Micro-LED (light-emitting diode)-based light-condensing micro-display

Abstract

The invention relates to a micro-LED (light-emitting diode)-based light-condensing micro-display and a manufacturing method, the display obtained by the display and the manufacturing method comprises a silicon substrate, a pixel driving circuit, a miniaturized micro LED array and a distributed light-condensing unit, each pixel unit in the array is provided with a plurality of light-condensing units, and the light-condensing units are arranged on the silicon substrate. The silicon substrate comprises a monocrystalline silicon layer, the pixel driving circuit comprises a CMOS (Complementary Metal Oxide Semiconductor) pixel driving circuit layer, the leveling layer, the electrode layer, the RGB micro LED layer, the graphene anti-dazzle protective layer and the distributed condensation unit are sequentially arranged from bottom to top, and the distributed condensation unit comprises micro units which are in one-to-one correspondence with pixels. According to the display, brighter impression under the same electricity consumption power is realized, and the electricity consumption demand is saved at low cost.

Description

Technical Field

[0001] The present invention relates to a manufacturing method of a microdisplay, and particularly to a manufacturing method of a condenser type microdisplay based on Micro-LEDs, belonging to the field of display structure design. Background Art

[0002] In the prior art, different pixel color requirements are obtained by combining the RGB primary color light points of pixels so as to adapt to changing pictures. Different display qualities are formed by different matrix arrangement modes of the primary color optoelectronics. The most common amoled is of this kind. Its purpose is to restore colors as accurately and realistically as possible. However, since each light point is actually a microplane and the light-emitting direction is divergent, a lot of light energy cannot be concentrated into the human eye, resulting in additional energy loss. Therefore, only more powerful electric energy endurance technology can be resorted to maintain the brightness. On the other hand, since devices such as smart phones and office displays generally involve private content. Therefore, while emphasizing how to re-adjust the divergent energy to enter the human eye, how to prevent peeping from the side needs to be considered. Summary of the Invention

[0003] Considering the above problems of the prior art, the present invention provides a condenser type microdisplay, in which condenser micro-elements are arranged in front of the RGB light points, and micro-elements with different condenser orientations are designed considering the visual field range of the human eye.

[0004] Therefore, the present invention provides a condenser type microdisplay based on Micro-LEDs, including a silicon substrate, a pixel driving circuit, a miniaturized micro LED array, and a distributed condenser unit. Among them, each pixel unit in the array, from bottom to top, successively includes a silicon substrate including a single crystal silicon layer, a pixel driving circuit including a CMOS pixel driving circuit layer, a planarization layer, an electrode layer, an RGB micro LED layer, a graphene anti-glare protection layer, and a distributed condenser unit. The distributed condenser unit includes micro-units corresponding to each pixel one by one.

[0005] Optionally, each pixel unit in the array, from bottom to top, successively includes a silicon substrate including a single crystal silicon layer, a pixel driving circuit including a CMOS pixel driving circuit layer, a planarization layer, an electrode layer, an RGB micro LED layer, and a distributed condenser unit.

[0006] In this optional solution, the graphene anti-glare protection layer is omitted. This is because it is considered that the distributed condenser unit can already attenuate the light intensity to a certain extent and play an anti-glare function. It is also considered that the attenuation of the original light point intensity should not be too large. At the same time, the cost is saved to a certain extent.

[0007] Optionally, the micro unit includes three microlenses, which are respectively arranged directly above three micro-photodiodes of R, G, and B, and the focal points of the microlenses are on the light-emitting planes of the corresponding micro-photodiodes, and at least a part of the light emitted from each light spot passes through the microlens corresponding to the focal point.

[0008] It should be understood that when irradiating the above configuration involving the micro unit, the originally divergent light spots are at least partially collimated, that is, they are refracted more towards the glasses direction, so that the light energy incident on the eyeball increases, thereby increasing the viewing intensity of each pixel, and thus reducing the demand for increasing the light intensity to a certain extent.

[0009] Preferably, the micro unit further includes concave conical light wedges with a preset conical angle arranged in front of the three microlenses respectively, and the preset conical angle has a preset spatial distribution within the display interface of the display, so that at least a part of the light emitted from each light spot passes through the microlens corresponding to the focal point and then enters the corresponding concave conical light wedge, so that for all micro units, all the light rays refracted from the concave conical light wedges approach the point far from the concave conical vertex on the central axis passing through the concave conical vertex.

