Synthetic leather

Abstract

A synthetic leather 1, 10 according to an embodiment comprises a fibrous base material 2 and a resin layer 3 provided on the fibrous base material 2, and has a plurality of openings 7 penetrating the fibrous base material 2 from a surface of the resin layer 3. The plurality of openings 7 each have an opening peripheral edge part 71 having a shape inclined so that the surface of the resin layer 3 goes down toward the center of the opening 7. The fibrous base material 2 includes: a warp knitted fabric 4 including a ground structure 41 and nap 42; and a mixed layer 6 provided between the ground structure 41 and the resin layer 3 and in which the nap 42 and a porous polyurethane resin 5 are mixed. The nap 42 does not protrude from the surface of the mixed layer 6.

Description

synthetic leather

[0001] The present invention relates to synthetic leather.

[0002] Synthetic leather has a surface covered with a resin layer. Therefore, when used for vehicle interior materials, particularly for seats, it can become stuffy and sticky due to sweating when sitting for long periods of time. Therefore, attempts have been made to solve these problems by forming multiple openings in the leather through perforation processing to improve the breathability of the leather.

[0003] For example, Patent Document 1 describes a vehicle upholstery material including synthetic leather with openings, in which a woven fabric is attached to the back surface of synthetic leather including a fibrous base material and a polyurethane resin layer via an adhesive layer. The synthetic leather is described as having a plurality of openings extending from the surface of the polyurethane resin layer through the fibrous base material, with an opening ratio of 1 to 15%.

[0004] Patent Document 2 describes a sheet-like material having an opening, which includes a fibrous base material and an inner layer and an outermost layer made of polyurethane resin laminated on the fibrous base material. The opening provided on the surface of the sheet-like material is configured to include an opening periphery in which the outermost layer is inclined toward the center of the opening. It is described that this provides the sheet-like material with good abrasion resistance and surface feel.

[0005] JP 2017-165209 A JP 2019-112737 A

[0006] In synthetic leather with openings, it is advantageous to form the openings by penetrating the fibrous substrate from the surface of the resin layer to further enhance breathability. However, in this case, there is a problem that fluff is easily generated from the fibrous substrate due to wear, etc., and the fluff is exposed on the surface of the synthetic leather through the openings, damaging the appearance. According to Patent Document 2, the above-mentioned inclined shape of the opening periphery can improve abrasion resistance, but when forming openings by penetrating the fibrous substrate, it is difficult to improve abrasion resistance while suppressing exposure of fluff.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide synthetic leather that is excellent in breathability, abrasion resistance and appearance.

[0008] The present invention includes the following embodiments. [1] A synthetic leather comprising a fibrous base material and a resin layer provided on the fibrous base material, wherein a plurality of openings are provided from the surface of the resin layer through the fibrous base material, the plurality of openings having opening peripheries sloping so that the surface of the resin layer slopes downward toward the center of the openings, the fibrous base material comprising a warp knitted fabric including a ground weave and raised nap, and a mixed layer provided between the ground weave and the resin layer and including a mixture of the raised nap and a porous polyurethane resin, the raised nap not protruding from the surface of the mixed layer facing the resin layer. [2] The synthetic leather described in [1], wherein the surface of the mixed layer facing the resin layer is substantially free of the porous polyurethane resin layer free of raised nap, where "substantially free" means that there is no layer free of raised nap, or even if there is a layer free of raised nap, the thickness of the layer free of raised nap is less than 50 μm. [3] The synthetic leather described in [1] or [2], wherein the resin layer has a thickness of 90 to 200 μm. [4] The synthetic leather according to any one of [1] to [3], wherein the opening ratio on the surface of the synthetic leather is 5 to 13%. [5] The synthetic leather according to any one of [1] to [4], wherein the porous polyurethane resin is impregnated into at least a part of the ground structure of the fibrous base material. [6] The synthetic leather according to any one of [1] to [5], wherein the resin layer comprises an adhesive layer, a surface layer, and a surface treatment layer, in this order, on the fibrous base material. [7] The synthetic leather according to any one of [1] to [6], wherein the thickness of the mixed layer is 0.4 to 1.2 mm.

[0009] According to an embodiment of the present invention, it is possible to provide synthetic leather that is excellent in breathability, abrasion resistance, and appearance.

[0010] 1 is a schematic cross-sectional view of a synthetic leather according to one embodiment; FIG. 2 is a schematic cross-sectional view of a synthetic leather according to another embodiment; FIG. 3 is a schematic cross-sectional view of a fibrous substrate for explaining the thickness of a mixed layer and the thickness of a layer without nap;

[0011] The synthetic leather according to this embodiment comprises a fibrous substrate and a resin layer disposed on the fibrous substrate. The synthetic leather is provided with a plurality of openings penetrating the fibrous substrate from the surface of the resin layer. The plurality of openings have opening peripheries that are inclined so that the surface of the resin layer slopes downward toward the center of the opening. The fibrous substrate comprises a warp knitted fabric including a ground weave and raised nap, and a mixed layer disposed between the ground weave and the resin layer, in which raised nap and porous polyurethane resin are mixed. The raised nap does not protrude from the surface of the mixed layer facing the resin layer.

[0012] According to this embodiment, by providing multiple openings penetrating the synthetic leather, the synthetic leather has excellent breathability. Furthermore, by using a warp-knitted fabric with raised nap and providing a mixed layer containing a mixture of raised nap and porous polyurethane resin on the raised nap surface, the porous polyurethane resin easily shrinks and deforms by embracing the raised nap during the perforation process to form the opening. This facilitates the formation of an opening periphery with a sloped shape that slopes downward toward the center of the opening. Furthermore, by providing such a depressed opening periphery and preventing the raised nap from protruding from the surface of the mixed layer, fibers are prevented from protruding from the opening, improving the appearance. Furthermore, the depressed shape of the opening periphery makes the opening less susceptible to friction. Furthermore, because the mixed layer contains not only raised nap but also porous polyurethane resin, the porous polyurethane resin can suppress distortion of the synthetic leather surface when external force is applied during use. This, combined with the depressed shape of the opening periphery, improves abrasion resistance.

[0013] 1 is a schematic diagram showing the cross-sectional structure of synthetic leather 1 according to one embodiment. Synthetic leather 1 comprises a fibrous base material 2 and a resin layer 3 laminated on one side thereof. The fibrous base material 2 comprises a warp knitted fabric 4 including a ground weave 41 and raised naps 42, and a mixed layer 6 between the ground weave 41 and the resin layer 3, in which the raised naps 42 and a porous polyurethane resin 5 are mixed together. That is, in this example, the fibrous base material 2 comprises a mixed layer 6 formed by laminating the porous polyurethane resin 5 mixed with the raised naps 42 on the raised surface side of the warp knitted fabric 4. A resin layer 3 is then laminated on the mixed layer 6.

