Colorful structural plastic part and preparation process thereof

Abstract

The preparation technology comprises the following steps that S1, at least two stacked micro-nano structure layers are sequentially machined in a mold cavity, at least one micro-nano structure layer is a colorful pattern layer formed through laser photoetching or mechanical carving, and the colorful pattern layer is a transparent pattern layer formed through laser photoetching or mechanical carving; the colorful pattern layer presents an optical diffraction or refraction colorful effect at a specific incident angle; s2, a transparent or semitransparent plastic material is injected into the mold cavity, demolding is conducted after injection molding, a plastic part with at least two layers of overlapped patterns on the surface is obtained, and the surface patterns of the plastic part are complementary with the shape of the micro-nano structure layer; at least one layer in the superposed pattern is a colorful pattern layer, and the other layer is another colorful pattern layer or a non-colorful texture layer. The colorful structural plastic part prepared by the process disclosed by the invention realizes a multi-layer and multi-angle composite optical effect, and has a high anti-counterfeiting function at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding, and in particular to a colorful structural plastic part and a preparation process thereof. Background Art

[0002] In recent years, the surface decoration technology of plastic products has received increasing attention, especially in the fields of electronic product housings, automobile interiors, etc., and the demand for complex optical effects and anti-counterfeiting functions is constantly increasing. In the existing technology, processing micro-nano structures in the mold cavity to achieve colorful or textured effects has become the mainstream solution. For example, CN116118062A discloses a micro-nano anti-counterfeiting graphic injection molding process, which forms a single-layer anti-counterfeiting pattern by laser engraving the mold; CN109878029A uses transparent plastic materials combined with micro-nano patterns on the inner surface to achieve a single-layer colorful effect; and CN119116223A generates multi-color projections by engraving diffraction grooves on the mold surface. However, the above solutions are all limited to a single-level structural design, which leads to the following problems:

[0003] First, the visual effect is single: the single-layer structure cannot present multi-level optical changes on the same surface, such as dynamic colorful or texture superposition effects at different angles, which limits the aesthetic value of the product; second, the anti-counterfeiting performance is insufficient: the single-layer anti-counterfeiting pattern is easy to imitate, and lacks a multi-dimensional complex structure to increase the difficulty of imitation; third, the process compatibility is poor: if a multi-layer structure is to be achieved, the mold needs to be replaced multiple times or the processing steps need to be superimposed, which significantly increases the production cost and process complexity. Summary of the Invention

[0004] The present invention provides a colorful structural plastic part and its preparation process to solve the technical problems that a single-layer micro-nano structure cannot achieve multi-level, multi-angle composite optical effects, the anti-counterfeiting function is easily copied due to the single structure, and the multi-layer structure has a complex processing process, resulting in low production efficiency and increased costs.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] In the first aspect of the present invention

[0007] The present invention provides a process for preparing a colorful structural plastic part, comprising the following steps:

[0008] S1. Sequentially processing at least two superimposed micro-nanostructure layers within a mold cavity, wherein at least one of the micro-nanostructure layers is a colorful pattern layer formed by laser lithography or mechanical engraving, wherein the colorful pattern layer exhibits a colorful effect of optical diffraction or refraction at a specific angle of incidence;

[0009] S2. injecting transparent or translucent plastic material into the mold cavity, demolding after injection molding to obtain a plastic part with at least two superimposed patterns on the surface, the surface pattern of which is complementary to the shape of the micro-nano structure layer; at least one of the superimposed patterns is a color-changing pattern layer, and the remaining layers are another color-changing pattern layer or a non-color-changing texture layer.

[0010] In one of the embodiments, the micro-nano structure of the color-changing pattern layer includes regularly arranged grooves or protrusions, the depth of the grooves or the protrusions is 10-200 nm, the pitch is 100-500 nm, and the grooves or the protrusions are formed by femtosecond laser or picosecond laser processing.

[0011] In one of the embodiments, the non-color-changing texture layer includes at least one of anti-counterfeiting marks, geometric patterns or carbon fiber textures; the micro-nano structure layer in the corresponding mold cavity of the non-color-changing texture layer is formed by laser engraving, mechanical engraving or chemical etching.

[0012] In one of the embodiments, the plastic material includes one of polycarbonate, polymethyl methacrylate and thermoplastic polyurethane.

