Mini-LED backlight module

Abstract

The invention discloses a Mini-LED backlight module. The Mini-LED backlight module comprises a substrate, a Mini-LED light-emitting layer and a double-layer gradient refractive index composite layer, the substrate is composed of a mixing layer, a heat conduction layer and a reflection layer which are arranged in sequence. The Mini-LED light-emitting layer is composed of a plurality of Mini-LED chips which are arranged at intervals and arranged on the substrate in an array mode, and the reflecting layer is provided with light-emitting holes corresponding to the light-emitting faces of the Mini-LED chips one to one. The double-layer gradient refractive index composite layer is composed of an inner layer film and an outer layer film, the inner layer film covers the light-emitting face of the Mini-LED chip, a microstructure is arranged on the face, attached to the Mini-LED chip, of the inner layer film, and the outer layer film covers the light-emitting side of the inner layer film. According to the backlight module, the double-layer gradient refractive index composite layer is adopted to replace a multi-layer membrane in an existing scheme, the overall thickness of the backlight module can be effectively reduced by controlling the refractive indexes and the thicknesses of the inner layer membrane and the outer layer membrane in the double-layer gradient refractive index composite layer, and uniform diffusion and focusing collimation of light can be achieved at the same time; and the requirements of the backlight module on uniformity and high luminous efficiency are met while ultrathin integration is realized.

Description

Technical Field

[0001] This invention relates to the field of LED display equipment technology, and in particular to a Mini-LED backlight module. Background Technology

[0002] Mini-LED backlight technology is widely used in flat panel and automotive display devices due to its advantages such as high contrast, high brightness, and fast response. However, in order to achieve uniform light diffusion and front-side brightness enhancement, the optical system of a Mini-LED backlight module usually requires the stacking of multiple optical films such as diffusion films, brightness enhancement films, and light-diffusing films, and the setting of light mixing distances. This results in a relatively large overall thickness of the Mini-LED backlight module, usually exceeding 1mm, making it difficult to meet the needs of ultra-thin display devices such as high-end TVs and automotive displays. In addition, the interface reflection of the multiple films stacked in the Mini-LED backlight module causes a light efficiency loss of about 15% to 30%, and the precise alignment and cutting requirements of each film in the multiple layers increase the complexity of the manufacturing process and production costs.

[0003] Chinese patent application CN114545683A discloses a backlight module and a Mini-LED display device. The backlight module includes a backplate, multiple arrayed circuit boards, multiple light emitters on each circuit board, a diffuser plate, a first optical film, and a second optical film. The first optical film has a first ink pattern at the position corresponding to the light emitter, and the second optical film has a second ink pattern at the position corresponding to the light emitter. The projections of the first and second ink patterns corresponding to each light emitter overlap in a reference plane, with the overlapping area opposite to the corresponding light emitter. The reference plane is parallel to the first and / or second optical film layers. This invention reduces the thickness of the diffuser plate by setting two sets of optical films and an oil film layer on the films, thereby reducing the overall thickness of the backlight module. However, this solution still requires a diffuser plate and does not directly change the traditional structure of the backlight module, thus failing to solve the problem of light efficiency loss. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a Mini-LED backlight module that can improve light efficiency while reducing the overall thickness of the backlight module.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a Mini-LED backlight module, comprising a substrate, a Mini-LED light-emitting layer, and a double-layer gradient refractive index composite layer; the substrate is composed of a mixing layer, a thermally conductive layer, and a reflective layer arranged sequentially; the Mini-LED light-emitting layer is composed of multiple Mini-LED chips arranged at intervals and in an array on the substrate, and the reflective layer is provided with light-emitting holes corresponding one-to-one with the light-emitting surfaces of the Mini-LED chips; the double-layer gradient refractive index composite layer is composed of an inner film and an outer film, the inner film covers the light-emitting surface of the Mini-LED chip, the side of the inner film that is in contact with the Mini-LED chip is provided with a microstructure, and the outer film covers the light-emitting side of the inner film.

[0006] As an improvement to the above scheme: the hybrid layer is a hybrid layer of BT resin and glass cloth; the thermally conductive layer is a copper foil thermally conductive layer or a graphene thermally conductive layer, and the thickness of the thermally conductive layer is 10-20 μm.

