A high-precision 3D relief pattern preparation method with color-changing effect

Abstract

The application discloses a high-precision 3D relief pattern preparation method with a color change effect, and comprises the following steps: step 1, cleaning the surface of a glass substrate by using a cleaning solution; step 2, spin coating a photoresist onto the surface of the cleaned glass substrate; step 3, combining a low-frequency sawtooth grating and a high-frequency blazed grating into a grayscale image, and importing the grayscale image into a laser direct writing device; step 4, etching the photoresist by using the laser direct writing device; step 5, developing the etched sample; and step 6, plating a metal thin film on the surface of the developed sample. The color change 3D relief pattern prepared by the method has high micro-nano structure morphology precision, obvious three-dimensional effect, color change effect under different viewing angles, and uniform color change. The preparation method is pollution-free to the environment and is a green preparation method.

Description

Technical Field

[0001] This invention relates to the field of photolithography, specifically to a method for preparing high-precision 3D relief patterns with color-changing effects. Background Technology

[0002] Color-changing anti-counterfeiting technology has great application prospects in tobacco, wine and currency industries, and therefore has received widespread attention from industry and academia. Ink color-changing has always been the mainstream technology for color-changing anti-counterfeiting.

[0003] Currently, inks used for color-changing anti-counterfeiting mainly include thermosensitive inks, optically variable inks, humidity-sensitive inks, and pressure-sensitive inks. For example, Chinese patent application CN108460444A discloses the use of thermosensitive ink to prepare QR code anti-counterfeiting labels. These labels are colorless and transparent at room temperature, but display color when heated. Chinese patent application CN101070040A discloses the use of optically variable ink to prepare patterned security devices, and in the embodiments, applies optically variable ink to banknote anti-counterfeiting. Chinese patents (CN 202677720U) and (CN213082551U) respectively use humidity-sensitive ink to prepare anti-counterfeiting labels and tags, which can display anti-counterfeiting information under different humidity conditions, thus quickly identifying authenticity. Chinese patent application CN103318523A discloses the placement of pressure-sensitive ink under a bottle cap to prepare an anti-counterfeiting bottle cap with a hidden mark. When the bottle cap is twisted down, the pressure-sensitive ink is compressed, and the transparent mark gradually appears.

[0004] All of the above methods use color-changing ink to achieve the purpose of anti-counterfeiting. However, color-changing ink will generate harmful gases and wastewater during production and use, posing a potential pollution hazard to the environment. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, this invention proposes a method for preparing high-precision 3D relief patterns with color-changing effects, which can replace ink dyes and eliminate the environmental pollution problems (harmful gases and harmful wastewater) caused by ink dyes during production and use.

[0006] One aspect of the present invention provides a method for preparing a high-precision 3D relief pattern with a color-changing effect, comprising the following steps: Step 1: Clean the surface of the glass substrate with a cleaning solution; Step 2: Spin-coat the photoresist onto the cleaned glass substrate surface; Step 3: Combine the low-frequency sawtooth grating and the high-frequency blazed grating to form a grayscale image, and import the grayscale image into the laser direct writing device; Step 4: Etch the photoresist using the laser direct writing equipment; Step 5: Develop the etched sample; and Step 6: Deposit a thin metal film on the surface of the developed sample.

[0007] Preferably, in step 2, the photoresist is S1818, the spin coating speed is 2000~4000rpm, and the photoresist thickness is 2~4μm.

[0008] Preferably, in step 3, the low-frequency sawtooth grating has a right-angled triangle structure with a height of 1~2μm, and the structure width is variable in the same relief pattern, ranging from 5~300μm.

[0009] Preferably, in step 3, the structure of the high-frequency blazed grating is an isosceles triangle with a height of 0.4~0.8μm and an aspect ratio of 1~2. The width is fixed within the same relief pattern, and the center-to-center spacing of the high-frequency blazed grating structure is the same as its structural width.

