Leather-like sheet and backpack using the leather-like sheet as a back surface material

Abstract

The present invention uses a leather-like sheet having a fiber substrate and a colored resin layer laminated on the fiber substrate. The colored resin layer includes an intermediate layer and an epidermis layer laminated on the intermediate layer. The epidermis layer is a layer containing polyurethane and a black pigment of 3 g / m² or more, and the intermediate layer is a layer containing polyurethane and a black pigment. In the L*a*b* colorimetric system, the brightness L* value ≤ 30.

Description

Technical Field

[0001] The present invention relates to a leather-like sheet having excellent detectability based on LIDAR (Laser Imaging Detection and Ranging), and a backpack using the leather-like sheet as a surface material for the back surface. Background Art

[0002] LIDAR is known as a technology that irradiates a laser such as near-infrared light, measures the time from irradiation to return after hitting an object, and determines the distance and direction to the object. It should be noted that such a technology is also called LiDAR (Light Detection and Ranging), and hereinafter will be referred to as LIDAR.

[0003] In recent years, with the increasing requirements for automotive autonomous driving technology, research and development for improving the detection sensitivity of LIDAR sensors, which are safety devices for LIDAR, have been accelerating. The purpose of adopting LIDAR sensors in automotive autonomous driving technology is to suppress traffic accidents by pre-detecting vehicles, people, objects, etc. around the vehicle being driven and reflecting them in the driving situation.

[0004] Most of the LIDAR sensors being promoted for use in automotive autonomous driving technology use pulsed lasers in the near-infrared range of 905 to 1600 nm. Such pulsed lasers have excellent distance measurement accuracy due to their high reflectivity.

[0005] In addition, leather-like sheets such as artificial leather having a grained resin layer are used as raw materials for bags, clothing, shoes, etc. The resin layer of the leather-like sheet is usually used after being colored. Among them, leather-like sheets having a grained resin layer colored black are most widely used.

[0006] For example, Patent Document 1 below discloses a synthetic leather having: a base material layer, a resin layer provided on the base material layer, and a topmost layer provided on the resin layer. The resin layer contains hygroscopic fine particles and an infrared reflecting pigment, and the topmost layer contains 0.2 g / m 2 or more and 1 g / m 2 or less of hygroscopic fine particles. In addition, it is disclosed that since such a synthetic leather contains an infrared reflecting pigment in the resin layer, it is not easily heated under sunlight even if it is black or dark, and since the topmost layer is provided on the resin layer, its fade resistance is also excellent. Further, it is disclosed that the average reflectance of the infrared reflecting pigment in the range of 780 to 1800 nm (near-infrared region) is 20% or more, and the average absorptance in the range of 400 to 760 nm (visible light region) is 70% or more.

[0007] In addition, regarding infrared reflective pigments, Patent Document 2 below discloses a method for manufacturing a black near-infrared reflective pigment, which is a method for manufacturing a black near-infrared reflective pigment by mixing at least a calcium compound, a titanium compound, and a manganese compound by a wet pulverization method and firing at a temperature higher than 1100°C. Among them, the black near-infrared reflective pigment has a perovskite phase as the main phase, and the BET specific surface area is 1.0 m 2 / g or more and less than 3.0 m 2 / g.

[0008] In addition, Patent Document 3 below discloses an artificial leather with a black-based grain layer, which is formed by laminating a resin layer with a thickness of 30 to 100 μm and mainly composed of polyurethane as the upper layer and a resin layer mainly composed of polyurethane containing carbon black as the lower layer. The resin layer as the upper layer contains perylene black at 2% or more based on the weight of the resin.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-168907

[0012] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2016-20549

[0013] Patent Document 3: International Publication WO2018 / 168596 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] Regarding the LIDAR sensors that are being promoted for use in autonomous driving technology, there is a problem of low detection sensitivity for black objects. This is because the pulsed laser in the range of 905 to 1600 nm used by the LIDAR sensor for distance measurement is absorbed by carbon black, which is widely used as a black pigment for black objects. Therefore, the reflected light weakens and it becomes difficult to detect.

[0016] The inventors of the present invention noticed that leather-like sheets with a resin layer having a black-colored grain surface worn or held by people are difficult to be detected by LIDAR sensors, and the presence of people blocked by them cannot be detected, and thus conducted in-depth research on technologies for improving safety, and as a result, came up with the present invention.

[0017] That is, an object of the present invention is to provide a dark-colored leather-like sheet that is easily detected by a LIDAR sensor.

[0018] Means for Solving the Problems

[0019] One aspect of the present invention is a leather-like sheet having a fibrous substrate and a colored resin layer laminated on the fibrous substrate. The colored resin layer includes an intermediate layer and an epidermis layer laminated on the intermediate layer. The epidermis layer is a layer containing polyurethane and an infrared-reflective black pigment of 3 g / m 2 or more. The intermediate layer is a layer containing polyurethane and a black pigment. The leather-like sheet has a surface with a brightness L * a * b * value of ≤ 30 in the L * *a*b color system. Such a leather-like sheet becomes a leather-like sheet having an epidermis layer that is black and easily detected by a LIDAR sensor emitting pulsed laser light of 905 to 1600 nm by including an epidermis layer containing an infrared-reflective black pigment with a high reflectance of near-infrared rays of 3 g / m 2 or more. However, the blackness of the epidermis layer colored only with an infrared-reflective black pigment is low, and it is difficult to obtain a leather-like sheet with high blackness. When carbon black is added to the epidermis layer to increase the blackness, the reflectance of near-infrared rays is significantly reduced. In such a case, by adding a black pigment to the intermediate layer, a leather-like sheet having a surface with a dark color such as a colored L * value of ≤ 30 can be obtained.

