Fiber-reinforced resin composite sheet, fiber-reinforced resin composite material, and resin molded product comprising the same

Abstract

To provide a fiber-reinforced resin composite sheet which has excellent flame retardancy, and has good moldability and sufficient tensile strength under high temperature condition.SOLUTION: A fiber-reinforced resin composite sheet includes a flame retardant resin film composed of a thermoplastic resin composition having a glass transition temperature Tg of 90°C or higher, and a plurality of reinforcement fibers in which a plurality of reinforcement fibers opened from a reinforcement fiber bundle are laminated on the flame-retardant resin film while being oriented in the same direction, wherein a combustibility classification of the flame-retardant resin film determined in UL94VTM combustion test according to ASTM D 4804 standard is VTM-0, a volume percentage content Vf of the reinforcement fiber is 30% or more and 65% or less, thickness of the fiber-reinforced resin composite sheet is 20 μm or more and 100 μm or less, and a combustibility classification of the fiber-reinforced resin composite sheet determined in UL94-5V combustion test according to ASTM D 5048 standard is 5V-A or 5V-B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fiber-reinforced resin composite sheet containing a flame-retardant resin film and reinforcing fibers.

Background Art

[0002] Fiber-reinforced resin composites are materials widely used in various fields, from members for sports and leisure applications to members for industrial applications such as automobiles and aircraft. Further, fiber-reinforced resin composites are manufactured using an intermediate material, that is, prepreg, in which a reinforcing material made of long fibers (continuous fibers) such as reinforcing fibers is impregnated into a resin matrix. Specifically, a molded product of a fiber-reinforced resin composite can be obtained by laminating a plurality of prepregs and heating and curing them, or heating and cooling them to solidify.

[0003] Conventionally, when manufacturing fiber-reinforced resin composites, thermosetting resins have been widely used as the resins used in prepregs from the viewpoint of excellent strength and rigidity (see, for example, Patent Document 1). However, prepregs using thermosetting resins have problems such as low impact resistance and difficulty in secondary processing. To solve these problems, prepregs in which reinforcing fibers are impregnated with a thermoplastic resin as the matrix resin have been widely developed. According to such prepregs, melting by heating and solidification by cooling are easy, so they are excellent in operability during the molding process of the prepregs, and effects such as shortening of production time are expected, which also leads to cost reduction.

[0004] Recently, fiber-reinforced resin composites have also been used as materials for casings and components of smartphones, tablets, laptops, video cameras, mobile devices, and other electrical or electronic equipment. Casings and components of electrical or electronic equipment may ignite and burn due to heat generated from inside the equipment or exposure to high-temperature environments. To prevent such accidents, the prepreg material needs to be flame-retardant. Generally, thermosetting resins have excellent flame retardancy, but thermoplastic resins have poor flame retardancy, and there are few thermoplastic resins that have sufficient flame retardancy on their own without the addition of flame retardants (see, for example, Patent Document 2). Therefore, when manufacturing fiber-reinforced resin composites that require flame retardancy, thermosetting resins are mainly used as the matrix resin.

[0005] However, depending on the type of molded product, such as the casings or components of electrical or electronic equipment, good moldability may be required for fiber-reinforced resin composite materials (hereinafter also referred to as "fiber-reinforced resin composite sheets") in order to increase the degree of freedom in shape. On the other hand, fiber-reinforced resin composite sheets using thermoplastic resin for the matrix resin have superior moldability compared to fiber-reinforced resin composite sheets using thermosetting resin, but have the problem of inferior strength. Depending on the type of casings or components of electrical or electronic equipment as described above, strength, such as tensile strength, may also be required. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-118381 [Patent Document 2] Japanese Patent Publication No. 2005-239939 [Overview of the Initiative]

[0007] Therefore, the present invention aims to provide a fiber-reinforced resin composite sheet that has excellent flame retardancy, good moldability, and sufficient tensile strength under high-temperature conditions.

[0008] A fiber-reinforced resin composite sheet according to the first aspect of the present invention is a fiber-reinforced resin composite sheet comprising a flame-retardant resin film made of a thermoplastic resin composition having a glass transition temperature Tg of 90°C or higher, and a plurality of reinforcing fibers laminated on the flame-retardant resin film in a state in which a plurality of reinforcing fibers opened from a reinforcing fiber bundle are oriented in the same direction. The flammability classification of the flame-retardant resin film determined in the UL94VTM flammability test, which conforms to the ASTM D4804 standard, is VTM-0. The volume content Vf of the reinforcing fiber is 30% or more and 65% or less. The thickness of the fiber-reinforced resin composite sheet is 20 μm or more and 100 μm or less. The flammability classification of the fiber-reinforced resin composite sheet, as determined in the UL94-5V flammability test compliant with the ASTM D5048 standard, is 5V-A or 5V-B. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of a schematic configuration of a manufacturing apparatus for fiber-reinforced resin composite sheets in this embodiment. [Figure 2] Figure 2 shows an example of a method for cutting chopped material from a fiber-reinforced resin composite sheet in this embodiment. [Figure 3] Figure 3 is a diagram illustrating a method for producing a laminated chopped sheet, which is an example of a fiber-reinforced resin composite material in this embodiment. [Figure 4] Figure 4 is a cross-sectional view of a laminated chopped sheet, which is an example of a fiber-reinforced resin composite material in this embodiment. [Figure 5] Figure 5 shows laser microscope images of cross-sections of test specimens of fiber-reinforced resin composite sheets in Examples 2-1 and 2-2, and Comparative Examples 2-1 and 2-2. [Figure 6] Figure 6 is an image showing the results of additional flame retardancy tests on test specimens of fiber-reinforced resin composite sheets in Examples 2-1 and 2-2, and Comparative Examples 2-1 and 2-2. [Modes for carrying out the invention]

[0010] In fiber-reinforced resin composites, the higher the volume content Vf of reinforcing fibers, the greater the tensile strength of the fiber-reinforced resin composite material tends to be. However, when manufacturing fiber-reinforced resin composite sheets, which are intermediate materials, simply increasing the amount of reinforcing fibers impregnated into the resin matrix will make the sheet thicker, reducing its moldability. Furthermore, the structure of the reinforcing fibers and the value of their volume content Vf are expected to affect the flame retardancy of fiber-reinforced resin composite sheets. Thus, it is difficult to adjust the properties of flame retardancy, moldability, and strength in fiber-reinforced resin composite sheets using thermoplastic resins to be all favorable.

[0011] Furthermore, when thermoplastic resins are used for the matrix resin, polyamide 6 resin is often used due to its superior physical properties such as impact resistance, toughness, and flexibility, as well as its cost-effectiveness and ease of handling. However, because polyamide 6 resin has a relatively low glass transition temperature (Tg), fiber-reinforced resin composite sheets manufactured using this polyamide 6 resin may experience a decrease in strength under high-temperature conditions. Therefore, polyamide 6 resin is unsuitable for materials that may be exposed to internal heat, such as the housings and components of electrical or electronic equipment.

[0012] Therefore, the inventors diligently studied fiber-reinforced resin composite sheets that possess excellent flame retardancy, good moldability, and sufficient tensile strength under high-temperature conditions. As a result, they arrived at the present invention. Specifically, by selecting a thermoplastic resin composition having predetermined properties, constructing a fiber-reinforced resin composite sheet having a predetermined structure, appropriately setting the type and amount of flame retardant to be added, and appropriately adjusting the volume content Vf of reinforcing fibers within a predetermined range, the aforementioned fiber-reinforced resin composite sheet can be provided.

[0013] Embodiments of the present invention will be described in detail below. However, the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without impairing the spirit of the invention.

[0014] <Fiber-reinforced resin composite sheet> The fiber-reinforced resin composite sheet in this embodiment includes a flame-retardant resin film and a plurality of reinforcing fibers laminated on the flame-retardant resin film. The plurality of reinforcing fibers are laminated on the flame-retardant resin film in a state in which the plurality of reinforcing fibers, which have been opened from a bundle of reinforcing fibers, are oriented in the same direction.

[0015] Hereinafter, throughout this specification, the term "laminated with reinforcing fibers" as used in "flame-retardant resin film" also includes, depending on the physical properties, shape, type and conditions of the treatment performed for lamination, the following meanings: "the reinforcing fibers are fused to the flame-retardant resin film in at least a portion of the way before lamination," "the reinforcing fibers are attached to the flame-retardant resin film in at least a portion of the way before lamination," "the reinforcing fibers are pressed to the flame-retardant resin film in at least a portion of the way before lamination," and "the reinforcing fibers are impregnated from the surface into the interior of the flame-retardant resin film in approximately half of each reinforcing fiber." More specifically, heating, cooling, and / or pressurizing treatments may be performed as needed during "lamination."

[0016] First, we will describe each component included in the fiber-reinforced resin composite sheet in this embodiment.

[0017] [Flame-retardant resin film] The flame-retardant resin film is made of a thermoplastic resin composition with a glass transition temperature Tg of 90 °C or higher. When the thermoplastic resin contained in the thermoplastic resin composition has flame-retardant properties, the thermoplastic resin composition may consist of only the thermoplastic resin. Alternatively, when the thermoplastic resin contained in the thermoplastic resin composition does not have flame-retardant properties, the thermoplastic resin composition contains a flame retardant. Furthermore, the thermoplastic resin composition may contain other additives etc. other than the flame retardant as necessary. Hereinafter, each component contained in the thermoplastic resin composition will be described.

