JP2010260890A - Prepreg using pyridobisimidazole fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg using a pyridobisimidazole fiber which has excellent heat resistance, flame retardancy, and a low linear expansion coefficient like a polybenzazole fiber, excels in post formability, and has low moisture-absorption characteristics. <P>SOLUTION: In the electron beam diffraction pattern obtained from the surface layer part (surface to 1 μm) of a pyridobisimidazole fiber, when the diffraction peak area derived from the crystal (200) plane in the equatorial direction profile is taken as S1 and the diffraction peak area derived from the crystal (110) plane, (210) plane, and (400) plane is taken as S2, the existing state of the pyridobisimidazole crystal has S2/S1 which meets 0.1-1.5 and the pyridobisimidazole fiber has a root-mean-square roughness of the fiber surface measured by an atomic force microscope of 20 nm or less. The prepreg uses such a pyridobisimidazole fiber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a prepreg using pyridobisimidazole fibers, and more specifically, a print having not only excellent post-processability but also lower hygroscopicity than a prepreg using conventional pyridobisimidazole fibers. The present invention relates to a prepreg suitable as an industrial material for wiring boards and the like.

  In recent years, there has been a remarkable trend toward downsizing and high-density mounting methods in the field of electronic devices for communications, industrial use, and consumer use. Along with this, heat resistance and dimensional stability are also superior in terms of materials. Electrical characteristics are now required. For example, in a printed wiring board, conventionally, a glass cloth base copper-clad laminate produced using a prepreg based on a glass cloth has been used, but in recent years, weight reduction, low dielectric constant, Due to demands for laser processability and the like, printed wiring boards using prepregs based on organic fibers such as wholly aromatic polyamide fibers and liquid crystal polyester fibers have been proposed. However, when these organic fibers are used, there are problems in terms of electrical insulation, heat resistance, coefficient of thermal expansion and the like of the laminate.

  Therefore, as a method for improving these drawbacks, a method of reinforcing with polybenzazole fiber having a negative coefficient of linear expansion has been proposed (for example, see Patent Document 1).

  Polybenzazole fibers have the highest level of performance among organic fibers in all respects, in terms of strength, elastic modulus, heat resistance and flame retardancy. Therefore, it is developed for various uses that make use of these features. However, in applications that make use of heat resistance and flame retardancy, the fibers are not easily cut due to the high strength and high elastic modulus of the reinforcing material fibers. Therefore, when polybenzazole fiber is used for a prepreg, there is a disadvantage that post-processability is poor, and improvement of post-processability and lower hygroscopicity are desired.

JP 2001-18324 A

  The object of the present invention has been made in view of the above circumstances, and has excellent heat resistance, flame retardancy, a low linear expansion coefficient, excellent post-processability, like polybenzazole fiber, and An object of the present invention is to provide a prepreg using low-hygroscopic pyridobisimidazole fibers.

That is, the present invention is as follows.
(1) In the electron diffraction pattern obtained from the surface layer portion (surface to 1 μm) of pyridobisimidazole fiber, the diffraction peak area derived from the crystal (200) plane in the equator profile is S1, the crystal (110) plane, ( 210) When the diffraction peak area derived from the (400) plane and (400) is S2, S2 / S1 is an existing state of pyridobisimidazole crystals satisfying 0.1 to 1.5, and with an atomic force microscope A prepreg using pyridobisimidazole fibers characterized in that the mean square roughness of the measured fiber surface is 20 nm or less.

(2) In the azimuth profile of electron diffraction of (200) plane of pyridobisimidazole crystals obtained from the surface layer part (surface to 1 μm) and the center part of the pyridobisimidazole fiber, the diffraction peak obtained from the surface layer part The pyridobisimidazole fiber according to (1) comprising a pyridobisimidazole fiber having a value T divided by the half-value width of the diffraction peak obtained from the center portion of 0.75 to 1.25 was used. Prepreg.

(3) The thermal expansion coefficient in the surface direction of the pyridobisimidazole fiber is −3 ppm / ° C. or more and 6 ppm / ° C. or less, and the pyridobisimidazole fiber according to (1) or (2) is used. Prepreg.

The pyridobisimidazole fiber used in the present invention, according to the analysis by the electron beam diffraction method, at least the selective orientation of the crystal of the fiber surface layer portion in the a and b axis directions is randomized, and the surface layer portion and the center portion of the fiber The difference in crystal orientation is small, and the orientation of the crystal as a whole is randomized. This makes it possible to achieve a fiber strength that does not hinder the post-processability even though the fiber belongs to a high-strength fiber. Furthermore, since the fiber surface structure is dense, the hygroscopicity is significantly reduced.
For this reason, the prepreg using the pyridobisimidazole fiber of the present invention has excellent heat resistance, flame retardancy, low linear expansion coefficient, and low hygroscopicity, and therefore has excellent insulating properties. Therefore, it is suitable as a prepreg for a printed wiring board.

It is explanatory drawing which shows the example of the equatorial direction profile of the limited visual field electron diffraction pattern of the surface layer part (surface-1 micrometer) of the pyridobisimidazole fiber used by this invention.

