Composite sheet

Abstract

The present invention relates to a composite sheet in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a coating material comprising a thermoplastic resin, wherein the tensile strength of the composite sheet in the warp direction of the fabric is 300 N / cm or more, and the ratio of the mass of the thermoplastic resin to the mass of the fabric is 5 to 25 mass%.

Description

Technology Field

[0001] The present invention relates to a composite sheet in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a coating material comprising a thermoplastic resin. Background Technology

[0002] Recently, technological advancements in the field of microelectronics have been remarkable, leading to a strong demand for miniaturization and lightweighting in portable electronic devices. Furthermore, regarding the components constituting these devices, there is a need to ensure that when an external load is applied, the constituent parts do not bend significantly to come into contact with other internal components or break; therefore, the simultaneous achievement of high strength and thinness is required.

[0003] Polyimide films are widely used as films for electronic components due to their heat resistance, dimensional stability, flexibility, high bendability, and desirable thin film properties (Patent Document 1). Additionally, as a protective sheet, Patent Document 2 proposes a composite sheet comprising a fabric sheet having a plurality of openings and a thermoplastic resin layer made of a resin-containing material containing a resin component including a thermoplastic polyurethane resin, wherein a portion of the resin-containing material penetrates into the openings of the fabric sheet to block all of the openings and the thermoplastic resin layer is integrated with the fabric sheet. It is shown that the strength, rigidity, and heat resistance of the fabric sheet and the flexibility, low-temperature properties, and heat fusion properties of the thermoplastic polyurethane resin are exhibited in good balance. In addition, Patent Document 3 proposes a composite sheet in which thermoplastic polyurethane sheets are positioned on both sides of glass fibers, wherein the thermoplastic polyurethane sheets on both sides are filled into the space of the glass fibers and the thermoplastic polyurethane is bonded through the glass fibers, thereby forming a composite sheet that is integrated as a whole. It is shown that a composite sheet with high tear strength, high dimensional stability, and good handling properties is obtained by having the thermoplastic polyurethane sheets placed on both sides filled into the space of the glass fibers and the thermoplastic polyurethane bonded through the glass fibers, thereby forming a composite sheet that is integrated as a whole. Prior art literature

[0004] Japanese Published Patent Application No. 2016-183224, Japanese Published Patent Application No. 2011-121284, Japanese Published Patent Application No. 2013-126749 The problem to be solved

[0005] However, in the composite sheet of Patent Document 2, fibers selected from polyester, nylon, and polypropylene are used in the woven sheet, so although flexibility is abundant and durability is exhibited, the strength of the fiber itself is low, so the strength as a composite sheet is insufficient.

[0006] In addition, in the composite sheet of Patent Document 3, glass fibers are used to achieve both tear strength and dimensional stability, so the specific gravity of the composite sheet is high, flexibility is insufficient, and there were challenges regarding lightweighting and durability. Furthermore, since this composite sheet is manufactured by laminating a thermoplastic polyurethane sheet onto a cloth made of glass fibers, there was a limit to thinning the composite sheet.

[0007] Therefore, the problem that the present invention aims to solve is to provide a composite sheet that is lightweight, high-strength, has excellent flexibility, and high flexural resistance. means of solving the problem

[0008] The inventors have repeatedly conducted detailed investigations to solve the above problem and have reached the completion of the present invention. That is, the present invention includes the following preferred embodiments.

[0009] [1] A composite sheet in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a coating material containing a thermoplastic resin, wherein the tensile strength of the composite sheet in the warp direction of the fabric is 300 N / cm or more, and the ratio of the mass of the thermoplastic resin to the mass of the fabric is 5 to 25 mass%.

[0010] [2] The above thermoplastic resin is selected from the group consisting of polyurethane resin and acrylic resin, and is a composite sheet as described in [1].

[0011] [3] A composite sheet described in [1] or [2], wherein the tensile strength of the composite sheet in a direction of 45° relative to the warp direction of the fabric is 50 N / cm or more.

[0012] [4] A composite sheet described in any one of [1] to [3], wherein the thickness of the composite sheet is 10 to 400 μm.

[0013] [5] A composite sheet described in any one of [1] to [4], wherein the tensile strength in the warp direction of the fabric per unit thickness of the composite sheet is 3.0 N / cm / µm or more.

[0014] [6] The above liquid crystal polyester fiber is a multifilament composite sheet described in any one of [1] to [5].

[0015] [7] A composite sheet described in any one of [1] to [6], wherein the opening rate of the composite sheet is less than 50%.

[0016] [8] The bending stiffness B value of the above composite sheet is 4.90 × 10 -2 A composite sheet described in any one of [1] to [7] above, having a thickness of N·㎠ / ㎝ or less. Effects of the invention

[0017] The present invention provides a composite sheet that is lightweight, high-strength, has excellent flexibility, and high flexural resistance. Specific details for implementing the invention

[0018] The composite sheet of the present invention is a composite sheet in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a coating material containing a thermoplastic resin, wherein the tensile strength of the composite sheet in the warp direction of the fabric is 300 N / cm or more, and the ratio of the mass of the thermoplastic resin to the mass of the fabric is 5 to 25 mass%.

