Brightness enhancement film sheet, attached brightness enhancement film, backlight module and display device

Abstract

The application relates to a brightness enhancement film sheet, a bonded brightness enhancement film, a backlight module and a display device, and solves the technical problem that high normal viewing angle brightness and spatial viewing angle uniformity are difficult to be considered by means of microstructure design. The film sheet comprises paralleled isosceles trapezoidal first prisms and second prisms, and at least one first prism is arranged between every two second prisms; the first prism expands large viewing angle light intensity through large slope design of the oblique side, and the second prism maintains high brightness at the normal viewing angle through the right-angle prism structure. The number ratio can be dynamically adjusted in the range of 1:1 to 1:2 or set as a fixed value, and an edge-to-center gradient design further optimizes the full-screen display effect; the first prism slope is differentiated in combination with the isosceles right-angle trapezoidal structure of the second prism, and the processing technology is simplified. The laminated architecture composites the prism film sheet through the bonding layer, improves the brightness while maintaining the viewing angle expansion effect, and has high performance and economy.

Description

Technical Field

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

[0002] Brightness enhancement films, as the core optical components of LCD backlight modules, use a prism structure to spatially redistribute scattered light, concentrating the originally uniformly distributed light intensity towards the frontal viewing angle, thereby significantly improving the brightness of the display at the frontal viewing angle and reducing energy consumption. However, the POP / MOP (double-layer prism / microlens prism composite structure) architecture has significant optical performance contradictions: taking a single prism film as an example, although it can significantly improve the brightness at the frontal viewing angle, the 1 / 2 intensity viewing angle (the viewing angle range when the brightness decays to 50%) is usually limited to within ±50° in the horizontal direction and further narrowed to within ±35° in the vertical direction; while using a double-layer prism architecture can further enhance the brightness at the frontal viewing angle, it simultaneously compresses the horizontal and vertical viewing angles to below ±35°, which cannot meet the requirements of applications such as automotive displays and medical imaging that have strict requirements for the uniformity of spatial viewing angle light intensity.

[0003] In existing technical solutions, three main solutions have been proposed in the industry to improve the uniformity of the spatial viewing angle: 1) Prism sharp corner R-angle design, which sacrifices the brightness of the positive viewing angle to improve the light intensity ratio of the large viewing angle, but the actual improvement in uniformity is limited; 2) Composite prism microstructure, which controls the light distribution curve by optimizing the slope of the microstructure, but its special curved surface processing requires high-precision mold processing and complex forming process, resulting in low mass production efficiency and high cost; 3) Double-layer prism angle off-axis design, which uses the light intensity superposition effect to adjust the viewing angle distribution, but this solution will cause the brightness of the positive viewing angle to decrease by more than 15%, making it difficult to balance the dual requirements of high brightness and uniformity.

[0004] While the aforementioned solutions have made progress in specific scenarios, they still share the following common problems: 1) The mutual constraints on optical performance have not been fundamentally resolved, making it difficult to achieve both high brightness and high uniformity; 2) Existing designs lack targeted optimization for dynamic viewing angle response characteristics (such as color shift control during viewing angle shifts). Therefore, developing a novel brightness enhancement film architecture that combines efficient light intensity redistribution capabilities, low-cost manufacturing processes, and wide viewing angle uniformity has become a technological requirement driving the display industry towards high-end development. Summary of the Invention

[0005] The purpose of this application is to provide a novel brightness enhancement film, which, as the upper microstructure of an laminated brightness enhancement film, maintains high brightness at a positive viewing angle while increasing light intensity at large angles, thereby improving the spatial viewing angle light intensity uniformity of display products. This purpose is achieved through the following technical solution: a brightness enhancement film comprising:

[0006] Multiple first prism structures;

[0007] Multiple second prism structures;

[0008] The cross-section of the first prism structure is an isosceles trapezoid, and the cross-section of the second prism structure is an isosceles triangle. The arrangement direction of the first prism structure is parallel to the arrangement direction of the second prism structure.

[0009] At least one of the first prism structures is included between the two second prism structures.

[0010] In one embodiment, the ratio of the number of the first prism structure to the number of the second prism structure is in the range of 1:1 to 1:2.

[0011] In one embodiment, the ratio of the number of the first prism structure to the number of the second prism structure in the brightness enhancement film is a fixed value.

[0012] In one embodiment, the ratio of the number of the first prism structure to the number of the second prism structure in the brightness enhancement film gradually decreases from the edge to the center.

