JP7719658B2 - Allyl group-containing polycarbonate resin and curable resin composition - Google Patents

Description

The present invention relates to an allyl group-containing polycarbonate resin that exhibits a low dielectric constant and a low dielectric dissipation factor. The present invention also relates to a curable resin composition that exhibits a low dielectric constant and a low dielectric dissipation factor and uses an allyl group-containing polycarbonate resin as a curing agent.

Mobile wireless communication services, typified by mobile phones, which were previously used for voice calls, are now being used as a means of accessing the Internet thanks to advances in communication and information processing technology. Furthermore, communication between machines and objects, rather than between people, is about to begin full-scale operation for purposes of control, sensing, and monitoring. To address the significant increase in network traffic, the next-generation wireless communication standard, 5G systems (hereinafter referred to as 5G), has begun operation. While previous communication systems (e.g., 4G LTE) have used low-frequency bands below 2.5 GHz, 5G will use high-frequency bands above 6 GHz. Therefore, future 5G-compatible devices will need to be compatible with high-frequency signals. For example, reducing transmission loss is one of the high-frequency countermeasures for printed circuit boards (hereinafter referred to as PCBs). Transmission loss here refers to conductor loss originating in the conductors (e.g., copper circuits) that make up the PCB, and dielectric loss originating in the dielectric (insulating material surrounding the circuit). While smoothing the conductor surface is one way to address the former, it is difficult to expect significant improvement. Therefore, the latter measure is important, and specifically, because dielectric loss depends on the frequency of the current and the dielectric constant and dielectric dissipation factor of the insulating material around the circuit, there is a demand for lower dielectric constant insulating materials. In addition, there is a need for insulating materials that combine the same processability and physical properties (e.g., heat resistance, adhesiveness, insulating properties, etc.) as conventional circuit board materials.

PCBs are divided into package substrates located directly under chips such as mobile processors; rigid mainboard substrates on which package substrates are mounted; and flexible printed circuit boards used for LCD drivers, camera modules, and film antennas. These insulating materials are made of thermosetting resins, whose composition consists of (i) thermosetting and crosslinking components such as epoxy resins and maleimide resins; (ii) filler components that impart flame retardancy, heat resistance, and a low linear expansion coefficient; and (iii) polymers used to improve flexibility and adhesion. Polymers used as PCB insulating materials generally require heat resistance, adhesion, processability, flexibility, and compatibility. Conventional polymers for PCBs include carboxyl-modified acrylonitrile-butadiene copolymer rubber, acrylic polymers, and urethane polymers. However, none of these materials possess the low dielectric properties required for high-frequency applications, and new materials are currently needed.

Therefore, curable resin compositions containing a specified amount of polycarbonate resin have been investigated to reduce dielectric constant and improve flexibility and adhesion. For example, Patent Document 1 discloses a resin composition containing an epoxy resin, a curing agent, a polycarbonate resin, and an inorganic filler. However, adding polycarbonate resin to a curable resin composition results in incompatibility during curing, making it difficult to achieve the desired effect of adding polycarbonate resin and limiting the amount that can be added. Patent Documents 2, 3, and 4 also disclose methods of adding an allyl group-containing aliphatic polycarbonate resin to a curable resin composition. However, while the inclusion of an allyl group improves the compatibility of the curable resin composition, copolymerizing an aliphatic diol increases the dielectric tangent, which is an issue.

Japanese Patent Application Laid-Open No. 2019-35056 Japanese Patent Application Laid-Open No. 2019-89965 Japanese Patent Application Laid-Open No. 2019-89966 Japanese Patent Application Laid-Open No. 2019-89967

An object of the present invention is to provide a polycarbonate resin that exhibits a low dielectric constant and a low dielectric dissipation factor. Another object of the present invention is to provide a curable resin composition containing the polycarbonate resin that exhibits a low dielectric constant and a low dielectric dissipation factor, and a cured product thereof.

After extensive research, the inventors surprisingly discovered that the above objectives could be achieved by using an allyl group-containing polycarbonate resin containing specific structural units. Further investigations based on this finding led to the completion of the present invention.

That is, according to the present invention, the following (Configuration 1) to (Configuration 7) are provided.
(Configuration 1)
A polycarbonate resin comprising a structural unit (A) represented by the following formula (1), wherein the proportion of the structural unit (A) in all structural units is 70 mol % or more, and wherein the following (a) to (c) are satisfied:
(a) the weight average molecular weight of the polycarbonate resin measured by gel permeation chromatography is in the range of 15,000 to 45,000;
(b) the relative dielectric constant of the polycarbonate resin at a frequency of 10 GHz measured in accordance with a cavity resonator perturbation method is in the range of 2.3 to 2.7, and the dielectric loss tangent is in the range of 0.0001 to 0.0030;
(c) The terminal structure of the polycarbonate resin contains a structure (B) derived from a monohydroxy compound represented by the following formula (2), and accounts for 10 mol % or more of all terminal structures constituting the polycarbonate resin:

(In formula (1), _R1 and _R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms; _R3 and _R4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms; and X represents a single bond, a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, a substituted or unsubstituted alkylidene group having 2 to 20 carbon atoms, a substituted or unsubstituted sulfur atom, or an oxygen atom.)

(In formula (2), _R5 is a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms, a linear or branched alkoxy group having 1 to 10 carbon atoms, or a linear or branched phenyl-substituted alkyl group having 1 to 20 carbon atoms, and _R6 is an allyl group having 3 to 20 carbon atoms.)

