Large-viewing-angle composite optical film and preparation method thereof

Abstract

The embodiment of the invention provides a large-viewing-angle composite optical film. The large-viewing-angle composite optical film comprises a base material film layer; the first prism film layer is arranged on one side of the base material film layer; the second prism film layer is arranged on the other side of the base material film layer; a plurality of first prism units extending in the first direction are arranged on the side, close to the base material film layer, of the first prism film layer, and a platform interval is formed between every two adjacent first prism units; a plurality of second prism units extending along a second direction are arranged on one side, adjacent to the base material film layer, of the second prism film layer; wherein the first direction intersects with the second direction, and the first prism units and the second prism units are oppositely arranged in the direction perpendicular to the base material film layer. The utilization rate of light energy is improved, and the loss of central brightness is effectively inhibited while the visual angle is obviously expanded. After the first prism film layer and the second prism film layer are compounded, on the basis of maintaining high brightness gain, the field angle is obviously widened, and collaborative optimization of brightness attenuation gentle and overall optical uniformity under a large angle of view is realized.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a wide-viewing-angle composite optical film and its preparation method. Background Technology

[0002] With the rapid development of educational informatization and smart office, interactive whiteboards and other display devices are becoming increasingly popular. Users' need to view screens from different positions and angles is becoming more common, thus placing higher demands on the optical performance of display panels, especially brightness retention, color consistency, and image clarity at wide viewing angles.

[0003] In existing technologies, optical films are a key component for improving display performance, but traditional optical films still have some limitations: Prism films concentrate light through a prism structure, effectively improving the brightness of the front of the display. However, when viewed from the side, the brightness of the display is significantly reduced, and color shift is prone to occur, affecting the viewing experience. Diffuser films rely on scattering particles inside the film layer to disperse light. Although this can expand the viewing angle, it will lead to a decrease in front brightness and may impair image clarity, resulting in a fogging phenomenon. Microlens array films use a microlens structure to modulate the light path, which can improve the viewing angle to some extent. However, the manufacturing process is complex and the production cost is high. Moreover, its optical design often involves a trade-off between viewing angle and front brightness. In application scenarios that pursue ultra-high brightness, its brightness improvement effect is limited.

[0004] Therefore, there is an urgent need for an optical film that can achieve a balance between high brightness, ultra-wide viewing angle and high definition, while also taking into account the feasibility of the manufacturing process and cost control, in order to meet the market's urgent demand for high-performance display devices. Summary of the Invention

[0005] The purpose of this application is to solve the problem that traditional optical films cannot simultaneously meet the requirements of high brightness, wide viewing angle and high definition in the prior art. It proposes a wide viewing angle composite optical film that achieves an ultra-wide viewing angle without significantly losing the center brightness.

[0006] In a first aspect, embodiments of this application provide a wide-viewing-angle composite optical film, comprising: a substrate film layer; a first prism film layer disposed on one side of the substrate film layer; and a second prism film layer disposed on the other side of the substrate film layer; wherein the first prism film layer has a plurality of first prism units extending along a first direction on the side adjacent to the substrate film layer, and a platform spacing is provided between adjacent first prism units; and the second prism film layer has a plurality of second prism units extending along a second direction on the side adjacent to the substrate film layer; wherein the first direction intersects the second direction, and the first prism units and the second prism units are disposed opposite each other in a direction perpendicular to the substrate film layer.

[0007] In some embodiments, the first direction and the second direction are perpendicular to each other.

[0008] In some embodiments, the cross-sections of each first prism unit form similar triangles with a vertex angle of 40° to 50°.

[0009] In some embodiments, the platform spacing is 5 μm to 15 μm.

[0010] In some embodiments, the center distance between adjacent first prism units is 20 μm to 60 μm.

[0011] In some embodiments, the cross sections of each second prism unit form similar triangles with apex angles of 80° to 100°.

[0012] In some embodiments, the center distance between adjacent second prism units is 50 μm to 70 μm.

[0013] In some embodiments, both the first prism film layer and the second prism film layer are composed of ultraviolet-curable resin, and the refractive index of the ultraviolet-curable resin is 1.50 to 1.60.

[0014] In some embodiments, the substrate material includes at least one of polyethylene terephthalate, cellulose triacetate, or polymethyl methacrylate.