[0013] In one embodiment, the hypotenuses of the isosceles trapezoids in the plurality of first prism structures have different slopes.

[0014] In one embodiment, the cross-section of the second prism structure is an isosceles right triangle.

[0015] This application also provides an adhesive brightness enhancement film, which includes the aforementioned brightness enhancement film sheet and a prism film sheet.

[0016] In one embodiment, a brightness enhancement film is disposed above the prism film, and an adhesive layer is included between the brightness enhancement film and the prism film.

[0017] This application further provides a backlight module, which includes the aforementioned laminated brightness enhancement film.

[0018] This application also provides a display device including the aforementioned backlight module.

[0019] Compared with the prior art, this application has the following beneficial effects:

[0020] This application utilizes a first prism structure and a second prism structure with isosceles trapezoidal cross-sections, arranged in parallel directions to create a synergistic optical path effect. The hypotenuse design of the first prism structure (isosceles trapezoid) effectively controls the refraction path of light, expanding the light intensity over a wide viewing angle. Simultaneously, the second prism, through its right-angle prism structure, repeatedly recovers and scatters large-angle light rays, maintaining high brightness at the positive viewing angle. This expands the total half-intensity viewing angle range to over ±60° horizontally and over ±50° vertically, improving the uniformity of spatial viewing angle light intensity. At the same time, the brightness decay at the positive viewing angle is controlled, resolving the contradiction between high brightness and high uniformity in existing technologies.

[0021] When the ratio of the first prism structure to the second prism structure is within the range of 1:1 to 1:2, the light intensity distribution can be balanced by adjusting the distribution density of the two types of prisms. This enhances light compensation over wide viewing angles. The proportion of the second prism in the central area is increased to maintain core brightness, achieving uniform light intensity distribution across the entire screen (both horizontally and vertically). This is suitable for scenarios with stringent requirements for edge viewing angle uniformity. The isosceles trapezoidal hypotenuse of the first prism structure uses different slopes, combined with the isosceles right-angled triangle design of the second prism structure. Microstructure morphology control can be achieved through simple mold adjustments, eliminating the need for complex surface processing or high-precision replication processes, thus improving product yield and reducing production costs.

[0022] The brightness enhancement film and prism film are laminated together, effectively improving the film's stiffness and reducing assembly steps to lower the risk of microstructure damage. Simultaneously, the prism structure of the upper film redistributes the emitted light from the lower prism film, increasing the positive viewing angle brightness compared to a single-layer prism solution. Furthermore, the 1 / 2 intensity viewing angle range extension effect is unaffected by the stacked structure. In summary, this application improves spatial viewing angle intensity uniformity while maintaining high positive viewing angle brightness through improvements in microstructure morphology and distribution ratio, while also reducing production costs by simplifying the processing. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of the brightness enhancement film in one embodiment of this application;

[0024] Figure 2 This is a three-dimensional structural diagram of the brightness enhancement film sheet in one embodiment of this application;

[0025] Figure 3 This is a three-dimensional structural diagram of the adhesive brightening film in one embodiment of this application.

[0026] Explanation of reference numerals in the attached figures: 100, brightness enhancement film; 110, first prism structure; 120, second prism structure; 200, prism film. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0028] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] As a core component providing a uniform surface light source, the backlight module's optical performance directly affects the display's brightness and viewing angle characteristics. The brightness enhancement film, a key optical film in the backlight module, redistributes light through a prism structure, concentrating scattered light towards the positive viewing angle, thus achieving the dual goals of energy saving and high brightness. However, traditional single-layer or double-layer prism structures, while improving brightness at the positive viewing angle, inevitably lead to a decrease in spatial viewing angle light intensity uniformity, making it difficult to meet the uniformity requirements of wide-viewing-angle applications. While existing technologies have proposed solutions such as prism radius reduction, complex microstructure optimization, and adjustment of the angle between double-layer prisms, all have limitations: some sacrifice brightness at the positive viewing angle for limited viewing angle expansion, some face mass production difficulties due to high processing complexity, and some suffer from excessive light intensity attenuation, making it impossible to balance brightness and uniformity.

