Secondary optical lens for backlight module

Abstract

This invention discloses a backlight module that can improve brightness and can be used with a liquid crystal display (LCD). The backlight module includes a secondary optical lens that appropriately distributes the light emitted by an LED, and a diffuser plate with a unique light diffusion effect. The backlight module of this invention not only uses a catadioptric secondary optical lens on the LED to appropriately distribute the light emitted by the LED, but also incorporates microstructures on the light-incident surface of the diffuser plate, adds diffusion particles to the diffuser plate, and uses a foaming technique to extrude microbubbles that are uniformly distributed within the diffuser plate. This optimizes the light distribution and diffusion of the LED light, thereby achieving MURA (luminance over light) shielding and producing a brighter and more uniform surface light source.

Claims

1. A secondary optical lens for a backlight module, the backlight module comprising a substrate, a light-emitting diode (LED) element, and a diffuser plate; the substrate having a top surface and a circuit layout and a reflective layer, the reflective layer being located on the top surface; the LED element being disposed on the top surface of the substrate and electrically coupled to the circuit layout; the LED element having a light-emitting area capable of emitting light upward; the light-emitting area defining a light-emitting axis extending vertically upward from a center point of the light-emitting area; the diffuser plate being located above the substrate and comprising a plate body having an upper surface and a lower surface, the lower surface facing the substrate; The secondary optical lens is fixed to the top surface of the substrate at a position corresponding to the LED light-emitting element and covers the light-emitting area of ​​the LED light-emitting element; its characteristic is that the secondary optical lens can diffuse the light emitted from the light-emitting area of ​​the LED light-emitting element by refraction, reflection, or a combination of both; the secondary optical lens includes: a lens body and a blind aperture space located inside the lens body; the LED light-emitting element is housed in the blind aperture space and covered by the lens body; the secondary optical lens is a catadioptric optical lens; wherein: the lens body of the secondary optical lens has at least one reflective element. The lens body has at least one reflective surface and at least one refractive surface. When the light-emitting area of ​​the LED light-emitting element located in the blind aperture space emits light, if the light is incident on the reflective surface, it will be reflected by the reflective surface; if the light is incident on the refractive surface, it will be refracted at least once and then emitted outside the lens body. The lens body has a bottom, a side extension, and a light-emitting part from bottom to top. The bottom is for fixing to the top surface of the substrate. The side extension extends upward from the bottom by a height, and the height of the extension is not less than the thickness of the LED light-emitting element. The light-emitting part is located at the top of the side extension and includes an outer curved surface exposed to the outside and a surface exposed to the blind aperture space. The at least one reflective surface is disposed on one of the following two locations: the at least one reflective surface is disposed on the inner curved surface of the light-emitting portion, or the at least one reflective surface is disposed on the outer curved surface of the light-emitting portion; wherein, when the at least one reflective surface is disposed on the inner curved surface of the light-emitting portion, all other areas of the inner curved surface of the light-emitting portion except for the area where the reflective surface is disposed belong to the refractive surface; the at least one reflective surface has one of the following structures: a reflective coating is applied to the inner curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, and a reflective coating is applied to the inner curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface. A reflective sheet is attached to the position. An inclined plane with an appropriate angle is provided on the inner curved surface of the light-emitting part, corresponding to the position of the at least one reflective surface, which can reflect the light emitted from the light-emitting area of ​​the LED light-emitting element. Alternatively, a curved surface with an appropriate curvature is provided on the inner curved surface of the light-emitting part, corresponding to the position of the at least one reflective surface, which can reflect the light emitted from the light-emitting area of ​​the LED light-emitting element. When the at least one reflective surface is provided on the outer curved surface of the light-emitting part, all other areas of the outer curved surface of the light-emitting part except for the reflective surface are all refractive surfaces.The at least one reflective surface has one of the following structures: a reflective coating is applied to the outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface; a reflective sheet is attached to the outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface; an inclined plane with an appropriate angle is provided on the outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, which can reflect the light emitted from the light-emitting area of ​​the LED light-emitting element; or, a curved surface with an appropriate curvature is provided on the outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, which can reflect the light emitted from the light-emitting area of ​​the LED light-emitting element.

2. The secondary optical lens for a backlight module as described in claim 1, wherein, The board is a multi-layer structure formed by coextrusion, which includes a main board layer, an upper surface layer, and a lower surface layer; the upper surface layer is stacked on the side of the main board layer facing the upper surface, and the lower surface layer is stacked on the side of the main board layer facing the lower surface. Furthermore, the diffusion plate also includes: a plurality of first diffusion particles added to the main body layer; a plurality of second diffusion particles added to the upper and lower surface layers; a plurality of microbubbles formed in the main body layer by a foaming extrusion molding process; and a plurality of microstructures arranged in an array on at least the lower surface of the plate; the material of the main body layer of the plate includes one of the following: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET); the material of the upper and lower surface layers of the plate includes PMMA; the plurality of first diffusion particles are formed by adding a first diffusion particle additive to the main body layer, and the first diffusion particle additive includes a plurality of first diffusion particles. The first diffusion particle additive is added to the main body layer at a weight percentage of a first weight percentage; each of the first diffusion particles has a first material refractive index; and a plurality of the second diffusion particles are formed by adding a second diffusion particle additive to the upper surface layer and the lower surface layer; the second diffusion particle additive contains a plurality of the second diffusion particles; the added second diffusion particle additive is added to the upper surface layer and the lower surface layer at a weight percentage of a second weight percentage; each of the second diffusion particles has a second material refractive index; wherein the diffusion plate meets at least one of the following two conditions: condition 1: the first material refractive index of the first diffusion particle is less than the second material refractive index of the second diffusion particle; condition 2: the first weight percentage of the first diffusion particle additive is less than the second weight percentage of the second diffusion particle additive.

