Vertically downward type back-light module

[0002] 1. Field of the Invention

[0003] The invention relates to a vertically downward back-light module and, more particularly, to a back-light module that transfers light rays into a light plane, suitable for use with LCD devices.

[0004] 2. Description of the Related Art

[0005] Traditionally, a display device uses electron beam technology to produce light and image on a curved or flat surface display screen. Due to the constraints of electron beam technology, this traditional display device usually requires the mount of a voluminous electron tube.

[0006] With the development of liquid crystal display (LCD) technology, the size and weight of the display device are substantially reduced, which not only improves the esthetic of the display device but also its carrying. The modern LCD device usually incorporates the mount of a back-light module that provides the adequate light to the flat display panel. An important factor then is the light uniformity provided by the back-light module at every position of the display screen.

[0007] As illustrated in FIG. 1, a conventional back-light module comprises a light-guiding panel 1a, a light source 2a, a reflective element 3a, and a base 4a. The light-guiding panel 1aincludes a top light outgoing surface 10aand a bottom light entry surface 11a. The light source 2ais mounted below the light entry surface 11aat a corresponding central location. The reflective element 3acovers the lateral sides of the light-guiding panel 1a. The base 4ais formed arcuate, receiving the mount of the light-guiding panel 1aand the light source 2athereon. The light from the light source 2ais thereby outputted via the light outgoing surface 10a, and loss of light through other parts of the light-guiding panel 1a, except the light outgoing surface 10a, is thereby prevented. The reflective element 40ais formed on the surface of the base 4aby, for example, plating, to provide light reflection and increase the brightness of the light outgoing surface 10a.

[0008] In the above back-light module, the light from the light outgoing surface is substantially concentrated around the light source at a central location below the light entry surface. The brightness of the light outgoing surface is therefore excessive at the central region and gradually decreases along the lateral sides. The light uniformity therefore is not satisfactory. Furthermore, due to the arcuate shape of the base, the size and more particularly the thickness of the back-light module are therefore relatively large, which increases the surface area of the reflective element and, consequently, the fabrication cost.

[0009] It is therefore a principal object of the invention to provide a vertically downward back-light module that improves the light uniformity and the brightness of the light outgoing surface of the light-guiding panel.

[0010] It is another object of the invention to provide a vertically downward back-light module that is dimensionally reduced to an adequate thinness.

[0011] To accomplish the above and other objectives, a vertically downward back-light module of the invention comprises a light-guiding panel, a light source, a reflective clement, and a base. The light-guiding panel includes a bottom reflecting surface in which is formed a slot having a corrugated diffusing surface and light entry side surfaces. The light-guiding panel includes lateral wings respectively extending at a side of each light entry side surface. Each lateral wing extends with an inclination angle relative to a horizontal plane including the opening of the slot through the bottom reflecting surface. The light source is placed in the slot. The reflective element covers the bottom reflecting surface and encapsulates the light source in the light-guiding panel. The light-guiding panel with the light source are mounted on the base.

[0012] To provide a further understanding of the invention, the following detailed description illustrates embodiments and examples of the invention, this detailed description being provided only for illustration of the invention.

[0013] The drawings included herein provide a further understanding of the invention. A brief introduction of the drawings is as follows:

[0014] FIG. 1 is a sectional view of a back-light module known in the prior art;

[0015] FIG. 2 is a perspective view of a light-guiding panel according to an embodiment of the invention;

[0016] FIG. 3 is a sectional view of a back-light module according to a first embodiment of the invention;

[0017] FIG. 3A is a locally enlarged view of the portion A of FIG. 3;

[0018] FIG. 4 is a sectional view of a back-light module according to a second embodiment of the invention; and

[0019] FIG. 5 is a sectional view of a back-light module according to a third embodiment of the invention.

[0020] Wherever possible in the following description, like reference numerals will refer to like elements and parts unless otherwise illustrated.

[0021] Reference now is made to FIG. 2, FIG. 3 and FIG. 3A to describe a vertically downward back-light module structure according to an embodiment of the invention. As illustrated, the back-light module comprises a light-guiding panel 1, a light source 2, a reflective element 3, and a base 4.

[0022] The light-guiding panel 1 includes a bottom reflecting surface 65 that is corrugated and has a plurality of ridges 66. Each ridge 66 has an inclined portion 67 the inclination angle of which adequately varies according to the location of the ridge 66. The reflecting surface 65 includes a slot 60 having a corrugated diffusing surface 51, including a plurality of ridges 52 spaced apart from one another by transparent valleys 55. Each ridge 52 includes a reflecting portion 54 and a transparent portion 53. The reflecting portion 54 is formed with an inclination angle that varies according to the location of the reflecting portion 54. The slot 60 further includes light entry side surfaces 61. A portion of the light-guiding panel 1 above the diffusing surface 51 of the slot 60 is referred to as a light source portion 5, upwardly limited by a top light outgoing surface 50. Portions of the light-guiding panel 1 respectively at one side of each the light entry side surface 61 are referred to as lateral wings 6, the top surfaces of which are referred to as light outgoing surfaces 62. The light outgoing surfaces 62 are corrugated, including a plurality of ridges 63 that respectively have inclined portions 64 the respective inclination angles of which vary according to the respective locations of the ridges 63. The lateral wings 6 respectively terminate in end surfaces 68 that are relatively far away from the light entry side surfaces 61 of the slot 60. The thickness of each lateral wing 6 gradually decreases from the light entry surface 61 to the corresponding end surface 68. Each lateral wing 6 further extends with an inclination angle 6 relative to a horizontal plane including the opening of the slot 60, so that its corresponding end surface 68 is distant a height H from the horizontal plane 69. It will be understood that the angle θ and the height H may be adequately adjusted to accord with the required dimensional volume of the back-light module and its light uniformity. The slot 60 oppositely terminates at a front side 70 and a rear side 71 of the light-guiding panel 1.

