Carbon fiber reinforced plastic laminate

Abstract

To provide a carbon fiber reinforced plastic laminate having superior appearance characteristics.SOLUTION: A carbon fiber reinforced plastic laminate 1 is constituted by laminating a first prepreg layer 30 having a resin 21 impregnated into carbon fibers 11 oriented in a first direction P, a second prepreg layer 40 having a resin 22 impregnated into carbon fibers 12 oriented in a second direction Q different from the first direction P, and a third prepreg layer 50 having substantially the same structure as the first prepreg layer 30. The flatness ratio (P1) of the carbon fibers 11 used in the first prepreg layer 30 is greater than the flatness ratio (P2) of the carbon fibers 12 used in the second prepreg layer 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbon fiber reinforced plastic laminate formed by laminating a plurality of prepreg layers.

Background Art

[0002] Conventionally, a plurality of prepreg layers in which carbon fibers are impregnated with a resin have been laminated to form a carbon fiber reinforced plastic laminate.

[0003] As a prepreg used for this type of carbon fiber reinforced plastic laminate, a prepreg in which carbon fibers having a substantially circular cross-sectional shape of single fibers are impregnated with a thermosetting resin so as to have a specific resin content has been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in recent years, attempts have been made to use carbon fiber reinforced plastic laminates instead of stainless steel, which has been conventionally used as a reinforcing member for screens provided in smartphones, tablet terminals, etc., for the purpose of weight reduction. In order to be used as such a reinforcing member, it is necessary to make the carbon fiber reinforced plastic laminate into a thin flat plate. However, when the carbon fiber reinforced plastic laminate is made thin, there is a risk that the bending durability (the performance of returning to its original state even when bent once) may decrease. In order to suppress such a decrease in bending durability, it is conceivable to laminate prepreg layers having different configurations in combination. However, when laminated in this way, due to the thinness of the layers constituting the carbon fiber reinforced plastic laminate, visible light passes through the upper prepreg layer, interferes with the lower prepreg layer, and moiré (interference fringes) may occur on the surface (the surface of the upper prepreg layer), resulting in a possible deterioration of the appearance characteristics. In particular, when the carbon fiber reinforced plastic laminate is used as a reinforcing member for the screen of a smartphone, tablet terminal, etc., moiré has an adverse effect on the image quality of the image displayed on the screen, so it is desirable to eliminate it as much as possible.

[0006] Regarding this point, the prepreg of Patent Document 1 is assumed to be used as a tubular molded body and does not focus on the occurrence of moiré when the prepreg layers are laminated.

[0007] In view of the above circumstances, an object of the present invention is to provide a carbon fiber reinforced plastic laminate having excellent appearance characteristics.

Means for Solving the Problems

[0008] The characteristic configuration of the carbon fiber reinforced plastic laminate according to the present invention for solving the above problems is a carbon fiber reinforced plastic laminate formed by laminating a first prepreg layer in which carbon fibers oriented in a first direction are impregnated with resin, a second prepreg layer in which carbon fibers oriented in a second direction different from the first direction are impregnated with resin, and a third prepreg layer having substantially the same configuration as the first prepreg layer, The flatness ratio (P1) of the carbon fiber used in the first prepreg layer is configured to be larger than the flatness ratio (P2) of the carbon fiber used in the second prepreg layer.

[0009] According to the carbon fiber reinforced plastic laminate of this configuration, by laminating the above first prepreg layer, second prepreg layer, and third prepreg layer, and setting the flatness ratio (P1) of the carbon fiber used in the first prepreg layer to be larger than the flatness ratio (P2) of the carbon fiber used in the second prepreg layer, the carbon fiber of the first prepreg layer has a larger surface area compared to the carbon fiber of the second prepreg layer, and accordingly, the gaps between the fibers become smaller. Therefore, the permeability and permeation unevenness of the first prepreg layer are suppressed. As a result, the generation of moiré on the surface of the first prepreg layer is suppressed. Further, since the third prepreg layer has substantially the same configuration as the first prepreg layer, the generation of moiré is also suppressed on the surface of the third prepreg layer in the same manner as the first prepreg layer. Thereby, the carbon fiber reinforced plastic laminate suppresses the generation of moiré when viewed from either the first prepreg layer side or the third prepreg layer side (that is, when the carbon fiber reinforced plastic laminate is viewed from either the front or back surface side), and has excellent appearance characteristics.

[0010] In the carbon fiber reinforced plastic laminate according to the present invention, The flatness ratio (P1) of the carbon fiber is preferably 33 to 75%.

[0011] According to the carbon fiber reinforced plastic laminate of this configuration, by setting the flatness ratio (P1) of the carbon fiber used in the first prepreg layer within the above appropriate range, the generation of moiré on the surface of the first prepreg layer is further suppressed.

[0012] In the carbon fiber reinforced plastic laminate according to the present invention, It is preferable that the fiber volume content (Vf2) of the second prepreg layer is configured to be larger than the fiber volume content (Vf1) of the first prepreg layer.

[0013] According to the carbon fiber reinforced plastic laminate of this configuration, by setting the fiber volume content (Vf2) of the second prepreg layer to be larger than the fiber volume content (Vf1) of the first prepreg layer, the concealability of the second prepreg layer is enhanced (the permeability is reduced), and the interference with the first prepreg layer and the third prepreg layer can be more suppressed. Therefore, the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer and the third prepreg layer.

[0014] In the carbon fiber reinforced plastic laminate according to the present invention, the fiber volume content (Vf1) of the first prepreg layer is 35 to 60%, and it is preferable that the fiber volume content (Vf2) of the second prepreg layer is 45 to 70%.

[0015] According to the carbon fiber reinforced plastic laminate of this configuration, by setting the fiber volume content (Vf1) of the first prepreg layer and the fiber volume content (Vf2) of the second prepreg layer within the above ranges respectively, the fiber volume contents (Vf1, Vf3, Vf2) of the carbon fibers in the first prepreg layer, the third prepreg layer having substantially the same configuration as the first prepreg layer, and the second prepreg layer become more appropriate. Therefore, the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer and the third prepreg layer.

[0016] In the carbon fiber reinforced plastic laminate according to the present invention, it is preferable that the angle formed by the first direction and the second direction is 90°.

[0017] According to the carbon fiber reinforced plastic laminate of this configuration, by setting the angle formed by the first direction and the second direction to 90°, the orientation direction of the carbon fibers in the first prepreg layer and the third prepreg layer and the orientation direction of the carbon fibers in the second prepreg layer are perpendicular. When these prepreg layers are stacked, compared with the case where they do not intersect perpendicularly (for example, when the intersection angle is 1 to 89° or 91 to 179°), the fiber spacing (period) and angle deviation are less likely to occur. Therefore, the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer and the third prepreg layer.

