JP7404709B2 - Artificial leather for light-transmissive display equipment - Google Patents

Description

The present invention relates to artificial leather for light-transmissive display equipment.

In recent years, mechanical switches for operating audio and heater control panels near the driver's seat of automobiles have been replaced by touch panels for aesthetic reasons. Mechanical switches have the advantage of being less likely to malfunction and have a good input feel, but by adopting a touch panel, the switch can be designed flat and integrated with the surrounding interior, so it is easy to see the switch when it is not in use. Its adoption is increasing because it makes it possible to give the impression that it does not exist. By using light-transmitting resin on the surface of in-vehicle display equipment other than the switches around the driver's seat, it is possible to create a design that does not separate from the surrounding interior when not in use. The use of mold display materials for automobile interior materials is increasing.

In addition, new surface decoration technologies are increasingly required for automobile interior parts in order to respond to product differentiation and diversification of user preferences. Therefore, we have proposed touch panels and light-transmissive display materials such as those mentioned above, as well as leather-like surface materials such as silver-tone and suede-like materials that have light transmission properties on their surfaces, as well as touch panels and light-transmissive display materials using them. has been done.

Patent Document 1 proposes a light-transmitting leather-like sheet that transmits light emitted from a light-emitting member through a transmitting portion formed in one area. By partially forming thin areas in the non-light-transmitting areas using a laser cutter or the like, a light-transmitting leather-like sheet that emits light and displays a desired design is obtained. In addition, light-transmissive display equipment has been proposed by in-mold molding using this light-transmissive leather-like sheet.

Patent Document 2 proposes a light-transmissive conductive molded body that uses a highly transparent skin material and has a good design because the switch is hidden in the skin material when the switch is not in use. In addition, since it can be textured, if it is used in an in-vehicle touch switch, it will be possible to recognize the position of the switch even when driving while facing forward, thereby preventing malfunctions.

JP2016-081817A Unexamined Japanese Patent Publication No. 2017-165100

However, with repeated use of light-transmissive display equipment and light-transmissive touch panels that use such skin materials, the appearance may deteriorate due to hand dirt and sebum adhering to the surface, or the naps on the surface becoming worn away. There is an issue of loss of dignity.

In Patent Document 1, in order to form a transparent portion, a thin region is partially created using a laser cutter or the like, and since the skin material is thin in this region, the wear resistance is poor.

In addition, the technology of Patent Document 2 is excellent in design because the color and design of the underlying layer is sufficiently blocked due to its high transparency, but in order to obtain sufficient light transparency, it is necessary to It is preferable to dye the product with dirt, as dirt from hands and sebum will reduce the quality of the product's appearance.

Therefore, an object of the present invention is to obtain an artificial leather for light-transmissive display materials that has sufficient light transmittance and can suppress deterioration in appearance quality due to repeated use.

The artificial leather for light-transmissive display equipment of the present invention is an artificial leather composed of a nonwoven fabric made of ultrafine fibers and an elastic polymer, wherein the ultrafine fibers form a fiber bundle, and the fiber bundle is Each contains 2 or more and 500 or less ultrafine fibers, and the porosity of the elastic polymer body is 1% or less.

According to a preferred embodiment of the present invention, the L value measured with a color difference meter is 50 or less.

According to a preferred embodiment of the present invention, the total light transmittance is 10% or more and 50% or less.

According to a preferred embodiment of the present invention, in the cross section of the artificial leather, the polymer elastic body is in close contact with 35% or more and 100% or less of the outer periphery of the cross section of the fiber bundle of the ultrafine fibers.

According to a preferred embodiment of the present invention, the thickness is 0.5 mm or more and 1.2 mm or less.

The artificial leather for light-transmissive display materials of the present invention can suppress deterioration in appearance quality due to repeated use while having sufficient light transmittance.

It is a micrograph showing an example of a polymer elastic body in a cross section of artificial leather cut in the thickness direction. FIG. 2 is a micrograph showing regions A and B in the cross-sectional micrograph of FIG. 1. FIG. FIG. 3 is a schematic diagram showing an elastic polymer body in close contact with the outer periphery of a cross section of a fiber bundle. 1 is a micrograph showing an example of an elastic polymer that is in close contact with the outer periphery of a cross section of a fiber bundle. 2 is a micrograph showing an example of the outer periphery of an elastic polymer body in close contact with the elastic polymer body in coverage measurement of the elastic polymer body.

The artificial leather for light-transmissive display equipment of the present invention is an artificial leather composed of a nonwoven fabric made of ultrafine fibers and an elastic polymer, wherein the ultrafine fibers form a fiber bundle, and the fiber bundle is Each contains 2 or more and 500 or less ultrafine fibers, and the porosity of the elastic polymer body is 1% or less. In this specification, "artificial leather for light-transmitting display equipment" may be simply referred to as "artificial leather."

As for the type of ultrafine fibers used in the artificial leather of the present invention, synthetic fibers are preferably used from the viewpoints of durability, particularly mechanical strength, heat resistance, and light resistance, as well as from the viewpoint of light transparency.

When synthetic fibers are used as the ultrafine fibers, examples of polymers constituting the ultrafine fibers include polyester, polyamide, polyolefin, acrylic, and polyphenylene sulfide. Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, potytrimethylene terephthalate, polylactic acid, and the like. Further, examples of the polyamide include polyamide 6, polyamide 66, polyamide 610, polyamide 12, and the like. Further, examples of the polyolefin include polyethylene and polypropylene. Preferably, by using polyester as the ultrafine fiber, it is possible to easily achieve both durability and light transmittance.

In the present invention, dicarboxylic acids and/or ester-forming derivatives thereof used in the polyester include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid and ester-forming derivatives thereof. Examples include. The ester-forming derivatives referred to in the present invention include lower alkyl esters, acid anhydrides, and acyl chlorides of these dicarboxylic acids, and specifically methyl esters, ethyl esters, hydroxyethyl esters, and the like are preferably used. A more preferred embodiment of the dicarboxylic acid and/or its ester-forming derivative used in the present invention is terephthalic acid and/or its dimethyl ester.

In the present invention, examples of the diol used in the polyester include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and cyclohexanedimethanol, among which ethylene glycol is preferably used.

When synthetic fibers are used as ultrafine fibers, the polymer forming the ultrafine fibers may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, It can contain a heat storage agent, an antibacterial agent, etc.

The average single fiber diameter of the ultrafine fibers is preferably 0.1 μm or more and 10 μm or less. By setting the average single fiber diameter to 10 μm or less, preferably 6 μm or less, it becomes easier to obtain artificial leather that is dense, soft to the touch, and has excellent surface quality. On the other hand, by setting the average single fiber diameter to 0.1 μm or more, preferably 1 μm or more, it becomes easier to achieve excellent color development and fastness after dyeing.

The average single fiber diameter here is determined by observing a cross section of the artificial leather cut in the thickness direction using a scanning electron microscope (SEM), measuring the single fiber diameter of 50 arbitrary microfibers at three locations, and calculating the total diameter. It is determined by calculating the average value of the diameters of 150 single fibers. To calculate the diameter of a single fiber, first measure the cross-sectional area of the single fiber, and then calculate the diameter of a circle that has the cross-sectional area using the following formula.
・Single fiber diameter (μm) = (4×(cross-sectional area of single fiber (μm ² ))/π) ^1/2
In addition, in this specification, unless otherwise specified, the cross section of artificial leather refers to a cross section of artificial leather cut in the thickness direction.

Ultrafine fibers are in the form of nonwoven fabrics in artificial leather. By using a nonwoven fabric, a uniform and elegant appearance and texture can be obtained when the surface is brushed.

Both long fiber nonwoven fabrics and short fiber nonwoven fabrics can be used as the form of the nonwoven fabric, but short fiber nonwoven fabrics are preferred because they have a large number of raised fibers on the product surface and are easy to obtain an elegant appearance.

When producing a nonwoven fabric by needle punching using short fibers, the fiber length of the ultrafine fibers is preferably 25 mm or more and 90 mm or less. By setting the fiber length to 90 mm or less, preferably 80 mm or less, and more preferably 70 mm or less, good quality and texture can be easily obtained. Furthermore, by setting the fiber length to 25 mm or more, preferably 35 mm or more, and more preferably 40 mm or more, it is possible to easily obtain artificial leather with excellent abrasion resistance.

