WO2021047412A1

WO2021047412A1 - Led screen

Info

Publication number: WO2021047412A1
Application number: PCT/CN2020/112640
Authority: WO
Inventors: 胡飞; 李士杰; 唐晓峰; 李屹
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2019-09-12
Filing date: 2020-08-31
Publication date: 2021-03-18
Also published as: CN211349975U

Abstract

An LED screen (100), comprising a PCB board (1), an LED light source (2), a diffusion layer (3), and a light homogenizing device (4). The LED light source (2) is provided on the PCB board (1) and comprises a plurality of LED units (21) evenly distributed on the PCB board (1) in an array mode, one LED unit (21) forms a pixel unit, and the LED unit (21) comprises an LED chip capable of emitting at least red light, green light, and blue light; the light homogenizing device (4) comprises a plurality of light guide rods (41) corresponding to the LED units (21), the light guide rods (41) are provided on light emitting paths of the LED units (21), and the areas of the light incident surfaces, right opposite to the LED units (21), of the light guide rods (41) are smaller than the areas of the light emitting surfaces, abutting against the diffusion layer (3), of the light guide rods (41); and the diffusion layer (3) is provided on a light emitting surface of the light homogenizing device (4). The LED screen (100) can effectively implement full mixing and homogenization of primary color light, and further improves the pixel filling rate of the LED screen (100).

Description

An LED screen

【Technical Field】

The utility model relates to the technical field of LED screens, in particular to an LED screen.

【Background technique】

The LED unit has the characteristics of high luminous brightness. The large screen composed of its dot matrix can display very high brightness (for example, higher than 500Nit). At the same time, because the LED unit can be individually controlled to turn on and off, the screen can span a large range from low to high. In the brightness range, it is easier to achieve HDR (High Dynamic Range) display effects. The light-emitting spectrum of the LED chip is relatively narrow, and the combination of red, green and blue colors cover a large color range, which can easily meet the DCI color gamut standard and challenge the REC2020 color gamut standard. In addition to the advantages of brightness and color gamut, the LED display has high display uniformity, which is very suitable for making large screens (above 50 square meters). Due to these advantages of LED light source display, coupled with the continuous reduction of the cost of related components and the continuous maturity of technology, LED large-screen displays have gradually entered the field of high-quality video projection. As the technology continues to mature, the application scenarios will continue to expand.

In related technologies, LED large screens still have some problems: the light on each pixel of the display is completely concentrated on the LED unit in the center of the pixel, which makes the brightness filling rate of the pixel very low, resulting in a bad viewing effect with obvious graininess during viewing. . At the same time, the local concentration of light energy is not conducive to the health of the retina. In order to solve the problem of viewing graininess, small-pitch LED displays came into being. This solution reduces the distance between LED units to a level that is imperceptible to the naked eye. Although it solves the problem of LED display fill rate, it greatly increases product costs.

[Utility model content]

The purpose of the present utility model is to provide an LED screen, which can solve the technical problem of the low brightness filling rate of the pixels in the LED large screen in the related art, which causes the poor viewing effect with obvious graininess during viewing.

In order to achieve the above purpose, the technical solution of the present invention is as follows:

An LED screen, which is characterized by comprising a PCB board, an LED light source, a diffusion layer, and a homogenizing device. The LED light source is arranged on the PCB board and includes a plurality of LED units uniformly arrayed on the PCB board , The LED unit constitutes a pixel unit, and the LED unit includes an LED chip capable of emitting at least red, green, and blue light;

The light homogenization device includes a plurality of light guide rods corresponding to the LED unit, the light guide rods are arranged on the light exit path of the LED unit, and the light guide rods are directly opposite to the LED unit. The area of the light surface is smaller than the area of the light exit surface of the light guide rod abutting the diffusion layer;

The diffusion layer is arranged on the light emitting surface of the light homogenizing device.

In one embodiment, the light guide rod includes a connecting part contacting the diffusion layer and a main body part extending from the connecting part and contacting the LED unit, and the cross-sectional area of the main body part is from The connecting portion gradually decreases toward the LED unit.