[0018] The characteristic configuration of the carbon fiber reinforced plastic laminate according to the present invention for solving the above problems is a carbon fiber reinforced plastic laminate formed by laminating a first prepreg layer in which carbon fibers oriented in a first direction are impregnated with resin, a second prepreg layer in which carbon fibers oriented in a second direction different from the first direction are impregnated with resin, and a third prepreg layer having substantially the same configuration as the first prepreg layer, wherein no moiré pattern is observed when viewed from the side of the first prepreg layer and / or the third prepreg layer.

[0019] According to the carbon fiber reinforced plastic laminate of this configuration, by laminating the above first prepreg layer, second prepreg layer, and third prepreg layer and ensuring that no moiré pattern is observed when viewed from the side of the first prepreg layer and / or the third prepreg layer, the carbon fiber reinforced plastic laminate has excellent appearance characteristics when viewed from either the side of the first prepreg layer or the side of the third prepreg layer (that is, when viewed from either the front or the back of the carbon fiber reinforced plastic laminate), and can be suitably used as a reinforcing member for the screens of smartphones, tablet terminals, etc.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying out the Invention

[0021] The carbon fiber reinforced plastic laminate of the present invention will be described with reference to the drawings. However, the layer configuration shown in the drawings is exaggerated or simplified as appropriate for ease of explanation, and the size relationship and scale relationship of the thickness of each layer do not necessarily accurately reflect the actual carbon fiber reinforced plastic laminate. In this specification, "laminating the first prepreg layer, the second prepreg layer, and the third prepreg layer in this order" is synonymous with "laminating the third prepreg layer, the second prepreg layer, and the first prepreg layer in this order", and "laminating the flat plate for the first prepreg layer, the flat plate for the second prepreg layer, and the flat plate for the third prepreg layer in this order" is synonymous with "laminating the flat plate for the third prepreg layer, the flat plate for the second prepreg layer, and the flat plate for the first prepreg layer in this order".

[0022] [Carbon Fiber Reinforced Plastic Laminate] Figure 1 is a perspective view schematically showing the carbon fiber reinforced plastic laminate 1 according to the present invention, and is shown together with the flat plate 31 for the first prepreg layer 30, the flat plate 41 for the second prepreg layer 40, and the flat plate 51 for the third prepreg layer 50 before lamination. Figure 2 is a photograph showing an example of a cross-section taken by a scanning electron microscope when cutting along the A-A arrow and B-B arrow in Figure 1.

[0023] The carbon fiber reinforced plastic laminate 1 is formed by laminating a first prepreg layer 30 obtained by impregnating carbon fibers 11 oriented in a first direction P with a resin 21, a second prepreg layer 40 obtained by impregnating carbon fibers 12 oriented in a second direction Q different from the first direction P with a resin 22, and a third prepreg layer 50 having substantially the same configuration as the first prepreg layer 30. The carbon fiber reinforced plastic laminate 1 is obtained by overlapping a flat plate 31 for the first prepreg layer 30, a flat plate 41 for the second prepreg layer 40, and a flat plate 51 for the third prepreg layer 50 in this order and performing hot pressing.

[0024] [First prepreg layer] The first prepreg layer 30 is obtained by impregnating carbon fibers 11 oriented in the first direction P with a resin 21. In the embodiment shown in FIG. 1, the first direction P is set in a direction perpendicular to the upper and lower sides (width direction) of the first prepreg layer 30.

[0025] The first prepreg layer 30 is obtained by producing a flat plate 31 for the first prepreg layer 30 obtained by impregnating carbon fibers 11 with a resin 21 and performing hot pressing.

[0026] The thickness of the flat plate 31 for the first prepreg layer 30 and the fiber areal weight (FAW) of the carbon fibers 11 in the flat plate 31 for the first prepreg layer 30 are appropriately set so that the first prepreg layer 30 in the carbon fiber reinforced plastic laminate 1 has a desired thickness and fiber areal weight.

[0027] <Carbon fiber> Examples of the carbon fibers 11 include polyacrylonitrile (PAN)-based carbon fibers and pitch-based carbon fibers. In the first prepreg layer 30, the carbon fibers 11 are contained in a state aligned in the first direction P.

[0028] The flatness ratio (P1) of the carbon fiber 11 is configured to be larger than the flatness ratio (P2) of the carbon fiber 12 used for the second prepreg layer 40 described later. By setting the flatness ratio (P1) of the carbon fiber 11 in the first prepreg layer 30 to be larger than the flatness ratio (P2) of the carbon fiber 12 in the second prepreg layer 40, the surface area of the carbon fiber 11 becomes larger compared to the carbon fiber 12 in the second prepreg layer 40, and accordingly, the gaps between the fibers become smaller. Therefore, the permeability and permeation unevenness of the first prepreg layer 30 are suppressed.

[0029] The flatness ratio (P1) is 33 to 75%, preferably 50 to 75%, and more preferably 60 to 75%. By setting the flatness ratio (P1) to be larger than the flatness ratio (P2) of the carbon fiber 12 used for the second prepreg layer 40 as described above and setting the flatness ratio (P1) within the above appropriate range, the occurrence of moiré on the surface of the first prepreg layer 30 is suppressed.

[0030] In this specification, the flatness ratio (P) is a value calculated by the following formula (1) using the minor axis (a) and major axis (b) in the cross-section of the carbon fiber, and is obtained as the average value of the values calculated for any 10 carbon fibers. Flatness ratio (P)% = (1 - a / b) × 100 ···(1)

[0031] For the carbon fiber 11, the ratio (a:b) of the minor axis (a) to the major axis (b) in the cross-section is preferably 1:1.5 to 1:4, more preferably 1:2 to 1:4, and even more preferably 1:2.5 to 1:4. By setting the ratio (a:b) of the minor axis (a) to the major axis (b) of the carbon fiber 11 within the above range, the flatness ratio (P1) determined by the ratio (a:b) of the carbon fiber 11 can be set within the above range.

[0032] In this specification, the ratio (a / b) of the minor axis (a) to the major axis (b) of the carbon fiber 11 is obtained as the average value when photographing the cross section of the carbon fiber reinforced plastic laminate 1 with a microscope at a magnification of 80 times or more and measuring the minor axes (a) and (b) of any 10 carbon fibers 11. Further, using the minor axis (a) and major axis (b) thus obtained, the flatness ratio (P1) is calculated by the above formula (1).