[0014] Figure 2 is a schematic diagram showing the cross-sectional structure of synthetic leather 10 according to another embodiment. This synthetic leather 10 differs from the synthetic leather 1 shown in Figure 1 in that the resin layer 3 is made up of an adhesive layer 31, a surface layer 32, and a surface treatment layer 33. In the example shown in Figure 2, a mixed layer 6 is provided on the napped surface side of warp knitted fabric 4, and is made up of porous polyurethane resin 5 mixed with napped fibers 42. On this mixed layer 6, an adhesive layer 31, a surface layer 32, and a surface treatment layer 33 are layered in this order.

[0015] 1 and 2, a plurality of openings 7 for improving breathability are provided on the front surface of the synthetic leather 1, 10 (i.e., the front surface of the resin layer 3). The openings 7 are provided so as to penetrate from the surface of the resin layer 3 through the fibrous base material 2. That is, the openings 7 are provided as holes that penetrate the resin layer 3 and the fibrous base material 2 (i.e., holes that penetrate the synthetic leather 1, 10).

[0016] 1 and 2 , the plurality of openings 7 are formed with opening peripheral portions 71 that are inclined such that the surface of the resin layer 3 slopes downward toward the center of the opening 7. In detail, the opening 7 includes the opening peripheral portion 71 formed by the resin layer 3 sloping downward in a tapered manner toward the center of the opening 7, and a through portion 72 that extends downward from the lower end of the opening peripheral portion 71 and penetrates the resin layer 3 and the fibrous base material 2. This inclined shape is formed mainly by the thickness of the mixed layer 6 shrinking at the opening peripheral portion 71.

[0017] The naps 42 do not protrude from the surface of the mixed layer 6 (the surface on the resin layer 3 side). That is, the naps 42 do not protrude upward beyond the upper surface of the porous polyurethane resin 5. The entire area in the thickness direction of the fibrous base material 2 where the naps 42 exist is impregnated with the porous polyurethane resin 5.

[0018] 1 and 2, the surface of the synthetic leather 1, 10 is flat, but considering the design, a textured pattern such as a leather-like grain pattern may be provided in a conventional manner. Here, the surface of the synthetic leather refers to the surface (design surface) of the front or back of the synthetic leather that is visible when in use. Specifically, the surface of the synthetic leather is the surface of the resin layer described above.

[0019] In this embodiment, the fibrous base material includes, as described above, a warp knitted fabric having nap on its surface (hereinafter also referred to as a napped warp knitted fabric), and a mixed layer provided on the napped surface of the warp knitted fabric in which nap and porous polyurethane resin are mixed.

[0020] By using a warp knitted fabric, a seamless long product can be obtained. Examples of warp knitted fabrics include tricot knitted fabrics and double raschel knitted fabrics. Among them, tricot knitted fabrics are preferred from the viewpoints that the raised state can be easily adjusted and high-density raised fabric can be obtained.

[0021] The warp knitted fabric may be colored with a dye or pigment, or may be uncolored. There are no particular limitations on the dye or pigment used for coloring.

[0022] The fiber material constituting the warp knitted fabric is not particularly limited, and conventionally known natural fibers, regenerated fibers, semi-synthetic fibers, synthetic fibers, etc. can be used. These can be used alone or in combination of two or more. Among them, from the viewpoint of strength, synthetic fibers are preferred as the fiber material, and polyester fibers are more preferred.

[0023] A warp knitted fabric has a ground structure and a raised nap. The warp knitted fabric has raised nap formed on at least one side thereof. Preferably, the raised nap is formed on only one side of the warp knitted fabric. Here, the ground structure is the main body of the warp knitted fabric that constitutes a predetermined knit structure, and is also called a non-raised portion. The raised nap is hair (fluff) that rises from the ground structure, and is also called a nap-bearing portion. The raised nap is made of fibers that constitute the ground structure, and is constrained by the knitted structure. This can improve the resistance to shedding and abrasion resistance. The raised nap can be formed, for example, by opening the knitted structure, raising the nap, or implanting the nap.

[0024] The length of the nap is not particularly limited, but is preferably 0.4 to 1.2 mm, more preferably 0.6 to 0.8 mm. When the nap length is equal to or greater than the lower limit, the peripheral edge of the opening is easily formed into the above-mentioned depressed shape during hole drilling. When the nap length is equal to or less than the upper limit, distortion of the synthetic leather surface caused by movement of the nap when an external force is applied during use of the synthetic leather is easily suppressed, thereby improving abrasion resistance.

[0025] The length of the raised nap is measured as follows. That is, before measurement, the raised surface is stroked three times by hand in the counter-grain direction to make the nap stand up, and then the length of the raised nap (the length from the base to the tip of the nap) is measured. For the measurement, the vertical cross section of the warp knitted fabric is observed at 100x magnification using a microscope (for example, VHX-200 / 100F, manufactured by Keyence Corporation), the lengths of any 10 raised naps are measured, and the average value is calculated. Here, the counter-grain direction is the direction opposite to the counter-grain direction, and the counter-grain direction is the direction in which the raised naps lie.

[0026] The length of the raised naps in the fibrous substrate and synthetic leather after the mixed layer is formed is measured as follows: A vertical cross section of the fibrous substrate or synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), and the length (length from the root to the tip of the hair) of any 10 raised naps is measured and the average value is calculated.

[0027] The density of the raised fibers is not particularly limited, but is preferably 158,400 fibers / (25.4 mm). ２ ~244,800 pieces / (25.4mm) ２ It is preferable that the density of the raised nap is equal to or greater than the lower limit, which can suppress distortion of the synthetic leather surface due to external forces, thereby improving abrasion resistance. When the density of the raised nap is equal to or less than the upper limit, it is easy to form the opening periphery into the above-mentioned depressed shape during hole-making processing. In addition, the tensile strength and tear strength are good.

[0028] The fineness of the fibers constituting the nap (single fiber fineness) is not particularly limited, but is preferably 0.5 to 2.2 dtex. When the single fiber fineness is equal to or greater than the lower limit, the synthetic leather has a cushioning feel and a good texture. When the single fiber fineness is equal to or less than the upper limit, the opening periphery can be easily formed into the above-mentioned depressed shape during hole-making.

[0029] The fineness of the yarns (yarn fineness) constituting the warp knitted fabric is not particularly limited, but is preferably 55 to 110 dtex. By having the yarn fineness equal to or greater than the lower limit, the tensile strength and tear strength can be improved. By having the yarn fineness equal to or less than the upper limit, the texture is good.

[0030] The density of the warp knitted fabric is not particularly limited, but is preferably 55 to 68 courses / 25.4 mm and 40 to 50 wells / 25.4 mm, and more preferably 59 to 65 courses / 25.4 mm and 44 to 48 wells / 25.4 mm. When the density of the warp knitted fabric is equal to or greater than the lower limit, the tensile strength and tear strength can be improved. When the density of the warp knitted fabric is equal to or less than the upper limit, the deterioration of elongation properties can be suppressed. In addition, the amount of yarn used can be reduced, resulting in cost reduction.