[0019] Liquid Crystal Polyester Fiber

[0020] The "liquid crystal polyester fiber" in the present invention can be manufactured by melt spinning a liquid crystal polyester. A liquid crystal polyester is a polyester that exhibits optical anisotropy (liquid crystallization) in the molten phase, and can be identified, for example, by placing a sample on a hot stage, heating it under a nitrogen atmosphere, and observing the transmitted light of the sample. Furthermore, the liquid crystal polyester is composed of repeating constituent units derived from, for example, aromatic diols, aromatic dicarboxylic acids, or aromatic hydroxycarboxylic acids, and the chemical composition of said constituent units is not particularly limited as long as it does not impede the effects of the present invention. Additionally, within a range that does not impede the effects of the present invention, the liquid crystal polyester may include constituent units derived from aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids.

[0021] For example, desirable constituent units can be given as shown in Table 1.

[0022]

[0023] Here, Y is selected from the group consisting of a maximum number of substitutables in an aromatic ring, each independently comprising a hydrogen atom, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., a 1- to 4 carbon alkyl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.), an alkoxy group (e.g., a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an aralkyl group [a benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.], an aryloxy group (e.g., a phenoxy group, etc.), and an aralkyloxy group (e.g., a benzyloxy group, etc.).

[0024] More preferred constituent units include the constituent units described in examples (1) to (18) shown in Tables 2, 3, and 4 below. In addition, if a constituent unit in the formula is a constituent unit capable of representing multiple structures, two or more such constituent units may be combined and used as constituent units for the polymer.

[0025]

[0026]

[0027]

[0028] In the constituent units of Tables 2, 3 and 4, n is an integer of 1 or 2, and each constituent unit n = 1, n = 2 may exist alone or in combination; and Y1 and Y2 may each independently be a hydrogen atom, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., a 1- to 4 carbon atom alkyl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.), an alkoxy group (e.g., a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an aralkyl group [benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.], an aryloxy group (e.g., a phenoxy group, etc.), an aralkyloxy group (e.g., a benzyloxy group, etc.). Among these, desirable Y can be a hydrogen atom, a chlorine atom, a bromine atom, or a methyl group.

[0029] Also, Z can be a substituent represented by the following formula.

[0030] [Chemical Formula 1]

[0031]

[0032] A preferred liquid crystal polyester preferably has two or more naphthalene backbones as constituent units. Particularly preferably, the liquid crystal polyester comprises both a constituent unit (A) derived from hydroxybenzoic acid and a constituent unit (B) derived from hydroxynaphthoic acid. For example, the following formula (A) may be used as the constituent unit (A) and the following formula (B) may be used as the constituent unit (B). From the viewpoint of facilitating the improvement of melt moldability, the ratio of constituent unit (A) to constituent unit (B) may preferably be in the range of 9 / 1 to 1 / 1, more preferably 7 / 1 to 1 / 1, and even more preferably 5 / 1 to 1 / 1.

[0033] [Chemical Formula 2]

[0034]

[0035] [Chemical Formula 3]

[0036]

[0037] In addition, the sum of the constituent units of (A) and (B) may, for example, be 65 mol% or more with respect to the total constituent units, more preferably 70 mol% or more, and even more preferably 80 mol% or more. Among the polymers, a liquid crystal polyester in which the constituent units of (B) are 4 to 45 mol% is particularly preferred.

[0038] The melting point of the liquid crystal polyester preferably used in the present invention is preferably 250 to 360 °C, more preferably 260 to 320 °C. Here, the melting point is the temperature of the main absorption peak observed by measuring with a differential scanning calorimeter (DSC; "TA3000" manufactured by Mettler, Inc.) in accordance with the JIS K7121 test method. Specifically, 10 to 20 mg of the sample is placed in an aluminum pan in the DSC apparatus, nitrogen as a carrier gas is circulated at 100 cc / min, and the endothermic peak is measured when the temperature is raised by 20 °C / min. If a clear peak does not appear in the 1st run of the DSC measurement depending on the type of polymer, the temperature can be raised to a temperature 50 ℃ higher than the expected flow temperature at a heating rate of 50 ℃ / min, maintained at that temperature for 3 minutes to completely melt, then cooled to 50 ℃ at a cooling rate of -80 ℃ / min, and then the endothermic peak can be measured at a heating rate of 20 ℃ / min.

[0039] In addition, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyetheretherketone, and fluoropolymer may be added to the liquid crystal polyester to the extent that it does not impede the effects of the present invention. Furthermore, various additives such as inorganic materials such as titanium oxide, kaolin, silica, and barium oxide, coloring agents such as carbon black, dyes, and pigments, antioxidants, UV absorbers, and light stabilizers may be added.

[0040] The liquid crystal polyester fibers included in the composite sheet of the present invention can be manufactured by melt spinning the liquid crystal polyester by a conventional method. Typically, spinning is performed at a temperature 10 to 50°C higher than the melting point of the liquid crystal polyester. The fibers after spinning may be subjected to heat treatment. Through heat treatment, solid-state polymerization (which may also be accompanied by some cross-linking reactions) occurs, improving strength and elastic modulus, and also raising the melting point.

