Optical film, composite brightness enhancement film and backlight module for effectively improving moiré patterns

Abstract

The present invention discloses an optical film, composite brightness enhancement film, and backlight module that effectively improve moiré patterns. The film comprises a substrate layer and a prismatic structure layer attached to one surface of the substrate layer. The prismatic structure layer includes a first protrusion located in the middle and a plurality of second protrusions arranged continuously on both sides of the first protrusion. In cross-section, the first protrusion is an isosceles triangle. The second protrusion is an "M"-shaped prism structure, comprising first, second, and fourth adjacent hypotenuses, with the first hypotenuse originating from the substrate layer surface and the fourth hypotenuse terminating therefrom. The first and second hypotenuses are arranged at an angle to form a first peak, while the third and fourth hypotenuses are arranged at an angle to form a second peak. The spacing between the first and second peaks gradually increases or decreases as the distance from the first protrusion increases. The present invention provides a novel anti-interference prism structure that balances optical performance, improves production efficiency, and controls costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical films, and in particular relates to an optical film, a composite brightness enhancement film and a backlight module for effectively improving moiré patterns. Background Art

[0002] Liquid crystal displays (LCDs) are the most common display technology. LCDs are non-luminous displays that require a backlight unit (BLU) to provide a bright, uniform light source. The backlight unit (BLU) includes a light source, a light guide plate, and three main optical films: reflective film, diffuser film, and brightness enhancement film.

[0003] The function of brightness enhancement film is to refocus most of the light that has been homogenized and scattered after passing through the diffuser back to the central viewing angle (±35° relative to the normal of the emitting surface), significantly improving the brightness when viewed from the center and reducing the loss of scattered light at low exit angles (relative to the emitting surface). Brightness enhancement film generally uses an isosceles triangle-shaped long micro-prism structure. Through refraction of light at the side of the prism, total internal reflection, and multiple refractions between prisms, it produces a positive accumulation effect and recycling effect of light, achieving control of the exit angle of most light.

[0004] Traditional brightness-enhancing films utilize isosceles triangles with 90° apex angles to achieve optimal brightness-boosting optical effects. However, this orderly, repeating prism array can cause optical interference with the periodically arranged pixel units of the LCD panel. When the pitch between the two is close or at a specific angle, a visual interference pattern known as moiré (or water ripples) forms, resulting in reduced image clarity. As display technology advances toward higher resolutions, the pixel pitch of LCDs continues to shrink, significantly increasing the interference sensitivity between the prism structure and the pixel units. Traditional prism designs are more prone to producing dense interference fringes, severely impacting display quality.

[0005] In the prior art, for example, patents CN202171652U and CN101666461B have proposed corresponding countermeasures for improving moiré patterns, namely, increasing the irregularity of the prism structure, reducing its consistency with the pixel arrangement of the liquid crystal panel, and thereby reducing the probability of the occurrence of moiré patterns. However, the prism structures designed in the above two patents are too complicated and random, involving many variables, and there are problems such as difficult mold processing, long processing time and uncontrollable costs.

[0006] Therefore, it is necessary to provide a new optical film, composite brightness enhancement film and backlight module that can effectively improve moiré patterns to solve the above technical problems. Summary of the Invention

[0007] The main purpose of the present invention is to provide an optical film that effectively improves moiré patterns, which is a new type of anti-interference prism structure to balance optical performance, thereby facilitating improved production efficiency and cost control.

