TWI400496B - Light guide plate and backlight module including the same - Google Patents

Description

Light guide plate and backlight module

The present invention relates to a light guide plate and a backlight module, and more particularly to a light guide plate having a plurality of grooves extending in the same direction on the light exit surface and the reflection surface, and a backlight module using the light guide plate.

The design of the conventional light guide plate generally includes a light incident surface, a light exit surface, and a reflective surface. The light provided by the light source enters the light guide plate from the light incident surface of the light guide plate, and after being mixed by the light guide plate, the light exit surface of the light guide plate provides a uniform surface light source, wherein the light source passing through the light guide plate can be more evenly distributed. Mixing, usually there are many microstructures on the light entrance surface, light exit surface or reflective surface of the light guide plate. In many designs, in order to make the light source have better guiding property, a plurality of micro-grooves are disposed on the light-emitting surface and the reflecting surface of the light guiding plate, and the light-emitting surface of the light guiding plate is far from the light source, which affects the light-emitting surface. The intensity of the emitted light is generally weaker than the intensity of the light emitted from the region farther from the light source on the light-emitting surface. Therefore, in order to adjust the uniformity of the intensity of the light emitted from the light surface, the extending direction of the micro-groove generally provided on the light-emitting surface is Different from the extending direction of the micro-grooves disposed on the reflecting surface, the extending directions of the micro-grooves on the general light-emitting surface and the reflecting surface are perpendicular to each other.

Although the above design has better light source directivity, it cannot effectively homogenize the light source incident inside the light guide plate. The light provided by the light source enters the light guide plate from the light incident surface of the light guide plate. After the light and the micro-groove provided on the reflective surface act, the light diffuses along the X-axis direction, and the micro-groove extending direction and setting provided on the light-emitting surface Since the micro-grooves on the reflecting surface are perpendicular to each other, the light diffused from the reflecting surface to the light-emitting surface is diffused along the Y-axis direction. For the above reasons, the light supplied from the light source to the light guide plate is diffused only once in the X-axis direction and the Y-axis direction, so that the light source incident on the inside of the light guide plate cannot be effectively made uniform.

Therefore, it is necessary to provide a novel light guide plate, which can provide a relatively uniform surface light source to a backlight module to which the light guide plate is applied.

Therefore, the object of the present invention is to provide a light guide plate and a backlight module using the light guide plate, wherein the light exit surface and the reflective surface of the light guide plate are disposed in the same direction, and the plurality of different depths in the groove are utilized. The light guide plate can provide a relatively uniform surface light source, and the backlight module using the light guide plate has better optical uniformity.

According to an embodiment of the present invention, a light guide plate including a light exit surface, a reflective surface, and a plurality of microstructures is provided. The light-emitting surface is provided with a plurality of first grooves extending in a straight line, wherein the cross-sectional profiles of the plurality of first grooves are similar to each other, and the plurality of first grooves have substantially the same extending direction. The reflecting surface is opposite to the light emitting surface, wherein the reflecting surface is provided with a plurality of second grooves extending in a straight line, and the cross-sectional profiles of the plurality of second grooves are similar to each other, and the plurality of second grooves have substantially the same extending direction And the extending direction of the second groove is substantially the same as the extending direction of the first groove. Each of the first or second grooves has a plurality of different depths. A plurality of microstructures are disposed on the light exit surface or on the reflective surface.

According to another embodiment of the present invention, a backlight module is provided. The backlight module comprises: a housing, a light guide plate disposed in the housing, and a light source. The light guide plate includes a light emitting surface, a reflecting surface, a light incident surface, and a plurality of microstructures. The light-emitting surface is provided with a plurality of first grooves extending in a straight line, wherein the cross-sectional profiles of the plurality of first grooves are similar to each other, and the plurality of first grooves have substantially the same extending direction. The reflecting surface is opposite to the light emitting surface, and the reflecting surface is provided with a plurality of second grooves extending in a straight line, wherein the cross-sectional profiles of the plurality of second grooves are similar to each other, and the plurality of second grooves have substantially the same extending direction And the extending direction of the second groove is substantially the same as the extending direction of the first groove, wherein each of the first or second grooves has a plurality of different depths. The light entrance surface is adjacent to the light emitting surface and the reflecting surface. The plurality of microstructures are disposed on the light emitting surface or the reflecting surface of the light guide plate. The light source is disposed in the housing and adjacent to the light incident surface of the light guide plate.