(Configuration 2)
The polycarbonate resin according to claim 1, wherein X in the formula (1) is at least one group selected from the group consisting of the following formula (3):

( _R7 and _R8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, and Z represents a substituted or unsubstituted alkylene group having 4 to 12 carbon atoms.)

(Configuration 3)
3. The polycarbonate resin according to claim 1, wherein the proportion of the structural unit (A) in all structural units of the polycarbonate resin is 90 mol % or more.
(Configuration 4)
The polycarbonate resin according to any one of configurations 1 to ₃ , wherein R ₁ and R ₂ in formula (1) are each at least one group selected from the group consisting of a methyl group, an isopropyl group, a tert-butyl group, a cyclohexyl group, and a phenyl group, and R ₃ and R 4 are each a hydrogen atom or a methyl group.
(Configuration 5)
5. The polycarbonate resin according to any one of configurations 1 to 4, wherein the polycarbonate resin is a polycarbonate resin produced by an interfacial polycondensation method between a dihydroxy compound and carbonyl chloride.
(Configuration 6)
A curable resin composition comprising the polycarbonate resin according to any one of Configurations 1 to 5, a maleimide compound, and an inorganic filler.
(Configuration 7)
7. The resin composition according to claim 6, which is for forming an insulating layer of a printed wiring board.

The allyl group-containing polycarbonate resin of the present invention exhibits a low dielectric constant and a low dielectric dissipation factor, and curable resin compositions using such allyl group-containing polycarbonate resins as curing agents can produce cured products with a low linear expansion coefficient and high strength, making them suitable for use as materials for high-frequency substrates.

The details of the present invention are explained below.

<Polycarbonate resin>
The polycarbonate resin of the present invention contains a structural unit (A) represented by the following formula (1).

In formula (1), _R1 and _R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms; and _R3 and _R4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

Examples of the substituted or unsubstituted alkyl group having 1 to 6 carbon atoms for _R1 and _R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a sec-pentyl group, and an n-hexyl group. Examples of the substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms include a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of the substituted or unsubstituted aryl group having 6 to 20 carbon atoms include a phenyl group, a benzyl group, a tolyl group, a 4-methylphenyl group, and a naphthyl group.

Among these, R ₁ and R ₂ are preferably a methyl group, an isopropyl group, a tert-butyl group, a cyclohexyl group or a phenyl group, and particularly preferably a methyl group.

Examples of the substituted or unsubstituted alkyl group having 1 to 6 carbon atoms for _R3 and _R4 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a sec-pentyl group, and an n-hexyl group. Examples of the substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms include a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of the substituted or unsubstituted aryl group having 6 to 20 carbon atoms include a phenyl group, a benzyl group, a tolyl group, a 4-methylphenyl group, and a naphthyl group.

Among these, _R3 and _R4 are preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or a 4-methylphenyl group, and particularly preferably a hydrogen atom or a methyl group. Here, the bonding positions of _R1 , _R2 , _R3 , and _R4 in formula (1) are any positions selected from the 2-, 3-, 5-, and 6-positions relative to X on the respective phenyl rings, and preferably the 3- and 5-positions.

In formula (1), X represents a single bond, a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, a substituted or unsubstituted alkylidene group having 2 to 20 carbon atoms, a substituted or unsubstituted sulfur atom, or an oxygen atom. Examples of the substituted or unsubstituted sulfur atom include -S- and _-SO2- . The substituted or unsubstituted alkylidene group is preferably at least one group selected from the group consisting of the following formula (3):

_R7 and _R8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, and Z represents a substituted or unsubstituted alkylene group having 4 to 12 carbon atoms.

Examples of the substituted or unsubstituted alkyl group having 1 to 20 carbon atoms for _R7 and _R8 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a sec-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, etc. Examples of the substituted or unsubstituted aryl group having 6 to 20 carbon atoms include a phenyl group, a benzyl group, a tolyl group, a 4-methylphenyl group, a naphthyl group, etc.

Among these, R ₇ and R ₈ are preferably a methyl group, an ethyl group, an n-propyl group or a 4-methylphenyl group, and particularly preferably a methyl group.

In formula (1), Z bonds to the carbon atom connecting the two phenyl groups to form a substituted or unsubstituted divalent carbocyclic ring. Examples of divalent carbocyclic rings include cycloalkylidene groups (preferably having 5 to 8 carbon atoms) such as cyclopentylidene, cyclohexylidene, cycloheptylidene, cyclododecylidene, and adamantylidene. Substituted versions of these include those having a methyl or ethyl substituent. Among these, methyl-substituted cyclohexylidene and cyclohexylidene groups are preferred.

The polycarbonate resin of the present invention must contain the structural unit (A) represented by formula (1). The proportion of the structural unit (A) in all structural units of the polycarbonate resin is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. If the structural unit (A) of formula (1) is less than 70 mol%, the dielectric properties will be inferior, which is not preferred.

The polycarbonate resin used in the present invention can typically be obtained by reacting a dihydroxy compound with a carbonyl compound. Examples of reaction methods include interfacial polycondensation, melt transesterification, solid-phase transesterification of carbonate prepolymers, and ring-opening polymerization of cyclic carbonate compounds. In the case of interfacial polycondensation, a monohydric phenol end-stopper is typically used. Alternatively, the polycarbonate may be a branched polycarbonate obtained by polymerizing a trifunctional component, or a copolymer polycarbonate obtained by copolymerizing an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and a vinyl monomer.

