Quantum dot microspheres, color conversion screen applying quantum dot microspheres and preparation method of color conversion screen

Abstract

The invention discloses quantum dot microspheres, a color conversion screen using the quantum dot microspheres and a preparation method of the color conversion screen. The preparation method comprises the following steps: firstly, uniformly distributing red quantum dots and green quantum dots in size-controllable microspheres through a microemulsion method to obtain quantum dot primary microspheres; coating the primary quantum dot microspheres with silicon dioxide, and modifying a surface ligand on the surface of the silicon dioxide to obtain quantum dot microspheres; the quantum dot microspheres prepared by the method are applied to a color conversion screen; the problems of quantum dot agglomeration, uncontrollable luminous intensity and fluorescence quenching caused by simple mechanical mixing of quantum dots and photoresist in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a quantum dot microsphere, a color conversion screen using the quantum dot microsphere and a preparation method thereof. Background Art

[0002] Quantum dots are widely used in the display and lighting fields due to their excellent optical properties. Compared with phosphors, quantum dots are smaller in size and can show better uniformity and fluorescence quantum yield when integrated into MicroLED devices through color conversion. In the prior art, red and green quantum dots are usually mixed in photoresist to prepare a color conversion layer. However, the surface of quantum dots has surface ligands such as oleic acid and oleylamine, while the photoresist contains polar ligands such as ether and ester groups. When quantum dots and photoresist are simply mechanically mixed, it will lead to quantum dot agglomeration, uncontrollable luminous intensity, fluorescence quenching and other problems. In addition, in the prior art, it is necessary to mix red or green quantum dots with photoresist separately to make a color conversion layer. The red or green quantum dot materials repeatedly undergo multiple photolithography processes such as pre-baking, exposure, development, and post-baking during the photolithography process, which increases the probability of quantum dot fluorescence quenching. Summary of the invention

[0003] In view of the problems of the prior art, one of the purposes of the present invention is to provide a quantum dot microsphere. The present invention successfully prepared quantum dot microspheres in which red quantum dots and green quantum dots are uniformly coated with silica through a large number of experimental condition screening.

[0004] The preparation method of quantum dot microspheres comprises the following steps: (1) uniformly distributing red quantum dots and green quantum dots in microspheres of controllable size by a microemulsion method to obtain quantum dot primary microspheres; (2) coating the quantum dot primary microspheres with silicon dioxide, and then modifying the surface ligands on the silicon dioxide surface to obtain quantum dot microspheres.

[0005] Preferably, the surface ligand is obtained by modification with γ-glycidyloxypropyltrimethoxysilane.

[0006] Preferably, the preparation method can be specifically as follows: (1) firstly add a surfactant into water and ultrasonically dissolve it until the solution is clear and colorless; then add a green quantum dot solution, and then add a red quantum dot solution, cover with plastic wrap, magnetically stir for 3 hours, and then place the above solution in an emulsifier for emulsification to obtain a quantum dot primary microsphere emulsion; (2) add water and ethanol to the quantum dot primary microsphere emulsion, ultrasonically homogenize it, then add ammonia water and TEOS to ultrasonically disperse it uniformly, and then stir and react for 24 hours. After the reaction is completed, centrifuge and wash to obtain silica-coated quantum dot primary microspheres, and then disperse them in ethanol, add ammonia water to adjust the pH to 9, and then add a chloroform solution of γ-glycidyloxypropyltrimethoxysilane. After stirring and reacting for 24 hours, the mixture is centrifuged and washed to obtain surface-modified silica-coated quantum dot primary microspheres, namely quantum dot microspheres.

[0007] Preferably, the surfactant is sodium lauryl sulfate.

[0008] Preferably, the mass volume ratio of the surfactant, red quantum dots, green quantum dots and TEOS is 5 mg: 4 mg: 4 mg: 0.16 mL.

[0009] Preferably, the interval between adding the green quantum dot solution and the red quantum dot solution in step (1) is 1 min; and the rotation speed of the magnetic stirring is 1000 r / min.

[0010] Preferably, in step (1), the emulsification speed of the emulsifier is 22000 r / min, and the emulsification time is 30 min.

[0011] The present invention also provides a color conversion screen using the quantum dot microspheres and a preparation method thereof.

