Fresnel reflecting plate array for regional dimming, backlight module and display equipment

Abstract

The invention discloses a Fresnel reflecting plate array for regional dimming, a backlight module and display equipment, and belongs to the technical field of display. The Fresnel reflecting plate array is formed by arranging and splicing a plurality of rectangular Fresnel reflecting plate units in a rectangular grid manner, each Fresnel reflecting plate unit comprises a main body structure substrate, a first reflecting surface, a second reflecting surface and an arc-shaped incident surface, and the main body structure substrate is made of a high-light-transmittance material; the first reflecting surface is arranged at the top of the main body structure substrate, the first reflecting surface is a rotational symmetric paraboloid, and the paraboloid covers a high-reflectivity coating; the second reflecting surface is arranged at the bottom of the main body structure substrate, the second reflecting surface is a zigzag Fresnel reflecting surface, and the zigzag Fresnel reflecting surface covers the high-reflectivity coating. Through the combined design of the rotary symmetrical paraboloid and the sawtooth-shaped Fresnel reflecting surface, the light mixing distance is shortened to 2 mm, the structural stability is improved, high-precision area dimming is achieved, and the lens is suitable for ultra-thin high-contrast display equipment.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and particularly relates to a Fresnel reflector array for regional dimming, a backlight module, and a display device. Background Art

[0002] With the popularization of liquid crystal display technology, users' requirements for image quality are increasing day by day, especially for contrast and regional dimming ability. Traditional LCD backlights use global dimming technology, with limited contrast (usually 1000:1) and unable to achieve independent control of local brightness.

[0003] Mini LED technology significantly improves contrast by dividing the backlight into multiple independent dimming zones. However, although the existing Mini LED technology improves contrast through zonal dimming, it still relies on lenses or dispensing for light mixing, resulting in a long light mixing distance (OD), with OD being 5 - 20 mm, which limits the thinness and lightness of the device. In addition, the diffusion plate and the lamp beads are fixed by support columns, which are prone to deformation after long-term use, affecting display uniformity and poor structural stability. Moreover, the light confinement ability of lenses or dispensing is limited, resulting in blurred edges of the light spot and difficult to achieve precise regional dimming. Summary of the Invention

[0004] The present invention provides a Fresnel reflector array for regional dimming, a backlight module, and a display device, which can solve the problems of large light mixing distance, poor structural stability, and low regional dimming accuracy in the existing Mini LED backlight technology.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A Fresnel reflector array for regional dimming, the Fresnel reflector array is formed by splicing a plurality of rectangular Fresnel reflector units in a rectangular grid arrangement, and the Fresnel reflector unit includes:

[0007] A main structure substrate, which is made of a material with high light transmittance;

[0008] A first reflection surface, which is disposed on the top of the main structure substrate, the first reflection surface is a rotationally symmetric paraboloid, and the rotationally symmetric paraboloid is covered with a high reflectivity coating;

[0009] A second reflection surface, which is disposed on the bottom of the main structure substrate, the second reflection surface is a plurality of concentric serrated Fresnel reflection surfaces, and the serrated Fresnel reflection surfaces are covered with a high reflectivity coating;

[0010] An arc incident surface, which is disposed at the center of the bottom of the main structure substrate and is directly below the first reflection surface.

[0011] The key points of the present invention are as follows:

[0012] a. The main structure substrate is made of a high transmittance material, such as polymethyl methacrylate or silicone rubber, with a light transmittance ≥ 92%, reducing the energy loss of light in the main structure substrate medium, and a large amount of light passes through where there is no high reflectivity coating;

[0013] b. The first reflecting surface of the main structure substrate is a rotationally symmetric paraboloid, and the rotationally symmetric paraboloid is covered with a high reflectivity coating. The rotationally symmetric paraboloid reflects and focuses the diverging light from the arc-shaped incident surface to the second reflecting surface, reducing lateral scattering;

[0014] c. The second reflecting surface of the main structure substrate is a serrated Fresnel reflecting surface specially designed according to the light reflected by the first reflecting surface, and the serrated Fresnel reflecting surface is covered with a high reflectivity coating. The serrated Fresnel reflecting surface adjusts the light to be parallel to the optical axis direction and perpendicularly irradiates the diffusion plate, avoiding the increase in optical path caused by oblique propagation;

[0015] d. The main structure substrate has a rectangular appearance, which can confine the light of each arc-shaped incident surface within the rectangular area.

