Quantum dot color conversion layer with static droplet array to reduce light crosstalk and preparation method thereof

Abstract

A quantum dot color conversion layer and preparation method for reducing optical crosstalk using a static droplet array relates to the field of Micro LED display technology, solving the problems of low photoluminescence efficiency, short service life, and severe optical crosstalk in existing technologies. The present invention proposes a quantum dot color conversion layer and preparation method for reducing optical crosstalk using droplet microfluidics. Compared with quantum dot color conversion layers prepared using traditional microfluidics, this method uses a special static droplet array design to prepare discrete droplet quantum dot pixels, avoiding the severe optical crosstalk effect caused by end-to-end connections between pixel particles of the same type. The preparation method is relatively simple, requires fewer consumables, avoids complex packaging, and can be quickly produced in batches.

Description

Technical Field

[0001] The present invention relates to the field of Micro LED display technology, and in particular to a quantum dot color conversion layer with a static droplet array to reduce light crosstalk and a preparation method thereof. Background Art

[0002] Compared to liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), Micro LEDs have attracted widespread attention due to their higher brightness, longer lifespan, and wider color gamut, and are expected to become the next generation of display technology. In terms of commercial applications, Micro LED displays have greater potential due to their self-luminous properties, good outdoor visibility, strong environmental tolerance, compact and stable microstructure, and excellent resolution.

[0003] Due to the lattice mismatch of the materials, it is difficult to achieve monolithic integration of RGB Micro LED substrates on a single wafer using a single, efficient epitaxial growth technology. Therefore, using blue or ultraviolet (UV) Micro LEDs as the excitation light source combined with a red and green quantum dot color conversion layer to achieve full-color display is a very simple and effective approach. There are two main approaches to preparing quantum dot color conversion layers: inkjet printing, which involves spraying a quantum dot solution onto an LED or transparent substrate to achieve full-color display; and photolithography, which involves mixing quantum dots with photoresist and patterning them using various photolithographic methods. However, inkjet printing struggles to produce color conversion layers with pixel sizes smaller than 30 microns. Photolithography, on the other hand, requires mixing with photoresist materials for lithography and development, resulting in wasted quantum dots. Furthermore, doped photoresist can easily degrade the quantum dot performance, reducing photoluminescence efficiency and significantly shortening its lifespan. Currently, quantum dot color conversion layers fabricated using microfluidics, because each pixel of the same color is interconnected, lacks pixel separation, resulting in severe optical crosstalk, which affects the display quality. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a quantum dot color conversion layer and a preparation method for reducing optical crosstalk with a static droplet array, which solves the problems of low photoluminescence efficiency, short service life and serious optical crosstalk effect in the prior art.

[0005] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0006] A quantum dot color conversion layer with a static droplet array to reduce light crosstalk, the quantum dot color conversion layer comprising: a bonded transparent substrate and a microfluidic substrate; the microfluidic substrate comprising: two quantum dot microfluidic channels with identical structures, the two microfluidic channels not crossing each other and arranged in a serpentine shape; each quantum dot microfluidic channel comprising: an auxiliary channel, a droplet generation point and an exhaust channel; the quantum dot solution flowing in the auxiliary channel sequentially enters the plurality of droplet generation points and is exhausted through the exhaust channel connected to the droplet generation point; the quantum dot solutions in the two quantum dot microfluidic channels with identical structures are respectively a red quantum dot solution and a green quantum dot solution.

[0007] Preferably, the droplet generation points form a droplet quantum dot array, and two droplet generation points with the same arrangement and one or two adjacent auxiliary flow channels form an auxiliary flow channel transmission area, forming a group of RGB pixel arrangements.

[0008] Preferably, the two quantum dot microchannels include at least one set of RGB pixel arrangements.

[0009] Preferably, each auxiliary flow channel is provided with a liquid inlet and a liquid outlet.

[0010] Preferably, the other end of the exhaust channel is connected to the auxiliary flow channel.

[0011] Preferably, it further comprises a main exhaust channel, wherein the main exhaust channel is located between the two quantum dot microchannels with the same structure, and the other end of the exhaust channel is connected to the main exhaust channel.

