JPWO2011010588A1 - Polyurethane film for keypad - Google Patents

Abstract

The present invention relates to a polyurethane film for a keypad comprising a polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender or a polyurethane composition mainly composed of the polyurethane, wherein at least one surface is JIS A polyurethane film for a keypad, which is a roughened surface having a surface roughness measured according to B0601-2001 of 10 μm or more is provided.

Description

  The present invention relates to a polyurethane film for a keypad used for a communication terminal such as a mobile phone, various instruments, a keyboard for personal computer input, and an operation unit such as a remote controller, a keypad comprising the same, and a key sheet.

  In recent years, a key sheet in which a key top (button key) is bonded to a keypad obtained from a keypad film made of a resin film such as thermoplastic polyurethane, polyethylene terephthalate, polyester elastomer, etc. by printing, printing adhesive, etc. Are widely used in operation parts such as communication terminals, various instruments, keyboards for personal computer input, and remote controllers (see, for example, Patent Documents 1 and 2). Among the materials of the keypad film constituting the keypad described above, it is known that thermoplastic polyurethane is particularly suitable because it has high durability in addition to moderate soft feeling and excellent cushioning properties. ing.

  For example, a keypad surface material that is laminated on silicone rubber or the like to form a keypad has soft touch, does not cause yellowing, has high water resistance and heat resistance, and has little deterioration in physical properties. For this purpose, it has been proposed to comprise a thermoplastic polyurethane resin synthesized using at least an isocyanate and a polyol selected from hexamethylene diisocyanate or hydrogenated diphenylmethane diisocyanate as synthesis components (see Patent Document 3).

  In addition, for the purpose of providing a polyurethane resin keypad with excellent secondary moldability, oleic acid resistance, discoloration resistance, transparency, and printability, organic diisocyanate based on hexamethylene diisocyanate and polycarbonate diol as the main component. Key made of a polyurethane resin obtained by thermoforming a thermoplastic polyurethane resin sheet obtained by melt-molding a resin pellet obtained by reacting a polymer polyol and a chain extender mainly composed of an aliphatic diol having 2 to 10 carbon atoms A pad has been proposed (see Patent Document 4).

  The keypad is generally produced by cutting the keypad film into a desired size and shape, etc., and the keypad is overlaid and sent to the printing process and other processing processes to produce the key sheet, It is widely performed to separate and process each keypad from the overlapped state in the processing step. At that time, the keypad made of polyurethane may cause a problem that the keypads overlapped with each other and are difficult to separate into individual keypads during processing to produce a keysheet. It contributes to the decline of sex.

  As a method for preventing such sticking, a method of blending a release agent with polyurethane in advance is known. However, this method may cause problems such as the release agent bleeding out on the surface repels ink in the printing process. From this point of view, there is a need for a polyurethane keypad that does not stick to each other without blending a release agent.

  In the prior arts of Patent Documents 3 and 4 described above, improvement in touch of a polyurethane keypad and a keypad surface material, prevention of yellowing (discoloration resistance), water resistance, heat resistance, oleic acid resistance, transparency, Although improvement of printability and the like is described, prevention of sticking between polyurethane keypad films and keypads is not disclosed.

JP 2004-327307 A JP 2004-111258 A JP 2005-25960 A International Publication No. 2004/106401

  The object of the present invention is to produce a keypad and a key sheet with good processability and process productivity without sticking to each other even if a release agent that tends to cause problems such as bleeding is not blended A polyurethane film for a keypad that can be manufactured and a method for producing the same.

  Another object of the present invention is to provide a keypad including at least a layer made of the above-described polyurethane film for a keypad, and further a key sheet having a key top disposed on the keypad.

  Furthermore, an object of the present invention is to provide a keypad polyurethane film with a protective layer in which one or both sides of a polyurethane film for a keypad capable of providing a polyurethane keypad are covered with a protective layer, and a method for producing the same. Is to provide.

  In order to solve the above problems, the present inventors have made various studies. As a result, when at least one surface of the keypad polyurethane film is a roughened surface having a predetermined surface roughness, no sticking occurs even if a release agent is not blended, and the keypad and key sheet can be produced. It has been found that the process can be carried out with good processability and process productivity.

  In addition, the inventors of the present invention may make the polyurethane film for the keypad to have a predetermined thickness so that the ease of manufacturing the polyurethane film for the keypad, heat resistance, process productivity during post-processing, keypad It has been found that it is preferable from the viewpoints of handleability and pad performance of the keypad obtained from the polyurethane film for use.

  Furthermore, the inventors of the present invention, if the tensile stress of the keypad polyurethane film is set to a predetermined value or more, even if a heat treatment is performed when manufacturing a keypad or a key sheet, a defective phenomenon such as warping or shrinkage. Further, it was found that the film does not stick to each other, and the shape is favorably maintained without using a reinforcing material.

  In addition, the inventors of the present invention can provide a key layer by covering the roughened surface of the above-described keypad polyurethane film having a roughened surface having a predetermined surface roughness with a protective layer. The handling of the polyurethane film for the pad can be improved during storage and transportation, the processing when manufacturing the keypad and key sheet from the polyurethane film for the keypad, and the damage to the polyurethane film for the keypad can be prevented. I found.

  Furthermore, the present inventors laminated polyurethane on the roughened surface of the base material having a roughened surface having a specific surface roughness in the form of a film in a molten state or a softened state, and then the base material is a polyurethane film layer. It was found that a polyurethane film for a keypad having a roughened surface having a desired predetermined surface roughness can be obtained smoothly and easily with good process productivity and operability.

Based on the above various findings, the present inventors have completed the following present invention.
[1] A polyurethane film for a keypad comprising a polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender or a polyurethane composition mainly composed of the polyurethane, wherein at least one surface is JIS B0601 A polyurethane film for a keypad, characterized in that the surface roughness measured according to 2001 is a roughened surface of 10 μm or more.

[2] The polyurethane film for a keypad according to [1] above, wherein the surface roughness of the roughened surface measured according to JIS B0601-2001 is 10 to 25 μm.

[3] The polyurethane film for a keypad according to [1] or [2], wherein the thickness is 40 to 300 μm.

[4] The polyurethane film for a keypad according to any one of [1] to [3], wherein a tensile stress (M ₁₀₀ ) at 100% elongation at 23 ° C. is 15 MPa or more.