A nonwoven fabric made of ultrafine fibers has a structure in which bundles of ultrafine fibers (fiber bundles) are entangled. The strength of artificial leather is improved by intertwining the ultrafine fibers in bundles. Such a nonwoven fabric can be obtained, for example, by intertwining microfiber-generating fibers in advance and then developing microfibers.

In the present invention, it is preferable that the artificial leather is a fiber bundle having 2 or more and 500 or less ultrafine fibers, and the periphery of the fiber bundle is substantially constrained by the elastic polymer. Sufficient strength of the artificial leather can be obtained by having two or more ultrafine fibers constituting the fiber bundle, preferably five or more fibers, and more preferably ten or more fibers. Further, by setting the number of ultrafine fibers constituting the fiber bundle to 500 or less, preferably 100 or less, and more preferably 50 or less, the ultrafine fiber generation type fibers can have a fiber diameter suitable for entanglement.

The elastomer polymer constituting the artificial leather of the present invention refers to a polymer compound that has rubber elasticity at room temperature. The binder effect of the polymer elastic body not only prevents the ultrafine fibers from falling out of the artificial leather, but also makes it possible to impart appropriate cushioning properties.

In the artificial leather for light-transmitting display materials of the present invention, it is important that the porosity of the elastic polymer is 1% or less. Since the porosity of the elastic polymer body is low, that is, the elastic polymer body is non-porous, it is possible to suppress diffuse reflection of light inside the artificial leather and improve the light transmittance of the artificial leather. Furthermore, by expanding the space between the ultrafine fibers and the polymer elastic body in the cross section of the artificial leather, the straightness of light is improved, leading to improved light transmittance. When the porosity of the elastic polymer is preferably 0.5% or less, more preferably 0.1% or less, the light transmittance is further improved.

Here, the porosity of the elastic polymer is defined as ``In a cross section of artificial leather cut in the thickness direction, the porosity of the elastic polymer existing in the section other than the fiber bundles of ultrafine fibers is When the area of the "molecular elastic body" (hereinafter sometimes referred to as area A) is taken as 100%, the ratio of the area of voids existing inside the area A (hereinafter sometimes referred to as area B) is expressed as a percentage. This is the numerical value expressed. Note that region A also includes voids in region B.

A specific example of measuring the porosity of an elastic polymer body is shown in FIGS. 1 and 2. FIG. 1 is a microscopic photograph showing an example of an elastic polymer material in a cross section of artificial leather cut in the thickness direction. Further, FIG. 2 shows region A and region B in the cross-sectional micrograph of FIG. 1. As shown in FIGS. 1 and 2, region A is the elastic polymer present on the cross section of the elastic polymer present in the portion other than the fiber bundle of the ultrafine fibers. That is, in the micrograph of the cross section, the elastic polymer that exists in the depth direction is not included in region A, and only the elastic polymer that exists on the surface of the cross section is included in region A. Region B is a void existing in region A.

As a means for making the porosity of the polymeric elastic material 1% or less, for example, when applying the polymeric elastic material to a nonwoven fabric made of ultrafine fibers, impregnating the nonwoven fabric with a solution containing the polymeric elastic material, One example of this method is to use a method in which the elastic polymer is solidified by evaporating the solvent. On the other hand, there is a method in which a nonwoven fabric impregnated with a solution containing an elastic polymer is immersed in a coagulating liquid such as a non-solvent for the elastic polymer to solidify the elastic polymer. This is not preferable because voids are generated when the coagulating liquid is replaced.

Examples of the polymeric elastomer include polyurethane, polyurea, ethylene/vinyl acetate elastomer, acrylic elastomer such as polyacrylic acid and acrylonitrile/butadiene elastomer, styrene/butadiene elastomer, polyvinyl alcohol, polyvinyl chloride, polyethylene glycol, etc. From the viewpoint of durability and compression properties, polyurethane, acrylic elastic material, and polyvinyl chloride are preferably used. The polymer elastic body can contain a plurality of polymer elastic bodies.

Polyurethane is an example of the polymer elastomer particularly preferably used in the present invention. In particular, water-dispersed polyurethane can be applied to a nonwoven fabric made of ultrafine fibers by a dry heat coagulation method in which water is evaporated. Therefore, it is difficult to generate voids inside the elastic polymer body.

As the water-dispersed polyurethane resin, a resin obtained by reacting a polymer polyol having a number average molecular weight of preferably 500 or more and 5000 or less, an organic polyisocyanate, and a chain extender is preferably used. Further, in order to improve the stability of the water-dispersed polyurethane dispersion, it is preferable to use an active hydrogen component-containing compound having a hydrophilic group. By setting the number average molecular weight of the polymer polyol to 500 or more, more preferably 1500 or more, it is possible to easily prevent the texture from becoming hard. Further, by setting the number average molecular weight to 5,000 or less, more preferably 4,000 or less, the strength of the polyurethane as a binder can be easily maintained. A case where a water-dispersed polyurethane resin is used as the polymer elastic body will be described below.

(1) Reactive components of water-dispersed polyurethane resin First, each reactive component of water-dispersed polyurethane resin will be explained.

(1-1) Polymer polyol Examples of polymer polyols that can be used in the artificial leather of the present invention include polyether polyols, polyester polyols, polycarbonate polyols, and the like.

Examples of polyether polyols include polyols obtained by adding and polymerizing monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, and cyclohexylene using a polyhydric alcohol or polyamine as an initiator, and the above-mentioned polyols. Examples include polyols obtained by ring-opening polymerization of monomers using a protonic acid, a Lewis acid, a cationic catalyst, or the like as a catalyst. Specifically, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and copolymerized polyols that are a combination thereof can be mentioned.

Examples of polyester polyols include polyester polyols obtained by condensing various low molecular weight polyols and polybasic acids, polyols obtained by depolymerizing lactones, and the like.

Examples of low molecular weight polyols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1.8-heptanediol. Linear alkylene glycols such as octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentane diol, branched alkylene glycol such as 2-methyl-1,8-octanediol, alicyclic diol such as 1,4-cyclohexanediol, aromatic dihydric alcohol such as 1,4-bis(β-hydroxyethoxy)benzene One or more types selected from the following may be mentioned. Further, adducts obtained by adding various alkylene oxides to bisphenol A can also be used as low molecular weight polyols.

Examples of polybasic acids include succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid. One or more types selected from the group consisting of acids and the like can be mentioned.

Examples of polycarbonate polyols include compounds obtained by reacting polyols with carbonate compounds such as dialkyl carbonates and diaryl carbonates.

As the polyol as a raw material for producing polycarbonate polyol, the polyols listed as raw materials for producing polyester polyol can be used. As the dialkyl carbonate, dimethyl carbonate, diethyl carbonate, etc. can be used. Diphenyl carbonate and the like can be used as the diaryl carbonate.

In the artificial leather of the present invention, it is preferable that the polymeric elastomer contains polyether polyol as a constituent component. In addition, in this specification, "containing as a constituent component" means containing as a monomer component or oligomer component constituting the polymeric elastomer. Polyether polyol has a low glass transition temperature due to its high degree of freedom in ether bonds, and has a weak cohesive force, making it easy to obtain polyurethane with excellent flexibility.

In the artificial leather of the present invention, it is also a preferred embodiment that the polymeric elastic body is composed of two or more types of polymeric elastic bodies. For example, an elastic polymer A having a hydrophilic group and containing a polyether polyol as a constituent, and an elastic polymer B having a hydrophilic group containing a polycarbonate diol as a constituent. Polymer elastomer A with a hydrophilic group, which contains a polyether polyol as a component with excellent flexibility, and a hydrophilic group with a polycarbonate diol as a component with excellent durability against external stimuli such as light and heat. By including both of the polymer elastic body B in the artificial leather, it becomes easier to obtain an artificial leather having excellent flexibility and durability.

(1-2) Organic diisocyanate The organic diisocyanate used in the present invention includes aromatic diisocyanates having 6 to 20 carbon atoms (excluding carbon in the NCO group, the same applies hereinafter), and aromatic diisocyanates having 2 to 18 carbon atoms. Aliphatic diisocyanates, alicyclic diisocyanates having 4 to 15 carbon atoms, aromatic aliphatic diisocyanates having 8 to 15 carbon atoms, modified products of these diisocyanates (carbodiimide modified products, urethane modified products, uretdione modified products, etc.). ) and mixtures of two or more of these.

