Direct type backlight module

Abstract

The invention provides a direct type backlight module. The direct type backlight module comprises a circuit board, a plurality of light-emitting elements and a light guide element, the light-emitting elements are arranged on the circuit board. The plurality of light-emitting elements includes a first light-emitting element and a second light-emitting element. The light-emitting elements are arranged between the light guide element and the circuit board. No other optical element is arranged between the light guide element and the light-emitting element. The light guide element is provided with a light guide part, and the light guide part is made of a light penetrating material. The light guide part comprises at least two first light guide parts and a second light guide part. The plurality of first light guide parts are respectively arranged on the first light-emitting element and the second light-emitting element. The second light guide parts are located among the multiple first light guide parts. The first light guide part and the second light guide part can be used for eliminating the light intensity difference provided by the light-emitting element on the first light guide part and the second light guide part, so that the light emitting uniformity of the direct type backlight module is improved.

Description

Technical Field

[0001] The invention relates to a direct-type backlight module. Background Art

[0002] At present, the display screens of the driving dashboard and the center console of the car are all moving towards large size, high brightness, high color saturation and high contrast, which are very different from the specifications of traditional car displays. In addition to meeting the high-specification design requirements of brightness, uniformity and viewing angle, the backlight module used in this type of car display screen also needs to be thin enough. Therefore, the traditional direct-type LED backlight design cannot meet the needs of car use and provide sufficient light uniformity. For example, in the 25-point light uniformity test commonly used in the industry, the traditional direct-type LED backlight module can only reach 75%, which can meet the needs of general displays, but the light uniformity of car displays needs to reach more than 85%. Therefore, how to improve the light uniformity of the backlight module to meet the specifications of car displays is a major challenge faced by developers. Summary of the invention

[0003] The invention provides a direct-type backlight module with high light output uniformity.

[0004] A direct-type backlight module according to an embodiment of the present invention comprises a circuit board, a plurality of light-emitting elements, a light-guiding element and at least one optical film. The plurality of light-emitting elements are arranged on the circuit board and electrically connected to the circuit board. The plurality of light-emitting elements include a first light-emitting element and a second light-emitting element. The plurality of light-emitting elements are arranged between the light-guiding element and the circuit board. There are no other optical elements between the light-guiding element and the light-emitting element. The light-guiding element has a light-guiding portion, which is made of a non-light-diffusing material, and the light-guiding portion includes at least two first light-guiding portions and a second light-guiding portion. At least two first light-guiding portions are respectively located on the first light-emitting element and the second light-emitting element. The second light-guiding portion is located between at least two first light-guiding portions. At least two first light-guiding portions have a first thickness in a first direction. The second light-guiding portion has a second thickness in the first direction. The first direction is substantially perpendicular to the circuit board. The second thickness is less than the first thickness. The light-guiding element is arranged between at least one optical film and the plurality of light-emitting elements.

[0005] The direct-type backlight module of the embodiment of the present invention includes a circuit board, a plurality of light-emitting elements, a light-guiding element and at least one optical film. The plurality of light-emitting elements are arranged on the circuit board and electrically connected to the circuit board. The plurality of light-emitting elements include a first light-emitting element and a second light-emitting element. The plurality of light-emitting elements are arranged between the light-guiding element and the circuit board. There is no other optical element between the light-guiding element and the light-emitting element. The light-guiding element has a light-guiding portion, which is made of a light-transmitting material. The light-guiding portion includes at least two first light-guiding portions and a second light-guiding portion. The plurality of first light-guiding portions are respectively located on the first light-emitting element and the second light-emitting element. The second light-guiding portion is located between the plurality of first light-guiding portions. The light-guiding element is arranged between at least one optical film and the plurality of light-emitting elements. The plurality of first light-guiding portions have a first sub-light-entry surface and a first sub-light-emitting surface. The second light-guiding portion has a second sub-light-entry surface and a second sub-light-emitting surface. The first sub-light-entry surface and the second sub-light-entry surface are substantially coplanar. The first sub-light-emitting surface is higher than the second sub-light-emitting surface in the first direction. The first direction is substantially perpendicular to the first sub-light incident surface and the second sub-light incident surface.

