured product of epoxy resin cured with phenol novolac resin, and also has sufficiently good thermal properties such as glass transition temperature, thermal decomposition temperature, and coefficient of linear thermal expansion.

[0056] When the present carbonate resin is used to cure an epoxy resin, it is believed that the curing occurs due to the following reactions (1) and (2). (1) Reaction of an epoxy group with a hydroxyl group and / or a carboxyl group. (2) Reaction between epoxy groups.

[0057] Furthermore, the present carbonate resin has excellent solubility in solvents commonly used to dissolve epoxy resins. Therefore, a resin varnish can be obtained in which both the present carbonate resin and the epoxy resin are dissolved in a solvent. Examples of the solvent include polar solvents such as methyl ethyl ketone.

[0058] Examples of uses of the present carbonate resin include known thermosetting molding materials. Examples of such uses include encapsulating materials, film materials, and laminate materials. More specific uses include, but are not limited to, semiconductor encapsulating materials, encapsulating resin materials for electronic components, electrical insulating materials, copper-clad laminate resin materials, build-up laminate resin materials, resist materials, resin materials for liquid crystal color filters, paints, various coating agents, adhesives, and fiber-reinforced plastic (FRP) materials.

[0059] <Method for producing carbonate resin> One aspect of the present invention relates to a method for producing a carbonate resin. Hereinafter, the "method for producing a carbonate resin according to one aspect of the present invention" may be abbreviated as "the present production method." The present production method is a method for producing an ester group-containing carbonate resin by esterifying a phenolic hydroxyl group at the end of a carbonate resin. According to the present production method, a resin can be produced that has an active ester group with a specific structure at the end, thereby forming a cured product that exhibits a low dielectric constant and a low dielectric loss tangent.

[0060] [Step of obtaining carbonate resin] The present production method preferably includes a step of reacting a carbonic acid diester with at least one diol compound selected from the group consisting of bisphenol compounds, biphenol compounds, and alicyclic dimethanol compounds to obtain a carbonate resin having a terminal phenolic hydroxyl group. By including a step of obtaining a carbonate resin, the present production method can obtain an ester group-containing carbonate resin having an appropriately selected structure. The step of obtaining a carbonate resin can typically be a step of producing a compound represented by formula (2) by transesterification using a carbonic acid diester and a diol compound as raw materials. In formula (2), the structures of n, R, and Ar can be the same as those described above for the ester group-containing carbonate resin according to one embodiment of the present invention.

[0061] [ka]

[0062] In the step of obtaining the carbonate resin, the bisphenol compound, biphenol compound, and alicyclic dimethanol compound used as raw materials may be the same as those described above.

[0063] In the process for obtaining a carbonate resin, the carbonate diester used as a raw material can be appropriately selected from those capable of undergoing an ester exchange reaction with a diol compound. Examples of carbonate diesters include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; alkylene carbonates such as ethylene carbonate; and diphenyl carbonate. The dialkyl carbonate preferably has an alkyl group having 1 to 4 carbon atoms. The alkylene carbonate preferably has an alkylene group having 1 to 4 carbon atoms. The carbonate diester is preferably diphenyl carbonate. Diphenyl carbonate is preferred because it has good reactivity with diol compounds, is relatively inexpensive, and is easy to handle. One type of carbonate diester may be used alone, or two or more types may be used in combination.

[0064] In the process of obtaining a carbonate resin, the higher the molar ratio of the carbonate diester to the total amount of the diol compound, i.e., carbonate diester (mol) / diol compound (mol), the more the amount of hydroxyl groups remaining in the reaction system is reduced, resulting in improved dielectric properties. This molar ratio is preferably 0.60 or higher, more preferably 0.70 or higher. Furthermore, the lower this molar ratio, the more the fluidity of the resulting carbonate resin is improved, making it easier to handle. This molar ratio is preferably 0.99 or lower, more preferably 0.95 or lower.

[0065] The process for obtaining a carbonate resin preferably includes a first reaction step and a second reaction step. This allows for better control of the structure of the carbonate resin. The first reaction step and the second reaction step are described in detail below.

[0066] (Primary reaction step) The primary reaction step is a step of reacting a carbonic acid diester with an alicyclic dimethanol compound to obtain a primary reaction product having at least one structure derived from the alicyclic dimethanol compound. The primary reaction step can typically be a step of obtaining a primary reaction product having a main chain structure represented by formula (3).

[0067] [ka]

[0068] The primary reaction step can be carried out, for example, by melt-mixing a carbonic acid diester, an alicyclic dimethanol compound, and, if necessary, at least one aromatic diol compound selected from the group consisting of bisphenol compounds and biphenol compounds, adding a catalyst, and maintaining a predetermined reaction temperature for a predetermined period of time. Each of the carbonic acid diester, the alicyclic dimethanol compound, and the aromatic diol compound may be used alone or in combination of two or more.

[0069] In the primary reaction step, the molar ratio of the carbonate diester to the total amount of the alicyclic dimethanol compound and the aromatic diol compound, i.e., carbonate diester (mol) / (alicyclic dimethanol compound + aromatic diol compound) (mol), is higher, which reduces the amount of hydroxyl groups in the alicyclic dimethanol compound remaining in the reaction system and improves the dielectric properties. This molar ratio is preferably 1.05 or higher, and more preferably 1.20 or higher. Furthermore, a lower molar ratio reduces the amount of aromatic diol compound used in the subsequent secondary reaction step and improves the dielectric properties. This molar ratio is preferably 3.00 or lower, and more preferably 2.50 or lower.

[0070] When an aromatic diol compound is used in the primary reaction step, various physical properties such as heat resistance, solvent solubility, and flame retardancy can be imparted. The higher the molar ratio of the aromatic diol compound to the total amount of the aromatic diol compound and the alicyclic dimethanol compound used in the primary reaction step, i.e., aromatic diol compound (mol) / (aromatic diol compound + alicyclic dimethanol compound) (mol), the better the various physical properties such as heat resistance, solvent solubility, and flame retardancy can be imparted. This molar ratio is preferably 0.01 or more, more preferably 0.10 or more. Furthermore, the lower this molar ratio, the higher the proportion of R, the residue derived from the alicyclic dimethanol compound, in the main chain structure represented by formula (3), and the more improved the dielectric properties can be. This molar ratio is preferably 0.90 or less, more preferably 0.70 or less.

[0071] The catalyst used in the first reaction step is not particularly limited as long as it can catalyze the transesterification reaction between the carbonate diester and the diol compound. Examples of catalysts include alkali metals such as lithium and sodium; metallic magnesium; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal hydrides such as lithium hydride and sodium hydride; metal acetates such as lithium acetate and zinc acetate; metal oxides such as zinc oxide, lead oxide, antimony oxide, germanium oxide, and manganese dioxide; metal halides; alkyl zinc compounds such as di-n-butyl zinc; titanium esters such as tetra-n-butyl titanate and tetraalkyl orthotitanate; and metal alkoxides such as potassium t-butoxide and sodium methoxide.

