Illuminated keyboard aims to solve the problem of users of unable to clearly distinguish notations and characters on the keycaps in a dark environment. To improve illumination characteristic of the illuminated keyboard, light transmission architecture and keycap structure are two main issues that have to be seriously focused. Compared with the more complex light transmission architecture, keycap is simpler in structure. The keycap mainly includes a press surface and a plurality of inclined surfaces extended from the press surface. Hence through a simple improvement a great effect can be accomplished.
Many prior techniques concerning improvement of the keycap focused on light emission structure of the press surface. For instance, Taiwan publication No. 200745915 proposes an opaque keycap with a transparent character notation formed thereon to highlight the character notation. U.S. Pat. No. 7,847,204 discloses a keycap with four different transparent colored layers respectively at four corners of the press surface. Taiwan utility model No. M419150 discloses a keycap having a press surface with a transparent portion to allow light to transmit. They all have the disadvantage of occupying too much area on the keyboard by the press surface of the keycap. With the light concentrating on the press surface for emission the entire keyboard is illuminated that makes distinguishing individual keycaps difficult.
There are other types of keycap structures that do not emit light through the press surface, such as Taiwan patent No. I283421. It discloses a backlit key assembly which includes an opaque key and a light guide element surrounding the key. It transfers the lighting element from the traditional press surface to the light guide element such that a ring of bright backlight is presented around the key. But it requires adding an extra light guide element around the key and results in the disadvantages of a higher cost and more complex fabrication and assembly processes.
Another Taiwan patent No. I340402 discloses a keycap capable of emitting light laterally. The keycap has a light incident surface at the bottom and a light emitting surface at one lateral side. The light emitting surface has a refractive surface corresponding to the keycap. When light projects to the light incident surface and is guided by the refractive surface to the light emitting surface, it emits laterally via the light emitting surface and projects to an identification zone corresponding to the keycap. Although it can emit light laterally, the conventional keyboard has the notations and characters located on the keycaps rather than on the identification zone. The transverse light cannot travel longitudinally to illuminate the notations and characters on the keycaps, hence it is not suitable for the conventional illuminated keyboards.