[0020] In addition, from the aspect of being easily detected by near-infrared rays in a wide wavelength range of the LIDAR sensor, it is preferable that the surface of the leather-like sheet has a reflectance of 10% or more for near-infrared rays of wavelength 905 nm and a reflectance of 10% or more for near-infrared rays of wavelength 1550 nm.

[0021] In addition, from the aspect of having a high reflectance for near-infrared rays and an increased reflectance in the visible light range, and thus being easily able to obtain a leather-like sheet with good color rendering, it is preferable that the average sunlight reflectance of the surface of the leather-like sheet in the wavelength range of 250 to 2500 nm is 10% or more.

[0022] In addition, for the case where the infrared-reflective black pigment has a reflectance of 25% or more for near-infrared rays of wavelength 905 nm, a reflectance of 50% or more for near-infrared rays of wavelength 1550 nm, and a transmittance of less than 50% for near-infrared rays of wavelength 905 nm, or for the case of a CaO-TiO₂-MnO₂-based titanium black pigment, it is preferable from the aspect of being easily detected by near-infrared rays in a wide wavelength range of the LIDAR sensor.

[0023] In addition, from the aspect of not significantly reducing the reflectance of near-infrared rays, it is preferable that the epidermis layer contains 0 to 0.5 g / m 2 of carbon black.

[0024] In addition, considering that it is easily detected by a LIDAR sensor in, for example, dark leather-like sheets for bags, clothing, etc., it is preferable that the reflection intensity of the surface of the leather-like sheet measured by HORIZON manufactured by Livox Technology Company Limited is 30 or more under the conditions of a wavelength of 905 nm and a measurement distance of 10 m.

[0025] Effects of the Invention

[0026] According to the present invention, it is possible to provide a dark leather-like sheet that is easily detected by a LIDAR sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a cross-sectional schematic view for explaining the layer structure of the grained artificial leather of the embodiment.

[0028] Figure 2 It is a diagram for explaining a method for measuring the LIDAR sensor reflection intensity of the surface of the leather-like sheet used in the examples.

[0029] Figure 3 It is a diagram showing the results when the surface of the leather-like sheet obtained in the examples is measured with a LIDAR sensor.

[0030] SYMBOL DESCRIPTION

[0031] 1 Fiber substrate

[0032] 2 Porous layer

[0033] 3 Intermediate layer

[0034] 4 Epidermal layer

[0035] 5 Coloring resin layer

[0036] 6 Adhesive layer

[0037] 10 Leather-like sheet DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, an embodiment of the leather-like sheet of the present invention will be described in detail. The leather-like sheet of this embodiment includes a fiber substrate and a coloring resin layer laminated on the fiber substrate. The coloring resin layer includes an intermediate layer and an epidermal layer laminated on the intermediate layer. The epidermal layer is a layer containing polyurethane and an infrared-reflecting black pigment of 3 g / m 2 or more, and the intermediate layer is a layer containing polyurethane and a black pigment. The above leather-like sheet has a surface with a brightness L * a * b * value ≤ 30 in the L*a*b* color system. * value ≤ 30 in the L*a*b* color system.

[0039] Figure 1 This is a cross-sectional schematic diagram for explaining the layer structure of the leather-like sheet 10, which is an example of the leather-like sheet of the present embodiment. The leather-like sheet 10 includes: a fiber base material 1, a porous layer 2 mainly composed of polyurethane laminated on the fiber base material 1, a colored resin layer 5 including an intermediate layer 3 and an epidermis layer 4 adhered to the intermediate layer 3, and an adhesive layer 6 mainly composed of polyurethane that bonds the porous layer 2 and the colored resin layer 5. It should be noted that the leather-like sheet is not limited to such a layer structure, as long as it is a leather-like sheet having a fiber base material and a colored resin layer including an intermediate layer and an epidermis layer as described above laminated on the fiber base material, and its layer structure is not particularly limited. It should be noted that for the epidermis layer, as long as the effects of the present invention are not impaired, a transparent layer with a thickness of about 1 to 5 μm, which is an uncolored transparent resin layer, can be further provided on its surface as needed.

[0040] As the fiber base material, known artificial leather base materials for the manufacture of artificial leather, such as non-woven fabrics, fabrics, knitted fabrics, or base materials impregnated with polymer elastomers such as polyurethane, and synthetic leather base materials for synthetic leather can be used without particular limitation. In addition, pigments can be blended in the polymer elastomer as needed. The thickness of the fiber base material is not particularly limited either. For example, it is preferably 0.3 to 3 mm, and more preferably about 0.5 to 1.5 mm. In addition, the type of fiber forming the fiber base material is not particularly limited. For example, it is nylon-based fiber, polyester-based fiber, polyolefin-based fiber, polyurethane-based fiber, etc., without particular limitation.

