Patent Application
20070139961
In a liquid crystal display (LCD), an array of liquid crystal molecules is trapped between two polarizing plates. One of the plates is horizontally polarized, and the other plate is vertically polarized. A backlight is positioned on one side of the LCD, and in response to varying electrical currents that are applied to the array of liquid crystal molecules, different amounts of the backlight's light are allowed to pass through the different pixels of the LCD, thereby producing an image.
The light produced by an LCD's backlight is typically mixed, and then directed toward an LCD, via a light guide. If the light guide is properly designed, the majority of the light produced by the backlight should be directed toward the LCD. However, it is inevitable that some of the light that a backlight produces will be reflected back toward the backlight (e.g., as a result of inefficiencies in the optical coupling between the backlight and the light guide, and for other reasons). These back-reflections of light, as well as the reletively high currents that are often necessary to drive the light emitting elements of the backlight, cause the backlight to generate a significant amount of heat. As a result, it is typically necessary to couple the backlight to a heat sink. However, while increased size, better airflow and water-cooling would all help to improve the efficiency of the heat sink, these attributes are difficult to implement in environments where space is limited (e.g., in the case of a mobile phone, personal digital assistant (PDA) or other small or hand-held electronic device).
In one embodiment, a method comprises 1) attaching a light source to a first side of a flexible printed circuit, and 2) conforming the flexible printed circuit to at least part of a heat sink. The heat sink has a cross-section that has surfaces facing in different directions, such that, by conforming the flexible printed circuit to the at least part of the heat sink, a second side of the flexible printed circuit, opposite the first side, is caused to contact ones of the surfaces of the heat sink facing in at least two different directions.
In another embodiment, apparatus comprises a heat sink, a flexible printed circuit and a light source. The heat sink defines a channel with a cross-section that has a plurality of interior surfaces facing in different directions. The flexible printed circuit has a first side opposite a second side, and is flexed to conform to at least part of the channel defined by the heat sink, such that the second side of the flexible printed circuit contacts ones of the interior surfaces of the channel facing in at least two different directions. The light source is mounted to the first side of the flexible printed circuit, at least partly within the channel defined by the heat sink.
In yet another embodiment, apparatus comprises a heat sink, a flexible printed circuit and a light source. The cross-section of the heat sink has exterior surfaces facing in different directions. The flexible printed circuit has a first side opposite a second side, and is flexed to conform to at least part of the heat sink, such that the second side of the flexible printed circuit contacts ones of the exterior surfaces of the heat sink facing in at least two different directions. The light source is mounted to the first side of the flexible printed circuit.
Other embodiments are also disclosed.
Illustrative embodiments of the invention are illustrated in the drawings, in which:
In an effort to improve heat dissipation for a backlight, and/or to cause a greater percentage of a backlight's light to be directed toward a light guide or other element that is to be lighted,
As shown in
The flexible printed circuit 104 has a first side 124 opposite a second side 126, and is flexed to conform to at least part of the channel 108 defined by the heat sink 102. In this manner, the second side 126 of the flexible printed circuit 104 is caused to contact ones of the interior surfaces 112, 114, 116 of the channel 108 facing in at least two different directions 118, 120, 122. Preferably, however, the second side 126 of the flexible printed circuit 104 is caused to contact ones of the interior surfaces 112, 114, 116 of the channel 108 facing in at least three different directions 118, 120, 122. In this manner, the light (λ) emitted by the light source 106 will be caused to project and reflect from the channel 108 in a uniform manner.
To secure the flexible printed circuit 104 within the channel 108, the flexible printed circuit 104 may be attached to the heat sink 102 by various means, such as screws, an adhesive, or both.
The light source 106 may be mounted to the first side 124 of the flexible printed circuit 104, at least partly, and preferably wholly, within the channel 108 defined by the heat sink 102. In some embodiments, the light source 106 may comprise one or more light emitting diodes (LEDs), such as a plurality of LEDs 128, 130, 132 arranged along an axis 134 or in some other configuration (e.g., two or more rows, or a staggered or patterned configuration).
Once formed, the assembly comprised of the heat sink 102, flexible printed circuit 104 and light source 106 may be abutted to a light-receiving portion 300 (e.g., an end for a side-firing backlight, or a surface for a direct backlight) of a light guide 302. See,
In
The apparatus 100 can be useful, in one respect, in that the contour of the flexible printed circuit 104 helps to direct more of the light emitted by the light source 106 toward its preferred destination, such as the light guide 302 (
The apparatus 100 can also be useful in that the shaped contour of the flexible printed circuit 104 helps to distribute the heat generated by the light source 106 over a greater number of surfaces 112, 114, 116 of the heat sink 102.
Although the heat sink 102 may have various compositions, it preferably has a composition with good heat-dissipating characteristics—such as a metallic composition comprising copper or aluminum.
With respect to the apparatus 100 shown in
Although the steps 402, 404 of the method 400 are shown with one exemplary order, their order of the method's steps 402, 404 could be swapped (i.e., the flexible printed circuit 104 could be pre-attached to the heat sink 102 before attachment of the light source 106 to the flexible printed circuit 104).
As shown in
Referring back to
The flexible printed circuit 504 has a first side 522 opposite a second side 524, and is flexed to conform to at least part of the heat sink 502. In this manner, the second side 524 of the flexible printed circuit 504 is caused to contact ones of the exterior surfaces 510, 512, 514 facing in at least two different directions 516, 518, 520. Preferably, however, the second side 524 of the flexible printed circuit 504 is caused to contact ones of the interior surfaces 510, 512, 514 facing in at least three different directions 516, 518, 520.
To secure the flexible printed circuit 504 to the heat sink 502, the flexible printed circuit 504 may be attached to the heat sink 502 by various means, such as screws, an adhesive, or both.
The light source 506 may be mounted to the first side 522 of the flexible printed circuit 504. In some embodiments, the light source 506 may comprise one or more light emitting diodes (LEDs), such as a plurality of LEDs 526, 528, 530 arranged along an axis 532 or in some other configuration (e.g., two or more rows, or a staggered or patterned configuration).
Once formed, the assembly comprised of the heat sink 502, flexible printed circuit 504 and light source 506 may be abutted to a light-receiving portion 300 (e.g., an end for a side-firing backlight, or a surface for a direct backlight) of a light guide 302. See,
The apparatus 500 can be useful in that the shaped contour of the flexible printed circuit 504 helps to distribute the heat generated by the light source 506 over a greater number of surfaces 510, 512, 514 of the heat sink 502.
Although the heat sink 502 may have various compositions, it preferably has a composition with good heat-dissipating characteristics—such as a metallic composition comprising copper or aluminum.
Similarly to the apparatus 100 (
Although the heat sinks 102, 502 are shown with exemplary shapes and cross-sections, it is noted that the heat sinks could assume various alternate shapes and cross-sections.