[0012] The structure diagram of the quantum dot color conversion screen is shown in Figure 1 , including: a blue light LED chip substrate; a light-blocking layer and a quantum dot microsphere layer arranged on the light-emitting side of the blue light LED chip substrate; a filter layer arranged on the backlight side of the quantum dot microsphere layer; the quantum dot microsphere layer and the light-blocking layer are arranged at intervals; the light-blocking layer is an inverted trapezoidal structure, and a reflective layer is arranged on the side wall of the light-blocking layer.

[0013] The present invention also provides a method for manufacturing the above-mentioned color conversion screen, comprising the following steps: S1. selecting a blue light LED chip substrate, spin-coating a black matrix material on the light-emitting side of the substrate to form a light-blocking layer through a photolithography process; evaporating a metal reflective layer in the light-blocking layer; S2. spin-coating quantum dot microspheres on the portion of the light-emitting side of the blue light LED chip substrate where the light-blocking layer is not formed to obtain a quantum dot microsphere layer through a photolithography process; S3. forming a filter layer on the backlight side of the quantum dot microsphere layer through a photolithography process; wherein the light-blocking layer is an inverted trapezoidal structure, and the metal reflective layer is located on the side wall of the light-blocking layer.

[0014] Preferably, the step S1 is specifically as follows: selecting a blue light LED chip substrate, mixing a fixed mass of black matrix material with 10 mL of AZ2020nlof negative photoresist solution with a concentration of 20 wt%, and dispersing by ultrasonic vibration to form a mixed solution; spin coating the mixed solution on the blue light LED chip substrate by spin coating at 1000 r for 10 s, and baking at 110° C. for 5 min. After baking, the film thickness is about 8 μm and the surface is flat; exposing to ultraviolet light for 15 s using a mask with a pixel size of 50 μm*50 μm, then baking at 100° C. for 5 min, and finally developing with a developer to obtain a patterned film; sending the above-mentioned substrate into a vacuum evaporation device, adjusting the equipment parameters, and evaporating a 1-3 nm metal reflective layer in the light-blocking layer formed on the above-mentioned substrate.

[0015] Preferably, step S2 is specifically as follows: a fixed mass of white light quantum dot microspheres is mixed with 10 mL of AZ2020nlof negative gel solution at a concentration of 20 wt%, and a mixed solution is formed after ultrasonic dispersion. The mixed solution is spin-coated on a blue light LED chip substrate at 2000 r for 10 s, and baked at 110°C for 5 min. After baking, the film thickness is about 6 μm and the surface is flat; a mask with a pixel size of 50 μm*50 μm is exposed to ultraviolet light for 15 s, then baked at 100°C for 5 min, and finally developed with a developer to obtain a patterned film.

[0016] Preferably, the step S3 is specifically as follows: a fixed mass of filter materials of different colors is mixed with 10 mL of AZ2020nlof negative photoresist solution with a concentration of 20 wt %, and a mixed solution is formed after ultrasonic dispersion; the mixed solution is spin-coated on a blue LED chip substrate at 2000 r for 10 s, and baked at 110° C. for 5 min. After baking, the film thickness is about 6 μm and the surface is flat; a mask with a pixel size of 50 μm*50 μm is used to expose to ultraviolet light for 15 s, and then baked at 100° C. for 5 min, and finally developed with a developer; the above steps are repeated three times to finally form a filter layer on the upper layer of the substrate.

[0017] The present invention firstly prepares quantum dot primary microspheres by a microemulsion method, thereby distributing red and green quantum dots in microspheres of controllable size; secondly, the quantum dot primary microspheres are coated with silicon dioxide, and then the surface ligands are modified on the surface of the silicon dioxide shell layer to obtain quantum dot microspheres; the quantum dot microspheres are applied to a color conversion screen, and the size of the microspheres can be used to increase the utilization rate of blue light and improve light efficiency; the strong bonding ability of silicon-oxygen bonds is used to reduce the aggregation of quantum dots and increase the uniformity of luminescence.

[0018] The beneficial effects of the present invention are:

[0019] The quantum dot microspheres of the present invention simultaneously coat red and green quantum dots by using surface-modified silicon dioxide; on the one hand, the dispersibility of the quantum dot material in the photoresist is improved and the influence of the complex components in the photoresist on the quantum dots is reduced; on the other hand, the strong bonding ability of the silicon-oxygen bond is utilized to reduce the aggregation of the quantum dots in the photoresist caused by the shedding of the surface ligands, thereby increasing the uniformity of luminescence.