[0010] Preferably, in step 3, the regions of the low-frequency sawtooth grating and the regions of the high-frequency blazed grating are arranged alternately in the horizontal and vertical directions to form the grayscale image.

[0011] Preferably, in step 3, the area ratio of the regions of the plurality of low-frequency sawtooth gratings to the regions of the plurality of high-frequency blazed gratings is 1:1.

[0012] Preferably, the etching rate of the laser direct writing device is 50~400mm / s, the laser power is 1000~2000μW, the laser frequency is 200~500KHz, and the spot diameter is 0.2~1.2μm.

[0013] Preferably, in step 5, the developer is AZ400K, the developer concentration is 10%~30%, and the development time is 20~80s.

[0014] Preferably, in step 6, the substrate of the metal film is one or more of the elemental metals gold, silver, aluminum, nickel and cadmium, or one or more of the compound materials of gold, silver, aluminum, nickel and cadmium.

[0015] Another aspect of the present invention provides a 3D embossed pattern with a high-precision color-changing effect, wherein the 3D embossed pattern is prepared by the aforementioned preparation method.

[0016] The beneficial effects of this invention are: This invention effectively combines sawtooth grating microstructures and high-frequency blazed grating microstructures, and fabricates 3D embossed patterns with color-changing effects through laser direct writing technology. The color-changing 3D embossed patterns prepared by this invention exhibit high precision in micro / nano structural morphology, a significant three-dimensional effect, and a uniform color-changing effect when viewed from different angles. Furthermore, the preparation method of this invention poses no environmental pollution risks and is a green preparation method. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 This is a flowchart illustrating the preparation process of a 3D relief pattern with high-precision color-changing effect according to Embodiment 1 of the present invention. Figure 2 This is a top view of the 3D relief pattern (conch) in Embodiment 1 of the present invention; Figure 3 This is a color comparison image of the same 3D relief pattern (conch) from different perspectives in Embodiment 1 of the present invention; Figure 4 The images show color comparisons of two 3D relief patterns (conch shells) with different frequencies from the same viewing angle. (A) is a schematic diagram of the 3D relief pattern (conch shell) of Example 1, and (B) is a schematic diagram of the 3D relief pattern (conch shell) of Example 2. Figure 5 The image shows the actual arrangement of low-frequency sawtooth grating and high-frequency blazing grating of the 3D relief pattern (conch) in Embodiment 1 of the present invention, wherein (A) is the laser confocal three-dimensional display mode, (B) is the laser + color display mode, and (C) is an enlarged image of the dotted part of (A). Figure 6 This is a schematic diagram of the 3D relief pattern (conch) in Embodiment 1 of the present invention, wherein (A) is an overall structural diagram, and (B) and (C) are partial structural diagrams.

[0018] In the diagram: 101-Beaker, 102-Cleaning solution, 103-Glass substrate, 104-Dropper, 105-Photoresist droplet, 106-Computer, 107-Laser direct writing equipment, 108-Photoresist film before exposure, 109-Developer, 110-Photoresist film before exposure, 111-Metal coating. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The present invention provides a method for preparing high-precision 3D relief patterns with color-changing effects. This method combines low-frequency sawtooth gratings and high-frequency blazed grating structures to produce 3D relief patterns with distinct three-dimensional structures. These relief patterns exhibit color-changing functionality, and the color change is uniform. Furthermore, the preparation method of the present invention is green, environmentally friendly, and pollution-free.

[0021] In the high-precision 3D embossed pattern preparation method with color-changing effect of the present invention, a low-frequency sawtooth grating enables the embossed pattern to have a significant three-dimensional effect, a high-frequency blazing grating enables the embossed pattern to display color, and a metal coating enhances the color effect of the embossed pattern. The present invention achieves the display of a color-changing 3D embossed pattern by combining a low-frequency sawtooth grating and a high-frequency blazing grating with laser direct writing and metal coating processes.