Specific examples of the aromatic diisocyanate having 6 to 20 carbon atoms include 1,3- and/or 1,4-phenylene diisocyanate, 2,4- and/2,6-tolylene diisocyanate, 2,4' - and/or 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'- Examples include dimethyl-4,4'-diisocyanatodiphenylmethane and 1,5-naphthylene diisocyanate.

Specific examples of the aliphatic diisocyanate having 2 or more and 18 or less carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6 -diisocyanatomethyl caproate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexaate.

Specific examples of the alicyclic diisocyanate having 4 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)- Examples include 4-cyclohexylene-1,2-dicarboxylate and 2,5- and/or 2,6-norbornane diisocyanate.

Specific examples of the aromatic aliphatic diisocyanate having 8 to 15 carbon atoms include m- and/or p-xylylene diisocyanate, α, α, α', α'-tetramethylxylylene diisocyanate, and the like. .

Among these, preferred organic diisocyanates are alicyclic diisocyanates. Furthermore, a particularly preferred organic diisocyanate is dicyclohexylmethane-4,4'-diisocyanate.

(1-3) Chain extender Chain extenders used in the present invention include water, ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol and neopentyl glycol, etc., alicyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane, aromatic diols such as 1,4-bis(hydroxyethyl)benzene, and ethylene diamine. aliphatic diamines such as isophorone diamine, aromatic diamines such as 4,4-diaminodiphenylmethane, aromatic aliphatic diamines such as xylene diamine, and alkanols such as ethanolamine. Examples include amines, hydrazine, dihydrazides such as "adipate dihydrazide," and mixtures of two or more of these.

Among these, preferred chain extenders are water, low-molecular diols, and aromatic diamines, and more preferred are water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane, and two or more of these. Mixtures may be mentioned.

(2) Additive for water-dispersed polyurethane resin In the present invention, it is preferable to include a monovalent cation-containing inorganic salt in the solution containing the water-dispersed polyurethane for reasons described later. In addition, if necessary, coloring agents such as titanium oxide, ultraviolet absorbers (benzophenone type, benzotriazole type, etc.), antioxidants [hinder such as 4,4-butylidene bis (3-methyl-6-1-butylphenol), etc. Various stabilizers such as dophenol; organic phosphites such as triphenyl phosphite and trichloroethyl phosphite], inorganic fillers (calcium carbonate, etc.), and the like can be contained.

(3) Structure of water-dispersed polyurethane resin In the water-dispersed polyurethane used in the present invention, an example of a component that causes polyurethane to contain a hydrophilic group is a hydrophilic group-containing active hydrogen component. Examples of the hydrophilic group-containing active hydrogen component include compounds containing a nonionic group and/or anionic group and/or cationic group and active hydrogen.

Examples of compounds having a nonionic group and active hydrogen include compounds containing two or more active hydrogen components or two or more isocyanate groups and having a polyoxyethylene glycol group or the like with a molecular weight of 250 to 9000 in the side chain; and triols such as trimethylolpropane and trimethylolbutane.

Examples of compounds having an anionic group and active hydrogen include carboxyl group-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, and derivatives thereof; , 3-phenylenediamine-4,6-disulfonic acid, 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid and other compounds containing sulfonic acid groups and their derivatives, as well as neutralizing these compounds. Examples include salts neutralized with agents.

Examples of compounds containing a cationic group and active hydrogen include tertiary amino group-containing compounds such as 3-dimethylaminopropanol, N-methyldiethanolamine, and N-propyldiethanolamine, and derivatives thereof.

The hydrophilic group-containing active hydrogen component can also be used in the form of a salt neutralized with a neutralizing agent.

The hydrophilic group-containing active hydrogen component used in the polyurethane molecule is 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and It is preferable to use these neutralized salts.

In the present invention, the hydrophilic group in the polymer elastomer having a hydrophilic group is a group having active hydrogen. Specific examples of hydrophilic groups include hydroxyl groups, carboxyl groups, sulfonic acid groups, and amino groups.

Further, as the polymer elastic body having a hydrophilic group, an elastic polymer body having an N-acylurea bond and/or an isourea bond can be used. When using a water-dispersed polyurethane resin as the polymeric elastomer having a hydrophilic group, the N-acylurea bond and/or isourea bond may be formed by, for example, the hydroxyl group and/or carboxyl group present as the hydrophilic group-containing active hydrogen component. It can be formed by reacting the group with a carbodiimide crosslinking agent. This imparts a three-dimensional cross-linked structure with N-acylurea bonds and/or isourea bonds, which has excellent physical properties such as light resistance, heat resistance, and abrasion resistance, and flexibility, to the molecules of the polymeric elastomer having hydrophilic groups. However, it is possible to dramatically improve physical properties such as abrasion resistance while maintaining the flexibility of artificial leather. The presence of the above-mentioned N-acylurea groups and isourea groups inside the elastic polymer body can be confirmed by mapping processing such as time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis on a cross section of artificial leather. It can be analyzed by doing this.

The number average molecular weight of the elastomeric polymer having a hydrophilic group used in the present invention is preferably 20,000 or more from the viewpoint of resin strength, and preferably 500,000 or less from the viewpoint of viscosity stability and workability. preferable. The number average molecular weight is more preferably 30,000 or more and 150,000 or less.

The number average molecular weight of the elastic polymer having a hydrophilic group can be determined by gel permeation chromatography, for example, under the following conditions.
・Equipment: HLC-8220 manufactured by Tosoh Corporation
・Column: Tosoh TSKgel α-M
・Solvent: N,N-dimethylformamide (DMF)
・Temperature: 40℃
・Calibration: Polystyrene The polymeric elastic material having a hydrophilic group used in the present invention appropriately grips the fibers in the artificial leather, and preferably has naps on at least one side of the artificial leather, so that it is suitable for nonwoven fabrics. In a preferred embodiment, it is present inside.

In the artificial leather of the present invention, it is also a preferred embodiment that the monovalent cation-containing inorganic salt is present in the elastomer polymer in an amount of 0.1% by mass or more and 1% by mass or less based on the mass of the elastomer polymer. When the content is 0.1% by mass or more, the inorganic salt inhibits the fusion between the elastic polymers, making it easier to obtain a flexible artificial leather that is an elastic polymer without voids. On the other hand, when the content is 1% by mass or less, it becomes easier to suppress the generation of voids inside the elastic polymer body. The presence of the inorganic salt inside the elastomer polymer can be analyzed by performing a mapping process such as TOF-SIMS analysis on a cross section of the artificial leather.

In the artificial leather of the present invention, it is preferable that the monovalent cation-containing inorganic salt is sodium chloride and/or sodium sulfate. The significance of using these monovalent cation-containing inorganic salts will be described later.

The artificial leather of the present invention has a basis weight measured according to JIS-L1913:2010 "General Nonwoven Fabric Test Method" 6.2 "Mass per unit area (ISO method)" in the range of 100 g/m ² to 500 g/m ² It is preferable that By setting the basis weight to preferably 100 g/m ² or more, more preferably 150 g/m ² or more, it becomes easier to obtain sufficient form stability and dimensional stability for artificial leather. On the other hand, by setting the basis weight to preferably 500 g/m ² or less, more preferably 300 g/m ² or less, it becomes easier to obtain sufficient flexibility in the artificial leather.

According to a preferred embodiment of the present invention, the artificial leather has a thickness of 0.5 mm or more and 12 mm or less as measured by JIS-L1913:2010 "General Nonwoven Fabric Test Method" 6.1 "Thickness (ISO method)" method A. It is preferable that it is in the range of . By setting the thickness to preferably 0.5 mm or more, preferably 0.7 mm or more, the abrasion resistance of the raised naps on the surface of the artificial leather improves, and when used on the surface of light-transmitting display equipment, it can be repeatedly touched by hands. This makes it easier to suppress the wear and tear of the raised naps. On the other hand, by setting the thickness to preferably 12 mm or less, more preferably 10 mm or less, sufficient flexibility can be obtained, and the resulting artificial leather is likely to have excellent moldability.

In a preferred embodiment of the artificial leather of the present invention, at least one side is subjected to a napping treatment. The napped treatment provides a fine touch when made into suede-like artificial leather.

The artificial leather of the present invention can be used as a silver-covered artificial leather by forming a resin layer on one or both sides.