[0006] Based on the above, the direct-type backlight module of the present invention utilizes the first light guide portion and the second light guide portion of different thicknesses (or whose sub-light emitting surfaces have height differences) to eliminate the difference in light intensity provided by the light-emitting element on the first light guide portion and the second light guide portion, thereby improving the light emission uniformity of the direct-type backlight module. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a cross-sectional schematic diagram of a backlight module according to an embodiment of the present invention;

[0008] Figure 2 A schematic diagram of light distribution of a light emitting element of a backlight module according to an embodiment of the present invention;

[0009] Figure 3 is a schematic top view of an optical microstructure and a light-emitting element of a backlight module according to an embodiment of the present invention;

[0010] Figure 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention;

[0011] Figure 5 is a cross-sectional schematic diagram of a backlight module according to yet another embodiment of the present invention;

[0012] Figure 6 A schematic diagram of light distribution of a light emitting element of a backlight module according to another embodiment of the present invention;

[0013] Figure 7 A schematic top view of an optical microstructure and a light-emitting element of a backlight module according to another embodiment of the present invention;

[0014] Figure 8 is a cross-sectional schematic diagram of a backlight module according to yet another embodiment of the present invention;

[0015] Fig. 9 is a cross-sectional schematic diagram of a backlight module according to an embodiment of the present invention;

[0016] Fig.10 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention.

[0017] Description of Reference Numerals

[0018] 10, 10A, 10B, 10C, 10D, 10E: backlight module;

[0019] 110: circuit board;

[0020] 120, 120B: light emitting element;

[0021] 120-1: a first light emitting element;

[0022] 120-2: a second light emitting element;

[0023] 130: reflective sheet;

[0024] 132: Open your mouth;

[0025] 140, 140B, 140D, 140E: light guide element;

[0026] 140a: light incident surface;

[0027] 140a-1: first light incident surface;

[0028] 140a-2: second light-entering surface;

[0029] 140a-3: the third son light-entering surface;

[0030] 140b: light emitting surface;

[0031] 140b-1: the first light-emitting surface;

[0032] 140b-2: the second son's light-emitting surface;

[0033] 140b-3: The third child emerges from the bright side;

[0034] 140c-2, 140c-3: sub-slope;

[0035] 140d-1, 140d-2, 140d-3: sub-convex surface;

[0036] 141, 141E: first light guide portion;

[0037] 142, 142D, 142E: second light guide portion;

[0038] 143, 143D, 143E: third light guide portion;

[0039] 150, 150B: optical microstructure;

[0040] 151: first optical microstructure;

[0041] 152: second optical microstructure;

[0042] 153: third optical microstructure;

[0043] 160: diffuser;

[0044] 170: optical film;

[0045] 180: diffusion; layer;

[0046] A: Spacing

[0047] D151, D152, D153: size;

[0048] g: gap;

[0049] t: thickness;

[0050] t1: first thickness;

[0051] t2: second thickness;

[0052] t3: third thickness;

[0053] x: second direction;

[0054] z: first direction;

[0055] θ2, θ3: angles. DETAILED DESCRIPTION

[0056] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0057] Figure 1 FIG. 1 is a cross-sectional diagram of a backlight module according to an embodiment of the present invention. Figure 1 The backlight module 10 is a direct-type backlight module, and the backlight module 10 includes a circuit board 110 and a plurality of light-emitting elements 120 disposed on the circuit board 110. The plurality of light-emitting elements 120 are electrically connected to the circuit board 110. The circuit board 110 is used to drive the light-emitting elements 120. For example, in the present embodiment, the circuit board 110 may be a printed circuit board (PCB), and the light-emitting element 120 may be a sub-millimeter light-emitting diode (mini-LED), but the present invention is not limited thereto.

[0058] In the present embodiment, the backlight module 10 may further selectively include a reflective sheet 130. The reflective sheet 130 covers the circuit board 110 and has a plurality of openings 132. The plurality of openings 132 respectively expose a plurality of light-emitting elements 120. The reflective sheet 130 is used to reflect the light beams emitted by the light-emitting elements 120 to improve light utilization efficiency. In the present embodiment, the reflectivity of the reflective sheet 130 may be above 95%, but the present invention is not limited thereto. In the present embodiment, the edges of the light-emitting elements 120 and the openings 132 of the reflective sheet 130 may have a gap g. Preferably, the size of the gap g falls within the range of 0.5 mm to 2 mm, but the present invention is not limited thereto.

[0059] The backlight module 10 also includes a light guide element 140 and at least one optical film 170. Different from the conventional direct-type backlight module, the backlight module 10 of the present invention replaces the conventional diffuser with the light guide element 140, and the plurality of light-emitting elements 120 are disposed between the light guide element 140 and the circuit board 110. There are no other optical elements between the light guide element 140 and the light-emitting elements 120. The light guide element 140 is disposed between at least one optical film 170 and the plurality of light-emitting elements 120. For example, in the present embodiment, the number of the optical films 170 may be selectively 2, and the optical films 170 may selectively include a brightness enhancement film and a diffuser. However, the present invention is not limited thereto, and in other embodiments, the number and / or type of the optical films 170 may be designed in other ways according to actual needs.