The polycarbonate resin of the present invention is produced by known reaction methods used to produce ordinary polycarbonate resins, such as reacting a dihydroxy compound with a carbonyl compound such as phosgene or a carbonate diester. The basic means for these production methods will be briefly explained below.

Reactions using carbonyl chloride (phosgene) as a carbonyl compound are usually carried out in the presence of an acid binder and a solvent. Examples of acid binders include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, or amine compounds such as pyridine. Examples of solvents include halogenated hydrocarbons such as methylene chloride and chlorobenzene. A catalyst such as a tertiary amine or quaternary ammonium salt can also be used to promote the reaction. The reaction temperature is usually 0 to 40°C, and the reaction time is between a few minutes and 5 hours.

The polycarbonate resin of the present invention contains structure (B) derived from a monohydroxy compound represented by the following formula (2), which is used as a terminal terminator in the polymerization reaction.

In formula (2), _R5 is a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms, a linear or branched alkoxy group having 1 to 10 carbon atoms, or a linear or branched phenyl-substituted alkyl group having 1 to 20 carbon atoms, and _R6 is an allyl group having 3 to 20 carbon atoms. Here, the bonding position of _R6 in formula (2) is any position selected relative to the OH group on each phenyl ring, and preferably the ortho position.

Specific examples of the monohydroxy compound include 2-allylphenol, chavicol, and eugenol. These may be used alone or in combination.

The terminal structures derived from these monohydroxy compounds account for 10 mol% or more, preferably 30 mol% or more, and more preferably 50 mol% or more of all terminal structures constituting the resulting polycarbonate resin.

The polycarbonate resin of the present invention can also be used in combination with commonly used monofunctional phenols as end-capping agents. In particular, in reactions using phosgene as the carbonate precursor, monofunctional phenols are commonly used as end-capping agents to adjust molecular weight. Furthermore, because the resulting polycarbonate resin has its ends blocked with groups based on monofunctional phenols, it has superior thermal stability compared to polycarbonate resins that are not.

Such monofunctional phenols may be any that can be used as end-terminators for polycarbonate resins, and are generally phenol or lower alkyl-substituted phenols, such as the monofunctional phenols represented by the following formula (4):

In formula (4), A is a linear or branched alkyl group or arylalkyl group having 1 to 9 carbon atoms, and r is an integer from 1 to 5, preferably an integer from 1 to 3.

Specific examples of the monofunctional phenols include phenol, p-tert-butylphenol, p-cumylphenol, and isooctylphenol.

Other monofunctional phenols that can be used include phenols or benzoic acid chlorides having a long-chain alkyl group or aliphatic ester group as a substituent, or long-chain alkylcarboxylic acid chlorides. When these are used to cap the ends of polycarbonate polymers, they not only function as end terminators or molecular weight regulators, but also improve the melt fluidity of the resin, facilitating molding and processing. They also have the effect of lowering the physical properties of the molded product, particularly the water absorption rate of the resin, and are also effective in reducing the birefringence of the molded product, making them preferred. Among these, phenols having a long-chain alkyl group as a substituent, represented by the following formulas (5) and (6), are preferred.

In formula (6), Z is -R-O-, -R-CO-O-, or -R-O-CO-, where R represents a single bond or a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, and n represents an integer from 10 to 50.

The substituted phenols of formula (5) are preferably those in which n is 10 to 30, and particularly preferably 10 to 26. Specific examples include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, and triacontylphenol.

Furthermore, as the substituted phenols of formula (6), compounds in which Z is -R-CO-O- and R is a single bond are preferred, and those in which n is 10 to 30, particularly 10 to 26, are preferred. Specific examples include decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate, and triacontyl hydroxybenzoate.

These monofunctional phenols can be used in an amount of up to 90 mol% of all terminal groups in the resulting polycarbonate resin. Furthermore, the monofunctional phenols may be used alone or in combination with two or more types.

Furthermore, the amount of terminal OH groups relative to all structural units of the polycarbonate resin is preferably 300 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less. A content of 300 ppm or less results in excellent thermal stability.

Reactions using the melt polymerization method are typically transesterification reactions between dihydric phenols and carbonate esters. They are carried out by mixing dihydric phenols and carbonate esters while heating them in the presence of an inert gas, and then distilling off the resulting alcohol or phenol. The reaction temperature varies depending on the boiling point of the resulting alcohol or phenol, but is usually in the range of 120 to 350°C. Toward the latter stage of the reaction, the system is reduced in pressure to approximately 10 to 0.1 Torr (1,300 Pa to 13 Pa) to facilitate the distillation of the resulting alcohol or phenol. The reaction time is usually around 1 to 4 hours.

Carbonate esters include esters of aryl groups or aralkyl groups having 6 to 10 carbon atoms, which may have a substituent, or alkyl groups having 1 to 4 carbon atoms. Specific examples include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, and dibutyl carbonate, with diphenyl carbonate being preferred.

In addition, a polymerization catalyst can be used to increase the polymerization rate. Examples of such polymerization catalysts include alkali metal compounds such as sodium hydroxide, potassium hydroxide, and sodium and potassium salts of dihydric phenols; alkaline earth metal compounds such as calcium hydroxide, barium hydroxide, and magnesium hydroxide; nitrogen-containing basic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylamine, and triethylamine; alkali metal and alkaline earth metal alkoxides; alkali metal and alkaline earth metal organic acid salts; and other catalysts typically used in esterification and transesterification reactions, such as zinc compounds, boron compounds, aluminum compounds, silicon compounds, germanium compounds, organotin compounds, lead compounds, osmium compounds, antimony compounds, manganese compounds, titanium compounds, and zirconium compounds. The catalysts may be used alone or in combination of two or more. The amount of these polymerization catalysts used is preferably selected from the range of 1×10 ⁻⁸ to 1×10 ⁻³ equivalents, more preferably 1×10 ⁻⁷ to 5×10 ⁻⁴ equivalents, per mole of the dihydric phenol as the raw material.

