Light guide plate and display module

Abstract

This application discloses a light guide plate and a display module. The light guide plate includes a light-emitting surface and a bottom surface facing each other, and a light-incoming surface connecting the light-emitting surface and the bottom surface. The light from the light source is suitable for entering the light guide plate from the light-incoming surface. The bottom surface of the light guide plate is provided with multiple microstructures. Each microstructure has a light-facing surface facing the light-incoming surface, a backlight surface opposite to the light-facing surface, and two connecting surfaces. The light-facing surface extends obliquely from the bottom surface in a direction away from the bottom surface, and the backlight surface extends obliquely from the bottom surface to the end of the light-facing surface away from the bottom surface. The two connecting surfaces connect the two sides of the light-facing surface and the backlight surface, respectively. The light-facing surface is an arc surface, and the light-facing surface bends in a direction close to the backlight surface.

Description

Technical Field

[0001] This application relates to the field of light guide plate technology, and more particularly to a light guide plate and a display module. Background Technology

[0002] The light guide plate plays a crucial role in the entire backlight module. It primarily diffuses point light sources such as LEDs into surface light sources through total internal reflection within the plate. Then, the microstructure on the light guide plate's surface disrupts this total internal reflection, guiding the light out and achieving uniform, high-brightness light output for a superior display effect. Therefore, the microstructure on the light guide plate's surface is key to achieving uniform light output.

[0003] Most light guide plates have microstructures on their surface processed into semi-circular pits using techniques such as impact or laser dotting. This microstructure disrupts total internal reflection, causing light to exit at various angles, resulting in poor directivity and low brightness at the target angle, leading to poor luminous efficiency. Furthermore, some light guide plates have microstructures processed using hot pressing; however, hot pressing cannot process microstructures with specific curvatures, significantly reducing light emission uniformity. Therefore, designing a light guide plate microstructure that achieves high brightness and uniform light emission is crucial for backlight systems. Summary of the Invention

[0004] The purpose of this application is to provide a light guide plate with good light emission uniformity.

[0005] Another objective of this application is to provide a light guide plate with high light output brightness.

[0006] Another objective of this application is to provide a display module including the aforementioned light guide plate.

[0007] According to one aspect of this application, a light guide plate is provided, comprising an opposing light-emitting surface and a bottom surface, and a light-incoming surface connecting the light-emitting surface and the bottom surface. Light from a light source is adapted to enter the light guide plate from the light-incoming surface. The bottom surface of the light guide plate is provided with a plurality of microstructures, each microstructure having a light-facing surface facing the light-incoming surface, a backlighting surface opposite to the light-facing surface, and two connecting surfaces. The light-facing surface extends obliquely from the bottom surface in a direction away from the bottom surface, and the backlighting surface extends obliquely from the bottom surface to one end of the light-facing surface away from the bottom surface. The two connecting surfaces respectively connect the two sides of the light-facing surface and the backlighting surface. The light-facing surface is an arc surface, and the light-facing surface bends in a direction close to the backlighting surface.

[0008] In some embodiments, the backlight surface is an arc surface, and the backlight surface is curved in a direction away from the light-facing surface.

[0009] In some embodiments, the X-axis, Y-axis, and Z-axis of the three-dimensional rectangular coordinate system respectively correspond to the width direction, length direction, and height direction of the light guide plate, where the Z-axis is perpendicular to the bottom surface, the X-axis is perpendicular to the light incident surface, the width of the microstructure in the X-axis direction is not greater than 10 μm, the length of the microstructure in the Y-axis direction is not greater than 25 μm, and the height of the microstructure in the Z-axis direction is not greater than 7.5 μm.

[0010] In some embodiments, the microstructure is recessed from the bottom surface into the light guide plate, and the light-facing surface protrudes in a direction away from the light incident surface; or, the microstructure protrudes from the bottom surface out of the light guide plate, and the light-facing surface protrudes in a direction close to the light incident surface.

[0011] In some embodiments, the two connecting surfaces are parallel to each other; or, the included angle between the two connecting surfaces does not exceed 10°.

[0012] In some embodiments, when viewed from above or below along the Z-axis, the outer contour of the microstructure is a quadrilateral, and the quadrilateral includes a first side, a second side, a third side, and a fourth side connected in sequence. The second side is the side of the light-facing surface on the bottom surface, the fourth side is the side of the light-backing surface on the bottom surface, and both the second side and the fourth side are arcs with the same bending direction.

[0013] In some embodiments, the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, 0 < R1 ≤ 50 μm, 0 < R2 ≤ 50 μm, and / or, 0.9 ≤ R2 / R1 ≤ 1.5.

[0014] In some embodiments, 1 ≤ R2 / R1 ≤ 1.3.

[0015] In some embodiments, the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, the chord length of the second side is L1, the chord length of the fourth side is L2, 0 < R1 / L1 ≤ 2.78, and / or, 0 < R2 / L2 ≤ 2.78.

[0016] In some embodiments, the chord length of the second side is L1, the chord length of the fourth side is L2; L1 = L2, and the first side is parallel to the third side; or, L1 ≠ L2, and the included angle between the first side and the third side does not exceed 10°.

[0017] In some embodiments, the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, the arc height of the second side is S1, the arc height of the fourth side is S2, 0 < S1 / R1 ≤ 1.5, and / or 0 < S2 / R2 ≤ 1.15.

[0018] In some embodiments, the longitudinal section of the microstructure is triangular, and the three sides of the triangle are a first section formed by the light-facing surface, a second section formed by the backlight surface, and a base formed by connecting the ends of the first section and the second section. The first section and the second section are both straight lines, or at least one of the first section and the second section is an arc.

[0019] In some embodiments, the intersection of the first and second segments is the third vertex, the vertical distance from the third vertex to the base is H, the distance between the foot of the third vertex perpendicular to the base and the first vertex on the light-facing side is W1, and the angle between the first segment and the base is α1, 22°≤α1≤48°, and / or 0.9≤W1 / H≤2.48.

[0020] In some embodiments, the intersection of the first and second segments is the third vertex, the vertical distance from the third vertex to the base is H, the distance between the foot of the third vertex perpendicular to the base and the first vertex on the light-facing side is W1, and the angle between the first segment and the base is α1, 49°≤α1≤56°, and / or 0.675≤W1 / H≤0.87.

