Cross-linking agent for thermosetting resin and composition for rigid substrate using this cross-linking agent

Abstract

To provide a cross-linking agent for a thermosetting resin that has excellent electrical properties, excellent thermosetting properties, and high glass transition temperature of a cured product thereof, enabling fabrication of a rigid substrate with excellent electrical properties required for next-generation high frequencies. A cross-linking agent for a thermosetting resin used for a rigid substrate material, containing three or more groups shown by the following formula (1) in a molecule. -O-R (1) In the formula, R represents a hydrocarbon group having at least one unsaturated bond and a cyclic structure in which all of the hydrogen atoms bonded to the cyclic structure are replaced by fluorine atoms.

Description

TITLE OF THE INVENTIONCROSS-LINKING AGENT FOR THERMOSETTING RESIN AND COMPOSITION FOR RIGID SUBSTRATE USING THIS CROSS-LINKING AGENTCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Japanese Application No. 2023-0188866 filed November 2, 2023, the disclosures of which are incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to a cross-linking agent for a thermosetting resin, and more specifically, to a cross-linking agent that can provide a rigid substrate having excellent electrical properties that can be suitably used for next-generation high-frequency substrates by cross-linking a cross-linkable compound.CONVENTIONAL TECHNOLOGY

[0003] In recent years, information and communication devices such as smartphones, tablet terminals, and the like have been developed for nextgeneration high frequencies that enable high-speed and large-capacity transmission, and in response, substrate materials used are required to have a low dielectric constant and low dielectric tangent to reduce transmission loss.

[0004] Conventionally, fluoropolymers are used as resin materials for highspeed communication and transmission because the electrical properties are excellent, and examples include epoxy resins, polyphenylene ether resins (Patent Document 1 ), fluorinated poly(arylene ether) and cross-linkable fluorinated poly(arylene ether) (Patent Documents 2 and 3), and perfluorinated resins in which all hydrogen atoms in the molecular chain are replaced with fluorine atoms, and the like.

[0005] However, to fabricate substrates that can support next-generation high frequencies above 5 GHz, the substrate material must have excellent electrical properties, a low coefficient of thermal expansion after thermosettingto enable use over a wide temperature range, a high glass transition temperature to enable use in high-temperature environments and soldering, the ability to form the prepreg used to fabricate the substrate securely, and the like.From this perspective, the present applicant has proposed a fluororesin as a substrate material having excellent electrical properties (low dielectric constant and low dielectric loss), excellent dimensional stability, high solvent solubility to facilitate thin film molding, excellent cross-linking properties that enable film formation by heating to about 200°C, and excellent heat resistance, as a substrate material for high-speed communication and transmission (Patent Document 4).PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0006] [Patent Document 1] Japanese Unexamined Patent Application 2017-128718

[0007] [Patent Document 2] US Patent No. 5115082 Specification

[0008] [Patent Document 3] US Patent No. 5179188 Specification

[0009] [Patent Document 4] Japanese Unexamined Patent Application 2022-89150SUMMARY OF THE INVENTIONPROBLEM TO BE SOLVED BY THE INVENTION

[0010] The aforementioned resin material itself has cross-linking properties, so a substrate can be formed even without using a cross-linking agent, but the use of a cross-linking agent improves performance by forming a stronger cross-linked structure, increasing the glass transition temperature, improving dimensional stability, and the like. Therefore, a cross-linking agent obtained from polyfunctional monomers such as isocyanurate derivatives, divinylbenzene, bismaleimides, and bis-triazene is conventionally used, especially triallyl isocyanate (TAIC).

[0011] However, new cross-linking agents that can provide rigid substrates with more suitable electrical properties, high glass transition temperature, and excellent heat resistance are anticipated in order to fabricate a next-generation substrate that can handle high frequencies above 5 GHz, especially a rigid substrate.

[0012] Therefore, an object of the present invention is to provide a crosslinking agent capable of forming a rigid substrate that has excellent thermosetting properties, a high glass transition temperature of the cured product, excellent flame retardancy, and excellent electrical properties required for next-generation high frequencies.

[0013] Another object of the present invention is to provide a rigid substrate composition containing a cross-linkable compound (prepolymer) and the cross-linking agent described above, especially a composition for a rigid substrate in which the cross-linkable compound is a specific fluorine- containing compound.MEANS FOR SOLVING THE PROBLEM

[0014] The present invention provides a cross-linking agent for a thermosetting resin used for a rigid substrate material, including: three or more groups shown by the following formula (1) in a molecule.-O-R (1 )

[0015] In the formula, R is a hydrocarbon group having at least one unsaturated bond and a cyclic structure in which the hydrogen atoms bonded to the cyclic structure are replaced by fluorine atoms.

[0016] In the cross-linking agent according to an embodiment of the present invention, the formula (1) is preferably a group represented by the following formula (2):[Chem. Fig.1]In the formula, X is a cross-linking group containing an unsaturated bond.

[0017] The present invention also provides a composition for a rigid substrate, containing the cross-linking agent and a cross-linkable compound having a plurality of unsaturated bonds.

[0018] The composition for a rigid substrate according to the present invention preferably has a composition ratio (molar ratio) of the cross-linking agent and the cross-linkable compound in a range of 1 :99 to 60:40.EFFECT OF THE INVENTION

[0019] The cross-linking agent of the present invention can be suitably used for crosslinking a crosslinkable compound (prepolymer) used for molding a rigid substrate, and the resulting cured product has excellent electrical properties and high glass transition temperature and has excellent flame retardancy and dimensional stability.

[0020] The effect of the fluorine-containing compound of the present invention is evident from the results of Experimental Examples 1 to 3 described below. That is, it is clear that the substrate molded from the composition for a rigid substrate material of Example 1 , in which the cross-linking agent of the present invention was used, has a higher glass transition temperature (Tg) and a significantly improved dielectric constant (Dk) at 28 GHz than a substrate molded from only the fluorine-containing compound of Example 1 without using a cross-linking agent (Example 4), or a substrate molded from a composition for a rigid substrate where the cross-linking agent of the present invention was replaced by the same amount of TAIC as the cross-linking agent (Example 5).MODE FOR CARRYING OUT THE INVENTION(cross-linking agent)

[0021] An important feature of the cross-linking agent of the invention is that it contains three or more groups expressed by the following formula (1) in a molecule.-0-R (1)

[0022] In the formula, R is a hydrocarbon group having at least one unsaturated bond and a cyclic structure in which the hydrogen atoms bonded to the cyclic structure are replaced by fluorine atoms.