In addition to the terminal structure (B) described above, in this polymerization reaction, in order to reduce the number of phenolic terminal groups, it is preferable to add compounds such as bis(chlorophenyl)carbonate, bis(bromophenyl)carbonate, bis(nitrophenyl)carbonate, bis(phenylphenyl)carbonate, chlorophenylphenylcarbonate, bromophenylphenylcarbonate, nitrophenylphenylcarbonate, phenylphenylcarbonate, methoxycarbonylphenylphenylcarbonate, and ethoxycarbonylphenylphenylcarbonate during the latter stages of the polycondensation reaction or after its completion. Of these, 2-chlorophenylphenylcarbonate, 2-methoxycarbonylphenylphenylcarbonate, and 2-ethoxycarbonylphenylphenylcarbonate are preferred, with 2-methoxycarbonylphenylphenylcarbonate being particularly preferred.

In the polycarbonate resin of the present invention, the proportion of structural units (A) among all structural units is 70 mol % or more, but it is not particularly problematic if structural units (C) derived from other dihydroxy components or diol components are contained within a range that does not impair the effects of the present invention, for example, 30 mol % or less, preferably 20 mol % or less, and more preferably 10 mol % or less of all structural units.

Examples of such dihydroxy components include hydroquinone, resorcinol, 4,4'-biphenol, 4,4'-bis(2,6-dimethyl)diphenol, 2,4'-dihydroxydiphenylmethane, bis(2-hydroxyphenyl)methane, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)cyclohexylmethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxy-2-chlorophenyl)ethane, 2,2-bis(4-hydroxyphenyl)-1-phenylpropane, 1,1-bis(4-hydroxyphenyl)decane, 1,1-bis(4-hydroxyphenyl)decane, 1,1-bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)-1-phenylprop ... Examples of suitable hydroxyphenyl compounds include 4,4'-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4'-(p-phenylenediisopropylidene)diphenol, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxyphenyl)-4-isopropylcyclohexane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, and 4,4'-dihydroxydiphenyl sulfide. These compounds can be used alone or in combination of two or more.

Diol components include, for example, isosorbide:1,4:3,6-dianhydro-D-sorbitol, tricyclodecane dimethanol (TCDDM), 4,8-bis(hydroxymethyl)tricyclodecane, tetramethylcyclobutanediol (TMCBD), 2,2,4,4-tetramethylcyclobutane-1,3-diol, mixed isomers, cis/trans-1,4-cyclohexanedimethanol (CHDM), cis/trans-1,4-bis(hydroxymethyl)cyclohexane, cyclohex-1,4-yl enediol, and cyclohex-1,4-yl enediol. Examples include methanol, trans-1,4-cyclohexanedimethanol (tCHDM), trans-1,4-bis(hydroxymethyl)cyclohexane, cis-1,4-cyclohexanedimethanol (cCHDM), cis-1,4-bis(hydroxymethyl)cyclohexane, cis-1,2-cyclohexanedimethanol, 1,1'-bi(cyclohexyl)-4,4'-diol, spiroglycol, dicyclohexyl-4,4'-diol, 4,4'-dihydroxybicyclohexyl, and poly(ethylene glycol).

(Characteristics of polycarbonate resin)
The number-average molecular weight and weight-average molecular weight of the polycarbonate resin of the present invention can be measured by gel permeation chromatography using standard polystyrene as the standard. The weight-average molecular weight of the polycarbonate resin of the present invention is in the range of 15,000 to 45,000, preferably 18,000 to 40,000, more preferably 20,000 to 35,000, and even more preferably 23,000 to 33,000. Within this range, compatibility with maleimide compounds is improved, the strength of the cured resin composition is improved, and the resin exhibits a low dielectric constant and a low dielectric dissipation factor. The number-average molecular weight of the polycarbonate resin of the present invention is also preferably in the range of 5,000 to 15,000, more preferably 8,000 to 14,000, and even more preferably 9,000 to 12,000.

The polycarbonate resin used in the present invention has a relative dielectric constant at a frequency of 10 GHz, measured by a perturbation method using a cavity resonator, in the range of 2.3 to 2.7, preferably 2.40 to 2.66. Furthermore, the dielectric dissipation factor at a frequency of 10 GHz, measured by the same method, is in the range of 0.0001 to 0.0030, preferably 0.0005 to 0.0025. Relative dielectric constant and dielectric dissipation factor within the above ranges are preferred because they reduce the dielectric loss of the insulating material.

The allyl group equivalent of the polycarbonate resin used in the present invention is preferably 50 to 1,000 eq/ton, more preferably 100 to 700 eq/ton, even more preferably 150 to 500 eq/ton, and particularly preferably 170 to 300 eq/ton. When the allyl group equivalent is equal to or greater than the lower limit, the dielectric properties are superior. When the allyl group equivalent is equal to or less than the upper limit, the reactivity with maleimide compounds is superior.

(Curable resin composition)
The polycarbonate resin used in the present invention has an allyl group, and therefore can be used as a curing agent (maleimide curing agent) for curing a maleimide compound, which can be cured by heating.