[0008] The present invention achieves the above-mentioned object through the following technical solution: an optical film that effectively improves moiré patterns, comprising a substrate layer and a prismatic structure layer attached to one surface of the substrate layer; the prismatic structure layer comprises a first protrusion located in the middle and a plurality of second protrusions arranged continuously along a first direction on both sides of the first protrusion, the first protrusion and the second protrusion extending to a desired length along a second direction, the first direction being perpendicular to the second direction;

[0009] From a cross-section, the first protrusion is an isosceles triangle; the second protrusion is a symmetrical "M"-shaped prism structure, and the second protrusion includes a first hypotenuse, a second hypotenuse, a third hypotenuse and a fourth hypotenuse adjacent to each other in sequence, the first hypotenuse starts from the surface of the substrate layer, and the fourth hypotenuse ends at the surface of the substrate layer; the first hypotenuse and the second hypotenuse are arranged at an angle and form a first peak, and the third hypotenuse and the fourth hypotenuse are arranged at an angle and form a second peak; the distance P3 between the first peak and the second peak increases or decreases as the second protrusion moves away from the first protrusion.

[0010] Furthermore, the spacing P3 increases or decreases according to a set rule as the second protrusion moves away from the first protrusion.

[0011] Furthermore, the included angle between the first hypotenuse and the second hypotenuse is 90±5°; the included angle between the third hypotenuse and the fourth hypotenuse is 90±5°; the top angle of the first protrusion is 90±5°; the bottom edge L1 of the first protrusion is equal to the bottom edge L2 of the second protrusion.

[0012] Furthermore, as the second protrusion moves away from the first protrusion, the bottom edge L2 of the second protrusion remains unchanged.

[0013] Furthermore, the center line OO' of the second protrusion passes through the adjacent point A of the second hypotenuse and the third hypotenuse, and the first hypotenuse and the fourth hypotenuse are symmetrically arranged about the center line OO'; the second hypotenuse and the third hypotenuse are symmetrically arranged about the center line OO'.

[0014] Furthermore, the distance between the center line of the first protrusion and the center line of the second protrusion is P1, the distance between any two adjacent center lines of the second protrusion is equal to P2, P1=P2 and is greater than or equal to 21um.

[0015] Furthermore, the angles formed between the first oblique side, the second oblique side, the third oblique side, and the fourth oblique side and the surface of the substrate layer are respectively the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2; the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2 are all the inner angles of the second protrusion; wherein,

[0016] The first angle β1 is equal to the fourth angle β2 and gradually increases as they move away from the first protrusion, and the corresponding second angle α1 is equal to the third angle α2 and gradually decreases as they move away from the first protrusion; or,

[0017] The first angle β1 is equal to the fourth angle β2 and gradually decreases as they move away from the first protrusion. Correspondingly, the second angle α1 is equal to the third angle α2 and gradually increases as they move away from the first protrusion.

[0018] Furthermore, the β1 and β2 increase or decrease at the same angle.

[0019] Furthermore, the height of the first protrusion is H1, the height of the second protrusion is H2, H1 is the vertical distance from the highest point of the first protrusion to the upper surface of the substrate layer, H2 is the vertical distance from the highest point of the second protrusion to the upper surface of the substrate layer, and,

[0020] ;

[0021] Wherein, P1 is the distance between the center line of the first protrusion and the center line of the adjacent second protrusion;

[0022] As the second protrusion moves away from the first protrusion, the height H2 of the second protrusion satisfies the following formula:

[0023] ;

[0024] Wherein, θ is the inner angle α1, α2, β1 or β2 of the second protrusion; P2 is the distance between the center lines of two adjacent second protrusions.

[0025] Furthermore, the material of the substrate layer is one or more combinations of polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polystyrene, and polyamide resin; the thickness of the substrate layer is 20~100um; the refractive index of the prism structure layer is greater than or equal to 1.58; and the number of the second protrusions on both sides of the first protrusion is the same.

[0026] Another object of the present invention is to provide a composite brightness enhancement film, comprising a first optical film and a second optical film stacked together, the first optical film and the second optical film having the same structure as the above-mentioned optical film; the first optical film is stacked on the second optical film, and an adhesive layer is provided on the lower surface of the first optical film to bond the first optical film and the second optical film together;

[0027] In the first optical film, the extension direction of the prism structure protrusion on the substrate layer is the third direction; in the second optical film, the extension direction of the prism structure protrusion on the substrate layer is the fourth direction, and the third direction is set at a set angle with the fourth direction, and the set angle is 45° or 90°.

