KR20100031158A - Thermoplastic polyurethane film - Google Patents

Abstract

PURPOSE: A thermoplastic polyurethane film is provided to ensure no discoloration in UV exposure, excellent thermal stability and thickness uniformity of a film and to be used as a base material for a keypad of cellular phone. CONSTITUTION: A thermoplastic polyurethane film is obtained from a thermoplastic polyurethane resin. The thermoplastic polyurethane resin is a reactant which is obtained by reacting organic diisocyanates, polyols and chain exteners. The organic diisocyanates includes isophorone diisocyanate and 1,6-hexamethylene diisocyanate. The polyol is a polycarbonate-based polyol or polycaprolactone-based polyol.

Description

Thermoplastic polyurethane film {Thermoplastic polyurethane film}

The present invention relates to a thermoplastic polyurethane film.

Thermoplastic polyurethanes (hereinafter referred to as TPUs) are of great industrial importance because of their superior elastomeric properties and thermoplastic processability.

Conventionally, TPU has been used in a wide range of fields such as paints, adhesives, rolls, tubes, and binders for magnetic recording media. TPU is also widely used as a synthetic leather, film, and molding sheet utilizing these characteristics because it has better low temperature characteristics, abundant flexibility, and good durability than other resins.

Among them, TPU thermoforming sheets are used for automobile handles, the skin of automotive instrument panels, bust cups for swimsuits and bras, keypads for electronic devices, trays of electronic components, air mats, water beds, and various protective cases. have.

Such thermoformed sheet TPUs are often used under conditions exposed to direct sunlight or back light sources. For this reason, the TPU for thermoforming sheets requires discoloration resistance.

On the other hand, the mobile phone is provided with a plurality of keys, each performing a variety of functions, each of the keys are formed integrally by the keypad. Of course, each key is protruded to the outside to select and press a key required by the user or the caller to communicate or obtain necessary information. These keypads are one of the next generation core electronic components that are being expanded in supply due to the explosive spread of mobile phones with the development of the global telecommunications and electronics industry.

Most mobile phone keypads are manufactured using materials such as transparent or silver polyurethane, silicone, PET, and PC. In addition, most mobile phones are equipped with a light source composed of light emitting elements such as LEDs on the outside of the bottom of the key so that the key can be accurately identified and pressed even at night. According to the above configuration, when light is emitted from the light source, the backlight is printed on the key. Recognized numbers or letters can be used.

In the conventional mobile phone keypad, the key injected into the mold is separated from the ribs, and the separated key pieces are arranged manually on the keypad, which takes a lot of work time and requires a lot of work. This causes a problem of low production efficiency. In addition, when each key is inserted into the assembly frame and a single key is not properly placed in place, a bad key is manufactured. When the adhesive is applied to the bottom of the key, a small amount of adhesive may cause a breakdown. If the amount is large, there was a disadvantage that the key operation is not smooth. In addition, a conventional mobile phone that attaches an adhesive to a bottom surface and re-coats a synthetic resin plate for that purpose, and then puts an upper frame on it and presses it with a press to integrally attach the plastic key and the synthetic resin plate and then remove the upper and lower molds to manufacture a keypad. The manufacturing method of the keypad for the production decreases as the manual process is performed by hand.

The current keypad manufacturing has been developed to compensate for the above-mentioned disadvantages. For example, a thin metal plate is a key attachment hole through a mechanical processing process such as laser processing, forming processing, punching press processing or chemical corrosion process such as chemical corrosion. Form a synthetic resin key (button) integrally through the trans-molding process in the keying hole, color the synthetic resin key, and peel off the colored surface with a laser processing machine to form letters, numbers, symbols, etc. A UV coating film is formed on it to protect the surface of the synthetic resin key, and a bottom protective pad made of silicone rubber or urethane rubber on the bottom of the metal keyframe, and a protective pad with a plurality of key insertion holes for inserting the synthetic resin key on the surface, respectively. The method of attaching is mentioned.