[0031] The above-mentioned nap length, nap density, single fiber fineness, yarn fineness, and density of the warp-knitted fabric are the single fiber fineness, yarn fineness, and density of the warp-knitted fabric before the porous polyurethane resin is applied. The nap length, nap density, single fiber fineness, yarn fineness, and density of the warp-knitted fabric in the fibrous substrate and synthetic leather after the porous polyurethane resin is applied may be set within the same ranges.

[0032] The weight per unit area of ​​the warp knitted fabric is 200 to 300 g / m from the viewpoint of weight reduction. ２ It is preferable that:

[0033] The tensile strength of the warp knitted fabric is not particularly limited. From the viewpoint that the resulting synthetic leather has a strength suitable for use as a vehicle interior material, the tensile strength of the warp and weft directions of the warp knitted fabric is preferably 100 N / cm or more. Here, the warp direction of the warp knitted fabric refers to the direction in which the warp knitted fabric is knitted, and the weft direction refers to the direction perpendicular to the warp direction.

[0034] The constant load elongation of the warp knitted fabric is not particularly limited. From the viewpoint that the resulting synthetic leather has elongation properties suitable for use as a vehicle interior material, it is preferable that the constant load elongation of the warp knitted fabric in the warp direction is 10% or more and that the constant load elongation in the weft direction is 30% or more.

[0035] The mixed layer is a porous resin layer laminated in a state in which a porous polyurethane resin and nap are mixed together. Here, "mixed" means that the porous polyurethane resin penetrates between the many naps on the napped surface, thereby mixing the napped and porous polyurethane resin. For example, a mixed layer can be formed by impregnating the napped surface with a porous polyurethane resin. "Porous" means a structure having many fine pores (air bubbles). Furthermore, the porous polyurethane resin refers to a polyurethane resin having a porous structure, but the polyurethane resin may contain not only polyurethane as a polymer but also additives such as colorants, and those containing such additives are also simply referred to as "porous polyurethane resin."

[0036] As described above, the naps do not protrude from the surface of the mixed layer, and the entire area where the naps exist in the thickness direction of the fibrous substrate is impregnated with the porous polyurethane resin. In addition, it is preferable that the surface of the mixed layer (the surface on the resin layer side) is substantially free of a porous polyurethane resin layer without naps. That is, it is preferable that a layer consisting of only a porous polyurethane resin does not exist substantially on the napped portion beyond the tip of the naps. The porous polyurethane resin layer without naps is not reinforced by naps and is therefore more easily broken than the mixed layer. Therefore, by substantially not providing a porous polyurethane resin layer without naps, it is advantageous to improve peel strength.

[0037] Here, "substantially no layer of porous polyurethane resin without nap" means that there is no layer without nap, or even if there is a layer without nap, the thickness of the layer without nap is less than 50 μm. The thickness of the layer without nap is preferably less than 40 μm, more preferably 30 μm or less. In the case of synthetic leather with openings, the thickness of the layer without nap is measured at a portion where the openings are not provided.

[0038] The thickness of the mixed layer is not particularly limited and may be, for example, 0.4 to 1.2 mm, or 0.6 to 0.8 mm. In the case of synthetic leather having openings, the thickness of the mixed layer is measured in a portion where no openings are provided.

[0039] The thickness of the mixed layer and the thickness of the layer without nap can be measured as follows. A vertical cross section of the fibrous substrate or synthetic leather is observed at 200x magnification using a microscope (e.g., VHX-200 / 100F manufactured by Keyence Corporation), and the distance T1 from the surface of the base structure 41 to the surface of the porous polyurethane resin 5 layer and the distance T2 from the surface of the base structure 41 to the tip of the nap 42 are determined (see FIG. 3). The distances T1 and T2 are determined for any five locations, and the average values ​​of T1 and T2 are calculated. Regarding the average values, if T1≧T2, T2 is defined as the thickness of the mixed layer, and if T1<T2, T1 is defined as the thickness of the layer without nap. Furthermore, if T1>T2, the difference between T1 and T2, i.e., T3 (=T1−T2), is defined as the thickness of the layer without nap.

[0040] The mixed layer is preferably formed by wet coagulating a solvent-based polyurethane resin on the napped surface of the warp-knitted fabric. Wet coagulation refers to coagulating a solvent-based polyurethane resin solution in an aqueous medium such as water, resulting in the formation of a microporous polyurethane resin with an interconnected pore structure. For example, at least the napped portion (the portion where naps exist) of the warp-knitted fabric is impregnated with a solvent-based polyurethane resin solution and coagulated in an aqueous medium. This fills the gaps between the naps in the napped portion, forming a mixed layer in which naps and porous polyurethane resin are mixed.

[0041] In the fibrous substrate, the porous polyurethane resin may be present only in the mixed layer, or may be impregnated into at least a part of the ground structure. In one embodiment, the porous polyurethane resin is preferably impregnated into the entire warp knitted fabric, i.e., the entire piled portion and the ground structure. This further enhances the effect of preventing fibers cut by the hole-making process from protruding into the openings.

[0042] In one embodiment, when the porous polyurethane resin is impregnated into the entire warp knitted fabric, the amount of porous polyurethane resin in the fibrous substrate is not particularly limited, but is preferably 40 to 130% by mass, more preferably 60 to 100% by mass, relative to the mass of the warp knitted fabric. Having the amount of porous polyurethane resin at or above the lower limit facilitates suppressing distortion of the synthetic leather surface caused by movement of the nap when external force is applied during use of the synthetic leather. Having the amount of porous polyurethane resin at or below the upper limit reduces the amount of porous polyurethane resin used, resulting in cost savings. Furthermore, during hole-making, a contraction force is generated in the porous polyurethane resin, making it easier to form an opening periphery with an inclined shape so that the mixed layer sinks toward the center of the opening.

[0043] Specific examples of polyurethane as a polymer constituting the porous polyurethane resin include polycarbonate-based polyurethane resin, polyether-based polyurethane resin, and polyester-based polyurethane resin. These polyurethane resins can be used alone or in combination of two or more. Among them, polycarbonate-based polyurethane resin is preferred from the viewpoint of chemical resistance, and polyether-based polyurethane resin is preferred from the viewpoint of texture. In one embodiment, from the viewpoint of low-temperature flexibility, it is preferable that polyether-based polyurethane resin is the main component, and for example, it is preferable that 50 mass% or more of the polyurethane is polyether-based polyurethane resin.

[0044] The porous polyurethane resin may contain conventionally known additives such as colorants, plasticizers, stabilizers, fillers, and lubricants, if necessary.

[0045] In addition, when the porous polyurethane resin constituting the mixed layer has the above-mentioned interconnected pore structure, a portion of the resin constituting the resin layer, such as the adhesive layer described below, may penetrate into the surface portion of the mixed layer, and such a situation is also included in this embodiment.

[0046] The basis weight (mass per unit area) of the fibrous base material is 280 to 690 g / m from the viewpoint of weight reduction. ２ It is preferable that the content is 300 to 400 g / m or less, and more preferably 300 to 400 g / m ２ The following is the result.

