Light guide element and backlight module

Abstract

The invention provides a light guide element which comprises a body and a first optical microstructure. The body has a first surface, a second surface and a light incident surface. The first optical microstructure comprises a first light facing surface. The first optical microstructure takes the first reference plane as a symmetry plane. The first reference plane is perpendicular to the second surface and passes through the vertex of the first optical microstructure. The boundary of the first light facing surface and the first reference plane has a first central symmetry curve. The first central symmetric curve has at least one inflection point. A first intersection arc line is formed at the junction of the first light facing face and the second face, and the curvature radius of the first intersection arc line is a fixed value. The invention further provides a backlight module comprising the light guide element. According to the light guide element and the backlight module, the visual angle can be adjusted to be concentrated, and the overall luminous intensity is effectively improved.

Description

Technical Field

[0001] The invention relates to an optical element and a light emitting device, and in particular to a light guide element and a backlight module. Background Art

[0002] Liquid crystal displays include liquid crystal display panels. Since the liquid crystal display panel itself does not have the ability to emit light, the liquid crystal display panel must rely on the surface light source provided by the backlight module in order for the user to view the image displayed by the liquid crystal display panel. In the current backlight module, the light guide plate of the backlight module is configured with a microstructure that adjusts and guides the angle of light beam transmission. By changing the light-facing angle of the light-facing surface of the microstructure, the energy can be concentrated on the vertical light output, which can effectively improve the light output concentration. However, in actual applications, due to the design of the reflective surface of the existing microstructure, the microstructure on the light guide plate cannot fully exert its function, resulting in poor brightness efficiency in some display devices. Summary of the invention

[0003] The present invention provides a light guide element and a backlight module, which can reduce energy loss, adjust the viewing angle concentration, and effectively improve the overall luminous intensity.

[0004] The present invention provides a light-guiding element, comprising a main body and a first optical microstructure. The main body has a first surface and a second surface opposite to each other, and a light incident surface connected between the first surface and the second surface. The first optical microstructure comprises a first light-facing surface. The first light-facing surface faces the light incident surface. The first optical microstructure takes a first reference plane as a symmetry plane. The first reference plane is perpendicular to the second surface and passes through the vertex of the first optical microstructure. The intersection of the first light-facing surface and the first reference plane has a first central symmetry curve. The first central symmetry curve has at least one inflection point. The intersection of the first light-facing surface and the second surface forms a first intersection arc, and the curvature radius of the first intersection arc is a constant value.

[0005] The present invention provides a backlight module, including a light-guiding element and a light-emitting element. The light-guiding element includes a body and a first optical microstructure. The body has a first surface and a second surface opposite to each other, and a light incident surface connected between the first surface and the second surface. The first optical microstructure includes a first light-facing surface. The first light-facing surface faces the light incident surface. The first optical microstructure uses a first reference plane as a symmetry plane. The first reference plane is perpendicular to the second surface and passes through the vertex of the first optical microstructure. The intersection of the first light-facing surface and the first reference plane has a first central symmetry curve. The first central symmetry curve has at least one inflection point. The intersection of the first light-facing surface and the second surface forms a first intersection arc, and the curvature radius of the first intersection arc is a constant. The light-emitting element is arranged on the light incident surface of the body, and the light-emitting element includes a plurality of light-emitting units for providing an illumination beam.

[0006] Based on the above, in the light-guiding element and the backlight module of the present invention, the light-guiding element includes a main body and a first optical microstructure. Among them, the first optical microstructure includes a first light-facing surface. The first optical microstructure uses the first reference plane as a symmetry plane. The first light-facing surface faces the light-incident surface of the main body, and the first reference plane is perpendicular to the second surface of the main body and passes through the vertex of the first optical microstructure. The intersection of the first light-facing surface and the first reference plane has a first central symmetry curve, and this first central symmetry curve has at least one inflection point. In this way, through the special design of the above-mentioned first optical microstructure, the backlight module can reduce energy loss and adjust the viewing angle concentration, thereby effectively improving the overall luminous intensity.

[0007] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. 4 is a schematic diagram of a backlight module according to an embodiment of the present invention.

[0009] Figure 2 FIG. 4 is a schematic side view of a first optical microstructure according to an embodiment of the present invention.

[0010] Figure 3 for Figure 2 A three-dimensional schematic diagram of the first optical microstructure.

[0011] Figure 4 for Figure 2 Schematic top view of the first optical microstructure.

[0012] Figure 5 for Figure 1 A bottom view schematically shows a backlight module of the backlight module.

