Inverse prismatic lens and backlight module with same

Abstract

The utility model relates to the technical field of display, in particular to an inverse prismatic lens and a backlight module with the same. The inverse prism sheet includes: a first main surface and a second main surface facing each other; the triangular prisms are convexly arranged on the first main surface, are arranged along a first direction, extend along a second direction perpendicular to the first direction, and are provided with first side surfaces and second side surfaces which are closer to the front side of the first direction than the first side surfaces; the first side surface and the first main surface define a first inner angle of the triangular prism, and the second side surface and the first main surface define a second inner angle of the triangular prism; the plurality of triangular prisms have the same first interior angles, and the second interior angles of any two triangular prisms are different from each other.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a reverse prism sheet and a backlight module having the same. BACKGROUND

[0002] The reverse prism sheet can turn off the light from the light guide plate, and has been widely used in the backlight module, thereby bringing the desired display effect to the display configured with the backlight module.

[0003] In the related art, the shape of each triangular prism microstructure on the reverse prism sheet for turning off the light is fixed, and the light emitted from the backlight module is perpendicular to the light emitting surface, that is, the emitted light is perpendicular to the display. However, in actual application, the position of the human eye is relatively fixed when observing the display, so when observing the four edges and corners of the display, the brightness of the display will be much lower than the center brightness, especially when the field of view of the display is small, and it is also not conducive to the privacy effect of the peripheral area of the display. SUMMARY

[0004] Therefore, the present application provides a reverse prism sheet and a backlight module having the same.

[0005] In a first aspect, a reverse prism sheet is provided, comprising:

[0006] a first main surface and a second main surface opposite to each other;

[0007] a plurality of triangular prisms protruding on the first main surface and arranged along a first direction, the triangular prisms extending along a second direction perpendicular to the first direction, and having a first side surface and a second side surface in front of the first side surface along the first direction, the first side surface and the first main surface defining a first internal angle of the triangular prism, and the second side surface and the first main surface defining a second internal angle of the triangular prism;

[0008] The plurality of triangular prisms have the same first internal angle, and the second internal angle of any two triangular prisms is different from each other.

[0009] In some possible embodiments, the reverse prism sheet is applied to the backlight module in a manner that the first main surface faces the light emitting surface of the light guide plate, and the peak light emitting angle of the light emitting surface in the first direction is θ;

[0010] For each of the plurality of triangular prisms, it is configured to satisfy:

[0011]

[0012] wherein ε is a first internal angle of the triangular prism, γ is a second internal angle of the triangular prism, n is a refractive index of the inverse prism sheet, λ is an angle between a first straight line and a second straight line, the first straight line is a straight line passing through a first point and being perpendicular to the second major surface, the second straight line is a line connecting the first point and a second point, the first point is a point on the second major surface and opposite to the triangular prism, the second point is a point spaced apart from the second major surface on the second major surface side of the inverse prism sheet, the plurality of triangular prisms correspond to the same second point, and λ takes a positive value when the second point is located on a front side of the first straight line in the first direction, and λ takes a negative value when the second point is located on a rear side of the first straight line in the first direction.

[0013] In some possible implementations, the first straight line and the second straight line are both perpendicular to the second direction.

[0014] In some possible implementations, the plurality of triangular prisms are sequentially adjacent in the first direction.

[0015] In some possible implementations, the plurality of triangular prisms are identical in period in the first direction, and the plurality of triangular prisms have different heights.

[0016] In a second aspect, a backlight module is provided, comprising:

[0017] A light guide plate having a light exit surface;

[0018] The inverse prism sheet according to the first aspect is configured in a manner that the first major surface faces the light exit surface.

[0019] In some possible implementations, the light exit surface is a major surface of the light guide plate.

[0020] In some possible implementations, the light guide plate has a light entrance surface, the light entrance surface is a side surface of the light guide plate, and the backlight module further comprises:

[0021] A light source configured on the light entrance surface side of the light guide plate.

[0022] In some possible implementations, the light entrance surface is parallel to the second direction, and in the first direction, the second side surface is farther away from the light entrance surface than the first side surface.

[0023] In some possible implementations, the light exit surface has a light exit peak angle of 70°-80° in the first direction.

