Optical film structure, backlight module and display device

Abstract

The application provides an optical film structure, a backlight module and a display device, comprising a first prism and a second prism, the first prism has a plurality of first prism monomers in a triangular prism shape arranged in parallel and equidistantly along a first direction, and the ridge peaks of the first prism monomers are arranged along a second direction perpendicular to the first direction; the second prism is arranged on the side of the ridge peaks of the first prism, has a plurality of second prism monomers, the light-out surface of the second prism monomers is the four side surfaces of a straight quadrangular pyramid, the light-in surface is a plane close to the first prism, the apex of the straight quadrangular pyramid is arranged towards or away from the first prism, the four light-out surfaces far away from the bottom edge of the apex enclose a rhombus shape, the rhombus shape comprises a first edge and a second edge intersecting with each other, the two edges are respectively arranged on the two sides of the ridge peak of the first prism, the second prism monomers are arranged in an array along the extension direction of the first edge and the second edge, the extension direction of the first edge is arranged at a first included angle with the second direction, the extension direction of the second edge is arranged at a second included angle with the second direction, and the two included angles are equal.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to an optical film structure, a backlight module, and a display device. Background Technology

[0002] With the development of LCD panels, the demand for low-power, high-brightness modules is becoming increasingly widespread. To increase module brightness without increasing power consumption, DBEF (Double Brightness Enhancement Film) is typically used. However, this solution is costly. Therefore, people have tried using double prisms to improve module brightness. Due to the light-focusing characteristics of prisms, although using a double prism solution can improve backlight brightness, it results in screen asymmetry. Utility Model Content

[0003] The purpose of this application is to provide an optical film structure, a backlight module, and a display device that achieves increased brightness while avoiding screen asymmetry. The specific technical solution is as follows:

[0004] The first aspect of this application provides an optical film structure, comprising:

[0005] The first prism has a plurality of first prism units that are parallel and equidistantly arranged along a first direction. Each first prism unit is a triangular prism, and the apex of the first prism is arranged along a second direction, which is perpendicular to the second direction.

[0006] The second prism, located on one side of the peak of the first prism, comprises several individual second prism units. The light-emitting surfaces of each second prism unit are the four lateral faces of a right square pyramid, and the light-incident surfaces are planes close to the first prism. The vertices of the right square pyramid are either facing or away from the first prism. The base edges of the four light-emitting surfaces away from the vertices form a rhombus shape, which includes intersecting first and second edges. The first and second edges are located on either side of the peak of the first prism. The individual second prism units are arranged in an array along the extension directions of the first and second edges. The extension direction of the first edge forms a first angle with the second direction, and the extension direction of the second edge forms a second angle with the second direction. The first and second angles are equal.

[0007] In some embodiments, the second prism unit has a structure with an inverted right square pyramidal groove.

[0008] In some embodiments, the second prism unit is an upright right square pyramid structure.

[0009] In some embodiments, the range of the first included angle and the second included angle is 40°-60°.

[0010] In some embodiments, the dihedral angle between adjacent light-emitting surfaces of adjacent second prism units ranges from 90° to 120°.

[0011] In some embodiments, the first included angle and the second included angle of the second prism unit located in the central region of the second prism are greater than the first included angle and the second included angle of the second prism unit located in the edge region of the second prism; and / or, the dihedral angle between adjacent sides of adjacent second prism units located in the central region of the second prism is greater than the dihedral angle between adjacent sides of adjacent second prism units located in the edge region of the second prism.

[0012] In some embodiments, when the dihedral angle between adjacent sides of adjacent second prism units located in the central region of the second prism is greater than the dihedral angle between adjacent sides of adjacent second prism units located in the edge region of the second prism: the interval between the vertices of adjacent second prism units is equal, and the height of the second prism unit located in the central region of the second prism is less than the height of the second prism unit located in the edge region of the second prism.

[0013] In some embodiments, the second prism units of the second prism are continuously distributed along the extension direction of the first edge and the extension direction of the second edge.

[0014] In some embodiments, the cross-section of the first prism unit along the thickness direction is an isosceles triangle.

[0015] In some embodiments, the first prism units of the first prism are continuously distributed along a first direction.