In one embodiment, the thickness of the connecting portion is 0.2mm-1.5mm, and the thickness of the main body portion is 3mm-8mm.

In one embodiment, the light-incident surface area of the light guide rod is larger than the light-emitting surface area of the LED light source.

In one embodiment, the distance between the light incident surface of the light guide rod and the LED light source is 0-1 mm.

In one embodiment, the diffusion layer is volume diffusion or surface diffusion, and the thickness of the diffusion layer is 0.05-0.3 mm.

In one embodiment, it is characterized in that it further includes a light-shielding frame arranged between the light source and the light homogenizing device, and the light-shielding frame includes an array of hollow areas composed of two or more grids.

In one embodiment, the distance between adjacent hollow areas is the same as the distance between the LED light sources, and the hollow area of the shading frame corresponds to the LED light source, and the hollow area accommodates the LED light source.

In one embodiment, the hollow area includes four sidewalls perpendicular or approximately perpendicular to the PCB board, and the four sidewalls are provided with a reflective layer or an absorbing layer.

In one embodiment, the light guide rod and the LED unit are bonded and fixed by an adhesive.

Compared with the related art, the present invention provides an LED screen. The LED screen includes an LED unit for emitting primary color light and a light homogenizing device arranged on the light emitting path of the LED unit. The light homogenizing device includes a plurality of The light guide rod corresponding to the LED unit one-to-one, most of the primary color light entering the light guide rod is totally reflected by the side wall of the light guide rod to achieve full mixing and homogenization of the primary color light, and further improve the pixel filling rate of the LED screen ; In addition, by setting a diffusion layer on the light-emitting surface of the homogenizing device, the viewing angle of the LED screen can be further improved.

【Explanation of the drawings】

In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings needed in the description of the embodiments. Obviously, the drawings in the following description are only some implementations of the present utility model. For example, for those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings, among which:

Figure 1 is a schematic diagram of the structure of the first embodiment of the LED screen of the present invention;

Fig. 2 is a schematic diagram of the structure of the light guide rod in Fig. 1;

Figure 3 is a schematic diagram of the homogenization device absorbing ambient light;

4 is a schematic diagram of the structure of the second embodiment of the LED screen of the present invention;

Figure 5 is a diagram of the illuminance distribution within a single pixel;

6A is a first schematic diagram of superposition of illuminances of adjacent pixel diffusion layers;

FIG. 6B is a second schematic diagram of superimposing the illuminance of adjacent pixel diffusion layers;

7 is a schematic diagram of the installation structure of the light homogenizing device, the adhesive, and the LED unit in the third embodiment of the LED screen of the present invention.

【detailed description】

The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, not all of them. Examples. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present utility model.

Example one

Referring to Figure 1, the present invention provides an LED screen 100. The LED screen 1 includes a PCB board 1, an LED light source 2, a diffusion layer 3, and a light homogenizing device 4. The LED light source 2 is disposed on the PCB board 1. And includes a plurality of LED units 21 uniformly arrayed on the PCB board 1, each of the LED units 21 constitutes a pixel unit and includes red, green and blue light-emitting chips, it is understandable that the LED unit 21 It may also include 4 light-emitting chips of red, green, blue and yellow. The light homogenization device 4 includes a plurality of light guide rods 41 corresponding to the LED units 21 one-to-one. The light guide rods 41 are arranged on the light emitting path of the LED unit 21, and the light output of the light homogenization device 4 The diffusion layer 3 is installed on the surface.

The specific solution of the light guide rod is described below. The light guide rod 41 includes a connecting portion 411 contacting the diffusion layer 3 and a body extending from the connecting portion 411 and contacting the LED unit 21 The function of the connecting portion 411 is to connect the light guide rod array, and at the same time to provide mechanical strength during injection molding. The main body 412 has a cross-sectional area from the connecting portion 411 toward the LED unit 21. Decrease the setting gradually. The distance between the light-incident surface of the light guide rod 41 and the light-emitting surface of the LED unit 21 is 0-1mm. Specifically, the thickness h2 of the connecting portion 411 is 0.2mm-1.5mm. The thickness h ₃ is 3mm-8mm, and the shape and size of the light incident surface of the light guide rod is specifically set by the arrangement of the LED units 21, which can be rectangular, square, circular, or other polygons, etc., in the present invention In a specific embodiment, the light incident surface of the light guide rod is square, and the side length d is 1 mm to 3 mm.