[0024] According to the inverse prism sheet provided in the application, when combined with the light guide plate into the backlight module, the backlight module can be customized to provide target outgoing light, and the light peak angle of each part of the display screen is always towards the observer, thus having excellent anti-peeping effect. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the application, but not limit the application.

[0026] Figure 1 FIG. 1 is a side view schematic diagram of the backlight module provided in the application.

[0027] Figure 2 FIG. 2 is an enlarged view of a part of FIG. 1, and schematically shows two complete light paths through the inverse prism sheet. Figure 1

[0028] FIG. 3 shows the relationship between the ideal light peak angle of any position point on the display along the first direction and the observation position. Figure 3 Legend of the drawings:

[0029] F1-first direction, F2-second direction;

[0030] 10-light source;

[0031] 20-light guide plate, 21-incoming light surface, 22-bottom surface, 23-outgoing light surface;

[0032] 30-inverse prism sheet, 31-first main surface, 32-second main surface;

[0033] 1-triangular prism, 1a-first side surface, 1b-second side surface, ε-first internal angle, γ-second internal angle, φ-third internal angle;

[0034] D1-first point, D2-second point;

[0035] L1-first straight line, L2-second straight line;

[0036] λ-angle between the first straight line and the second straight line.

[0037] DETAILED DESCRIPTION

[0038] ​In order to make the objects, technical solutions and advantages of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort fall within the protection scope of the present application. It can be understood that some technical means of the various embodiments described herein can be replaced or combined with each other without conflict.

[0039] In the description of the present application, if there are terms "first", "second", etc., they are only used to distinguish the described objects, and do not have any order or technical meaning. Therefore, the objects defined with "first", "second", etc. can explicitly or implicitly include one or more of the objects, and for example, the term "first element" itself does not mean the existence of "second element", and the term "second element" itself does not mean the existence of "first element". In addition, "one" or "an" and the like do not represent a quantity limitation, but represent the existence of at least one, and "multiple" represents no less than two.

[0040] In the description of the present application, the terms "include", "have" indicate the existence of the described features, numbers, operations, elements and / or their combinations, but do not exclude the existence or addition of one or more other features, numbers, operations, elements and / or their combinations.

[0041] In the description of the present application, the reference to "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in other some embodiments" and the like appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized.

[0042] Figure 1 The backlight module provided by the embodiments of the present application is schematically shown, which includes a light guide plate 20, a light source 10 and an inverse prism sheet 30. Moreover, Figure 2 A part of the inverse prism sheet 30 and the complete light path of the part at the inverse prism sheet 30 are shown. Figure 1

[0043] ​The light guide plate 20 has a light-incident surface 21, a light-emitting surface 23, and a bottom surface 22. The light-emitting surface 23 and the bottom surface 22 are opposite to each other in the thickness direction of the light guide plate 20. The bottom surface 22 is provided with a plurality of light-guiding microstructures, which can be concave microstructures recessed in the bottom surface 22 or convex microstructures protruding from the bottom surface 22. The light-guiding microstructures are used to guide the light rays so as to obtain desired light rays on the light-emitting surface 23 of the light guide plate 20. The light-incident surface 21 is a side surface of the light guide plate 20, which connects the light-emitting surface 23 and the bottom surface 22 on one side of the light-emitting surface 23 and the bottom surface 22. Since the light guide plate 20 and the light-guiding microstructures on the light guide plate 20 are well known to those skilled in the art, they will not be described in detail, and the illustration of the light-guiding microstructures is omitted.

[0044] The light source 10 can be an LED, which is arranged on the light-incident surface 21 side of the light guide plate 20 and can generate light rays directed to the light-incident surface 21 of the light guide plate 20 under the drive of electricity. Therefore, the light source 10 becomes a side-in type light source.

[0045] As a well-known technology, based on the corresponding design of the shape of the light-guiding microstructures on the bottom surface 22 of the light guide plate 20, the light-emitting surface 23 of the light guide plate 20 can emit light rays at a desired emission angle (i.e., the light-emitting peak angle of the light guide plate 20, which is the angle formed by the normal of the light-emitting surface 23 and the direction of the maximum light intensity in the light intensity distribution).

