Inverse prismatic lens, design and manufacturing method thereof, backlight module and manufacturing method thereof

Abstract

The invention relates to the technical field of display, in particular to an inverse prismatic lens, a design and manufacturing method thereof, a backlight module and a manufacturing method thereof. The prism units on the inverse prismatic lens have subarea gradually-changing angles, and the gradually-changing prism units enable the peak angle of emergent light to be gradually changed after the light emitted from the light guide plate is guided by the prism units on the inverse prismatic lens, and the emergent light basically points to a specific position, so that the display screen adopting the inverse prismatic lens has the advantages that the display effect is good, and the display effect is good. According to the invention, the brightness of a plurality of areas of the display screen at a specific observation position is close to the central brightness, and the directions with the strongest brightness of numerous parts also point to the specific observation position, so that a good peep-proof effect is achieved. Moreover, the relative included angles corresponding to the prism units in the same area are set to be equal to each other, and the included angles corresponding to the prism units in every adjacent areas are set to have the same angle difference, so that the inverse prism sheet can be easily designed and manufactured.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to an inverse prism sheet and a design and manufacturing method thereof, a backlight module and a manufacturing method thereof. Background Art

[0002] LCD (Liquid Crystal Display) screens are widely used in various fields, such as mobile phones, tablets, laptops, LCD TVs, car displays, etc. For different application fields and environments, users have different requirements for the viewing angle of the display screen. For example, for display screens with high anti-peeping requirements, the full field 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 light emitted by the display screen is generally required to be around 25° horizontally and around 15° vertically. Only in this way can a relatively narrow field angle be achieved to achieve an anti-peeping effect.

[0003] The anti-peep backlight module is usually composed of a light guide plate, a reflective sheet, and a reverse prism sheet. In the related art, the microstructure (prism unit) on the reverse prism sheet used to deflect light is fixed, and the light emitted from all parts of the backlight module is perpendicular to the light-emitting surface, that is, the emitted light is perpendicular to the display screen. For traditional backlight modules, when evaluating performance indicators (brightness and brightness uniformity), frontal measurement is often used, that is, the detector is perpendicular to the display screen. In actual applications, when the human eye observes the display screen, the position of the human eye is relatively fixed. Therefore, when observing the four sides and corners of the display screen, the brightness of the display screen will be much lower than the center brightness, especially when the field of view of the display screen is small. For example, for a 14-inch display, the distance between the human eye and the display is 500mm, and when it is located in the center of the display, the upper and lower edges of the display are about 20° to the human eye. At this time, it is equivalent to observing the display at an angle of 10°, and the brightness will be greatly reduced, especially when the FWHM is small, such as FWHM=14°, and the brightness has dropped to 30% of the normal field of view when observed at a position of 10°. Not only is the brightness reduced, but it is also not conducive to the anti-peeping effect of the surrounding area of ​​the display. Summary of the invention

[0004] In view of this, the present application provides a reverse prism sheet and a design and manufacturing method thereof, a backlight module and a manufacturing method thereof.

[0005] In a first aspect, a reverse prism sheet is provided, comprising a first light-transmitting surface and a second light-transmitting surface arranged opposite to each other in a thickness direction, and a plurality of prism units arranged on the first light-transmitting surface and arranged along a second direction, wherein the prism unit is formed into a triangular prism shape extending along a first direction perpendicular to the second direction, and comprises a first side surface and a second side surface closer to the front side of the second direction than the first side surface, the first side surface and the first light-transmitting surface have a first angle, the second side surface and the first light-transmitting surface have a second angle, and the first side surface and the second side surface have a third angle, and the first angle, the second angle and the third angle respectively correspond to three inner angles of a cross section of the triangular prism; The inverse prism sheet comprises a plurality of regions arranged along the second direction and each of which is provided with the prism units, the first angles corresponding to the prism units in the same region are equal to each other, and the second angles corresponding to the prism units in the same region are equal to each other; Each of the two adjacent regions is a front region close to the front side and a rear region close to the rear side in the first direction, and the inverse prism sheet is configured to satisfy one of the following conditions: The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference; The first angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed second angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference.

[0006] In some possible implementations, a plurality of imaginary straight lines perpendicular to the second light-transmitting surface and extending in the same imaginary plane pass through the plurality of regions one by one, thereby forming a plurality of imaginary intersection points intersecting the second light-transmitting surface and corresponding to the plurality of regions one by one, and the imaginary plane is perpendicular to the first direction; For each of the imaginary intersection points, an imaginary line connecting the imaginary intersection point and the same imaginary observation point has a fourth angle with the corresponding imaginary straight line, wherein the imaginary observation point is a point located in the imaginary plane and at a certain distance from the second light-transmitting surface of the inverse prism sheet on the second light-transmitting surface side; Each two adjacent fourth angles are respectively a front fourth angle on the front side and a rear fourth angle on the rear side in the second direction, and the front fourth angle and the rear fourth angle have a fixed fourth angle difference.

[0007] In some possible implementations, the inverse prism sheet is configured to satisfy one of the following: The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the first angle difference; The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the first angle difference; The first angles corresponding to each of the prism units are equal to each other, and the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by the second angle difference; The first angles corresponding to each of the prism units are equal to each other, and the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the second angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by a third angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the third angle difference.

[0008] In some possible implementations, in at least one area among the multiple areas, the corresponding imaginary straight line is located in the middle of the area along the second direction.

[0009] In a second aspect, a design method for an inverse prism sheet is proposed, wherein the inverse prism sheet includes a first light-transmitting surface and a second light-transmitting surface arranged opposite to each other in a thickness direction, and a plurality of prism units arranged on the first light-transmitting surface and arranged along a second direction, wherein the prism unit is formed into a triangular prism shape extending along a first direction perpendicular to the second direction, and includes a first side surface and a second side surface closer to the front side of the second direction than the first side surface, the first side surface and the first light-transmitting surface have a first angle, the second side surface and the first light-transmitting surface have a second angle, the first side surface and the second side surface have a third angle, the first angle, the second angle and the third angle respectively correspond to three internal angles of the cross section of the triangular prism, and the design method includes: Determine an imaginary observation point, wherein the imaginary observation point is a point located in an imaginary plane and at a certain distance from the second light-transmitting surface of the inverse prism sheet on the second light-transmitting surface side, and the imaginary plane is perpendicular to the first direction and passes through the inverse prism sheet; Determine a plurality of imaginary observation directions, wherein each of the imaginary observation directions extends within the imaginary plane and takes the imaginary observation point as a starting point and points to the second light-transmitting surface, so as to obtain a plurality of observed points spaced along the second direction on the second light-transmitting surface, and the angles between each two adjacent imaginary observation directions are equal; Dividing the inverse prism sheet into a plurality of regions corresponding to the positions of the plurality of observed points one by one and arranged along the second direction, wherein each two adjacent regions are a front region close to the front side and a rear region close to the rear side in the second direction; The prism unit is designed to satisfy: the first angles corresponding to the prism units in the same region are equal to each other, the second angles corresponding to the prism units in the same region are equal to each other, and one of the following is satisfied: Based on making the third angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle of the same prism unit equal, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction.

[0010] In some possible implementations, the design method includes designing the prism unit to satisfy one of the following: Based on making the third angles corresponding to each of the prism units equal to each other, and the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the third angles corresponding to each of the prism units equal to each other, and the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle corresponding to the same prism unit equal, the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by the third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle corresponding to the same prism unit equal to each other, the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction.