[5] A keypad formed using the polyurethane film for a keypad according to any one of [1] to [4].

[6] A key sheet in which a key top is disposed on the keypad according to [5].

[7] A keypad polyurethane film with a protective layer, wherein the roughened surface of the keypad polyurethane film according to any one of [1] to [4] is covered with a protective layer.

[8] The polyurethane film for a keypad with a protective layer according to the above [7], wherein the peel strength between the polyurethane film for a keypad and the protective layer is 0.1 to 0.5 N / cm.

[9] The polyurethane film for a keypad with a protective layer according to the above [7] or [8], wherein the protective layer is a layer made of polyester.

[10] A polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender on a roughened surface of a substrate having a roughened surface or a polyurethane composition mainly composed of the polyurethane is melted. The roughened surface of the polyurethane film layer having a roughened surface having a surface roughness of 10 μm or more measured by JIS B0601-2001, which is laminated in a film state in a state or a softened state, comprises a substrate. A method for producing a polyurethane film for a keypad with a protective layer coated with a protective layer.

[11] A keypad polyurethane film having a roughened surface with a surface roughness measured according to JIS B0601-2001 is 10 μm or more by peeling the protective layer from the polyurethane film for keypad with protective layer. The method according to [10] above.

[12] The method according to [10] or [11] above, wherein the surface roughness of the roughened surface of the substrate measured in accordance with JIS B0601-2001 is 10 μm or more.

  The keypad polyurethane film of the present invention comprising at least one surface having a roughened surface having a specific surface roughness defined in the present invention is used for storing the keypad polyurethane film or for transporting the keypad polyurethane film. When processing for manufacturing a keypad or key sheet from a polyurethane film, even if the polyurethane films for keypads are overlapped with each other in contact with each other, the keypad polyurethane films are stuck together, and the predetermined shape and dimensions are obtained. Thus, the keypad and the key sheet can be smoothly manufactured with good process productivity and operability.

  Among the polyurethane films for keypads of the present invention, the polyurethane film for keypads further having a specific tensile stress specified in the present invention is warped or shrunk even when heat treatment is performed when manufacturing the keypad or key sheet. Such a defect phenomenon and sticking between films do not occur, and the shape can be satisfactorily maintained without using a reinforcing material.

  Among the polyurethane films for keypads of the present invention, the polyurethane film for keypads with a protective layer whose roughened surface is coated with a protective layer is a polyurethane for keypads when the polyurethane film for keypads is stored or transported. Good handleability during processing when producing a keypad or key sheet from the film, and damage to the polyurethane film for the keypad is prevented.

  By laminating polyurethane with a roughened surface of a substrate in a molten or softened state as in the present invention, at least one surface is a roughened surface having a specific surface roughness defined by the present invention. A keypad polyurethane film having a protective layer or a keypad polyurethane film with a protective layer can be produced smoothly and easily.

2 is a photomicrograph of a roughened surface (a surface from which a polyethylene terephthalate film has been peeled off) in a polyurethane film for a keypad of Example 1. FIG. 2 is a micrograph of a roughened surface (a surface from which a polyethylene terephthalate film has been peeled) in a polyurethane film for a keypad of Comparative Example 1.

The present invention is described in detail below.
The polyurethane film for a keypad of the present invention is formed from a polyurethane alone obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender, or is formed from a polyurethane composition mainly composed of the polyurethane. .

  The “polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender” (hereinafter sometimes simply referred to as “polyurethane”) forming the polyurethane film for a keypad of the present invention is one kind of It may be made of polyurethane or may be made of two or more types of polyurethane.

  When the polyurethane film for keypads of the present invention is formed from a polyurethane composition mainly composed of polyurethane, the polyurethane content in the polyurethane composition is preferably 50% by mass or more, and 80% by mass or more. More preferably, it is more preferably 95% by mass or more.

  The polyurethane forming the polyurethane film for a keypad of the present invention is preferably a thermoplastic polyurethane.

  As the polymer polyol used in the production of the polyurethane forming the polyurethane film for keypad of the present invention, any polymer polyol conventionally used in the production of polyurethane can be used. Examples of such polymer polyols include polyester polyols, polyether polyols, polycarbonate polyols, polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols that may be hydrogenated, castor oil polyols, vinyl polymer polyols, and the like. These polymer polyols may be used alone or in combination of two or more. Among them, as the polymer polyol, one or more of polyester polyol, polyether polyol, and polycarbonate polyol are preferably used, and polyester polyol and / or polyether polyol are more preferably used.

  Examples of the above-described polyester polyol that can be used as a polymer polyol for producing polyurethane include, for example, a polyol component and a polycarboxylic acid component such as an ester-forming derivative such as a polycarboxylic acid, its ester, and an anhydride according to a conventional method. And polyester polyols obtained by direct esterification reaction or transesterification reaction, and polyester polyols obtained by ring-opening polymerization of a lactone using a polyol as an initiator.

  As the above-described polyol component used in the production of the polyester polyol, a diol and / or a polyol generally used in the production of a polyester can be used. Examples of the diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, , 3-butanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6- Hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 1,9-nonanediol, 2- Methyl-1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, 1,10- An aliphatic diol having 2 to 15 carbon atoms such as candiol (preferably an aliphatic diol having 4 to 10 carbon atoms, more preferably a linear aliphatic diol having 4 to 10 carbon atoms); 1,4-cyclohexanediol, Mention may be made of alicyclic diols such as cyclohexanedimethanol, cyclooctanedimethanol and dimethylcyclooctanedimethanol; aromatic dihydric alcohols such as 1,4-bis (β-hydroxyethoxy) benzene. Examples of the polyol having three or more hydroxyl groups per molecule include trimethylolpropane, trimethylolethane, glycerin, 1,2,6-hexanetriol, pentaerythritol, and diglycerin. In the production of the polyester polyol, these polyols may be used alone or in combination of two or more. Among these, 1,4-butane can be obtained from polyurethane that is more excellent in non-adhesiveness, workability when imparting surface roughness, mechanical properties represented by tensile stress and tear strength, and heat resistance. Aliphatic diols having 4 to 10 carbon atoms such as diol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and 1,8-octanediol are preferably used, and 1,4-butanediol, C4-C10 linear aliphatic diols such as 1,6-hexanediol and 1,8-octanediol are more preferably used.