[0015] Secondly, embodiments of this application provide a method for preparing a wide-viewing-angle composite optical film, comprising the following steps: Preparation of diffusion film and back coating film: The first PET substrate is subjected to thermosetting treatment to form diffusion film; the second PET substrate is subjected to UV curing treatment to form back coating film; Forming the first prism film layer and performing the first bonding: The first prism unit is initially cured on the diffusion film through the first mold to form the first prism film layer; the first prism unit is laminated to the upper surface of the intermediate PET substrate layer while maintaining the incompletely cured state, and the intermediate film layer is obtained after a second curing. Forming a second prism film layer and performing a second bonding: The second prism unit is initially cured on the back coating film using a second mold to obtain the second prism film layer; the second prism unit is laminated to the lower surface of the intermediate PET substrate layer while remaining in an incompletely cured state, and after a second curing, a large-viewing-angle composite optical film is obtained.

[0016] The wide-viewing-angle composite optical film of this application improves light energy utilization by setting a first prism film layer and a second prism film layer on both sides of the substrate film layer, and setting the prism extension directions of the two to intersect and to be positioned opposite each other in the direction perpendicular to the substrate film layer. This significantly expands the viewing angle while effectively suppressing the loss of center brightness.

[0017] The cross-sections of multiple first prism units form similar triangles, which can guide light to undergo asymmetrical refraction to expand its diffusion angle. The apex angle of the triangle is a small acute angle, making its slope more gentle, thereby improving the brightness uniformity of the screen under different viewing angles and avoiding obvious color drift or dark areas. At the same time, the setting of the platform spacing can reduce light interference and stray reflection between adjacent first prism units, effectively suppress moiré patterns and further improve brightness uniformity.

[0018] After the first prism film layer and the second prism film layer are combined, the field of view is significantly widened while maintaining high brightness gain, and the brightness attenuation is smoothed and the overall optical uniformity is optimized in a coordinated manner under a large viewing angle. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the large-viewing-angle composite optical film according to an embodiment of this application.

[0020] Figure 2 This is a flowchart illustrating the preparation of a wide-viewing-angle composite optical film according to an embodiment of this application.

[0021] Explanation of reference numerals in the attached figures: 1. First prism film layer; 11. First prism unit; 2. Substrate film layer; 3. Second prism film layer; 31. Second prism unit. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application will be presented in conjunction with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0023] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] This application provides a wide-viewing-angle composite optical film. This wide-viewing-angle composite optical film can be widely used in liquid crystal displays, televisions, tablet computers, automotive displays, advertising screens, and other display devices that require improved viewing angles and brightness, and is particularly suitable for backlight module structures that need to maintain high brightness gain over a wide angle range. To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0027] like Figure 1 As shown, this application embodiment provides a wide-viewing-angle composite optical film, which includes: a substrate film layer 2; a first prism film layer 1 disposed on one side of the substrate film layer 2; and a second prism film layer 3 disposed on the other side of the substrate film layer 2. The first prism film layer 1 has a plurality of first prism units 11 extending along a first direction on the side adjacent to the substrate film layer 2, and a platform spacing is provided between adjacent first prism units 11. The second prism film layer 3 has a plurality of second prism units 31 extending along a second direction on the side adjacent to the substrate film layer 2. The first direction intersects the second direction, and the first prism unit 11 and the second prism unit 31 are disposed opposite each other in a direction perpendicular to the substrate film layer 2.

[0028] Specifically, wide-viewing-angle composite optical films are used in the backlight modules of display devices to improve the light emission angle and brightness uniformity of liquid crystal displays. The substrate film layer 2, as the main carrier of the entire composite optical film, needs to possess high light transmittance, good mechanical strength, and excellent dimensional stability to withstand the coating and curing processes of the functional film layers on both sides. The first prism film layer 1 is located on one side of the substrate film layer 2, mainly responsible for wide-angle diffusion in the horizontal or vertical direction; the first direction is typically any direction between the horizontal and vertical axes. The second prism film layer 3 is located on the other side of the substrate film layer 2, mainly responsible for converging light from the other direction. The second direction intersects with the first direction, achieving a bidirectional composite optical control effect.