[0023] Examples of the cyclic structure of R in the above formula (1 ) include benzene rings, cyclopentenyl groups, biphenyl groups, and the like, but a benzene ring is particularly preferable. If the ring structure is a benzene ring, the electrical properties (dielectric properties) can be improved and the glass transition temperature and decomposition temperature can be increased, providing the cured product with excellent heat resistance.The excellent electrical properties and flame retardancy of fluorine can be provided and a cured product with improved decomposition temperature (heat resistance) can be provided to the cured product by substituting the hydrogen atoms bonded in the cyclic structure with fluorine atoms.

[0024] The above formula (1) can be specifically exemplified by the following formulas (2) and (3) below.[Chem. Fig. 2]

[0025] In the formula, X represents a cross-linking group containing an unsaturated bond.[Chem. Fig. 3]

[0026] In the above formula (2), the cross-linking group X containing an unsaturated bond is preferably in the para position of the oxygen atom. The cross-linking reaction is more likely to occur with less steric hindrance when the cross-linking group X is in the para position, and the molecular structure will be more symmetrical than when the cross-linking group is in the ortho or meta positions, thus resulting in better electrical properties.Formulas (4) and (5) below are preferable as the above formula (1) in the cross-linking agent of the present invention, and formula (4) below is particularly preferable.[Chem. Fig. 4][Chem. Fig. 5]

[0027] In the cross-linking agent of the present invention, the basic back bone into which the group expressed by the above formula (1 ) is introduced is preferably a trivalent or tetravalent organic group. Trivalent and tetravalent organic groups are residual groups including an organic compound from which three or four hydrogen atoms are removed. Organic compounds that form the aforementioned groups include, for example: aliphatic compounds such as 2,2-dimethylpropane and the like; alicyclic compounds such as cyclohexane and the like; aromatic compounds such as benzene, triphenylmethane, triphenylethane and the like; and heterocyclic compounds such as triazine, isocyanurate, and the like.

[0028] The following formulas (6) to (9) can be exemplified as specific examples of the cross-linking agent of the present invention, with formulas (6) and (7) being particularly preferable, and formula (6) being most preferable.[Chem. Fig. 6][Chem. Fig. 7][Chem. Fig. 9]

[0029] The cross-linking agent of the present invention is preferably soluble in a solvent. The point that the cross-linking agent is soluble in a solvent means that 1 g or more, preferably 10 g or more, of the cross-linking agent will dissolve to form 100 g of the solution obtained from a given solvent.The cross-linking agent of the present invention is preferably soluble in hydrocarbons such as benzene, toluene, xylene, heptane, cyclohexane, methylcyclohexane, and mineral spirits, and is especially preferably soluble in toluene, from a cost perspective.(Composition for a rigid substrate)

[0030] The cross-linking agent of the present invention can be used as a cross-linking agent for thermosetting resins used for molding rigid substrates used for pre-pregs, copper clad laminates, printed circuit boards, and the like.

[0031] Examples of such thermosetting resins include polyphenylene ether resins, fluorine-containing resins, polymaleimide resins, epoxy resins, and other thermosetting resins conventionally used for molding rigid substrates, but a fluorine-containing resin is particularly preferable.

[0032] The composition for a rigid substrate containing the cross-linking agent of the present invention can be combined with modified phenylene ether, maleimide, citraconimide, and the like, which are precursors of the above thermosetting resins and cross-linkable compounds (prepolymers) having a plurality of unsaturated bonds, but of these, the following fluorine-containing compounds with excellent electrical properties and flame retardance can be preferably used.

[0033] In other words, the cross-linkable compound is preferably a fluorine- containing compound, containing: constituent unit A containing a 3 - to 12-membered cyclic structure in a main backbone and having a structure in which 50% or more of hydrogen atoms in the cyclic structure are substituted with fluorine atoms; constituent unit B containing a benzene ring in a main backbone and having a structure in which fluorine atoms account for 30% or less of the number of atoms in the constituent unit; and constituent unit C having an olefinic carbon-carbon double bond or a carbon-carbon triple bond; wherein constituent units A to C are made by bonding the constituent unit C at an end.

[0034] The fluorine-containing compound has excellent electrical properties (low dielectric constant and low dielectric loss) and flame retardancy provided by the constituent unit A, excellent solvent solubility and high glass transition temperature provided by the constituent unit B, and excellent reactivity provided by the constituent unit C, which is located at the end of the compound, enabling the compound to have excellent thermosetting properties that enable molding of a cured product with high gel fraction.

[0035] The aforementioned constituent units A to C in the fluorine- containing compound are bonded in the order of C-B-(A-B)n-C (i) or C-A-(B- A)n-C (ii), and the value of n ranges from 1 to 4, but a low molecular weight compound where the value of n is 1 is particularly preferable.

[0036] Thereby the proportion of cross-linked points in the compound is increased, and a cured product with a high gel fraction (cross-link density) can be obtained. Hence in Formulas (i) and (ii) above, n represents the average degree of polymerization. The average degree of polymerization can be predicted from the stoichiometric ratio of the monomers and can also be measured by a conventionally known method such as nuclear magnetic resonance spectroscopy and the like. In the present invention, "n is 1" means that the average degree of polymerization of the compound is 0.5 to 1 .4. In the present invention, n is sometimes expressed as an integer, but n can similarly be a distribution.[Constituent Unit A]

[0037] Constituent unit A contains a 3 - to 12-membered cyclic structure in a main skeleton and has a structure in which 50% or more of the hydrogen atoms in the cyclic structure are substituted with fluorine atoms. The excellent electrical properties and flame retardancy of fluorine can be provided to the fluorine-containing compound by having 50% or more, suitably 100%, of the hydrogen atoms in the cyclic structure of the constituent unit A substituted with fluorine atoms.

[0038] The 3- to 12-membered cyclic structure in the constituent unit A can have three or more ring structures in the main backbone, but one or two may be provided in the main backbone, and having one to three ring structures including the side chains is preferable. The elements constituting the cyclic structure are not particularly limited, and include carbon, nitrogen, oxygen, sulfur, and silicon atoms, and the like.

