Inverse prismatic lens, backlight module with same and liquid crystal display equipment

Abstract

The utility model relates to the technical field of display, in particular to an inverse prismatic lens, a backlight module with the inverse prismatic lens and liquid crystal display equipment with the inverse prismatic lens. The inverse prism sheet includes a first light-transmitting surface, a plurality of prism units arranged on the first light-transmitting surface and arranged in a second direction, each prism unit being formed in a triangular prism shape extending in a first direction perpendicular to the second direction, and including a first side surface and a second side surface, the first side surface and the second side surface respectively form a first included angle and a second included angle with the first light-transmitting surface; the inverse prism sheet comprises a plurality of areas arranged along a second direction, the first included angles corresponding to the prism units in the same area are equal, and the second included angles corresponding to the prism units in the same area are equal; for every two adjacent areas, the second included angle corresponding to each prism unit in one area is not equal to the second included angle corresponding to each prism unit in the other area.

Description

TECHNICAL FIELD

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

[0002] LCD (Liquid Crystal Display) display screens are widely used in various fields, such as mobile phones, tablets, notebook computers, liquid crystal televisions, vehicle-mounted displays, and the like. For different application fields and environments, users have different requirements for the viewing angle of the display screen. For example, a display screen with high privacy requirements generally requires the full field of view angle half peak width (referring to the viewing angle width when the light intensity is 50% of the peak intensity, hereinafter referred to as FWHM) of the display screen to be about 25° horizontally and about 15° vertically, so that a relatively narrow field of view angle can be achieved to achieve the privacy effect.

[0003] A privacy backlight module is usually composed of a light guide plate, a reflective sheet, and an inverse prism sheet. In the related art, the microstructure (prism unit) on the inverse prism sheet for turning light is fixed, and the light emitted from each part of the backlight module is emitted perpendicular to the light emitting surface, i.e., the emitted light is perpendicular to the display screen. For a traditional backlight module, when evaluating performance indicators (brightness and brightness uniformity), a normal view measurement is often used, i.e., the detector is perpendicular to the display screen. In actual application, when observing the display screen with the human eye, the position of the human eye is relatively fixed, so when observing the four edges and corners of the display screen, the brightness of the display screen will be much lower than the central brightness, especially when the field of view angle of the display screen is small. For example, for a 14-inch display screen, the distance between the human eye and the display screen is 500 mm, and the human eye is located at the center of the display screen, the angular aperture of the human eye to the upper and lower edges of the display screen is about 20°, so at this time, the display screen is observed at an angle of 10°, the brightness is greatly reduced, especially when the FWHM is small, such as FWHM = 14°, when observed at 10°, the brightness is reduced to 30% of the normal view observation. Not only the brightness is reduced, but also the privacy effect of the peripheral area of the display screen is not conducive. SUMMARY

[0004] Therefore, the present application provides an inverse prism sheet, a backlight module and a liquid crystal display device having the same.

[0005] In a first aspect, there is provided an inverse prism sheet including a first light-transmissive surface on one side in a thickness direction, a plurality of prism units arranged in a second direction on the first light-transmissive surface, the prism units being formed in a shape of a triangular prism extending in a first direction perpendicular to the second direction, and including a first side surface having a first included angle with the first light-transmissive surface, and a second side surface on a front side of the second direction further than the first side surface, the second side surface having a second included angle with the first light-transmissive surface, the first included angle and the second included angle corresponding to two internal angles of a cross section of the triangular prism, respectively.

[0006] The inverse prism sheet includes a plurality of regions in which the prism units are arranged in the second direction and each of which is provided with the prism units, the first included angles corresponding to the respective prism units in the same region are equal to each other, the second included angles corresponding to the respective prism units in the same region are equal to each other, and for each of two adjacent regions, the second included angles corresponding to the respective prism units in one region are not equal to the second included angles corresponding to the respective prism units in the other region.

[0007] In some possible implementations, for the plurality of regions, the second included angles corresponding to the respective prism units in each region are not equal to the second included angles corresponding to the respective prism units in all other regions.

[0008] In some possible implementations, for the plurality of regions, the first included angles corresponding to the respective prism units in each region are equal to the first included angles corresponding to the respective prism units in all other regions.

[0009] In some possible implementations, the first side surface and the second side surface have a third included angle corresponding to the other internal angle of the cross section of the triangular prism, respectively.

[0010] For the plurality of regions, the third included angles corresponding to the respective prism units in each region are equal to the third included angles corresponding to the respective prism units in all other regions.

[0011] In some possible implementations, the inverse prism sheet further includes a second light-transmissive surface on the other side in the thickness direction, the second light-transmissive surface being a complete flat surface.

[0012] In some possible implementations, the plurality of prism units are continuously arranged in the second direction.

[0013] In some possible implementations, the heights of the respective prism units in the same region are equal, and for the plurality of regions, the heights of the prism units in each region are not equal to the heights of the prism units in all other regions.

[0014] In some possible implementation manners, the plurality of regions define all or part of the inverse prism sheet.

[0015] In a second aspect, a backlight module is provided, comprising:

[0016] The inverse prism sheet according to the first aspect;

[0017] A light guide plate is arranged on the first light-transmitting surface side of the inverse prism sheet and has a light-in surface and a light-out surface facing the first light-transmitting surface, wherein the light-out surface is a main surface of the light guide plate, and the light-in surface is a side surface of the light guide plate.

[0018] A light source is arranged on the light-in surface side of the light guide plate.

[0019] The first direction is parallel to the light-in surface and the light-out surface, the second direction is perpendicular to the light-in surface, and in the second direction, the first side surface is closer to the light-in surface than the second side surface.

[0020] In a third aspect, a liquid crystal display device is provided, comprising:

[0021] The backlight module according to the second aspect;

[0022] A liquid crystal panel is arranged on a side of the inverse prism sheet opposite to the light guide plate.

[0023] According to the inverse prism sheet provided in the present application, the prism units thereon have angles that are gradually changed in zones, and the gradually changed prism units make the peak angle of the light emitted from the light guide plate also gradually changed after being guided by the prism units on the inverse prism sheet, and the peak angle is basically directed to a specific position. Therefore, the display screen using the inverse prism sheet can satisfy that the brightness of each zone of the display screen is close to the central brightness at a specific observation position, and has a good anti-peeping effect. In addition, the related angles corresponding to each prism unit in the same zone are set to be equal to each other, which is helpful to easily design and manufacture the inverse prism sheet. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present 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 present application, but not limit the present application.

[0025] Figure 1 is a side view schematic diagram of the backlight module provided in the present application, and part of the light path is schematically shown.

[0026] Figure 2 is Figure 1 is a schematic diagram of a part of the inverse prism sheet in

[0027] Figure 3 is a diagram illustrating the relationship between the light-out angle of any point on the display screen and the observation position.

[0028] Figure 4 is a diagram illustrating the light paths of two light rays emitted by the light guide plate via two adjacent areas of the inverse prism sheet.

[0029] Figure 5 is a schematic diagram of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0030] Figure 6 is a schematic diagram of the inverse prism sheet provided by the embodiment of the present application.

[0031] Figure 7 is a flowchart of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0032] Figure 8 is the light-out angle distribution of the center field of view of the backlight module in the second direction provided by the embodiment of the present application.

[0033] Figure 9 is the result of intensity normalization of the data of Figure 8 .

