Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
  • D01F6/74—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polycondensates of cyclic compounds, e.g. polyimides, polybenzimidazoles
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate

Definitions

• the present invention relates to polyparaphenylene benzobisoxazole fibers, and fiber-reinforced base materials, laminated base materials and circuit boards using the same.
• the present invention also relates to a method for producing the polyparaphenylenebenzobisoxazole fiber.
• Transmission loss can be distinguished into "dielectric loss” originating from the insulating material surrounding the dielectric, that is, the conductor (e.g., copper circuit), and “conductor loss” originating from the copper circuit itself, both of which need to be suppressed. .
• the conductor e.g., copper circuit
• conductor loss originating from the copper circuit itself
• conductor loss originating from the copper circuit itself
• conductor loss originating from the copper circuit itself
• conductor loss originating from the copper circuit itself, both of which need to be suppressed.
• a material having a low dielectric constant and a low dielectric loss tangent as the insulating material
• fluororesins, polyphenylene ether resins, and the like are used as such materials.
• resins with low dielectric loss such as fluororesins and polyphenylene ether resins, have high coefficients of linear expansion and are therefore used as composite materials with glass cloth and inorganic fillers.
• Patent Document 1 discloses a fiber-reinforced base material composed of polyparaphenylenebenzobisoxazole fiber and fluororesin.
• fiber-reinforced base materials using conventional polyparaphenylenebenzobisoxazole fibers sometimes had a higher dielectric loss tangent in the high-frequency band over time.
• the present invention was made against the background of such problems of the prior art. That is, the present invention provides a polyparaphenylenebenzobisoxazole fiber capable of producing a fiber-reinforced base material capable of suppressing an increase in dielectric loss tangent over time.
• the present invention is as follows.
• [1] A polyparaphenylenebenzobisoxazole fiber having a content insoluble in methanesulfonic acid of 10% by mass or more.
• [2] The fiber according to [1], which has a water absorption of 0.45% or less after conditioning for one week in an atmosphere of 20°C and 65% RH.
• a sheet material composed of the fiber according to any one of [1] to [3].
• [5] A fiber-reinforced base material comprising the sheet material according to [4] and a resin.
• a laminated substrate comprising the fiber-reinforced substrate according to [5] and a metal layer laminated on at least one side of the fiber-reinforced substrate.
• a circuit board comprising the fiber-reinforced base material according to [5] and a patterned metal layer laminated on at least one side of the fiber-reinforced base material.
• the circuit board according to [7] which is for a high frequency band of 1 GHz or more.
• the production method according to [9] wherein the heat treatment is performed under a tension of less than 0.3 gf/dtex.
• a polyparaphenylene benzobisoxazole fiber capable of producing a fiber-reinforced base material capable of suppressing an increase in dielectric loss tangent over time.
• the polyparaphenylenebenzobisoxazole (hereinafter also referred to as PBO) fiber of the present invention has an insoluble content in methanesulfonic acid of 10% by mass or more, preferably 15% by mass or more, and 20% by mass or more. It is more preferable that the content is 30% by mass or more.
• PBO fibers having an insoluble content within the above range it is possible to obtain a fiber-reinforced base material capable of suppressing an increase in dielectric loss tangent over time.
• the insoluble content of PBO fibers in methanesulfonic acid can be measured by the method described in Examples below.
• a fibrous PBO fiber itself may be used, or a sheet material formed into a sheet, which will be described later, may be used. That is, the insoluble portion of the sheet material in methanesulfonic acid also preferably satisfies the above range.
• the insoluble content in methanesulfonic acid can be adjusted by adjusting the heat treatment conditions described below.
• the PBO fiber of the present invention preferably has a water absorption rate of 0.45% or less, more preferably 0.40% or less after being subjected to humidity conditioning for one week in an atmosphere of 20°C and 65% RH. By keeping the water absorption low, it is possible to obtain a fiber-reinforced base material with more excellent stability over time.
• the lower limit of the water absorption rate of the PBO fiber of the present invention is not particularly limited, it may be 0%, 0.05% or more, or 0.1% or more.