[0016] As a further solution of the present invention: the distance between the first reflecting surface and the second reflecting surface is 0.8 - 1.2 mm.

[0017] As a further solution of the present invention: the material of the main structure substrate is polymethyl methacrylate or silicone rubber, with a light transmittance ≥ 92%, a thickness of 0.8 - 1.5 mm, and a surface roughness Ra ≤ 0.02 μm.

[0018] As a further solution of the present invention: the serrated angle of the second reflecting surface is 10° - 45°, the serrated height of the second reflecting surface is 50 - 150 μm, and the serrated density is 10 - 30 per mm.

[0019] As a further solution of the present invention: the radius of curvature of the first reflecting surface is 3 - 8 mm, and the focal length is 1 - 3 mm.

[0020] As a further solution of the present invention: the distance between adjacent Fresnel reflecting plate units in the Fresnel reflecting plate array ≤ 1 mm.

[0021] As a further solution of the present invention: the high reflectivity coating covered on the first reflecting surface and the second reflecting surface is a metal coating with a reflectivity ≥ 95%.

[0022] As a further solution of the present invention: the main structure substrate is integrally formed by an injection molding technique and is coated with an anti-blue light nano-coating on the surface.

[0023] The present invention also provides a backlight module, which includes a diffusion plate and a back plate. Between the diffusion plate and the back plate, there is provided the above-mentioned Fresnel reflector array for zonal dimming. The Fresnel reflector array is fixedly bonded to the diffusion plate through planar bonding, replacing the traditional support column structure. The back plate and the Fresnel reflector are fixedly bonded through integral injection molding or gluing, canceling the support column design.

[0024] The present invention also provides a display device, which includes the above-mentioned backlight module and is applicable to high-precision display fields such as ultra-thin TVs and in-vehicle display screens.

[0025] Beneficial effects of the present invention:

[0026] (1) The Fresnel reflector array of the present invention is formed by splicing a plurality of rectangular Fresnel reflector units in a rectangular grid arrangement. Each Fresnel reflector unit corresponds to a Mini LED zone, forming an independent dimming unit. The Fresnel reflector unit includes a main structure substrate, a first reflecting surface, a second reflecting surface, and an arc-shaped incident surface. During operation, the light emitted by the Mini LED light source within the arc-shaped incident surface first irradiates the first reflecting surface. The first reflecting surface is a rotationally symmetric paraboloid. When the light reaches the first reflecting surface, the rotationally symmetric paraboloid reflects and focuses the diverging light from the arc-shaped incident surface to the second reflecting surface, reducing lateral scattering. The second reflecting surface is a serrated Fresnel reflecting surface specially designed according to the light reflected by the first reflecting surface. The serrated Fresnel reflecting surface adjusts the light to be parallel to the optical axis direction and perpendicularly irradiates the diffusion plate, avoiding the increase in optical path caused by oblique propagation. After the light is reflected twice, the actual propagation path is "arc-shaped incident surface → first reflecting surface → second reflecting surface → diffusion plate". The total optical path is shortened by more than 60% compared with the traditional straight-line propagation. Through the innovative optical path design of the present invention, the mixing distance is breakthrough shortened to 2 mm, and the module thickness is reduced by more than 50%. At the same time, the optical performance and reliability are ensured, providing key technical support for the ultra-thinning and high-image-quality of the Mini LED backlight module.

[0027] (2) The rectangular Fresnel reflector units of the present invention are arranged and spliced in a rectangular grid, and the second reflecting surface of the main structure substrate has a rectangular appearance, which can effectively confine the light of each LED light source within the rectangular area, avoid light crosstalk between adjacent areas, realize precise zonal dimming, greatly improve the contrast ratio, and the contrast ratio reaches 5000:1, supporting HDR display.