[0013] Figure 6 for Figure 5 A schematic top view of a second optical microstructure of a backlight module.

[0014] Figure 7 for Figure 5 A schematic top view of a third optical microstructure of a backlight module.

[0015] Description of reference numerals:

[0016] 50: Backlight module

[0017] 100,100A: Light guide element

[0018] 110: Ontology

[0019] 120: The first optical microstructure

[0020] 130: Second optical microstructure

[0021] 140: The third optical microstructure

[0022] 200: Light-emitting element

[0023] 210: Light emitting unit

[0024] A1: First page

[0025] A2: Second side

[0026] A21: Light entry area

[0027] A22: Setting area

[0028] A3: Light incident side

[0029] B1: First light-facing side

[0030] B2: Second light-facing side

[0031] B3: The third light-facing side

[0032] C1: First central symmetric curve

[0033] C2: Second central symmetric curve

[0034] C3: The third central symmetric curve

[0035] D1: First direction

[0036] D2: Second direction

[0037] D3: Third direction

[0038] E1: First reference plane

[0039] E2: Second reference plane

[0040] E3: Third reference plane

[0041] F: Light Curve

[0042] H,L,S: distance

[0043] I: optical axis

[0044] J: Axis of symmetry

[0045] K, W: length

[0046] L1: illumination beam

[0047] L2: Image beam

[0048] M: Auxiliary light-facing surface

[0049] N: Side light-facing surface

[0050] P: Spacing

[0051] Q1, Q2, Q3: Vertex

[0052] R1: First intersection arc

[0053] R2: Second intersection arc

[0054] R3: The third intersection arc

[0055] T: Thickness

[0056] U: Starting point. DETAILED DESCRIPTION

[0057] Figure 1 FIG. 1 is a schematic diagram of a backlight module according to an embodiment of the present invention. Figure 1 The present invention provides a backlight module 50, for example, applied to a display device (not shown), and the backlight module 50 is used to provide an illumination beam L1. In other embodiments, the backlight module 50 may further include different types of optical films, such as prism films, diffusion films and other optical elements. In one embodiment, the illumination beam L1 of the backlight module 50 can be provided to a display panel of the display device (not shown), and the illumination beam L1 is transmitted through the display panel to form an image beam (not shown).

[0058] The backlight module 50 includes a light guide element 100 and a light emitting element 200. The light guide element 100 is, for example, a light-transmitting element, suitable for transmitting the illumination light beam L1 therein, and includes a body 110 and a first optical microstructure 120. The body 110 has a first surface A1 and a second surface A2 opposite to each other, and a light incident surface A3 connected between the first surface A1 and the second surface A2. The number of the first optical microstructures 120 is plural, distributed on the first surface A1 or the second surface A2 of the body 110, and the first optical microstructures 120 can be a geometric microstructure protruding from the surface or a geometric microstructure recessed from the surface to the inside (i.e., a recessed structure). For example, in the present embodiment, the first surface A1 is the top surface of the body 110, and the second surface A2 is the bottom surface of the body 110. The second surface A2 is perpendicular to the light incident surface A3. The first optical microstructure 120 is a geometric microstructure distributed on the second surface A2 of the body 110 and recessed from the surface to the inside. However, the present invention does not limit the configuration surface and type of the first optical microstructure 120. The light emitting element 200 is configured on one side of the light incident surface A3 of the body 110. The light emitting element 200 includes a plurality of light emitting units 210 for providing an illumination beam L1. The light emitting unit 210 is, for example, a light emitting diode or other element suitable for emitting a light beam, but the present invention is not limited thereto.