[0072] In the primary reaction step, the higher the amount of catalyst used relative to the carbonic acid diester, the faster the reaction rate and the easier it is to obtain a resin with a high degree of polymerization. The amount used is preferably 0.00001% by mass or more, and more preferably 0.0001% by mass or more. Furthermore, the lower the amount used, the less turbid the resulting resin becomes and the better its appearance can be. The amount used is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less.

[0073] In the primary reaction step, the higher the reaction temperature, the faster the reaction rate, making it easier to obtain a resin with a high degree of polymerization. The reaction temperature is preferably 130°C or higher, more preferably 150°C or higher. Furthermore, the lower the reaction temperature, the more stable the quality of the resin obtained. The reaction temperature is preferably 250°C or lower, more preferably 200°C or lower.

[0074] In the first reaction step, the reaction time can be appropriately selected depending on the reaction conditions such as the reaction temperature and the amount of the raw materials used, etc. The reaction time can be, for example, 0.5 hours or more and 10 hours or less.

[0075] In the first reaction step, the reaction pressure may be normal pressure or reduced pressure and can be appropriately selected. For example, by carrying out the first reaction step under reduced pressure, by-products such as alcohols and phenols produced by the reaction may be removed.

[0076] After the completion of the primary reaction step, the reaction system containing the primary reaction product may be directly subjected to the subsequent secondary reaction step, or the reaction system may be purified at the end of the primary reaction step to obtain a highly purified primary reaction product which may be subjected to the secondary reaction step.

[0077] (Secondary reaction process) The secondary reaction step is a step of reacting the primary reaction product with at least one aromatic diol compound selected from the group consisting of bisphenol compounds and biphenol compounds to obtain a carbonate resin having a terminal phenolic hydroxyl group. The secondary reaction step can typically be a step of introducing a phenolic hydroxyl group into the primary reaction product having a main chain structure represented by formula (3) to obtain a compound represented by formula (2).

[0078] [ka]

[0079] The secondary reaction step can be carried out, for example, by adding an aromatic diol compound to the primary reaction product obtained in the primary reaction step and maintaining a predetermined reaction temperature for a predetermined time. The aromatic diol compound may be used alone or in combination of two or more.

[0080] The amount of aromatic diol compound used in the secondary reaction step can be selected depending on the amount of carbonate diester used in the primary reaction step. The higher the amount of aromatic diol compound used in the secondary reaction step relative to the amount of carbonate diester used in the primary reaction step (100 mol%), the more reliably phenolic hydroxyl groups can be introduced, and the more improved the dielectric properties can be. The amount used is preferably 5 mol% or more, more preferably 15 mol% or more. Furthermore, the lower the amount used, the more reduced the production costs can be. The amount used is preferably 80 mol% or less, more preferably 60 mol% or less.

[0081] In the secondary reaction step, the higher the reaction temperature, the faster the reaction rate and the shorter the reaction time. The reaction temperature is preferably 130°C or higher, more preferably 170°C or higher. Furthermore, the lower the reaction temperature, the more stable the quality of the resin obtained. The reaction temperature is preferably 250°C or lower, more preferably 230°C or lower.

[0082] In the secondary reaction step, the reaction time can be appropriately selected depending on the reaction conditions such as the reaction temperature and the amount of raw materials used, etc. The reaction time can be, for example, 0.5 hours or more and 10 hours or less.

[0083] In the secondary reaction step, the reaction pressure is preferably reduced. By carrying out the secondary reaction step under reduced pressure, by-products such as alcohols and phenols produced by the reaction can be removed, and the dehydrochlorination condensation reaction can proceed efficiently in the subsequent esterification step. When the secondary reaction step is carried out under reduced pressure, the reaction pressure is not particularly limited as long as it is a pressure that allows the by-products to be removed. When the secondary reaction step is carried out under reduced pressure, the reaction pressure may be 5 mmHg to 80 mmHg, or may be 5 mmHg to 20 mmHg.

[0084] At the end of the secondary reaction step, the reaction system may be subjected to treatments such as washing with water and concentration, if necessary.

[0085] [Esterification step] This production method includes an esterification step in which a carbonate resin having a terminal phenolic hydroxyl group is reacted with at least one carboxylic acid compound selected from the group consisting of carboxylic acids and carboxylic acid halides to esterify the phenolic hydroxyl group. The esterification step is a step in which the terminal phenolic hydroxyl group of the carbonate resin is esterified to produce an ester group-containing carbonate resin. Here, the terminal phenolic hydroxyl group of the carbonate resin may be a group derived from an aromatic diol compound.

[0086] The esterification step can be carried out, for example, by adding a carboxylic acid compound to a carbonate resin having a terminal phenolic hydroxyl group, optionally adding a catalyst, and maintaining a predetermined reaction temperature for a predetermined time. The carboxylic acid compound may be used alone or in combination of two or more.

[0087] In the esterification step, the carbonate resin used as a raw material may be one obtained by the above-mentioned step of obtaining a carbonate resin, or may be a commercially available one.

[0088] In the esterification step, the carboxylic acid and carboxylic acid halide used as raw materials are not particularly limited as long as they can undergo dehydrochlorination condensation with the phenolic hydroxyl group to form an active ester group. Examples of carboxylic acids include benzoic acid; alkylbenzoic acids such as methylbenzoic acid, 2,4-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 2,4,6-trimethylbenzoic acid, 2-ethylbenzoic acid, 4-ethylbenzoic acid, 2-t-butyl-4-ethylbenzoic acid, 4-i-propylbenzoic acid, and 4-t-butylbenzoic acid; naphthoic acids such as 1-naphthoic acid and 2-naphthoic acid; 2-methyl-1-benzoic acid; and the like. Examples of suitable carboxylic acid compounds include alkyl naphthoic acids such as 2-t-naphthoic acid, 4-methyl-1-naphthoic acid, 2-ethyl-1-naphthoic acid, 3-methyl-4-ethyl-2-naphthoic acid, 2-propyl-1-naphthoic acid, 2-propyl-4-ethyl-1-naphthoic acid, 6-propyl-2-naphthoic acid, 2-t-butyl-1-naphthoic acid, 3-t-butyl-1-naphthoic acid, and 4-t-butyl-1-naphthoic acid. Examples of suitable carboxylic acid halides include acid fluorides, acid chlorides, acid bromides, and acid iodides of these carboxylic acids. The preferred carboxylic acid compound is benzoyl chloride. Benzoyl chloride is relatively inexpensive and easily available. The use of benzoyl chloride can further improve dielectric properties. The carboxylic acid compounds may be used alone or in combination.

