JP3755787B2 - Covered keypad - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicone rubber keypad with a coating layer used for an input pushbutton switch of an electric device, a precision device, a mobile phone, an automobile, etc., and particularly has a soft touch, a small increase in pressing load, and wear resistance. It is related with the keypad with a covering layer.
[0002]
[Prior art]
Conventionally, silicone rubber keypads used for input pushbutton switches in electrical equipment, precision equipment, mobile phones, automobiles, etc. have been studied for various ways to improve their surface wear resistance and antifouling properties. Has been. For example, Japanese Patent Laid-Open No. 7-282687 discloses a structure in which a surface of a rubber key top portion is modified with ultraviolet rays and then a reaction curable coating layer is provided. In Japanese Patent Laid-Open No. 7-296676, a silicone rubber surface is subjected to plasma treatment. Then, a method and a structure for providing a coating film made of a normal urethane paint having an isocyanate cross-link have been proposed.
[0003]
[Problems to be solved by the invention]
Although the intended wear resistance and antifouling properties can be improved by conventional methods, the hardness of the coating layer is significantly higher than the silicone rubber that is the base material of the keypad, and the JIS-A hardness is 85 It has the above. Therefore, this keypad with a cover layer forms a very hard layer compared to the normal hardness 60 of the base flexible silicone rubber keypad. It had been.
[0004]
Further, when the coating layer is formed on the skirt portion corresponding to the click portion when the switch is pressed by the conventional method, there is a problem that the pressing load is greatly different from that of the keypad not forming the coating layer. In order to solve this problem, that is, to reduce the pushing load, a method of reducing the thickness of the keypad rubber member of the base has been studied. However, stress concentration occurs locally on the thinned portion, and locally. There was a problem that it was easy to break.
[0005]
[Means for Solving the Problems]
The present invention relates to a keypad with a cover layer that solves such drawbacks.
[0006]
That is, the present invention forms a urethane-based coating layer having a soft feel and containing 5 to 40% by weight of a plasticizer having a hardness y of Formula 1 and a molecular weight of 300 or more on the surface of a silicone rubber keypad having a hardness x. This is a keypad with a covering layer.
[0007]
[Expression 1]
The paint or ink used as the material for the urethane-based coating layer used in the present invention does not specify the molecular structure or production method.
[0008]
The feature of the present invention is that the relationship between the hardness x of the silicone rubber keypad and the hardness y of the urethane-based coating layer after curing satisfies Equation 1. The hardness expressed in the present invention means the JIS-A hardness of JIS-K6253.
[0009]
If the hardness y of the urethane-based coating layer is lower than (x-10), the tactile sensation is soft and the increase in the pushing load is small and good, but the wear resistance is inferior. On the other hand, if y is higher than (x + 20), the wear resistance is excellent, but the tactile sensation is hard and the pushing load increases greatly, and the thickness of the keypad rubber member must be reduced, resulting in stress. It is unsuitable due to destruction caused by concentration.
[0010]
A more preferable relationship between x and y is given by Equation 2.
[0011]
[Expression 2]
In Equation 1, the hardness x of the silicone rubber keypad is not limited, but a hardness in the range of 40-80 is practical. A hardness lower than 40 is not preferable because it is too flexible and has a low tensile strength and tear strength, while a hardness higher than 80 results in an excessively large pressing load and a hard feeling. Further, the hardness x of the silicone rubber keypad is preferably in the range of 50 to 70.
[0012]
Therefore, for example, when the hardness x of the silicone rubber keypad is 55, the hardness y of the urethane-based coating layer is preferably in the range of 45 to 75 that satisfies Equation 1. If the hardness y of the urethane-based coating layer is lower than 45, the key top portion has a soft feel and an increase in the pressing load can be reduced, but it is inappropriate because the wear resistance of the urethane-based coating layer is inferior. . On the other hand, although the wear resistance is good at a hardness higher than 75, neither the intended soft and flexible feel nor the reduction of the pushing load can be realized. Further, the hardness of the urethane-based coating layer is in the range of 55 to 65 that satisfies the formula 2. Similarly, when the hardness x of the silicone rubber keypad is 60, the hardness y of the urethane-based coating layer is preferably in the range of 50 to 80 satisfying Equation 1, and more preferably in the range of 60 to 70 satisfying Equation 2. is there.
[0013]
Polyol compounds that form urethane-based coating layers include polyoxyalkylene polyols, modified polyether polyols, polyether polyols such as polytetramethylene ether glycol, condensation polyester polyols, lactone polyester polyols, and polyesters such as polycarbonate diols. Polyols, urethane-modified polyols, acrylic polyols, polybutadiene-based polyols, polyisoprene-based polyols, polyolefin-based polyols, saponified ethylene vinyl acetate copolymers, phosphorus-containing polyols, silicon-containing polyols, halogen-containing polyols It is at least one known compound selected from polyols, flame retardant polyols and the like.