Hereinafter, the present invention will be described in detail.
At least 50% of the fiber made of pyridobisimidazole used in the present invention is composed of repeating units of pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene). On the other hand, the remainder is replaced by 2,5-dihydroxy-p-phenylene substituted or unsubstituted arylene and / or pyridobisimidazole is benzobisimidazole, benzobisthiazole, benzobis It is replaced by oxazole, pyridobisthiazole and / or pyridobisoxazole.

  In this case, a ladder polymer is preferred in which at least 75% of the repeating units are made from pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene). On the other hand, the remainder is replaced with 2,5-dihydroxy-p-phenylene substituted or unsubstituted arylene and / or pyridobisimidazole is benzobisimidazole, benzobisthiazole, benzobis It is replaced by oxazole, pyridobisthiazole and / or pyridobisoxazole.

  In the case of partial replacement of 2,5-dihydroxy-p-phenylene (up to 50%), arylene dicarboxylic acids such as isophthalic acid, terephthalic acid, 2,5-pyridinedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4 4,4'-diphenyldicarboxylic acid, 2,6-quinolinedicarboxylic acid and 2,6-bis (4-carboxyphenyl) pyridobisimidazole are preferred compounds that remain after removal of the carboxyl group.

  The structural unit of pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) is represented by [Chemical Formula 1].

  Suitable solvents for forming the polymer dope include cresol and non-oxidizing acids that can dissolve the polymer. Suitable acid solvents include, for example, polyphosphoric acid, methanesulfonic acid, high concentration sulfuric acid, or mixtures thereof. More preferred solvents are polyphosphoric acid and methanesulfonic acid, and particularly preferred solvents are polyphosphoric acid.

  The 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. For example, the maximum concentration is limited by practical handling properties such as polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration usually does not exceed 20% by weight.

  In the present invention, a suitable polymer or copolymer and dope are synthesized by a known method (for example, JP-A-8-509516). Suitable monomers should be heated in a non-oxidizing and dehydrating acid solution at a stepwise or constant heating rate from 60 ° C to 230 ° C under fast stirring and high shear conditions in a non-oxidizing atmosphere. Can be reacted.

  The dope thus polymerized is supplied to the spinning section and discharged from the spinneret at a temperature of usually 100 ° C. or higher. A plurality of base pores are usually arranged in a circumferential shape or a lattice shape, but may be other types. The number of nozzle holes is not particularly limited, but it is important that the arrangement of the spinning holes on the spinneret surface has a hole density that does not cause fusion between the spun yarns (dope filaments).

  In order to obtain a sufficient draw ratio (SDR) in the spun yarn, it is important to set a sufficiently long draw zone length as described in US Pat. No. 5,296,185. Furthermore, it is preferable to cool uniformly with rectified cooling air having a relatively high temperature (specifically, higher than the solidification temperature of the dope and lower than the spinning temperature). The length (L) of the draw zone is required to be a length that completes solidification in a non-solidifying gas, and is roughly determined by the single-hole discharge amount (Q). In order to obtain good fiber properties, it is preferable that the take-out stress in the draw zone is 2.2 g / dtex or more in terms of polymer (assuming that only the polymer is stressed).

  In the present invention, the pyridobisimidazole dope filament (stretched or unstretched) obtained above is a liquid in which pyridobisimidazole is incompatible before being immersed in the coagulation bath, that is, a coagulant. It is preferable to perform a steam treatment for positively contacting the steam.

  As a coagulant for polybenzazole, at least one of water, methanol, ethanol, acetone, and ethylene glycol is preferable, and water is more preferable in terms of simplicity.

  According to this vapor treatment, since the dope filament is positively brought into contact with the gas (air) containing the liquid vapor, the coagulant rapidly penetrates and diffuses throughout the fiber inside the dope filament, and solidification nuclei. It is thought that such a thing is formed in the fiber center part direction.

  Surprisingly, when the fiber cross-section is observed after fiber formation, it is surprisingly recognized that the boundary line, which is considered to be generated based on the difference in the timing of the start of structure formation, the expression of a so-called two-layer that can be expressed as a sheath core. is there. The better the coagulant penetrates to the center, the smaller the core layer and eventually the borderline will not be recognized. In addition, in the conventional fiber which is not subjected to steam treatment, a two-layer structure of the sheath / core is not recognized.

  The temperature of the steam treatment varies depending on the type of coagulant, but in the case of water, the temperature of the steam atmosphere or the temperature of the sprayed steam is preferably 50 to 200 ° C, more preferably 60 to 160 ° C. If the said temperature is less than 50 degreeC, the effect of reducing an intensity | strength will become small. On the other hand, when the temperature exceeds 200 ° C., yarn breakage frequently occurs and the productivity tends to be remarkably lowered. Any coagulant having a boiling point lower than that of water may be used at a lower temperature. Further, if it is a coagulant having a boiling point higher than that of water, it may be higher and can be appropriately selected in consideration of the boiling point and the vapor pressure.

  The content of the vapor component with respect to the total gas components in the vapor phase is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more for short-time treatment. .