[0029] The first prism unit 11 and the second prism unit 31 are arranged opposite each other in a direction perpendicular to the substrate film layer 2. Specifically, the prism projection positions of the first prism unit 11 and the second prism unit 31 avoid each other or partially overlap in the plane of the substrate film layer 2, but preferably are staggered. This can effectively reduce the moiré pattern phenomenon caused by the periodic overlap between the two prism structures, thereby improving the clarity and uniformity of the displayed image.

[0030] In this embodiment, the first direction and the second direction are perpendicular to each other, that is, the extension direction of the first prism unit 11 intersects the extension direction of the second prism unit 31 at a 90° angle. This perpendicularly intersecting arrangement enables independent control of light rays in both horizontal and vertical directions, allowing the composite optical film to achieve significant viewing angle expansion and brightness optimization in both orthogonal directions. The perpendicularly intersecting structure also makes it easier to achieve mold alignment and structural stability during processing, making it particularly suitable for mass production.

[0031] In one implementation, the angle between the first direction and the second direction can be set to a non-right angle such as 60 degrees or 45 degrees. Although this non-perpendicular arrangement increases the difficulty of manufacturing, it can optimize the lighting for specific viewing angles in certain display applications, such as vehicle displays or specially shaped advertising screens, thereby meeting the requirements of asymmetrical viewing angles.

[0032] In this embodiment, the cross-sections of the first prism unit 11 form similar triangles, and the triangular shapes of each first prism unit 11 remain highly similar within the allowable process error range. The apex angle of the similar triangles is 40° to 50°.

[0033] Preferably, the apex angle is further limited to between 44° and 48°, for example, 44°, 45°, 46°, 47° or 48°. The size of the apex angle directly affects the tilt of the inclined surface of the first prism unit 11: the smaller the apex angle, the gentler the inclined surface, which helps to improve the viewing angle in the horizontal and vertical directions, making the brightness distribution of the screen more uniform under different viewing angles, and reducing the occurrence of "color shift" or "dark areas".

[0034] In this embodiment of the application, a platform spacing of 5 μm to 15 μm is provided between adjacent first prism units 11.

[0035] In one embodiment, the platform spacing is 10 μm. The presence of the platform spacing can effectively prevent the prism apex from sticking together due to mold wear or resin shrinkage during the manufacturing process of adjacent prism units. At the same time, it can also reduce stress concentration at the prism apex caused by external forces, thereby improving the scratch resistance of the composite optical film.

[0036] In this embodiment, the center distance between adjacent first prism units 11 is controlled between 20 μm and 60 μm.

[0037] Preferably, the center distance is between 50μm and 60μm. The selection of the center distance needs to take into account both brightness gain and moiré suppression effect. If the center distance is too small, it will result in too high prism density, which is prone to producing moiré patterns with the dots of the lower light guide plate; if the center distance is too large, it will reduce the prism's ability to control light, resulting in a decrease in brightness gain.

[0038] In the embodiments of this application, the cross-section of the second prism unit 31 forms a similar triangle with a vertex angle of 80° to 100°.

[0039] Preferably, the apex angle is 85° to 95°, for example, 85°, 90° or 95°. A larger apex angle makes the two inclined surfaces of the second prism unit 31 steeper, which increases the degree of light deflection at the interface, thereby playing a significant light-focusing role and making the light more concentrated in the central direction.

[0040] For example, when the apex angle of the second prism unit 31 is 90°, its two inclined surfaces and the bottom surface form an angle of 45° respectively. The incident light rays are directionally deflected on the inclined surfaces, converging the light rays towards the normal direction, thereby increasing the positive light intensity.

[0041] In this embodiment of the application, the center distance between adjacent second prism units 31 is 50 μm to 70 μm.

[0042] Preferably, the center distance is 55μm to 65μm.

[0043] In this embodiment, the first prism film layer 1 is composed of ultraviolet-curable resin, and the refractive index of the ultraviolet-curable resin is 1.50 to 1.60.

[0044] Preferably, the refractive index is between 1.56 and 1.58.