[0047] The tensile strength of the fibrous substrate is not particularly limited. From the viewpoint of obtaining a strength suitable for use in a vehicle interior material, the tensile strength of the fibrous substrate in the warp and weft directions is preferably 100 N / cm or more.

[0048] The constant-load elongation of the fibrous substrate is not particularly limited. From the viewpoint of obtaining elongation properties suitable for use in a vehicle interior material, it is preferable that the constant-load elongation of the fibrous substrate in the warp direction is 5% or more and the constant-load elongation in the weft direction is 30% or more.

[0049] As described above, the synthetic leather according to this embodiment includes a resin layer provided on a fibrous substrate. The resin layer may be porous or non-porous. From the viewpoint of abrasion resistance, it is preferable that at least the outermost layer is non-porous. Here, non-porous refers to a structure that does not have micropores (air bubbles).

[0050] The resin constituting the resin layer is not particularly limited, and examples thereof include polyurethane resin, acrylic resin, etc. These resins can be used alone or in combination of two or more. Among them, polyurethane resin is preferred from the viewpoints of low-temperature flexibility, cold resistance, and texture.

[0051] The polyurethane resin is not particularly limited, and examples thereof include polyether-based polyurethane resins, polyester-based polyurethane resins, polycarbonate-based polyurethane resins, etc. These polyurethane resins can be used alone or in combination of two or more.

[0052] The form of the polyurethane resin is not particularly limited and may be appropriately selected depending on the application. For example, it may be a solventless system (solvent-free system), a hot melt system, a solvent system, or a water system, and may be a one-component system or a two-component curing system.

[0053] If necessary, the polyurethane resin may contain conventionally known additives such as colorants, plasticizers, stabilizers, fillers, lubricants, foaming agents, mold release agents, etc. These may be used alone or in combination of two or more.

[0054] The thickness of the resin layer is preferably 90 to 200 μm, more preferably 130 to 170 μm. When the thickness of the resin layer is equal to or greater than the lower limit, the abrasion resistance is improved. When the thickness of the resin layer is equal to or less than the upper limit, the opening periphery is easily formed into the above-mentioned depressed shape during hole drilling. When the resin layer is composed of multiple resin layers, the thickness of the resin layer is the sum of the thicknesses of the multiple resin layers. For example, as shown in FIG. 2, when a surface treatment layer, a surface layer, and an adhesive layer are provided as the resin layer, the thickness of the resin layer is the sum of the thicknesses of the surface treatment layer, the surface layer, and the adhesive layer.

[0055] The thickness of the resin layer in synthetic leather is measured as follows: A vertical cross section of the synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), the layer thickness is measured at any 10 points, and the average value is calculated.

[0056] The resin layer consists of at least one resin layer, but can be composed of two or more resin layers of the same or different compositions. The resin layer preferably includes an adhesive layer, a surface layer, and a surface treatment layer, in this order, on a fibrous substrate. Here, the surface layer is a resin layer for coloring the synthetic leather to a desired color. The surface treatment layer is a resin layer for imparting the synthetic leather with a desired feel, appearance (gloss), and durability (abrasion resistance). The surface treatment layer is a general term for a resin layer formed on the surface of the surface layer as the outermost layer that protects the surface layer. The surface layer and the surface treatment layer each consist of at least one resin layer, but can be composed of two or more resin layers of the same or different compositions.

[0057] The resin constituting the surface treatment layer is preferably a polyurethane resin from the viewpoint of texture. The polyurethane resin preferably contains a polycarbonate-based polyurethane resin from the viewpoint of abrasion resistance. More preferably, the polyurethane resin constituting the surface treatment layer consists solely of a polycarbonate-based polyurethane resin, but may optionally contain additives such as a smoothing agent, an antifouling agent, or an antibacterial agent.

[0058] The thickness of the surface treatment layer is not particularly limited, and is preferably 10 to 20 μm, more preferably 10 to 15 μm. When the thickness of the surface treatment layer is equal to or greater than the lower limit, the abrasion resistance is improved. When the thickness of the surface treatment layer is equal to or less than the upper limit, the flex resistance is improved.

[0059] The resin constituting the surface layer is preferably a polyurethane resin from the viewpoint of texture. The polyurethane resin preferably contains a polycarbonate-based polyurethane resin from the viewpoint of durability. The proportion of the polycarbonate-based polyurethane resin in the polyurethane resin constituting the surface layer is more preferably 30 mass % or more.

[0060] The thickness of the surface layer is not particularly limited, but is preferably 30 to 60 μm, more preferably 45 to 55 μm. When the thickness of the surface layer is equal to or greater than the lower limit, the abrasion resistance is improved. When the thickness of the surface layer is equal to or less than the upper limit, the synthetic leather is lightweight.

[0061] From the viewpoint of texture, the resin constituting the adhesive layer is preferably a polyurethane resin. The polyurethane resin is not particularly limited, and examples thereof include polyether-based polyurethane resin, polyester-based polyurethane resin, polycarbonate-based polyurethane resin, etc. These polyurethane resins can be used alone or in combination of two or more.

[0062] The thickness of the adhesive layer is not particularly limited, but is preferably 50 to 120 μm, more preferably 75 to 100 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, good abrasion resistance is achieved. When the thickness of the adhesive layer is equal to or less than the upper limit, a lightweight synthetic leather is obtained.

[0063] As described above, the synthetic leather according to this embodiment has a plurality of openings. The openings can be formed by a conventionally known method such as needle punching. The openings are holes that penetrate from the surface of the resin layer to the fibrous substrate.

[0064] The opening has an opening periphery that is inclined so that the surface of the resin layer slopes down toward the center of the opening. The opening angle of the opening periphery is not particularly limited and may be 100° to 170°, 110° to 165°, or 125° to 160°. Here, the opening angle of the opening periphery is the taper angle θ of the tapered opening periphery 71, as shown in Figures 1 and 2.

[0065] The depth of the opening periphery is not particularly limited and may be 5 to 225 μm or 30 to 110 μm. Here, the depth of the opening periphery is the depth H from the surface of the synthetic leather to the bottom end of the tapered opening periphery 71, as shown in Figures 1 and 2.

[0066] The opening angle and depth of the opening periphery can be determined as follows. A vertical cross section of the synthetic leather is observed at 200x magnification using a microscope (for example, VHX-200 / 100F, manufactured by Keyence Corporation), and the opening angle and depth of the opening periphery are measured. The opening angle and depth are measured at any five locations, and the average values ​​are calculated.

[0067] The opening rate, which is the proportion (area ratio) of openings on the synthetic leather surface (i.e., the surface of the resin layer), is not particularly limited, but is preferably 5 to 13%. When the opening rate is equal to or greater than the lower limit, sufficient breathability can be obtained to eliminate stuffiness and stickiness. On the other hand, when the opening rate is equal to or less than the upper limit, excellent abrasion resistance, elongation, and strength are achieved. The opening rate is more preferably 5 to 12%, and even more preferably 5 to 8%. Here, the opening rate is the ratio of the total area of ​​the multiple openings present on the surface (openings including not only the through-holes but also the opening peripheries) to the total area of ​​the surface including the openings when the surface of the synthetic leather is viewed in plan.

