Key sheets and method of producing the same

1. A key sheet comprising:

a base sheet; and

a plurality of key tops arranged on the base sheet and exposed from an operation opening formed in a case of a device, the operation opening having no partition bridge,

wherein the base sheet includes:

a plurality of bases for fixing the key tops on the base sheet; and

a resin film having through holes to fix the bases thereon by bridging over the bases.

2. A key sheet according to claim 1 , further comprising:

a reinforcing member mounted on the resin film to suppress distortion of the base sheet.

3. A key sheet according to claim 2 , wherein the reinforcing member comprises a resin molded product adhered on the resin film.

4. A key sheet according to claim 2 , wherein the reinforcing member comprises a resin molded product integrally molded with the resin film by die-molding.

5. A key sheet according to claim 2 , wherein the reinforcing member comprises a cured product of a liquefied resin applied on the resin film.

6. A key sheet according to claim 1 , wherein the base is made of a rubber-like elastic body, and the base has a flexible portion to be displaced by pushing the key top.

7. A key sheet according to claim 1 , wherein the base is made of a hard resin, and the resin film has a flexible portion to be displaced by pushing the key top.

8. A key sheet comprising:

a base sheet; and

a plurality of key tops arranged on the base sheet and exposed from an operation opening formed in a case of a device, the operation opening having no partition bridge,

wherein the base sheet includes:

a plurality of bases made of a rubber-like elastic body for fixing the key tops; and

a thin-plate like reinforcing member made of a hard resin for supporting the bases while allowing displacement upon pushing.

9. A key sheet according to claim 2 or 8 , wherein the reinforcing member is made of a heat-resistant hard resin having a deflection temperature under load of 170° C. or more.

10. A key sheet according to claim 9 , wherein the hard resin that constitutes the reinforcing member comprises a heat-resistant hard resin selected from the group consisting of a polyacrylate resin, a polyallylsulfonate resin, a polyethersulfonate resin, and a polysulfonate resin.

11. A key sheet according to claim 9 , wherein the hard resin that constitutes the reinforcing member comprises a heat-resistant polycarbonate resin including a constitutional unit represented by the following general formula (1):

(wherein X represents a carbon atom and m represents an integer of 4 to 7, R1 and R2 may be individually selected for each X, and each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 40 to 100).

12. A key sheet according to claim 2 or 8 , wherein the hard resin that constitutes the reinforcing member contains a resin reinforcement.

13. A key sheet according to claim 12 , wherein the resin reinforcement contains at least one selected from the group consisting of a glass fiber, a metal fiber, a carbon fiber, an aramid fiber, and a ceramic fiber.

14. A key sheet according to claim 8 , wherein the reinforcing member is constructed of a single plate having through holes to fix the bases thereon by bridging over the bases.

15. A key sheet according to claim 8 , wherein:

the base sheet is formed of an elastic sheet made of a rubber-like elastic body having bases; and

the reinforcing member is partially mounted between the adjacent bases.

16. A key sheet according to claim 8 , wherein:

the base sheet is formed of an elastic sheet made of a rubber-like elastic body having bases; and

the reinforcing member is mounted on an outer edge portion of the elastic sheet.

17. A key sheet according to claim 2 or 8 , wherein a pressure-contact portion made of a rubber-like elastic body is formed on the base sheet.