[0041] Heat treatment can be performed in an inert atmosphere such as nitrogen, in an oxygen-containing active atmosphere such as air, or under reduced pressure. It is preferable to perform heat treatment in a gaseous atmosphere with a dew point of -40°C or lower. Preferred temperature conditions include a temperature condition in which the temperature is sequentially increased from below the melting point of the liquid crystal polyester fiber. Depending on the desired performance, heat treatment can be performed for several seconds to several tens of hours. Typically, heat treatment is performed in the fiber state, but it may also be performed in the fabric state if necessary.

[0042] The liquid crystal polyester fiber in the present invention may be either monofilament or multifilament. From the perspective of facilitating the attainment of high tensile strength of the composite sheet and facilitating the adjustment of the thickness and opening ratio of the composite sheet by thinning treatment after forming into a fabric, it is preferable that the liquid crystal polyester fiber be multifilament.

[0043] When the liquid crystal polyester fiber is a multifilament, the single filament fineness of the liquid crystal polyester fiber is preferably 0.1 to 50 dtex, more preferably 1 to 20 dtex, and particularly preferably 1 to 10 dtex. If the single filament fineness is within the above range, fiber breakage does not occur easily during the manufacture of the liquid crystal polyester fiber and fabric, making it easy to obtain sufficient adhesion with the thermoplastic resin (i.e., tensile strength and flexural resistance of the composite sheet). In addition, the total fineness is, for example, 10 to 10,000 dtex, preferably 10 to 5,000 dtex, more preferably 50 to 3,000 dtex (particularly 70 to 2,000 dtex). The number of filaments is, for example, 2 to 500, preferably 3 to 300, and more preferably 5 to 200. If the total fineness and the number of filaments are within the above ranges, it is easy to achieve both lightness and high strength in the composite sheet.

[0044] The multifilament may be loosely twisted, but it is preferable that it be substantially untwisted. Additionally, the multifilament may be subjected to fiber opening and / or smoothing treatment. By manufacturing a fabric using multifilament that has undergone such fiber opening and / or smoothing treatment, the fabric can be made thinner, and it becomes easier to adjust the ratio of the fabric to the thermoplastic resin described later to a desirable range.

[0045] Commercial products may be used as "liquid crystal polyester fibers." Examples of such commercial products include Vectran UM (product name) manufactured by Kuraray Co., Ltd., Vectran HT (product name) manufactured by Kuraray Co., Ltd., Siveras (product name) manufactured by Toray Corporation, and Zexion (product name) manufactured by KB Seiren Co., Ltd.

[0046] Liquid crystal polyester fibers can be used alone or in combination.

[0047] Liquid crystal polyester fibers are included in the composite sheet of the present invention in the form of a fabric. As a result, the composite sheet of the present invention can have excellent tensile strength and thinness (lightweightness). One composite sheet contains one fabric, and from the perspective of lightweightness, the composite sheet is not typically used in a laminated form.

[0048] Examples of fabrics include a fabric structure (I) in which mono or multifilaments made of liquid crystal polyester fibers are interlocked as warp and weft threads, and a fabric structure (II) in which mono or multifilaments made of liquid crystal polyester fibers are arranged parallel to each other, but the filaments are not interlocked with each other and are connected by auxiliary threads.

[0049] Examples of fabric structures (I) include plain weave, twill, and satin. Plain weave is preferred from the perspective of being less dependent on the tensile direction and being easier to obtain higher tensile strength.

[0050] The fabric structure (II) may be, for example, a unidirectional fabric having one layer of filaments in which mono or multifilaments made of liquid crystal polyester fibers are arranged parallel to each other (e.g., cord fabric, etc.); or a multi-layer fabric in which mono or multifilaments made of liquid crystal polyester fibers are arranged parallel to each other and are arranged at different angles (e.g., bidirectional fabric, tridirectional fabric, etc.). Among these, a unidirectional fabric is preferred from the perspective of the lightness of the composite sheet.

[0051] In the fabric structure (II), as described above, mono or multifilaments made of liquid crystal polyester fibers are not interlocked but are integrated by an auxiliary yarn. The auxiliary yarn is not particularly limited as long as it can connect mono or multifilaments made of liquid crystal polyester fibers, but, for example, a yarn made of polyester, nylon, acrylic, polyolefin, or polyurethane can be used.

[0052] In addition, the interlocking state of the auxiliary yarn to the mono or multifilament made of liquid crystal polyester fiber is not particularly limited as long as the filament can be integrated.

[0053] A fabric made of liquid crystal polyester fibers can be manufactured by using liquid crystal polyester fibers as warp and weft yarns and weaving them by a conventional method.

[0054] When weaving, sizing treatment may be applied to the warp threads. Through sizing treatment, troubles such as thread breakage or yarn breakage are less likely to occur even when weaving at high speeds, thereby improving weaving efficiency. Examples of sizing agents used for sizing treatment include sizing agents containing polyvinyl alcohol resin or acrylic acid ester resin.

