TWI910079B - Backlight module capable of enhancing brightness - Google Patents

Abstract

A backlight module capable of enhancing brightness can be used with a Liquid Crystal Display (LCD). The backlight module comprises a secondary optical lens that can appropriately distribute the light emitted by the LED, and a diffusion plate with a unique light diffusion effect. The backlight module not only provides a catadioptric secondary optical lens on the LED to appropriately distribute the light emitted by the LED, but also provides a plurality of microstructures on the light-inlet surface of the diffuser plate, and provides a plurality of diffusion particles in the diffuser plate, and also provides a plurality of microbubbles evenly distributed in the diffuser plate by using extruding foaming technology. In this way, the light of the LED can be optimally distributed and diffused, thereby shielding the MURA to produce a surface light source with increased brightness and uniformity.

Description

Backlight module that can improve brightness

This invention relates to a backlight module that can improve brightness, and more particularly to a backlight module that can be used with a liquid crystal display and includes components such as a light-emitting diode, a secondary optical lens, and a diffuser, thereby providing better optical characteristics.

With the development of backlight displays and the trend towards thinner designs, backlight modules inevitably face the demand for ultra-thin designs. Direct-lit backlight modules using light-emitting diodes (LEDs) as direct light sources, while achieving higher light intensity due to their reduced optical distance (OD) caused by thinner designs, also suffer from more severe mullion-like defects (MURA, i.e., bright and dark bands or moiré patterns on the light-emitting surface). Current technology uses secondary optical lenses on the LEDs to diffuse the light emitted, thereby reducing the thickness of the backlight module. However, the larger the spacing between adjacent LEDs and the smaller the OD distance, the more overly bright the center of the light spot directly above the LEDs becomes, resulting in MURA. Existing technologies that use secondary optical lenses to redistribute light emitted from LEDs aim to achieve uniformity by scattering the light across a wide angle. However, this alters the central light intensity of the LED, resulting in lower central luminance and limiting the effectiveness of improving MURA (Muller-Ray Effect).

Therefore, if existing secondary optical lenses are continued to be used in conjunction with traditional diffusers in low-path-distance backlight modules, the light diffusion effect will no longer meet the requirements.

Therefore, this invention is a combination of a light-distributing secondary optical lens and a unique diffuser plate applied to a backlight module. Not only is a catadioptric secondary optical lens placed on the LED to appropriately distribute the light emitted by the LED, but a microstructure is also placed on the light-incident surface of the diffuser plate. Furthermore, diffusing particles are added to the diffuser plate, and a foaming technique is used to extrude uniformly distributed microbubbles within the diffuser plate. This multi-layered structure diffuses the light from the LED, thereby achieving MURA (mullion beam) shielding and producing a brighter and more uniform surface light source.

The primary objective of this invention is to provide a backlight module that enhances brightness for use with LCD displays. This backlight module includes a secondary optical lens that appropriately distributes the light emitted by an LED, and a diffuser plate with a unique light-diffusing 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, and adds diffusing particles to the diffuser plate, extruding them using a foaming technique to create uniformly distributed microbubbles within the diffuser plate. This optimizes the light distribution and diffusion of the LED light, thereby achieving MURA (luminous luminance) shielding and producing a brighter and more uniform surface light source.

To achieve the above objectives, this invention discloses a backlight module that can improve brightness, comprising:

A substrate having a top surface; a circuit layout and a reflective layer are disposed on the substrate, the reflective layer being located on the top surface;

A plurality of light-emitting diode (LED) elements are arranged in an array on the top surface of the substrate and electrically coupled to the circuit layout;

A plurality of secondary optical lenses, each of which is fixed to the top surface of the substrate at a position corresponding to one of the LED light-emitting elements and covers the light-emitting area of the LED light-emitting element; and

A diffusion plate, located above the substrate, includes:

A board having an upper surface and a lower surface, the lower surface facing the substrate; the board is a multi-layer structure formed by co-extrusion, comprising a main board layer, an upper surface layer, and a lower surface layer; the upper surface layer is laminated on the side of the main board layer facing the upper surface, and the lower surface layer is laminated on the side of the main board layer facing the lower surface;

A plurality of first diffuse particles are added to the motherboard layer;

A plurality of second diffuse particles are added to the upper and lower surface layers;

Multiple microbubbles are formed in the motherboard layer by a foaming extrusion molding process; and

A plurality of microstructures are arranged in an array on at least the lower surface of the plate;

Each of the secondary optical lenses can diffuse the light emitted from the emitting region of the corresponding LED emitting element by refraction, reflection, or a combination of both. Furthermore, the combined light intensity of the light emitted upwards from the emitting region of the LED emitting element within an angle range of +30° to -30° with respect to the emitting axis accounts for 15% to 25% of the total luminous intensity of the LED emitting element, and the combined light intensity within angle ranges of +60° to +70° and -60° to -70° with respect to the emitting axis accounts for 75% to 85% of the total luminous intensity of the LED emitting element.

In one embodiment, the main body layer of the board is made of one of the following materials: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET); the upper and lower surface layers of the board are made of PMMA.

The plurality of the first diffusing particles are constituted by adding a first diffusing particle additive to the motherboard layer, the first diffusing particle additive comprising the plurality of the first diffusing particles; the weight percentage of the added first diffusing particle additive in the motherboard layer is a first weight percentage; each of the first diffusing particles has a first material refractive index; and

A plurality of the second diffusing particles are formed by adding a second diffusing particle additive to the upper surface layer and the lower surface layer; the second diffusing particle additive comprises a plurality of the second diffusing particles; the weight percentage of the added second diffusing particle additive in the upper surface layer and the lower surface layer is a second weight percentage; each of the second diffusing particles has a second material refractive index;

The diffuser plate meets at least one of the following two conditions:

Condition 1: The refractive index of the first material of the first diffusing particle is less than the refractive index of the second material of the second diffusing particle;

Condition 2: The first weight percentage of the first diffusing particle additive is less than the second weight percentage of the second diffusing particle additive.

