JPS6217947Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a membrane keyboard.

In a membrane keyboard, appropriately arranged switch elements are covered with a highly flexible top sheet, and the opening and closing of the switch elements is controlled via this top sheet. FIG. 1 is a sectional view showing an example of a switch element of such a membrane keyboard. In the figure, 1 is a substrate such as a printed wiring board, 2a and 2b are fixed electrodes formed on the substrate 1 by means such as photoetching, and 3
4 is a movable electrode formed by means such as carbon printing on the back side of the top sheet 3, and 5 is a movable electrode made of a highly flexible film such as polyester. This is an insulating sheet for keeping 2a, 2b and the movable electrode 4 apart.

When pressure is applied to the switch element configured in this way in the direction indicated by arrow A in the same figure, the movable electrode 4 bridges between the two fixed electrodes 2a and 2b, creating an electrical connection between the two fixed electrodes 2a and 2b. Conductive state. When this pressing force is removed, the movable electrode 4 returns to its original position due to the elasticity of the top sheet, and the fixed electrode 4
Electrical continuity between a and 2b is cut off.

FIG. 2 is an exploded perspective view showing an example of a membrane keyboard using such a switch element.
In the figure, reference numeral 1 denotes a board made of a printed wiring board, and on its upper surface are comb-shaped fixed electrodes 2a and 2b arranged so as to mesh with each other, connector terminals 11 for connection with the outside, and these. Printed wiring 12, jumper terminals 13, etc. that connect the two are formed by photo-etching. Here, the connector terminal 11, jumper terminal 13, etc. are concentrated in one place for convenience of connection work, and this part 14 is called a connector part.

Further, reference numeral 5 denotes an insulating sheet made of an insulating material having an appropriate thickness, and has through holes 51 formed at positions corresponding to the fixed electrodes 2a and 2b and slightly larger than the fixed electrodes 2a and 2b. Furthermore, numeral 3 is a highly flexible top sheet made of polyester, and on the surface of this top sheet 3 there is a switch display section 31 on which the name of each switch is printed.
Furthermore, a movable electrode 4 formed by carbon printing or the like is provided on the back surface of the device facing the fixed contacts 2a, 2b. The keyboard is connected to the outside by, for example, a flexible printed wiring board 6. That is, connection with the outside is performed by soldering the wiring pattern 61 of the flexible printed wiring board 6 to each connector terminal 11 of the connector section 14. Such a membrane keyboard is not very suitable as a keyboard switch for a device that handles minute signals due to the influence of externally induced noise.

The present invention was developed in view of this point, and uses a surface sheet laminated with a metal layer, covers the entire surface of the keyboard with this surface sheet, and uses the shielding effect of the metal layer to eliminate noise. By providing a spacer portion at a position corresponding to the connector portion of the insulating sheet, the metal layer is prevented from being damaged by the solder of the connector terminal, and
The present invention provides a membrane keyboard that prevents the generation of abnormal noise when operating a switch by providing a slit near the spacer section. Embodiments will be described in detail below according to embodiments shown in the drawings.

FIG. 3 is a sectional view showing an example of a top sheet used in a membrane keyboard according to the present invention. In the figure, reference numeral 71 denotes an elastic sheet that serves as the base of the top sheet 7, and a base film 72 that is highly flexible, such as a polyester film, for example.
It is composed of a printed layer 73 on which the switch display section 31 and the like are printed on the back surface of this base film 72, and an insulating protective layer 74 for protecting this printed layer 73. Therefore, since the printed layer 73 cannot be directly touched from the surface of the elastic sheet 71, it will not become dirty or disappear.
The back surface of this elastic sheet 71, that is, the insulating protective layer 7
A metal layer 75 is closely arranged on the lower surface of 4.
An insulating layer 76 is further disposed in close contact with this metal layer 75. The movable electrode 4 is placed at a predetermined position on the back surface of the topsheet 7, which is constructed of five layers as described above, by carbon printing or the like. Here, the insulating layer 76 is for electrically separating each movable electrode 4.