[0028] Another object of the present invention is to provide a backlight module, which comprises, from bottom to top, a reflective film, a light guide plate, a diffusion film, the composite brightness enhancement film as described above, and a liquid crystal panel, wherein an LED light source is provided on one side of the light guide plate.

[0029] Compared to the prior art, the present invention provides an optical film, composite brightness enhancement film, and backlight module that effectively improves moiré patterns. By adopting an "M"-shaped prism structure with a gradient double-peak spacing, the irregularity of the prism structure is increased compared to a single prism, reducing the probability of moiré patterns, while also increasing the forward convergence of light and reducing the brightness loss rate. Symmetrical M-shaped prism structures with unequal heights are arranged on both sides of an isosceles right triangle, resulting in relatively regular light convergence on both sides. Furthermore, the "M"-shaped prism structure maintains the prism spacing and vertex angle unchanged, only changing the base angle to achieve a change in the double-peak spacing. This reduces the number of variables and effectively reduces the difficulty of mold processing, processing time, and the complexity of cost control. In particular, the composite brightness enhancement film formed by stacking the above optical films balances optical performance and production efficiency, providing a reliable solution for high-resolution display devices. Furthermore, the stacked design of the composite brightness enhancement film further optimizes the optical effect, making it suitable for use in backlight modules for a variety of display devices and promising broad market applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the three-dimensional structure of the optical film in Example 1 of the present invention;

[0031] Figure 2 Schematic diagram of a partial structure of a cross section of an optical film in Example 1 of the present invention;

[0032] Figure 3 Schematic diagram of the cross-sectional structure of the second protrusion in the first embodiment of the present invention;

[0033] Figure 4Schematic diagram of the cross-sectional structure of the optical film in Example 1 of the present invention;

[0034] Figure 5 Schematic diagram of the cross-sectional structure of the optical film in Example 2 of the present invention;

[0035] Figure 6 Schematic diagram of the structure of the composite brightness enhancement film in Example 3 of the present invention;

[0036] Figure 7 Schematic diagram of the structure of the backlight module in the fourth embodiment of the present invention;

[0037] The numbers in the figure represent:

[0038] 100-Optical film that effectively improves moiré patterns; 200-Compound brightness enhancement film; 300-Backlight module;

[0039] 1- substrate layer;

[0040] 2- prism structure layer, 21- first protrusion, 22- second protrusion, 221- first hypotenuse, 222- second hypotenuse, 223- third hypotenuse, 224- fourth hypotenuse, 225- first peak, 226- second peak. DETAILED DESCRIPTION

[0041] Example 1:

[0042] Please refer to Figures 1-4 This embodiment is an optical film 100 that effectively improves moiré patterns, which includes a substrate layer 1 and a prismatic structure layer 2 attached to one surface of the substrate layer 1; the prismatic structure layer 2 includes a first protrusion 21 located in the middle position and a plurality of second protrusions 22 continuously arranged along a first direction on both sides of the first protrusion 21, the first protrusion 21 and the second protrusion 22 extending along a second direction to a desired length, and the first direction is perpendicular to the second direction.

[0043] From a cross-sectional view, the first protrusion 21 is an isosceles triangle with a vertex angle of 90±5°, preferably 90°.

[0044] The cross-section of the second protrusion 22 is a symmetrical "M"-shaped prism structure. Specifically, from a cross-section, the second protrusion 22 includes a first hypotenuse 221, a second hypotenuse 222, a third hypotenuse 223, and a fourth hypotenuse 224, which are adjacent to each other in sequence. The first hypotenuse 221 originates from the surface of the substrate layer 1, and the fourth hypotenuse 224 terminates there. The first hypotenuse 221 and the second hypotenuse 222 are arranged at a 90° angle and form a first peak 225. The third hypotenuse 223 and the fourth hypotenuse 224 are arranged at a 90° angle and form a second peak 226. The spacing P3 between the first peak 225 and the second peak 226 decreases as the second protrusion 22 moves away from the first protrusion 21. Preferably, the spacing P3 decreases according to a predetermined rule as the second protrusion 22 moves away from the first protrusion 21; the predetermined rule includes any one or a combination of two or more of the following: linear rule, random change, ordered change, waveform change, and quadratic change.