[0022] This invention provides a method for preparing a high-precision 3D relief pattern with a color-changing effect, the method comprising the following steps: Step 1: Clean the surface of the glass substrate with a cleaning solution. Preferably, acetone, alcohol, and deionized water are used to clean the substrate in sequence.

[0023] Step 2: Spin-coat the photoresist onto the cleaned glass substrate surface. In this step, S1818 photoresist is preferred, as it exhibits excellent performance when the film thickness is between 2 and 4 μm. Preferably, the spin-coating speed is 2000-4000 rpm, and the photoresist thickness is 2-4 μm.

[0024] Step 3: Combine multiple low-frequency sawtooth gratings and multiple high-frequency blazed gratings to form a grayscale image, and import the grayscale image into a laser direct writing device.

[0025] In a preferred embodiment of the present invention, the high-frequency blazed grating is an isosceles triangle with a height of 0.4~0.8μm (e.g., the height can be 0.4μm, 0.5μm, 0.6μm, 0.7μm, or 0.8μm). The aspect ratio of the high-frequency blazed grating is 1~2 (e.g., the aspect ratio can be 1, 1.5, or 2), and the width cannot be changed within the same relief pattern. The center-to-center spacing of the grating structure is the same as its structural width (width of the isosceles triangle). The high-frequency isosceles triangle imparts color to the relief structure through diffraction. The grating diffraction formula is... Where d is the grating constant, The diffraction angle, Let m be the incident angle and m be the diffraction order. The wavelength of light; by adjusting the height and width of the isosceles triangle, the wavelength can be changed. and With m constant, As the color changes, the color of the relief structure also changes, thus achieving a color-changing effect.

[0026] Furthermore, in a preferred embodiment of the present invention, the low-frequency sawtooth grating structure is an isosceles triangle with a height of 1~2μm. The structure width is variable within the same relief pattern, ranging from 5 to 300μm. The principle behind the low-frequency sawtooth grating's ability to create a distinct three-dimensional effect in the relief pattern is the contrast between light and shadow. When light shines on the right-angled triangular micro-pattern, areas of varying brightness are created. The longer the hypotenuse of the right-angled triangle, the gentler the slope formed by the hypotenuse and base, resulting in more light reflected into the human eye, making that area brighter; conversely, the area is darker. This contrast between light and shadow creates a 3D effect in the human eye, with bright areas appearing as convex and dark areas as concave. Brighter areas have longer hypotenuses and longer triangle periods; conversely, darker areas have shorter periods.

[0027] Furthermore, in a preferred embodiment of the present invention, the low-frequency sawtooth grating region and the high-frequency blazed grating region are arranged alternately in the horizontal and vertical directions to form the grayscale image. In this arrangement, the ratio of the area of ​​the low-frequency sawtooth grating region to the area of ​​the high-frequency blazed grating region is 1:1, that is, the area of ​​the low-frequency sawtooth grating region is the same as the area of ​​the high-frequency blazed grating region.

[0028] Step 4: Use a laser direct writing device to etch the photoresist.

[0029] In a preferred embodiment of the present invention, the etching rate of the laser direct writing device is 50~400 mm / s (e.g., 50 mm / s, 100 mm / s, 150 mm / s, 200 mm / s, 250 mm / s, 300 mm / s, 350 mm / s, 400 mm / s). Under the same conditions, the smaller the etching rate of the laser direct writing device, the finer the etched structure, but the slower the speed; the larger the etching rate, the faster the etching speed, but the coarser the structure.

[0030] In the preferred embodiment of the high-precision 3D relief pattern preparation method with color-changing effect of the present invention, the laser power of the laser direct writing device is 1000~2000 μW (e.g., 1000 μW, 1250 μW, 1500 μW, 1750 μW, 2000 μW). Under the same conditions, the lower the laser power, the shallower the etching depth, that is, the smaller the height value of the isosceles triangle; the higher the laser power, the larger the height value of the etched pattern.