[0055] In the case of sizing treatment, the adhesion between the thermoplastic resin-containing composition for forming the coating material and the fabric is reduced. To prevent the possibility of a decrease in the strength and flexural strength of the composite sheet resulting from this, it is preferable to remove the sizing agent from the fabric before the process of impregnating or attaching the thermoplastic resin-containing composition to the fabric. As a method for removing the sizing agent, general removal methods may be employed, and for example, the sizing agent can be removed by washing with water, a caustic soda solution, or a detergent.

[0056] In order to obtain a more homogeneous fabric, in either fabric structure (I) or fabric structure (II), it is desirable to make the amplitude of the weave wave formed by both the warp and weft yarns mono or multifilament as small as possible. For example, the amplitude of the weave wave may be reduced by using multifilaments that have undergone opening treatment and / or smoothing treatment as described above, or by thinning the fabric using a roller or the like after manufacturing the fabric as described below.

[0057] The apparent weight of the fabric made of liquid crystal polyester fibers may be, for example, 10 to 500 g / m², and preferably 15 to 200 g / m². The warp density and weft density are appropriately selected based on the yarn fineness and opening ratio, but may be, for example, 10 to 200 threads / 2.54 cm (1 inch), and preferably 30 to 150 threads / 2.54 cm. In addition, the thickness of the fabric may be, for example, 10 to 400 μm, and preferably 20 to 200 μm. If the apparent weight, warp density, weft density, and thickness are within the above ranges, it is easy to achieve both lightness and high strength of the composite sheet.

[0058] A fabric made of liquid crystal polyester fibers is preferably subjected to a thinning treatment. Examples of thinning treatment methods include (1) a method of tensioning the fabric between rotating rollers or between heating rollers, and (2) a method of pressurizing the fabric between a heating roller and a nip roller (e.g., a calendering method). By performing the thinning treatment, the fabric waves are stretched to become more homogeneous, making it easier to obtain high tensile strength and bending resistance of the composite sheet. Additionally, as the weave of the fabric becomes denser, it becomes easier to obtain the desirable ratio of the fabric to the thermoplastic resin described later, and the lightness of the composite sheet can also be improved.

[0059] In addition, regarding the liquid crystal polyester fibers constituting the fabric, it is preferable that the ratio of the major axis to the minor axis of the fiber cross-section (major axis / minor axis) is 1.1 to 3.0. If the above ratio is less than 1.1, the effect of thinning may not be obtained, and if it is greater than 3.0, tearing or breakage may occur, and a composite sheet with excellent tensile strength and flexural resistance, which is the objective of the present invention, may not be obtained. More preferably, the above ratio is 1.3 to 2.8.

[0060] In addition, the above ratio is an average value obtained by photographing a cross-section of a fabric with a scanning electron microscope (SEM), measuring the major and minor axes of 100 randomly selected liquid crystalline polyester fibers from the cross-sectional image, and calculating the ratio of the major axis to the minor axis of each fiber.

[0061] <Thermoplastic Resin>

[0062] As the thermoplastic resin in the present invention, a resin may be used such that a coating material containing said resin can cover one or both sides of the fabric to form a composite sheet. Since the fabric is coated with a coating material containing a thermoplastic resin, the intersection points of the warp and weft threads of the fabric are bonded by the coating material; therefore, the composite sheet of the present invention may have excellent tensile properties in the warp and weft directions, as well as excellent tensile properties in the diagonal direction of the foot (e.g., a direction at 45° relative to the warp direction). Furthermore, when the composite sheet of the present invention is bonded to another member, for example, when the composite sheet of the present invention is used as a reinforcing member for another member, the coating of the coating material containing the thermoplastic resin may act as an adhesive between the composite sheet of the present invention and the other member, thereby ensuring good bonding between them.

[0063] Examples of such thermoplastic resins include polyester resins such as polyethylene terephthalate, modified polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resins such as polypropylene, modified polypropylene, and polyethylene; polyamide resins such as polyamide 6, polyamide 66, polyamide 12, polyamide 6-12, polyamide 9T, and polyamide 66IT; polycarbonate, polyarylate, polyimide, polyphenylene sulfide, polyether ester ketone, and fluoropolymer resins; and thermoplastic elastomers such as polyurethane resin, acrylic resin, styrene-based elastomer, and olefin-based elastomer. These resins may be used alone or in combination of two or more types. From the perspective of easily obtaining a composite sheet with excellent tensile properties in the warp and weft directions as well as in the diagonal direction of the foot, it is preferable that the thermoplastic resin be selected from the group consisting of polyurethane resin and acrylic resin.