[0039] Specific examples of the constituent unit A include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cyclobutadiene, cyclopentadiene, cyclohexadiene, cycloheptadiene, cyclooctadiene, cyclononadiene, cyclodecadiene, cycloheptatriene,cyclooctatriene, cyclododecatriene, benzene, biphenyl, terphenyl, pentalene, indene, naphthalene, azulene, heptalene, indane, acenaphthylene, fluorene, spirofluorene, benzofluorene, dibenzofluorene, phenalene, phenanthrene, anthracene, fluoranthene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphene, hexacene, pentacene, rubicene, coronene, ovalene, pyrrole, thiophene, furan, imidazole, pyrazole, thiazole, isothiazole, oxazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine, isoindoline, indoline, indazoline, purine, quinoline, isoquinoline, benzoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, galvazole, phenanthridine, acridine, phenanthroline, phenazine, benzimidazole, benzofuran, benzothiophene, isobenzothiazole, benzoxazole, isobenzoxazole, triazole, tetrazole, oxadiazole, triazine, dibenzofuran, dibenzothiophene, benzocarbazole, dibenzocarbazole, thiadiazole, imidazopyridine, and the like, which may each have a substitution group.

[0040] When a plurality of 3- to 12-membered cyclic structures are included in the constituent unit A, the ring structures can be the same or different structures.Examples of substitution groups include the following substitution groups.

[0041] Fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, hydroxyl groups, cyano groups, nitro groups, amino groups, amidino groups, hydrazine groups, hydrazone groups, carboxylic acid groups or salts thereof, sulfonic acid groups or salts thereof, phosphoric acid groups or salts thereof, C1 to C60 alkyl groups, C2 to C60 alkenyl groups, C2 to C60 alkynyl groups, and C1 to C60 alkoxy groups;C1 to C60 alkyl groups, C2 to C60 alkenyl groups, C2 to C60 alkynyl groups and C1 - C60 alkoxy groups substituted with at least one substituent selected from a group consisting of fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, hydroxyl groups, cyano groups, nitro groups, amino groups, amidino groups, hydrazine groups, hydrazone groups, carboxylic acid groups or salts thereof, sulfonic acid groups or salts thereof, phosphoric acid groupsor salts thereof, cyclopentyl groups, cyclohexyl groups, cycloheptyl groups, cyclopentenyl groups, cyclohexenyl groups, phenyl groups, biphenyl groups, terphenyl groups, pentalenyl groups, indenyl groups, naphthyl groups, azulenyl groups, heptalenyl groups, indanyl groups, acenaphthyl groups, fluorenyl groups, spiro-fluorenyl groups, benzofluorenyl groups, dibenzofluorenyl groups, phenalenyl groups, phenanthrenyl groups, anthracenyl groups, fluoranthenyl groups, triphenylenyl groups, pyrenyl groups, chrysenyl groups, naphthacenyl groups, picenyl groups, perylenyl groups, pentaphenyl groups, hexacenyl groups, pentacenyl groups, rubicenyl groups, coronenyl groups, obarenyl groups, pyrrolyl groups, thiophenyl groups, furanyl groups, imidazolyl groups, pyrazolyl groups, thiazolyl groups, isothiazolyl groups, oxazolyl groups, isoxazolyl groups, pyridinyl groups, pyrazinyl groups, pyrimidinyl groups, pyridazinyl groups, isoindolyl groups, indolyl groups, indazolyl groups, purinyl groups, quinolinyl groups, isoquinolinyl groups, benzoquinolinyl groups, phthalazinyl groups, naphthyridinyl groups, quinoxalinyl groups, quinazolinyl groups, cinnolinyl groups, carbazolyl groups, phenanthridinyl groups, acridinyl groups, phenanthrolinyl groups, phenazinyl groups, benzimidazolyl groups, benzofuranyl groups, benzothiophenyl groups, isobenzothiazolyl groups, benzoxazolyl groups, isobenzoxazolyl groups, triazolyl groups, tetrazolyl groups, oxadiazolyl groups, triazinyl groups, dibenzofuranyl groups, dibenzothiophenyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, thiadiazolyl groups, imidazopyridinyl groups, and imidazopyrimidinyl groups;

[0042] cyclopentyl groups, cyclohexyl groups, cycloheptyl groups, cyclopentenyl groups, cyclohexenyl groups, phenyl groups, biphenyl groups, terphenyl groups, pentalenyl groups, indenyl groups, naphthyl groups, azulenyl groups, heptalenyl groups, indanyl groups, acenaphthyl groups, fluorenyl groups, spiro-fluorenyl groups, benzofluorenyl groups, dibenzofluorenyl groups, phenalenyl groups, phenanthrenyl groups, anthracenyl groups, fluoranthenyl groups, triphenylenyl groups, pyrenylgroups, chrysenyl groups, naphthacenyl groups, picenyl groups, perylenyl groups, pentaphenyl groups, hexacenyl groups, pentacenyl groups, rubicenyl groups, coronenyl groups, obarenyl groups, pyrrolyl groups, thiophenyl groups, furanyl groups, imidazolyl groups, pyrazolyl groups, thiazolyl groups, isothiazolyl groups, oxazolyl groups, isoxazolyl groups, pyridinyl groups, pyrazinyl groups, pyrimidinyl groups, pyridazinyl groups, isoindolyl groups, indolyl groups, indazolyl groups, purinyl groups, quinolinyl groups, isoquinolinyl groups, benzoquinolinyl groups, phthalazinyl groups, naphthyridinyl groups, quinoxalinyl groups, quinazolinyl groups, cinnolinyl groups, carbazolyl groups, phenanthridinyl groups, acridinyl groups, phenanthrolinyl groups, phenazinyl groups, benzimidazolyl groups, benzofuranyl groups, benzothiophenyl groups, isobenzothiazolyl groups, benzoxazolyl groups, isobenzoxazolyl groups, triazolyl groups, tetrazolyl groups, oxadiazolyl groups, triazinyl groups, dibenzofuranyl groups, dibenzothiophenyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, thiadiazolyl groups, imidazopyridinyl groups, and imidazopyrimidinyl groups;