[0059] Figure 2 FIG. 4 is a schematic side view of a first optical microstructure according to an embodiment of the present invention. Figure 3 for Figure 2A three-dimensional schematic diagram of the first optical microstructure. Figure 4 for Figure 2 In this embodiment, the first direction D1 can be defined as a direction perpendicular to the second surface A2, the second direction D2 can be defined as a direction perpendicular to the light incident surface A3, and the third direction D3 can be defined as a direction parallel to the second surface A2 and the light incident surface A3. It is particularly noted that, for the convenience of description, Figures 2 to 4 The first optical microstructure 120 is represented by a solid geometric shape. However, in this embodiment, the first optical microstructure 120 is formed by being recessed into the body 110, but the present invention is not limited thereto. Figures 2 to 4 In the present embodiment, the first optical microstructure 120 is, for example, a symmetrical structure, including a first light-facing surface B1, a vertex Q1, and a first central symmetry curve C1. The first light-facing surface B1, for example, faces the light-incident surface A3 of the body 110, and is suitable for reflecting a light beam passing through the light-incident surface A3 (for example, a light beam from the light-emitting unit 210). The vertex Q1 is, for example, the point at which the first optical microstructure 120 (or the first light-facing surface B1) is farthest from the second surface A2. The first optical microstructure 120 takes the first reference plane E1 as a symmetry plane. The boundary between the first light-facing surface B1 and the first reference plane E1 is the first central symmetry curve C1, and the first central symmetry curve C1 has at least one inflection point. The first central symmetry curve C1 is, for example, a ridge line (a portion of) the first optical microstructure 120. In the present embodiment, the first reference plane E1 is, for example, perpendicular to the second surface A2 and the light-incident surface A3 of the body 110 and passes through the vertex Q1 of the first optical microstructure 120. It is particularly noted that, in the present embodiment, the first direction D1 is, for example, a direction perpendicular to the second surface A2, the third direction D3 is, for example, a direction perpendicular to the first reference plane E1, and the second direction D2 is, for example, perpendicular to the first direction D1 and the third direction D3. In other embodiments, the angle between the first reference plane E1 and the light incident surface A3 is, for example, greater than or equal to 75 degrees and less than or equal to 90 degrees. On the other hand, the intersection of the first light-facing surface B1 and the second surface A2 of the body 110 forms a first intersection arc R1, and the radius of curvature R of the first intersection arc R1 is, for example, a constant value (or the radius of curvature of at least 90% of the line segments of the first intersection arc R1 are the same). That is, any part of the first intersection arc R1 has the same curvature on the second surface A2 of the body 110. In this way, by means of the special design of the first optical microstructure 120, the backlight module 50 can reduce energy loss and adjust the viewing angle concentration, thereby effectively improving the overall luminous intensity.

[0060] Specifically, in this embodiment, the light guiding element 100 and the first optical microstructure 120 satisfy the following conditional formula: S = T / 75, where S is the distance between the vertex Q1 of the first optical microstructure 120 and the second surface A2, that is, the maximum height of the first optical microstructure 120 in the first direction D1, and T is the thickness of the main body 110 in the first direction D1. The first direction D1 is perpendicular to the second surface A2. However, the present invention is not limited thereto. In other embodiments, the light guiding element 100 and the first optical microstructure 120 satisfy the following conditional formula: T / 100 < S < T / 45. In addition, in a preferred embodiment, the length of the first optical microstructure 120 in the second direction D2 is between 20 micrometers and 60 micrometers, and the width of the first optical microstructure 120 in the third direction D3 is between 20 micrometers and 100 micrometers. In addition, the first central symmetry curve C1 conforms to a binary quartic equation. For example, in this embodiment, the first central symmetry curve C1 of the first optical microstructure 120 conforms to the equation: H = -1.255x10 -5 L 4 +5x10 -4 L 3 +3.9x10 -3 L 2 +4.7x10 -3 L, where L is the distance between a point on the first central symmetry curve C1 and the starting point U in the second direction D2, and H is the distance between the above point on the first central symmetry curve C1 and the second surface A2 in the first direction D1. The starting point U is the intersection point of the first central symmetry curve C1 and the second surface A2 (in this embodiment, it can also be the end of the first optical microstructure 120 closest to the light incident surface A3). Through the above design, the first light incident surface B1 can effectively increase the light extraction efficiency of the forward beam.

[0061] On the other hand, considering that there is an obliquely transmitted part of the light provided by the light emitting unit 210 (such as Figure 1 ), the curvature radius R of the first intersection arc R1 of the first optical microstructure 120 can be further designed to conform to the equation: R = 2.2x10 -3 πx(W / K)xP x cosθ, where W is the length of the first optical microstructure 120 in the third direction D3, K is the length of the first optical microstructure 120 in the second direction D2, P is the pitch of the plurality of light emitting units 210 (marked in Figure 5 ), and θ is the half luminous angle of the light emitting unit 210. In this way, the design of the first intersection arc R1 of the first light incident surface B1 can further increase the efficiency of reflecting the obliquely incident light to the first surface A1.

[0062] On the other hand, the first light-facing surface B1 of the first optical microstructure 120 has a plurality of light-facing curves F at the intersection with the plurality of light-incident reference planes, wherein the light-incident reference plane is perpendicular to the second surface A2 and perpendicular to the first reference plane E1 (in this embodiment, for example, a reference plane parallel to the light-incident surface A3), and the curvature of each light-facing curve F decreases as it moves away from the light-incident surface A3 (e.g., Figure 3 In this way, the optical effect can be further improved.