[0041] In addition, the fineness and morphology of the fiber are not particularly limited. For example, it can be a normal fiber with a fineness exceeding 1 dtex, or an ultrafine fiber with a fineness less than 1 dtex. In addition, the morphology of the fiber can be a solid fiber, or a fiber with voids such as a hollow fiber or a lotus root-like fiber.

[0042] The epidermis layer is a polyurethane layer that colors the surface and contains more than 3 g / m 2 of an infrared-reflective black pigment.

[0043] By making the epidermis layer a polyurethane layer containing more than 3 g / m 2 of an infrared-reflective black pigment, as described later, it can become a colored polyurethane layer with a high reflectivity to pulsed laser of near-infrared rays.

[0044] An infrared-reflective black pigment is a black pigment with a high reflectivity to near-infrared rays. Its reflectivity to near-infrared rays with a wavelength of 905 nm is 25% or more, its reflectivity to near-infrared rays with a wavelength of 1550 nm is 50% or more, and its transmittance to near-infrared rays with a wavelength of 905 nm is 50% or less. Additionally, it is preferable that the infrared-reflective black pigment has a reflectivity to near-infrared rays with a wavelength of 905 nm of 30% or more, and a transmittance to near-infrared rays with a wavelength of 905 nm of 30% or less, further 20% or less, especially 10% or less. As a specific example of such an infrared-reflective black pigment, for example, there can be cited: titanium-based black pigments of the CaO-TiO2-MnO2 type (e.g., TIPAQUE BLACK SG-103 manufactured by Ishihara Sangyo Co., Ltd.), titanium-based black pigments (Tilack D) manufactured by Akaho Kasei Co., Ltd., composite oxide pigments of chromium oxide and iron oxide, etc. Titanium-based black pigments of the CaO-TiO2-MnO2 type have a reflectivity to near-infrared rays with a wavelength of 905 nm of 30% or more, a reflectivity to near-infrared rays with a wavelength of 1550 nm of 55% or more, and a transmittance to near-infrared rays with a wavelength of 905 nm of 10% or less.

[0045] For example, in the case of titanium-based black pigments of the CaO-TiO2-MnO2 type, they are manufactured by a method of mixing a calcium compound, a titanium compound, and a manganese compound using a wet grinding method and firing at a temperature higher than 1100°C. It is preferable that such titanium-based black pigments of the CaO-TiO2-MnO2 type have a perovskite phase as the main phase, and a BET specific surface area of 1.0 m 2 / g or more and less than 3.0 m 2 / g.

[0046] The skin layer contains 3 g / m 2 or more of the infrared-reflective black pigment, preferably containing 3 - 5 g / m 2 . When the content of the infrared-reflective black pigment is less than 3 g / m 2 , the reflectivity of the leather-like sheet to near-infrared rays decreases, and the detectability based on the LIDAR sensor decreases. Additionally, when the content of the infrared-reflective black pigment is excessive, the blackness decreases, and the cost-effectiveness also decreases.

[0047] The skin layer only needs to contain 3 g / m 2 or more of the infrared-reflective black pigment, and its thickness is not particularly limited, preferably 10 μm or more, further 20 - 30 μm. When the skin layer is too thin, there is a tendency that it is difficult to contain 3 g / m 2 or more of the infrared-reflective black pigment.

[0048] In addition, as long as the skin layer contains 3 g / m 2Regarding the above infrared-reflecting black pigment, the content ratio of the infrared-reflecting black pigment in the epidermal layer is not particularly limited, preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more. When the content ratio of the infrared-reflecting black pigment is too low, it becomes difficult to contain 3 g / m 2 of the above infrared-reflecting black pigment. When it is too high, there is a tendency for the blackness to decrease and the cost performance to decrease.

[0049] It should be noted that the epidermal layer does not contain carbon black, or within the range not impairing the effects of the present invention, depending on the type of carbon black, it may contain carbon black in the range of 0 to 0.5 g / m 2 and further 0 to 0.1 g / m 2 . When the epidermal layer contains more than 0.5 g / m 2 of carbon black, the carbon black preferentially absorbs the near-infrared rays irradiated onto the surface of the obtained leather-like sheet, so there is a tendency for the reflectance of the near-infrared rays to decrease and the detectability based on the LIDAR sensor to decrease.

[0050] In addition, within the range not impairing the effects of the present invention, the epidermal layer may also contain other pigments other than carbon black. As long as the absorption rate of the near-infrared rays in the wavelength range of 905 to 1600 nm is not too high, the other pigments are not particularly limited, and specific examples include, for example, anthraquinone pigments, diketopyrrolopyrrole pigments, perylene pigments such as perylene black, etc.

[0051] It should be noted that, for example, since the transmittance of perylene black for near-infrared rays with a wavelength of 905 nm is 60% or more, when used alone, the reflectance of the near-infrared rays is low, so the detectability based on the LIDAR sensor is low, and the color development of dark colors is also low.