[0033] Examples of the cross-sectional shape of the carbon fiber 11 include an elliptical shape as illustrated in Fig. 3(a), a heart shape as illustrated in Fig. 3(b), a circular shape as illustrated in Fig. 3(c), etc. In this specification, the shape of the carbon fiber 11 is obtained as the shape most frequently included in any 10 carbon fibers 11 by photographing the cross section of the carbon fiber reinforced plastic laminate 1 with a microscope at a magnification of 80 times or more.

[0034] The tensile elastic modulus of the carbon fiber 11 measured in accordance with JIS R7601 is preferably 210 to 300 GPa, more preferably 230 to 290 GPa. By setting the tensile elastic modulus of the carbon fiber 11 within the above range, the flexural elastic modulus (Ea1) in the first direction P of the carbon fiber reinforced plastic laminate 1 becomes more appropriate, and the bending durability and flatness can be enhanced.

[0035] A plurality of the carbon fibers 11 are bundled and treated as a carbon fiber bundle. The number of carbon fibers in the carbon fiber bundle of the carbon fiber 11 is preferably 1000 to 30000, more preferably 3000 to 24000. By setting the number of carbon fibers in the carbon fiber bundle of the carbon fiber 11 within the above range, the tensile strength of the carbon fiber 11 can be made appropriate.

[0036] The fineness of the carbon fiber 11 is preferably 350 to 16500 dtex, more preferably 350 to 1800 dtex, and particularly preferably 400 to 1650 dtex. By setting the fineness of the carbon fiber 11 within the above range, the tensile strength of the carbon fiber 11 can be made appropriate.

[0037] The fiber weight per unit area (F1) of the first prepreg layer 30 is preferably set to be smaller than the fiber weight per unit area (F2) of the second prepreg layer 40 described later. That is, the fiber weight per unit area (F2) of the second prepreg layer 40 is preferably set to be larger than the fiber weight per unit area (F1) of the first prepreg layer 30. By setting the fiber weight per unit area (F1) of the first prepreg layer 30 to be smaller than the fiber weight per unit area (F2) of the second prepreg layer 40, the concealability of the second prepreg layer 40 is enhanced (the transparency is reduced), and the interference with the first prepreg layer 30 and the third prepreg layer 50 can be suppressed. Therefore, the occurrence of moiré on the surface of the first prepreg layer 30 is more suppressed. In addition, since the flexural modulus (Ea1) in the first direction P and the flexural modulus (Ea2) in the second direction Q can be more surely set within a desired range, the bending durability and flatness can be more surely enhanced.

[0038] The fiber weight per unit area (F1) of the first prepreg layer 30 can be appropriately set so as to further suppress the occurrence of moiré. For example, in order to further enhance the concealability of the second prepreg layer 40 and suppress the occurrence of moiré, within the preferable total thickness range of the carbon fiber reinforced plastic laminate 1, it is preferable to increase the thickness of the second prepreg layer 40 and use more carbon fibers 12. For this purpose, it is preferable that the first prepreg layer 30 (and the third prepreg layer 50) be as thin as possible and set to the minimum necessary fiber weight per unit area, in terms of being able to relatively increase the thickness of the second prepreg layer 40. On the other hand, if the fiber weight per unit area (F1) of the first prepreg layer 30 is set too small, as a result, the gap between the carbon fibers 11 becomes larger, and interference may occur, which may promote the occurrence of moiré. Considering such a viewpoint, the fiber weight per unit area (F1) of the first prepreg layer 30 is preferably 20 to 30 g / m 2 is preferable. By setting the fiber weight per unit area (F1) of the first prepreg layer 30 to 20 g / m 2 or more, the gap between the carbon fibers 11 can be reduced, so that the occurrence of moiré is more suppressed. By setting the fiber weight per unit area (F1) of the first prepreg layer 30 to 30 g / m 2By setting as follows, the first prepreg layer 30 can be made thinner, and correspondingly, the second prepreg layer 40 can be made thicker, so that the occurrence of moiré is more suppressed. Also, by setting the fiber areal density (F1) of the first prepreg layer 30 to 20~30 g / m 2 it is possible to more reliably set the flexural modulus (Ea1) in the first direction P and the flexural modulus (Ea2) in the second direction Q within a desired range, so that the bending durability and flatness can be more reliably enhanced.

[0039] In this specification, the fiber areal density (F) is measured in accordance with JIS K7071.

[0040] The fiber volume fraction (Vf1) of the first prepreg layer 30 is preferably configured to be smaller than the fiber volume fraction (Vf2) of the second prepreg layer 40 described later. That is, the fiber volume fraction (Vf2) of the second prepreg layer 40 is preferably configured to be larger than the fiber volume fraction (Vf1) of the first prepreg layer 30. By setting the fiber volume fraction (Vf2) of the second prepreg layer 40 to be larger than the fiber volume fraction (Vf1) of the first prepreg layer 30, the concealability of the second prepreg layer 40 is enhanced (the permeability decreases), and interference with the first prepreg layer 30 and the third prepreg layer 50 can be suppressed, so that the occurrence of moiré on the surface of the first prepreg layer 30 is more suppressed.

[0041] In this specification, the fiber volume fraction (Vf) is measured in accordance with JIS K7071.

[0042] The fiber volume fraction (Vf1) of the first prepreg layer 30 is preferably 35~60%. By setting the fiber volume fraction (Vf1) of the first prepreg layer 30 to 35% or more, the gaps between the carbon fibers 11 can be reduced, so that the occurrence of moiré is more suppressed. By setting the fiber volume fraction (Vf1) of the first prepreg layer 30 to 60% or less, the first prepreg layer 30 can be made thinner, and correspondingly, the second prepreg layer 40 can be made thicker, so that the occurrence of moiré is more suppressed.

[0043] <Resin> The resin 21 is preferably a thermosetting resin in that it is excellent in the strength, heat stability, etc. of the first prepreg layer 30. A thermosetting resin is a resin that is cured by using this as a main agent and mixing it with a curing agent as necessary.

[0044] (Thermosetting resin) Examples of the thermosetting resin include phenol resin, urea resin, melamine resin, bismaleimide resin, unsaturated polyester resin, vinyl ester resin, epoxy ester resin, epoxy resin, bismaleimide triazine resin (BT resin), cyanate ester resin, triazine resin, epoxy acrylate resin, urethane methacrylate resin, and the like. Among these, an epoxy resin is preferable in that it is excellent in strength, heat resistance, moldability, etc. The thermosetting resin can be used alone as one kind, or can also be used as a mixture of two or more kinds.