[0031] Preferably, the laser spot diameter of the laser direct writing device is 0.2~1.2μm (e.g. 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm). The smaller the spot diameter, the finer the etched structure, but the slower the speed; the larger the spot diameter, the faster the etching speed, but the coarser the structure.

[0032] Step 5: Develop the etched sample.

[0033] In a preferred embodiment of the present invention, the concentration of the developer is 10% to 30% (e.g., 10%, 15%, 20%, 25%, 30%). If the concentration of the developer is too low, the photoresist after exposure cannot be fully removed, and the prepared 3D relief cannot show the full picture. If the concentration of the developer is too high, too much photoresist will be removed, damaging the morphology of the 3D relief.

[0034] In a preferred embodiment of the present invention, the development time is 20~80s (e.g., 20s, 30s, 40s, 50s, 60s, 70s, 80s). If the development time is too short, the developing solution cannot fully remove the photoresist after exposure, and the prepared 3D relief cannot show the full picture. If the development time is too long, the developing solution will easily remove too much photoresist, damaging the morphology of the 3D relief.

[0035] Step 6: Deposit a metal thin film onto the surface of the developed sample to form the 3D relief pattern. In this step, the substrate of the metal thin film is one or more of the elemental metals gold, silver, aluminum, nickel, and cadmium, or one or more of the compound materials of gold, silver, aluminum, nickel, and cadmium.

[0036] Example 1

[0037] The following is combined Figure 1-3 Sections 5-6 provide a detailed description of Embodiment 1 of the present invention. Figure 1 This is a flowchart illustrating the preparation process of a high-precision 3D relief pattern with color-changing effect according to Embodiment 1 of the present invention. Figure 1 As shown, the preparation method of Example 1 includes the following steps: S1. Pour 50 ml of acetone (washing solution 102) into beaker 101 to remove organic impurities from the surface of the 2-inch glass substrate 103; discard the acetone solution, then pour 40 ml of alcohol (washing solution 102) into beaker 101 to remove any remaining acetone from the surface of the glass substrate 103; discard the alcohol solution, then pour 60 ml of deionized water (washing solution 102) into beaker 101 to remove any remaining alcohol from the surface of the glass substrate 103. After cleaning, dry the glass substrate 103 with nitrogen (N2). S2. Use dropper 104 to transfer S1818 photoresist 105 to glass substrate 103, turn on spin coater, set spin coat speed to 2000 rpm, spin coat time to 35s; S3. Import the grayscale image composed of the low-frequency sawtooth grating and the high-frequency blazed grating into the computer host 105. The high-frequency blazed grating has an isosceles triangle structure with a height of 0.5 μm, a base length of 1 μm, and a center-to-center distance of 1 μm. The low-frequency sawtooth grating has a right-angled triangle structure with a height of 1.55 μm and a width (base length) of 5–300 μm. In other words, the width of the low-frequency sawtooth grating in different areas of the same relief pattern can be varied.

[0038] S4. Photoresist is exposed using a laser direct writing device. The laser power of the direct writing device is set to 1.25mW, the spot size to 0.6μm, and the laser frequency to 500KHz. S5. Place the exposed photoresist sample in the developer solution with a concentration of 20% and a development time of 30 seconds; S6. After developing the photoresist sample, a metal coating is applied to it. The coating metal is aluminum and the coating thickness is 100nm, thereby preparing a 3D relief pattern (conch) with high-precision color-changing effect.

[0039] Figure 2 This is a top view of the actual 3D relief pattern (conch shell) in Embodiment 1 of the present invention. Figure 2 As shown, under natural light conditions and when viewed from above, the 3D relief pattern appears colorless and transparent. Figure 3 These are real-life images of the same 3D relief pattern (conch shell) under natural light conditions and from different viewing angles. Figure 3 It can be clearly seen that the 3D relief pattern has color when viewed from three different angles; secondly, the color of the 3D relief pattern is different when viewed from different angles, (a) it is blue-green, (b) it is milky white, and (c) it is orange-red, thus having a color-changing effect.