[0034] Figure 10 is the relationship curve between the light-out angle of the backlight module and the second included angle obtained by fitting the data of Table 2.

[0035] Figure 11 is the relationship curve between the light-out angle of the backlight module and the second included angle obtained by fitting the data of Table 3.

[0036] Figure 12 is the relationship curve between the light-out angle of the backlight module and the third included angle obtained by fitting the data of Table 4.

[0037] Figure 13 is a flowchart of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0038] Figure 14 is a flowchart of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0039] Figure 15 is a flowchart of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0040] Figure 16 is a flowchart of the design method of the inverse prism sheet provided by the embodiment of the present application.

[0041] Explanation of reference signs:

[0042] DR1-first direction, DR2-second direction;

[0043] 1000-backlight module;

[0044] 2000, 3000-design method;

[0045] 100-reverse prism sheet, 200-light guide plate, 300-light source, 400-reflective sheet;

[0046] PT-region, PT1-first region, PT2-second region;

[0047] dl-boundary line between two adjacent regions;

[0048] 1-first light-transmitting surface;

[0049] 2-second light-transmitting surface;

[0050] 3-prism unit, 3a-first side surface, 3b-second side surface;

[0051] α-first included angle, β-second included angle, φ-third included angle;

[0052] j-fourth included angle;

[0053] δ-angle between adjacent imaginary observation directions;

[0054] 4-imaginary straight line, 5-imaginary plane, 6-imaginary observation point, 7-imaginary line,

[0055] 8-observed point, 8A-first observed point, 8B-second observed point;

[0056] 9-imaginary observation direction, 9A-first imaginary observation direction, 9B-second imaginary observation direction;

[0057] 10-light-incident surface;

[0058] 11-light-emitting surface;

[0059] 12-bottom surface. DETAILED DESCRIPTION

[0060] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. 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 belong to the scope of protection 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.

[0061] 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.

[0062] 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.

[0063] In the description of the present application, 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.

[0064] Figure 1 A backlight module 1000 provided by an embodiment of the present application is shown, which includes a light source 300, a light guide plate 200, a reflective sheet 400 and an inverse prism sheet 100.

[0065] The light source 300 can be a LED (light-emitting diode), which can generate light rays directed to the light entrance surface 10 of the light guide plate 200 under the driving of electricity.

[0066] The light guide plate 200 has a light entrance surface 10, a light exit surface 11 and a bottom surface 12. The light exit surface 11 and the bottom surface 12 are oppositely arranged in the thickness direction of the light guide plate 200, so that the light exit surface 11 and the bottom surface 12 are two main surfaces of the light guide plate 200, respectively. And, the bottom surface 12 is formed with a plurality of light guide microstructures for guiding the running direction of light rays, which are omitted from the drawing. The light entrance surface 10 is an elongated side surface of the light guide plate 200, which connects the light exit surface 11 and the bottom surface 12 on one side of the two. In the present embodiment, the backlight module 1000 adopts a side-in type light source structure, and the aforementioned light source 300 is arranged on the light entrance surface 10 side of the light guide plate 200.

[0067] For the purpose of illustration of the present technology, a first direction DR1 and a second direction DR2 perpendicular to each other are defined, wherein the first direction DR1 is a direction parallel to the light-incident surface 10 and the light-emitting surface 11, and the second direction DR2 is a direction perpendicular to the light-incident surface 10 and also parallel to the light-emitting surface 11, and the light guide plate 200, the reflective sheet 400 and the inverse prism sheet 100 all extend in the first direction DR1 and the second direction DR2. In the second direction DR2, the direction toward the arrow is the front side of the second direction DR2, and the direction away from the arrow is the back side of the second direction DR2. In addition, considering that the backlight module 1000 is applied to a display screen, and the display screen is observed by an observer in an upright posture (such as Figure 3 ), the light source 300 and the light-incident surface 10 of the light guide plate 200 are usually at the lower side or the upper side of the display screen, and therefore in some embodiments, the first direction DR1 is also referred to as the horizontal direction, and the second direction DR2 is referred to as the vertical direction.

[0068] In the present embodiment, at the inverse prism sheet 100, the front side of the second direction DR2 is the direction away from the light-incident surface 10 and the light source 300, and the back side of the second direction DR2 is the direction close to the light-incident surface 10 and the light source 300. In other embodiments, the second direction DR2 can also be reversed, so that at the inverse prism sheet 100, the front side of the second direction DR2 becomes the direction close to the light-incident surface 10 and the light source 300, and the back side of the second direction DR2 becomes the direction away from the light-incident surface 10 and the light source 300.

[0069] As a known technology, based on corresponding design of the structure of the light guide plate 200 (such as the shape of the light-guiding microstructure on the bottom surface 12 thereof), the light-emitting surface 11 of the light guide plate 200 can be made to emit light rays (i.e. light rays received from the light-incident surface 10) from the light source 300 at a desired emission angle (i.e. the light-emitting peak angle of the light guide plate 200, which is the angle formed by the normal of the light-emitting surface 11 and the direction with the maximum light intensity in the light intensity distribution).

[0070] Please refer to Figure 2, the inverse prism sheet 100 is arranged on the light exit surface 11 side of the light guide plate 200 in a stacked manner, and includes a first light transmission surface 1 and a second light transmission surface 2 arranged opposite to each other in a thickness direction thereof, and a plurality of prism units 3 arranged on the first light transmission surface 1 and aligned in a second direction DR2, wherein the first light transmission surface 1 faces the light exit surface 11 of the light guide plate 200. The prism unit 3 is formed in a triangular prism shape extending in a first direction DR1, and includes a first side surface 3a and a second side surface 3b located in front of the first side surface 3a in the second direction DR2, wherein the first side surface 3a has a first included angle a with the first light transmission surface 1, the second side surface 3b has a second included angle β with the first light transmission surface 1, and the first side surface 3a has a third included angle φ with the second side surface 3b, and the first included angle a, the second included angle β and the third included angle φ correspond to three internal angles of a cross section of the triangular prism, respectively. Therefore, in the second direction DR2, the first side surface 3a of the prism unit 3 is closer to the light entrance surface 10 of the light guide plate 200 and the light source 300 than the second side surface 3b. The period Pitch of each prism unit 3 can be 10-50 μm, and can be the same or varied in the second direction DR2.

[0071] The reflective sheet 400 is arranged on the bottom surface 12 side of the light guide plate 200 in a stacked manner, i.e., the reflective sheet 400 and the inverse prism sheet 100 are arranged on opposite sides of the light guide plate 200 in a thickness direction, respectively. In this way, the light emitted by the light source 300 and directed to the light entrance surface 10 is guided by the light guide plate 200, and most of the light directly exits from the light exit surface 11 and enters the inverse prism sheet 100, and a small part of the light inevitably transmits from the bottom surface 12 of the light guide plate 200, and the part of the light transmitting from the bottom surface 12 of the light guide plate 200 is reflected by the reflective sheet 400, and then returns to the light guide plate 200 from the bottom surface 12 and exits from the light exit surface 11 and enters the inverse prism sheet 100, in this way, the amount of light directed to the inverse prism sheet 100 can be increased, and the amount of light exiting from the second light transmission surface 2 of the inverse prism sheet 100 can be increased, and the light efficiency of the backlight module 1000 can be improved.

