Fluororesin

Abstract

To provide a novel fluororesin useful as an electronic substrate material for high speed transmission.SOLUTION: There is provided a fluororesin having a structure of the formula (I) (wherein, n is within a range of 1 to 100, L is a specific divalent group, R3 and R4 are independently a hydrogen atom, a fluorine atom, a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms in which a part or all of hydrogen atoms may be substituted with a halogen atom or an aryl group having 6 to 10 carbon atoms in which a part or all of hydrogen atoms may be substituted with a halogen atom, X is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom.).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a novel fluororesin. More specifically, the present invention relates to a novel fluororesin useful as an electronic substrate material for high-speed transmission.

Background Art

[0002] In recent years, the demands for high-speed communication and high-speed transmission have been increasing. For high-speed transmission, it is necessary to transmit high-frequency signals without attenuation. Therefore, materials having a low dielectric constant and a low dielectric loss are required for wire coating materials and substrate materials for signal transmission.

[0003] Conventionally, materials such as epoxy resins and polyphenylene ether resins have been used as resin materials for high-speed communication and transmission (see Patent Document 1). However, the electrical properties (dielectric constant, dielectric loss, etc.) of conventionally known epoxy resins and polyphenylene ether resins are insufficient with respect to the demands of recent high-speed communication and transmission.

[0004] On the other hand, fluororesins are known as materials having excellent electrical properties. In particular, perfluororesins in which all hydrogens in the molecular chain are replaced by fluorine are known to exhibit particularly excellent electrical properties (dielectric constant, dielectric loss, etc.). However, fluororesins (perfluororesins) have problems such as being prone to deformation due to stress and having a large coefficient of thermal expansion, and it is difficult to use them as substrate materials. In order to solve the above-mentioned problems, attempts have been made to mix fillers with fluororesins. However, it is known that the mixing of fillers affects the electrical properties.

[0005] The use of fluorinated poly(arylene ether) and crosslinkable fluorinated poly(arylene ether) as dielectric materials in electronic components has been proposed (see Patent Documents 2 and 3). However, the electrical properties of these materials do not satisfy the current demands for high-speed communication and transmission.

[0006] In addition, from the viewpoints of mass production and reduction of manufacturing costs, it is required to lower the crosslinking treatment temperature.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] As a substrate material for high-speed communication and transmission, a resin material having excellent electrical properties (low dielectric constant and low dielectric loss), excellent dimensional stability (low coefficient of thermal expansion), high solvent solubility for facilitating thin film formation, and excellent crosslinkability enabling film formation by heating at about 200°C is required.

Means for Solving the Problems

[0009] The first embodiment of the present invention is represented by the formula (I):

[0010]

Chemical Formula

[0011] (In the formula, L has a structure of formula (II) or formula (III),

[0012]

Chemical Formula

[0013] R 1 and R 2 are each independently a hydrogen atom, C1-C10 An alkyl group, C1-C 10 A haloalkyl group, C6-C 10 A group selected from the group consisting of aryl groups, or R 1 And R 2 Are groups that may together form a ring structure having a substituent, R 3 And R 4 Are each independently hydrogen, fluorine, a C1-C in which some or all of the hydrogens may be substituted with halogen 10 Saturated or unsaturated hydrocarbon group, and a C6-C in which some or all of the hydrogens may be substituted with halogen 10 A group selected from the group consisting of aryl groups, n is in the range of 1 to 100, X is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom) It relates to a fluororesin characterized by having the structure of

[0014] The second embodiment of the present invention relates to a resin composition containing the fluororesin of the first embodiment and a crosslinking agent.

[0015] The third embodiment of the present invention relates to a prepreg containing a semi-cured product of the fluororesin of the first embodiment and a fibrous substrate.

[0016] The fourth embodiment of the present invention relates to a prepreg containing a semi-cured product of the resin composition described in the second embodiment and a fibrous substrate.

[0017] The fifth embodiment of the present invention relates to a copper-clad laminate containing a cured product of the prepreg described in the third or fourth embodiment and at least one copper layer.

