Brightness enhancement film

Abstract

The application relates to a brightness enhancement film, comprising a substrate layer, a functional structure area and two auxiliary structure areas on the same side of the substrate layer, and a first protective film. The functional structure area contains a plurality of single optical structures, the auxiliary structure areas are located on both sides of the functional structure area and each contains at least one protective structure, the height of the protective structure is higher than that of the single optical structure, and the two sides of the first protective film are attached to the protective structure. The structure makes the first protective film be lifted when being rolled up, a buffer space is formed between the functional structure area and the protective film, and the optical structure is prevented from being pressed to generate white stains. The height ratio of the protective structure to the single optical structure can be 1.8-2.2, and the cross-sectional shape can adopt a triangle, a trapezoid or a rectangle. The brightness enhancement film can further comprise a back coating layer on the back of the substrate layer and a second protective film covering the back coating layer. The traditional edge strip is replaced by an integrated structure, white stains are solved, production cost is reduced, and production efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of optical film technology, and more particularly to a brightness enhancement film. Background Technology

[0002] Brightness enhancement film is an optical thin film used in TFT-LCD backlight modules, its core function being to improve the luminous efficiency of the entire backlight system. A common structure includes a flat substrate and multiple prism structures for converging light. As LCD devices become thinner and higher-definition, the market demands higher brightness and image quality, driving the demand for high-performance optical films.

[0003] In the production process of brightness enhancement films, to ensure proper winding, the industry addresses the issue of "white stains" caused by insufficient resilience due to the use of rigid adhesive on the front surface of high-folding brightness enhancement films shipped in roll form during winding, which results in localized pressure. Please refer to [link to relevant documentation]. Figure 1 The currently commonly used technical solution is to attach edge strips 230 (which can be made of PET material) between the molding bare mold material and the protective film on the left and right edges of the roll material to raise it. This method can effectively reduce the degree of "white stains".

[0004] While the edge strip method can alleviate whitening to some extent, this existing solution has the following drawbacks: increased manufacturing costs, as edge strips need to be attached to both sides of each roll of material, and the large amount of edge strips used increases direct material costs. Increased production efficiency and resource consumption, as adding a raw material to the lamination process requires additional machine adjustments to ensure accurate edge strip positioning. This not only consumes manufacturing time and labor costs, but also leads to increased material consumption and significant waste during the adjustment process. Furthermore, the brightening film roll product places higher demands on the control of subsequent processing (such as die-cutting depth), and any changes in any production stage may introduce new quality risks. Therefore, optimization is needed. Utility Model Content

[0005] The purpose of this application is to provide a brightness enhancement film that, by setting higher protective structures on both sides of the functional structure area, replaces the traditional external edge strip, effectively supporting the protective film during winding, thereby solving the white stain problem, avoiding the need for additional edge strip processes, and achieving the effects of reducing material costs and improving production efficiency. This purpose is achieved through the following technical solution: the brightness enhancement film of this application includes a substrate layer, a functional structure area, an auxiliary structure area, and a first protective film; The functional structure region and the auxiliary structure region are located on the same side of the substrate layer, including two auxiliary structure regions, which are located on both sides of the functional structure region, respectively. The functional structure region includes multiple individual optical structures, and each auxiliary structure region includes at least one protective structure; The first protective film is attached to both sides of the protective structure; The height of the protective structure exceeds the height of the individual optical structure.

[0006] In one embodiment, the ratio of the height of the protective structure to the height of the single optical structure is in the range of 1.8-2.2.

[0007] In one embodiment, the width of the auxiliary structure region is less than 10% of the width of the functional structure region.

[0008] In one embodiment, the aspect ratio of the protective structure is greater than 2.

[0009] In one embodiment, the protective structure is tilted outward from bottom to top in a direction away from the functional structure area.

[0010] In one embodiment, the top of the protective structure is flat and includes an adhesive layer.

[0011] In one embodiment, the cross-sectional shape of the protective structure is triangular, trapezoidal, or rectangular.

[0012] In one embodiment, both the single optical structure and the protective structure are prism structures.

