TWI843169B - Manufacturing method for microlens array - Google Patents

Abstract

A manufacturing method for microlens array includes steps as following. A grayscale digital photomask data corresponded to a microlens array pattern is provided. A transparent plate is provided. A light device is disposed below the transparent plate, the light device includes a light source and a light modulator. The light source is configured to emit a light. The light modulator is disposed on the path of the light and configured to reflect and modulate the light. A liquid photocurable resin is disposed on the top surface of the transparent plate. the light source is switched on, the emitted light would be reflected to the photocurable resin by the light modulator to form the microlens array pattern on the photocurable resin. The photocurable resin which is not cured is clean, and a microlens array is obtained.

Description

Method for manufacturing microlens array

A method for manufacturing a microstructure, in particular a method for manufacturing a microlens array.

Microlens array is one of the widely used microstructure components. It can be seen in different technology fields such as biomedicine, optoelectronics, information storage, communications and LEDs.

Microlens arrays are mostly manufactured based on soft lithography technology supplemented by different processes such as reflow, etching, extrusion, etc. This technology has many limitations in the process, such as high production costs and long process time, which makes it impossible to mass produce.

In recent years, DLP-based printing technology has gradually been used in high-precision 3D microstructures. The principle of DLP (Digital Light Process)-SLA (Stereolithography) 3D printing technology is to use computer numerical control of the projection of ultraviolet UV (Ultraviolet) light source to trigger local resin cross-linking reaction to form solidification. At present, the DMD chip in the DLP-SLA printer can achieve single-pixel size level solidification adjustment, but the microstructure produced by DLP technology still cannot meet the requirements of optical level.

Therefore, how to solve the above problems and identify the knowledgeable people in this field is worth considering.

In view of the above problems, the present invention proposes a method for manufacturing a microlens array, which is made by photocuring resin to produce a microlens array that meets the optical grade requirements. The specific technical means are as follows: A method for manufacturing a microlens array, including: S10: providing data corresponding to a grayscale digital mask, the grayscale digital mask corresponds to a microlens array pattern; S20: providing a transparent substrate; S30: setting an optical machine under the transparent substrate, the optical machine includes: a light source, suitable for emitting a light; and a light modulator, the light modulator is set in the path of the light, suitable for reflecting and modulating the light, The light is directed to the transparent substrate; S40; the light modulator is controlled according to the grayscale digital mask; S50: a liquid photocurable resin is disposed on an upper surface of the transparent substrate; S60: the light source is activated, and the light emitted by the light source is reflected by the light modulator and is directed to the photocurable resin to form the microlens array pattern on the photocurable resin; and S70: the uncured photocurable resin is removed to obtain a microlens array.

Wherein, step S40 also includes S41: a focusing lens is arranged between the light modulator and the transparent substrate so that the reflection focal point of the light passing through the focusing lens is not on the upper surface of the transparent substrate.

In the above-mentioned method for manufacturing a microlens array, in step S10, when the grayscale value range of the grayscale is distributed between 0 and 255, the grayscale value of the grayscale digital mask is between 50 and 200.

In the above-mentioned method for manufacturing a microlens array, step S40 further includes: S42: Setting the grayscale value and duration of the light source.

In the above-mentioned method for manufacturing a microlens array, in step S41, the distance between the focal point and the upper surface of the transparent substrate is greater than 0 μm and less than 3000 μm.

In the above-mentioned method for manufacturing a microlens array, in step S50, the photocurable resin also includes a photoinhibitor.

In the above-mentioned method for manufacturing the microlens array, the weight percent concentration of the light inhibitor is 0.4wt%.

In the above-mentioned method for manufacturing a microlens array, in step S70, alcohol and an air gun are used to remove the uncured photocurable resin.

In the above-mentioned method for manufacturing a microlens array, the light modulator is a digital microlens device.

In the above-mentioned method for manufacturing a microlens array, in step S70, the microlens array is a multi-focal length microlens array or a high filling factor microlens array.