[0040] As mentioned above Figure 2 and Figure 3 As shown, the relief pattern (conch) prepared in Embodiment 1 of the present invention has a significant 3D effect, presents a bright color, and presents different colors under different viewing angles, exhibiting a color-changing effect.

[0041] like Figure 5 The image shown is a physical image of the arrangement of low-frequency and high-frequency gratings in the 3D relief pattern (conch) in Embodiment 1 of the present invention. (A) is a laser confocal three-dimensional display mode, (B) is a laser + color display mode, and (C) is an enlarged image of the dotted line part in (A), which presents the measured curve morphology of the low-frequency sawtooth grating and the high-frequency blazed grating. Figure 5In the image, 51 represents a low-frequency sawtooth grating region, and 52 represents a high-frequency blazed grating region. The low-frequency sawtooth grating region 51 and the high-frequency blazed grating region 52 are arranged alternately in the horizontal and vertical directions to form the grayscale image. In this arrangement, the area ratio of the low-frequency sawtooth grating region 51 to the area of ​​the high-frequency blazed grating region 52 is 1:1. This arrangement has the advantage of ensuring both good 3D effects and vibrant colors.

[0042] Figure 6 This is a schematic diagram of the 3D relief pattern (conch) in Embodiment 1 of the present invention, wherein (A) is an overall structural diagram, and (B) and (C) are partial structural diagrams. Figure 6 (B) in the image presents the structure of the 3D relief recess. Figure 6 (C) in the image presents the structure of the 3D relief protrusion, and Figure 6 (B) and Figure 6 (C) clearly shows the different period lengths of the low-frequency grating in different design areas.

[0043] Example 2

[0044] This embodiment provides a method for preparing a high-precision 3D relief pattern with a color-changing effect, including the following steps: S1. Pour 40 ml of acetone (washing solution 102) into beaker 101 to remove organic impurities from the surface of the 2-inch glass substrate 103; discard the acetone solution, then pour 30 ml of alcohol (washing solution 102) into beaker 101 to remove any remaining acetone from the surface of the glass substrate 103; discard the alcohol solution, then pour 80 ml of deionized water (washing solution 102) into beaker 101 to remove any remaining alcohol from the surface of the glass substrate 103. After cleaning, dry the glass substrate 103 with nitrogen (N2). S2. Use dropper 104 to transfer S1818 photoresist 105 onto the glass substrate, turn on the spin coater, set the spin coater speed to 2500 rpm and the spin coater time to 30s; S3. Import the grayscale image composed of the sawtooth grating and the high-frequency blazed grating into the computer host 105. The high-frequency blazed grating is an isosceles triangle with a height of 0.5μm, a base length of 1.18μm, and a center-to-center distance of 1.18μm. The low-frequency sawtooth grating is also an isosceles triangle with a height of 1.55μm and a structural width (base length) of 5~300μm. In other words, the width of the low-frequency sawtooth grating in different areas of the same relief pattern can vary.

[0045] S4. Photoresist is exposed using a laser direct writing device. The laser power of the direct writing device is set to 1.25mW, the spot size to 0.6μm, and the laser frequency to 500KHz. S5. Place the exposed photoresist sample in the developer solution with a concentration of 20% and a development time of 30 seconds; S6. After developing the photoresist sample, a metal coating is applied to it. The coating metal is aluminum, and the coating thickness is 100 nm. The relief pattern (conch) prepared in Example 2 is as follows: Figure 4 As shown in (B), it has a clear 3D effect and also presents vibrant colors. When viewed from the same viewing angle, the colors presented in this embodiment 2 are similar to... Figure 4 The color of the relief pattern in Example 1 (A) is different. It can be seen that in Example 2, by changing the width of the high-frequency blazed grating, the color of the prepared relief pattern can be changed accordingly. That is, when the width of the high-frequency blazed grating is different, the prepared relief pattern presents different colors under the same viewing angle.