Since the light exit surface area of the light guide rod is larger than the light entrance surface area of the light guide rod, according to the conservation of optical expansion, the divergence angle of the light emitted from the light exit surface of the light guide rod is smaller than that of the light entrance surface of the light guide rod. The divergence angle of the light. The area of the light entrance surface of the light guide rod is larger than that of the light exit surface of the light emitting chip, so that the light emitted by the light emitting chip is coupled into the light guide rod with a higher light efficiency, so that the light emitted from the light exit surface of the light guide rod is The divergence angle is smaller than the divergence angle of the light emitted from the light-emitting surface of the light-emitting chip.

Specifically, after the LED light enters the light incident surface of the light guide rod 41, the light with a smaller direction angle (such as light 1) directly reaches the light exit surface, and the light with a larger direction angle (such as light 2) ) The light guide rod 41 is used as an optical waveguide device to reach the light exit surface after being reflected by the side wall or total reflection, so as to achieve the purpose of uniform light and improve the uniformity of the illuminance at the light exit position. Therefore, the LED screen using the light guide rod reduces the divergence angle of the emitted light to a certain extent and further reduces the light crosstalk between different pixels, but at the same time it brings about the problem of smaller viewing angle.

Further, in order to improve the uniform light effect of the light guide rod, scattering particles can also be added to the light guide rod; in other embodiments, in order to make the LED unit have a narrower wavelength range, light absorbing particles can be added to the light guide rod, Light-absorbing particles will absorb light of certain wavelengths but not other wavelengths. The choice of absorbing particles is related to the wavelength of the absorbed light, which can be calculated from Beer Lambert's law. In this embodiment, the light-absorbing particles are preferably at least one of colored glass particles and metal nanoparticles.

As shown in FIG. 2, the present application further solves the problem of a small viewing angle of the emitted light by arranging a diffusion layer 3 on the light-emitting surface of the homogenization device. The diffusion layer 3 is made of a light-transmitting diffusion material, and a bulk diffusion Or surface diffusion structure. Preferably, the thickness h1 of the diffusion layer 3 is 0.05mm-0.3mm, the light transmittance is greater than 90%, and the diffusion angle of the diffusion layer 3 is greater than 70°, so that the uniformity of the emitted light is relatively high. On a good basis, further increase the divergence angle of the emitted light, thereby increasing the viewing angle of the LED screen.

Of course, in order to further improve the uniformity of illuminance in the pixels of the diffusion layer 3, in the specific embodiment of the present invention, the diffusion layer 3 is correspondingly disposed on the light-emitting surface of the light homogenization device 4, and the homogenization device 4 The light device 4 includes the light guide rod 41 corresponding to the LED unit 21. In a preferred embodiment of the present invention, the light guide rod 41 is a tapered light guide rod. It should be further explained that the area of the light incident surface of the light guide rod 41 directly opposite to the LED unit 21 is smaller than the area of the light exit surface abutting the diffusion layer 3, and the light guide rod 41 is made of transparent solid Made of materials.

Referring again to FIG. 3, the light homogenization device 4 composed of the light guide rod 41 can not only improve the uniformity of the illuminance of the light exiting surface, but also fully absorb the ambient light, so that once the ambient light enters the guide It is difficult for the light rod 41 to reflect out, so as to improve the contrast of the screen. The ambient light irradiates the diffusion layer 3, and the diffused light has different exit directions. The light A is refracted on the side wall of the light guide rod 41 and is absorbed by the black PCB board 1; the light B is totally reflected on the side wall of the light guide rod 41, and then exits from the light entrance port. A part of the light is absorbed by the PCB board 1, and the other part The light is reflected and attenuated inside the LED unit 21 and enters the light guide rod 31 again, but the reflection area of the LED unit 21 is much smaller than the pixel area, so this part of the light is very small; the light C is refracted on the side wall of the light guide rod 41 and reaches the adjacent guide rod. The side wall of the light rod 41 refracts again, and is finally absorbed by the PCB board 1.