[0018] (Thermoplastic resin) The thermoplastic resin composition is not particularly limited as long as the glass transition temperature Tg is 90 °C or higher, and may consist of only the thermoplastic resin, or may be a composition containing the thermoplastic resin and a flame retardant. Alternatively, commercially available products can also be used. Examples of the types of thermoplastic resins include methacrylic resins such as polymethyl methacrylate resin, polystyrene resins, polystyrene-based resins such as ABS resin and AS resin, polyamide (PA) resins such as PA9T, polycarbonate (PC) resin, polyphenylene sulfide (PPS) resin, modified polyphenylene ether (PPE) resin, polyetherimide (PEI) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polyarylate (PAR) resin, polyether nitrile (PEN) resin, polyether ketone (PEK) resin, polyether ether ketone (PEEK) resin, polyether ketone ketone (PEKK) resin, polyimide (PI) resin, polyamideimide (PAI) resin, fluorine (F) resin; liquid crystal polymer (LCP) resins such as liquid crystal polyester resin, or copolymers or modified resins thereof etc. can be mentioned. In the thermoplastic resin composition, these thermoplastic resins may be contained alone or in combination.

[0019] Of these thermoplastic resins, it is preferable to use a high-heat-resistant plastic resin, known as a super engineering plastic, which offers excellent properties such as heat resistance, flame retardancy, and strength. Specifically, the thermoplastic resin composition preferably includes one or more selected from polyphenylene sulfide (PPS) resin, polyetheretherketone (PEEK) resin, polyetherketoneketone (PEKK) resin, polyetherimide (PEI) resin, polyethersulfone (PES) resin, and liquid crystal polymer (LCP) resin. Since these thermoplastic resins have excellent flame retardancy properties, the thermoplastic resin composition may consist of these thermoplastic resins alone. Specifically, if these resin films satisfy the flammability classification conditions described later, and the fiber-reinforced resin composite sheet manufactured using said resin films also satisfies the flammability classification conditions described later, then a flame retardant may not be included. Furthermore, from the viewpoint of having a high continuous operating temperature, among these super engineering plastics, it is more preferable that the thermoplastic resin composition contains one or more selected from polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, and polyether ketone ketone (PEKK) resin. For example, a flame-retardant resin film made from a thermoplastic resin composition may consist of any one of the resins selected from polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, and polyether ketone ketone (PEKK) resin.

[0020] These super engineering plastics may use known commercially available products. Examples of commercially available products of polyphenylene sulfide (PPS) resin include "Torayna (registered trademark)" manufactured by Toray Industries, Inc., "Durafide (registered trademark)" manufactured by Polyplastics Co., Ltd., "Ryton (registered trademark)" manufactured by Solvay, etc. Examples of commercially available products of polyether ether ketone (PEEK) resin include "TORAY TPS (registered trademark) PEEK" manufactured by Toray Industries, Inc., "Vestakeep" manufactured by Daicel - Evonik Co., Ltd., "PEEK Polymer" manufactured by Victrex, etc. Examples of commercially available products of polyether ketone ketone (PEKK) resin include "Kepstan (registered trademark) PEKK" manufactured by Arkema, etc. Examples of commercially available products of polyether imide (PEI) resin include "Ultem (registered trademark)" manufactured by Sabic, etc. Examples of commercially available products of polyether sulfone (PES) resin include "Sumika Excel PES" manufactured by Sumitomo Chemical Co., Ltd., "Mitsui PES (registered trademark)" manufactured by Mitsui Chemicals Fine Inc., "Ultrason (registered trademark) E" manufactured by BASF, etc. Examples of commercially available products of liquid crystal polymer (LCP) resin include "Sumika Super LCP" manufactured by Sumitomo Chemical Co., Ltd., "Laperos (registered trademark) LCP" manufactured by Polyplastics Co., Ltd., "UENOLCP (registered trademark)" manufactured by Ueno Fine Chemicals Co., Ltd., etc.

[0021] Alternatively, from the viewpoint of obtaining a fiber - reinforced resin composite sheet with excellent processability, it is preferable that the thermoplastic resin composition contains polycarbonate (PC) resin. When the thermoplastic resin composition contains polycarbonate (PC) resin as the thermoplastic resin, it is preferable that the thermoplastic resin composition further contains one or more flame retardants selected from halogen - based flame retardants, phosphorus - based flame retardants, silicone - based flame retardants, and inorganic - based flame retardants.

[0022] In this embodiment, since the glass transition temperature Tg of the thermoplastic resin composition constituting the flame-retardant resin film is 90°C or higher, it is expected that the fiber-reinforced resin composite sheets, etc., manufactured using this thermoplastic resin composition will not experience a decrease in properties such as tensile strength or flexural strength even under high-temperature conditions. In contrast, for example, the glass transition temperature Tg of polyamide 6 resin matrix, which is widely used as a resin matrix for prepregs, is around 50°C (see Comparative Example 1-1 described later). Therefore, it is expected that the fiber-reinforced resin composite sheets, etc., manufactured using polyamide 6 resin will experience a decrease in properties such as strength under high-temperature conditions.

[0023] (Flame retardant) The thermoplastic resin composition may contain a flame retardant as needed. In particular, if the thermoplastic resin contained in the thermoplastic resin composition does not have flame retardant properties, the thermoplastic resin composition shall contain a flame retardant as an essential component. Even if the thermoplastic resin contained in the thermoplastic resin composition has flame retardant properties, the composition may further contain a flame retardant from the viewpoint of improving the flame retardant properties, etc.

[0024] The flame retardant is not particularly limited, but examples include halogen-based flame retardants, phosphorus-based flame retardants, silicone-based flame retardants, inorganic flame retardants, and other flame retardants. Each of these will be explained below.

[0025] Examples of halogen-based flame retardants include bromine-based flame retardants and chlorine-based flame retardants.

[0026] Examples of brominated flame retardants include decabromodiphenyl ether; tetrabromobisphenol A, its derivatives such as tetrabromobisphenol A carbonate oligomer and tetrabromobisphenol A epoxy oligomer; polybenzene ring compounds such as bis(pentabromophenyl)ethane and 1,2-bis(2,4,6-tribromophenoxy)ethane; brominated polystyrene compounds such as brominated polystyrene and polybrominated styrene; phthalic acid compounds such as ethylenebistetrabromophthalimide; cyclic aliphatic compounds such as hexabromocyclododecane; or other hexabromobenzenes, pentabromobenzyl acrylates, etc. Examples of chlorinated flame retardants include chlorinated paraffins, dechloran, chlorendic acid, and chlorendic anhydride.

[0027] Examples of phosphorus-based flame retardants include aromatic phosphate ester flame retardants, aromatic condensed phosphate ester flame retardants, halogenated phosphate ester flame retardants, and other phosphorus-based flame retardants.

[0028] Examples of aromatic phosphate ester flame retardants include triphenyl phosphate, cresylphenyl phosphate, tricresyl phosphate, trixylinyl phosphate, tris(t-butylated phenyl) phosphate, tris(i-propylated phenyl) phosphate, and 2-ethylhexyldiphenyl phosphate. Examples of aromatic condensation type phosphate ester flame retardants include 1,3-phenylenebis(diphenyl phosphate) and 1,2-phenylenebis(dixylenyl phosphate). Examples of halogenated phosphate ester flame retardants include tris(dichloropropyl) phosphate, trischloroethyl phosphate, and 2,2-bis(dichloromethyl)trimethylene,bis(2-chloroethyl) phosphate. Examples of other phosphorus-based flame retardants include red phosphorus, phosphate ester amides, and ammonium polyphosphate.

[0029] Examples of silicone-based flame retardants include polydimethylsiloxane, polymethylethylsiloxane, polymethyloctylsiloxane, polymethylvinylsiloxane, polydimethylphenylsiloxane, polydiphenylsiloxane, polydimethyldiphenylsiloxane, and polymethyl(3,3,3-trifluoropropyl)siloxane.

[0030] Examples of inorganic flame retardants include antimony compounds such as antimony trioxide, antimony tetroxide, antimony pentoxide, and sodium antimonate; molybdenum compounds such as molybdenum oxide and ammonium molybdate; hydrated metal compounds such as aluminum hydroxide and magnesium hydroxide; nanofillers such as titanium dioxide, montmorillonite, and silica; or zinc borate, zinc stagnate, zinc sulfide, tin oxide, zirconium oxide, zeolite, and low-melting-point glass.

[0031] Other flame retardants include, for example, melamine compounds such as melamine cyanurate and melamine sulfate, nitrogen compounds such as triazine compounds and guanidine compounds; organometallic compounds such as calcium perfluorobutanesulfonate, potassium perfluorobutanesulfonate, potassium diphenylsulfonate, potassium diphenylsulfon-3-sulfonate, and potassium p-toluenesulfonate; or hindered amine compounds and expandable graphite.

[0032] Of the flame retardants mentioned above, halogenated flame retardants, phosphorus-based flame retardants, hindered amine compounds, and antimony compounds exhibit flame retardancy through radical trapping action. Hydrated metal compounds and expansive graphite exhibit flame retardancy through endothermic action. Phosphorus-based flame retardants, halogenated flame retardants, nitrogen compounds, hydrated metal compounds, antimony compounds, and ammonium polyphosphate exhibit flame retardancy through oxygen barrier action or flammable gas dilution action. Silicone-based flame retardants, low-melting-point glass, hydrated metal compounds, red phosphorus, ammonium polyphosphate, expansive graphite, and organometallic compounds exhibit flame retardancy through thermal insulation action. By combining these flame retardants with different effects to achieve the desired flame retardancy, a thermoplastic resin composition with the desired flame retardancy can be obtained.