Some problems have been found in the mobile phone having such a keypad, in particular, the keypad is discolored to yellow or a similar color as time goes by, and the merchandise or productability is remarkably inferior.

In order to solve this problem, conventional efforts have been made to improve the thermal stability of the polyurethane sheet constituting the keypad of a mobile phone. For example, Korean Patent Laid-Open Publication No. 2002-0046186 discloses thermoplastics having a constant melt flow behavior. An economical and process suitable method for producing polyurethane elastomers which can be processed is described.

As another example, Korean Patent Laid-Open Publication No. 2005-0123505 discloses a TPU keypad having excellent secondary moldability, oleic acid resistance, discoloration resistance, transparency, and printability. A keypad comprising a TPU obtained by reacting a chain extender containing methylene diisocyanate as a main component, a polycarbonate polyol as a main component, and an aliphatic diol having 2 to 10 carbon atoms as a main component is described.

In one embodiment of the present invention to provide a thermoplastic polyurethane film does not change color when exposed to ultraviolet light.

In addition, one embodiment of the present invention to provide a thermoplastic polyurethane film excellent in heat resistance.

In one embodiment of the present invention to provide a polyurethane film with a uniform thickness of the film.

In one embodiment of the present invention is an organic diisocyanate including isophorone diisocyanate and 1,6-hexamethylene diisocyanate; Polyols; And a thermoplastic polyurethane resin obtained from a thermoplastic polyurethane resin which is a reactant of one containing chain extenders.

In the thermoplastic polyurethane film according to one embodiment of the present invention, the organic diisocyanates include isophorone diisocyanate at 10 to 50 mole% of all organic diisocyanates and 50 to 1,6-hexamethylene diisocyanate. It may be included in 90mole%.

In the thermoplastic polyurethane film according to a preferred embodiment of the present invention, the organic diisocyanates include isophorone diisocyanate at 20 to 30 mole% of all organic diisocyanates, and 70 1,6-hexamethylene diisocyanate is used. To 80mole% may be included.

In the thermoplastic polyurethane film according to one embodiment of the present invention, the polyol may be a polycarbonate polyol or polycaprolactone polyol.

In the thermoplastic polyurethane film according to a preferred embodiment, the polyol may be a polycarbonate-based polyol.

In the thermoplastic polyurethane film according to one embodiment of the present invention, the chain extenders may be mainly composed of aliphatic diols having 2 to 10 carbon atoms.

The thermoplastic polyurethane film according to one embodiment of the present invention may have a thickness variation of 10% or less based on the film thickness of 150 μm.

In addition, the thermoplastic polyurethane film according to the preferred embodiment may have a melting point of 135 ° C. or more measured by DSC.

In the preferred thermoplastic polyurethane film of the present invention, the reactant may have a molar ratio (NCO / OH) of organic diisocyanates, polyols, and chain extenders of 0.97 to 1.01.

In addition, in the preferred thermoplastic polyurethane film, the reactant may include an organic titanium compound catalyst, and preferably, the organic titanium compound catalyst may include 100 parts by weight of the total solid content of organic diisocyanates, polyols, and chain extenders. It may be included in less than 0.003 parts by weight.

In an exemplary embodiment of the present invention, the above-mentioned thermoplastic polyurethane film layer; And it can provide a thermoplastic polyurethane composite film comprising a release film layer.

In an exemplary embodiment of the present invention may be to include a protective film on the other side of the thermoplastic polyurethane film layer.

According to one embodiment of the present invention, there is no discoloration upon UV exposure, it is possible to provide a thermoplastic polyurethane film having excellent thermal stability and excellent thickness uniformity, which may be particularly useful as a base material for a keypad of a mobile phone.

Referring to the present invention in more detail as follows.

When explaining the thermoplastic polyurethane resin which is a raw material of the polyurethane film of this invention is as follows.

