Light guide and thin film keyboard having the same

A light guide includes a main body and a curved refracting face formed in the main body. As light enters the main body, a bright zone and a secondary bright zone less brighter than the bright zone are formed in the main body. The curved refracting face can be an inner wall face of a curved groove or a cavity disposed in the main body. Through the formation of the curved refracting face, the light in the secondary bright zone can be directed such that, when the light guide is disposed in a thin film keyboard, the brightness of a portion of the keyboard that corresponds to the secondary bright zone has improved brightness.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Application No. 098211451, filed on Jun. 25, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light guide and a thin film keyboard with the light guide, more particularly to a light guide capable of enhancing brightness at parts thereof and to a thin film keyboard with the light guide.

2. Description of the Related Art

Referring toFIG. 1, a thin film keyboard1of a typical electronic device such as a cell phone generally includes a keyboard surface layer11, a light guide12that is disposed under the keyboard surface layer11, and one or more light-emitting components13(such as light-emitting diodes) which emit incident light that enters from one side of the light guide12. The keyboard surface layer11is generally printed with numerals, letters, etc. As the light-emitting components13emit light into the light guide12, the light guide12illuminates the keyboard surface layer11such that the numerals and symbols on the keyboard surface layer11appear more visible in a dim environment.

Nevertheless, due to the dimensions of the light guide12and the characteristics of light-emitting angle of the light-emitting components13, as the light-emitting components13emit light into the light guide12, bright zones121and secondary bright zones122less brighter than the bright zones121are formed in the light guide12. As shown inFIG. 1, the secondary bright zones122are formed proximate to the two lateral sides of each of the light-emitting components13and proximate to the corners of the light guide12away from the light-emitting components13. Moreover, if opaque ink is used in printing the keyboard surface layer11, lower illumination brightness is provided to the numerals or symbols by the secondary bright zones122.

Referring toFIGS. 2 and 4, current approaches to resolve the problem described hereinabove include printing121on a top face of a light guide12(illustrated inFIG. 2), forming V-shaped grooves124in a top face of a light guide12(illustrated inFIG. 3), and forming cylindrical holes123in a light guide12(illustrated inFIG. 4). Although these approaches attempt to refract a portion of incident light from the light-emitting components13in the light guide12toward and out of the secondary bright zones122, the control of the locations toward which the refracted light is directed is compromised, and hence the increase in brightness is limited.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a light guide that is capable of focusing light locally and controlling the location toward which the light is focused.

Another object of the present invention is to provide a thin film keyboard with the light guide.

Accordingly, the thin film keyboard of the present invention includes a circuit unit, a light guide, and a keyboard surface layer. The circuit unit includes a circuit board and a light-emitting component that is disposed on the circuit board. The light guide is disposed on the circuit board, and includes a main body and a curved groove disposed in the main body. The main body has a top face, a bottom face that faces the circuit board, and a light incident lateral face that faces the light-emitting component. The curved groove is disposed between the top face and the bottom face of the main body, and has a first curved refracting face that defines a convex-side zone and a concave-side zone in the main body. The keyboard surface layer is disposed on the top face of the main body of the light guide, and has an upper surface provided with a plurality of press parts for pressing. One of said press parts is disposed proximate to the concave-side zone.

Preferably, the curved groove extends through the top face and the bottom face of the main body.

Preferably, the curved groove extends through the top face of the main body of the light guide. The bottom face of the main body is formed with a cavity that is in spatial communication with the curved groove and that has an inner wall face. A portion of the inner wall face is a sunken curved face and defines a second curved refracting face that is connected to the first curved refracting face of the curved groove.

According to another aspect, the thin film keyboard of the present invention includes a circuit unit, a light guide, and a keyboard surface layer. The circuit unit includes a circuit board and a light-emitting component that is disposed on the circuit board. The light guide is disposed on the circuit board and includes a main body and a cavity. The main body has a top face, a bottom face that faces the circuit board, and a light incident lateral face that faces the light-emitting component. The cavity sinks from the bottom face of the main body, and has a curved refracting face that is in a shape of a sunken curved face and that defines a convex-side zone and a concave-side zone in the main body. The keyboard surface layer is disposed on the top face of the main body of the light guide, and has an upper surface provided with a plurality of press parts for pressing. One of the press parts is disposed above the cavity.

Preferably, the cavity extends through the top face of the main body.