• the water absorption of the PBO fiber can be measured by the method described in Examples below. As a sample for measuring the water absorption rate, a fibrous PBO fiber itself may be used, or a sheet material formed into a sheet, which will be described later, may be used. That is, the water absorption of the sheet material also preferably satisfies the above range.
• the tensile strength of the PBO fiber of the present invention is not particularly limited, it is preferably 2 GPa or more, more preferably 3 GPa or more, and still more preferably 4 GPa or more. If the PBO fiber has such a strength, the fiber performance as a reinforcing fiber can be fully reflected in the matrix resin. From the viewpoint of workability such as drilling, the tensile strength of the PBO fiber is preferably 10 GPa or less.
• the tensile modulus of the PBO fiber of the present invention is also not particularly limited, but is preferably 100 GPa or more, more preferably 150 GPa or more, and still more preferably 200 GPa or more. By having a tensile modulus in the above range, the effect of reducing the coefficient of linear expansion of the PBO fiber can be sufficiently exhibited. Moreover, the tensile modulus of the PBO fiber may be 260 GPa or more. From the viewpoint of workability such as drilling, the tensile modulus of the PBO fiber is preferably 500 GPa or less. Also, the tensile modulus of the PBO fiber may be 250 GPa or less.
• the single filament diameter of the PBO fiber of the present invention is preferably 5-20 ⁇ m, more preferably 7-18 ⁇ m, still more preferably 9-16 ⁇ m.
• a sheet material having a thickness suitable for use as a fiber-reinforced base material can be obtained, and since it has a sufficient surface area, it has good adhesion with the resin composition described later. can be improved.
• the single yarn diameter is set to a predetermined value or more, the impregnation property of the resin composition and the productivity of the PBO fiber, which will be described later, are improved.
• the PBO fiber of the present invention is most preferably a continuous fiber having a length of 100 mm or more. By spinning or making paper, it can be used as a sheet material to be described later.
• the PBO fiber of the present invention is obtained by heat-treating PBO fiber (hereinafter sometimes referred to as "pre-treatment PBO fiber") at a temperature of over 400°C to 700°C for over 1 minute to 10 hours in an inert gas atmosphere.
• pre-treatment PBO fiber heat-treating PBO fiber
• the insoluble portion of the PBO fiber in methanesulfonic acid can be adjusted to the above range, probably because a crosslinked structure is formed.
• the water absorption and/or tensile modulus can be adjusted within the above range.
• the fiber-reinforced base material formed from the PBO fibers of the present invention obtained through the above heat treatment can suppress the increase in dielectric loss tangent over time, and in a preferred embodiment, compared with the case of using pre-treated PBO fibers can reduce the dielectric loss tangent and/or the dielectric constant.
• the heat treatment may be applied to the fibrous PBO fibers themselves, or may be applied to a sheet material formed into a sheet, which will be described later.
• the PBO fiber before treatment can be produced by a conventionally known method, for example, it is produced from a dope containing polyparaphenylenebenzobisoxazole polymer (hereinafter referred to as PBO polymer).
• Suitable solvents for preparing the dope include cresol and non-oxidizing acids capable of dissolving the polymer.
• suitable non-oxidizing acids include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Among them, polyphosphoric acid and methanesulfonic acid are preferred, and polyphosphoric acid is particularly preferred.
• the PBO polymer concentration in the dope is preferably 7% by mass or more, more preferably 10% by mass or more, and particularly preferably 14% by mass or more.
• the maximum concentration is limited by practical handling properties such as PBO polymer solubility and dope viscosity. Because of these limiting factors, the polymer concentration usually does not exceed 20% by weight.
• the dope obtained in this way is extruded from a spinneret and stretched in a space to form a filament.
• the dope exiting the spinneret enters the space between the spinneret and the wash bath.
• This space is commonly called an air gap, but need not be air.
• This space must be filled with a gas that does not remove the solvent and does not react with the dope, such as air, nitrogen, argon, helium, carbon dioxide, and the like.