[0060] The plurality of light-emitting elements 120 at least include a first light-emitting element 120-1 and a second light-emitting element 120-2. The light-guiding portion of the main body of the light-guiding element 140 may be made of polycarbonate (PC), polymethylmethacrylate (PMMA), styrene methylmethacrylate (SMMA or MS) or other optical grade materials with high light transmittance, and the light-guiding portion has at least two first light-guiding portions 141 and a second light-guiding portion 142. The at least two first light-guiding portions 141 are respectively located on the first light-emitting element 120-1 and the second light-guiding portion 142. The second light-guiding portion 142 is located between the at least two first light-guiding portions 141. In the present embodiment, the light-guiding element 140 further includes at least two third light-guiding portions 143, respectively located between the at least two first light-guiding portions 141 and the second light-guiding portion 142. The first direction z is substantially perpendicular to the circuit board 110. The first light guide portion 141 has a first thickness t1 in the first direction z. The second light guide portion 142 has a second thickness t2 in the first direction z. The third light guide portion 143 has a third thickness t3 in the first direction z.

[0061] The light guide element 140 has a light incident surface 140a and a light emitting surface 140b. The light emitting surface 140b is disposed opposite to the light incident surface 140a. The light incident surface 140a is located between the light emitting surface 140b and the plurality of light emitting elements 120. The light incident surface 140a includes a first sub-light incident surface 140a-1, a second sub-light incident surface 140a-2, and a third sub-light incident surface 140a-3, and the first sub-light incident surface 140a-1, the second sub-light incident surface 140a-2, and the third sub-light incident surface 140a-3 belong to the first light guide portion 141, the second light guide portion 142, and the third light guide portion 143, respectively. In the present embodiment, the first sub-light incident surface 140a-1, the second sub-light incident surface 140a-2, and the third sub-light incident surface 140a-3 may be substantially coplanar. The light emitting surface 140b of the light guide element 140 includes a first sub-light emitting surface 140b-1, a second sub-light emitting surface 140b-2, and a third sub-light emitting surface 140b-3, wherein the first sub-light emitting surface 140b-1, the second sub-light emitting surface 140b-2, and the third sub-light emitting surface 140b-3 respectively belong to the first light guide portion 141, the second light guide portion 142, and the third light guide portion 143. In the present embodiment, the first sub-light emitting surface 140b-1 is higher than the second sub-light emitting surface 140b-2 in the first direction z, and the third sub-light emitting surface 140b-3 is higher than the second sub-light emitting surface 140b-2 and lower than the first sub-light emitting surface 140b-1 in the first direction z, wherein the first direction z is substantially perpendicular to the first sub-light incident surface 140a-1 and the second sub-light incident surface 140a-2.

[0062] It is worth noting that the thickness of each light-guiding portion of the light-guiding element 140 is designed accordingly according to the light intensity distribution provided by the light-emitting element 120 on the light-entering surface 140a. At higher light intensity, the thickness of the light-guiding element 140 can be designed to be thicker to reduce the light transmittance. At lower light intensity, the thickness of the light-guiding element 140 can be designed to be thinner to increase the light transmittance, so the heights of the sub-light-emitting surfaces are not the same. As a result, the overall light-emitting uniformity of the backlight module 10 is improved. Figure 1 and Figure 2 Give an example.

[0063] Figure 2 FIG. 1 is a schematic diagram of the light distribution of the light emitting element of the backlight module according to an embodiment of the present invention. Figure 1 and Figure 2In this embodiment, the light type of the light emitting element 120 can be Gaussian distribution or Lambertian distribution. When the light type distribution of the light emitting element 120 is Gaussian distribution or Lambertian distribution, the light emission direction is more concentrated, so on the light incident surface 140a of the light guide element 140, the farther away from the top of two adjacent light emitting elements 120, the weaker the received light intensity will be. In detail, in the present embodiment, the first sub-light incident surface 140a-1 is located directly above two adjacent light-emitting elements 120, the second sub-light incident surface 140a-2 is located outside the first sub-light incident surface 140a-1, and the third sub-light incident surface 140a-3 is located between the first sub-light incident surface 140a-1 and the second sub-light incident surface 140a-2. The second sub-light incident surface 140a-2 is farther away from directly above the two adjacent light-emitting elements 120 than the third sub-light incident surface 140a-3. The light intensity on the second sub-light incident surface 140a-2 is less than the light intensity on the first sub-light incident surface 140a-1, and the light intensity on the third sub-light incident surface 140a-3 is between the light intensity on the first sub-light incident surface 140a-1 and the light intensity on the second sub-light incident surface 140a-2. At this time, the thickness t2 of the second light guide portion 142 can be designed to be smaller than the thickness t1 of the first light guide portion 141, and the third thickness t3 of the third light guide portion 143 can be designed to be larger than the second thickness t2 and smaller than the first thickness t1. This is because the light transmitted to the first sub-light incident surface 140a-1, the second sub-light incident surface 140a-2 and the third sub-light incident surface 140a-3 will have high light intensity, low light intensity and medium light intensity, respectively. According to this design, light with high light intensity will have a greater degree of energy loss after passing through the first light guide portion 141 with a thick thickness, light with low light intensity will have a smaller degree of energy loss after passing through the second light guide portion 142 with a thin thickness, and a light beam with medium light intensity will have a medium degree of energy loss after passing through the third light guide portion 143 with a medium thickness. Therefore, the difference in the intensity of light emitted from the first sub-light emitting surface 140b-1, the second sub-light emitting surface 140b-2 and the third sub-light emitting surface 140b-3 through the light guide element 140 can be reduced, thereby improving the light emission uniformity of the backlight module 10.