S10~S70: Flowchart steps

110: Transparent substrate

120: Optical machine

121: Light source

1211: Light

122: Optical modulator

1221: Base plate

1222a~1222e: Microscope

1223:Microcontroller

123: Lens set

124: Prism

125: Focusing lens

126: Transparent workbench

130: Light-curing resin

131: Abandonment Department

132, 232a, 232b, 232c: microstructure

140: Microlens array

240: Multi-focal microlens array

300: Pattern

F, F’: focus position

H, H’: distance

A-A: Line

FIG1 shows the manufacturing method of the microlens array of the present invention.

Figure 2A shows a schematic diagram of a grayscale digital mask.

Figure 2B shows a schematic diagram of the projection pattern.

FIG2C is a schematic diagram of an optical modulator.

Figure 3A shows how to set the light.

Figure 3B shows a schematic diagram of the focal position.

Figure 4A shows a schematic diagram of the curing of a light-curing resin.

FIG4B is a schematic diagram of the photocurable resin being cleared and cured.

Figure 5 shows a schematic diagram of the optical machine setup.

Figure 6A shows the effect of defocus distance on surface roughness.

Figure 6B shows the effect of defocus distance on resolution.

FIG7A is a schematic diagram of a multi-focal microlens array.

Figure 7B shows the Z-axis height difference diagram of the multi-focal microlens array.

Figure 7C shows a schematic diagram of a microlens array with a high fill factor.

Please refer to FIG. 1, which shows the manufacturing method of the microlens array of the present invention. First, step S10 is performed to provide data corresponding to a grayscale digital mask, which corresponds to a microlens array pattern. Specifically, in a DLP (Direct Light Processing) photocuring 3D printer, the grayscale value of the digital mask is proportional to the exposure energy, and the exposure energy is proportional to the height of the microlens to be formed. Therefore, a digital mask with a grayscale value change, that is, a grayscale digital mask, can be designed to achieve the effect of forming a curved surface.

Please refer to FIG. 2A, which is a schematic diagram of a grayscale digital mask. In this embodiment, the grayscale digital mask is produced using the MATLAB software of MathWorks. The grayscale reduction formula is introduced into the code to produce the grayscale reduction effect, thereby producing the grayscale digital mask of FIG. 2A. The gray dots are the positions of the microlens structures. Among them, this code can also define the size, shape and grayscale value of the pattern in the digital mask.

Please refer back to Figure 1, and then proceed to step S20 to provide a transparent substrate. In this embodiment, glass is selected as the transparent substrate. Then, proceed to step S30 to set an optical machine under the transparent substrate. The optical machine includes a light source and a light modulator. Among them, the light source is suitable for emitting a light ray, and the light modulator is set on the path of the light ray. The light modulator is suitable for modulating the light ray and allowing the light ray to be emitted to the transparent substrate. The light modulator is, for example, a digital micromirror device (DMD), whose reflective surface is composed of multiple micro-mirrors, and the light reflection can be controlled by adjusting the angles of these mirrors.

Then proceed to step S40, controlling the light modulator according to the grayscale digital mask, that is, controlling the reflective surface of the light modulator (such as the reflection angle of multiple micro-mirrors) through the input grayscale digital mask data, so that after the light is reflected by the light modulator, it can form a corresponding micro-lens array pattern when irradiating the object.

Please refer to FIG. 2B and FIG. 2C. FIG. 2B is a schematic diagram of a projection pattern, and FIG. 2C is a schematic diagram of a light modulator. The data corresponding to the grayscale digital mask is a control instruction of the light modulator 122, which allows the light modulator 122 to control each micromirror. The light modulator 122 includes a base plate 1221, a plurality of micromirrors 1222a~1222e, and a microcontroller 1223. The micromirrors 1222a~1222e are arranged on the base plate 1221, and the angles of the micromirrors 1222a~1222e are controlled by the microcontroller 1223. The data corresponding to the grayscale digital mask is input into the microcontroller 1223 of the light modulator 122, so that the microcontroller 1223 controls the angles of the micromirrors 1222a~1222e according to the data corresponding to the grayscale digital mask. After the light 1211 is reflected by the micromirrors 1222a~1222e, the pattern 300 is formed.