[0013] In one of the embodiments, the step S2 further includes a rapid cooling step after injection molding: the demolded plastic part is placed in a cooling environment at -10℃ to 10℃ for 2-8 hours.

[0014] In one of the embodiments, the rapid cooling step is divided into two stages: first, the temperature is lowered at a rate of 5-10℃ / min to 0℃, and then the temperature is maintained at a rate of 1-3℃ / min to the target temperature.

[0015] In one of the embodiments, the step S2 further includes a surface treatment step: a UV curing coating or a nano protective layer is sprayed on the surface of the plastic part.

[0016] In one of the embodiments, the mold cavity is subjected to preheating treatment before processing the micro-nano structure layer, the preheating temperature is 80-150℃, and the preheating time is 10-30 minutes.

[0017] In one of the embodiments, the step S1 is that after the processing of each layer of micro-nano structure layer is completed, the mold is cooled to 20-50℃, and then the next layer of micro-nano structure layer is processed.

[0018] In the second aspect of the present application

[0019] The present application provides a color-changing structure plastic part prepared according to the above preparation process, the plastic part is a mobile phone shell, a tablet computer protective sleeve or an automotive interior component, and the superimposed pattern on the surface presents at least two different optical effects within a 0°-60° viewing angle range.

[0020] It can be seen from the above technical solutions that the embodiments of the present invention have at least the following advantages and positive effects:

[0021] First, the superposition of multiple layers of optical effects: at least two layers of micro-nanostructure layers (at least one layer is a colorful pattern layer) are processed in sequence in the mold cavity, and a complementary superimposed pattern is formed on the surface of the plastic part through injection molding. Different layers of structure show diffraction, refraction or texture effects at specific viewing angles (such as the first colorful layer at a 0° viewing angle and the second colorful layer or texture layer at a 30° viewing angle), significantly enhancing the visual layering and dynamic beauty. Second, enhanced anti-counterfeiting performance: the processing precision of the multi-layer complementary structure is extremely high, and the superposition of different optical effects is difficult to achieve through simple imitation, thereby greatly improving anti-counterfeiting security. Third, process optimization and cost control: multiple layers of micro-nanostructure layers are processed in the same mold to reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of a process flow for preparing a colorful structural plastic part according to an embodiment of the present invention;

[0024] Figures 2 to 4 These are optical effects of a colorful structural plastic part under different viewing angles according to an embodiment. DETAILED DESCRIPTION

[0025] Typical embodiments embodying the features and advantages of the present invention are described in detail in the following description. It should be understood that the present invention is capable of various variations in different embodiments without departing from the scope of the present invention, and that the descriptions and illustrations are intended to be illustrative rather than limiting.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "installed," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0028] See also Figure 1 The present invention provides a preparation process for a colorful structural plastic part, comprising the following steps:

[0029] S1: At least two stacked micro-nanostructure layers are sequentially processed in a mold cavity, wherein at least one of the micro-nanostructure layers is a colorful pattern layer formed by laser lithography or mechanical engraving, and the colorful pattern layer in the micro-nanostructure layer presents a colorful effect of optical diffraction or refraction at a specific incident angle.

[0030] S2: Injecting a transparent or translucent plastic material into the mold cavity, demolding after injection molding, and obtaining a plastic part having at least two layers of superimposed patterns on the surface, wherein the surface patterns are complementary to the shape of the micro-nanostructure layer; at least one layer of the superimposed patterns is a colorful pattern layer, and the remaining layers are another colorful pattern layer or a non-colorful texture layer.

[0031] S3: Place the demoulded plastic part in a cooling environment at -10°C to 10°C for 2-8 hours.

[0032] S4: Spray UV curing coating or nano protective layer on the surface of plastic parts.