[0064] For example, in this embodiment, the thickness ratios of the light guide portions are: 40%≦(t2 / t1)≦60%, 70%≦(t3 / t1)≦90%. However, the present invention is not limited thereto, and in other embodiments, the ratio (t2 / t1) of the second thickness t2 of the second light guide portion 142 to the first thickness t1 of the first light guide portion 141 and the ratio (t3 / t1) of the third thickness t3 of the third light guide portion 143 to the first thickness t1 of the first light guide portion 141 can be appropriately designed according to the change of the light distribution of the light emitting element 120.

[0065] Figure 3FIG. 1 is a top view of an optical microstructure and a light emitting element of a backlight module according to an embodiment of the present invention. Figure 1 The multiple optical microstructures 150 shown are used to schematically represent the arrangement density of the optical microstructures 150 at various locations. Figure 1 The sizes of the optical microstructures 150 shown in the figure are not intended to represent the relative sizes of the optical microstructures 150 at various locations. For the relative sizes of the optical microstructures 150 at various locations, please refer to Figure 3 .

[0066] Please refer to Figure 1 and Figure 3 In this embodiment, the light incident surface 140a of the light guide element 140 may have a plurality of optical microstructures 150. The optical microstructures 150 are used to block and reflect the light beams emitted by the light emitting element 120. In this embodiment, the plurality of optical microstructures 150 are, for example, a plurality of micro depressions, and the depression depth of the micro depressions is, for example, at the level of several μm. The micro depressions may be formed on the light incident surface 140a by, for example, a hot rolling process, but the present invention is not limited thereto.

[0067] It is worth mentioning that by adjusting the size of the optical microstructures 150 and / or the density of the arrangement of the optical microstructures 150 at various locations on the light incident surface 140 a , hot spots of light intensity can be effectively eliminated, further improving the light uniformity of the backlight module 10 .

[0068] For example, in the present embodiment, the plurality of optical microstructures 150 may include a plurality of first optical microstructures 151, a plurality of second optical microstructures 152, and a plurality of third optical microstructures 153; the first sub-light incident surfaces 140a-1, the second sub-light incident surfaces 140a-2, and the third sub-light incident surfaces 140a-3 of the first light guide portion 141, the second light guide portion 142, and the third light guide portion 143 may respectively have the first optical microstructure 151, the second optical microstructure 152, and the third optical microstructure 153; the second direction x is substantially parallel to the circuit board 110; the dimension D151 (indicated at Figure 3 ) is larger than the dimension D152 (indicated at Figure 3 ), the dimension D153 of the third optical microstructure 153 in the second direction x (indicated at Figure 3) is larger than the size D152 of the second optical microstructure 152 in the second direction x and smaller than the size D151 of the first optical microstructure 151 in the second direction x. In other words, as the optical microstructure 150 moves away from directly above the light-emitting element 120, the size of the optical microstructure 150 also decreases. Specifically, in this embodiment, the size D152 of the second optical microstructure 152 and the size D153 of the third optical microstructure 153 can be reduced by 1% to 10% of the size D151 of the first optical microstructure 151 compared to the size D151 of the first optical microstructure 151. However, the present invention is not limited to this. In other embodiments, the relative size relationship of the size D151 of the first optical microstructure 151, the size D152 of the second optical microstructure 152 and the size D153 of the third optical microstructure 153 can be appropriately designed according to the change of the light distribution of the visible light-emitting element 120, and the height of the first optical microstructure 151, the second optical microstructure 152 and the third optical microstructure 153 can be changed like the size, or the optical microstructure 150 can only change in height but keep the size the same, all of which can achieve the effect of improving the uniformity of light.