[0014]
Examples of the isocyanate compound forming the coating layer include tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 3,3′-bitolylen-4,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, 3 , 3'-dimethyldiphenylmethane-4,4'-diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, triphenylmethane triisocyanate, dimer of tolylene-2,4-diisocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate, dicyclohexyl Methane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, naphthalene-1,5-diisocyanate, urethane-modified polyisocyanate, urea-modified polyisocyanate Examples thereof include at least one known compound selected from nates, masked blocked isocyanates, isocyanate polymers and the like.
[0015]
Moreover, the urethane type coating layer of this invention contains 5-40 weight% of plasticizers with a molecular weight of 300 or more. Plasticizers include adipic acid esters such as di (2-ethylhexyl) adipate, diisodecyl adipate and di (butoxyethoxyethyl) adipate, azelaic acid esters such as di (2-ethylhexyl) azelate, citric acid Citric acid esters such as tri-n-butyl, epoxy derivatives of tetrahydroxyphthalic anhydride and epoxidized unsaturated oils, glycol derivatives, hydrogenated terphenyl, chlorinated paraffin, oleic acid esters, ricinoleic acid ester , Phosphate esters such as tricresyl phosphate and cresyl diphenyl phosphate, phthalate esters such as di (2-ethylhexyl) phthalate, tetrahydrophthalate esters, tri (2-ethylhexyl) trimellitic acid Trimellitic acid esters, pyromellitic Esters, polyesters of adipic acid and azelaic acid, ricinoleic acid derivatives, sebacic acid esters, fumaric acid esters, itaconic acid esters, stearic acid esters, other fatty acid esters, sulfonic acid esters, ethylene vinyl acetate Copolymers and copolymers with carbon monoxide can be used. These plasticizers may be used in combination of two or more.
[0016]
If the concentration of the plasticizer contained in the urethane-based coating layer of the present invention is less than 5% by weight, the urethane-based coating layer has insufficient hardness reduction and pushing load reduction. Exceeding 40% by weight is not preferable because wear resistance is lowered and a defective phenomenon such as bleed out of the plasticizer on the keypad surface or transfer to another material occurs.
[0017]
Moreover, it is preferable that the molecular weight is 300 or more as a plasticizer which does not bleed out on the keypad surface or shift to other materials. If the molecular weight of the plasticizer is less than 300, there is a problem that the plasticizer tends to bleed out on the surface of the keypad or shift to another material. Moreover, when forming a urethane-type coating layer by thermosetting reaction, when the molecular weight of a plasticizer is less than 300, there also exists a fault that a plasticizer volatilizes with the heat history at the time of hardening. When the molecular weight of the plasticizer is large, there is no problem of bleeding out to the keypad surface or shifting to another material, but compatibility and affinity with urethane are lowered and low temperature characteristics are inferior. Therefore, the molecular weight of the more preferable plasticizer is in the range of 400 to 3000.
[0018]
Moreover, this invention is a keypad with a coating layer characterized by the said plasticizer being a plasticizer containing the functional group which reacts with an isocyanate group. Examples of the functional group that reacts with an isocyanate group include a hydroxyl group, an amino group, and a carboxyl group. Specifically, aliphatic polyesters and aromatic polyesters such as adipic acid-based polyesters and azelaic acid-based polyesters containing a hydroxyl group in the molecule or at the molecular terminal. The functional group such as a hydroxyl group in the molecule or at the molecular end reacts with an isocyanate group in the isocyanate compound, thereby suppressing bleed out to the keypad surface and migration to other materials, and an object of the present invention. It is possible to combine soft tactile sensation with reduced pressing load and wear resistance.
[0019]
The urethane-based coating layer of the present invention includes known reaction catalysts, coupling agents, colorants, inorganic fillers such as silica and titanium oxide, matting agents such as resin beads, anti-settling agents, and fluctuations for viscosity adjustment. An agent, an antioxidant, an ultraviolet absorber, and a hydrolysis-resistant stabilizer can be contained depending on applications and purposes. In addition, when painting or printing, an organic solvent such as an aromatic hydrocarbon, aliphatic hydrocarbon, ketone or ester can be appropriately blended with the urethane paint or ink used as a raw material.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The keypad with a coating layer according to the present invention is a urethane-based coating having a soft feel and containing 5 to 40% by weight of a plasticizer having a hardness y of formula 1 and a molecular weight of 300 or more on the surface of a silicone rubber keypad having hardness x It can be obtained by painting or printing a paint or ink forming the layer.
[0021]
[Expression 1]
The presence or absence of letters and symbols on the surface of the silicone rubber keypad, the material and color tone, the presence or absence of light transmission, and the printing and painting methods are not specified.
