Synthetic leather

Abstract

To provide a synthetic leather available as, for example, sensor materials and monitoring materials.SOLUTION: A synthetic leather 1 is formed by laminating at least a base material 10, an adhesion layer 20, and a skin layer 30. The base material 10, the adhesion layer 20, and the skin layer 30 respectively have conductivity. Whole volume resistivity R1 measured in a thickness direction is 1.0×10-1 to 1.0×104 (Ω m). Volume resistivity R2 of the base material 10 is set to be smaller than the whole volume resistivity R1 of the synthetic leather 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an artificial leather comprising at least a substrate, an adhesive layer, and a surface layer laminated together. [Background technology]

[0002] Synthetic leather has a luxurious appearance, is pleasant to the touch, and is highly durable, and is therefore used, for example, as exterior materials for electrical appliances, medical bedding, the covering material for general household bedding, etc. Examples of electrical appliances include personal computers, tablet devices, mobile phones, headphones, etc., and synthetic leather is applied to the surfaces of their cases, covers, etc.

[0003] One proposed synthetic leather of this type is one in which a substrate, an adhesive layer, and a skin layer are laminated, the skin layer and the adhesive layer contain additives that are solid at room temperature, and the substrate contains fibers that have been treated to be conductive (see Patent Document 1). In this synthetic leather, the surface resistance value of the skin layer has been measured, and it is said that conductive particles can be used as the additive that is solid at room temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-72684 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the surface of the synthetic leather is made conductive (that is, the surface is made conductive in a direction parallel to the surface), thereby making it possible to eliminate electricity (that is, to release static electricity).

[0006] Meanwhile, it is desired that synthetic leather has further functionality in addition to the static electricity removal function. For example, if it is possible to impart electrical conductivity not only in the direction parallel to the surface of synthetic leather but also in the thickness direction (direction perpendicular to the surface), the three-dimensional electrical conductivity would enable the synthetic leather to be used as a sensor material such as a touch sensor or a monitoring material for a monitoring system.

[0007] In this regard, in conventional synthetic leather, including Patent Document 1, although the electrical conductivity in the direction parallel to the surface has been considered, no consideration has been given to the electrical conductivity in the thickness direction.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide a synthetic leather that can be used, for example, as a sensor material or a monitoring material. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors have conducted intensive research as follows. That is, in order to increase the overall conductivity of synthetic leather, it is necessary that at least the substrate, adhesive layer, and skin layer among the constituent layers of the synthetic leather have conductivity, and parameters that serve as indicators of conductivity between one side and the other side of the synthetic leather have been studied. Here, although thickness is an extremely important factor in considering conductivity in the thickness direction, the ground resistance value (e.g., volume resistance value) is not a parameter that takes thickness into consideration. On the other hand, volume resistivity is a parameter that takes thickness into consideration. Therefore, by adopting such volume resistivity as a parameter that represents the conductivity in the thickness direction of the synthetic leather, setting the overall volume resistivity of the synthetic leather to a specific range, and setting the volume resistivity of the substrate, which is usually thicker than other layers, to be smaller than the overall volume resistivity, it has been found that conductivity can be expressed and controlled in the thickness direction of the synthetic leather, and the present invention has been completed.

[0010] That is, the characteristic configuration of the synthetic leather of the present invention for solving the above problems is as follows: A synthetic leather comprising at least a substrate, an adhesive layer, and a skin layer, the substrate, the adhesive layer, and the skin layer each have electrical conductivity; The overall volume resistivity measured through the thickness is 1.0×10 -1 ~1.0×10 4 (Ω m), The volume resistivity of the substrate is set to be smaller than the volume resistivity of the entire substrate.

[0011] According to the synthetic leather of this configuration, the substrate, adhesive layer, and skin layer each have electrical conductivity, and by setting the overall volume resistivity measured in the thickness direction to the above range, electrical conductivity can be exhibited not only in the direction parallel to the surface but also in the thickness direction. In addition, since the substrate is usually thicker than other layers, if the volume resistivity of the substrate is large, the electrical conductivity of the synthetic leather tends to decrease. However, by setting the volume resistivity of the substrate to be smaller than the overall volume resistivity, the volume resistivity of the substrate can be made smaller than the volume resistivity of the layers with relatively small thicknesses, such as the skin layer and adhesive layer, so that the electrical conductivity of the synthetic leather as a whole can be increased. Therefore, the synthetic leather of this configuration has excellent electrical conductivity in the thickness direction and can be used as a sensor material or a monitoring material.

[0012] In the synthetic leather according to the present invention, The volume resistivity of the substrate is 1.0×10 -2 ~1.0×10 3 (Ω·m) is preferred.

[0013] According to the synthetic leather of this configuration, by setting the volume resistivity of the base material in the above range, the volume resistivity of the entire synthetic leather can be increased to 1.0×10 -1 ~1.0×10 4 (Ω·m). As a result, the synthetic leather of this configuration has excellent electrical conductivity in the thickness direction.

[0014] In the synthetic leather according to the present invention, The substrate is preferably a metal-containing fibrous substrate.

[0015] According to the synthetic leather of the present configuration, the base material is a fibrous base material containing a metal, so that the synthetic leather can be made conductive while ensuring its softness and flexibility.

[0016] In the synthetic leather according to the present invention, The adhesive layer and / or the surface layer is preferably a resin film containing fine metal particles.

[0017] In the synthetic leather of this configuration, the adhesive layer and / or the skin layer is a resin film containing fine metal particles, so that the strength of the synthetic leather can be ensured while electrical conductivity can be imparted.

[0018] In the synthetic leather according to the present invention, The resin film preferably contains 15 to 75% by weight of the metal fine particles.