[0010] Preferably, the projections of the concave conical light wedge and the microlens on the light-emitting plane of the micro-photodiode are both circles, and the projection diameter of the concave conical light wedge is not greater than the projection diameter of the microlens.

[0011] Optionally, the preset spatial distribution is such that the solid angle of the concave conical light wedge corresponding to the light spot in the pixel points closer to the midpoint of the display field of view is smaller.

[0012] Optionally, the electrode layer is a graphene film formed on the silicon substrate by chemical CVD or plasma deposition methods.

[0013] Optionally, the anti-glare protective film is a directly formed graphene film with a high light transmittance.

[0014] Optionally, the distributed light condensing unit is made of a highly transparent material.

[0015] Optionally, the distributed light condensing unit is made of a highly transparent material by photolithography or electron etching.

[0016] On the other hand, the present invention provides a method for manufacturing the above-mentioned light condensing type micro display based on Micro-LED, including the following steps:

[0017] A) Micro display chip design;

[0018] B) Substrate wafer preparation;

[0019] C) Fabricating a pixel driving circuit using CMOS integrated circuits and processes;

[0020] D) Prepare a planarization layer (aluminum nitride + silicon dioxide);

[0021] E) Preparation of the graphene electrode layer

[0022] F) Use MOCVD epitaxy to prepare a blue light epitaxial layer and pattern it to form a blue pixel array;

[0023] G) Use green and red light conversion materials (phosphors or quantum dots) to make a conversion material coating through planar processes (coating, printing, spraying), and perform overlay with a lithography system device to achieve an RGB micro-LED array;

[0024] H) Prepare a graphene anti-glare and protective layer using a high transmittance graphene film, or skip this step and directly proceed to the next step;

[0025] I) Set up a distributed light condensing unit;

[0026] J) Chip dicing, testing, module packaging, and wire bonding packaging.

[0027] Advantageous Effects

[0028] A microlens or a microlens and a concave conical light wedge are provided in front of the RGB light points of the RGB micro-LED array, achieving a brighter visual experience under the same power consumption, and saving power demand at low cost. Description of the Drawings

[0029] Figure 1 Comparison diagram of the display structure in the prior art and Embodiment 1 of the present invention,

[0030] Figure 2a and Figure 2b respectively, schematic diagrams of the refraction of scattered light of the R light point in the pixel X structure of the display in Embodiment 1 of the present invention when a microlens L and a microlens L and a concave conical light wedge are applied, Figure 1 Schematic diagram of the refraction of different light rays incident on the crystalline lens, and enlarged view of the incident situation near the local crystalline lens,

[0031] Figure 3 Schematic diagrams of the distribution of concave conical light wedges with different solid angles in the display, the left side is a side cross-sectional view, and the right side is a front view.

[0032] Figure 4 Figure 5 : A method for manufacturing a new type of microdisplay device based on micro LED technology. Detailed Embodiments

[0033] Embodiment 1

[0034] As Figure 1 ​As shown, taking a pixel point X on the display as an example, it includes micro-units. The micro-units have three light-emitting circular regions of R, G, and B. The three circular regions are composed of three light points of R, G, and B, which are respectively realized by using red and green light conversion materials (phosphors or quantum dots) to make a conversion material coating through planar processes (coating, printing, spraying) and the overlay of a lithography system device, and by using MOCVD epitaxy to prepare a blue light epitaxial layer and patterning it, which belongs to the prior art.

[0035] In this embodiment of the present invention, a microlens L (biconvex type, the downward convex surface is omitted in the figure for the sake of clearly showing the light path) is also provided in front of the three light points of R, G, and B. The focus f of the microlens L is located on the light-emitting plane of the light point. Therefore, the light-emitting surface of the R light point actually coincides with the focal plane of the R light point, and the center of the lens axis is O.

[0036] Specifically, as Figure 2a shown. Taking a cross-section of the R light point on the left side of the 0° horizontal line of sight of the human eye (presented in a vertical state, and the same analysis applies to other orientations) ( Figure 1 a cross-section parallel to the short side direction in

[0037] as an example, from bottom to top, it successively includes a silicon substrate including a single-crystalline silicon layer, a pixel driving circuit including a CMOS pixel driving circuit layer, a planarizing layer, an electrode layer, an RGB micro LED layer, a graphene anti-glare protection layer, and a distributed light condensing unit

[0038] According to geometric optics, Figure 2a among all the light rays between the outermost divergent light rays α' and β' on the outermost edge side after the focus f passes through the lens L in

[0039] since the lens L is set to be collimated, the light cones originally in α' and β' (and the light rays in the same direction as the dotted lines in other cases without the microlens L) and near them are converged more towards the eye direction due to the lens L, increasing the light-receiving intensity of the eye.