[0043] cyclopentyl groups, cyclohexyl groups, cycloheptyl groups, cyclopentenyl groups, cyclohexenyl groups, phenyl groups, biphenyl groups, terphenyl groups, pentalenyl groups, indenyl groups, naphthyl groups, azulenyl groups, heptalenyl groups, indanyl groups, acenaphthyl groups, fluorenyl groups, spiro-fluorenyl groups, benzofluorenyl groups, dibenzofluorenyl groups, phenalenyl groups, phenanthrenyl groups, anthracenyl groups, fluoranthenyl groups, triphenylenyl groups, pyrenyl groups, chrysenyl groups, naphthacenyl groups, picenyl groups, perylenyl groups, pentaphenyl groups, hexacenyl groups, pentacenyl groups, rubicenyl groups, coronenyl groups, obarenyl groups, pyrrolyl groups, thiophenyl groups, furanyl groups, imidazolyl groups, pyrazolyl groups, thiazolyl groups, isothiazolyl groups, oxazolyl groups, isoxazolyl groups, pyridinyl groups, pyrazinyl groups, pyrimidinyl groups, pyridazinyl groups, isoindolyl groups, indolyl groups, indazolyl groups, purinyl groups,quinolinyl groups, isoquinolinyl groups, benzoquinolinyl groups, phthalazinyl groups, naphthyridinyl groups, quinoxalinyl groups, quinazolinyl groups, cinnolinyl groups, carbazolyl groups, phenanthridinyl groups, acridinyl groups, phenanthrolinyl groups, phenazinyl groups, benzimidazolyl groups, benzofuranyl groups, benzothiophenyl groups, isobenzothiazolyl groups, benzoxazolyl groups, isobenzoxazolyl groups, triazolyl groups, tetrazolyl groups, oxadiazolyl groups, triazinyl groups, di benzofuranyl groups, dibenzothiophenyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, thiadiazolyl groups, imidazopyridinyl groups, and imidazopyrimidinyl groups, any of which may be substituted with at least one substituent selected from a group consisting of fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, hydroxyl groups, cyano groups, nitro groups, amino groups, amidino groups, hydrazine groups, hydrazone groups, carboxylic acid groups or salts thereof, sulfonic acid groups or salts thereof, phosphoric acid groups or salts thereof, C1 to C60 alkyl groups, C2 to C60 alkenyl groups, C2 to C60 alkynyl groups, C1 to C60 alkoxy groups, cyclopentyl groups, cyclohexyl groups, cycloheptyl groups, cyclopentenyl groups, cyclohexenyl groups, phenyl groups, biphenyl groups, terphenyl groups, pentalenyl groups, indenyl groups, naphthyl groups, azulenyl groups, heptalenyl groups, indanyl groups, acenaphthyl groups, fluorenyl groups, spiro-fluorenyl groups, benzofluorenyl groups, dibenzofluorenyl groups, phenalenyl groups, phenanthrenyl groups, anthracenyl groups, fluoranthenyl groups, triphenylenyl groups, pyrenyl groups, chrysenyl groups, naphthacenyl groups, picenyl groups, perylenyl groups, pentaphenyl groups, hexacenyl groups, pentacenyl groups, rubicenyl groups, coronenyl groups, obarenyl groups, pyrrolyl groups, thiophenyl groups, furanyl groups, imidazolyl groups, pyrazolyl groups, thiazolyl groups, isothiazolyl groups, oxazolyl groups, isoxazolyl groups, pyridinyl groups, pyrazinyl groups, pyrimidinyl groups, pyridazinyl groups, isoindolyl groups, indolyl groups, indazolyl groups, purinyl groups, quinolinyl groups, isoquinolinyl groups, benzoquinolinyl groups, phthalazinyl groups, naphthyridinyl groups, quinoxalinyl groups, quinazolinyl groups,cinnolinyl groups, carbazolyl groups, phenanthridinyl groups, acridinyl groups, phenanthrolinyl groups, phenazinyl groups, benzimidazolyl groups, benzofuranyl groups, benzothiophenyl groups, isobenzothiazolyl groups, benzoxazolyl groups, isobenzoxazolyl groups, triazolyl groups, tetrazolyl groups, oxadiazolyl groups, triazinyl groups, dibenzofuranyl groups, dibenzothiophenyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, thiadiazolyl groups, imidazopyridinyl groups, and imidazopyrimidinyl groups; and the like.

[0044] A plurality of substitution groups may be present, in which case the substitution groups may be the same or different.

[0045] Constituent unit A preferably contains a benzene ring or cyclopentenyl group. More preferably examples include benzene, which may have a substitution group; cyclopentenyl groups, which may have a substitution group; compounds with a benzene ring bonded to another aromatic ring, such as biphenyl, terphenyl, and the like, which may have a substitution group; and compounds with a benzene ring condensed with another aromatic ring, such as naphthalene and the like, which may have a substitution group. Particularly preferred are compounds expressed by the following structural formulas (A-1) to (A-5).[Chem. Fig. 10](where m independently represents an integer from 0 to 6)

[0046] In the above structural formula, R independently represents a substitution group as described above.

[0047] As mentioned above, a structure in which 100% of the hydrogen atoms in the cyclic structure of the main backbone are substituted with fluorine atoms is more suitable as constituent unit A.

[0048] Example of compounds capable of forming constituent unit A include constituent units derived from monomers having a benzene ring, such as hexafluorobenzene, perfluorobiphenyl, perfluoronaphthalene, 4,4- difluorobenzophenone, 1 ,1'-(1 ,1 ,2,2,3,3,4,4,5,5,6,6-dodecafluoro-1 ,6- hexanediyl)bis4-fluorobenzene, and the like, or constituent units derived from monomers having a cyclopentenyl group such as octafluorocyclopentene, and the like. As expressed in formulas (A-1 ) to (A-5), more preferable examples are those derived from hexafluorobenzene, perfluorobiphenyl, perfluoronaphthalene, and octafluorocyclopentene.[Constituent Unit B]

[0049] Constituent unit B of the fluorine-containing compound of the present invention contains a benzene ring in a main backbone, and has a structure in which fluorine atoms account for 30% or less of the number of atoms in the constituent unit. The constituent unit B preferably does not have a fluorine atom, and if a fluorine atom is included, it is important that the number of fluorine atoms in constituent unit B be 30% or less than the number of atoms in constituent unit B. This ensures excellent solvent solubility in fluorine-containing compounds and reliable synthesis of fluorine-containing compounds.

[0050] The benzene ring in the constituent unit B can have four or more ring structures in the main backbone, but two or three in the main backbone is preferable, and having one to four ring structures including the side chains is preferable.

[0051] Examples of the constituent unit B include benzene, biphenyl, terphenyl, indene, naphthalene, indane, acenaphthylene, fluorene, spirofluorene, benzofluorene, dibenzofluorene, phenalene, phenanthrene, anthracene, fluoranthene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphene, hexacene, pentacene, rubicene, coronene, ovalene, isoindoline, indoline, indazoline, quinoline, isoquinoline, benzoquinoline, phthalazine, quinoxaline, quinazoline, cinnoline, galvazole, phenanthridine, acridine, phenanthroline, phenazine, benzimidazole, benzofuran, benzothiophene, isobenzothiazole, benzoxazole, isobenzoxazole, dibenzofuran, dibenzothiophene, benzocarbazole, dibenzocarbazole, and the like, which may have a substitution group.