[0028] (3) The Fresnel reflector array of the present invention is fixedly bonded to the diffusion plate through planar bonding, replacing the traditional support column structure. The back plate and the Fresnel reflector are fixedly bonded through integral injection molding or gluing, canceling the support column design. The structural strength is improved, the anti-deformation ability is enhanced, the production process is simplified, and the yield is increased to more than 98%. Description of the Drawings

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] Figure 1 is a schematic diagram of the Fresnel reflector array structure of the present invention;

[0031] Figure 2 is a perspective schematic diagram of the Fresnel reflector array structure of the present invention;

[0032] Figure 3 is a schematic diagram of the Fresnel reflector unit structure of the present invention;

[0033] Figure 4 is a perspective schematic diagram of the Fresnel reflector unit structure of the present invention;

[0034] Figure 5 is a schematic diagram of the principle of the Fresnel reflector unit of the present invention.

[0035] In the figure: 1, Fresnel reflector array; 2, Fresnel reflector unit; 21, main structure substrate; 22, first reflection surface; 23, second reflection surface; 24, arc incident surface; 3, Mini LED light source. Specific embodiments

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, specific orientation structure and operation. Therefore, it should not be construed as a limitation of the present invention.

[0038] In addition, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] Embodiment 1

[0040] Please refer to Figures 1-5As shown in the figure, Embodiment 1 of the present invention provides a Fresnel reflector array 1 for area dimming. The Fresnel reflector array 1 is formed by splicing a plurality of rectangular Fresnel reflector units 2 in a rectangular grid arrangement. Each Fresnel reflector unit 2 corresponds to a Mini LED partition to form an independent dimming unit. The spacing between adjacent Fresnel reflector units 2 in the Fresnel reflector array 1 is ≤ 1 mm, and the splicing tolerance of the Fresnel reflector array 1 is ≤ 0.05 mm to ensure seamless splicing.

[0041] Please refer to Figure 3 and Figure 4 As shown in the figure, the Fresnel reflector unit 2 includes a main structure substrate 21, a first reflecting surface 22, a second reflecting surface 23, and an arc-shaped incident surface 24. The main structure substrate 21 is made of a material with a high light transmittance, such as polymethyl methacrylate (PMMA) or silicone rubber, and the light transmittance is ≥ 92%, reducing the energy loss of light in the medium of the main structure substrate 21, and a large amount of light passes through where there is no high-reflectivity coating on the top of the main structure substrate. The main structure substrate 21 can be made into a flat plate with a thickness of 0.8 - 1.5 mm and a surface roughness Ra ≤ 0.02 μm through an injection molding process. Preferably, nano-pores with a pore diameter of 10 - 50 nm and a porosity of 5% - 10% can be formed inside the main structure substrate 21 through a supercritical CO2 foaming technique to reduce the material density and improve the light scattering uniformity. A dovetail groove structure can also be machined on the edge of the main structure substrate 21. After tenon-and-mortise splicing with adjacent main structure substrates 21, the overall flatness error < 0.05 mm / m 2 , ensuring that light propagates without deflection. An anti-blue light nano-coating is also coated on the surface of the main structure substrate 21, with a blue light band of 400 - 450 nm and a transmittance ≤ 70%. The anti-blue light nano-coating material is a CeO2-TiO2 composite with a thickness of 200 nm. After testing with a spectrophotometer, the transmittance of 450 nm blue light drops to 65%, while the transmittance of 550 nm green light remains 92%. When the main structure substrate 21 is placed in a high-temperature environment of 85 °C for 48 hours, the anti-blue light nano-coating has no cracks, the light transmittance change < 0.5%, and the thermal deformation amount ≤ 0.01 mm.

[0042] Please refer to Figure 4As shown in the figure, the first reflecting surface 22 is disposed on the top of the main structure substrate 21. The first reflecting surface 22 is a rotationally symmetric paraboloid, and the rotationally symmetric paraboloid is coated with a high-reflectivity coating. The radius of curvature of the first reflecting surface 22 is 3 - 8 mm, and the focal length is 1 - 3 mm. The second reflecting surface 23 is disposed at the bottom of the main structure substrate 21. The second reflecting surface 23 is a serrated Fresnel reflecting surface. The serration angle of the second reflecting surface 23 is 10° - 45°, the serration height of the second reflecting surface 23 is 50 - 150 μm, the serration density is 10 - 30 serrations / mm, and the serrated Fresnel reflecting surface is also coated with a high-reflectivity coating. The high-reflectivity coating is a metal coating with a reflectivity ≥ 95%, which can be metallic silver or a nano-titanium oxide composite material, reducing the heat absorption of the reflecting surface and improving the light energy utilization rate. The distance between the first reflecting surface 22 and the second reflecting surface 23 is 0.8 - 1.2 mm. The arc-shaped incident surface 24 is located at the center of the bottom of the main structure substrate 21 and directly below the first reflecting surface 22. Each arc-shaped incident surface 24 corresponds to a Mini LED light source 3, and the arc-shaped incident surface 24 is used to concentrate the incident light.

