Viewing film and backlight module

Abstract

In order to solve the technical problem that two-dimensional viewing angle cannot be differentiated under a collimated backlight, the application provides a viewing angle film for a collimated backlight and a backlight module. The viewing angle film comprises, from bottom to top, an optical deflection layer, a functional layer, a lower prism layer and an upper prism layer. The microstructure of the functional layer is a circular ring Fresnel prism structure, the top angle of the cross-section of the prism structure is upward, two base angles of the triangle are large and small, β1<β2, the smaller base angle β1 is away from the center point of the Fresnel structure, and the larger base angle β2 is close to the center point of the Fresnel structure. In the collimated backlight, the viewing angle film provided by the application can effectively realize the differentiation of two-dimensional brightness viewing angle in horizontal and vertical directions, and realize the viewing angle offset of the central high-brightness display area.

Description

Technical Field

[0001] This invention relates to an optical viewing angle film, and more particularly to a viewing angle film and backlight module suitable for collimated backlights. Background Technology

[0002] With the continuous development of information technology, display technology is being used more and more widely in daily life, and the performance requirements for display devices are also increasing. For example, in in-vehicle displays, drivers often need to turn their heads or look down to switch viewing angles when viewing the instrument panel or central control display, creating blind spots for a short period of time. Therefore, in-vehicle displays often require specific viewing angles. In addition, smartphones and other portable electronic products are often widely used as navigation systems, but these devices are usually placed to one side during use, causing inconvenience in viewing or poor display effects. The above situations require display modules to have differentiated viewing angle performance in two dimensions, such as a wide brightness viewing angle in the horizontal direction and a narrow brightness viewing angle in the vertical direction, or the ability to emit light at specific angles.

[0003] Conventional solutions to this problem often involve incorporating complex backlight controls into the display panel, such as LED strips with different emission angles, raster films, and wide-viewing-angle films, to achieve narrow or wide viewing angles in the final displayed image. Meeting specific viewing angle requirements is achieved through light guide films to deflect light, i.e., shifting the center brightness viewing angle. These solutions typically only allow for single-dimensional control and cannot simultaneously achieve multi-dimensional control, such as horizontal or vertical adjustment.

[0004] In addition, current conventional display modules typically use Lambertian light sources for backlighting. These sources initially emit light at large angles, which cannot be utilized, resulting in reduced luminous efficiency. To achieve higher brightness, collimated light sources are increasingly being used in display backlighting. Collimated light sources with extremely small emission angles offer more concentrated light and better center brightness. However, to date, research on using optical films to achieve two-dimensional viewing angle differentiation and viewing angle shift in collimated backlighting is still limited.

[0005] Therefore, it is necessary to design an optical film to achieve differentiation of two-dimensional viewing angles and shift of viewing angle under collimated backlight. Summary of the Invention

[0006] To address the technical problem of the inability to differentiate two-dimensional viewing angles under collimated backlights, this invention provides a viewing angle film and a backlight module for collimated backlights. In collimated backlights, particularly those including a reflective module, the viewing angle film provided by this invention can effectively achieve differentiation of two-dimensional brightness viewing angles in the horizontal and vertical directions, and also achieve viewing angle shifting of the central high-brightness display area.

[0007] Two-dimensional perspective differentiation refers to the difference between the horizontal and vertical viewing angles, i.e., the creation of a difference. For example, as the horizontal viewing angle increases, the vertical viewing angle decreases. Furthermore, differentiation refers to the difference in the magnitude of the viewing angles in the horizontal and vertical directions, and the different changes in the increase or decrease of the viewing angle.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0009] The present invention provides a viewing angle film, which comprises, from bottom to top, an optical deflection layer, a functional layer, a lower prism layer and an upper prism layer.

[0010] The present invention provides a viewing angle film, which comprises a four-layer structure from bottom to top: an optical deflection layer, a functional layer, a lower prism layer, and an upper prism layer.

[0011] When light passes through the viewing angle film provided by this invention, its horizontal half-peak brightness viewing angle can be adjusted from 22° to 56°, and its vertical half-peak brightness viewing angle can be adjusted from 40° to 74°, thus presenting a flat, high-brightness display effect in the central area in actual display (i.e., a brightness display effect that is wide in the horizontal direction and narrow in the vertical direction).