  As the above-mentioned polycarboxylic acid component used in the production of the polyester polyol, those commonly used in the production of polyester can be used. For example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Azelaic acid, sebacic acid, dodecanedioic acid, methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, trimethyladipic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyl C4-C12 (preferably C6-C12) aliphatic dicarboxylic acid such as decanedioic acid; cycloaliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid, dimer acid, hydrogenated dimer acid; terephthalic acid, isophthalic acid, Aromatic dicarboxylic acids such as orthophthalic acid and naphthalenedicarboxylic acid; trimellitic acid Polycarboxylic acids having three or more functional, such as pyromellitic acid; and the like or ester-forming derivatives thereof can be mentioned. These polycarboxylic acid components may be used alone or in combination of two or more. Among them, non-adhesiveness, workability when imparting surface roughness, mechanical properties typified by tensile stress and tear strength, and polyurethane having further excellent heat resistance can be obtained. Group dicarboxylic acids are preferably used, adipic acid, azelaic acid, and sebacic acid are more preferable, and adipic acid is more preferably used.

  Moreover, (epsilon) -caprolactone, (beta) -methyl-delta-valerolactone etc. can be mentioned as above-mentioned lactone used for manufacture of a polyester polyol.

  Examples of the polyether polyol that can be used as a polymer polyol for producing polyurethane include, for example, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol obtained by ring-opening polymerization of a cyclic ether in the presence of a polyol. , Poly (methyltetramethylene glycol) and the like, and one or more of these can be used. Among them, non-adhesiveness, workability when imparting surface roughness, mechanical properties represented by tensile stress and tear strength, and polyurethane having further excellent heat resistance can be obtained, so polytetramethylene glycol and / or Poly (methyltetramethylene glycol) is preferably used.

  Examples of the above-described polycarbonate polyol that can be used as a polymer polyol for producing a polyurethane include those obtained by a reaction between a polyol component and a carbonate compound such as dialkyl carbonate, alkylene carbonate, and diaryl carbonate. As the polyol component used for the production of the polycarbonate polyol, the polyol components exemplified above as the components that can be used for the production of the polyester polyol can be used. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate. Examples of the alkylene carbonate include ethylene carbonate. Examples of the diaryl carbonate include diphenyl carbonate.

  Examples of the above-described polyester polycarbonate polyol that can be used as a polymer polyol for producing polyurethane include, for example, (1) those obtained by simultaneously reacting a polyol component, a polycarboxylic acid component and a carbonate compound; (2) Those obtained by previously synthesizing the above-described polyester polyol and polycarbonate polyol, respectively, and then reacting them with a carbonate compound; or (3) preliminarily synthesizing the above-described polyester polyol and polycarbonate polyol, respectively, and then synthesizing them with the polyol component and And the like obtained by reacting with a polycarboxylic acid component.

  Specific examples of the polymer polyol for producing the polyurethane that forms the polyurethane film for the keypad of the present invention include poly (1,4-tetramethylene adipate) diol, poly (3-methyl-1,5-pentamethylene Adipate) diol, poly (ε-caprolactone) diol, polytetramethylene glycol, and the like, and one or more of these can be used.

The number average molecular weight of the polymer polyol for producing the polyurethane is preferably in the range of 500 to 8,000, more preferably in the range of 600 to 5,000, and 800 to 3,000. More preferably, it is within the range. By using a polymer polyol having a number average molecular weight within the above range, the processability when producing the polyurethane film for a keypad of the present invention is low, the adhesiveness is low, and the mechanics represented by tensile stress and tear strength are used. Polyurethane with excellent mechanical properties and heat resistance can be obtained.
Here, the number average molecular weight of the polymer polyol in the present specification is a number average molecular weight calculated based on the hydroxyl value measured according to JIS K1557.

  Further, the number of hydroxyl groups per molecule of the polymer polyol is excellent in processability when producing a polyurethane film for a keypad having the surface roughness specified in the present invention, has low adhesiveness, and has a tensile stress and tear strength. From the point of obtaining a polyurethane having excellent mechanical properties and heat resistance represented by the formula, it is preferably in the range of 2.0 to 2.1, more preferably in the range of 2.0 to 2.07. More preferably, it is substantially 2.0 (that is, the polymer polyol is a polymer diol).

  As the organic polyisocyanate for producing the polyurethane that forms the polyurethane film for a keypad of the present invention, any organic polyisocyanate conventionally used in the production of polyurethane can be used. Specific examples of such organic polyisocyanates include 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, 3,3′-dichloro-4,4′-diphenylmethane. Aromatic diisocyanates such as diisocyanates; aliphatic or cycloaliphatic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, hydrogenated xylylene diisocyanate, and the like. 1 type (s) or 2 or more types can be used. Among them, it is excellent in processability when producing the polyurethane film for keypads of the present invention, has low adhesiveness, and can obtain a polyurethane excellent in mechanical properties and heat resistance represented by tensile stress and tear strength. An organic polyisocyanate mainly composed of 4,4′-diphenylmethane diisocyanate is preferably used. The organic polyisocyanate preferably contains 4,4′-diphenylmethane diisocyanate in a proportion of 50 mol% or more, more preferably in a proportion of 80 mol% or more, and in a proportion of 95 mol% or more. More preferably, it consists of 4,4′-diphenylmethane diisocyanate alone (100 mol%).

  As the chain extender for producing the polyurethane forming the polyurethane film for a keypad of the present invention, any chain extender conventionally used in the production of polyurethane can be used. Specific examples of such chain extenders include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, Diols such as bis (β-hydroxyethyl) terephthalate and xylylene glycol; hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, piperazine or derivatives thereof, phenylenediamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, Examples include diamines such as isophthalic acid dihydrazide; amino alcohols such as aminoethyl alcohol and aminopropyl alcohol, and one or more of these can be used. The Among these, it is possible to obtain a polyurethane having excellent workability when producing the polyurethane film for keypads of the present invention, low adhesiveness, and excellent mechanical properties and heat resistance represented by tensile stress and tear strength. From this point, a chain extender mainly composed of an aliphatic diol having 2 to 10 carbon atoms is preferably used. The chain extender preferably contains an aliphatic diol having 2 to 10 carbon atoms in a proportion of 50 mol% or more, more preferably in a proportion of 80 mol% or more, and in a proportion of 95 mol% or more. More preferably, it consists only of an aliphatic diol having 2 to 10 carbon atoms (100 mol%). In this case, 1,4-butanediol is particularly preferably used as the aliphatic diol having 2 to 10 carbon atoms.