[0045] Examples of the epoxy resin include bifunctional epoxy resins, trifunctional or higher-functional epoxy resins, etc. Examples of the bifunctional epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, and epoxy resins modified therefrom. Examples of the trifunctional or higher-functional epoxy resin include phenol novolak type epoxy resin, cresol novolak type epoxy resin, glycidylamine type epoxy resins such as tetraglycidyl diaminodiphenylmethane, triglycidyl aminophenol, and tetraglycidylamine, glycidyl ether type epoxy resins such as tetrakis (glycidyloxyphenyl) ethane and tris (glycidyloxymethane), epoxy resins modified therefrom, and halogenated epoxy resins modified with these. From the viewpoint of impregnation property, it is preferable that the viscosity of the epoxy resin is low. The epoxy resin can be used alone as one kind, or can also be used as a mixture of two or more kinds.

[0046] (Curing agent) Examples of the curing agent include amines, carboxylic acid anhydrides, phenols (such as novolak resins), mercaptans, Lewis acid amine complexes, onium salts, imidazoles, etc. Among these, amine-type curing agents are preferred. The curing agent can be used alone as one kind, or can also be used as a mixture of two or more kinds.

[0047] Examples of the amine-type curing agent include aromatic amines such as diaminodiphenyl sulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, etc. Among these, diaminodiphenyl sulfone, dicyandiamide, etc. are more preferred in terms of excellent storage stability after curing.

[0048] To these curing agents, appropriate curing accelerators may be combined to enhance the curing activity. Examples of such combinations include, for example, a combination of dicyandiamide as the curing agent and urea derivatives such as 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 2,4-bis(3,3-dimethylureido)toluene as the curing accelerator; a combination of carboxylic acid anhydride, novolak resin, etc. as the curing agent and a tertiary amine, etc. as the curing accelerator; a combination of diaminodiphenyl sulfone, etc. as the curing agent and an amine complex such as an imidazole compound, a urea derivative such as phenyldimethylurea (PDMU), monoethylamine trifluoride, amine complex of aluminum trichloride, etc. as the curing accelerator; a combination of dicyandiamide, diaminodiphenyl sulfone as the curing agent and the above-mentioned urea derivative as the curing accelerator, etc. The curing accelerator can be used alone as one kind, or can also be used as a mixture of two or more kinds. In addition, the curing accelerator may be used instead of the curing agent without using the above-mentioned curing agent.

[0049] The resin content (RC1) in the first prepreg layer 30 can be appropriately set so that the fixing force of the carbon fiber 11 by the resin becomes appropriate. For example, if there is too little resin in the first prepreg layer 30, the space for the carbon fiber 11 to move sufficiently decreases, and the force for fixing the carbon fiber 11 weakens, which may make it difficult to achieve uniform alignment. Conversely, if there is too much resin, the carbon fiber 11 may swim (move freely) in the resin, which may make it difficult to control the uniform arrangement. Considering such a viewpoint, the resin content (RC1) in the first prepreg layer 30 is preferably 32 to 55% by mass. By setting the resin content (RC1) within the above range, the carbon fiber 11 can be appropriately fixed, so that the occurrence of moiré is more suppressed on the surface of the first prepreg layer 30.

[0050] In this specification, the resin content (RC) is measured in accordance with JIS K7071.

[0051] <Other components> In addition to the above-described carbon fiber 11 and resin 21, the first prepreg layer 30 may appropriately contain inorganic fine particles such as fine powder silica, pigments, elastomers, aluminum hydroxide as a flame retardant, brominated compounds as a flame retardant, phosphorus-based compounds as a flame retardant, defoaming agents, thermoplastic resins soluble in epoxy resins such as polyvinyl acetal resins and phenoxy resins for the purpose of improving handleability and flexibility, additives such as imidazole derivatives, metal complex salts, and tertiary amine compounds that serve as catalysts for the curing reaction.

[0052] The flat plate 31 for the first prepreg layer 30 can be manufactured by impregnating the carbon fiber 11 with the resin 21. As a method of impregnating the carbon fiber 11 with the resin 21, an uncured resin 21 is previously applied to a release sheet (not shown), and the carbon fiber 11 aligned in one direction is placed on the applied uncured resin 21, and impregnated by passing it between a pair of rollers (not shown). Examples include a method of impregnating, and a method of applying an uncured resin 21 to the carbon fiber 11 aligned in one direction and then impregnating by passing it between a pair of rollers (not shown). In these cases, the thickness of the flat plate 31 for the first prepreg layer 30 can be adjusted by adjusting the nip pressure of the pair of rollers. Further, the pair of rollers may be heated to lower the viscosity of the resin 21 while performing impregnation.

[0053] [Third prepreg layer] The third prepreg layer 50 has substantially the same configuration as the first prepreg layer 30. Specifically, the third prepreg layer 50 is obtained by impregnating carbon fibers 13 oriented in the first direction P with a resin 23. As the carbon fibers 13, the same carbon fibers as the carbon fibers 11 of the first prepreg layer 30 are used, and as the resin 23, the same resin as the resin 21 of the first prepreg layer 30 is used, and it is configured to have substantially the same configuration as the first prepreg layer 30.

[0054] Here, the fact that the configuration of the third prepreg layer 50 is "substantially the same" as the configuration of the first prepreg layer 30 does not completely exclude the case where the components, content, fiber basis weight, etc. of the third prepreg layer 50 are slightly different from those of the first prepreg layer 50. Even if at least one of these is slightly different, when it has substantially no effect on the physical properties of the prepreg layer, the configuration of the third prepreg layer 50 is treated as being substantially the same as the configuration of the first prepreg layer 30.

[0055] The third prepreg layer 50 is obtained by producing a flat plate 51 for the third prepreg layer 50 formed by impregnating carbon fibers 13 with a resin 23 to have the same configuration as the flat plate 31 for the first prepreg layer 30 and performing hot pressing.

[0056] When the first prepreg layer 30 contains the other components described above, the third prepreg layer 50 contains the same other components as those of the first prepreg layer 30.

[0057] Since the third prepreg layer 50 has substantially the same configuration as the first prepreg layer 30, the third prepreg layer 50 has the same characteristics as the first prepreg layer 30.