[0046] The inverse prism sheet 30 is located on the light-emitting surface 23 side of the light guide plate 20 and includes a first major surface 31 and a second major surface 32 opposite to each other in the thickness direction thereof, and a plurality of triangular prisms 1 arranged on the first major surface 31 in a first direction F1, wherein the first major surface 31 faces the light-emitting surface 23 of the light guide plate 20. The triangular prisms 1 extend in a second direction F2 perpendicular to the first direction F1 and include a first side surface la and a second side surface lb in front of the first side surface la in the first direction F1 (the right side in the figure), wherein the first side surface la and the first major surface 31 define a first internal angle ε of the triangular prism 1, the second side surface lb and the first major surface 31 define a second internal angle γ of the triangular prism 1, and the first side surface la and the second side surface lb define a third internal angle φ of the triangular prism 1. Figure 1

[0047] The first direction F1 and the second direction F2 are directions parallel to the inverse prism sheet 30 and the light guide plate 20, more specifically, the first direction F1 is a direction perpendicular to the light-incident surface 21 and parallel to the light-emitting surface 23, and the second direction F2 is a direction parallel to the light-incident surface 21 and the light-emitting surface 23. Therefore, in the first direction F1, the first side surface la of the triangular prism 1 is closer to the light-incident surface 21 of the light guide plate 20 and the light source 10 than the second side surface lb. In addition, as shown in the figure, the second side surface lb of the triangular prism 1 is closer to the light-emitting surface 23 of the light guide plate 20 than the first side surface la. Figure 3 ​In the illustrated embodiment, at the inverse prism sheet 30, the front side of the first direction F1 is a direction away from the light-incident surface 21, and the rear side of the first direction F1 is a direction close to the light-incident surface 21. In other embodiments, the first direction F1 is reversed, such that at the inverse prism sheet 30, the front side of the first direction F1 becomes a direction close to the light-incident surface 21, and the rear side of the first direction F1 becomes a direction away from the light-incident surface 21.

[0048] In Figure 1 In the illustrated embodiment, at the inverse prism sheet 30, the front side of the first direction F1 is a direction away from the light-incident surface 21, and the rear side of the first direction F1 is a direction close to the light-incident surface 21. In other embodiments, the first direction F1 is reversed, such that at the inverse prism sheet 30, the front side of the first direction F1 becomes a direction close to the light-incident surface 21, and the rear side of the first direction F1 becomes a direction away from the light-incident surface 21.

[0049] In the present embodiment, the plurality of triangular prisms 1 on the inverse prism sheet 30 are designed to have the same first internal angle ε, and the second internal angle γ of any two triangular prisms 1 is different, and based on such design, the light-emitting peak angle of the plurality of positions on the second major surface 32 in the first direction F1 all point to the same observation position, and further, when the backlight module provided with the inverse prism sheet is applied to a display, a clear display image can be observed at a specific position. Moreover, when the first internal angle ε of each triangular prism 1 on the inverse prism sheet 30 is designed to be the same angle value, the inverse prism sheet 30 and / or the manufacturing mold of the inverse prism sheet 30 can be easily processed.

[0050] Specifically, for each of the plurality of triangular prisms 1, the following formula (1) is satisfied:

[0051] ;

[0052] Referring to Figure 1 wherein θ is the light-emitting peak angle of the light-emitting surface 23 of the light guide plate 20 in the first direction F1 (which can be referred to simply as the light-emitting angle of the light guide plate 20 in the first direction F1, or further referred to simply as the light-emitting angle of the light guide plate 20); ε is the first internal angle of the triangular prism 1, and the ε corresponding to each of the triangular prisms 1 are the same as each other; γ is the second internal angle of the triangular prism 1; n is the refractive index of the inverse prism sheet 30; λ is the included angle between the first straight line and the second straight line, the first straight line L1 is a straight line passing through the first point D1 and perpendicular to the second major surface 32, and the second straight line L2 is a line connecting the first point D1 and the second point D2, the first point D1 is a point on the second major surface 32 and opposite to the triangular prism 1, the second point D2 is a point on the side of the second major surface 32 of the inverse prism sheet 30 and separated from the second major surface 32, and the plurality of triangular prisms 1 correspond to the same second point D2; and when the second point D2 is located on the front side of the first straight line L1 in the first direction F1, λ takes a positive value (such as in the illustrated embodiment); and when the second point D2 is located on the rear side of the first straight line L1 in the first direction F1, λ takes a negative value (such as in the embodiment shown in FIG. 6). Figure 1the left one among the three λs shown in FIG. 6) when the second point D2 is located on the rear side of the first straight line L1 in the first direction F1, λ takes a negative value (such as in Figure 1 the right one among the three λs shown in FIG. 6).