[0052] The average dispersed particle diameter of the infrared-reflecting black pigment in the colored resin layer is not particularly limited, preferably 1 to 10 μm, more preferably 1.5 to 8 μm. By making the average dispersed particle diameter of the infrared-reflecting black pigment within such a range, there is a tendency to easily suppress the diffuse reflection of light on the surface of the infrared-reflecting black pigment particles and easily form a black-colored colored resin layer with high blackness. When the average dispersed particle diameter of the infrared-reflecting black pigment is too small, light easily undergoes diffuse reflection on the surface of the infrared-reflecting black pigment particles, so there is a tendency for the surface of the leather-like sheet to easily become colored with a red tone. In addition, when the average dispersed particle diameter of the infrared-reflecting black pigment is too large, the mechanical properties of the film of the colored resin layer decrease, so there is a tendency for the abrasion resistance of the surface of the leather-like sheet to easily decrease.

[0053] On the other hand, the intermediate layer is a layer containing polyurethane and a black pigment, and is colored dark.

[0054] The intermediate layer is a layer containing a black pigment, thereby becoming a polyurethane layer colored dark. Such an intermediate layer is a layer for adjusting the color visually recognized from the surface to a dark color when a large amount of carbon black is not incorporated in the skin layer.

[0055] Examples of the black pigment contained in the intermediate layer include carbon blacks such as furnace black, channel black, and acetylene black, infrared reflection black pigments, composite oxide black pigments, etc. Among them, from the aspect of easily obtaining a dark-colored surface, carbon black is preferred. In addition, from the aspect of further improving the infrared reflectance, an infrared reflection black pigment is preferred.

[0056] It should be noted that as long as the effects of the present invention are not impaired, other pigments in addition to the black pigment may be contained in the intermediate layer for color adjustment. The other pigments are not particularly limited, and specific examples include, for example, anthraquinone pigments, diketopyrrolopyrrole pigments, perylene pigments, etc.

[0057] In the case of containing carbon black as the black pigment, from the aspect of easily obtaining a leather-like sheet with a dark-colored surface having an L * value ≤ 30, it is preferred that the intermediate layer contains 0.2 g / m 2 or more, and further 0.5 to 5 g / m 2 of carbon black. In addition, in the case of containing an infrared reflection black pigment as the black pigment, from the aspect of easily obtaining a leather-like sheet with a dark-colored surface having an L * value ≤ 30, it is preferred that the intermediate layer contains 2 g / m 2 or more, and further 2 to 5 g / m 2 of the infrared reflection black pigment.

[0058] As long as the surface of the leather-like sheet can be adjusted to a surface with a brightness L * value ≤ 30, the thickness of the intermediate layer is not particularly limited, and it is preferably 10 to 50 μm, and further 20 to 30 μm. When the intermediate layer is too thin, there is a tendency that it is difficult to adjust to a dark-colored surface with an L * value ≤ 30.

[0059] In addition, as long as the surface of the leather-like sheet can be adjusted to a surface with an L * value ≤ 30, the content ratio of the black pigment in the intermediate layer is not particularly limited. In the case of containing carbon black as the black pigment, it is preferably 2% by mass or more, and further 2 to 10% by mass of carbon black. In addition, in the case of containing an infrared reflection black pigment as the black pigment, it is preferably 10% by mass or more, and further 10 to 20% by mass of the infrared reflection black pigment. When the content ratio of the black pigment is too small, there is a tendency that it is difficult to obtain a dark-colored surface with an L * value ≤ 30.

[0060] The polyurethane used to form the intermediate layer, skin layer, and porous layer can be obtained by reacting a urethane raw material containing a high molecular polyol, an organic polyisocyanate, and a chain extender. When manufacturing a leather-like sheet, the polyurethane can be prepared as a melt, an organic solvent solution (e.g., a solution of an organic solvent such as dimethylformamide, methyl ethyl ketone, acetone, toluene, etc.), an aqueous dispersion, or an emulsion.

[0061] Specific examples of the high molecular polyol include, for example: polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly(methyltetramethylene glycol); polycarbonate polyols such as polyhexamethylene carbonate diol, poly(3-methyl-1,5-pentylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol; polyester polyols such as polyethylene adipate diol, polybutylene adipate diol, polypropylene adipate diol, polybutylene sebacate diol, polyethylene hexamethylene adipate diol, poly(3-methyl-1,5-pentanediol adipate) diol, poly(3-methyl-1,5-pentanediol sebacate) diol, polycaprolactone diol, or copolymers thereof. These compounds can be used alone or in combination of two or more.

[0062] In addition, specific examples of the organic polyisocyanate include, for example: yellowing-resistant diisocyanates containing aromatic diisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; non-yellowing diisocyanates such as aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc. In addition, according to needs, polyfunctional isocyanates such as trifunctional isocyanates and tetrafunctional isocyanates can also be used in combination. These polyisocyanates can be used alone or in combination of two or more.

