NAK80 die steel surface pyramid-like micron structure and photoetching method thereof

Abstract

The invention discloses a near-pyramid micron structure on the surface of NAK80 die steel and a photoetching method of the near-pyramid micron structure. According to the method, firstly, a photoresist mask pattern is machined on the surface of NAK80 die steel through the photoetching technology, and then the NAK80 micro-die with the near-pyramid-shaped periodic array micron structure is obtained by regulating and controlling the components and the etching time of wet etching liquid. The micro-mold can be used for micro-imprinting processing of plastic products, and an inverted pyramid frame structure complementary with the mold is constructed on the surface of plastic. In the prior art, the pyramid-shaped periodic array structure is generally manufactured by photoetching a silicon template, but monocrystalline silicon is high in manufacturing cost, fragile in texture and poor in mechanical stability. The method has the advantages that the NAK80 micro-mold prepared through photoetching not only has a pyramid-shaped array microstructure similar to that obtained through wet etching of a silicon wafer, but also is low in price and high in mechanical stability; and meanwhile, the wet etching step is simple, the etching efficiency is high, and batch processing can be realized.

Description

Technical Field

[0001] The invention relates to the field of micron structure processing, and in particular to a near-pyramid-shaped micron structure on the surface of a NAK80 die steel and a photolithography method thereof. Background Art

[0002] Plastic, as a polymer material, has a high surface energy and often produces many adverse phenomena at the interface of plastic products, such as yogurt sticking to the lid, rainwater sticking to umbrellas, and dust sticking to fan blades, which affect the appearance or make them difficult to clean; ice forms in the freezer of refrigerators, causing inconvenience and power consumption; and plastic tableware is more difficult to clean than metal and ceramic tableware.

[0003] Inspired by the super-hydrophobic ability of lotus leaves, roses, water striders and other materials in nature, scientists discovered that their surfaces have unique micro-nano composite structures. Therefore, by constructing micro-nano composite structures, they make the material surface super-hydrophobic. However, the current super-hydrophobic surfaces have bottleneck problems such as easy damage to the structure and poor durability.

[0004] Studies have shown that a continuous inverted frame structure has better wear resistance and durability than the traditional continuous columnar microstructure. In the prior art, this inverted frame structure is prepared by photolithography of single crystal silicon to obtain a pyramid-shaped periodic array microstructure, and then micro-embossing on the surface of the substrate to obtain an inverted frame structure complementary to the mold. This is mainly due to the different atomic arrangement densities of single crystal silicon, and the anisotropy in wet etching, so etching can present a very regular periodically arranged pyramid-shaped microstructure. However, single crystal silicon is expensive and brittle, especially large-sized silicon molds are very easy to break during embossing, so it is not suitable for large-scale production.

[0005] Microstructures prepared by photolithography have the advantages of high precision and high efficiency. Literature research on photolithographic metals found that copper, aluminum, and some carbon steels can also be photoetched to obtain periodic array microstructures with high precision, and the prepared metal micro molds have better mechanical stability than silicon molds.

[0006] NAK80 plastic mold steel has good polishing performance, excellent carving performance, good discharge performance, and good etching performance. It is a widely used plastic mold steel that can be used in precision wrinkle plastic processing molds such as TV filter plates, fan blades, and cosmetic boxes. Therefore, how to construct a periodic array microstructure on the surface of NAK80 by photolithography as a mold to emboss a wear-resistant inverted frame structure on the plastic surface has important research significance and application value.

[0007] At present, there are few research reports on photolithography of NAK80 to obtain periodic array microstructures at home and abroad, and there are no relevant research results to refer to. Therefore, it is urgent to explore an efficient, economical and versatile photolithography method for preparing periodic array microstructures on the surface of NAK80 independent mold steel. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art and to provide a near-pyramid-shaped micron structure on the surface of NAK80 mold steel and a photolithography method thereof.

[0009] The present invention is achieved through the following technical solutions: A method for photolithography of a near-pyramid-shaped microstructure on a NAK80 die steel surface comprises the following steps: S100. Photolithography mask pattern design: designing a periodically arranged square pattern as a photolithography mask pattern; S200. Photolithography to prepare a photoresist mask: A pre-designed photoresist pattern is prepared on the surface of a NAK80 steel sheet by a photolithography method as a mask; S300. Wet etching: immerse the NAK80 covered with a square photoresist mask in a 1wt.% FeCl3+1wt.% HNO3 etching solution and etch for 25-30 min to obtain a NAK80 with a near-pyramid array microstructure covered with a photoresist mask; S400. Removing the photoresist mask: taking out the etched NAK80 from the etching solution, rinsing it with deionized water, and then ultrasonically treating it in an acetone solution for 7 minutes to remove the photoresist, thereby obtaining a NAK80 micro mold having a pyramid-type periodic array microstructure.