[0012] The viewing angle film provided by this invention can achieve an appropriate vertical offset of the originally centered high-brightness display area to meet the needs of a specific viewing angle, with the offset amount ranging from -9.7° to 30.0°.

[0013] Furthermore, each of the four layers can consist of a base layer and a structural layer, or it can be a single structural layer. When the structural layer is formed using a molding process, the base layer may not exist, and only the structural layer remains. When the structural layer is formed using a photopolymerization process, the base layer is a conventional substrate layer, and the structural layer of the optical deflection layer is located below the substrate layer, while the structural layers of the functional layer and the prism layer are located above the substrate layer.

[0014] Furthermore, all of the substrate layers are transparent substrates.

[0015] Furthermore, the substrate material can be selected from one or more combinations of polyethylene terephthalate (PET), cellulose triacetate (TAC), polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), etc.

[0016] Furthermore, the thickness of the substrate layer is 25-250 μm.

[0017] Furthermore, the primary function of the first structural layer, the optical deflection layer, is to deflect the collimated light emitted from the collimated backlight in a directional manner, thereby achieving a viewing angle shift in the center brightness of the final displayed image.

[0018] The optical polarization layer is the first structural layer. The functional layer is the second structural layer. The lower prism layer is the third structural layer. The upper prism layer is the fourth structural layer.

[0019] Furthermore, the microstructure of the first structural layer optical deflection layer is formed by tiling prisms, the cross-section of which is a common triangle or a right triangle, and the width of the base of the triangle can be 50-200μm.

[0020] Furthermore, the apex angle of the triangle in the cross-section of the prism of the optical deflection layer points downwards. The apex angle of the triangle in the cross-section of the prism structure of the functional layer points upwards; the apex angles of the prism structures of the upper and lower prism layers also point upwards.

[0021] Furthermore, the two base angles of the triangle in the cross-section of the first structural layer optical deflection layer are one large and one small (i.e., α1 < α2), so as to deflect the light towards the side with the larger base angle α2.

[0022] Furthermore, the smaller base angle α1 of the triangle is preferably between 0° and 30°. When the base angle α1 = 45°, the collimated light mainly undergoes total internal reflection on the optical deflection layer, losing its structural effectiveness. The larger base angle α2 is selected between α1 and 90°. When α2 is 90°, the cross-section is a right triangle; when α2 is less than 90°, the cross-section is a regular triangle.

[0023] Furthermore, the material of the first structural layer optical polarization layer can be selected from acrylic resin, PMMA, PC, etc. When the material is acrylic resin, UV curing process is preferred. When the material is PMMA, PC, etc., compression molding process is preferred, in which case the base layer of the optical polarization layer may not exist (i.e., the base layer and the structural layer are made of the same material).

[0024] Furthermore, the refractive index of the material of the optical deflection layer is selected from 1.4-1.6.

[0025] Furthermore, the main function of the second structural layer is to differentiate the exit angles of all incident light rays, such as creating differences in the horizontal and vertical viewing angle distributions.

[0026] Furthermore, the microstructure of the functional layer is a ring-shaped Fresnel prism structure. The Fresnel prism structure is a constant-type Fresnel prism structure with constant width and angle.

[0027] Furthermore, the constant-type Fresnel prism structure described above has the function of centrally converging light rays.

[0028] The apex of the triangle in the cross-section of the Fresnel structure of the functional layer's prism structure points upwards.

[0029] Furthermore, the outer cross-section of the functional layer Fresnel structure is a regular triangle, with its central region being an isosceles triangle. The base length (width) of the outer regular triangle is a fixed constant. The two base angles of the triangle exhibit a larger-than-smaller property, β1 < β2, with the smaller base angle β1 being farther from the central point of the Fresnel structure, and the larger base angle β2 being closer to the central point of the Fresnel structure. The central isosceles triangle is formed by overlapping the outer regular triangles, and its base angle is β1 (e.g., ...). Figure 3 (As shown).

[0030] When collimated rays are incident on a regular prism or similar structure, all outgoing refracted or reflected rays still maintain good collimation performance, making it difficult to differentiate the brightness viewing angles in the horizontal and vertical directions. However, the Fresnel structure is anisotropic in all three dimensions for all collimated incident rays, thus effectively differentiating collimated rays and achieving differentiation in the two-dimensional brightness viewing angles.

[0031] Furthermore, the smaller base angle β1 of the Fresnel structure cross-section triangle is selected from 20°-30°. The larger base angle β2 is selected from 60°-90°, and the two base angles satisfy β1<β2.