FIG. 4 is an exploded perspective view showing an embodiment of the present invention, in which a top sheet 7 having a five-layer structure as described above is used. In order to further enhance the noise removal effect, this top sheet 7
It is arranged to cover the entire top surface of the Here, each connector terminal 11 and the like is filled with solder for connection to the flexible printed wiring board 6, and is in a slightly protruding state. Therefore, if the back side of the top sheet 7 is in direct contact with this solder surface, it will be rubbed every time the switch is operated, and over a long period of time, the insulating layer will be destroyed, causing a short circuit between the connector terminals 11. Become.

Therefore, in the present invention, this problem is solved by providing a spacer portion on the insulating sheet. That is, what is shown by 8 in the figure is an insulating sheet having through holes 81 at predetermined positions, and a spacer portion 82 that covers the connector portion 14 of the substrate 1 is provided. Therefore, the solder surface of the connector terminal 11 and the top sheet 7
Since a strong spacer part 82 is interposed between the insulating layer 76 and the insulating layer 76, the spacer part 82 will not be destroyed by the friction caused by operating the switch, and short circuit accidents between the connector terminals 11 will be avoided. can be prevented.

However, such a substrate 1 and an insulating sheet 8
When a membrane keyboard is assembled by sequentially pasting the top sheet 7 with an adhesive, an abnormal sound such as a popping sound may be generated when a switch near the connector section 14 is operated. FIG. 5a is a sectional view of the vicinity of the connector portion for explaining such a state. As shown by the solid line in the figure, since the solder 15 of the connector terminal 11 protrudes somewhat, the entire surface of the spacer portion 82 does not stick to the connector portion 14, and this connector portion 14
If a nearby switch is operated, the spacer section 82
A part of it sticks to the connector portion 14 as shown by the two-dot chain line, and returns to its original position again as shown by the solid line after the switch operation is completed. At this time, the sticking and peeling of the adhesive causes the above-mentioned crackling noise.

In the present invention, in order to prevent such abnormal noise from occurring, a slit 83 is provided at or near the base of the spacer portion 82. The silencing effect will be explained with reference to FIG. 5b. As shown in the figure,
By providing the slit 83 at the base of the spacer portion 82, the spacer portion 82 on the insulating sheet 8 side is completely adhered to the connector portion 14. Therefore, even if a switch is operated in the vicinity of the connector section 14, the spacer section 82 will not stick to or peel off from the connector section 14, thereby eliminating the generation of abnormal noises such as crackling.

In the above, an embodiment using a switch element in which electrical continuity is established between two fixed electrodes by bridging the two fixed electrodes with a movable electrode has been described, but the present invention is limited only to this. Needless to say, the present invention is not limited to this, but can also be realized by a switch element that establishes electrical continuity between one fixed electrode and a movable electrode.

As explained in detail above, according to the present invention,
To obtain a membrane keyboard which is not affected by externally induced noise, has little fear of short-circuit accidents between connector terminals, and does not generate abnormal noises due to switch operations.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of a switch element of a membrane keyboard, Fig. 2 is an exploded perspective view showing an example of a conventional membrane keyboard, and Fig. 3 is a cross-sectional view showing an example of a top sheet used in the membrane keyboard of the present invention. FIG. 4 is an exploded perspective view showing an embodiment of the present invention, and FIG. 5 is a sectional view of the vicinity of the connector portion for explaining the generation and removal of abnormal noise. 1... Board, 14... Connector part, 2a, 2b
...Fixed electrode, 3,7...Surface sheet, 71...
Elastic sheet, 75...metal layer, 76...insulating layer,
4...Movable electrode, 5, 8...Insulating sheet, 51,
81...Through hole, 82...Spacer portion, 83...Slit.

Claims (1)

[Scope of utility model registration request] A board with a fixed electrode arranged on its surface and a connector part for connection with the outside, a spacer part arranged on this board and covering the upper surface of the connector part, and a base part of the spacer part or in the vicinity thereof. An insulating sheet having a slit provided therein and a through hole drilled above the fixed electrode, an elastic sheet, a metal layer disposed in close contact with the elastic sheet, and an insulating layer disposed in close contact with the metal layer. A membrane keyboard comprising a top sheet placed over an insulating sheet so as to cover the entire substrate, and a movable electrode placed on the top sheet at a position facing the fixed electrode.