[0040] Generally speaking, the light rays located at the outermost edge of the microlens L scattered by the points between point B and the focal point f are located between Figure 2a the included angle between the light ray α' and the light ray δ'. The light rays in this part are refracted into the solid angle θ' as a whole.

[0041] Therefore, for the circular region, at the outermost edge, the generatrices of all the light cones between the generatrices of the main light intensity part σ or 2σ of the light spot are located inside the solid angle θ' and the solid angle with the size of θ respectively. That is to say, when the points around the focal point f are continuously moving away from the focal point f (regardless of whether it is calculated within the solid angle θ' or the solid angle with the size of θ), the generatrices of the light cones start from the light rays α and β and always gradually converge towards the optical axis (as shown by the arrows indicating the angle change in the figure).

[0042] Similarly, the light ray γ' refracted from point A becomes the light ray γ that converges more towards the 0° horizontal line of sight reference line. For the non-edge part, it is within all possible solid angles with the size of θ during the movement of the solid angle θ along the convex surface of the microlens L on the curve of the interface in the figure.

[0043] Therefore, Figure 2a When the microlens L is not set, point B scatters the light ray δ' at the above-mentioned projection. After the microlens L is set, it converges towards the 0° horizontal line of sight reference line. That is to say, the light rays δ', including α', β', γ', and the generatrices of the light cones inside the solid angle θ' and the solid angle with the size of θ, which were originally 100% unable to enter the eye, all produce a light ray deflection effect due to the microlens L and converge towards the 0° horizontal line of sight reference line as a whole. Therefore, the probability of entering the eye is increased.

[0044] For the corresponding multiple points on the right side of the focal point f in the figure, for the generatrices of all the light cones, whether the microlens L is set or not, they are refracted away from the 0° horizontal line of sight reference line. The probability of most of these light rays (except for the generatrices of the light cones close to the light ray β) entering the eye is low both before and after the microlens L is set. That is to say, most of the light rays have an approximate zero contribution to the probability of entering the eye. Therefore, overall, the probability of the light spot R entering the eye after the microlens L is set is increased.

[0045] Similarly analyzed Figure 2a in the case on the right side of the 0° horizontal line of sight reference line converging, the contribution comes from the points on the right side of the focal point f on the focal plane. Therefore, within the circular region, the total probability of the light spot R entering the eye after the microlens L is set is still increased. Similarly analyzing the light spot G and the light spot B, therefore, for each pixel, the total probability of entering the eye after the microlens L is set is increased.

[0046] Specifically, as Figure 3 shown, still taking Figure 1Take the light spot R in pixel X of the display as an example. Light ray a (represented by a dashed line) is the outermost light ray emitted by the light spot R that can be refracted by the lens in the perspective shown in the figure and without setting the microlens L. It has a very small angle with Figure 2a light ray α (which belongs to the outermost light ray not refracted by the lens). In the enlarged view from another perspective below in the figure, referring to Figure 2a it can be seen more clearly that the point emitting light ray a comes from a point symmetric to point B with respect to the focal point f and a point between the focal point f (including the focal point f, as shown in the non-enlarged figure in Figure 3 ) (that is, a point on the right side of the focal point f) and is very close to the focal point f (when it is not the focal point f).

[0047] Therefore, when the microlens L is not set, it can never be received by the eye anyway; but when the microlens L is set as in Figure 3 , the light ray a' (represented by a solid line) collimated to be parallel to the light ray α is received by the lens. In the figure, due to the different perspectives of the surrounding circular area, the relative positions of the light ray α and the light ray a are different from the relative positions of the collimated light ray a' and the light ray α in the enlarged view.

[0048] Similarly, analyzing a light ray I' between the light ray α' and the light ray δ', the light ray I refracted by the microlens L is incident on the other outermost edge of the lens. The angle between the light ray I and the light ray α is still very small. For the non-outermost edge of the lens, the scattered light rays are also collimated or refracted into a solid angle of size θ' with another vertex on the aforementioned curve. Therefore, for this point (that is, the aforementioned point on the right side of the focal point f), overall, the light incident amount is increased. The same analysis can be done for the points on other focal planes to obtain the overall increased incident light amount.