The invention has the advantages that the light guide plate can provide a relatively uniform surface light source by using simple production design changes by using existing production technology, and can avoid adding additional production cost.

Please refer to FIG. 1 , which is a schematic diagram of a backlight module according to a first embodiment of the present invention. The backlight module 100 includes a housing 200, a light guide plate 300, and at least one light source 400. The housing 200 is used to accommodate the light guide plate 300 and the light source 400, and provides a protection function. Therefore, the housing 200 can be made of a metal material, and the metal has a mechanical strength characteristic of better strength for protection purposes. The housing 200 can also be made of other materials such as reinforced plastic, thereby reducing the overall weight of the backlight module 100.

In the first embodiment, the backlight module 100 is a backlight module of the edge illumination type, and the light guide plate 300 has a flat plate structure and is disposed in the housing 200. In other specific embodiments, the backlight module of the present invention may also be a Bottom Lighting backlight module, and the geometry of the light guide plate may be a wedge plate structure.

Please refer to FIG. 2A to FIG. 2C simultaneously, which are respectively a perspective view, a side view and a top view of the light guide plate in the first embodiment. In the present embodiment, FIG. 2A shows a microstructure 307 which will be described later, and for the sake of clarity of the drawing, the microstructure 307 is not shown in FIGS. 2B and 2C. The light-emitting surface 302 of the light guide plate 300 is provided with a plurality of first grooves 308 extending in a straight line. The first grooves 308 have a V-shaped cross-sectional profile (see FIG. 2B) and have the same angle of angle. The cross-sectional profiles of the first grooves 308 are similar to each other, and in addition, the plurality of first grooves 308 have substantially the same extending direction. The reflective surface 304 is disposed on the bottom surface of the light guide plate 300 opposite to the light exit surface 302. The reflective surface 304 is provided with a plurality of second recesses 310 extending in a straight line. The cross-sectional contours of the second recesses 310 are all V characters. Type (see FIG. 2B) and having the same angle of angle, so that the cross-sectional profiles of the second grooves 310 are similar to each other, and further, the plurality of second grooves 310 have substantially the same extending direction, and the second grooves 310 The extending direction is substantially the same as the extending direction of the first groove 308. In the first embodiment, the first groove 308 and the second groove 310 extend substantially perpendicular to the direction of the light incident surface 306, and extend from the light incident surface 306 toward the other side of the light incident surface 306, but The extending direction of the first groove 308 and the second groove 310 is not limited to be perpendicular to the light incident surface 306.

In order to enable the light guide plate 300 to sufficiently mix the light from the light source 400 to generate a uniform surface light source, in the first embodiment, each of the first grooves 308 disposed on the light exit surface 302 has a plurality of different depths. The depth 308a and the depth 308b are shown in FIG. 2D, wherein the 2D figure is a schematic cross-sectional view along the line AA' in the 2C. In a particular embodiment, the second recess of the present invention (e.g., the second recess 310 shown in Figures 2A and 2B) can also include a plurality of different depths as described above. Since the cross-sectional profiles of each of the first grooves 308 are similar, when the depth 308a is different from the depth 308b, the first grooves 308 will form different groove widths on the light-emitting surface 302 of the light guide plate 300 (see FIG. 2C). The advantage of this design is that the first groove 308 is formed with an arc as shown in FIG. 2C due to the change of the groove width, and the first groove 308 having an arc can diffuse the incident light that acts therewith as indicated by the arrow. The multiple directions make the mixing of light better and even. In contrast, the other grooves 312 shown in FIGS. 2A to 2C are also V-shaped grooves, but the depths of the points of the grooves 312 are the same, so that the light-emitting surface 302 of the light guide plate 300 forms the groove 312 having the same width. (See Figure 2C), so the incident light that interacts with it can only diffuse in a single direction as indicated by the arrow.