[0089] In the esterification step, the higher the molar ratio of the carboxylic acid compound to the amount of phenolic hydroxyl groups in the carbonate resin used as a raw material, i.e., (carboxylic acid compound (mol)) / (carbonate resin (mol) × 2), the more the amount of hydroxyl groups remaining in the reaction system is reduced, and the more the dielectric properties can be improved. This molar ratio is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 0.9 or more. Furthermore, since a lower molar ratio can contribute to lower dielectric properties, this molar ratio is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less.

[0090] The catalyst used in the esterification step is not particularly limited as long as it can catalyze the dehydrochlorination condensation reaction between a phenolic hydroxyl group and a carboxylic acid compound. Examples of catalysts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; tertiary amines such as triethylamine and tributylamine; and pyridine. The catalyst is preferably triethylamine. Triethylamine can be easily removed from the reaction system by washing with water, thereby reducing production costs. These catalysts used in the esterification step also function as acid scavengers.

[0091] In the esterification step, the higher the amount of catalyst used relative to the carboxylic acid compound, the shorter the reaction time. The amount used is preferably 1 or more, more preferably 1.2 or more, in terms of the sum of the hydroxyl group equivalents. Furthermore, the lower the amount used, the more effectively the generation of by-products can be suppressed. The amount used is preferably 2 or less, more preferably 1.5 or less.

[0092] Examples of the reaction solvent used in the esterification step include aromatic solvents such as toluene and chlorinated solvents such as dichloromethane. The reaction solvent is preferably toluene.

[0093] In the esterification step, the higher the reaction temperature, the shorter the reaction time. The reaction temperature is preferably 0°C or higher, and more preferably 10°C or higher. Furthermore, the lower the reaction temperature, the less impurities are produced. The reaction temperature is preferably 100°C or lower, and more preferably 60°C or lower.

[0094] In the esterification step, the reaction time can be appropriately selected depending on the reaction conditions such as the reaction temperature and the amount of raw materials used, etc. The reaction time can be, for example, 2 hours or more and 36 hours or less.

[0095] In the esterification step, the reaction pressure may be normal pressure or reduced pressure and can be appropriately selected.

[0096] At the end of the esterification step, the reaction system may be subjected to treatments such as washing with water and concentration, if necessary.

[0097] <Resin Varnish (First Aspect)> One aspect of the present invention relates to a resin varnish. Hereinafter, "a resin varnish according to one aspect of the present invention (first aspect)" may be abbreviated as "the present resin varnish 1." The present resin varnish 1 contains an ester group-containing carbonate resin according to one aspect of the present invention, an epoxy compound having two or more glycidyl ether groups, and a solvent. By containing these components, the present resin varnish 1 can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0098] The resin varnish 1 may contain a curing reaction catalyst. Furthermore, the resin varnish 1 may contain other components in addition to the ester group-containing carbonate resin according to one embodiment of the present invention, the epoxy compound having two or more glycidyl ether groups, the solvent, and the curing reaction catalyst. Each component contained in the resin varnish 1 will be described in detail below.

[0099] [Ester group-containing carbonate resin] The present carbonate resin contained in the present resin varnish 1 is the same as that described above. In the present resin varnish 1, the present carbonate resin mainly functions as an epoxy resin curing agent.

[0100] [Epoxy Compound] The epoxy compound is not particularly limited as long as it is an epoxy resin having two or more glycidyl ether groups. Examples of epoxy resins include phenol novolac epoxy resins, phenol-phenylene epoxy resins, orthocresol novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, biphenol epoxy resins, naphthalene epoxy resins, anthracene epoxy resins, naphthol epoxy resins, xylylene epoxy resins, biphenyl epoxy resins, triphenylmethane epoxy resins, dicyclopentadiene epoxy resins, stilbene epoxy resins, sulfur-containing epoxy resins, and phosphorus-containing epoxy resins. These epoxy resins may be used alone or in combination of two or more.

[0101] The content of the epoxy compound in the present resin varnish 1 can be appropriately selected so that the molar ratio of the glycidyl ether groups of the epoxy compound to the ester groups of the present carbonate resin, i.e., glycidyl ether groups (mol) / ester groups (mol), is the desired value. The higher this molar ratio, the lower the gelation temperature of the present resin varnish 1. This molar ratio is preferably 0.8 or higher, more preferably 0.9 or higher, and even more preferably 0.95 or higher. Furthermore, the lower this molar ratio, the higher the glass transition temperature, thermal decomposition temperature, linear expansion coefficient, dielectric constant, and dielectric dissipation factor of the cured product of the present resin varnish 1. This molar ratio is preferably 1.2 or lower, more preferably 1.1 or lower, and even more preferably 1.05 or lower.

[0102] 〔solvent〕 The solvent is not particularly limited as long as it can dissolve the components contained in the resin varnish 1, such as the carbonate resin, epoxy compound, and curing reaction catalyst. Typically, a polar solvent is used. Examples of polar solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, methyl propyl ketone, methyl amyl ketone, isophorone, diisobutyl ketone, diacetone alcohol, and cyclohexanone; N,N-dimethylformamide, N-methyl-2-pyrrolidone, methanol, ethanol, butanol, ethyl acetate, butyl acetate, methyl cellosolve, ethyl diglycol acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and tetrahydrofuran. The solvent is preferably a ketone-based solvent, more preferably methyl ethyl ketone. One type of solvent may be used alone, or two or more types may be mixed and used.

[0103] The content of the solvent in the present resin varnish 1 can be selected appropriately so that the solid content concentration of the present resin varnish 1 becomes the desired value. The solid content concentration of the present resin varnish 1 can be selected appropriately depending on the application of the present resin varnish 1. The solid content concentration of the present resin varnish 1 is, for example, preferably 20% by mass or more, more preferably 50% by mass or more. Furthermore, the solid content concentration of the present resin varnish 1 is, for example, preferably 80% by mass or less, more preferably 70% by mass or more. The solid content concentration of the present resin varnish 1 means the ratio of the mass of the present resin varnish 1 excluding the solvent to the total mass of the present resin varnish 1.

[0104] [Curing reaction catalyst] The curing catalyst is not particularly limited as long as it can catalyze the reaction between the ester group and the glycidyl ether group. Examples of the curing catalyst include phosphorus compounds, tertiary amines, imidazole compounds, organic acid metal salts, Lewis acids, and amine complex salts. Examples of the phosphorus compounds include triphenylphosphine, tris-2,6-dimethoxyphenylphosphine, tri-p-tolylphosphine, and triphenyl phosphite. Examples of the tertiary amines include dimethylaminopyridine, 2-dimethylaminomethylphenol, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo[5.4.0]undecene-7. 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. The curing reaction catalyst may be used alone or in combination of two or more.