[0045] In one embodiment, the formation process of the first prism film layer 1 includes the following steps. First, a UV-curable resin is uniformly coated on one side surface of the substrate film layer 2. This resin has good flowability and wettability in its uncured state. The coating method can employ precision coating techniques such as microgravure coating, slot coating, or comma coating, with the wet coating thickness controlled within the range of 15μm to 40μm. Subsequently, the coated substrate film layer 2 is bonded to a roller mold having a first prism structure. The surface of the roller mold is engraved with a microstructure array complementary to the first prism unit 11. Under UV irradiation, the resin rapidly crosslinks and cures, simultaneously and precisely replicating the microstructure on the roller mold, thereby forming a highly consistent first prism film layer 1 on one side of the substrate film layer 2. Finally, after removing it from the roller mold, a semi-finished product with the first prism film layer 1 is obtained.

[0046] In this embodiment, the second prism film layer 3 also uses a UV-curable resin with a refractive index of 1.50 to 1.60, and is obtained by UV-curable resin through a roller mold pressing process.

[0047] Preferably, the refractive index is also limited to the range of 1.56 to 1.58, and the same batch or the same formula of resin is used as the first prism film layer 1 to ensure that the thermal expansion coefficients of the two prism film layers are consistent and to prevent warping or peeling under high temperature and high humidity conditions.

[0048] In this embodiment, the raw material for the substrate film layer 2 is selected from at least one of polyethylene terephthalate, cellulose triacetate, or polymethyl methacrylate. Polyethylene terephthalate is currently the most commonly used material for the substrate film layer 2, with a light transmittance of over 90% and high tensile strength and dimensional stability, making it suitable for large-area display devices. Cellulose triacetate, due to its excellent surface smoothness and low birefringence, is often used in displays with extremely high image quality requirements. Although polymethyl methacrylate has a slightly lower light transmittance than the former two, it has higher hardness and excellent scratch resistance, making it suitable for portable devices susceptible to external forces.

[0049] Preferably, optical grade polyethylene terephthalate is used as the main raw material of the substrate film layer 2, and its thickness is controlled between 50 μm and 250 μm. Further, in most display applications, the thickness of the substrate film layer 2 is preferably between 100 μm and 188 μm, so as to achieve a balance between mechanical strength and overall optical film flexibility.

[0050] In one embodiment, a small amount of UV absorber or antistatic agent may be added to the substrate film layer 2 during preparation to improve optical stability and ease of application during long-term use. After corona treatment or plasma treatment of both surfaces of the substrate film layer 2, the adhesion of the subsequent UV-curable resin coating can be significantly improved.

[0051] In one embodiment, the substrate film layer 2 is made of a blend of polyethylene terephthalate and a small amount of polymethyl methacrylate, and is formed into a double-layer structure through a co-extrusion process, which not only ensures the overall flexibility of the film material, but also improves the surface wear resistance.

[0052] like Figure 2 As shown, in a second aspect, embodiments of this application provide a method for preparing a wide-viewing-angle composite optical film. This method achieves precise composite of multi-layer optical structures through a step-by-step molding and lamination process, effectively improving the viewing angle and brightness performance of the optical film. The preparation method includes the following steps: S1. Preparation of diffusion film and back coating film: A diffusion film is prepared by coating the lower surface of the first PET substrate and then using a thermosetting method to form a microstructure layer with light scattering function on the surface.

[0053] The upper surface of the second PET substrate is coated and UV-cured to form a coating with anti-scratch, anti-sticking and enhanced adhesion functions, thereby obtaining a back coating film.

[0054] S2. Form the first prism film layer and perform the first bonding: The diffusion film is imprinted using a first mold with a pre-defined prism structure, and then subjected to a first stage of UV irradiation to pre-cure it, thus forming the first prism unit and obtaining the first prism film layer. The degree of curing in this stage is controlled between 50% and 80% to ensure that the prism unit is shaped and has a certain degree of adhesion on the surface.

[0055] Subsequently, while the first prism unit remains in an incompletely cured viscous state, it is pressed and bonded to the upper surface of an intermediate PET substrate layer using a laminating roller.

[0056] After lamination, a second stage of full UV irradiation (secondary curing) is performed to completely cure the first prism unit and firmly bond it with the intermediate PET substrate layer to obtain the intermediate film layer.

[0057] S3. Form the second prism film layer and perform a second bonding: The back coating film is imprinted using a second mold with a different prism structure and pre-cured by UV irradiation in the first stage to form the second prism unit, thereby obtaining the second prism film layer.