[0033] The flame retardant should be added to the thermoplastic resin composition in an appropriate amount so that the flame retardant resin film, made from the thermoplastic resin composition, achieves a flammability classification of VTM-0 in the UL94VTM combustion test compliant with the ASTM D4804 standard. The UL94VTM combustion test compliant with the ASTM D4804 standard will be explained in detail in the examples described later. Furthermore, the amount of the flame retardant added should be adjusted while considering the volume content Vf of the reinforcing fibers so that the fiber-reinforced resin composite sheet manufactured using the flame retardant resin film also satisfies the conditions for the flammability classification described later.

[0034] Specifically, for example, the thermoplastic resin composition may contain a flame retardant in an amount of 1 to 30 parts by mass per 100 parts by mass of the thermoplastic resin. Alternatively, as mentioned above, if the thermoplastic resin itself contained in the thermoplastic resin composition has suitable flame retardant properties, it is not necessary to include a flame retardant.

[0035] (Other additives) The thermoplastic resin composition may optionally contain various known additives, provided that they do not impair the effects of the present invention. For example, antioxidants, light stabilizers, weather resistance modifiers, etc., can be added to improve the storage stability of the thermoplastic resin composition and to prevent discoloration or deterioration of the solidified product.

[0036] Other specific additives include, for example, thermosetting elastomers, thermoplastic elastomers, silicone oils, wetting and dispersing agents, defoaming agents, natural waxes, synthetic waxes, release agents such as metal salts of linear fatty acids, acid amides, esters, and paraffins, powders such as crystalline silica, fused silica, calcium silicate, alumina, calcium carbonate, talc, and barium sulfate, inorganic fillers such as metal oxides, metal hydroxides, glass fibers, carbon nanotubes, and fullerenes, organic fillers such as carbon fibers and cellulose nanofibers, colorants such as red iron oxide, silane coupling agents, conductive materials, slip agents, leveling agents, polymerization inhibitors such as hydroquinone monomethyl ether, and ultraviolet absorbers. These additives can be used individually or in combination of two or more as appropriate.

[0037] Furthermore, flame-retardant resin films made from thermoplastic resin compositions can be manufactured by any method known to those skilled in the art. While not particularly limited, the manufacturing method of the film includes, for example, roll coating, reverse coating, comma coating, knife coating, die coating, gravure coating, melt extrusion, solution casting, T-die method, and calendering. Additionally, by using co-extrusion or lamination methods, the film can be manufactured with increased thickness or by laminating resin films with different resin compositions.

[0038] The lower limit of the thickness of the flame-retardant resin film is not particularly limited, but preferably it is 5 μm or more, as this makes it easier to maintain the shape of the film during film molding. Furthermore, the thickness of the flame-retardant resin film is preferably 50 μm or less, more preferably 45 μm or less, even more preferably 40 μm or less, and even more preferably 30 μm or less, 25 μm or less, or 20 μm or less. By setting the thickness of the flame-retardant resin film to 50 μm or less, the fiber-reinforced resin composite sheet in this embodiment can also be made thin, and as a result, good moldability can be achieved.

[0039] A flame-retardant resin film made from such a thermoplastic resin composition is an intermediate material for manufacturing the fiber-reinforced resin composite sheet in this embodiment. A fiber-reinforced resin composite sheet in this embodiment is obtained by laminating a plurality of reinforcing fibers, opened from a reinforcing fiber bundle, in the same direction on one or both sides of the flame-retardant resin film, and then subjecting it to heating, cooling, and / or pressurizing treatment. From the viewpoint of obtaining better flame-retardant properties, it is preferable that the plurality of reinforcing fibers are laminated on both sides of the flame-retardant resin film.

[0040] [Reinforced fiber] The reinforcing fibers are laminated onto a flame-retardant resin film made of the aforementioned thermoplastic resin composition, with multiple reinforcing fibers opened from a bundle of reinforcing fibers oriented in the same direction. In this specification, "a state in which multiple reinforcing fibers are oriented in the same direction" means a state in which each of the multiple reinforcing fibers extends in substantially parallel directions.

[0041] Because multiple reinforcing fibers are laminated on the flame-retardant resin film (specifically on the surface of the flame-retardant resin film) in this manner, the fiber-reinforced resin composite sheet in this embodiment has excellent flame retardancy. Specifically, not only does the resin film itself have flame-retardant properties, but because multiple non-combustible reinforcing fibers (preferably carbon fibers) are laminated on the flame-retardant resin film in an exposed state without being completely impregnated, the spread of flames can be suppressed compared to a sheet in which the reinforcing fibers are completely impregnated in the molten resin.

[0042] The material for the reinforcing fiber is not particularly limited, but any fiber known as a reinforcing fiber constituting a fiber-reinforced resin composite sheet, and which satisfies the conditions for the flammability classification described in detail later when the sheet is formed, can be appropriately selected according to the application. Specific examples include various fibers such as carbon fiber, aramid fiber, glass fiber, boron fiber, alumina fiber, silicon nitride fiber, and basalt fiber. Of these, carbon fiber, aramid fiber, glass fiber, boron fiber, alumina fiber, and silicon nitride fiber are preferred from the viewpoint of specific strength and specific elasticity. Furthermore, carbon fiber is more preferable because it can improve the strength and corrosion resistance of molded products using the fiber-reinforced resin composite sheet in this embodiment. As for carbon fiber, it is preferable to use PAN (polyacrylonitrile) based carbon fiber, which has particularly high strength. When using carbon fiber as the reinforcing fiber, a metal surface treatment may be applied. The reinforcing fibers opened from these reinforcing fiber bundles can be used in combination of one or more types, provided they are oriented in the same direction.

[0043] In this embodiment, the fiber-reinforced resin composite sheet has a volume content Vf of reinforcing fibers of 30% to 65%. By setting the volume content Vf of reinforcing fibers to 30% or more, the fiber-reinforced resin composite sheet is sufficiently reinforced by the reinforcing fibers and therefore has excellent strength, especially tensile strength. On the other hand, by setting the volume content Vf of reinforcing fibers to 65% or less, the good moldability of the fiber-reinforced resin composite sheet made of thermoplastic resin can be maintained. Furthermore, by adjusting the volume content Vf of reinforcing fibers within the range of 30% to 65%, while considering the type of resin selected and the type and amount of flame retardant optionally added, the fiber-reinforced resin composite sheet can be made to satisfy the conditions of the flammability classification described in detail later.

[0044] The volume content Vf of reinforcing fibers is preferably 35% or more, more preferably 40% or more, and even more preferably 44% or more. Furthermore, the volume content Vf of reinforcing fibers is preferably 60% or less, more preferably 55% or less, and even more preferably 53% or less. The volume content Vf of reinforcing fibers in a fiber-reinforced resin composite sheet can be adjusted within the above range by appropriately controlling not only the type and thickness of the reinforcing fibers, the fiber width in which the reinforcing fibers are oriented, and the thickness of the flame-retardant resin film, but also the temperature and pressure applied during the manufacturing of the fiber-reinforced resin composite sheet. The volume content Vf of reinforcing fibers can be measured by combustion, nitric acid decomposition, sulfuric acid decomposition, etc., but the volume content Vf of reinforcing fibers in this specification is the value measured by the same combustion method as in the examples.

[0045] Furthermore, the thickness of the fiber-reinforced resin composite sheet in this embodiment is 20 μm or more and 100 μm or less. Preferably, the thickness of the fiber-reinforced resin composite sheet is 25 μm or more, more preferably 30 μm or more, even more preferably 35 μm or more, and even more preferably 40 μm or more. Also, preferably the thickness of the fiber-reinforced resin composite sheet is 90 μm or less, more preferably 80 μm or less, even more preferably 70 μm or less, and even more preferably 60 μm or less, 55 μm or less, or 50 μm or less.

[0046] Specifically, by making the thickness of the fiber-reinforced resin composite sheet as thin as possible within the above range, the flame-retardant resin film and reinforcing fibers are largely fused together before lamination, allowing the strength of the reinforcing fibers to be fully utilized. Furthermore, when stress is applied, delamination of the laminate made of the fiber-reinforced composite sheet (the fiber-reinforced resin composite material described later) is less likely to occur, and it exhibits excellent fatigue properties. In addition, the moldability when using the fiber-reinforced resin composite sheet can be improved. Note that the thickness of the fiber-reinforced resin composite sheet is also affected by the thickness of the flame-retardant resin film, but it can be kept within the above range by appropriately controlling the temperature and pressure applied during the manufacturing of the fiber-reinforced resin composite sheet.

[0047] The fiber-reinforced resin composite sheet in this embodiment has a flammability classification of 5V-A or 5V-B as determined in the UL94-5V combustion test in accordance with the ASTM D5048 standard. The UL94-5V combustion test in accordance with the ASTM D5804 standard will be described in detail in the examples below. Preferably, the flammability classification determined in the UL94-5V combustion test in accordance with the ASTM D5048 standard is 5V-A. As described above, the flammability of the fiber-reinforced resin composite sheet can be made to satisfy the conditions of the flammability classification by the type of resin selected, the type and amount of flame retardant added optionally, and the adjustment ratio within the range of 30% to 65% of the volume content Vf of the reinforcing fibers.