[0105] The content of the curing reaction catalyst in the present resin varnish 1 is preferably 0.1% by mass or more and preferably 5.0% by mass or less relative to the content of the epoxy compound.

[0106] [Other ingredients] As long as the effects of the present invention are not impaired, other components can be appropriately selected depending on the application of the present resin varnish 1. Examples of other components include a curing agent for an epoxy resin other than the present carbonate resin, a filler, a flame retardant, a release agent, a surface treatment agent, a colorant, and a flexibility-imparting agent.

[0107] As the epoxy resin curing agent other than the carbonate resin, a conventionally known epoxy resin curing agent can be used, for example, a novolac type resin such as a phenol novolac resin.

[0108] Examples of fillers include carbon black, crystalline silica powder, fused silica powder, quartz glass powder, talc, calcium silicate powder, zirconium silicate powder, alumina powder, and calcium carbonate powder. The filler is preferably at least one of crystalline silica powder and fused silica powder. Examples of release agents include waxes such as carnauba wax. Examples of surface treatment agents include known silane coupling agents. Examples of colorants include carbon black. Examples of flexibility-imparting agents include silicone resins and butadiene-acrylonitrile rubber.

[0109] The content of other curing agents in the present resin varnish 1 is preferably 10% by mass or less, and more preferably 0% by mass, relative to the solid content of the present resin varnish 1. The solid content of the present resin varnish 1 is the mass of the present resin varnish 1 excluding the solvent.

[0110] <Resin varnish (second embodiment)> The resin varnish according to one embodiment of the present invention is not limited to the resin varnish described above. Hereinafter, the "resin varnish according to one embodiment of the present invention (second embodiment)" may be abbreviated as "the present resin varnish 2." The present resin varnish 2 contains the ester group-containing carbonate resin according to one embodiment of the present invention, a maleimide compound having two or more maleimide groups, and a solvent. By containing these components, the present resin varnish 2 can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0111] The resin varnish 2 may contain a curing reaction catalyst. Furthermore, the resin varnish 2 may contain other components in addition to the ester group-containing carbonate resin according to one embodiment of the present invention, the maleimide compound having two or more maleimide groups, the solvent, and the curing reaction catalyst. Each component contained in the resin varnish 2 will be described in detail below.

[0112] [Ester group-containing carbonate resin] The present carbonate resin contained in the present resin varnish 2 preferably has an allyl group. That is, in the present resin varnish 2, the present carbonate resin mainly functions as a maleimide curing agent.

[0113] [Maleimide Compound] The maleimide compound is not particularly limited as long as it has two or more maleimide groups, and examples of the maleimide compound include bismaleimide compounds and polyphenylmethanemaleimide.

[0114] Examples of bismaleimide compounds include 4,4'-diphenylmethane bismaleimide, alkyl bismaleimide, diphenylmethane bismaleimide, phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, and 1,3-bis(4-maleimidophenoxy)benzene. The bismaleimide compound may be commercially available. Examples of commercially available bismaleimide compounds include 4,4'-diphenylmethane bismaleimide (manufactured by Daiwa Chemical Industry Co., Ltd., trade name "BMI-1100"); bisphenol A diphenyl ether bismaleimide (manufactured by Daiwa Chemical Industry Co., Ltd., trade name "BMI-4000"); and 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide (manufactured by Daiwa Chemical Industry Co., Ltd., trade name "BMI-5100");

[0115] Polyphenylmethane maleimide is a polymer in which three or more benzene rings substituted with maleimide groups are bonded via methylene groups. Commercially available polyphenylmethane maleimides include those manufactured by Daiwa Chemical Industry Co., Ltd. under the trade name "BMI-2300."

[0116] These maleimide compounds may be used singly or in combination of two or more.

[0117] The content of the maleimide compound in the resin varnish 2 can be appropriately selected so that the molar ratio of maleimide groups of the maleimide compound to allyl groups of the carbonate resin, i.e., maleimide groups (mol) / allyl groups (mol), is the desired value. The higher this molar ratio, the lower the gelation temperature of the resin varnish 2. This molar ratio is preferably 0.50 or higher, more preferably 0.75 or higher, and even more preferably 0.95 or higher. Furthermore, the lower this molar ratio, the higher the glass transition temperature, thermal decomposition temperature, linear expansion coefficient, dielectric constant, and dielectric loss tangent of the cured product of the resin varnish 2. This molar ratio is preferably 2.00 or lower, more preferably 1.75 or lower, and even more preferably 1.50 or lower.

[0118] 〔solvent〕 The solvent is the same as that described above for the resin varnish according to one embodiment of the present invention (first embodiment), and therefore a description thereof will be omitted.

[0119] [Curing reaction catalyst] The curing reaction catalyst is not particularly limited as long as it can catalyze the reaction between the allyl group and the maleimide group. Examples of the curing reaction catalyst include imidazole compounds and organic peroxides. 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. Examples of organic peroxides include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters. In dialkyl peroxides, the alkyl group may be substituted with a phenyl group or the like. Examples of such dialkyl peroxides include dicumyl peroxide. The curing reaction catalysts may be used alone or in combination of two or more.

[0120] The content of the curing reaction catalyst in the present resin varnish 2 is preferably 0.1% by mass or more and preferably 5.0% by mass or less relative to the content of the maleimide compound.

[0121] [Other ingredients] The other components are the same as those described above for the resin varnish according to one embodiment of the present invention (first embodiment), and therefore a description thereof will be omitted.

[0122] <Resin varnish (another embodiment)> The resin varnish according to one embodiment of the present invention is not limited to the resin varnish described above. Hereinafter, "resin varnish according to one embodiment of the present invention (another embodiment)" may be abbreviated as "this other resin varnish." This other resin varnish may be a mixture of the resin varnish according to one embodiment of the present invention (first embodiment) and the resin varnish according to one embodiment of the present invention (second embodiment). That is, the resin varnish according to one embodiment of the present invention (another embodiment) contains the ester group-containing carbonate resin according to one embodiment of the present invention, an epoxy compound having two or more glycidyl ether groups, a maleimide compound having two or more maleimide groups, and a solvent. This allows the resin varnish according to one embodiment of the present invention to form a ternary cured product of the ester group-containing carbonate resin, the epoxy compound, and the maleimide compound, thereby allowing for a wider range of desired properties to be selected. The composition of this other resin varnish is similar to that of the resin varnish according to one embodiment of the present invention (first embodiment) and the resin varnish according to one embodiment of the present invention (second embodiment), and therefore a description thereof will be omitted.

[0123] <Laminate manufacturing method> One aspect of the present invention relates to a method for producing a laminate. Hereinafter, the "method for producing a laminate according to one aspect of the present invention" may be abbreviated as "the present production method." The present production method includes an impregnation step and a curing step. According to the present production method, a laminate exhibiting a low dielectric constant and a low dielectric loss tangent can be produced.