[0016] In some embodiments, the refractive index of the first prism is 1.48-1.63, and the refractive index of the second prism is 1.48-1.63.

[0017] In some embodiments, the optical film structure further includes a diffusion film, the first prism is disposed on the diffusion film, the prism peak of the first prism is away from the diffusion film, and the second prism is disposed on the side of the first prism away from the diffusion film.

[0018] A second aspect of this application provides a backlight module, including the optical film structure described above.

[0019] A third aspect of this application provides a display device including the backlight module described above.

[0020] Beneficial effects of the embodiments in this application:

[0021] The optical film structure, backlight module, and display device provided in this application embodiment include a first prism and a second prism. The first prism is a single strip-shaped triangular prism, and the second prism has four light-emitting surfaces arranged in the shape of a right square pyramid. This results in the lines connecting the peaks of the second prism having two different directions: one parallel to one of the base edges of the right square pyramid, and the other parallel to another edge. The lines connecting the peaks in the two different directions intersect. Although a single peak is also tilted relative to the peak of the first prism, the second prism as a whole has peaks in two directions, and these peaks are symmetrical about the peak of the first prism, as shown in the figure. Therefore, the final light pattern is also symmetrical. Thus, the image formed after passing through the double prism is symmetrical, which can improve brightness while also addressing image quality issues and optimizing the viewing angle-to-brightness ratio.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0024] Figure 1 This is a schematic diagram of the structure of the double prism provided in an embodiment of this application;

[0025] Figure 2 This is a schematic diagram of the structure of the first prism provided in an embodiment of this application;

[0026] Figure 3 A partial isometric schematic diagram of the second prism provided in one embodiment of this application;

[0027] Figure 4a for Figure 3 Top view of the second prism;

[0028] Figure 4b for Figure 3 Top view of the second prism;

[0029] Figure 5 A top view of the second prism provided in an embodiment of this application in another embodiment;

[0030] Figure 6 A schematic diagram of the full-view light pattern using a traditional double prism;

[0031] Figure 7This is a schematic diagram of the full-view light pattern using the double prism of this application;

[0032] Figure 8a A schematic diagram of the full-view light pattern of a biprism where the second prism is a cross prism when the included angle is 60°;

[0033] Figure 8b A schematic diagram of the full-view light pattern of a biprism where the second prism is a cross prism when the included angle is 45°;

[0034] Figure 9a Schematic diagrams of the horizontal light patterns of the cross prism when the included angle is 60° and 45°;

[0035] Figure 9b Schematic diagrams of the vertical light patterns of the cross prism when the included angle is 60° and 45°;

[0036] Figure 10a A schematic diagram of the full-view light pattern of a biprism where the second prism is a cross prism when the included angle is 45°;

[0037] Figure 10b A schematic diagram of the full-view light pattern of a pyramid-shaped prism when the included angle is 45°;

[0038] Figure 11a A schematic diagram of the horizontal light patterns of the cross prism and the pyramid prism when the included angle is 45°.

[0039] Figure 11b This is a schematic diagram of the perpendicular light patterns of the intersecting prism and the pyramidal prism when the included angle is 45°.

[0040] Figure 12a Schematic diagrams of horizontal light patterns of cross prisms with different dihedral angles when the included angle is 45°;

[0041] Figure 12b This is a schematic diagram of the vertical light patterns of intersecting prisms with different dihedral angles when the included angle is 45°.

[0042] Figure 13a Schematic diagrams of horizontal light patterns of cross prisms with different included angles when the dihedral angle is 90°;

[0043] Figure 13b This is a schematic diagram of the vertical light patterns of a cross prism with different included angles when the dihedral angle is 90°;

[0044] Figure 14 This is a schematic diagram showing the brightness distribution of the backlight module and display module.

[0045] Figure 15 A schematic diagram illustrating the change in the included angle of the cross prisms used to improve the darkening of the module edges;

[0046] Figure 16A schematic diagram showing the brightness gradient distribution and corresponding dihedral angle changes of the light-emitting surfaces of the backlight module and display module;

[0047] Figure 17 This is a partial schematic diagram of a backlight module provided in one embodiment of the present application.