In one embodiment, the plurality of first diffusing particles included in the first diffusing particle additive comprises one of the following: silicone beads, acrylic beads, polystyrene beads, or acrylic-polystyrene copolymer beads (PMMA-PS beads); wherein the particle size of the first diffusing 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 diffusing particle additive added to the mainboard layer is between 1 and 4%.

In one embodiment, the second diffusing particle additive comprises a plurality of the following: silicone beads, acrylic beads, polystyrene beads, or acrylic-polystyrene copolymer beads (PMMA-PS beads); wherein the particle size of the second diffusing 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 diffusing particle additive added to the upper and lower surfaces is between 5% and 10%; wherein the second weight percentage is greater than the first weight percentage, and the particle size of the second diffusing particles is greater than the particle size of the first diffusing particles.

In one embodiment, the plurality of second diffusing particles included in the second diffusing particle additive comprise one of the following inorganic particles: calcium carbonate, barium sulfate, titanium oxide, talc, mica, or boron nitride; wherein the particle size of the second diffusing 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 diffusing particle additive added to the upper and lower surface layers is between 0.1% and 1.5%.

In one embodiment, a plurality of microbubbles are generated by adding a foaming agent and a nucleating agent during the foaming extrusion molding process of the motherboard layer; the nucleating agent comprises at least one of the following: calcium carbonate, silica, 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 to the motherboard layer is between 10% and 20%, and the average size of the plurality of microbubbles is between 60 and 800 μm;

The formula for calculating the weight loss rate is as follows:

Weight loss rate (%) = (W1 - W2) / W2 * 100%;

W1 = H * (L1 * L2 * D);

in:

H is the average thickness (mm) of this motherboard layer;

L1 is the length (mm) of this motherboard layer;

L2 is the width (mm) of this motherboard layer;

D is the specific gravity (g/mm3) of the material in this motherboard layer;

W1 is the theoretical weight (g) of this motherboard layer, which is the weight excluding the multiple microbubbles.

W2 is the actual weight (g) of the motherboard layer, which is the actual weight of the motherboard layer containing multiple of the microbubbles, as measured using a scale.

In one embodiment, each of the secondary optical lenses 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; the lens body of the secondary optical lens 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. The light is reflected from the surface; if the light is incident on the refractive surface, it will be refracted at least once before exiting the lens body. The lens body has, from bottom to top, a bottom, a side extension, and a light-emitting portion. The bottom is the top surface for fixing to the substrate. The side extension extends upwards from the bottom by a height not less than the thickness of the LED light-emitting element. The light-emitting portion is located at the top end of the side extension and includes an outer curved surface exposed to the outside and an inner curved surface exposed to the blind hole space.

In one embodiment, the at least one reflective surface is disposed on the inner curved surface of the light-emitting portion, and 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 adhered 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, and an inclined plane with an appropriate angle is provided on the inner 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. Alternatively, a curved surface with an appropriate curvature is provided on the inner 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.

In one embodiment, the at least one reflective surface is disposed on the outer curved surface of the light-emitting portion, and all other areas of the outer 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 outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, and a reflective coating is adhered 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, and 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. Alternatively, 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.

In one embodiment, each of the microstructures comprises a plurality of N-sided prisms, where N is a positive integer greater than or equal to three; and the backlight module further comprises:

An optical film is directly adhered to the upper surface of the diffuser plate.

A brightness enhancement film (BEF) is directly applied to the optical film; and

A dual brightness enhancement film (DBEF) is directly applied to the brightness enhancement film.

The backlight module can be assembled into a liquid crystal display (LCD), and the LCD is located above the polarizing brightness enhancement film.

1: Diffuser Plate

10: Plate

101: Motherboard Layer

1011, 1021, 1031: Diffused particles

1012: Microbubbles

102, 103: Surface layer

1032: Microstructure

151: Optical film

152: Brightening Film

153: Polarizing Brightness Enhancement Film

20: Secondary Optical Lens

21: Lens Body

211: Reflective surface

212: Refractive surface

213: Bottom

214: Lateral extension

2141: Outer curved surface

2142: Inner Curved Surface

215: Light department

22: Blind Hole Space

91:Substrate

911: Top

92: Light-emitting element

921: Light-emitting axis

93: LCD Display

Figure 1 is a cross-sectional schematic diagram of an embodiment of the backlight module of the present invention, which improves brightness, and is used with a liquid crystal display to form a backlit display.

Figures 2A, 2B, and 2C are schematic diagrams of three different embodiments of the microstructure provided on the lower surface of the diffuser plate of the present invention.

Figures 3A, 3B, and 3C are schematic diagrams of the light intensity distribution (light distribution) of a conventional reflective secondary optical lens, a conventional refractive secondary optical lens, and the catadioptric secondary optical lens of this invention, respectively.

Figure 4 is a schematic diagram of an embodiment of the catadioptric secondary optical lens of the backlight module that can improve brightness according to the present invention.

