Composite brightness enhancement film and preparation method and application thereof

Abstract

The invention discloses a composite brightness enhancement film and a preparation method and application thereof, and belongs to the technical field of optical films. The composite brightness enhancement film comprises a first prism layer, a first base material layer, a first back coating layer, a second prism layer, a second base material layer and a second back coating layer. The upper surface of the first base material layer is coated with the first prism layer, the lower surface of the first base material layer is bonded with the second prism layer through the first back coating layer, the second prism layer is arranged on the upper surface of the second base material layer, the second back coating layer is coated on the lower surface of the second base material layer, and an included angle exists between prism structure arrays of the first prism layer and the second prism layer. The range of the included angle is larger than or equal to 40 degrees and smaller than or equal to 60 degrees, or larger than or equal to-60 degrees and smaller than or equal to-40 degrees, and the haze of the first back coating layer is 10%-20%. According to the composite brightness enhancement film, the emergent surface of light can be more comprehensive, and the brightness uniformity is effectively considered while the front-view brightness is remarkably improved; and meanwhile, the first back coating layer with medium haze is matched, so that certain atomization and light leakage effects are achieved, and the emergent surface of light rays is more uniform.

Description

Technical Field

[0001] The present invention relates to the field of optical films, and in particular to a composite brightness enhancement film that improves the brightness of a display and meets TCO standards, and a preparation method and application thereof. Background Art

[0002] Liquid crystal display is the most widely used display technology at present. Because it does not have the ability to emit light by itself, it needs other light sources in the backlight module to display. Generally speaking, the existing backlight module uses a point light source, which needs to be converted into a surface light source with uniform brightness with the assistance of an optical film. Among them, the diffusion film in the backlight module mainly plays the role of correcting the angle of the light source, which will increase the light radiation area, but will reduce the light intensity per unit area; while the brightness enhancement film can refract and fully reflect the light through the prism structure, thereby collecting the scattered light to the positive viewing direction within a certain angle, thereby improving the brightness of the LCD (Liquid Crystal Display) and the utilization rate of the emitted light energy. As energy efficiency policies become more and more stringent, the number of brightness enhancement films used in displays will inevitably increase greatly.

[0003] The existing MNT (monitor) edge-entry display meets the TCO 9.0 standard, which is a display certification standard promoted by the Swedish Federation of Professional Employees (TCO). Usually, a film structure of a lower diffusion film, a brightness enhancement film, an upper diffusion film, or a lower diffusion film, a lower diffusion film, and an upper brightness enhancement film is used in the backlight module. Due to the small number of brightness enhancement films used, it is difficult for the brightness of the display to pass the "Energy Star" certification. If the brightness enhancement-brightness enhancement composite film (POP) is used directly, the brightness of the display can be improved, but it is difficult to meet the TCO 9.0 standard. In order to meet both energy efficiency and TCO standards, the whole machine factory usually uses the reflective polarized brightness enhancement film (DBEF) of 3M Company in the United States. This film is based on the polarization characteristics of light. It reflects S light by itself and re-projects it, thereby improving the efficiency of the light source to improve the brightness. The disadvantage is that this film is expensive, which greatly increases the cost of the display.

[0004] Prior art CN108205218A discloses a composite brightness enhancement film and its preparation method and application. The composite brightness enhancement film includes a first prism layer, a first substrate layer, an adhesive layer, a second prism layer, a second substrate layer and a back coating layer from top to bottom. The prism direction of the first prism layer is non-vertically crossed with the prism direction of the second prism layer. Preferably, the prism direction of the first prism layer and the prism direction of the second prism layer form an angle of positive 80°-89° or negative 80°-89°. The invention can effectively avoid interference by non-vertically crossing the prism direction of the first prism layer with the prism direction of the second prism layer, but the composite brightness enhancement film does not meet the TCO standard.