Example two

4, in the second embodiment, an LED screen 100 is provided, which is different from the LED screen 100 in the first embodiment in that it further includes a light-shielding frame 5, and the light homogenizing device 4 is different from the LED screen 100 in the first embodiment. The LED light source 2 is installed and fixed by the light shielding frame 5. The light-shielding frame 5 is fixed on the PCB board 1 through positioning posts, inverted buckles and other structures. The light-shielding frame 5 includes a hollow area distributed in an array composed of a plurality of grids, wherein the center distance of the hollow area and the LED unit The 21 pitch is the same as 5mm. In the second embodiment, the light-shielding frame 5 is made of black PET, PC, PMMA, TPU, ABS and other materials through an injection molding process, and has a thickness of 2 mm and a side length of the hollow area of 2.8 mm. The light guide rod of the light homogenization device 4 is inserted into the hollow area of the light shielding frame 5 to achieve fixed assembly. The black shading frame 5 further improves the environmental resistance of the LED screen.

Further, the light-shielding frame 5 is arranged between the LED light source 2 and the diffusion film 300, and the light-shielding frame 5 includes a hollow area distributed in an array composed of a plurality of grids. The distance between adjacent hollow areas is consistent with the distance between the LED light source 2 and has a one-to-one correspondence with the LED light source 2. The shading frame has a uniform spacing and a certain thickness of side walls. Each LED light source is placed directly under the hollow area of the shading frame 5, and it is okay to be aligned with each other or slightly off-center, as long as the hollow area is projected on the substrate 10. Just surround the corresponding LED light source. Each hollow area of the light-shielding frame includes four sidewalls perpendicular to the PCB board. The four sidewalls can be either an absorbing layer or a reflective layer. In short, none of the four sidewalls can transmit light. This arrangement utilizes highly reflective sidewalls to homogenize the LEDs, so that the brightness of each pixel can be evenly distributed, and at the same time, the light crosstalk between the pixels is avoided. The light guide rod of the light homogenization device is arranged in the hollow area of the light shielding frame, so the light shielding frame can not only improve the contrast of the LED screen, but also can realize the rapid positioning and installation of the light guide rod, and further improve the assembly efficiency.

As shown in FIG. 2 again, it should be further explained that in the second embodiment, the diffusion layer 3 is bulk diffusion, the thickness h1 is 0.2mm, the diffusion angle is 80° Gaussian, and carbon black is preferably added to the bulk diffusion layer. The light-absorbing particles make the light transmittance of the diffusion layer 3 70% and improve the anti-ambient light contrast of the LED screen 100. The thickness h2 of the connecting layer 411 is 1 mm, and the thickness h ₃ of the light guide rod 41 is 6 mm. The distance h4 between the light incident surface of the LED unit 21 and the light guide rod 41 is 0.1 mm, and the side length d of the light incident surface is 2 mm. The light guide rod 41 and the diffusion layer 3 are made of colorless and transparent materials, such as PET, PC, PMMA, TPU, ABS, etc., and some diffusion particles can be added to the material of the light guide rod 41 to obtain the body Diffusion effect.

The LED unit 21 is a 1mm*1mm LED chip, including red, green, and blue LED chips. The LED unit 21 as a pixel unit corresponds to the light guide rod 41 one-to-one, and the center distance is 5mm.

Next, we will perform simulation analysis on the illuminance and uniformity of the second embodiment. Through simulation calculation, we can get the illuminance distribution diagram within a single pixel as shown in Figure 5. It can be seen that the LED screen in the second embodiment is very good. The illuminance filling rate and uniformity of the illuminance in the pixel are improved. Within the pixel area of 5mm*5mm, the illuminance attenuation in the center 4mm*4mm area is very small, even in the edge area, that is, the illuminance only drops at the position ±2.5mm from the pixel center half. The calculation result shows that the LED screen 100 provided in the second embodiment can effectively improve the pixel filling rate and the illumination uniformity of the LED display screen.