[0031] To address the aforementioned technical problems, this application proposes a brightness enhancement film 100 and a laminated brightness enhancement film based thereon. Through microstructure improvements, it enhances the uniformity of light intensity distribution over a wide viewing angle while maintaining high brightness at a positive viewing angle. Please refer to [link to relevant documentation]. Figures 1 to 2In a preferred embodiment of this application, the brightness enhancement film 100 includes a plurality of first prism structures 110 and a plurality of second prism structures 120. The cross-section of the first prism structure 110 is an isosceles trapezoid, and the cross-section of the second prism structure 120 is an isosceles triangle. The arrangement direction of the first prism structures 110 is parallel to the arrangement direction of the second prism structures 120, wherein at least one first prism structure 110 is included between two second prism structures 120. The beveled design of the first prism structure can effectively control the refraction path of light. While expanding the light intensity at a large viewing angle, the second prism maintains high brightness at the positive viewing angle by repeatedly recovering and scattering large-angle light through its right-angle prism structure. This expands the total 1 / 2 light intensity viewing angle range to more than ±60° in the horizontal direction and more than ±50° in the vertical direction, improving the uniformity of light intensity at a spatial viewing angle, while controlling the brightness decay at the positive viewing angle.

[0032] In a further embodiment, the ratio of the number of first prism structures 110 to the number of second prism structures 120 is within the range of 1:1 to 1:2. The hypotenuse design of the first prism structure (isosceles trapezoid) effectively controls the refraction path of light, expanding the light intensity over a wide viewing angle. Meanwhile, the right-angle design of the second prism can recycle and rescatter light rays at large angles, enhancing brightness in the direct viewing angle direction. Light intensity redistribution is controlled by adjusting the distribution density of the two types of prisms, and this ratio range allows for dynamic adjustment based on the optical requirements of the display area.

[0033] In the brightness enhancement film 100, the ratio of the number of the first prism structure 110 to the number of the second prism structure 120 is a fixed value. When the ratio of the number of the first prism to the number of the second prism is fixed, the optical redistribution characteristics of the film are highly consistent. The fixed ratio ensures that the synergistic effect of the two types of prisms is evenly distributed throughout the entire film, avoiding light intensity fluctuations caused by local ratio deviations. The contribution of the first prism and the second prism can be controlled, and the brightness attenuation at the positive viewing angle is strictly controlled. In addition, there is no need to design complex mold cavities corresponding to the gradient ratio. Only a fixed ratio layout can be achieved by periodically arranging units, which reduces the mold manufacturing cost.

[0034] In another specific embodiment, the ratio of the number of the first prism structure 110 to the number of the second prism structure 120 in the brightness enhancement film 100 gradually decreases from the edge to the center. Through the gradual change in ratio from the edge to the center, the optical performance can be controlled in different regions. The first prism has a higher proportion in the edge region, and its isosceles trapezoidal base angle design can enhance the intensity of light from a wide viewing angle. The proportion of the second prism in the center region is increased, which can maintain the intensity of light from a positive viewing angle and ensure that the brightness attenuation of the positive viewing angle in the center region is controlled within 3%.

[0035] In one specific embodiment, the hypotenuses of the isosceles trapezoids in the multiple first prism structures 110 have different slopes. The hypotenuses of the isosceles trapezoids in the first prism structures 110 adopt a differentiated slope design, which can realize the decentralized control of the light path. By extending the different propagation paths of light in the prism, the scattering ability of large-angle light is enhanced.

[0036] To effectively provide high brightness, the cross-section of the second prism structure 120 is an isosceles right triangle.

[0037] Please see Figure 3 This application also provides a laminated brightness enhancement film, which includes the aforementioned brightness enhancement film 100 and a prism film 200. The total optical benefit is the sum of the upper brightness enhancement film 100 and the lower prism film 200. The brightness enhancement film 100 is disposed above the prism film 200, and an adhesive layer is included between the brightness enhancement film 100 and the prism film 200 to fix the two films relative to each other.

[0038] This application further relates to a backlight module including the aforementioned laminated brightness enhancement film, which can maintain high brightness at a normal viewing angle while improving light intensity at a wide viewing angle. Display devices using this backlight module exhibit high spatial viewing angle light intensity uniformity and high brightness. Specific Implementation

[0040] The following will further introduce some specific implementation methods to provide a more detailed explanation of the technical solution of this application.

[0041] Example 1

[0042] A laminated brightness enhancement film. The lower prism sheet has a prism microstructure with a width of 70 μm and a height of 35 μm. In the upper brightness enhancement film, the triangular prism structure has a width of 20 μm and a height of 10 μm; the isosceles trapezoidal structure in the upper brightness enhancement film has a hypotenuse length of 14.6 μm, a top plane width of 5 μm, and a hypotenuse angle of 70°; the ratio of trapezoids to prisms in the upper brightness enhancement film is 1:1.