In the case of silvered artificial leather, examples of the resin forming the resin layer include polyurethane, acrylic elastic, silicone elastic, diene elastic, nitrile elastic, fluorine elastic, and polystyrene elastic. Examples include resin liquids such as emulsions, suspensions, dispersions, and solutions of elastomers such as polyolefin elastomers and polyamide elastomers. These may be used alone or in combination of two or more. Among these, polyurethane is preferably used because it has excellent wear resistance and mechanical properties. Further, the resin may contain a colorant, an ultraviolet absorber, a surfactant, a flame retardant, an antioxidant, and the like, if necessary.

The artificial leather of the present invention preferably has a total light transmittance of 10% or more and 50% or less. Here, the total light transmittance is measured based on JIS-K7361:1997 "Plastics - Test method for total light transmittance of transparent materials - Part 1: Single beam method". By having a total light transmittance of 10% or more, preferably 15% or more, and more preferably 20% or more, characters and symbols can be easily recognized when placed on a decorative light source or the surface of a liquid crystal display. Become. In addition, when the content is 50% or less, preferably 45% or less, and more preferably 40% or less, there is less blurring of light transmitted through the artificial leather, and the clarity of characters and symbols is more likely to be improved.

As a means for setting the total light transmittance to 10% or more and 50% or less, for example, the above-mentioned porosity of the elastic polymer body is set to 1% or less. Furthermore, the total light transmittance can be further improved by adjusting the thickness of the artificial leather, the L value, and the ratio of the outer circumference of the fiber bundle of ultrafine fibers to which the polymer elastic body described below is in close contact.

In addition, the artificial leather of the present invention was tested in the Martindale abrasion test 2 specified by JIS-L1096:2010 "Testing methods for woven and knitted fabrics" 8.19 "Abrasion strength and abrasion discoloration" method E (Martindale method). It is preferable that the abrasion loss after 10,000 cycles is 25 mg or less. By setting the abrasion loss in the Martindale abrasion test to 25 mg or less in 20,000 times, it becomes easier to suppress fluffing during actual use and deterioration of appearance due to repeated use. The wear loss is preferably 10 mg or less, more preferably 8 mg or less, even more preferably 5 mg or less.

Next, the method for manufacturing the artificial leather of the present invention will be explained by giving an example.

In the present invention, as a means for obtaining ultrafine fibers constituting artificial leather, it is a preferred embodiment to use ultrafine fiber-expressing fibers. By preliminarily entangling ultrafine fiber-expressing fibers to form a nonwoven fabric and then ultrafine the fibers, a nonwoven fabric in which ultrafine fiber bundles are entangled can be obtained.

The ultrafine fiber developing fiber is made of two thermoplastic resin components with different solvent solubility, a sea component and an island component, and the island component is made into ultrafine fibers by dissolving and removing the sea component using a solvent or the like. Adopting sea-island type composite fibers or peelable type composite fibers in which two-component thermoplastic resins are arranged alternately in a radial or multilayered manner, and each component is split into ultra-fine fibers by peeling and splitting. I can do it.

Among these, sea-island type composite fibers are effective in improving the texture and surface quality of artificial leather because by removing the sea component, it is possible to create appropriate voids between the island components, that is, between the ultrafine fibers inside the fiber bundle. is also preferably used.

For sea-island type composite fibers, there are two methods: using a sea-island type composite spinneret, and using a polymer mutual array in which two components, a sea component and an island component, are mutually arranged and spun, and a method in which two components, a sea component and an island component, are mixed. Although it is possible to use a mixed spinning method in which fibers are spun using a single fiber, a sea-island type composite fiber using a method using mutually arranged polymers is preferably used from the viewpoint of obtaining ultrafine fibers with uniform single fiber fineness.

As the nonwoven fabric made of ultrafine fibers in the present invention, either a short fiber nonwoven fabric or a long fiber nonwoven fabric can be used. A short fiber nonwoven fabric has more fibers oriented in the thickness direction of the artificial leather than a long fiber nonwoven fabric, and a high density feeling can be obtained on the surface of the artificial leather when raised.

When short fibers are used as a nonwoven fabric and made into a nonwoven fabric by needle punching, the obtained ultrafine fiber-expressing fibers are preferably crimped and cut into a predetermined length to obtain raw cotton. A known method can be used for crimping and cutting.

Next, the obtained raw cotton is made into a fiber web using a cross wrapper or the like and entangled to obtain a nonwoven fabric. A needle punch, a water jet punch, or the like can be used as a method for entangling fiber webs to obtain a nonwoven fabric.

In the needle used for needle punching, the number of needle barbs (cuts; hereinafter sometimes simply referred to as barbs) is preferably 1 to 9. By preferably using one or more needle barbs, efficient fiber entanglement becomes possible. On the other hand, if the number of needle barbs is preferably 9 or less, fiber damage can be suppressed.

The number of composite fibers such as microfiber-expressing fibers that are caught on the barb is determined by the shape of the barb and the diameter of the composite fiber. Therefore, the barb shape of the needle used in the needle punching process has a kickup of 0 to 50 μm, an undercut angle of 0 to 40°, a throat depth of 40 to 80 μm, and a throat length of 0.5 μm. A barb of ~1.0 mm is preferably used.

Further, the number of punches is preferably 1000 punches/cm ² or more and 8,000 punches/cm ² or less. By making the number of punches preferably 1,000 punches/cm ² or more, denseness can be obtained and a highly accurate finish can be obtained. On the other hand, by preferably setting the number of punches to 8000 punches/cm ² or less, deterioration of processability, fiber damage, and decrease in strength can be prevented.

Furthermore, when water jet punching is performed, it is preferable to use water in a columnar flow state. Specifically, it is a preferred embodiment to jet water at a pressure of 1 MPa or more and 60 MPa or less from a nozzle with a diameter of 0.05 mm or more and 1.0 mm or less.

The apparent density calculated by dividing the basis weight by the thickness of a nonwoven fabric made of composite fibers (ultrafine fiber developed fibers) after needle punching or water jet punching is 0.15 g/cm 3 or more and 0.45 g/cm ³ or more. It is preferably ³ or less. By setting the apparent density to preferably 0.15 g/cm ³ or more, the artificial leather base material can have sufficient morphological stability and dimensional stability. On the other hand, by setting the apparent density to preferably 0.45 g/cm ³ or less, sufficient space for applying the elastic polymer can be maintained.

In a preferred embodiment, the nonwoven fabric is subjected to heat shrinkage treatment using hot water or steam treatment in order to improve the denseness of the fibers.

Next, the nonwoven fabric can be impregnated with an aqueous solution of the water-soluble resin and dried to impart the water-soluble resin. By adding a water-soluble resin to the nonwoven fabric, the fibers are fixed and the dimensional stability is easily improved.

As the water-soluble resin, PVA is preferably used because it has a high reinforcing effect on nonwoven fabrics and is difficult to dissolve in water. Among PVA, it is more preferable to apply PVA with a high degree of saponification, which is more water-resistant, from the viewpoint of making it difficult to elute a water-soluble resin when applying an aqueous dispersion containing an elastomer having a hydrophilic group. It is a mode.

The high saponification degree PVA preferably has a saponification degree of 95% or more and 100% or less, more preferably 98% or more and 100% or less. By setting the degree of saponification to 95% or more, it is possible to suppress elution when applying a dispersion of a polymeric elastomer having a hydrophilic group.

The degree of polymerization of PVA is preferably 500 or more and 3,500 or less, more preferably 500 or more and 2,000 or less. By setting the degree of polymerization of PVA to 500 or more, it is possible to suppress the elution of PVA with a high degree of saponification during application of the polymer elastomer dispersion. Moreover, by setting the polymerization degree of PVA to 3500 or less, the viscosity of the high saponification degree PVA liquid does not become too high, and the high saponification degree PVA can be stably applied to the nonwoven fabric.

The amount of PVA applied to the nonwoven fabric is 0.1% by mass or more and 50% by mass or less, preferably 1% by mass or more and 45% by mass or less, based on the fiber mass of the nonwoven fabric. By setting the amount of PVA to be 0.1% by mass or more, it becomes easier to obtain artificial leather with good flexibility and texture. Furthermore, by controlling the amount of PVA to be applied to 50% by mass or less, it becomes easier to obtain artificial leather with good processability and good physical properties such as abrasion resistance.