[0013] In one embodiment, a back coating is also included, the back coating being formed on the side of the substrate layer opposite to the functional structure region.

[0014] In one embodiment, a second protective film is also included, which covers the back coating.

[0015] Compared with the prior art, this application has the following beneficial effects: This application sets up protective structures in the auxiliary structural areas on both sides of the brightness enhancement film body, with a height exceeding that of the single optical structure in the functional structural area. The protective structures can effectively support the first protective film covering them during winding, replacing the PET edge strips that are additionally attached in the traditional process to prevent "white stains". This directly saves the consumption of edge strip materials and reduces the direct material cost of the brightness enhancement film product.

[0016] In existing technologies, applying an external edge strip requires the introduction of additional raw materials and precise alignment during the film application process, leading to increased machine adjustments and significant material waste. This application replaces the external edge strip with an integrated, molded protective structure, simplifying the film application process, reducing machine adjustment time and material waste due to edge strip alignment, thereby improving production speed and capacity. Eliminating the external edge strip step also reduces the complexity of the film application process and its reliance on manual operation.

[0017] The height design of the protective structure, with a height-to-single-optical-structure ratio within the range of 1.8-2.2, provides suitable support gaps, helping to avoid the "whitening" problem caused by localized pressure. Simultaneously, the flat top of the protective structure (e.g., a trapezoidal or rectangular cross-section) and any applicable adhesive layer can enhance adhesion to the first protective film and improve the bonding between the film layers. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a brightness enhancement film in the prior art; Figure 2 This is a schematic diagram of the structure of the brightness enhancement film in one embodiment of this application; Figure 3 This is a schematic diagram of the structure of the brightness enhancement film in another embodiment of this application.

[0019] Explanation of reference numerals in the attached drawings: 100, substrate layer; 210, functional structure area; 211, single optical structure; 220, auxiliary structure area; 221, protective structure; 230, edge strip; 300, first protective film; 400, back coating; 500, second protective film. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] As described in the background section, during the winding process of brightness enhancement film rolls, the lack of resilience due to the use of rigid adhesive in the functional structural areas makes them prone to "whitening" defects under localized pressure. To address this issue, existing technologies typically use PET edge strips attached to both sides of the roll for elevation, but this method introduces additional material costs and process complexity. To overcome the aforementioned shortcomings of the prior art, this application provides a structurally integrated brightness enhancement film implementation scheme. The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. The brightness enhancement film of this embodiment, by forming auxiliary protective structures with specific height relationships on both sides of the functional structural areas, effectively supports the protective film during winding, thereby alleviating the whitening problem without the need for external edge strips. The following description will detail the layered structure of the brightness enhancement film, the structural characteristics of each region, and its optional implementation schemes. Please refer to... Figures 2 to 3 The brightness enhancement film includes a substrate layer 100, a functional structure region 210, an auxiliary structure region 220, and a first protective film 300. The functional structure region 210 and the auxiliary structure region 220 are located on the same side of the substrate layer 100. The auxiliary structure region 220 includes two auxiliary structure regions, which are located on both sides of the functional structure region 210. Each functional structure region 210 includes a plurality of individual optical structures 211. Each auxiliary structure region 220 includes at least one protective structure 221. The two sides of the first protective film 300 are attached to the protective structures 221. The height of the protective structure 221 exceeds the height of the individual optical structures 211.

[0024] In the brightness enhancement film structure involved in this application, a technical solution to solve the "white stain" problem during the roll winding process is constructed by integrating a functional structure region 210 and an auxiliary structure region 220 on the same side of the substrate layer 100, and utilizing a first protective film 300 in conjunction with a specifically designed protective structure 221 in the auxiliary structure region 220. Firstly, the substrate layer 100, as the supporting body of the brightness enhancement film, is typically made of transparent polymer materials such as optical-grade polyester (PET). The functional structure region 210, located on one side of the substrate layer 100, contains multiple individual optical structures 211. These individual optical structures 211 are typically prism structures, such as the positive or negative prism structures widely used in backlight modules, which converge light through refraction and reflection principles to enhance the brightness of the front of the backlight module. For example, existing brightness enhancement films using specific microstructure designs can increase the brightness of the backlight center by more than 130%. The functional structure region 210 in this application performs a similar brightness enhancement function.

