JP4117693B2 - Manufacturing method of illuminated sheet key top for pushbutton switch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an illuminated sheet key top of a pushbutton switch in various electrical components such as a telephone, a personal computer keyboard, and a controller.
[0002]
[Prior art]
2. Description of the Related Art With the downsizing and porting of electric and electronic devices, there has been a demand for downsizing, thinning, and weight reduction of push button switches used in the operation unit.
[0003]
In response to this demand, it consists of a resin film printed with a display portion and a thermoplastic resin of the key top body formed by molding, and the film is provided with a curved portion having the same shape as the top surface of the key top body. The structure of a pushbutton switch in which the upper surface of the key top main body is housed in a curved portion and the film and the key top main body are integrated is described in Japanese Utility Model Laid-Open No. 2-14726 and Japanese Patent Publication No. 7-54656. It is publicly known.
[0004]
Further, the invention described in Japanese Patent Publication No. 7-54656 discloses that a resin film is sandwiched between molds, and the resin film is deformed by the pressure and heat of the molten resin at the time of injection molding. And a manufacturing method of a pushbutton switch that is taken out from the mold after the molten resin is solidified.
[0005]
[Problems to be solved by the invention]
The invention described in Japanese Utility Model Laid-Open No. 2-14726 is a structure for the push button switch to be waterproof, and there is a problem that chattering malfunction occurs due to non-adhesion between the resin film and the key body in actual use. there were.
[0006]
In the manufacturing method of the pushbutton switch described in Japanese Patent Publication No. 7-54656, since the flat resin film is stretched into a curved shape by the molten resin, the characters and symbols on the printed display portion are enlarged, and the key top Since the elongation of the resin film is larger in the vicinity of the end portion than in the vicinity of the central portion, the characters and symbols are deformed. This deformation phenomenon is more prominent when the shape of the key top is an irregular key shape such as a triangular key or a square key, as compared with a round key.
[0007]
Furthermore, in the case of an illuminated key top, uneven thickness of the printed light-shielding ink layer is caused by the non-uniform elongation of the resin film at the key top portion, and the light-shielding ink layer becomes thin. A serious defect occurred where light leaked from the part.
[0008]
[Means for Solving the Problems]
In the present invention, a resin film on which a display portion is printed is curved and formed in advance in the same shape as the upper surface side of the key top body, set in a mold for molding the key top body, and then penetrated into the curved portion of the film. Injection molding was performed so as to fill the photothermoplastic resin. As a result, since the elongation and thickness of the resin film at the key top portion are uniform, the characters and symbols on the display portion are not enlarged and deformed, and light shielding leakage is eliminated.
[0009]
As a method of pre-curving the resin film on which the display portion is printed, a method using a mold or jig different from the key top body molding die, a resin film is sandwiched between the key top body molding die, A method of forming a curve by press-fitting a mold core that is movably mounted in the mold, a resin film is sandwiched between the molds for molding the key top body, and inside the mold, inside the cavity on the injection mold side A method of forming a curve by providing a pin hole for ejecting air and ejecting air from the pin hole into the cavity, and a suction having a key top body cavity by sandwiching a resin film in a mold for molding the key top body A method of forming a curve by vacuum suction from the side of the mold in which a hole or groove is provided, a resin film is sandwiched between the mold for molding the key top body, and A pin hole for injecting air into the cavity is provided on the mold side. Air is injected from the pin hole into the cavity, and from the mold side having a suction hole or groove having a key top body cavity. There is also a method of forming a curve by vacuum suction.
[0010]
Examples of the method for printing the display portion on the resin film include a screen printing method, a pad printing method, a gravure printing method, an offset printing method, and the like. A screen printing method in which the thickness of the printing layer can be appropriately adjusted is preferable. In addition, when a reinforcing layer is provided at a portion where the key top is formed when the display portion is printed, an effect is exhibited by avoiding enlargement deformation of the display portion. This reinforcing layer only needs to have characteristics such as higher stress or higher hardness than other printing layers, and inks similar to the inks of other layers can be used, and the adhesion of each printing layer may be impaired. Absent. Furthermore, in order to impart the properties of the reinforcing layer to the ink, adjustment is performed by increasing the crosslink density of the ink or adding a filler to the ink. You may heat to 50-120 degreeC as needed immediately before carrying out curve formation of the resin film which printed this display part. This heating temperature is appropriately selected according to the material of the film and the forming method.
[0011]
As a constituent member suitable for the production method of the present invention, the translucent thermoplastic resin is at least selected from polypropylene, polyurethane, polyamide, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polystyrene, and polyacrylonitrile butadiene styrene. One resin is preferable, and the resin film on which the display portion is printed is a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, a polyamide film, a polypropylene film, a polystyrene film, a fluorine film, an ionomer film, a polycarbonate film, or polyvinyl chloride. At least one film selected from film films is preferred and printed on a resin film Ink, acrylic, PVC, urethane, ester, at least one of the ink is preferably selected from epoxy-based.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will be described by way of examples.