[0053] Next, the theoretical basis for the above design of each triangular prism 1 of the inverse prism sheet 30 according to the present application is described in detail.

[0054] For a general display such as a 16-inch display, in order to realize a narrow-frame display, the light source 10 is generally arranged on the lower side of the display (when placed vertically), i.e., bottom side-in light. In this case, generally, in the first direction F1, the backlight module is required to have a relatively narrow full width at half maxima (FWHM) of the total field angle, generally 14-18°; while in the second direction F2, the full width at half maxima of the total field angle is required to be relatively wide, about 30°. Thus, generally, the light emitting angle of the light rays in the first direction F1 needs to be adjusted to obtain a narrow full width at half maxima of the total field angle in the first direction F1.

[0055] Please refer to Figure 3 According to the vertical distance D of the human eye to the display and the distance H of each position point on the display to the human eye in the first direction F1 i the height difference), the light emitting angle υ of any position point on the display in the first direction F1 can be determined according to the following formula (2). i .

[0056]

[0057] Thus, according to the observation distance D and position of the human eye relative to the display, the ideal light emitting peak angle of any position point on the display in the first direction F1 can be determined, i.e., the light emitting peak angle of each part of the backlight module and the inverse prism sheet 30 in the first direction F1 needs to be designed. Figure 3 The reference sign H in FIG. 6 represents the total width of the display in the vertical direction.

[0058] Figure 2 Two light rays emitted from the light emitting surface 23 of the light guide plate 20 in the first direction F1 at the light emitting peak angle θ are shown, which are respectively incident on two adjacent triangular prisms 1 of the inverse prism sheet 30 and output from different positions of the second main surface 32 of the inverse prism sheet 30. It can be seen that the light ray propagation law followed in this process satisfies the following formulas (3) to (7):

[0059] η = θ - ε (3)

[0060] sin(η) = n*sin(ρ) (4)

[0061] σ=180°-ε-γ-ρ (5)

[0062] τ=σ-γ (6)

[0063] n*sin(τ)=sin(υ) (7)

[0064] Based on equations (3) to (7) above, we can obtain equation (8):

[0065] υ=arcsin{n*sin[180°-ε-2γ-arcsin(sin(θ-ε) / n)]} (8)

[0066] See the preceding introduction and combine it with... Figure 2 In equations (3) to (8) above, n is the refractive index of the reverse prism 30; θ is the peak angle of light emission from the light-emitting surface 23 of the light guide plate 20 in the first direction F1, generally 70°-80°; η is the incident angle of light rays on the first side surface 1a of the triangular prism 1, ρ is the refraction angle of light rays on the first side surface 1a of the triangular prism 1; σ is the incident angle of light rays on the second side surface 1b of the triangular prism 1; τ is the incident angle of light rays on the second principal surface 32 of the reverse prism 30, corresponding to... Figure 2 τ in i and τ i-1 ε is the angle between the first lateral surface 1a and the first principal surface 31 of the triangular prism 1, which is also the first interior angle of the corresponding triangular prism 1. Figure 2 ε i and ε i-1 γ is the angle between the second lateral surface 1b and the first main surface 31 of the triangular prism 1, which is also the second interior angle of the triangular prism 1. Figure 2 γ in i and γ i-1 φ is the third interior angle between the first lateral surface 1a and the second lateral surface 1b of the triangular prism 1, which is also the third interior angle φ of the corresponding triangular prism 1. Figure 2 φ in i and φ i-1 υ represents the peak light emission angle along the first direction F1 at a corresponding point on the second main surface 32 of the reverse prism 30, and is also the peak light emission angle along the first direction F1 of the backlight module and display configured with the reverse prism 30 near that corresponding position. Figure 2 υ in i and υ i-1 Furthermore, it should be understood that, depending on the position of the ray emitted from the second principal surface 32 on the positive side of the normal in the first direction F1 (corresponding to...), Figure 1 (Left side) or negative side (corresponding to) Figure 1 (on the right side of the image), the angle υ can be positive or negative.