[0048] The attached figures are labeled as follows:

[0049] First prism 1; First substrate 11; First prism unit 12; First prism peak 13;

[0050] Second prism 2; Second substrate 21; Second prism unit 22; Vertex 221; First edge 222; Second edge 223; Light-emitting surface 224; Peak of the second prism 23; First included angle α; Second included angle β; Dihedral angle θ; Central region A; Edge region B; Diffuse film 3; Light guide plate 4; Light source 5; First direction X; Second direction Y. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0052] To address the image asymmetry issue caused by using a dual-prism solution in existing technologies to enhance module brightness, this application provides an optical film structure, such as... Figure 1 As shown, it includes a first prism 1 and a second prism 2. Figure 2 As shown, the first prism 1 includes several first prism units 12 arranged parallel to and equidistantly along the first direction X. Each first prism unit 12 is a triangular prism, and the peaks 13 of the first prisms are arranged along the second direction Y. The second prism 2 is located on one side of the peaks 13 of the first prisms, as shown... Figure 3 , Figure 4a , Figure 4b and Figure 5As shown, the second prism 2 comprises several individual second prisms. The light-emitting surfaces 224 of each second prism are the four lateral faces of a right square pyramid. The light-incident surfaces of each second prism are planes closer to the first prism 1. The vertices 221 of the right square pyramid are positioned facing or away from the first prism 1. The base edges of the four light-emitting surfaces 224 away from the vertices 221 form a rhombus shape. The rhombus includes intersecting first edges 222 and second edges 223. The first edges 222 and second edges 223 are located on either side of the peak 13 of the first prism. The individual second prisms are arranged in an array along the extension directions of the first edges 222 and second edges 223. The extension direction of the first edges 222 forms a first angle α with the second direction Y, and the extension direction of the second edges 223 forms a second angle β with the second direction Y. The first angle α and the second angle β are equal.

[0053] In this embodiment, the first prism unit 12 is a strip-shaped triangular prism, and the light-emitting surface 224 of the second prism unit 22 has four surfaces arranged in the shape of a right square pyramid. This results in the lines connecting the peaks 23 of the second prism having two different directions: one parallel to one of the base edges of the right square pyramid, and the other parallel to another edge. The lines connecting the peaks in the two different directions intersect. Although each individual peak is also inclined relative to the peak of the first prism unit 12, the second prism 2 as a whole has peaks in two directions, and the peaks in the two directions are symmetrical about the peak of the first prism unit 12. Figure 4a , Figure 5 As shown, the final light pattern is also symmetrical. Therefore, the image formed after passing through the double prism is symmetrical, which can improve brightness while addressing image issues and optimizing the brightness ratio at a specific viewing angle. Thus, using the aforementioned optical film structure in the backlight module and display device can balance brightness and viewing angle requirements, achieving better brightness gain while meeting the brightness ratio requirements at a specific viewing angle. It should be noted that a right square pyramid refers to a square pyramid whose vertex 221's projection onto the base is located at the center of the base.

[0054] In some examples, such as Figure 2 As shown, the first prism 1 may include a first substrate 11 and a first prism layer located on one side of the first substrate 11. The first prism layer may include a plurality of first prism units 12, and the prism peaks 13 of the first prisms are far away from the first substrate 11. Specifically, the first prism layer may be formed by: firstly, coating the first substrate 11 with UV (ultraviolet) curable adhesive or acrylic resin; secondly, using a pre-cast microstructure roller transfer mold, replicating the microprism structure to the resin layer by photocuring or thermocuring to form periodically arranged first prism units 12.

[0055] In some examples, such as Figure 3As shown, the second prism 2 may include a second substrate 21 and a second prism layer. The second prism layer may include a plurality of second prism units 22. The second substrate 21 is disposed close to the first prism 1. The molding process of the second prism layer is the same as that of the first prism layer.

[0056] The thickness of the first substrate 11 and the second substrate 21 can be in the range of 180μm-400μm, and the thickness of the first prism unit 12 and the second prism unit 22 can be in the range of 25μm-55μm. The thickness of the first prism unit 12 and the second prism unit 22 refers to the distance between the highest point and the bottom plane.

[0057] The first substrate 11 and the second substrate 21 can be made of polyethylene terephthalate (PET). PET material has good transparency and the greatest toughness among thermoplastics, which can ensure the structural integrity of the prism sheet. In addition, PET material has good electrical insulation properties and is less affected by temperature, which can ensure the stability of the optical performance of the prism sheet.