[0005] Prior art CN116107000A discloses a quantum dot composite brightness enhancement film and its preparation method, and a backlight display device. The composite brightness enhancement film is sequentially arranged from top to bottom with a first upper prism layer, a first barrier film, a quantum dot glue layer, a second barrier film, and a lower prism layer, and the first direction and the second direction form an angle of 67.2° to 112.2°. In this invention, the first upper prism layer and the quantum dot glue layer share the first barrier film as a carrier, and the lower prism layer and the quantum dot glue layer share the second barrier film as a carrier, which can effectively reduce the thickness of the module structure, so that the product meets the requirements of light and thin design, and solves the problem of too long film assembly process. However, similarly, whether the composite brightness enhancement film meets the TCO standard and related structural parameters has not been studied and tested.

[0006] Prior art CN213149292U discloses a novel composite brightness enhancement film, including a first prism film layer, a second prism film layer and an acrylic adhesive layer, wherein the first prism film layer and the prism unit structure on the second prism film layer have an angle, and the angle between the prism unit structures on the first prism film layer and the second prism film layer is 45°. The angle set between the two prism unit structures can increase the viewing angle of the observer to the display device; at the same time, the first prism part and the second prism part on the prism unit structure are arranged in a ring shape to form a ring-shaped light-emitting surface, and each light-emitting surface can focus light to improve the brightness enhancement effect of the prism unit structure. However, the invention does not conduct detailed research and testing on the TCO-related prism angle range and the haze matching of the adhesive layer. Summary of the invention

[0007] In order to solve the technical problem that the optical film used in the MNT edge-entry display can improve the brightness while being difficult to meet the TCO standard, and to achieve the purpose of not increasing the module cost, the present invention provides a composite brightness enhancement film that combines the basic optical principles of the diffusion film and the brightness enhancement film. Compared with the prior art, the present invention preferably uses two-layer prism structure units with different and specific prism angle designs to optimize the distribution of light in the backlight module. Through continuous refraction and reflection, the light emission surface can be made more comprehensive, and while significantly improving the front view brightness, the brightness uniformity is effectively taken into account; at the same time, with the first back coating with medium haze, it has a certain atomization and light leakage effect, and also makes the light emission surface more uniform.

[0008] In order to solve the above technical problems, the present invention adopts the following technical scheme: a composite brightness enhancing film, comprising a first prism layer, a first substrate layer, a first back coating layer, a second prism layer, a second substrate layer and a second back coating layer, the upper surface of the first substrate layer is coated with the first prism layer, the lower surface of the first substrate layer is bonded to the second prism layer through the first back coating layer, the second prism layer is arranged on the upper surface of the second substrate layer, the second back coating layer is coated on the lower surface of the second substrate layer, the prism structure arrays of the first prism layer and the second prism layer have an angle, the range of the angle is greater than or equal to 40° and less than or equal to 60°, or greater than or equal to -60° and less than or equal to -40°, and the haze of the first back coating layer is 10%-20%.

[0009] Among them, a plurality of prism structures are respectively provided on the first prism layer and the second prism layer, the prism structures in the first prism layer extend along a first preset direction, and the prism structures in the second prism layer extend along a second preset direction, the first preset direction and the second preset direction are different, and the angle range between the two is greater than or equal to 40° and less than or equal to 60°, or greater than or equal to -60° and less than or equal to -40°, the first prism layer and the second prism layer each have a plurality of parallel and juxtaposed prism structures, so that the first prism layer and the second prism layer form an array, that is, a prism structure array, wherein the angle between the first preset direction and the second preset direction is the angle between the prism structure arrays of the first prism layer and the second prism layer.

[0010] When the absolute value of the angle between the two-layer prism structure array is too large, the center brightness of the display is improved, but the TCO level deteriorates rapidly; when the absolute value of the angle between the two-layer prism structure array is too small, the brightness gain effect of the membrane is poor and the center brightness of the display is limited.

[0011] Furthermore, the included angle between the prism structure arrays of the first prism layer and the second prism layer is 45°, 50°, 55° or -45°, -50°, -55°.

[0012] Furthermore, the angle between the prism structure array of the first prism layer and the long side of the first substrate layer is greater than or equal to 0° and less than or equal to 20°, or greater than or equal to 160° and less than or equal to 180°.