[0011] In some possible implementations, the multiple imaginary observation directions include a first imaginary direction and a second imaginary direction located at the extreme side, the multiple observed points include a first observed point corresponding to the first imaginary observation direction and a second observed point corresponding to the second imaginary direction, and the multiple regions include a first region corresponding to the first imaginary direction and a second region corresponding to the second imaginary direction; The method is based on making the third angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a first target angle of a first angle corresponding to the prism unit in the first area, wherein the first target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, Determine a second target angle of the first angle corresponding to the prism unit in the second area, wherein the second target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, Determine a quotient obtained by dividing a difference between the first target angle and the second target angle by a first natural number as the first angle difference, wherein the first natural number is a number that is 1 less than the total number of the plurality of regions; The method is based on making the first angles corresponding to each of the prism units equal to each other, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a third target angle of a third angle corresponding to the prism unit in the first area, wherein the third target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, determining a fourth target angle of the third angle corresponding to the prism unit in the second area, wherein the fourth target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, The quotient obtained by dividing the difference between the third target angle and the fourth target angle by the first natural number is determined as the second angle difference; Based on making the first angle and the second angle of the same prism unit equal, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a fifth target angle of the third angle corresponding to the prism unit in the first area, wherein the fifth target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, Determine a sixth target angle of the third angle corresponding to the prism unit in the second area, wherein the sixth target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, A quotient obtained by dividing the difference between the fifth target angle and the sixth target angle by the first natural number is determined as the third angle difference.

[0012] In some possible implementations, the light emission peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: The difference between the light emission peak angle of each observed point along the second direction and the corresponding observation angle does not exceed a specified value, wherein the observation angle is the angle between the corresponding imaginary observation direction and the imaginary straight line.

[0013] In a third aspect, a method for manufacturing a reverse prism sheet is provided, comprising: Design the inverse prism sheet according to the design method as described in the second aspect; The inverse prism sheet is manufactured.

[0014] In a fourth aspect, a backlight module is provided, comprising: The inverse prism sheet as described in the first aspect; A light guide plate, arranged on the first light-transmitting surface side of the inverse prism sheet, and having a light incident surface and a light emitting surface facing the first light-transmitting surface, wherein the light emitting surface is the main surface of the light guide plate, and the light incident surface is located on the side surface of the light guide plate; A light source, arranged 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, 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.

[0015] In a fifth aspect, a method for manufacturing the backlight module according to the fourth aspect is provided, comprising: Providing a light guide plate and a light source; Based on the light output peak angle of the light guide plate, the inverse prism sheet is designed according to the design method described in the second aspect; The inverse prism sheet is manufactured.

[0016] According to the inverse prism sheet provided by the present application, the prism units thereon have a zoned gradient angle. These gradient prism units make the peak angle of the light emitted from the light guide plate gradually change after being guided by the prism units on the inverse prism sheet, and basically point to a specific position. Therefore, the display screen using the inverse prism sheet can meet the requirement that at a specific observation position, the brightness of multiple areas of the display screen is close to the central brightness, and the direction with the strongest brightness in many parts also points to the specific observation position, which has a good anti-peeping effect. In addition, based on the fact that the relevant angles corresponding to each prism unit in the same area are set to be equal to each other, and the angles corresponding to the prism units in each adjacent area are set to have the same angle difference, it is helpful to easily design and manufacture such an inverse prism sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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, rather than limiting the present application.

[0018] Figure 1 1 is a side view schematic diagram of a backlight module provided in an embodiment of the present application, which schematically shows a part of the light path.

[0019] Figure 2 yes Figure 1 Schematic diagram of a portion of the inverse prism sheet.

[0020] Figure 3 It illustrates the relationship between the light output angle and the observation position at any point on the display screen.

[0021] Figure 4 It is a schematic diagram of the light path provided by the light guide plate for two light beams to be emitted through two adjacent areas of the inverse prism sheet respectively.

[0022] Figure 5 It is a schematic diagram of the reverse prism sheet design method provided in an embodiment of the present application.

[0023] Figure 6 It is a schematic diagram of the structure of the inverse prism sheet provided in an embodiment of the present application.

[0024] Figure 7 It is a flow chart of the design method of the inverse prism sheet provided in the embodiment of the present application.

[0025] Figure 8 It is the light output angle distribution of the central field of view of the backlight module in the second direction provided by the embodiment of the present application.

[0026] Fig. 9 For Figure 8 The data were intensity normalized.

[0027] Fig.10 This is a relationship curve between the light output angle of the backlight module and the second angle obtained after fitting the data in Table 2.

[0028] Fig.11 This is a relationship curve between the light output angle of the backlight module and the second angle obtained after fitting the data in Table 3.

[0029] Fig.12 This is a relationship curve between the light output angle of the backlight module and the third angle obtained after fitting the data in Table 4.

[0030] Fig.13 It is a flow chart of the design method of the inverse prism sheet provided in the embodiment of the present application.

[0031] Fig.14 It is a flow chart of the design method of the inverse prism sheet provided in the embodiment of the present application.

[0032] Fig.15 It is a flow chart of the design method of the inverse prism sheet provided in the embodiment of the present application.

[0033] Fig.16 It is a flow chart of the design method of the inverse prism sheet provided in the embodiment of the present application.

[0034] Description of reference numerals: DR1-first direction, DR2-second direction; 1000-backlight module; 2000, 3000 - Design methods; 100-inverse prism sheet, 200-light guide plate, 300-light source, 400-reflector sheet; PT-region, PT1-first region, PT2-second region; dl-the dividing line between two adjacent areas; 1- first light-transmitting surface; 2- second light-transmitting surface; 3-prism unit, 3a-first side surface, 3b-second side surface; α-first angle, β-second angle, ϕ-third angle; j-the fourth angle; δ - the angle between adjacent imaginary observation directions; 4-imaginary straight line, 5-imaginary plane, 6-imaginary observation point, 7-imaginary connecting line, 8-observed point, 8A-first observed point, 8B-second observed point; 9-imaginary observation direction, 9A-first imaginary observation direction, 9B-second imaginary observation direction; 10-light incident surface; 11-light emitting surface; 12-Underside. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the embodiment of the present application will be clearly and completely described below in conjunction with the drawings of the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all the embodiments. Based on the described embodiment of the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application. It can be understood that, in the absence of conflict, some technical means of the various embodiments described herein can be replaced or combined with each other.

[0036] In the description of this application, if there are terms such as "first", "second", etc., they are only used to distinguish the objects described and do not have any order or technical meaning. Therefore, an object defined as "first", "second", etc. may explicitly or implicitly include one or more of the objects, and, for example, the term "first element" itself does not mean the existence of the "second element", and the term "second element" itself does not mean the existence of the "first element". In addition, "one" or "a" and similar words do not indicate a quantity limitation, but rather indicate the existence of at least one, and "multiple" means not less than two.

[0037] In the description of the present application, the terms “including”, “having” 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.

[0038] In the description of the present application, reference to "one embodiment" or "some embodiments" etc. means that one or more embodiments of the present application include a particular feature, structure or characteristic described in conjunction with the embodiment. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. appearing in different places in the present specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways.

[0039] Figure 1 A backlight module 1000 provided in an embodiment of the present application is shown. The backlight module 1000 includes a light source 300 , a light guide plate 200 , a reflective sheet 400 and a reverse prism sheet 100 .

[0040] The light source 300 may be an LED (light-emitting diode), which can generate light directed toward the light incident surface 10 of the light guide plate 200 when driven by electricity.

[0041] The light guide plate 200 has a light incident surface 10, a light emitting surface 11 and a bottom surface 12. The light emitting surface 11 and the bottom surface 12 are arranged opposite to each other in the thickness direction of the light guide plate 200, so the light emitting surface 11 and the bottom surface 12 are respectively two main surfaces of the light guide plate 200. In addition, many light-guiding microstructures for guiding the direction of light, which are omitted from the figure, are formed on the bottom surface 12. The light incident surface 10 is an elongated side surface of the light guide plate 200, which connects the light emitting surface 11 and the bottom surface 12 on one side. In the present embodiment, the backlight module 1000 adopts a side-entry light source structure, and the aforementioned light source 300 is arranged on the light incident surface 10 side of the light guide plate 200.