[0021] In some embodiments, the angle between the first slit and the bottom edge is α1, and the peak light emission angle of the light guide plate is β, |β|=|K×(α1-56)|, 1.3≤K≤1.6.

[0022] In some embodiments, the intersection of the first and second segments is the third vertex, the vertical distance from the third vertex to the bottom edge is H, the distance between the foot of the third vertex perpendicular to the bottom edge and the second vertex on the backlight side is W2, the angle between the second segment and the bottom edge is α2, 0.577≤W2 / H≤5.67, and / or 10°≤α2≤58°.

[0023] In some embodiments, the angle between the second slit line and the bottom edge is α2, and the light emission range of the light guide plate is positively correlated with α2.

[0024] In some embodiments, the intersection of the first and second segments is the third vertex, the distance between the foot of the third vertex perpendicular to the bottom edge and the first vertex on the light-facing side is W1, and the distance between the foot of the third vertex perpendicular to the bottom edge and the second vertex on the shaded side is W2, where 0.85 ≤ W1 / W2 ≤ 2.26.

[0025] According to another aspect of this application, a display module is provided, including a backlight unit and a liquid crystal unit, wherein the backlight unit includes the aforementioned light guide plate.

[0026] In some embodiments, the backlight unit includes at least two light guide plates, each light guide plate corresponding to an independently controlled light source, and the absolute values ​​of the peak light emission angle β of each light guide plate are not equal, and / or the signs of the peak light emission angle β of each light guide plate are different.

[0027] In some embodiments, the light guide plate of the display module is a type I light guide plate or a type II light guide plate, and multiple light guide plates may be the same or different.

[0028] The peak light emission angle of the type I light guide plate is β1, where |β1| ranges from 10.4° to 54.4°.

[0029] The peak light emission angle of the type II light guide plate is β2, and |β2| takes a value in the range of 0° to 11.2°.

[0030] In some embodiments, the backlight unit includes at least two of the I-type light guide plates, wherein at least one of the I-type light guide plates has a positive peak light emission angle and at least one of the I-type light guide plates has a negative peak light emission angle.

[0031] In some embodiments, the backlight unit includes at least one type I light guide plate and at least one type II light guide plate, wherein the angle between the principal ray of the type I light guide plate and the normal is greater than the angle between the principal ray of the type II light guide plate and the normal.

[0032] In some embodiments, the longitudinal section of the microstructure of the light guide plate is triangular, and the three sides of the triangle are a first section formed by the light-facing surface, a second section formed by the backlight surface, and a base formed by connecting the ends of the first section and the second section. The intersection of the first section and the second section is the third vertex. The vertical distance from the third vertex to the base is H. The distance between the foot of the third vertex on the base and the first vertex on the light-facing side is W1. The angle between the first section and the base is α1.

[0033] The microstructure of the type I light guide plate has the following characteristics: 22°≤α1≤48°, and / or 0.9≤W1 / H≤2.48;

[0034] The microstructure of the type II light guide plate has the following characteristics: 49°≤α1≤56°, and / or 0.675≤W1 / H≤0.87;

[0035] The peak light emission angle of the light guide plate is β, |β|=|K×(α1-56)|, 1.3≤K≤1.6.

[0036] The above-mentioned beneficial effects and other beneficial effects of this application can be further described in the specific embodiments. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of one embodiment of the light guide plate of this application.

[0038] Figure 2 This is a schematic diagram of one embodiment of a single microstructure of this application.

[0039] Figure 3 This is a cross-sectional view of one embodiment of the light guide plate of this application.

[0040] Figure 4 This is a cross-sectional view of another embodiment of the light guide plate of this application.

[0041] Figure 5 This is a schematic diagram of the light distribution of an embodiment of the light guide plate of this application, showing that the brightness is greater on the side closer to the light source and less on the side farther from the light source.

[0042] Figure 6 This is a schematic diagram illustrating the light emission principle of one embodiment of the light guide plate of this application.

[0043] Figure 7A This is a top view of one embodiment of the microstructure of this application.

[0044] Figure 7B This is a top view of another embodiment of the microstructure of this application.

[0045] Figure 8 This is a cross-sectional view of one embodiment of the microstructure of this application.

[0046] Figure 9 This is a cross-sectional view of another embodiment of the microstructure of this application.

[0047] Figure 10A A digital photograph of an existing light guide plate.

[0048] Figure 10B This is a digital photograph of one embodiment of the light guide plate of this application.

[0049] Figure 11A This is a brightness distribution diagram of one embodiment of the light guide plate of this application.

[0050] Figure 11B This is a brightness distribution diagram of another embodiment of the light guide plate of this application.

[0051] Figure 11C This is a brightness distribution diagram of another embodiment of the light guide plate of this application.

[0052] Figure 12A This is a light emission angle diagram of one embodiment of the light guide plate of this application.

[0053] Figure 12BThis is a light emission angle diagram of another embodiment of the light guide plate of this application.

[0054] Figure 13A This is a light output brightness diagram of one embodiment of the light guide plate of this application.

[0055] Figure 13B This is a light output brightness diagram of another embodiment of the light guide plate of this application.

[0056] Figure 14A This is a partial top view of the light guide plate in Example 1.

[0057] Figure 14B This is a diagram showing the light emission angle of the light guide plate in Example 1.

[0058] Figure 14C This is a brightness distribution diagram of the light guide plate in Example 1.

[0059] Figure 15A This is a partial top view of the light guide plate in Example 2.

[0060] Figure 15B This is a diagram showing the light emission angle of the light guide plate in Example 2.

[0061] Figure 15C This is a brightness distribution diagram of the light guide plate in Example 2.

[0062] Figure 16A This is a partial top view of the light guide plate in Example 3.

[0063] Figure 16B This is a diagram showing the light emission angle of the light guide plate in Example 3.

[0064] Figure 16C This is a brightness distribution diagram of the light guide plate in Example 3.

[0065] Figure 17A This is a schematic diagram of the microstructure of a light guide plate for comparison.

[0066] Figure 17B This is a brightness distribution diagram of a comparative light guide plate.

[0067] Figure 18A This is a schematic diagram of the first operating state of an embodiment of the backlight unit of this application.

[0068] Figure 18B This is a schematic diagram of the second operating state of an embodiment of the backlight unit of this application.