• washing is the removal of acid solvent from the dope by contacting the fiber or filament with a liquid that is compatible with the solvent in which the PBO polymer is dissolved, but which does not dissolve the PBO polymer.
• Suitable washing liquids include water and mixtures of water and acid solvents.
• the drying temperature may be any temperature at which the coagulant and solvent for polyparaphenylenebenzobisoxazole are easily dried, and is preferably 50 to 400°C, for example.
• the upper limit of the drying temperature is more preferably 300°C, particularly preferably 270°C.
• the lower limit of the drying temperature is more preferably 200°C, particularly preferably 220°C.
• heat treatment may be performed under tension as necessary, and the heat treatment under tension may be stretching treatment.
• the temperature of the heat treatment under tension (especially the stretching treatment) is preferably in the range of 400 to 700°C.
• the upper limit of the treatment temperature is more preferably 680°C, particularly preferably 630°C.
• the lower limit of the treatment temperature is more preferably 500°C, particularly preferably 550°C.
• the treatment time for the heat treatment under tension is usually 0.1 second to 1 minute.
• the tension applied during the heat treatment under tension (especially the stretching treatment) is preferably in the range of 0.3 to 1.2 gf/dtex.
• the upper limit of the tension applied during the treatment is more preferably 1.1 gf/dtex, particularly preferably 1.0 gf/dtex.
• the lower limit of the tension applied during the treatment is more preferably 0.5 gf/dtex, particularly preferably 0.6 gf/dtex.
• pre-treatment PBO fibers commercially available products may be used, for example, Zylon AS and Zylon HM manufactured by Toyobo Co., Ltd. can be used.
• the untreated PBO fibers thus obtained are heat-treated in an inert gas atmosphere at a temperature of over 400°C to 700°C for over 1 minute to 10 hours.
• Nitrogen, carbon dioxide, helium, argon, etc. can be exemplified as inert gases, but it is preferable to use nitrogen, which is easily available.
• the treatment temperature of the heat treatment is above 400°C to 700°C, preferably 450°C to 650°C, and more preferably 500°C to 600°C.
• the treatment time of the heat treatment is over 1 minute to 10 hours, preferably 30 minutes to 5 hours.
• the heat treatment is preferably performed under conditions in which tension is not actively applied (preferably under non-stretching conditions), for example, the heat treatment is performed under a tension of less than 0.3 gf/dtex, preferably 0.1 gf/dtex or less. is preferred.
• the method for performing the heat treatment is not particularly limited, and known methods can be used.
• the surface of the PBO fiber of the present invention may optionally be treated with a coupling agent (aminosilane, epoxysilane, etc.), sandblasted, wet blasted, hauled, corona treated, plasma treated, ion gun treated, or etched. etc. may be applied.
• a coupling agent aminosilane, epoxysilane, etc.
• sandblasted, wet blasted, hauled corona treated, plasma treated, ion gun treated, or etched. etc.
• the fiber-reinforced base material of the present invention includes a sheet material composed of the PBO fibers of the present invention and a resin composition.
• a resin composition is a composition containing a resin as a main component, preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.
• the fiber-reinforced base material of the present invention can be said to be a fiber-reinforced base material containing a sheet material composed of the PBO fiber of the present invention and a resin.
• the resin composition also includes an embodiment in which the resin content is 100% by mass.
• the form of the sheet material formed from the PBO fibers of the present invention is not particularly limited, but examples include woven fabric, nonwoven fabric, UD material (nonwoven fabric in which fibers are aligned in one direction), and paper. From the viewpoint of reducing the coefficient of linear expansion of the fiber-reinforced base material, woven fabrics and non-woven fabrics are preferable.
• the basis weight of the sheet material is preferably 10 g/m 2 or more, more preferably 25 g/m 2 or more, and preferably 300 g/m 2 or less, more preferably 250 g/m 2 or less.
• the content of the sheet material (in particular, the content of PBO fibers) is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 40% by mass or less, in the fiber-reinforced base material. is 30% by mass or less.