  In the production of polyurethane by reacting the above-mentioned polymer polyol, organic polyisocyanate and chain extender, the mixing ratio of each component is the hardness, mechanical performance, etc. to be given to the polyurethane forming the keypad polyurethane film. The molar ratio of active hydrogen atoms: isocyanate groups present in the reaction system is in the range of 1: 0.9 to 1.1, particularly in the range of 1: 0.95 to 1.05. It is preferable to use each component in such a ratio that it is inside. By using each component in the above proportion, the polyurethane becomes thermoplastic, and it has excellent processability when producing the polyurethane film for keypads of the present invention, has low adhesiveness, and has tensile stress and tear strength. A polyurethane having excellent mechanical properties and heat resistance can be obtained.

  The reaction mode in producing the polyurethane is not particularly limited, and a known urethanization reaction technique can be employed using a polymer polyol, an organic polyisocyanate and a chain extender. As a known urethanization reaction technique, either a prepolymer method or a one-shot method can be employed. In the production of polyurethane, it is preferable to perform melt polymerization in the substantial absence of a solvent, and it is more preferable to employ a continuous melt polymerization method using a multi-screw extruder. As the polymerization temperature at the time of melt polymerization, the range of 180 to 280 ° C is preferably employed, and the range of 200 to 260 ° C is more preferably employed.

  In obtaining polyurethane by reacting the above-mentioned polymer polyol, organic polyisocyanate and chain extender, a urethanization reaction catalyst may be used. The type of the urethanization reaction catalyst is not particularly limited, and any urethanization reaction catalyst conventionally used in the production of polyurethane can be used. Examples of such urethanization reaction catalysts include organotin compounds, organozinc compounds, organobismuth compounds, organotitanium compounds, organozirconium compounds, amine compounds, and the like. Only one type of urethanization reaction catalyst may be used, or two or more types may be used in combination.

The polyurethane forming the polyurethane film for keypads of the present invention has excellent processability when producing a polyurethane film for keypads, low adhesion, and mechanical properties and heat resistance represented by tensile stress and tear strength. From the point that a polyurethane excellent in the above can be obtained, the content of nitrogen atoms derived from isocyanate groups is preferably in the range of 3.0 to 6.5% by mass, and in the range of 4.0 to 6.5% by mass. It is more preferable that In particular, in order to make the tensile stress (M ₁₀₀ ) of the polyurethane film for a keypad of the present invention 15 MPa or more, which will be described later, the content of nitrogen atoms derived from isocyanate groups in the polyurethane is 4.5 to 6.5% by mass. It is preferably within the range, more preferably within the range of 4.6 to 6.0% by mass, even more preferably within the range of 4.7 to 5.7% by mass. It is particularly preferable that the amount be in the range of 5.5% by mass.

The logarithmic viscosity of the polyurethane forming the polyurethane film for keypad of the present invention is preferably in the range of 0.7 to 1.5 dl / g. Polyurethanes having the logarithmic viscosity have low adhesiveness and excellent mechanical properties and heat resistance represented by tensile stress and tear strength.
In addition, the logarithmic viscosity (η _inh ) of polyurethane in the present specification refers to a value measured by the method described in the following examples.

The polyurethane forming the polyurethane film for a keypad of the present invention preferably has an ASTM D hardness of 52 or more, more preferably 55 or more, and even more preferably 58 or more. Polyurethane having a preferable hardness is excellent in processability when producing the polyurethane film for keypad of the present invention, has low adhesiveness, and is excellent in mechanical properties and heat resistance represented by tensile stress and tear strength.
In addition, the ASTM D hardness of the polyurethane in this specification is a value measured according to ASTM D2240, as described in Examples.

  The polyurethane film for a keypad of the present invention may be formed only from the above-described polyurethane, or may be formed from a polyurethane composition mainly composed of the above-described polyurethane.

  The polyurethane composition is within a range not impairing the effects of the present invention, and if necessary, a mold release agent, a reinforcing agent, a colorant, a flame retardant, an ultraviolet absorber, an antioxidant, a weather resistance improver, and a light resistance improvement. Agents, hydrolysis resistance improvers, fungicides, antibacterial agents, stabilizers, urethanization catalyst deactivators, etc .; glass fibers, polyester fibers and other fibers; talc, silica and other inorganic materials; Coupling agent; optional components such as other resins than the above polyurethane can be included. The content of these optional components in the polyurethane composition is preferably 50% by mass or less, more preferably 20% by mass or less, and further preferably 5% by mass or less.

  In order to prevent the polyurethane film for a keypad of the present invention from sticking to each other even if a release agent is not blended, at least one side of the polyurethane film for a keypad, that is, one side or both sides is JIS The surface roughness measured in accordance with B0601-2001 needs to be a roughened surface having a surface roughness of 10 μm or more.

  The surface roughness of the roughened surface of the polyurethane film for keypad is preferably 12 μm or more, more preferably 14 μm or more, and further preferably 16 μm or more. Further, the surface roughness can be appropriately adjusted depending on the thickness of the polyurethane film for keypad, but generally it is preferably 25 μm or less, more preferably 23 μm or less, and 21 μm or less. Is more preferable.

  When the surface roughness of at least one surface of the keypad polyurethane film is smaller than the value specified in the present invention (that is, the surface roughness of both surfaces of the keypad polyurethane film is less than the surface roughness specified in the present invention) In other words, sticking easily occurs between the polyurethane films for the keypad, and thus between the keypads. On the other hand, if the surface roughness of the polyurethane film for the keypad is too large, the heat resistance is lowered and a defective phenomenon such as warpage tends to occur.

  Here, the “surface roughness measured in accordance with JIS B0601-2001” of the polyurethane film for keypads in this specification is an arbitrary 2.8 mm square measurement target surface on the surface of the polyurethane film for keypads. The arithmetic average roughness is measured in accordance with JIS B0601-2001, and the sum of the five arithmetic average roughnesses is divided by five. The detailed measurement method is as described in the examples.