[0020] The present invention uses silicon dioxide to simultaneously coat red and green quantum dots to obtain quantum dot microspheres, and then mixes the quantum dot microspheres with photoresist; this can effectively avoid fluorescence quenching of the quantum dots caused by the photolithography process after mixing the red or green quantum dots with the photoresist.

[0021] The silica in the shell of the quantum dot microsphere of the present invention can refract the incident blue light multiple times, thereby achieving the effect of multiple effective utilizations, thereby improving the utilization rate of the blue light and reducing the probability of blue light being wasted due to the blue light not being able to irradiate the quantum dots and being emitted through the photoresist. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of a color conversion screen using quantum dot microspheres of the present invention;

[0023] Figure 2 This is a spectrum analysis diagram of the prepared color conversion screen using quantum dot microspheres; DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Unless otherwise defined, all professional terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention; unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0026] Example 1

[0027] Preparation of quantum dot microspheres

[0028] (1) Take a 100 mL beaker, weigh 50 mg of sodium dodecyl sulfate, add 50 mL of water, and dissolve by ultrasonication to obtain a clear colorless solution; add 4 mL of 10 mg / mL green quantum dot (CdSe / ZnS) chloroform solution thereto, and then add 4 mL of 10 mg / mL red quantum dot (CdSe / ZnS) chloroform solution after an interval of one minute; add a magnetic bar, cover with plastic wrap, adjust the speed to 1000 r / min, and stir for 3 h; put the stirred solution into an emulsifier, immerse the bottom of the emulsifier rotor in the solution, and emulsify at a speed of 22000 r / min for 30 min to obtain quantum dot primary microspheres;

[0029] (2) The emulsified quantum dot primary microsphere solution in (1) was collected by centrifugation, and 0.5 mL of water was added. The solution was then transferred to a 100 mL single-mouth bottle, 20 mL of ethanol was added, and ultrasonication was performed uniformly. 2.4 mL of ammonia water and 1.6 mL of TEOS were added for ultrasonic dissolution, and the reaction was stirred for 24 h. After the reaction was completed, the solution was collected by centrifugation, and the silica-coated quantum dot primary microspheres were obtained after washing twice with ethanol, and the silica-coated quantum dot primary microspheres were dispersed in 10 mL of ethanol. Then, 0.1 mL of 30% ammonia water was added to adjust the pH of the system to 9. Subsequently, 1 mL of 20 wt% γ-glycidyloxypropyltrimethoxysilane chloroform solution was added and stirred for 24 h. The mixture was collected by centrifugation, and washed three times with ethanol to obtain quantum dot microspheres.

[0030] Example 2

[0031] This embodiment adopts the preparation method of the above-mentioned embodiment 1 to prepare quantum dot microspheres, the difference is that InP / ZnS quantum dots of different colors (green or red) are used instead of CdSe / ZnS quantum dots of different colors (green or red) in step (1), and the rest is the same as embodiment 1.

[0032] Example 3

[0033] This embodiment adopts the preparation method of the above-mentioned embodiment 1 to prepare quantum dot microspheres, except that the γ-glycidyloxypropyltrimethoxysilane in step (2) is replaced by trimethoxyoctadecylsilane, and the rest is the same as embodiment 1.

[0034] Example 4

[0035] This embodiment adopts the preparation method of the above-mentioned embodiment 1 to prepare quantum dot microspheres, except that the γ-glycidyloxypropyltrimethoxysilane in step (2) is replaced by 3-aminopropyltriethoxysilane, and the rest is the same as embodiment 1.

[0036] Example 5

[0037] This embodiment adopts the preparation method of the above-mentioned embodiment 1 to prepare quantum dot microspheres, except that the γ-glycidyloxypropyltrimethoxysilane in step (2) is replaced by 3-mercaptopropyltriethoxysilane, and the rest is the same as embodiment 1.