[0007] As an improvement to the above scheme: the reflective layer is a silver foil reflective layer or an aluminum film reflective layer; the thickness of the reflective layer is 5-10 μm, and the reflectivity of the reflective layer is ≥95%; the diameter of the light-emitting hole of the reflective layer is larger than the diameter of the light-emitting surface of the Mini-LED chip.

[0008] As an improvement to the above scheme: the size of the Mini-LED chip in the Mini-LED light-emitting layer is 75 to 300 μm, the spacing between adjacent Mini-LED chips is 100 to 500 μm, and the half-maximum divergence angle of the Mini-LED chip is ±60°.

[0009] As an improvement to the above scheme: the inner and outer layers of the double-layer gradient refractive index composite layer are bonded together by optical adhesive; the refractive index of the optical adhesive is 1.50 to 1.55, the thickness of the optical adhesive is 1 to 3 μm, and the transmittance of the optical adhesive is ≥98%.

[0010] As an improvement to the above scheme: the refractive index of the inner layer film decreases parabolically along the direction of light propagation, and the refractive index of the inner layer film is 1.50 to 1.75; the refractive index of the outer layer film decreases parabolically along the direction of light propagation, and the refractive index of the outer layer film is 1.40 to 1.55.

[0011] As an improvement to the above scheme: the microstructure set on the inner film is a micro-pit array structure, and the micro-pits correspond one-to-one with the light emission center of the Mini-LED chip; the diameter of the micro-pits is 5 to 10 μm, the depth of the micro-pits is 2 to 5 μm, and the spacing between adjacent micro-pits is 10 to 15 μm.

[0012] As an improvement to the above scheme: the material of the inner layer film is a polycarbonate-based material doped with nano-scattering particles, the nano-scattering particles are silicon dioxide or titanium, the particle size of the nano-scattering particles is 50-200nm, and the doping amount is 1-3wt%; the material of the outer layer film is a chalcogenide glass-based material or an epoxy resin-based material.

[0013] As an improvement to the above scheme: an anti-reflective coating is provided on the contact surface between the inner layer film and the outer layer film, the refractive index of the anti-reflective coating is 1.20 to 1.30, and the thickness of the anti-reflective coating is 50 to 100 nm.

[0014] As an improvement to the above scheme, it also includes a quantum dot film disposed on the light-emitting side of the outer film, the thickness of which is 10-20 μm; the quantum dot film is bonded to the outer film.

[0015] The beneficial effects of this invention are as follows: This invention replaces the multilayer film in the existing solution with a double-layer gradient refractive index composite layer in the Mini-LED backlight module. The double-layer gradient refractive index composite layer can achieve good control of light through the continuously changing refractive index inside the gradient refractive index material. Thus, by controlling the refractive index and thickness of the inner and outer layers of the double-layer gradient refractive index composite layer, the overall thickness of the backlight module can be effectively reduced. Furthermore, since the double-layer gradient refractive index composite layer uses both inner and outer layers, it can simultaneously achieve uniform diffusion and focusing collimation of light, thus meeting the requirements of uniformity and high luminous efficiency of the backlight module while achieving ultra-thin integration. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the first embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the second embodiment of the present invention; Figure 3 This is a schematic diagram showing the gradient change of the refractive index of the inner and outer layers of the film in the direction of light propagation with thickness, according to the first embodiment of the present invention. Figure 4 This is a schematic diagram showing the gradient change of the refractive index of the inner and outer layers of the film in the direction of light propagation with thickness, according to a second embodiment of the present invention. Figure 5 The results are simulation results of the uniformity test in the first embodiment of the present invention; Figure 6 The results are simulation results of the uniformity test in the second embodiment of the present invention.

[0017] The following are labeled in the diagram: 100-substrate, 110-hybrid layer, 120-thermal conductive layer, 130-reflective layer, 200-Mini-LED light-emitting layer, 300-double-layer gradient refractive index composite layer, 310-inner layer film, 311-microstructure, 320-outer layer film, 321-anti-reflective coating, 400-quantum dot film. Detailed Implementation

[0018] To facilitate understanding of the present invention, the invention will be further described below with reference to the accompanying drawings.

[0019] In the description of this invention, it should be noted that the terms "front", "rear", "left", "right", "up", "down", "inner", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] like Figure 1 and Figure 2 As shown, the Mini-LED backlight module disclosed in this invention consists of a substrate 100, a Mini-LED light-emitting layer 200, and a double-layer gradient refractive index composite layer 300.