[0124] [Impregnation process] The impregnation step is a step of impregnating a fibrous substrate with the resin varnish according to one embodiment of the present invention (first embodiment) or the resin varnish according to one embodiment of the present invention (second embodiment). Hereinafter, "the resin varnish according to one embodiment of the present invention (first embodiment) or the resin varnish according to one embodiment of the present invention (second embodiment)" may be abbreviated as "the present resin varnish 1 or 2."

[0125] The resin varnish 1 or 2 can be impregnated into the fibrous substrate by any of the conventionally known impregnation methods.

[0126] In the impregnation step, examples of fibers contained in the fibrous substrate used as a raw material include inorganic fibers such as glass fiber, carbon fiber, ceramic fiber, and stainless steel fiber; natural fibers such as cotton, hemp, and paper; synthetic organic fibers such as polyester resin and polyamide resin; etc. One type of fibrous substrate may be used alone, or two or more types may be used in combination.

[0127] The shape of the fibrous substrate is not particularly limited, and examples thereof include staple fibers, yarns, mats, and sheets.

[0128] There are no particular limitations on the amount of the present resin varnish 1 or 2 impregnated into the fibrous substrate. For example, the amount may be such that the solid content of the present resin varnish 1 or 2 impregnated into the fibrous substrate is 30% by mass or more and 50% by mass or less.

[0129] In the impregnation step, after the fibrous substrate is impregnated with Resin Varnish 1 or 2, the fibrous substrate may be dried to such an extent that the solvent contained in Resin Varnish 1 or 2 is removed, thereby obtaining a prepreg. The drying temperature and drying time can be appropriately selected depending on the composition of Resin Varnish 1 or 2. The drying temperature is preferably 60°C or higher and preferably 250°C or lower. The drying time is preferably 30 seconds or longer and preferably 1 hour or shorter.

[0130] In the impregnation step, if necessary, a plurality of prepregs may be laminated, and if necessary, a metal foil may be further laminated on one or both sides of the prepreg or the laminate thereof.

[0131] [Curing process] The curing step is a step in which the fibrous substrate impregnated with the present resin varnish 1 or 2 is heated and pressurized to cure the present resin varnish 1 or 2, thereby obtaining a laminate.

[0132] The heating temperature and heating time when heating and pressurizing the fibrous substrate impregnated with Resin Varnish 1 or 2 can be appropriately selected depending on the composition of Resin Varnish 1 or 2. The heating temperature is preferably 60° C. or higher and preferably 250° C. or lower. The heating time is preferably 1 hour or higher and preferably 20 hours or lower.

[0133] The pressure when heating and pressing the fibrous substrate impregnated with the present resin varnish 1 or 2 can be appropriately selected depending on the desired thickness of the laminate. The pressure is preferably 2 kN / m 2 or more, preferably 20 kN / m 2 The following is the result.

[0134] [Configuration of laminate] The laminate obtained by this manufacturing method has a fiber-reinforced resin layer containing a fibrous base material and a cured product of the present resin varnish 1 or 2. The fiber-reinforced resin layer has excellent insulating properties because the cured product has a low dielectric constant and a low dielectric loss tangent. Furthermore, the fiber-reinforced resin layer has excellent heat resistance because the cured product has a high glass transition temperature, a high thermal decomposition temperature, and a low thermal expansion coefficient. The number of fiber-reinforced resin layers provided in the laminate may be one or two or more.

[0135] The laminate produced by this production method may further include layers other than the fiber-reinforced resin layer, such as a metal foil layer such as copper foil.

[0136] <Summary> A carbonate resin according to one embodiment of the present invention is a carbonate resin represented by formula (1), [ka] In the formula (1), n ​​is an integer of 1 or more, each Ar is independently a residue derived from a bisphenol compound or a biphenol compound, each of the n Rs is independently a residue derived from a bisphenol compound, a biphenol compound, or an alicyclic dimethanol compound, at least one R among the n Rs is the residue derived from the alicyclic dimethanol compound, and each of the two Xs in the formula (1) is an arylcarbonyl group, or one is an arylcarbonyl group and the other is a hydrogen atom. This makes it possible to provide a carbonate resin that can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0137] In one aspect of the present invention, the carbonate resin of formula (1) is such that, in formula (1), Ar are each independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), formula (R6), or formula (R6); n R are each independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), formula (R6), or formula (R7), and at least one R of the n R is a group represented by formula (R7); [ka] In the formula (R4), the formula (R5), and the formula (R6), p is 1 or 2, q is an integer of 0 to 2, and in the formula (R7), R 8 is more preferably an alicyclic group, which can reduce the production cost of the carbonate resin according to one embodiment of the present invention.

[0138] In one aspect of the present invention, in the carbonate resin of formula (1), each X is independently an arylcarbonyl group represented by formula (X1), formula (X2), or formula (X3), [ka] In the formulas (X1), (X2), and (X3), A, B, D, E, and G each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, or a halogen group, a and g each independently represent an integer from 0 to 5, b each independently represent an integer from 0 to 3, d and e each independently represent an integer from 0 to 4, and Z preferably represents a carbon-carbon single bond, -O-, -CO-, -CH-, -C(CH)-, or -SO-. This can enhance the reactivity with an epoxy compound, allowing the arylcarbonyl group to react with the hydroxyl group generated by cleavage of the epoxy.

[0139] A method for producing a carbonate resin according to one embodiment of the present invention includes an esterification step of reacting a carbonate resin derived from an aromatic diol compound and having at least two terminal phenolic hydroxyl groups with a carboxylic acid compound to esterify the phenolic hydroxyl groups, the carboxylic acid compound including at least a carboxylic acid halide. This allows the production of a carbonate resin that can form a cured product exhibiting a low dielectric constant and a low dielectric dissipation factor. This allows the production of a carbonate resin that can form a cured product exhibiting a low dielectric constant and a low dielectric dissipation factor.

[0140] In the method for producing a carbonate resin according to one aspect of the present invention, the carbonate resin preferably has a structure derived from an alicyclic dimethanol compound, thereby making it possible to produce a carbonate resin that can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0141] In the method for producing a carbonate resin according to one aspect of the present invention, in the esterification step, the molar ratio of the carboxylic acid compound to the amount of phenolic hydroxyl groups in the carbonate resin is preferably 0.5 or more and 2.0 or less, thereby enabling the production of a carbonate resin that can form a cured product exhibiting a lower dielectric constant and a lower dielectric loss tangent.

[0142] A method for producing a carbonate resin according to one aspect of the present invention preferably includes a step of reacting a carbonic acid diester, an alicyclic dimethanol compound, and at least one aromatic diol compound selected from the group consisting of bisphenol compounds and biphenol compounds to obtain the carbonate resin having a terminal phenolic hydroxyl group, thereby producing a carbonate resin having enhanced reactivity with epoxy groups at the terminal.