[0069] For example, in the present embodiment, the arrangement density of the plurality of first optical microstructures 151 is greater than the arrangement density of the plurality of second optical microstructures 152, and the arrangement density of the plurality of third optical microstructures 153 is greater than the arrangement density of the plurality of second optical microstructures 152 and less than the arrangement density of the plurality of first optical microstructures 151. That is, in the present embodiment, the farther the optical microstructure 150 is from directly above the light emitting element 120, the wider the interval A between adjacent optical microstructures 150, or the smaller the size of the optical microstructure 150. However, the present invention is not limited thereto, and in other embodiments, the size relationship of the arrangement density of the first optical microstructure 151, the arrangement density of the second optical microstructure 152, and the arrangement density of the third optical microstructure 153 can be matched with different height variation differences of the optical microstructure 150, and other appropriate designs can be made depending on the change in the light type distribution of the light emitting element 120.

[0070] Please refer to Figure 1 In this embodiment, the backlight module 10 may further selectively include a diffuser 160 disposed between at least one optical film 170 and the light guide element 140. The diffuser 160 can scatter the light beam from the light emitting surface 140b of the light guide element 140, thereby further improving the light emitting uniformity of the backlight module 10.

[0071] It must be noted that the following embodiments use the component numbers and some contents of the previous embodiments, wherein the same number is used to represent the same or similar components, and the description of the same technical contents is omitted. The description of the omitted parts can refer to the previous embodiments, and the following embodiments will not be repeated.

[0072] Figure 4 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention. Figure 4 The backlight module 10A and Figure 1 The backlight module 10 is similar to the backlight module 10, and the difference between the two is: Figure 4 The backlight module 10A includes the diffusion layer 180 but does not include Figure 1 The diffusion sheet 160 of the backlight module 10 is provided.

[0073] Please refer to Figure 4 In the present embodiment, a diffusion layer 180 is provided on the upper portion of the light guide element 140, which is formed on the first sub-light emitting surface 140b-1, the second sub-light emitting surface 140b-2 and the third sub-light emitting surface 140b-3 having height differences. The diffusion layer 180 includes a plurality of diffusion particles (not shown) that can reflect or refract the light beam, so as to increase the number of refractions of the light beam inside the light guide element 140, thereby extending the transmission range of the light beam inside the light guide element 140, thereby achieving good light mixing uniformity. For example, in the present embodiment, the material of the diffusion particles may be polymethylmethacrylate (PMMA), polystyrene (PS) or titanium oxide (TiO2), but the present invention is not limited thereto.

[0074] The diffusion layer 180 may be formed by coating diffusion particle ink and has a thickness t required for forming the backlight module 10A in the first direction z. For example, in this embodiment, the thickness t may fall within the range of 1 μm to 100 μm, but the present invention is not limited thereto. Figure 4 The backlight module 10A adopts a diffusion layer 180 disposed on the light emitting surface 140b, replacing Figure 1 The diffuser 160 of the backlight module 10 is thus Figure 1 The backlight module 10, Figure 4 The backlight module 10A also has the advantage of being thin.

[0075] Figure 5 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention. Figure 5 The backlight module 10B and Figure 1 The backlight module 10 is similar to the backlight module 10, and the difference between the two is: Figure 5 The light distribution of the light emitting element 120B of the backlight module 10B is Figure 1 The light pattern distribution of the light emitting element 120 of the backlight module 10 is different.

[0076] Figure 6 FIG. 1 is a schematic diagram of the light distribution of the light emitting element of the backlight module according to another embodiment of the present invention. Figure 5 and Figure 6The light type of the light emitting element 120B of the backlight module 10B is a non-Gaussian light type distribution and a non-Lambertian distribution. Due to the different light type distribution of the light emitting element 120B, the thickness distribution position of the light guide element 140B of the backlight module 10B is different from that of the light guide element 140 of the aforementioned embodiment. In addition, the relative size and relative arrangement density of the optical microstructure 150B of the backlight module 10B at each location of the light incident surface 140a are also different from those of the aforementioned embodiment.

[0077] Please refer to Figure 5 and Figure 6 Specifically, in this embodiment, the light distribution of the light emitting element 120B of the backlight module 10B may be a batwing distribution. That is, in this embodiment, the light intensity on the third sub-light incident surface 140a-3 is greater than the light intensity on the first sub-light incident surface 140a-1, and the light intensity on the first sub-light incident surface 140a-1 is greater than the light intensity on the second sub-light incident surface 140a-2. In response to the light intensity distribution provided by the above-mentioned light-emitting element 120B on the first sub-light incident surface 140a-1, the second sub-light incident surface 140a-2 and the third sub-light incident surface 140a-3, in the present embodiment, the third thickness t3 of the third light guide portion 143 having the third sub-light incident surface 140a-3 is greater than the first thickness t1 of the first light guide portion 141 having the first sub-light incident surface 140a-1, and the first thickness t1 of the first light guide portion 141 having the first sub-light incident surface 140a-1 is greater than the second thickness t2 of the second light guide portion 142 having the second sub-light incident surface 140a-2, so that the thickness of the light guide element 140B corresponding to the position with higher incident light intensity is thicker and the thickness of the position with lower incident light intensity is thinner, so as to make the light output uniform. For example, in the present embodiment, 70%≦(t1 / t3)≦90%, 40%≦(t2 / t3)≦60%, but the present invention is not limited thereto.