[0023] The light source 2 is placed inside the slot 60 of the light-guiding panel 1, and emits a light that travels through the light-guiding panel 1.

[0024] The reflective element 3 respectively covers the reflecting surface 65, the front and rear sides 70, 71, and the end surfaces 68 of the lateral wings 6, while encapsulating the light source 2 in the light-guiding panel 1.

[0025] The light-guiding panel 1, with the light source 2, is mounted on the base 4. The light from the light source 2 substantially passes through the diffusing surface 51 and the light entry side surfaces 61 into the light-guiding panel 1, which prevents light loss. In the assembly of the light-guiding panel 1 with the base 4, the reflective element 3 contacts with the top of the base 4.

[0026] Referring to FIG. 3A, the light emitted from the light source 2 strikes the diffusing surface 51 that, by means of the ridges 52, controls the brightness and the light uniformity of the light outgoing surface 50 over the light source portion 5. A part of light passes through the transparent valleys 55 and the transparent portions 53 of the ridges 52 on the diffusing surface 51, and travels through the light source portion 5 of the light-guiding panel 1 to its light outgoing surface 50.

[0027] Meanwhile, another portion of light is reflected from the reflecting portions 54. (via their respective inclination angles) of the ridges 52 of the diffusing surface 51 toward the light entry side surfaces 61 of the slot 60, and subsequently travels through the lateral wings 6. The brightness from the light source portion 5 of the light-guiding panel 1 and the excessive brightness proximate to the light source 2 are thereby reduced since a portion of light is deviated through the lateral wings 6 to compensate the brightness of other parts of the light-guiding panel 1.

[0028] The light from the light source 2 that reflects via the ridges 52 is directed to the light entry side surfaces 61 of the slot 60. Provided with adequate inclinations, the inclined portions 67 of the ridges 66 on the reflecting surface 65 further reflect the light travelling inside the light-guiding panel 1 to the light outgoing surfaces 62. Meanwhile, due to the gradual decrease of the thickness of the lateral wings 6, the light inside the light-guiding panel 1 is favorably guided toward the end surfaces 68. As a result, the brightness of the light outgoing surfaces 62 of the lateral wings 6 is more uniform.

[0029] Referring to FIG. 3, a diffusing element 8 may be further placed over the light-guiding panel 1. Because the difference of brightness between the light outgoing surface 50 of the light source portion 5 and the light outgoing surfaces 62 of the lateral wings 6 is reduced, the light that comes to the diffusing element 8 produces a more uniform brightness. By refraction via the inclined portions 64 of the ridges 63, the light outgoing surface 62 is rendered dulled, which increases the glow.

[0030] Referring to FIG. 4, the diffusing surface 5 of the slot 60 may be formed arcuate to further provide an adequate light uniformity.

[0031] Referring to FIG. 5, the light outgoing surfaces 62 of the lateral wings 6 may be also formed arcuate to provide the desired light uniformity.

[0032] As described above, the vertically downward type back-light module of the invention therefore includes the following characteristics and advantages.

[0033] (1) By providing a corrugated diffusing surface in the slot, the brightness of the light source portion of the light-guiding panel, proximate to the location of the light source, is reduced. Meanwhile, the brightness of the lateral wings is increased. The consequent difference of brightness there between is therefore reduced, which improves the light uniformity of the light outgoing surfaces of the light-guiding panel.

[0034] (2) By providing a corrugated reflecting surface of the lateral wings, accompanied with corrugated light outgoing surfaces, the light uniformity of the light outgoing surfaces of the light-guiding panel is rendered more uniform.

[0035] (3) By inclining the lateral wings so that its end surfaces are elevated and, furthermore, by forming the lateral wings with a gradually decreased thickness, the light propagation toward the end surfaces is promoted. As a result, the light uniformity of the light outgoing surfaces of the light-guiding panel is improved.

[0036] (4) Via the specific arrangement of the lateral wings as described above, the size of the back-light module is favorably reduced.

[0037] Those skilled in the art will readily appreciate that the above description is only illustrative of specific embodiments and examples of the invention. The invention should therefore cover various modifications and variations made to the herein-described structure and operations of the invention, provided they fall within the scope of the invention as defined in the following appended claims.