[0042] For the convenience of explaining 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, the second direction DR2 is a direction perpendicular to the light incident surface 10 and is also a direction 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 rear 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 located at the lower side or the upper side of the display screen. 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.

[0043] In this embodiment, at the inverse prism sheet 100, the front side of the second direction DR2 is a direction away from the light incident surface 10 and the light source 300, and the rear side of the second direction DR2 is a direction close to the light incident surface 10 and the light source 300. In other embodiments, the second direction DR2 may also be reversed, so that at the inverse prism sheet 100, the front side of the second direction DR2 becomes a direction close to the light incident surface 10 and the light source 300, and the rear side of the second direction DR2 becomes a direction away from the light incident surface 10 and the light source 300.

[0044] As a well-known technology, based on the corresponding design of the structure of the light guide plate 200 (for example, the shape of the light-guiding microstructure on its bottom surface 12), the light emitting surface 11 of the light guide plate 200 can emit the light from the light source 300 (that is, the light received from the light incident surface 10) at a desired emission angle (that is, the peak light emission angle of the light guide plate 200, which is the angle formed by the normal of the light emitting surface 11 and the direction of the maximum light intensity in the light intensity distribution).

[0045] Please combine Figure 2The inverse prism sheet 100 is stacked and arranged on the light-emitting surface 11 side of the light guide plate 200, and includes a first light-transmitting surface 1 and a second light-transmitting surface 2 arranged opposite to each other in the thickness direction thereof, and a plurality of prism units 3 arranged on the first light-transmitting surface 1 and arranged along the second direction DR2, wherein the first light-transmitting surface 1 faces the light-emitting surface 11 of the light guide plate 200. The prism unit 3 is formed in a triangular prism shape extending along the first direction DR1, and includes a first side surface 3a and a second side surface 3b which is closer to the front side of the second direction DR2 than the first side surface 3a, the first side surface 3a and the first light-transmitting surface 1 have a first angle α, the second side surface 3b and the first light-transmitting surface 1 have a second angle β, and the first side surface 3a and the second side surface 3b have a third angle φ, and the first angle α, the second angle β and the third angle φ respectively correspond to the three internal angles of the cross section of the triangular prism. Therefore, in the second direction DR2, the first side surface 3a of the prism unit 3 is closer to the light incident 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 may be 10-50 μm, and may be the same or variable along the second direction DR2.

[0046] The reflective sheet 400 is stacked and arranged on the bottom surface 12 side of the light guide plate 200, that is, the reflective sheet 400 and the inverse prism sheet 100 are respectively arranged on opposite sides of the light guide plate 200 along the thickness direction. In this way, the light emitted by the light source 300 and directed to the light incident surface 10 is guided by the light guide plate 200 and most of it is directly emitted from the light exit surface 11 and enters the inverse prism sheet 100, and a small part is inevitably transmitted from the bottom surface 12 of the light guide plate 200. After being reflected by the reflective sheet 400, this part of the light transmitted from the bottom surface 12 of the light guide plate 200 returns to enter the light guide plate 200 from the bottom surface 12 again and is emitted 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 thereby the amount of light emitted from the second light-transmitting surface 2 of the inverse prism sheet 100 is increased, thereby improving the light efficiency of the backlight module 1000.

[0047] In other embodiments, the light transmitted 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 in order to save manufacturing costs and reduce the overall thickness of the module.

[0048] For a general display screen, in order to achieve a narrow frame display, the light source 300 is generally arranged at the lower side of the display screen (when placed vertically), that is, the bottom light is incident. Usually in this case, in the vertical direction (the second direction DR2), the backlight module 1000 has a narrower full field angle half maximum width FWHM, generally around 14~18°; and in the horizontal direction (the first direction DR1), the full field angle half maximum width FWHM is relatively wide, about 30°. Therefore, it is usually necessary to adjust the light output angle of the outgoing light in the second direction DR2 to obtain a narrow full field angle half maximum width FWHM in the second direction DR2.

[0049] See also Figure 3 According to the display range or display height Wi of the display screen in the vertical direction and the distance D between the observer and the display screen, the light output angle ωi at any point on the display screen along the vertical direction can be determined according to the following relationship (1).

[0050] For example, for a 16-inch 16:9 display screen, the required height of the backlight module is 218 mm. Therefore, in the vertical direction (second direction DR2), different observer positions and different directly viewed point positions require the light output angle distribution of the display screen to be as shown in Table 1 below.

[0051] Table 1: In Table 1 and the following Tables 2 to 4, when used to display distance, the negative sign "-" indicates a position below the center of the display screen; when used to indicate angle, the negative sign "-" indicates that the light output angle is in the counterclockwise direction, that is, the light output angle is in the counterclockwise direction of the normal to the output surface.

[0052] Figure 4 The schematic diagram of the optical path of two light rays emitted from the light emitting surface 11 of the light guide plate 200 at the light emitting peak angle, respectively emitted to two adjacent prism units 3 and output from different positions of the second light transmitting surface 2 of the inverse prism sheet 100 is shown. It can be seen that the light propagation law followed by this process satisfies the following relations (2) to (6): According to the above equations (2) to (6), the following equations (7) and (8) can be obtained: In the above-mentioned equations, n is the refractive index of the inverse prism sheet 100; θ is the peak light output angle of the light guide plate 200 along the second direction DR2 (referred to as the output angle of the light guide plate 200), which is generally 70°-80°; α corresponds to Figure 4 α in i and αi-1 , is the first angle between the first side surface 3a of the corresponding prism unit 3 and the first light-transmitting surface 1; β corresponds to Figure 4 β 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-transmitting surface 1; φ corresponds to Figure 4 ϕ in i and ϕ i-1 , is the third angle between the first side surface 3a and the second side surface 3b of the corresponding prism unit 3; ω corresponds to Figure 4 ω in i and ω i-1 , is the light output angle at the corresponding position of the inverse prism sheet 100, and is also the peak light output angle of the inverse prism sheet 100 and the backlight module 1000 at the corresponding position.

[0053] 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 output angle (peak light output angle) of the inverse prism sheet 100 and the backlight module 1000 is related to the first angle α, the second angle β and the third angle ϕ corresponding to the prism unit 3. Since the sum of the first angle α, the second angle β and the third angle ϕ is 180°, it can be more simply said that the peak light output angle ω of the backlight module 1000 is related to any two of the first angle α, the second angle β and the third angle ϕ corresponding to the prism unit 3.

[0054] Therefore, in combination with the aforementioned relationship (1) and relationship (7) or (8), the ideal structure of the prism unit 3 on the inverse prism sheet 100 in the backlight module 1000 corresponding to the display screen at this time, that is, the ideal first angle α, the second angle β and the third angle ϕ, can be calculated by reverse calculation based on the target value of ω.

[0055] Based on the above discussion, the present invention provides a design method 2000 of the inverse prism sheet 100. The designed inverse prism sheet 100 can be applied to similar Figure 1 In the backlight module 1000, the light emitting surface 11 of the light guide plate 200 is used to receive the light emitted from the light emitting surface 11, and guide the light to be emitted from the second light-transmitting surface 2 to supply the liquid crystal panel (not shown). Figure 7 Combined with Figure 5 , the design method 200 includes the following steps S701 to S704: S701, determine an imaginary observation point 6, wherein the imaginary observation point 6 is located in an imaginary plane 5 and is at a certain distance from the second light-transmitting surface 2 of the inverse prism sheet 100, and the imaginary plane 5 is perpendicular to the second direction DR2 and passes through the inverse prism sheet 100.

