JP2005251640A - Keytop - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a keytop which is hard to slip when pushing-down operated, having a soft feel as a rubber, in which resistance to scratch and heat resistance are enhanced. <P>SOLUTION: A soft type resin layer is formed on the surface of the key top main body. That soft type resin layer comprising a polymer blend composed of a urethane based thermoplastic elastomer and an amide based thermoplastic elastomer combined at the weight ratio of 99:1 to 20:80. Kinetic friction coefficient on the surface of the soft type resin layer is 1.3 or more and 1.8 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a key top used for an electronic device such as a mobile phone.

  2. Description of the Related Art Conventionally, a key top made of a hard resin or a key top made by covering the surface of a key top body made of a hard resin with a hard resin film is used as a push button switch in an input unit of a portable device. In a pushbutton switch, such a hard key top can reliably press a contact electrode disposed below the key top and function as a switch.

  Since the key tops as described above are all made of a hard resin, the tactile sensation when touched with a fingertip was very hard. Therefore, it is easy to slip when the key top is pressed and operated with a fingertip or toe, and the operability may be adversely affected. Such a problem is particularly remarkable in a key top used in an input unit of a small electronic device such as a mobile phone. Further, when the key top is pressed with a hard object such as a toe, there is a problem that a scratch or an indentation is generated on the surface of the key top.

  In order to solve the above problem, Patent Document 1 discloses a keypad in which a key top body is covered with a laminate composed of a hard transparent thermoplastic resin film and a urethane resin film having a Shore hardness of 60 to 90 Hs. ing. According to this keypad, scratch resistance and wear resistance are improved.

  Patent Document 2 discloses a pushbutton switch having a key top in which a key top body is covered with a laminate composed of a soft urethane resin film having a Shore A hardness of 60 to 100 and a hard resin film. According to this, a pushbutton switch having a soft touch is provided.

However, since these key tops all use urethane-based resins, there is a problem that they are inferior in weather resistance and easily yellowed. Furthermore, the urethane-based resin is poor in heat resistance, and when the urethane-based resin film and the key top body are integrally molded by heating in the mold, the urethane-based resin film is softened by heat and the handling property is deteriorated. There was a thing.
JP 2000-113758 A JP 2000-268662 A

  Accordingly, an object of the present invention is to provide a key top that is hard to slip during operation and has a soft touch like rubber. Another object of the key top is to improve the scratch resistance and heat resistance.

  In order to solve the above-mentioned problem, the invention according to claim 1 is the key top in which the soft resin layer is formed on the surface of the key top body, and the soft resin layer includes the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer. And a weight ratio of 99: 1 to 20:80, and the dynamic friction coefficient on the surface of the soft resin layer is 1.3 or more and 1.8 or less. .

The invention according to claim 2 is characterized in that the key top according to claim 1 further comprises a base material layer between the key top body and the soft resin layer.
The invention according to claim 3 is the key top according to claim 2, wherein a laminated film is formed by laminating a soft resin layer on the base material layer, and the laminated film is integrated with the surface of the key top body. It is characterized by being formed by forming.

  According to the invention of claim 1, by forming the soft resin layer on the key top surface from a polymer blend of urethane-based thermoplastic elastomer and amide-based thermoplastic elastomer, it is difficult to slip during operation, has a soft tactile sensation, and is excellent. A key top having scratch resistance and heat resistance is provided.

  According to invention of Claim 2 and 3, it is possible to provide the key top excellent in productivity.

An embodiment of a key top of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a key top 10 according to a first embodiment of the present invention. The key top 10 includes a key top body 4 composed of a cylindrical portion 4 a that forms a button portion and a peripheral edge portion 4 b, and the soft resin layer 1 is directly formed on the key top body 4.

(Second Embodiment)
FIG. 2 shows a key top 20 according to the second embodiment of the present invention. The key top 20 includes a substantially columnar key top body 4 on which a base material layer 2 and a soft resin layer 1 are formed. The soft resin layer 1 and the base material layer 2 are preferably composed of a laminated film 3 in which the soft resin layer 1 is laminated on the base material layer 2. The key top 20 can be formed by integrating such a laminated film 3 on the surface of the key top body 4.