In one embodiment of the method for producing artificial leather of the present invention, an elastomeric polymer resin having a hydrophilic group is provided to a nonwoven fabric. The elastomeric polymer resin having a hydrophilic group can be applied to either a nonwoven fabric made of composite fibers or a nonwoven fabric made into ultrafine fibers.

In one embodiment of the method for producing artificial leather of the present invention, water containing a polymeric elastomer having a hydrophilic group, an inorganic salt containing a monovalent cation, and a crosslinking agent, based on the weight of fibers of the nonwoven fabric. It is preferable that the elastomer is impregnated with a dispersion liquid and heat-treated at a temperature of 100° C. or more and 180° C. or less to dry heat solidify the elastic polymer body.

With other coagulation methods, such as the hydrothermal coagulation method in which an elastic polymer having a hydrophilic group is coagulated in hot water, the elastic polymer diffuses into the hot water and partially falls off, resulting in concerns about processability. There is. Furthermore, in the acid coagulation method in which an elastomer polymer having a hydrophilic group is coagulated with an acid, it is necessary to neutralize the acidic solution remaining in the sheet, which is not preferable in terms of processing operability. On the other hand, the dry heat coagulation method is a very simple method in which a sheet impregnated with an elastic polymer having hydrophilic groups is heated in a hot air dryer, etc., and there is no fear of the elastic polymer falling off. , is a method with excellent workability.

In one embodiment of the method for producing artificial leather of the present invention, an inorganic salt containing a monovalent cation is contained in an aqueous dispersion of an elastomer having a hydrophilic group. By containing the monovalent cation-containing inorganic salt, heat-sensitive coagulability can be imparted to the aqueous dispersion of the polymeric elastomer having a hydrophilic group. In the present invention, heat-sensitive coagulation property means that when an aqueous dispersion of an elastomer polymer having a hydrophilic group is heated, when a certain temperature (thermal coagulation temperature) is reached, the elastomer's water dispersion has a hydrophilic group. Refers to the property that the fluidity of a dispersion liquid decreases and coagulates.

If the elastomer polymer having a hydrophilic group does not have heat-sensitive coagulability, migration is likely to occur, in which the elastomer polymer having a hydrophilic group migrates to the sheet surface as water evaporates. Due to migration, the elastic polymer material is unevenly distributed only on the surface of the artificial leather, which significantly hardens the texture of the artificial leather.

In a preferred embodiment, the heat-sensitive solidification temperature of the aqueous dispersion of the elastomer having a hydrophilic group is 80°C or more and 95°C or less. By setting the heat-sensitive coagulation temperature to 80°C or higher, it is possible to create a structure in which the polymeric elastic body is in close contact with the fiber bundle, and it is also possible to suppress the adhesion of the polymeric elastic body to the machine during operation. . In addition, by setting the heat-sensitive coagulation temperature to 95°C or lower, it is possible to suppress the migration phenomenon of the polymer elastic material to the surface layer of the nonwoven fabric, and it is possible to achieve both excellent wear resistance and good quality. .

In one aspect of the method for producing artificial leather of the present invention, it is preferable to use an inorganic salt containing a monovalent cation as the inorganic salt used as the heat-sensitive coagulant. The monovalent cation-containing inorganic salt is preferably sodium chloride and/or sodium sulfate. In conventional methods, inorganic salts with divalent cations such as magnesium sulfate and calcium chloride have been suitably used as heat-sensitive coagulants; Depending on the type of polymer elastomer, it is difficult to strictly control the heat-sensitive gelation temperature by adjusting the content, as this greatly affects the stability of the aqueous dispersion of the elastomer. There were issues such as concerns about gelation during preparation and storage of the aqueous dispersion of the elastic material. On the other hand, monovalent cation-containing inorganic salts with low ionic valences have little effect on the stability of aqueous dispersions, and by adjusting their content, thermosensitive This makes it easier to strictly control the solidification temperature.

Further, in one embodiment of the method for producing the artificial leather of the present invention, it is preferable that the monovalent cation-containing inorganic salt is contained in an amount of 1% by mass or more and 10% by mass or less based on the solid content of the elastomer polymer having a hydrophilic group. . By setting the content to 1% by mass or more, the aqueous dispersion of the elastomer polymer having a hydrophilic group exhibits dry heat coagulation properties, and migration of the elastomer polymer can be suppressed. On the other hand, by setting the content to 10% by mass or less, good light transmittance and excellent abrasion resistance can be easily obtained. Furthermore, the stability of an aqueous dispersion of an elastomer having a hydrophilic group can be easily maintained.

In one aspect of the method for producing artificial leather of the present invention, the heating temperature in dry heat coagulation is 100°C or more and 180°C or less. More preferably, the temperature is 120°C or more and 160°C or less. By setting the heating temperature to 100° C. or higher, the elastic polymer having a hydrophilic group can be rapidly solidified, and uneven distribution of the elastic polymer on the lower surface of the sheet due to its own weight can be suppressed. Furthermore, in the present invention, it is necessary to use a crosslinking agent in combination, but by setting the temperature above, the crosslinking reaction can be sufficiently promoted and the physical properties can be improved. Furthermore, by setting the heating temperature to 180° C. or lower, thermal deterioration of the elastic polymer can be suppressed.

The concentration of the aqueous dispersion of the elastomer polymer having hydrophilic groups (the content of the elastomer polymer in the aqueous dispersion of the elastomer polymer having hydrophilic groups) is the concentration of the elastomer polymer having hydrophilic groups. From the viewpoint of storage stability of the aqueous dispersion, the content is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 40% by mass or less.

In addition, in order to improve storage stability and film forming properties, a water-soluble organic solvent is added to an aqueous dispersion of an elastomer polymer having a hydrophilic group. The organic solvent content may be 40% by mass or less, but from the viewpoint of preserving the film forming environment, the content of the organic solvent is preferably 1% by mass or less.

In one embodiment of the method for producing artificial leather of the present invention, it is preferable that the aqueous dispersion of the elastomer polymer having a hydrophilic group contains a crosslinking agent. By introducing a three-dimensional network structure into the polymer elastic body using a crosslinking agent, physical properties such as abrasion resistance can be improved. Furthermore, when used in combination with the above-mentioned monovalent cation-containing inorganic salt, it is possible to soften the artificial leather by controlling the adhesive structure between the polymer elastic body and the fibers, and at the same time, it is possible to achieve high physical properties of the artificial leather.

The crosslinking agent is preferably a carbodiimide crosslinking agent because the polymeric elastomer obtained after the reaction has excellent light resistance, heat resistance, abrasion resistance, and good flexibility.

In one embodiment of the method for producing artificial leather of the present invention, it is a preferred embodiment that the polymeric elastomer contains polyether polyol as a constituent component. The reason is as described in the section (1-1) High molecular weight polyol above.

Further, in one embodiment of the method for producing artificial leather of the present invention, an elastic polymer X having a hydrophilic group and an elastic polymer Y having a hydrophilic group, which have different compositions from each other, are mixed into the aqueous dispersion. It is also possible to coagulate the elastic polymer Y having a hydrophilic group after coagulating the elastic polymer X having a hydrophilic group. By adjusting the content of the inorganic salt having a monovalent cation, each heat-sensitive coagulation is performed so that the elastic polymer B having a hydrophilic group is coagulated after the elastic polymer A having a hydrophilic group is coagulated. It is possible to adjust the temperature and control the distribution of the two types of polymer elastic bodies in the artificial leather. As a result, for example, the elastic polymer X having a hydrophilic group is made into an elastic polymer having excellent flexibility such as a polyether-based elastic polymer, and the elastic polymer Y having a hydrophilic group is made into an elastic polymer having excellent durability. By using a polycarbonate-based polymer elastic body with excellent physical properties, it becomes easier to obtain artificial leather that is flexible and has excellent physical properties.

Next, the obtained nonwoven fabric is treated with a solvent to develop ultrafine fibers. The ultrafine fiber development treatment can be carried out by immersing a nonwoven fabric made of sea-island composite fibers in a solvent to dissolve and remove sea components. Incidentally, the ultrafine fiber development treatment may be performed before imparting the polymer elastic body to the nonwoven fabric.

When the ultrafine fiber-expressing fiber is a sea-island composite fiber, the solvent for dissolving and removing the sea component may be an organic solvent such as toluene or trichlorethylene when the sea component is polyethylene, polypropylene, or polystyrene. Moreover, when the sea component is copolymerized polyester or polylactic acid, an alkaline aqueous solution such as sodium hydroxide can be used. Moreover, when the sea component is a water-soluble thermoplastic polyvinyl alcohol resin, hot water can be used.