[0045] In other embodiments, the included angle between the first oblique side 221 and the second oblique side 222 and the included angle between the third oblique side 223 and the fourth oblique side 224 may also be other angles, and the angle range is 90±5°. Both angles are preferably 90°.

[0046] In this embodiment, the length L1 of the base of the first protrusion 21 is equal to the length L2 of the base of the second protrusion 22 .

[0047] As the second protrusion 22 moves away from the first protrusion 21, the length L2 of the base of the second protrusion 22 remains constant. The centerline OO' of all second protrusions 22 passes through the junction point A of the second oblique side 222 and the third oblique side 223. The first oblique side 221 and the fourth oblique side 224 are symmetrically arranged about the centerline OO'; and the second oblique side 222 and the third oblique side 223 are symmetrically arranged about the centerline OO'.

[0048] The distance between the center line of the first protrusion 21 and the center line of the adjacent second protrusion 22 is P1, and the distance between the center lines of any two adjacent second protrusions 22 is equal and is P2, P1=P2 and is greater than or equal to 21um, so as to avoid interference caused by too small a spacing of the prism structure.

[0049] By keeping the bottom side length L2 and the spacing of the second protrusion 22 unchanged and setting it to an "M"-shaped axially symmetrical structure, only the double-peak spacing of the second protrusion 22 is changed, which involves fewer variables and can effectively reduce the difficulty of mold processing, reduce the difficulty of optical film manufacturing, improve processing efficiency, and easily control costs.

[0050] At the same time, the double-peak distance at the top of the second protrusion 22 is designed to be gradually changed as it moves away from the first protrusion 21, thereby increasing the overall irregularity of the prism structure and effectively reducing the probability of moiré patterns.

[0051] In this embodiment, the extension line of the second hypotenuse 222 of the second protrusion 22 toward the base passes through the vertex B on one side of the base, and the extension line of the third hypotenuse 223 toward the base passes through the vertex C on the other side of the base. Through this structural design, the "M"-shaped prism structure can be regarded as consisting of two triangles Δ1 and Δ2 superimposed on each other. Triangle Δ1 and triangle Δ2 are mirror-image structures, and the bases of the two coincide to form the second protrusion 22 in this embodiment. The symmetrical design of the "M"-shaped prism structure can regulate light in both directions. The oblique surfaces of triangles Δ1 and Δ2 refract incident light at different angles respectively, correcting high-angle scattered light to a direction perpendicular to the screen, reducing the loss of light outside the viewing angle. In addition, the superposition of the two triangles produces cooperative refraction. Compared with a single prism structure, it can more efficiently "fold" oblique light into a forward output, improve axial brightness, and thus enhance the brightening effect of the brightness enhancement film.

[0052] In this embodiment, the rule that the structure of the second protrusion 22 gradually changes as it moves away from the first protrusion 21 is described as follows:

[0053] The angles formed between the first oblique side 221, the second oblique side 222, the third oblique side 223, and the fourth oblique side 224 and the surface of the substrate layer 1 are the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2 respectively; the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2 are all the internal angles of the second protrusion 22; β1+α1=90°, α2+β2=90°; wherein,

[0054] The first angle β1 and the fourth angle β2 are equal and gradually decrease as they move away from the first protrusion 21; the corresponding second angle α1 and the third angle α2 are equal and gradually increase as they move away from the first protrusion 21. By setting β1 and β2 to gradually decrease in the direction away from the first protrusion 21, or setting α1 and α2 to gradually increase in the direction away from the first protrusion 21, the distance P3 between the first peak 225 and the second peak 226 gradually decreases as they move away from the first protrusion 21.