[0069] Figure 18C This is a schematic diagram of the third operating state of an embodiment of the backlight unit of this application.

[0070] Figure 18DThis is a schematic diagram of the working state of another embodiment of the backlight unit of this application.

[0071] In the diagram: 1. Light-entering surface; 2. Light-exiting surface; 3. Bottom surface; 4. Microstructure; 41. Light-facing surface; 42. Backlighting surface; 43. Connecting surface; 401. First side; 402. Second side; 403. Third side; 404. Fourth side; 5. Longitudinal section; 51. First section line; 52. Second section line; 53. Bottom edge; 501. First vertex; 502. Second vertex; 503. Third vertex; 504. Foot of perpendicular; 6. Light source; 60. Principal ray; 61. First ray; 62. Second ray; 603. Normal; 7. Observer. Detailed Implementation

[0072] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0073] In the description of this application, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this application.

[0074] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0075] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0076] According to a first embodiment of this application, a light guide plate is provided, such as... Figure 1As shown, the light guide plate includes: a light-inlet surface 1, a light-outlet surface 2, a bottom surface 3, and multiple microstructures 4. The light-outlet surface 2 and the bottom surface 3 are arranged opposite to each other, the light-inlet surface 1 connects the light-outlet surface 2 and the bottom surface 3, and the microstructures 4 are disposed on the bottom surface 3. Light emitted by the light source 6 enters from the light-inlet surface 1 of the light guide plate, is diffused by the microstructures 4 on the bottom surface 3, and then exits from the light-outlet surface 2. It is worth mentioning that... Figure 1 The X-axis, Y-axis, and Z-axis of the medium-space rectangular coordinate system correspond to the width, length, and height directions of the light guide plate and the microstructure 4, respectively. The X-axis is perpendicular to the light-inlet surface 1, the Y-axis is parallel to the light-inlet surface 1, and the Z-axis is perpendicular to the bottom surface 3.

[0077] Figure 2 This is a schematic diagram of one embodiment of a single microstructure 4 of this application. The microstructure 4 has a light-facing surface 41 facing the light-incoming surface 1 and a backlighting surface 42 opposite to the light-facing surface 41. The microstructure 4 also has two connecting surfaces 43, which connect the two sides of the light-facing surface 41 and the backlighting surface 42, respectively. The light entering the light guide plate from the light-incoming surface 1 is mainly reflected by the light-facing surface 41 and emitted from the light-exiting surface 2 of the light guide plate. Further, the light-facing surface 41 extends obliquely from the bottom surface 3 in a direction away from the bottom surface 3, and the backlighting surface 42 extends obliquely from the bottom surface 3 to the end of the light-facing surface 41 away from the bottom surface 3.

[0078] The light-facing surface 41 is curved, and it bends towards the shaded surface 42. The curved shape of the light-facing surface 41 better disperses light and improves light uniformity. When the microstructure 4 is a triangle without a specific curvature, such as... Figure 17A , 17B As shown, due to the excessively concentrated light emission angle, the brightness of the light emitted from different positions on the light-emitting plate varies, especially in the area near the light source 6, where bright and dark stripes appear, resulting in poor uniformity. Furthermore, this application can adjust the light emission angle of the light guide plate by adjusting the tilt angle of the light-facing surface 41, ensuring that the main light beam 60 is emitted at the required angle, thus guaranteeing high brightness.

[0079] Preferably, the backlight surface 42 is also curved, and the backlight surface 42 bends away from the light-facing surface 41. For example Figure 2 As shown, the shape of the entire microstructure 4 resembles a triangular prism with two sides curved to one side. This shape allows for adjustment of the angle in the vertical direction of light propagation (i.e., the direction of the LED arrangement or the Y-axis direction), which is beneficial for light diffusion between the LEDs and ensures the overall uniformity of light output from the light guide plate. Furthermore, the arc-shaped backlight surface 42 can further adjust the light, allowing it to be emitted as a wide or narrow beam as needed. Of course, in some embodiments, the backlight surface 42 can also be planar.

[0080] In some embodiments, the arc-shaped light-facing surface 41 or the shadow-facing surface 42 is a circular arc surface.

[0081] The microstructure 4 in this application can be recessed from the bottom surface 3 into the light guide plate, such as... Figure 3 As shown, the light-facing surface 41 is close to the light-inlet surface 1, and the backlight surface 42 is away from the light-inlet surface 1. Both the light-facing surface 41 and the backlight surface 42 are curved in a direction away from the light-inlet surface 1. The recessed microstructure 4 helps to eliminate obvious dark areas between light sources 6, increases the degree of light divergence, and can further improve the light output efficiency and illuminance uniformity of the light guide plate. Compared with the microstructure 4 protruding from the bottom surface 3, the recessed microstructure 4 in the light guide plate can achieve higher light efficiency and make the light output uniformity of the light guide plate better.

[0082] The microstructure 4 in this application can also protrude from the light guide plate on the bottom surface 3, such as... Figure 4 As shown, the backlight surface 42 is close to the light-inlet surface 1, and the front light surface 41 is far from the light-inlet surface 1. The front light surface 41 and the backlight surface 42 are bent towards the direction closer to the light-inlet surface 1. When the microstructure 4 is protruding, the light emitted by the light source 6 first directly reaches the front light surface 41. Most of the light is reflected by the front light surface 41 and then exits the light guide plate from the light-outlet surface 2. Some of the light undergoes multiple refractions or reflections within the light guide plate and is reflected by the backlight surface 42 towards the light-outlet surface 2. Of course, some of the light is refracted by the front light surface 41 to reach the backlight surface 42 of the adjacent microstructure 4, and then refracted out by the backlight surface 42. However, because the path of light to the front light surface 41 of the microstructure 4 becomes longer, the light reflection ability of the microstructure 4 farther from the light source 6 is relatively poor. Therefore, its brightness distribution diagram shows that the side closer to the light source 6 is brighter, and the side farther away from the light source 6 is weaker, as shown in the figure. Figure 5 As shown. To address the issue of poor uniformity of the light source 6 when the microstructure 4 is protruding from the bottom surface 3 of the light guide plate, the distribution density of the microstructure 4 on the side closer to the light source 6 can be reduced, while the distribution density on the side farther from the light source 6 can be increased, thereby achieving a light guide plate module with high uniformity and high luminous efficiency. Furthermore, the protruding microstructure 4 also serves to prevent adhesion and top-whitening between the light guide plate and other films.