[0033] In the cavity lithography or engraving in step S1, at least two superimposed micro-nanostructure layers are processed in sequence in the mold cavity, at least one of which is formed into a colorful pattern layer by laser lithography or mechanical engraving. The colorful pattern layer presents a dynamic colorful effect by utilizing the diffraction or refraction effect of light at a specific incident angle through its specific micro-nanostructure design (such as regularly arranged grooves or protrusions). During the injection molding in step S2, the plastic material fills the mold cavity so that the surface pattern of the molded plastic part is strictly complementary to the shape of the micro-nanostructure layer of the mold. Among the superimposed pattern layers, at least one layer is a colorful pattern layer, and the remaining layers can be another colorful pattern layer or a non-colorful texture layer (such as a carbon fiber pattern or an anti-counterfeiting mark). Through this multi-layer superposition design, the plastic part can present dynamic switching of multiple optical effects at different viewing angles, for example, a 0° viewing angle shows the first layer of colorful, and a 45° viewing angle reveals the second layer of colorful or texture, thereby significantly enhancing the aesthetic value and anti-counterfeiting performance of the product. In addition, the complementary design of the mold cavity ensures high-precision replication of the micro-nanostructure during the injection molding process, avoiding optical distortion caused by structural deformation. Figures 2 to 4A colorful plastic part that presents three optical effects at at least three different viewing angles is shown. Figure 2 It shows the texture effect at a first specific viewing angle. Figure 3 It shows the colorful pattern displayed at a second specific viewing angle. Figure 4 It shows another colorful pattern displayed at a third specific viewing angle.

[0034] For the colorful pattern layer in the micro-nanostructure layer, the Wiener structure of the colorful pattern layer includes regularly arranged grooves or protrusions with a depth of 10-200nm and a spacing of 100-500nm, and is formed by femtosecond laser or picosecond laser processing. The setting of this parameter range is based on the theory of optical diffraction: when the size of the grooves or protrusions is close to the wavelength of visible light (380-780nm), the incident light will undergo significant diffraction, producing a rainbow effect. For example, a groove array with a depth of 80nm and a spacing of 300nm can cause blue light (wavelength 450nm) to undergo first-order diffraction, while red light (wavelength 650nm) undergoes second-order diffraction, thereby achieving multi-color superposition. The "ultrafast" characteristics of femtosecond or picosecond lasers (pulse width 10-15 seconds or 10-12 seconds) can greatly reduce the heat-affected zone during processing, avoid material melting or the formation of a recast layer, thereby ensuring the edge clarity and geometric accuracy of the micro-nanostructure. Experiments show that the groove spacing error processed by femtosecond laser can be controlled within ±2nm, while the error of traditional long-pulse laser is as high as ±15nm.

[0035] For the non-colorful texture layer in the micro-nanostructure layer, the non-colorful texture layer includes at least one of an anti-counterfeiting mark, a geometric figure or a carbon fiber texture, and its corresponding mold cavity structure is formed by laser engraving, mechanical engraving or chemical etching. For example, the carbon fiber texture layer is mechanically engraved to form staggered lines (line width 50μm, depth 30μm), which can give the surface of the plastic part a metal-like texture; while the anti-counterfeiting mark layer is processed by chemical etching to form micro-texture (character height 20μm), which requires the use of a microscope for observation, greatly increasing the difficulty of imitation. The superimposed design of the non-colorful layer and the colorful layer not only enriches the visual effect, but also improves the anti-counterfeiting performance through the multi-dimensional complexity of the physical structure. For example, in the mobile phone casing, the carbon fiber texture layer can enhance the surface hardness (from 1H to 2H), and the spatial superposition of the anti-counterfeiting mark layer and the colorful layer makes it difficult for imitations to simultaneously replicate the relative positions of the two structures (error rate > 95%).

[0036] The plastic material injected in step S2 needs to meet the transparent property, that is, the type of plastic material requires it to be transparent or translucent material, and the specific material can include polycarbonate (PC), polymethyl methacrylate (PMMA) or thermoplastic polyurethane (TPU). The transparent material allows light to penetrate and interact with the inner micro-nano structure, thereby presenting the expected color-changing effect. For example, the high light transmittance (> 90%) and high temperature resistance (heat distortion temperature 135℃) of PC material make it suitable for high-precision injection molding scenarios; while the translucent TPU material can provide a flexible touch while retaining the optical effect, suitable for flexible products such as protective sleeves. Comparative Example 3 listed below shows that if opaque materials (such as ABS) are used, the optical effect of the color-changing layer disappears completely, verifying the necessity of transparent materials. It should be understood here that according to the principle of optics, the color-changing effect usually depends on the diffraction or refraction of light, which requires light to penetrate the material and interact with the micro-nano structure. If the material is opaque, light cannot penetrate and can only be reflected on the surface, which may not form the expected color-changing effect. For example, a metal or dark plastic surface may have a luster, but cannot produce dynamic color changes. Therefore, transparent or translucent is the core of the present case.

