Liquid crystal display device and backlight module thereof

The present invention mainly relates to a liquid crystal display device which comprises a casing and a backlight module; wherein the casing comprises a frame and an opening formed at a central region of the casing, the opening defining an active area; the backlight module used in providing light source via the active area comprises at least one lamp distributed equally in regions defined by the frame and the active area. The at least one lamp comprising an even luminance portion and a dense luminance portion, wherein the even luminance portion is located in the region defined by the active area while the dense luminance portion is located in the region defined by the frame. Because the dense luminance portion is located outside the active area in the invention, the luminance uniformity in the active area is raised without complex treatments thereby.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention mainly relates to a liquid crystal display device, more particularly, to a backlight module used in a liquid crystal display device.

2. Description of the Related Art

Nowadays, liquid crystal display devices are applied much in personal computers, laptop computers and various kinds of communication equipment. However, liquid crystal itself does not emit light, and a backlight module must be applied to provide luminance to the liquid crystal display device. There are various kinds of backlight module used in the liquid crystal device. A direct under type backlight module usually comprises at least one linear lamp in parallel to each other disposed under a diffusing plate, and has advantages of light weight, high luminance and simple structure as compared with other kinds of backlight module.

Besides linear lamps applied in a direct under type backlight module, U-shaped lamps can also be applied (referring to Japan. Patent NO. 7-272507 and 9-320320). Referring toFIG. 1, a liquid crystal display device1comprises a casing11and the casing11comprising a frame111and an opening112formed at a central region of the casing11to define an active area12and show specific data of a liquid crystal panel. A backlight module comprising at least one lamp13to provide light source to the active area12, wherein each lamp13is in a U-shape formed by two parallel straight tube parts131and a bent tube part132all disposed in the active area12, and comprises an electrode133at each end.

Comparing the U-shaped lamps with the linear lamps, uses and assemblies of the electrodes can be reduced. Besides, only a circuit board for connecting the electrodes133is needed to be disposed at one side of the liquid crystal display device, and the cost of manufacturing is reduced thereby. On the other hand, when using the U-shaped lamps13, luminance of the bent tube part132nearby is much brighter than that of other regions to be uneven. In order to resolve the problem, a specially treated diffusing plate (not shown) is disposed above the lamps13. Such treatment comprises printing or coating with specific materials in regions above the bent tube part132of the diffusing plate to make luminance of the bent tube part132nearby be the same as that of other parts after diffused by the diffusing plate. Such treatment is more difficult and the diffusing plate is damaged if unsuitable manipulated, and the cost of manufacturing rises also.

Therefore, the present invention is engaged in developing a novel and improved backlight module and a liquid crystal display device thereof to attain luminance uniformity and low cost.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a liquid crystal display device which comprises a casing and a backlight module; wherein the casing comprises a frame and an opening formed at a central region of the casing, the opening defining an active area; the backlight module used in providing light source via the active area comprises at least one lamp distributed equally in regions defined by the frame and the active area. The at least one lamp comprising an even luminance portion and a dense luminance portion, wherein the even luminance portion is located in the region defined by the active area while the dense luminance portion is located in the region defined by the frame. Because the dense luminance portion is located outside the active area in the invention, the luminance uniformity in the active area is raised without complex treatments thereby.

The other objective of the present invention is to provide a backlight module used in a liquid crystal display device, the liquid crystal display device comprising a casing; wherein the casing comprises a frame and an opening formed at a central region of the casing, the opening defining an active area; the backlight module used in providing light source via the active area comprises at least one lamp distributed equally in regions defined by the frame and the active area. The at least one lamp comprising an even luminance portion and a dense luminance portion, wherein the even luminance portion is located in the region defined by the active area while the dense luminance portion is located in the region defined by the frame.

Still another objective of the present invention is to provide a liquid crystal display device comprising a casing and a backlight module. The casing comprises a frame and an opening formed at a central region of the casing, the opening defining an active area. The backlight module is adapted to act as a light source for the liquid crystal display device. The backlight module comprises a housing and at least one lamp, wherein each lamp comprises an even luminance portion and a dense luminance portion, the even luminance portion is disposed within the active area while the dense luminance portion is disposed outside the active area. The housing has at least one cavity corresponding to each lamp; the cavity is disposed outside the active area for accommodating the dense luminance portion of the lamp. Because the dense luminance portion of the lamp is in the cavity, the heat flow of the dense luminance portion of the lamp due to air convention can be reduced. Therefore, the dense luminance portion of the lamp can maintain a stable temperature, so as to avoid rapid decrease thereof.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments in the invention are described below.