[0052] Examples of these substitution groups include the substitution groups suggested in the aforementioned constituent unit A.

[0053] Such a constituent unit B preferably is a constituent unit derived from bisphenols as shown in the following formula (B).[Chem. Fig. 11]

[0054] In the formula, L represents a structure according to the following Formulas (b-1 ) or (b-2).[Chem. Fig. 12]

[0055] R1and R2in the aforementioned formulas (b-1 ) and (b-2) each independently represent a group selected from a group consisting of hydrogen atoms, Ci to C10 alkyl groups, Ci to Cw haloalkyl groups, and Ce to C10 aryl groups, or R1and R2may be combined together to form a ring structure that may include substitution groups.

[0056] Examples of Ci to Cw alkyl groups include methyl groups, ethyl groups, propyl groups, 2-m ethylpropyl groups (isobutyl groups), butyl groups, pentyl groups, and the like. Examples of Ci to Cw haloalkyl groups include trifluoromethyl groups, pentafluoroethyl groups, perfluoropropyl groups, and the like. Examples of Ce to Cw aryl groups include phenyl groups and naphthyl groups (including 1 -isomers and 2-isomers).

[0057] Alternatively, R1and R2together may be a group forming a ring structure which may have a substitution group. Examples of groups forming the ring structure include tetramethylene groups (forming a cyclopentane ring), pentamethylene groups (forming a cyclohexane ring), undecamethylene groups (forming a cyclododecane ring), 2-methyl-pentamethylene groups (forming a methylcyclohexane ring), 2,2,4-trimethyl-pentamethylene group (forming a trimethylcyclohexane ring), biphenyl -2,2'-diyl groups (forming a fluorene ring), and the like.

[0058] In Formula (B) above, R3 and R4 may each independently represent a hydrogen atom, a fluorine atom, a Ci to Cw saturated or unsaturated hydrocarbon group in which some or all hydrogens may be substituted by a halogen or a Ce to Cw aryl group in which some or all hydrogens may besubstituted by a halogen. Examples of Ci to Cw saturated or unsaturated hydrocarbon groups in which some or all hydrogens may be substituted with a halogen include methyl groups, ethyl groups, propyl groups, 2-methylpropyl groups (isobutyl groups), butyl groups, pentyl groups, trifluoromethyll groups, pentafluoroethyl groups, perfluoropropyl groups, vinyl groups, allyl groups, 1- methylvinyl groups, 2-butenyl groups, 3-butenyl groups, and the like. Examples of Ce to Cw aryl groups in which some or all hydrogens may be substituted with a halogen include phenyl groups, naphthyl groups (including 1 -isomers and 2-isomers), perfluorophenyl groups, and the like.

[0059] Preferred examples of the constituent unit B include bisphenol AF (2,2-bis(4-hydroxyphenyl) hexafluoropropane), bisphenol F (bis(4- hydroxyphenyl) methane), bisphenol Z (1 ,1-bis(hydroxyphenyl) cyclohexane), bisphenol A (2,2'-bis(4-hydroxyphenyl) propane), bisphenol C (2,2-bis(3- methyl-4-hydroxyphenyl) propane), 4-hydroxyphenylbutane, and 4,4'-(1 ,3- dimethylbutylidene) diphenol, bisphenol P (1 ,4-bis(2-(4-hydroxyphenyl)-2- propyl) benzene), 2,2-bis(3,5-dimethyl-4-hydroxyphenyl) propane, 1 ,1-bis(4- hydroxy-3-methylphenyl)cyclohexane, 4,6-di-tert-butylresorcinol, 1 ,7- dihydroxynaphthalene, and the like, and among these, constituent units derived from bisphenol AF and bisphenol Z are preferable.[Constituent Unit C]

[0060] The constituent unit C of the fluorine-containing compound of the present invention has a structure derived from a reactive compound having an olefinic carbon-carbon double bond or carbon-carbon triple bond, thereby provide excellent thermosetting (crosslinking) properties that enable molding of cured products with a high gel fraction even without using a crosslinking agent. Furthermore, constituent unit C preferably contains at least one fluorine atom, and specifically, the number of fluorine atoms is preferably 50% or less of the number of atoms in the constituent unit. Thereby, in conjunction with the fluorine atom in the constituent unit A, excellent electrical properties and flame retardancy can be provided.

[0061] Furthermore, the constituent unit C preferably has a benzene ring.A preferable constituent unit C includes one of structures (C-1) to (C-10) below.[Chem. Fig. 13]

[0062] In the formula, p is an integer from 0 to 4. In some aspects, p is 4. In another aspect, p is 0. R represents a group selected from a group consisting of Ci to C alkyl groups and Ce to Cw aryl groups. R' represents a hydrogen atom or a C 1 to C alkyl group.

[0063] Constituent unit C particularly preferably has the following structures (C-11) to (C-15).[Chem. Fig. 14][Other]

[0064] The fluorine-containing compound is not excluded from containing small amounts of other constituent units other than constituent units A to C to the extent that the aforementioned various functions provided by constituent units A to C are not impaired.

[0065] For example, for improvement of electrical properties, a constituent unit derived from an aliphatic diol compound that does not contain a benzene ring and a fluorine atom, or an alicyclic diol compound that does not contain a benzene ring and fluorine atom can be included in an amount of 20 mol% or less of all constituent units included in the fluorine-containing compound.

[0066] Examples of these aliphatic diol compounds containing neither a benzene ring nor a fluorine atom include: ethylene glycol, 1 ,2-propanediol, 1 ,3- propanediol, 1 ,2-butanediol, 1 ,3-butanediol, 1 ,4-butanediol, 2,3-butanediol, 1 ,5-pentanediol, 1 ,5-hexanediol, 2,5-hexanediol, 1 ,6-hexanediol, 1 ,7- heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,10-decanediol, 1 ,12- dodecanediol, 2-methyl-1 ,3-propanediol, 2-butyl-2-ethyl-1 ,3-propanediol, neopentyl glycol, 3-methyl-1 ,5-pentanediol, 2-n-butyl-2-ethyl-1 ,3-propanediol, 2,2-diethyl-1 ,3-propanediol, 2, 4-diethyl- 1 ,5-pentanediol, 1 ,2-hexaneglycol,1 .2-octylglycol, 2-ethyl-1 ,3-hexanediol, 2-ethyl-1 ,6-hexanediol, 2,3-diisobutyl-1 .3-propanediol, 2,2-diisoamyl-1 ,3-propanediol, 2-methyl-2-propyl-1 ,3- propanediol, 2-methyl-1 ,8-octanediol, and the like.