[0058] Similarly, the second prism unit is kept in an incompletely cured viscous state and is aligned and laminated with the lower surface of the intermediate film layer (i.e., the intermediate PET substrate layer).

[0059] Finally, after a second curing process, the layers are fully bonded together, resulting in a wide-viewing-angle composite optical film.

[0060] In steps S2 and S3, the prism structure axes of the first prism unit and the second prism unit are perpendicular to each other.

[0061] The method for preparing a wide-view composite optical film provided in this application utilizes the surface adhesion of the incompletely cured layer to achieve direct interlayer bonding without additional adhesive, simplifying the process, reducing interface loss, and improving optical efficiency. Simultaneously, the step-by-step independent molding of the prism layer allows for more precise control of the microstructure quality of each layer, and the supporting effect of the intermediate layer ensures the overall flatness and dimensional stability of the composite film.

[0062] Example 1 The preparation of a wide-viewing-angle composite optical film includes the following steps: S1. Preparation of diffusion film and back coating film: A diffusion film is prepared by coating the lower surface of the first PET substrate and then using a thermosetting method to form a microstructure layer with light scattering function on the surface.

[0063] The upper surface of the second PET substrate is coated and UV-cured to form a coating with anti-scratch, anti-sticking and enhanced adhesion functions, thereby obtaining a back coating film.

[0064] S2. Form the first prism film layer and perform the first bonding: The diffusion film is imprinted using a first mold with a pre-defined prism structure, and then subjected to a first stage of UV irradiation to initially cure it and form a first prism unit, thereby obtaining the first prism film layer. The degree of curing in this stage is controlled at 60%. The apex angle of the first prism unit of the first prism film layer is 44°, the center distance between adjacent first prism units is 60 μm, and the plateau distance between adjacent first prism units is 10 μm.

[0065] Subsequently, while the first prism unit remains in an incompletely cured viscous state, it is pressed and bonded to the upper surface of an intermediate PET substrate layer using a laminating roller.

[0066] After lamination, a second stage of full UV irradiation (secondary curing) is performed to completely cure the first prism unit and firmly bond it with the intermediate PET substrate layer to obtain the intermediate film layer.

[0067] S3. Form the second prism film layer and perform a second bonding: The back coating film is imprinted using a second mold with a different prism structure, and then pre-cured by UV irradiation in the first stage to form the second prism unit, thereby obtaining the second prism film layer. The apex angle of the second prism unit of the second prism film layer is 90°, and the center distance between adjacent second prism units is 60μm.

[0068] Similarly, the second prism unit is kept in an incompletely cured viscous state and is aligned and laminated with the lower surface of the intermediate film layer (i.e., the intermediate PET substrate layer).

[0069] Finally, after a second curing process, the layers are fully bonded together, resulting in a wide-viewing-angle composite optical film.

[0070] In steps S2 and S3, the prism structure axes of the first prism unit and the second prism unit are perpendicular to each other.

[0071] The refractive index of both the first and second prism films is 1.55.

[0072] Example 2 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0073] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 46°; the center distance between adjacent first prism units is 60μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 10μm.

[0074] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 85°; the center distance between adjacent second prism units is 60μm.

[0075] Example 3 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0076] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 48°; the center distance between adjacent first prism units is 60μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 10μm.

[0077] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 90°; the center distance between adjacent second prism units is 60μm.

[0078] Example 4 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0079] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 50°; the center distance between adjacent first prism units is 60μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 10μm.

[0080] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 95°; the center distance between adjacent second prism units is 60 μm.

[0081] Example 5 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0082] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 46°; the center distance between adjacent first prism units is 50μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 10μm.

[0083] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 90°; the center distance between adjacent second prism units is 70 μm.

[0084] Example 6 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0085] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 46°; the center distance between adjacent first prism units is 25μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 10μm.

[0086] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 90°; the center distance between adjacent second prism units is 70 μm.

[0087] Example 7 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0088] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 46°; the center distance between adjacent first prism units is 50μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 5μm.

[0089] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 90°; the center distance between adjacent second prism units is 70 μm.