[0013] Generally, to meet the TCO standard, when the angle between the prism structure array of the first prism layer and the long side of the first substrate layer is greater than or equal to 0° and less than or equal to 20°, the angle between the first prism layer and the prism structure array on the second prism layer is in the range of greater than or equal to -60° and less than or equal to -40°; when the angle between the prism structure array of the first prism layer and the long side of the first substrate layer is greater than or equal to 160° and less than or equal to 180°, the angle between the prism structure array of the first prism layer and the second prism layer is in the range of greater than or equal to 40° and less than or equal to 60°.

[0014] Furthermore, the angle between the prism structure array of the first prism layer and the long side of the first substrate layer is 10° or 170°.

[0015] Furthermore, the cross-section of the prism structure in the prism structure array of the first prism layer is an isosceles right triangle with a vertex angle of 90°. The spacing between the prism vertex angles is 20-60μm. In addition to these two end values, it can also be 25μm, 30μm, 35μm, 40μm, and 50μm. The prism structure of the first prism layer is usually a jitter design with a jitter amplitude of 1-3μm. In addition to these two end values, it can also be 1.5μm, 2.0μm, and 2.5μm. Through this jitter design, not only can the adsorption of the first prism layer and the panel be avoided, but the jitter design can also appropriately disrupt the light and increase the uniformity of brightness. The jitter amplitude is measured using a microscope to test the height distribution of a single prism peak within a jitter cycle. The height difference between the highest point and the lowest point is the jitter amplitude. Among them, the jitter design means that the height of the top of the prism structure is not equal in its extension direction, and it fluctuates, so that the top of the prism structure has a shape similar to the shaking of a rope.

[0016] The cross section of the prism structure in the prism structure array of the second prism layer is an isosceles right triangle with a vertex angle of 90°. The spacing between the vertex angles of the prism structure is 50-70μm. In addition to these two end values, it can also be 55μm, 58μm, 60μm, 65μm, and 68μm. In order to reduce the brightness loss caused by the bonding of the first prism layer and the second prism layer, the multiple prism structures of the second prism layer are usually designed as a high-low structure. The high-low structure includes one high and one low, or one high and two low.

[0017] The material of the first substrate layer and the second substrate layer is selected from one or a combination of two of polycarbonate (PC), polyethylene terephthalate (PET), polyamide resin (PA), polystyrene (PS), polyethylene (PE) and polymethyl methacrylate (PMMA). The thickness of the first substrate layer and the second substrate layer are each independently 75-125 μm. In addition to these two end values, the specific thickness can also be 80 μm, 85 μm, 90 μm, 100 μm, and 110 μm.

[0018] The first back coating layer comprises diffusion particles, and the material of the diffusion particles is selected from one or a combination of at least two of polymethyl methacrylate particles, polybutyl methacrylate particles, polystyrene particles and silicone resin particles.

[0019] Furthermore, the particle size of the diffusion particles is 2-15 μm. In addition to these two extreme values, the particle size may also be 3 μm, 5 μm, 8 μm, 10 μm, or 12 μm.

[0020] Furthermore, the haze of the first back coating layer is 10%-20%. In addition to the above two end values, it can also be 12%, 15%, and 18%. Through the scattering effect of the diffused particles dispersed in the back coating layer on light, the composite brightness enhancement film can improve the image quality of the display. At the same time, the medium haze produces a certain degree of "light leakage" phenomenon, which improves the TCO level of the display.

[0021] The haze of the second back coating layer is 2%-5%. In addition to these two extreme values, it can also be 3% or 4%.

[0022] Furthermore, the main function of the second back coating layer is to prevent scratches and adsorption problems on the back of the composite brightness enhancement film. At the same time, the lower haze can also reduce the brightness loss caused by scattering of incident light, thereby further improving the brightness.

[0023] The present invention also provides a method for preparing the composite brightness enhancement film, comprising the following steps: The second back coating layer is coated on one side of the second substrate layer, and the second prism layer is prepared by UV curing on the other side of the second substrate layer. Then, the first back coating layer is coated on one side of the first substrate layer and then laminated to the second prism layer. High pressure (high pressure energy: 300~600mJ / cm 2 ) after curing, a first prism layer is formed by UV curing on the other side opposite to the first substrate layer.

