Patent Application
20120002439
1. Technical Field
The disclosure generally relates to backlight modules, and more particularly relates to a backlight module used in a liquid crystal display (LCD).
2. Description of the Related Art
LCD devices are thin and light weight, and are driven by low voltages. Thus, the LCD devices are extensively employed in electronic devices, such as mobile phones.
In many LCD devices, a backlight module having a light source, a light guide device, and a light reflecting device is used to provide the needed brightness. The light source emits light beams to the light guide device and the light reflective device, which then transmits the light beams to illuminate liquid crystal molecules in a liquid crystal panel. It is important that the light guide device uniformly transmit light beams to the liquid crystal panel. However, conventional backlight modules are not always able to provide uniform brightness due to light leakage from the light guide device.
Therefore, there is room for improvement within the art.
Many aspects of an exemplary backlight module can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the exemplary backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.
The drawing is a schematic view of a backlight module according to an exemplary embodiment.
The drawing shows an exemplary embodiment of a backlight module 100 used in a liquid crystal display (LCD) of an electronic device, which may be, for example, a mobile phone or a personal digital assistant (PDA). The backlight module 100 includes a first light guide plate 10, a second light guide plate 20, a diffuser plate 30, a first prism plate 40, a second prism plate 50, and a light source 60 received in that order from bottom to top within a housing 8 of the backlight module 100. In this exemplary embodiment, the housing 8 is an LCD housing.
The light source 60 may be a point light source, such as a light emitting diode (LED), or may be a linear light source, such as a cold cathode fluorescent lamp (CCFL). The light source 60 emits and provides light beams for the first light guide plate 10 and the second light guide plate 20. Thus, most of the light beams emitted from the light source 60 enter the diffuser plate 30 through the first light guide plate 10 and the second light guide plate 20, and pass through the diffuser plate 30 to enter the first prism plate 40 and the second prism plate 50.
The housing 8 may be made from metal or plastic with high reflectance, or be made from metal or plastic with high reflective coatings. Thus, the housing 8 can reflect the emitted light beams from the light source 60 to the first light guide plate 10 and the second light guide plate 20.
The first light guide plate 10 and the second light guide plate 20 are made from a transparent material, such as glass or plastic. The plastic material can be any of acrylic, polyvinylchloride resin (PVC), polycarbonate (PC), polystyrene (PS) or polypropylene (PP). In this exemplary embodiment, a reflective layer 12 is coated on the lower surface of the first light guide plate 10 facing the bottom of the housing 8. The reflective layer 12 is made from aluminum, silver, or other reflective material. Some light beams directly enter the second light guide plate 20, and some enter the first light guide plate 10. Thus, the light beams entering the first light guide plate 10 are reflected to the second light guide plate 20 by the reflective layer 12.
The second light guide plate 20 is substantially parallel to and mounted on the first light guide plate 10, and includes an emitting surface 21 adjacent to the first light guide plate 10. The emitting surface 21 includes an array of optical dots 22. The optical dots 22 may be formed by cutting or etching, and are substantially arranged in a matrix formation, and are substantially frustum-shaped.
The optical dots 22 on the emitting surface 21 scatter and reflect incident light beams, to make the light beams emit uniformly and convert the point light or the linear light into surface light. Moreover, some light beams may be scattered and reflected by the optical dots 22 to the first light guide plate 10, and then are mostly reflected back to the second light guide plate 20 to be converted into surface light by the optical dots 22.
The diffuser plate 30 is mounted on the second light guide plate 20 relative to the emitting surface 21 and is substantially parallel to the second light guide plate 20. The diffuser plate 30 is made from polyethylene terephthalate (PET) or polycarbonate (PC), and may be formed by diffuser film(s), and makes the light beams from the second light guide plate 20 emit more uniformly thus further enhancing uniformity of surface light for the LCD.
The first prism plate 40 is mounted on the diffuser plate 30 and the second prism plate 50 is mounted on the first prism plate 40 so that all are substantially parallel to each other. The first prism plate 40 and the second prism plate 50 are made from polyester or PC and comprise a plurality of brightness enhancement films (BEFs). The first prism plate 40 and the second prism plate 50 refract and reflect the light beams from the diffuser plate 30 to increase the brightness and change the direction of the light beams.
The light source 60 is located between the housing 8 and the light guide plates 10 and 20, and faces the side surfaces of the first light guide plate 10 and the second light guide plate 20. The light source 60 is capable of providing point light or linear light for the first light guide plate 10 and the second light guide plate 20.
In use, the light source 60 emits light beams to the first light guide plate 10 and the second light guide plate 20. Parts of the emitted light beams enter the second light guide plate 20 and are scattered and reflected by the optical dots 22, to make the light beams emit uniformly and convert the point light or the linear light into surface light. Other parts of the emitted light beams enter the first light guide plate 10 through the optical dots 22 and are reflected by reflective layer 12 back to the second light guide plate 20, and then are scattered and reflected by the optical dots 22. The light beams from the second light guide plate 20 are diffused by the diffuser plate 30 to provide and emit a uniform light. The first prism plate 40 and the second prism plate 50 refract and reflect the light beams from the diffuser plate 30 to increase the brightness and change the direction of the light beams.
Moreover, a reflective coating (not shown) can be formed on peripheral surfaces of the first light guide plate 10 and the second light guide plate 20, except portions directly in the path of light from the light source 60. The reflective coating has high reflectance and can reflect the light beams back to the first light guide plate 10 and the second light guide plate 20.
In summary, in the backlight module 100 of the exemplary embodiment, parts of the light beams from the second light guide plate 20 and most of emitted light beams from the light source 60 enter the first light guide plate 10, and are reflected back to the second light guide plate 20 through the optical dots 22, thus reducing light leakage without the need of reflective devices such as reflective plates. Thus, the backlight module 100 can increase the brightness and provide a uniform light for the LCD of the electronic device.
It is to be understood, however, that even though numerous characteristics and advantages of the exemplary disclosure have been set forth in the foregoing description, together with details of the structure and function of the exemplary disclosure, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of exemplary disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201020243362.0 | Jun 2010 | CN | national |