(Third embodiment)
FIG. 3 shows a key top 30 according to the third embodiment of the present invention. The key top main body 4 of the key top 30 includes a cylindrical portion 4a, a protrusion 4c that extends downward from the center of the lower surface of the cylindrical portion 4a, and a peripheral wall 4d that extends downward from the peripheral edge of the lower portion of the cylindrical portion 4a. . A conductive portion (not shown) for exhibiting a switch function may be provided at the tip of the protrusion 4c by contacting an electrical contact (not shown) disposed below the key top 30. A light shielding layer 5 and a light transmitting layer 6 are formed on the surfaces of the columnar portion 4a and the peripheral wall 4d of the key top body 4, and a base material layer 2 and a soft resin layer 1 are formed on these layers. .

  A space corresponding to the outer shape of characters and symbols may be formed in the light shielding layer 5, and the light transmitting layer 6 may be formed in the space. In this case, the light of a light source (not shown) disposed below the key top 30 is illuminated with characters and symbols through the light-transmitting layer 6 and is visually recognized from the outside. The soft resin layer 1 and the base material layer 2 are preferably composed of a laminated film 3 in which the soft resin layer 1 is laminated on the base material layer 2 as in the case of the second embodiment. After the light shielding layer 5 and the light transmitting layer 6 are formed on the surface of the key top body 4, the key top 30 can be formed by integrating the laminated film 3 with the key top body 4 through these layers. .

Hereinafter, the soft resin layer 1 will be described in more detail.
The soft resin layer 1 is formed from a polymer blend of a urethane-based thermoplastic elastomer excellent in scratch resistance and abrasion resistance and an amide-based thermoplastic elastomer excellent in heat resistance and providing a soft feel. The mixing ratio of the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer is 99: 1 to 20:80 by weight. By mixing the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer at such a ratio to form the soft resin layer 1, a key top having excellent scratch resistance and heat resistance and having a soft tactile sensation is obtained. be able to. If the weight ratio of the amide-based thermoplastic elastomer is less than 1, in the formed soft resin layer, heat resistance may be reduced, and a soft tactile sensation may not be obtained. On the other hand, if the weight ratio of the amide-based thermoplastic elastomer exceeds 80, the soft resin layer may have poor scratch resistance, which is not preferable.

  The dynamic friction coefficient on the surface of the soft resin layer 1 is 1.3 or more and 1.8 or less. More preferably, the dynamic friction coefficient is 1.5 or more and 1.8 or less. When the surface of the soft resin layer 1 has a dynamic friction coefficient in such a range, when the key top is pressed with the fingertip or the like, the fingertip is difficult to slip and a keytop having excellent operability can be obtained. Such a dynamic friction coefficient on the surface of the soft resin layer 1 can be obtained by adjusting the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer used for the soft resin layer 1 within the above-mentioned mixing ratio range.

  It is particularly preferable that the hardness of the surface of the soft resin layer 1 is A90 to A95 (measured with a type A durometer in accordance with JIS-K6253) because a softer tactile sensation is obtained when the key top is pressed. When the hardness of the soft resin layer 1 is less than A90, the heat resistance is not sufficient, the handleability at the time of manufacturing the key top is deteriorated due to softening by heat, and the scratch resistance of the obtained key top is also sufficient. May disappear. If the hardness of the soft resin layer 1 exceeds A95, a flexible feel may not be obtained during operation.

The urethane thermoplastic elastomer used for the soft resin layer 1 is a reaction product of a polyol and an isocyanate.
Examples of such polyols include, for example, low molecular polyols such as ethylene glycol, propylene glycol, and glycerin; and alkylene oxides such as diethylene oxide, propylene oxide, 1,2-butadiene oxide, and styrene oxide added to polyphenols. Polyether polyols obtained by the above method; polyester polyols obtained by a dehydration condensation reaction between the low-molecular polyols and dicarboxylic acids such as adipic acid and phthalic acid.

  As the isocyanate, it is particularly preferable to use an aliphatic diisocyanate, an alicyclic polyisocyanate, and an arylaliphatic polyisocyanate in consideration of weather resistance including yellowing. More specifically, examples of the aliphatic diisocyanate include hexamethylene diisocyanate; examples of the alicyclic polyisocyanate include dicyclohexylmethane diisocyanate, cyclohexyl diisocyanate, and isophorone diisocyanate; examples of the aryl aliphatic polyisocyanate include xylylene diisocyanate; Adduct type, burette type, isocyanurate type, and urethane imine type polyisocyanates can be used.

  And aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, para-phenylene diisocyanate; and their adduct types It is also possible to use isocyanates such as burette type, isocyanurate type and uretonimine type polyisocyanates. When these isocyanates are used, it is desirable to incorporate an ultraviolet absorber in consideration of weather resistance.

