Developing roller

Abstract

To provide a developing roller with excellent triboelectric charging properties (toner charge amount) and toner transport properties for toner with reduced particle size. [Solution] Shaft and, An elastic layer formed on the outer circumference of the shaft, A resin coating layer formed on the outermost surface of the elastic layer, It has, The elastic layer has a hardness (Duro-A) of 30 degrees or more and 50 degrees or less. The aforementioned resin coating layer contains 0.8% to 12% by mass of fluorine-containing resin, has a hardness (Duro-A) of 81 degrees to 96 degrees, a thickness of 0.8 μm to 4.5 μm, and a surface roughness (RzJIS) of 3 μm to 10 μm. A developing roller characterized by being used for transporting positively charged toner with a non-magnetic, single-component developing method, and having a perfectly spherical shape with an average particle diameter of 6 μm to 10 μm.

Description

Technical Field

[0001] The present invention relates to a developing roller used for a non-magnetic one-component toner in an electrophotographic apparatus such as a printer or a copier.

Background Art

[0002] Electrophotographic apparatuses are roughly classified into a two-component system using a two-component developer mainly composed of toner and carrier, and a one-component system using a developer composed only of toner. The non-magnetic one-component system has become the mainstream because it is suitable for color printing, does not require toner density control, has a simple configuration, and can be miniaturized and cost-reduced. Currently, in electrophotographic apparatuses, the method in which both the photoreceptor and the toner are negatively charged is the mainstream, but the method in which the toner is positively charged is also partly used. When the toner is positively charged, if the surface of the developing roller is a conventionally commonly used acrylic resin or urethane resin, there is a problem that it is difficult to impart sufficient positive charge to the toner. In addition, there is a problem that toner filming occurs easily where external additives of the toner adhere to the surface of the developing roller during use, and the characteristics of the developing roller deteriorate.

[0003] Here, fluorine is easily negatively charged and has a low surface free energy. Therefore, a developing roller having fluorine blended in the outermost surface can easily charge the toner positively by friction, and toner filming is unlikely to occur because the toner hardly adheres. For example, in Patent Document 1, there is proposed an invention of a developing roller for supplying toner to a photoreceptor by positively charging the toner in a non-magnetic one-component developing type electrophotographic apparatus, which includes a surface layer formed of a resin in which an acrylic resin and a fluorine resin are blended on the surface of the developing roller and the blending amount of the acrylic resin is 5 to 40% by weight, and can charge the toner sufficiently.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-223046 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In electrophotographic equipment, the average particle size of toner is being reduced to improve image quality. However, as the toner particle size decreases, the surface area increases, which negatively impacts the toner's electrostatic properties. Furthermore, as the toner particle size decreases, the proportion of external additives required increases, making toner filming more likely. In the conventional developing roller described in Patent Document 1, when the amount of fluorine-containing resin was increased to enhance the electrostatic properties of the toner, the coefficient of friction of the developing roller surface became too low, resulting in insufficient friction with the toner and a further decrease in electrostatic properties. In other words, conventional developing rollers, such as the one described in Patent Document 1, which have a layer containing fluorine-containing resin on the outermost surface, have problems with insufficient triboelectric charging (toner charge amount) and toner transport amount for toner with smaller particle sizes. [Means for solving the problem]

[0006] The means to solve the above problems are as follows: 1. The shaft and, An elastic layer formed on the outer circumference of the shaft, A resin coating layer formed on the outermost surface of the elastic layer, It has, The elastic layer has a hardness (Duro-A) of 30 degrees or more and 50 degrees or less. The aforementioned resin coating layer contains 0.8% to 12% by mass of fluorine-containing resin, has a hardness (Duro-A) of 81 degrees to 96 degrees, a thickness of 0.8 μm to 4.5 μm, and a surface roughness (RzJIS) of 3 μm to 10 μm. A developing roller characterized by being used for transporting positively charged toner with a non-magnetic, single-component developing method, and having a perfectly spherical shape with an average particle diameter of 6 μm to 10 μm. 2. The developing roller according to claim 1, characterized in that the elastic layer contains thermosetting polyurethane. 3. The developing roller according to 1. or 2., characterized in that the resin coating layer contains thermoplastic polyurethane. [Effects of the Invention]