This invention relates to a backlight module that improves brightness and can be used with an LCD display. 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, and adds diffusing particles to the diffuser plate, extruding them using a foaming technique to create uniformly distributed microbubbles within the diffuser plate. This optimizes the light distribution and diffusion of the LED light, thereby achieving MURA (luminous luminance) shielding and producing a brighter and more uniform surface light source.

To more clearly describe the brightness-enhancing backlight module and its manufacturing method proposed in this invention, a detailed explanation with accompanying figures will follow.

Please refer to Figure 1, which is a cross-sectional schematic diagram of an embodiment of the backlight module of the present invention used with a liquid crystal display to form a backlit display. The backlight module of the present invention is mounted below a liquid crystal display 93 to form a backlit display. In this first embodiment, the backlight module includes, from bottom to top: a substrate 91, a plurality of light-emitting elements 92, a diffuser 1, an optical film 151, a brightness enhancement film (BEF) 152, and a dual brightness enhancement film (DBEF) 153. The substrate 91 has a top surface 911. A circuit layout (not shown) and a reflective layer are provided on the substrate 91, and the reflective layer is located on the top surface 911. A plurality of light-emitting elements 92 are arranged in an array on the top surface 911 of the substrate 91 and electrically coupled to the circuit layout. Each light-emitting element 92 has a light-emitting region (not numbered in the figure) that emits light upward toward the plate 10 of the diffuser. The light-emitting region is defined by a light-emitting axis that extends vertically upward from a center point of the light-emitting region. In this embodiment, the light-emitting elements 92 are light-emitting diode (LED) elements, such as, but not limited to: general light-emitting diode (LED) elements, sub-millimeter light-emitting diode (Mini LED) elements, or even micro light-emitting diode (Micro LED) elements. A reflective layer is disposed on the top surface 911 of the substrate 91. This reflective layer can be white or other colors or surfaces with good light reflection effects, used to reflect light upwards towards the plate 10 of the diffuser 1.

A plurality of secondary optical lenses 20 are respectively corresponding to and covering a plurality of light-emitting elements 92. Each of the secondary optical lenses 20 is fixed on the top surface 911 of the substrate 91 at a position corresponding to a light-emitting element 92 and covers the light-emitting area of the light-emitting element 92. One of the technical features of this invention is that each of the secondary optical lenses 20 can diffuse the light emitted by the light-emitting area of the corresponding light-emitting element 92 by refraction, reflection, or a combination of both; and the light intensity of the light emitted upward from the light-emitting area of the light-emitting element 92 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 light-emitting element 92, and the 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 light-emitting element 92. The backlight module of this invention, through the unique light distribution design of the secondary optical lens 20, combined with the multi-diffraction effect provided by the diffuser plate 1 described below, can effectively block MURA, thereby producing a brighter and more uniform surface light source. The shape of the secondary optical lens 20 shown in Figure 1 is only a simplified schematic diagram and not a true representation; an embodiment of the shape of the secondary optical lens 20 of this invention will be described later.

The diffuser plate 1 has a plate body 10 positioned above and adjacent to the substrate 91 containing the plurality of light-emitting elements 92. In this embodiment, there are no other components between the diffuser plate 1 and the secondary optical lens 20 disposed on the substrate 91. In this invention, the diffuser plate 1 includes: a plate body 10, a first diffusing particle additive, a second diffusing particle additive, a plurality of microbubbles 1012, and a plurality of microstructures 1032. The plate body 10 has an upper surface and a lower surface. The lower surface of the plate body 10 faces the substrate 91 and serves as a light-incident surface; light emitted by the light-emitting elements 92 enters the plate body 10 through the lower surface (light-incident surface). Conversely, the upper surface of the board 10 is the light-emitting surface. Light entering the board 10 undergoes multiple refractions and diffusion effects before being emitted from the upper surface (light-emitting surface) and directed towards the liquid crystal display 93 located above it. The board 10 is a multi-layer board structure constructed by coextrusion, comprising a main board layer 101, an upper surface layer 102, and a lower surface layer 103. The upper surface layer 102 is laminated to the side of the main board layer 101 facing the upper surface, and the lower surface layer 103 is laminated to the side of the main board layer 101 facing the lower surface. The substrate of the main body layer 101 of the board 10 can be an amorphous or semi-crystalline organic polymer plastic material, including one of the following: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), or a copolymer of any of the aforementioned materials. The substrate of the upper surface layer 102 and the lower surface layer 103 of the board 10 is preferably polymethyl methacrylate (PMMA, commonly known as acrylic). In this embodiment, the thickness ratio of the main body layer 101 to the total thickness of the two surface layers 102 and 103 (the sum of the thicknesses of the upper and lower surface layers) can be between 9.5:0.5 and 1:1, with a preferred range between 9:1 and 7:3. The substrate of the motherboard layer 101 and the two surface layers 102 and 103 can be the same material or different materials.

In this embodiment, the first diffusing particle additive comprises a plurality of first diffusing particles 1011, which are added to the motherboard layer 101. The weight percentage of the added first diffusing particle additive in the motherboard layer 101 is a first weight percentage; each of the first diffusing particles 1011 has a first material refractive index. The second diffusing particle additive comprises a plurality of second diffusing particles 1021 and 1031, which are added to the upper surface layer 102 and the lower surface layer 103, respectively. The weight percentage of the added second diffusing particle additive in the upper surface layer 102 and the lower surface layer 103 is a second weight percentage; each of the second diffusing particles 1021 and 1031 has a second material refractive index. In this embodiment, the diffuser 1 meets at least one of the following two conditions:

Condition 1: The refractive index of the first material of the first diffusing particle 1011 is less than the refractive index of the second material of the second diffusing particles 1021 and 1031;

Condition 2: The first weight percentage of the first diffusing particle additive is less than the second weight percentage of the second diffusing particle additive.