In order to form the soft resin layer 1 that is not easily scratched by a nail or the like, that is, has good scratch resistance and has a soft touch like rubber, the urethane-based thermoplastic elastomer is a simple substance, It preferably has a hardness of A70 to A90 (measured with a type A durometer in accordance with JIS-K6253). A urethane-based thermoplastic elastomer having a hardness of less than A70 tends to have poor scratch resistance and heat resistance. On the other hand, if a urethane-based thermoplastic elastomer having a hardness greater than A90 is used, a soft tactile sensation like rubber cannot be obtained. Therefore, the desired characteristics may not be obtained even if the blending ratio with the amide-based thermoplastic elastomer is adjusted.

  The amide thermoplastic elastomer is a block copolymer having a polyamide component as a hard segment and a polyether component as a soft segment. Examples of the polyamide component include polycapramide, polyhexamethylene adipamide, polyhexamethylene sebamide, polyundecanamide, polydodecanamide and the like. Examples of the polyether component include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  In order to form the soft resin layer 1 having good scratch resistance and having a soft touch like rubber, the amide-based thermoplastic elastomer is used alone, particularly with a hardness of D25 to D72 (according to JIS-K6253). It is preferable to have a type D durometer). If the hardness of the amide-based thermoplastic elastomer alone is less than D25, the heat resistance is not sufficient, and the handleability at the time of manufacturing the key top may deteriorate due to softening by heat. If an amide-based thermoplastic elastomer having a hardness exceeding D72 is used, the compatibility with the urethane-based elastomer deteriorates, so that the resulting soft resin layer has poor scratch resistance, and the soft resin layer has low transparency. There is.

  In addition to the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer, the soft resin layer 1 includes a crosslinking agent, an emulsifier, an antioxidant, an ultraviolet absorber, an anti-hydrolysis agent, an antistatic agent, as necessary. It may be formed by adding a flame retardant, a colorant, a surfactant, a filler, a foaming agent and the like.

  In the first embodiment, the soft resin layer 1 is directly formed on the surface of the key top body 4. A method for forming such a soft resin layer 1 is a method in which a melt of a polymer blend of the urethane thermoplastic elastomer and the amide thermoplastic elastomer is applied to the surface of the key top body 4 and then cooled and cured. Alternatively, there is a method in which the polymer blend is formed into a film shape by extrusion molding or calendar molding, and then the surface of the key top body 4 is covered with the film and integrated. In the case where a polymer blend of a urethane-based thermoplastic elastomer and an amide-based thermoplastic elastomer is formed into a film shape, in consideration of the wear resistance and moldability of the soft resin layer 1 to be formed, the thickness of the film is 0.04. It is preferable to be in the range of ~ 0.2 mm.

  In addition, since the soft resin layer 1 formed into a film is very soft, as described in the second and third embodiments, the soft resin layer 1 is laminated on the surface of the base material layer 2 to form the laminated film 3. After the formation, the key tops 20 and 30 may be formed by integrating the laminated film 3 with the surface of the key top body 4. According to this method, the workability and moldability of the key top can be improved. For this lamination, a lamination method such as wet lamination, hot melt lamination, dry lamination, or lamination by coextrusion can be used.

As the base material layer 2, it is preferable to use a thermoplastic resin film excellent in transparency and moldability. Examples of such a resin film include polycarbonate, polyethylene terephthalate, polybutylene terephthalate, which are crystalline or amorphous thermoplastic resins,
Examples thereof include a resin film made of polyethylene naphthalate, polyamide, polypropylene, polystyrene, polyvinyl chloride, polyacrylic acid ester, polymethacrylic acid ester, or a copolymer or a mixture thereof.

  For the key top body 4, it is preferable to use a hard resin, and examples thereof include polycarbonate, polyacrylonitrile butadiene styrene, polymethyl methacrylate, acrylonitrile styrene, polyamide, polyurethane, polystyrene, polyester, and the like, which are excellent in moldability.

The above embodiment can be modified as follows.
In the description of the first to third embodiments, only one key top 10, 20, 30 is shown in FIGS. 1 to 3, but the key top of the present invention has a plurality of key tops. It may be embodied in a key sheet. For example, the key top 10 of the first embodiment can form a key sheet having a plurality of button parts by connecting a plurality of button parts (columnar part 4a) to each other by a peripheral edge part 4b.