[0090] Example 8 This embodiment provides another method for preparing a large-view composite optical film. The basic steps are the same as in Embodiment 1. The main difference is that the structures of the first mold and the second mold are adjusted to adapt to different optical performance and process requirements.

[0091] In step S2, the first prism film layer formed by pressing with the first mold has the following structural features: The apex angle of the first prism unit is 46°; the center distance between adjacent first prism units is 50μm; a platform structure is provided between adjacent first prism units, and the platform spacing is 15μm.

[0092] In step S3, the second prism film layer formed by the second mold imprinting has the following structural features: The apex angle of the second prism unit is 90°; the center distance between adjacent second prism units is 70 μm.

[0093] The apex angle of the first prism unit, the center distance between adjacent first prism units, the platform spacing between adjacent first prism units, the apex angle of the second prism unit, and the center distance between adjacent second prism units in each embodiment are listed in Table 1.

[0094]

[0095] The performance test results of each embodiment and the conventional composite film are listed in Table 2. Among them, the luminance percentage refers to the relative luminance ratio of the wide-viewing-angle composite optical film prepared in the embodiments of this application at the positive viewing angle, with the luminance at the center point (positive viewing angle) of the conventional composite film as 100% as the benchmark.

[0096]

[0097] As can be seen from Table 2, all embodiments suffered a loss in brightness (72%-84%), but the viewing angle was improved.

[0098] In Example 1, the luminance percentage is 75%. This means that after using this wide-viewing-angle optical film, the brightness at the center of the screen is only 75% of that of a traditional film, resulting in a 25% loss of brightness. However, at the same time, its viewing angle is expanded from the traditional 41° to 56°.

[0099] Example 6 has a luminance percentage of 84%. Example 6 only loses 16% of brightness, but its viewing angle is significantly expanded to 60°-61°. For scenarios such as educational whiteboards and conference screens where multiple people need to view from the side, this trade-off of a small amount of brightness for a much wider viewing angle is worthwhile and efficient.

[0100] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A wide-viewing-angle composite optical film, characterized in that, include: Substrate film layer; The first prism film layer is disposed on one side of the substrate film layer; The second prism film layer is disposed on the other side of the substrate film layer; The first prism film layer has a plurality of first prism units extending along a first direction on one side adjacent to the substrate film layer, and a platform spacing is provided between adjacent first prism units. The second prism film layer has a plurality of second prism units extending along the second direction on one side adjacent to the substrate film layer; Wherein, the first direction intersects the second direction, and the first prism unit and the second prism unit are arranged opposite each other in a direction perpendicular to the substrate film layer.

2. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The first direction and the second direction are perpendicular to each other.

3. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The cross-sections of each of the first prism units form similar triangles; their apex angles are 40° to 50°.

4. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The platform spacing is 5μm to 15μm.

5. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The center distance between adjacent first prism units is 20 μm to 60 μm.

6. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The cross-sections of each of the second prism units form similar triangles with apex angles of 80° to 100°.

7. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The center distance between adjacent second prism units is 50 μm to 70 μm.

8. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, Both the first prism film layer and the second prism film layer are composed of ultraviolet light-curing resin, and the refractive index of the ultraviolet light-curing resin is 1.50 to 1.

60.

9. The wide-viewing-angle composite optical film as described in claim 1, characterized in that, The substrate material includes at least one of polyethylene terephthalate, cellulose triacetate, or polymethyl methacrylate.

10. The method for preparing a large-viewing-angle composite optical film according to any one of claims 1-9, characterized in that, Includes the following steps: Preparation of diffusion film and back coating film: The first PET substrate is subjected to thermosetting treatment to form a diffusion film; The second PET substrate is subjected to UV curing treatment to form a back coating film; Forming the first prism film layer and performing the first bonding: The first prism unit is initially cured on the diffusion film by the first mold to form the first prism film layer; the first prism unit is laminated to the upper surface of the intermediate PET substrate layer while maintaining the incompletely cured state, and the intermediate film layer is obtained after a second curing. Forming a second prism film layer and performing a second bonding: The second prism unit is initially cured on the back coating film using a second mold to obtain the second prism film layer; the second prism unit is laminated to the lower surface of the intermediate PET substrate layer while remaining in an incompletely cured state, and after a second curing, the wide-angle composite optical film is obtained.

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