In the first embodiment, the light incident surface 306 of the light guide plate 300 is adjacent to the light exit surface 302 and the reflective surface 304, and the light source 400 is disposed in the housing, and is disposed adjacent to the light incident surface 306. . In addition, in the present embodiment, the light guide plate 300 is disposed on the light-emitting surface 302 in order to adjust the intensity of the light emitted from the light-emitting surface in the light-emitting surface of the light-guide plate. The microstructures 307 having a plurality of protrusions and uniform sizes are arranged by the microstructures 307 from the light incident surface 306 of the light guide plate 300 toward the opposite side surface to make the light beams emitted from the light exit surface of the light guide plate have the same intensity. In a specific embodiment, the light guide plate of the present invention may also have a plurality of microstructures disposed on the reflective surface, such as the reflective surface 304 shown in FIG. 2A. In addition, the microstructure may be designed as a recessed and different size structure. The arrangement of the microstructures is dense and the microstructures are different in size, so as to achieve the same intensity of light emitted from the light surface. Light guide plate microstructure manufacturing techniques can generally be divided into two categories: printed and non-printed. The printing type uses a screen printing method to print ink on a light guide plate to produce a microstructure shape and distribution. The non-printing type directly uses the injection molding technology to design the microstructure in the mold, which is simplified in production and high in precision, and is currently the mainstream of the light guide plate technology. In addition, non-printing methods include precision machining.

In the first embodiment, the cross-section of each of the first groove 308 and the second groove 310 is a V-shaped groove as viewed in the longitudinal direction of the first groove 308 or the second groove 310. Please refer to FIG. 3A, which is a side view showing a light guide plate according to a second embodiment of the present invention. In the second embodiment, the cross-section of each of the first recess 308' and the second recess 310' is substantially U-shaped by the longitudinal direction of the first recess 308' or the second recess 310'. (U-shaped) groove. In Fig. 3B, there is shown a side view of a light guide plate according to a third embodiment of the present invention. In the third embodiment, the cross section of each of the first groove 308'' and the second groove 310'' is also viewed from the longitudinal direction of the first groove 308'' or the second groove 310''. A U-shaped groove in which the contour of such a U-shaped groove is formed by sequential joining of a straight line 314, an arc 316, and a straight line 318. In the first, second, and third embodiments, the first groove of the light-emitting surface and the second groove of the reflective surface have the same profile, that is, the first groove and the second groove are both V-shaped. Or U-shaped, but not limited thereto. For example, in a specific embodiment, the cross-sections of the first groove of the light-emitting surface and the second groove of the reflective surface may be V-shaped and U-like, respectively. Font type. In the first embodiment, the first grooves of the light-emitting surface are all V-shaped, and in a specific embodiment, the first grooves may include two different types of grooves, for example, including V-shaped grooves at the same time. With a U-shaped groove.

Please refer to FIGS. 4A and 4B, which are respectively top views of the light-emitting surface and the reflecting surface of the light guide plate according to the fourth embodiment of the present invention. In the fourth embodiment, the light guide plate 500 includes a light emitting surface 502, a reflecting surface 504, and a light incident surface 506 adjacent to the light emitting surface 502 and the reflecting surface 504. The first region 512 and the second region 514 are respectively disposed on the light-emitting surface 502 and the reflective surface 504, wherein the second region 514 and the first region 512 are disposed corresponding to each other, that is, the second region 514 is adjacent to the first region 512. It is disposed on the light incident surface 506. In this embodiment, the areas of the first area 512 and the second area 514 occupy substantially half of the area of the light-emitting surface 502 and the reflective surface 504, respectively. However, in other specific embodiments, the first area and the second area occupy the light. The ratio of the area of the face to the reflective surface is not the same, for example, the first area occupies one-third of the area of the light-emitting surface, and the second area occupies one-half of the area of the reflective surface.

In the fourth embodiment, the first groove 508 extends linearly to the first region 512 of the light exit surface 502, and the second groove 510 extends linearly to the second region 514 of the reflective surface 504. Further, for the above reasons, In order to make the intensity of the light emitted from the light-emitting surface of the light guide plate uniform, a plurality of microstructures (not shown) are disposed on the first region 512 or the second region 514. In the fourth embodiment, the area of the first region 512 of the light guide plate 500 is smaller than the area of the light exit surface 502, and the area of the second region 514 is smaller than the area of the reflective surface 504. According to the first region and the second region, respectively, for defining the first groove and the second groove, in the first embodiment shown in the foregoing 2A to 2D, the first region of the light guide plate 300 The area is the area of the light exit surface 302, and the area of the second area is the area of the reflective surface 304.