  If the vapor phase temperature is too low, the thickness of the sheath layer will not develop, and conversely if the temperature is too high, the sheath / core structure will appear, but the temperature of the passing filament will rise and the yarn will tend to break frequently. is there. If the vapor content is too low, the sheath / core structure is hardly developed.

  The apparatus for performing the steam treatment is not particularly limited as long as the dope filament is in contact with the steam and can at least solidify the surface layer, and is not particularly limited to a continuous type, a non-continuous type, a sealed type, and a non-sealed type.

  After passing through the vapor phase, the filament is then directed to a coagulation (extraction) bath for solvent extraction of pyridobisimidazole and complete coagulation of the filament. The coagulation bath is not particularly limited, and any type of coagulation bath may be used. For example, funnel type, water tank type, aspirator type or waterfall type can be used.

  Finally, extraction is performed so that the solvent remaining in the filament in the coagulation bath is 1% by mass or less, preferably 0.5% by mass or less. The liquid used as the extraction medium in the present invention is not particularly limited, but preferably water, methanol, ethanol, acetone, ethylene glycol or the like that is substantially incompatible with pyridobisimidazole. The extract is preferably a simple phosphoric acid solution or water.

  Further, a method of separating the coagulation (extraction) bath in multiple stages, gradually decreasing the concentration of the phosphoric acid aqueous solution, and finally washing with water can be employed. In the coagulation (extraction) step, it is a preferred method to neutralize the filament bundle with an aqueous sodium hydroxide solution and then wash with water. Thereafter, drying and heat treatment can be applied to form a fiber that can be distinguished into two layers of a sheath and a core.

  The pyridobisimidazole fiber used in the present invention has a mean square roughness of the fiber surface of 20 nm or less, preferably 16 nm or less, more preferably 10 nm or less. This indicates that the fiber surface structure is particularly dense compared to the conventional one, and this reduces the hygroscopicity, so that when used as a printed wiring board member, the reliability is increased. Is obtained.

  The mean square roughness Rms of the fiber surface can be measured using an atomic force microscope (AFM). For example, as AFM, SPI3800N-SPA300 manufactured by Seiko Instruments (SII) is used. The probe uses Si-DF3 from Si rectangular cantilever SII having a spring constant of 2 N / m, a length of 450 μm, a width of 60 μm, and a thickness of 4 μm. The scanner adopts a 100 μm scanner and the observation mode adopts the DFM mode. The scanning is performed at a speed of 0.5 Hz, the scanning direction is parallel to the fiber axis, and the conditions are 20 ° C. in the atmosphere and 65% relative humidity.

The fiber used for the measurement was used after washing with ethanol and n-hexane mixed solution and drying. The observation visual field range is a square area of 5 μm square, and after observation, the three-dimensional tilt correction of the attached software is performed and the planarization process is performed. In order to take into account the distortion caused when the image is flattened due to the presence of the curvature of the fiber, the mean square roughness Rms of only the 3 μm square area at the center is calculated after correction using the attached software. Observation was performed at random at 10 or more locations, and each Rms was obtained, and an average value was calculated. Rms can be expressed using the following equation.
Rms = [(1 / N) Σ (Zi−Z0) ² ] ^0.5
Here, Zi represents the height at each measurement point, Z0 represents the average height over the entire measurement site, and N represents the number of measurement points.

Next, a method for densifying the fiber surface structure by setting the mean square roughness of the fiber surface to 20 nm or less will be described.
In order to reduce the hygroscopicity, it is important to increase the crystal orientation on the fiber surface. For this reason, it is important to change the structure in the inner and outer layers of the fiber by slowing the solidification rate of the fiber dope in the extraction process.

  As a method for slowing the coagulation rate, it is effective to increase the concentration of the phosphoric acid aqueous solution in the coagulation liquid, lower the bath temperature, or select a non-aqueous coagulant. The concentration of the phosphoric acid aqueous solution is preferably 50% or more and less than 80%. More preferably, it is 55% or more and less than 70%, and particularly preferably 60% or more and less than 65%.

  The higher the concentration, the greater the effect. However, if the concentration is higher than important, the fiber strength decreases, which is not preferable. The coagulation bath temperature may be 5 ° C. or less. The temperature range is preferably 4 ° C to -30 ° C, more preferably 0 ° C to -15 ° C. However, if the temperature is lowered too much, dew is generated around the bath, which is not preferable for the operation of the production machine.

  When a non-aqueous coagulant is selected, an organic solvent having an affinity for water, such as alcohols such as ethanol and methanol, ketones such as acetone, and glycols such as ethylene glycol, is preferable. Of course, a plurality of non-aqueous coagulants and water may be mixed and used. Thereafter, the fiber is dried and further subjected to a heat treatment step.

  The drying temperature may be any temperature that does not cause a decrease in fiber strength, and is, for example, 150 ° C. or higher and 400 ° C. or lower, preferably 200 ° C. or higher and 300 ° C. or lower, more preferably 220 ° C. or higher and 270 ° C. or lower. The heat treatment temperature is 400 ° C. or higher and 700 ° C. or lower, preferably 500 ° C. or higher and 680 ° C. or lower, more preferably 550 ° C. or higher and 630 ° C. or lower.