[0058] Specifically, the flatness ratio (P3) of the carbon fiber 13 used in the third prepreg layer 50 is configured to be larger than the flatness ratio (P2) of the carbon fiber 12 used in the second prepreg layer 40 described later. The flatness ratio (P3) of the carbon fiber 13 is preferably 33 to 75%. The carbon fiber 13 preferably has a ratio (a:b) of the minor axis (a) to the major axis (b) in the cross section of 1:1.5 to 1:4, more preferably 1:2 to 1:4, and even more preferably 1:2.5 to 1:4. Examples of the shape of the carbon fiber 13 include an elliptical shape, a heart shape, and a circular shape. The tensile elastic modulus of the carbon fiber 13 measured in accordance with JIS R7601 is preferably 210 to 300 GPa, and more preferably 230 to 290 GPa. The number of carbon fiber bundles of the carbon fiber 13 is preferably 1000 to 30000, and more preferably 3000 to 24000. The fineness of the carbon fiber 13 is preferably 350 to 16500 dtex, more preferably 350 to 1800 dtex, and particularly preferably 400 to 1650 dtex.

[0059] The fiber weight per unit area (F3) of the third prepreg layer 50 is preferably set to be smaller than the fiber weight per unit area (F2) of the second prepreg layer 40 described later. That is, the fiber weight per unit area (F2) of the second prepreg layer 40 is preferably set to be larger than the fiber weight per unit area (F3) of the third prepreg layer 30. The fiber weight per unit area (F3) of the third prepreg layer 50 is 20 to 30 g / m 2is preferred. The fiber volume fraction (Vf3) of the third prepreg layer 50 is preferably configured to be smaller than the fiber volume fraction (Vf2) of the second prepreg layer 40 described later. That is, the fiber volume fraction (Vf2) of the second prepreg layer 40 is preferably configured to be larger than the fiber volume fraction (Vf3) of the third prepreg layer 50. The fiber volume fraction (Vf3) of the third prepreg layer 50 is preferably 35 to 60%.

[0060] The resin content (RC3) in the third prepreg layer 50 is preferably 32 to 55% by mass.

[0061] Thus, since the third prepreg layer 50 has the same characteristics as the first prepreg layer 30, it can exhibit the same effects as those of the first prepreg layer 30 described above.

[0062] The flat plate 51 for the third prepreg layer 50 can be manufactured in the same manner as the flat plate 31 for the first prepreg layer 30.

[0063] [Second prepreg layer] The second prepreg layer 40 is obtained by impregnating carbon fibers 12 oriented in a second direction Q different from the first direction P with a resin 22. In the embodiment shown in FIG. 1, the second direction Q is set to a direction perpendicular to the left and right sides (width direction) of the second prepreg layer 40.

[0064] The second prepreg layer 40 is obtained by producing a flat plate 41 for the second prepreg layer 40 obtained by impregnating carbon fibers 12 with a resin 22 and performing hot pressing.

[0065] The thickness of the flat plate 41 for the second prepreg layer 40 and the fiber areal density of the carbon fibers 12 in the flat plate 41 for the second prepreg layer 40 are appropriately set so that the second prepreg layer 40 has a desired thickness and fiber areal density in the carbon fiber reinforced plastic laminate 1.

[0066] As the carbon fiber 12, carbon fibers of the same material as the carbon fiber 11 of the first prepreg layer 30 can be used. As the resin 22, the same resin as the resin 21 of the first prepreg layer 30 can be used. In the second prepreg layer 40, the same components as the other components that can be added to the first prepreg layer 30 can be added.

[0067] As described above, the flatness ratio (P1) of the carbon fiber 11 of the first prepreg layer 30 is configured to be larger than the flatness ratio (P2) of the carbon fiber 12 used in the second prepreg layer 40. That is, the flatness ratio (P2) of the carbon fiber 12 of the second prepreg layer 40 is configured to be smaller than the flatness ratio (P1) of the carbon fiber 11 used in the first prepreg layer 30. Thereby, as described above, the occurrence of moiré is suppressed on the surface of the first prepreg layer 30. Further, since the first prepreg layer 30 and the third prepreg layer 50 are substantially the same, the flatness ratio (P2) of the carbon fiber 12 of the second prepreg layer 40 is configured to be smaller than the flatness ratio (P3) of the carbon fiber 13 used in the third prepreg layer 50. Thereby, similar to the first prepreg layer 30, the occurrence of moiré is suppressed on the surface of the third prepreg layer 50.

[0068] The flatness ratio (P2) of such carbon fiber 12 is preferably 0 to 31%, more preferably 9 to 29%. By setting the flatness ratio (P2) of the carbon fiber 12 within the above range, the flatness ratio (P2) of the carbon fiber 12 can be more surely smaller than the flatness ratios (P1, P3) of the carbon fibers 11 and 13 of the first prepreg layer 30 and the third prepreg layer 50. Therefore, the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer 30 and the third prepreg layer 50.

[0069] The carbon fiber 12 preferably has a ratio (a:b) of the minor axis (a) to the major axis (b) in the cross section of 1:1 to 1:1.45, more preferably 1:1.1 to 1:1.4. By setting the ratio (a:b) of the minor axis (a) to the major axis (b) of the carbon fiber 12 within the above range, the flatness ratio (P2) of the carbon fiber 12 can be made 0 to 31% as described above. That is, by setting the ratio (a:b) of the minor axis (a) to the major axis (b) in the cross section of the carbon fiber 12 within the above range, the flatness ratio (P2) determined by the ratio (a:b) of the carbon fiber 12 can be set within the above appropriate range.

[0070] Examples of the shape of the carbon fiber 12 include a perfect circular shape as shown in Fig. 3(c) and an elliptical shape as shown in Fig. 3(a).

[0071] The tensile elastic modulus of the carbon fiber 12 measured in accordance with JIS R7601 is preferably 210 to 800 GPa, more preferably 230 to 300 GPa. By setting the tensile elastic modulus of the carbon fiber 12 within the above range, the flexural elastic modulus (Ea2) in the second direction Q of the carbon fiber reinforced plastic laminate 1 becomes more appropriate, and the bending durability and flatness can be improved.

[0072] The number of carbon fiber bundles of the carbon fiber 12 is preferably 1000 to 30000, more preferably 3000 to 24000. By setting the number of carbon fiber bundles of the carbon fiber 12 within the above range, the tensile strength of the carbon fiber 12 can be made appropriate.

[0073] The fineness of the carbon fiber 12 is preferably 350 to 16500 dtex, more preferably 350 to 1800 dtex, and particularly preferably 400 to 1650 dtex. By setting the fineness of the carbon fiber 12 within the above range, the tensile strength of the carbon fiber 12 can be made appropriate.