Thermoplastic polyurethane resins are usually reactants of organic diisocyanates, polyols, and chain extenders as necessary components. Generally, yellowing of polyurethane may be caused by various causes such as heat, UV, and gas. In particular, in the case of polyurethane, the effect of UV yellowing is greatest depending on the type of raw material used, and isocyanate among them.

Many thermoplastic polyurethane resins use aromatic diisocyanates in terms of heat resistance and elasticity, which have a quinon imide structure due to ultraviolet rays, resulting in yellowing. When hexamethylene diisocyanate is used as the diisocyanate in consideration of the effect on yellowing, it is advantageous in terms of discoloration resistance but falls in soft touch. In addition, hardness may be disadvantageous in terms of durability.

In this regard, the thermoplastic polyurethane resin according to one embodiment of the present invention uses isophorone diisocyanate together with 1,6-hexamethylene diisocyanate as diisocyanate.

In this case, it is preferable to mix isophorone diisocyanate and 1,6-hexamethylene diisocyanate at 10 to 50 mole% and 50 to 90 mole%, respectively, based on the total content of the diisocyanates to achieve tensile strength, modulus, and soft touch. It may be desirable in terms of being able to satisfy the appropriate durability.

More preferably in terms of durability, 20 to 30 mole% of isophorone diisocyanate and 70 to 80 mole% of hexamethylene diisocyanate are mixed.

 Meanwhile, thermoplastic polyurethane resins require heat resistance when considering various post-processing through thermal molding. In the case of the above-mentioned diisocyanates, heat resistance may be somewhat lower than that of aromatic diisocyanates. In this regard, in one embodiment of the present invention, it may be preferable to use a polycaprolactone polyol or a polycarbonate polyol as the polyol. In particular, it may be to use a polycarbonate polyol.

The preferred number average molecular weight of the polyol is 800 to 4,000, more preferably 1,000 to 2,500 may be advantageous in terms of flexibility.

On the other hand, the chain extender may be an aliphatic diol having 2 to 10 carbon atoms as a main component, specific examples include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentylglycol, 1,8-octanediol, 1,9-nonanediol, 3,3-dimetholol Heptane, diethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2-ethyl-1,3-propanediol, 2-normalpropyl-1,3-propanediol, 2-isopropyl -1,3-propanediol, 2-normalbutyl-1,3-propanediol, 2-ethyl-3-ethyl-1,4-butanediol, 2-methyl-3-ethyl-1,4-butanediol, 2, 3-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, etc. are mentioned. In terms of mechanical strength, preferably 1,4-butanediol may be mainly included in the chain extender.

The amount of the chain extender can be adjusted in consideration of hardness. Since the hardness increases as the ratio of the chain extender to the polyol increases, it is preferable to adjust the use ratio of the chain extender according to the required hardness.

The molar ratio of the preferred chain extender / polyol in this aspect may be 1.0 to 9.0, more preferably 3.0 to 6.0.

Meanwhile, the molar ratio (NCO / OH) of the OH group and the isocyanate group of the chain extender and the polyol may be 0.97 to 1.03, preferably 0.97 to 1.01, and more preferably 0.97 to 1.006.

The method for producing a thermoplastic polyurethane resin using such diisocyanates, polyols and chain extenders is not limited thereto. For example, polyols, diisocyanates and chain extenders can be reacted in the presence of a catalyst. have.

In this case, a urethane-catalyzed catalyst which is commonly used may be used. For example, tin, iron, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, and manganese And organic compounds or inorganic compounds such as zirconium, calcium and titanium. More specific examples include organometallic compounds, in particular dialkyl tin compounds, for example stannous octanoate, stannous oleate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin Acrylate, dibutyltin mercapto propionate, dibutyltin dodecyl mercaptide, and the like. As another preferred example, an organic titanium compound such as tertiary-n-butyl titanate may be used as a catalyst.

Depending on the amount of the catalyst used may affect the physical properties after the film or sheet processing, 0.01 parts by weight or less, preferably 0.003 parts by weight or less, based on 100 parts by weight of the total amount of the polyols, diisocyanates and chain extenders described above Most preferably, it may be 0.002 weight part or less.