[0055] In this embodiment, β1 and β2 decrease at equal angles. For example, the second protrusions 22 are counted in a direction away from the first protrusion 21, and the second protrusion 22 closest to the first protrusion 21 is recorded as the first second protrusion 22, and its first angle is recorded as β 11 The first included angle of the second protrusion 22 is denoted as β 12 , and so on, the first angle of the i-th second protrusion 22 is recorded as β 1i , i=1,2,……,n, n is the number of second protrusions located on the same side of the first protrusion 21; then β 11 -β 12 =β 12 -β 13 =……=β1 (n-1) -β 1n .

[0056] In this embodiment, the height of the first peak 225 is the same as the height of the second peak 226 .

[0057] The height of the first protrusion 21 is H1, and the height of the second protrusion 22 is H2. H1 is the vertical distance from the highest point of the first protrusion 21 to the upper surface of the substrate layer 1, and H2 is the vertical distance from the highest point of the second protrusion 22 to the upper surface of the substrate layer 1, which is also equal to the height of the first peak 225 or the second peak 226.

[0058] Among them, the height of the first protrusion 21 is .

[0059] As the second protrusion 22 moves away from the first protrusion 21 , the height H2 of the second protrusion 22 satisfies the following formula:

[0060] ;

[0061] Here, θ is the inner angle α1, α2, β1 or β2 of the second protrusion 22 .

[0062] In this embodiment, the height of the second protrusion 22 changes accordingly with the change of its own inner angle as it moves away from the first protrusion 21, and the resulting different height differences can also prevent the occurrence of adsorption problems.

[0063] The number of the second protrusions 22 on both sides of the first protrusion 21 is the same, so that the light convergence directions on both sides are relatively regular.

[0064] The refractive index of the prismatic structure layer 2 is greater than or equal to 1.58. The specific value of the refractive index of the prismatic structure layer 2 needs to be adjusted according to the actual application scenario, but should always meet the requirement of being greater than or equal to 1.58.

[0065] Substrate layer 1 is made from one or more of polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), and polyamide resin (PA). PET is preferred. Substrate layer 1 has a thickness of 20 to 100 μm. This thickness range ensures a balance between optical performance and mechanical strength. Substrate layer 1 provides stable support for prismatic structure layer 2 while ensuring the flexibility and durability of the overall structure.

[0066] This embodiment addresses the problem of moiré patterns generated by conventional brightness enhancement films in liquid crystal display backlight modules due to the easy overlap of traditional periodic prism structures and pixels. By designing a novel asymmetric "M"-shaped prism structure and combining specific geometric parameters, the brightness enhancement film reduces the probability of moiré patterns while also balancing production efficiency and cost control.

[0067] In terms of operating principle, the optical film of this embodiment achieves efficient light convergence and uniform distribution through the gradual design of an "M"-shaped prism structure. When light is emitted from the light source of the backlight module, it first passes through the light guide plate for initial diffusion, and then enters the prism layer of the brightness enhancement film. Due to the irregular design of the "M"-shaped prism structure, the light undergoes multiple reflections and refractions when passing through the prism layer, thereby achieving light redistribution and concentration. This design not only significantly improves light utilization, but also effectively avoids the moiré problem caused by the superposition of traditional periodic prism structures and pixel points.

[0068] In actual operation, the following steps need to be followed to produce the optical film of this embodiment: S1, select a suitable substrate material and cut it to the required thickness; S2, apply a layer of high-refractive index glue on the surface of the substrate, and the refractive index of the glue must be greater than 1.58; S3, use a precision mold to form the "M"-shaped prism structure as described above on the glue layer, ensuring that the prism spacing is greater than 21μm and the top angle is 90°; S4, by controlling the mold temperature and pressure, the glue is cured and a stable prism layer is formed; S5, the optical performance of the finished optical film is tested, including the brightness enhancement effect and the moiré suppression effect.