[0074] The fiber weight (F2) of the second prepreg layer 40 is preferably set to be larger than the fiber weight (F1) of the first prepreg layer 30. By setting the fiber weight (F2) of the second prepreg layer 40 to be larger than the fiber weight (F1) of the first prepreg layer 30, as described above, the occurrence of moiré on the surface of the first prepreg layer 30 is more suppressed. Also, since the flexural modulus (Ea1) in the first direction P and the flexural modulus (Ea2) in the second direction Q can be more reliably set within a desired range, the bending durability and flatness can be more reliably enhanced. The fiber weight (F2) of the second prepreg layer 40 is preferably set to be larger than the fiber weight (F3) of the third prepreg layer 50. By setting the fiber weight (F2) of the second prepreg layer 40 to be larger than the fiber weight (F3) of the third prepreg layer 50, similar to the first prepreg layer 30, the occurrence of moiré on the surface of the third prepreg layer 50 is more suppressed. Also, since the flexural modulus (Ea1) in the first direction P and the flexural modulus (Ea2) in the second direction Q can be more reliably set within a desired range, the bending durability and flatness can be more reliably enhanced.

[0075] The fiber weight (F2) of the second prepreg layer 40 is preferably 80 to 140 g / m 2 . By setting the fiber weight (F2) of the second prepreg layer 40 within the above range, sufficient concealability can be ensured and interference with the first prepreg layer 30 and the third prepreg layer 50 can be suppressed. Therefore, the occurrence of moiré on the surfaces of the first prepreg layer 30 and the third prepreg layer 50 is more suppressed. Also, since the flexural modulus (Ea1) in the first direction P and the flexural modulus (Ea2) in the second direction Q can be more reliably set within a desired range, the bending durability and flatness can be more reliably enhanced.

[0076] The fiber volume fraction (Vf2) of the second prepreg layer 40 is preferably configured to be larger than the fiber volume fraction (Vf1) of the first prepreg layer 30. By setting the fiber volume fraction (Vf2) of the second prepreg layer 40 to be larger than the fiber volume fraction (Vf1) of the first prepreg layer 30, as described above, the occurrence of moiré is more suppressed on the surface of the first prepreg layer 30. Also, the fiber volume fraction (Vf2) of the second prepreg layer 40 is preferably configured to be larger than the fiber volume fraction (Vf3) of the third prepreg layer 50. By setting the fiber volume fraction (Vf2) of the second prepreg layer 40 to be larger than the fiber volume fraction (Vf3) of the third prepreg layer 50, the occurrence of moiré is more suppressed on the surface of the third prepreg layer 50, similar to the first prepreg layer 30.

[0077] The fiber volume fraction (Vf2) of the second prepreg layer 40 is preferably 45 - 70%. By setting the fiber volume fraction (Vf2) of the second prepreg layer 40 within the above range, sufficient concealability can be ensured and interference with the first prepreg layer 30 and the third prepreg layer 50 can be suppressed, so the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer 30 and the third prepreg layer 50.

[0078] The resin content (RC2) in the second prepreg layer 40 is preferably 20 - 45% by mass. By setting the resin content (RC2) within the above range, similar to the resin content (RC1) in the first prepreg layer 30 described above, the carbon fiber 12 can be appropriately fixed, so the occurrence of moiré is more suppressed on the surfaces of the first prepreg layer 30 and the third prepreg layer 50.

[0079] The second prepreg layer 40 can be manufactured in the same manner as the first prepreg layer 30.

[0080] [Properties of Carbon Fiber Reinforced Plastic Laminate] In the carbon fiber reinforced plastic laminate 1 of the present embodiment, it is preferable that the angle formed by the first direction P and the second direction Q is 90°. By setting the angle formed by the first direction P and the second direction Q to 90°, the orientation directions of the carbon fibers 11 and 13 in the first prepreg layer 30 and the third prepreg layer 50 and the orientation direction of the carbon fiber 12 in the second prepreg layer 40 are perpendicular to each other. When these prepreg layers are overlapped, compared with the case where they do not intersect perpendicularly (for example, when the intersection angle is 1 to 89° or 91 to 179°), the interval (period) and angle deviation of the fibers are less likely to occur. Therefore, the generation of moiré is more suppressed on the surfaces of the first prepreg layer 30 and the third prepreg layer 50.

[0081] The carbon fiber reinforced plastic laminate 1 preferably has a flexural modulus of elasticity (Ea1) measured in accordance with JIS K7074 in the first direction P of 10 to 60 GPa and a flexural modulus of elasticity (Ea2) measured in accordance with JIS K7074 in the second direction Q of 55 to 95 GPa. By setting the flexural modulus of elasticity (Ea1) in the first direction P and the flexural modulus of elasticity (Ea2) in the second direction Q within the above ranges, the carbon fiber reinforced plastic laminate 1 becomes excellent in bending durability and flatness.

[0082] The thickness of the carbon fiber reinforced plastic laminate 1 is preferably from 0.11 to 0.25 mm, more preferably from 0.14 to 0.18 mm. By setting the thickness of the carbon fiber reinforced plastic laminate 1 to be not less than the above lower limit, when applied to a support (reinforcing member) such as a display support, insufficient reinforcing function can be suppressed. By setting the thickness of the carbon fiber reinforced plastic laminate 1 to be not more than the above upper limit, when applied to the above support, it can be suppressed from becoming bulky, and it becomes more suitable for products with a thin design. The thickness of the first prepreg layer 30 and the third prepreg layer 50 is preferably from 0.02 to 0.05 mm, more preferably from 0.025 to 0.040 mm. By setting the thicknesses of the first prepreg layer 30 and the third prepreg layer 50 within the above range, while making these layers relatively thin, interference with the second prepreg layer 40 can be suppressed. The thickness of the second prepreg layer 40 is preferably from 0.07 to 0.15 mm, more preferably from 0.09 to 0.14 mm. By setting the thickness of the second prepreg layer 40 within the above range, it is possible to make it as thin as possible while suppressing moiré more, while having stiffness and firmness in balance with the first prepreg layer 30 and the third prepreg layer 50.

[0083] When the carbon fiber reinforced plastic laminate 1 of the present embodiment described above is viewed from the side of the first prepreg layer 30 and / or the third prepreg layer 50, no moiré pattern is observed. That is, the carbon fiber reinforced plastic laminate 1 of the present embodiment is a carbon fiber reinforced plastic laminate 1 formed by laminating a first prepreg layer 30 in which carbon fibers 11 oriented in a first direction P are impregnated with a resin 21, a second prepreg layer 40 in which carbon fibers 12 oriented in a second direction Q different from the first direction P are impregnated with a resin 22, and a third prepreg layer 50 having substantially the same configuration as the first prepreg layer 30, and when viewed from the side of the first prepreg layer 30 and / or the third prepreg layer 50, no moiré pattern is observed.