By satisfying one of the above conditions, or condition two, or both of the above conditions, the refractive index of the upper and lower surface layers 102 and 103, which have a relatively high refractive index and/or concentration (by weight percentage) of a plurality of second diffusing particles 1021 and 1031, can be substantially higher than the refractive index of the mainboard layer 101, which has a relatively low refractive index and/or concentration (by weight percentage) of a plurality of first diffusing particles 1011, thereby providing a slight reflective effect on the side of the upper and lower surface layers 102 and 103 facing the mainboard layer 101. Therefore, after the light emitted by the light-emitting element 92 enters the interior of the board 10, a portion of the light is refracted or reflected several times within the main board layer 101 between the upper and lower surface layers 102 and 103 before being emitted from the upper surface (light-emitting surface). This increased refraction or reflection enhances the light diffusion, thereby strengthening the MURA shielding effect and producing a uniform surface light source.

In this embodiment, the plurality of first diffusing particles 1011 included in the first diffusing particle additive comprise at least one of the following polymeric material diffusing particles: silicone beads, acrylic beads, polystyrene beads, and acrylic-polystyrene copolymer beads (PMMA-PS beads). The particle size of the first diffusing particles 1011 is preferably between 0.5 and 10 μm, but between 1 and 4 μm. The refractive index of the first material is between 1.42 and 1.5. The first weight percentage of the first diffusing particle additive added to the mainboard layer 101 is preferably between 0.5 and 10%, but between 1 and 4%. While the first and second diffusing particle additives described herein are commercially available and known products, the selection of their added amount (weight percentage) and the range of material refractive index and particle size is original to this invention.

In this invention, the plurality of second diffusing particles 1021, 1031 contained in the second diffusing particle additive can have two embodiments: the first is inorganic diffusing particles, and the other is polymeric material diffusing particles. In the first embodiment, the plurality of second diffusing particles 1021, 1031 included in the second diffusing particle additive may include at least one of the following inorganic particles: calcium carbonate, barium sulfate, titanium oxide, talc, mica, and boron nitride; wherein, the particle size of the second diffusing particles 1021, 1031 is preferably between 0.01 and 10 μm, but preferably between 0.05 and 8 μm; the refractive index of the second material is preferably between 1.5 and 2.6; and the second weight percentage of the second diffusing particle additive added to the upper surface layer 102 and the lower surface layer 103 is preferably between 0.1 and 3%, but preferably between 0.1 and 1.5%. In the second embodiment, the plurality of second diffusing particles 1021, 1031 included in the second diffusing particle additive include at least one of the following polymeric material diffusing particles: silicone beads, acrylic beads, polystyrene beads, and acrylic-polystyrene copolymer beads (PMMA-PS). (beads); wherein, the particle size of the second diffusing particles 1021 and 1031 is preferably between 10 and 50 μm, but between 15 and 25 μm; the refractive index of the second material is preferably between 1.42 and 1.5; the second weight percentage of the second diffusing particle additive added to the upper surface layer 102 and the lower surface layer 103 is preferably between 1 and 20%, but between 5 and 10%; and, in this second embodiment, the second weight percentage must be greater than the first weight percentage, and the particle size of the second diffusing particles 1021 and 1031 is greater than the particle size of the first diffusing particle 1011. By using the second diffusing particle additive as defined in the first and second embodiments above in conjunction with the first diffusing particle additive as defined above, it can be ensured that the refractive indices of the upper and lower surface layers 102 and 103 are substantially higher than the refractive index of the motherboard layer 101, thereby achieving the effects of more effectively diffusing light, enhancing the shielding of MURA, and generating a uniform surface light source.

As shown in Figure 1, in a first embodiment of the diffuser plate of the present invention, a plurality of microstructures 1032 are arranged in an array on at least the lower surface of the plate 10, which can further improve the light diffusion effect of the diffuser plate. Each microstructure includes a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three. In the preferred embodiment, each microstructure is a pyramidal structure with a quadrilateral base, so that the plurality of microstructures 1032 present a plurality of pyramidal microstructures. In addition, the main plate layer 101 of the plate 10 is formed by a foaming extrusion molding process to generate a plurality of microbubbles 1012 in the main plate layer 101. The feasible weight reduction rate of the plurality of microbubbles 1012 on the motherboard layer 101 is between 5% and 30%, but a weight reduction rate between 10% and 20% is preferred. The average size of the plurality of microbubbles 1012 is between 60 and 800 μm. The formula for calculating the weight reduction rate is:

Weight loss rate (%) = (W1 - W2) / W2 * 100%;

W1 = H * (L1 * L2 * D);

in:

H is the average thickness (mm) of this motherboard layer;

L1 is the length (mm) of this motherboard layer;

L2 is the width (mm) of this motherboard layer;

D is the specific gravity of the material in the motherboard layer (g/ ^mm³ );

W1 is the theoretical weight (g) of this motherboard layer, which is the weight excluding the multiple microbubbles.

W2 is the actual weight (g) of the motherboard layer, which is the actual weight of the motherboard layer containing multiple of the microbubbles, as measured using a scale.