[0012] A method for preparing a quantum dot color conversion layer with a static droplet array to reduce optical crosstalk, the method comprising the following steps:

[0013] Step 1: According to the arrangement of the droplet generation points, a photoresist substrate containing a raised pixel array pattern is prepared by photolithography process as a template for microfluidic channel molding;

[0014] Step 2: pouring the sol for preparing the microfluidic substrate on a photoresist substrate, removing bubbles, curing and molding to prepare the microfluidic substrate, and drilling holes at the liquid inlet and liquid outlet positions; bonding the microfluidic substrate to the transparent substrate to complete the microfluidic chip;

[0015] Step 3: Place the bonded microfluidic chip horizontally, inject the red quantum dot solution and the green quantum dot solution into the corresponding liquid inlet holes, fill the auxiliary flow channel and the droplet quantum dot array, and then flow out from the liquid outlet hole, and the excess air is discharged through the exhaust channel;

[0016] Step 4: After the quantum dot solution is injected, the transparent sealing liquid is injected from the two liquid inlets respectively to occupy the auxiliary flow channel and fully drain the quantum dot solution in the auxiliary flow channel;

[0017] Step 5: Exposing the microfluidic chip after step 4 to ultraviolet light to solidify the droplet quantum dot pixel positions, and heating the microfluidic chip at a constant temperature to solidify the transparent sealing liquid to form a quantum dot color conversion layer;

[0018] Step 6: Align and bond the quantum dot color conversion layer with the blue light Micro-LED to achieve full-color display.

[0019] Preferably, the transparent substrate is made of PDMS, glass, quartz, or acrylic plate; and the microfluidic substrate is made of PDMS, PMMA, PI, or PVA.

[0020] Preferably, the refractive index of the transparent sealing liquid is 1.4-1.41, the refractive index of the PDMS microfluidic substrate is 1.406, and the viscosity of the transparent sealing liquid is 350 cs.

[0021] The beneficial effects of the present invention are: the present invention proposes a quantum dot color conversion layer and a preparation method thereof that utilizes droplet microfluidic technology to reduce optical crosstalk. Compared with the quantum dot color conversion layer prepared by traditional microfluidic technology, this method adopts a special static droplet array design, which can prepare discrete droplet quantum dot pixels, avoiding the serious optical crosstalk effect caused by the end-to-end connection between the same pixel particles. The preparation method is relatively simple, requires less consumables, can avoid complex packaging, and can be quickly prepared in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view of a microfluidic substrate in a quantum dot color conversion layer for reducing optical crosstalk using a static droplet array according to the present invention;

[0023] Figure 2 1. It is a top view of a microfluidic substrate of a quantum dot color conversion layer for reducing optical crosstalk in a static droplet array according to the present invention;

[0024] Figure 3 1. It is a top view of the microfluidic substrate of the second embodiment of the quantum dot color conversion layer for reducing optical crosstalk using a static droplet array according to the present invention;

[0025] Figure 4 This is a flow chart of the method for preparing the quantum dot color conversion layer of the present invention;

[0026] Figure 5 It is a dynamic diagram of the quantum dot color conversion layer bonding and solution injection of the present invention;

[0027] Figure 6 This is a schematic diagram of the integration of the quantum dot color conversion layer and the blue light Micro-LED backlight array in Example 3 of the present invention.

[0028] In the figure: 1, microfluidic substrate, 2, photoresist substrate, 3, transparent substrate, 11, red droplet quantum dot position, 111, red droplet auxiliary flow channel, 112, red droplet exhaust channel, 113, red droplet auxiliary flow channel inlet, 114, red droplet auxiliary flow channel outlet, 12, green droplet quantum dot position, 121, green droplet auxiliary flow channel, 122, green droplet exhaust channel, 123, green droplet auxiliary flow channel inlet, 124, green droplet auxiliary flow channel outlet, 13, auxiliary flow channel Transmission area, 14. First RGB pixel arrangement, 15. Second RGB pixel arrangement, 16. Main exhaust channel, 161. First exhaust port, 162. Second exhaust port, 4. Quantum dot color conversion layer, 41. Red quantum dot solution, 42. Green quantum dot solution, 43. Transparent sealing liquid, 5. Blue light Micro-LED array backlight layer, 51. Blue light Micro-LED array substrate, 52. Blue light Micro-LED array, 53. Black isolation barrier. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, a quantum dot color conversion layer with a static droplet array to reduce light crosstalk, the quantum dot color conversion layer includes: a transparent substrate 3 and a microfluidic substrate 1 bonded together; the microfluidic substrate 1 includes: two quantum dot microfluidic channels with identical structures, and the two microfluidic channels do not cross each other and are arranged in a serpentine shape; each quantum dot microfluidic channel includes: an auxiliary channel, a droplet generation point and an exhaust channel; the quantum dot solution flowing in the auxiliary channel sequentially enters the multiple droplet generation points and is exhausted through the exhaust channel connected to the droplet generation point; the quantum dot solutions in the two quantum dot microfluidic channels with identical structures are red quantum dot solution 41 and green quantum dot solution 42, respectively.