[0067] Examples of alicyclic diol compounds containing neither a benzene ring nor a fluorine atom include cyclohexanediols such as 1 ,2-cyclohexanediol,1 .3-cyclohexanediol, 1 ,4-cyclohexanediol and 2-methyl-1 ,4-cyclohexanediol and the like; cyclohexanedimethanols such as 1 ,2-cyclohexanedimethanol,1 .3-cyclohexanedimethanol and 1 ,4-cyclohexanedimethanol, and the like; norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5- norbornanedimethanol; tricyclodecanedimethanol; pentacyclopentadecanedimethanol; 1 ,3-adamantanediol; 2,2- adamantanediol; decalindimethanol; 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol; isosorbide; 3,9-bis(2-hydroxyethyl)-2,4,8,10-tetraoxaspiro(5.5) undecane; 3,9- bis(2-hydroxy-1 , 1 -dimethylethyl)-2,4,8, 10-tetraoxaspiro(5.5) undecane; 3,9- bis(2-hydroxy-1 , 1 -diethylethyl)-2,4,8, 10 -tetraoxaspiro(5.5) undecane; 3,9- bis(2-hydroxy-1 , 1 -d ipropy lethyl)-2 , 4 , 8, 10-tetraoxaspiro(5.5) undecane, and the like.[Preferred Embodiments]

[0068] Examples of preferable fluorine-containing compounds used in the composition for a rigid substrate of the present invention include, but are not limited to, compounds having the following structures, (where n is a value from 1 to 4, and "(*)" indicates the bonding position.)[Chem. Fig. 15][Chem. Fig. 16]

[0069] The fluorine-containing compound is preferably soluble in a solvent. The fluorine-containing compound is "soluble in a solvent" means 1 g or more, preferably 10 g or more, of the fluorine-containing compound is dissolved per 100 g of a solution obtained from a given solvent. The fluorine-containing compound is preferably soluble in hydrocarbons described later. Furthermore, from the perspective of cost, the fluorine-containing compound is particularly preferably soluble in toluene.

[0070] The fluorine content of the fluorine-containing compound is preferably 20 to 40 mass% of the total mass of the fluorine-containing compound, although there is no limitation to this range as long as the fluorine atom content ratio specified in each of the aforementioned constituent units A to C is satisfied. Thereby excellent electrical properties as well as excellent solvent solubility and flame retardancy can be provided.

[0071] The fluorine-containing compound preferably has a number average molecular weight in a range of 500 to 4000, particularly 1000 to 2000. Having a number average molecular weight in the above range improves the solvent solubility and crosslinking properties, and increases the gel fraction of the cured product as described later.

[0072] The composition for a rigid substrate according to the present invention preferably has a composition ratio (molar ratio) between the crosslinking agent and the cross-linkable compound in a range of 1 :99 to 60:40, particularly preferably between 5:95 and 50:50, and even more preferably between 10:90 and 40:60.

[0073] This makes it possible to obtain a cured product with high glass transition and decomposition temperatures, excellent heat resistance, and excellent electrical properties, as well as to provide sufficient hardness to the cured product.

[0074] The composition for a rigid substrate of the present invention may further contain a solvent, a reaction initiator, and a filler. Moreover, the composition for a rigid substrate of the present invention may further containany additives known in the art, such as antifoaming agents, thermal stabilizers, antistatic agents, ultraviolet absorbers, colorants (dyes or pigments), flame retardants, lubricants, and dispersants.

[0075] The composition for a rigid substrate may be a varnish-like composition containing a solvent, and various solvents can be used. From the perspective of solvent solubility, an aprotic solvent is preferably used in the present invention. The aprotic solvent may include: hydrocarbons such as benzene, toluene, xylene, heptane, cyclohexane, methylcyclohexane, mineral spirit, and the like; ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), and the like; cyclic ketones such as cyclohexanone, cycloheptanone, cyclooctanone, and the like; esters such as ethyl acetate, butyl acetate, y -butyrolactone, and the like; cyclic ethers such as tetrahydrofuran (THF), 1 ,3-dioxolane, and the like; amides such as N,N-dimethylformamide (DMF), diethylformamide (DEF), N,N- dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N-cyclohexyl pyrrolidone, and the like; sulfones such as sulfolane, dimethylsulfone, and the like; and sulfoxides such as dimethylsulfoxide (DMSO). Preferable solvents for the present invention are hydrocarbons, and particularly preferably aromatic hydrocarbons.

[0076] The composition for a rigid substrate of the present invention can also contain reaction initiators. This allows for more efficient cross-linking and curing under milder conditions. Examples of the reaction initiators that can be used include benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, dicumyl peroxide, cumyl hydroperoxide, a ,a'-di (t-butylperoxy)- diisopropylbenzene (Perbutyl P (registered trademark) available from NOF Corporation), bis(1-methyl-1 -phenylethyl) peroxide (Percumyl D (registered trademark) available from NOF Corporation), 2,5-dimethyl-2,5-di(t- butylperoxy)-3-hexyne (Perbutyl C (registered trademark) available from NOF Corporation), 3,3',5,5'-tetramethyl-1 ,4-diphenaquinone, chloranyl, 2,4,6-tri-t- butylphenoxyl, t-butyl peroxyisopropyl monocarbonate, azobisisobutyronitrile, and the like.

[0077] The composition for a rigid substrate may further include one or a plurality of fillers. The filler may be an organic filler or an inorganic filler. Examples of organic fillers that can be used include: engineering plastics such as polyphenylene sulfide, polyether ether ketone (PEEK), polyamide, polyimide, polyamide-imide, and the like; and solvent-insoluble fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), and copolymer (FEP) of tetrafluoroethylene, hexafluoropropylene, and the like. Examples of inorganic fillers that can be used include: metals; aluminum oxide, zinc oxide, tin oxide, titanium oxide, and other metal oxides; metal hydroxides; titanic acid metal salts; zinc borate; zinc stannate; boehmite; silica; glass; silicon oxide; silicon carbide; boron nitride; calcium fluoride; carbon black; mica; talc; barium sulfate; molybdenum disulfide; and the like. Solventinsoluble fluororesin is preferable in terms of improving the electrical properties (dielectric constant, dielectric loss, and the like) of the cured product of the fluorine-containing composition. Furthermore, silica is preferable in that the coefficient of thermal expansion can be reduced without impairing the electrical properties (dielectric constant, dielectric loss, and the like) of the cured product of the fluorine-containing composition.