[0068] The shape of the opening is not particularly limited, and can be selected from geometric patterns such as circles, triangles, and squares, taking into consideration the design. From the viewpoint of durability, circles are preferred. The size of the opening is also not particularly limited, and can be, for example, 0.60 to 1.30 mm. ２ Or 0.64 to 1.14 mm ２ Here, the size of the opening is the area of ​​the opening on the surface of the synthetic leather, and when the opening is circular, it is the area calculated using the symbol D shown in Figures 1 and 2 as the opening diameter.

[0069] The breathability of the synthetic leather according to this embodiment is 58 cm ３ / cm ２ When the air permeability is equal to or greater than the lower limit, air permeability sufficient to eliminate stuffiness and stickiness can be obtained.

[0070] The constant load elongation of the synthetic leather according to this embodiment is preferably 10% or more in both the warp and weft directions, and more preferably 14% or more in both the warp and weft directions. Having a constant load elongation equal to or greater than the lower limit in both the warp and weft directions provides elongation characteristics suitable for use in vehicle interior materials. Therefore, the synthetic leather is less likely to wrinkle when upholstered in a seat, resulting in a synthetic leather with excellent upholstery appearance. Here, the warp and weft directions of the synthetic leather are the same as those of the warp-knitted fabric.

[0071] The tear strength of the synthetic leather according to this embodiment is preferably 20 N or more in both the warp and weft directions, more preferably 22 N or more in both the warp and weft directions. Having tear strengths equal to or greater than the lower limit in both the warp and weft directions provides sufficient strength for use as a vehicle interior material, improving durability. While the upper limit is not particularly limited, it is preferably 40 N or less.

[0072] The tensile strength of the synthetic leather according to this embodiment is preferably 50 N / cm or more in both the warp and weft directions, more preferably 55 N / cm or more in both the warp and weft directions. Having a tensile strength equal to or greater than the lower limit in both the warp and weft directions ensures sufficient strength for use as a vehicle interior material and improves durability. While the upper limit is not particularly limited, it is preferably 80 N / cm or less.

[0073] Next, a method for producing synthetic leather will be described. The production method is not particularly limited, and in one embodiment, the synthetic leather according to the embodiment can be produced by sequentially performing the following steps. That is, the production method includes: (1) a step of raising a warp knitted fabric to form nap; (2) a step of adjusting the napped warp knitted fabric to a desired density; (3) a step of wet-impregnating the napped warp knitted fabric with a solvent-based polyurethane resin to obtain a fibrous substrate; (4) a step of applying a resin liquid for the resin layer onto a releasable substrate to form a resin layer; (5) a step of bonding the resin layer and the fibrous substrate together; (6) a step of peeling off the releasable substrate; and (7) a step of perforating.

[0074] In step (1), the method for raising the warp knitted fabric is not particularly limited, and examples thereof include clothed card raising using clothed cards and emery raising using sandpaper. In the case of clothed card raising, the state of nap raising can be appropriately set by selecting various conditions such as the density, length, angle, and tip shape of the clothed cards, the rotation speed of the clothed cards during raising, the contact pressure with the fibrous substrate, and the number of contacts. In the case of emery raising, the state of nap raising can also be appropriately set by selecting various conditions such as the paper mesh of the sandpaper and the number of contacts between the sandpaper and the fibrous substrate during raising. If necessary, a hair straightening step can be provided to adjust the pile height after raising.

[0075] In step (2), the method for adjusting the napped warp knitted fabric to the desired density is not particularly limited. For example, it is preferable to perform so-called width setting and / or width adjustment in a heat treatment step such as heat setting. Specifically, a napped warp knitted fabric fixed at a desired width is heat treated at 90 to 150°C for 2 to 6 minutes to obtain a napped warp knitted fabric of the desired density (55 to 68 courses / 25.4 mm, 40 to 50 wells / 25.4 mm).

[0076] In step (3), the method of wet impregnating the napped warp knitted fabric with the solvent-based polyurethane resin includes a method of applying a solvent-based polyurethane resin solution to the napped warp knitted fabric and immersing it in an aqueous medium to solidify it, thereby obtaining a fibrous substrate containing a mixed layer. By wet impregnation in this manner, the nap can be sufficiently restrained while preventing the texture from becoming hard.

[0077] For example, a method can be used in which a napped warp knitted fabric is dipped in a solvent-based polyurethane resin solution, and then the excess solvent-based polyurethane resin solution is scraped off by passing the napped warp knitted fabric through a coater with an adjusted clearance to ensure a constant coating amount. This method ensures that no naps protrude from the surface of the mixed layer, and that a layer consisting solely of porous polyurethane resin is substantially absent from the surface of the mixed layer. The napped warp knitted fabric impregnated with the solvent-based polyurethane resin solution is then immersed in an aqueous medium such as water. This method replaces the solvent in the solvent-based polyurethane resin solution contained in the napped warp knitted fabric with water and removes it (desolvation), and the polyurethane resin in the solvent-based polyurethane resin solution coagulates.

[0078] Next, the napped warp knitted fabric in which the polyurethane resin has been coagulated is dried to produce a fibrous substrate. For example, the napped warp knitted fabric containing the coagulated porous polyurethane resin and water is dehydrated using a mangle, and then dried under hot air at 100°C to 120°C to produce a fibrous substrate.

[0079] In step (4), the method for applying the resin liquid for the resin layer onto the releasable substrate can be any of various conventionally known methods, and is not particularly limited. Examples include methods using devices such as a comma coater, reverse roll coater, spray coater, roll coater, and knife coater. Among these, application using a comma coater or knife coater is preferred because it allows the formation of a uniform thin film layer. The application thickness of the resin liquid for the resin layer can be appropriately set as needed.

[0080] The releasable substrate is not particularly limited, and may be a substrate that has releasability to resins or a substrate that has been subjected to a release treatment. Examples of the releasable substrate include release paper, release-treated cloth, water-repellent cloth, olefin sheets or films made of polyethylene resin or polypropylene resin, fluororesin sheets or films, and plastic films with release paper. The releasable substrate may have an uneven pattern, and the use of such a releasable substrate can impart a design to the surface of the synthetic leather.

[0081] After applying the resin liquid for the resin layer to the releasable substrate, a heat treatment is carried out as necessary. The heat treatment is carried out to evaporate the solvent in the resin liquid for the resin layer and dry the resin. Furthermore, when a crosslinking agent that undergoes a crosslinking reaction by heat treatment is used or when a two-component curing resin is used, the heat treatment is carried out to promote the reaction and form a coating with sufficient strength.

[0082] Next, in step (5), the resin layer and the fibrous substrate are bonded together. Examples of bonding methods include conventionally known methods such as transfer, heat fusion, thermocompression, and bonding using an adhesive. When using an adhesive (when forming an adhesive layer), the adhesive may be applied to the resin layer, and then the fibrous substrate may be bonded together. Various known methods may be used for applying the adhesive, and the method is not particularly limited. Examples include methods using a device such as a comma coater, reverse roll coater, spray coater, roll coater, gravure coater, kiss roll coater, or knife coater.