  The fiber is then dried and further subjected to a heat treatment step if necessary. The drying temperature is not particularly limited as long as the coagulant and the solvent are easy to fly. Specifically, it is set to 150 to 400 ° C, preferably 200 to 300 ° C, more preferably 220 to 270 ° C. For the purpose of improving the elastic modulus, heat treatment may be performed under tension as necessary. About heat processing temperature, it is 400-700 degreeC, Preferably it is 500-680 degreeC, More preferably, you may be 550-630 degreeC. The tension applied is 0.3 to 1.2 g / dtex, preferably 0.5 to 1.1 g / dtex, more preferably 0.6 to 1.0 g / dtex.

The pyridobisimidazole fiber used in the present invention produced by the method as described above has the following characteristics by fiber fine structure analysis by an electron diffraction method.
That is, the pyridobisimidazole fiber used in the present invention is derived from the crystal (200) plane in the equatorial profile in the electron diffraction pattern (see FIG. 1) of the polybenzazole crystal obtained from the surface layer portion (surface to 1 μm). When the diffraction peak area of (S1) and the diffraction peak area derived from the crystal (110), (210) plane and (400) plane are (S2), S2 / S1 is 0.1 to 1.5. is important.

  S2 / S1 is preferably 0.2 to 1.3. If it is less than 0.1, the fiber strength tends to be insufficiently reduced. Conversely, if it exceeds 1.5, even if post-processability is high, the fiber strength decreases too much, resulting in poor operability and processability. May be.

  In addition, in the azimuth angle profile of electron diffraction of the (200) plane of the polybenzazole crystal obtained from the surface portion (1 μm from the surface) and the center portion of the pyridobisimidazole fiber, half of the diffraction peak obtained from the surface layer portion. It is preferable that the ratio T of the value width to the half value width of the diffraction peak obtained from the center is 0.75 to 1.25. More preferably, it is 0.85-1.15.

  When the half width ratio T is less than 0.75, the strength of the fiber may not be sufficiently lowered. On the other hand, if it exceeds 1.25, the strength of the fiber is excessively lowered, and the operability, process passability and the like may be deteriorated.

  For the pyridobisimidazole fiber used in the present invention, a known method can be adopted to obtain a diffraction diagram and an analysis result by an analysis method using an electron diffraction method. As the measurement fiber, an ultrathin section having a thickness of about 70 nm is used so as to be in the fiber axis (length) direction and include the surface layer portion and the center portion of the fiber.

  That is, a single fiber was embedded in an epoxy resin prepared according to the Luft method (J. Biophys. Biochem. Cytol., 9, 409 (1961)), left in an oven at 60 ° C. overnight, solidified and fixed, and A resin block in which is embedded is obtained. Next, the resin block is attached to an ultra microtome manufactured by Reichert, and is polished using a glass knife until the embedded fibers appear in the vicinity of the block surface, and then a single fiber using a diamond knife manufactured by Diatom Cut in a direction parallel to the axial direction.

  For example, when the diameter of a single fiber is 10 μm, when an ultrathin section having a thickness of about 70 nm is continuously cut from the fiber surface, it can be cut into about 140 sections. All cut sections were selectively collected on a copper grid as a group of every 10 sheets in the cutting order. The first to tenth sheets from the start of cutting are defined as group 1, and are sequentially defined as group 1, group 2... Group n.

  Among these groups, when n is an even number, the (n / 2) th group is used for the limited-field electron diffraction measurement when the nth group is odd, and when the n is an odd number, the (n / 2-0.5) th group is used. When one single fiber is all cut into ultrathin sections having substantially the same thickness, the above-described group of fiber sections includes both the surface layer portion (surface) and the center portion of the fibers.

  After making an ultrathin slice with a thickness of about 70 nm and including both the surface layer (surface) and the center of the fiber, the resulting ultrathin slice is collected on a 300 mesh copper grid and thinly carbonized. Vapor deposition is performed. The central part in the present invention is a place including a part that can be regarded as a central point when the cross section of the fiber is regarded as a circle, and means a core part having a diameter of up to several microns. , The middle part of both surfaces.

  Next, an ultrathin section is introduced into the electron microscope, and a limited-field electron diffraction image is taken for both the surface layer portion and the center portion of the fiber to obtain an electron diffraction pattern. When taking the electron beam diffraction image, the diameter of the limited field of view (aperture) is 1 μm or less, and a portion free from artifacts (for example, wrinkles and blurring of the section) generated in the ultrathin section of the fiber is cut. It was selected as a diffraction image photographing site.

Among the obtained electron diffraction patterns, the profile in the equator direction is approximated using a Lorentz function, and the integrated intensity (area) of diffraction peaks derived from (200) and (110), (210) and (400). The half width is calculated, and the area derived from (200) is S1, and the sum of the areas derived from (110), (210) and (400) is S2, and S2 / S1 is calculated.
The apparent crystal size (ACS) is calculated using the following equation.
ACS = 0.9λ / βcosθ
Here, λ is the wavelength of the electron beam, β is the full width at half maximum (in radians), and θ is the half value of the diffraction angle 2θ.