[0058] like Figure 6 , Figure 7 As shown, Figure 6 To achieve a full-view light pattern using a traditional double prism, Figure 7 To utilize the full-view light pattern of the double prism of this application, the light pattern of a traditional double prism is obviously distorted and tilted, while the light pattern of the double prism structure of this application is symmetrical. Therefore, the use of a traditional double prism will lead to unevenness in the displayed image due to the distortion and tilt of the light pattern, while the use of the double prism structure of this application can avoid this phenomenon.

[0059] It should be noted that, Figure 6 , Figure 7 In the diagram, 90V to -90V represents the horizontal angle from 90° to -90°, and 90H to -90H represents the vertical angle from 90° to -90°. The center of the diagram has the highest brightness, followed by the light gray areas radiating outwards, and then the darker areas near the circular edge. The brightness of the edge area decreases as the color deepens. (The following...) Figure 8a , Figure 8b , Figure 10a , Figure 10b In the context of 90V to -90V and 90H to -90H, the terms represent the same meaning, and the relationship between brightness and color changes is similar to... Figure 6 , Figure 7 same.

[0060] Understandable, such as Figure 3 , Figure 4a , Figure 4bAs shown, when the vertex 221 of the right square pyramid faces the first prism 1, the second prism unit can be considered as having a right square pyramid groove structure, or it can be imagined as a first prism unit 12 like the first prism 1. The shape formed by the intersection of two first prism units 12 in different directions is called a cross prism. Figure 5 As shown, when the vertex 221 of the right square pyramid is away from the first prism 1, the second prism unit takes the shape of an upright pyramid, and the vertex 221 of the second prism unit is the peak 23 of the second prism. At this time, the second prism 2 can be called a pyramid-shaped prism.

[0061] As a feasible embodiment, the range of the first included angle α and the second included angle β can be 40°-60°. By changing the range of the first included angle α and the second included angle β, the center brightness and the degree of divergence of the light pattern can be changed. Taking the second prism 2 as a cross prism as an example, when the included angle (i.e., the first included angle α and the second included angle β) is 60° and the included angle (i.e., the first included angle α and the second included angle β) is 45°, the full-view light patterns are as follows: Figure 8a , Figure 8b As shown, the light pattern from a horizontal perspective is as follows: Figure 9a As shown in the diagram, the gray lines represent curves with an angle of 45°, and the black lines represent curves with an angle of 60°. The light pattern from a vertical viewing angle is as follows: Figure 9b As shown in the figure, the gray lines represent curves with an angle of 45°, and the black lines represent curves with an angle of 60°. Figure 9a , Figure 9b The horizontal axis represents the angle change in degrees, and the vertical axis represents the brightness change in nits. The results show that both 45° and 60° angles meet the testing requirements for the brightness ratio at a specific viewing angle, and the image is symmetrical. At 60°, the center brightness is low, but the light pattern is more diffused; at 45°, the brightness is high, but the brightness is relatively concentrated at the frontal viewing angle. Therefore, the range of the first angle α and the second angle β can be adjusted according to actual needs, i.e., adjusting the intersection angle of the first edge 222 and the second edge 223 of the second prism 2.

[0062] Through practical verification, the dual-prism architecture using cross-prisms presents a more symmetrical and uniform image. Furthermore, the brightness ratio at specific viewing angles is around 1.42, significantly lower than the upper limit of 1.73. These specific viewing angles are approximately 17° and 40° horizontally, and 7° and 21° vertically. Here, 1.73 represents the upper limit for the brightness ratio between the horizontal viewing angles of 17° and 40°, and the upper limit for the brightness ratio between the vertical viewing angles of 7° and 21°. The closer the ratio is to 1, the better the image uniformity.