In the present invention, the curved refracting face in the light guide is capable of directing light that passes through the curved refracting face to one area in the main body, and hence can enhance the brightness of the press part that corresponds to and that is disposed above the curved refracting face.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.

Referring toFIGS. 5,6, and7, the first preferred embodiment of a thin film keyboard2according to the present invention includes a circuit unit21, a light guide3, and a keyboard surface layer22. Of course, the thin film keyboard2may also include other components that ensure the normal operation of the thin film keyboard2.

In the present embodiment, the circuit unit21includes a circuit board211, at least one light-emitting component212that is disposed on the circuit board211, and a plurality of tactile parts (not shown) that are disposed on the circuit board211. In the present embodiment, the light-emitting components212are light-emitting diodes and are soldered onto the circuit board211. The tactile parts can be metallic dome contact members that are disposed on the circuit board211and that can provide trigger signals upon pressing.

The light guide3is disposed on the circuit board211and includes a main body30and a plurality of curved grooves34that are formed in the main body30. The main body30has a top face31, a bottom face32that faces the circuit board211, and a light incident lateral face33. The light incident lateral face33faces the light-emitting components212and can receive light therefrom. As the light-emitting components212emit light toward the light incident lateral face33, bright zones221and secondary bright zones222that are less brighter than the bright zones221are formed in the main body30. The bright zones221are the zones of the main body30that face the light-emitting components212(i.e., as shown inFIG. 6, the zones that are inside the pairs of dashed lines that radiate from the light-emitting components212). The secondary bright zones222are the zones of the main body30that are proximate to the two lateral sides of each of the light-emitting components212(i.e., as shown inFIG. 6, the zones that are outside the pairs of dashed lines that radiate from the light-emitting components212) and the zones that are proximate to the corners of the main body30away from the light-emitting components212.

The curved grooves34are disposed between the top face31and the bottom face32of the main body30. The locations of curved grooves34are partially or entirely in the secondary bright zones222. In the present embodiment, each of the curved grooves34extends through the top face31and the bottom face32of the main body30. Each of the curved grooves34has a curved refracting face341that defines a convex-side zone342and a concave-side zone343in the main body30. In the present embodiment, the convex-side zone342is the zone toward which the curved refracting face341appears to bulge. On the other hand, the concave-side zone343is the zone from which the curved refracting face341appears to be recessed. As light enters from the light incident lateral face33into the main body30, light traveling toward the convex-side zone342is refracted in the X-Y plane by the curved refracting face341toward the concave-side zone343, the refraction being of the same principle as a convex lens refraction.

The keyboard surface layer22is disposed on the top face31of the main body30to serve as a keyboard surface for pressing. An upper surface of the keyboard surface layer22has a plurality of press parts220. Depending on the purpose of the thin film keyboard, each of the press parts220is one of a letter, numeral, a symbol, and a pattern printed on the upper surface of the keyboard surface layer22. The thin film keyboard22can be entirely or have at least the press parts220made of a light-transmissive material. Furthermore, as the keyboard surface layer22is disposed on the light guide3, several of the press parts220on the keyboard surface layer22are proximate to the concave-side zones343of the curved grooves34of the light guide3. In other words, when disposing the curved grooves34of the light guide3, the positions thereof correspond to the press parts220of the keyboard surface layer22that are likely to be in the secondary bright zones222.

Referring toFIG. 8, as the light-emitting components212emit light toward the light incident lateral face33of the main body30of the light guide3, the bright zones221and the secondary bright zones222are formed such that several of the press parts220of the keyboard surface layer22are in the secondary bright zones222. However, through the arrangement of the curved grooves34in the main body30of the light guide3, light in the secondary bright zones222is directed toward the concave-side zones343. As a result, the brightness of the secondary bright zones222of the light guide3is increased, and thus the press parts220of the keyboard surface layer22that are in the secondary bright zones222have improved brightness. Furthermore, because the curved refracting faces341of the curved grooves34extend from the top face31to the bottom face32of the main body30of the light guide3, a wider range of light can be directed and hence the higher brightness can be achieved.

Therefore, as described heretofore, through disposing the curved grooves34at the secondary bright zones222of the main body30of the light guide3, the curved refracting faces341are formed. The curved refracting faces341improve the brightness of the press parts220of the keyboard surface layer22that correspond with and that are disposed above the curved refracting faces341. In addition, by adjusting the radii and hence the curvatures of the curved grooves34, the locations toward which the directed light are focused can be adjusted.