[0010] S500. Embossed plastic (as a verification of the effect): PP plastic is hot embossed using a NAK80 micro mold prepared by photolithography, and an inverted pyramid framework structure complementary to the mold is pressed on the plastic surface.

[0011] In step S100 , the photoresist mask pattern is periodically arranged squares with a side length of 60 μm and a spacing between adjacent squares of 10 μm.

[0012] In step S200, the thickness of the NAK80 steel sheet is 1-2 mm.

[0013] In step S200, the photolithography step uses AZ4620 positive photoresist to prepare the photoresist mask, which is spin-coated on the surface of NAK80 mold steel at a speed of 3000 rpm, with a spin coating thickness of 1.3 μm, an exposure energy of 50 J, and a development time of 60 s. In step S500, the temperature of hot stamping PP plastic is 125° C. and the pressure is 15 MPa.

[0014] By adopting the method of the present invention, a near-pyramid-shaped periodic array micrometer structure can be obtained on NAK80 die steel.

[0015] Compared with the prior art, the present invention has the following advantages and effects: Compared with the prior art, the advantages and beneficial effects of the patent of the present invention include: the NAK80 mold steel of this method is cheaper than silicon wafers, the wet etching process is simple, and no heating and magnetic stirring are required. In particular, the NAK80 mold steel has high structural stability and will not crack or break after repeated use. It is an efficient and reliable method for preparing near-pyramid periodic array microstructures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a NAK80 substrate covered with a periodic photoresist square mask; the side length (pitch) is a (b) = 60 (10); Figure 2 The scanning electron microscope micrographs of the NAK80 micro mold obtained by wet etching in 1wt.% HNO3 etchant are as follows: (a) low-magnification microstructure morphology; (b) local magnification of the microstructure; (c) cross-sectional view of the microstructure; (d) morphology of the plastic surface after embossing (Example 1); Figure 3 The scanning electron microscope micrographs of the NAK80 micromold with a pyramid array obtained by wet etching in a mixed etchant of 1wt.% HNO3+1%wt.% FeCl3: (a) low-magnification morphology of the pyramid microstructure; (b) local magnification of the microstructure; (c) cross-sectional view of the microstructure; (d) morphology of the plastic surface after embossing (Example 2). DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with specific embodiments.

[0018] The present invention discloses a method for photolithography of a near-pyramid-shaped micron structure on the surface of NAK80 mold steel. The technical solution of the present invention is further described in detail below in combination with two embodiments of different components of wet etchants and the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0019] Embodiment 1: S100. Photolithography mask pattern design: Design a periodically arranged square pattern as the photolithography mask pattern, with a side length of a = 60 μm and a spacing of b = 10 μm, as shown in the schematic diagram Figure 1 As shown; S200. Prepare photoresist mask by photolithography: Use AZ4620 positive photoresist and spin-coat it on the surface of 1mm thick NAK80 mold steel sheet at 3000rpm. The thickness of the spin-coated photoresist is 1.3μm, the exposure energy is 50J, and the development time is 60s. Prepare a pre-designed photoresist mask pattern, which is a square with a side length of 60μm and a spacing of 10μm. S300. Wet etching: The NAK80 covered with a square photoresist mask was immersed in a 1wt.% HNO3 solution at room temperature and etched for 40-50min to obtain a NAK80 micro mold with a columnar periodic array microstructure covered with a photoresist mask; S400. Removing the photoresist mask: The etched NAK80 is taken out from the etching solution, rinsed with deionized water, and then ultrasonically treated in an acetone solution for 7 minutes to remove the photoresist, thereby obtaining a NAK80 micro mold with a columnar periodic array microstructure, the morphology of which is as follows: Figure 2 (ac) shown.

[0020] S500. Embossed plastic (as a validation): NAK80 micro mold prepared by etching in 1wt.% HNO3 etchant was used to micro-emboss PP plastic, and an inverted frame structure complementary to the mold was pressed on the plastic surface. Figure 2 (d) shown.