  The thickness of the polyurethane film for a keypad of the present invention is not particularly limited, and can be adjusted according to the content of nitrogen atoms derived from isocyanate groups in polyurethane or the hardness of the polyurethane, but the film is easy to manufacture. From the viewpoints of heat resistance, post-process productivity, keypad and key sheet handling properties obtained from a keypad polyurethane film, and pad performance, it is preferably 40 to 300 μm, and preferably 40 to 200 μm. Is more preferable, and it is further more preferable that it is 40-150 micrometers.

The polyurethane film for a keypad of the present invention preferably has a tensile stress (M ₁₀₀ ) of 15 MPa or more, more preferably 16 to 30 MPa, and even more preferably 18 to 25 MPa. Because the polyurethane film for keypads has the above-mentioned tensile stress (M ₁₀₀ ), even when heat treatment is applied during the production of keypads and key sheets, defects such as warping and shrinkage, and sticking between films occur. In addition, it is possible to obtain a keypad polyurethane film that maintains a good shape without using a reinforcing material, and thus a keypad and a key sheet.
Here, the tensile stress (M ₁₀₀ ) referred to in the present specification is a value measured according to JIS K 7311-1995 as described in Examples.

The polyurethane film for a keypad of the present invention can be obtained by producing a polyurethane film for a keypad using a polyurethane or a polyurethane composition that forms a film having a tensile stress (M ₁₀₀ ) of 15 MPa or more.

The polyurethane or polyurethane composition forming a film having a tensile stress (M ₁₀₀ ) of 15 MPa or more is not particularly limited.
<1> The content of nitrogen atoms derived from isocyanate groups obtained by reacting poly (1,4-tetramethylene adipate) diol, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol is 4.8. A polyurethane having a mass% or more;
<2> Content of nitrogen atom derived from isocyanate group, obtained by reacting poly (3-methyl-1,5-pentamethylene adipate) diol, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol Having a polyurethane content of 4.7% by mass or more;
<3> The content of nitrogen atoms derived from isocyanate groups obtained by reacting poly (ε-caprolactone) diol, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol is 4.9% by mass or more. A polyurethane; and
<4> Polyurethane obtained by reacting polytetramethylene glycol, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol, and having a content of nitrogen atoms derived from isocyanate groups of 5.1% by mass or more;
At least one polyurethane selected from the group consisting of or a polyurethane composition mainly composed of the polyurethane is preferred.

The manufacturing method of the polyurethane film for keypads of this invention is not restrict | limited in particular, Any can be employ | adopted if it can manufacture the polyurethane film for keypads provided with the requirements prescribed | regulated by this invention. As a typical manufacturing method,
(I) After producing a polyurethane film by extrusion molding, injection molding, inflation molding, calendar molding, press molding, or the like using the above-described polyurethane or a polyurethane composition mainly composed of the polyurethane, at least one of the polyurethane films The surface is subjected to blasting (sandblasting, etc.), surface roughening (etching) using an alkali saponification solution or an organic solvent, and at least one surface has a specific surface roughness specified in the present invention. A method for producing a keypad polyurethane film comprising a roughened surface having a thickness;
(Ii) The above-described polyurethane or a polyurethane composition mainly composed of the polyurethane is brought into contact with a member having a roughened surface having a specific surface roughness defined in the present invention in a melted state or a softened state in a film shape. Thereafter, a method for producing a polyurethane film for a keypad having a roughened surface by solidifying or curing the polyurethane or the polyurethane composition;
Can be mentioned.

  Among the methods (i) and (ii) described above, the method (ii) is preferably employed because it can reliably and stably obtain a keypad polyurethane film having the desired surface roughness. The

As a specific manufacturing method of the above (ii), for example,
(Ii-1) On the roughened surface of the base material having a roughened surface having a specific surface roughness defined in the present invention, the above-described polyurethane or a polyurethane composition mainly composed of the polyurethane is in a molten state or After laminating into a film shape in a softened state, a laminated structure (that is, a polyurethane film for a keypad with a protective layer of the present invention coated with a protective layer comprising the base material) is produced, and then the base material is produced from the laminated structure. A method for producing a polyurethane film for a keypad of the present invention by peeling off the layers;
(Ii-2) A roll (such as an embossing roll) having a specific surface roughness (roughened surface) defined in the present invention (such as an embossing roll), a drum, an endless belt, or a press die is in a molten state or a softened state. A method for producing the polyurethane film for a keypad of the present invention by molding the above-mentioned polyurethane or a polyurethane composition mainly composed of the polyurethane into a film-like shape;
(Ii-3) The above-described polyurethane or a polyurethane composition mainly composed of the polyurethane in a mold in which at least one inner surface in the cavity is a roughened surface having a specific surface roughness defined in the present invention. A process for producing a polyurethane film for a keypad according to the present invention;
And so on.

  In the above method (ii-1), if the base material is not peeled off from the laminated structure, the polyurethane film for a keypad with a protective layer of the present invention coated with a protective layer made of the base material is used. Can be manufactured.

  In the above-described methods (ii-1) to (ii-3), the surface roughness of the roughened surface in the base material layer or the like is approximately the same as the surface roughness to be imparted to the polyurethane film for keypad of the present invention. If it is. In these methods, as shown in the following examples, the surface roughness of the roughened surface of the polyurethane film obtained is larger than the surface roughness of the roughened surface of the substrate. Therefore, even if the base material etc. whose surface roughness of a roughening surface is less than 10 micrometers is used, the polyurethane film for keypads of this invention whose surface roughness of a roughening surface is 10 micrometers or more can be manufactured (for example, Example 2 below. However, in order to ensure that the surface roughness of the roughened surface of the polyurethane film is 10 μm or more, the surface roughness of the roughened surface of the substrate or the like is preferably 10 μm or more, more preferably 12 μm or more, Preferably it is 14 micrometers or more, Most preferably, it is 16 micrometers or more. The surface roughness of the roughened surface of the substrate or the like is preferably 25 μm or less, more preferably 23 μm or less, and even more preferably 21 μm or less.

  Among the manufacturing methods of (ii-1) to (ii-3) described above, the manufacturing method of (ii-1) has a roughened surface with a specific surface roughness defined in the present invention. A polyurethane film for a keypad with protection, in which the roughened surface of the polyurethane film for a keypad or the roughened surface of the keypad polyurethane film is covered with a protective layer made of a substrate, can be preferably used.