[0084] According to the carbon fiber reinforced plastic laminate 1, when the carbon fiber reinforced plastic laminate 1 is viewed from the side of the first prepreg layer 30 and when viewed from the side of the third prepreg layer 50 (that is, when the carbon fiber reinforced plastic laminate 1 is viewed from either the front or the back side), it has excellent appearance characteristics and can be suitably used as a reinforcing member for the screens of smartphones, tablet terminals, etc.

[0085] [Manufacture of Carbon Fiber Reinforced Plastic Laminate] The carbon fiber reinforced plastic laminate 1 is manufactured by stacking a flat plate 41 for the second prepreg layer 40 on a flat plate 51 for the third prepreg layer 50 such that the orientation direction (second direction Q) of the carbon fibers 12 in the flat plate 41 for the second prepreg layer 40 is at an angle different from the orientation direction (first direction P) of the carbon fibers 13 in the flat plate 51 for the third prepreg layer 50, and then stacking a flat plate 31 for the first prepreg layer 30 on the flat plate 41 for the second prepreg layer 40 such that the orientation direction (first direction P) of the carbon fibers 11 in the flat plate 31 for the first prepreg layer 30 is parallel to the orientation direction (first direction P) of the carbon fibers 13 in the flat plate 51 for the third prepreg layer 50, and then performing hot pressing (heating and pressurizing). The pressure in the hot pressing is preferably set to 1 - 2 MPa, the heating temperature is preferably set to 110 - 150 °C, and the holding time (the time during which the pressurized state and the heated state are maintained) is preferably set to 100 - 140 minutes.

Examples

[0086] Hereinafter, the carbon fiber reinforced plastic laminate of the present invention will be described more specifically with reference to examples.

[0087] [Raw Materials Used] [Carbon Fiber] (a - 1) TAIRYFIL TC - 33 - 1.5K (manufactured by FORMOSA PLASTICS CORPORATION): number of filaments 1500, fineness 1000 dtex, tensile strength 3450 MPa, tensile modulus 230 GPa (a-2) TAIRYFIL TC-33-3K (manufactured by Formosa Plastics Corporation): 3,000 filaments, fineness 2,000 dtex, tensile strength 3,450 MPa, tensile modulus 230 GPa (a-3) TAIRYFIL TC-33-6K (manufactured by Formosa Plastics Corporation): 6,000 filaments, fineness 4,000 dtex, tensile strength 3,450 MPa, tensile modulus 230 GPa (b-1) PYROFIL TR50S-3L (manufactured by Mitsubishi Chemical Corporation): 3,000 filaments, fineness 2,000 dtex, tensile strength 4,900 MPa, tensile modulus 235 GPa (b-2) PYROFIL TR50S-6L (manufactured by Mitsubishi Chemical Corporation): 6,000 filaments, fineness 4,000 dtex, tensile strength 4,900 MPa, tensile modulus 235 GPa (b-3) PYROFIL TR50S-12L (manufactured by Mitsubishi Chemical Corporation): 12,000 filaments, fineness 8,000 dtex, tensile strength 4,900 MPa, tensile modulus 235 GPa (c-1) Torayca T700-SC-6000 (manufactured by Toray Industries, Inc.): 6,000 filaments, fineness 4,000 dtex, tensile strength 4,900 MPa, tensile modulus 230 GPa (c-2) Torayca T700-SC-12000 (manufactured by Toray Industries, Inc.): 12,000 filaments, fineness 8,000 dtex, tensile strength 4,900 MPa, tensile modulus 230 GPa (c-3) Torayca T700-SC-24000 (manufactured by Toray Industries, Inc.): 24,000 filaments, fineness 16,500 dtex, tensile strength 4,900 MPa, tensile modulus 230 GPa (d-1) GRANOC YS80A-60S (manufactured by Nippon Graphite Fiber Corporation): 6,000 filaments, fineness 5,200 dtex, tensile strength 3,630 MPa, tensile modulus 785 GPa

[0088] <Resin for the first prepreg layer, the second prepreg layer, and the third prepreg layer> Base resin: A mixture of jER828 and jER1001 (both manufactured by Mitsubishi Chemical Corporation), which are bisphenol A type epoxy resins, mixed at a mass ratio of 18:22 Curing agent: jER Cure DICY15 (manufactured by Mitsubishi Chemical Corporation), used in an amount of 8 parts by mass with respect to 100 parts by mass of the base resin Curing accelerator: Phenyl-1,1-dimethylurea (DCMU99, manufactured by Hodogaya Chemical Co., Ltd.), used in an amount of 3 parts by mass with respect to 100 parts by mass of the base resin

[0089] [Examples 1 to 10, Comparative Examples 1 to 3] The base resin, the curing agent, and the curing accelerator were mixed so as to have the layer configurations shown in Tables 1 to 3, and impregnated into unidirectionally oriented carbon fibers to obtain rectangular flat plates for the first and third prepreg layers and a rectangular flat plate for the second prepreg layer. In each flat plate, the orientation direction of the carbon fibers was set to be parallel to a pair of opposing edges of the flat plate. The flat plate for the first prepreg layer, the flat plate for the second prepreg layer, and the flat plate for the third prepreg layer were laminated in this order such that the orientation direction of the carbon fibers in the flat plate for the first prepreg layer (the first direction) and the orientation direction of the carbon fibers in the flat plate for the second prepreg layer (the second direction) were 90° (i.e., perpendicular), and the orientation direction of the carbon fibers in the flat plate for the first prepreg layer (the first direction) and the orientation direction of the carbon fibers in the flat plate for the third prepreg layer (the first direction) were 0° (i.e., parallel), thereby obtaining a laminate having a size of 520 mm × 520 mm. Subsequently, the laminate was press-molded using a hot press machine under the conditions of a pressure of 1.5 MPa, a temperature of 130°C, and a holding time of 120 minutes to obtain carbon fiber reinforced plastic laminates of Examples 1 to 10 and Comparative Examples 1 to 3 in which the first prepreg layer, the second prepreg layer, and the third prepreg layer were laminated in this order. The overall thickness (total thickness) of these carbon fiber reinforced plastic laminates and the thicknesses of the first, second, and third prepreg layers were set as shown in Tables 1 to 3.

[0090] For the obtained carbon fiber reinforced plastic laminate, an appearance inspection was carried out by the evaluation method shown below, and the flatness (warpage) and flexural modulus were evaluated. The results are shown in Tables 1 to 3.

