A method for manufacturing a microlens array

Abstract

The application relates to a preparation method of a microlens array, comprising the following steps: preparing a surface-smooth substrate from a variable-wettability material; spraying a polymer solution on the substrate to form a plurality of microdroplets; positioning the plurality of microdroplets on the substrate through an external field to form a microdroplet array; changing the wettability of the substrate to reduce the contact angle of each microdroplet to the substrate, and then forming a plurality of microlenses on the substrate; and solidifying the plurality of microlenses to form a microlens array. The method can realize in-situ preparation of the microlenses, avoids a mold transfer step in mainstream preparation methods, and can effectively improve the surface quality and precision of the microlenses. Meanwhile, according to actual conditions, the distribution of the external field and the intensity of external stimulation can be changed to conveniently prepare microlens arrays with different arrangements and different sizes.

Description

[0001] The present application is a divisional application of application number 202110798555.5, entitled "Preparation method of microlens array", applicant: South China University of Technology TECHNICAL FIELD

[0002] The present application relates to the field of precision manufacturing and micro-optical device preparation, in particular to a preparation method of microlens array. BACKGROUND

[0003] Among various micro-optical elements, microlens and its array structure are important basic elements, which are composed of many uniformly arranged micro lens units, and the size of each lens unit is mostly tens of microns to hundreds of microns.

[0004] With the miniaturization of optical elements, many manufacturing technologies of microlens and its array have been developed. These include template method, photoresist melting method, femtosecond laser lithography, acid etching method, ion beam etching, gray mask method, laser direct writing technology, hot mold pressing forming method, etc. Among them, the template method is one of the most commonly used methods at present. For example, the patent with publication number CN112630872A discloses a preparation method of microlens. The method comprises: processing a metal substrate to obtain a mold of three-dimensional microlens array; preparing a pre-set thickness of imprinting glue on the surface of the material for preparing three-dimensional microlens array, and using the mold to press and solidify the imprinting glue to obtain a three-dimensional microlens array of imprinting glue material; and using dry etching to etch the three-dimensional microlens array of imprinting glue material until a microlens array is obtained on the material for preparing three-dimensional microlens array. However, like all template methods, this method inevitably involves a demolding process, which cannot realize in-situ preparation of microlens, seriously affecting the precision of microlens, and needs to introduce a large number of cumbersome processes. SUMMARY

[0005] In view of the technical problems existing in the prior art, the purpose of the present application is to provide a preparation method of microlens array, which can realize in-situ preparation of microlens and effectively improve the surface quality and precision of microlens.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A preparation method of microlens array, comprising the following steps,

[0008] A wetting variable material is prepared into a substrate with smooth surface; the wetting of the substrate can respond to changes in external environment (such as temperature, light and other factors);

[0009] Spray a polymer solution on the substrate to form a plurality of microdroplets;

[0010] Positioning a plurality of microdroplets on a substrate by an external field to form a microdroplet array;

[0011] Changing the wettability of the substrate to make the contact angle of each microdroplet to the substrate smaller, and then forming a plurality of microlenses on the substrate;

[0012] Solidifying the plurality of microlenses to form a microlens array.

[0013] The present application utilizes the wettability variable substrate to change the contact angle of the polymer microdroplet on the substrate surface, and realizes the in-situ preparation of the microlens array by the external field assisted positioning. On the wettability variable material substrate, the microdroplet has a larger contact angle and a smaller rolling angle initially, and the microdroplet can be moved and positioned under the assistance of the external field. After the surface of the wettability variable substrate is stimulated by the external field, the chemical composition begins to change, the contact angle of the microdroplet gradually becomes smaller, and then the shape of the microlens is formed, and finally the microlens is formed after solidification.

[0014] Further, the configuration method of the polymer solution is that the PDMS is mixed with the curing agent, then diluted by adding ethyl acetate to obtain, wherein the mass ratio of the PDMS to the curing agent is 10:1, and the volume ratio of the PDMS to the ethyl acetate is 1:1. The polymer solution can also be configured by using other solidifiable polymers in the prior art, such as UV glue.

[0015] Further, the wettability of the substrate is changed by the following steps: the wettability of the substrate is changed by irradiating the substrate with ultraviolet light, so that the microdroplets on the substrate present the shape of the microlens.

[0016] Further, the ultraviolet light irradiation time is 2.5-3.5h.

[0017] Further, the microdroplets initially present superhydrophobicity on the substrate.

[0018] Further, the wettability variable material is ZnO.

[0019] Further, the external field is a magnetic field.

[0020] Further, the solidification method of the microlens is heating solidification.

[0021] Further, the heating temperature is 90℃, and the heating time is 1h.

