Direct backlight modules

Direct backlight modules are provided. A direct backlight module includes a liquid crystal panel, a plurality of light tubes disposed below the liquid crystal panel, a reflecting plate disposed below the light tubes, and a transparent plate disposed between the light tubes and the liquid crystal panel. Additionally, a lens array is formed on one surface of the transparent plate facing the light tubes and a prism array is formed on the other surface of the transparent plate facing the liquid crystal panel.

BACKGROUND

The invention relates to direct backlight modules, and in particular to direct backlight modules with transparent plates having microstructure to facilitate illumination uniformity.

FIG. 1ais a side view of a conventional direct backlight module. Some light emitting from illumination tubes4directly passes through a diffusion plate8aand a diffusion sheet7to a liquid crystal display2; the reminder is reflected by a reflecting plate5and then passes through the diffusion plate8aand the diffusion sheet7to the liquid crystal display2. To attain uniform brightness in the liquid crystal display2, the diffusion plate8ais formed of opaque resin. A great deal of light is, however, inevitably lost.

FIG. 1bis a side view of another conventional direct backlight module. As shown inFIG. 1b, the diffusion plate8bis constructed by irregularly meshed dot distribution to provide an even brightness for the liquid crystal display2. The dot distribution, however, reduces light transmission efficiency.

US Patent No. 2003/0184993, as shown inFIG. 1c, discloses a direct backlight module having a lens array8don a translucent substrate8cas well as a diffusion sheet7disposed between a liquid crystal display2and illumination tubes4. The light emitting from the illumination tubes4is condensed while passing through the lens array8d. Further, the condensed light travels forward while diverging, and is then diffused by the diffusion sheet7, and finally illuminates the liquid crystal display2. Although this direct backlight module can help avoid the absorption of light, the light passing through the lens array8dwill crossly diverge such that a great deal of light will illuminate the liquid crystal panel2beyond the viewable angle. Thus, brightness on the liquid crystal display2cannot effectively be increased.

SUMMARY

Direct backlight modules are provided. An exemplary embodiment of a direct backlight includes a liquid crystal panel, a plurality of light tubes disposed below the liquid crystal panel, a reflecting plate disposed below the light tubes, and a transparent plate disposed between the light tubes and the liquid crystal panel. Additionally, a lens array is formed on one surface of the transparent plate facing the light tubes and a prism array is formed on the other surface of the transparent plate facing the liquid crystal panel.

DETAILED DESCRIPTION

Direct backlight modules will be described in greater detail in the following. Please refer toFIG. 2.FIG. 2shows a side view of an embodiment of a direct backlight module. The direct backlight module comprises a plurality of light tubes21, a reflecting plate23, a diffusion sheet24, a liquid crystal panel25, and a transparent plate22. The light tubes21are disposed between the reflecting plate23and the transparent plate22as light sources and the reflecting plate23is disposed below the light tubes21to reflect light toward the liquid crystal panel25. Furthermore, the transparent plate22comprises highly penetrable plastic capable of allowing light to pass through. Thus, by means of changing the light path, the transparent plate22can substantially facilitate the uniformity and the brightness.

As shown inFIG. 3a,FIG. 3ais a three-dimensional view of the transparent plate22. Referring next toFIG. 3bshowing a side view of the transparent plate22, the transparent plate22is formed with a double-faced microstructure having a lens array32formed on one surface of the transparent plate22facing the light tubes21and a prism array31formed on the other surface of the transparent plate22facing the liquid crystal panel25. The lens array32and the prism array31are periodically arranged and also extend along the same direction as the light tubes21to effectively control the light path.

Finally, please refer toFIG. 4.FIG. 4is a partially enlarged diagram A of the transparent plate22. As shown inFIG. 4, the light passing through the lens array32will diverge and then be condensed when passing through the prism array31.

Hence, the light under control can substantially decrease the loss of the light and illuminate the liquid crystal panel within the viewable angle. Simultaneously, the brightness of the liquid crystal panel can be substantially improved.

Additionally, the prism array (first lenses)31and the lens array (second lenses)32may be preferably arranged with a width d ranging from several microns to hundreds of microns.