  Further, for (200) diffraction, the half-value width is calculated by approximating the diffraction profile in the azimuth angle direction with a Lorentz function.

  In the pyridobisimidazole fiber used in the present invention, when a two-layer structure of a sheath layer and a core layer is formed, simple discrimination thereof can be performed by observing the fiber cross section with an optical microscope. That is, when the fiber cross section is cut to a thickness that can be observed with an optical microscope, and magnified about 40 times with an optical microscope, the boundary between the sheath layer and the core layer is recognized as a circular line. The outer side of the circular line is a sheath layer, and the inner side is a core layer.

When the sheath layer is formed due to the penetration of the coagulant vapor, it is preferable that the thickness of the sheath layer is as large as possible and the diameter of the core layer is as small as possible. The ratio of the core layer in the pyridobisimidazole fiber used in the present invention, that is, the ratio of the average diameter r ₂ of the core layer in the fiber cross-sectional direction to the fiber cross-sectional diameter r ₁ R (%) [= (r ₂ / r ₁ ) × 100] is preferably 90% or less. More preferably, it is 80% or less, more preferably 60% or less, and most preferably close to 0%. If steam treatment conditions are selected so that the steam penetrates and diffuses well, the ratio of the core layer can be lowered, and the ratio of the core layer can be finally reduced to 0%.

The reason why the pyridobisimidazole fiber used in the present invention moderately decreases in strength and improves the post-processability is not clear.
However, it is estimated as follows from the electron diffraction pattern of the pyridobisimidazole crystal by the above-mentioned electron beam diffraction method.
(A) At least the selective orientation of the crystals in the fiber surface layer portion in the a and b axis directions is randomized as compared with the conventional one.
(B) The difference in crystal orientation between the surface layer portion and the center portion of the fiber is reduced, and the crystal orientation of the fiber as a whole is randomized as compared with the conventional one.
(C) It is considered that this reduces the fiber strength and improves the post-processability of the pyridobisimidazole fiber.

  In addition, the selective orientation of crystals is moderately disturbed, stress concentration in a specific direction is relaxed, and latent strain inside the fiber is reduced, so that fibrillation can be suppressed.

  Examples of the usage of the pyridobisimidazole fiber used in the present invention include woven fabric using the filament obtained by the above method, UD (reinforcing material prepared by arranging fibers in parallel in a uniaxial direction), and non-woven fabric sheet. Is mentioned. Glass, aramid, natural cellulosic fiber cloth or microfibrils may be mixed for the purpose of adjusting the density of the sheet-like material.

In the case of making a woven fabric, for example, it can be suitably obtained by the method described in JP-A No. 2006-203142.
The texture of the woven fabric may be any of a plain structure, a twill structure, or any other structure that is usually used for a prepreg, but preferably exhibits a high reinforcing performance when a structure such as a plain structure or a twill structure that does not cause misalignment is used. Can be made. If the fibers used in the woven fabric have a low fineness of 600 dtex or less, preferably 300 dtex or less, more preferably 200 dtex or less, high performance is easily obtained. What is the weaving density? It is also important that the number is 40/25 mm or less. Furthermore, when the fabric weight is 200 g / m ² or less, and preferably 150 g / m ² , performance can be exhibited.

  Furthermore, the prepreg using pyridobisimidazole fiber can be used for a base fabric for a printed wiring board. That is, the printed wiring board is configured by laminating a prepreg impregnated with a curable resin on the sheet-like material.

  As the curable resin composition used for the printed wiring board, a curable resin composition containing an epoxy resin as a component is preferable. As said epoxy resin, what is necessary is just a resin containing 2 or more epoxy groups in 1 molecule, and well-known resin is used 1 type or in combination of 2 or more types. Further, as the curable resin other than the epoxy resin, for example, a cyanate resin and a bismaleimide triazine resin are also suitable.

  As such an epoxy resin, for example, a glycidyl ether type epoxy resin obtained by reaction of phenols or alcohols with epichlorohydrin, a glycidyl ester type epoxy resin obtained by reaction of carboxylic acids with epichlorohydrin, amines or cyanuric Examples thereof include a glycidyl type epoxy resin obtained by a reaction between an acid and epichlorohydrin, an internal epoxy resin obtained by oxidation of a double bond, etc., an epoxy resin modified BT resin, and an epoxy resin modified cyanate ester resin.

  Examples of the epoxy resin curing agent include polyamine curing agents, polymercaptan curing agents, anionic polymerization catalyst curing agents, cationic polymerization catalyst curing agents, and latent curing agents. Further, for the purpose of expressing desired performance depending on the use, a filler or an additive may be added to the curable resin composition within a range that does not impair the original properties.

  The proportion of the pyridobisimidazole fiber in the prepreg is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass. When the ratio of the pyridobisimidazole fiber is less than 5% by mass, the dimensional stability and strength after curing tend to be insufficient. On the other hand, if this ratio exceeds 90% by mass, insufficient adhesion and peeling of the metal foil are likely to occur.