[0031] Example 1:

[0032] like Figure 2As shown, the specific pattern of the microfluidic substrate 1 includes: a red droplet quantum dot position microfluidic channel and a green droplet quantum dot position microfluidic channel. The red droplet quantum dot position microfluidic channel includes: a red droplet quantum dot position 11, a red droplet auxiliary flow channel 111, a red droplet exhaust flow channel 112, a red droplet auxiliary flow channel inlet 113, and a red droplet auxiliary flow channel outlet 114. The green droplet quantum dot position microfluidic channel includes: a green droplet quantum dot position 12, a green droplet auxiliary flow channel 121, a green droplet exhaust flow channel 122, a green droplet auxiliary flow channel inlet 123, and a green droplet auxiliary flow channel outlet 124. It also includes: an auxiliary flow channel transmission area 13, a first RGB pixel array 14, and a second GRB pixel array 15. The red droplet quantum dot sites 11 are connected to the red droplet auxiliary flow channel 111 and the red droplet exhaust flow channel 112, respectively. One end of the red droplet exhaust flow channel 112 is connected to the red droplet quantum dot site 11, and the other end is connected to the red droplet auxiliary flow channel 111. The red light quantum dot solution 41 enters the red droplet auxiliary flow channel 111 through the red droplet auxiliary flow channel inlet 113. Under the action of pressure, the red light quantum dot solution 41 flows forward along the red droplet auxiliary flow channel 111 and sequentially enters multiple red droplet quantum dot sites 11 before flowing out through the red droplet auxiliary flow channel outlet 114. Each red droplet quantum dot position 11 is provided with a red droplet exhaust channel 112, so that the red light quantum dot solution 41 can easily fill all the red droplet quantum dot positions 11, and because the red droplet exhaust channel 112 is very small relative to the red droplet auxiliary channel 111, due to the huge pressure difference, the red light quantum dot solution 42 is not easy to enter the red droplet exhaust channel 112 after filling the red droplet quantum dot position 11, but flows along the red droplet auxiliary channel 111 and flows out at the red droplet auxiliary channel outlet 114. Among them, the structure of the green droplet quantum dot position microchannel and the direction of the green quantum dot solution 42 are exactly the same as those of the red droplet quantum dot position microchannel. Starting from the liquid inlet, each quantum dot position is assigned a serial number in the order of injecting the quantum dot solution, and each quantum dot position forms a droplet quantum dot array; the red droplet quantum dot position 11, the green droplet quantum dot position 12 and one or two adjacent auxiliary channels with the same serial number form an auxiliary channel transmission area 13, forming a group of RGB pixels. Figure 2 The first RGB pixel arrangement 14 and the second GRB pixel arrangement 15 are shown. The auxiliary flow channel transmission area 13 is used for blue light Micro-LED backlight transmission.