Further analysis, because the illuminance between adjacent pixels of the LED screen has overlapping parts, as shown in Figure 6A, the overlapping parts are added to obtain the adjacent pixel illuminance distribution curve shown in Figure 6B, and the uniformity of the illuminance of the overlapping part of the pixel can be seen It is further improved to reduce the edge blackening of each pixel when viewing the LED screen.

Example three

As shown in FIG. 7, in the third embodiment, the present invention provides an LED screen 100, which is different from the LED screen 100 in the second embodiment in that there is no shading frame, and the light guide rod 41 It is bonded and fixed to the LED unit 21 with an adhesive 6. By adding the adhesive 6, while bonding the light guide rod 41 and the LED unit 21, compared with the air gap, the difference in refractive index between the adhesive and the light guide rod is smaller, and the matching is Even better, the light emitted from the LED unit enters the light guide rod. Due to the matching of the refractive index, the Fresnel loss is reduced, and the light coupling efficiency of the LED unit can be greatly improved.

It can be understood that the adhesive 6 is a diffuse reflective adhesive material _{containing scattering particles such as TiO 2} and/or Al ₂ O _3. In other embodiments, the adhesive 6 can also be a transparent adhesive material.

The light emitted from the LED light source is scattered by the scattering particles in the adhesive to achieve preliminary homogenization; the preliminary homogenized light enters the light guide rod from the light incident surface of the light guide rod, and part of the light is emitted to the side of the light guide rod Because the roughness of the side wall 133 is small and the refractive index of the light guide rod is high, the light will be totally internally reflected on the side wall to achieve the mixing and homogenization of the three primary colors of red, green and blue. Light emerges from the light-emitting surface of the light guide rod

Compared with related technologies, the LED screen provided by the present invention has the following advantages: combining a homogenizing device in front of the LED light source can effectively improve the pixel illumination filling rate and uniformity of the light-emitting surface, thereby enhancing the pixel brightness of the LED screen Fill rate and uniformity.

Although the embodiments of the present utility model have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present utility model. For those familiar with the field, Additional modifications are easily implemented, so without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

An LED screen, which is characterized by comprising a PCB board, an LED light source, a diffusion layer, and a homogenizing device. The LED light source is arranged on the PCB board and includes a plurality of LED units uniformly arrayed on the PCB board , The LED unit constitutes a pixel unit, and the LED unit includes an LED chip capable of emitting at least red, green, and blue light;

The light homogenization device includes a plurality of light guide rods corresponding to the LED unit, the light guide rods are arranged on the light exit path of the LED unit, and the light guide rods are directly opposite to the LED unit. The area of the light surface is smaller than the area of the light exit surface of the light guide rod abutting the diffusion layer;

The diffusion layer is arranged on the light emitting surface of the light homogenizing device.
The LED screen according to claim 1, wherein the light guide rod includes a connecting portion contacting the diffusion layer and a main body portion extending from the connecting portion and contacting the LED unit, so The cross-sectional area of the main body portion gradually decreases from the connecting portion toward the LED unit.
The LED screen according to claim 2, wherein the thickness of the connecting portion is 0.2mm-1.5mm, and the thickness of the main body portion is 3mm-8mm.
The LED screen of claim 1, wherein the light-incident surface area of the light guide rod is larger than the light-emitting surface area of the LED light source.
The LED screen according to claim 1, wherein the distance between the light incident surface of the light guide rod and the LED light source is 0-1 mm.
The LED screen of claim 1, wherein the diffusion layer is volume diffusion or surface diffusion, and the thickness of the diffusion layer is 0.05-0.3 mm.
The LED screen according to claim 1, further comprising a light shielding frame arranged between the light source and the light homogenizing device, the light shielding frame comprising an array distribution composed of two or more grids Hollow area.
The LED screen according to claim 7, wherein the distance between adjacent hollow areas is the same as the distance between the LED light sources, and the hollow area of the shading frame corresponds to the LED light source, and the hollow area The LED light source is accommodated.
7. The LED screen according to claim 7, wherein the hollow area includes four sidewalls perpendicular or approximately perpendicular to the PCB board, and a reflective layer or an absorption layer is provided on the four sidewalls.
The LED screen of claim 1, wherein the light guide rod and the LED unit are bonded and fixed by an adhesive.