[0063] Figure 5 for Figure 1 A bottom view schematically shows a backlight module of the backlight module. Figure 6 for Figure 5 A schematic top view of a second optical microstructure of a backlight module. Figure 7 for Figure 5 A top view of the third optical microstructure of the backlight module. Figures 5 to 7 . In the present embodiment, the light guide element 100A includes a plurality of first optical microstructures 120, and also includes a plurality of second optical microstructures 130 and a plurality of third optical microstructures 140. The second surface A2 of the light guide element 100A includes, for example, a light incident area A21 and a setting area A22. The light incident area A21 is located between the light incident surface A3 and the setting area A22. In one embodiment, the length of the light incident area A21 in the second direction D2 is, for example, 1 / 20 to 1 / 5 times the length of the second surface A2 in the second direction. The plurality of first optical microstructures 120 are, for example, uniformly distributed in the setting area A22 of the second surface A2 of the light guide element 100A (in other embodiments, the plurality of first optical microstructures 120 may also be disposed in the light incident area A21). The plurality of second optical microstructures 130 and the plurality of third optical microstructures 140 are, for example, disposed in the light incident area A21, but not disposed in the setting area A22.

[0064] In this embodiment, each second optical microstructure 130 includes a second light-facing surface B2, a vertex Q2, a second central symmetric curve C2, and an auxiliary light-facing surface M. The second optical microstructure 130 takes the second reference plane E2 as a symmetric surface. The second light-facing surface B2, the second intersection arc R2, the vertex Q2, the second central symmetric curve C2, and the second reference plane E2 are similar to the first light-facing surface B1, the vertex Q1, the first central symmetric curve C1, and the first reference plane E1 of the first optical microstructure 120, and are not described in detail here. The difference lies in the shapes of the auxiliary light-facing surface M and the second light-facing surface B2 (the second intersection arc R2, the second central symmetric curve C2) provided in the second optical microstructure 130. The auxiliary light-facing surface M is located between the light-entering surface A3 and the vertex Q2 (for example, the orthographic projection of the second optical microstructure on the second surface A2, the auxiliary light-facing surface M is located between the light-entering surface A3 and the vertex Q2), and is located between the second light-facing surface B2 and the second surface A2, and the contour of the orthographic projection of the auxiliary light-facing surface M on the second surface A2 is an arc curved away from the light-entering surface A3, that is, the auxiliary light-facing surface M is an arc surface perpendicular to the second surface A2, and takes the second reference plane E2 as a symmetric plane. In other words, the second optical microstructure 130 is similar to the first optical microstructure 120 (that is, the second optical microstructure 130 has a partial structure identical to that of the first optical microstructure), except that the second optical microstructure 130 further includes the auxiliary light-facing surface M on the side close to the light-entering surface A3, and the first light-facing surface B1 (first intersection arc R1, first central symmetry curve C1) of the first optical microstructure 120 is cut off by the auxiliary light-facing surface M to form the second light-facing surface B2 (second intersection arc R2, second central symmetry curve C2). The auxiliary light-facing surface M is used to refract the light beam transmitted to the second optical microstructure 130 to multiple directions (such as Figure 6 As shown, the normal direction of the incident light surface A3 is deviated from, which can reduce the brightness of the bright area caused by excessive concentration of light. For example, the second optical microstructure 130 is configured on the optical axis I of the plurality of light-emitting units 210. It is particularly noted that in the second optical microstructure 130, the second intersection arc R2 is divided into two sections, and the starting point can be defined by the intersection of the virtual extension curves of the two sections of the second intersection arc R2 (equivalent to the shape of the first intersection arc R1) and the second reference plane E2.