As for the method of combining the resin composition and the substrate, for example, a melting method in which the resin product is melted and impregnated in the substrate, the resin composition is dissolved in a solvent, impregnated in the substrate, and then the solvent is dried. A wet method for obtaining a prepreg is preferred. Molding and curing are preferably performed at a temperature of 80 to 300 ° C., a time of 1 minute to 10 hours, and a pressure of 0.1 to 500 kg / cm ² , more preferably a temperature of 150 to 250 ° C., a time of 1 minute to 5 hours, and a pressure of 1 It is the range of -100 kg / cm < ² >.

  As metal foil used for a laminated body, copper foil and aluminum foil are mentioned, for example. The thickness is preferably, for example, 3 to 200 microns, more preferably 5 to 120 microns. The prepreg of the present invention can obtain a copper clad laminate by laminating and curing a copper foil on both sides. Alternatively, the prepreg can be used as a prepreg for a so-called bull-up method in which via holes are formed by laser irradiation after the prepregs are laminated on the upper and lower sides of a printed wiring board and then plated to form a connection and pattern of via holes. At this time, it may be used in the form of a so-called resin-coated copper foil in which a prepreg is laminated on one side of a metal foil in advance. Moreover, when laminating a prepreg on the outside of the printed wiring board, a copper foil can be simultaneously laminated on the outermost layer. In this case, the outermost copper foil can be used when forming vias by laser.

  Furthermore, after drilling the prepreg of the present invention by laser or mechanical punching, and then filling the hole with a conductive paste, a copper foil is laminated on both sides and cured to form a core material. The core material can be patterned to produce a printed wiring board, and the filler-containing prepreg produced in the same manner can be used for a multilayer wiring board that is subsequently laminated.

  Hereinafter, although an example is illustrated and the present invention is explained concretely, the present invention is not limited by these. In addition, the measurement and various evaluation of the characteristic value of the pyridobisimidazole fiber used in the Example and a printed wiring board using the same are as follows.

(1) Intrinsic Viscosity The viscosity of a polymer solution prepared to a concentration of 0.5 g / L using methanesulfonic acid as a solvent was measured using a Ostwald viscometer in a thermostatic chamber controlled at 25 ° C.

(2) ratio of the fiber cross-sectional diameter _{r 1} of the average diameter _{r 2} of the core layer in the fiber cross section R (%)
After burying the measurement fiber in an epoxy resin (manufactured by Gatan, G-2), argon ion etching was performed using a cross section polisher (manufactured by JEOL Ltd., SM-09010), and the cross section of the observation fiber was obtained. Obtained. Then, observing the boundary line between the core layer and the sheath layer by light microscopy, to the average diameter r ₂ and the fiber cross-sectional diameter r ₁ and measured, the fiber cross sectional diameter r ₁ of the average diameter r ₂ of the core layer of the core layer The ratio R (%) was calculated by the following formula.
R (%) = (r ₂ / r ₁ ) × 100

(3) Tensile strength and elastic modulus After standing for 24 hours or more in a test chamber in a standard state (temperature: 20 ± 2 ° C., relative humidity (RH): 65 ± 2%), the tensile strength and elastic modulus of the fiber are measured according to JIS L. It was measured with a tensile tester according to 1013.

(4) Heat resistance When using a thermogravimetric analyzer (TA Instrument, TGA Q50) and increasing the temperature from room temperature at a temperature increase rate of 20 ° C./min in the air, the weight retention rate [(there is Sample weight at the time of temperature / original sample weight) × 100] was evaluated at a temperature at which 90%.

(5) S2 / S1, apparent crystal size, and full width at half maximum The sample for electron diffraction measurement is the method described below, and the measurement fiber is in the fiber axis (length) direction, and the surface layer portion and the center of the fiber. And an ultra-thin slice having a thickness of about 70 nm was used.

  That is, the monofilament was embedded in an epoxy resin prepared according to the Luft method (J. Biophys. Biochem. Cytol., 9, 409 (1961)), left in an oven controlled at 60 ° C. overnight, and solidified and fixed. Thus, a resin block in which fibers were embedded was obtained. Next, this resin block was attached to an ultra microtome (manufactured by Reichert) and polished using a glass knife until the embedded fibers appeared near the block surface. Next, using a diamond knife made by Diatome, cut in a direction parallel to the fiber axis direction of a single fiber, and an ultrathin slice having a thickness of about 70 nm and including both the surface layer portion (surface) and the center portion of the fiber It was created.

  The obtained ultrathin sections are collected on a 300-mesh copper grid, thinly carbon-deposited, and then introduced into an electron microscope, and a limited-field electron beam is applied to both the surface layer and the center of the fiber. A diffraction image is taken (in this case, the diameter of the limited field of view (aperture) is 1 μm or less, and an ultrathin section of the fiber is free from artifacts (for example, wrinkles and blurring of the section) that occur during cutting. An electron diffraction pattern was selected.

Among the obtained electron diffraction patterns, the profile in the equator direction is approximated using a Lorentz function, and the integrated intensity (area) of diffraction peaks derived from (200) and (110), (210) and (400). And the full width at half maximum was calculated. The area derived from (200) was S1, and the sum of the areas derived from (110), (210) and (400) was S2, and S2 / S1 was calculated.
The apparent crystal size (ACS) was calculated using the following formula.
ACS = 0.9λ / βcosθ
Here, λ is the wavelength of the electron beam, β is the full width at half maximum (in radians), and θ is the half value of the diffraction angle 2θ.