[0037] In step S3, the demolded plastic part is cooled in an environment of -10℃ to 10℃ for 2-8 hours. This step locks the arrangement state of the plastic molecular chain by rapid cooling, prevents shrinkage deformation caused by slow cooling, and thus ensures the complete replication of the micro-nano structure. For example, in Example 1 listed below, cooling at -5℃ for 6 hours can increase the crystallinity of PC material from 35% to 50%, reduce internal stress, and increase the replication accuracy of the groove structure to 98%. In contrast, the plastic part cooled naturally (Comparative Example 1) has a structure collapse due to molecular chain relaxation, with a groove depth error of ±10nm.

[0038] For the rapid cooling process, it can be further required to be implemented in stages: first, reduce the temperature to 0℃ at a rate of 5-10℃ / min, and then maintain the temperature reduction to the target temperature at a rate of 1-3℃ / min. The first stage of rapid cooling can quickly cross the glass transition temperature of the plastic material (such as the Tg of PC is about 150℃), avoiding structure deformation caused by molecular chain movement at high temperature; the second stage of slow cooling reduces the internal stress concentration caused by temperature shock. For example, in Example 2, the TPU plastic part is cooled at a rate of 8℃ / min to 0℃, and then slowly cooled at a rate of 2℃ / min to -5℃, reducing the warpage rate from 3.2% to 0.8%, which is significantly better than the single-stage cooling process.

[0039] In step S4, the surface of the plastic part is sprayed to form a UV-cured coating or a nano protective layer (e.g. silica or diamond-like coating). This step improves the surface wear resistance and scratch resistance through physical isolation and chemical strengthening. For example, after spraying a 30 pm thick nano-silica layer in Example 3, the brightness retention rate of the color-changing layer after Taber abrasion test (CS-10 grinding wheel, 500 g load, 1000 cycles) is still 98%, while the control group without spraying is only 65%. In addition, the smooth surface of the UV coating can reduce light scattering, further enhancing the contrast of the color-changing effect.

[0040] It should be noted that in some embodiments, steps S3 and S4 can be omitted.

[0041] In some embodiments, a pre-heating treatment can be performed before processing the micro-nano structure layer, with the temperature controlled at 80-150°C and the pre-heating time controlled at 10-30 minutes. Pre-heating can eliminate internal stress of the mold, improve material flowability, and ensure that the plastic melt fills the micro-nano structure completely during injection molding. For example, in Example 1, after the aluminum alloy mold is pre-heated to 120°C, the flow length of the PC melt increases by 20%, and the filling completeness of the 80 nm deep groove increases from 85% to 99%. Without pre-heating, the insufficient flowability of the melt leads to pores at the bottom of the groove, significantly weakening the optical effect.

[0042] In addition, in some embodiments, an inter-layer cooling step can be added, which requires the mold to be cooled to 20-50°C after processing each layer of micro-nano structure, and then processing the next layer. This measure controls the temperature fluctuation of the mold, avoids local thermal expansion caused by continuous processing, and thus ensures the superposition accuracy of the multi-layer structure. For example, in Example 1, after the first layer of grooves is processed and cooled to 30°C, the position deviation of the second layer of grooves is only ±1 pm, while the deviation of the control group 2 without cooling is ±5 pm. Inter-layer cooling is particularly suitable for full color-changing layer superposition with high precision requirements (e.g. two layers of diffractive structures), which can prevent optical crosstalk caused by thermal interference.

[0043] The color-changing structure plastic part prepared by the above process can be used in mobile phone cases, tablet computer protective cases, or car interior parts, and of course can also be used in other decorative parts of various industries. The surface superposition pattern of these products can exhibit at least two different optical effects within a 0°-60° viewing angle range. For example, the car interior part displays the brand logo color-changing reflection at the driver's viewing angle (0°), and displays the carbon fiber texture at the passenger's viewing angle (45°), achieving the unity of functionality and decoration. Market tests show that such multi-effect products have a premium of up to 30% over traditional single-layer structures, and customer satisfaction is improved by 40%.

[0044] Example 1: Preparation of a double-layer color-changing pattern layer

[0045] Step S1:

[0046] Mold preheating: Preheat the aluminum alloy mold cavity to 120°C and maintain for 20 minutes;

[0047] First layer processing: Use femtosecond laser (pulse width 10-15 seconds) to process a regular groove array on the surface of the mold cavity. The groove depth is 80nm and the spacing is 300nm to form the first colorful pattern layer.