[0067] And from equation (8), it can be seen that the peak light emission angle υ of the inverse prism sheet 30, the backlight module and the display along the first direction F1 is related to the two base angles of the triangular prism 1 on the inverse prism sheet 30, i.e. the first internal angle ε and the second internal angle γ, therefore, by changing the first internal angle ε and / or the second internal angle γ, the peak light emission angle υ of the inverse prism sheet 30, the backlight module and the display along the first direction F1 can be changed.

[0068] And, according to equation (8), the following equation (9) can be obtained:

[0069]

[0070] From equation (9), it can be easily seen that, when n, θ and ε remain unchanged, υ varies according to γ. Therefore, in the case that the manufacturer of the inverse prism sheet 30 already knows the human eye observation position of the display to which the inverse prism sheet 30 is to be applied, and the light emission angle θ of the light guide plate 20, the human eye observation position can be set as the position of the second point D2, and the value of the second internal angle γ of each triangular prism 1 on the inverse prism sheet 30 can be determined based on the aforementioned equation (1), and for the convenience of manufacturing, the first internal angle ε of each triangular prism 1 is set as the same value as each other.

[0071] It can be understood that, since the inverse prism sheet 30 of the present embodiment adopts the design of equation (1), the peak brightness light ray along the first direction F1 emitted from each position (the first point D1) of the second main surface 32 all points to the second point D2, therefore, the human eye can observe a clear display screen at the second point D2.

[0072] And, by using equation (2), the target light emission angle υ of any position of the inverse prism sheet 30, the backlight module or the display screen to be designed (characterized by the vertical distance H i between the position and the observation point along the first direction F1) can be determined according to the position of the observation point, and then the determined aforementioned target light emission angle υ is taken as the value of λ in equation (1), and by using equation (1) in the case that the first internal angle ε of each triangular prism 1 is set as a known fixed value, the second internal angle γ of the position triangular prism 1 can be directly calculated.

[0073] As a more specific example, in the case that the first internal angle ε of each triangular prism 1 on the inverse prism sheet 30 is fixed as 50°, the light emission angle θ of the light guide plate 20 is 75°, the refractive index of the inverse prism sheet 30 is 1.56, and the vertical observation distance D of the human eye to the display is 650mm, from equation (1) and equation (2), the vertical distance H i between each position point on the display and the human eye along the first direction F1, and the corresponding ideal light emission angle υ iand the relationship between the corresponding ideal light-emitting angle υ i Corresponding to λ in formula (1), the use of H i The position points of the characterization correspond to the first point D1 in formula (1), and the position of the human eye corresponds to the second point D2 in formula (1).

[0074] Table 1:

[0075] Distance H i (mm) Outcoupling angle υ i (°), corresponding to λ in formula (1) Distance H i corresponding second interior angle γ (°) at point H 140 12.1549 53.1116 120 10.4599 53.6483 100 8.7462 54.1930 80 7.0165 54.7444 60 5.2739 55.3010 40 3.5215 55.8618 20 1.7624 56.4253 0 0.0000 56.9901 -20 -1.7624 57.5550 -40 -3.5215 58.1185 -60 -5.2739 58.6792 -80 -7.0165 59.2359 -100 -8.7462 59.7872 -120 -10.4599 60.3320 -140 -12.1549 60.8690

[0076] As another more specific example, in the case where the first internal angle ε of each triangular prism 1 on the inverse prism sheet 30 is fixed to 55°, the light-emitting angle θ of the light guide plate 20 is 75°, the refractive index of the inverse prism sheet 30 is 1.56, and the vertical viewing distance D of the human eye to the display is 650 mm, the relationship between the vertical distance H i corresponding to the ideal light-emitting angle υ i corresponding to λ in formula (1) and the second internal angle γ of the triangular prism 1 on the inverse prism sheet 30 at the position point can be obtained from formula (1) and formula (2) as shown in Table 2.

[0077] Table 2:

[0078]

[0079] Now, return to Figure 1 and observe formula (1) again, the plane defined by the first straight line L1 and the second straight line L2 is perpendicular to the second direction F2, that is, the first straight line L1 and the second straight line L2 are both perpendicular to the second direction F2.