[0007] The developing roller of the present invention is suitable for transporting positively charged toner with a spherical shape, average particle diameter of 6 μm to 10 μm, and a non-magnetic, single-component developing method. The developing roller of the present invention has a large charge capacity, an appropriate transport volume, is less prone to toner filming, and can suppress the decrease in toner charge capacity even after long-term use. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing the structure of a developing roller. [Modes for carrying out the invention]

[0009] The basic structure of the developing roller of the present invention is shown in Figure 1. The developing roller 1 comprises a shaft 2, an elastic layer 3 formed on the outer circumference of the shaft 2, and a resin coating layer 4 formed on the outermost surface of the elastic layer 3. The developing roller 1 has an elastic layer 3 with a hardness (Duro-A) of 30 degrees or more and 50 degrees or less, and a resin coating layer 4 containing 0.8% to 12% by mass of fluorine-containing resin with a hardness (Duro-A) of 81 degrees or more and 96 degrees or less, a thickness of 0.8 μm to 4.5 μm or less, and a surface roughness (RzJIS) of 3 μm to 10 μm or less. The developing roller 1 is for transporting positively charged toner with a perfect spherical shape and an average particle diameter of 6 μm to 10 μm, using a non-magnetic, one-component developing method. The developing roller 1 is particularly suitable for transporting this toner because the elastic layer 3 and the resin coating layer 4 satisfy the above physical properties. A perfect spherical shape means that the average ratio of the major axis to the minor axis (major axis / minor axis) of 100 or more particles observed with an electron microscope or the like is 1.5 or less.

[0010] (shaft) The shaft 2 is the axis that rotatably supports the developing roller 1. Both ends of the shaft 2 are precision machined to engage with drive components such as toothed belts. The material forming the shaft 2 can be any material that is conductive, and metal is preferably used. Suitable metals include, for example, iron, copper, aluminum alloy, stainless steel, and nickel. Furthermore, materials that have been plated by methods such as hot-dip plating, electrolytic plating, or electroless plating can be used.

[0011] (Elastic layer) The elastic layer 3 is a layer that exhibits properties such as compression set and surface hardness required for the developing roller 1, and is formed to cover the outer circumference of the shaft 2. The elastic layer 3 is formed to cover the outer circumference of the shaft 2 by conventional methods such as extrusion molding or injection molding. The length of the elastic layer 3 in the axial direction of the shaft 2 is determined by the size of the printing paper; it is in the range of 220-250 mm for A4 size paper and 310-330 mm for A3 size paper. The thickness of the elastic layer 3 is usually 2-5 mm. The formed elastic layer 3 can be shaped by polishing. In this specification, the notation "A-B (A and B are numerical values)" means a numerical range that includes both ends of that range.

[0012] The elastic layer 3 has a hardness (Duro-A) of 30 degrees or more and 50 degrees or less. The elastic layer 3 is not particularly limited as long as it satisfies this hardness, and can be used by mixing one or more of the following materials: thermosetting polyurethane, ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), acrylonitrile-butadiene rubber (NBR), silicone rubber, fluororubber, natural rubber (NR), etc. Among these, it is preferable to include thermosetting polyurethane, which has an excellent balance of performance, and it is more preferable to use thermosetting polyurethane as the main raw material. Furthermore, the elastic layer 3 may contain additives such as conductivity imparters, reaction-promoting catalysts, vulcanizing agents, vulcanization accelerators, softeners, fillers, processing aids, mold release agents, defoamers, flame retardants, etc., as needed. In this specification, "main raw material" means that it accounts for 50% or more by weight of the total material constituting the component.