[0019] According to the synthetic leather of this configuration, by setting the content of metal fine particles in the resin film to the above-mentioned lower limit or more, it is possible to impart electrical conductivity to the synthetic leather that can be used as a sensor material or a monitoring material. Also, by setting the content to the above-mentioned upper limit or less, it is possible to prevent a decrease in the strength and abrasion resistance of the synthetic leather. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a synthetic leather according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view that illustrates a state in which a release paper is laminated on a skin layer of the synthetic leather during production of the synthetic leather according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The synthetic leather of the present invention will be described below with reference to the drawings. However, the present invention is not intended to be limited to the configuration described below or the examples described later. Note that the actual size relationships of the layers of the synthetic leather are not strictly reproduced in each drawing, but are appropriately exaggerated for ease of explanation. In this specification, the "surface" of the synthetic leather means the surface exposed to the outside on the side opposite the applied article when the synthetic leather is provided on the surface of the applied article.

[0022] <Synthetic leather> Fig. 1 is a cross-sectional view showing a schematic structure of synthetic leather 1 according to one embodiment of the present invention. Synthetic leather 1 is formed by laminating a substrate 10, an adhesive layer 20, and a skin layer 30. However, synthetic leather 1 may include an additional layer. An example of the additional layer is a protective layer (described later) provided on skin layer 30.

[0023] (base material) A fibrous base material or a resin film can be used as the substrate 10, and either is configured to have electrical conductivity. Hereinafter, a fibrous base material having electrical conductivity may be referred to as a "conductive fibrous base material," and a resin film having electrical conductivity may be referred to as a "conductive resin film."

[0024] A conductive fibrous substrate is a fibrous substrate containing a metal. In this case, the physical properties of the fibrous substrate are not significantly impaired, so that the synthetic leather 1 can be made conductive while maintaining its softness and flexibility. Specific examples of conductive fibrous substrates include non-conductive (non-conductive) fibrous substrates plated with metal, fibrous substrates having metal fine particles kneaded into threads constituting the fibrous substrate, and fibrous substrates made of conductive threads.

[0025] Examples of the fibrous substrate include knitted fabrics such as plain knit, rib knit, pearl knit, and smooth knit, woven fabrics such as plain weave, twill weave, and satin weave, and nonwoven fabrics. The material of the fiber constituting the fibrous substrate is not particularly limited, and examples thereof include conventionally known fibers such as natural fibers, regenerated fibers, semi-synthetic fibers, and synthetic fibers. Among them, synthetic fibers are preferred from the viewpoint of heat resistance and light resistance, and polyester fibers such as polyethylene terephthalate are more preferred. Also, a mixed fiber in which two or more types of fibers are combined may be used.

[0026] Metal plating treatments performed on fibrous substrates include dry and wet methods. Dry methods include deposition and sputtering, while wet methods include electroless plating and electroplating.

[0027] The conductive fibrous substrate may be a conductive thread, so long as at least a part of the threads constituting the above-mentioned fibrous substrate is a conductive thread. Examples of the conductive thread include a thread made of a conductive polymer, a metal wire, a metal-plated thread obtained by plating a non-conductive thread with metal, and a covering thread in which a conductive sheath thread containing a metal wire is wound around a core thread that is a non-conductive thread. Examples of the conductive polymer include polyacetylene, poly(p-phenylene vinylene), polypyrrole, polythiophene, polyaniline, poly(p-phenylene), and the like. Examples of the non-conductive thread include polyester fibers such as polyethylene terephthalate.

[0028] The metal contained in the conductive fibrous substrate is preferably made into a metal film on the surface of the fibrous substrate by electroless plating and electroplating. In this case, it is more preferable to form a multi-layered metal film, such as first forming a copper film on the surface of the fibrous substrate by electroless plating, and then forming a nickel film by electroless plating. In addition, when forming a multi-layered metal film, the stacking order is not particularly limited and can be set appropriately. As the type of metal, aluminum, nickel, copper, titanium, magnesium, tin, zinc, iron, silver, gold, platinum, vanadium, molybdenum, tungsten, chromium, manganese, silicon, lead, bismuth, boron, germanium, arsenic, antimony, tellurium, cobalt, and other simple metals and alloys thereof can be used, and among these, copper or nickel is preferably used. The above simple metals and alloys can be used alone as the metal, but they can also be used as a mixture of two or more kinds.

[0029] In addition, the conductive fibrous base material may be any material that has been imparted with electrical conductivity, and in addition to conductive fibrous base materials containing metal, fibrous base materials containing conductive carbon, conductive ceramics, etc. may also be used.

[0030] The metal content in the conductive fibrous substrate is preferably 15 to 50% by weight. By setting the metal content in the conductive fibrous substrate within the above range, the softness and flexibility of the synthetic leather 1 can be further increased, while the synthetic leather 1 can be provided with sufficient conductivity that allows it to be used as a sensor.

[0031] A conductive resin film is a resin film containing a conductive material. Examples of materials for the resin film include polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyethylene terephthalate (PET), polyurethane (PU), polypropylene (PP), polyacrylate, polyethylene (PE), polycarbonate (PC), polymethyl methacrylate, polyvinyl chloride, etc. Among these, polyurethane is preferred in terms of flexibility, elongation, adhesion, etc.

[0032] Examples of the conductive material include metal particles (powders) made of the above-mentioned metals, conductive carbon black, carbon nanotubes, non-metallic particles plated with metal, organic particles made of conductive resin, etc. Among these, the conductive material is preferably metal particles, and more preferably nickel particles. By using metal particles as the conductive material, the conductivity of the synthetic leather 1 can be further increased.