[0063] Keeping the ranges of the first included angle α and the second included angle β unchanged, the cross prism is replaced with a pyramidal prism. A model is built with an included angle of 45°, and the two are compared. The full-view light pattern of the cross prism is as follows: Figure 10a As shown, the full-view light pattern of the pyramid-shaped prism is as follows: Figure 10b As shown, the horizontal viewing angle light patterns of the cross prism and the pyramid prism when the included angle is 45° are as follows: Figure 11a As shown in the diagram, the black lines represent pyramidal prisms, and the gray lines represent intersecting prisms. The vertical viewing angle light pattern is as follows: Figure 11b As shown in the diagram, the black lines represent pyramid-shaped prisms, and the gray lines represent intersecting prisms. Figure 11a , Figure 11b The horizontal axis represents angle change in degrees, and the vertical axis represents brightness change in nits. It can be seen that upgrading the cross prism to a pyramid prism does not significantly change the brightness near a specific test angle; however, the pyramid prism has higher brightness at its center and a more uniform light pattern across the entire viewing angle. Actual test results show an approximately 5% gain in brightness compared to the cross prism.

[0064] In some embodiments, the dihedral angle θ between adjacent sides of adjacent second prism units ranges from 90° to 120°, for example, it can be 90°, 95°, 100°, 105°, 110°, 115°, or 120°. When the ranges of the first included angle α and the second included angle β are fixed, as the degree of the dihedral angle θ between adjacent sides of adjacent second prism units increases, the center brightness of both the horizontal and vertical light patterns decreases.

[0065] For example, when the angles of the first included angle α and the second included angle β are 45°, the light pattern data of the dihedral angle θ between adjacent sides of adjacent second prism units at different degrees (90°-120°) are simulated and analyzed. Figure 12a , Figure 12b As shown, Figure 12a , Figure 12b The horizontal axis represents angular change in degrees, and the vertical axis represents luminance change in nits. Figure 12a The diagram shows the horizontal beam patterns of a cross prism with different dihedral angles θ. As can be seen from the figure, with the increase of the dihedral angle θ, not only does the central brightness increase (i.e., the peak value near 0° decreases successively), but the secondary peak value, symmetrical about the peak value, also gradually approaches 40°. Figure 12b The figure shows the vertical light patterns of a cross prism with different dihedral angles θ. As can be seen from the figure, the distribution curve of the vertical light pattern becomes shorter and wider as the dihedral angle θ increases. Combined with the attached figure, it can be concluded that when the dihedral angle θ is not less than 90°, the larger the dihedral angle θ, the lower the brightness of the module when viewed directly, but the brightness at a specific viewing angle will be better than horizontal.

[0066] Also based on cross-prism analysis, with a dihedral angle θ of 90 degrees, the light pattern data obtained from analyzing the first included angle α and the second included angle β with different degrees (e.g., 40°-50°) are as follows: Figure 13a , Figure 13b As shown, Figure 13a , Figure 13b The horizontal axis represents angle change in degrees, and the vertical axis represents brightness change in nits. From the above light patterns, it can be seen that the center brightness of the backlight reaches its maximum when both the first angle α and the second angle β are 45 degrees. As the angles α and β increase or decrease, the center brightness decreases. Figure 13a The horizontal beam patterns of the cross prism with different first angle α and second angle β are shown. From the perspective of the horizontal beam patterns, when the first angle α and the second angle β increase sequentially from 45 degrees, the small convex hulls of the secondary peaks on both sides of the central peak gradually move towards 40 degrees. When the first angle α and the second angle β decrease sequentially from 45 degrees, the small convex hulls of the secondary peaks on both sides of the central peak gradually move towards the central region A. Therefore, it can be concluded that the cross prism has the highest backlight brightness when the first angle α and the second angle β are both 45 degrees. Furthermore, when the first angle α and the second angle β are greater than 45 degrees, the prism's brightness ratio at a specific viewing angle will be better.

[0067] Therefore, based on the above conclusions, by reasonably designing the range of the first included angle α and the second included angle β, as well as the degree of the dihedral angle θ, it can be used to improve the uniformity of screen brightness of the backlight module and the display module.

[0068] In some embodiments, the dihedral angle θ between adjacent sides of adjacent second prism units remains unchanged, and the first included angle α and the second included angle β of the second prism unit located in the central region A of the second prism 2 are greater than the first included angle α and the second included angle β of the second prism unit located in the edge region B of the second prism 2.