[0013] The thermosetting polyurethane is not particularly limited, and a general combination of polyol and isocyanate can be used. Furthermore, as the polyol, one or more types such as polyether polyols, polyester polyols, polylactone polyols, and polycarbonate polyols can be used in mixture form. Among these, trifunctional polyether polyols with a number average molecular weight of 2500 to 3500 are preferred because they result in low hardness and low compression set when made into urethane.

[0014] Examples of polyether polyols include polyoxyalkylene polyols, polyoxytetramethylene glycol, and mixtures thereof. For example, polyoxyalkylene polyols can be obtained by ring-opening addition reactions of alkylene oxides such as ethylene oxide, propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, and styrene oxide, using a compound having two or more active hydrogen-containing groups as a starting material.

[0015] In addition, examples of the compound having two or more active hydrogen-containing groups include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, and 1,6-hexanediol; polyhydric alcohols having three or more valences such as glycerin, trimethylolpropane, pentaerythritol, diglycerin, dextrose, sorbitol, and sucrose; polyhydric phenols such as resorcinol, hydroquinone, and bisphenol A; polyhydric amines such as ethylenediamine, tolylenediamine, 1,3-propanediamine, and isophoronediamine; alkanolamines such as diethanolamine and triethanolamine, and modified products thereof. These can be used alone or in combination of two or more thereof.

[0016] As the polyester polyol, for example, those obtained by the condensation reaction of a dicarboxylic acid and a polyhydric alcohol can be employed. Examples of the dicarboxylic acid include saturated aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; saturated aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; halogen-containing dicarboxylic acids such as tetrabromophthalic acid; ester-forming derivatives thereof, acid anhydrides thereof, etc. These can be used alone or in combination of two or more thereof. Examples of the polyhydric alcohol that constitutes the polyester polyol together with the dicarboxylic acid include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, glycerin, pentaerythritol, diglycerin, dextrose, sorbitol, etc. These can be used alone or in combination of two or more thereof.

[0017] The isocyanates are not particularly limited, but examples include aromatic polyisocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI); hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMH) Examples include aliphatic polyisocyanates such as DI, lysine diisocyanate, norbornene diisocyanate methyl (NBDI), xylylene diisocyanate (XDI), and tetramethyl xylylene diisocyanate (TMXDI); alicyclic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), and H12MDI (hydrogenated MDI); carbodiimide-modified polyisocyanates of the above polyisocyanates, or isocyanurate-modified polyisocyanates thereof, and these can be used individually or in combination of two or more.

[0018] (Resin coating layer) The resin coating layer 4 is a coating layer formed on the outermost surface of the elastic layer 3 by methods such as dip coating, roll coating, or spray coating. The resin coating layer 4 can be formed directly on the elastic layer 3 or through other layers. In the present invention, the resin coating layer 4 contains 0.8% to 12% by mass of fluorine-containing resin, has a hardness (Duro-A) of 81 degrees to 96 degrees, a thickness of 0.8 μm to 4.5 μm, and a surface roughness (RzJIS) of 3 μm to 10 μm.

[0019] The resin coating layer 4 is formed by coating with a coating liquid containing a binder resin (including a fluorine-containing resin), a conductive agent, etc., but its composition is not particularly limited as long as it satisfies the above-mentioned amount of fluorine-containing resin, hardness, thickness, and surface roughness. As the binder resin, one or more types of thermoplastic polyurethane resin, acrylic resin, acrylic urethane resin, lactone-modified acrylic urethane resin, acrylic-modified silicone resin, phenolic resin, cellulose-based resin, melamine resin, alkyd resin, fluororesin, acrylic-fluorine mixed resin, fluorine-containing acrylic resin, fluororesin-based urethane resin, etc., can be used in mixtures. Among these, it is preferable to include thermoplastic polyurethane, which has an excellent balance of performance, and it is more preferable to use thermoplastic polyurethane as the main raw material.