[0069] In order to verify the beneficial effects of the optical film of this embodiment, this embodiment designed several comparative examples and embodiments with different bottom angle change values ​​to test and compare the anti-interference effects. The results are shown in Table 1.

[0070] Table 1

[0071]

[0072] Note:

[0073] (1) i = 1, 2, 3, ..., n, where n is the number of second protrusions;

[0074] (2) The vertex angle η is the angle between the first hypotenuse 221 and the second hypotenuse 222, and the angle between the third hypotenuse 223 and the fourth hypotenuse 224; β 1i α is the angle between the first oblique side 221 and the bottom side (or the substrate layer 1 ) of the i-th second protrusion 22 along the first direction or the opposite direction of the first direction from the first protrusion 21 ; 1iα is the angle between the second oblique side 222 and the bottom side (or the substrate layer 1 ) of the i-th second protrusion 22 along the first direction or the opposite direction of the first direction from the first protrusion 21 ; 2i β is the angle between the third oblique side 223 and the bottom side (or the substrate layer 1 ) of the i-th second protrusion 22 along the first direction or the opposite direction of the first direction from the first protrusion 21 ; 2i is the angle between the fourth oblique side 224 and the bottom side (or the substrate layer 1 ) of the i-th second protrusion 22 , counted from the first protrusion 21 along the first direction or the opposite direction of the first direction;

[0075] (3) (gradual bottom angle difference), 、 、 Similarly;

[0076] (4) Anti-interference evaluation level: excellent > good > medium > poor > bad.

[0077] From the above test results we can see that:

[0078] 1. As can be seen from Examples 1-3 and Comparative Example 1, maintaining the same degree of gradient difference design for the left and right base angles, the overall symmetrical M-shaped prism can enhance the anti-interference effect. At the same time, as the gradient base angle difference increases, the anti-interference effect also increases.

[0079] 2. As can be seen from Examples 4-6 and Comparative Example 1, by keeping the left set of base angles unchanged and applying the same degree of gradient difference design to the right set of base angles, the overall asymmetric M-shaped prism is presented. As the gradient difference of the right set of base angles increases, the anti-interference effect is generally improved.

[0080] 3. It can be seen from Example 2 and Comparative Examples 1-3 that by keeping the gradient difference of the left bottom corner unchanged and gradually increasing the gradient difference of the right bottom corner, the anti-interference effect is also improved.

[0081] In summary, based on the fact that the left and right bottom angles of the M-type prism described in the present invention are themselves designed with gradient bottom angles, the anti-interference effect has been improved to a certain extent. Table 1 lists several groups of preferred embodiments based on this, not all embodiments.

[0082] Example 2:

[0083] Please refer to Figure 1-Figure 3 、 Figure 5This embodiment is an optical film 100 that effectively improves moiré patterns. Its structure is substantially the same as that of the optical film in Example 1, except that the spacing P3 between the first peak 225 and the second peak 226 increases as the second protrusion 22 moves away from the first protrusion 21. Preferably, the spacing P3 increases according to a predetermined rule as the second protrusion 22 moves away from the first protrusion 21; the predetermined rule includes any one of a linear rule, a random change, an ordered change, a waveform change, and a quadratic change, or a combination of two or more of these.

[0084] Correspondingly, the first angle β1 and the fourth angle β2 are equal and gradually increase as they move away from the first protrusion 21 ; correspondingly, the second angle α1 and the third angle α2 are equal and gradually decrease as they move away from the first protrusion 21 .

[0085] In this embodiment, β1 and β2 increase at equal angles.

[0086] Example 3:

[0087] Please refer to Figure 6 This embodiment is a composite brightness enhancement film 200, which includes a first optical film 201 and a second optical film 202 stacked together.

[0088] The structures of the first optical film 201 and the second optical film 202 are the same as the structures of the optical film 100 in the first or second embodiment.