[0083] The tilt angle of the light-facing surface 41 in this application significantly affects the peak light emission angle β of the light guide plate. By reasonably selecting the tilt angle of the light-facing surface 41, the light guide plate can have good light emission directionality, ensuring that the main light beam 60 is emitted along the required angle, guaranteeing high brightness and achieving different display angles. The tilt angle of the backlight surface 42 significantly affects the light emission range of the light guide plate; that is, changing the tilt angle of the backlight surface 42 can adjust the width of the light emission range to meet different display requirements. (Referring to Embodiment 1...) Figure 14B Let's take an example to illustrate. Figure 14BThe emission angle (peak emission angle β) at the point of maximum brightness is approximately 30°. The area in the diagram where the brightness is not less than 50% of the peak value is the emission range, i.e., the area between the two arrows. Good display performance is achieved within this range. The emission range is defined by the angle θ between two light rays with a brightness of 50% of the peak value. Further illustrations... Figure 6 This diagram primarily illustrates the light rays at the light-emitting surface 2 of the light guide plate. The dashed line perpendicular to the light guide plate is the normal 603. Another ray with an angle β to the normal 603 is the main ray 60, which is the ray with the peak brightness value. The angle β between the main ray 60 and the normal 603 is the peak light emission angle of the light guide plate or the light emission angle of the main ray 60, representing the directionality of the light guide plate. That is, in the direction of the main ray 60, the observer 7 can receive the most light. When the light guide plate is used in a display device, the display content can be clearly seen in the direction of the main ray 60. The first ray 61 and the second ray 62 are two rays with a brightness value of 50% of the peak value. The angle θ between the first ray 61 and the second ray 62 represents the light emission angle range or the light emission angle width, that is, the light emission range. Within the light emission range, most of the light can be received by the observer 7. When the light guide plate is used in a display device, the display content can be clearly seen within the light emission range.

[0084] In some embodiments, the width of the microstructure 4 along the X-axis does not exceed 10 μm, the length along the Y-axis does not exceed 25 μm, and the height along the Z-axis does not exceed 7.5 μm. By reducing the size of the microstructure 4, this application can obtain a light guide plate with better transparency, and by increasing the distribution density of the microstructure 4 on the bottom surface 3, the light guide plate can achieve higher light efficiency, which is beneficial for obtaining a high-brightness backlight module. Figure 10A The image shows an existing light guide plate, in which the width and / or length of microstructure 4 is greater than that of microstructure 4 in this application. Figure 10B The photo shows the light guide plate of the microstructure 4 in this application. By comparing the two photos, it can be clearly seen that the surface transparency of conventional light guide plates is poor, and they are basically semi-transparent or opaque. In contrast, the surface transparency of the light guide plate in this application is good, and it is basically transparent, which can meet the requirements for the appearance of the light guide plate in certain scenarios.

[0085] The width of microstructure 4 along the X-axis does not exceed 10 μm, for example, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, etc. The length of microstructure 4 along the Y-axis does not exceed 25 μm, for example, 24 μm, 23 μm, 22 μm, 21 μm, 20 μm, 19 μm, 18 μm, 17 μm, 16 μm, 15 μm, 10 μm, etc. The height of microstructure 4 along the Z-axis does not exceed 7.5 μm, for example, 7 μm, 6.5 μm, 6 μm, 5.5 μm, 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, etc.

[0086] Figure 7A and Figure 7B This is a schematic diagram of the outer contour of the microstructure 4 viewed from above or below the light-emitting surface 2. The top-view outer contour of the microstructure 4 is quadrilateral, consisting of a first side 401, a second side 402, a third side 403, and a fourth side 404 connected sequentially. This quadrilateral corresponds to the projection shape of the microstructure 4 along the Z-axis onto the bottom surface 3. The first side 401 and the third side 403 correspond to the sides of the two connecting surfaces 43 on the bottom surface 3, the second side 402 corresponds to the side of the light-facing surface 41 on the bottom surface 3, and the fourth side 404 corresponds to the side of the backlight surface 42 on the bottom surface 3. The second side 402 is an arc curving away from the light-receiving surface 1 in its middle, and its radius of curvature is denoted as R1. The fourth side 404 is also an arc curving away from the light-receiving surface 1 in its middle, and its radius of curvature is denoted as R2. When both the second side 402 and the fourth side 404 are arcs, the top-view outer contour of the microstructure 4 is approximately crescent-shaped. Furthermore, both the first side 401 and the third side 403 are straight lines. In some other embodiments, the fourth side 404 can also be a straight line (e.g., when the backlight surface 42 is a plane), and the first side 401 and the third side 403 can also be arcs. The dashed line connecting the two ends of the second side 402 in the figure represents the chord of the second side 402, with a chord length denoted as L1. The dashed line connecting the two ends of the fourth side 404 represents the chord of the fourth side 404, with a chord length denoted as L2. The arc height S1 of the second side 402 is the maximum distance along the X-axis between the chord of the second side 402 and the second side 402. The arc height S2 of the fourth side 404 is the maximum distance along the X-axis between the chord of the fourth side 404 and the fourth side 404.

[0087] Figure 8 This is a schematic diagram of the longitudinal section 5 of the microstructure 4 on the light guide plate. The longitudinal section 5 is a cross-section perpendicular to the Y-axis. The longitudinal section of the microstructure 4 is triangular, and the three sides of the triangle are the first segment 51 of the light-facing surface 41 on the cross-section, the second segment 52 of the light-reflecting surface 42 on the cross-section, and the base 53 formed by connecting the ends of the two segments. It is understood that the triangle referred to in this application is not limited to a geometrically standard triangle, but also includes shapes that approximate a triangle, such as a rounded triangle or a triangle with at least one curved side, for example... Figure 9The shape shown. When the triangle of the longitudinal section is a rounded triangle, it means that there is a smooth transition between the light-facing surface 41 and the backlight surface 42, and there is also a smooth transition between the light-facing surface 41 and the backlight surface 42 and the bottom surface 3. This smooth transition microstructure 4 helps to reduce the deformation of the light guide plate due to thermal stress during use, thereby extending the service life of the light guide plate. The intersection of the bottom edge 53 and the first segment 51 is the first vertex 501, the intersection of the bottom edge 53 and the second segment 52 is the second vertex 502, the intersection of the first segment 51 and the second segment 52 is the third vertex 503, the distance between the third vertex 503 and its perpendicular foot 504 on the bottom edge 53 is H, the distance between the first vertex 501 and the second vertex 502 is W, the distance between the first vertex 501 and the perpendicular foot 504 is W1, the distance between the second vertex 502 and the perpendicular foot 504 is W2, the interior angle at the first vertex 501 is α1, and the interior angle at the second vertex 502 is α2. It is worth mentioning that when the microstructure 4 is a structure that protrudes from the bottom surface 3, its cross-sectional shape is the same as that when it is concave, which will not be described again here.