  In producing the polyurethane film for a keypad of the present invention or the polyurethane film for a keypad with a protective layer by the production method of (ii-1) above, a specific surface roughness is roughened by using an extruder. A method of laminating the above-described polyurethane or a polyurethane composition mainly composed of the polyurethane in a film state in a molten state or a softened state is preferably employed on the roughened surface of the substrate having a surface.

  Moreover, in the manufacturing method of said (ii-1), leaving a base material layer as a protective layer, without peeling a base material layer from the laminated structure which consists of a polyurethane film layer and a base material layer, with a protective layer When a polyurethane film for keypads is used, the polyurethane film for keypads with a protective layer is shipped to the keypad manufacturing site with the protective layer (base material layer) still attached, and at the keypad manufacturing site. Since the protective layer (base material layer) is peeled off, the keypad polyurethane film is protected by the protective layer (base material layer) up to the keypad manufacturing site.

  As the base material used in the production method (ii-1), paper, fabric, metal, ceramic, wood, plastic, and two types thereof having a roughened surface having a specific surface roughness defined in the present invention. The composite material etc. which the above combined are mentioned. The thickness of the substrate is not particularly limited, but is preferably 30 to 150 μm, and preferably 40 to 100 μm from the viewpoints of availability, handling, and operability when producing a keypad polyurethane film. It is more preferable that the thickness is 50 to 80 μm.

  The substrate is preferably made of plastic, particularly a plastic film or a plastic sheet. Examples of the plastic include polyester, polyamide, polycarbonate, polyvinylidene chloride, polyvinyl chloride, acrylic resin, polyoxymethylene resin, saponified ethylene-vinyl acetate copolymer, aromatic vinyl compound and vinyl cyanide compound, Examples thereof include a copolymer with at least one selected from conjugated dienes and olefins. Among these, the base material is more preferably made of polyester, polyamide or polycarbonate, and more preferably made of polyester, from the viewpoint of adhesion to the keypad polyurethane film layer and heat resistance. As the polyester, polyethylene terephthalate, polybutylene terephthalate, or the like is preferably used.

  Moreover, in the laminated structure formed with the manufacturing method of said (ii-1), ease of peeling of a base material layer (protective layer), ensuring of the protective function at the time of making a base material layer function as a protective layer, etc. From the viewpoint, the peel strength between the polyurethane film layer and the base material layer (protective layer) is preferably in the range of 0.1 to 0.5 N / cm, and preferably in the range of 0.1 to 0.3 N / cm. It is more preferable that

  Using the above-described polyurethane film for a keypad according to the present invention, a keypad having a predetermined shape and size is produced according to each application.

  The keypad may be formed from a single layer of the polyurethane film for the keypad of the present invention, or may be a laminate in which the layer made of the polyurethane film for the keypad of the present invention and other layers are bonded and laminated. Good. In the case of a laminate, the other layers may be laminated only on one side of the keypad polyurethane film, or may be laminated on both sides.

  When the keypad is a laminate in which the layer made of the polyurethane film for keypad of the present invention and other layers are bonded and laminated, the other layers are polyester, polyamide, polycarbonate, polyolefin, silicone, polyurethane film for keypad Resin such as thermoplastic polyurethane and thermosetting polyurethane other than polyurethane forming metal, metal, paper, fabric, composite materials in which two or more of them are combined, and the like can be employed.

  In addition, the keypad may have a layer composed of paint or ink, a layer composed of an adhesive, a primer, or the like as the other layers described above. When forming a layer composed of paint or ink or a layer composed of an adhesive or a primer on the polyurethane film for the keypad, it is preferable to perform heat treatment. As the temperature of the heat treatment at that time, for example, 40 to 160 ° C. is exemplified. Examples of the heat treatment time include 5 seconds to 3 hours.

  The method for manufacturing the keypad is not particularly limited, and can be performed in the same manner as in the past. Specifically, a single layer film of a polyurethane film for a keypad of the present invention, a polyurethane film for a keypad with a protective layer, and a laminate (laminated film) obtained by laminating and bonding the above-mentioned other layers to the polyurethane film for a keypad of the present invention Etc.) can be processed by cutting, punching, cutting, etc. to produce a keypad having a desired shape and dimensions. Further, a desired groove or hole may be formed on the keypad by grinding or laser. In addition to this, the keypad has an uneven surface for arranging the key top, an uneven surface for disposing a pusher for pressing the key switch installed on the lower surface of the key sheet, and the keypad itself is the key top. Various irregularities such as irregularities for enabling functions such as a pusher and a pusher may be provided. These irregularities are compression-molded (pressed) on a single-layer film of the polyurethane film for keypads of the present invention and a laminate (laminated film) obtained by laminating and bonding the above-mentioned other layers to the polyurethane film for keypads of the present invention. Forming), vacuum forming, and the like.

  When the keypad polyurethane film is a keypad polyurethane film with a protective layer, the protective layer is peeled off from the keypad polyurethane film prior to processing such as cutting, punching and cutting to produce the keypad. Alternatively, a keypad having a predetermined shape and size may be formed by performing processing such as cutting, punching, and cutting, and then peeling from the polyurethane film layer.

  By disposing key tops such as button keys at predetermined positions on the keypad described above, a key sheet having key tops on the keypad can be obtained. In addition to the key top, the key sheet may have a pusher as necessary. Use a chemically reactive adhesive (such as cyanoacrylate-based adhesive), UV-curable adhesive, thermosetting adhesive, hot-melt adhesive, etc. Can be done.

  When storing or transporting the polyurethane film for keypad of the present invention, or processing the keypad or keysheet from the polyurethane film for keypad of the present invention, the polyurethane film or the same is cut into a predetermined shape and size. These are overlapped in a state where the polyurethane film surfaces are in contact with each other, and are stored, transported, transported to a processing step, and the like. Since at least one surface of the polyurethane film for keypads of the present invention is a roughened surface having the specific surface roughness defined in the present invention, the polyurethane film for keypads or the It is possible to prevent sticking between keypad cut pieces cut into a predetermined shape and size.

  Keypads and key sheets obtained using the polyurethane film for keypads of the present invention are suitably used as members constituting operation units such as communication terminals such as mobile phones, various instruments, keyboards for PC input, and remote controllers. can do.

  The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to the following examples.