[0025] On both sides of the functional structure region 210, auxiliary structure regions 220 are provided. Each auxiliary structure region 220 contains at least one protective structure 221. This is a key feature that distinguishes this application from the prior art and solves the "white stain" problem. Its height is designed to exceed the height of the individual optical structure 211 in the functional structure region 210. This height difference allows the first protective film 300 covering it to be effectively supported by the protective structure 221 when the roll is wound up, thereby forming a buffer space between the optical structure of the functional structure region 210 and the first protective film 300. This avoids indentation or deformation of the optical structure due to excessive local pressure, thus preventing the "white stain" phenomenon. In a preferred embodiment, the functional structure region 210 and the auxiliary structure region 220 are made of the same material and are formed simultaneously in the same step.

[0026] Finally, the first protective film 300 is attached to both sides of the protective structure 221, so that during the winding process, the stress fulcrum of the protective film is located on the protective structures 221 on both sides, rather than directly pressing on the optical structure of the functional structure area 210. This further isolates the direct effect of external pressure on the optical structure, ensuring that the functional structure area 210 is not damaged during transportation and storage. It is a targeted structural optimization for preventing white staining in roll-to-roll shipments.

[0027] In one embodiment of this application, the ratio of the height of the protective structure 221 to the height of the single optical structure 211 is set within the range of 1.8 to 2.2. Specifically, the height of the protective structure 221 is designed to exceed the height of the single optical structure 211 by 80% to 120%, so that when the first protective film 300 covers it and is rolled up, the protective structure 221 can establish sufficient support space between the film layers. For example, if the height of the single optical structure 211 of the functional structure region 210 is 24 micrometers, then the height of the protective structures 221 on both sides is set at about 48 micrometers, which can effectively bear the pressure from the protective film, thereby preventing the precise prism structure of the functional structure region 210 from being indented or deformed due to direct pressure. On the other hand, the setting of this height range also avoids the negative effects that may be caused by the protective structure 221 being too high. If the height of the protective structure 221 exceeds the height of the single optical structure 211 by more than 2.2 (i.e., more than 120%), it will result in an excessively large gap between the protective film of each layer of roll material and the functional structure region 210. After being wound into a roll, excessively large local gaps may cause the protective film to collapse to varying degrees in the direction of the functional structure region 210 under lamination. After long-term storage, this collapse may eventually lead to irreversible deformation of the optical film surface, resulting in poor image quality. Therefore, a ratio range of 1.8 to 2.2 is a technical solution that strikes a balance between effectively raising the film and avoiding film surface collapse.

[0028] From the perspective of mold manufacturing and processing, the protective structure 221 in this embodiment mainly serves as a riser, and there are no specific requirements for its optical performance. Therefore, during mold processing, structures with simpler cross-sectional shapes, such as trapezoids or rectangles, can be selected, or even directly formed by mold grooving. This reduction in requirements for structural consistency and processing precision helps to improve the processing efficiency of the mold.

[0029] In the structural design of the brightness enhancement film, the width of the auxiliary structural area 220 is limited to less than 10% of the width of the functional structural area 210. Controlling the width of the auxiliary structural area 220 within this range ensures that it can accommodate the necessary height of the protective structure 221 to achieve effective elevation, while maximizing the optically effective area of ​​the functional structural area 210. The auxiliary structural area 220 itself does not perform the core brightness enhancement function; its main purpose is to provide support for the protective film during roll winding. Therefore, while meeting the requirements for support strength and process feasibility (e.g., the width of the auxiliary structural area 220 can be set at 1-1.5 cm), limiting its width to a relatively small proportion helps reduce the material occupation of non-optical functional areas. An excessively wide auxiliary structural area 220 would make the sides of the roll too rigid, potentially affecting the flatness of the roll winding, increasing the difficulty of subsequent cutting processes, and generating more waste. Limiting its width to less than 10% of the width of the functional structural area 210 balances the edge support strength required during winding with the overall flexibility of the film material.