FIGS. 9 and 10illustrate the second preferred embodiment of the present invention, wherein, as compared with the first preferred embodiment, a different light refracting mechanism is used in the light guide. In the second preferred embodiment, the bottom face32′ of the main body30′ of the light guide3′ is recessed and is formed with a plurality of cavities35. The cavities35replace the curved grooves34of the main body30of the light guide3of the first preferred embodiment such that the press parts220on the keyboard surface layer22are disposed above the cavities35. Each of the cavities35sinks from the bottom face32′ of the main body30′ and is formed with a shape of a sunken curved face. The sunken curved face of each of the cavities35defines a curved refracting face351. The convex-side zone342′ is the zone toward which the curved refracting face351appears to bulge. On the other hand, the concave-side zone343′ is the zone from which the curved refracting face351appears to be recessed. Preferably, each cavity35extends through the top face31′ of the main body30′ of the light guide3′.

As shown inFIG. 8, light passing through the curved refracting face341of the first preferred embodiment is refracted only in the X-Y plane. Whereas, in the second embodiment, the curved refracting faces351of the cavities35are curved in the three dimensions and thus are capable of refracting light in the direction of the Z-axis, in addition to the X-Y plane, toward the concave-side zones343′. Thus, the brightness of the secondary bright zones of the main body30′ of the light guide3′ is improved, and hence the press parts220of the keyboard surface layer22that are disposed in the secondary bright zones222have improved brightness.

Preferably, in the second preferred embodiment, when the light guide3′ is disposed on the circuit board211, the locations of the cavities35correspond to the tactile parts213(metallic dome contact members) on the circuit board211. That is to say, the tactile parts213are disposed in the cavities35. If the tactile parts213are made of a material that has better light reflectivity, more light can be directed toward the press parts220of the keyboard surface layer22to further increase the brightness.

Referring toFIGS. 11 and 12, in the third preferred embodiment of a light guide according to the present invention, a light guide3″ includes a main body30″, a plurality of curved grooves34′ that are disposed in the main body30″, and a plurality of cavities35′ that are disposed under and that are in spatial communication with the respective curved grooves34′. Each of the curved grooves34′ extends through the top face31″ of the main body30″ and has a first curved refracting face341′. Each of the cavities35′ is formed at the bottom face32″ of the main body30″, is in spatial communication with one of the curved grooves34′, and has a second curved refracting face351′. The configuration of the curved grooves34′ can be identical to that in the first preferred embodiment. On the other hand, the configuration of the cavities35′ can be identical to that in the second preferred embodiment. In other words, in the third preferred embodiment, the curved refracting face341of the first preferred embodiment and the curved refracting face351of the second preferred embodiment are combined together. In particular, the first curved refracting face341′ is capable of directing light through refraction in the X-Y plane, whereas the second curved refracting face351′ is capable of directing light through refraction in the three dimensions. Therefore, the third preferred embodiment has the respective effects of the first preferred embodiment and the second preferred embodiment. Thus, brightness of local sections of the light guide3″ is improved, and, consequently, the press parts220of the keyboard surface layer22that are in the secondary bright zone have improved brightness.

Of course, a portion of the light that is refracted by each of the cavities35′ is reflected by one of the tactile parts213toward the corresponding press part220. This arrangement can direct additional light toward the press parts220of the keyboard surface layer22and further improve the brightness.

It is noted that, the light guides3,3′, and3″ of the preferred embodiments can be formed by extrusion molding (0.1 mm-0.3 mm) or injection molding. If formed by extrusion molding, the curved grooves34and34′ and the cavities35and35′ can be formed by etching, cutting, or punching. Alternatively, if formed by injection molding, the curved grooves34and34′ and the cavities35and35′ can be formed integrally during the molding process.

Furthermore, each curve can be constituted by a smooth curve, or multiple straight lines (or planes) that are interconnected end-to-end to form a generally curved shape.

In the present invention, through disposing the curved grooves34, the cavities35and35′, or a combination of both in the light guides3,3′, and3″ to form the curved refracting faces341,351,341′, and351′, light in the secondary bright zones222can be refracted to improve the brightness of the press parts220of the keyboard surface layer22that are in the secondary bright zones222. In addition, the locations where the refracted light is to be directed can be adjusted by adjusting the curvatures of the curved refracting faces341,351,341′, and351′.