[0043] Through material modification, structural innovation, and process optimization, the main structure substrate 21 is endowed with characteristics such as high light transmittance, light weight, anti-deformation, and environmental adaptability, providing core support for the precise optical performance and long-term reliability of the Fresnel reflector array 1, and is particularly suitable for harsh application scenarios such as vehicle-mounted displays and outdoor large screens.

[0044] Working principle

[0045] Please refer to Figure 5 As shown in the figure, first, the light emitted by the Mini LED light source 3 in the arc-shaped incident surface 24 irradiates the first reflecting surface 22. The first reflecting surface 22 is a rotationally symmetric paraboloid. When the light reaches the first reflecting surface 22, most of the light will be reflected to the second reflecting surface 23. Secondly, the second reflecting surface 23 is a serrated Fresnel reflecting surface specially designed according to the light reflected by the first reflecting surface 22, which can reflect the light along a direction approximately parallel to the optical axis and propagate in a direction approximately perpendicular to the plane of the diffusion plate. The purpose of this is to reduce the situation where the reflectivity is high due to too large an incident angle, which can effectively improve the light energy utilization rate and enhance the brightness. Through reflection, the mixing distance of the light becomes three segments, which can reduce the OD and expand the irradiation area. Thirdly, the second reflecting surface 23 has a rectangular appearance, which can confine the light of each arc-shaped incident surface 24 within a rectangular area, facilitating the realization of local dimming and increasing the contrast. Finally, the light reaches the diffusion plate for light mixing and homogenization.

[0046] Embodiment 2

[0047] Embodiment 2 of the present invention provides a Mini LED backlight module, including a diffusion plate and a back plate. A Fresnel reflector array 1 for local dimming as described in the embodiment is disposed between the diffusion plate and the back plate.

[0048] Specifically, the Mini LED backlight module adopts a stacked structure, and the arrangement order of each component from top to bottom is as follows:

[0049] The diffusion plate, the top layer, is used to homogenize light;

[0050] The Fresnel reflector array 1, located below the diffusion plate, is used to confine the light path;

[0051] The backplane, the bottom layer, provides mechanical support.

[0052] The connection between the Fresnel reflector array 1 and the backplane is directly fixed by a hot pressing process or a high light transmittance gluing process (such as UV curable glue, epoxy resin), canceling the traditional support column structure, and the interfacial tensile strength ≥ 10 MPa to ensure no deformation during long-term use.

[0053] The arc incident surface 24 and the backplane are directly mounted on the PCB substrate of the backplane through the pad + SMT process to ensure heat dissipation and circuit connection. The spacing of the arc incident surface 24 is 0.5 - 2 mm, and the partition size of the Fresnel reflector array 1 is the same as the spacing of the arc incident surface 24 to ensure 1:1 optical mapping. The angle of the serrated Fresnel reflection surface of the Fresnel reflector unit 2 is optimized according to the light output angle of the arc incident surface 24 to ensure that the light is perpendicularly incident on the diffusion plate.

[0054] The spacing between the Fresnel reflector array 1 and the diffusion plate is 0.5 mm - 1 mm to avoid scratches caused by direct contact and friction.

[0055] In the backlight module, the mixing light distance (Optical Distance, OD) refers to the optical path length of the light from the arc incident surface 24 to the diffusion plate, which is the core index to measure the compactness of the backlight module. In the traditional scheme, the light needs to be refracted and diffused multiple times through the lens or the light guide plate, resulting in an OD as long as 5 - 20 mm, which limits the ultra-thin design of the display device.