[0043] Example 2

[0044] The difference from Example 1 is that the ratio of trapezoids to prisms in the upper brightening film is 1:1.5.

[0045] Comparative Example 1

[0046] In a conventional orthogonal POP (Polymer Orthogonal Array), the lower prism sheet has a prism microstructure with a width of 70 μm and a height of 35 μm. The upper prism structure has a width of 20 μm and a height of 10 μm.

[0047] Comparative Example 2

[0048] The difference from Comparative Example 1 is that the angle between the upper and lower prisms is 45 degrees.

[0049] The half-light intensity angle, brightness, and brightness ratio of each implementation method were tested, and the test results are shown in Table 1.

[0050] Table 1 shows the performance test results for each embodiment.

[0051]

[0052] Based on the test results of the above embodiments, the new structure provided by the technical solution of this application can maintain a brightness of more than 90% of the brightness of the brightening film while having a wide viewing angle.

[0053] As described above, this application addresses the technical problem of simultaneously achieving high brightness at a positive viewing angle and uniform light intensity at a spatial viewing angle in existing brightness enhancement film technologies. It proposes a brightness enhancement film sheet comprising a first prism structure and a second prism structure with an isosceles trapezoidal cross-section. The two prisms are arranged in parallel directions, with at least one first prism positioned between every two second prisms. The first prism expands the light intensity over a wide viewing angle through a design with a large slope on its hypotenuse, while the second prism recovers and reuses the light intensity from the wide viewing angle through a right-angle prism structure to maintain high brightness at a positive viewing angle.

[0054] When the ratio of the first prism to the second prism is between 1:1 and 1:2, the redistribution of light intensity can be balanced by adjusting the distribution density, ensuring brightness at the positive viewing angle while enhancing light intensity compensation at a wide viewing angle. When the ratio is fixed, the two types of prisms work together to distribute evenly, avoiding local light intensity fluctuations and simplifying mold design. When the ratio is not fixed, a higher proportion of the first prism in the edge area enhances edge viewing angle compensation, while an increased proportion of the second prism in the center area maintains core brightness, achieving uniform light intensity distribution across the entire image.

[0055] The first prism employs a design with varying slopes, combined with the isosceles right trapezoidal structure of the second prism. Through simple mold adjustments, dispersed control of the light path is achieved, both extending the light propagation path to enhance scattering ability and avoiding the high-cost processing issues associated with complex microstructures. This application, through the synergistic effect of the above technical solutions, improves the uniformity of light intensity from a spatial viewing angle while maintaining high brightness at the positive viewing angle.

[0056] The above is only one specific implementation of this application, and any other improvements made based on the concept of this application shall be considered within the scope of protection of this application.

Claims

1. A brightness enhancement film, characterized in that, include: Multiple first prism structures; Multiple second prism structures; The cross-section of the first prism structure is an isosceles trapezoid, and the cross-section of the second prism structure is an isosceles triangle. The arrangement direction of the first prism structure is parallel to the arrangement direction of the second prism structure. At least one of the first prism structures is included between the two second prism structures.

2. The brightness enhancement film according to claim 1, characterized in that, The ratio of the number of the first prism structure to the number of the second prism structure is in the range of 1:1 to 1:

2.

3. The brightness enhancement film according to claim 2, characterized in that, The ratio of the number of the first prism structure to the number of the second prism structure in the brightness enhancement film is a fixed value.

4. The brightness enhancement film according to claim 2, characterized in that, The ratio of the number of the first prism structure to the number of the second prism structure in the brightness enhancement film gradually decreases from the edge to the center.

5. The brightness enhancement film according to claim 1, characterized in that, The hypotenuses of the isosceles trapezoids in the multiple first prism structures have different slopes.

6. The brightness enhancement film according to claim 1, characterized in that, The cross-section of the second prism structure is an isosceles right triangle.

7. A laminated brightening film, characterized in that, Includes a brightness enhancement film as described in any one of claims 1-6 and a prism film.

8. The laminated brightening film according to claim 7, characterized in that, A brightness enhancement film is disposed above the prism film, and an adhesive layer is included between the brightness enhancement film and the prism film.

9. A backlight module, characterized in that, Including the laminated brightening film as described in claim 7 or 8.

10. A display device, characterized in that, Includes the backlight module as described in claim 9.

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