[0063] In addition, as specific examples of chain extenders, diamines such as hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, benzenedimethyldiamine, isophoronediamine, piperazine and its derivatives, adipic dihydrazide, isophthalic dihydrazide, etc. can be cited; triamines such as diethylenetriamine; tetraamines such as triethylenetetramine; diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, etc.; triols such as trimethylolpropane; tetrols such as pentaerythritol; amino alcohols such as aminoethanol, aminopropanol, etc. These chain extenders can be used alone or in combination of two or more. In addition, when carrying out the chain extension reaction, monoamines such as ethylamine, propylamine, butylamine, etc.; monoamine compounds containing carboxyl groups such as 4-aminobutyric acid, 6-aminohexanoic acid, etc.; and monohydric alcohols such as methanol, ethanol, propanol, butanol, etc. can be used in combination with the chain extender.

[0064] The polyurethane for forming the porous layer can be formed, for example, by the following method: After coating a solution of the polyurethane to be wet-set on the surface of the fiber substrate, it is immersed in an aqueous coagulation bath to solidify the porous polyurethane. In addition, for the porous layer, in order to impart morphological stability, etc. to the fiber substrate, it can penetrate into its interior. In this case, the fiber substrate is impregnated with the polyurethane solution in advance, and the polyurethane solution is further coated thereon, and then, it is immersed in an aqueous coagulation bath to solidify it, whereby the interior of the fiber substrate can also be provided with porous polyurethane. The thickness of the porous layer is not particularly limited, and for example, it is preferably 100 to 600 μm, more preferably about 200 to 400 μm.

[0065] In order to form an intermediate layer and an epidermal layer on the surface of the porous layer, for example, the method using the dry surface forming method described below can be cited.

[0066] A polyurethane film for forming the epidermal layer is formed on the release paper. Then, a polyurethane film for forming the intermediate layer is formed on the polyurethane film of the epidermal layer, thereby forming a colored resin layer including the intermediate layer and the epidermal layer laminated on the intermediate layer. It should be noted that the colored resin layer may further include other layers other than the intermediate layer in a layer below the epidermal layer.

[0067] Then, an adhesive is coated on the colored resin layer, and the solvent is completely or incompletely removed and dried. Then, after laminating and pressing the adhesive laminated on the colored resin layer formed on the release paper onto the surface of the porous layer, the adhesive is cured, whereby the porous layer and the colored resin layer are bonded together via the adhesive layer. Then, by peeling the release paper from the surface of the colored resin layer, a leather-like sheet having a fiber substrate and a colored resin layer laminated on the fiber substrate is obtained.

[0068] For the leather-like sheet of the present embodiment, by including a colored resin layer having an epidermis layer containing the infrared-reflective black pigment as described above and an intermediate layer containing a black pigment, the leather-like sheet is colored in such a way that it has a surface with an L value ≤ 30 in the L * a * b * colorimetric system. * value ≤ 30.

[0069] It should be noted that coloring in such a way that it has a surface with a brightness L value ≤ 30 in the L * a * b * colorimetric system means that a spectrophotometer is used to measure the color of the dark-colored colored surface, which is the appearance design surface of the leather-like sheet, and the brightness L value ≤ 30 is calculated based on the coordinate values of the L * a * a * b * colorimetric system obtained. As the brightness of the dark-colored surface, it is preferably L * value ≤ 30, more preferably L * value ≤ 25. * value ≤ 25.

[0070] The leather-like sheet of the present embodiment can obtain a leather-like sheet with a high reflectivity for near-infrared rays by having an epidermis layer containing the infrared-reflective black pigment as described above. Thus, a dark-colored leather-like sheet that is easily detected by a LIDAR sensor can be obtained.

[0071] As the reflectivity of the surface of such a leather-like sheet with an L * value ≤ 30 for near-infrared rays, the reflectivity for near-infrared rays with a wavelength of 905 nm is preferably 10% or more, more preferably 15% or more. In addition, the reflectivity for near-infrared rays with a wavelength of 1550 nm is preferably 10% or more, more preferably 15% or more.

[0072] In addition, as the solar reflectance of the surface of the leather-like sheet in the wavelength range of 250 to 2500 nm, it is preferably 10% or more, more preferably 15% or more. When the solar reflectance is in such a range, in addition to having a high reflectivity for near-infrared rays, it is also preferable in terms of easily obtaining a leather-like sheet with good color rendering and an L * value ≤ 30.

[0073] The leather-like sheet of the present embodiment described above can preferably be used as a leather-like sheet with a grain surface similar to natural leather, which is used as a surface material for bags, clothing, shoes, etc. In particular, for example, in the case of using a leather-like sheet as a back surface material of a cover that covers many areas of the wearer's body, such as a backpack (ransel) or a raw material for clothing, it is preferably used as a leather-like sheet with a grain surface that can be detected by a LIDAR sensor with high precision even when many areas of the body are covered by them.

[0074] Especially when a child with a small body carries a backpack, most of the body is sometimes blocked by the backpack. In such a case, it is difficult for a car equipped with a LIDAR sensor to detect a child carrying a backpack that is difficult to be detected by the LIDAR sensor. According to the backpack of the present embodiment, since the back surface material is easily detected by a car equipped with a LIDAR sensor, the possibility of traffic accidents occurring when children go to school can be reduced.

[0075] For such a leather-like sheet, for example, from the aspect of being easily detected by a LIDAR sensor installed in a car as a safety device, it is preferably that the reflection intensity under the conditions of a use wavelength of 905 nm and a measurement distance of 10 m measured by the LIDAR sensor HORIZON manufactured by Livox Technology Company Limited is 40 or more, and further 50 or more, when measured from the epidermis layer side.