[0020] As the fluorine-containing resin, any resin that contains fluorine is acceptable. In addition to the fluorine resins, acrylic-fluorine mixed resins, fluorine-containing acrylic resins, and fluorine-based urethane resins mentioned above, fluorine-based surfactants and fluorine-based silane coupling agents can also be used. The fluorine-containing resin is blended in a ratio such that the fluorine-containing resin content relative to the entire resin coating layer 4 is 0.8% by mass or more and 12% by mass or less.

[0021] The conductive agent can be any conductive carbon such as carbon, resin-coated carbon, or graphite; metal oxide particles such as zinc oxide, tin oxide, or titanium oxide; metal particles such as nickel, copper, or silver; conductive polymers such as polyacetylene or polypyrrole; or ionic conductive agents such as lithium-based, potassium-based, fluoro-based, sulfonyl-based, quaternary ammonium-based, or carboxylic acid-based agents, without any particular limitations. The amount of conductive agent added should be adjusted according to the volume resistivity required for the resin coating layer 4. One or more conductive agents can be used. Among these, carbon black is preferred because it exhibits stable conductivity against environmental fluctuations.

[0022] The resin coating layer 4 is formed by coating the elastic layer 3 with a resin composition in which a conductivity imparting agent is added to a binder resin. Before coating the resin coating layer 4, the elastic layer 3 is polished to form the desired shape as a developing roller 1. The fluorine-containing resin content in the resin coating layer 4 is 0.8% by mass or more and 12% by mass or less. If this content is less than 0.8% by mass, the amount of charge does not increase, and if it exceeds 12% by mass, the amount of charge does not increase due to the reduction in friction. The fluorine-containing resin content is preferably 11% by mass or less.

[0023] The thickness of the resin coating layer 4 is 0.8 μm or more and 4.5 μm or less. If this thickness is less than 0.8 μm, the amount of toner transported will be too large, and if it exceeds 4.5 μm, the amount of toner transported will be too small. This thickness is preferably 0.9 μm or more, preferably 4.3 μm or less, and more preferably 4.1 μm or less. The surface roughness (RzJIS) of the resin coating layer 4 is 3 μm or more and 10 μm or less. The surface roughness (RzJIS) of the resin coating layer 4 can be adjusted by its thickness and the surface roughness (degree of polishing) of the elastic layer 3. If this surface roughness is less than 3 μm, the toner transport performance will decrease, and if it exceeds 10 μm, the amount of toner transported will increase too much. This surface roughness is preferably 3.5 μm or more, more preferably 4 μm or more, and preferably 9.5 μm or less. The hardness (Duro-A) of the resin coating layer 4 is between 81 and 96 degrees. If the hardness is less than 81 degrees, the toner transport volume increases too much, and if it exceeds 96 degrees, the toner transport volume decreases too little. A hardness of 82 or higher is preferred, 83 or higher is more preferred, and 84 or higher is even more preferred.

[0024] (developing roller) The developing roller 1 of the present invention is for transporting positively charged toner with a spherical shape and an average particle diameter of 6 μm to 10 μm, using a non-magnetic, one-component developing method. By satisfying the specific configuration described above, the developing roller 1 of the present invention is suitable for transporting positively charged toner with a small diameter of 6 μm to 10 μm, which is spherical in shape. This is because the frictional charging properties, surface hardness, film thickness, and surface roughness of the fluororesin result in an appropriate frictional area and coefficient of friction for the positively charged toner with a spherical shape and an average particle diameter of 6 μm to 10 μm, thereby improving toner charging properties and toner transportability.

[0025] The shape of the developing roller 1 of the present invention is not particularly limited. It may be a straight shape in which the outer diameter is substantially the same from one end to the other in the axial direction, a crown shape in which the outer diameter at the axial center is larger than the outer diameters at both ends, or an inverted crown shape in which the outer diameter at the axial center is smaller than the outer diameters at both ends. The crown shape and the inverted crown shape can be formed by plunge polishing.