The First Embodiment

FIG. 2illustrates a liquid crystal display device2comprising a casing21for receiving a backlight module comprising a frame211and an opening212formed at a central region of the casing21, the opening to define an active area22to show specific data of a liquid crystal panel. The backlight module comprises an inner side wall24and at least one lamp23. The inner side wall24defines an enclosure area substantially complementary to the active area22. The lamp23is shaped by a serpentine tube comprising a plurality of parallel straight tube parts231which connect to adjacent ones by a bent tube part232, more preferably, the straight tube parts231are generally paralleled to each other.

The present invention is characterized by disposing the lamps23; wherein the straight tube part231forming an even luminance portion is almost located in the active area22while the bent tube part232forming a dense luminance portion is located outside of the active area22. The bent tube part232is disposed in a region covered by the frame211and the inner side wall24to shelter light emitted by the bent tube part232. Specifically, the inner side wall24is substantially located under the edges defining the opening212. Preferably, the inner side wall24is adapted to be superimposed over the frame211which defines the active area22. It follows that assembly of the inner side wall24and the frame211can enhance the effect of sheltering the light emitted by the bent tube part232. As the reason, luminance of the active area22is almost emitted evenly by the straight tube parts231to be uniform. Therefore, a diffusing plate in the backlight module used in the present invention needs no special treatments and the costs and difficulties of manufacturing are significantly reduced.

The Second Embodiment

FIG. 3illustrates a liquid crystal display device3similar to the liquid crystal display device2comprising an active area32defined by a casing31and backlight module having at least one lamp33to provide luminance. Each lamp33comprises two straight tube parts331almost in parallel to each other and a bent tube part332connecting therebetween to form a U-shape. The straight tube parts331are located in the active area32while the bent tube parts332are located outside of the active area32. More preferably, the backlight module comprises three such lamps.

The Third Embodiment

FIGS. 4 and 5illustrate a liquid crystal display device4comprising a casing41for receiving a backlight module50, whereinFIG. 5illustrates a perspective partial enlarged view ofFIG. 4from it backside. The casing41comprising a frame411and an opening412formed at a central region of the frame411. The opening412defines an active area42to show specific data of a liquid crystal panel. The backlight module50comprises at least one lamp43and a housing51. Each lamp43comprises two straight tube parts431almost in parallel to each other and a bent tube part432connecting therebetween to form a U-shape. The straight tube part431forming an even luminance portion is almost located within the active area42while the bent tube part432forming a dense luminance portion is located outside the active area42.

The housing51has a front housing511, a back housing512, at least one cavity53and at least one inner side wall57. In this embodiment, the front housing511has three side walls54,55,56. The side walls54,55,56and the inner side wall57define the cavity53for accommodating the bent tube part432of the lamp43. Alternatively, the side walls54,55,56may be disposed on the back housing512for defining the cavity53. The back housing512is attached to the front housing511and is used for reflecting the light from the lamp43.

In this embodiment, the bent tube part432of the lamp43and the cavity53are disposed outside the active area42. Alternatively, the bent tube part432of the lamp43and the cavity53may be disposed inside the active area42, as shown inFIG. 6. Because the bent tube part432of the lamp43is disposed inside the cavity53, the heat flow of the bent tube part432of the lamp43due to air convection can be reduced. Therefore, the bent tube part432of the lamp43can maintain a stable temperature, so as to avoid the condensation of the mercury in the lamp43when operating in the cold temperature of the environment.

Alternatively, as shown inFIG. 7, the lamp63is shaped by a serpentine tube comprising a plurality of parallel straight tube parts631which connect to adjacent ones by a bent tube part632, more preferably, the straight tube parts631are generally paralleled to each other. The straight tube part631forming an even luminance portion and the bent tube part632forming a dense luminance portion are all located inside the active area42.

The liquid crystal display device of the present invention can be in any sizes, and luminance can be adjusted by changing positions, density and length of the lamp. The size and number of the lamps are not limited in the disclosure in the embodiments mentioned above. Liquid crystal display devices and backlight modules thereof having dense luminance portions sheltered by the frames are in the scope of the present invention.

As embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by persons skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention is not limited to the particular forms as illustrated, and that all the modifications not departing from the spirit and scope of the present invention are within the scope as defined in the appended claims.