[0083] Next, in step (6), the releasable substrate is peeled off from the resin layer, thereby obtaining a laminate of the resin layer and the fibrous substrate.

[0084] When forming a plurality of resin layers, there can be mentioned a method in which, after forming a resin layer on a releasable substrate, before applying adhesive, the resin layer surface is further coated with a resin liquid for resin layer to form.For example, when forming an adhesive layer, a surface layer and a surface treatment layer as the resin layer, in step (6), the releasable substrate is peeled off to obtain a laminate of the surface layer, the adhesive layer and the fibrous substrate, and then the resin liquid for surface treatment layer is coated on the surface of the surface layer to form the resin layer.

[0085] To form a surface treatment layer, various conventionally known methods can be used to apply the resin liquid for the surface treatment layer to the surface layer, and the method is not particularly limited. Examples include methods using devices such as rotary screen printing, reverse roll coater, spray coater, roll coater, gravure coater, kiss roll coater, knife coater, and comma coater. Among these, application by rotary screen printing or reverse roll coater is preferred because it allows the formation of a uniform thin film layer. The application thickness of the resin liquid for the surface treatment layer may be appropriately set depending on the required thickness of the surface treatment layer. Subsequently, heat treatment may be performed as necessary.

[0086] Next, in step (7), a hole-punching process is carried out to form a plurality of openings. The hole-punching process is not particularly limited, and a conventionally known method such as needle punching can be used. In this way, the synthetic leather according to the embodiment is obtained.

[0087] The synthetic leather according to this embodiment can be used for various vehicle interior materials, including, but not limited to, automobile seats, ceiling materials, dashboards, door linings, and steering wheels.

[0088] The various numerical ranges described in this specification can be arbitrarily combined with their respective upper and lower limit values, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0090] Each evaluation item was performed according to the following method.

[0091] [Air permeability] Air permeability was measured at room temperature (23°C) in accordance with JIS L1096:2010 8.26.1 Method A (Fragile method). A higher measured value indicates higher air permeability.

[0092] [Tensile Strength] The tensile strength is the value (N / cm) obtained by dividing the maximum load (N) until the test piece broke by the width (cm) of the test piece in the following tensile test. Specifically, three test pieces each having a width of 50 mm and a length of 300 mm were taken from the warp and weft directions. Under conditions of room temperature 20±2°C and humidity 65±5% RH, both ends of the test piece were clamped with grippers so as not to slacken, and the maximum load (N) until the test piece broke was measured using a tensile tester Autograph AG-100A (manufactured by Shimadzu Corporation) with a grip width of 50 mm, a grip spacing of 200 mm, and a grip movement speed of 200 mm / min. The maximum load (N) was then divided by the width of the test piece (50 mm) to determine the maximum load per unit width (N / cm), and the average value was calculated. If the average tensile strength of the synthetic leather is 50 N / cm or more, it can be said that the tensile strength is sufficient for use as a vehicle interior material, and the larger the value, the better the tensile strength.

[0093] [Tear Strength] The tear strength is the maximum load (N) applied until the test piece broke due to tearing in the following tear test. Specifically, three test pieces, each 40 mm wide and 150 mm long, were taken from each of the warp and weft directions. A 75 mm long incision was made in the test piece from the center of the short side parallel to the long side. Using a tensile tester Autograph AG-100A (manufactured by Shimadzu Corporation) at room temperature of 20±2°C and humidity of 65±5% RH, both sides of the incised side of the test piece were attached to a pair of grippers with a gripping distance of 10 mm, with the front and back facing each other, and the test piece was torn at a movement speed of 200 mm / min. The maximum load (N) applied until the test piece broke was measured, and the average value was calculated. If the average tear strength of the synthetic leather was 20 N or more, it could be said that the tear strength was sufficient for use as a vehicle interior material, and the higher the value, the better the tear strength.

[0094] [Constant Load Elongation] Measurement was performed in accordance with JIS L1096:2010 8.16 D method. Specifically, three 50 mm wide and 250 mm long test pieces were taken in each of the warp and weft directions. Each test piece was marked with a gauge mark at 100 mm intervals along the longitudinal center of the test piece. The test piece was attached to the grips of a constant load elongation tester (Martens type) (manufactured by Universal Automotive Interiors (Suzhou) Co., Ltd.) at a room temperature of 20±2°C and a humidity of 65±5% RH, with a grip spacing of 150 mm and no slack. A load of 78.4 N was applied to the lower grip, including the lower grip. After leaving the test piece for 10 minutes, the distance between the gauge marks (L) was measured, and the constant load elongation (%) was calculated using the following formula. The results were averaged for both the warp and weft directions. If the average constant load elongation of synthetic leather is 10% or more in both the warp and weft directions, the synthetic leather will have elongation properties suitable for use in vehicle interior materials and will have good stretchability. Constant load elongation (%) = L - 100

[0095] [Peel Strength] The peel strength is the value (N / cm) obtained by dividing the maximum load (N) until the test piece peeled off by the width (cm) of the test piece in the following peel test. Specifically, three test pieces, each 30 mm wide and 120 mm long, were taken from the warp and weft directions. The resin layer and fibrous substrate were peeled 40 mm from one end of the short side of the test piece. Under conditions of room temperature 20±2°C and humidity 65±5% RH, the resin layer and fibrous substrate were clamped with grippers so as not to slacken, and the resin layer was peeled off using a tensile tester Autograph AG-100A (manufactured by Shimadzu Corporation) with a gripping width of 30 mm and a gripper movement speed of 200 mm / min. The maximum load (N / cm) during peeling was measured, and the average value was taken as the peel strength. A measured value of 5 N / cm or more can be said to be sufficient peel strength for synthetic leather, and the larger the value, the better the peel strength.

[0096] [Abrasion Resistance] A piece of cotton canvas (equivalent to JIS L 3102 No. 6) measuring 30 mm in width and 250 mm in length was taken from the weft direction and fixed to a Gakushin type abrasion tester RT-300S (manufactured by Daiei Scientific Instruments Manufacturing Co., Ltd.). Test pieces measuring 10 mm in width and 100 mm in length were taken from the warp direction and the weft direction, and then a 10 mm wide, 100 mm long, 0.030 g / cm3 thick sheet was attached to the back surface. ３ A friction element was prepared by attaching a 4 mm thick urethane foam sheet to the friction element. A load of 9.8 N was applied to the friction element and the cotton canvas was rubbed. The friction element was reciprocated 30,000 times at a speed of 30 reciprocations / minute over a distance of 100 mm on the surface of the cotton canvas. The number of times the test piece was abraded until it broke was counted and judged according to the following criteria. (Judgment Criteria) A: 30,000 times or more B: 20,000 times or more, but less than 30,000 times C: Less than 20,000 times

[0097] [Example 1] Using a two-reed 32-gauge tricot knitting machine, a 1-0 / 1-2 Denbigh knit structure was formed on the back side using 75 dtex / 36 f polyester multifilament textured yarn, and a 1-0 / 3-4 cord knit structure was formed on the front side using 75 dtex / 36 f polyester multifilament textured yarn, and these were knitted on the machine to a width of 165 cm and 62 courses / 25.4 mm to obtain a tricot knit fabric.