[0026] Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. [Examples]

[0027] "Example 1" A polyol composition was prepared by blending 65 parts by mass of a trifunctional polyether polyol with a number average molecular weight of 5000 (manufactured by Asahi Glass Co., Ltd., trade name: Preminol S3006, OHv = 33 mg KOH / g, degree of unsaturation 0.006 g / meq) and 35 parts by mass of a trifunctional polyether polyol with a number average molecular weight of 3000 (manufactured by Asahi Glass Co., Ltd., trade name: Preminol S3003, OHv = 56 mg KOH / g, degree of unsaturation 0.007 g / meq). To 100 parts by mass of this polyol composition, conductive carbon (manufactured by Mitsubishi Chemical Corporation, trade name: #45L, pH 8.0, DBP absorption 45 ml / 100 g, volatile content 1.1% by mass) and resin-coated carbon (acidic carbon black (trade name "MA8", pH 3.0, DBP absorption 57 ml / 100 g, volatile content 3.0% by mass) manufactured by Mitsubishi Chemical Corporation, coated with epoxy resin) were mixed in a mass ratio of 30:70 and roll-dispersed to a total of 6.5 parts by mass.

[0028] Furthermore, as a reaction-enhancing catalyst, dimethyl fatty acid monocarboxylate (manufactured by Katsuzai Chemical Co., Ltd., product name: UL28) was added and mixed at a concentration of 150 ppm relative to the total amount of urethane, and this was used as the main component. As an isocyanate, 6.9 parts by mass of 1,3-bis(isocyanatemethyl)benzene were mixed with 100 parts by mass of the main component so that the NCO index value was 1.05 to obtain a resin composition.

[0029] A resin composition was poured into a mold with a metal shaft at its center and cured at 110°C for 20 minutes. After demolding, an aging treatment was performed at room temperature for 12 hours to form an elastic layer consisting of polyurethane elastomer, 319 mm in length and 4 mm in thickness, covering the outer circumference of the shaft.

[0030] A binder resin was prepared by mixing 90 parts by mass of thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., product name: E185) with 10 parts by mass of fluorine-containing resin (manufactured by AGC Seimi Chemical Co., Ltd., product name: SF Coat KTS300H) with solid content. To 100 parts by mass of this binder resin, 12.5 parts by mass of carbon (manufactured by Dainichi Seika Co., Ltd., product name: Seika Black SS-01-942) was added to obtain a resin composition for forming a resin coating layer. This resin composition for forming a resin coating layer was applied to an elastic layer by dip coating to form a 2.5 μm thick resin coating layer, and a developing roller was obtained.

[0031] Example 2 A developing roller was obtained in the same manner as in Example 1, except that the thickness of the resin coating layer was set to 4.0 μm. "Example 3" A developing roller was obtained in the same manner as in Example 1, except that the thickness of the resin coating layer was set to 1.0 μm. "Example 4" A developing roller was obtained in the same manner as in Example 1, except that a thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., product name: E195) was used for the resin coating layer, and its thickness was set to 3.0 μm. Example 5 A developing roller was obtained in the same manner as in Example 1, except that the resin coating layer consisted of 99 parts by mass of thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., product name: E195) and 1 part by mass of fluorine-containing resin (manufactured by AGC Seimi Chemical Co., Ltd., product name: SF Coat KTS300H), with a thickness of 3.0 μm.

[0032] "Comparative Example 1" A developing roller was obtained in the same manner as in Example 1, except that the resin coating layer consisted of 99.2 parts by mass of thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., product name: E185) and 0.8 parts by mass of fluorine-containing resin (manufactured by AGC Seimi Chemical Co., Ltd., product name: SF Coat KTS3000H) with a solid content. "Comparative Example 2" A developing roller was obtained in the same manner as in Example 1, except that the resin coating layer consisted of 85 parts by mass of thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., product name: E185) and 15 parts by mass of fluorine-containing resin (manufactured by AGC Seimi Chemical Co., Ltd., product name: SF Coat KTS300H) with a solid content of 15 parts by mass.