If necessary, the method may include a step of removing PVA from the nonwoven fabric provided with the polymer elastic body having hydrophilic groups. A flexible artificial leather is obtained by removing PVA from a nonwoven fabric having a hydrophilic group-containing polymer elastomer, but the method for removing PVA is not particularly limited. In a preferred embodiment, the sheet is dissolved and removed by immersing the sheet in hot water at a temperature of 0.degree.

In the cross-section of the artificial leather of the present invention, it is preferable that the polymeric elastic body is in close contact with 35% or more and 100% or less of the outer periphery of the cross-section of the fiber bundle of ultrafine fibers. Preferably 35% or more, more preferably 45% or more of the outer periphery of the cross-section of the microfiber bundle is in close contact with the polymeric elastic material, so that light at the interface between the microfibers or the polymeric elastic material and air is reduced. Since the reflection and refraction of the artificial leather is suppressed, even if the artificial leather is thick, it tends to have sufficient light transmittance. In addition, the ratio of the outer periphery of the ultrafine fiber bundle to which the polymer elastic body is in close contact is preferably 100% or less, more preferably 80% or less, so that the area where the polymer elastic body restrains the ultrafine fiber bundle is preferably 100% or less, and more preferably 80% or less. This can prevent the texture of artificial leather from becoming hard.

FIG. 3 shows a schematic diagram of an example of the outer periphery of a cross-section of a fiber bundle of ultrafine fibers in close contact with a polymeric elastic body in the present invention. In FIG. 3, the ultrafine fibers 1 form a fiber bundle. In a part of the outer periphery 2 of the cross section of the fiber bundle of ultrafine fibers, there is a portion 4 in which the polymer elastic body 3 is in close contact.

In the present invention, the polymer elastic body is in close contact with 35% or more and 100% or less of the outer circumference of the cross-section of the fiber bundle of ultra-fine fibers, which means that the elastic polymer is in close contact with 100% of the entire outer circumference of the cross-section of the fiber bundle of ultra-fine fibers. This means that the length of the outer circumference of the part where the polymeric elastic body is in close contact is 35% or more and 100% or less.

FIG. 4 shows an example of a microscopic photograph of an elastic polymer that is in close contact with the outer periphery of a cross-section of a fiber bundle of ultrafine fibers. In FIG. 5, of the outer periphery of the cross-section of the microfiber bundle of FIG. 4, the portion where the polymer elastic body is in close contact is shown with a solid line, and the portion with which it is not in close contact is shown with a dotted line.

As a means for making the ratio of the fiber bundle outer periphery to which the polymeric elastic body is in close contact with 35% or more and 100% or less, for example, as described above, an aqueous dispersion of a polymeric elastic body having a hydrophilic group is used. When creating artificial leather by using the monovalent cation-containing inorganic salt, the content of the monovalent cation-containing inorganic salt may be 10% by mass or less based on the solid content of the polymer elastomer having a hydrophilic group.

From the viewpoint of manufacturing efficiency, the artificial leather to which the polymeric elastic body has been added may be cut in half in the thickness direction.

A raising treatment can be applied to the surface of artificial leather to which a polymeric elastomer has been applied or artificial leather that has been cut in half. The raising treatment can be performed by, for example, a method of grinding using sandpaper, a roll sander, or the like.

When a napping treatment is performed, a lubricant such as a silicone emulsion can be applied before the napping treatment. Further, it is a preferable embodiment to apply an antistatic agent before the raising treatment because grinding powder generated from the artificial leather during grinding becomes difficult to accumulate on the sandpaper. In this way, raised artificial leather is formed.

The density of the artificial leather of the present invention is preferably 0.2 to 0.7 g/cm ³ . By setting the density to 0.2 g/cm ³ or more, more preferably 0.3 g/cm ³ or more, the surface appearance becomes dense and high quality is easily expressed. On the other hand, by setting the density to 0.7 g/cm ³ or less, more preferably 0.6 g/cm ³ or less, it is possible to prevent the texture of the artificial leather from becoming hard.

The artificial leather of the present invention preferably has an L value of 50 or less as measured by a color difference meter. Here, the L value represents the L* value defined in JIS-Z8781-4:2013 "Colorimetry - Part 4: CIE 1976 L*a*b* Color Space". The L value is more preferably 40 or less, still more preferably 30 or less. When the L value is within this range, when used as artificial leather for a light-transmissive touch panel, changes in appearance due to dirt such as sebum that adheres due to repeated use are easily suppressed. Further, since the L value is preferably 10 or more, and more preferably 20 or more, good visibility is likely to be obtained when used as artificial leather for a light-transmitting touch panel.

Examples of methods for achieving an L value of 50 or less include methods of adding pigments to ultrafine fibers, methods of including pigments to polymeric elastomers, and methods of coloring ultrafine fibers by dyeing. One method is to do so. In the method of incorporating pigments into ultrafine fibers and/or polymeric elastomer, transmitted light may be absorbed and scattered by the pigment, so a method of coloring the ultrafine fibers by dyeing is more preferable.

As a method for dyeing artificial leather, it is preferable to use a jet dyeing machine, since it is possible to dye the artificial leather and at the same time give a rubbing effect to soften the artificial leather. If the dyeing temperature of artificial leather is too high, the elastic resin may deteriorate, and if it is too low, the dyeing temperature on the fibers will be insufficient, so it is preferable to set it depending on the type of fiber. The dyeing temperature is generally preferably 80°C or higher and 150°C or lower, more preferably 110°C or higher and 130°C or lower.

The dye can be selected depending on the type of fiber constituting the artificial leather. For example, disperse dyes can be used for polyester fibers, acid dyes or metal-containing dyes can be used for polyamide fibers, and combinations thereof can be used.

It is also a preferred embodiment to use a dyeing aid when dyeing artificial leather. By using a dyeing aid, the uniformity and reproducibility of dyeing can be improved. Further, in the same bath as dyeing or after dyeing, a finishing agent treatment using a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a light stabilizer, an antibacterial agent, etc. can be performed.

EXAMPLES Hereinafter, the present invention will be explained in more detail using Examples, but the present invention is not limited to the following Examples.
[Evaluation method]
(1) Porosity of elastic polymer body Ten cross-sectional images of artificial leather taken randomly at 500x magnification using a scanning electron microscope (SEM) were printed on A4 size paper, and the area around the cut surface of the elastic polymer body ( Area A) and the periphery of the voids existing inside the elastic polymer body (area B) are surrounded by black lines. At the time of photographing, the boundaries of the cut surfaces of the elastic polymer were confirmed by moving the focus of the SEM back and forth. A cut surface of the elastic polymer body was cut out along the black line, and the weight was measured using an electronic balance (weight A). Next, voids in the elastic polymer were cut out along the black lines surrounding region B, and the weight of region B was measured using an electronic balance (weight B). The porosity of the polymer elastic body in each artificial leather cross-sectional image was calculated from the measured weight using the following formula, and the arithmetic average value of 10 images was taken as the porosity.

(Formula 1) (Porosity of elastic polymer body (%)) = {(Weight B)/(Weight A)} x 100
(2) Total light transmittance of artificial leather Based on JIS-K7361:1997 "Plastics - Test method for total light transmittance of transparent materials - Part 1: Single beam method", a turbidity meter (Nippon Denshoku Kogyo Co., Ltd. Measurements were made using the "NDH4000" manufactured by ), so that the light was incident on the artificial leather from a half-cut surface.
(3) Color difference measurement Using a color difference meter (manufactured by Konica Minolta, CR-410), as specified in JIS-Z8781-4:2013 "Color measurement - Part 4: CIE 1976 L*a*b* color space" L*a*b* values (herein simply referred to as "L value", "a value", and "b value") were measured. Select 10 measurement points at random in the in-plane direction on the surface opposite to the adhesive surface with the light-transmissive display material, or the surface opposite to the half-cut surface, and measure the L value, a value, and b value respectively. The average was calculated. However, if artificial leather of sufficient size cannot be obtained to select 10 measurement points, the average of 10 measurements at one measurement point was calculated and used as the L value, a value, and b value.
(4) Percentage of elastic polymer that is in close contact with the outer periphery of the cross section of the fiber bundle (elastic polymer coverage)
Ultrafine fibers in which the angle between the length direction of the ultrafine fibers and the cross section of the artificial leather is between 45° and 90° in 10 cross-sectional images of artificial leather taken randomly at 500x magnification using a scanning electron microscope (SEM). Among the fiber bundles, five ultrafine fiber bundles in which the angle between the length direction of the fibers and the cross section of the artificial leather is closer to 90° are randomly selected from among the ultrafine fiber bundles in which the polymeric elastic material is in close contact with each other. The outer circumferential length of the cross section (outer circumferential length A) and the outer circumferential length of the ultrafine fiber bundle (outer circumferential length B) in the part where the polymeric elastic body is in close contact were measured using ImageJ (version: 1.44p). The polymer elastic material coverage of each ultrafine fiber bundle was calculated from the measured outer circumferential length using the following formula, and the arithmetic average of a total of 50 fiber bundles was taken as the polymer elastic material coverage.