[0072] In other embodiments, the light transmitting from the bottom surface 12 of the light guide plate 200 accounts for a very small proportion, or the reflective sheet 400 can be omitted for the purpose of saving manufacturing cost and reducing the overall thickness of the module.

[0073] For a general display screen, in order to realize narrow frame display, the light source 300 is generally arranged at the lower side of the display screen (when placed vertically), i.e. bottom light input. In this case, the backlight module 1000 generally has a relatively narrow full field angle half peak width FWHM in the vertical direction (second direction DR2), generally about 14-18°; while in the horizontal direction (first direction DR1), the full field angle half peak width FWHM is relatively wide, about 30°. Therefore, it is generally necessary to adjust the light output angle of the light rays in the second direction DR2 to obtain a narrow full field angle half peak width FWHM in the second direction DR2.

[0074] Please refer to Figure 3 According to the display range or display height Wi of the display screen in the vertical direction and the distance D of the observer from the display screen, the light output angle ωi of any point on the display screen in the vertical direction can be determined according to the following relationship (1).

[0075]

[0076] For example, for a 16:9 display screen of 16 inches, the height of the backlight module is required to be 218 mm, so in the vertical direction (second direction DR2), the light output angle distribution of the display screen needs to be as shown in Table 1 for different observer positions and different direct viewing point positions.

[0077] Table 1:

[0078]

[0079] In Table 1 and Tables 2-4 described below, the negative sign "-" used to show the distance indicates a position below the center of the display screen, and the negative sign "-" used to show the angle indicates that the light output angle is in the counterclockwise direction, i.e. the light output angle is in the counterclockwise direction of the normal line of the exit surface.

[0080] Figure 4 A diagram showing the light paths of two light rays emitted from the light output surface 11 of the light guide plate 200 at the light output peak angle, respectively towards two adjacent prism units 3 and outputted from different positions of the second light transmission surface 2 of the inverse prism sheet 100. It can be seen that the light propagation law followed in this process satisfies the following relationships (2)-(6):

[0081] ψ = θ - α (2)

[0082] sin(ψ) = n*sin(ρ) (3)

[0083] σ = 180 - α - β - ρ (4)

[0084] τ = σ - β (5)

[0085] n * sin (τ) = sin (ω) (6)

[0086] According to the above relational expressions (2) to (6), the following relational expressions (7) and (8) can be obtained:

[0087] ω = arcsin {n * sin [180° - α - 2β - arcsin (sin (θ - α) / n)]} (7)

[0088] ω = arcsin {n * sin [φ - β - arcsin (sin (θ - 180° + φ + β) / n)]} (8)

[0089] In the above relational expressions, n is the refractive index of the inverse prism sheet 100; θ is the peak light-exit angle of the light guide plate 200 along the second direction DR2 (simply referred to as the exit angle of the light guide plate 200), generally 70°-80°; α corresponds to the first included angle between the first side surface 3a of the corresponding prism unit 3 and the first light-transmissive surface 1; β corresponds to the second included angle between the second side surface 3b of the corresponding prism unit 3 and the first light-transmissive surface 1; φ corresponds to the third included angle between the first side surface 3a and the second side surface 3b of the corresponding prism unit 3; and ω corresponds to the light-exit angle of the corresponding position of the inverse prism sheet 100, which is also the peak light-exit angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position. Figure 4 i and α i-1 , is the first included angle between the first side surface 3a of the corresponding prism unit 3 and the first light-transmissive surface 1; β corresponds to the second included angle between the second side surface 3b of the corresponding prism unit 3 and the first light-transmissive surface 1; φ corresponds to the third included angle between the first side surface 3a and the second side surface 3b of the corresponding prism unit 3; and ω corresponds to the light-exit angle of the corresponding position of the inverse prism sheet 100, which is also the peak light-exit angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position. Figure 4 i and β i-1 , is the second included angle between the second side surface 3b of the corresponding prism unit 3 and the first light-transmissive surface 1; φ corresponds to the third included angle between the first side surface 3a and the second side surface 3b of the corresponding prism unit 3; and ω corresponds to the light-exit angle of the corresponding position of the inverse prism sheet 100, which is also the peak light-exit angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position. Figure 4 i and φ i-1 , is the third included angle between the first side surface 3a and the second side surface 3b of the corresponding prism unit 3; and ω corresponds to the light-exit angle of the corresponding position of the inverse prism sheet 100, which is also the peak light-exit angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position. Figure 4 i and ω i-1 , is the light-exit angle of the corresponding position of the inverse prism sheet 100, which is also the peak light-exit angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position.

[0090] It can be understood that, when the light guide plate 200 is selected and the material of the prism sheet is selected, n and θ are determined accordingly. At this time, the light-exit angle (peak light-exit angle) of the inverse prism sheet 100 and the backlight module 1000 is related to the first included angle α, the second included angle β, and the third included angle φ of the corresponding prism unit 3. Since the sum of the first included angle α, the second included angle β, and the third included angle φ is 180°, it can be more simply stated that the peak light-exit angle ω of the backlight module 1000 is related to any two of the first included angle α, the second included angle β, and the third included angle φ of the corresponding prism unit 3.

[0091] ​​​​Therefore, in combination with the aforementioned relation (1) and relation (7) or (8), the ideal structure of the prismatic unit 3 on the inverse prism sheet 100 in the backlight module 1000 corresponding to the display screen at this time, i.e., the ideal first included angle a, second included angle β and third included angle φ, can be inversely calculated according to the target value of ω.

[0092] Based on the above discussion, the embodiment of the present application provides a design method 2000 of the inverse prism sheet 100. The designed inverse prism sheet 100 can be applied to a backlight module 1000 similar to Figure 1 for receiving the light rays emitted from the light exit face 11 of the light guide plate 200 at the side of the light exit face 11 and guiding the light rays to be emitted from the second light transmission face 2 to supply the liquid crystal panel (not shown). Please refer to Figure 7 and in combination with Figure 5 The design method 200 includes the following steps S701 to S704:

[0093] S701, determining a virtual observation point 6, wherein the virtual observation point 6 is a point located in a virtual plane 5 and having a certain distance from the second light transmission face 2 at the side of the second light transmission face 2 of the inverse prism sheet 100, and the virtual plane 5 is perpendicular to the second direction DR2 and passes through the inverse prism sheet 100.

[0094] The virtual observation point 6 can be a position point such that, in the case that the inverse prism sheet 100 is applied to a backlight module 1000 similar to Figure 1 and further to a display screen, the virtual observation point 6 is the best observation point of the picture in the display screen, and when the eyes of an observer observe the display screen at the virtual observation point 6, the light intensity of the light rays emitted from each position of the second light transmission face 2 of the inverse prism sheet 100 to the eyes of the observer is close to the central intensity of the light rays emitted from the position (for example, more than 85% of the central intensity), so that the observer can watch a very clear picture of the display screen from the virtual observation point 6.