[0033] "Comparative Example 3" A developing roller was obtained in the same manner as in Example 1, except that the thickness of the resin coating layer was set to 0.5 μm. "Comparative Example 4" A developing roller was obtained in the same manner as in Example 1, except that the thickness of the resin coating layer was set to 5.0 μm. "Comparative Example 5" A developing roller was obtained using a resin composition prepared in the same manner as in Example 1, except that the elastic layer contained 100 parts by mass of a trifunctional polyether polyol with a number average molecular weight of 3000 (manufactured by Asahi Glass Co., Ltd., trade name: Preminol S3003, OHv = 56 mg KOH / g, degree of unsaturation 0.007 g / meq) as the polyol composition, and 9.4 parts by mass of isocyanate were mixed in such a way that the NCO index value was 1.05. Furthermore, a developing roller was obtained in the same manner as in Example 1, except that the resin coating layer was made of thermoplastic polyurethane resin (manufactured by Nippon Miractran Co., Ltd., trade name: E180).

[0034] • Test and evaluation methods "Hardness (Duro-A)" For the coating resin layer forming composition, a 2 mm thick sheet was prepared, and six of these sheets were stacked to create a total thickness of 12 mm. The hardness (duro A) was measured according to JIS-K-6253-3:2012, type A. Measurements were taken at five arbitrary locations on the sheet under conditions of 23°C and 50% RH, and the arithmetic mean of the individual measurements is shown. "Surface roughness (RzJIS)" The resin coating layer of the roller was measured in accordance with JIS B 0601:1994 and RzJIS.

[0035] "Toner charge amount, toner transport amount" The developing rollers manufactured in the above examples and comparative examples were installed in a printer with a non-magnetic single-component developing method (Brother Industries, Ltd., HL6400DW, cartridge TN63J, toner with an average particle size of 8 μm and a perfectly spherical shape), and 20,000 sheets of paper were printed as a running test for image evaluation and at 1% image density. To evaluate the toner charge amount and transport amount, after printing a black image, the toner on the developing roller was drawn into a Faraday cage fitted with a PTFE filter (Shibata Scientific Industries, Ltd., TF98R), the charge amount was measured in the Faraday cage, and the toner transport amount was calculated from the amount of toner accumulated in the PTFE filter. These were then evaluated according to the following criteria. Initial assessment (before running trial) ○: Toner charge amount is 15 μQ / mg or more, Toner transport rate: 0.3 mg / cm² 2 More than 1.0cm 2 below. ×: Except for the conditions of ○ Post-running trial evaluation ○: Toner charge amount is 10 μQ / mg or more, Toner transport rate: 0.3 mg / cm² 2 More than 1.0cm 2 below. ×: Except for the conditions of ○

[0036] The results of each measurement are shown in Table 1. [Table 1] [Explanation of Symbols]

[0037] 1. Developing roller 2. Shaft 3. Elastic layer 4. Resin coating layer

Claims

1. The shaft and An elastic layer formed on the outer circumference of the shaft, A resin coating layer formed on the outermost surface of the elastic layer, It has, The elastic layer has a hardness (Duro-A) of 30 degrees or more and 50 degrees or less. The aforementioned resin coating layer contains 0.8% to 12% by mass of fluorine-containing resin, has a hardness (Duro-A) of 81 degrees to 96 degrees, a thickness of 0.8 μm to 4.5 μm, and a surface roughness (RzJIS) of 3 μm to 10 μm. A developing roller characterized by being used for transporting positively charged toner with a non-magnetic, single-component developing method, and having a perfectly spherical shape with an average particle diameter of 6 μm to 10 μm.

2. The developing roller according to claim 1, characterized in that the elastic layer includes thermosetting polyurethane.

3. The developing roller according to claim 1 or 2, characterized in that the resin coating layer includes thermoplastic polyurethane.

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