[0078] Figure 7 FIG. 1 is a top view of an optical microstructure and a light emitting element of a backlight module according to another embodiment of the present invention. Figure 5 The multiple optical microstructures 150B shown are used to schematically represent the arrangement density of the optical microstructures 150B at various locations. Figure 5 The sizes of the optical microstructures 150B shown in the figure do not represent the relative sizes of the optical microstructures 150B at various locations. For the relative sizes of the optical microstructures 150B at various locations, please refer to Figure 7 .

[0079] Please refer to Figure 5 , Figure 6 and Figure 7In response to the light type distribution of the light-emitting element 120B, in the present embodiment, the size D153 of the third optical microstructure 153 disposed on the third sub-light incident surface 140a-3 in the second direction x is larger than the size D151 of the first optical microstructure 151 disposed on the first sub-light incident surface 140a-1 in the second direction x, and the size D151 of the first optical microstructure 151 disposed on the first sub-light incident surface 140a-1 in the second direction x is larger than the size D152 of the second optical microstructure 152 disposed on the second sub-light incident surface 140a-2 in the second direction x. In this embodiment, the arrangement density of the third optical microstructure 153 arranged on the third sub-light incident surface 140a-3 is greater than the arrangement density of the first optical microstructure 151 arranged on the first sub-light incident surface 140a-1, and the arrangement density of the first optical microstructure 151 arranged on the first sub-light incident surface 140a-1 is greater than the arrangement density of the second optical microstructure 152 arranged on the second sub-light incident surface 140a-2.

[0080] Figure 8 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention. Figure 8 The backlight module 10C and Figure 5 The backlight module 10B is similar to the backlight module 10B, and the difference between the two is: Figure 8 The backlight module 10C includes the diffusion layer 180 but does not include Figure 5 The diffusion sheet 160 of the backlight module 10B.

[0081] Please refer to Figure 8 In this embodiment, the backlight module 10C includes a diffusion layer 180 formed on the first sub-light emitting surface 140b-1, the second sub-light emitting surface 140b-2 and the third sub-light emitting surface 140b-3 having height differences. The diffusion layer 180 can be used to replace Figure 5 The diffusion sheet 160 of the backlight module 10B is formed Figure 8 The backlight module 10C. Figure 8 The backlight module 10C adopts the diffusion layer 180 disposed on the light emitting surface 140b. Therefore, compared with Figure 5 The backlight module 10B, Figure 8 The backlight module 10C also has the advantage of being thin.

[0082] Fig. 9 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to an embodiment of the present invention. Fig. 9 The backlight module 10D and Figure 1 The backlight module 10 is similar to the backlight module 10, and the difference between the two is: Fig. 9 The light guide element 140D of the backlight module 10D is Figure 1 The light guide element 140 of the backlight module 10 is different.

[0083] Please refer to Fig. 9 In this embodiment, the light guide element 140D may be designed as a special-shaped polygonal light guide plate. Specifically, in this embodiment, at least one of the first sub-light emitting surface 140b-1 of the first light guide portion 141, the second sub-light emitting surface 140b-2 of the second light guide portion 142D, and the third sub-light emitting surface 140b-3 of the third light guide portion 143D may include at least one sub-inclined surface 140c-2, 140c-3, wherein at least one sub-inclined surface 140c-2, 140c-3 is inclined relative to the circuit board 110 and has at least one angle θ2, θ3 with the circuit board 110. The light energy distribution on the light emitting surface 140b can be controlled by at least one sub-inclined surface 140c-2, 140c-3 having at least one angle θ2, θ3 with the circuit board 110. In other words, different light energy distribution effects can be achieved by changing the size of at least one angle θ2, θ3.