[0056] The imaginary observation point 6 may be a position point where the inverse prism sheet 100 is applied to a similar Figure 1 In the case of the backlight module 1000 and further the display screen, for the best observation point of the image on the display screen, when the observer's eyes observe the display screen at the imaginary observation point 6, the intensity of light emitted to the observer's eyes from each position of the second light-transmitting surface 2 of the inverse prism sheet 100 is close to the central intensity of the emitted light at that position (for example, more than 85% of the central intensity). Therefore, the observer can view a very clear display screen image from the imaginary observation point 6.

[0057] In some embodiments, the imaginary observation point 6 is directly opposite to the center of the inverse prism sheet 100 and the display screen, that is, the orthographic projection of the imaginary observation point 6 on the second light-transmitting surface 2 is exactly at the center of the second light-transmitting surface 2. In other embodiments, the orthographic projection of the imaginary observation point 6 on the second light-transmitting surface 2 deviates from the center of the second light-transmitting surface 2, such as, Figure 5 In some other embodiments, the imaginary observation point 6 is completely separated from the second light-transmitting surface 2 in the second direction DR2, so that the line connecting any point on the second light-transmitting surface 2 and the imaginary observation point 6 is not perpendicular to the second light-transmitting surface 2, or in other words, the imaginary observation point 6 has no orthographic projection on the second light-transmitting surface 2 with a limited area. For example, the imaginary observation point 6 is a point below the lower side of the inverse prism sheet 100 and the display screen, or a point above the upper side of the inverse prism sheet 100 and the display screen.

[0058] exist Figure 5 In the figure, the imaginary plane 5 is the paper surface.

[0059] S702, determining a plurality of imaginary observation directions 9, wherein each imaginary observation direction 9 points to the second light-transmitting surface 2 with the imaginary observation point 6 as a starting point, 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, and the plurality of observed points 8 each define 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 has a fourth angle j with the imaginary straight line 4, and it can be understood that the fourth angle j is within the imaginary plane 5.

[0060] S703, dividing the inverse prism sheet 100 into a plurality of regions PT corresponding one-to-one to the positions of the plurality of observed points 8 and arranged continuously along the second direction DR2, wherein each two adjacent regions PT are respectively a front side region on the front side and a rear side region on the rear side in the second direction DR2.

[0061] Please review Figure 4 , showing the adjacent front side area and rear side area. Figure 4 In the example above, use the marker PTi Indicates the front side area and uses the symbol PT i-1 represents the rear side area, and the front side area PT i and rear side area PT i-1 exist Figure 6 This is also indicated in the diagram; using the symbol α i , β i , ϕ i In order to indicate the front side area PT i The first angle α, the second angle β and the third angle φ corresponding to a prism unit 3 are marked with α i-1 , β i-1 , ϕ i-1 Respectively represent the rear side area PT i-1 The first angle α, the second angle β and the third angle ϕ corresponding to a prism unit 3; the mark ω is used i Indicates that the light passes through the front side area PT i When the light is emitted from the second light-transmitting surface 2 of the inverse prism sheet 100 through one of the prism units 3, the light emission angle along the second direction DR2 is denoted by ω. i-1 Indicates that the light passes through the rear side area PT i-1 When the light is emitted from the second light-transmitting surface 2 of the inverse prism sheet 100 through a prism unit 3, the light output angle along the second direction DR2 is Figure 4 In the case where the two light rays emitted from the light guide plate 200 are the light rays corresponding to the light output peak angle of the light guide plate 200, ω i and ω i-1 They respectively correspond to the light output peak angles at two different positions of the inverse prism sheet 100 .

[0062] exist Figure 5 and Figure 6 In the embodiment, the divided regions PT define the entire inverse prism sheet 100. In other embodiments, the divided regions PT may define only a portion of the inverse prism sheet 100, for example, only a middle portion of the inverse prism sheet 100 or a portion close to the light source 300.

[0063] S704, designing the prism unit 3 such that the first angles α corresponding to the prism units 3 in the same region PT are equal to each other, the second angles β corresponding to the prism units 3 in the same region PT are equal to each other, and the first angles α and the second angles β corresponding to the prism units 3 in the same region PT satisfy the following relationship (9): In this relationship, α is the first angle, β is the second angle, j is the fourth 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 output peak angle of the light guide plate 200 along the second direction DR2.

[0064] It can be understood that, since 180°=α+β+ϕ, the first angle α and the second angle β corresponding to each prism unit 3 in the same area PT satisfy the relationship (9), which is equivalent to the second angle β and the third angle ϕ corresponding to each prism unit 3 in the same area PT satisfying the following relationship (10): Obviously, the aforementioned imaginary straight line 4 is also the normal line of the second light-transmitting surface 2 of the inverse prism sheet 100 at the corresponding observed point 8 .

[0065] Figure 8 The light output angle distribution of the central field of view of the backlight module 1000 in the second direction DR2 (vertical direction) is provided as an example. Fig. 9 For Figure 8 The result after the data is normalized. It can be seen that in order to control the light intensity to more than 95% of the center intensity, the angle offset of the light peak can be + / -2°, that is, the light peak angle deviates from the center within + / - 2°. When observed within this angle, its intensity is reduced within the range of 95%. This can be used as a tolerance to control the light angle of the backlight module 1000.

[0066] Of course, if the client requires a higher intensity, the intensity reduction must be controlled within the range of 97%, and the peak angle of light output deviates from the center within + / - 1°. If the client requires a lower intensity, the intensity reduction must be within the range of 90%, and the peak angle of light output deviates from the center within + / - 3°. If the client requires a further reduction, the intensity reduction must be within the range of 85%, and the peak angle of light output deviates from the center within + / - 4°.

[0067] Therefore, the backlight module 1000, especially the inverse prism sheet 100, can be divided into regions according to the needs of the client, especially according to the specific tolerance or tolerance range of the light output angle, and the relevant angles corresponding to each prism unit 3 in the same region PT are set to be the same, and the relevant angles corresponding to the prism units 3 in different regions PT are designed to be different based on the positions of different region PTs, which not only facilitates the manufacture of the designed inverse prism sheet 100, but also meets the needs of the client. Specifically, the inverse prism sheet 100 can be divided into a plurality of regions PT along the second direction DR2 according to the format and the observation distance, and preferably, for each adjacent two region PT, the angle between each adjacent two observation directions is the same for the observer, that is, in step S702, the angle δ between each adjacent two observation directions is set to be the same, for example, δ is 2°, or 1°, or 3°. It can be understood that the higher the specific tolerance or tolerance range of the light output angle required by the client, the smaller the δ value is set in the design method 2000, and the closer the intensity of light emitted from various positions of the inverse prism sheet 100 and the display screen to the observer's eyes is to the central intensity of the light emitted from that position.

[0068] In order to make it easier to manufacture the designed inverse prism sheet 100, in step S702, the third angles φ corresponding to the multiple regions PT can be set to be equal to each other, and only the first angle α and the second angle β in different regions PT can be changed. For example, the third angle φ (vertex angle) corresponding to the prism unit 3 in each region PT is fixed to 64°, and only the first angle α and the second angle β in different regions PT are adjusted according to the relationship (9). In addition, the first angles α corresponding to the multiple regions PT can also be set to be equal to each other, and only the second angle β and the third angle φ in different regions PT can be changed.

[0069] After the inverse prism sheet 100 designed by the design method 2000 is applied to the backlight module 1000 and a further display screen, based on the differentiated design of at least two of the first angle α, the second angle β and the third angle ϕ corresponding to each prism unit 3, it can provide customized output light with different target angles for different parts of the backlight module 1000 and the display screen, and has both a narrow ideal viewing angle distribution and extremely high brightness gain. The brightness peak angles of different parts of the display screen are roughly toward the observer at the imaginary observation point 6, with excellent brightness uniformity and excellent anti-peeping effect.