[0033] The average particle diameter of the conductive material is preferably 1 to 10 μm. By setting the average particle diameter of the conductive material to the above lower limit or more, the conductive material in the substrate 10 has a size that allows the conductive material to easily come into contact with each other, so that the conductivity of the synthetic leather 1 can be further increased. By setting the average particle diameter to the above upper limit or less, the conductive material can be dispersed more widely in the substrate 10 compared with the same content, so that the conductivity of the synthetic leather 1 can be further increased and the strength of the substrate 10 can be prevented from decreasing. The average particle diameter of the conductive material can be determined, for example, by a particle size distribution measuring device (Shimadzu Corporation, fully automatic dry particle size measuring device (Subsieve Auto Sizer)) (the same applies to other layers).

[0034] The thickness of the substrate 10 is preferably 0.01 to 0.3 mm (10 μm to 300 μm). As described later, the volume resistivity is a value calculated by dividing the volume resistivity by the thickness. Therefore, when comparing the same volume resistivity, the smaller the thickness of the substrate 10, the larger the volume resistivity R2 tends to be, while the larger the thickness of the substrate 10, the smaller the volume resistivity R2 tends to be. In addition, the smaller the thickness of the substrate 10, the higher the softness and flexibility of the substrate 10, while the larger the thickness of the substrate 10, the higher the strength of the substrate 10 tends to be. Therefore, by setting the thickness of the substrate 10 to the above lower limit or more, the strength of the synthetic leather 1 can be ensured while the conductivity can be increased, and by setting the thickness to the above upper limit or less, the softness and flexibility of the synthetic leather 1 can be increased while preventing a decrease in conductivity. The thickness of the substrate 10 can be determined, for example, by photographing a vertical cross section of the synthetic leather 1 using a microscope (digital HF microscope VH-8000, manufactured by Keyence Corporation), measuring the thickness of the substrate 10 at any 10 points in the obtained image (photograph), and calculating the average value of the measurement results (the same applies to the other layers).

[0035] The content (solid content ratio) of the conductive material in the substrate 10 is preferably 15% by weight or more. By setting the content of the conductive material in the substrate 10 to the above lower limit or more, it is possible to impart conductivity that can be used as a sensor to the synthetic leather 1. The upper limit of the content of the conductive material in the substrate 10 is preferably 75% by weight or less. By setting the content to the above upper limit or less, it is possible to prevent a decrease in the strength of the synthetic leather. Here, the content of the conductive material in the substrate 10 is the content on a raw material basis, and is specifically calculated as the ratio (percentage) of the weight of the conductive material to the total weight of the solid components in the material forming the substrate 10 (the same applies to other layers).

[0036] The volume resistivity R2 of the substrate 10 before lamination (or after peeling from the synthetic leather) is 1.0×10 -2 ~1.0×10 3 By setting the volume resistivity R2 of the substrate 10 in the above range, the overall volume resistivity R1 of the synthetic leather 1 can be set to 1.0×10 -1 ~1.0×104 (Ω·m). As a result, the synthetic leather 1 has excellent electrical conductivity in the thickness direction.

[0037] The volume resistivity R2 of the substrate 10 was measured by removing the skin layer 30 and the adhesive layer 20 from the synthetic leather 1, and measuring the remaining substrate 10 to a size of 10 cm long x 10 cm wide (measurement area, 0.01 m 2 ) to prepare a measurement sample, which was then sandwiched between two metal plates measuring 10 cm long x 10 cm wide. Contacts were made on each of the two metal plates, which were then connected to a resistance meter to measure the resistance (volume resistance, Ω). The volume resistance thus obtained was then calculated based on the measurement area (m 2 ) and the thickness of the synthetic leather 1 (m = 1000 mm). Volume resistivity = (volume resistivity × area) / thickness (1) 1, the volume resistivity R2 measured between one surface (front surface) 10a and the other surface (back surface) 10b of the substrate 10, i.e., the volume resistivity R2 in the thickness direction (the vertical direction in FIG. 1) of the substrate 10, is obtained. As will be described later, the volume resistivity R2 of the substrate 10 is set to be smaller than the overall volume resistivity R1 of the synthetic leather 1.

[0038] (Adhesive layer) The adhesive layer 20 is disposed between the substrate 10 and the skin layer 30, and bonds the substrate 10 and the skin layer 30. The adhesive layer 20 is configured to have electrical conductivity, and contains, for example, a polyurethane resin and a conductive material.

[0039] The polyurethane resin is not particularly limited, but may be the same as the curable polyurethane resin used in conventionally known synthetic leather. Examples of such polyurethane resins include polyether-based polyurethane resins, polyester-based polyurethane resins, and polycarbonate-based polyurethane resins. Among them, polycarbonate-based polyurethane resins are preferred from the viewpoint of durability. The polyurethane resins may be used alone or in the form of a mixture of two or more kinds.

[0040] The polyurethane resin is usually a single layer in the adhesive layer 20. The polyurethane resin may be in any form, including solventless, hot melt, solvent, or water-based, and may be one-component, two-component curing, or moisture curing, and may be appropriately selected according to the purpose and application.

[0041] The polyurethane resin is obtained by the reaction of a polyol having a hydroxyl group with a polyisocyanate. In addition to the crosslinking agent, the raw material of the polyurethane resin may contain optional components such as a wettability improver, a flame retardant, a defoaming agent, a filler, and a pigment, if necessary. As for the crosslinking agent, an isocyanate-based crosslinking agent is preferable.

[0042] The conductive material may be the same as the conductive material used in the above-mentioned base material 10, and among these, metal fine particles are preferred, and nickel fine particles are more preferred. By using metal fine particles as the conductive material, the conductivity of the synthetic leather 1 can be further increased.