(Formula 2) (Polymer elastic body coverage (%)) = (Outer circumference length B) / (Outer circumference length A) x 100
(5) Abrasion evaluation of artificial leather Abrasion evaluation was performed based on JIS-L1096:2010 "Testing methods for woven and knitted fabrics" 8.19 "Abrasion strength and abrasion discoloration" E method (Martindale method). As a Martindale abrasion tester, James H. Heal&Co. Model 406 manufactured by the same company was used, and ABRASTIVE CLOTHSM25 manufactured by the same company was used as the standard friction cloth. After applying a load of 12 kPa to the artificial leather and abrading it 20,000 times, the appearance of the artificial leather was visually observed and pilling was evaluated. The evaluation criteria were as follows: 5th grade was when the appearance of the artificial leather had not changed at all from before wear, 1st grade was when a large number of pilling occurred, and 0.5 grades were divided between the two.

Furthermore, the weight loss due to abrasion was calculated using the following formula using the mass of the artificial leather before and after abrasion.
Wear loss (mg) = Mass before wear (mg) - Mass after wear (mg)
(6) Solidification temperature of an aqueous dispersion of an elastomer polymer having a hydrophilic group Testing 20 g of an aqueous dispersion containing an elastomer polymer having a hydrophilic group prepared in each Example and Comparative Example with an inner diameter of 12 mm. After inserting the thermometer into the tube so that the tip is below the liquid level, the test tube is sealed and the aqueous dispersion of the polymeric elastomer having hydrophilic groups is placed in a hot water bath at a temperature of 95°C. immersed in water so that the liquid level was below the liquid level in the hot water bath. While checking the temperature rise in the test tube with a thermometer, lift the test tube for up to 5 seconds at a time to check whether the liquid surface of the aqueous dispersion of the elastomer having a hydrophilic group has fluidity. The sample was shaken to such an extent that the dispersion of the elastomer polymer having a hydrophilic group could be confirmed, and the temperature at which the liquid surface of the aqueous dispersion of the elastomer having a hydrophilic group lost its fluidity was defined as the solidification temperature. This measurement was performed three times for each type of aqueous dispersion of an elastomer having a hydrophilic group, and the average value was calculated.
(7) Measurement of inorganic salt species and content contained in artificial leather 10 g of artificial leather was immersed in 100 mL of dimethylformamide at room temperature overnight, and the solution in which the polymeric elastomer and inorganic salts were eluted was heated at 140°C. It was concentrated and solidified by drying. 100 mL of distilled water was added to the obtained solid to elute only the inorganic salt. After drying the aqueous solution containing the inorganic salt by heating, the amount of the inorganic salt contained in the artificial leather was measured. Further, the solidified polymer elastic body was also heated and dried, and its weight was measured, and the weight of the inorganic salt relative to the mass of the polymer elastic body was calculated.

The type of inorganic salt was identified using an ion chromatography device, ICS-3000 manufactured by Dionex, for the aqueous solution containing the above-mentioned inorganic salt.
[Example 1]
(Nonwoven fabric)
Using 8 mol% SSIA (sodium 5-sulfoisophthalate) copolyester as the sea component and polyethylene terephthalate as the island component, the number of islands was determined with a composite ratio of 20% by mass for the sea component and 80% by mass for the island component. A sea-island composite fiber with 16 islands/1 filament and an average single fiber fineness of 20 μm was obtained. The obtained sea-island composite fibers were cut into staples with a fiber length of 51 mm, passed through a card and a cross wrapper to form a fiber web, and subjected to needle punching to produce a nonwoven fabric with a basis weight of 700 g/m ² and a thickness of 3.1 mm. was manufactured. The nonwoven fabric thus obtained was immersed in hot water at a temperature of 98°C for 2 minutes to shrink, and dried at a temperature of 100°C for 5 minutes.

(fiber reinforcement)
The above nonwoven fabric was impregnated with a 10% by mass aqueous solution of PVA (NM-14 manufactured by Nippon Gosei Kagaku Co., Ltd.) with a degree of saponification of 99% and a degree of polymerization of 1400, and heated and dried at a temperature of 140°C for 10 minutes to form the nonwoven fabric. A PVA-applied sheet was obtained in which the amount of PVA attached to the mass was 30% by mass.

(Applying polymeric elastomer resin)
A prepolymer was created in a toluene solvent using polytetramethylene ether glycol with a number average molecular weight (Mn) of 2,000 as a polyol, MDI as an isocyanate, and 2,2-dimethylolpropionic acid as a component containing a hydrophilic group. did. Ethylene glycol and ethylene diamine were added as chain extenders, and polyoxyethylene nonylphenyl ether and water were added as external emulsifiers, followed by stirring. Toluene was removed under reduced pressure to obtain an aqueous dispersion Wa of elastomer polymer a having hydrophilic groups. In addition, the polymer elastic body a corresponds to the polymer elastic body A. 5% by mass of sodium sulfate as a heat-sensitive coagulant and 3% by mass of a carbodiimide crosslinking agent are added to 100% by mass of solid content of elastomer a having a hydrophilic group, and the solid content is 12% by mass with water. % to obtain an aqueous dispersion containing a polymeric elastomer a having a hydrophilic group. The thermal coagulation temperature of the aqueous dispersion was measured and found to be 90°C. The obtained PVA-applied microfiber nonwoven fabric was immersed in the aqueous dispersion, and then heated with hot air at 150° C. for 15 minutes. As a result, a 1.9 mm thick elastomer polymer resin-applied sheet was obtained, in which 25% by mass of the elastomer polymer A was added based on the weight of the fibers.

(ultra-fine fiber)
The resulting polymeric elastomer resin-applied sheet was immersed in a sodium hydroxide aqueous solution with a concentration of 8 g/L heated to a temperature of 95°C and treated for 30 minutes to obtain ultrafine fibers from which the sea component of the sea-island composite fibers was removed. A sheet made of an elastic polymer was obtained.

(Removal of reinforcing resin)
The resulting polymer elastomer resin-applied sheet was immersed in water heated to 95°C for 10 minutes to remove the applied PVA, thereby obtaining artificial leather.

(Half-cut and brushed)
The resulting polymer elastomer resin-applied sheet after PVA removal was cut in half perpendicularly to the thickness direction, and the opposite side of the half-cut surface was ground with endless sandpaper with a sandpaper size of 240 to a thickness of 0.7 mm. An artificial leather having raised naps was obtained.