[0095] In some embodiments, the virtual observation point 6 is directly opposite the central position of the inverse prism sheet 100 and the display screen, i.e., the orthographic projection of the virtual observation point 6 on the second light transmission face 2 is just at the central position of the second light transmission face 2. In other embodiments, the orthographic projection of the virtual observation point 6 on the second light transmission face 2 deviates from the central position of the second light transmission face 2, such as Figure 5The observed point 8 at j=0 corresponds to such an orthographic projection. In some embodiments, the hypothetical observation point 6 is completely separated from the second light-transmitting surface 2 in the second direction DR2. Therefore, the line connecting any point on the second light-transmitting surface 2 to the hypothetical observation point 6 is not perpendicular to the second light-transmitting surface 2. In other words, the hypothetical observation point 6 has no orthographic projection on the second light-transmitting surface 2, which has a limited area. For example, the hypothetical observation point 6 is located lower than the lower edge of the reverse prism 100 and the display screen, or higher than the upper edge of the reverse prism 100 and the display screen.

[0096] exist Figure 5 In the middle, the imaginary plane 5 is the paper surface.

[0097] S702, a plurality of imaginary observation directions 9 are determined, wherein each imaginary observation direction 9 originates from an imaginary observation point 6 and points towards the second light-transmitting surface 2, and extends within the aforementioned imaginary plane 5, thereby obtaining a plurality of observed points 8 sequentially spaced along the first direction DR1 on the second light-transmitting surface 2. Each of the plurality of observed points 8 defines an imaginary straight line 4 passing through the observed point 8 and perpendicular to the second light-transmitting surface 2. The corresponding imaginary observation direction 9 and the imaginary straight line 4 have a fourth included angle j, and it can be understood that the fourth included angle j lies within the imaginary plane 5.

[0098] S703, the reverse prism 100 is divided into multiple regions PT that correspond one-to-one with the positions of multiple observed points 8 and are continuously arranged along the second direction DR2, wherein each pair of adjacent regions PT is the front side region on the front side and the rear side region on the rear side in the second direction DR2.

[0099] Please review Figure 4 This shows the adjacent frontal and rearal regions. Figure 4 In the middle, the PT tag is used. i Indicates the frontal side area, and uses the marker PT. i-1 This indicates the rear side region, and the front side region PT. i and rear side area PT i-1 exist Figure 6 The diagram is also shown in the middle; using the marker α. i β i φ i The front side regions PT are represented sequentially. i The first included angle α, the second included angle β, and the third included angle φ are corresponding to one prism unit 3, and α is marked with a symbol. i-1 β i-1 φ i-1 Representing the rear side region PT respectively i-1 The first included angle α, the second included angle β, and the third included angle φ correspond to one prism unit 3; use the notation ω. i This indicates that the light passes through the front side region PT.i the light exit angle along the second direction DR2 when the light ray exits from the second light-transmissive surface 2 of the inverse prism sheet 100 through one of the prism units 3. It can be understood that, i-1 the light ray passes through the rear side region PT i-1 the light exit angle along the second direction DR2 when the light ray exits from the second light-transmissive surface 2 of the inverse prism sheet 100 through one of the prism units 3. It can be understood that, Figure 4 the light exit angle along the second direction DR2 when the light ray exits from the second light-transmissive surface 2 of the inverse prism sheet 100 through one of the prism units 3. It can be understood that, i and ω i-1 correspond to the light exit peak angles at two different positions of the inverse prism sheet 100, respectively.

[0100] In Figure 5 and Figure 6 the plurality of regions PT divide the entire inverse prism sheet 100. In other embodiments, the plurality of regions PT can only divide a portion of the inverse prism sheet 100, for example, only the middle portion or the portion close to the light source 300 of the inverse prism sheet 100.

[0101] S704, the prism units 3 are designed such that the first included angles a corresponding to each of the prism units 3 in the same region PT are equal to each other, the second included angles β corresponding to each of the prism units 3 in the same region PT are equal to each other, and the first included angles a and the second included angles β corresponding to each of the prism units 3 in the same region PT satisfy the following relationship (9):

[0102] j = arcsin{n*sin[180°-a-2β-arcsin(sin(θ-a) / n)]} (9)

[0103] In the relationship, a is the first included angle, β is the second included angle, j is the fourth included angle between the imaginary straight line 4 and the imaginary observation direction 9, n is the refractive index of the inverse prism sheet 100, and θ is the light exit peak angle along the second direction DR2 of the light guide plate 200.

[0104] It can be understood that, since 180° = a + β + φ, the first included angles a and the second included angles β corresponding to each of the prism units 3 in the same region PT satisfy the relationship (9) is equivalent to that the second included angles β and the third included angles φ corresponding to each of the prism units 3 in the same region PT satisfy the following relationship (10):

[0105] j = arcsin{n*sin[φ-β-arcsin(sin(θ-180°+φ+β) / n)]} (10)

[0106] Obviously, the aforementioned imaginary straight line 4 is also the normal of the second light-transmitting surface 2 of the reverse prism 100 at the corresponding observed point 8.

[0107] Figure 8 The light emission angle distribution of the center field of view of the backlight module 1000 provided as an example is shown in the second direction DR2 (vertical direction). Figure 9 To Figure 8 The data is normalized for intensity. It can be seen that in order to control the light intensity to be above 95% of the center intensity, the angular offset of the light peak can be + / -2°. That is, the light peak angle deviates from the center by + / -2°. When observed within this angle, the intensity decreases within 95%. This can be used as the tolerance to control the light emission angle of the backlight module 1000.

[0108] Of course, if the customer's requirements are higher, the intensity reduction must be controlled within 97%, and the peak emission angle will deviate from the center by + / - 1°. If the customer's requirements are lower, the intensity reduction must be within 90%, and the peak emission angle will deviate from the center by + / - 3°. If the customer's requirements are lowered further, the intensity reduction must be within 85%, and the peak emission angle will deviate from the center by + / - 4°.

[0109] Therefore, the backlight module 1000, especially the reverse prism 100, can be divided into regions according to customer needs, particularly based on the specific tolerance or range of the light emission angle. The relevant included angles corresponding to each prism unit 3 within the same region PT can be set to be the same, and the relevant included angles corresponding to the prism unit 3 in different regions PT can be designed to be different based on their positions. This facilitates the manufacturing of the designed reverse prism 100 and meets customer requirements. Specifically, the reverse prism 100 can be divided into multiple regions PT along the second direction DR2 according to the image size and viewing distance. Preferably, for the observer, the included angle between each two adjacent regions PT is the same; that is, in step S702, the included angle δ between each two adjacent viewing directions is set to be the same, for example, δ is always 2°, always 1°, or always 3°. Understandably, the higher the client's specific tolerance or tolerance range requirement for the light emission angle, the smaller the δ value will be set in this design method 2000, and the closer the intensity of light emitted from various positions of the reverse prism 100 and the display screen to the observer's eye will be to the center intensity of the light emitted from that position.

[0110] In order to make it easier to manufacture the designed inverse prism sheet 100, in step S702, the third included angles φ corresponding to the plurality of regions PT can be set to be equal to each other, and only the sizes of the first included angles α and the second included angles β in different regions PT are changed. For example, the third included angles φ (apex angles) corresponding to the prism units 3 in each region PT are fixed to 64°, and only the sizes of the first included angles α and the second included angles β in different regions PT are adjusted according to the relationship (9). In addition, the first included angles α corresponding to the plurality of regions PT can also be set to be equal to each other, and only the sizes of the second included angles β and the third included angles φ in different regions PT are changed.