[0065] The third optical microstructure 140 includes a third light-facing surface B3, a vertex Q3, a third central symmetric curve C3, and two side light-facing surfaces N. The third optical microstructure 140 takes the third reference plane E3 as a symmetric plane. The third light-facing surface B3, the vertex Q3, the third central symmetric curve C3, and the third reference plane E3 are similar to the first light-facing surface B1, the vertex Q1, the first central symmetric curve C1, and the first reference plane E1 of the first optical microstructure 120, and are not described in detail here. The difference lies in the shapes of the two side light-facing surfaces N and the third light-facing surface B3 (third intersection arc R3) provided in the third optical microstructure 140. The two side light-facing surfaces N are respectively located on both sides of the third reference plane E3 and are symmetrical with respect to the third reference plane E3. The two side light-facing surfaces N are respectively located between the third light-facing surface B3 and the second surface A2. The contour of the orthographic projection of each side light-facing surface N on the second surface A2 is an arc curved away from the light-incident surface A3, that is, each side light-facing surface N is an arc surface perpendicular to the second surface A2. In other words, the third optical microstructure 140 is similar to the first optical microstructure 120 (i.e., the third optical microstructure 140 has the same partial structure as the first optical microstructure), except that the third optical microstructure 140 also includes two side light-facing surfaces N on both sides, and the first light-facing surface B1 (first intersection arc R1) of the first optical microstructure 120 is cut off by the two side light-facing surfaces N to form a third light-facing surface B3 (third intersection arc R3). The two side light-facing surfaces N are used to refract the light beam transmitted to the third microstructure 140 in the side direction to the forward direction (such as Figure 7 As shown, it is closer to the normal direction parallel to the light incident surface A3), increasing the brightness of the dark area formed by the excessive dispersion of the light beam between the two light emitting units 210. For example, the third optical microstructure 140 is disposed on the symmetry axis J of the two adjacent light emitting units 210. In other embodiments, the light guide element may include only the first optical microstructure 120 and the second optical microstructure 130, or only the first optical microstructure 120 and the third optical microstructure 140.

[0066] In summary, in the light-guiding element and the backlight module of the present invention, the light-guiding element includes a main body and a first optical microstructure. Among them, the first optical microstructure includes a first light-facing surface. The first light-facing surface faces the light incident surface of the main body. The first optical microstructure takes the first reference plane as a symmetry plane. The first reference plane is perpendicular to the second surface of the main body and passes through the vertex of the first optical microstructure. The intersection of the first light-facing surface and the first reference plane has a first central symmetry curve, and this first central symmetry curve has at least one inflection point. In this way, through the special design of the above-mentioned first optical microstructure, the backlight module can reduce energy loss and adjust the viewing angle concentration, thereby effectively improving the overall luminous intensity.

[0067] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the appended claims.

Claims

1. A light guide element, characterized in that: The light guide element comprises a body and a first optical microstructure, wherein: The body has a first surface and a second surface opposite to each other, and a light incident surface connected between the first surface and the second surface; and The first optical microstructure includes a first light-facing surface, the first light-facing surface faces the light-incident surface, the first optical microstructure takes a first reference plane as a symmetry plane, the first reference plane is perpendicular to the second surface and passes through the vertex of the first optical microstructure, the intersection of the first light-facing surface and the first reference plane has a first central symmetry curve, the first central symmetry curve has at least one inflection point, the intersection of the first light-facing surface and the second surface forms a first intersection arc, and the curvature radius of the first intersection arc is a constant.

2. The light guide element according to claim 1, characterized in that The light guide element satisfies the following conditional expression: S=T / 75, wherein S is the distance between the vertex of the first optical microstructure and the second surface, and T is the thickness of the body in a first direction, and the first direction is perpendicular to the second surface.

3. The light guide element according to claim 1, characterized in that The first central symmetric curve conforms to a binary quartic equation.

4. The light guide element according to claim 1, characterized in that The first central symmetry curve of the first optical microstructure meets the equation: H = -1.255 x 10 -5 L 4 +5x10 -4 L 3 +3.9x 10 -3 L 2 +4.7x 10 -3 L, wherein L is the distance between a point of the first central symmetry curve and a starting point in the second direction, and H is the distance between the point of the first central symmetry curve and the second surface in the first direction, the starting point is the intersection of the first central symmetry curve and the second surface, the first direction is perpendicular to the second surface, and the second direction is perpendicular to the light incident surface.

5. The light guide element according to claim 1, characterized in that: The light-guiding element also includes a second optical microstructure, which includes a second light-facing surface and an auxiliary light-facing surface. The second light-facing surface faces the light-incident surface. The second optical microstructure uses a second reference plane as a symmetry plane. The second reference plane is perpendicular to the second surface and passes through the vertex of the second optical microstructure. The intersection of the second light-facing surface and the second reference plane has a second central symmetry curve, and the second central symmetry curve has at least one inflection point. The intersection of the second light-facing surface and the second surface forms a second intersection arc, and the curvature radius of the second intersection arc is a constant. The auxiliary light-facing surface is located between the second light-facing surface and the second surface, and the contour of the auxiliary light-facing surface's positive projection on the second surface is an arc that bends away from the light-incident surface.