[0070] And in Figure 5In each of the remaining six regions PT, except for the two regions PT at the end, the corresponding observed point 8 (also the imaginary intersection described later) and the corresponding imaginary straight line 4 are located exactly in the middle of the region PT along the second direction DR2. With such a design, it is easy to make the light output peak angles of each part of the region PT along the second direction DR2 close to the observation angle from the imaginary observation point 6.

[0071] It must be noted that, in step S704 of the design method 2000, when the first angle α and the second angle β are designed to satisfy the above relationship (9), a certain deviation (for example, not exceeding 2%) is allowed between α and β.

[0072] It can also be understood that the inverse prism sheet 100 designed by the design method 2000 includes a plurality of regions PT arranged continuously along the second direction DR2 and each of which is provided with a prism unit 3, the first angles α corresponding to the prism units 3 in the same region PT are equal to each other, and the second angles β corresponding to the prism units 3 in the same region PT are equal to each other. Moreover, with the inverse prism sheet 100 as a reference, it is possible to find an imaginary observation point 6 and a plurality of imaginary observation directions 9 that make the first angle α and the second angle β satisfy the aforementioned relational expression (9). The imaginary observation point 6 is a point located in the imaginary plane 5 and at a certain distance from the second light-transmitting surface 2 on the second light-transmitting surface 2 of the inverse prism sheet 100. The imaginary plane 5 is a plane perpendicular to the second direction DR2 and passing through the inverse prism sheet 100. Each of the multiple imaginary observation directions 9 points to the second light-transmitting surface 2 with the imaginary observation point 6 as the starting point, and extends in the imaginary plane 5, thereby forming multiple observed points 8 spaced in sequence along the second direction DR2 in the second light-transmitting surface 2. Preferably, the angle δ between each two adjacent imaginary observation directions 9 is equal. In the above relationship, j is the fourth angle j between the corresponding imaginary straight line 4 and the imaginary observation direction 9.

[0073] As mentioned above, the first angle α and the second angle β satisfying the aforementioned relationship (7) is equivalent to the second angle β and the third angle φ satisfying the relationship (10). In addition, for other features of the inverse prism sheet 100 designed by the design method 2000, those skilled in the art can determine based on the introduction of the design method 2000 above, so they are not described in detail.

[0074] In addition, the inventors have the following three findings.

[0075] Finding 1: The third angle ϕ corresponding to the prism unit 3 is set to be fixed, such as ϕ=68° or 70°, and the second angle β changes, so the first angle α also changes. According to the relationship (8), since the light output peak angle θ of the light guide plate 200 is a fixed value, such as θ=75°, and the refractive index of the inverse prism sheet 100 is a fixed value, such as n=1.56, in this case, it can be calculated that when the third angle ϕ is fixed to 68° and 70° respectively, the light output peak angle ω of the backlight module 1000 (and the inverse prism sheet 100) changes with the second angle β as shown in Table 2 below.

[0076] Table 2: Changes of the light output peak angle ω of the backlight module 1000 with the second angle β when the third angle φ is φ=68° and 70° Fig.10 The curve of the relationship between the light output angle ω and the second angle β of the backlight module 1000 when the third angle φ is 68° and 70° is obtained by fitting the data in Table 2. It can be seen that when the third angle φ is fixed, the peak light output angle of the backlight module 1000 shifts by about 2.53° for every 1° change in the second angle β, and the second angle β has a roughly linear relationship with the peak light output angle of the backlight module 1000.

[0077] Although Table 2 only shows the cases where ϕ is 68° and 70°, the inventors have found that when ϕ is selected as other angle values, the second angle β and the peak light output angle of the backlight module 1000 also have a roughly linear relationship.

[0078] Since the first angle α and the second angle β correspond to the 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, Fig.10 and the following Fig.11 and Fig.12 In the figure, the first angle α is also called the base angle α, the second angle β is called the base angle β, and the third angle ϕ is called the vertex angle ϕ.

[0079] Finding 2: The first angle α corresponding to the prism unit 3 is set to be fixed, such as α=50° or 56°, and the second angle β changes, so the third angle φ also changes. According to the relationship (7), since the light output peak angle θ of the light guide plate 200 is a fixed value, such as θ=75°, and the refractive index of the inverse prism sheet 100 is a fixed value, such as n=1.56, in this case, it can be calculated that when the first angle α is fixed to 50° and 56° respectively, the light output peak angle ω of the backlight module 1000 changes with the second angle β as shown in Table 3 below.

[0080] Table 3: Changes of the light output peak angle ω of the backlight module 1000 with the second angle β when the first angle α is 50° and 56° respectively Fig.11 The curve of the relationship between the light output angle ω and the second angle β of the backlight module 1000 when the first angle α is 50° and 56° is obtained by fitting the data in Table 3. It can be seen that when the first angle α is fixed, the peak light output angle of the backlight module 1000 shifts by about 3.14° for every 1° change in the second angle β, and the second angle β has a roughly linear relationship with the peak light output angle of the backlight module 1000.

[0081] Although Table 3 only shows the cases where α is 50° and 56°, the inventors have found that when α is selected as other angle values, the second angle β and the peak light output angle of the backlight module 1000 also have a substantially linear relationship.

[0082] Finding 3: The first angle α and the second angle β corresponding to the same prism unit 3 are set to be equal, that is, the cross section of each prism unit 3 is an isosceles triangle, and the third angle ϕ changes. 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 light output angle ω of the backlight module 1000 can be calculated as the change of the third angle ϕ is shown in Table 4 below.

[0083] Table 4: When the first angle α and the second angle β corresponding to the same prism unit 3 are equal, the change of the light output peak angle ω of the backlight module 1000 with the third angle ϕ Fig.12 This is a curve of the relationship between the light output angle ω and the third angle ϕ of the backlight module 1000 when the first angle α and the second angle β are equal, obtained by fitting the data in Table 4. It can be seen that for every 1° change in the third angle ϕ, the peak light output angle of the backlight module 1000 shifts by about 1.87°, and the third angle ϕ and the peak light output angle of the backlight module 1000 have a roughly linear relationship.

[0084] Based on the above three findings of the inventor, the present invention provides another design method 3000 of the inverse prism sheet 100. The designed inverse prism sheet 100 can be applied to similar Figure 1 In the backlight module 1000, the light emitting surface 11 side of the light guide plate 200 receives the light emitted from the light emitting surface 11, guides the light and then emits it from the second light-transmitting surface 2 to supply the liquid crystal panel. Fig.13 And also combined Figure 5, the design method 3000 includes the following steps S131 to S134: S131 , determining an imaginary observation point 6 , wherein the imaginary observation point 6 is located in an imaginary plane 5 and is at a certain distance from the second light-transmitting surface 2 on the second light-transmitting surface 2 of the inverse prism sheet 100 , and the imaginary plane 5 is perpendicular to the first direction DR1 and passes through the inverse prism sheet 100 .

[0085] Similar to the design method 2000, in the design method 3000, the imaginary observation point 6 may also be a position point where the inverse prism sheet 100 is applied to the Figure 1 In the case of the backlight module 1000 and further the display screen shown, the best observation point for the image on the display screen. When the observer's eyes observe the display screen at the imaginary observation point 6, the intensity of the light emitted from each position of the second light-transmitting surface 2 of the inverse prism sheet 100 to the observer's eyes is close to the central intensity of the light emitted from the position (for example, more than 85% of the central intensity), so the observer can see a very clear display screen image from the imaginary observation point 6.