In addition, the cured product obtained by curing a maleimide compound with the polycarbonate resin of the present invention exhibits a high glass transition temperature, high thermal decomposition temperature, and low coefficient of linear thermal expansion due to the use of the maleimide compound.

The curable resin composition of the present invention contains a polycarbonate resin. Polycarbonate resin has excellent impact resistance and therefore excellent mechanical strength. As a result, it acts to increase the toughness of the cured product.

The content of the polycarbonate resin component, when the resin component of the resin composition is taken as 100% by weight, is preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 2% by weight or more. The upper limit is preferably 30% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less. By keeping the content of the polycarbonate resin component within the above range, the toughness of the cured product can be improved.

Furthermore, because the polycarbonate resin of the present invention is used, the cured product obtained from the curable resin composition of the present invention has a lower dielectric constant and lower dielectric dissipation factor than cured products obtained by curing a maleimide compound with an allylphenol resin or cured products obtained by curing an epoxy resin with a phenol novolac resin.

When the maleimide compound is cured using the polycarbonate resin of the present invention, it is believed that the following reactions (1) to (3) occur to cause curing.
(1) Reaction of a maleimide group with an allyl group.
(2) Reaction between maleimide groups.
(3) Reaction between allyl groups.

Furthermore, the polycarbonate resin of the present invention has excellent solubility in solvents that are generally used to dissolve maleimide compounds. Therefore, a resin varnish can be obtained in which the polycarbonate resin of the present invention, the maleimide compound, and, if necessary, the epoxy resin described below are all dissolved in a solvent.

The solvent is generally a polar solvent such as methyl ethyl ketone.
The polycarbonate resin of the present invention can be cured by itself through the reaction (3) without being combined with a maleimide compound. However, by combining it with a maleimide compound, the curing temperature can be lowered and thermal properties such as the glass transition temperature can be improved compared to when the polycarbonate resin is cured alone. Therefore, it is preferable to combine it with a maleimide compound and subject it to a curing reaction.

The uses of the curable resin composition of the present invention are not particularly limited. For example, the uses may be similar to those of known thermosetting molding materials, such as encapsulating materials, film materials, and laminate materials. More specific examples of uses include interlayer insulating layers for printed wiring boards, semiconductor encapsulating materials, encapsulating resin materials for electronic components, electrical insulating materials, resin materials for copper-clad laminates, build-up laminate materials, resist materials, resin materials for liquid crystal color filters, paints, various coating agents, adhesives, and fiber-reinforced plastic (FRP) materials.

<Maleimide Compound>
The maleimide compound is not particularly limited as long as it is a compound having two or more maleimide groups, and examples thereof include bismaleimide compounds and polyphenylmethane maleimide. Examples of the bismaleimide compound include 4,4'-diphenylmethane bismaleimide (e.g., BMI-1100 manufactured by Daiwa Chemical Industry Co., Ltd.), alkyl bismaleimide, diphenylmethane bismaleimide, phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide (e.g., BMI-4000 manufactured by Daiwa Chemical Industry Co., Ltd.), 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide (e.g., BMI-5100 manufactured by Daiwa Chemical Industry Co., Ltd.), 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.

Polyphenylmethane maleimide is a polymer in which three or more benzene rings substituted with maleimide groups are linked via methylene groups; for example, BMI-2300 manufactured by Daiwa Chemical Industry Co., Ltd. is one example. These maleimide compounds may be used alone or in combination of two or more.

The content of the maleimide compound in the curable resin composition of the present invention is preferably 10 to 300 parts by weight, more preferably 15 to 200 parts by weight, and even more preferably 20 to 150 parts by weight, per 100 parts by weight of polycarbonate resin. When the content of the maleimide compound is within this range, the gelation temperature of the curable resin composition can be lowered, for example, to 200°C or below. Furthermore, the cured product of the curable resin composition will exhibit a higher glass transition temperature, a higher thermal decomposition temperature, a lower linear expansion coefficient, a lower dielectric constant, and a lower dielectric loss tangent.

<Epoxy resin>
The curable resin composition of the present invention may contain an epoxy resin as needed. The polycarbonate resin used in the present invention may have a phenolic hydroxyl group, and therefore may also be used as a curing agent (epoxy resin curing agent) for curing the epoxy resin. The epoxy resin can be cured by heating.

When an epoxy resin is cured using the polycarbonate resin of the present invention, it is believed that the curing occurs through the aforementioned reaction (3) and the following reactions (4) and (5).
(4) Reaction of an epoxy group with a hydroxyl group.
(5) Reaction between epoxy groups.

Examples of epoxy resins include bixylenol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, bisphenol AF-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol novolac-type epoxy resins, phenol novolac-type epoxy resins, tert-butyl-catechol-type epoxy resins, naphthalene-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, glycidylamine-type epoxy resins, glycidyl ester-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane-type epoxy resins, cyclohexanedimethanol-type epoxy resins, naphthylene ether-type epoxy resins, trimethylol-type epoxy resins, and tetraphenylethane-type epoxy resins. These epoxy resins may be used alone or in combination.

<Solvent>
The solvent is not particularly limited as long as it dissolves the components contained in the curable resin composition of the present invention (the polycarbonate resin of the present invention, the maleimide compound, and, if necessary, the epoxy resin and curing reaction catalyst, etc.). Typically, a polar solvent is used as the solvent. 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, as well as 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. Any one of these solvents may be used alone, or two or more may be used in combination. Among the above, ketone-based solvents are preferred, and methyl ethyl ketone is more preferred.