[0033] Example 2:

[0034] like Figure 3As shown, the microfluidic substrate 1 specifically includes a red droplet quantum dot microfluidic channel and a green droplet quantum dot microfluidic channel. The red droplet quantum dot microfluidic channel includes a red droplet quantum dot site 11, a red droplet auxiliary channel 111, a red droplet exhaust channel 112, a red droplet auxiliary channel inlet 113, and a red droplet auxiliary channel outlet 114. The green droplet quantum dot microfluidic channel includes a green droplet quantum dot site 12, a green droplet auxiliary channel 121, a green droplet exhaust channel 122, a green droplet auxiliary channel inlet 123, and a green droplet auxiliary channel outlet 124. The substrate also includes an auxiliary channel transmission area 13, a first RGB pixel array 14, a second GRB pixel array 15, a main exhaust channel 16, a first exhaust port 161, and a second exhaust port 162. The red droplet quantum dot sites 11 are connected to the red droplet auxiliary flow channel 111 and the red droplet exhaust flow channel 112, respectively. One end of the red droplet exhaust flow channel 112 is connected to the red droplet quantum dot site 11, and the other end is connected to the main exhaust channel 16. The red light quantum dot solution 41 enters the red droplet auxiliary flow channel 111 through the red droplet auxiliary flow channel inlet 113. Under the action of pressure, the red light quantum dot solution 41 flows forward along the red droplet auxiliary flow channel 111, and sequentially enters multiple red droplet quantum dot sites 11, and flows out through the red droplet auxiliary flow channel outlet 114. Each red droplet quantum dot site 11 is equipped with a red droplet exhaust channel 112, allowing the red light quantum dot solution 41 to easily fill all red droplet quantum dot sites 11. Furthermore, since the red droplet exhaust channel 112 is much smaller than the red droplet auxiliary channel 111, the pressure difference is significant. As a result, after filling the red droplet quantum dot sites 11, the red light quantum dot solution 42 is unlikely to enter the red droplet exhaust channel 112. Instead, it flows along the red droplet auxiliary channel 111 and out of the red droplet auxiliary channel outlet 114. Excess gas is transported through the main exhaust channel 16 connected to the red droplet exhaust channel 112 and discharged through the first and second exhaust ports 161 and 162. The structure of the green droplet quantum dot microchannel and the flow path of the green quantum dot solution 42 are identical to those of the red droplet quantum dot microchannel. Starting from the liquid inlet, each quantum dot position is assigned a serial number in the order of injection of the quantum dot solution, and each quantum dot position forms a droplet quantum dot array; the red droplet quantum dot position 11, the green droplet quantum dot position 12 and one or two adjacent auxiliary flow channels with the same serial number form an auxiliary flow channel transmission area 13, forming a group of RGB pixel arrangements. Figure 3 The first RGB pixel arrangement 14 and the second GRB pixel arrangement 15 are shown. The auxiliary flow channel transmission area 13 is used for blue light Micro-LED backlight transmission.

[0035] The red droplet quantum dot 11 is used to convert blue light into red light, the green droplet quantum dot 12 is used to convert blue light into green light, and the auxiliary flow channel transmission area 13 is used to directly transmit blue light without changing the color of the blue light. One red droplet quantum dot 11, one green droplet quantum dot 12 and one auxiliary flow channel transmission area 13 form a pixel. The microfluidic substrate 1 includes at least one pixel. According to the principle of three primary colors, each pixel contains two circular droplet sub-pixel points and one blank sub-pixel point. The two circular droplet sub-pixel points serve as red droplet quantum dot 11 and green droplet quantum dot 12, respectively. After being formed into quantum dots, they solidify to form red and green quantum dots, which emit red and green light respectively when facing blue light. The blank sub-pixel point serves as a blue light quantum dot. It is an area composed of two opposing auxiliary flow channels and allows blue light Micro-LEDs to be directly transmitted as backlight.

[0036] When there are multiple pixel points, each pixel point is converted into a circular droplet sub-pixel point of the same color, which is connected to each other in the order of injection through the auxiliary microfluidic channel structure that runs through it.

[0037] like Figure 4 As shown, a method for preparing a quantum dot color conversion layer with a static droplet array to reduce light crosstalk comprises the following steps:

[0038] Step 1: Prepare a photolithography mask based on the arrangement of the droplet pixels. Then, use a photolithography process to create a photoresist substrate 3 containing a raised pixel array pattern, which serves as a template for the microchannel mold. Specifically, the height of the photoresist pixel layer is determined by the spin-coating speed of the photoresist: the faster the spin-coating speed, the thinner the photoresist layer.