• the resin used in the present invention is not particularly limited, but examples include epoxy resins, polyimide resins, polyphenylene ether resins, and fluorine resins.
• the resin composition can also contain additives such as inorganic fillers that lower the dielectric constant and dielectric loss tangent.
• Inorganic filler materials include silica, clay, talc, calcium carbonate, mica, diatomaceous earth, alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, calcium hydroxide, and magnesium hydroxide.
• an inorganic filler may be used individually by 1 type, and may use 2 or more types together.
• the content of the additive is preferably 50% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less in the resin composition.
• the content of the resin composition (in particular, the content of resin) is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 95% by mass or more in the fiber-reinforced base material. It is preferably 90% by mass or less, more preferably 90% by mass or less.
• the total content of the sheet material and the resin composition (preferably the total content of the PBO fiber and the resin composition) in the fiber-reinforced base material of the present invention is preferably 60% by mass or more, more preferably 80% by mass. % by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, may be 100% by mass, or may be 99.5% by mass or less.
• the thickness of the entire fiber-reinforced base material is preferably 20-5000 ⁇ m, more preferably 20-1000 ⁇ m, and even more preferably 20-500 ⁇ m.
• the linear expansion coefficient of the fiber-reinforced base material of the present invention is preferably -10 to 30 ppm/°C, more preferably -5 to 25 ppm/°C, and still more preferably 0 to 20 ppm/°C. If the coefficient of linear expansion is within this range, the dimensional stability is high, so thermal fatigue can be suppressed.
• the coefficient of linear expansion of the fiber-reinforced base material can be controlled within the above range by adjusting the contents of the PBO fiber and the resin composition. That is, increasing the content of PBO fibers decreases the coefficient of linear expansion, and increasing the content of the resin composition increases the coefficient of linear expansion.
• the method for producing the fiber-reinforced base material of the present invention is not particularly limited, and a known method can be adopted.
• the sheet material When the sheet material is impregnated with the resin composition, it is preferable to dilute the resin composition with a solvent.
• the solvent include methyl ethyl ketone, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and the like.
• a solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
• a cross-linking agent may be added to the diluted solution.
• an organic peroxide-based cross-linking agent is preferable.
• the organic peroxide-based cross-linking agent include dicumyl peroxide, dimethyldi(t-butylperoxy)hexane, 1,1-di(t-butyl peroxy)cyclohexane, ⁇ , ⁇ '-di(t-butylperoxy)diisopropylbenzene and the like.
• the cross-linking agents may be used singly or in combination of two or more.
• the amount of the cross-linking agent is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the resin.
• the heat and pressure molding is preferably performed under conditions of 150 to 300°C, 10 to 50 MPa, and 30 minutes to 5 hours.
• the dielectric loss tangent (10 GHz) of the fiber-reinforced base material of the present invention after being subjected to humidity conditioning for one week in an atmosphere of 20° C. and 65% RH is preferably 0.0070 or less, more preferably 0.0065 or less. more preferred.
• the lower limit is not particularly limited, and may be 0.0005 or more, or 0.0010 or more.
• the dielectric loss tangent (10 GHz) of the fiber-reinforced base material of the present invention after being subjected to humidity conditioning for 4 weeks in an atmosphere of 20° C. and 65% RH is preferably 0.0080 or less, and is 0.0070 or less. is more preferable.
• the lower limit is not particularly limited, and may be 0.0005 or more, or 0.0010 or more.
• the dielectric loss tangent at 10 GHz can be measured by the method described in Examples below.
• the fiber-reinforced base material of the present invention can also suppress an increase in dielectric constant over time.
• the dielectric constant (10 GHz) of the fiber-reinforced base material of the present invention after being subjected to humidity conditioning for one week in an atmosphere of 20° C. and 65% RH is preferably 3.0 or less, more preferably 2.8 or less. more preferred.
• the lower limit is not particularly limited, and may be 0.1 or more.