[0030] In the structural design of the brightness enhancement film, the aspect ratio of the protective structure 221 is set to be greater than 2, and its dimension (height) in the direction perpendicular to the substrate layer 100 is greater than its dimension (width) in the direction parallel to the substrate layer 100. This structural form makes it easy for the protective structure 221 to generate tension on the protective film when it is subjected to interlayer pressure from the first protective film 300 and during winding. This, together with other technical features defined in this application, such as the height of the protective structure 221 exceeding the height of the single optical structure 211 of the functional structure area 210 by 80%-120%, and the width of the auxiliary structure area 220 being less than 10% of the width of the functional structure area 210, ensures that the formed protective structure 221 can achieve the necessary support height within the limited width of the auxiliary structure area 220 (e.g., 1-1.5 cm), thereby achieving a balance between space utilization and structural efficiency.

[0031] In a further embodiment, the protective structure 221 is configured to slope outwards from bottom to top in a direction away from the functional structure region 210. When the sloped side of the protective structure 221 comes into contact with the first protective film 300 covering it, it generates a force component parallel to the surface of the substrate layer 100 and pointing outwards from the roll. This force substantially applies a tension effect to the protective film. Under the interlayer pressure of the roll, this tension effect helps reduce the tendency of the protective film to loosen and wrinkle when crossing the functional structure region 210, causing the protective film to adhere more tightly to the sloped top surfaces of the two protective structures 221, thereby improving the flatness and adhesion stability of the protective film in the winding state. This sloped design can be combined with the height setting and aspect ratio limit of the protective structure 221 in the foregoing embodiments. The outward tilt can be seen to some extent as increasing the actual contact area between the top surface of the protective structure 221 and the protective film or changing the direction of the contact force. This helps to transmit and disperse the vertical pressure between layers more evenly during winding, thereby improving the stability of the support and potentially reducing the risk of deformation or crushing of the protective structure 221 itself due to stress concentration.

[0032] In a specific embodiment, the top of the protective structure 221 is constructed as a plane, and an adhesive layer is provided on this plane to provide a continuous and stable support surface for the first protective film 300 covering it, thus more effectively dispersing interlayer pressure during winding. The adhesive layer on the top plane of the protective structure 221 primarily enhances the interfacial bonding between the first protective film 300 and the top surface of the protective structure 221, and can be made of materials such as acrylic adhesive, polyurethane adhesive, or silicone adhesive.

[0033] The protective structure 221 itself can have various cross-sectional shapes, such as triangular, trapezoidal, or rectangular structures. The selection of these structures is mainly based on their ease of processing and their support effect on the protective film. Compared with the complex prisms designed for specific optical performance in the functional structure area 210, the protective structure 221 of the auxiliary structure area 220 can adopt simpler structural features, such as forming a strip-like shape by carving a rectangular groove in a mold, which helps to improve the processing efficiency of the mold.

[0034] In one specific embodiment, both the single optical structure 211 in the functional structure region 210 and the protective structure 221 in the auxiliary structure region 220 are implemented as prism structures. Prism structures (e.g., positive or negative prisms) are a recognized mature technology in the field of optical films. The technical solution of this application further sets the protective structure 221 in the auxiliary structure region 220 as a prism structure as well. Firstly, this brings consistency in material selection and molding process. The prisms in the functional structure region 210 and the prisms in the protective structure 221 can be manufactured using the same mold in a one-time molding process, for example, by transferring the UV-cured resin onto a mold with the corresponding microstructure. This process integration avoids the introduction of different materials or multiple processing steps, which helps to improve production efficiency and reduce process complexity. Although the protective structure 221 is also a prism in shape, its main function is mechanical support rather than optical modulation. Therefore, the prism structure in this area can be simplified during mold processing and structural design. For example, a more regular triangular cross-section prism, or a trapezoidal or rectangular cross-section as previously mentioned in the dialogue, can be used, without pursuing complex prism profiles (such as combinations of high and low prisms or jitter structures) that may be optimized for specific optical performance, as in functional structure area 210. This ensures effective elevation while reducing the extreme requirements for machining accuracy in the corresponding areas of the mold.