[0018] The sixth embodiment of the present invention relates to a printed circuit board containing a cured product of the prepreg described in the third or fourth embodiment and a conductor pattern formed on the surface of the cured product.

Advantages of the Invention

[0019] By adopting the above configuration, the present invention can provide a fluororesin having excellent electrical properties (low dielectric constant and low dielectric loss), excellent dimensional stability, high solvent solubility, and excellent crosslinkability. The fluororesin of the present invention can be suitably used as a material for substrates for high-speed communication and transmission.

Embodiments for Carrying Out the Invention

[0020] The fluororesin according to the first embodiment of the present invention has the formula (I):

[0021]

Chemical formula

[0022] (In the formula, L has a structure of formula (II) or formula (III),

[0023]

Chemical formula

[0024] R 1 and R 2 are each independently a group selected from the group consisting of a hydrogen atom, a C1-C 10 alkyl group, a C1-C 10 haloalkyl group, and a C6-C 10 aryl group, or R 1 and R 2 together form a group having a substituent and forming a ring structure, R 3 and R 4 are each independently a group selected from the group consisting of hydrogen, fluorine, a C1-C 10 saturated or unsaturated hydrocarbon group in which some or all of the hydrogens may be substituted with halogen, and a C6-C 10 aryl group in which some or all of the hydrogens may be substituted with halogen, n is in the range of 1 to 100, X is a group containing an olefinic carbon-carbon double bond or carbon-carbon triple bond and at least one fluorine atom) characterized by having the structure of

[0025] In formula (I), n is in the range of 1 to 100, preferably in the range of 3 to 50, more preferably in the range of 5 to 30. By setting n within the above-mentioned range, sufficient heat resistance, an appropriate glass transition temperature (Tg), and sufficient solvent solubility can be achieved simultaneously. Further, by setting n within the above-mentioned range, the number of substituents X contained in the resin per unit weight can be adjusted to achieve appropriate crosslinkability and excellent electrical properties (dielectric constant, dielectric loss, etc.). Also, when forming a varnish using a fluororesin having the structure of formula (I), by setting n within the above-mentioned range, an appropriate viscosity can be imparted to the varnish.

[0026] In formula (II) and formula (III), R 1 and R 2 may independently be a group selected from the group consisting of a hydrogen atom, a C1-C 10 alkyl group, a C1-C 10 haloalkyl group, and a C6-C 10 aryl group. Examples of the C1-C 10 alkyl group include a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group (isobutyl group), a butyl group, a pentyl group, etc. Examples of the C1-C 10 haloalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, etc. Examples of the C6-C 10 aryl group include a phenyl group, a naphthyl group (including 1-isomer and 2-isomer).

[0027] Alternatively, R 1 and R 2may combine together to form a ring structure which may have a substituent. Examples of the group forming the ring structure include a tetramethylene group (forming a cyclopentane ring), a pentamethylene group (forming a cyclohexane ring), an undecamethylene group (forming a cyclododecane ring), a 2-methyl-pentamethylene group (forming a methylcyclohexane ring), a 2,2,4-trimethyl-pentamethylene group (forming a trimethylcyclohexane ring), a biphenyl-2,2'-diyl group (forming a fluorene ring), and the like.

[0028] In formula (I), R 3 ~R 4 are each independently hydrogen, fluorine, a C1-C 10 saturated or unsaturated hydrocarbon group in which some or all of the hydrogens may be substituted with halogen, or a C6-C 10 aryl group in which some or all of the hydrogens may be substituted with halogen. Examples of the C1-C 10 saturated or unsaturated hydrocarbon group in which some or all of the hydrogens may be substituted with halogen include a methyl group, an ethyl group, a propyl group, a 2-methylpropyl group (isobutyl group), a butyl group, a pentyl group, a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, a vinyl group, an allyl group, a 1-methylvinyl group, a 2-butenyl group, a 3-butenyl group, and the like. Examples of the C6-C 10 aryl group in which some or all of the hydrogens may be substituted with halogen include a phenyl group, a naphthyl group (including 1-isomer and 2-isomer), a perfluorophenyl group, and the like.

[0029] In formula (I), X is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom. Examples of X include the following structures of (X-1) to (X-9).