[0021] like Figure 1 and Figure 2 As shown, the substrate 100 in this invention is composed of a hybrid layer 110, a thermally conductive layer 120, and a reflective layer 130 arranged sequentially. The hybrid layer 110 is a hybrid layer of BT resin and glass cloth, the thermally conductive layer 120 is a copper foil thermally conductive layer or a graphene thermally conductive layer, the thickness of the thermally conductive layer 120 is 10-20 μm, the thickness of the reflective layer 130 is 5-10 μm, and the reflectivity of the reflective layer 130 is ≥95%.

[0022] like Figure 1 and Figure 2 As shown, the Mini-LED light-emitting layer 200 in this invention is composed of a plurality of Mini-LED chips arranged in an array on the substrate 100 at intervals. The Mini-LED chips in the Mini-LED light-emitting layer 200 have a size of 75 to 300 μm, a spacing of 100 to 500 μm between adjacent Mini-LED chips, and a half-maximum divergence angle of ±60°. The reflective layer 130 is provided with light-emitting holes that correspond one-to-one with the light-emitting surfaces of the Mini-LED chips. The diameter of the light-emitting holes in the reflective layer 130 is larger than the diameter of the light-emitting surfaces of the Mini-LED chips.

[0023] like Figure 1 and Figure 2As shown, the double-layer gradient refractive index composite layer 300 of this invention, also known as a double-layer GRIN composite film, consists of an inner layer film 310 and an outer layer film 320. The inner layer film 310 covers the light-emitting surface of the Mini-LED chip, and a microstructure 311 is provided on the side of the inner layer film 310 that is in contact with the Mini-LED chip. The outer layer film 320 covers the light-emitting side of the inner layer film 310. The inner layer film 310 and the outer layer film 320 constituting the double-layer gradient refractive index composite layer 300 are bonded together by optical adhesive; the refractive index of the optical adhesive is 1.50 to 1.55, the thickness of the optical adhesive is 1 to 3 μm, and the transmittance of the optical adhesive is ≥98%. Figure 3 and Figure 4 As shown, the refractive index of the inner layer film 310 decreases parabolically along the direction of light propagation, and the refractive index of the inner layer film 310 is 1.50–1.75; the refractive index of the outer layer film 320 decreases parabolically along the direction of light propagation, and the refractive index of the outer layer film 320 is 1.40–1.55. The material of the inner layer film 310 is a polycarbonate-based material doped with nano-scattering particles, the nano-scattering particles being silicon dioxide or titanium, the particle size of the nano-scattering particles being 50–200 nm, and the doping amount being 1–3 wt%; the material of the outer layer film 320 is a chalcogenide glass-based material or an epoxy resin-based material.

[0024] Furthermore, such as Figure 1 and Figure 2 As shown, the microstructure 311 set on the inner layer film 310 of the present invention is a micro-pit array structure, and the micro-pits correspond one-to-one with the light emission center of the Mini-LED chip; the diameter of the micro-pit is 5 to 10 μm, the depth of the micro-pit is 2 to 5 μm, and the spacing between adjacent micro-pits is 10 to 15 μm.

[0025] Furthermore, such as Figure 1 and Figure 2 As shown, the present invention provides an anti-reflective coating 321 on both the contact surfaces of the inner layer film 310 and the outer layer film 320. The refractive index of the anti-reflective coating 321 is 1.20–1.30, and the thickness of the anti-reflective coating 321 is 50–100 nm. Figure 2 As shown, the present invention may further provide a quantum dot film 400 on the light-emitting side of the outer film 320, the thickness of the quantum dot film 400 being 10-20 μm; the quantum dot film 400 is bonded to the outer film 320.