[0089] In the first optical film 201 and the second optical film 202 , the double-peak distance of the second protrusions 22 gradually increases as it moves away from the first protrusions 21 .

[0090] In another embodiment, the double-peak distance between the second protrusions 22 in the first optical film 201 and the second optical film 202 gradually decreases as it moves away from the first protrusion 21 .

[0091] In another embodiment, the double-peak distance of the second protrusions 22 in the first optical film 201 gradually increases as they move away from the first protrusions 21 , and the double-peak distance of the second protrusions 22 in the second optical film 202 gradually decreases as they move away from the first protrusions 21 .

[0092] In another embodiment, the double-peak distance of the second protrusions 22 in the first optical film 201 gradually decreases as they move away from the first protrusions 21 , and the double-peak distance of the second protrusions 22 in the second optical film 202 gradually increases as they move away from the first protrusions 21 .

[0093] The first optical film 201 is stacked on the second optical film 202 , and an adhesive layer 203 is provided on the lower surface of the first optical film 201 to bond the first optical film 201 and the second optical film 202 together.

[0094] The first optical film 201 and the second optical film 202 can be stacked in various arrangements. For example, the prism structure of the first layer of brightness enhancement film can be staggered with the prism structure of the second layer of brightness enhancement film at a certain angle to further optimize the optical effect. The specific value of the stacking angle should be determined based on actual test results. Generally, a staggered arrangement of 45° or 90° is recommended.

[0095] In this embodiment, in the first optical film 201 , the prism structure protrusions on the substrate layer 1 extend in the third direction, and in the second optical film 201 , the prism structure protrusions on the substrate layer 1 extend in the fourth direction, and the third direction is set at 90° to the fourth direction.

[0096] In other embodiments, the number of stacked optical film layers can also be adjusted based on actual needs. For example, a composite brightness enhancement film is formed by stacking three single-layer optical films, where the prism structures of the first and third optical films are oriented in the same direction, while the prism structure of the second optical film is staggered at 90° to the first and third layers.

[0097] Example 4:

[0098] Please refer to Figure 7 This embodiment provides a backlight module 300, which comprises, from bottom to top, a reflective film 301, a light guide plate 302, a diffusion film 303, a composite brightness enhancement film 304, and a liquid crystal panel 305. An LED light source 306 is provided on one side of the light guide plate 302. The composite brightness enhancement film 304 has the same structure as the composite brightness enhancement film 200 of the third embodiment. The composite brightness enhancement film 304 is particularly effective in high-resolution display devices, significantly improving the moiré problem caused by reduced pixel pitch.

[0099] For those skilled in the art, several variations and improvements can be made without departing from the inventive concept of the present invention, and all of these fall within the scope of protection of the present invention.

Claims

1. An optical film that effectively improves moiré patterns, characterized by: The prism structure layer includes a substrate layer and a prism structure layer attached to one surface of the substrate layer; the prism structure layer includes a first protrusion located in the middle and a plurality of second protrusions arranged continuously along a first direction on both sides of the first protrusion, the first protrusion and the second protrusion extending to a desired length along a second direction, and the first direction is perpendicular to the second direction; From a cross-section, the first protrusion is an isosceles triangle; the second protrusion is a symmetrical "M"-shaped prism structure, and the second protrusion includes a first hypotenuse, a second hypotenuse, a third hypotenuse and a fourth hypotenuse adjacent to each other in sequence, the first hypotenuse starts from the surface of the substrate layer, and the fourth hypotenuse ends at the surface of the substrate layer; the first hypotenuse and the second hypotenuse are arranged at an angle and form a first peak, and the third hypotenuse and the fourth hypotenuse are arranged at an angle and form a second peak; the distance P3 between the first peak and the second peak increases or decreases as the second protrusion moves away from the first protrusion.

2. The optical film for effectively improving moiré patterns according to claim 1, wherein: The spacing P3 increases or decreases according to a set rule as the second protrusion moves away from the first protrusion.