[0024] The present invention also provides a use of the composite brightness enhancement film in a display, including being used to enhance the central brightness of the display and meeting the TCO standard.

[0025] Furthermore, the display is an MNT edge-entry display.

[0026] Furthermore, the composite brightness enhancement film improves the brightness of the display while maintaining the uniformity of the brightness.

[0027] Compared with the prior art, the composite brightness enhancement film provided by the present invention has the following advantages or functions: The two-layer prism structure is used, and the specific angle design and the haze of the first back coating are used to improve the center brightness of the display and meet the TCO standard; at the same time, the number of films is not increased, and the module cost is not increased. In addition, the overall thickness of the composite brightness enhancement film after bonding is improved compared to a single diffusion film and a brightness enhancement film. The stiffness of the product can meet the requirements of large-size modules and can reduce the occurrence of film warping in the module. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the composite brightness enhancement film structure of some embodiments of the present invention.

[0029] Figure 2 Schematic diagram of the principle of concentrated light focusing of the first prism layer and the second prism layer of the composite brightness enhancement film.

[0030] Figure 3 Schematic diagram of the angle between the first prism layer and the second prism layer prism structure array of the composite brightness enhancement film when viewed from above (negative angle, i.e., angle of the first prism layer minus angle of the second prism layer).

[0031] Figure 4 Schematic diagram of the angle between the first prism layer and the second prism layer prism structure array of the composite brightness enhancement film when viewed from above (positive angle, i.e., first prism layer angle minus second prism layer angle).

[0032] Figure 5 Schematic diagram of the prism structure designed for the dithering of the first prism layer of the composite brightness enhancement film.

[0033] Figure 6 This is a schematic diagram of the high and low prism structure of the second prism layer of the composite brightness enhancement film.

[0034] Figure 7 This is a schematic diagram of the prism structure of the second prism layer of the composite brightness enhancement film, which has one high and two low prisms.

[0035] Figure 8 The following are the actual product photos corresponding to Example 1.

[0036] Explanation of the accompanying drawings: 11, first prism layer; 12, first substrate layer; 13, first back coating layer; 21, second prism layer; 22, second substrate layer; 23, second back coating layer; d1, first preset direction; d2, second preset direction; α, angle between the prism structure array of the first prism layer and the long side of the first substrate layer. DETAILED DESCRIPTION

[0037] In order to make it easier to understand the structure of the present invention and the functional features and advantages that can be achieved, the preferred embodiments of the present invention are described in detail below with reference to the drawings.

[0038] like Figure 1 As shown, the present invention provides a composite brightness enhancement film, which includes, from top to bottom, a first prism layer 11, a first substrate layer 12, a first back coating layer 13, a second prism layer 21, a second substrate layer 22, and a second back coating layer 23. When the composite brightness enhancement film provided by the present invention is placed in a backlight module, light passes through the composite brightness enhancement film from bottom to top, such as Figure 2 As shown, when light passes through the prism layers (the second prism layer 21 and the first prism layer 11) from bottom to top, the incident light is incident from the bottom surface of the prism structure, and the exit angle of the exiting light is greater than the incident angle of the incident light. Therefore, the light will be deflected and converged toward the top of the prism structure.

[0039] Continue to refer Figure 2 When the light passes through the second prism layer 21 from bottom to top, the outgoing light converges toward the top of each prism structure, and is reflected on the entire second prism layer 21 as the outgoing light is concentrated in the direction perpendicular to the second preset direction d2, achieving the first stage of brightening effect. Then, after passing through the first back coating layer 13 and the first prism layer 11, the outgoing light is concentrated again in the direction perpendicular to the first preset direction d1. Since the prism structure arrays of the first prism layer 11 and the second prism layer 21 are specially designed non-orthogonal angles, the light concentration effect is not as strong as the concentration effect produced by the orthogonal prism angles; and the first back coating layer 13 has diffusion particles with medium haze, part of the light is diffused, and part of the light directly penetrates, that is, a "light leakage" phenomenon occurs, so that the composite brightness enhancement film can maintain brightness uniformity while improving the brightness of the display.