[0043] The average particle size of the conductive material is preferably 1 to 10 μm. By setting the average particle size of the conductive material to the above lower limit or more, the conductive material particles in the adhesive layer 20 are of a size that allows them to easily come into contact with each other, thereby making it possible to further increase the conductivity of the synthetic leather 1. By setting the average particle size to the above upper limit or less, the conductive material can be dispersed more widely in the adhesive layer 20 compared with the same content, making it possible to further increase the conductivity of the synthetic leather 1 and prevent a decrease in the strength of the adhesive layer 20.

[0044] The content (solid content ratio) of the conductive material in the adhesive layer 20 is preferably 15 to 75% by weight. By setting the content of metal fine particles in the adhesive layer 20 (e.g., resin film) to the above lower limit or more, it is possible to impart conductivity to the synthetic leather 1 that allows it to be used as a sensor. Furthermore, by setting the content to the above upper limit or less, it is possible to prevent a decrease in the strength and abrasion resistance of the synthetic leather 1.

[0045] As described above, a resin film containing metal fine particles is preferable for the adhesive layer 20. By forming the adhesive layer 20 as a resin film containing metal fine particles, it is possible to impart electrical conductivity while ensuring the strength of the synthetic leather 1.

[0046] The weight of the adhesive layer 20 (amount of dry coating after drying) is 30 to 150 g / m 2 is preferable, and 50 to 80 g / m 2 By setting the basis weight of the adhesive layer 20 within the above range, the strength of the synthetic leather 1 can be increased, and at the same time, the electrical conductivity can be increased.

[0047] The thickness of the adhesive layer 20 is preferably 0.1 mm or less. By setting the thickness within the above range, it is possible to increase the strength and electrical conductivity of the synthetic leather 1. Note that, due to the penetration of the adhesive into the fibrous base material, the thickness of the adhesive layer 20 may be measured as 0 mm, and taking this into consideration, the thickness of the adhesive layer 20 is preferably 0 to 0.1 mm.

[0048] The volume resistivity of the adhesive layer 20 before lamination is 1.0×10 -1 ~1.0×10 5 It is preferable to set the resistance to Ω m, and the resistance is preferably set to 1.0×10 to 1.0×10 3 It is more preferable to set the volume resistivity of the adhesive layer 20 to within the above range, so that the overall volume resistivity R1 of the synthetic leather 1 is 1.0×10 -1 ~1.0×10 4 (Ω·m). As a result, the synthetic leather 1 has excellent electrical conductivity in the thickness direction.

[0049] (epidermal layer) The skin layer 30 is conductive and is attached to the substrate 10 via the adhesive layer 20. The skin layer 30 contains, for example, a polyurethane resin and a conductive material.

[0050] The polyurethane resin may be the same as the curable polyurethane resin used in conventionally known synthetic leather. The type of polyurethane resin and the layer structure of the resin film are not particularly limited. Examples of the polyurethane resin include polyether-based polyurethane resin, polyester-based polyurethane resin, and polycarbonate-based polyurethane resin. Among them, polycarbonate-based polyurethane resin is preferable from the viewpoint of wear resistance and durability. In addition, silicone-modified polyurethane resin is more preferable, and silicone-modified polycarbonate-based polyurethane resin is even more preferable from the viewpoint of further improving wear resistance. By using a silicone-modified polyurethane resin as the polyurethane resin of the skin layer 30, wear resistance is improved, and this makes it unnecessary to provide a protective layer on the surface layer. In addition, when a silicone-modified polycarbonate-based polyurethane resin is used for the skin layer 30, the polycarbonate-based polyurethane resin used for the adhesive layer 20 may be silicone-modified.

[0051] The polyurethane resin may be in the form of a solventless system, a hot melt system, a solvent system, or a water system, and may be in the form of a one-component system, a two-component curing system, or a moisture curing system, and may be appropriately selected according to the purpose and application. The polyurethane resin may be used alone or in the form of a mixture of two or more types.

[0052] In addition to the crosslinking agent, the polyurethane resin may be mixed with optional components such as colorants (pigments, dyes), wettability improvers, film-forming assistants, smoothing agents, matting agents, thickeners, defoamers, and fillers, as necessary. The crosslinking agent is used to reduce the process load and improve the properties of the synthetic leather. The crosslinking agent is preferably an isocyanate-based crosslinking agent.

[0053] The conductive material may be the same as the conductive material used in the above-mentioned base material 10, of which metal fine particles are preferred, and nickel fine particles are more preferred. By using metal fine particles as the conductive material, the conductivity of the synthetic leather 1 can be further increased.

[0054] The average particle size of the conductive material is preferably 1 to 10 μm. By setting the average particle size of the conductive material to the above lower limit or more, the conductive material particles in the epidermis 30 can be easily brought into contact with each other, thereby further increasing the conductivity of the synthetic leather 1. By setting the average particle size to the above upper limit or less, the conductive material can be dispersed more widely in the epidermis 30 compared with the same content, thereby further increasing the conductivity of the synthetic leather 1 and preventing a decrease in the strength of the epidermis 30.

[0055] The content (solid content ratio) of the conductive material in the skin layer 30 is preferably 15 to 75% by weight. By setting the content of the conductive material in the skin layer 30 (e.g., a resin film) to be equal to or higher than the above lower limit, the synthetic leather 1 can be endowed with conductivity that allows it to be used as a sensor. Furthermore, by setting the content to be equal to or lower than the above upper limit, the strength and abrasion resistance of the synthetic leather 1 can be prevented from decreasing.

[0056] As described above, a resin film containing metal fine particles is preferable for the skin layer 30. By forming the skin layer 30 as a resin film containing metal fine particles, it is possible to impart electrical conductivity while ensuring the strength of the synthetic leather 1.