[0088] In some embodiments, the microstructure 4 further has the following characteristics: the distance along the X-axis at each point of the second side 402 and the fourth side 404 does not exceed 10 μm, or the length W of the bottom side 53 is ≤10 μm; the chord lengths L1 and L2 of the second side 402 and the fourth side 404 are ≤25 μm and ≤25 μm, respectively, preferably L1 ≤20 μm and L2 ≤20 μm. The smaller size of the microstructure 4 can effectively improve the transparency of the light guide plate, resulting in a substantially transparent light guide plate. Furthermore, because the microstructure 4 of this application is small, the distribution density of the microstructure 4 on the bottom surface 3 can be increased, and the combination diversity of the microstructure 4 on the bottom surface 3 can be increased, enriching the means of adjusting light and making the light propagation efficiency higher, thus significantly increasing the overall brightness of the light guide plate.

[0089] In some embodiments, the microstructure 4 has the following characteristics: 0 < R1 ≤ 50 μm, 0 < R2 ≤ 50 μm, and / or, 0.9 ≤ R2 / R1 ≤ 1.5. More preferably, 1 ≤ R2 / R1 ≤ 1.3. By adjusting the curvature of the light-facing surface 41 and the backlight surface 42 of the microstructure 4, the angle of light propagation along the Y-axis can be adjusted, reducing the uneven distribution of light along the Y-axis, which is beneficial to improving the light output uniformity of the light guide plate. Thus, a uniform brightness distribution can be achieved with a single-layer light guide plate, and its light output brightness distribution diagram can be referenced. Figure 11A When the radius of curvature R1 of the second side 402 of microstructure 4 is greater than 50 μm, it means that the curvature of the light-facing surface 41 and the back-facing surface 42 is smaller and closer to a plane. At this time, more obvious bright and dark stripes are likely to appear near the light source 6, such as... Figure 11BAs shown, this reduces the uniformity of light output; or when R2 / R1 < 0.9 or R2 / R1 > 1.5, it means that the curvature of the light-facing surface 41 and the backlight surface 42 differs greatly, and more obvious bright and dark stripes are also likely to appear near the light source 6, such as... Figure 11C As shown.

[0090] This application allows the desired light emission angle to be obtained by adjusting the angle α1, thereby giving the light guide plate good light emission directionality. For example, it can obtain a type I light guide plate with a larger peak light emission angle β, or a type II light guide plate with a smaller peak light emission angle β.

[0091] Specifically, the microstructure 4 of the Type I light guide plate has the following characteristics: 22°≤α1≤48°, and / or, 0.9≤W1 / H≤2.48. Because the Type I light guide plate has a large peak emission angle β, several Type I light guide plates with different peak emission angles β can be combined for use in a display device, allowing observers in different positions to clearly see the displayed content, achieving a shared display effect.

[0092] The microstructure 4 of the Type II light guide plate has the following characteristics: 49°≤α1≤56°, and / or, 0.675≤W1 / H≤0.87. Because the Type II light guide plate has a smaller peak emission angle β, display devices with Type II light guide plates can only provide a clear display to observers in the direct viewing direction. The Type II light guide plate allows for individual viewing from a single location, emphasizing the protection of user privacy.

[0093] Furthermore, the relationship between the peak light emission angle β and α1 of the light guide plate is: |β|=|K×(α1-56)|, 1.3≤K≤1.6, where K can be, for example, 1.3, 1.35, 1.4, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.5, 1.55, 1.6, etc. It is worth noting that when the light source is located on the right side of the light guide plate, β=-K×(α1-56); when the light source is located on the left side of the light guide plate, β=K×(α1-56). For Type I light guide plates, the smaller α1 is, the larger |β| is. This means that when a Type I light guide plate is applied to a display device, the smaller α1 is, the clearer the display content will be for observers further away from the display device, while observers directly in front of the display device will have difficulty seeing the display content. For Type II light guide plates, the larger α1 is, the smaller β is. When a Type II light guide plate is applied to a display device, the larger α1 is, the clearer the displayed content will be for an observer directly in front of the display device, while it will be difficult for an observer far from the display device to see the displayed content. It is worth mentioning that the peak light emission angle β of the light guide plate is the angle between the light ray at the position of maximum light emission (i.e., the principal ray) and the surface normal of the light emission surface 2.

[0094] When light refracts on the light-facing surface 41 of the microstructure 4 and reaches the backlight surface 42, secondary refraction will occur on the backlight surface 42. Therefore, the surface profile characteristics of the backlight surface 42 also affect the light-emitting angle of the light, which can be used to increase the range of the light-emitting angle θ. θ is the maximum angle between the lights with a brightness value of 50% of the peak value. In some embodiments, the microstructure 4 has the following characteristics: 0.577 ≤ W2 / H ≤ 5.67, and / or, 10° ≤ α2 ≤ 58°. Further, θ is positively correlated with α2. When θ is relatively large, multi-viewpoint light emission of the light guide plate can be achieved. When θ is relatively small, single-viewpoint high-brightness light emission of the light guide plate can be achieved. By adjusting the far-light angle α2, the viewing requirements of different display devices can be met. As Figure 12A shown, when α2 is relatively small, the range of the light-emitting angle of the light guide plate is relatively narrow. The black arrows in the figure indicate the range of the light-emitting angle; as Figure 12B shown, when α2 is relatively large, the range of the light-emitting angle of the light guide plate is relatively wide. The black arrows in the figure indicate the range of the light-emitting angle. It is worth mentioning that Figure 12A and Figure 12B the difference between the light guide plates is only the difference in the angle between the backlight surface 42 of the microstructure 4 and the bottom surface 3.