[0039] Step 2: A sol for preparing a microfluidic substrate, such as PDMS, PMMA, PI, PVA, or other transparent materials, is poured onto a photoresist substrate 3, de-bubbled, cured, and molded to prepare a microfluidic substrate 1. Holes are then punched at the liquid inlet and outlet. The microfluidic substrate 1 is then bonded to a transparent substrate 2 to form a microfluidic chip. Preferably, the prepared photoresist pixel has a diameter of 100 microns and a height of 20 microns. The material of the transparent substrate 2 can be selected from transparent materials such as PDMS, glass, quartz, and acrylic. The prepared droplet quantum dots have a diameter of 5-500 microns and a height of 5-300 microns. The exhaust channel width is 1-100 microns.

[0040] Step 3: Place the bonded microfluidic chip horizontally, inject the red quantum dot solution 41 and the green quantum dot solution 42 from the corresponding liquid inlets, fill the auxiliary flow channel and the droplet quantum dot array, and then flow out from the liquid outlet. Figure 2As shown, the pattern of the microfluidic substrate 1 contains an exhaust channel. Since the exhaust channel connects the auxiliary flow channel and the droplet generation point, the quantum dot solution can easily fill the entire droplet generation point. Figure 3 As shown, each exhaust channel is connected to the main exhaust channel 16 , and excess gas is transmitted through the main exhaust channel 16 connected to the exhaust flow channel and discharged through the first exhaust port 161 and the second exhaust port 162 .

[0041] Step 4: After the quantum dot solution is injected, the transparent sealing liquid 43 is injected from the two liquid inlets respectively, so that it occupies the entire width of the microchannel and fully drains the quantum dot solution in the auxiliary channel. Similarly, since the size of the exhaust channel is much smaller than that of the auxiliary flow channel, due to the huge pressure difference, it is difficult for the sealing liquid to penetrate into the droplet quantum dot position. Instead, it flows along the auxiliary flow channel and drains the quantum dot solution in the auxiliary flow channel, leaving only the quantum dot solution in the droplet generation point as the droplet quantum dot pixel position; preferably, the transparent sealing liquid 43 should be a transparent liquid with a higher viscosity, so that it has greater adhesion to the side wall of the flow channel, and then fully occupies the flow channel, drains the quantum dot solution in the auxiliary flow channel, and is not easy to flow into the droplet quantum dot pixel position; in addition, the transparent sealing liquid 43 should also be selected to have a refractive index close to that of the microchannel substrate, because the blue light quantum dot vacancy is an area composed of two opposite auxiliary flow channels. When facing blue light, if the refractive index difference between the two is too large, it will cause the blue light to form total reflection in the auxiliary flow channel, causing light leakage or light crosstalk; on the contrary, if the refractive index of the two is the same, the blue light quantum dot vacancy area can be regarded as a homogeneous material, and light will not leak.

[0042] Step 5: The microfluidic chip after injection is fully exposed to ultraviolet light to solidify the droplet quantum dot pixel positions, and the microfluidic chip is heated at a constant temperature to solidify the transparent sealing liquid to form a quantum dot color conversion layer 4.

[0043] Step 6: Align and bond the quantum dot color conversion layer 4 and the blue light Micro-LED array backlight layer 5 so that the blue light Micro-LED array backlight layer 5 overlaps with the red droplet quantum dot positions 11, the green droplet quantum dot positions 12 and the auxiliary flow channel transmission area 13 in the quantum dot color conversion layer respectively to achieve full-color display.

[0044] like Figure 5 As shown, a photoresist microfluidic substrate 2 is first prepared using photolithography technology, and then the material for preparing the microfluidic channel is overmolded on the photoresist substrate 2, and then the microfluidic substrate 1 is prepared by reverse molding; then the microfluidic substrate 1 is bonded to the transparent substrate 3 and holes are punched to prepare a microfluidic chip;

[0045] Then, the red quantum dot solution 41 and the green quantum dot solution 42 are injected through the two liquid inlet holes respectively, so that they fill the entire auxiliary flow channel and the droplet pixel array, and then flow out through the two liquid outlet holes respectively;

[0046] Then, the transparent sealing liquid 43 is injected through the two liquid inlets to drain the quantum dot solution in the auxiliary flow channel. Finally, the quantum dot solution is solidified under ultraviolet light, and then constant temperature heating is performed to solidify the transparent sealing liquid.