[0048] Thus, the fiber-reinforced resin composite sheet in this embodiment not only possesses excellent flame retardancy and high heat resistance, but also excellent reinforcing effect and fatigue resistance due to the volume content Vf of reinforcing fibers which account for a sufficient value, and excellent moldability due to the relatively thin thickness of the fiber-reinforced resin composite sheet. In other words, the fiber-reinforced resin composite sheet in this embodiment is particularly suitable as a material for manufacturing resin molded products such as housings and components of electrical or electronic equipment such as smartphones, tablets, and laptop computers, where there is a risk of heat generation, ignition, and combustion from inside the device. Furthermore, with the fiber-reinforced resin composite sheet in this embodiment, multiple fiber-reinforced resin composite sheets can be laminated while minimizing voids to form various shapes at high density, making it possible to manufacture fiber-reinforced resin composite materials and resin molded products with excellent strength.

[0049] An example of a method for manufacturing a fiber-reinforced resin composite sheet in this embodiment will be described with reference to Figure 1. In Figure 1, each reference numeral represents a fiber-reinforced resin composite sheet manufacturing apparatus 1, a heating roller 2, a cooling roller 3, an endless belt 4, a pull-out roller 5, a bobbin 6, a fiber-reinforced resin composite sheet S, a flame-retardant resin film R0, a reinforcing fiber bundle F0, and a reinforcing fiber (a reinforcing fiber opened from the reinforcing fiber bundle) F.

[0050] The fiber-reinforced resin composite sheet S can be continuously manufactured, for example, using the fiber-reinforced resin composite sheet manufacturing apparatus 1 shown in Figure 1. This fiber-reinforced resin composite sheet manufacturing apparatus 1 is a device that continuously manufactures the fiber-reinforced resin composite sheet S from a flame-retardant resin film R0 consisting of a reinforcing fiber bundle F0 and a thermoplastic resin composition.

[0051] Specifically, the fiber-reinforced resin composite sheet manufacturing apparatus 1 comprises multiple pairs (two pairs in Figure 1) of heating rollers 2 arranged vertically, multiple pairs (two pairs in Figure 1) of cooling rollers 3 arranged vertically below the heating rollers 2, a pair of endless belts 4 wrapped between the heating rollers 2 and the cooling rollers 3, a pair of pull-out rollers 5 located below the endless belts 4, and a winding bobbin 6 positioned below the pull-out rollers 5.

[0052] Although not shown in the diagram, a fiber-opening mechanism is provided near the uppermost heating roller 2 to open the reinforcing fiber bundle F0 and spread it into a strip. This fiber-opening mechanism makes it possible to form a large number of continuous reinforcing fibers F that are oriented and extending in the same direction by continuously opening the reinforcing fiber bundle F0. Any mechanism capable of such processing can be used as the fiber-opening mechanism, and various mechanisms can be used, such as a mechanism that spreads the reinforcing fiber bundle F0 by beating it, a mechanism that spreads the reinforcing fiber bundle F0 by blowing air on it, or a mechanism that spreads the reinforcing fiber bundle F0 by applying ultrasonic waves.

[0053] In the example shown in Figure 1, the fiber-opening mechanism includes a mechanism for supplying the opened reinforcing fibers F to one side of the flame-retardant resin film R0, and a mechanism for supplying the opened reinforcing fibers F to the other side of the flame-retardant resin film R0. The former mechanism is provided to introduce the reinforcing fibers F between one side of the flame-retardant resin film R0 and the heating roller 2 in contact with that side, and the latter mechanism is provided to introduce the reinforcing fibers F between the other side of the flame-retardant resin film R0 and the heating roller 2 in contact with that side. However, the fiber-opening mechanism may also supply the reinforcing fibers F to only one side of the flame-retardant resin film R0.

[0054] The heating roller 2 is a high-temperature roller heated by an electric heater or a heating medium (e.g., a heating fluid). The two pairs of heating rollers 2 heat the flame-retardant resin film R0 and the reinforcing fibers F introduced on both sides of it, sandwiching them from both sides via the endless belt 4, thereby continuously laminating the reinforcing fibers F onto the flame-retardant resin film R0. The reinforcing fibers F are laminated onto the flame-retardant resin film R0 in a state where they are oriented in the same direction (aligned in the vertical direction in Figure 1).

[0055] The cooling roller 3 is a low-temperature roller cooled by a cooling medium (e.g., a cooling fluid). The cooling roller 3 cools the flame-retardant resin film R0, on which the reinforcing fibers F are laminated, by sandwiching it from both sides via the endless belt 4, thereby fixing the reinforcing fibers F to the flame-retardant resin film R0. As a result, a fiber-reinforced resin composite sheet S is formed in which the flame-retardant resin film R0 (resin matrix) and the reinforcing fibers F are integrated.

[0056] The pull-out roller 5 is a roller that applies tension to the molded fiber-reinforced resin composite sheet S and pulls it downward.

[0057] The winding bobbin 6 is a core material for winding the fiber-reinforced resin composite sheet S. The bobbin 6 is rotationally driven by a drive source such as a motor, and sequentially winds the fiber-reinforced resin composite sheet S that has been pulled out by the pull-out roller 5, thereby forming a roll-shaped fiber-reinforced resin composite sheet S.

[0058] Furthermore, it is also possible to manufacture the fiber-reinforced resin composite sheet S by winding the flame-retardant resin film R0 and the opened reinforcing fibers together in the same direction without using the endless belt 4 shown in Figure 1.

[0059] When laminating reinforcing fibers onto one side of a flame-retardant resin film R0 with the opened reinforcing fibers oriented in the same direction, a fiber-reinforced resin composite sheet S can be obtained by feeding the reinforcing fibers F shown in Figure 1 from one side instead of both sides.

[0060] <Fiber-reinforced resin composite material> The fiber-reinforced resin composite material in this embodiment is a fiber-reinforced composite material in which multiple fiber-reinforced resin composite sheets from the above-described embodiment are laminated in the thickness direction.

[0061] Herein, throughout this specification, the term "lamination" as used in "a fiber-reinforced resin composite sheet (or its chopped material) is laminated" also includes the meanings of "lamination with at least a portion fixed," "lamination with at least a portion bonded," "lamination with at least a portion fused," "lamination with at least a portion attached," and "lamination with at least a portion compressed," depending on the physical properties, shape, type of treatment and conditions of the fiber-reinforced resin composite sheet (or its chopped material). More specifically, heating, cooling, and / or pressurizing treatments may be performed as necessary during the "lamination."

[0062] The fiber-reinforced resin composite sheets to be laminated may be cut or otherwise processed as needed to match the desired shape of the fiber-reinforced resin composite material. The number of fiber-reinforced resin composite sheets to be laminated is not particularly limited and can be set appropriately according to the desired size of the fiber-reinforced resin composite material. The fiber-reinforced resin composite sheets may be laminated in any manner regarding the fiber direction of their reinforcing fibers, but preferably, the reinforcing fibers of multiple fiber-reinforced resin composite sheets are laminated in such a way that there is an angular difference in the two-dimensional direction.

[0063] For example, a fiber-reinforced composite material can be described as one in which two or more fiber-reinforced resin composite sheets are laminated in the thickness direction, preferably 4 × n sheets (where n is an integer of 1 or more), such that the fiber directions of the reinforcing fibers have an angle difference of approximately 45° in the two-dimensional direction, in other words, there are four axial directions in the two-dimensional plane: 0°, 45°, -45°, and 90° (hereinafter also referred to as "four axial directions with an angle difference of 45°"). By laminating the fiber-reinforced resin composite sheets in this way, the tensile strength and bending strength along each fiber direction can be improved, thereby effectively improving the overall strength of the fiber-reinforced resin composite material.

[0064] Alternatively, in this embodiment, another fiber-reinforced resin composite material may be formed by laminating the fiber-reinforced resin composite sheet in the above-described embodiment in the thickness direction in the shape of multiple chopped materials.

[0065] Multiple chopped materials can be produced, for example, by shredding the fiber-reinforced resin composite sheet S shown in Figure 1 of the above embodiment in both the longitudinal and width directions.

[0066] As a specific example, chopped material can be produced by the following procedure. The procedure will be explained using Figure 2. In Figure 2, each symbol represents a fiber-reinforced resin composite sheet S, cut X, cut Y, section I, section II, and chopped material C. First, as shown in Figure 2, cuts X extending in the longitudinal direction are formed. That is, while feeding the fiber-reinforced resin composite sheet S in the longitudinal direction, a number of continuous cuts X in the longitudinal direction are formed in section I along the feeding path. Cuts X can be formed, for example, using a shredding device that includes a number of blades arranged at equal intervals in the width direction of the fiber-reinforced resin composite sheet S.

[0067] Next, in the following section II, a continuous cut Y is formed from one end to the other in the width direction of the fiber-reinforced resin composite sheet S. The cut Y can be formed using, for example, a rotary cutter. The cut Y is formed each time the fiber-reinforced resin composite sheet S is fed out a certain distance in the longitudinal direction. As a result, a number of rectangular chopped pieces C are cut out, each having a short side with a length corresponding to the pitch of the cuts X and a long side with a length corresponding to the pitch of the cuts Y.

[0068] As described above, the fiber-reinforced resin composite sheet S is a sheet in which numerous reinforcing fibers F are laminated in the longitudinal direction with all fibers oriented in the same direction. Therefore, each chopped material C cut from the fiber-reinforced resin composite sheet S is also laminated in the longitudinal direction (long side direction) with all reinforcing fibers F oriented in the same direction. In other words, the chopped material C contains a flame-retardant resin film R0 and numerous reinforcing fibers F laminated on the flame-retardant resin film R0 with all fibers oriented in the same direction.