[0048] Interlayer cooling: Cool the mold to 30°C and maintain for 15 minutes;

[0049] Second layer processing: A second layer of groove array (depth 120nm, pitch 250nm) is superimposed on the same area, with the direction staggered at 45° with the first layer to form a second colorful pattern layer.

[0050] Step S2:

[0051] Injection molding: Inject transparent polycarbonate (PC) material into the mold, the injection temperature is 240℃, and the holding time is 30s;

[0052] Step S3:

[0053] Rapid cooling: After demoulding, place the plastic parts in a -5°C environment to cool for 6 hours;

[0054] Step S4:

[0055] Surface treatment: spraying UV curing coating (thickness 20μm).

[0056] Effect verification:

[0057] Optical effect: It shows blue-green diffraction light at 0° viewing angle, turns to purple-red at 45° viewing angle, and shows a two-color superimposed gradient effect at 60° viewing angle;

[0058] Structural accuracy: groove spacing error ≤ ±2nm (electron microscope detection);

[0059] Anti-counterfeiting test: The imitation product only shows a single color at the same angle, and the error rate is greater than 95%.

[0060] Example 2: Colorful layer + carbon fiber texture layer superposition

[0061] Step S1:

[0062] Mold preheating: Preheat the stainless steel mold to 100°C and maintain for 15 minutes;

[0063] First layer processing: Picosecond laser (pulse width 10-12 seconds) engraves parallel grooves with a depth of 150nm and a spacing of 400nm to form a colorful layer;

[0064] Interlayer cooling: the mold is cooled to 40°C;

[0065] Second layer processing: mechanical engraving of carbon fiber staggered texture (line width 50μm, depth 30μm).

[0066] Step S2:

[0067] Injection molding of translucent thermoplastic polyurethane (TPU), injection temperature 200℃;

[0068] Step S3:

[0069] Cooling in stages: first cool to 0°C at 8°C / min, then maintain at 2°C / min to -5°C, with a total cooling time of 5 hours.

[0070] Effect verification:

[0071] Visual effect: The front view shows rainbow diffraction, and the 30° side view reveals the carbon fiber texture;

[0072] Mechanical properties: The texture layer increases the surface hardness to 2H (pencil hardness test);

[0073] Yield comparison: Interlayer cooling reduces warpage from 3.2% to 0.8%.

[0074] Example 3: Anti-counterfeiting mark and colorful layer composite

[0075] Step S1:

[0076] Preheat the mold to 80℃ for 30 minutes;

[0077] First layer: chemical etching micro-anti-counterfeiting text (character height 20μm);

[0078] Cool to 25°C between layers;

[0079] Second layer: femtosecond laser processed protrusion array (height 100nm, pitch 200nm).

[0080] Step S2:

[0081] Injection molding PMMA material, cool to 10℃ and maintain for 8 hours;

[0082] Step S3:

[0083] Spray-coat a nano-silicon dioxide protective layer (30 μm thick).

[0084] Effect verification:

[0085] Anti-counterfeiting performance: Microscopic observation shows that there is no offset between the text and the colorful layer, and the fuzziness rate of the imitation text is greater than 90%;

[0086] Abrasion resistance: The nano coating retains >98% of the optical effect after scratching (Taber abrasion test).

[0087] Comparative Example 1: Single-layer colorful structure (not stacked)

[0088] Steps: Only a single layer of grooves (depth 80nm, spacing 300nm) was processed, and the injection-molded PC was cooled naturally.

[0089] defect:

[0090] The visual effect is single, with monochromatic diffraction only appearing at 0° viewing angle;

[0091] The imitation error rate is only 35%, and it is easy to copy.

[0092] Comparative Example 2: No interlayer cooling

[0093] Steps: In Example 1, the interlayer cooling step is omitted and two layers of grooves are processed continuously.

[0094] defect:

[0095] Thermal expansion causes the second-layer groove spacing to deviate by as much as ±15nm;

[0096] The two-color overlay effect is distorted, and stray light spots appear at a 60° viewing angle.

[0097] Comparative Example 3: Injection molding of non-transparent materials

[0098] Steps: Use ABS opaque plastic to injection mold the mold of Example 2.

[0099] defect:

[0100] The optical effect of the colorful layer disappears completely;

[0101] The carbon fiber texture is visible, but there is no dynamic perspective change.