[0095] In some embodiments, the microstructure 4 has the following characteristics: 0 < R1 / L1 ≤ 2.78, 0 < R2 / L2 ≤ 2.78, and / or 0.85 ≤ W1 / W2 ≤ 2.26. The ratio of R to L is used to characterize the degree of bending of the microstructure 4, and this degree of bending mainly affects the light-emitting uniformity of the light guide plate. W1 and W2 are used to characterize the relative relationship of the inclination degrees of the light-facing surface 41 and the backlight surface 42 of the microstructure 4, mainly affecting the light-emitting angle and the width range of the light guide plate. By defining the foregoing parameters of the microstructure 4, it is more conducive to obtaining a light guide plate with uniform light emission, high brightness, and wide viewing field light emission.

[0096] In some embodiments, the microstructure 4 has the following characteristics: 0 < S1 / R1 ≤ 1.5, 0 < S2 / R2 ≤ 1.15. By controlling the ratio relationship between the arc height and the radius of curvature of the arc, the regulation of the surface profile and size of the microstructure 4 is achieved. When the surface profile characteristics of the microstructure 4 satisfy the foregoing relational expressions, the light-emitting uniformity of the light guide plate is better. In addition, by controlling the size of the microstructure 4, the microstructure 4 is made to have processability and is conducive to improving the surface permeability of the light guide plate.

[0097] In some embodiments, the microstructure 4 has the following characteristics: the angle between the two connecting surfaces 43 does not exceed 10°; preferably, the angle between the two connecting surfaces 43 does not exceed 5°; further preferably, the two connecting surfaces 43 are parallel to each other. Or rather, the angle between the first side 401 and the third side 403 does not exceed 10°; preferably, the angle between the first side 401 and the third side 403 does not exceed 5°; more preferably, the first side 401 and the third side 403 are parallel to each other, as Figure 7AAs shown, L1 = L2 at this time. This feature of microstructure 4 is beneficial to improving the light output brightness of the light guide plate. Figure 13A and Figure 13B These are schematic diagrams showing the brightness of light guide plates with different microstructures 4. Figure 13A The first side 401 and the third side 403 of the microstructure are parallel to each other. Figure 13A A top view of the microstructure 4 of the light guide plate is shown below. Figure 7A As shown, Figure 13B A top view of the microstructure 4 of the light guide plate is shown below. Figure 7B As shown, the angle between the first side 401 and the third side 403 of the microstructure is greater than 10°, at which point the light output brightness of the light guide plate is poor.

[0098] In some embodiments, the microstructure 4 further has the following characteristics: both the first segment 51 and the second segment 52 are straight lines. That is, the light-facing surface 41 and the back-facing surface 42 of the microstructure 4 are single-curved surfaces. Of course, in other embodiments, the first segment 51 and / or the second segment 52 are arcs, that is, the light-facing surface 41 and / or the back-facing surface 42 are hyperboloids.

[0099] The following provides specific embodiments of the light guide plate.

[0100]

Example 1

[0101] A light guide plate with a size of 301mm × 139mm is provided, and microstructures 4 are set on its bottom surface 3. A top view of part of the plate is shown below. Figure 14A As shown, the microstructure 4 is recessed inside the light guide plate. The light-facing surface 41 and the backlight surface 42 of the microstructure 4 are both curved surfaces that curve away from the light-receiving surface 1. The two connecting surfaces 43 of the microstructure 4 are parallel planes. The microstructure 4 has L1 = L2 = 18 μm, the lengths of the first side 401 and the third side 403 are both 8.585 μm, the height of the cross-section of the microstructure 4 is H = 3.3978 μm, α1 = 29.2°, α2 = 53.6°, R1 = 13.2 μm, R2 = 15.8 μm, and R2 / R1 = 1.197.

[0102] The light guide plate in Example 1 is a Type I light guide plate, with an outgoing light angle of 30° in its region, as shown in Figure 14B. The entire light guide plate achieves a final effect of high brightness and uniform light output, and its brightness distribution is as follows. Figure 14CAs shown. When the light guide plate provided in Embodiment 1 is applied to a display device, an observer directly in front of the light guide plate receives less light and cannot clearly see the display content. Only within a viewing angle tilt of approximately +30° can the observer receive more light and clearly see the display content. At a position of -30°, the display content is also unclear. In practical use, the two light guide plates of Embodiment 1 can be used in combination. When the light source corresponding to one of the light guide plates emits light, the observer at the tilt position corresponding to that light guide plate can clearly see the display content. When the light sources corresponding to both light guide plates emit light, the observers at two different positions can clearly see the display content.

[0103]

Example 2

[0104] The difference between Example 2 and Example 1 is that the lengths of the first side 401 and the third side 403 of the microstructure 4 are both 5 μm, α1 = 53.7°, α2 = 53.6°, R1 = 12.5 μm, R2 = 15.8 μm, and R2 / R1 = 1.264.

[0105] The light guide plate in Example 2 is a Type II light guide plate. Figure 15A This is a top view of a portion of the image, where the emitted light angle is 0°. The distribution diagram is shown in Figure 15B. The light guide plate achieves the final effect of high brightness and uniform light emission, and its brightness distribution is as follows. Figure 15C As shown. When the light guide plate provided in Embodiment 2 is applied to a display device, the observer located directly in front of the light guide plate receives more light and can see the display content clearly, while the observers in other directions receive less light and cannot see the display content clearly.

[0106]

Example 3

[0107] The difference between Example 3 and Example 1 is that the lengths of the first side 401 and the third side 403 of the microstructure 4 are both 7.66 μm, α1 = 29.2°, α2 = 65°, R1 = 13.2 μm, R2 = 16.8 μm, and R2 / R1 = 1.273.

[0108] The light guide plate in Example 3 is a Type I light guide plate, such as... Figure 16A As shown, the peak emission angle of the main ray from the light guide plate in Example 3 is approximately 38°, and the light emission range is >38°±a. The value of 'a' is defined by the ray at 50% of the peak energy, and is adjusted by α2. Figure 16B As shown, the light guide plate achieves the final effect of high brightness and uniform light output, and its brightness distribution is as follows. Figure 16C As shown.