[0084] For example, in the present embodiment, the second sub-light emitting surface 140b-2 of the second light guide portion 142D may include a sub-inclined surface 140c-2, and the sub-inclined surface 140c-2 and the circuit board 110 are sandwiched at an angle θ2, and the third sub-light emitting surface 140b-3 of the third light guide portion 143D may include a sub-inclined surface 140c-3, and the sub-inclined surface 140c-3 and the circuit board 110 are sandwiched at an angle θ3, and θ3>θ2, but the present invention is not limited thereto. However, the present invention is not limited thereto, and in other embodiments, the relative sizes of the inclination degrees of the plurality of sub-inclined surfaces 140c-2 and 140c-3 may be designed differently depending on the light energy distribution effect to be achieved.

[0085] Fig.10 FIG. 4 is a cross-sectional schematic diagram of a backlight module according to another embodiment of the present invention. Fig.10 The backlight module 10E and Figure 1 The backlight module 10 is similar to the backlight module 10, and the difference between the two is: Fig.10 The light guide element 140E of the backlight module 10E and Figure 1 The light guide element 140 of the backlight module 10 is different.

[0086] Please refer to Fig.10 In this embodiment, the light guide element 140E may be designed as a light guide plate with a special-shaped sphere as the structure. In detail, in this embodiment, at least one of the first sub-light emitting surface 140b-1 of the first light guide portion 141E, the second sub-light emitting surface 140b-2 of the second light guide portion 142E, and the third sub-light emitting surface 140b-3 of the third light guide portion 143E may include at least one sub-convex surface 140d-1, 140d-2, 140d-3. By changing the curvature radius of the at least one sub-convex surface 140d-1, 140d-2, 140d-3, the light energy distribution on the light emitting surface 140b can be controlled, thereby achieving different light energy distribution effects.

[0087] For example, in the present embodiment, the first sub-light emitting surface 140b-1 of the first light guide portion 141E, the second sub-light emitting surface 140b-2 of the second light guide portion 142E, and the third sub-light emitting surface 140b-3 of the third light guide portion 143E may include a sub-convex surface 140d-1, a sub-convex surface 140d-2, and a sub-convex surface 140d-3, respectively, wherein the radius of curvature of the sub-convex surface 140d-2 may be greater than the radius of curvature of the sub-convex surface 140d-1, and the radius of curvature of the sub-convex surface 140d-3 may be between the radius of curvature of the sub-convex surface 140d-2 and the radius of curvature of the sub-convex surface 140d-1. However, the present invention is not limited thereto, and in other embodiments, the relative sizes of the radii of curvature of the multiple sub-convex surfaces 140d-1, 140d-2, and 140d-3 may be designed differently depending on the light energy distribution effect to be achieved. In addition, in some embodiments, Fig. 9 The light guide element 140D and Fig.10 The light guide element 140E may include a diffusion layer 180 , and the backlight module 10D and the backlight module 10E do not include a diffusion sheet 160 , so as to achieve a thin design.

[0088] It must be pointed out that in Figure 1 , Figure 4 , Figure 5 , Figure 8 , Fig. 9 and Fig.10 In the figure, the first optical microstructure 151, the second optical microstructure 152 and the third optical microstructure 153 shown are only schematic diagrams representing the difference in arrangement density, and are not the specific number, size and position of the first optical microstructure 151, the second optical microstructure 152 and the third optical microstructure 153 on the first sub-light incident surface 140a-1, the second sub-light incident surface 140a-2 and the third sub-light incident surface 140a-3. As mentioned above, the size, density and structure height of the first optical microstructure 151, the second optical microstructure 152 and the third optical microstructure 153 can be changed to achieve the effect of improving the uniformity of light.

[0089] In summary, a backlight module of an embodiment of the present invention includes a plurality of light-emitting elements, a light guide element and at least one optical film. The light guide element is disposed between at least one optical film and the plurality of light-emitting elements. The light guide element includes a first light guide portion located above the plurality of light-emitting elements and a second light guide portion located away from the plurality of light-emitting elements. In particular, the thickness of the first light guide portion and the thickness of the second light guide portion are designed to have different thicknesses according to the light type distribution of the light-emitting elements, and an optical microstructure is arranged on the light incident surface corresponding to the light type distribution. Thus, the light uniformity of the backlight module can be increased to more than 85% in a 25-point light uniformity test. In addition, compared with a conventional direct-type backlight module, the conventional direct-type backlight module uses a diffuser plate and a backlight film design that requires a height of about 1 cm, while the backlight module of the present invention uses a microstructure light guide plate instead of a diffuser plate. Under the condition of using the same number of light-emitting elements 120, the optical cavity height of the backlight module of the present invention only needs to be 2.5 cm, and the thickness of the optical film only needs to be 2.5 cm, which can better meet the requirements of a thin display device.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These multiple modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A direct-type backlight module, characterized in that: include: Circuit boards; A plurality of light-emitting elements are disposed on the circuit board and electrically connected to the circuit board, wherein the plurality of light-emitting elements include a first light-emitting element and a second light-emitting element; A light guide element, wherein the plurality of light emitting elements are disposed between the light guide element and the circuit board, and no other optical element is disposed between the light guide element and the plurality of light emitting elements, and the light guide element has a light guide portion, the light guide portion is composed of a non-light diffusing material, and the light guide portion includes: at least two first light guide portions, wherein the at least two first light guide portions are respectively located on the first light emitting element and the second light emitting element; and a second light guide portion, wherein the second light guide portion is located between the at least two first light guide portions, the at least two first light guide portions have a first thickness in a first direction, the second light guide portion has a second thickness in the first direction, the first direction is substantially perpendicular to the circuit board, and the second thickness is less than the first thickness; and At least one optical film, wherein the light guide element is disposed between the at least one optical film and the plurality of light emitting elements.