In this embodiment, a plurality of microbubbles 1012 are generated by appropriately adding a foaming agent and a nucleating agent during the foaming extrusion molding process of the main board layer 101. The nucleating agent comprises at least one of the following: calcium carbonate, silica, and calcium oxide; the weight percentage of the added nucleating agent is feasible in the range of 0.01%-5%, but preferably in the range of 0.1%-0.5%. The weight loss rate of the microbubbles 1012 can be controlled by the amount of foaming agent added, and the bubble size of the microbubbles 1012 can be controlled by adding the nucleating agent and adjusting the process temperature. The processing temperature of the foaming co-extrusion process of the multilayer board 10 of the diffuser plate of this invention is adjusted according to the type of raw material resin and foaming agent. The processing temperature of this invention is the general processing temperature of polycarbonate, with an optimal range of 220~270℃.

In this embodiment, the diffuser 1 further includes the optical film 151, the brightness enhancement film 152 (BEF), and the polarizing brightness enhancement film 153 (DBEF). The optical film 151 is directly adhered to the upper surface of the plate body 10 of the diffuser 1 with optical adhesive; the brightness enhancement film 152 is directly adhered to the optical film 151 with optical adhesive; and the polarizing brightness enhancement film 153 is directly adhered to the brightness enhancement film 152 with optical adhesive. Both the brightness enhancement film 152 (BEF) and the polarizing brightness enhancement film 153 (DBEF) are films that improve the light extraction efficiency in the backlight system. When the light-emitting element 92 is a white LED, the optical film 151 can be an optical diffuser film with light diffusion function. When using a blue LED, the optical film 151 can be a quantum dot optical conversion film with color conversion function, capable of converting blue light into white light. The backlight module of this invention can be assembled into a liquid crystal display (LCD) 93, with the LCD 93 positioned above the polarizing brightness enhancement film 153. The optical adhesive, optical film 151, brightness enhancement film 152, and polarizing brightness enhancement film 153 described herein are all commercially available and known products.

Please refer to Figures 2A, 2B, and 2C, which are schematic diagrams of three different embodiments of the microstructures provided on the lower surface of the diffuser plate 1 of the present invention. The diffuser plate of the present invention extrudes a plurality of microstructures 1032 on the lower surface of the plate body 10 by an extrusion process. These microstructures 1032 have a plurality of protrusions or recesses, and their protrusion-recessed structure can be regularly or irregularly distributed on the lower surface of the diffuser plate body 10. These microstructures 1032, when viewed from above, can take on various shapes, including circular, worm-like (as shown in Figure 2A), irregular matte (as shown in Figure 2B), pyramidal (as shown in Figure 2C), etc. Among these, the pyramidal microstructure on the light-incident surface of the plate 10 provides the best overall brightness enhancement. This is because the pyramidal microstructure can reflect some of the light traveling downwards (towards the LED element) upwards, thus increasing brightness.

This invention's backlight module uses a direct-lit LED light source paired with a catadioptric secondary optical lens. The lens focuses light directly in front of the LED light-emitting element and reflects side light through its reflective surface, altering the light output of the LED light source. The light intensity within a +30° to -30° angle range above the LED light-emitting element increases due to the light distribution effect of the catadioptric secondary optical lens. Therefore, this invention incorporates multiple pyramidal microstructures on the light-incident surface of the diffuser plate. These, combined with the secondary optical lens, increase total internal reflection, improving light efficiency (brightness). Furthermore, the diffuser plate, co-extruded using foaming technology, achieves excellent light diffusion rate through the diffusing particles and microbubbles within the mainboard layer, resulting in more uniform light emission and effective MURA shielding.

Common secondary optical lenses used in LED light-emitting elements include reflective and refractive secondary optical lenses. Conventional reflective secondary optical lenses can maximize the focusing of light emitted by the LED light-emitting element along its optical axis. Conventional refractive secondary optical lenses can diffuse most of the light emitted by the LED light-emitting element to a larger angle, while the light intensity along the optical axis is much lower. The refractive secondary optical lens of this invention combines reflection and refraction, optimizing the light distribution of the light emitted by the LED light-emitting element. This allows most of the light emitted by the LED light-emitting element to be diffused to a larger angle while also ensuring that there is a suitable intensity of light directly above the LED light-emitting element. Therefore, this invention, by incorporating a refractive secondary optical lens on the LED light-emitting element and combining it with a uniquely designed diffuser, can simultaneously improve the light output brightness and uniformity of the backlight module (reducing MURA).

Please refer to Figures 3A, 3B, and 3C, which are schematic diagrams of the light intensity distribution (light distribution) of a conventional reflective secondary optical lens, a conventional refractive secondary optical lens, and the catadioptric secondary optical lens of this invention, respectively. As shown in Figure 3A, when using a conventional reflective secondary optical lens, the light intensity emitted by the LED emitting element at the point directly above the LED (within ±5 degrees of the optical axis) accounts for almost 100% of the total light intensity emitted by the LED emitting element. In contrast, as shown in Figure 2A, when using a conventional refractive secondary optical lens, the light intensity emitted by the LED emitting element directly above the LED (within ±5 degrees of the emitting axis) accounts for only about 10% or less of the total light intensity emitted by the LED emitting element, while the light intensity within the angle range of +60° to +70° and -60° to -70° with respect to the emitting axis accounts for about 90% or more of the total light intensity emitted by the LED emitting element. As shown in Figure 3C, when using the catadioptric secondary optical lens of this invention, the total light intensity of the light emitted by the LED emitting element within the angle range of +30° to -30° with respect to the emitting axis is between 15% and 25% of the total light intensity of the LED emitting element (20% being optimal), and the total light intensity within the angle ranges of +60° to +70° and -60° to -70° with respect to the emitting axis is between 75% and 85% of the total light intensity of the LED emitting element (80% being optimal). Please refer to Table 1 below for a comparison of the light intensity at different angles when the LED emitting element is used with a conventional reflective secondary optical lens, a conventional refractive secondary optical lens, and the catadioptric secondary optical lens of this invention. As shown in Figures 3A to 3C and Table 1, the catadioptric secondary optical lens of this invention, compared to the prior art, can appropriately distribute the light emitted by the LED light-emitting element. This allows most of the light emitted by the LED (between 75% and 85%) to be diffused to a wider angle (+60° to +70° and -60° to -70°), while also ensuring that light directly above the LED (within the +30° to -30° angle range) has a suitable intensity (between 15% and 25%). This light distribution method provided by the catadioptric secondary optical lens of this invention, when used in conjunction with the aforementioned diffuser plate, effectively optimizes the light distribution and diffusion of the LED light, thereby achieving MURA shielding and producing a brighter and more uniform surface light source.

