Optical plate with V-shaped protrusions on both sides and backlight module using the same

An optical plate includes a first surface and a second surface opposite to the first surface. A plurality of elongated, arc-shaped depressions is defined in the first surface. A plurality of first elongated, V-shaped protrusions aligned in a first direction and a plurality of second elongated, V-shaped protrusions aligned in a second direction are protruded from the second surface. The first direction and the second direction cooperatively define an angle which is larger than 0 degrees and less than 90 degrees.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to five co-pending U.S. patent applications, which are: Ser. Nos. 12/319,007, 12/319,046, 12/319,045, 12/319,042, and 12/319,006, and all entitled “OPTICAL PLATE AND BACKLIGHT MODULE USING THE SAME”. In the co-pending applications, the inventor is Shao-Han Chang. The co-pending applications have the same assignee as the present application. The disclosure of the above identified applications is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an optical plate and a backlight module using the optical plate.

2. Description of the Related Art

Referring toFIG. 8, a typical direct type backlight module100includes a frame11, a plurality of lamps12positioned above a base of the frame11, a light diffusion plate13, and a prism sheet10stacked on top of the frame11in that order. Inside walls of the frame11are configured for reflecting certain of the light upwards. The light diffusion plate13includes a plurality of dispersion particles (not shown) for scattering light to enhance the uniformity of light exiting the light diffusion plate13.

Referring toFIG. 9, the prism sheet10includes a base layer101and a prism layer103formed on the base layer101. The prism layer103includes a plurality of parallel prism lenses105having a triangular cross section. The prism lenses105collimate received light. Typically, a method of manufacturing the prism sheet10includes coating the base layer101with a melted ultraviolet(UV)-cured transparent resin to form V-shaped lenses, then solidifying the melted UV-cured transparent resin to form the prism lenses105.

In use, light from the lamps12enters the diffusion plate13and becomes scattered, before leaving the light diffusion plate13to the prism sheet10. The scattered light then travels through the prism sheet10and is refracted out at the prism layer103of the prism lenses105. Thus, the refracted light leaving the prism sheet10is concentrated at the prism layer103and a brightness (illumination) of the prism sheet10is increased. The refracted light then propagates into an LCD panel (not shown) positioned above the prism sheet10.

However, although light from the light sources12enters the diffusion plate13and becomes scattered, strong light spots of the light sources12directly above the light sources12are often formed. Therefore, an upper diffusion film14may be positioned on the prism sheet10to reduce or eliminate light spots of the light sources12. Although the upper light diffusion film14and the prism sheet10are in contact with each other, a plurality of air pockets may still exist around the boundaries of the light diffusion film14and the prism sheet10. When the backlight module100is in use, light passes through the air pockets, and some of the light undergoes total reflection by the air pockets along one or more corresponding boundaries. In addition, the upper light diffusion film14may absorb a certain amount of the light from the prism sheet10. As a result, a brightness of light illumination of the backlight module100is reduced.

What is needed, therefore, is a new optical plate and a backlight module using the optical plate that can overcome the above-mentioned shortcomings.

DETAILED DESCRIPTION

Referring toFIG. 1, a first embodiment of a backlight module200includes an optical plate20, a frame21, and a plurality of lamps22regularly aligned above a base of the frame21. The optical plate20is positioned on the top of the frame21.

Referring toFIGS. 2 and 3, the optical plate20includes a first surface201and an opposite second surface203. The first surface201defines a plurality of elongated, arc-shaped depressions202. A plurality of first elongated, V-shaped protrusions204are aligned in a first direction Y and a plurality of second elongated, V-shaped protrusions205are aligned in a second direction extending from the second surface203. The first direction Y and the second direction X cooperatively define an angle which is about 0 degrees to about 90 degrees. An extending direction of the elongated, arc-shaped depressions202is substantially parallel to edges of the optical plate20.