[0038] Performance Test:

[0039] Preparation of quantum dot photoresist: 2 mg of the quantum dot microspheres prepared in Example 1-5 of the present invention are mixed with 10 mg of AZ2020nlof negative photoresist solution at a concentration of 20 wt %, and dispersed by ultrasonic vibration to form quantum dot photoresist, and the sample number corresponds to (1-5).

[0040] 4 mg of the quantum dot microspheres prepared in Example 1 of the present invention were mixed with 10 mg of AZ2020nlof negative resist solution at a concentration of 40 wt %, and dispersed by ultrasonic vibration to form a quantum dot photoresist, the sample number of which is 6.

[0041] The quantum dot photoresists of the above samples numbered 1-6 were subjected to transmittance test, quantum dot content test, dispersion test, stability test, and fluorescence intensity test of the cured film. The test results are shown in Table 1.

[0042] Table 1: Test data of quantum dot photoresists 1-6

[0043]

[0044]

[0045] Samples 1-6 in Table 1 correspond to the quantum dot photoresists prepared by mixing the quantum dot microspheres prepared in Examples 1-5 of the present invention with photoresists, wherein Sample 6 is prepared when the concentration of the quantum dot microspheres in Example 1 is adjusted to 40wt%. It can be seen from the data in Table 1 that the transmittances of quantum dot photoresists 1-2 and 6 are not less than 80%, indicating that the quantum dot microspheres prepared in Examples 1-2 of the present invention can be evenly dispersed in the photoresist and have good stability, and when the concentration of the quantum dot microspheres in the photoresist is adjusted from 20wt% (sample 1) to 40wt% (sample 6), it still shows good dispersibility and stability in the photoresist; the transmittances of quantum dot photoresists 3-5 are not more than 70%, indicating that the quantum dot microspheres prepared in Examples 3-5 of the present invention have obvious agglomeration in the photoresist and precipitate after being placed for a long time. It can be seen that the quantum dot microspheres prepared in Examples 1-2 of the present invention have better dispersibility and stability in the photoresist; it can effectively solve the problem of easy agglomeration and instability of quantum dots in quantum dot photoresists in the prior art.

[0046] Application Examples

[0047] The color conversion screen of the quantum dot microspheres prepared in the above embodiment 1 is shown in FIG. Figure 1 , comprising: a blue light LED chip substrate; a light-blocking layer and a quantum dot microsphere layer arranged on the light-emitting side of the blue light LED chip substrate; a filter layer arranged on the backlight side of the quantum dot microsphere layer; the quantum dot microsphere layer and the light-blocking layer are arranged at intervals; the light-blocking layer is an inverted trapezoidal structure, and a reflective layer is arranged on the side wall of the light-blocking layer; the preparation method specifically comprises the following steps:

[0048] S1. A blue light LED chip substrate is prepared by forming a light-blocking layer on the substrate using a black matrix photoresist. The specific method is to mix a fixed mass of black matrix material with 10 mL of AZ2020nlof negative photoresist solution with a concentration of 20 wt %, and disperse the mixture by ultrasonic vibration to form a mixed solution; the mixed solution is spin-coated on the blue light LED chip substrate by spin coating at 1000 r for 10 s, and baked at 110°C for 5 min. After baking, the film thickness is about 8 μm and the surface is flat; a mask with a pixel size of 50 μm*50 μm is used to expose the film to ultraviolet light for 15 s, and then baked at 100°C for 5 min. Finally, the film is developed with a developer to obtain a patterned film.

[0049] S2. Send the above substrate into a vacuum evaporation device, adjust the device parameters, and evaporate a 1-3 nm metal reflective layer in the light-blocking layer formed on the above substrate.

[0050] S3. Forming a quantum dot microsphere layer: Mix a fixed mass of quantum dot microspheres with 10 mL of AZ2020nlof negative gel solution at a concentration of 20 wt%, and disperse by ultrasonic vibration to form a mixed solution; Spin-coat the mixed solution on a blue LED chip substrate at 2000 r for 10 s, and bake at 110 ° C for 5 min. After baking, the film thickness is about 6 μm and the surface is flat; then use a mask with a pixel size of 50 μm*50 μm to expose to ultraviolet light for 15 s, then bake at 100 ° C for 5 min, and finally develop with a developer to obtain a patterned film.