[0032] It is worth noting that the current functional layer structure of this invention is a constant Fresnel structure, but a conventional variable Fresnel structure with varying angles / heights can also be selected according to optical performance, without any special constraints here.

[0033] Furthermore, the material of the second structural layer functional layer can be selected from acrylic resin, PMMA, PC, etc. When the material is acrylic resin, UV curing process is preferred. When the material is PMMA, PC, etc., compression molding process is preferred, in which case the base layer of the functional layer may not exist.

[0034] Furthermore, the refractive index of the material of the functional layer is selected from 1.4-1.6.

[0035] Furthermore, the prism layers of the third and fourth structural layers function to converge the light pattern.

[0036] Furthermore, the prism layers of the third and fourth structural layers have the same structural properties, both being composed of lattice-shaped prisms, and the cross-sections of these prisms are isosceles right triangles. The apex angle of the triangles in the cross-sections of the prism layers of the third and fourth structural layers points upwards.

[0037] Furthermore, the isosceles right triangle has a base width of 10-150 μm and two base angles of 45°.

[0038] Furthermore, the prism layer material of the third and fourth structural layers can be selected from acrylic resin, PMMA, PC, etc. When the material is acrylic resin, UV curing process is preferred. When the material is PMMA, PC, etc., compression molding process is preferred, in which case the base layer of the prism layer may not exist.

[0039] Furthermore, the refractive index of the prism layer material in the third and fourth structural layers is selected from 1.4-1.6. The refractive indices of the materials in the third and fourth structural layers can be the same or different.

[0040] Furthermore, the third and fourth structural prism layers can be bonded together with intersecting structural directions or with parallel directions, with parallel direction bonding being preferred.

[0041] Furthermore, when the third and fourth structural prism layers are combined in parallel, the first structural layer optical deflection layer can be combined orthogonally or in parallel with it. Orthogonal combination is preferred; that is, when the structural direction of the first structural layer optical deflection layer is 90°, the structural directions of the third and fourth prism layers are both 0°.

[0042] Furthermore, the four structural layers of the viewing angle film can be bonded together using commercially available optical-grade OCA optical adhesive or PSA pressure-sensitive adhesive.

[0043] Furthermore, the refractive index combination of each layer of the viewing angle film can be selected according to the actual optical performance requirements, and the present invention does not make a preferred option.

[0044] Furthermore, the method for preparing the viewing angle film includes the following steps:

[0045] (1) Prepare the mold roller 1 for the first structural layer optical bias layer;

[0046] (2) Using roller 1, the first structural layer optical bias layer is prepared on the substrate layer by UV curing or molding process to obtain semi-finished product 1;

[0047] (3) Prepare the mold roller 2 for the second structural layer functional layer;

[0048] (4) Using roller 2, a second structural functional layer is prepared on the base layer by UV curing or molding process to obtain semi-finished product 2;

[0049] (5) Prepare the mold roller 3 for the third and fourth structural prism layers;

[0050] (6) Using roller 3, the third / fourth structural layer prism layer is prepared on the base layer by UV curing or molding process to obtain semi-finished product 3 and semi-finished product 4.

[0051] (7) Use OCA optical adhesive or PSA pressure-sensitive adhesive to sequentially bond the semi-finished products 1-4 to obtain the finished viewing angle film.

[0052] Furthermore, the first and second structural layers of the viewing membrane can be fabricated on both sides of a substrate, depending on the feasibility of the process.

[0053] Furthermore, the method for preparing the viewing angle film includes the following steps:

[0054] (1) Prepare the mold roller 1 for the first structural layer optical bias layer;

[0055] (2) Using roller 1, the first structural layer optical polarization layer is prepared on the back of the substrate layer by UV curing or molding process to obtain semi-finished product 1;

[0056] (3) Prepare the mold roller 2 for the second structural layer functional layer;

[0057] (4) Using roller 2, a second structural layer functional layer is prepared on the front side of the semi-finished product 1 by UV curing or molding process to obtain the semi-finished product 2.

[0058] (5) Prepare the mold roller 3 for the third and fourth structural prism layers;

[0059] (6) Using roller 3, the third / fourth structural layer prism layer is prepared on the base layer by UV curing or molding process to obtain semi-finished product 3 and semi-finished product 4.