[0057] The weight of the surface layer 30 (amount of dry coating after drying) is 20 to 100 g / m 2 is preferable, and 30 to 70 g / m 2 By setting the basis weight of the skin layer 30 within the above range, the strength of the synthetic leather 1 can be increased, and at the same time, the electrical conductivity can be increased.

[0058] The thickness of the skin layer 30 is preferably 0.02 to 0.1 mm. By setting the thickness within the above range, the strength and electrical conductivity of the synthetic leather 1 can be increased. Furthermore, the durability of the skin layer 30 and the synthetic leather 1 can be increased.

[0059] The volume resistivity of the skin layer 30 before lamination is 1.0×10 -1 ~1.0×10 5It is preferable to set the resistance to Ω m, and the resistance is preferably set to 1.0×10 to 1.0×10 3 It is more preferable to set the volume resistivity of the skin layer 30 to the above range, so that the overall volume resistivity R1 of the synthetic leather 1 is 1.0×10 -1 ~1.0×10 4 (Ω·m). As a result, the synthetic leather 1 has excellent electrical conductivity in the thickness direction.

[0060] (Characteristics of synthetic leather) Synthetic leather 1 has an overall volume resistivity R1 measured in the thickness direction of 1.0×10 -1 ~1.0×10 4 (Ω m), which is 1.0×10 -1 ~3.0×10 3 (Ω·m). By setting the volume resistivity R1 of the synthetic leather 1 within the above range, it is possible to exhibit conductivity not only in the direction parallel to the surface but also in the thickness direction. The volume resistivity R1 of the synthetic leather 1 can be measured in the same manner as the volume resistivity R2 of the substrate 10.

[0061] As described above, the volume resistivity R2 of the base material 10 is set to be smaller than the overall volume resistivity R1 of the synthetic leather 1 (R2 < R1). In the synthetic leather 1, the base material 10, the adhesive layer 20, and the surface layer 30 form a series circuit. Therefore, by setting the volume resistivity R2 of the base material 10 to be smaller than the overall volume resistivity R1 of the synthetic leather 1, the volume resistivity of the adhesive layer 20 and the surface layer 30 will be set to be larger than the volume resistivity R2 of the base material 10. Since the adhesive layer 20 and the surface layer 30 are relatively thinner than the base material 10, even if the volume resistivity becomes relatively large, the influence on the overall conductivity of the synthetic leather 1 is relatively small. On the other hand, as the volume resistivity R2 of the base material 10 increases, the volume resistivity of the adhesive layer 20 and the surface layer 30 becomes relatively smaller. In this case, however, the influence of the increase in the volume resistivity R2 of the base material 10 (i.e., the decrease in conductivity) on the increase in the overall volume resistivity R1 of the synthetic leather 1 becomes larger. However, by setting the volume resistivity R2 in the base material 10 to be smaller than the overall volume resistivity R1, the volume resistivity R2 of the base material 10 can be made smaller than the volume resistivity of relatively thin layers such as the surface layer 30 and the adhesive layer 20. Therefore, the conductivity of the synthetic leather 1 as a whole can be enhanced. The synthetic leather 1 of the present embodiment has a volume resistivity R1 of the synthetic leather 1 of 1.0×10 -1 ~1.0×10 4 (Ω·m), and when combined with the fact that the volume resistivity R2 of the base material 10 is set to be smaller than the volume resistivity R1 of the synthetic leather 1, it becomes excellent in conductivity in the thickness direction and can be used as a material for sensors and monitoring materials.

[0062] The synthetic leather 1 complies with the JIS K7204 Taber abrasion test method. When using a rotary Taber abrasion machine, setting the rotation speed to 60 revolutions / min and the load of a pair of friction wheels to 1 kg and placing it on the surface layer, the number of rotations (limit number of rotations) until the base material is exposed is preferably 1000 rotations or more, more preferably 3000 rotations or more, and even more preferably 5000 rotations or more. By satisfying the above range of the limit number of rotations, the synthetic leather becomes more excellent in abrasion resistance.

[0063] (Other layers) The synthetic leather 1 may have layers other than the substrate 10, adhesive layer 20, and skin layer 30 laminated thereon. Examples of the other layers include a protective layer. The protective layer is laminated on the skin layer 30 (the side opposite the adhesive layer 20) to protect the surface of the skin layer 30 (the side opposite the adhesive layer 20). Examples of the protective layer include a non-conductive polyurethane resin film and a conductive polyurethane resin film. Of these, the non-conductive polyurethane resin film is preferred in terms of its pleasant feel. When a non-conductive polyurethane resin film is used as the protective layer, the synthetic leather 1 as a whole, including the protective layer, has a volume resistivity R1 of 1.0×10 -1 ~1.0×10 4 (Ω·m), and the basis weight and thickness must be set so that the volume resistivity R2 of the substrate 10 is smaller than the overall volume resistivity R1 of the synthetic leather 1. In this regard, the basis weight of the protective layer (dry coating amount after drying) is 5 g / m 2 The following is preferred:

[0064] (Manufacturing method of synthetic leather) The synthetic leather 1 of this embodiment can be manufactured by carrying out the following steps. That is, a coating liquid for forming the skin layer 30 (skin layer forming coating liquid) and a coating liquid for forming the adhesive layer 20 (adhesive layer forming coating liquid) are prepared (preparation step). The skin layer forming coating liquid is applied onto the release paper 50, dried and cured to form the skin layer 30 (skin layer forming step). The adhesive layer forming coating liquid is applied onto the formed skin layer 30 (i.e., onto the surface of the skin layer 30 opposite the release paper 50), and dried so as not to completely cure, to form the semi-cured adhesive layer 20 (adhesive layer forming step). The substrate 10 is placed on the semi-cured adhesive layer 20, pressurized, and then dried to cure the semi-cured adhesive layer 20 (aging to promote crosslinking), thereby bonding the skin layer 30 and the substrate 10 via the adhesive layer 20 (bonding step). As a result, as shown in FIG. 2, a laminate 1' with release paper is obtained in which the release paper 50, the surface layer 30, the adhesive layer 20, and the substrate 10 are laminated in this order. The release paper 50 is then peeled off from the resulting laminate 1' with release paper (i.e., the release paper 50 is laminated on the surface layer 30 of the laminate 60 (synthetic leather 1)) (peeling step). In this manner, the synthetic leather 1 can be manufactured by carrying out the surface layer forming step, the adhesive layer forming step, the adhesion step, and the peeling step. When a protective layer is laminated on the surface layer 30, a coating liquid for forming a protective layer (protective layer forming coating liquid) is applied and dried before applying the coating liquid for forming a surface layer on the release paper 50, and then the surface layer forming step, the adhesive layer forming step, the adhesion step, and the peeling step are carried out on the protective layer in the same manner as described above.

[0065] As described above, according to the synthetic leather 1 of this embodiment, at least the substrate 10, adhesive layer 20, and skin layer 30 each have electrical conductivity, and by setting the overall volume resistivity R1 measured in the thickness direction within the above range, it is possible to increase the overall electrical conductivity of the synthetic leather 1. Thus, the synthetic leather 1 has excellent electrical conductivity in the thickness direction, and can be used as a sensor material or monitoring material.

[0066] (Uses of synthetic leather) The uses of the synthetic leather 1 are not particularly limited, but for example, by connecting one side and / or the other side of the synthetic leather 1 to the main body of a touch sensor, a monitoring system, or the like with a conductor, the synthetic leather 1 can be used as a sensor material such as a touch sensor, or as a monitoring material for a monitoring system, or the like. EXAMPLES

[0067] Synthetic leathers having the characteristic features of the present invention (Examples 1 to 12) were produced, and various characteristics were measured. For comparison, synthetic leathers not having the characteristic features of the present invention (Comparative Examples 1 to 11) were produced, and characteristics were similarly measured. The items measured were the thickness of the skin layer, adhesive layer, and synthetic leather (product), their volume resistivity, volume resistivity, and abrasion resistance of the synthetic leather.

[0068] [Raw materials used] The raw materials used in producing the synthetic leathers of Examples 1 to 12 and Comparative Examples 1 to 11 are shown below. The solid content ratio (weight %) of each raw material is shown in Tables 1 to 6. In Tables 1 to 6, the solid content ratio (weight %) is abbreviated to "solid content (%)." In Tables 1 to 6, "-" indicates that the component was not blended.

[0069] <Coating liquid for epidermal layer formation> NY-328 (Crisbon, manufactured by DIC Corporation, polycarbonate-based polyurethane resin): polyurethane base (PU base) NY-373 (Crisbon, manufactured by DIC Corporation, silicone modified polycarbonate polyurethane resin): polyurethane base (PU base) DMF (Dimethylformamide): Diluent (solvent) DN9590 (Burnoc, manufactured by DIC Corporation): Crosslinking agent Black L-1770S (DIALAC, manufactured by DIC Corporation): Carbon black pigment Ni powder (nickel powder, average particle size 1-10μm, manufactured by DIC Corporation): conductive material MHI Black #273 (manufactured by Mikuni Pigment Co., Ltd.): Conductive material DENTOL WK-200B (Otsuka Chemical Co., Ltd.): Conductive material

[0070] <Coating solution for forming adhesive layer> TA205FT (Crisbon, manufactured by DIC Corporation, polycarbonate-based polyurethane resin): polyurethane base (PU base) DMF (Dimethylformamide): Diluent (solvent) MEK (methyl ethyl ketone): Diluent (solvent) Accel F (Crisbon, manufactured by DIC Corporation): Crosslinking accelerator (catalyst) NE crosslinking agent (Rezamin, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.): crosslinking agent (isocyanate-based crosslinking agent) Ni powder (nickel powder, average particle size 1-10μm, manufactured by DIC Corporation): conductive material MHI Black #273 (manufactured by Mikuni Pigment Co., Ltd.): Conductive material WK-200B (Dentall, manufactured by Otsuka Chemical Co., Ltd.): Conductive material

[0071] <Coating solution for forming protective layer> BAYDERM Finish 61D (LANXESS, polycarbonate-based polyurethane resin): polyurethane base (PU base) HYDRHOLAC UD-2 (LANXESS, polycarbonate-based polyurethane resin): polyurethane base (PU base) HM-186 (LANXESS): Silicone adhesive (silicone) AQUADERM XL-50 (manufactured by LANXESS KK): Crosslinking agent AQUADERM Fluid H (LANXESS KK): Leveling agent Water: Diluent (solvent)

[0072] <Conductive base material> A polyester yarn (manufactured by Nan Ya Plastics Processing Factory Co., Ltd., multifilament yarn with 6 filaments, total fineness 33 dtex) was used as the non-conductive yarn. The non-conductive yarn was used to obtain a non-conductive plain weave fabric (taffeta, warp density: 70 threads / 2.54 cm, weft density: 90 threads / 2.54 cm) on a loom. The non-conductive plain weave fabric was plated with copper and then nickel (Cu / Ni plating) to obtain a conductive plain weave fabric with a metal content of 30% by weight as the substrate.

[0073] <Non-conductive base material> In producing the conductive plain weave fabric, a non-conductive plain weave fabric before plating was used as the substrate.