[0069] The larger the size of the chopped material C, the higher the strength of the fiber-reinforced resin composite or resin molded product that can be manufactured, but the shapeability will be lower. On the other hand, the smaller the size of the chopped material C, the better the shapeability will be, and the fiber-reinforced resin composite or resin molded product with a high degree of freedom in shape can be manufactured, but the strength of the manufactured product will be reduced. Considering this balance between shapeability and mechanical properties depending on the size of the chopped material C, the size of the chopped material C can be adjusted and this balance can be appropriately controlled to impart properties suitable for the intended use of the molded product.

[0070] The length of the short side of chopped material C is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 4 mm or more, and even more preferably 4.5 mm or more, and also preferably 50 mm or less, more preferably 40 mm or less, even more preferably 30 mm or less, or even more preferably 20 mm or less, 15 mm or less, or 10 mm or less. The length of the long side of chopped material C is preferably 2 mm or more, more preferably 4 mm or more, even more preferably 6 mm or more, or even more preferably 8 mm or more or 10 mm or more, and also preferably 80 mm or less, more preferably 70 mm or less, even more preferably 60 mm or less, or even more preferably 50 mm or less or 45 mm or less.

[0071] The thickness of the chopped material C is the same as the thickness of the fiber-reinforced resin composite sheet in the above-described embodiment, and is between 20 μm and 100 μm. The preferred thickness is also the same as the thickness of the fiber-reinforced resin composite sheet in the above-described embodiment. That is, similar to the fiber-reinforced resin composite sheet in the above-described embodiment, multiple sheets of chopped material C can be laminated in a small size while minimizing voids due to its thinness. As a result, it is possible to manufacture a fiber-reinforced resin composite material with significantly higher density, superior strength, and low water absorption, as well as resin molded products using the same. Furthermore, by shaping the chopped material C, its shapeability is improved, and it is possible to manufacture resin molded products with complex shapes.

[0072] In the fiber-reinforced composite material of this embodiment, the arrangement of the multiple chopped materials C in terms of the fiber direction of their reinforcing fibers may vary, but it is preferable that the arrangement of the multiple chopped materials C in terms of the fiber direction of their reinforcing fibers is random in two dimensions (pseudoisotropic).

[0073] An example of a method for manufacturing such a fiber-reinforced composite material will be explained with reference to Figure 3. In Figure 3, each reference numeral represents a belt conveyor 7, release film 8, heating roller 9, bobbin for laminated chopped sheet 10, chopped material C, section XI, section XII, section XIII, and laminated chopped sheet CS. First, as shown in Figure 3, a belt conveyor 7, which is positioned and rotating almost horizontally, is rotated while a large number of chopped materials C are dispersed and placed on its upper surface. For this dispersion of chopped material C, for example, a dropping device can be used to drop the chopped material C from above the belt conveyor 7 while vibrating it. Then, by repeating the dropping operation of the chopped material C using such a dropping device, the density of chopped material C on the upper surface of the belt conveyor 7 and the number of layers are increased. In other words, by repeatedly dropping chopped material C using a dropping device in multiple sections XI, XII, XIII, etc. in the rotational direction of the belt conveyor 7, the fiber direction of the reinforcing fibers F contained in each chopped material C (in other words, the longitudinal direction of the chopped material C) is varied in various directions on the horizontal plane, and multiple chopped material C pieces are stacked on top of each other in the thickness direction, thereby stacking a large number of chopped material C pieces on the belt conveyor 7.

[0074] Then, from the end side where numerous chopped material C is stacked, the chopped material C stacked on the upper surface of the belt conveyor 7 is subjected to pressure and heat treatment using a heating roller 9 via a release film 8 or a heat-resistant endless belt, thereby integrating the numerous chopped material C. That is, the stacked chopped material C is bonded together by the pressure and heat treatment using the heating roller 9. In this way, the dispersion and stacking of numerous chopped material C on the upper surface of the belt conveyor 7 and the pressure and heat treatment using the heating roller 9 are performed continuously. After that, the stacked chopped sheet CS, in which multiple chopped material C has been integrated and stacked together, is continuously formed in a roll shape using a bobbin 10 for stacked chopped sheets, etc. A partial cross-section of the continuously formed roll-shaped stacked chopped sheet CS is shown in Figure 4. In Figure 4, each reference numeral represents the chopped material C, the stacked chopped sheet (fiber-reinforced composite material) CS, and the thickness t of the stacked chopped sheet CS. The thickness t of this stacked chopped sheet CS, that is, the total thickness of multiple or more stacked chopped material C, can be set as appropriate.

[0075] Alternatively, as another example of a method for manufacturing fiber-reinforced composite materials, when producing a laminated chopped sheet, a number of chopped materials C may be laminated on a carrier sheet made of a thermoplastic resin composition.

[0076] In detail, the carrier sheet is fed in the longitudinal direction as shown by the belt conveyor 7 in Figure 3, while a large number of chopped materials C are distributed and arranged on the upper surface of the carrier sheet. For this distribution of chopped materials C, for example, a dropping device similar to the one described above can be used from above the carrier sheet. Furthermore, the operation of dropping the chopped materials C using such a dropping device may be repeated at multiple locations in the feeding direction of the carrier sheet, as described above, to increase the density and number of layers of chopped materials C on the carrier sheet. That is, a large number of chopped materials C may be stacked on the carrier sheet such that the fiber direction of the reinforcing fibers F contained in each chopped material C varies in various directions on the horizontal plane, and multiple layers of chopped materials C are stacked in the thickness direction.

[0077] Subsequently, a heating roller is used to apply pressure and heat to the carrier sheet and the chopped material C on top of it, integrating the carrier sheet and the chopped material C together. That is, the pressure and heat treatment using the heating roller causes the carrier sheet to support the chopped material C in a laminated state, and the laminated chopped material C pieces bond to each other. In this way, a laminated chopped sheet CS can be formed in which multiple chopped material C pieces are laminated on the upper surface of the carrier sheet.

[0078] The carrier sheet material can be basically the same thermoplastic resin composition as the chop material C, a resin composition containing other thermoplastic resins having flame-retardant properties, or a thermoplastic resin composition that does not have flame-retardant properties. These thermoplastic resin compositions may consist of thermoplastic resin alone without any additives.

[0079] The explanation described how to create a laminated chopped sheet CS by laminating chopped material C only on the top surface of the carrier sheet. However, it is also possible to laminate chopped material C on both sides of the carrier sheet. In this case, the process of laminating chopped material C onto the carrier sheet (i.e., the process of randomly arranging multiple layers of chopped material C and then heating and pressurizing it) should be performed sequentially on the top and bottom surfaces of the carrier sheet. That is, after laminating chopped material C onto the top surface of the carrier sheet, the carrier sheet is turned over so that the bottom surface is facing upwards, and the process of laminating chopped material C is repeated in the same manner. As a result, a laminated chopped sheet can be created in which chopped material C is laminated on both sides of the carrier sheet.

[0080] <Resin molded products> The resin molded product in this embodiment comprises the fiber-reinforced resin composite material described in the above-described embodiment.

[0081] The resin molded product may be any molded product of any shape that can be manufactured using the fiber-reinforced resin composite material in the above-described embodiment by any molding method known to those skilled in the art. Examples include molded products such as housings and parts used in electrical or electronic devices such as smartphones, tablets, laptop computers, video cameras, mobile devices, and other household electrical appliances.

[0082] The method for manufacturing the resin molded product in this embodiment is not particularly limited. For example, first, a plurality of plate-shaped laminated chopped sheets CS as described in the above embodiment, cut to a predetermined size, are prepared and placed in a mold such as a hot press while stacking them in the thickness direction. Then, the stacked plurality of laminated chopped sheets CS can be subjected to heating and / or pressurizing treatment and, if necessary, cooling treatment to manufacture the resin molded product.

[0083] According to the manufacturing method described above, since a flame-retardant resin film R0 made of a highly heat-resistant thermoplastic resin composition is used, it is possible to obtain a resin molded product in which the physical properties of the resin molded product, such as tensile strength and flexural strength, do not easily decrease even under high-temperature conditions. Furthermore, since the resin molded product is formed using a laminated chopped sheet CS containing a sufficient amount of reinforcing fibers F such that the volume content Vf of reinforcing fibers is 30% or more and 65% or less, an excellent reinforcing effect by the reinforcing fibers F can be obtained, and the strength of the resin molded product can be increased. Moreover, a laminated chopped sheet CS in which the fiber directions of the reinforcing fibers F of multiple chopped materials C are laminated in a state where the fiber directions are random in two dimensions (pseudo-isotropic) can reduce the possibility of the reinforcing fibers F being shredded when the laminated chopped sheet CS is pressed, and can also promote the flow of the resin during pressing, thereby increasing the degree of freedom in the shape of the resin molded product. As a result, it is possible to mold resin molded products of various shapes without problems while exhibiting the reinforcing effect of the reinforcing fibers F isotropically.

[0084] The outline of the present invention has been described above, and the fiber-reinforced resin composite sheet, fiber-reinforced resin composite material, and resin molded product comprising them in this embodiment can be summarized as follows.

[0085] A fiber-reinforced resin composite sheet according to the first aspect of the present invention is a fiber-reinforced resin composite sheet comprising a flame-retardant resin film made of a thermoplastic resin composition having a glass transition temperature Tg of 90°C or higher, and a plurality of reinforcing fibers laminated on the flame-retardant resin film in a state in which a plurality of reinforcing fibers opened from a reinforcing fiber bundle are oriented in the same direction. The flammability classification of the flame-retardant resin film determined in the UL94VTM flammability test, which conforms to the ASTM D4804 standard, is VTM-0. The volume content Vf of the reinforcing fiber is 30% or more and 65% or less. The thickness of the fiber-reinforced resin composite sheet is 20 μm or more and 100 μm or less. The flammability classification of the fiber-reinforced resin composite sheet, as determined in the UL94-5V flammability test compliant with the ASTM D5048 standard, is 5V-A or 5V-B.

