Key switch sheet and key switch module

1. A key switch sheet comprising:

a pressure sensitive adhesive layer for holding a contact spring by adhering to an apex portion of a dome-shaped contact spring at a back surface of a base material sheet;

wherein a thickness of the pressure sensitive adhesive layer at a region to be made to adhere to the apex portion of the contact spring is thicker than a thickness of the pressure sensitive adhesive layer at a peripheral region; and

wherein the thickness of the pressure sensitive adhesive layer at a region to be made to adhere to the apex portion of the contact spring is thicker than or equal to a thickness of the pressure sensitive adhesive layer at a region where the base material sheet is made to adhere to a substrate.

2. The key switch sheet according to claim 1 , wherein the apex portion of the contact spring is made to adhere to the pressure sensitive adhesive layer for holding the contact spring to hold the contact spring.

3. The key switch sheet according to claim 1 , wherein the pressure sensitive adhesive layer does not exist at the peripheral region.

4. The key switch sheet according to claim 1 , wherein the pressure sensitive adhesive layer formed at the back surface of the base material sheet is formed by applying a pressure sensitive adhesive to the back surface of the base material sheet using a screen printing method, a gravure printing method, or a roll coater method.

5. The key switch sheet according to claim 1 , wherein the thickness of the pressure sensitive adhesive layer formed at the region to be made to adhere to the apex portion of the contact spring is at least 0.1 mm and at most 0.2 mm.

6. The key switch sheet according to claim 1 , wherein a diameter of the region to be made to adhere to the apex portion of the contact spring is at most 0.5 times a diameter of the contact spring.

7. The key switch sheet according to claim 1 , wherein the pressure sensitive adhesive layer thicker than the thickness of the pressure sensitive adhesive layer at the peripheral region is formed at a region further on the outer side than the peripheral region.

8. The key switch sheet according to claim 7 , wherein the pressure sensitive adhesive layer formed at the back surface of the base material sheet is simultaneously formed at the back surface of the base material sheet.

9. A key switch module comprising:

the key switch module substrate according to claim 1 ; and

a key top arranged on a front surface side of the key switch module substrate;

wherein the key top is arranged with, in correspondence to the position of the contact spring, a push-button for switch operating by pushing down the contact spring from the outside.

10. The key switch module according to claim 9 , wherein a light guide sheet for illuminating the key top from a back surface side is arranged between the key top and the key switch module substrate.

11. The key switch module according to claim 9 , wherein a pusher made of a pressure sensitive adhesive is arranged at a back surface of the push-button so as to project from the back surface, the pusher being made to adhere to a member facing a rear surface of the key top at a position corresponding to the apex portion of the contact spring.

12. A key switch module substrate comprising:

an apex portion of a dome-shaped contact spring that is made to adhere to a back surface of a base material sheet by a pressure sensitive adhesive or an adhesive,

wherein the back surface of the base material sheet is made to adhere to a substrate formed with a first fixed contact and a second fixed contact, which are switched to a conduction state or an insulation state by the contact spring, by pressure sensitive adhesive or adhesive,

wherein the contact spring is faced to the first fixed contact and the second fixed contact, wherein a thickness of the layer of the pressure sensitive adhesive or the adhesive at a region where the apex portion of the contact spring is made to adhere to the base material sheet is thicker than a thickness of the layer of the pressure sensitive adhesive or the adhesive at a peripheral region,

wherein a thickness of the layer of the pressure sensitive adhesive or the adhesive at a region where the base material sheet is made to adhere to the substrate is thicker than a thickness of the layer of the pressure sensitive adhesive or the adhesive at the peripheral region, and

wherein the thickness of the layer of the pressure sensitive adhesive or the adhesive at a region where the apex portion of the contact spring is made to adhere to the base material sheet is thicker than or equal to the thickness of the layer of the pressure sensitive adhesive or the adhesive at a region where the base material sheet is made to adhere to the substrate.

13. The key switch module substrate according to claim 12 , wherein part of the pressure sensitive adhesive or the adhesive applied to the outer side of the peripheral region is made to adhere to an outer peripheral portion of the contact spring, and some or all of the remaining portions are made to adhere to the substrate.

14. The key switch module substrate according to claim 12 , wherein a key switch sheet is fabricated in which the contact spring is fixed to the base material sheet by making the apex portion of the contact spring to adhere to the back surface of the base material sheet by the pressure sensitive adhesive or the adhesive, and a back surface of the key switch sheet is made to adhere to the substrate by the pressure sensitive adhesive or the adhesive to sandwich the contact spring between the substrate and the base material sheet.

15. The key switch module substrate according to claim 12 , wherein the thickness of the pressure sensitive adhesive or the adhesive formed at the region to be made to adhere to the apex portion of the contact spring is at least 0.1 mm and at most 0.2 mm.

16. The key switch module substrate according to claim 12 , wherein a diameter of the region to be made to adhere to the apex portion of the contact spring is at most 0.5 times a diameter of the contact spring.

17. A key switch sheet comprising:

a pressure sensitive adhesive layer for holding a contact spring by adhering to an apex portion of the dome-shaped contact spring at a back surface of a base material sheet;

wherein a region in which the pressure sensitive adhesive layer does not exist is formed at the periphery of the pressure sensitive adhesive layer formed at the region to be made to adhere to the apex portion of the contact spring, and the pressure sensitive adhesive layer is formed at a region further on the outer side of the region in which the pressure sensitive adhesive does not exist;

wherein the pressure sensitive adhesive layer formed at the region to be made to adhere to the apex portion of the contact spring and the pressure sensitive adhesive layer formed at the region on the outer side of the region in which the pressure sensitive adhesive layer does not exist are of same material;

wherein a thickness of the pressure sensitive adhesive layer formed at the region to be made to adhere to the apex portion of the contact spring is thicker than or equal to a thickness of the pressure sensitive adhesive layer formed at the region on the outer side of the region in which the pressure sensitive adhesive does not exist.

18. The key switch sheet according to claim 17 , wherein the apex portion of the contact spring is made to adhere to the pressure sensitive adhesive layer for holding the contact spring to hold the contact spring.

19. The key switch sheet according to claim 17 , wherein the thickness of the pressure sensitive adhesive layer formed at the region to be made to adhere to the apex portion of the contact spring is at least 0.1 mm and at most 0.2 mm.

20. The key switch sheet according to claim 17 , wherein a diameter of the region to be made to adhere to the apex portion of the contact spring is at most 0.5 times a diameter of the contact spring.

21. The key switch sheet according to claim 17 , wherein the pressure sensitive adhesive layer formed at the back surface of the base material sheet is a two-sided pressure sensitive adhesive tape having one pressure sensitive adhering surface adhered to the base material sheet.

22. The key switch sheet according to claim 17 , wherein the base material sheet is a reflecting sheet having a surface reflectivity of at least 70%.

23. The key switch sheet according to claim 17 , wherein the base material sheet is a light guide sheet for illuminating a key top.