[0098] Next, the sinker loop surface of the tricot knitted fabric was subjected to a raising treatment using a clothed raising machine equipped with three clothed rolls, each having 12 pile rollers and 12 counter pile rollers, at a clothed roller torque of 2.5 MPa and a fabric speed of 12 m / min, with raising alternately from the knitting end direction and the knitting start direction 13 times to give the knitted fabric a fluffy surface.

[0099] Next, a heat setter was used to heat-treat the first section (90°C, 7.5 m), the second section (120°C, 7.5 m), the third section (150°C, 7.5 m), and the fourth section (140°C, 7.5 m) at a pin width of 150 cm at a rate of 5.5 m / min to obtain a napped warp knitted fabric. ２ The tricot knit fabric has a fiber fineness (single fiber fineness) of 2.08 dtex and a fiber density of 205,344 threads / (25.4 mm). ２ The pile length was 0.7 mm, the density was 62 courses / 25.4 mm, and 46 wells / 25.4 mm, the tensile strength was 110 N / cm in the warp direction and 116 N / cm in the weft direction, and the constant load elongation was 17% in the warp direction and 50% in the weft direction. Here, the pile density was calculated by (number of filaments of the raised yarn) x (course density) x (well density) x 2, since it was full-cut raised.

[0100] A solvent-based polyurethane resin solution was prepared by adding dimethylformamide solution so that the solids content of the polyether-based polyurethane resin was 23% by mass. A napped warp knitted fabric was dipped into the resin solution, and then passed through a knife coater with a clearance adjusted to 1.0 mm to scrape off any excess resin solution. The napped warp knitted fabric impregnated with the resin solution was then immersed in a 20% by mass aqueous dimethylformamide solution to solidify the polyurethane resin. After dehydration with a mangle, the fabric was heat-treated at 5.0 m / min using a heat setter with a pin width of 145 cm, in sections 1 (90 ° C, 5 m), 2 (120 ° C, 5 m), 3 (150 ° C, 5 m), and 4 (140 ° C, 5 m). A porous polyurethane resin-imparted fibrous substrate was obtained. The obtained fibrous base material had a pile length of 0.7 mm, a mixed layer thickness of 0.7 mm, a density of 62 courses / 25.4 mm, 46 wells / 25.4 mm, a tensile strength of 129 N / cm in the warp direction and 108 N / cm in the weft direction, a constant load elongation of 10% in the warp direction and 62% in the weft direction, and a basis weight of 376 g / m ２ The impregnation amount of the porous polyurethane resin in the fibrous substrate was 67% by mass relative to the mass of the napped warp knitted fabric. In the fibrous substrate, no naps protruded from the surface of the mixed layer. In addition, the thickness of the porous polyurethane resin layer on the mixed layer where no naps existed was 30 μm.

[0101] A surface layer resin liquid was prepared by adding 84 parts by mass of dimethylformamide, 7 parts by mass of isopropyl alcohol, 33.5 parts by mass of methyl ethyl ketone, and 4 parts by mass of pigment to 34 parts by mass of polycarbonate-based polyurethane resin and adjusting the viscosity to approximately 2500 mPa s. The surface layer resin liquid was coated onto release paper using a comma coater so that the coating thickness after drying would be 50 μm, and then dried at 130° C. for 2 minutes to form a surface layer.

[0102] An adhesive was prepared by adding 85 parts by weight of dimethylformamide, 30 parts by weight of methyl ethyl ketone, 10 parts by weight of flame retardant, 2 parts by weight of curing agent, and 0.1 parts by weight of pigment to 36 parts by weight of polyether-based polyurethane resin and 9 parts by weight of polyester-based polyurethane resin, and adjusting the viscosity to approximately 5000 mPa·s. The adhesive was coated onto the surface layer formed above using a comma coater to a coating thickness of 100 μm after drying, and then dried at 60°C for 2 minutes to form an adhesive layer. The resulting adhesive layer and fibrous substrate were combined and pressed under 0.3 MPa for 1 second to obtain a laminate.

[0103] The laminate was peeled from the releasable substrate, and the surface of the surface layer was coated with a resin liquid for a surface treatment layer using a reverse roll coater so that the coating thickness after drying would be 13 μm. The resin liquid for the surface treatment layer was a dimethylformamide solution prepared so that the solid content of the polycarbonate-based polyurethane resin was 20 mass %. After the coating, the surface treatment layer was formed on the surface layer by drying at 130 ° C for 2 minutes, and synthetic leather was obtained.

[0104] The resulting synthetic leather was punched on the surface side using a punching machine. The punching process was carried out using punching pins with a hole diameter (inner diameter) of 1.0 mm, spaced 5 mm apart (the distance between the centers of the pins) in both the vertical and horizontal directions. This resulted in a synthetic leather having multiple openings with opening peripheries that were inclined so that the surface of the resin layer fell toward the center of the opening. In the resulting synthetic leather, the average opening diameter of the openings on the surface of the resin layer was 1.05 mm, the opening ratio was 6.9%, the opening angle of the opening peripheries was 156°, and the depth of the opening peripheries was 75.4 μm. Furthermore, when the thicknesses of the resin layers in the resulting synthetic leather were measured, the thickness of the surface treatment layer was 13 μm, the thickness of the surface layer was 50 μm, and the thickness of the adhesive layer was 80 μm, resulting in a total resin layer thickness of 143 μm.

[0105] The breathability of synthetic leather is 66 cm ３ / cm ２ / s, eliminating stuffiness and stickiness during extended use as a vehicle interior material. Furthermore, the tensile strength was 71 N / cm in the warp direction and 69 N / cm in the weft direction, the tear strength was 23 N in the warp direction and 26 N in the weft direction, the constant load elongation was 15% in the warp direction and 68% in the weft direction, and the peel strength was 7 N / cm in the warp direction and 8 N / cm in the weft direction, providing sufficient strength for vehicle interior material applications and elongation characteristics suitable for such applications. Furthermore, the abrasion resistance was evaluated as A in the warp direction and A in the weft direction, demonstrating excellent abrasion resistance for vehicle interior material applications. Furthermore, no fibers protruded from the openings, providing excellent appearance. When the synthetic leather was applied to a vehicle seat, wrinkles were suppressed and the upholstery was excellent.

[0106] [Example 2] The conditions for punching using a punching machine were changed so that the hole diameter of the punching pins was 1.2 mm and the spacing between the pins was 4.5 mm in both the vertical and horizontal directions, so that the opening ratio of the synthetic leather was 12.1%. The synthetic leather of Example 2 was obtained in the same manner as in Example 1.