[0030]

Chemical formula

[0031] In the formula, p is an integer from 1 to 4, preferably 4. q is an integer from 0 to 4, preferably 4. R represents a group selected from the group consisting of an alkyl group of C1-C 10 and an aryl group of C6-C 10 .

[0032] Preferably, X has the structure of the following (X-10) or (X-11).

[0033] [Chemical formula]

[0034] Preferred fluororesins in the present invention include, for example, resins having the following structure (wherein, "(*)" indicates the bonding position).

[0035] [Chemical formula]

[0036] [Chemical formula]

[0037] In the present invention, it is preferable that the fluororesin is solvent-soluble. That the fluororesin is "solvent-soluble" means that 1 g or more, preferably 10 g or more, of the fluororesin is dissolved per 100 g of the solution obtained from a given solvent. The fluororesin of the present embodiment is preferably soluble in hydrocarbons described later. Further, from the viewpoint of cost, the fluororesin of the present embodiment is particularly preferably soluble in toluene.

[0038] The fluororesin of the present invention can be produced by a method including (1) a step of condensing a bisphenol derivative (A) and a perfluorobiphenyl (B) in the presence of a base, and (2) a step of condensing a precursor (C) of a substituent X with the obtained condensate.

[0039] [Chemical formula]

[0040] In the precursor (C), Z is a leaving group, preferably selected from the group consisting of F, Cl, Br, and I, more preferably F.

[0041] The base used preferably includes carbonates, hydrogencarbonates, and hydroxides of alkali metals. Examples of preferred bases include sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium hydroxide, and potassium hydroxide. It is preferable to use 1 mol or more, preferably 2.0 to 2.6 mol, of the base per 1 mol of the bisphenol derivative (A).

[0042] It is preferable to carry out Step (1) and Step (2) in an aprotic polar solvent or a mixed solvent containing an aprotic polar solvent. Preferred aprotic polar solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), sulfolane, etc. The mixed solvent may contain a low-polarity solvent as long as it does not reduce the solubility of the fluororesin and does not affect the condensation reaction. Low-polarity solvents that can be used include toluene, xylene, benzene, tetrahydrofuran, benzotrifluoride ((trifluoromethyl)benzene), xylene hexafluoride (1,3-bis(trifluoromethyl)benzene), etc. By adding a low-polarity solvent, the polarity (dielectric constant) of the solvent mixture can be changed to control the rate of the condensation reaction.

[0043] It is preferable to carry out Step (1) and (2) continuously. The entire Step (1) and (2) is preferably carried out under the conditions of a reaction temperature of 10 to 200°C and a reaction time of 1 to 80 hours, more preferably a reaction temperature of 20 to 180°C and a reaction time of 2 to 60 hours, still more preferably a reaction temperature of 50 to 160°C and a reaction time of 3 to 40 hours.

[0044] The second embodiment of the present invention relates to a resin composition containing a fluororesin of the first embodiment and a crosslinking agent.

[0045] The crosslinking agent used in this embodiment includes a compound having two or more olefinic carbon-carbon double bonds in the molecule. Examples of the crosslinking agent used in this embodiment include polyfunctional methacrylate compounds having two or more methacryl groups in the molecule, polyfunctional acrylate compounds having two or more acryl groups in the molecule, trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC), and divinylbenzene. Examples of polyfunctional acrylate / methacrylate compounds include dicyclopentadiene-type acrylate compounds such as tricyclodecane dimethanol diacrylate, and dicyclopentadiene-type methacrylate compounds such as tricyclodecane dimethanol dimethacrylate.

[0046] The resin composition of this embodiment may contain 50% by mass, preferably 20% by mass of the crosslinking agent based on the total mass of the resin composition. Also, in the resin composition of this embodiment, the mass ratio of fluororesin:crosslinking agent is preferably in the range of 9.5:0.5 to 5:5, more preferably 7.5:2.5 to 5.5:4.5. By using the mass ratio within this range, sufficient hardness can be imparted to the cured product of the resin composition.