• the dielectric constant (10 GHz) of the fiber-reinforced base material of the present invention after being subjected to humidity conditioning for 4 weeks in an atmosphere of 20° C. and 65% RH is preferably 3.0 or less, and 2.8 or less. is more preferable.
• the lower limit is not particularly limited, and may be 0.1 or more.
• the dielectric constant at 10 GHz can be measured by the method described in Examples below.
• a metal layer is laminated on at least one side of the fiber-reinforced base material of the present invention to form a laminated base material.
• a post-attached thick metal layer may be further formed on the metal layer of the laminated substrate.
• the metal material of the metal layer and the thick metal layer is not particularly limited as long as it is a conductive metal material, but silver, copper, gold, platinum, rhodium, nickel, aluminum, iron, chromium, zinc , tin, brass, cupronickel, bronze, monel, molybdenum, tungsten, tin-lead solder, tin-copper solder, tin-silver solder, etc., or their alloys are usually used, and copper is used for performance and economy. is preferable in the balance of
• the method for laminating the fiber-reinforced base material and the metal layer is not particularly limited, and the following methods (1) to (4) are exemplified.
• the laminated base material comprising the fiber reinforced base material of the present invention and a metal layer laminated on at least one side of the fiber reinforced base material can be obtained by any one of the following methods (1) to (4) alone or in combination. obtained by (1) A method in which a fiber-reinforced base material and a metal foil are fused by heating and pressure molding without an adhesive layer. (2) A method of fusing a fiber-reinforced base material and a metal foil through an adhesive layer by heat and pressure molding.
• a vacuum coating technique such as vapor deposition, sputtering, or ion plating.
• a coating film made of an inorganic substance such as a metal element or a metal oxide is formed on the surface of the metal layer used in the laminated base material of the present invention and, if necessary, the surface of the thick film metal layer to be subsequently applied thereon.
• a coating film made of an inorganic substance such as a metal element or a metal oxide is formed.
• the surface of the metal layer or, if necessary, a post-attached thick metal layer formed thereon may be treated with a coupling agent (aminosilane, epoxysilane, etc.), sandblasted, wet blasted, hauled, corona treated, It may be subjected to plasma treatment, ion gun treatment, etching treatment, or the like.
• the circuit board of the present invention includes the fiber-reinforced base material and a patterned metal layer laminated on at least one side of the fiber-reinforced base material. Since the fiber-reinforced base material of the present invention suppresses an increase in dielectric loss tangent over time as described above, it can be suitably used as a circuit board for a high frequency band of 1 GHz or higher.
• the method of manufacturing various circuit boards such as circuit boards for high frequency bands using the laminated base material of the present invention is not particularly limited, and ordinary methods can be employed.
• a photoresist is applied onto the metal layer of the laminated base material or, if necessary, a post-attached thick film metal layer formed thereon, and after drying, exposure, development, etching, and photoresist peeling processes are performed to remove the metal layer.
• a part of the layer is removed to form a conductor pattern such as a wiring circuit pattern or an antenna pattern, and if necessary, solder resist film formation and electroless tin plating are performed.
• a flexible printed wiring board, a multilayer printed wiring board obtained by multilayering them, a printed wiring board having a semiconductor chip directly mounted thereon, or various circuit boards such as an antenna substrate can be obtained.
• the procedure for producing the conductor pattern, the method for multilayering, and the method for mounting the semiconductor chip are not particularly limited, and may be appropriately selected from conventionally known methods and implemented.
• Tensile strength and tensile modulus of fiber were measured using "Autograph AG-I" manufactured by Shimadzu Corporation, sample length 250 mm (length between chucks), elongation speed 100%. / min conditions strain-stress curve was measured under conditions of atmospheric temperature 20 ° C. and relative humidity 65%, tensile strength (GPa) was calculated from the stress and elongation at the maximum point, and further near the origin of the curve The tensile modulus (GPa) was calculated from the tangent line giving the maximum gradient. In addition, each value used the average value of 5 times.