(dyeing and finishing)
The resulting raised artificial leather was dyed using a jet dyeing machine at a temperature of 120°C using disperse dye A (anthraquinone type), and then dried in a drier to obtain an average of ultrafine fibers. An artificial leather having a single fiber fineness of 4.4 μm was obtained. The obtained artificial leather had an L value of 49, an a value of 9, a b value of 52, and a good total light transmittance of 37%. The porosity of the polymer elastic body was 0%, and it had excellent wear resistance.
[Example 2]
(dyeing and finishing)
The same process as in Example 1 was carried out, including half-cutting and napping. (a mixture of azo and anthraquinone) was used for staining. Next, it was dried in a dryer to obtain artificial leather having an average single fiber fineness of ultrafine fibers of 4.4 μm. The obtained artificial leather had an L value of 37, an a value of -10, a b value of -11, and a good total light transmittance of 23%. The porosity of the polymer elastic body was 0%, and it had excellent wear resistance.
[Example 3]
(dyeing and finishing)
The process was carried out in the same manner as in Example 1, including half-cutting and raising, and the resulting raised artificial leather was dyed with a different dispersion than the disperse dyes A and B of Example 1 using a jet dyeing machine at a temperature of 120°C. Dyeing was performed using dye C (a mixture of azo and anthraquinone). Next, it was dried in a dryer to obtain artificial leather having an average single fiber fineness of ultrafine fibers of 4.4 μm. The obtained artificial leather had an L value of 28, an a value of 50, a b value of 2, and a good total light transmittance of 21%. The porosity of the polymer elastic body was 0%, and it had excellent wear resistance.
[Example 4]
Artificial leather was obtained in the same manner as in Example 3, except that the thickness was set to 0.9 mm when cutting in half and raising. The obtained artificial leather had a good total light transmittance of 17%, and the porosity of the elastomer polymer was 0%, indicating excellent abrasion resistance.
[Example 5]
Artificial leather was obtained in the same manner as in Example 3, except that the material was not cut in half during the raising process and the thickness was set to 1.2 mm. The obtained artificial leather had a good total light transmittance of 12%, the porosity of the elastic polymer body was 0%, and had excellent abrasion resistance.
[Example 6]
In the step of imparting a polymeric elastomer, polyhexamethylene carbonate having an Mn of 2,000 is used as a polyol, hydrogenated MDI is used as an isocyanate, a diol compound having polyethylene glycol in the side chain as a component containing a hydrophilic group, and 2, A prepolymer was prepared using 2-dimethylolpropionic acid in an acetone solvent. Ethylene glycol, ethylene diamine, and water were added as chain extenders and stirred. Acetone was removed under reduced pressure to obtain an aqueous dispersion Wb of the elastomer b having hydrophilic groups. The aqueous dispersion Wa and the aqueous dispersion Wb are mixed, and a polymer elastomer a having a hydrophilic group having a solid content of each elastomer polymer of 20% by mass and a total solid content of 40% by mass is prepared. An aqueous dispersion Wc containing b was obtained. By adding 5% by mass of sodium chloride as a heat-sensitive coagulant, the heat-sensitive coagulation temperature of the elastomer polymer a having a hydrophilic group is 85°C, and the heat-sensitive coagulation temperature of the elastomer polymer b having a hydrophilic group is 90°C. Prepared as follows. An artificial leather was obtained in the same manner as in Example 3 except that this aqueous polymer elastomer dispersion was used. The obtained artificial leather had a good total light transmittance of 20%, the porosity of the elastic polymer body was 0%, and had excellent abrasion resistance.
[ Comparative example 4 ]
Artificial leather was obtained in the same manner as in Example 1 except that the thickness was set to 0.4 mm when cutting in half and raising. The porosity of the polymer elastic body was 0%, the total light transmittance of the obtained artificial leather was as high as 52%, and it had good abrasion resistance.
[Comparative example 1]
When applying the polymer elastomer, a DMF (N,N-dimethylformamide) solution of polycarbonate polyurethane adjusted to a solid content concentration of 12% by mass is impregnated, and the polyurethane is coagulated in an aqueous solution with a DMF concentration of 30% by mass. Ta. Thereafter, polyvinyl alcohol and DMF were removed with hot water, and the product was dried with hot air at a temperature of 150° C. for 15 minutes. Artificial leather was obtained in the same manner as in Example 1 except for the above. In the obtained artificial leather, the porosity of the polymer elastic body was 2.1%. The L value was 49, the a value was 9, the b value was 52, and the total light transmittance was 9%.
[Comparative example 2]
(Nonwoven fabric)
Using polystyrene as the sea component and polyethylene terephthalate as the island component, the composite ratio is 20% by mass for the sea component and 80% by mass for the island component, the number of islands is 16 islands/1 filament, and the average single fiber fineness is 20 μm. A sea-island composite fiber was obtained. The obtained sea-island composite fibers were cut into staples with a fiber length of 51 mm, passed through a card and a cross wrapper to form a fiber web, and subjected to needle punching to produce a nonwoven fabric with a basis weight of 700 g/m ² and a thickness of 3.1 mm. was manufactured.

(fiber reinforcement)
The above nonwoven fabric was immersed in a 12% by mass aqueous solution of PVA with a degree of saponification of 88% and a degree of polymerization of 500 heated to 95°C, and was subjected to shrinkage treatment for 2 minutes at the same time as the PVA impregnation. Drying was performed by heating for a minute. A PVA-applied sheet was obtained in which the amount of PVA attached to the fiber mass of the nonwoven fabric was 25% by mass.

(ultra-fine fiber)
The obtained PVA-applied sheet was treated with trichlene at 30° C. until the polystyrene was completely removed, thereby obtaining a nonwoven fabric made of ultrafine fibers from which the sea component of the sea-island composite fibers had been removed.

(Applying polymeric elastomer resin)
The resulting nonwoven fabric made of ultrafine fibers was impregnated with a DMF (N,N-dimethylformamide) solution of polycarbonate polyurethane adjusted to a solid content concentration of 12% by mass, and the polyurethane was coagulated in an aqueous solution with a DMF concentration of 30% by mass. . Thereafter, polyvinyl alcohol and DMF were removed with hot water, and the product was dried with hot air at a temperature of 120° C. for 10 minutes. As described above, artificial leather was obtained in which 30% by mass of a polymeric elastic material was added to a nonwoven fabric made of ultrafine fibers. This polymeric elastomer resin-applied sheet was cut in half, raised, dyed, and finished in the same manner as in Example 1 to obtain raised artificial leather. The porosity of the obtained raised artificial leather was as high as 1.8%, and the total light transmittance of the obtained artificial leather was insufficient at 7%.
[Comparative example 3]
An artificial leather was obtained in the same manner as in Example 1, except that 20% by mass of sodium sulfate was added to the aqueous dispersion of the elastomer polymer. The porosity of the polymer elastic body was as high as 1.5%, and the total light transmittance of the obtained artificial leather was insufficient at 8%.

The artificial leather of the present invention has sufficient light transmittance and can suppress deterioration of appearance quality due to repeated use, so it can be used for home appliances and other products by placing it on the surface of a decorative light source or liquid crystal display. It can be used as a good light-transmitting display material that improves design in vehicles and building materials.

1 Ultrafine fibers 2 Outer periphery of the cross section of the fiber bundle of ultrafine fibers 3 Elastic polymer body 4 Close contact portion

Claims (3)

An artificial leather made of a nonwoven fabric made of ultrafine fibers and an elastic polymer, the ultrafine fibers forming a fiber bundle,
Each of the fiber bundles includes 2 or more and 500 or less ultrafine fibers,
The porosity of the elastic polymer body is 1% or less,
The L value measured with a color difference meter is 50 or less,
The total light transmittance is 10% or more and 50% or less,
In the cross section of the artificial leather, the polymer elastic body is in close contact with 35% or more and 100% or less of the outer periphery of the cross section of the fiber bundle of the ultrafine fibers,
The thickness is 0.5 mm or more and 1.2 mm or less,
An inorganic salt containing a monovalent cation is present in the elastic polymer body in an amount of 0.1% by weight or more and 1% by weight or less based on the mass of the elastic polymer body .
Artificial leather for light-transmitting display equipment. The artificial leather for light-transmissive display equipment according to claim 1, wherein the L value measured by the color difference meter is 40 or less. A nonwoven fabric made of entangled ultrafine fiber-expressing fibers, which are sea-island composite fibers consisting of a sea component and an island component, is impregnated with an aqueous solution of a water-soluble resin, and dried to impart the water-soluble resin.
The nonwoven fabric provided with the water-soluble resin is impregnated with an aqueous dispersion containing an elastomer having a hydrophilic group, an inorganic salt containing a monovalent cation, and a crosslinking agent, and the temperature is at 100°C or more and 180°C or less. heat treatment at a temperature of to thermally solidify the elastomer polymer having the hydrophilic group,
removing the water-soluble resin from the nonwoven fabric obtained by thermally coagulating the polymeric elastomer having a hydrophilic group;
A method for producing artificial leather for light-transmissive display equipment, the method comprising:
The water-soluble resin is PVA with a high saponification degree of 95% or more and 100% or less,
In the aqueous dispersion, the monovalent cation-containing inorganic salt is contained in an amount of 1% by mass or more and 10% by mass or less based on the solid content of the polymeric elastomer having a hydrophilic group.
A method for producing artificial leather for light-transmissive display equipment according to claim 1 or 2.