[0060] (7) Use OCA optical adhesive or PSA pressure-sensitive adhesive to sequentially bond the semi-finished products 2-4 to obtain the finished viewing angle film.

[0061] Furthermore, the viewing angle film preparation method provided by the present invention is applicable to the production of sheets and also applicable to the production of rolls.

[0062] It is worth noting that the two-dimensional brightness viewing angle differentiation involved in this invention is not limited to the horizontal and vertical directions; viewing angle differentiation at other angles can be achieved by deflecting the diaphragm as needed. Simultaneously, the viewing angle shift effect of the central high-brightness display area can also be adjusted by changing the diaphragm structure orientation to regulate the shift direction. This invention does not require further explanation.

[0063] Furthermore, the upper and lower prism layers are oriented parallel to each other and are orthogonally superimposed on the optical deflection layer structure.

[0064] When the upper and lower prism layers are parallel and orthogonally superimposed on the optical deflection layer, the high-brightness display area is flat, and its full width at half maximum (FWHM) brightness angle indicates that its horizontal and vertical viewing angles are both above 50°. Furthermore, it effectively achieves viewing angle shifting in the high-brightness display area.

[0065] Furthermore, the bottom angles of the prism structure in the functional layer are β1 = 20°-30° and β2 = 60°-90°.

[0066] Furthermore, the bottom angle of the prism structure in the optical deflection layer is 0°<α1<30°, 60°≤α2≤90°.

[0067] Furthermore, the bottom angle of the prism structure in the optical deflection layer is α1, which is 5°-25°, and α2, which is 60°-90°.

[0068] Furthermore, the optical deflection layer has a structural orientation of 90°, a cross-section of a standard triangle with base angles α1 and α2, a base length of 100 μm, and a refractive index of 1.53; the functional layer has a toroidal constant Fresnel structure with a triangular cross-section, base angles β1 and β2, a base length of 50 μm, and a refractive index of 1.5; the lower prism layer has a structural orientation of 0°, a triangular cross-section with two base angles of 45°, a base length of 50 μm, and a refractive index of 1.55; and the upper prism layer has a structural orientation of 0°, a triangular cross-section with two base angles of 45°, a base length of 50 μm, and a refractive index of 1.55.

[0069] The viewing angle film provided by this invention can be used as an optical component in optical systems that require differentiation of two-dimensional brightness viewing angles in the horizontal and vertical directions, as well as viewing angle shift. It is particularly suitable for backlight module systems where the light source is a collimated backlight and includes a reflection module.

[0070] On the other hand, the present invention also provides a backlight module, including the viewing angle film provided by the present invention.

[0071] The viewing angle film provided by this invention can achieve a wide horizontal viewing angle and a narrow vertical viewing angle in actual illumination display, and can also shift the central high-brightness display area at a certain angle to meet specific viewing angle requirements.

[0072] The viewing angle film functional layer structure provided by this invention adopts a Fresnel prism structure, which can effectively achieve convergence with a straight light source and realize the differentiation of two-dimensional brightness viewing angle.

[0073] The backlight module provided by this invention can achieve a wide brightness viewing angle in the horizontal direction and a narrow brightness viewing angle in the vertical direction (differentiation of two-dimensional brightness viewing angle), and can shift the central high-brightness display area at a certain angle to meet specific viewing angle requirements. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the structure of the viewing membrane provided in an embodiment of the present invention;

[0075] Figure 2 A schematic diagram of the microstructure of the viewing angle film optical deflection layer provided in an embodiment of the present invention;

[0076] Figure 3 This is a schematic cross-sectional view of the microstructure of the viewing membrane functional layer provided in an embodiment of the present invention;

[0077] Figure 4 This is a schematic diagram of the light path of the optical deflection layer microstructure of the viewing angle film of the present invention;

[0078] Figure 5 This is a schematic diagram of the cross-sectional light path of the microstructure of the viewing membrane functional layer of the present invention;

[0079] Figure 6 This is a top-view light path diagram of the microstructure of the viewing membrane functional layer of the present invention;

[0080] Figure 7 This is the illumination diagram when the viewing film of the present invention only contains an optical bias layer and a functional layer;

[0081] Figure 8 This is a schematic diagram illustrating the display effect of the viewing membrane of the present invention after use;

[0082] Figure 9A This is a brightness viewing angle curve of the viewing angle film in Embodiment 1 of the present invention;