[0069] In this embodiment, since the backlight module and display module generally have higher brightness in the central area A and lower brightness in the edge area B, a larger first angle α and a smaller angle β are used in the central area A with higher brightness, while a smaller first angle α and a smaller angle β are used in the edge area B with lower brightness. The angles of the first angle α and the second angle β used in the edge area B with lower brightness are approximately 45°, which can improve the problem of poor brightness uniformity between the backlight module and the display module.

[0070] Specifically, such as Figure 14 As shown in the diagram, the brightness distribution of the backlight module and display module is as follows: Figure 14As shown, the areas with lower brightness are distributed on both sides and are arc-shaped, bulging outwards from the center of the image. Within this arc-shaped area, the brightness gradually decreases as the distance from the center of the image increases. The solution of this application is to change the range of the first included angle α and the second included angle β within this arc-shaped area. Specifically, the rule of change is that as the distance from the center of the image increases, the first included angle α and the second included angle β gradually decrease (approaching 45 degrees).

[0071] For example, such as Figure 15 As shown, in this embodiment... Figure 14 The two dark waist positions shown are such that the first included angle α and the second included angle β are equal to 45°, the central area A is equal to 60°, and the boundary position is uniformly transitioned, achieving high brightness gain in the two dark waist positions and low brightness gain in the central area. This makes the overall brightness uniformity of the backlight module and display module higher, reducing the phenomenon of dark waists. Similarly, the central area also has a better brightness ratio level for a specific viewing angle.

[0072] In other embodiments, the degrees of the first included angle α and the second included angle β of the second prism unit remain unchanged, and the dihedral angle θ between adjacent sides of adjacent second prism units located in the central region A of the second prism 2 is greater than the dihedral angle θ between adjacent sides of adjacent second prism units located in the edge region B of the second prism 2.

[0073] In this embodiment, since the backlight module and the display module generally have higher brightness in the central area A and lower brightness in the edge area B, a dihedral angle θ with a larger degree is used in the central area A with higher brightness, and a dihedral angle θ with a smaller degree is used in the edge area B with lower brightness. For example, the degree of the dihedral angle θ used in the edge area B with lower brightness is about 90°, which can improve the problem of poor brightness uniformity of the backlight module and the display module.

[0074] For example, such as Figure 16 As shown, by setting the dihedral angle θ to 90° at the two darkened positions and gradually transitioning to 110° towards the middle area, the brightness of the darkened positions increases, while the brightness of the central area A decreases. This achieves brightness adjustment of the backlight module and the display module, resulting in higher uniformity of screen brightness. At the same time, using a larger dihedral angle θ in the middle area also allows the backlight module and the display module to perform better in terms of brightness ratio at specific viewing angles.

[0075] In some other embodiments, the first included angle α and the second included angle β of the second prism unit located in the central region A of the second prism 2, as well as the dihedral angle θ between adjacent sides of adjacent second prism units located in the central region A of the second prism 2, are all variable. That is, the first included angle α and the second included angle β of the second prism unit located in the central region A of the second prism 2 are greater than the first included angle α and the second included angle β of the second prism unit located in the edge region B of the second prism 2; at the same time, the dihedral angle θ between adjacent sides of adjacent second prism units located in the central region A of the second prism 2 is greater than the dihedral angle θ between adjacent sides of adjacent second prism units located in the edge region B of the second prism 2.

[0076] By setting the first included angle α and the second included angle β of the central region A and the edge region B of the second prism 2 to be different, and also setting the dihedral angle θ between adjacent sides of adjacent second prism units in the central region A and the edge region B of the second prism 2 to be different, the brightness difference between the central region A and the edge region B can be improved from two different angles, thereby achieving a wider range of brightness adjustment and making the uniformity of the backlight module and the display module better.

[0077] When the dihedral angle θ between adjacent sides of adjacent second prism units located in the central region A of the second prism 2 is greater than the dihedral angle θ between adjacent sides of adjacent second prism units located in the edge region B of the second prism 2: the interval between vertices 221 of adjacent second prism units is equal, and the height of the second prism unit located in the central region A of the second prism 2 is less than the height of the second prism unit located in the edge region B of the second prism 2.

[0078] In this embodiment, the spacing between adjacent second prism units remains unchanged, so that light can be refracted uniformly when passing through the second prism 2. By changing the height of the second prism unit, the dihedral angle θ is changed, thereby changing the convergence of light after refraction by the second prism unit, thus changing the light pattern in the horizontal and vertical directions after passing through the second prism 2, thereby improving the brightness uniformity of the backlight module and the display module.