[0076] Examples

[0077] Hereinafter, the present invention will be described more specifically by way of examples. It should be noted that the scope of the present invention is not limited by any of these examples.

[0078] [Example 1]

[0079] The sea-island composite fiber containing 45 parts by mass of 6-nylon (sea component) and 55 parts by mass of polystyrene (island component) was melt-spun, stretched to 3 times, an oil agent was imparted to the fiber, mechanical crimping was applied, and then it was dried. The obtained crimped fiber was cut into 51 mm to make 3 dtex staple fibers, and a web was formed. Then, needle punching was alternately performed about 500 stitches / cm in total from both sides of the web 2 to obtain a bonded nonwoven fabric. The unit area weight of this bonded nonwoven fabric was 350 g / m 2, the apparent specific gravity is 0.17. The conjugated nonwoven fabric is treated with a 4% aqueous solution of polyvinyl alcohol, the thickness is compressed and fixed to about 1.3 mm, and the surface is polished to smooth it. Then, it is impregnated with a dimethylformamide (hereinafter referred to as DMF) solution of polyurethane with a 13% concentration of polyester-based polyurethane as the main body. Further, the same polyurethane solution is coated on its surface in an amount of 100 g / m 2 in terms of solid content, and then immersed in a mixed solution of DMF / water to wet-set the polyurethane into a porous state. Then, the island component is eluted and removed in hot toluene to convert the sea-island composite fiber into a hollow fiber. Thus, a fiber substrate laminated with a porous layer permeating to the surface layer is obtained. The thickness of the porous layer is 300 μm.

[0080] Next, a polyurethane composition solution containing 100 parts by mass of a 22% DMF solution of non-yellowing polycarbonate-based polyurethane, 30 parts by mass of a black carrier containing 20% by mass of an infrared-reflecting black pigment (titanium-based black pigment), and 30 parts by mass of DMF is coated on a release paper (R-70 manufactured by LINTEC Corporation) at 100 g / m 2 so that the thickness after drying reaches about 20 μm, and it is dried at 120 °C for 2 minutes, thereby forming a black skin layer. It should be noted that as the titanium-based black pigment, TIPAQUE BLACK SG103 manufactured by Ishihara Sangyo Co., Ltd., which is a CaO-TiO2-MnO2-based black pigment with a reflectance of 30.1% at 905 nm, a reflectance of 57.1% at 1550 nm, and a transmittance of 10% or less for near-infrared rays with a wavelength of 905 nm, is used. The obtained skin layer does not contain carbon black, and the amount of the titanium-based black pigment contained in the skin layer is 4.8 g / m 2 . In addition, the content ratio of the titanium-based black pigment in the skin layer is 20% by mass.

[0081] Then, a polyurethane composition solution containing 100 parts by mass of a 30% DMF solution of non-yellowing polyether-based polyurethane, 20 parts by mass of a black carrier containing 5% by mass of carbon black (furnace black), 30 parts by mass of DMF, and 30 parts by mass of MEK is coated on the skin layer at 120 g / m 2 so that the thickness after drying reaches about 20 μm, and it is dried at 120 °C for 2 minutes, thereby forming a black intermediate layer. It should be noted that the reflectance of the furnace black at 905 nm is about 5%, the reflectance at 1550 nm is about 6%, and the transmittance of the near-infrared rays with a wavelength of 905 nm is 5% or less. The amount of carbon black per unit area of the obtained intermediate layer is 0.6 g / m 2 . In addition, the content ratio of carbon black in the intermediate layer is 3% by mass.

[0082] Then, a polyurethane-based adhesive solution was coated on the surface of the intermediate layer formed on the release paper at 110 g / m 2 , and dried at 120 °C for 2 minutes to evaporate the solvent, thereby forming an adhesive layer. Then, the adhesive layer on the release paper was laminated onto the porous layer laminated on the fibrous substrate to produce a laminated intermediate. Then, the laminated intermediate was pressed with a roller having a surface temperature of 75 °C with a gap to perform crimping. Then, after aging treatment at 50 °C for 3 days, the release paper was peeled off, thereby obtaining artificial leather with a grained surface having a black surface, i.e., a leather-like sheet.

[0083] Then, the leather-like sheet was evaluated as described below.

[0084] (Measurement of L * value)

[0085] The L * a * b * coordinate values of the surface color system of the leather-like sheet were measured using a spectrophotometer (manufactured by Minolta Co., Ltd.: CM-3700), and the L * value was calculated. It should be noted that the number of samples was N = 3, and its average value was calculated.

[0086] (Reflectance, transmittance)

[0087] Using a spectroscopic analysis device (V-770 type spectrophotometer, ISN-923 type integrating sphere manufactured by JASCO Corporation), the spectrum of the reflectance in the wavelength range of 250 nm to 2500 nm was measured, and the reflectance at 905 nm and 1550 nm was read to obtain the reflectance of the surface of the leather-like sheet. In addition, the average value of the reflectance over the entire wavelength range of 250 nm to 2500 nm was calculated as the sunlight reflectance. In addition, for the reflectance and transmittance of the titanium-based black pigment, a UV-visible near-infrared spectrophotometer (V-670 manufactured by Nippon Denshoku Industries Co., Ltd.) was used to directly place the sample in the form of powder into the measurement cell, and the spectral reflectance and transmittance in the range of 300 nm to 2500 nm were measured.