[0078] The composition for a rigid substrate can be formed by mixing the cross-linking agent, the cross-linkable compound, and optionally selected components. Heating may be carried out during mixing. Mixing can also be carried out using an arbitrary mixing device known in the art, such as various stirrers, ball mills, bead mills, planetary mixers, roll mills, and the like.(Rigid substrate)

[0079] The gel fraction (cross-link density) of the cured product where the composition for a rigid substrate of the present invention was cured at 200°C for 120 minutes is preferably 80% or more, even more preferably 90% or more, and most preferably 100%. A large gel fraction (crosslink density) may have the effect of suppressing a reduction in durability due to the presence of unreacted crosslinking sites and reducing the coefficient of thermal expansiondue to an increase in crosslink density. A method of measuring gel fraction is described later.

[0080] Furthermore, the glass transition temperature of the cured product is high, at 200°C or higher; therefore, the coefficient of thermal expansion is reduced in a normal use environment, and durability is improved when used as an electronic substrate. In addition, the low coefficient of thermal expansion at high temperatures offers advantages such as use in high-temperature environments, easier soldering, and the like.

[0081] Furthermore, the coefficient of thermal expansion in a temperature environment above the glass transition temperature is preferably less than 200 ppm / °C, more preferably less than 180 ppm / °C, and even more preferably less than 150 ppm / °C. Methods for measuring the glass transition temperature and coefficient of thermal expansion are described below.

[0082] The cured product of the fluorine-containing compound of the present invention has excellent electrical properties, thermosetting properties, and flame retardancy, and thus is suitable for use in pre-pregs, copper clad laminated sheet, and printed circuits.[Pre-preg]

[0083] The composition for a rigid substrate can be preferably used for prepregs containing a semi-cured product of this composition and a fibrous substrate.

[0084] Examples of fibrous base materials that can be used in the pre-preg include glass woven fabrics, aramid woven fabrics, polyester woven fabrics, carbon fiber woven fabrics, glass nonwoven fabrics, aramid nonwoven fabrics, polyester nonwoven fabrics, carbon fiber nonwoven fabrics, pulp paper, linter paper, and the like. A preferable fibrous base material is a glass woven fabric capable of achieving excellent mechanical strength. The fibrous base material desirably has a thickness of 0.01 mm to 0.3 mm.

[0085] In particular, the composition for a rigid substrate of the present invention has excellent flame retardancy, so the amount of flame retardantconventionally added to the pre-preg can be reduced or eliminated. As a result, the effect of flame retardants on electrical properties can be reduced or eliminated.

[0086] The pre-preg can be formed by impregnating the composition for a rigid substrate or the fluorine-containing composition into the fibrous base material and then drying. Herein, the composition for a rigid substrate to be impregnated is preferably in a varnish-like state containing a solvent. The solvent can be any of the aforementioned solvents that can be used for the composition for a rigid substrate. As a result of the drying process, the solvent in the varnish is at least partially removed and the composition for a rigid substrate becomes semi-cured (so-called "B-stage"). The impregnating step can be performed by an arbitrary method known in the art, such as dipping, application, or the like. By impregnating the composition for a rigid substrate a plurality of times, the amount of composition for a rigid substrate in the prepreg can be adjusted. The conditions (temperature and time) of the drying step depend on the type of reaction initiator and / or the type of solvent. For example, the drying step can be performed by heating to a temperature of 80°C to 170°C for 1 to 60 minutes.[Copper clad laminated sheet]

[0087] The cured product of the pre-preg can be preferably used in a copper clad laminated sheet.

[0088] The copper clad laminated sheet can be formed by laminating one or a plurality of pre-pregs, laminating a copper foil on one or both surfaces thereof, and heating and pressurizing the obtained laminated product to integrate them. The composition for a rigid substrate in the copper clad laminated plate is preferably in a state in which curing is complete (so-called "C stage"). The conditions of the heating and pressurizing process can be appropriately set based on the thickness of the copper clad laminated sheet to be manufactured, the composition of the composition for a rigid substrate in the pre-preg, and the like. For example, the copper clad laminated sheet canbe manufactured by heating to a temperature of 170°C to 220°C for 60 to 150 minutes and applying a pressure of 1 .0 MPa to 10 MPa.[Printed circuit board]

[0089] The cured product of the pre-preg can be preferably used in a printed circuit board.

[0090] The printed circuit board can be manufactured by etching the copper layer of the aforementioned copper clad laminated sheet to form a conductor pattern. Alternatively, the printed circuit board can be manufactured via a method in which one or a plurality of pre-pregs are laminated, heated, and pressurized to form a laminated body, with the conductive material laminated in a pattern on the surface of the laminated body to form a conductor pattern.EXAMPLES(Example 1) Synthesis of cross-linking agent of formula (6)

[0091] A glass reaction vessel was charged with 0.126 g (1.0 mmol) of phloroglucinol (anhydrous) and 0.160 g (4.0 mmol) of sodium hydroxide. The glass reaction container was decompressed to a vacuum and then substituted with nitrogen. Next, 5 ml_ of DMAc and 0.582 g (3.0 mmol) of 2, 3, 4,5,6- pentafluorostyrene were added to the glass reaction container. The reaction mixture was shielded from light, heated to 40°C with stirring, and then stirred for 24 hours. Upon completion of heating, the reaction mixture was cooled to room temperature. The reaction mixture was subsequently poured into 0.3 L of pure water. The reaction mixture was suction filtered and the obtained solid was washed with pure water and methanol. After washing, the solid fraction was dried under reduced pressure to obtain 0.63 g of the cross-linking agent of Formula (6).(Example 2) Synthesis of cross-linking agent of formula (7)

[0092] 0.74 g of the cross-linking agent of formula (7) was obtained by repeating the procedures of Example 1 , except that 0.136 g (1.0 mmol) ofpentaerythritol was used instead of the phloroglucinol (anhydrous), 0.281 g (5.0 mmol) of potassium hydroxide was used instead of the sodium hydroxide, and 0.776 g (4.0 mmol) of 2,3,4,5,6-pentafluorostyrene was used.(Synthesis of fluorine-containing compound)