Since the first groove of the light-emitting surface of the present invention has the same change as the second groove of the reflective surface, for the convenience of description, the following describes only the first groove of the light-emitting surface as an example to describe the groove geometry and configuration. Change. The change of each first groove also has the same change. Therefore, only the single first groove is used to describe the change of the groove geometry. The number and position of the first groove are set to be visible to the optical plate. The characteristics are adjusted and changed.

Please refer to FIG. 5A, which is a cross-sectional view showing a longitudinal section of a first groove according to a fifth embodiment of the present invention, wherein the cutting direction of the fifth embodiment is the same as the cutting direction shown in FIG. 2D. . In the first groove 602 of the fifth embodiment, the depth of the first groove 602 changes periodically. The first recess 602 includes four relatively depressed recessed regions, and the depths of the four recessed regions are respectively depth 602a, depth 602b, depth 602a, and depth 602b, so the depth of the first recess 602 is determined by One side of the 5A diagram is periodically changed toward the other side. In the first recess 602 of the fifth embodiment, between the adjacent two recessed regions having the depth 602a and the depth 602b, respectively, the depth of the first recess 602 exhibits a smooth change, and due to the change in depth, the first The bottom of the groove 602 forms a curve as shown in Fig. 5A, wherein the curve includes an arc 602c.

Please refer to FIG. 5B, which is a cross-sectional view showing a longitudinal section of a first groove according to a sixth embodiment of the present invention, wherein the cutting direction of the sixth embodiment is the same as the cutting direction shown in FIG. 2D. . In the first groove 604 of the sixth embodiment shown in Fig. 5B, the depth thereof is aperiodically changed from one side of the fifth drawing to the other side. In the first groove 604, a relatively depressed recessed area 604a, a recessed area 604b, and a recessed area 604c are included. Between the adjacent recessed area 604a and the recessed area 604b, the depth of the first recess 604 exhibits a smooth change, and the bottom of the first recess 604 at the interval forms a curve as shown in FIG. 5B. This curve includes arcs 604d and 604e adjacent to each other. In addition, between the recessed area 604b and the recessed area 604c, the depth of the first recess 604 changes non-smoothly, and the curve formed by the bottom of the first recess 604 includes a line 604f and a line 604g adjacent to each other.

Please refer to FIG. 5C, which is a cross-sectional view showing a longitudinal section of a first groove according to a seventh embodiment of the present invention, wherein the cutting direction of the seventh embodiment is the same as the cutting direction shown in FIG. 2D. . In the first recess 606 of the seventh embodiment, the depth thereof is aperiodically changed from one side end to the other side end, wherein between the adjacent adjacent two recessed areas, the bottom of the first recess 606 is formed as The curve shown in Fig. 5C includes a straight line 606a, a straight line 606b and a straight line 606c which are sequentially joined, and the straight line 606b is substantially perpendicular to the straight line 606a and the straight line 606c, forming a non-smoothly varying square wave curve. Between the other two adjacent recessed regions, the straight line 606d is not perpendicular to the straight line 606c and the straight line 606e, and the straight line 606d is an oblique straight line. Between the adjacent two recessed regions of the fifth to seventh embodiments described in the above 5A to 5C, various changes in the curve formed by the bottoms of the first recesses 602, 604, and 606 can be applied to the depth The first groove that changes periodically or non-periodically is not limited to the corresponding embodiment.

Please refer to FIG. 6A, which is a top plan view of a first recess according to an eighth embodiment of the present invention. In the eighth embodiment, the area of the first region of the light guide plate 700 where the first groove is disposed is equal to the area of the light exit surface 702, that is, the light exit surface 702 is defined as the first region as a whole. In this embodiment, the plurality of first grooves 708 are disposed along the plurality of straight lines 704 on the first region, and each of the straight lines 704 is distributed with two first grooves 708, and the second portion is shown in FIG. 2C. In one embodiment, a single first groove 308 extends through the entire light exiting surface 302 (first region), that is, only a single first groove 308 is provided on one of the lines of the light exiting surface 302.