[0143] In a method for producing a carbonate resin according to one embodiment of the present invention, the step of obtaining the carbonate resin preferably includes a primary reaction step of reacting the carbonic acid diester with the alicyclic dimethanol compound to obtain a primary reaction product having a structure derived from at least one alicyclic dimethanol compound, and a secondary reaction step of reacting the primary reaction product with at least one aromatic diol compound selected from the group consisting of bisphenol compounds and biphenol compounds to obtain the carbonate resin having terminal phenolic hydroxyl groups. This allows for the successful production of a carbonate resin with enhanced terminal reactivity to epoxy groups.

[0144] In the method for producing a carbonate resin according to one aspect of the present invention, it is more preferable that in the primary reaction step, the molar ratio of the carbonic acid diester to the total amount of the alicyclic dimethanol compound and the aromatic diol compound is 1.05 or more and 3.00 or less, thereby further improving the dielectric properties.

[0145] A resin varnish according to an embodiment of the present invention includes the carbonate resin according to an embodiment of the present invention, an epoxy compound having two or more glycidyl ether groups, and a solvent. By including these components, the resin varnish according to an embodiment of the present invention can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0146] A resin varnish according to an embodiment of the present invention includes the carbonate resin according to an embodiment of the present invention, a maleimide compound having two or more maleimide groups, and a solvent. By including these components, the resin varnish according to an embodiment of the present invention can form a cured product exhibiting a low dielectric constant and a low dielectric loss tangent.

[0147] A method for producing a laminate according to one embodiment of the present invention includes an impregnation step of impregnating a fibrous substrate with the resin varnish according to one embodiment of the present invention, and a curing step of heating and pressurizing the fibrous substrate impregnated with the resin varnish to cure the resin varnish to obtain a laminate, thereby producing a laminate exhibiting a low dielectric constant and a low dielectric loss tangent.

[0148] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0149] An example of the present invention will be described below. In this example, an ester group-containing carbonate resin was produced. Then, a resin varnish containing the ester group-containing carbonate resin was produced. Next, a cured product was produced using the resin varnish, and the cured product was evaluated.

[0150] <Production of ester group-containing carbonate resin> Carbonate resins were prepared with and without ester groups.

[0151] Example 1 (Synthesis of Diallylbisphenol F) A 3-L reactor equipped with a thermometer, stirrer, and condenser was charged with 1000.0 g of bisphenol F (manufactured by Gun-ei Chemical Industry Co., Ltd., product name (BPF-SG)) and 800.0 g of methanol, and 480 g of sodium hydroxide was added in portions to prevent a large temperature rise. Next, 995.0 g of allyl chloride was added dropwise over 2 hours, while maintaining the system temperature at 35°C or below. After the dropwise addition, the reaction was continued for 2 hours at a system temperature of 35°C. The system temperature was then raised to 65°C, and the reaction was continued for 5 hours to convert bisphenol F into an allyl ether. Methanol was then removed from the system under reduced pressure, and the large amount of salt produced was removed by washing with water. The reaction solution after water washing was heated to 190°C under a nitrogen atmosphere and reacted for 5 hours to transfer the allyl groups, yielding diallyl bisphenol F. The obtained diallyl bisphenol F was liquid at room temperature, and its viscosity at 25°C was 0.8 Pa·s measured with an E-type viscometer.

[0152] (Primary reaction step) 214.2 g (1.0 mol) of diphenyl carbonate and 157.0 g (0.80 mol) of tricyclodecane dimethanol were placed in a 1 L reaction vessel equipped with a thermometer, a stirrer, and a condenser, and melt-mixed at a system temperature of 100° C. Next, 0.02 g of a 48% aqueous potassium hydroxide solution was added, and the system temperature was raised to 180° C. while taking care to avoid heat generation, and the reaction was carried out under normal pressure for 1 hour.

[0153] (Secondary reaction process) The system temperature was then cooled to 130°C, and 93.0 g (0.31 mol) of the resulting diallyl bisphenol F was added. The system temperature was raised to 180°C, and the reaction was carried out under normal pressure for 1 hour. The system temperature was then maintained at 180°C, and the pressure was slowly reduced to -10 mmHg. The system temperature was then raised to 220°C while still under reduced pressure, and the reaction was carried out under reduced pressure for 2 hours. The reaction solution was then washed with water and concentrated to obtain a carbonate resin having a terminal phenolic hydroxyl group.

[0154] (Esterification step) 100 g of carbonate resin and 14.4 g of benzoyl chloride were dissolved in toluene to a solids content of 50%. Next, 10.4 g of triethylamine was added dropwise over 2 hours while maintaining the system temperature at 30°C or below. The system was then allowed to react for 24 hours at 25°C to esterify the carbonate resin. The reaction solution was then washed with water and concentrated to obtain a resin solution containing ester group-containing carbonate resin 1 in toluene. Hereinafter, "ester group-containing carbonate resin 1" may be abbreviated as "carbonate resin 1."

[0155] Example 2 (Primary reaction step) The same operation as in the primary reaction step of Example 1 was carried out, except that 375.0 g (1.75 mol) of diphenyl carbonate was used instead of 214.2 g (1.0 mol) of diphenyl carbonate, 171.8 g (0.88 mol) of tricyclodecane dimethanol was used instead of 157.0 g (0.80 mol) of tricyclodecane dimethanol, and 0.04 g of 48% aqueous potassium hydroxide solution was used instead of 0.02 g of 48% aqueous potassium hydroxide solution.

[0156] (Secondary reaction process) The same operation as in the secondary reaction step of Example 1 was carried out, except that 213.6 g (1.07 mol) of bisphenol F (manufactured by Gun-ei Chemical Industry Co., Ltd., trade name (BPF-SG)) was used instead of 93.0 g (0.31 mol) of diallyl bisphenol F, to obtain a carbonate resin having a phenolic hydroxyl group at its terminal.

[0157] (Esterification step) The same operation as in the esterification step of Example 1 was carried out, except that 15.8 g of benzoyl chloride was used instead of 14.4 g of benzoyl chloride and 11.4 g of triethylamine was used instead of 10.4 g of triethylamine, to obtain a resin solution in toluene containing ester group-containing carbonate resin 2. Hereinafter, "ester group-containing carbonate resin 2" may be abbreviated as "carbonate resin 2."

[0158] Comparative Example 1 By carrying out the same operations as in the synthesis of diallyl bisphenol F, the first reaction step, and the second reaction step of Example 1, a carbonate resin C1 having a terminal phenolic hydroxyl group was obtained.

[0159] Comparative Example 2 By carrying out the same operations as in the first reaction step and the second reaction step of Example 2, a carbonate resin C2 having a terminal phenolic hydroxyl group was obtained.