2. The direct-lit backlight module according to claim 1, wherein: The light guide element further comprises: At least two third light guide portions are respectively located between the at least two first light guide portions and the second light guide portion, wherein the third light guide portions have a third thickness in the first direction, and the third thickness is greater than the second thickness.

3. The direct-lit backlight module according to claim 1, wherein: The at least two first light guide portions have a first sub-light incident surface, and the first sub-light incident surface has a first optical microstructure; The second light guide portion has a second sub-light incident surface, and the second sub-light incident surface has a second optical microstructure; The size of the first optical microstructure in the second direction is greater than the size of the second optical microstructure in the second direction, and the second direction is substantially parallel to the circuit board.

4. The direct-lit backlight module according to claim 3, wherein: The light guide element further comprises: At least two third light guide portions are respectively located between the at least two first light guide portions and the second light guide portions, wherein the at least two third light guide portions have a third sub-light incident surface, the third sub-light incident surface has a third optical microstructure, and the size of the third optical microstructure in the second direction is greater than the size of the second optical microstructure in the second direction.

5. The direct-lit backlight module according to claim 1, wherein: The at least two first light guide portions have a first sub-light incident surface, and the first sub-light incident surface has a plurality of first optical microstructures; The second light guide portion has a second sub-light incident surface, and the second sub-light incident surface has a plurality of second optical microstructures; The arrangement density of the plurality of first optical microstructures is greater than that of the plurality of second optical microstructures.

6. The direct-lit backlight module according to claim 5, characterized in that: The light guide element further comprises: At least two third light guide portions are respectively located between the at least two first light guide portions and the second light guide portions, wherein the at least two third light guide portions have a third sub-light incident surface, and the third sub-light incident surface has a plurality of third optical microstructures, and the arrangement density of the plurality of third optical microstructures is greater than the arrangement density of the plurality of second optical microstructures.

7. The direct-lit backlight module according to claim 1, wherein: Also includes: The diffusion sheet is disposed between the at least one optical film and the light guide element.

8. The direct-lit backlight module according to claim 1, wherein: The at least two first light guide parts respectively have a first sub-light emitting surface, the second light guide part has a second sub-light emitting surface, and the light guide part further includes: The diffusion layer is formed on the first sub-light emitting surface and the second sub-light emitting surface.

9. The direct-lit backlight module according to claim 8, characterized in that: The light guide element further comprises: At least two third light guide parts are respectively located between the at least two first light guide parts and the second light guide part, wherein the at least two third light guide parts respectively have a third sub-light emitting surface, and the diffusion layer is further formed on the third sub-light emitting surface.

10. A direct-type backlight module, characterized in that: include: a circuit board; A plurality of light-emitting elements are disposed on the circuit board and electrically connected to the circuit board, wherein the plurality of light-emitting elements include a first light-emitting element and a second light-emitting element; A light guide element, wherein the plurality of light emitting elements are disposed between the light guide element and the circuit board, and no other optical element is disposed between the light guide element and the plurality of light emitting elements, and the light guide element has a light guide portion, the light guide portion is composed of a light-transmitting material, and the light guide portion includes: at least two first light guide portions, wherein the plurality of first light guide portions are respectively located on the first light emitting element and the second light emitting element; as well as a second light guiding portion, wherein the second light guiding portion is located between the plurality of first light guiding portions; and at least one optical film, wherein the light guide element is disposed between the at least one optical film and the plurality of light emitting elements; The multiple first light guiding portions have a first sub-light incident surface and a first sub-light emitting surface, the second light guiding portion has a second sub-light incident surface and a second sub-light emitting surface, the first sub-light incident surface and the second sub-light incident surface are substantially coplanar, the first sub-light emitting surface is higher than the second sub-light emitting surface in a first direction, and the first direction is substantially perpendicular to the first sub-light incident surface and the second sub-light incident surface.

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