In addition, additives may be used during the reaction, and examples thereof include lubricants, antioxidants, UV stabilizers, ultraviolet absorbers, fillers, reinforcing fibers, and the like, as necessary.

The amount of the additive may be preferably 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the polyols, diisocyanates and chain extenders described above in terms of heat resistance and processability.

The additive may be added after the reaction to compound with the thermoplastic polyurethane resin.

The thermoplastic polyurethane resin obtained may have a weight average molecular weight of 50,000 to 500,000 in consideration of mechanical properties and moldability.

The thermoplastic polyurethane film can be obtained by melting and extruding the pellet of such a thermoplastic polyurethane resin, and extending | stretching in a traveling direction.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely illustrative of one embodiment of the present invention and the scope of the present invention is not limited by the following examples.

Preparation Examples 1 to 22 and Comparative Examples 1 to 6

In the reaction vessel, polyols, chain extenders, and catalysts, if necessary, were weighed into the contents as described in Table 1 below, stirred for 5 minutes, and then maintained at 80 ° C. The diisocyanate of Table 1 was added, and it stirred for 2 minutes, and obtained the polymerization reaction.

After the polymerization reaction was pulverized, dried, and aged, the physical properties were measured by injection molding the specimen to a thickness of 2 mm.

However, when isophorone diisocyanate is used alone or in combination as diisocyanates, the polymerization is further aged for 8 to 12 hours at 100 to 150 ° C.

In the following Table 1, the amount of catalyst is based on 100 parts by weight of the solids of the entire reaction mixture except for the catalyst.

Polyol Index (NCO / OH) Isocyanates Chain extender 1,4-BD (R ') catalyst NCO-1 NCO-2 NCO-1 / NCO-2 (mole ratio) Type, parts by weight       Manufacturing Example One T-5652 1.006 HDI IPDI 70/30 3.9 TnBT, 0.002 2 T-5652 1.006 HDI IPDI 75/25 3.9 TnBT, 0.002 3 T-5652 1.006 HDI IPDI 80/20 3.9 TnBT, 0.002 4 T-5652 1.006 HDI IPDI 75/25 3.9 - 5 T-4692 1.006 HDI IPDI 70/30 3.9 TnBT, 0.002 6 T-4692 1.006 HDI IPDI 75/25 3.9 TnBT, 0.002 7 T-4692 1.006 HDI IPDI 80/20 3.9 TnBT, 0.002 8 T-4692 1.006 HDI IPDI 75/25 3.9 - 9 220N 1.020 HDI IPDI 70/30 3.8 T-9, 0.01 10 220N 1.020 HDI IPDI 70/30 9.0 T-9, 0.01 11 220N 1.020 HDI IPDI 75/25 5.0 T-9, 0.01 12 220N 1.020 HDI IPDI 75/25 5.5 T-9, 0.01 13 220N 1.020 HDI IPDI 75/25 6.0 T-9, 0.01 14 220N 1.020 HDI IPDI 80/20 3.8 T-9, 0.01 15 220N 1.020 HDI IPDI 80/20 8.5 T-9, 0.01 16 220N 1.020 HDI IPDI 83/17 2.8 T-9, 0.01 17 220N 1.020 HDI IPDI 83/17 3.2 T-9, 0.01 18 T-5652 1.020 HDI IPDI 75/25 3.8 T-9, 0.01 19 T-5652 1.020 HDI IPDI 75/25 3.9 T-9, 0.01 20 T-5652 1.020 HDI IPDI 75/25 3.9 T-12, 0.01 21 T-4692 1.020 HDI IPDI 75/25 3.9 T-9, 0.01 22 T-4692 1.020 HDI IPDI 75/25 3.9 T-12, 0.01 Manufacture Comparative Example One T-5650 1.020 HDI - 100 4 T-9, 0.01 2 T-5651 1.020 HDI - 100 4 T-9, 0.01 3 T-4671 1.020 HDI - 100 4 T-9, 0.01 4 T-4691 1.020 HDI - 100 4 T-9, 0.01 5 T-6001 1.020 HDI - 100 4 T-9, 0.01 6 T-5651 1.020 IPDI - 100 4 T-9, 0.01