[0064] <Composite Sheet>

[0065] The composite sheet of the present invention has a high tensile strength in the warp direction of the fabric of 300 N / cm or more. Such high tensile strength is achieved by the composition of the composite sheet of the present invention, in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a thermoplastic resin-containing coating material. The tensile strength is preferably 400 N / cm or more, more preferably 500 N / cm or more. The upper limit of the tensile strength is not particularly limited, but is typically 8000 N / cm or less, preferably 5000 N / cm or less, and more preferably 3000 N / cm or less. In addition, the composite sheet of the present invention has a tensile strength in a direction at 45° to the warp direction of the fabric of 50 N / cm or more, more preferably 70 N / cm or more, and even more preferably 90 N / cm or more. The tensile strength in the warp direction and the tensile strength in the direction at 45° relative to the warp direction can be adjusted above the lower limit value by adjusting the apparent weight of the fabric, the ratio of the mass of the thermoplastic resin to the mass of the fabric, or the opening ratio. The upper limit value of the tensile strength in the direction at 45° relative to the warp direction is not particularly limited, but is typically 4000 N / cm or less, preferably 2000 N / cm or less, more preferably 1000 N / cm or less, and particularly preferably 500 N / cm or less. The tensile strength in the present invention is a value measured according to the method described in the examples below.

[0066] In addition, in the present invention, as long as the composite sheet has a tensile strength of 300 N / cm or more and has a ratio of the mass of the thermoplastic resin to the mass of the fabric described below of 5 to 25 mass%, the thermoplastic resin-containing coating material may cover one side of the fabric or cover both sides. Due to the coating material film, the fabric and the coating material containing the thermoplastic resin in the composite sheet are integrated.

[0067] In the composite sheet of the present invention, the ratio of the mass of the thermoplastic resin to the mass of the fabric (mass of thermoplastic resin / mass of fabric) is 5 to 25 mass%. If the ratio is less than 5 mass%, the composite sheet cannot have the desired high strength, and if the ratio is greater than 25 mass%, the excellent flexibility and flexural resistance of the fabric are not sufficiently maintained, so the flexibility and flexural resistance of the composite sheet decrease, and the lightness also decreases. That is, since the excellent flexibility and flexural resistance of the fabric are maintained in the composite sheet by the ratio being 25 mass% or less, the composite sheet of the present invention can have flexibility. Also, the composite sheet of the present invention is not a prepreg. The ratio is preferably 6 to 25 mass%, more preferably 8 to 20 mass%. The ratio can be adjusted within the above range by adjusting the apparent weight of the fabric, the thinning treatment of the fabric, or the single-sided or double-sided covering of the fabric. The above ratio can be measured according to the method described in the embodiments below.

[0068] The thickness of the composite sheet of the present invention is preferably 10 to 400 μm, more preferably 20 to 300 μm, and even more preferably 30 to 200 μm. If the thickness of the composite sheet is within the above range, it is easy to obtain flexibility and lightness of the composite sheet. The thickness of the composite sheet can be adjusted to within the above range by adjusting the apparent weight of the fabric, the thinning treatment of the fabric, the ratio of the mass of the thermoplastic resin to the mass of the fabric, or the single-sided or double-sided covering of the fabric. The thickness of the composite sheet can be measured according to the method described in the examples described below.

[0069] The tensile strength per unit thickness of the composite sheet of the present invention in the warp direction of the fabric is preferably 3.0 N / cm / µm or higher, more preferably 4.0 N / cm / µm or higher, and even more preferably 5.0 N / cm / µm or higher. The fact that the composite sheet has such high tensile strength per unit thickness indicates that the composite sheet is high strength even when thin. The above tensile strength per unit thickness is not particularly limited, but is typically 800 N / cm / µm or lower, preferably 500 N / cm / µm or lower, more preferably 100 N / cm / µm or lower, and particularly preferably 50 N / cm / µm or lower.

[0070] The opening ratio of the composite sheet of the present invention is preferably less than 50%, more preferably 30% or less, even more preferably 20% or less, and particularly preferably 10% or less. In the present invention, the opening ratio refers to the ratio of the area occupied by a plurality of openings in the fabric (i.e., a portion where the coating material is present but the fabric threads are absent) to the total area of ​​the composite sheet. If the opening ratio of the composite sheet is below the upper limit value, it is difficult for the ratio of the mass of the thermoplastic resin to the mass of the fabric to become excessively high, making it easy to obtain flexibility, flexural resistance, and lightness of the composite sheet. The opening ratio can be adjusted to be below or below the upper limit value by adjusting the apparent weight of the fabric, the thinning treatment of the fabric, or the single-sided or double-sided coating of the fabric. The lower limit of the opening ratio is not particularly limited. The opening ratio is typically 0.01% or more. The opening ratio can be measured according to the method described in the examples described below.

[0071] In terms of flexibility, the composite sheet of the present invention has a bending stiffness B value, which indicates the bending characteristics of the composite sheet, preferably 4.90 × 10 -2 N·cm² / cm or less (5.00 gf·cm² / cm or less), more preferably 3.92 × 10⁻⁶ -2N·cm² / cm or less (4.00 gf·cm² / cm or less), more preferably 2.94 × 10⁻⁶ -2 It is N·cm² / cm or less (3.00 gf·cm² / cm or less), and the hysteresis width 2HB value is preferably 1.08 × 10⁻⁶ -2 N·cm / cm or less (1.10 gf·cm / cm or less), more preferably 1.03 × 10 -2 N·cm / cm or less (1.05 gf·cm / cm or less), more preferably 9.81 × 10 -3 N·cm / cm or less (1.00 gf·cm / cm or less). In the present invention, bending characteristics refer to a numerical representation of the flexibility of the composite sheet, specifically the ease of bending. A smaller B value and 2HB value indicates that the sheet is easier to bend and therefore has superior flexibility. The bending characteristics of the composite sheet can be adjusted to be below the upper limit value mentioned above by adjusting the composition of the coating material, the apparent weight of the fabric, the thinning treatment of the fabric, or whether the fabric is covered on one side or on both sides. Among these, it is preferable to adjust the bending characteristics to be below the upper limit value mentioned above by using a thermoplastic resin instead of a thermosetting resin, such as the epoxy resin conventionally used as the composition of the coating material. The bending characteristics can be measured according to the method described in the examples described below.