[0091] <Appearance inspection> By preliminary experiments, for reference samples with four different levels of the degree of occurrence of carbon fiber reinforced plastic laminates, while irradiating each reference sample with white light in a space covered with a dark curtain, photographs were taken with a camera from a position 60 cm away in the direction perpendicular to each reference sample, and as shown in Fig. 5, photographs of references 1 to 4 were obtained. The four references are as follows, indicating that stronger moiré occurs from reference 1 to reference 4. (Reference) Reference 1: No moiré occurs (no moiré). Reference 2: Tiny moiré occurs (tiny moiré). Reference 3: Weak moiré occurs (weak moiré). Reference 4: Strong moiré occurs (strong moiré).

[0092] As shown in Fig. 4(a), place the carbon fiber reinforced plastic laminate on a flat surface, with the observation angle in the direction parallel to the surface of the first prepreg layer being 0° and the observation angle in the direction perpendicular to the first prepreg layer being 90°. In the first direction P, take photographs of the surface of the carbon fiber reinforced plastic laminate from positions 30 cm away in the directions of observation angles 30°, 60°, and 90°, compare them with the photographs of references 1 to 4 shown in Fig. 5, and evaluate the suppression of moiré according to the following criteria. [Judgment criteria] AA: Corresponds between reference 1 and reference 2, or is equivalent to reference 2. A: Corresponds between reference 2 and reference 3, or is equivalent to reference 3. B: Corresponds between reference 3 and reference 4, or is equivalent to reference 4. C: Stronger moiré than reference 4 occurs.

[0093] <Flatness (warpage)> A test piece for evaluation was obtained by cutting a carbon fiber reinforced plastic laminate into a rectangular shape with dimensions of 10 mm in the first direction and 15 mm in the second direction. As shown in Fig. 4(b), the test piece was placed on a flat surface, and the height at which each side (4 sides) of the test piece was lifted from the flat surface was measured. The maximum value among the measured values of the 4 sides was taken as the warpage degree (mm), which is an index of flatness.

[0094] <Flexural modulus of elasticity> In accordance with JIS K7074, the flexural modulus of elasticity Ea1 in the first direction (designated as 0°) and the flexural modulus of elasticity Ea2 in the second direction (designated as 90°) of the carbon fiber reinforced plastic laminate were measured.

[0095]

Table 1

[0096]

Table 2

[0097]

Table 3

[0098] From Tables 1 to 2, a first prepreg layer in which carbon fibers oriented in a first direction are impregnated with a resin, a second prepreg layer in which carbon fibers oriented in a second direction different from the first direction are impregnated with a resin, and a third prepreg layer having substantially the same configuration as the first prepreg layer are laminated. Among Examples 1 to 10 configured such that the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is larger than the flatness ratio (P2) of the carbon fibers used in the second prepreg layer, the carbon fiber reinforced plastic laminates of Examples 1 to 9 have a moiré evaluation of AA evaluation, A evaluation, or B evaluation at any of the observation angles of 30°, 60°, and 90°, indicating that the occurrence of moiré is suppressed. It was also shown to be excellent in flatness and flexural modulus. Further, for the carbon fiber reinforced plastic laminate of Example 10, the moiré evaluation at 90° among the observation angles of 30°, 60°, and 90° was A evaluation, indicating that the occurrence of moiré is suppressed. From the comparison between Examples 1 to 9 and Example 10, it was shown that the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is preferably 33 to 75%.

[0099] From Table 3, even if the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is configured to be larger than the flatness ratio (P2) of the carbon fibers used in the second prepreg layer, the carbon fiber reinforced plastic laminate of Comparative Example 1 in which the first prepreg layer and the third prepreg layer are not substantially the same has a C evaluation for moiré at least at observation angles of 30° and 60°, indicating that the occurrence of moiré is not suppressed. Even if the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is configured to be larger than the flatness ratio (P2) of the carbon fibers used in the second prepreg layer, the carbon fiber reinforced plastic laminate of Comparative Example 2 in which the first prepreg layer and the third prepreg layer are not substantially the same has a C evaluation for moiré at any of the observation angles of 30°, 60°, and 90°, indicating that the occurrence of moiré is not suppressed, and it is also shown that the flatness is inferior. The carbon fiber reinforced plastic laminate of Comparative Example 3 in which the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is configured to be smaller than the flatness ratio (P2) of the carbon fibers used in the second prepreg layer has a C evaluation for moiré at least at observation angles of 30° and 60°, indicating that the occurrence of moiré is not suppressed, and it is also shown that the flatness is inferior.

[0100] In addition, the same test results as above were obtained in both the case of performing an appearance inspection on the surface on the first prepreg layer side and the case of performing appearance characteristics on the surface on the third prepreg layer side.

Industrial Applicability

[0101] The carbon fiber reinforced plastic laminate of the present invention can be suitably used, for example, as a reinforcing member for displays such as desktop or notebook computers, tablet computers, and smartphones.

Explanation of Signs

[0102] 1 Carbon fiber reinforced plastic laminate 11, 12, 13 Carbon fibers 21, 22, 23 Resins 30 First prepreg layer 40 Second prepreg layer 50 Third prepreg layer P First direction Q Second direction

Claims

1. A carbon fiber reinforced plastic laminate formed by laminating a first prepreg layer in which carbon fibers oriented in a first direction are impregnated with a resin, a second prepreg layer in which carbon fibers oriented in a second direction different from the first direction are impregnated with a resin, and a third prepreg layer having substantially the same configuration as the first prepreg layer, wherein the flatness ratio (P1) of the carbon fibers used in the first prepreg layer is configured to be greater than the flatness ratio (P2) of the carbon fibers used in the second prepreg layer.

2. The carbon fiber reinforced plastic laminate according to Claim 1, wherein the flatness ratio (P1) of the carbon fibers is 33 to 75%.

3. The carbon fiber reinforced plastic laminate according to Claim 1, wherein the fiber volume content (Vf2) of the second prepreg layer is configured to be greater than the fiber volume content (Vf1) of the first prepreg layer.

4. The fiber volume content (Vf1) of the first prepreg layer is 35 to 60%, and the fiber volume content (Vf2) of the second prepreg layer is 45 to 70%. The carbon fiber reinforced plastic laminate according to Claim 3.

5. The carbon fiber reinforced plastic laminate according to any one of Claims 1 to 4, wherein the angle formed between the first direction and the second direction is 90°.

6. A carbon fiber reinforced plastic laminate formed by laminating a first prepreg layer in which carbon fibers oriented in a first direction are impregnated with a resin, a second prepreg layer in which carbon fibers oriented in a second direction different from the first direction are impregnated with a resin, and a third prepreg layer having substantially the same configuration as the first prepreg layer, wherein no moire pattern is observed when viewed from the side of the first prepreg layer and / or the third prepreg layer.

Images