<Curing reaction catalyst>
The curing reaction catalyst (curing accelerator) preferably contains a catalyst (hereinafter also referred to as "catalyst (1)") that has the effect of accelerating the reaction between an allyl group and a maleimide group. Examples of catalyst (1) 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 the dialkyl peroxides, the alkyl group may be substituted with a phenyl group or the like. An example of such a dialkyl peroxide is dicumyl peroxide.

When the curable resin composition of the present invention contains an epoxy resin, it may contain a catalyst (hereinafter also referred to as "catalyst (2)") that promotes the reaction between hydroxyl groups and epoxy groups as a curing reaction catalyst. Examples of catalyst (2) include phosphorus-based compounds, tertiary amines, imidazole compounds, organic acid metal salts, Lewis acids, and amine complex salts. Examples of phosphorus-based compounds include triphenylphosphine, tris-2,6-dimethoxyphenylphosphine, tri-p-tolylphosphine, and triphenyl phosphite. Examples of tertiary amines include 2-dimethylaminomethylphenol, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo[5.4.0]undecene-7. Examples of imidazole compounds include those similar to those described above.

<Inorganic filler>
The curable resin composition of the present invention contains an inorganic filler, which can reduce the linear expansion coefficient of the cured product of the curable resin composition.

The inorganic filler material is not particularly limited as long as it is an inorganic compound. Examples include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium titanate zirconate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silica is particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. Spherical silica is preferred. These inorganic fillers may be used alone or in combination.

The average particle size of the inorganic filler is typically 5 μm or less, preferably 2.5 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. There is no particular lower limit to the average particle size, but it can be 1 nm (0.001 μm) or more, 5 nm or more, or 10 nm or more, for example. The average particle size of the inorganic filler can be measured using a laser diffraction/scattering method based on Mie scattering theory.

The inorganic filler is preferably treated with a surface treatment agent, more preferably with one or more surface treatment agents such as fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilane compounds, organosilazane compounds, and titanate coupling agents, and even more preferably with an aminosilane silane coupling agent. The surface treatment agent preferably has a functional group that reacts with other components, such as resins, such as an epoxy group, amino group, or mercapto group, and more preferably the functional group is bonded to the terminal group.

From the perspective of reducing the average linear expansion coefficient of the cured resin composition and improving dielectric performance, the content of the inorganic filler component is preferably 45 parts by weight or more, more preferably 50 parts by weight or more, and even more preferably 60 parts by weight or more, based on 100 parts by weight of the nonvolatile content in the resin composition. There is no particular upper limit, but it is preferably 85 parts by weight or less, more preferably 80 parts by weight or less, and even more preferably 75 parts by weight or less.

<Flame retardants>
The curable resin composition of the present invention may contain a flame retardant. Examples of the flame retardant include phosphazene compounds, organic phosphorus flame retardants, organic nitrogen-containing phosphorus compounds, nitrogen compounds, silicone flame retardants, and metal hydroxides. The flame retardants may be used alone or in combination of two or more.

When the curable resin composition contains a flame retardant, the content of the flame retardant is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 0.7 parts by weight or more, based on 100 parts by weight of the non-volatile content in the resin composition. This allows the resin composition and its cured product to be endowed with significant flame retardancy. The upper limit is preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and even more preferably 3 parts by weight or less.

<Optional Additives>
The resin composition of the present invention may contain other additives as needed. Examples of such other additives include thermoplastic resins, organic fillers, organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds, as well as resin additives such as thickeners, antifoaming agents, leveling agents, adhesion promoters, and colorants.

Examples of thermoplastic resins include phenoxy resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyimide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polyetheretherketone resin, and polyester resin. However, the term "thermoplastic resin" as used herein does not include the polycarbonate resin of the present invention.

The organic filler may be any organic filler that can be used when forming an insulating layer on a printed wiring board, such as rubber particles, polyamide fine particles, silicone particles, etc.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the methods for measuring each property are as follows:

(1) Weight average molecular weight (Mw)
The resulting polycarbonate resin was used as a measurement sample, and the weight-average molecular weight Mw was measured by gel permeation chromatography (GPC) and calculated using the polystyrene conversion method. A calibration curve was created using standard polystyrenes with known molecular weights (12 types, from Tosoh PS Oligomer Kit A-500 to F-128). Measurements were performed using a Tosoh "HLC-8220GPC" column, with three Tosoh "TSK-gel Super HZ4000/3000/2000" columns. The sample used was a solution of 10 mg of polycarbonate copolymer in 5 mL of chloroform (containing 0.05% internal standard toluene) and filtered using a Millipore "Millex LG4" column. Measurements were performed at 40°C and a flow rate of 0.35 mL/min. Chloroform for high-performance liquid chromatography, manufactured by Wako Pure Chemical Industries, Ltd., was used as the eluent.