※ T-5650: Polycaprolactone diol (number average molecular weight 800, product of Asahi KASEI company)

T-5651: polycarbonate-based diol (number average molecular weight 1,000, product of Asahi KASEI)

T-5652: polycarbonate-based diol (number average molecular weight 2,000, manufactured by Asahi KASEI)

T-4671: polycarbonate-based diol (number average molecular weight 1,000, product of Asahi KASEI)

T-4691: polycarbonate-based diol (number average molecular weight 1,000, product of Asahi KASEI)

T-4692: polycarbonate-based diol (number average molecular weight 2,000, product of Asahi KASEI)

T-6001: polycarbonate-based diol (number average molecular weight 1,000, product of Asahi KASEI)

220N: polycaprolactone diol (number average molecular weight 2,000, Daicel Co., Ltd. product)

T-9: Stannous Octoate, manufactured by Air Product

T-12: Dibutyltin dilaurate, manufactured by Air Product

TnBT: Tert-n-butyl titanate, manufactured by Dupont

R ': molar ratio to polyol

The composites obtained from the above production examples and production comparison examples were pulverized and injected into a sheet having a thickness of 2.0 mm, and then yellowing resistance, hardness, tensile strength, 100% modulus, tear strength, elongation and melting point were measured. It is shown in Table 2 below.

Specific evaluation methods are as follows.

(1) Yellowing resistance: A gray scale was determined by accelerating weathering test according to KS M ISO 4892-1: 2002 under the following conditions.

-UV Lamp: UVA-340, Irradiance: 0.89W / ㎡, Exposure Time / Temp .: 4hrs UV / 60 ℃ ± 1 ℃, Condensation Time / Temp .: 4hrs Con / 50 ℃ ± 1 ℃, Total Exposure Time: 72hrs .

(2) Shore: Measured according to JIS K 7311.

(3) Tensile strength: measured according to JIS K 7311.

(4) 100% modulus: measured according to JIS K 7311.

(5) Tear strength: measured according to JIS K 7311.

(6) Elongation: Measured according to JIS K 7311.

(7) Melting point (Tm): measured by DSC according to KS M ISO 11357-3.

Yellowing resistance (Grey scale, grade) Heat resistance (Tm, ℃) Shore Tensile Strength (kg / ㎠) 100% Modulus (kg / ㎠) Tear strength (kg / cm) Elongation (%)        Manufacturing Example One 4 ~ 5 161 94A 255 82 101 620 2 4 ~ 5 162 94A 259 82 100 594 3 4 ~ 5 162 94A 277 85 105 590 4 4 ~ 5 162 94A 274 83 101 607 5 4 ~ 5 161 94A 252 76 100 633 6 4 ~ 5 162 94A 255 76 101 612 7 4 ~ 5 162 94A 265 79 104 607 8 4 ~ 5 163 93A 261 75 99 641 9 4 ~ 5 138 90 A 355 68 95 599 10 4 ~ 5 146 96A 560 154 188 601 11 4 ~ 5 143 94A 619 93 143 753 12 4 ~ 5 146 95A 608 93 143 778 13 4 ~ 5 147 96A 676 97 150 758 14 4 ~ 5 140 91A 449 70 113 720 15 4 ~ 5 148 97A 354 195 183 406 16 4 ~ 5 139 88A 289 85 133 567 17 4 ~ 5 140 90 A 489 79 148 529 18 4 ~ 5 160 93A 282 88 115 491 19 4 ~ 5 163 95A 277 87 104 561 20 4 158 94A 377 80 109 662 21 4 ~ 5 163 94A 237 79 105 569 22 4 159 93A 515 71 103 735 Manufacture Comparative Example One 4 172 60D 359 200 185 378 2 4 170 57D 375 178 207 461 3 4 169 59D 553 187 206 594 4 4 169 57D 297 225 178 265 5 4 170 58D 321 214 191 333 6 4 ~ 5 140 75 D 302 218 175 283