[0083] Figure 9B This is an illumination diagram of the viewing angle film in Embodiment 1 of the present invention;

[0084] Figure 10A This is a brightness viewing angle curve of the viewing angle film in Comparative Example 2 of the present invention;

[0085] Figure 10B This is an illumination diagram of the viewing angle film of Comparative Example 2 of the present invention;

[0086] Figure 11A This is a brightness viewing angle curve of the comparative example 3 viewing angle film of the present invention;

[0087] Figure 11BThis is an illumination diagram of the comparative example 3-view film of the present invention;

[0088] Figure 12A This is a brightness viewing angle curve of the viewing angle film in Embodiment 2 of the present invention;

[0089] Figure 12B This is an illumination diagram of the viewing angle film in Embodiment 2 of the present invention;

[0090] Figure 13A This is a brightness viewing angle curve of the viewing angle film in Embodiment 5 of the present invention;

[0091] Figure 13B This is an illumination diagram of the viewing angle film in Embodiment 5 of the present invention;

[0092] Figure 14A This is a brightness viewing angle curve of the viewing angle film in Embodiment 6 of the present invention;

[0093] Figure 14B This is an illumination diagram of the viewing angle film in Embodiment 6 of the present invention;

[0094] Figure 15A This is a brightness viewing angle curve of the viewing angle film in Embodiment 8 of the present invention;

[0095] Figure 15B This is an illumination diagram of the viewing angle film in Embodiment 8 of the present invention.

[0096] Note: In the brightness-viewing-angle curve, the solid line represents the horizontal viewing angle data, and the dashed line represents the vertical viewing angle data.

[0097] Explanation of the markings in the image:

[0098] 1-Optical deflection layer; 11-Main active surface of the optical deflection layer microstructure; 12-Secondary active surface of the optical deflection layer microstructure; α1-Smaller bottom angle of the optical deflection layer microstructure; α2-Larger bottom angle of the optical deflection layer microstructure;

[0099] 2 - Functional layer; 211 - Main active surface of the convergent optical microstructure in the functional layer; 212 - Secondary active surface of the convergent optical microstructure in the functional layer; 221 - Main active surface of the divergent optical microstructure in the functional layer; 222 - Secondary active surface of the divergent optical microstructure in the functional layer; β1 - Smaller bottom angle of the functional layer microstructure; β2 - Larger bottom angle of the functional layer microstructure;

[0100] 3-Lower prism layer.

[0101] 4-Upper prism layer. Detailed Implementation

[0102] To better understand the structure, functional features, and advantages of the present invention, preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings:

[0103] like Figure 1 As shown, the viewing angle film provided by the present invention includes, from bottom to top, an optical deflection layer 1, a functional layer 2, a lower prism layer 3, and an upper prism layer 4.

[0104] like Figure 2 and Figure 5 As shown, the microstructure of the optical deflection layer 1 of the viewing angle film provided by the present invention is triangular. When the two base angles α1 < α2 of the triangle, the collimating light source mainly illuminates the main working surface 11 of the optical deflection layer 1 (e.g., Figure 5 As shown in the figure, the collimated light rays are refracted and deflected in the α2 direction, and most of the emitted light rays still have good collimation performance.

[0105] like Figure 3 , Figure 5 and Figure 6 As shown, the viewing angle film functional layer 2 structure provided by this invention is a constant-type Fresnel prism structure. After receiving light rays emitted from the optical deflection layer 1, the Fresnel structure can effectively achieve center convergence processing of the light rays. Firstly, taking… Figure 6 As shown in the cross-section, the collimated light rays incident on the left side of the Fresnel structure's center deflect towards the center after exiting, and the deflection angle is relatively large; while the collimated light rays incident on the right side of the Fresnel structure also deflect towards the centerline after exiting, but their deflection angle is relatively small. Figure 6 As shown in the top view, the emitted light rays from the left structure converge at a large angle from the periphery towards the center, while the emitted light rays from the right structure also converge at a small angle from the periphery towards the center. Thus, the Fresnel structure of its functional layer 2 achieves asymmetrical convergence in two dimensions (horizontal and vertical) towards the direct light source, realizing differentiation in brightness viewing angles in two dimensions (horizontal and vertical) (e.g., ...). Figure 7 (As shown).