[0056] The Mini LED backlight module provided in this embodiment compresses the OD to 2 mm through the three-stage optical path design of the Fresnel reflector array 1. The specific principle is as follows:

[0057] The first reflecting surface 22 (rotationally symmetric paraboloid) reflects and focuses the diverging light rays from the arc-shaped incident surface 24 onto the second reflecting surface 23, reducing lateral scattering; the second reflecting surface 23 (serrated Fresnel reflecting surface) adjusts the light rays to be parallel to the optical axis direction and perpendicularly irradiates the diffusion plate, avoiding the increase in optical path caused by oblique propagation; after the light rays are reflected twice, the actual propagation path is "arc-shaped incident surface 24 → first reflecting surface 22 → second reflecting surface 23 → diffusion plate", and the total optical path is shortened by more than 60% compared with the traditional straight-line propagation. Through the innovative optical path design and the collaboration of multi-disciplinary technologies, the mixing distance is breakthrough shortened to 2 mm, while ensuring the optical performance and reliability, providing key technical support for the ultra-thinning and high picture quality of the Mini LED backlight module.

[0058] Embodiment III

[0059] Embodiment III of the present invention provides a display device, including a Mini LED backlight module of Embodiment II, and this display device is applicable to high-precision display fields such as ultra-thin TVs and in-vehicle displays.

[0060] Through the combined design of a rotationally symmetric paraboloid and a serrated Fresnel reflecting surface, the present invention realizes that the mixing distance is shortened to 2 mm, the contrast is greatly improved, the structural stability is enhanced, and high-precision regional dimming is achieved, and it is applicable to ultra-thin high-contrast display devices.

[0061] The above has described the preferred embodiments of the present invention in detail, and it cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. Fresnel reflector array for area dimming, characterized in that: The Fresnel reflector array (1) is formed by splicing a plurality of rectangular Fresnel reflector units (2) arranged in a rectangular grid. The Fresnel reflector unit (2) includes: A main structure substrate (21), which is made of a material with a high light transmittance; A first reflecting surface (22), which is disposed on the top of the main structure substrate (21). The first reflecting surface (22) is a rotationally symmetric paraboloid, and the rotationally symmetric paraboloid is coated with a high reflectivity coating; A second reflecting surface (23), which is disposed on the bottom of the main structure substrate (21). The second reflecting surface (23) is a plurality of concentric serrated Fresnel reflecting surfaces, and the serrated Fresnel reflecting surfaces are coated with a high reflectivity coating; An arc-shaped incident surface (24), which is disposed at the center of the bottom of the main structure substrate (21) and is directly below the first reflecting surface (22).

2. The Fresnel reflector array for area dimming according to claim 1, wherein: The distance between the first reflecting surface (22) and the second reflecting surface (23) is 0.8 - 1.2 mm.

3. The Fresnel reflector array for area dimming according to claim 1, wherein: The material of the main structure substrate (21) is polymethyl methacrylate or silicone rubber, with a light transmittance ≥ 92%, a thickness of 0.8 - 1.5 mm, and a surface roughness Ra ≤ 0.02 μm.

4. The Fresnel reflector array for area dimming according to claim 1, wherein: The serration angle of the second reflecting surface (23) is 10° - 45°, the serration height of the second reflecting surface (23) is 50 - 150 μm, and the serration density is 10 - 30 per mm.

5. The Fresnel reflector array for area dimming according to claim 1, characterized in that: The radius of curvature of the first reflecting surface (22) is 3 - 8 mm, and the focal length is 1 - 3 mm.

6. The Fresnel reflector array for area dimming according to claim 1, wherein: The distance between adjacent Fresnel reflector units (2) in the Fresnel reflector array (1) is ≤ 1 mm.

7. The Fresnel reflector array for area dimming according to claim 1, characterized in that: The high reflectivity coating covered on the first reflecting surface (22) and the second reflecting surface (23) is a metal coating with a reflectivity ≥ 95%.

8. The Fresnel reflector array for area dimming according to claim 1, characterized in that: The main structure substrate (21) is integrally formed by an injection molding technique and is coated with an anti-blue light nano-coating on the surface.

9. A backlight module, comprising a diffusion plate and a back plate, characterized in that: A Fresnel reflector array (1) for area dimming according to any one of claims 1 - 8 is provided between the diffuser plate and the back plate.

10. A display device, characterized in that: Including the backlight module according to claim 9.

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