[0074] [Examples 1 to 12] A coating solution for forming a surface layer and a coating solution for forming an adhesive layer were prepared according to the formulations in Tables 1 and 2. The viscosity of the coating solution for forming a surface layer was adjusted to 2000 mPa s (BH type viscometer, rotor: No. 3, 10 rpm, 23°C). The viscosity of the coating solution for forming an adhesive layer was adjusted to 200 mPa s (BH type viscometer, rotor: No. 1, 12 rpm, 23°C).

[0075] The surface layer was formed by applying the surface layer forming coating solution in a sheet form to a coating thickness (wet thickness before drying) of 200 μm on a release paper (AR-209, Asahi Roll Co., Ltd.) having a leather-like grain pattern (uneven pattern) using a comma coater, and curing the coating by heat treatment at 100° C. for 3 minutes in a dryer. The surface layer weight (dry coating amount after drying) was set to the values ​​shown in Tables 1 to 2.

[0076] Next, the adhesive layer-forming coating liquid is applied onto the surface layer in a sheet form using a comma coater so that the coating thickness (wet thickness before drying) is 130 μm. The conductive substrate is laminated while the adhesive layer-forming coating liquid is in a viscous state (semi-cured state), and the adhesive layer-forming coating liquid is applied with a mangle at a pressure of 49 N / m 2The adhesive layer was then cured by aging for 2 days in an atmosphere at a temperature of 40°C and a relative humidity of 65%, and the release paper was then peeled off to obtain synthetic leathers of Examples 1 to 12. The basis weight of the adhesive layer (dry coating amount after drying) was set to the values ​​shown in Tables 1 and 2. Tables 1 and 2 also show the solid content in the coating solution for forming the surface layer, the conductive material content in the surface layer, the solid content in the coating solution for forming the adhesive layer, and the conductive material content in the adhesive layer.

[0077] [Comparative Example 1] According to the recipe in Table 3, a coating solution for forming a protective layer was prepared. According to the recipe in Table 3, the surface layer, the adhesive layer, and the substrate were laminated on the release paper in the same manner as in Examples 1 to 12, and then the release paper was peeled off. On the exposed surface layer, the coating solution for forming a protective layer was applied in a sheet form using a roll coater so that the basis weight of the protective layer (dry coating amount after drying) was the value shown in Table 3, and the protective layer was cured by heat treatment at 100°C for 3 minutes in a dryer, thereby obtaining a synthetic leather of Comparative Example 1. The thickness of the protective layer was 15 μm. Table 3 shows the solid content in the coating solution for forming a protective layer, the solid content in the coating solution for forming a surface layer, the conductive material content in the surface layer, the solid content in the coating solution for forming an adhesive layer, and the conductive material content in the adhesive layer.

[0078] [Comparative Examples 2 to 10] Synthetic leathers of Comparative Examples 2 to 10 were obtained in the same manner as in Examples 1 to 12, except that the coating liquid for forming a surface layer and the coating liquid for forming an adhesive layer were prepared according to the formulations in Tables 3 to 6. Tables 3 to 6 show the basis weight of the surface layer (dry coating amount after drying), the solid content in the coating liquid for forming a surface layer, the conductive material content in the surface layer, the basis weight of the adhesive layer (dry coating amount after drying), the solid content in the coating liquid for forming an adhesive layer, and the conductive material content in the adhesive layer for Comparative Examples 2 to 10.

[0079] [Comparative Example 11] According to the formulations in Table 6, a coating liquid for forming a surface layer and a coating liquid for forming an adhesive layer were prepared, and the synthetic leather of Comparative Example 11 was obtained in the same manner as in Examples 1 to 12, except that a non-conductive substrate was used.

[0080] The synthetic leathers of Examples 1 to 12 and Comparative Examples 1 to 11 were measured for their properties, such as thickness, volume resistivity, volume resistivity, and abrasion resistance, according to the following test methods. The substrates and layers used in Examples 1 to 12 and Comparative Examples 1 to 11 were also measured for their individual thicknesses according to the following test methods.

[0081] [Synthetic leather thickness test] The vertical cross section of each synthetic leather was photographed using a microscope (Keyence Corporation, Digital HF Microscope VH-8000), and the thickness of the epidermis layer was measured at any 10 points in the obtained image (photograph), and the average value of the measurement results was calculated to measure the thickness of the epidermis layer. The thickness of the adhesive layer and the entire synthetic leather was also measured in the same manner. The results are shown in Tables 1 to 6.

[0082] [Individual thickness test of the substrate and each layer] The thickness of each substrate (conductive substrate, non-conductive substrate) used in Examples 1 to 12 and Comparative Examples 1 to 11 before lamination was measured at three arbitrary points using a digital thickness gauge (Peacock G2N-255, manufactured by Ozaki Manufacturing Co., Ltd.), and the average of the measured values ​​was calculated. The thickness of each skin layer used in Examples 1 to 12 and Comparative Examples 1 to 11 before lamination was measured in the same manner as the above substrate. Instead of applying the adhesive-forming coating solution used in Examples 1 to 12 and Comparative Examples 1 to 11 on the skin layer, it was applied in a sheet form on a release paper with a flat surface so that the coating thickness (wet thickness before drying) was 130 μm, and each adhesive layer was formed by heat treatment at 100 ° C. for 3 minutes in a dryer and curing it, and after peeling off the release paper, the thickness of each adhesive layer was measured in the same manner as the above substrate. The thickness of such an adhesive layer may correspond to the thickness of the adhesive layer before lamination. As a result of the above, the thickness of the substrate and the skin layer alone was not different from the thickness in the synthetic leather. In contrast, the adhesive layer penetrates into the substrate during lamination, so the thickness in the synthetic leather is smaller than the thickness of the adhesive layer alone. For this reason, only the measurement results of the thickness of the adhesive layer alone are shown in Tables 1 to 6.