Measurement of logarithmic viscosity and ASTM D hardness of polyurethane, surface roughness of roughened surface of film, and peel strength of protective layer in polyurethane film for keypad with protective layer in the following production examples, examples and comparative examples, The tensile stress (M ₁₀₀ ) and adhesiveness of the keypad polyurethane film and the peel strength between the keypad polyurethane film and the polycarbonate plate were measured and evaluated by the following methods. These results are shown in Table 1.

(1) Measurement of logarithmic viscosity of polyurethane :
200 ml of N, N-dimethylformamide (DMF) was added to 1 g of the polyurethane obtained in the following production example, and the mixture was stirred at room temperature for 24 hours. When insoluble matter was generated, 200 ml of DMF was further added to the insoluble matter, and the operation of stirring for 1 hour and separating by filtration was repeated three times, and the collected filtrates were combined. After distilling off DMF from the filtrate, it was vacuum-dried at room temperature for 24 hours, and the mass of the obtained polyurethane component was measured to confirm that 100% by mass of the polyurethane forming the keypad polyurethane film was extracted. confirmed.
The extracted polyurethane was dissolved again in DMF to a concentration of 0.5 g / dl, and the flow time of the polyurethane in DMF solution at 30 ° C. was measured using an Ubbelohde viscometer. The logarithmic viscosity (η _inh ) was determined.
Logarithmic viscosity of polyurethane (η _inh ) (dl / g) = [ln (t / t ₀ )] / c
[Wherein, t is the flow time (second) of the DMF solution of polyurethane, t ₀ is the flow time (second) of the solvent (DMF), and c is the concentration (g / dl) of the DMF solution of polyurethane. ]
In addition, the logarithmic viscosity of polyurethane in the polyurethane film can be measured in the same manner as described above by collecting 1 g of film. When the extraction rate is less than about 100% by mass, it is determined that the portion not extracted is insoluble in DMF because the molecular weight of polyurethane is sufficiently high, and it is removed from the logarithmic viscosity measurement target.

(2) Measurement of ASTM D hardness of polyurethane :
The polyurethane produced in Production Example 1 below is injection molded using a mold having a mirror-finished surface (cylinder temperature 185 to 210 ° C., mold temperature 30 ° C.), and a disk-shaped molded product (diameter 120 mm, (Thickness 2 mm) was manufactured, and ASTM D hardness of the molded product (polyurethane) was measured in accordance with ASTM D2240 using a stack of three obtained disk-shaped molded products.

(3) Measurement of the surface roughness of the roughened surface of the film :
A polyurethane film for a keypad obtained in the following examples or comparative examples, or a roughened surface of a resin film used as a base material (protective layer) was subjected to a laser microscope [“SLM700” manufactured by Lasertec Corporation; Using the formula (optical type)], image observation was performed at a magnification of 10 times to obtain image observation data. Next, image analysis of arbitrary 5 points in the range of 2.8 mm × 2.8 mm was performed from the image observation data, and arithmetic average roughness was measured at each of the 5 points in accordance with JIS B0601-2001 (each evaluation The length was 300 μm). The total of the five arithmetic average roughness obtained was divided by 5 to obtain the surface roughness of the roughened surface of the film.

(4) Measurement of tensile stress (M ₁₀₀ ) of polyurethane film for keypad :
The polyurethane film for keypads obtained in the following examples or comparative examples was cut to produce a dumbbell-shaped test piece (width 5 mm at the center) defined in JIS K 7311-1995. Using the Instron testing machine (Instron Japan Ltd. “Instron 5566”) at a temperature of 23 ° C. and a tensile speed of 300 mm / min, the above dumbbell-shaped test piece was stretched 100%. Tensile stress was measured and used as the tensile stress (M ₁₀₀ ) of the polyurethane film for keypad.

(5) Measurement of peel strength of protective layer in polyurethane film for keypad with protective layer :
Using the polyurethane film for keypads with a protective layer (laminated structure) obtained in the following examples or comparative examples, the polyurethane film layer and the polyethylene terephthalate film layer (protective layer) in the 180-degree peel test are peeled off. The resistance value (peel strength) was measured using “Instron 5566” manufactured by Instron Japan Company Limited at room temperature under a tensile speed of 100 mm / min. This peel strength was used as an index of adhesiveness of the protective layer.

(6) Evaluation of stickiness of polyurethane film for keypad :
Two keypad polyurethane films (length × width × thickness = 120 mm × 50 mm × 50 μm) obtained in the following examples or comparative examples, and their roughened and unroughened surfaces Were placed in contact with each other and left in a hot air dryer at 60 ° C. for 24 hours under a load of 9.8 N (1 kgf). Then, after cooling, removing the load, and lifting one of the polyurethane films by hand, the state in which the other polyurethane film is not attached is evaluated as “good” (no sticking), and the other The state in which one polyurethane film was adhered was evaluated as “bad” (with stickiness).

(7) Measurement of peel strength between polyurethane film for keypad and polycarbonate plate Polycarbonate plate used for light guide plate of key part (polycarbonate “Iupilon S-3000R” manufactured by Mitsubishi Engineering Plastics Co., Ltd., vertical) × width × thickness = 120 mm × 50 mm × 150 μm) and a polyurethane film for keypad are stacked so that the polycarbonate plate and the roughened surface of the film are in contact with each other, and a load of 13.4 N (1.37 kgf) is applied. In the applied state, it was left in a hot air dryer at 80 ° C. for 24 hours. After cooling, the load is removed, and the resistance value (peeling strength) when the polycarbonate plate and the polyurethane film are peeled off is pulled at room temperature using “Instron 5566” manufactured by Instron Japan Company Limited. The measurement was performed at a speed of 100 mm / min. When the peel strength is 0 gf / cm, the polycarbonate plate and the polyurethane film do not adhere to each other, and the polyurethane film is peeled off from the polycarbonate plate without any resistance. If a polyurethane film having a peel strength of 0 gf / cm is used for the keypad, the key portion (polycarbonate) and the polyurethane film do not adhere to each other during key operation, and good key operability can be realized.