[0049] From Figure 3 it can be seen that since the angles between the light rays incident on the lens are all very small, as long as there are some scattered light rays with a slightly larger angle with these light rays, then regardless of whether the microlens L is set or not, these light rays cannot be incident on the lens. Take the light ray δ' as an example. Without setting, it is the light ray δ', and after setting, it deviates outside the light ray I instead and still cannot be incident on the lens. But by setting the microlens L, for the overall circular area, the light amount incident on the lens is increased.

[0050] Taking the pixel Y below the 0° horizontal line of sight reference line as an example, there is also a light ray α" symmetric to the light ray α' in the same way. The light ray b entering the lens is refracted through the microlens in front of the light spot R in the pixel Y. Similarly, for those refracted light rays with too large an angle with the light ray b, the contribution to the incident light is zero regardless of whether the microlens L is set or not. Figure 3For all pixels on all displays within the optimal field of view range of ±30°, a similar analysis can be performed, and it can be obtained that the total amount of incident light increases due to the setting of the microlens L.

[0051] It is easy to understand that for different focal lengths, the solid angles of the light cones at the same position on the microlens are different. However, since the distance between the lens and the pixel points is large, the required light angle is small, and the allowable change range is also small. Therefore, the change in the focal length does not significantly affect the increase in the incident light amount. No matter how the focal length is selected, as long as it is within the allowable range of the display thickness control, the incident amount can be increased. This provides a better controllable thinning range for the display thickness.

[0052] Embodiment 2

[0053] Figure 2b As shown, for the pixels on the right side of the 0° horizontal line of sight reference line by hundreds of millions of pixels, that is Figure 3 taking the pixel Y in [the text] as an example, a concave conical light wedge φ can be further provided in front of the microlens L. In this way, the original non-incident light rays δ and γ can both change the refraction direction again, and the angles of the concave light cones are different, that is, from the cross-section view, the maximum thickness of one side edge of the light wedge is different, and the refraction angles are also different. Therefore, in the general scenario where the 0° horizontal line of sight passes through the center of the display range, for pixels farther away from the reference line, they need to converge towards the reference line (that is, the angle with the reference line is larger) to increase the incident light amount as much as possible.

[0054] In this way, the probability that the original light rays that cannot enter the lens can enter is increased, and the part that could originally enter comes from the part near the edge of the microlens L. This part of the light has a small intensity, and even if it is refracted and deviated by the light wedge and cannot enter, it can be ignored for the increase in the incident probability of this middle strong light part. Therefore, the actual overall incident light amount is further increased.

[0055] In this way, as Figure 4 shown, for the spatial distribution of the concave conical light wedge φ, all the light rays refracted from the concave conical light wedge approach a point on the central axis away from the vertex of the concave cone passing through the vertex of the concave cone. Therefore, within the circular area of the pixel clock farther away from the accurate line, the solid angle of the concave conical light wedge φ is larger (as shown in the left cross-sectional view in the figure). In this way, the closer to the edge of the display, the smaller the change in the refraction angle after exiting the microlens L.

[0056] Embodiment 3

[0057] This embodiment provides a method for manufacturing a condensing microdisplay based on Micro-LED as in Embodiment 1 or Embodiment 2. As Figure 5 shown, it includes the following steps:

[0058] A) Microdisplay chip design;

[0059] B) Substrate wafer preparation;

[0060] C) Fabricating a pixel driving circuit using CMOS integrated circuits and processes;

[0061] D) Preparing a planarization layer (aluminum nitride + silicon dioxide);

[0062] E) Preparation of the graphene electrode layer

[0063] F) Using MOCVD to epitaxially grow and pattern a blue light epitaxial layer to form a blue pixel array;

[0064] G) Using green and red light conversion materials (phosphors or quantum dots) to form a conversion material coating through planar processes (coating, printing, spraying), and performing overlay with a lithography system to achieve an RGB micro-LED array;

[0065] I) Setting up a distributed light condensing unit;

[0066] J) Chip dicing, testing, module packaging, and wire bonding packaging.

[0067] In this embodiment, the step of preparing a graphene anti-glare and protective layer from a high transmittance graphene film is omitted to reduce light attenuation.