• Sheet material content (%) ⁇ (sheet material basis weight)/(fiber reinforced base material basis weight) ⁇ x 100
• Dielectric constant and dielectric loss tangent of fiber-reinforced base material The dielectric constant and dielectric loss tangent at 10 GHz were measured by the cavity resonance method using “Network Analyzer MS46122B” manufactured by Anritsu Corporation. The dielectric constant and dielectric loss tangent were measured after heating and pressure molding (before humidity conditioning, which will be described later in Comparative Examples 1 and 2), and after humidity conditioning at 20° C. and 65% for one week and four weeks, respectively.
• Example 1 A woven fabric made of Zylon AS manufactured by Toyobo Co., Ltd. (single yarn diameter: about 10 ⁇ m, basis weight: 50 g/m 2 ) was heat-treated at 550° C. for 1 hour in a nitrogen atmosphere. The obtained woven fabric is referred to as sheet material 1 . Next, 10 g of a polyphenylene ether resin (SA-9000) manufactured by SABIC and 0.2 g of a cross-linking agent (Perbutyl P) manufactured by NOF Corporation were dissolved in 10 g of methyl ethyl ketone to prepare a varnish. The sheet material 1 was impregnated with varnish, dried, and vacuum-heated and pressure-molded at 200° C.
• SA-9000 polyphenylene ether resin
• Perbutyl P cross-linking agent
• Table 1 shows the evaluation results of the obtained sheet material and fiber-reinforced base material.
• Zylon AS manufactured by Toyobo Co., Ltd. (single filament diameter: about 10 ⁇ m) was heat-treated under the same conditions as above, and the tensile strength and tensile modulus of the obtained fiber were measured. Table 1 shows the evaluation results of the obtained fibers.
• Example 2 instead of sheet material 1, a sheet material obtained by heat-treating a woven fabric (single yarn diameter: about 10 ⁇ m, basis weight: 50 g/m 2 ) made of Zylon HM manufactured by Toyobo Co., Ltd. at 550° C. for 1 hour in a nitrogen atmosphere. A fiber-reinforced base material was produced and evaluated in the same manner as in Example 1, except that No. 2 was used. Table 1 shows the obtained evaluation results. Also, Zylon HM manufactured by Toyobo Co., Ltd. (single filament diameter: about 10 ⁇ m) was heat-treated under the same conditions as above, and the tensile strength and tensile modulus of the obtained fiber were measured. Table 1 shows the evaluation results of the obtained fibers.
• Example 1 The same method as in Example 1 was performed except that instead of the sheet material 1, a woven fabric made of Zylon AS (that is, a woven fabric made of Zylon AS without heat treatment, single yarn diameter: about 10 ⁇ m) was used. Fiber reinforced substrates were made and evaluated. Table 1 shows the obtained evaluation results. In addition, the tensile strength and tensile modulus of Zylon AS (that is, Zylon AS not subjected to heat treatment, single filament diameter: about 10 ⁇ m) were measured. Table 1 shows the evaluation results.
• Example 2 In the same manner as in Example 1, except that a woven fabric made of Zylon HM (i.e., a woven fabric made of Zylon HM without heat treatment, single yarn diameter: about 10 ⁇ m) was used instead of the sheet material 1. Fiber reinforced substrates were made and evaluated. Table 1 shows the obtained evaluation results. In addition, the tensile strength and tensile modulus of Zylon HM (that is, Zylon HM without heat treatment, single filament diameter: about 10 ⁇ m) were measured. Table 1 shows the evaluation results.
• the heat-treated PBO fibers of the present invention have an increased insoluble content in methanesulfonic acid and a suppressed water absorption rate.
• the dielectric loss tangent is kept low even after four weeks of humidity conditioning. That is, it can be seen that the fiber-reinforced base material obtained from the PBO fiber of the present invention has excellent stability over time.
• the present invention it is possible to provide a fiber-reinforced base material that can suppress an increase in dielectric loss tangent over time, and can be used in a wide range of fields.

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• 2022
  • 2022-12-14 JP JP2023573924A patent/JPWO2023136037A1/ja active Pending
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