In the eighth embodiment, the plurality of first grooves 708 disposed along the adjacent two straight lines 704 are disposed at corresponding positions in a one-to-one manner, and in the first grooves 708, The first grooves 708 corresponding to each other are substantially identical. In the eighth embodiment, the first grooves 708 have two different versions, and in a particular embodiment, the first grooves 708 may include more different ones. Type or only a single type.

Please refer to FIG. 6B, which is a top plan view of a first recess according to a ninth embodiment of the present invention. In the ninth embodiment, the plurality of first recesses 708' of the light guide plate 700' are disposed along a plurality of straight lines 704' of the light exiting surface 702' (first region), wherein the two straight lines 704 are disposed on the left and right sides of the sixth plane The first groove 708' on the upper side is disposed at a corresponding position in a one-to-one manner, and the first grooves 708' corresponding to each other are substantially identical. In the eighth and ninth embodiments of the above-described 6A and 6B drawings, the number of straight lines can be adjusted as needed, and is not limited to the number shown in the drawings.

Please refer to FIG. 7 , which is a top plan view of a first recess according to a tenth embodiment of the present invention. Three first grooves 808 are disposed on the light-emitting surface 802 of the light guide plate 800. The distance between the centers of the two first grooves 808 on the left side of the seventh figure is relatively close to each other, so that it is formed as a dotted line. Structure that interferes with each other.

Please refer to FIG. 8 , which is a top plan view showing a first recess according to an eleventh embodiment of the present invention. Two first grooves 908 are disposed on the light-emitting surface 902 of the light guide plate 900, wherein the extending direction of the first groove 908 on the left side of the eighth figure is substantially perpendicular to the light-incident surface 906 of the light guide plate 900, and The extending direction of the first groove 908 on the right side of the eighth figure is at an angle θ with the light incident surface 906 of the light guide plate 900, wherein the angle θ is greater than or equal to 45 degrees and less than or equal to 135 degrees.

In a specific embodiment, the backlight module of the present invention further includes at least one optical film (not shown), and the optical characteristics of the backlight module are improved by the arrangement of the optical film, wherein the optical film is disposed in the guide. Above the light exit surface of the light panel. The optical film may be a diffusion sheet, a ruthenium film, a brightness enhancement film, a reflective brightness enhancement film, a non-multilayer film reflection polarizer, or any combination thereof, in consideration of different optical purposes.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100. . . Backlight module

200. . . case

300. . . Light guide

302. . . Glossy surface

304. . . Reflective surface

306. . . Glossy surface

307. . . microstructure

308. . . First groove

308’. . . First groove

308’’. . . First groove

308a. . . depth

308b. . . depth

310. . . Second groove

310’. . . Second groove

310"‧‧‧second groove

312‧‧‧ Groove

314‧‧‧ Straight line

316‧‧‧ arc

318‧‧‧ Straight line

400‧‧‧Light source

500‧‧‧Light guide plate

502‧‧‧Glossy surface

504‧‧‧reflecting surface

506‧‧‧Into the glossy surface

508‧‧‧first groove

510‧‧‧second groove

512‧‧‧First area

514‧‧‧First area

602‧‧‧First groove

602a‧‧ depth

602b‧‧ depth

602c‧‧‧Arc

604‧‧‧First groove

604a‧‧‧Depression

604b‧‧‧Depression

604c‧‧‧Depression

604d‧‧‧Arc

604e‧‧‧ Straight line

604f‧‧‧ Straight line

604g‧‧‧ straight line

606‧‧‧First groove

606a‧‧‧ Straight line

606b‧‧‧ Straight line

606c‧‧‧ Straight line

606d‧‧‧ Straight line

606e‧‧‧ Straight line

700‧‧‧Light guide plate

700’‧‧‧Light Guide

702‧‧‧Glossy

702’‧‧‧Glossy

704‧‧‧ Straight line

704’‧‧‧ Straight line

708‧‧‧First groove

708’‧‧‧first groove

800‧‧‧Light guide plate

802‧‧‧ shine surface

808‧‧‧first groove

900‧‧‧Light guide plate

902‧‧‧Glossy

906‧‧‧Into the glossy surface

908‧‧‧first groove

AA’‧‧‧ line

Θ‧‧‧ angle

For a better understanding of the present invention, reference is made to the above detailed description and the accompanying drawings. It is emphasized that, in accordance with the standard of the industry, the various features in the drawings are not to scale. In fact, the dimensions of the various features may be arbitrarily enlarged or reduced in order to clearly illustrate the above embodiments. The relevant schema description is as follows:

1 is a schematic view showing a backlight module according to a first embodiment of the present invention.