[0093] A glass reaction container was filled with 0.805 g (3.0 mmol) of 1 , 1- bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 0.501 g (1.5 mmol) of decafluorobiphenyl and 0.912 g (6.6 mmol) of potassium carbonate. The glass reaction container was decompressed to a vacuum and then substituted with nitrogen. Next, 10 mL of DMAc and 0.582 g (3.0 mmol) of 2,3,4,5,6- pentafluorostyrene were added to the glass reaction container. The reaction mixture was shielded from light, heated to 80°C with stirring, and then stirred for 15 hours. Upon completion of heating, the reaction mixture was cooled to room temperature. The reaction mixture was subsequently poured into 0.5 L of pure water. The reaction mixture was suction filtered and the obtained solid was washed with pure water and methanol. After washing, the solid fraction was dried under reduced pressure to obtain 1.54 g of a fluorine-containing compound. The resulting fluorine-containing compound has the structural formula of formula (10) (n is 1 in the formula).(Evaluation 1 : Solvent solubility)

[0094] 0.5 g of each of the cross-linking agents obtained in Examples 1 to2 were weighed, toluene was added, and the mixtures were heated to 80°C and mixed. If a solution containing 50 mass% of toluene was obtained, the mixture was deemed to be toluene soluble. The results of the evaluation showed that Examples 1 and 2 were insoluble.(Evaluation 2: Thermosetting evaluation (gel fraction))

[0095] Mixtures containing 0.5 g of the fluorine-containing compound of formula (10) and the cross-linking agent obtained in Examples 1 or 2, or triallylisocyanurate (TAIC), blended at the ratios (molar %) shown in Table 1 with regard to the fluorine-containing compound, were heated to 80°C with toluene to obtain a 50 mass% solution (varnish-like composition).0.005 g of Perbutyl (registered trademark) P (produced by Nichiyu Co., Ltd.) was added as a reaction initiator to the resulting solution (varnish-like composition), all of which was transferred into an aluminum cup and heated and dried at 200°C for 2 hours using a constant temperature oven (SPHH-102 by ESPEC Co., Ltd.) to obtain a cured product. The cured product was removed from the aluminum cup and the weight was measured. A 9 m L sample tube was filled with 5 g of methyl ethyl ketone (MEK) and the cured product, and the cured product was immersed in MEK for 24 hours. Thereafter, the solvent was volatilized, washed with MEK, and the cured product was dried at 90°C for 3 hours using a hot plate. The mass after drying was measured and used as the mass of the dried cured product after MEK immersion.The gel fraction was calculated as mass of dried cured product after MEK immersion I mass of cured product before MEK immersion x 100 (%). The obtained results are shown in Table 1.(Evaluation 3: Electrical properties)[Preparation of pre-preg]

[0096] 0.005 g of Perbutyl (registered trademark) P (manufactured byNichiyu Co., Ltd.) was added as a reaction initiator to each of the varnish-like compositions obtained by the same method as the evaluation method of the thermosetting properties (gel fraction), then dripped onto an 8 cm x 7 cm piece of glass cloth (L2-1078 manufactured by Asahi Kasei Corporation) to impregnate uniformly. Thereafter, the impregnated material was then dried at 110°C for 10 minutes to obtain a pre-preg.[Preparation of copper clad laminated sheet]

[0097] The pre-preg obtained by the method described above was cut into 6 cm x 6 cm pieces, and together with an electrolytic copper foil (thickness: 18 pm) (HVLP available from FURUKAWA ELECTRIC CO., LTD.), the temperature was raised to 240°C while reducing the pressure using a vacuum hot press machine (manual hydraulic vacuum heating press IMC-4900 available from Imoto machinery Co., LTD.), and the pre-preg and copper foil were further adhered by pressing at 240°C for 120 minutes at 4 MPa.

[0098] The copper foil of the copper clad laminated sheet was removed and cut into 4 cm x 4 cm test pieces (thickness of approximately 0.1 mm), and the dielectric constant was measured using a vector network analyzer (KEYSIGHT 5247B) using the split cylinder method under conditions of 28 GHz and 25°C. The obtained results are shown in Table 1 .(Evaluation 4: Measurement of glass transition temperature (Tg))

[0099] The copper-clad laminates prepared for the above electrical property evaluation were cut into pieces 25 mm long x 5 mm wide at an angle 45 degrees to the mesh of the glass cloth, and used as test pieces.

[0100] The test pieces were set in a dynamic viscoelasticity measuring device (DMAARES-G2, TA Instruments) using a jig for films with a distance of 10 mm between chucks. The measurements were made at the following temperature profile in Torsion mode at a frequency of 1.0 Hz and a strain of 0.1 %.(1 ) Hold at 25°C for 60 seconds and then heat from 25°C to 360°C at a rate of 5°C / min.(2) Maintain at a temperature of 360°C for 60 seconds, and end measurement. The temperature at the peak position of the obtained tanO (ratio of storage modulus to loss modulus) curve was set as the glass transition temperature (Tg). The results are shown in Table 1.Table 1

[0101] As shown in Table 1 , the dielectric constant of the rigid substrate samples (Examples 1 to 3) which used the cross-linking agent of the presentinvention was lower than that of the rigid substrate sample containing a fluorine-containing compound without a cross-linking agent (Example 4) and the rigid substrate sample using a general-purpose TAIC as a cross-linking agent for a rigid substrate (Example 5), and thus excellent electrical properties were obtained. Furthermore, the glass transition temperature of Examples 1 and 2, which used a trifunctional cross-linking agent, was higher than that of Examples 4 and 5. Example 3, which used a tetrafunctional cross-linking agent, had a lower glass transition temperature than that of Examples 4 and 5, but was still at a level sufficient for practical use.INDUSTRIAL APPLICABILITY

[0102] The cross-linking agent of the present invention has excellent thermosetting (cross-linking) and solvent solubility, and can impart excellent electrical properties (low dielectric constant) and flame resistance to the cured product. In particular, it can be used as a cross-linking agent for a rigid substrate material for next-generation high-frequency devices that are capable of high-speed and large-capacity transmission.

Claims

Claims1 . A cross-linking agent for a thermosetting resin used for a rigid substrate material, comprising: three or more groups shown by the following formula (1 ) in a molecule.-O-R (1 )In the formula, R represents a hydrocarbon group having at least one unsaturated bond and a cyclic structure in which all of the hydrogen atoms bonded to the cyclic structure are replaced by fluorine atoms.

2. The cross-linking agent according to claim 1 , wherein the formula (1) is a group expressed by the following formula (2).[Chem. Fig. 1]In the formula, X represents a cross-linking group having an unsaturated bond.

3. A composition for a rigid substrate, comprising: the cross-linking agent according to claim 1 and a cross-linkable compound having a plurality of unsaturated bonds.

4. The composition for a rigid substrate according to claim 3, wherein the composition ratio (molar ratio) of the cross-linking agent and the cross-linkable compound is in a range of 1 :99 to 60:40.