(2-1) Allyl Group Equivalent Weight The obtained polycarbonate resin was used as a measurement sample, and ¹ H-NMR spectrum was measured at room temperature using a JNM-AL400 (resonance frequency 400 MHz) manufactured by JEOL Ltd., and the allyl group equivalent weight in the polymer was calculated from the signal intensity ratio based on the structural units derived from each compound.
Amount of polymer: 40 mg
Solvent: deuterated chloroform 0.6 mL
Number of times accumulated: 256

(2-2) Terminal Proportion of Structure (B) The obtained polycarbonate resin was used as a measurement sample, and ¹ H-NMR spectrum was measured at room temperature using a JNM-AL400 (resonance frequency 400 MHz) manufactured by JEOL Ltd., and the signal intensity ratio based on the structural units derived from the allyl group-containing monohydroxy group and the allyl group-free monohydroxy group constituting the terminal, and the OH group which is the unreacted terminal, was calculated. The sum of the signal intensity ratios at the terminals was defined as all terminals, and the proportion of the signal intensity ratios of the allyl group-containing monohydroxy group was calculated as the terminal ratio (mol %).
Amount of polymer: 40 mg
Solvent: deuterated chloroform 0.6 mL
Number of times accumulated: 256

(3) Glass Transition Temperature The obtained polycarbonate resin was used as a measurement sample, and the glass transition temperature was measured using a thermal analysis system DSC-2910 manufactured by TA Instruments in accordance with JIS K7121 under the conditions of a nitrogen atmosphere (nitrogen flow rate: 40 ml/min) and a temperature rise rate of 20°C/min.

(4) Preparation of Laminate To 100 g of the obtained polycarbonate resin, BMI-2300 (polyphenylmethane maleimide, maleimide equivalent: 186.0 g/eq) manufactured by Daiwa Chemical Industry Co., Ltd. was added as a maleimide compound in an amount calculated by the following formula (1), and 1.2 g (1% with respect to the total resin amount) of dicumyl peroxide as a curing reaction catalyst was dissolved in methyl ethyl ketone to a solid content of 60%, to obtain a resin varnish.

The resulting resin varnish was impregnated into glass cloth (E-glass) to a resin content of 40% by weight, and then dried at 100°C for 10 minutes to remove the solvent, yielding a prepreg. Six of these prepregs were stacked and press-molded at 180°C, followed by after-baking at 230°C for 5 hours to obtain a molded product (laminate) with a thickness of 1.5 mm. The resin content refers to the proportion of resin (cured product) relative to the total weight of the molded product.
Amount of maleimide compound (g)=maleimide equivalent (g/eq)÷allyl group equivalent of polycarbonate resin (eq/ton)×10 ⁶ ×100 g÷5×10 ⁻⁶ (Equation 1)

(5) Linear Expansion Coefficient A test piece measuring 5 mm square and 1.5 mm thick was cut out from the laminate. The linear expansion coefficient at 30° C. was measured at a heating rate of 2° C./min using a linear expansion coefficient measuring device "TMA4000SE" manufactured by NETZSCH.

(6) Relative dielectric constant and dielectric loss tangent Using the polycarbonate resin and the laminate produced in (4) above as samples, the relative dielectric constant and dielectric loss tangent at a frequency of 10 GHz were measured using a dielectric constant meter (Anritsu Network Analyzer MS46122B, AET Cavity Resonator for 10 GHz).

[Example 1]
A reactor equipped with a thermometer, a stirrer, and a reflux condenser was charged with 4,190 parts of a 25% aqueous sodium hydroxide solution and 8,754 parts of ion-exchanged water, to which 1,915 parts of bisphenol C (referred to as BPC in the table; S-BOC manufactured by Honshu Chemical Industry Co., Ltd.) and 3.8 parts of sodium hydrosulfite (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.) were dissolved, followed by the addition of 7,631 parts of methylene chloride, and 1,000 parts of phosgene was blown in over approximately 75 minutes at 15 to 25° C. with stirring. After completion of the phosgene blowing, 598 parts of a 25% aqueous sodium hydroxide solution and 61 parts of o-allylphenol (hereinafter abbreviated as o-AP; manufactured by Tokyo Chemical Industry Co., Ltd.) were added, stirring was resumed, and after emulsification, 2.6 parts of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by further stirring at 26 to 33° C. for 1 hour to complete the reaction.

After the reaction was complete, the product was diluted with methylene chloride and washed with water, then acidified with hydrochloric acid and washed with water. Washing was repeated until the conductivity of the aqueous phase was approximately the same as that of ion-exchanged water, yielding a methylene chloride solution of polycarbonate resin. This solution was then passed through a filter with 0.3 μm openings and added dropwise to warm water in a kneader with an isolation chamber and a foreign matter outlet in the bearing section. The polycarbonate resin was flaked while the methylene chloride was distilled off, and the liquid-containing flakes were then crushed and dried to obtain a powder. Each property was measured, and the results are shown in Table 1.

[Example 2]
A reactor equipped with a thermometer, a stirrer, and a reflux condenser was charged with 5016 parts of 25% aqueous sodium hydroxide solution and 4013 parts of ion-exchanged water, to which 178 parts of bisphenol C, 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane (referred to as BP-OTBPA in the table, manufactured by Honshu Chemical Industry Co., Ltd.), 2132 parts, and 4.6 parts of sodium hydrosulfite were dissolved. Then, 17,760 parts of methylene chloride and 108 g of tetrabutylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and 1,000 parts of phosgene were blown in over about 75 minutes at 15 to 25 ° C. with stirring. After completion of the phosgene blowing, 307 parts of 25% aqueous sodium hydroxide solution and 61 parts of o-AP were added, stirring was resumed, and after emulsification, 2.6 parts of triethylamine was added. The mixture was further stirred at 26 to 33 ° C. for 1 hour to complete the reaction.