FIG. 2A is a perspective view showing the light guide plate in FIG. 1 .

2B is a side view showing the light guide plate of FIG. 1.

FIG. 2C is a schematic plan view showing the light guide plate in FIG. 1 .

2D is a schematic cross-sectional view taken along line AA' of FIG. 2C;

Fig. 3A is a side elevational view showing a light guide plate according to a second embodiment of the present invention.

Fig. 3B is a side elevational view showing a light guide plate according to a third embodiment of the present invention.

4A and 4B are top views respectively showing a light-emitting surface and a reflecting surface of a light guide plate according to a fourth embodiment of the present invention.

5A to 5C are schematic cross-sectional views showing a longitudinal section of a first groove according to fifth to seventh embodiments of the present invention.

6A and 6B are schematic plan views showing the first grooves according to the eighth and ninth embodiments of the present invention.

Figure 7 is a top plan view showing a first recess according to a tenth embodiment of the present invention.

Figure 8 is a top plan view showing a first recess according to an eleventh embodiment of the present invention.

300. . . Light guide

302. . . Glossy surface

304. . . Reflective surface

306. . . Glossy surface

307. . . microstructure

308. . . First groove

310. . . Second groove

312. . . Groove

Claims (24)

A light guide plate includes: a light exiting surface, wherein the light emitting surface is provided with a plurality of first grooves extending in a straight line, the first grooves have similar cross-sectional profiles, and the first grooves have substantially the same a direction of extension; a reflecting surface is opposite to the light emitting surface, wherein the reflecting surface is provided with a plurality of second grooves extending in a straight line, the cross-sectional profiles of the second grooves are similar to each other, and the second The grooves have substantially the same extending direction, and the extending directions of the second grooves are substantially the same as the extending direction of the first grooves; and a plurality of microstructures are disposed on the light emitting surface or the reflecting surface; Each of the first recesses or each of the second recesses has a plurality of depths, at least two of which are different from each other, wherein the first recesses are disposed in a first region of the light exiting surface, The area of the first area is smaller than the area of the light-emitting surface, and the second grooves are disposed in a second area of the reflective surface, and the area of the second area is smaller than the area of the reflective surface, the first area Setting bit with the second area Correspond to each other. The light guide plate of claim 1, wherein the cross-sections of the first grooves or the second grooves are substantially V-shaped or substantially U-shaped. The light guide plate of claim 1 is viewed by the longitudinal grooves of the first grooves or the second grooves, wherein the depths of the first grooves or the second grooves are It changes periodically. The light guide plate of claim 1, wherein the first grooves are disposed along a plurality of straight lines along the light exiting surface, and at least two of the first grooves are distributed on each of the straight lines. . The light guide plate of claim 1, wherein the second grooves are disposed along a plurality of straight lines on the reflective surface, and at least two of the second grooves are distributed on each of the straight lines. By. The light guide plate of claim 1, wherein the first grooves are disposed along a plurality of straight lines on the light-emitting surface, and the first grooves disposed along two adjacent straight lines are one-to-one. The manners are set at corresponding positions, and in the first grooves disposed along two adjacent straight lines, the two corresponding to each other are substantially the same. The light guide plate of claim 1 , wherein the first grooves are disposed along a plurality of straight lines on the light-emitting surface, and the first grooves disposed along the portions of the lines are one-to-one The manners are set at corresponding positions, and the first grooves corresponding to each other are substantially the same. The light guide plate of claim 1 , wherein the second grooves are disposed along a plurality of straight lines on the reflective surface, and the second grooves disposed along adjacent two straight lines are one to one The manner is set at a corresponding position, and among the second grooves disposed along two adjacent straight lines, the two corresponding to each other are substantially the same. The light guide plate of claim 1 , wherein the second grooves are disposed along a plurality of straight lines on the reflective surface, and the second grooves disposed along the plurality of straight lines are one to one The manners are set at corresponding positions, and the second grooves corresponding to each other are substantially the same. The light guide plate of claim 1, wherein the microstructures are