[0022] Further, after the microlens is solidified, the following step is further included: the microlens is placed in anhydrous ethanol for ultrasonic cleaning.

[0023] In general, the present application has the following advantages:

[0024] The micro-lens array is prepared by using a method of variable-wetting substrate with additional field assistance. In the initial state, the micro-droplets on the substrate surface show super-hydrophobicity, and the micro-droplets have a larger contact angle and a smaller rolling angle. With the assistance of the external field, the micro-droplets can quickly roll on the substrate surface and be arranged in order. As the wettability of the substrate starts to change under the external stimulation, the contact angle of the micro-droplets gradually decreases, and finally the shape of the micro-lens is formed. After heating and curing, the micro-lens array is formed.

[0025] Compared with the prior art, the micro-lens array is prepared by using the variable-wetting characteristic of the substrate. The method can realize in-situ preparation of the micro-lens, avoids the mold transfer step in the mainstream preparation method, and can effectively improve the surface quality and precision of the micro-lens. Meanwhile, according to the actual conditions, by changing the distribution of the external field, the micro-lens array with different arrangements and different sizes can be conveniently prepared. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a schematic diagram of a spraying device in the preparation method of the micro-lens array.

[0027] Figure 2 It is a flowchart of the preparation method of the micro-lens array.

[0028] BRIEF DESCRIPTION OF DRAWINGS:

[0029] 1 - substrate, 2 - micro-droplet, 3 - piezoelectric ceramic actuator, 4 - micro-nozzle. DETAILED DESCRIPTION

[0030] The application will be further described in detail as follows.

[0031] A preparation method of a micro-lens array, comprising the following steps,

[0032] (1) polish and clean the ZnO substrate to make it a smooth ZnO substrate 1;

[0033] (2) mix 3g of PDMS with 0.3g of curing agent, add 10mL of ethyl acetate for dilution to obtain a polymer solution, and vacuum degas the polymer solution;

[0034] (3) spray a plurality of micro-droplets 2 on the ZnO substrate 1 through a spraying device (piezoelectric ceramic actuator 3 and micro-nozzle 4) as shown in Figure 1 , and the spraying time is about 1s, and the volume of each micro-droplet 2 is about 2μL; Figure 2

[0035] (4) as shown in Figure 2 (b), the plurality of micro-droplets 2 on the surface of the ZnO substrate 1 are arranged in order by an external electric field E to form a micro-droplet 2 array;​

[0036] (5) as shown in Figure 2 (c) using 10W 355nm ultraviolet light irradiation ZnO substrate 1 surface 3h, so that the microdroplets 2 on the surface of the ZnO substrate 1 on the ZnO substrate 1 gradually reduced contact angle, to the microdroplets 2 after the microlens shape stop irradiation, thereby obtaining a microlens array;

[0037] (6) as shown in Figure 2 (d) by constant temperature heating furnace, at 90℃ on the surface of the ZnO substrate 1 microlens array curing, curing time is about 1h. As shown in Figure 2 (e) after curing, using anhydrous ethanol ultrasonic cleaning microlens surface.

[0038] In other embodiments of the present application, the external field is a magnetic field.

[0039] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application, should be equivalent to the replacement method, all included in the protection scope of the present application.

Claims

1. A method for fabricating a microlens array, characterized in that: Includes the following steps, A substrate with a smooth surface was prepared using a material with variable wettability, wherein the material with variable wettability was ZnO. The polymer solution is sprayed onto the substrate to form multiple microdroplets. The polymer solution is prepared by mixing PDMS and curing agent and then diluting with ethyl acetate. The mass ratio of PDMS to curing agent is 10:1, and the volume ratio of PDMS to ethyl acetate is 1:

1. Multiple microdroplets on a substrate are positioned by an external field to form a microdroplet array; The microdroplets initially exhibit superhydrophobicity on the substrate, altering the wettability of the substrate and reducing the contact angle of each microdroplet with the substrate, thereby forming multiple microlenses on the substrate. The wettability of the substrate was altered by the following steps: the substrate was irradiated with ultraviolet light to change its wettability, causing the microdroplets on the substrate to take the shape of microlenses. The ultraviolet light irradiation time was 2.5-3.5 hours. Multiple microlenses are solidified to form a microlens array; The applied field is an electric field.

2. The method for fabricating a microlens array according to claim 1, characterized in that: The microlenses are cured by heating.

3. The method for fabricating a microlens array according to claim 2, characterized in that: The heating temperature is 90℃ and the heating time is 1 hour.

4. A method for fabricating a microlens array according to claim 1, characterized in that: After curing the microlens, the following steps are also included: The microlens was ultrasonically cleaned in anhydrous ethanol.

Images