Table 1: Comparison of light intensity of different secondary optical lenses at different angles

Please refer to Figure 4, which is a schematic diagram of an embodiment of the catadioptric secondary optical lens for improving brightness in the backlight module of the present invention. In the present invention, the secondary optical lens 20 is a catadioptric optical lens. Each of the secondary optical lenses 20 includes: a lens body 21, and a blind aperture space 22 located inside the lens body. The LED light-emitting element 92 is housed in the blind aperture space 22 and covered by the lens body 21. The lens body 21 of the secondary optical lens 20 has at least one reflective surface 211 and at least one refractive surface 212. When the light-emitting area of the LED light-emitting element 92 located in the blind aperture space 22 emits light, if the light is incident on the reflective surface 211, it will be reflected by the reflective surface; if the light is incident on the refractive surface 212, it will be refracted at least once before exiting the lens body 21. The lens body 21 has a bottom 213, a side extension 214, and a light-emitting part 215 from bottom to top. The bottom 213 is for fixing to the top surface 911 of the substrate 91. The side extension 214 extends upward from the bottom 213 by a height, and the height of the extension is not less than the thickness (height) of the LED light-emitting element 92. The light-emitting portion 215 is located at the top end of the side extension 214 and includes an outer curved surface 2141 exposed to the outside and an inner curved surface 2142 exposed to the blind hole space 22.

In this embodiment, the top (upper) region of the outer curved surface 2141 generally presents a convex curved surface that bulges outward (upward) similar to a sphere or a bullet surface; while the region of the outer curved surface 2141 closer to the bottom 213 presents a cylindrical side surface similar to a cylindrical side surface, that is, the curvature of different regions along the vertical direction remains generally constant. The inner curved surface 2142 includes at least two regions. The region of the inner curved surface 2142 closer to the top (upper) presents a convex curved surface that bulges downward into the blind hole space 22; while the region of the inner curved surface 2142 closer to the bottom 213 presents a conical surface similar to a cone, that is, a concave curved surface with a greater curvature the closer to the bottom 213 along the vertical direction. By combining the outer curved surface 2141 and the inner curved surface 2142, the area of the lens body 21 directly above the LED light-emitting element 92, within an angle of ±30 degrees with the light-emitting axis, provides the light-focusing function of a convex lens. This increases the amount of light emitted by the LED light-emitting element 92 within this ±30-degree angle range. In contrast, other areas provide the light-diffusing function of a concave lens. The reflective surface is located adjacent to the convex and concave lenses to reflect and diffuse a portion of the light entering the lens body 21 from the convex lens area, thus balancing the light output in the area directly above the LED light-emitting element 92 with other side areas. The placement, area, curvature, etc., of the reflective surface 211 and the refracting surface 212 are designed based on the physical laws of light refraction and reflection and the refractive index of the lens body 21 material. This aims to ensure that the total light intensity of the light emitted by the LED light-emitting element 92 within an angle range of +30° to -30° with respect to the light-emitting axis 921 is between 15% and 25% (ideally 20%) of the total light intensity of the LED light-emitting element 92, and the total light intensity within angle ranges of +60° to +70° and -60° to -70° with respect to the light-emitting axis 922 is between 75% and 85% (ideally 80%) of the total light intensity of the LED light-emitting element 92.

In one embodiment, the at least one reflective surface is disposed on the inner curved surface of the light-emitting portion, and 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. In this embodiment, 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; a reflective sheet is adhered to the inner 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 inner curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, capable of reflecting 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 inner curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, capable of reflecting the light emitted from the light-emitting area of the LED light-emitting element.

In another embodiment, the at least one reflective surface is disposed on the outer curved surface of the light-emitting portion, and all other areas of the outer curved surface of the light-emitting portion, except for the area where the reflective surface is disposed, belong to the refractive surface. In this embodiment, 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, capable of reflecting 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, capable of reflecting the light emitted from the light-emitting area of the LED light-emitting element.

Based on the aforementioned technical concept, this invention fabricated several different diffusers paired with different types of secondary optical lenses for testing. Each diffuser was given different structural parameters, including: the presence of diffusing particles and microbubbles on the plate, the type of microstructure on the incident light surface, the type of secondary optical lens, etc. Then, several optical effects (including: luminosity, chromaticity, tint, etc.) of these diffusers and secondary optical lenses with different parameters were tested or observed one by one, and these optical effects were analyzed and compared. The results are summarized in Table 2 below.

