Edge-lit light guide plate with frustoconically-shaped microstructures

1. A light guide plate, comprising:

a plate body having a plate thickness, the plate body comprising a first surface, a second surface opposite to the first surface and a side surface connected between the first surface and the second surface; and

a plurality of light-uniformity microstructures arranged periodically on the first surface, wherein the plurality of light-uniformity microstructures are indented from the first surface towards the second surface to define an indentation depth, each of the plurality of light-uniformity microstructures substantially has a shape of an inverted truncated cone, and the indentation depth is less than a half of the plate thickness,

wherein the inverted truncated cone comprises a bottom surface and a surrounding surface, the bottom surface is non-planar, and the surrounding surface is connected to the bottom surface and the first surface of the plate body, and

the bottom surface is a circular arc surface protruding towards the first surface, and an included angle between a tangent plane to an edge of the circular arc surface and a horizontal plane defined by a base plane ranges between 10 degrees and 70 degrees, the base plane defined by a boundary between the bottom surface and the surrounding surface, and being parallel to the first surface.

2. The light guide plate as claimed in claim 1 , wherein the inverted truncated cone form an opening at the first surface, and a distance between two adjacent light-uniformity microstructures is greater than a diameter of the opening.

3. The light guide plate as claimed in claim 1 , wherein the plate thickness is greater than or equal to 75 times the indentation depth.

4. The light guide plate as claimed in claim 1 , wherein a distance between an apex of the circular arc surface and the base plane is greater than 0.05 mm.

5. The light guide plate as claimed in claim 4 , wherein the distance between the apex of the circular arc surface and the base plane is smaller than 0.75 mm.

6. A light source module, comprising:

a light guide plate, comprising:

a plate body having a plate thickness, the plate body comprising a first surface, a second surface opposite to the first surface and a side surface connected between the first surface and the second surface; and

a plurality of light-uniformity microstructures, arranged periodically on the first surface, wherein the plurality of light-uniformity microstructures are indented from the first surface towards the second surface to define an indentation depth, and each of the plurality of light-uniformity microstructures substantially has a shape of an inverted truncated cone, and the indentation depth is less than a half of the plate thickness,

wherein the inverted truncated cone comprises a bottom surface and a surrounding surface, the bottom surface is non-planar, and the surrounding surface is connected to the bottom surface and the first surface of the plate body;

at least one light source providing a light beam and configured at the side surface of the plate body; and

a reflection layer configured on the first surface of the plate body to reflect light,

wherein the light beam is incident from the side surface of the plate body, a transmission path of the light is changed through the light-uniformity microstructures and the reflection layer, and the light beam is emitted out from the second surface,

wherein the bottom surface is a circular arc surface protruding towards the first surface, and an included angle between a tangent plane to an edge of the circular arc surface and a horizontal plane defined by a base plane ranges between 10 degrees and 70 degrees, the base plane defined by a boundary between the bottom surface and the surrounding surface, and being parallel to the first surface.

7. The light source module as claimed in claim 6 , wherein two light sources are respectively disposed at two side of the light guide plate.