[0021] The surface microstructure morphology of the NAK80 micro mold obtained by the steps in Example 1 (1wt.% HNO3 etchant) is similar to the surface microstructure morphology after plastic embossing. Figure 2 The columnar array microstructure obtained by etching with 1wt.% HNO3 has a wide spacing between the tops (about 56μm), and the spacing between the inverted frame microcavity structures obtained by imprinting plastic is wide (about 5μm).

[0022] Embodiment 2: The present embodiment 2 and the embodiment 1 use the same mask pattern, photolithography method and hot pressing method, the only difference is that the etchant in the wet etching step S300 is a 1wt.% HNO3+1wt.% FeCl3 mixed solution. The microstructure morphology of the NAK80 surface after photolithography in the embodiment 2 is as follows: Figure 3 As shown in (ac), the surface of the NAK80 micro mold presents a nearly pyramidal array microstructure, and the distance between the tops of adjacent micro structures is narrower (about 37 μm). The mold is used to emboss the plastic surface morphology as shown in Figure 3 As shown in (d), the spacing between the inverted pyramid microcavity structures on the plastic surface is narrower (about 1-2μm).

[0023] In the present invention, a NAK80 micro template is prepared by photolithography, and a near-pyramid microstructure is obtained on the surface, which has high dimensional accuracy, good structural stability, and can be reused. The NAK80 micro template is used to print and prepare a micrometer-scale inverted pyramid structure on a plastic surface, which has the characteristics of resistance to external force friction, low cost, high efficiency, and good formability.

[0024] In view of the current situation that the microstructure dimensional accuracy of metal molds used in plastic imprinting is not high and the mechanical stability of silicon molds is not high, the present invention prepares NAK80 mold steel with high dimensional accuracy and good mechanical stability through photolithography, effectively solving the difficulty of achieving high-precision, low-cost and repeated imprinting on plastics.

[0025] As described above, the present invention can be better implemented.

[0026] The implementation methods of the present invention are not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A photolithography method for forming a near-pyramid-shaped microstructure on the surface of NAK80 die steel, characterized in that: The following steps are involved: S100 photolithography mask pattern design: Design a periodically arranged square pattern as a photolithography mask pattern; Preparation of photoresist mask by S200 photolithography: A pre-designed photoresist pattern is prepared on the surface of NAK80 steel sheet by photolithography as a mask; S300 wet etching: immerse the NAK80 covered with a square photoresist mask in a 1wt.% FeCl3+1wt.% HNO3 etching solution and etch for 25-30 minutes to obtain a NAK80 with a pyramid array microstructure covered with a photoresist mask; S400: Removal of photoresist mask: The wet-etched NAK80 is taken out from the etching solution, rinsed with deionized water, and then ultrasonically treated in an acetone solution for 7 minutes to remove the photoresist, thereby obtaining a NAK80 micro mold with a pyramid-shaped periodic array microstructure; S500 Embossed Plastic: Polypropylene (PP) plastic is hot embossed using a NAK80 micro-mold made by photolithography, with an inverted pyramid framework structure complementary to the mold pressed onto the plastic surface.

2. The photolithography method for etching the near-pyramid-shaped microstructure on the surface of NAK80 mold steel according to claim 1, characterized in that: In step S100 , the photoresist mask pattern is periodically arranged squares with a side length of 60 μm and a spacing between adjacent squares of 10 μm.

3. The photolithography method for etching the near-pyramid-shaped microstructure on the surface of NAK80 mold steel according to claim 1, characterized in that: In step S200, the thickness of the NAK80 mold steel sheet is 1-2 mm.

4. The photolithography method for etching the near-pyramid-shaped microstructure on the surface of NAK80 mold steel according to claim 1, characterized in that: In step S200, AZ4620 positive photoresist is used in photolithography to prepare a photoresist mask.

5. The photolithography method for etching the near-pyramid-shaped microstructure on the surface of NAK80 mold steel according to claim 4, characterized in that: In step S200, AZ4620 positive photoresist is spin-coated on the surface of NAK80 at a speed of 3000 rpm, the spin-coating thickness is 1.3 μm, the exposure energy is 50 J, and the development time is 60 s.

6. The photolithography method for etching the near-pyramid-shaped microstructure on the surface of NAK80 mold steel according to claim 1, characterized in that: In step S500, the PP plastic hot stamping temperature is 125°C and the pressure is 15 MPa.

7. An inverted pyramid frame structure, characterized in that The method is obtained by using the light-emitting etching method described in any one of claims 1 to 6.

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