[0086] Fiber-reinforced resin composite sheets having such a structure possess excellent flame retardancy, good moldability, and sufficient tensile strength under high-temperature conditions.

[0087] Preferably, the plurality of reinforcing fibers are laminated on one or both sides of the flame-retardant resin film.

[0088] Because fiber-reinforced resin composite sheets having this configuration have multiple reinforcing fibers laminated on one or both surfaces of the flame-retardant resin film, they exhibit significantly superior flame retardancy compared to prepregs in which the reinforcing fibers are completely impregnated into the molten resin.

[0089] It is more preferable that the plurality of reinforcing fibers are laminated on both sides of the flame-retardant resin film.

[0090] Fiber-reinforced resin composite sheets with this configuration reliably possess significantly superior flame retardancy compared to prepregs in which reinforcing fibers are completely impregnated into the molten resin.

[0091] The thermoplastic resin composition is more preferably composed of a polycarbonate resin and one or more flame retardants selected from halogen-based flame retardants, phosphorus-based flame retardants, silicone-based flame retardants, and inorganic flame retardants.

[0092] Fiber-reinforced resin composite sheets with this configuration are guaranteed to have excellent flame retardancy.

[0093] The thermoplastic resin composition is particularly preferably composed of one or more selected from polyphenylene sulfide resin, polyetheretherketone resin, polyetherketoneketone resin, polyetherimide resin, polyethersulfone resin, and liquid crystal polymer resin.

[0094] Fiber-reinforced resin composite sheets with this configuration are guaranteed to have excellent flame retardancy.

[0095] The reinforcing fiber is more preferably a carbon fiber.

[0096] Fiber-reinforced resin composite sheets having such a structure can improve the strength and corrosion resistance of molded products using them, and also reliably possess extremely excellent flame retardancy due to the non-combustible carbon fibers.

[0097] The thickness of the flame-retardant resin film is more preferably 5 μm or more and 50 μm or less.

[0098] A fiber-reinforced resin composite sheet having such a structure can be made thin, and as a result, it can have good moldability.

[0099] The fiber-reinforced resin composite material according to the second aspect of the present invention is a fiber-reinforced composite material in which multiple fiber-reinforced resin composite sheets of the fiber-reinforced resin composite sheet according to the first aspect are laminated in the thickness direction. The fiber-reinforced composite material is formed by laminating a plurality of fiber-reinforced resin composite sheets such that the fiber directions of the reinforcing fibers have an angular difference in the two-dimensional direction.

[0100] A fiber-reinforced resin composite material having such a configuration can effectively improve the overall strength of the fiber-reinforced resin composite material.

[0101] Alternatively, the fiber-reinforced resin composite material according to the second aspect of the present invention is a fiber-reinforced resin composite material in which the fiber-reinforced resin composite sheet according to the first aspect is laminated in the thickness direction in the shape of a plurality of chopped materials. The chopped material is formed such that the fiber-reinforced resin composite sheet has a rectangle with a short side length of 2 mm or more and a long side length of 2 mm or more and a long side length of 80 mm. The fiber-reinforced composite material is laminated in such a way that the fiber orientation of the reinforcing fibers of the multiple chopped materials is random in two dimensions.

[0102] Fiber-reinforced resin composites having this configuration can isotropically exhibit the reinforcing effect of the reinforcing fibers while enabling the molding of resin molded products of various shapes without any problems.

[0103] A resin molded article according to the third aspect of the present invention comprises a fiber-reinforced resin composite material according to the second aspect.

[0104] Resin molded products having such a configuration possess excellent flame retardancy and sufficient tensile strength under high-temperature conditions. [Examples]

[0105] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0106] The test specimens of the fiber-reinforced resin composite sheets and fiber-reinforced resin composite materials for Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5 were prepared as follows.

[0107] (Example 1-1) To produce a fiber-reinforced resin composite sheet, a flame-retardant resin film made from a thermoplastic resin composition was prepared. In Example 1-1, a flame-retardant resin film was used, made from a thermoplastic resin composition containing polycarbonate resin and to which a non-brominated and non-phosphorus flame retardant was added. The glass transition temperature (Tg) of this thermoplastic resin composition is 148°C to 150°C. The thickness of the flame-retardant resin film is 20 μm.

[0108] Using this flame-retardant resin film and carbon fiber (Toray Industries, Ltd., "TORAYCA", grade: T-700 (PAN-based carbon fiber), fiber diameter: 7 μm, filament count: 12K, fineness: 800 tex) as reinforcing fibers, the fiber-reinforced resin composite sheet described above was obtained by opening the carbon fiber bundles using the manufacturing apparatus shown in Figure 1. At this time, the pressing force was set to 0.5 MPa, the roll temperature (temperature of heating roller 2 shown in Figure 1) was set to 270°C, and the feed speed was set to 10 m / min. In the obtained fiber-reinforced resin composite sheet, the opened carbon fiber bundles are laminated on both sides of the flame-retardant resin film. The volume content Vf of carbon fiber relative to the fiber-reinforced resin composite sheet was 53%, and the thickness of the fiber-reinforced resin composite sheet was 40 μm to 50 μm.

[0109] Forty of the obtained fiber-reinforced resin composite sheets were laminated so that the opened carbon fibers were oriented in a direction with an angle difference of 0°. The laminated fiber-reinforced resin composite sheets were placed in a mold and heated and pressurized for 15 minutes under conditions of 300°C and 2 MPa, and then cooled and pressurized for 10 minutes under conditions of room temperature and 3 MPa. A fiber-reinforced resin composite material measuring 300 mm × 300 mm × 2 mm (thickness) was removed from the mold, and this fiber-reinforced resin composite material was cut to obtain a test specimen of fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness). The volume content Vf of the carbon fibers in this test specimen was also 53%.

[0110] (Examples 1-2) In Example 1-2, instead of the thermoplastic resin composition containing the flame retardant-added polycarbonate resin of Example 1-1, a thermoplastic resin composition consisting solely of flame-retardant polyphenylene sulfide (PPS) resin (Solvay, "Ryton® QC200N") was used. The glass transition temperature Tg of the thermoplastic resin composition made of polyphenylene sulfide (PPS) resin is 90°C. A flame-retardant resin film made of polyphenylene sulfide (PPS) resin with a thickness of 25 μm was produced by molding polyphenylene sulfide (PPS) resin pellets in an extrusion molding machine equipped with a T-die at a molding temperature of 280°C.

[0111] Using this flame-retardant resin film and the carbon fibers described in Example 1-1, a fiber-reinforced resin composite sheet was obtained by opening the carbon fiber bundles using the manufacturing apparatus shown in Figure 1. At this time, the pressing force was set to 0.5 MPa, the roll temperature (temperature of heating roller 2 shown in Figure 1) was set to 280°C, and the feed speed was set to 20 m / min, obtaining a fiber-reinforced resin composite sheet with the same shape as in Example 1-1. The volume content Vf of carbon fibers relative to the fiber-reinforced resin composite sheet was 44.7%, and the thickness of the fiber-reinforced resin composite sheet was 50 μm.

[0112] Using the obtained fiber-reinforced resin composite sheet, a test specimen of fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness) was obtained by the same method as described in Example 1-1 above. The volume content Vf of the carbon fibers in this test specimen was also 44.7%.

[0113] (Examples 1-3) Except for adding a 25 μm thick film made of polyphenylene sulfide (PPS) resin when laminating the carbon fiber fiber-reinforced resin composite sheet so that the volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 35%, a 50 μm thick fiber-reinforced resin composite sheet and a 150 mm × 150 mm × 2 mm (thickness) fiber-reinforced resin composite material test piece was obtained using the same method as in Examples 1-2 described above.

[0114] (Examples 1-4) In Examples 1-2, instead of the flame-retardant resin film made of polyphenylene sulfide (PPS) resin with a thickness of 25 μm, a polyether ether ketone (PEEK) resin film (manufactured by Mitsubishi Chemical, "Superio UT(registered trademark) αKN-type") with flame-retardant properties and a thickness of 20 μm was used. The glass transition temperature Tg of the thermoplastic resin composition made of polyether ether ketone (PEEK) resin is 143°C to 147°C.

[0115] Using this flame-retardant resin film and the carbon fibers described in Example 1-1, a fiber-reinforced resin composite sheet was obtained by opening the carbon fiber bundles using the manufacturing apparatus shown in Figure 1. At this time, the pressing force was set to 0.5 MPa, the roll temperature (temperature of heating roller 2 shown in Figure 1) was set to 360°C, and the feed speed was set to 10 m / min, obtaining a fiber-reinforced resin composite sheet with the same shape as in Example 1-1. The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 53%, and the thickness of the fiber-reinforced resin composite sheet was 40 μm.

[0116] Using the obtained fiber-reinforced resin composite sheet, a test specimen of fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness) was obtained by the same method as described in Example 1-1 above. The volume content Vf of the carbon fibers in this test specimen was also 53%.

[0117] (Comparative Example 1-1) As Comparative Example 1-1, a commercially available polyamide 6 resin matrix fiber-reinforced resin composite sheet (TC910, manufactured by TCAC Corporation) was used, which is manufactured by impregnating carbon fiber bundles directly into the molten resin without opening the fibers. The glass transition temperature Tg of the polyamide 6 resin matrix is ​​approximately 50°C (reference value). The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 48%, and the thickness of the fiber-reinforced resin composite sheet was 180 μm.