[0026] Example 1 like Figure 1As shown, in the first embodiment of the present invention, the substrate 100 of the Mini-LED backlight module includes a 50μm thick hybrid layer 110 made of a mixture of BT resin and glass cloth. A 10μm thick copper foil thermally conductive layer 120 is covered on the hybrid layer 110, and the thermal conductivity of the thermally conductive layer is ≥400W / (m·K). The reflective layer 130 is made of silver foil, has a thickness of 8μm, a reflectivity of 98%, and a light-emitting aperture with a diameter of 160μm. The Mini-LED light-emitting chip in the Mini-LED light-emitting layer 200 has a size of 150μm × 150μm, a spacing of 300μm between adjacent Mini-LED light-emitting chips, a half-maximum divergence angle of ±60°, and a peak emission wavelength of 450nm. The bilayer gradient refractive index composite layer 300 consists of an inner layer film 310 and an outer layer film 320 located near the light-emitting surface of the Mini-LED chip. The inner layer film 310 has a thickness of 30 μm and is made of a polycarbonate-based material doped with 2 wt% silica nanoparticles with a particle size of 100 nm. Figure 3 As shown, the refractive index of the inner layer film 310 decreases parabolically from 1.65 to 1.50 along the thickness direction; the incident light side of the inner layer film 310 has a microstructure 311 with an array of micro-pits, the diameter of which is 8 μm, the depth of which is 3 μm, and the spacing between adjacent micro-pits is 12 μm. The outer layer film 320 has a thickness of 30 μm and is made of a chalcogenide glass-based material, such as... Figure 3 As shown, the refractive index of the outer layer 320 decreases linearly from 1.50 to 1.35 along the thickness direction. An anti-reflective coating 321 with a thickness of 80 nm is provided on the outer side of the outer layer 320. The anti-reflective coating 321 has a refractive index of 1.25 and a light transmittance of 99%. The inner layer 310 is bonded to the outer layer 320 with an optical adhesive with a thickness of 1.5 μm. The optical adhesive has a refractive index of 1.50 and a light transmittance of 99%.

[0027] In this embodiment 1, the overall thickness of the Mini-LED backlight module is 94μm. Figure 5 As shown in the simulation, the light extraction efficiency of the Mini-LED backlight module in this embodiment 1 is 88%, the brightness uniformity is 96%, the brightness of the front center is 55% higher than that of the traditional module, and the light emission half-intensity angle is ±20°. The brightness and uniformity are significantly better than those of the traditional module.

[0028] Example 2 like Figure 2As shown, in the second embodiment of the present invention, the substrate 100 of the Mini-LED backlight module includes a 40μm thick hybrid layer 110 made of a mixture of BT resin and glass cloth. A 15μm thick copper foil thermally conductive layer 120 is covered on the hybrid layer 110, with a thermal conductivity ≥300W / (m·K). The reflective layer 130 is made of aluminum film material, with a thickness of 6μm and a reflectivity of 95%. The diameter of the light-emitting aperture on the reflective layer 130 is 210μm. The Mini-LED light-emitting chip in the Mini-LED light-emitting layer 200 has a size of 200μm × 200μm, a spacing of 400μm between adjacent Mini-LED light-emitting chips, a half-maximum divergence angle of ±60°, and a peak emission wavelength of 450nm. The bilayer gradient refractive index composite layer 300 consists of an inner layer film 310 and an outer layer film 320 located near the light-emitting surface of the Mini-LED chip. The inner layer film 310 has a thickness of 35 μm and is made of a polycarbonate-based material doped with 3 wt% silica nanoparticles with a particle size of 150 nm. Figure 4 As shown, the refractive index of the inner layer film 310 decreases parabolically from 1.70 to 1.55 along the thickness direction; the incident light side of the inner layer film 310 has a microstructure 311 with an array of micro-pits, the diameter of the micro-pits being 10 μm, the depth of the micro-pits being 4 μm, and the spacing between adjacent micro-pits being 15 μm. The outer layer film 320 has a thickness of 30 μm, and the material of the outer layer film 320 is a chalcogenide glass-based material, such as... Figure 4 As shown, the refractive index of the outer layer film 320 decreases linearly from 1.55 to 1.45 along the thickness direction. An anti-reflective coating 321 with a thickness of 100 nm is provided on the outer side of the outer layer film 320. The anti-reflective coating 321 has a refractive index of 1.28 and a light transmittance of 99%. The inner layer film 310 and the outer layer film 320 are bonded together with an optical adhesive with a thickness of 2 μm. The optical adhesive has a refractive index of 1.55 and a light transmittance of 99%. A quantum dot film 400 is bonded to the light-emitting side of the outer layer film 320. The quantum dot film 400 is a 15 μm thick CdSe / ZnS quantum dot-doped silicone color conversion film.