[0083] [Volume resistance and volume resistivity measurement test] Each piece of synthetic leather was measured using a sheet of paper measuring 10 cm in length and 10 cm in width (measurement area, 0.01 m 2 ) to prepare a measurement sample, which was then sandwiched between two metal plates measuring 10 cm long x 10 cm wide, with contacts taken on each of the two metal plates, which were then connected to a resistance meter (HIOKI RM3544, manufactured by HIOKI EE Corporation) to measure the resistance (volume resistance, Ω). The volume resistance thus obtained and the measurement area (m 2 ) and the thickness of the synthetic leather (m = 1000 mm), the volume resistivity (Ω·m) was calculated using the following formula (1). The volume resistivity and volume resistivity of each substrate, adhesive layer, and skin layer before lamination were also measured in the same manner as for the synthetic leather. The results are shown in Tables 1 to 6. The measurement limits of the resistance meter were 3,000,000.000 (Ω) for the synthetic leather and skin layer, 3,000,000.00 (Ω) for the adhesive layer, and 3,000,000.0000 (Ω) for the substrate. Volume resistivity = (volume resistivity × area) / thickness (1)

[0084] [Wear resistance test] The abrasion resistance of each synthetic leather was evaluated according to the JIS K7204 Taber abrasion test method. Specifically, a rotary Taber abrasion machine was used, and the synthetic leather as a test piece was attached to a rotating horizontal disk (rotation speed: 60 rpm) so that the surface layer was located upward (i.e., the substrate was in contact with the horizontal disk), and a pair of friction wheels (abrasion wheel type: CS-10, load 1 kg) with abrasive paper attached was placed on the surface layer of the synthetic leather and rolled to examine the number of rotations (limit number of rotations) until the substrate was exposed. The higher the number of rotations, the better the abrasion resistance. The upper limit of the number of rotations was set to 5000 times (limit upper limit), and if the substrate was not exposed after 5000 rotations, it was evaluated as "5000 times or more". The results are shown in Tables 1 to 6.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] [Table 5]

[0090] [Table 6]

[0091] The overall volume resistivity of the synthetic leather is 1.0×10 -1 ~1.0×10 4 (Ω m), It was shown that the synthetic leathers of Examples 1 to 12, in which the volume resistivity of the substrate is set smaller than the overall volume resistivity, can exhibit conductivity not only in the direction parallel to the surface but also in the thickness direction. A comparison of Example 2 with Examples 1 and 3 to 12 showed that the abrasion resistance of synthetic leather is improved when a silicone-modified polyurethane resin is used as the raw material for the resin film that constitutes the skin layer. When the volume resistivity of the substrate is 1.0×10 -2 ~1.0×10 3 (Ω m), the overall volume resistivity of the synthetic leather is 1.0×10 -1 ~1.0×10 4 It was shown that the inductance can be easily set to (Ω·m).

[0092] By setting the content of metal microparticles in the resin film constituting the adhesive layer and the skin layer to 15 to 75 weight %, it is possible to impart conductivity to the synthetic leather that can be used as a sensor, and it is reasonably assumed that by containing such a relatively large amount of metal microparticles, it is possible to prevent a decrease in the strength and abrasion resistance of the synthetic leather.

[0093] In contrast, the synthetic leathers of Comparative Example 1, in which the protective layer was too thick, Comparative Examples 2 to 5, in which the content of the conductive material in the skin layer was too low at 0 (no compounding) to 11.1% by weight, Comparative Examples 6 to 10, in which the content of the conductive material in the adhesive layer was too low at 0 (no compounding) to 11.1% by weight, and Comparative Example 11, in which the substrate had no conductivity, had an overall volume resistivity of 1.0 × 10 -1 ~1.0×10 4 This indicates that the conductivity is outside the range of (Ω·m) and that it is not possible to achieve conductivity in the thickness direction.

[0094] In addition, the volume resistivity tends to decrease as the content of the conductive material in the surface layer, adhesive layer, and base material increases. However, even if the conductive material is added to each layer so as to be 70% by weight or more, the volume resistivity of the synthetic leather is less than 1.0×10 -1 In consideration of this point, it was found that it is preferable to set the upper limit of the conductive material content in each layer appropriately, for example, in the range of 15% by weight or more, taking into account factors other than the volume resistivity (e.g., strength, etc.). [Industrial Applicability]

[0095] The synthetic leather of the present invention can be suitably used, for example, as a sensor material or a monitoring material. [Explanation of symbols]

[0096] 1 Synthetic leather 10 Base material 20 Adhesive layer 30 Epidermal layer 50 Release paper 60 Laminate

Claims

1. A synthetic leather comprising at least a substrate, an adhesive layer, and a skin layer, the substrate, the adhesive layer, and the skin layer each have electrical conductivity; The overall volume resistivity measured in the thickness direction is 1.0×10 －１ ~1.0 x 10 ４ (Ω·m), The synthetic leather has a volume resistivity of the base material set to be smaller than the volume resistivity of the entire synthetic leather.

2. The volume resistivity of the substrate is 1.0×10 －２ ~1.0 x 10 ３ 2. The synthetic leather according to claim 1, wherein the elastic modulus is (Ω·m).

3. 3. The synthetic leather according to claim 1, wherein the substrate is a fibrous substrate containing a metal.

4. 3. The synthetic leather according to claim 1, wherein the adhesive layer and / or the surface layer is a resin film containing fine metal particles.

5. 5. The synthetic leather according to claim 4, wherein the resin film contains 15 to 75% by weight of the metal particles.

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