In the pattern 300, the block with denser cross-section lines indicates a lower grayscale value, while the center point is a block with a higher grayscale value. A higher grayscale value means that more exposure energy is required. This is because the rotation angles of the microlenses 1222a, 1222b, 1222d, and 1222e reflect more light 1211 to the center of the pattern 300, and form a block with a higher grayscale value in the center of the pattern 300, while forming a block with a lower grayscale value in the periphery. It should be noted that the grayscale value distribution of the pattern 300 is only for illustration and does not represent the actual situation. In this embodiment, when the grayscale value range of the overall grayscale is distributed in the range of 0-255, the grayscale value of the pixel in the grayscale digital mask falls in the range of 50 to 200. Therefore, when the light 1211 is directed to the light modulator 122, it is reflected by the micro-mirrors 1222a-1222e at different angles, and a pattern 300 corresponding to a grayscale digital mask can be formed on the irradiated object (such as light-cured resin).

In other words, the grayscale digital mask referred to in the present invention is a pattern that is expected to be obtained after light projection, and is used to control the light modulator, which controls the light modulator to project the corresponding pattern after light reflection, thereby producing an effect similar to a mask. However, it should be noted that the grayscale digital mask referred to in the present invention is not a physical mask.

Please refer to FIG. 3A , which shows a method for setting light. In one embodiment, when performing step S40, steps S41 and S42 are also included. Among them, step S41 is to set a focusing lens between the light modulator and the transparent substrate so that the reflection focus position of the light passing through the focusing lens is not on the upper surface of the transparent substrate. The reason for doing so is that the gap between each micro-mirror on the DMD chip will produce a tiny dead space between the projected pixels, resulting in a micron-sized saw-tooth rough surface during the curing process. The inventor of this case has found that the light can be adjusted to irradiate the light-curing resin in a defocused state. This method may be called a defocusing method, thereby modifying the microstructure surface formed by curing to have a lower surface roughness. In this embodiment, the focus of the light is controlled through a focusing lens to achieve a defocusing effect.

Specifically, please refer to FIG. 3B , which is a schematic diagram of the focal position. The photocurable resin 130 is disposed on the upper surface 111 of the transparent substrate 110 , and the photocurable resin 130 is irradiated by the light 1211 at the portion in contact with the upper surface 111 , so that the focal position of the light 1121 does not fall on the upper surface 111 of the transparent substrate 110 , that is, the focal position of the light 1211 does not fall on the position where the photocurable resin 130 is irradiated by the light 1211 , thereby achieving a defocusing effect.

For example, in FIG. 3B , the focus of the light 1211 can be set at a focus position F below the upper surface or a focus position F' above the upper surface, wherein the distance between the focus position F and the upper surface 111 is H, and the distance between the focus position F' and the upper surface 111 is H'. In one embodiment, the distance H or H' is greater than 0 μm and less than or equal to 3000 μm. By setting the defocus method, the surface roughness of the photocurable resin after curing can be effectively reduced.

Step S42 is to set the grayscale value and duration. It should be noted that the grayscale value multiplied by the duration equals the exposure energy. Therefore, in step S42, the output energy of the light source is controlled, and different exposure energies determine the height and diameter of the photocurable resin after curing.

Please refer back to Figure 1. After the light source is set, step S50 is performed to set a liquid photocurable resin on the upper surface of the transparent substrate. The photocurable resin is a high molecular polymer that will solidify into a solid after being irradiated with a specific wavelength. In one embodiment, a photoinhibitor is also added to the photocurable resin set in step S50, and the added weight percentage concentration is 0.4wt%. The addition of the photoinhibitor makes the photocurable resin more suitable for making optical components. Specifically, this embodiment uses the transparent resin Durable developed by Fanyi Technology, and an additional 0.4wt% photoinhibitor is added. Its maximum tensile strength is 45MPa, the maximum elongation is 60%, the tensile modulus is 1.6GPa, and the Schroeder hardness is 83.