[0029] In this embodiment 1, the overall thickness of the Mini-LED backlight module is 94μm, such as Figure 6 As shown in the simulation, the light extraction efficiency of the Mini-LED backlight module in this embodiment 1 is 86%, the brightness uniformity is 93%, the brightness of the front center is 52% higher than that of the traditional module, the light emission half-intensity angle is ±25°, and the brightness and uniformity are significantly better than those of the traditional module. At the same time, it can also achieve full-color display.

Claims

1. A Mini-LED backlight module, characterized in that: The system includes a substrate (100), a Mini-LED light-emitting layer (200), and a double-layer gradient refractive index composite layer (300). The substrate (100) is composed of a mixing layer (110), a thermally conductive layer (120), and a reflective layer (130) arranged sequentially. The Mini-LED light-emitting layer (200) is composed of multiple Mini-LED chips arranged at intervals and in an array on the substrate (100). The reflective layer (130) is provided with light-emitting holes that correspond one-to-one with the light-emitting surfaces of the Mini-LED chips. The double-layer gradient refractive index composite layer (300) is composed of an inner film (310) and an outer film (320). The inner film (310) covers the light-emitting surface of the Mini-LED chip. The side of the inner film (310) that is in contact with the Mini-LED chip is provided with a microstructure (311). The outer film (320) covers the light-emitting side of the inner film (310).

2. The Mini-LED backlight module as described in claim 1, characterized in that: The hybrid layer (110) is a hybrid layer of BT resin and glass cloth; the thermally conductive layer (120) is a copper foil thermally conductive layer or a graphene thermally conductive layer, and the thickness of the thermally conductive layer (120) is 10-20 μm.

3. The Mini-LED backlight module as described in claim 1, characterized in that: The reflective layer (130) is a silver foil reflective layer or an aluminum film reflective layer; the thickness of the reflective layer (130) is 5-10 μm, and the reflectivity of the reflective layer (130) is ≥95%; the diameter of the light-emitting hole of the reflective layer (130) is larger than the diameter of the light-emitting surface of the Mini-LED chip.

4. The Mini-LED backlight module as described in claim 1, characterized in that: The Mini-LED chip in the Mini-LED light-emitting layer (200) has a size of 75 to 300 μm, a spacing of 100 to 500 μm between adjacent Mini-LED chips, and a half-maximum divergence angle of ±60°.

5. The Mini-LED backlight module as described in claim 1, characterized in that: The inner layer film (310) and the outer layer film (320) that make up the double-layer gradient refractive index composite layer (300) are bonded together by optical adhesive; the refractive index of the optical adhesive is 1.50 to 1.55, the thickness of the optical adhesive is 1 to 3 μm, and the transmittance of the optical adhesive is ≥98%.

6. The Mini-LED backlight module as described in claim 5, characterized in that: The refractive index of the inner film (310) decreases parabolically along the direction of light propagation, and the refractive index of the inner film (310) is 1.50 to 1.75; the refractive index of the outer film (320) decreases parabolically along the direction of light propagation, and the refractive index of the outer film (320) is 1.40 to 1.

55.

7. The Mini-LED backlight module as described in claim 5, characterized in that: The microstructure (311) set on the inner layer film (310) is a micro-pit array structure, and the micro-pits correspond one-to-one with the light-emitting center of the Mini-LED chip; the diameter of the micro-pit is 5 to 10 μm, the depth of the micro-pit is 2 to 5 μm, and the spacing between adjacent micro-pits is 10 to 15 μm.

8. The Mini-LED backlight module as described in claim 5, characterized in that: The inner layer film (310) is made of polycarbonate-based material doped with nano-scattering particles. The nano-scattering particles are silicon dioxide or titanium, with a particle size of 50-200 nm and a doping amount of 1-3 wt%. The outer layer film (320) is made of chalcogenide glass-based material or epoxy resin-based material.

9. The Mini-LED backlight module as described in claim 5, characterized in that: An anti-reflective coating (321) is provided on the contact surface between the inner layer film (310) and the outer layer film (320). The refractive index of the anti-reflective coating (321) is 1.20 to 1.30, and the thickness of the anti-reflective coating (321) is 50 to 100 nm.

10. The Mini-LED backlight module as described in claim 1, characterized in that: It also includes a quantum dot film (400) disposed on the light-emitting side of the outer film (320), the thickness of the quantum dot film (400) being 10-20 μm; the quantum dot film (400) is bonded to the outer film (320).

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