[0047] The resin composition of this embodiment may further contain a solvent, a reaction initiator, and / or a filler. Also, the resin composition of this embodiment may further contain any additives known in the art, such as an antifoaming agent, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a colorant (dye or pigment), a flame retardant, a lubricant, and a dispersant.

[0048] The resin composition of this embodiment may be a varnish-like composition containing a solvent. In this embodiment, various solvents can be used. From the perspective of solvent solubility, it is preferable to use an aprotic solvent in the present invention. The solvents used in this embodiment include: hydrocarbons such as benzene, toluene, xylene, heptane, cyclohexane, methylcyclohexane, and mineral spirits; ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and diisobutyl ketone (DIBK); cyclic ketones such as cyclohexanone, cycloheptanone, and cyclooctanone; esters such as ethyl acetate, butyl acetate, and γ-butyrolactone; cyclic ethers such as tetrahydrofuran (THF) and 1,3-dioxolane; amides such as N,N-dimethylformamide (DMF), diethylformamide (DEF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and N-cyclohexylpyrrolidone; sulfones such as sulfolane and dimethyl sulfone; and sulfoxides such as dimethyl sulfoxide (DMSO). The preferred solvent in the present invention is hydrocarbons, and particularly preferably aromatic hydrocarbons.

[0049] The resin composition of this embodiment preferably contains a reaction initiator for the crosslinking reaction. Crosslinking and curing by heating are possible even in the absence of a reaction initiator, but when a reaction initiator is present, crosslinking and curing can be carried out more efficiently under milder conditions. The reaction initiators that can be used include, for example, benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, dicumyl peroxide, cumyl hydroperoxide, α,α'-di(t-butylperoxy)-diisopropylbenzene (Perbutyl P manufactured by NOF Corporation), 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, azobisisobutyronitrile, and the like.

[0050] The resin composition of this embodiment may further contain one or more fillers. The filler may be an organic filler or an inorganic filler. The organic fillers that can be used include: engineering plastics such as polyphenylene sulfide, polyether ether ketone (PEEK), polyamide, polyimide, and polyamideimide; and solvent-insoluble fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), and copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). The inorganic fillers that can be used include: metals; metal oxides such as aluminum oxide, zinc oxide, tin oxide, and titanium oxide; metal hydroxides; metal titanates; zinc borate; zinc stannate; boehmite; silica; glass; silicon oxide; silicon carbide; boron nitride; calcium fluoride; carbon black; mica; talc; barium sulfate; molybdenum disulfide, etc. Solvent-insoluble fluororesins are preferable in terms of improving the electrical properties (dielectric constant, dielectric loss, etc.) of the cured product of the resin composition. Also, silica is preferable in that it can reduce the coefficient of thermal expansion without impairing the electrical properties (dielectric constant, dielectric loss, etc.) of the cured product of the resin composition.

[0051] The resin composition of this embodiment can be formed by mixing the fluororesin of the first embodiment, a crosslinking agent, and optional components. Heating may be performed during mixing. Also, the mixing can be carried out using any mixing device known in the art, such as various stirrers, ball mills, bead mills, planetary mixers, roll mills, etc.

[0052] The third embodiment of the present invention relates to a prepreg containing a semi-cured product of the fluororesin described in the first embodiment and a fibrous substrate. The prepreg of this embodiment may further contain a reaction initiator for the crosslinking reaction. The reaction initiator that can be used in this embodiment is the same as that in the second embodiment.

[0053] The fibrous base material that can be used in this embodiment includes glass woven fabric, aramid woven fabric, polyester woven fabric, carbon fiber woven fabric, glass non-woven fabric, aramid non-woven fabric, polyester non-woven fabric, carbon fiber non-woven fabric, pulp paper, linter paper, and the like. A preferable fibrous base material is a glass woven fabric that can achieve excellent mechanical strength. The fibrous base material desirably has a thickness of 0.01 mm to 0.3 mm.