After the photocurable resin is placed on the transparent substrate, step S60 is performed to start the light source, and the light emitted by the light source is reflected by the light modulator and injected into the photocurable resin. At this time, the photocurable resin is irradiated by the light, and the irradiated part will begin to cure to form the microlens array on the photocurable resin.

Since the light is reflected by the light modulator, a microlens array pattern is formed on the photocurable resin (such as the pattern in Figure 2A), so the photocurable resin will not be completely cured, only the irradiated part will be cured, and it will be cured into different heights, diameters and shapes according to the different exposure energy. Next, step S70 is performed to remove the uncured photocurable resin to obtain a microlens array. For example, alcohol and air gun are used to remove liquid photocurable resin, and the cured photocurable resin that has not been washed away is left on the transparent substrate, which is to form a microlens array.

Please refer to FIG. 4A , which is a schematic diagram of curing of a photocurable resin. The photocurable resin 130 is disposed on the transparent substrate 110 , and the modulated light 1211 passes through the transparent substrate 110 from below to irradiate the photocurable resin 130 . At this time, the irradiated photocurable resin 130 will be cured to form a plurality of microstructures 132 , while the discarded portion 131 that is not irradiated will remain in a liquid state.

Next, please refer to FIG. 4B , which is a schematic diagram of removing the uncured light-cured resin. Then, the discarded portion 131 is removed, for example, using alcohol and an air gun to remove the discarded portion 131. The cured microstructure 132 is adhered to the transparent substrate 110 and therefore will not be removed. Afterwards, the multiple microstructures 132 remaining on the transparent substrate 110 form a microlens array 140.

Please refer to FIG. 5 , which is a schematic diagram of the optical machine configuration. The optical machine 120 is disposed below the transparent substrate 110. A photocurable resin 130 is disposed on the transparent substrate 110. The optical machine 120 includes a light source 121, a lens assembly 123, a prism 124, a light modulator 122, a focusing lens 125, and a transparent workbench 126. The light 1211 emitted by the light source 121 passes through the lens assembly 123 and the prism 124 in sequence, and then contacts the light modulator 122. The lens assembly 123 is suitable for refracting the light 1211 emitted by the light source 121 and making the light 1211 approach parallel light, while the prism 124 is suitable for changing the optical path of the light 1211 so that the light 1211 is directed toward the reflective surface of the light modulator 122. The light modulator 122 is a DMD chip, which is suitable for modulating the light 1211 into a projection pattern corresponding to a grayscale digital mask. The focusing lens 125 is arranged between the light modulator and the transparent substrate 110, and is suitable for adjusting the focus of the light reflected by the light modulator 122 so that the reflection focus position of the light passing through the focusing lens is not on the upper surface of the transparent substrate. The transparent workbench 126 is arranged above the focusing lens 125 to carry the transparent substrate 110.

Through the setting of the optical machine 120, the above steps S10~S70 can be used to complete the production of the microlens array. The optical machine 120 can be a DLP light-curing 3D printer. In this embodiment, the optical machine 120 is a high-precision 3D printer U-light produced by Fanyi Technology. After experiments, the manufacturing method of the microlens array of the present invention uses the defocusing method and light-curing method to make the microlens array, which can effectively reduce the surface roughness of the microlens array and improve its resolution. The results of the experiment will be described below.

Please refer to Figure 6A, which shows the effect of defocus distance on surface roughness. The defocus distance is equivalent to the distance H or H' in Figure 3B, that is, the distance between the light focus and the upper surface of the transparent substrate, and the surface roughness is the surface roughness of the microstructure when the microlens array is formed. As can be seen from Figure 6A, when the defocus distance is 0 (i.e., no defocus), the surface roughness is about 0.55μm. As the defocus distance increases, the surface roughness gradually decreases. When the defocus distance reaches 3000μm, the surface roughness can reach 0.1μm (100nm), which is significantly lower than the surface roughness without defocus distance.