[0111] After the inverse prism sheet 100 designed by the design method 2000 is applied to the backlight module 1000 and further to the display screen, based on the design of differentiating at least two of the first included angles α, the second included angles β and the third included angles φ corresponding to each prism unit 3, different target angles of outgoing light can be provided for different parts of the backlight module 1000 and the display screen, and the ideal viewing angle distribution is relatively narrow, and the brightness gain is extremely high. In addition, the brightness peak angle of different parts of the display screen is generally directed to the observer at the imaginary observation point 6, and the display screen has excellent brightness uniformity and excellent anti-peeping effect.

[0112] In addition, in the design method 2000, Figure 5 In addition, in the design method 2000,

[0113] It should be noted that in step S704 of the design method 2000, when the first included angles α and the second included angles β are designed to satisfy the above relationship (9), a certain deviation (for example, not more than 2%) of α and β is allowed.

[0114] It can also be understood that the inverse prism sheet 100 designed by the design method 2000 comprises a plurality of regions PT which are arranged continuously along the second direction DR2 and each of which is provided with a plurality of prism units 3, the first included angles a corresponding to each of the prism units 3 in the same region PT are equal to each other, and the second included angles β corresponding to each of the prism units 3 in the same region PT are equal to each other. And with the inverse prism sheet 100 as a reference, an imaginary observation point 6 and a plurality of imaginary observation directions 9 can be found, which make the first included angles a and the second included angles β satisfy the aforementioned relationship (9). The imaginary observation point 6 is a point located in an imaginary plane 5 and on the second light-transmitting surface 2 side of the inverse prism sheet 100 and having a certain distance from the second light-transmitting surface 2, the imaginary plane 5 is a plane perpendicular to the second direction DR2 and passing through the inverse prism sheet 100, each of the plurality of imaginary observation directions 9 is directed to the second light-transmitting surface 2 with the imaginary observation point 6 as a starting point and extends in the imaginary plane 5, so as to form a plurality of observed points 8 in the second light-transmitting surface 2 which are sequentially spaced apart along the second direction DR2, and preferably, the included angles δ between each adjacent two imaginary observation directions 9 are equal. In the aforementioned relationship, j is the fourth included angle j between the corresponding imaginary straight line 4 and the imaginary observation direction 9.

[0115] As mentioned above, the first included angles a and the second included angles β satisfying the aforementioned relationship (7) are equivalent to the second included angles β and the third included angles φ satisfying the relationship (10). In addition, for other characteristics of the inverse prism sheet 100 designed by the design method 2000, those skilled in the art can determine based on the foregoing introduction of the design method 2000, and therefore will not be described here.

[0116] In some embodiments, the plurality of prism units 3 are arranged continuously along the second direction DR2 on the second light-transmitting surface 2, which can increase the number of prism units 3 and thereby enhance the turning effect of the inverse prism sheet 100 on light.

[0117] In some embodiments, the heights of the prism units 3 in the same region PT are equal, and for the plurality of regions PT, the height of the prism units 3 in each region is not equal to the height of the prism units 3 in all other regions. Specifically, the height of the prism units 3 in each region PT can be adjusted accordingly according to the change of the related included angles in the region PT, so as to obtain better optical quality.

[0118] In addition, the inventors also have the following three findings.

[0119] Discovery 1: Set the third angle φ corresponding to the prism unit 3 to be fixed, such as φ = 68° or 70°, and the second angle β varies, so the first angle α also varies. According to the relationship (8), since the light-out peak angle θ of the light guide plate 200 is a constant value, such as θ = 75°, and the refractive index of the inverse prism sheet 100 is a constant value, such as n = 1.56, in this case, it can be calculated that when the third angle φ is fixed at 68° and 70° respectively, the light-out peak angle ω of the backlight module 1000 (and the inverse prism sheet 100) varies with the second angle β as shown in Table 2.

[0120] Table 2: The light-out peak angle ω of the backlight module 1000 varies with the second angle β when the third angle φ is fixed at φ = 68° and 70° respectively

[0121]

[0122] Figure 10 The data in Table 2 is fitted to obtain the relationship curve between the light-out angle ω of the backlight module 1000 and the second angle β when the third angle φ is fixed at 68° and 70° respectively. It can be seen that when the third angle φ is fixed, the light-out peak angle of the backlight module 1000 is shifted by about 2.53° for every 1° change in the second angle β, and the second angle β and the light-out peak angle of the backlight module 1000 have a roughly linear linear relationship.

[0123] Although Table 2 only gives the case when φ is 68° and 70°, the inventors have found that when φ is selected as other angle values, the second angle β and the light-out peak angle of the backlight module 1000 also have a roughly linear linear relationship.

[0124] Since the first angle α and the second angle β correspond to two base angles of the triangular cross section of the prism unit 3, and the third angle φ corresponds to a vertex angle of the triangular cross section of the prism unit 3, in this case Figure 10 and the later described Figure 11 and Figure 12 , the first angle α is also referred to as the base angle α, the second angle β is also referred to as the base angle β, and the third angle φ is also referred to as the vertex angle φ.

[0125] Discovery 2: Set the first angle α corresponding to the prism unit 3 to be fixed, such as α = 50° or 56°, and the second angle β varies, so the third angle φ also varies. According to the relationship (7), since the light-out peak angle θ of the light guide plate 200 is a constant value, such as θ = 75°, and the refractive index of the inverse prism sheet 100 is a constant value, such as n = 1.56, in this case, it can be calculated that when the first angle α is fixed at 50° and 56° respectively, the light-out peak angle ω of the backlight module 1000 varies with the second angle β as shown in Table 3.

[0126] Table 3: The peak light output angle ω of the backlight module 1000 varies with the second included angle β when the first included angle α is 50° and 56° respectively

[0127]

[0128] Figure 11 is a curve of the light output angle ω of the backlight module 1000 versus the second included angle β when the first included angle α is 50° and 56° respectively, which is obtained by fitting the data in Table 3. It can be seen that when the first included angle α is fixed, the peak light output angle of the backlight module 1000 shifts by about 3.14° for each 1° change in the second included angle β, and the second included angle β and the peak light output angle of the backlight module 1000 have a substantially linear linear relationship.

[0129] Although Table 3 only gives the case where α is 50° and 56°, the inventors have found that when α is selected as other angle values, the second included angle β and the peak light output angle of the backlight module 1000 also have a substantially linear linear relationship.

[0130] Discovery three: Set the first included angle α and the second included angle β corresponding to the same prism unit 3 to be equal, i.e., the cross section of each prism unit 3 is an isosceles triangle, and the third included angle φ varies. According to the relationship (7), since the light output peak angle θ of the light guide plate 200 is a constant value, such as θ = 75°, and the refractive index of the inverse prism sheet 100 is a constant value, such as n = 1.56, in this case, the change value of the light output angle ω of the backlight module 1000 with the third included angle φ can be calculated as shown in Table 4.

[0131] Table 4: The peak light output angle ω of the backlight module 1000 varies with the third included angle φ when the first included angle α and the second included angle β corresponding to the same prism unit 3 are equal

[0132] φ (°) 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 ω (°) 14.41 12.53 10.64 876 689 5.03 3.16 13 -0.55 -2.41 -427 -613 -7.99 -986 -11.73 -13.61 -15.5

[0133] Figure 12 is a curve of the light output angle ω of the backlight module 1000 versus the third included angle φ when the first included angle α and the second included angle β are equal, which is obtained by fitting the data in Table 4. It can be seen that for each 1° change in the third included angle φ, the peak light output angle of the backlight module 1000 shifts by about 1.87°, and the third included angle φ and the peak light output angle of the backlight module 1000 have a substantially linear linear relationship.