[0040] The evaluation of the performance of the composite brightness enhancement film includes: 1) Total thickness: measured according to the method specified in GB / T 33399; 2) TCO value: measured according to the TCO 9.0 specification method, the test platform is the Foster optical measurement system, and the monitor model is Lenovo A24270QN0; 3) Center brightness: Take a 27-inch full-size film and put it into a 27-inch monitor (model: Lenovo A24270QN0) according to the test framework. Use a brightness meter (model: BM-5AS) to test the brightness value of the center point in the lit state. The unit is nit. 4) Haze: measured according to the method specified in GB / T 2410.

[0041] The test structure of the composite brightness enhancement film in Examples 1-6 is: lower diffusion film + composite brightness enhancement film; the test structure of Comparative Example 1 is: lower diffusion film + lower diffusion film + upper brightness enhancement film; the test structure of Comparative Example 2 is: lower diffusion film + ordinary brightness enhancement-brightness enhancement composite film (POP). The lower diffusion film used is a lower diffusion film of model B100CM produced by Ningbo Jizhi Technology Co., Ltd.

[0042] Example 1

[0043] like Figure 1 As shown, the present invention provides a composite brightness enhancement film, which includes, from top to bottom, a first prism layer 11, a first substrate layer 12, a first back coating layer 13, a second prism layer 21, a second substrate layer 22, and a second back coating layer 23. The angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 0°, wherein the long side of the first substrate layer 12 refers to the side of the first substrate layer 12 that is longer than other sides. Generally, the shape of the first substrate layer 12 is a rectangle, and its long side is the side extending along its length direction, such as Figures 2 to 4 The edge extending along the 0° direction as shown in . Figure 3 As shown, the angle between the prism structure arrays of the first prism layer 11 and the second prism layer 21 is -60°, the prism structure vertex spacing of the first prism layer 11 is 20-40μm jitter, and the amplitude is 1μm; the prism structure vertex spacing of the second prism layer 21 is 50μm equal height; the thickness of the first substrate layer 12 and the second substrate layer 22 are both 75μm; the haze of the first back coating layer 13 is 10%, and the haze of the second back coating layer 23 is 2%. Figure 8 As shown, it is a physical picture of the composite brightness enhancing film product in Example 1.

[0044] Example 2

[0045] The composite brightness enhancement film in Example 1 is different from that in that the angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 10°. Figure 3 As shown, the angle between the prism structure arrays of the first prism layer 11 and the second prism layer 21 is -50°, and the prism structure vertex spacing of the first prism layer 11 is 30-50 μm (eg Figure 5 As shown), the amplitude is 3μm; the prism structure of the second prism layer 21 has a 65μm top angle spacing, one high and one low (as shown Figure 6 As shown); the thickness of the first substrate layer 12 and the second substrate layer 22 are both 125 μm; the haze of the first back coating layer 13 is 15%, and the haze of the second back coating layer 23 is 5%.

[0046] Example 3

[0047] The composite brightness enhancement film in Example 1 is different from that in that the angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 20°, and the angle between the prism structure array of the first prism layer 11 and the second prism layer 21 is -40° (e.g. Figure 3 As shown in FIG. 1 ), the prism structure of the first prism layer 11 has a 40-60 μm angular spacing with an amplitude of 3 μm; the prism structure of the second prism layer 21 has a 65-65-60 μm angular spacing with one high and two low (as shown in FIG. 1 ). Figure 7 As shown); the thickness of the first substrate layer 12 and the second substrate layer 22 are both 100 μm; the haze of the first back coating layer 13 is 20%, and the haze of the second back coating layer 23 is 3%.