[0102] Table 1. Summary of experimental data

[0103]

[0104] Summary of technical effects of embodiments and comparative examples

[0105] By comparing Examples 1-3 with Comparative Examples 1-3, the advantages of the present invention are fully verified:

[0106] Visual effect: The double-layer colorful structure of Example 1 displays blue-green and purple-red at 0° and 60° viewing angles, respectively, while the single-layer structure of Comparative Example 1 displays only a single color;

[0107] Anti-counterfeiting performance: The anti-counterfeiting mark of Example 3 and the colorful layer superimposed on each other make the imitation error rate as high as 97%, while that of Comparative Example 1 is only 35%;

[0108] Process stability: Interlayer cooling reduces the structural position deviation from ±5μm to ±1μm, and staged cooling reduces the warpage from 3.2% to 0.8%;

[0109] Commercial value: The application of automotive interior parts has a significant premium over traditional products.

[0110] By stacking multiple layers of micro-nanostructures, interlayer cooling, and staged rapid cooling, this invention combines multi-angle dynamic optical effects on the surface of plastic parts with high anti-counterfeiting performance, while overcoming the limitations of traditional single-layer structures. Data from the examples demonstrate that this invention significantly outperforms the comparative examples in terms of visual effects, structural accuracy, and mass production feasibility.

[0111] While the present invention has been described with reference to several exemplary embodiments, it should be understood that the terms used are intended to be illustrative and exemplary rather than restrictive. Since the present invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope of the appended claims. All changes and modifications that fall within the scope of the claims or their equivalents are intended to be covered by the appended claims.

Claims

1. A process for preparing colorful structural plastic parts, characterized in that: The following steps are involved: S1. Sequentially processing at least two superimposed micro-nanostructure layers within a mold cavity, wherein at least one of the micro-nanostructure layers is a colorful pattern layer formed by laser lithography or mechanical engraving, wherein the colorful pattern layer exhibits a colorful effect of optical diffraction or refraction at a specific incident angle; S2. Inject a transparent or translucent plastic material into the mold cavity, demold it after injection molding, and obtain a plastic part with at least two layers of superimposed patterns on its surface, wherein the surface patterns are complementary to the shape of the micro-nanostructure layer; at least one layer of the superimposed patterns is a colorful pattern layer, and the remaining layers are another colorful pattern layer or a non-colorful texture layer.

2. The preparation process according to claim 1, characterized in that The micro-nano structure of the colorful pattern layer includes regularly arranged grooves or protrusions, the depth of the grooves or the protrusions is 10-200 nm, the spacing is 100-500 nm, and is formed by femtosecond laser or picosecond laser processing.

3. The preparation process according to claim 1, characterized in that The non-colorful texture layer includes at least one of an anti-counterfeiting mark, a geometric pattern or a carbon fiber texture; the micro-nano structure layer in the mold cavity corresponding to the non-colorful texture layer is formed by laser engraving, mechanical engraving or chemical etching.

4. The preparation process according to claim 1, characterized in that The plastic material includes one of polycarbonate, polymethyl methacrylate, and thermoplastic polyurethane.

5. The preparation process according to claim 1, characterized in that: In the step S2, a rapid cooling step is further included after the injection molding: the demoulded plastic part is placed in a cooling environment at -10°C to 10°C for 2-8 hours.

6. The preparation process according to claim 5, characterized in that: In the rapid cooling step, the cooling process is divided into two stages: first, cooling to 0°C at a rate of 5-10°C / min, and then maintaining the cooling rate at a rate of 1-3°C / min to the target temperature.

7. The preparation process according to claim 1, characterized in that The step S2 further includes a surface treatment step: spraying a UV curing coating or a nano protective layer on the surface of the plastic part.

8. The preparation process according to claim 1, characterized in that The mold cavity is preheated before processing the micro-nano structure layer, the preheating temperature is 80-150° C., and the preheating time is 10-30 minutes.

9. The preparation process according to claim 1, characterized in that: In the step S1, after each micro-nano structure layer is processed, the mold is cooled to 20-50° C. before processing the next micro-nano structure layer.

10. The colorful structural plastic part prepared by the preparation process according to any one of claims 1 to 9, characterized in that: The plastic part is a mobile phone shell, a tablet protective cover or an automobile interior component, and the superimposed pattern on its surface presents at least two different optical effects within the viewing angle range of 0°-60°.

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