In the first embodiment, a decoration layer for displaying characters and symbols on the surface of the key top may be provided between the soft resin layer 1 and the key top body 4.
-In 2nd Embodiment, you may provide the decorating layer for displaying a character and a symbol on the surface of this keytop between the base material layer 2 and the keytop main body 4. FIG.

In the second and third embodiments, an adhesive layer for adhering these two layers may be provided between the base material layer 2 and the soft resin layer 1.
The soft resin layer 1 according to the first embodiment may be directly formed on the surface of the key top body 4 according to the second and third embodiments.

  The base material layer 2 and the soft resin layer 1 in the second and third embodiments may be formed on the surface of the key top body 4 in the first embodiment.

(Examples 1-6)
Urethane-based thermoplastic elastomer ("pandex T-7890N" manufactured by DIC Bayer Polymer Co., Ltd.) and amide-based thermoplastic elastomer ("PEBAX (registered trademark) 6333" manufactured by ATOFINA) are mixed in the weight ratio shown in Table 1. Using each of the polymer blends, the key top 30 shown in FIG. First, the soft resin layer 1 obtained by forming the polymer blend into a film was laminated with a base material layer 2 (“Bayhole CR1-4” manufactured by Bayer) by a hot melt laminating method to produce a laminated film 3. . Next, the light-shielding layer 5 (“NORIPHAN (registered trademark)” manufactured by Proell) and the light-transmitting layer 6 (“NORIPHAN (registered trademark)” manufactured by Proell) are provided on the lower surface of the laminated film 3 by screen printing. Formed. This film is pre-formed according to the shape of the key top 30, and the pre-formed film and the key top body 4 made of polycarbonate resin (“Makrolon (registered trademark) 2405” manufactured by Bayer) are integrated by injection molding. The key tops 30 of the respective examples were obtained. In Table 1, TPU represents a polyurethane-based thermoplastic elastomer, and PAE represents an amide-based thermoplastic elastomer.

(Comparative Example 1)
A key top 10 having the configuration shown in FIG. 1 was produced using only the same urethane-based thermoplastic elastomer (“PANEX T-7890N” manufactured by DIC Bayer Polymer Co., Ltd.) used in Examples 1 to 6. Melting the urethane-based thermoplastic elastomer,
The melt was applied to the upper surface of the key top body 4 made of polycarbonate resin (“Makrolon (registered trademark) 2405” manufactured by Bayer) to form the soft resin layer 1, thereby obtaining the key top 10.

(Comparative Example 2)
The key top 10 having the configuration shown in FIG. 1 was produced using only the same amide-based thermoplastic elastomer (“PEBAX (registered trademark) 6333” manufactured by ATOFINA) used in Examples 1 to 6. The amide-based thermoplastic elastomer was melted, and the melt was applied to the surface of the key top body 4 made of polycarbonate resin, whereby the soft resin layer 1 was formed and the key top 10 was obtained.

(Comparative Example 3)
As shown in Table 1, the key top having the structure shown in FIG. 3 was used in the same manner as in Examples 1 to 6 except that the weight ratio of the urethane-based thermoplastic elastomer and the amide-based thermoplastic elastomer was changed to 10:90. 30 was produced.

For the key tops obtained in each of the examples and comparative examples, the surface dynamic friction coefficient and hardness were measured, and scratch resistance and heat resistance were evaluated.
The dynamic friction coefficient was measured according to JIS K7125 by using a tensile tester (“Strograph” manufactured by Toyo Seiki Co., Ltd.), the friction coefficient between a copper weight weighing 500 g and the surface of the key top.

The hardness was measured with a type A durometer according to JIS-K6253.
For scratch resistance, a polycarbonate plate having a thickness of 0.5 mm was pressed against the key top surface with a load of 300 gf. By visual observation, immediately after the load was pressed, the surface of the key top had no scratches ◎, but immediately after the load was pressed, the scratches remained, but after leaving for 10 minutes, The case where the scratches on the surface were recovered and disappeared was indicated as ◯, and the case where the scratches still remained was indicated as ×.

  The heat resistance was evaluated by measuring the heat of dissolution. The measurement of the heat of dissolution consists of each soft resin layer 1 using a differential scanning calorimeter (“DSC-50” manufactured by Shimadzu Corporation) at a constant temperature increase rate (10 ° C./min) from 30 ° C. to 200 ° C. The test piece was heated to measure the heat of dissolution when it was melted in the range of about 100 to 150 ° C.