[0048] Example 4

[0049] The composite brightness enhancement film in Example 1 is different from that in that the angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 160°, and the angle between the prism structure array of the first prism layer 11 and the second prism layer 21 is 40° (e.g. Figure 4 As shown in FIG. 1 ), the prism structure of the first prism layer 11 has a 30-50 μm angular pitch (as shown in FIG. 1 ). Figure 5 As shown), the amplitude is 3μm; the prism structure vertex spacing of the second prism layer 21 is 65-65-60μm, one high and two low (as shown Figure 7 As shown); the thickness of the first substrate layer 12 and the second substrate layer 22 are both 125 μm; the haze of the first back coating layer 13 is 10%, and the haze of the second back coating layer 23 is 3%.

[0050] Example 5

[0051] The composite brightness enhancement film in Example 1 is different from that in that the angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 170°, and the angle between the prism structure array of the first prism layer 11 and the second prism layer 21 is 50° (e.g. Figure 4 As shown in FIG. 1 ), the prism structure of the first prism layer 11 has a 30-50 μm angular pitch (as shown in FIG. 1 ). Figure 5 As shown), the amplitude is 3μm; the prism structure of the second prism layer 21 has a 65μm top angle spacing, one high and one low (as shown Figure 6 As shown); the thickness of the first substrate layer 12 and the second substrate layer 22 are both 125 μm; the haze of the first back coating layer 13 is 15%, and the haze of the second back coating layer 23 is 3%.

[0052] Example 6.

[0053] For example, in the composite brightness enhancement film of Example 1, the angle α between the prism structure array of the first prism layer 11 and the long side of the first substrate layer 12 is 180°, and the angle between the prism structure array of the first prism layer 11 and the second prism layer 21 is 60° (e.g. Figure 4 As shown in FIG. 1 ), the prism structure of the first prism layer 11 has a 30-50 μm angular pitch (as shown in FIG. 1 ). Figure 5 As shown), the amplitude is 3μm; the prism structure of the second prism layer 21 has a 65μm top angle spacing, one high and one low (as shown Figure 6 As shown); the thickness of the first substrate layer 12 and the second substrate layer 22 are both 125 μm; the haze of the first back coating layer 13 is 20%, and the haze of the second back coating layer 23 is 3%.

[0054] Comparative Example 1

[0055] The existing film structure in the display is used, that is, lower diffusion film + lower diffusion film + upper brightness enhancement film. For example, the lower diffusion film is a lower diffusion film of model B100CM produced by Ningbo Jizhi Technology Co., Ltd., which can be purchased on the market. The upper brightness enhancement film can be a conventional brightness enhancement film, for example, it can be an upper brightness enhancement film of model P188ML-F produced by Ningbo Jizhi Technology Co., Ltd., which can be purchased on the market.

[0056] Comparative Example 2

[0057] A composite brightness enhancement film is used, which is different from the embodiment in that, in the composite film, the angle α between the prism structure array of the first prism layer and the first substrate layer is 9°, the angle between the prism structure array of the first prism layer and the second prism layer is 90°, the prism structure top angle spacing of the first prism layer is 25μm jitter, and the amplitude is 3μm; the prism structure top angle spacing of the second prism layer is 57μm, one high and one low; the thickness of the first substrate layer and the second substrate layer are both 125μm; the haze of the first back coating layer is 30%, and the haze of the second back coating layer is 3%.

[0058] Comparative Example 3

[0059] A composite brightness enhancement film (such as the composite brightness enhancement film in CN108205218A) is used, which is different from the embodiment in that the angle between the prism direction of the first prism layer and the prism direction of the second prism layer is 80° or -80°, the haze of the first back coating layer is 30%, and the haze of the second back coating layer is 40%.

[0060] Table 1 Performance test comparison of the composite brightness enhancement film prepared in the embodiment of the present invention and the comparative example

[0061] It can be concluded from the test results of the above embodiments and comparative examples that the composite brightness enhancement film provided by the present invention can effectively improve the brightness compared with the existing film structure in the display and meet the TCO 9.0 standard (<1.73). Comparative Examples 2 and 3 do not meet the TCO standard.

[0062] The above is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. All equivalent changes and modifications made according to the content of the present invention are included in the patent scope of the present invention.