[0106] like Figure 9B , 10B As shown in the illumination diagram of the equal-viewing-angle film, when the light emitted from the functional layer passes through the two upper prism layers again, its light pattern can achieve further convergence and deformation. When the structural directions (prism extension directions) of the lower prism layer 3 and the upper prism layer 4 are parallel and perpendicular to the structural direction of the optical deflection layer 1, the central high-brightness display area achieves a flat brightness display effect, with a wide brightness viewing angle in the horizontal direction and a narrower brightness viewing angle in the vertical direction.

[0107] like Figure 9A , 10AAs shown in the brightness viewing angle curves of the viewing angle film, after collimated backlight passes through the viewing angle film of this invention, it will exhibit different brightness viewing angles in the horizontal and vertical directions. In the data of the following embodiments, the half-width at half-maximum (FWHM) data (angle) of its brightness viewing angle curve is used to quantitatively characterize the differences in brightness viewing angle performance of each viewing angle film in the horizontal and vertical directions; that is, the width (viewing angle) on the horizontal axis at half-maximum peak value in the brightness viewing angle curve represents the FWHM brightness viewing angle involved in this invention. If the central peak value does not reach its maximum value, but the distance between the central peak and the two side peak values ​​is relatively close and the difference is not significant, then the central peak is treated as the central maximum peak for calculation (e.g., the brightness viewing angle curve in the vertical direction in 9A). If the central peak value is low and the difference between it and the two side maximum peaks is large (e.g., ... Figure 11A (The brightness-viewing angle curve in the middle) At this time, the center brightness is low and does not meet the optical requirements, so no full width at half maximum (FWHM) brightness-viewing angle calculation is performed.

[0108] like Figure 8 As shown, when a uniform collimated light source passes through the viewing angle film provided by this invention and reaches the high-brightness display area at the center of the display panel, it exhibits a flattened viewing angle effect. This high-brightness display area has a wider viewing angle range in the horizontal direction (y-direction) and a narrower viewing angle range in the vertical direction (x-direction). Simultaneously, the center point of this high-brightness display area will experience a certain angle of viewing angle offset (θ) in its vertical direction to achieve the desired viewing angle. The viewing angle offset (θ) is calculated as follows:

[0109]

[0110] Where d represents the distance from the center point O2 of the highlighted display area to the center O1 of the panel in the vertical x direction; h represents the parallel distance between the viewing angle film and the display panel. In the viewing angle offset θ data of the viewing angle film provided in the following embodiments of the present invention, a negative number indicates that the highlighted display area is offset in the positive x direction, and a positive number indicates that the highlighted display area is offset in the negative x direction.

[0111] Example 1

[0112] This invention provides a viewing membrane, such as Figure 1As shown, the first structural layer is an optical deflection layer 1, the second structural layer is a functional layer 2, the third structural layer is a lower prism layer 3, and the fourth structural layer is an upper prism layer 4. The detailed design parameters of each structural layer are as follows: (1) Optical deflection layer: The structural direction is 90° (the structural direction is the extension direction of the prism strip; its angle is defined as 90° in the direction perpendicular to the paper and 0° in the direction parallel to the paper). The cross-section of this microstructure is a normal triangle with base angles α1 of 25° and α2 of 90°, a base length of 100μm, and a refractive index of 1.53; (2) Functional layer: The microstructure is a toroidal constant Fresnel structure with base angles β1 of 20° and β2 of 80°, a base length of 50μm, and a refractive index of 1.5; (3) Lower prism layer: The structural direction is 0°, both base angles are 45°, the base length is 50μm, and the refractive index is 1.55; (4) Upper prism layer: The structural direction is 0°, both base angles are 45°, the base length is 50μm, and the refractive index is 1.55.

[0113] Comparative Examples 1-2

[0114] The viewing membrane design parameters provided in Example 1 are as follows, and the other parameters are as shown in Table 1.

[0115] Table 1 shows the design parameters and optical properties of the viewing films provided in Example 1 and Comparative Examples 1-2.

[0116]

[0117]

[0118] Note: (1) Highlight display area morphology: The morphological structure of the central highlight display area in the illumination diagram. Flat shape - indicates that the horizontal viewing angle is wider and the vertical viewing angle is narrower in the actual display; Circular spot - indicates that the horizontal and vertical viewing angle ranges are similar and that the two-dimensional brightness viewing angle differentiation has not been achieved.