  Further, for (200) diffraction, the FWHM was calculated by approximating the diffraction profile in the azimuth direction with a Lorentz function.

(6) Mean square roughness of fiber surface (Rms)
Rms uses an atomic force microscope (manufactured by Seiko Instruments (SII), SPI3800N-SPA300). Si-DF3 was used. The scanner was a 100 μm scanner, the observation mode was the DFM mode, the scanning was performed at a speed of 0.5 Hz, the scanning direction was parallel to the fiber axis, and measurement was performed in the atmosphere at 20 ° C. and relative humidity of 65%.

The fiber used for the measurement was used after washing with ethanol and n-hexane mixed solution and drying. The observation visual field range was a square area of 5 μm square, and after the observation, the three-dimensional tilt correction of the attached software was performed and the planarization process was performed. In order to take into account the distortion that occurs when the image is flattened due to the presence of the curvature of the fiber, the mean square roughness Rms of only the 3 μm square area at the center is calculated after correction using the attached software. Observation was performed at random at 10 or more locations, and each Rms was obtained, and an average value was calculated. Rms was calculated using the following formula.
Rms = [(1 / N) Σ (Zi−Z0) ² ] ^0.5
(Here, Zi is the height at each measurement point, Z0 is the average height over the entire measurement point, and N is the number of measurement points.)

(7) Post-workability The evaluation fiber which gave buckling crimp by the indentation crimping method was cut into a cut length of 44 mm to obtain a staple. The obtained staple was opened with an opener, and then a web having a basis weight of 450 g / m ² was produced with a roller card. Nine sheets of the obtained webs were laminated in sequence, using a Foster needle (product number: 15 × 18 × 40 × 3.5 PB-A F20 2-18-3B / LI / CC / CONICAL) at a needle depth of 7 mm. A felt was obtained by needle punching only from one side of the felt until the needle punching number reached 2000 / cm ² . The number of needles (converted to the number per 1 m ^{2 of} finished felt) was examined until the felt was obtained by sequentially laminating the webs. The smaller the number of broken wires, the better the post-processability.

(8) Process passability The process passability was judged based on the occurrence of production troubles in the processes from spinning to fiber web production.

(9) Printed wiring board migration test A voltage (DC60V) is imprinted on a 40 μm pitch comb-shaped electrode and placed in a constant temperature and humidity chamber (FX412P type, manufactured by ETAC) at 85 ° C. and 85% RH. The insulation resistance value was measured and recorded every 5 minutes in the loaded state. The time for the resistance value between the lines to reach 100 M ohms or less was measured and used as an evaluation of migration.

(10) Linear expansion coefficient The thermal expansion coefficient was measured by a thermomechanical analysis method (TMA method) using TMA (Seiko Instruments Inc.).

Example 1
First, the fiber adjustment method will be described.
Pyridobisimidazole (14.0% by mass) and pentoxide obtained by the method shown in US Pat. No. 4,533,693 and having an intrinsic viscosity of 19.3 dL / g measured with a methanesulfonic acid solution at 30 ° C. A spinning dope composed of polyphosphoric acid having a phosphorus content of 83.17% was used for spinning.

  The dope was passed through a metal net-like filter medium and then kneaded and defoamed with a biaxial kneader. Subsequently, the pressure was increased, while the polymer solution temperature was maintained at 170 ° C., spinning was performed at 170 ° C. from a spinneret having a number of holes 66, and the discharged yarn was cooled using cooling air having a temperature of 60 ° C. Further, the discharged yarn was cooled to 40 ° C. by natural cooling, and then introduced into the coagulation bath. In the coagulation bath, it was first exposed to steam for 0.3 seconds and then contacted with the coagulation liquid. The coagulation liquid was isopropanol, and the temperature was adjusted to 20 ° C. to prepare a fiber.

  Next, the fiber is wound around a gosset roll, the yarn is washed with ion-exchanged water in a second extraction bath at a constant speed, and then immersed in a 0.1 N sodium hydroxide solution for neutralization treatment. did. Further, after washing with water in a water bath, it was wound up, dried in a drying oven at 80 ° C., and allowed to stand until the moisture content in the fiber was 2% or less. Next, heat treatment was performed for 2.4 seconds in a tension of 5.0 g / d and a temperature of 600 ° C.

The obtained fiber had S2 / S1 of 1.1, T of 0.98, an average square roughness of 15.4 nm, and a linear expansion coefficient of −4 ppm / ° C.
In addition, the processability of the obtained pyridobisimidazole fiber is not particularly problematic, and in the evaluation of post-processability in which a felt is produced by laminating fiber webs, the number of broken needles is 60 / m ^2. It was confirmed that the post-processability was excellent.

Next, using the fibers (104 dtex) obtained by the above-described method, a plain woven fabric (weave density: 25 warps and wefts per 25 mm) was obtained.
Furthermore, bisphenol A epoxy resin (100 parts by mass) and 2-methyl-4-methylimidazole (3 parts by mass) were dissolved in methyl ethyl ketone (100 parts by mass) to prepare a varnish. Subsequently, the varnish was impregnated into a plain fabric using the above pyridobisimidazole fiber to prepare a prepreg.