Claims

1. A composite brightness enhancement film, characterized in that: The invention comprises a first prism layer (11), a first substrate layer (12), a first back coating layer (13), a second prism layer (21), a second substrate layer (22) and a second back coating layer (23), wherein the first prism layer (11) is coated on the upper surface of the first substrate layer (12), the lower surface of the first substrate layer (12) is bonded to the second prism layer (21) via the first back coating layer (13), the second prism layer (21) is arranged on the upper surface of the second substrate layer (22), and the second back coating layer (23) is coated on the lower surface of the first substrate layer (12). On the lower surface of the second substrate layer (22), there is an angle between the first prism layer (11) and the prism structure array of the second prism layer (21), and the range of the angle is greater than or equal to 40° and less than or equal to 60°, or greater than or equal to -60° and less than or equal to -40°. The haze of the first back coating layer (13) is 10%-20%, the haze of the second back coating layer (23) is 2%-5%, and the prism structure in the prism structure array of the first prism layer (11) is a jitter design, and the jitter amplitude is 1-3 μm.

2. The composite brightness enhancement film according to claim 1, characterized in that: The included angle (α) between the prism structure array of the first prism layer (11) and the long side of the first substrate layer (12) is greater than or equal to 0° and less than or equal to 20°, or greater than or equal to 160° and less than or equal to 180°.

3. The composite brightness enhancement film according to claim 1 or 2, characterized in that: When the included angle (α) between the long sides of the first prism layer (11) and the first substrate layer (12) is greater than or equal to 0° and less than or equal to 20°, the included angle between the first prism layer (11) and the prism structure array on the second prism layer (21) is in the range of greater than or equal to -60° and less than or equal to -40°; when the included angle (α) between the long sides of the first prism layer (11) and the first substrate layer (12) is greater than or equal to 160° and less than or equal to 180°, the included angle between the first prism layer (11) and the prism structure array on the second prism layer (21) is in the range of greater than or equal to 40° and less than or equal to 60°.

4. The composite brightness enhancement film according to claim 1 or 2, characterized in that: The cross-section of the prism structure in the prism structure array of the first prism layer (11) is an isosceles right triangle with a vertex angle of 90°, and the spacing between the vertex angles of the prism structure is 20-60 μm.

5. The composite brightness enhancement film according to claim 1 or 2, characterized in that: The cross-section of the prism structure in the prism structure array of the second prism layer (21) is an isosceles right triangle with a vertex angle of 90°, and the spacing between the vertex angles of the prism structure is 50-70 μm.

6. The composite brightness enhancement film according to claim 1 or 2, characterized in that: The material of the first substrate layer (12) and the second substrate layer (22) is selected from one or a combination of two of polycarbonate, polyethylene terephthalate, polyamide resin, polystyrene, polyethylene and polymethyl methacrylate, and the thickness of the first substrate layer (12) and the second substrate layer (22) are independently 75-125 μm.

7. The composite brightness enhancement film according to claim 1 or 2, characterized in that: The first back coating layer (13) comprises diffusion particles, the material of which is selected from one or a combination of at least two of polymethyl methacrylate particles, polybutyl methacrylate particles, polystyrene particles and silicone resin particles.

8. The composite brightness enhancement film according to claim 7, characterized in that: The particle size of the diffusion particles is 2-15 μm.

9. A method for preparing a composite brightness enhancement film as claimed in any one of claims 1 to 8, comprising the following steps: coating a second back coating layer (23) on one side of a second substrate layer (22), preparing a second prism layer (21) on the other side opposite to the second substrate layer (22) by UV curing molding, then coating a first back coating layer (13) on one side of a first substrate layer (12) and laminating the first prism layer (21), and after high-pressure curing, forming a first prism layer (11) on the other side opposite to the first substrate layer (12) by UV curing molding.

10. Use of the composite brightness enhancement film according to any one of claims 1 to 8 in a display, comprising being used to enhance the central brightness of the display and meeting the TCO standard.

11. The use according to claim 10, characterized in that The display is an MNT edge-lit display.

12. The use according to claim 10 or 11, characterized in that The composite brightness enhancement film improves the brightness of the display while maintaining the uniformity of the brightness.

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