[0054] The prepreg of this embodiment can be formed by impregnating a fibrous base material with the fluororesin and an optional reaction initiator described in the first embodiment and then drying it. Here, the fluororesin to be impregnated is desirably in a varnish state containing a solvent. The solvents that can be used are the same as those in the second embodiment. As a result of the drying treatment, at least part of the solvent in the varnish is removed, and the fluororesin becomes in a semi-cured state (so-called "B stage"). The impregnation step can be carried out by any method known in the art, such as dipping or coating. By carrying out the impregnation of the fluororesin and the optional reaction initiator a plurality of times, the resin content in the prepreg can be adjusted. The conditions (temperature and time) of the drying step depend on the type of the fluororesin and the type of the optional reaction initiator and / or solvent. For example, the drying step can be carried out by heating to a temperature of 80°C to 170°C for 1 to 10 minutes.

[0055] The fourth embodiment of the present invention relates to a prepreg including a semi-cured product of the resin composition described in the second embodiment and a fibrous base material. The fibrous base material that can be used in this embodiment is the same as that in the third embodiment.

[0056] The prepreg of this embodiment can be formed by impregnating a fibrous substrate with the resin composition of the second embodiment and drying it. Here, it is desirable that the resin composition to be impregnated is in a varnish state containing a solvent. As a result of the drying process, at least part of the solvent in the varnish is removed, and the resin composition becomes in a semi-cured state (so-called "B-stage"). The impregnation process can be carried out by any method known in the art such as dipping or coating. By carrying out the impregnation of the resin composition a plurality of times, the resin content in the prepreg can be adjusted. The conditions (temperature and time) of the drying process depend on the types of fluororesin, crosslinking agent, and optional solvent contained in the resin composition. For example, the drying process can be carried out by heating to a temperature of 80°C to 170°C for 1 to 10 minutes.

[0057] The fifth embodiment of the present invention relates to a copper-clad laminate including a cured product of the prepreg described in the third or fourth embodiment and at least one copper layer.

[0058] The copper-clad laminate of this embodiment can be formed by laminating one or more prepregs, laminating copper foils on one or both surfaces thereof, and integrating the obtained laminate by heating and pressing. It is desirable that the resin composition in the copper-clad laminate is in a state where curing is completed (so-called "C-stage"). The conditions of the heating and pressing process can be appropriately set based on the thickness of the copper-clad laminate to be manufactured, the composition of the resin composition in the prepreg, and the like. For example, the copper-clad laminate can be manufactured by heating to a temperature of 170°C to 220°C for 60 to 150 minutes and applying a pressure of 1.5 MPa (gauge pressure) to 5.0 MPa (gauge pressure).

[0059] The sixth embodiment of the present invention relates to a printed circuit board including a cured product of the prepreg described in the third or fourth embodiment and a conductor pattern formed on the surface of the cured product.

[0060] The printed circuit board of this embodiment can be manufactured by etching the copper layer of the copper-clad laminate of the fifth embodiment to form a conductor pattern. Alternatively, the printed circuit board can be manufactured by laminating and heat-pressing one or more prepregs to form a laminate, and laminating a conductive material in a pattern on the surface of the laminate to form a conductor pattern.

Example

[0061] (Example 1) Synthesis of Fluororesin (I-1) A glass reaction vessel was charged with 1.009 g (3.0 mmol) of 2,2-bis(4-hydroxyphenyl)hexafluoropropane (bisphenol AF) and 0.912 g (6.6 mmol) of potassium carbonate. After evacuating the inside of the glass reaction vessel to a vacuum, it was purged with nitrogen. Next, 10 mL of DMAc was added to the glass reaction vessel. The reaction mixture was heated to 150 °C with stirring and stirred for 3 hours. After completion of heating, the reaction mixture was cooled to room temperature. Next, 0.802 g (2.4 mmol) of decafluorobiphenyl was added to the reaction mixture. The reaction mixture was heated to 70 °C with stirring and stirred for 4 hours. Next, the reaction mixture was shielded from light, and 0.17 mL (0.233 g, 1.2 mmol) of 2,3,4,5,6-pentafluorostyrene was added. Stirring was continued at a temperature of 70 °C for 15 hours. After completion of stirring, the reaction mixture was cooled to room temperature. Subsequently, the reaction mixture was 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. The washed solid was dried under reduced pressure to obtain about 1.52 g of fluororesin (I-1).