  The results are shown in Table 1 and FIG. FIG. 4 shows the relationship between the compounding amount of the urethane-based thermoplastic elastomer and the dynamic friction coefficient in the soft resin layers of Examples 1 to 6 and Comparative Examples 1 to 3.

実施例１〜６のキートップの表面が１．３１〜１．８の動摩擦係数を有することにより、押下操作の際に滑り難く、操作性が良好なキートップとなった。また、それらのキートップでは、適度な範囲の硬度を有することにより、柔軟な触感が得られた。また、耐熱性に関しては、ウレタン系熱可塑性エラストマーのみからなる比較例１と比較して、アミン系熱可塑性樹脂が配合されている実施例１〜６の軟質樹脂層１では、溶解熱が上昇しており、耐熱性が向上していることが分かる。また、耐傷付性に関しても、実施例１〜６のキートップは、いずれも良好な結果を得た。

Since the surfaces of the key tops of Examples 1 to 6 had a dynamic friction coefficient of 1.31 to 1.8, the key tops were difficult to slip during the pressing operation and had good operability. In addition, these key tops have a suitable range of hardness, so that a soft tactile sensation was obtained. Moreover, regarding the heat resistance, the heat of dissolution increases in the soft resin layers 1 of Examples 1 to 6 in which the amine-based thermoplastic resin is blended, as compared with the comparative example 1 made of only the urethane-based thermoplastic elastomer. It can be seen that the heat resistance is improved. Moreover, regarding the scratch resistance, the key tops of Examples 1 to 6 all obtained good results.

  The key top of Comparative Example 1 gave good results in scratch resistance, but had a small coefficient of dynamic friction and was easy to slip during operation. Further, in this key top, the heat of dissolution of the soft resin layer 1 was small, and sufficient heat resistance could not be obtained.

In the key tops of Comparative Examples 2 and 3, the dynamic friction force was too large, and on the contrary, it was difficult to be caught by the fingertip. Also, the scratch resistance was poor.
The technical idea grasped from the above embodiment will be summarized below.

  In the key top according to any one of claims 1 to 3, the urethane thermoplastic elastomer is a reaction product of a polyol and a polyisocyanate, and the polyisocyanate is an aliphatic polyisocyanate or an aryl aliphatic poly A key top selected from an isocyanate and an alicyclic polyisocyanate. According to this invention, a key top that hardly yellows is obtained.

  The key top according to any one of claims 1 to 3, wherein the soft resin layer has a hardness of A90 to A95 (measured with a type A durometer in accordance with JIS-K6253). Key top. According to this invention, it is possible to obtain a key top having a more flexible tactile sensation.

  The key top according to any one of claims 1 to 3, wherein the urethane-based thermoplastic elastomer is a simple substance having a hardness of A70 to A90 (measured with a type A durometer in accordance with JIS-K6253). A key top characterized by having. According to the present invention, it is possible to obtain a key top having excellent scratch resistance and a soft tactile sensation.

  The key top according to any one of claims 1 to 3, wherein the coefficient of dynamic friction is 1.5 or more and 1.8 or less. According to the present invention, it is possible to obtain a key top that is less likely to slip when pressed and has excellent operability.

1 is a longitudinal sectional view of a soft tactile key top according to a first embodiment of the present invention. The longitudinal cross-sectional view of the soft touch key top of 2nd Embodiment of this invention Longitudinal sectional view of a soft tactile key top according to a third embodiment of the present invention The graph which shows the relationship between the compounding quantity of the urethane type thermoplastic elastomer in the soft resin layer of an Example and a comparative example, and a dynamic friction coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Soft resin layer, 2 ... Base material layer, 3 ... Laminated film, 4 ... Key top main body, 5 ... Light-shielding layer, 6 ... Translucent layer, 10, 20, 30 ... Key top

Claims (3)

A key top in which a soft resin layer is formed on the surface of the key top body,
The soft resin layer is composed of a polymer blend in which a urethane thermoplastic elastomer and an amide thermoplastic elastomer are blended at a weight ratio of 99: 1 to 20:80,
A key top having a dynamic friction coefficient on the surface of the soft resin layer of 1.3 to 1.8.   The key top according to claim 1, further comprising a base material layer between the key top main body and the soft resin layer.   3. The key top according to claim 2, wherein a laminated film is formed by laminating a soft resin layer on the base material layer, and the laminated film is integrated with the surface of the key top body. .

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