  Eight prepregs obtained in this manner were stacked, 18 μm thick copper foils were stacked on the top and bottom, sandwiched between stainless plates, and subjected to heat molding at 170 ° C. for 90 minutes at a pressure of 4 MPa using a vacuum press molding machine. . Thus, the core material of the multilayer printed wiring board for semiconductor packages was manufactured.

  Furthermore, a print in which two layers of build-up layers are formed by a conventional semi-additive method using ABF SH-9K (product name, manufactured by Ajinomoto Techno Fine Co., Ltd.) having a thickness of 40 μm as an adhesive sheet on both surfaces of the same core material. A wiring board was manufactured.

  The obtained prepreg had a moisture absorption rate of 1.7% and a thermal expansion coefficient in the plane direction of 1 ppm / ° C. The printed wiring board had a migration test result of 473 hours.

(Comparative Example 1)
Fibers were produced in the same manner as in Example 1 except that 20% phosphoric acid aqueous solution (40 ° C.) was used as the coagulation liquid.
The obtained fiber had S2 / S1 of 0.97, T of 1.1, an average square roughness of 39.1 nm, and a linear expansion coefficient of −4 ppm / ° C.
Further, the processability of the obtained pyridobisimidazole fiber is not a problem, and in the evaluation of the post-processability for producing a felt by laminating fiber webs, the number of broken needles is 370 / m ^2. And there was a problem in post-workability.

Further, a plain woven fabric, a prepreg, and a printed wiring board were produced from the obtained fibers in the same manner as in Example 1.
The obtained prepreg had a moisture absorption rate of 4.5% and a thermal expansion coefficient in the plane direction of 1 ppm / ° C. The printed wiring board had a migration test result of 171 hours.

  From these results, it can be understood that the present invention is remarkably reduced in moisture absorption rate as compared with the prior art and is extremely excellent in physical properties.

  The present invention uses a pyridobisimidazole fiber having a unique fiber microstructure in which a fiber surface that has not been obtained so far is dense, excellent in post-processing properties, low hygroscopicity, and low dielectric constant. Because it is a prepreg, it contributes greatly in expanding the field of use as an industrial material.

  In other words, not only for high-density and high-performance circuit boards for mounting silicon chips, but also for tension members such as cables, electric wires and optical fibers, ropes, etc., rocket insulation, rocket casing, pressure vessels, space suits Aviation such as strings, planetary exploration balloons, impact materials such as space materials, bulletproof materials, cut resistant materials such as gloves, fire clothes, heat felt, plant gaskets, heat resistant fabrics, various seals, heat cushions, Heat-resistant flame-resistant members such as filters, rubber reinforcements such as belts, tires, shoe soles, ropes, hoses, fishing lines, fishing rods, tennis rackets, table tennis rackets, badminton rackets, golf shafts, club heads, guts, strings, sail cloths , Running shoes, marathon shoes, spike shoes, skate shoes, Athletic shoes such as ketball shoes, volleyball shoes, bicycles for competition (running) and its wheels, road racers, pis racers, mountain bikes, composite wheels, disc wheels, tension discs, spokes, brake wires, transmission wires, competitions ( Running wheelchairs and their wheels, protectors, racing suits, sports materials such as skis, stocks, helmets, parachutes, friction materials such as avant belts, clutch facings, various building material reinforcements and other rider suits, speakers Suitable for a wide range of applications such as cones, lightweight baby carriages, lightweight wheelchairs, lightweight nursing beds, lifeboats, life jackets.

  Further, since it is highly excellent in low dielectric constant and moisture absorption, which has not been obtained so far, it is particularly useful in printed wiring board materials, semiconductor mounting fields and next-generation information mobile phone fields.

Claims (3)

  In the electron diffraction pattern obtained from the surface layer portion (surface to 1 μm) of pyridobisimidazole fiber, the diffraction peak area derived from the crystal (200) plane in the equatorial profile is S1, the crystal (110) plane, and the (210) plane. And when the diffraction peak area derived from (400) is S2, S2 / S1 is an existing state of pyridobisimidazole crystals satisfying 0.1 to 1.5, and is measured by an atomic force microscope. A prepreg using a pyridobisimidazole fiber having an average square roughness of the fiber surface of 20 nm or less.   In the azimuth profile of electron diffraction of the (200) plane of the pyridobisimidazole crystal obtained from the surface layer part (surface to 1 μm) and the center part of the pyridobisimidazole fiber, the half width of the diffraction peak obtained from the surface layer part The prepreg using the pyridobisimidazole fiber of Claim 1 which consists of a pyridobisimidazole fiber whose value T which divided by the half width of the diffraction peak obtained from the center part is 0.75-1.25.   The prepreg using the pyridobisimidazole fiber according to claim 1 or 2, wherein a thermal expansion coefficient in a plane direction of the pyridobisimidazole fiber is -3 ppm / ° C or more and 6 ppm / ° C or less.

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