[0051] S4. Forming a filter layer: Mix a fixed mass of filter materials of different colors with 10mL of AZ2020nlof negative photoresist solution with a concentration of 20wt%, and disperse by ultrasonic vibration to form a mixed solution; Spin-coat the mixed solution on the blue light LED chip substrate by spin coating at 2000r for 10s, and bake at 110℃ for 5min. After baking, the film thickness is about 6μm and the surface is flat; Use a mask with a pixel size of 50μm*50μm to expose to ultraviolet light for 15s, then bake at 100℃ for 5min, and finally develop with a developer; Repeat three times to finally form a filter layer on the upper layer of the substrate.

[0052] The luminescent spectrum of the color conversion screen prepared above is as follows: Figure 2 As shown by Figure 2 It can be seen that the spectrum of the color conversion screen prepared by the present invention presents a typical white light spectrum.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A quantum dot microsphere, characterized in that: The preparation method comprises the following steps: (1) uniformly distributing red quantum dots and green quantum dots in microspheres of controllable size by a microemulsion method to obtain quantum dot primary microspheres; (2) coating the quantum dot primary microspheres with silica, and then modifying the surface ligands on the silica surface to obtain quantum dot microspheres.

2. The quantum dot microsphere according to claim 1, characterized in that: The surface ligand is obtained by modification of gamma-glycidyloxypropyltrimethoxysilane.

3. The quantum dot microsphere according to claim 2, characterized in that: The preparation method is specifically as follows: (1) first add a surfactant into water and ultrasonically dissolve it until the solution is clear and colorless; then add a green quantum dot solution, and then add a red quantum dot solution, cover with plastic wrap, and after magnetic stirring for 3 hours, place the above solution in an emulsifier for emulsification to obtain a quantum dot primary microsphere emulsion; (2) add water and ethanol to the quantum dot primary microsphere emulsion, after ultrasonic homogenization, add ammonia water and TEOS to react for 24 hours, after the reaction is completed, centrifuge and wash to obtain silica-coated quantum dot primary microspheres, and then disperse them in ethanol, add ammonia water to adjust the pH to 9, add chloroform solution of γ-glycidyloxypropyltrimethoxysilane, stir the reaction for 24 hours, and then centrifuge and wash the mixture to obtain surface-modified silica-coated quantum dot primary microspheres, namely quantum dot microspheres.

4. The quantum dot microsphere according to claim 3, characterized in that: The surfactant is sodium lauryl sulfate.

5. The quantum dot microsphere according to claim 3, characterized in that: The mass volume ratio of the surfactant, red quantum dots, green quantum dots and TEOS is 5 mg: 4 mg: 4 mg: 0.16 mL.

6. The quantum dot microsphere according to claim 3, characterized in that: The interval between adding the green quantum dot solution and the red quantum dot solution in step (1) is 1 min; the rotation speed of the magnetic stirring is 1000 r / min; the emulsification speed of the emulsifier is 22000 r / min, and the emulsification time is 30 min.

7. Use of the quantum dot microspheres according to any one of claims 1 to 6 in quantum dot photoresists.

8. A color conversion screen made using the quantum dot microspheres described in any one of claims 1 to 6.

9. The quantum dot microsphere color conversion screen as claimed in claim 8, characterized in that: include: Blue LED chip substrate; A light-blocking layer and a quantum dot microsphere layer are provided on the light-emitting side of the blue LED chip substrate; The filter layer is arranged on the backlight side of the quantum dot microsphere layer; the quantum dot microsphere layer and the light blocking layer are arranged at intervals; the light blocking layer is an inverted trapezoidal structure, and the side wall of the light blocking layer is provided with a reflective layer.

10. A method for manufacturing a quantum dot microsphere color conversion screen as claimed in claim 9, characterized in that: The specific steps include: S1. Select a blue LED chip substrate, spin-coat a black matrix material on the light-emitting side of the substrate, and form a light-blocking layer by photolithography; evaporate a metal reflective layer in the light-blocking layer; S2. Spin-coating quantum dot microspheres on the part of the blue light LED chip substrate on which the light-blocking layer is not formed, and obtaining a quantum dot microsphere layer by photolithography; S3. Forming a filter layer on the backlight side of the quantum dot microsphere layer by photolithography; wherein the light-blocking layer is an inverted trapezoidal structure, and the metal reflective layer is located on the side wall of the light-blocking layer.

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