From the results of Table 2, when 1,6-hexamethylene diisocyanate and isophorone diisocyanate are mixed as the isocyanates, it is excellent in heat resistance while satisfying the yellowing-free property, and excellent hardness and other physical properties are also at or above the appropriate level. Able to know.

However, when only 1,6-hexamethylene diisocyanate is used, the hardness is not satisfactory and the touch is not soft.

In addition, when only isophorone diisocyanate is used, the hardness is not excellent, and there is a problem of inferior reactivity.

Examples 1 to 22 and Comparative Examples 1 to 6

The thermoplastic polyurethane resins obtained from Preparation Examples 1 to 22 and Comparative Examples 1 to 6 were pulverized, dried and extruded to prepare pellets, and the prepared pellets were remelted at 150 to 220 ° C. to extrude into T-die films. (150 micrometers in thickness) was manufactured.

The obtained film was evaluated for yellowing resistance, film thickness variation and heat resistance, and the results are shown in Table 3 below.

Specific evaluation methods are as follows.

(1) Yellowing resistance: Gray scales were determined by accelerated weathering test according to KS M ISO 4892-1: 2002 under the following conditions.

-UV Lamp: UVA-340, Irradiance: 0.89W / ㎡, Exposure Time / Temp .: 4hrs UV / 60 ℃ ± 1 ℃, Condensation Time / Temp .: 4hrs Con / 50 ℃ ± 1 ℃, Total Exposure Time: 72hrs .

(2) Film thickness variation: measured according to KS M 3089.

(3) Heat resistance: Melting point (Tm) was measured by DSC according to KS M ISO 11357-3.

Film thickness (㎛) Yellowing resistance (Grey scale, grade) Heat resistance (Tm, ℃) Shore        Example One 150 4 ~ 5 158 94A 2 149 4 ~ 5 159 94A 3 149 4 ~ 5 159 94A 4 148 4 ~ 5 157 94A 5 151 4 ~ 5 157 94A 6 148 4 ~ 5 158 94A 7 151 4 ~ 5 159 94A 8 148 4 ~ 5 160 93A 9 140 4 ~ 5 135 90 A 10 150 4 ~ 5 143 96A 11 148 4 ~ 5 141 94A 12 150 4 ~ 5 142 95A 13 151 4 ~ 5 143 96A 14 146 4 ~ 5 137 91A 15 153 4 ~ 5 144 97A 16 140 4 ~ 5 135 88A 17 142 4 ~ 5 136 90 A 18 148 4 ~ 5 154 93A 19 149 4 ~ 5 159 95A 20 149 4 157 94A 21 149 4 ~ 5 160 94A 22 148 4 155 93A  Comparative example One 172 4 168 60D 2 168 4 168 57D 3 170 4 165 59D 4 167 4 165 57D 5 167 4 167 58D 6 180 4 ~ 5 135 75 D

From the results of Table 3, according to one embodiment of the present invention, it is possible to provide a thermoplastic polyurethane film having excellent yellowing resistance and excellent heat resistance and less variation in film thickness.

Although not specifically disclosed in the embodiment of the present invention, it is a matter of course that the thermoplastic polyurethane film may be processed into a roll by laminating a release paper or a release film on one surface of the obtained thermoplastic polyurethane film or additionally laminating a protective film.

Reference Example: Selecting the Best TPU Film for Mobile Phone Keypads

In order to select the film which expresses the optimal adhesive property as a film for keypads about the polyurethane films obtained from the said Examples 1-22 and Comparative Examples 1-6, the keypad was produced as follows.