[0134] Based on the above three discoveries of the inventors, the embodiment of the present application provides another design method 3000 of the inverse prism sheet 100, and the designed inverse prism sheet 100 can be applied to similar backlight modules 1000. Figure 1In the backlight module 1000, light rays emitted from the light exit surface 11 of the light guide plate 200 are received at the light exit surface 11 side of the inverse prism sheet 100 and guided to be emitted from the second light transmission surface 2 to supply the liquid crystal panel. Please refer to Figure 13 and also in conjunction with Figure 5 The design method 3000 includes the following steps S131-S134:

[0135] S131, determining a virtual observation point 6, wherein the virtual observation point 6 is a point located in a virtual plane 5 and at a distance from the second light transmission surface 2 on the second light transmission surface 2 side of the inverse prism sheet 100, and the virtual plane 5 is perpendicular to the first direction DR1 and passes through the inverse prism sheet 100.

[0136] Similar to the aforementioned design method 2000, in the design method 3000, the virtual observation point 6 can also be a position point at which the inverse prism sheet 100 is applied to Figure 1 the backlight module 1000 and the further display screen as shown in the drawings, the optimal observation point of the picture in the display screen. When the observer's eye observes the display screen at the virtual observation point 6, the light intensity of the light rays emitted from each position of the second light transmission surface 2 of the inverse prism sheet 100 to the observer's eye is close to the central intensity of the light emitted from the position (for example, more than 85% of the central intensity), and thus the observer can view a very clear picture of the display screen from the virtual observation point 6.

[0137] In some embodiments, the virtual observation point 6 is directly opposite the center position of the inverse prism sheet 100 and the display screen, i.e., the orthographic projection of the virtual observation point 6 on the second light transmission surface 2 is exactly at the center position of the second light transmission surface 2. In other embodiments, the orthographic projection of the virtual observation point 6 on the second light transmission surface 2 (such as the virtual observation point 6 when j=0 in the drawings) deviates from the center position of the second light transmission surface 2. In still other embodiments, the virtual observation point 6 is completely separated from the second light transmission surface 2 in the second direction DR2, and thus the line connecting any point on the second light transmission surface 2 and the virtual observation point 6 is not perpendicular to the second light transmission surface 2, or in other words, the virtual observation point 6 has no orthographic projection on the second light transmission surface 2 with limited area, for example, the virtual observation point 6 is a position point lower than the lower side of the inverse prism sheet 100 and the display screen, or a position point higher than the upper side of the inverse prism sheet 100 and the display screen. Figure 5 In

[0138] the virtual plane 5 is a paper plane. Figure 5

[0139] ​S132, determining a plurality of imaginary observation directions 9, each of which extends in the imaginary plane 5 and is directed from the imaginary observation point 6 to the second light-transmissive surface 2, so as to obtain a plurality of observed points 8 on the second light-transmissive surface 2 which are spaced apart along the second direction DR2, and an included angle δ between each two adjacent imaginary observation directions 9 is equal. The corresponding imaginary observation direction 9 has a fourth included angle j with the imaginary straight line 4, and it can be understood that the fourth included angle j and the included angle δ are both in the imaginary plane 5.

[0140] S133, dividing the inverse prism sheet 100 into a plurality of regions PT which correspond one-to-one to the positions of the plurality of observed points 8 and are arranged continuously along the second direction DR2, wherein each two adjacent regions PT are a front side region PT and a rear side region PT which are on the front side and the rear side in the second direction DR2, respectively.

[0141] Please refer again to Figure 4 , which shows adjacent front side regions and rear side regions. In Figure 4 , the front side region is denoted by the mark PT i , and the rear side region is denoted by the mark PT i-1 , and the front side region PT i and the rear side region PT i-1 are also shown in Figure 6 ; the first included angle α, the second included angle β and the third included angle φ corresponding to one prism unit 3 in the front side region PT i are denoted by the marks α i , β i , φ i in sequence, and the first included angle α, the second included angle β and the third included angle φ corresponding to one prism unit 3 in the rear side region PT i-1 are denoted by the marks α i-1 , β i-1 , φ i-1 , respectively; the light exit angle along the second direction DR2 when a light ray exits from the second light-transmissive surface 2 of the inverse prism sheet 100 via one prism unit 3 in the front side region PT i is denoted by the mark ω i-1 , and the light exit angle along the second direction DR2 when a light ray exits from the second light-transmissive surface 2 of the inverse prism sheet 100 via one prism unit 3 in the rear side region PT i-1 is denoted by the mark ω i . It can be understood that Figure 4 , when the two light rays exiting from the light guide plate 200 are light rays corresponding to the light exit peak angles of the light guide plate 200, ω i-1 and ω correspond to the light exit peak angles at two different positions of the inverse prism sheet 100, respectively.

[0142] S134, the inverse prism sheet 100 is designed to satisfy: the first included angles a corresponding to each prism unit 3 in the same region PT are equal to each other, the second included angles β corresponding to each prism unit 3 in the same region PT are equal to each other (thus, the third included angles φ corresponding to each prism unit 3 in the same region PT are also equal to each other), and one of the following ①, ② and ③ is satisfied:

[0143] ① based on making the third included angles φ corresponding to each prism unit 3 equal to each other, and the second included angles β corresponding to the front-side region PT and the second included angles β corresponding to the rear-side region PT have a fixed first angular difference, so that the light emission peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding virtual observation direction 9;

[0144] ② based on making the first included angles a corresponding to each prism unit 3 equal to each other, and the third included angles φ corresponding to the front-side region PT and the third included angles φ corresponding to the rear-side region PT have a fixed second angular difference, so that the light emission peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding virtual observation direction 9;

[0145] ③ based on making the first included angles a and the second included angles β of the same prism unit 3 equal to each other, and the third included angles φ corresponding to the front-side region PT and the third included angles φ corresponding to the rear-side region PT have a fixed third angular difference, so that the light emission peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding virtual observation direction 9.

[0146] Here, the light emission peak angle in the second direction DR2 of each observed point 8 corresponding to the corresponding virtual observation direction 9 not only includes the case where the peak emission light ray of the observed point 8 coincides with the virtual observation direction 9, but also includes the case where the included angle between the peak emission light ray of the observed point 8 and the virtual observation direction 9 is within a prescribed range (for example, 0-5°). That is, the light emission peak angle in the second direction DR2 of each observed point 8 corresponding to the corresponding virtual observation direction 9 can be specifically that the difference between the light emission peak angle in the second direction DR2 of each observed point 8 and the corresponding observation angle, which is the included angle between the corresponding virtual observation direction 9 and the virtual straight line 4, does not exceed a prescribed value of, for example, 5°, and corresponds to Figure 5 the fourth included angle j in the formula (1).