3. The optical film for effectively improving moiré patterns according to claim 1, wherein: The included angle between the first hypotenuse and the second hypotenuse is 90±5°; the included angle between the third hypotenuse and the fourth hypotenuse is 90±5°; the top angle of the first protrusion is 90±5°; the bottom edge L1 of the first protrusion is equal to the bottom edge L2 of the second protrusion.

4. The optical film for effectively improving moiré patterns according to claim 1 or 3, wherein: As the second protrusion moves away from the first protrusion, the bottom side L2 of the second protrusion remains unchanged.

5. The optical film for effectively improving moiré patterns according to claim 1, wherein: The center line OO' of the second protrusion passes through the adjacent point A of the second hypotenuse and the third hypotenuse, and the first hypotenuse and the fourth hypotenuse are symmetrically arranged about the center line OO'; the second hypotenuse and the third hypotenuse are symmetrically arranged about the center line OO'.

6. The optical film for effectively improving moiré patterns according to claim 1, wherein: The distance between the center line of the first protrusion and the center line of the second protrusion is P1, and the distance between any two adjacent center lines of the second protrusion is equal to P2, P1=P2 and is greater than or equal to 21um.

7. The optical film for effectively improving moiré patterns according to claim 1, wherein: The angles formed between the first oblique side, the second oblique side, the third oblique side, and the fourth oblique side and the surface of the substrate layer are respectively the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2; the first angle β1, the second angle α1, the third angle α2, and the fourth angle β2 are all the inner angles of the second protrusion; wherein, The first angle β1 is equal to the fourth angle β2 and gradually increases as they move away from the first protrusion, and the corresponding second angle α1 is equal to the third angle α2 and gradually decreases as they move away from the first protrusion; or, The first angle β1 is equal to the fourth angle β2 and gradually decreases as they move away from the first protrusion. Correspondingly, the second angle α1 is equal to the third angle α2 and gradually increases as they move away from the first protrusion.

8. The optical film for effectively improving moiré patterns according to claim 7, wherein: The β1 and β2 or the α1 and α2 increase or decrease at the same angle.

9. The optical film for effectively improving moiré patterns according to claim 1, wherein: The height of the first protrusion is H1, the height of the second protrusion is H2, H1 is the vertical distance from the highest point of the first protrusion to the upper surface of the substrate layer, H2 is the vertical distance from the highest point of the second protrusion to the upper surface of the substrate layer, and, ； Wherein, P1 is the distance between the center line of the first protrusion and the center line of the adjacent second protrusion; As the second protrusion moves away from the first protrusion, the height H2 of the second protrusion satisfies the following formula: ； Wherein, θ is the inner angle α1, α2, β1 or β2 of the second protrusion; and P2 is the distance between the center lines of two adjacent second protrusions.

10. The optical film for effectively improving moiré patterns according to claim 1, wherein: The material of the substrate layer is one or more combinations of polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polystyrene, and polyamide resin; the thickness of the substrate layer is 20~100um; the refractive index of the prism structure layer is greater than or equal to 1.58; the number of the second protrusions on both sides of the first protrusion is the same.

11. A composite brightness enhancement film, characterized in that: The invention comprises a first optical film and a second optical film stacked together; the first optical film and the second optical film have the same structure as the optical film according to claim 1; the first optical film is stacked on the second optical film and an adhesive layer is provided on the lower surface of the first optical film to bond the first optical film and the second optical film together; In the first optical film, the extension direction of the prism structure protrusion on the substrate layer is the third direction; in the second optical film, the extension direction of the prism structure protrusion on the substrate layer is the fourth direction, and the third direction is set at a set angle with the fourth direction, and the set angle is 45° or 90°.

12. A backlight module, characterized in that: It comprises, from bottom to top, a reflective film, a light guide plate, a diffusion film, the composite brightness enhancement film according to claim 11, and a liquid crystal panel, wherein an LED light source is provided on one side of the light guide plate.

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