[0109] Comparative Example 1

[0110] The difference between Comparative Example 1 and Example 1 is that the light-facing surface 41 and the back-facing surface 42 of the microstructure 4 are both planar, such as... Figure 17A As shown, microstructure 4 is a triangle without curvature. Because the triangular slope lacks a specific curvature, light entering the light guide plate is concentrated and emitted from the same position on the light-emitting surface 2. This excessive concentration of light emission angles results in different light emission brightnesses at different positions on the light guide plate. Figure 17B As shown, the light guide plate with a triangular microstructure 4 without a specific curvature exhibits obvious brightness unevenness in the near light source 6 area.

[0111] This application also provides a display module, including a backlight unit and a liquid crystal unit, wherein the backlight unit includes the aforementioned light guide plate.

[0112] Preferably, the backlight unit includes at least two of the aforementioned light guide plates, and each light guide plate corresponds to an independently controlled light source. The absolute values ​​of the peak light emission angle β of each light guide plate are not equal, and / or the signs of the peak light emission angle β of each light guide plate are different. By combining light guide plates with different light emission angles, different display modes of the display module can be switched.

[0113] For example, when the peak light emission angle β of the two light guide plates has the same sign but different values, it means that clear display content can be obtained at two observation positions on the same side of the normal; when the peak light emission angle β of the two light guide plates has different signs, it means that clear display content can be obtained at two observation positions on different sides of the normal.

[0114] Figures 18A-18D This is a schematic diagram of a specific embodiment of a backlight unit, showing that the backlight unit includes two light guide plates. The two light guide plates are stacked one above the other. The peak light emission angle of the first light guide plate is β1, and the peak light emission angle of the second light guide plate is β2, |β1|≠|β2|, and β1 and β2 have the same sign. That is, the principal rays 60 of the two light guide plates are located on the same side of the normal 603. When only the light source 6 opposite to the first light guide plate is turned on, the observer 7 can clearly see the displayed content in the β1 direction, such as... Figure 18A As shown; when only the light source 6 opposite to the second light guide plate is turned on, the observer 7 can clearly see the displayed content in the β2 direction, as shown. Figure 18B As shown; when the light sources 6 opposite to the two light guide plates are turned on simultaneously, the observer 7 can clearly see the displayed content in the β1 and β2 directions, as shown. Figure 18CAs shown; when the direction of the first light guide plate is rotated 180°, its peak light emission angle is -β1, and the peak light emission angle of the second light guide plate is β2. That is, the principal rays 60 of the two light guide plates are located on different sides of the normal 603. At this time, the light sources corresponding to the two light guide plates are also located on different sides. When the two light sources are turned on simultaneously, the observer 7 can clearly see the displayed content in the -β1 and β2 directions, such as... Figure 18D As shown.

[0115] In one application example, the display module provided in this application can be applied to a car center console screen. The driver's seat and the passenger seat have different angles relative to the display screen. The peak light emission angle of one light guide plate can be set to face the driver's seat, and the peak light emission angle of the other light guide plate can be set to face the passenger seat. When it is desired that only one position can see the screen content clearly, only the light source of the corresponding light guide plate on that side can be turned on. When it is desired that both positions can see the screen content clearly, the light sources of both light guide plates can be turned on.

[0116] When the display module is positioned between the driver's seat and the passenger seat, the driver's seat and the passenger seat are located to the left and right of the display module, respectively. At this time, two Type I light guide plates can be selected, with the two Type I light guide plates set in opposite directions, so that the peak light output angle of one light guide plate is for the driver's seat and the peak light output angle of the other light guide plate is for the passenger seat.

[0117] When the display module is positioned directly in front of the driver's seat, the passenger seat is located to the side of the display module. In this case, one type I light guide plate and one type II light guide plate can be selected. The peak light output angle of the type II light guide plate is for the driver's seat, and the peak light output angle of the type I light guide plate is for the passenger seat.

[0118] When the display module is positioned directly in front of the passenger seat, the driver's seat is located to the side of the display module. In this case, one type I light guide plate and one type II light guide plate can be selected. The peak light output angle of the type II light guide plate is for the passenger seat position, and the peak light output angle of the type I light guide plate is for the driver's seat position.

[0119] In some embodiments, the peak light emission angle of the type I light guide plate is β1, where |β1| is taken in the range of 10.4° to 54.4°, and the peak light emission angle of the type II light guide plate is β2, where |β2| is taken in the range of 0° to 11.2°.

[0120] In some embodiments, the backlight unit includes at least two I-shaped light guide plates, wherein at least one of the I-shaped light guide plates has a positive peak light emission angle, and at least one of the I-shaped light guide plates has a negative peak light emission angle. Preferably, the peak light emission angle β1 of at least one I-shaped light guide plate is between 15° and 50°, and the peak light emission angle β1 of at least one I-shaped light guide plate is between -15° and -50°. More preferably, the peak light emission angle β1 of at least one I-shaped light guide plate is between 20° and 40°, and the peak light emission angle β1 of at least one I-shaped light guide plate is between -20° and -40°.

[0121] In some embodiments, the backlight unit includes at least one type I light guide plate and at least one type II light guide plate, wherein the angle between the principal ray of the type I light guide plate and the normal is greater than the angle between the principal ray of the type II light guide plate and the normal. Preferably, the peak light emission angle β2 of at least one type II light guide plate is -10° to 10°, and the peak light emission angle β2 of at least one other type I light guide plate is 15° to 50° or -15° to -50°. More preferably, the peak light emission angle β2 of at least one type II light guide plate is -5° to 5°, and the peak light emission angle β2 of at least one other type I light guide plate is 20° to 40° or -20° to -40°.

[0122] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A light guide plate includes an opposite light-emitting surface and a bottom surface, and a light-incident surface connecting the light-emitting surface and the bottom surface. The light of a light source is adapted to enter the light guide plate from the light-incident surface. The bottom surface of the light guide plate is provided with a plurality of microstructures, and is characterized in that the microstructures have a light-facing surface facing the light-incident surface, a light-backing surface opposite to the light-facing surface, and two connecting surfaces. The light-facing surface extends obliquely away from the bottom surface, the light-backing surface extends obliquely from the bottom surface to an end of the light-facing surface away from the bottom surface, and the two connecting surfaces respectively connect two sides of the light-facing surface and the light-backing surface; the light-facing surface is an arc surface and curves towards the light-backing surface.