raised structures or recessed structures. The light guide plate of claim 10, wherein the microstructures are formed by screen printing, injection molding or precision machining. A backlight module includes: a casing; a light guide plate disposed in the casing, wherein the light guide plate comprises: a light emitting surface, wherein the light emitting surface is provided with a plurality of first grooves extending in a straight line, The cross-sectional profiles of the first grooves are similar to each other, and the first grooves have substantially the same extending direction; a reflecting surface is opposite to the light-emitting surface, wherein the reflecting surface is provided with a plurality of straight lines extending a second groove having a cross-sectional profile similar to each other, wherein the second grooves have substantially the same extending direction, and the second grooves extend substantially the same as the first grooves An extending direction; a light entering surface, wherein the light incident surface is adjacent to the light emitting surface and the light emitting surface a reflective surface; and a plurality of microstructures disposed on the light emitting surface or the reflecting surface; wherein each of the first grooves or each of the second grooves has a plurality of depths, at least two different from each other The first grooves of the light guide plate are disposed in a first region of the light exit surface, the area of the first region is smaller than the area of the light exit surface, and the second grooves are disposed on the reflection In a second area of the surface, the area of the second area is smaller than the area of the reflective surface, the first area and the second area are disposed corresponding to each other; and a light source is disposed in the housing and adjacent The light incident surface of the light guide plate. The backlight module of claim 12, further comprising at least one optical film, wherein the optical film is disposed on the light emitting surface of the light guide plate. The backlight module of claim 13, wherein the optical film is a diffusion sheet, a gusset, a brightness enhancement film, a reflective brightness enhancement film, a non-multilayer film reflection polarizer, or any combination thereof. The backlight module of claim 12, wherein the first grooves or the second grooves of the light guide plate are substantially V-shaped or substantially U-shaped. The backlight module of claim 12, wherein the first grooves or the second grooves of the light guide plate are viewed from a longitudinal section of the light guide plate, wherein the first grooves or the light guide plates The depths of the second grooves vary periodically. The backlight module of claim 12, wherein the first grooves of the light guide plate are disposed along a plurality of straight lines along the light exiting surface, and at least the first concaves are distributed on each of the straight lines. Both of the slots. The backlight module of claim 12, wherein the second grooves of the light guide plate are disposed along a plurality of straight lines of the reflective surface, and at least the second concaves are distributed on each of the straight lines. Both of the slots. The backlight module of claim 12, wherein the first grooves of the light guide plate are disposed along a plurality of straight lines on the light exiting surface, and the first concave portions are disposed along adjacent two straight lines. The slots are disposed at corresponding positions in a one-to-one manner, and the first recesses disposed along the adjacent two straight lines are substantially identical to each other. The backlight module of claim 12, wherein the first grooves of the light guide plate are disposed along a plurality of straight lines along the light exiting surface, and the first grooves are disposed along the plurality of straight lines They are disposed in a one-to-one manner at corresponding positions, and the first grooves corresponding to each other are substantially the same. The backlight module of claim 12, wherein the light guide plate The second grooves are disposed along a plurality of straight lines on the reflecting surface, and the second grooves disposed along the adjacent two straight lines are disposed in a one-to-one manner at corresponding positions, and along the phase Among the second grooves provided by the adjacent two straight lines, the two corresponding to each other are substantially the same. The backlight module of claim 12, wherein the second grooves of the light guide plate are disposed along a plurality of straight lines on the reflective surface, and the second grooves are disposed along the plurality of straight lines They are disposed in a one-to-one manner at corresponding positions, and the second grooves corresponding to each other are substantially the same. The backlight module of claim 12, wherein the microstructures of the light guide plate are convex structures or recessed structures. The backlight module of claim 23, wherein the microstructures of the light guide plate are formed by screen printing, injection molding or precision machining.