[0013]
The present invention relates to a sheet-like key of a pushbutton switch in which a resin film having a display portion curved in the same shape is integrally formed on the upper surface side of a key top body made of a light-transmitting thermoplastic resin formed by a mold. In the top manufacturing method, the resin film on which the display portion is printed is preliminarily formed in the same shape as the top surface of the key top main body, and then set in the key top main body molding die. This is a method for manufacturing an illuminated sheet-like key top of a pushbutton switch that is molded by injection so as to be filled with a light-transmitting thermoplastic resin.
[0014]
By using a resin film that is pre-curved to the same shape as the top surface of the key top body, the elongation and thickness of the resin film on the key top section will be uniform even after integral molding with the key top body. The letters and symbols of the above are no longer deformed and there is no light leakage.
[0015]
Examples of the present invention will be described below using a resin film having a display portion printed thereon.
[0016]
[Example 1]
A polyethylene terephthalate film having a display portion printed with an ester-based ink was curved and molded in advance to the same shape as the upper surface side of the key top body using another mold. The curved film was set in a keytop main body molding die, and then injected to fill the curved portion with polycarbonate resin, and the film on which the display portion was printed and the keytop main body were integrally molded. When bending the polyethylene terephthalate film, the top part of the male mold was blasted to make the polyethylene terephthalate film difficult to slip .
[0017]
When a flat resin film is used to manufacture a push-button switch described in Japanese Patent Publication No. 7-54656 as a prior art, the character size is 1.2 when the curve is formed by the melting temperature and injection pressure of the thermoplastic resin. The size of the letters on the illuminated sheet-like key top obtained in Example 1 was 1.01 times, whereas the size of the letters on the flat resin film was not different. . There was no light leakage.
[0018]
After preparing a polyamide film with a display part printed with urethane ink, sandwiching the film in the mold for molding the main body of the key top, the key top that is movably attached to the injection mold side in the mold A molding core to be inserted into the main body cavity was provided, and the polyamide film was bent into the same shape as the upper surface side of the key top main body by press-fitting the core. Then, it shape | molded by injection so that a polycarbonate resin might be filled in a curved part. When bending a polyamide film, for hard slippery polyamide film was subjected to a blast treatment on the top portion of the molding core.
[0019]
The size of the letters on the obtained illuminated sheet key top was 1.01 times the letter size on the flat resin film after printing, no difference, no deformation, and no light-blocking leakage.
[0020]
[Example 3]
Prepare a polyethylene terephthalate film with the display part printed with acrylic ink. After pinching the film in the mold for molding the key top body, drill a pin hole to eject air into the cavity on the injection mold side. At the same time, a pin inserted in the pin hole so as to be movable up and down was provided, and a polyethylene terephthalate film was curved and formed in the same shape as the upper surface side of the key top body by blowing hot air from the pin hole. Thereafter, it was molded by injection so as to fill the polymethyl methacrylate resin in the curved portion.
[0021]
The size of the letters on the obtained illuminated sheet key top was 1.04 times the letter size on the flat resin film after printing, there was no difference, no deformation was observed, and there was no light shielding leakage.
[0022]
[Example 4]
A mold in which a polyurethane film with a display portion printed with ester-based ink is prepared, the film is sandwiched between molds for molding the key top body, and then a suction hole or groove having a key top body cavity is formed. The polyurethane film was curved and molded in the same shape as the upper surface side of the key top body by vacuum suction from the side. Thereafter, it was molded by injection so as to fill the polyacrylonitrile butadiene styrene resin in the curved portion.
[0023]
The size of the letters on the obtained illuminated sheet key top was 1.05 times the letter size on the flat resin film after printing, no difference was observed, and there was no light leakage.
[0024]
【The invention's effect】
The sheet-like key top of the pushbutton switch in which the film on which the display part manufactured according to the present invention is printed is integrally formed has a variety of designs, with the light-transmitting thermoplastic resin and the display part printed layer of the film in close contact with the film. Even with the key top, the characters and symbols were displayed with high quality, and when printed on a flat resin film, the size and deformation of the characters were not seen, and there was no light leakage.

Claims (2)

Manufacturing method of sheet-like key top of pushbutton switch, in which a resin film having a display portion curved in the same shape is integrally formed on the upper surface side of a key top body made of a light-transmitting thermoplastic resin formed by a mold In
The top surface shape of the key top body using a different mold or jig from the mold for molding the key top body and the top part of the male mold or male jig previously blasted on the resin film with the display part printed pushbutton is curved in the same shape, and set the key top body mold in, then, characterized by molding by injection to fill the translucent thermoplastic resin in the curved portion of the set resin film Manufacturing method for illuminated sheet key tops for switches. Manufacturing method of sheet-like key top of pushbutton switch, in which a resin film having a display portion curved in the same shape is integrally formed on the upper surface side of a key top body made of a light-transmitting thermoplastic resin formed by a mold In
The resin film on which the display part is printed is sandwiched between the molds for molding the key top body, and then inserted into the key top body cavity that is movably attached to the injection mold side, and the top part is blasted A press button characterized in that a resin film is bent into the same shape as the upper surface side of the key top body by press-fitting a formed molding core, and is molded by injection so that a translucent thermoplastic resin is filled in the bending portion. Manufacturing method for illuminated sheet key tops for switches.