[0062] (Example 2) Synthesis of Fluororesin (I-2) The procedure of Example 1 was repeated except that 0.811 g (3.0 mmol) of 2,2-bis(4-hydroxyphenyl)-4-methylpentane was used instead of bisphenol AF, to obtain about 1.21 g of fluororesin (I-2).

[0063] (Example 3) Synthesis of Fluororesin (I-3) Except for using 0.805 g (3.0 mmol) of 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z) instead of bisphenol AF, the procedure of Example 1 was repeated to obtain about 1.14 g of fluororesin (I-3).

[0064] (Example 4) Synthesis of fluororesin (I-5) Except for using 1.039 g (3.0 mmol) of 1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene (bisphenol P) instead of bisphenol AF, the procedure of Example 1 was repeated to obtain about 1.12 g of fluororesin (I-5).

[0065] (Example 5) Synthesis of fluororesin (I-6) Except for using 0.21 mL (0.359 g, 1.2 mmol) of 3-(pentafluorophenyl)pentafluoro-1-propene instead of 2,3,4,5,6-pentafluorostyrene, the procedure of Example 3 was repeated to obtain about 1.22 g of fluororesin (I-6).

[0066] (Comparative Example 1) Synthesis of fluororesin (C-1) Except for using 0.14 mL (0.143 g, 1.2 mmol) of 4-fluorostyrene instead of 2,3,4,5,6-pentafluorostyrene, the procedure of Example 1 was repeated to obtain about 1.09 g of fluororesin (C-1).

[0067] [Chemical formula]

[0068] (Comparative Example 2) Synthesis of fluororesin (C-2) Except for using 0.12 mL (0.125 g, 1.2 mmol) of methacryloyl chloride instead of 2,3,4,5,6-pentafluorostyrene, the procedure of Example 1 was repeated to obtain about 1.11 g of fluororesin (C-2).

[0069] [Chemical]

[0070] (Evaluation 1) Approximately 5 mg of the fluororesin obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was weighed, and using a thermogravimetric differential thermal analyzer (TG-DTA), the thermogravimetric (TG) curve was measured when heated from 23°C to 500°C at a heating rate of 10°C / min. The obtained TG curve was analyzed, and the temperature at which the weight decreased by 1% from before the measurement was defined as the 1% decomposition temperature. The results obtained are shown in Table 1.

[0071] (Evaluation 2) Using a differential scanning calorimeter (manufactured by PerkinElmer), the fluororesins obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were analyzed. The temperature profile used was as follows. (1) Heat from 30°C to 350°C at a heating rate of 50°C / min. (2) Maintain the temperature of 350°C for 1 minute. (3) Cool to 30°C at a heating rate of 10°C / min. (4) Maintain the temperature of 30°C for 1 minute. (5) Heat to 350°C at a heating rate of 10°C / min.

[0072] From the melting curve obtained in step (5), the Tmg (midpoint temperature, the temperature at the point where a straight line equidistant from the vertical axis direction from the extended straight line of each baseline intersects the curve of the stepped change part of the glass transition) described in ASTM D3418-15 was determined and defined as the glass transition temperature (Tg) of the fluororesin. The results obtained are shown in Table 1.

[0073] (Evaluation 3) Toluene was added to the fluororesins obtained in Examples 1 to 5 and Comparative Examples 1 and 2, and the mixture was heated to 80°C to obtain a 50 mass% toluene solution of the fluororesin. Here, when the fluororesin was completely dissolved, it was determined that the fluororesin was toluene-soluble.

[0074] (Evaluation 4) An equal amount of cyclohexanone was added to the fluororesins obtained in Examples 1 to 5, and the mixture was heated and stirred at 80°C to obtain a 50% by mass solution of the fluororesin. The obtained cyclohexanone solution was applied onto an aluminum sheet with a thickness of 0.1 mm. The obtained coated material was heated at 110°C for 30 minutes and then at 160°C for 1 hour using a hot plate to remove the solvent (cyclohexanone). The sheet coated with the obtained fluororesin was heated at 220°C for 2 hours using a hot plate to melt the fluororesin. Thereafter, the sheet was cooled to room temperature overnight, and then the coating film was peeled off to obtain a test piece.