[0080] In order to improve the light emission uniformity and delicacy of the second main surface 32, the plurality of triangular prisms 1 are arranged to be sequentially adjacent along the first direction F1, and the pitches of the plurality of triangular prisms 1 along the first direction F1 are the same, i.e., the distance between the vertexes of any two adjacent triangular prisms 1 along the first direction F1 is the same. Since the first internal angles ε of the triangular prisms 1 are the same and the second internal angles γ are different, the plurality of triangular prisms 1 have different heights. In some embodiments, the plurality of triangular prisms 1 are sequentially adjacent and arranged along the first direction F1 from one side edge of the first main surface 31 to the other side edge of the first main surface 31, i.e., the triangular prisms 1 are arranged on the second main surface (the area coverage ratio is substantially 100%), so that the light turning ability of the triangular prisms 1 can be fully utilized to improve the light energy utilization of the backlight module and the delicacy of the display. The pitch of the plurality of triangular prisms 1 along the first direction F1 can be set to be between 15 and 30 um, so as to effectively avoid the Moire stripe phenomenon of the display module, especially for UHD (4K, 10K) display.

[0081] As described above, since the first internal angles ε of the triangular prisms 1 are the same and the second internal angles γ are different, the processing difficulty is reduced when the inverse prism sheet 30 and / or the manufacturing mold of the inverse prism sheet 30 is manufactured, but the performance of the backlight module is not affected.

[0082] After the inverse prism sheet 30 is combined with the light guide plate 20 into the backlight module, the backlight module can provide target emitted light, has a narrow ideal viewing angle distribution and high brightness gain, the brightness peak angle of the display screen is always towards the observer, has good brightness uniformity and excellent anti-peeping effect.

Claims

1. A reverse prism lens, comprising: The first and second principal surfaces that are opposite to each other; A plurality of triangular prisms protruding from the first main surface and arranged along a first direction, the triangular prisms extending along a second direction perpendicular to the first direction and having a first side surface and a second side surface further forward in the first direction than the first side surface, the first side surface and the first main surface defining a first interior angle of the triangular prism, the second side surface and the first main surface defining a second interior angle of the triangular prism; The feature is that the plurality of triangular prisms have the same first interior angle as each other, and the second interior angles of any two of the triangular prisms are different from each other.

2. The reverse prism sheet according to claim 1, characterized in that, The reverse prism is applied in the backlight module with the first main surface facing the light-emitting surface of the light guide plate, and the light-emitting peak angle of the light-emitting surface in the first direction is θ. For each of the plurality of triangular prisms, it is constructed to satisfy: Wherein, ε is the first interior angle of the triangular prism, γ is the second interior angle of the triangular prism, n is the refractive index of the reverse prism, and λ is the angle between the first line and the second line. The first line is a line passing through the first point and perpendicular to the second principal surface. The second line is the line connecting the first point and the second point. The first point is a point on the second principal surface opposite to the triangular prism. The second point is a point on the second principal surface of the reverse prism that is separated from the second principal surface. The plurality of triangular prisms correspond to the same second point. When the second point is located on the front side of the first line along the first direction, λ takes a positive value. When the second point is located on the rear side of the first line along the first direction, λ takes a negative value.

3. The reverse prism sheet according to claim 2, characterized in that, Both the first straight line and the second straight line are perpendicular to the second direction.

4. The reverse prism sheet according to claim 1, characterized in that, The plurality of triangular prisms are sequentially adjacent along the first direction.

5. The reverse prism sheet according to claim 4, characterized in that, The plurality of triangular prisms have the same period along the first direction, and the plurality of triangular prisms have different heights.

6. A backlight module, characterized in that, include: Light guide plate, with light emitting surface; The reverse prism sheet as described in any one of claims 1 to 5 is configured such that the first main surface faces the light-emitting surface.

7. The backlight module according to claim 6, characterized in that, The light-emitting surface is the main surface of the light guide plate.

8. The backlight module according to claim 7, characterized in that, The light guide plate has a light incident surface, which is a side surface of the light guide plate. The backlight module further includes: A light source is disposed on the light incident surface side of the light guide plate.

9. The backlight module according to claim 8, characterized in that, The light-incident surface is parallel to the second direction, and in the first direction, the second side surface is further away from the light-incident surface than the first side surface.

10. The backlight module according to any one of claims 6 to 9, characterized in that, The light-emitting surface has a peak light-emitting angle of 70°-80° in the first direction.

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