[0086] In some embodiments, the imaginary observation point 6 is directly opposite to the center of the inverse prism sheet 100 and the display screen, that is, the orthographic projection of the imaginary observation point 6 on the second light-transmitting surface 2 is exactly at the center of the second light-transmitting surface 2. In other embodiments, the orthographic projection of the imaginary observation point 6 on the second light-transmitting surface 2 (such as Figure 5 The imaginary observation point 6 when j=0 corresponds to the orthographic projection) deviates from the center position of the second light-transmitting surface 2. In some other embodiments, the imaginary observation point 6 is completely separated from the second light-transmitting surface 2 in the second direction DR2, so that the line connecting any point on the second light-transmitting surface 2 and the imaginary observation point 6 is not perpendicular to the second light-transmitting surface 2, or in other words, the imaginary observation point 6 has no orthographic projection on the second light-transmitting surface 2 with a limited area. For example, the imaginary 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.

[0087] exist Figure 5 In the figure, the imaginary plane 5 is the paper surface.

[0088] S132, determining a plurality of imaginary observation directions 9, wherein each imaginary observation direction 9 extends within the imaginary plane 5 and points to the second light-transmitting surface 2 with the imaginary observation point 6 as a starting point, thereby obtaining a plurality of observed points 8 separated along the second direction DR2 on the second light-transmitting surface 2, and the angle δ between each two adjacent imaginary observation directions 9 is equal. The corresponding imaginary observation direction 9 has a fourth angle j with the imaginary straight line 4, and it can be understood that the fourth angle j and the angle δ are both within the imaginary plane 5.

[0089] S133, dividing the inverse prism sheet 100 into a plurality of regions PT corresponding one-to-one to the positions of a plurality of observed points 8 and arranged continuously along the second direction DR2, wherein each two adjacent regions PT are respectively a front side region PT on the front side and a rear side region PT on the rear side in the second direction DR2.

[0090] Please see again Figure 4 , showing the adjacent front side area and rear side area. Figure 4 In the example above, use the marker PT i Indicates the front side area and uses the symbol PT i-1 represents the rear side area, and the front side area PT i and rear side area PT i-1 exist Figure 6 This is also indicated in the diagram; using the symbol α i , β i , ϕ i In order to indicate the front side area PT i The first angle α, the second angle β and the third angle φ corresponding to a prism unit 3 are marked with α i-1 , β i-1 , ϕ i-1 Respectively represent the rear side area PT i-1 The first angle α, the second angle β and the third angle ϕ corresponding to a prism unit 3; the mark ω is used i Indicates that the light passes through the front side area PT i When the light is emitted from the second light-transmitting surface 2 of the inverse prism sheet 100 through one of the prism units 3, the light emission angle along the second direction DR2 is denoted by ω. i-1 Indicates that the light passes through the rear side area PT i-1 When the light is emitted from the second light-transmitting surface 2 of the inverse prism sheet 100 through a prism unit 3, the light output angle along the second direction DR2 is Figure 4 In the case where the two light rays emitted from the light guide plate 200 are the light rays corresponding to the light output peak angle of the light guide plate 200, ω i and ω i-1 They respectively correspond to the light output peak angles at two different positions of the inverse prism sheet 100 .

[0091] S134, the inverse prism sheet 100 is designed to satisfy: the first angles α corresponding to the prism units 3 in the same area PT are equal to each other, the second angles β corresponding to the prism units 3 in the same area PT are equal to each other (therefore, the third angles ϕ corresponding to the prism units 3 in the same area PT are also equal to each other), and one of the following ①, ② and ③ is satisfied: ① Based on making the third angle φ corresponding to each prism unit 3 equal to each other, and the second angle β corresponding to the front side area PT and the second angle β corresponding to the rear side area PT having a fixed first angle difference, the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ② Based on making the first angle α corresponding to each prism unit 3 equal to each other, and the third angle ϕ corresponding to the front side area PT and the third angle ϕ corresponding to the rear side area PT having a fixed second angle difference, the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ③ Based on making the first angle α and the second angle β of the same prism unit 3 equal, and the third angle ϕ corresponding to the front side area PT and the third angle ϕ corresponding to the rear side area PT have a fixed third angle difference, the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9.

[0092] Here, the peak light emission angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9, which includes not only the case where the peak emission light of the observed point 8 completely coincides with the imaginary observation direction 9, but also the case where the angle between the peak emission light of the observed point 8 and the imaginary observation direction 9 is within a specified range (for example, 0-5°). That is, the peak light emission angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9, which can be specifically: the difference between the peak light emission angle of each observed point 8 along the second direction DR2 and the corresponding observation angle does not exceed a specified value of, for example, 5°, wherein the observation angle is the angle between the corresponding imaginary observation direction 9 and the imaginary straight line 4, corresponding to Figure 5 The fourth angle j in .

[0093] It can be understood that the theoretical basis of the above schemes ①, ② and ③ corresponds to the inventor's above discovery 1, discovery 2 and discovery 3 respectively. In step S132, the angle δ between each two adjacent imaginary observation directions 9 is set to be equal to each other in order to make the target light output angles corresponding to any two adjacent areas PT divided in step S133 have a fixed (i.e., the same) angle difference, and then in step S134, based on the inventor's above three discoveries, the first angle α, the second angle β and the third angle φ corresponding to each prism unit 3 in the same area PT can be set to be the same, and one of the three angles corresponding to different areas PT is set to a fixed value, and the other two angles are set to variable values ​​and the relevant angles corresponding to each two adjacent areas PT differ by the same value. As a result, while ensuring that a particularly clear display screen image can be observed from the imaginary observation point 6, it also helps to easily manufacture the designed inverse prism sheet 100.

[0094] In such Figure 5 In some embodiments shown, ①, ② and ③ mentioned in step S134 of the design method 3000 may be specifically: ① Based on making the third angle φ corresponding to each prism unit 3 equal to each other, and the second angle β corresponding to the front side area PT is greater than the second angle β corresponding to the rear side area PT by a first angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ② Based on making the first angle α corresponding to each prism unit 3 equal to each other, the second angle β corresponding to the front side area PT is greater than the second angle β corresponding to the rear side area PT by a second angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ③ Based on making the first angle α and the second angle β corresponding to the same prism unit 3 equal to each other, the third angle ϕ corresponding to the front side area PT is smaller than the third angle ϕ corresponding to the rear side area PT by a third angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9.

[0095] It is understandable that if the positive and negative directions of the second direction DR2 are reversed, then ①, ② and ③ mentioned in step S134 of the design method 3000 may be specifically: ① Based on making the third angle φ corresponding to each prism unit 3 equal to each other, and the second angle β corresponding to the front side area PT is smaller than the second angle β corresponding to the rear side area PT by a first angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ② Based on making the first angle α corresponding to each prism unit 3 equal to each other, the second angle β corresponding to the front side area PT is smaller than the second angle β corresponding to the rear side area PT by a second angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9; ③ Based on making the first angle α and the second angle β corresponding to the same prism unit 3 equal to each other, the third angle ϕ corresponding to the front side area PT is larger than the third angle ϕ corresponding to the rear side area PT by a third angle difference, so that the light output peak angle of each observed point 8 along the second direction DR2 corresponds to the corresponding imaginary observation direction 9.

[0096] It is understandable that, according to the data in Table 2, when the refractive index of the target inverse prism sheet 100 designed by the design method 3000 is 1.56, and the light output peak angle of the light guide plate 200 matched therewith is 75°, the angle between any two adjacent imaginary observation directions 9 in step S132 can be configured to be 2.35°, and the first angle difference in solution ① can be configured to be 1°. In this case, Figure 5 There are 8 second angles β of different sizes corresponding to the 8 regions PT, which are an arithmetic progression with a tolerance of 1° in the second direction DR2.

[0097] According to the data in the aforementioned Table 3, when the refractive index of the target inverse prism sheet 100 of the design method 3000 is 1.56 and the peak light output angle of the light guide plate 200 matched therewith is 75°, the angle between any two adjacent imaginary observation directions 9 in step S132 can be configured to be 3.14°, and the second angle difference in scheme ② can be configured to be 1°.