The display part of the number, code | symbol, or letter formed in the key for keypad was printed on the original fabric of the polyurethane film obtained from the said Examples 1-22 and Comparative Examples 1-6.

The primer was then applied to the bottom of the polyurethane film and dried at 80 ° C. for 40 minutes.

The two-component liquid silicone rubber was then applied onto the primer and compression molded to form a silicone rubber layer.

The edges of the polyurethane film were cut to correspond to the phone size.

Then, the injection molding was performed using a polycarbonate liquid resin to have a key shape.

The injection molded and cured keys were sprayed and glued primers onto a polyurethane film printed with letters or numbers formed on the keys.

Since the post-treatment process is known in the art, detailed description thereof will be omitted.

Evaluation of molding processability and adhesiveness through the above-described process is shown in Table 4 below.

Adhesiveness was evaluated by the following method.

(Circle): When the adhesive force was measured according to JIS Z 0237 after adhesion, the interface fracture of the adherend appeared.

X: No interface breakage of the adherend

Adhesion Silicone Rubber Layer / Polyurethane Film Polyurethane Film / Polycarbonate Layer        Example One ○ ○ 2 ○ ○ 3 ○ ○ 4 ○ ○ 5 ○ ○ 6 ○ ○ 7 ○ ○ 8 ○ ○ 9 × ○ 10 × ○ 11 × ○ 12 × ○ 13 × ○ 14 × ○ 15 × ○ 16 × ○ 17 × ○ 18 × ○ 19 × ○ 20 × ○ 21 × ○ 22 × ○  Comparative example One × ○ 2 × ○ 3 × ○ 4 × ○ 5 × ○ 6 × ○

From the results of Table 4, the polyurethane film of the most preferred in the polyurethane film of Examples 1 to 22 in the application for the keypad is especially the polyurethane of Examples 1 to 8 when considering the adhesiveness with silicone rubber It can be seen that the film.

Claims (13)

Organic diisocyanates containing isophorone diisocyanate and 1,6-hexamethylene diisocyanate; Polyols; And a thermoplastic polyurethane film obtained from a thermoplastic polyurethane resin which is a reactant of one containing chain extenders. The organic diisocyanate comprises 10 to 50 mole% of isophorone diisocyanate and 50 to 90 mole% of 1,6-hexamethylene diisocyanate according to claim 1. Thermoplastic polyurethane film. The organic diisocyanate according to claim 1 or 2, comprising 20 to 30 mole% of isophorone diisocyanate and 70 to 80 mole% of 1,6-hexamethylene diisocyanate in all organic diisocyanates. Thermoplastic polyurethane film, characterized in that. The thermoplastic polyurethane film according to claim 1, wherein the polyol is a polycarbonate polyol or a polycaprolactone polyol. The thermoplastic polyurethane film according to claim 1 or 2, wherein the polyol is a polycarbonate-based polyol. The thermoplastic polyurethane film according to claim 1, wherein the chain extenders are mainly composed of aliphatic diols having 2 to 10 carbon atoms. The thermoplastic polyurethane film of claim 1, wherein the thickness variation is 10% or less based on a film thickness of 150 μm. The thermoplastic polyurethane film according to claim 1 or 8, wherein the melting point measured by DSC is 135 ° C or higher. The thermoplastic polyurethane film of claim 1, wherein the reactant has a molar ratio (NCO / OH) of organic diisocyanates to polyols and chain extenders of 0.97 to 1.01. The thermoplastic polyurethane film of claim 1, wherein the reactant comprises an organic titanium compound catalyst. The thermoplastic polyurethane film of claim 10, wherein the organic titanium compound catalyst is included in an amount of 0.003 parts by weight or less based on 100 parts by weight of the total solid content of organic diisocyanates, polyols, and chain extenders. The thermoplastic polyurethane film layer of claim 1; And thermoplastic polyurethane composite film comprising a release film layer. 13. The thermoplastic polyurethane composite film of claim 12, further comprising a protective film on the other side of the thermoplastic polyurethane film layer.