[0072] <Method for manufacturing a composite sheet>

[0073] The composite sheet of the present invention can be manufactured by preparing a fabric made of liquid crystal polyester fibers and impregnating or attaching a thermoplastic resin-containing composition for forming a coating material to the fabric.

[0074] In the preparation process for preparing the fabric, physical and / or chemical treatments may be performed on the fabric as necessary to improve adhesion with the thermoplastic resin-containing composition to be impregnated or attached.

[0075] Examples of physical treatments include corona discharge treatment, glow discharge treatment, plasma treatment, electron beam treatment, ultraviolet treatment, heat treatment under an oxygen-containing atmosphere, and heat treatment under a moisture-containing atmosphere. Examples of chemical treatments include acid treatment, alkali treatment, and treatment using an oxidizing agent. Chemical treatments may be performed at room temperature or under heating, but it is preferable to perform them under heating. These treatments may be performed individually or in combination of two or more types. From the perspective of efficiently manufacturing the composite sheet, physical treatments such as ultraviolet treatment or heat treatment are preferred among these treatments.

[0076] For the ultraviolet treatment, ultraviolet lamps such as low-pressure mercury lamps or excimer lamps may be used. The energy density of the ultraviolet treatment is, for example, 0.1 to 50 mW / cm², preferably 1 to 40 mW / cm², in order to improve adhesion without degrading the fabric. In addition, the irradiation time can be appropriately set according to the energy density, etc., for example, 10 seconds to 10 minutes, preferably 20 seconds to 5 minutes.

[0077] In the heat treatment under an oxygen-containing atmosphere, the heat treatment may be carried out at, for example, 230 to 350°C, preferably 250 to 330°C. The heating time is, for example, 1 to 100 hours, preferably 10 to 80 hours.

[0078] The method of impregnating or attaching a thermoplastic resin-containing composition to a fabric is not particularly limited, and conventionally known methods, such as impregnation, coating, or transfer methods, may be used. Specifically, methods such as impregnating or attaching a thermoplastic resin-containing composition prepared by dissolving a thermoplastic resin and optionally an additive in a solvent and drying it, impregnating or attaching a thermoplastic resin-containing composition containing a thermoplastic resin in a heated molten state and optionally an additive to a fabric, fixing a powdered thermoplastic resin to a fabric together with optionally an additive, or forming a layer of a coating material on a release film or sheet and then transferring it to a fabric may be employed. Furthermore, when drying the thermoplastic resin-containing composition impregnated or attached to the fabric, it is preferable to dry it in a non-contact state using a vertical dryer. In addition, solvents and additives blended into the thermoplastic resin-containing composition, depending on the case, are not particularly limited as long as they do not impede the effects of the present invention, and commonly used solvents and additives may be used alone or in combination of two or more types. In cases where solvents and additives are not blended into the thermoplastic resin-containing composition, the thermoplastic resin-containing composition consists of a thermoplastic resin.

[0079] The composite sheet of the present invention has a mass ratio of the thermoplastic resin to the mass of the fabric of 5 to 25 mass%. In order to adjust to the above ratio, or to thin (lighten) the composite sheet, a portion of the impregnated or attached thermoplastic resin-containing composition may be removed as needed. The method of removing the thermoplastic resin-containing composition is not particularly limited, and, for example, a method using a roller or a doctor knife may be employed.

[0080] Examples

[0081] The present invention will be explained in more detail below by way of examples, but the present invention is not limited by these examples at all.

[0082] [Measurement method or evaluation method]

[0083] <Ratio of the mass of thermoplastic resin to the mass of fabric>

[0084] The mass of each fabric and each composite sheet prepared in the examples and comparative examples were measured, and from these values, the mass of the thermoplastic resin for each composite sheet was calculated, and the ratio of the mass of the thermoplastic resin to the mass of the fabric was calculated.

[0085] <Thickness of fabric and thickness of composite sheet>

[0086] Using the static pressure thickness gauge “PG-15J” manufactured by Techlock Co., Ltd., the thickness of the fabric and the thickness of the composite sheet were measured at three points each, and the average values ​​were calculated for each.

[0087] <Tensile Strength and Tensile Elongation of Composite Sheets in the Inclined Direction>

[0088] Tensile strength and tensile elongation were measured for a 1 cm wide sample using an Instron 3365 type testing machine manufactured by Instron Japan Company Limited, under conditions of a test length of 10 cm and a test speed of 5 cm / min. The number of measurements was set to N = 3, and the average values ​​were calculated for each of the tensile strength and tensile elongation. In addition, the sample was cut so that the test length was parallel to the slope.