After the reaction was complete, the product was diluted with methylene chloride and washed with water, then acidified with hydrochloric acid and washed with water. Washing was repeated until the conductivity of the aqueous phase was approximately the same as that of ion-exchanged water, yielding a methylene chloride solution of polycarbonate resin. This solution was then passed through a filter with 0.3 μm openings and added dropwise to warm water in a kneader with an isolation chamber and a foreign matter outlet in the bearing section. The polycarbonate resin was flaked while the methylene chloride was distilled off, and the liquid-containing flakes were then crushed and dried to obtain a powder. Each property was measured, and the results are shown in Table 1.

[Example 3]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that 2062 parts of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (referred to as BP-OCZ in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used instead of bisphenol C, and 65 parts of o-AP was used. Each property was measured, and the results are shown in Table 1.

[Example 4]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that 2062 parts of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (referred to as BP-OCZ in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used instead of bisphenol C, and 69 parts of eugenol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of o-AP. Each property was measured, and the results are shown in Table 1.

[Example 5]
A polycarbonate resin powder was obtained in the same manner as in Example 2, except that 474 parts of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (referred to as BP-TMC in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used instead of bisphenol C, and 2132 parts of 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane (referred to as BP-OTBPA in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used. Each property was measured, and the results are shown in Table 1.

[Example 6]
A polycarbonate resin powder was obtained in the same manner as in Example 2, except that 417 parts of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (referred to as BP-TMC in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used instead of bisphenol C, and 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane was used instead of 2,2-bis(4-hydroxy-3-cyclohexylphenyl)propane (referred to as BP-OCHPA in the table, manufactured by Honshu Chemical Industry Co., Ltd.). Each property was measured, and the results are shown in Table 1.

[Example 7]
A polycarbonate resin powder was obtained in the same manner as in Example 2, except that 862 parts of bisphenol C were used, 956 parts of 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane (referred to as BPWC in the table, manufactured by Honshu Chemical Industry Co., Ltd.) was used instead of 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, and 36 g of o-AP and 32 parts of p-tert-butylphenol (referred to as PTBP in the table, manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.). Each property was measured, and the results are shown in Table 1.

[Comparative Example 1]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that the amount of o-AP was 46 parts. Each property was measured, and the results are shown in Table 2.

[Comparative Example 2]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that 64 parts of p-tert-butylphenol (referred to as PTBP in the table, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of o-AP. Each property was measured, and the results are shown in Table 2.

[Comparative Example 3]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that 958 parts of bisphenol C and 853 parts of bisphenol A (referred to as BPA in the table, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) were added. Each property was measured, and the results are shown in Table 2.

[Comparative Example 4]
A polycarbonate resin powder was obtained in the same manner as in Example 1, except that 1706 parts of bisphenol A (referred to as BPA in the table, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was used instead of bisphenol C. Each property was measured, and the results are shown in Table 2.

The present invention provides a polycarbonate resin with a low dielectric constant and a low dielectric dissipation factor. Furthermore, the polycarbonate resin can be used to obtain a cured product with a low linear expansion coefficient and high strength. Such cured products are extremely useful as highly functional polymer materials, and as electrically and thermally excellent materials, they can be used in a wide range of applications, including interlayer insulating layers for printed wiring boards, semiconductor encapsulants, electrical insulating materials, resins for copper-clad laminates, resists, encapsulating resins for electronic components, resins for liquid crystal color filters, paints, various coating agents, adhesives, build-up laminate materials, and FRP.

Claims (6)

A polycarbonate resin comprising a structural unit (A) represented by the following formula (1), wherein the proportion of the structural unit (A) in all structural units is 70 mol % or more, and wherein the following (a) to (c) are satisfied:
(a) the weight average molecular weight of the polycarbonate resin measured by gel permeation chromatography is in the range of 15,000 to 45,000;
(b) the relative dielectric constant of the polycarbonate resin at a frequency of 10 GHz measured in accordance with a cavity resonator perturbation method is in the range of 2.3 to 2.7, and the dielectric loss tangent is in the range of 0.0001 to 0.0030;
(c) The terminal structure of the polycarbonate resin contains a structure (B) derived from a monohydroxy compound represented by the following formula (2), and accounts for 10 mol % or more of all terminal structures constituting the polycarbonate resin:
(In formula (1), _R1 and _R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms; _R3 and _R4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 6 to 20 carbon atoms; and X represents a single bond, a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, a substituted or unsubstituted alkylidene group having 2 to 20 carbon atoms, a substituted or unsubstituted sulfur atom, or an oxygen atom.)
(In formula (2), _R5 is a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms, a linear or branched alkoxy group having 1 to 10 carbon atoms, or a linear or branched phenyl-substituted alkyl group having 1 to 20 carbon atoms, and _R6 is an allyl group having 3 to 20 carbon atoms.) 2. The polycarbonate resin according to claim 1, wherein X in the formula (1) is at least one group selected from the group consisting of the following formula (3):
( _R7 and _R8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, and Z represents a substituted or unsubstituted alkylene group having 4 to 12 carbon atoms.) The polycarbonate resin according to claim 1 or 2, wherein the proportion of structural unit (A) in all structural units of the polycarbonate resin is 90 mol % or more. The polycarbonate resin according to any one of claims ₁ to ₃ , wherein _R1 and _R2 in formula (1) each represent at least one group selected from the group consisting of a methyl group, an isopropyl group, a tert-butyl group , and a cyclohexyl group, and R3 and R4 each represent a hydrogen atom or a methyl group. A curable resin composition comprising the polycarbonate resin according to any one of claims 1 to 4 , a maleimide compound, and an inorganic filler. The resin composition according to claim 5 , which is used to form an insulating layer of a printed wiring board.