[0079] In a preferred embodiment, the second prism units of the second prism 2 are continuously distributed along the extension directions of the first edge 222 and the second edge 223. That is, the spacing between the second prism units of the second prism 2 is zero. This allows more second prism units to be arranged on the second prism 2, so that the light emitted from the first prism 1 can be refracted by the second prism 2, thereby adjusting the emission angle of the light and improving the brightness uniformity of the backlight module and the display module.

[0080] In the above embodiments, the cross-section of the first prism unit 12 along the thickness direction is an isosceles triangle. When the incident light enters from the bottom surface of the first prism unit 12, that is, the base of the isosceles triangle, the light refracted by the two sides can be evenly distributed on both sides of the prism peak, so that the light distribution is more uniform after passing through the second prism 2.

[0081] Optionally, the vertex angle of the isosceles triangle can be in the range of 80°-100°. The brightness gain effect is best when the vertex angle of the isosceles triangle is 90°. Therefore, to ensure brightness gain, the vertex angle can be as close to 90° as possible.

[0082] In some embodiments, on the first substrate 11, the first prism units 12 of the first prism 1 are continuously distributed along the first direction X. The spacing between the first prism units 12 is zero, so that all light rays incident from the bottom surface can be refracted by the first prism, avoiding the light rays from shooting out perpendicularly, which would result in a large difference in brightness between the positive viewing angle and other viewing angles.

[0083] Understandably, the first base 11 is generally a rectangle or a square, and the first direction X and the second direction Y can be parallel to the side length of the rectangle or square, or they can form a certain angle.

[0084] The refractive index of the first prism 1 is 1.48-1.63, and the refractive index of the second prism 2 is 1.48-1.63. The refractive indices of the first prism 1 and the second prism 2 can be selected according to actual needs. Generally speaking, a higher refractive index will result in a better brightness gain.

[0085] In some embodiments, such as Figure 17 As shown, the optical film structure also includes a diffusion film 3. A first prism 1 is disposed on the diffusion film 3, with the prism peak 13 of the first prism being away from the diffusion film 3. A second prism 2 is disposed on the side of the first prism 1 away from the diffusion film 3. The light source 5 can be, for example, a point light source or a line light source. The emitted light is converted into a surface light source after passing through the light guide plate 4, and then diffused by the diffusion film 3 to obtain a uniformly distributed surface light source. The brightness is further enhanced by the first prism 1 and the second prism 2, ultimately obtaining a surface light source with sufficient brightness and uniform distribution.

[0086] A second aspect of this application provides a backlight module, wherein the backlight module has the optical film structure described above, such as... Figure 17The diagram illustrates a side-lit backlight module as an example. The light emitted from the light source 5 of the backlight module first passes through the light guide plate 4 and then enters the diffusion film 3 above the light guide plate 4, making the light sufficiently uniform. The brightness of the emitted light at the front and side viewing angles is adjusted through a double-prism structure, ensuring that the light pattern of the backlight module satisfies image symmetry while providing better brightness gain. Specifically, the backlight module in this embodiment uses a double-prism structure, where the first prism 1 (lower prism) is a triangular prism structure, and the second prism 2 (upper prism) is a right square pyramidal prism structure. The peak 23 of the second prism is symmetrical about the peak of the first prism unit 12. Therefore, after passing through the double prism, the brightness distribution at specific viewing angles is more uniform, optimizing the brightness ratio at specific viewing angles and providing better brightness gain.

[0087] Of course, the backlight module can also be a direct-lit backlight module, and this application does not impose any restrictions on this.

[0088] A third aspect of this application provides a display device including the aforementioned backlight module. The display device in this embodiment can be a mobile device, such as a smartphone, tablet computer, or laptop computer; a wearable terminal, such as a smartwatch, smart bracelet, smart glasses, or augmented reality device; or a fixed terminal, such as a desktop computer or television. Because the backlight module of the display device has uniform brightness distribution across all viewing angles and excellent brightness gain, the displayed image of the display device satisfies the requirement of symmetry and also has excellent brightness gain.

[0089] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0090] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0091] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

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