[0089] <Tensile strength of composite sheet at 45° direction>

[0090] Tensile strength was measured for a 1 cm wide sample using an Instron Japan Company Limited Instron 3365 type testing machine under conditions of a test length of 3 cm and a test speed of 5 cm / min. The number of measurements was set to N = 3, and the average value was calculated. In addition, the sample was cut so that the test length was parallel to the direction of 45° with respect to the slope.

[0091] <Flexibility of Composite Sheets: MIT Flexural Test>

[0092] In accordance with JISP8115:2010, using an MIT oil-resistant fatigue testing machine manufactured by Toyo Seiki Co., Ltd., the number of reciprocating cycles until breakage was measured for a 1 cm wide sample under conditions of a load of 0.5 kgf, a bending speed of 175 cycles / min, and a bending angle of 270° (approx. 135° to the left and right). The number of measurements was set to N = 3, and the average value was calculated. In addition, the upper limit of the number of measurements was set to 60,000 cycles.

[0093] <Opening Ratio of Composite Sheet>

[0094] For each composite sheet prepared in the examples and comparative examples, observation was performed using a VHX-5000 microscope manufactured by Keyence Co., Ltd., and the aperture ratio was calculated using the attached image analysis software.

[0095] <Bending Characteristics (Bending Stiffness B Value and Hysteresis Width 2HB Value)>

[0096] An automated pure bending tester (manufactured by Kato Tech Co., Ltd., "KES-FB2-AUTO-A") was used to measure bending characteristics. Each composite sheet prepared in the examples and comparative examples was cut to a size of 2 cm × 22 cm with the weft direction being the longer side, and used as a test specimen. The bending test of this specimen was -2.5 cm -1 ~ +2.5 cm -1 Curvature within the range, also constant velocity (deformation rate 0.5 cm) -1The test was performed at a rate of 1 / sec. The bending test was conducted as one cycle, and the bending stiffness B value per unit length (unit: gf·cm² / cm) and the hysteresis width 2HB value (unit: gf·cm / cm) were determined. The number of measurements was set to N = 3, and the average values ​​were calculated and converted to SI units (bending stiffness B value per unit length: N·cm² / cm, hysteresis width 2HB value: N·cm / cm).

[0097] Example 1

[0098] (1) A liquid crystalline polyester polymer was used in which the ratio (molar ratio) of constituent unit (A) to constituent unit (B) was 75 / 25. The logarithmic viscosity η of this polymer inh The nitrate was 5.6 dL / g, and the melting point was 281 °C. This polymer was spun from a die with a nozzle diameter of 0.15 mmφ using a commonly used melt spinning device to obtain a multifilament of 220 dtex / 40 filaments. This multifilament was treated at 270 °C for 20 hours in a nitrogen atmosphere. The tensile strength of the multifilament after the above treatment, measured in accordance with JIS L1013, was 22.2 cN / dtex.

[0099] (2) Sizing treatment was performed on the multifilament after the above treatment. The multifilament after sizing treatment was used as the warp, and the multifilament before sizing treatment was used as the weft, and a plain weave fabric with a warp density of 35 threads / 2.54 cm and a weft density of 35 threads / 2.54 cm was produced by a conventional method. In addition, the sizing agent used in the sizing treatment was removed from the plain weave fabric by washing the plain weave fabric. After that, the plain weave fabric was placed between stainless steel mirror rolls and calendered at a linear pressure of 160 kg / cm and a temperature of 150 ℃. The apparent weight and thickness of the plain weave fabric after calendering are shown in Table 5.

[0100] (3) A thermoplastic resin-containing composition comprising polyurethane resin and a solvent was applied to the surface of a plain weave fabric after calendering, and dried at 120°C for 5 minutes to produce a composite sheet.

[0101] (4) Using the obtained composite sheet, tensile strength and tensile elongation in the warp direction, tensile strength in the 45° direction, flexural strength, and opening ratio were evaluated. In addition, the tensile strength of the plain weave in the warp direction per unit thickness of the composite sheet was calculated. The results obtained are shown in Table 5.

[0102] (5) In addition, the adhesion of the obtained composite sheet to the hot melt sheet was investigated. Specifically, a hot melt tape manufactured by Sanhwasung Industrial Co., Ltd. was heat-pressed onto a composite sheet cut to dimensions of 30 mm in width and 200 mm in length so that the test length was parallel to the slope, and the peel strength was measured with N = 1 using a tensile testing machine (TENSILON RTG-1250) at a test speed of 200 mm / min. The results are shown in Table 6.

[0103] Examples 2 to 4

[0104] A composite sheet was manufactured and evaluated in the same manner as in Example 1, except that the yarn fineness, warp density, weft density, apparent weight of the fabric, and thickness were changed as described in Table 5. The results obtained are shown in Table 5.

[0105] Example 5

[0106] A composite sheet was prepared and evaluated in the same manner as in Example 1, except that an acrylic resin was used instead of a polyurethane resin. The results obtained are shown in Table 5.