[0047] like Figure 6 As shown, the blue Micro-LED array backlight layer 5 includes: a blue Micro-LED array substrate 51, a blue Micro-LED array 52, and a black isolation barrier 53. In particular, the black isolation barrier is mainly used to reduce the optical crosstalk effect of the blue LED, and includes but is not limited to black photoresist, black printing material, chrome plating, etc.

Claims

1. A quantum dot color conversion layer with a static droplet array to reduce optical crosstalk, characterized in that: The quantum dot color conversion layer includes: a transparent substrate and a microfluidic substrate bonded together; the microfluidic substrate includes: two quantum dot microfluidic channels with identical structures, and the two microfluidic channels do not cross each other and are arranged in a serpentine shape; each quantum dot microfluidic channel includes: an auxiliary channel, a droplet generation point and an exhaust channel; the quantum dot solution flowing in the auxiliary channel sequentially enters the multiple droplet generation points and is exhausted through the exhaust channel connected to the droplet generation point; the quantum dot solutions in the two quantum dot microfluidic channels with identical structures are respectively a red quantum dot solution and a green quantum dot solution.

2. The quantum dot color conversion layer with static droplet array to reduce optical crosstalk according to claim 1, characterized in that: The droplet generation points form a droplet quantum dot array, and two droplet generation points with the same arrangement and one or two adjacent auxiliary flow channels form an auxiliary flow channel transmission area, forming a group of RGB pixel arrangements.

3. The quantum dot color conversion layer with static droplet array to reduce optical crosstalk according to claim 1, characterized in that: The two quantum dot microchannels include at least one group of RGB pixel arrangements.

4. The quantum dot color conversion layer with static droplet array to reduce optical crosstalk according to claim 1, characterized in that: Each of the auxiliary flow channels is provided with a liquid inlet and a liquid outlet.

5. The quantum dot color conversion layer with static droplet array to reduce optical crosstalk according to claim 1, characterized in that: The other end of the exhaust channel is connected to the auxiliary flow channel.

6. The quantum dot color conversion layer with static droplet array to reduce optical crosstalk according to claim 1, characterized in that: It also includes a main exhaust channel, which is located between the two quantum dot microchannels with the same structure, and the other end of the exhaust channel is connected to the main exhaust channel.

7. A method for preparing a quantum dot color conversion layer with reduced optical crosstalk based on a static droplet array according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: Step 1: According to the arrangement of the droplet generation points, a photoresist substrate containing a raised pixel array pattern is prepared by photolithography process as a template for microfluidic channel molding; Step 2: pouring the sol for preparing the microfluidic substrate on a photoresist substrate, removing bubbles, curing and molding to prepare the microfluidic substrate, and drilling holes at the liquid inlet and liquid outlet positions of the auxiliary flow channel; bonding the microfluidic substrate to the transparent substrate to complete the microfluidic chip; Step 3: Place the bonded microfluidic chip horizontally, inject the red quantum dot solution and the green quantum dot solution into the corresponding liquid inlet holes, fill the auxiliary flow channel and the droplet quantum dot array, and then flow out from the liquid outlet hole, and the excess air is discharged through the exhaust channel; Step 4: After the quantum dot solution is injected, the transparent sealing liquid is injected from the two liquid inlets respectively to occupy the auxiliary flow channel and fully drain the quantum dot solution in the auxiliary flow channel; Step 5: Exposing the microfluidic chip after step 4 to ultraviolet light to solidify the droplet quantum dot pixel positions, and heating the microfluidic chip at a constant temperature to solidify the transparent sealing liquid to form a quantum dot color conversion layer; Step 6: Align and bond the quantum dot color conversion layer with the blue light Micro-LED to achieve full-color display.

8. The preparation method according to claim 7, characterized in that The transparent substrate is made of PDMS, glass, quartz, or acrylic plate; the microchannel substrate is made of PDMS, PMMA, PI, or PVA.

9. The preparation method according to claim 8, characterized in that The refractive index of the transparent sealing liquid is 1.4-1.41, the viscosity is 350 cs, and the refractive index of the PDMS microfluidic channel substrate is 1.406.

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