[0022]
About the film thickness of a coating layer, 5-100 micrometers is preferable. If it is thinner than 5 μm, the wear resistance is insufficient, and if it is thicker than 100 μm, the pressing load increases and it is economically disadvantageous.
[0023]
After coating or printing, the keypad with a coating layer of the present invention can be produced by heat treatment under drying and curing conditions at a predetermined temperature and time.
[0024]
Hereinafter, the keypad with a coating layer of the present invention will be specifically described with reference to examples.
[0025]
[Example 1]
Characters and symbols 2 were screen-printed on the key top portion of the silicone rubber keypad 1 having a hardness of 60 in the shape shown in FIG. A urethane coating consisting of a polyol compound (Fantas Coat FS-6 manufactured by Origin Electric Co., Ltd.) and an isocyanate curing agent (manufactured by Origin Electric Co., Ltd.) has a concentration of 90% by weight, excluding the solvent, and a hydroxyl group at the end as a plasticizer. A urethane-based paint for a coating layer containing 10% by weight of a reactive polyester (Dainippon Ink Chemical Co., Ltd., Polycizer W, molecular weight of about 1300) and a designated dilution solvent was prepared, and the surface was modified by ultraviolet irradiation. The entire surface of the quality silicone rubber keypad was sprayed evenly. The film thickness of the urethane-based coating layer 3 after heat curing was 40 μm.
[0026]
[Example 2]
The top surface of the key top portion on which the characters and symbols 2 are printed on the key top portion of the silicone rubber keypad 1 having a hardness of 60 shown in FIG. 2 is subjected to corona discharge treatment, and the same urethane-based paint and plasticizer as in Example 1 are used. The resulting urethane coating for the coating layer was screen-printed only on the top surface of the key top portion and cured by heating. The film thickness of the urethane-based coating layer 4 after curing was 30 μm.
[0027]
Examples 3 to 6
As in Example 1, as shown in Table 1, four types of coating-type urethane coatings were spray-coated on the entire surface of a silicone rubber keypad whose surface was modified by irradiation with short-wave ultraviolet rays. . The film thickness of the urethane-based coating layer 3 after heat curing was 40 μm.
[0028]
[Comparative Examples 1-4]
As in Example 1, four types of urethane-based paints shown in Table 1 were used, and spray coating was performed on the entire surface of a silicone rubber keypad whose surface was modified by irradiation with short-wavelength ultraviolet rays. The film thickness of the urethane-based coating layer 3 after heat curing was 40 μm.
[0029]
The keypads with coating layers obtained in the examples and comparative examples were evaluated by the following method and the results are summarized in Table 1. The weight% of the urethane paint in Table 1 means the concentration excluding the solvent.
[0030]
[Table 1]
[0031]
According to Table 1, in the keypads with coating layers of Examples 1 to 6, the hardness y of the urethane-based coating layer satisfies the formula 1 with respect to the hardness x of the silicone rubber keypad, and the touch feeling is It can be seen that it is flexible, has little increase in pushing load, and also has wear resistance. In addition, the adhesion of the urethane coating layer was good, and the plasticizer did not bleed out to the keypad surface.
[0032]
On the other hand, the conventional keypads with a coating layer of Comparative Examples 1 to 3 had good wear resistance and adhesion, but had a hard feel and a large increase in the pressing load. The keypad with a cover layer of Comparative Example 4 has a low hardness y of the urethane-based cover layer, so that the tactile sensation is soft and the increase in pushing load is small, but the plasticizer bleeds out to the surface and the wear resistance is poor. Met.
[0033]
【The invention's effect】
The keypad with a covering layer of the present invention is soft and flexible, has a small increase in pushing load, and has excellent wear resistance, and is an input pushbutton for electrical equipment, precision equipment, mobile phones, automobiles, etc. Very useful for switches.
[Brief description of the drawings]
FIG. 1 shows a longitudinal sectional view of a keypad with a cover layer in Examples 1 and 3 to 6 of the present invention.
FIG. 2 is a longitudinal sectional view of a keypad with a cover layer according to a second embodiment of the present invention.
FIG. 3 shows an example of a longitudinal sectional view of another keypad with a cover layer according to the present invention.
[Explanation of symbols]
1 Silicone rubber keypad 2 Printed layer of characters and symbols 3 Painted urethane coating layer 4 Printed urethane coating layer 5 Colored light shielding layer

Claims (2)

A urethane-based coating layer formed on the surface of a silicone rubber keypad having a hardness x has a hardness y defined by Formula 1 and contains 5 to 40% by weight of a plasticizer having a molecular weight of 300 or more. A keypad with a coating layer, characterized by being a urethane-based coating layer .
2. The keypad with a coating layer according to claim 1 , wherein the plasticizer is a plasticizer containing a functional group that reacts with an isocyanate group.