The elongated, arc-shaped depressions202are aligned side by side on the first surface201of the optical plate20. Each elongated, arc-shaped depression202may have a semi-circular cross-section taken along a direction perpendicular to the extending direction thereof. A pitch P1between adjacent elongated, arc-shaped depressions202is about 0.025 millimeters (mm) to about 1.5 mm. A radius R of a circular arc defined by the semi-circular cross section taken along a direction perpendicular to the extending direction of the elongated, arc-shaped depressions202is equal to or larger than 0.01 mm, and less than 3 mm. A depth H1of each elongated, arc-shaped depression202is equal to or larger than 0.01 mm, and less than 3 mm.

Each first elongated, V-shaped protrusion204may have a triangular cross section taken along a direction perpendicular to an extending direction of the first elongated, V-shaped protrusions204. A vertex angle of the triangular cross section is about 80 degrees to about 100 degrees. A pitch P2between adjacent first elongated, V-shaped protrusions204is about 0.025 mm to about 1.5 mm.

Each second elongated, V-shaped protrusion205has a triangular cross section taken along a direction perpendicular to an extending direction of the second elongated, V-shaped protrusions205. A vertex angle of the triangular cross section is about 80 degrees to about 100 degrees. A pitch P3between adjacent second elongated, V-shaped protrusions205is about 0.025 mm to about 1.5 mm. In addition, a height H2of the first elongated, V-shaped protrusions204and the second elongated, V-shaped protrusions205is equal to or larger than 0.01 mm, and less than 3 mm.

A thickness T of the optical plate20is about 0.5 mm to about 3 mm. The optical plate20may be made of transparent material such as polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), copolymer of methylmethacrylate and styrene (MS), and any suitable combination thereof.

Referring toFIG. 1again, each lamp22may be replaced by a plurality of point light sources, such as light emitting diodes, distributed along a line. In the illustrated embodiment, the lamps22are cold cathode fluorescent lamps. The interior of the frame21is highly reflective.

The optical plate20is positioned on the frame21such that the first surface201is adjacent to the lamps22, and an extending direction of the lamps22is substantially parallel to the extending direction of the elongated, arc-shaped depressions202. Light enters the optical plate20via the first surface201. Since the inner surfaces of the elongated, arc-shaped depressions202are curved and the outer surface of the first elongated, V-shaped protrusions204and the second elongated, V-shaped protrusions205are slanted, incident light that may have been internally reflected on a flat surface, are refracted, reflected, and diffracted. As a result, light outputted from the second surface203is more uniform than light outputted from a light output surface of the typical prism sheet10. Since strong light spots of the light sources seldom occur, an extra upper light diffusion film on the optical plate20is unnecessary. Thus, the efficiency of light utilization is enhanced.

Referring to the Table 1 below, test samples are provided.

FIGS. 4,5, and10reflect the test results from the test conditions in Table 1. As can be seen, light spots formed on the typical prism sheet10are relatively strong. In contrast, light spots formed on the optical plate20are relatively weak. Therefore, the test results show light emitting from the optical plate20is more uniform.

Moreover, in contrast to the typical prism sheet10, the optical plate20may be integrally formed by injection molding technology. Injection molding technology is easier to mass-produce than the typical prism sheet10. Typical prism sheets10are formed by solidifying melted ultraviolet-cured transparent resin, and as such, the prism lenses are easily damaged due to poor rigidity and mechanical strength and scratched. The optical plate20has better rigidity and mechanical strength, and therefore, has a relatively high reliability.

Referring toFIG. 6, a second embodiment of an optical plate30is similar in principle to the optical plate20. The first surface31defines a plurality of elongated, arc-shaped depressions302. A plurality of first elongated, V-shaped protrusions (not labeled) and a plurality of elongated, V-shaped protrusions (not labeled) protrude from the second surface (not labeled). The first elongated, V-shaped protrusions intersect with the second elongated, V-shaped protrusions. However, each of the elongated, arc-shaped depressions302has a semi-elliptical cross section taken along a direction perpendicular to an extending direction thereof.

Referring toFIG. 7, a third embodiment of an optical plate40is similar in principle to the optical plate20. The first surface401defines a plurality of elongated, arc-shaped depressions402. However, each of the elongated, arc-shaped depressions402extends along an imaginary curved line. Thus moiré patterns, caused by the pixels of a liquid crystal display panel and the structural patterns of a typical prism sheet can be minimized or eliminated.