2. The light guide plate according to claim 1, wherein The light-backing surface is an arc surface and curves away from the light-facing surface.

3. The light guide plate according to claim 1, wherein The X-axis, Y-axis, and Z-axis of a spatial rectangular coordinate system respectively correspond to the width direction, length direction, and height direction of the light guide plate, where the Z-axis is perpendicular to the bottom surface, the X-axis is perpendicular to the light-incident surface, the width of the microstructures in the X-axis direction is not greater than 10 μm, the length of the microstructures in the Y-axis direction is not greater than 25 μm, and the height in the Z-axis direction is not greater than 7.5 μm.

4. The light guide plate according to claim 1, wherein The microstructures are recessed from the bottom surface into the light guide plate, and the light-facing surface protrudes away from the light-incident surface, or the microstructures protrude from the bottom surface out of the light guide plate, and the light-facing surface protrudes towards the light-incident surface.

5. The light guide plate according to claim 1, wherein The two connecting surfaces are parallel to each other, or the included angle between the two connecting surfaces does not exceed 10°.

6. The light guide plate according to any one of claims 1 to 5, wherein When viewed from above or below in the Z-axis direction, the outer contour of the microstructures is a quadrilateral, and the quadrilateral includes a first side, a second side, a third side, and a fourth side connected in sequence. The second side is the side of the light-facing surface on the bottom surface, the fourth side is the side of the light-backing surface on the bottom surface, and both the second side and the fourth side are arcs and have the same bending direction; the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, 0 < R1 ≤ 50 μm, 0 < R2 ≤ 50 μm, and / or, 0.9 ≤ R2 / R1 ≤ 1.5; preferably, 1 ≤ R2 / R1 ≤ 1.3; the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, the chord length of the second side is L1, the chord length of the fourth side is L2, 0 < R1 / L1 ≤ 2.78, and / or, 0 < R2 / L2 ≤ 2.

78.

7. The light guide plate according to claim 6, characterized in that, The chord length of the second side is L1, and the chord length of the fourth side is L2; L1 = L2, and the first side is parallel to the third side; or, L1 ≠ L2, and the included angle between the first side and the third side does not exceed 10°.

8. The light guide plate according to claim 6, characterized in that, the radius of curvature of the second side is R1, the radius of curvature of the fourth side is R2, the arc height of the second side is S1, the arc height of the fourth side is S2, 0 < S1 / R1 ≤ 1.5, and / or 0 < S2 / R2 ≤ 1.15; The longitudinal section of the microstructure is triangular, and the three sides of the triangle are the first section formed by the light-facing surface, the second section formed by the back-facing surface, and the base formed by connecting the ends of the first section and the second section. The first section and the second section are both straight lines, or at least one of the first section and the second section is an arc. The intersection of the first and second segments is the third vertex. The vertical distance from the third vertex to the base is H. The distance between the foot of the third vertex perpendicular to the base and the first vertex on the light-facing side is W1. The angle between the first segment and the base is α1, 22°≤α1≤48°, and / or 0.9≤W1 / H≤2.

48. Alternatively, the intersection of the first and second segments is the third vertex, the vertical distance from the third vertex to the base is H, the distance between the foot of the third vertex perpendicular to the base and the first vertex on the light-facing side is W1, and the angle between the first segment and the base is α1, 49°≤α1≤56°, and / or 0.675≤W1 / H≤0.87; The angle between the first slit and the bottom edge is α1, and the peak light emission angle of the light guide plate is β, |β|=|K×(α1-56)|, 1.3≤K≤1.6; The intersection of the first and second segments is the third vertex. The vertical distance from the third vertex to the bottom edge is H. The distance between the foot of the third vertex perpendicular to the bottom edge and the second vertex on the backlit side is W2. The angle between the second segment and the bottom edge is α2, 0.577≤W2 / H≤5.67, and / or 10°≤α2≤58°. The angle between the second segment and the bottom edge is α2, and the light emission range of the light guide plate is positively correlated with α2; The intersection of the first and second segments is the third vertex. The distance between the foot of the third vertex perpendicular to the bottom edge and the first vertex on the light-facing side is W1. The distance between the foot of the third vertex perpendicular to the bottom edge and the second vertex on the shaded side is W2. 0.85≤W1 / W2≤2.

26.

9. A display module comprising a backlight unit and a liquid crystal unit, wherein the backlight unit comprises a light guide plate as described in any one of claims 1-18.

10. The display module according to claim 19, characterized in that, The backlight unit includes at least two light guide plates, each light guide plate corresponds to an independently controlled light source, and the absolute values ​​of the peak light emission angle β of each light guide plate are not equal, and / or the positive and negative signs of the peak light emission angle β of each light guide plate are different. The light guide plate is either a type I light guide plate or a type II light guide plate, and multiple light guide plates may be the same or different. The peak light emission angle of the type I light guide plate is β1, where |β1| ranges from 10.4° to 54.4°. The peak light emission angle of the type II light guide plate is β2, and |β2| takes a value in the range of 0° to 11.2°. The backlight unit includes at least two I-shaped light guide plates, wherein at least one of the I-shaped light guide plates has a positive peak light emission angle, and at least the other I-shaped light guide plate has a negative peak light emission angle. Alternatively, the backlight unit may include at least one type I light guide plate and at least one type II light guide plate, wherein the angle between the principal ray of the type I light guide plate and the normal is greater than the angle between the principal ray of the type II light guide plate and the normal. The longitudinal section of the microstructure of the light guide plate is triangular. The three sides of the triangle are the first section formed by the light-facing surface, the second section formed by the backlight surface, and the base formed by connecting the ends of the first section and the second section. The intersection of the first section and the second section is the third vertex. The vertical distance from the third vertex to the base is H. The distance between the foot of the third vertex on the base and the first vertex on the light-facing side is W1. The angle between the first section and the base is α1. The microstructure of the type I light guide plate has the following characteristics: 22°≤α1≤48°, and / or 0.9≤W1 / H≤2.48; The microstructure of the type II light guide plate has the following characteristics: 49°≤α1≤56°, and / or 0.675≤W1 / H≤0.87; The peak light emission angle of the light guide plate is β, |β|=|K×(α1-56)|, 1.3≤K≤1.6.

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