[0046] Compare with Example 1 The difference between this comparative example and Example 1 is that a high-frequency blazed grating is not used in step S3, but a high-frequency block grating is used instead. The other steps and methods are the same as in Example 1, and will not be repeated here.

[0047] The relief pattern (conch) prepared in Comparative Example 1 has a clear 3D effect, but does not show color.

[0048] Compare with Example 2 The difference between this comparative example and Example 1 is that a high-frequency blazed grating is not used in step S3, but a high-frequency sin grating is used instead. The other steps and methods are the same as in Example 1, and will not be repeated here.

[0049] The relief pattern (conch) prepared in Comparative Example 2 has a clear 3D effect and also presents color, but the color difference uniformity is not good and it is rather messy.

[0050] In summary, the high-precision 3D relief pattern preparation method with color-changing effect provided by this invention combines low-frequency sawtooth grating and high-frequency blazed grating structures in its design, and integrates laser direct writing and metal coating processes in its fabrication. The resulting high-precision 3D relief pattern exhibits a distinct three-dimensional effect. This invention displays a color-changing effect from different viewing angles, with uniform color change and no risk of fading. Furthermore, the preparation method of this invention poses no environmental pollution risks and is a green preparation method.

[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, which is defined by the claims and their equivalents.

Claims

1. A method for preparing a high-precision 3D relief pattern with a color-changing effect, characterized in that, The method includes the following steps: Step 1: Clean the surface of the glass substrate with a cleaning solution; Step 2: Spin-coat the photoresist onto the cleaned glass substrate surface; Step 3: Combine the low-frequency sawtooth grating and the high-frequency blazed grating to form a grayscale image, and import the grayscale image into a laser direct writing device; wherein, the regions of the low-frequency sawtooth grating and the regions of the high-frequency blazed grating are arranged alternately in the horizontal and vertical directions to form the grayscale image; the structure of the low-frequency sawtooth grating is a right-angled triangle, and the width of the structure can be varied within the same relief pattern; the structure of the high-frequency blazed grating is an isosceles triangle, and the width of the structure cannot be varied within the same relief pattern; Step 4: Etch the photoresist using the laser direct writing equipment; Step 5: Develop the etched sample; and Step 6: Deposit a thin metal film on the surface of the developed sample to form the 3D relief pattern.

2. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, In step 2, the photoresist is S1818, the spin coating speed is 2000~4000rpm, and the photoresist thickness is 2~4μm.

3. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, In step 3, the structural height of the low-frequency sawtooth grating is 1~2μm, and the structural width varies from 5~300μm in the same relief pattern.

4. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, In step 3, the height of the high-frequency blazed grating is 0.4~0.8μm, the aspect ratio is 1~2, and the center-to-center spacing of the high-frequency blazed grating structure is the same as its structural width.

5. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 4, characterized in that, In step 3, the area ratio of the regions of the multiple low-frequency sawtooth gratings to the regions of the multiple high-frequency blazed gratings is 1:

1.

6. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, The etching rate of the laser direct writing device is 50~400mm / s, the laser power is 1000~2000μW, the laser frequency is 200~500KHz, and the spot diameter is 0.2~1.2μm.

7. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, In step 5, the developer is AZ400K, the developer concentration is 10%~30%, and the development time is 20~80s.

8. The method for preparing a high-precision 3D relief pattern with color-changing effect according to claim 1, characterized in that, In step 6, the substrate of the metal film is one or more of the elemental metals gold, silver, aluminum, nickel and cadmium, or one or more of the compound materials of gold, silver, aluminum, nickel and cadmium.

9. A 3D relief pattern with high-precision color-changing effect, characterized in that, The 3D relief pattern is prepared by the preparation method according to any one of claims 1 to 8.

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