Next, please refer to FIG. 6B, which shows the effect of defocus distance on resolution. As can be seen from FIG. 6B, when the defocus distance is 0, the resolution is 0 lp/mm, and when the defocus distance reaches about 1500μm, the resolution rises to about 47 lp/mm. When the defocus distance is between 1500μm and 3000μm, the resolution falls between 30~45 lp/mm, and there is no continuous improvement. However, it can still be seen that compared with no defocus distance, the resolution is significantly improved before the defocus distance is 1500μm. It can be seen that the manufacturing method of the microlens array of the present invention can produce a microlens array of better quality.

Please refer to FIG. 7A to FIG. 7C. FIG. 7A is a schematic diagram of a multi-focal microlens array, FIG. 7B is a Z-axis height difference diagram of a multi-focal microlens array, and FIG. 7C is a schematic diagram of a microlens array with a high filling factor. FIG. 7B is a Z-axis height difference diagram of line A-A in FIG. 7A. By changing the configuration of the grayscale value in the grayscale digital mask, the manufacturing method of the microlens array of the present invention can also manufacture a multi-focal microlens array 240 and a microlens array with a high filling factor. It can be seen from FIG. 7A and FIG. 7B that the multi-focal microlens array 240 includes a plurality of microstructures 232a, 232b, and 232c with different heights. Figure 7C shows a microlens array with a fill factor of 77.98%.

The manufacturing method of the microlens array of the present invention uses photocuring to manufacture the microstructure of the microlens array, which can produce a microlens array with lower surface roughness and higher resolution, and can meet the low surface roughness requirements of optical components.

The invention is described above, but it is not intended to limit the scope of the patent rights claimed by this creation. The scope of patent protection shall be determined by the scope of the patent application attached hereto and its equivalent field. Any changes or modifications made by those with common knowledge in this field without departing from the spirit or scope of this patent shall be considered as equivalent changes or designs completed under the spirit disclosed by this creation, and shall be included in the scope of the patent application described below.

S10~S70: Flowchart steps

Claims (9)

A method for manufacturing a microlens array includes: S10: providing data corresponding to a grayscale digital mask, the grayscale digital mask corresponding to a microlens array pattern; S20: providing a transparent substrate; S30: setting an optical machine under the transparent substrate, the optical machine including: a light source, suitable for emitting a light; and a light modulator, the light modulator is set in the path of the light, suitable for reflecting and modulating the light, so that the light is emitted to the transparent substrate; S40; controlling the light modulator according to the grayscale digital mask; S50: A liquid photocurable resin is disposed on an upper surface of a transparent substrate; S60: the light source is activated, and the light emitted by the light source is reflected by the light modulator and injected into the photocurable resin to form the microlens array pattern on the photocurable resin; and S70: the uncured photocurable resin is removed to obtain a microlens array; wherein step S40 further includes S41: a focusing lens is disposed between the light modulator and the transparent substrate, so that the reflection focus position of the light passing through the focusing lens is not on the upper surface of the transparent substrate. The manufacturing method of the microlens array as described in claim 1, wherein, in step S10, when the grayscale value range of the grayscale is distributed between 0 and 255, the grayscale value of the grayscale digital mask is between 50 and 200. The manufacturing method of the microlens array as described in claim 1, wherein step S40 further includes: S42: setting the grayscale value and duration of the light source. The method for manufacturing a microlens array as described in claim 1, wherein, in step S41, the distance between the focal point and the upper surface of the transparent substrate is greater than 0 μm and less than or equal to 3000 μm. The method for manufacturing a microlens array as described in claim 1, wherein in step S50, the photocurable resin further includes a photoinhibitor. A method for manufacturing a microlens array as described in claim 5, wherein the weight percent concentration of the light inhibitor is 0.4wt%. The method for manufacturing a microlens array as described in claim 1, wherein in step S70, alcohol and an air gun are used to remove the uncured photocurable resin. A method for manufacturing a microlens array as described in claim 1, wherein the light modulator is a digital microlens device. The method for manufacturing a microlens array as described in claim 1, wherein in step S70, the microlens array is a multi-focal length microlens array or a high filling factor microlens array.

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