[0147] It can be understood that the theoretical basis of the aforementioned schemes ①, ② and ③ corresponds to the aforementioned findings one, two and three of the inventor in turn. In step S132, the reason why the included angle δ between every two adjacent imaginary observation directions 9 is set to be equal to each other is to make the target light-out angle corresponding to any two adjacent regions PT divided in step S133 have a fixed (i.e. same) angle difference, and then in step S134, based on the aforementioned three findings of the inventor, the first included angle α, the second included angle β and the third included angle φ corresponding to each prism unit 3 in the same region PT can be set to be respectively the same, one of the three included angles corresponding to different regions PT can be set to be a fixed value, and the other two included angles can be set to be variable values and the relevant included angles corresponding to every two adjacent regions PT differ by the same value, as a result of which, while ensuring that the display screen can be observed from the imaginary observation point 6 to be particularly clear, it is also helpful to easily manufacture the designed inverse prism sheet 100.

[0148] In some embodiments, as shown in FIG. 3, the step S134 of the design method 3000 can be specifically: Figure 5

[0149] ① based on making the third included angle φ corresponding to each prism unit 3 equal to each other, and the second included angle β corresponding to the front side region PT greater than the second included angle β corresponding to the rear side region PT by a first angle difference, so that the light-out peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9;

[0150] ② based on making the first included angle α corresponding to each prism unit 3 equal to each other, and the second included angle β corresponding to the front side region PT greater than the second included angle β corresponding to the rear side region PT by a second angle difference, so that the light-out peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9;

[0151] ③ based on making the first included angle α and the second included angle β corresponding to the same prism unit 3 equal to each other, and the third included angle φ corresponding to the front side region PT smaller than the third included angle φ corresponding to the rear side region PT by a third angle difference, so that the light-out peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9.

[0152] It can be understood that if the positive and negative of the second direction DR2 are reversed, the aforementioned ①, ② and ③ in step S134 of the design method 3000 can be specifically:

[0153] ​① based on making the third included angle φ corresponding to each prism unit 3 equal to each other, and making the second included angle β corresponding to the front side region PT smaller than the second included angle β corresponding to the rear side region PT by a first angle difference, so that the light-out peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding imaginary observation direction 9;

[0154] ② based on making the first included angle a corresponding to each prism unit 3 equal to each other, and making the second included angle β corresponding to the front side region PT smaller than the second included angle β corresponding to the rear side region PT by a second angle difference, so that the light-out peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding imaginary observation direction 9;

[0155] ③ based on making the first included angle a and the second included angle β corresponding to the same prism unit 3 equal to each other, and making the third included angle φ corresponding to the front side region PT larger than the third included angle φ corresponding to the rear side region PT by a third angle difference, so that the light-out peak angle in the second direction DR2 of each observed point 8 corresponds to the corresponding imaginary observation direction 9.

[0156] It can be understood that, according to the data in the foregoing Table 2, when the refractive index of the target inverse prism sheet 100 designed by using the design method 3000 is 1.56, and the light-out peak angle of the light guide plate 200 matched therewith is 75°, the included angle of any two adjacent imaginary observation directions 9 in step S132 can be configured as 2.35°, and the first angle difference in scheme ① can be configured as 1°. In this case, Figure 5 The eight different sizes of the second included angle β corresponding to the eight regions PT in the foregoing Table 2 are an arithmetic progression with a tolerance of 1° in the second direction DR2.

[0157] According to the data in the foregoing Table 3, when the refractive index of the target inverse prism sheet 100 designed by using the design method 3000 is 1.56, and the light-out peak angle of the light guide plate 200 matched therewith is 75°, the included angle of any two adjacent imaginary observation directions 9 in step S132 can be configured as 3.14°, and the second angle difference in scheme ② can be configured as 1°.

[0158] According to the data in the foregoing Table 4, when the refractive index of the target inverse prism sheet 100 designed by using the design method 3000 is 1.56, and the light-out peak angle of the light guide plate 200 matched therewith is 75°, the included angle of any two adjacent imaginary observation directions 9 in step S132 can be configured as 1.87°, and the first angle difference in scheme ③ can be configured as 1°.

[0159] As Figure 5As shown, in step S132, the determined plurality of hypothetical observation directions 9 includes a first hypothetical direction and a second hypothetical direction located at the most end side, the plurality of observed points 8 includes a first observed point 8A corresponding to the first hypothetical observation direction 9A and a second observed point 8B corresponding to the second hypothetical direction, and the plurality of regions PT includes a first region PT1 corresponding to the first hypothetical direction and a second region PT2 corresponding to the second hypothetical direction.

[0160] Based on this, if scheme I is adopted in step S134, scheme I can specifically include Figure 14 The steps S141 to S143 shown:

[0161] S141, determining a first target angle of the first included angle a corresponding to the prism unit 3 in the first region PT1, wherein the first target angle of the first included angle a is an angle that makes the light-out peak angle of the first observed point 8A along the second direction DR2 correspond to the first hypothetical observation direction 9A.

[0162] S142, determining a second target angle of the first included angle a corresponding to the prism unit 3 in the second region PT2, wherein the second target angle is an angle that makes the light-out peak angle of the second observed point 8B along the second direction DR2 correspond to the second hypothetical observation direction 9B.

[0163] In some embodiments, the first target angle and the second target angle can be determined based on the aforementioned relationship (8).

[0164] S143, determining a first angle difference between the first target angle and the second target angle by dividing the difference between the first target angle and the second target angle by a first natural number, wherein the first natural number is a number that is less than 1 than the total number of the plurality of regions PT.

[0165] For example, in Figure 5 , the total number of the plurality of regions PT is 8, and the corresponding first natural number is 7.

[0166] If scheme II is adopted in step S134, scheme II can specifically include Figure 15 The steps S151 to S153 shown:

[0167] S151, determining a third target angle of the third included angle φ corresponding to the prism unit 3 in the first region PT1, wherein the third target angle is an angle that makes the light-out peak angle of the first observed point 8A along the second direction DR2 correspond to the first hypothetical observation direction 9A.

[0168] S152, determining a fourth target angle of the third angle corresponding to the prism unit 3 in the second region PT2, wherein the fourth target angle is an angle corresponding to the light-out peak angle of the second observation point 8B along the second direction DR2 and the second imaginary observation direction 9B.

[0169] In some embodiments, the third target angle and the fourth target angle can be determined based on the aforementioned relationship (7).

[0170] S153, determining a second angle difference by dividing the difference between the third target angle and the fourth target angle by the aforementioned first natural number (i.e., a number less than the total number of the plurality of regions PT by 1).

[0171] If scheme III is adopted in step S134, the scheme III can specifically include Figure 16 the steps S161 to S163 shown in the figure:

[0172] S161, determining a fifth target angle of the third included angle φ corresponding to the prism unit 3 in the first region PT1, wherein the fifth target angle is an angle corresponding to the light-out peak angle of the first observation point 8A along the second direction DR2 and the first imaginary observation direction 9A.

[0173] S162, determining a sixth target angle of the third angle corresponding to the prism unit 3 in the second region PT2, wherein the sixth target angle is an angle corresponding to the light-out peak angle of the second observation point 8B along the second direction DR2 and the second imaginary observation direction 9B.

[0174] In some embodiments, the fifth target angle and the sixth target angle can be determined based on the aforementioned relationship (7).

[0175] S163, determining a third angle difference by dividing the difference between the fifth target angle and the sixth target angle by the aforementioned first natural number.