6. The light guide element according to claim 1, characterized in that The light-guiding element also includes a third optical microstructure, which includes a third light-facing surface and two side light-facing surfaces. The third light-facing surface faces the light-incident surface. The third optical microstructure takes the third reference plane as a symmetry plane. The third reference plane is perpendicular to the second surface and passes through the vertex of the third optical microstructure. The two side light-facing surfaces are respectively located on both sides of the third reference plane. The intersection of the third light-facing surface and the third reference plane has a third central symmetry curve, and the third central symmetry curve has at least one inflection point. The intersection of the third light-facing surface and the second surface forms a third intersection arc, and the curvature radius of the third intersection arc is a constant. The two side light-facing surfaces are respectively located between the third light-facing surface and the second surface, and the contour of the positive projection of each of the two side light-facing surfaces on the second surface is an arc curved away from the light-incident surface.

7. The light guide element according to claim 1, characterized in that A light-facing curve is provided at the junction of the first light-facing surface and the light-incident reference plane. The light-incident reference plane is perpendicular to the second surface and the first reference plane. The curvature of the light-facing curve gradually decreases as it moves away from the light-incident surface.

8. A backlight module, characterized in that: The backlight module includes a light guide element and a light emitting element, wherein: The light guide element comprises a body and a first optical microstructure, wherein: The body has a first surface and a second surface opposite to each other, and a light incident surface connected between the first surface and the second surface; and The first optical microstructure comprises a first light-facing surface, the first light-facing surface faces the light-incident surface, the first optical microstructure takes a first reference plane as a symmetry plane, the first reference plane is perpendicular to the second surface and passes through a vertex of the first optical microstructure, the first light-facing surface and the first reference plane have a first central symmetry curve at their intersection, the first central symmetry curve has at least one inflection point, the first light-facing surface and the second surface form a first intersection arc, and the curvature radius of the first intersection arc is a constant value; and The light emitting element is disposed on the light incident surface of the body, and the light emitting element includes a plurality of light emitting units for providing an illumination beam.

9. The backlight module according to claim 8, characterized in that: The first intersection arc meets the equation: R = 2.2 x 10 -3 πx(W / K)x P x cosθ, wherein R is the radius of curvature of the first intersection arc, W is the length of the first optical microstructure in the third direction, K is the length of the first intersection arc in the second direction, P is the pitch of a plurality of light-emitting units, and θ is a half-light-emitting angle of the plurality of light-emitting units, wherein the second direction is perpendicular to the light incident surface, and the third direction is parallel to the light incident surface and the second surface.

10. The backlight module according to claim 8, characterized in that: The light-guiding element also includes a second optical microstructure, which includes a second light-facing surface and an auxiliary light-facing surface, the second light-facing surface faces the light-incident surface, the second optical microstructure uses a second reference plane as a symmetry plane, the second reference plane is perpendicular to the second surface and passes through the vertex of the second optical microstructure, the intersection of the second light-facing surface and the second reference plane has a second central symmetry curve, the second central symmetry curve has at least one inflection point, the intersection of the second light-facing surface and the second surface forms a second intersection arc, the curvature radius of the second intersection arc is a constant, the auxiliary light-facing surface is located between the second light-facing surface and the second surface, and the contour of the auxiliary light-facing surface's positive projection on the second surface is an arc that bends away from the light-incident surface, and the second optical microstructure is configured on the optical axis of the multiple light-emitting units.

11. The backlight module according to claim 8, characterized in that: The light-guiding element also includes a third optical microstructure, which includes a third light-facing surface and two side light-facing surfaces. The third light-facing surface faces the light-incident surface. The third optical microstructure uses a third reference plane as a symmetry plane. The third reference plane is perpendicular to the second surface and passes through the vertex of the third optical microstructure. The two side light-facing surfaces are respectively located on both sides of the third reference plane. The intersection of the third light-facing surface and the third reference plane has a third central symmetry curve, and the third central symmetry curve has at least one inflection point. The intersection of the third light-facing surface and the second surface forms a third intersection arc, and the curvature radius of the third intersection arc is a constant. Each of the side light-facing surfaces is respectively located between the third light-facing surface and the second surface, and the contour of the positive projection of each of the side light-facing surfaces on the second surface is an arc curved away from the light-incident surface. The third optical microstructure is arranged on the symmetry axis of two adjacent multiple light-emitting units.

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