[0075] Regarding the fluororesins obtained in Comparative Examples 1 to 2, it was difficult to dissolve them in cyclohexanone. Therefore, twice the amount of dimethylacetamide (DMAc) of the fluororesin was added, and the mixture was heated and stirred at 80°C to obtain an approximately 33% by mass solution of the fluororesin. Thereafter, a test piece was obtained by the same procedure as above.

[0076] Using an RF impedance / material analyzer (E4991A manufactured by Agilent Technologies), the dielectric constant and dielectric loss of the test piece at a frequency of 1 GHz were measured. The obtained results are shown in Table 1.

[0077] (Example 6) Production of a resin composition containing fluororesin (I-1) Toluene was added to 0.5 g of fluororesin (I-1), and the mixture was heated at 80°C to obtain a 50% by mass toluene solution of fluororesin (I-1). At a temperature of 80°C, 0.05 g (10% by mass based on the fluororesin) of benzoyl peroxide and 0.2 g of triallyl isocyanurate (TAIC) were added to the obtained toluene solution, and the mixture was stirred for 10 minutes to obtain a resin composition. The mass ratio of fluororesin (I-1) to TAIC was 7:3.

[0078] (Evaluation 5) The resin composition obtained in Example 6 was applied onto an aluminum sheet with a thickness of 0.1 mm. The obtained coating was heated at 110°C for 60 minutes using a hot plate to remove toluene. The sheet coated with the obtained resin composition was heated at 220°C for 2 hours using a hot plate to obtain a cured product of the resin composition. Then, after cooling the sheet to room temperature overnight, the coating film was peeled off to obtain a test piece.

[0079] The dielectric constant and dielectric loss of the test piece at a frequency of 1 GHz were measured using an RF impedance / material analyzer (E4991A manufactured by Agilent Technologies). The obtained results are shown in Table 1.

[0080]

Table 1

Claims

1. Formula (I): 【Chemical Formula 1】 (In the formula,[[]] L has the structure of formula (II) or formula (III), 【Chemical Formula 2】 R １ and R ２ are each independently a group selected from the group consisting of a hydrogen atom, an alkyl group of C １ to C １０ an alkyl group, a haloalkyl group of C １ to C １０ an aryl group of C ６ to C １０ or R １ and R ２ together may form a ring structure having a substituent, R ３ and R ４ are each independently hydrogen, fluorine, a saturated or unsaturated hydrocarbon group of C １ to C １０ in which some or all of the hydrogens may be substituted with halogen, and a saturated or unsaturated hydrocarbon group of C ６ to C １０ in which some or all of the hydrogens may be substituted with halogen, and an aryl group of C n is in the range of 1 to 100, X is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom)) A prepreg characterized by comprising a semi-cured product of a fluororesin having the structure of and a fibrous substrate.

2. Formula (I): 【Chemical Formula 3】 (In the formula,[[]] L has the structure of formula (II) or formula (III), 【Chemical Formula 4】 R1 and R2 are each independently a group selected from the group consisting of a hydrogen atom, a C1-C10 alkyl group, a C1-C10 haloalkyl group, and a C6-C10 aryl group, or R1 and R2 together form a group that may have a substituent and form a ring structure. R3 and R4 are each independently a group selected from the group consisting of hydrogen, fluorine, a C1-C10 saturated or unsaturated hydrocarbon group in which some or all of the hydrogens may be substituted with halogen, and a C6-C10 aryl group in which some or all of the hydrogens may be substituted with halogen. n is in the range of 1 to 100. X is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom. A prepreg characterized by comprising a semi-cured product of a resin composition containing a fluororesin having the structure and a crosslinking agent, and a fibrous substrate.

3. A copper-clad laminate characterized by comprising a cured product of the prepreg according to claim 1 or 2 and at least one copper layer.

4. A printed circuit board characterized by comprising a cured product of the prepreg according to claim 1 or 2 and a conductor pattern formed on its surface.

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