[0107] In the obtained synthetic leather, the average opening diameter of the openings on the surface of the resin layer was 1.25 mm, the opening ratio was 12.1%, the opening angle of the opening periphery was 140°, and the depth of the opening periphery was 105.3 μm. The breathability of the synthetic leather was 124 cm ３ / cm ２ / s, which was higher in breathability than Example 1. The tensile strength was 55 N / cm in the warp direction and 51 N / cm in the weft direction, the tear strength was 22 N in the warp direction and 22 N in the weft direction, and the peel strength was 6 N / cm in the warp direction and 6 N / cm in the weft direction. Although the strength was lower than that of Example 1, it was sufficient for use as a vehicle interior material. In addition, the constant load elongation was 24% in the warp direction and 70% in the weft direction, indicating elongation characteristics suitable for use as a vehicle interior material. Furthermore, the abrasion resistance was evaluated as B in the warp direction and B in the weft direction. Although inferior to that of Example 1, it was excellent in abrasion resistance for use as a vehicle interior material. Furthermore, there was no protrusion of fibers from the openings, and the appearance was excellent. When the synthetic leather was used to upholster a vehicle seat, wrinkles were suppressed and the upholstery appearance was excellent.

[0108] [Comparative Example 1] Synthetic leather of Comparative Example 1 was obtained in the same manner as in Example 1, except that the raising treatment was not performed. Specifically, the tricot knit fabric of Example 1 (knitted on the machine to a width of 165 cm and 62 courses / 25.4 mm) was not raised, and the density was adjusted by heat setting. The resulting warp-knitted fabric was impregnated with a porous polyurethane resin in the same manner as in Example 1 to produce a fibrous substrate. The resulting fibrous substrate had a density of 56 courses / 25.4 mm, 42 wel / 25.4 mm, tensile strength: 208 N / cm in the warp direction and 197 N / cm in the weft direction, constant load elongation: 15% in the warp direction and 70% in the weft direction, and basis weight of 281 g / m ２ The impregnation amount of the porous polyurethane resin in the fibrous base material was 52 mass % relative to the mass of the warp knitted fabric. In the fibrous base material, a porous polyurethane resin layer having a thickness of 20 μm was formed on the warp knitted fabric, but a mixed layer was not formed.

[0109] A resin layer was formed on the above fibrous substrate in the same manner as in Example 1, and perforations were then performed to obtain synthetic leather of Comparative Example 1. In the obtained synthetic leather, the average opening diameter of the openings on the surface of the resin layer was 1.0 mm, the opening ratio was 6.3%, and no peripheral openings were formed. The air permeability of the synthetic leather was 68 cm ３ / cm ２ / s, which was sufficient for vehicle interior material applications, similar to that of Example 1. The tensile strength was 93 N / cm in the warp direction and 86 N / cm in the weft direction, the tear strength was 27 N in the warp direction and 27 N in the weft direction, and the peel strength was 11 N / cm in the warp direction and 11 N / cm in the weft direction, which was higher than that of Example 1. The constant load elongation was 20% in the warp direction and 72% in the weft direction, which was suitable for vehicle interior material applications. The abrasion resistance was evaluated as C in the warp direction and C in the weft direction, indicating poor abrasion resistance for vehicle interior material applications. There was no fiber protrusion from the openings, and the appearance was excellent.

[0110] Comparative Example 2: A synthetic leather of Comparative Example 2 was obtained in the same manner as in Example 1, except that the mixed layer of the fibrous substrate was buffed with an emery brush to cause the nap to protrude 0.1 mm above the mixed layer. Specifically, the mixed layer was impregnated with the porous polyurethane resin in Example 1 and then buffed. The resulting fibrous substrate had a nap length of 0.7 mm, a mixed layer thickness of 0.6 mm, a density of 62 courses / 25.4 mm and 46 wells / 25.4 mm, a tensile strength of 118 N / cm in the warp direction and 102 N / cm in the weft direction, a constant load elongation of 13% in the warp direction and 68% in the weft direction, and a basis weight of 293 g / m. ２ The amount of porous polyurethane resin impregnated in the fibrous base material was 62% by mass relative to the mass of the napped warp knitted fabric. In the fibrous base material, naps protruded by 0.1 μm from the surface of the mixed layer.

[0111] A resin layer was formed on the above fibrous substrate in the same manner as in Example 1, and holes were then drilled to obtain synthetic leather of Comparative Example 2. In the obtained synthetic leather, the average opening diameter of the openings on the surface of the resin layer was 1.05 mm, the opening ratio was 6.9%, the opening angle at the opening periphery was 158°, and the depth at the opening periphery was 72.6 μm. The synthetic leather had an air permeability of 60 cm ３ / cm ２ / s, which was lower than that of Example 1, but had sufficient breathability for use as a vehicle interior material. The tensile strength was 66 N / cm in the warp direction and 62 N / cm in the weft direction, and the tear strength was 21 N in the warp direction and 23 N in the weft direction, which were lower than those of Example 1. The constant load elongation was 19% in the warp direction and 73% in the weft direction, which were elongation properties suitable for use as a vehicle interior material. The abrasion resistance was evaluated as B in the warp direction and B in the weft direction. However, fibers protruded from the openings, and the appearance was poor.

[0112] The configurations and results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

[0113] REFERENCE SIGNS LIST 1, 10... synthetic leather, 2... fibrous base material, 3... resin layer, 31... adhesive layer, 32... surface layer, 33... surface treatment layer, 4... warp knitted fabric, 41... ground weave, 42... raised nap, 5... porous polyurethane resin, 6... mixed layer, 7... opening, 71... opening periphery, 72... through-hole

Claims

1. A synthetic leather comprising a fibrous base material and a resin layer provided on the fibrous base material, wherein a plurality of openings are provided from a surface of the resin layer through the fibrous base material, the plurality of openings having opening peripheries that are inclined such that the surface of the resin layer slopes down toward the center of the openings, the fibrous base material comprises a warp knitted fabric including a ground structure and raised nap, and a mixed layer provided between the ground structure and the resin layer in which the raised nap and a porous polyurethane resin are mixed, the raised nap not protruding from the surface of the mixed layer facing the resin layer.

2. The synthetic leather according to claim 1, wherein the layer of the porous polyurethane resin not having any raised nap is substantially absent on the surface of the mixed layer facing the resin layer, and here, "substantially absent" means that there is no layer not having any raised nap, or even if there is a layer not having any raised nap, the thickness of the layer not having any raised nap is less than 50 μm.

3. The synthetic leather according to claim 1 or 2, wherein the resin layer has a thickness of 90 to 200 μm.

4. The synthetic leather according to claim 1 or 2, wherein the opening ratio on the surface of the synthetic leather is 5 to 13%.

5. The synthetic leather according to claim 1 or 2, wherein the porous polyurethane resin is impregnated into at least a part of the ground structure of the fibrous base material.

6. The synthetic leather according to claim 1 or 2, wherein the resin layer comprises an adhesive layer, a surface layer, and a surface treatment layer in this order on the fibrous base material.

7. The synthetic leather according to claim 1 or 2, wherein the thickness of the mixed layer is 0.4 to 1.2 mm.

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