[0098] According to the data in the aforementioned Table 4, when the refractive index of the target inverse prism sheet 100 designed using the design method 3000 is 1.56, and the peak light output angle of the light guide plate 200 matched therewith is 75°, the angle between any two adjacent imaginary observation directions 9 in step S132 can be configured to be 1.87°, and the first angle difference in scheme ③ can be configured to be 1°.

[0099] like Figure 5 As shown, in step S132, the determined multiple imaginary observation directions 9 include a first imaginary direction and a second imaginary direction located at the extreme side, the multiple observed points 8 include a first observed point 8A corresponding to the first imaginary observation direction 9A and a second observed point 8B corresponding to the second imaginary direction, and the multiple regions PT include a first region PT1 corresponding to the first imaginary direction and a second region PT2 corresponding to the second imaginary direction.

[0100] Based on this, if solution ① is adopted in step S134, the solution ① may specifically include: Fig.14 Steps S141 to S143 shown: S141, determining a first target angle of a first angle α corresponding to the prism unit 3 in the first area PT1, wherein the first target angle of the first angle α is an angle that makes the peak angle of light emitted from the first observed point 8A along the second direction DR2 correspond to the first imaginary observation direction 9A.

[0101] S142, determining a second target angle of the first angle α corresponding to the prism unit 3 in the second area PT2, wherein the second target angle is an angle that makes the light output peak angle of the second observed point 8B along the second direction DR2 correspond to the second imaginary observation direction 9B.

[0102] In some implementations, the first target angle and the second target angle may be determined based on the aforementioned equation (8).

[0103] S143: Determine a quotient obtained by dividing the difference between the first target angle and the second target angle by a first natural number as a first angle difference, wherein the first natural number is a number that is 1 less than the total number of the plurality of regions PT.

[0104] For example, in Figure 5 In the example, the total number of the plurality of regions PT is 8, and the corresponding first natural number is 7.

[0105] If solution ② is adopted in step S134, the solution ② may specifically include: Fig.15 Steps S151 to S153 shown: S151, determining a third target angle of the third angle φ corresponding to the prism unit 3 in the first area PT1, wherein the third target angle is an angle that makes the peak angle of light emitted from the first observed point 8A along the second direction DR2 correspond to the first imaginary observation direction 9A.

[0106] S152, determining a fourth target angle of the third angle corresponding to the prism unit 3 in the second area PT2, wherein the fourth target angle is an angle that makes the light output peak angle of the second observed point 8B along the second direction DR2 correspond to the second imaginary observation direction 9B.

[0107] In some implementations, the third target angle and the fourth target angle may be determined based on the aforementioned equation (7).

[0108] S153 , dividing the difference between the third target angle and the fourth target angle by the aforementioned first natural number (ie, a number that is 1 less than the total number of the plurality of regions PT) to obtain a quotient as a second angle difference.

[0109] If solution ③ is adopted in step S134, the solution ③ may specifically include: Fig.16 Steps S161 to S163 shown: S161, determining a fifth target angle of the third angle φ corresponding to the prism unit 3 in the first area PT1, wherein the fifth target angle is an angle that makes the peak light output angle of the first observed point 8A along the second direction DR2 correspond to the first imaginary observation direction 9A.

[0110] S162, determining a sixth target angle of the third angle corresponding to the prism unit 3 in the second area PT2, wherein the sixth target angle is an angle that makes the light output peak angle of the second observed point 8B along the second direction DR2 correspond to the second imaginary observation direction 9B.

[0111] In some implementations, the fifth target angle and the sixth target angle may be determined based on the aforementioned equation (7).

[0112] S163, dividing the difference between the fifth target angle and the sixth target angle by the aforementioned first natural number to obtain a quotient, and determining the quotient as the third angle difference.

[0113] It can be understood that the inverse prism sheet 100 designed by the design method 3000 includes a plurality of regions PT continuously arranged along the second direction DR2 and each of which is provided with a prism unit 3, the first angles α corresponding to the prism units 3 in the same region PT are equal to each other, and the second angles β corresponding to the prism units 3 in the same region PT are equal to each other, and has one of the following three characteristics: The third angles φ corresponding to each prism unit 3 are equal to each other, and the second angle β corresponding to the front side area and the second angle β corresponding to the rear side area have a fixed first angle difference; The first angles α corresponding to each prism unit 3 are equal to each other, and the second angle β corresponding to the front side area and the second angle β corresponding to the rear side area have a fixed second angle difference; The first angle α and the second angle β corresponding to the same prism unit 3 are equal, and the third angle ϕ corresponding to the front side area and the third angle ϕ corresponding to the rear side area have a fixed third angle difference.

[0114] Moreover, with the inverse prism sheet 100 as a reference, a plurality of imaginary straight lines 4 can be found: the plurality of imaginary straight lines 4 are perpendicular to the second light-transmitting surface 2 and extend in the same imaginary plane 5 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, an imaginary connecting line 7 (corresponding to the aforementioned imaginary observation direction 9) between the imaginary intersection point and the same imaginary observation point 6 has a fourth angle j with the corresponding imaginary straight line 4, wherein the imaginary observation point 6 is a point located in the imaginary plane 5 and at 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 two adjacent fourth angles j are respectively referred to as the front fourth angle j on the front side and the rear fourth angle j on the rear side in the second direction DR2, the front fourth angle j and the rear fourth angle j have a fixed fourth angle difference. Figure 5 , the fourth angle difference is equal to δ.

[0115] And in Figure 5In each of the remaining six regions PT, except for the first region PT1 and the second region PT2 at the extreme ends, the corresponding imaginary intersection and imaginary straight line 4 are located exactly in the middle of the region PT along the second direction DR2. With such a design, it is easy to make the light output peak angles of each part of the region PT along the second direction DR2 close to the fourth angle j.

[0116] For other features of the inverse prism sheet 100 designed by the design method 3000 , those skilled in the art can determine them based on the above introduction to the design method 3000 , which will not be elaborated here.

[0117] In addition, referring to the introduction to the design method 3000 in the previous text, in the design method 2000, in order to simplify the method, the inverse prism sheet 100 can also be designed as follows: in multiple areas PT, the first angles α corresponding to each prism unit 3 are equal to each other, or the third angles φ corresponding to each prism unit 3 are equal to each other, or the first angle α and the second angle β corresponding to the same prism unit 3 are equal to each other.

[0118] Each of the regions PT may be a rectangular region and extends throughout the inverse prism sheet 100 in the first direction DR1.

[0119] The present application also provides a method for manufacturing the inverse prism sheet 100, comprising: Design the inverse prism sheet 100 according to the aforementioned design method 2000 or design method 3000; The designed inverse prism sheet 100 is manufactured.

[0120] Please combine Figure 1 The embodiment of the present application also provides a method for manufacturing a backlight module 1000, comprising: A light guide plate 200 and a light source 300 are provided, wherein the light guide plate 200 has a light incident surface 10 and a light emitting surface 11, the light emitting surface 11 is the main surface of the light guide plate 200, the light incident surface 10 is located on the side surface of the light guide plate 200, and the light source 300 is an LED; Based on the light output peak angle of the light guide plate 200 , the inverse prism sheet 100 is designed according to the design method 2000 or the design method 3000 ; The designed inverse prism sheet 100 is manufactured, and the first light-transmitting surface 1 of the inverse prism sheet 100 is configured to face the light-emitting surface 11 of the light guide plate 200 .