[0118] Fourteen fiber-reinforced resin composite sheets were laminated so that the carbon fiber bundles were oriented with an angle difference of approximately 0°. Subsequently, a test specimen of fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness) was obtained using the same method as described in Example 1-1 above. The volume content Vf of the carbon fibers in this test specimen was also 48%.

[0119] (Comparative Example 1-2) In Comparative Example 1-2, a fiber-reinforced resin composite sheet with a thickness of 30 μm was obtained using the same method as in Example 1-1, except that the amount of carbon fibers laminated on both sides of a flame-retardant resin film containing a flame retardant-added polycarbonate resin was reduced so that the volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 25%.

[0120] The obtained fiber-reinforced resin composite sheets were laminated in a 74-sheet configuration, with the opened carbon fibers facing in a direction with an angle difference of 0°. Subsequently, a test specimen of the fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness) was obtained using the same method as described in Example 1-1. The volume content Vf of the carbon fibers in this test specimen was also 25%.

[0121] (Comparative Examples 1-3) In Comparative Example 1-3, a fiber-reinforced resin composite sheet with a thickness of 70 μm was obtained using the same method as in Example 1-1, except that the amount of carbon fibers laminated on both sides of a flame-retardant resin film containing a flame retardant-added polycarbonate resin was increased so that the volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 70%.

[0122] Using the obtained fiber-reinforced resin composite sheet, we attempted to prepare a 150mm x 150mm x 2mm (thickness) fiber-reinforced resin composite test piece using the same method as in Example 1-1 described above. However, due to poor impregnation between the fibers and the resin, it was not possible to mold the test piece.

[0123] (Comparative Examples 1-4) In Comparative Example 1-4, a fiber-reinforced resin composite sheet with a thickness of 35 μm was obtained using the same method as in Example 1-2 described above, except that the amount of carbon fibers laminated on both sides of a flame-retardant resin film made of polyphenylene sulfide (PPS) resin was reduced so that the volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 25%.

[0124] Sixty-four of the obtained fiber-reinforced resin composite sheets were laminated so that the opened carbon fibers were oriented in a direction with an angle difference of 0°. Subsequently, a test specimen of fiber-reinforced resin composite material measuring 150 mm × 150 mm × 2 mm (thickness) was obtained using the same method as described in Example 1-2 above. The volume content Vf of the carbon fibers in this test specimen was also 25%.

[0125] (Comparative Examples 1-5) In Comparative Examples 1-5, a fiber-reinforced resin composite sheet with a thickness of 85 μm was obtained using the same method as in Examples 1-2, except that the amount of carbon fibers laminated on both sides of a flame-retardant resin film made of polyphenylene sulfide (PPS) resin was increased so that the volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 70%.

[0126] Using the obtained fiber-reinforced resin composite sheet, we attempted to prepare a 150mm x 150mm x 2mm (thickness) fiber-reinforced resin composite test piece using the same method as in Examples 1-2 described above. However, due to poor impregnation between the fibers and the resin, it was not possible to mold the test piece.

[0127] The volume content Vf of reinforcing fibers in fiber-reinforced resin composite sheets and fiber-reinforced resin composite materials was measured by combustion. The glass transition temperature Tg of each thermoplastic resin composition or the thermoplastic resin itself is the temperature measured by scanning calorimeter (DSC).

[0128] <Evaluation of flame retardancy of thermoplastic resin films or resin matrices> The flammability of the resin films prepared in Examples 1-1 to 1-4 and Comparative Examples 1-2 to 1-5, as well as the polyamide 6 resin matrix used in Comparative Example 1-1, was determined by the UL94VTM combustion test in accordance with the ASTM D4804 standard. Specifically, a test specimen (dimensions: 200±5mm × 50±1mm × tmm) was rolled into a cylinder, mounted vertically on a clamp, and subjected to two 3-second indirect flame tests with a 20mm flame. The combustion behavior was then judged as "VTM-0", "VTM-1", "VTM-2", or "Not". The thickness was set to t=20~25μm. The specific criteria for judgment are shown in Table 1 below.

[0129] [Table 1]

[0130] <Evaluation of flame retardancy of fiber-reinforced resin composite sheets> The flammability of the fiber-reinforced resin composite sheets prepared in Examples 1-1 to 1-4 and Comparative Examples 1-1, 1-2, and 1-4 was determined by the UL94-5V combustion test in accordance with the ASTM D5048 standard. Specifically, a strip-shaped test piece (dimensions: 125±5mm × 13±0.5 × tmm) was mounted vertically on a clamp, and five 5-second indirect flame tests were performed using a 125mm flame. Furthermore, a flat plate test piece (dimensions: 150±5mm × 150±5 × tmm) was held horizontally, and five 5-second indirect flame tests were performed using a 125mm flame from below. Based on these combustion behaviors, a judgment of "5V-B", "5V-A", or "Not" was made. The thickness was set to t=2mm. The specific judgment criteria are shown in Table 2 below. Note that in Comparative Examples 1-3 and 1-5, the fiber-reinforced resin composite sheet test pieces could not be tested due to poor impregnation between the fibers and resin.

[0131] [Table 2]

[0132] <Evaluation of tensile strength (MPa) of test specimens of fiber-reinforced resin composite material> The tensile strength of the fiber-reinforced resin composite test specimens for Examples 1-1 to 1-4, as well as Comparative Examples 1-1, 1-2, and 1-4, was measured in accordance with JIS K 7165:2008. However, as mentioned above, testing could not be performed on Comparative Examples 1-3 and 1-5 because the fiber-reinforced resin composite test specimens could not be molded.

[0133] The properties and evaluation results of the thermoplastic resin films or resin matrices and fiber-reinforced resin composite sheets in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5 are summarized in Tables 3 and 4 below.

[0134] [Table 3]

[0135] [Table 4]

[0136] As is clear from the results in Table 3 above, the resin films of Examples 1-1 to 1-4 and their fiber-reinforced resin composite sheets exhibited superior flame retardancy compared to the polyamide 6 resin matrix and its fiber-reinforced resin composite sheet of Comparative Example 1-1.

[0137] Furthermore, the fiber-reinforced resin composite sheets of Examples 1-1 to 1-4 could be formed with significantly thinner thicknesses compared to the fiber-reinforced resin composite sheet of Comparative Example 1-1, which was made by impregnating carbon fiber bundles into a resin matrix without opening the fibers. In addition, the test specimens of the fiber-reinforced resin composite materials of Examples 1-2 and 1-3 exhibited high tensile strength, contrary to what would normally be expected, despite having a smaller volume content Vf of reinforcing fibers compared to the test specimen of the fiber-reinforced resin composite material of Comparative Example 1-1. This is presumed to be because the fiber-reinforced resin composite sheets of Examples 1-1 to 1-4 are composed of multiple layers of thin fiber-reinforced resin composite sheets, resulting in good dispersion of reinforcing fibers and resin. Therefore, compared to the laminate in Comparative Example 1-1, which is composed of thicker layers, delamination is less likely to occur, and the inherent strength of the fibers is expressed. Thus, the fiber-reinforced resin composite sheets of Examples 1-1 to 1-4 exhibit excellent moldability as intermediate materials, and the tensile strength of the fiber-reinforced resin composite materials produced from these sheets is also excellent.

[0138] Furthermore, as can be seen from the results of Comparative Examples 1-2 and 1-4 in Table 4 above, when the volume content Vf of reinforcing fibers was reduced to 25%, the tensile strength of the fiber-reinforced resin composite material decreased significantly. Also, as can be seen from the results of Comparative Examples 1-3 and 1-5 in Table 4 above, when the volume content Vf of reinforcing fibers was increased to 70%, the impregnation of the fibers and resin in the resulting fiber-reinforced resin composite sheet deteriorated, resulting in poor moldability, and thus the fiber-reinforced resin composite material could not be molded. From these results, it can be seen that unless the volume content Vf of reinforcing fibers is adjusted to a value within the specific range specified for the fiber-reinforced resin composite sheet of this embodiment, it is not possible to obtain a fiber-reinforced resin composite sheet that achieves both good moldability and sufficient tensile strength under high-temperature conditions.

[0139] The glass transition temperature (Tg) of the resin films (thermoplastic resin compositions or thermoplastic resins) used in Examples 1-1 to 1-4 is significantly higher than that of the polyamide 6 resin matrix used in Comparative Example 1-1. Therefore, it is expected that the fiber-reinforced resin composite sheets of Examples 1-1 to 1-4 and the fiber-reinforced resin composite materials produced therefrom will have heat resistance and good strength, such as tensile strength (or flexural strength), even under high-temperature conditions. Furthermore, it is expected that the thermoplastic resins of Reference Examples 1 to 4 (polyetherketone (PEKK) resin, polyetherimide (PEI) resin, polyethersulfone (PES) resin, and liquid crystal polymer (LCP) resin), which have high glass transition temperatures (Tg) and are highly flammable, as shown in Table 5 below, will exhibit the same effects as the present invention.

[0140] [Table 5]

[0141] Furthermore, additional experiments were conducted to evaluate the flame retardancy of the fiber-reinforced resin composite sheets. Specifically, additional experiments were conducted to investigate the relationship between the structure of the fiber-reinforced resin composite sheet and its flame retardancy properties. First, test specimens of the fiber-reinforced resin composite sheets in Examples 2-1 and 2-2, and Comparative Examples 2-1 and 2-2 were prepared using the following method.