[0160] <Analysis of carbonate resin> The molecular weight distributions of carbonate resins 1 and 2, and the molecular weight distributions, softening points, and melt viscosities of carbonate resins C1 and C2 were analyzed.

[0161] [Weight average molecular weight (Mw), number average molecular weight (Mn), dispersity (Mw / Mn)] Gel permeation chromatography (GPC) was used to analyze the molecular weight distribution of Carbonate Resin 1. The GPC conditions were as follows: GPC measuring device: Tosoh Corporation, product name "HLC-8120GPC" ("HLC" is a registered trademark of the company) Column: A column consisting of three connected columns (manufactured by Tosoh Corporation, product names "TSKgel G3000HHR", "TSKgel G2000HHR", and "TSKgel" are registered trademarks of the company).

[0162] The molecular weight distribution of carbonate resin 2, and carbonate resins C1 and C2 was analyzed in the same manner as for carbonate resin 1. Table 1 shows the weight average molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) of carbonate resins 1 and 2, and carbonate resins C1 and C2.

[0163] The ester group equivalent weights of carbonate resins 1 and 2 and the hydroxyl group equivalent weights of carbonate resins C1 and C2 are shown in Table 1. The equivalent weights were calculated based on the following formula. Equivalent weight (g / eq)=Mn / 2

[0164] [Softening point] The softening points of carbonate resins C1 and C2 were analyzed by a method in accordance with JIS K 6910. The softening points of carbonate resins C1 and C2 are shown in Table 1.

[0165] [Melt Viscosity] Using a melt viscometer (manufactured by Brookfield, product name "CAP2000 VISCOMETER"), the melt viscosity of carbonate resins C1 and C2 at 200°C was measured at a shear rate of 12.5 s -1 The melt viscosities of carbonate resins C1 and C2 are shown in Table 1.

[0166] [Solution viscosity] Using an E-type viscometer, the solution viscosity of the resin solution containing carbonate resin 1 of Example 1 was measured at a solution temperature of 25°C and a shear rate of 0.33 s -1 The evaluation was carried out under the following conditions: Shear rate 0.33 s -1 Instead, a shear rate of 0.05 s -1 The solution viscosity of the resin solution containing carbonate resin 2 of Example 2 was measured in the same manner as in Example 1, except that the above-mentioned procedure was changed to the following.

[0167] [Table 1]

[0168] <Manufacturing of resin varnish and film> A resin varnish containing the produced carbonate resin was produced, and a resin film and a cured product were produced using the resin varnish.

[0169] [Raw materials] The following epoxy resins were used as raw materials for producing the resin varnish. Epoxy resin 1: orthocresol novolac epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "EOCN1020", epoxy group equivalent: 199 g / eq) Epoxy resin 2: phenol biphenylene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-3000H", epoxy group equivalent: 290 g / eq) Epoxy resin 3: Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "Epikote 828", epoxy group equivalent: 208 g / eq)

[0170] [Resin varnish 1] The resin solution in an amount sufficient to give 100 g of solids, i.e., carbonate resin 1 of Example 1, 16.3 g of epoxy resin 1, and dimethylaminopyridine as a catalyst in an amount equivalent to 0.5 mass% of the solid content of these resins, were dissolved in methyl ethyl ketone as a solvent and mixed to produce resin varnish 1 with a solid content of 50 wt%.

[0171] [Film 1] Resin varnish 1 was applied to a PET film and pre-dried in an oven at 80° C. for 1 hour. The temperature was then raised to 180° C. over 1 hour, and the film was dried at 180° C. for 5 hours to obtain film 1.

[0172] [Film 2] Film 2 was obtained in the same manner as in Film 1, except that 23.7 g of Epoxy Resin 2 was used instead of 16.3 g of Epoxy Resin 1.

[0173] [Film 3] Resin varnish 2 was produced using a resin solution containing 91.6 g of carbonate resin 2 as solid content instead of 100 g of carbonate resin 1, and film 3 was obtained by performing the same operations as for film 1 except that resin varnish 2 was used.

[0174] [Film 4] Film 4 was obtained in the same manner as in Film 3, except that 23.7 g of Epoxy Resin 2 was used instead of 16.3 g of Epoxy Resin 1.

[0175] [Film 5] Film 5 was obtained in the same manner as in Film 3, except that 17.0 g of Epoxy Resin 3 was used instead of 16.3 g of Epoxy Resin 1.

[0176] [Film C1] As a comparative example, 100 g of carbonate resin C1, 25.0 g of epoxy resin 2, and triphenylphosphine (2.0 mass % of the solid content of these resins) were dissolved in methyl ethyl ketone and mixed to produce resin varnish C1 with a solid content of 60 wt %. Resin varnish C1 was applied to a PET film and pre-dried in an oven at 80°C for 1 hour. The temperature was then raised to 180°C over 1 hour and dried at 180°C for 5 hours to obtain film C1.

[0177] [Film C2] As a comparative example, film C2 was obtained by the same procedure as film C1, except that 87.6 g of carbonate resin C2 was used instead of 100 g of carbonate resin C1 and 15.6 g of epoxy resin 3 was used instead of 25.0 g of epoxy resin 2.

[0178] <Film Analysis> The glass transition temperature, 5% thermal decomposition temperature, room temperature linear expansion coefficient, and dielectric properties of Films 1 to 5 and Films C1 and C2 were analyzed.

[0179] [Glass transition temperature] Film 1 was processed to a size of 10.0 mm wide x 5.5 mm long x 0.05 mm thick to prepare a measurement sample. For this measurement sample, tan δ (loss factor) was measured in the range of 30°C to 400°C at a frequency of 10 Hz and a heating rate of 2°C / min using a viscoelasticity measuring device (manufactured by Hitachi High-Tech Science Corporation, product name "DMA7100"), and the glass transition temperature Tg was calculated from the measured tan δ.

[0180] The glass transition temperatures Tg of Films 2 to 5 and Films C1 and C2 were determined in the same manner as for Film 1. Table 2 shows the glass transition temperatures Tg of Films 1 to 5 and Films C1 and C2.

[0181] [5% pyrolysis temperature] Film 1 was pulverized to prepare a measurement sample. The thermal weight loss of this measurement sample was measured in an air atmosphere at a temperature increase rate of 10°C / min in the range of 30 to 800°C using a simultaneous differential thermal and thermogravimetric analyzer (manufactured by Seiko Instruments Inc., product name "TG / DTA6300"), and the 5% thermal decomposition temperature was determined.

[0182] The 5% thermal decomposition temperatures of Films 2 to 5 and Films C1 and C2 were determined in the same manner as for Film 1. Table 2 shows the 5% thermal decomposition temperatures of Films 1 to 5 and Films C1 and C2.