[0119] Table 1 shows examples of viewing angle films with different combinations of the structural orientations of the upper prism layer, lower prism layer, and optical deflection layer. It can be observed that when the structural orientations of the upper and lower prisms (prism extension direction) are consistent with the structural orientation of the optical deflection layer (Comparative Example 1), the morphology of the high-brightness display area is approximately circular, and the viewing angle film does not effectively achieve differentiation in the two-dimensional brightness viewing angle. However, when the upper and lower prism layers are orthogonally combined (Comparative Example 2), although the high-brightness display area is flat, the half-peak brightness viewing angle data shows that the half-peak brightness viewing angles in both the horizontal and vertical directions are relatively narrow (25° horizontally, 36° vertically). When the structural orientations of the upper and lower prism layers are parallel and orthogonally superimposed with the optical deflection layer structure (Example 1), the high-brightness display area is flat, and its half-peak brightness viewing angle indicates that the viewing angle range in both the horizontal and vertical directions is above 50°. While differences in module architecture can result in different structures in the actual optical path, all the above solutions can effectively achieve viewing angle shift in the high-brightness display area.

[0120] Example 2

[0121] This invention provides a viewing membrane, such as Figure 1 As shown, the first structural layer is an optical deflection layer 1, the second structural layer is a functional layer 2, the third structural layer is a lower prism layer, and the fourth structural layer is an upper prism layer. The detailed design parameters of each structural layer are as follows: (1) Optical deflection layer: The structural direction is 90° (the direction perpendicular to the paper is defined as 90°, and the direction parallel to the paper is 0°). The cross-section of this microstructure is a normal triangle with base angles α1 of 25°, α2 of 90°, base of 100μm, and refractive index of 1.53; (2) Functional layer: The microstructure is a toroidal constant Fresnel structure with base angles β1 of 30°, β2 of 80°, base of 50μm, and refractive index of 1.5; (3) Lower prism layer: The structural direction is 0°, both base angles are 45°, base of 50μm, and refractive index of 1.55; (4) Upper prism layer: The structural direction is 0°, both base angles are 45°, base of 50μm, and refractive index of 1.55.

[0122] Examples 3-5

[0123] The viewing membrane design parameters provided in Example 2 are as follows, and the other parameters are as described in Table 2.

[0124] Table 2 shows the design parameters and optical performance of the viewing films provided in Examples 2-5 and Comparative Examples 3-6. Note: The unlabeled half-peak brightness viewing angle refers to the fact that the high-brightness areas of the brightness viewing angle curve of the film are mainly distributed on both sides, while the brightness of the central area differs significantly from that of the two side peaks (e.g., Figure 11A(As shown in the image). The entire brightness viewing angle curve shows a trend of low in the middle and high on both sides. At this time, the brightness display effect is poor, and the half-peak brightness viewing angle has no practical significance.

[0125] Table 2 shows examples of viewing angle films with different Fresnel structure parameters in the functional layer. It can be seen that when the two base angles (β1 / β2) of the Fresnel prism structure in the functional layer are not appropriately sized, even if the central high-brightness display area can form a flattened effect, the brightness viewing angle curve does not meet the requirements (i.e., the brightness viewing angle is mainly distributed on both sides, resulting in low brightness in the central area (as shown in Comparative Examples 4-6)), and the overall light pattern does not meet the performance requirements. Therefore, the viewing angle film exhibits optimal performance when β1 is 20°-30° and β2 is 60°-90°.

[0126] Example 6

[0127] This invention provides a viewing membrane, such as Figure 1 As shown, the first structural layer is an optical deflection layer 1, the second structural layer is a functional layer 2, the third structural layer is a lower prism layer 3, and the fourth structural layer is an upper prism layer 4. The detailed design parameters of each structural layer are as follows: (1) Optical deflection layer: The structural direction is 90° (the direction perpendicular to the paper is defined as 90°, and the direction parallel to the paper is 0°). The cross-section of this microstructure is a common triangle with base angles α1 of 5°, α2 of 90°, base length of 100μm, and refractive index of 1.53; (2) Functional layer: The microstructure is a toroidal Fresnel structure with base angles β1 of 20°, β2 of 80°, base length of 50μm, and refractive index of 1.5; (3) Lower prism layer: The structural direction is 0°, both base angles are 45°, base length of 50μm, and refractive index of 1.55; (4) Upper prism layer: The structural direction is 0°, both base angles are 45°, base length of 50μm, and refractive index of 1.55. Examples 7-8 and Comparative Examples 7-9

[0128] The viewing membrane design parameters provided in Example 6 are as follows, and the other parameters are as shown in Table 3.