Table 2: Comparison of optical effects of different diffusers paired with different secondary optical lenses

In Table 2 above, "diffusing particles" in the "diffuser plate" field indicates that the diffuser plate contains a plurality of diffusing particles but no microbubble structures, while "diffusing particles + microbubbles" indicates that the diffuser plate contains both a plurality of diffusing particles and a plurality of microbubbles. "mat" in the "light-incident surface" field indicates that a matte microstructure is provided on the lower surface (light-incident surface) of the plate, while "pyramid" indicates that a pyramid-shaped microstructure is provided on the lower surface (light-incident surface) of the plate. The value in the "Tt%" field is the total light transmittance (%) of the diffuser plate. The values in the "thickness" and "OD" fields refer to the thickness and optical path distance (mm) of the diffuser plate, respectively. The value of "LED per row" refers to the number of LED light-emitting element arrays (per row) on the substrate. The "Quality" field is the optical quality of the light-emitting surface of the diffuser, visually assessed, and is represented by a value from 1 to 5, where 1 indicates the worst visual optical quality and 5 indicates the best quality. The value of the "L center" field indicates the luminance value of the central area of the light-emitting surface, and the value within the scratch mark indicates the percentage increase or decrease in luminance value compared to the previous embodiment. The values in the "x" and "y" fields refer to the chromaticity values in the x and y directions, respectively. As shown in Table 2, compared to Comparative Example 2, the difference in brightness (luminance) is not significant when the light-incident surface of the diffuser is set with a matte or pyramidal microstructure and paired with the same refractive secondary optical lens. In Comparative Example 3, the diffuser's incident light surface features a pyramidal microstructure, paired with a catadioptric secondary optical lens. While brightness increases, the optical quality deteriorates. In Embodiment 1, the diffuser's pyramidal microstructure, combined with a catadioptric secondary optical lens, not only increases brightness but also maintains good optical quality, achieving a better optical effect than Comparative Examples 1-3. In Embodiments 2 and 3, if the diffuser's incident light surface features a pyramidal microstructure, paired with a catadioptric secondary optical lens, not only does brightness increase but good optical quality is also maintained, achieving a better optical effect than Comparative Examples 1-3. Furthermore, the difference in the "L center" field values obtained from Embodiments 2 and 3, where the "incident surface" field of the diffuser is configured with two different microstructures ("mat" and "pyramid"), shows that when the incident surface of the diffuser is configured with a pyramidal microstructure, its luminance value (brightness) can be increased by at least 6% compared to when the incident surface is matte. This demonstrates that the diffuser of the present invention can indeed improve brightness (light extraction efficiency) when the incident surface is configured with a pyramidal microstructure.

However, the embodiments described above should not be used to limit the scope of application of this invention. The scope of protection of this invention shall be primarily defined by the technical spirit and equivalent variations thereof as defined in the patent application. That is, all equivalent variations and modifications made within the scope of the patent application will not deviate from the essence of this invention, nor will they depart from its spirit and scope; therefore, they should all be considered further embodiments of this invention.

1: Diffuser Plate

10: Plate

101: Motherboard Layer

1011, 1021, 1031: Diffused particles

1012: Microbubbles

102, 103: Surface layer

1032: Microstructure

151: Optical film

152: Brightening Film

153: Polarizing Brightness Enhancement Film

20: Secondary Optical Lens

91:Substrate

911: Top

92: Light-emitting element

93: LCD Display

Claims (9)