Claims

1. An inverse prism sheet, comprising a first light-transmitting surface and a second light-transmitting surface arranged opposite to each other in a thickness direction, and a plurality of prism units arranged on the first light-transmitting surface and arranged along a second direction, wherein the prism unit is formed into a triangular prism shape extending along a first direction perpendicular to the second direction, and comprises a first side surface and a second side surface closer to the front side of the second direction than the first side surface, the first side surface and the first light-transmitting surface have a first angle, the second side surface and the first light-transmitting surface have a second angle, the first side surface and the second side surface have a third angle, the first angle, the second angle and the third angle respectively correspond to three internal angles of a cross section of the triangular prism, characterized in that: The inverse prism sheet comprises a plurality of regions arranged along the second direction and each of which is provided with the prism units, the first angles corresponding to the prism units in the same region are equal to each other, and the second angles corresponding to the prism units in the same region are equal to each other; Each of the two adjacent regions is a front region close to the front side and a rear region close to the rear side in the first direction, and the inverse prism sheet is configured to satisfy one of the following conditions: The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference; The first angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed second angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference.

2. The inverse prism sheet according to claim 1, characterized in that: A plurality of imaginary straight lines perpendicular to the second light-transmitting surface and extending in the same imaginary plane pass through the plurality of regions one by one, thereby forming a plurality of imaginary intersection points intersecting the second light-transmitting surface and corresponding to the plurality of regions one by one, and the imaginary plane is perpendicular to the first direction; For each of the imaginary intersection points, an imaginary line connecting the imaginary intersection point and the same imaginary observation point has a fourth angle with the corresponding imaginary straight line, wherein the imaginary observation point is a point located in the imaginary plane and at a certain distance from the second light-transmitting surface of the inverse prism sheet on the second light-transmitting surface side; Each two adjacent fourth angles are respectively a front fourth angle on the front side and a rear fourth angle on the rear side in the second direction, and the front fourth angle and the rear fourth angle have a fixed fourth angle difference.

3. The inverse prism sheet according to claim 2, characterized in that: The inverse prism sheet is configured to satisfy one of the following: The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the first angle difference; The third angles corresponding to each of the prism units are equal to each other, and the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the first angle difference; The first angles corresponding to each of the prism units are equal to each other, and the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by the second angle difference; The first angles corresponding to each of the prism units are equal to each other, and the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the second angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by a third angle difference; The first angle and the second angle corresponding to the same prism unit are equal to each other, and the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the third angle difference.

4. The inverse prism sheet according to any one of claims 1 to 3, characterized in that: In at least one area among the plurality of areas, the corresponding imaginary straight line is located in the middle of the area along the second direction.

5. A method for designing an inverse prism sheet, the inverse prism sheet comprising a first light-transmitting surface and a second light-transmitting surface arranged opposite to each other in a thickness direction, and a plurality of prism units arranged on the first light-transmitting surface and arranged along a second direction, the prism unit being formed into a triangular prism shape extending along a first direction perpendicular to the second direction, and comprising a first side surface and a second side surface closer to the front side of the second direction than the first side surface, the first side surface and the first light-transmitting surface have a first angle, the second side surface and the first light-transmitting surface have a second angle, the first side surface and the second side surface have a third angle, the first angle, the second angle and the third angle respectively correspond to the three inner angles of the cross section of the triangular prism, characterized in that: The design method comprises: Determine an imaginary observation point, wherein the imaginary observation point is a point located in an imaginary plane and at a certain distance from the second light-transmitting surface of the inverse prism sheet on the second light-transmitting surface side, and the imaginary plane is perpendicular to the first direction and passes through the inverse prism sheet; Determine a plurality of imaginary observation directions, wherein each of the imaginary observation directions extends within the imaginary plane and takes the imaginary observation point as a starting point and points to the second light-transmitting surface, so as to obtain a plurality of observed points spaced along the second direction on the second light-transmitting surface, and the angles between each two adjacent imaginary observation directions are equal; Dividing the inverse prism sheet into a plurality of regions corresponding to the positions of the plurality of observed points one by one and arranged along the second direction, wherein each two adjacent regions are a front region close to the front side and a rear region close to the rear side in the second direction; The prism unit is designed to satisfy: the first angles corresponding to the prism units in the same region are equal to each other, the second angles corresponding to the prism units in the same region are equal to each other, and one of the following is satisfied: Based on making the third angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle of the same prism unit equal, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction.

6. The design method according to claim 5, characterized in that: The design method includes designing the prism unit to satisfy one of the following: Based on making the third angles corresponding to each of the prism units equal to each other, and the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the third angles corresponding to each of the prism units equal to each other, and the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area is greater than the second angle corresponding to the rear side area by the second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area is smaller than the second angle corresponding to the rear side area by the second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle corresponding to the same prism unit equal, the third angle corresponding to the front side area is greater than the third angle corresponding to the rear side area by the third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction; Based on making the first angle and the second angle corresponding to the same prism unit equal to each other, the third angle corresponding to the front side area is smaller than the third angle corresponding to the rear side area by the third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction.

7. The design method according to claim 5 or 6, characterized in that: The multiple imaginary observation directions include a first imaginary direction and a second imaginary direction located at the extreme end, the multiple observed points include a first observed point corresponding to the first imaginary observation direction and a second observed point corresponding to the second imaginary direction, and the multiple regions include a first region corresponding to the first imaginary direction and a second region corresponding to the second imaginary direction; The method is based on making the third angles corresponding to each of the prism units equal to each other, the second angle corresponding to the front side area and the second angle corresponding to the rear side area have a fixed first angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a first target angle of a first angle corresponding to the prism unit in the first area, wherein the first target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, Determine a second target angle of the first angle corresponding to the prism unit in the second area, wherein the second target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, Determine a quotient obtained by dividing a difference between the first target angle and the second target angle by a first natural number as the first angle difference, wherein the first natural number is a number that is 1 less than the total number of the plurality of regions; The method is based on making the first angles corresponding to each of the prism units equal to each other, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed second angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a third target angle of a third angle corresponding to the prism unit in the first area, wherein the third target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, determining a fourth target angle of the third angle corresponding to the prism unit in the second area, wherein the fourth target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, The quotient obtained by dividing the difference between the third target angle and the fourth target angle by the first natural number is determined as the second angle difference; Based on making the first angle and the second angle of the same prism unit equal, the third angle corresponding to the front side area and the third angle corresponding to the rear side area have a fixed third angle difference, so that the light output peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: Determine a fifth target angle of the third angle corresponding to the prism unit in the first area, wherein the fifth target angle is an angle that makes the light output peak angle of the first observed point along the second direction correspond to the first imaginary observation direction, Determine a sixth target angle of the third angle corresponding to the prism unit in the second area, wherein the sixth target angle is an angle that makes the light output peak angle of the second observed point along the second direction correspond to the second imaginary observation direction, A quotient obtained by dividing the difference between the fifth target angle and the sixth target angle by the first natural number is determined as the third angle difference.

8. The design method according to claim 5 or 6, characterized in that: The light emission peak angle of each observed point along the second direction corresponds to the corresponding imaginary observation direction, including: The difference between the light emission peak angle of each observed point along the second direction and the corresponding observation angle does not exceed a specified value, wherein the observation angle is the angle between the corresponding imaginary observation direction and the imaginary straight line.

9. A method for manufacturing an inverse prism sheet, characterized in that: include: Design the inverse prism sheet according to the design method according to any one of claims 6 to 8; The inverse prism sheet is manufactured.

10. A backlight module, comprising: The inverse prism sheet as claimed in any one of claims 1 to 5; A light guide plate, arranged on the first light-transmitting surface side of the inverse prism sheet, and having a light incident surface and a light emitting surface facing the first light-transmitting surface, wherein the light emitting surface is the main surface of the light guide plate, and the light incident surface is located on the side surface of the light guide plate; A light source, arranged 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, 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.

11. A method for manufacturing the backlight module according to claim 10, characterized in that: include: Providing a light guide plate and a light source; Based on the light output peak angle of the light guide plate, the inverse prism sheet is designed according to the design method described in any one of claims 6 to 8; The inverse prism sheet is manufactured.

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