[0129] Table 3 shows the design parameters and optical properties of the viewing films provided in Examples 6-8 and Comparative Examples 7-9.

[0130]

[0131] Table 3 shows examples of viewing angle films with different combinations of optical deflection layer structural parameters. As the smaller angle α1 of the optical deflection layer microstructure gradually increases, the viewing angle shift gradually increases. When α1 increases to 30°, it results in high brightness on both sides and low brightness in the center, leading to a poor final display effect. Conversely, when the larger angle α2 gradually decreases from 90° and approaches α1, the light emission ratio of the secondary action surface 12 gradually increases and gradually counteracts part of the light deflection effect of the primary action surface 11. At this time, the viewing angle shift decreases, resulting in a change in the final light pattern.

[0132] In summary, when the upper and lower prism layers are parallel and orthogonal to the optical polarization layer, and the bottom angle of the Fresnel prism structure in the functional layer is 20°≤β1≤30°, 60°≤β2≤90°, and the bottom angle of the prism structure in the optical polarization layer is 0°<α1<30°, 60°≤α2≤90°, the optical morphology of the viewing angle film is optimal. The central bright display area in the illumination diagram has a flat shape (which can meet the wide viewing angle requirement in the horizontal direction), and its half-peak brightness viewing angle can be adjusted from 22° to 56° in the horizontal direction and from 40° to 74° in the vertical direction; the viewing angle offset can be adjusted between -9.7° and 30.0°.

[0133] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent variations and modifications made based on the content of the present invention are covered within the patent scope of the present invention.

Claims

1. A viewing angle film, characterized in that, The viewing angle film, from bottom to top, includes an optical polarization layer, a functional layer, a lower prism layer, and an upper prism layer; The microstructure of the functional layer is a ring-shaped Fresnel prism structure; The apex angle of the triangle in the cross-section of a Fresnel prism structure points upwards; the outer cross-section of the Fresnel prism structure is a regular triangle, while the central region is a central isosceles triangle; the base length of the outer regular triangle is a fixed constant, and the two base angles of the outer regular triangle are one larger and one smaller. β 1< β 2. Bottom corner β 1. Far from the center of the Fresnel structure, at the bottom corner β 2. Close to the center of the Fresnel structure; the central isosceles triangle is formed by overlapping the outer ordinary triangles, with base angles of _____. β 1.

2. The viewing angle film according to claim 1, characterized in that, The microstructure of the optical deflection layer is formed by tiling prisms, the cross-section of which is a regular triangle or a right triangle, with the apex angle of the triangle facing downwards; the apex angles of the prism structures in the upper and lower prism layers face upwards.

3. The viewing angle film according to claim 1, characterized in that, The optical deflection layer is made of one of acrylic resin, PMMA, or PC, and its refractive index is selected from 1.4-1.

6.

4. The viewing angle film according to claim 1, characterized in that, The structural layers of the viewing film are bonded together using optical-grade OCA optical adhesive or PSA pressure-sensitive adhesive.

5. The viewing angle film according to claim 1, characterized in that, The upper and lower prism layers are parallel in structure and orthogonally superimposed with the optical deflection layer structure; the bottom corner of the prism structure in the functional layer... β 1 represents 20°-30°. β 2 is 60°-90°; the bottom angle of the prism structure of the optical polarization layer is α 1 represents 5°-25°. α 2 is 60°-90°.

6. The viewing angle film according to claim 5, characterized in that, The optical polarization layer has a 90° structural orientation and a standard triangular cross-section with base angles. α 1, α 2. The base length is 100 μm, and the refractive index is 1.53; the microstructure of the functional layer is a toroidal Fresnel structure with a triangular cross-section and a base angle of 1.

53. β 1, β 2. The base length is 50μm and the refractive index is 1.5; the structural orientation of the lower prism layer is 0°, the cross-section is triangular, both base angles are 45°, the base length is 50μm, and the refractive index is 1.55; the structural orientation of the upper prism layer is 0°, the cross-section is triangular, both base angles are 45°, the base length is 50μm, and the refractive index is 1.

55.

7. A backlight module, characterized in that, The viewing membrane included in any one of claims 1-6.

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