[0142] (Example 2-1) In Example 2-1, a fiber-reinforced resin composite sheet containing a flame retardant-added polycarbonate resin was obtained using the same method as in Example 1-1. The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 53%, and the thickness of the fiber-reinforced resin composite sheet was 40-50 μm. Next, a test piece of the fiber-reinforced resin composite sheet measuring 13 mm × 125 mm × 40-50 μm (thickness) was cut from the obtained fiber-reinforced resin composite sheet.

[0143] The cross-section of the test specimen of the fabricated fiber-reinforced resin composite sheet was observed using a laser microscope ("VK-X160", Keyence). As shown in Figure 5, the cross-sectional view of the test specimen of the fiber-reinforced resin composite sheet in Example 2-1 showed a state in which multiple carbon fibers were laminated on both sides of a flame-retardant resin film containing a polycarbonate resin to which a flame retardant had been added. Specifically, approximately half of each carbon fiber was impregnated from the surface into the interior of the film.

[0144] (Example 2-2) In Example 2-2, a fiber-reinforced resin composite sheet containing polyphenylene sulfide (PPS) resin was obtained using the same method as in Example 1-2. The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 44.7%, and the thickness of the fiber-reinforced resin composite sheet was 50 μm. Next, a test specimen of the fiber-reinforced resin composite sheet measuring 13 mm × 125 mm × 50 μm (thickness) was cut from the obtained fiber-reinforced resin composite sheet.

[0145] The cross-section of the test specimen of the fabricated fiber-reinforced resin composite sheet was observed in the same manner as in Example 2-1. As shown in Figure 5, the cross-sectional view of the test specimen of the fiber-reinforced resin composite sheet in Example 2-2 showed a state in which multiple carbon fibers were laminated on both sides of a flame-retardant resin film made of polyphenylene sulfide (PPS) resin. Specifically, approximately half of each carbon fiber was impregnated from the surface into the interior of the film.

[0146] (Comparative Example 2-1) In Comparative Example 2-1, first, a fiber-reinforced resin composite sheet containing a flame retardant-added polycarbonate resin was obtained using the same method as in Example 1-1 described above. Furthermore, the sheet was sandwiched between iron plates heated to 300°C and pressed using a press machine at 5 kgf for 60 seconds to obtain the fiber-reinforced resin composite sheet containing a flame retardant-added polycarbonate resin in Comparative Example 2-1. The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 53%, and the thickness of the fiber-reinforced resin composite sheet was 38 μm. Next, a test piece of the fiber-reinforced resin composite sheet measuring 13 mm × 125 mm × 38 μm (thickness) was cut from the obtained fiber-reinforced resin composite sheet.

[0147] The cross-section of the test specimen of the fabricated fiber-reinforced resin composite sheet was observed in the same manner as in Example 2-1. As shown in Figure 5, the cross-sectional view of the test specimen of the fiber-reinforced resin composite sheet in Comparative Example 2-1 showed that multiple carbon fibers were completely impregnated inside the flame-retardant resin film containing polycarbonate resin to which a flame retardant had been added.

[0148] (Comparative Example 2-2) In Comparative Example 2-2, first, a fiber-reinforced resin composite sheet containing polyphenylene sulfide (PPS) resin was obtained using the same method as in Example 1-2 described above. Furthermore, the sheet was sandwiched between iron plates heated to 330°C and pressed using a press machine at 5 kgf for 60 seconds to obtain the fiber-reinforced resin composite sheet containing polyphenylene sulfide (PPS) resin in Comparative Example 2-2. The volume content Vf of carbon fibers in the fiber-reinforced resin composite sheet was 44.7%, and the thickness of the fiber-reinforced resin composite sheet was 42 μm. Next, a test piece of fiber-reinforced resin composite sheet measuring 13 mm × 125 mm × 42 μm (thickness) was cut from the obtained fiber-reinforced resin composite sheet.

[0149] The cross-section of the test specimen of the fabricated fiber-reinforced resin composite sheet was observed in the same manner as in Example 2-1. As shown in Figure 5, the cross-sectional view of the test specimen of the fiber-reinforced resin composite sheet in Comparative Example 2-2 showed that multiple carbon fibers were completely impregnated inside the flame-retardant resin film made of polyphenylene sulfide (PPS) resin.

[0150] <Additional flame retardancy testing of fiber-reinforced resin composite sheets> The flame retardancy of the fiber-reinforced resin composite sheets prepared in Examples 2-1 and 2-2, and Comparative Examples 2-1 and 2-2, was determined by a method different from the one described above. As a test method, first, the prepared fiber-reinforced resin composite sheet test specimens were suspended by clamps. Next, the prepared gas burner was adjusted so that the flame turned blue. Then, the gas burner was moved so that the fiber-reinforced resin composite sheet test specimen suspended by the clamp was positioned approximately 1 cm away from the tip of the flame. In this way, the flame was applied to the lower part of the fiber-reinforced resin composite sheet test specimen suspended by the clamp, and the initial ignition, specifically 1 second after ignition, was observed.

[0151] Figure 6 shows images of the results of additional flame retardancy tests on test specimens of each fiber-reinforced resin composite sheet. Specifically, Figure 6 shows images of each fiber-reinforced resin composite sheet test specimen 1 second after ignition. As can be seen from Figure 6, the test specimens of Examples 2-1 and 2-2, in which approximately half of each carbon fiber was impregnated from the film surface into the interior, showed a tendency for flames to spread less easily compared to the test specimens of Comparative Examples 2-1 and 2-2, in which multiple carbon fibers were completely impregnated into the resin film. This is thought to be because in the test specimens of Examples 2-1 and 2-2, multiple non-combustible carbon fibers were laminated on the flame-retardant resin film in an exposed state without being completely impregnated, thus suppressing the spread of flames. Thus, the fiber-reinforced resin composite sheet in this embodiment is considered to have excellent flame retardancy because, in addition to the resin film having flame-retardant properties, it has a structure in which multiple reinforcing fibers are laminated on the flame-retardant resin film.

[0152] This application is based on Japanese Patent Application No. 2020-075392, filed on April 21, 2020, and its contents are included in this application.

[0153] In order to express the present invention, the invention has been adequately and sufficiently described above through embodiments and examples with reference to specific examples, etc. However, those skilled in the art should recognize that it is easy to modify and / or improve the above embodiments and examples. Therefore, unless such modifications or improvements implemented by those skilled in the art fall outside the scope of the claims described in the claims, such modifications or improvements shall be interpreted as being included within the scope of the claims. [Industrial applicability]

[0154] In the technical field relating to fiber-reinforced resin composite sheets, the present invention can improve the flame retardancy, moldability, and strength under high-temperature conditions of the sheet, and can be widely used as a material for sports and leisure equipment, industrial equipment such as automobiles and aircraft, and housings and components of electrical or electronic equipment.

Claims

1. A fiber-reinforced resin composite sheet comprising a flame-retardant resin film made of a thermoplastic resin composition having a glass transition temperature Tg of 90°C or higher, and a plurality of carbon fibers in which multiple carbon fibers opened from a carbon fiber bundle are oriented in the same direction and approximately half of each carbon fiber is impregnated into the flame-retardant resin film. The carbon fibers are impregnated in a manner that is exposed on both surfaces of the flame-retardant resin film, with approximately half of the fibers remaining unimpregnated. The flammability classification of the flame-retardant resin film determined in the UL94VTM combustion test compliant with the ASTM D4804 standard is VTM-0. The volume content Vf of the carbon fiber is 30% or more and 65% or less. The thickness of the fiber-reinforced resin composite sheet is 20 μm or more and 80 μm or less. The flammability classification of the fiber-reinforced resin composite sheet determined in the UL94-5V flammability test compliant with the ASTM D5048 standard is 5V-A or 5V-B. The thermoplastic resin composition comprises a polycarbonate resin and one or more flame retardants selected from halogen-based flame retardants, phosphorus-based flame retardants, silicone-based flame retardants, and inorganic flame retardants, and is a fiber-reinforced resin composite sheet.

2. The fiber-reinforced resin composite sheet according to claim 1, wherein the thickness of the flame-retardant resin film is 5 μm or more and 50 μm or less.

3. The fiber-reinforced resin composite sheet according to claim 1 or 2, wherein the thickness of the flame-retardant resin film is 5 μm or more and 40 μm or less, and the thickness of the fiber-reinforced resin composite sheet is 25 μm or more and 60 μm or less.

4. The fiber-reinforced resin composite sheet according to any one of claims 1 to 3 is a fiber-reinforced composite material in which multiple layers are laminated in the thickness direction, The fiber-reinforced composite material is a fiber-reinforced resin composite material in which a plurality of fiber-reinforced resin composite sheets are laminated in such a manner that the fiber directions of the carbon fibers have an angular difference in the two-dimensional direction.

5. The fiber-reinforced resin composite sheet according to any one of claims 1 to 3 is a fiber-reinforced composite material in which a plurality of chopped material shapes are laminated in the thickness direction, The chopped material is formed such that the fiber-reinforced resin composite sheet has a rectangle with a short side length of 2 mm or more and a long side length of 2 mm or more and a long side length of 80 mm or less. The fiber-reinforced composite material is a fiber-reinforced resin composite material in which a plurality of the chopped materials are laminated in such a state that the fiber directions of the carbon fibers are random in two dimensions.

6. A resin molded article comprising the fiber-reinforced resin composite material according to claim 4 or 5.

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