[0176] It can be understood that the inverse prism sheet 100 designed by the design method 3000 includes a plurality of regions PT arranged continuously along the second direction DR2 and each provided with a prism unit 3, the first included angle α corresponding to each prism unit 3 in the same region PT is equal to each other, the second included angle β corresponding to each prism unit 3 in the same region PT is equal to each other, and has one of the following three characteristics:

[0177] the third included angle φ corresponding to each prism unit 3 is equal to each other, and the second included angle β corresponding to the front region has a fixed first angle difference with the second included angle β corresponding to the rear region;

[0178] The first included angle a corresponding to each prism unit 3 is equal to each other, and the second included angle β corresponding to the front side region has a fixed second angle difference with the second included angle β corresponding to the rear side region.

[0179] The first included angle a corresponding to each prism unit 3 is equal to each other, and the second included angle β corresponding to the front side region has a fixed second angle difference with the second included angle β corresponding to the rear side region.

[0180] And, with the inverse prism sheet 100 as a reference, a plurality of imaginary straight lines 4 can be found, which extend in the same imaginary plane 5 and perpendicularly to the second light-transmitting surface 2 and pass through the plurality of regions PT one by one, thereby forming a plurality of imaginary intersection points (corresponding to the aforementioned observed points 8) intersecting the second light-transmitting surface 2 and corresponding to the plurality of regions PT one by one, wherein the imaginary plane 5 is a plane perpendicular to the first direction DR1. For each imaginary intersection point, the imaginary straight line 4 corresponding to the imaginary intersection point and the imaginary connecting line 7 (corresponding to the aforementioned imaginary observation direction 9) of the same imaginary observation point 6 have a fourth included angle j, wherein the imaginary observation point 6 is a point located in the imaginary plane 5 and having a certain distance from the second light-transmitting surface 2 on the side of the second light-transmitting surface 2 of the inverse prism sheet 100. If each adjacent two fourth included angles j are respectively referred to as a front side fourth included angle j on the front side in the second direction DR2 and a rear side fourth included angle j on the rear side, then the front side fourth included angle j and the rear side fourth included angle j have a fixed fourth angle difference, and in Figure 5 the fourth angle difference is equal to δ.

[0181] And in Figure 5 addition to the first region PT1 and the second region PT2 at the most end sides, in each of the remaining six regions PT, the corresponding imaginary intersection point and the imaginary straight line 4 are located at the middle position of the region PT in the second direction DR2. Through such a design, the light-emitting peak angle of each part of the region PT in the second direction DR2 can be easily made close to the fourth included angle j.

[0182] For other features of the inverse prism sheet 100 designed by the design method 3000, those skilled in the art can determine based on the foregoing introduction to the design method 3000, which will not be repeated here.

[0183] In addition, referring to the foregoing introduction to the design method 3000, in the design method 2000, in order to simplify the method, the inverse prism sheet 100 can also be designed as follows: in the plurality of regions PT, the first included angle a corresponding to each prism unit 3 is equal to each other, or the third included angle φ corresponding to each prism unit 3 is equal to each other, or the first included angle a and the second included angle β corresponding to the same prism unit 3 are equal to each other.

[0184] Each region PT can be a rectangular region, and extends throughout the inverse prism sheet 100 in the first direction DR1.

[0185] The application also provides a manufacturing method of the inverse prism sheet 100, comprising:

[0186] designing the inverse prism sheet 100 according to the aforementioned design method 2000 or design method 3000;

[0187] manufacturing the designed inverse prism sheet 100.

[0188] Please combine Figure 1 The application also provides a manufacturing method of the backlight module 1000, comprising:

[0189] providing the light guide plate 200 and the light source 300, wherein the light guide plate 200 has a light-in surface 10 and a light-out surface 11, the light-out surface 11 is a main surface of the light guide plate 200, the light-in surface 10 is a side surface of the light guide plate 200, and the light source 300 is an LED;

[0190] designing the inverse prism sheet 100 according to the aforementioned design method 2000 or design method 3000 based on the light-out peak angle of the light guide plate 200;

[0191] manufacturing the designed inverse prism sheet 100, and configuring the first light-transmitting surface 1 of the inverse prism sheet 100 to face the light-out surface 11 of the light guide plate 200.

[0192] The application also provides a liquid crystal display device, which comprises the backlight module 1000 having the aforementioned configuration and a liquid crystal panel, and the liquid crystal panel is configured on the side of the inverse prism sheet 100 opposite to the light guide plate 200, i.e. on the side of the second light-transmitting surface 2.

Claims

1. An inverse prism sheet comprising a first light-transmissive surface on one side in a thickness direction, a plurality of prism units arranged in a second direction on the first light-transmissive surface, the prism units being formed in a shape of a triangular prism extending in a first direction perpendicular to the second direction, and comprising a first side surface having a first included angle with the first light-transmissive surface, and a second side surface on a front side of the second direction than the first side surface, the second side surface having a second included angle with the first light-transmissive surface, the first included angle and the second included angle respectively corresponding to two internal angles of a cross section of the triangular prism, characterized in that, the inverse prism sheet comprises a plurality of regions each of which is arranged in the second direction and in which the prism units are arranged, the first included angles corresponding to the respective prism units in the same region are equal to each other, the second included angles corresponding to the respective prism units in the same region are equal to each other, and for each of two adjacent regions, the second included angles corresponding to the respective prism units in one region are not equal to the second included angles corresponding to the respective prism units in the other region.

2. The inverse prism sheet according to claim 1, wherein for the plurality of regions, the second included angles corresponding to the respective prism units in each region are not equal to the second included angles corresponding to the respective prism units in all other regions.

3. The inverse prism sheet according to claim 1, wherein for the plurality of regions, the first included angles corresponding to the respective prism units in each region are equal to the first included angles corresponding to the respective prism units in all other regions.

4. The inverse prism sheet according to claim 1, wherein the first side surface and the second side surface have a third included angle, the third included angle respectively corresponding to the other internal angle of the cross section of the triangular prism; for the plurality of regions, the third included angles corresponding to the respective prism units in each region are equal to the third included angles corresponding to the respective prism units in all other regions.

5. The inverse prism sheet according to claim 1, wherein the inverse prism sheet further comprises a second light-transmissive surface on the other side in the thickness direction, the second light-transmissive surface being a complete flat surface.

6. The inverse prism sheet according to claim 1, wherein the plurality of prism units are continuously arranged in the second direction.

7. The inverse prism sheet according to claim 1, wherein the heights of the respective prism units in the same region are equal, and for the plurality of regions, the height of the prism units in each region is not equal to the height of the prism units in all other regions.

8. The inverse prism sheet according to any one of claims 1 to 7, characterized by the plurality of regions define all or part of the inverse prism sheet. 9.A backlight module comprising: the inverse prism sheet according to any one of claims 1 to 8; a light guide plate disposed on the first light-transmissive surface side of the inverse prism sheet, and having a light-incident surface and a light-emitting surface facing the first light-transmissive surface, wherein the light-emitting surface is a main surface of the light guide plate, and the light-incident surface is a side surface of the light guide plate; a light source disposed on the light-incident surface side of the light guide plate; the first direction is parallel to the light-incident surface and the light-emitting surface, and the second direction is perpendicular to the light-incident surface, and in the second direction, the first side surface is closer to the light-incident surface than the second side surface.

10. A liquid crystal display device, characterized by comprising: comprising: the backlight module according to claim 9; a liquid crystal panel disposed on the side of the inverse prism sheet opposite to the light guide plate.

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