[0107] Comparative Example 1

[0108] A composite sheet was manufactured and evaluated in the same manner as in Example 1, except that the yarn fineness, warp density, weft density, apparent weight of the fabric, and thickness were changed as described in Table 5. The results obtained are shown in Table 5.

[0109] Comparative Example 2

[0110] A plain weave fabric was manufactured in the same manner as in Example 1, except that the fabric thickness was changed as described in Table 5. The calendering process performed in the example was not performed, and the plain weave fabric obtained after weaving was evaluated in the same way as the composite sheet of Example 1. The results obtained are shown in Table 5. In addition, the adhesion of the obtained plain weave fabric to a hot melt sheet was evaluated in the same manner as in Example 1. The results are shown in Table 6.

[0111] Comparative Examples 3 and 4

[0112] For each of the 75 μm thick polyimide film [Manufactured by Toray DuPont, Inc., Kapton (Trademark) 300H] and the 125 μm thick polyimide film [Manufactured by Toray DuPont, Inc., Kapton (Trademark) 500H], the apparent weight, tensile strength (MD direction), tensile elongation (MD direction), and tensile strength per unit thickness (MD direction) were calculated from the catalog, and the flexural strength was evaluated in the same manner as in Example 1. The obtained results are shown in Table 5.

[0113] Comparative Example 5

[0114] A calendered plain weave fabric was manufactured by carrying out processes (1) and (2) of Example 1. Its apparent weight and thickness are shown in Table 7.

[0115] Next, an epoxy resin sheet was laminated onto the surface of a calendered plain weave fabric, and the epoxy resin was cured by heating at 130°C for 120 minutes to produce a composite sheet.

[0116] Bending characteristics were measured for the composite sheet using the thermoplastic resin obtained in Example 1 and the composite sheet using the thermosetting resin obtained in Comparative Example 5. The results obtained are shown in Table 7.

[0117]

[0118]

[0119]

[0120] As can be seen from Table 5, in Examples 1 to 5, the apparent weight of the composite sheet was small, the tensile strength was high not only in the warp direction but also in the 45° direction, and in addition to the high tensile strength per unit thickness, the flexural resistance and flexibility were also excellent. In other words, the composite sheet of the present invention possessed lightness, high strength, excellent flexibility, and high flexural resistance. On the other hand, in Comparative Example 1, the tensile strength in the warp direction was low, and the tensile strength in the warp direction per unit thickness was also low, so lightness (thinning) and high strength could not be achieved simultaneously; in Comparative Example 2, the flexural resistance was excellent but the tensile strength in the 45° direction was very low; and in Comparative Examples 3 and 4, the tensile strength, tensile strength per unit thickness, and flexural resistance were all low.

[0121] As can be seen from Table 6, in Example 1, the coating of the coating material containing a thermoplastic resin could act as an adhesive for the composite sheet and the hot melt sheet of the present invention, and good bonding between them could be secured, whereas in Comparative Example 2, only low adhesion to the hot melt sheet was exhibited.

[0122] As can be seen from Table 7, in Example 1, a composite sheet was manufactured using a thermoplastic resin, specifically urethane resin, as the coating material, so a sheet with low bending characteristics and excellent flexibility was obtained. On the other hand, in Comparative Example 5, a composite sheet was manufactured using a thermosetting resin, specifically epoxy resin, as the coating material, so compared to Example 1, the sheet had high bending characteristics and lower flexibility.

[0123] Industrial applicability

[0124] The composite sheet of the present invention can be preferably used as a reinforcing member, for example, a flexible substrate, internal member, various arms, various frames, and various hinges of an electrical or electronic device.

Claims

Claim 1 A reinforcing member for a flexible substrate, internal member, various arm, various frame, or various hinge of an electrical or electronic device, comprising a composite sheet in which one or both sides of a fabric made of liquid crystal polyester fibers are coated with a coating material including a thermoplastic resin, wherein the tensile strength of the composite sheet in the warp direction of the fabric is 300 N / cm or more, the opening ratio of the composite sheet is 20% or less, and the mass ratio of the thermoplastic resin to the mass of the fabric is 5 to 25 mass%. Claim 2 A reinforcing member according to claim 1, wherein the thermoplastic resin is selected from the group consisting of polyurethane resin and acrylic resin. Claim 3 A reinforcing member according to claim 1, wherein the tensile strength of the composite sheet in a direction at 45° with respect to the warp direction of the fabric is 50 N / cm or more. Claim 4 A reinforcing member according to claim 1, wherein the thickness of the composite sheet is 10 to 400 μm. Claim 5 A reinforcing member according to claim 1, wherein the tensile strength in the warp direction of the fabric per unit thickness of the composite sheet is 3.0 N / cm / ㎛ or more. Claim 6 A reinforcing member according to any one of claims 1 to 5, wherein the liquid crystal polyester fiber is a multifilament. Claim 7 delete Claim 8 In any one of claims 1 to 5, the bending stiffness B value of the composite sheet is 4.90 × 10 -2 Reinforcing member with a value of N·㎠ / ㎝ or less.

Images