[0088] (LIDAR sensor reflection intensity)

[0089] As Figure 2As shown, a leather-like sheet of 26 cm × 26 cm was vertically arranged in a frame surrounded by black cardboard. At a position 10 m away from the measurement point, a HORIZON manufactured by Livox Technology Company Limited was set up so that the light-emitting part reached a height of 41 cm, and a laser with a wavelength of 905 nm was irradiated. Then, the reflection intensity was measured in such a way that the energy when the laser was reflected from the object was digitized and expressed in the range of 0 (total absorption) to 255 (total reflection). It should be noted that Figure 3 is a graph showing the results when measuring the near-infrared reflection intensity of the surface of the leather-like sheet by a LIDAR sensor. (a) is a graph obtained by measuring the surface of the leather-like sheet of Example 1, and (b) is a graph obtained by measuring the surface of the leather-like sheet of Comparative Example 1.

[0090] (Average dispersion particle size)

[0091] Using a scanning electron microscope (JSM-IT500 manufactured by JEOL Ltd.), a 2000-fold SEM photograph of the cross-section in the thickness direction of the colored resin layer of the test piece cut out from the leather-like sheet was taken. Then, for all n infrared reflection black pigment particle sizes Rn observed in an arbitrary range of 2500 μm 2 were measured. It should be noted that the longest part of the observed infrared reflection black pigment was taken as the particle size. In addition, when multiple particles aggregated to form secondary particles, the longest part of the secondary particles was taken as the particle size. In addition, when there were multiple types of black pigment particles within the SEM photographing range, qualitative analysis based on EDS elemental analysis was performed in the SEM photographing range in advance to identify the infrared reflection black pigment that was the object of particle size measurement.

[0092] Then, the following calculation formula was used to calculate each volume Vn based on the obtained n particle sizes Rn. It should be noted that each volume Vn was a value calculated assuming a spherical shape.

[0093] Volume Vn of the particles of the infrared reflection black pigment = 4 / 3 × π × (Rn / 2) 3

[0094] Then, the obtained n volumes Vn were arranged in ascending order of the particle size Rn, and the cumulative sum was calculated as the volume cumulative frequency. Then, based on the graph obtained by plotting the volume cumulative frequency against the particle size Rn, the particle size when the volume cumulative frequency reached 50% was taken as the dispersion particle size (D50). The above measurements were performed at any 5 points on the leather-like sheet, and the average of the dispersion particle sizes (D50) at the 5 points was taken as the average dispersion particle size.

[0095] The above results are shown in Table 1 below.

[0096] [Table 1]

[0097]

[0098] [Example 2]

[0099] In Example 1, the skin layer containing 4.8 g / m 2 of infrared-reflective black pigment was replaced with a skin layer containing 3.4 g / m 2 of infrared-reflective black pigment. Otherwise, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0100] [Example 3]

[0101] In Example 1, the intermediate layer containing 0.6 g / m 2 of carbon black was replaced with an intermediate layer containing 3.4 g / m 2 of infrared-reflective black pigment. Otherwise, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0102] [Example 4]

[0103] In Example 3, the skin layer containing 4.8 g / m 2 of infrared-reflective black pigment and 0.5 g / m 2 of carbon black was replaced with a skin layer containing 4.8 g / m 2 of infrared-reflective black pigment. Otherwise, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0104] [Comparative Example 1]

[0105] In Example 1, the skin layer containing 4.8 g / m 2 of infrared-reflective black pigment was replaced with a skin layer containing 3.4 g / m 2 of carbon black, and adjusted to a black of approximate brightness. Otherwise, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0106] [Comparative Example 2]

[0107] In Example 1, the intermediate layer containing 0.6 g / m 2 of carbon black was replaced with an intermediate layer without pigment. Otherwise, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0108] [Comparative Example 3]

[0109] In Example 1, it was changed to a skin layer containing 1.9 g / m 2 of an infrared-reflecting black pigment and 1.9 g / m 2 of carbon black to replace the skin layer containing 4.8 g / m 2 of an infrared-reflecting black pigment. Other than this, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0110] [Comparative Example 4]

[0111] In Example 1, it was changed to a skin layer containing 2.9 g / m 2 of an infrared-reflecting black pigment and 1.9 g / m 2 of carbon black to replace the skin layer containing 4.8 g / m 2 of an infrared-reflecting black pigment. Other than this, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0112] [Comparative Example 5]

[0113] In Example 1, it was changed to a skin layer containing 4.8 g / m 2 of an infrared-reflecting black pigment and 0.6 g / m 2 of carbon black to replace the skin layer containing 4.8 g / m 2 of an infrared-reflecting black pigment, and it was changed to an intermediate layer without pigment to replace the intermediate layer containing 0.6 g / m 2 of carbon black. Other than this, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0114] [Comparative Example 6]

[0115] In Example 1, a change was made to swap the skin layer and the intermediate layer. Other than this, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0116] [Comparative Example 7]

[0117] In Example 1, it was changed to a skin layer containing 4.8 g / m 2 of a perylene-based black pigment to replace the skin layer containing 4.8 g / m 2 of an infrared-reflecting black pigment. Other than this, artificial leather was obtained in the same manner as in Example 1 and evaluated. It should be noted that the perylene-based black pigment used was perylene black (Paliogen Black L0084) with a transmittance of 65% or more for near-infrared light with a wavelength of 905 nm. The results are shown in Table 1.