3. The secondary optical lens for a backlight module as described in claim 2, wherein, The plurality of first diffused particles contained in the first diffused particle additive include one of the following: silicone beads, acrylic beads, polystyrene beads, and acrylic-polystyrene copolymer beads; wherein the particle size of the first diffused particles is between 1 and 4 μm, the refractive index of the first material is between 1.42 and 1.5, and the first weight percentage of the first diffused particle additive added to the main board layer is between 1 and 4%.

4. The secondary optical lens for a backlight module as described in claim 3, wherein, The plurality of second diffused particles contained in the second diffused particle additive include one of the following: silicone beads, acrylic beads, polystyrene beads, and acrylic-polystyrene copolymer beads; wherein the particle size of the second diffused particles is between 15 and 25 μm, the refractive index of the second material is between 1.42 and 1.5, and the second weight percentage of the second diffused particle additive added to the upper and lower surface layers is between 5 and 10%; wherein the second weight percentage is greater than the first weight percentage, and the particle size of the second diffused particles is greater than the particle size of the first diffused particles.

5. A secondary optical lens for a backlight module as described in claim 3, wherein, The plurality of second diffused particles contained in the second diffused particle additive include one of the following inorganic particles: calcium carbonate, barium sulfate, titanium oxide, talc, mica, and boron nitride; wherein the particle size of the second diffused particles is between 0.05 and 8 μm, the refractive index of the second material is between 1.5 and 2.6, and the second weight percentage of the second diffused particle additive added to the upper and lower surface layers is between 0.1 and 1.5%.

6. A secondary optical lens for a backlight module as described in claim 5, wherein: The plurality of microbubbles are generated by adding a foaming agent and a nucleating agent during the foaming extrusion molding process of the main board layer; the nucleating agent comprises at least one of the following: calcium carbonate, silicon dioxide, and calcium oxide; the weight percentage of the added nucleating agent is 0.1%-0.5%; the weight reduction rate of the plurality of microbubbles on the main board layer is between 10% and 20%, and the average size of the plurality of microbubbles is between 60 and 800 μm; wherein, the weight reduction rate is calculated by the formula: weight reduction rate (%) = (W1 - W2) / W2*100%;W1=H*(L1*L2*D);W1 is the average thickness of the main board layer (mm);L1 is the length of the main board layer (mm);L2 is the width of the main board layer (mm);D is the specific gravity of the main board layer material (g / mm3);W1 is the theoretical weight of the main board layer (g), which is the weight without the multiple microbubbles;W2 is the actual weight of the main board layer (g), which is the actual weight of the main board layer containing the multiple microbubbles as measured by a scale.

7. A secondary optical lens for a backlight module as described in claim 1, wherein, Of the light emitted upward from the light-emitting area of ​​the LED light-emitting element, the total light intensity within the angle range of +30° to -30° with respect to the light-emitting axis is between 15% and 25% of the total light intensity of the LED light-emitting element, and the total light intensity within the angle ranges of +60° to +70° and -60° to -70° with respect to the light-emitting axis is between 75% and 85% of the total light intensity of the LED light-emitting element.

8. The secondary optical lens for a backlight module as described in claim 7, wherein, The upper part of the outer curved surface is an upwardly convex surface, while the area of ​​the outer curved surface closer to the bottom has a fixed curvature in different areas along the vertical direction. The inner curved surface is a downwardly convex surface protruding into the blind hole space in the area closer to the upper part, while the area of ​​the inner curved surface closer to the bottom has a larger curvature in the vertical direction as it approaches the bottom. By combining the outer and inner curved surfaces, the lens body provides a convex lens focusing function in the area directly above the LED light-emitting element, with an angle of approximately ±30 degrees with the light-emitting axis, while providing a concave lens light-diffusing function in other areas. The reflective surface is located at the junction of the convex and concave lenses to reflect and diffuse a portion of the light entering the lens body from the convex lens area.

9. A secondary optical lens for a backlight module as described in claim 6, wherein, Each of the microstructures comprises a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three; and the backlight module further comprises: an optical film directly attached to the upper surface of the diffuser plate; a brightness enhancement film (BEF) directly attached to the optical film; and a dual brightness enhancement film (DBEF) directly attached to the brightness enhancement film; wherein the backlight module can be assembled into a liquid crystal display (LCD), and the liquid crystal display is located above the dual brightness enhancement film.

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