[0035] In a further embodiment of this application, the brightening film further includes a back coating 400, which is formed on the surface of the substrate layer 100 opposite to the functional structure region 210. The back coating 400 can provide a physical barrier for the substrate layer 100, and can also introduce specific functional materials. Through specific microstructure design of the back coating 400 (such as a compound microlens structure), high haze and high opacity can be achieved.

[0036] Furthermore, it also includes a second protective film 500, which covers the back coating 400 and provides a physical barrier for the back coating 400. The back coating 400 itself may have specific surface microstructures or functional components, which are at risk of being scratched, contaminated or damaged during subsequent die-cutting, transportation or assembly. The presence of the second protective film 500 can effectively isolate such external physical contact and chemical contamination, thereby maintaining the integrity and functionality of the back coating 400 structure.

[0037] As described above, the brightness enhancement film provided in this application, by integrating a functional structure area and an auxiliary structure area on the same side of the substrate layer, is a technical solution to solve the "white stain" problem during the winding process of roll materials. The functional structure area includes multiple individual optical structures for optical brightness enhancement, and the auxiliary structure areas on both sides each include at least one protective structure. The height of the protective structure exceeds the height of the individual optical structure, so that the first protective film covering it is effectively supported during winding, thereby forming a buffer space between the optical structure in the functional structure area and the first protective film, avoiding indentation or deformation of the optical structure due to local pressure.

[0038] The height ratio of the protective structure to the individual optical structure is set within the range of 1.8 to 2.2, striking a balance between providing effective elevation and preventing membrane collapse. The width of the auxiliary structure area is less than 10% of the width of the functional structure area, maximizing the effective optical area and reducing material usage while ensuring support strength. The height-to-width ratio of the protective structure is greater than 2, enhancing its vertical stiffness and compressive stability. The cross-sectional shape of the protective structure can adopt simple structures such as triangles, trapezoids, or rectangles to improve mold processing efficiency. Both the individual optical structure and the protective structure can be implemented as prism structures, achieving material and process consistency through a one-time molding process.

[0039] This solution, through the above structural design, effectively solves the white stain problem during roll winding while achieving the brightening function, and also reduces material costs and improves production efficiency.

[0040] 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, It includes a substrate layer, a functional structural region, an auxiliary structural region, and a first protective film; The functional structure region and the auxiliary structure region are located on the same side of the substrate layer, including two auxiliary structure regions, which are located on both sides of the functional structure region, respectively. The functional structure region includes multiple individual optical structures, and each auxiliary structure region includes at least one protective structure; The first protective film is attached to both sides of the protective structure; The height of the protective structure exceeds the height of the individual optical structure.

2. The brightening film according to claim 1, characterized in that, The ratio of the height of the protective structure to the height of the single optical structure is in the range of 1.8-2.

2.

3. The brightening film according to claim 1, characterized in that, The width of the auxiliary structure area is less than 10% of the width of the functional structure area.

4. The brightening film according to claim 1, characterized in that, The aspect ratio of the protective structure is greater than 2.

5. The brightening film according to claim 4, characterized in that, The protective structure tilts outward from bottom to top in the direction away from the functional structure area.

6. The brightening film according to claim 4, characterized in that, The top of the protective structure is flat and includes an adhesive layer.

7. The brightening film according to claim 1, characterized in that, The cross-sectional shape of the protective structure is triangular, trapezoidal, or rectangular.

8. The brightening film according to claim 1, characterized in that, Both the single optical structure and the protective structure are prism structures.

9. The brightening film according to claim 1, characterized in that, It also includes a back coating layer, which is formed on the side of the substrate layer opposite to the functional structure region.

10. The brightening film according to claim 9, characterized in that, It also includes a second protective film, which covers the back coating.

Images