[0118] [Comparative Example 8]

[0119] In Example 3, it was changed to an epidermal layer containing 4.8 g / m 2 of perylene black pigment (Paliogen Black L0084) to replace the epidermal layer containing 4.8 g / m 2 of the infrared-reflective black pigment. Except for this, artificial leather was obtained in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

[0120] Referring to Table 1, the leather-like sheets of artificial leather in Examples 1 to 4, where the epidermal layer contains 3 g / m 2 or more of the infrared-reflective black pigment and the intermediate layer is a layer containing a black pigment, all have a dark surface with an L * value ≤ 30 and high detectability based on the LIDAR sensor. On the other hand, the leather-like sheets in Comparative Examples 1, 3, 4, and 6, where the epidermal layer does not contain 3 g / m 2 or more of the infrared-reflective black pigment, all have insufficient detectability based on the LIDAR sensor. In addition, although the epidermal layer contains 3 g / m 2 or more of the infrared-reflective black pigment, the leather-like sheet of artificial leather in Comparative Example 2, where the intermediate layer does not contain a black pigment, did not obtain a dark surface with an L * value ≤ 30. Furthermore, the leather-like sheet of artificial leather in Comparative Example 5, where the epidermal layer contains 3 g / m 2 or more of the infrared-reflective black pigment and also contains carbon black, and the intermediate layer does not contain a black pigment, obtained a dark surface with an L * value ≤ 30, but due to the absorption of near-infrared rays by carbon black, the detectability based on the LIDAR sensor is insufficient. In addition, the leather-like sheet of artificial leather in Comparative Example 7, where the epidermal layer contains a perylene black pigment and the intermediate layer is a layer containing a black pigment, obtained a dark surface with an L * value ≤ 30, but due to the easy transmission of near-infrared rays through the epidermal layer, the detectability based on the LIDAR sensor is insufficient. In addition, the leather-like sheet in Comparative Example 8, where the epidermal layer contains a perylene black pigment and the intermediate layer is a layer containing an infrared-reflective black pigment, has good detectability based on the LIDAR sensor, but did not obtain a dark surface with an L * value ≤ 30.

Claims

1. A leather-like sheet comprising a fibrous substrate and a colored resin layer laminated on the fibrous substrate, wherein, the colored resin layer includes an intermediate layer and an epidermis layer laminated on the intermediate layer, The epidermis layer contains polyurethane and an infrared-reflective black pigment of 3 g / m 2 or more. the intermediate layer is a layer containing polyurethane and a black pigment, The colored resin layer has a surface with a brightness L value ≤ 30 in the L * a * b * colorimetric system * value ≤ 30, the infrared-reflective black pigment includes at least one selected from titanium-based black pigments of the CaO-TiO₂-MnO₂ type, titanium-based black pigment Tilack D manufactured by Akaho Kasei Co., Ltd., and composite oxide pigments of chromium oxide and iron oxide, the reflection intensity of the surface under the conditions of a use wavelength of 905 nm and a measurement distance of 10 m measured by HORIZON manufactured by Livox Technology Company Limited is 40 or more.

2. The leather-like sheet according to claim 1, having a reflectance of 10% or more for near-infrared rays with a wavelength of 905 nm and a reflectance of 10% or more for near-infrared rays with a wavelength of 1550 nm.

3. The leather-like sheet according to claim 1, having an average sunlight reflectance of 10% or more in the wavelength range of 250 to 2500 nm.

4. The leather-like sheet according to claim 1, wherein, the infrared-reflective black pigment has a reflectance of 25% or more for near-infrared rays with a wavelength of 905 nm, a reflectance of 50% or more for near-infrared rays with a wavelength of 1550 nm, and a transmittance of less than 50% for near-infrared rays with a wavelength of 905 nm.

5. The leather-like sheet according to claim 1, wherein, the infrared-reflective black pigment is a titanium-based black pigment of the CaO-TiO₂-MnO₂ type.

6. The leather-like sheet according to claim 1, wherein, The epidermis layer contains 0 to 0.5 g / m of carbon black 2 .

7. The leather-like sheet according to claim 1, wherein, the epidermis layer does not contain carbon black.

8. The leather-like sheet according to claim 1, wherein, the intermediate layer contains carbon black as a black pigment.

9. The leather-like sheet according to claim 1, wherein, the thickness of the epidermis layer is 10 to 30 μm.

10. The leather-like sheet according to claim 1, wherein, the thickness of the intermediate layer is 10 to 50 μm.

11. The leather-like sheet according to claim 1, further comprising a porous layer with a thickness of 100 to 600 μm between the fibrous substrate and the colored resin layer.

12. A backpack using the leather-like sheet according to any one of claims 1 to 11 as a back surface material.

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