Claims

1. A condensing microdisplay based on Micro-LED, characterized in that, It includes a silicon substrate, a pixel driving circuit, a miniaturized micro-LED array, and a distributed light condensing unit. Each pixel unit in the array, from bottom to top, successively includes a silicon substrate including a single-crystalline silicon layer, a pixel driving circuit including a CMOS pixel driving circuit layer, a planarization layer, an electrode layer, an RGB micro-LED layer, a graphene anti-glare protection layer, and a distributed light condensing unit. The distributed light condensing unit includes micro-units corresponding to each pixel one by one.

2. A condensing microdisplay based on Micro-LED, characterized in that, It includes a silicon substrate, a pixel driving circuit, a miniaturized micro-LED array, and a distributed light condensing unit. Each pixel unit in the array, from bottom to top, successively includes a silicon substrate including a single-crystalline silicon layer, a pixel driving circuit including a CMOS pixel driving circuit layer, a planarization layer, an electrode layer, an RGB micro-LED layer, and a distributed light condensing unit. The distributed light condensing unit includes micro-units corresponding to each pixel one by one.

3. The display according to claim 1 or 2, characterized in that, The micro-unit includes three microlenses, which are respectively arranged directly above the three micro-photodiodes of R, G, and B. And the foci of the respective microlenses are on the light-emitting planes of the corresponding micro-photodiodes. At least a part of the light emitted from each light point passes through the microlens corresponding to the focus.

4. The display according to claim 1 or 2, characterized in that, The micro-unit includes three microlenses, which are respectively arranged directly above the three micro-photodiodes of R, G, and B. And the foci of the respective microlenses are on the light-emitting planes of the corresponding micro-photodiodes. At least a part of the light emitted from each light point passes through the microlens corresponding to the focus. The micro-unit further includes concave conical light wedges with a preset conical angle arranged in front of the three microlenses respectively, and the preset conical angle has a preset spatial distribution within the display interface of the display, so that at least a part of the light emitted from each light point passes through the microlens corresponding to the focus and then enters the corresponding concave conical light wedge. For all micro-units, all the light rays refracted from the concave conical light wedges approach a point on the central axis away from the apex of the concave cone.

5. The display according to claim 4, wherein The projections of the concave conical light wedge and the microlens on the light-emitting plane of the micro-photodiode are both circles, and the projection diameter of the concave conical light wedge is not greater than the projection diameter of the microlens.

6. The display according to claim 4, characterized in that, The preset spatial distribution is that the solid angle of the concave conical light wedge corresponding to the light point in the pixel point closer to the midpoint of the display field of view is smaller.

7. The display according to claim 5, wherein The preset spatial distribution is that the solid angle of the concave conical light wedge corresponding to the light point in the pixel point closer to the midpoint of the display field of view is smaller.

8. The display according to any one of claims 1, 2, 5 - 7, characterized in that The electrode layer is a graphene thin film formed on the silicon substrate by chemical CVD or plasma deposition method.

9. The display according to claim 1, wherein The anti-glare protection film is a directly formed graphene thin film with high light transmittance.

10. The display according to any one of claims 1, 2, 5 - 7, 9, characterized in that The distributed light condensing unit is made of a highly transparent material.

11. The display according to claim 10, characterized in that, The distributed light condensing unit is made of a highly transparent material by photolithography or electron etching.

12. A method of manufacturing a Micro-LED based condenser microdisplay as claimed in any one of claims 1-11, characterized in that, It includes the following steps: A) Micro-display chip design; B) Substrate wafer preparation; C) Fabricating a pixel driving circuit using CMOS integrated circuits and processes; D) Preparing a planarization layer; E) Preparation of the graphene electrode layer F) Use MOCVD epitaxy to prepare a blue light epitaxial layer and pattern it to form a blue pixel array; G) Use green and red light conversion materials to make a conversion material coating through a planar process, and perform overlay with a lithography system equipment to achieve an RGB micro-LED array; H) Use a high transmittance graphene film to prepare a graphene anti-glare protection layer, or skip this step directly and proceed to the next step; I) Set up a distributed light concentration unit; J) Chip dicing, testing, module packaging, and lead wire soldering packaging.

13. The method according to claim 12, wherein The green and red light conversion materials are phosphors or quantum dots. The planar process includes any one of coating, printing, and spraying. The planarization layer includes aluminum nitride and silicon dioxide.

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