A backlight module that can improve brightness includes: A substrate having a top surface; a circuit layout and a reflective layer are disposed on the substrate, the reflective layer being located on the top surface; A plurality of light-emitting diodes (LEDs) are arranged in an array on the top surface of the substrate and electrically coupled to the circuit layout; each LED has an upward-emitting region; the emitting region is defined by a light-emitting axis extending vertically upward from a center point of the emitting region; A plurality of secondary optical lenses, each of which is fixed to the top surface of the substrate at a position corresponding to one of the LED light-emitting elements and covers the light-emitting area of the LED light-emitting element; and A diffuser plate, positioned above the substrate and comprising a plate body, having an upper surface and a lower surface, the lower surface facing the substrate; Each of these secondary optical lenses can diffuse the light emitted from the light-emitting region of the corresponding LED light-emitting element through refraction, reflection, or a combination of both. Each of the secondary optical lenses 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 secondary optical lens 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 before exiting the lens body. The lens body has, from bottom to top, a bottom, a side extension, and a light-emitting portion; the bottom is for fixing to the top surface of the substrate; the side extension extends upward from the bottom by a height not less than the thickness of the LED light-emitting element; the light-emitting portion is located at the top end of the side extension and includes an outer curved surface exposed to the outside and an inner curved surface exposed to the blind hole space; The at least one reflective surface is disposed on one of two of the following: 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, or a reflective surface is adhered to the inner curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface. A light-emitting sheet has an inclined plane with an appropriate angle on the inner curved surface of the light-emitting portion, corresponding to the position of the at least one reflective surface, capable of reflecting 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 inner curved surface of the light-emitting portion, corresponding to the position of the at least one reflective surface, capable of reflecting the light emitted from the light-emitting area of the LED light-emitting element. Wherein, when the at least one reflective surface is disposed on the outer curved surface of the light-emitting portion, all other areas of the outer 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 outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface, and a reflective coating is adhered to the outer curved surface of the light-emitting portion at a position corresponding to the at least one reflective surface. A reflector has an inclined plane with an appropriate angle on the outer curved surface of the light-emitting portion, corresponding to the position of the at least one reflective surface, capable of reflecting 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, corresponding to the position of the at least one reflective surface, capable of reflecting the light emitted from the light-emitting area of the LED light-emitting element. The backlight module for improving brightness as described in claim 1, wherein the board body is a multi-layer structure constructed by co-extrusion, comprising a main board layer, an upper surface layer, and a lower surface layer; the upper surface layer is laminated on the side of the main board layer facing the upper surface, and the lower surface layer is laminated on the side of the main board layer facing the lower surface; and the diffuser further comprises: A plurality of first diffuse particles are added to the motherboard layer; A plurality of second diffuse particles are added to the upper and lower surface layers; Multiple microbubbles are formed in the motherboard layer by a foaming extrusion molding process; and A plurality of microstructures are arranged in an array on at least the lower surface of the plate; The main body layer of the board is made of one of the following materials: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET); the upper and lower surface layers of the board are made of PMMA. The plurality of the first diffusing particles are constituted by adding a first diffusing particle additive to the motherboard layer, the first diffusing particle additive comprising the plurality of the first diffusing particles; the weight percentage of the added first diffusing particle additive in the motherboard layer is a first weight percentage; each of the first diffusing particles has a first material refractive index; and A plurality of the second diffusing particles are formed by adding a second diffusing particle additive to the upper surface layer and the lower surface layer; the second diffusing particle additive comprises a plurality of the second diffusing particles; the weight percentage of the added second diffusing particle additive in the upper surface layer and the lower surface layer is a second weight percentage; each of the second diffusing particles has a second material refractive index; The diffuser plate meets at least one of the following two conditions: Condition 1: The refractive index of the first material of the first diffusing particle is less than the refractive index of the second material of the second diffusing particle; Condition 2: The first weight percentage of the first diffusing particle additive is less than the second weight percentage of the second diffusing particle additive. As described in claim 2, the backlight module with improved brightness includes a plurality of first diffusing particles comprising one of the following: silicone beads, PMMA beads, PS beads, or PMMA-PS copolymer beads; wherein the particle size of the first diffusing 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 diffusing particle additive added to the motherboard layer is between 1 and 4%. As described in claim 3, the backlight module with improved brightness includes a plurality of second diffusing particles comprising one of the following: silicone beads, PMMA beads, PS beads, or PMMA-PS copolymer beads; wherein the particle size of the second diffusing 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 diffusing particle additive added to the upper and lower surfaces is between 5% and 10%; wherein the second weight percentage is greater than the first weight percentage, and the particle size of the second diffusing particles is greater than the particle size of the first diffusing particles. As described in claim 3, the backlight module with improved brightness comprises a plurality of second diffusing particles in the second diffusing particle additive, each comprising one of the following inorganic particles: calcium carbonate, barium sulfate, titanium oxide, talc, mica, or boron nitride; wherein the particle size of the second diffusing 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 diffusing particle additive added to the upper and lower surfaces is between 0.1% and 1.5%. The backlight module for improving brightness as described in claim 5, wherein: A plurality of these microbubbles are generated by adding a foaming agent and a nucleating agent during the foaming extrusion molding process on the motherboard layer; The nucleating agent comprises at least one of the following: calcium carbonate, silicon dioxide, or calcium oxide; the weight percentage of the added nucleating agent is 0.1%-0.5%. The weight reduction rate of the multiple microbubbles on the motherboard layer is between 10% and 20%, and the average size of the multiple microbubbles is between 60 and 800 μm; The formula for calculating the weight loss rate is as follows: Weight loss rate (%) = (W1 - W2) / W2 * 100%; W1 = H * (L1 * L2 * D); in: H is the average thickness (mm) of this motherboard layer; L1 is the length (mm) of this motherboard layer; L2 is the width (mm) of this motherboard layer; D is the specific gravity of the material in the motherboard layer (g/ ^mm³ ); W1 is the theoretical weight (g) of this motherboard layer, which is the weight excluding the multiple microbubbles. W2 is the actual weight (g) of the motherboard layer, which is the actual weight of the motherboard layer containing multiple of the microbubbles, as measured using a scale. As described in claim 1, in the backlight module for improving brightness, the light intensity of the upward-emitting light from the emitting region of the LED light-emitting element, within an angle range of +30° to -30° with respect to the emitting axis, totals between 15% and 25% of the total luminous intensity of the LED light-emitting element; and the light intensity within angle ranges of +60° to +70° and -60° to -70° with respect to the emitting axis, totals between 75% and 85% of the total luminous intensity of the LED light-emitting element. As described in claim 7, the backlight module that can improve brightness, wherein the upper region of the outer curved surface is an upwardly convex outer curved surface, and the region of the outer curved surface closer to the bottom has a fixed curvature in different regions along the vertical direction; wherein the inner curved surface closer to the upper region is a downwardly convex inner curved surface protruding into the blind hole space, and the region of the inner curved surface closer to the bottom has a curvature that increases as it approaches the bottom along the vertical direction. The inner concave surface, through the combination of the outer and inner curved surfaces, allows the lens body to provide a convex lens focusing function in the area directly above the LED light-emitting element, approximately at an angle of ±30 degrees to the light-emitting axis. In other areas, it provides a concave lens light-diffusing function. The reflective surface is located on the inner curved surface adjacent to the convex and concave lenses, used to reflect and diffuse a portion of the light entering the lens body from the convex lens area. The backlight module for improving brightness as described in claim 6, wherein each of the microstructures comprises a plurality of N-sided prisms, where N is a positive integer greater than or equal to three; and the backlight module further comprises: An optical film is directly adhered to the upper surface of the diffuser plate. A brightness enhancement film (BEF) is directly applied to the optical film; and A dual brightness enhancement film (DBEF) is directly applied to the brightness enhancement film. The backlight module can be assembled into a liquid crystal display (LCD), and the LCD is located above the polarizing brightness enhancement film.