<< Production Example 1 >> [Production of polyurethane]
Polymer polyol containing 10 ppm of dibutyltin diacetate (urethanization reaction catalyst) produced by reacting 1,4-butanediol and adipic acid, the number of hydroxyl groups per molecule is 2.00, and the number average molecular weight is 1,000 Polyester diol) (POH), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (chain extender) (BD), and the molar ratio of POH: MDI: BD is 1.0: 3 .7: 2.7 (content ratio of nitrogen atom derived from isocyanate group: 4.8% by mass), and a twin screw type extruder rotating in the coaxial direction so that the total supply amount thereof is 200 g / min. (Single diameter = 30 mmφ, L / D = 36; heating zone divided into three zones: front, center, and rear) Continuously supplied to the front of the heating zone for polymerization Under conditions in degrees 260 ° C. by continuous melt polymerization was conducted polyurethane-forming reaction. The obtained melt was continuously extruded into water in a strand shape, and then cut with a pelletizer to obtain pellets. The obtained pellets were dehumidified and dried at 80 ° C. for 4 hours to obtain polyurethane.

Example 1
The polyurethane obtained in Production Example 1 was melt-kneaded by a T-die type extruder (25 mmφ, cylinder temperature = 180 to 200 ° C., die temperature = 200 ° C.), and T-die (lip width = 0) of the extruder. 0.7 mm, die width = 350 mm) and a discharge roll of 3 kg / hr, a 30 ° C. cooling roll, and a polyethylene terephthalate film whose one surface is roughened by sand mat processing (surface roughness of the roughened surface = 10.2 μm, supplied between the roughened surface of a polyethylene terephthalate film “Embret MB75” manufactured by Unitika Ltd. and subjected to sand matting), and a gauge pressure of 0.147 MPa (1.5 kgf / cm ² ) It consists of a polyethylene terephthalate film that is wound at a winding speed of about 1.5 m / min and pressed with a sand mat. A polyurethane film for a keypad with a protective layer coated with a protective layer was produced. The thickness of the polyurethane film after peeling off the protective layer was 50 μm. Moreover, the photograph which image | photographed the roughened surface of the obtained polyurethane film for keypads with the microscope (10-times multiplication factor) is shown in FIG.

Example 2
In Example 1, polyethylene terephthalate subjected to etching treatment (surface roughness of the roughened surface = 9.8 μm, polyethylene terephthalate film “Embret MB75” manufactured by Unitika Co., Ltd.) was used instead of the sand matt treated polyethylene terephthalate A polyurethane film for a keypad with a protective layer coated with a protective layer made of an etched polyethylene terephthalate film was produced in the same manner as in Example 1 except that the one subjected to the etching treatment was used. The thickness of the polyurethane film for keypads after peeling off the protective layer was 50 μm.

Example 3
In Example 1, in place of polyethylene terephthalate subjected to sand mat treatment, polyethylene terephthalate subjected to etching treatment (surface roughness of roughened surface = 14.9 μm, polyethylene terephthalate film “Embret MB75” manufactured by Unitika Ltd.) A polyurethane film for a keypad with a protective layer coated with a protective layer made of an etched polyethylene terephthalate film was produced in the same manner as in Example 1 except that the one subjected to the etching treatment was used. The thickness of the polyurethane film for keypads after peeling off the protective layer was 50 μm.

<< Comparative Example 1 >>
In Example 1, instead of polyethylene terephthalate subjected to sand matting, polyethylene terephthalate subjected to matting (surface roughness of roughened surface = 4.6 μm, polyethylene terephthalate film “Embret MB75” manufactured by Unitika Ltd.) A polyurethane film for a keypad with a protective layer coated with a protective layer made of a matted polyethylene terephthalate film was produced in the same manner as in Example 1 except that the matted one was used. The thickness of the polyurethane film after peeling off the protective layer was 50 μm. Moreover, the photograph which image | photographed the roughened surface of the obtained polyurethane film for keypads with the microscope (10-times multiplication factor) is shown in FIG.

  The polyurethane film for a keypad of the present invention does not stick to each other even if a release agent is not blended in the polyurethane forming the film. In addition, it is easy to handle when manufacturing key sheets. The keypad produced using the polyurethane film for the keypad of the present invention, which is excellent in handleability, is operated in the form of a key sheet, for example, a communication terminal such as a mobile phone, various instruments, a keyboard for personal computer input, a remote control, etc. It can be suitably used in the part.

  This invention is based on Japanese Patent Application No. 2009-171378 for which it applied to Japan, The content is altogether included in this specification.

Claims (12)

  A polyurethane film for a keypad comprising a polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender or a polyurethane composition mainly composed of the polyurethane, wherein at least one surface is in accordance with JIS B0601-2001. A polyurethane film for a keypad, characterized in that the surface roughness measured in conformity is a roughened surface having a surface roughness of 10 μm or more.   The polyurethane film for a keypad according to claim 1, wherein the surface roughness of the roughened surface measured according to JIS B0601-2001 is 10 to 25 µm.   The polyurethane film for a keypad according to claim 1 or 2, wherein the thickness is 40 to 300 µm. The polyurethane film for a keypad according to any one of claims 1 to 3, wherein a tensile stress (M ₁₀₀ ) at 100% elongation at 23 ° C is 15 MPa or more.   The keypad formed using the polyurethane film for keypads as described in any one of Claims 1-4.   A key sheet in which a key top is disposed on the keypad according to claim 5.   The polyurethane film for keypads with a protective layer by which the roughening surface of the polyurethane film for keypads as described in any one of Claims 1-4 is coat | covered with the protective layer.   The polyurethane film for a keypad with a protective layer according to claim 7, wherein the peel strength between the polyurethane film for the keypad and the protective layer is 0.1 to 0.5 N / cm.   The polyurethane film for a keypad with a protective layer according to claim 7 or 8, wherein the protective layer is a layer made of polyester.   A polyurethane obtained by reacting a polymer polyol, an organic polyisocyanate and a chain extender on a roughened surface of a substrate having a roughened surface or a polyurethane composition mainly composed of the polyurethane is melted or softened. It is a protective layer in which the roughened surface of the polyurethane film layer having a roughened surface having a surface roughness measured in accordance with JIS B0601-2001 and having a roughened surface of 10 μm or more is a substrate. A method for producing a coated polyurethane film for a keypad with a protective layer.   A protective layer is peeled off from a polyurethane film for a keypad with a protective layer to produce a polyurethane film for a keypad having a roughened surface with a surface roughness measured according to JIS B0601-2001 of 10 μm or more. 10. The method according to 10.   The method according to claim 10 or 11, wherein the surface roughness of the roughened surface of the substrate measured in accordance with JIS B0601-2001 is 10 µm or more.

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