[0183] [Room temperature linear expansion coefficient] Film 1 was processed to a size of 5.0 mm wide x 5.0 mm long x 0.05 mm thick to prepare a measurement sample. The thermal expansion of this measurement sample was measured in the range of 30°C to 400°C at a temperature increase rate of 2°C / min using a thermomechanical analyzer (manufactured by Hitachi High-Tech Science Corporation, product name "TMA7100") to determine the room-temperature linear expansion coefficient. The room-temperature linear expansion coefficient refers to the linear expansion coefficient at 30°C.

[0184] The room temperature linear expansion coefficients of Films 2 to 5 and Films C1 and C2 were also determined in the same manner as Film 1. Table 2 shows the room temperature linear expansion coefficients of Films 1 to 5 and Films C1 and C2.

[0185] [Dielectric properties] Film 1 was processed to a size of 3.0 mm wide x 50.0 mm long x 0.05 mm thick to be used as a measurement sample. The relative dielectric constant ε of this measurement sample at a frequency of 10 GHz was measured by the cavity resonance perturbation method. r , and the dielectric tangent tanδ were calculated.

[0186] As with Film 1, Films 2 to 5 and Films C1 and C2 also have a relative dielectric constant ε r The dielectric constant ε of films 1 to 5 and films C1 and C2 was calculated.r , and the dielectric tangent tanδ are shown in Table 2.

[0187] [Table 2]

[0188] As shown in Table 2, carbonate resins 1 and 2 could be used as curing agents to form cured products, ie, films 1 to 5, that exhibited low dielectric constants and low dielectric loss tangents.

[0189] Furthermore, as shown in Table 1, carbonate resins 1 and 2 had a large ester group equivalent of 1000 g / eq or more, and although the number of ester groups per number average molecular weight of the carbonate resin was low, carbonate resins 1 and 2 were able to form cured products exhibiting low dielectric constants and low dielectric dissipation factors. [Industrial Applicability]

[0190] The ester group-containing carbonate resin according to one embodiment of the present invention can be used in a wide range of applications, such as semiconductor encapsulation materials, electrical insulating materials, resins for copper-clad laminates, resists, encapsulation resins for electronic components, resins for liquid crystal color filters, paints, various coating agents, adhesives, build-up laminate materials, and FRP.

Claims

1. A carbonate resin represented by formula (1): 【Chemistry 1】 In the formula (1), n is an integer of 1 or more, Ar each independently represents a residue derived from a bisphenol compound or a residue derived from a biphenol compound; n R's each independently represent a residue derived from a bisphenol compound, a residue derived from a biphenol compound, or a residue derived from an alicyclic dimethanol compound; At least one R among n R's is a residue derived from the alicyclic dimethanol compound, In the formula (1), each of the two Xs is an arylcarbonyl group, or one of the Xs is an arylcarbonyl group and the other is a hydrogen atom. Carbonate resin.

2. In the formula (1), Ar is each independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), or formula (R6), n R's are each independently a group represented by formula (R1), formula (R2), formula (R3), formula (R4), formula (R5), formula (R6), or formula (R7), At least one R among n R is a group represented by formula (R7), 【Chemistry 2】 In the formula (R4), the formula (R5), and the formula (R6), p is 1 or 2; q is an integer from 0 to 2, In the formula (R7), R ８ is an alicyclic group, The carbonate resin according to claim 1.

3. In the formula (1), X's are each independently an arylcarbonyl group represented by formula (X1), formula (X2), or formula (X3), 【Chemistry 3】 In the formula (X1), the formula (X2), and the formula (X3), A, B, D, E, and G each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, or a halogen group; a and g are each independently an integer from 0 to 5; b is an integer from 0 to 3; d and e each independently represent an integer from 0 to 4; Z is a single bond between carbon atoms, -O-, -CO-, or -CH ２ -, -C(CH ３ ) ２ - or -SO ２ - is, The carbonate resin according to claim 1 or 2.

4. a carbonate resin derived from an aromatic diol compound and having at least two terminal phenolic hydroxyl groups; an esterification step of reacting the phenolic hydroxyl group with a carboxylic acid compound to esterify the phenolic hydroxyl group, The carboxylic acid compound includes at least a carboxylic acid halide, The carbonate resin is a carbonate resin represented by formula (1), 【Chemistry 4】 In the formula (1), n is an integer of 1 or more, Ar each independently represents a residue derived from a bisphenol compound or a residue derived from a biphenol compound; n R's each independently represent a residue derived from a bisphenol compound, a residue derived from a biphenol compound, or a residue derived from an alicyclic dimethanol compound; At least one R among n R's is a residue derived from the alicyclic dimethanol compound, In the formula (1), each of the two Xs is an arylcarbonyl group, or one of the Xs is an arylcarbonyl group and the other is a hydrogen atom. A method for producing carbonate resin.

5. The method for producing a carbonate resin according to claim 4, wherein the carbonate resin has a structure derived from an alicyclic dimethanol compound.

6. In the esterification step, the molar ratio of the carboxylic acid compound to the amount of the phenolic hydroxyl group in the carbonate resin is 0.5 or more and 2.0 or less; The method for producing the carbonate resin according to claim 4 or 5.

7. Carbonic acid diester, an alicyclic dimethanol compound; a step of reacting a carbonate resin having a phenolic hydroxyl group at a terminal thereof with at least one aromatic diol compound selected from the group consisting of a bisphenol compound and a biphenol compound, The method for producing the carbonate resin according to any one of claims 4 to 6.

8. The step of obtaining the carbonate resin includes: a primary reaction step of reacting the carbonic acid diester with the alicyclic dimethanol compound to obtain a primary reaction product having at least one structure derived from the alicyclic dimethanol compound; a secondary reaction step of reacting the primary reaction product with at least one aromatic diol compound selected from the group consisting of the bisphenol compounds and the biphenol compounds to obtain the carbonate resin having a phenolic hydroxyl group at its terminal; The method for producing a carbonate resin according to claim 7, comprising the steps of:

9. 9. The method for producing a carbonate resin according to claim 8, wherein in the first reaction step, a molar ratio of the carbonate diester to a total amount of the alicyclic dimethanol compound and the aromatic diol compound is 1.05 or more and 3.00 or less.

10. A resin varnish comprising the carbonate resin according to any one of claims 1 to 3, an epoxy compound having two or more glycidyl ether groups, and a solvent.

11. A resin varnish comprising the carbonate resin according to any one of claims 1 to 3, a maleimide compound having two or more maleimide groups, and a solvent.

12. An impregnation step of impregnating a fibrous substrate with the resin varnish according to claim 10 or 11; a curing step of heating and pressurizing the fibrous substrate impregnated with the resin varnish to cure the resin varnish to obtain a laminate; The method for producing a laminate includes the steps of:

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